Science.gov

Sample records for address wavelength shifts

  1. Wavelength-shifted Cherenkov radiators

    NASA Technical Reports Server (NTRS)

    Krider, E. P.; Jacobson, V. L.; Pifer, A. E.; Polakos, P. A.; Kurz, R. J.

    1976-01-01

    The scintillation and Cherenkov responses of plastic Cherenkov radiators containing different wavelength-shifting fluors in varying concentrations have been studied in beams of low energy protons and pions. For cosmic ray applications, where large Cherenkov to scintillation ratios are desired, the optimum fluor concentrations are 0.000025 by weight or less.

  2. Apparatus for shifting the wavelength of light

    DOEpatents

    McCulla, William H.; Allen, Jr., John D.

    1983-01-01

    A light beam is reflected back and forth between a rotating body having a retroreflection corner at opposite ends thereof and a fixed mirror to change the wavelength of the light beam by the Doppler effect.

  3. Wavelength Shifting Efficiency of Tetraphenyl Butadiene (TPB) at Extreme Ultraviolet Wavelengths

    NASA Astrophysics Data System (ADS)

    Benson, Christopher; Orebi Gann, Gabriel; Gehman, Victor

    2015-10-01

    Tetraphenyl Butadiene (TPB) is a commonly used wavelength shifter (WLS) in neutrino and dark matter liquid noble gas scintillator detectors. Thin films of wavelength shifters are used to shift ultraviolet scintillation light into the visible spectrum for event reconstruction. The wavelength shifting efficiency of TPB is a function of the incident ultraviolet photon wavelength and is an important parameter for detector design, simulation and reconstruction. The wavelength shifting efficiency and emission spectrum has been previously measured down to 120 nm [Gehman et al., 2011]. To build liquid noble gas scintillator detectors with lighter elements (Ne, He) that use TPB as a WLS medium, the wavelength shifting efficiency must be known closer to 80 nm. This talk will present the current status and preliminary results from a set of measurements that will improve the precision of the efficiency of 120 nm, and extend the data to wavelengths as low as 45 nm.

  4. Wavelength shifting of intra-cavity photons: Adiabatic wavelength tuning in rapidly wavelength-swept lasers.

    PubMed

    Jirauschek, Christian; Huber, Robert

    2015-07-01

    We analyze the physics behind the newest generation of rapidly wavelength tunable sources for optical coherence tomography (OCT), retaining a single longitudinal cavity mode during operation without repeated build up of lasing. In this context, we theoretically investigate the currently existing concepts of rapidly wavelength-swept lasers based on tuning of the cavity length or refractive index, leading to an altered optical path length inside the resonator. Specifically, we consider vertical-cavity surface-emitting lasers (VCSELs) with microelectromechanical system (MEMS) mirrors as well as Fourier domain mode-locked (FDML) and Vernier-tuned distributed Bragg reflector (VT-DBR) lasers. Based on heuristic arguments and exact analytical solutions of Maxwell's equations for a fundamental laser resonator model, we show that adiabatic wavelength tuning is achieved, i.e., hopping between cavity modes associated with a repeated build up of lasing is avoided, and the photon number is conserved. As a consequence, no fundamental limit exists for the wavelength tuning speed, in principle enabling wide-range wavelength sweeps at arbitrary tuning speeds with narrow instantaneous linewidth. PMID:26203373

  5. Wavelength shifting of intra-cavity photons: Adiabatic wavelength tuning in rapidly wavelength-swept lasers

    PubMed Central

    Jirauschek, Christian; Huber, Robert

    2015-01-01

    We analyze the physics behind the newest generation of rapidly wavelength tunable sources for optical coherence tomography (OCT), retaining a single longitudinal cavity mode during operation without repeated build up of lasing. In this context, we theoretically investigate the currently existing concepts of rapidly wavelength-swept lasers based on tuning of the cavity length or refractive index, leading to an altered optical path length inside the resonator. Specifically, we consider vertical-cavity surface-emitting lasers (VCSELs) with microelectromechanical system (MEMS) mirrors as well as Fourier domain mode-locked (FDML) and Vernier-tuned distributed Bragg reflector (VT-DBR) lasers. Based on heuristic arguments and exact analytical solutions of Maxwell’s equations for a fundamental laser resonator model, we show that adiabatic wavelength tuning is achieved, i.e., hopping between cavity modes associated with a repeated build up of lasing is avoided, and the photon number is conserved. As a consequence, no fundamental limit exists for the wavelength tuning speed, in principle enabling wide-range wavelength sweeps at arbitrary tuning speeds with narrow instantaneous linewidth. PMID:26203373

  6. Three dimensional imaging detector employing wavelength-shifting optical fibers

    DOEpatents

    Worstell, W.A.

    1997-02-04

    A novel detector element structure and method for its use is provided. In a preferred embodiment, one or more inorganic scintillating crystals are coupled through wavelength shifting optical fibers (WLSFs) to position sensitive photomultipliers (PS-PMTs). The superior detector configuration in accordance with this invention is designed for an array of applications in high spatial resolution gamma ray sensing with particular application to SPECT, PET and PVI imaging systems. The design provides better position resolution than prior art devices at a lower total cost. By employing wavelength shifting fibers (WLSFs), the sensor configuration of this invention can operate with a significant reduction in the number of photomultipliers and electronics channels, while potentially improving the resolution of the system by allowing three dimensional reconstruction of energy deposition positions. 11 figs.

  7. Three dimensional imaging detector employing wavelength-shifting optical fibers

    DOEpatents

    Worstell, William A.

    1997-01-01

    A novel detector element structure and method for its use is provided. In a preferred embodiment, one or more inorganic scintillating crystals are coupled through wavelength shifting optical fibers (WLSFs) to position sensitive photomultipliers (PS-PMTs). The superior detector configuration in accordance with this invention is designed for an array of applications in high spatial resolution gamma ray sensing with particular application to SPECT, PET and PVI imaging systems. The design provides better position resolution than prior art devices at a lower total cost. By employing wavelength shifting fibers (WLSFs), the sensor configuration of this invention can operate with a significant reduction in the number of photomultipliers and electronics channels, while potentially improving the resolution of the system by allowing three dimensional reconstruction of energy deposition positions.

  8. Bragg wavelength shift for irradiated polymer fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Hamdalla, Taymour A.; Nafee, Sherif S.

    2015-11-01

    The effect of neutron-irradiation from a 5 Ci Am-241/Be-9 neutron source on the characteristics of Polymer Fiber Bragg Grating (PFBG) has been studied in the present work. The PFBG has been irradiated using fast neutrons with different doses range from 24 up to 720 Gy. The transmittance and reflectance of the PFBG have been recorded and interpreted before and after the irradiation. Results in this study showed that the neutron irradiation might cause a structural degradation of the polymer's main chain, which led to a shift in the Central Bragg Wavelength (CBW). In addition, the CBW increased from 4 pm to 14 pm when the neutron dose increased from 24 to 720 Gy. Moreover, no saturation has been observed in the CBW under the effect of the applied doses. Therefore, the PFBG of high Bragg wavelength is a suitable candidate for the use in the dosimetry systems.

  9. Two-wavelength phase shift interferometry to characterize ballistic features

    NASA Astrophysics Data System (ADS)

    Pagano, Glenn W.; Mann, Christopher J.

    2014-05-01

    We apply two-wavelength phase shifting interferometry to generate 3D surface profile maps of spent bullet cartridge cases. From the captured interferograms, an optimized algorithm was used to calculate a phase profile from which a precise digital surface map of the cartridge casing may be produced. This 3D surface profile is used to enhance a firearms examiner's ability to uniquely identify distinct features or toolmarks imprinted on the casing when the weapon is fired. These features play a key role in the matching process of ballistic forensic examination.

  10. PMT signal increase using a wavelength shifting paint

    NASA Astrophysics Data System (ADS)

    Allada, K.; Hurlbut, Ch.; Ou, L.; Schmookler, B.; Shahinyan, A.; Wojtsekhowski, B.

    2015-05-01

    We report a 1.65 times increase of the PMT signal and a simple procedure of application of a new wavelength shifting (WLS) paint for PMTs with non-UV-transparent windows. Samples of four different WLS paints, made from hydrocarbon polymers and organic fluors, were tested on a 5-in. PMT (ET 9390KB) using Cherenkov radiation produced in fused silica disks by 106Ru electrons on a 'table-top' setup. The best performing paint was employed on two different types of 5-in. PMTs (ET 9390KB and XP4572B), installed in atmospheric pressure CO2 gas Cherenkov detectors, and tested using GeV electrons.

  11. Environmental effects on TPB wavelength-shifting coatings

    NASA Astrophysics Data System (ADS)

    Chiu, C. S.; Ignarra, C.; Bugel, L.; Chen, H.; Conrad, J. M.; Jones, B. J. P.; Katori, T.; Moult, I.

    2012-07-01

    The scintillation detection systems of liquid argon time projection chambers (LArTPCs) require wavelength shifters to detect the 128 nm scintillation light produced in liquid argon. Tetraphenyl butadiene (TPB) is a fluorescent material that can shift this light to a wavelength of 425 nm, lending itself well to use in these detectors. We can coat the glass of photomultiplier tubes (PMTs) with TPB or place TPB-coated plates in front of the PMTs. In this paper, we investigate the degradation of a solution-based, embedded TPB coating in a laboratory or factory environment to assess the viability of long-term TPB film storage prior to its initial installation in an LArTPC. We present evidence for severe degradation of this type of coating due to common fluorescent lights and ambient sunlight in laboratories, with potential losses at the 40% level in the first day and eventual losses at the 80% level after a month of exposure. We determine the degradation is due to wavelengths in the UV spectrum, and we demonstrate mitigating methods for retrofitting lab and factory environments.

  12. Improved Detection of Cherenkov Radiation using Wavelength-Shifting Paints

    NASA Astrophysics Data System (ADS)

    Schmookler, Barak; Ou, Longwu

    2014-03-01

    Photomultiplier Tubes (PMTs) are often used to detect Cherenkov radiation in accelerator-based physics experiments. Since the Cherenkov spectrum is inversely proportional to the square of the photon's wavelength, PMTs with relatively good quantum efficiencies in the ultraviolet region can produce on average a higher number of photoelectrons. The application of certain paints, which absorb light at ultraviolet wavelengths and emit in the visible spectrum, to the surface of some PMTs allows for better sampling of the Cherenkov spectrum. The effects of various wavelength-shifting (WLS) paints designed by Eljen Technologies were tested on ET Enterprises, Model: 9390KB PMTs. Using a 106Ru β-source, Cherenkov light was produced in disks of fused silica. The charge spectrums of the PMTs were measured before and after application of the paint. The average number of photoelectrons produced from the Cherenkov radiation could be determined by knowing the value of the single-photoelectron peak and the mean of the charge spectrum. Four paints were tested, and the gain in the number photoelectrons produced varied from 10-35% for the different paints. Work Conducted at Thomas Jefferson National Accelerator Facility.

  13. Individual Optical Addressing of Atomic Clock Qubits With Stark Shifts

    NASA Astrophysics Data System (ADS)

    Lee, Aaron; Smith, Jacob; Richerme, Phillip; Neyenhuis, Brian; Hess, Paul; Zhang, Jiehang; Monroe, Chris

    2016-05-01

    In recent years, trapped ions have proven to be a versatile quantum information platform, enabled by their long lifetimes and high gate fidelities. Some of the most promising trapped ion systems take advantage of groundstate hyperfine ``clock'' qubits, which are insensitive to background fields to first order. This same insensitivity also makes σz manipulations of the qubit impractical, eliminating whole classes of operations. We prove there exists a fourth-order light shift, or four-photon Stark shift, of the clock states derived from two coherent laser beams whose beatnote is close to the qubit splitting. Using a mode-locked source generates a large light shift with only modest laser powers, making it a practical σz operation on a clock qubit. We experimentally verify and measure the four-photon Stark shift and demonstrate its use to coherently individually address qubits in a chain of 10 Yb 171 ions with low crosstalk. We use this individual addressing to prepare arbitrary product states with high fidelity and also to apply independent σz terms transverse to an Ising Hamiltonian. This work is supported by the ARO Atomic Physics Program, the AFOSR MURI on Quantum Measurement and Verification, and the NSF Physics Frontier Center at JQI.

  14. Phase-shifting point-diffraction interferometry at EUV wavelengths

    SciTech Connect

    Goldberg, K.A.; Tejnil, E.; Sang Lee

    1997-04-01

    A novel phase-shifting point-diffraction interferometer (PS/PDI) operating at the Advanced Light Source (ALS) is being used to perform wavefront-measuring metrology at 13.4-nm wavelength to characterize aberrations in a multilayer-coated 10x Schwarzschild objective designed for extreme ultraviolet (EUV) projection lithography experiments. To achieve 0.1-micron critical dimension pattern transfer with EUV projection lithography at 13.4-nm wavelength, nearly diffraction-limited all-reflective multilayer-coated optical systems with 0.1 numerical aperture are required. The EUV wavefront, determined by the mirror surfaces and the reflective multilayer coatings, is measurable only at the operational wavelength of the system. The authors goal is to measure the EUV wavefront to an accuracy of 0.01 waves rms (0.13 nm). The PS/PDI is a type of point-diffraction interferometer, modified for significantly improved throughput and phase-shifting capability. The interferometer design utilizes a grating beamsplitter and pinhole spatial filters in the object and image planes of the optical system under test. The 10x-reduction Schwarzschild objective, with image-side numerical aperture of 0.08, is illuminated by a sub-micron pinhole in the object plane. A coarse, 20-micron pitch grating placed between the illumination pinhole and the Schwarzschild system serves a dual role as a small-angle beam-splitter and a phase-shifting element. The first-order diffracted beam from the grating is spatially filtered in the image plane of the Schwarzschild with a sub-100-nm pinhole and becomes the `D reference` wave in the interferometer. The zero-order beam is the `test` wave, and it passes unobstructed through a 4.5-{mu}m window in the image plane. The test and reference beams are separated by several microns in the image plane to minimize beam overlap. The interference fringes are recorded with a CCD detector placed about 12 cm from the Schwarzschild image plane.

  15. Widely Wavelength-Tunable Blue-Shifted Dispersive Waves for Broadband Visible Wavelength Generation in a Photonic Crystal Fiber Cladding

    NASA Astrophysics Data System (ADS)

    Yuan, Jin-Hui; Sang, Xin-Zhu; Yu, Chong-Xiu; Shen, Xiang-Wei; Wang, Kui-Ru; Yan, Bin-Bin; Han, Ying; Zhou, Gui-Yao; Hou, Lan-Tian

    2012-10-01

    Blue-shifted dispersive waves (DWs) are efficiently generated from the red-shifted solitons by coupling the 120 fs pulses into the fundamental mode of the multi-knots of a photonic crystal fiber cladding. When the femtosecond pulses at the wavelength of 825 nm and the average power of 300 mW are coupled into knots 1-3, the conversion efficiency ηDW of 32% and bandwidth BDW of 50 nm are obtained. The ultrashort pulses generated by the DWs can be tunable over the whole visible wavelength by adjusting the wavelengths of the pump pulses coupled into different knots. It can be believed that this widely wavelength-tunable ultrashort visible pulse source has important applications in ultrafast photonics and resonant Raman scattering.

  16. Frequency domain phase retrieval of simultaneous multi-wavelength phase-shifting interferometry

    NASA Astrophysics Data System (ADS)

    Yin, Zhenxing; Zhong, Liyun; Xu, Xiaofei; Zhang, Wangping; Tian, Jindong; Lu, Xiaoxu

    2016-05-01

    In simultaneous multi-wavelength phase-shifting interferometry, we propose a novel frequency domain phase retrieval (FDPR) algorithm. First, using only a one-time phase-shifting operation, a sequence of simultaneous multi-wavelength phase-shifting interferograms (SPSMWIs) are captured by a monochrome charge-coupled device. Second, by performing a Fourier transform for each pixel of SPSMWIs, the wrapped phases of each wavelength can be retrieved from the complex amplitude located in the spectral peak of each wavelength. Finally, the phase of the synthetic wavelength can be obtained by the subtraction between the wrapped phases of a single wavelength. In this study, the principle and the application condition of the proposed approach are discussed. Both the simulation and the experimental result demonstrate the simple and convenient performance of the proposed FDPR approach.

  17. A paradigm shift in the excitation wavelength of upconversion nanoparticles

    NASA Astrophysics Data System (ADS)

    Jayakumar, Muthu Kumara Gnanasammandhan; Idris, Niagara Muhammad; Huang, Kai; Zhang, Yong

    2014-07-01

    The past two decades witnessed the emergence of upconversion nanoparticles as promising luminophores finding multifarious uses from biological studies to solar cells. Progress in their practical use, however, has been hampered by requirements to be excited within a narrow absorption band at around 980 nm. Since the main constituent of biological tissue - water - absorbs strongly in this region, significant reduction in the penetration depth is anticipated as the 980 nm light gets attenuated travelling through tissues, besides also risking tissue damage from the overheating effect. Just recently, remarkable efforts to engineer the excitation of upconversion nanoparticles to a more suitable wavelength for biological applications were reported. This article gives an insightful view on the different ingenious designs that have been reported and their progression towards the development of upconversion nanoparticles with biologically friendlier excitation wavelength.

  18. One factor of resonant wavelength shift from onewavelength to two-wavelength resonance in loop-tube-type thermoacoustic cooling system

    NASA Astrophysics Data System (ADS)

    Sakamoto, Shin-ichi; Shibata, Kenji; Kitadani, Yuji; Inui, Yoshitaka; Watanabe, Yoshiaki

    2012-05-01

    Results of this study show that the resonant wavelength of the sound generated in a loop-tube-type thermoacoustic cooling system shifts from one-wavelength to two-wavelength resonance during system operation. The effect of the viscous boundary layer upon the resonant wavelength shift is discussed. The viscous boundary layer thickness is always less than the stack channel radius because the loop tube increases the resonance frequency and shifts the resonant wavelength from one-wavelength to two-wavelength resonance, which reduces the influence of viscosity and allows the loop tube to maintain the thermoacoustic self-sustained sound.

  19. Electrically tunable zero dispersion wavelengths in photonic crystal fibers filled with a dual frequency addressable liquid crystal

    SciTech Connect

    Wahle, Markus Kitzerow, Heinz-Siegfried

    2015-11-16

    We present a liquid crystal (LC) infiltrated photonic crystal fiber, which enables the electrical tuning of the position of zero dispersion wavelengths (ZDWs). A dual frequency addressable liquid crystal is aligned perpendicular on the inclusion walls of a photonic crystal fiber, which results in an escaped radial director field. The orientation of the LC is controlled by applying an external electric field. Due to the high index of the liquid crystal the fiber guides light by the photonic band gap effect. Multiple ZDWs exist in the visible and near infrared. The positions of the ZDWs can be either blue or red shifted depending on the frequency of the applied voltage.

  20. Electrically tunable zero dispersion wavelengths in photonic crystal fibers filled with a dual frequency addressable liquid crystal

    NASA Astrophysics Data System (ADS)

    Wahle, Markus; Kitzerow, Heinz-Siegfried

    2015-11-01

    We present a liquid crystal (LC) infiltrated photonic crystal fiber, which enables the electrical tuning of the position of zero dispersion wavelengths (ZDWs). A dual frequency addressable liquid crystal is aligned perpendicular on the inclusion walls of a photonic crystal fiber, which results in an escaped radial director field. The orientation of the LC is controlled by applying an external electric field. Due to the high index of the liquid crystal the fiber guides light by the photonic band gap effect. Multiple ZDWs exist in the visible and near infrared. The positions of the ZDWs can be either blue or red shifted depending on the frequency of the applied voltage.

  1. Multi-channel multi-carrier generation using multi-wavelength frequency shifting recirculating loop.

    PubMed

    Li, Xinying; Yu, Jianjun; Dong, Ze; Zhang, Junwen; Shao, Yufeng; Chi, Nan

    2012-09-24

    We propose and experimentally demonstrate a novel scheme to generate optical frequency-locked multi-channel multi-carriers (MCMC), using a recirculating frequency shifter (RFS) loop based on multi-wavelength frequency shifting single side band (MWFS-SSB) modulation. In this scheme, optical subcarriers with multiple wavelengths can be generated each round. Furthermore, the generated MCMC are frequency- and phase-locked within each channel, and therefore can be effectively used for WDM superchannel. Dual-wavelength frequency shifting SSB modulation is carried out with dual-wavelength optical seed source in our experimental demonstration. Using this scheme, we successfully generate dual-channel multi-carriers, and one channel has 28 subcarriers while the other has 29 ones with 25-GHz subcarrier spacing. We also experimentally demonstrate that this kind of source can be used to carry 50-Gb/s optical polarization-division-multiplexing quadrature phase shift keying (PDM-QPSK) signal. PMID:23037333

  2. Oscillation wavelength shifts of visible and infrared laser diodes in a magnetic field

    NASA Astrophysics Data System (ADS)

    Sato, Takashi; Matsumoto, Kouichi; Toujou, Shin-ya; Nakagawa, Takayuki; Nakano, Hiroyuki; Ohkawa, Masashi; Maruyama, Takeo; Shimba, Minoru

    1998-10-01

    The shift, which occurs in the oscillation wavelength of a semiconductor laser in a magnetic field, has been the subject of great interest, since the early 60's. During the course of the investigation, the observed shift was toward the short wavelength side, i.e., a blue shift, which was well accounted for, in terms of the Landau level. At present, we are studying how wavelength shift is affected, by applying, at room temperature, a relatively weak magnetic field, using recently developed visible and infrared diode lasers. By doing so, we have observed a red shift and a decrease in laser output-power, under a certain magnetic field conditions in its strength and direction. Since these two changes in wavelength and output power correspond to those observed at higher temperatures, we assumed that the orientation of the magnetic field affects current density in laser diodes. And then it alters temperatures around the active layer, which in turn influence oscillation wavelength and laser output-power. Also of note, was the fact that the red shift and the decrease in laser output-power occurred simultaneously, revealing an almost linear dependency on one another. This might possibly explain the heat, which developed as the result of applying the magnetic field. However, we recently observed an instance, in which visible MQW laser diodes did not exhibit this linear dependence. Because this phenomenon cannot be traced simply to the effects of heat, we are now examining it in terms of current-density alteration.

  3. SERTS-95 Measurements of Wavelength Shifts in Coronal Emission Lines Across a Solar Active Region

    NASA Technical Reports Server (NTRS)

    Brosius, Jeffery W.; Thomas, Roger; Davila, Joseph

    1999-01-01

    We used slit spectra from the 1995 flight of Goddard Space Flight Center's Solar EUV Rocket Telescope and Spectrograph (SERTS-95) to measure wavelength shifts of coronal emission lines in the core of NOAA active region 7870 relative to its immediate surroundings (its "edge"). This method circumvents the unavailability of reliable laboratory rest wavelengths for the observed lines by using wavelengths from the edge spectrum as references. We derived the, SERTS-95 wavelength calibration from measurements of a post-flight laboratory spectrum containing 28 He II and Ne II EUV standard wavelengths known to high accuracy. Wavelength measurements for lines of He I, Ne III, and additional lines of Ne II in the laboratory calibration spectrum provide more accurate values than were previously available, enabling these lines also to serve as future calibration standards. Six solar lines were chosen for this study, namely, He II at 303.78 A, Fe XII at 193.51 A, Fe XIII at 202.05 A, Fe XIV at 211.33 A, Fe XV at 284.15 A, and Fe XVI at 335.41 A. Because these lines are free from known blends in the SERTS-95 spectra and are either intrinsically strong or near the SERTS-95 peak sensitivity, they are our most reliable lines for measuring relative wavelength shifts in the spatially resolved active region core spectra. The iron ions are the hottest ions ever used for this type of analysis. All six lines reveal statistically significant spatial variations in their measured relative wavelength shifts in the active region core, including mixtures of blueshifts and redshifts (each with maximum values corresponding to relative Doppler velocities approximately 15 km/s), indicating a dynamic, turbulent corona. For each of these lines we calculated weighted-average relative Doppler velocities from the wavelength shifts in the spatially resolved core spectra by weighting the shifts in the individual spatial pixels with their respective measurement uncertainties.

  4. Shifted excitation Raman difference spectroscopy using a dual-wavelength DBR diode laser at 785 nm

    NASA Astrophysics Data System (ADS)

    Maiwald, M.; Eppich, B.; Fricke, J.; Ginolas, A.; Bugge, F.; Klehr, A.; Sumpf, B.; Erbert, G.; Tränkle, G.

    2015-03-01

    The application of shifted excitation Raman difference spectroscopy (SERDS) using a dual wavelength distributed Bragg reflector (DBR) diode laser at 785 nm will be presented. Both excitation wavelengths necessary for SERDS provide an optical power of more than 160 mW in continuous wave operation. Raman experiments are carried out and demonstrate the suitability of the excitation light source for SERDS. Moreover, a dual-wavelength master-oscillator power amplifier diode laser system is presented. The diode laser system reaches optical powers larger 750 mW while the spectral properties of the dual-wavelength laser remain unchanged.

  5. Wavelength shifts of cladding-mode resonance in corrugated long-period fiber gratings under torsion.

    PubMed

    Ivanov, Oleg V; Wang, Lon A

    2003-05-01

    A finite deformation theory of elasticity and a theory of nonlinear photoelasticity are applied to describe the wavelength shifts of cladding-mode resonance in corrugated long-period fiber gratings under torsion. The deformation of fiber is found by use of the Murnaghan model of a solid elastic body. The quadratic photoelastic effect that is proportional to the second-order displacement gradient is investigated and compared with the classical photoelastic effect. The electromagnetic field in the twisted corrugated structure is presented as a superposition of circularly polarized modes of the etched fiber section. The wavelength shift is found to be proportional to the square of the twist angle. As predicted by our theory, a wavelength shift of the same nature has been found in a conventionally photoinduced long-period fiber grating. PMID:12737456

  6. Measurement of a wavelength of light for which the energy shift for an atom vanishes.

    PubMed

    Holmgren, William F; Trubko, Raisa; Hromada, Ivan; Cronin, Alexander D

    2012-12-14

    Light at a magic-zero wavelength causes a zero energy shift for an atom. We measured the longest magic-zero wavelength for ground state potassium atoms to be λ(zero)=768.9712(15) nm, and we show how this measurement provides an improved experimental benchmark for atomic structure calculations. This λ(zero) measurement determines the ratio of the potassium atom D1 and D2 line strengths with record precision. It also demonstrates a new application for atom interferometry, and we discuss how decoherence will fundamentally limit future measurements of magic-zero wavelengths. PMID:23368315

  7. Wavelength conversion through soliton self-frequency shift in tellurite microstructured fiber with picosecond pump pulse

    NASA Astrophysics Data System (ADS)

    Bi, Wanjun; Li, Xia; Xing, Zhaojun; Zhou, Qinling; Fang, Yongzheng; Gao, Weiqing; Xiong, Liangming; Hu, Lili; Liao, Meisong

    2016-01-01

    Wavelength conversion to the wavelength range that is not covered by commercially available lasers could be accomplished through the soliton self-frequency shift (SSFS) effect. In this study, the phenomenon of SSFS pumped by a picosecond-order pulse in a tellurite microstructured fiber is investigated both theoretically and experimentally. The balance between the dispersion and the nonlinearity achieved by a 1958 nm pump laser induces a distinct SSFS effect. Attributed to the large spectral distance between the pump pulse and the fiber zero-dispersion wavelength, the SSFS is not cancelled due to energy shedding from the soliton to the dispersive wave. Details about the physical mechanisms behind this phenomenon and the variations of the wavelength shift, the conversion efficiency are revealed based on numerical simulations. Owing to the large soliton number N, the pulse width of the first split fundamental soliton is approximately 40 fs, producing a pulse compression factor of ˜38, much higher than that pumped by a femtosecond pulse. Experiments were also conducted to confirm the validity of the simulation results. By varying the pump power, a continuous soliton shift from 1990 nm to 2264 nm was generated. The generation of SSFS in tellurite microstructured fibers with picosecond pump pulse can provide a new approach for wavelength conversion in the mid-infrared range and could be useful in medical and some other areas.

  8. Improved selectivity from a wavelength addressable device for wireless stimulation of neural tissue

    PubMed Central

    Seymour, Elif Ç.; Freedman, David S.; Gökkavas, Mutlu; Özbay, Ekmel; Sahin, Mesut; Ünlü, M. Selim

    2014-01-01

    Electrical neural stimulation with micro electrodes is a promising technique for restoring lost functions in the central nervous system as a result of injury or disease. One of the problems related to current neural stimulators is the tissue response due to the connecting wires and the presence of a rigid electrode inside soft neural tissue. We have developed a novel, optically activated, microscale photovoltaic neurostimulator based on a custom layered compound semiconductor heterostructure that is both wireless and has a comparatively small volume (<0.01 mm3). Optical activation provides a wireless means of energy transfer to the neurostimulator, eliminating wires and the associated complications. This neurostimulator was shown to evoke action potentials and a functional motor response in the rat spinal cord. In this work, we extend our design to include wavelength selectivity and thus allowing independent activation of devices. As a proof of concept, we fabricated two different microscale devices with different spectral responsivities in the near-infrared region. We assessed the improved addressability of individual devices via wavelength selectivity as compared to spatial selectivity alone through on-bench optical measurements of the devices in combination with an in vivo light intensity profile in the rat cortex obtained in a previous study. We show that wavelength selectivity improves the individual addressability of the floating stimulators, thus increasing the number of devices that can be implanted in close proximity to each other. PMID:24600390

  9. Doppler wavelength shifts of transition zone lines measured in Skylab solar spectra

    NASA Technical Reports Server (NTRS)

    Doschek, G. A.; Bohlin, J. D.; Feldman, U.

    1976-01-01

    Wavelengths of lines of the transition-zone ions Si IV, C IV, O IV, N V, and O V are observed to be redshifted relative to the wavelengths of chromospheric lines in XUV spectra obtained from the normal-incidence spectrograph on Skylab. The spectra cover the wavelength range from 1200 to 1565 A and were obtained with the slit positioned over chromospheric network and cell regions, on coronal holes, and above the limb. The network-area and coronal-hole spectra were obtained near the disk center. Only some of the spectra show redshifted transition-zone lines. The observed shifts are between 0.03 and 0.08 A, implying velocities of 15 km/s or less. The amount of wavelength shift does not always appear to be the same for lines of different ions. The shifts imply that descending plasma in the solar atmosphere produces more emission than ascending plasma at temperatures between approximately 70,000 and 200,000 K.

  10. 9125B ET Photomultiplier Tubes with a Wavelength Shifting Paint for a Gas Cherenkov Counter

    NASA Astrophysics Data System (ADS)

    Barcus, Scott; Averett, Todd; Wojtsekhowski, Bogdan

    2015-04-01

    This presentation will describe a method to increase the amount of Cherenkov light detected by photomultiplier tubes using a wavelength shifting paint and Electron Tubes' 9125B PMTs. A Cherenkov spectrum was generated via cosmic rays striking a polished rectangular fused silica crystal and observed by PMTs. By applying a wavelength shifting paint to the faces of the PMTs photons outside of the normal sensitivity range for the PMTs can be shifted into the sensitive range. A number of PMTs were tested with and without the paint to observe the change in the detected number of Cherenkov photons. The wavelength shifting paint was found to increase the number of photoelectrons seen by as much as 50 %. However, the response of individual tubes was found to be highly variable ranging from increases in light of 5 - 50 % with an average of 22.4 %. The variable nature of the PMTs' responses indicates that tubes may still need to be individually tested after the paint is applied to select the most desirable tubes. This method can be applied to the PMTs in a gas Cherenkov detector to increase the number of photons collected.

  11. Low-coherence wavelength shifting interferometry for high-speed quantitative phase imaging.

    PubMed

    Chen, Shichao; Li, Chengshuai; Zhu, Yizheng

    2016-08-01

    We propose low-coherence wavelength shifting interferometry and demonstrate its application to quantitative phase imaging of dynamic specimens. By shifting the source wavelength, multiple interferograms of the sample can be acquired at different spectral bands. A sample phase is thus encoded in the phase step between consecutive acquisitions. For the particular case of four-band imaging, we show that the phase can be extracted with a modified Carré algorithm. We describe signal demodulation in detail and discuss its implication on system implementation. A swept laser-based Mach-Zehnder interferometer is used to demonstrate the technique for real-time imaging of live sperm cells at 62.5 Hz. The dynamic dry mass of the sperm head is measured with a full-scale error of ±2%, validating the technique's capability for high-sensitivity, high-speed quantitative phase imaging. PMID:27472586

  12. Strain gradient chirp of uniform fiber Bragg grating without shift of central Bragg wavelength

    NASA Astrophysics Data System (ADS)

    Dong, Xinyong; Guan, Bai-Ou; Yuan, Shuzhong; Dong, Xiaoyi; Tam, Hwa-Yaw

    2002-02-01

    A novel technique to introduce large linear chirp to an uniform fiber Bragg grating (FBG) is realized by gluing the grating in a slanted direction onto the side face of a simple supported beam. Strain gradient is formed along the length of the grating when the beam is bent, and produces a linear variation in the grating pitch. This permits a tunable chirp without central wavelength shift. The maximum bandwidth of the chirped FBG produced was 11.32 nm.

  13. Single-shot dual-wavelength phase unwrapping in parallel phase-shifting digital holography.

    PubMed

    Lee, Yonghee; Ito, Yasunori; Tahara, Tatsuki; Inoue, Junichi; Xia, Peng; Awatsuji, Yasuhiro; Nishio, Kenzo; Ura, Shogo; Matoba, Osamu

    2014-04-15

    We propose a single-shot phase-unwrapping method using two wavelengths in parallel phase-shifting digital holography (PPSDH). The proposed method enables one to solve the phase ambiguity problem in PPSDH. We conducted an experiment of the proposed method using two lasers whose wavelengths are 473 and 532 nm. An object having about 1.9 μm step, which is 7.1 times larger than the half wavelength of one of the lasers (266 nm), was fabricated by using vapor deposition of aluminum. Single-shot measurement of the height of the object was successfully demonstrated, and the validity of the proposed method was verified. PMID:24978996

  14. Influence of wavelength-shifting films on multianode PMTs with UV-extended windows

    NASA Astrophysics Data System (ADS)

    Adamczewski-Musch, J.; Becker, K.-H.; Belogurov, S.; Boldyreva, N.; Chernogorov, A.; Deveaux, C.; Dobyrn, V.; Dürr, M.; Eom, J.; Eschke, J.; Höhne, C.; Kampert, K.-H.; Kleipa, V.; Kochenda, L.; Kolb, B.; Kopfer, J.; Kravtsov, P.; Lebedev, S.; Lebedeva, E.; Leonova, E.; Linev, S.; Mahmoud, T.; Michel, J.; Miftakhov, N.; Nam, Y.; Niebur, W.; Oh, K.; Ovcharenko, E.; Pauly, C.; Pouryamout, J.; Querchfeld, S.; Rautenberg, J.; Reinecke, S.; Riabov, Y.; Roshchin, E.; Samsonov, V.; Song, J.; Tarasenkova, O.; Torres de Heidenreich, T.; Traxler, M.; Ugur, C.; Vznuzdaev, E.; Vznuzdaev, M.; Yi, J.; Yoo, I.-K.

    2015-05-01

    Wavelength-shifting (WLS) films were applied on UV-extended front windows of multianode photomultiplier tubes (MAPMTs) in order to increase the sensitivity of the MAPMTs at shorter wavelengths. The WLS material contained p-Terphenyl as photoactive component, which absorbs shorter wavelength photons (< 300 nm) and re-emits fluorescence photons around 350 nm, i.e., at the maximum of the PMTs' sensitivity. The films were applied by means of dip-coating and the film performance was studied with respect to quantum efficiency, film homogeneity, and crosstalk on the MAPMTs. Using WLS-film-covered MAPMTs in a gaseous Ring Imaging Cherenkov detector, the number of detected photoelectrons per ring increased by up to 21% in an in-beam test.

  15. A Wavelength-shifting Optical Module (WOM) for in-ice neutrino detectors

    NASA Astrophysics Data System (ADS)

    Hebecker, Dustin; Archinger, Markus Gerhard; Böser, Sebastian; Brostean-Kaiser, Jannes; Del Pino Rosendo, Esther; Di Lorenzo, Vincenzo; DuVernois, Michael; Falke, Peter Johannes; Fösig, Carl-Christian; Karg, Timo; Köpke, Lutz; Kowalski, Marek; Looft, Andreas; Sand, Krystina; Tosi, Delia

    2016-04-01

    We report on the development status of a single-photon sensor that employs wavelength-shifting and light-guiding techniques to maximize the collection area while minimizing the dark noise rate. The sensor is tailored towards application in ice-Cherenkov neutrino detectors embedded in inert and cold, low-radioactivity and UV transparent ice as a detection medium, such as IceCube-Gen2 or MICA. The goal is to decrease the energy threshold as well as to increase the energy resolution and the vetoing capability of the neutrino telescope, when compared to a setup with optical sensors similar to those used in IceCube. The proposed sensor captures photons with wavelengths between 250 nm and 400 nm. These photons are re-emitted with wavelengths above 400 nm by a wavelength shifting coating applied to a 90 mm diameter polymer tube. The tube guides the light towards a small-diameter PMT via total internal reflection. By scaling the results from smaller laboratory prototypes, the total efficiency of the proposed detector for a Cherenkov spectrum is estimated to exceed that of a standard IceCube optical module. The status of the prototype development and the performance of its main components will be discussed.

  16. ``Ultimate'' information content in solar and stellar spectra. Photospheric line asymmetries and wavelength shifts

    NASA Astrophysics Data System (ADS)

    Dravins, Dainis

    2008-12-01

    Context: Spectral-line asymmetries (displayed as bisectors) and wavelength shifts are signatures of the hydrodynamics in solar and stellar atmospheres. Theory may precisely predict idealized lines, but accuracies in real observed spectra are limited by blends, few suitable lines, imprecise laboratory wavelengths, and instrumental imperfections. Aims: We extract bisectors and shifts until the “ultimate” accuracy limits in highest-quality solar and stellar spectra, so as to understand the various limits set by (i) stellar physics (number of relevant spectral lines, effects of blends, rotational line broadening); by (ii) observational techniques (spectral resolution, photometric noise); and by (iii) limitations in laboratory data. Methods: Several spectral atlases of the Sun and bright solar-type stars were examined for those thousands of “unblended” lines with the most accurate laboratory wavelengths, yielding bisectors and shifts as averages over groups of similar lines. Representative data were obtained as averages over groups of similar lines, thus minimizing the effects of photometric noise and of random blends. Results: For the solar-disk center and integrated sunlight, the bisector shapes and shifts were extracted for previously little-studied species (Fe II, Ti I, Ti II, Cr II, Ca I, C I), using recently determined and very accurate laboratory wavelengths. In Procyon and other F-type stars, a sharp blueward bend in the bisector near the spectral continuum is confirmed, revealing line saturation and damping wings in upward-moving photospheric granules. Accuracy limits are discussed: “astrophysical” noise due to few measurable lines, finite instrumental resolution, superposed telluric absorption, inaccurate laboratory wavelengths, and calibration noise in spectrometers, together limiting absolute lineshift studies to ≈50-100 m s-1. Conclusions: Spectroscopy with resolutions λ/Δλ ≈ 300 000 and accurate wavelength calibration will enable

  17. A dual-energy transmission detector for vehicle scanning using wavelength-shifting fibers

    NASA Astrophysics Data System (ADS)

    Van Liew, Seth; Zhang, Ming

    2014-09-01

    A new dual energy detector for vehicle scanning is presented. The system is composed of a three-sided Compton backscatter imaging system utilizing flying-spot x-rays concurrent with a transmission detector using the same x-ray beam. This detector is under the vehicle and is thin enough to be driven over with a modest bump which does not impede vehicle trac. It uses sheet scintillator with wavelength-shifting fibers as light pipes. Results are presented on steel penetration, calibration procedures and issues, and dual energy performance. The system's dose is low enough for scanning people, including passenger vehicles.

  18. The fabrication of wavelength shifting lightguides from clear acrylic sheet by disperse dyeing

    NASA Astrophysics Data System (ADS)

    McMillan, J. E.

    2015-06-01

    Wavelength shifting lightguides have found extensive use as a means of collecting scintillation or cherenkov light from large areas onto a smaller area photodetector and for matching the emitted spectrum to the spectral response of the photodetector. Conventionally, such lightguides are fabricated by casting acrylic polymer with the fluorescent dye incorporated in the bulk. A technique has been developed in which plain cast acrylic sheet is disperse dyed in an aqueous bath. The resulting lightguide has the fluorescent dye held in a thin layer at the surface of the material. A number of different fluorescent dyes are demonstrated

  19. Dual-wavelength in-line phase-shifting interferometry based on two dc-term-suppressed intensities with a special phase shift for quantitative phase extraction.

    PubMed

    Xu, Xiaoqing; Wang, Yawei; Xu, Yuanyuan; Jin, Weifeng

    2016-06-01

    To efficiently promote the phase retrieval in quantitative phase imaging, a new approach of quantitative phase extraction is proposed based on two intensities with dual wavelength after filtering the corresponding dc terms for each wavelength, in which a special phase shift is used. In this approach, only the combination of the phase-shifting technique and subtraction procedures is needed, and no additional algorithms are required. The thickness of the phase object can be achieved from the phase image, which is related to the synthetic beat wavelength. The feasibility of this method is verified by the simulated experiments of the optically transparent objects. PMID:27244381

  20. Discrimination, developmental science, and the law: addressing dramatic shifts in civil rights jurisprudence.

    PubMed

    Levesque, Roger J R

    2014-01-01

    The civil rights movement fostered dramatic shifts in legal responses to discrimination based on race, gender, and a host of other group characteristics. The legal system now evinces yet another dramatic shift, as it moves from considering difference to focusing on neutrality, from efforts that seek to counter subjugation to those that adopt a "color-blind" approach. The shifting approach already has reached laws regulating responses to the group that spurred massive civil rights reform: minority youth. The shift requires a different body of empirical evidence to address it and a new look at equality jurisprudence. This article notes the need to turn to the current understanding of prejudice and discrimination for guidance, and uses, as illustration, developmental science to shed light on the development, manifestation, and alleviation of invidious discrimination. Using that understanding, the analysis details how the legal system can benefit from that research and better address discrimination in light of dramatic changes in law. The article articulates the need to address discrimination by recognizing and enlisting the law's inculcative powers through multiple sites of inculcation, ranging from families, schools, health and justice systems to religious and community groups. The discussion concludes with brief suggestions for reform benefiting from understandings of prejudice and its expression. PMID:24826823

  1. Single-frame digital phase-shifting 3D shape measurement using pixel-wise moiré-wavelength refinement

    NASA Astrophysics Data System (ADS)

    Mohammadi, Fatemeh; Kofman, Jonathan

    2016-03-01

    A novel pixel-wise moiré-wavelength refinement technique was developed for system calibration in single-frame digital phase-shifting 3D shape measurement. The method requires projection of only a single binary grid and capture of a single image frame. Phase-shifted images are generated by digitally phase-shifting a synthetic grid superimposed on the captured frame. The grid patterns are removed from the generated images by wavelet-Fourier transform to extract moiré patterns, from which phase and surface height are computed. A wavelength-height function, computed during system calibration, accounts for moiré-wavelength variation over calibration depth in phase-to-height mapping. Novel pixel-wise wavelength and height (depth) refinement, using this function, improved measurement accuracy compared to measurement using a single global wavelength across all pixels. The method was demonstrated in measurement of a flat plate, hemispherical object, and manikin head.

  2. Wavelength Shifts of the 7.7 Micron Emission Band in Reflection Nebulae

    NASA Technical Reports Server (NTRS)

    Bregman, Jesse; Temi, Pasquale

    2003-01-01

    Using spatial-spectral data cubes of reflection nebulae obtained by ISOCAM, we have observed a shift in the central wavelength of the 7.7 micron band within several reflection nebulae. The band shifts progressively from approx. 7.8 microns near the edge of the nebulae to approx. 7.6 microns towards the center of the nebulae. The ratio of the 11.3/7.7 micron bands also changes with distance from the central star, first rising from the center towards the edge of the nebula, then falling at the largest distances from the star, consistent with the 11.3/7.7 micron band ratio being controlled by the PAH ionization state. The behavior of the 7.7 micron band center can be explained either by assuming that anions are the origin of the 7.85 micron band and cations the 7.65 micron band, or that the band center wavelength depends on the chemical nature of the PAHs.

  3. Study of wavelength-shifting chemicals for use in large-scale water Cherenkov detectors

    SciTech Connect

    Sweany, M; Bernstein, A; Dazeley, S; Dunmore, J; Felde, J; Svoboda, R; Tripathi, S M

    2011-09-21

    Cherenkov detectors employ various methods to maximize light collection at the photomultiplier tubes (PMTs). These generally involve the use of highly reflective materials lining the interior of the detector, reflective materials around the PMTs, or wavelength-shifting sheets around the PMTs. Recently, the use of water-soluble wavelength-shifters has been explored to increase the measurable light yield of Cherenkov radiation in water. These wave-shifting chemicals are capable of absorbing light in the ultravoilet and re-emitting the light in a range detectable by PMTs. Using a 250 L water Cherenkov detector, we have characterized the increase in light yield from three compounds in water: 4-Methylumbelliferone, Carbostyril-124, and Amino-G Salt. We report the gain in PMT response at a concentration of 1 ppm as: 1.88 {+-} 0.02 for 4-Methylumbelliferone, stable to within 0.5% over 50 days, 1.37 {+-} 0.03 for Carbostyril-124, and 1.20 {+-} 0.02 for Amino-G Salt. The response of 4-Methylumbelliferone was modeled, resulting in a simulated gain within 9% of the experimental gain at 1 ppm concentration. Finally, we report an increase in neutron detection performance of a large-scale (3.5 kL) gadolinium-doped water Cherenkov detector at a 4-Methylumbelliferone concentration of 1 ppm.

  4. Enhancement of astaxanthin production using Haematococcus pluvialis with novel LED wavelength shift strategy.

    PubMed

    Xi, Tianqi; Kim, Dae Geun; Roh, Seong Woon; Choi, Jong-Soon; Choi, Yoon-E

    2016-07-01

    Haematococcus pluvialis is a green microalga of particular interest, since it is considered the best potential natural source of astaxanthin, which is widely used as an additive for natural pigmentation. In addition, astaxanthin has recently garnered commercial interest as a nutraceutical, cosmetic, and pharmaceutical. However, producing astaxanthin from H. pluvialis necessitates separation with distinctive culture conditions, dividing between the microalgae growth and the astaxanthin production stages. Light-emitting diodes (LEDs) have emerged as a replacement for traditional light sources, and LED applications are now rapidly expanding to multiple areas in fields such as biotechnology. However, further detail application into microalgae biotechnology remains limited. In this study, we have attempted to establish new protocols based on the specific wavelength of LEDs for the cultivation and production of astaxanthin using H. pluvialis. Specifically, we applied red LEDs for microalgae cell growth and then switched to blue LEDs to induce astaxanthin biosynthesis. The result showed that astaxanthin productions based on a wavelength shift from red to blue were significantly increased, compared to those with continuous illumination using red LEDs. Furthermore, additional increase of astaxanthin production was achieved with simultaneous application of exogenous carbon with blue LED illumination. Our approach based on the proper manipulation of LED wavelengths upon H. pluvialis cell stages will enable the improvement of biomass and enhance astaxanthin production using H. pluvialis. PMID:26860938

  5. Phase retrieval based on temporal and spatial hybrid matching in simultaneous phase-shifting dual-wavelength interferometry.

    PubMed

    Qiu, Xiang; Zhong, Liyun; Xiong, Jiaxiang; Zhou, Yunfei; Tian, Jindong; Li, Dong; Lu, Xiaoxu

    2016-06-13

    In simultaneous phase-shifting dual-wavelength interferometry, by matching both the phase-shifting period number and the fringe number in interferogram of two wavelengths to the integers, the phase with high accuracy can be retrieved through combining the principle component analysis (PCA) and least-squares iterative algorithm (LSIA). First, by using the approximate ratio of two wavelengths, we can match both the temporal phase-shifting period number and the spatial fringe number in interferogram of two wavelengths to the integers. Second, using above temporal and spatial hybrid matching condition, we can achieve accurate phase shifts of single-wavelength of phase-shifting interferograms through using PCA algorithm. Third, using above phase shifts to perform the iterative calculation with the LSIA method, the wrapped phases of single-wavelength can be determined. Both simulation calculation and experimental research demonstrate that by using the temporal and spatial hybrid matching condition, the PCA + LSIA based phase retrieval method possesses significant advantages in accuracy, stability and processing time. PMID:27410297

  6. Wavelength-spacing-tunable multichannel filter incorporating a sampled chirped fiber Bragg grating based on a symmetrical chirp-tuning technique without center wavelength shift

    NASA Astrophysics Data System (ADS)

    Han, Young-Geun; Dong, Xinyong; Lee, Ju Han; Lee, Sang Bae

    2006-12-01

    We propose and experimentally demonstrate a simple and flexible scheme for a wavelength-spacing-tunable multichannel filter exploiting a sampled chirped fiber Bragg grating based on a symmetrical modification of the chirp ratio. Symmetrical bending along a sampled chirped fiber Bragg grating attached to a flexible cantilever beam induces a variation of the chirp ratio and a reflection chirp bandwidth of the grating without a center wavelength shift. Accordingly, the wavelength spacing of a sampled chirped fiber Bragg grating is continuously controlled by the reflection chirp bandwidth variation of the grating corresponding to the bending direction, which allows for realization of an effective wavelength-spacing-tunable multichannel filter. Based on the proposed technique, we achieve the continuous tunability of the wavelength spacing in a range from 1.51 to 6.11 nm, depending on the bending direction of the cantilever beam.

  7. Final results from the SDC dopant search for new green wavelength shifting (WLS) fibers: Volume 1

    SciTech Connect

    Pla-Dalmau, A.; Foster, G.W.; Zhang, G.

    1993-12-01

    A scintillating tile/fiber design had been selected for the SDC calorimeter. It consisted of scintillator plates embedded with a wavelength shifting (WLS) fiber which was spliced to a clear fiber. Based on the results from previous radiation damage studies on different scintillating materials, SCSN38 had been chosen for the scintillating tile and BCF91 or Y7 for the WLS fiber. SCSN38 is a blue-emitting scintillator and both WLS fibers use K-27, a green-emitting compound, as dopant. K-27 has a decay time of approximately 12 ns which is long in comparison to that of most blue-emitting materials. Of all the factors that affect the speed of the scintillator tile/fiber calorimeter, the lifetime of the green-emitting dopant is the dominant component. To increase the speed of the calorimeter, it would be desirable that the green WLS fibers utilized had lifetimes between 3 and 5 ns. However, currently available green WLS fibers exhibit decay times between 7 and 12 ns. Development of new green-emitting WLS fibers with short decay times must be investigated. The goal of this project was to search for commercially available fluorescent compounds with {lambda}{sub abs} = 400--450 nm, {lambda}{sub em} = 450--550 nm, {tau} = 3--7 ns, and quantum efficiency of minimum 0.7 (current K-27 baseline). Large Stokes shift and low self-absorption were not important requirements since the optical pathlength for the shifted light was small. Characterization of the spectroscopic properties of these compounds after styrene polymerization is important since this is an essential part of the manufacturing of WLS fibers. This summary presents the transmittance and fluorescence data for each dopant tested. However, many fluorescence measurements using different excitation wavelengths and orientations were recorded. Volume 1 presents a plot for each dopant combining transmittance and the most representative fluorescence measurement.

  8. Shifted excitation Raman difference spectroscopy at multiple wavelengths for in-situ meat species differentiation

    NASA Astrophysics Data System (ADS)

    Sowoidnich, Kay; Kronfeldt, Heinz-Detlef

    2012-09-01

    Two miniaturized Raman measurement heads containing microsystem diode lasers emitting at 783 and 671 nm suitable for shifted excitation Raman difference spectroscopy (SERDS) were applied for the non-invasive in situ differentiation of selected meat species. This allows using the fingerprint characteristics of Raman spectra without a disturbing fluorescence background. At 783 nm, two emission lines with a spectral shift of 0.5 nm (7 cm-1) and optical powers of up to 110 mW were realized. For 671 nm excitation, the spectral shift amounts to 0.6 nm (12 cm-1) and optical powers of up to 40 mW were obtained. In both cases, meat Raman spectra could be recorded with integration times of 10 s. The investigations were carried out using selected cuts from the most commonly consumed meat species in the US and Europe, i.e. beef, pork, chicken, and turkey. A principal components analysis of the SERDS spectra revealed a clear separation of the meat species into four distinct groups for both excitation wavelengths. This classification is based on the myoglobin content and gradual differences of protein Raman band intensities and positions. The results demonstrate the potential of SERDS as rapid and non-destructive screening method for the discrimination of selected meat species.

  9. High-speed 3D imaging using two-wavelength parallel-phase-shift interferometry.

    PubMed

    Safrani, Avner; Abdulhalim, Ibrahim

    2015-10-15

    High-speed three dimensional imaging based on two-wavelength parallel-phase-shift interferometry is presented. The technique is demonstrated using a high-resolution polarization-based Linnik interferometer operating with three high-speed phase-masked CCD cameras and two quasi-monochromatic modulated light sources. The two light sources allow for phase unwrapping the single source wrapped phase so that relatively high step profiles having heights as large as 3.7 μm can be imaged in video rate with ±2  nm accuracy and repeatability. The technique is validated using a certified very large scale integration (VLSI) step standard followed by a demonstration from the semiconductor industry showing an integrated chip with 2.75 μm height copper micro pillars at different packing densities. PMID:26469586

  10. Performance improvements of wavelength-shifting-fiber neutron detectors using high-resolution positioning algorithms.

    PubMed

    Wang, C L

    2016-05-01

    Three high-resolution positioning methods based on the FluoroBancroft linear-algebraic method [S. B. Andersson, Opt. Express 16, 18714 (2008)] are proposed for wavelength-shifting fiber (WLSF) neutron detectors. Using a Gaussian or exponential-decay light-response function, the non-linear relation of photon-number profiles vs. x-pixels was linearized and neutron positions were determined. After taking the super-Poissonian photon noise into account, the proposed algorithms give an average of 0.03-0.08 pixel position error much smaller than that (0.29 pixel) from a traditional maximum photon algorithm (MPA). The new algorithms result in better detector uniformity, less position misassignment (ghosting), better spatial resolution, and an equivalent or better instrument resolution in powder diffraction than the MPA. These improvements will facilitate broader applications of WLSF detectors at time-of-flight neutron powder diffraction beamlines, including single-crystal diffraction and texture analysis. PMID:27250410

  11. Development of a converter made of scintillator and wavelength-shifting fibers for fast neutron radiography

    NASA Astrophysics Data System (ADS)

    Zou, Yubin; Guo, Li'an; Guo, Zhiyu; Tang, Guoyou; Zhang, Guohui

    2009-06-01

    Wavelength-shifting fiber (WSF) converter is a novel converter for fast neutron (FN) radiography, which has high light output, high detection efficiency and low gamma sensitivity. In order to improve the performance of WSF converter, we optimized the WSF converter design with a simple model and manufactured it with a new method, which can increase the scintillation material concentration. The light output and gamma sensitivity of WSF converters were measured on accelerator-based fast neutron sources, and gamma sensitivity was measured with an activated indium gamma source. FN radiographs were taken with WSF converter and some other traditional converters for comparison. We found that the light output of the new WSF converter is more than 5 times that of a 2 mm polypropylene (PP) converter for 5.8 MeV neutron beam, while its relative gamma sensitivity is still low.

  12. Performance improvements of wavelength-shifting-fiber neutron detectors using high-resolution positioning algorithms

    DOE PAGESBeta

    Wang, C. L.

    2016-05-17

    On the basis of FluoroBancroft linear-algebraic method [S.B. Andersson, Opt. Exp. 16, 18714 (2008)] three highly-resolved positioning methodswere proposed for wavelength-shifting fiber (WLSF) neutron detectors. Using a Gaussian or exponential-decay light-response function (LRF), the non-linear relation of photon-number profiles vs. x-pixels was linearized and neutron positions were determined. The proposed algorithms give an average 0.03-0.08 pixel position error, much smaller than that (0.29 pixel) from a traditional maximum photon algorithm (MPA). The new algorithms result in better detector uniformity, less position misassignment (ghosting), better spatial resolution, and an equivalent or better instrument resolution in powder diffraction than the MPA. Moreover,more » these characters will facilitate broader applications of WLSF detectors at time-of-flight neutron powder diffraction beamlines, including single-crystal diffraction and texture analysis.« less

  13. Simultaneous multi-wavelength phase-shifting interferometry based on principal component analysis with a color CMOS

    NASA Astrophysics Data System (ADS)

    Fan, Jingping; Lu, Xiaoxu; Xu, Xiaofei; Zhong, Liyun

    2016-05-01

    From a sequence of simultaneous multi-wavelength phase-shifting interferograms (SMWPSIs) recorded by a color CMOS, a principal component analysis (PCA) based multi-wavelength interferometry (MWI) is proposed. First, a sequence of SMWPSIs with unknown phase shifts are recorded with a single-chip color CMOS camera. Subsequently, the wrapped phases of single-wavelength are retrieved with the PCA algorithm. Finally, the unambiguous phase of the extended synthetic wavelength is achieved by the subtraction between the wrapped phases of single-wavelength. In addition, to eliminate the additional phase introduced by the microscope and intensity crosstalk among three-color channels, a two-step phase compensation method with and without the measured object in the experimental system is employed. Compared with conventional single-wavelength phase-shifting interferometry, due to no requirements for phase shifts calibration and the phase unwrapping operation, the actual unambiguous phase of the measured object can be achieved with the proposed PCA-based MWI method conveniently. Both numerical simulations and experimental results demonstrate that the proposed PCA-based MWI method can enlarge not only the measuring range, but also no amplification of noise level.

