Sample records for wave short wavelength

  1. Transparency of the atmosphere to short horizontal wavelength gravity waves

    NASA Astrophysics Data System (ADS)

    Preusse, Peter; Eckermann, Stephen D.; Ern, Manfred

    2008-12-01

    We use theory and global ray modeling to investigate how the potential of gravity waves to transport momentum flux globally from the lower atmosphere into the mesosphere and lower thermosphere (MLT) varies with horizontal wavelength and ground-based phase speed. Ray modeling is performed using the Gravity Wave Regional or Global Ray Tracer (GROGRAT) interfaced to realistic three-dimensional global winds and temperatures from 0 to 100 km altitude, specified by fusing analysis fields at lower altitudes to GCM results higher up. We focus on gravity waves in the short 10- to 50-km horizontal wavelength range that are unresolved by global models and, according to theory, can transport appreciable momentum flux into the MLT. Ray results for different seasons reproduce some of the limits derived from simple wave theory: that horizontal wavelengths shorter than 10 km tend to be removed by vertical reflection or evanescence at the source and slower phase speeds are more prone to critical level removal, leading to a preference for waves with longer horizontal wavelengths and faster ground-based phase speeds to reach the MLT. These findings are compared to the wavelength scales currently resolved by satellite limb and nadir sounders, highlighting wavelength ranges currently measured and those currently unresolved. A road map is developed for how current and future satellite measurements can be combined to measure the full space-time spectrum of gravity waves relevant to eddy flux deposition and momentum forcing of the global MLT. In particular, recommendations for new satellite measurement strategies that fill current measurement gaps are provided.

  2. Short Wavelength Ion Waves Upstream of the Earth’s Bow Shock

    Microsoft Academic Search

    S. A. Fuselier; D. A. Gurnett

    1984-01-01

    ISEE-1 wide-band electric field data, antenna interference effects have been identified in the ion waves upstream of the earth's bow shock. This identification implies that wavelengths of the upstream ion waves are shorter than the antenna length. The interference effects also provide new measurements of the direction of propagation of the ion waves. The new measurements show that the wave

  3. Continuous-wave, short-wavelength infrared mixer using dispersion-stabilized highly-nonlinear fiber.

    PubMed

    Kuo, Bill P-P; Hirano, Masaaki; Radic, Stojan

    2012-07-30

    A new type of highly nonlinear fiber (HNLF) was designed and fabricated. The new HNLF was engineered to reduce dispersion shift due to transverse fluctuations while maintaining the modal confinement superior to that of the conventional fibers. The new design strategy was validated by the measurements of the global and local dispersive characteristics under considerable core and index profile deformation induced by tensile stress, which indicated that the dispersive and phase matching characteristics of the fiber did not change even under the highest tensile stress. The characteristics effectively decoupled tension-based Brillouin suppression from phase-matching impairments in parametric mixers for the first time. The new HNLF was used to demonstrate the first coherence-preserving mixer operating in the short-wavelength infrared (SWIR) band. The SWIR mixer was driven by continuous-wave near-infrared (NIR) pump and did not require pump phase dithering to suppress Brillouin scattering. PMID:23038393

  4. Short wavelength laser

    DOEpatents

    Hagelstein, P.L.

    1984-06-25

    A short wavelength laser is provided that is driven by conventional-laser pulses. A multiplicity of panels, mounted on substrates, are supported in two separated and alternately staggered facing and parallel arrays disposed along an approximately linear path. When the panels are illuminated by the conventional-laser pulses, single pass EUV or soft x-ray laser pulses are produced.

  5. A modified beam-to-earth transformation to measure short-wavelength internal waves with an acoustic Doppler current profiler

    USGS Publications Warehouse

    Scotti, A.; Butman, B.; Beardsley, R.C.; Alexander, P.S.; Anderson, S.

    2005-01-01

    The algorithm used to transform velocity signals from beam coordinates to earth coordinates in an acoustic Doppler current profiler (ADCP) relies on the assumption that the currents are uniform over the horizontal distance separating the beams. This condition may be violated by (nonlinear) internal waves, which can have wavelengths as small as 100-200 m. In this case, the standard algorithm combines velocities measured at different phases of a wave and produces horizontal velocities that increasingly differ from true velocities with distance from the ADCP. Observations made in Massachusetts Bay show that currents measured with a bottom-mounted upward-looking ADCP during periods when short-wavelength internal waves are present differ significantly from currents measured by point current meters, except very close to the instrument. These periods are flagged with high error velocities by the standard ADCP algorithm. In this paper measurements from the four spatially diverging beams and the backscatter intensity signal are used to calculate the propagation direction and celerity of the internal waves. Once this information is known, a modified beam-to-earth transformation that combines appropriately lagged beam measurements can be used to obtain current estimates in earth coordinates that compare well with pointwise measurements. ?? 2005 American Meteorological Society.

  6. A two-stage photonic crystal fiber / silicon photonic wire short-wave infrared wavelength converter/amplifier based on a 1064 nm pump source.

    PubMed

    Kuyken, B; Leo, F; Mussot, A; Kudlinski, A; Roelkens, G

    2015-05-18

    We demonstrate a two-stage wavelength converter that uses compact near-infrared sources to amplify and convert short-wave infrared signals. The first stage consists of a photonic crystal fiber wavelength converter pumped by a Q-switched 1064 nm pump source, while the second stage consists of a silicon photonic wire waveguide wavelength converter. The system enables on-chip amplification and conversion of up to 30 dB . We demonstrate amplification in a broad wavelength range around 2344 nm using temporally long pulses (>300ps). PMID:26074555

  7. Improved limits on short-wavelength gravitational waves from the cosmic microwave background

    NASA Astrophysics Data System (ADS)

    Sendra, Irene; Smith, Tristan L.

    2012-06-01

    The cosmic microwave background (CMB) is affected by the total radiation density around the time of decoupling. At that epoch, neutrinos comprised a significant fraction of the radiative energy, but there could also be a contribution from primordial gravitational waves with frequencies greater than ˜10-15Hz. If this cosmological gravitational wave background were produced under adiabatic initial conditions, its effects on the CMB and matter power spectrum would mimic massless noninteracting neutrinos. However, with homogenous initial conditions—as one might expect from certain models of inflation, prebig bang models, phase transitions, and other scenarios—the effect on the CMB would be distinct. We present updated observational bounds for both initial conditions using the latest CMB data at small scales from the South Pole Telescope in combination with Wilkinson Microwave Anisotropy Probe, current measurements of the baryon acoustic oscillations, and the Hubble parameter. With the inclusion of the data from the South Pole Telescope, the adiabatic bound on the cosmological gravitational wave background density is improved by a factor of 1.7 to 106?gwh2?8.7 at the 95% confidence level, with weak evidence in favor of an additional radiation component consistent with previous analyses. The constraint can be converted into an upper-limit on the tension of horizon-sized cosmic strings that could generate this gravitational wave component, with G??2×10-7 at 95% C. L., for string tension G?. The homogeneous bound improves by a factor of 3.5 to 106?gwh2?1.0 at 95% C. L., with no evidence for such a component from current data.

  8. Modulating short wavelength fluorescence with long wavelength light.

    PubMed

    Copley, Graeme; Gillmore, Jason G; Crisman, Jeffrey; Kodis, Gerdenis; Gray, Christopher L; Cherry, Brian R; Sherman, Benjamin D; Liddell, Paul A; Paquette, Michelle M; Kelbauskas, Laimonas; Frank, Natia L; Moore, Ana L; Moore, Thomas A; Gust, Devens

    2014-08-27

    Two molecules in which the intensity of shorter-wavelength fluorescence from a strong fluorophore is modulated by longer-wavelength irradiation of an attached merocyanine-spirooxazine reverse photochromic moiety have been synthesized and studied. This unusual fluorescence behavior is the result of quenching of fluorophore fluorescence by the thermally stable, open, zwitterionic form of the spirooxazine, whereas the photogenerated closed, spirocyclic form has no effect on the fluorophore excited state. The population ratio of the closed and open forms of the spirooxazine is controlled by the intensity of the longer-wavelength modulated light. Both square wave and sine wave modulation were investigated. Because the merocyanine-spirooxazine is an unusual reverse photochrome with a thermally stable long-wavelength absorbing form and a short-wavelength absorbing photogenerated isomer with a very short lifetime, this phenomenon does not require irradiation of the molecules with potentially damaging ultraviolet light, and rapid modulation of fluorescence is possible. Molecules demonstrating these properties may be useful in fluorescent probes, as their use can discriminate between probe fluorescence and various types of adventitious "autofluorescence" from other molecules in the system being studied. PMID:25072525

  9. Widely-tunable, multi-wavelength short wave infrared light source based on fiber optical parametric oscillator

    Microsoft Academic Search

    Bill P. P. Kuo; Andreas O. J. Wiberg; Evgeny Myslivets; Daniel Blessing; Nikola Alic; Stojan Radic

    2010-01-01

    We demonstrate a fiber-optical-parametric-oscillator-based multi-wavelength pulse source operating at 1.9 ¿m. Multiple time- and wavelength-distinct pulse seeds were used to cover wavelength range from 1904 to 1924 nm and generate new tones with linewidths below 0.1 nm.

  10. Transition operators in acoustic-wave diffraction theory. I - General theory. II - Short-wavelength behavior, dominant singularities of Zk0 and Zk0 exp -1

    NASA Technical Reports Server (NTRS)

    Hahne, G. E.

    1991-01-01

    A formal theory of the scattering of time-harmonic acoustic scalar waves from impenetrable, immobile obstacles is established. The time-independent formal scattering theory of nonrelativistic quantum mechanics, in particular the theory of the complete Green's function and the transition (T) operator, provides the model. The quantum-mechanical approach is modified to allow the treatment of acoustic-wave scattering with imposed boundary conditions of impedance type on the surface (delta-Omega) of an impenetrable obstacle. With k0 as the free-space wavenumber of the signal, a simplified expression is obtained for the k0-dependent T operator for a general case of homogeneous impedance boundary conditions for the acoustic wave on delta-Omega. All the nonelementary operators entering the expression for the T operator are formally simple rational algebraic functions of a certain invertible linear radiation impedance operator which maps any sufficiently well-behaved complex-valued function on delta-Omega into another such function on delta-Omega. In the subsequent study, the short-wavelength and the long-wavelength behavior of the radiation impedance operator and its inverse (the 'radiation admittance' operator) as two-point kernels on a smooth delta-Omega are studied for pairs of points that are close together.

  11. Short wavelength fluctuations and electron transport in TFTR

    NASA Astrophysics Data System (ADS)

    Wong, K. L.; Itoh, K.; Itoh, S.-I.; Fukuyama, A.; Yagi, M.

    2000-11-01

    Correlation between electron heat diffusivity and short wavelength ( k?i˜5) fluctuation amplitude was observed in the TFTR tokamak in the core of ERS plasmas (Phys. Lett. A 236 (1997) 339). These fluctuations propagate in the ion diamagnetic drift direction with wave number comparable to ?pe/ c. Further analysis of these data yields the ratios ?e/ ?i and ?e/ De, and their values are consistent with the picture that the electron transport is mainly induced by the short wavelength fluctuations in the plasma core where the long wavelength ( k?i˜1) fluctuations are absent. Although there is not enough information to identify these short wavelength modes, the values of ?e is found to be comparable to theoretical predictions based on the current diffusive ballooning mode theory (Plasma Phys. Control. Fusion 36 (1994) 279).

  12. Short wavelength FELs using the SLAC linac

    SciTech Connect

    Winick, H.; Bane, K.; Boyce, R. [Stanford Linear Accelerator Center, Menlo Park, CA (United States)] [and others

    1993-08-01

    Recent technological developments have opened the possibility to construct a device which we call a Linac Coherent Light Source (LCLS); a fourth generation light source, with brightness, coherence, and peak power far exceeding other sources. Operating on the principle of the free electron laser (FEL), the LCLS would extend the range of FEL operation to much aborter wavelength than the 240 mn that has so far been reached. We report the results of studies of the use of the SLAC linac to drive an LCLS at wavelengths from about 3-100 nm initially and possibly even shorter wavelengths in the future. Lasing would be achieved in a single pass of a low emittance, high peak current, high energy electron beam through a long undulator. Most present FELs use an optical cavity to build up the intensity of the light to achieve lasing action in a low gain oscillator configuration. By eliminating the optical cavity, which is difficult to make at short wavelengths, laser action can be extended to shorter wavelengths by Self-Amplified-Spontaneous-Emission (SASE), or by harmonic generation from a longer wavelength seed laser. Short wavelength, single pass lasers have been extensively studied at several laboratories and at recent workshops.

  13. Undulators for short wavelength FEL amplifiers

    SciTech Connect

    Schlueter, R.D.

    1994-12-01

    Issues critical to the design of undulators for use in short wavelength FEL amplifiers, such as attainable on-axis field strength, device compactness, field quality, required magnetic gap, and strong focusing schemes, are discussed. The relative strength of various undulator technologies, including pure permanent magnet, hybrid, warm electromagnetic, pulsed, and superconducting electromagnetic devices in both helical and planar configurations are reviewed. Favored design options for proposed short wavelength FELs, such as the Linac Coherent Light Source at SLAC and the DUV Free-Electron Laser at BNL, are presented.

  14. Undulators for short wavelength FEL amplifiers

    SciTech Connect

    Schlueter, R. [Lawrence Berkeley Lab., CA (United States). Accelerator and Fusion Research Div.

    1994-08-01

    Issues critical to the design of undulators for use in short wavelength FEL amplifiers, such as attainable on-axis field strength, device compactness, field quality, required magnetic gap, and strong focusing schemes, are discussed. The relative strength of various undulator technologies, including pure permanent magnet, hybrid, warm electromagnetic, pulsed, and superconducting electromagnetic devices in both helical and planar configurations are reviewed. Favored design options for proposed short wavelength FELs, such as the Linac Coherent Light Source at SLAC and the DUV Free-Electron Laser at BNL, are presented.

  15. Undulators for short wavelength FEL amplifiers

    NASA Astrophysics Data System (ADS)

    Schlueter, R.

    1994-08-01

    Issues critical to the design of undulators for use in short wavelength FEL amplifiers, such as attainable on-axis field strength, device compactness, field quality, required magnetic gap, and strong focusing schemes, are discussed. The relative strength of various undulator technologies, including pure permanent magnet, hybrid, warm electromagnetic, pulsed, and superconducting electromagnetic devices in both helical and planar configurations are reviewed. Favored design options for proposed short wavelength FEL's, such as the Linac Coherent Light Source at SLAC and the DUV Free-Electron Laser at BNL, are presented.

  16. Electricity and short wavelength radiation generator

    DOEpatents

    George, E.V.

    1985-08-26

    Methods and associated apparati for use of collisions of high energy atoms and ions of He, Ne, or Ar with themselves or with high energy neutrons to produce short wavelength radiation (lambda approx. = 840-1300 A) that may be utilized to produce cathode-anode currents or photovoltaic currents.

  17. Far-field measurements of short-wavelength surface plasmons

    NASA Astrophysics Data System (ADS)

    Blau, Yochai; Gjonaj, Bergin; David, Asaf; Dolev, Shimon; Shterman, Doron; Bartal, Guy

    2015-03-01

    We present direct far-field measurements of short-wavelength surface plasmon polaritons (SPP) by conventional optics means. Plasmonic wavelength as short as 231 nm was observed for 532 nm illumination on a A g - S i 3 N 4 platform, demonstrating the capability to characterize SPPs well below the optical diffraction limit. This is done by scaling a sub-wavelength interferometric pattern to a far-field resolvable periodicity. These subwavelength patterns are obtained by coupling light into counter-propagating SPP waves to create a standing-wave pattern of half the SPP wavelength periodicity. Such patterns are mapped by a scattering slit, tilted at an angle so as to increase the periodicity of the intensity pattern along it to more than the free-space wavelength, making it resolvable by diffraction limited optics. The simplicity of the method as well as its large dynamic range of measurable wavelengths make it an optimal technique to characterize the properties of plasmonic devices and high-index dielectric waveguides, to improve their design accuracy and enhance their functionality.

  18. PHYSICAL REVIEW A 84, 043423 (2011) Dynamic of rescattering-electron wave packets in strong and short-wavelength laser fields

    E-print Network

    2011-01-01

    and short-wavelength laser fields: Roles of Coulomb potential and excited states Yanjun Chen* Beijing that the electronic rescattering trajectory depends strongly on the property of the Coulomb potential. Using numerical the potential, to explain the electronic response in intense and relatively high-frequency laser fields. DOI: 10

  19. Deformable mirror for short wavelength applications

    DOEpatents

    Chapman, Henry N. (2417 Kilkare Rd., Sunol, CA 94586); Sweeney, Donald W. (5020 Canyon Crest Dr., San Ramon, CA 94583)

    1999-01-01

    A deformable mirror compatible with short wavelength (extreme ultraviolet) radiation that can be precisely controlled to nanometer and subnanometer accuracy is described. Actuators are coupled between a reaction plate and a face plate which has a reflective coating. A control system adjusts the voltage supplied to the actuators; by coordinating the voltages supplied to the actuators, the reflective surface of the mirror can be deformed to correct for dimensional errors in the mirror or to produce a desired contour.

  20. ISO'S SHORT WAVELENGTH SPECTROMETER ULTIMATE SENSITIVITY

    E-print Network

    effects. For instance, for the small (120 \\Theta120 ¯m) InSb diode­detectors, which hardly have any memory/s 1 In:Sb 0.6 0.6 ­ 1.0 2 Si:Ga 0.6 1.5 ­ 3.5 3 Si:As BIBIB 0.5 4 ­ 5 4 Ge:Be 0.9 5 ­ 15 5 Si:Sb 0.5 2, the in­orbit noise levels of the Short Wavelength Spectrometer (SWS) detectors show a sig­ nificant

  1. Review -EM Waves Wavelengths of 108 to

    E-print Network

    Bertulani, Carlos A. - Department of Physics and Astronomy, Texas A&M University

    #12;Review - EM Waves EM Waves Wavelengths of 108 to 10-16 meters (10-1024 Hz) Traveling wave) given by BES rrr ×= 0 1 )(sin 111 22 0 2 00 tkxE c E c EBS m -=== Review - EM Waves 2 0 1 mpeak E c pr = c I pr = c I pr 2 = Total absorption Total reflection EM Waves: Radiation pressure #12;Source

  2. Dynamic of rescattering-electron wave packets in strong and short-wavelength laser fields: Roles of Coulomb potential and excited states

    SciTech Connect

    Chen Yanjun [Beijing Computational Science Research Center, Beijing (China)

    2011-10-15

    We investigate the high-order harmonic generation of atoms and molecules exposed in strong and short-wavelength (shorter than 800 nm) laser fields. Our simulations show that the electronic rescattering trajectory depends strongly on the property of the Coulomb potential. Using numerical schemes, we identify the important role of excited states in the emission times of harmonics from molecules. We propose a model, which considers the initial position when electrons tunnel out from the potential, to explain the electronic response in intense and relatively high-frequency laser fields.

  3. Short wavelength regenerative amplifier free electron lasers

    E-print Network

    Dunning, D J; Thompson, N R

    2008-01-01

    In this paper we discuss extending the operating wavelength range of tunable Regenerative Amplifier FELs to shorter wavelengths than current design proposals, notably into the XUV regions of the spectrum and beyond where the reflectivity of broadband optics is very low. Simulation studies are presented which demonstrate the development of good temporal coherence in generic systems with a broadband radiation feedback of less than one part in ten thousand.

  4. Lithographic spiral antennas at short wavelengths

    NASA Technical Reports Server (NTRS)

    Grossman, E. N.; Sauvageau, J. E.; Mcdonald, D. G.

    1991-01-01

    We have extended the high efficiency of lithographic antennas to mid-infrared wavelengths. Pattern measurements made at 9.5/zm wavelength on a 65 deg, self-complementary, spiral antenna exhibit a ratio of response to orthogonal linear polarizations of 1.35 dB, a beamwidth of 85 deg (3 dB full width), a directivity of 8.2 dB, and surprisingly, a close resemblance to the theoretical pattern for a 65 deg spiral in free space. Direct detection measurements made with an ambient temperature blackbody source yield an antenna efficiency of 52 +/- 7 percent, when corrected for incomplete filling of the antenna beam by the source, at a mean effective wavelength of 19 micron.

  5. Electric Field and Plasma Density Observations of Long Wavelength Structures and Localized Packets of Short Scale Waves Associated with Sporadic-E Layers in the Presence of QP Radar Echoes

    NASA Astrophysics Data System (ADS)

    Pfaff, R. F.; Freudenreich, H.; Kudeki, E.; Larsen, M.

    2006-05-01

    Electric field and plasma density data gathered on sounding rockets launched in the presence of sporadic-E layers and QP radar echoes reveal a complex electrodynamics including both DC parameters and plasma waves detected over a large range of scales. We present results from two different sounding rocket experiments equipped with similar instrumentation which were conducted in the presence of intense QP radar echoes: a NASA sporadic-E investigation launched from Wallops Island, Va., in 1999 and the Japanese "SEEK-2" rocket launched from Uchinoura, Japan in 2002. Electric field data from both experiments reveal the presence of km-scale waves as well as well-defined packets of broadband (10's of meters to meters) irregularities. What is surprising is that in both experiments, neither the large scale nor short scale waves appear to be distinctly organized by the sporadic-E density layer. Data from the NASA rocket revealed large scale structures with wavelengths of 2-4 km and amplitudes of 1-2 mV/m that were most intense in the region of 90-110 km during the downleg trajectory of this flight. The waves were oriented in the NE-SW quadrants. On the other hand, during the SEEK-2 experiment, the electric field data above the sporadic-E layer on the upleg, from 110 km to the rocket apogee of 151 km, revealed a continuous train of distinct, large scale, quasi-periodic structures with wavelengths of 10-15 km that also propagated between the NE-SW quadrants. The electric field structures had typical amplitudes of 3-5 mV/m with some excursions to 8-9 mV/m, and had associated perturbations in the plasma density. The electric field waveforms showed evidence for steepening and/or convergence effects and may have mapped upwards along the magnetic field from the sporadic-E region below. Candidate mechanisms to explain the origin of these structures include the Kelvin-Helmholtz instability and the Es Layer instability. In both cases, the same shear that formed the sporadic-E layer would presumably provide the energy to generate the km-scale structures. Other possibilities include a gravity wave explanation or a combination of these processes. The data suggest that these structures were associated with the lower altitude density striations that were the seat of the QP radar echoes observed simultaneously. The SEEK-2 structures may also have been associated with the mechanism responsible for a well-defined pattern of "whorls" in the neutral wind data that were revealed in a chemical trail released by a second sounding rocket launched 15 minutes later. Well-defined packets of higher frequency (shorter scales < 100 m) broadband waves were also observed in-situ on both rockets, consistent with the observations of intense radar backscatter during the times of each launch. The linear gradient drift instability involving the DC electric field and the vertical plasma gradient is shown to be incapable of driving most, although not all, of the short scale waves observed during each flight. The data suggest that other sources of free energy may have been important factors for wave growth, and we conclude that drift waves associated with winds and horizontal plasma density gradients, as well as thermal or other instabilities, are necessary to explain the short-scale wave generation observed during these sporadic-E encounters.

  6. Lethal effects of short-wavelength visible light on insects

    PubMed Central

    Hori, Masatoshi; Shibuya, Kazuki; Sato, Mitsunari; Saito, Yoshino

    2014-01-01

    We investigated the lethal effects of visible light on insects by using light-emitting diodes (LEDs). The toxic effects of ultraviolet (UV) light, particularly shortwave (i.e., UVB and UVC) light, on organisms are well known. However, the effects of irradiation with visible light remain unclear, although shorter wavelengths are known to be more lethal. Irradiation with visible light is not thought to cause mortality in complex animals including insects. Here, however, we found that irradiation with short-wavelength visible (blue) light killed eggs, larvae, pupae, and adults of Drosophila melanogaster. Blue light was also lethal to mosquitoes and flour beetles, but the effective wavelength at which mortality occurred differed among the insect species. Our findings suggest that highly toxic wavelengths of visible light are species-specific in insects, and that shorter wavelengths are not always more toxic. For some animals, such as insects, blue light is more harmful than UV light. PMID:25488603

  7. Short-wavelength Yb:fiber laser analysis

    NASA Astrophysics Data System (ADS)

    Yi, J. Y.; Chang, S. F.; Hsu, C. N.

    2013-12-01

    Yb:fiber lasers have shown excellent performance in the 980–1100 nm wavelength range. To extend the range below 980 nm, it becomes difficult to reach the transparent condition due to the smaller ratio between emission and absorption cross sections. As a result, a high demand of population inversion is needed, and the selection of pump wavelength as well as other intra-cavity parameters are crucial for lasing in the 920–960 nm wavelength range. To find a feasible solution, the pump wavelength, fiber length, and laser cavity transmittance were systematically studied. Based on the experimental result of a 960 nm Yb:fiber laser, the re-absorption loss and temperature dependent gain can be reliably modeled. The result shows promise in the development of a Yb:fiber laser at a wavelength as short as 920 nm.

  8. Wavelength conversion experiment using fiber four-wave mixing

    Microsoft Academic Search

    Kyo Inoue; Hiromu Toba

    1992-01-01

    Wavelength conversion using fiber four-wave mixing in an optical fiber is demonstrated. Utilizing the wavelength region around the zero-dispersion wavelength of a fiber, 622 Mbt\\/s FSK signal light is converted from 1555.2 to 1547.6 nm with a conversion efficiency of -24 dB

  9. Four-wave mixing wavelength conversion efficiency in semiconductor traveling-wave amplifiers measured to 65 nm of wavelength shift

    Microsoft Academic Search

    Jianhui Zhou; K. J. Vahala; M. A. Newkirk; B. I. Miller

    1994-01-01

    The efficiency of broadband optical wavelength conversion by four-wave mixing in semiconductor traveling-wave amplifiers is measured for wavelength shifts up to 65 nm using a tandem amplifier geometry. A quantity we call the relative conversion efficiency function, which determines the strength of the four-wave mixing nonlinearity, was extracted from the data. Using this quantity, gain requirements for lossless four-wave mixing

  10. Applications Of Stimulated Raman Scattering To Short Wavelength Lasers

    NASA Astrophysics Data System (ADS)

    Trainor, Daniel W.

    1989-03-01

    The Raman process has been extensively used with short wavelength excimer lasers almost since excimers were first made to lase in the mid 70's.(1,2,3) Operating in the ultraviolet, they are used to perform a variety of research and development tasks, as well as participate in a variety of commercial activities. They represent a major laser market and are available commercially around the world.

  11. Alerting effects of short-wavelength (blue) and long-wavelength (red) lights in the afternoon.

    PubMed

    Sahin, Levent; Figueiro, Mariana G

    2013-05-27

    Light has an acute effect on neuroendocrine responses, performance, and alertness. Most studies to date have linked the alerting effects of light to its ability to suppress melatonin, which is maximally sensitive to short-wavelength light. Recent studies, however, have shown alerting effects of white or narrowband short-wavelength lights during daytime, when melatonin levels are low. While the use of light at night to promote alertness is well understood, it is important to develop an understanding of how light impacts alertness during the daytime, especially during the post-lunch hours. The aim of the current study was to investigate how 48-minute exposures to short-wavelength (blue) light (40 lux, 18.9 microWatts/cm(2) ?(max) = 470 nanometers [nm]) or long-wavelength (red) light (40 lux, 18.9 microWatts/cm(2) ?(max) = 630 nm) close to the post-lunch dip hours affect electroencephalogram measures in participants with regular sleep schedules. Power in the alpha, alpha theta, and theta ranges was significantly lower (p<0.05) after participants were exposed to red light than after they remained in darkness. Exposure to blue light reduced alpha and alpha theta power compared to darkness, but these differences did not reach statistical significance (p>0.05). The present results extend those performed during the nighttime, and demonstrate that light can be used to increase alertness in the afternoon, close to the post-lunch dip hours. These results also suggest that acute melatonin suppression is not needed to elicit an alerting effect in humans. PMID:23535242

  12. Short wavelength limits of current shot noise suppression

    NASA Astrophysics Data System (ADS)

    Nause, Ariel; Dyunin, Egor; Gover, Avraham

    2014-08-01

    Shot noise in electron beam was assumed to be one of the features beyond control of accelerator physics. Current results attained in experiments at Accelerator Test Facility in Brookhaven and Linac Coherent Light Source in Stanford suggest that the control of the shot noise in electron beam (and therefore of spontaneous radiation and Self Amplified Spontaneous Emission of Free Electron Lasers) is feasible at least in the visible range of the spectrum. Here, we present a general linear formulation for collective micro-dynamics of e-beam noise and its control. Specifically, we compare two schemes for current noise suppression: a quarter plasma wavelength drift section and a combined drift/dispersive (transverse magnetic field) section. We examine and compare their limits of applicability at short wavelengths via considerations of electron phase-spread and the related Landau damping effect.

  13. Short wavelength limits of current shot noise suppression

    SciTech Connect

    Nause, Ariel, E-mail: arielnau@post.tau.ac.il [Faculty of Exact Sciences, Department of Physics, Tel Aviv University, Tel Aviv (Israel); Dyunin, Egor; Gover, Avraham [Faculty of Engineering, Department of Physical Electronics, Tel Aviv University, Tel Aviv (Israel)

    2014-08-15

    Shot noise in electron beam was assumed to be one of the features beyond control of accelerator physics. Current results attained in experiments at Accelerator Test Facility in Brookhaven and Linac Coherent Light Source in Stanford suggest that the control of the shot noise in electron beam (and therefore of spontaneous radiation and Self Amplified Spontaneous Emission of Free Electron Lasers) is feasible at least in the visible range of the spectrum. Here, we present a general linear formulation for collective micro-dynamics of e-beam noise and its control. Specifically, we compare two schemes for current noise suppression: a quarter plasma wavelength drift section and a combined drift/dispersive (transverse magnetic field) section. We examine and compare their limits of applicability at short wavelengths via considerations of electron phase-spread and the related Landau damping effect.

  14. On the wavelength of self-organized shoreline sand waves

    NASA Astrophysics Data System (ADS)

    Falqués, A.; van den Berg, N.; Ribas, F.; Caballeria, M.; Calvete, D.

    2012-04-01

    Shoreline sand waves are undulations of the shoreline that extend into the bathymetry up to a certain depth. Here we will focus on self-organized sand waves that form due to shoreline instability in case of very oblique wave incidence (Ashton et al., 2001). The model of Ashton and co-authors did not predict any wavelength selection for the emerging sand waves whereas Falqués and Calvete (2005) predicted a wavelength selection in the range 4-15 km. This difference is attributable to that Falqués and Calvete (2005) computed wave refraction and shoaling over the actual curvilinear depth contours while Ashton et al. (2001) assumed locally rectilinear and parallel contours. Although there exist shoreline features at a larger scale (Ashton et al. 2001; Falqués et al. 2011) sand waves at a few km scale are more common (Ruessink and Jeuken, 2002; Davidson-Arnott and van Heyningen, 2003; Falqués et al., 2011; Medellin et al., 2008) . While their characteristic wavelength is a robust model output (Falqués and Calvete, 2005; Uguccioni et al., 2006; van den Berg et al., 2011) the physical reasons for the existence of a wavelength selection are still unknown. Furthermore, the parameter dependence of the dominant wavelength, Lm, is largely unexplored. In particular, the disparity between the large length scale of sand waves and the relevant length scales of the problem: width of the surf zone, water wave wavelength, etc. is intriguing. The aim of the present contribution is to gain insight into those physical reasons and the dependence of Lm on beach profile and water wave properties. The essence of sandwave behaviour can be captured with the simple one-line shoreline modelling concept by looking at the alongshore position of the maximum in total transport rate Q, which is here investigated with both the linearized model of Falqués and Calvete (2005) and the nonlinear model of van den Berg et al. (2011) . It is found that the position of that maximum is largely controlled by the alongshore distribution of wave energy associated to the sand wave, mainly affected in turn by : A) refractive wave energy spreading and B) refractive energy focusing by the crest. Furthermore, for large L the growthrate decreases to 0 since the gradients in wave energy and hence the gradients in Q decrease. As a result, there is a minimum wavelength, Lc, for growth and an optimum wavelength Lm > Lcof maximum growth. Experiments with different bathymetric profiles and different wave conditions are made to investigate the sensitivity of Lm . It is found that Lm scales with ?0/? where ?0 is the water wave wavelength in deep water and ? the beach slope.

  15. The Equilibration of Short Baroclinic Waves

    Microsoft Academic Search

    Balasubramanian Govindasamy; S. T. Garner

    1997-01-01

    The life cycles of short baroclinic waves are investigated with the intention of completing a simple classification of nonlinear equilibration scenarios. Short waves become important in moist environments as latent heating reduces the scale of maximum baroclinic instability. Long-wave life cycles (wavenumber 6) were previously found to depend on details of the low-level momentum fluxes established during the earliest stages

  16. Ultraintense ion beams driven by a short-wavelength short-pulse laser

    SciTech Connect

    Badziak, J.; Jablonski, S. [Institute of Plasma Physics and Laser Microfusion, Euratom Association, 01-497 Warsaw (Poland)

    2010-07-15

    The results of particle-in-cell simulations are reported which demonstrate that a short-wavelength (lambda<=0.5 mum) short-pulse laser driver can produce much more intense ion beams than the commonly used long-wavelength (lambdaapprox1 mum) ones. In particular, such a driver allows for efficient generation of ultrashort (<=100 fs), multi-MeV proton bunches of extremely high intensities (>10{sup 21} W/cm{sup 2}) and current densities (>10{sup 14} A/cm{sup 2}) even at moderate values of dimensionless laser amplitude a{sub 0}<=10.

  17. Tunable Parametric All-Fiber Short-Wavelength IR Transmitter

    Microsoft Academic Search

    J. M. Chavez Boggio; S. Moro; B. P.-P. Kuo; N. Alic; B. Stossel; S. Radic

    2010-01-01

    In this paper, the performance of an all-fiber short-wave IR (SWIR) transmitter with wideband tunability and high peak power is reported. Transmitter construction relied on parametric process in highly nonlinear fiber to convert a seed laser at 1260 nm to 2155 nm SWIR channel with record 39 dB efficiency and translation over 900 nm spectral range. We demonstrated 61 W

  18. Short-wavelength visible light emission from silicon nanocrystals

    NASA Astrophysics Data System (ADS)

    Pi, Xiaodong; Liptak, Rick; Campbell, Stephen; Kortshagen, Uwe

    2007-03-01

    Si is the material of choice for modern microelectronics but, as an indirect-bandgap semiconductor, it is not an efficient light emitter. An electrically pumped Si laser would present a breakthrough for optoelectronic integration that may enable optical interconnect to make computers faster. Si light emitting diodes may revolutionize solid-state lighting and displays because of the low cost and environmental friendliness of Si. One of the most challenging problems of Si-based lighting and displays is the lack of a reliable and efficient full visible spectrum emission. Si nanocrystals (Si-NCs) have so far been the most promising form of Si to emit light. Most of the synthesis approaches of Si-NCs, however, only lead to red light emission. Our recent work on Si-NCs synthesized by non-thermal plasmas has focused on extending their light emission into the short-wavelength range. Firstly, the process of oxidation-etching-oxidation of Si-NCs is investigated. This process causes the size of Si-NCs to decrease, leading to shorter wavelength light emission from Si-NCs. Yellow or green photoluminescence (PL) has been observed from initially oxidized red light emitting Si-NCs after HF vapour etching and atmospheric oxidation. The intensity of PL from Si-NCs, however, decreases by a factor up to 100. It is found that HF etching restructures the surface of Si-NCs. This leads to a decrease in the incorporation of O during subsequent oxidation, which finally results in silicon suboxide SiO1.9. Such an understoichiometry indicates a high density of defects such as Si dangling bonds at the Si-NC/oxide interface. Therefore, the PL efficiency is extremely low for short-wavelength light emitting Si-NCs obtained by the process of oxidation-etching-oxidation. Secondly, an integrated two-stage plasma system is employed to achieve the light emission from Si-NCs in the full visible spectrum range. Red-light-emitting Si-NCs are produced in the first stage by the plasma decomposition of SiH4. In the second stage a tetrafluoromethane (CF4)-based plasma etches Si-NCs and at the same time passivates them with carbon and fluorine. After the two-stage process Si-NCs emit light in the short-wavelength region from yellow to blue. We find that a self-limited oxidation process blueshifts the light emission until saturation is reached. Significantly, relatively high quantum yields of short-wavelength light emission from Si-NCs are obtained in spite of oxidation. It is interesting to note that Si-NCs treated by CF4-based plasma are hydrophilic while those without CF4-based plasma treatment are hydrophobic.

  19. Determination of vertical and horizontal wavelengths of gravity waves

    NASA Technical Reports Server (NTRS)

    Rottger, J.

    1983-01-01

    The determination of horizontal and vertical wavelengths of gravity waves obviously relies on measurement of wave parameters in horizontal and vertical directions. A very suitable parameter, measured fairly easily with MST radars, is the fluid velocity. Average velocities and superimposed turbulent fluctuations are much larger in the horizontal than in the vertical direction. Vertical and horizontal fluid velocities due to wave-like events are mostly about equal in magnitude. Vertical fluid velocities due to waves therefore can be more reliably detected than horizontal velocities. Estimates of gravity wave events using MST radar data are calculated and results are indicated.

  20. Sub-wavelength position measurements with running wave driving fields

    E-print Network

    J. Evers; S. Qamar

    2009-01-29

    A scheme for sub-wavelength position measurements of quantum particles is discussed, which operates with running-wave laser fields as opposed to standing wave fields proposed in previous setups. The position is encoded in the phase of the applied fields rather than in the spatially modulated intensity of a standing wave. Therefore, disadvantages of standing wave schemes such as cases where the atom remains undetected since it is at a node of the standing wave field are avoided. Reversing the directions of parts of the driving laser fields allows to switch between different magnification levels, and thus to optimize the localization.

  1. Dual-wavelength ultra-short pulse laser damage testing

    NASA Astrophysics Data System (ADS)

    Gyamfi, Mark; Jürgens, Peter; Mende, Mathias; Jensen, Lars; Ristau, Detlev

    2014-11-01

    In the femtosecond regime laser damage thresholds are often determined by the electric field distribution within the optical component. Commercially available ultra-short pulse laser systems provide ever increasing output powers in fundamental and harmonic wavelengths. Therefore, an increasing demand for frequency conversion or multiwavelengths optics with high damage thresholds for both, fundamental and second harmonic wavelengths is given. These optics are under increased strain and face even more design difficulties. Also, the electric field distribution is of higher complexity and favors multi-photon excitation of high efficiencies. We investigate the LIDT of dichroic high reflecting mirrors under simultaneous exposure to fundamental and second harmonic radiation. As laser source we use a Ti:Sa system delivering sub 200 fs pulses at 780nm/390nm. A delay-line was incorporated to ensure temporal overlap of the 2 pulses in the test plane. Further, the LIDT of a single layer of Ta2O5 under irradiation with fundamental and second harmonic radiation is calculated and results are compared with our experiment.

  2. Short communication Routing and wavelength assignment for core-based

    E-print Network

    Yang, Mei

    -based tree (CBT) service in a wavelength-di- vision-multiplexing (WDM) network, where k sources need to send from sources to the core with the constraint of wavelength collision free. To address different

  3. Accommodation with and without short-wavelength-sensitive cones and chromatic aberration.

    PubMed

    Kruger, Philip B; Rucker, Frances J; Hu, Caitlin; Rutman, Hadassa; Schmidt, Nathan W; Roditis, Vasilios

    2005-05-01

    Accommodation was monitored while observers (23) viewed a square-wave grating (2.2 cycles/deg; 0.53 contrast) in a Badal optometer. The grating moved sinusoidally (0.2 Hz) to provide a stimulus between -1.00 D and -3.00 D during trials lasting 40.96 s. There were three illumination conditions: 1. Monochromatic 550 nm light to stimulate long-wavelength-sensitive cones (L-cones) and medium-wavelength-sensitive cones (M-cones) without chromatic aberration; 2. Monochromatic 550 nm light+420 nm light to stimulate long-, medium- and short-wavelength-sensitive cones (S-cones) with longitudinal chromatic aberration (LCA); 3. Monochromatic 550 nm light+420 nm light to stimulate L-, M- and S-cones viewed through an achromatizing lens. In the presence of LCA mean dynamic gain decreased (p=0.0003; ANOVA) and mean accommodation level was reduced (p=0.001; ANOVA). The reduction in gain and increased lag of accommodation in the presence of LCA could result from a blue-yellow chromatic signal or from a larger depth-of-focus. PMID:15733959

  4. Single-arm three-wave interferometer for measuring dispersion of short lengths of fiber

    E-print Network

    Qian, Li

    Single-arm three-wave interferometer for measuring dispersion of short lengths of fiber Michael A interferometer to measure directly the second-order dispersion parameter of short lengths of fiber ( on system parameters, such as required bandwidth, wavelength resolution, and fiber length, are discussed

  5. Short Wave Echoes and the Aurora Borealis

    Microsoft Academic Search

    Carl Størmer

    1928-01-01

    ON Feb. 29 of this year I received a letter from Engineer Jørgen Hals, Bygdø, Oslo, in which he says: ``I herewith have the honour to advise you that at the end of the summer 1927 I repeatedly heard signals from the Dutch short-wave transmitter station PCJJ (Eindhoven). At the same time as I heard the telegraph-signals I also heard

  6. Dual-band ultraviolet-short-wavelength infrared imaging via luminescent downshifting with colloidal quantum dots

    E-print Network

    Geyer, Scott M.

    The performance of short-wavelength infrared (SWIR) cameras in the visible and ultraviolet (UV) regions is limited by the absorption of high-energy photons in inactive regions of the imaging array. Dual-band UV-SWIR imaging ...

  7. GHz low noise short wavelength infrared (SWIR) photoreceivers

    Microsoft Academic Search

    Xiaogang Bai; Ping Yuan; Paul McDonald; Joseph Boisvert; James Chang; Robyn Woo; Eduardo Labios; Rengarajan Sudharsanan; Michael Krainak; Guangning Yang; Xiaoli Sun; Wei Lu; Dion McIntosh; Qiugui Zhou; Joe Campbell

    2011-01-01

    Next generation LIDAR mapping systems require multiple channels of sensitive photoreceivers that operate in the wavelength region of 1.06 to 1.55 microns, with GHz bandwidth and sensitivity less than 300 fW\\/&surd;Hz. Spectrolab has been developing high sensitivity photoreceivers using InAlAs impact ionization engineering (I2E) avalanche photodiodes (APDs) structures for this application. APD structures were grown using metal organic vapor epitaxy

  8. SHORT-WAVELENGTH, SINGLE-PASS FREE-ELECTRON LASERS J. Rossbach, DESY, 22603 Hamburg, Germany

    E-print Network

    SHORT-WAVELENGTH, SINGLE-PASS FREE-ELECTRON LASERS J. Rossbach, DESY, 22603 Hamburg, Germany in demonstration of high power gain at single- pass free-electron lasers operating in the wavelength range from in the undulator. Eq. (1) exhibits two main advantages of the free-electron laser: the free tunability

  9. Experimental studies of X-ray emission physics and hydrodynamics using short wavelength lasers

    Microsoft Academic Search

    P. D. Goldstone; D. E. Casperson; J. A. Cobble; S. V. Coggeshall; C. C. Gomez; A. Hauer; G. A. Kyrala; P. H. Y. Lee; W. C. Mead; G. T. Schappert

    1988-01-01

    Several experimental efforts are currently under way at Low Alamos to study issues of importance for inertial confinement fusion with short wavelength lasers. These issues include the physics of X-ray conversion and the dynamics of short-wavelength laser interaction with high-Z plasmas; filamentation and self-focusing processes; and the growth of instabilities in laser-driven implosions. Most of these experiments are being pursued

  10. Non-linear plasma wave decay to longer wavelength

    NASA Astrophysics Data System (ADS)

    Anderegg, F.; Affolter, M.; Ashourvan, A.; Dubin, D. H. E.; Valentini, F.; Driscoll, C. F.

    2015-06-01

    We measure the decay of plasma waves to longer wavelengths, for both "standard" Trivelpiece-Gould waves with v??v¯ , and for the lower phase velocity "EAW" modes with v?˜v¯ . These are ?-symmetric standing modes on pure ion or pure electron plasma columns with discrete wavenumbers kz = mz ?/Lp. A large amplitude mz = 2 Trivelpiece-Gould wave causes phase-locked exponential growth of the mz = 1 wave when they are near resonant, at growth rates ?e ? ?n2/n consistent with cold fluid theory. For larger detuning ? ? 2f1-f2, mode amplitude A1 is observed to "bounce" at rate ?f, with amplitude excursions ?A1 ? ?n2/n also consistent with cold fluid theory; but A1 often exhibits a slower overall growth, as yet unexplained by theory. In contrast, a large amplitude mz = 2 EAW mode generally causes either strong phase-locked mz = 1 growth or no growth at all, apparently because the EAW "frequency fungibility" enables ?f = 0, and EAW mode damping is strong until the velocity distribution F(vphase) is "flattened."

  11. Interpretation of long- and short-wavelength magnetic anomalies

    USGS Publications Warehouse

    DeNoyer, John M.

    1980-01-01

    Magset was launched on October 30, 1979. More than a decade of examining existing data, devising appropriate models of the global magnetic field, and extending methods for interpreting long-wavelength magnetic anomalies preceded this launch Magnetic data collected by satellite can be interrupted by using a method of analysis that quantitively describes the magnetic field resulting from three-dimensional geologic structures that are bounded by an arbitrary number of polygonal faces, Each face my have any orientation and three or more sides. At each point of the external field, the component normal to each face is obtained by using an expression for the solid angle subtended by a generalized polygon. The "cross" of tangential components are relatively easy to obtain for the same polygons. No approximations have been made related to orbit height that restrict the dimensions of the polygons relative to the distance from the external field points. This permits the method to be used to model shorter wavelength anomalies obtained from aircraft or ground surveys. The magnetic fields for all the structures considered are determine in the same rectangular coordinate system. The coordinate system is in depended from the orientation of geologic trends and permits multiple structures or bodies to be included in the same magnetic field calculations. This single reference system also simplified adjustments in position and direction to account for earth curvature in regional interpretation.

  12. Nine wave-length THz spectrum for identification using backward wave oscillator

    Microsoft Academic Search

    Mo Lv; Hua Zhong; Xin-Hao Ge; Ting He; Kaijun Mu; Cun-Lin Zhang

    2009-01-01

    The sensing of the explosive is very important for homeland security and defense. We present a nine-wavelength continuous wave (CW) Terahertz (THz) spectroscopy for identification of explosive compounds (2,4-DNT, RDX and TNT) using three Backward Wave Oscillator (BWO) sources, which emit radiations from 0.2 THz to 0.38THz, 0.18THz to 0.26THz and 0.6THz to 0.7THz, respectively. To identify the target materials,

  13. LSWAVE 2000: Lasers and short-wavelength applications

    NASA Astrophysics Data System (ADS)

    Sandner, W.

    2001-07-01

    LSWAVE 2000 was organized as a Satellite Workshop to the Seventh International Conference on Synchrotron Radiation Instrumentation SRI 2000. It was held on Saturday, August 26, 2000, at the Technische Universität Berlin, and was jointly organized by the Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy (MBI) and the Technical University Berlin (TUB). The organizing committee consisted of Wilhelm Raith (chairman), Wolfgang Sandner, Ingolf Hertel, Manfred Wick, Bernd Winter, Tatjana Gießel, Holger Stiel, Ingo Will, Ursula Bayr (secretary) and Silvia Szlapka (secretary). Continuing information on the Workshop and its proceedings may be found under http://www.mbi-berlin.de/lswave2000/.

  14. Stylus contact on short wavelength random surfaces: a simulation study

    NASA Astrophysics Data System (ADS)

    Tian, Ailing; Liu, X.; Chetwynd, D. G.; Cai, Zhijian

    2007-06-01

    Stylus scanning remains a crucial method in surface micro- and nano-topography measurement. Its accuracy, especially at shorter wavelengths, depends on the relation of the stylus geometry to surface parameters. We present a 3D computer simulation of measuring non-Gaussian random surfaces with arbitrary tip shapes, studying both the surface distortion and the stylus contact distribution. After a brief discussion of the surface generation and geometrical contact algorithms, this paper concentrates on examples of symmetrical styli having characteristic sizes not much smaller than the surface correlation lengths. It thus attempts to examine the breakdown region as we seek to measure finer topographies. The measuring error appears to be generally smaller with a three-pyramid stylus than with other styli as limits are approached. Perhaps counter-intuitively, the errors in common parameters on surfaces of a similar correlation length and roughness amplitude can be smaller when their kurtosis is high, a condition that might become more common with deliberately imposed nanostructuring.

  15. The Shoelace Antenna : a device to induce short-wavelength fluctuations in the edge plasma of the Alcator C-Mod Tokamak

    E-print Network

    Golfinopoulos, Theodore

    2014-01-01

    The "Shoelace" antenna is a unique device built to induce short-wavelength fluctuations in the edge plasma of the Alcator C-Mod tokamak, at a wave number and in the frequency range associated with the Quasi-Coherent Mode ...

  16. Dark- and bright-rogue-wave solutions for media with long-wave-short-wave resonance.

    PubMed

    Chen, Shihua; Grelu, Philippe; Soto-Crespo, J M

    2014-01-01

    Exact explicit rogue-wave solutions of intricate structures are presented for the long-wave-short-wave resonance equation. These vector parametric solutions feature coupled dark- and bright-field counterparts of the Peregrine soliton. Numerical simulations show the robustness of dark and bright rogue waves in spite of the onset of modulational instability. Dark fields originate from the complex interplay between anomalous dispersion and the nonlinearity driven by the coupled long wave. This unusual mechanism, not available in scalar nonlinear wave equation models, can provide a route to the experimental realization of dark rogue waves in, for instance, negative index media or with capillary-gravity waves. PMID:24580164

  17. Correlation between the specific surface area and the short wave infrared (SWIR) reflectance of snow

    E-print Network

    Domine, Florent

    Correlation between the specific surface area and the short wave infrared (SWIR) reflectance infrared (SWIR). Many models of snow albedo represent snow crystals by spheres of surface/volume (S spectral albedo in the SWIR (linear correlation coefficient R2 >0.98 for the last 3 wavelengths). Snow

  18. Low Noise, High Gain Short-Wave Infrared Nano-Injection Photon Detectors with Low Jitter

    E-print Network

    Mohseni, Hooman

    in short wave infrared (SWIR) spectrum, particularly focusing at 1.55 m wavelength. Spanning a wide range of applications from slow imaging technologies to very high speed fiber telecommunications, SWIR contains both of detectors have been created. Common technologies for SWIR detection are InGaAs/InP based detectors (P

  19. Skylab radar altimeter - Short-wavelength perturbations detected in ocean surface profiles

    NASA Technical Reports Server (NTRS)

    Leitao, C. D.; Mcgoogan, J. T.

    1974-01-01

    Short-wavelength anomalies in sea surface topography, caused by the gravitational effects of major ocean bottom topographic features, have been detected by the radar altimeter aboard Skylab. Some features, such as deep ocean trenches, seamounts, and escarpments, displace the ocean surface by as much as 15 meters over 100-kilometer wavelengths. This experiment demonstrates the potential of satellite altimetry for determining the ocean geoid and for mapping major features of the ocean bottom.

  20. Enhancement of the short wavelength upconversion emission in inverse opal photonic crystals.

    PubMed

    Wu, Hangjun; Zhu, Jialun; Yang, Zhengwen; Yan, Dong; Wang, Rongfei; Qiu, Jianbei; Song, Zhiguo; Yu, Xue; Yang, Yong; Zhou, Dacheng; Yin, Zhaoyi

    2014-05-01

    Upconversion luminescence properties of Yb-Tb codoped Bi4Ti3O12 inverse opals have been investigated. The results show that the upconversion emission can be modulated by the photonic band gap. More significantly, in the upconversion inverse opals, the excited-state absorption of Tb3+ is greatly enhanced by the suppression of upconversion spontaneous emissions of the intermediate excited state, and thus the short wavelength upconversion emission from Tb3+ is considerably improved. We believe that the present work will be valuable for not only the foundational study of upconversion emission modifications but also new optical devices in upconversion displays and short wavelength upconversion lasers. PMID:24734648

  1. Excitation Wavelength Dependence of Terahertz Electromagnetic Wave Generation from Quantum Wire

    Microsoft Academic Search

    Isao Morohashi; Kazuhiro Komori; Xue-Lun Wang; Takehiko Hidaka; Mutsuo Ogura; Masanobu Watanabe

    2002-01-01

    We have investigated terahertz (THz) electromagnetic wave generation from a semiconductor crescent-shaped quantum wire structure. The THz electromagnetic wave was generated by ultrashort optical pulse excitation, and detected with the free-space electrooptic (EO) sampling method. THz electromagnetic wave generation from the quantum wire exhibited excitation wavelength dependence. The amplitude of the THz electromagnetic wave was at a maximum at a

  2. Detection of dry body fluids by inherent short wavelength UV luminescence: preliminary results.

    PubMed

    Springer, E; Almog, J; Frank, A; Ziv, Z; Bergman, P; Qiang, W G

    1994-06-01

    Dry stains of blood, semen and saliva invisible to the naked eye could be detected by their inherent short wavelength UV luminescence. The source was a frequency quadrupled Nd:YAG laser, emitting at 266 nm. A plausible explanation for this phenomenon as due to the presence of amino acids in these secretions is presented. PMID:8063277

  3. Short-wavelength sensitive opsin (SWS1) as a new marker for vertebrate phylogenetics

    Microsoft Academic Search

    Ilke van Hazel; Francesco Santini; Johannes Müller; Belinda SW Chang

    2006-01-01

    BACKGROUND: Vertebrate SWS1 visual pigments mediate visual transduction in response to light at short wavelengths. Due to their importance in vision, SWS1 genes have been isolated from a surprisingly wide range of vertebrates, including lampreys, teleosts, amphibians, reptiles, birds, and mammals. The SWS1 genes exhibit many of the characteristics of genes typically targeted for phylogenetic analyses. This study investigates both

  4. Measurements of short wavelength VLF bursts in the auroral ionosphere: A case for electromagnetic mode conversion?

    E-print Network

    California at Berkeley, University of

    1 Measurements of short wavelength VLF bursts in the auroral ionosphere: A case for electromagnetic emissions were mea- sured on the University of California at Berkeley Alaska `93 auroral sounding rocket responsi- ble for their generation. The presence of electromagnetic modes in the VLF frequency range

  5. The PS/PDI: a high accuracy development tool for diffraction limited short-wavelength optics

    E-print Network

    The PS/PDI: a high accuracy development tool for diffraction limited short-wavelength optics ultraviolet (EUV) phase-shifting point diffraction interferometer (PS/PDI) was developed and implemented projection lithography optics. The PS/PDI has been in continuous use and under ongoing development since 1996

  6. Is the Local Density Approximation Exact for Short Wavelength Fluctuations? Kieron Burke and John P. Perdew

    E-print Network

    Langreth, David C.

    for the success of the local spin density (LSD) approximation is that it correctly accounts for short wavelength on a specific system (Hooke's atom). Nevertheless, we find that LSD is rather accurate for small interelectronic density (LSD) approximation [2]. Recently, systematic improvements on LSD have become possible

  7. Short-wavelength enrichment of polychromatic light enhances human melatonin suppression potency.

    PubMed

    Brainard, George C; Hanifin, John P; Warfield, Benjamin; Stone, Marielle K; James, Mary E; Ayers, Melissa; Kubey, Alan; Byrne, Brenda; Rollag, Mark

    2015-04-01

    The basic goal of this research is to determine the best combination of light wavelengths for use as a lighting countermeasure for circadian and sleep disruption during space exploration, as well as for individuals living on Earth. Action spectra employing monochromatic light and selected monochromatic wavelength comparisons have shown that short-wavelength visible light in the blue-appearing portion of the spectrum is most potent for neuroendocrine, circadian, and neurobehavioral regulation. The studies presented here tested the hypothesis that broad spectrum, polychromatic fluorescent light enriched in the short-wavelength portion of the visible spectrum is more potent for pineal melatonin suppression in healthy men and women. A total of 24 subjects were tested across three separate experiments. Each experiment used a within-subjects study design that tested eight volunteers to establish the full-range fluence-response relationship between corneal light irradiance and nocturnal plasma melatonin suppression. Each experiment tested one of the three types of fluorescent lamps that differed in their relative emission of light in the short-wavelength end of the visible spectrum between 400 and 500 nm. A hazard analysis, based on national and international eye safety criteria, determined that all light exposures used in this study were safe. Each fluence-response curve demonstrated that increasing corneal irradiances of light evoked progressively increasing suppression of nocturnal melatonin. Comparison of these fluence-response curves supports the hypothesis that polychromatic fluorescent light is more potent for melatonin regulation when enriched in the short-wavelength spectrum. PMID:25726691

  8. Terahertz imaging of sub-wavelength particles with Zenneck surface waves

    NASA Astrophysics Data System (ADS)

    Navarro-Cía, M.; Natrella, M.; Dominec, F.; Delagnes, J. C.; Kužel, P.; Mounaix, P.; Graham, C.; Renaud, C. C.; Seeds, A. J.; Mitrofanov, O.

    2013-11-01

    Impact of sub-wavelength-size dielectric particles on Zenneck surface waves on planar metallic antennas is investigated at terahertz (THz) frequencies with THz near-field probe microscopy. Perturbations of the surface waves show the particle presence, despite its sub-wavelength size. The experimental configuration, which utilizes excitation of surface waves at metallic edges, is suitable for THz imaging of dielectric sub-wavelength size objects. As a proof of concept, the effects of a small strontium titanate rectangular particle and a titanium dioxide sphere on the surface field of a bow-tie antenna are experimentally detected and verified using full-wave simulations.

  9. Analysis of multiple wavelengths of Lamb waves generated by meander-line coil EMATs.

    PubMed

    Zhai, Guofu; Jiang, Tao; Kang, Lei

    2014-02-01

    The electromagnetic acoustic transducers (EMATs) with a meander-line coil possess the capability of generating Lamb waves carrying multiple wavelengths, and the characteristics of multiple wavelengths is analyzed by developing a spatial transversal filter model for the EMAT. It is shown that the characteristics is due to the wavelength spectrum of the EMATs, which is a wavelength-domain representation of information about the wavelength components, and the magnitude of each components is modulated by an envelope which depends on the geometric pattern of the meander-line coil. The characteristics of multiple wavelengths might cause the multi-modes phenomenon, therefore a method for removing the effect of multiple wavelengths is proposed. It is shown that the effect can be removed by designing an EMAT which can produce a special envelop to suppress the harmonic wavelengths. Experiments are set up to study the characteristics of multiple wavelengths and verify the validity of the proposed method. PMID:24074750

  10. Zero-dispersion wavelength uniformity and four-wave mixing in optical fiber

    Microsoft Academic Search

    J. B. Schlager; S. E. Mechels; D. L. Franzen

    1996-01-01

    The efficiency of four-wave mixing (FWM) in optical fiber is maximum with optimal phase matching at the zero-dispersion wavelength, but this wavelength can vary along the fiber's length. In this paper, we describe measurements of partially degenerate four-wave mixing efficiency in a 10 km fiber with varying ?o. In partially degenerate four-wave mixing the pump provides two of the four

  11. Low work function surface layers produced by laser ablation using short-wavelength photons

    DOEpatents

    Balooch, Mehdi (Berkeley, CA); Dinh, Long N. (Concord, CA); Siekhaus, Wigbert J. (Berkeley, CA)

    2000-01-01

    Short-wavelength photons are used to ablate material from a low work function target onto a suitable substrate. The short-wavelength photons are at or below visible wavelength. The elemental composition of the deposit is controlled by the composition of the target and the gaseous environment in which the ablation process is performed. The process is carried out in a deposition chamber to which a short-wavelength laser is mounted and which includes a substrate holder which can be rotated, tilted, heated, or cooled. The target material is mounted onto a holder that spins the target during laser ablation. In addition, the deposition chamber is provided with a vacuum pump, an external gas supply with atomizer and radical generator, a gas generator for producing a flow of molecules on the substrate, and a substrate cleaning device, such as an ion gun. The substrate can be rotated and tilted, for example, whereby only the tip of an emitter can be coated with a low work function material.

  12. Holography, wave-length diversity and inverse scattering

    Microsoft Academic Search

    N. H. Farhat

    1980-01-01

    The use of wavelength diversity to enhance the performance of thinned coherent imaging apertures is discussed. It is shown that wavelength diversity lensless Fourier transform recording arrangements that utilize a reference point source in the vicinity of the object can be used to access the three-dimensional Fourier space of nondispersive perfectly reflecting or weakly scattering objects. Hybrid (opto-digital) computing applied

  13. Finite element modeling of short-wavelength folding on Venus: Implications for the plume hypothesis for crustal plateau formation

    E-print Network

    Hansen, Vicki

    Finite element modeling of short-wavelength folding on Venus: Implications for the plume hypothesis element modeling of short-wavelength folding on Venus: Implications for the plume hypothesis for crustal plateaus preserve some of Venus' oldest observed and most extensive structural deformation. If crustal

  14. Four-wave mixing in wavelength-division-multiplexed soliton systems: damping and amplification

    NASA Astrophysics Data System (ADS)

    Ablowitz, M. J.; Biondini, G.; Chakravarty, S.; Jenkins, R. B.; Sauer, J. R.

    1996-10-01

    Four-wave mixing in wavelength-division-multiplexed soliton systems with damping and amplification is studied. An analytical model is introduced that explains the dramatic growth of the four-wave terms. The model yields a resonance condition relating the soliton frequency and the amplifier distance. It correctly predicts all essential features regarding the resonant growth of the four-wave contributions.

  15. On the Wavelength of the Rossby Waves Radiated by Tropical Cyclones KYLE D. KROUSE

    E-print Network

    Sobel, Adam

    On the Wavelength of the Rossby Waves Radiated by Tropical Cyclones KYLE D. KROUSE Department depression­type disturbances, which occur as a result of Rossby wave radiation from a preexisting tropical flow of the radiated Rossby waves and that of the TC. The authors argue that either horizontal

  16. NEW INSIGHT INTO SHORT-WAVELENGTH SOLAR WIND FLUCTUATIONS FROM VLASOV THEORY

    SciTech Connect

    Sahraoui, F.; Belmont, G. [Laboratoire de Physique des Plasmas, CNRS-Ecole Polytechnique-UPMC, Observatoire de Saint-Maur, 4 avenue de Neptune, 94107 Saint-Maur-des-Fosses (France); Goldstein, M. L., E-mail: fouad.sahraoui@lpp.polytechnique.fr [NASA Goddard Space Flight Center, Code 673, Greenbelt, MD 20771 (United States)

    2012-04-01

    The nature of solar wind (SW) turbulence below the proton gyroscale is a topic that is being investigated extensively nowadays, both theoretically and observationally. Although recent observations gave evidence of the dominance of kinetic Alfven waves (KAWs) at sub-ion scales with {omega} < {omega}{sub ci}, other studies suggest that the KAW mode cannot carry the turbulence cascade down to electron scales and that the whistler mode (i.e., {omega} > {omega}{sub ci}) is more relevant. Here, we study key properties of the short-wavelength plasma modes under limited, but realistic, SW conditions, typically {beta}{sub i} {approx}> {beta}{sub e} {approx} 1 and for high oblique angles of propagation 80 Degree-Sign {<=} {Theta}{sub kB} < 90 Degree-Sign as observed from the Cluster spacecraft data. The linear properties of the plasma modes under these conditions are poorly known, which contrasts with the well-documented cold plasma limit and/or moderate oblique angles of propagation ({Theta}{sub kB} < 80 Degree-Sign ). Based on linear solutions of the Vlasov kinetic theory, we discuss the relevance of each plasma mode (fast, Bernstein, KAW, whistler) in carrying the energy cascade down to electron scales. We show, in particular, that the shear Alfven mode (known in the magnetohydrodynamic limit) extends at scales k{rho}{sub i} {approx}> 1 to frequencies either larger or smaller than {omega}{sub ci}, depending on the anisotropy k{sub ||}/k . This extension into small scales is more readily called whistler ({omega} > {omega}{sub ci}) or KAW ({omega} < {omega}{sub ci}), although the mode is essentially the same. This contrasts with the well-accepted idea that the whistler branch always develops as a continuation at high frequencies of the fast magnetosonic mode. We show, furthermore, that the whistler branch is more damped than the KAW one, which makes the latter the more relevant candidate to carry the energy cascade down to electron scales. We discuss how these new findings may facilitate resolution of the controversy concerning the nature of the small-scale turbulence, and we discuss the implications for present and future spacecraft wave measurements in the SW.

