WorldWideScience

Sample records for single mode emission

  1. Linearly Polarized, Single-Mode Spontaneous Emission in a Photonic Nanowire

    DEFF Research Database (Denmark)

    Munsch, Mathieu; Claudon, Julien; Bleuse, Joël

    2012-01-01

    We introduce dielectric elliptical photonic nanowires to funnel efficiently the spontaneous emission of an embedded emitter into a single optical mode. Inside a wire with a moderate lateral aspect ratio, the electromagnetic environment is largely dominated by a single guided mode, with a linear...

  2. Lateral emission highly polarized single-mode nanobelt laser (Conference Presentation)

    Science.gov (United States)

    Xu, Pengfei; Liu, Shikai; Li, Ming; Zhou, Zheng; Ren, Zhaohui; Yang, Qing

    2017-02-01

    Nanoscale lasers are the key component in the integrated photonics chips and have attracted much interests. Nanoblets and nanowires lasers, as one of the candidates for the nanoscale lasers, have been developed for one more decades. Many kinds of nanowire lasers with different functionalities, such as wavelength tunable, single mode, polarized emission and so on, have been demonstrated. However, the reported single mode nanowire lasers are mostly realized through microfabrication process, careful manipulation and complicated structures. Here, we present a new type of lateral emission single mode nanobelt lasers with high polarization ratio which are fabricated by the one step traditional VLS (Vapor Liquid Solid) growth. Different from the traditional nanobelt lasers which are based on the FP cavity formed in the longitudinal direction, the emission of this novel nanoblet laser is lateral which is contribute to the special wire-like structures grown on the nanobelt. It shows band edge emission and the wavelength is centered at 712.6 nm with linewidth about 0.18 nm. The threshold reach as low as 15 uJ/cm2 benefit from the unique morphology which provides enhanced confinement factor for optical modes. Meanwhile the laser emission is highly polarized with polarization ration as high as 0.91. This lateral emission single mode nanobelt laser with high polarization ratio, low threshold and simple fabrication technique offers an economic and effective choice to the future optical applications.

  3. Spontaneous emission of two quantum dots in a single-mode cavity

    International Nuclear Information System (INIS)

    Qiu Liu; Zhang Ke; Li Zhi-Yuan

    2013-01-01

    The spontaneous emission spectrum from two quantum dots (QDs) that are strongly coupled with a single-mode nanocavity is investigated using rigorous numerical calculations and simple analytical solutions of quantum dynamics. The emission spectra both from the side and along the axis of the cavity are considered. Modification of two parameters, the coupling strength and the detuning between the transition frequencies of the two quantum dots, allows us to efficiently control the shape of the spontaneous emission spectrum. Different profiles and their physical origins can be well understood in the dressed-state picture for the light—QD interaction in the on-resonance and off-resonance situations. In the on-resonance situation, the emission spectra exhibit symmetric features, and they are not altered by the asymmetry in the coupling parameters. The axis spectra show two emission peaks while the side spectra have three emission peaks. In the off-resonance situation, the emission spectra always show an asymmetrical three-peak feature. When the two QDs have different decay parameters, singular features (a peak or a dip) can take place at the frequency of the cavity mode, and this is attributed to the unbalanced process of the emission and absorption of a single photon. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  4. Single-Mode VCSELs

    Science.gov (United States)

    Larsson, Anders; Gustavsson, Johan S.

    The only active transverse mode in a truly single-mode VCSEL is the fundamental mode with a near Gaussian field distribution. A single-mode VCSEL produces a light beam of higher spectral purity, higher degree of coherence and lower divergence than a multimode VCSEL and the beam can be more precisely shaped and focused to a smaller spot. Such beam properties are required in many applications. In this chapter, after discussing applications of single-mode VCSELs, we introduce the basics of fields and modes in VCSELs and review designs implemented for single-mode emission from VCSELs in different materials and at different wavelengths. This includes VCSELs that are inherently single-mode as well as inherently multimode VCSELs where higher-order modes are suppressed by mode selective gain or loss. In each case we present the current state-of-the-art and discuss pros and cons. At the end, a specific example with experimental results is provided and, as a summary, the most promising designs based on current technologies are identified.

  5. Watt-level widely tunable single-mode emission by injection-locking of a multimode Fabry-Perot quantum cascade laser

    Science.gov (United States)

    Chevalier, Paul; Piccardo, Marco; Anand, Sajant; Mejia, Enrique A.; Wang, Yongrui; Mansuripur, Tobias S.; Xie, Feng; Lascola, Kevin; Belyanin, Alexey; Capasso, Federico

    2018-02-01

    Free-running Fabry-Perot lasers normally operate in a single-mode regime until the pumping current is increased beyond the single-mode instability threshold, above which they evolve into a multimode state. As a result of this instability, the single-mode operation of these lasers is typically constrained to few percents of their output power range, this being an undesired limitation in spectroscopy applications. In order to expand the span of single-mode operation, we use an optical injection seed generated by an external-cavity single-mode laser source to force the Fabry-Perot quantum cascade laser into a single-mode state in the high current range, where it would otherwise operate in a multimode regime. Utilizing this approach, we achieve single-mode emission at room temperature with a tuning range of 36 cm-1 and stable continuous-wave output power exceeding 1 W at 4.5 μm. Far-field measurements show that a single transverse mode is emitted up to the highest optical power, indicating that the beam properties of the seeded Fabry-Perot laser remain unchanged as compared to free-running operation.

  6. Single-mode biological distributed feedback laser

    DEFF Research Database (Denmark)

    Vannahme, Christoph; Maier-Flaig, Florian; Lemmer, Uli

    2013-01-01

    Single-mode second order distributed feedback (DFB) lasers of riboflavin (vitamin B2) doped gelatine films on nanostructured low refractive index material are demonstrated. Manufacturing is based on a simple UV nanoimprint and spin-coating. Emission wavelengths of 543 nm and 562 nm for two...

  7. Single transverse mode protein laser

    Science.gov (United States)

    Dogru, Itir Bakis; Min, Kyungtaek; Umar, Muhammad; Bahmani Jalali, Houman; Begar, Efe; Conkar, Deniz; Firat Karalar, Elif Nur; Kim, Sunghwan; Nizamoglu, Sedat

    2017-12-01

    Here, we report a single transverse mode distributed feedback (DFB) protein laser. The gain medium that is composed of enhanced green fluorescent protein in a silk fibroin matrix yields a waveguiding gain layer on a DFB resonator. The thin TiO2 layer on the quartz grating improves optical feedback due to the increased effective refractive index. The protein laser shows a single transverse mode lasing at the wavelength of 520 nm with the threshold level of 92.1 μJ/ mm2.

  8. Single-mode optical fibres

    CERN Document Server

    Cancellieri, G

    1991-01-01

    This book describes signal propagation in single-mode optical fibres for telecommunication applications. Such description is based on the analysis of field propagation, considering waveguide properties and also some of the particular characteristics of the material fibre. The book covers such recent advances as, coherent transmissions; optical amplification; MIR fibres; polarization maintaining; polarization diversity and photon counting.

  9. 1.9 W continuous-wave single transverse mode emission from 1060 nm edge-emitting lasers with vertically extended lasing area

    Energy Technology Data Exchange (ETDEWEB)

    Miah, M. J., E-mail: jarez.miah@tu-berlin.de; Posilovic, K.; Kalosha, V. P.; Rosales, R.; Bimberg, D. [Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin (Germany); Kettler, T. [Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin (Germany); PBC Lasers GmbH, Hardenbergstr. 36, 10623 Berlin (Germany); Skoczowsky, D. [PBC Lasers GmbH, Hardenbergstr. 36, 10623 Berlin (Germany); Pohl, J.; Weyers, M. [Ferdinand-Braun-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin (Germany)

    2014-10-13

    High-brightness edge-emitting semiconductor lasers having a vertically extended waveguide structure emitting in the 1060 nm range are investigated. Ridge waveguide (RW) lasers with 9 μm stripe width and 2.64 mm cavity length yield highest to date single transverse mode output power for RW lasers in the 1060 nm range. The lasers provide 1.9 W single transverse mode optical power under continuous-wave (cw) operation with narrow beam divergences of 9° in lateral and 14° (full width at half maximum) in vertical direction. The beam quality factor M{sup 2} is less than 1.9 up to 1.9 W optical power. A maximum brightness of 72 MWcm{sup −2}sr{sup −1} is obtained. 100 μm wide and 3 mm long unpassivated broad area lasers provide more than 9 W optical power in cw operation.

  10. Measurement of flow fluctuations in single longitudinal mode pulsed ...

    Indian Academy of Sciences (India)

    2014-02-12

    Feb 12, 2014 ... The single mode dye laser is a very useful tool for high-resolution spectroscopy, resonance ionization spec- troscopy (RIS), coherent control etc. For many spectroscopic applications it is however necessary to have a control over the emission linewidth of the dye laser. The frequency- stabilized tunable laser ...

  11. EMISAR single pass topographic SAR interferometer modes

    DEFF Research Database (Denmark)

    Madsen, Søren Nørvang; Skou, Niels; Woelders, Kim

    1996-01-01

    The Danish Center for Remote Sensing (DCRS) has augmented its dual-frequency polarimetric synthetic aperture radar system (EMISAR) with single pass across-track interferometric (XTI) modes. This paper describes the system configuration, specifications and the operating modes. Analysis of data acq...

  12. Single mode dye-doped polymer photonic crystal lasers

    DEFF Research Database (Denmark)

    Christiansen, Mads Brøkner; Buss, Thomas; Smith, Cameron

    2010-01-01

    Dye-doped polymer photonic crystal (PhC) lasers fabricated by combined nanoimprint and photolithography are studied for their reproducibility and stability characteristics. We introduce a phase shift in the PhC lattice that substantially improves the yield of single wavelength emission. Single mode...... emission and reproducibility of laser characteristics are important if the lasers are to be mass produced in, e. g., optofluidic sensor chips. The fabrication yield is above 85% with highly reproducible wavelengths (within 0.5%), and the temperature dependence on the wavelength is found to be -0.045 or -0...

  13. Single VDTA Based Dual Mode Single Input Multioutput Biquad Filter

    Directory of Open Access Journals (Sweden)

    Rajeshwari Pandey

    2016-01-01

    Full Text Available This paper presents a dual mode, single input multioutput (SIMO biquad filter configuration using single voltage differencing transconductance amplifier (VDTA, three capacitors, and a grounded resistor. The proposed topology can be used to synthesize low pass (LP, high pass (HP, and band pass (BP filter functions. It can be configured as voltage mode (VM or current mode (CM structure with appropriate input excitation choice. The angular frequency (ω0 of the proposed structure can be controlled independently of quality factor (Q0. Workability of the proposed biquad configuration is demonstrated through PSPICE simulations using 0.18 μm TSMC CMOS process parameters.

  14. Single photon emission computerized tomography

    International Nuclear Information System (INIS)

    Hooge, P. de.

    1983-01-01

    In this thesis two single-photon emission tomographic techniques are presented: (a) longitudinal tomography with a rotating slanting-hole collimator, and (b) transversal tomography with a rotating gamma camera. These methods overcome the disadvantages of conventional scintigraphy. Both detection systems and the image construction methods are explained and comparisons with conventional scintigraphy are drawn. One chapter is dedicated to the determination of system parameters like spatial resolution, contrast, detector uniformity, and size of the object, by phantom studies. In separate chapters the results are presented of detection of tumors and metastases in the liver and the liver hilus; skeletal diseases; various pathological aberrations of the brain; and myocardial perfusion. The possible use of these two ect's for other organs and body areas is discussed in the last chapter. (Auth.)

  15. Single-mode quantum cascade lasers employing a candy-cane shaped monolithic coupled cavity

    Science.gov (United States)

    Liu, Peter Q.; Sladek, Kamil; Wang, Xiaojun; Fan, Jen-Yu; Gmachl, Claire F.

    2011-12-01

    We demonstrate single-mode quantum cascade lasers emitting at ˜4.5 μm by employing a monolithic "candy-cane" shaped coupled-cavity consisting of a straight section connecting at one end to a spiral section. The fabrication process is identical to those for simple Fabry-Perot-type ridge lasers. Continuously tunable single-mode emission across ˜8 cm-1 with side mode suppression ratio up to ˜25 dB and a single-mode operating current range of more than 70% above the threshold current is achieved when the lasers are operated in pulsed-mode from 80 K to 155 K.

  16. Modes of an endlessly single-mode photonic crystal fiber: a finite element investigation

    NARCIS (Netherlands)

    Uranus, H.P.; Hoekstra, Hugo; van Groesen, Embrecht W.C.

    2004-01-01

    Using a finite-element mode solver, the modes of a commercial endlessly single-mode photonic crystal fiber (ESM-PCF) were investigated. Based on the loss discrimination between the dominant and the nearest higher order mode, we set-up a criterion for the single-modeness. Using that measure, we

  17. Single photon detection in the SQS mode

    International Nuclear Information System (INIS)

    Alves, M.A.; Fraga, M.M.; Lima, E.P. de; Marques, R.F.; Neves, F.; Policarpo, A.

    1997-01-01

    Results are presented concerning the detection of single UV photons in self quenching streamer detectors by photoionization of one of the gas mixture components, in this case TEA (tri ethyl-amine), whose molecules have low photoionization potential and large absorption cross section. As a UV light source, a gas scintillation counter filled with krypton was used, whose emission light spectrum, centered at approximately 150 nm, overlaps well the photoionization spectrum of TEA. The mixtures studied were argon/ethane/TEA, argon/isobutane/TEA, argon/ethane/methylal/TEA and argon/isobutane/methylal/ TEA. (author). 4 refs., 4 figs

  18. Physics and technology of tunable pulsed single longitudinal mode ...

    Indian Academy of Sciences (India)

    The single longitudinal mode (SLM) dye laser generates single-mode laser beams of ∼ 400 MHz (GIG configuration) and ∼ 600 MHz (Littrow configuration) bandwidth. Detailed performance studies of the Littrow and GIG dye laser resonators showed that GIG dye laser results in narrower linewidth and broad mode hop free ...

  19. A novel hybrid III–V/silicon deformed micro-disk single-mode laser

    International Nuclear Information System (INIS)

    Feng Peng; Zhang Yejin; Liu Lei; Zhang Siriguleng; Wang Hailing; Zheng Wanhua; Wang Yufei

    2015-01-01

    A novel hybrid III–V/silicon deformed micro-disk single-mode laser connecting to a Si output waveguide is designed, and fabricated through BCB bonding technology and standard i-line photolithography. Compared to a traditional circular micro-disk in multi-longitudinal-mode operation, unidirectional emission and single longitudinal-mode output from a Si waveguide are realized. In the experiments, an output power of 0.31 mW and a side-mode suppression ratio of 27 dB in the continuous-wave regime are obtained. (semiconductor devices)

  20. Mode coupling in hybrid square-rectangular lasers for single mode operation

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Xiu-Wen; Huang, Yong-Zhen, E-mail: yzhuang@semi.ac.cn; Yang, Yue-De; Xiao, Jin-Long; Weng, Hai-Zhong; Xiao, Zhi-Xiong [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors and University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100083 (China)

    2016-08-15

    Mode coupling between a square microcavity and a Fabry-Pérot (FP) cavity is proposed and demonstrated for realizing single mode lasers. The modulations of the mode Q factor as simulation results are observed and single mode operation is obtained with a side mode suppression ratio of 46 dB and a single mode fiber coupling loss of 3.2 dB for an AlGaInAs/InP hybrid laser as a 300-μm-length and 1.5-μm-wide FP cavity connected to a vertex of a 10-μm-side square microcavity. Furthermore, tunable single mode operation is demonstrated with a continuous wavelength tuning range over 10 nm. The simple hybrid structure may shed light on practical applications of whispering-gallery mode microcavities in large-scale photonic integrated circuits and optical communication and interconnection.

  1. Crosstalk-Managed Heterogeneous Single-Mode 32-Core Fibre

    DEFF Research Database (Denmark)

    Sasaki, Y.; Fukumoto, Ryohei; Takenaga, Katsuhiro

    2016-01-01

    A heterogeneous single-mode 32-core fibre with a cladding diameter of 243 micrometer is designed and fabricated. The highest core count in single-mode multi-core fibres and low worst-case crosstalk of less than -24 dB/1000 km in C-band are achieved simultaneously.......A heterogeneous single-mode 32-core fibre with a cladding diameter of 243 micrometer is designed and fabricated. The highest core count in single-mode multi-core fibres and low worst-case crosstalk of less than -24 dB/1000 km in C-band are achieved simultaneously....

  2. Physics and technology of tunable pulsed single longitudinal mode ...

    Indian Academy of Sciences (India)

    Design and technology demonstration of compact, narrow bandwidth, high repetition rate, tunable SLM dye lasers in two different configurations, namely Littrow and grazing incidence grating (GIG), were carried out in our lab at BARC, India. The single longitudinal mode (SLM) dye laser generates single-mode laser beams ...

  3. Transverse single-mode edge-emitting lasers based on coupled waveguides.

    Science.gov (United States)

    Gordeev, Nikita Yu; Payusov, Alexey S; Shernyakov, Yuri M; Mintairov, Sergey A; Kalyuzhnyy, Nikolay A; Kulagina, Marina M; Maximov, Mikhail V

    2015-05-01

    We report on the transverse single-mode emission from InGaAs/GaAs quantum well edge-emitting lasers with broadened waveguide. The lasers are based on coupled large optical cavity (CLOC) structures where high-order vertical modes of the broad active waveguide are suppressed due to their resonant tunneling into a coupled single-mode passive waveguide. The CLOC lasers have shown stable Gaussian-shaped vertical far-field profiles with a reduced divergence of ∼22° FWHM (full width at half-maximum) in CW (continuous-wave) operation.