  14. Measurement of Cerenkov Radiation Induced by the Gamma-Rays of Co-60 Therapy Units Using Wavelength Shifting Fiber

    PubMed Central

    Jang, Kyoung Won; Shin, Sang Hun; Kim, Seon Geun; Kim, Jae Seok; Yoo, Wook Jae; Ji, Young Hoon; Lee, Bongsoo

    2014-01-01

    In this study, a wavelength shifting fiber that shifts ultra-violet and blue light to green light was employed as a sensor probe of a fiber-optic Cerenkov radiation sensor. In order to characterize Cerenkov radiation generated in the developed wavelength shifting fiber and a plastic optical fiber, spectra and intensities of Cerenkov radiation were measured with a spectrometer. The spectral peaks of light outputs from the wavelength shifting fiber and the plastic optical fiber were measured at wavelengths of 500 and 510 nm, respectively, and the intensity of transmitted light output of the wavelength shifting fiber was 22.2 times higher than that of the plastic optical fiber. Also, electron fluxes and total energy depositions of gamma-ray beams generated from a Co-60 therapy unit were calculated according to water depths using the Monte Carlo N-particle transport code. The relationship between the fluxes of electrons over the Cerenkov threshold energy and the energy depositions of gamma-ray beams from the Co-60 unit is a near-identity function. Finally, percentage depth doses for the gamma-ray beams were obtained using the fiber-optic Cerenkov radiation sensor, and the results were compared with those obtained by an ionization chamber. The average dose difference between the results of the fiber-optic Cerenkov radiation sensor and those of the ionization chamber was about 2.09%. PMID:24755521

  15. Measurement of Cerenkov radiation induced by the gamma-rays of Co-60 therapy units using wavelength shifting fiber.

    PubMed

    Jang, Kyoung Won; Shin, Sang Hun; Kim, Seon Geun; Kim, Jae Seok; Yoo, Wook Jae; Ji, Young Hoon; Lee, Bongsoo

    2014-01-01

    In this study, a wavelength shifting fiber that shifts ultra-violet and blue light to green light was employed as a sensor probe of a fiber-optic Cerenkov radiation sensor. In order to characterize Cerenkov radiation generated in the developed wavelength shifting fiber and a plastic optical fiber, spectra and intensities of Cerenkov radiation were measured with a spectrometer. The spectral peaks of light outputs from the wavelength shifting fiber and the plastic optical fiber were measured at wavelengths of 500 and 510 nm, respectively, and the intensity of transmitted light output of the wavelength shifting fiber was 22.2 times higher than that of the plastic optical fiber. Also, electron fluxes and total energy depositions of gamma-ray beams generated from a Co-60 therapy unit were calculated according to water depths using the Monte Carlo N-particle transport code. The relationship between the fluxes of electrons over the Cerenkov threshold energy and the energy depositions of gamma-ray beams from the Co-60 unit is a near-identity function. Finally, percentage depth doses for the gamma-ray beams were obtained using the fiber-optic Cerenkov radiation sensor, and the results were compared with those obtained by an ionization chamber. The average dose difference between the results of the fiber-optic Cerenkov radiation sensor and those of the ionization chamber was about 2.09%. PMID:24755521

  16. Water-vapor line broadening and shifting by air, nitrogen, oxygen, and argon in the 720-nm wavelength region

    NASA Technical Reports Server (NTRS)

    Grossmann, Benoist E.; Browell, Edward V.

    1989-01-01

    High-resolution spectroscopic measurements of H2O vapor in the 720-nm wavelength region were conducted to investigate the broadening and shifting of H2O lines by air, nitrogen, oxygen, and argon over a wide range of pressures and temperatures. For each of the buffer gases under study, a linear relationship was found between the widths and the shifts, with the broader lines having the smaller pressure shifts. The pressure shifts measured compared favorably with theoretical values reported by Bykov et al. (1988). The temperature-dependence exponents for air-broadening were found to be J-dependent, with the lower-J lines having the higher exponents.

  17. Monolithic Single-Mode DFB Laser Array with Precise Wavelength Control for Optoelectronic Integration using an Equivalent Phase Shift Method

    NASA Astrophysics Data System (ADS)

    Li, Jingsi; Cheng, Julian; Microelectronics Research Center Team

    2013-03-01

    The integrated distributed feedback (DFB) laser array is a key component in photonic integrated circuits for wavelength-division multiplexing (WDM) system. However, it is difficult to precisely control the wavelength of individual lasers. When the rear facet of the laser is coated with a high-reflectivity mirror, a random phase change is introduced that shifts the lasing wavelength, making monolithic integration of a wavelength-controlled WDM array very difficult. To solve this problem, we propose a method to precisely control the lasing wavelength of DFB lasers over a wide range by introducing an equivalent phase shift in the cavity using sampled Bragg gratings, using wafer-scale optical lithography and requiring only coarse dimension control. The wavelength can be fine-tuned by applying different DC currents. It is shown that a WDM-DFB laser array with uniform wavelength spacing can be controlled accurately in this manner. Integrated arrays of single-mode DFB lasers for WDM systems can thus be fabricated in a low-cost manner without using low-throughput e-beam lithography, and is scalable for mass-manufacturing.

  18. Wavelength-Shifting-Fiber Scintillation Detectors for Thermal Neutron Imaging at SNS

    SciTech Connect

    Clonts, Lloyd G; Cooper, Ronald G; Crow, Lowell; Diawara, Yacouba; Ellis, E Darren; Funk, Loren L; Hannan, Bruce W; Hodges, Jason P; Richards, John D; Riedel, Richard A; Wang, Cai-Lin

    2012-01-01

    We have developed wavelength-Shifting-fiber Scintillator Detector (SSD) with 0.3 m2 area per module. Each module has 154 x 7 pixels and a 5 mm x 50 mm pixel size. Our goal is to design a large area neutron detector offering higher detection efficiency and higher count-rate capability for Time-Of-Flight (TOF) neutron diffraction in Spallation Neutron Source (SNS). A ZnS/6LiF scintillator combined with a novel fiber encoding scheme was used to record the neutron events. A channel read-out-card (CROC) based digital-signal processing electronics and position-determination algorithm was applied for neutron imaging. Neutron-gamma discrimination was carried out using pulse-shape discrimination (PSD). A sandwich flat-scintillator detector can have detection efficiency close to He-3 tubes (about 10 atm). A single layer flat-scintillator detector has count rate capability of 6,500 cps/cm2, which is acceptable for powder diffractometers at SNS.

  19. Doppler wavelength shifts of ultraviolet spectral lines in solar active regions

    NASA Technical Reports Server (NTRS)

    Feldman, U.; Doschek, G. A.; Cohen, L.

    1982-01-01

    Doppler shifts are measured for solar UV emission lines formed in the lower transition region of active regions. Doppler shifts in different regions at the same solar location, variations of Doppler shift with position of an active region on the disk, and variations of Doppler shift with time at the same solar location in the same active region were studied. Observations were made with the NRL slit spectrograph on Skylab. Excluding flare and flare-related phenomena, only redshifts are found whose magnitudes correspond to downflow velocities between about 4 and 17 km/s. Shifts are largest for lines formed between about 50,000 and 100,000 K, and are distinctly less for lines formed above 100,000 K. The shifts persist out to the limb, but not above it. There is no obvious change in redshift for lines measured at the same solar location over time intervals of about 20 minutes.

  20. Dual-wavelength Y-branch distributed Bragg reflector diode laser at 785 nanometers for shifted excitation Raman difference spectroscopy.

    PubMed

    Maiwald, Martin; Eppich, Bernd; Fricke, Jörg; Ginolas, Arnim; Bugge, Frank; Sumpf, Bernd; Erbert, Götz; Tränkle, Günther

    2014-01-01

    A dual-wavelength Y-branch distributed Bragg reflector (DBR) diode laser at 785 nm is presented as an excitation light source for shifted excitation Raman difference spectroscopy (SERDS). The monolithic device was realized with deeply etched surface DBR gratings using one-step epitaxy. An optical output power of 140 mW was obtained in continuous-wave (CW) operation for each laser cavity, with emission wavelengths of the device at 784.50 and 785.12 nm. A spectral width of the laser emission of 30 pm (0.5 cm(-1)), including 95% of optical power, was measured. The mean spectral distance of both excitation lines is 0.63 nm (10.2 cm(-1)) over the whole operating range. Raman experiments using polystyrene as the test sample and ambient light as the interference source were carried out and demonstrate the suitability of the dual-wavelength diode laser for SERDS. PMID:25061785

  1. Wavelength shifts in fluorescence maxima of stressed and non-stressed Norway spruce needles over the growing season

    NASA Technical Reports Server (NTRS)

    Banninger, Cliff; Chappelle, E.

    1991-01-01

    Laboratory fluorescence measurements of first and third year metal stressed and non stressed Norway spruce needles collected in May, Jul. Sep. and Nov. display significant wavelength shifts in the intensity maxima in the blue, green, red, and near infrared spectral regions, with the largest shifts occurring in the blue spectral region for both first and third year needles from Nov. Smaller, but the otherwise significant shifts also take place in the blue spectral region for first year needles from Sep. in the red spectral region for third year neddles from May, Jul. and Sep. and in the near infrared spectral region for first and third year needles from Jul. and Sep. Wavelength shifts in needle fluorescence maxima over the growing season are greatest in the blue and to a lesser extent, greenspectral regions from Sep. to Nov. but are also significant in the red and near infrared spectral regions from Jul. to Sep. and Sep. to Nov., and in the near infrared spectral region also from May to Jul.

  2. Two-wavelength method for endoscopic shape measurement by spatial phase-shifting speckle-interferometry.

    PubMed

    Kandulla, Jochen; Kemper, Björn; Knoche, Sabine; von Bally, Gert

    2004-10-10

    A two-wavelength method for endoscopic topography reconstruction is introduced that can be applied to out-of-plane sensitive electronic-speckle-pattern interferometry systems based on rigid endoscope imaging systems. The surface measurement is performed by detection of the phase-difference distribution affected by a change in the applied laser wavelength. Furthermore, the off-axis endoscopic illumination geometry is taken into account by an approximation. Experimental results of the characterization of the endoscopic surface reconstruction technique and the measurement accuracy obtained are described and discussed. Finally, the applicability of the method is demonstrated with results from the topographic reconstruction of a free-form surface. PMID:15508598

  3. 2000 ICA Presidential Address: Shifting Voices, Oppositional Discourse, and New Visions for Communication Studies.

    ERIC Educational Resources Information Center

    Putnam, Linda L.

    2001-01-01

    Advocates using the construct of voice rather than paradigms, theories, and academic divisions to develop complimentary ways of understanding. Advocates taking inventory of multiple and shifting voices in reviews and critiques of the literature; connecting through exploring shifting concepts and theories; and engaging in joint actions in ways that…

  4. Two-way shift of wavelength in holographic sensing of organic vapor in nanozeolites dispersed acrylamide photopolymer.

    PubMed

    Mao, Dongyao; Geng, Yaohui; Liu, Hongpeng; Zhou, Ke; Xian, Lihong; Yu, Dan

    2016-08-10

    Holographic sensing of alcohol organic vapor is characterized in detail at transmission and reflection geometries in Y nanozeolites dispersed acrylamide photopolymer. The two-way shift of the diffraction spectrum and its temporal evolution with various vapor concentrations are measured. Obvious blueshifts of diffraction spectrum peaks are observed and analyzed in two recording geometries. The competition mechanism between decreasing the average refractive index and swelling the grating fringe space is proposed for exploring the wavelength shift mechanism. In the reflection grating, as organic vapor increases, the redshift after the blueshift of the wavelength peaks are observed clearly. We further demonstrate the significance of this competition mechanism. In the low concentration region, at transmission <700  ppm and reflection <400  ppm in nanozeolites dispersed polymer, the blueshift of the wavelength is a significant factor in identifying an organic vapor with a low refractive index. These experimental results provide a probability for improving the applicability of a holographic sensor. This work can accelerate the development of the holographic sensing strategy and provide a novel identification method for organic vapor. PMID:27534461

  5. Enhancement and wavelength-shifted emission of Cerenkov luminescence using multifunctional microspheres.

    PubMed

    Li, Joanne; Dobrucki, Lawrence W; Marjanovic, Marina; Chaney, Eric J; Suslick, Kenneth S; Boppart, Stephen A

    2015-01-21

    Cerenkov luminescence (CL) imaging is a new molecular imaging modality that utilizes the photons emitted during radioactive decay when charged particles travel faster than the phase velocity of light in a dielectric medium. Here we present a novel agent to convert and increase CL emission at longer wavelengths using multimodal protein microspheres (MSs). The (64)Cu-labeled protein microspheres contain quantum dots (QDs) encapsulated within a high-refractive-index-oil core. Dark box imaging of the MSs was conducted to demonstrate the improvement in CL emission at longer wavelengths. To illustrate the versatile design of these MSs and the potential of CL in disease diagnosis, these MSs were utilized for in vitro cell targeting and ex vivo CL-excited QD fluorescence (CL-FL) imaging of atherosclerotic plaques in rats. It was shown that by utilizing both QDs and MSs with a high-refractive-index-oil core, the CL emission increases by four-fold at longer wavelengths. Furthermore, we demonstrate that these MSs generate both an in vivo and ex vivo contrast signal. The design concept of utilizing QDs and high-index core MSs may contribute to future developments of in vivo CL imaging. PMID:25555157

  6. Enhancement and wavelength-shifted emission of Cerenkov luminescence using multifunctional microspheres

    PubMed Central

    Li, Joanne; Dobrucki, Lawrence W.; Marjanovic, Marina; Chaney, Eric J.; Suslick, Kenneth S.; Boppart, Stephen A.

    2015-01-01

    Cerenkov luminescence (CL) imaging is a new molecular imaging modality that utilizes the photons emitted during radioactive decay when charged particles travel faster than the phase velocity of light in a dielectric medium. Here we present a novel agent to convert and increase CL emission at longer wavelengths using multimodal protein microspheres (MSs). The 64Cu-labeled protein microspheres contain quantum dots (QDs) encapsulated within a high-refractive-index-oil core. Dark box imaging of the MSs was conducted to demonstrate the improvement in CL emission at longer wavelengths. To illustrate the versatile design of these MSs and the potential of CL in disease diagnosis, these MSs were utilized for in vitro cell targeting and ex vivo CL-excited QD fluorescence (CL-FL) imaging of atherosclerotic plaques in rats. It was shown that by utilizing both QDs and MSs with a high-refractive-index-oil core, the CL emission increases by four-fold at longer wavelengths. Furthermore, we demonstrate that these MSs generate both an in vivo and ex vivo contrast signal. The design concept of utilizing QDs and high-index core MSs may contribute to future developments of in vivo CL imaging. PMID:25555157

  7. Multi-wavelength phase-shifting interferometry for micro-structures measurement based on color image processing in white light interference

    NASA Astrophysics Data System (ADS)

    Guo, Tong; Li, Feng; Chen, Jinping; Fu, Xing; Hu, Xiaotang

    2016-07-01

    Conventional multi-wavelength phase-shifting interferometry utilizes two or three monochromatic light sources, such as lasers, to realize the measurement of the surface topography with large discontinuity. In this paper, the white light source, with a single-chip CCD color camera, is used to accomplish multi-wavelength phase-shifting interferometry. In addition, we propose an algorithm which combines white light phase-shifting algorithm, equivalent wavelength method and fringe order method to achieve measuring and calibrating the micro-structures ranging from nanometer scale to micrometer scale. Finally, the proposed method is validated by a traceable step height standard.

  8. Beam test results for a tungsten-cerium fluoride sampling calorimeter with wavelength-shifting fiber readout

    NASA Astrophysics Data System (ADS)

    Becker, R.; Candelise, V.; Cavallari, F.; Dafinei, I.; Della Ricca, G.; Diemoz, M.; del Re, D.; D'Imperio, G.; Dissertori, G.; Donegà, M.; Dröge, M.; Gelli, S.; Haller, C.; Jorda Lope, C.; Lustermann, W.; Martelli, A.; Meridiani, P.; Micheli, F.; Nessi-Tedaldi, F.; Nuccetelli, M.; Organtini, G.; Quittnat, M.; Pandolfi, F.; Paramatti, R.; Pastrone, N.; Pellegrino, F.; Peruzzi, M.; Rahatlou, S.; Rovelli, C.; Santanastasio, F.; Schönenberger, M.; Soffi, L.; Tabarelli de Fatis, T.; Vazzoler, F.

    2015-07-01

    A sampling calorimeter using cerium fluoride scintillating crystals as active material, interleaved with heavy absorber plates, and read out by wavelength-shifting (WLS) fibers is being studied as a calorimeter option for detectors at the upgraded High-Luminosity LHC (HL-LHC) collider at CERN. A prototype has been exposed to electron beams of different energies at the INFN Frascati (Italy) Beam Test Facility. This paper presents results from the studies performed on the prototype, such as signal amplitudes, light yield and energy resolution.

  9. Design optimization, manufacture and response measurements for fast-neutron radiography converters made of scintillator and wavelength-shifting fibers

    NASA Astrophysics Data System (ADS)

    Li, Hang; Wu, Yang; Cao, Chao; Huo, Heyong; Tang, Bin

    2014-10-01

    In order to improve the image quality of fast neutron radiography, a converter made of scintillator and wavelength-shifting fibers has been developed. The appropriate parameters of the converter such as fibers arrangement, distance between fibers are optimized theoretically, and manufacture of the converter are also optimized. Fast neutron radiography experiments by 14 MeV neutrons are used to test this converter and kinds of traditional converters. The experiments' results matched the calculations. The novel converter's resolution is better than 1 mm and the light output is high.

  10. Addressing the "Shift": Preparing Preservice Secondary Teachers for the Common Core

    ERIC Educational Resources Information Center

    Bennett, Stephanie M.; Hart, Steven M.

    2014-01-01

    Common Core represents a shift in content-area literacy instruction, broadening from a narrow focus on generalizable skills to also include a disciplinary perspective of literacies specific to the specialized language and habits of thinking within particular subjects. This requires teachers to be knowledgeable in their content and possess…

  11. Line centers, pressure shift, and pressure broadening of 1530-1560 nm hydrogen cyanide wavelength calibration lines

    SciTech Connect

    Swann, William C.; Gilbert, Sarah L.

    2005-08-01

    We have measured the line centers and pressure-induced shift and broadening of 25 lines in the 2{nu}{sub 3} rotational-vibrational band of hydrogen cyanide H{sup 13}C{sup 14}N. These lines can be used as wavelength references in the optical fiber communication wavelength division multiplexing C-band (approximately 1530-1565 nm). We find that the pressure shift varies with line number from +0.09 pm/kPa to -0.15 pm/kPa (approximately -1.5 to +2.5 MHz/Torr). The pressure broadening also varies with line number and is typically between 1 and 5.4 pm/kPa (17-90 MHz/Torr). We determined the line centers of 21 lines with an expanded uncertainty (2{sigma}) of 0.01 pm ({approx_equal}1 MHz), an improvement of more than 1 order of magnitude over previous line center measurements of this band. We also calculate the molecular constants for the band, yielding improved determination of the band origin frequency and the excited-state molecular constants.

  12. Spectral Broadening and Wavelength Shift of Emission Lines of Li2+ Ions in Magnetically Confined Plasmas

    NASA Astrophysics Data System (ADS)

    Zou, S.; Kato, T.; Murakami, I.

    2003-02-01

    A detailed calculation is presented of the line emission profiles of Li2+ ions in a magnetically confined plasma, and applied to interpret the measured spectra from a fusion device [K. Kondo et al.: J. Nucl. Matter 241-243 (1997) 956]. Transition probabilities and wavelengths of Li2+ ions are computed by diagonalizing the Hamiltonian including interactions with the magnetic field. The nl-resolved population densities of exited Li2+ ions are calculated up to n=20 using a collisional-radiative model including the charge exchange process. The calculations show that 1) spectral profiles emitted by excitation, recombination and charge exchange are quite different, which is due to the different n and l-distributions of these basic atomic rate coefficients; and 2) in order to properly interpret low temperature sepctra the Zeeman effect has to be accounted for.

  13. Using optical parametric oscillators (OPO) for wavelength shifting IR images to visible spectrum

    SciTech Connect

    McDonald, T.E. Jr.; Numkena, D.M.; Payton, J.; Yates, G.J.; Zagarino, P.

    1998-12-31

    The authors have carried out preliminary investigations into coherent imaging using Optical Parametric Oscillators (OPO) for wavelength conversion of near IR images to visible spectrum. A nonlinear crystal, second harmonic generator (SHG), was used for degenerate optical parametric up-conversion. A Potassium Titanyl Phosphate (KTP) doubling crystal was used to convert incident 1,540 nm flux to 772 nm. Experiments included investigation of spatial resolution and responsivity of the OPO. Spatial resolution of 1.3 1p/mm was attained in both horizontal and vertical axis. Measured responsivity for this OPO configuration compared well with that attained from image intensifier-based systems. Equipment used for this experiment included an ORION SB2-2R pulsed solid state laser used as a light source and a CCD camera and frame grabber to capture and record all data. The experiment and results are discussed.

  14. Mathematical approximations for the amplitude of the fundamental mode field (LP01) of a dispersion shifted fiber at six wavelengths

    NASA Astrophysics Data System (ADS)

    Lamarche, Louis

    2009-06-01

    Hydro-Quebec optical network includes more than 5,000 km of optical ground wires [1] (OPGW) using dispersion shifted fibers (SMF-DSTM) [2]-[3]. This paper provides a model of the index profile for a typical reference fiber and the mathematical approximations of the amplitude of the LP01 mode at six important wavelengths (1.31, 1.41, 1.45, 1.48, 1.55, 1.625 μm). The fiber model has a triangular core and a quadratic ring shape. The weakly guided mode is obtained using the variational principle [4] implemented using an algorithm based on a Laguerre-Gauss-Bessel approximation of the field [5]. We modeled the wavelength dependence of the index of refraction of germanium doped silica using an experimental formula [6]. A comprehensive algorithm was developed to compute the normalized damping factor W and the normalized propagation constant U in the variational algorithm. The mode field diameter, group velocity and chromatic dispersion were also computed at the above wavelengths.

  15. Shifting the HIV Training and Research Paradigm to Address Disparities in HIV Outcomes.

    PubMed

    Levison, Julie H; Alegría, Margarita

    2016-09-01

    Tailored programs to diversify the pool of HIV/AIDS investigators and provide sufficient training and support for minority investigators to compete successfully are uncommon in the US and abroad. This paper encourages a shift in the HIV/AIDS training and research paradigm to effectively train and mentor Latino researchers in the US, Latin America and the Caribbean. We suggest three strategies to accomplish this: (1) coaching senior administrative and academic staff of HIV/AIDS training programs on the needs, values, and experiences unique to Latino investigators; (2) encouraging mentors to be receptive to a different set of research questions and approaches that Latino researchers offer due to their life experiences and perspectives; and (3) creating a virtual infrastructure to share resources and tackle challenges faced by minority researchers. Shifts in the research paradigm to include, retain, and promote Latino HIV/AIDS researchers will benefit the scientific process and the patients and communities who await the promise of HIV/AIDS research. PMID:27501811

  16. Wavelength control of erbium-doped fiber ring lasers by means of π-shifted variable long-period fiber gratings

    NASA Astrophysics Data System (ADS)

    Sakata, H.; Ono, Y.; Dodo, S.

    2016-04-01

    In this paper, fiber ring resonators are composed of an erbium-doped fiber amplifier (EDFA) with a π-shifted long-period fiber grating (PS-LPFG) to control the lasing wavelength. The PS-LPFG forms the passband inside the rejection band in the transmission spectrum, and the passband is shifted to longer wavelengths by stretching a coil spring that presses the fiber with an electromagnet. The oscillation wavelength is shifted from 1532.8 to 1565.1 nm depending on the variable grating period by using the C-band EDFA. By replacing to the L-band EDFA, the tunable wavelength range is moved to the range from 1586.8 to 1613.8 nm. The laser emission spectra exhibit the 3 dB spectral bandwidth of ~0.1 nm with a side-mode suppression ratio of ~40 dB.

  17. Performance Evaluation of Tunable Channel-Selective Wavelength Shift by Cascaded Sum- and Difference-Frequency Generation in Periodically Poled Lithium Niobate Waveguides

    NASA Astrophysics Data System (ADS)

    Gao, Shiming; Yang, Changxi; Xiao, Xiaosheng; Tian, Yu; You, Zheng; Jin, Guofan

    2007-03-01

    We theoretically evaluate the performance of tunable channel-selective wavelength shift based on cascaded sum- and difference-frequency generation by the use of two pump lights in periodically poled lithium niobate waveguides. In double-pass configurations, the functions of wavelength add/drop and wavelength shift are easy to integrate in the same waveguide. Analysis shows that a longer waveguide more competently adapts narrower channel spacing in wavelength-division-multiplexed (WDM) systems. This wavelength shifter is flexible due to the almost separable operations of the two pumps: The channel is selected by setting the first pump, and the wavelength-shifting value is tuned by adjusting the second pump. This wavelength shifter has a very large dynamic region. For a 2.56-cm-long waveguide, the maximum dynamic region is as broad as 67 nm in a 0.4-nm channel-spacing WDM system. The dynamic region is mainly dominated by the limitation of multiple-channel crosstalk in a dense WDM system. However, it is dominated by the limitation of single-channel efficiency fluctuation in a coarse one.

  18. Quality control studies of wavelength shifting fibers for a scintillator-based tail-catcher muon-tracker linear collider prototype detector

    SciTech Connect

    Dyshkant, A.; Beznosko, D.; Blazey, G.; Rykalin, V.; Zutshi, V.; Fisk, E.; Hahn, E.; Wayne, M.; /Notre Dame U.

    2006-05-01

    Detailed measurements of the wavelength shifting fiber response to a stable and reliable light source are presented. Details about materials, a double reference method, and measurement technique are included. The fibers studied were several hundred KURARAY, Y-11, multiclad, 1.2mm outer diameter wavelength shifting fibers each cut from a reel to about one meter length. The fibers were polished, mirrored, and the mirrors were UV epoxy protected. Each fiber passed quality control requirements before installation. About 94% of the fibers have a response within 1% of the overall mean.

  19. Compact Handheld Probe for Shifted Excitation Raman Difference Spectroscopy with Implemented Dual-Wavelength Diode Laser at 785 Nanometers.

    PubMed

    Maiwald, Martin; Eppich, Bernd; Ginolas, Arnim; Sumpf, Bernd; Erbert, Götz; Tränkle, Günther

    2015-10-01

    A compact handheld probe for shifted-excitation Raman difference spectroscopy (SERDS) with an implemented dual-wavelength diode laser with an emission at 785 nm is presented. The probe is milled from aluminum and has dimensions 100 × 28 × 12 mm. The diode laser provides two excitation lines with a spectral distance of 10 cm(-1) (0.62 nm), has a spectral width smaller than 11 pm, and reaches an optical power of 120 mW ex probe. Raman experiments were carried out using polystyrene (PS) as the test sample. During a measurement time of over 1 h, a stable spectral center position of the Raman line at 999 cm(-1) of PS was achieved within a spectral window of 0.1 cm(-1). Here, the Raman intensity of this line was observed with a peak-to-peak variation smaller than ±2%, dominated by shot noise interference. A deviation of the center position of a Raman line with <±1 cm(-1) was observed over the whole excitation power range. Raman investigations of the quartz glass window of the SERDS probe showed minor interference. The results demonstrate the suitability of the developed handheld probe for Raman investigations and the application of in situ SERDS experiments to fields such as food safety control, medical diagnostics, and process control. PMID:26449807

  20. Highly coherent red-shifted dispersive wave generation around 1.3 μm for efficient wavelength conversion

    SciTech Connect

    Li, Xia; Bi, Wanjun; Chen, Wei; Xue, Tianfeng; Hu, Lili; Liao, Meisong; Gao, Weiqing

    2015-03-14

    This research investigates the mechanism of the optical dispersive wave (DW) and proposes a scheme that can realize an efficient wavelength conversion. In an elaborately designed photonic crystal fiber, a readily available ytterbium laser operating at ∼1 μm can be transferred to the valuable 1.3 μm wavelength range. A low-order soliton is produced to concentrate the energy of the DW into the target wavelength range and improve the degree of coherence. The input chirp is demonstrated to be a factor that enhances the wavelength conversion efficiency. With a positive initial chirp, 76.6% of the pump energy in the fiber can be transferred into a spectral range between 1.24 and 1.4 μm. With the use of a grating compressor, it is possible to compress the generated coherent DW of several picoseconds into less than 90 fs.

  1. Monte-Carlo simulation of a compact gamma-ray detector using wavelength-shifting fibers coupled to a YAP scintillation crystal

    NASA Astrophysics Data System (ADS)

    Zhu, Jie; Ma, Hong-Guang; Ma, Wen-Yan; Zeng, Hui; Wang, Zhao-Min; Xu, Zi-Zong

    2008-05-01

    The production and transportation of fluorescent light produced in wavelength-shifting fibers (WSFs) coupled to YAP scintillation crystal is simulated using the GEANT4 codes. An advantage of the wavelength-shifting fiber readout technique over a direct readout with a position-sensitive photo-sensor is the reduced requirement for position sensitive photomultiplier tube photocathode area. With this gamma-ray detector, the gamma camera is small and flexible and has larger effective field of view and low cost. Simulation results show that a) a mean 12 of photons per 59.5 keV gamma ray interaction is produced in the WSF located nearest to the incident gamma ray, and a spatial resolution of 3.6 mm FWHM is obtained, b) a mean 27 of photons per 140 keV gamma ray interaction is produced and a spatial resolution of 3.1 mm FWHM is obtained. Results demonstrate the feasibility of this concept of a compact gamma-ray detector based on wavelength-shifting fibers readout. However, since the very low photoelectron levels, it is very important to use a photon counting device with good single photo-electron response to readout the WSFs. Supported by National Nature Science Foundation of China (10275063)

  2. Isotope shift measurements in the 660 spectral lines of Er I covering the 340-605 nm wavelength region with a Fourier Transform Spectrometer

    NASA Astrophysics Data System (ADS)

    Ankush, B. K.; Deo, M. N.

    2015-04-01

    Isotope shift measurements in 660 spectral lines covering the 340-605 nm wavelength region of Er I were carried out using a Fourier Transform Spectrometer. The spectra were recorded using a liquid nitrogen cooled hollow cathode discharge source containing highly enriched 166Er and 170Er isotopes in the oxide form and two different detectors namely PMT and silicon photo diodes. Out of 660 spectral lines involving 216 even and 182 odd Er I levels, the isotope shift data were new in the 406 lines. On the basis of their level isotope shifts out of 114 unassigned even parity levels 27 levels assigned to 4f116s26p, 72 to 4f115d6s6p and 15 to 4f126s6d configuration whereas 12 each of unassigned odd parity levels assigned to 4f115d6s2, and 4f126s6p configurations and 16 unassigned odd parity levels assigned to 4f115d26s configuration. Configuration mixing for 30 odd parity energy levels has been theoretically calculated applying 'Sharing Rule' to the experimentally derived level isotope shifts, which were finally compared with mixings available in the literature.

  3. Widely tunable dispersive wave generation and soliton self-frequency shift in a tellurite microstructured optical fiber pumped near the zero dispersion wavelength

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Tuan, Tong-Hoang; Liu, Lai; Gao, Wei-Qing; Kawamura, Harutaka; Suzuki, Takenobu; Ohishi, Yasutake

    2015-12-01

    Widely tunable dispersive waves (DW) and Raman solitons are generated in a tellurite microstructured optical fiber (TMOF) by pumping in the anomalous dispersion regime, close to the zero dispersion wavelength (ZDW). The DW can be generated from 1518.3 nm to 1315.5 nm, and the soliton can be shifted from the pump wavelength of 1570 nm to 1828.7 nm, by tuning the average pump power from 3 dBm to 17.5 dBm. After the average pump power is increased to 18.8 dBm, two DW peaks (centered at 1323 nm and 1260 nm) and three soliton peaks (centered at 1762 nm, 1825 nm, and 1896 nm) can be observed simultaneously. When the average pump power is greater than 23.4 dBm, a flat and broadband supercontinuum (SC) can be formed by the combined nonlinear effects of soliton self-frequency shift (SSFS), DW generation, and cross phase modulation (XPM).

  4. Noise tolerance in wavelength-selective switching of optical differential quadrature-phase-shift-keying pulse train by collinear acousto-optic devices.

    PubMed

    Goto, Nobuo; Miyazaki, Yasumitsu

    2014-06-01

    Optical switching of high-bit-rate quadrature-phase-shift-keying (QPSK) pulse trains using collinear acousto-optic (AO) devices is theoretically discussed. Since the collinear AO devices have wavelength selectivity, the switched optical pulse trains suffer from distortion when the bandwidth of the pulse train is comparable to the pass bandwidth of the AO device. As the AO device, a sidelobe-suppressed device with a tapered surface-acoustic-wave (SAW) waveguide and a Butterworth-type filter device with a lossy SAW directional coupler are considered. Phase distortion of optical pulse trains at 40 to 100  Gsymbols/s in QPSK format is numerically analyzed. Bit-error-rate performance with additive Gaussian noise is also evaluated by the Monte Carlo method. PMID:24922411

  5. Raman Shifting a Tunable ArF Excimer Laser to Wavelengths of 190 to 240 nm With a Forced Convection Raman Cell

    NASA Technical Reports Server (NTRS)

    Balla, R. Jeffrey; Herring, G. C.

    2000-01-01

    Tunable radiation, at ultraviolet wavelengths, is produced by Raman shifting a modified 285-mJ ArF excimer laser. Multiple Stokes outputs are observed in H2, CH4, D2, N2, SF6, and CF4 (20, 22, 53, 21, 2.1, and 0.35 percent, respectively). Numbers in parentheses are the first Stokes energy conversion efficiencies. We can access 70 percent of the frequency range 42000-52000 cm (exp -1) (190-240 nm) with Stokes energies that vary from 0.2 microJoule to 58 mJ inside the Raman cell. By using 110 mJ of pump energy and D 2 , the tunable first Stokes energy varies over the 29-58 mJ range as the wavelength is tuned over the 204-206 nm range. Dependence on input energy, gas pressure, He mixture fraction, and circulation of the gas in the forced convection Raman cell is discussed; Stokes conversion is also discussed for laser repetition rates from 1 to 100 Hz. An empirical equation is given to determine whether forced convection can improve outputs for a given repetition rate.

  6. Comparison of two concepts for dual-wavelength DBR ridge waveguide diode lasers at 785 nm suitable for shifted excitation Raman difference spectroscopy

    NASA Astrophysics Data System (ADS)

    Sumpf, Bernd; Maiwald, Martin; Müller, André; Fricke, Jörg; Ressel, Peter; Bugge, Frank; Erbert, Götz; Tränkle, Günther

    2015-08-01

    Two concepts of dual-wavelength 785-nm DBR ridge waveguide (RW) lasers, i.e. RW mini-arrays consisting of two DBR-RW lasers and Y-branch DBR-RW lasers, will be compared with respect to their usability as excitation light sources for shifted excitation Raman difference spectroscopy (SERDS). For both types of devices for each wavelength, output powers up to 215 mW were measured. A stable spectral distance between the laser emissions of the two resonator branches with the targeted value of 0.6 nm, i.e. 10 cm-1, is observed. In the case of the mini-array up to an output power of about 70 mW, the device shows single-mode operation. Although at higher power levels, mode hops and multi-mode operation occur, the emission width smaller than 0.15 nm still meets the requirements for Raman measurements of solids and liquids. Over the whole working range, the spectral distance between the two wavelengths is approximately constant with 0.62 nm. The near field shows two emission spots according to the dimension of the RW and their processed distance of 20 µm. The Y-branch laser shows single-mode operation up to 150 mW with a narrow spectral emission width. At higher powers also, multi-mode operation with an emission width of 0.15 nm occurs. The nearly diffraction-limited emission comes from one output aperture; the far-field emission shows a pronounced asymmetry between the two branches. Both types of devices fulfil the spectral requirements from Raman spectroscopy and SERDS up to 215 mW output power.

  7. The Buffalo Model: Shifting the Focus of Clinical Licensure Exams in Dentistry to Address Ethical Concerns Regarding Patient Care.

    PubMed

    Gambacorta, Joseph E; Glick, Michael; Anker, Ashley E; Shampaine, Guy S

    2016-06-01

    Most jurisdictions grant dental licensure to graduating students following successful completion of a clinical exam. Testing agencies, which are independent of dental schools, nevertheless conduct their exams at school facilities. Patient participation in these exams raises ethical concerns regarding such issues as unlicensed providers' performing irreversible procedures with minimal supervision and graduates' limited accessibility to provide follow-up treatment. To address these concerns, a collaborative effort between University at Buffalo School of Dental Medicine faculty and testing agency personnel was launched. The aims of this article are to describe the development and implementation of the resulting Buffalo Model, to highlight ethical advantages in its application, and to identify areas of improvement to be addressed in future iterations. With the Buffalo Model, modifications were made to the traditional exam format in order to integrate the exam into the school curriculum, enabling candidates to take it at various points during their fourth year. In addition, after calibration of school faculty members, 98.5% of cases verified by faculty were accepted by the Commission on Dental Competency Assessments for use in the exam. In two cases, restorative treatment completed during the exam did not meet the school's competency standard. This new approach ameliorates ethical concerns associated with clinical licensure exams because treatment is provided only to patients of record within a sequenced treatment plan and timely and appropriate treatment is provided to all patients. The results of this first year of implementation also suggest that calibrated faculty members will not show bias in the selection of lesions or competency evaluations of candidates. PMID:27251344

  8. The influence of hyperfine structure and isotope shift on the detection of Rb by 2 f-wavelength modulation diode laser absorption spectrometry—experimental verification of simulations

    NASA Astrophysics Data System (ADS)

    Gustafsson, Jörgen; Axner, Ove

    1998-12-01

    This work presents an experimental verification of a previously developed methodology for simulation of the 2 f-wavelength modulation diode laser absorption spectrometry technique (2 f-WM-DLAS) when the influence of hyperfine structure, isotope shift and collisional broadening and shift of an atomic transition is taken into account [J. Gustafsson, D. Rojas and O. Axner, Spectrochim. Acta, 52B, 1937-1953 (1997)]. The pilot element in the simulations was Rb, detected at the 780 nm 5s 2S 1/2-5p 2P 3/2 transition, in low-pressure cells and atmospheric-pressure reservoirs (e.g. graphite furnaces). This experimental investigation verifies that the simulations are able to predict, with good accuracy, experimental 2 f-WM signals from Rb atoms under both low-pressure, room-temperature conditions and atmospheric-pressure, high-temperature conditions. This implies that the previously published simulation methodology can be used for predicting and optimizing 2 f-WM signal strengths and shapes from Rb atoms (and thereby presumably also from other atoms) under a variety of pressure and temperature conditions.

  9. Wavelength-shifting fiber signal readout from Transparent RUbber SheeT (TRUST) type LiCaAlF6 neutron scintillator

    NASA Astrophysics Data System (ADS)

    Watanabe, Kenichi; Yamazaki, Takuya; Sugimoto, Dai; Yamazaki, Atsushi; Uritani, Akira; Iguchi, Tetsuo; Fukuda, Kentaro; Ishidu, Sumito; Yanagida, Takayuki; Fujimoto, Yutaka

    2015-06-01

    As an alternative to the standard 3He neutron detector, we are developing the Transparent RUbber SheeT type (TRUST) Eu doped LiCaAlF6 (Eu:LiCAF) scintillator. This type of neutron scintillator can easily be fabricated as a large area sheet. In order to take advantage of a large area detector, we try to readout scintillation photons using a wavelength-shifting fiber (WLSF) from a TRUST Eu:LiCAF scintillator. The TRUST Eu:LiCAF scintillator with the size of 50×50×5 mm3 was mounted on the WLSF plate and the end of the WLSFs was connected with a PMT. In order to reject high pulse height events induced in the WLSFs, we applied the pulse shape discrimination technique. The gamma-ray intrinsic and neutron absolute detection efficiency is evaluated to be 8.8×10-7 and 9×10-3 cps/ng Cf (2 m) for the TRUST Eu:LiCAF scintillator with the size of 50×50×5 mm3.

  10. Utilization of wavelength-shifting fibers coupled to ZnS(Ag) and plastic scintillator for simultaneous detection of alpha/beta particles

    NASA Astrophysics Data System (ADS)

    Ifergan, Y.; Dadon, S.; Israelashvili, I.; Osovizky, A.; Gonen, E.; Yehuda-Zada, Y.; Smadja, D.; Knafo, Y.; Ginzburg, D.; Kadmon, Y.; Cohen, Y.; Mazor, T.

    2015-06-01

    Low level radioactive surface contamination measurements require lightweight, large area and high efficiency detector. In most existing scintillation detectors there is a tradeoff between effective area and scintillation light collection. By using wavelength shifting (WLS) fibers the scintillation light may be collected efficiently also in a large area detector. In this study, WLS fibers were coupled to a beta sensitive plastic scintillator layer and to a alpha sensitive silver-activated zinc sulfide ZnS(Ag) layer for detecting both alpha and beta particles. The WLS fibers collect the scintillation light from the whole detector and transfer it to a single PMT. This first prototype unique configuration enables monitoring radioactive contaminated surfaces by both sides of the detector and provides high gamma rejection. In this paper, the detector structure, as well as the detector's measured linear response, will be described. The measured detection efficiency of 238Pu alpha particles (5.5 MeV) is ~63%. The measured detection efficiency for beta particles is ~89% for 90Sr-90Y (average energy of 195.8 keV, 934.8 keV), ~50% for 36Cl (average energy of 251.3 keV), and 35% for 137Cs (average energy of 156.8 keV).

  11. Measurement of wavelengths and lamb shifts for inner-shell transitions in Fe XVIII-XXIV. [from solar flare X-ray spectra

    NASA Technical Reports Server (NTRS)

    Seely, J. F.; Feldman, U.; Safronova, U. I.

    1986-01-01

    The wavelengths of inner-shell 1s-2p transitions in the ions Fe XVIII-XXIV have been measured in solar flare spectra recorded by the Naval Research Laboratory crystal spectrometer (SOLFLEX) on the Air Force P78-1 spacecraft. The measurements are compared with previous measurements and with recently calculated wavelengths. It is found that the measured wavelengths are systematically larger than the wavelengths calculated using the Z-expansion method by up to 0.65 mA. For the more highly charged ions, these differences can be attributed to the QED contributions to the transition energies that are not included in the Z-expansion calculations.

  12. Shifting scintillator neutron detector

    SciTech Connect

    Clonts, Lloyd G; Cooper, Ronald G; Crow, Jr., Morris Lowell; Hannah, Bruce W; Hodges, Jason P; Richards, John D; Riedel, Richard A

    2014-03-04

    Provided are sensors and methods for detecting thermal neutrons. Provided is an apparatus having a scintillator for absorbing a neutron, the scintillator having a back side for discharging a scintillation light of a first wavelength in response to the absorbed neutron, an array of wavelength-shifting fibers proximate to the back side of the scintillator for shifting the scintillation light of the first wavelength to light of a second wavelength, the wavelength-shifting fibers being disposed in a two-dimensional pattern and defining a plurality of scattering plane pixels where the wavelength-shifting fibers overlap, a plurality of photomultiplier tubes, in coded optical communication with the wavelength-shifting fibers, for converting the light of the second wavelength to an electronic signal, and a processor for processing the electronic signal to identify one of the plurality of scattering plane pixels as indicative of a position within the scintillator where the neutron was absorbed.

  13. Broadband ultrasound field mapping system using a wavelength tuned, optically scanned focused laser beam to address a Fabry Perot polymer film sensor.

    PubMed

    Zhang, Edward; Beard, Paul

    2006-07-01

    An optical system for rapidly mapping broad-band ultrasound fields with high spatial resolution has been developed. The transduction mechanism is based upon the detection of acoustically induced changes in the optical thickness of a thin polymer film acting as a Fabry Perot sensing interferometer (FPI). By using a PC-controlled galvanometer mirror to line-scan a focused laser beam over the surface of the FPI, and a wavelength-tuned phase bias control system to optimally set the FPI working point, a notional 1D ultrasound array was synthesized. This system enabled ultrasound fields to be mapped over an aperture of 40 mm, in 50-microm steps with an optically defined element size of 50 microm and an acquisition time of 50 ms per step. The sensor comprised a 38-microm polymer film FPI which was directly vacuum-deposited onto an impedance-matched polycarbonate backing stub. The -3 dB acoustic bandwidth of the sensor was 300 kHz to 28 MHz and the peak noise-equivalent-pressure was 10 kPa over a 20-MHz measurement bandwidth. To demonstrate the system, the outputs of various planar and focused pulsed ultrasound transducers with operating frequencies in the range 3.5 to 20 MHz were mapped. It is considered that this approach offers a practical and inexpensive alternative to piezoelectric-based arrays and scanning systems for rapid transducer field characterization and biomedical and industrial ultrasonic imaging applications. PMID:16889340

  14. Demystifying fluorine chemical shifts: electronic structure calculations address origins of seemingly anomalous (19)F-NMR spectra of fluorohistidine isomers and analogues.

    PubMed

    Kasireddy, Chandana; Bann, James G; Mitchell-Koch, Katie R

    2015-11-11

    Fluorine NMR spectroscopy is a powerful tool for studying biomolecular structure, dynamics, and ligand binding, yet the origins of (19)F chemical shifts are not well understood. Herein, we use electronic structure calculations to describe the changes in (19)F chemical shifts of 2F- and 4F-histidine/(5-methyl)-imidazole upon acid titration. While the protonation of the 2F species results in a deshielded chemical shift, protonation of the 4F isomer results in an opposite, shielded chemical shift. The deshielding of 2F-histidine/(5-methyl)-imidazole upon protonation can be rationalized by concomitant decreases in charge density on fluorine and a reduced dipole moment. These correlations do not hold for 4F-histidine/(5-methyl)-imidazole, however. Molecular orbital calculations reveal that for the 4F species, there are no lone pair electrons on the fluorine until protonation. Analysis of a series of 4F-imidazole analogues, all with delocalized fluorine electron density, indicates that the deshielding of (19)F chemical shifts through substituent effects correlates with increased C-F bond polarity. In summary, the delocalization of fluorine electrons in the neutral 4F species, with gain of a lone pair upon protonation may help explain the difficulty in developing a predictive framework for fluorine chemical shifts. Ideas debated by chemists over 40 years ago, regarding fluorine's complex electronic effects, are shown to have relevance for understanding and predicting fluorine NMR spectra. PMID:26524669

  15. Using Dual-wavelength Fiber Bragg Gratings for Temperature and Strain Sensing at Cryogenic Temperature

    NASA Technical Reports Server (NTRS)

    Wu, Meng-Chou; Prosser, William H.; Rogowski, Robert S.; DeHaven, Stanton L.

    2003-01-01

    By using dual-wavelength fiber-optic Bragg gratings, a new technique has been developed for sensing both temperature and strain simultaneously in cryogenic temperature range. Two Bragg gratings with different wavelengths were inscribed at the same location in an optical fiber to form a dual-wavelength sensor. By measuring the wavelength shifts that resulted from the fiber being subjected to different temperatures and strains, the wavelength-dependent thermo-optic coefficients and photoelastic coefficients of the fiber were determined. These coefficients were used to construct the elements of the K matrix, which enables to determine inversely the strain and temperature changes by measuring the wavelength shifts of the dual-wavelength Bragg grating. In this study, measurements were made over the temperature range from room temperature down to about 10 K, addressing much of the low temperature range of cryogenic tanks. A structure transition of the optical fiber during the temperature change was found from about 70 K to 140 K. This transition caused splitting of the waveforms characterizing the Bragg gratings, and the determination of wavelength shifts was consequently complicated. Several alternatives are proposed to resolve this problem. The effectiveness and sensitivities of these measurements in different temperature ranges are discussed. The separation of two wavelengths for the dual-wavelength Bragg grating has been widened to increase the sensitivities of measurement; however, this separation can still be covered in the scanning range from single scanning laser.

  16. Simultaneous Temperature and Strain Sensing for Cryogenic Applications Using Dual-Wavelength Fiber Bragg Gratings

    NASA Technical Reports Server (NTRS)

    Wu, Meng-Chou; Prosser, William H.

    2003-01-01

    A new technique has been developed for sensing both temperature and strain simultaneously by using dual-wavelength fiber-optic Bragg gratings. Two Bragg gratings with different wavelengths were inscribed at the same location in an optical fiber to form a sensor. By measuring the wavelength shifts that resulted from the fiber being subjected to different temperatures and strains, the wavelength-dependent thermo-optic coefficients and photoelastic coefficients of the fiber were determined. This enables the simultaneous measurement of temperature and strain. In this study, measurements were made over the temperature range from room temperature down to about 10 K, addressing much of the low temperature range of cryogenic tanks. A structure transition of the optical fiber during the temperature change was found. This transition caused splitting of the waveforms characterizing the Bragg gratings, and the determination of wavelength shifts was consequently complicated. The effectiveness and sensitivities of these measurements in different temperature ranges are also discussed.

  17. High-power frequency comb in the range of 2-2.15  μm based on a holmium fiber amplifier seeded by wavelength-shifted Raman solitons from an erbium-fiber laser.

    PubMed

    Coluccelli, Nicola; Cassinerio, Marco; Gambetta, Alessio; Laporta, Paolo; Galzerano, Gianluca

    2014-03-15

    We demonstrate a room-temperature high-power frequency comb source covering the spectral region from 2 to 2.15 μm. The source is based on a femtosecond erbium-fiber laser operating at 1.55 μm with a repetition rate of 250 MHz, wavelength-shifted up to 2.06 μm by the solitonic Raman effect, seeding a large-mode-area holmium (Ho) fiber amplifier pumped by a thulium (Tm) fiber laser emitting at 1.94 μm. The frequency comb has an integrated power of 2 W, with overall power fluctuations as low as 0.3%. The beatnote between the comb and a high-spectral-purity, single-frequency Tm-Ho laser has a linewidth of 32 kHz over 1 ms observation time, with a signal-to-noise ratio in excess of 30 dB. PMID:24690863

  18. Stark shift of the absorption spectra in Ge/Ge1-xSnx/Ge type-I single QW cell for mid-wavelength infra-red modulators

    NASA Astrophysics Data System (ADS)

    Yahyaoui, N.; Sfina, N.; Lazzari, J.-L.; Bournel, A.; Said, M.

    2015-09-01

    For mid-wavelength infra-red (MWIR) modulation or detection applications, we propose α-Sn rich Ge/Ge1-xSnx/Ge a type-I single quantum wells (SQW) partially strain compensated on Ge1-ySny relaxed layers grown onto (0 0 1)-oriented Ge substrate. Such elementary cells with W-like potential profiles of conduction and valence bands have been modeled by solving the one-dimensional Schrödinger equation under an applied external electrical field. First, strain effects on electrons, heavy holes (hh) and light holes (lh) energy bands for strained/relaxed Ge1-xSnx/Ge1-ySny heterointerfaces are investigated using the model-solid theory in the whole ranges (0 ⩽ x, y ⩽ 1) of Sn compositions. From the obtained band-discontinuities, band gaps and effective masses, Ge1-ySny/Ge/Ge0.80Sn0.20/Ge/Ge1-ySny cells are computed as a function of the Ge0.80Sn0.20 well width for three compositions of the Ge1-ySny buffer layer (y = 0.05, 0.07 and 0.09) in order to get the optimum quantum confinement of electrons and holes levels while keeping a reasonable amount of averaged strain in the cell. The electric field effect on the absorption spectra is given. An absorption coefficient in the 6× to 3 × 103 cm-1 range is reasonably obtained for a SQW at room temperature with a rather large Stark shift of the direct transition between 0.46 and 0.38 eV (i.e., λ = 3.26-2.70 μm) at large external fields (50 kV/cm). These characteristics are attractive for the design of MWIR optical modulators.

  19. Instrument Measures Shift In Focus

    NASA Technical Reports Server (NTRS)

    Steimle, Lawrence J.

    1992-01-01

    Optical components tested at wavelengths from ultraviolet to infrared. Focus-shift-measuring instrument easy to use. Operated in lighted room, without having to make delicate adjustments while peering through microscope. Measures distance along which focal point of converging beam of light shifted by introduction of nominally plane parallel optical component into beam. Intended primarily for measuring focus shifts produced by windows and filters at wavelengths from 120 to 1,100 nanometers. Portable, compact, and relatively inexpensive for degree of precision.

  20. Addressing healthcare.

    PubMed

    Daly, Rich

    2013-02-11

    Though President Barack Obama has rarely made healthcare references in his State of the Union addresses, health policy experts are hoping he changes that strategy this year. "The question is: Will he say anything? You would hope that he would, given that that was the major issue he started his presidency with," says Dr. James Weinstein, left, of the Dartmouth-Hitchcock health system. PMID:23487896

  1. Wavelength-division multiplexing of nano-optomechanical doubly clamped beam systems.

    PubMed

    Sauer, Vincent T K; Diao, Zhu; Freeman, Mark R; Hiebert, Wayne K

    2015-05-01

    Wavelength-division multiplexing is demonstrated for a set of two doubly clamped beams. Using a single input/output waveguide in a nanophotonic detection system, the two mechanical beams are independently addressable using different wavelength channels as determined by their respective racetrack resonator detection cavities. The two cavities slightly overlap, which also enables the mechanical frequency of both beams to be detected simultaneously with a single wavelength. Finally, to physically map which wavelength channel corresponds to which specific device, a heating laser is targeted individually on each beam to create a reversible mechanical frequency shift. This multiplexing method would allow for the simpler detection of large arrays of nanomechanical devices in a sensor system. PMID:25927755

  2. Dual-wavelength erbium-doped fiber laser with tunable wavelength spacing using a twin core fiber-based filter

    NASA Astrophysics Data System (ADS)

    Yin, Guolu; Lou, Shuqin; Wang, Xin; Han, Bolin

    2014-05-01

    A dual-wavelength erbium-doped fiber laser with tunable wavelength spacing was proposed and experimentally demonstrated by using a twin core fiber (TCF)-based filter. Benefiting from the polarization dependence of the TCF-based filter, the laser operated in dual-wavelength oscillation with two orthogonal polarization states. By adjusting the polarization controller, the wavelength spacing was tuned from 0.1 nm to 1.2 nm without shifting the centre position of the two wavelengths. By stretching the TCF, the two wavelengths were simultaneously tuned with fixed wavelength spacing. Such a dual-wavelength fiber laser could find applications in optical fiber sensors and microwave photonics generation.

  3. Inaugural address

    NASA Astrophysics Data System (ADS)

    Joshi, P. S.

    2014-03-01

    From jets to cosmos to cosmic censorship P S Joshi Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India E-mail: psj@tifr.res.in 1. Introduction At the outset, I should like to acknowledge that part of the title above, which tries to capture the main flavour of this meeting, and has been borrowed from one of the plenary talks at the conference. When we set out to make the programme for the conference, we thought of beginning with observations on the Universe, but then we certainly wanted to go further and address deeper questions, which were at the very foundations of our inquiry, and understanding on the nature and structure of the Universe. I believe, we succeeded to a good extent, and it is all here for you in the form of these Conference Proceedings, which have been aptly titled as 'Vishwa Mimansa', which could be possibly translated as 'Analysis of the Universe'! It is my great pleasure and privilege to welcome you all to the ICGC-2011 meeting at Goa. The International Conference on Gravitation and Cosmology (ICGC) series of meetings are being organized by the Indian Association for General Relativity and Gravitation (IAGRG), and the first such meeting was planned and conducted in Goa in 1987, with subsequent meetings taking place at a duration of about four years at various locations in India. So, it was thought appropriate to return to Goa to celebrate the 25 years of the ICGC meetings. The recollections from that first meeting have been recorded elsewhere here in these Proceedings. The research and teaching on gravitation and cosmology was initiated quite early in India, by V V Narlikar at the Banares Hindu University, and by N R Sen in Kolkata in the 1930s. In course of time, this activity grew and gained momentum, and in early 1969, at the felicitation held for the 60 years of V V Narlikar at a conference in Ahmedabad, P C Vaidya proposed the formation of the IAGRG society, with V V Narlikar being the first President. This

  4. Opening addresses.

    PubMed

    Chukudebelu, W O; Lucas, A O; Ransome-kuti, O; Akinla, O; Obayi, G U

    1988-01-01

    The theme of the 3rd International Conference of the Society of Gynecology and Obstetrics of Nigeria (SOGON) held October 26, 1986 in Enugu was maternal morbidity and mortality in Africa. The opening addresses emphasize the high maternal mortality rate in Africa and SOGON's dedication to promoting women's health and welfare. In order to reduce maternal mortality, the scope of this problem must be made evident by gathering accurate mortality rates through maternity care monitoring and auditing. Governments, health professionals, educators, behavioral scientists, and communication specialists have a responsibility to improve maternal health services in this country. By making the population aware of this problem through education, measures can be taken to reduce the presently high maternal mortality rates. Nigerian women are physically unprepared for childbirth; therefore, balanced diets and disease prevention should be promoted. Since about 40% of deliveries are unmanaged, training for traditional birth attendants should be provided. Furthermore, family planning programs should discourage teenage pregnancies, encourage birth spacing and small families, and promote the use of family planning techniques among men. The problem of child bearing and rearing accompanied by hard work should also be investigated. For practices to change so that maternal mortality rates can be reduced, attitudes must be changed such that the current rates are viewed as unacceptable. PMID:12179275

  5. Opening Address

    NASA Astrophysics Data System (ADS)

    Yamada, T.