  17. Water Surface Currents, Short Gravity-Capillary Waves and Radar Backscatter

    NASA Technical Reports Server (NTRS)

    Atakturk, Serhad S.; Katsaros, Kristina B.

    1993-01-01

    Despite their importance for air-sea interaction and microwave remote sensing of the ocean surface, intrinsic properties of short gravity-capillary waves are not well established. This is largely due to water surface currents and their effects on the direct measurements of wave parameters conducted at a fixed point. Frequencies of small scale waves propagating on a surface which itself is in motion, are subject to Doppler shifts. Hence, the high frequency tail of the wave spectra obtained from such temporal observations is smeared. Conversion of this smeared measured-frequency spectra to intrinsic-frequency (or wavenumber) spectra requires corrections for the Doppler shifts. Such attempts in the past have not been very successful in particular when field data were used. This becomes evident if the amplitude modulation of short waves by underlying long waves is considered. Microwave radar studies show that the amplitude of a short wave component attains its maximum value near the crests and its minimum in the troughs of the long waves. Doppler-shifted wave data yield similar results but much larger in modulation magnitude, as expected. In general, Doppler shift corrections reduce the modulation magnitude. Overcorrection may result in a negligible modulation or even in a strong modulation with the maximum amplitude in the wave troughs. The latter situation is clearly contradictory to our visual observations as well as the radar results and imply that the advection by currents is overestimated. In this study, a differential-advection approach is used in which small scale waves are advected by the currents evaluated not at the free surface, but at a depth proportional to their wavelengths. Applicability of this approach is verified by the excellent agreement in phase and magnitude of short-wave modulation between results based on radar and on wave-gauge measurements conducted on a lake.

  18. Short-wavelength electroluminescence from single-walled carbon nanotubes with high bias voltage.

    PubMed

    Hibino, Norihito; Suzuki, Satoru; Wakahara, Hiroyuki; Kobayashi, Yoshihiro; Sato, Tetsuya; Maki, Hideyuki

    2011-02-22

    Short-wavelength electroluminescence (EL) emission is observed from unipolar and ambipolar carbon nanotube field-effect transistors (CNFETs) under high bias voltage. EL measurements were carried out with an unsuspended single-walled carbon nanotube (SWNT) in high vacuum to prevent the oxidation damage induced by current heating. Short-wavelength emission under high bias voltage is obtained because of the Schottky barrier reduction and the electric field increase in a SWNT. The simultaneous measurements of transport and EL spectra revealed the excitation mechanism of impact excitation or electron and hole injection dependent on the conduction type of unipolar or ambipolar characteristics. In addition to the EL emission, blackbody radiation was also observed in a p-type CNFET. Taking into account the device temperature estimated from blackbody radiation, the contribution of impact excitation and thermal effect to the exciton production rate was evaluated. PMID:21204568

  19. Experimental studies of x-ray emission physics and hydrodynamics using short wavelength lasers

    SciTech Connect

    Goldstone, P.D.; Casperson, D.E.; Cobble, J.A.; Coggeshall, S.V.; Gomez, C.C.; Hauer, A.; Kyrala, G.A.; Lee, P.H.Y.; Mead, W.C.; Schappert, G.T.

    1988-01-01

    Several experimental efforts are currently under way at Low Alamos to study issues of importance for inertial confinement fusion with short wavelength lasers. These issues include the physics of x-ray conversion and the dynamics of short-wavelength laser interaction with high-Z plasmas; filamentation and self-focusing processes; and the growth of instabilities in laser-driven implosions. Most of these experiments are being pursued in collaboration with other laboratories, notably the University of Rochester and Lawrence Livermore National Laboratory. In addition, we are undertaking basic studies of the interaction of both atomic systems and solids with ultra-intense (/approximately/10/sup 17/ W/cm/sup 2/) subpicosecond lasers at Los Alamos. These experiments explore the response of atomic systems to strong fields, multiphoton excitation, and transient phenomena in dense plasmas. 15 refs., 3 figs.

  20. Observation of Rayleigh{endash}Taylor growth to short wavelengths on Nike

    SciTech Connect

    Pawley, C.J.; Bodner, S.E.; Dahlburg, J.P.; Obenschain, S.P.; Schmitt, A.J.; Sethian, J.D.; Sullivan, C.A. [Plasma Physics Division, Naval Research Laboratory, Washington DC 20375 (United States)] [Plasma Physics Division, Naval Research Laboratory, Washington DC 20375 (United States); Gardner, J.H. [Laboratory for Computational Physics and Fluid Dynamics, Naval Research Laboratory, Washington DC 20375 (United States)] [Laboratory for Computational Physics and Fluid Dynamics, Naval Research Laboratory, Washington DC 20375 (United States); Aglitskiy, Y.; Chan, Y.; Lehecka, T. [Science Applications International Corp., McLean, Virginia 22310 (United States)] [Science Applications International Corp., McLean, Virginia 22310 (United States)

    1999-02-01

    The uniform and smooth focal profile of the Nike KrF laser [S. Obenschain {ital et al.}, Phys. Plasmas {bold 3}, 2098 (1996)] was used to ablatively accelerate 40 {mu}m thick polystyrene planar targets with pulse shaping to minimize shock heating of the compressed material. The foils had imposed small-amplitude sinusoidal wave perturbations of 60, 30, 20, and 12.5 {mu}m wavelength. The shortest wavelength is near the ablative stabilization cutoff for Rayleigh{endash}Taylor growth. Modification of the saturated wave structure due to random laser imprint was observed. Excellent agreement was found between the two-dimensional simulations and experimental data for most cases where the laser imprint was not dominant. {copyright} {ital 1999 American Institute of Physics.}

  1. Emittance-Exchange-Based High Harmonic Generation Scheme for a Short-Wavelength Free Electron Laser

    NASA Astrophysics Data System (ADS)

    Jiang, B.; Power, J. G.; Lindberg, R.; Liu, W.; Gai, W.

    2011-03-01

    Generation of short-wavelength radiation by a free-electron laser using up-frequency conversion of an electron bunch density modulation is currently an area of active research. We propose a new scheme for producing the longitudinal electron bunch density modulation similar to the recently proposed echo-enabled harmonic generation but based on an emittance exchange beam line and a multislit mask. Beam line analysis and start-to-end simulation are presented.

  2. Emittance-Exchange-Based High Harmonic Generation Scheme for a Short-Wavelength Free Electron Laser

    SciTech Connect

    Jiang, B. [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States)] [Shanghai Institute of Applied Physics, CAS, Shanghai 201800 (China); Power, J. G.; Lindberg, R.; Liu, W.; Gai, W. [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States)

    2011-03-18

    Generation of short-wavelength radiation by a free-electron laser using up-frequency conversion of an electron bunch density modulation is currently an area of active research. We propose a new scheme for producing the longitudinal electron bunch density modulation similar to the recently proposed echo-enabled harmonic generation but based on an emittance exchange beam line and a multislit mask. Beam line analysis and start-to-end simulation are presented.

  3. Emittance-exchange-based high harmonic generation scheme for short-wavelength free electron laser.

    SciTech Connect

    Power, J. G.; Jiang, B.; Gai, W.; Liu, W.; Lindberg, R. (Advanced Photon Source); ( HEP); (Shanghai Inst. of Applied Physics)

    2011-03-16

    Generation of short-wavelength radiation by a free-electron laser using up-frequency conversion of an electron bunch density modulation is currently an area of active research. We propose a new scheme for producing the longitudinal electron bunch density modulation similar to the recently proposed echo-enabled harmonic generation but based on an emittance exchange beam line and a multislit mask. Beam line analysis and start-to-end simulation are presented.

  4. Short-Wavelength Solar Wind Turbulence: Kinetic Alfven vs. Whistler Fluctuations

    Microsoft Academic Search

    S. Peter Gary

    2009-01-01

    The inertial range of solar wind turbulence corresponds to magnetic power spectra which scale as f^-alpha with alpha˜ 5\\/3. Many observations show, however, that at observed frequencies f ˜ 0.2 Hz, there is a ``breakpoint'' such that power spectra at higher frequencies follow a steeper power-law dependence with alpha> 5\\/3. The constituent modes of this high-frequency, short-wavelength regime are often

  5. Why are very short times so long and very long times so short in elastic waves?

    E-print Network

    Parravicini, Guido

    2010-01-01

    In the study of elastic waves, physicists commonly understand that when the given period is very short, waves are isentropic because heat conduction does not set in, while if the given period is very long waves are isothermal because there is enough time for thermalization to be thoroughly accomplished. On the other hand, the mathematical inspection of the complete thermoelastic wave equation shows that if the period is very short, much shorter than a characteristic time of the material, the wave is isothermal, while if it is very long, much longer than the characteristic time, the wave is isentropic, a fact that is supported by experiments. The authors show that there is no contradiction between the physicists' understanding and the mathematical treatment of the elastic wave equation: for thermal effects very long periods are so short and very short periods are so long.

  6. Observation of Rayleigh-Taylor growth to short wavelengths on Nike

    Microsoft Academic Search

    C. J. Pawley; S. E. Bodner; J. P. Dahlburg; S. P. Obenschain; A. J. Schmitt; J. D. Sethian; C. A. Sullivan; J. H. Gardner; Y. Aglitskiy; Y. Chan; T. Lehecka

    1999-01-01

    The uniform and smooth focal profile of the Nike KrF laser [S. Obenschain et al., Phys. Plasmas 3, 2098 (1996)] was used to ablatively accelerate 40 mum thick polystyrene planar targets with pulse shaping to minimize shock heating of the compressed material. The foils had imposed small-amplitude sinusoidal wave perturbations of 60, 30, 20, and 12.5 mum wavelength. The shortest

  7. Modulation and kinematics of mechanically-generated short gravity waves riding on long waves 

    E-print Network

    Spell, Charles Anthony

    1992-01-01

    in earlier experiments by Plant & Wright (1979). The study of the short- and long-wave interaction has also been extended to full-scale ocean surface measurements using microwave radar imaging techniques. Since the short waves are the predominant radar...MODULATION AND KINEMATICS OF MECHANICALLY- GENERATED SHORT GRAVITY WAVES RIDING ON LONG WAVES A Thesis by CHARLES ANTHONY SPELL Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements...

  8. Standard Copper Wave-Lengths in the Region 100A to 450A

    Microsoft Academic Search

    P. Gerald Kruger; F. S. Cooper

    1933-01-01

    The copper spectrum has been photographed in the region 100A to 450A with a twenty-one foot grazing incidence vacuum spectrograph. The wave-length of sharp copper lines (approximately two every Angstrom) have been determined by interpolating between known aluminum and oxygen lines with the formula lambda=lambda0+Ax+Bx2+Cx3.... A discussion of the errors in the wave-lengths is given.

  9. Task I: A Computational Model for Short Wavelength Stall Inception and Development In Multi-Stage Compressors

    NASA Technical Reports Server (NTRS)

    Suder, Kenneth (Technical Monitor); Tan, Choon-Sooi

    2003-01-01

    A computational model is presented for simulating axial compressor stall inception and development via disturbances with length scales on the order of several (typically about three) blade pitches. The model was designed for multi-stage compressors in which stall is initiated by these short wavelength disturbances, also referred to as spikes. The inception process described is fundamentally nonlinear, in contrast to the essentially linear behavior seen in so-called modal stall inception . The model was able to capture the following experimentally observed phenomena: (1) development of rotating stall via short wavelength disturbances, (2) formation and evolution of localized short wavelength stall cells in the first stage of a mismatched compressor, (3) the switch from long to short wavelength stall inception resulting from the re-staggering of the inlet guide vane, (4) the occurrence of rotating stall inception on the negatively sloped portion of the compressor characteristic. Parametric investigations indicated that (1) short wavelength disturbances were supported by the rotor blade row, (2) the disturbance strength was attenuated within the stators, and (3) the reduction of inter-blade row gaps can suppress the growth of short wavelength disturbances. It is argued that each local component group (rotor plus neighboring stators) has its own instability point (i.e. conditions at which disturbances are sustained) for short wavelength disturbances, with the instability point for the compressor set by the most unstable component group.

  10. Wavelength conversion via four-wave mixing in a triple-coupled multilayer cavity

    NASA Astrophysics Data System (ADS)

    Kitada, Takahiro; Yasunaga, Yukinori; Nakagawa, Yoshinori; Morita, Ken; Isu, Toshiro

    2013-09-01

    Four-wave mixing in a triple-coupled multilayer cavity has been investigated for planar-type wavelength conversion devices. Three half-wavelength cavity layers are connected in series using GaAs/AlAs distributed Bragg reflector multilayers to yield three cavity modes with equal frequency separation. The enhanced internal electric fields of the three cavity modes indicate that efficient ultrafast wavelength conversion via four-wave mixing can be achieved even in the normal incidence configuration. Wavelength conversion was experimentally demonstrated using spectrally shaped laser pulses. A clear converted wavelength signal was observed in the measured spectrum. The temporal response was almost limited by the photon lifetime of each cavity mode.

  11. Comment on "Orbital stability of solitary wave solutions for an interaction equation of short and long dispersive waves"

    E-print Network

    Borys Alvarez-Samaniego

    2007-05-23

    J. Angulo and J. F. Montenegro (J. Differential Equations 174 (2001), no. 1, 181-199) published a paper about nonlinear stability of solitary waves for an interaction system between a long internal wave and a short surface wave in a two layer fluid considering that the fluid depth of the lower layer is sufficiently large in comparison with the wavelength of the internal wave. In this note, we show that in a critical step during the proof of Lemma 2.4 in the above mentioned paper, there is a claim used by the authors which fails to be true. Lemma 2.4 is crucial for the proof of Lemma 2.7, and for the proof of stability in Theorem 2.1 in the paper before mentioned.

  12. High-power parametric conversion from near-infrared to short-wave infrared.

    PubMed

    Billat, Adrien; Cordette, Steevy; Tseng, Yu-Pei; Kharitonov, Svyatoslav; Brès, Camille-Sophie

    2014-06-16

    We report the design of an all-fiber continuous wave Short-Wave Infrared source capable to output up to 700 mW of power at 1940 nm. The source is tunable over wavelength intervals comprised between 1850 nm and 2070 nm depending on its configuration. The output can be single or multimode while the optical signal to noise ratio ranges from 25 and 40 dB. The architecture is based on the integrated association of a fiber optical parametric amplifier and a Thulium doped fiber amplifier. PMID:24977531

  13. Implications of controlled short-wavelength light exposure for sleep in older adults

    PubMed Central

    2011-01-01

    Background Environmental and physiological conditions make older adults more likely to lose synchronization to their local time and experience sleep disturbances. A regular, 24-hour light/dark cycle promotes synchronization. It is now well established that the circadian system is maximally sensitive to short-wavelength (blue) light. The purpose of the present study was to measure dose effectiveness (amounts and durations) of short-wavelength (blue) light for stimulating the circadian systems of older adults. We investigated the impact of six corneal irradiances (0.7 to 72 ?W/cm2) of 470-nm light on nocturnal melatonin production. Nine participants, each over 50 years of age completed a within-subjects study. Each week, participants were exposed to one of the six irradiances of 470-nm light for 90 minutes. Findings A two-factor (6 corneal irradiances × 10 exposure durations), within-subjects analysis of variance (ANOVA) was conducted using the melatonin suppression levels. The ANOVA revealed a significant main effect of corneal irradiance (F5, 30 = 9.131, p < 0.0001), a significant main effect of exposure duration (F9, 54 = 5.731, p < 0.0001), and a significant interaction between these two variables (F45,270 = 1.927, p < 0.001). Post hoc t-tests revealed that corneal irradiances as low as 2 ?W/cm2 reliably suppressed melatonin after 90-minute exposure whereas 0.7 ?W/cm2 did not. Conclusions Sleep disorders are common and a serious problem for millions of older adults. The present results showed that comfortable, precise and effective doses of light can be prescribed to older adults to reliably stimulate the circadian system that presumably would promote entrainment and, thus, regular sleep. Field studies on the impact of short-wavelength-light doses on sleep efficiency in older adults should be performed. PMID:21902824

  14. Sub-surface Models of Long- and Short-wavelength Gravity Anomalies in Pennsylvania

    NASA Astrophysics Data System (ADS)

    Malinconico, L. L.; Morabito, J.; Hudacek, W.; Harhen, M.; McAtee, B.

    2008-12-01

    Over the past several years we have been collecting and compiling gravity data in various areas in Pennsylvania to complement existing data previously compiled by the National Image and Mapping Agency and GeoNet. Supported by the Pennsylvania Geological Survey, the aim of this project is to generate a gravity map for the state. This has involved the collection of approximately 4000 new observations and identification of previously acquired data from other sources that had not been included in the above listed data bases. While we are still in the process of cleaning up the data set, it is now possible to use the data to model subsurface density changes for both short and long-wavelength anomalies. An intriguing feature of the gravity map of Pennsylvania is the long-wavelength NE-SW-trending positive and negative anomalies that have little direct correlation with the observed surface geology. The negative anomalies range in amplitude from -12 to - 40 mgals, with wavelengths from 80 to 150 km, while the positive anomalies have amplitudes from 11 to 54 mgals and wavelengths between 100 and 135 km. We have modeled several of these using both wavelength analysis and simple two-dimensional modeling. The results suggest that, unlike previous interpretations that suggested shallow basins or intrusions, part of the cause of these anomalies may be as deep as topographic variations at the crust-mantle boundary. With well-constrained regional trends we have also been able to use these data to isolate and model short- wavelength anomalies. Within the Newark Basin in southeastern Pennsylvania one focus has been on the diabase intrusions. The gravity data demonstrate a remarkable special coincidence of 5 to 10 mgal positive anomalies with the known outcrop pattern of the sills, however there are also some areas where the sill is observed to outcrop, but where the gravity signature is minimal or does not exist. The density models of the sills range in thickness from .3 km to almost 1 km and generally increase in structural thickness from east to west, suggesting a possible source towards the west-central portion of the basin, or conversely greater removal of material (and uplift) towards the east.

  15. Short wavelength automated perimetry, frequency doubling technology perimetry, and pattern electroretinography for prediction of progressive glaucomatous standard visual field defects

    Microsoft Academic Search

    Andreas U Bayer; Carl Erb

    2002-01-01

    PurposeTo evaluate the clinical use of a test battery of short wavelength automated perimetry (SWAP), frequency doubling technology perimetry (FDT), and pattern electroretinography (PERG) in predicting progressive glaucomatous visual field defects on standard automated perimetry (SAP).

  16. Electrostatic, short-wavelength, turbulence as the source of ion heating in the solar wind

    NASA Technical Reports Server (NTRS)

    Papadoupoulis, K.

    1971-01-01

    A mechanism is proposed for the nonthermal ion heating observed in the solar wind at 1 A.U. based on an electrostatic, short wavelength, instability between the ions in the observed colliding plasma streams. The modes lying on a plane perpendicular to the magnetic field thermalize most of the differential energy. The model suggests local electrostatic turbulence, that alpha-particles are heated more than protons, a maximum proton temperature T sub P 1 million k, and for the bulk speed U possibly a sq root of T sub P = aU + b relationship. These predictions are consistent with observations.

  17. A numerical study of the long wave-short wave interaction equations

    Microsoft Academic Search

    H. Borluk; G. M. Muslu; H. A. Erbay

    2007-01-01

    Abstract Two numerical methods,are presented for the periodic initial-value problem,of the long wave–short wave interaction equations describing the interaction between,one long longitudinal wave and two short transverse waves propagating in a generalized elastic medium. The first one is the relaxation method, which is implicit with second-order accuracy in both space and time. The second one is the split-step Fourier method,

  18. Photonic band gaps of wurtzite GaN and AlN photonic crystals at short wavelengths

    NASA Astrophysics Data System (ADS)

    Melo, E. G.; Alayo, M. I.

    2015-04-01

    Group III-nitride materials such as GaN and AlN have attracted a great attention in researches on photonic devices that operate at short light wavelengths. The large band gaps of these materials turn them suitable for nanophotonic devices that operate in light ranges from visible to deep ultraviolet. The physical properties of wurtzite GaN and AlN such as their second and third order nonlinear susceptibilities, and their thermal and piezoelectric coefficients, also make them excellent candidates for integrate photonic devices with electronics, microelectromechanics, microfluidics and general sensing applications. Using a plane wave expansion method (PWE) the photonic band gap maps of 36 different two-dimensional photonic crystal lattices in wurtzite GaN and AlN were obtained and analyzed. The wavelength dependence and the effects of the material anisotropy on the position of the photonic band gaps are also discussed. The results show regions with slow group velocity at the edges of a complete photonic band gap in the M-K direction of the triangular lattices with circular, hexagonal, and rhombic air holes. Was also found a very interesting disposition of the photonic band gaps in the lattices composed of rhombic air holes.

  19. An Automated Short-Period Surface-Wave Detection Algorithm

    Microsoft Academic Search

    Ileana M. Tibuleac; James M. Britton

    2006-01-01

    We describe an automated short-period Rayleigh wave (Rg) detector designed to work on local (2.5 epicentral distance) events recorded at three- component stations. The detector was modeled after an automatic 17- to 22-sec Rayleigh-wave detection method; however, we have modified the algorithms for local distance and short-period applications. We have tested the detector on a well-located cluster of mining events

  20. Stress field of Italy — Mean stress orientation at different depths and wave-length of the stress pattern

    NASA Astrophysics Data System (ADS)

    Pierdominici, Simona; Heidbach, Oliver

    2012-04-01

    We have studied the stress pattern of Italy using a dataset with 590 data records from the World Stress Map database release 2008 and 106 new data records to test the hypothesis the mean orientation of maximum horizontal stress SH is different at different depth sections. For this, we split the dataset into a shallow (0-6 km) and a deep (6-40 km) depth section. For the data analysis we used a new statistical tool that calculates the mean SH orientation on a 0.2° grid. The tool takes into account the distance to each grid point, number and quality of the data records within the search radius, and the radial distribution. The result is a smoothed Italian stress map that displays both; the mean SH orientation and the wave-length of the stress pattern. The stress pattern does not vary in depth except for two areas (Sardinia and southern Apulia). Therefore stress data from different depths can be used to estimate the mean SH orientation and the wave-length of the stress pattern in Italy. Furthermore, the smoothed Italian stress map reveals that most of Italy has short wave-length stress patterns (< 150 km). This indicates that the stress field is not controlled by first-order stress sources of plate tectonics, i.e. the convergence of Africa with respect to Eurasia, but that second-order stress sources such as topography, density, strength contrasts, and major faults systems are of great importance. In four regions (western part of the Alps, northern Tuscany, northern Adriatic Sea, Calabria and eastern part of Sicily) the wave-length is < 100 km. High values of the circular variance of the mean SH orientation observed here are driven by third-order local stress sources, such as basins or local neotectonic structures.

  1. Contribution of Long Wavelength Gravitational Waves to the CMB Anisotropy

    E-print Network

    Martin White

    1992-07-14

    We present an in depth discussion of the production of gravitational waves from an inflationary phase that could have occurred in the early universe, giving derivations for the resulting spectrum and energy density. We also consider the large-scale anisotropy in the cosmic microwave background radiation coming from these waves. Assuming that the observed quadrupole anisotropy comes mostly from gravitational waves (consistent with the predictions of a flat spectrum of scalar density perturbations and the measured dipole anisotropy) we describe in detail how to derive a value for the scale of inflation of $(1.5-5)\\times 10^{16}$GeV, which is at a particularly interesting scale for particle physics. This upper limit corresponds to a 95\\% confidence level upper limit on the scale of inflation assuming only that the quadrupole anisotropy from gravitational waves is not cancelled by another source. Direct detection of gravitational waves produced by inflation near this scale will have to wait for the next generation of detectors.

  2. Short wavelength (visible) quantum well lasers grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Blood, P.; Fletcher, E. D.; Woodbridge, K.; Hulyer, P. J.

    1985-03-01

    We have fabricated AlGaAs multiple quantum well lasers from a variety of structures grown by molecular beam epitaxy with the objective of achieving operation at a short wavelength with GaAs wells. A series of structures with well widths from 55Å down to 13Å gave pulsed room temperature laser operation at wavelengths from 837nm to 707nm. All the devices operated at longer wavelengths than that calculated for the n=1(e-hh) transition, though from measurements of their electroluminescence spectra at currents as low as 7% of threshold we find no evidence for changes in the sub-band separation at high injection. The threshold current density of a simple broad area MQW device with 160Å wide GaAs wells operating at ?880nm was 1.2kA cm -2 and an analysis of the threshold current density and losses in these device suggests that interface optical scattering is small.

  3. Short-wavelength infrared defect emission as probe for degradation effects in diode lasers

    NASA Astrophysics Data System (ADS)

    Hempel, Martin; Tomm, Jens W.; Yue, Fangyu; Bettiati, Mauro; Elsaesser, Thomas

    2015-03-01

    The infrared emission from 980-nm single-mode high power diode lasers is analyzed in the wavelength range from 0.8 to 7.0 ?m. A pronounced short-wavelength infrared (SWIR) emission band with a maximum at 1.3 ?m is found to originate from defect states located within the waveguide of the devices. The SWIR intensity is verified to represent a measure of the non-equilibrium carrier concentration in the waveguide, allowing for non-destructive waveguide mapping in spatially resolved detection schemes. The potential of this approach is demonstrated by measuring spatially resolved profiles of SWIR emission and correlating them with mid-wavelength infrared thermal emission along the cavity of devices undergoing repeated catastrophic optical damage. The enhancement of SWIR emission in the damaged parts of the cavity is due to a locally enhanced carrier density in the waveguide and allows for in situ analysis of the damage patterns. Moreover, spatial resolved SWIR measurements are a promising tool for device inspecting even in low-power operation regimes.

  4. Why are very short times so long and very long times so short in elastic waves?

    E-print Network

    Guido Parravicini; Serena Rigamonti

    2010-09-23

    In a first study of thermoelastic waves, such as on the textbook of Landau and Lifshitz, one might at first glance understand that when the given period is very short, waves are isentropic because heat conduction does not set in, while if the given period is very long waves are isothermal because there is enough time for thermalization to be thoroughly accomplished. When one pursues the study of these waves further, by the mathematical inspection of the complete thermoelastic wave equation he finds that if the period is very short, much shorter than a characteristic time of the material, the wave is isothermal, while if it is very long, much longer than the characteristic time, the wave is isentropic. One also learns that this fact is supported by experiments: at low frequencies the elastic waves are isentropic, while they are isothermal when the frequencies are so high that can be attained in few cases. The authors show that there is no contradiction between the first glance understanding and the mathematical treatment of the elastic wave equation: for thermal effects very long periods are so short and very short periods are so long.

  5. Chromatic aberration short-wave infrared spectroscopy: nanoparticle spectra without a spectrometer.

    PubMed

    Streit, Jason K; Bachilo, Sergei M; Weisman, R Bruce

    2013-02-01

    A new method is described for measuring the short-wave infrared (SWIR) emission wavelengths of numerous individual nanoparticles without using a dedicated spectrometer. Microscope objectives designed for use at visible wavelengths often show severe axial chromatic aberration in the SWIR. This makes coplanar objects emitting at different SWIR wavelengths appear to focus at different depths. After this aberration has been calibrated for a particular objective lens, the depth at which an emissive nanoparticle appears brightest and best focused can be used to deduce its peak emission wavelength. The method is demonstrated using a dilute, structurally polydisperse sample of single-walled carbon nanotubes deposited onto a microscope slide. Discrete emission centers in this sample have different peak wavelengths corresponding to specific nanotube structural species. A set of images was recorded at stepped focus settings and analyzed to find the sharpest focus depth of each nanotube. The chromatic aberration calibration curve converted these depths into peak emission wavelengths with a spectral resolution better than 3 nm, allowing identification of each nanotube's structure. Chromatic aberration spectroscopy is a practical tool for using existing microscopic equipment to extract significant spectral information on coplanar nanoparticle samples that emit or scatter light. PMID:23286305

  6. Wavelength-converted wave-guiding in dye-doped polymer nanofibers.

    PubMed

    Yu, Huaqing; Li, Baojun

    2013-01-01

    Nanoscale wavelength-converted optical components are promising components for communication and optical information processing in integrated photonic system. In this work, we report a facile strategy for realizing continuously tunable wavelength-converted wave-guiding in dye-doped nanofibers. The nanofibers with diameters of 200-800?nm have an absorption coefficient of about 80?cm(-1) and a self-absorption coefficient of about 30?cm(-1), and exhibit relatively high PL efficiency and high photobleaching resistance under an optical pump. By launching the pump light into the nanofibers, the excited light in the nanofibers got self-absorption and reemitted at a longer wavelength, resulting in a gradual wavelength conversion during propagation. On the basis of this wavelength-converted wave-guiding, nanoscale wavelength-converted splitters were demonstrated by assembling the nanofibers into crossed structures. We believe that the dye-doped nanofibers would bring new exciting opportunities in developing new wavelength-converted optical components for nanophotonic device integration. PMID:23591750

  7. High-power and wavelength-tunable traveling-wave semiconductor ring laser

    E-print Network

    Peng, En Titus

    1991-01-01

    HIGH-POWER AND WAVELENGTH-TUNABLE TRAVELING-WAVE SEMICONDUCTOR RING LASER A Thesis EN TITUS PENG Submitted to the Office of Graduate Studies of Texas ARM University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE... May 1991 Major Subject: Electrical Engineering HIGH-POWER AND WAVELENGTH-TUNABLE TRAVELING-WAVE SEMICONDUCTOR RING LASER A Thesis by EN TITUS PENG Approved as to style and content by: Ch' B. Su (Chair of Committee) 0, 4 Ohannes E n yan...

  8. Directional short wind wave spectra derived from the sea surface photography

    NASA Astrophysics Data System (ADS)

    Dulov, Vladimir; Yurovskaya, Maria; Chapron, Bertrand; Kudryavtsev, Vladimir

    2014-05-01

    New field measurements of 2-D wave number short wind wave spectra in the wavelength range from few millimeters to few decimeters are reported and discussed. The measurement method proposed by [Kosnik and Dulov, 2011] is based on stereophotography and image brightness contrast processing. The method strongly builds on the brightness cross-spectral analysis to reduce the noise within this short wave gravity and capillary range. Field measurements of wind wave spectra are still rare, and the reported data thus provide valuable information to bring new evidences on the 2-D spectral distribution of short wind waves in the wavelength range from decimeters to millimeters. As found, the folded spectra of decimeter waves are very weakly dependent on the wind speed and its direction. Wind speed and direction sensitivity only starts to appear in the short wavelength range, more precisely in the vicinity of the wave number 100 rad/m, where the wind exponent grows from 0.5 to 1.5-2.5 at 800 rad/m, and angular anisotropy parameter introduced by [Elfouhaily et al., 1997] amounts the value of 0.5. These aspects are consistent with other previously reported optical and radar data. For the latter, we solely extracted the polarization sensitivity to best isolate the contribution associated to the wave saturation spectrum around the Bragg resonant wave number. For the former, mean-squared slope statistics were used to assess the integrated shortscale directional spectral properties. As revealed, observed direction spectral distributions are significantly different from those previously suggested [Elfouhaily et al., 1997; Kudryavtsev et al., 2003, 2005]. On the basis of these new in situ measurements, we then propose to revise the semiempirical analytical model of short wind wave spectra developed by [Kudryavtsev et al., 2003, 2005]. In this model the key parameter is exponent n governing the nonlinear dissipation rate as D ~ Bn+1, where B is saturation spectrum. Accordingly, new additional constraints are used to refine the dependence of the n on dimensionless wave number to match the inferred wind exponent data. As appeared, such a constraint is a key to refine the directional spectrum. The mean saturation spectrum is further adjusted to be consistent with the robust Cox and Munk [1954] dependence of mean-square slope on wind speed. As developed, the proposed two-dimensional wave number spectrum is valid over the ultragravity and capillary large wave numbers, and is analytically amenable to different usage. This revised model can readily be implemented in other studies (radar scattering, air-sea interaction issues, etc.), where detailed knowledge of short wind wave spectra is crucial. The core support of this work was provided by the mega grant of the Russian Federation Government under grant 11.G34.31.0078, and IFREMER-DVS contracts 2011 2 20712376 and 2012 2 20712805. The research leading to these results has also received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant Agreement 287844 for the project COCONET, the Russian Federal Programme under contracts N14.B37.21.0619 and N2012-1.2.1-12-000-2007-078 and Ukrainian State Agency of Science, Innovations and Information under contracts F53/117-2013 and M/281-2013. Authors gratefully acknowledge continuing support of these foundations.

  9. Determining the wavelength of Langmuir wave packets at the Earth's bow shock

    E-print Network

    Krasnoselskikh, V V; Bale, S D; 10.5194/angeo-29-613-2011

    2011-01-01

    The propagation of Langmuir waves in plasmas is known to be sensitive to density fluctuations. Such fluctuations may lead to the coexistence of wave pairs that have almost opposite wave-numbers in the vicinity of their reflection points. Using high frequency electric field measurements from the WIND satellite, we determine for the first time the wavelength of intense Langmuir wave packets that are generated upstream of the Earth's electron foreshock by energetic electron beams. Surprisingly, the wavelength is found to be 2 to 3 times larger than the value expected from standard theory. These values are consistent with the presence of strong inhomogeneities in the solar wind plasma rather than with the effect of weak beam instabilities.

  10. Destabilization of long-wavelength Love and Stoneley waves in slow sliding

    E-print Network

    K. Ranjith

    2009-03-04

    Love waves are dispersive interfacial waves that are a mode of response for anti-plane motions of an elastic layer bonded to an elastic half-space. Similarly, Stoneley waves are interfacial waves in bonded contact of dissimilar elastic half-spaces, when the displacements are in the plane of the solids. It is shown that in slow sliding, long wavelength Love and Stoneley waves are destabilized by friction. Friction is assumed to have a positive instantaneous logarithmic dependence on slip rate and a logarithmic rate weakening behavior at steady-state. Long wavelength instabilities occur generically in sliding with rate- and state-dependent friction, even when an interfacial wave does not exist. For slip at low rates, such instabilities are quasi-static in nature, i.e., the phase velocity is negligibly small in comparison to a shear wave speed. The existence of an interfacial wave in bonded contact permits an instability to propagate with a speed of the order of a shear wave speed even in slow sliding, indicating that the quasi-static approximation is not a valid one in such problems.

  11. Emitted short wavelength infrared radiation for detection and monitoring of volcanic activity

    NASA Technical Reports Server (NTRS)

    Rothery, D. A.; Francis, P. W.; Wood, C. A.

    1988-01-01

    Thematic Mapper images from LANDSAT were used to monitor volcanoes. Achievements include: (1) the discovery of a magmatic precursor to the 16 Sept. 1986 eruption of Lascar, northern Chile, on images from Mar. and July 1985 and of continuing fumarolic activity after the eruption; (2) the detection of unreported major changes in the distribution of lava lakes on Erta'Ale, Ethiopia; and (3) the mapping of a halo of still-hot spatter surrounding a vent on Mount Erebus, Antarctica, on an image acquired 5 min after a minor eruption otherwise known only from seismic records. A spaceborne short wavelength infrared sensor for observing hot phenomena of volcanoes is proposed. A polar orbit is suggested.

  12. Steady State Analysis of Short-wavelength, High-gainFELs in a Large Storage Ring

    SciTech Connect

    Huang, Z.; Bane, K.; Cai, Y.; Chao, A.; Hettel, R.; /SLAC; Pellegrini, C.; /UCLA

    2007-10-15

    Storage ring FELs have operated successfully in the low-gain regime using optical cavities. Discussions of a high-gain FEL in a storage ring typically involve a special bypass to decouple the FEL interaction from the storage ring dynamics. In this paper, we investigate the coupled dynamics of a high-gain FEL in a large storage ring such as PEP and analyze the equilibrium solution. We show that an FEL in the EUV and soft x-ray regimes can be integrated into a very bright storage ring and potentially provides three orders of magnitude improvement in the average brightness at these radiation wavelengths. We also discuss possibilities of seeding with HHG sources to obtain ultra-short, high-peak power EUV and soft x-ray pulses.

  13. SWAT system performance predictions. Project report. [SWAT (Short-Wavelength Adaptive Techniques)

    SciTech Connect

    Parenti, R.R.; Sasiela, R.J.

    1993-03-10

    In the next phase of Lincoln Laboratory's SWAT (Short-Wavelength Adaptive Techniques) program, the performance of a 241-actuator adaptive-optics system will be measured using a variety of synthetic-beacon geometries. As an aid in this experimental investigation, a detailed set of theoretical predictions has also been assembled. The computational tools that have been applied in this study include a numerical approach in which Monte-Carlo ray-trace simulations of accumulated phase error are developed, and an analytical analysis of the expected system behavior. This report describes the basis of these two computational techniques and compares their estimates of overall system performance. Although their regions of applicability tend to be complementary rather than redundant, good agreement is usually obtained when both sets of results can be derived for the same engagement scenario.... Adaptive optics, Phase conjugation, Atmospheric turbulence Synthetic beacon, Laser guide star.

  14. Extraordinarily low evolutionary rates of short wavelength-sensitive opsin pseudogenes

    PubMed Central

    Yokoyama, Shozo; Starmer, William T.; Liu, Yang; Tada, Takashi; Britt, Lyle

    2013-01-01

    Aquatic organisms such as cichlids, coelacanths, seals, and cetaceans are active in UV-blue color environments, but many of them mysteriously lost their abilities to detect these colors. The loss of these functions is a consequence of the pseudogenization of their short wavelength-sensitive (SWS1) opsin genes without gene duplication. We show that the SWS1 gene (BdenS1?) of the deep-sea fish, pearleye (Benthalbella dentata), became a pseudogene in a similar fashion about 130 million years ago (Mya) yet it is still transcribed. The rates of nucleotide substitution (~1.4 × 10?9 /site/year) of the pseudogenes of these aquatic species as well as some prosimian and bat species are much smaller than the previous estimates for the globin and immunoglobulin pseudogenes. PMID:24125953

  15. Short wavelength x-ray laser research at the Lawrence Livermore National Laboratory

    SciTech Connect

    MacGowan, B.J.; Da Silva, L.B.; Fields, D.J.; Keane, C.J.; Koch, J.A.; London, R.A.; Matthews, D.L.; Maxon, S.; Mrowka, S.; Osterheld, A.L.; Scofield, J.H.; Shimkaveg, G.; Trebes, J.E.; Walling, R.S. (Lawrence Livermore National Laboratory, University of California, L-476, P.O. Box 808, Livermore, California 94550 (United States))

    1992-07-01

    Laboratory x-ray lasers are currently being studied by researchers worldwide. This paper reviews some of the recent work carried out at Lawrence Livermore National Laboratory. Laser action has been demonstrated at wavelengths as short as 35.6 A while saturation of the small signal gain has been observed with longer wavelength schemes. Some of the most successful schemes to date have been collisionally pumped x-ray lasers that use the thermal electron distribution within a laser-produced plasma to excite electrons from closed shells in neon- and nickel-like ions to metastable levels in the next shell. Attempts to quantify and improve the longitudinal and transverse coherence of collisionally pumped x-ray lasers are motivated by the desire to produce sources for specific applications. Toward this goal there is a large effort underway to enhance the power output of the Ni-like Ta x-ray laser at 44.83 A as a source for x-ray imaging of live cells. Improving the efficiency of x-ray lasers in order to produce saturated output with smaller pump lasers is also a goal of this work.

  16. Design considerations for the development of a space qualification Short Wavelength Imaging Fourier Transform Spectrometer (SWIFTS)

    SciTech Connect

    Abbink, R.E.

    1997-06-01

    This document is the final report on work performed at Sandia National Laboratories during FY 1992 and 1993 for a Laboratory Directed Research and Development (LDRD) program to look at problems associated with the design and long term operation of a short wavelength imaging Fourier Transform (FT) spectrometer for use in space. In attempts to answer two fundamental questions: is a FT spectrometer with a resolution of 1 cm{sup {minus}1} covering the silicon detector wavelength range of 0.4 to 1.1 microns feasible in a long life space instrument and, if so, is it the best method of obtaining the desired information? Emphasis has been on identifying methods which minimize reliance on precision mechanical alignment and precise velocity control. An important consideration has also been to develop methods which will be compatible with a variety of self-scanning solid state imaging devices. A breadboard instrument was constructed using cube corner retroreflectors and a laser diode position reference. Some preliminary results are reported. This work is primarily intended to act as an aid to engineers at Sandia who wish to pursue the fabrication of a flight qualified instrument. The theoretical parts are intended to be somewhat tutorial in nature to aid the engineer who is not familiar with FT spectroscopy.

  17. All-Optical Wavelength Conversion using Multi-Pump Raman-assisted Four-Wave Mixing

    E-print Network

    Wai, Ping-kong Alexander

    -pump Raman amplifier to further improve the conversion efficiency and increase the operating bandwidth of the FWM process. The multi-pump Raman amplifier extends the relatively narrow gain peak of a single RamanAll-Optical Wavelength Conversion using Multi-Pump Raman-assisted Four-Wave Mixing S. H. Wang,1

  18. Electromagnetic wave propagation on human trunk models excited by half-wavelength dipoles

    Microsoft Academic Search

    Markus Grimm; Dirk Manteuffel

    2010-01-01

    This paper presents a numerical analysis (FDTD) of the electromagnetic wave propagation mechanism at f = 2.45 GHz around the human trunk. Different body models starting from planar models, to cylindrical models up to realistic trunk models are considered. In addition homogeneous and inhomogeneous model structures are compared with each other. For excitation a half-wavelength dipole in close proximity to

  19. Wavelength dependence in radio-wave scattering and specular-point theory

    NASA Technical Reports Server (NTRS)

    Tyler, G. L.

    1976-01-01

    Radio-wave scattering from natural surfaces contains a strong quasispecular component that at fixed wavelengths is consistent with specular-point theory, but often has a strong wavelength dependence that is not predicted by physical optics calculations under the usual limitations of specular-point models. Wavelength dependence can be introduced by a physical approximation that preserves the specular-point assumptions with respect to the radii of curvature of a fictitious, effective scattering surface obtained by smoothing the actual surface. A uniform low-pass filter model of the scattering process yields explicit results for the effective surface roughness versus wavelength. Interpretation of experimental results from planetary surfaces indicates that the asymptotic surface height spectral densities fall at least as fast as an inverse cube of spatial frequency. Asymptotic spectral densities for Mars and portions of the lunar surface evidently decrease more rapidly.

  20. Solar irradiance short wave radiation users guide. Final report

    SciTech Connect

    Martinolich, P.; Arnone, R.A.

    1995-05-19

    Solar irradiance for short wave radiation (400-700 nm) at the sea surface can be calculated using inputs obtained from satellite systems and model estimates. The short wave solar irradiance is important for estimating the surface heating that occurs in the near surface and estimating the available irradiance for biological growth in the upper ocean. The variability of the solar irradiance is believed to have significant influence on the global carbon cycle. This users guide provides an understanding of the models and operational procedures for using the software and understanding the results.

  1. Spatio-Temporal Measurements of Short Wind Water Waves

    Microsoft Academic Search

    Roland Rocholz; Bernd Jähne

    2010-01-01

    Spatio-temporal measurements of wind-driven short-gravity capillary waves are reported for a wide range of experimental conditions, including wind, rain and surface slicks. The experiments were conducted in the Hamburg linear wind\\/wave flume in cooperation with the Institute of Oceanography at the University of Hamburg, Germany. Both components of the slope field were measured optically at a fetch of 14.4 m

  2. Automated model-based calibration of short-wavelength infrared (SWIR) imaging spectrographs.

    PubMed

    Kosec, Matjaž; Bürmen, Miran; Tomaževi?, Dejan; Pernuš, Franjo; Likar, Boštjan

    2012-10-01

    Among the variety of available hyperspectral imaging systems, the line-scan technique stands out for its short acquisition time and good signal-to-noise ratio. However, due to imperfections in the camera lens and, in particular, optical components of the imaging spectrograph, the acquired images are spatially and spectrally distorted, which can significantly degrade the accuracy of the subsequent hyperspectral image analysis. In this work, we propose and evaluate an automated method for correction of spatial and spectral distortions introduced by a line-scan hyperspectral imaging system operating in the short wavelength infrared (SWIR) spectral range from 1000 nm to 2500 nm. The proposed method is based on non-rigid registration of the distorted and reference images corresponding to two passive calibration objects. The results of the validation show that the proposed method is accurate, efficient, and applicable for calibration of line-scan hyperspectral imaging systems. Moreover, the design of the method and of the calibration objects allows integration with systems operating in diffuse reflectance or transmittance modes. PMID:23031695

  3. Quantitative short-wave infrared multispectral imaging of in vivo tissue optical properties.

    PubMed

    Wilson, Robert H; Nadeau, Kyle P; Jaworski, Frank B; Rowland, Rebecca; Nguyen, John Q; Crouzet, Christian; Saager, Rolf B; Choi, Bernard; Tromberg, Bruce J; Durkin, Anthony J

    2014-08-01

    Extending the wavelength range of spatial frequency domain imaging (SFDI) into the short-wave infrared (SWIR) has the potential to provide enhanced sensitivity to chromophores such as water and lipids that have prominent absorption features in the SWIR region. Here, we present, for the first time, a method combining SFDI with unstructured (zero spatial frequency) illumination to extract tissue absorption and scattering properties over a wavelength range (850 to 1800 nm) largely unexplored by previous tissue optics techniques. To obtain images over this wavelength range, we employ a SWIR camera in conjunction with an SFDI system. We use SFDI to obtain in vivo tissue reduced scattering coefficients at the wavelengths from 850 to 1050 nm, and then use unstructured wide-field illumination and an extrapolated power-law fit to this scattering spectrum to extract the absorption spectrum from 850 to 1800 nm. Our proof-of-principle experiment in a rat burn model illustrates that the combination of multispectral SWIR imaging, SFDI, and unstructured illumination can characterize in vivo changes in skin optical properties over a greatly expanded wavelength range. In the rat burn experiment, these changes (relative to normal, unburned skin) included increased absorption and increased scattering amplitude and slope, consistent with changes that we previously reported in the near-infrared using SFDI. PMID:25120175

  4. Strong localization of an acoustic wave in a sub-wavelength slot between two plates.

    PubMed

    Cai, Feiyan; Li, Fei; Meng, Long; Wu, Junru; Zheng, Hairong

    2015-03-01

    The dispersion relation of the acoustic field in a sub-wavelength slot (its width is smaller than the acoustic wavelength) between two identical plates immersed in an inviscid liquid is theoretically analyzed. Each plate has a phononic crystal structure consisting of periodical grooves drilled in one of outer sides of each plate. It is found that highly localization of acoustic energy can be achieved in the sub-wavelength slot when a traveling acoustic wave is incident upon the slots. The associate physical principle is as follows: The lowest anti-symmetric non-leaky A0 mode of the Lamb wave of each individual thin plate propagating as an evanescent wave extends to the liquid from opposite direction; when the width of the slot is much smaller than the characteristic decay length of the evanescent wave in the liquid, the constructive interference of evanescent waves of the both plates takes place, leading to a strong acoustic field in the slot. This system has potential to serve as an excellent candidate for the ultrasensitive microscopic chemical/biological stimulators and sensors. PMID:25786938

  5. Concentric waves and short-period oscillations observed in the ionosphere after the 2013 Moore EF5 tornado

    NASA Astrophysics Data System (ADS)

    Nishioka, Michi; Tsugawa, Takuya; Kubota, Minoru; Ishii, Mamoru

    2013-11-01

    We detected clear concentric waves and short-period oscillations in the ionosphere after an Enhanced Fujita scale (EF)5 tornado hit Moore, Oklahoma, U.S., on 20 May 2013 using dense wide-coverage ionospheric total electron content (TEC) observations in North America. These concentric waves were nondispersive, with a horizontal wavelength of ~120 km and a period of ~13 min. They were observed for more than 7 h throughout North America. TEC oscillations with a period of ~4 min were also observed to the south of Moore for more than 8 h. A comparison between the TEC observations and infrared cloud image from the GOES satellite indicates that the concentric waves and short-period oscillations are caused by supercell-induced atmospheric gravity waves and acoustic resonances, respectively. This observational result provides the first clear evidence of a severe meteorological event causing atmospheric waves propagating upward in the upper atmosphere and reaching the ionosphere.

  6. Diffraction of short pulses with boundary diffraction wave theory.

    PubMed

    Horváth, Z L; Bor, Z

    2001-02-01

    The diffraction of short pulses is studied on the basis of the Miyamoto-Wolf theory of the boundary diffraction wave, which is a mathematical formulation of Young's idea about the nature of diffraction. It is pointed out that the diffracted field is given by the superposition of the boundary wave pulse (formed by interference of the elementary boundary diffraction waves) and the geometric (direct) pulse (governed by the laws of geometrical optics). The case of a circular aperture is treated in details. The diffracted field on the optical axis is calculated analytically (without any approximation) for an arbitrary temporal pulse shape. Because of the short pulse duration and the path difference the geometric and the boundary wave pulses appear separately, i.e., the boundary waves are manifested in themselves in the illuminated region (in the sense of geometrical optics). The properties of the boundary wave pulse is discussed. Its radial intensity distribution can be approximated by the Bessel function of zero order if the observation points are in the illuminated region and far from the plane of the aperture and close to the optical axis. Although the boundary wave pulse propagates on the optical axis at a speed exceeding c, it does not contradict the theory of relativity. PMID:11308595

  7. Short Wave Fadeout (SWF) equipment and operational procedures

    Microsoft Academic Search

    K. E. Eis

    1977-01-01

    This Technical Note explains the new AWS short wave fadeout (SWF) instrumentation, its installation, calibration and use. Details of SWF observation are discussed. This paper can be used by local equipment technicians as a Technical Order (T.O.) on the SWF equipment until a formal T.O. exists.

  8. Rough surface wavelength measurement through self mixing of Doppler microwave backscatter. [from ocean waves

    NASA Technical Reports Server (NTRS)

    Weissman, D. E.; Johnson, J. W.

    1979-01-01

    A microwave backscatter technique is presented that has the ability to sense the dominant surface wavelength of a random rough surface. The purpose of this technique is to perform this measurement from an aircraft or spacecraft, wherein the horizontal velocity of the radar is an important parameter of the measurement system. Attention will be directed at water surface conditions for which a dominant wavelength can be defined, then the spatial variations of reflectivity will have a two dimensional spectrum that is sufficiently close to that of waves to be useful. The measurement concept is based on the relative motion between the water waves and a nadir looking radar, and the fact that while the instantaneous Doppler frequency at the receiver returned by any elementary group of scatterers on a water wave is monotonically changing, the difference in the Doppler frequency between any two scattering 'patches' stays approximately constant as these waves travel parallel to the major axis of an elliptical antenna footprint. The results of a theoretical analysis and a laboratory experiment with a continuous wave (CW) radar that encompasses several of the largest waves in the illuminated area show how the structure in the Doppler spectrum of the backscattered signal is related to the surface spectrum and its parameters in an especially direct and simple way when an incoherent envelope detector is the receiver.

  9. GEOPHYSICS, ASTRONOMY AND ASTROPHYSICS: Numerical method of studying nonlinear interactions between long waves and multiple short waves

    NASA Astrophysics Data System (ADS)

    Xie, Tao; Kuang, Hai-Lan; William, Perrie; Zou, Guang-Hui; Nan, Cheng-Feng; He, Chao; Shen, Tao; Chen, Wei

    2009-07-01

    Although the nonlinear interactions between a single short gravity wave and a long wave can be solved analytically, the solution is less tractable in more general cases involving multiple short waves. In this work we present a numerical method of studying nonlinear interactions between a long wave and multiple short harmonic waves in infinitely deep water. Specifically, this method is applied to the calculation of the temporal and spatial evolutions of the surface elevations in which a given long wave interacts with several short harmonic waves. Another important application of our method is to quantitatively analyse the nonlinear interactions between an arbitrary short wave train and another short wave train. From simulation results, we obtain that the mechanism for the nonlinear interactions between one short wave train and another short wave train (expressed as wave train 2) leads to the energy focusing of the other short wave train (expressed as wave train 3). This mechanism occurs on wave components with a narrow frequency bandwidth, whose frequencies are near that of wave train 3.

  10. Phosphate coverglasses and hybrid adhesives - protective materials for short-wavelength-cut-on photovoltaics

    Microsoft Academic Search

    R. H. Woodman; L. Gonzalez; J. B. Belcher; C. M. Ferreira; D. Yuhas; C. Click; D. Haines; J. Du

    2009-01-01

    This paper describes the development of two technologies intended to support the exploitation of shorter-wavelength light by photovoltaics-radiation-hard phosphate glasses with lower-wavelength cut-on values, and a radiation-resistant silicate-elastomer hybrid bonding agent (SEHB). Phosphate glasses with lower ultraviolet (UV) cut-on wavelength than current materials have been developed, but the cut-on wavelength shows a pronounced red shift after radiation exposure. The hybrid

  11. VANISHING VISCOSITY WITH SHORT WAVE LONG WAVE INTERACTIONS FOR SYSTEMS OF CONSERVATION LAWS

    E-print Network

    VANISHING VISCOSITY WITH SHORT WAVE LONG WAVE INTERACTIONS FOR SYSTEMS OF CONSERVATION LAWS JO systems of conservation laws. We prove the strong convergence of the solutions of the vanishing viscosity of the representative examples such as scalar conservation laws, general symmetric systems, nonlinear elasticity

  12. Color Tuning in Short Wavelength-Sensitive Human and Mouse Visual Pigments: Ab initio Quantum Mechanics/Molecular Mechanics Studies

    E-print Network

    Yokoyama, Shozo

    Color Tuning in Short Wavelength-Sensitive Human and Mouse Visual Pigments: Ab initio Quantum-retinal in human blue and mouse UV cone visual pigments as well as in bovine rhodopsin by hybrid quantum mechanical energies show that UV-sensitive pigments have deprotonated SB nitrogen, while violet-sensitive pigments

  13. A short-wavelength infrared emitting multimodal probe for non-invasive visualization of phagocyte cell migration in living mice.

    PubMed

    Tsukasaki, Y; Komatsuzaki, A; Mori, Y; Ma, Q; Yoshioka, Y; Jin, T

    2014-11-28

    For the non-invasive visualization of cell migration in deep tissues, we synthesized a short-wavelength infrared (SWIR) emitting multimodal probe that contains PbS/CdS quantum dots, rhodamine 6G and iron oxide nanoparticles. This probe enables multimodal (SWIR fluorescence/magnetic resonance) imaging of phagocyte cell migration in living mice. PMID:25296382

  14. Travelling-wave resonant four-wave mixing breaks the limits of cavity-enhanced all-optical wavelength conversion

    PubMed Central

    Morichetti, Francesco; Canciamilla, Antonio; Ferrari, Carlo; Samarelli, Antonio; Sorel, Marc; Melloni, Andrea

    2011-01-01

    Wave mixing inside optical resonators, while experiencing a large enhancement of the nonlinear interaction efficiency, suffers from strong bandwidth constraints, preventing its practical exploitation for processing broad-band signals. Here we show that such limits are overcome by the new concept of travelling-wave resonant four-wave mixing (FWM). This approach combines the efficiency enhancement provided by resonant propagation with a wide-band conversion process. Compared with conventional FWM in bare waveguides, it exhibits higher robustness against chromatic dispersion and propagation loss, while preserving transparency to modulation formats. Travelling-wave resonant FWM has been demonstrated in silicon-coupled ring resonators and was exploited to realize a 630-?m-long wavelength converter operating over a wavelength range wider than 60 nm and with 28-dB gain with respect to a bare waveguide of the same physical length. Full compatibility of the travelling-wave resonant FWM with optical signal processing applications has been demonstrated through signal retiming and reshaping at 10 Gb s?1 PMID:21540838

  15. Morphological changes of short-wavelength cones in the developing S334ter-3 Transgenic rat

    PubMed Central

    Hombrebueno, Jose R.; Tsai, Melody M.; Kim, Hong-Lim; De Juan, Joaquin; Grzywacz, Norberto M.; Lee, Eun-Jin

    2010-01-01

    The S334ter-3 rat is a transgenic model of retinal degeneration (RD) developed to express a rhodopsin mutation similar to that found in human retinitis pigmentosa. Due to this advantage over other models of RD, a few retina transplant studies have been reported on this animal model. Currently, no information is available on cone photoreceptor changes that occur in the S334ter RD model. In this study, we investigated the effect of RD on the morphology, distribution, and synaptic connectivity of short-wavelength cones (S-cones) during development of S334ter-3 rat retinas. At P21 RD retinas, the outer-nuclear layer was significantly narrower, while S-cones showed shortening of their segments and axons compared to control retinas. From P90 onward, S-opsin-immunoreactive cells appeared at the outer margin of the inner-nuclear layer of RD retinas. Double-labelling experiments showed these cells contained recoverin and cone arrestin. Furthermore, ultra-structure study showed that synaptic ribbons are conserved in the S-cone at P180 RD retinas. Although cell density of S-cones significantly dropped after P90, survival rates depended on the retinal region. Overall, the S334ter-3 RD model shows hallmarks of cone remodelling due to photoreceptor degeneration. PMID:20114037

  16. Short-wavelength ablation of polymers in the high-fluence regime

    NASA Astrophysics Data System (ADS)

    Liberatore, Chiara; Mann, Klaus; Müller, Matthias; Pina, Ladislav; Juha, Libor; Vyšín, Ludek; Rocca, Jorge J.; Endo, Akira; Mocek, Tomas

    2014-05-01

    Short-wavelength ablation of poly(1,4-phenylene ether-ether-sulfone) (PPEES) and poly(methyl methacrylate) (PMMA) was investigated using extreme ultraviolet (XUV) and soft x-ray (SXR) radiation from plasma-based sources. The initial experiment was performed with a 10 Hz desktop capillary-discharge XUV laser lasing at 46.9 nm. The XUV laser beam was focused onto the sample by a spherical mirror coated with a Si/Sc multilayer. The same materials were irradiated with 13.5 nm radiation emitted by plasmas produced by focusing an optical laser beam onto a xenon gas-puff target. A Schwarzschild focusing optics coated with a Mo/Si multilayer was installed at the source to achieve energy densities exceeding 0.1 J cm-2 in the tight focus. The existing experimental system at the Laser Laboratorium Göttingen was upgraded by implementing a 1.2 J driving laser. An increase of the SXR fluence was secured by improving the alignment technique.

  17. Large-amplitude plasma wave generation with a high-intensity short-pulse beat wave.

    PubMed

    Walton, B; Najmudin, Z; Wei, M S; Marle, C; Kingham, R J; Krushelnick, K; Dangor, A E; Clarke, R J; Poulter, M J; Hernandez-Gomez, C; Hawkes, S; Neely, D; Collier, J L; Danson, C N; Fritzler, S; Malka, V

    2002-12-15

    A short-pulse laser beat wave scheme for advanced particle accelerator applications is examined. A short, intense (3-ps, >10(18)-W cm(-2)) two-frequency laser pulse is produced by use of a modified chirped-pulse amplification scheme and is shown to produce relativistic plasma waves during interactions with low-density plasmas. The generation of plasma waves was observed by measurement of forward Raman scattering. Resonance was found to occur at an electron density many times that expected, owing to ponderomotive displacement of plasma within the focal region. PMID:18033483

  18. Millimeter waves for short-range multimedia communication systems

    Microsoft Academic Search

    ORESTE ANDRISANO; VELIO TRALLI; ROBERTO VERDONE

    1998-01-01

    A framework for the performance characterization of short-range communications systems is developed with the intention of investigating the feasibility of new multimedia wireless services at millimeter waves (MMWs). Both narrow- and wide-band systems are considered for mobile and\\/or fixed users. This paper aims at defining and evaluating proper metrics to characterize the service quality for the user and jointly takes

  19. Wavelength conversion, time demultiplexing and multicasting based on cross-phase modulation and four-wave mixing in dispersion-flattened highly nonlinear photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Hui, Zhan-Qiang; Zhang, Jian-Guo

    2012-05-01

    We propose the use of cross-phase modulation (XPM) and four-wave mixing (FWM) in dispersion-flattened highly nonlinear photonic crystal fibers (HNL-PCFs) to implement the functionalities of wavelength conversion, simultaneous time demultiplexing and wavelength multicasting in optical time-division multiplexing (OTDM) systems. The experiments on wavelength conversion at 80 Gbit s-1and OTDM demultiplexing from 80 to 10 Gbit s-1 with wavelength multicasting of two channels are successfully demonstrated to validate the proposed scheme, which are carried out by using two segments of dispersion-flattened HNL-PCFs with lengths of 100 and 50 m, respectively. Moreover, the bit error rate (BER) performance is also measured. The results show that our designed system can achieve a power penalty of less than 4.6 dB for two multicasting channels with a 24 nm wavelength span at the BER of 10-9 when compared with the 10 Gbit/s back-to-back measurement. The proposed system is transparent to bit rate since only an ultrafast third-order nonlinear effect is used. The resulting configuration is compact, robust and reliable, benefiting from the use of dispersion-flattened HNL-PCFs with short lengths. This also makes the proposed system more flexible in the operational wavelengths than those based on dispersion-shifted fibers and traditional highly nonlinear fibers. The work was supported in part by the CAS/SAFEA International Partnership Program for Creative Research Teams.

  20. Polarization independent wavelength conversion using fiber four-wave mixing with two orthogonal pump lights of different frequencies

    Microsoft Academic Search

    Kyo Inoue

    1994-01-01

    This paper describes polarization independent wavelength conversion, utilizing fiber four-wave mixing. By using two orthogonal pump lights having different frequencies, the baseband signal of the wavelength converted light is insensitive to the polarization state of the original signal light. Experiments that include bit error measurements confirm the polarization independent operation

  1. Experimental observation of long-wavelength dispersive wave generation induced by self-defocusing nonlinearity in BBO crystal

    E-print Network

    Zhou, Binbin

    2015-01-01

    We experimentally observe long-wavelength dispersive waves generation in a BBO crystal. A soliton was formed in normal GVD regime of the crystal by a self-defocusing and negative nonlinearity through phase-mismatched quatradic interaction. Strong temporal pulse compression confirmed the formation of soliton during the pulse propagation inside the crystal. Significant dispersive wave radiation was measured in the anomalous GVD regime of the BBO crystal. With the pump wavelengths from 1.24 to 1.4 $\\mu$m, tunable dispersive waves are generated around 1.9 to 2.2 $\\mu$m. The observed dispersive wave generation is well understood by simulations.