  4. Cross-correlated imaging of single-mode photonic crystal rod fiber with distributed mode filtering

    DEFF Research Database (Denmark)

    Laurila, Marko; Barankov, Roman; Jørgensen, Mette Marie

    2013-01-01

    Photonic crystal bandgap fibers employing distributed mode filtering design provide near diffraction-limited light outputs, a critical property of fiber-based high-power lasers. Microstructure of the fibers is tailored to achieve single-mode operation at specific wavelength by resonant mode...... identify regimes of resonant coupling between higher-order core modes and cladding band. We demonstrate a passive fiber design in which the higher-order modal content inside the single-mode guiding regime is suppressed by at least 20 dB even for significantly misaligned input-coupling configurations....

  5. Quasi-single-mode homogeneous 31-core fibre

    DEFF Research Database (Denmark)

    Sasaki, Y.; Saitoh, S.; Amma, Y.

    2015-01-01

    A homogeneous 31-core fibre with a cladding diameter of 230 μm for quasi-single-mode transmission is designed and fabricated. LP01-crosstalk of -38.4 dB/11 km at 1550 nm is achieved by using few-mode trench-assisted cores.......A homogeneous 31-core fibre with a cladding diameter of 230 μm for quasi-single-mode transmission is designed and fabricated. LP01-crosstalk of -38.4 dB/11 km at 1550 nm is achieved by using few-mode trench-assisted cores....

  6. Electron Bernstein Wave Emission and Mode Conversion Physics on NSTX

    International Nuclear Information System (INIS)

    Diem, S.J.; Taylor, G.; Caughman, J.B.; Efthimion, P.; Kugel, H.; LeBlanc, B.P.; Preinhaelter, J.; Sabbagh, S.A.; Urban, J.; Wilgen, J.

    2008-01-01

    NSTX is a spherical tokamak (ST) that operates with ne up to 1020 m-3 and BT less than 0.6 T, cutting off low harmonic electron cyclotron (EC) emission widely used for Te measurements on conventional aspect ratio tokamaks. The electron Bernstein wave (EBW) can propagate in ST plasmas and is emitted at EC harmonics. These properties suggest thermal EBW emission (EBE) may be used for local Te measurements in the ST. Practically, a robust Te(R,t) EBE diagnostic requires EBW transmission efficiencies of > 90% for a wide range of plasma conditions. EBW emission and coupling physics were studied on NSTX with an obliquely viewing EBW to O-mode (B-X-O) diagnostic with two remotely steered antennas, coupled to absolutely calibrated radiometers. While Te(R,t) measurements with EBW emission on NSTX were possible, they were challenged by several issues. Rapid fluctuations in edge ne scale length resulted in > 20% changes in the low harmonic B-X-O transmission efficiency. Also, B-X-O transmission efficiency 2 during H-modes was observed to decay by a factor of 5-10 to less than a few percent. The B-X-O transmission behavior during H-modes was reproduced by EBE simulations that predict that EBW collisional damping can significantly reduce emission when Te < 30 eV inside the B-X-O mode conversion (MC) layer. Initial edge lithium conditioning experiments during H-modes have shown that evaporated lithium can increase Te inside the B-X-O MC layer, significantly increasing B-X-O transmission.

  7. Physics and technology of tunable pulsed single longitudinal mode ...

    Indian Academy of Sciences (India)

    Figure 8. Principle of two-mode operation. Figure 9. Amplifier efficiency vs. wavelength. Experimentally observed wavelength change is 2.5 pm/◦C = 2.39 GHz/◦C at. 560 nm. It was observed that if the dye temperature was stabilized there was no transition from single-mode to twin-mode over an hour operation. Change in ...

  8. LOPUT Laser: A novel concept to realize single longitudinal mode ...

    Indian Academy of Sciences (India)

    2014-02-05

    Feb 5, 2014 ... Contributed Papers Volume 82 Issue 2 February 2014 pp 185-190 ... Abstract. We propose a novel type of cavity design to generate single longitudinal mode laser known as LOPUT cavity. LOPUT cavity stands for linear orthogonally polarized modes resulting in unidirectional travelling wave cavity.

  9. Single-mode ytterbium-doped large-mode-area photonic bandgap rod fiber amplifier

    DEFF Research Database (Denmark)

    Alkeskjold, Thomas Tanggaard; Scolari, Lara; Broeng, Jes

    2011-01-01

    Enabling Single-Mode (SM) operation in Large-Mode-Area (LMA) fiber amplifiers and lasers is critical, since a SM output ensures high beam quality and excellent pointing stability. In this paper, we demonstrate and test a new design approach for achieving SM LMA rod fibers by using a photonic...... bandgap structure. The structure allows resonant coupling of higher-order modes from the core and acts as a spatially Distributed Mode Filter (DMF). With this approach, we demonstrate passive SM performance in an only ~50cm long and straight ytterbium-doped rod fiber. The amplifier has a mode field...

  10. Efficient multi-mode to single-mode conversion in a 61 port photonic lantern

    DEFF Research Database (Denmark)

    Noordegraaf, Danny; Skovgaard, Peter M. W.; Dybendahl Maack, Martin

    2010-01-01

    We demonstrate the fabrication of a multi-mode (MM) to 61 port single-mode (SM) splitter or "Photonic Lantern". Low port count Photonic Lanterns were first described by Leon-Saval et al. (2005). These are based on a photonic crystal fiber type design, with air-holes defining the multi-mode fiber ...... of astrophotonics for coupling MM star-light to an ensemble of SM fibers in order to perform fiber Bragg grating based spectral filtering....

  11. Damping of unbound single-particle modes

    International Nuclear Information System (INIS)

    Fortier, S.; Beaumel, D.; Gales, S.; Guillot, J.; Langevin-Joliot, H.; Laurent, H.; Maison, J.M.; Bordewijk, J.; Brandenburg, S.; Krasznahorkay, A.; Crawley, G.M.; Massolo, C.P.; Renteria, M.; Khendriche, A.

    1995-01-01

    The (α, 3 He-n) reaction has been investigated at 120 MeV incident energy on 64 Ni, 90 Zr, and 120 Sn target nuclei. Neutrons in coincidence with 3 He particles emitted at 0 degree were detected using the multidetector array EDEN, in order to get information about the decay of single-particle states embedded in the (α, 3 He) continuum. Neutron angular correlations, multiplicity values, and branching ratios to low-lying states of the final nuclei have been compared with the predictions of the statistical decay model. Evidence for a significant nonstatistical decay branch has been observed in the three nuclei below about 15 MeV excitation energy. Direct branching ratios in 91 Zr deduced from this analysis are compared with the predictions of two nuclear structure models. At higher excitation energy, the decay characteristics of the (α, 3 He) continuum are shown to be mainly statistical

  12. Efficient multi-mode to single-mode coupling in a photonic lantern

    DEFF Research Database (Denmark)

    Noordegraaf, Danny; Skovgaard, Peter M.; Nielsen, Martin D.

    2009-01-01

    We demonstrate the fabrication of a high performance multi-mode (MM) to single-mode (SM) splitter or “photonic lantern”, first described by Leon-Saval et al. (2005). Our photonic lantern is a solid all-glass version, and we show experimentally that this device can be used to achieve efficient and...

  13. Linear optical quantum computing in a single spatial mode.

    Science.gov (United States)

    Humphreys, Peter C; Metcalf, Benjamin J; Spring, Justin B; Moore, Merritt; Jin, Xian-Min; Barbieri, Marco; Kolthammer, W Steven; Walmsley, Ian A

    2013-10-11

    We present a scheme for linear optical quantum computing using time-bin-encoded qubits in a single spatial mode. We show methods for single-qubit operations and heralded controlled-phase (cphase) gates, providing a sufficient set of operations for universal quantum computing with the Knill-Laflamme-Milburn [Nature (London) 409, 46 (2001)] scheme. Our protocol is suited to currently available photonic devices and ideally allows arbitrary numbers of qubits to be encoded in the same spatial mode, demonstrating the potential for time-frequency modes to dramatically increase the quantum information capacity of fixed spatial resources. As a test of our scheme, we demonstrate the first entirely single spatial mode implementation of a two-qubit quantum gate and show its operation with an average fidelity of 0.84±0.07.

  14. Damping of unbound single-particle modes

    Energy Technology Data Exchange (ETDEWEB)

    Fortier, S.; Beaumel, D.; Gales, S.; Guillot, J.; Langevin-Joliot, H.; Laurent, H.; Maison, J.M.; Bordewijk, J.; Brandenburg, S.; Krasznahorkay, A.; Crawley, G.M.; Massolo, C.P.; Renteria, M.; Khendriche, A. [Institut de Physique Nucleaire, IN2P3-CNRS, 91406 Orsay Cedex (France)]|[Kernfysisch Versneller Instituut, 9747 AA Groningen (Netherlands)]|[Nuclear Research Institute, Debrecen P.O. Box 51, H-4001 (Hungary)]|[NSCL, Michigan State University, East Lansing, Michigan 48824 (United States)]|[Dep. Fisica, Fac. Cs. Exactas, UNLP, CC Nio 67, 1900 La Plata (Argentina)]|[Institut de Sciences Exactes,Universite de Tizi-Ouzou, 15000 Tizi-Ouzou (Algeria)

    1995-11-01

    The ({alpha},{sup 3}He-{ital n}) reaction has been investigated at 120 MeV incident energy on {sup 64}Ni, {sup 90}Zr, and {sup 120}Sn target nuclei. Neutrons in coincidence with {sup 3}He particles emitted at 0{degree} were detected using the multidetector array EDEN, in order to get information about the decay of single-particle states embedded in the ({alpha},{sup 3}He) continuum. Neutron angular correlations, multiplicity values, and branching ratios to low-lying states of the final nuclei have been compared with the predictions of the statistical decay model. Evidence for a significant nonstatistical decay branch has been observed in the three nuclei below about 15 MeV excitation energy. Direct branching ratios in {sup 91}Zr deduced from this analysis are compared with the predictions of two nuclear structure models. At higher excitation energy, the decay characteristics of the ({alpha},{sup 3}He) continuum are shown to be mainly statistical.

  15. New results of investigations of whistler-mode chorus emissions

    Directory of Open Access Journals (Sweden)

    O. Santolík

    2008-07-01

    Full Text Available This review summarizes selected recent results obtained during investigation of whistler-mode chorus emissions in the Earth's magnetosphere. Special attention is paid to results published during the last five years, with a focus on the results of the CLUSTER project. The nonlinear nature of chorus emissions is demonstrated using both theoretical results and measurements. Selected areas of research on whistler-mode chorus are covered and the paper especially reports new results on substructure and amplitudes of chorus wave packets, on new observations of frequency differences of chorus wave packets at different points in space and on their possible interpretations, on results concerning determination of position and size of the source region of chorus, on recent observational and theoretical results which lead to improved description of propagation of chorus from its source, and, finally, on comparison of chorus measurements with corresponding values deduced from nonlinear theory and simulations.

  16. New results of investigations of whistler-mode chorus emissions

    Czech Academy of Sciences Publication Activity Database

    Santolík, Ondřej

    2008-01-01

    Roč. 15, č. 4 (2008), s. 621-630 ISSN 1023-5809 R&D Projects: GA AV ČR IAA301120601 Grant - others: NASA (US) NNX07AI24G; ESA PECS(XE) 98025 Institutional research plan: CEZ:AV0Z30420517 Keywords : chorus emissions * whistler-mode * Earth's magnetosphere Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.022, year: 2008 http://www.nonlin-processes-geophys.net/15/621/2008/

  17. Volume production of polarization controlled single-mode VCSELs

    Science.gov (United States)

    Grabherr, Martin; King, Roger; Jäger, Roland; Wiedenmann, Dieter; Gerlach, Philipp; Duckeck, Denise; Wimmer, Christian

    2008-02-01

    Over the past 3 years laser based tracking systems for optical PC mice have outnumbered the traditional VCSEL market datacom by far. Whereas VCSEL for datacom in the 850 nm regime emit in multipe transverse modes, all laser based tracking systems demand for single-mode operation which require advanced manufacturing technology. Next generation tracking systems even require single-polarization characteristics in order to avoid unwanted movement of the pointer due to polarization flips. High volume manufacturing and optimized production methods are crucial for achieving the addressed technical and commercial targets of this consumer market. The resulting ideal laser source which emits single-mode and single-polarization at low cost is also a promising platform for further applications like tuneable diode laser absorption spectroscopy (TDLAS) or miniature atomic clocks when adapted to the according wavelengths.

  18. New theory for Mode I crack-tip dislocation emission

    Science.gov (United States)

    Andric, Predrag; Curtin, W. A.

    2017-09-01

    A material is intrinsically ductile under Mode I loading when the critical stress intensity KIe for dislocation emission is lower than the critical stress intensity KIc for cleavage. KIe is usually evaluated using the approximate Rice theory, which predicts a dependence on the elastic constants and the unstable stacking fault energy γusf for slip along the plane of dislocation emission. Here, atomistic simulations across a wide range of fcc metals show that KIe is systematically larger (10-30%) than predicted. However, the critical (crack tip) shear displacement is up to 40% smaller than predicted. The discrepancy arises because Mode I emission is accompanied by the formation of a surface step that is not considered in the Rice theory. A new theory for Mode I emission is presented based on the ideas that (i) the stress resisting step formation at the crack tip creates "lattice trapping" against dislocation emission such that (ii) emission is due to a mechanical instability at the crack tip. The new theory is formulated using a Peierls-type model, naturally includes the energy to form the step, and reduces to the Rice theory (no trapping) when the step energy is small. The new theory predicts a higher KIe at a smaller critical shear displacement, rationalizing deviations of simulations from the Rice theory. Specific predictions of KIe for the simulated materials, usually requiring use of the measured critical crack tip shear displacement due to complex material non-linearity, show very good agreement with simulations. An analytic model involving only γusf, the surface energy γs, and anisotropic elastic constants is shown to be quite accurate, serves as a replacement for the analytical Rice theory, and is used to understand differences between Rice theory and simulation in recent literature. The new theory highlights the role of surface steps created by dislocation emission in Mode I, which has implications not only for intrinsic ductility but also for crack tip

  19. Tunable single-longitudinal-mode fiber optical parametric oscillator.

    Science.gov (United States)

    Yang, Sigang; Cheung, Kim K Y; Zhou, Yue; Wong, Kenneth K Y

    2010-02-15

    A tunable single-longitudinal-mode (SLM) fiber optical parametric oscillator (FOPO) is proposed and demonstrated experimentally. A sub-ring cavity with a short cavity length is used to suppress the longitudinal modes and broaden the longitudinal mode spacing. A fiber loop mirror, consisted of an unpumped erbium-doped fiber, acts as an autotracking filter for providing fine mode restriction and ensuring the single-frequency operation. The measurement based on a homodyne method shows that the FOPO provides the SLM output. Furthermore the SLM FOPO can be tunable over 14 nm for each of the signal and the idler, which is limited only by the gain bandwidth of the fiber optical parametric amplifier.

  20. A Calculation Method of PKA, KERMA and DPA from Evaluated Nuclear Data with an Effective Single-particle Emission Approximation (ESPEA) and Introduction of Event Generator Mode in PHITS Code

    International Nuclear Information System (INIS)

    Fukahori, Tokio; Iwamoto, Yosuke

    2012-01-01

    The displacement calculation method from evaluated nuclear data file has been developed by using effective single-particle emission approximation (ESPEA). The ESPEA can be used effectively below about 50 MeV, because of since multiplicity of emitted particles. These are also reported in the Ref. 24. The displacement calculation method in PHITS has been developed. In the high energy region (≥ 20 MeV) for proton and neutron beams, DPA created by secondary particles increase due to nuclear reactions. For heavy-ion beams, DPA created by the primaries are dominant to total DPA due to the large Coulomb scattering cross sections. PHITS results agree with FLUKA ones within a factor of 1.7. In the high-energy region above 10 MeV/nucleon, comparisons among codes and measurements of displacement damage cross section are necessary. (author)

  1. Terahertz light-emitting graphene-channel transistor toward single-mode lasing

    Directory of Open Access Journals (Sweden)

    Yadav Deepika

    2018-03-01

    Full Text Available A distributed feedback dual-gate graphene-channel field-effect transistor (DFB-DG-GFET was fabricated as a current-injection terahertz (THz light-emitting laser transistor. We observed a broadband emission in a 1–7.6-THz range with a maximum radiation power of ~10 μW as well as a single-mode emission at 5.2 THz with a radiation power of ~0.1 μW both at 100 K when the carrier injection stays between the lower cutoff and upper cutoff threshold levels. The device also exhibited peculiar nonlinear threshold-like behavior with respect to the current-injection level. The LED-like broadband emission is interpreted as an amplified spontaneous THz emission being transcended to a single-mode lasing. Design constraints on waveguide structures for better THz photon field confinement with higher gain overlapping as well as DFB cavity structures with higher Q factors are also addressed towards intense, single-mode continuous wave THz lasing at room temperature.