    2014-12-01

    Ladies and Gentlemen, it is my great honor and pleasure to present an opening address of the 3rd International Workshop on "State of the Art in Nuclear Cluster Physics"(SOTANCP3). On the behalf of the organizing committee, I certainly welcome all your visits to KGU Kannai Media Center belonging to Kanto Gakuin University, and stay in Yokohama. In particular, to whom come from abroad more than 17 countries, I would appreciate your participations after long long trips from your homeland to Yokohama. The first international workshop on "State of the Art in Nuclear Cluster Physics", called SOTANCP, was held in Strasbourg, France, in 2008, and the second one was held in Brussels, Belgium, in 2010. Then the third workshop is now held in Yokohama. In this period, we had the traditional 10th cluster conference in Debrecen, Hungary, in 2012. Thus we have the traditional cluster conference and SOTANCP, one after another, every two years. This obviously shows our field of nuclear cluster physics is very active and flourishing. It is for the first time in about 10 years to hold the international workshop on nuclear cluster physics in Japan, because the last cluster conference held in Japan was in Nara in 2003, about 10 years ago. The president in Nara conference was Prof. K. Ikeda, and the chairpersons were Prof. H. Horiuchi and Prof. I. Tanihata. I think, quite a lot of persons in this room had participated at the Nara conference. Since then, about ten years passed. So, this workshop has profound significance for our Japanese colleagues. The subjects of this workshop are to discuss "the state of the art in nuclear cluster physics" and also discuss the prospect of this field. In a couple of years, we saw significant progresses of this field both in theory and in experiment, which have brought better and new understandings on the clustering aspects in stable and unstable nuclei. I think, the concept of clustering has been more important than ever. This is true also in the

  6. Presidential address.

    PubMed

    Vohra, U

    1993-07-01

    The Secretary of India's Ministry of Health and Family Welfare serves as Chair of the Executive Council of the International Institute for Population Sciences in Bombay. She addressed its 35th convocation in 1993. Global population stands at 5.43 billion and increases by about 90 million people each year. 84 million of these new people are born in developing countries. India contributes 17 million new people annually. The annual population growth rate in India is about 2%. Its population size will probably surpass 1 billion by the 2000. High population growth rates are a leading obstacle to socioeconomic development in developing countries. Governments of many developing countries recognize this problem and have expanded their family planning programs to stabilize population growth. Asian countries that have done so and have completed the fertility transition include China, Japan, Singapore, South Korea, and Thailand. Burma, Malaysia, North Korea, Sri Lanka, and Vietnam have not yet completed the transition. Afghanistan, Bangladesh, Iran, Nepal, and Pakistan are half-way through the transition. High population growth rates put pressure on land by fragmenting finite land resources, increasing the number of landless laborers and unemployment, and by causing considerable rural-urban migration. All these factors bring about social stress and burden civic services. India has reduced its total fertility rate from 5.2 to 3.9 between 1971 and 1991. Some Indian states have already achieved replacement fertility. Considerable disparity in socioeconomic development exists among states and districts. For example, the states of Bihar, Madhya Pradesh, Rajasthan, and Uttar Pradesh have female literacy rates lower than 27%, while that for Kerala is 87%. Overall, infant mortality has fallen from 110 to 80 between 1981 and 1990. In Uttar Pradesh, it has fallen from 150 to 98, while it is at 17 in Kerala. India needs innovative approaches to increase contraceptive prevalence rates

  7. Welcome Address

    NASA Astrophysics Data System (ADS)

    Kiku, H.

    2014-12-01

    Ladies and Gentlemen, It is an honor for me to present my welcome address in the 3rd International Workshop on "State of the Art in Nuclear Cluster Physics"(SOTANCP3), as the president of Kanto Gakuin University. Particularly to those from abroad more than 17 countries, I am very grateful for your participation after long long trips from your home to Yokohama. On the behalf of the Kanto Gakuin University, we certainly welcome your visit to our university and stay in Yokohama. First I would like to introduce Kanto Gakuin University briefly. Kanto Gakuin University, which is called KGU, traces its roots back to the Yokohama Baptist Seminary founded in 1884 in Yamate, Yokohama. The seminary's founder was Albert Arnold Bennett, alumnus of Brown University, who came to Japan from the United States to establish a theological seminary for cultivating and training Japanese missionaries. Now KGU is a major member of the Kanto Gakuin School Corporation, which is composed of two kindergartens, two primary schools, two junior high schools, two senior high schools as well as KGU. In this university, we have eight faculties with graduate school including Humanities, Economics, Law, Sciences and Engineering, Architecture and Environmental Design, Human and Environmental Studies, Nursing, and Law School. Over eleven thousands students are currently learning in our university. By the way, my major is the geotechnical engineering, and I belong to the faculty of Sciences and Engineering in my university. Prof. T. Yamada, here, is my colleague in the same faculty. I know that the nuclear physics is one of the most active academic fields in the world. In fact, about half of the participants, namely, more than 50 scientists, come from abroad in this conference. Moreover, I know that the nuclear physics is related to not only the other fundamental physics such as the elementary particle physics and astrophysics but also chemistry, medical sciences, medical cares, and radiation metrology

  8. Shifting tools

    SciTech Connect

    Fisher, E.P.; Welch, W.R.

    1984-03-13

    An improved shifting tool connectable in a well tool string and useful to engage and position a slidable sleeve in a sliding sleeve device in a well flow conductor. The selectively profiled shifting tool keys provide better fit with and more contact area between keys and slidable sleeves. When the engaged slidable sleeve cannot be moved up and the shifting tool is not automatically disengaged, emergency disengagement means may be utilized by applying upward force to the shifting tool sufficient to shear pins and cause all keys to be cammed inwardly at both ends to completely disengage for removal of the shifting tool from the sliding sleeve device.

  9. Method of Controlling Lasing Wavelength(s)

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P. (Inventor); Murray, Keith E. (Inventor); Hutcheson, Ralph L. (Inventor)

    2000-01-01

    A method is provided to control the lasing wavelength of a laser material without changing or adjusting the mechanical components of a laser device, The rate at which the laser material is pumped with the pumping energy is controlled so that lasing occurs at one or more lasing wavelengths based on the rate. The lasing wavelengths are determined by transition lifetimes and/or energy transfer rates.

  10. Wavelength Anomalies in UV-Vis Spectrophotometry

    NASA Astrophysics Data System (ADS)

    Tellinghuisen, J.

    2012-06-01

    Commercial spectrophotometers are great tools for recording absorption spectra of low-to-moderate resolution and high photometic quality. However, in the case of at least one such instrument, the Shimadzu UV-2101PC (and by assumption, similar Shimadzu models), the wavelength accuracy may not match the photometric accuracy. In fact the wavelength varies with slit width, spectral sampling interval, and even the specified range, with a smoothing algorithm invoked any time the spectrum includes more than 65 sampled wavelengths. This behavior appears not to be documented anywhere, but it has been present for at least 20 years and persists even in the latest software available to run the instrument. The wavelength shifts can be as large as 1 nm, so for applications where wavelength accuracy better than this is important, wavelength calibration must be done with care to ensure that the results are valid for the parameters used to record the target spectra.

  11. Shifting Attention

    ERIC Educational Resources Information Center

    Ingram, Jenni

    2014-01-01

    This article examines the shifts in attention and focus as one teacher introduces and explains an image that represents the processes involved in a numeric problem that his students have been working on. This paper takes a micro-analytic approach to examine how the focus of attention shifts through what the teacher and students do and say in the…

  12. Shifting Up a Gear.

    ERIC Educational Resources Information Center

    Palmer, Martin

    1997-01-01

    Shift workers are often excluded from educational opportunities on and off the job. General education and leisure learning needs are addressed less than job-specific training needs. Providers should consider open/distance learning, creative marketing, targeted funding, and consortia of employer-developed programs. (SK)

  13. Dual Wavelength Lasers

    NASA Technical Reports Server (NTRS)

    Walsh, Brian M.

    2010-01-01

    Dual wavelength lasers are discussed, covering fundamental aspects on the spectroscopy and laser dynamics of these systems. Results on Tm:Ho:Er:YAG dual wavelength laser action (Ho at 2.1 m and Er at 2.9 m) as well as Nd:YAG (1.06 and 1.3 m) are presented as examples of such dual wavelength systems. Dual wavelength lasers are not common, but there are criteria that govern their behavior. Based on experimental studies demonstrating simultaneous dual wavelength lasing, some general conclusions regarding the successful operation of multi-wavelength lasers can be made.

  14. Fluid Shifts

    NASA Technical Reports Server (NTRS)

    Stenger, Michael B.; Hargens, Alan R.; Dulchavsky, Scott A.; Ebert, Douglas J.; Lee, Stuart M. C.; Laurie, Steven S.; Garcia, Kathleen M.; Sargsyan, Ashot E.; Martin, David S.; Liu, John; Macias, Brandon R.; Arbeille, Philippe; Danielson, Richard; Chang, Douglas; Gunga, Hanns-Christian; Johnston, Smith L.; Westby, Christian M.; Ploutz-Snyder, Robert J.; Smith, Scott M.

    2016-01-01

    We hypothesize that microgravity-induced cephalad fluid shifts elevate intracranial pressure (ICP) and contribute to VIIP. We will test this hypothesis and a possible countermeasure in ISS astronauts.

  15. Diffuse optical tomography using wavelength-swept laser

    NASA Astrophysics Data System (ADS)

    Cho, Jaedu; Lim, Gukbin; Jeong, Myung Yung; Nalcioglu, Orhan; Kim, Chang-Seok; Gulsen, Gultekin

    2013-03-01

    The design and implementation of a diffuse optical tomography system using wavelength-swept laser is described. Rapid and continuous wavelength change is utilized for high speed spectral scanning from 775 nm to 875 nm optical wavelength. Maximum speed of wavelength repetition is 1 kHz and averaged output power of the wavelength-swept laser is 20 mW. A fiber-optic Sagnac interferometer is incorporated to conduct passive amplitude modulation of the wavelength-swept laser. It is shown that the wavelength-swept laser can be successfully incorporated to the DOT system, and then reduces wavelength-shifting time and hardware complexity in multi-wavelength DOT implementation.

  16. Ambiguous red shifts

    NASA Astrophysics Data System (ADS)

    Wulfman, Carl E.

    2010-12-01

    A one-parameter conformal invariance of Maxwell's equations allows the wavelengths of electromagnetic waves to change as they propagate, and do so even in otherwise field-free space. This produces an ambiguity in interpretations of stellar red shifts. Experiments that will determine the value of the group parameter, and thereby remove the ambiguity, are proposed. They are based on an analysis of the anomalous frequency shifts uncovered in the Pioneer 10 and 11 spacecraft studies, and physical interpretation of an isomorphism discovered by E.L. Hill. If the group parameter is found to be non-zero, Hubble's relations will have to be reinterpreted and space-time metrics will have to be altered. The cosmological consequences of the transformations are even more extensive because, though they change frequencies they do not alter the energy and momentum conservation laws of classical and quantum-electrodynamical fields established by Cunningham and by Białynicki-Birula.

  17. Fluid Shifts

    NASA Technical Reports Server (NTRS)

    Stenger, M. B.; Hargens, A.; Dulchavsky, S.; Ebert, D.; Lee, S.; Laurie, S.; Garcia, K.; Sargsyan, A.; Martin, D.; Lui, J.; Macias, B.; Arbeille, P.; Danielson, R.; Chang, D.; Gunga, H.; Johnston, S.; Westby, C.; Ribeiro, L.; Ploutz-Snyder, R.; Smith, S.

    2015-01-01

    INTRODUCTION: Mechanisms responsible for the ocular structural and functional changes that characterize the visual impairment and intracranial pressure (ICP) syndrome (VIIP) are unclear, but hypothesized to be secondary to the cephalad fluid shift experienced in spaceflight. This study will relate the fluid distribution and compartmentalization associated with long-duration spaceflight with VIIP symptoms. We also seek to determine whether the magnitude of fluid shifts during spaceflight, as well as the VIIP-related effects of those shifts, can be predicted preflight with acute hemodynamic manipulations, and also if lower body negative pressure (LBNP) can reverse the VIIP effects. METHODS: Physiologic variables will be examined pre-, in- and post-flight in 10 International Space Station crewmembers including: fluid compartmentalization (D2O and NaBr dilution); interstitial tissue thickness (ultrasound); vascular dimensions and dynamics (ultrasound and MRI (including cerebrospinal fluid pulsatility)); ocular measures (optical coherence tomography, intraocular pressure, ultrasound); and ICP measures (tympanic membrane displacement, otoacoustic emissions). Pre- and post-flight measures will be assessed while upright, supine and during 15 deg head-down tilt (HDT). In-flight measures will occur early and late during 6 or 12 month missions. LBNP will be evaluated as a countermeasure during HDT and during spaceflight. RESULTS: The first two crewmembers are in the preflight testing phase. Preliminary results characterize the acute fluid shifts experienced from upright, to supine and HDT postures (increased stroke volume, jugular dimensions and measures of ICP) which are reversed with 25 millimeters Hg LBNP. DISCUSSION: Initial results indicate that acute cephalad fluid shifts may be related to VIIP symptoms, but also may be reversible by LBNP. The effect of a chronic fluid shift has yet to be evaluated. Learning Objectives: Current spaceflight VIIP research is described

  18. Fluid Shifts

    NASA Technical Reports Server (NTRS)

    Stenger, M.; Hargens, A.; Dulchavsky, S.; Ebert, D.; Lee, S.; Lauriie, S.; Garcia, K.; Sargsyan, A.; Martin, D.; Ribeiro, L.; Lui, J.; Macias, B.; Arbeille, P.; Danielson, R.; Chang, D.; Johnston, S.; Ploutz-Snyder, R.; Smith, S.

    2016-01-01

    NASA is focusing on long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low-Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but more than 50% of ISS astronauts experienced more profound, chronic changes with objective structural and functional findings such as papilledema and choroidal folds. Globe flattening, optic nerve sheath dilation, and optic nerve tortuosity also are apparent. This pattern is referred to as the visual impairment and intracranial pressure (VIIP) syndrome. VIIP signs and symptoms, as well as postflight lumbar puncture data, suggest that elevated intracranial pressure (ICP) may be associated with the spaceflight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration spaceflight, and to correlate these findings with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during spaceflight, as well as the VIIP-related effects of those shifts, is predicted by the crewmember's preflight conditions and responses to acute hemodynamic manipulations (such as head-down tilt). Lastly, we will evaluate the patterns of fluid distribution in ISS astronauts during acute reversal of fluid shifts through application of lower body negative pressure (LBNP) interventions to characterize and explain general and individual responses. METHODS: We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the Figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, calcaneus tissue thickness (by

  19. Optimum wavelengths for two color ranging

    NASA Technical Reports Server (NTRS)

    Degnan, John J.

    1993-01-01

    The range uncertainties associated with the refractive atmosphere can be mitigated by the technique of two color, or dual wavelength, ranging. The precision of the differential time of flight (DTOF) measurement depends on the atmospheric dispersion between the two wavelengths, the received pulsewidths and photoelectron counts, and on the amount of temporal averaging. In general, the transmitted wavelengths are not independently chosen but instead are generated via nonlinear optics techniques (harmonic crystals, Raman scattering, etc.) which also determine their relative pulsewidths. The mean received photoelectrons at each wavelength are calculated via the familiar radar link equation which contains several wavelength dependent parameters. By collecting the various wavelength dependent terms, one can define a wavelength figure of merit for a two color laser ranging system. In this paper, we apply the wavelength figure of merit to the case of an extremely clear atmosphere and draw several conclusions regarding the relative merits of fundamental-second harmonic, fundamental-third harmonic, second-third harmonic, and Raman two color systems. We find that, in spite of the larger dispersion between wavelengths, fundamental-third harmonic systems have the lowest figure of merit due to a combination of poor detector performance at the fundamental and poor atmospheric transmission at the third harmonic. The fundamental-second harmonic systems (approximately 700 nm and 350 nm) have the highest figure of merit, but second-third harmonic systems, using fundamental transmitters near 1000 nm, are a close second. Raman-shifted transmitters appear to offer no advantage over harmonic systems because of the relatively small wavelength separation that can be achieved in light gases such as hydrogen and the lack of good ultrashort pulse transmitters with an optimum fundamental wavelength near 400 nm.

  20. Wavelength independent interferometer

    NASA Technical Reports Server (NTRS)

    Hochberg, Eric B. (Inventor); Page, Norman A. (Inventor)

    1991-01-01

    A polychromatic interferometer utilizing a plurality of parabolic reflective surfaces to properly preserve the fidelity of light wavefronts irrespective of their wavelengths as they pass through the instrument is disclosed. A preferred embodiment of the invention utilizes an optical train which comprises three off-axis parabolas arranged in conjunction with a beam-splitter and a reference mirror to form a Twyman-Green interferometer. An illumination subsystem is provided and comprises a pair of lasers at different preselected wavelengths in the visible spectrum. The output light of the two lasers is coaxially combined by means of a plurality of reflectors and a grating beam combiner to form a single light source at the focal point of the first parabolic reflection surface which acts as a beam collimator for the rest of the optical train. By using visible light having two distinct wavelengths, the present invention provides a long equivalent wavelength interferogram which operates at visible light wherein the effective wavelength is equal to the product of the wavelengths of the two laser sources divided by their difference in wavelength. As a result, the invention provides the advantages of what amounts to long wavelength interferometry but without incurring the disadvantage of the negligible reflection coefficient of the human eye to long wavelength frequencies which would otherwise defeat any attempt to form an interferogram at that low frequency using only one light source.

  1. Wavelength Swept Lasers

    NASA Astrophysics Data System (ADS)

    Yun, Seok Hyun; Bouma, Brett E.

    In optical interferometric metrology, the wavelength of light serves as a reference for length. At a given optical wavelength, an interference signal varies as a sinusoidal function of distance with a period equal to the wavelength. Although this approach offers unrivaled precision, the periodic signal results in a 2π ambiguity for measurement of lengths greater than one wavelength. In optical coherence tomography (OCT), one wishes to determine light scattering distances and distribution within a sample, but without the ambiguity. To accomplish this, OCT is based on interferometry using many optical wavelengths, each serving as a "ruler" with different periodicities. OCT traditionally has used broadband light sources providing a wide range of wavelengths, all simultaneously. Alternatively, a tunable light source emitting one wavelength at a time, rapidly swept over a broad spectral range, can also be used to achieve the absolute ranging capability in OCT. In this chapter, we describe a technical overview of these new emerging sources. We begin with a discussion general specifications of these light sources, the review basic fundamentals of laser and wavelength tuning. Finally, we discuss the principles of various techniques developed to date for high-speed and wide tuning range.

  2. Reduction of initial collision effects by adiabatic expansion in soliton wavelength-division multiplexed systems

    NASA Astrophysics Data System (ADS)

    Kumar, Shiva; Hasegawa, Akira

    1996-12-01

    Properly designed adiabatic expansion of soliton reduces permanent frequency shifts of wavelength-division multiplexed solitons caused by initial overlap. The scheme combined with a dispersion-managed transmission line provides solutions to soliton wavelength-division multiplexing problems.

  3. Fluid Shifts

    NASA Technical Reports Server (NTRS)

    Stenger, Michael; Hargens, A.; Dulchavsky, S.; Ebert, D.; Lee, S.; Sargsyan, A.; Martin, D.; Lui, J.; Macias, B.; Arbeille, P.; Platts, S.

    2014-01-01

    NASA is focusing on long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but more than 30% of ISS astronauts experience more profound, chronic changes with objective structural and functional findings such as papilledema and choroidal folds. Globe flattening, optic nerve sheath dilation, and optic nerve tortuosity also are apparent. This pattern is referred to as the visual impairment and intracranial pressure (VIIP) syndrome. VIIP signs and symptoms, as well as postflight lumbar puncture data, suggest that elevated intracranial pressure (ICP) may be associated with the space flight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration space flight, and to correlate these findings with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during space flight, as well as the VIIP-related effects of those shifts, is predicted by the crewmember's pre-flight condition and responses to acute hemodynamic manipulations (such as head-down tilt). Lastly, we will evaluate the patterns of fluid distribution in ISS astronauts during acute reversal of fluid shifts through application of lower body negative pressure (LBNP) interventions to characterize and explain general and individual responses. We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the Figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, calcaneus tissue thickness (by ultrasound

  4. Experimental verification of acoustic trace wavelength enhancement.

    PubMed

    Cray, Benjamin A

    2015-12-01

    Directivity is essentially a measure of a sonar array's beamwidth that can be obtained in a spherically isotropic ambient noise field; narrow array mainbeam widths are more directive than broader mainbeam widths. For common sonar systems, the directivity factor (or directivity index) is directly proportional to the ratio of an incident acoustic trace wavelength to the sonar array's physical length (which is always constrained). Increasing this ratio, by creating additional trace wavelengths for a fixed array length, will increase array directivity. Embedding periodic structures within an array generates Bragg scattering of the incident acoustic plane wave along the array's surface. The Bragg scattered propagating waves are shifted in a precise manner and create shorter wavelength replicas of the original acoustic trace wavelength. These replicated trace wavelengths (which contain identical signal arrival information) increase an array's wavelength to length ratio and thus directivity. Therefore, a smaller array, in theory, can have the equivalent directivity of a much larger array. Measurements completed in January 2015 at the Naval Undersea Warfare Center's Acoustic Test Facility, in Newport, RI, verified, near perfectly, these replicated, shorter, trace wavelengths. PMID:26723331

  5. The Compton Effect Red Shift

    NASA Astrophysics Data System (ADS)

    Kierein, John

    2004-05-01

    In 1923 (Phil Mag. 46, 897.) A. H. Compton noted that the Compton effect produces a red shift for all wavelengths when the scattered electron is free and not bound to an atom or molecule. He suggested that the red shift in the visible spectrum at the limb of the sun is larger than that at the center due to the Compton effect from the greater number of free electrons in the sun's atmosphere along the line of sight. Kierein and Sharp (1968, Solar Physics 3, 450) quantified this and showed a good correlation of red shift observations with the variation in the number of these electrons along the line of sight from center to limb and suggested that the quasar red shift and cosmological red shift could be similarly explained. Grote Reber mapped and measured the background hectometric radiation and found it to be unexpectedly bright. In 1968 (J. Franklin Inst. 285,1), while describing these measurements and maps he explained this brightness as being due to the Compton effect causing the cosmological red shift and accelerating intergalactic electrons. The resulting universe is static. The predicted red shift from the Compton effect deviates from Hubble's law only at large red shifts.

  6. Short wavelength FELS

    SciTech Connect

    Sheffield, R.L.

    1991-01-01

    The generation of coherent ultraviolet and shorter wavelength light is presently limited to synchrotron sources. The recent progress in the development of brighter electron beams enables the use of much lower energy electron rf linacs to reach short-wavelengths than previously considered possible. This paper will summarize the present results obtained with synchrotron sources, review proposed short- wavelength FEL designs and then present a new design which is capable of over an order of magnitude higher power to the extreme ultraviolet. 17 refs., 10 figs.

  7. Long-wavelength shift and enhanced room temperature photoluminescence efficiency in GaAsSb/InGaAs/GaAs-based heterostructures emitting in the spectral range of 1.0–1.2 μm due to increased charge carrier's localization

    SciTech Connect

    Kryzhkov, D. I. Yablonsky, A. N.; Morozov, S. V.; Aleshkin, V. Ya.; Krasilnik, Z. F.; Zvonkov, B. N.; Vikhrova, O. V.

    2014-11-28

    In this work, a study of the photoluminescence (PL) temperature dependence in quantum well GaAs/GaAsSb and double quantum well InGaAs/GaAsSb/GaAs heterostructures grown by metalorganic chemical vapor deposition with different parameters of GaAsSb and InGaAs layers has been performed. It has been demonstrated that in double quantum well InGaAs/GaAsSb/GaAs heterostructures, a significant shift of the PL peak to a longer-wavelength region (up to 1.2 μm) and a considerable reduction in the PL thermal quenching in comparison with GaAs/GaAsSb structures can be obtained due to better localization of charge carriers in the double quantum well. For InGaAs/GaAsSb/GaAs heterostructures, an additional channel of radiative recombination with participation of the excited energy states in the quantum well, competing with the main ground-state radiative transition, has been revealed.

  8. Light detection and the wavelength shifter deposition in DEAP-3600

    NASA Astrophysics Data System (ADS)

    Broerman, B.; Retière, F.

    2016-02-01

    The Dark matter Experiment using Argon Pulse-shape discrimination (DEAP) uses liquid argon as a target medium to perform a direct-detection dark matter search. The 3600 kg liquid argon target volume is housed in a spherical acrylic vessel and viewed by a surrounding array of photomultiplier tubes. Ionizing particles in the argon volume produce scintillation light which must be wavelength shifted to be detected by the photomultiplier tubes. Argon scintillation and wavelength shifting, along with details on the application of the wavelength shifter to the inner surface of the acrylic vessel are presented.

  9. Terahertz phase microscopy in the sub-wavelength regime

    NASA Astrophysics Data System (ADS)

    Yi, Minwoo; Lee, Kanghee; Song, Jin-Dong; Ahn, Jaewook

    2012-04-01

    Gouy phase shift is a well-known behavior that occurs when a propagating light is focused, but its behavior in the sub-wavelength confinement is not yet known. Here, we report the theoretical and experimental study of the aperture-size dependency of the Gouy phase shift in the sub-wavelength diffraction regime. In experiments carried out with laser-induced terahertz (THz) wave emission from various semiconductor apertures, we demonstrate the use of Guoy phase shit for sub-wavelength THz microscopy.

  10. Dispersion management for wavelength-division-multiplexed soliton transmission.

    PubMed

    Forysiak, W; Devaney, J F; Smith, N J; Doran, N J

    1997-05-01

    Residual frequency shifts that are due to two-soliton collisions in stepwise exponentially dispersion-tapered fiber are calculated. Two-step dispersion profiles to minimize the frequency shifts and associated timing jitter are specifically identified. These profiles will improve the performance of wavelength-division-multiplexed soliton systems and permit operation with longer amplifier spans over an increased bandwidth. PMID:18185603

  11. Multi-wavelength fluorescence tomography

    NASA Astrophysics Data System (ADS)

    Kwong, Tiffany C.; Lo, Pei-An; Cho, Jaedu; Nouizi, Farouk; Chiang, Huihua K.; Kim, Chang-Seok; Gulsen, Gultekin

    2016-03-01

    The strong scattering and absorption of light in biological tissue makes it challenging to model the propagation of light, especially in deep tissue. This is especially true in fluorescent tomography, which aims to recover the internal fluorescence source distribution from the measured light intensities on the surface of the tissue. The inherently ill-posed and underdetermined nature of the inverse problem along with strong tissue scattering makes Fluorescence Tomography (FT) extremely challenging. Previously, multispectral detection fluorescent tomography (FT) has been shown to improve the image quality of FT by incorporating the spectral filtering of biological tissue to provide depth information to overcome the inherent absorption and scattering limitations. We investigate whether multi-wavelength fluorescent tomography can be used to distinguish the signals from multiple fluorophores with overlapping fluorescence spectrums using a unique near-infrared (NIR) swept laser. In this work, a small feasibility study was performed to see whether multi-wavelength FT can be used to detect subtle shifts in the absorption spectrum due to differences in fluorophore microenvironment.

  12. Multicolor Holography With Phase Shifting

    NASA Technical Reports Server (NTRS)

    Vikram, Chandra S.

    1996-01-01

    Prototype apparatus constructed to test feasibility of two-color holographic interferometric scheme in which data for reconstructing holographic wavefront obtained with help of phase-shifting technique. Provides two sets of data needed to solve equations for effects of temperature and concentration. Concept extended to holography at three or more wavelengths to measure three or more phenomena associated with significant variations in index of refraction

  13. Phase shifting diffraction interferometer

    DOEpatents

    Sommargren, Gary E.

    1996-01-01

    An interferometer which has the capability of measuring optical elements and systems with an accuracy of .lambda./1000 where .lambda. is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about .lambda./50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms.

  14. Phase shifting interferometer

    DOEpatents

    Sommargren, G.E.

    1999-08-03

    An interferometer is disclosed which has the capability of measuring optical elements and systems with an accuracy of {lambda}/1000 where {lambda} is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about {lambda}/50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. Whereas current interferometers illuminate the optic to be tested with an aberrated wavefront which also limits the accuracy of the measurement, this interferometer uses an essentially perfect spherical measurement wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms. 11 figs.

  15. Phase shifting interferometer

    DOEpatents

    Sommargren, Gary E.

    1999-01-01

    An interferometer which has the capability of measuring optical elements and systems with an accuracy of .lambda./1000 where .lambda. is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about .lambda./50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. Whereas current interferometers illuminate the optic to be tested with an aberrated wavefront which also limits the accuracy of the measurement, this interferometer uses an essentially perfect spherical measurement wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms.

  16. Phase shifting diffraction interferometer

    DOEpatents

    Sommargren, G.E.

    1996-08-29

    An interferometer which has the capability of measuring optical elements and systems with an accuracy of {lambda}/1000 where {lambda} is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about {lambda}/50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms. 8 figs.

  17. Dynamic wavelength conversion in copropagating slow-light pulses.

    PubMed

    Kondo, K; Baba, T

    2014-06-01

    Dynamic wavelength conversion (DWC) is obtained by controlling copropagating slow-light signal and control pulse trajectories. Our method is based on the understanding that conventional resonator-based DWC can be generalized, and is linked to cross-phase modulation. Dispersion-engineered Si photonic crystal waveguides produce such slow-light pulses. Free carriers generated by two-photon absorption of the control pulse dynamically shift the signal wavelength. Matching the group velocities of the two pulses enhances the shift, elongating the interaction length. We demonstrate an extremely large wavelength shift in DWC (4.9 nm blueshift) for the signal wavelength. Although DWC is similar to the Doppler effect, we highlight their essential differences. PMID:24949770

  18. Awards and Addresses Summary

    PubMed Central

    2008-01-01

    Each year at the annual ASHG meeting, addresses are given in honor of the society and a number of award winners. A summary of each of these addresses is given below. On the next pages, we have printed the Presidential Address and the addresses for the William Allan Award. The other addresses, accompanied by pictures of the speakers, can be found at www.ashg.org.

  19. Tuning the Activation Wavelength of Photochromic Oxazines.

    PubMed

    Swaminathan, Subramani; Garcia-Amorós, Jaume; Thapaliya, Ek Raj; Nonell, Santi; Captain, Burjor; Raymo, Françisco M

    2016-06-17

    The activation wavelength of a photochromic oxazine can be shifted bathochromically with the introduction of a methoxy substituent on the chromophore responsible for initiating the photochemical transformation. This structural modification permits switching under mild illumination conditions, enhances the photoisomerization quantum yield and ensures outstanding fatigue resistance. Thus, these results can guide the design of new members of this family of photoresponsive molecular switches with improved photochemical and photophysical properties. PMID:27003328

  20. Dynamic polarizabilities and magic wavelengths for dysprosium

    SciTech Connect

    Dzuba, V. A.; Flambaum, V. V.; Lev, Benjamin L.

    2011-03-15

    We theoretically study dynamic scalar polarizabilities of the ground and select long-lived excited states of dysprosium, a highly magnetic atom recently laser cooled and trapped. We demonstrate that there is a set of magic wavelengths of the unpolarized lattice laser field for each pair of states, which includes the ground state and one of these excited states. At these wavelengths, the energy shift due to laser field is the same for both states, which can be useful for resolved sideband cooling on narrow transitions and precision spectroscopy. We present an analytical formula that, near resonances, allows for the determination of approximate values of the magic wavelengths without calculating the dynamic polarizabilities of the excited states.

  1. Long wavelength infrared detector

    NASA Technical Reports Server (NTRS)

    Vasquez, Richard P. (Inventor)

    1993-01-01

    Long wavelength infrared detection is achieved by a detector made with layers of quantum well material bounded on each side by barrier material to form paired quantum wells, each quantum well having a single energy level. The width and depth of the paired quantum wells, and the spacing therebetween, are selected to split the single energy level with an upper energy level near the top of the energy wells. The spacing is selected for splitting the single energy level into two energy levels with a difference between levels sufficiently small for detection of infrared radiation of a desired wavelength.

  2. 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.

  3. Measurement of Magic Wavelengths for the ^{40}Ca^{+} Clock Transition.

    PubMed

    Liu, Pei-Liang; Huang, Yao; Bian, Wu; Shao, Hu; Guan, Hua; Tang, Yong-Bo; Li, Cheng-Bin; Mitroy, J; Gao, Ke-Lin

    2015-06-01

    We demonstrate experimentally the existence of magic wavelengths and determine the ratio of oscillator strengths for a single trapped ion. For the first time, two magic wavelengths near 396 nm for the ^{40}Ca^{+} clock transition are measured simultaneously with high precision. By tuning the applied laser to an intermediate wavelength between transitions 4s_{1/2}→4p_{1/2} and 4s_{1/2}→4p_{3/2}, the sensitivity of the clock transition Stark shift to the oscillator strengths is greatly enhanced. Furthermore, with the measured magic wavelengths, we determine the ratio of the oscillator strengths with a deviation of less than 0.5%. Our experimental method may be applied to measure magic wavelengths for other ion clock transitions. Promisingly, the measurement of these magic wavelengths paves the way to building all-optical trapped ion clocks. PMID:26196619

  4. Short wavelength laser

    DOEpatents

    Hagelstein, Peter L.

    1986-01-01

    A short wavelength laser (28) is provided that is driven by conventional-laser pulses (30, 31). A multiplicity of panels (32), mounted on substrates (34), are supported in two separated and alternately staggered facing and parallel arrays disposed along an approximately linear path (42). When the panels (32) are illuminated by the conventional-laser pulses (30, 31), single pass EUV or soft x-ray laser pulses (44, 46) are produced.

  5. Galactic Astronomy at Long Wavelengths: Past Prologue

    NASA Astrophysics Data System (ADS)

    Lazio, T. J. W.

    2005-12-01

    In the course of his long career, Bill Erickson has conducted long wavelength observations on a number of Galactic objects. These include observations of or searches for supernova remnants, pulsars, extrasolar planets, and the interstellar medium. Throughout, he has been instrumental in attempting to obtain higher angular resolution and higher sensitivity at long wavelengths. Perhaps not surprisingly, many of the questions that Bill tried to address with his observations remain unsolved today. These include such fundamental issues as, How are particles accelerated? Where are particles accelerated? What are the environmental impact, both direct and indirect, of particle acceleration? I shall provide a brief and necessarily incomplete survey of Bill's work in the Galaxy and show how it sets the stage for many of the questions facing modern long-wavelength instruments.

  6. Wavelength dependent mask defects

    NASA Astrophysics Data System (ADS)

    Badger, Karen; Butt, Shahid; Burnham, Jay; Faure, Tom; Hibbs, Michael; Rankin, Jed; Thibault, David; Watts, Andrew

    2005-05-01

    For years there has been a mismatch between the photomask inspection wavelength and the usage conditions. While the non-actinic inspection has been a source for concern, there has been essentially no evidence that a defect "escaped" the mask production process due to the inspection mismatch. This paper will describe the discovery of one such defect, as well as the diagnostic and inspection techniques used to identify the location, analyze the composition, and determine the source of the printed wafer defect. Conventional mask inspection techniques revealed no defects, however an actinic Aerial Image Metrology System (AIMS) revealed a 1.5 mm region on the mask with up to 59% transmission reduction at 193 nm. Further diagnostics demonstrated a strong wavelength dependence which accounted for the near invisibility of the defect at I line (365 nm) or even DUV (248 nm) wavelengths, which had 0% and 5% respective transmission reductions. Using some creative imaging techniques via AIMS tool and modeling, the defect was deduced to have a three dimensional Gaussian absorption character, with total width approximately 1.5 mm. Several non-destructive diagnostic techniques were developed to determine the composition and location of the defect within the substrate. These results will be described in addition to identifying methods for ensuring product quality in the absence of actinic inspection.

  7. Aperture-synthesis interferometry at optical wavelengths

    NASA Technical Reports Server (NTRS)

    Burke, Bernard F.

    1987-01-01

    The prospects for applying aperture-synthesis interferometry to the optical domain are reviewed. The radio examples such as the VLA provide a model, since the concepts are equally valid for radio and optical wavelengths. If scientific problems at the milliarc-second resolution level (or better) are to be addressed, a space-based optical array seems to be the only practical alternative, for the same reasons that dictated array development at radio wavelengths. One concept is examined, and speculations are offered concerning the prospects for developing real systems. Phase-coherence is strongly desired for a practical array, although self-calibration and phase-closure techniques allow one to relax the restriction on absolute phase stability. The design of an array must be guided by the scientific problems to be addressed.

  8. Dual-wavelength diode laser with electrically adjustable wavelength distance at 785  nm.

    PubMed

    Sumpf, Bernd; Kabitzke, Julia; Fricke, Jörg; Ressel, Peter; Müller, André; Maiwald, Martin; Tränkle, Günther

    2016-08-15

    A spectrally adjustable monolithic dual-wavelength diode laser at 785 nm as an excitation light source for shifted excitation Raman difference spectroscopy (SERDS) is presented. The spectral distance between the two excitation wavelengths can be electrically adjusted between 0 and 2.0 nm using implemented heater elements above the distributed Bragg reflector (DBR) gratings. Output powers up to 180 mW at a temperature of 25°C were measured. The spectral width is smaller than 13 pm, limited by the spectrum analyzer. The device is well-suited for Raman spectroscopy, and the flexible spectral distance allows a target-specific adjustment of the excitation light source for shifted excitation Raman difference spectroscopy (SERDS). PMID:27519065

  9. Red-shifted fluorescence of sound dental hard tissue

    NASA Astrophysics Data System (ADS)

    Zhang, Liang; Nelson, Leonard Y.; Seibel, Eric J.

    2011-07-01

    Autofluorescence spectra were recorded in vitro from dentin, enamel, and whole teeth. The spectra exhibited a broad peak shifted by about 50 to 75 nm from the excitation wavelength and the shape of the spectra remained similar regardless of the excitation wavelength. The maximum of the autofluorescence spectra also exhibited a red-shift that depended upon the laser excitation wavelength. The amplitude of the red-shifted fluorescence spectra produced by 444 and 532 nm excitation lasers were compared to that produced by a 405 nm excitation laser. It was determined that the autofluorescence amplitude was not proportional to the inverse fourth power of the excitation laser wavelength. Therefore, the red-shifted fluorescence is not compatible with the previously proposed mechanism of Raman scattering. Instead, the mechanism giving rise to the laser-induced dental autofluorescence is explained by the red-edge-excitation effect.

  10. Geometric phase shifting digital holography.

    PubMed

    Jackin, Boaz Jessie; Narayanamurthy, C S; Yatagai, Toyohiko

    2016-06-01

    A new phase shifting digital holographic technique using a purely geometric phase in Michelson interferometric geometry is proposed. The geometric phase in the system does not depend upon either optical path length or wavelength, unlike dynamic phase. The amount of geometric phase generated is controllable through a rotating wave plate. The new approach has unique features and major advantages in holographic measurement of transparent and reflecting three-dimensional (3D) objects. Experimental results on surface shape measurement and imaging of 3D objects are presented using the proposed method. PMID:27244436

  11. Zero-Points of FOS Wavelength Scales

    NASA Astrophysics Data System (ADS)

    Rosa, Michael R.; Kerber, Florian

    We have investigated the internal zero-points of the HST's Faint object spectrograph (FOS) on-orbit wavelength calibration between 1990 (launch) and 1997 (de-commissioning). The analysis is based on cross-correlating about 1200 WAVECAL exposures for the high-resolution dispersers, using as templates those exposures which define the dispersion solutions currently in use by the FOS pipeline. FOS has two channels BLUE/RED using two independent Digicon detectors. For BLUE systematic shifts of the zero-points are present, which amount to a maximum offset of 7 pixels (1.75 diodes) over the entire period. The zero-points for RED modes present an apparently random distribution with a peak-to-peak range of 7 pixels. We discu ss the effect of the geomagnetic environment as a possible cause for the observed behaviour and describe the ongoing work to reduce the uncertainty in the wavelength scale.

  12. Fabrication of a microtoroidal resonator with picometer precise resonant wavelength.

    PubMed

    Liu, Xiao-Fei; Lei, Fuchuan; Gao, Ming; Yang, Xu; Qin, Guo-Qing; Long, Gui-Lu

    2016-08-01

    Fabricating an optical microresonator with precise resonant wavelength is of significant importance for fundamental research and practical applications. Here, we develop an effective method to fabricate ultra-high Q microtoroid with picometer-precise resonant wavelength. Our method adds a tuning reflow process, using low-power CO2 laser pulses, to the traditional fabrication process. It can tailor resonant wavelength to a red or blue direction by choosing a proper laser power. Also, this shift can be controlled by the exposure time. Meanwhile, quality factor remains nearly unchanged during this tailoring process. Our method can greatly reduce the difficulties of experiments where precise resonances are required. PMID:27472629

  13. Wavelength meter having elliptical wedge

    DOEpatents

    Hackel, Richard P.; Feldman, Mark

    1992-01-01

    A wavelength meter is disclosed which can determine the wavelength of a laser beam from a laser source within an accuracy range of two parts in 10.sup.8. The wavelength meter has wedge having an elliptically shaped face to the optical path of the laser source and includes interferometer plates which form a vacuum housing.

  14. Wavelength meter having elliptical wedge

    DOEpatents

    Hackel, R.P.; Feldman, M.

    1992-12-01

    A wavelength meter is disclosed which can determine the wavelength of a laser beam from a laser source within an accuracy range of two parts in 10[sup 8]. The wavelength meter has wedge having an elliptically shaped face to the optical path of the laser source and includes interferometer plates which form a vacuum housing. 7 figs.

  15. MEMS-based beam steering system for individual addressing of trapped ions

    NASA Astrophysics Data System (ADS)

    Kim, Taehyun; Knoernschild, Caleb; Mount, Emily; Crain, Stephen; Noek, Rachel; Gaultney, Daniel; van Rynbach, Andre; Maunz, Peter; Kim, Jungsang

    2011-05-01

    One of the important components to implement large-scale trapped ion quantum information processing is a scalable technology to manipulate individual ions in a long linear chain of ions. So far, individual addressing has been demonstrated by steering a focused laser beam on individual ions with acousto-optic and electro-optic deflectors, by utilizing the Zeeman shift due to a magnetic field gradient, and by separating a single ion from the rest of the chain for individual exposure to laser light. Micro-mirrors based on microelectromechanical system (MEMS) technology can be used to design an alternative beam steering system which can handle multiple beams with different wavelengths and address locations in multiple dimensions. We will report our progress in integrating a MEMS beam steering system with an Yb ion trap experiment. Our MEMS system is designed to steer an ultraviolet beam with a waist of ~1.5 μm across a 20 μm range. To demonstrate the individual addressing capability, we plan to measure the Ramsey interference of the differential AC Stark shift induced by an individually-focused, far-detuned laser beam.

  16. Addressivity in cogenerative dialogues

    NASA Astrophysics Data System (ADS)

    Hsu, Pei-Ling

    2014-03-01

    Ashraf Shady's paper provides a first-hand reflection on how a foreign teacher used cogens as culturally adaptive pedagogy to address cultural misalignments with students. In this paper, Shady drew on several cogen sessions to showcase his journey of using different forms of cogens with his students. To improve the quality of cogens, one strategy he used was to adjust the number of participants in cogens. As a result, some cogens worked and others did not. During the course of reading his paper, I was impressed by his creative and flexible use of cogens and at the same time was intrigued by the question of why some cogens work and not others. In searching for an answer, I found that Mikhail Bakhtin's dialogism, especially the concept of addressivity, provides a comprehensive framework to address this question. In this commentary, I reanalyze the cogen episodes described in Shady's paper in the light of dialogism. My analysis suggests that addressivity plays an important role in mediating the success of cogens. Cogens with high addressivity function as internally persuasive discourse that allows diverse consciousnesses to coexist and so likely affords productive dialogues. The implications of addressivity in teaching and learning are further discussed.

  17. ECM at millimeter wavelengths

    NASA Astrophysics Data System (ADS)

    Copper, H. W.; Littlepage, R. S.

    1982-09-01

    ECM techniques appropriate to the millimeter wave band are examined with particular reference to the physics of the atmosphere and component performance capability. Model calculations show that even for state-of-the-art threat radars, the required ECM receiver sensitivity is well within the state-of-the-art for broadband superheterodyne systems. For ECM jammers, the most fundamental limitation arises from deficiencies in broadband/high power amplifiers. The solution to this problem will require different ECM system architectures than used at the lower frequencies. At millimeter wavelengths, atmospheric effects permit new jamming techniques requiring lower jamming power. For example, scattering by hydrometeors significantly raises the apparent sidelobe level of even low sidelobe antennas of threat radars, which reduces the power required to infringe through the sidelobes.

  18. Quadrature wavelength scanning interferometry.

    PubMed

    Moschetti, Giuseppe; Forbes, Alistair; Leach, Richard K; Jiang, Xiang; O'Connor, Daniel

    2016-07-10

    A novel method to double the measurement range of wavelength scanning interferometery (WSI) is described. In WSI the measured optical path difference (OPD) is affected by a sign ambiguity, that is, from an interference signal it is not possible to distinguish whether the OPD is positive or negative. The sign ambiguity can be resolved by measuring an interference signal in quadrature. A method to obtain a quadrature interference signal for WSI is described, and a theoretical analysis of the advantages is reported. Simulations of the advantages of the technique and of signal errors due to nonideal quadrature are discussed. The analysis and simulation are supported by experimental measurements to show the improved performances. PMID:27409307

  19. Holographic topography using acousto-optically generated large synthetic wavelengths

    NASA Astrophysics Data System (ADS)

    Abeywickrema, U.; Beamer, D.; Banerjee, P.; Poon, T.-C.

    2016-03-01

    Digital holography uses phase imaging in a variety of techniques to produce a three-dimensional phase resolved image that includes accurate depth information about the object of interest. Multi-wavelength digital holography is an accurate method for measuring the topography of surfaces. Typically, the object phases are reconstructed for two wavelengths separately and the phase corresponding to the synthetic wavelength (obtained from the two wavelengths) is obtained by calculating the phase difference. Then the surface map can be obtained using proper phase-unwrapping techniques. Usually these synthetic wavelengths are on the order of microns which can be used to resolve depths on the order of microns. In this work, two extremely close wavelengths generated by an acousto-optic modulator (AOM) are used to perform two-wavelength digital holography. Since the difference between the two wavelengths is on the order of picometers, a large synthetic wavelength (on the order of centimeters) can be obtained which can be used to determine the topography of macroscopic surface features. Also since the synthetic wavelength is large, an accurate surface map can be obtained without using a phase-unwrapping technique. A 514 nm Argon-ion laser is used as the optical source, and used with an AOM to generate the zeroth-order and frequency-shifted first-order diffracted orders which are used as the two wavelengths. Both beams are aligned through the same spatial filter assembly. Holograms are captured sequentially using a typical Mach-Zehnder interferometric setup by blocking one beam at a time. Limitations of the large synthetic wavelength are also discussed.

  20. Portable shift register

    SciTech Connect

    Halbig, J.K.; Bourret, S.C.; Hansen, W.J.; Hicks, D.V.; Klosterbuer, S.F.; Krick, M.S.

    1994-01-01

    An electronics package for a small, battery-operated, self-contained, neutron coincidence counter based on a portable shift-register (PSR) has been developed. The counter was developed for applications not adequately addressed by commercial packages, including in-plant measurements to demonstrate compliance with regulations (domestic and international), in-plant process control, and in-field measurements (environmental monitoring or safeguards). Our package's features, which address these applications, include the following: Small size for portability and ease of installation;battery or mains operation; a built-in battery to power the unit and a typical detector such as a small sample counter, for over 6 h if power lines are bad or noisy, if there is a temporary absence of power, or if portability is desired; complete support, including bias, for standard neutron detectors; a powerful communications package to easily facilitate robust external control over a serial port; and a C-library to simplify creating external control programs in computers or other controllers. Whereas the PSR specifically addresses the applications mentioned above, it also performs all the measurements made by previous electronics packages for neutron coincidence counters developed at Los Alamos and commercialized. The PSR electronics package, exclusive of carrying handle, is 8 by 10 by 20 cm; it contains the circuit boards, battery, and bias supply and weighs less than 2 kg. This instrument package is the second in an emerging family of portable measurement instruments being developed; the first was the Miniature and Modular Multichannel Analyzer (M[sup 3]CA). The PSR makes extensive use of hardware and software developed for the M[sup 3]CA; like the M[sup 3]CA, it is intended primarily for use with an external controller interfaced over a serial channel.

  1. Magic wavelengths for the 5 s -18 s transition in rubidium

    NASA Astrophysics Data System (ADS)

    Goldschmidt, E. A.; Norris, D. G.; Koller, S. B.; Wyllie, R.; Brown, R. C.; Porto, J. V.; Safronova, U. I.; Safronova, M. S.

    2015-03-01

    Magic wavelengths, for which there is no differential ac Stark shift for the ground and excited state of the atom, allow trapping of excited Rydberg atoms without broadening the optical transition. This is an important tool for implementing quantum gates and other quantum information protocols with Rydberg atoms, and reliable theoretical methods to find such magic wavelengths are thus extremely useful. We use a high-precision all-order method to calculate magic wavelengths for the 5 s -18 s transition of rubidium, and compare the calculation to experiment by measuring the light shift for atoms held in an optical dipole trap at a range of wavelengths near a calculated magic value.

  2. Interrogation of a cascaded FBG sensor using a wavelength-to-delay mapping technique

    NASA Astrophysics Data System (ADS)

    Clement, Juan; Hervás, Javier; Fernández-Pousa, Carlos R.; Barrera, David; Pastor, Daniel; Sales, Salvador; Capmany, José

    2015-09-01

    An optical fiber sensor composed of six standard FBGs in cascade is interrogated by use of a technique based on wavelength to delay mapping. A microwave-modulated optical signal enters the FBG cascade and, after being sliced and reflected, experiences dispersion in standard single-mode fiber. The Bragg wavelengths of the FBGs are mapped into the delays that determine the peaks in the system's electrical impulse response. The Bragg wavelength shifts are calculated from the difference of the delays undergone by FBGs samples. A resolution of 9.2 pm in Bragg wavelength shift is demonstrated.

  3. Psychopathology of Shift Work.

    ERIC Educational Resources Information Center

    Akinnawo, Ebenezer Olutope

    1989-01-01

    Examined incidence and nature of general psychopathology among Nigerian shift workers (N=320). Found shift workers more significantly psychopathological than non-shift workers (p<0.001). Prominent disorders among shift workers were intellectual, sleep, mood, and general somatic disorders. No significant difference could be attributed to gender and…

  4. Wavelength-conserving grating router for intermediate wavelength density

    DOEpatents

    Deri, Robert J.; Patel, Rajesh R.; Bond, Steven W.; Bennett, Cory V.

    2007-03-20

    A wavelength router to be used for fiber optical networking router is based on a diffraction grating which utilizes only N wavelengths to interconnect N inputs to N outputs. The basic approach is to augment the grating with additional couplers or wavelength selective elements so than N-1 of the 2N-1 outputs are combined with other N outputs (leaving only N outputs). One embodiment uses directional couplers as combiners. Another embodiment uses wavelength-selective couplers. Another embodiment uses a pair of diffraction gratings to maintain parallel propagation of all optical beams. Also, beam combining can be implemented either by using retroflection back through the grating pair or by using couplers.

  5. GLAST Science Across Wavelengths

    NASA Astrophysics Data System (ADS)

    Blandford, R. D.

    2006-12-01

    The GLAST satellites is almost guaranteed to revolutionize GeV gamma ray astronomy because of the great discoveries that are being made at hard X-ray energy by the Suzaku and Swift satellites and in the TeV range using the H.E.S.S. and Magic telescopes. Unidentified EGRET sources are likely to be identified and new and fainter sources will be found. Known classes of sources blazars, pulsars, gamma ray bursts, supernova remnants, binary X-ray sources and so on will be monitored in much greater detail. Finally, there is the need to limit or even detect dark matter through its annihilation signature. The science that will emerge from GLAST will be determined in large measure by the effort that is put into multiwavelength observing. This will require significant commitments of observing time for monitoring pulsar arrival times, measuring faint galaxy spectra, detecting GeV gamma rays gamma ray bursts and so on. In this talk I will attempt to summarize current thinking on the GLAST multi-wavelength observing program and propose some new approaches.

  6. Addressing Social Issues.

    ERIC Educational Resources Information Center

    Schoebel, Susan

    1991-01-01

    Maintains that advertising can help people become more aware of social responsibilities. Describes a successful nationwide newspaper advertising competition for college students in which ads address social issues such as literacy, drugs, teen suicide, and teen pregnancy. Notes how the ads have helped grassroots programs throughout the United…

  7. States Address Achievement Gaps.

    ERIC Educational Resources Information Center

    Christie, Kathy

    2002-01-01

    Summarizes 2 state initiatives to address the achievement gap: North Carolina's report by the Advisory Commission on Raising Achievement and Closing Gaps, containing an 11-point strategy, and Kentucky's legislation putting in place 10 specific processes. The North Carolina report is available at www.dpi.state.nc.us.closingthegap; Kentucky's…

  8. Address of the President

    ERIC Educational Resources Information Center

    Ness, Frederic W.

    1976-01-01

    The president of the Association of American Colleges addresses at the 62nd annual meeting the theme of the conference: "Looking to the Future--Liberal Education in a Radically Changing Society." Contributions to be made by AAC are examined. (LBH)

  9. Addressing Sexual Harassment

    ERIC Educational Resources Information Center

    Young, Ellie L.; Ashbaker, Betty Y.

    2008-01-01

    This article discusses ways on how to address the problem of sexual harassment in schools. Sexual harassment--simply defined as any unwanted and unwelcome sexual behavior--is a sensitive topic. Merely providing students, parents, and staff members with information about the school's sexual harassment policy is insufficient; schools must take…

  10. Space sciences - Keynote address

    NASA Technical Reports Server (NTRS)

    Alexander, Joseph K.

    1990-01-01

    The present status and projected future developments of the NASA Space Science and Applications Program are addressed. Emphasis is given to biochemistry experiments that are planned for the Space Station. Projects for the late 1990s which will study the sun, the earth's magnetosphere, and the geosphere are briefly discussed.

  11. ac Stark shift of the Cs microwave atomic clock transitions

    NASA Astrophysics Data System (ADS)

    Rosenbusch, P.; Ghezali, S.; Dzuba, V. A.; Flambaum, V. V.; Beloy, K.; Derevianko, A.

    2009-01-01

    We analyze the ac Stark shift of the Cs microwave atomic clock transition theoretically and experimentally. Theoretical and experimental data are in good agreement with each other. Results indicate the absence of a magic wavelength at which there would be no differential shift of the clock states having zero projections of the total angular momentum.

  12. COS Internal FUV Wavelength Verification

    NASA Astrophysics Data System (ADS)

    Keyes, Charles

    2009-07-01

    This program will be executed after the uplink of the OSM1 position updates derived from the determination of the wavelength-scale zero points and desired spectral ranges for each grating in activity COS29 {program 11487 - COS FUV Internal/External Wavelength Scales}. This program will verify that the operational spectral ranges for each grating, central wavelength, and FP-POS are those desired. Subsequent to a successful verification, COS FUV ERO observations that require accurate wavelength scales {if any} and FUV science can be enabled. An internal wavelength calibration spectrum using the default PtNe lamp {lamp 1} with each FUV grating at each central wavelength setting and each FP-POS position will be obtained for the verification. Additional exposures and waits between certain exposures will be required to avoid - and to evaluate - mechanism drifts.

  13. Gear shift control mechanism

    SciTech Connect

    Janson, D.A.

    1987-03-10

    A gear shift control mechanism is described comprising: multiple shift rods directed substantially parallel to one another, each rod carrying a shift fork for axial movement; a shift lever supported for pivotal movement about a first axis directed parallel to the axes of the shift rods and for pivotal movement about a second axis directed substantially perpendicular to the axes of the shift rods. The lever is moveable about the first axis and the second axis into engagement with a selected shift fork; interlock means located on each lateral side of the shift lever and mounted for pivotal movement about the first axis for blocking engagement with the shift forks; detent means for holding the shift lever in multiple predetermined angular positions about the second axis; and spring means located on a lateral side of the shift lever and mounted for pivotal movement about the first axis into interference contact with the shift forks for producing a force tending to resiliently bias the shift lever out of engagement with the selected shift fork.

  14. Shifting tolerance for multilayer collinear holographic data storage

    NASA Astrophysics Data System (ADS)

    Liu, Jinqiu; Cao, Liangcai; He, Qingsheng; Jin, Guofan

    2014-09-01

    The shifting tolerance of the collinear holographic data storage system is discussed considering its influences on the quality of the reconstructed data pages and the precision of the holographic disk actuator. The diffractive efficiencies with shifting along the x-axis and the z-axis are calculated respectively based on the bit error rates of the reconstructed data pages. The numerical aperture of the objective lens and the recording wavelength show different impacts on the shifting tolerance and the storage density. The orthogonal reference pattern shift multiplexing method is investigated. It is proved that the method could improve the data storage density by keeping the shifting tolerance.

  15. Excerpts from keynote address

    SciTech Connect

    Creel, G.C.

    1995-06-01

    Excerpts from the keynote principally address emissions issues in the fossil power industry as related to heat rate improvements. Stack emissions of both sulfur and nitrogen oxides are discussed, and a number of examples are given: (1) PEPCO`s Potomac River Station, and (2) Morgantown station`s NOX reduction efforts. Circulating water emissions are also briefly discussed, as are O & M costs of emission controls.

  16. Holographic content addressable storage

    NASA Astrophysics Data System (ADS)

    Chao, Tien-Hsin; Lu, Thomas; Reyes, George

    2015-03-01

    We have developed a Holographic Content Addressable Storage (HCAS) architecture. The HCAS systems consists of a DMD (Digital Micromirror Array) as the input Spatial Light Modulator (SLM), a CMOS (Complementary Metal-oxide Semiconductor) sensor as the output photodetector and a photorefractive crystal as the recording media. The HCAS system is capable of performing optical correlation of an input image/feature against massive reference data set stored in the holographic memory. Detailed system analysis will be reported in this paper.

  17. A novel technique for an integrated optical wavelength demultiplexer

    NASA Astrophysics Data System (ADS)

    Lotfy Rabeh, M.; Mohanna, M.; Hosny, Tarek; Gabr, Mohamed I.