  2. Wavelength and temperature dependence of continuous-wave laser absorptance in Kapton thin films

    NASA Astrophysics Data System (ADS)

    Palm, William J.; Marciniak, Michael A.; Perram, Glen P.; Gross, Kevin C.; Bailey, William F.; Walters, Craig T.

    2012-12-01

    Optical properties and laser damage characteristics of thin-film aluminized Kapton were investigated. Spectral absorptance of virgin and irradiated samples was measured from the Kapton side of multilayered insulation over 0.2 to 15 ?m wavelengths at both room temperature and 150°C. The laser-damage parameters of penetration time and maximum temperature were then measured in a vacuum environment at laser wavelengths of 1.07 and 10.6 ?m. Differences in damage behavior at these two wavelengths were observed due to differences in starting absorption properties at these wavelengths. During laser irradiation, the Kapton thin film was observed with a calibrated FLIR thermal imager in the 8 to 9.2 ?m band to determine its temperature evolution. Spectral radiance throughout the mid- and long-wave infrared was also observed with a Fourier transform spectrometer, allowing temperature-dependent spectral emittance to be determined. Kapton emittance increased after the material heated past approximately 500°C, and continued to increase as it cooled posttest. This evolving temperature-dependent spectral emittance successfully predicts the increasing absorptance that led to shortened penetration times and increased heating rates for the 1.07 ?m laser. For tests with constant absorptance and no material breakdown, a simplified one-dimensional thermal conduction and radiation model successfully predicts the temporally evolving temperature.

  3. Wavelength Conversion Based on Raman and Non-Resonant Four-Wave Mixing in Silicon Nanowire Rings Without Dispersion Engineering

    Microsoft Academic Search

    Nathalie Vermeulen; John E. Sipe; Yannick Lefevre; Christof Debaes; Hugo Thienpont

    2011-01-01

    We propose an efficient wavelength conversion scheme that is based on either Raman-resonant four-wave mix- ing or non-resonant Kerr-induced four-wave mixing in a silicon nanowire ring, and that does not require dispersion engineering of the nanowire. We rely on the spatial variation of the Raman and Kerr susceptibilities around the ring to quasi-phase match the wavelength conversion processes for TE

  4. Wavelength Switchable Semiconductor Laser Based on Half-Wave Coupled Fabry–Pérot and Rectangular Ring Resonators

    Microsoft Academic Search

    Lin Wu; Yin Wang; Tingting Yu; Lei Wang; Jian-Jun He

    2012-01-01

    A wavelength switchable semiconductor laser based on half-wave coupled Fabry–Pérot and rectangular ring resonators is proposed and demonstrated. The device consists of all-active waveguides to facilitate the fabrication. The cavity lengths are designed with a small difference to employ the Vernier effect to obtain large wavelength tuning. A half-wave coupler is used to produce a phase-dependent loss, thus achieving a

  5. Modulation and kinematics of mechanically-generated short gravity waves riding on long waves

    E-print Network

    Spell, Charles Anthony

    1992-01-01

    -measuring gauge, and a laser Doppler anemometer (LDA). Both the short and long waves are mechanically generated, thus allowing a high degree of control and repeatability in the absence of wind effects and wave breaking. The envelope of the modulated short... aid and information on data ac- quisition and analysis, and David Panak and Professor Robert E. DeOtte for their assistance with the laser Doppler anemometer. Special thanks to my colleagues in this research, K. Hong, M. Ye, L. Chen, and K...

  6. Spin-(flavor) precession and short wavelength vacuum oscillation as a solution for the solar neutrino puzzle

    SciTech Connect

    Mohapatra, P.K. (Physics Dept., C.B. 390, Univ. of Colorado, Boulder, CO (US))

    1991-12-07

    This paper investigates the possibility of spin-(flavor) precession combined with short wavelength vacuum oscillation as a solution for the solar neutrino puzzle. A large frozen-in magnetic field inside the sun with a neutrino magnetic moment of the order of 10{sup {minus}10} Bohr magneton can completely depolarize the {nu}{sub eL} resulting in a factor of half of the emitted number. With a short wavelength vacuum oscillation and maximal mixing, the number of {nu}{sub eL}'s reaching the earth is reduced by another factor of half; this explains the Homestake chlorine experiment. The difference between the Homestake and the Kamiokande-II experiments can be attributed to the contribution to the Cherenkov radiation in the latter through the neutral current and electromagnetic interactions of the components which are inert in the former.

  7. Simultaneous wavelength conversion of ASK and DPSK signals based on four-wave-mixing in dispersion engineered silicon waveguides.

    PubMed

    Xu, Lin; Ophir, Noam; Menard, Michael; Lau, Ryan Kin Wah; Turner-Foster, Amy C; Foster, Mark A; Lipson, Michal; Gaeta, Alexander L; Bergman, Keren

    2011-06-20

    We experimentally demonstrate four-wave-mixing (FWM)-based continuous wavelength conversion of optical differential-phase-shift-keyed (DPSK) signals with large wavelength conversion ranges as well as simultaneous wavelength conversion of dual-wavelength channels with mixed modulation formats in 1.1-cm-long dispersion-engineered silicon waveguides. We first validate up to 100-nm wavelength conversion range for 10-Gb/s DPSK signals, showcasing the capability to perform phase-preserving operations at high bit rates in chip-scale devices over wide conversion ranges. We further validate the wavelength conversion of dual-wavelength channels modulated with 10-Gb/s packetized phase-shift-keyed (PSK) and amplitude-shift-keyed (ASK) signals; demonstrate simultaneous operation on multiple channels with mixed formats in chip-scale devices. For both configurations, we measure the spectral and temporal responses and evaluate the performances using bit-error-rate (BER) measurements. PMID:21716454

  8. Determination of front surface recombination velocity of silicon solar cells using the short-wavelength spectral response

    Microsoft Academic Search

    A. K. Sharma; S. K. Agarwal; S. N. Singh

    2007-01-01

    A method of determination of recombination velocity Sf of minority carriers at the front surface of an n+–p–p+(p+–n–n+) silicon solar cell in which the n+(p+) front emitter is made by diffusion of dopant impurity in the p(n) region is presented. This method uses the short-wavelength spectral response of the cell to determine Sf and is applicable if the front emitter

  9. Latent Period and Antigenicity of Murine Tumors Induced in C3H Mice by Short-Wavelength Ultraviolet Radiation

    Microsoft Academic Search

    Patsy H. Lill

    1983-01-01

    Skin tumors were induced in C3H\\/HeNCr1BR mice with chronic short-wavelength ultraviolet (UVC) irradiation using a germicidal lamp (254 nm). Fifty percent of mice had developed tumors by 9 1\\/2 months (range 8–12 months). With progressive irradiation, mice developed multiple tumors on the back reaching a mean of 2.9 tumors\\/mouse at 11 1\\/2 months. No tumors developed on the ears. Of

  10. Improvement of quantum efficiency at short wavelengths in a high-low junction emitter silicon solar cells made by diffusion

    Microsoft Academic Search

    Feng Sheng Zhang; Shu Chun Hu; Xuan Huang; Xian Gang Zhu; Shen Jun Zhang

    1985-01-01

    A new simple diffusion process was developed to form a high-low junction emitter silicon p(+)\\/p\\/n solar cell for improved quantum efficiency at short wavelengths. This solar cell offers a significantly improved UV and blue efficiency in comparison with conventional silicon solar cells. Experimental results show that the new cell offers an internal quantum efficiency of more than 80 percent at

  11. Results of testing short wavelength HgCdTe hybrid focal plane arrays for earth remote sensing applications

    Microsoft Academic Search

    M. A. Blessinger; M. Herring

    1984-01-01

    The NASA Imaging Spectrometer program has the objective to develop the next generation of earth remote sensing systems. One part of the program is concerned with the production of advanced short-wavelength mercury cadmium telluride (HgCdTe) hybrid focal plane arrays (FPAs). These arrays are needed for several instruments, including the Shuttle Imaging Spectrometer (SIS), which requires a mosaic of six 64

  12. Measurements for enhanced bandwidth performance over 62.5-?m multimode fiber in short-wavelength local area networks

    Microsoft Academic Search

    J. B. Schlager; Michael J. Hackert; Petar Pepeljugoski; J. Gwinn

    2003-01-01

    The Telecommunications Industry Association (TIA) FO-2.2.1 Working Group on the modal dependence of bandwidth has conducted industrywide interlaboratory comparisons on measurements aimed at improving the bandwidth performance of short-wavelength, laser-based, multimode-fiber local area networks (LANs). Measurements of both transceiver encircled flux and fiber restricted-mode-launch bandwidth can together successfully predict an enhanced system performance, provided that the proper limiting criteria are

  13. Photonic crystal fibre enables short-wavelength two-photon laser scanning fluorescence microscopy with fura-2

    Microsoft Academic Search

    Gail McConnell; Erling Riis

    2004-01-01

    We report on a novel and compact reliable laser source capable of short-wavelength two-photon laser scanning fluorescence microscopy based on soliton self-frequency shift effects in photonic crystal fibre. We demonstrate the function of the system by performing two-photon microscopy of smooth muscle cells and cardiac myocytes from the rat pulmonary vein and Chinese hamster ovary cells loaded with the fluorescent

  14. First Demonstration of the Echo-Enabled Harmonic Generation Technique for Short-Wavelength Seeded Free Electron Lasers

    SciTech Connect

    Xiang, D.; Colby, E.; Dunning, M.; Gilevich, S.; Hast, C.; Jobe, K.; McCormick, D.; Nelson, J.; Raubenheimer, T.O.; Soong, K.; Stupakov, G.; Szalata, Z.; Walz, D.; Weathersby, S.; Woodley, M.; /SLAC; Pernet, P.-L.; /Ecole Polytechnique, Lausanne

    2010-08-25

    We report the first experimental demonstration of the echo-enabled harmonic generation (EEHG) technique which holds great promise for generation of high power, fully coherent short-wavelength radiation. In this experiment, coherent radiation at the 3rd and 4th harmonic of the second seed laser is generated from the so-called beam echo effect. The experiment confirms the physics behind this technique and paves the way for applying the EEHG technique for seeded x-ray free electron lasers.

  15. Effective suppression of stray light in rotational coherent anti-stokes Raman spectroscopy using an angle-tuned short-wave-pass filter.

    PubMed

    Bohlin, Alexis; Bengtsson, Per-Erik

    2010-08-01

    Stray light interference is a common problem in spontaneous rotational Raman spectroscopy and rotational coherent anti-Stokes Raman spectropscopy (CARS). The reason is that the detected spectrum appears in the spectral vicinity of the probe beam wavelength, and stray light at this wavelength from optics and surfaces is hard to suppress. In this Note, efficient suppression of stray light is demonstrated for rotational CARS measurements using a commercially available short-wave-pass filter. By angle-tuning this filter with a specified cut-off wavelength at 561 nm, the cut-off wavelength could be tuned to a desired spectral position so that more than 80% transmission is achieved as close as 15 cm(-1) (approximately 0.4 nm) from the probe beam wavelength of 532.0 nm, while the intensity at this wavelength is suppressed by two orders of magnitude. PMID:20719063

  16. Retrieval of short ocean wave slope using polarimetric imaging

    NASA Astrophysics Data System (ADS)

    Zappa, Christopher J.; Banner, Michael L.; Schultz, Howard; Corrada-Emmanuel, Andres; Wolff, Lawrence B.; Yalcin, Jacob

    2008-05-01

    We present a passive optical remote sensing technique for recovering shape information about a water surface, in the form of a two-dimensional slope map. The method, known as polarimetric slope sensing (PSS), uses the relationship between surface orientation and the change in polarization of reflected light to infer the instantaneous two-dimensional slope across the field-of-view of an imaging polarimeter. For unpolarized skylight, the polarization orientation and degree of linear polarization of the reflected skylight provide sufficient information to determine the local surface slope vectors. A controlled laboratory experiment was carried out in a wave tank with mechanically generated gravity waves. A second study was performed from a pier on the Hudson River, near Lamont-Doherty Earth Observatory. We demonstrated that the two-dimensional slope field of short gravity waves could be recovered accurately without interfering with the fluid dynamics of the air or water, and water surface features appear remarkably realistic. The combined field and laboratory results demonstrate that the polarimetric camera gives a robust characterization of the fine-scale surface wave features that are intrinsic to wind-driven air-sea interaction processes.

  17. Spoof four-wave mixing for all-optical wavelength conversion.

    PubMed

    Gong, Yongkang; Huang, Jungang; Li, Kang; Copner, Nigel; Martinez, J J; Wang, Leirang; Duan, Tao; Zhang, Wenfu; Loh, W H

    2012-10-01

    We present for the first time an all-optical wavelength conversion (AOWC) scheme supporting modulation format independency without requiring phase matching. The new scheme is named "spoof" four wave mixing (SFWM) and in contrast to the well-known FWM theory, where the induced dynamic refractive index grating modulates photons to create a wave at a new frequency, the SFWM is different in that the dynamic refractive index grating is generated in a nonlinear Bragg Grating (BG) to excite additional reflective peaks at either side of the original BG bandgap in reflection spectrum. This fundamental difference enable the SFWM to avoid the intrinsic shortcoming of stringent phase matching required in the conventional FWM, and allows AOWC with modulation format transparency and ultrabroad conversion range, which may have great potential applications for next generation of all-optical networks. PMID:23188370

  18. Electron density distribution of Ba1-xKxBiO3 (x = 0.43) by ultra-short-wavelength x-ray diffraction

    NASA Astrophysics Data System (ADS)

    Takahashi, Yasuhiko; Ji, Xioali; Nishio, Taichiro; Uwe, Hiromoto; Ohshima, Ken-ichi

    2002-06-01

    The crystal structure and electron density distribution (EDD) of superconducting Ba0.57K0.43BiO3 have been studied by the maximum-entropy method using ultra-short-wavelength x-ray diffraction data for a single crystal at 295 and 108 K. It is found that the bonding between the Bi and O atoms is covalent, though there is no overlapping of electron density between (Ba, K) and O atoms. The EDD around O atoms shows spatial anisotropy and the result is in agreement with anisotropic thermal motion of O atoms. No peculiar change of chemical bonding nature appears, comparing the EDD at 295 K with that at 108 K. The calculated EDD for cubic BaBiO3 using the first-principles full-potential linearized augmented plane-wave method is compared with the experimental EDD for Ba0.57K0.43BiO3.

  19. Effect of nonlinear optical three-wave interaction on the lasing parameters of a dual-wavelength vertical-external-cavity surface-emitting laser

    SciTech Connect

    Morozov, M Yu; Morozov, Yu A [Kotel'nikov Institute of Radio Engineering and Electronics, Russian Academy of Sciences, Saratov Branch, Saratov (Russian Federation); Krasnikova, I V [Yu A Gagarin Saratov State Technical University, Saratov (Russian Federation)

    2013-09-30

    The influence of nonlinear optical interaction in a semiconductor dual-wavelength vertical-external-cavity surface-emitting laser on the main parameters of dual-wavelength radiation and lasing in the long-wavelength part of the mid-IR range, obtained in this laser as a result of nonlinear wave mixing, is investigated. An increase in the pump power leads to saturation of the short-wavelength lasing intensity and to a more rapid rise in the long-wavelength lasing intensity in comparison with the linear increase in lasing intensity in these regions in the absence of nonlinear interaction. Under the conditions of nonlinear interaction, the carrier concentration in the active layers is not stabilised near the lasing threshold but changes with an increase in the pump intensity and provides the corresponding gain in the laser active region, thus maintaining steadystate lasing. Some ways for modifying the laser active region in order to obtain the most efficient lasing in the mid-IR range are proposed. (nonlinear optical phenomena)

  20. Internal structure of laser supported detonation waves by two-wavelength Mach-Zehnder interferometer

    SciTech Connect

    Shimamura, Kohei; Kawamura, Koichi; Fukuda, Akio; Wang Bin; Yamaguchi, Toshikazu; Komurasaki, Kimiya [Department of Advanced Energy, University of Tokyo, 5-1-5 Kashiwa-no-ha, Kashiwa, Chiba 277-8561 (Japan); Hatai, Keigo; Fukui, Akihiro; Arakawa, Yoshihiro [Department of Aeronautics and Astronautics, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan)

    2011-04-15

    Characteristics of the internal structure of the laser supported detonation (LSD) waves, such as the electron density n{sub e} and the electron temperature T{sub e} profiles behind the shock wave were measured using a two-wavelength Mach-Zehnder interferometer along with emission spectroscopy. A TEA CO{sub 2} laser with energy of 10 J/pulse produced explosive laser heating in atmospheric air. Results show that the peak values of n{sub e} and T{sub e} were, respectively, about 2 x 10{sup 24} m{sup -3} and 30 000 K, during the LSD regime. The temporal variation of the laser absorption coefficient profile estimated from the measured properties reveals that the laser energy was absorbed perfectly in a thin layer behind the shock wave during the LSD regime, as predicted by Raizer's LSD model. However, the absorption layer was much thinner than a plasma layer, the situation of which was not considered in Raizer's model. The measured n{sub e} at the shock front was not zero while the LSD was supported, which implies that the precursor electrons exist ahead of the shock wave.

  1. Group III nitride semiconductors for short wavelength light-emitting devices

    NASA Astrophysics Data System (ADS)

    Orton, J. W.; Foxon, C. T.

    1998-01-01

    The group III nitrides (AlN, GaN and InN) represent an important trio of semiconductors because of their direct band gaps which span the range 1.95-6.2 eV, including the whole of the visible region and extending well out into the ultraviolet (UV) range. They form a complete series of ternary alloys which, in principle, makes available any band gap within this range and the fact that they also generate efficient luminescence has been the main driving force for their recent technological development. High brightness visible light-emitting diodes (LEDs) are now commercially available, a development which has transformed the market for LED-based full colour displays and which has opened the way to many other applications, such as in traffic lights and efficient low voltage, flat panel white light sources. Continuously operating UV laser diodes have also been demonstrated in the laboratory, exciting tremendous interest for high-density optical storage systems, UV lithography and projection displays. In a remarkably short space of time, the nitrides have therefore caught up with and, in some ways, surpassed the wide band gap II-VI compounds (ZnCdSSe) as materials for short wavelength optoelectronic devices. The purpose of this paper is to review these developments and to provide essential background material in the form of the structural, electronic and optical properties of the nitrides, relevant to these applications. We have been guided by the fact that the devices so far available are based on the binary compound GaN (which is relatively well developed at the present time), together with the ternary alloys AlGaN and InGaN, containing modest amounts of Al or In. We therefore concentrate, to a considerable extent, on the properties of GaN, then introduce those of the alloys as appropriate, emphasizing their use in the formation of the heterostructures employed in devices. The nitrides crystallize preferentially in the hexagonal wurtzite structure and devices have so far been based on this material so the majority of our paper is concerned with it, however, the cubic, zinc blende form is known for all three compounds, and cubic GaN has been the subject of sufficient work to merit a brief account in its own right. There is significant interest based on possible technological advantages, such as easier doping, easier cleaving (for laser facets) and easier contacting. It also appears, at present, that the cubic form gives higher electron and hole mobilities than the hexagonal form. The dominant hexagonal structure is similar to that found in a number of II-VI compounds such as CdS and they can therefore be taken as role models. In particular, the lower symmetry gives rise to three separate valence bands at the zone centre and exciton spectra associated with each of these have been reported by many workers for GaN. Interpretation is complicated by the presence of strain in many samples due to the fact that most material consists of epitaxial thin films grown on non-lattice-matched substrates (bulk GaN crystals not being widely available). However, much progress has been made in understanding the physics of these films and we discuss the current position with regard to band gaps, effective masses, exciton binding energies, phonon energies, dielectric constants, etc. Apart from a lack of knowledge of the anticipated valence band anisotropy, it can be said that GaN is now rather well documented. Less detail is available for AlN or InN and we make no attempt to provide similar data for them. The structure of the paper is based on a historical introduction, followed by a brief account of the various crystal growth methods used to produce bulk GaN and epitaxial films of GaN and the ternary alloys. This is then followed by an account of the structural properties of hexagonal GaN as measured by x-ray diffraction and electron microscopy, phonon properties from infrared and Raman spectroscopy, electrical properties, with emphasis on n- and p-type doping, and optical properties, measured mainly by photoluminescence. A brief comparative acco

  2. Higher-order statistical analysis of short wind wave fields Guillemette Caulliez1

    E-print Network

    Higher-order statistical analysis of short wind wave fields Guillemette Caulliez1 and Charles: Caulliez, G., and C.-A. Guérin (2012), Higher-order statistical analysis of short wind wave fields, J al., 2010, 2011]. [4] Very little is actually known about the higher-order statistics of short wind

  3. Radiation force on a compressible cylinder in a standing wave: Long-wavelength approximation

    NASA Astrophysics Data System (ADS)

    Wei, Wei; Thiessen, David B.; Marston, Philip L.

    2003-10-01

    For situations where compressible cylinders are manipulated using acoustic standing waves, it is desirable to have a simple long wavelength approximation of the radiation force analogous to the sphere result published by Yosioka and Kawasima in 1955. That result has also been derived from the Rayleigh scattering approximation of the monopole and dipole scattering contributions. The analogous result for a rigid-movable cylinder (that may have a different density than the surroundings) was given by the first line of Eq. (24) of Wu et al. [J. Wu, G. Du, S. S. Work, and D. M. Warshaw, J. Acoust. Soc. Am. 87, 581-586 (1990)]. The cylinders axis is parallel to the standing wave nodal planes. To generalize that result to a compressible cylinder it is only necessary to replace a monopole term [the final unity term in the curly brackets in the first line of Eq. (24)] by (l-R) where R denotes the ratio of the adiabatic compressibility of the inner fluid to that of the outer fluid. This modification agrees with the form of the monopole scattering contribution for cylinders in the Rayleigh approximation and recovers numerically the low frequency limit for the radiation force-per-length based on the full partial-wave series. [Work supported by NASA.

  4. Scaling of Ne-like x-ray laser schemes to short wavelength

    SciTech Connect

    Rosen, M.D.; London, R.A.; Hagelstein, P.L.

    1988-03-01

    The driver and target parameters required to extend the successful results from an exploding foil Ne-like-Se soft x-ray laser at 206 A towards wavelengths of 40 A are investigated. The power requirements are found to scale as lambda/sup -4/, which is quite costly. The principal constraint is the refraction of the x-ray laser beam in these high density, single pass, exploding foil targets. Correcting mirrors or nonrefracting target designs could reduce this costly scaling.

  5. Demonstration of the Echo-Enabled Harmonic Generation Technique for Short-Wavelength Seeded Free Electron Lasers

    SciTech Connect

    Xiang, D.; Colby, E.; Dunning, M.; Gilevich, S.; Hast, C.; Jobe, K.; McCormick, D.; Nelson, J.; Raubenheimer, T. O.; Soong, K.; Stupakov, G.; Szalata, Z.; Walz, D.; Weathersby, S.; Woodley, M.; Pernet, P.-L. [SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Ecole Polytechnique Federale de Lausanne, Lausanne (Switzerland)

    2010-09-10

    We report the first experimental demonstration of the echo-enabled harmonic generation technique, which holds great promise for generation of high-power, fully coherent short-wavelength radiation. In this experiment, coherent radiation at the 3rd and 4th harmonics of the second seed laser is generated from the so-called beam echo effect. The experiment confirms the physics behind this technique and paves the way for applying the echo-enabled harmonic generation technique for seeded x-ray free electron lasers.

  6. Short-wavelength soft-x-ray laser pumped in double-pulse single-beam non-normal incidence

    SciTech Connect

    Zimmer, D. [LASERIX-CLUPS, LPGP UMR 8578, Universite Paris-Sud 11, F-91405 Orsay (France); GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Institut fuer Physik, Johannes Gutenberg-Universitaet Mainz, D-55099 Mainz (Germany); Ros, D.; Guilbaud, O.; Habib, J.; Kazamias, S. [LASERIX-CLUPS, LPGP UMR 8578, Universite Paris-Sud 11, F-91405 Orsay (France); Zielbauer, B. [LASERIX-CLUPS, LPGP UMR 8578, Universite Paris-Sud 11, F-91405 Orsay (France); GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Helmholtz Institut Jena, Friedrich-Schiller Universitaet, D-07743 Jena (Germany); Bagnoud, V. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Helmholtz Institut Jena, Friedrich-Schiller Universitaet, D-07743 Jena (Germany); Ecker, B.; Aurand, B.; Kuehl, T. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Institut fuer Physik, Johannes Gutenberg-Universitaet Mainz, D-55099 Mainz (Germany); Helmholtz Institut Jena, Friedrich-Schiller Universitaet, D-07743 Jena (Germany); Hochhaus, D. C.; Neumayer, P. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum fuer Schwerionenforschung, D-64291 Darmstadt (Germany); Institut fuer Angewandte Physik, Goethe-Universitaet Frankfurt am Main, D-60438 Frankfurt am Main (Germany)

    2010-07-15

    We demonstrated a 7.36 nm Ni-like samarium soft-x-ray laser, pumped by 36 J of a neodymium:glass chirped-pulse amplification laser. Double-pulse single-beam non-normal-incidence pumping was applied for efficient soft-x-ray laser generation. In this case, the applied technique included a single-optic focusing geometry for large beam diameters, a single-pass grating compressor, traveling-wave tuning capability, and an optimized high-energy laser double pulse. This scheme has the potential for even shorter-wavelength soft-x-ray laser pumping.

  7. Mid-frequency sound propagation through internal waves at short range with

    E-print Network

    Mid-frequency sound propagation through internal waves at short range with synoptic oceanographic, during, and after the passage of a nonlinear internal wave on 18 August, 2006. Using oceanographic data collected at a nearby location, a plane-wave model for the nonlinear internal wave's posi- tion

  8. Conductors, semiconductors, and insulators irradiated with short-wavelength free-electron laser

    SciTech Connect

    Krzywinski, J.; Sobierajski, R; Jurek, M.; Nietubyc, R.; Pelka, J. B.; Juha, L.; Bittner, M.; Letal, V.; Vorlicek, V.; Andrejczuk, A.; Feldhaus, J.; Keitel, B.; Saldin, E. L.; Schneidmiller, E. A.; Treusch, R.; Yurkov, M. V. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, PL-02-668 Warsaw (Poland); Soltan Institute for Nuclear Studies, PL-05-400 Swierk (Poland); Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, PL-02-668 Warsaw (Poland); Institute of Physics, Czech Academy of Sciences, Na Slovance 2, 182 21 Prague 8 (Czech Republic); Institute of Experimental Physics, University of Bialystok, Lipowa 41, PL-15-424 Bialystok (Poland); Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22603 Hamburg (Germany)

    2007-02-15

    The results of a study of irreversible changes induced at surfaces of metals, semiconductors, and insulators by extreme ultraviolet ({lambda}<100 nm) ultrashort pulses provided by TESLA Test Facility Free-Electron Laser, Phase 1 (TTF1 FEL) are reported and discussed. The laser was tuned at 86, 89, and 98 nm during the experiments reported here. Energy spectra of ions ejected from the irradiated surfaces are also reported. Special attention is paid to the difference in the ablation behavior of (semi)conductors and insulators that we have observed. The difference is dramatic, while the absorption coefficients are similar for all materials at the TTF1 FEL wavelength.

  9. Mixed solitons in a (2+1)-dimensional multicomponent long-wave-short-wave system.

    PubMed

    Kanna, T; Vijayajayanthi, M; Lakshmanan, M

    2014-10-01

    We derive a (2+1)-dimensional multicomponent long-wave-short-wave resonance interaction (LSRI) system as the evolution equation for propagation of N-dispersive waves in weak Kerr-type nonlinear medium in the small-amplitude limit. The mixed- (bright-dark) type soliton solutions of a particular (2+1)-dimensional multicomponent LSRI system, deduced from the general multicomponent higher-dimensional LSRI system, are obtained by applying the Hirota's bilinearization method. Particularly, we show that the solitons in the LSRI system with two short-wave components behave like scalar solitons. We point out that for an N-component LSRI system with N>3, if the bright solitons appear in at least two components, interesting collision behavior takes place, resulting in energy exchange among the bright solitons. However, the dark solitons undergo standard elastic collision accompanied by a position shift and a phase shift. Our analysis on the mixed bound solitons shows that the additional degree of freedom which arises due to the higher-dimensional nature of the system results in a wide range of parameters for which the soliton collision can take place. PMID:25375561

  10. Mixed solitons in a (2+1)-dimensional multicomponent long-wave-short-wave system

    NASA Astrophysics Data System (ADS)

    Kanna, T.; Vijayajayanthi, M.; Lakshmanan, M.

    2014-10-01

    We derive a (2+1)-dimensional multicomponent long-wave-short-wave resonance interaction (LSRI) system as the evolution equation for propagation of N-dispersive waves in weak Kerr-type nonlinear medium in the small-amplitude limit. The mixed- (bright-dark) type soliton solutions of a particular (2+1)-dimensional multicomponent LSRI system, deduced from the general multicomponent higher-dimensional LSRI system, are obtained by applying the Hirota's bilinearization method. Particularly, we show that the solitons in the LSRI system with two short-wave components behave like scalar solitons. We point out that for an N-component LSRI system with N >3, if the bright solitons appear in at least two components, interesting collision behavior takes place, resulting in energy exchange among the bright solitons. However, the dark solitons undergo standard elastic collision accompanied by a position shift and a phase shift. Our analysis on the mixed bound solitons shows that the additional degree of freedom which arises due to the higher-dimensional nature of the system results in a wide range of parameters for which the soliton collision can take place.

  11. Monitoring quality loss of pasteurized skim milk using visible and short wavelength near-infrared spectroscopy and multivariate analysis.

    PubMed

    Al-Qadiri, H M; Lin, M; Al-Holy, M A; Cavinato, A G; Rasco, B A

    2008-03-01

    Visible and short wavelength near-infrared diffuse reflectance spectroscopy (600 to 1,100 nm) was evaluated as a technique for detecting and monitoring spoilage of pasteurized skim milk at 3 storage temperatures (6, 21, and 37 degrees C) over 3 to 30 h (control, t = 0 h; n = 3). Spectra, total aerobic plate count, and pH were obtained, with a total of 60 spectra acquired per sample. Multivariate statistical procedures, including principal component analysis, soft independent modeling of class analogy, and partial least squares calibration models were developed for predicting the degree of milk spoilage. Principal component analysis showed apparent clustering and segregation of milk samples that were stored at different time intervals. Milk samples that were stored for 30 h or less at different temperatures were noticeably separated from control and distinctly clustered. Soft independent modeling of class analogy analysis could correctly classify 88 to 93% of spectra of incubated samples from control at 30 h. A partial least squares model with 5 latent variables correlating spectral features with bacterial counts and pH yielded a correlation coefficient (R = 0.99 and 0.99) and a standard error of prediction (0.34 log(10) cfu/mL and 0.031 pH unit), respectively. It may be feasible to use short wavelength near-infrared spectroscopy to detect and monitor milk spoilage rapidly and noninvasively by correlating changes in spectral features with the level of bacterial proliferation and milk spoilage. PMID:18292250

  12. Short-wavelength infrared (1.3-2.6 ?m) observations of the nucleus of Comet 19P/Borrelly

    USGS Publications Warehouse

    Soderblom, L.A.; Britt, D.T.; Brown, R.H.; Buratti, B.J.; Kirk, R.L.; Owen, T.C.; Yelle, R.V.

    2004-01-01

    During the last two minutes before closest approach of Deep Space 1 to Comet 19P/Borrelly, a long exposure was made with the short-wavelength infrared (SWIR) imaging spectrometer. The observation yielded 46 spectra covering 1.3–2.6 ?m; the footprint of each spectrum was ?160 m × width of the nucleus. Borrelly's highly variegated and extremely dark 8-km-long nucleus exhibits a strong red slope in its short-wavelength infrared reflection spectrum. This slope is equivalent to J–K and H–K colors of ?0.82 and ?0.43, respectively. Between 2.3–2.6 ?m thermal emission is clearly detectable in most of the spectra. These data show the nucleus surface to be hot and dry; no trace of H2O ice was detected. The surface temperature ranged continuously across the nucleus from ?300 K near the terminator to a maximum of ?340 K, the expected sub-solar equilibrium temperature for a slowly rotating body. A single absorption band at ?2.39 ?m is quite evident in all of the spectra and resembles features seen in nitrogen-bearing organic molecules that are reasonable candidates for compositional components of cometary nuclei. However as of yet the source of this band is unknown.

  13. A Short Wavelength GigaHertz Clocked Fiber-Optic Quantum Key Distribution System

    E-print Network

    Karen J. Gordon; Veronica Fernandez; Paul D. Townsend; Gerald S. Buller

    2006-05-26

    A quantum key distribution system has been developed, using standard telecommunications optical fiber, which is capable of operating at clock rates of greater than 1 GHz. The quantum key distribution system implements a polarization encoded version of the B92 protocol. The system employs vertical-cavity surface-emitting lasers with emission wavelengths of 850 nm as weak coherent light sources, and silicon single photon avalanche diodes as the single photon detectors. A distributed feedback laser of emission wavelength 1.3 micro-metres, and a linear gain germanium avalanche photodiode was used to optically synchronize individual photons over the standard telecommunications fiber. The quantum key distribution system exhibited a quantum bit error rate of 1.4%, and an estimated net bit rate greater than 100,000 bits-per-second for a 4.2 km transmission range. For a 10 km fiber range a quantum bit error rate of 2.1%, and estimated net bit rate of greater than 7,000 bits-per-second was achieved.

  14. Optical property of Ce3+-doped lutetium lithium fluoride for the short-wavelength device application

    NASA Astrophysics Data System (ADS)

    Shimizu, Toshihiko; Yamanoi, Kohei; Arita, Ren; Hori, Tatsuhiro; Fukuda, Kazuhito; Minami, Yuki; Cadatal-Raduban, Marilou; Sarukura, Nobuhiko; Fukuda, Tsuguo; Nagasono, Mitsuru; Ishikawa, Tetsuya

    2014-10-01

    We report on the optical properties of Ce:LLF excited by the 61-nm wavelength emission of the SPring-8 compact self amplification of spontaneous emission source (SCSS) test accelerator, which is a prototype self-amplified stimulated emission (SASE)-type free electron laser (FEL) that emits extreme ultraviolet (EUV) radiation. Ce:LLF fluorescence at 308 nm and 322 nm wavelength was observed using a streak camera. The temporal profile exhibited a 62.1-ns fast decay component and 8.63-ns slow decay component. This double exponential behavior is observed with EUV-FEL excitation and is due to the de-excitation process involving several relaxation steps because of the energetically long distance and intricate band structure between the excitation and emission states. The double exponential nature of fluorescence decay is not observable with low-energy excitation sources; hence, our results show the importance of novel light sources, such as the FEL, for the development and characterization of new materials.

  15. High sensitivity of the human circadian melatonin rhythm to resetting by short wavelength light.

    PubMed

    Lockley, Steven W; Brainard, George C; Czeisler, Charles A

    2003-09-01

    The endogenous circadian oscillator in mammals, situated in the suprachiasmatic nuclei, receives environmental photic input from specialized subsets of photoreceptive retinal ganglion cells. The human circadian pacemaker is exquisitely sensitive to ocular light exposure, even in some people who are otherwise totally blind. The magnitude of the resetting response to white light depends on the timing, intensity, duration, number and pattern of exposures. We report here that the circadian resetting response in humans, as measured by the pineal melatonin rhythm, is also wavelength dependent. Exposure to 6.5 h of monochromatic light at 460 nm induces a two-fold greater circadian phase delay than 6.5 h of 555 nm monochromatic light of equal photon density. Similarly, 460 nm monochromatic light causes twice the amount of melatonin suppression compared to 555 nm monochromatic light, and is dependent on the duration of exposure in addition to wavelength. These studies demonstrate that the peak of sensitivity of the human circadian pacemaker to light is blue-shifted relative to the three-cone visual photopic system, the sensitivity of which peaks at approximately 555 nm. Thus photopic lux, the standard unit of illuminance, is inappropriate when quantifying the photic drive required to reset the human circadian pacemaker. PMID:12970330

  16. Continuous wave-pumped wavelength conversion in low-loss silicon nitride waveguides.

    PubMed

    Krückel, Clemens J; Torres-Company, Víctor; Andrekson, Peter A; Spencer, Daryl T; Bauters, Jared F; Heck, Martijn J R; Bowers, John E

    2015-03-15

    In this Letter we introduce a complementary metal-oxide semiconductor (CMOS)-compatible low-loss Si3N4 waveguide platform for nonlinear integrated optics. The waveguide has a moderate nonlinear coefficient of 285??W/km, but the achieved propagation loss of only 0.06??dB/cm and the ability to handle high optical power facilitate an optimal waveguide length for wavelength conversion. We observe a constant quadratic dependence of the four-wave mixing (FWM) process on the continuous-wave (CW) pump when operating in the C-band, which indicates that the waveguide has negligible high-power constraints owing to nonlinear losses. We achieve a conversion efficiency of -26.1??dB and idler power generation of -19.6??dBm. With these characteristics, we present for the first time, to the best of our knowledge, CW-pumped data conversion in a non-resonant Si3N4 waveguide. PMID:25768135

  17. The traveling wave MRI in cylindrical Taylor-Couette flow: comparing wavelengths and speeds in theory and experiment

    E-print Network

    Guenther Ruediger; Rainer Hollerbach; Frank Stefani; Thomas Gundrum; Gunter Gerbeth; Robert Rosner

    2006-09-18

    We study experimentally the flow of a liquid metal confined between differentially rotating cylinders, in the presence of externally imposed axial and azimuthal magnetic fields. For increasingly large azimuthal fields a wave-like disturbance arises, traveling along the axis of the cylinders. The wavelengths and speeds of these structures, as well as the field strengths and rotation rates at which they arise, are broadly consistent with theoretical predictions of such a traveling wave magnetorotational instability.

  18. Material processing with ultra-short pulse lasers working in 2?m wavelength range

    NASA Astrophysics Data System (ADS)

    Voisiat, B.; Gaponov, D.; Ge?ys, P.; Lavoute, L.; Silva, M.; Hideur, A.; Ducros, N.; Ra?iukaitis, G.

    2015-03-01

    New wavelengths of laser radiation are of interest for material processing. Results of application of the all-fiber ultrashort pulsed laser emitting in 2 µm range, manufactured by Novae, are presented. Average output power was 4.35 W in a single-spatial-mode beam centered at the 1950 nm wavelength. Pulses duration was 40 ps, and laser operated at 4.2 MHz pulse repetition rate. This performance corresponded to 25 kW of pulse peak power and almost 1 µJ in pulse energy. Material processing was performed using three different focusing lenses (100, 30 and 18 mm) and mechanical stages for the workpiece translation. 2 µm laser radiation is strongly absorbed by some polymers. Swelling of PMMA surface was observed for scanning speed above 5 mm/s using the average power of 3.45 W focused with the 30 mm lens. When scanning speed was reduced below 4 mm/s, ablation of PMMA took place. The swelling of PMMA is a consequence of its melting due to absorbed laser power. Therefore, experiments on butt welding of PMMA and overlapping welding of PMMA with other polymers were performed. Stable joint was achieved for the butt welding of two PMMA blocks with thickness of 5 mm. The laser was used to cut a Kapton film on a paper carrier with the same set-up as previous. The cut width depended on the cutting speed and focusing optics. A perfect cut with a width of 11 µm was achieved at the translation speed of 60 mm/s.

  19. Short Wave Amplification and Extreme Runup by the 2011 Tohoku Tsunami

    NASA Astrophysics Data System (ADS)

    Shimozono, Takenori; Cui, Haiyang; Pietrzak, Julie D.; Fritz, Hermann M.; Okayasu, Akio; Hooper, Andrew J.

    2014-12-01

    Watermarks found during the post-event surveys of the 2011 Tohoku tsunami confirmed extreme runup heights at several locations along the central to northern part of the Sanriku coast, Japan. We measured the maximum height of nearly 40 m above mean sea level at a narrow coastal valley of the Aneyoshi district. Wave records by offshore GPS-buoys suggest that the remarkably high runup was associated with a leading, impulsive crest of the tsunami amplified by local bathymetry and topography. In order to elucidate the underlying amplification mechanism, we apply a numerical model to reproduce the measured distribution of tsunami heights along the target coastline. A series of numerical tests under different boundary conditions suggests that a spectral component with a dominant period of 4-5 min in the leading wave play a key role in generating the extreme runup. Further analyses focusing on the Aneyoshi district confirm that the short wavelength component undergoes critical amplification in a narrow inlet. Our findings highlight the importance of resolving offshore waveforms as well as local bathymetry and topography when simulating extreme runup events.

  20. Polarization insensitive wavelength conversion based on four-wave mixing for polarization multiplexing signal in high-nonlinear fiber

    Microsoft Academic Search

    J. Lu; Z. Dong; L. Chen; J. Yu

    2009-01-01

    We have theoretically and experimentally investigated polarization insensitive of all optical wavelength conversion for polarization multiplexing signal based on four-wave mixing (FWM) in nonlinear optical fiber. Optical polarization multiplexing technique can be used to double the transmission bit rate by adding data on each of two orthogonal optical states. At the receiver side, the two orthogonal signals can be obtained

  1. Optimal demodulation of wavelength shifts in a fiber Bragg grating sensor using an adaptive two wave mixing photorefractive interferometer

    Microsoft Academic Search

    Oluwaseyi Balogun; Goutham R. Kirikera; Sridhar Krishnaswamy

    2008-01-01

    Recent work by our research group on the dynamic demodulation of strain-induced wavelength shifts in fiber Bragg grating (FBG) sensors show that these sensors are suitable for the detection of high frequency ultrasonic waves produced by impact loading. A FBG sensor is incorporated into an optical detection system that uses a broadband tunable laser source in the C-band, a two

  2. Investigating Gait Recognition in the Short-Wave Infrared (SWIR) Spectrum: Dataset and Challenges

    E-print Network

    Ross, Arun Abraham

    Investigating Gait Recognition in the Short-Wave Infrared (SWIR) Spectrum: Dataset and Challenges piqued interest in performing gait recognition in other spectral bands such as short-wave infrared (SWIR of performing gait recognition in the SWIR spectrum by first assembling a dataset, referred to as the WVU

  3. Chemical composition of high proper-motion stars based on short-wavelength optical spectra

    NASA Astrophysics Data System (ADS)

    Klochkova, V. G.; Mishenina, T. V.; Panchuk, V. E.; Korotin, S. A.; Marsakov, V. A.; Usenko, I. A.; Tsymbal, V. V.

    2011-01-01

    The results of spectroscopic observations made with the NES echelle spectrograph of the 6-m BTA telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences in the wavelength interval of 3550-5100 Å with a spectral resolution of R?50000 are used to determine the fundamental parameters and atmospheric abundances of more than 20 chemical elements including heavy s- and r-process elements from Sr to Dy for a total of 14 metal-poor G-K-type stars. The abundances of Mg, Al, Sr, and Ba were calculated with non-LTE line-formation effects accounted for. The inferred overabundance of europium with respect to iron agrees with the results obtained for the stars of similar metallicity. The chemical composition of the star BD+80°245 located far from the Galactic plane is typical of stars of the accreted halo: this star exhibits, in addition to the over-deficiency of ?-process elements, also the over-deficiency of the ?-process element Ba: [Ba/Fe]= -1.46. The kinematical parameters and chemical composition imply that the stars studied belong to different Galactic populations. The abundance of the long-living element Th relative to that of the r-process element Eu is determined for six stars using the synthetic-spectrum method.

  4. Analysis, modeling, and design of short-wavelength laser-plasma experiments

    SciTech Connect

    Mead, W.C.; Coggeshall, S.V.; Goldman, S.R.; Stover, E.K.; Goldstone, P.D.; Hauer, A.; Kindel, J.M.; Montierth, L.

    1985-01-01

    We present analysis and LASNEX modeling of two experiments designed to explore the mechanisms and scaling of laser-plasma coupling in high-Z plasmas. The first used layered Au-on-CH spheres irradiated symmetrically using the Omega (Laboratory for Laser Energetics) 0.35 ..mu..m laser to observe the x-ray emission and energy penetration in gold plasmas. Measurements of the subkilovolt and kilovolt emission from targets with varying Au-coating thicknesses were made using diagnostics of varying spectral, temporal, and spatial resolution. The results indicate that the x-ray conversion efficiency is a function of target size, with larger targets yielding x-ray emission in excellent agreement with calculations. The x-ray emission fall-off with decreasing gold thickness agrees well with predictions. The second experiment used the Novette (Lawrence Livermore National Laboratory) laser to irradiate solid gold disk targets, examining wavelength scaling to 0.26 ..mu..m. The measured subkilovolt x-ray emission is in good agreement with calculations using mildly inhibited thermal electron transport, indicating enhanced target coupling, compared with previous experiments using smaller spot sizes. The experiment also indicates very low suprathermal electron populations, on the order of 0.1% at about 30 keV effective temperature. Finally, we present preliminary plans and designs for experiments which will use the Aurora 5 kJ, 5 ns, 0.25 ..mu..m KrF laser now being constructed at Los Alamos.

  5. Short-wavelength infrared photodetector on Si employing strain-induced growth of very tall InAs nanowire arrays

    PubMed Central

    Wook Shin, Hyun; Jun Lee, Sang; Gun Kim, Doo; Bae, Myung-Ho; Heo, Jaeyeong; Jin Choi, Kyoung; Jun Choi, Won; Choe, Jeong-woo; Cheol Shin, Jae

    2015-01-01

    One-dimensional crystal growth enables the epitaxial integration of III-V compound semiconductors onto a silicon (Si) substrate despite significant lattice mismatch. Here, we report a short-wavelength infrared (SWIR, 1.4–3??m) photodetector that employs InAs nanowires (NWs) grown on Si. The wafer-scale epitaxial InAs NWs form on the Si substrate without a metal catalyst or pattern assistance; thus, the growth is free of metal-atom-induced contaminations, and is also cost-effective. InAs NW arrays with an average height of 50??m provide excellent anti-reflective and light trapping properties over a wide wavelength range. The photodetector exhibits a peak detectivity of 1.9?×?108 ?cm·Hz1/2/W for the SWIR band at 77?K and operates at temperatures as high as 220?K. The SWIR photodetector on the Si platform demonstrated in this study is promising for future low-cost optical sensors and Si photonics. PMID:26035286

  6. Short-wavelength light beam in situ monitoring growth of InGaN/GaN green LEDs by MOCVD

    PubMed Central

    2012-01-01

    In this paper, five-period InGaN/GaN multiple quantum well green light-emitting diodes (LEDs) were grown by metal organic chemical vapor deposition with 405-nm light beam in situ monitoring system. Based on the signal of 405-nm in situ monitoring system, the related information of growth rate, indium composition and interfacial quality of each InGaN/GaN QW were obtained, and thus, the growth conditions and structural parameters were optimized to grow high-quality InGaN/GaN green LED structure. Finally, a green LED with a wavelength of 509?nm was fabricated under the optimal parameters, which was also proved by ex situ characterization such as high-resolution X-ray diffraction, photoluminescence, and electroluminescence. The results demonstrated that short-wavelength in situ monitoring system was a quick and non-destroyed tool to provide the growth information on InGaN/GaN, which would accelerate the research and development of GaN-based green LEDs. PMID:22650991

  7. Short-wavelength infrared photodetector on Si employing strain-induced growth of very tall InAs nanowire arrays.

    PubMed

    Wook Shin, Hyun; Jun Lee, Sang; Gun Kim, Doo; Bae, Myung-Ho; Heo, Jaeyeong; Jin Choi, Kyoung; Jun Choi, Won; Choe, Jeong-Woo; Cheol Shin, Jae

    2015-01-01

    One-dimensional crystal growth enables the epitaxial integration of III-V compound semiconductors onto a silicon (Si) substrate despite significant lattice mismatch. Here, we report a short-wavelength infrared (SWIR, 1.4-3??m) photodetector that employs InAs nanowires (NWs) grown on Si. The wafer-scale epitaxial InAs NWs form on the Si substrate without a metal catalyst or pattern assistance; thus, the growth is free of metal-atom-induced contaminations, and is also cost-effective. InAs NW arrays with an average height of 50??m provide excellent anti-reflective and light trapping properties over a wide wavelength range. The photodetector exhibits a peak detectivity of 1.9?×?10(8) ?cm·Hz(1/2)/W for the SWIR band at 77?K and operates at temperatures as high as 220?K. The SWIR photodetector on the Si platform demonstrated in this study is promising for future low-cost optical sensors and Si photonics. PMID:26035286

  8. Anodic fluoride passivation of type II InAs/GaSb superlattice for short-wavelength infrared detector

    NASA Astrophysics Data System (ADS)

    Zhang, Li Xue; Sun, Wei Guo; Lv, Yan Qiu; Li, Mo; Ding, Jia Xin; Si, Jun Jie

    2014-09-01

    One of the major challenges of antimonide-based devices arises owing to the large number of surface states generated during fabrication processes. Surface passivation and subsequent capping of the surfaces are absolutely essential for any practical applicability of this material system. In this paper, we proposed a new passivation method (zinc sulfide coating after anodic fluoride) for InAs/GaSb superlattice infrared detectors. InAs/GaSb superlattice short-wavelength infrared materials were grown by molecular beam epitaxy on GaSb (100) substrates. A GaSb buffer layer, which can decrease the occurrence of defects with similar pyramidal structure, was grown for optimized superlattice growth condition. High resolution X-ray diffraction indicated that the period of the superlattice corresponding to fourth satellite peak was 39.77 Å. The atomic force microscopy images show the roughness was below 1.7 nm. The result of photoresponse spectra shows that the cutoff wavelength was 3.05 ?m at 300 K.

  9. Performance Comparisons of InGaAs, extended InGaAs, and Short-wave HgCdTe Detectors between 1 µm and 2.5 µm

    Microsoft Academic Search

    Howard W. Yoon; Matt C. Dopkiss; George P. Eppeldauer

    In this study, three different detectors, regular InGaAs, short-wave infrared extended-InGaAs (exInGaAs) with the bandgap wavelength at 2.6 µm and short-wave HgCdTe (swMCT) with the bandgap wavelength at 2.8 µm are studied. The detectors have active areas of 3 mm or 1 mm diameter with all the detectors capable of being cooled from room temperatures to -85 oC with 4-stage

  10. Performance comparisons of InGaAs, extended InGaAs, and short-wave HgCdTe detectors between 1 mum and 2.5 mum

    Microsoft Academic Search

    Howard W. Yoon; Matt C. Dopkiss; George P. Eppeldauer

    2006-01-01

    In this study, three different detectors, regular InGaAs, short-wave infrared extended-InGaAs (exInGaAs) with the bandgap wavelength at 2.6 mum and short-wave HgCdTe (swMCT) with the bandgap wavelength at 2.8 mum are studied. The detectors have active areas of 3 mm or 1 mm diameter with all the detectors capable of being cooled from room temperatures to -85 °C with 4-stage

  11. Wavelength conversion based on four-wave mixing in high-nonlinear dispersion shifted fiber using a dual-pump configuration

    Microsoft Academic Search

    Jianxin Ma; Jianjun Yu; Chongxiu Yu; Zhensheng Jia; Xinzhu Sang; Zhen Zhou; Ting Wang; Gee Kung Chang

    2006-01-01

    The dual-pump all-optical wavelength conversion based on a four-wave mixing (FWM) in a high-nonlinear dispersion shifted fiber (HNL-DSF) is demonstrated experimentally. The polarization sensitivity of the wavelength converter based on this dual-pump figuration is investigated experimentally and theoretically. The experimental results indicate that the wavelength-conversion configuration with copolarization pumps shows the smallest polarization sensitivity. A model of the beating-wave modulation

  12. Short-wavelength turbulence in the solar wind: Linear theory of whistler and kinetic Alfvén fluctuations

    NASA Astrophysics Data System (ADS)

    Gary, S. Peter; Smith, Charles W.

    2009-12-01

    There is a debate as to the identity of the fluctuations which constitute the relatively high-frequency plasma turbulence observed in the solar wind. One school holds that these modes are kinetic Alfvén waves, whereas another opinion is that they are whistler modes. Here linear kinetic theory for electromagnetic fluctuations in homogeneous, collisionless, magnetized plasmas is used to compute two dimensionless transport ratios, the electron compressibility Ce and the magnetic compressibility C$\\parallel$ for these two modes. The former is a measure of the amplitude of density fluctuations, and the latter indicates the relative energy in magnetic fluctuations in the component parallel to the background magnetic field Bo. For ?e $\\ll$ 1, [C$\\parallel$]Alfven $\\ll$ [C$\\parallel$]whistler, and the latter quantity is of order 0.5 at whistler propagation strongly oblique to Bo. Such values of C$\\parallel$ are sometimes measured at relatively high frequencies and ?e $\\ll$ 1 in the solar wind; thus, it is concluded that such observations correspond to whistler mode turbulence. But other solar wind observations indicate that kinetic Alfvén fluctuations also contribute to relatively high-frequency solar wind turbulence.

  13. Three-dimensional blast-wave-driven Rayleigh-Taylor instability and the effects of long-wavelength modes

    SciTech Connect

    Kuranz, C. C.; Drake, R. P.; Grosskopf, M. J.; Budde, A.; Krauland, C.; Marion, D. C.; Visco, A. J.; Ditmar, J. R. [University of Michigan, Ann Arbor, Michigan 48109 (United States); Robey, H. F.; Remington, B. A.; Miles, A. R.; Cooper, A. B. R.; Sorce, C. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Plewa, T. [Department of Scientific Computing, Florida State University, Tallahassee, Florida 32306 (United States); Hearn, N. C. [ASC Flash Center, University of Chicago, Chicago, Illinois 60637 (United States); Killebrew, K. L. [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States); Knauer, J. P. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York (United States); Arnett, D. [Steward Observatory, University of Arizona, Tucson, Arizona 85721 (United States); Donajkowski, T. [Jet Propulsion Laboratory, Pasadena, California 91109 (United States)

    2009-05-15

    This paper describes experiments exploring the three-dimensional (3D) Rayleigh-Taylor instability at a blast-wave-driven interface. This experiment is well scaled to the He/H interface during the explosion phase of SN1987A. In the experiments, {approx}5 kJ of energy from the Omega laser was used to create a planar blast wave in a plastic disk, which is accelerated into a lower-density foam. These circumstances induce the Richtmyer-Meshkov instability and, after the shock passes the interface, the system quickly becomes dominated by the Rayleigh-Taylor instability. The plastic disk has an intentional pattern machined at the plastic/foam interface. This perturbation is 3D with a basic structure of two orthogonal sine waves with a wavelength of 71 {mu}m and an amplitude of 2.5 {mu}m. Additional long-wavelength modes with a wavelength of either 212 or 424 {mu}m are added onto the single-mode pattern. The addition of the long-wavelength modes was motivated by the results of previous experiments where material penetrated unexpectedly to the shock front, perhaps due to an unintended structure. The current experiments and simulations were performed to explore the effects of this unintended structure; however, we were unable to reproduce the previous results.

  14. Optimal demodulation of wavelength shifts in a fiber Bragg grating sensor using an adaptive two wave mixing photorefractive interferometer

    NASA Astrophysics Data System (ADS)

    Balogun, Oluwaseyi; Kirikera, Goutham R.; Krishnaswamy, Sridhar

    2008-03-01

    Recent work by our research group on the dynamic demodulation of strain-induced wavelength shifts in fiber Bragg grating (FBG) sensors show that these sensors are suitable for the detection of high frequency ultrasonic waves produced by impact loading. A FBG sensor is incorporated into an optical detection system that uses a broadband tunable laser source in the C-band, a two wave-mixing photorefractive interferometer, and a high-speed photodetector. When an ultrasonic wave interacts with the FBG sensor, the wavelength of the reflected light in the fiber is dynamically shifted due to strain-induced perturbation of the index of refraction and/or the period of the grating in the fiber. The wavelength shift is converted into an intensity change by splitting the light into signal and pump beams and interfering the beams in an InP:Fe photorefractive crystal (PRC). The resulting intensity change is measured by a photodetector. The two-wave mixing (TWM) photorefractive interferometer allows for several FBG sensors to be wavelength multiplexed in one PRC and it also actively compensates for low frequency signal drifts associated with unwanted room vibrations and temperature excursions. In this work, we present preliminary experimental results on the detection of impact signals using a low power (1 mW) TWM PRC based demodulation system. The response time of the PRC is optimized by focusing the signal and pump beams into the crystal allowing for adaptivity of the demodulation system to quasi-static strains or temperature drifts. The TWM intensity gain of the system is optimized for efficient wavelength demodulation through resonant enhancement of the space charge electric field formed in the PRC. The low power demodulation system would facilitate significant reduction in the overall cost of the system.

  15. Short wavelength heterogeneity in the Galápagos plume: Evidence from compositionally diverse basalts on Isla Santiago

    NASA Astrophysics Data System (ADS)

    Gibson, S. A.; Geist, D. G.; Day, J. A.; Dale, C. W.

    2012-09-01

    Analyses of basalts from the Galápagos archipelago and adjacent spreading center have shown that the underlying mantle plume is isotopically heterogeneous over length scales of 10s to 100s of km. We show that the convecting mantle is also compositionally heterogeneous on smaller length scales (kms). Our evidence comes from recent small-volume mildly alkaline and tholeiitic basalts on Isla Santiago, central Galápagos. Flows from volcanic vents <5 km apart are homogeneous in terms of incompatible-trace element and isotopic ratios but inter-vent variations in these ratios are large, such that Santiago basalts display some of the most extensive ranges known for any Galápagos island. Geochemical indexes of depth of melting correlate with an eastward decrease in geophysical estimates of lithospheric thickness-from 55 to 43 km over a ˜10 km horizontal distance beneath Isla Santiago-suggesting that melts have not undergone significant lateral transport in the underlying crust. This lithospheric `step' below the center of the island generally results in a greater proportion of enriched mantle melts contributing to basalts from west Santiago, than to those in the east, due to less melting of more depleted mantle as the plume upwells beneath thicker lithosphere. Nevertheless, the sporadic occurrence of isotopically enriched flows with low [Sm/Yb]n, and more isotopically depleted compositions with elevated [Sm/Yb]n, across Santiago suggests that portions of the underlying Galápagos plume are compositionally heterogeneous in terms of enriched and depleted reservoirs over short length scales (kilometers). In this respect the Galápagos mantle plume is similar to plumes beneath Hawaii and Canary Islands.

  16. Thermal scene analysis via finite element model and finite difference time domain numerical solution of the electromagnetic wave propagation in the short wave and long wave infrared bandarch

    Microsoft Academic Search

    Alessandro Albertoni

    2009-01-01

    We utilize the Finite Element Model (FEM) and Finite Difference Time Domain (FDTD) numerical solution of the Electromagnetic wave propagation in the Short Wave Infrared (SWIR) and Long Wave Infrared (LWIR) bands in order to calculate the target radiance propagation and environment attenuation due to transmission, absorption and reflections in atmosphere and obstacles. We leave to traditional minimum resolvable temperature

  17. Short-wave infrared (SWIR) spectral imager based on Fabry-Perot interferometer for remote sensing

    NASA Astrophysics Data System (ADS)

    Mannila, Rami; Holmlund, Christer; Ojanen, Harri J.; Näsilä, Antti; Saari, Heikki

    2014-10-01

    VTT Technical Research Centre of Finland has developed a spectral imager for short-wave infrared (SWIR) wavelength range. The spectral imager is based on a tunable Fabry-Perot interferometer (FPI) accompanied by a commercial InGaAs Camera. The FPI consists of two dielectric coated mirrors separated by a tunable air gap. Tuning of the air gap tunes also transmitted wavelength and therefore FPI acts as a tunable band bass filter. The FPI is piezo-actuated and it uses three piezo-actuators in a closed capacitive feedback loop for air gap tuning. The FPI has multiple order transmission bands, which limit free spectral range. Therefore spectral imager contains two FPI in a stack, to make possible to cover spectral range of 1000 - 1700 nm. However, in the first tests imager was used with one FPI and spectral range was limited to 1100-1600 nm. The spectral resolution of the imager is approximately 15 nm (FWHM). Field of view (FOV) across the flight direction is 30 deg. Imaging resolution of the spectral imager is 256 x 320 pixels. The focal length of the optics is 12 mm and F-number is 3.2. This imager was tested in summer 2014 in an unmanned aerial vehicle (UAV) and therefore a size and a mass of the imager were critical. Total mass of the imager is approximately 1200 grams. In test campaign the spectral imager will be used for forest and agricultural imaging. In future, because results of the UAV test flights are promising, this technology can be applied to satellite applications also.

  18. Hydrodynamic modulation of short wind-wave spectra by long waves and its measurement using microwave backscatter

    Microsoft Academic Search

    Tetsu Hara; William J. Plant

    1994-01-01

    In this paper we use results of microwave backscattering experiments over the past decade to attempt to present a coherent picture of the ocean wave-radar modulation transfer function (MTF) based on composite surface theory, short-wave modulation, and modulated wind stress. A simplified relaxation model is proposed for the modulation of the gravity-capillary wavenumber spectrum by long waves. The model is

  19. Large Scale (~25 m2) metal diffraction grating of submicron period as possible optoelectronic detector for short scalar gravitational waves

    NASA Astrophysics Data System (ADS)

    Zhukov, Valery A.

    2014-12-01

    A method of detecting of short scalar gravitational waves with a wavelength of ? ~ 0.5 ?m is proposed, in contrast to LIGO Project, aimed at detecting of long quadrupole gravitational waves (? ~ 43 ÷ 10000 km). The conduction electrons in a metal are proposed to use as gravitational receiving antennas instead of massive pendulums. It is shown that using a Large Scale metal diffraction grating you can convert the mechanical vibrations of the conduction electrons of metal into a plane electromagnetic wave propagating along the normal to the grating. It is shown that when the amplitude of the scalar gravitational wave in a source (in quasar at the center of our galaxy) is greater than Ago ? 5 1020cm/s2, you can register it with the help of a large optical telescope equipped with the proposed diffraction grating. It is shown that the special theory of relativity allows the amplitude of the scalar gravitational waves in this source by 5 orders of magnitude greater than the above-mentioned minimum value.

  20. Dynamics of PDE, Vol.6, No.4, 291-310, 2009 Wave breaking in the short-pulse equation

    E-print Network

    Pelinovsky, Dmitry

    transformation for the short- pulse equationDynamics of PDE, Vol.6, No.4, 291-310, 2009 Wave breaking in the short-pulse equation Yue Liu. Sufficient conditions for wave breaking are found for the short- pulse equation describing wave packets

  1. A tunable dual-wavelength pump source based on simulated polariton scattering for terahertz-wave generation

    NASA Astrophysics Data System (ADS)

    Sun, Bo; Liu, Jinsong; Yao, Jianquan; Li, Enbang

    2013-11-01

    We propose a dual-wavelength pump source by utilizing stimulated polariton scattering in a LiNbO3 crystal. The residual pump and the generated tunable Stokes waves can be combined to generate THz-wave generation via difference frequency generation (DFG). With a pump energy of 49 mJ, Stokes waves with a tuning range from 1067.8 to 1074 nm have been generated, and an output energy of up to 14.9 mJ at 1070 nm has been achieved with a conversion efficiency of 21.7%. A sum frequency generation experiment was carried out to demonstrate the feasibility of the proposed scheme for THz-wave DFG.