  2. Single Mode ZnO Whispering-Gallery Submicron Cavity and Graphene Improved Lasing Performance.

    Science.gov (United States)

    Li, Jitao; Lin, Yi; Lu, Junfeng; Xu, Chunxiang; Wang, Yueyue; Shi, Zengliang; Dai, Jun

    2015-07-28

    Single-mode ultraviolet (UV) laser of ZnO is still in challenge so far, although it has been paid great attention along the past decades. In this work, single-mode lasing resonance was realized in a submicron-sized ZnO rod based on serially varying the dimension of the whispering-gallery mode (WGM) cavities. The lasing performance, such as the lasing quality factor (Q) and the lasing intensity, was remarkably improved by facilely covering monolayer graphene on the ZnO submicron-rod. The mode structure evolution from multimodes to single-mode was investigated systematically based on the total internal-wall reflection of the ZnO microcavities. Graphene-induced optical field confinement and lasing emission enhancement were revealed, indicating an energy coupling between graphene SP and ZnO exciton emission. This result demonstrated the response of graphene in the UV wavelength region and extended its potential applications besides many previous reports on the multifunctional graphene/semiconductor hybrid materials and devices in advanced electronics and optoelectronics areas.

  3. Investigation of EBW Thermal Emission and Mode Conversion Physics in H-Mode Plasmas on NSTX

    International Nuclear Information System (INIS)

    Diem, S.J.; Taylor, G.; Efthimion, P.C.; Kugel, H.W.; LeBlanc, B.P.; Phillips, C.K.; Caughman, J.B.; Wilgen, J.B.; Harvey, R.W.; Preinhaelter, J.; Urban, J.; Sabbagh, S.A.

    2008-01-01

    High β plasmas in the National Spherical Torus Experiment (NSTX) operate in the overdense regime, allowing the electron Bernstein wave (EBW) to propagate and be strongly absorbed/emitted at the electron cyclotron resonances. As such, EBWs may provide local electron heating and current drive. For these applications, efficient coupling between the EBWs and electromagnetic waves outside the plasma is needed. Thermal EBW emission (EBE) measurements, via oblique B-X-O double mode conversion, have been used to determine the EBW transmission efficiency for a wide range of plasma conditions on NSTX. Initial EBE measurements in H-mode plasmas exhibited strong emission before the L-H transition, but the emission rapidly decayed after the transition. EBE simulations show that collisional damping of the EBW prior to the mode conversion (MC) layer can significantly reduce the measured EBE for T e < 20 eV, explaining the observations. Lithium evaporation was used to reduce EBE collisional damping near the MC layer. As a result, the measured B-X-O transmission efficiency increased from < 10% (no Li) to 60% (with Li), consistent with EBE simulations.

  4. Single-Mode WGM Resonators Fabricated by Diamond Turning

    Science.gov (United States)

    Grudinin, Ivan; Maleki, Lute; Savchenkov, Anatoliy; Matsko, Andrewy; Strekalov, Dmitry; Iltchenko, Vladimir

    2008-01-01

    A diamond turning process has made possible a significant advance in the art of whispering-gallery-mode (WGM) optical resonators. By use of this process, it is possible to fashion crystalline materials into WGM resonators that have ultrahigh resonance quality factors (high Q values), are compact (ranging in size from millimeters down to tens of microns), and support single electromagnetic modes. This development combines and extends the developments reported in "Few- Mode Whispering-Gallery-Mode Resonators" (NPO-41256), NASA Tech Briefs, Vol. 30, No. 1 (January 2006), page 16a and "Fabrication of Submillimeter Axisymmetric Optical Components" (NPO-42056), NASA Tech Briefs, Vol. 31, No. 5 (May 2007), page 10a. To recapitulate from the first cited prior article: A WGM resonator of this special type consists of a rod, made of a suitable transparent material, from which protrudes a thin circumferential belt of the same material. The belt is integral with the rest of the rod and acts as a circumferential waveguide. If the depth and width of the belt are made appropriately small, then the belt acts as though it were the core of a single-mode optical fiber: the belt and the rod material adjacent to it support a single, circumferentially propagating mode or family of modes. To recapitulate from the second cited prior article: A major step in the fabrication of a WGM resonator of this special type is diamond turning or computer numerically controlled machining of a rod of a suitable transparent crystalline material on an ultrahigh-precision lathe. During the rotation of a spindle in which the rod is mounted, a diamond tool is used to cut the rod. A computer program is used to control stepping motors that move the diamond tool, thereby controlling the shape cut by the tool. Because the shape can be controlled via software, it is possible to choose a shape designed to optimize a resonator spectrum, including, if desired, to limit the resonator to supporting a single mode

  5. Characteristics of SBS dynamics in single-mode optical fibres

    Science.gov (United States)

    Gordeev, A. A.; Efimkov, V. F.; Zubarev, I. G.; Mikhailov, S. I.; Sobolev, V. B.

    2016-03-01

    The characteristics of the gain of Stokes pulses in single-mode optical fibres by stimulated Brillouin scattering (SBS) of monochromatic and nonmonochromatic pump signals have been investigated by numerical simulation using a spectral approach. Conditions under which 'slow light' (caused by a group delay) can be implemented are found (it is reasonable to apply this term to a process in which a pulse is delayed with conservation of its shape). The plane-wave interaction model is shown to describe adequately the dynamics of this process in single-mode fibres. A number of gain modes are investigated for Stokes pulses with different time structures upon monochromatic and nonmonochromatic excitation. A new data transfer technique is proposed, which is based on the conversion of stepwise phase modulation of the input Stokes signal into amplitude modulation of the output signal.

  6. Characteristics of SBS dynamics in single-mode optical fibres

    Energy Technology Data Exchange (ETDEWEB)

    Gordeev, A A; Efimkov, V F; Zubarev, I G; Mikhailov, S I; Sobolev, V B [P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    2016-03-31

    The characteristics of the gain of Stokes pulses in single-mode optical fibres by stimulated Brillouin scattering (SBS) of monochromatic and nonmonochromatic pump signals have been investigated by numerical simulation using a spectral approach. Conditions under which 'slow light' (caused by a group delay) can be implemented are found (it is reasonable to apply this term to a process in which a pulse is delayed with conservation of its shape). The plane-wave interaction model is shown to describe adequately the dynamics of this process in single-mode fibres. A number of gain modes are investigated for Stokes pulses with different time structures upon monochromatic and nonmonochromatic excitation. A new data transfer technique is proposed, which is based on the conversion of stepwise phase modulation of the input Stokes signal into amplitude modulation of the output signal. (nonlinear optical phenomena)

  7. Measurement of flow fluctuations in single longitudinal mode pulsed ...

    Indian Academy of Sciences (India)

    2014-02-12

    Feb 12, 2014 ... A simple technique had been demonstrated for measuring flow-induced fluctuations in the single longitudinal mode (SLM) pulsed dye laser. Two prominent frequency components of 10.74 Hz and 48.83 Hz were present in the output of the Nd:YAG-pumped SLM dye laser. The flow-induced frequency ...

  8. Single-mode fibre coupler as refractometer sensor

    Indian Academy of Sciences (India)

    We report a simple, non-intrusive fibre-optic refractometer sensor for measuring the refractive index of liquid and optically transparent solid medium. Sensing principle of the proposed sensor is based on monitoring the back-reflected light signal through the second input port of a 2 × 1 single-mode fibre coupler when light ...

  9. Single-mode multicore fiber for dense space division multiplexing

    DEFF Research Database (Denmark)

    Sasaki, Yusuke; Amma, Yoshimichi; Takenaga, Katsuhiro

    2016-01-01

    Single-mode multicore fiber (SM-MCF) is attractive for high-capacity transmission. Our fabricated SM-MCFs achieve high core count and low crosstalk with a cladding diameter of 230 µm. Characteristics of fan-in/fan-out for the SM-MCFs are also investigated....

  10. The combination of directional outputs and single-mode operation in circular microdisk with broken PT symmetry.

    Science.gov (United States)

    Song, Qinghai; Li, Jiankai; Sun, Wenzhao; Zhang, Nan; Liu, Shuai; Li, Meng; Xiao, Shumin

    2015-09-21

    Monochromaticity and directionality are two key characteristics of lasers. However, the combination of directional emission and single-mode operation is quite challenging, especially for the on-chip devices. Here we propose a microdisk laser with single-mode operation and directional emissions by exploiting the recent developments associated with parity-time (PT) symmetry. This is accomplished by introducing one-dimensional periodic gain and loss into a circular microdisk, which induces a coupling between whispering gallery modes with different radial numbers. The lowest threshold mode is selected at the positions with least initial wavelength difference. And the directional emissions are formed by the introduction of additional grating vectors by the periodic distribution of gain and loss regions. We believe this research will impact the practical applications of on-chip microdisk lasers.

  11. A finite element characterization of a commercial endlessly single-mode photonic crystal fiber: is it really single mode?

    NARCIS (Netherlands)

    Uranus, H.P.; Hoekstra, Hugo; van Groesen, Embrecht W.C.

    2007-01-01

    One of interesting properties of photonic crystal fibers (PCFs) is their possibility to be single-moded over a wide wavelength range, down to UV, while still having a reasonably large modal profile. Such properties are attractive for applications like optical sensing, interferometry, and transport

  12. Research status of large mode area single polarization active fiber

    Science.gov (United States)

    Xiao, Chun; Zhang, Ge; Yang, Bin-hua; Cheng, Wei-feng; Gu, Shao-yi

    2018-03-01

    As high power fiber laser used more and more widely, to increase the output power of fiber laser and beam quality improvement have become an important goal for the development of high power fiber lasers. The use of large mode fiber is the most direct and effective way to solve the nonlinear effect and fiber damage in the fiber laser power lifting process. In order to reduce the effect of polarization of the fiber laser system, the study found that when introduces a birefringence in the single-mode fiber, the polarization state changes caused by the birefringence is far greater than the random polarization state changes, then the external disturbance is completely submerged, finally the polarization can be controlled and stabilized. Through the fine design of the fiber structure, if the birefringence is high enough to achieve the separation of the two polarization states, the fiber will have a different cut-off mechanism to eliminate polarization which is not need, which will realize single mode single polarization transmission in a band. In this paper, different types of single polarization fiber design are presented and the application of these fibers are also discussed.

  13. Vibration modes of a single plate with general boundary conditions

    Directory of Open Access Journals (Sweden)

    Phamová L.

    2016-06-01

    Full Text Available This paper deals with free flexural vibration modes and natural frequencies of a thin plate with general boundary conditions — a simply supported plate connected to its surroundings with torsional springs. Vibration modes were derived on the basis of the Rajalingham, Bhat and Xistris approach. This approach was originally used for a clamped thin plate, so its adaptation was needed. The plate vibration function was usually expressed as a single partial differential equation. This partial differential equation was transformed into two ordinary differential equations that can be solved in the simpler way. Theoretical background of the computations is briefly described. Vibration modes of the supported plate with torsional springs are presented graphically and numerically for three different values of stiffness of torsional springs.

  14. Multi-mode to single-mode conversion in a 61 port photonic lantern

    DEFF Research Database (Denmark)

    Noordegraaf, Danny; Skovgaard, Peter M.W.; Maack, Martin D.

    2010-01-01

    Efficient multi-mode (MM) to single-mode (SM) conversion in a 61 port splitter or “Photonic Lantern” is demonstrated. The coupling loss from a 100 µm core diameter MM section to an ensemble of 61 SM fibers and back to another 100 µm core MM section is measured to be as low as 0.76 dB. This demons......B. This demonstration shows the feasibility of using the Photonic Lanterns within the field of astrophotonics for coupling MM star-light to an ensemble of SM fibers in order to perform fiber Bragg grating based spectral filtering."...

  15. Single mode operation of a TEA CO2 laser

    International Nuclear Information System (INIS)

    Wada, Kazuhiro; Tunawaki, Yoshiaki; Yamanaka, Masanobu.

    1993-01-01

    Single mode operation of a TEA CO 2 laser was performed by using an optical system of Fox-Smith type. Laser beam was taken out from the cavity by using a beam splitter, and was reflected by a mirror back to the cavity. By inserting a Fabry-Perot etalon between the splitter and the mirror, beat of laser pulses can be removed completly. (author)

  16. Current-Mode Universal Filters Employing Single FDCCII

    Directory of Open Access Journals (Sweden)

    F. Kacar

    2012-12-01

    Full Text Available In this study, to realize current-mode multifunction filters, three new circuit configurations are presented. The circuits include fully differential current conveyor (FDCCII and four passive components. First proposed circuit is a universal filter with single-input and three-outputs, which can simultaneously realize current mode low-pass, band-pass and high-pass filter responses employing all grounded passive components. The last two proposed are universal filters with three-inputs single-output, which can realize current mode low-pass, band-pass, high-pass, band-stop and all-pass filter responses employing single FDCCII. Furthermore, each of the proposed circuits still enjoys realization using a minimum number of active and passive components. First and last of the proposed circuits have no requirement with the component choice conditions to realize specific filtering functions. No parameter matching condition is required. Active and passive sensitivities of filters are investigated and calculated 5 percentage hangings. Simulation results are found in close agreement with the theoretical results.

  17. Coherence properties of a single-mode polariton laser

    Science.gov (United States)

    Kim, Seonghoon; Zhang, Bo; Wang, Zhaorong; Deng, Hui; Fischer, Julian; Brodbeck, Sebastian; Kamp, Martin; Schneider, Christian; Hofling, Sven; Univ of Michigan-Ann Arbor Collaboration; Univ of Wuerzberg Collaboration

    2016-05-01

    Exciton-polariton condensation is a promising low threshold coherent light source, namely a polariton laser. However, first- and second-order coherences of a polariton laser has been poor and not well understood in two dimensional microcavity systems. Here, we show experimentally that full second-order coherence is established in a single-mode polariton laser and maintained far above the lasing threshold. The coherence time of first-order coherence functions increases initially and then reduces as the number of polaritons in a ground state increases due to the polariton-polariton interaction. Moreover, a transition in spectral lineshape from Lorentzian to Gaussian was observed as the occupation number increases as a result of the large interaction energy. These results are in very good agreement with a single-mode atom laser theory. The single-mode polariton laser was realized by designing a subwavelength grating (SWG) mirror which provides strong lateral confinement for discrete polariton states and polarization-selective reflectance for lifted spin-degeneracy. The results would be important for making fully coherent polariton lasers, as well as nonlinear polariton devices.

  18. Positron emission tomography with gamma camera in coincidence mode

    International Nuclear Information System (INIS)

    Hertel, A.; Hoer, G.

    1999-01-01

    Positron emission tomography using F-18 FDG has been estbalished in clinical diagnostics with first indications especially in oncology. To install a conventional PET tomography (dedicated PET) is financially costly and restricted to PET examinations only. Increasing demand for PET diagnostics on one hand and restricted financial resources in the health system on the other hand led industry to develop SPECT cameras to be operated in coincidence mode (camera PET) in order to offer nuclear medicine physicians cost-effective devices for PET diagnostic. At the same time camera PET is inferior to conventional PET regarding sensitivity and detection-efficiency for 511 keV photons. Does camera-PET offer a reliable alternative to conventional PET? The first larger comparative studies are now available, so a first apraisal about the technical clinical performance of camera-PET can be done. (orig.) [de

  19. Zero-mode waveguide nanophotonic structures for single molecule characterization

    Science.gov (United States)

    Crouch, Garrison M.; Han, Donghoon; Bohn, Paul W.

    2018-05-01

    Single-molecule characterization has become a crucial research tool in the chemical and life sciences, but limitations, such as limited concentration range, inability to control molecular distributions in space, and intrinsic phenomena, such as photobleaching, present significant challenges. Recent developments in non-classical optics and nanophotonics offer promising routes to mitigating these restrictions, such that even low affinity (K D ~ mM) biomolecular interactions can be studied. Here we introduce and review specific nanophotonic devices used to support single molecule studies. Optical nanostructures, such as zero-mode waveguides (ZMWs), are usually fabricated in thin gold or aluminum films and serve to confine the observation volume of optical microspectroscopy to attoliter to zeptoliter volumes. These simple nanostructures allow individual molecules to be isolated for optical and electrochemical analysis, even when the molecules of interest are present at high concentration (µM–mM) in bulk solution. Arrays of ZMWs may be combined with optical probes such as single molecule fluorescence, single molecule fluorescence resonance energy transfer, and fluorescence correlation spectroscopy for distributed analysis of large numbers of single-molecule reactions or binding events in parallel. Furthermore, ZMWs may be used as multifunctional devices, for example by combining optical and electrochemical functions in a single discrete architecture to achieve electrochemical ZMWs. In this review, we will describe the optical properties, fabrication, and applications of ZMWs for single-molecule studies, as well as the integration of ZMWs into systems for chemical and biochemical analysis.

  20. Stable Single-Mode Operation of Distributed Feedback Quantum Cascade Laser by Optimized Reflectivity Facet Coatings.

    Science.gov (United States)

    Wang, Dong-Bo; Zhang, Jin-Chuan; Cheng, Feng-Min; Zhao, Yue; Zhuo, Ning; Zhai, Shen-Qiang; Wang, Li-Jun; Liu, Jun-Qi; Liu, Shu-Man; Liu, Feng-Qi; Wang, Zhan-Guo

    2018-02-02

    In this work, quantum cascade lasers (QCLs) based on strain compensation combined with two-phonon resonance design are presented. Distributed feedback (DFB) laser emitting at ~ 4.76 μm was fabricated through a standard buried first-order grating and buried heterostructure (BH) processing. Stable single-mode emission is achieved under all injection currents and temperature conditions without any mode hop by the optimized antireflection (AR) coating on the front facet. The AR coating consists of a double layer dielectric of Al 2 O 3 and Ge. For a 2-mm laser cavity, the maximum output power of the AR-coated DFB-QCL was more than 170 mW at 20 °C with a high wall-plug efficiency (WPE) of 4.7% in a continuous-wave (CW) mode.