    2015-12-01

    In this paper we propose a new technique for optical wavelength demultiplexing (DEMUX) relaying on two phenomena: Goos-Haenchen (GH) shift and continuous refraction at a graded-index medium interface. In the first case, two light beams are totally reflected at a plane interface separating two dielectric lossless media. The reflected beams suffer different lateral shifts (GH shifts) depending on the wavelength; thus accomplishing the required spatial beam separation. In the second case, the two light beams have different "turning points" inside the graded index medium; hence, the "back-refracted" beams are spatially separated. In this paper, we optimized the conditions of operation of such demultiplexing technique. This makes possible the integration of such technique in "planar integrated-optics" structures which can be used reliably in optical fiber communication networks.

  18. The Long Wavelength Array

    NASA Astrophysics Data System (ADS)

    Taylor, G. B.

    2006-08-01

    The Long Wavelength Array (LWA) will be a new, open, user-oriented astronomical instrument operating in the poorly explored window from 20-80 MHz at arcsecond level resolution and mJy level sensitivity. Key science drivers include (1) acceleration, propagation, and turbulence in the ISM, including the space-distribution and spectrum of Galactic cosmic rays, supernova remnants, and pulsars; (2) the high redshift universe, including the most distant radio galaxies and clusters - tools for understanding the earliest black holes and the cosmological evolution of Dark Matter and Dark Energy; (3) planetary, solar, and space science, including space weather prediction and extra-solar planet searches; and (4) the radio transient universe: including the known (e.g., SNe, GRBs) and the unknown. Because the LWA will explore one of the last and least investigated regions of the spectrum, the potential for new discoveries, including new classes of physical phenomena, is high, and there is a strong synergy with exciting new X-ray and Gamma-ray measurements, e.g. for cosmic ray acceleration, transients, and galaxy clusters. Operated by the University of New Mexico on behalf of the South West Consortium (SWC) the LWA will also provide a unique training ground for the next generation of radio astronomers. Students may also put skills learned on the LWA to work in computer science, electrical engineering, and the communications industry, among others. The development of the LWA will follow a phased build, which benefits from lessons learned at each phase. Four university-based Scientific Testing and Evaluation (ST&E) teams with different areas of concentration (1. High resolution imaging and particle acceleration; 2. Wide field imaging and large scale structures; 3. Ionosphere, and 4. RFI suppression and transient detection) will provide the feedback needed to assure that science objectives are met as the build develops. Currently in its first year of construction funding, the LWA

  19. Tunable and switchable dual-wavelength erbium-doped fiber laser based on in-line tapered fiber filters

    NASA Astrophysics Data System (ADS)

    Tong, Zheng-rong; Yang, He; Cao, Ye

    2016-07-01

    A tunable and switchable dual-wavelength erbium-doped fiber laser (EDFL) based on all-fiber single-mode tapered fiber structure has been demonstrated. By adjusting the variable optical attenuator (VOA), the laser can be switched between the single-wavelength mode and the dual-wavelength mode. When the temperature applied on the tapered fiber structure varies, the pass-band varies and the wavelength of the output laser shifts correspondingly. When the temperature changes from 30 °C to 180 °C, the central wavelength of the EDFL generated by branch A shifts from 1 550.7 nm to 1 560.3 nm, while that of branch B shifts from 1 530.8 nm to 1 540.4 nm, indicating the wavelength interval is tunable. These advantages enable this laser to be a potential candidate for high-capacity wavelength division multiplexing systems and mechanical sensors.

  20. Interference comparator for laser diode wavelength and wavelength instability measurement

    NASA Astrophysics Data System (ADS)

    Dobosz, Marek; KoŻuchowski, Mariusz

    2016-04-01

    Method and construction of a setup, which allows measuring the wavelength and wavelength instability of the light emitted by a laser diode (or a laser light source with a limited time coherence in general), is presented. The system is based on Twyman-Green interferometer configuration. Proportions of phases of the tested and reference laser's interference fringe obtained for a set optical path difference are a measure of the unknown wavelength. Optical path difference in interferometer is stabilized. The interferometric comparison is performed in vacuum chamber. The techniques of accurate fringe phase measurements are proposed. The obtained relative standard uncertainty of wavelength evaluation in the tested setup is about 2.5 ṡ 10-8. Uncertainty of wavelength instability measurement is an order of magnitude better. Measurement range of the current setup is from 500 nm to 650 nm. The proposed technique allows high accuracy wavelength measurement of middle or low coherence sources of light. In case of the enlarged and complex frequency distribution of the laser, the evaluated wavelength can act as the length master in interferometer for displacement measurement.

  1. Interference comparator for laser diode wavelength and wavelength instability measurement.

    PubMed

    Dobosz, Marek; Kożuchowski, Mariusz

    2016-04-01

    Method and construction of a setup, which allows measuring the wavelength and wavelength instability of the light emitted by a laser diode (or a laser light source with a limited time coherence in general), is presented. The system is based on Twyman-Green interferometer configuration. Proportions of phases of the tested and reference laser's interference fringe obtained for a set optical path difference are a measure of the unknown wavelength. Optical path difference in interferometer is stabilized. The interferometric comparison is performed in vacuum chamber. The techniques of accurate fringe phase measurements are proposed. The obtained relative standard uncertainty of wavelength evaluation in the tested setup is about 2.5 ⋅ 10(-8). Uncertainty of wavelength instability measurement is an order of magnitude better. Measurement range of the current setup is from 500 nm to 650 nm. The proposed technique allows high accuracy wavelength measurement of middle or low coherence sources of light. In case of the enlarged and complex frequency distribution of the laser, the evaluated wavelength can act as the length master in interferometer for displacement measurement. PMID:27131662

  2. COS Internal NUV Wavelength Verification

    NASA Astrophysics Data System (ADS)

    Keyes, Charles

    2009-07-01

    This program will be executed after the uplink of the OSM2 position updates derived from the determination of the wavelength-scale zero points and desired spectral ranges for each grating in activity COS14 {program 11474 - COS NUV Internal/External Wavelength Scales}. This program will verify that the operational spectral ranges for each grating, central wavelength, and FP-POS are those desired. Subsequent to a successful verification, COS NUV ERO observations and NUV science can be enabled. An internal wavelength calibration spectrum using the default PtNe lamp {lamp 1} with each NUV grating at each central wavelength setting and each FP-POS position will be obtained for the verification. Additional exposures and waits between certain exposures will be required to avoid - and to evaluate - mechanism drifts.

  3. Content addressable memory project

    NASA Technical Reports Server (NTRS)

    Hall, J. Storrs; Levy, Saul; Smith, Donald E.; Miyake, Keith M.

    1992-01-01

    A parameterized version of the tree processor was designed and tested (by simulation). The leaf processor design is 90 percent complete. We expect to complete and test a combination of tree and leaf cell designs in the next period. Work is proceeding on algorithms for the computer aided manufacturing (CAM), and once the design is complete we will begin simulating algorithms for large problems. The following topics are covered: (1) the practical implementation of content addressable memory; (2) design of a LEAF cell for the Rutgers CAM architecture; (3) a circuit design tool user's manual; and (4) design and analysis of efficient hierarchical interconnection networks.

  4. Bioreactors Addressing Diabetes Mellitus

    PubMed Central

    Minteer, Danielle M.; Gerlach, Jorg C.

    2014-01-01

    The concept of bioreactors in biochemical engineering is a well-established process; however, the idea of applying bioreactor technology to biomedical and tissue engineering issues is relatively novel and has been rapidly accepted as a culture model. Tissue engineers have developed and adapted various types of bioreactors in which to culture many different cell types and therapies addressing several diseases, including diabetes mellitus types 1 and 2. With a rising world of bioreactor development and an ever increasing diagnosis rate of diabetes, this review aims to highlight bioreactor history and emerging bioreactor technologies used for diabetes-related cell culture and therapies. PMID:25160666

  5. Tunable all-optical wavelength broadcasting in a PPLN with multiple QPM peaks.

    PubMed

    Ahlawat, Meenu; Tehranchi, Amirhossein; Pandiyan, Krishnamoorthy; Cha, Myoungsik; Kashyap, Raman

    2012-11-19

    We experimentally demonstrate tunable multiple-idler wavelength broadcasting of a signal to selective channels for wavelength division multiplexing (WDM). This is based on cascaded χ(2) nonlinear mixing process in a novel multiple-QPM 10-mm-long periodically poled LiNbO3 having an aperiodic domain in the center. The idlers' spacing is varied utilizing detuning of the pump wavelength within the SHG bandwidth. The temperature-assisted tuning of QPM pump wavelengths allows shifting the idlers together to different set of WDM channels. Our experimental results indicate that an overall idler wavelength shift of less than 10 nm realized by selecting pump wavelengths via temperature tuning, is sufficient to cover up to 40 WDM channels for multiple idlers broadcasting. PMID:23187600

  6. Addressing Environmental Health Inequalities.

    PubMed

    Gouveia, Nelson

    2016-01-01

    Environmental health inequalities refer to health hazards disproportionately or unfairly distributed among the most vulnerable social groups, which are generally the most discriminated, poor populations and minorities affected by environmental risks. Although it has been known for a long time that health and disease are socially determined, only recently has this idea been incorporated into the conceptual and practical framework for the formulation of policies and strategies regarding health. In this Special Issue of the International Journal of Environmental Research and Public Health (IJERPH), "Addressing Environmental Health Inequalities-Proceedings from the ISEE Conference 2015", we incorporate nine papers that were presented at the 27th Conference of the International Society for Environmental Epidemiology (ISEE), held in Sao Paulo, Brazil, in 2015. This small collection of articles provides a brief overview of the different aspects of this topic. Addressing environmental health inequalities is important for the transformation of our reality and for changing the actual development model towards more just, democratic, and sustainable societies driven by another form of relationship between nature, economy, science, and politics. PMID:27618906

  7. Regime shifts in the anthropocene: drivers, risks, and resilience.

    PubMed

    Rocha, Juan Carlos; Peterson, Garry D; Biggs, Reinette

    2015-01-01

    Many ecosystems can experience regime shifts: surprising, large and persistent changes in the function and structure of ecosystems. Assessing whether continued global change will lead to further regime shifts, or has the potential to trigger cascading regime shifts has been a central question in global change policy. Addressing this issue has, however, been hampered by the focus of regime shift research on specific cases and types of regime shifts. To systematically assess the global risk of regime shifts we conducted a comparative analysis of 25 generic types of regime shifts across marine, terrestrial and polar systems; identifying their drivers, and impacts on ecosystem services. Our results show that the drivers of regime shifts are diverse and co-occur strongly, which suggests that continued global change can be expected to synchronously increase the risk of multiple regime shifts. Furthermore, many regime shift drivers are related to climate change and food production, whose links to the continued expansion of human activities makes them difficult to limit. Because many regime shifts can amplify the drivers of other regime shifts, continued global change can also be expected to increase the risk of cascading regime shifts. Nevertheless, the variety of scales at which regime shift drivers operate provides opportunities for reducing the risk of many types of regime shifts by addressing local or regional drivers, even in the absence of rapid reduction of global drivers. PMID:26267896

  8. Regime Shifts in the Anthropocene: Drivers, Risks, and Resilience

    PubMed Central

    Rocha, Juan Carlos; Peterson, Garry D.; Biggs, Reinette

    2015-01-01

    Many ecosystems can experience regime shifts: surprising, large and persistent changes in the function and structure of ecosystems. Assessing whether continued global change will lead to further regime shifts, or has the potential to trigger cascading regime shifts has been a central question in global change policy. Addressing this issue has, however, been hampered by the focus of regime shift research on specific cases and types of regime shifts. To systematically assess the global risk of regime shifts we conducted a comparative analysis of 25 generic types of regime shifts across marine, terrestrial and polar systems; identifying their drivers, and impacts on ecosystem services. Our results show that the drivers of regime shifts are diverse and co-occur strongly, which suggests that continued global change can be expected to synchronously increase the risk of multiple regime shifts. Furthermore, many regime shift drivers are related to climate change and food production, whose links to the continued expansion of human activities makes them difficult to limit. Because many regime shifts can amplify the drivers of other regime shifts, continued global change can also be expected to increase the risk of cascading regime shifts. Nevertheless, the variety of scales at which regime shift drivers operate provides opportunities for reducing the risk of many types of regime shifts by addressing local or regional drivers, even in the absence of rapid reduction of global drivers. PMID:26267896

  9. Flexible shift scheduling of physicians.

    PubMed

    Brunner, Jens O; Bard, Jonathan F; Kolisch, Rainer

    2009-09-01

    This research addresses a shift scheduling problem in which physicians at a German university hospital are assigned to demand periods over a planning horizon that can extend up to several weeks. When performing the scheduling it is necessary to take into account a variety of legal and institutional constraints that are imposed by a national labor agreement, which governs all physicians in German university hospitals. Currently, most medical departments develop their staff schedules manually at great cost and time. To solve the problem, a new modeling approach is developed that requires shifts to be generated implicitly. Rather than beginning with a predetermined number of shift types and start times, shifts are allowed to start at every pre-defined period in the planning horizon and extend up to 13 h with an hour-long break included. The objective is to find an assignment such that the total hours that have to be paid out as overtime are minimal under the restrictions given by the labor agreement. The problem is formulated as a mixed-integer program and solved with CPLEX. During the solution process individual lines-of-work are constructed for each physician. Using data from an anesthesia department, computational results indicate that high quality schedules can be obtained much more quickly than by current practice. PMID:19739361

  10. Collisionally induced atomic clock shifts and correlations

    SciTech Connect

    Band, Y. B.; Osherov, I.

    2011-07-15

    We develop a formalism to incorporate exchange symmetry considerations into the calculation of collisional frequency shifts for atomic clocks using a density-matrix formalism. The formalism is developed for both fermionic and bosonic atomic clocks. Numerical results for a finite-temperature {sup 87}Sr {sup 1}S{sub 0} (F=9/2) atomic clock in a magic wavelength optical lattice are presented.

  11. Content addressable memory project

    NASA Technical Reports Server (NTRS)

    Hall, Josh; Levy, Saul; Smith, D.; Wei, S.; Miyake, K.; Murdocca, M.

    1991-01-01

    The progress on the Rutgers CAM (Content Addressable Memory) Project is described. The overall design of the system is completed at the architectural level and described. The machine is composed of two kinds of cells: (1) the CAM cells which include both memory and processor, and support local processing within each cell; and (2) the tree cells, which have smaller instruction set, and provide global processing over the CAM cells. A parameterized design of the basic CAM cell is completed. Progress was made on the final specification of the CPS. The machine architecture was driven by the design of algorithms whose requirements are reflected in the resulted instruction set(s). A few of these algorithms are described.

  12. Bax: Addressed to kill.

    PubMed

    Renault, Thibaud T; Manon, Stéphen

    2011-09-01

    The pro-apoptototic protein Bax (Bcl-2 Associated protein X) plays a central role in the mitochondria-dependent apoptotic pathway. In healthy mammalian cells, Bax is essentially cytosolic and inactive. Following a death signal, the protein is translocated to the outer mitochondrial membrane, where it promotes a permeabilization that favors the release of different apoptogenic factors, such as cytochrome c. The regulation of Bax translocation is associated to conformational changes that are under the control of different factors. The evidences showing the involvement of different Bax domains in its mitochondrial localization are presented. The interactions between Bax and its different partners are described in relation to their ability to promote (or prevent) Bax conformational changes leading to mitochondrial addressing and to the acquisition of the capacity to permeabilize the outer mitochondrial membrane. PMID:21641962

  13. Anthropometric changes and fluid shifts

    NASA Technical Reports Server (NTRS)

    Thornton, W. E.; Hoffler, G. W.; Rummel, J. A.

    1977-01-01

    In an effort to obtain the most comprehensive and coherent picture of changes under weightlessness, a set of measurements on Skylab 2 was initiated and at every opportunity, additional studies were added. All pertinent information from ancillary sources were gleaned and collated. On Skylab 2, the initial anthropometric studies were scheduled in conjunction with muscle study. A single set of facial photographs was made in-flight. Additional measurements were made on Skylab 3, with photographs and truncal and limb girth measurements in-flight. Prior to Skylab 4, it was felt there was considerable evidence for large and rapid fluid shifts, so a series of in-flight volume and center of mass measurements and infrared photographs were scheduled to be conducted in the Skylab 4 mission. A number of changes were properly documented for the first time, most important of which were the fluid shifts. The following description of Skylab anthropometrics address work done on Skylab 4 primarily.

  14. Multiple-wavelength tunable laser

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P. (Inventor); Walsh, Brian M. (Inventor); Reichle, Donald J. (Inventor)

    2010-01-01

    A tunable laser includes dispersion optics for separating generated laser pulses into first and second wavelength pulses directed along first and second optical paths. First and second reflective mirrors are disposed in the first and second optical paths, respectively. The laser's output mirror is partially reflective and partially transmissive with respect to the first wavelength and the second wavelength in accordance with provided criteria. A first resonator length is defined between the output mirror and the first mirror, while a second resonator length is defined between the output mirror and the second mirror. The second resonator length is a function of the first resonator length.

  15. AWG Filter for Wavelength Interrogator

    NASA Technical Reports Server (NTRS)

    Black, Richard J. (Inventor); Costa, Joannes M. (Inventor); Faridian, Fereydoun (Inventor); Moslehi, Behzad (Inventor); Sotoudeh, Vahid (Inventor)

    2015-01-01

    A wavelength interrogator is coupled to a circulator which couples optical energy from a broadband source to an optical fiber having a plurality of sensors, each sensor reflecting optical energy at a unique wavelength and directing the reflected optical energy to an AWG. The AWG has a detector coupled to each output, and the reflected optical energy from each grating is coupled to the skirt edge response of the AWG such that the adjacent channel responses form a complementary pair response. The complementary pair response is used to convert an AWG skirt response to a wavelength.

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

    PubMed

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

    2010-06-20

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

  17. Magnetic content addressable memories

    NASA Astrophysics Data System (ADS)

    Jiang, Zhenye

    Content Addressable Memories are designed with comparison circuits built into every bit cell. This parallel structure can increase the speed of searching from O(n) (as with Random Access Memories) to O(1), where n is the number of entries being searched. The high cost in hardware limits the application of CAM within situations where higher searching speed is extremely desired. Spintronics technology can build non-volatile Magnetic RAM with only one device for one bit cell. There are various technologies involved, like Magnetic Tunnel Junctions, off-easy-axis programming method, Synthetic Anti-Ferromagnetic tri-layers, Domain Wall displacement, Spin Transfer Torque tri-layers and etc. With them, particularly the Tunnel Magneto-Resistance variation in MTJ due to difference in magnetization polarity of the two magnets, Magnetic CAM can be developed with reduced hardware cost. And this is demonstrated by the discussion in this dissertation. Six MCAM designs are discussed. In the first design, comparand (C), local information (S) and their complements are stored into 4 MTJs connected in XOR gate pattern. The other five designs have one or two stacks for both information storage and comparison, and full TMR ratio can be taken advantage of. Two challenges for the five are specifically programming C without changing S and selectively programming a cell out of an array. The solutions to specific programming are: by confining the programming field for C in a ring structure design; by using field programming and spin polarized current programming respectively for C and S in the SAF+DW and SAF+STT tri-layer design; by making use of the difference in thresholds between direct mode and toggle mode switching in the SAF+SAF design. The problem of selective programming is addressed by off-easy-axis method and by including SAF tri-layers. Cell with STT tri-layers for both C and S can completely avoid the problems of specific and selective programming, but subject to the limit of

  18. A color sensor wavelength meter

    NASA Astrophysics Data System (ADS)

    Durfee, Dallin; Jackson, Jarom; Otterstrom, Nils; Jones, Tyler; Archibald, James

    2016-05-01

    We will discuss a laser wavelength meter based on a commercial color sensor chip consisting of an array of photodiodes with different absorptive color filters. By comparing the relative amplitudes of light on the photodiodes, the wavelength of light can be determined with picometer-level precision and with picometer-scale calibration drift over a period longer than a month. This work was supported by NSF Grant Number PHY-1205736.

  19. SWOC: Spectral Wavelength Optimization Code

    NASA Astrophysics Data System (ADS)

    Ruchti, G. R.

    2016-06-01

    SWOC (Spectral Wavelength Optimization Code) determines the wavelength ranges that provide the optimal amount of information to achieve the required science goals for a spectroscopic study. It computes a figure-of-merit for different spectral configurations using a user-defined list of spectral features, and, utilizing a set of flux-calibrated spectra, determines the spectral regions showing the largest differences among the spectra.

  20. Solid colloidal optical wavelength filter

    NASA Astrophysics Data System (ADS)

    Alvarez, J. L.

    1990-05-01

    A method for constructing a solid colloidal optical wavelength filter is discussed. The device was developed to filter optical wavelengths for spectroscopy, protection from intense radiation, monochromatizing, and analyzing optical radiation. The filter is formed by suspending spherical particles in a coagulable medium (such as setting plastic); agitating the particles and coagulable medium to produce an emulsion of particles suspended in the coagulable medium; and allowing the coagulable medium and suspended emulsion of particles to cool.

  1. Towards short wavelengths FELs workshop

    SciTech Connect

    Ben-Zvi, I.; Winick, H.

    1993-12-01

    This workshop was caged because of the growing perception in the FEL source community that recent advances have made it possible to extend FEL operation to wavelengths about two orders of magnitude shorter than the 240 nm that has been achieved to date. In addition short wavelength FELs offer the possibilities of extremely high peak power (several gigawatts) and very short pulses (of the order of 100 fs). Several groups in the USA are developing plans for such short wavelength FEL facilities. However, reviewers of these plans have pointed out that it would be highly desirable to first carry out proof-of-principle experiments at longer wavelengths to increase confidence that the shorter wavelength devices will indeed perform as calculated. The need for such experiments has now been broadly accepted by the FEL community. Such experiments were the main focus of this workshop as described in the following objectives distributed to attendees: (1) Define measurements needed to gain confidence that short wavelength FELs will perform as calculated. (2) List possible hardware that could be used to carry out these measurements in the near term. (3) Define a prioritized FEL physics experimental program and suggested timetable. (4) Form collaborative teams to carry out this program.

  2. High channel count and high precision channel spacing multi-wavelength laser array for future PICs.

    PubMed

    Shi, Yuechun; Li, Simin; Chen, Xiangfei; Li, Lianyan; Li, Jingsi; Zhang, Tingting; Zheng, Jilin; Zhang, Yunshan; Tang, Song; Hou, Lianping; Marsh, John H; Qiu, Bocang

    2014-01-01

    Multi-wavelength semiconductor laser arrays (MLAs) have wide applications in wavelength multiplexing division (WDM) networks. In spite of their tremendous potential, adoption of the MLA has been hampered by a number of issues, particularly wavelength precision and fabrication cost. In this paper, we report high channel count MLAs in which the wavelengths of each channel can be determined precisely through low-cost standard μm-level photolithography/holographic lithography and the reconstruction-equivalent-chirp (REC) technique. 60-wavelength MLAs with good wavelength spacing uniformity have been demonstrated experimentally, in which nearly 83% lasers are within a wavelength deviation of ±0.20 nm, corresponding to a tolerance of ±0.032 nm in the period pitch. As a result of employing the equivalent phase shift technique, the single longitudinal mode (SLM) yield is nearly 100%, while the theoretical yield of standard DFB lasers is only around 33.3%. PMID:25488111

  3. High channel count and high precision channel spacing multi-wavelength laser array for future PICs

    PubMed Central

    Shi, Yuechun; Li, Simin; Chen, Xiangfei; Li, Lianyan; Li, Jingsi; Zhang, Tingting; Zheng, Jilin; Zhang, Yunshan; Tang, Song; Hou, Lianping; Marsh, John H.; Qiu, Bocang

    2014-01-01

    Multi-wavelength semiconductor laser arrays (MLAs) have wide applications in wavelength multiplexing division (WDM) networks. In spite of their tremendous potential, adoption of the MLA has been hampered by a number of issues, particularly wavelength precision and fabrication cost. In this paper, we report high channel count MLAs in which the wavelengths of each channel can be determined precisely through low-cost standard μm-level photolithography/holographic lithography and the reconstruction-equivalent-chirp (REC) technique. 60-wavelength MLAs with good wavelength spacing uniformity have been demonstrated experimentally, in which nearly 83% lasers are within a wavelength deviation of ±0.20 nm, corresponding to a tolerance of ±0.032 nm in the period pitch. As a result of employing the equivalent phase shift technique, the single longitudinal mode (SLM) yield is nearly 100%, while the theoretical yield of standard DFB lasers is only around 33.3%. PMID:25488111

  4. Shifted excitation Raman difference spectroscopy for authentication of cheese and cheese analogues

    NASA Astrophysics Data System (ADS)

    Sowoidnich, Kay; Kronfeldt, Heinz-Detlef

    2016-04-01

    Food authentication and the detection of adulterated products are recent major issues in the food industry as these topics are of global importance for quality control and food safety. To effectively address this challenge requires fast, reliable and non-destructive analytical techniques. Shifted Excitation Raman Difference Spectroscopy (SERDS) is well suited for identification purposes as it combines the chemically specific information obtained by Raman spectroscopy with the ability for efficient fluorescence rejection. The two slightly shifted excitation wavelengths necessary for SERDS are realized by specially designed microsystem diode lasers. At 671 nm the laser (optical power: 50 mW, spectral shift: 0.7 nm) is based on an external cavity configuration whereas an emission at 783 nm (optical power: 110 mW, spectral shift: 0.5 nm) is achieved by a distributed feedback laser. To investigate the feasibility of SERDS for rapid and nondestructive authentication purposes four types of cheese and three different cheese analogues were selected. Each sample was probed at 8 different positions using integration times of 3-10 seconds and 10 spectra were recorded at each spot. Principal components analysis was applied to the SERDS spectra revealing variations in fat and protein signals as primary distinction criterion between cheese and cheese analogues for both excitation wavelengths. Furthermore, to some extent, minor compositional differences could be identified to discriminate between individual species of cheese and cheese analogues. These findings highlight the potential of SERDS for rapid food authentication potentially paving the way for future applications of portable SERDS systems for non-invasive in situ analysis.

  5. Experimental observation of magic-wavelength behavior of {sup 87}Rb atoms in an optical lattice

    SciTech Connect

    Lundblad, N.; Schlosser, M.; Porto, J. V.

    2010-03-15

    We demonstrate the cancellation of the differential ac Stark shift of the microwave hyperfine clock transition in trapped {sup 87}Rb atoms. Recent progress in metrology exploits so-called magic wavelengths, whereby an atomic ensemble can be trapped with laser light whose wavelength is chosen so that both levels of an optical atomic transition experience identical ac Stark shifts. Similar magic-wavelength techniques are not possible for the microwave hyperfine transitions in the alkali metals due to their simple electronic structure. We show, however, that ac Stark shift cancellation is indeed achievable for certain values of wavelength, polarization, and magnetic field. The cancellation comes at the expense of a small magnetic-field sensitivity. The technique demonstrated here has implications for experiments involving the precise control of optically trapped neutral atoms.

  6. Experimental observation of magic-wavelength behavior of Rb87 atoms in an optical lattice

    NASA Astrophysics Data System (ADS)

    Lundblad, N.; Schlosser, M.; Porto, J. V.

    2010-03-01

    We demonstrate the cancellation of the differential ac Stark shift of the microwave hyperfine clock transition in trapped Rb87 atoms. Recent progress in metrology exploits so-called magic wavelengths, whereby an atomic ensemble can be trapped with laser light whose wavelength is chosen so that both levels of an optical atomic transition experience identical ac Stark shifts. Similar magic-wavelength techniques are not possible for the microwave hyperfine transitions in the alkali metals due to their simple electronic structure. We show, however, that ac Stark shift cancellation is indeed achievable for certain values of wavelength, polarization, and magnetic field. The cancellation comes at the expense of a small magnetic-field sensitivity. The technique demonstrated here has implications for experiments involving the precise control of optically trapped neutral atoms.

  7. Spatially compressed dual-wavelength excitation Raman spectrometer.

    PubMed

    Cooper, John B; Marshall, Sarah; Jones, Richard; Abdelkader, Mohamed; Wise, Kent L

    2014-05-20

    The design and operation of a novel dual-laser excitation Raman instrument is described. The use of two lasers of differing wavelengths allows for a Raman spectrum covering all fundamental modes of vibration to be collected while minimizing fluorescence and allowing for spatial compression of the spectrum on an imaging detector. The use of diode lasers with integrated distributed Bragg reflector gratings facilitates the use of an integrated thermoelectric cooler to allow collection of shifted excitation spectra for both of the lasers, further enhancing the rejection of fluorescence. An example is given, which uses seven excitation wavelengths for each laser to reconstruct the Raman spectrum of a solvent in the presence of a highly fluorescent dye by using a sequentially shifted excitation Raman reconstruction algorithm. PMID:24922223

  8. Magic wavelengths for the 5 s - 18 s transition in rubidium

    NASA Astrophysics Data System (ADS)

    Goldschmidt, Elizabeth; Norris, David; Koller, Silvio; Wyllie, Robert; Brown, Roger; Porto, Trey; Safronova, Ulyana; Safronova, Marianna

    2015-05-01

    Magic wavelengths, for which there is no differential ac Stark shift for the ground and excited state of the atom, allow trapping of excited Rydberg atoms without broadening the optical transition. This is an important tool for implementing quantum gates and other quantum information protocols with Rydberg atoms, and reliable theoretical methods to find such magic wavelengths are thus extremely useful. We use a high-precision all-order method to calculate magic wavelengths for the 5 s - 18 s transition of rubidium near the 18 s - 6 p resonances. We compare the calculation to experiment by measuring the light shift for atoms held in a crossed optical dipole trap with wavelength tuned around the 18 s - 6p3 / 2 resonance at the experimentally convenient wavelength of 1064 nm.

  9. Measurement of thin films using very long acoustic wavelengths

    NASA Astrophysics Data System (ADS)

    Clement, G. T.; Nomura, H.; Adachi, H.; Kamakura, T.

    2013-12-01

    A procedure for measuring material thickness by means of necessarily long acoustic wavelengths is examined. The approach utilizes a temporal phase lag caused by the impulse time of wave momentum transferred through a thin layer that is much denser than its surrounding medium. In air, it is predicted that solid or liquid layers below approximately 1/2000 of the acoustic wavelength will exhibit a phase shift with an arctangent functional dependence on thickness and layer density. The effect is verified for thin films on the scale of 10 μm using audible frequency sound (7 kHz). Soap films as thin as 100 nm are then measured using 40 kHz air ultrasound. The method's potential for imaging applications is demonstrated by combining the approach with near-field holography, resulting in reconstructions with sub-wavelength resolution in both the depth and lateral directions. Potential implications at very high and very low acoustic frequencies are discussed.

  10. Wavelength stabilized multi-kW diode laser systems

    NASA Astrophysics Data System (ADS)

    Köhler, Bernd; Unger, Andreas; Kindervater, Tobias; Drovs, Simon; Wolf, Paul; Hubrich, Ralf; Beczkowiak, Anna; Auch, Stefan; Müntz, Holger; Biesenbach, Jens

    2015-03-01

    We report on wavelength stabilized high-power diode laser systems with enhanced spectral brightness by means of Volume Holographic Gratings. High-power diode laser modules typically have a relatively broad spectral width of about 3 to 6 nm. In addition the center wavelength shifts by changing the temperature and the driving current, which is obstructive for pumping applications with small absorption bandwidths. Wavelength stabilization of high-power diode laser systems is an important method to increase the efficiency of diode pumped solid-state lasers. It also enables power scaling by dense wavelength multiplexing. To ensure a wide locking range and efficient wavelength stabilization the parameters of the Volume Holographic Grating and the parameters of the diode laser bar have to be adapted carefully. Important parameters are the reflectivity of the Volume Holographic Grating, the reflectivity of the diode laser bar as well as its angular and spectral emission characteristics. In this paper we present detailed data on wavelength stabilized diode laser systems with and without fiber coupling in the spectral range from 634 nm up to 1533 nm. The maximum output power of 2.7 kW was measured for a fiber coupled system (1000 μm, NA 0.22), which was stabilized at a wavelength of 969 nm with a spectral width of only 0.6 nm (90% value). Another example is a narrow line-width diode laser stack, which was stabilized at a wavelength of 1533 nm with a spectral bandwidth below 1 nm and an output power of 835 W.

  11. Multi-wavelength narrow linewidth fiber laser based on distributed feedback fiber lasers

    NASA Astrophysics Data System (ADS)

    Lv, Jingsheng; Qi, Haifeng; Song, Zhiqiang; Guo, Jian; Ni, Jiasheng; Wang, Chang; Peng, Gangding

    2016-06-01

    A narrow linewidth laser configuration based on distributed feedback fiber lasers (DFB-FL) with eight wavelengths in the international telecommunication union (ITU) grid is presented and realized. In this laser configuration, eight phase-shifted gratings in series are bidirectionally pumped by two 980-nm laser diodes (LDs). The final laser output with over 10-mW power for each wavelength can be obtained, and the maximum power difference within eight wavelengths is 1.2 dB. The laser configuration with multiple wavelengths and uniform power outputs can be very useful in large scaled optical fiber hydrophone fields.

  12. Sub-wavelength plasmon laser

    DOEpatents

    Bora, Mihail; Bond, Tiziana C.

    2016-04-19

    A plasmonic laser device has resonant nanocavities filled with a gain medium containing an organic dye. The resonant plasmon frequencies of the nanocavities are tuned to align with both the absorption and emission spectra of the dye. Variables in the system include the nature of the dye and the wavelength of its absorption and emission, the wavelength of the pumping radiation, and the resonance frequencies of the nanocavities. In addition the pumping frequency of the dye is selected to be close to the absorption maximum.

  13. Innovative Long Wavelength Infrared Detector Workshop Proceedings

    NASA Technical Reports Server (NTRS)

    Grunthaner, Frank J.

    1990-01-01

    The focus of the workshop was on innovative long wavelength (lambda less than 17 microns) infrared (LWIR) detectors with the potential of meeting future NASA and DoD long-duration space application needs. Requirements are for focal plane arrays which operate near 65K using active refrigeration with mission lifetimes of five to ten years. The workshop addressed innovative concepts, new material systems, novel device physics, and current progress in relation to benchmark technology. It also provided a forum for discussion of performance characterization, producibility, reliability, and fundamental limitations of device physics. It covered the status of the incumbent HgCdTe technology, which shows encouraging progress towards LWIR arrays, and provided a snapshot of research and development in several new contender technologies.

  14. Solid colloidal optical wavelength filter

    DOEpatents

    Alvarez, Joseph L.

    1992-01-01

    A solid colloidal optical wavelength filter includes a suspension of spheal particles dispersed in a coagulable medium such as a setting plastic. The filter is formed by suspending spherical particles in a coagulable medium; agitating the particles and coagulable medium to produce an emulsion of particles suspended in the coagulable medium; and allowing the coagulable medium and suspended emulsion of particles to cool.

  15. Quantum cascade lasers with dual-wavelength interdigitated cascades

    NASA Astrophysics Data System (ADS)

    Mosely, Trinesha S.; Straub, Axel; Gmachl, Claire; Colombelli, Raffaele; Troccoli, Mariano; Capasso, Federico; Sivco, Deborah L.; Cho, Alfred Y.

    2002-03-01

    A quantum cascade (QC) laser with a dual-wavelength interdigitated cascade is presented. Its active core consists of a stack of active regions and injectors designed for emission at one wavelength (8.0 μm) interleaved with a second stack emitting at a substantially different wavelength (9.5 μm), and the two injectors were designed to either bridge the 8.0 μm active region to the 9.5 μm one, or vice versa. Clear two-wavelength laser action is observed, demonstrating the viability of this approach to achieve multi-wavelength laser emission in the mid-infrared. Aside from providing two-wavelength operation, this laser design can also be used to test the role of charge transport in the injectors, which customarily bridge successive active regions together. We will present early results of this study. The work was partly supported by DARPA/US ARO under contract number DAAD19-00-C-0096. A. S. acknowledges the support of the Deutsche Studienstiftung. T. S. M. present address: Southern University and A&M College, Baton Rouge, LA.

  16. Our World: Fluid Shift

    NASA Video Gallery

    Learn about the circulatory system and how gravity aids blood flow in our bodies here on Earth. Find out how NASA flight surgeons help the astronauts deal with the fluid shift that happens during s...

  17. Shape-Shifting Plastic

    SciTech Connect

    2015-05-20

    A new plastic developed by ORNL and Washington State University transforms from its original shape through a series of temporary shapes and returns to its initial form. The shape-shifting process is controlled through changes in temperature

  18. Molecular Electronic Shift Registers

    NASA Technical Reports Server (NTRS)

    Beratan, David N.; Onuchic, Jose N.

    1990-01-01

    Molecular-scale shift registers eventually constructed as parts of high-density integrated memory circuits. In principle, variety of organic molecules makes possible large number of different configurations and modes of operation for such shift-register devices. Several classes of devices and implementations in some specific types of molecules proposed. All based on transfer of electrons or holes along chains of repeating molecular units.

  19. 2014 ASHG Awards and Addresses

    PubMed Central

    2015-01-01

    Each year at the annual meeting of The American Society of Human Genetics (ASHG), addresses are given in honor of The Society and a number of award winners. A summary of each of these addresses is given below. On the following pages, we have printed the presidential address and the addresses for the William Allan Award, the Curt Stern Award, and the Victor A. McKusick Leadership Award. Webcasts of these addresses, as well as those of many other presentations, can be found at http://www.ashg.org.

  20. 2013 ASHG Awards and Addresses

    PubMed Central

    2014-01-01

    Each year at the annual meeting of The American Society of Human Genetics (ASHG), addresses are given in honor of The Society and a number of award winners. A summary of each of these addresses is given below. On the following pages, we have printed the Presidential Address and the addresses for the William Allan Award, the Curt Stern Award, and the Victor A. McKusick Leadership Award. Webcasts of these addresses, as well as those of many other presentations, can be found at http://www.ashg.org.

  1. Operating principle, saturable loss, and self-frequency shift in Kerr-shift mode-locked lasers

    NASA Astrophysics Data System (ADS)

    Herrmann, J.; Müller, M.

    1995-01-01

    The operating principle of a recently demonstrated new Kerr-induced ultrashort-pulse-generation technique called Kerr-shift mode locking is analyzed. It is shown that in Kerr-shift mode-locked lasers an intensity-dependent red shift of the central laser frequency is caused by the combined action of the self-phase modulation that is due to the nonlinear index laser host medium and the Lorentzian-shaped profile of the homogeneously broadened gain. The introduction of a long-pass wavelength filter (knife-edge) transforms this intensity-dependent frequency shift into fast self-amplitude modulation (SAM), which is accompanied by an additional linear red shift of the central laser frequency. The SAM parameter and the linear frequency shift are calculated and compared with the experimental results.

  2. High power pumped MID-IR wavelength devices using nonlinear frequency mixing (NFM)

    NASA Technical Reports Server (NTRS)

    Sanders, Steven (Inventor); Lang, Robert J. (Inventor); Waarts, Robert G. (Inventor)

    2001-01-01

    Laser diode pumped mid-IR wavelength sources include at least one high power, near-IR wavelength, injection and/or sources wherein one or both of such sources may be tunable providing a pump wave output beam to a quasi-phase matched (QPM) nonlinear frequency mixing (NFM) device. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Wavelength tuning of at least one of the sources advantageously provides the ability for optimizing pump or injection wavelengths to match the QPM properties of the NFM device enabling a broad range of mid-IR wavelength selectivity. Also, pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

  3. High power pumped mid-IR wavelength systems using nonlinear frequency mixing (NFM) devices

    NASA Technical Reports Server (NTRS)

    Sanders, Steven (Inventor); Lang, Robert J. (Inventor); Waarts, Robert G. (Inventor)

    1999-01-01

    Laser diode pumped mid-IR wavelength systems include at least one high power, near-IR wavelength, injection and/or sources wherein one or both of such sources may be tunable providing a pump wave output beam to a quasi-phase matched (QPM) nonlinear frequency mixing (NFM) device. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Wavelength tuning of at least one of the sources advantageously provides the ability for optimizing pump or injection wavelengths to match the QPM properties of the NFM device enabling a broad range of mid-IR wavelength selectivity. Also, pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

  4. Measurement of Magic Wavelengths for the Ca+ 40 Clock Transition

    NASA Astrophysics Data System (ADS)

    Liu, Pei-Liang; Huang, Yao; Bian, Wu; Shao, Hu; Guan, Hua; Tang, Yong-Bo; Li, Cheng-Bin; Mitroy, J.; Gao, Ke-Lin

    2015-06-01

    We demonstrate experimentally the existence of magic wavelengths and determine the ratio of oscillator strengths for a single trapped ion. For the first time, two magic wavelengths near 396 nm for the Ca40 + clock transition are measured simultaneously with high precision. By tuning the applied laser to an intermediate wavelength between transitions 4 s1 /2→4 p1 /2 and 4 s1 /2→4 p3 /2, the sensitivity of the clock transition Stark shift to the oscillator strengths is greatly enhanced. Furthermore, with the measured magic wavelengths, we determine the ratio of the oscillator strengths with a deviation of less than 0.5%. Our experimental method may be applied to measure magic wavelengths for other ion clock transitions. Promisingly, the measurement of these magic wavelengths paves the way to building all-optical trapped ion clocks.

  5. Addressable Inverter Matrix Tests Integrated-Circuit Wafer

    NASA Technical Reports Server (NTRS)

    Buehler, Martin G.

    1988-01-01

    Addressing elements indirectly through shift register reduces number of test probes. With aid of new technique, complex test structure on silicon wafer tested with relatively small number of test probes. Conserves silicon area by reduction of area devoted to pads. Allows thorough evaluation of test structure characteristics and of manufacturing process parameters. Test structure consists of shift register and matrix of inverter/transmission-gate cells connected to two-by-ten array of probe pads. Entire pattern contained in square area having only 1.6-millimeter sides. Shift register is conventional static CMOS device using inverters and transmission gates in master/slave D flip-flop configuration.

  6. Scaled Strong Field Interactions at Long Wavelengths

    NASA Astrophysics Data System (ADS)

    Sistrunk, Emily Frances

    The strong field regime describes interactions between light and matter where the electric field of the laser is a significant fraction of the binding field of the atom. Short pulsed lasers are capable of producing local fields on the order of the atomic unit of electric field. Under the influence of such strong fields, the ionization regime and electron dynamics are highly dependent on the wavelength used to drive the interaction. Few studies have been performed in the mid-infrared (MIR) spectral range. Using MIR wavelengths, the ponderomotive energy, Up, imposed on the electrons can be a factor of 20 greater than in the visible and near-infrared. Experiments on above threshold ionization (ATI) of cesium, nonsequential ionization (NSI) of noble gases, and high harmonic generation (HHG) in condensed phase media highlight the benefits of performing strong field investigations in the MIR. The photoelectron energy spectrum from above threshold ionization (ATI) of atoms provides details about the strong field interaction. Cesium atoms driven by a 3.6 mum laser indicate that excited states can play a large role in ionization from the ground state. Previous experiments on argon in the near-infrared can be compared to cesium at 3.6 im due to their similar Keldysh-scaling. Unlike argon, the measured ionization yield in cesium saturates at a higher intensity than predicted due to the Stark shift of the ground state. Such shifts have not been detected in argon. The low-lying 6P excited states of cesium produce a strong effect on the photoelectron energy spectrum, resulting in a splitting of each ATI peak. Enhancements in the photoelectron energy spectrum similar to those found in argon are observed in cesium. These enhancements are relatively insensitive to ellipticity of the drive laser. To take advantage of the large ponderomotive energy associated with Mid-IR lasers, ionization of argon, krypton and xenon is studied at 3.6 im. The factor of 20 increase in Up between the

  7. Differential Shift Estimation in the Absence of Coherence: Performance Analysis and Benefits of Polarimetry

    NASA Astrophysics Data System (ADS)

    Villano, Michelangelo; Papathanassiou, Konstantinos P.

    2011-03-01

    The estimation of the local differential shift between synthetic aperture radar (SAR) images has proven to be an effective technique for monitoring glacier surface motion. As images acquired over glaciers by short wavelength SAR systems, such as TerraSAR-X, often suffer from a lack of coherence, image features have to be exploited for the shift estimation (feature-tracking).The present paper addresses feature-tracking with special attention to the feasibility requirements and the achievable accuracy of the shift estimation. In particular, the dependence of the performance on image characteristics, such as texture parameters, signal-to-noise ratio (SNR) and resolution, as well as on processing techniques (despeckling, normalised cross-correlation versus maximum likelihood estimation) is analysed by means of Monte-Carlo simulations. TerraSAR-X data acquired over the Helheim glacier, Greenland, and the Aletsch glacier, Switzerland, have been processed to validate the simulation results.Feature-tracking can benefit of the availability of fully-polarimetric data. As some image characteristics, in fact, are polarisation-dependent, the selection of an optimum polarisation leads to improved performance. Furthermore, fully-polarimetric SAR images can be despeckled without degrading the resolution, so that additional (smaller-scale) features can be exploited.

  8. Observation of dual-wavelength solitons and bound states in a nanotube/microfiber mode-locking fiber laser

    NASA Astrophysics Data System (ADS)

    Zeng, C.; Cui, Y. D.; Guo, J.

    2015-07-01

    We report on the experimental observation of dual-wavelength soliton and the phase-locked bound state in an all-fiber laser mode-locked by a carbon nanotubes/microfiber saturable absorber. The operation wavelengths are strongly dependent on the intracavity loss. By adjusting an attenuator to increase the intracavity loss, mode-locking wavelength shifts from 1557 to 1531 nm. With the appropriate pump power and intracavity loss, dual-wavelength solitons are achieved simultaneously. In addition, the phase-locked bound-state solitons are also observed at the two wavelengths. The pulse separation and phase difference are related to the first-order Kelly sidebands.

  9. Wavelength Selection in Gyrotactic Bioconvection.

    PubMed

    Ghorai, S; Singh, R; Hill, N A

    2015-06-01

    We investigate pattern formation by swimming micro-organisms (bioconvection), when their orientation is determined by balance between gravitational and viscous torques (gyrotaxis), due to being bottom heavy. The governing equations, which consist of the Navier-Stokes equations for an incompressible fluid coupled with a micro-organism conservation equation, are solved numerically in a large cross section chamber with periodic boundary conditions in the horizontal directions. The influence of key parameters on wavelength selection in bioconvection patterns is investigated numerically. For realistic ranges of parameter values, the computed wavelengths are in good agreement with the experimental observations provided that the diffusion due to randomness in cell swimming behaviour is small, refuting a recently published claim that the mathematical model becomes inaccurate at long times. We also provide the first computational evidence of "bottom-standing" plumes in a three-dimensional simulation. PMID:25963246

  10. Multi-wavelength holographic profilometry

    NASA Astrophysics Data System (ADS)

    Barbosa, E. A.; Gesualdi, M. R.; Muramatsu, M.

    2006-01-01

    A novel method for surface profilometry by holography is presented. We used a diode laser emitting at many wavelengths simultaneously as the light source and a Bi 12TiO 20 (BTO) crystal as the holographic medium in single exposure processes. The employ of multi-wavelength, large free spectral range (FSR) lasers leads to holographic images covered of interference fringes corresponding to the contour lines of the studied surface. In order to obtain the relief of the studied surface, the fringe analysis was performed by the phase stepping technique (PST) and the phase unwrapping was carried out by the Cellular-automata method. We analysed the relief of a tilted flat metallic bar and a tooth prosthesis.

  11. Review of short wavelength lasers

    SciTech Connect

    Hagelstein, P.L.

    1985-03-18

    There has recently been a substantial amount of research devoted to the development of short wavelength amplifiers and lasers. A number of experimental results have been published wherein the observation of significant gain has been claimed on transitions in the EUV and soft x-ray regimes. The present review is intended to discuss the main approaches to the creation of population inversions and laser media in the short wavelength regime, and hopefully aid workers in the field by helping to provide access to a growing literature. The approaches to pumping EUV and soft x-ray lasers are discussed according to inversion mechanism. The approaches may be divided into roughly seven categories, including collisional excitation pumping, recombination pumping, direct photoionization and photoexcitation pumping, metastable state storage plus optical pumping, charge exchange pumping, and finally, the extension of free electron laser techniques into the EUV and soft x-ray regimes. 250 references.

  12. Absorption driven focus shift

    NASA Astrophysics Data System (ADS)

    Harrop, N.; Wolf, S.; Maerten, O.; Dudek, K.; Ballach, S.; Kramer, R.

    2016-03-01

    Modern high brilliance near infrared lasers have seen a tremendous growth in applications throughout the world. Increased productivity has been achieved by higher laser power and increased brilliance of lasers. Positive impacts on the performance and costs of parts are opposed to threats on process stability and quality, namely shift of focus position over time. A high initial process quality will be reduced by contamination of optics, eventually leading to a focus shift or even destruction of the optics. Focus analysis at full power of multi-kilowatt high brilliance lasers is a very demanding task because of high power densities in the spot and the high power load on optical elements. With the newly developed high power projection optics, the High-Power Micro-Spot Monitor High Brilliance (HP-MSM-HB) is able to measure focus diameter as low as 20 μm at power levels up to 10 kW at very low internal focus shift. A main driving factor behind thermally induced focus shift is the absorption level of the optical element. A newly developed measuring system is designed to determine the relative absorption level in reference to a gold standard. Test results presented show a direct correlation between absorption levels and focus shift. The ability to determine the absorption level of optical elements as well as their performance at full processing power before they are put to use, enables a high level of quality assurance for optics manufacturers and processing head manufacturers alike.

  13. Geometric basis for the far red shift. [in crop canopies

    NASA Technical Reports Server (NTRS)

    Vanderbilt, V. C.; Grant, L.

    1985-01-01

    An alternative explanation is offered for the redshift (an abrupt change in the ratio of scattering to absorption in the radiance spectra of heading canopies of such crops as wheat and grain sorghum). The shift occurs abruptly at wavelengths near the red-infrared boundary towards the longer wavelengths. The new explanation, following that of Collins (1978) and Schutt et al. (1984), is based on one particular architectural change that occurs in any heading plant canopy. Specifically, the newly extended heads alter the interaction between light and the established foliage. The heads reduce the amount of sunlight striking the topmost leaves which are generally comparatively good specular reflectors. The heads also reduce the ability to observe the specularly reflecting leaves. The reduction in the amplitude of the radiance (due to decreased specularly reflected light) at heading appears to be a shift in the wavelength of the red edge. It is proposed that vertical (amplitude) shifts - due to changes in the amount of specularly reflected light as a function of heading - have been misinterpreted as horizontal (wavelength) shifts due in part to the characteristic shape of the radiance curve at the red edge.

  14. Interferometric fiber Bragg grating shift demodulation

    NASA Astrophysics Data System (ADS)

    Stepien, Karol; Jóźwik, Michalina; Nasilowski, Tomasz

    2015-09-01

    In this paper we present a fiber Bragg grating shift demodulator with changeable resolution based on an unbalanced fiber Mach-Zehnder interferometer. Preliminary research proves phase sensitivity to Bragg wavelength changes of 6,83 rad/mɛ. Phase sensitivity can be modified by changing the optical path difference witch is only limited by the coherence length of light reflected by the fiber Bragg grating. This solution can be used as a single sensor or as a part of a more complex system.

  15. A Shift in Emphasis: Comments on CAE's New Mission Statement

    ERIC Educational Resources Information Center

    Anderson-Levitt, Kathryn M.

    2007-01-01

    In a presidential address prepared for the 2006 Council on Anthropology and Education (CAE) meeting, I argue that the new mission statement for CAE represents not a new direction for the organization, but simply a shift in emphasis, albeit an important and timely shift.

  16. Effects of filtering visual short wavelengths during nocturnal shiftwork on sleep and performance.

    PubMed

    Rahman, Shadab A; Shapiro, Colin M; Wang, Flora; Ainlay, Hailey; Kazmi, Syeda; Brown, Theodore J; Casper, Robert F

    2013-10-01

    Circadian phase resetting is sensitive to visual short wavelengths (450-480 nm). Selectively filtering this range of wavelengths may reduce circadian misalignment and sleep impairment during irregular light-dark schedules associated with shiftwork. We examined the effects of filtering short wavelengths (<480 nm) during night shifts on sleep and performance in nine nurses (five females and four males; mean age ± SD: 31.3 ± 4.6 yrs). Participants were randomized to receive filtered light (intervention) or standard indoor light (baseline) on night shifts. Nighttime sleep after two night shifts and daytime sleep in between two night shifts was assessed by polysomnography (PSG). In addition, salivary melatonin levels and alertness were assessed every 2 h on the first night shift of each study period and on the middle night of a run of three night shifts in each study period. Sleep and performance under baseline and intervention conditions were compared with daytime performance on the seventh day shift, and nighttime sleep following the seventh daytime shift (comparator). On the baseline night PSG, total sleep time (TST) (p < 0.01) and sleep efficiency (p = 0.01) were significantly decreased and intervening wake times (wake after sleep onset [WASO]) (p = 0.04) were significantly increased in relation to the comparator night sleep. In contrast, under intervention, TST was increased by a mean of 40 min compared with baseline, WASO was reduced and sleep efficiency was increased to levels similar to the comparator night. Daytime sleep was significantly impaired under both baseline and intervention conditions. Salivary melatonin levels were significantly higher on the first (p < 0.05) and middle (p < 0.01) night shifts under intervention compared with baseline. Subjective sleepiness increased throughout the night under both conditions (p < 0.01). However, reaction time and throughput on vigilance tests were similar to daytime performance under intervention but impaired

  17. Predicting catastrophic shifts.

    PubMed

    Weissmann, Haim; Shnerb, Nadav M

    2016-05-21

    Catastrophic shifts are known to pose a serious threat to ecology, and a reliable set of early warning indicators is desperately needed. However, the tools suggested so far have two problems. First, they cannot discriminate between a smooth transition and an imminent irreversible shift. Second, they aimed at predicting the tipping point where a state loses its stability, but in noisy spatial system the actual transition occurs when an alternative state invades. Here we suggest a cluster tracking technique that solves both problems, distinguishing between smooth and catastrophic transitions and to identify an imminent shift in both cases. Our method may allow for the prediction, and thus hopefully the prevention of such transitions, avoiding their destructive outcomes. PMID:26970446

  18. Isotope shift in chromium

    NASA Astrophysics Data System (ADS)

    Furmann, B.; Jarosz, A.; Stefańska, D.; Dembczyński, J.; Stachowska, E.

    2005-01-01

    Thirty-three spectral lines of chromium atom in the blue-violet region (425-465 nm) have been investigated with the method of laser-induced resonance fluorescence on an atomic beam. For all the lines, the isotope shifts for every pair of chromium isotopes have been determined. The lines can be divided into six groups, according to the configuration of the upper and lower levels. Electronic factors of the field shift and the specific mass shift ( Fik and MikSMS, respectively) have been evaluated and the values for each pure configuration involved have been determined. Comparison of the values Fik and MikSMS to the ab initio calculations results has been performed. The presence of crossed second order (CSO) effects has been observed.

  19. Passive cavity surface-emitting lasers: option of temperature-insensitive lasing wavelength for uncooled dense wavelength division multiplexing systems

    NASA Astrophysics Data System (ADS)

    Shchukin, V. A.; Ledentsov, N. N.; Slight, T.; Meredith, W.; Gordeev, N. Y.; Nadtochy, A. M.; Payusov, A. S.; Maximov, M. V.; Blokhin, S. A.; Blokhin, A. A.; Zadiranov, Yu. M.; Maleev, N. A.; Ustinov, V. M.; Choquette, K. D.

    2016-03-01

    A concept of passive cavity surface-emitting laser is proposed aimed to control the temperature shift of the lasing wavelength. The device contains an all-semiconductor bottom distributed Bragg reflector (DBR), in which the active medium is placed, a dielectric resonant cavity and a dielectric top DBR, wherein at least one of the dielectric materials has a negative temperature coefficient of the refractive index, dn/dT < 0. This is shown to be the case for commonly used dielectric systems SiO2/TiO2 and SiO2/Ta2O5. Two SiO2/TiO2 resonant structures having a cavity either of SiO2 or TiO2 were deposited on a substrate, their optical power reflectance spectra were measured at various temperatures, and refractive index temperature coefficients were extracted, dn/dT = 0.0021 K-1 for SiO2 and dn/dT = -0.0092 K-1 for TiO2. Using such dielectric materials allows designing passive cavity surface-emitting lasers having on purpose either positive, or zero, or negative temperature shift of the lasing wavelength dλ/dT. A design for temperature-insensitive lasing wavelength (dλ/dT = 0) is proposed. Employing devices with temperature-insensitive lasing wavelength in wavelength division multiplexing systems may allow significant reducing of the spectral separation between transmission channels and an increase in number of channels for a defined spectral interval enabling low cost energy efficient uncooled devices.

  20. Phase-Shifting Zernike Interferometer Wavefront Sensor

    NASA Technical Reports Server (NTRS)

    Wallace, J. Kent; Rao, Shanti; Jensen-Clem, Rebecca M.

    2011-01-01

    The canonical Zernike phase-contrast technique transforms a phase object in one plane into an intensity object in the conjugate plane. This is done by applying a static pi/2 phase shift to the central core (approx. lambda/diameter) of the PSF which is intermediate between the input and output plane. Here we present a new architecture for this sensor. First, the optical system is simple and all reflective, and second the phase shift in the central core of the PSF is dynamic and can be made arbitrarily large. This common-path, all-reflective design makes it minimally sensitive to vibration, polarization and wavelength. We review the theory of operation, describe the optical system, summarize numerical simulations and sensitivities and review results from a laboratory demonstration of this novel instrument.