  2. Two-dimensional radiation and scattering at short wave length

    NASA Technical Reports Server (NTRS)

    Yoon, W. S.; Park, J. M.; Eversman, W.

    1990-01-01

    In the present investigation of radiation and scattering by objects when the wavelengths are much smaller than the characteristic dimensions of the radiator or scatterer, the boundary-element method is used to obtain computational accuracy and efficiency. The approach employed for wavelengths less than 5 percent of object characteristic dimensions involves cubic elements, approximate polynomial and asymptotic evaluations of the fundamental solution, and a tailoring of the order of the Gaussian quadrature according to the local demands dictated by the distance between sending and receiving points. The method addresses the propagation of low-frequency sound over large terrain features.

  3. ARM: Short Wave Flux Analysis: 15-min resolution on SIRS data, Long algorithm

    DOE Data Explorer

    Stoffel, Tom; Kay, Bev; Habte, Aron; Anderberg, Mary; Kutchenreiter, Mark

    Short Wave Flux Analysis: 15-min resolution on SIRS data, Long algorithm. Measurements began in January, 1994, and have continued to the present time. Data collected are from the Southern Great Plains (SGP) location.

  4. MULTI-WAVELENGTH OBSERVATION OF A MORETON WAVE ON NOVEMBER 3, 1997

    E-print Network

    California at Berkeley, University of

    wave. Assuming that the X-ray wave is the MHD fast shock, we can estimate the propagation speed-like disturbances ("X-ray wave" and "EIT wave") were also found. The propagation speed of the X-ray wave (630 km that the estimated fast shock speed is 400­760 km/s, in rough agreement with the observed propagation speed of the X

  5. A short wave infrared hyperspectral imager for landmine detection

    Microsoft Academic Search

    John E. McFee; Steve Achal; Tyler Ivanco; Cliff Anger

    2005-01-01

    DRDC Suffield and Itres Research have jointly investigated the use of visible and infrared hyperspectral imaging for landmine detection since 1988. There has been considerable success detecting surface-laid landmines by classification of their visible\\/near infrared (VNIR - 400 to 1000 nm wavelength) spectral signatures, but it has not been possible to find VNIR spectral characteristics that would generically distinguish anthropogenic

  6. DNA damage induced by lithotripter generated shock waves: short report.

    PubMed

    Kocha?ski, A M; Mejnartowicz, J P; Latos-Biele?ska, A; Etienne, J; Filipczy?iski, L

    2001-01-01

    The side effects of shock waves on biological tissues have been intensively investigated in past years. In contrast to the morphological studies, only a little information exists up to now about molecular effects of shock waves at the DNA level. To study the shock wave effects on DNA in water solution, 100, 500, 1,000, 1,500 wave shocks, generated with a experimental lithotripter, were applied at 18 kV and 20 kV, corresponding to the positive pressure peaks of 16 and 30 MPa and negative ones of 5 and 9 MPa. The DNA damage was evaluated in two "submarine" electrophoresis approaches. In the first - standard DNA electrophoresis - no DNA damage was detected, confirming previously described results. In the second electrophoresis, performed under changed conditions, sever double strand DNA damage was found. Our results strongly suggest that shock waves applied at the therapeutical level of energy may generate the double strand DNA damage. PMID:11583365

  7. External excitation of a short-wavelength fluctuation in the Alcator C-Mod edge plasma and its relationship to the quasi-coherent mode

    E-print Network

    Parker, R. R.

    A novel “Shoelace” antenna has been used to inductively excite a short-wavelength edge fluctuation in a tokamak boundary layer for the first time. The principal design parameters, k[subscript ?] = 1.5 ± 0.1 cm[superscript ...

  8. Detection of optic neuropathy in glaucomatous eyes with normal standard visual fields using a test battery of short-wavelength automated perimetry and pattern electroretinography

    Microsoft Academic Search

    Andreas U Bayer; Klaus-Peter Maag; Carl Erb

    2002-01-01

    PurposeTo evaluate the clinical use of a test battery of short-wavelength automated perimetry (SWAP), frequency-doubling technology (FDT) perimetry, and pattern-electroretinography (PERG) in patients with definite primary open-angle glaucoma (POAG) but normal results on standard automated perimetry (SAP).

  9. Short-wavelength upconversion emissions in Ho3+/Yb3+ codoped glass ceramic and the optical thermometry behavior.

    PubMed

    Xu, Wei; Gao, Xiaoyang; Zheng, Longjiang; Zhang, Zhiguo; Cao, Wenwu

    2012-07-30

    Ho(3+)/Yb(3+) codoped glass ceramic was prepared by melt-quenching and subsequent thermal treatment. Under a 980 nm diode laser excitation, upconversion emissions from Ho(3+) ions centered at 540, 650, and 750 nm were greatly enhanced compared with those in the precursor glass. Especially, the short-wavelength upconversion emissions centered at 360, 385, 418, 445, and 485 nm were successfully obtained in the glass ceramic. An explanation for this phenomenon is given based on the fluorescence decay curve measurements. In addition, an optical temperature sensor based on the blue upconversion emissions from (5)F(2,3)/(3)K(8)?(5)I(8) and (5)F(1)/(5)G(6)?(5)I(8) transitions in Ho(3+)/Yb(3+) codoped glass ceramic has been developed. It was found that by using fluorescence intensity ratio technique, appreciable sensitivity for temperature measurement can be achieved by using the Ho(3+)/Yb(3+) codoped glass ceramic. This result makes the Ho(3+)/Yb(3+) codoped glass ceramic be a promising candidate for sensitive optical temperature sensor with high resolution and good accuracy. PMID:23038360

  10. Multiple pathways carry signals from short-wavelength-sensitive (‘blue’) cones to the middle temporal area of the macaque

    PubMed Central

    Jayakumar, Jaikishan; Roy, Sujata; Dreher, Bogdan; Martin, Paul R; Vidyasagar, Trichur R

    2013-01-01

    We recorded spike activity of single neurones in the middle temporal visual cortical area (MT or V5) of anaesthetised macaque monkeys. We used flashing, stationary spatially circumscribed, cone-isolating and luminance-modulated stimuli of uniform fields to assess the effects of signals originating from the long-, medium- or short- (S) wavelength-sensitive cone classes. Nearly half (41/86) of the tested MT neurones responded reliably to S-cone-isolating stimuli. Response amplitude in the majority of the neurones tested further (19/28) was significantly reduced, though not always completely abolished, during reversible inactivation of visuotopically corresponding regions of the ipsilateral primary visual cortex (striate cortex, area V1). Thus, the present data indicate that signals originating in S-cones reach area MT, either via V1 or via a pathway that does not go through area V1. We did not find a significant difference between the mean latencies of spike responses of MT neurones to signals that bypass V1 and those that do not; the considerable overlap we observed precludes the use of spike-response latency as a criterion to define the routes through which the signals reach MT. PMID:23070701

  11. Intrinsic frequency spectra of short gravity-capillary waves obtained from temporal measurements of wave height on a lake

    NASA Technical Reports Server (NTRS)

    Atakturk, S. S.; Katsaros, K. B.

    1987-01-01

    Intrinsic frequency spectra of water waves in the range of 6-17 Hz were obtained as a function of both wind speed and wind stress from point measurements of wave height. In a lake with a limited fetch, there are two types of surface motions causing Doppler shift in the frequencies of short waves: orbital velocity of long waves and surface wind drift. The former was estimated from long-wave amplitude by using a linear wave theory. The error in this estimate is of the order of the long-wave slope, and for this work it is typically 10 percent. The latter was approximated by the friction velocity. The friction velocity could be either taken as 3 percent of the mean wind speed measured at a height of 10 m or obtained from direct measurements of the wind stress. The surface drift velocities obtained by these two approaches were found to be in close agreement. Doppler frequency shift can be corrected in either the frequency or the equivalent spatial domain. The two techniques were found to produce comparable results. Experimental results showed that the spectral energy of short waves rapidly increased in response to increasing winds and jumped up by an order of magnitude when wave breaking occurred.

  12. Bismuth-Oxide-Based Nonlinear Fiber With a High SBS Threshold and Its Application to Four-Wave-Mixing Wavelength Conversion Using a Pure Continuous-Wave Pump

    NASA Astrophysics Data System (ADS)

    Lee, Ju Han; Nagashima, Tatsuo; Hasegawa, Tomoharu; Ohara, Seiki; Sugimoto, Naoki; Kikuchi, Kazuro

    2006-01-01

    The unique and practical benefits of the use of bismuth-oxide-based nonlinear fiber (Bi-NLF) in implementing a four-wave-mixing (FWM)-based wavelength converter for fiber-optic-communication-system applications are experimentally demonstrated. First, the Kerr-nonlinearity and stimulated-Brillouin-scattering (SBS) characteristics of our fabricated Bi-NLF are experimentally investigated. The Bi-NLF is found to have the superior advantage of a significantly high SBS threshold in addition to its ultrahigh Kerr nonlinearity gamma of sim 1100 W-1 · km-1, compared to the conventional silica-based highly nonlinear fiber. Next, the authors perform an experiment for the FWM-based wavelength conversion of a non-return-to-zero (NRZ) signal within a 40-cm length of the Bi-NLF fusion spliced to standard silica fibers by using a continuous-wave (CW) high-power pump beam. Error-free tunable wavelength conversion over a 10-nm bandwidth is readily achieved. No SBS-suppression scheme is employed for the pump due to the high SBS threshold, which simplifies the system configuration and improves the quality of the wavelength-converted signal.

  13. [The impact of ZnS/CdS composite window layer on the quantun efficiency of CdTe solar cell in short wavelength].

    PubMed

    Zhang, Li-xiang; Feng, Liang-huan; Wang, Wen-wu; Xu, Hang; Wu, Li-li; Zhang, Jing-quan; Li, Wei; Zeng, Guang-gen

    2015-02-01

    ZnS/CdS composite window layer was prepared by magnetron sputtering method and then applied to CdTe solar cell. The morphology and structure of films were measured. The data of I-V in light and the quantum efficiency of CdTe solar cells with different window layers were also measured. The effect of ZnS films prepared in different conditions on the performance of CdTe solar cells was researched. The effects of both CdS thickness and ZnS/CdS composite layer on the transmission in short wavelength were studied. Particularly, the quantum efficiency of CdTe solar cells with ZnS/CdS window layer was measured. The results show as follows. With the thickness of CdS window layer reducing from 100 to 50 nm, the transmission increase 18.3% averagely in short wavelength and the quantum efficiency of CdTe solar cells increase 27.6% averagely. The grain size of ZnS prepared in 250 degrees C is smaller than prepared at room temperature. The performance of CdTe solar cells with ZnS/CdS window layer is much better if ZnS deposited at 250 degrees C. This indicates grain size has some effect on the electron transportation. When the CdS holds the same thickness, the transmission of ZnS/CdS window layer was improved about 2% in short wavelength compared with CdS window layer. The quantum efficiency of CdTe solar cells with ZnS/CdS window layer was also improved about 2% in short wavelength compared with that based on CdS window layer. These indicate ZnS/CdS composite window layer can increase the photon transmission in short wavelength so that more photons can be absorbed by the absorbent layer of CdTe solar cells. PMID:25970885

  14. Bismuth-oxide-based nonlinear fiber with a high SBS threshold and its application to four-wave-mixing wavelength conversion using a pure continuous-wave pump

    Microsoft Academic Search

    Ju Han Lee; Tatsuo Nagashima; Tomoharu Hasegawa; Seiki Ohara; Naoki Sugimoto; Kazuro Kikuchi

    2006-01-01

    The unique and practical benefits of the use of bismuth-oxide-based nonlinear fiber (Bi-NLF) in implementing a four-wave-mixing (FWM)-based wavelength converter for fiber-optic-communication-system applications are experimentally demonstrated. First, the Kerr-nonlinearity and stimulated-Brillouin-scattering (SBS) characteristics of our fabricated Bi-NLF are experimentally investigated. The Bi-NLF is found to have the superior advantage of a significantly high SBS threshold in addition to its ultrahigh

  15. Short-and-intermediate-period surface wave tomography from ambient seismic noise in Europe

    Microsoft Academic Search

    Y. Yang; M. H. Ritzwoller; N. M. Shapiro

    2006-01-01

    Green functions of surface waves between two seismic stations can be estimated from cross correlations of long-duration ambient seismic noise. Surface wave tomography based on cross correlations of ambient seismic noise has been demonstrated to produce high-resolution short-period (7-18 s) surface wave dispersion maps in Southern California (Shapiro et al., Science, 307, 1615, 2005). In this study, we extend ambient

  16. Laboratory research on effective test area of short-crested waves generated by two-sided segmented wavemakers

    NASA Astrophysics Data System (ADS)

    Li, Jun; Chen, Gang; Yang, Jian-min; Peng, Tao

    2014-04-01

    The size and shape of the effective test area are crucial to consider when short-crested waves are created by segmented wavemakers. The range of the effective test area of short-crested waves simulated by two-sided segmented wavemakers is analyzed in this paper. The experimental investigation on the wave field distribution of short-crested waves generated by two-sided segmented wavemakers is conducted by using an array of wave gauges. Wave spectra and directional spreading function are analyzed and the results show that when the main direction is at a certain angle with the normal line of wave generators, the wave field of 3D short-crested waves generated by two-sided segmented wavemakers has good spatial uniformity within the model test area. The effective test area can provide good wave environments for seakeeping model tests of various ocean engineering structures in the deep ocean engineering basin.

  17. Effect of Yellow-Tinted Intraocular Lens on Standard Automated Perimetry and Short Wavelength Automated Perimetry in Patients with Glaucoma

    PubMed Central

    Nilforushan, Naveed; Parsamanesh, Mohammad; Yu, Fei; Nassiri, Nariman; Miraftabi, Arezoo; Coleman, Anne L.

    2014-01-01

    Purpose: To investigate the effect of cataract surgery and yellow-tinted intraocular lens (IOLs) implantation on perimetry indices of short-wavelength automated perimetry (SWAP) and standard automated perimetry (SAP) testing in patients with coexisting cataract and glaucoma. Materials and Methods: In this prospective comparative case series, phacoemulsification with implantation of yellow-tinted Acrysof Natural IOL was performed in 16 eyes of 16 patients with visually significant cataract (best-corrected visual acuity (VA) better than 20/120) and mild to moderate glaucoma. Pre- and postoperative values for VA and for perimetry indices including mean deviation (MD), pattern standard deviation (PSD), and foveal threshold (FT) from both SAP and SWAP testing were compared. Results: Postoperative VA improved significantly after cataract surgery and yellow-tinted IOL implantation (P < 0.001). After cataract extraction and IOL implantation, MD and FT on SWAP testing improved significantly (P = 0.001); however, there was no statistically significant change with SAP testing between the pre- and postoperative perimetry indices. There was no statistically significant change in PSD with either SAP or SWAP testing postoperatively. The differences between pre- and postoperative values for all perimetry indices under study were not significant when comparing SAP with SWAP tests, except for MD which had improved statistically significantly in SWAP testing (P = 0.03). Conclusions: In mild to moderate glaucoma patients with cataracts, the perimetry indices of SWAP testing improved after phacoemulsification and yellow-tinted IOL implantation. This suggests that the yellow-tinted IOLs have less effect on SWAP testing than visually significant cataracts. PMID:25100904

  18. Short wavelength lateral variability of lithospheric mantle beneath the Middle Atlas (Morocco) as recorded by mantle xenoliths

    NASA Astrophysics Data System (ADS)

    El Messbahi, Hicham; Bodinier, Jean-Louis; Vauchez, Alain; Dautria, Jean-Marie; Ouali, Houssa; Garrido, Carlos J.

    2015-05-01

    The Middle Atlas is a region where xenolith-bearing volcanism roughly coincides with the maximum of lithospheric thinning beneath continental Morocco. It is therefore a key area to study the mechanisms of lithospheric thinning and constrain the component of mantle buoyancy that is required to explain the Moroccan topography. Samples from the two main xenolith localities, the Bou Ibalghatene and Tafraoute maars, have been investigated for their mineralogy, microstructures, crystallographic preferred orientation, and whole-rock and mineral compositions. While Bou Ibalghatene belongs to the main Middle Atlas volcanic field, in the 'tabular' Middle Atlas, Tafraoute is situated about 45 km away, on the North Middle Atlas Fault that separates the 'folded' Middle Atlas, to the South-East, from the 'tabular' Middle Atlas, to the North-West. Both xenolith suites record infiltration of sub-lithospheric melts that are akin to the Middle Atlas volcanism but were differentiated to variable degrees as a result of interactions with lithospheric mantle. However, while the Bou Ibalghatene mantle was densely traversed by high melt fractions, mostly focused in melt conduits, the Tafraoute suite records heterogeneous infiltration of smaller melt fractions that migrated diffusively, by intergranular porous flow. As a consequence the lithospheric mantle beneath Bou Ibalghaten was strongly modified by melt-rock interactions in the Cenozoic whereas the Tafraoute mantle preserves the record of extensional lithospheric thinning, most likely related to Mesozoic rifting. The two xenolith suites illustrate distinct mechanisms of lithospheric thinning: extensional thinning in Tafraoute, where hydrous incongruent melting triggered by decompression probably played a key role in favouring strain localisation, vs. thermal erosion in Bou Ibalghatene, favoured and guided by a dense network of melt conduits. Our results lend support to the suggestion that lithospheric thinning beneath the Atlas mountains results from the combination of different mechanisms and occurred in a piecewise fashion at a short wavelength scale.

  19. Short-wave infrared barriode detectors using InGaAsSb absorption material lattice matched to GaSb

    NASA Astrophysics Data System (ADS)

    Craig, A. P.; Jain, M.; Wicks, G.; Golding, T.; Hossain, K.; McEwan, K.; Howle, C.; Percy, B.; Marshall, A. R. J.

    2015-05-01

    Short-wave infrared barriode detectors were grown by molecular beam epitaxy. An absorption layer composition of In0.28Ga0.72As0.25Sb0.75 allowed for lattice matching to GaSb and cut-off wavelengths of 2.9 ?m at 250 K and 3.0 ?m at room temperature. Arrhenius plots of the dark current density showed diffusion limited dark currents approaching those expected for optimized HgCdTe-based detectors. Specific detectivity figures of around 7 × 10 10 Jones and 1 × 10 10 Jones were calculated, for 240 K and room temperature, respectively. Significantly, these devices could support focal plane arrays working at higher operating temperatures.

  20. Digital Audio Broadcasting in the Short Wave Bands

    NASA Technical Reports Server (NTRS)

    Vaisnys, Arvydas

    1998-01-01

    For many decades the Short Wae broadcasting service has used high power, double-sideband AM signals to reach audiences far and wide. While audio quality was usually not very high, inexpensive receivers could be used to tune into broadcasts fro distant countries.

  1. The Velocity of Radio Waves over Short Paths

    Microsoft Academic Search

    R. C. Colwell; H. Atwood; J. E. Bailey; C. O. Marsh

    1942-01-01

    The velocity of radio waves was measured directly in the following manner. Two radio stations were set up on frequencies of 3492.5 and 2398 kilocycles, respectively. One station was fixed while the other was portable. The fixed station sent out pulses which were received at the portable station. A thyratron control set off return pulses which came back to the

  2. Design, Construction, and Calibration of a Portable Short Wave Infrared Spectroradiometer

    NASA Astrophysics Data System (ADS)

    Smith, Mark William

    This dissertation describes the design, construction, and calibration of a portable short wave infrared (SWIR) spectroradiometer. The main use for the instrument is the collection of ground reflectance and radiance data for the radiometric calibration of operational and proposed high spectral resolution remote-sensing systems, such as the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS), the Moderate Resolution Imaging Spectroradiometer (MODIS), the High Resolution Imaging Spectrometer (HIRIS), and the Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER). The instrument will also be used for cross calibrating Earth Observing System (EOS) calibration facilities and for a variety of high spectral resolution studies in earth science. The instrument is designed to be carried as a backpack unit, on a vehicle, or in a helicopter or airplane. The spectroradiometer covers the range from 1.05 to 2.45 mum. The spectral sampling interval is 1.37 nm and the spectral resolution is variable from about 5 nm to more than 100 nm. A single spectrum can be acquired in as little as 1 s. The signal-to-noise ratio (SNR) for a single 1-s scan is about 90 at a wavelength of 2.2 ?m for a lambertian surface of 100% reflectance illuminated by the sun at normal incidence with 14-nm spectral resolution, a 25^circ background temperature, and no atmospheric attenuation. The SNR can be improved by averaging multiple scans. Field -of-view defining optics are coupled by a flexible fiber optics bundle to the spectroradiometer, which consists of a non-scanning concave holographic diffraction grating with flat focal field imaged onto a 1024-element liquid -nitrogen-cooled PtSi linear-array detector. The combination of concave grating and linear-array detector was chosen in preference to Fourier transform, Hadamard transform, and scanned grating monochromator systems on the basis of simplicity, high SNR, and greatest radiometric accuracy.

  3. Improved methods for detecting gravitational waves associated with short gamma-ray bursts

    E-print Network

    A. R. Williamson; C. Biwer; S. Fairhurst; I. W. Harry; E. Macdonald; D. Macleod; V. Predoi

    2014-10-22

    In the era of second generation ground-based gravitational wave detectors, short gamma-ray bursts (GRBs) will be among the most promising astrophysical events for joint electromagnetic and gravitational wave observation. A targeted search for gravitational wave compact binary merger signals in coincidence with short GRBs was developed and used to analyze data from the first generation LIGO and Virgo instruments. In this paper, we present improvements to this search that enhance our ability to detect gravitational wave counterparts to short GRBs. Specifically, we introduce an improved method for estimating the gravitational wave background to obtain the event significance required to make detections; implement a method of tiling extended sky regions, as required when searching for signals associated to poorly localized GRBs from Fermi Gamma-ray Burst Monitor or the InterPlanetary Network; and incorporate astrophysical knowledge about the beaming of GRB emission to restrict the search parameter space. We describe the implementation of these enhancements and demonstrate how they improve the ability to observe binary merger gravitational wave signals associated with short GRBs.

  4. Wavelength conversion in silicon using Raman induced four-wave mixing V. Raghunathan,a)

    E-print Network

    Jalali. Bahram

    silicon-on-insulator SOI guiding structures and foundry compatible processing technology. However, silicon index con- trast between silicon and SiO2/air) offers the possibility to achieve amplification a means to transfer information between the Stokes and anti-Stokes wavelength channels while preserving

  5. High power, high efficiency millimeter wavelength traveling wave tubes for high rate communications from deep space

    Microsoft Academic Search

    James A. Dayton Jr.

    1991-01-01

    The high-power transmitters needed for high data rate communications from deep space will require a new class of compact, high efficiency traveling wave tubes (TWT's). Many of the recent TWT developments in the microwave frequency range are generically applicable to mm wave devices, in particular much of the technology of computer aided design, cathodes, and multistage depressed collectors. However, because

  6. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Laser spectroscopy of the products of photoevaporation with a short-wavelength (? = 193 nm) excimer laser

    NASA Astrophysics Data System (ADS)

    Gochelashvili, K. S.; Zemskov, M. E.; Evdokimova, O. N.; Mikhkel'soo, V. T.; Prokhorov, A. M.

    1999-02-01

    An excimer laser spectrometer was designed and constructed. It consists of a high-vacuum interaction chamber, a short-wavelength (? = 193 nm) excimer ArF laser used for evaporation, a probe dye laser pumped by an XeCl excimer laser, and a system for recording a laser-induced fluorescence signal. This spectrometer was used to investigate nonthermal mechanisms of photoevaporation of a number of wide-gap dielectrics.

  7. A feasibility study on the use of visible and short wavelengths in the near-infrared region for the non-destructive measurement of wine composition

    Microsoft Academic Search

    D. Cozzolino; M. J. Kwiatkowski; E. J. Waters; M. Gishen

    2007-01-01

    The aim of this study was to explore the capability of spectroscopy in the visible (Vis) and short wavelength near-infrared\\u000a (NIR) regions for the non-destructive measurement of wine composition in intact bottles. In this study we analysed a wide\\u000a range of commercial wines obtained in Australia in different types of bottles (e.g. colours, diameters and heights), including\\u000a different wine styles

  8. Spacing-tunable multi-wavelength fiber laser based on cascaded four-wave mixing in highly nonlinear photonic-crystal fiber

    Microsoft Academic Search

    H. B. Sun; X. M. Liu; L. R. Wang; X. H. Li; D. Mao

    2010-01-01

    A multi-wavelength fiber laser based on the cascaded four-wave mixing in highly-nonlinear photonic-crystal fiber is proposed\\u000a and investigated. The cascade operation is initiated by two strong pump waves boosted by multi-mode pumping erbium\\/ytterbium\\u000a co-doped double-cladding fiber amplification technique. A segment of highly-nonlinear near-zero-dispersion-flattened photonic\\u000a crystal fiber is employed to induce highly efficient cascaded four-wave mixing. The wavelength spacing can be

  9. Spacing-tunable multi-wavelength fiber laser based on cascaded four-wave mixing in highly nonlinear photonic-crystal fiber

    Microsoft Academic Search

    H. B. Sun; X. M. Liu; L. R. Wang; X. H. Li; D. Mao

    2010-01-01

    A multi-wavelength fiber laser based on the cascaded four-wave mixing in highly-nonlinear photonic-crystal fiber is proposed and investigated. The cascade operation is initiated by two strong pump waves boosted by multi-mode pumping erbium\\/ytterbium co-doped double-cladding fiber amplification technique. A segment of highly-nonlinear near-zero-dispersion-flattened photonic crystal fiber is employed to induce highly efficient cascaded four-wave mixing. The wavelength spacing can be

  10. PHYSICAL REVIEW A 83, 013405 (2011) Precision calculation of above-threshold multiphoton ionization in intense short-wavelength laser

    E-print Network

    Chu, Shih-I

    2011-01-01

    ) to infrared radiations (1×105 nm). With the recent development of intense and ultrashort-wavelength free-electron lasers [32­34], the study of multiphoton * zyzhou@ku.edu sichu@ku.edu processes in the high

  11. Skin damage thresholds with continuous-wave laser exposures at the infrared wavelength of 1319 nm

    NASA Astrophysics Data System (ADS)

    Oliver, Jeffrey W.; Harbert, Corey A.; Noojin, Gary D.; Noojin, Isaac D.; Schuster, Kurt J.; Shingledecker, Aurora D.; Stolarski, David J.; Kumru, Semih S.

    2011-03-01

    ABSTRACT Damage thresholds (ED50) for skin using Yucatan mini-pig (Sus scrofa domestica) have been determined at the operational wavelength of 1319 nm with beam diameters of 0.61 cm and 0.96 cm. Exposure durations of 0.25, 1.0, 2.5 and 10 seconds were used to determine trends in damage threshold with respect to exposure time and beam diameter at this moderately-high penetrating wavelength. A relatively narrow range of total radiant exposure from 37.4 J/cm2 to 62.3 J/cm2 average was observed for threshold damage with laser parameters encompassing a factor of two in beam area and a factor of forty in exposure duration.

  12. Polypropylene Embedded Metal-Mesh Broadband Achromatic Half Wave Plate for Millimeter Wavelengths

    E-print Network

    Zhang, Jin; Mauskopf, Philip; Savini, Giorgio; Moncelsi, Lorenzo; Whitehouse, Nicola; 10.1364/AO.50.003750

    2011-01-01

    We describe a novel multi-layered metal mesh achromatic half wave plate for use in astronomical polarimetric instruments. The half wave plate is designed to operate across the frequency range from 125-250 GHz. The wave plate is manufactured from 12-layers of thin film metallic inductive and capacitive grids patterned onto polypropylene sheets, which are then bonded together using a hot pressing technique. Transmission line modelling and 3-D electromagnetic simulations are used to optimize the parameters of the metal-mesh patterns and to evaluate their optical properties. A prototype half wave plate has been fabricated and its performance characterized in a polarizing Fourier transform spectrometer. The device performance is consistent with the modelling although the measured differential phase shift for two orthogonal polarizations is lower than expected. This difference is likely to result from imperfect patterning of individual layers and misalignment of the grids during manufacture.

  13. Integro-differential modeling of ICRH wave propagation and damping at arbitrary cyclotron harmonics and wavelengths in tokamaks

    SciTech Connect

    Van Eester, D.; Lerche, E. [LPP-ERM/KMS, Association Euratom-Belgian State, TEC Partner, Brussels (Belgium)

    2014-02-12

    Both at low and higher cyclotron harmonics, properly accounting for finite Larmor radius effects is crucial in many ion cyclotron resonance frequency heating scenarios creating high energy tails. The present paper discusses ongoing work to extend the 1D TOMCAT wave equation solver [D. Van Eester and R. Koch, Plasma Phys. Contr. Fusion 40 (1998) 1949] to arbitrary harmonics and arbitrary wavelengths. Rather than adopting the particle position, the guiding center position is used as the independent variable when writing down an expression for the dielectric response. Adopting a philosophy originally due to Kaufman [A.N. Kaufman, Phys. Fluids 15 (1972) 1063], the relevant dielectric response in the Galerkin formalism is written in a form where the electric field and the test function vector appear symmetrically, which yields a power balance equation that guarantees non-negative absorption for any wave type for Maxwellian plasmas. Moreover, this choice of independent variable yields intuitive expressions that can directly be linked to the corresponding expressions in the RF diffusion operator. It also guarantees that a positive definite power transfer from waves to particles is ensured for any of the wave modes in a plasma in which all populations have a Maxwellian distribution, as is expected from first principles. Rather than relying on a truncated Taylor series expansion of the dielectric response, an integro-differential approach that retains all finite Larmor radius effects [D. Van Eester and E. Lerche, Plasma Phys. Control. Fusion 55 (2013) 055008] is proposed.

  14. THE TEMPORAL PROPERTIES OF THE HUMAN SHORT-WAVE PHOTORECEPTORS AND THEIR ASSOCIATED PATHWAYS

    Microsoft Academic Search

    ANDREW STOCKMAN; DONALD I. A. MACLEOD; DERRYL D. DEFTEST

    1991-01-01

    Flicker modulation sensitivity measurements made on high intensity orange steady back- grounds indicate that signals from short-wavelength sensitive cones (S-cones) have access to two pathways. At low Scone adaptation levels the frequency response falls quickly with increasing frequency, but at higher adaptation levels it extends to much higher frequencies. At these higher S-cone adaptation levels, the following procedures can selectively

  15. Chapter 10: Waves Did you read chapter 10

    E-print Network

    Hart, Gus

    in a fluid (air, water, etc). Long wavelength, low frequency low pitch Short wavelength, high frequency: Compression Waves Come from compressing atoms (or molecules) close together and then pulling them apart light Short wavelength, high frequency blue light Speed is the same for all colors in vacuum/air

  16. Multicomponent long-wave-short-wave resonance interaction system: Bright solitons, energy-sharing collisions, and resonant solitons

    NASA Astrophysics Data System (ADS)

    Sakkaravarthi, K.; Kanna, T.; Vijayajayanthi, M.; Lakshmanan, M.

    2014-11-01

    We consider a general multicomponent (2+1)-dimensional long-wave-short-wave resonance interaction (LSRI) system with arbitrary nonlinearity coefficients, which describes the nonlinear resonance interaction of multiple short waves with a long wave in two spatial dimensions. The general multicomponent LSRI system is shown to be integrable by performing the Painlevé analysis. Then we construct the exact bright multisoliton solutions by applying the Hirota's bilinearization method and study the propagation and collision dynamics of bright solitons in detail. Particularly, we investigate the head-on and overtaking collisions of bright solitons and explore two types of energy-sharing collisions as well as standard elastic collision. We have also corroborated the obtained analytical one-soliton solution by direct numerical simulation. Also, we discuss the formation and dynamics of resonant solitons. Interestingly, we demonstrate the formation of resonant solitons admitting breather-like (localized periodic pulse train) structure and also large amplitude localized structures akin to rogue waves coexisting with solitons. For completeness, we have also obtained dark one- and two-soliton solutions and studied their dynamics briefly.

  17. Wind-wave tank measurements of bound and freely propagating short gravity-capillary waves

    Microsoft Academic Search

    Martin Gade; Werner Alpers; Stanislav A. Ermakov; Heinrich Hühnerfuss; Philipp A. Lange

    1998-01-01

    Measurements of the surface elevation and slope and of the backscattered radar power at X and Ka band were carried out in a wind-wave tank with mechanically generated gravity waves as well as with wind waves on slick-free and slick-covered water surfaces. The measured radar Doppler shifts show that on a slick-free water surface, bound gravity-capillary (X and Ka band

  18. Quantitative short-wave infrared multispectral imaging of in vivo tissue

    E-print Network

    Choi, Bernard

    (SFDI) into the short-wave infra- red (SWIR) has the potential to provide enhanced sensitivity to chromophores such as water and lipids that have prominent absorption features in the SWIR region. Here, we employ a SWIR camera in conjunction with an SFDI system. We use SFDI to obtain in vivo tissue reduced

  19. Cross-Spectral Face Verification in the Short Wave Infrared (SWIR) Band

    Microsoft Academic Search

    Thirimachos Bourlai; Nathan D. Kalka; Arun Ross; Bojan Cukic; Lawrence Hornak

    2010-01-01

    The problem of face verification across the short wave infrared spectrum (SWIR) is studied in order to illustrate the advantages and limitations of SWIR face verification. The contributions of this work are two-fold. First, a database of 50 subjects is assembled and used to illustrate the challenges associated with the problem. Second, a set of experiments is performed in order

  20. A singular perturbation analysis of the weakly nonlinear evolution of long and short water waves and waves in boundary layers

    Microsoft Academic Search

    Stephen Laurence Woodruff

    1987-01-01

    A singular-perturbation method is introduced for the solution of multiple-scale problems. The use of the method is first illustrated with some relatively simple ordinary and partial differential equations; it is then applied to two problems in fluid mechanics: the nonlinear interaction of long and short water waves and boundary-layer stability. The proposed method is referred to as the invariance-condition to

  1. Experimental Study of Single and Multicast Wavelength Conversion at 10 Gb\\/s Exploiting Four-Wave Mixing in Highly Non-Linear-Photonic Crystal Fiber with Widely Tunable Conversion Range

    Microsoft Academic Search

    Zhan-Qiang Hui; Jia-Min Gong; Meng Liang; Yi Yang; Hui-Min Wu

    2012-01-01

    Optical networking applications require the use of all-optical wavelength converters with input and output wavelength tenability as well as large numbers of multicasting channels. This article demonstrates the single-to-multiple wavelength conversion via multiple four-wave mixings between a 10-Gbit\\/s return-to-zero signal and several continuous waves co-propagating in a dispersion-flattened highly non-linear photonic crystal fiber. For single-to-single channel wavelength conversion, a wide

  2. Polarization-insensitive wavelength conversion up to 10 Gb\\/s based on four-wave mixing in a semiconductor optical amplifier

    Microsoft Academic Search

    L. Y. Lin; J. M. Wiesenfeld; J. S. Perino; A. H. Gnauck

    1998-01-01

    Polarization-insensitive wavelength conversion at 2.5 and 10 Gb\\/s using four-wave mixing in a bulk semiconductor optical amplifier is reported. At 10 Gb\\/s, a conversion range from 6.4-nm wavelength downshift to 4.8-nm upshift has been demonstrated. The conversion efficiency and signal-to-noise ratio versus conversion range are also characterized

  3. Polarization Insensitive Wavelength Conversion Based on Orthogonal Pump Four-Wave Mixing for Polarization Multiplexing Signal in High-Nonlinear Fiber

    Microsoft Academic Search

    Jia Lu; Lin Chen; Z. Dong; Z. Cao; Shuangchun Wen

    2009-01-01

    We have theoretically and experimentally investigated polarization insensitive all-optical wavelength conversion for polarization multiplexing signal based on orthogonal pump four-wave mixing in nonlinear optical fiber. After wavelength conversion based on 1 km high-nonlinear optical fiber with polarization insensitivity, the power penalties of 2.5 Gbit\\/s optical OOK intensity and 10 Gbit\\/s differential phase-shift keying orthogonal signals are less than 0.5 and

  4. Four-wave-mixing-based wavelength conversion of 40Gb\\/s nonreturn-to-zero signal using 40-cm bismuth oxide nonlinear optical fiber

    Microsoft Academic Search

    Ju Han Lee; Tatsuo Nagashima; Tomoharu Hasegawa; Seiki Ohara; Naoki Sugimoto; Kazuro Kikuchi

    2005-01-01

    We experimentally demonstrate a compact and tunable four-wave-mixing-based wavelength converter using a Bi2O3-based nonlinear fiber (Bi-NLF). An only 40-cm-long Bi-NLF is used as a nonlinear optical medium for wavelength conversion of a 40-Gb\\/s nonreturn-to-zero (NRZ) signal with no additional stimulated Brillouin scattering (SBS) suppression scheme. The Bi-NLF used in this experiment has an extremely high SBS threshold owing to both

  5. Injectorless quantum cascade lasers for room-temperature short-wavelength emission by efficient second-harmonic generation

    Microsoft Academic Search

    A. Vizbaras; S. Katz; M. Anders; C. Grasse; G. Boehm; R. Meyer; M. A. Belkin; M.-C. Amann

    2010-01-01

    In this paper we demonstrate RT second-harmonic generation around 2.7 ?m with peak output powers close to 10 ?W at current densities of around 2 kA\\/cm2. We also discuss possible device structures for wavelengths around 3.5 ?m and a future development strategy for single-mode, two-color tunable laser sources.

  6. Thermal scene analysis via finite element model and finite difference time domain numerical solution of the electromagnetic wave propagation in the short wave and long wave infrared bandarch

    NASA Astrophysics Data System (ADS)

    Albertoni, Alessandro

    2009-09-01

    We utilize the Finite Element Model (FEM) and Finite Difference Time Domain (FDTD) numerical solution of the Electromagnetic wave propagation in the Short Wave Infrared (SWIR) and Long Wave Infrared (LWIR) bands in order to calculate the target radiance propagation and environment attenuation due to transmission, absorption and reflections in atmosphere and obstacles. We leave to traditional minimum resolvable temperature (MRTD) the model of the camera radiance collection (actual thermal sensitivity of the camera). The main advantage of the numerical propagation is that there is the possibility to model exactly the specific target shape and the specific environment (depending of the computational power) and calculate the residual temperature.

  7. High-power and wavelength-tunable traveling-wave semiconductor ring laser 

    E-print Network

    Peng, En Titus

    1991-01-01

    . FUTURE WORK VIII, CONCLUSIONS 25 REFERENCES 28 VITA 30 LIST OF FIGURES FIGURE Page 1. Cross-section of Tilted-stripe Ridge Waveguide Optical Amplifier . 2. TE and TM Spectra without Input into Optical Amplifier 3. Ring Laser Cavity... of light. CIIAPTER III EXPERIMENTAL CONHGURATION The gain medium of our ring laser is a traveling-wave ridge waveguide optical amplifier, A schematic diagram of the ridge waveguide structure is shown in Fig. 1 Tilted-stripe ridge waveguide optical...

  8. Improved performance of P3HT:PCBM solar cells by both anode modification and short-wavelength energy utilization using Tb(aca)3phen

    NASA Astrophysics Data System (ADS)

    Zhuo, Zu-Liang; Wang, Yong-Sheng; He, Da-Wei; Fu, Ming

    2014-09-01

    The performance of P3HT:PCBM solar cells was improved by anode modification using spin-coated Tb(aca)3phen ultrathin films. The modification of the Tb(aca)3phen ultrathin film between the indium tin oxide (ITO) anode and the PE-DOT:PSS layer resulted in a maximum power conversion efficiency (PCE) of 2.99% compared to 2.66% for the reference device, which was due to the increase in the short-circuit current density (Jsc). The PCE improvement could be attributed to the short-wavelength energy utilization and the optimized morphology of the active layers. Tb(aca)3phen with its strong down-conversion luminescence properties is suitable for the P3HT:PCBM blend active layer, and the absorption region of the ternary blend films is extended into the near ultraviolet region. Furthermore, the crystallization and the surface morphology of P3HT:PCBM films were improved with the Tb(aca)3phen ultrathin film. The ultraviolent—visible absorption spectra, atomic force microscope (AFM), and X-ray diffraction (XRD) of the films were investigated. Both anode modification and short-wavelength energy utilization using Tb(aca)3phen in P3HT:PCBM solar cells led to about a 12% PCE increase.

  9. Approximating SIR-B response characteristics and estimating wave height and wavelength for ocean imagery

    NASA Technical Reports Server (NTRS)

    Tilley, David G.

    1987-01-01

    NASA Space Shuttle Challenger SIR-B ocean scenes are used to derive directional wave spectra for which speckle noise is modeled as a function of Rayleigh random phase coherence downrange and Poisson random amplitude errors inherent in the Doppler measurement of along-track position. A Fourier filter that preserves SIR-B image phase relations is used to correct the stationary and dynamic response characteristics of the remote sensor and scene correlator, as well as to subtract an estimate of the speckle noise component. A two-dimensional map of sea surface elevation is obtained after the filtered image is corrected for both random and deterministic motions.

  10. Properties of High-Frequency Sub-Wavelength Ripples on Stainless Steel 304L under Ultra Short Pulse Laser Irradiation

    Microsoft Academic Search

    V. S. Mitko; G. R. B. E. Römer; A. J. Huis in ‘t Veld; J. Z. P. Skolski; J. V. Obona; V. Ocelík; J. T. M. De Hosson

    2011-01-01

    The paper concentrates on surface texturing on sub-micro meter scale with ultra short laser pulses that has several applications, e.g. changing the hydrophilic\\/hydrophobic performance, optical or tribological properties of materials. In general, the formations of wavy structures, or ripples on a surface irradiated by short pulse lasers has been observed experimentally since 1965, and are usually referred to as Laser

  11. A Fully Analytic Model of Large Area Silicon p-i-n Photodiodes Verified at Short Wavelengths

    Microsoft Academic Search

    Sven Loquai; Christian-Alexander Bunge; Olaf Ziemann; Bernhard Schmauss; Roman Kruglov

    2010-01-01

    A fully analytic analysis of the frequency response of a homo-structure p-i-n photodiode is developed to characterize high-speed large-area p-i-n photodiodes. Therefore, the model can easily be implemented in mathematical simulation tools for system analysis. The model accurately describes drift-, diffusion- and parasitic effects and has been experimentally verified up to 3 GHz for a variety of different wavelength from

  12. Spectroscopic and thermal properties of short wavelength metal (II) complexes containing ?-isoxazolylazo-?-diketones as co-ligands

    Microsoft Academic Search

    Fuxin Huang; Yiqun Wu; Donghong Gu; Fuxi Gan

    2005-01-01

    Two new azo dyes of ?-isoxazolylazo-?-diketones and their Ni(II) and Cu(II) complexes with blue-violet light wavelength were synthesized using a coupling component, different diazo components and metal (II) ions (Ni2+ and Cu2+). Based on the elemental analysis, MS spectra and FT-IR spectral analyses, azo dyes were unequivocally shown to exist as hydrazoketo and azoenol forms which were respectively obtained from

  13. 25 kHz narrow spectral bandwidth of a wavelength tunable diode laser with a short waveguide-based external cavity

    E-print Network

    Oldenbeuving, R M; Offerhaus, H L; Lee, C J; Song, H; Boller, K -J

    2012-01-01

    We report on the spectral properties of a diode laser with a tunable external cavity in integrated optics. Even though the external cavity is short compared to other small-bandwidth external cavity lasers, the spectral bandwidth of this tunable laser is as small as 25 kHz (FWHM), at a side-mode suppression ratio (SMSR) of 50 dB. Our laser is also able to access preset wavelengths in as little as 200 us and able to tune over the full telecom C-band (1530 nm - 1565 nm).

  14. Reactions of N/sub 2/(A/sup 3/SIGMA/sub u//sup +/) and candidates for short wavelength lasers, March 1, 1984-February 28, 1985

    SciTech Connect

    Setser, D.W.

    1987-12-07

    There are several potential schemes for efficiently generating high concentrations of the first electronically excited state of nitrogen, N/sub 2/(A/sup 3/..sigma../sub u//sup +/, 6.2 eV) by either chemical or electrical pumping. The goal of this proposal is to study ways of utilizing the energy of the N/sub 2/(A) molecules for developing efficient, short wavelength gas lasers. Such lasers are of potential interest for laser fusion. The authors report both excitation-transfer and dissociative excitation-transfer reactions of N/sub 2/(A) that yield electronically-excited diatomic molecules as products. 25 refs.

  15. The occurrence of thin cirrus clouds with short-period gravity waves over the tropical Indian Ocean during CINDY2011/DYNAMO

    NASA Astrophysics Data System (ADS)

    Suzuki, J.; Fujiwara, M.; Nishizawa, T.; Shirooka, R.; Yoneyama, K.; Matsui, I.; Sugimoto, N.

    2012-12-01

    Cirrus variability in association with short-period gravity waves is investigated using the shipboard a 532nm high spectral resolution lidar system (1?(532)+2?(532,1064)+1?(532)), Vaisala RS92 radiosondes at 3-hourly intervals, and 15 balloon-borne cryogenic Frostpoint hygrometers (CFH) in the tropical Indian Ocean (8.0°S, 80.5°E) during the CINDY2011/DYNAMO field campaign. Around the cold-point tropopause (CPT), gravity waves with the vertical wavelength of ~5 km and the temperature amplitude of ~3 K were dominant during early November. Thin cirrus clouds appearance (disappearance) corresponded with the cold (warm) anomalies of the waves. Supersaturation (relative humidity with respect to ice; RHi > 100 %) layers also co-existed with cold anomalies. Backward trajectories near the CPT showed the air parcels almost stayed over the vessel during this period, indicating in situ cirrus formation. Our multi-instrument cirrus measurements in the TTL have revealed the role of short-period gravity waves in the cirrus formation.

  16. Metal-mesh achromatic half-wave plate for use at submillimeter wavelengths.

    PubMed

    Pisano, Giampaolo; Savini, Giorgio; Ade, Peter A R; Haynes, Vic

    2008-11-20

    A metal-mesh achromatic half-wave plate (HWP) has been designed, manufactured, and tested for potential use in millimeter and submillimeter astronomical instruments. The prototype device presented here is based on a 12-grid Shatrow [IEEE Trans. Antennas Propag. 43, 109 (1995)] recipe to operate over the frequency range of 120-180 GHz. Transmission line modeling and finite-element analysis [Ansoft HFSS website: http://www.ansoft.com/hfss/] were used to optimize the design geometrical parameters in terms of the device transmission, reflection, absorption, phase-shift, and cross-polarization as a function of frequency. The resulting prototype device was constructed and characterized using incoherent radiation from a polarizing Fourier transform spectrometer to explore its frequency and polarization behavior. These measurements are shown to be in excellent agreement with the models. Lists of the achieved HWP performance characteristics are reported. PMID:19023391

  17. Powerful short-pulse lasers pumped by the light of a shock wave front

    NASA Astrophysics Data System (ADS)

    Kirillov, Gennadi A.; Eroshenko, V. A.; Kochemasov, Gennady G.; Kulikov, Stanislav M.; Pevny, S. N.; Sukharev, Stanislav A.

    2000-04-01

    Radiation of a shock wave front proved to be very powerful light source for pumping of high power lasers. Particularly, explosively pumped iodine photodissociation lasers (EPIL) are nowadays well developed type of device of multikilojoule level, rather convenient for many applications. Usually such lasers work in free running mode and generate pulses of microsecond duration. Generating short pulses of nanosecond range require employing amplification scheme where amplifiers must work in waiting mode. It implies substantially other composition of active medium and entails rather important consequences for kinetics of the processes which follow photodissociation. Present report considers these problems as well as some experimental results obtained with short pulse EPIL.

  18. Wakefield effects and solitary waves of an intense short laser pulse propagation in a plasma channel

    SciTech Connect

    Hong Xueren [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); Xie Baisong; Zhao Xueyan [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Zhang Shan [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Department of Mathematics and Physics, Shijiazhuang Tiedao University, Shijiazhuang 050043 (China); Wu Haicheng [Center for Applied Physics and Technology, Peking University, Beijing 100084 (China)

    2011-10-15

    In the presence of relativistic and channel-coupling nonlinearity and wakefield effects, the propagation characteristics and solitary waves of an intense short laser pulse in a preformed plasma channel are investigated. The evolution equation of the laser spot size is derived by using variational technique, the initial laser and plasma parameters for propagation with constant spot size, periodic defocusing and focusing oscillations, and solitary waves are identified. For illustration, some numerical results are also presented. It is found that the laser focusing is enhanced by the wakefield effects that result in a significant reduced focusing power.

  19. A Unified Directional Spectrum for Long and Short Wind-Driven Waves

    NASA Technical Reports Server (NTRS)

    Elfouhaily, T.; Chapron, B.; Katsaros, K.; Vandemark, D.

    1997-01-01

    Review of several recent ocean surface wave models finds that while comprehensive in many regards, these spectral models do not satisfy certain additional, but fundamental, criteria. We propose that these criteria include the ability to properly describe diverse fetch conditions and to provide agreement with in situ observations of Cox and Munk [1954] and Jiihne and Riemer [1990] and Hara et al. [1994] data in the high-wavenumber regime. Moreover, we find numerous analytically undesirable aspects such as discontinuities across wavenumber limits, nonphysical tuning or adjustment parameters, and noncentrosymmetric directional spreading functions. This paper describes a two-dimensional wavenumber spectrum valid over all wavenumbers and analytically amenable to usage in electromagnetic models. The two regime model is formulated based on the Joint North Sea Wave Project (JONSWAP) in the long-wave regime and on the work of Phillips [1985] and Kitaigorodskii [1973] at the high wavenumbers. The omnidirectional and wind-dependent spectrum is constructed to agree with past and recent observations including the criteria mentioned above. The key feature of this model is the similarity of description for the high- and low-wavenumber regimes; both forms are posed to stress that the air-sea interaction process of friction between wind and waves (i.e., generalized wave age, u/c) is occurring at all wavelengths simultaneously. This wave age parameterization is the unifying feature of the spectrum. The spectrum's directional spreading function is symmetric about the wind direction and has both wavenumber and wind speed dependence. A ratio method is described that enables comparison of this spreading function with previous noncentrosymmetric forms. Radar data are purposefully excluded from this spectral development. Finally, a test of the spectrum is made by deriving roughness length using the boundary layer model of Kitaigorodskii. Our inference of drag coefficient versus wind speed and wave age shows encouraging agreement with Humidity Exchange Over the Sea (HEXOS) campaign results.

  20. A unified directional spectrum for long and short wind-driven waves

    NASA Astrophysics Data System (ADS)

    Elfouhaily, T.; Chapron, B.; Katsaros, K.; Vandemark, D.

    1997-07-01

    Review of several recent ocean surface wave models finds that while comprehensive in many regards, these spectral models do not satisfy certain additional, but fundamental, criteria. We propose that these criteria include the ability to properly describe diverse fetch conditions and to provide agreement with in situ observations of Cox and Munk [1954] and Jähne and Riemer [1990] and Hara et al. [1994] data in the high-wavenumber regime. Moreover, we find numerous analytically undesirable aspects such as discontinuities across wavenumber limits, nonphysical tuning or adjustment parameters, and noncentrosymmetric directional spreading functions. This paper describes a two-dimensional wavenumber spectrum valid over all wavenumbers and analytically amenable to usage in electromagnetic models. The two regime model is formulated based on the Joint North Sea Wave Project (JONSWAP) in the long-wave regime and on the work of Phillips [1985] and Kitaigorodskii [1973] at the high wavenumbers. The omnidirectional and wind-dependent spectrum is constructed to agree with past and recent observations including the criteria mentioned above. The key feature of this model is the similarity of description for the high- and low-wavenumber regimes; both forms are posed to stress that the air-sea interaction process of friction between wind and waves (i.e., generalized wave age, u/c) is occurring at all wavelengths simultaneously. This wave age parameterization is the unifying feature of the spectrum. The spectrum's directional spreading function is symmetric about the wind direction and has both wavenumber and wind speed dependence. A ratio method is described that enables comparison of this spreading function with previous noncentrosymmetric forms. Radar data are purposefully excluded from this spectral development. Finally, a test of the spectrum is made by deriving roughness length using the boundary layer model of Kitaigorodskii. Our inference of drag coefficient versus wind speed and wave age shows encouraging agreement with Humidity Exchange Over the Sea (HEXOS) campaign results.

  1. Polarization-Insensitive Wavelength Conversion of DPSK Signal Using Four-Wave Mixing in 32-cm Bismuth-Oxide Highly Nonlinear Fiber

    Microsoft Academic Search

    Mable P. Fok; Chester Shu

    2007-01-01

    We demonstrate polarization-insensitive wavelength conversion of 10-Gb\\/s DPSK signal using a polarization-diversity scheme for four-wave mixing in 32-cm bismuth-oxide highly nonlinear fiber. The polarization dependence is <1 dB and the power penally is 3 dB.

  2. Repetition rate variable and wavelength-tunable picosecond optical pulse source employing square-wave-driven intensity modulator and comb-like profiled fiber

    Microsoft Academic Search

    Yasuyuki Ozeki; Shigehiro Takasaka; Misao Sakano; Shu Namiki

    2005-01-01

    We present a picosecond optical pulse source with repetition rate variability and wavelength tunability. The key to realize the repetition rate variability in our proposal is the method of generating seed pulse, where an intensity modulator is driven by a half-clock square wave. The advantage of this method is that the duration of the seed pulse is approximately half of

  3. Realization of quantum dot-based polarized white LEDs using short-wavelength pass dichroic filters and reflective polarizer films

    NASA Astrophysics Data System (ADS)

    Yang, Su Ji; Oh, Ji Hye; Lee, Keyong Nam; Do, Young Rag

    2014-09-01

    This study introduces quantum dot (QD)-based polarized white light-emitting diodes (W-LEDs) combined with a shortwavelength pass dichroic filter (SPDF), which transmit blue wavelength regions and reflect yellow wavelength regions, and a reflective polarizer film (RPF)-sandwiched AgIn5S8-ZnS QD layer using an electrospray (e-spray) method. The AgIn5S8-ZnS QDs are good candidates for W-LEDs because of their broad emission band (~100 nm) from the donoracceptor emission. The yellow emitting AgIn5S8-ZnS QDs are synthesized using a colloidal hot injection method and mixed with dimethylformamide (DMF), toluene, and poly(methyl methacrylate) (PMMA) for e-spray coating on glass. Furthermore, SPDFs are used instead of glass substrates to enhance the yellow emission from the QD layer. To create the polarized light, the RPF is fabricated on QD-coated glass and SPDFs. To create white light, a blue LED chip (?max = 450 nm) is used as the blue light source and an excitation source for the yellow QD film with an applied current of 60 mA. The electroluminescence (EL) intensity with an angular orientation of the polarizer is measured as a function of the polarizer-rotating angle from -90° to 90° at 10° intervals.

  4. Correlation between the specific surface area and the short wave infrared (SWIR) reflectance of snow

    Microsoft Academic Search

    Florent Domine; Rosamaria Salvatori; Loic Legagneux; Roberto Salzano; Michel Fily; Ruggero Casacchia

    2006-01-01

    The albedo of snow is determined in part by the size and shape of snow crystals, especially in the short wave infrared (SWIR). Many models of snow albedo represent snow crystals by spheres of surface\\/volume (S\\/V) ratio equal to that of snow crystals. However, the actual S\\/V ratio of snow has never been measured simultaneously with the albedo, for a

  5. 1.0 to 2.5 micrometer short wavelength infrared /SWIR/ linear array technology for low background applications

    NASA Technical Reports Server (NTRS)

    Stobie, J.; Iwasa, S.

    1981-01-01

    A design concept is presented for a hybrid linear focal plane array operating in the 1.0 to 2.5 micron band under low background conditions such as encountered in spaceborne missions. The concept is based on direct gate coupling of the input from a photovoltaic mercury-cadmium telluride detector into a CCD multiplexer. Theoretical analysis indicates a specific detectivity at peak wavelength on the order of 10 to the 12th cm sq rt Hz/W when the system is operating at 200 K. Values of the voltage responsivity, specific detectivity and the relative voltage noise levels of the coupled system obtained in experimental studies with direct-gate-coupled 4.0-micron detectors support the theoretical analysis performed for the case of system detectivity limited by the CCD 1/f noise.

  6. The assessment of a towed laser slopemeter for measuring short scale sea surface wave slopes

    NASA Astrophysics Data System (ADS)

    Willoughby, Barrie John

    The advent of satellite-borne Synthetic Aperture Radar (SAR) has generated much interest in sea surface waves of less than a metre in wavelength. Many oceanographic processes can be identified within SAR images of the world's oceans. The limited understanding of the interactions between these phenomena and the wind-wave field and the scatter mechanisms leading to the returned radar signal has restricted the full quantitative application of this important remote sensing tool. In an effort to address this gap in our understanding there is a need for in-situ measurements. A Towed Laser Slopemeter has been designed and developed at the University of Southampton. This is capable of measuring two orthogonal components of surface slope of between +/-35° over a wavelength range of 1m to 0.007m at a rate of 250 Hz. Values of slope are determined using a laser beam and an optical detection system without the need to measure surface wave height. The instrument is towed parallel to a larger vessel to ensure that an undisturbed surface profile is sampled. It has been established that the effect of towing the slopemeter leads to a hybrid wavenumber-frequency spectrum Studies conducted in this thesis are concerned with the characterisation of the TLS and the verification of its ability to measure sea surface wave slope. To investigate the effect of vehicle velocity on the observed spectrum a new numerical model was developed. The model was capable of providing true wavenumber, true wave frequency and wavenumber-frequency spectra. The direction between the true and observed wavenumbers was found to be a minimum at small angles to the direction of travel of the wave and at high tow speeds. Using the numerical model methods for providing a true wavenumber spectrum from the wavenumber-frequency spectrum were investigated. Data from the first deployment of the slopemeter was thoroughly investigated to assess its oceanographic content. Wave profiles, spectra and slope distributions were found to agree with accepted forms. The wave profile was noisier than expected. From an analysis of this noise, sources were identified and this led directly to a refit of the TLS. Slicks evident on the sea surface were sampled by the slopemeter during the trial. The time at which these features were intercepted by the TLS was logged. The logged time agreed with a decrease in the recorded wave slopes. The ability of the TLS to provide a sensitive and precise measurement of sea surface roughness was reinforced with an extensive comparison of the TLS and video records from the second deployment. Waves seen within the video could be seen within the TLS record. The TLS proved to be more sensitive to changes in wave slope for a larger range of sea states than the video record. A variety of signal processing tools were found to be useful in the analysis of the TLS data sets. Confidence was gained in the ability of the TLS as a device capable of providing sensitive in-situ measurements of the interaction of ocean processes with the sea surface wave profile. (Abstract shortened by UMI.)

  7. Resonant interaction between a localized fast wave and a slow wave with constant asymptotic amplitude

    SciTech Connect

    Zabolotskii, A. A., E-mail: zabolotskii@iae.nsk.s [Russian Academy of Sciences, Institute of Automation and Electrometry, Siberian Branch (Russian Federation)

    2009-11-15

    An integrable Yajima-Oikawa system is solved in the case of a finite density, which corresponds to a slowly varying (long-wavelength) wave with finite amplitude at infinity and a localized fast-oscillating (short-wavelength) wave. Application of the results to spinor Bose-Einstein condensates and other physical systems is discussed.

  8. Field trial of active remote sensing using a high-power short-wave infrared supercontinuum laser.

    PubMed

    Alexander, Vinay V; Shi, Zhennan; Islam, Mohammed N; Ke, Kevin; Kalinchenko, Galina; Freeman, Michael J; Ifarraguerri, Agustin; Meola, Joseph; Absi, Anthony; Leonard, James; Zadnik, Jerome A; Szalkowski, Anthony S; Boer, Gregory J

    2013-09-20

    Field trial results of a 5 W all-fiber broadband supercontinuum (SC) laser covering the short-wave infrared (SWIR) wavelength bands from ~1.55 to 2.35 ?m are presented. The SC laser is kept on a 12 story tower at the Wright Patterson Air Force Base and propagated through the atmosphere to a target 1.6 km away. Beam quality of the SC laser after propagating through 1.6 km is studied using a SWIR camera and show a near diffraction limited beam with an M(2) value of <1.3. The SC laser is used as the illumination source to perform spectral reflectance measurements of various samples at 1.6 km, and the results are seen to be in good agreement with in-lab measurements using a conventional lamp source. Spectral stability measurements are performed after atmospheric propagation through 1.6 km and show a relative variability of ~4%-8% across the spectrum depending on the atmospheric turbulence effects. Spectral stability measurements are also performed in-lab and show a relative variability of <0.6% across the spectrum. PMID:24085183

  9. Structure optimisation of short-wavelength ridge-waveguide InGaN\\/GaN diode lasers

    Microsoft Academic Search

    P. Karbownik; R. P. Sarza?a

    2008-01-01

    Room-temperature (RT) continuous-wave (CW) operation of the 405-nm ridge-waveguide (RW) InGaN\\/GaN quantum-well diode lasers\\u000a equipped with the n-type GaN substrate and two contacts on both sides of the structure has been investigated with the aid\\u000a of the comprehensive self-consistent simulation model. As expected, the mounting configuration (p-side up or down) has been\\u000a found to have a crucial impact on the

  10. Advanced short-wavelength infrared range-gated imaging for ground applications in monostatic and bistatic configurations.

    PubMed

    Repasi, Endre; Lutzmann, Peter; Steinvall, Ove; Elmqvist, Magnus; Göhler, Benjamin; Anstett, Gregor

    2009-11-01

    Some advanced concepts for gated viewing are presented, including spectral diversity illumination techniques, non-line-of-sight imaging, indirect scene illumination, and in particular setups in bistatic configurations. By using a multiple-wavelength illumination source target speckles could be substantially reduced, leading to an improved image quality and enhanced range accuracy. In non-line-of-sight imaging experiments we observed the scenery through the reflections in a window plane. The scene was illuminated indirectly as well by a diffuse reflection of the laser beam at different nearby objects. In this setup several targets could be spotted, which, e.g., offers the capability to look around the corner in urban situations. In the presented measuring campaigns the advantages of bistatic setups in comparison with common monostatic configurations are discussed. The appearance of shadows or local contrast enhancements as well as the mitigation of retroreflections supports the human observer in interpreting the scene. Furthermore a bistatic configuration contributes to a reduced dazzling risk and to observer convertness. PMID:19881663

  11. Investigation of the effect of bilayer membrane structures and fluctuation amplitudes on SANS/SAXS profile for short membrane wavelength

    SciTech Connect

    Lee, Victor; Hawa, Takumi [School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, Oklahoma 73019 (United States)] [School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, Oklahoma 73019 (United States)

    2013-09-28

    The effect of bilayer membrane structures and fluctuation amplitudes on small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS) profile is investigated based on harmonic motions of the surfactant bilayers with bending as well as thickness fluctuation motions. In this study we consider the case in which the wavelength of the bilayer membrane is shorter than the thickness of the membrane. We find that the thickness of the surfactant bilayer membrane, d{sub m}, affects both q{sub dip} and q{sub peak} of I(q,0) profile, and that the fluctuation amplitude, a, of the membrane changes the peak of I(q,0). A simple formula is derived to estimate the thickness of the bilayer based on the q{sub dip} of the profile obtained from the simulation. The resulting estimates of the thickness of the bilayer with harmonic motion showed accuracy within 1%. Moreover, the bilayer thicknesses estimated from the proposed formula show an excellent agreement with the SANS and SAXS experimental results available in the literatures. We also propose a curve fit model, which describes the relationship between the fluctuation amplitude and the normalized q{sub peak} ratio. The present results show the feasibility of the simple formula to estimate the fluctuation amplitude based on the SANS and SAXS profiles.