  1. Piezoelectric transducer parameter selection for exciting a single mode from multiple modes of Lamb waves

    International Nuclear Information System (INIS)

    Zhang Hai-Yan; Yu Jian-Bo

    2011-01-01

    Excitation and propagation of Lamb waves by using rectangular and circular piezoelectric transducers surface-bonded to an isotropic plate are investigated in this work. Analytical stain wave solutions are derived for the two transducer shapes, giving the responses of these transducers in Lamb wave fields. The analytical study is supported by a numerical simulation using the finite element method. Symmetric and antisymmetric components in the wave propagation responses are inspected in detail with respect to test parameters such as the transducer geometry, the length and the excitation frequency. By placing only one piezoelectric transducer on the top or the bottom surface of the plate and weakening the strength of one mode while enhancing the strength of the other modes to find the centre frequency, with which the peak wave amplitude ratio between the S0 and A0 modes is maximum, a single mode excitation from the multiple modes of the Lamb waves can be achieved approximately. Experimental data are presented to show the validity of the analyses. The results are used to optimize the Lamb wave detection system. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  2. Selective mode coupling in microring resonators for single mode semiconductor lasers

    Science.gov (United States)

    Arbabi, Amir

    Single mode semiconductor laser diodes have many applications in optical communications, metrology and sensing. Edge-emitting single mode lasers commonly use distributed feedback structures, or narrowband reflectors such as distributed Bragg reflectors (DBRs) and sampled grating distributed Bragg reflectors (SGDBRs). Compact, narrowband reflectors with high reflectivities are of interest to replace the commonly used DBRs and SGDBRs. This thesis presents our work on the simulation, design, fabrication, and characterization of devices operating based on the coupling of degenerate modes of a microring resonator, and investigation of the possibility of using them for improving the performance of laser diodes. In particular, we demonstrate a new type of compact, narrowband, on-chip reflector realized by selectively coupling degenerate modes of a microring resonator. For the simulation and design of reflective microring resonators, a fast and accurate analysis method is required. Conventional numerical methods for solving Maxwell's equations such as the finite difference time domain and the finite element method (FEM) provide accurate results but are computationally intense and are not suitable for the design of large 3D structures. We formulated a set of coupled mode equations that, combined with 2D FEM simulations, can provide a fast and accurate tool for the modeling and design of reflective microrings. We developed fabrication processing recipes and fabricated passive reflective microrings on silicon substrates with a silicon nitride core and silicon dioxide cladding. Narrowband single wavelength reflectors were realized which are 70 times smaller than a conventional DBR with the same bandwidth. Compared to the conventional DBR, they have faster roll-off, and no side modes. The smaller footprint saves real estate, reduces tuning power and makes these devices attractive as in-line mirrors for low threshold narrow linewidth laser diodes. Self-heating caused by material

  3. Single-mode theory of diffusive layers in thermohaline convection

    Science.gov (United States)

    Gough, D. O.; Toomre, J.

    1982-01-01

    A two-layer configuration of thermohaline convection is studied, with the principal aim of explaining the observed independence of the buoyancy-flux ratio on the stability parameter when the latter is large. Temperature is destabilizing and salinity is stabilizing, so diffusive interfaces separate the convecting layers. The convection is treated in the single-mode approximation, with a prescribed horizontal planform and wavenumber. Surveys of numerical solutions are presented for a selection of Rayleigh numbers R, stability parameters lambda and horizontal wavenumbers. The solutions yield a buoyancy flux ratio chi that is insensitive to lambda, in accord with laboratory experiments. However chi increases with increasing R, in contradiction to laboratory observations.

  4. Single-mode optical-waveguide fiber coupler.

    Science.gov (United States)

    Noda, J; Mikami, O; Minakata, M; Fukuma, M

    1978-07-01

    A single-mode fiber coupler to the Ti diffused LiNbO(3) strip waveguide has been devised. The influences of three axial displacements and two angular misalignments on the coupling efficiency have been investigated at 6328-A wavelength. The coupler has a special feature wherein coupling degradation caused by fiber displacement after connection can be recovered to the initial state. The total optical insertion loss is 3 dB after fixing the fiber to the LiNbO(3) strip waveguide, which is 4 microm wide and 8 mm long.

  5. Mid-Infrared Continuously Tunable Single Mode VECSEL

    Science.gov (United States)

    Khiar, A.; Rahim, M.; Felder, F.; Fill, M.; Zogg, H.

    2011-12-01

    Tunable mid-infrared vertical external cavity surface emitting lasers were developed for the wavelength range around 3.8-3.9 μm and 3.2-3.3 μm, respectively. The devices are based on lead salt materials epitaxially grown by MBE on a Si substrate. The active part consists of PbSe QW in a PbSrSe host layer. Both devices are operated around -20 °C and have output power of several 10 mW. By changing the cavity length, a single mode hop free tuning range up to 80 cm-1 is achieved.

  6. Unified Scattering Parameters formalism in terms of Coupled-Mode Theory for investigating hybrid single-mode/two-mode photonic interconnects

    Directory of Open Access Journals (Sweden)

    Boucher Yann G.

    2017-01-01

    Full Text Available In terms of Linear Algebra, a directional coupler between a single-mode waveguide and a two-mode waveguide can be thought of as formally equivalent to a set of three mutually coupled single-mode waveguides. Its responses, easily derived in the frame of ternary Coupled-Mode Theory, are used to establish analytically the scattering parameters of a hybrid ring-based modal multiplexer.

  7. Optically pumped semiconductor lasers: Conception and characterization of a single mode source for Cesium atoms manipulation

    International Nuclear Information System (INIS)

    Cocquelin, B.

    2009-02-01

    Lasers currently used in atomic clocks or inertial sensors are suffering from a lack of power, narrow linewidth or compactness for future spatial missions. Optically pumped semiconductor lasers, which combine the approach of classical solid state lasers and the engineering of semiconductor laser, are considered here as a candidate to a metrological laser source dedicated to the manipulation of Cesium atoms in these instruments. These lasers have demonstrated high power laser emission in a circular single transverse mode, as well as single longitudinal mode emission, favoured by the semiconductor structure and the external cavity design. We study the definition and the characterization of a proper semiconductor structure for the cooling and the detection of Cesium atoms at 852 nm. A compact and robust prototype tunable on the Cesium D2 hyperfine structure is built. The laser frequency is locked to an atomic transition thanks to a saturated absorption setup. The emission spectral properties are investigated, with a particular attention to the laser frequency noise and the laser linewidth. Finally, we describe and model the thermal properties of the semiconductor structure, which enables the simulation of the laser power characteristic. The experimental parameters are optimised to obtain the maximum output power with our structure. Thanks to our analysis, we propose several ways to overcome these limitations, by reducing the structure heating. (authors)

  8. Multiplexing 200 spatial modes with a single hologram

    Science.gov (United States)

    Rosales-Guzmán, Carmelo; Bhebhe, Nkosiphile; Mahonisi, Nyiku; Forbes, Andrew

    2017-11-01

    The on-demand tailoring of light's spatial shape is of great relevance in a wide variety of research areas. Computer-controlled devices, such as spatial light modulators (SLMs) or digital micromirror devices, offer a very accurate, flexible and fast holographic means to this end. Remarkably, digital holography affords the simultaneous generation of multiple beams (multiplexing), a tool with numerous applications in many fields. Here, we provide a self-contained tutorial on light beam multiplexing. Through the use of several examples, the readers will be guided step by step in the process of light beam shaping and multiplexing. Additionally, we provide a quantitative analysis on the multiplexing capabilities of SLMs to assess the maximum number of beams that can be multiplexed on a single SLM, showing approximately 200 modes on a single hologram.

  9. Coupled-Mode Theory derivation of the formal equivalence between a three-mode waveguide and a set of three mutually coupled single-mode waveguides

    Directory of Open Access Journals (Sweden)

    Boucher Yann G.

    2017-01-01

    Full Text Available The formal identification between a two-mode waveguide and a system of two mutually coupled single-mode waveguides stems from the symmetries of the evolution operator. When the gap tends to zero, the super-modes of the coupled system merge continuously into the modes of the multimode waveguide. For modelling purposes, it is very tempting to extend the analogy to three-mode waveguides (and beyond. But not without some precautions…

  10. Demonstration of orbital angular momentum (OAM) modes emission from a silicon photonic integrated device for 20 Gbit/s QPSK carrying data transmission in few-mode fiber

    DEFF Research Database (Denmark)

    Liu, Jun; Li, Shimao; Ding, Yunhong

    2016-01-01

    We experimentally demonstrate orbital angular momentum (OAM) mode emission from a high emission efficiency OAM emitter for 20 Gbit/s QPSK carrying data transmission in few-mode fiber (FMF). Two modes propagate through a 3.6km three-mode FMF with measured OSNR penalties less than 4 dB at a BER of ...

  11. Single CFTA Based Current-Mode Universal Biquad Filter

    Directory of Open Access Journals (Sweden)

    S.V. Singh

    2016-12-01

    Full Text Available This paper introduces a new current-mode (CM universal biquad filter structure with optimum number of active and passive elements. In the design, the proposed circuit uses a single active element namely, current follower trans-conductance amplifier (CFTA and two grounded capacitors as passive elements. The main feature of the proposed circuit is that it can realize all five standard filtering functions such as low pass (LP, band pass (BP, high pass (HP, band stop (BS and all pass (AP responses across an explicit high impedance output terminal through the appropriate selection of three inputs. In addition, the same circuit is also capable to simultaneously realize three filtering functions (LP, BP and HP by the use of single current input signal. Moreover, the proposed structure is suited for low voltage, low power operations and offers the feature of electronic tunability of pole-frequency and quality factor. Further to extend the utility of the proposed circuit block higher order current-mode filters are also realized through direct cascading. A detailed non-ideal and parasitic study is also included. The performance of the circuits has been examined using standard 0.25 μ m CMOS parameters from TSMC.

  12. Mid-infrared performance of single mode chalcogenide fibers

    Science.gov (United States)

    Cook, Justin; Sincore, Alex; Tan, Felix; El Halawany, Ahmed; Riggins, Anthony; Shah, Lawrence; Abouraddy, Ayman F.; Richardson, Martin C.; Schepler, Kenneth L.

    2018-02-01

    Due to the intrinsic absorption edge in silica near 2.4 μm, more exotic materials are required to transmit laser power in the IR such as fluoride or chalcogenide glasses (ChGs). In particular, ChG fibers offer broad IR transmission with low losses fibers at four different infrared wavelengths: 2053 nm, 2520 nm and 4550 nm. Polymer clad ChG fibers were drawn with 12.3 μm and 25 μm core diameters. Testing at 2053 nm was accomplished using a > 15 W, CW Tm:fiber laser. Power handling up to 10.2 W with single mode beam quality has been demonstrated, limited only by the available Tm:fiber output power. Anti-reflective coatings were successfully deposited on the ChG fiber facets, allowing up to 90.6% transmission with 12.2 MW/cm2 intensity on the facet. Single mode guidance at 4550 nm was also demonstrated using a quantum cascade laser (QCL). A custom optical system was constructed to efficiently couple the 0.8 NA QCL radiation into the 0.2 NA ChG fiber, allowing for a maximum of 78% overlap between the QCL radiation and fundamental mode of the fiber. With an AR-coated, 25 μm core diameter fiber, >50 mW transmission was demonstrated with > 87% transmission. Finally, we present results on fiber coupling from a free space Cr:ZnSe resonator at 2520 nm.

  13. Directional emission from a single plasmonic scatterer

    NARCIS (Netherlands)

    Coenen, T.; Bernal Arango, F.; Koenderink, A.F.; Polman, A.

    2014-01-01

    Directing light emission is key for many applications in photonics and biology. Optical antennas made from nanostructured plasmonic metals are suitable candidates for this purpose but designing antennas with good directional characteristics can be challenging, especially when they consist of

  14. Non-Markovian spontaneous emission from a single quantum dot

    DEFF Research Database (Denmark)

    Madsen, Kristian Høeg; Ates, Serkan; Lund-Hansen, Toke

    2011-01-01

    We observe non-Markovian dynamics of a single quantum dot when tuned into resonance with a cavity mode. Excellent agreement between experiment and theory is observed providing the first quantitative description of such a system....

  15. Identifying modes of large whispering-gallery mode resonators from the spectrum and emission pattern

    DEFF Research Database (Denmark)

    Schunk, Gerhard; Fuerst, Josef U.; Förtsch, Michael

    2014-01-01

    Identifying the mode numbers in whispering-gallery mode resonators (WGMRs) is important for tailoring them to experimental needs. Here we report on a novel experimental mode analysis technique based on the combination of frequency analysis and far-field imaging for high mode numbers of large WGMR...

  16. 3-4.5 μm continuously tunable single mode VECSEL

    Science.gov (United States)

    Fill, M.; Felder, F.; Rahim, M.; Khiar, A.; Zogg, H.

    2012-11-01

    We present continuously tunable Vertical External Cavity Surface Emitting Lasers (VECSEL) in the mid-infrared. The structure based on IV-VI semiconductors is epitaxially grown on a Si-substrates. The VECSEL emit one single mode, which is mode hop-free tunable over 50-100 nm around the center wavelength. In this work, two different devices are presented, emitting at 3.4 μm and 3.9 μm, respectively. The lasers operate near room temperature with thermoelectric stabilization. They are optically pumped, yielding an output power >10 mWp. The axial symmetric emission beam has a half divergence angle of <3.3∘.

  17. On-chip Mode Multiplexer Based on a Single Grating Coupler

    DEFF Research Database (Denmark)

    Ding, Yunhong; Ou, Haiyan; Xu, Jing

    2012-01-01

    A two-mode multiplexer based on a single grating coupler is proposed and demonstrated on a silicon chip. The LP01 and LP11 modes of a few-mode fiber are excited from TE0 and TE1 silicon waveguide modes.......A two-mode multiplexer based on a single grating coupler is proposed and demonstrated on a silicon chip. The LP01 and LP11 modes of a few-mode fiber are excited from TE0 and TE1 silicon waveguide modes....

  18. Mode Selection for a Single-Frequency Fiber Laser

    Science.gov (United States)

    Liu, Jian

    2010-01-01

    A superstructured fiber-grating-based mode selection filter for a single-frequency fiber laser eliminates all free-space components, and makes the laser truly all-fiber. A ring cavity provides for stable operations in both frequency and power. There is no alignment or realignment required. After the fibers and components are spliced together and packaged, there is no need for specially trained technicians for operation or maintenance. It can be integrated with other modules, such as telescope systems, without extra optical alignment due to the flexibility of the optical fiber. The filter features a narrow line width of 1 kHz and side mode suppression ratio of 65 dB. It provides a high-quality laser for lidar in terms of coherence length and signal-to-noise ratio, which is 20 dB higher than solid-state or microchip lasers. This concept is useful in material processing, medical equipment, biomedical instrumentation, and optical communications. The pulse-shaping fiber laser can be directly used in space, airborne, and satellite applications including lidar, remote sensing, illuminators, and phase-array antenna systems.

  19. Ultrasonic Motor Using Bending Modes with Single Foot

    Directory of Open Access Journals (Sweden)

    Xiaohui Yang

    2013-01-01

    Full Text Available A new ultrasonic motor using bending modes with single foot is proposed in this study. Two groups of PZT elements are clamped between two horns and two ending caps, respectively, by bolts. Two horns are connected by the driving foot in the middle of the motor. Two orthogonal 3rd bending vibrations of the motor are superimposed and generate elliptical movement at the driving foot. The structure and working principle of the proposed motor are introduced. The structure parameters of the motor are obtained via the ANSYS software. A prototype is fabricated and tested using an impedance analyzer and a scanning laser Doppler vibrometer. The maximum mechanical output force and power of the prototype are measured to be 23 N and 2.9 W, respectively.

  20. Single-Mode, Distributed Feedback Interband Cascade Lasers

    Science.gov (United States)

    Frez, Clifford F. (Inventor); Borgentun, Carl E. (Inventor); Briggs, Ryan M. (Inventor); Bagheri, Mahmood (Inventor); Forouhar, Siamak (Inventor)

    2016-01-01

    Single-mode, distributed feedback interband cascade lasers (ICLs) using distributed-feedback gratings (e.g., lateral Bragg gratings) and methods of fabricating such ICLs are provided. The ICLs incorporate distributed-feedback gratings that are formed above the laser active region and adjacent the ridge waveguide (RWG) of the ICL. The ICLs may incorporate a double-ridge system comprising an optical confinement structure (e.g., a RWG) disposed above the laser active region that comprises the first ridge of the double ridge system, a DFB grating (e.g., lateral Bragg grating) disposed above the laser active region and adjacent the optical confinement structure, and an electric confinement structure that passes at least partially through the laser active region and that defines the boundary of the second ridge comprises and the termination of the DFB grating.