  1. Phase-Shifting Zernike Interferometer Wavefront Sensor

    NASA Technical Reports Server (NTRS)

    Wallace, J. Kent; Rao, Shanti; Jensen-Clemb, Rebecca M.; Serabyn, Gene

    2011-01-01

    The canonical Zernike phase-contrast technique1,2,3,4 transforms a phase object in one plane into an intensity object in the conjugate plane. This is done by applying a static pi/2 phase shift to the central core (approx. lambda/D) of the PSF which is intermediate between the input and output planes. Here we present a new architecture for this sensor. First, the optical system is simple and all reflective. Second, the phase shift in the central core of the PSF is dynamic and or arbitrary size. This common-path, all-reflective design makes it minimally sensitive to vibration, polarization and wavelength. We review the theory of operation, describe the optical system, summarize numerical simulations and sensitivities and review results from a laboratory demonstration of this novel instrument

  2. Tunable microring based on-chip interrogator for wavelength-modulated optical sensors

    NASA Astrophysics Data System (ADS)

    Shen, Ao; Qiu, Chen; Yang, Longzhi; Dai, Tingge; Li, Yubo; Yu, Hui; Hao, Yinlei; Jiang, Xiaoqing; Yang, Jianyi

    2015-04-01

    An interrogation system for wavelength-modulated optical sensors based on tunable microring filter has been proposed and demonstrated both theoretically and experimentally. The wavelength shift of the sensors can be readout from the shift of the peak optical output of the system by scanning the resonant wavelength of the microring filter. We fabricate the interrogator on the silicon-on-insulator platform and a fiber Bragg grating sensor (FBG) is precisely interrogated. The Lorentz spectrum of the microring filter can de-flatten the output spectrum of the FBG and improve the interrogating resolution efficiently. Such a technique potentially provides a compact (only 50×50 μm2), low-cost, and high-performance (1 pm resolution) approach for the interrogation of the wavelength-modulated sensor and distributed sensor arrays.

  3. Optical extension at the 193-nm wavelength

    NASA Astrophysics Data System (ADS)

    Zandbergen, Peter; McCallum, Martin; Amblard, Gilles R.; Domke, Wolf-Dieter; Smith, Bruce W.; Zavyalova, Lena; Petersen, John S.

    1999-07-01

    Lithography at 193nm is the first optical lithography technique that will be introduced for manufacturing of technology levels. where the required dimensions are smaller than the actual wavelength. This paper explores several techniques to extend 193nm to low k1 lithography. Most attention is given to binary mask solution in at 130nm dimensions, where k1 is 0.4. Various strong and Gaussian quadrupole illuminators were designed, manufactured and tested for this application. Strong quadrupoles show that largest DOF improvements. The drawback however, is that these strong quadrupoles are very duty cycle and dimensions specific, resulting in large proximity biases between different duty cycles. Due to their design, Gaussian quadrupoles sample much wider frequency ranges, resulting in less duty cycles specific DOF improvements and less proximity basis. At sub-130nm dimensions, strong phase shift masks provide significant latitude improvements, when compared to binary masks with quadrupole illumination. However, differences in dose to size for different duty cycles were up to 25 percent. For definition of contact holes, linewidth biasing through silylation, a key feature of the CARL bi-layer resist approach, demonstrated significant DOF latitude improvements compared to SLR at 140nm and 160nm contact holes.

  4. Lattice-induced nonadiabatic frequency shifts in optical lattice clocks

    SciTech Connect

    Beloy, K.

    2010-09-15

    We consider the frequency shift in optical lattice clocks which arises from the coupling of the electronic motion to the atomic motion within the lattice. For the simplest of three-dimensional lattice geometries this coupling is shown to affect only clocks based on blue-detuned lattices. We have estimated the size of this shift for the prospective strontium lattice clock operating at the 390-nm blue-detuned magic wavelength. The resulting fractional frequency shift is found to be on the order of 10{sup -18} and is largely overshadowed by the electric quadrupole shift. For lattice clocks based on more complex geometries or other atomic systems, this shift could potentially be a limiting factor in clock accuracy.

  5. Activating the Disadvantaged. Variations in Addressing Youth Transitions across Europe

    ERIC Educational Resources Information Center

    Pohl, Axel; Walther, Andreas

    2007-01-01

    The term activation refers to a shift in social policies, through which individuals are given more responsibility for their own social inclusion. This article provides a comparative analysis of the different ways in which EU member states interpret and implement the concept of activation by addressing the transitions of disadvantaged young people…

  6. Eluding catastrophic shifts

    PubMed Central

    Villa Martín, Paula; Bonachela, Juan A.; Levin, Simon A.; Muñoz, Miguel A.

    2015-01-01

    Transitions between regimes with radically different properties are ubiquitous in nature. Such transitions can occur either smoothly or in an abrupt and catastrophic fashion. Important examples of the latter can be found in ecology, climate sciences, and economics, to name a few, where regime shifts have catastrophic consequences that are mostly irreversible (e.g., desertification, coral reef collapses, and market crashes). Predicting and preventing these abrupt transitions remains a challenging and important task. Usually, simple deterministic equations are used to model and rationalize these complex situations. However, stochastic effects might have a profound effect. Here we use 1D and 2D spatially explicit models to show that intrinsic (demographic) stochasticity can alter deterministic predictions dramatically, especially in the presence of other realistic features such as limited mobility or spatial heterogeneity. In particular, these ingredients can alter the possibility of catastrophic shifts by giving rise to much smoother and easily reversible continuous ones. The ideas presented here can help further understand catastrophic shifts and contribute to the discussion about the possibility of preventing such shifts to minimize their disruptive ecological, economic, and societal consequences. PMID:25825772

  7. Eluding catastrophic shifts.

    PubMed

    Villa Martín, Paula; Bonachela, Juan A; Levin, Simon A; Muñoz, Miguel A

    2015-04-14

    Transitions between regimes with radically different properties are ubiquitous in nature. Such transitions can occur either smoothly or in an abrupt and catastrophic fashion. Important examples of the latter can be found in ecology, climate sciences, and economics, to name a few, where regime shifts have catastrophic consequences that are mostly irreversible (e.g., desertification, coral reef collapses, and market crashes). Predicting and preventing these abrupt transitions remains a challenging and important task. Usually, simple deterministic equations are used to model and rationalize these complex situations. However, stochastic effects might have a profound effect. Here we use 1D and 2D spatially explicit models to show that intrinsic (demographic) stochasticity can alter deterministic predictions dramatically, especially in the presence of other realistic features such as limited mobility or spatial heterogeneity. In particular, these ingredients can alter the possibility of catastrophic shifts by giving rise to much smoother and easily reversible continuous ones. The ideas presented here can help further understand catastrophic shifts and contribute to the discussion about the possibility of preventing such shifts to minimize their disruptive ecological, economic, and societal consequences. PMID:25825772

  8. Trophic shift, not collapse

    USGS Publications Warehouse

    Madenjian, Charles P.; Rutherford, Edward S.; Stow, Craig A.; Roseman, Edward F.; He, Ji X.

    2013-01-01

    scientists who are closely monitoring Lake Huron’s food web, we believe that the ongoing changes are more accurately characterized as a trophic shift in which benthic pathways have become more prominent. While decreases in abundance have occurred for some species, others are experiencing improved reproduction resulting in the restoration of several important native species.

  9. Fourier transform infrared phase shift cavity ring down spectrometer

    NASA Astrophysics Data System (ADS)

    Schundler, Elizabeth; Mansur, David J.; Vaillancourt, Robert; Benedict-Gill, Ryan; Newbry, Scott P.; Engel, James R.; Rentz Dupuis, Julia

    2013-05-01

    We report on our current status towards the development of a prototype Fourier transform infrared phase shift cavity ring down spectrometer (FTIR-PS-CRDS) system under a U.S. EPA SBIR contract. Our system uses the inherent wavelength-dependent modulation imposed by the FTIR on a broadband thermal source for the phase shift measurement. This spectrally-dependent phase shift is proportional to the spectrally-dependent ring down time, which is proportional to the losses of the cavity including those due to molecular absorption. Our approach is a broadband and spectral range enhancement to conventional CRDS which is typically done in the near IR at a single wavelength; at the same time our approach is a sensitivity enhancement to traditional FTIR owing to the long effective path of the resonant cavity. In this paper we present a summary of the theory including performance projections and the design details of the prototype FTIR-PS-CRDS system.

  10. Wavelength tunable alexandrite regenerative amplifier

    SciTech Connect

    Harter, D.J.; Bado, P.

    1988-11-01

    We describe a wavelength tunable alexandrite regenerative amplifier which is used to amplify nanosecond slices from a single-frequency cw dye laser or 50-ps pulses emitted by a diode laser to energies in the 10-mJ range. The amplified 5-ns slices generated by the cw-pumped line narrowed dye laser are Fourier transform limited. The 50-ps pulses emitted by a gain-switched diode laser are amplified by more than 10 orders of magnitude in a single stage.

  11. Plasmonic lens for ultraviolet wavelength

    NASA Astrophysics Data System (ADS)

    Takeda, Minoru; Tanimoto, Takuya; Inoue, Tsutomu; Aizawa, Kento

    2016-09-01

    A plasmonic lens (PL) is one of the promising photonic devices utilizing the surface plasmon wave. In this study, we have newly developed a PL with a 3.5 µm diameter for a wavelength of 375 nm (ultraviolet region). It is composed of multiple circular slit apertures milled in aluminum (Al) thin film. We have simulated the electric field distribution of the PL, and confirmed that a tightly focused beam spot of subwavelength size in the far-field region was attained. We have also measured the focusing characteristics of the PL using a near-field scanning optical microscope (NSOM) and compared them with the calculated results.

  12. BIN Diode For Submillimeter Wavelengths

    NASA Technical Reports Server (NTRS)

    Maserjian, J.

    1989-01-01

    Diode formed by selective doping during epitaxial growth, starting with semi-insulating substrate. Use of high-mobility semiconductors like GaAs extends cutoff frequency. Either molecular-beam epitaxy (MBE) or organometallic chemical-vapor deposition used to form layers of diode. Planar growth process permits subsequent fabrication of arrays of diodes by standard photolithographic techniques, to achieve quasi-optical coupling of submillimeter radiation. Useful for generation of harmonics or heterodyne mixing in receivers for atmospheric and space spectroscopy operating at millimeter and submillimeter wavelengths. Used as frequency doublers or triplers, diodes of new type extend frequency range of present solid-state oscillators.

  13. A superradiant clock laser on a magic wavelength optical lattice.

    PubMed

    Maier, Thomas; Kraemer, Sebastian; Ostermann, Laurin; Ritsch, Helmut

    2014-06-01

    An ideal superradiant laser on an optical clock transition of noninteracting cold atoms is predicted to exhibit an extreme frequency stability and accuracy far below mHz-linewidth. In any concrete setup sufficiently many atoms have to be confined and pumped within a finite cavity mode volume. Using a magic wavelength lattice minimizes light shifts and allows for almost uniform coupling to the cavity mode. Nevertheless, the atoms are subject to dipole-dipole interaction and collective spontaneous decay which compromises the ultimate frequency stability. In the high density limit the Dicke superradiant linewidth enhancement will broaden the laser line and nearest neighbor couplings will induce shifts and fluctuations of the laser frequency. We estimate the magnitude and scaling of these effects by direct numerical simulations of few atom systems for different geometries and densities. For Strontium in a regularly filled magic wavelength configuration atomic interactions induce small laser frequency shifts only and collective spontaneous emission weakly broadens the laser. These interactions generally enhance the laser sensitivity to cavity length fluctuations but for optimally chosen operating conditions can lead to an improved synchronization of the atomic dipoles. PMID:24921521

  14. Note: Laser wavelength precision measurement based on a laser synthetic wavelength interferometer.

    PubMed

    Yan, Liping; Chen, Benyong; Zhang, Shihua; Liu, Pengpeng; Zhang, Enzheng

    2016-08-01

    A laser wavelength precision measurement method is presented based on the laser synthetic wavelength interferometer (LSWI). According to the linear relation between the displacements of measurement and reference arms in the interferometer, the synthetic wavelength produced by an unknown wavelength and a reference wavelength can be measured by detecting the phase coincidences of two interference signals. The advantage of the method is that a larger synthetic wavelength resulting from an unknown wavelength very close to the reference wavelength can be easily determined according to the linear relation in the interferometer. Then the unknown wavelength is derived according to the one-to-one corresponding relationship between single wavelength and synthetic wavelength. Wavelengths of an external cavity diode laser and two He-Ne lasers were determined experimentally. The experimental results show that the proposed method is able to realize a relative uncertainty on the order of 10(-8). PMID:27587172

  15. Note: Laser wavelength precision measurement based on a laser synthetic wavelength interferometer

    NASA Astrophysics Data System (ADS)

    Yan, Liping; Chen, Benyong; Zhang, Shihua; Liu, Pengpeng; Zhang, Enzheng

    2016-08-01

    A laser wavelength precision measurement method is presented based on the laser synthetic wavelength interferometer (LSWI). According to the linear relation between the displacements of measurement and reference arms in the interferometer, the synthetic wavelength produced by an unknown wavelength and a reference wavelength can be measured by detecting the phase coincidences of two interference signals. The advantage of the method is that a larger synthetic wavelength resulting from an unknown wavelength very close to the reference wavelength can be easily determined according to the linear relation in the interferometer. Then the unknown wavelength is derived according to the one-to-one corresponding relationship between single wavelength and synthetic wavelength. Wavelengths of an external cavity diode laser and two He-Ne lasers were determined experimentally. The experimental results show that the proposed method is able to realize a relative uncertainty on the order of 10-8.

  16. Absolute analytical prediction of photonic crystal guided mode resonance wavelengths

    SciTech Connect

    Hermannsson, Pétur Gordon; Vannahme, Christoph; Smith, Cameron L. C.; Kristensen, Anders

    2014-08-18

    A class of photonic crystal resonant reflectors known as guided mode resonant filters are optical structures that are widely used in the field of refractive index sensing, particularly in biosensing. For the purposes of understanding and design, their behavior has traditionally been modeled numerically with methods such as rigorous coupled wave analysis. Here it is demonstrated how the absolute resonance wavelengths of such structures can be predicted by analytically modeling them as slab waveguides in which the propagation constant is determined by a phase matching condition. The model is experimentally verified to be capable of predicting the absolute resonance wavelengths to an accuracy of within 0.75 nm, as well as resonance wavelength shifts due to changes in cladding index within an accuracy of 0.45 nm across the visible wavelength regime in the case where material dispersion is taken into account. Furthermore, it is demonstrated that the model is valid beyond the limit of low grating modulation, for periodically discontinuous waveguide layers, high refractive index contrasts, and highly dispersive media.

  17. Output characteristics of SASE-driven short-wavelength FELs

    NASA Astrophysics Data System (ADS)

    Fawley, William M.

    1997-05-01

    This paper investigates various properties of the 'microspikes' associated with self-amplified spontaneous emission (SASE) in a short wavelength free-electron laser (FEL). Using results from the 2-D numerical simulation code GINGER, we confirm theoretical predictions such as the convective group velocity in the exponential gain regime. In the saturated gain regime beyond the initial saturation, we find that the average radiation power continues to grow with an approximately linearly dependence upon undulator length. Moreover, the spectrum significantly broadens and shifts in wavelength to the redward direction, with P(omega) approaching a constant, asymptotic value. This is in marked contrast to the exponential gain regime where the spectrum steadily narrows, P(omega) grows, and the central wavelength remains constant with z. Via use of a spectrogram diagnostic S(omega, t), it appears that the radiation pattern in the saturated gain regime is composed of an ensemble of distinct 'sinews' whose widths (Delta) (lambda) remain approximately constant but whose central wavelengths can 'chirp' by varying a small extent with t.

  18. Magic and tune-out wavelengths for atomic francium

    NASA Astrophysics Data System (ADS)

    Dammalapati, U.; Harada, K.; Sakemi, Y.

    2016-04-01

    The frequency dependent polarizabilities of the francium atom are calculated from the available data of energy levels and transition rates. Magic wavelengths for the state insensitive optical dipole trapping are identified from the calculated light shifts of the 7 s 2S1/2, 7 p 2P1/2,3/2, and 8 s 2S1/2 levels of the 7 s -7 p 2S1/2 2P1/2,3/2 and 7 s -8 s 2S1/2 2S1/2 transitions, respectively. Wavelengths in the ultraviolet, visible, and near infrared region are identified that are suitable for cooling and trapping. Magic wavelengths between the 600-700 nm and 700-1000 nm regions, which are blue and red detuned with the 7 s -7 p and 7 s -8 s transitions, are feasible to implement as lasers with sufficient power are available. In addition, we calculated the tune-out wavelengths where the ac polarizability of the ground 7 s 2S1/2 state in francium is zero. These results are beneficial as laser cooled and trapped francium has been in use for fundamental symmetry investigations like searches for an electron permanent electric dipole moment in an atom and for atomic parity nonconservation.

  19. 12 hour shifts the Nambour Hospital experience.

    PubMed

    2007-08-01

    Union members have a lengthy history of campaigning for fair working hours and conditions. The success of such campaigns has led to the implementation of the eight hour working day and the 40 hour and then 38 hour week as industrial standards. More recently though, calls for greater flexibility in their shift arrangements by nurses at Nambour Hospital have led to a voluntary 12 hour shift being implemented in their Intensive Care Unit. While union members are protective of their hard won gains in achieving reduced working hours through the 8 hour day--ICU nurses at Nambour Hospital say the voluntary 12 hour shift initiative goes a way in addressing their work/life balance issues. PMID:17879604

  20. Addressing single trapped ions for Rydberg quantum logic

    NASA Astrophysics Data System (ADS)

    Bachor, P.; Feldker, T.; Walz, J.; Schmidt-Kaler, F.

    2016-08-01

    We demonstrate the excitation of ions to the Rydberg state 22F by vacuum ultraviolet radiation at a wavelength of 123 nm combined with the coherent manipulation of the optical qubit transition in {}40{{Ca}}+. With a tightly focused beam at 729 nm wavelength we coherently excite a single ion from a linear string into the metastable 3{D}5/2 state before a VUV pulse excites it to the Rydberg state. In combination with ion shuttling in the trap, we extend this approach to the addressed excitation of multiple ions. The coherent initialization as well as the addressed Rydberg excitation are key prerequisites for more complex applications of Rydberg ions in quantum simulation or quantum information processing.

  1. COS FUV Internal/External Wavelength Scales

    NASA Astrophysics Data System (ADS)

    Keyes, Charles

    2009-07-01

    Observe external radial velocity standard targets in TIME-TAG {FLASH=YES} mode with all grating and central wavelength combinations. The purpose is to obtain zero-point offsets for the wavelength scale {internal wavecal lamp scale to external standard wavelength scale} and PSA dispersion relations for all central wavelengths. Following this determination, adjustments of the nominal science target spectral range for each grating and central wavelength combination will be made via SMS patchable constant for nominal OSM1 positions corresponding to each central wavelength. Subsequent to this modification of the wavelength scale {and its verification via analysis of COS30 - program 11488}, FUV science-related operations and wavelength-dependent EROs can commence.

  2. COS NUV Internal/External Wavelength Scales

    NASA Astrophysics Data System (ADS)

    Keyes, Charles

    2009-07-01

    Observe external radial velocity standard targets {preferably, though not required, in CVZ} in TIME-TAG {FLASH=YES} mode with as many grating and central wavelength combinations as feasible. The purpose is to obtain zero-point offsets for the wavelength scale {internal wavecal lamp scale to external standard wavelength scale} for all central wavelengths. Following this determination, adjustments of the nominal science target spectral range for each grating and central wavelength combination will be made via SMS patchable constant for nominal OSM2 positions corresponding to each central wavelength. Subsequent to this modification of the wavelength scale {and its verification in COS 15 - program 11475}, NUV science-related operations and wavelength-scale dependent EROs can commence.

  3. Sub-wavelength diffractive optics

    SciTech Connect

    Warren, M.E.; Wendt, J.R.; Vawter, G.A.

    1998-03-01

    This report represents the completion of a three-year Laboratory-Directed Research and Development (LDRD) program to investigate sub-wavelength surface relief structures fabricated by direct-write e-beam technology as unique and very high-efficiency optical elements. A semiconductor layer with sub-wavelength sized etched openings or features can be considered as a layer with an effective index of refraction determined by the fraction of the surface filled with semiconductor relative to the fraction filled with air or other material. Such as a layer can be used to implement planar gradient-index lenses on a surface. Additionally, the nanometer-scale surface structures have diffractive properties that allow the direct manipulation of polarization and altering of the reflective properties of surfaces. With this technology a single direct-write mask and etch can be used to integrate a wide variety of optical functions into a device surface with high efficiencies; allowing for example, direct integration of polarizing optics into the surface with high efficiencies; allowing for example, direct integration of polarizing optics into the surfaces of devices, forming anti-reflection surfaces or fabricating high-efficiency, high-numerical aperture lenses, including integration inside vertical semiconductor laser cavities.

  4. Compact silicon photonic wavelength-tunable laser diode with ultra-wide wavelength tuning range

    SciTech Connect

    Kita, Tomohiro Tang, Rui; Yamada, Hirohito

    2015-03-16

    We present a wavelength-tunable laser diode with a 99-nm-wide wavelength tuning range. It has a compact wavelength-tunable filter with high wavelength selectivity fabricated using silicon photonics technology. The silicon photonic wavelength-tunable filter with wide wavelength tuning range was realized using two ring resonators and an asymmetric Mach-Zehnder interferometer. The wavelength-tunable laser diode fabricated by butt-joining a silicon photonic filter and semiconductor optical amplifier shows stable single-mode operation over a wide wavelength range.

  5. Flexible wavelength de-multiplexer for elastic optical networking.

    PubMed

    Zhou, Rui; Gutierrez Pascual, M Deseada; Anandarajah, Prince M; Shao, Tong; Smyth, Frank; Barry, Liam P

    2016-05-15

    We report an injection locked flexible wavelength de-multiplexer (de-mux) that shows 24-h frequency stability of 1 kHz for optical comb-based elastic optical networking applications. We demonstrate 50 GHz, 87.5 GHz equal spacing and 6.25G-25G-50 GHz, 75G-50G-100 GHz unequal spacing for the de-multiplexer outputs. We also implement an unequally spaced (75G-50G-100 GHz), mixed symbol rate (12.5 GBaud and 40 GBaud) and modulation format (polarization division multiplexed quadrature phase shift keying and on-off keying) wavelength division multiplexed transmission system using the de-multiplexer outputs. The results show 0.6 dB receiver sensitivity penalty, at 7% hard decision forward error correction coding limit, of the 100 km transmitted de-mux outputs when compared to comb source seeding laser back-to-back. PMID:27176972

  6. At-wavelength interferometry of extreme ultraviolet lithographic optics

    SciTech Connect

    Lee, Sang Hun; Naulleau, Patrick; Goldberg, Kenneth; Medecki, Hector; Bresloff, Cynthia; Chang, Chang; Attwood, David; Bokor, Jeffrey; Chang, Chang; Attwood, David; Bokor, Jeffrey Tejnil, Edita

    1998-11-01

    A phase-shifting point diffraction interferometer (PS/PDI) has recently been developed to evaluate optics for extreme ultraviolet (EUV) projection lithography systems. The interferometer has been implemented at the Advanced Light Source at Lawrence Berkeley National Laboratory and is currently being used to test experimental EUV Schwarzschild objectives. Recent PS/PDI measurements indicate these experimental objectives to have wavefront errors on the order of 0.1 waves ({approximately}1 nm at a wavelength of 13.4 nm) rms. These at-wavelength measurements have also revealed the multilayer phase effects, demonstrating the sensitivity and importance of EUV characterization. The measurement precision of the PS/PDI has been experimentally determined to be better than 0.01 waves. Furthermore, a systematic-error-limited absolute measurement accuracy of 0.004 waves has been demonstrated. {copyright} {ital 1998 American Institute of Physics.}

  7. Addressing Transgender Issues in Schools

    ERIC Educational Resources Information Center

    Cavanagh, Marian

    2016-01-01

    As mainstream media focus more attention on transgender issues, and as anti-discrimination laws evolve, a shift is taking place on campuses. Many schools now include gender identity and expression in their inclusivity work and seek to establish policies and procedures to support transgender students and their families. It's not an easy task. In…

  8. Phase unwrapping method based on multiple fringe patterns without use of equivalent wavelengths

    NASA Astrophysics Data System (ADS)

    Song, Limei; Chang, Yulan; Xi, Jiangtao; Guo, Qinghua; Zhu, Xinjun; Li, Xiaojie

    2015-11-01

    In order to decrease the noise enhancement in the process of phase unwrapping, we present a new phase unwrapping approach for multiple wavelength phase shift profilometry. In this approach, a series of fringe images with only three wavelengths are captured by the 3D measurement system, and it does not need to calculate the equivalent wavelengths and the equivalent phases. As a result, the noise enhancement is avoided, leading to improved precision in the absolute phase map recovery. Experiment results demonstrate that the proposed method is more robust and effective compared to the existing TWPSP method.

  9. Wavelength dependence of maximal diffraction-limited output power of fiber lasers

    NASA Astrophysics Data System (ADS)

    Otto, Hans-Jürgen; Modsching, Norbert; Jauregui, Cesar; Limpert, Jens; Tünnermann, Andreas

    2015-03-01

    The threshold-like onset of mode instabilities is currently the main limitation for the scaling of the average output power of fiber-laser systems with diffraction limited beam quality. In this contribution wavelength shifting of the seed signal has been experimentally investigated in order to mitigate mode instabilities. Against the expectations, it is experimentally shown that the highest mode instabilities threshold is reached around 1030 nm and not for the smallest wavelength separation between pump and signal wavelength. This finding implies that the quantum defect is not the sole significant source for thermal heating in the fiber.

  10. Multiple wavelength light collimator and monitor

    NASA Technical Reports Server (NTRS)

    Gore, Warren J. (Inventor)

    2011-01-01

    An optical system for receiving and collimating light and for transporting and processing light received in each of N wavelength ranges, including near-ultraviolet, visible, near-infrared and mid-infrared wavelengths, to determine a fraction of light received, and associated dark current, in each wavelength range in each of a sequence of time intervals.

  11. High-capacity content-addressable memory architecture

    NASA Astrophysics Data System (ADS)

    Henshaw, Philip D.; Lis, Steven A.

    1993-11-01

    This paper describes a new hardware architecture for searching and accessing data. This Content Addressable Memory (CAM) can be implemented using holographic storage in spectral hole burning media. The use of laser wavelength as a fourth dimension for volume holographic recording provides an additional addressing variable which can be used to advantage in a CAM architecture. This paper consists of three parts: definition of a CAM, presentation of two CAM concepts for digital data string and analog function search, and a discussion of architecture issues.

  12. Use of two wavelengths in microscopic TV holography for nondestructive testing

    NASA Astrophysics Data System (ADS)

    Upputuri, Paul Kumar; Umapathy, Somasundaram; Pramanik, Manojit; Kothiyal, Mahendra Prasad; Nandigana, Krishna Mohan

    2014-11-01

    Single wavelength TV holography is a widely used whole-field noncontacting optical method for nondestructive testing (NDT) of engineering structures. However, with a single wavelength configuration, it is difficult to quantify the large amplitude defects due to the overcrowding of fringes in the defect location. In this work, we propose a two wavelength microscopic TV holography using a single-chip color charge-coupled device (CCD) camera for NDT of microspecimens. The use of a color CCD allows simultaneous acquisition of speckle patterns at two different wavelengths and makes the data acquisition as simple as that of the single wavelength case. For the quantitative measurement of the defect, an error compensating eight-step phase-shifted algorithm is used. The design of the system and a few experimental results on small-scale rough specimens are presented.

  13. Fiber-optic current sensor with self-compensation of source wavelength changes.

    PubMed

    Müller, G M; Quan, W; Lenner, M; Yang, L; Frank, A; Bohnert, K

    2016-06-15

    We demonstrate a method for self-compensation of scale factor changes of an interferometric fiber-optic current sensor caused by source wavelength shifts, e.g., due to changes in source temperature or drive current. An adequately tailored fiber-optic retarder in the optical circuit introduces wavelength-dependent mixing of the orthogonal polarization modes of the sensor. The resulting change in scale factor balances the variation of the Faraday effect with wavelength. The wavelength dependence of the sensor is suppressed by more than an order of magnitude to <0.2% over wavelength spans of at least 10 nm around 1305 nm. The retarder is designed as an athermal device for operation between -40°C and 80°C. PMID:27304309

  14. Beam propagation near the dispersionless wavelength at 790 nm in rubidium

    NASA Astrophysics Data System (ADS)

    Xia, Hui; O'Brien, Christopher; Suckewer, Szymon; Scully, Marlan O.

    2016-05-01

    Between any two resonance lines for an atomic medium there exists a dispersionless wavelength where the ac Stark shift from the two resonances cancel and the real part of the resonant susceptibility is 0. We experimentally demonstrate the effects of this wavelength in a pump-probe experiment in high-density atomic vapor. A strong pump field excites the medium, in which we counterpropagate a broadband probe field. In a long cell, only at the dispersionless wavelength will scattering and self-focusing or defocusing not cause attenuation, allowing a spectrometer to read off the dispersionless wavelength. We perform a propagation experiment that shows the passband centered around the 790-nm dispersionless wavelength between the D1 and the D2 lines of rubidium.

  15. Shifts that divide population

    NASA Astrophysics Data System (ADS)

    Muneepeerakul, Rachata; Qubbaj, Murad; Aggarwal, Rimjhim; Anderies, John M.; Janssen, Marco

    2014-05-01

    How does a population of organisms in an ecosystem or of people in a society respond to rapid shifts in the environment? Answers to this question are critical to our ability to anticipate and cope with a changing ecohydrological system. We have developed a generic model of adaptation mechanisms, based on replicator dynamics, in which we derive a simple and insightful threshold condition that separates two important types of responses: 'cohesive transition' in which the whole population changes gradually together, and 'population-dividing transition' in which the population splits into two groups with one eventually dominating the other. The threshold depends on the magnitude of the shift and the shape of the fitness landscape. Division in populations can fundamentally alter the functioning of and induce subsequent feedbacks within the system; knowing the condition that gives rise to such division is thus fundamentally important.

  16. The shifted penalty method

    NASA Astrophysics Data System (ADS)

    Zavarise, Giorgio

    2015-07-01

    The method presented here is a variation of the classical penalty one, suited to reduce penetration of the contacting surfaces. The slight but crucial modification concerns the introduction of a shift parameter that moves the minimum point of the constrained potential toward the exact value, without any penalty increase. With respect to the classical augmentation procedures, the solution improvement is embedded within the original penalty contribution. The problem is almost consistently linearized, and the shift is updated before each Newton's iteration. However, adding few iterations, with respect to the original penalty method, a reduction of the penetration of several orders of magnitude can be achieved. The numerical tests have shown very attractive characteristics and very stable solution paths. This permits to foresee a wide area of applications, not only in contact mechanics, but for any problem, like e.g. incompressible materials, where a penalty contribution is required.

  17. Ultra-low-power silicon photonics wavelength converter for phase-encoded telecommunication signals

    NASA Astrophysics Data System (ADS)

    Lacava, C.; Ettabib, M. A.; Cristiani, I.; Fedeli, J.-M.; Richardson, D. J.; Petropoulos, P.

    2016-03-01

    The development of compact, low power, silicon photonics CMOS compatible components for all-optical signal processing represents a key step towards the development of fully functional platforms for next generation all-optical communication networks. The wavelength conversion functionality at key nodes is highly desirable to achieve transparent interoperability and wavelength routing allowing efficient management of network resources operated with high speed, phase encoded signals. All optical wavelength conversion has already been demonstrated in Si-based devices, mainly utilizing the strong Kerr effect that silicon exhibits at telecommunication wavelengths. Unfortunately, Two Photon Absorption (TPA) and Free Carrier (FC) effects strongly limit their performance, even at moderate power levels, making them unsuitable for practical nonlinear applications. Amorphous silicon has recently emerged as a viable alternative to crystalline silicon (c-Si), showing both an enhanced Kerr as well as a reduced TPA coefficient at telecom wavelengths, with respect to its c-Si counterpart. Here we present an ultra-low power wavelength converter based on a passive, CMOS compatible, 1-mm long amorphous silicon waveguide operated at a maximum pump power level of only 70 mW. We demonstrate TPA-free Four Wave Mixing (FWM)-based wavelength conversion of Binary Phase Shift Keyed (BPSK) and Quadrature Phase Shift Keyed (QPSK) signals at 20 Gbit/s with <1 dB power penalty at BER = 10-5.

  18. Sub-microsecond wavelength stabilization of tunable lasers with the internal wavelength locker

    NASA Astrophysics Data System (ADS)

    Kimura, Ryoga; Tatsumoto, Yudai; Sakuma, Kazuki; Onji, Hirokazu; Shimokozono, Makoto; Ishii, Hiroyuki; Kato, Kazutoshi

    2016-08-01

    We proposed a method of accelerating the wavelength stabilization after wavelength switching of the tunable distributed amplification-distributed feedback (TDA-DFB) laser using the internal wavelength locker to reduce the size and the cost of the wavelength control system. The configuration of the wavelength stabilization system based on this locker was as follows. At the wavelength locker, the light intensity after an optical filter is detected as a current by the photodiodes (PDs). Then, for estimating the wavelength, the current is processed by the current/voltage-converting circuit (IVC), logarithm amplifier (Log Amp) and field programmable gate array (FPGA). Finally, the laser current is tuned to the desired wavelength with reference to the estimated wavelength. With this control system the wavelength is stabilized within 800 ns after wavelength switching, which is even faster than that with the conventional control system.

  19. Long-wavelength photonic integrated circuits and avalanche photodetectors

    NASA Astrophysics Data System (ADS)

    Tsou, Yi-Jen D.; Zaytsev, Sergey; Pauchard, Alexandre; Hummel, Steve; Lo, Yu-Hwa

    2001-10-01

    Fast-growing internet traffic volume require high data communication bandwidth over longer distances. Access network bottlenecks put pressure on short-range (SR) telecommunication systems. To effectively address these datacom and telecom market needs, low-cost, high-speed laser modules at 1310 to 1550 nm wavelengths and avalanche photodetectors are required. The great success of GaAs 850nm VCSEls for Gb/s Ethernet has motivated efforts to extend VCSEL technology to longer wavelengths in the 1310 and 1550 nm regimes. However, the technological challenges associated with materials for long wavelength VCSELs are tremendous. Even with recent advances in this area, it is believed that significant additional development is necessary before long wavelength VCSELs that meet commercial specifications will be widely available. In addition, the more stringent OC192 and OC768 specifications for single-mode fiber (SMF) datacom may require more than just a long wavelength laser diode, VCSEL or not, to address numerous cost and performance issues. We believe that photonic integrated circuits (PICs), which compactly integrate surface-emitting lasers with additional active and passive optical components with extended functionality, will provide the best solutions to today's problems. Photonic integrated circuits have been investigated for more than a decade. However, they have produced limited commercial impact to date primarily because the highly complicated fabrication processes produce significant yield and device performance issues. In this presentation, we will discuss a new technology platform of InP-based PICs compatible with surface-emitting laser technology, as well as a high data rate externally modulated laser module. Avalanche photodetectors (APDs) are the key component in the receiver to achieve high data rate over long transmission distance because of their high sensitivity and large gain- bandwidth product. We have used wafer fusion technology to achieve In

  20. Microsystem 671 nm light source for shifted excitation Raman difference spectroscopy.

    PubMed

    Maiwald, Martin; Schmidt, Heinar; Sumpf, Bernd; Erbert, Götz; Kronfeldt, Heinz-Detlef; Tränkle, Günther

    2009-05-20

    We present a compact wavelength stabilized diode laser system at 671 nm on a micro-optical bench as a light source for shifted excitation Raman difference spectroscopy (SERDS). The laser system consists of two broad-area gain media in separate laser cavities using two reflection Bragg gratings with slightly different center wavelengths. A spectral width below 100 pm and a constant wavelength shift of 0.57 +/- 0.06 nm is obtained up to output powers of 250 mW. The suitability of this light source for SERDS is demonstrated using Raman spectra of ethanol with increasing concentrations of Cresyl Violet as the fluorescent contaminant. PMID:19458726

  1. Refraction effects and wavelength dependence

    NASA Astrophysics Data System (ADS)

    Claverie, J.; Dion, D.

    2006-09-01

    The performances of Electro-Optical (EO) systems such as visible or infrared cameras, lasers, operating within the Marine Surface Boundary Layer (MSBL), i.e. at heights up to a few tens of meters above the sea surface, are disturbed by various propagation mechanisms: molecular attenuation, aerosol extinction, refraction and turbulence. Refraction is responsible for focusing and defocusing of rays, detection range limitations, mirage formation and angular deviation. The refractive index depends on atmospheric pressure, air temperature and air humidity. Within the optical transmission bands, it also depends on the wavelength. In this paper, the results provided by two different formulations of the refractive index associated with the same ray tracing program are compared and discussed.

  2. Bolometric Arrays for Millimeter Wavelengths

    NASA Astrophysics Data System (ADS)

    Castillo, E.; Serrano, A.; Torres-Jácome, A.

    2009-11-01

    During last years, semiconductor bolometers using thin films have been developed at INAOE, specifically boron-doped hydrogenated amorphous silicon films. The characteristics shown by these devices made them attractive to be used in astronomical instrumentation, mainly in two-dimentional arrays. These detector arrays used at the Large Millimeter Telescope will make possible to obtain astronomical images in millimeter and sub-millimeter wavelengths. With this in mind, we are developing a method to produce, with enough reliability, bolometer arrays at INAOE. Until now, silicon nitride diaphragm arrays, useful as radiation absorbers, have succesfully been obtained. Sizes going from one to four millimeter by element in a consistent way; however we have not tested thermometers and metallic contact deposition yet. At the same time, we are working on two possible configurations for the readout electronics; one of them using commercial components while the other will be an integrated circuit specifically designed for this application. Both versions will work below 77K.

  3. Retinal spot size with wavelength

    NASA Astrophysics Data System (ADS)

    Rockwell, Benjamin A.; Hammer, Daniel X.; Kennedy, Paul K.; Amnotte, Rodney E.; Eilert, Brent; Druessel, Jeffrey J.; Payne, Dale J.; Phillips, Shana L.; Stolarski, David J.; Noojin, Gary D.; Thomas, Robert J.; Cain, Clarence P.

    1997-06-01

    We have made an indirect in-vivo determination of spot size focusing in the rhesus monkey model. Measurement of the laser induced breakdown threshold both in-vitro and in-vivo allow correlation and assignment of a spot size after focusing through the living eye. We discuss and analyze the results and show how trends in minimum visible lesion data should be assessed in light of chromatic aberration. National laser safety standards are based on minimal visual lesion (MVL) threshold studies in different animal models. The energy required for a retinal lesion depends upon may parameters including wavelength and retinal spot size. We attempt to explain trends in reported MVL threshold studies using a model of the eye which allows calculation of changes in retinal spot size due to chromatic aberration.

  4. Experimental observation of magic-wavelength behavior of a microwave transition in optical lattice-trapped rubidium

    NASA Astrophysics Data System (ADS)

    Lundblad, Nathan; Schlosser, Malte; Porto, Trey

    2010-03-01

    We demonstrate the cancellation of the differential ac Stark shift of the microwave hyperfine clock transition in trapped ^87Rb atoms. Recent progress in metrology exploits so-called ``magic wavelengths," whereby an atomic ensemble can be trapped with laser light whose wavelength is chosen so that both levels of an optical atomic transition experience identical ac Stark shifts. Similar magic-wavelength techniques are not possible for the microwave hyperfine transitions in the alkalis, due to their simple electronic structure. We show, however, that ac Stark shift cancellation is indeed achievable for certain values of wavelength, polarization, and magnetic field. The cancellation comes at the expense of a small magnetic-field sensitivity. The technique demonstrated here has implications for experiments involving the precise control of optically-trapped neutral atoms.

  5. Vernier-cascade label-free biosensor with integrated arrayed waveguide grating for wavelength interrogation with low-cost broadband source

    NASA Astrophysics Data System (ADS)

    Claes, Tom; Bogaerts, Wim; Bienstman, Peter

    2011-09-01

    Recently, cheap silicon-on-insulator label-free biosensors have been demonstrated that allow fast and accurate quantitative detection of biologically relevant molecules for applications in medical diagnostics and drug development. However, whereas the sensor chip can be made cheaply, an expensive tunable laser is typically required to accurately monitor spectral shifts in the sensor's transmission spectrum (wavelength interrogation). To address this issue, we integrated a very sensitive Vernier-cascade sensor with an arrayed waveguide grating spectral filter that divides the sensor's transmission spectrum in multiple wavelength channels and transmits them to spatially separated output ports, allowing wavelength interrogation with a much cheaper broadband light source. Experiments show that this sensor can monitor refractive index changes of watery solutions in real time with a detection limit (1.6 . 10-5RIU) competitive with more expensive interrogation schemes, indicating its applicability in low-cost label-free biosensing. The relaxation on the complexity of the source, moreover, offers the prospect to integrate the source and detectors to further reduce the device cost and to increase its portability.

  6. Array of Bolometers for Submillimeter- Wavelength Operation

    NASA Technical Reports Server (NTRS)

    Bock, James; Turner, Anthony

    2007-01-01

    A feed-horn-coupled monolithic array of micromesh bolometers is undergoing development for use in a photometric camera. The array is designed for conducting astrophysical observations in a wavelength band centered at 350 m. The bolometers are improved versions of previously developed bolometers comprising metalized Si3N4 micromesh radiation absorbers coupled with neutron- transmutation-doped Ge thermistors. Incident radiation heats the absorbers above a base temperature, changing the electrical resistance of each thermistor. In the present array of improved bolometers (see figure), the thermistors are attached to the micromesh absorbers by indium bump bonds and are addressed by use of lithographed, vapor-deposited electrical leads. This architecture reduces the heat capacity and minimizes the thermal conductivity to 1/20 and 1/300, respectively, of earlier versions of these detectors, with consequent improvement in sensitivity and speed of response. The micromesh bolometers, intended to operate under an optical background set by thermal emission from an ambient-temperature space-borne telescope, are designed such that the random arrival of photons ("photon noise") dominates the noise sources arising from the detector and readout electronics. The micromesh is designed to be a highly thermally and optically efficient absorber with a limiting response time of about 100 s. The absorber and thermistor heat capacity are minimized in order to give rapid speed of response. Due to the minimization of the absorber volume, the dominant source of heat capacity arises from the thermistor.

  7. Observation of giant Goos-Hänchen and angular shifts at designed metasurfaces.

    PubMed

    Yallapragada, Venkata Jayasurya; Ravishankar, Ajith P; Mulay, Gajendra L; Agarwal, Girish S; Achanta, Venu Gopal

    2016-01-01

    Metasurfaces with sub-wavelength features are useful in modulating the phase, amplitude or polarization of electromagnetic fields. While several applications are reported for light manipulation and control, the sharp phase changes would be useful in enhancing the beam shifts at reflection from a metasurface. In designed periodic patterns on metal film, at surface plasmon resonance, we demonstrate Goos-Hanchen shift of the order of 70 times the incident wavelength and the angular shifts of several hundred microradians. We have designed the patterns using rigorous coupled wave analysis (RCWA) together with S-matrices and have used a complete vector theory to calculate the shifts as well as demonstrate a versatile experimental setup to directly measure the shifts. The giant shifts demonstrated could prove to be useful in enhancing the sensitivity of experiments ranging from atomic force microscopy to gravitational wave detection. PMID:26758471

  8. Observation of giant Goos-Hänchen and angular shifts at designed metasurfaces

    PubMed Central

    Yallapragada, Venkata Jayasurya; Ravishankar, Ajith P.; Mulay, Gajendra L.; Agarwal, Girish S.; Achanta, Venu Gopal

    2016-01-01

    Metasurfaces with sub-wavelength features are useful in modulating the phase, amplitude or polarization of electromagnetic fields. While several applications are reported for light manipulation and control, the sharp phase changes would be useful in enhancing the beam shifts at reflection from a metasurface. In designed periodic patterns on metal film, at surface plasmon resonance, we demonstrate Goos-Hanchen shift of the order of 70 times the incident wavelength and the angular shifts of several hundred microradians. We have designed the patterns using rigorous coupled wave analysis (RCWA) together with S-matrices and have used a complete vector theory to calculate the shifts as well as demonstrate a versatile experimental setup to directly measure the shifts. The giant shifts demonstrated could prove to be useful in enhancing the sensitivity of experiments ranging from atomic force microscopy to gravitational wave detection. PMID:26758471

  9. Numerical analysis of dual-wavelength nonreciprocal phase shifter for magneto-optical isolators on silicon-on-insulator system

    NASA Astrophysics Data System (ADS)

    Huang, Tianze; Sun, Yiling; Ouyang, Zhengbiao

    2014-11-01

    The wavelength dependence of the nonreciprocal phase shift (NPS) in a magneto-optical (MO) waveguide is investigated from the aspect of the geometrical structure. In an MO nonreciprocal waveguide, the effect of the waveguide dispersion on the NPS is being demonstrated to compensate the dispersion of the Faraday rotation coefficients. By accurately controlling the structure parameter of the MO waveguide, the wavelength-insensitive NPS can be obtained. According to this principle, we proposed the dual-wavelength nonreciprocal phase shifter at the wavelengths of 1.31 and 1.55 μm.

  10. Addressing the water budget with SMOS

    NASA Astrophysics Data System (ADS)

    Kerr, Y. H.; AlBitar, A.; Tomer, S. K.; Merlin, O.; Pellarin, T.

    2012-12-01

    SMOS, a L Band radiometer using aperture synthesis to achieve a good spatial resolution, was successfully launched on November 2, 2009. It was developed and made under the leadership of the European Space Agency (ESA) as an Earth Explorer Opportunity mission. It is a joint program with the Centre National d'Etudes Spatiales (CNES) in France and the Centro para el Desarrollo Teccnologico Industrial (CDTI) in Spain. SMOS carries a single payload, an L band 2D interferometric,radiometer in the 1400-1427 MHz h protected band. This wavelength penetrates well through the vegetation and the atmosphere is almost transparent enabling to infer both soil moisture and vegetation water content. SMOS achieves an unprecedented spatial resolution of 50 km at L-band maximum (43 km on average) with multi angular-dual polarized (or fully polarized) brightness temperatures over the globe and with a revisit time smaller than 3 days. SMOS as been now acquiring data for almost 2 years. The data quality exceeds what was expected, showing very good sensitivity and stability. The data is however very much impaired by man made emission in the protected band, leading to degraded measurements in several areas including parts of Europe and of China. However, many different international teams are now addressing cal val activities in various parts of the world, with notably large field campaigns either on the long time scale or over specific targets to address the specific issues. In parallel different teams are now starting addressing data use in various fields including hydrology. It requires coupling with other models and or disaggregation to address soil moisture distribution over watersheds. Significant new results were obtained for floods and drought events, together with new potential applications in terms of precipitation monitoring This paper thus gives an overview of the science goals of the SMOS mission, a description of its main elements, and a taste of the first results including

  11. Addressing problems of employee performance.

    PubMed

    McConnell, Charles R

    2011-01-01

    Employee performance problems are essentially of 2 kinds: those that are motivational in origin and those resulting from skill deficiencies. Both kinds of problems are the province of the department manager. Performance problems differ from problems of conduct in that traditional disciplinary processes ordinarily do not apply. Rather, performance problems are addressed through educational and remedial processes. The manager has a basic responsibility in ensuring that everything reasonable is done to help each employee succeed. There are a number of steps the manager can take to address employee performance problems. PMID:21537142

  12. Photonic downconversion with tunable wideband phase shift.

    PubMed

    Jiang, Tianwei; Yu, Song; Wu, Ruihuan; Wang, Dongsheng; Gu, Wanyi

    2016-06-01

    A microwave photonic frequency downconversion system with wideband and continuous phase-shift function is proposed and experimentally demonstrated. In the proposed system, a radio frequency (RF) and a local oscillator (LO) signal drive two arms of a dual-drive Mach-Zehnder modulator (DMZM). A fiber Bragg grating (FBG) is used for reflecting the first-order sidebands of both RF and LO signals. Due to phase independence between RF and LO optical sidebands, the phase-shifting operation for an output intermediate frequency (IF) signal can be implemented either by adjusting the bias voltage of DMZM or by controlling the optical wavelength of laser. Experimental results demonstrate a full 0° to 360° phase shift, while an RF signal between 12 GHz to 20 GHz is downconverted to IFs below 4 GHz. The phase deviation is measured less than 2°, and the fluctuation of magnitude response is measured less than ±1  dB over a wideband frequency range. PMID:27244434

  13. Dual-excitation wavelength resonance Raman explosives detector

    NASA Astrophysics Data System (ADS)

    Yellampalle, Balakishore; Sluch, Mikhail; Wu, Hai-Shan; Martin, Robert; McCormick, William; Ice, Robert; Lemoff, Brian E.

    2013-05-01

    Deep-ultraviolet resonance Raman spectroscopy (DUVRRS) is a promising approach to stand-off detection of explosive traces due to: 1) resonant enhancement of Raman cross-section, 2) λ-4-cross-section enhancement, and 3) fluorescence and solar background free signatures. For trace detection, these signal enhancements more than offset the small penetration depth due to DUV absorption. A key challenge for stand-off sensors is to distinguish explosives, with high confidence, from a myriad of unknown background materials that may have interfering spectral peaks. To address this, we are developing a stand-off explosive sensor using DUVRRS with two simultaneous DUV excitation wavelengths. Due to complex interplay of resonant enhancement, self-absorption and laser penetration depth, significant amplitude variation is observed between corresponding Raman bands with different excitation wavelengths. These variations with excitation wavelength provide an orthogonal signature that complements the traditional Raman signature to improve specificity relative to single-excitation-wavelength techniques. As part of this effort, we are developing two novel CW DUV lasers, which have potential to be compact, and a compact dual-band high throughput DUV spectrometer, capable of simultaneous detection of Raman spectra in two spectral windows. We have also developed a highly sensitive algorithm for the detection of explosives under low signal-to-noise situations.

  14. Shifted genus expanded W ∞ algebra and shifted Hurwitz numbers

    NASA Astrophysics Data System (ADS)

    Zheng, Quan

    2016-05-01

    We construct the shifted genus expanded W ∞ algebra, which is isomorphic to the central subalgebra A ∞ of infinite symmetric group algebra and to the shifted Schur symmetrical function algebra Λ* defined by Okounkov and Olshanskii. As an application, we get some differential equations for the generating functions of the shifted Hurwitz numbers; thus, we can express the generating functions in terms of the shifted genus expanded cut-and-join operators.

  15. Wavelength-Modulated Differential Photoacoustic (WM-DPA) imaging: a high dynamic range modality towards noninvasive diagnosis of cancer

    NASA Astrophysics Data System (ADS)

    Dovlo, Edem; Lashkari, Bahman; Choi, Sung soo Sean; Mandelis, Andreas

    2016-03-01

    This study explores wavelength-modulated differential photo-acoustic (WM-DPA) imaging for non-invasive early cancer detection via sensitive characterization of functional information such as hemoglobin oxygenation (sO2) levels. Well-known benchmarks of tumor formation such as angiogenesis and hypoxia can be addressed this way. While most conventional photo-acoustic imaging has almost entirely employed high-power pulsed lasers, frequency-domain photo-acoustic radar (FD-PAR) has seen significant development as an alternative technique. It employs a continuous wave laser source intensity-modulated and driven by frequency-swept waveforms. WM-DPA imaging utilizes chirp modulated laser beams at two distinct wavelengths for which absorption differences between oxy- and deoxygenated hemoglobin are minimum (isosbestic point, 805 nm) and maximum (680 nm) to simultaneously generate two signals detected using a standard commercial array transducer as well as a single-element transducer that scans the sample. Signal processing is performed using Lab View and Matlab software developed in-house. Minute changes in total hemoglobin concentration (tHb) and oxygenation levels are detectable using this method since background absorption is suppressed due to the out-of-phase modulation of the laser sources while the difference between the two signals is amplified, thus allowing pre-malignant tumors to become identifiable. By regulating the signal amplitude ratio and phase shift the system can be tuned to applications like cancer screening, sO2 quantification and hypoxia monitoring in stroke patients. Experimental results presented demonstrate WM-DPA imaging of sheep blood phantoms in comparison to single-wavelength FD-PAR imaging. Future work includes the functional PA imaging of small animals in vivo.

  16. Reduction of reabsorption effects in scintillators by employing solutes with large Stokes shifts

    DOEpatents

    Harrah, L.A.; Renschler, C.L.

    1984-08-01

    A radiation or high energy particle responsive system useful as a scintillator comprises, a first component which interacts with radiation or high energy particles to emit photons in a certain first wavelength range, and at least one additional solute component which absorbs the photons in said first wavelength range and thereupon emits photons in another wavelength range higher than said first range. An improvement is provided wherein at least one of said components absorbs substantially no photons in the wavelength range in which it emits photons, due to a large Stokes shift caused by an excited state intramolecular rearrangement.

  17. Reduction of reabsorption effects in scintillators by employing solutes with large Stokes shifts

    DOEpatents

    Harrah, Larry A.; Renschler, Clifford L.

    1986-01-01

    In a radiation or high energy particle responsive system useful as a scintillator, and comprising, a first component which interacts with said radiation or high energy particle to emit photons in a certain first wavelength range; and at least one additional solute component which absorbs the photons in said first wavelength range and thereupon emits photons in another wavelength range higher than said first range; an improvement is provided wherein at least one of said components absorbs substantially no photons in said wavelength range in which it emits photons, due to a large Stokes shift caused by an excited state intramolecular rearrangement.

  18. Refraction-dependent kinematic shift of spectral lines

    NASA Astrophysics Data System (ADS)

    Chyla, W. T.

    2015-04-01

    If a luminous source moves with respect to the medium in which it is embedded, the kinematic shift of spectral lines depends both on the relative velocity and on the (relativistic) index of refraction of the medium. This effect is frequency-dependent, which makes it distinguishable from the cosmological redshift, the gravitational redshift and the regular Doppler shift in vacuum, which are all achromatic. The refraction-dependent shift of spectral lines is considered in more detail in the case of Ia supernovae, where the thermally generated electron-positron plasma ball, which expands with relativistic speeds, constitutes the refractive medium; it turns out that the discussed effect is relatively small at the UV and visible frequencies, but it can be significantly larger at longer wavelengths (the IR band). Other examples are given in optics and in other situations, where the refraction-dependent kinematic shift of frequency can be of significance.

  19. Transmission shift control assembly

    SciTech Connect

    Dzioba, D.L.

    1989-04-18

    This patent describes a transmission shift control assembly mounted on a steering column having a longitudinal axis comprising: bracket means secured to the steering column; transmission shift cable means having a portion secured to the bracket means and a portion linearly movable relative to the secured portion; mounting means on the bracket cable drive arm means having an axis and being rotatably mounted on the rotary axis on the mounting means oblique to the longitudinal axis and including a cable connecting portion secured to the movable portion of the cable means and lever mounting means adjacent the mounting means; operator control means including lever means, pin means for pivotally mounting the lever means on the lever mounting means on an axis substantially perpendicular to the rotary axis and positioning arm means formed on the lever means and extending from the pin means; and detent gate means disposed on the bracket means in position to abut the positioning arm means for limiting the extent of pivotal movement of the lever means.

  20. Shifted nondiffractive Bessel beams

    NASA Astrophysics Data System (ADS)

    Kovalev, Alexey A.; Kotlyar, Victor V.; Porfirev, Alexey A.

    2015-05-01

    Nondiffractive Bessel beams are well known to have infinite energy and infinite orbital angular momentum (OAM). However, when normalized to unity of energy, their OAM is finite. In this work, we derive an analytical relationship for calculating the normalized OAM of the superposition of off-axis Bessel beams characterized by the same topological charge. We show that if the constituent beams of the superposition have real-valued weight coefficients, the total OAM of the superposition of the Bessel beams equals that of an individual nonshifted Bessel beam. This property enables generating nondiffractive beams with different intensity distributions but identical OAM. The superposition of a set of identical Bessel beams centered on an arbitrary-radius circle is shown to be equivalent to an individual constituent Bessel beam put in the circle center. As a result of a complex shift of the Bessel beam, the transverse intensity distribution and OAM of the beam are also shown to change. We show that, in the superposition of two or more complex-shifted Bessel beams, the OAM may remain unchanged, while the intensity distribution is changed. Numerical simulation is in good agreement with theory.

  1. Addressing Phonological Questions with Ultrasound

    ERIC Educational Resources Information Center

    Davidson, Lisa

    2005-01-01

    Ultrasound can be used to address unresolved questions in phonological theory. To date, some studies have shown that results from ultrasound imaging can shed light on how differences in phonological elements are implemented. Phenomena that have been investigated include transitional schwa, vowel coalescence, and transparent vowels. A study of…

  2. Communities Address Barriers to Connectivity.

    ERIC Educational Resources Information Center

    Byers, Anne

    1996-01-01

    Rural areas lag behind urban areas in access to information technologies. Public institutions play a critical role in extending the benefits of information technologies to those who would not otherwise have access. The most successful rural telecommunications plans address barriers to use, such as unawareness of the benefits, technophobia, the…

  3. Keynote Address: Rev. Mark Massa

    ERIC Educational Resources Information Center

    Massa, Mark S.

    2011-01-01

    Rev. Mark S. Massa, S.J., is the dean and professor of Church history at the School of Theology and Ministry at Boston College. He was invited to give a keynote to begin the third Catholic Higher Education Collaborative Conference (CHEC), cosponsored by Boston College and Fordham University. Fr. Massa's address posed critical questions about…

  4. State of the Lab Address

    ScienceCinema

    King, Alex

    2013-03-01

    In his third-annual State of the Lab address, Ames Laboratory Director Alex King called the past year one of "quiet but strong progress" and called for Ames Laboratory to continue to build on its strengths while responding to changing expectations for energy research.

  5. State of the Lab Address

    SciTech Connect

    King, Alex

    2010-01-01

    In his third-annual State of the Lab address, Ames Laboratory Director Alex King called the past year one of "quiet but strong progress" and called for Ames Laboratory to continue to build on its strengths while responding to changing expectations for energy research.