  12. Spectroscopic and thermal properties of short wavelength metal (II) complexes containing ?-isoxazolylazo-?-diketones as co-ligands

    NASA Astrophysics Data System (ADS)

    Huang, Fuxin; Wu, Yiqun; Gu, Donghong; Gan, Fuxi

    2005-10-01

    Two new azo dyes of ?-isoxazolylazo-?-diketones and their Ni(II) and Cu(II) complexes with blue-violet light wavelength were synthesized using a coupling component, different diazo components and metal (II) ions (Ni 2+ and Cu 2+). Based on the elemental analysis, MS spectra and FT-IR spectral analyses, azo dyes were unequivocally shown to exist as hydrazoketo and azoenol forms which were respectively obtained from the solution forms and from the solid forms. The action of sodium methoxide (NaOMe) on azo dyes in solutions converts hydrazoketo form into azoenol form, so azo dyes are coordinated with metal (II) ions as co-ligands in the azoenol forms. The solubility of all the compounds in common organic solvents such as 2,2,3,3-tetrafluoro-1-propanol (TFP) or chloroform (CHCl 3) and absorption properties of spin-coating thin films were measured. The difference of absorption maxima from the complexes to their ligands was discussed. In addition, the TG analysis of the complexes was also determined, and their thermal stability was evaluated. It is found that these new metal (II) complexes had potential application for high-density digital versatile disc-recordable (HD-DVD-R) system due to their good solubility in organic solvents, reasonable and controllable absorption spectra in blue-violet light region and high thermal stability.

  13. Testing gravitational parity violation with coincident gravitational waves and short gamma-ray bursts

    SciTech Connect

    Yunes, Nicolas [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States); Department of Physics, Institute for Gravitation and the Cosmos, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); O'Shaughnessy, Richard [Department of Physics, Institute for Gravitation and the Cosmos, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Owen, Benjamin J. [Department of Physics, Institute for Gravitation and the Cosmos, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Max Planck Institut fuer Gravitationsphysik (Albert Einstein Institut), Callinstr. 38, 30167 Hannover (Germany); Alexander, Stephon [Department of Physics, Institute for Gravitation and the Cosmos, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Department of Physics and Astronomy, Haverford College, Haverford, Pennsylvania 19041 (United States)

    2010-09-15

    Gravitational parity violation is a possibility motivated by particle physics, string theory, and loop quantum gravity. One effect of it is amplitude birefringence of gravitational waves, whereby left and right circularly polarized waves propagate at the same speed but with different amplitude evolution. Here we propose a test of this effect through coincident observations of gravitational waves and short gamma-ray bursts from binary mergers involving neutron stars. Such gravitational waves are highly left or right circularly polarized due to the geometry of the merger. Using localization information from the gamma-ray burst, ground-based gravitational wave detectors can measure the distance to the source with reasonable accuracy. An electromagnetic determination of the redshift from an afterglow or host galaxy yields an independent measure of this distance. Gravitational parity violation would manifest itself as a discrepancy between these two distance measurements. We exemplify such a test by considering one specific effective theory that leads to such gravitational parity violation, Chern-Simons gravity. We show that the advanced LIGO-Virgo network and all-sky gamma-ray telescopes can be sensitive to the propagating sector of Chern-Simons gravitational parity violation to a level roughly 2 orders of magnitude better than current stationary constraints from the LAGEOS satellites.

  14. Waveform modeling of short-scale shear-wave splitting variations across the Dead Sea basin

    NASA Astrophysics Data System (ADS)

    Kaviani, A.; Rumpker, G.

    2010-12-01

    The Dead Sea basin forms the largest pull-apart basin along the Dead Sea transform fault. As part of the DESIRE project, we investigate the seismic anisotropy across the Dead Sea basin to study mantle deformation processes. We examine shear-wave splitting of SKS waveforms collected by a temporary array of 68 stations along the Dead Sea basin. The observed splitting parameters (i.e. the delay time between the fast and slow shear waves and the polarization direction of the fast shear wave) exhibit systematic variations along an EW-trending profile across the basin. The delay times vary between 1.0 and 2.8 seconds and are among the largest observed in the world. The fast polarizations are oriented more-or-less parallel to the strike of the Dead Sea transform fault and vary between -10 and 20 degrees with respect to North. Full finite-difference waveform modeling reveals that the source-region of the small-scale lateral variations is likely located within the crust. The modeling further shows that purely isotropic velocity variations can affect shear-wave splitting. To a large degree, the observed variations of splitting parameters can be explained by the sedimentary fill of the basin and its low seismic velocities. Our study indicates that precaution must be taken when interpreting short-scale lateral variations of shear wave splitting in terms of anisotropic structures in the crust or upper mantle.

  15. Testing gravitational parity violation with coincident gravitational waves and short gamma-ray bursts

    E-print Network

    Nicolas Yunes; Richard O'Shaughnessy; Benjamin J. Owen; Stephon Alexander

    2010-05-18

    Gravitational parity violation is a possibility motivated by particle physics, string theory and loop quantum gravity. One effect of it is amplitude birefringence of gravitational waves, whereby left and right circularly-polarized waves propagate at the same speed but with different amplitude evolution. Here we propose a test of this effect through coincident observations of gravitational waves and short gamma-ray bursts from binary mergers involving neutron stars. Such gravitational waves are highly left or right circularly-polarized due to the geometry of the merger. Using localization information from the gamma-ray burst, ground-based gravitational wave detectors can measure the distance to the source with reasonable accuracy. An electromagnetic determination of the redshift from an afterglow or host galaxy yields an independent measure of this distance. Gravitational parity violation would manifest itself as a discrepancy between these two distance measurements. We exemplify such a test by considering one specific effective theory that leads to such gravitational parity-violation, Chern-Simons gravity. We show that the advanced LIGO-Virgo network and all-sky gamma-ray telescopes can be sensitive to the propagating sector of Chern-Simons gravitational parity violation to a level roughly two orders of magnitude better than current stationary constraints from the LAGEOS satellites.

  16. Multi-Year Analysis of Short-Period Gravity Waves Over Alaska

    NASA Astrophysics Data System (ADS)

    Johnson, Kasey; Nielsen, Kim; Negale, Michael; Pautet, Pierre-Dominique; Taylor, Michael; Chandran, Amal; Harvey, Lynn

    2014-05-01

    We present a four-year analysis of short period gravity waves measured by an airglow imager situated in Poker Flat, Alaska (65 N, 147 W). The imager is the cornerstone of the mesospheric airglow imaging and dynamics (MAID) project. This project is a collaborative effort between Utah Valley University, University of Alaska, Fairbanks and Utah State University, and employs the NICT Rayleigh Lidar System together with support observations from the co-located MF Radar and the NSF sponsored Poker Flat ISR. The overarching goal of the project is to characterize the waves, their variability, and how stratospheric weather impacts the observed wave field. A recent study utilizing two years of data (2011-2012) showed a preponderance for eastward propagating waves, which is in stark contrast to other polar sites that have shown dominant westward motions. Furthermore, the study revealed a significant year to year variability in the observed phase speeds. In the study presented here, two years of additional data have been analyzed to further investigate the year to year variability and correlate the observed wave parameters to stratospheric weather phenomena including the Aleutian low, the polar vortex, and sudden stratospheric warming events.

  17. Multi-physics investigation on the failure mechanism and short-time scale wave motion in flip-chip configuration 

    E-print Network

    Oh, Yoonchan

    2005-11-01

    thermal stresses and improving solder joint fatigue performance in thermal cycling tests of long-time scale, underfill material viscoelasticity was found to be insignificant in attenuating short-time scale wave propagation. On the other hand...

  18. ERS-1 and Seasat scatterometer measurements of ocean winds: Model functions and the directional distribution of short waves

    NASA Technical Reports Server (NTRS)

    Freilich, Michael H.; Dunbar, R. Scott

    1993-01-01

    Calculation of accurate vector winds from scatterometers requires knowledge of the relationship between backscatter cross-section and the geophysical variable of interest. As the detailed dynamics of wind generation of centimetric waves and radar-sea surface scattering at moderate incidence angles are not well known, empirical scatterometer model functions relating backscatter to winds must be developed. Less well appreciated is the fact that, given an accurate model function and some knowledge of the dominant scattering mechanisms, significant information on the amplitudes and directional distributions of centimetric roughness elements on the sea surface can be inferred. accurate scatterometer model functions can thus be used to investigate wind generation of short waves under realistic conditions. The present investigation involves developing an empirical model function for the C-band (5.3 GHz) ERS-1 scatterometer and comparing Ku-band model functions with the C-band model to infer information on the two-dimensional spectrum of centimetric roughness elements in the ocean. The C-band model function development is based on collocations of global backscatter measurements with operational surface analyses produced by meteorological agencies. Strengths and limitations of the method are discussed, and the resulting model function is validated in part through comparison with the actual distributions of backscatter cross-section triplets. Details of the directional modulation as well as the wind speed sensitivity at C-band are investigated. Analysis of persistent outliers in the data is used to infer the magnitudes of non-wind effects (such as atmospheric stratification, swell, etc.). The ERS-1 C-band instrument and the Seasat Ku-band (14.6 GHz) scatterometer both imaged waves of approximately 3.4 cm wavelength assuming that Bragg scattering is the dominant mechanism. Comparisons of the C-band and Ku-band model functions are used both to test the validity of the postulated Bragg mechanism and to investigate the directional distribution of the imaged waves under a variety of conditions where Bragg scatter is dominant.

  19. Potential of short Si–Ti–C–O fiber-reinforced epoxy matrix composite as electromagnetic wave absorbing material

    Microsoft Academic Search

    Y. Kagawa; K. Matsumura; H. Iba; Y. Imahashi

    2007-01-01

    The effects of fiber electrical properties on electromagnetic wave absorbing potential in short Si–Ti–C–O fiber-dispersed\\u000a epoxy matrix composites were studied. Six kinds of short Si–Ti–C–O fibers with different respective electrical resistivity\\u000a were incorporated into an epoxy matrix and the dielectric properties of the composites in a frequency range from 1 MHz to\\u000a 1 GHz were measured. The penetration depth of electromagnetic wave,

  20. Detailed gravimetric geoid confirmation of short wavelength features of sea surface topography detected by the Skylab S-193 altimeter in the Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    Marsh, J. G.; Vincent, S.; Mcclinton, A. T.; Chang, E. S.

    1975-01-01

    A detailed gravimetric geoid was computed for the Northwest Atlantic Ocean and Caribbean Sea area in support of the calibration and evaluation of the GEOS-C altimeter. This geoid, computed on a 15 ft. x 15 ft. grid was based upon a combination of surface gravity data with the GSFC GEM-6 satellite derived gravity data. A comparison of this gravimetric geoid with 10 passes of SKYLAB altimeter data is presented. The agreement of the two data types is quite good with the differences generally less than 2 meters. Sea surface manifestations of numerous short wavelength (approximately 100 km) oceanographic features are now indicated in the gravimetric geoid and are also confirmed by the altimetry data.

  1. Electron acceleration in relativistic plasma waves generated by a single frequency short-pulse laser

    SciTech Connect

    Coverdale, C.A.; Darrow, C.B.; Decker, C.D. [Lawrence Livermore National Lab., CA (United States); Mori, W.B.; Tzeng, K.C., Clayton, C.E.; Marsh, K.A.; Joshi, C. [California Univ., Los Angeles, CA (United States)

    1995-04-27

    Experimental evidence for the acceleration of electrons in a relativistic plasma wave generated by Raman forward scattering (SRS-F) of a single-frequency short pulse laser are presented. A 1.053 {mu}m, 600 fsec, 5 TW laser was focused into a gas jet with a peak intensity of 8{times}10{sup 17} W/cm{sup 2}. At a plasma density of 2{times}10{sup 19} cm{sup {minus}3}, 2 MeV electrons were detected and their appearance was correlated with the anti-Stokes laser sideband generated by SRS-F. The results are in good agreement with 2-D PIC simulations. The use of short pulse lasers for making ultra-high gradient accelerators is explored.

  2. In-depth Plasma-Wave Heating of Dense Plasma Irradiated by Short Laser Pulses

    NASA Astrophysics Data System (ADS)

    Sherlock, M.; Hill, E. G.; Evans, R. G.; Rose, S. J.; Rozmus, W.

    2014-12-01

    We investigate the mechanism by which relativistic electron bunches created at the surface of a target irradiated by a very short and intense laser pulse transfer energy to the deeper parts of the target. In existing theories, the dominant heating mechanism is that of resistive heating by the neutralizing return current. In addition to this, we find that large amplitude plasma waves are induced in the plasma in the wake of relativistic electron bunches. The subsequent collisional damping of these waves represents a source of heating that can exceed the resistive heating rate. As a result, solid targets heat significantly faster than has been previously considered. A new hybrid model, capable of reproducing these results, is described.

  3. Simultaneous multichannel wavelength multicasting and XOR logic gate multicasting for three DPSK signals based on four-wave mixing in quantum-dot semiconductor optical amplifier.

    PubMed

    Qin, Jun; Lu, Guo-Wei; Sakamoto, Takahide; Akahane, Kouichi; Yamamoto, Naokatsu; Wang, Danshi; Wang, Cheng; Wang, Hongxiang; Zhang, Min; Kawanishi, Tetsuya; Ji, Yuefeng

    2014-12-01

    In this paper, we experimentally demonstrate simultaneous multichannel wavelength multicasting (MWM) and exclusive-OR logic gate multicasting (XOR-LGM) for three 10Gbps non-return-to-zero differential phase-shift-keying (NRZ-DPSK) signals in quantum-dot semiconductor optical amplifier (QD-SOA) by exploiting the four-wave mixing (FWM) process. No additional pump is needed in the scheme. Through the interaction of the input three 10Gbps DPSK signal lights in QD-SOA, each channel is successfully multicasted to three wavelengths (1-to-3 for each), totally 3-to-9 MWM, and at the same time, three-output XOR-LGM is obtained at three different wavelengths. All the new generated channels are with a power penalty less than 1.2dB at a BER of 10(-9). Degenerate and non-degenerate FWM components are fully used in the experiment for data and logic multicasting. PMID:25606876

  4. Six-Wave Forward Scattering of Short-Pulse Laser Light at Relativistic Intensities

    NASA Astrophysics Data System (ADS)

    Barr, H. C.; Berwick, S. J.; Mason, P.

    1998-10-01

    Forward scattering of short linearly polarized laser pulses in underdense plasma at relativistic intensities is examined. The linear polarization gives rise to a six-wave hybrid of the Raman forward scattering and relativistic modulational instabilities. Destructive interference between fluctuations in electron density and relativistic mass through the intervention of two high-frequency electrostatic modes decouples higher-order harmonics. This allows simple spacetime and spectral laser-pulse rest-frame models to be derived which are valid for arbitrarily high-laser intensities.

  5. [A case of hypertrophic obstructive cardiomyopathy with marked T wave changes during the short-term].

    PubMed

    Kageyama, F; Iida, H; Yositomi, A; Ikegaya, H; Okano, H; Fujimoto, K; Tagata, M; Nagao, M; Yosimi, T; Itou, T

    1993-01-01

    A 72-years-old woman was admitted to our hospital for evaluation of giant negative T waves, which appeared for only two days. Chest X-p revealed a cardiomegaly of slight degree and UCG showed ASH (IVS = 21 mm). Coronary arteriography presented no significant stenosis and the left ventricle was spade-shaped. There was a pressure gradient of 65 mmHg between the aorta and the left ventricle during isoproterenol infusion. Furthermore, endomyocardial biopsy showed disarray and fibrosis to a slight degree and fatty degeneration of myocytes with contraction bands. Based on these findings, calcium blocker was administrated under the diagnosis of HOCM. One month after the initiation of this drug, negative T waves gradually became shallow and finally upright with thinning of IVS (12 mm) four month later. We swimise that this T-wave change is primarily based on myocardial hypertrophy as well as being due to the abnormality of myocardial depolarization. We presented a case of HOCM with negative T-wave change of very short duration, which was improved by calcium-blocker and beta-blocker. PMID:8094573

  6. Polarization-independent wavelength conversion at 2.5 Gb\\/s by dual-pump four-wave mixing in a strained semiconductor optical amplifier

    Microsoft Academic Search

    Guido Hunziker; Roberto Paiella; David F. Geraghty; Kerry J. Vahala; Uzi Koren

    1996-01-01

    We give a general expression for the polarization dependence of the four-wave mixing (FWM) efficiency in the dual-pump configuration. This expression, along with some general properties of the FWM susceptibility tensor, is used to propose a simple scheme to generate a nearly (1.5-dB variation) polarization independent FWM converted signal. The viability of this scheme is verified in a wavelength conversion

  7. Polarization-Independent Wavelength Conversion at 2.5 Gb\\/s by Dual-Pump Four-Wave Mixing in a Strained Semiconductor Opticall Amplifier

    Microsoft Academic Search

    Guido Hunziker; Roberto Paiella; David F. Geraghty; Kerry J. Vahala; Uzi Koren

    1996-01-01

    We give a general expression for the polarization dependence of the four-wave mixing (FWM) efficiency in the dual-pump configuration. This expression, along with some gen- eral properties of the FWM susceptibility tensor, is used to propose a simple scheme to generate a nearly (1.5-dB variation) polarization independent FWM converted signal. The viability of this scheme is verified in a wavelength

  8. Broad-band continuous-wave-pumped fiber optical parametric amplifier with 49dB gain and wavelength-conversion efficiency

    Microsoft Academic Search

    Jonas Hansryd; Peter A. Andrekson

    2001-01-01

    A broad-band continuous-wave (CW) pumped fiber-based parametric amplifier with 39 dB of internal gain and wavelength conversion efficiency, corresponding to a black box gain\\/efficiency of 38 dB, is demonstrated. Bit-error-rate (BER) measurements indicate performance comparable to erbium-doped fiber amplifiers (EDFAs). These amplifiers may thus find new applications in future lightwave systems

  9. Wavelength converter based on four-wave mixing in a bulk semiconductor optical amplifier assisted by a Sagnac Interferometer and polarizer

    NASA Astrophysics Data System (ADS)

    Enríquez, M. C. Acosta; Soto, H.; Basilio, R. G. Maldonado

    2008-04-01

    Several works has recently been focused on the study of the Four Wave Mixing (FWM) process developed into a Semiconductor Optical Amplifier (SOA) for the implementation of all-optical wavelength converters. In this process, the maximum conversion efficiency is generally obtained at very close pump and probe wavelengths. In this condition, however, the engendered signal has a significant intensity. For this reason, it is important to develop filtering techniques allowing isolating the conjugated signal from all the others. In this manner, we show in this work a novel configuration of a wavelength converter based on FWM developed into a SOA and assisted by a Sagnac interferometer and a polarizer. In particular, the Sagnac interferometer is used to filter out the input pump and probe signals, whilst the polarizer filters the engendered signal and suppress the SOA-amplified spontaneous emission. As a result, it was obtained that for a wavelength difference as small as 0.43 nm between the pump and probe beams, the overall system output powers corresponding to the pump, probe and engendered signals were reduced approximately in 27, 29 and 29 dBm, respectively, allowing a complete filtering of the wavelength converted conjugated signal.

  10. Short Wavelength Electromagnetic Perturbations Excited Near the Solar Probe Plus Spacecraft in the Inner Heliosphere: 2.5D Hybrid Modeling

    NASA Technical Reports Server (NTRS)

    Lipatov, Alexander S.; Sittler, Edward C.; Hartle, Richard E.; Cooper, John F.

    2011-01-01

    A 2.5D numerical plasma model of the interaction of the solar wind (SW) with the Solar Probe Plus spacecraft (SPPSC) is presented. These results should be interpreted as a basic plasma model derived from the SW-interaction with the spacecraft (SC), which could have consequences for both plasma wave and electron plasma measurements on board the SC in the inner heliosphere. Compression waves and electric field jumps with amplitudes of about 1.5 V/m and (12-18) V/m were also observed. A strong polarization electric field was also observed in the wing of the plasma wake. However, 2.5D hybrid modeling did not show excitation of whistler/Alfven waves in the upstream connected with the bidirectional current closure that was observed in short-time 3D modeling SPPSC and near a tether in the ionosphere. The observed strong electromagnetic perturbations may be a crucial point in the electromagnetic measurements planned for the future Solar Probe Plus (SPP) mission. The results of modeling electromagnetic field perturbations in the SW due to shot noise in absence of SPPSC are also discussed.

  11. Design and development of wafer-level short wave infrared micro-camera

    NASA Astrophysics Data System (ADS)

    Sood, Ashok K.; Richwine, Robert A.; Pethuraja, Gopal; Puri, Yash R.; Lee, Je-Ung; Haldar, Pradeep; Dhar, Nibir K.

    2013-06-01

    Low cost IR Sensors are needed for a variety of Defense and Commercial Applications as low cost imagers for various Army and Marine missions. SiGe based IR Focal Planes offers a low cost alternative for developing wafer-level shortwave infrared micro-camera that will not require any cooling and can operate in the Visible-NIR band. The attractive features of SiGe based IRFPA's will take advantage of Silicon based technology, that promises small feature size and compatibility with the low power silicon CMOS circuits for signal processing. SiGe technology offers a low cost alternative for developing Visible-NIR sensors that will not require any cooling and can operate from 0.4- 1.7 microns. The attractive features of SiGe based IRFPA's will take advantage of Silicon based technology that can be processed on 12-inch silicon substrates, that can promise small feature size and compatibility with the Silicon CMOS circuit for signal processing. In this paper, we will discuss the design and development of Wafer-Level Short Wave Infrared (SWIR) Micro-Camera. We will discuss manufacturing approaches and sensor configurations for short wave infrared (SWIR) focal plane arrays (FPAs) that significantly reduce the cost of SWIR FPA packaging, optics and integration into micro-systems.

  12. [Use of short wave ultraviolet radiation for disinfection in operating rooms].

    PubMed

    Bånrud, H; Moan, J

    1999-08-10

    Over a number of years, short wave ultraviolet radiation (UVC; 200-280 nm) has been used to disinfect air and surfaces in operating rooms, patient rooms, laboratories and so on, as well as air in ventilation ducts. Despite the well-documented effect of ultraviolet radiation on air quality, thus reducing the occurrence of infections, this technology has been relatively little used. One advantage of this method is that the UVC sources ensure a continuous reduction in the number of airborne microorganisms that are generated all the time. There are, however, some disadvantages with this method. Human exposure to ultraviolet C may cause keratoconjunctivitis and erythema and requires protection of the skin and the eyes of people exposed to levels above recommended exposure limits. However, by enclosing the UVC sources or by irradiating in the absence of human activity, human exposure is eliminated. These and other aspects concerning the use of short wave ultraviolet radiation as a disinfection agent in operating rooms are discussed in this article. PMID:10479982

  13. An analysis of short pulse and dual frequency radar techniques for measuring ocean wave spectra from satellites

    NASA Technical Reports Server (NTRS)

    Jackson, F. C.

    1980-01-01

    Scanning beam microwave radars were used to measure ocean wave directional spectra from satellites. In principle, surface wave spectral resolution in wave number can be obtained using either short pulse (SP) or dual frequency (DF) techniques; in either case, directional resolution obtains naturally as a consequence of a Bragg-like wave front matching. A four frequency moment characterization of backscatter from the near vertical using physical optics in the high frequency limit was applied to an analysis of the SP and DF measurement techniques. The intrinsic electromagnetic modulation spectrum was to the first order in wave steepness proportional to the large wave directional slope spectrum. Harmonic distortion was small and was a minimum near 10 deg incidence. NonGaussian wave statistics can have an effect comparable to that in the second order of scattering from a normally distributed sea surface. The SP technique is superior to the DF technique in terms of measurement signal to noise ratio and contrast ratio.

  14. Determination of Seed Soundness in Conifers Cryptomeria japonica and Chamaecyparis obtusa Using Narrow-Multiband Spectral Imaging in the Short-Wavelength Infrared Range

    PubMed Central

    Matsuda, Osamu; Hara, Masashi; Tobita, Hiroyuki; Yazaki, Kenichi; Nakagawa, Toshinori; Shimizu, Kuniyoshi; Uemura, Akira; Utsugi, Hajime

    2015-01-01

    Regeneration of planted forests of Cryptomeria japonica (sugi) and Chamaecyparis obtuse (hinoki) is the pressing importance to the forest administration in Japan. Low seed germination rate of these species, however, has hampered low-cost production of their seedlings for reforestation. The primary cause of the low germinability has been attributed to highly frequent formation of anatomically unsound seeds, which are indistinguishable from sound germinable seeds by visible observation and other common criteria such as size and weight. To establish a method for sound seed selection in these species, hyperspectral imaging technique was used to identify a wavelength range where reflectance spectra differ clearly between sound and unsound seeds. In sound seeds of both species, reflectance in a narrow waveband centered at 1,730 nm, corresponding to a lipid absorption band in the short-wavelength infrared (SWIR) range, was greatly depressed relative to that in adjacent wavebands on either side. Such depression was absent or less prominent in unsound seeds. Based on these observations, a reflectance index SQI, abbreviated for seed quality index, was formulated using reflectance at three narrow SWIR wavebands so that it represents the extent of the depression. SQI calculated from seed area-averaged reflectance spectra and spatial distribution patterns of pixelwise SQI within each seed area were both proven as reliable criteria for sound seed selection. Enrichment of sound seeds was accompanied by an increase in germination rate of the seed lot. Thus, the methods described are readily applicable toward low-cost seedling production in combination with single seed sowing technology. PMID:26083366

  15. Signature of gravitational wave radiation in afterglows of short gamma-ray bursts?

    NASA Astrophysics Data System (ADS)

    Fan, Yi-Zhong; Wu, Xue-Feng; Wei, Da-Ming

    2013-09-01

    Short gamma-ray bursts (GRBs), brief intense emission of ? rays characterized by a duration shorter than 2 s that are plausibly powered by the coalescence of binary neutron stars, are believed to be strong gravitational wave radiation (GWR) sources. The test of such a speculation has been thought to be impossible until the performance of the detectors like advanced LIGO. Recently there has been growing evidence for the formation of a highly magnetized neutron star (i.e., magnetar) in the double neutron star mergers. In this work we reexamine the interpretation of the x-ray plateau followed by an abrupt decline detected in some short GRB afterglows within the supramassive magnetar model and find that the maximum gravitational mass of the nonrotating neutron stars is ˜2.3M? and the observed duration of some x-ray plateaus are significantly shorter than that expected in the magnetic dipole radiation scenario, suggesting that the collapse of the supramassive magnetars has been considerably enhanced by the energy loss via GWR. Such a result demonstrates that the signature of GWR may have already existed in current electromagnetic data of short GRBs.

  16. Influence of tropical F region in ionosphere on propagation of short radio waves

    NASA Astrophysics Data System (ADS)

    Kolomiytsev, O. P.; Savchenko, P. P.

    1985-05-01

    Tropical ionospheric waveguides in the presence of stratification of the electron concentration maximum were studied. Under these conditions a specific form of vertical electron concentration profile is formed which to a great extent determines the nature and conditions of propagation of short radio waves in the low latitudes. The phase trajectories were computed for a spherically stratified ionosphere. Three approaches for description of the ionospheric waveguide were used: comparative, temporal, latitudinal. Examples of computations are given which show that in a wide spatial-temporal range in the tropical ionosphere there is an additional ionospheric waveguide in which radio waves can be propagated along ricochetting trajectories. At identical time there can be three types of phases trajectories or three types of adjacent channels, each of which is characterized by a definite working frequency and definite conditions for the propagation of radio waves in it. The computations presented give a qualitative representation of the influence of stratification of the electron concentration on the formation, dynamics and degeneration of the additional ionospheric waveguides in the tropical latitudes.

  17. Con_A-carbone nanotube conjugate with short wave near-infrared laser ablation for tumor therapy

    NASA Astrophysics Data System (ADS)

    Lei, Huan-Yao; Peng, Ching-An; Tang, Ming-Jer; Reindhart, Kit; Szu, Harold H.

    2009-04-01

    Using the characteristics of T cell mitogen called lectin protein from the jack-beam Canavalia ensiformis Concanavalin A (Con_A) with dual activities, cytotoxicity and immunomodulation, we have shown it has a therapeutic effect on hepatoma. Injection of Con_A can eradicate the established malign tumor, because Con_A can induce tumor cell autophagic, cell-programmed death, as well as activate the effector T cells. Combined, in this paper, with the absorption exceeding the Carbon NanoTube (CNT) band-gap (?bg=~1/CNT diameter) with an active short wave near-infrared (SWIR) (1.2~1.5 micron wavelengths), which happened to be translucent to the irradiation upon animal skin, similar to that used in hospital fingertip-clamped Pulse Oxymetry. Once the Con_ACNT is guided to hepatoma cells, it is bonded and internalized into the mitochondria (MC) compartment, the cellular energy factory. Con_A has the higher specificity for tumor cells useful for targeting because of the abnormal glycosylation on tumor cells. When CNT hitch hike with Con_A, they can t together like a laser-denotable chemical missile surgically targeting at the tumor cells precisely by Con_A-guidance. We switch on SWIR laser, when the Con_A-CNT conjugated complex has been bonded and internalized to MC of malign cells and already commenced cellular programmed death. Thus, it might appear to casual readers that we have initiated an overkill, chemical drugged autophage followed with physical laser ablation, but what if we can eradicate hepatoma totally if no blue print is left behind inadvertently in case of a partial failure. We conclude that using Con_A-CNT conjugated complex targeting specifically at malign tumor cells is a novel targeted-laser-radiation therapy for tumors in mice.

  18. On-chip interconnect for mm-wave applications using an all-copper technology and wavelength reduction

    Microsoft Academic Search

    T. S. D. Cheung; J. R. Long; K. Vaed; R. Volant; A. Chinthakindi; C. M. Schnabel; J. Florkey; K. Stein

    2003-01-01

    Transmission lines are implemented using an all-copper backend developed for RF and microwave applications. Wavelength reduction is used to achieve a Q factor >20 from 20GHz to 40GHz, about three times higher than conventional transmission lines implemented with the same technology. It has 0.3dB\\/mm loss, and reduces the wavelength of a conventional transmission line by half thereby minimizing the space

  19. Investigating Propagation of Short-period Gravity Waves at High Altitudes Utilizing Re-analysis and Ray Tracing Models

    NASA Astrophysics Data System (ADS)

    Nielsen, K.; Pautet, P.; Taylor, M. J.; Broutman, D.; Collins, R. L.; Irving, B.; Negale, M.; Siskind, D. E.; Eckermann, S. D.; Hoppel, K.; Martin, T.; Harvey, V.

    2012-12-01

    Short-period gravity waves exhibiting periods <1 hour are of great interest as these waves propagate near vertically and transport large amount of momentum flux into the mesosphere and lower thermosphere (MLT) region. They have preponderance for propagation against the background flow and, when breaking and depositing the momentum flux decrease or even reverse this flow. The propagation nature and sources of short-period mesospheric gravity waves have been studied extensively at low and mid-latitudes, while their extent and nature at the Polar Regions are less known. During the last decade, observations from select sites on the Antarctic continent have revealed a significant presence of short-period gravity waves over the southern Polar Region as well as shown unexpected dynamical behavior. A most recent study from Halley, Antarctica, have shown the majority of the waves to be vertically propagating in the MLT region, which is in stark contrast to similar studies at mid-latitudes, where the waves are prone to ducted motion. In this presentation, we elaborate on the propagation characteristics throughout the middle atmosphere of waves observed over the Polar Regions by using global scale reanalysis and ray tracing models.

  20. Generation of visible wavelength by the phase-matching four-wave mixing in an Yb-doped V-shape photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Li, Lixiao; Yuan, Jinhui; Sang, Xinzhu; Yan, Binbin; Wang, Kuiru; Yu, Chongxiu; Han, Ying; Xia, Changming; Zhou, Guiyao; Wei, Shuai; Wang, Chao; Yang, Jianju; Wang, Shuang; Cheng, Xu; Hou, Lantian

    2015-07-01

    In this paper, an Ytterbium-doped V-shape photonic crystal fiber (Yb-VPCF) with low dispersion and high nonlinearity is designed and fabricated in our laboratory. Through coupling femtosecond pulses into the fundamental mode of Yb-VPCF, the tunable anti-Stokes signals at the visible wavelength are efficiently generated based on the phase-matching four-wave mixing. When the pump wavelength is changed from 810, to 820, and to 830 nm and the input average power is increased from 0.4, to 0.5, and to 0.6 W, respectively, the anti-Stokes signals are generated within the wavelength range of 562-477 nm. The wavelength-tunable range is over 100 nm, and the maximum power ratio of anti-Stokes signal at 477 nm and the residual pump at 830 nm can be up to 23.9:1. The anti-Stokes signals generated can be used as the ultrashort pulse sources for ultrafast optoelectronics and spectroscopy.

  1. Short pulse radar used to measure sea surface wind speed and SWH. [Significant Wave Height

    NASA Technical Reports Server (NTRS)

    Hammond, D. L.; Mennella, R. A.; Walsh, E. J.

    1977-01-01

    A joint airborne measurement program is being pursued by NRL and NASA Wallops Flight Center to determine the extent to which wind speed and sea surface significant wave height (SWH) can be measured quantitatively and remotely with a short pulse (2 ns), wide-beam (60 deg), nadir-looking 3-cm radar. The concept involves relative power measurements only and does not need a scanning antenna, Doppler filters, or absolute power calibration. The slopes of the leading and trailing edges of the averaged received power for the pulse limited altimeter are used to infer SWH and surface wind speed. The interpretation is based on theoretical models of the effects of SWH on the leading edge shape and rms sea-surface slope on the trailing-edge shape. The models include the radar system parameters of antenna beam width and pulsewidth.

  2. Tumor selective hyperthermia induced by short-wave capacitively-coupled RF electric-fields.

    PubMed

    Raoof, Mustafa; Cisneros, Brandon T; Corr, Stuart J; Palalon, Flavio; Curley, Steven A; Koshkina, Nadezhda V

    2013-01-01

    There is a renewed interest in developing high-intensity short wave capacitively-coupled radiofrequency (RF) electric-fields for nanoparticle-mediated tumor-targeted hyperthermia. However, the direct thermal effects of such high-intensity electric-fields (13.56 MHZ, 600 W) on normal and tumor tissues are not completely understood. In this study, we investigate the heating behavior and dielectric properties of normal mouse tissues and orthotopically-implanted human hepatocellular and pancreatic carcinoma xenografts. We note tumor-selective hyperthermia (relative to normal mouse tissues) in implanted xenografts that can be explained on the basis of differential dielectric properties. Furthermore, we demonstrate that repeated RF exposure of tumor-bearing mice can result in significant anti-tumor effects compared to control groups without detectable harm to normal mouse tissues. PMID:23861912

  3. Resonant excitation of coupled Rayleigh waves in a short and narrow fluid channel clad between two identical metal plates

    DOE PAGESBeta

    García-Chocano, Victor M.; López-Rios, Tomás; Krokhin, Arkadii; Sanchez-Dehesa, Jose

    2011-12-23

    Transmission of ultrasonic waves through a slit between two water immersed brass plates is studied for sub-wavelength plate thicknesses and slit apertures. Extraordinary high absorption is observed at discrete frequencies corresponding to resonant excitation of Rayleigh waves on the both sides of the channel. The coupling of the Rayleigh waves occurs through the fluid and the corresponding contribution to the dispersion has been theoretically derived and also experimentally confirmed. Symmetric and anti-symmetric modes are predicted but only the symmetric mode resonances have been observed. It follows from the dispersion equation that the coupled Rayleigh waves cannot be excited in amore »channel with apertures less than the critical one. The calculated critical aperture is in a good agreement with the measured acoustic spectra. These findings could be applied to design a broadband absorptive metamaterial.« less

  4. Dispersion engineered As(2)S(3) planar waveguides for broadband four-wave mixing based wavelength conversion of 40 Gb/s signals.

    PubMed

    Luan, Feng; Pelusi, Mark D; Lamont, Michael R E; Choi, Duk-Yong; Madden, Steve; Luther-Davies, Barry; Eggleton, Benjamin J

    2009-03-01

    We demonstrate broadband wavelength conversion of a 40 Gb/s return-to-zero signal using four-wave-mixing (FWM) in a dispersion engineered chalcogenide glass waveguide. The 6 cm long planar rib waveguide 2 mum wide was fabricated in a 0.87 mum thick film etched 350nm deep to correspond to a design where waveguide dispersion offsets the material leading to near-zero dispersion in the C-band and broadband phase matched FWM. The reduced dimensions also enhance the nonlinear coefficient to 9800 W(-1)km(-1) at 1550 nm enabling broadband conversion in a shorter device. In this work, we demonstrate 80 nm wavelength conversions with 1.65 dB of power penalty at a bit-error rate of 10(-9). Spectral measurements and simulations indicate extended broadband operation is possible. PMID:19259190

  5. Whole Mantle 1-D Structure From Short-period Body Waves

    NASA Astrophysics Data System (ADS)

    Shearer, P.; Oki, S.

    2007-12-01

    Modeling Earth's anelastic structure as well as elastic structure is important for several reasons: (1) the depth dependence of attenuation and the shear-to-bulk Q ratio constrain the physical state of the deep Earth including its melt content, (2) attenuation can be a strong indicator of temperature variations because they have a larger effect on attenuation than on elastic velocity, and (3) attenuation causes physical dispersion of seismic velocities, which must be taken into account when interpreting travel time data. However, attenuation studies have proven challenging because of the typically large scatter in attenuation measurements and the difficulty in separating out source and elastic propagation effects from the intrinsic attenuation signal. We describe a new 1-dimensional Q model for short-period body waves. It is modeled from a dataset of 15,000 differential t* measurements of teleseismic P and S waves recorded in broadband seismograms. The S waveform is synthesized from the observed P wave and then cross-correlated to the observed S wave. The t* that gives the best correlation coefficient provides an estimate of attenuation along the ray path. To avoid biases from multipathing and other propagation path effects, we perform the cross- correlation only on the first half swing of the waveform. An advantage of our dataset is that it is little affected by the source-time function or instrument response, since the P and S waves are recorded at the same station from the same event. We invert our t* measurements for a 3-layer Q? model (2 in upper mantle and 1 in lower mantle). Our new Q model has higher Q values (less attenuation) compared to existing Q models derived from longer period datasets, especially in the lower mantle. This is consistent with frequency dependence of Q as has been suggested both from laboratory experiments and previous seismic observations. The attenuation is strongest in the upper mantle and we examine regional variations in Q by computing station and event terms (i.e., by averaging the t* residuals). These results show correlations with tectonics that are generally consistent with regional attenuation studies.

  6. Geoacoustic inversion of short range source data using a plane wave reflection coefficient approach.

    PubMed

    Stotts, S A; Knobles, D P; Keller, J A; Piper, J N; Thompson, L A

    2006-12-01

    Acoustic time series data were collected in a shallow, hard bottom lake environment located in central Texas using both short range (2 m) implosive data, obtained with the source and a single hydrophone located near mid-depth in the waveguide, along with longer range implosive and explosive data from a near surface source to a bottom mounted hydrophone. Matched field inversions using simulated annealing were performed with a ray trace plus complex plane wave reflection coefficient forward propagation model that was validated in previous work. Isolating bottom interacting paths to perform the inversions is shown to be essential to reduce parameter uncertainties in the hard bottom environment and enables a systematic approach to the inversions which establishes the number of layers needed to represent the lake environment. Measured transmission loss data from a towed source were compared through a RMS error analysis to modeled transmission loss, constructed with the parameters from inversions of data from several source types, to further establish the validity of the inversion approach for this environment. Geoacoustic parameters obtained by inversions of short range, low frequency impulsive data are used to predict transmission loss at longer ranges and higher frequencies. The range dependence of the global minimum is discussed. PMID:17225390

  7. Design of readout IC for photoelectron detector of short-wave high frequency IRFPA

    NASA Astrophysics Data System (ADS)

    Wang, Pan; Ding, Rui-jun; Chen, Guo-qiang; Chen, Honglei

    2013-01-01

    Design of readout-integrated circuit(ROIC) with high frequency and low signal for 512×256 short wavelength(SW) inferred-focal-plane-arrays(IRFPAs) is presented. The ROIC with high performance in frame rate can integrate and read out the low signal. An analog signal chain, which contains CTIA, CDS module, amplifier of charge and complementary output stage, can satisfy the high frequency and low signal application. A reliable digital control structure of IRFPA ROIC is presented, with which the integral voltage of arbitrary contiguous or noncontiguous lines, rather than regular lines, can be selected to readout. The simulation and verification are completed both before and after completing the layout. The circuit's structure and operation principle are analyzed under the environment of mix-signal, and the result shows that the output dynamic range is over 2.5V, the charge capacity is more than 1Me-, the frame rate is 250Hz, the linearity within useful dynamic range is above 99.9 percent.

  8. Optimal design of high frequency readout IC for short-wave IRFPA

    NASA Astrophysics Data System (ADS)

    Wang, Pan; Chen, Guo-qiang; Gao, Lei; Zhou, Jie; Ding, Rui-jun

    2012-12-01

    High frequency readout-integrated circuit(ROIC) of 512×256 staring short wavelength(SW) infrared focal plane arrays(IRFPAs), focusing on high-frame rate output and noise suppression is implemented in this paper. The design of ROIC mentioned in it takes the previous version into account. The complete analog signal chain contains a novel input stage of capacitor feedback transimpedance amplifier(CTIA) preamplifier, a CDS (correlated double sampling) module, an amplifier of charge and complementary output stage. This ROIC is a full-custom flow integrated circuit design. The parasitic parameters are extracted once the layout is finished. Then the design is improved according to the result of post-layout simulation, which leads to the great improvements of the majority of parameters. The test and simulation results show that the output voltage range is 2.8V, the frame rate is 250Hz and the linearity within useful voltage range is above 99.1 percent, even when the temperature is 77K.

  9. A modified beam-to-earth transformation to measure short-wavelength internal waves with an Acoustic Doppler

    E-print Network

    Scotti, Alberto

    .S. Geological Survey, Woods Hole, MA 02543, USA 3 Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, MA 02543 4 Horizon Marine, Inc., Marion, MA 02738 Submitted, Journal of Oceanic, especially in coastal areas (Colosi et al. 2001; Holloway et al. 2001; Holt and Thorpe 1997; Liu et al. 1998

  10. The Effect of Concentration, Temperature and Wave-Length of Light upon the Verdet Constant of Cerous Chloride Solutions

    Microsoft Academic Search

    Francis G. Slack; Ralph L. Reeves; James A. Peoples

    1934-01-01

    The Verdet constants of solutions of cerous chloride in water have been measured at concentrations varying from zero to an almost saturated solution. Measurements were made at temperatures from 10 to 45°C and for the wavelengths 5893, 5461 and 4481A. The results are given in the form of curves showing the Verdet constant as a function of temperature and as

  11. Continuous Wave Laser Welding of Copper with Combined Beams at Wavelengths of 1030 nm and of 515 nm

    Microsoft Academic Search

    Axel Hess; Rainer Schuster; Andreas Heider; Rudolf Weber; Thomas Graf

    2011-01-01

    The low absorptivity of ?1?m laser *beam sources in copper materials is a major challenge. Deep penetration welding at ?1?m is only possible with brilliant lasers providing high power and small focus diameters. The absorptivity increases with shorter wavelengths and higher temperature of the surface of the specimen. To exploit these facts, a 1?m and a frequency doubled thindisk laser

  12. Gravitational wave signal of the short rise fling of galactic runaway pulsars

    NASA Astrophysics Data System (ADS)

    Mosquera Cuesta, Herman J.; Bonilla Quintero, Carlos A.

    2008-11-01

    Determination of pulsar parallaxes and proper motions addresses fundamental astrophysical open issues. Here, after scrutinizing the ATNF Catalog searching for pulsar distances and proper motions, we verify that for an ATNF sample of 212 galactic runaway pulsars (RAPs), which currently run across the Galaxy at very high speed and undergo large displacements, some gravitational wave (GW) signals produced by such present accelerations appear to be detectable after calibration against the Advanced LIGO (LIGO II). Motivated by this insight, we address the issue of the pulsar kick at birth, or the short rise fling from a supernova explosion, by adapting the theory for emission of GW by ultrarelativistic sources in this case in which the Lorentz factor is ?~1. We show that during the short rise fling each runaway pulsar (RAP) generates a GW signal with characteristic amplitude and frequency that makes it detectable by current GW interferometers. For a realistic analysis, an efficiency parameter is introduced to quantify the expenditure of the rise fling kinetic energy, which is estimated from the linear momentum conservation law applied to the supernova explosion that kicks out the pulsar. The remaining energy is supposed to be used to make the star spin. Thus, a comparison with the spin of ATNF pulsars having velocities in the range 400-500 km s-1 is performed. The resulting difference suggests that other mechanisms (like differential rotation, magnetic breaking or magneto-rotational instability) should dissipate part of that energy to produce the observed pulsar spin periods. Meanwhile, the kick phenomenon may also occur in globular and open star clusters at the formation or disruption of very short period compact binary systems wherein abrupt velocity and acceleration similar to those given to RAPs during the short rise fling can be imparted to each orbital partner. To better analyze these cases, pulsar astrometry from micro-to nano-arcsec scales might be of great help. In the case of a supernova, the RAP GW signal could be a benchmark for the GW signal from the core collapse.

  13. Comparison of photonic integrated circuits for millimeter-wave signal generation between dual-wavelength sources for optical heterodyning and pulsed mode-locked lasers

    NASA Astrophysics Data System (ADS)

    Carpintero, Guillermo; Gordon, Carlos; Guzman, Robinson; Leijtens, Xaveer; Van Dijk, Frédéric; Kervella, Gaël.; Fice, Martyn J.; Balakier, Katarzyna; Renaud, Cyril C.

    2015-03-01

    A comparative study of two different Photonic Integrated Circuits (PICs) structures for continuous-wave generation of millimeter-wave (MMW) signals is presented, each using a different approach. One approach is optical heterodyning, using an integrated dual-wavelength laser source based on Arrayed Waveguide Grating. The other is based on ModeLocked Laser Diodes (MLLDs). A novel building block -Multimode Interference Reflectors (MIRs) - is used to integrate on-chip both structures, without need of cleaved facets to define the laser cavity. This fact enables us to locate any of these structures at any location within the photonic chip. As will be shown, the MLLD structure provides a simple source for low frequencies. Higher frequencies are easier to achieve by optical heterodyne. Both types of structures have been fabricated on a generic foundry in a commercial MPW PIC technology.

  14. Application of pulsed and continuous wave 1.32 and 1.06 microns wavelengths of the Nd:YAG laser in the canine tracheobronchial tree: a comparative study.

    PubMed

    Rebeiz, E E; Aretz, H T; Shapshay, S M; Pankratov, M M

    1990-01-01

    Previous investigations have shown good clinical potential for the use of the 1.32 microns wavelength Nd:YAG laser because its soft tissue absorption is better than that of the 1.06 microns wavelength Nd:YAG laser. The 1.32 microns wavelength Nd:YAG laser has an absorption coefficient in water that is 10 times higher than the 1.06 microns wavelength Nd:YAG laser. A comparative in vivo study of laser soft tissue effects was performed by using the 1.32 microns wavelength and the 1.06 microns wavelength Nd:YAG lasers in a pulsed wave (PW) mode and continuous wave (CW) mode using a non-contact endoscopic delivery system. A standard 5 mm mucosal lesion was made in the canine tracheobronchial tree down to the level of the perichondrium. Soft tissue and cartilage effects were examined by light and scanning electron microscopy, acutely, 1 week and 2 weeks after operation, and a comparison was made between the different laser modalities. To create similar lesions, higher energy was required when using the 1.06 microns wavelength Nd:YAG laser. Soft tissue injury was greater with the 1.06 microns wavelength in CW mode, and no cartilage damage occurred in the PW mode. Soft tissue and cartilage repair after 1 and 2 weeks was better with the 1.32 microns wavelength laser. In comparison, the CO2 laser and the contact Nd:YAG laser proved to be more precise cutting tools than the 1.32 microns wavelength or the 1.06 microns wavelength Nd:YAG lasers. Both Nd:YAG laser wavelengths were useful for coagulation and vaporization of tissues and blood vessels. More studies are needed to determine the effect of the new 1.32 microns wavelengths on endotracheal tumors. PMID:2263149

  15. VEGETATION WATER CONTENT ESTIMATION FOR CORN AND SOYBEANS USING SPECTRAL INDICES DERIVED FROM MODIS NEAR- AND SHORT- WAVE INFRARED BANDS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Vegetation water content (VWC) information can be valuable in hydrology, forestry, agriculture and meteorology. The estimation of VWC over a full crop-growing period was performed here using the near infrared (NIR) and short-wave infrared (SWIR) bands of the Terra - MODerate Resolution Imaging Spect...

  16. Finite Element Analysis of Thermal Characteristics in Continuous Wave Long Wavelength Surface Emitting Lasers (II): Semiconductor Distributed Bragg Reflectors

    Microsoft Academic Search

    Toshihiko Baba; Tomonobu Kondoh; Fumio Koyama; Kenichi Iga

    1995-01-01

    We have numerically analyzed some thermal characteristics of cw long wavelength surface emitting lasers with epitaxially grown semiconductor distributed Bragg reflectors (DBRs). It was shown that the device thermal resistance for GaAs\\/AlAs DBRs epitaxially fused to GalnAsP\\/InP emitting layers is 1\\/3 of that for GalnAsP\\/InP DBRs and almost comparable to that for the optimum dielectric cavity. The threshold current lower

  17. Pulsed and continuous-wave operation of long wavelength infrared (?=9.3 ?m) quantum cascade lasers

    Microsoft Academic Search

    C. Sirtori; J. Faist; F. Capasso; D. L. Sivco; A. L. Hutchinson; A. Y. Cho

    1997-01-01

    The operation of quantum cascade lasers at a wavelength (?≃9.3 ?m) well within the 8-13-?m atmospheric window is reported. A detailed study of intersubband luminescence in a vertical transition structure shows linewidths as narrow as ~10 meV at cryogenic temperatures, increasing to 20 meV at room temperature. Pulsed operation is demonstrated up to 220 K with a peak power ≈10

  18. Cross-spectral Face Verification in the Short Wave Infrared (SWIR) Band Thirimachos Bourlai Nathan Kalka Arun Ross Bojan Cukic Lawrence Hornak

    E-print Network

    Ross, Arun Abraham

    Cross-spectral Face Verification in the Short Wave Infrared (SWIR) Band Thirimachos Bourlai Nathan the short wave infrared spectrum (SWIR) is studied in order to illustrate the advantages and limitations of SWIR face verification. The contributions of this work are two-fold. First, a database of 50 subjects

  19. Wavelength and Energy

    NSDL National Science Digital Library

    2012-08-03

    This is an activity about wavelength and frequency. Using a 30 to 50 foot rope and two volunteers, learners will observe as one end of the rope is shaken and wavelength patterns are created. They will estimate the wavelength, the distance between two similar points of a wave, such as peak-to-peak, and the frequency of the waves, the number of waves reaching the far end of the rope per second. Through group discussion afterwards, this information is then related electromagnetic spectrum. This activity requires a long length of rope and a large enough space for the entire group to see the whole rope at once. This activity is from the Stanford Solar Center's All About the Sun: Sun and Stars activity guide for Grades 5-8 and can also accompany the Stanford Solar Center's Build Your Own Spectroscope activity.

  20. Integrated Analysis of Carbonatite using Short Wave Infra-Red and Visible/Near Infra-Red Reflectance Characteristics

    NASA Astrophysics Data System (ADS)

    Assiri, A.; Rooney, T. O.; Velbel, M. A.

    2012-12-01

    Carbonatites are among the most important hosts for economically important rare-earth element (REE) deposits. An ongoing challenge has been the identification of carbonatites, which may outcrop as small bodies with indistinct field characteristics. Remote sensing techniques may provide a routine and reliable method to identify such deposits. We have used short wave infra-red (SWIR) and visible/near infra-red (VNIR) reflectance characteristics of a well exposed carbonatite located in the north east of the United Arab Emirates to develop techniques to facilitate the distinction of carbonatites from other rock types. This project has focused on the wavelength region from 0.45 to 2.43 ?m of SWIR and VNIR subsystems on the imaging instrument onboard ASTER. We hypothesize that based on spectral and spatial data derived from computer segmentation algorithms of the SWIR (7) and VNIR (4, 1) bands we will be able to identify carbonatite rocks. In order to build a technique that can capture the intrinsic associations between carbonatite anomalies, rock class types, and attributes, we assembled the spectral and spatial information derived from computer segmentation algorithms into a single segment image. During our investigation of the spatial data two principal questions arose: 1) How should spatial structures, or "neighborhoods" for each pixel within the image be automatically defined? 2) How should spatial and spectral information be combined in the classification? We addressed these questions by using unsupervised and supervised segmentation algorithm strategies based on pixel values and locations. Pixels that are spatially connected and have similar values were grouped in a single segment (fixed neighborhood pixels) on the basis of the integration of the maximum-likelihood supervised classification technique within a Markov Random Fields framework. We then developed guidelines for combining the spatial information extracted through segmentation with spectral information within a classifier. These techniques allowed us to devise classification techniques using region-growing segmentation based upon automatically derived markers for identifying spatial structures of carbonatite. We were able to develop methods that are able to handle high-dimensional data and use adaptive spatial neighborhoods derived from segmentation results. The final strategy concentrated on techniques to reduce over-segmentation of the resulting images. An important component of this strategy consisted of analyzing potential classification results for the most reliably classified pixels to be used as markers of spatial zones. We present our results as a thematic image in which pixel values represent a specific spectra signature of class types of contiguous raster objects of carbonatites materials.

  1. Observation of Gravity-Capillary Wave Turbulence Eric Falcon,1,* Claude Laroche,1

    E-print Network

    Falcon, Eric

    Observation of Gravity-Capillary Wave Turbulence E´ric Falcon,1,* Claude Laroche,1 and Ste of the crossover between gravity and capillary wave turbulence on the surface of mercury. The probability density or gravity waves. For short wavelengths, capillary wave turbulence has been observed by optical techniques [7

  2. Short wavelength and high amplitude (~ 1 km) surface uplift in the western Colorado Plateau driven by recent and ongoing mantle flow

    NASA Astrophysics Data System (ADS)

    Crow, R.; Karlstrom, K. E.

    2011-12-01

    On the southwestern edge of the Colorado Plateau, two tributaries to the Virgin River record differing amounts of epeirogenic uplift in their longitudinal profiles and thus provide a geologic test for models of mantle-driven dynamic topography. The North and East Forks of the Virgin River have similar bedrock lithologies and drainage basin areas such that they should have similar longitudinal profiles and incision histories. Instead, the North Fork is steeper with an average channel slope of 0.023 compared to the East Fork which has a slope of 0.014. The headwaters of the North Fork are also ca. 500 m higher than that of the East Fork. These differences in the longitudinal profiles of the rivers are best explained by the fact that they straddle one of the largest mantle velocity gradients (4.5% at 80 km depth over 200 km) in the western U.S. The East Fork drains a region that has ca. 1% higher upper mantle velocity than the North Fork. Throughout this area of high mantle velocity gradient, between the Colorado Plateau rim and the Escalante, UT area, channel slope at a given drainage basin area is strongly linked to the upper mantle velocity structure. At drainage basin areas less than 0.5 km2, only streams underlain by upper mantle with negative velocities have channel slope values greater than 0.015. This relationship is seen despite bedrock strength variations along the streams and the presence of transient kickpoints due to old base level falls and strongly indicates that uplift of the area is recent if not ongoing. Recent and ongoing uplift of the area under the North Fork can explain the high relief and dramatic slot canyons of Zion National Park, which it flows through. Published Virgin River incision rates also show differential block uplift of ca. 1000 m across the Hurricane and Washington faults. Similar differential block uplift of ca. 700 m has been documented across the Hurricane fault in Grand Canyon. This indicates that buoyancy differences in the upper mantle are driving differential uplift of the lithosphere along the western flank of the Colorado Plateau. The differential uplift across the faults and the length scale of the high mantle velocity gradient area indicate that the zone of uplift has an amplitude of ca. 1000 m and a wavelength of ca. 200 m. High amplitude and short wavelength dynamic topography reflect mantle flow forcings, suggested by the extremely sharp mantle velocity gradients, filtered through a thinned lithosphere with high heat flow and thin effective elastic thickness that suggest upper mantle melt-filled shear zone conduits. This new geologic evidence for recent and ongoing surface uplift offers an important constraint for geodynamic models which are beginning to elucidate the mantle processes that are producing dynamic topography on the western edge of the Colorado Plateau.

  3. Effects of confinement on short-period surface waves: Observations from a new dataset

    SciTech Connect

    Hooper, H.; Bonner, J.; Leidig, M. [Weston Geophysics Corp., Lexington, MA (United States)

    2006-04-15

    The Source Phenomenology Experiment (SPE) was conducted during the summer of 2003 in Arizona. Single-fired chemical shots were detonated and recorded at two locations, including a coal mine in the Black Mesa district of northern Arizona. This article reports on research into the effects of confinement on the generation of short-period, fundamental-mode Rayleigh waves (Rg), using a subset of the SPE data. Results show important differences between the Rg amplitudes of confined and unconfined explosions which must be understood to develop discriminants for mining explosions, which are an important aspect of nuclear test monitoring. Rg energy and frequency content depend on explosive weight and confinement, and unconfined explosions generate up to eight times less energy than equivalent confined explosions. For this reason, unconfined mining explosions cannot be simulated using a Mueller and Murphy (1971) source without including an empirical chemical decoupling factor. Rg chemical decoupling factors for unconfined shots vary from 0.5 to 8.2 at frequencies between 0.5 and 11 Hz. The effects of the bench free face are evident in radiation patterns. Explosions on the topographic bench show increased spectral energies for Rg (by a factor of 1.5) at azimuths behind the bench. This suggests that a discriminant based on the relative azimuthal spectral energies of Rg may be a possibility.

  4. Short-Wave Infrared Reflectance Investigation of Sites of Paleobiological Interest: Applications for Mars Exploration

    NASA Astrophysics Data System (ADS)

    Brown, Adrian; Walter, Malcolm; Cudahy, Thomas

    2004-09-01

    Rover missions to the rocky bodies of the Solar System and especially to Mars require lightweight, portable instruments that use minimal power, require no sample preparation, and provide suitably diagnostic mineralogical information to an Earth-based exploration team. Short-wave infrared (SWIR) spectroscopic instruments such as the Portable Infrared Mineral Analyser (PIMA, Integrated Spectronics Pty Ltd., Baulkham Hills, NSW, Australia) fulfill all these requirements. We describe an investigation of a possible Mars analogue site using a PIMA instrument. A survey was carried out on the Strelley Pool Chert, an outcrop of stromatolitic, silicified Archean carbonate and clastic succession in the Pilbara Craton, interpreted as being modified by hydrothermal processes. The results of this study demonstrate the capability of SWIR techniques to add significantly to the geological interpretation of such hydrothermally altered outcrops. Minerals identified include dolomite, white micas such as illite- muscovite, and chlorite. In addition, the detection of pyrophyllite in a bleached and altered unit directly beneath the succession suggests acidic, sulfur-rich hydrothermal activity may have interacted with the silicified sediments of the Strelley Pool Chert.

  5. Characterization results of the TROPOMI Short Wave InfraRed detector

    NASA Astrophysics Data System (ADS)

    Hoogeveen, R. W. M.; Voors, R.; Robbins, M. S.; Tol, P. J. J.; Ivanov, T. I.

    2013-10-01

    The TROPOMI Earth-observing instrument is the single payload on board ESA's Sentinel-5 Precursor mission. It is the successor of the Sciamachy instrument (ESA ENVISAT) and the OMI instrument (NASA EOS/Aura), and combines and improves the best of both instruments. TROPOMI copies the push broom observation geometry of OMI allowing for daily global coverage due to its instantaneous field of view of 108 degrees, or 2600 km swath on ground. From Sciamachy the 2305 - 2385 nm Short-Wave Infra-Red (SWIR) observational band is copied with which methane and carbon monoxide are observed. This paper reports on the development of the SWIR detector module and the detailed characterization of the 1000x256 SWIR Saturn detector array produced by Sofradir (F) as measured with the SRON-developed Front-End Electronics. The detailed characterization comprises not only the regular properties such as dark current, noise and photo-response, but also more complex characteristics including non-linearity and memory. Characterization of the detection module was performed for all operational parameters: detector temperature (135 - 145 K), bias voltage and integration time. Thanks to the detector-characterization program, the operational clocking of the detector could be optimized, resulting in significantly improved performance.

  6. Outgassing models for Landsat-4 thematic mapper short wave infrared bands

    NASA Astrophysics Data System (ADS)

    Micijevic, Esad; Helder, Dennis L.

    2005-08-01

    Detector responses to the Internal Calibrator (IC) pulses in the Landsat-4 Thematic Mapper (TM) have been observed to follow an oscillatory behavior. This phenomenon is present only in the Short Wave Infrared (SWIR) bands and has been observed throughout the lifetime of the instrument, which was launched in July 1982 and imaged the Earth's surface until late 1993. These periodic changes in amplitude, which can be as large as 7.5 percent, are known as outgassing effects and are believed to be due to optical interference caused by a gradual buildup of an ice-like material on the window of the cryogenically cooled dewar containing the SWIR detectors. Similar outgassing effects in the Landsat-5 TM have been characterized using an optical thin-film model that relates detector behavior to the ice film growth rate, which was found to gradually decrease with time. A similar approach, which takes into consideration the different operational history of the instrument, has been applied in this study to three closely sampled data sets acquired throughout the lifetime of the Landsat-4 TM. Although Landsat-4 and Landsat-5 Thematic Mappers are essentially identical instruments, data generated from analyses of outgassing effects indicate subtle, but important, differences between the two. The estimated lifetime model could improve radiometric accuracy by as much as five percent.

  7. Improvement in the GERB short wave flux estimations over snow covered surfaces

    NASA Astrophysics Data System (ADS)

    Bertrand, C.; Gonzalez, L.; Ipe, A.; Clerbaux, N.; Dewitte, S.