  1. Picosecond chirped pulse compression in single-mode fibers

    International Nuclear Information System (INIS)

    Wenhua Cao; Youwei Zhang

    1995-01-01

    In this paper, the nonlinear propagation of picosecond chirped pulses in single mode fibers has been investigated both analytically and numerically. Results show that downchirped pulses can be compressed owing to normal group-velocity dispersion. The compression ratio depends both on the initial peak power and on the initial frequency chirp of the input pulse. While the compression ratio depends both on the initial peak power and on the initial frequency chirp of the input pulse. While the compression ratio increases with the negative frequency chirp, it decreases with the initial peak power of the input pulse. This means that the self-phase modulation induced nonlinear frequency chirp which is linear and positive (up-chirp) over a large central region of the pulse and tends to cancel the initial negative chirp of the pulse. It is also shown that, as the negative chirped pulse compresses temporally, it synchronously experiences a spectral narrowing

  2. GaSb-based single-mode distributed feedback lasers for sensing (Conference Presentation)

    Science.gov (United States)

    Gupta, James A.; Bezinger, Andrew; Lapointe, Jean; Poitras, Daniel; Aers, Geof C.

    2017-02-01

    GaSb-based tunable single-mode diode lasers can enable rapid, highly-selective and highly-sensitive absorption spectroscopy systems for gas sensing. In this work, single-mode distributed feedback (DFB) laser diodes were developed for the detection of various trace gases in the 2-3.3um range, including CO2, CO, HF, H2S, H2O and CH4. The lasers were fabricated using an index-coupled grating process without epitaxial regrowth, making the process significantly less expensive than conventional DFB fabrication. The devices are based on InGaAsSb/AlGaAsSb separate confinement heterostructures grown on GaSb by molecular beam epitaxy. DFB lasers were produced using a two step etch process. Narrow ridge waveguides were first defined by optical lithography and etched into the semiconductor. Lateral gratings were then defined on both sides of the ridge using electron-beam lithography and etched to produce the index-grating. Effective index modeling was used to optimize the ridge width, etch depths and the grating pitch to ensure single-lateral-mode operation and adequate coupling strength. The effective index method was further used to simulate the DFB laser emission spectrum, based on a transfer matrix model for light transmission through the periodic structure. The fabricated lasers exhibit single-mode operation which is tunable through the absorption features of the various target gases by adjustment of the drive current. In addition to the established open-path sensing applications, these devices have great potential for optoelectronic integrated gas sensors, making use of integrated photodetectors and possibly on-chip Si photonics waveguide structures.

  3. Fracto-emission from single fibres of Kevlar

    Science.gov (United States)

    Dickinson, J. T.; Jahan-Latibari, A.; Jensen, L. C.

    1985-01-01

    Fracto-emission (FE) is the emission of particles (e.g. electrons, ions and photons) during and following fracture. In this paper, we present data on electron emission (EE) and positive ion emission (PIE) from the tensile fracture of Kevlar single fibers. The fibers were initially fractured in pure tension, where a stranded form of fracture was observed, often with multiple peaks spread over several hundred microseconds. The loading condition was then changed by stretching and breaking the fibers over a dull metal edge. With this change in the loading, different forms of fracture were observed, each with distinctive forms of emission curves. When fracture was accompanied by extensive fibril formation, total emission was high and both EE and PIE decay times were long relative to fractures in which little fibril formation occurred. The results of this study suggest that FE has some applicability as a tool for the detection of fracture mechanisms of single fibers.

  4. Emissions from Ethanol-Gasoline Blends: A Single Particle Perspective

    Directory of Open Access Journals (Sweden)

    Peter H. McMurry

    2011-06-01

    Full Text Available Due to its agricultural origin and function as a fuel oxygenate, ethanol is being promoted as an alternative biomass-based fuel for use in spark ignition engines, with mandates for its use at state and regional levels. While it has been established that the addition of ethanol to a fuel reduces the particulate mass concentration in the exhaust, little attention has been paid to changes in the physicochemical properties of the emitted particles. In this work, a dynamometer-mounted GM Quad-4 spark ignition engine run without aftertreatment at 1,500 RPM and 100% load was used with four different fuel blends, containing 0, 20, 40 and 85 percent ethanol in gasoline. This allowed the effects of the fuel composition to be isolated from other effects. Instrumentation employed included two Aerosol Time-of-Flight Mass Spectrometers covering different size ranges for analysis of single particle composition, an Aethalometer for black carbon, a Scanning Mobility Particle Sizer for particle size distributions, a Photoelectric Aerosol Sensor for particle-bound polycyclic aromatic hydrocarbon (PAH species and gravimetric filter measurements for particulate mass concentrations. It was found that, under the conditions investigated here, additional ethanol content in the fuel changes the particle size distribution, especially in the accumulation mode, and decreases the black carbon and total particulate mass concentrations. The molecular weight distribution of the PAHs was found to decrease with added ethanol. However, PAHs produced from higher ethanol-content fuels are associated with NO2− (m/z—46 in the single-particle mass spectra, indicating the presence of nitro-PAHs. Compounds associated with the gasoline (e.g., sulfur-containing species are diminished due to dilution as ethanol is added to the fuel relative to those associated with the lubricating oil (e.g., calcium, zinc, phosphate in the single particle spectra. These changes have potential

  5. Combustion Mode Design with High Efficiency and Low Emissions Controlled by Mixtures Stratification and Fuel Reactivity

    Directory of Open Access Journals (Sweden)

    Hu eWang

    2015-08-01

    Full Text Available This paper presents a review on the combustion mode design with high efficiency and low emissions controlled by fuel reactivity and mixture stratification that have been conducted in the authors’ group, including the charge reactivity controlled homogeneous charge compression ignition (HCCI combustion, stratification controlled premixed charge compression ignition (PCCI combustion, and dual-fuel combustion concepts controlled by both fuel reactivity and mixture stratification. The review starts with the charge reactivity controlled HCCI combustion, and the works on HCCI fuelled with both high cetane number fuels, such as DME and n-heptane, and high octane number fuels, such as methanol, natural gas, gasoline and mixtures of gasoline/alcohols, are reviewed and discussed. Since single fuel cannot meet the reactivity requirements under different loads to control the combustion process, the studies related to concentration stratification and dual-fuel charge reactivity controlled HCCI combustion are then presented, which have been shown to have the potential to achieve effective combustion control. The efforts of using both mixture and thermal stratifications to achieve the auto-ignition and combustion control are also discussed. Thereafter, both charge reactivity and mixture stratification are then applied to control the combustion process. The potential and capability of thermal-atmosphere controlled compound combustion mode and dual-fuel reactivity controlled compression ignition (RCCI/highly premixed charge combustion (HPCC mode to achieve clean and high efficiency combustion are then presented and discussed. Based on these results and discussions, combustion mode design with high efficiency and low emissions controlled by fuel reactivity and mixtures stratification in the whole operating range is proposed.

  6. Identifying modes of large whispering-gallery mode resonators from the spectrum and emission pattern.

    Science.gov (United States)

    Schunk, Gerhard; Fürst, Josef U; Förtsch, Michael; Strekalov, Dmitry V; Vogl, Ulrich; Sedlmeir, Florian; Schwefel, Harald G L; Leuchs, Gerd; Marquardt, Christoph

    2014-12-15

    Identifying the mode numbers in whispering-gallery mode resonators (WGMRs) is important for tailoring them to experimental needs. Here we report on a novel experimental mode analysis technique based on the combination of frequency analysis and far-field imaging for high mode numbers of large WGMRs. The radial mode numbers q and the angular mode numbers p = ℓ-m are identified and labeled via far-field imaging. The polar mode numbers ℓ are determined unambiguously by fitting the frequency differences between individual whispering gallery modes (WGMs). This allows for the accurate determination of the geometry and the refractive index at different temperatures of the WGMR. For future applications in classical and quantum optics, this mode analysis enables one to control the narrow-band phase-matching conditions in nonlinear processes such as second-harmonic generation or parametric down-conversion.

  7. Enhancement mode single electron transistor in pure silicon

    Science.gov (United States)

    Hu, Binhui; Yang, C. H.; Jones, G. M.; Yang, M. J.

    2007-03-01

    Solid state implementations of lateral qubits offer the advantage of being scalable and can be easily integrated by existing main stream IC technologies. In addition, the two Zeeman states of an electron spin in a quantum dot (QD) provide a promising candidate for a qubit. Spins in lateral QDs in the GaAs/AlGaAs single electron transistors (SETs) have been intensively investigated. In contrast, Si provides a number of advantages, including long spin coherence time, large g-factor, and small spin-orbit coupling effect. We have demonstrated Si SET in the few electron regime.* In this talk, we will report the isolation of a single electron in a Si QD using a fabrication technique that incorporates the standard Al/SiO2/Si system with an enhancement mode SET structure. Our SET is built in highly resistive Si substrates with bilayer gates. The high purity Si minimizes the potential disorder from impurities. The top gate induces 2D electrons, and several side gates help define the tunneling barriers, fine tune the shape of the QD, and control the number of electrons in it. We will discuss the operating principle, computer simulation, and low temperature transport data. *APPLIED PHYSICS LETTERS 89, 073106 (2006)

  8. Strain sensor based on gourd-shaped single-mode-multimode-single-mode hybrid optical fibre structure.

    Science.gov (United States)

    Tian, Ke; Farrell, Gerald; Wang, Xianfan; Yang, Wenlei; Xin, Yifan; Liang, Haidong; Lewis, Elfed; Wang, Pengfei

    2017-08-07

    A fibre-optic strain sensor based on a gourd-shaped joint multimode fibre (MMF) sandwiched between two single-mode fibres (SMFs) is described both theoretically and experimentally. The cladding layers of the two MMFs are reshaped to form a hemisphere using an electrical arc method and spliced together, yielding the required gourd shape. The gourd-shaped section forms a Fabry-Perot cavity between the ends of two adjacent but non-contacting multimode fibres' core. The effectiveness of the multimode interference based on the Fabry-Perot interferometer (FPI) formed within the multimode inter-fibre section is greatly improved resulting in an experimentally determined strain sensitivity of -2.60 pm/με over the range 0-1000 με. The sensing characteristics for temperature and humidity of this optical fibre strain sensor are also investigated.

  9. DBD plasma source operated in single-filamentary mode for therapeutic use in dermatology

    Energy Technology Data Exchange (ETDEWEB)

    Rajasekaran, Priyadarshini; Mertmann, Philipp; Bibinov, Nikita; Awakowicz, Peter [Institute for Electrical Engineering and Plasma Technology, Ruhr-Universitaet Bochum, Universitaetsstr. 150, 44801 Bochum (Germany); Wandke, Dirk [CINOGY GmbH, Max-Naeder-Str. 15, 37114 Duderstadt (Germany); Vioel, Wolfgang, E-mail: rajasekaran@aept.rub.d, E-mail: mertmann@aept.rub.d, E-mail: Nikita.Bibinov@rub.d, E-mail: dirk.wandke@cinogy.co, E-mail: vioel@hawk-hhg.d, E-mail: awakowicz@aept.rub.d [University of Applied Sciences and Arts, Faculty of Natural Sciences and Technology, Von-Ossietzky-Str. 99, 37085 Goettingen (Germany)

    2009-11-21

    Our dielectric barrier discharge (DBD) plasma source for bio-medical application comprises a copper electrode covered with ceramic. Objects of high capacitance such as the human body can be used as the opposite electrode. In this study, the DBD source is operated in single-filamentary mode using an aluminium spike as the opposite electrode, to imitate the conditions when the discharge is ignited on a raised point, such as hair, during therapeutic use on the human body. The single-filamentary discharge thus obtained is characterized using optical emission spectroscopy, numerical simulation, voltage-current measurements and microphotography. For characterization of the discharge, averaged plasma parameters such as electron distribution function and electron density are determined. Fluxes of nitric oxide (NO), ozone (O{sub 3}) and photons reaching the treated surface are simulated. The calculated fluxes are finally compared with corresponding fluxes used in different bio-medical applications.

  10. Performance and Emissions of a Small Compression Ignition Engine Run on Dual-fuel Mode (Diesel-Raw biogas)

    Science.gov (United States)

    Ambarita, H.; Sinulingga, E. P.; Nasution, M. KM; Kawai, H.

    2017-03-01

    In this work, a compression ignition (CI) engine is tested in dual-fuel mode (Diesel-Raw biogas). The objective is to examine the performance and emission characteristics of the engine when some of the diesel oil is replaced by biogas. The specifications of the CI engine are air cooled single horizontal cylinder, four strokes, and maximum output power of 4.86 kW. It is coupled with a synchronous three phase generator. The load, engine revolution, and biogas flow rate are varied from 600 W to 1500 W, 1000 rpm to 1500 rpm, 0 to 6 L/minute, respectively. The electric power, specific fuel consumption, thermal efficiency, gas emission, and diesel replacement ratio are analyzed. The results show that there is no significant difference of the power resulted by CI run on dual-fuel mode in comparison with pure diesel mode. However, the specific fuel consumption and efficiency decrease significantly as biogas flow rate increases. On the other hand, emission of the engine on dual-fuel mode is better. The main conclusion can be drawn is that CI engine without significant modification can be operated perfectly in dual-fuel mode and diesel oil consumption can be decreased up to 87.5%.

  11. Effect of localized surface-plasmon mode on exciton transport and radiation emission in carbon nanotubes.

    Science.gov (United States)

    Roslyak, Oleksiy; Cherqui, Charles; Dunlap, David H; Piryatinski, Andrei

    2014-07-17

    We report on a general theoretical approach to study exciton transport and emission in a single-walled carbon nanotube (SWNT) in the presence of a localized surface-plasmon (SP) mode within a metal nanoparticle interacting via near-field coupling. We derive a set of quantum mechanical equations of motion and approximate rate equations that account for the exciton, SP, and the environmental degrees of freedom. The material equations are complemented by an expression for the radiated power that depends on the exciton and SP populations and coherences, allowing for an examination of the angular distribution of the emitted radiation that would be measured in experiment. Numerical simulations for a (6,5) SWNT and cone-shaped Ag metal tip (MT) have been performed using this methodology. Comparison with physical parameters shows that the near-field interaction between the exciton-SP occurs in a weak coupling regime, with the diffusion processes being much faster than the exciton-SP population exchange. In such a case, the effect of the exciton population transfer to the MT with its subsequent dissipation (i.e., the Förster energy transfer) is to modify the exciton steady state distribution while reducing the equilibration time for excitons to reach a steady sate distribution. We find that the radiation distribution is dominated by SP emission for a SWNT-MT separation of a few tens of nanometers due to the fast SP emission rate, whereas the exciton-SP coherences can cause its rotation.

  12. Single photon emission from ZnO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Sumin; Ton-That, Cuong; Phillips, Matthew R.; Aharonovich, Igor, E-mail: igor.aharonovich@uts.edu.au [School of Physics and Advanced Materials, University of Technology Sydney, Ultimo, New South Wales 2007 (Australia); Johnson, Brett C. [Centre for Quantum Computation and Communication Technology, School of Physics, University of Melbourne, Parkville, Victoria 3010 (Australia); Castelletto, Stefania [School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University, Melbourne, Victoria 3000 (Australia)

    2014-06-30

    Room temperature single photon emitters are very important resources for photonics and emerging quantum technologies. In this work, we study single photon emission from defect centers in 20 nm zinc oxide (ZnO) nanoparticles. The emitters exhibit bright broadband fluorescence in the red spectral range centered at 640 nm with polarized excitation and emission. The studied emitters showed continuous blinking; however, bleaching can be suppressed using a polymethyl methacrylate coating. Furthermore, hydrogen termination increased the density of single photon emitters. Our results will contribute to the identification of quantum systems in ZnO.

  13. Directional emission of single photons from small atomic samples

    DEFF Research Database (Denmark)

    Miroshnychenko, Yevhen; V. Poulsen, Uffe; Mølmer, Klaus

    2013-01-01

    We provide a formalism to describe deterministic emission of single photons with tailored spatial and temporal profiles from a regular array of multi-level atoms. We assume that a single collective excitation is initially shared by all the atoms in a metastable atomic state, and that this state i...... is coupled by a classical laser field to an optically excited state which rapidly decays to the ground atomic state. Our model accounts for the different field polarization components via re-absorption and emission of light by the Zeeman manifold of optically excited states.......We provide a formalism to describe deterministic emission of single photons with tailored spatial and temporal profiles from a regular array of multi-level atoms. We assume that a single collective excitation is initially shared by all the atoms in a metastable atomic state, and that this state...

  14. Estimating accidental coincidences for pixelated PET detectors and singles list-mode acquisition

    International Nuclear Information System (INIS)

    Rafecas, M.; Torres, I.; Spanoudaki, V.; McElroy, D.P.; Ziegler, S.I.

    2007-01-01

    We have studied the validity of random estimation techniques for various low energy thresholds (LETs) and single list-mode data sets in small animal PET. While a LET below 255 keV helps to increase the sensitivity, it also results in an increase of random coincidences and inter-crystal scatter (ICS). The study is carried out for MADPET-II, a dual-layer positron emission tomography (PET) scanner prototype consisting of LSO crystals read out individually by APDs. The data are acquired in singles list-mode format, and coincidences are computed post-acquisition. To estimate randoms, we have used the delayed coincidence window method (DW), and the singles rate model (SR). Various phantoms were simulated using GATE. For LETs under 255 keV, the number of random events R, estimated using the SR and the DW methods, is larger than the number of randoms which was directly computed from GATE simulations, and R(SR)>R(DW)>R(GATE). The higher the LET, the smaller the overestimation. For LETs >255 keV, R(DW)/R(GATE) ∼1. If scattered singles were excluded from the file, this discrepancy between R(DW or SR) and R(GATE) significantly diminished. This fact points out to ICS as the effect responsible for the mismatch, since for LETs lower than 255 keV, all singles related to an ICS event can be detected independently, thus altering the singles rate. Therefore, if low LETs are used, random estimation techniques should account for ICS

  15. Modeling bidirectionally coupled single-mode semiconductor lasers

    International Nuclear Information System (INIS)

    Mulet, Josep; Masoller, Cristina; Mirasso, Claudio R.