  6. Interferometric measurement of surface shape by wavelength tuning suppressing random intensity error.

    PubMed

    Kim, Yangjin; Hibino, Kenichi; Sugita, Naohiko; Mitsuishi, Mamoru

    2016-08-10

    In this research, the susceptibility of the phase-shifting algorithms to the random intensity error is formulated and estimated. The susceptibility of the random intensity error of conventional windowed phase-shifting algorithms is discussed, and the 7N-6 phase-shifting algorithm is developed to minimize the random intensity error using the characteristic polynomial theory. Finally, the surface shape of the transparent wedge plate is measured using a wavelength-tuning Fizeau interferometer and the 7N-6 algorithm. The experimental results indicate that the surface shape measurement accuracy for the transparent plate is 2.5 nm. PMID:27534496

  7. Detection of Extensive Cosmic Air Showers by Small Scintillation Detectors with Wavelength-Shifting Fibres

    ERIC Educational Resources Information Center

    Aiola, Salvatore; La Rocca, Paola; Riggi, Francesco; Riggi, Simone

    2012-01-01

    A set of three small scintillation detectors was employed to measure correlated events due to the passage of cosmic muons originating from extensive air showers. The coincidence rate between (any) two detectors was extracted as a function of their relative distance. The difference between the arrival times in three non-aligned detectors was used…

  8. Design of a muon tomography system with a plastic scintillator and wavelength-shifting fiber arrays

    NASA Astrophysics Data System (ADS)

    Jo, Woo Jin; Kim, Hyun-Il; An, Su Jung; Lee, Chae Young; Baek, Cheol-Ha; Chung, Yong Hyun

    2013-12-01

    Recently, monitoring nuclear materials to avoid nuclear terrorism has become an important area of national security. It can be difficult to detect gamma rays from nuclear material because they are easily shielded by shielding material. Muon tomography using multiple -Coulomb scattering derived from muons can be utilized to detect special nuclear materials (SNMs) such as uranium-235 and plutonium-239. We designed a muon tomography system composed of four detector modules. The incident and scattered muon tracks can be calculated by two top and two bottom detectors, respectively. 3D tomographic images are obtained by extracting the crossing points of muon tracks with a point-of-closest-approach algorithm. The purpose of this study was to optimize the muon tomography system using Monte Carlo simulation code. The effects of the geometric parameters of the muon tomography system on material Z-discrimination capability were simulated and evaluated.

  9. Wavelength Shifting Phoswich Detectors for Superior Depth-of-Interaction Resolution

    SciTech Connect

    Melcher, Charles L; Eriksson, Lars

    2012-10-25

    In order to simultaneously achieve both high spatial resolution and high sensitivity in small Positron Emission Tomography (PET) systems, scintillation detectors must be long in the radial direction as well as able to provide depth-of-interaction (DOI) information. DOI information is typically provided by constructing detectors from two or more layers of scintillators that are identifiable due to their different decay times. This approach has worked well in tomographs such as the High Resolution Research Tomograph (HRRT, CTI PET Systems, Inc.) in which the emission and excitation bands of the scintillator layers do not overlap each other. However, many potentially important pairs of scintillator crystals exist in which the emission of one crystal is, in fact, absorbed and re-emitted by the second crystal, thus impacting the pulse shape discrimination process used to identify the scintillator layers. These potentially useful pairs of scintillators are unlikely to be implemented in phoswich detectors without a comprehensive understanding of the complex emission that results when the light of one crystal is absorbed by the second crystal and then reemitted. Our objective is to develop a fundamental understanding of the optical phenomena that occur in phoswich detectors and to exploit these phenomena to achieve improved spatial resolution in small high sensitivity PET scanners.

  10. Light-addressable bacteriorhodopsin photocell

    NASA Astrophysics Data System (ADS)

    Wang, Wei W.; Knopf, George K.; Bassi, Amarjeet S.

    2004-09-01

    Bacteriorhodopsin (bR) thin films have been investigated in recent years as a viable biomaterial for constructing micro- or nanoscale optical devices. During illumination, the bR molecules in the thin film undergo a photocycle that is followed by a proton transport from the cytoplasmatic side to the extracellular side of the cell membrane. The photoelectric response induced by the charge displacement can be influenced by both the wavelength and intensity of the impinging light sources. A photocell based on the photoelectric properties of a thin bR film is described in this paper. The bR-based photocell is built as a sandwich-structural device with an ITO (Indium Tin Oxide) electrode/bR film/ITO electrode configuration. The photocell is fabricated by depositing the oriented bR film onto the grounded ITO electrode. The cytoplasmic side of the bR membrane is attached to the ITO conductive surface and the extracelluar side is placed in contact with the second ITO electrode that provides the signal input to the instrumentation circuit. A polyester thin film was used as the spacer separating the two ITO electrodes. The size of the active area of the photocell is about 10×10 mm. A HeNe laser coupled with an acoustic-optical scanning system is used as the light source. Experimental results confirm that the photoelectric response generated by the bR-photocell prototype is durable, stable, and highly sensitive to changes in light intensity. The sensitivity of the proposed signal transducer is 10.25mV/mW. The wavelength dependence of the photoelectric responses is similar to the optical absorption spectrum of bR membrane.

  11. Wavelength Scaling of High Harmonic Generation Efficiency

    SciTech Connect

    Shiner, A. D.; Trallero-Herrero, C.; Kajumba, N.; Corkum, P. B.; Villeneuve, D. M.; Bandulet, H.-C.; Comtois, D.; Legare, F.; Giguere, M.; Kieffer, J-C.

    2009-08-14

    Using longer wavelength laser drivers for high harmonic generation is desirable because the highest extreme ultraviolet frequency scales as the square of the wavelength. Recent numerical studies predict that high harmonic efficiency falls dramatically with increasing wavelength, with a very unfavorable lambda{sup -(5-6)} scaling. We performed an experimental study of the high harmonic yield over a wavelength range of 800-1850 nm. A thin gas jet was employed to minimize phase matching effects, and the laser intensity and focal spot size were kept constant as the wavelength was changed. Ion yield was simultaneously measured so that the total number of emitting atoms was known. We found that the scaling at constant laser intensity is lambda{sup -6.3+}-{sup 1.1} in Xe and lambda{sup -6.5+}-{sup 1.1} in Kr over the wavelength range of 800-1850 nm, somewhat worse than the theoretical predictions.

  12. 4D PhaseCam(Trade Mark) Capabilities: Modal Analysis and Multiple-Wavelength Mirror Phasing

    NASA Technical Reports Server (NTRS)

    Millerd, James E.; Hayes, John B.; Schmucker, Mark; Eng, Ron (Technical Monitor)

    2002-01-01

    The PhaseCam is a dynamic phase shifting interferometer system manufactured by 4D Technology Corporation that is capable of very fast data acquisition. This rapid acquisition extends the capability of conventional interferometry to enable measurement in unstable environments, the generation of phase movies of surface shape and to facilitate modal analysis of structures. The PhaseCam hardware and software have been modified for MSFC to include synchronous modal optical measurement and analysis. These modifications will be discussed and data presented. The dynamic range of a phase shifting measurement is limited by local slope and pixel sampling to lambda/4 wave steps. Two-wavelength techniques can increase the effective measurement wavelength from microns to tens of centimeters and permit the phasing of mirror segments. A two wavelength PhaseCam will be discussed and measurement results presented.

  13. Wavelength-selective plasmonics for enhanced cultivation of microalgae

    SciTech Connect

    Ooms, Matthew D.; Jeyaram, Yogesh; Sinton, David

    2015-02-09

    Optimal photon management is a key challenge for photobioreactor design, since light gradients and varying spectral sensitivities between organisms result in uneven illumination and unused photons. This paper demonstrates wavelength specific scattering from plasmonic nano-patterned surfaces as a means of addressing the challenge of photon management in photobioreactors. Modular photobioreactors were constructed with different reflective substrates including arrays of plasmonic nanodisks, broadband reflectors, and untreated glass. It was found that the growth rate of cyanobacterium S. elongatus in photobioreactors equipped with a plasmonic substrate (R{sub 623 nm} ∼ 35%) was enhanced by 6.5% compared to photobioreactors equipped with untreated glass. Furthermore, plasmonic reflectors showed a normalized power efficiency improvement of 52% over broadband reflectors. Wavelength-specific reflection from plasmonic reflectors increases the flux of useful light to cultures without sacrificing the full spectrum.

  14. Wavelength-doubling optical parametric oscillator

    DOEpatents

    Armstrong, Darrell J.; Smith, Arlee V.

    2007-07-24

    A wavelength-doubling optical parametric oscillator (OPO) comprising a type II nonlinear optical medium for generating a pair of degenerate waves at twice a pump wavelength and a plurality of mirrors for rotating the polarization of one wave by 90 degrees to produce a wavelength-doubled beam with an increased output energy by coupling both of the degenerate waves out of the OPO cavity through the same output coupler following polarization rotation of one of the degenerate waves.

  15. Dispersion blue-shift in an aperiodic Bragg reflection waveguide

    NASA Astrophysics Data System (ADS)

    Fesenko, Volodymyr I.; Tuz, Vladimir R.

    2016-04-01

    A particular feature of an aperiodic design of cladding of Bragg reflection waveguides to demonstrate a dispersion blue-shift is elucidated. It is made on the basis of a comparative study of dispersion characteristics of both periodic and aperiodic configurations of Bragg mirrors in the waveguide system, wherein for the aperiodic configuration three procedures for layers alternating, namely Fibonacci, Thue-Morse and Kolakoski substitutional rules are considered. It was found out that, in a Bragg reflection waveguide with any considered aperiodic cladding, dispersion curves of guided modes appear to be shifted to shorter wavelengths compared to the periodic configuration regardless of the modes polarization.

  16. Soliton Self-Frequency Shift: Experimental Demonstrations and Applications

    PubMed Central

    Lee, Jennifer H.; van Howe, James; Liu, Xiang; Xu, Chris

    2012-01-01

    Soliton self-frequency shift (SSFS), a consequence of Raman self-pumping that continuously red-shifts a soliton pulse, has been widely studied recently for applications to fiber-based sources and signal processing. In this paper, the fundamentals of SSFS are reviewed. Various fiber platforms for SSFS (single-mode fiber, microstructured fiber, and higher order mode fiber) are presented and experimental SSFS demonstrations in these fibers are discussed. Observation of Cerenkov radiation in fibers exhibiting SSFS is also presented. A number of interesting applications of SSFS, such as wavelength-agile lasers, analog-to-digital conversion, and slow light, are briefly discussed. PMID:23055656

  17. Ammonia sensing system based on wavelength modulation spectroscopy

    NASA Astrophysics Data System (ADS)

    Viveiros, Duarte; Ferreira, João; Silva, Susana O.; Ribeiro, Joana; Flores, Deolinda; Santos, José L.; Frazão, Orlando; Baptista, José M.

    2015-06-01

    A sensing system in the near infrared region has been developed for ammonia sensing based on the wavelength modulation spectroscopy (WMS) principle. The WMS is a rather sensitive technique for detecting atomic/molecular species, presenting the advantage that it can be used in the near-infrared region by using the optical telecommunications technology. In this technique, the laser wavelength and intensity were modulated by applying a sine wave signal through the injection current, which allowed the shift of the detection bandwidth to higher frequencies where laser intensity noise was typically lower. Two multi-pass cells based on free space light propagation with 160 cm and 16 cm of optical path length were used, allowing the redundancy operation and technology validation. This system used a diode laser with an emission wavelength at 1512.21 nm, where NH3 has a strong absorption line. The control of the NH3 gas sensing system, as well as acquisition, processing and data presentation was performed.

  18. Shifting epidemiology of Flaviviridae.

    PubMed

    Petersen, Lyle R; Marfin, Anthony A

    2005-04-01

    The dengue, West Nile, Japanese encephalitis and yellow fever viruses are important mosquito-borne viruses whose epidemiology is shifting in response to changing societal factors, such as increasing commerce, urbanization of rural areas, and population growth. All four viruses are expanding geographically, as exemplified by the emergence of West Nile virus in the Americas and Japanese encephalitis virus in Australasia. The large, recent global outbreaks of severe neurological disease caused by West Nile virus, the increasing frequency of dengue hemorrhagic fever outbreaks in the Americas, and the emergence of yellow fever virus vaccination-associated viscerotropic disease, are new clinical epidemiologic trends. These worrisome epidemiologic trends will probably continue in coming decades, as a reversal of their societal and biological drivers is not in sight. Nevertheless, the substantial reductions in Japanese encephalitis virus incidence resulting from vaccination programs and economic development in some Asian countries provide some encouragement within this overall guarded outlook. PMID:16225801

  19. Wavelength dependence of high-harmonic yield from aligned molecules: roles of structure and electron dynamics

    NASA Astrophysics Data System (ADS)

    Li, Y. P.; Yu, S. J.; Duan, X. Y.; Shi, Y. Z.; Chen, Y. J.

    2016-04-01

    We study high-order harmonic generation (HHG) from aligned molecules {{{H}}}2+ by varying the laser wavelength from 400 to 2300 nm. Our simulations show that the wavelength dependence of the integrated HHG yield is influenced significantly by the molecular orientation. Our analyses reveal that the electronic dynamics and the interference effect relating to the molecular structure and orientation play a dominating role in the wavelength-orientation-dependent HHG yield. The wavelength scaling of the HHG yield associated with long and short electron trajectories is also addressed. We find the contribution of short trajectory scales vary differently for short and long laser wavelengths, which provides important suggestions for the experimental study of the HHG scaling law.

  20. Optimizing constant wavelength neutron powder diffractometers

    NASA Astrophysics Data System (ADS)

    Cussen, Leo D.

    2016-06-01

    This article describes an analytic method to optimize constant wavelength neutron powder diffractometers. It recasts the accepted mathematical description of resolution and intensity in terms of new variables and includes terms for vertical divergence, wavelength and some sample scattering effects. An undetermined multiplier method is applied to the revised equations to minimize the RMS value of resolution width at constant intensity and fixed wavelength. A new understanding of primary spectrometer transmission (presented elsewhere) can then be applied to choose beam elements to deliver an optimum instrument. Numerical methods can then be applied to choose the best wavelength.

  1. Effective wavelength calibration for moire fringe projection

    SciTech Connect

    Purcell, Daryl; Davies, Angela; Farahi, Faramarz

    2006-12-01

    The fringe patterns seen when using moire instruments are similar to the patterns seen in traditional interferometry but differ in the spacing between consecutive fringes. In traditional interferometry, the spacing is constant and related to the wavelength of the source. In moire fringe projection, the spacing (the effective wavelength) may not be constant over the field of view and the spacing depends on the system geometry. In these cases, using a constant effective wavelength over the field of view causes inaccurate surface height measurements. We examine the calibration process of the moirefringe projection measurement, which takes this varying wavelength into account to produce a pixel-by-pixel wavelength map. The wavelength calibration procedure is to move the object in the out-of-plane direction a known distance until every pixel intensity value goes through at least one cycle. A sinusoidal function is then fit to the data to extract the effective wavelength pixel by pixel, yielding an effective wavelength map. A calibrated step height was used to validate the effective wavelength map with results within 1% of the nominal value of the step height. The error sources that contributed to the uncertainty in determining the height of the artifact are also investigated.

  2. Starbursts at space ultraviolet wavelengths

    NASA Astrophysics Data System (ADS)

    González Delgado, Rosa M.

    2006-06-01

    Starbursts are systems with very high star formation rate per unit area. They are the preferred place where massive stars form; the main source of thermal and mechanical heating in the interstellar medium, and the factory where the heavy elements form. Thus, starbursts play an important role in the origin and evolution of galaxies. The similarities between the physical properties of local starbursts and high-z star-forming galaxies, highlight the cosmological relevance of starbursts. On the other hand, nearby starbursts are laboratories where to study violent star formation processes and their interaction with the interstellar and intergalactic media, in detail and deeply. Starbursts are bright at ultraviolet (UV) wavelengths, as they are in the far-infrared, due to the ‘picket-fence’ interstellar dust distribution. After the pioneering IUE program, high spatial and spectral resolution UV observations of local starburst galaxies, mainly taken with HST and FUSE, have made relevant contributions to the following issues: The determination of the initial mass function (IMF) in violent star forming systems in low and high metallicity environments, and in dense (e.g. in stellar clusters) and diffuse environments: A Salpeter IMF with high-mass stars constrains well the UV properties. The modes of star formation: Starburst clusters are an important mode of star formation. Super-stellar clusters have properties similar to globular clusters. The role of starbursts in AGN: Nuclear starbursts can dominate the UV light in Seyfert 2 galaxies, having bolometric luminosities similar to the estimated bolometric luminosities of the obscured AGN. The interaction between massive stars and the interstellar and intergalactic media: Outflows in cold, warm and coronal phases leave their imprints on the UV

  3. 2011 Society of Counseling Psychology Presidential Address: Exploring Privilege in Counseling Psychology--Shifting the Lens

    ERIC Educational Resources Information Center

    Israel, Tania

    2012-01-01

    Within a system of societal inequities, privilege consists of unearned advantages that are conferred on individuals based on membership or assumed membership in a dominant group. This article describes the relationship between privilege and oppression, dimensions of privilege, characteristics of privilege, costs of privilege, and resistance to…

  4. Hydraulically actuated well shifting tool

    SciTech Connect

    Roth, B.A.

    1992-10-20

    This patent describes a hydraulically actuated shifting tool for actuating a sliding member in a well tool. It comprises: a housing having a hydraulic fluid bore therein; shifting dog means positioned on the housing for movement away and toward the housing; locking dog means positioned on the housing for movement away and toward the body; shifting dog hydraulic actuating means in fluid communication with the bore for causing engagement of the shifting dogs with the sliding member; locking dog hydraulic actuating means in communication with the bore for causing engagement of the locking dogs with the locking means; and hydraulic shifting means in communication with the bore for causing relative movement between the shifting dog means and the locking dog means for shifting the sliding sleeve.

  5. Quantized beam shifts in graphene

    NASA Astrophysics Data System (ADS)

    Kort-Kamp, Wilton; Sinitsyn, Nikolai; Dalvit, Diego

    We show that the magneto-optical response of a graphene-on-substrate system in the presence of an external magnetic field strongly affects light beam shifts. In the quantum Hall regime, we predict quantized Imbert-Fedorov, Goos-Hänchen, and photonic spin Hall shifts. The Imbert-Fedorov and photonic spin Hall shifts are given in integer multiples of the fine structure constant α, while the Goos-Hänchen ones in discrete multiples of α2. Due to time-reversal symmetry breaking the IF shifts change sign when the direction of the applied magnetic field is reversed, while the other shifts remain unchanged. We investigate the influence on these shifts of magnetic field, temperature, and material dispersion and dissipation. An experimental demonstration of quantized beam shifts could be achieved at terahertz frequencies for moderate values of the magnetic field. We acknowledge the LANL LDRD program for financial support.

  6. The photobleaching sequence of a short-wavelength visual pigment.

    PubMed

    Kusnetzow, A; Dukkipati, A; Babu, K R; Singh, D; Vought, B W; Knox, B E; Birge, R R

    2001-07-01

    The photobleaching pathway of a short-wavelength cone opsin purified in delipidated form (lambda(max) = 425 nm) is reported. The batho intermediate of the violet cone opsin generated at 45 K has an absorption maximum at 450 nm. The batho intermediate thermally decays to the lumi intermediate (lambda(max) = 435 nm) at 200 K. The lumi intermediate decays to the meta I (lambda(max) = 420 nm) and meta II (lambda(max) = 388 nm) intermediates at 258 and 263 K, respectively. The meta II intermediate decays to free retinal and opsin at >270 K. At 45, 75, and 140 K, the photochemical excitation of the violet cone opsin at 425 nm generates the batho intermediate at high concentrations under moderate illumination. The batho intermediate spectra, generated via decomposing the photostationary state spectra at 45 and 140 K, are identical and have properties typical of batho intermediates of other visual pigments. Extended illumination of the violet cone opsin at 75 K, however, generates a red-shifted photostationary state (relative to both the dark and the batho intermediates) that has as absorption maximum at approximately 470 nm, and thermally reverts to form the normal batho intermediate when warmed to 140 K. We conclude that this red-shifted photostationary state is a metastable state, characterized by a higher-energy protein conformation that allows relaxation of the all-trans chromophore into a more planar conformation. FTIR spectroscopy of violet cone opsin indicates conclusively that the chromophore is protonated. A similar transformation of the rhodopsin binding site generates a model for the VCOP binding site that predicts roughly 75% of the observed blue shift of the violet cone pigment relative to rhodopsin. MNDO-PSDCI calculations indicate that secondary interactions involving the binding site residues are as important as the first-order chromophore protein interactions in mediating the wavelength maximum. PMID:11425310

  7. Analysis of Relationship between Wavelength Selectivity and Angular Selectivity of Rugate coating

    NASA Astrophysics Data System (ADS)

    Guangwei, Zheng; yang, Wang

    2016-01-01

    Based on Bragg law, Airy's formulae, and second-order Taylor series expansion, the relationships between wavelength selectivity and angular selectivity of the ordinary and phase-shifted Rugate coatings are investigated, respectively. And their expressions of the wavelength selectivity bandwidth and the angular selectivity bandwidth of these two types of Rugate gratings are put forward. The results show that when the incidence angle is far away from 0 rad, the bandwidth of the wavelength selectivity is proportional to that of the angular selectivity. And when the incidence angle approaches or even equals 0 rad (frequently-used cases), the bandwidth of the wavelength selectivity is squarely proportional to that of the angular selectivity. The results are instructive for the design and application of Rugate coatings.

  8. All-optical wavelength conversion of a 100-Gb/s polarization-multiplexed signal.

    PubMed

    Martelli, P; Boffi, P; Ferrario, M; Marazzi, L; Parolari, P; Siano, R; Pusino, V; Minzioni, P; Cristiani, I; Langrock, C; Fejer, M M; Martinelli, M; Degiorgio, V

    2009-09-28

    We present the results of an in-depth experimental investigation about all-optical wavelength conversion of a 100-Gb/s polarization-multiplexed (POLMUX) signal. Each polarization channel is modulated at 25 Gbaud by differential quadrature phase-shift keying (DQPSK). The conversion is realized exploiting the high nonlinear chi((2)) coefficient of a periodically poled lithium niobate waveguide, in a polarization-independent configuration. We find that slight non-idealities in the polarization independent setup of the wavelength converter can significantly impair the performance of POLMUX systems. We show that high-quality wavelength conversion can be nevertheless achieved for both the polarization channels, provided that an accurate optimization of the setup is performed. This is the first demonstration, to the best of our knowledge, of the possibility to obtain penalty-free all-optical wavelength conversion in a 100-Gb/s POLMUX transmission system using direct-detection. PMID:19907562

  9. Wavelength stabilizer based on dual fiber Bragg gratings for 980nm Mini-uncooled pump laser

    NASA Astrophysics Data System (ADS)

    Hu, Shuangshuang; Li, Yi; Jiang, Qunjie; Wu, Bin; Yu, Xiaojing; Wang, Haifang

    2008-12-01

    High power 980nm pump lasers are the key components in optical fiber amplifier. Wavelength stability for 980nm Miniuncooled pump laser is required to maintain the amplifier's efficiency throughout its lifetime. In this paper, a new type of wavelength stabilizer for uncooled pump laser which utilizes two fiber Bragg gratings (FBGs) matched in wavelength, bandwidth, and reflectivity is presented. The characteristics of transmissivity and reflectivity for the dual FBGs stabilized 980nm pump laser are theoretically modeled and experimentally studied. The results show that the output spectral characteristics of the uncooled pump laser with the dual FBGs have been greatly improved. The laser module can work steadily over a wide temperature range from 0°C to 70°C, with 0.2nm wavelength shift, along with more than 45dB side mode suppression ratio, and less than 1.57nm spectral bandwidth.

  10. Optically addressed near and long-wave infrared multiband photodetectors

    NASA Astrophysics Data System (ADS)

    Cellek, O. O.; Reno, J. L.; Zhang, Y.-H.

    2012-06-01

    Optically addressed dual-band photodetector incorporating of a 0.82 μm cut-off wavelength near-infrared (NIR) AlGaAs/GaAs p-i-n photodetector and a 8.2 μm peak wavelength long-wave infrared (LWIR) AlGaAs/GaAs quantum well infrared photodetector on GaAs substrate is fabricated and characterized. Switching between NIR and LWIR bands is demonstrated by using external light bias. The dual-band photodetector gives 65% quantum efficiency in NIR band and specific detectivity of 2 × 109cm Hz1/2/W in LWIR band at 68 K. Spectral crosstalk is better than 25 dB. These devices enable the use of only a single indium-bump per pixel for multiband image sensor arrays to have maximum fill factor.

  11. 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.

  12. Optical wavelength modulation in free electron lasers

    SciTech Connect

    Mabe, R.M.; Wong, R.K.; Colson, W.B.

    1995-12-31

    An attribute of the free electron laser (FEL) is the continuous tunability of the optical wavelength by modulation of the electron beam energy. The variation of the wavelength and power of the optical beam is studied as a function of FEL operating parameters. These results will be applied to the Stanford SCA FEL and Boeing FEL.

  13. Wavelength scaling of laser plasma coupling

    SciTech Connect

    Kruer, W.L.

    1983-11-03

    The use of shorter wavelength laser light both enhances collisional absorption and reduces deleterious collective plasma effects. Coupling processes which can be important in reactor-size targets are briefly reviewed. Simple estimates are presented for the intensity-wavelength regime in which collisional absorption is high and collective effects are minimized.

  14. Semiconductor laser with multiple lasing wavelengths

    DOEpatents

    Fischer, Arthur J.; Choquette, Kent D.; Chow, Weng W.

    2003-07-29

    A new class of multi-terminal vertical-cavity semiconductor laser components has been developed. These multi-terminal laser components can be switched, either electrically or optically, between distinct lasing wavelengths, or can be made to lase simultaneously at multiple wavelengths.

  15. Nanoscale content-addressable memory

    NASA Technical Reports Server (NTRS)

    Davis, Bryan (Inventor); Principe, Jose C. (Inventor); Fortes, Jose (Inventor)

    2009-01-01

    A combined content addressable memory device and memory interface is provided. The combined device and interface includes one or more one molecular wire crossbar memories having spaced-apart key nanowires, spaced-apart value nanowires adjacent to the key nanowires, and configurable switches between the key nanowires and the value nanowires. The combination further includes a key microwire-nanowire grid (key MNG) electrically connected to the spaced-apart key nanowires, and a value microwire-nanowire grid (value MNG) electrically connected to the spaced-apart value nanowires. A key or value MNGs selects multiple nanowires for a given key or value.

  16. Addressing the workforce pipeline challenge

    SciTech Connect

    Leonard Bond; Kevin Kostelnik; Richard Holman

    2006-11-01

    A secure and affordable energy supply is essential for achieving U.S. national security, in continuing U.S. prosperity and in laying the foundations to enable future economic growth. To meet this goal the next generation energy workforce in the U.S., in particular those needed to support instrumentation, controls and advanced operations and maintenance, is a critical element. The workforce is aging and a new workforce pipeline, to support both current generation and new build has yet to be established. The paper reviews the challenges and some actions being taken to address this need.

  17. Identifying and Addressing Vaccine Hesitancy

    PubMed Central

    Kestenbaum, Lori A.; Feemster, Kristen A.

    2015-01-01

    In the 20th century, the introduction of multiple vaccines significantly reduced childhood morbidity, mortality, and disease outbreaks. Despite, and perhaps because of, their public health impact, an increasing number of parents and patients are choosing to delay or refuse vaccines. These individuals are described as vaccine hesitant. This phenomenon has developed due to the confluence of multiple social, cultural, political and personal factors. As immunization programs continue to expand, understanding and addressing vaccine hesitancy will be crucial to their successful implementation. This review explores the history of vaccine hesitancy, its causes, and suggested approaches for reducing hesitancy and strengthening vaccine acceptance. PMID:25875982

  18. Identifying and addressing vaccine hesitancy.

    PubMed

    Kestenbaum, Lori A; Feemster, Kristen A

    2015-04-01

    In the 20th century, the introduction of multiple vaccines significantly reduced childhood morbidity, mortality, and disease outbreaks. Despite, and perhaps because of, their public health impact, an increasing number of parents and patients are choosing to delay or refuse vaccines. These individuals are described as "vaccine hesitant." This phenomenon has developed due to the confluence of multiple social, cultural, political, and personal factors. As immunization programs continue to expand, understanding and addressing vaccine hesitancy will be crucial to their successful implementation. This review explores the history of vaccine hesitancy, its causes, and suggested approaches for reducing hesitancy and strengthening vaccine acceptance. PMID:25875982

  19. Antiretroviral therapy: Shifting sands.

    PubMed

    Sashindran, V K; Chauhan, Rajeev

    2016-01-01

    HIV/AIDS has been an extremely difficult pandemic to control. However, with the advent of antiretroviral therapy (ART), HIV has now been transformed into a chronic illness in patients who have continued treatment access and excellent long-term adherence. Existing indications for ART initiation in asymptomatic patients were based on CD4 levels; however, recent evidence has broken the shackles of CD4 levels. Early initiation of ART in HIV patients irrespective of CD4 counts can have profound positive impact on morbidity and mortality. Early initiation of ART has been found not only beneficial for patients but also to community as it reduces the risk of transmission. There have been few financial concerns about providing ART to all HIV-positive people but various studies have proven that early initiation of ART not only proves to be cost-effective but also contributes to economic and social growth of community. A novel multidisciplinary approach with early initiation and availability of ART at its heart can turn the tide in our favor in future. Effective preexposure prophylaxis and postexposure prophylaxis can also lower transmission risk of HIV in community. New understanding of HIV pathogenesis is opening new vistas to cure and prevention. Various promising candidate vaccines and drugs are undergoing aggressive clinical trials, raising optimism for an ever-elusive cure for HIV. This review describes various facets of tectonic shift in management of HIV. PMID:26900224

  20. Marine regime shifts: drivers and impacts on ecosystems services

    PubMed Central

    Rocha, J.; Yletyinen, J.; Biggs, R.; Blenckner, T.; Peterson, G.

    2015-01-01

    Marine ecosystems can experience regime shifts, in which they shift from being organized around one set of mutually reinforcing structures and processes to another. Anthropogenic global change has broadly increased a wide variety of processes that can drive regime shifts. To assess the vulnerability of marine ecosystems to such shifts and their potential consequences, we reviewed the scientific literature for 13 types of marine regime shifts and used networks to conduct an analysis of co-occurrence of drivers and ecosystem service impacts. We found that regime shifts are caused by multiple drivers and have multiple consequences that co-occur in a non-random pattern. Drivers related to food production, climate change and coastal development are the most common co-occurring causes of regime shifts, while cultural services, biodiversity and primary production are the most common cluster of ecosystem services affected. These clusters prioritize sets of drivers for management and highlight the need for coordinated actions across multiple drivers and scales to reduce the risk of marine regime shifts. Managerial strategies are likely to fail if they only address well-understood or data-rich variables, and international cooperation and polycentric institutions will be critical to implement and coordinate action across the scales at which different drivers operate. By better understanding these underlying patterns, we hope to inform the development of managerial strategies to reduce the risk of high-impact marine regime shifts, especially for areas of the world where data are not available or monitoring programmes are not in place.

  1. Current-induced spin wave Doppler shift

    NASA Astrophysics Data System (ADS)

    Bailleul, Matthieu

    2010-03-01

    In metal ferromagnets -namely Fe, Co and Ni and their alloys- magnetism and electrical transport are strongly entangled (itinerant magnetism). This results in a number of properties such as the tunnel and giant magnetoresistance (i.e. the dependence of the electrical resistance on the magnetic state) and the more recently addressed spin transfer (i.e. the ability to manipulate the magnetic state with the help of an electrical current). The spin waves, being the low-energy elementary excitations of any ferromagnet, also exist in itinerant magnets, but they are expected to exhibit some peculiar properties due the itinerant character of the carriers. Accessing these specific properties experimentally could shed a new light on the microscopic mechanism governing itinerant magnetism, which -in turn- could help in optimizing material properties for spintronics applications. As a simple example of these specific properties, it was predicted theoretically that forcing a DC current through a ferromagnetic metal should induce a shift of the frequency of the spin waves [1,2]. This shift can be identified to a Doppler shift undergone by the electron system when it is put in motion by the electrical current. We will show how detailed spin wave measurements allow one to access this current-induced Doppler shift [3]. From an experimental point of view, we will discuss the peculiarities of propagating spin wave spectroscopy experiments carried out at a sub-micrometer length-scale and with MHz frequency resolution. Then, we will discuss the measured value of the Doppler shift in the context of both the old two-current model of spin-polarized transport and the more recent model of adiabatic spin transfer torque. [4pt] [1] P.Lederer and D.L. Mills, Phys.Rev. 148, 542 (1966).[0pt] [2] J. Fernandez-Rossier et al., Phys. Rev. B 69, 174412 (2004)[0pt] [3] V. Vlaminck and M. Bailleul, Science 322, 410 (2008).

  2. GEOSS: Addressing Big Data Challenges

    NASA Astrophysics Data System (ADS)

    Nativi, S.; Craglia, M.; Ochiai, O.

    2014-12-01

    In the sector of Earth Observation, the explosion of data is due to many factors including: new satellite constellations, the increased capabilities of sensor technologies, social media, crowdsourcing, and the need for multidisciplinary and collaborative research to face Global Changes. In this area, there are many expectations and concerns about Big Data. Vendors have attempted to use this term for their commercial purposes. It is necessary to understand whether Big Data is a radical shift or an incremental change for the existing digital infrastructures. This presentation tries to explore and discuss the impact of Big Data challenges and new capabilities on the Global Earth Observation System of Systems (GEOSS) and particularly on its common digital infrastructure called GCI. GEOSS is a global and flexible network of content providers allowing decision makers to access an extraordinary range of data and information at their desk. The impact of the Big Data dimensionalities (commonly known as 'V' axes: volume, variety, velocity, veracity, visualization) on GEOSS is discussed. The main solutions and experimentation developed by GEOSS along these axes are introduced and analyzed. GEOSS is a pioneering framework for global and multidisciplinary data sharing in the Earth Observation realm; its experience on Big Data is valuable for the many lessons learned.

  3. Phase-Shifted Laser Feedback Interferometry

    NASA Technical Reports Server (NTRS)

    Ovryn, Benjie

    1999-01-01

    Phase-shifted, laser feedback interferometry is a new diagnostic tool developed at the NASA Lewis Research Center under the Advanced Technology Development (ATD) Program directed by NASA Headquarters Microgravity Research Division. It combines the principles of phase-shifting interferometry (PSI) and laser-feedback interferometry (LFI) to produce an instrument that can quantify both optical path length changes and sample reflectivity variations. In a homogenous medium, the optical path length between two points is the product of the index of refraction and the geometric distance between the two points. LFI differs from other forms of interferometry by using the laser as both the source and the phase detector. In LFI, coherent feedback of the incident light either reflected directly from a surface or reflected after transmission through a region of interest will modulate the output intensity of the laser. The combination of PSI and LFI has produced a robust instrument, based on a low-power helium-neon (HeNe) gas laser, with a high dynamic range that can be used to measure either static or oscillatory changes of the optical path length. Small changes in optical path length are limited by the fraction of a fringe that can be measured; we can measure nonoscillatory changes with a root mean square (rms) error of the wavelength/1000 without averaging.

  4. Adaptive two-wave mixing wavelength demodulation of fiber Bragg grating sensor for monitoring dynamic strains

    NASA Astrophysics Data System (ADS)

    Qiao, Yi; Zhou, Yi; Krishnaswamy, Sridhar

    2005-05-01

    A two-wave mixing (TWM) wavelength demodulator using InP:Fe photorefractive crystal (PRC) in the C-band (1530-1570nm) is demonstrated. The system can be used as a wavelength demodulator for use with Fiber Bragg Grating (FBG) sensors to monitor dynamic strains. In this configuration, the FBG is illuminated with a broadband source, and any strain in the FBG is encoded as a wavelength shift of the light reflected by the FBG. The reflected light from the FBG is spilt into two unbalanced paths and both beams (pump and signal) mix in the PRC. Any wavelength shift of the reflected light results in an equivalent phase shift between the pump and signal beams as they travel unbalanced path lengths. Since TWM is an adaptive process, the two interfering beams are naturally in quadrature and remain in quadrature even in the presence of large quasi-static strains. We demonstrate that FBG demodulation using TWM has the ability to selectively monitor dynamic strains without the need for active compensation of large quasi-static strains that otherwise would cause the FBG sensor to drift. As TWM interferometers can be readily multiplexed at relatively low cost; the proposed technique can be used to demodulate signals from a network of FBG sensors for use in structural health monitoring.

  5. Zero-shifted accelerometer outputs

    NASA Astrophysics Data System (ADS)

    Galef, Arnold

    1986-08-01

    It is claimed that the commonly appearing zero-shift in pyroshock data is usually a symptom of a malfunctioning measurement system, so that the data can not be repaired (by high-pass filtering or equivalent) unless tests can be devised that permit the demonstration that the system is operating in a linear mode in all respects other than the shift. The likely cause of the zero-shift and its prevention are discussed.

  6. Silicon photonic device for wavelength sensing and monitoring

    NASA Astrophysics Data System (ADS)

    Vargas Lopez, German R.

    Over the last decade advances and innovations from Silicon Photonics technology were observed in the telecommunications and computing industries. This technology which employs Silicon as an optical medium, relies on current CMOS micro-electronics fabrication processes to enable medium scale integration of many nano-photonic devices to produce photonic integrated circuitry. However, other fields of research such as optical sensor processing can benefit from silicon photonics technology, specially in sensors where the physical measurement is wavelength encoded. In this research work, we present a design and application of a thermally tuned silicon photonic device as an optical sensor interrogator. The main device is a micro-ring resonator filter of 10 mum of diameter. A photonic design toolkit was developed based on open source software from the research community. With those tools it was possible to estimate the resonance and spectral characteristics of the filter. From the obtained design parameters, a 7.8 x 3.8 mm optical chip was fabricated using standard micro-photonics techniques. In order to tune a ring resonance, Nichrome micro-heaters were fabricated on top of the device. Some fabricated devices were systematically characterized and their tuning response were determined. From measurements, a ring resonator with a free-spectral-range of 18.4 nm and with a bandwidth of 0.14 nm was obtained. Using just 5 mA it was possible to tune the device resonance up to 3 nm. In order to apply our device as a sensor interrogator in this research, a model of wavelength estimation using time interval between peaks measurement technique was developed and simulations were carried out to assess its performance. To test the technique, an experiment using a Fiber Bragg grating optical sensor was set, and estimations of the wavelength shift of this sensor due to axial strains yield an error within 22 pm compared to measurements from spectrum analyzer. Results from this study

  7. Addressing viral resistance through vaccines

    PubMed Central

    Laughlin, Catherine; Schleif, Amanda; Heilman, Carole A

    2015-01-01

    Antimicrobial resistance is a serious healthcare concern affecting millions of people around the world. Antiviral resistance has been viewed as a lesser threat than antibiotic resistance, but it is important to consider approaches to address this growing issue. While vaccination is a logical strategy, and has been shown to be successful many times over, next generation viral vaccines with a specific goal of curbing antiviral resistance will need to clear several hurdles including vaccine design, evaluation and implementation. This article suggests that a new model of vaccination may need to be considered: rather than focusing on public health, this model would primarily target sectors of the population who are at high risk for complications from certain infections. PMID:26604979

  8. Addressing failures in exascale computing

    SciTech Connect

    Snir, Marc; Wisniewski, Robert W.; Abraham, Jacob A.; Adve, Sarita; Bagchi, Saurabh; Balaji, Pavan; Belak, Jim; Bose, Pradip; Cappello, Franck; Carlson, William; Chien, Andrew A.; Coteus, Paul; Debardeleben, Nathan A.; Diniz, Pedro; Engelmann, Christian; Erez, Mattan; Saverio, Fazzari; Geist, Al; Gupta, Rinku; Johnson, Fred; Krishnamoorthy, Sriram; Leyffer, Sven; Liberty, Dean; Mitra, Subhasish; Munson, Todd; Schreiber, Robert; Stearly, Jon; Van Hensbergen, Eric

    2014-05-01

    We present here a report produced by a workshop on “Addressing Failures in Exascale Computing” held in Park City, Utah, August 4–11, 2012. The charter of this workshop was to establish a common taxonomy about resilience across all the levels in a computing system; discuss existing knowledge on resilience across the various hardware and software layers of an exascale system; and build on those results, examining potential solutions from both a hardware and software perspective and focusing on a combined approach. The workshop brought together participants with expertise in applications, system software, and hardware; they came from industry, government, and academia; and their interests ranged from theory to implementation. The combination allowed broad and comprehensive discussions and led to this document, which summarizes and builds on those discussions.

  9. Light addressable photoelectrochemical cyanide sensor

    SciTech Connect

    Licht, S.; Myung, N.; Sun, Y.

    1996-03-15

    A sensor is demonstrated that is capable of spatial discrimination of cyanide with use of only a single stationary sensing element. Different spatial regions of the sensing element are light activated to reveal the solution cyanide concentration only at the point of illumination. In this light addressable photoelectrochemical (LAP) sensor the sensing element consists of an n-CdSe electrode immersed in solution, with the open-circuit potential determined under illumination. In alkaline ferro-ferri-cyanide solution, the open-circuit photopotential is highly responsive to cyanide, with a linear response of (120 mV) log [KCN]. LAP detection with a spatial resolution of {+-}1 mm for cyanide detection is demonstrated. The response is almost linear for 0.001-0.100 m cyanide with a resolution of 5 mV. 38 refs., 7 figs., 1 tab.

  10. Addressing Failures in Exascale Computing

    SciTech Connect

    Snir, Marc; Wisniewski, Robert; Abraham, Jacob; Adve, Sarita; Bagchi, Saurabh; Balaji, Pavan; Belak, J.; Bose, Pradip; Cappello, Franck; Carlson, Bill; Chien, Andrew; Coteus, Paul; DeBardeleben, Nathan; Diniz, Pedro; Engelmann, Christian; Erez, Mattan; Fazzari, Saverio; Geist, Al; Gupta, Rinku; Johnson, Fred; Krishnamoorthy, Sriram; Leyffer, Sven; Liberty, Dean; Mitra, Subhasish; Munson, Todd; Schreiber, Rob; Stearley, Jon; Van Hensbergen, Eric

    2014-01-01

    We present here a report produced by a workshop on Addressing failures in exascale computing' held in Park City, Utah, 4-11 August 2012. The charter of this workshop was to establish a common taxonomy about resilience across all the levels in a computing system, discuss existing knowledge on resilience across the various hardware and software layers of an exascale system, and build on those results, examining potential solutions from both a hardware and software perspective and focusing on a combined approach. The workshop brought together participants with expertise in applications, system software, and hardware; they came from industry, government, and academia, and their interests ranged from theory to implementation. The combination allowed broad and comprehensive discussions and led to this document, which summarizes and builds on those discussions.

  11. Short wavelength FELs using the SLAC linac

    SciTech Connect

    Winick, H.; Bane, K.; Boyce, R.

    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.

  12. Wavelengths Effective in Induction of Malignant Melanoma

    NASA Astrophysics Data System (ADS)

    Setlow, Richard B.; Grist, Eleanor; Thompson, Keith; Woodhead, Avril D.

    1993-07-01

    It is generally agreed that sunlight exposure is one of the etiologic agents in malignant melanoma of fair-skinned individuals. However, the wavelengths responsible for tumorigenesis are not known, although DNA is assumed to be the target because individuals defective in the repair of UV damage to DNA are several thousandfold more prone to the disease than the average population. Heavily pigmented backcross hybrids of the genus Xiphophorus (platyfish and swordtails) are very sensitive to melanoma induction by single exposures to UV. We irradiated groups of five 6-day-old fish with narrow wavelength bands at 302, 313, 365, 405, and 436 nm and scored the irradiated animals for melanomas 4 months later. We used several exposures at each wavelength to obtain estimates of the sensitivity for melanoma induction as a function of exposure and wavelength. The action spectrum (sensitivity per incident photon as a function of wavelength) for melanoma induction shows appreciable sensitivity at 365, 405, and probably 436 nm, suggesting that wavelengths not absorbed directly in DNA are effective in induction. We interpret the results as indicating that light energy absorbed in melanin is effective in inducing melanomas in this animal model and that, in natural sunlight, 90-95% of melanoma induction may be attributed to wavelengths > 320 nm-the UV-A and visible spectral regions.

  13. Wavelengths effective in induction of malignant melanoma

    SciTech Connect

    Setlow, R.B.; Grist, E.; Thompson, K.; Woodhead, A.D. )

    1993-07-15

    It is generally agreed that sunlight exposure is one of the etiologic agents in malignant melanoma of fair-skinned individuals. However, the wavelengths responsible for tumorigenesis are not known, although DNA is assumed to be the target because individuals defective in the repair of UV damage to DNA are several thousandfold more prone to the disease than the average population. Heavily pigmented back-cross hybrids of the genus Xiphophorus (platyfish and swordtails) are very sensitive to melanoma induction by single exposures to UV. The authors irradiated groups of five 6-day-old fish with narrow wavelength bands at 302, 313, 365, 405, and 436 nm and score the irradiated animals for melanomas 4 months later. They used several exposures at each wavelength to obtain estimates of the sensitivity for melanoma induction as a function of exposure and wavelength. The action spectrum (sensitivity per incident photon as a function of wavelength) for melanoma induction shows appreciable sensitivity at 365, 405, and probably 436 nm, suggesting that wavelengths not absorbed directly in DNA are effective in induction. They interpret the results as indicating that light energy absorbed in melanin is effective in inducing melanomas in this animal model and that, in natural sunlight, 90-95% of melanoma induction may be attributed to wavelengths >320 nm-the UV-A and visible spectral regions. 25 refs., 4 figs., 1 tab.

  14. Quantized beam shifts in graphene

    SciTech Connect

    de Melo Kort-Kamp, Wilton Junior; Sinitsyn, Nikolai; Dalvit, Diego Alejandro Roberto

    2015-10-08

    We predict the existence of quantized Imbert-Fedorov, Goos-Hanchen, and photonic spin Hall shifts for light beams impinging on a graphene-on-substrate system in an external magnetic field. In the quantum Hall regime the Imbert-Fedorov and photonic spin Hall shifts are quantized in integer multiples of the fine structure constant α, while the Goos-Hanchen ones in multiples of α2. We investigate the influence on these shifts of magnetic field, temperature, and material dispersion and dissipation. An experimental demonstration of quantized beam shifts could be achieved at terahertz frequencies for moderate values of the magnetic field.

  15. Wavelength initialization employing wavelength recognition scheme in WDM-PON based on tunable lasers

    NASA Astrophysics Data System (ADS)

    Mun, Sil-Gu; Lee, Eun-Gu; Lee, Jong Hyun; Lee, Sang Soo; Lee, Jyung Chan

    2015-01-01

    We proposed a simple method to initialize the wavelength of tunable lasers in WDM-PON employing wavelength recognition scheme with an optical filter as a function of wavelength and accomplished plug and play operation. We also implemented a transceiver based on our proposed wavelength initialization scheme and then experimentally demonstrated the feasibility in WDM-PON configuration guaranteeing 16 channels with 100 GHz channel spacing. Our proposal is a cost-effective and easy-to-install method to realize the wavelength initialization of ONU. In addition, this method will support compatibility with all kind of tunable laser regardless of their structures and operating principles.

  16. Shifts in fisheries management: adapting to regime shifts

    PubMed Central

    King, Jacquelynne R.; McFarlane, Gordon A.; Punt, André E.

    2015-01-01

    For many years, fisheries management was based on optimizing yield and maintaining a target biomass, with little regard given to low-frequency environmental forcing. However, this policy was often unsuccessful. In the last two to three decades, fisheries science and management have undergone a shift towards balancing sustainable yield with conservation, with the goal of including ecosystem considerations in decision-making frameworks. Scientific understanding of low-frequency climate–ocean variability, which is manifested as ecosystem regime shifts and states, has led to attempts to incorporate these shifts and states into fisheries assessment and management. To date, operationalizing these attempts to provide tactical advice has met with limited success. We review efforts to incorporate regime shifts and states into the assessment and management of fisheries resources, propose directions for future investigation and outline a potential framework to include regime shifts and changes in ecosystem states into fisheries management.

  17. Magic wavelengths for terahertz clock transitions

    SciTech Connect

    Zhou Xiaoji; Xu Xia; Chen Xuzong; Chen Jingbiao

    2010-01-15

    Magic wavelengths for laser trapping of boson isotopes of alkaline-earth metal atoms Sr, Ca, and Mg are investigated while considering terahertz clock transitions between the {sup 3}P{sub 0}, {sup 3}P{sub 1}, and {sup 3}P{sub 2} metastable triplet states. Our calculation shows that magic wavelengths for laser trapping do exist. This result is important because those metastable states have already been used to make accurate clocks in the terahertz frequency domain. Detailed discussions for magic wavelengths for terahertz clock transitions are given in this article.

  18. Laser wavelength metrology with color sensor chips.

    PubMed

    Jones, Tyler B; Otterstrom, Nils; Jackson, Jarom; Archibald, James; Durfee, Dallin S

    2015-12-14

    We present a laser wavelength meter based on a commercial color sensor chip. The chip consists of an array of photodiodes with different absorptive color filters. By comparing the relative amplitudes of light on the photodiodes, the wavelength of light can be determined. In addition to absorption in the filters, etalon effects add additional spectral features which improve the precision of the device. Comparing the measurements from the device to a commercial wavelength meter and to an atomic reference, we found that the device has picometer-level precision and picometer-scale drift over a period longer than a month. PMID:26699036

  19. Multimode fiber optic wavelength division multiplexing

    NASA Technical Reports Server (NTRS)

    Spencer, J. L.

    1982-01-01

    Optical wavelength division multiplexing (WDM) systems, with signals transmitted on different wavelengths through a single optical fiber, can have increased bandwidth and fault isolation properties over single wavelength optical systems. Two WDM system designs that might be used with multimode fibers are considered and a general description of the components which could be used to implement the system are given. The components described are sources, multiplexers, demultiplexers, and detectors. Emphasis is given to the demultiplexer technique which is the major developmental component in the WDM system.

  20. Optical amplification at the 1. 31 wavelength

    DOEpatents

    Cockroft, N.J.

    1994-02-15

    An optical amplifier operating at the 1.31 [mu]m wavelength for use in such applications as telecommunications, cable television, and computer systems is described. An optical fiber or other waveguide device is doped with both Tm[sup 3+] and Pr[sup 3+] ions. When pumped by a diode laser operating at a wavelength of 785 nm, energy is transferred from the Tm[sup 3+] ions to the Pr[sup 3+] ions, causing the Pr[sup 3+] ions to amplify at a wavelength of 1.31. 1 figure.

  1. Precision measurement of transition matrix elements via light shift cancellation.

    PubMed

    Herold, C D; Vaidya, V D; Li, X; Rolston, S L; Porto, J V; Safronova, M S

    2012-12-14

    We present a method for accurate determination of atomic transition matrix elements at the 10(-3) level. Measurements of the ac Stark (light) shift around "magic-zero" wavelengths, where the light shift vanishes, provide precise constraints on the matrix elements. We make the first measurement of the 5s - 6p matrix elements in rubidium by measuring the light shift around the 421 and 423 nm zeros through diffraction of a condensate off a sequence of standing wave pulses. In conjunction with existing theoretical and experimental data, we find 0.3235(9)ea(0) and 0.5230(8)ea(0) for the 5s - 6p(1/2) and 5s - 6p(3/2) elements, respectively, an order of magnitude more accurate than the best theoretical values. This technique can provide needed, accurate matrix elements for many atoms, including those used in atomic clocks, tests of fundamental symmetries, and quantum information. PMID:23368314

  2. Enhanced two-frequency phase-shifting method.

    PubMed

    Hyun, Jae-Sang; Zhang, Song

    2016-06-01

    One of the major challenges of employing a two-frequency (or two-wavelength) phase-shifting algorithm for absolute three-dimensional shape measurement is its sensitivity to noise. Therefore, three- or more-frequency phase-shifting algorithms are often used in lieu of a two-frequency phase-shifting algorithm for applications where the noise is severe. This paper proposes a method to use geometric constraints of digital fringe projection system to substantially reduce the noise impact by allowing the use of more than one period of equivalent phase map for temporal phase unwrapping. Experiments successfully verified the enhanced performance of the proposed method without increasing the number of patterns. PMID:27411193

  3. Optical Lattice Induced Light Shifts in an Yb Atomic Clock

    SciTech Connect

    Barber, Z. W.; Stalnaker, J. E.; Lemke, N. D.; Poli, N.; Oates, C. W.; Fortier, T. M.; Diddams, S. A.; Hollberg, L.; Hoyt, C. W.; Taichenachev, A. V.; Yudin, V. I.

    2008-03-14

    We present an experimental study of the lattice-induced light shifts on the {sup 1}S{sub 0}{yields}{sup 3}P{sub 0} optical clock transition ({nu}{sub clock}{approx_equal}518 THz) in neutral ytterbium. The 'magic' frequency {nu}{sub magic} for the {sup 174}Yb isotope was determined to be 394 799 475(35) MHz, which leads to a first order light shift uncertainty of 0.38 Hz. We also investigated the hyperpolarizability shifts due to the nearby 6s6p{sup 3}P{sub 0}{yields}6s8p{sup 3}P{sub 0}, 6s8p{sup 3}P{sub 2}, and 6s5f{sup 3}F{sub 2} two-photon resonances at 759.708, 754.23, and 764.95 nm, respectively. By measuring the corresponding clock transition shifts near these two-photon resonances, the hyperpolarizability shift was estimated to be 170(33) mHz for a linear polarized, 50 {mu}K deep, lattice at the magic wavelength. These results indicate that the differential polarizability and hyperpolarizability frequency shift uncertainties in a Yb lattice clock could be held to well below 10{sup -17}.

  4. Wavelength and opto-electro-opto sharing and optimization in wavelength division multiplexing mesh networks with path protection

    NASA Astrophysics Data System (ADS)

    Wang, Kefei; Hamza, Haitham S.; Deogun, Jitender S.

    2006-03-01

    Given a physical network topology and a traffic demand, the problem of designing a survivable network with path protection is to select primary and backup paths based on resource optimization. A common approach to minimize resources is sharing. This problem has been investigated with the goal of optimizing the number of channels (i.e., wavelengths) needed for backup paths by imposing capacity sharing. However, because of the need and the cost for other devices, such as opto-electro-opto (OEO) regenerators, network provisioning should also take into consideration such resources in the optimization process. We address the problem of routing and wavelength assignment (RWA) for survivable networks with the objective of simultaneously optimizing wavelength links and OEOs. An integer linear program solution, a tabu search heuristic, and a genetic algorithm are proposed, and their performance is experimentally evaluated through extensive simulation. Our simulation results confirm an average of 30% reduction in the number of OEOs compared to that required with the well known shared-path protection scheme.

  5. Magic Wavelength to Make Optical Lattice Clocks Insensitive to Atomic Motion

    SciTech Connect

    Katori, Hidetoshi; Hashiguchi, Koji; Il'inova, E. Yu.; Ovsiannikov, V. D.

    2009-10-09

    In a standing wave of light, a difference in spatial distributions of multipolar atom-field interactions may introduce atomic-motion dependent clock uncertainties in optical lattice clocks. We show that the magic wavelength can be defined so as to eliminate the spatial mismatch in electric dipole, magnetic dipole, and electric quadrupole interactions for specific combinations of standing waves by allowing a spatially constant light shift arising from the latter two interactions. Experimental prospects of such lattices used with a blue magic wavelength are discussed.

  6. Method and apparatus for simultaneously measuring a plurality of spectral wavelengths present in electromagnetic radiation

    DOEpatents

    Buican, Tudor N.; Martin, John C.

    1990-01-01

    An apparatus and method simultaneously measures a plurality of spectral wavelengths present in electromagnetic radiation. A modulatable birefringent optical element is employed to divide a polarized light beam into two components, thereby producing a phase difference in two resulting light beams such that the two beams can be made to interfere with one another when recombined, the interference pattern providing the wavelength information required for the analysis of the incident light. The interferometer thus created performs in a similar manner to a Michelson interferometer, but with no moving parts, and with a resolution dependent on the degree of phase shift introduced by the modulator.

  7. Optically addressed multiband photodetector for infrared imaging applications

    NASA Astrophysics Data System (ADS)

    Cellek, O. O.; Zhang, Y.-H.

    2012-01-01

    Multiband infrared focal plane arrays (FPAs) with small pixel pitch have increased device processing complexity since they often need more than two terminals per pixel for readouts. Simpler FPAs are enabled by our newly demonstrated optically-addressed two-terminal multiband photodetector architecture. For long-wavelength infrared (LWIR) and midwavelength infrared (MWIR) imaging applications, the use of quantum well infrared photodetectors (QWIP) has been investigated. The results show that the utilization of unipolar QWIPs with bipolar near infrared (NIR) devices is feasible with this new optical-addressing scheme. Potential device performance is analyzed with an equivalent AC circuit model. Proposed design maximizes fill factor and enables small pixel-pitch FPA with single indium-bump per pixel for NIR/MWIR/LWIR multiband detection capability.

  8. Wavelength mismatch effect in electromagnetically induced absorption

    NASA Astrophysics Data System (ADS)

    Bharti, Vineet; Wasan, Ajay; Natarajan, Vasant

    2016-07-01

    We present a theoretical investigation of the phenomenon of electromagnetically induced absorption (EIA) in a 4-level system consisting of vee and ladder subsystems. The four levels are coupled using one weak probe field, and two strong control fields. We consider an experimental realization using energy levels of Rb. This necessitates dealing with different conditions of wavelength mismatch-near-perfect match where all three wavelengths are approximately equal; partial mismatch where the wavelength of one control field is less than the other fields; and complete mismatch where all three wavelengths are unequal. We present probe absorption profiles with Doppler averaging at room temperature to account for experiments in a room temperature Rb vapor cell. Our analysis shows that EIA resonances can be studied using Rydberg states excited with diode lasers.

  9. Multiple-Wavelength Pyrometry Independent Of Emissivity

    NASA Technical Reports Server (NTRS)

    Ng, Daniel

    1996-01-01

    Multiple-wavelength pyrometric method provides for determination of two sequential temperatures of same surface or temperatures of two surfaces made of same material. Temperatures measured, without knowing emissivity, by uncalibrated spectral radiometer.