    Because space-borne radiometers do not measure the Earth’s outgoing fluxes directly, angular distribution models (ADMs) are required to relate actual radiance measurement to flux at given solar angle, satellite-viewing geometries, surface, and atmospheric conditions. The conversion of one footprint broad-band radiance into the corresponding flux requires therefore one to first characterize each footprint in terms of surface type and cloud cover properties to properly select the adequate ADM. A snow (and sea-ice) retrieval technique based on spectral measurements from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on board Meteosat 8 is presented. It has been developed to improve the scene identification and thus the ADM selection in the near-real time processing of the Geostationary Earth Radiation Budget (GERB) data at the Royal Meteorological Institute of Belgium. The improvement in the GERB short wave flux estimations over snow covered scene types resulting from angular conversion using dedicated snow ADMs (e.g., empirical snow ADMs and/or pre-computed theoretical snow ADM) instead of empirical snow-free ADMs is discussed.

  8. Emerging liquid crystal waveguide technology for low SWaP active short-wave infrared imagers

    NASA Astrophysics Data System (ADS)

    Keller, Sean D.; Uyeno, Gerald P.; Lynch, Ted; Davis, Scott R.; Rommel, Scott D.; Pino, Juan

    2015-03-01

    Raytheon's innovative active short wave infrared (SWIR) imager uses Vescent Photonic's emerging liquid crystal waveguide (LCWG) technology to continuously steer the illumination laser beam over the imager field of view (FOV). This approach instantly illuminates a very small fraction of the FOV, which significantly reduces the laser power compared to flash illumination. This reduced laser power directly leads to a reduction in the size, weight and power (SWaP) of the laser. The reduction in laser power reduces the input power and thermal rejection, which leads to additional reduction in the SWaP of the power supplies and thermal control. The high-speed steering capability of the LCWG enables the imager's SWaP reduction. The SWaP reduction is possible using either global or rolling shutter detectors. In both cases, the LCWG steers the laser beam over the entire FOV while the detector is integrating. For a rolling shutter detector, the LCWG synchronizes the steering with the rolling shutter to illuminate only regions currently integrating. Raytheon's approach enables low SWaP active SWIR imagers without compromising image quality. This paper presents the results of Raytheon's active SWIR imager demonstration including steering control and synchronization with the detector integration.

  9. Short-wave infrared reflectance investigation of sites of paleobiological interest: applications for Mars exploration.

    PubMed

    Brown, Adrian; Walter, Malcolm; Cudahy, Thomas

    2004-01-01

    Rover missions to the rocky bodies of the Solar System and especially to Mars require lightweight, portable instruments that use minimal power, require no sample preparation, and provide suitably diagnostic mineralogical information to an Earth-based exploration team. Short-wave infrared (SWIR) spectroscopic instruments such as the Portable Infrared Mineral Analyser (PIMA, Integrated Spectronics Pty Ltd., Baulkham Hills, NSW, Australia) fulfill all these requirements. We describe an investigation of a possible Mars analogue site using a PIMA instrument. A survey was carried out on the Strelley Pool Chert, an outcrop of stromatolitic, silicified Archean carbonate and clastic succession in the Pilbara Craton, interpreted as being modified by hydrothermal processes. The results of this study demonstrate the capability of SWIR techniques to add significantly to the geological interpretation of such hydrothermally altered outcrops. Minerals identified include dolomite, white micas such as illite-muscovite, and chlorite. In addition, the detection of pyrophyllite in a bleached and altered unit directly beneath the succession suggests acidic, sulfur-rich hydrothermal activity may have interacted with the silicified sediments of the Strelley Pool Chert. PMID:15383240

  10. High Harmonic Fast Wave Heating Efficiency Enhancemen and Current Drive at Longer Wavelength on the National Spherical Torus Experiment

    SciTech Connect

    J. Hosea, R. E. Bell, B.P. LeBlanc, C.K. Phillips, G. Taylor, E. Valeo, J.R. Wilson, E.F. Jaeger, P.M. Ryan, J. Wilgen, H. Yuh, F. Levinton, S. Sabbagh, K. Tritz, J. Parker, P.T. Bonoli, R. Harvey, and the NSTX Team

    2008-01-14

    High harmonic fast wave heating and current drive (CD) are being developed on the National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 41, 1435 (2001)] for supporting startup and sustainment of the ST plasma. Considerable enhancement of the core heating efficiency (?) from 44% to 65% has been obtained for CD phasing of the antenna (strap-to-strap ? = -90o, k? = -8 m-1) by increasing the magnetic field from 4.5 kG to 5.5 kG. This increase in efficiency is strongly correlated to moving the location of the onset density for perpendicular fast wave propagation (nonset ? ??× k|| 2/w) away from the antenna face and wall, and hence reducing the propagating surface wave fields. RF waves propagating close to the wall at lower B? and k|| can enhance power losses from both the parametric decay instability (PDI) and wave dissipation in sheaths and structures around the machine. The improved efficiency found here is attributed to a reduction in the latter, as PDI losses are little changed at the higher magnetic field. Under these conditions of higher coupling efficiency, initial measurements of localized CD effects have been made and compared with advanced RF code simulations

  11. High harmonic fast wave heating efficiency enhancement and current drive at longer wavelength on the National Spherical Torus Experimenta)

    NASA Astrophysics Data System (ADS)

    Hosea, J.; Bell, R. E.; Leblanc, B. P.; Phillips, C. K.; Taylor, G.; Valeo, E.; Wilson, J. R.; Jaeger, E. F.; Ryan, P. M.; Wilgen, J.; Yuh, H.; Levinton, F.; Sabbagh, S.; Tritz, K.; Parker, J.; Bonoli, P. T.; Harvey, R.; NSTX Team

    2008-05-01

    High harmonic fast wave heating and current drive (CD) are being developed on the National Spherical Torus Experiment [M. Ono et al., Nucl. Fusion 41, 1435 (2001)] for supporting startup and sustainment of the spherical torus plasma. Considerable enhancement of the core heating efficiency (?) from 44% to 65% has been obtained for CD phasing of the antenna (strap-to-strap ? =-90°, k?=-8m-1) by increasing the magnetic field from 4.5to5.5kG. This increase in efficiency is strongly correlated to moving the location of the onset density for perpendicular fast wave propagation (nonset?B×k?2/?) away from the antenna face and wall, and hence reducing the propagating surface wave fields. Radio frequency (RF) waves propagating close to the wall at lower B and k? can enhance power losses from both the parametric decay instability (PDI) and wave dissipation in sheaths and structures around the machine. The improved efficiency found here is attributed to a reduction in the latter, as PDI losses are little changed at the higher magnetic field. Under these conditions of higher coupling efficiency, initial measurements of localized CD effects have been made and compared with advanced RF code simulations.

  12. High Harmonic Fast Wave Heating Efficiency Enhancement and Current Drive at Longer Wavelength on the National Spherical Torus Experiment

    SciTech Connect

    Hosea, J. [Princeton Plasma Physics Laboratory (PPPL); Bell, R. E. [Princeton Plasma Physics Laboratory (PPPL); LeBlanc, B [Princeton Plasma Physics Laboratory (PPPL); Phillips, Cynthia [Princeton Plasma Physics Laboratory (PPPL); Taylor, G. [Princeton Plasma Physics Laboratory (PPPL); Valeo, Dr Ernest [Princeton Plasma Physics Laboratory (PPPL); Wilson, J. R. [Princeton Plasma Physics Laboratory (PPPL); Jaeger, Erwin Frederick [ORNL; Ryan, Philip Michael [ORNL; Wilgen, John B [ORNL; Yuh, H. [Nova Photonics; Levinton, F. [Fusion Physics and Technology; Sabbagh, S. A. [Columbia University; Tritz, K. [Johns Hopkins University; Parker, J. [Cornell University; Bonoli, P. [Massachusetts Institute of Technology (MIT); Harvey, R. W. [CompX, Del Mar, CA

    2008-01-01

    High harmonic fast wave heating and current drive CD are being developed on the National Spherical Torus Experiment M. Ono et al., Nucl. Fusion 41, 1435 2001 for supporting startup and sustainment of the spherical torus plasma. Considerable enhancement of the core heating efficiency from 44% to 65% has been obtained for CD phasing of the antenna strap-to-strap = 90 , k= 8 m 1 by increasing the magnetic field from 4.5 to 5.5 kG. This increase in efficiency is strongly correlated to moving the location of the onset density for perpendicular fast wave propagation nonsetBk 2 / away from the antenna face and wall, and hence reducing the propagating surface wave fields. Radio frequency RF waves propagating close to the wall at lower B and k can enhance power losses from both the parametric decay instability PDI and wave dissipation in sheaths and structures around the machine. The improved efficiency found here is attributed to a reduction in the latter, as PDI losses are little changed at the higher magnetic field. Under these conditions of higher coupling efficiency, initial measurements of localized CD effects have been made and compared with advanced RF code simulations.

  13. High harmonic fast wave heating efficiency enhancement and current drive at longer wavelength on the National Spherical Torus Experiment

    SciTech Connect

    Hosea, J.; Bell, R. E.; LeBlanc, B. P.; Phillips, C. K.; Taylor, G.; Valeo, E.; Wilson, J. R. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08540 (United States); Jaeger, E. F.; Ryan, P. M.; Wilgen, J. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Yuh, H.; Levinton, F. [Nova Photon Incorporated, Princeton, New Jersey 08543 (United States); Sabbagh, S. [Columbia University, New York, New York 10025 (United States); Tritz, K. [Johns Hopkins University, Baltimore, Maryland 21218 (United States); Parker, J. [Cornell University, Ithaca, New York 14853 (United States); Bonoli, P. T. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Harvey, R. [CompX, Del Mar, California 92014 (United States)

    2008-05-15

    High harmonic fast wave heating and current drive (CD) are being developed on the National Spherical Torus Experiment [M. Ono et al., Nucl. Fusion 41, 1435 (2001)] for supporting startup and sustainment of the spherical torus plasma. Considerable enhancement of the core heating efficiency ({eta}) from 44% to 65% has been obtained for CD phasing of the antenna (strap-to-strap {phi}=-90 deg., k{sub {phi}}=-8 m{sup -1}) by increasing the magnetic field from 4.5 to 5.5 kG. This increase in efficiency is strongly correlated to moving the location of the onset density for perpendicular fast wave propagation (n{sub onset}{proportional_to}Bxk{sub parallel}{sup 2}/{omega}) away from the antenna face and wall, and hence reducing the propagating surface wave fields. Radio frequency (RF) waves propagating close to the wall at lower B and k{sub parallel} can enhance power losses from both the parametric decay instability (PDI) and wave dissipation in sheaths and structures around the machine. The improved efficiency found here is attributed to a reduction in the latter, as PDI losses are little changed at the higher magnetic field. Under these conditions of higher coupling efficiency, initial measurements of localized CD effects have been made and compared with advanced RF code simulations.

  14. Application of Artificial Neural Network to Search for Gravitational-Wave Signals Associated with Short Gamma-Ray Bursts

    E-print Network

    Kim, Kyungmin; Hodge, Kari A; Kim, Young-Min; Lee, Chang-Hwan; Lee, Hyun Kyu; Oh, John J; Oh, Sang Hoon; Son, Edwin J

    2014-01-01

    We apply a machine learning algorithm, the artificial neural network, to the search for gravitational-wave signals associated with short gamma-ray bursts. The multi-dimensional samples consisting of data corresponding to the statistical and physical quantities from the coherent search pipeline are fed into the artificial neural network to distinguish simulated gravitational-wave signals from background noise artifacts. Our result shows that the data classification efficiency at a fixed false alarm probability is improved by the artificial neural network in comparison to the conventional detection statistic. Therefore, this algorithm increases the distance at which a gravitational-wave signal could be observed in coincidence with a gamma-ray burst. In order to demonstrate the performance, we also evaluate a few seconds of gravitational-wave data segment using the trained networks and obtain the false alarm probability. We suggest that the artificial neural network can be a complementary method to the conventio...

  15. On the onset of surface wind drift at short fetches as observed in a wind wave flume

    NASA Astrophysics Data System (ADS)

    Ocampo-Torres, Francisco J.; Branger, Hubert; Osuna, Pedro; Robles, Lucia

    2014-05-01

    Ocean surface drift is of great relevance to properly model wind waves and specially the early stages of surface waves development and ocean-atmosphere fluxes during incipient wind events and storms. In particular, wave models are not so accurate predicting wave behaviour at short fetches, where wind drift onset might be very important. The onset of surface drift induced by wind and waves is being studied through detailed laboratory measurements in a large wind-wave flume. Wind stress over the water surface, waves and surface drift are measured in the 40m long wind-wave tank at IRPHE, Marseille. While momentum fluxes are estimated directly through the eddy correlation method in a station about the middle of the tank, they provide reference information to the corresponding surface drift onset recorded at rather short non-dimensional fetches. At each experimental run very low wind was on (about 1m/s) for a certain period and suddenly it was constantly accelerated to reach about 13 m/s (as well as 8 and 5 m/s during different runs) in about 15 sec to as long as 600 sec. The wind was kept constant at that high speed for 2 to 10 min, and then suddenly and constantly decelerate to 0. Surface drift values were up to 0.5 cm/s for the highest wind while very distinctive shear was detected in the upper 1.5 cm. Rather linear variation of surface drift was observed with depth. Evolution of the surface drift velocity is analysed and onset behaviour is addressed with particular emphasis in accelerated winds. This work represents a RugDiSMar Project (CONACYT 155793) contribution. The support from ANUIES-ECOS M09-U01 project, CONACYT-187112 Estancia Sabática, and Institute Carnot, is greatly acknowledged.

  16. Two-channel surface-normal wavelength division demultiplexer using substrate guided waves in conjunction with multiplexed waveguide

    E-print Network

    Chen, Ray

    in conjunction with multiplexed waveguide holograms Maggie M. Li and Ray T. Chen Microelectronics Research Center waveguide holograms in conjunction with substrate guided waves. A two-channel WDDM device operating at 700 bandwidth of optical communications and sensor systems. During the past 20 years, various types of WDMs

  17. Study of degenerate four-wave mixing in germanium and rhenate-doped potassium chloride at carbon dioxide laser wavelengths

    SciTech Connect

    Watkins, D.E.

    1982-02-01

    Theoretical and experimental studies of degenerate four-wave mixing (DFWM) by three different mechanisms are presented. These are the nonlinear index of refraction of a lossless, Kerr-like medium, the saturable absorption of a resonant optical transition, and the formation of a free-carrier grating.

  18. Application of Artificial Neural Network to Search for Gravitational-Wave Signals Associated with Short Gamma-Ray Bursts

    E-print Network

    Kyungmin Kim; Ian W. Harry; Kari A. Hodge; Young-Min Kim; Chang-Hwan Lee; Hyun Kyu Lee; John J. Oh; Sang Hoon Oh; Edwin J. Son

    2015-03-03

    We apply a machine learning algorithm, the artificial neural network, to the search for gravitational-wave signals associated with short gamma-ray bursts. The multi-dimensional samples consisting of data corresponding to the statistical and physical quantities from the coherent search pipeline are fed into the artificial neural network to distinguish simulated gravitational-wave signals from background noise artifacts. Our result shows that the data classification efficiency at a fixed false alarm probability is improved by the artificial neural network in comparison to the conventional detection statistic. Therefore, this algorithm increases the distance at which a gravitational-wave signal could be observed in coincidence with a gamma-ray burst. In order to demonstrate the performance, we also evaluate a few seconds of gravitational-wave data segment using the trained networks and obtain the false alarm probability. We suggest that the artificial neural network can be a complementary method to the conventional detection statistic for identifying gravitational-wave signals related to the short gamma-ray bursts.

  19. 40 Gb/s optical wavelength converter for NRZ-DPSK signal based on four wave mixing in semiconductor optical amplifier

    NASA Astrophysics Data System (ADS)

    Sidhu, Harmanjeet Kaur; Kaler, R. S.

    2006-10-01

    We simulated, 40 Gb/s wavelength converter for non-return to zero differential phase shift keying (NRZ-DPSK) signal using four wave mixing in semiconductor optical amplifier (SOA), for the first time. Also optimize the signal-to-pump ratio for NRZ-DPSK. The optimum signal-to-pump ratio is 12 dB & 10 dB with Q-factor penalty of 0.685 dB & 0.663 dB. The dependence of four wave mixing efficiency and converted signal power with signal input power studied & it is evaluated that four wave mixing efficiency decrease with increase in input power. The impact of pump power, signal-to-pump ratio, SOA parameters with Q-factor penalty for 40 Gb/s has been illustrated. We show that converted signal power increase up to saturation power of semiconductor optical amplifier, then decreases. It is observed that for optimum pump power, OSNR varies small with signal input power. Investigation also made for transmission distance after conversion.

  20. Modeling short wave radiation and ground surface temperature: a validation experiment in the Western Alps

    NASA Astrophysics Data System (ADS)

    Pogliotti, P.; Cremonese, E.; Dallamico, M.; Gruber, S.; Migliavacca, M.; Morra di Cella, U.

    2009-12-01

    Permafrost distribution in high-mountain areas is influenced by topography (micro-climate) and high variability of ground covers conditions. Its monitoring is very difficult due to logistical problems like accessibility, costs, weather conditions and reliability of instrumentation. For these reasons physically-based modeling of surface rock/ground temperatures (GST) is fundamental for the study of mountain permafrost dynamics. With this awareness a 1D version of GEOtop model (www.geotop.org) is tested in several high-mountain sites and its accuracy to reproduce GST and incoming short wave radiation (SWin) is evaluated using independent field measurements. In order to describe the influence of topography, both flat and near-vertical sites with different aspects are considered. Since the validation of SWin is difficult on steep rock faces (due to the lack of direct measures) and validation of GST is difficult on flat sites (due to the presence of snow) the two parameters are validated as independent experiments: SWin only on flat morphologies, GST only on the steep ones. The main purpose is to investigate the effect of: (i) distance between driving meteo station location and simulation point location, (ii) cloudiness, (iii) simulation point aspect, (iv) winter/summer period. The temporal duration of model runs is variable from 3 years for the SWin experiment to 8 years for the validation of GST. The model parameterization is constant and tuned for a common massive bedrock of crystalline rock like granite. Ground temperature profile is not initialized because rock temperature is measured at only 10cm depth. A set of 9 performance measures is used for comparing model predictions and observations (including: fractional mean bias (FB), coefficient of residual mass (CMR), mean absolute error (MAE), modelling efficiency (ME), coefficient of determination (R2)). Results are very encouraging. For both experiments the distance (Km) between location of the driving meteo station and location of simulation doesn't play a significant effect (below 230 Km) on ME and R2 values. The incoming short wave radiation on flat sites is very well modeled and only the cloudiness can be a significant source of error in therms of underestimation. Also the GST on steep sites is very well modeled and very good values of both ME and R2 are obtained. MAE values are always quite big (1÷5°C) but the role of fixed parameterization is probably strong is such sense. Over and under-estimations occur during winter and summer respectively and can be an effect of not well modeling of SWin on near-vertical morphologies. In the future the direct validation of SWin on steep sites is needed together with a validation of snow accumulation/melting on flat sites and relative analysis of the effect on ground thermal regime. This require very good precipitation datasets in middle-high-mountain areas.

  1. A new numerical method for the problem of nonlinear long-short wave interactions

    E-print Network

    Kofiani, Kirki N. (Kirki Nikolaos)

    2009-01-01

    The scope of this thesis is the development of a new numerical method to address the problem of nonlinear interactions of free-surface gravity waves. More specifically, this study addresses the case of wave interactions ...

  2. A hybrid method to compute short-period synthetic seismograms of teleseismic body waves in a 3-D regional model

    NASA Astrophysics Data System (ADS)

    Monteiller, Vadim; Chevrot, Sébastien; Komatitsch, Dimitri; Fuji, Nobuaki

    2013-01-01

    We present a hybrid method to simulate the propagation of short-period teleseismic body waves through 3-D regional models. The incident wavefield is computed in an spherically symmetric reference earth model based on the direct solution method. The global and regional wavefields are matched at the boundaries of the regional mesh. In the regional domain, we implement a spectral-element method with absorbing boundaries to cancel the outgoing scattered wavefield. The hybrid method is successfully benchmarked against the direct solution method in the reference earth model iasp91. The potential of the method is illustrated by computing short-period P-wave synthetic seismograms in a 3-D model with a 20 km Moho offset and/or topography on the free surface, focusing on the actual example of the Pyrenees.

  3. Response Time Measurements in Short-Wave Infrared HgCdTe e-APDs

    NASA Astrophysics Data System (ADS)

    Rothman, Johan; Foubert, Kevin; Lasfargues, Gilles; Largeron, Christophe

    2014-08-01

    The impulse response time has been measured as a function of reverse bias, gain, and temperature in backside-illuminated short-wave infrared HgCdTe avalanche photodiodes (APDs) with variable junction geometry. The APD geometry was altered using HgCdTe substrates of variable thickness and by variation of device fabrication parameters. This approach allowed study of the drift-diffusion dynamics of the electrons before entering the junction and the electron and hole dynamics during the junction transition in APDs with different carrier collection distances and junction widths. The response time was typically limited by a double exponential decay, which is attributed to contributions from the impedance mismatch between the interconnection circuit and the 50-? radiofrequency probe, and a delayed diffusion response from carriers generated far from the junction. These contributions limited the maximum bandwidth of the diodes to about 600 MHz, independently of gain and temperature. The hot carrier velocities are estimated by fitting the measured response with numerical calculations, taking into account contributions from a direct drift-multiplication response and a delayed diffusion response. This analysis shows that the hot carrier dynamics is close to independent of temperature and that the electron drift velocity saturates at the gain onset to a value of 1 × 107 cm/s, decreasing upon a further increase of the electric field E to a value of about 3 × 106 cm/s at E = 100 kV/cm. The hole velocity shows a slow variation from 3 × 106 cm/s at low electric fields to 1.5 × 106 cm/s at high electric fields.

  4. Stabilized platform for tethered balloon soundings of broadband long- and short-wave radiation

    SciTech Connect

    Alzheimer, J.M.; Anderson, G.A.; Whiteman, C.D.

    1993-01-01

    Changes in the composition of trace gases in the earth's atmosphere have been reported by many observers, and a general concern has been expressed regarding possible changes to the earth's climate that may be caused by radiatively active gases introduced into the earth's atmosphere by man's activities. Radiatively active trace gases produce temperature changes in the earth's atmosphere through changes in radiative flux divergence. Our knowledge of and means of measuring radiative flux divergence is very limited. A few observations of vertical radiative flux divergences have been reported from aircraft from radiometersondes from towers and from large tethered balloons. These measurement techniques suffers from one or more drawbacks, including shallow sounding depths (towers), high cost (aircraft), complicated logistics (large tethered balloons), and limitation to nighttime hours (radiometersondes). Changes in radiative flux divergence caused by anthropogenic trace gases are expected to be quite small, and will be difficult to measure with existing broadband radiative flux instruments. The emphasis of present research in global climate change is thus being focused on improving radiative transfer algorithms in global climate models. The radiative parameterizations in these models are at an early stage of development and information is needed regarding their performance, especially in cloudy conditions. The impetus for the research reported in this paper is the need for a device that can supplement existing means of measuring vertical profiles of long- and short-wave irradiance and radiative flux divergence. We have designed a small tethered-balloon-based system that can make radiometric soundings through the atmospheric boundary layer. This paper discusses the concept, the design considerations, and the design and construction of this sounding system. The performance of the system will be tested in a series of balloon flights scheduled for the fall and winter of 1992.

  5. Stabilized platform for tethered balloon soundings of broadband long- and short-wave radiation

    SciTech Connect

    Alzheimer, J.M.; Anderson, G.A.; Whiteman, C.D.

    1993-01-01

    Changes in the composition of trace gases in the earth`s atmosphere have been reported by many observers, and a general concern has been expressed regarding possible changes to the earth`s climate that may be caused by radiatively active gases introduced into the earth`s atmosphere by man`s activities. Radiatively active trace gases produce temperature changes in the earth`s atmosphere through changes in radiative flux divergence. Our knowledge of and means of measuring radiative flux divergence is very limited. A few observations of vertical radiative flux divergences have been reported from aircraft from radiometersondes from towers and from large tethered balloons. These measurement techniques suffers from one or more drawbacks, including shallow sounding depths (towers), high cost (aircraft), complicated logistics (large tethered balloons), and limitation to nighttime hours (radiometersondes). Changes in radiative flux divergence caused by anthropogenic trace gases are expected to be quite small, and will be difficult to measure with existing broadband radiative flux instruments. The emphasis of present research in global climate change is thus being focused on improving radiative transfer algorithms in global climate models. The radiative parameterizations in these models are at an early stage of development and information is needed regarding their performance, especially in cloudy conditions. The impetus for the research reported in this paper is the need for a device that can supplement existing means of measuring vertical profiles of long- and short-wave irradiance and radiative flux divergence. We have designed a small tethered-balloon-based system that can make radiometric soundings through the atmospheric boundary layer. This paper discusses the concept, the design considerations, and the design and construction of this sounding system. The performance of the system will be tested in a series of balloon flights scheduled for the fall and winter of 1992.

  6. Investigating gait recognition in the short-wave infrared (SWIR) spectrum: dataset and challenges

    NASA Astrophysics Data System (ADS)

    DeCann, Brian; Ross, Arun; Dawson, Jeremy

    2013-05-01

    In the biometrics community, challenge datasets are often released to determine the robustness of state-of-the- art algorithms to conditions that can confound recognition accuracy. In the context of automated human gait recognition, evaluation has predominantly been conducted on video data acquired in the active visible spectral band, although recent literature has explored recognition in the passive thermal band. The advent of sophisticated sensors has piqued interest in performing gait recognition in other spectral bands such as short-wave infrared (SWIR), due to their use in military-based tactical applications and the possibility of operating in nighttime environments. Further, in many operational scenarios, the environmental variables are not controlled, thereby posing several challenges to traditional recognition schemes. In this work, we discuss the possibility of performing gait recognition in the SWIR spectrum by first assembling a dataset, referred to as the WVU Outdoor SWIR Gait (WOSG) Dataset, and then evaluate the performance of three gait recognition algorithms on the dataset. The dataset consists of 155 subjects and represents gait information acquired under multiple walking paths in an uncontrolled, outdoor environment. Detailed experimental analysis suggests the benefits of distributing this new challenging dataset to the broader research community. In particular, the following observations were made: (a) the importance of SWIR imagery in acquiring data covertly for surveillance applications; (b) the difficulty in extracting human silhouettes in low-contrast SWIR imagery; (c) the impact of silhouette quality on overall recognition accuracy; (d) the possibility of matching gait sequences pertaining to different walking trajectories; and (e) the need for developing sophisticated gait recognition algorithms to handle data acquired in unconstrained environments.

  7. Dependence of the Normalized Radar Cross Section of Water Waves on Bragg Wavelength-Wind Speed Sensitivity

    NASA Technical Reports Server (NTRS)

    Long, David G.; Collyer, R. Scott; Reed, Ryan; Arnold, David V.

    1996-01-01

    Measurements of the normalized radar cross section (sigma(sup o)) made by the YSCAT ultrawideband scatterometer during an extended deployment on the Canada Centre for Inland Waters(CCIW) Research Tower located at Lake Ontario are analyzed and compared with anemometer wind measurements to study the sensitivity of (sigma(sup o)) to the wind speed as a function of the Bragg wavelength. This paper concentrates on upwind and downwind azimuth angles in the wind speed range of 4.5-12 m/s. While YSCAT collected measurements of sigma(sup o) at a variety of frequencies and incidence angles, this paper focuses on frequencies of 2.0, 3.05, 5.30, 10.02, and 14.0 GHz and incidence angles within the Bragg regime, 30-50 deg. Adopting a power law model to describe the relationship between sigma(sup o) and wind speed, both wind speed exponents and upwind/downwind (u/d) ratios of sigma(sup o) are found using least squares linear regression. The analysis of the wind speed exponents and u/d ratios show that shorter Bragg wavelengths (Lambda less than 4 cm) are the most sensitive to wind speed and direction. Additionally, vertical polarization (V-pol) sigma(sup o) is shown to be more sensitive to wind speed than horizontal polarization (H-pol) sigma(sup o), while the H-pol u/d ratio is larger than the V-pol u/d ratio.

  8. Rapidly swept, continuous-wave cavity ringdown spectroscopy with optical heterodyne detection: single- and multi-wavelength sensing of gases

    Microsoft Academic Search

    Y. He; B. J. Orr

    2002-01-01

    .   Spectroscopic sensing of gases can be performed with high sensitivity and photometric precision by cavity ringdown (CRD) absorption\\u000a spectroscopy. Our cavity ringdown spectrometer incorporates continuous-wave (cw) tunable diode lasers, fibre-optic coupling\\u000a and standard photonics and optical telecommunications components. It comprises a rapidly swept optical cavity in a single-ended\\u000a optical heterodyne transmitter–receiver configuration, enabling optical absorption of gases to be

  9. Interference of birefractive waves in CdGa2S4 crystals

    NASA Astrophysics Data System (ADS)

    Syrbu, N. N.; Tiron, A. V.; Parvan, V. I.; Zalamai, V. V.; Tiginyanu, I. M.

    2015-04-01

    In ?dG?2S4 crystals the Fabry-Perot and birefringence interference spectra were investigated. Spectral dependences of refraction indexes for ordinary (no) and extraordinary (ne) light waves are defined. The spectral dependence ?n=ne-no from the short and long-wavelength parts of isotropic wavelength ?0=485.7 nm (300 K) is determined. It is established that at ?>?0 ?n is positive and at ?Wavelength ?0=485.7 nm shifts with decreasing temperature to short-wavelengths. The phase difference of ordinary and extraordinary light waves for ?>?0 and ?wavelength has a small halfwidth (?3-5 Å). Another isotropic wavelength was found in the short-wavelength region (433 nm) for crystals obtained by iodine transport method.

  10. Enhancement of the evanescent wave coupling effect in a sub-wavelength-sized GaAs/AlGaAs ridge structure by low-refractive-index surface layers.

    PubMed

    Wang, Xue-Lun; Hao, Guo-Dong; Takahashi, Tokio

    2014-10-20

    We have investigated the three-dimensional emission patterns of GaAs/AlGaAs ridge structures with a sub-wavelength-sized top-flat facet by angle-resolved photoluminescence (PL). We found that the integrated PL intensity, and hence the light-extraction efficiency, can be enhanced by about 34% just by covering the ridge surface with a thin SiO2 layer. A double-coupling effect of evanescent waves that occurs at both the semiconductor-SiO2 and SiO2-air interfaces is suggested to be responsible for the improvement, based on a finite-difference time-domain simulation of the electromagnetic field around the ridge top. PMID:25607313

  11. Exploring binary-neutron-star-merger scenario of short-gamma-ray bursts by gravitational-wave observation.

    PubMed

    Kiuchi, Kenta; Sekiguchi, Yuichiro; Shibata, Masaru; Taniguchi, Keisuke

    2010-04-01

    We elucidate the feature of gravitational waves (GWs) from a binary-neutron-star merger collapsing to a black hole by general relativistic simulation. We show that GW spectrum imprints the coalescence dynamics, formation process of disk, equation of state for neutron stars, total masses, and mass ratio. A formation mechanism of the central engine of short-gamma-ray bursts, which are likely to be composed of a black hole and surrounding disk, therefore could be constrained by GW observation. PMID:20481927

  12. Effects of lateral velocity heterogeneity under the Nevada Test Site on short-period P wave amplitudes and travel times

    Microsoft Academic Search

    Christopher S. Lynnes; Thorne Lay

    1990-01-01

    Short-period teleseismicP waves from the Nevada Test Site (NTS) show systematic variations in amplitudes and travel times, with low amplitudes corresponding to fast travel times, suggesting elastic focussing-defocussing effects. Also, the azimuthal amplitude and travel time patterns for events at the Pahute Mesa subsite are systematically different from those at the Yucca Flat subsite, indicating the presence of a near-source

  13. Two-color GaN/AlGaN quantum cascade detector at short infrared wavelengths of 1 and 1.7 ?m

    NASA Astrophysics Data System (ADS)

    Sakr, S.; Giraud, E.; Dussaigne, A.; Tchernycheva, M.; Grandjean, N.; Julien, F. H.

    2012-04-01

    A two-color GaN-based quantum cascade detector is demonstrated. This photodetector operates simultaneously at a peak wavelength of 1.7 and 1 ?m at room temperature without any external voltage. These peaks correspond, respectively, to the e1e2 and e1e3 intersubband absorption of the active GaN quantum well. The extractor has been designed to allow for efficient transfer of electrons from both the e2 and e3 states to the next period. The 1 ?m detected wavelength is the shortest value reported for an intersubband semiconductor based detector.

  14. Improving atmospheric correction for highly productive coastal waters using the short wave infrared retrieval algorithm with water-leaving reflectance constraints at 412 nm.

    PubMed

    Oo, Min; Vargas, Marco; Gilerson, Alex; Gross, Barry; Moshary, Fred; Ahmed, Sam

    2008-07-20

    The recently developed short wave infrared (SWIR) atmospheric correction algorithm for ocean color retrieval uses long wavelength channels to retrieve atmospheric parameters to avoid bright pixel contamination. However, this retrieval is highly sensitive to errors in the aerosol model, which is magnified by the higher variability of aerosols observed over urban coastal areas. While adding extra regional aerosol models into the retrieval lookup tables would tend to increase retrieval error since these models are hard to distinguish in the IR, we explore the possibility that for highly productive waters with high colored dissolved organic matter, an estimate of the 412 nm channel water-leaving reflectance can be used to constrain the aerosol model retrieval and improve the water-leaving reflectance retrieval. Simulations show that this constraint is particularly useful where aerosol diversity is significant. To assess this algorithm we compare our retrievals with the operational SeaWiFS Data Analysis System (SeaDAS) SWIR and near infrared retrievals using in situ validation data in the Chesapeake Bay and show that, especially for absorbing aerosols, significant improvement is obtained. Further insight is also obtained by the intercomparison of retrieved remote sensing reflectance images at 443 and 551 nm, which demonstrates the removal of anomalous artifacts in the operational SeaDAS retrieval. PMID:18641754

  15. X-ray conversion of ultra-short laser pulses on a solid sample: Role of electron waves excited in the pre-plasma

    SciTech Connect

    Baffigi, F., E-mail: federica.baffigi@ino.it; Cristoforetti, G.; Fulgentini, L.; Giulietti, A.; Koester, P.; Labate, L.; Gizzi, L. A. [Intense Laser Irradiation Laboratory, Istituto Nazionale di Ottica, CNR Campus, Via G. Moruzzi 1, 56124, Pisa (Italy)

    2014-07-15

    Flat silicon samples were irradiated with 40 fs, 800?nm laser pulses at an intensity at the best focus of 2·10{sup 18} Wcm{sup ?2}, in the presence of a pre-plasma on the sample surface. X-ray emission in the spectral range from 2 to 30?keV was detected inside and outside the plane of incidence, while varying pre-plasma scale length, laser intensity, and polarization. The simultaneous detection of 2? and 3?/2 emission allowed the contributions to the X-ray yield to be identified as originating from laser interaction with either the near-critical density (n{sub c}) region or with the n{sub c}/4 region. In the presence of a moderate pre-plasma, our measurements reveal that, provided the pre-plasma reaches a scale-length of a few laser wavelengths, X-ray emission is dominated by the contribution from the interaction with the under dense plasma, where electron plasma waves can grow, via laser stimulated instabilities, and, in turn, accelerate free electrons to high energies. This mechanism leads also to a clear anisotropy in the angular distribution of the X-ray emission. Our findings can lead to an enhancement of the conversion efficiency of ultra short laser pulses into X-rays.

  16. Key words: GPS, attitude, inertial GPS was used with ultra-short baselines (2-3 carrier wavelengths) in a triple antenna configuration to obtain aircraft atti-

    E-print Network

    Stanford University

    wavelengths) in a triple antenna configuration to obtain aircraft atti- tude in real time. Through algorithm at Stanford with futuristic high resolution displays[1]. Introduction Attitude information for aircraft is currently obtained by spinning rotor or ring laser gyros. In General Aviation (GA) applications a vertical

  17. Determination of thickness and elastic constants of aluminum plates from full-field wavelength measurements of single-mode narrowband Lamb waves.

    PubMed

    Deán, J Luis; Trillo, Cristina; Doval, Angel F; Fernández, José L

    2008-09-01

    A method based on fitting the theoretical dispersion curves of Lamb waves to experimental data is presented to determine the thickness and two independent elastic constants of aluminum plates a few millimeters thick. The waves are generated by means of the wedge method using a narrowband source, selecting the wedge angle and the acoustic frequency f so that mainly one mode is excited. A self-developed pulsed electronic speckle pattern interferometry system renders a two dimensional map of the out-of-plane acoustic displacement field at the plate surface, which allows an accurate measurement of the acoustic wavelength lambda(1). For any mode, the relation between lambda(1) and f depends on the three unknown parameters, so at least three experimental measurements (lambda(1i),f(i)) with different frequencies and/or different modes are required to calculate them. The suitability of different Lamb modes to determine each parameter when the others are known is studied, as well as the conditions that the experimental set of values must fulfill to calculate all three parameters. Numerous Lamb modes at different frequencies are generated in each plate, and a fitting is made based on the minimization of the error function, resulting in an accuracy better than 1%. PMID:19045639

  18. Shallow seismic attenuation and shear-wave splitting in the short period range of Deception Island volcano (Antarctica)

    NASA Astrophysics Data System (ADS)

    Martínez-Arévalo, Carmen; Bianco, Francesca; Ibáñez, Jesús M.; Del Pezzo, Edoardo

    2003-11-01

    The occurrence of a seismic series in Deception Island volcano (Antarctica), composed of hundreds of local volcano-tectonic earthquakes, has permitted us to study the seismic attenuation of such a volcanic environment in the short-distance and high-frequency range. This study has been performed using P-waves, S-waves and coda-waves and applying different, frequency dependent and independent, techniques. The methods used for this analysis have been: spectral and broadening-of-the-pulse, for direct P- and S-waves, coda normalization for S-waves, and single back-scattering model for coda-waves. The results show that, in general, Q values are significantly smaller for the entire frequency range used (6-30 Hz) than those found in other volcanic and tectonic areas. The attenuation for P-waves is greater than for S-waves in the frequency independent methods, with a Q ?/ QP ratio that ranges between 1.9 and 3.2. Comparing the Q-factor obtained for S-waves we have observed clear differences as a function of the method used; the coda normalization method has supplied significantly higher Q values ( Q d) than the other two methods ( Q ?). We have interpreted this discrepancy as an effect of the methods: coda normalization and single back-scattering methods eliminate the contribution of the near-surface attenuation in their Q values. Comparing both Q ? and Q d we have estimated the near-surface attenuation under the recording site, named Q ?. On the other hand, we have observed that Q d has anomalous frequency dependence, with a minimum value at 21 Hz. This pattern is interpreted as an effect of strong scattering of the seismic waves in the source area of the earthquakes. Q c values depend clearly with frequency and lapse time and the lapse time dependence could be interpreted as a depth dependence of the seismic attenuation in Deception Island volcano, Antarctica. The obtained Q values have allowed us to separate the contribution of intrinsic and scattering attenuation, deriving that the scattering attenuation is predominant over the intrinsic effects. Finally, in order to investigate how the heterogeneous medium of the volcanic island could produce other effects, we have checked whether it produces polarization of the shear-waves. The preliminary results of the polarization direction indicate a main E-W strain direction. All these evidences reveal the strongly heterogeneous structure of Deception Island volcano.

  19. High-power parametric conversion from near-infrared to short-wave infrared

    E-print Network

    Dalang, Robert C.

    association of a fiber optical parametric amplifier and a Thulium doped fiber amplifier. 2014 Optical Society for the 2 m wavelength range employing an intra-cavity thulium doped fiber active filter," Opt. Commun. 284-1141 (2004). 11. S. D. Agger, and J. H. Povlsen, "Emission and absorption cross section of thulium doped

  20. Observation of strong oscillations of areal mass in an unsupported shock wave produced by a short laser pulse

    NASA Astrophysics Data System (ADS)

    Aglitskiy, Y.; Karasik, M.; Velikovich, A. L.; Serlin, V.; Weaver, J. L.; Kessler, T. J.; Schmitt, A. J.; Obenschain, S. P.; Metzler, N.; Oh, J.

    2011-10-01

    The first experimental study of hydrodynamic perturbation evolution in a strong unsupported shock wave, which is immediately followed by a rarefaction wave, is reported. Our planar solid polystyrene laser-machined targets, 50 to 100 ?m thick, rippled from the front side with a single-mode wavelength 30 or 45 ?m and peak-to-valley amplitude 4 to 6 ?m, were irradiated with a 350 ps long Nike KrF laser pulse at peak intensity of up to 330 TW/cm2. The perturbation evolution in the target was observed using face-on monochromatic x-ray radiography while the pulse lasted and for 3 to 4 ns after it ended. While the driving pulse was on, the areal mass modulation amplitude in the target was observed to grow by a factor of up to ~4 due to the ablative Richtmyer-Meshkov instability. After the end of the pulse, while the strong unsupported shock wave propagated through the unperturbed target, the theoretically predicted large oscillations of the areal mass [A. L. Velikovich et al., Phys. Plasmas 10, 3270 (2003)] were observed. Multiple phase reversals of the areal mass modulation have been detected. Work supported by DOE/NNSA and Office of Naval Research.

  1. VARIABLE GAMMA-RAY EMISSION FROM THE CRAB NEBULA: SHORT FLARES AND LONG 'WAVES'

    SciTech Connect

    Striani, E.; Tavani, M.; Vittorini, V.; Donnarumma, I.; Argan, A.; Cardillo, M.; Costa, E.; Del Monte, E.; Pacciani, L.; Piano, G.; Sabatini, S. [INAF/IASF-Roma, I-00133 Roma (Italy)] [INAF/IASF-Roma, I-00133 Roma (Italy); Giuliani, A.; Mereghetti, S. [INAF/IASF-Milano, I-20133 Milano (Italy)] [INAF/IASF-Milano, I-20133 Milano (Italy); Pucella, G.; Rapisarda, M. [ENEA Frascati, I-00044 Frascati (Roma) (Italy)] [ENEA Frascati, I-00044 Frascati (Roma) (Italy); Bulgarelli, A. [INAF/IASF-Bologna, I-40129 Bologna (Italy)] [INAF/IASF-Bologna, I-40129 Bologna (Italy); Colafrancesco, S. [INAF - Osservatorio Astronomico di Roma via Frascati 33, I-00040 Monteporzio (Italy)] [INAF - Osservatorio Astronomico di Roma via Frascati 33, I-00040 Monteporzio (Italy); Ferrari, A. [CIFS-Torino, I-10133 Torino (Italy)] [CIFS-Torino, I-10133 Torino (Italy); Pellizzoni, A. [INAF-Osservatorio Astronomico di Cagliari, localita' Poggio dei Pini, strada 54, I-09012 Capoterra (Italy)] [INAF-Osservatorio Astronomico di Cagliari, localita' Poggio dei Pini, strada 54, I-09012 Capoterra (Italy); Pittori, C. [ASI Science Data Center, I-00044 Frascati (Roma) (Italy)] [ASI Science Data Center, I-00044 Frascati (Roma) (Italy); and others

    2013-03-01

    Gamma-ray emission from the Crab Nebula has been recently shown to be unsteady. In this paper, we study the flux and spectral variability of the Crab above 100 MeV on different timescales ranging from days to weeks. In addition to the four main intense and day-long flares detected by AGILE and Fermi-LAT between 2007 September and 2012 September, we find evidence for week-long and less intense episodes of enhanced gamma-ray emission that we call 'waves'. Statistically significant 'waves' show timescales of 1-2 weeks, and can occur by themselves or in association with shorter flares. We present a refined flux and spectral analysis of the 2007 September-October gamma-ray enhancement episode detected by AGILE that shows both 'wave' and flaring behavior. We extend our analysis to the publicly available Fermi-LAT data set and show that several additional 'wave' episodes can be identified. We discuss the spectral properties of the 2007 September 'wave'/flare event and show that the physical properties of the 'waves' are intermediate between steady and flaring states. Plasma instabilities inducing 'waves' appear to involve spatial distances l {approx} 10{sup 16} cm and enhanced magnetic fields B {approx} (0.5-1) mG. Day-long flares are characterized by smaller distances and larger local magnetic fields. Typically, the deduced total energy associated with the 'wave' phenomenon (E{sub w} {approx} 10{sup 42} erg, where E{sub w} is the kinetic energy of the emitting particles) is comparable with that associated to the flares, and can reach a few percent of the total available pulsar spin-down energy. Most likely, flares and waves are the product of the same class of plasma instabilities that we show acting on different timescales and radiation intensities.

  2. A statistical study of short period waves in the ionosphere above Central Europe

    NASA Astrophysics Data System (ADS)

    Sindelarova, Tereza; Chum, Jaroslav; Mosna, Zbysek; Buresova, Dalia; Potuznikova, Katerina; Base, Jiri; Fiser, Jiri

    2015-04-01

    We present a statistical study of waves of periods 0.5-6 min that occurred in the ionosphere above the Czech Republic. The dataset covers one year period from April 2013 to March 2014. Data were obtained from Doppler ionospheric sounding. The sounding is based on measurements of frequency shift between the transmitted wave of a stable known frequency and the wave received after its reflection in the ionosphere. It is a suitable tool for observations of wave activity in the ionosphere, particularly in the period range up to 60 min. The main objective of the study was to find whether there exist a preferred season and time of the day in the occurrence of these waves. We identified altogether 247 events of duration between 1minute and 13 hours. The highest number of events occurred in September 2013 (44 events). Contrary, only 5 events appeared in May 2013. In the diurnal course, the waves tend to occur mainly between sunset and sunrise. The described diurnal variability can be to some measure explained by diurnal changes of electron concentrations in the ionosphere and consequent changes of the reflection height of the Doppler sounding wave. The 3.59 MHz radio wave usually reflects from the ionospheric F layer at night and from the E layer during the daytime. When the sounding wave reflects in the E region, it usually experiences zero or only negligible Doppler shift. Similarly, low number of events in May (and also in July) can be related with seasonal variability of electron concentration in the ionosphere. Sources of oscillations measured by the Doppler sounding system in the studied period range of 0.5-6 min include infrasound, geomagnetic micropulsations or transient changes of electron concentration caused by x-rays arrivals. We will present the interpretation of the statistical study with relation to the stated sources.

  3. Title of Document: A WAVE-CHAOTIC APPROACH TO PREDICTING AND MEASURING

    E-print Network

    Anlage, Steven

    ABSTRACT Title of Document: A WAVE-CHAOTIC APPROACH TO PREDICTING AND MEASURING ELECTROMAGNETIC The coupling of short-wavelength electromagnetic waves into large complicated enclosures is of great interest in a statistical sense through Random Matrix Theory- by assuming that the waves possess chaotic ray-dynamics within

  4. Parametric Excitations of Fast Plasma Waves by Counter-propagating Laser Beams

    SciTech Connect

    G. Shvets; N.J. Fisch

    2001-03-19

    Short- and long-wavelength plasma waves can become strongly coupled in the presence of two counter-propagating laser pump pulses detuned by twice the cold plasma frequency. What makes this four-wave interaction important is that the growth rate of the plasma waves occurs much faster than in the more obvious co-propagating geometry.

  5. Short time scale thermal mechanical shock wave propagation in high performance microelectronic packaging configuration 

    E-print Network

    Nagaraj, Mahavir

    2004-11-15

    The generalized theory of thermoelasticity was employed to characterize the coupled thermal and mechanical wave propagation in high performance microelectronic packages. Application of a Gaussian heat source of spectral profile similar to high...

  6. Diurnal variations of the propagation conditions of short-wave signals on a high-latitude path in the winter

    NASA Astrophysics Data System (ADS)

    Mingalev, V. S.; Orlova, M. I.; Evlashina, M. L.; Krivilev, V. N.; Mingaleva, G. I.

    1987-08-01

    The propagation trajectories of short waves on a path from the North Magnetic Pole to Murmansk in the course of a complete winter day is calculated on the basis of the electron density distribution determined using a numerical model of the convective polar ionosphere. It is shown that the propagation of the signals may be impossible at certain hours of local time, while, at those hours when it is possible, the ray trajectories can be of different types: beat, channeled between the E and F layers, ricocheting with chord propagation, and their combinations.

  7. Application of ZnO nanoparticles to enhance photoluminescence in porous silicon and its possible utilization for improving the short wavelength quantum efficiency of silicon solar cell

    NASA Astrophysics Data System (ADS)

    Verma, Daisy; Kharkwal, Aneeta; Singh, S. N.; Singh, P. K.; Sharma, S. N.; Mehdi, S. S.; Husain, M.

    2014-11-01

    We have formed photoluminescent porous silicon (PS) layers and over which a ZnO layer (hereafter called ZnOPS layers) is deposited. We studied the photoluminescent properties of individual layers as well as the composite layer under excitation with 405 nm wavelength. Using the data of PL a theoretical analysis of a solar cell having such a composite layer of a given photoluminescent conversion efficiency ?PL on the front surface has been done. The condition of a photoluminescent composite layer (ZnOPS) useful for enhancing the spectral response of n+-p-p+ structured silicon solar cell has been identified.

  8. TRIGGERING COLLAPSE OF THE PRESOLAR DENSE CLOUD CORE AND INJECTING SHORT-LIVED RADIOISOTOPES WITH A SHOCK WAVE. II. VARIED SHOCK WAVE AND CLOUD CORE PARAMETERS

    SciTech Connect

    Boss, Alan P.; Keiser, Sandra A., E-mail: boss@dtm.ciw.edu, E-mail: keiser@dtm.ciw.edu [Department of Terrestrial Magnetism, Carnegie Institution, 5241 Broad Branch Road, NW, Washington, DC 20015-1305 (United States)

    2013-06-10

    A variety of stellar sources have been proposed for the origin of the short-lived radioisotopes that existed at the time of the formation of the earliest solar system solids, including Type II supernovae (SNe), asymptotic giant branch (AGB) and super-AGB stars, and Wolf-Rayet star winds. Our previous adaptive mesh hydrodynamics models with the FLASH2.5 code have shown which combinations of shock wave parameters are able to simultaneously trigger the gravitational collapse of a target dense cloud core and inject significant amounts of shock wave gas and dust, showing that thin SN shocks may be uniquely suited for the task. However, recent meteoritical studies have weakened the case for a direct SN injection to the presolar cloud, motivating us to re-examine a wider range of shock wave and cloud core parameters, including rotation, in order to better estimate the injection efficiencies for a variety of stellar sources. We find that SN shocks remain as the most promising stellar source, though planetary nebulae resulting from AGB star evolution cannot be conclusively ruled out. Wolf-Rayet (WR) star winds, however, are likely to lead to cloud core shredding, rather than to collapse. Injection efficiencies can be increased when the cloud is rotating about an axis aligned with the direction of the shock wave, by as much as a factor of {approx}10. The amount of gas and dust accreted from the post-shock wind can exceed that injected from the shock wave, with implications for the isotopic abundances expected for a SN source.

  9. Shallow Seismic Attenuation and Shear Waves Splitting In The Short Period Range of Deception Island Volcano (antarctica)

    NASA Astrophysics Data System (ADS)

    Martínez-Arévalo, C.; Bianco, F.; Ibáñez, J. M.; del Pezzo, E.

    The occurrence of a seismic series in Deception Island volcano (Antarctica), com- posed by hundreds of local volcano-tectonic earthquakes, has permitted us to study the seismic attenuation of such a volcanic environment in the short-distance and high- frequency range. This study has been performed using P, S and coda waves and ap- plying different, frequency dependent and independent, techniques. The methods used for this analysis have been: Spectral and Broadening of the Pulse, for direct P and S waves, Coda Normalization for S-waves and Single Back-Scattering model for coda waves. The results show that, in general, Q values are significantly smaller, for all the frequency range used (6-30 Hz), than those found in other volcanic and tectonic areas. The attenuation for P-waves is greater than for S-waves in the frequency in- dependent methods, with a Qb/QP ratio that ranges between 1.9 and 3.2. Comparing the Q factor obtained for S-waves we have observed clear differences as a function of the method used; the Coda Normalization Method has supplied significantly higher Q values (Qd) than the other two methods (Qb). These Qd values are similar to the Q factor for coda waves (Qc). We have interpreted this discrepancy as an effect of the methods: Coda Normalization and Single Back-Scattering methods eliminate the con- tribution of the near surface attenuation in their Q values. Comparing both Qb and Qd we have estimated the near surface attenuation under the recording site, named Qk. On the other hand, we have observed that Qd has an anomalous frequency dependence, with a minimum value at 21 Hz. This pattern is interpreted as an effect of strong scat- tering of the seismic waves in the source area of the earthquakes. Qc values depend clearly with frequency and lapse time, and the lapse time dependence is interpreted as a depth dependence of the seismic attenuation in Deception Island volcano. The de- rived Q values have allowed us to separate the contribution of intrinsic and scattering attenuation, deriving that the scattering attenuation is predominant over the intrinsic effects. Finally, in order to investigate how the heterogeneous medium of the volcanic island could produce other effects, we have measured the splitting of the shear waves of the same data set. The observations reveal that the arrival delay of the shear waves horizontal components varies between 0.02 and 0.14 seconds, a big amount if we take into account the short hypocentral distances (less than 5 km). The study of the polar- 1 ization direction indicates a main E-W direction. All these evidences reveal the strong heterogeneous structure of Deception Island volcano. 2

  10. All-optical frequency downconversion technique utilizing a four-wave mixing effect in a single semiconductor optical amplifier for wavelength division multiplexing radio-over-fiber applications.

    PubMed

    Kim, Hyoung-Jun; Song, Jong-In

    2012-03-26

    An all-optical frequency downconversion utilizing a four-wave mixing effect in a single semiconductor optical amplifier (SOA) was experimentally demonstrated for wavelength division multiplexing (WDM) radio-over-fiber (RoF) applications. Two WDM optical radio frequency (RF) signals having 155 Mbps differential phase shift keying (DPSK) data at 28.5 GHz were simultaneously down-converted to two WDM optical intermediate frequency (IF) signals having an IF frequency of 4.5 GHz by mixing with an optical local oscillator (LO) signal having a LO frequency of 24 GHz in the SOA. The bit-error-rate (BER) performance of the RoF up-links with different optical fiber lengths employing all-optical frequency downconversion was investigated. The receiver sensitivity of the RoF up-link with a 6 km single mode fiber and an optical IF signal in an optical double-sideband format was approximately -8.5 dBm and the power penalty for simultaneous frequency downconversion was approximately 0.63 dB. The BER performance showed a strong dependence on the fiber length due to the fiber dispersion. The receiver sensitivity of the RoF up-link with the optical IF signal in the optical single-sideband format was reduced to approximately -17.4 dBm and showed negligible dependence on the fiber length. PMID:22453476

  11. Dual-wavelength multifrequency photothermal wave imaging combined with optical coherence tomography for macrophage and lipid detection in atherosclerotic plaques using gold nanoparticles.

    PubMed

    Wang, Tianyi; Mancuso, J Jacob; Sapozhnikova, Veronika; Dwelle, Jordan; Ma, Li L; Willsey, Brian; Kazmi, S M Shams; Qiu, Jinze; Li, Xiankai; Asmis, Reto; Johnston, Keith P; Feldman, Marc D; Milner, Thomas E

    2012-03-01

    The objective of this study was to assess the ability of combined photothermal wave (PTW) imaging and optical coherence tomography (OCT) to detect, and further characterize the distribution of macrophages (having taken up plasmonic gold nanorose as a contrast agent) and lipid deposits in atherosclerotic plaques. Aortas with atherosclerotic plaques were harvested from nine male New Zealand white rabbits divided into nanorose- and saline-injected groups and were imaged by dual-wavelength (800 and 1210 nm) multifrequency (0.1, 1 and 4 Hz) PTW imaging in combination with OCT. Amplitude PTW images suggest that lateral and depth distribution of nanorose-loaded macrophages (confirmed by two-photon luminescence microscopy and RAM-11 macrophage stain) and lipid deposits can be identified at selected modulation frequencies. Radiometric temperature increase and modulation amplitude of superficial nanoroses in response to 4 Hz laser irradiation (800 nm) were significantly higher than native plaque (P<0.001). Amplitude PTW images (4 Hz) were merged into a coregistered OCT image, suggesting that superficial nanorose-loaded macrophages are distributed at shoulders on the upstream side of atherosclerotic plaques (P<0.001) at edges of lipid deposits. Results suggest that combined PTW-OCT imaging can simultaneously reveal plaque structure and composition, permitting characterization of nanorose-loaded macrophages and lipid deposits in atherosclerotic plaques. PMID:22502567

  12. Dynamic characteristics of a multi-wavelength Brillouin-Raman fiber laser assisted by multiple four-wave mixing processes in a ring cavity

    NASA Astrophysics Data System (ADS)

    Shirazi, M. R.; Mohamed Taib, J.; De La Rue, R. M.; Harun, S. W.; Ahmad, H.

    2015-03-01

    Dynamic characteristics of a multi-wavelength Brillouin-Raman fiber laser (MBRFL) assisted by four-wave mixing have been investigated through the development of Stokes and anti-Stokes lines under different combinations of Brillouin and Raman pump power levels and different Raman pumping schemes in a ring cavity. For a Stokes line of order higher than three, the threshold power was less than the saturation power of its last-order Stokes line. By increasing the Brillouin pump power, the nth order anti-Stokes and the (n+4)th order Stokes power levels were unexpectedly increased almost the same before the Stokes line threshold power. It was also found out that the SBS threshold reduction (SBSTR) depended linearly on the gain factor for the 1st and 2nd Stokes lines, as the first set. This relation for the 3rd and 4th Stokes lines as the second set, however, was almost linear with the same slope before SBSTR -6 dB, then, it approached to the linear relation in the first set when the gain factor was increased to 50 dB. Therefore, the threshold power levels of Stokes lines for a given Raman gain can be readily estimated only by knowing the threshold power levels in which there is no Raman amplification.

  13. Prediction and measurement of the electromagnetic environment of high-power medium-wave and short-wave broadcast antennas in far field.

    PubMed

    Tang, Zhanghong; Wang, Qun; Ji, Zhijiang; Shi, Meiwu; Hou, Guoyan; Tan, Danjun; Wang, Pengqi; Qiu, Xianbo

    2014-12-01

    With the increasing city size, high-power electromagnetic radiation devices such as high-power medium-wave (MW) and short-wave (SW) antennas have been inevitably getting closer and closer to buildings, which resulted in the pollution of indoor electromagnetic radiation becoming worsened. To avoid such radiation exceeding the exposure limits by national standards, it is necessary to predict and survey the electromagnetic radiation by MW and SW antennas before constructing the buildings. In this paper, a modified prediction method for the far-field electromagnetic radiation is proposed and successfully applied to predict the electromagnetic environment of an area close to a group of typical high-power MW and SW wave antennas. Different from currently used simplified prediction method defined in the Radiation Protection Management Guidelines (H J/T 10. 3-1996), the new method in this article makes use of more information such as antennas' patterns to predict the electromagnetic environment. Therefore, it improves the prediction accuracy significantly by the new feature of resolution at different directions. At the end of this article, a comparison between the prediction data and the measured results is given to demonstrate the effectiveness of the proposed new method. PMID:24553048

  14. Rarefaction shock wave: formation under short pulse laser ablation of solids.

    PubMed

    Bulgakova, N M; Bourakov, I M; Bulgakova, N A

    2001-04-01

    We investigate formation, dynamics, and decay of the rarefaction shock wave under the conditions of ultrashort pulse laser ablation of solids. On the basis of the Euler equation and the van der Waals equation, we consider the planar and spherical expansion into vacuum matter heated instantaneously above the thermodynamic critical temperature. When the expansion occurs along an abnormal adiabat, in a part of which ( partial differential(2)p/ partial differentialv(2))/(S)<0, a rarefaction shock wave moving toward the target is formed. After its reflection from the nonvaporized material of the target, a thin dense layer of the expanding material is found to be formed. We suggest that this is the explanation for interference patterns observed experimentally above laser ablated surfaces. It has been speculated that the rarefaction shock wave may be formed on nova outbursts. PMID:11308949

  15. Short-time-evolved wave functions for solving quantum many-body problems 

    E-print Network

    Ciftja, O.; Chin, Siu A.

    2003-01-01

    to a shadow wave function with an optimized Jastrow particle- particle pseudopotential ~OJ! and scaled Aziz HFDHE2 shadow-shadow pseudopotential ~AS!.24 GFMC is the Green?s-Function Monte Carlo calculations with Mcmillan form for importance... variational Monte Carlo calculation with the indi- cated wave function. All simulations use the Aziz HFDHE2 poten- tial and have been performed for systems of N5108 particles. The M1MS results are taken from Vitiello et al. ~Ref. 23!. The M 1AS and OJ...

  16. An airborne short wave infrared /SWIR/ pushbroom imaging system using a 64-element PbS detector array

    NASA Technical Reports Server (NTRS)

    Husain-Abidi, A. S.; Tom, D.; Blaine, L. R.; Ostrow, G.

    1980-01-01

    Research evidence indicates that data in the short wave infrared (SWIR) spectral region will greatly improve the information content of remotely sensed data. Bands are required in the 1.55-1.75 micron and 2.08-2.35 micron spectral regions for a variety of agricultural and geological investigations. It is anticipated that future Landsat sensors will use pushbroom linear array technology to obtain high resolution, improved sensitivity and increased system reliability. To obtain early laboratory and field data, an airborne pushbroom image system has been designed for operation in the short wave infrared spectral region. The system uses a 64-element staggered PbS array and is operated at 195 K; the instrument has been designed to operate in an aircraft and will view a 19 degree swath width with a 5.8 mrad IFOV. The spectral bandwidth of each channel is .05 micron and the noise equivalent reflectivity in the order of .2% is provided. The requirements for more advanced detector arrays for use in future NASA spacecraft remote sensing instruments are also discussed.

  17. Spin-wave logic devices based on isotropic forward volume magnetostatic waves

    NASA Astrophysics Data System (ADS)

    Klingler, S.; Pirro, P.; Brächer, T.; Leven, B.; Hillebrands, B.; Chumak, A. V.

    2015-05-01

    We propose the utilization of isotropic forward volume magnetostatic spin waves in modern wave-based logic devices and suggest a concrete design for a spin-wave majority gate operating with these waves. We demonstrate by numerical simulations that the proposed out-of-plane magnetized majority gate overcomes the limitations of anisotropic in-plane magnetized majority gates due to the high spin-wave transmission through the gate, which enables a reduced energy consumption of these devices. Moreover, the functionality of the out-of-plane majority gate is increased due to the lack of parasitic generation of short-wavelength exchange spin waves.