    2002-01-01

    We develop a dynamical model suitable for the description of two mutually coupled semiconductor lasers in a face-to-face configuration. Our study considers the propagation of the electric field along the compound system as well as the evolution of the carrier densities within each semiconductor laser. Mutual injection, passive optical feedback, and multiple reflections are accounted for in this framework, although under weak to moderate coupling conditions. We systematically describe the effect of the coupling strength on the spectrum of monochromatic solutions and on the respective dynamical behavior. By assuming single-longitudinal-mode operation, weak mutual coupling and slowly varying approximation, the dynamical model can be reduced to rate equations describing the mutual injection from one laser to its counterpart and vice versa. A good agreement between the complete and simplified models is found for small coupling. For larger coupling, higher-order terms lead to a smaller threshold reduction, reflected itself in the spectrum of the monochromatic solutions and in the dynamics of the optical power

  16. Comparison of high power large mode area and single mode 1908nm Tm-doped fiber lasers

    Science.gov (United States)

    Johnson, Benjamin R.; Creeden, Daniel; Limongelli, Julia; Pretorius, Herman; Blanchard, Jon; Setzler, Scott D.

    2016-03-01

    We compare large mode area (LMA) and single-mode (SM) double-clad fiber geometries for use in high power 1908nm fiber lasers. With a simple end-pumped architecture, we have generated 100W of 1908nm power with LMA fiber at 40% optical efficiency and 117W at 52.2% optical efficiency with single-mode fiber. We show the LMA fiber is capable of generating >200W and the SM fiber is capable of >300W at 1908nm. In all cases, the fiber lasers are monolithic power-oscillators with no free-space coupling.

  17. Highly efficient high power single-mode fiber amplifier utilizing the distributed mode filtering bandgap rod fiber

    DEFF Research Database (Denmark)

    Laurila, Marko; Alkeskjold, Thomas T.; Jørgensen, Mette Marie

    2012-01-01

    We report on an ytterbium doped single mode distributed mode filtering rod fiber in an amplifier configuration delivering high average output power, up to 292 watts, using a mode-locked 30ps source at 1032nm with good power conversion efficiency. We study the modal stability of the output beam...... at high average output power levels and demonstrate a 44% power improvement before the threshold-like onset of mode instabilities by operating the rod fiber in a leaky waveguide regime. We investigate the guiding dynamics of the rod fiber and explain the improved performance by thermally induced...

  18. Single photon infrared emission spectroscopy: a study of IR emission from UV laser excited PAHs between 3 and 15 micrometers

    Science.gov (United States)

    Cook, D. J.; Schlemmer, S.; Balucani, N.; Wagner, D. R.; Harrison, J. A.; Steiner, B.; Saykally, R. J.

    1998-01-01

    Single-photon infrared emission spectroscopy (SPIRES) has been used to measure emission spectra from polycyclic aromatic hydrocarbons (PAHs). A supersonic free-jet expansion has been used to provide emission spectra of rotationally cold and vibrationally excited naphthalene and benzene. Under these conditions, the observed width of the 3.3-micrometers (C-H stretch) band resembles the bandwidths observed in experiments in which emission is observed from naphthalene with higher rotational energy. To obtain complete coverage of IR wavelengths relevant to the unidentified infrared bands (UIRs), UV laser-induced desorption was used to generate gas-phase highly excited PAHs. Lorentzian band shapes were convoluted with the monochromator-slit function in order to determine the widths of PAH emission bands under astrophysically relevant conditions. Bandwidths were also extracted from bands consisting of multiple normal modes blended together. These parameters are grouped according to the functional groups mostly involved in the vibration, and mean bandwidths are obtained. These bandwidths are larger than the widths of the corresponding UIR bands. However, when the comparison is limited to the largest PAHs studied, the bandwidths are slightly smaller than the corresponding UIR bands. These parameters can be used to model emission spectra from PAH cations and cations of larger PAHs, which are better candidate carriers of the UIRs.

  19. Investigation of single-mode and multi-mode hydromagnetic Rayleigh-Taylor instability in planar geometry

    International Nuclear Information System (INIS)

    Roderick, N.F.; Cochrane, K.; Douglas, M.R.

    1998-01-01

    Previous investigations carried out to study various methods of seeding the hydromagnetic Rayleigh-Taylor instability in magnetohydrodynamic simulations showed features similar to those seen in hydrodynamic calculations. For periodic single-mode initiations the results showed the appearance of harmonics as the single modes became nonlinear. For periodic multi-mode initiations new modes developed that indicated the presence of mode coupling. The MHD simulations used parameters of the high velocity large radius z-pinch experiments performed in the Z-accelerator at Sandia National Laboratories. The cylindrical convergent geometry and variable acceleration of these configurations made comparison with analytic, developed for planar geometry with constant acceleration, difficult. A set of calculations in planar geometry using constant current to produce acceleration and parameters characteristic of the cylindrical implosions has been performed to allow a better comparison. Results of these calculations, comparison with analytic theory, and comparison with the cylindrical configuration calculations will be discussed

  20. Tripartite entanglement of bosonic systems in a noninertial frame beyond the single- mode approximation

    Directory of Open Access Journals (Sweden)

    M Soltani

    2015-12-01

    Full Text Available In this work, we generalize the entanglement of three-qbit Bosonic systems beyond the single-mode approximation when one of the observers is accelerated. For this purpose, we review the effects of acceleration on field modes and quantum states. The single-mode approximation and beyond the single-mode approximation methods are introduced. After this brief introduction, the main problem of this paper, tripartite entanglement of bosonic systems in a noninertial frame beyond the single- mode approximation is investigated. The tripartite entangled states have different classes with GHZ and W states being most important. Here, we choose &pi-tangle as a measure of tripartite entanglement. If the three parties share GHZ state, the corresponding &pi-tangle will increase by increasing acceleration for some Unruh modes. This phenomenon, increasing entanglement, has never been observed in the single-mode approximation for bosonic case. Moreover, the &pi-tangle dose not exhibit a monotonic behavior with increasing acceleration. In the infinite acceleration limit, the &pi-tangle goes to different nonzero values for distinct Unruh modes. Unlike GHZ state, the entanglement of the W state shows only monotonically increasing and decreasing behaviors with increasing acceleration. Also, the entanglement for all possible choices of Unruh modes approaches only 0.176 in the high acceleration limit. Therefore, according to the quantum entanglement, there is no distinction between the single-mode approximation and beyond the single-mode approximation methods in this limit.

  1. Detecting mode hopping in single-longitudinal-mode fiber ring lasers based on an unbalanced fiber Michelson interferometer.

    Science.gov (United States)

    Ma, Mingxiang; Hu, Zhengliang; Xu, Pan; Wang, Wei; Hu, Yongming

    2012-10-20

    A method of detecting mode hopping for single-longitudinal-mode (SLM) fiber ring lasers has been proposed and experimentally demonstrated. The method that is based on an unbalanced Michelson interferometer (MI) utilizing phase generated carrier modulation instantly transforms mode-hopping dynamics into steep phase changes of the interferometer. Multiform mode hops in an SLM erbium-doped fiber ring laser with an 18.6 MHz mode spacing have been detected exactly in real-time domain and discussed in detail. Numerical results show that the MI-based method has a high testing sensitivity for identifying mode hopping, which will play a significant role in evaluating the output stability of SLM fiber lasers.

  2. Optical transmission through a polarization preserving single mode optical fiber at two Ar(+) laser wavelengths

    Science.gov (United States)

    Tedjojuwono, Ken K.; Hunter, William W., Jr.

    1989-01-01

    The transmission characteristics of two Ar(+) laser wavelengths through a twenty meter Panda type Polarization Preserving Single Mode Optical Fiber (PPSMOF) were measured. The measurements were done with both single and multi-longitudinal mode radiation. In the single longitudinal mode case, a degrading Stimulated Brillouin Scattering (SBS) is observed as a backward scattering loss. By choosing an optimum coupling system and manipulating the input polarization, the threshold of the SBS onset can be raised and the transmission efficiency can be increased.

  3. Diagnosis of dementia with single photon emission computed tomography

    International Nuclear Information System (INIS)

    Jagust, W.J.; Budinger, T.F.; Reed, B.R.

    1987-01-01

    Single photon emission computed tomography is a practical modality for the study of physiologic cerebral activity in vivo. We utilized single photon emission computed tomography and N-isopropyl-p-iodoamphetamine iodine 123 to evaluate regional cerebral blood flow in nine patients with Alzheimer's disease (AD), five healthy elderly control subjects, and two patients with multi-infarct dementia. We found that all subjects with AD demonstrated flow deficits in temporoparietal cortex bilaterally, and that the ratio of activity in bilateral temporoparietal cortex to activity in the whole slice allowed the differentiation of all patients with AD from both the controls and from the patients with multi-infarct dementia. Furthermore, this ratio showed a strong correlation with disease severity in the AD group. Single photon emission computed tomography appears to be useful in the differential diagnosis of dementia and reflects clinical features of the disease

  4. Low-bending loss and single-mode operation in few-mode optical fiber

    Science.gov (United States)

    Yin, Ping; Wang, Hua; Chen, Ming-Yang; Wei, Jin; Cai, Zhi-Min; Li, Lu-Ming; Yang, Ji-Hai; Zhu, Yuan-Feng

    2016-10-01

    The technique of eliminating the higher-order modes in a few-mode optical fiber is proposed. The fiber is designed with a group of defect modes in the cladding. The higher-order modes in the fiber can be eliminated by bending the fiber to induce strong coupling between the defect modes and the higher-order modes. Numerical simulation shows the bending losses of the LP01 mode are lower than 1.5×10-4 dB/turn for the wavelength shorter than 1.625 μm. The proposed fiber can be bent multiple turns at small bending radius which are preferable for FTTH related applications.

  5. Pump combiner for air-clad fiber with PM single-mode signal feed-through

    DEFF Research Database (Denmark)

    Noordegraaf, Danny; Nielsen, Martin D.; Skovgaard, Peter M.W.

    2009-01-01

    A pump combiner with single-mode PM signal feed-through designed for an air-clad photonic crystal fiber is demonstrated. Signal coupling is realized by a novel taper element allowing single-mode guidance at a taper ratio of 3.7.......A pump combiner with single-mode PM signal feed-through designed for an air-clad photonic crystal fiber is demonstrated. Signal coupling is realized by a novel taper element allowing single-mode guidance at a taper ratio of 3.7....

  6. Single-mode distributed feedback laser operation with no dependence on the morphology of the gain medium

    Energy Technology Data Exchange (ETDEWEB)

    Umar, Muhammad [Department of Energy Systems Research, Ajou University, Suwon (Korea, Republic of); Min, Kyungtaek [Department of Energy Systems Research, Ajou University, Suwon (Korea, Republic of); Inter-university Semiconductor Research Center, Seoul National University (Korea, Republic of); Jeon, Heonsu [Department of Physics and Astronomy, Seoul National University (Korea, Republic of); Kim, Sunghwan [Department of Energy Systems Research, Ajou University, Suwon (Korea, Republic of); Department of Physics, Ajou University, Suwon (Korea, Republic of)

    2017-06-15

    Organic distributed feedback (DFB) lasers can be useful photonic tools for biological applications where the roles of organic materials are important, because highly coherent single mode emission with broad tuning range can be obtained. However, the formulaic structures of organic lasers, and the uses of gain media as resonators themselves, are not suitable for inducing laser emission from irregular shaped gain media, such as dye-staining cells and tissues. Here, we report a reusable photonic template comprising an exceedingly thin and discrete titanium dioxide (TiO{sub 2}) layer on a one-dimensional (1D) quartz grating to induce single mode DFB lasing from a variety of states of optical gain media. Using the same template, the external gain media of optically thick and thin casted film, liquid, and a free-standing thick film reveal single mode lasing with reliable performance. Numerical simulations demonstrate that the 25-nm thick TiO{sub 2} disconnected grating lines support a spatially confined DFB mode in the vertical direction, even under no index difference between superstrate and substrate. Additionally, not using the typical waveguide gain layer promises high sensitivity and detection limit in refractometric sensing. These results suggest that the photonic structure may serve as a versatile sensing platform for bioapplications. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. 1540-nm single frequency single-mode pulsed all fiber laser for coherent Doppler lidar

    Science.gov (United States)

    Zhang, Xin; Diao, Weifeng; Liu, Yuan; Liu, Jiqiao; Hou, Xia; Chen, Weibiao

    2015-02-01

    A single-mode single frequency eye-safe pulsed all fiber laser based on master oscillator power amplification structure is presented. This laser is composed of a narrow linewidth distributed laser diode seed laser and two-stage cascade amplifiers. 0.8 m longitudinally gradient strained erbium/ytterbium co-doped polarization-maintaining fiber with a core diameter of 10 μm is used as the gain fiber and two acoustic-optics modulators are adopted to enhance pulse extinction ratio. A peak power of 160 W and a pulse width of 200 ns at 10 kHz repetition rate are achieved with transform-limited linewidth and diffraction-limited beam quality. This laser will be employed in a compact short range coherent Doppler wind lidar.

  8. Spontaneous emission of a cesium atom near a nanofiber: Efficient coupling of light to guided modes

    International Nuclear Information System (INIS)

    Le Kien, Fam; Hakuta, K.; Dutta Gupta, S.; Balykin, V.I.

    2005-01-01

    We study the spontaneous emission of a cesium atom in the vicinity of a subwavelength-diameter fiber. We show that the confinement of the guided modes and the degeneracy of the excited and ground states substantially affect the spontaneous emission process. We demonstrate that different magnetic sublevels have different decay rates. When the fiber radius is about 200 nm, a significant fraction (up to 28%) of spontaneous emission by the atom can be channeled into guided modes. Our results may find applications for developing nanoprobes for atoms and efficient couplers for subwavelength-diameter fibers

  9. Cyclotron absorption and emission in mode conversion layers emdash a new paradigm

    International Nuclear Information System (INIS)

    Swanson, D.G.

    1995-01-01

    When the analysis of absorption with mode conversion effects included began to mature in recent years, the study of the corresponding effects on emission began and has led to some surprising results. The classical expressions for cyclotron or synchrotron emission from a harmonic resonance were originally derived from models that did not include mode conversion or its attendant reflection, and classical expressions for the optical depth and opacity were obtained. When mode conversion was included, the principal surprise was that the transmission coefficient, which was understood as being due to absorption, is totally independent of absorption and due exclusively to tunneling. The other surprise from the mode conversion analysis is that the observed emission arises from two distinct sources, one direct and one from an indirect Bernstein wave source which is partially converted in the cyclotron layer to outgoing electromagnetic waves, with the net result that mode conversion cancels out for the electron case, but not for ions. The only corrections to electron cyclotron emission are then due to reflection effects, and these have been shown to be small for many laboratory plasmas, leading to the validation of the classical formula for these cases, but via an entirely new paradigm in its interpretation. This review includes a summary of the absorption process for both electron and ion cyclotron harmonics, and reviews carefully the emission physics, including both potential error estimates and a discussion of the emission source distribution in space

  10. Single-Mode to Multi-Mode Crossover in Thin-Load Polymethyl Methacrylate Plasmonic Waveguides

    DEFF Research Database (Denmark)

    Großmann, Malte; Thomaschewski, Martin; Klick, Alwin

    2018-01-01

    Mode character and mode dispersion of sub-60-nm-thick polymethyl methacrylate dielectric-loaded surface plasmon-polariton waveguides (DLSPPWs) are investigated using photoemission electron microscopy and finite element method simulations. Experiment and simulation show excellent agreement and all...

  11. Investigation of the state of polarization of light in a single-mode fiber waveguide

    Science.gov (United States)

    Kozel, S. M.; Kreopalov, V. I.; Listvin, V. N.; Glavatskikh, N. A.

    1983-01-01

    An analysis is made of the polarization anisotropy of a single-mode fiber with a twisted elliptic core. The Jones matrix is obtained and the complex function of the state of polarization of light in a fiber is investigated. The results are reported of measurements of the linear and circular birefringence of a borosilicate single-mode glass fiber.

  12. 40 CFR 1033.515 - Discrete-mode steady-state emission tests of locomotives and locomotive engines.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Discrete-mode steady-state emission... Procedures § 1033.515 Discrete-mode steady-state emission tests of locomotives and locomotive engines. This... a warm-up followed by a sequence of nominally steady-state discrete test modes, as described in...

  13. Over 19 W Single-Mode 1545 nm Er,Yb Codoped All-Fiber Laser

    Directory of Open Access Journals (Sweden)

    Jiadong Wu

    2017-01-01

    Full Text Available We report a high-power cladding-pumped Er,Yb codoped all-fiber laser with truly single transverse mode output. The fiber laser is designed to operate at 1545 nm by the use of a pair of fiber Bragg gratings (FBGs to lock and narrow the output spectrum, which can be very useful in generating the eye-safe ~1650 nm laser emission through the Stimulated Raman Scattering (SRS in silica fibers that is of interest in many applications. Two pieces of standard single-mode fibers are inserted into the laser cavity and output port to guarantee the truly single-mode output as well as good compatibility with other standard fiber components. We have obtained a maximum output power of 19.2 W at 1544.68 nm with a FWHM spectral width of 0.08 nm, corresponding to an average overall slope efficiency of 31.9% with respect to the launched pump power. This is, to the best of our knowledge, the highest output power reported from simple all-fiber single-mode Er,Yb codoped laser oscillator architecture.