  10. Controllable Dual-Wavelength Fiber Laser

    NASA Astrophysics Data System (ADS)

    Li, Zhen; Zhou, Jun; He, Bing; Liu, Hou-Kang; Liu, Chi; Wei, Yun-Rong; Dong, Jing-Xing; Lou, Qi-Hong

    2012-07-01

    We demonstrate a controllable dual-wavelength fiber laser which contains a master laser and a slave laser. The master laser is a kind of ring cavity laser which can be injected into by the slave laser. The output laser wavelength is controlled by injected power of the slave laser; both single- and dual-wavelength operation can be achieved. Under free running, the master laser generates 1064 nm laser output. Here the slave laser is a 1072 nm fiber laser. The 1064 nm and 1072 nm laser coexist in output spectrum for relatively low injected power. Dual-wavelength and power-ratio-tunable operation can be achieved. If the injected power of the slave laser is high enough, the 1064 nm laser is extinguished automatically and there is only 1072 nm laser output.

  11. Multiple wavelength photolithography for preparing multilayer microstructures

    DOEpatents

    Dentinger, Paul Michael; Krafcik, Karen Lee

    2003-06-24

    The invention relates to a multilayer microstructure and a method for preparing thereof. The method involves first applying a first photodefinable composition having a first exposure wavelength on a substrate to form a first polymeric layer. A portion of the first photodefinable composition is then exposed to electromagnetic radiation of the first exposure wavelength to form a first pattern in the first polymeric layer. After exposing the first polymeric layer, a second photodefinable composition having a second exposure wavelength is applied on the first polymeric layer to form a second polymeric layer. A portion of the second photodefinable composition is then exposed to electromagnetic radiation of the second exposure wavelength to form a second pattern in the second polymeric layer. In addition, a portion of each layer is removed according to the patterns to form a multilayer microstructure having a cavity having a shape that corresponds to the portions removed.

  12. Water-gas shift reaction

    SciTech Connect

    Newsome, D.S.

    1980-01-01

    A review covers the industrial applications of the water-gas shift reaction in hydrogen manufacturing, removing CO from ammonia synthesis feeds, and detoxifying town gas; and the catalyst characteristics, reaction kinetics, and reaction mechanisms of the water-gas shift reactions catalyzed by iron-based, copper-based, or sulfided cobalt-molybdenum catalysts.

  13. Flexible Schedules and Shift Work.

    ERIC Educational Resources Information Center

    Beers, Thomas M.

    2000-01-01

    Flexible work hours have gained prominence, as more than 25 million workers (27.6% of all full-time workers) can now vary their schedules. However, there has been little change since the mid-1980s in the proportion who work a shift other than a regular daytime shift. (JOW)

  14. In-service communication channel sensing based on reflectometry for dynamic wavelength assigned wavelength- and time-division multiplexed passive optical network systems

    NASA Astrophysics Data System (ADS)

    Iida, Daisuke; Kuwano, Shigeru; Terada, Jun

    2015-04-01

    In future radio access systems, base stations will be mainly accommodated in wavelength- and time-division multiplexing passive optical network (PON) based mobile backhaul and fronthaul networks, and in such networks, failed connections in an optical network unit (ONU) wavelength channel will severely degrade mobile system performance. A cost-effective in-service ONU wavelength channel monitor is essential to ensure proper system operation without failed connections. To address this issue, we propose a reflectometry-based remote sensing method that provides ONU wavelength channel information with the optical line terminal-ONU distance. The proposed method enables real-time monitoring of ONU wavelength channels without data signal quality degradation and is also able to determine if the ONUs are connected to the PON. Experimental results show that it achieves wavelength channel distinction with a high distance resolution (˜10 m). Additionally, with the method, the distance resolution for distinguishing the ONUs after the PON splitter is determined by the received signal bandwidth or the test light modulation speed rather than by the pulse width as in conventional optical time-domain reflectometry.

  15. Addressing neurological disorders with neuromodulation.

    PubMed

    Oluigbo, Chima O; Rezai, Ali R

    2011-07-01

    Neurological disorders are becoming increasingly common in developed countries as a result of the aging population. In spite of medications, these disorders can result in progressive loss of function as well as chronic physical, cognitive, and emotional disability that ultimately places enormous emotional and economic on the patient, caretakers, and the society in general. Neuromodulation is emerging as a therapeutic option in these patients. Neuromodulation is a field, which involves implantable devices that allow for the reversible adjustable application of electrical, chemical, or biological agents to the central or peripheral nervous system with the objective of altering its functioning with the objective of achieving a therapeutic or clinically beneficial effect. It is a rapidly evolving field that brings together many different specialties in the fields of medicine, materials science, computer science and technology, biomedical, and neural engineering as well as the surgical or interventional specialties. It has multiple current and emerging indications, and an enormous potential for growth. The main challenges before it are in the need for effective collaboration between engineers, basic scientists, and clinicians to develop innovations that address specific problems resulting in new devices and clinical applications. PMID:21193369

  16. Gender: addressing a critical focus.

    PubMed

    Thornton, L; Wegner, M N

    1995-01-01

    The definition of gender was addressed at the Fourth World Conference on Women (Beijing, China). After extensive debate, the definition developed by the UN Population Fund in 1995 was adopted: "a set of qualities and behaviors expected from a female or male by society." The sustainability of family planning (FP) programs depends on acknowledgment of the role gender plays in contraceptive decision-making and use. For example, programs must consider the fact that women in many cultures do not make FP decisions without the consent of their spouse. AVSC is examining providers' gender-based ideas about clients and the effects of these views on the quality of reproductive health services. Questions such as how service providers can encourage joint responsibility for contraception without requiring spousal consent or how they can make men feel comfortable about using a male method in a society where FP is considered a woman's issue are being discussed. Also relevant is how service providers can discuss sexual matters openly with female clients in cultures that do not allow women to enjoy their sexuality. Another concern is the potential for physical violence to a client as a result of the provision of FP services. PMID:12294397

  17. Wavelength scanning achieves pixel super-resolution in holographic on-chip microscopy

    NASA Astrophysics Data System (ADS)

    Luo, Wei; Göröcs, Zoltan; Zhang, Yibo; Feizi, Alborz; Greenbaum, Alon; Ozcan, Aydogan

    2016-03-01

    Lensfree holographic on-chip imaging is a potent solution for high-resolution and field-portable bright-field imaging over a wide field-of-view. Previous lensfree imaging approaches utilize a pixel super-resolution technique, which relies on sub-pixel lateral displacements between the lensfree diffraction patterns and the image sensor's pixel-array, to achieve sub-micron resolution under unit magnification using state-of-the-art CMOS imager chips, commonly used in e.g., mobile-phones. Here we report, for the first time, a wavelength scanning based pixel super-resolution technique in lensfree holographic imaging. We developed an iterative super-resolution algorithm, which generates high-resolution reconstructions of the specimen from low-resolution (i.e., under-sampled) diffraction patterns recorded at multiple wavelengths within a narrow spectral range (e.g., 10-30 nm). Compared with lateral shift-based pixel super-resolution, this wavelength scanning approach does not require any physical shifts in the imaging setup, and the resolution improvement is uniform in all directions across the sensor-array. Our wavelength scanning super-resolution approach can also be integrated with multi-height and/or multi-angle on-chip imaging techniques to obtain even higher resolution reconstructions. For example, using wavelength scanning together with multi-angle illumination, we achieved a halfpitch resolution of 250 nm, corresponding to a numerical aperture of 1. In addition to pixel super-resolution, the small scanning steps in wavelength also enable us to robustly unwrap phase, revealing the specimen's optical path length in our reconstructed images. We believe that this new wavelength scanning based pixel super-resolution approach can provide competitive microscopy solutions for high-resolution and field-portable imaging needs, potentially impacting tele-pathology applications in resource-limited-settings.

  18. Interrogation of a wavelength tunable fiber Bragg grating sensor based ring laser for dynamic strain monitoring

    NASA Astrophysics Data System (ADS)

    Balogun, Oluwaseyi; Zhu, Yinian; Krishnaswamy, Sridhar

    2010-03-01

    Fiber Bragg gratings (FBGs) are wavelength selective optical reflectors with excellent strain sensitivity and small sensing footprint, which makes them suitable as diagnostic sensors for structural health monitoring applications. In this work, we explore the narrowband wavelength selectivity of FBGs for optical feedback in a tunable fiber ring laser. The fiber ring laser consists of an erbium doped fiber laser that is pumped with a Raman laser (980 nm) to produce population inversion and amplified spontaneous emission (ASE) in the C-band. The ASE light is used to illuminate a FBG sensor connected to the ring, and the reflected light from the sensor is fed back into the laser cavity to produce stimulated emission at the instantaneous center wavelength of the sensor. As the wavelength of the sensor shifts due mechanical or thermal strains, the wavelength of the optical output from the ring laser shifts accordingly. By combining the ring laser with a dynamic spectral demodulator for optical readout, the instantaneous wavelength of the ring laser is tracked with high temporal resolution. The fiber ring laser system offers several potential advantages in the diagnostic sensing of mechanical strains for SHM applications including, fully integrated laser and sensor system, high source power levels at the sensor wavelength, narrow spectral line-width, coherent spectral demodulation, and low system costs. In this work, we present experimental results that detail the feasibility of dynamic spectral tuning of the fiber ring laser at frequencies up to hundreds of kilohertz using a single FBG sensing element. Using multiple sensing elements, the fiber ring laser system would allow for active monitoring of dynamic strains in a multi-point sensor array configuration, which is particularly suitable for the localization of high frequency mechanical strains produced by impact loading and cracking events in structures.

  19. Point diffraction interferometry at soft x-ray wavelengths

    SciTech Connect

    Sommargren, G.E.; Hostetler, R.

    1993-07-01

    To achieve the image performance necessary for soft x-ray projection lithography, interferometric testing at the design wavelength is required to accurately characterize the wavefront of the imaging system. The wavefront depends not only on the surface figure of the individual optics and on their relative alignment, but also on aperture dependent phase shifts induced by the resonant multilayer coatings on the optical surfaces. This paper describes the design and lithographic fabrication of an array of point diffraction interferometers on a silicon nitride membrane that has been over-coated with a spatially graded partially transmitting film to provide fringe contrast control. Experimental results using a visible light analogue (larger pinholes and different transmission gradient) will be shown.

  20. Integrated optical, acoustically tunable wavelength filter

    NASA Astrophysics Data System (ADS)

    Frangen, J.; Herrmann, H.; Ricken, R.; Seibert, H.; Sohler, W.

    1989-11-01

    A TM/TE convertor is combined with a TE-pass polarizer on a common LiNbO3 chip to obtain an integrated optical, acoustically tunable wavelength filter. Its tuning range is 1.45-1.57 micron wavelength with a filter half-width of 2.8 nm. Due to the combined acoustical/optical strip guide structure used in the mode convertor, a very low acoustic drive power of only 9 mW is required.

  1. Long Wavelength Monitoring of Protein Kinase Activity

    PubMed Central

    Oien, Nathan P.; Nguyen, Luong T.; Jernigan, Finith E.; Priestman, Melanie A.

    2014-01-01

    A family of long wavelength protein kinase fluorescent reporters is described in which the probing wavelength is pre-programmed using readily available fluorophores. These agents can assess protein kinase activity within the optical window of tissue, as exemplified by monitoring endogenous cAMP-dependent protein kinase activity (1) in erythrocyte lysates and (2) in intact erythrocytes using a light-activatable reporter. PMID:24604833

  2. Observations of Venus at 1-meter wavelength

    NASA Astrophysics Data System (ADS)

    Butler, Bryan J.

    2014-11-01

    Radio wavelength observations of Venus (including from the Magellan spacecraft) have been a powerful method of probing its surface and atmosphere since the 1950's. The emission is generally understood to come from a combination of emission and absorption in the subsurface, surface, and atmosphere at cm and shorter wavelengths [1]. There is, however, a long-standing mystery regarding the long wavelength emission from Venus. First discovered at wavelengths of 50 cm and greater [2], the effect was later confirmed to extend to wavelengths as short as 13 cm [1,3]. The brightness temperatures are depressed significantly 50 K around 10-20 cm, increasing to as much as 200 K around 1 m) from what one would expect from a "normal" surface (e.g., similar to the Moon or Earth) [1-3].No simple surface and subsurface model of Venus can reproduce these large depressions in the long wavelength emission [1-3]. Simple atmospheric and ionospheric models fail similarly. In an attempt to constrain the brightness temperature spectrum more fully, new observations have been made at wavelengths that cover the range 60 cm to 1.3 m at the Very Large Array, using the newly available low-band receiving systems there [4]. The new observations were made over a very wide wavelength range and at several Venus phases, with that wide parameter space coverage potentially allowing us to pinpoint the cause of the phenomenon. The observations and potential interpretations will be presented and discussed.[1] Butler et al. 2001, Icarus, 154, 226. [2] Schloerb et al. 1976, Icarus, 29, 329; Muhleman et al. 1973, ApJ, 183, 1081; Condon et al. 1973, ApJ, 183, 1075; Kuzmin 1965, Radiophysics. [3] Butler & Sault 2003, IAUSS, 1E, 17B. [4] Intema et al. 2014, BASI, 1.

  3. Long-wavelength VCSELs for sensing applications

    NASA Astrophysics Data System (ADS)

    Ortsiefer, M.; Rosskopf, J.; Neumeyr, C.; Gründl, T.; Grasse, C.; Chen, J.; Hangauer, A.; Strzoda, R.; Gierl, C.; Meissner, P.; Küppers, F.; Amann, M.-C.

    2012-03-01

    Long-wavelength VCSELs with emission wavelengths beyond 1.3 μm have seen a remarkable progress over the last decade. This success has been accomplished by using highly advanced device concepts which effectively overcome the fundamental technological drawbacks related with long-wavelength VCSELs such as inferior thermal properties and allow for the realization of lasers with striking device performance. In this presentation, we will give an overview on the state of the technology for long-wavelength VCSELs in conjunction with their opportunities in applications for optical sensing. While VCSELs based on InP are limited to maximum emission wavelengths around 2.3 μm, even longer wavelengths up to the mid-infrared range beyond 3 μm can be achieved with VCSELs based on GaSb. For near-infrared InP-based VCSELs, the output characteristics include sub-mA threshold currents, up to several milliwatts of singlemode output power and ultralow power consumption. New concepts for widely tunable VCSELs with tuning ranges up to 100 nm independent from the material system for the active region are also presented. Today, optical sensing by Tunable Diode Laser Spectroscopy is a fast emerging market. Gas sensing systems are used for a wide range of applications such as industrial process control, environmental monitoring and safety applications. With their inherent and compared to other laser types superior properties including enhanced current tuning rates, wavelength tuning ranges, modulation frequencies and power consumption, long-wavelength VCSELs are regarded as key components for TDLS applications.

  4. Grating cavity dual wavelength dye laser.

    PubMed

    Zapata-Nava, Oscar Javier; Rodríguez-Montero, Ponciano; Iturbe-Castillo, M David; Treviño-Palacios, Carlos Gerardo

    2011-02-14

    We report simultaneous dual wavelength dye laser emission using Littman-Metcalf and Littrow cavity configurations with minimum cavity elements. Dual wavelength operation is obtained by laser operation in two optical paths inside the cavity, one of which uses reflection in the circulating dye cell. Styryl 14 laser dye operating in the 910 nm to 960 nm was used in a 15%:85% PC/EG solvent green pumped with a Q-switched doubled Nd3+:YAG laser. PMID:21369171

  5. Absolute distance measurements by variable wavelength interferometry

    NASA Astrophysics Data System (ADS)

    Bien, F.; Camac, M.; Caulfield, H. J.; Ezekiel, S.

    1981-02-01

    This paper describes a laser interferometer which provides absolute distance measurements using tunable lasers. An active feedback loop system, in which the laser frequency is locked to the optical path length difference of the interferometer, is used to tune the laser wavelengths. If the two wavelengths are very close, electronic frequency counters can be used to measure the beat frequency between the two laser frequencies and thus to determine the optical path difference between the two legs of the interferometer.

  6. Chemical shift driven geometry optimization.

    PubMed

    Witter, Raiker; Priess, Wolfram; Sternberg, Ulrich

    2002-01-30

    A new method for refinement of 3D molecular structures by geometry optimization is presented. Prerequisites are a force field and a very fast procedure for the calculation of chemical shifts in every step of optimization. To the energy, provided by the force field (COSMOS force field), a pseudoenergy, depending on the difference between experimental and calculated chemical shifts, is added. In addition to the energy gradients, pseudoforces are computed. This requires the derivatives of the chemical shifts with respect to the coordinates. The pseudoforces are analytically derived from the integral expressions of the bond polarization theory. Single chemical shift values attributed to corresponding atoms are considered for structural correction. As a first example, this method is applied for proton position refinement of the D-mannitol X-ray structure. A crystal structure refinement with 13C chemical shift pseudoforces is carried out. PMID:11924742

  7. Theoretical Study of SOA-Based Wavelength Conversion with NRZ and RZ Format at 40 Gb/s

    NASA Astrophysics Data System (ADS)

    Dong, Jian-Ji; Zhang, Xin-Liang; Fu, Song-Nian; Shum, Ping; Huang, De-Xiu

    2007-04-01

    We theoretically discuss 40 Gb/s semiconductor optical amplifier (SOA)-based wavelength conversion (WC) using a detuning optical bandpass filter based on ultrafast dynamic characteristics of SOA. Both the inverted and non-inverted WCs are obtained by shifting the filter central wavelength with respect to the probe wavelength when input data signal is in return-to-zero (RZ) format. However, we can obtain format conversion from nonreturn-to-zero (NRZ) to pseudo-return-to-zero (PRZ) and inverted WC when the input signal is in NRZ format.

  8. Shining a Light on Task-Shifting Policy

    PubMed Central

    Katende, Godfrey; Donnelly, Mary

    2016-01-01

    In terms of disease burden, many low- and middle-income countries are currently experiencing a transition from infectious to chronic diseases. In Uganda, non-communicable diseases (NCDs) have increased significantly in recent years; this challenge is compounded by the healthcare worker shortage and the underfunded health system administration. Addressing the growing prevalence of NCDs requires evidence-based policies and strategies to reduce morbidity and mortality rates; however, the integration and evaluation of new policies and processes pose many challenges. Task-shifting is the process whereby specific tasks are transferred to health workers with less training and fewer qualifications. Successful implementation of a task-shifting policy requires appropriate skill training, clearly defined roles, adequate evaluation, an enhanced training capacity and sufficient health worker incentives. This article focuses on task-shifting policy as a potentially effective strategy to address the growing burden of NCDs on the Ugandan healthcare system. PMID:27226906

  9. Wavelength division demultiplexing with photonic crystal self-collimation interference

    NASA Astrophysics Data System (ADS)

    Wang, Yufei; Qiu, Yishen; Chen, Xiyao; Lin, Guimin; Hong, Hailian

    2007-11-01

    A theoretical model of wavelength division demultiplexer (WDD), which is based on an asymmetric Mach-Zehnder interferometer (AMZI) constructed in a two-dimensional photonic crystal (2D PhC), is proposed and numerically demonstrated. The 2D PhC consists of a square lattice of cylindric air holes in silicon. The AMZI includes two mirrors and two splitters. Lights propagate between them employing self-collimation effect. The two interferometer branches have different path lengths. By using the finite-difference time-domain method, the calculation results show that the transmission spectras at two AMZI output ports are in the shape of sinusoidal curves and have a uniform peak spacing in the frequency range from 0.26c/a to 0.27c/a. When the path length of the longer branch is increased and the shorter one is fixed, the peaks shift to the lower frequencies and the peak spacing decreases nonlinearly. Consequently, the transmission can be designed to meet various application demands by changing the length difference between the two branches. For the dimensions of the WDD are about tens of operating wavelengths, this PhC WDD may be applied in future photonic integrated circuits.

  10. A programmable optical few wavelength source for flexgrid optical networks

    NASA Astrophysics Data System (ADS)

    Imran, M.; Fresi, F.; Meloni, G.; Bhowmik, B. B.; Sambo, N.; Potì, L.

    2016-07-01

    Multi-wavelength (MW) sources will probably replace discrete lasers or laser arrays in next generation multi-carrier transponders (e.g., 1 Tb/s), currently called multi-flow transponders or sliceable bandwidth variable transponders (SBVTs). We present design and experimental demonstration of a few wavelength (FW) source suitable for SBVTs in a flexgrid scenario. We refer to FW instead of MW since for an SBVT just few subcarriers are required (e.g., eight). The proposed FW source does not require optical filtering for subcarrier modulation. The design exploits frequency shifting in IQ modulators by using single side band suppressed carrier modulation. A reasonable number of lines can be provided depending on the chosen architecture, tunable in the whole C-band. The scheme is also capable of providing symmetric (equally spaced) and asymmetric subcarrier spacing arbitrarily tunable from 6.25 GHz to 37.5 GHz. The control on the number of subcarriers (increase/decrease depending on line rate) provides flexibility to the SBVT, being the spacing dependent on transmission parameters such as line rate or modulation format. Transmission performance has been tested and compared with an array of standard lasers considering a 480 Gb/s transmission for different carrier spacing. Additionally, an integrable solution based on complementary frequency shifter is also presented to improve scalability and costs. The impact on transceiver techno-economics and network performance is also discussed.

  11. Active wavelength selection for mixture identification with tunable mid-infrared detectors.

    PubMed

    Huang, Jin; Gutierrez-Osuna, Ricardo

    2016-09-21

    This article presents a wavelength selection framework for mixture identification problems. In contrast with multivariate calibration, where the mixture constituents are known and the goal is to estimate their concentration, in mixture identification the goal is to determine which of a large number of chemicals is present. Due to the combinatorial nature of this problem, traditional wavelength selection algorithms are unsuitable because the optimal set of wavelengths is mixture dependent. To address this issue, our framework interleaves wavelength selection with the sensing process, such that each subsequent wavelength is determined on-the-fly based on previous measurements. To avoid early convergence, our approach starts with an exploratory criterion that samples the spectrum broadly, then switches to an exploitative criterion that selects increasingly more relevant wavelengths as the solution approaches the true constituents of the mixture. We compare this "active" wavelength selection algorithm against a state-of-the-art passive algorithm (successive projection algorithm), both experimentally using a tunable spectrometer and in simulation using a large spectral library of chemicals. Our results show that our active method can converge to the true solution more frequently and with fewer measurements than the passive algorithm. The active method also leads to more compact solutions with fewer false positives. PMID:27590540

  12. Measurement of absolute optical thickness distribution of a mask-glass by wavelength tuning interferometry

    NASA Astrophysics Data System (ADS)

    Hibino, Kenichi; Yangjin, Kim; Bitou, Youichi; Ohsawa, Sonko; Sugita, Naohiko; Mitsuishi, Mamoru

    2008-08-01

    The surface flatness and the uniformity in thickness and refractive index of a mask-blank glass have been requested in semiconductor industry. The absolute optical thickness of a mask-blank glass of seven-inch square and 3mm thickness was measured by three-surface interferometry in a wavelength tuning Fizeau interferometer. Wavelength-tuning interferometry can separate in frequency space the three interference signals of the surface shape and the optical thickness. The wavelength of a tunable laser diode source was scanned linearly from 632 nm to 642 nm and a CCD detector recorded two thousand interference images. The number of phase variation of the interference fringes during the wavelength scanning was counted by a temporal discrete Fourier transform. The initial and final phases of the interferograms before and after the scanning were measured by a phase shifting technique with fine tunings of the wavelengths at 632 nm and 642 nm. The optical thickness defined by the group refractive index at the central wavelength of 337 nm can be measured by this technique. Experimental results show that the cross talk in multiple-surface interferometry caused a systematic error of 2.0 microns in the measured optical thickness.

  13. Stable multi-wavelength fiber laser based on a compounded nonlinear polarization rotation effect

    NASA Astrophysics Data System (ADS)

    Zou, Hui; Lou, Shuqin; Ma, Jianli; Su, Wei; Han, Bolin; Shen, Xiao

    2014-11-01

    A stable multi-wavelength polarization-maintaining erbium-doped fiber (PM-EDF) laser with high signal-to-noise ratio (SNR) based on a compounded nonlinear polarization rotation effect (CNPRE) is proposed and demonstrated. In order to effectively reduce homogeneous broadening of EDF and then to the alleviate mode competition, two sandwich configurations formed by a polarization dependent isolator (PDI) or a segment of single-mode fiber sandwiched between two polarization controllers (PC), are introduced into the ring cavity to generate the CNPRE. A home-made asymmetry twin-core fiber (ATCF) is also incorporated in the ring cavity as a comb filter. With only 150 mW pump power, there are up to 45-wavelengths lasing with the approximate amplitude in a 3 dB bandwidth generated at room temperature. The wavelength spacing between the adjacent peaks is 0.29 nm and the highest SNRs reach 41.5 dB by optimizing the state of polarization of PCs. The power fluctuation and wavelength shift for each lasing wavelength are less than 0.05 dB and 0.02 nm, respectively. This indicates that the proposed multi-wavelength fiber laser can be stably operated at room temperature.

  14. An address geocoding solution for Chinese cities

    NASA Astrophysics Data System (ADS)

    Zhang, Xuehu; Ma, Haoming; Li, Qi

    2006-10-01

    We introduce the challenges of address geocoding for Chinese cities and present a potential solution along with a prototype system that deal with these challenges by combining and extending current geocoding solutions developed for United States and Japan. The proposed solution starts by separating city addresses into "standard" addresses which meet a predefined address model and non-standard ones. The standard addresses are stored in a structured relational database in their normalized forms, while a selected portion of the non-standard addresses are stored as aliases to the standard addresses. An in-memory address index is then constructed from the address database and serves as the basis for real-time address matching. Test results were obtained from two trials conducted in the city Beijing. On average 80% matching rate were achieved. Possible improvements to the current design are also discussed.

  15. Raman shifting of KrF laser radiation for tropospheric ozone measurements

    NASA Technical Reports Server (NTRS)

    Grant, William B.; Browell, Edward V.; Higdon, Noah S.; Ismail, Syed

    1991-01-01

    The differential absorption lidar (DIAL) measurement of tropospheric ozone requires use of high average power UV lasers operating at two appropriate DIAL wavelengths. Laboratory experiments have demonstrated that a KrF excimer laser can be used to generate several wavelengths with good energy conversion efficiencies by stimulated Raman shifting using hydrogen (H2) and deuterium (D2). Computer simulations for an airborne lidar have shown that these laser emissions can be used for the less than 5 percent random error, high resolution measuremment of ozone across the troposphere using the DIAL technique. In the region of strong ozone absorption, laser wavelengths of 277.0 and 291.7 nm were generated using H2 and D2, respectively. In addition, a laser wavelength at 302.0 nm was generated using two cells in series, with the first containing D2 and the second containing H2. The energy conversion efficiency for each wavelength was between 14 and 27 percent.

  16. Magneto-exciton-polariton condensation in a sub-wavelength high contrast grating based vertical microcavity

    SciTech Connect

    Fischer, J.; Brodbeck, S.; Worschech, L.; Kamp, M.; Schneider, C.; Höfling, S.; Zhang, B.; Wang, Z.; Deng, H.

    2014-03-03

    We comparably investigate the diamagnetic shift of an uncoupled quantum well exciton with a microcavity exciton-polariton condensate on the same device. The sample is composed of multiple GaAs quantum wells in an AlAs microcavity, surrounded by a Bragg reflector and a sub-wavelength high contrast grating reflector. Our study introduces an independent and easily applicable technique, namely, the measurement of the condensate diamagnetic shift, which directly probes matter contributions in polariton condensates and hence discriminates it from a conventional photon laser.

  17. Measurement of optical thickness variation of BK7 plate by wavelength tuning interferometry.

    PubMed

    Kim, Yangjin; Hibino, Kenichi; Sugita, Naohiko; Mitsuishi, Mamoru

    2015-08-24

    This paper presents the derivation of a 17-sample phase-shifting algorithm that can compensate the miscalibration and first-order nonlinearity of phase shift error, coupling error, and bias modulation of the intensity and satisfy the fringe contrast maximum condition. The phase error of measurements performed using the 17-sample algorithm is discussed and compared with those of measurements obtained using other algorithms. Finally, the optical thickness variation of a BK7 optically transparent plate obtained using a wavelength tuning Fizeau interferometer and the 17-sample algorithm are presented. The experimental results indicate that the optical thickness variation measurement accuracy for the BK7 plate was 3 nm. PMID:26368260

  18. Dynamic phase-shifting photoelasticity.

    PubMed

    Asundi, A; Tong, L; Boay, C G

    2001-08-01

    The application of phase-shifting photoelasticity to a real-time dynamic event involves simultaneous recording of the four phase-shifted images. Here an instrument, believed to be novel, is developed and described for this purpose. Use of a Multispec Imager is introduced into digital photoelasticity for the first time to our knowledge. This device enables splitting the optical energy of an object into four identical paths, thus permitting recording of the required four phase-shifted images. Experimental demonstration is provided for validation. PMID:18360395

  19. Interpretations of cosmological spectral shifts

    NASA Astrophysics Data System (ADS)

    Østvang, Dag

    2013-03-01

    It is shown that for Robertson-Walker models with flat or closed space sections, all of the cosmological spectral shift can be attributed to the non-flat connection (and thus indirectly to space-time curvature). For Robertson-Walker models with hyperbolic space sections, it is shown that cosmological spectral shifts uniquely split up into "kinematic" and "gravitational" parts provided that distances are small. For large distances no such unique split-up exists in general. A number of common, but incorrect assertions found in the literature regarding interpretations of cosmological spectral shifts, is pointed out.

  20. Multiple soliton self-frequency shift cancellations in a temporally tailored photonic crystal fiber

    SciTech Connect

    Liu, Lai; Kang, Zhe; Li, Qing; Gao, Xuejian; Qin, Guanshi E-mail: wpqin@jlu.edu.cn; Qin, Weiping E-mail: wpqin@jlu.edu.cn; Liao, Meisong; Hu, Lili; Ohishi, Yasutake

    2014-11-03

    We report the generation of multiple soliton self-frequency shift cancellations in a temporally tailored tellurite photonic crystal fiber (PCF). The temporally regulated group velocity dispersion (GVD) is generated in the fiber by soliton induced optical Kerr effect. Two red-shifted dispersive waves spring up when two Raman solitons meet their own second zero-dispersion-wavelengths in the PCF. These results show how, through temporally tailored GVD, nonlinearities can be harnessed to generate unexpected effects.

  1. Silicon waveguide polarization rotation Bragg grating with phase shift section and sampled grating scheme

    NASA Astrophysics Data System (ADS)

    Okayama, Hideaki; Onawa, Yosuke; Shimura, Daisuke; Yaegashi, Hiroki; Sasaki, Hironori

    2016-08-01

    We describe a Bragg grating with a phase shift section and a sampled grating scheme that converts input polarization to orthogonal polarization. A very narrow polarization-independent wavelength peak can be generated by phase shift structures and polarization-independent multiple diffraction peaks by sampled gratings. The characteristics of the device were examined by transfer matrix and finite-difference time-domain methods.

  2. Nurse Fatigue and Shift Length: A Pilot Study.

    PubMed

    Martin, Deborah Maust

    2015-01-01

    Increasing emphasis on patient quality and concerns about the impact of health care worker fatigue has stimulated efforts for leaders to address patient quality and caregiver satisfaction. Shift length has been associated with nurse fatigue and has become a growing concern in the United States with the routine shift length of 12 hours. In this project, shift lengths from 12 hours to 8 hours for a 4-week period to evaluate fatigue levels associated with 12-hour and 8-hour shifts. Lessons learned from this experience: nurses are agreeable to try a proposed change, numerous ideas should be tried to develop additional innovative solutions to the issue of nurse fatigue, and nurses may not want to work 5 days per week. PMID:26281278

  3. Efficient multicast routing in wavelength-division-multiplexing networks with light splitting and wavelength conversion

    NASA Astrophysics Data System (ADS)

    Zheng, Sheng; Tian, Jinwen; Liu, Jian

    2005-04-01

    We propose wavelength-division-multiplexing (WDM) networks with light splitting and wavelength conversion that can efficiently support multicast routing between nodes. Our iterative algorithm analyzes the original multicast routing network by decomposing it into multicast subgroups. These subgroups have the same wavelength, and the individual subgroup is combined to build a multicast tree. From the multicast tree, we can compute efficiently to multicast for short paths. Numerical results obtained for the ARPANET show that our algorithm can greatly reduce the optical blocking probability and the number of required wavelength conversions.

  4. Issues in Multi-Wavelength Optical Network Design

    NASA Astrophysics Data System (ADS)

    Ramaswami, Rajiv

    1990-01-01

    Our investigation of optical amplifiers begins with a model to study their saturation characteristics, followed by an analysis of amplifier-induced spontaneous emission noise. These two factors are then used to determine the optimal position of an amplifier in a simple single -channel link. The optimal position involves a trade-off between amplifier noise and saturation. We then consider networks using amplifiers and quantify the penalty due to crosstalk when several channels at different wavelengths are amplified simultaneously using a single amplifier, as a function of the number of channels, amplifier input power, and extinction ratio. Results indicate that when the number of channels is small, the crosstalk component dominates, but when the number of channels is large, the component due to the steady state gain reduction becomes significant. For the high data-rate case, the crosstalk penalty is no longer present and only the component due to the steady-state gain reduction is retained. Hence, the overall penalty is lower than in the low data-rate case. Our results apply to both semiconductor laser amplifiers and doped fiber amplifiers. We expect smaller crosstalk penalties with fiber amplifiers. These results are then used in a network design example to determine the number of stations that can be supported using amplifiers. We also study the performance of frequency-shift keying and polarization-shift keying as alternatives to on-off keying. Moving to the media-access layer, we propose a dynamic time/wavelength-division multi-access protocol (DT-WDMA) for metropolitan-sized multi-channel optical networks employing fixed-wavelength transmitters and tunable optical receivers. A global but distributed arbitration algorithm is used to resolve conflicts when packets from many transmitters contend for the same receiver. This eliminates the need for explicit acknowledgements. The protocol is capable of achieving high bandwidth utilization (0.6 packets per station per

  5. Coherent ultra dense wavelength division multiplexing passive optical networks

    NASA Astrophysics Data System (ADS)

    Shahpari, Ali; Ferreira, Ricardo; Ribeiro, Vitor; Sousa, Artur; Ziaie, Somayeh; Tavares, Ana; Vujicic, Zoran; Guiomar, Fernando P.; Reis, Jacklyn D.; Pinto, Armando N.; Teixeira, António

    2015-12-01

    In this paper, we firstly review the progress in ultra-dense wavelength division multiplexing passive optical network (UDWDM-PON), by making use of the key attributes of this technology in the context of optical access and metro networks. Besides the inherit properties of coherent technology, we explore different modulation formats and pulse shaping. The performance is experimentally demonstrated through a 12 × 10 Gb/s bidirectional UDWDM-PON over hybrid 80 km standard single mode fiber (SSMF) and optical wireless link. High density, 6.25 GHz grid, Nyquist shaped 16-ary quadrature amplitude modulation (16QAM) and digital frequency shifting are some of the properties exploited together in the tests. Also, bidirectional transmission in fiber, relevant in the context, is analyzed in terms of nonlinear and back-reflection effects on receiver sensitivity. In addition, as a basis for the discussion on market readiness, we experimentally demonstrate real-time detection of a Nyquist-shaped quaternary phase-shift keying (QPSK) signal using simple 8-bit digital signal processing (DSP) on a field-programmable gate array (FPGA).

  6. Long-wavelength-emitting nanocrystals for bioassay applications

    NASA Astrophysics Data System (ADS)

    Leppert, Valerie J.; Harvey, Ashley S.; McCool, Geoff D.; Quinlan, Forest T.; Feng, Jun; Shan, Guomin; Stroeve, Pieter; Risbud, Subhash H.; Hammock, Bruce D.; Kennedy, Ian M.

    2002-11-01

    New fluorophores that can be excited using visible or near-infrared radiation are of considerable interest for application in environmental and complex bioassays, where background fluorescence is exacerbated by ultra-violet or blue excitation. Useful labels for biomolecules include infrared emitting semiconductor nanoparticles that can be blue-shifted into the near-infrared and visible through quantum confinement effects, oxides of iron, and rare earth oxides. In this work, the synthesis of 6 nm average diameter lead selenide nanocrystals (well below the Bohr exciton diameter of 92 nm) through a reverse micelle technique; and the synthesis of iron and europium oxides with particles less than 5 nm in diameter by pulsed laser ablation is reported. The europium oxide nanoparticles' emission showed a large Stokes shift (144 nm or 216 nm, depending on excitation wavelength); a narrow, symmetric emission line at 610 nm (FWHM of 8 nm); and long lifetime (300 μs). The Eu2O3 nanoparticles, which were coated with silica for functionalization, displayed a greatly enhanced sensitivity over a conventional ELISA (0.025 ng ml-1 vs. 0.1 ng ml-1) when run in an atrazine immunoassay.

  7. Two wavelength satellite laser ranging using SPAD

    NASA Technical Reports Server (NTRS)

    Prochazka, Ivan; Hamal, Karel; Jelinkova, Helena; Kirchner, Georg; Koidl, F.

    1993-01-01

    When ranging to satellites with lasers, there are several principal contributions to the error budget: from the laser ranging system on the ground, from the satellite retroarray geometry, and from the atmosphere. Using a single wavelength, we have routinely achieved a ranging precision of 8 millimeters when ranging to the ERS-1 and Starlette satellites. The systematic error of the atmosphere, assuming the existing dispersion models, is expected to be of the order of 1 cm. Multiple wavelengths ranging might contribute to the refinement of the existing models. Taking into account the energy balance, the existing picosecond lasers and the existing receiver and detection technology, several pairs or multiple wavelengths may be considered. To be able to improve the atmospheric models to the subcentimeter accuracy level, the differential time interval (DTI) has to be determined within a few picoseconds depending on the selected wavelength pair. There exist several projects based on picosecond lasers as transmitters and on two types of detection techniques: one is based on photodetectors, like photomultipliers or photodiodes connected to the time interval meters. Another technique is based on the use of a streak camera as an echo signal detector, temporal analyzer, and time interval vernier. The temporal analysis at a single wavelength using the streak camera showed the complexity of the problem.

  8. Correlated errors in phase-shifting laser Fizeau interferometry.

    PubMed

    de Groot, Peter J

    2014-07-01

    High-performance data processing algorithms for phase-shifting interferometry accommodate adjustment errors in the phase shift increment as well as harmonic distortions in the interference signal. However, a widely overlooked error source is the combination of these two imperfections. Phase shift tuning errors increase the sensitivity of phase estimation algorithms to second-order and higher harmonics present in Fizeau interference signals. I derive an analytical formula for evaluating these errors more realistically, in part to identify the characteristics of the optimal PSI algorithm. Even for advanced algorithms, it is found that multiple reflections increase the error contribution of detuning by orders of magnitude compared with the two-beam calculation and impose a practical limit of 30% in tuning error for sub-nm metrology in a 4%-4% Fizeau cavity. Consequently, a preferred approach for high precision spherical cavities is to use either wavelength tuning in place of mechanical phase shifting or an iterative solver that accommodates unknown phase shifts as a function of field position. PMID:25089998

  9. Active Region Moss: Doppler Shifts from Hinode/EIS Observations

    NASA Technical Reports Server (NTRS)

    Tripathi, Durgesh; Mason, Helen E.; Klimchuk, James A.

    2012-01-01

    Studying the Doppler shifts and the temperature dependence of Doppler shifts in moss regions can help us understand the heating processes in the core of the active regions. In this paper we have used an active region observation recorded by the Extreme-ultraviolet Imaging Spectrometer (EIS) onboard Hinode on 12-Dec- 2007 to measure the Doppler shifts in the moss regions. We have distinguished the moss regions from the rest of the active region by defining a low density cut-off as derived by Tripathi et al. (2010). We have carried out a very careful analysis of the EIS wavelength calibration based on the method described in Young, O Dwyer and Mason (2012). For spectral lines having maximum sensitivity between log T = 5.85 and log T = 6.25 K, we find that the velocity distribution peaks at around 0 km/s with an estimated error of 4 km/s. The width of the distribution decreases with temperature. The mean of the distribution shows a blue shift which increases with increasing temperature and the distribution also shows asymmetries towards blue-shift. Comparing these results with observables predicted from different coronal heating models, we find that these results are consistent with both steady and impulsive heating scenarios. Further observational constraints are needed to distinguish between these two heating scenarios.

  10. Phase-shifted helical long-period grating-based temperature-insensitive optical fiber twist sensors

    NASA Astrophysics Data System (ADS)

    Gao, Ran; Zhu, Yinian; Krishnaswamy, Sridhar; Yi, Jiang

    2015-03-01

    In smart structure monitoring, twist angle is one of the most critical mechanical parameters for infrastructure deterioration. A compact temperature-insensitive optical fiber twist sensor based on multi-phase-shifted helical long period fiber grating has been proposed and experimentally demonstrated in this paper. A multi-phase-shifted helical long period fiber grating is fabricated with a multi-period rotation technology. A π / 2 and a 3π / 2 phase shift is introduced in the helical long period fiber grating by changing the period. The helical pitch can be effectively changed with a different twist rate, which is measured by calculating the wavelength difference between two phase shift peaks. Although the wavelength of the phase shift peak also shifts with a change of the temperature, the wavelength difference between two phase shift peaks is constant due to two fixed phase shifts in the helical long period fiber grating, which is extremely insensitive to temperature change for the multi-phase-shifted helical long period fiber grating. The experimental results show that a sensitivity of up to 1.959 nm/(rad/m) is achieved.

  11. New type high-index dielectric nanosensors based on the scattering intensity shift.

    PubMed

    Yan, Jiahao; Liu, Pu; Lin, Zhaoyong; Yang, Guowei

    2016-03-21

    Sensing is regarded as one of the most important applications of noble metal-based nanoplasmonics. However, all previous designs have been based on the wavelength-shift of the localized surface plasmon resonance, in which the sensitivity is intrinsically limited by the low quality factors induced by metal losses, and meanwhile the large ohmic loss, high cost and inevitable toxicity and biofouling for detection in vivo greatly hinder their further applications in biosensors. Beyond noble metals, high-refractive index dielectric materials (HRDMs) like silicon with low-loss and strong magnetic response have drawn more attention. Here, for the first time, we proposed a HRDM nanosphere as a new nanosensor for biomolecule detection, and experimentally demonstrated a HRDM sensor working on the intensity-shift but not wavelength-shift of the scattering. The sensing mechanism based on the synergistic effect of the broadening electric mode shift of HRDMs and the Kerker's scattering intensity-shift is beneficial to achieve higher sensitivity. We validated the efficacy of our sensor to detect refractive index changes and trace amounts of streptavidin molecules, and the sensitivity can reach 27 times as high as the highest sensitivity reported to date for nanoplasmonic structures. These findings showed that monitoring the change of the scattering intensity of HRDM nanostructures is superior to monitoring the wavelength-shift of nanoplasmonic structures, as is widely used in nanoplasmonic sensors, for biosensing, meaning HRDM nanosensors could be an important tool in biomolecule detection. PMID:26926420

  12. Color Shift Investigations for LED Secondary Optical Designs: Comparison between BPA-PC and PMMA

    NASA Astrophysics Data System (ADS)

    Lu, Guangjun; Yazdan Mehr, M.; van Driel, W. D.; Fan, Xuejun; Fan, Jiajie; Jansen, K. M. B.; Zhang, G. Q.

    2015-07-01

    Recently, color shift of LED-based lighting products has attracted much attention due to its increasing impact on the field application. However, significant research investigations on the color shift mechanisms are not publically available especially for important transmission materials used for secondary optical design. In this paper, broadly used such commercial materials (BPA-PC and PMMA) are experimentally investigated on the color shift effects during aging. Besides this, color shift mechanisms of degradation of transmittance are also studied. Results revealed: (1) Inconsistent degradation of wavelength-dependent transmittance induces the decrease of the blue/yellow light intensity ratio and thus gives rise to the color shift toward the yellow field, which is the color shift mechanism of BPA-PC; (2) Even for the non-aged BPA-PC, the transmittance varies with wavelength in the visible light field due to the chemistry of the material, which caused the change of intensify ratio of blue light to yellow light in the SPD, leading to color change in perception; (3) Oxidation plays a key role in the degradation of transmittance at around the peak wavelength of the blue light field, which is in correlation with the discoloration of thermally-aged BPA-PC materials. By contrast, for the PMMA specimen aged up to 3000 h, oxidation was neither occurred at 85 °C, nor with additional exposure to blue light, nor even with additional humidity of 85%RH.

  13. Refining the shifted topological vertex

    SciTech Connect

    Drissi, L. B.; Jehjouh, H.; Saidi, E. H.

    2009-01-15

    We study aspects of the refining and shifting properties of the 3d MacMahon function C{sub 3}(q) used in topological string theory and BKP hierarchy. We derive the explicit expressions of the shifted topological vertex S{sub {lambda}}{sub {mu}}{sub {nu}}(q) and its refined version T{sub {lambda}}{sub {mu}}{sub {nu}}(q,t). These vertices complete results in literature.

  14. Fourier transform infrared phase shift cavity ring down spectrometer

    NASA Astrophysics Data System (ADS)

    Schundler, Elizabeth; Mansur, David J.; Vaillancourt, Robert; Benedict-Gill, Ryan; Newbry, Scott P.; Engel, James R.; Dupuis, Julia Rentz

    2014-05-01

    OPTRA has developed a Fourier transform infrared phase shift cavity ring down spectrometer (FTIR-PS-CRDS) system under a U.S. EPA SBIR contract. This system uses the inherent wavelength-dependent modulation imposed by the FTIR on a broadband thermal source for the phase shift measurement. This spectrally-dependent phase shift is proportional to the spectrally-dependent ring down time. The spectral dependence of both of these values is introduced by the losses of the cavity including those due to the molecular absorption of the sample. OPTRA's approach allows broadband detection of chemicals across the feature-rich fingerprint region of the long-wave infrared. This represents a broadband and spectral range enhancement to conventional CRDS which is typically done at a single wavelength in the near IR; at the same time the approach is a sensitivity enhancement to traditional FTIR, owing to the long effective path of the resonant cavity. In previous papers1,2, OPTRA has presented a breadboard system aimed at demonstrating the feasibility of the approach and a prototype design implementing performance enhancements based on the results of breadboard testing. In this final paper in the series, we will present test results illustrating the realized performance of the fully assembled and integrated breadboard, thereby demonstrating the utility of the approach.

  15. Quantification of different water species in acetone using a NIR-triple-wavelength fiber laser.

    PubMed

    Andrews, Nicholas L P; MacLean, Amy G; Saunders, John E; Barnes, Jack A; Loock, Hans-Peter; Saad, Mohammed; Jia, Chenglai; Ramaswamy, Kishor; Chen, Lawrence R

    2014-08-11

    A fiber laser using a thulium-doped ZBLAN gain medium was used to generate laser radiation simultaneously at 1461, 1505 and 1874 nm, with > 5 mW output power at each of the wavelengths. The laser was used to quantify the near-infrared absorption of liquid water in acetone. Additionally, near-infrared spectra were recorded using a broad band source and were interpreted using parallel factor (PARAFAC) analysis to rationalize the concentration-dependent peak shifts. PMID:25321018

  16. Effect of diode wavelength broadening in a diode end-pumped solid-state amplifier.

    PubMed

    Bourdet, Gilbert L; Casagrande, Olivier

    2007-05-10

    The effect of the spectral broadening in cw diode pumping and the wavelength shift in pulsed pumping of a solid-state laser is investigated theoretically. A very simple model allowing the computation of the reduction of the absorbed pump energy is developed. The results are applied to an ytterbium-doped solid-state laser and should be fruitful for amplifier and laser design. PMID:17446921

  17. Fast gain recovery rates with strong wavelength dependence in a non-linear SOA.

    PubMed

    Cleary, Ciaran S; Power, Mark J; Schneider, Simon; Webb, Roderick P; Manning, Robert J

    2010-12-01

    We report remarkably fast and strongly wavelength-dependent gain recovery in a single SOA without the aid of an offset filter. Full gain recovery times as short as 9 ps were observed in pump-probe measurements when pumping to the blue wavelength side of a continuous wave probe, in contrast to times of 25 to 30 ps when pumping to the red wavelength side. Experimental and numerical analysis indicate that the long effective length and high gain led to deep saturation of the second half of the SOA by the probe. The consequent absorption of blue-shifted pump pulses in this region resulted in device dynamics analogous to those of the Turbo-Switch. PMID:21164918

  18. Non-dipole effects on high-order harmonic generation towards the long wavelength region

    NASA Astrophysics Data System (ADS)

    Zhu, Xiaosong; Wang, Zhe

    2016-04-01

    The non-dipole (ND) effects on high-order harmonic generation (HHG) with the laser wavelength increasing towards the long wavelength region are investigated. Two major phenomena due to the ND effects, the decrease of the HHG intensity and the shift of the harmonic spectrum, are discussed. It is shown that, for the commonly used laser intensity I∼1014 W/cm2 and target with ionization potential Ip ∼ 0.5 a . u ., the ND effects become nonnegligible when the laser wavelength is increased to the mid-infrared region of several thousand nanometers. It is also found that the variation of the ND effects presents different rules compared with those towards the high intensity region. Two fitting formulas are proposed to describe the variation rules. The physical meanings of the fitting results are discussed with classical calculation.

  19. Revised wavelength and spectral response calibrations for AKARI near-infrared grism spectroscopy: Cryogenic phase

    NASA Astrophysics Data System (ADS)

    Baba, Shunsuke; Nakagawa, Takao; Shirahata, Mai; Isobe, Naoki; Usui, Fumihiko; Ohyama, Youichi; Onaka, Takashi; Yano, Kenichi; Kochi, Chihiro

    2016-04-01

    We perform revised spectral calibrations for the AKARI near-infrared grism to correct quantitatively for the effect of the wavelength-dependent refractive index. The near-infrared grism covering the wavelength range of 2.5-5.0 μm, with a spectral resolving power of 120 at 3.6 μm, is found to be contaminated by second-order light at wavelengths longer than 4.9 μm, which is especially serious for red objects. First, we present the wavelength calibration considering the refractive index of the grism as a function of the wavelength for the first time. We find that the previous solution is positively shifted by up to 0.01 μm compared with the revised wavelengths at 2.5-5.0 μm. In addition, we demonstrate that second-order contamination occurs even with a perfect order-sorting filter owing to the wavelength dependence of the refractive index. Secondly, the spectral responses of the system from the first- and second-order light are simultaneously obtained from two types of standard objects with different colors. The response from the second-order light suggests leakage of the order-sorting filter below 2.5 μm. The relations between the output of the detector and the intensities of the first- and second-order light are formalized by a matrix equation that combines the two orders. The removal of the contaminating second-order light can be achieved by solving the matrix equation. The new calibration extends the available spectral coverage of the grism mode from 4.9 μm up to 5.0 μm. The revision can be used to study spectral features falling in these extended wavelengths, e.g., the carbon monoxide fundamental ro-vibrational absorption within nearby active galactic nuclei.

  20. Fast wavelength-tunable picosecond pulses from a passively mode-locked Er fiber laser using a galvanometer-driven intracavity filter.

    PubMed

    Ozeki, Yasuyuki; Tashiro, Daigo

    2015-06-15

    We experimentally investigate fast wavelength-tuning characteristics of a polarization-maintaining Er fiber laser, which is mode-locked with a semiconductor saturable absorber mirror. Wavelength tuning was accomplished with an intracavity filter incorporating a galvanometer mirror and a diffraction grating. Within the tunability of 30 nm, we achieved a wavelength-tuning speed of <5 ms. We also show that the variation of repetition rates can be suppressed to <200 Hz by simply shifting the position of the grating. The presented scheme for generating wavelength-tunable pulses will be potentially useful for coherent Raman spectral imaging. PMID:26193501

  1. Integrated nonlinear interferometer with wavelength multicasting functionality.

    PubMed

    Yang, Weili; Yu, Yu; Zhang, Xinliang

    2016-08-01

    Nonlinear interference based on four wave mixing (FWM) is extremely attractive due to its phase sensitivity. On the other hand, wavelength multicasting, which supports data point-to-multipoint connections, is a key functionality to increase the network efficiency and simplify the transmitter and receiver in the wavelength-division multiplexing systems. We propose and experimentally demonstrate a nonlinear interferometer with wavelength multicasting functionality based on single-stage FWM in an integrated silicon waveguide. With a three-pump and dual-signal input, four phase sensitive idlers are obtained at the interferometer output. For a proof-of-concept application, we further theoretically demonstrate the multicasting logic exclusive-OR (XOR) gate for both intensity and phase modulated signals. The proposed scheme would be potentially applied in various on-chip applications for future optical communication system. PMID:27505786

  2. Cryogenic Amplifier Based Receivers at Submillimeter Wavelengths

    NASA Technical Reports Server (NTRS)

    Chattopadhyay, Goutam; Reck, Theodore and; Schlecht, Erich; Lin, Robert; Deal, William

    2012-01-01

    The operating frequency of InP high electron mobility transistor (HEMT) based amplifiers has moved well in the submillimeter-wave frequencies over the last couple of years. Working amplifiers with usable gain in waveguide packages has been reported beyond 700 GHz. When cooled cryogenically, they have shown substantial improvement in their noise temperature. This has opened up the real possibility of cryogenic amplifier based heterodyne receivers at submillimeter wavelengths for ground-based, air-borne, and space-based instruments for astrophysics, planetary, and Earth science applications. This paper provides an overview of the science applications at submillimeter wavelengths that will benefit from this technology. It also describes the current state of the InP HEMT based cryogenic amplifier receivers at submillimeter wavelengths.

  3. Mechanisms and Methods for Selective Wavelength Filtering

    NASA Technical Reports Server (NTRS)

    Tuma, Margaret (Inventor); Brown, Thomas G. (Inventor); Gruhlke, Russell (Inventor)

    2007-01-01

    An optical filter includes a dielectric waveguide layer, supporting waveguide modes at specific wavelengths and receiving incident light, a corrugated film layer, composed of one of a metal and a semiconductor and positioned adjacent to a second surface of the waveguide layer and a sensor layer, wherein the sensor layer is capable of absorbing optical energy and generating a corresponding electrical signal. The metal film layer supports a plurality of plasmons, the plurality of plasmons producing a first field and is excited by a transverse mode of the waveguide modes at a wavelength interval. The first field penetrates the sensor layer and the sensor layer generates an electrical signal corresponding to an intensity of received incident light within the wavelength interval.

  4. Device for wavelength-selective imaging

    DOEpatents

    Frangioni, John V.

    2010-09-14

    An imaging device captures both a visible light image and a diagnostic image, the diagnostic image corresponding to emissions from an imaging medium within the object. The visible light image (which may be color or grayscale) and the diagnostic image may be superimposed to display regions of diagnostic significance within a visible light image. A number of imaging media may be used according to an intended application for the imaging device, and an imaging medium may have wavelengths above, below, or within the visible light spectrum. The devices described herein may be advantageously packaged within a single integrated device or other solid state device, and/or employed in an integrated, single-camera medical imaging system, as well as many non-medical imaging systems that would benefit from simultaneous capture of visible-light wavelength images along with images at other wavelengths.

  5. Wavelength Dependence on the Space Charge Collection

    SciTech Connect

    Washington, A.; Teague, L.; Duff, M.; Burger, A.; Groza, M.; Buliga, V.

    2012-05-31

    The distribution of the internal electric field in Cd{sub 1-x}Zn{sub x}Te (CZT) materials has significant effects on the charge collection ability. Light exposure at various wavelengths is a relatively unexplored process that alters charge collection at the anode contact. The use of multiple wavelengths can target charge carriers at various trap energies and positions throughout the crystal. The controlled illumination increases charge collection by releasing trapped electron and hole carriers in the crystal despite differences in light energy. Our study presents the results from our investigation of the effect of external illumination of CZT on the internal electric field via the Pockels effect. The space charge collection is further analyzed based on location and intensity relative to the specific wavelength of illumination.

  6. All-optical wavelength conversion for mode division multiplexed superchannels.

    PubMed

    Gong, Jiaxin; Xu, Jing; Luo, Ming; Li, Xiang; Qiu, Ying; Yang, Qi; Zhang, Xinliang; Yu, Shaohua

    2016-04-18

    We report in this work the first all-optical wavelength conversion (AOWC) of a mode division multiplexed (MDM) superchannel consisting of 2N modes by dividing the superchannel into N single-mode (SM) tributaries, wavelength converting N SM signals using well developed SM-AOWC techniques, and finally combining the N SM tributaries back to an MDM superchannel at the converted wavelength, inspired by the idea of using SM filtering techniques to filter multimode signals in astronomy. The conversions between multimode and SM are realized by 3D laser-writing photonic lanterns and SM-AOWCs are realized based on polarization insensitive four wave mixing (FWM) configuration in N semiconductor optical amplifiers (SOAs). As a proof of concept demonstration, the conversion of a 6-mode MDM superchannel with each mode modulated with orthogonal frequency division multiplexed (OFDM) quadrature phase-shift keying (QPSK)/16 quadrature amplitude modulation (QAM) signals is demonstrated in this work, indicating that the scheme is transparent to data format, polarization and compatible with multi-carrier signals. Data integrity of the converted superchannel has been verified by using coherent detection and digital signal processing (DSP). Bit error rates (BERs) below the forward error correction (FEC) hard limit (3.8 × 10-3) have been obtained for QPSK modulation at a net bitrate of 104.2 Gbit/s and BERs below the soft decision FEC threshold (1.98 × 10-2) have been achieved for 16-QAM format, giving a total aggregate bit rate of 185.8 Gbit/s when taking 20% coding overhead into account. Add and drop functionalities that usually come along with wavelength conversion in flexible network nodes have also been demonstrated. The working conditions of the SOAs, especially the pump and signal power levels, are critical for the quality of the converted signal and have been thoroughly discussed. The impact of imbalanced FWM conversion efficiency among different SM

  7. Integrated Optical, Acoustically Tunable Wavelength Filter

    NASA Astrophysics Data System (ADS)

    Frangen, J.; Herrmann, Harald; Ricken, Raimund; Seibert, Holger; Sohler, Wolfgang; Strake, E.