  18. Growth of InAs\\/GaSb short-period superlattices for high-resolution mid-wavelength infrared focal plane array detectors

    Microsoft Academic Search

    M. Walther; J. Schmitz; R. Rehm; S. Kopta; F. Fuchs; J. Fleißner; W. Cabanski; J. Ziegler

    2005-01-01

    InAs\\/GaSb short-period superlattices (SLs) with a broken gap type-II band alignment are investigated for the fabrication of photovoltaic pin-photodetectors on GaSb substrates. The structures were grown by molecular beam epitaxy using valved cracker cells for arsenic and antimony. Effective bandgap and strain in the SL were adjusted by varying the thickness of the InAs and GaSb layers in the SL

  19. Short-period body wave constraints on properties of the earth's inner core boundary

    Microsoft Academic Search

    Phil Cummins

    1988-01-01

    Short-period waveform data were modeled in an attempt to constrain the P and S velocity structure at the earth's inner core boundary (ICB). The data set consists of recordings from 10 events in the South Pacific, and the data selection criteria as well as the methods of analysis are designed to avoid problems with receiver response. These data are modeled

  20. A unified directional spectrum for long and short wind-driven waves

    Microsoft Academic Search

    T. Elfouhaily; B. Chapron; K. Katsaros; D. Vandemark

    1997-01-01

    Review of several recent ocean surface wave models finds that while comprehensive in many regards, these spectral models do not satisfy certain additional, but fundamental, criteria. We propose that these criteria include the ability to properly describe diverse fetch conditions and to provide agreement with in situ observations of Cox and Munk [1954] and Jähne and Riemer [1990] and Hara

  1. Localization of Short Duration Gravitational-wave Transients with the Early Advanced LIGO and Virgo Detectors

    NASA Astrophysics Data System (ADS)

    Essick, Reed; Vitale, Salvatore; Katsavounidis, Erik; Vedovato, Gabriele; Klimenko, Sergey

    2015-02-01

    The Laser Interferometer Gravitational wave Observatory (LIGO) and Virgo advanced ground-based gravitational-wave detectors will begin collecting science data in 2015. With first detections expected to follow, it is important to quantify how well generic gravitational-wave transients can be localized on the sky. This is crucial for correctly identifying electromagnetic counterparts as well as understanding gravitational-wave physics and source populations. We present a study of sky localization capabilities for two search and parameter estimation algorithms: coherent WaveBurst, a constrained likelihood algorithm operating in close to real-time, and LALInferenceBurst, a Markov chain Monte Carlo parameter estimation algorithm developed to recover generic transient signals with latency of a few hours. Furthermore, we focus on the first few years of the advanced detector era, when we expect to only have two (2015) and later three (2016) operational detectors, all below design sensitivity. These detector configurations can produce significantly different sky localizations, which we quantify in detail. We observe a clear improvement in localization of the average detected signal when progressing from two-detector to three-detector networks, as expected. Although localization depends on the waveform morphology, approximately 50% of detected signals would be imaged after observing 100-200 deg2 in 2015 and 60-110 deg2 in 2016, although knowledge of the waveform can reduce this to as little as 22 deg2. This is the first comprehensive study on sky localization capabilities for generic transients of the early network of advanced LIGO and Virgo detectors, including the early LIGO-only two-detector configuration.

  2. Short-term effectiveness of bi-phase oscillatory waves versus hyperthermia for isolated long head biceps tendinopathy

    PubMed Central

    Oliva, Francesco; Via, Alessio Giai; Rossi, Silvio

    2011-01-01

    Summary Introduction: Long head biceps (LHB) tendinopathy is a common cause of anterior shoulder pain. Isolated LHB pathology is most common among younger people who practise overhead sports. The authors conducted a short-term prospective randomised study to test the effectiveness of two different methods for the treatment of isolated LHB tendinopathy: biphasic oscillatory waves and hyperthermia. Study design: The study is a prospective randomised study (Level II). Material and methods: The authors identified 20 patients who had clinical and ultrasound (US) evidence of LHB tendinopathy. No patient was a high-level athlete. The patients were randomly assigned to two groups. Group A (10 patients) was treated with bi-phasic oscillatory waves, while Group B received hyperthermia. During the treatment period, no other electromedical therapy, injections with corticosteroids, oral analgesics or nonsteroidal anti-inflammatory drugs were allowed. All the patients were assessed at baseline (T0), immediately after the end of the treatment period (T1) and 6 months after the end of treatment (T2) using a visual analogic scale (VAS) and Constant-Murley Score (CMS). Furthermore, all patients underwent US examinations at T0 and at T1. All the US examinations were performed by the same radiologist. Results: The VAS scores showed a highly statistically significant reduction of pain at T1 both in Group A (65%; p=0,004) and in Group B (50%; p=0,0002). The CMS also showed a statistically significant improvement between the pre-intervention, the post-treatment and the short-term follow-up in both groups. In addition, the peritendinous fluid evident on US examination at T0 was no longer present in all cases at T1. Conclusion: These findings suggest that both bi-phasic oscillatory waves and hyperthermia are able to relieve pain in patients with isolated LHB tendinopathy. This is a Class II level of evidence. PMID:23738257

  3. Improving Atmospheric Correction for Visible/Short Wave Infrared (VSWIR) Imaging Spectrometers with Iterative Fitting of Absorption By Three Phases of Water

    NASA Astrophysics Data System (ADS)

    Pennington, E. A.; Thompson, D. R.; Green, R. O.; Gao, B. C.

    2014-12-01

    Airborne imaging spectrometers like the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) offer valuable insight into the Earth's terrestrial and ocean ecosystems, mineralogy, and land use. Estimating surface reflectance requires accounting for atmospheric absorption, which is sensitive to the local abundance of water vapor. Analysts typically estimate water vapor concentrations using the depths of absorption features, which can be inaccurate by up to 50% over surface features containing liquid water or ice. This can bias the retrieved water vapor maps and create atmospheric artifacts in reflectance spectra. A new retrieval method offers significant accuracy improvements over plant canopies or ice by estimating the path lengths of all three phases of water simultaneously, adjusting absorptions to best fit the measurement over a broader spectral interval. This paper assesses the remaining sources of error for the three-phase retrieval technique. We analyze retrievals for synthetic data when the 940 and 1140 nm wavelength features are fitted, for initial vapor path estimates ranging from 0 to ±50% accuracy. These tests indicate that most error comes from inaccuracy in the initial path estimate used to obtain vapor absorption coefficients. We evaluate a modified algorithm that uses multiple iterations to refine this estimate. Error is found to approach a constant value, demonstrating improved robustness to initialization conditions. We also assess the new iterative method using corrected AVIRIS data over various environments. The iterative method yields significantly better water vapor maps, reducing spurious correlations between vegetation canopy water and vapor estimates. The new iterative method offers accuracy improvements over traditional Visible/Short Wave Infrared (VSWIR) atmospheric correction methods, at modest computational cost.

  4. Design and Characterization of Fabry Pérot MEMS-Based Short-Wave Infrared Microspectrometers

    NASA Astrophysics Data System (ADS)

    Keating, A. J.; Antoszewski, J.; Silva, K. K. M. B. D.; Winchester, K. J.; Nguyen, T.; Dell, J. M.; Musca, C. A.; Faraone, L.; Mitra, P.; Beck, J. D.; Skokan, M. R.; Robinson, J. E.

    2008-12-01

    Microspectrometers based on the monolithic integration of a microelectromechanical system (MEMS) Fabry Pérot filter and a Hg x Cd1 x Te-based infrared detector are discussed and measured results presented. The microspectrometers are designed to operate in the 1.5 ?m to 2.6 ?m wavelength range. Design equations are presented which account for the mechanical and optical characteristics of the device. Measurements indicate linewidths as narrow as 55 nm, switching times of 40 ?s, and a tuning range of 380 nm, which is limited by snap-down. Optical characterization of the distributed Bragg mirrors and the Fabry Pérot filter are presented, and these are shown to be in good agreement with simple first-order analytical models. Bowing of the movable Fabry Pérot mirror due to stress gradients is identified as the dominant source of linewidth broadening.

  5. Precision calculation of above-threshold multiphoton ionization in intense short-wavelength laser fields: The momentum-space approach and time-dependent generalized pseudospectral method

    E-print Network

    Chu, Shih-I; Zhou, Zhongyuan

    2011-01-19

    large distance, even to infinity. To solve the time-dependent Schro¨dinger equation (TDSE) in spatial coordinate (R) space, the boundary has to be set at a very large distance to avoid the reflection of the wave function. This will require the use of a... is given by A(t) = ez c?0 ? f (t) sin(?t + ?), (32) with the envelope shape factor given by f (t) = { sin2 ( ?t 2?R ) , 0 #2; t #2; ?R, 1, t > ?R, (33) where ?R = 10Toc, Toc = 2?/? is the optical cycle of the laser field, ? is the carrier-envelope phase...

  6. Completion of spectral rotating shadowband radiometers and analysis of ARM spectral short-wave data

    NASA Astrophysics Data System (ADS)

    Michalsky, J.; Harrison, L.

    1994-07-01

    Our ARM goal is to help improve both longwave and shortwave models used in GCM's by providing improved radiometric shortwave data. The inference of cloud cover and optical properties of clouds is another goal of this research effort. At the Atmospheric Sciences Research Center (ASRC) in Albany, New York, we are acquiring downwelling shortwave, including direct and diffuse irradiance, at six wavelengths, plus downwelling longwave, upwelling and downwelling broadband shortwave, and aerosol optical depth that we combine with National Weather Service surface and upper air data as a model test data set for ARM researchers. The major objective of our program has been to develop two spectral versions of the rotating shadowband radiometer (RSR). The multi-filter rotating shadowband radiometer (MFRSR) contains six filtered, narrow-passband detectors, and one unfiltered silicon detector that serves as a surrogate total shortwave sensor. The rotating shadowband spectroradiometer (RSS) contains a 256-channel diode array that spans the wavelengths 350-1050 nm with resolution varying between 0.6 nm and 8 nm. With some of the instrument development complete we are devoting more effort to analysis of the MFRSR data. Progress was made on several fronts this year, resulting in conference papers and submissions to refereed journals. Data from the ASRC roof has been used to develop corrections of the MFRSR shortwave sensor. SGP data has been used to develop and validate a retrieval technique for total column water vapor. Total column ozone has been estimated using MFRSR data, but validation at the SGP was not possible for lack of a suitable ozone column standard. Some progress has been made on cloud cover detection, but it is not yet implemented as a routine classification and reporting procedure.

  7. Wave Properties

    NSDL National Science Digital Library

    In this lesson plan students will learn the components of a wave, then discuss the effects of wave height, wavelength, and wave period in determining the overall size of a wave. They will use the National Geographic Wave Simulator to experiment with creating different kinds of waves. Discussion will then focus on the effects of geography on wave size as well as additional forces on boats trying to navigate waves.

  8. Wave Function and Strange Correlator of Short-Range Entangled States

    NASA Astrophysics Data System (ADS)

    You, Yi-Zhuang; Bi, Zhen; Rasmussen, Alex; Slagle, Kevin; Xu, Cenke

    2014-06-01

    We demonstrate the following conclusion: If |?? is a one-dimensional (1D) or two-dimensional (2D) nontrivial short-range entangled state and |?? is a trivial disordered state defined on the same Hilbert space, then the following quantity (so-called "strange correlator") C(r,r')=??|?(r)?(r')|??/??|?? either saturates to a constant or decays as a power law in the limit |r-r'|?+?, even though both |?? and |?? are quantum disordered states with short-range correlation; ?(r) is some local operator in the Hilbert space. This result is obtained based on both field theory analysis and an explicit computation of C(r,r') for four different examples: 1D Haldane phase of spin-1 chain, 2D quantum spin Hall insulator with a strong Rashba spin-orbit coupling, 2D spin-2 Affleck-Kennedy-Lieb-Tasaki state on the square lattice, and the 2D bosonic symmetry-protected topological phase with Z2 symmetry. This result can be used as a diagnosis for short-range entangled states in 1D and 2D.

  9. Wave function and strange correlator of short-range entangled states.

    PubMed

    You, Yi-Zhuang; Bi, Zhen; Rasmussen, Alex; Slagle, Kevin; Xu, Cenke

    2014-06-20

    We demonstrate the following conclusion: If |?? is a one-dimensional (1D) or two-dimensional (2D) nontrivial short-range entangled state and |?? is a trivial disordered state defined on the same Hilbert space, then the following quantity (so-called "strange correlator") C(r,r('))=??|?(r)?(r('))|??/??|?? either saturates to a constant or decays as a power law in the limit |r-r(')|?+?, even though both |?? and |?? are quantum disordered states with short-range correlation; ?(r) is some local operator in the Hilbert space. This result is obtained based on both field theory analysis and an explicit computation of C(r,r(')) for four different examples: 1D Haldane phase of spin-1 chain, 2D quantum spin Hall insulator with a strong Rashba spin-orbit coupling, 2D spin-2 Affleck-Kennedy-Lieb-Tasaki state on the square lattice, and the 2D bosonic symmetry-protected topological phase with Z(2) symmetry. This result can be used as a diagnosis for short-range entangled states in 1D and 2D. PMID:24996105

  10. Horizontal coherence of low-frequency fixed-path sound in a continental shelf region with internal-wave activity

    E-print Network

    Horizontal coherence of low-frequency fixed-path sound in a continental shelf region with internal-wave) populated with tidally generated long- and short-wavelength internal waves. Sound paths are 19 km in the along-shore (along internal-wave crest) direction and 30 km in the cross-shore direction. Spatial

  11. Dual-wavelength InP quantum dot lasers

    SciTech Connect

    Shutts, S.; Smowton, P. M. [School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA (United Kingdom); Krysa, A. B. [EPSRC National Centre for III-V Technologies, Department of Electronic and Electrical Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom)

    2014-06-16

    We have demonstrated a two-section dual-wavelength diode laser incorporating distributed Bragg reflectors, with a peak-wavelength separation of 62.5?nm at 300?K. Each lasing wavelength has a different temperature dependence, providing a difference-tuning of 0.11?nm/K. We discuss the mechanisms governing the light output of the two competing modes and explain how the short wavelength can be relatively insensitive to output changes at the longer wavelength. Starting from an initial condition when the output at both wavelengths are equal, a 500% increase in the long wavelength output causes the short wavelength output to fall by only 6%.

  12. Active and passive infrared imager based on short-wave and mid-wave type-II superlattice dual-band detectors.

    PubMed

    Huang, Edward Kwei-wei; Haddadi, Abbas; Chen, Guanxi; Hoang, Anh-Minh; Razeghi, Manijeh

    2013-01-01

    A versatile dual-band detector capable of active and passive use is demonstrated using short-wave (SW) and mid-wave (MW) IR type-II superlattice photodiodes. A bilayer etch-stop scheme is introduced for back-side-illuminated detectors, which enhanced the external quantum efficiency both in the SWIR and MWIR spectral regions. Temperature-dependent dark current measurements of pixel-sized 27 ?m detectors found the dark current density to be ~1 × 10(-5) A/cm(2) for the ~4.2 ?m cutoff MWIR channel at 140 K. This corresponded to a reasonable imager noise equivalent difference in temperature of ~49 mK using F/2.3 optics and a 10 ms integration time (t(int)), which lowered to ~13 mK at 110 K using t(int)=30 ms, illustrating the potential for high-temperature operation. The SWIR channel was found to be limited by readout noise below 150 K. Excellent imagery from the dual-band imager exemplifying pixel coincidence is shown. PMID:23282825

  13. Acousto-optic tunable wavelength and selective packet filter by simultaneously launching of acousto-optic waves of different frequency for TE-TM mode conversion in diffused optical and acoustic waveguides

    Microsoft Academic Search

    Le Nguyen Binh

    2009-01-01

    Optical filters employing acousto-optic polarized mode conversion techniques are implemented to demonstrate the filtering, selection, and switching of packets of wavelength multiplexed optical channels in LiNbO3 diffused optical waveguides. Geometrically tilted and chirped digital electrodes of the metallic interdigital transducer are used to excite acoustic surface waves for phase matching of the optical transverse electric (TE) and transverse magnetic (TM)

  14. High-speed and high-power performances of LTG-GaAs based metal-semiconductor-metal traveling-wave-photodetectors in 1.3-?m wavelength regime

    Microsoft Academic Search

    Jin-Wei Shi; Yen-Hung Chen; Kian-Giap Gan; Yi-Jen Chiu; Chi-Kuang Sun; John E. Bowers

    2002-01-01

    In this letter, we demonstrated ultrahigh bandwidth and high output power performances of low-temperature-grown (LTG) GaAs-based metal-semiconductor-metal traveling wave photodetectors (MSM TWPDs) in the long wavelength regime (~1300 nm). Ultrahigh bandwidth (1.3-ps pulsewidth with 234 GHz transformed 3-dB electrical bandwidth) was achieved with long-absorption-length (70-?m) devices due to the improved microwave property in the MSM TWPDs and their high velocity-mismatch

  15. Epitaxial seeded growth of rare-earth nanocrystals with efficient 800 nm near-infrared to 1525 nm short-wavelength infrared downconversion photoluminescence for in?vivo bioimaging.

    PubMed

    Wang, Rui; Li, Xiaomin; Zhou, Lei; Zhang, Fan

    2014-11-01

    Novel ?-NaGdF4/Na(Gd,Yb)F4:Er/NaYF4:Yb/NaNdF4:Yb core/shell?1/shell?2/shell?3 (C/S1/S2/S3) multi-shell nanocrystals (NCs) have been synthesized and used as probes for in?vivo imaging. They can be excited by near-infrared (800?nm) radiation and emit short-wavelength infrared (SWIR, 1525?nm) radiation. Excitation at 800?nm falls into the "biological transparency window", which features low absorption by water and low heat generation and is considered to be the ideal excitation wavelength with the least impact on biological tissues. After coating with phospholipids, the water-soluble NCs showed good biocompatibility and low toxicity. With efficient SWIR emission at 1525?nm, the probe is detectable in tissues at depths of up to 18?mm with a low detection threshold concentration (5?nM for the stomach of nude mice and 100?nM for the stomach of SD rats). These results highlight the potential of the probe for the in?vivo monitoring of areas that are otherwise difficult to analyze. PMID:25196421

  16. Revisiting Coincidence Rate between Gravitational Wave Detection and Short Gamma-Ray Burst for the Advanced and Third Generation

    NASA Astrophysics Data System (ADS)

    Regimbau, T.; Siellez, K.; Meacher, D.; Gendre, B.; Boër, M.

    2015-01-01

    We use realistic Monte Carlo simulations including both gravitational-wave (GW) and short gamma-ray burst (sGRB) selection effects to revisit the coincident rate of binary systems composed of two neutron stars or a neutron star and a black hole. We show that the fraction of GW triggers that can be observed in coincidence with sGRBs is proportional to the beaming factor at z = 0, but increases with the distance until it reaches 100% at the GW detector horizon distance. When this is taken into account the rate is improved by a factor of three compared to the simple beaming factor correction. We provide an estimate of the performance future GRB detectors should achieve in order to fully exploit the potentiality of the planned third-generation GW antenna Einstein Telescope, and we propose a simple method to constrain the beaming angle of sGRBs.

  17. Revisiting coincidence rate between Gravitational Wave detection and short Gamma-Ray Burst for the Advanced and third generation

    E-print Network

    Regimbau, T; Meacher, D; Gendre, B; er, M Bo\\"

    2014-01-01

    We use realistic Monte-Carlo simulations including both gravitational-wave and short gamma-ray burst selection effects to revisit the coincident rate of binary systems composed of two neutron stars or a neutron star and a black hole. We show that the fraction of GW triggers that can be observed in coincidence with sGRBs is proportional to the beaming factor at $z=0$, but increases with the distance, until it reaches 100 \\% at the GW detector horizon distance. When this is taken into account the rate is improved by a factor of $~3$ compared to the simple beaming factor correction. We provide an estimate of the performance future GRB detectors should achieve in order to fully exploit the potentiality of the planned third generation GW antenna Einstein Telescope, and we propose a simple method to constrain the beaming angle of sGRBs.

  18. [Study on phase-matching of four-wave mixing spectrum in photonic crystal fiber].

    PubMed

    Liu, Xiao-xu; Wang, Shu-tao; Zhao, Xing-tao; Chen, Shuang; Zhou, Gui-yao; Wu, Xi-jun; Li, Shu-guang; Hou, Lan-Tian

    2014-06-01

    In the present paper, the four-wave mixing principle of fiber was analyzed, and the high-gain phase-matching conditions were shown. The nonlinear coefficient and dispersion characteristics of photonic crystal fibers were calculated by multipole method. The phase mismatch characteristics of fibers with multiple zero-dispersion wavelengths were analyzed for the first time. The changing rules of phase matching wavelength with the pump wavelength and the pump power were obtained, and the phase matching curves were shown. The characteristics of phase matching wavelengths for different dispersion curves were analyzed. There are four new excitation wavelengths of four-wave mixing spectrum in two zero-dispersion wavelength photonic crystal fiers. Four-wave mixing spectroscopy of photonic crystal fibers with two zero-dispersion wavelengths was obtained in the experi-ent, which is consistent with the theoretical analysis, and verified the reliability of the phase matching theory. The fiber with multiple zero-dispersion wavelengths can create a ricbhphase-matching topology, excite more four-wave mixing wavelengths, ena-ling enhanced control over the spectral locations of the four-wave mixing and resonant-radiation bands emitted by solitons and short pulses. These provide theoretical guidance for photonic crystal fiber wavelength conversion and supercontinoum generation based on four-wave mixing. PMID:25358145

  19. Attenuating Photostress and Glare Disability in Pseudophakic Patients through the Addition of a Short-Wave Absorbing Filter.

    PubMed

    Hammond, Billy R

    2015-01-01

    To evaluate the effects of filtering short wavelength light on visual performance under intense light conditions among pseudophakic patients previously implanted with a clear intraocular lens (IOL). This was a patient-masked, randomized crossover study conducted at 6 clinical sites in the United States between September 2013 and January 2014. One hundred fifty-four bilaterally pseudophakic patients were recruited. Photostress recovery time and glare disability thresholds were measured with clip-on blue-light-filtering and placebo (clear; no blue-light filtration) glasses worn over patients' habitual correction. Photostress recovery time was quantified as the time necessary to regain sight of a grating target after intense light exposure. Glare disability threshold was assessed as the intensity of a white-light annulus necessary to obscure a central target. The order of filter used and test eye were randomized across patients. Photostress recovery time and glare disability thresholds were significantly improved (both P < 0.0001) when patients used blue-light-filtering glasses compared with clear, nonfiltering glasses. Compared with a nonfiltering placebo, adding a clip-on blue-absorbing filter to the glasses of pseudophakic patients implanted with clear IOLs significantly increased their ability to cope with glare and to recover normal viewing after an intensive photostress. This result implies that IOL designs with blue-light-filtering characteristics may be beneficial under intense light conditions. PMID:25838942

  20. Impacts of aerosol scattering on the short-wave infrared satellite observations of CO2

    NASA Astrophysics Data System (ADS)

    Fan, M.; Chen, L.; Li, S.; Tao, J.; Su, L.; Zou, M.

    2014-12-01

    Atmospheric aerosols and carbon dioxide (CO2), as two key factors driving the global climate change, have earned enormous attention from scientist around the world. One challenge for the satellite measurements of CO2 using this SWIR wavelength range (~1.6?m) is the impact of multiple scattering by aerosols and cirrus. Since the rapid economic growth and associated increase in fossil fuel consumption have caused serious particulate pollution in many regions of China, remote sensing of CO2 using SWIR band in China needs to pay more attention to the scattering properties of aerosol particles and the multiple scattering. Considering the complexity of morphological and chemical properties, aerosol particles are grouped based on a large number of TEM/SEM images, and then their scattering properties at 1.6?m band are calculated by the T-matrix method and GMM method. In this study, the Monte Carlo method is used to solve the multiple scattering problem by simulating photons transport in the scattering media. We combined this multiple scattering model with the LBLRTM as a forward radiative transfer model for studying the impact of aerosol scattering on the satellite observations of CO2 using SWIR band. Finally, based on the GOCART aerosol component products, AERONET aerosol size distribution products, CALIPSO aerosol profile products, and MODIS aerosol optical depth and surface albedo products, the monthly variability of errors in CO2 concentrations over China were calculated and analyzed. The results indicate that CO2 concentrations are overestimated in western regions of China, especially in desert areas (a maximum of ~7.08%), and those are underestimated in eastern regions (a minimum of ~-6.9%).

  1. Dynamics of shock waves and cavitation bubbles in bilinear elastic-plastic media, and the implications to short-pulsed laser surgery

    NASA Astrophysics Data System (ADS)

    Brujan, E.-A.

    2005-01-01

    The dynamics of shock waves and cavitation bubbles generated by short laser pulses in water and elastic-plastic media were investigated theoretically in order to get a better understanding of their role in short-pulsed laser surgery. Numerical simulations were performed using a spherical model of bubble dynamics which include the elastic-plastic behaviour of the medium surrounding the bubble, compressibility, viscosity, density and surface tension. Breakdown in water produces a monopolar acoustic signal characterized by a compressive wave. Breakdown in an elastic-plastic medium produces a bipolar acoustic signal, with a leading positive compression wave and a trailing negative tensile wave. The calculations revealed that consideration of the tissue elasticity is essential to describe the bipolar shape of the shock wave emitted during optical breakdown. The elastic-plastic response of the medium surrounding the bubble leads to a significant decrease of the maximum size of the cavitation bubble and pressure amplitude of the shock wave emitted during bubble collapse, and shortening of the oscillation period of the bubble. The results are discussed with respect to collateral damage in short-pulsed laser surgery.

  2. Generating wave vector specific Damon-Eshbach spin waves in Py using a diffraction grating

    NASA Astrophysics Data System (ADS)

    Sklenar, J.; Bhat, V. S.; Tsai, C. C.; DeLong, L. E.; Ketterson, J. B.

    2012-07-01

    A patterned square silver antidot lattice on a thin uniform permalloy film facilitates direct coupling of a quasi-uniform microwave field to short wavelength magnetic modes. The resulting modes are studied as a function of both the magnitude and orientation (relative to the symmetry axes of the array) of an in-plane, external DC magnetic field. The observed modes are identified as surface spin waves with wavelengths matching the Fourier components of the silver array.

  3. Gravity waves generated by convection during TWP-ICE: I. Inertia-gravity waves

    NASA Astrophysics Data System (ADS)

    Hankinson, Mai C. N.; Reeder, M. J.; Lane, T. P.

    2014-05-01

    Gravity waves are analyzed in radiosonde soundings taken during the Tropical Warm Pool-International Cloud Experiment (TWP-ICE) campaign. The properties of the inertia-gravity waves are analyzed in Part I, whereas Part II focuses on high-frequency gravity waves. Two groups of inertia-gravity waves are detected: group L (Long vertical wavelength) in the middle stratosphere during the suppressed monsoon period and group S (Short vertical wavelength) in the lower stratosphere during the monsoon break period. Waves belonging to group L propagate to the southeast with a mean intrinsic period of 35 h and have vertical and horizontal wavelengths of about 5-6 km and 3000-6000 km, respectively. Ray-tracing calculations indicate that these waves originate from a deep convective region near Indonesia. Waves belonging to group S propagate to the south-southeast with an intrinsic period, vertical wavelength, and horizontal wavelength of about 45 h, 2 km, and 2000-4000 km, respectively. These waves appear to originate from convection in the vicinity of New Guinea.

  4. Improvement in the GERB short wave flux estimations over snow covered surfaces

    NASA Astrophysics Data System (ADS)

    Bertrand, C.; Gonzalez, L.; Ipe, A.; Clerbaux, N.; Dewitte, S.

    Because space-borne radiometers do not measure the Earth s outgoing fluxes directly angular distribution models ADMs are required to relate actual radiance measurement to flux at given solar angle satellite-viewing geometries surface and atmospheric conditions The conversion of one footprint broadband radiance into the corresponding flux requires therefore to first characterize each footprint in terms of surface type and cloud cover properties to properly select the adequate ADM In the GERB ground segment as implemented at the Royal Meteorological Institute of Belgium RMIB this information i e cloud fraction cloud phase and cloud optical depth is retrieved from the SEVIRI spectral measurements and the IGBP Global Land Cover Map is used to associate one of the five following classes e g ocean moderate-to-high vegetation low-to-moderate vegetation dark desert or bright desert to each SEVIRI pixels The SEVIRI pixel registration according to the five classes is taken invariant in time and does not take care of the presence of ice snow covered areas permanent snow being assimilated to bright desert surface in the operational version of the algorithm However snow cover is among the most important of the Earth s surface characteristics that influence surface radiation energy and hydrological budgets Compared to other land covers its areal extent varies dramatically on very short time scales hours -months And while snow is the most isotropic reflector of all natural surfaces on Earth it still exhibits substantial anisotropy which differs from a

  5. Triggering collapse of the presolar dense cloud core and injecting short-lived radioisotopes with a shock wave. III. Rotating three-dimensional cloud cores

    SciTech Connect

    Boss, Alan P.; Keiser, Sandra A., E-mail: boss@dtm.ciw.edu [Department of Terrestrial Magnetism, Carnegie Institution for Science, 5241 Broad Branch Road, NW, Washington, DC 20015-1305 (United States)

    2014-06-10

    A key test of the supernova triggering and injection hypothesis for the origin of the solar system's short-lived radioisotopes is to reproduce the inferred initial abundances of these isotopes. We present here the most detailed models to date of the shock wave triggering and injection process, where shock waves with varied properties strike fully three-dimensional, rotating, dense cloud cores. The models are calculated with the FLASH adaptive mesh hydrodynamics code. Three different outcomes can result: triggered collapse leading to fragmentation into a multiple protostar system; triggered collapse leading to a single protostar embedded in a protostellar disk; or failure to undergo dynamic collapse. Shock wave material is injected into the collapsing clouds through Rayleigh-Taylor fingers, resulting in initially inhomogeneous distributions in the protostars and protostellar disks. Cloud rotation about an axis aligned with the shock propagation direction does not increase the injection efficiency appreciably, as the shock parameters were chosen to be optimal for injection even in the absence of rotation. For a shock wave from a core-collapse supernova, the dilution factors for supernova material are in the range of ?10{sup –4} to ?3 × 10{sup –4}, in agreement with recent laboratory estimates of the required amount of dilution for {sup 60}Fe and {sup 26}Al. We conclude that a type II supernova remains as a promising candidate for synthesizing the solar system's short-lived radioisotopes shortly before their injection into the presolar cloud core by the supernova's remnant shock wave.

  6. VOLUME 77, NUMBER 2 P H Y S I C A L R E V I E W L E T T E R S 8 JULY 1996 Short-Wave Limit of Hydrodynamics: A Soluble Example

    E-print Network

    Gorban, Alexander N.

    in balance equations for density, momentum, and energy. Retaining the first order term (e) in the latter of the acoustic spectrum in the short-wave domain is obtained. [S0031-9007(96)00642-4] PACS numbers: 47.10.+g, 05- dynamics violate the basic physics behind the Boltzmann equation. Namely, sufficiently short acoustic waves

  7. Advances in Submillimeter Wave Semiconductor-Based Device Designs and Processes at JPL

    Microsoft Academic Search

    R. P. Smith; S. C. Martin; Moonil Kim; Jean Bruston; Dexter Humphrey; Neal Erickson; P. H. Seigel

    1997-01-01

    Planar submillirneter wave circuits are slowly replacing whisker-contacted devices at frequencies above 100 GHz, but in many cases the size constraints dictated by the short wavelengths found at high frequencies have not been adequately addressed. In the last year we have been responding to the challenges of implementing submillimeter wave circuits in GaAs by using processing technologies somewhat new to

  8. Research of the solar photovoltaic cells output characteristics influenced by infrared wave in the solar spectrum

    Microsoft Academic Search

    Bo Su; Guoteng Duan

    2010-01-01

    The energy of solar radiation on the earth mainly concentrates in 0.29~3mum wavelength range, where infrared wave accounts for 53 percent, visible light accounts for 44% and ultraviolet accounts for 3%. For the photovoltaic cells, different light coming from solar radiation has different energy and different penetration depth. For the short waves, the photovoltaic cells have large absorption coefficient and

  9. Continuous-wave operation up to 20 °C of deep-ridge npn-InGaAsP/InP multiple quantum well transistor laser emitting at 1.5-?m wavelength.

    PubMed

    Qiao, L J; Liang, S; Han, L S; Xu, J J; Zhu, H L; Wang, W

    2015-05-01

    We report continuous-wave (CW) operation up to 20 °C of 1.5-?m wavelength npn-InGaAsP/InP multiple quantum well (MQW) transistor laser (TL) with a deep-ridge structure. With CW laser emission, the common emitter current gain of the device can be over 3.5, which is significantly larger than those of the previously reported long wavelength TLs. It is found that at low base current, the laser operation occurs on the first excited state of the MQWs. At high base current, however, the device shows stimulated emissions on the ground state transition. The trend is contrary to what has been observed in the GaAs based TLs and is explained by the change of carrier flow at different base currents. PMID:25969233

  10. Nonlinear wavelength conversion in photonic crystal fibers with three zero-dispersion points

    SciTech Connect

    Stark, S. P.; Biancalana, F.; Podlipensky, A.; St. J. Russell, P. [Max Planck Institute for the Science of Light Guenther-Scharowsky Str. 1/Bau 24, D-91058 Erlangen (Germany)

    2011-02-15

    In this theoretical study, we show that a simple endlessly single-mode photonic crystal fiber can be designed to yield, not just two, but three zero-dispersion wavelengths. The presence of a third dispersion zero creates a rich phase-matching topology, enabling enhanced control over the spectral locations of the four-wave-mixing and resonant-radiation bands emitted by solitons and short pulses. The greatly enhanced flexibility in the positioning of these bands has applications in wavelength conversion, supercontinuum generation, and pair-photon sources for quantum optics.

  11. Nonlinear wavelength conversion in photonic crystal fibers with three zero dispersion points

    E-print Network

    Stark, S P; Podlipensky, A; Russell, P St J

    2010-01-01

    In this theoretical study, we show that a simple endlessly single-mode photonic crystal fiber can be designed to yield, not just two, but three zero-dispersion wavelengths. The presence of a third dispersion zero creates a rich phase-matching topology, enabling enhanced control over the spectral locations of the four-wave-mixing and resonant-radiation bands emitted by solitons and short pulses. The greatly enhanced flexibility in the positioning of these bands has applications in wavelength conversion, supercontinuum generation and pair-photon sources for quantum optics.

  12. Spuriousless single wavelength quartz resonators

    Microsoft Academic Search

    Y. Nagaura; K. Nagaura; Z. Nagaura

    2004-01-01

    The primary research objective is to manufacture quartz resonators that can oscillate elastic waves with a single wavelength and a precise directional performance. This objective has been the dream of many researchers since the discovery of the piezoelectric effect of quartz in 1880 by the brothers Pierre and Jacques Curie who brought into being the development of the ultrasonic and

  13. Theory of waves incoherently scattered

    NASA Technical Reports Server (NTRS)

    Bauer, P.

    1974-01-01

    Electromagnetic waves impinging upon a plasma at frequencies larger than the plasma frequency, suffer weak scattering. The scattering arises from the existence of electron density fluctuations. The received signal corresponds to a particular spatial Fourier component of the fluctuations, the wave vector of which is a function of the wavelength of the radiowave. Wavelengths short with respect to the Debye length of the medium relate to fluctuations due to non-interacting Maxwellian electrons, while larger wavelengths relate to fluctuations due to collective Coulomb interactions. In the latter case, the scattered signal exhibits a spectral distribution which is characteristic of the main properties of the electron and ion gases and, therefore, provides a powerful diagnosis of the state of the ionosphere.

  14. Nonlinear wavelength conversion in photonic crystal fibers with three zero-dispersion points

    Microsoft Academic Search

    S. P. Stark; F. Biancalana; A. Podlipensky; P. St. J. Russell

    2011-01-01

    In this theoretical study, we show that a simple endlessly single-mode photonic crystal fiber can be designed to yield, not just two, but three zero-dispersion wavelengths. The presence of a third dispersion zero creates a rich phase-matching topology, enabling enhanced control over the spectral locations of the four-wave-mixing and resonant-radiation bands emitted by solitons and short pulses. The greatly enhanced

  15. Genomic organization of duplicated short wave-sensitive and long wave-sensitive opsin genes in the green swordtail, Xiphophorus helleri

    PubMed Central

    2010-01-01

    Background Long wave-sensitive (LWS) opsin genes have undergone multiple lineage-specific duplication events throughout the evolution of teleost fishes. LWS repertoire expansions in live-bearing fishes (family Poeciliidae) have equipped multiple species in this family with up to four LWS genes. Given that color vision, especially attraction to orange male coloration, is important to mate choice within poeciliids, LWS opsins have been proposed as candidate genes driving sexual selection in this family. To date the genomic organization of these genes has not been described in the family Poeciliidae, and little is known about the mechanisms regulating the expression of LWS opsins in any teleost. Results Two BAC clones containing the complete genomic repertoire of LWS opsin genes in the green swordtail fish, Xiphophorus helleri, were identified and sequenced. Three of the four LWS loci identified here were linked in a tandem array downstream of two tightly linked short wave-sensitive 2 (SWS2) opsin genes. The fourth LWS opsin gene, containing only a single intron, was not linked to the other three and is the product of a retrotransposition event. Genomic and phylogenetic results demonstrate that the LWS genes described here share a common evolutionary origin with those previously characterized in other poeciliids. Using qualitative RT-PCR and MSP we showed that each of the LWS and SWS2 opsins, as well as three other cone opsin genes and a single rod opsin gene, were expressed in the eyes of adult female and male X. helleri, contributing to six separate classes of adult retinal cone and rod cells with average ?max values of 365 nm, 405 nm, 459 nm, 499 nm, 534 nm and 568 nm. Comparative genomic analysis identified two candidate teleost opsin regulatory regions containing putative CRX binding sites and hormone response elements in upstream sequences of LWS gene regions of seven teleost species, including X. helleri. Conclusions We report the first complete genomic description of LWS and SWS2 genes in poeciliids. These data will serve as a reference for future work seeking to understand the relationship between LWS opsin genomic organization, gene expression, gene family evolution, sexual selection and speciation in this fish family. PMID:20353595

  16. Physics of short-wavelength-laser design

    SciTech Connect

    Hagelstein, P.L.

    1981-01-01

    The physics and design of vuv and soft x-ray lasers pumped by ICF class high intensity infrared laser drivers are described (for example, the SHIVA laser facility at LLNL). Laser design and physics issues are discussed in the case of a photoionization pumping scheme involving Ne II and line pumping schemes involving H-like and He-like neon.

  17. The dynamics of interacting nonlinearities governing long wavelength driftwave turbulence

    SciTech Connect

    Newman, D.E.

    1993-09-01

    Because of the ubiquitous nature of turbulence and the vast array of different systems which have turbulent solutions, the study of turbulence is an area of active research. Much present day understanding of turbulence is rooted in the well established properties of homogeneous Navier-Stokes turbulence, which, due to its relative simplicity, allows for approximate analytic solutions. This work examines a group of turbulent systems with marked differences from Navier-Stokes turbulence, and attempts to quantify some of their properties. This group of systems represents a variety of drift wave fluctuations believed to be of fundamental importance in laboratory fusion devices. From extensive simulation of simple local fluid models of long wavelength drift wave turbulence in tokamaks, a reasonably complete picture of the basic properties of spectral transfer and saturation has emerged. These studies indicate that many conventional notions concerning directions of cascades, locality and isotropy of transfer, frequencies of fluctuations, and stationarity of saturation are not valid for moderate to long wavelengths. In particular, spectral energy transfer at long wavelengths is dominated by the E {times} B nonlinearity, which carries energy to short scale in a manner that is highly nonlocal and anisotropic. In marked contrast to the canonical self-similar cascade dynamics of Kolmogorov, energy is efficiently passed between modes separated by the entire spectrum range in a correlation time. At short wavelengths, transfer is dominated by the polarization drift nonlinearity. While the standard dual cascade applies in this subrange, it is found that finite spectrum size can produce cascades that are reverse directed and are nonconservative in enstrophy and energy similarity ranges. In regions where both nonlinearities are important, cross-coupling between the nolinearities gives rise to large no frequency shifts as well as changes in the spectral dynamics.

  18. Continuous wave terahertz generation up to 2 THz by photomixing on ion-irradiated In{sub 0.53}Ga{sub 0.47}As at 1.55 {mu}m wavelengths

    SciTech Connect

    Mangeney, J.; Merigault, A.; Zerounian, N.; Crozat, P.; Blary, K.; Lampin, J. F. [Institut d'Electronique Fondamentale, UMR CNRS 8622, Universites Paris-Sud, Orsay Cedex 91405 (France); Institut d'Electronique de Microelectronique et de Nanotechnologie, UMR CNRS 8520, Cite Scientifique, Villeneuve d'Ascq Cedex 59652 (France)

    2007-12-10

    We report the generation of continuous terahertz waves from microwave frequencies of up to 2 THz obtained by photomixing two optical waves at 1.55 {mu}m wavelengths in ion-irradiated In{sub 0.53}Ga{sub 0.47}As interdigitated photomixers. A 200 nm thick silicon nitride coating is used for antireflection and passivation layer, improving the reliability and the heat tolerance of the photomixer. In such devices, output powers greater than 40 nW at 0.5 THz and 10 nW at 1 THz have been achieved. Considering the observed saturation of the output power with the increase of bias voltage, the optimum excitation conditions regarding optical power and bias voltage are discussed.

  19. Short-period variability of hydrophysical fields and internal wave characteristics during a semidiurnal tidal cycle on the White Sea shelf

    NASA Astrophysics Data System (ADS)

    Zimin, A. V.

    2013-05-01

    Experimental data obtained in the summer of 2011 in three White Sea continental shelf areas with different stratification are analyzed. The measurements were conducted using a unified procedure that combines frequent oceanographic stations (scanning) and deployment of moorings. It is shown that the tide-induced variability of the thermohaline fields and internal waves is of different types. A shelf area is detected where intense short-period internal waves are observed during every tidal cycle and their contribution to water mixing is significant.

  20. Treatment of renal calculi by lithotripsy: minimizing short-term shock wave induced renal damage by using antioxidants.

    PubMed

    Al-Awadi, Khaleel A; Kehinde, Elijah O; Loutfi, Issa; Mojiminiyi, Olusegun A; Al-Hunayan, Adel; Abdul-Halim, Hamdy; Al-Sarraf, Ahmed; Memon, Anjum; Abraham, Mathew P

    2008-02-01

    Treatment with extracorporeal shock wave lithotripsy (ESWL), the preferred method of treating kidney stones <3 cm in size, has been shown to induce silent and often self-limiting acute and chronic lesions in the kidneys and adjacent organs. We conducted a randomized clinical trial to determine whether ESWL produces ischaemia and reperfusion injury in the kidneys and whether oral administration of antioxidants reduces the degree of short-term renal injury in patients treated with ESWL. The study included 120 patients with renal stones (1-3 cm in size) treated with ESWL. The patients were divided into three groups--patients in group A (n=39) served as a control group and were not given any antioxidants; patients in group B (n=41) were given two capsules of antioxidants "Nature Made R: " 2 h before ESWL, and 2 and 8 h after ESWL; and patients in group C (n=40) were given two capsules of the antioxidants 2 and 8 h after ESWL. Double 'J' stents were inserted in patients before treatment with ESWL. Blood and urine samples were obtained from all patients just before the start of treatment with ESWL, and at 2 and 24 h and on 7th and 28th day after ESWL. Serum levels of malondialdehyde (MDA), alpha-tocopherol, cholesterol, albumin and ascorbic acid, and alpha-tocopherol/cholesterol ratio were determined. Urinary levels of albumin and beta(2) microglobulin were also determined as measures of renal tubular injury. At 24 h after ESWL, patients given antioxidants (groups B + C) had significantly reduced mean serum concentration of MDA (P<0.001); higher levels of serum ascorbic acid (P<0.001) and serum albumin (P<0.001); lower alpha-tocopherol/cholesterol ratio, lower urinary albumin and beta(2 )microglobulin levels compared with patients who did not receive antioxidants (group A). These findings suggest that treatment with ESWL generates free radicals through ischaemic/reperfusion injury mechanism, and that oral administration of antioxidant may protect these patients from short term renal injury caused by ESWL. PMID:18064446

  1. Development of HgCdTe single-element APDs based detectors for low flux short wave infrared applications

    NASA Astrophysics Data System (ADS)

    Foubert, K.; Lasfargues, G.; Mathieu, L.; Benahmed, S.; Vojetta, G.; Rothman, J.; Benoît à la Guillaume, Q.; Calvo, Vincent; Picot-Clemente, Jérémy; Le Mounier, Florent; Gibert, Fabien

    2013-03-01

    The remarkable properties (internal gain larger than 100 and close to unity excess noise factor) of Short Wave Infrared (SWIR) HgCdTe electron-initiated Avalanche Photodiodes (e-APDs) are put to good use to demanding applications, i.e. spectroscopy and LIDAR. Knowing the requirements of both situations, we have designed specific models based on highly sensitive single elements APDs and adapted proximity electronics. On one hand, we use the e-APDs low noise equivalent power (NEP) at 180K (few fW/Hz1/2). We simultaneously designed a specific Transimpedance Amplifier (TIA) which allows us to take advantage of the low APD NEP. The combination of both elements along with a dedicated cryostat enables direct LIDAR detection at moderate bandwidth (BW = 20 MHz) without the need for long time averaging, which is crucial in far field (>= 5 km) analysis. One the other hand, we have optimized a low-noise and low-frequency LN2 cooled prototype operating with an external commercial amplifier. It allows us to observe the photoluminescence of Ge nanostructures in the range 1.5-2.5 ?m with a significantly increased SNR along with a reduce pump laser power. The possibility to use these detectors in the photon counting limit will be discussed in light of our recent results. In parallel, we present preliminary time response measurements performed on SWIR APD suggesting that a higher GHz BW could be reached with this type of detector. This is however subjected to optical optimization at the moment.

  2. Waves

    NSDL National Science Digital Library

    Mr. Hansen

    2010-11-12

    The following websites are useful tools in understanding how energy is transferred from place to place through waves. Start by downloading the assignment and then begin with website number 1 and continue until you have visited all three websites. Begin by downloading the IA Waves Internet Assignment: IA Waves Internet Assignment You will answer the questions in Microsoft Word and then e-mail the assignment to me. Website #1: Read about basic information on waves and answer the questions from part 1 of the IA Waves Guide: Basic Wave Information Website #2: Follow the instructions for the following ...

  3. Mapping Fe-bearing hydrated sulphate minerals with short wave infrared (SWIR) spectral analysis at San Miguel mine environment, Iberian Pyrite Belt (SW Spain)

    Microsoft Academic Search

    Francisco Velasco; Ana Alvaro; Saioa Suarez; José-Miguel Herrero; Iñaki Yusta

    2005-01-01

    Short-wave infrared reflectance (SWIR) spectra obtained from a Portable Infrared Mineral Analyser (PIMA) were applied to map acidic mine soils at San Miguel massive sulphide deposit, Iberian Pyrite Belt, Spain. Field spectral measurements and laboratory analysis were performed on samples from 58 stations from two very polluted grounds. These analyses identified secondary and tertiary Fe-rich sulphate–hydrate minerals associated with the

  4. Photon's Wavelength Stretching and Shrinking?

    NASA Astrophysics Data System (ADS)

    Smarandache, Florentin

    2013-09-01

    The photon is considered of having a dual form: wave and particle. (a) If the photon is a wave, it has been asserted that the photon's wavelength is stretched inside the intergalactic space, because of the expansion of the universe. But what happens with the photon's wavelength when the photon enters a galactic space (which is not expanding), and afterwards it exists the galactic space and enters an intergalactic space (which is expanding), and so on? But, when the wavelength increases the wave frequency decreases (redshift); therefore the wave's momentum and energy are diminished in the expansion of the universe. It seems to be an antithesis between the quantum mechanics (Copenhagen style) and the universe expansion. (b) If the photon is a particle, similarly because of the so-called expansion of the universe, does its pathlength increases inside the intergalactic space (which is expanding) and decreases inside the galactic space (which is not expanding)? Thus, what happens with its pathlength when the photon passes from an intergalactic space to a galactic space, then again to intergalactic space, and so on?

  5. Langmuir waves in magnetic holes: source mechanism and consequences

    SciTech Connect

    MacDowall, R. J.; Lin, N.; Kellogg, P. J.; Balogh, A.; Forsyth, R. J.; Neugebauer, M. [Laboratory for Extraterrestrial Physics, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States); University of Minnesota, Minneapolis, Minnesota 55455 (United States); Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom); Jet Propulsion Laboratory, Pasadena, California 91109 (United States)

    1996-07-20

    Plasma wave observations from the Ulysses spacecraft indicate that electrostatic waves at frequencies approximately equal to the electron plasma frequency f{sub pe} are commonly found in magnetic holes. Magnetic holes are short-duration reductions in the amplitude of the interplanetary magnetic field. A model of the electron dynamics in a magnetic hole suggests that the waves are generated by electron beams of thermal energies, formed by adiabatic focusing of the electrons. These waves, presumed to be Langmuir mode, will have extremely short wavelengths, of the order of 100-1000 m. Such waves, observed in the solar wind, would be significantly Doppler shifted, which can be measured by the plasma wave receiver. The prevalence of waves in magnetic holes suggests that the magnetic structures are not stable and can provide constraints on their formation and evolution.

  6. Wave Heights

    NSDL National Science Digital Library

    In this lesson plan students will learn about the varying heights of ocean waves and what causes the variation. They will begin by learning the parts of a wave, and then discuss the meaning of wave height and wavelength in terms of various points of reference. A demonstration will spark discussion about how geography affects wave heights, and will allow students to experiment with various forces to create different sized waves. Students will use the National Geographic Wave Simulator to experiment with creating different types of waves, and will draw waves based on the heights and lengths of familiar structures around the school.

  7. The first space-based gravitational-wave detectors

    SciTech Connect

    Caldwell, R.R. [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, Pennsylvania 19104 (United States)] [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, Pennsylvania 19104 (United States); Kamionkowski, M.; Wadley, L. [Department of Physics, Columbia University, 538 West 120th Street, New York, New York 10027 (United States)] [Department of Physics, Columbia University, 538 West 120th Street, New York, New York 10027 (United States)

    1999-01-01

    Gravitational waves provide a laboratory for general relativity and a window to energetic astrophysical phenomena invisible with electromagnetic radiation. Several terrestrial detectors are currently under construction, and a space-based interferometer is envisioned for launch early next century to detect test-mass motions induced by waves of relatively short wavelength. Very-long-wavelength gravitational waves can be detected using the plasma in the early Universe as test masses; the motion induced in the plasma by a wave is imprinted onto the cosmic microwave background (CMB). While the signature of gravitational waves on the CMB temperature fluctuations is not unique, the {ital polarization} pattern can be used to unambiguously detect gravitational radiation. Thus, forthcoming CMB polarization experiments, such as the Microwave Anisotropy Probe and Planck, will be the first space-based gravitational-wave detectors. {copyright} {ital 1998} {ital The American Physical Society}

  8. THz wave up-frequency turning by rapidly plasma creation

    NASA Astrophysics Data System (ADS)

    Nishida, Akinori; Nakata, Masahiro; Oba, Takafumi; Higashiguchi, Takeshi; Yugami, Noboru; Sentoku, Yasuhiko; Kodama, Ryosuke

    2011-10-01

    When plasmas are instantaneously created around an electromagnetic wave, frequency of the wave up-converted to the frequency, which depends on the plasma frequency. This phenomenon is called as the flash-ionization predicted by S. C. Wilks et al [1]. The theory requires not only the plasma creation in time much shorter than an oscillation period of the electromagnetic wave but also plasma length much longer than a wavelength of it. We have demonstrated the proof of principle experiment using the interaction between a terahertz wave and plasmas created by an ultra short laser pulse, which ensures the plasma creation time-scale much shorter than a period of electromagnetic source wave and plasma length longer than a wavelength of the wave. We observed frequency upconversion from 0.35 THz to 3.3 THz by the irradiance of the Ti:sapphire laser in ZnSe crystal.

  9. Wave basics

    NSDL National Science Digital Library

    University of Utah. Astrophysics Science Project Integrating Research and Education (ASPIRE)

    2003-01-01

    Wave properties are the basis for many concepts in science. This activity, part of an interactive laboratory series for grades 8-12, introduces students to waves, wavelength, amplitude, and frequency. Here students can drag a chain of particles in any direction to simulate the resulting wave motion. Students can also manipulate the density of the fluid. Three pop-up boxes provide students with activities and explanations for amplitude, frequency, and wavelength. The amplitude activity enables students to vary and view the swing of a pendulum over time. Students study frequency by varying the period of a wave and watching the response graphed over time. The wavelength activity has students measure the wavelength of a wave. Students are informed when they have answered correctly. Copyright 2005 Eisenhower National Clearinghouse

  10. Numerical analysis of quasiperiodic perturbations for the Alfven wave

    SciTech Connect

    Yamakoshi, Y.; Muto, K.; Yoshida, Z. (Department of Quantum Engineering and Systems Science, The University of Tokyo, Hongo, Tokyo 113 (Japan))

    1994-08-01

    The Alfven wave may have a localized eigenfunction when it propagates on a chaotic magnetic field. The Arnold-Beltrami-Childress (ABC) flow is a paradigm of chaotic stream lines and is a simple exact solution to the three-dimensional force-free plasma equilibrium equations. The three-dimensional structure of the magnetic field is represented by sinusoidal quasiperiodic modulation. The short wavelength Alfven wave equation for the ABC-flow magnetic field has a quasiperiodic potential term, which induces interference among Bragg-reflected'' waves with irregular phases. Then the eigenfunction decays at long distance and a point spectrum occurs. Two different types of short wavelength modes have numerically analyzed to demonstrate the existence of localized Alfven wave eigenmodes.

  11. Chemical Sensing Using Infrared Cavity Enhanced Spectroscopy: Short Wave Infrared Cavity Ring Down Spectroscopy (SWIR CRDS) Sensor

    SciTech Connect

    Williams, Richard M.; Harper, Warren W.; Aker, Pam M.; Thompson, Jason S.; Stewart, Timothy L.

    2003-10-01

    The principal goal of Pacific Northwest National Laboratory's (PNNL's) Remote Spectroscopy Project is to explore and develop the science and technology behind point and stand off infrared (IR) spectroscopic chemical sensors that are needed for detecting weapons proliferation activity and countering terrorism. Missions addressed include detecting chemical, biological, and nuclear weapons and their production; counter terrorism measures that involve screening luggage, personnel, and shipping containers for explosives, firearms, narcotics, chemical weapons and/or their residues; and mapping of contaminated areas. The science and technology developed in this program is dual use in that it additionally supports progress in a diverse set of agendas that include chemical weapons defense programs, air operations activities, emissions monitoring, law enforcement, and medical diagnostics. Sensors for these missions require extremely low limits of detection because many of the targeted signature species are either present in low concentrations or have extremely low vapor pressures. The sensors also need to be highly selective as the environments that they will be operated in will contain a variety of interferent species and false positive detection is not an option. PNNL has been working on developing a class of sensors that draw vapor into optical cavities and use laser-based spectroscopy to identify and quantify the vapor chemical content. The cavity enhanced spectroscopies (CES) afford extreme sensitivity, excellent selectivity, noise immunity, and rapid, real-time, in-situ chemical characterization. PNNL's CES program is currently focused on developing two types of sensors. The first one, which is based on cavity ring down spectroscopy (CRDS), uses short wave infrared (SWIR) lasers to interrogate species. The second sensor, which is based on noise immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE OHMS), uses long wave infrared (LWIR) quantum cascade lasers as the light source. This report details the research and discoveries made on the SWIR CRDS project. While chemical detection limits in the SWIR is not expected to be as low as that in the LWIR, there are a number of reasons for designing sensors that operate in this region. First and foremost is that high quality SWIR lasers, detectors and optics are commercially available. Technological advances made in the telecommunications sector have yielded photonic components that are robust, low power, compact and operate at room temperature. These components can be quickly combined and assembled to produce a sensor prototype. This is exactly what we have done with our cavity ring down sensor. We assembled our first prototype instrument in FY02, tested it in the laboratory, developed the chemometrics, and defined several improvements that needed to be implemented before trialing this sensor in the field. In FY03 we completed the refinements, retested the sensor in the laboratory, and then conducted our first field campaign. Our success was demonstrated by the ability of our SWIR CRDS to run autonomously and continuously for 7 days when located in PNNL's Shipping and Receiving Building. No false positive alarms were detected even though the environment was contaminated with vehicle exhaust fumes, dirt, dust, and volatile organic chemicals associated with packaging materials. The instrument maintained its detection threshold and calibration throughout the test. Small fluctuations that we observed in the background concentration levels have led us to develop a more robust method for calibrating the instrument, and separate tests we conducted in the laboratory have afforded a means to account interference from species that have very broad, but weak absorption in this spectral region. We outline all of these accomplishments in detail in the body of this report.

  12. Short wave infrared InGaAs focal plane arrays detector: the performance optimization of photosensitive element

    NASA Astrophysics Data System (ADS)

    Gao, Xin-jiang; Tang, Zun-lie; Zhang, Xiu-chuan; Chen, Yang; Jiang, Li-qun; Cheng, Hong-bing

    2009-07-01

    Significant progress has been achieved in technology of the InGaAs focal plane arrays (FPA) detector operating in short wave infrared (SWIR) last two decades. The no cryogenic cooling, low manufacturing cost, low power, high sensitivity and maneuverability features inherent of InGaAs FPA make it as a mainstream SWIR FPA in a variety of critical military, national security, aerospace, telecommunications and industrial applications. These various types of passive image sensing or active illumination image detecting systems included range-gated imaging, 3-Dimensional Ladar, covert surveillance, pulsed laser beam profiling, machine vision, semiconductor inspection, free space optical communications beam tracker, hyperspectroscopy imaging and many others. In this paper the status and perspectives of hybrid InGaAs FPA which is composed of detector array (PDA) and CMOS readout integrate circuit (ROIC) are reviewed briefly. For various low light levels applications such as starlight or night sky illumination, we have made use of the interface circuit of capacitive feedback transimpedance amplifier (CTIA) in which the integration capacitor was adjustable, therefore implements of the physical and electrical characteristics matches between detector arrays and readout intergrate circuit was achieved excellently. Taking into account the influences of InGaAs detector arrays' optoelectronic characteristics on performance of the FPA, we discussed the key parameters of the photodiode in detailed, and the tradeoff between the responsivity, dark current, impedance at zero bias and junction capacitance of photosensitive element has been made to root out the impact factors. As a result of the educed approach of the photodiode's characteristics optimizing which involve with InGaAs PDA design and process, a high performance InGaAs FPA of 30um pixel pitch and 320×256 format has been developed of which the response spectrum range over 0.9um to 1.7um, the mean peak detectivity (?=1.55?m) was 6×1012 cmHz1/2W-1 and dynamics range reached 68 dB at room temperature. Making use of the fabricated 320×256 InGaAs FPA, the concerning objects can be imaged in the low light level or nightglow background.

  13. Drift wave transport scalings introduced by varying correlation length

    SciTech Connect

    Weiland, J.; Holod, I. [Department of Electromagnetics, Chalmers University of Technology and EURATOM-VR Association, 41296 Goeteborg (Sweden)

    2005-01-01

    Scalings of the correlation length of drift wave turbulence with magnetic current q, shear, elongation, and temperature ratio have been introduced into a drift wave transport model. The correlation length is calculated from linear scaling of the fastest growing mode. Such a procedure is supported by previous turbulence simulations with absorbing boundaries for short and long wavelengths. The resulting q and s scalings are now in better agreement with experimental scalings. In particular, the simulation results for transport barrier shots improve.

  14. Improved optical transmission and current matching of a triple-junction solar cell utilizing sub-wavelength structures.

    PubMed

    Chiu, M-Y; Chang, C-H; Tsai, M-A; Chang, F-Y; Yu, Peichen

    2010-09-13

    Sub-wavelength antireflective structures are fabricated on a silicon nitride passivation layer of a Ga?.?In?.?P/GaAs/Ge triple-junction solar cell using polystyrene nanosphere lithography followed by anisotropic etching. The fabricated structures enhance optical transmission in the ultraviolet wavelength range, compared to a conventional single-layer antireflective coating (ARC). The transmission improvement contributes to an enhanced photocurrent, which is also verified by the external quantum efficiency characterization of the fabricated solar cells. Under one-sun illumination, the short-circuit current of a cell with sub-wavelength structures is enhanced by 46.1% and 3.4% due to much improved optical transmission and current matching, compared to cells without an ARC and with a conventional SiN(x) ARC, respectively. Further optimizations of the sub-wavelength structures including the periodicity and etching depth are conducted by performing comprehensive calculations based on a rigorous couple-wave analysis method. PMID:21165062

  15. Extreme events in Faraday waves

    NASA Astrophysics Data System (ADS)

    Punzmann, Horst; Shats, Michael; Xia, Hua

    2014-05-01

    Observations of extreme wave events in the ocean are rare due to their low statistical probability. In the laboratory however, the evolution of extreme wave events can be studied in great detail with high spatial and temporal resolution. The reported surface wave experiments in the short wavelength gravity-capillary range aim to contribute to the understanding of some of the underlying mechanisms for rogue wave generation. In this talk, we report on extreme wave events in parametrically excited Faraday waves. Faraday waves appear if a fluid is accelerated (normal to the fluid surface) above a critical threshold. A variety of novel tools have been deployed to characterize the 2D surface elevation. The results presented show spatio-temporal and statistical data on the surface wave conditions leading up to extreme wave events. The peak in wave amplitude during such an event is shown to exceed six times the standard deviation of the average wave field with significantly increased statistical probability compared to the background wave field [1]. The experiments also show that parametrically excited waves can be viewed as assembles of oscillons [2] (or oscillating solitons) where modulation instability seems to play a crucial role in their formation. More detailed studies on the oscillon dynamics reveal that the onset of an increased probability of extreme wave events correlates with the increase in the oscillons mobility and merger [3]. Reference: 1. Xia H., Maimbourg T., Punzmann H., and Shats M., Oscillon dynamics and rogue wave generation in Faraday surface ripples, Physical Review Letters 109, 114502 (2012) 2. Shats M., Xia H., and Punzmann H., Parametrically excited water surface ripples as ensembles of oscillons, Physical Review Letters 108, 034502 (2012) 3. Shats M., Punzmann H., Xia H., Capillary rogue waves, Physical Review Letters, 104, 104503 (2010)

  16. Functional characterization of spectral tuning mechanisms in the great bowerbird short-wavelength sensitive visual pigment (SWS1), and the origins of UV/violet vision in passerines and parrots

    PubMed Central

    2013-01-01

    Background One of the most striking features of avian vision is the variation in spectral sensitivity of the short wavelength sensitive (SWS1) opsins, which can be divided into two sub-types: violet- and UV- sensitive (VS & UVS). In birds, UVS has been found in both passerines and parrots, groups that were recently shown to be sister orders. While all parrots are thought to be UVS, recent evidence suggests some passerine lineages may also be VS. The great bowerbird (Chlamydera nuchalis) is a passerine notable for its courtship behaviours in which males build and decorate elaborate bower structures. Results The great bowerbird SWS1 sequence possesses an unusual residue combination at known spectral tuning sites that has not been previously investigated in mutagenesis experiments. In this study, the SWS1 opsin of C. nuchalis was expressed along with a series of spectral tuning mutants and ancestral passerine SWS1 pigments, allowing us to investigate spectral tuning mechanisms and explore the evolution of UV/violet sensitivity in early passerines and parrots. The expressed C. nuchalis SWS1 opsin was found to be a VS pigment, with a ?max of 403 nm. Bowerbird SWS1 mutants C86F, S90C, and C86S/S90C all shifted ?max into the UV, whereas C86S had no effect. Experimentally recreated ancestral passerine and parrot/passerine SWS1 pigments were both found to be VS, indicating that UV sensitivity evolved independently in passerines and parrots from a VS ancestor. Conclusions Our mutagenesis studies indicate that spectral tuning in C. nuchalis is mediated by mechanisms similar to those of other birds. Interestingly, our ancestral sequence reconstructions of SWS1 in landbird evolution suggest multiple transitions from VS to UVS, but no instances of the reverse. Our results not only provide a more precise prediction of where these spectral sensitivity shifts occurred, but also confirm the hypothesis that birds are an unusual exception among vertebrates where some descendants re-evolved UVS from a violet type ancestor. The re-evolution of UVS from a VS type pigment has not previously been predicted elsewhere in the vertebrate phylogeny. PMID:24499383

  17. Transport equations for lower hybrid waves in a turbulent plasma

    NASA Astrophysics Data System (ADS)

    Mendonça, J. T.; Horton, W.; Galvão, R. M. O.; Elskens, Yves

    2015-04-01

    We consider the limits of validity of ray tracing and ray diffusion equations, for short wavelength waves propagating in a turbulent plasma background. We derive an improved transport equation for the electric field autocorrelation function, where first order diffraction effects associated with these waves are included. We apply this description to the case of lower hybrid (LH) waves propagating in non-stationary plasma where density perturbations can occur due to drift wave turbulence, as well as magnetic field perturbations due to MHD turbulence. This is relevant to the problem of LH current drive.