  14. On the Uncertainty in Single Molecule Fluorescent Lifetime and Energy Emission Measurements

    Science.gov (United States)

    Brown, Emery N.; Zhang, Zhenhua; McCollom, Alex D.

    1996-01-01

    Time-correlated single photon counting has recently been combined with mode-locked picosecond pulsed excitation to measure the fluorescent lifetimes and energy emissions of single molecules in a flow stream. Maximum likelihood (ML) and least squares methods agree and are optimal when the number of detected photons is large, however, in single molecule fluorescence experiments the number of detected photons can be less than 20, 67 percent of those can be noise, and the detection time is restricted to 10 nanoseconds. Under the assumption that the photon signal and background noise are two independent inhomogeneous Poisson processes, we derive the exact joint arrival time probability density of the photons collected in a single counting experiment performed in the presence of background noise. The model obviates the need to bin experimental data for analysis, and makes it possible to analyze formally the effect of background noise on the photon detection experiment using both ML or Bayesian methods. For both methods we derive the joint and marginal probability densities of the fluorescent lifetime and fluorescent emission. The ML and Bayesian methods are compared in an analysis of simulated single molecule fluorescence experiments of Rhodamine 110 using different combinations of expected background noise and expected fluorescence emission. While both the ML or Bayesian procedures perform well for analyzing fluorescence emissions, the Bayesian methods provide more realistic measures of uncertainty in the fluorescent lifetimes. The Bayesian methods would be especially useful for measuring uncertainty in fluorescent lifetime estimates in current single molecule flow stream experiments where the expected fluorescence emission is low. Both the ML and Bayesian algorithms can be automated for applications in molecular biology.

  15. Impacts of Urban Transportation Mode Split on CO2 Emissions in Jinan, China

    Directory of Open Access Journals (Sweden)

    Kebin He

    2011-04-01

    Full Text Available As the world’s largest developing country, China currently is undergoing rapid urbanization and motorization, which will result in far-reaching impacts on energy and the environment. According to estimates, energy use and carbon emissions in the transportation sector will comprise roughly 30% of total emissions by 2030. Since the late 1990s, transportation-related issues such as energy, consumption, and carbon emissions have become a policy focus in China. To date, most research and policies have centered on vehicle technologies that promote vehicle efficiency and reduced emissions. Limited research exists on the control of greenhouse gases through mode shifts in urban transportation—in particular, through the promotion of public transit. The purpose of this study is to establish a methodology to analyze carbon emissions from the urban transportation sector at the Chinese city level. By using Jinan, the capital of China’s Shandong Province, as an example, we have developed an analytical model to simulate energy consumption and carbon emissions based on the number of trips, the transportation mode split, and the trip distance. This model has enabled us to assess the impacts of the transportation mode split on energy consumption and carbon emissions. Furthermore, this paper reviews a set of methods for data collection, estimation, and processing for situations where statistical data are scarce in China. This paper also describes the simulation of three transportation system development scenarios. The results of this study illustrate that if no policy intervention is implemented for the transportation mode split (the business-as-usual (BAU case, then emissions from Chinese urban transportation systems will quadruple by 2030. However, a dense, mixed land-use pattern, as well as transportation policies that encourage public transportation, would result in the elimination of 1.93 million tons of carbon emissions—approximately 50% of the BAU

  16. Measurement of flow fluctuations in single longitudinal mode pulsed ...

    Indian Academy of Sciences (India)

    2014-02-12

    Feb 12, 2014 ... The plano-convex lens was mounted on a translation stage for precise position- ing of the focal spot on the dye cell. By using longitudinal pumping, shorter gain region was achieved, resulting in shorter cavity length (∼50 mm) for the SLM dye laser. The shorter cavity length provided larger axial mode ...

  17. LOPUT Laser: A novel concept to realize single longitudinal mode ...

    Indian Academy of Sciences (India)

    2014-02-05

    Feb 5, 2014 ... Solid State Laser Division, Raja Ramanna Centre for Advanced Technology, Indore 452 013, India. ∗ ... terpropagating waves inside the gain medium to suppress the effect of SHB in the laser cavity [4–6]. ... propagating linearly polarized modes add up to result in a travelling wave along the gain medium ...

  18. Single-transverse-mode Ti:sapphire rib waveguide laser

    NARCIS (Netherlands)

    Grivas, C.; Shepherd, D.P.; May-Smith, T.C.; Eason, R.W.; Pollnau, Markus

    2005-01-01

    Laser operation of Ti:sapphire rib waveguides fabricated using photolithography and ion beam etching in pulsed laser deposited layers is reported. Polarized laser emission was observed at 792.5 nm with an absorbed pump power threshold of 265 mW, which is more than a factor of 2 lower in comparison

  19. Infrared single mode chalcogenide glass fiber for space

    NARCIS (Netherlands)

    Houlzot, P.; Boussard-Plédel, C.; Faber, A.J.; Cheng, L.K.; Bureau, B.; Nijnatten, P.A. van; Gielesen, W.L.M.; Do Carmo, J.P.; Lucas, J.

    2007-01-01

    An important measuring technique under study for the DARWIN planet finding mission, is nulling interferometry, enabling the detection of the weak infrared emission lines of an orbiting planet. This technique requires a perfect wavefront of the light beams to be combined in the interferometer. By

  20. Comparison of single-/few-/multi-mode 850 nm VCSELs for optical OFDM transmission.

    Science.gov (United States)

    Kao, Hsuan-Yun; Tsai, Cheng-Ting; Leong, Shan-Fong; Peng, Chun-Yen; Chi, Yu-Chieh; Huang, Jian Jang; Kuo, Hao-Chung; Shih, Tien-Tsorng; Jou, Jau-Ji; Cheng, Wood-Hi; Wu, Chao-Hsin; Lin, Gong-Ru

    2017-07-10

    For high-speed optical OFDM transmission applications, a comprehensive comparison of the homemade multi-/few-/single-transverse mode (MM/FM/SM) vertical cavity surface emitting laser (VCSEL) chips is performed. With microwave probe, the direct encoding of pre-leveled 16-QAM OFDM data and transmission over 100-m-long OM4 multi-mode-fiber (MMF) are demonstrated for intra-datacenter applications. The MM VCSEL chip with the largest emission aperture of 11 μm reveals the highest differential quantum efficiency which provides the highest optical power of 8.67 mW but exhibits the lowest encodable bandwidth of 21 GHz. In contrast, the SM VCSEL chip fabricated with the smallest emission aperture of only 3 μm provides the highest 3-dB encoding bandwidth up to 23 GHz at a cost of slight heat accumulation. After optimization, with the trade-off set between the receiving signal-to-noise ratio (SNR) and bandwidth, the FM VCSEL chip guarantees the highest optical OFDM transmission bit rate of 96 Gbit/s under back-to-back case with its strongest throughput. Among three VCSEL chips, the SM VCSEL chip with nearly modal-dispersion free feature is treated as the best candidate for carrying the pre-leveled 16-QAM OFDM data over 100-m OM4-MMF with same material structure but exhibits different oxide-layer confined gain cross-sections with one another at 80-Gbit/s with the smallest receiving power penalty of 1.77 dB.

  1. Refractive index sensor based on an abrupt taper Michelson interferometer in a single-mode fiber.

    Science.gov (United States)

    Tian, Zhaobing; Yam, Scott S-H; Loock, Hans-Peter

    2008-05-15

    A simple refractive index sensor based on a Michelson interferometer in a single-mode fiber is constructed and demonstrated. The sensor consists of a single symmetrically abrupt taper region in a short piece of single-mode fiber that is terminated by approximately 500 nm thick gold coating. The sensitivity of the new sensor is similar to that of a long-period-grating-type sensor, and its ease of fabrication offers a low-cost alternative to current sensing applications.

  2. Interaction of solitary pulses in single mode optical fibres | Usman ...

    African Journals Online (AJOL)

    Two solitary waves launched, by way of incidence, into an optical fibre from a single pulse if the pulses are in-phase as understood from results of inverse scattering transform method applied to the cubic nonlinear Schrödinger equations, (CNLSE\\'s). The single CNLSE is then understood to describe evolution of coupled ...

  3. Choosing a Better Delay Line Medium between Single-Mode and Multi-Mode Optical Fibers: the Effect of Bending

    Directory of Open Access Journals (Sweden)

    Auwal Mustapha Imam

    2017-12-01

    Full Text Available Optical fiber cables are materials whose core is made of silica and other materials such as chalcogenide glasses; they transmit a digital signal via light pulses through an extremely thin strand of glass. The light propagates and is being guided by the core which is surrounded by the cladding. Light travels in the optical fiber in the form of total internal reflection in the core of the fibers. The flexibility, low tensile strength, low signal loss, high bandwidth and other characteristics of optical fibers favors it for use as a delay medium in many applications. Another favorable characteristic of optical fiber delay lines is are their relative insensitivities to environmental effects and electromagnetic interferences. The immunity of optical fibers to interferences and their less weight added advantages to it for use as delay medium. Single-mode and multi-mode are the two most popular types of optical fibers. Single-mode fibers have good propagation and delay properties with a minimal loss that allows the signal to propagate in a large distance with insignificant distortion or attenuation. The percentage of power transmission of single-mode fibers is found to be higher than that of the multi-mode fibers. It is, therefore, a preferred type for use as a delay line. In this paper, relative studies of the two optical fibers modes, and the results of power input/output measurement of the two modes are presented with a view to coming up with a better type for use as a delay medium.

  4. Tunable single and dual mode operation of an external cavity quantum-dot injection laser

    Energy Technology Data Exchange (ETDEWEB)

    Biebersdorf, A [Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universitaet, Amalienstrasse 54, D-80799 Munich (Germany); Lingk, C [Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universitaet, Amalienstrasse 54, D-80799 Munich (Germany); De Giorgi, M [Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universitaet, Amalienstrasse 54, D-80799 Munich (Germany); Feldmann, J [Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universitaet, Amalienstrasse 54, D-80799 Munich (Germany); Sacher, J [Sacher Lasertechnik GmbH, Hannah Arendt Strasse 3-7, D-35037 Marburg (Germany); Arzberger, M [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall, D-85748 Garching (Germany); Ulbrich, C [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall, D-85748 Garching (Germany); Boehm, G [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall, D-85748 Garching (Germany); Amann, M-C [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall, D-85748 Garching (Germany); Abstreiter, G [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall, D-85748 Garching (Germany)

    2003-08-21

    We investigate quantum-dot (QD) lasers in an external cavity using Littrow and Littman configurations. Here, we report on a continuously tunable QD laser with a broad tuning range from 1047 to 1130 nm with high stability and efficient side mode suppression. The full-width at half-maximum of the laser line is 0.85 nm determined mainly by the quality of the external grating. This laser can be operated in a dual-mode modus, where the mode-spacing can be tuned continuously between 1.1 and 34 nm. Simultaneous emission of the two laser modes is shown by sum frequency generation experiments.

  5. Sensors Based on Thin-Film Coated Cladding Removed Multimode Optical Fiber and Single-Mode Multimode Single-Mode Fiber: A Comparative Study

    Directory of Open Access Journals (Sweden)

    Ignacio Del Villar

    2015-01-01

    Full Text Available Two simple optical fibre structures that do not require the inscription of a grating, a cladding removed multimode optical fibre (CRMOF and a single-mode multimode single-mode structure (SMS, are compared in terms of their adequateness for sensing once they are coated with thin-films. The thin-film deposited (TiO2/PSS permits increasing the sensitivity to surrounding medium refractive index. The results obtained can be extrapolated to other fields such as biological or chemical sensing just by replacing the thin-film by a specific material.

  6. Damage Modes Recognition and Hilbert-Huang Transform Analyses of CFRP Laminates Utilizing Acoustic Emission Technique

    Science.gov (United States)

    WenQin, Han; Ying, Luo; AiJun, Gu; Yuan, Fuh-Gwo

    2016-04-01

    Discrimination of acoustic emission (AE) signals related to different damage modes is of great importance in carbon fiber-reinforced plastic (CFRP) composite materials. To gain a deeper understanding of the initiation, growth and evolution of the different types of damage, four types of specimens for different lay-ups and orientations and three types of specimens for interlaminar toughness tests are subjected to tensile test along with acoustic emission monitoring. AE signals have been collected and post-processed, the statistical results show that the peak frequency of AE signal can distinguish various damage modes effectively. After a AE signal were decomposed by Empirical Mode Decomposition (EMD) method, it may separate and extract all damage modes included in this AE signal apart from damage mode corresponding to the peak frequency. Hilbert-Huang Transform (HHT) of AE signals can clearly illustrate the frequency distribution of Intrinsic Mode Functions (IMF) components in time-scale in different damage stages, and can calculate accurate instantaneous frequency for damage modes recognition to help understanding the damage process.

  7. Manipulating single second mode transparency in a corrugated waveguide via the thickness of sputtered gold

    International Nuclear Information System (INIS)

    Xu, Dan; Fan, Ya-Xian; Sang, Tang-Qing; Xu, Lan-Lan; Bibi, Aysha; Tao, Zhi-Yong

    2016-01-01

    We propose a classical analog of electromagnetically induced transparency in a cylindrical waveguide with undulated metallic walls. The transparency, induced by multi-mode interactions in waveguides, not only has a narrow line-width, but also consists of a single second-order transverse mode, which corresponds to the Bessel function distributions investigated extensively due to their unique characteristics. By increasing the thickness of sputtered gold layers of the waveguide, we demonstrate a frequency-agile single mode transparency phenomenon in a terahertz radiation. It is found that the center frequency of the transparency is linearly related to the gold thickness, indicating the achievement of a controllable single mode terahertz device. The field distributions at the cross-sections of outlets verify the single second mode transparency and indicate the mechanism of its frequency manipulation, which will significantly benefit the mode-control engineering in terahertz applications. - Highlights: • An analog of electromagnetically induced transparency in terahertz tubes is proposed. • A single second transverse mode of Bessel distributions is observed in the pass band. • The operating frequency can be linearly controlled by the sputtered gold thickness. • We can effectively manipulate the slow down factor of light by the gold thickness. • The transparency characteristics rely on the transition of multi-mode interactions.

  8. Manipulating single second mode transparency in a corrugated waveguide via the thickness of sputtered gold

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Dan [Key Lab of In-fiber Integrated Optics, Ministry of Education of China, Harbin Engineering University, Harbin 150001 (China); Photonics Research Center, College of Science, Harbin Engineering University, Harbin 150001 (China); Fan, Ya-Xian, E-mail: yxfan@hrbeu.edu.cn [Key Lab of In-fiber Integrated Optics, Ministry of Education of China, Harbin Engineering University, Harbin 150001 (China); Photonics Research Center, College of Science, Harbin Engineering University, Harbin 150001 (China); Sang, Tang-Qing; Xu, Lan-Lan; Bibi, Aysha [Key Lab of In-fiber Integrated Optics, Ministry of Education of China, Harbin Engineering University, Harbin 150001 (China); Photonics Research Center, College of Science, Harbin Engineering University, Harbin 150001 (China); Tao, Zhi-Yong, E-mail: zytao@hrbeu.edu.cn [Key Lab of In-fiber Integrated Optics, Ministry of Education of China, Harbin Engineering University, Harbin 150001 (China); Photonics Research Center, College of Science, Harbin Engineering University, Harbin 150001 (China)

    2016-03-11

    We propose a classical analog of electromagnetically induced transparency in a cylindrical waveguide with undulated metallic walls. The transparency, induced by multi-mode interactions in waveguides, not only has a narrow line-width, but also consists of a single second-order transverse mode, which corresponds to the Bessel function distributions investigated extensively due to their unique characteristics. By increasing the thickness of sputtered gold layers of the waveguide, we demonstrate a frequency-agile single mode transparency phenomenon in a terahertz radiation. It is found that the center frequency of the transparency is linearly related to the gold thickness, indicating the achievement of a controllable single mode terahertz device. The field distributions at the cross-sections of outlets verify the single second mode transparency and indicate the mechanism of its frequency manipulation, which will significantly benefit the mode-control engineering in terahertz applications. - Highlights: • An analog of electromagnetically induced transparency in terahertz tubes is proposed. • A single second transverse mode of Bessel distributions is observed in the pass band. • The operating frequency can be linearly controlled by the sputtered gold thickness. • We can effectively manipulate the slow down factor of light by the gold thickness. • The transparency characteristics rely on the transition of multi-mode interactions.