    1989-12-01

    An integrated optical, acoustically tunable wavelength filter, consisting of a combination of TM-TE converter and integrated polarizer in LiNbO3, is demonstrated. The filter bandwidth is 2.8 nm; the center wavelength can be tuned from λ = 1.45 pm to λ = 1.57 pm by adjusting the driving acoustic frequency. Due to the combined acoustical/optical strip guide structure, used in the mode converter, a very low acoustic drive power of only 9 mW is required.

  8. Undulators for short wavelength FEL amplifiers

    SciTech Connect

    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 FELs, such as the Linac Coherent Light Source at SLAC and the DUV Free-Electron Laser at BNL, are presented.

  9. Miniature integrated-optical wavelength analyzer chip

    NASA Astrophysics Data System (ADS)

    Kunz, R. E.; Dübendorfer, J.

    1995-11-01

    A novel integrated-optical chip suitable for realizing compact miniature wavelength analyzers with high linear dispersion is presented. The chip performs the complete task of converting the spectrum of an input beam into a corresponding spatial irradiance distribution without the need for an imaging function. We demonstrate the feasibility of this approach experimentally by monitoring the changes in the mode spectrum of a laser diode on varying its case temperature. Comparing the results with simultaneous measurements by a commercial spectrometer yielded a rms wavelength deviation of 0.01 nm.

  10. Modulation compression for short wavelength harmonic generation

    SciTech Connect

    Qiang, J.

    2010-01-11

    Laser modulator is used to seed free electron lasers. In this paper, we propose a scheme to compress the initial laser modulation in the longitudinal phase space by using two opposite sign bunch compressors and two opposite sign energy chirpers. This scheme could potentially reduce the initial modulation wavelength by a factor of C and increase the energy modulation amplitude by a factor of C, where C is the compression factor of the first bunch compressor. Such a compressed energy modulation can be directly used to generate short wavelength current modulation with a large bunching factor.

  11. Wavelength-tunable microbolometers with metamaterial absorbers.

    PubMed

    Maier, Thomas; Brückl, Hubert

    2009-10-01

    Microbolometers are modified by metallic resonant absorber elements, leading to an enhanced responsivity at selectable wavelengths. The dissipative energy absorption of tailored metamaterials allows for engineering the response of conventional bolometer microbridges. The absorption peak position and height are determined by the geometry of the metamaterial. Square-shaped metal/dielectric/metal stacks as absorber elements show spectral resonances at wavelengths between 4.8 and 7.0 microm in accordance with numerical simulations. Total peak absorptions of 0.8 are obtained. The metamaterial modified bolometers are suitable for multispectral thermal imaging systems in the mid-IR and terahertz regime. PMID:19794799

  12. 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.

  13. Effects of Laser Wavelength on Ablator Testing

    NASA Technical Reports Server (NTRS)

    White, Susan M.

    2014-01-01

    Wavelength-dependent or spectral radiation effects are potentially significant for thermal protection materials. NASA atmospheric entry simulations include trajectories with significant levels of shock layer radiation which is concentrated in narrow spectral lines. Tests using two different high powered lasers, the 10.6 micron LHMEL I CO2 laser and the near-infrared 1.07 micron fiber laser, on low density ablative thermal protection materials offer a unique opportunity to evaluate spectral effects. Test results indicated that the laser wavelength can impact the thermal response of an ablative material, in terms of bond-line temperatures, penetration times, mass losses, and char layer thicknesses.

  14. Second level exposure for phase shift mask applications using an SLM-based DUV mask writer

    NASA Astrophysics Data System (ADS)

    Chandramouli, Mahesh; Olshausen, Bob; Korobko, Yulia; Henrichs, Sven; Qu, Ping; Ma, Jian; Auches, Bruce; Cole, Damon; Ostrom, Thomas; Beyerl, Angela; Eklund, Robert; Zerne, Raoul; Goransson, Peter; Persson, Magnus; Newman, Tom

    2005-06-01

    Phase shift mask (PSM) applications are becoming essential for addressing the lithography requirements of the 65 nm technology node and beyond. Many mask writer properties must be under control to expose the second level of advanced PSM: second level alignment system accuracy, resolution, pattern fidelity, critical dimension (CD) uniformity and registration. Optical mask writers have the advantage of process simplicity for this application, as they do not require a discharge layer. This paper discusses how the mask writer properties affect the error budget for printing the second level. A deep ultraviolet (DUV) mask writer with a spatial light modulator (SLM) is used in the experimental part of the paper. Partially coherent imaging optics at the 248 nm wavelength provide improved resolution over previous systems, and pattern fidelity is optimized by a real-time corner enhancement function. Lithographic performance is compared to the requirements for second level exposure of advanced PSM. The results indicate sufficient capability and stability for 2nd level alternating PSM patterning at the 65 nm and 45 nm nodes.

  15. Noninvasive diagnosis of oral cancer by Stokes shift spectroscopy

    NASA Astrophysics Data System (ADS)

    Ebenezar, Jeyasingh; Ganesan, Singaravelu; Aruna, Prakasrao; Muralinaidu, Radhakrishnan

    2014-03-01

    The objective of this study is to evaluate the diagnostic potential of stokes shift (SS) spectroscopy (S3) for normal, precancer and cancerous oral lesions in vivo. The SS spectra were recorded in the 250 - 650 nm spectral range by simultaneously scanning both the excitation and emission wavelengths while keeping a fixed wavelength interval Δλ=20 nm between them. Characteristic, highly resolved peaks and significant spectral differences between normal and different pathological oral lesions observed around 300, 355, 395, and 420 nm which are attributed to tryptophan, collagen, and NADH respectively. Using S3 technique one can obtain the key fluorophores in a single scan and hence they can be targeted as a tumor markers in this study. In order to quantify the altered spectral differences between normal and different pathological oral lesions are verified by different ratio parameters.

  16. 32 CFR 516.7 - Mailing addresses.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 32 National Defense 3 2011-07-01 2009-07-01 true Mailing addresses. 516.7 Section 516.7 National Defense Department of Defense (Continued) DEPARTMENT OF THE ARMY AID OF CIVIL AUTHORITIES AND PUBLIC RELATIONS LITIGATION General § 516.7 Mailing addresses. Mailing addresses for organizations referenced...

  17. 47 CFR 97.23 - Mailing address.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Mailing address. 97.23 Section 97.23 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AMATEUR RADIO... name and mailing address. The mailing address must be in an area where the amateur service is...

  18. 47 CFR 97.23 - Mailing address.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Mailing address. 97.23 Section 97.23 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AMATEUR RADIO... name and mailing address. The mailing address must be in an area where the amateur service is...

  19. 47 CFR 97.23 - Mailing address.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Mailing address. 97.23 Section 97.23 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AMATEUR RADIO... name and mailing address. The mailing address must be in an area where the amateur service is...

  20. 47 CFR 97.23 - Mailing address.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Mailing address. 97.23 Section 97.23 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AMATEUR RADIO... name and mailing address. The mailing address must be in an area where the amateur service is...

  1. 47 CFR 97.23 - Mailing address.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Mailing address. 97.23 Section 97.23 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AMATEUR RADIO... name and mailing address. The mailing address must be in an area where the amateur service is...

  2. 47 CFR 13.10 - Licensee address.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false Licensee address. 13.10 Section 13.10 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL COMMERCIAL RADIO OPERATORS General § 13.10 Licensee address. In accordance with § 1.923 of this chapter all applications must specify an address where...

  3. CCCC Chair's Address: Representing Ourselves, 2008

    ERIC Educational Resources Information Center

    Glenn, Cheryl

    2008-01-01

    This article presents the text of the author's address at the fifty-ninth annual convention of the Conference on College Composition and Communication (CCCC) in March 2008. In her address, the author picks up strands of previous Chairs' addresses and weaves them through the fabric of her remarks. What she hopes will give sheen to the fabric is her…

  4. 75 FR 49813 - Change of Address

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-16

    ... COMMISSION 11 CFR Parts 9405, 9407, 9409, 9410, 9420, and 9428 Change of Address AGENCY: United States... Assistance Commission (EAC) is amending its regulations to reflect a change of address for its headquarters. This technical amendment is a nomenclature change that updates and corrects the address for...

  5. 32 CFR 516.7 - Mailing addresses.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 32 National Defense 3 2010-07-01 2010-07-01 true Mailing addresses. 516.7 Section 516.7 National Defense Department of Defense (Continued) DEPARTMENT OF THE ARMY AID OF CIVIL AUTHORITIES AND PUBLIC RELATIONS LITIGATION General § 516.7 Mailing addresses. Mailing addresses for organizations referenced...

  6. Efficient wavelength multiplexers based on asymmetric response filters.

    PubMed

    Wade, Mark T; Popović, Miloš A

    2013-05-01

    We propose integrated photonic wavelength multiplexers based on serially cascaded channel add-drop filters with an asymmetric frequency response. By utilizing the through-port rejection of the previous channel to advantage, the asymmetric response provides optimal rejection of the adjacent channels at each wavelength channel. We show theoretically the basic requirements to realize an asymmetric filter response, and propose and evaluate the possible implementations using coupled resonators. For one implementation, we provide detailed design formulas based on a coupled-mode theory model, and more generally we provide broad guidelines that enumerate all structures that can provide asymmetric passbands in the context of a pole-zero design approach to engineering the device response. Using second-order microring resonator filter stages as an example, we show that the asymmetric multiplexer can provide 2.4 times higher channel packing (bandwidth) density than a multiplexer using the same order stages (number of resonators) using conventional all-pole maximally-flat designs. We also address the sensitivities and constraints of various implementations of our proposed approach, as it affects their applicability to CMOS photonic interconnects. PMID:23669947

  7. Integrated reformer and shift reactor

    SciTech Connect

    Bentley, Jeffrey M.; Clawson, Lawrence G.; Mitchell, William L.; Dorson, Matthew H.

    2006-06-27

    A hydrocarbon fuel reformer for producing diatomic hydrogen gas is disclosed. The reformer includes a first reaction vessel, a shift reactor vessel annularly disposed about the first reaction vessel, including a first shift reactor zone, and a first helical tube disposed within the first shift reactor zone having an inlet end communicating with a water supply source. The water supply source is preferably adapted to supply liquid-phase water to the first helical tube at flow conditions sufficient to ensure discharge of liquid-phase and steam-phase water from an outlet end of the first helical tube. The reformer may further include a first catalyst bed disposed in the first shift reactor zone, having a low-temperature shift catalyst in contact with the first helical tube. The catalyst bed includes a plurality of coil sections disposed in coaxial relation to other coil sections and to the central longitudinal axis of the reformer, each coil section extending between the first and second ends, and each coil section being in direct fluid communication with at least one other coil section.

  8. Resolving the Moth at Millimeter Wavelengths

    NASA Astrophysics Data System (ADS)

    Ricarte, Angelo; Moldvai, Noel; Hughes, A. Meredith; Duchêne, Gaspard; Williams, Jonathan P.; Andrews, Sean M.; Wilner, David J.

    2013-09-01

    HD 61005, also known as "The Moth," is one of only a handful of debris disks that exhibit swept-back "wings" thought to be caused by interaction with the ambient interstellar medium (ISM). We present 1.3 mm Submillimeter Array observations of the debris disk around HD 61005 at a spatial resolution of 1.''9 that resolve the emission from large grains for the first time. The disk exhibits a double-peaked morphology at millimeter wavelengths, consistent with an optically thin ring viewed close to edge-on. To investigate the disk structure and the properties of the dust grains we simultaneously model the spatially resolved 1.3 mm visibilities and the unresolved spectral energy distribution (SED). The temperatures indicated by the SED are consistent with expected temperatures for grains close to the blowout size located at radii commensurate with the millimeter and scattered light data. We also perform a visibility-domain analysis of the spatial distribution of millimeter-wavelength flux, incorporating constraints on the disk geometry from scattered light imaging, and find suggestive evidence of wavelength-dependent structure. The millimeter-wavelength emission apparently originates predominantly from the thin ring component rather than tracing the "wings" observed in scattered light. The implied segregation of large dust grains in the ring is consistent with an ISM-driven origin for the scattered light wings.

  9. RESOLVING THE MOTH AT MILLIMETER WAVELENGTHS

    SciTech Connect

    Ricarte, Angelo; Moldvai, Noel; Hughes, A. Meredith; Duchene, Gaspard; Williams, Jonathan P.; Andrews, Sean M.; Wilner, David J.

    2013-09-01

    HD 61005, also known as ''The Moth'', is one of only a handful of debris disks that exhibit swept-back ''wings'' thought to be caused by interaction with the ambient interstellar medium (ISM). We present 1.3 mm Submillimeter Array observations of the debris disk around HD 61005 at a spatial resolution of 1.''9 that resolve the emission from large grains for the first time. The disk exhibits a double-peaked morphology at millimeter wavelengths, consistent with an optically thin ring viewed close to edge-on. To investigate the disk structure and the properties of the dust grains we simultaneously model the spatially resolved 1.3 mm visibilities and the unresolved spectral energy distribution (SED). The temperatures indicated by the SED are consistent with expected temperatures for grains close to the blowout size located at radii commensurate with the millimeter and scattered light data. We also perform a visibility-domain analysis of the spatial distribution of millimeter-wavelength flux, incorporating constraints on the disk geometry from scattered light imaging, and find suggestive evidence of wavelength-dependent structure. The millimeter-wavelength emission apparently originates predominantly from the thin ring component rather than tracing the ''wings'' observed in scattered light. The implied segregation of large dust grains in the ring is consistent with an ISM-driven origin for the scattered light wings.

  10. The wavelength dependence of Triton's light curve

    NASA Technical Reports Server (NTRS)

    Hillier, J.; Veverka, J.; Helfenstein, P.; Mcewen, A.

    1991-01-01

    Using Voyager observations, it is demonstrated that Triton's orbital light curve is strongly wavelength-dependent, a characteristic which readily explains some of the apparent discrepancies among pre-Voyager telescopic measurements. Specifically, a light curve amplitude (peak to peak) is found that decreases systematically with increasing wavelength from about 0.08 magnitude (peak to peak) near 200 nm to less than 0.02 magnitude near 1000 nm. Peak brightness occurs near 90 deg orbital longitude (leading hemisphere). The brightness variation across this hemisphere is close to sinusoidal; the variation across the darker hemisphere is more complex. The decrease in light curve amplitude with increasing wavelength appears to be due to a decrease in contrast among surface markings, rather than to atmospheric obscuration. The model also explains the observed decrease in the amplitude of Triton's light curve at visible wavelengths over the past decade, a decrease related to the current migration of the subsolar latitude toward the south pole; it is predicted that this trend will continue into the 1990s.

  11. 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.

  12. Making Precise Antenna Reflectors For Millimeter Wavelengths

    NASA Technical Reports Server (NTRS)

    Sharp, G. Richard; Wanhainen, Joyce S.; Ketelsen, Dean A.

    1994-01-01

    In improved method of fabrication of precise, lightweight antenna reflectors for millimeter wavelengths, required precise contours of reflecting surfaces obtained by computer numberically controlled machining of surface layers bonded to lightweight, rigid structures. Achievable precision greater than that of older, more-expensive fabrication method involving multiple steps of low- and high-temperature molding, in which some accuracy lost at each step.

  13. Photomultiplier sensitivity improvement by using wavelength shifters

    NASA Astrophysics Data System (ADS)

    Kozma, Peter; Bajgar, Robert; Kozma, Petr, Jr.

    1999-01-01

    Photomultiplier quantum sensitivity in the UV region of the photomultipliers FEU-85, FEU-130 and FEU-140 can be improved by a wave-shifter covering. The best results were obtained for PMMA-polymethylmetacrylate and P-P' diphenylstilbene wavelength shifters.

  14. Two-wavelength spatial-heterodyne holography

    DOEpatents

    Hanson, Gregory R.; Bingham, Philip R.; Simpson, John T.; Karnowski, Thomas P.; Voelkl, Edgar

    2007-12-25

    Systems and methods are described for obtaining two-wavelength differential-phase holograms. A method includes determining a difference between a filtered analyzed recorded first spatially heterodyne hologram phase and a filtered analyzed recorded second spatially-heterodyned hologram phase.

  15. SDIO long wavelength infrared detector requirements

    NASA Technical Reports Server (NTRS)

    Duston, Dwight

    1990-01-01

    The Strategic Defense Initiative Organization (SDIO) has a significant requirement for infrared sensors for surveillance, tracking and discrimination of objects in space. Projected SDIO needs cover the range from short wavelengths out to 30 microns. Large arrays are required, and producibility and cost are major factors. The SDIO is pursuing several approaches including innovative concepts based on semiconductors and superconductors.

  16. Fiber optics wavelength division multiplexing(components)

    NASA Technical Reports Server (NTRS)

    Hendricks, Herbert D.

    1985-01-01

    The long term objectives are to develop optical multiplexers/demultiplexers, different wavelength and modulation stable semiconductor lasers and high data rate transceivers, as well as to test and evaluate fiber optic networks applicable to the Space Station. Progress in each of the above areas is briefly discussed.

  17. Measurement of isotope shifts and hyperfine structure in Zr II

    NASA Astrophysics Data System (ADS)

    Rosner, S. D.; Holt, R. A.

    2016-06-01

    We have applied fast-ion-beam laser-fluorescence spectroscopy to measure the isotope shifts (IS) of 51 optical transitions in the wavelength range 420.6–461.4 nm and the hyperfine structures (hfs) of 11 even parity and 30 odd parity levels in Zr II. The IS and many of the hfs measurements are the first for these transitions and levels. These atomic data are very important for astrophysical studies of chemical abundances, allowing correction for saturation and the effects of blended lines. They also provide important constraints on stellar diffusion modeling and provide a benchmark for theoretical atomic structure calculations.

  18. Neural signals encoding shifts in beliefs.

    PubMed

    Schwartenbeck, Philipp; FitzGerald, Thomas H B; Dolan, Ray

    2016-01-15

    Dopamine is implicated in a diverse range of cognitive functions including cognitive flexibility, task switching, signalling novel or unexpected stimuli as well as advance information. There is also longstanding line of thought that links dopamine with belief formation and, crucially, aberrant belief formation in psychosis. Integrating these strands of evidence would suggest that dopamine plays a central role in belief updating and more specifically in encoding of meaningful information content in observations. The precise nature of this relationship has remained unclear. To directly address this question we developed a paradigm that allowed us to decompose two distinct types of information content, information-theoretic surprise that reflects the unexpectedness of an observation, and epistemic value that induces shifts in beliefs or, more formally, Bayesian surprise. Using functional magnetic-resonance imaging in humans we show that dopamine-rich midbrain regions encode shifts in beliefs whereas surprise is encoded in prefrontal regions, including the pre-supplementary motor area and dorsal cingulate cortex. By linking putative dopaminergic activity to belief updating these data provide a link to false belief formation that characterises hyperdopaminergic states associated with idiopathic and drug induced psychosis. PMID:26520774

  19. Testability and epistemic shifts in modern cosmology

    NASA Astrophysics Data System (ADS)

    Kragh, Helge

    2014-05-01

    During the last decade new developments in theoretical and speculative cosmology have reopened the old discussion of cosmology's scientific status and the more general question of the demarcation between science and non-science. The multiverse hypothesis, in particular, is central to this discussion and controversial because it seems to disagree with methodological and epistemic standards traditionally accepted in the physical sciences. But what are these standards and how sacrosanct are they? Does anthropic multiverse cosmology rest on evaluation criteria that conflict with and go beyond those ordinarily accepted, so that it constitutes an "epistemic shift" in fundamental physics? The paper offers a brief characterization of the modern multiverse and also refers to a few earlier attempts to introduce epistemic shifts in the science of the universe. It further discusses the several meanings of testability, addresses the question of falsifiability as a sine qua non for a theory being scientific, and briefly compares the situation in cosmology with the one in systematic biology. Multiverse theory is not generally falsifiable, which has led to proposals from some physicists to overrule not only Popperian standards but also other evaluation criteria of a philosophical nature. However, this is hardly possible and nor is it possible to get rid of explicit philosophical considerations in some other aspects of cosmological research, however advanced it becomes.

  20. Neural signals encoding shifts in beliefs

    PubMed Central

    Schwartenbeck, Philipp; FitzGerald, Thomas H.B.; Dolan, Ray

    2016-01-01

    Dopamine is implicated in a diverse range of cognitive functions including cognitive flexibility, task switching, signalling novel or unexpected stimuli as well as advance information. There is also longstanding line of thought that links dopamine with belief formation and, crucially, aberrant belief formation in psychosis. Integrating these strands of evidence would suggest that dopamine plays a central role in belief updating and more specifically in encoding of meaningful information content in observations. The precise nature of this relationship has remained unclear. To directly address this question we developed a paradigm that allowed us to decompose two distinct types of information content, information-theoretic surprise that reflects the unexpectedness of an observation, and epistemic value that induces shifts in beliefs or, more formally, Bayesian surprise. Using functional magnetic-resonance imaging in humans we show that dopamine-rich midbrain regions encode shifts in beliefs whereas surprise is encoded in prefrontal regions, including the pre-supplementary motor area and dorsal cingulate cortex. By linking putative dopaminergic activity to belief updating these data provide a link to false belief formation that characterises hyperdopaminergic states associated with idiopathic and drug induced psychosis. PMID:26520774

  1. Schedule shifts, cancer and longevity

    PubMed Central

    Cornélissen, Germaine; Halberg, Julia; Halberg, Franz; de la Pena, Salvador Sanchez; Nelson, Walter; Schwartzkopff, Othild; Stoynev, Alexander; Haus, Erhard

    2008-01-01

    Prompted by a recent report of the possible carcinogenic effect of shiftwork focusing on the disruption of circadian rhythms, we review studies involving shifts in schedule implemented at varying intervals in unicells, insects and mammals, including humans. Results indicate the desirability to account for a broader-than-circadian view. They also suggest the possibility of optimizing schedule shifts by selecting intervals between consecutive shifts associated with potential side-effects such as an increase in cancer risk. Toward this goal, marker rhythmometry is most desirable. The monitoring of blood pressure and heart rate present the added benefit of assessing cardiovascular disease risks resulting not only from an elevated blood pressure but also from abnormal variability in blood pressure and/or heart rate of normotensive as well as hypertensive subjects. PMID:19227006

  2. Low-Light-Shift Cesium Fountain without Mechanical Shutters

    NASA Technical Reports Server (NTRS)

    Enzer, Daphna

    2008-01-01

    A new technique for reducing errors in a laser-cooled cesium fountain frequency standard provides for strong suppression of the light shift without need for mechanical shutters. Because mechanical shutters are typically susceptible to failure after operating times of the order of months, the elimination of mechanical shutters could contribute significantly to the reliability of frequency standards that are required to function continuously for longer time intervals. With respect to the operation of an atomic-fountain frequency standard, the term "light shift" denotes an undesired relative shift in the two energy levels of the atoms (in this case, cesium atoms) in the atomic fountain during interrogation by microwaves. The shift in energy levels translates to a frequency shift that reduces the precision and possibly accuracy of the frequency standard. For reasons too complex to describe within the space available for this article, the light shift is caused by any laser light that reaches the atoms during the microwave- interrogation period, but is strongest for near-resonance light. In the absence of any mitigating design feature, the light shift, expressed as a fraction of the standard fs frequency, could be as large as approx. 2 x 10(exp -11), the largest error in the standard. In a typical prior design, to suppress light shift, the intensity of laser light is reduced during the interrogation period by using a single-pass acoustooptic modulator to deflect the majority of light away from the main optical path. Mechanical shutters are used to block the remaining undeflected light to ensure complete attenuation. Without shutters, this remaining undeflected light could cause a light shift of as much as .10.15, which is unacceptably large in some applications. The new technique implemented here involves additionally shifting the laser wavelength off resonance by a relatively large amount (typically of the order of nanometers) during microwave interrogation. In this

  3. Digital spatial wavelength domain multiplexing (DSWDM) using a prism-grating-prism (PGP) and a CMOS imager: implementation and initial testing

    NASA Astrophysics Data System (ADS)

    Christiansen, Martin B.; Chen, Steve; Baldwin, Christopher S.; Niemczuk, John B.; Kiddy, Jason S.; Chen, Peter C.; Kopola, Harri K.; Aikio, Mauri; Suopajarvi, Pekka; Buckley, Steven G.

    2001-08-01

    A CMOS imager-based spectrometer is used to interrogate a network containing a large number of Bragg grating sensors on multiple fibers as part of a proprietary structural health monitoring system. The spectrometer uses a Prism-Grating-Prism (PGP) to spectrally separate serially multiplexed Bragg reflections on a single fiber. As a result, each Bragg grating produces a discrete spot on the CMOS imager that shifts horizontally as the Bragg grating experiences changes in strain or temperature. The reflected wavelength of the Bragg grating can be determined by finding the center of the spot produced. The use of a random addressing CMOS imager enables a flexible sampling rate. Some fibers can be interrogated at a high sampling rate while others can be interrogated at a lower sampling rate. However, the use of a CMOS camera brings several specific problems in terms of signal processing. These include a logarithmic pixel response, a low signal-to-noise ratio, the long pixel time constant, obtaining sufficient process priority for the control program, and proper selection of the window of interest. In this paper we investigate computer algorithms and hardware solutions to address these problems. We also present experimental data to validate these solutions including calibration data and initial field-testing data with 24 sensors on 4 fibers.

  4. Two-Color Laser Speckle Shift Strain Measurement System

    NASA Technical Reports Server (NTRS)

    Tuma, Margaret L.; Krasowski, Michael J.; Oberle, Lawrence G.; Greer, Lawrence C., III; Spina, Daniel; Barranger, John

    1996-01-01

    A two color laser speckle shift strain measurement system based on the technique of Yamaguchi was designed. The dual wavelength light output from an Argon Ion laser was coupled into two separate single-mode optical fibers (patchcords). The output of the patchcords is incident on the test specimen (here a structural fiber). Strain on the fiber, in one direction, is produced using an Instron 4502. Shifting interference patterns or speckle patterns will be detected at real-time rates using 2 CCD cameras with image processing performed by a hardware correlator. Strain detected in fibers with diameters from 21 microns to 143 microns is expected to be resolved to 15 mu epsilon. This system was designed to be compact and robust and does not require surface preparation of the structural fibers.

  5. Fracture toughness curve shift method

    SciTech Connect

    Nanstad, R.K.; Sokolov, M.A.; McCabe, D.E.

    1995-10-01

    The purpose of this task is to examine the technical basis for the currently accepted methods for shifting fracture toughness curves to account for irradiation damage, and to work through national codes and standards bodies to revise those methods, if a change is warranted. During this reporting period, data from all the relevant HSSI Programs were acquired and stored in a database and evaluated. The results from that evaluation have been prepared in a draft letter report and are summarized here. A method employing Weibull statistics was applied to analyze fracture toughness properties of unirradiated and irradiated pressure vessel steels. Application of the concept of a master curve for irradiated materials was examined and used to measure shifts of fracture toughness transition curves. It was shown that the maximum likelihood approach gave good estimations of the reference temperature, T{sub o}, determined by rank method and could be used for analyzing of data sets where application of the rank method did not prove to be feasible. It was shown that, on average, the fracture toughness shifts generally exceeded the Charpy 41-J shifts; a linear least-squares fit to the data set yielded a slope of 1.15. The observed dissimilarity was analyzed by taking into account differences in effects of irradiation on Charpy impact and fracture toughness properties. Based on these comparisons, a procedure to adjust Charpy 41-J shifts for achieving a more reliable correlation with the fracture toughness shifts was evaluated. An adjustment consists of multiplying the 41-J energy level by the ratio of unirradiated to irradiated Charpy upper shelves to determine an irradiated transition temperature, and then subtracting the unirradiated transition temperature determined at 41 J. For LUS welds, however, an unirradiated level of 20 J (15 ft-1b) was used for the corresponding adjustment for irradiated material.

  6. Remote picometer fiber Bragg grating demodulation using a dual-wavelength source.

    PubMed

    Clement, Juan; Torregrosa, Germán; Maestre, Haroldo; Fernández-Pousa, Carlos R

    2016-08-10

    We report on the self-referenced, intensity-based, remote and passive interrogation of a fiber Bragg grating (FBG) for point sensing, by use of a reconfigurable dual-wavelength source composed of a tunable wavelength and subsequent suppressed-carrier, electro-optic amplitude modulation. The demodulation procedure is based on the measurement of the reflected power at two different wavelengths within the FBG spectral response. The grating was interrogated by use of conventional spectral analysis, and also after 32.9 km of single-mode fiber using a dispersive incoherent optical Fourier-domain reflectometry technique. Both procedures provide picometer resolution in the determination of Bragg wavelength shifts at a comparatively similar scan time (∼1  s) and received power (-16  dBm). The main limitations in each interrogation scheme have been identified. These results show the feasibility of interrogation systems incorporating relatively simple frequency combs at a calibrated, and eventually reconfigurable, wavelength grid with an, at least, similar performance to that of commercial FBG interrogators. PMID:27534505

  7. Wavelength-Scale Structures as Extremely High Haze Films for Efficient Polymer Solar Cells.

    PubMed

    Ham, Juyoung; Dong, Wan Jae; Jung, Gwan Ho; Lee, Jong-Lam

    2016-03-01

    Wavelength-scale inverted pyramid structures with low reflectance and excellent haze have been designed for application to polymer solar cells (PSCs). The wavelength-scale structured haze films are fabricated on the back surface of glass without damages to organic active layer by using a soft lithographic technique with etched GaN molds. With a rigorous coupled-wave analysis of optical modeling, we find the shift of resonance peaks with the increase of pattern's diameter. Wavelength-scale structures could provide the number of resonances at the long wavelength spectrum (λ = 650-800 nm), yielding enhancement of power conversion efficiency (PCE) in the PSCs. Compared with a flat device (PCE = 7.12%, Jsc = 15.6 mA/cm(2)), improved PCE of 8.41% is achieved in a haze film, which is mainly due to the increased short circuit current density (Jsc) of 17.5 mA/cm(2). Hence, it opens up exciting opportunities for a variety of PSCs with wavelength-scale structures to further improve performance, simplify complicated process, and reduce costs. PMID:26901630

  8. Broadband optical serrodyne frequency shifting.

    PubMed

    Johnson, D M S; Hogan, J M; Chiow, S-w; Kasevich, M A

    2010-03-01

    We demonstrate serrodyne frequency shifting of light from 200 MHz to 1.2 GHz with an efficiency of better than 60%. The frequency shift is imparted by an electro-optic phase modulator driven by a high-frequency high-fidelity sawtooth waveform that is passively generated by a commercially available nonlinear transmission line. We also implement a push-pull configuration using two serrodyne-driven phase modulators, allowing for continuous tuning between -1.6 GHz and +1.6 GHz. Compared with competing technologies, this technique is simple and robust, and it offers the largest available tuning range in this frequency band. PMID:20195339

  9. Measurement of absolute optical thickness of mask glass by wavelength-tuning Fourier analysis.

    PubMed

    Kim, Yangjin; Hbino, Kenichi; Sugita, Naohiko; Mitsuishi, Mamoru

    2015-07-01

    Optical thickness is a fundamental characteristic of an optical component. A measurement method combining discrete Fourier-transform (DFT) analysis and a phase-shifting technique gives an appropriate value for the absolute optical thickness of a transparent plate. However, there is a systematic error caused by the nonlinearity of the phase-shifting technique. In this research the absolute optical-thickness distribution of mask blank glass was measured using DFT and wavelength-tuning Fizeau interferometry without using sensitive phase-shifting techniques. The error occurring during the DFT analysis was compensated for by using the unwrapping correlation. The experimental results indicated that the absolute optical thickness of mask glass was measured with an accuracy of 5 nm. PMID:26125394

  10. Frequency-shift vs phase-shift characterization of in-liquid quartz crystal microbalance applications

    NASA Astrophysics Data System (ADS)

    Montagut, Y. J.; García, J. V.; Jiménez, Y.; March, C.; Montoya, A.; Arnau, A.

    2011-06-01

    The improvement of sensitivity in quartz crystal microbalance (QCM) applications has been addressed in the last decades by increasing the sensor fundamental frequency, following the increment of the frequency/mass sensitivity with the square of frequency predicted by Sauerbrey. However, this sensitivity improvement has not been completely transferred in terms of resolution. The decrease of frequency stability due to the increase of the phase noise, particularly in oscillators, made impossible to reach the expected resolution. A new concept of sensor characterization at constant frequency has been recently proposed. The validation of the new concept is presented in this work. An immunosensor application for the detection of a low molecular weight contaminant, the insecticide carbaryl, has been chosen for the validation. An, in principle, improved version of a balanced-bridge oscillator is validated for its use in liquids, and applied for the frequency shift characterization of the QCM immunosensor application. The classical frequency shift characterization is compared with the new phase-shift characterization concept and system proposed.

  11. Frequency-shift vs phase-shift characterization of in-liquid quartz crystal microbalance applications.

    PubMed

    Montagut, Y J; García, J V; Jiménez, Y; March, C; Montoya, A; Arnau, A

    2011-06-01

    The improvement of sensitivity in quartz crystal microbalance (QCM) applications has been addressed in the last decades by increasing the sensor fundamental frequency, following the increment of the frequency/mass sensitivity with the square of frequency predicted by Sauerbrey. However, this sensitivity improvement has not been completely transferred in terms of resolution. The decrease of frequency stability due to the increase of the phase noise, particularly in oscillators, made impossible to reach the expected resolution. A new concept of sensor characterization at constant frequency has been recently proposed. The validation of the new concept is presented in this work. An immunosensor application for the detection of a low molecular weight contaminant, the insecticide carbaryl, has been chosen for the validation. An, in principle, improved version of a balanced-bridge oscillator is validated for its use in liquids, and applied for the frequency shift characterization of the QCM immunosensor application. The classical frequency shift characterization is compared with the new phase-shift characterization concept and system proposed. PMID:21721715

  12. Short wavelength FELs using the SLAC linac

    NASA Astrophysics Data System (ADS)

    Winick, H.; Bane, K.; Boyce, R.; Cobb, J.; Loew, G.; Morton, P.; Nuhn, H.-D.; Paterson, J.; Pianetta, P.; Raubenheimer, T.; Seeman, J.; Tatchyn, R.; Vylet, V.; Pellegrini, C.; Rosenzweig, J.; Travish, G.; Prosnitz, D.; Scharlemann, E. T.; Halbach, K.; Kim, K.-J.; Schlueter, R.; Xie, M.; Bonifacio, R.; De Salvo, L.; Pierini, P.

    1994-08-01

    Recent technological developments have opened the possibility to construct a device which we call a linac coherent light source (LCLS) (C. Pellegrini et al., Nucl. Instr. and Meth. A 331 (1993) 223; H. Winick et al., Proc. IEEE 1993 Particle Accelerator Conf., Washington, DC, May 1993; C. Pellegrini, Nucl. Instr. and Meth. A 341 (1994) 326; J. Seeman, SPIE Meet. on Electron Beam Sources of High Brightness Radiation, San Diego, CA, July 1993 [1-4]); it would be 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 shorter wavelength than the 240 nm 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 to 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 (M. Cornacchia and H. Winick (eds.), SLAC Report 92/02; I. Ben-Zvi and H. Winick (eds.), BNL report 49651 [5,6]). The required low-emittance electron beam can be achieved with recently-developed rf photocathode electron guns (B.E. Carlsten, Nucl. Instr. and Meth. A 285 (1989) 313; J. Rosenzweig and L. Serafini, Proc. IEEE 1993 Particle Accelerator Conf., Washington, DC, 1993 [7,8]). The peak current is increased by about an

  13. Wavelength-tunable laser based on electro-optic effect

    NASA Astrophysics Data System (ADS)

    Wu, Pengfei; Tang, Suning

    2015-03-01

    Currently available wavelength-tunable lasers have technical difficulty in combining high-speed, continuous and wide wavelength tunability with high output power. We demonstrated a high-speed wavelength-tunable laser based on a fast electro-optic effect. We observed that the wavelength-swept speed exceeds 107 nm/s at center wavelength of 1550 nm with continuous wavelength tunability. Moreover, the maximum output power is over 100 mW and the wavelength tuning range is near 100 nm with a full width at half maximum of less than 0.5 nm.

  14. Choice of the proper wavelength for photochemotherapy

    NASA Astrophysics Data System (ADS)

    Moan, Johan; Iani, Vladimir; Ma, LiWei

    1996-01-01

    All photosensitizers applied in experimental- and clinical-photochemotherapy (PCT) have broad absorption spectra stretching from the ultraviolet up to 6 - 700 nm. Light of wavelengths in the red part of the spectrum is chosen for PCT even though the extinction coefficients of the sensitizers are usually smaller in this wavelength region than at shorter wavelengths. Thus, if one wants to treat superficial tumors or skin disorders, this may be a wrong choice. Two pieces of information are needed in order to make a proper choice of wavelength to treat a lesion of a given depth: the wavelength dependence of the optical penetration depth into tissue, and the action spectrum for tumor destruction. Additionally, the skin photosensitivity induced by the drug should be considered. We have non-invasively measured the optical penetration spectra of human tissues in vivo and the fluorescence excitation spectra for several sensitizers, including protoporphyrin (PpIX), in cells. Assuming that the action spectrum for cell inactivation can be approximated by the fluorescence excitation spectrum of the sensitizer -- which is indeed the case for a number of sensitizers in cells in vitro -- we have considered the situation for 5-aminolevulinic acid-induced PpIX in human tissue. All the way down to about 2 mm below the surface light in the Soret band (-410 nm) would give the largest cell inactivation, while at depth exceeding 2 mm, the conventional 635 nm light would be optimal. Light at the argon laser wavelength 514.5 nm is more efficient than light at 635 nm down to 1 mm. From the surface and down to 6 mm, the 635 nm peak of the excitation spectrum of PpIX, as evaluated per photon incident on the skin surface, is redshifted by less than 2 nm. In some cases photosensitizing photoproducts are formed during PCT, such as photoprotoporphyrin during PCT with PpIX. In such cases it may be advantageous to apply a broad-band light source with a spectrum that covers also part of the action

  15. Foundation Shifts Tack on Studies

    ERIC Educational Resources Information Center

    Viadero, Debra

    2006-01-01

    Five years into an eight-year study of its high school improvement efforts, the Bill & Melinda Gates Foundation is shifting its strategy for evaluating the $1.3 billion grant program. The foundation's initiative, which is underwriting change efforts in more than 1,800 schools, is the nation's largest privately funded attempt to improve high…

  16. Leadership Shifts in Changing Field

    ERIC Educational Resources Information Center

    Zubrzycki, Jaclyn

    2013-01-01

    As groups representing local and state education players struggle to remain relevant in a policy conversation often dominated by foundations, think tanks, new advocacy groups, and political and business figures, a shift in leadership has been under way at major associations. Most of the changes have come as part of the natural churn; former…

  17. Illinois Shifting Gears Policy Evaluation

    ERIC Educational Resources Information Center

    Weitzel, Peter C.

    2009-01-01

    Illinois Shifting Gears is a multilevel initiative that has simultaneously created bridge programs in the field and altered state policy to facilitate the creation of more programs in the future. These efforts have informed each other, giving policymakers the opportunity to interact with practitioners, troubleshoot bridge programs, and make…

  18. The Shift Needed for Sustainability

    ERIC Educational Resources Information Center

    Smith, Peter A. C.; Sharicz, Carol

    2011-01-01

    Purpose: The purpose of this action research is to begin to assess to what extent organizations have in practice begun to make the shift towards triple bottom line (TBL) sustainability. Design/methodology/approach: A definition of TBL sustainability is provided, and key elements of TBL sustainability considered necessary to success are identified…

  19. Technology Counts 2012: Virtual Shift

    ERIC Educational Resources Information Center

    Education Week, 2012

    2012-01-01

    Virtual education is moving into that intersection where rising popularity meets calls for greater accountability. How the virtual education movement responds to those calls will have a significant impact on how it evolves in K-12 over the next five to 10 years. This report tackles this shift in the virtual education landscape. It examines the…

  20. Shifting Patterns of Deadly Violence.

    ERIC Educational Resources Information Center

    Seiden, Richard H.; Freitas, Raymond P.

    1980-01-01

    While it is true that the total suicide rates has varied little, this composite figure masks a dramatic shift in the risk of suicide by age. In recent years there has been a reduction of suicide at older ages reciprocated by an unprecedented increase of suicide and homicide at younger ages. (Author)

  1. Spectral shifts near compact objects

    NASA Astrophysics Data System (ADS)

    Lake, K.; Myra, E.

    1981-10-01

    It is shown that radiation emitted from material freely falling toward a black hole or neutron star cannot be blue shifted as recently claimed by Cohen and Struble (1980). The relativistic corrections to the classical apparent limb angle are given explicitly for spherical sources in collapse.

  2. Anthropometric changes and fluid shifts

    NASA Technical Reports Server (NTRS)

    Thornton, W. E.; Hoffler, G. W.; Rummel, J. A.

    1974-01-01

    Several observations of body size, shape, posture, and configuration were made to document changes resulting from direct effects of weightlessness during the Skylab 4 mission. After the crewmen were placed in orbit, a number of anatomical and anthropometric changes occurred including a straightening of the thoracolumbar spine, a general decrease in truncal girth, and an increase in height. By the time of the earliest in-flight measurement on mission day 3, all crewmen had lost more than two liters of extravascular fluid from the calf and thigh. The puffy facies, the bird legs effect, the engorgement of upper body veins, and the reduced volume of lower body veins were all documented with photographs. Center-of-mass measurements confirmed a fluid shift cephalad. This shift remained throughout the mission until recovery, when a sharp reversal occurred; a major portion of the reversal was completed in a few hours. The anatomical changes are of considerable scientific interest and of import to the human factors design engineer, but the shifts of blood and extravascular fluid are of more consequence. It is hypothesized that the driving force for the fluid shift is the intrinsic and unopposed lower limb elasticity that forces venous blood and then other fluid cephalad.

  3. Field shifts in hafnium II

    NASA Astrophysics Data System (ADS)

    Aufmuth, P.; Henneberg, I.; Siminski, A.; Steudel, A.

    1991-03-01

    By means of classical interference spectroscopy, using enriched isotope samples, the isotope shift between178Hf and180Hf has been measured for 33 transitions in the Hf II spectrum. For the pure Russell-Saunders terms 5 d 26 s 4 F and2 F the parametric analysis yields a field-shift difference of 17(2) mK produced by the second-order interaction of the electrostatic operator and the field-shift operator. Semi-empirical calculations based on the non-relativistic Hartree-Fock method reproduce this value as well as the experimental field shifts if a factor of 1.68(6) is used to scale the ab initio electron densities at the nucleus. The corresponding factor for the Hf atom is much smaller. This leads to a re-evaluation of screening ratios for Hf and to a more accurate value of the nuclear parameter λ178,180 (Hf)=0.072(4) fm2.

  4. Quantitative phase imaging by three-wavelength digital holography

    SciTech Connect

    Mann, Christopher J; Bingham, Philip R; Tobin Jr, Kenneth William; Paquit, Vincent C

    2008-01-01

    Three-wavelength digital holography is applied to obtain surface height measurements over several microns of range, while simultaneously maintaining the low noise precision of the single wavelength phase measurement. The precision is preserved by the use of intermediate synthetic wavelength steps generated from the three wavelengths and the use of hierarchical optical phase unwrapping. As the complex wave-front of each wavelength can be captured simultaneously in one digital image, real-time performance is achievable.

  5. Filter-less frequency-doubling microwave signal generator with tunable phase shift

    NASA Astrophysics Data System (ADS)

    Li, Yueqin; Pei, Li; Li, Jing; Wang, Yiqun; Yuan, Jin

    2016-07-01

    A prototype for frequency-doubling microwave signal generator with tunable phase shift based on a filter-less architecture is proposed and analyzed. In the proposal, one dual parallel polarization modulator is used as the key component to generate two ±1st order sidebands along the orthogonal polarization directions with suppressed carrier. Then the polarization states of the two sidebands are aligned with the principal axes of an electro-optical phase modulator (EOPM). Tunable phase shift is implemented by controlling the direct current voltage applied to the EOPM. Without using any filters or wavelength-dependent components, the system possesses good frequency tunability and it can be applied to multi-wavelength operation. Taking advantage of the ability of frequency multiplication, the frequency tuning range can be wider than the operation bandwidth of the modulator. By theoretical analyses and simulated verifications, a frequency-doubling microwave signal ranging from 22 to 40 GHz with full range phase shift is achieved.

  6. Shift control mechanism for a manual transmission

    SciTech Connect

    Gugin, D.G.

    1991-08-06

    This patent describes a shift control mechanism for a manual transmission having a transmission gear housing and a manual shift selecting lever. It comprises a shift selecting shaft mounted within the transmission gear housing for rotation and axial translation in response to selective manipulation of the shift selecting lever; a shift sleeve supported from the transmission gear housing; an actuating member secured to the shift selecting shaft for rotation and axial translation with the shift selecting shaft; synchronizer assemblies; the actuating member individually operating the synchronizer assemblies in response to selected manipulation of the shift selecting lever; alignment guide means interactive between the shift selecting shaft and the transmission gear housing to permit axial translation of the shift selecting shaft only when the shift selecting shaft has been rotated to align a locator means with a locating means.

  7. Size-Dependent Raman Shifts for nanocrystals

    PubMed Central

    Gao, Yukun; Zhao, Xinmei; Yin, Penggang; Gao, Faming

    2016-01-01

    Raman spectroscopy is a very sensitive tool for probing semiconductor nanocrystals. The underlying mechanism behind the size-dependent Raman shifts is still quite controversial. Here we offer a new theoretical method for the quantum confinement effects on the Raman spectra of semiconductor nanocrystals. We propose that the shift of Raman spectra in nanocrystals can result from two overlapping effects: the quantum effect shift and surface effect shift. The quantum effect shift is extracted from an extended Kubo formula, the surface effect shift is determined via the first principles calculations. Fairly good prediction of Raman shifts can be obtained without the use of any adjustable parameter. Closer analysis shows that the size-dependent Raman shifts in Si nanocrystals mainly result from the quantum effect shifts. For nanodiamond, the proportion of surface effect shift in Raman shift is up to about 40%. Such model can also provide a good baseline for using Raman spectroscopy as a tool to measure size. PMID:27102066

  8. Radio wavelength transients: Current and emerging prospects

    NASA Astrophysics Data System (ADS)

    Lazio, J.

    2008-03-01

    Known classes of radio wavelength transients range from the nearby stellar flares and radio pulsars to the distant Universe γ-ray burst afterglows. Hypothesized classes of radio transients include analogs of known objects, e.g., extrasolar planets emitting Jovian-like radio bursts and giant-pulse emitting pulsars in other galaxies, to the exotic, prompt emission from γ-ray bursts, evaporating black holes, and transmitters from other civilizations. A number of instruments and facilities are either under construction or in early observational stages and are slated to become available in the next few years. With a combination of wide fields of view and wavelength agility, the detection and study of radio transients will improve immensely.

  9. Coordinated observations of PHEMU at radio wavelengths.

    NASA Astrophysics Data System (ADS)

    Pluchino, S.; Schillirò, F.; Salerno, E.; Pupillo, G.; Kraus, A.; Mack, K.-H.

    We present preliminary results for our study of mutual phenomena of the Galilean satellites performed at radio wavelengths with the Medicina and Noto antennas of the Istituto di Radioastronomia \\textendash{} INAF, and with the Effelsberg 100-m radio telescope of the Max-Planck-Institute for Radioastronomy. Measurements of the radio flux density variation occurred during the mutual occultations of Io by Europa and Ganymede were carried out during the PHEMU09 campaign at K- and Q-band. Flux density variations observed for the first time at radio wavelengths are consistent with the typical optical patterns measured when partial occultations occurred. The flux density drops indicate a non-linear dependence with the percentage of overlapped area.

  10. Discrete Wavelength-Locked External Cavity Laser

    NASA Technical Reports Server (NTRS)

    Pilgrim, Jeffrey S.; Silver, Joel A.

    2004-01-01

    A prototype improved external cavity laser (ECL) was demonstrated in the second phase of a continuing effort to develop wavelength-agile lasers for fiber-optic communications and trace-gas-sensing applications. This laser is designed to offer next-generation performance for incorporation into fiber-optic networks. By eliminating several optical components and simplifying others used in prior designs, the design of this laser reduces costs, making lasers of this type very competitive in a price-sensitive market. Diode lasers have become enabling devices for fiber optic networks because of their cost, compactness, and spectral properties. ECLs built around diode laser gain elements further enhance capabilities by virtue of their excellent spectral properties with significantly increased (relative to prior lasers) wavelength tuning ranges. It is essential to exploit the increased spectral coverage of ECLs while simultaneously insuring that they operate only at precisely defined communication channels (wavelengths). Heretofore, this requirement has typically been satisfied through incorporation of add-in optical components that lock the ECL output wavelengths to these specific channels. Such add-in components contribute substantially to the costs of ECL lasers to be used as sources for optical communication networks. Furthermore, the optical alignment of these components, needed to attain the required wavelength precision, is a non-trivial task and can contribute substantially to production costs. The design of the present improved ECL differs significantly from the designs of prior ECLs. The present design relies on inherent features of components already included within an ECL, with slight modifications so that these components perform their normal functions while simultaneously effecting locking to the required discrete wavelengths. Hence, add-in optical components and the associated cost of alignment can be eliminated. The figure shows the locking feedback signal

  11. Dual-wavelength laser with topological charge

    NASA Astrophysics Data System (ADS)

    Yu, Haohai; Xu, Miaomiao; Zhao, Yongguang; Wang, Yicheng; Han, Shuo; Zhang, Huaijin; Wang, Zhengping; Wang, Jiyang

    2013-09-01

    We demonstrate the simultaneous oscillation of different photons with equal orbital angular momentum in solid-state lasers for the first time to our knowledge. Single tunable Hermite-Gaussian (HG0,n) (0 ≤ n ≤ 7) laser modes with dual wavelength were generated using an isotropic cavity. With a mode-converter, the corresponding Laguerre-Gaussian (LG0,n) laser modes were obtained. The oscillating laser modes have two types of photons at the wavelengths of 1077 and 1081 nm and equal orbital angular momentum of nħ per photon. These results identify the possibility of simultaneous oscillation of different photons with equal and controllable orbital angular momentum. It can be proposed that this laser should have promising applications in many fields based on its compact structure, tunable orbital angular momentum, and simultaneous oscillation of different photons with equal orbital angular momentum.

  12. Effect of wavelength shifter on Indus-1

    NASA Astrophysics Data System (ADS)

    Fakhri, Ali Akbar; Ghodke, A. D.; Singh, Gurnam

    2010-01-01

    The Indus-1 is a 450 MeV synchrotron radiation source for the production of VUV radiation ( λc=61 Å). In order to produce the radiation of shorter wavelength ( λc=31 Å), a superconducting wavelength shifter (WLS) with a peak field of 3 T is being considered for Indus-1. In the Indus-1 beam lifetime is short; therefore, WLS will be kept on during beam injection. To predict WLS effect, Smith's Hamiltonian for Halbach's magnetic field model has been re-derived to estimate linear and nonlinear component under the compensated electron beam trajectory transformation. To minimize the linear effects of WLS, various linear compensation schemes and its effects on Indus-1 operation are presented.

  13. The Long Wavelength Array Software Library

    NASA Astrophysics Data System (ADS)

    Dowell, Jayce; Wood, Daniel; Stovall, Kevin; Ray, Paul S.; Clarke, Tracy; Taylor, Gregory

    2012-12-01

    The Long Wavelength Array Software Library (LSL) is a Python module that provides a collection of utilities to analyze and export data collected at the first station of the Long Wavelength Array, LWA1. Due to the nature of the data format and large-N (≳100 inputs) challenges faced by the LWA, currently available software packages are not suited to process the data. Using tools provided by LSL, observers can read in the raw LWA1 data, synthesize a filter bank, and apply incoherent de-dispersion to the data. The extensible nature of LSL also makes it an ideal tool for building data analysis pipelines and applying the methods to other low frequency arrays.

  14. Sinusoidal nonlinearity in wavelength-sweeping interferometry.

    PubMed

    Perret, Luc; Pfeiffer, Pierre

    2007-11-20

    We report the influence of the nonlinearities in the wavelength-sweeping speed on the resulting interferometric signals in an absolute distance interferometer. The sweeping signal is launched in the reference and target interferometers from an external cavity laser source. The experimental results demonstrate a good resolution in spite of the presence of nonlinearities in the wavelength sweep. These nonlinearities can be modeled by a sum of sinusoids. A simulation is then implemented to analyze the influence of their parameters. It shows that a sinusoidal nonlinearity is robust enough to give a good final measurement uncertainty through a Fourier transform technique. It can be concluded that an optimal value of frequency and amplitude exists in the case of a sinusoidal nonlinearity. PMID:18026546

  15. Metallic photonic crystals at optical wavelengths

    NASA Astrophysics Data System (ADS)

    El-Kady, I.; Sigalas, M. M.; Biswas, R.; Ho, K. M.; Soukoulis, C. M.

    2000-12-01

    We theoretically study three-dimensional metallic photonic-band-gap (PBG) materials at near-infrared and optical wavelengths. Our main objective is to find the importance of absorption in the metal and the suitability of observing photonic band gaps in this structure. For that reason, we study simple cubic structures and the metallic scatterers are either cubes or interconnected metallic rods. Several different metals have been studied (aluminum, gold, copper, and silver). Copper gives the smallest absorption and aluminum is more absorptive. The isolated metallic cubes are less lossy than the connected rod structures. The calculations suggest that isolated copper scatterers are very attractive candidates for the fabrication of photonic crystals at the optical wavelengths.

  16. Multi-Wavelength Observations of Supernova Remnants

    NASA Technical Reports Server (NTRS)

    Williams, B.

    2012-01-01

    Supernova remnants (SNRs) provide a laboratory for studying various astrophysical processes, including particle acceleration, thermal and non thermal emission processes across the spectrum, distribution of heavy elements, the physics of strong shock waves, and the progenitor systems and environments of supernovae. Long studied in radio and X-rays, the past decade has seen a dramatic increase in the detection and subsequent study of SNRs in the infrared and gamma-ray regimes. Understanding the evolution of SNRs and their interaction with the interstellar medium requires a multi-wavelength approach. I will review the various physical processes observed in SNRs and how these processes are intertwined. In particular, I will focus on X-ray and infrared observations, which probe two very different but intrinsically connected phases of the ISM: gas and dust. I will discuss results from multi-wavelength studies of several SNRs at various stages of evolution, including Kepler, RCW 86, and the Cygnus Loop.

  17. Quasi-optical components at submillimeter wavelengths

    NASA Astrophysics Data System (ADS)

    Ediss, G. A.; Keen, N. J.; Mischerikow, K.-D.; Schulz, A.; Korn, A.

    1987-02-01

    Individual components of the Max-Planck-Institut fuer Radioastonomie 650 micron Schottky barrier diode waveguide mixer-receiver and their performance at 650 microns wavelength are reported on. Scalar, dual-mode, and pyramidal horns are considered, and attempts to measure insertion losses by comparing the gain of the horn with that of a fundamental moded waveguide lead to estimates of the upper limits for horn losses at 650 microns. Radiometric loss measurements of an 8-mm thick Teflon lens and a 5-mm thick Rexolite lens are both larger than would be expected from the material loss tangents, probably due to reflections. The performance of various diplexers is also considered. Performance of the present quasi-optical components at 650 and 172 microns is not found to be significantly worse than at 1300 microns wavelength, with the probable exception of horn insertion losses.

  18. Eye-safe visible wavelength lidar

    NASA Technical Reports Server (NTRS)

    Cooley, T. W.; Reagan, J. A.

    1992-01-01

    Recent technological advances on several fronts offer the possibility for relatively low-cost, eye-safe visible-wavelength lidar systems for autonomous aerosol/environmental monitoring applications. Improved silicon photodiodes and avalanche photodiodes that have become available offer high-quantum-efficiency detection at very low dark counts (10 to 1000 count/s) and can be used in a photon counting mode for signal plus background and dark current photoelectron count rates of megahertz. The essential requirements and features of a possible lidar system that capitalizes on technical advances on several fronts are outlined. A baseline lidar system is suggested for monitoring tropospheric and stratospheric aerosols. Sensitivity to wavelength, background radiation, detector characteristics, and other system parameters is discussed for several simulated data sets.

  19. Sinusoidal nonlinearity in wavelength-sweeping interferometry

    SciTech Connect

    Perret, Luc; Pfeiffer, Pierre

    2007-11-20

    We report the influence of the nonlinearities in the wavelength-sweeping speed on the resulting interferometric signals in an absolute distance interferometer. The sweeping signal is launched in the reference and target interferometers from an external cavity laser source. The experimental results demonstrate a good resolution in spite of the presence of nonlinearities in the wavelength sweep. These nonlinearities can be modeled by a sum of sinusoids. A simulation is then implemented to analyze the influence of their parameters. It shows that a sinusoidal nonlinearity is robust enough to give a good final measurement uncertainty through a Fourier transform technique. It can be concluded that an optimal value of frequency and amplitude exists in the case of a sinusoidal nonlinearity.

  20. WAVELENGTH CALIBRATION OF THE HAMILTON ECHELLE SPECTROGRAPH

    SciTech Connect

    Pakhomov, Yu. V.; Zhao, G.

    2013-10-01

    We present the wavelength calibration of the Hamilton Echelle Spectrograph at Lick Observatory. The main problem with the calibration of this spectrograph arises from the fact that thorium lines are absent in the spectrum of the presumed ThAr hollow-cathode lamp now under operation; numerous unknown strong lines, which have been identified as titanium lines, are present in the spectrum. We estimate the temperature of the lamp's gas which permits us to calculate the intensities of the lines and to select a large number of relevant Ti I and Ti II lines. The resulting titanium line list for the Lick hollow-cathode lamp is presented. The wavelength calibration using this line list was made with an accuracy of about 0.006 Å.