  18. Emergence of body waves from cross-correlation of short period seismic noise1 , H. A. Pedersen1

    E-print Network

    Boyer, Edmond

    reflected from the Moho. Because the crustal model of the area12 is well known, we also compared the noise S reflected phases from the Moho interface at the critical distance in two shield44 areas. The S waves

  19. PdSi focal-plane array detectors for short-wave infrared Raman spectroscopy of biological tissue: a feasibility study

    NASA Astrophysics Data System (ADS)

    Brennan, James F., III; Beattie, Mark E.; Wang, Yang; Cantella, Michael J.; Tsaur, Bor-Yeu; Dasari, Ramachandra R.; Feld, Michael S.

    1996-10-01

    We have used a PdSi focal-plane array detector to measure short-wave infrared Raman spectra of pure compounds and human tissue. Raman bands of the pure compounds are clearly visible in the spectra, and a calcification feature at 960 cm -1 is readily identifiable in the spectra of diseased human aorta. The performance characteristics of our detection device were good; dark noise contributed approximately 60 (electrons/s)/pixel, and the read noise was approximately 50 rms electrons/pixel. The primary noise in the spectra was due to fixed-pattern noise, which is the variation in measured signal across a detector when it is uniformly illuminated.

  20. Waves

    E-print Network

    LaCure, Mari Mae

    2010-04-29

    travel as waves through space and time. Waves can also manifest visibly through other mediums, water for example, as they travel outward from where an object disturbs the surface. As the title of my thesis exhibit, Waves refers to my aim to imbue.... As a viewer approaches a drawing from different angles the light reflected by the image subtly changes intensity. 4 Sewing by hand further adds dimension where it is seen in the front, and creates a shadow where it can be seen through the back...

  1. Collaborative research in tunneling and field emission pumped surface wave local oscillators and amplifiers for infrared and submillimeter wavelengths under director's discretionary fund

    NASA Technical Reports Server (NTRS)

    Gustafson, T. K.

    1982-01-01

    Progress is reported in work towards the development of surface wave sources for the infrared and sub-millimeter portion of the spectrum to be based upon electron pumping by tunneling electrons in metal-barrier-metal or metal-barrier-semiconductor devices. Tunneling phenomena and the coupling of radiation to tunnel junctions were studied. The propagation characteristics of surface electro-magnetic modes in metal-insulator-p(++) semiconductor structures as a function of frequency were calculated. A model for the gain process based upon Tucker's formalism was developed and used to estimate what low frequency gain might be expected from such structures. The question of gain was addressed from a more fundamental viewpoint using the method of Lasher and Stern.

  2. Anomalous absorption of a lower hybrid wave in a plasma with density fluctuations

    NASA Astrophysics Data System (ADS)

    Kumar, Asheel

    2015-06-01

    Anomalous absorption of a lower hybrid wave via mode coupling to short parallel wavelength density fluctuations in a magnetized plasma is investigated. The mode coupling produces a beat mode with the frequency of the lower hybrid wave but an enhanced parallel wave number. This mode is Landau damped on electrons. The oscillatory velocity associated with the beat mode couples with the density ripple to modify the density perturbation of the lower hybrid wave introducing anomalous resistivity. The anomalous resistivity increases with the normalized wave number of the density ripple.

  3. Theoretical study of the optical gain characteristics of a Ge1?xSnx alloy for a short-wave infrared laser

    NASA Astrophysics Data System (ADS)

    Dong-Liang, Zhang; Bu-Wen, Cheng; Chun-Lai, Xue; Xu, Zhang; Hui, Cong; Zhi, Liu; Guang-Ze, Zhang; Qi-Ming, Wang

    2015-02-01

    Optical gain characteristics of Ge1?xSnx are simulated systematically. With an injection carrier concentration of 5 × 1018/cm3 at room temperature, the maximal optical gain of Ge0.922Sn0.078 alloy (with n-type doping concentration being 5 × 1018/cm3) reaches 500 cm?1. Moreover, considering the free-carrier absorption effect, we find that there is an optimal injection carrier density to achieve a maximal net optical gain. A double heterostructure Ge0.554Si0.289Sn0.157/Ge0.922Sn0.078/Ge0.554Si0.289Sn0.157 short-wave infrared laser diode is designed to achieve a high injection efficiency and low threshold current density. The simulation values of the device threshold current density Jth are 6.47 kA/cm2 (temperature: 200 K, and ? = 2050 nm), 10.75 kA/cm2 (temperature: 200 K, and ? = 2000 nm), and 23.12 kA/cm2 (temperature: 300 K, and ? = 2100 nm), respectively. The results indicate the possibility to obtain a Si-based short-wave infrared Ge1?xSnx laser. Project supported by the Major State Basic Research Development Program of China (Grant No. 2013CB632103), the National High-Technology Research and Development Program of China (Grant No. 2012AA012202), and the National Natural Science Foundation of China (Grant Nos. 61177038 and 61176013).

  4. 1534 IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. 53, NO. 9, SEPTEMBER 2005 Spherical-Wave Model for Short-Range MIMO

    E-print Network

    Ingram, Mary Ann

    [3], [4]. Presence of a strong line-of-sight (LOS) component is sometimes viewed as a degradation-input multiple-output (MIMO) channels with a line-of-sight (LOS) component, the plane-wave assumption affects for accurate performance estimation in ray tracing. Index Terms--Channel capacity, line-of-sight (LOS), mul

  5. Short-scale variations of shear-wave splitting across the Dead Sea basin: Evidence for the effects of sedimentary fill

    NASA Astrophysics Data System (ADS)

    Kaviani, Ayoub; Rümpker, Georg; Weber, Michael; Asch, Günter

    2011-02-01

    We examine shear-wave splitting of SKS waveforms collected by a temporary array of 68 stations in the region of the Dead Sea basin. The observed splitting parameters exhibit systematic variations along a dense, EW-trending 60 km profile across the basin. The delay times vary significantly between 1.0 and 2.8 seconds with smaller values in the very center of the profile. The fast polarizations are oriented more-or-less parallel to the strike of the Dead Sea transform fault and vary between -10 and 20 degrees with respect to North. Finite-frequency waveform modeling reveals that the source-region of the small-scale lateral variations is likely located within the crust. The modeling further shows that purely isotropic velocity variations affect shear-wave splitting: To a large degree, the observed variations of splitting parameters can be explained by the sedimentary fill of the basin and its low isotropic seismic velocities, whereas the mantle is uniformly anisotropic. Our study indicates that precaution must be taken when interpreting short-scale lateral variations of shear wave splitting in terms of anisotropic structures in the crust or upper mantle.

  6. Short-range incommensurate d-wave charge order from a two-loop renormalization group calculation of the ferm-ionic hot spot model

    NASA Astrophysics Data System (ADS)

    Freire, Hermann; de Carvalho, Vanuildo

    2015-03-01

    The two-loop renormalization group (RG) calculation is considerably extended here for a two-dimensional (2D) fermionic effective field theory model, which includes only the so-called ``hot spots'' that are connected by the spin-density-wave (SDW) ordering wavevector on a Fermi surface generated by the 2D t -t' Hubbard model at low hole doping. We compute the Callan-Symanzik RG equation up to two loops describing the flow of the single-particle Green's function, the corresponding spectral function, the Fermi velocity, and some of the most important order-parameter susceptibilities in the model at lower energies. As a result, we establish that - in addition to clearly dominant SDW correlations - an approximate (pseudospin) symmetry relating a short-range incommensurate d-wave charge order to the d-wave superconducting order indeed emerges at lower energy scales, which is in agreement with recent works available in the literature addressing the 2D spin-fermion model. We derive implications of this possible electronic phase in the ongoing attempt to describe the phenomenology of the pseudogap regime in underdoped cuprates. We acknowledge financial support from CNPq under Grant No. 245919/2012-0 and FAPEG under Grant No. 201200550050248 for this project.

  7. Validation of S-wave Velocity beneath the Ise Bay, Central Japan, Using Continuous Short-period Ambient Noise Data

    NASA Astrophysics Data System (ADS)

    Hayashida, T.; Yoshimi, M.; Horikawa, H.

    2014-12-01

    We have applied seismic interferometry to three-component ambient noise data recorded around the Ise bay area, central Japan, to validate published three-dimensional S-wave velocity models. For the bay area, detailed seismic velocity structure models have been constructed based on P-wave reflection surveys. There is no direct information on the S-wave velocities beneath the bay and the parameters are assigned by reference to those in a land area. We used one-year continuous data from 20 permanent stations of the NIED Hi-net (High-sensitivity seismograph network) to obtain stacked cross-correlation functions (CCFs) of ambient noise between station pairs that cross the bay. The CCFs were calculated, using one-hour data in the radial-radial (R-R), transverse-transverse (T-T) and vertical-vertical (Z-Z) directions for time lags of ±500s. Horizontal distances between the stations range form 15 km to 103 km. Although the Hi-net stations deploy seismometers with the natural period of 1 s, we found that the yearly stacked CCFs for selected 101 Hi-net station pairs are comparable with those derived from neighboring broadband seismic stations in the frequency range between 0.1 and 0.5 Hz, by deconvolving the instrument response. The CCFs shows clear Rayleigh waves from all directions in the R-R and Z-Z components, and clear Love waves in the T-T component with reasonable signal-to-noise ratios. The derived group velocities and waveforms of the wave trains are variable in the higher frequency range (> 0.2 Hz), indicating deep sedimentary basin beneath the bay. We compared obtained group velocities with theoretical ones to find systematic differences between the expected structure model from the CCFs and the published models in the northwest part of the bay, while the agreements are generally good for many other station pairs. This result indicates that the seismic interferometry technique provides valuable information for validation and improvement of a velocity structure model beneath bay or ocean areas. Acknowledgements: We used continuous waveform records from Hi-net of the National Research Institute for Earthquake Science and Disaster Prevention (NIED).

  8. Characterization of gravity waves at Venus cloud top from the Venus Monitoring Camera images

    NASA Astrophysics Data System (ADS)

    Piccialli, A.; Titov, D.; Svedhem, H.; Markiewicz, W. J.

    2012-04-01

    Since 2006 the European mission Venus Express (VEx) is studying Venus atmosphere with a focus on atmospheric dynamics and circulation. Recently, several experiments on board Venus Express have detected waves in the Venus atmosphere both as oscillations in the temperature and wind fields and as patterns on the cloud layer. Waves could be playing an important role in the maintenance of the atmospheric circulation of Venus since they can transport energy and momentum. High resolution images of Venus Northern hemisphere obtained with the Venus Monitoring Camera (VMC/VEx) show distinct wave patterns at the cloud tops (~70 km altitude) interpreted as gravity waves. Venus Monitoring Camera (VMC) is a CCD-based camera specifically designed to take images of Venus in four narrow band filters in UV (365 nm), visible (513 nm), and near-IR (965 and 1000 nm). A systematic visual search of waves in VMC images was performed; more than 1700 orbits were analyzed and wave patterns were observed in about 200 images. With the aim to characterize the wave types and their possible origin, we retrieved wave properties such as location (latitude and longitude), local time, solar zenith angle, packet length and width, and orientation. A wavelet analysis was also applied to determine the wavelength and the region of dominance of each wave. Four types of waves were identified in VMC images: long, medium, short and irregular waves. The long type waves are characterized by long and narrow straight features extending more than a few hundreds kilometers and with a wavelength within the range of 7 to 48 km. Medium type waves have irregular wavefronts extending more than 100 km and with wavelengths in the range 8 - 21 km. Short wave packets have a width of several tens of kilometers and extends to few hundreds kilometers and are characterized by small wavelengths (3 - 16 km). Often short waves trains are observed at the edges of long features and seem connected to them. Irregular wave fields extend beyond the field of view of VMC and appear to be the result of wave breaking or wave interference. The waves are often identified in all channels and are mostly found at high latitudes (60-80°N) in the Northern hemisphere and seem to be concentrated above Ishtar Terra, a continental size highland that includes the highest mountain belts of the planet, thus suggesting a possible orographic origin of the waves. However, at the moment it is not possible to rule out a bias in the observations due to the spacecraft orbit that prevents waves to be seen at lower latitudes, because of lower resolution, and on the night side of the planet.

  9. Multivariate analysis of waveguide effects on short-period regional wave propagation in Eurasia and its application in seismic discrimination

    Microsoft Academic Search

    Tian-Run Zhang; Susan Y. Schwartz; Thorne Lay

    1994-01-01

    Four data sets characterizing gross crustal waveguide configuration and attenuation properties in Eurasia (surface topography, Moho depth, sediment thickness, and L(sub g) coda Q value) are used to examine path influences on short-period regional P\\/L(sub g) ratios. Linear regressions show considerable correlations between log P\\/L(sub g) and waveguide properties for both earthquake and explosion data. This is of interest because

  10. Yield estimation of Novaya Zemlya explosions from short-period body waves. Final technical report, June 1987-June 1988

    SciTech Connect

    Chan, W.W.; McLaughlin, K.L.; Cessaro, R.K.; Marshall, M.E.; Lees, A.C.

    1988-08-01

    This study investigates the characteristics of Novaya Zemlya explosions using various body wave phases. This information will be used to calibrate the yields of these explosions. The azimuthal variation of amplitude for the Novaya Zemlya explosions as seen from WWSSN recordings indicates that there is a strong component of near-source heterogeneity due to multiple-source excitation, near-source structural heterogeneity, or source anisotropy. The systematic azimuthal variation in amplitude may be modeled with a sin (2 Theta) curve, which allows an estimate of the magnitude bias due to certain network-station distributions. Several events that have an azimuthal variation in amplitude which departs from a sin (2 Theta) curve may be possible multiple explosions. Clear pP and pPcP depth phases can be observed in deconvolved teleseismic P-wave and PcP-wave source time functions from Novaya Zemlya events. With few exceptions, pP and pPcP delay times show a systematic increase with increasing size. Relative explosion-source size estimates are presented based on spectral measures of P, PcP, and P diff at EKA and WRA arrays. These spectral energy measurements may be correlated with the mb estimates to provide an independent calibration of magnitudes. The time-domain measurements of P'P' for Novaya Zemlya recorded on WWSSN stations are used to provide a calibration of the mb estimates from P waves which are quite often clipped for large events. Using a distance-amplitude correction obtained from the data set, the mb estimates for P'P' are computed using a generalized linear model.

  11. Full-wave analysis of microwave scattering from short vegetation: an investigation on the effect of multiple scattering

    Microsoft Academic Search

    Yisok Oh; Young-Mi Jang; K. Sarabandi

    2002-01-01

    A full-wave solution for polarimetric scattering from a cluster of randomly oriented three-dimensional lossy dielectric structures above an impedance surface is presented to investigate the importance of multiple scattering. The problem is formulated using an integral equation in conjunction with the exact image representation of dyadic Green's function for the half-space problem. Then, the integral equation is solved for the

  12. Colliding Blast Waves Driven by the Interaction of a Short-Pulse Laser with a Gas of Atomic Clusters

    Microsoft Academic Search

    Roland A. Smith; James Lazarus; Matthias Hohenberger; Alastair S. Moore; Joseph S. Robinson; Edward T. Gumbrell; Mike Dunne

    Collisions between shocks are commonly found in many astrophysical objects, however robust numerical models or laboratory\\u000a analogues of these complex systems remain challenging to implement. We report on the development of scaled laboratory experiments\\u000a which employ new techniques for launching and diagnosing colliding shocks and high Mach number blast waves, scalable to a\\u000a limited subset of astrophysically-relevant regimes. Use of

  13. Colliding Blast Waves Driven by the Interaction of a Short-Pulse Laser with a Gas of Atomic Clusters

    Microsoft Academic Search

    Roland A. Smith; James Lazarus; Matthias Hohenberger; Alastair S. Moore; Joseph S. Robinson; Edward T. Gumbrell; Mike Dunne

    2007-01-01

    Collisions between shocks are commonly found in many astrophysical objects, however robust numerical models or laboratory\\u000a analogues of these complex systems remain challenging to implement. We report on the development of scaled laboratory experiments\\u000a which employ new techniques for launching and diagnosing colliding shocks and high Mach number blast waves, scalable to a\\u000a limited subset of astrophysically-relevant regimes. Use of

  14. Nonlinear interactions of spin waves with parametric pumping in permalloy metal films

    NASA Astrophysics Data System (ADS)

    Melkov, G. A.; Koblyanskiy, Yu. V.; Slipets, R. A.; Talalaevskij, A. V.; Slavin, A. N.

    2009-04-01

    Nonlinear interactions of dipolar and dipole-exchange spin waves with microwave magnetic field of parametric electromagnetic pumping were studied experimentally in thin permalloy (Py) films. It was demonstrated that parametric pumping in Py films leads to efficient amplification of the “trace” of quasistanding spin waves created due to the two-magnon scattering by the input signal pulse of long-wavelength dipolar spin waves and, then, to suppression of the amplified signal due to the parametric excitation of short-wavelength exchange-dominated spin waves. It was, also, shown that nonlinear interactions of spin waves in Py films can be used for the development of microwave signal processing devices and for the measurement of relaxation characteristics of different spin-wave groups.

  15. Wavelength conversion of nanosecond pulses to the mid-IR in photonic crystal fibers.

    PubMed

    Herzog, Amir; Shamir, Avishay; Ishaaya, Amiel A

    2012-01-01

    We investigate degenerate four wave mixing with nanosecond pulses in fused silica photonic crystal fibers. Phase-matching curves are calculated taking into account the material and waveguide dispersion. Experiments with a nanosecond pulsed Nd:YAG pump laser and relatively short fiber lengths show more than an octave spanning conversion to idler and signal wavelengths at 3.105 ?m and 0.642 ?m, respectively. Conversion efficiency depends on the fiber length and pump intensity and is limited in our experiments by damage of the fiber input facet. Our results represent a new stretch towards the limit of the silica transmission window in the mid-infrared (IR). PMID:22212798

  16. Nonlinear wavelength conversion in photonic crystal fibers with three zero dispersion points

    Microsoft Academic Search

    S. P. Stark; F. Biancalana; A. Podlipensky; P. St. J. Russell

    2010-01-01

    In this theoretical study, we show that a simple endlessly single-mode\\u000aphotonic crystal fiber can be designed to yield, not just two, but three\\u000azero-dispersion wavelengths. The presence of a third dispersion zero creates a\\u000arich phase-matching topology, enabling enhanced control over the spectral\\u000alocations of the four-wave-mixing and resonant-radiation bands emitted by\\u000asolitons and short pulses. The greatly enhanced

  17. Radiative Electron Capture to the Continuum and the Short-Wavelength Limit of Electron-Nucleus Bremsstrahlung in 90A MeV U{sup 88+}(1s{sup 2}2s{sup 2})+N{sub 2} Collisions

    SciTech Connect

    Nofal, M. [Max Planck Institut fuer Kernphysik, D-69117 Heidelberg (Germany); Institut fuer Kernphysik, Universitaet Frankfurt, D-60438 Frankfurt (Germany); Gesellschaft fuer Schwerionenforschung GSI, D-64291 Darmstadt (Germany); Hagmann, S. [Institut fuer Kernphysik, Universitaet Frankfurt, D-60438 Frankfurt (Germany); Gesellschaft fuer Schwerionenforschung GSI, D-64291 Darmstadt (Germany); Stoehlker, Th.; Kozhuharov, Ch.; Gumberidze, A.; Spillmann, U.; Reuschl, R.; Hess, S.; Trotsenko, S.; Banas, D.; Bosch, F.; Liesen, D.; Steck, M.; Nolden, F.; Beller, P.; Beckert, K.; Franczak, B. [Gesellschaft fuer Schwerionenforschung GSI, D-64291 Darmstadt (Germany); Jakubassa-Amundsen, D. H. [Mathematisches Institut, Ludwig-Maximilans-Universitaet, D-80333 Munich (Germany); Wang, X. [Modern Physics Institute, Fudan University, Shanghai 200433 (China); Moshammer, R. [Max Planck Institut fuer Kernphysik, D-69117 Heidelberg (Germany)] (and others)

    2007-10-19

    We have measured the continuum momentum distribution for radiative electron capture to the continuum (RECC) cusp electrons in 90A MeV U{sup 88+}+N{sub 2}{yields}U{sup 88+}+(N{sub 2}{sup +}*)+e{sub cusp}(0 deg.)+h{nu} (RECC) collisions. We demonstrate that x rays coincident with RECC cusp electrons originate from the short-wavelength limit of the electron-nucleus bremsstrahlung and explain the asymmetric cusp shape by comparison with theory within the relativistic impulse approximation.

  18. Photoelectron circular dichroism in the multiphoton ionization by short laser pulses. I. Propagation of single-active-electron wave packets in chiral pseudo-potentials.

    PubMed

    Artemyev, Anton N; Müller, Anne D; Hochstuhl, David; Demekhin, Philipp V

    2015-06-28

    A theoretical method to study the angle-resolved multiphoton ionization of polyatomic molecules is developed. It is based on the time-dependent formulation of the Single Center (TDSC) method and consists in the propagation of single-active-electron wave packets in the effective molecular potentials in the presence of intense laser pulses. For this purpose, the time-dependent Schrödinger equation for one electron, moving in a molecular field and interacting with an arbitrary laser pulse, is solved in spherical coordinates by an efficient numerical approach. As a test, the method is applied to the one- and two-photon ionizations of a model methane-like chiral system by circularly polarized short intense high-frequency laser pulses. Thereby, we analyze the photoelectron circular dichroism (PECD) in the momentum distribution. The considered model application illustrates the capability of the TDSC method to study multiphoton PECD in fixed-in-space and randomly oriented chiral molecules. PMID:26133408

  19. Photoelectron circular dichroism in the multiphoton ionization by short laser pulses. I. Propagation of single-active-electron wave packets in chiral pseudo-potentials

    NASA Astrophysics Data System (ADS)

    Artemyev, Anton N.; Müller, Anne D.; Hochstuhl, David; Demekhin, Philipp V.

    2015-06-01

    A theoretical method to study the angle-resolved multiphoton ionization of polyatomic molecules is developed. It is based on the time-dependent formulation of the Single Center (TDSC) method and consists in the propagation of single-active-electron wave packets in the effective molecular potentials in the presence of intense laser pulses. For this purpose, the time-dependent Schrödinger equation for one electron, moving in a molecular field and interacting with an arbitrary laser pulse, is solved in spherical coordinates by an efficient numerical approach. As a test, the method is applied to the one- and two-photon ionizations of a model methane-like chiral system by circularly polarized short intense high-frequency laser pulses. Thereby, we analyze the photoelectron circular dichroism (PECD) in the momentum distribution. The considered model application illustrates the capability of the TDSC method to study multiphoton PECD in fixed-in-space and randomly oriented chiral molecules.

  20. Multichannel analysis of surface waves to map bedrock

    USGS Publications Warehouse

    Miller, Richard D.; Xia, Jianghai; Park, Choon B.; Ivanov, Julian M.

    1999-01-01

    High velocity gradients within the shear wave velocity field consistent with drill confirmed bedrock are considered diagnostic of the bedrock surface and were used to map the top of bedrock on all four lines connected at this site. Calculating the shear wave velocity field from surface wave arrivals was accomplished with a high degree of accuracy regardless of cultural noise. Improved resolution on the surface of the bedrock provides insight into the texture of bedrock and permits identification and appraisal of short wavelength variations in the bedrock surface.

  1. Wavelength-domain RF photonic signal processing

    NASA Astrophysics Data System (ADS)

    Gao, Lu

    This thesis presents a novel approach to RF-photonic signal processing applications based on wavelength-domain optical signal processing techniques using broadband light sources as the information carriers, such as femtosecond lasers and white light sources. The wavelength dimension of the broadband light sources adds an additional degree of freedom to conventional optical signal processing systems. Two novel wavelength-domain optical signal processing systems are presented and demonstrated in this thesis. The first wavelength-domain RF photonic signal processing system is a wavelength-compensated squint-free photonic multiple beam-forming system for wideband RF phased-array antennas. Such a photonic beam-forming system employs a new modulation scheme developed in this thesis, which uses traveling-wave tunable filters to modulate wideband RF signals onto broadband optical light sources in a frequency-mapped manner. The wavelength dimension of the broadband light sources provides an additional dimension in the wavelength-compensated Fourier beam-forming system for mapping the received RF frequencies to the linearly proportional optical frequencies, enabling true-time-delay beam forming, as well as other novel RF-photonic signal processing functions such as tunable filtering and frequency down conversion. A new slow-light mechanism, the SLUGGISH light, has also been discovered with an effective slow-light velocity of 86 m/s and a record time-bandwidth product of 20. Experimental demonstration of true-time-delay beam forming based on the SLUGGISH light effect has also been presented in this thesis. In the second wavelength-domain RF photonic signal processing system, the wavelength dimension increases the information carrying capacity by spectrally multiplexing multiple wavelength channels in a wavelength-division-multiplexing fiber-optic communication system. A novel ultrafast all-optical 3R (Re-amplification, Retiming, Re-shaping) wavelength converter based on interactions between (3+1)-D optical solitons has been developed and demonstrated numerically in this thesis, which can exchange information between different wavelength channels and enhance the network maneuverability. Dispersion management for the generation of (3+1)-D optical solitons using a pair of negative dispersive mirrors is proposed and demonstrated. An ultrafast all-optical wavelength converter based on the dragging interaction between light bullets with different colors is presented, which features a compact size of 100mumx 100mumx 1mm, an ultra-high conversion speed of over 1 TB/s, and a wavelength conversion range of more than 50 nm.

  2. Polarization-Insensitive Wavelength Conversion by FWM in a Highly Nonlinear PCF of Polarization-Scrambled 10Gb\\/s RZ-OOK and RZ-DPSK Signals

    Microsoft Academic Search

    W. Astar; A. S. Lenihan; G. M. Carter

    2007-01-01

    Wavelength conversion of polarization-scrambled 10-Gb\\/s on-off keyed and differential phase-shift-keyed signals for which the pulse format was 33% return-to-zero, has been achieved by partially degenerate four-wave mixing in a record 20-m-short highly nonlinear photonic crystal fiber. It was found that a minimum pump-probe detuning of ~9 nm was required to achieve polarization-insensitive wavelength conversion of <1 dB, resulting in a

  3. Engineering polarization entanglement at telecom wavelengths

    E-print Network

    Paris-Sud XI, Université de

    photonic bandwidths ranging from 25 MHz to 1 THz, and creating any two-photon state. OCIS codes: 270]. The association of standard low-loss optical fibers and reliable guided-wave components make it possible to create and distribute photonic entanglement in the telecom C-band of wavelengths (1530-1565nm). In addition

  4. Influence of atmospheric aerosol single backscattering on waveform of target-reflected signal in incoherent frequency-modulation continuous-wave short-distance laser detection

    NASA Astrophysics Data System (ADS)

    Liu, Kai; Cui, Zhan-Zhong

    2011-01-01

    The atmospheric aerosol scattering is considered as a major distortion mechanism in laser detection. Its influence on the target-reflected signal in incoherent frequency-modulation continuous-wave (FMCW) short-distance laser detection, which has not yet been well addressed, has been theoretically and experimentally studied in this paper. Assuming intensity of one-particle backscattering as an interference signal, the expression of this interference signal is calculated based on the model of one-particle backscattering and the Mie theory. Only single scattering is considered when optical thickness of the particle group is low. Broadenings of the hybrid signal formed with the particle group backscattering signal and the target-reflected signal are emulated, combining the model of particle group backscattering with the particle distribution function. The broadening time caused by the particle group is far less than the minimum response time of the photodiode. Experimental results confirm that the output voltage of the hybrid signal is identical to the output voltage of the target-reflected signal, except for attenuation in amplitude. Therefore, the incoherent FMCW short-distance laser detection shows a good capability of antiaerosol interference, which is very important for signal processing and target identification.

  5. Suppression of infrared instability in trans-sonic flows by condensation of zero-frequency short wave length phonons

    E-print Network

    Xavier Busch; Florent Michel; Renaud Parentani

    2015-02-06

    We analyze the peculiar infrared instability that characterizes stationary inhomogeneous flows when their velocity crosses the sound speed by decreasing values. For definiteness, we work in the context of one dimensional atomic Bose condensates. These flows are unstable under ultra low real frequency perturbations because of the unbounded mode amplification near the sonic horizon. This results in a condensation of low frequency phonons which produces a spatially structured flow in the supersonic domain. Numerical simulations reveal that this zero-frequency undulation suppresses the instability when its spatial extension is infinite, and when its phase is near that of a "shadow soliton" solution attached to the sonic horizon. These phenomena are akin to the condensation of rotons in flowing superfluid helium-4 when exceeding the Landau velocity. They also pertain to shallow water waves propagating on transcritical flows.

  6. Global integration of the Schrödinger equation: a short iterative scheme within the wave operator formalism using discrete Fourier transforms

    NASA Astrophysics Data System (ADS)

    Leclerc, Arnaud; Jolicard, Georges

    2015-06-01

    A global solution of the Schrödinger equation for explicitly time-dependent Hamiltonians is derived by integrating the nonlinear differential equation associated with the time-dependent wave operator. A fast iterative solution method is proposed in which, however, numerous integrals over time have to be evaluated. This internal work is done using a numerical integrator based on fast Fourier transforms (FFT). The case of a transition between two potential wells of a model molecule driven by intense laser pulses is used as an illustrative example. This application reveals some interesting features of the integration technique. Each iteration provides a global approximate solution on grid points regularly distributed over the full time propagation interval. Inside the convergence radius, the complete integration is competitive with standard algorithms, especially when high accuracy is required.

  7. ANALYTICAL SOLUTION FOR WAVES IN PLANETS WITH ATMOSPHERIC SUPERROTATION. I. ACOUSTIC AND INERTIA-GRAVITY WAVES

    SciTech Connect

    Peralta, J.; López-Valverde, M. A. [Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía, 18008 Granada (Spain); Imamura, T. [Institute of Space and Astronautical Science-Japan Aerospace Exploration Agency 3-1-1, Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Read, P. L. [Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford (United Kingdom); Luz, D. [Centro de Astronomia e Astrofísica da Universidade de Lisboa (CAAUL), Observatório Astronómico de Lisboa, Tapada da Ajuda, 1349-018 Lisboa (Portugal); Piccialli, A., E-mail: peralta@iaa.es [LATMOS, UVSQ, 11 bd dAlembert, 78280 Guyancourt (France)

    2014-07-01

    This paper is the first of a two-part study devoted to developing tools for a systematic classification of the wide variety of atmospheric waves expected on slowly rotating planets with atmospheric superrotation. Starting with the primitive equations for a cyclostrophic regime, we have deduced the analytical solution for the possible waves, simultaneously including the effect of the metric terms for the centrifugal force and the meridional shear of the background wind. In those cases when the conditions for the method of the multiple scales in height are met, these wave solutions are also valid when vertical shear of the background wind is present. A total of six types of waves have been found and their properties were characterized in terms of the corresponding dispersion relations and wave structures. In this first part, only waves that are direct solutions of the generic dispersion relation are studied—acoustic and inertia-gravity waves. Concerning inertia-gravity waves, we found that in the cases of short horizontal wavelengths, null background wind, or propagation in the equatorial region, only pure gravity waves are possible, while for the limit of large horizontal wavelengths and/or null static stability, the waves are inertial. The correspondence between classical atmospheric approximations and wave filtering has been examined too, and we carried out a classification of the mesoscale waves found in the clouds of Venus at different vertical levels of its atmosphere. Finally, the classification of waves in exoplanets is discussed and we provide a list of possible candidates with cyclostrophic regimes.

  8. Modulation of ion-acoustic waves in a nonextensive plasma with two-temperature electrons

    E-print Network

    Shalini,; Misra, A P

    2015-01-01

    We study the amplitude modulation of ion-acoustic wave (IAW) packets in an unmagnetized electron-ion plasma with two-temperature (cool and hot) electrons in the context of the Tsallis' nonextensive statistics. Using the multiple-scale technique, a nonlinear Schr{\\"o}dinger (NLS) equation is derived which governs the dynamics of modulated wave packets. It is shown that in nonextensive plasmas, the IAW envelope is always stable for long-wavelength modes $(k\\rightarrow0)$ and unstable for short-wavelengths with $k \\gtrsim1$. However, the envelope can be unstable at an intermediate scale of perturbations with $0electrons. It is found that the m...

  9. Light-current characterization of dual-wavelength VCSELs

    Microsoft Academic Search

    Vlad Badilita; Jean-Francois Carlin; Marcel Brunner; Marc Ilegems

    2002-01-01

    The purpose of this paper is to present a detailed characterization of a dual-wavelength VCSEL - the BiVCSEL. This device consists of two active optical cavities, which share a coupling mirror and can be independently electrically pumped. We present the output powers for the two emitted wavelengths (short - (lambda) S, long - (lambda) L versus the currents in the

  10. Wavelength modulation spectroscopy with a pulsed quantum cascade laser

    NASA Astrophysics Data System (ADS)

    Manne, Jagadeeshwari; Lim, Alan; Jäger, Wolfgang; Tulip, John

    2011-08-01

    A pulsed distributed feedback quantum cascade laser (QCL) operating near 957 cm-1 was employed in wavelength modulation mode for spectroscopic trace gas sensing applications. The laser was excited with short current pulses (5-10 ns) with < 2% duty cycle. The pulse amplitude was modulated with a linear sub-threshold current ramp at 20 Hz resulting in a ~ 2.5 cm-1 frequency scan, which is typically wider than what has been reported for these lasers, and would allow one to detect molecular absorption features with line widths up to 1 cm-1. A demodulation approach followed by numerical filtering was utilized to improve the signal-to-noise ratio. We then superimposed a sine wave current modulation at 10 kHz onto the 20 Hz current ramp. The resulting high frequency temperature modulation of the distributed feedback (DFB) structure results in wavelength modulation (WM). The set-up was tested by recording relatively weak absorption lines of carbon dioxide. We demonstrated a minimum detectable absorbance of 10-5 for this spectrometer. Basic instrument performance and optimization of the experimental parameters for sensitivity improvement are discussed.

  11. Prototype for Long Wavelength Array Sees First Light

    NASA Astrophysics Data System (ADS)

    2007-03-01

    Astronomers at the Naval Research Laboratory have produced the first images of the sky from a prototype of the Long Wavelength Array (LWA), a revolutionary new radio telescope to be constructed in southwestern New Mexico. The images show emissions from the center of our Galaxy, a supermassive black hole, and the remnant of a star that exploded in a supernova over 300 years ago. Not only a milestone in the development of the LWA, the images are also a first glimpse through a new window on the cosmos. "First light" is an astronomical term for the first image produced with a telescope. It is a key milestone for any telescope because it indicates that all of the individual components are working in unison as planned. Once completed, the LWA will provide an entirely novel view of the sky, in the radio frequency range of 20-80 MHz, currently one of the most poorly explored regions of the electromagnetic spectrum in astronomy. The LWA will be able to make sensitive high-resolution images, and scan the sky rapidly for new and transient sources of radio waves, which might represent the explosion of distant, massive stars, the emissions from planets outside of our own solar system or even previously unknown objects or phenomena. "The LWA will allow us to make the sharpest images ever possible using very long wavelength radio waves. This newly opened window on the universe will help us understand the acceleration of relativistic particles in a variety of extreme astrophysical environments including from the most distant supermassive black holes. But perhaps most exciting is the promise of new source classes waiting to be discovered," says Dr. Namir Kassim, an NRL astronomer in the Remote Sensing Division and LWA Project Scientist. Dr. Tracy Clarke, of Interferometrics, Inc. in Herndon, Virginia, another astronomer on the NRL team adds, "By detecting distant clusters of galaxies the LWA may also provide new insights on the cosmological evolution of the mysterious dark matter and dark energy." Although radio astronomy was discovered at low frequencies (near 20 MHz, corresponding to wavelengths of 15 meters), well below the current FM band, astronomers quickly moved up to higher frequencies (centimeter wavelengths) in search of higher resolution and to escape the corrupting effects of the Earth's ionosphere, a region of charged particles between about 50 and 600 miles above the surface. The ionosphere, which can "bend" radio waves to produce long-distance reception of AM and short-wave radio signals, also causes distortions in radio telescope images in much the same way that atmospheric irregularities cause twinkling of stars. Ionospheric effects become much worse at low frequencies, but new imaging techniques developed at NRL and elsewhere have allowed the "ionospheric barrier" to be broken and enabled high-resolution astronomical imaging at these low frequencies for the first time. These new imaging techniques provide an improved view of not only the astronomical sky, but the Earth's ionosphere as well. The full LWA will generate richly detailed measurements of the ionosphere that will complement other ionospheric data sources. Understanding the ionosphere is critically important to the Department of Defense because of its effects on communications and navigation systems. The current prototype, referred to as the Long Wavelength Demonstrator Array (LWDA) to differentiate it from the larger LWA project, completed installation on the Plains of San Agustin in southwestern New Mexico in the fall of 2006. Funded by NRL and built by the Applied Research Laboratories of the University of Texas, Austin (ARL:UT), the telescope consists of 16 antennas connected to a suite of electronics that combine the signals from each antenna. Each antenna is only 4 feet tall and acts much like an old style television antenna, receiving radio waves from many different directions simultaneously. When combined, the data from the individual antennas is comparable to that from a more traditional dish style tele

  12. Short-range force between two Higgs bosons

    E-print Network

    Feng Feng; Yu Jia; Wen-Long Sang

    2014-06-10

    The $S$-wave scattering length and the effective range of the Higgs boson in Standard Model are studied using effective-field-theory approach. After incorporating the first-order electroweak correction, the short-range force between two Higgs bosons remains weakly attractive for $M_H=126$ GeV. It is interesting to find that the force range is about two order-of-magnitude larger than the Compton wavelength of the Higgs boson, almost comparable with the typical length scale of the strong interaction.

  13. CONFIRMING THE PRIMARILY SMOOTH STRUCTURE OF THE VEGA DEBRIS DISK AT MILLIMETER WAVELENGTHS

    SciTech Connect

    Hughes, A. Meredith; Plambeck, Richard; Chiang, Eugene [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Wilner, David J.; Andrews, Sean M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Mason, Brian [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475 (United States); Carpenter, John M. [California Institute of Technology, Department of Astronomy, MC 105-24, Pasadena, CA 91125 (United States); Chiang, Hsin-Fang [Institute for Astronomy, University of Hawaii, 640 North Aohoku Place, Hilo, HI 96720 (United States); Williams, Jonathan P. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Hales, Antonio [Joint ALMA Observatory, Av. El Golf 40, Piso 18, Santiago (Chile); Su, Kate [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Dicker, Simon; Korngut, Phil; Devlin, Mark, E-mail: mhughes@astro.berkeley.edu [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States)

    2012-05-01

    Clumpy structure in the debris disk around Vega has been previously reported at millimeter wavelengths and attributed to concentrations of dust grains trapped in resonances with an unseen planet. However, recent imaging at similar wavelengths with higher sensitivity has disputed the observed structure. We present three new millimeter-wavelength observations that help to resolve the puzzling and contradictory observations. We have observed the Vega system with the Submillimeter Array (SMA) at a wavelength of 880 {mu}m and an angular resolution of 5''; with the Combined Array for Research in Millimeter-wave Astronomy (CARMA) at a wavelength of 1.3 mm and an angular resolution of 5''; and with the Green Bank Telescope (GBT) at a wavelength of 3.3 mm and angular resolution of 10''. Despite high sensitivity and short baselines, we do not detect the Vega debris disk in either of the interferometric data sets (SMA and CARMA), which should be sensitive at high significance to clumpy structure based on previously reported observations. We obtain a marginal (3{sigma}) detection of disk emission in the GBT data; the spatial distribution of the emission is not well constrained. We analyze the observations in the context of several different models, demonstrating that the observations are consistent with a smooth, broad, axisymmetric disk with inner radius 20-100 AU and width {approx}> 50 AU. The interferometric data require that at least half of the 860 {mu}m emission detected by previous single-dish observations with the James Clerk Maxwell Telescope be distributed axisymmetrically, ruling out strong contributions from flux concentrations on spatial scales of {approx}<100 AU. These observations support recent results from the Plateau de Bure Interferometer indicating that previous detections of clumpy structure in the Vega debris disk were spurious.

  14. Non-destructive analysis of the two subspecies of African elephants, mammoth, hippopotamus, and sperm whale ivories by visible and short-wave near infrared spectroscopy and chemometrics.

    PubMed

    Shimoyama, Masahiko; Morimoto, Susumu; Ozaki, Yukihiro

    2004-06-01

    Visible (VIS) and short-wave near infrared (SW-NIR) spectroscopy was used for non-destructive analysis of ivories. VIS-SW-NIR (500-1000 nm) spectra were measured in situ for five kinds of ivories, that is two subspecies of African elephants, mammoth, hippopotamus, and sperm whale. Chemometrics analyses were carried out for the spectral data from 500 to 1000 nm region. The five kinds of ivories were clearly discriminated from each other on the scores plot of two principal components (PCs) obtained by principal component analysis (PCA). It was noteworthy that the ivories of the two subspecies of African elephants were discriminated by the scores of PC 1. The loadings plot for PC 1 showed that the discrimination relies on the intensity changes in bands due to collagenous proteins and water interacting with proteins. It was found that the scores plot of PC 2 is useful to distinguish between the ivories of the two subspecies of African elephants and the other ivories. We also developed a calibration model that predicted the specific gravity of five kinds of ivories from their VIS-SW-NIR spectral data using partial least squares (PLS)-1 regression. The correlation coefficient and root mean square error of cross validation (RMSECV) of this model were 0.960 and 0.037, respectively. PMID:15152335

  15. Traveling Waves and Superposition Demonstration

    NSDL National Science Digital Library

    Wolfgang Christian

    The applet shows two waves and their superposition. While keeping the parameters for one wave the same, change the parameters for the other wave to create a standing wave. Note that you can't change the speed directly. Change the wavelength and frequency in order that both waves have the same speed.

  16. Finite-Difference Time-Domain Analysis of Wavelength-Selective Characteristics in Weighted Acoustooptic Switches for Wavelength-Division-Multiplexed Photonic Routing

    Microsoft Academic Search

    Nobuo Goto; Yasumitsu Miyazaki

    2004-01-01

    Waveguide-type acoustooptic (AO) switches can switch optical waves wavelength-selectively for wavelength-division-multiplexed (WDM) signals. The switches can be expected to be used in WDM photonic networks. In this paper, finite-difference time-domain (FDTD) analysis is presented for wavelength-selective switching with a collinear weighted AO device consisting of an optical directional coupler, input\\/output Y-branches and a tapered surface acoustic wave (SAW) waveguide. The

  17. THE EFFECTS OF WAVE ESCAPE ON FAST MAGNETOSONIC WAVE TURBULENCE IN SOLAR FLARES

    SciTech Connect

    Pongkitiwanichakul, Peera; Chandran, Benjamin D. G. [Space Science Center and Department of Physics, University of New Hampshire, Durham, NH 03824 (United States); Karpen, Judith T. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); DeVore, C. Richard, E-mail: pbu3@unh.edu, E-mail: benjamin.chandran@unh.edu, E-mail: judy.karpen@nasa.gov, E-mail: devore@nrl.navy.mil [Naval Research Laboratory, Washington, DC 20375 (United States)

    2012-09-20

    One of the leading models for electron acceleration in solar flares is stochastic acceleration by weakly turbulent fast magnetosonic waves ({sup f}ast waves{sup )}. In this model, large-scale flows triggered by magnetic reconnection excite large-wavelength fast waves, and fast-wave energy then cascades from large wavelengths to small wavelengths. Electron acceleration by large-wavelength fast waves is weak, and so the model relies on the small-wavelength waves produced by the turbulent cascade. In order for the model to work, the energy cascade time for large-wavelength fast waves must be shorter than the time required for the waves to propagate out of the solar-flare acceleration region. To investigate the effects of wave escape, we solve the wave kinetic equation for fast waves in weak turbulence theory, supplemented with a homogeneous wave-loss term. We find that the amplitude of large-wavelength fast waves must exceed a minimum threshold in order for a significant fraction of the wave energy to cascade to small wavelengths before the waves leave the acceleration region. We evaluate this threshold as a function of the dominant wavelength of the fast waves that are initially excited by reconnection outflows.

  18. [1] Cox, C. and Munk, W. 1954. Measurements of the Roughness of the Sea Surface from Photographs of the Sun's Glitter. J. Opt. Soc. America. 44(11):838-50 [2] Waas, S. and Jhne, B. 1992. Combined slope-height measurements of short wind waves: first result

    E-print Network

    Jaehne, Bernd

    -height measurements of short wind waves: first results from field and laboratory measurements. SPIE Optics of the Air for the measurement of water wave statistics in the field Proc. of the 6th Int. Symp. Gas Transfer at Water Surfaces of Heidelberg, Germany Measurement of Ocean Wave Statistics with the Reflective Stereo Slope Gauge Institut für

  19. Evolution of surface gravity waves over a submarine canyon

    E-print Network

    Magne, R; Herbers, T H C; Ardhuin, F; O'Reilly, W C; Rey, V; Magne, Rudy; Belibassakis, Kostas; Herbers, Thomas H. C.; Ardhuin, Fabrice; Reilly, William C. O'; Rey, Vincent

    2006-01-01

    The effects of a submarine canyon on the propagation of ocean surface waves are examined with a three-dimensional coupled-mode model for wave propagation over steep topography. Whereas the classical geometrical optics approximation predicts an abrupt transition from complete transmission at small incidence angles to no transmission at large angles, the full model predicts a more gradual transition with partial reflection/transmission that is sensitive to the canyon geometry and controlled by evanescent modes for small incidence angles and relatively short waves. Model results for large incidence angles are compared with data from directional wave buoys deployed around the rim and over Scripps Canyon, near San Diego, California, during the Nearshore Canyon Experiment (NCEX). Wave heights are observed to decay across the canyon by about a factor 5 over a distance shorter than a wavelength. Yet, a spectral refraction model predicts an even larger reduction by about a factor 10, because low frequency components c...

  20. Intrinsically stable light source at telecom wavelengths

    E-print Network

    Monteiro, Fernando; Sanguinetti, Bruno; Zbinden, Hugo

    2013-01-01

    We present a highly stable light source at telecom wavelengths, based on a short erbium doped fiber. The high stability arises from the high inversion of the Er3+ion population. This source is developed to work as a stable reference in radiometric applications and is useful in any application where high stability and/or a large bandwidth are necessary. The achieved long-term stability is 10 ppm.

  1. Freestanding GaN grating couplers at visible wavelengths

    NASA Astrophysics Data System (ADS)

    Liu, Qifa; Shi, Zheng; Zhu, Gangyi; Wang, Wei; Wang, Zhenhai; Wang, Yongjin

    2015-04-01

    A freestanding GaN grating coupler is proposed for planar photonic applications within the visible-wavelength spectrum. This freestanding device was produced by double-sided fabrication, combining GaN front patterning with Si substrate back releasing and GaN slab back thinning. Transverse-electric (TE) and transverse-magnetic (TM) light-wave conversion into and out of the membrane through grating coupling was determined by optical measurement. The maximum coupling efficiency is up to 69% for TE waves and 66% for TM waves at each particular wavelength according to the finite element method (FEM) simulation results. The experimental results were also supported by reflective simulation based on rigorous coupled-wave analysis (RCWA). This work opens the way for freestanding GaN planar photonic devices operating within the visible-wavelength range. It also provides the possibility of monolithic integration of planar photonic and light sources on III-nitride active platforms.

  2. 2011 Interference -1 INTERFERENCE OF SOUND WAVES

    E-print Network

    Glashausser, Charles

    2011 Interference - 1 INTERFERENCE OF SOUND WAVES The objectives of this experiment are: · To measure the wavelength, frequency, and propagation speed of ultrasonic sound waves. · To observe interference phenomena with ultrasonic sound waves. APPARATUS: Oscilloscope, function generator, ultrasonic

  3. Perfect porcupines: ideal networks for low frequency gravitational wave astronomy

    E-print Network

    Boyle, Latham

    2010-01-01

    Perfect porcupines are specially-configured networks of gravitational wave detectors, in the limit that the individual detectors and the distances between them are short relative to the gravitational wavelengths of interest. They have beautiful properties which make them ideal gravitational wave telescopes. I present the most important cases explicitly. For a network of one-arm detectors (like "AGIS" \\cite{Dimopoulos:2008sv}), the minimal perfect porcupine has 6 detectors, oriented along the 6 diameters of a regular icosahedron. For a network of two-arm detectors (like the equal-arm Michelson interferometers LIGO/VIRGO) the minimal perfect porcupine is a certain 5 detector configuration.

  4. Perfect porcupines: ideal networks for low frequency gravitational wave astronomy

    E-print Network

    Latham Boyle

    2010-04-12

    Perfect porcupines are specially-configured networks of gravitational wave detectors, in the limit that the individual detectors and the distances between them are short relative to the gravitational wavelengths of interest. They have beautiful properties which make them ideal gravitational wave telescopes. I present the most important cases explicitly. For a network of one-arm detectors (like "AGIS" \\cite{Dimopoulos_et_al}), the minimal perfect porcupine has 6 detectors, oriented along the 6 diameters of a regular icosahedron. For a network of two-arm detectors (like the equal-arm Michelson interferometers LIGO/VIRGO) the minimal perfect porcupine is a certain 5 detector configuration.

  5. Wavelength-stable, narrow-spectral-width oscillation of an AlGaInP diode laser coupled to a BaTiO3:Co stimulated photorefractive backscattering phase conjugator

    Microsoft Academic Search

    A. Shiratori; M. Obara

    1997-01-01

    3  ) stimulated photorefractive backscattering (SPBS) phase conjugator. The SPBS process was successfully achieved by the combination\\u000a of the short-wavelength diode laser and the highly doped photorefractive BaTiO3:Co crystal. The spectral width of the diode laser is reduced to 7.2 pm because of the narrow spectral bandwidth of the gratings\\u000a [with wave number of K=2k(2k gratings)] formed in the SPBS phase conjugator,

  6. Surface-emitting, multiple quantum well GaAs/AlGaAs laser with wavelength-resonant periodic gain medium

    SciTech Connect

    Raja, M.Y.A.; Brueck, S.R.J.; Osin-acute-accentski, M.; Schaus, C.F.; McInerney, J.G.; Brennan, T.M.; Hammons, B.E.

    1988-10-31

    A novel surface-emitting semiconductor laser with a vertical resonator, extremely short gain length, and enhanced gain at a specific design wavelength has been demonstrated. The gain medium consists of a series of GaAs quantum wells separated by AlGaAs spacers whose thicknesses are chosen to be one-half the wavelength of a particular transition in the quantum wells. This structure forces the antinodes of the standing-wave optical field to coincide with the gain elements, enhancing the gain and frequency selectivity in the vertical direction and substantially reducing amplified spontaneous emission. We have achieved optically pumped lasing with a threshold of 6 MW/cm/sup 2/ at room temperature in a molecular beam epitaxially grown structure of thickness 4.3 ..mu..m, of which only 320 nm provided gain.

  7. Optical wavelength image slicer

    Microsoft Academic Search

    Matthew C. Doolan; Michael A. Dopita; Liam E. Waldron; John Hart; Ross Zhelem; Gabe Bloxham; Peter Conroy; Peter McGregor; Leigh Pfitzner

    2004-01-01

    The Wide Field Spectrograph (WiFeS) is a high-throughput double-beam image-slicing spectrograph that will operate over the visible wavelength range 320nm to 1000nm. Designed by the Australian National University's Research School of Astronomy and Astrophysics (RSAA) at Mount Stromlo, WiFeS is based on an Integral Field Unit (IFU) and Volume Phased Holographic (VPH) grating technology. Central to the IFU design is

  8. The Long Wavelength Array

    Microsoft Academic Search

    E. Polisensky; N. Kassim; T. J. W. Lazio; K. Weiler; P. Crane; P. Ray; K. Stewart; B. Hicks; A. Cohen; W. Peters; M. Nord; W. C. Erickson

    2004-01-01

    Sub-arcminute resolution and sub-Jy sensitivity below 100 MHz is now being obtained on a routine basis using self-calibration or field-based calibration techniques with the 74 MHz system on the NRAO Very Large Array (VLA). The VLA 74 MHz breakthrough has inspired an emerging suite of new low frequency instruments, including the Long Wavelength Array (LWA), an electronic array planned to

  9. Investigations of medium wavelength magnetic anomalies in the eastern Pacific using Magsat data

    NASA Technical Reports Server (NTRS)

    Harrison, C. G. A. (principal investigator)

    1980-01-01

    The author has identified the following significant results. Three long total magnetic field profiles taken over ocean basins were analyzed. It is found that there is a significant signal in the wavelength range of 1500 to 150 km. This is too short a wavelength to be caused by the core field, which becomes insignificant at about a wavelength of 1500 km; this intermediate wavelength signal is not caused by a typical sea floor spreading process, which should give maximum power in the wavelength region about 50 km. It is shown that the external magnetic field contributes very little to this intermediate wavelength signal. Efforts to explain the cause of this signal have failed.

  10. ABSTRACT : Wave propagation phenomena in soils can be experimentally simulated using centrifuge scale models. An original excitation device (drop-ball arrangement) is proposed to generate short wave trains.

    E-print Network

    Paris-Sud XI, Université de

    ABSTRACT : Wave propagation phenomena in soils can be experimentally simulated using centrifuge propagation experiments in a centrifuged medium. Wave propagation experiments in centrifuged scaled models [2.2 Drop-ball arrangement Classical devices for wave propagation analysis in a centrifuged medium

  11. VOLUME 79, NUMBER 10 P HY S I CA L R E V I EW L E T T ER S 8 SEPTEMBER 1997 Fractal Particle Trajectories in Capillary Waves: Imprint of Wavelength

    E-print Network

    Levinsen, Mogens T.

    1997) We examine particle trajectories in capillary waves formed on a water surface subject to vertical­ length l of the surface waves. We observe non­Brownian particle trajectories with a fractal dimen­ sion D the horizontal position of the particles at 20 ms intervals [5]. Thousands of particle trajectories were

  12. Flat supercontinuum generation pumped by femtosecond pulses in zero-dispersion wavelength of photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Guo, Yuan; Ruan, Shuangchen; Yu, Yongqin; Du, Chenlin; Yan, Peiguang

    2009-10-01

    Two kinds of supercontinuum (SC) sources are successfully generated by propagating 200-fs unamplified and amplified pulses through a 0.85-m long nonlinear photonic crystal fiber (PCF), respectively. The spectra bandwidth of amplified-femtosecond-pumped SC is about 870 nm spanning 480 nm to 1350 nm, which is flat to 1.2dB over 100 nm spreading from 550nm to 650 nm. With the same PCF, SC spectra pumped by unamplified-femtosecond-pulses are narrower and unevener. A detailed simulation is carried out to help us understand the mechanism of supercontinuum evolution. For pump wavelength located at the zero dispersion wavelength of the PCF, spectra are broadened by the interaction between SPM and higher-order dispersion at early stage. With increasing the pump power, the spectra are broadened by fission of higher solitons and parametric four-wave mixing (FWM). When the peak power is up to mega-watt, FWM plays a notable role in flattening and further broadening the supercontinuum spectra in short wavelength side. An effective way to generate a flat SC laser source pumped by femtosecond pulses is also demonstrated.

  13. Waves and Photons

    NSDL National Science Digital Library

    David Stern

    This lesson introduces students to electromagnetic waves, the concept of photons, and the relation between photon wavelength and energy. This is tied to solar observations at various wavelengths using the many types of electromagnetic waves. Students will discover that electromagnetic waves are a linked oscillation of magnetic fields and electric currents, spreading through space. They will also discover that although light spreads like a wave, it only gives up its energy in well-defined amounts, known as photons, and when an individual atom emits light, it usually changes from some excited state of higher energy to one with lower energy. The energy (color) of the emitted photon is very precisely determined by the difference between those levels and the shorter the wavelength, the bigger the photon energy. Thus hot regions of the Sun, whose atoms move faster and therefore have more energy, are likely to emit shorter wavelengths. The work of James Clerk Maxwell and Heinrich Hertz is also discussed.

  14. Laser-Matter Interactions at SubMicron Laser Wavelengths

    Microsoft Academic Search

    Daniel Pasini

    1984-01-01

    In recent years there has been considerable interest in the use of sub-micron wavelength lasers for target irradiation in laser fusion experiments. We present here an experimental investiation of laser-matter interaction in this short wavelength regime. We have irradiated planar targets with 0.532, 0.355 and 0.266 (mu)m laser light with pulse lengths of 2 ns and at intensities ranging from

  15. Water Waves Roger Grimshaw

    E-print Network

    Water Waves Roger Grimshaw May 7, 2003 Abstract A short review of the theory of weakly nonlinear water waves, prepared for the forthcoming Encyclopedia of Nonlinear Science 1 Introduction Water waves nonlinear waves. Throughout the theory is based on the traditional assumptions that water is inviscid

  16. Waves and Water Beetles

    ERIC Educational Resources Information Center

    Tucker, Vance A.

    1971-01-01

    Capillary and gravity water waves are related to the position, wavelength, and velocity of an object in flowing water. Water patterns are presented for ships and the whirling beetle with an explanation of how the design affects the objects velocity and the observed water wavelengths. (DS)

  17. Explaining Polarization Reversals in STEREO Wave Data

    NASA Technical Reports Server (NTRS)

    Breneman, A.; Cattell, C.; Wygant, J.; Kersten, K.; Wilson, L, B., III; Dai, L.; Colpitts, C.; Kellogg, P. J.; Goetz, K.; Paradise, A.

    2012-01-01

    Recently Breneman et al. reported observations of large amplitude lightning and transmitter whistler mode waves from two STEREO passes through the inner radiation belt (L<2). Hodograms of the electric field in the plane transverse to the magnetic field showed that the transmitter waves underwent periodic polarization reversals. Specifically, their polarization would cycle through a pattern of right-hand to linear to left-hand polarization at a rate of roughly 200 Hz. The lightning whistlers were observed to be left-hand polarized at frequencies greater than the lower hybrid frequency and less than the transmitter frequency (21.4 kHz) and right-hand polarized otherwise. Only righthand polarized waves in the inner radiation belt should exist in the frequency range of the whistler mode and these reversals were not explained in the previous paper. We show, with a combination of observations and simulated wave superposition, that these polarization reversals are due to the beating of an incident electromagnetic whistler mode wave at 21.4 kHz and linearly polarized, symmetric lower hybrid sidebands Doppler-shifted from the incident wave by +/-200 Hz. The existence of the lower hybrid waves is consistent with the parametric decay mechanism of Lee and Kuo whereby an incident whistler mode wave decays into symmetric, short wavelength lower hybrid waves and a purely growing (zero-frequency) mode. Like the lower hybrid waves, the purely growing mode is Doppler-shifted by 200 Hz as observed on STEREO. This decay mechanism in the upper ionosphere has been previously reported at equatorial latitudes and is thought to have a direct connection with explosive spread F enhancements. As such it may represent another dissipation mechanism of VLF wave energy in the ionosphere and may help to explain a deficit of observed lightning and transmitter energy in the inner radiation belts as reported by Starks et al.

  18. The Massachusetts Bay internal wave experiment, August 1998: data report

    USGS Publications Warehouse

    Butman, Bradford; Alexander, P. Soupy; Anderson, Steven P.; Lightsom, Frances L.; Scotti, Alberto; Beardsley, Robert C.

    2006-01-01

    This data report presents oceanographic observations made in Massachusetts Bay (fig. 1) in August 1998 as part of the Massachusetts Bay Internal Wave Experiment (MBIWE98). MBIWE98 was carried out to characterize large-amplitude internal waves in Massachusetts Bay and to investigate the possible resuspension and transport of bottom sediments caused by these waves. This data report presents a description of the field program and instrumentation, an overview of the data through summary plots and statistics, and the time-series data in NetCDF format. The objective of this report is to make the data available in digital form and to provide summary plots and statistics to facilitate browsing of the data set. The existence of large-amplitude internal waves in Massachusetts Bay was first described by Halpern (1971). In summer when the water is stratified, packets of waves propagate westward into the bay on the flood (westward flowing) tide at about 0.5 m/s. The internal waves are observed in packets of 5-10 waves, have periods of 5-10 minutes and wavelengths of 200-400 m, and cause downward excursions of the thermocline of as much as 30 m. The waves are generated by interaction of the barotropic tide with Stellwagen Bank (Haury and others (1979). Several papers present analyses and interpretations of the data collected during the MBIWE98. Grosenbaugh and others (2002) report on the results of the horizontal array, Scotti and others (2005) describe a strategy for processing observations made by Acoustic Doppler Current Profilers (ADCPs) in the presence of short-wavelength internal waves, Butman and others (in press) describe the effect of these waves on sediment transport, and Scotti and others (in press) describe the energetics of the internal waves.

  19. Shapes of star-gas waves in spiral galaxies

    NASA Technical Reports Server (NTRS)

    Lubow, Stephen H.

    1988-01-01

    Density-wave profile shapes are influenced by several effects. By solving viscous fluid equations, the nonlinear effects of the gas and its gravitational interaction with the stars can be analyzed. The stars are treated through a linear theory developed by Lin and coworkers. Short wavelength gravitational forces are important in determining the gas density profile shape. With the inclusion of disk finite thickness effects, the gas gravitational field remains important, but is significantly reduced at short wavelengths. Softening of the gas equation of state results in an enhanced response and a smoothing of the gas density profile. A Newtonian stress relation is marginally acceptable for HI gas clouds, but not acceptable for giant molecular clouds.

  20. Physically Based Parameterizations of the Short-Wave Radiative Characteristics of Weakly Absorbing Optically Thick Media: Application to Liquid-Water Clouds

    Microsoft Academic Search

    Alexander A. Kokhanovsky; Teruyuki Nakajima; Eleonora P. Zege

    1998-01-01

    We propose the physically based parameterization of the radiative characteristics of liquid-water clouds as functions of the wavelength, effective radius, and refractive index of particles, liquid-water path, ground albedo, and solar and observation angles. The formulas obtained are based on the approximate analytical solutions of the radiative transfer equation for optically thick, weakly absorbing layers and the geometrical optics approximation