  9. single photon emission tomography and positron emission tomography - Part 1 (October 2012), Part 2 (October 2010)

    International Nuclear Information System (INIS)

    Buvat, Irene

    2010-10-01

    The objective of this lecture is to present the single photon emission computed tomography (SPECT) and the positron emission tomography (PET) imaging techniques. Part 1 Content: 1 - Introduction: anatomic, functional and molecular imaging; 2 - Radiotracers: chemical and physical constraints, gamma photon emitters, positon emitters, radioisotopes production, emitters type and imaging techniques; 3 - Gamma cameras; 4 - Quantification in emission tomography: attenuation, scattering, un-stationary spatial resolution; 5 - Synthesis and conclusion. Part 2 content: 1 - Positon emitters; 2 - Positons detection: Coincidence detection (electronic collimation, PET detectors with gamma cameras, dedicated PET detectors, spectrometry); PET detectors type; time-of-flight PET; 2D PET; 3D PET; 3 - Quantification in emission tomography: detected events, attenuation, scattering, fortuitous coincidences, standardisation; 4 - Common SPECT and PET problems: partial volume effect, movement, tomographic reconstruction, calibration, dead time; 5 - Synthesis and conclusion

  10. Raman-active modes in homogeneous and inhomogeneous bundles of single-walled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Sbai, K; Rahmani, A; Chadli, H [Laboratoire de Physique des materiaux et Modelisation des Systemes, Universite Moulay Ismail, Faculte des Sciences, BP 11201, Zitoune, 50000 Meknes (Morocco); Sauvajol, J-L [Laboratoire des Colloides, Verres et Nanomateriaux (UMR CNRS 5587), Universite Montpellier II, F-34095 Montpellier Cedex 5 (France)], E-mail: rahmani@fs-umi.ac.ma

    2009-01-28

    In the present work, the non-resonant Raman-active modes are calculated for several diameters, chiralities and sizes for homogeneous and inhomogeneous bundles of single-walled carbon nanotubes (BWCNTs), using the spectral moment's method (SMM). Additional intense Raman-active modes are present in the breathing-like modes (BLM) spectra of these systems in comparison with a single fully symmetric A{sub 1g} mode characteristic of isolated nanotubes (SWCNTs). The dependence of the wavenumber of these modes in terms of diameters, lengths and number of tubes was investigated. We found that, for a finite (in)homogeneous bundle, additional breathing-like modes appear as a specific signature.

  11. Decay properties of high-lying single-particles modes

    NARCIS (Netherlands)

    Beaumel, D; Fortier, S; Gales, S; Guillot, J; LangevinJoliot, H; Laurent, H; Maison, JM; Vernotte, J; Bordewijck, J; Brandenburg, S; Krasznahorkay, A; Crawley, GM; Massolo, CP; Renteria, M; Khendriche, A

    1996-01-01

    The neutron decay of high-lying single-particle states in Ni-64, Zr-90, Sn-120 and (208)pb excited by means of the (alpha,He-3) reaction has been investigated at 120 MeV incident energy using the multidetector EDEN. The characteristics of this reaction are studied using inclusive spectra and angular

  12. Center deviation of localized modes in a one-dimension anharmonic single impurity chain

    Science.gov (United States)

    Chen, Xuan-Lin; Zhu, Gang-Bei; Jiang, Ze-Hui; Yang, Yan-Qiang

    2018-04-01

    A 1D anharmonic chain with a single impurity particle is used to study the center deviation and stability of the localized modes. The displacement patterns of the localized modes for a variable impurity mass and anharmonic parameter are studied. The pattern center is shifted away from the impurity with decreasing anharmonic parameter for both symmetric and asymmetric anharmonic impurity modes. In the limit of a heavy-mass impurity, the energy localization is constrained to the three particles nearest to the impurity.

  13. Attenuation Coefficient of Single-Mode Periodic Waveguides

    Science.gov (United States)

    Baron, A.; Mazoyer, S.; Smigaj, W.; Lalanne, P.

    2011-10-01

    It is widely accepted that, on ensemble average, the transmission T of guided modes decays exponentially with the waveguide length L due to small imperfections, leading to the important figure of merit defined as the attenuation-rate coefficient α=-⟨ln⁡(T)⟩/L. In this Letter, we evidence that the exponential-damping law is not valid in general for periodic monomode waveguides, especially as the group velocity decreases. This result, that contradicts common beliefs and experimental practices aiming at measuring α, is supported by a theoretical study of light transport in the limit of very small imperfections, and by numerical results obtained for two waveguide geometries that offer contrasted damping behaviors.

  14. Amplitude Noise Suppression and Orthogonal Multiplexing Using Injection-Locked Single-Mode VCSEL

    DEFF Research Database (Denmark)

    Lyubopytov, Vladimir; von Lerber, Tuomo; Lassas, Matti

    2017-01-01

    We experimentally demonstrate BER reduction and orthogonal modulation using an injection locked single-mode VCSEL. It allows us suppressing an amplitude noise of optical signal and/or double the capacity of an information channel....

  15. Celiac disease biodetection using lossy-mode resonances generated in tapered single-mode optical fibers

    Science.gov (United States)

    Socorro, A. B.; Corres, J. M.; Del Villar, I.; Matias, I. R.; Arregui, F. J.

    2014-05-01

    This work presents the development and test of an anti-gliadin antibodies biosensor based on lossy mode resonances (LMRs) to detect celiac disease. Several polyelectrolites were used to perform layer-by-layer assembly processes in order to generate the LMR and to fabricate a gliadin-embedded thin-film. The LMR shifted 20 nm when immersed in a 5 ppm anti-gliadin antibodies-PBS solution, what makes this bioprobe suitable for detecting celiac disease. This is the first time, to our knowledge, that LMRs are used to detect celiac disease and these results suppose promising prospects on the use of such phenomena as biological detectors.

  16. Plasmon enhanced terahertz emission from single layer graphene.

    Science.gov (United States)

    Bahk, Young-Mi; Ramakrishnan, Gopakumar; Choi, Jongho; Song, Hyelynn; Choi, Geunchang; Kim, Yong Hyup; Ahn, Kwang Jun; Kim, Dai-Sik; Planken, Paul C M

    2014-09-23

    We show that surface plasmons, excited with femtosecond laser pulses on continuous or discontinuous gold substrates, strongly enhance the generation and emission of ultrashort, broadband terahertz pulses from single layer graphene. Without surface plasmon excitation, for graphene on glass, 'nonresonant laser-pulse-induced photon drag currents' appear to be responsible for the relatively weak emission of both s- and p-polarized terahertz pulses. For graphene on a discontinuous layer of gold, only the emission of the p-polarized terahertz electric field is enhanced, whereas the s-polarized component remains largely unaffected, suggesting the presence of an additional terahertz generation mechanism. We argue that in the latter case, 'surface-plasmon-enhanced optical rectification', made possible by the lack of inversion symmetry at the graphene on gold surface, is responsible for the strongly enhanced emission. The enhancement occurs because the electric field of surface plasmons is localized and enhanced where the graphene is located: at the surface of the metal. We believe that our results point the way to small, thin, and more efficient terahertz photonic devices.

  17. Decay properties of high-lying single-particles modes

    Science.gov (United States)

    Beaumel, D.; Fortier, S.; Galès, S.; Guillot, J.; Langevin-Joliot, H.; Laurent, H.; Maison, J. M.; Vernotte, J.; Bordewijck, J.; Brandenburg, S.; Krasznahorkay, A.; Crawley, G. M.; Massolo, C. P.; Renteria, M.; Khendriche, A.

    1996-02-01

    The neutron decay of high-lying single-particle states in 64Ni, 90Zr, 120Sn and 208Pb excited by means of the (α, 3He) reaction has been investigated at 120 MeV incident energy using the multidetector EDEN. The characteristics of this reaction are studied using inclusive spectra and angular correlation analysis. The structure located between 11 and 15 MeV in 91Zr, and between 8 and 12 MeV excitation energy in 209Pb display large departures from a pure statistical decay. The corresponding non-statistical branching ratios are compared with the results of two theoretical calculations.

  18. Low-NA single-mode LMA photonic crystal fiber amplifier

    DEFF Research Database (Denmark)

    Alkeskjold, Thomas Tanggaard; Laurila, Marko; Scolari, Lara

    2011-01-01

    Enabling Single-Mode (SM) operation in Large-Mode-Area (LMA) fiber amplifiers and lasers is critical, since a SM output ensures high beam quality and excellent pointing stability. In this paper, we demonstrate and test a new design approach for achieving ultra-low NA SM rod fibers by using...... a spatially Distributed Mode Filter (DMF). This approach achieves SM performance in a short and straight rod fiber and allows preform tolerances to be compensated during draw. A low-NA SM rod fiber amplifier having a mode field diameter of ~60μm at 1064nm and a pump absorption of 27dB/m at 976nm...

  19. Controllable Synthesis of Organic Microcrystals with Tunable Emission Color and Morphology Based on Molecular Packing Mode.

    Science.gov (United States)

    Li, Zhi-Zhou; Liao, Liang-Sheng; Wang, Xue-Dong

    2018-01-01

    Organic microcrystals are of essential importance for high fluorescence efficiency, ordered molecular packing mode, minimized defects, and smooth shapes, which are extensively applied in organic optoelectronics. The molecular packing mode significantly influences the optical/electrical properties of organic microcrystals, which makes the controllable preparation of organic microcrystals with desired molecular packing mode extremely important. In the study, yellow-emissive α phase organic microcrystals with rectangular morphology and green-emissive β phase perylene microcrystals with rhombic morphology are separately prepared by simply controlling the solution concentration. The distinct molecular staking modes of the H/J-aggregate are found in these two types of perylene microcrystals, which contribute to the different emission color, morphology, and radiative decay rate. What is more interesting, the α-doped β phase and the β-doped α phase organic microcrystals can also be fabricated by modulating the evaporation rate from 100 to 10 µL min -1 . The findings can contribute to the future development of organic optoelectronics at the microscale. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Nonlinear growth of a single neoclassical MHD tearing mode in a tokamak

    International Nuclear Information System (INIS)

    Qu, W.X.; Callen, J.D.

    1985-10-01

    The nonlinear evolution equation for the growth of a single neoclassical MHD tearing mode is derived from the usual resistive MHD equations with neoclassical effects included. For the case Δ' > 0 where the usual resistive MHD modes are unstable, in nonlinear neoclassical MHD there is an intermediate time regime in which the island width w grows only as t/sup 1/2/. However, eventually the neoclassical MHD tearing modes are found to enter the usual resistive MHD Rutherford regime where w infinity t. Physically, the neoclassical MHD bootstrap current effects modify the linear and early nonlinear growth of tearing modes. However, eventually the magnetic islands flatten the pressure gradient within the island to remove these effects and return, at long times, to the usual quasilinear picture for the nonlinear evolution of a single resistive MHD tearing mode

  1. X-mode artificial optical emissions and attendant phenomena at EISCAT/Heating

    Science.gov (United States)

    Blagoveshchenskaya, Nataly; Sergienko, Tima; Rietveld, Michael; Brandstrom, Urban; Senior, Andrew; Haggstrom, Ingemar; Kosch, Michael; Borisova, Tatiana; Yeoman, Tim

    We present the experimental evidence for the formation of the artificial optical emissions induced by the X-mode powerful HF radio waves injected towards the magnetic zenith (MZ) into the high latitude F region of the ionosphere. The experiments were conducted in the course of Russian EISCAT heating campaigns in October 2012 and October 2013 at the Heating facility at Tromsø, Norway. The HF pump wave with the X-mode polarization was radiated at 7.1 or 6.2 MHz. The phased array 1, resulting in an ERP = 430 - 600 MW was used. Optical emissions at red (630 nm) and green (557 nm) lines were imaged from Tromsø site by the digital All-Sky Imager mark 2 (DASI - 2) and from a remote site at Abisco by the Auroral Large Imaging System (ALIS) in Scandinavia. The intensities of X-mode emissions at red and green lines varied between about of 150 - 1000 R and 50 - 300 R above the background respectively in different experiments. The artificial optical emissions were accompanied by very strong HF-enhanced ion lines and HF induced plasma lines from the EISCAT UHF incoherent scatter radar measurements and artificial small-scale field-aligned irregularities from CUTLASS (SuperDARN) HF coherent radar in Finland. The results obtained are discussed.

  2. Effect of injection pressure on performance, emission, and combustion characteristics of diesel-acetylene-fuelled single cylinder stationary CI engine.

    Science.gov (United States)

    Srivastava, Anmesh Kumar; Soni, Shyam Lal; Sharma, Dilip; Jain, Narayan Lal

    2018-03-01

    In this paper, the effect of injection pressure on the performance, emission, and combustion characteristics of a diesel-acetylene fuelled single cylinder, four-stroke, direct injection (DI) diesel engine with a rated power of 3.5 kW at a rated speed of 1500 rpm was studied. Experiments were performed in dual-fuel mode at four different injection pressures of 180, 190, 200, and 210 bar with a flow rate of 120 LPH of acetylene and results were compared with that of baseline diesel operation. Experimental results showed that highest brake thermal efficiency of 27.57% was achieved at injection pressure of 200 bar for diesel-acetylene dual-fuel mode which was much higher than 23.32% obtained for baseline diesel. Carbon monoxide, hydrocarbon, and smoke emissions were also measured and found to be lower, while the NO x emissions were higher at 200 bar in dual fuel mode as compared to those in other injection pressures in dual fuel mode and also for baseline diesel mode. Peak cylinder pressure, net heat release rate, and rate of pressure rise were also calculated and were higher at 200 bar injection pressure in dual fuel mode.

  3. Decay properties of high-lying single-particles modes

    Energy Technology Data Exchange (ETDEWEB)

    Beaumel, D. [Institut de Physique Nucleaire, 91 - Orsay (France); Fortier, S. [Institut de Physique Nucleaire, 91 - Orsay (France); Gales, S. [Institut de Physique Nucleaire, 91 - Orsay (France); Guillot, J. [Institut de Physique Nucleaire, 91 - Orsay (France); Langevin-Joliot, H. [Institut de Physique Nucleaire, 91 - Orsay (France); Laurent, H. [Institut de Physique Nucleaire, 91 -Orsay (France); Maison, J.M. [Institut de Physique Nucleaire, 91 - Orsay (France); Vernotte, J. [Institut de Physique Nucleaire, 91 - Orsay (France); Bordewijck, J. [Kernfysisch Versneller Instituut, 9747 Groningen (Netherlands); Brandenburg, S. [Kernfysisch Versneller Instituut, 9747 Groningen (Netherlands); Krasznahorkay, A. [Kernfysisch Versneller Instituut, 9747 Groningen (Netherlands); Crawley, G.M. [NSCL, Michigan State University, East Lansing, MI 48824 (United States); Massolo, C.P. [Universitad Nacional de La Plata, 1900 La Plata (Argentina); Renteria, M. [Universitad Nacional de La Plata, 1900 La Plata (Argentina); Khendriche, A. [University of Tizi-Ouzou, Tizi-Ouzou (Algeria)

    1996-03-18

    The neutron decay of high-lying single-particle states in {sup 64}Ni, {sup 90}Zr, {sup 120}Sn and {sup 208}Pb excited by means of the ({alpha},{sup 3}He) reaction has been investigated at 120 MeV incident energy using the multidetector EDEN. The characteristics of this reaction are studied using inclusive spectra and angular correlation analysis. The structure located between 11 and 15 MeV in {sup 91}Zr, and between 8 and 12 MeV excitation energy in {sup 209}Pb display large departures from a pure statistical decay. The corresponding non-statistical branching ratios are compared with the results of two theoretical calculations. (orig.).

  4. The Influence of Various Operation Modes on Diesel Passenger Cars CO2 Emissions

    Directory of Open Access Journals (Sweden)

    Arina Negoițescu

    2015-07-01

    Full Text Available The amount of emissions released into the atmosphere by polluting sources was significantly reduced due to the limitations introduced by the EU. Since one of the main sources affecting air quality is the car, researches regarding the influence of various factors on exhaust emissions are carried out. As CO2 is the main pollutant responsible for the greenhouse effect, the article treats the influence of vehicle load and traffic levels, running modes, the electric consumer’s utilization, and driving style on CO2 emissions for cars equipped with diesel engine. The results from the conducted study can contribute to adopt solutions in order to decrease the concentration of CO2 emissions from cars equipped with diesel engines.

  5. Whistler mode electron cyclotron emission from energetic electrons in TMX-upgrade

    International Nuclear Information System (INIS)

    Lasnier, C.J.; Ellis, R.F.; Tsakiris, G.D.

    1988-01-01

    Measurements are presented of axially propagating whistler mode electron cyclotron emission (WECE) from the energetic electrons in the East end cell of TMX-Upgrade. The measurements were made in the frequency ranges 12.5-18 GHz and 29-40 GHz employing swept and fixed frequency super-heterodyne receivers and a spherical dish antenna. These measurements are compared with a one dimensional radiation transport model which treats whistler mode emission, absorption, and propagation for an electron population which has two components: a cold thermal component and an energetic relativistic, mirror trapped component. It is shown firstly that the measured emission is in good agreement with the predictions of the WECE model. Secondly, for low to moderate cold electron densities, and for detection frequencies slightly less than the minimum electron cyclotron frequency in the magnetic well, the emission achieves black body levels, yielding an effective hot electron temperature. At higher cold electron densities and/or higher frequencies cold plasma effects limit the diagnostic capabilities of whistler emission in so far as the hot electrons are concerned. (author)

  6. Single-mode annular chirally-coupled core fibers for fiber lasers

    Science.gov (United States)

    Zhang, Haitao; Hao, He; He, Linlu; Gong, Mali

    2018-03-01

    Chirally-coupled core (CCC) fiber can transmit single fundamental mode and effectively suppresses higher-order mode (HOM) propagation, thus improve the beam quality. However, the manufacture of CCC fiber is complicated due to its small side core. To decrease the manufacture difficulty in China, a novel fiber structure is presented, defined as annular chirally-coupled core (ACCC) fiber, replacing the small side core by a larger side annulus. In this paper, we designed the fiber parameters of this new structure, and demonstrated that the new structure has a similar property of single mode with traditional CCC fiber. Helical coordinate system was introduced into the finite element method (FEM) to analyze the mode field in the fiber, and the beam propagation method (BPM) was employed to analyze the influence of the fiber parameters on the mode loss. Based on the result above, the fiber structure was optimized for efficient single-mode transmission, in which the core diameter is 35 μm with beam quality M2 value of 1.04 and an optical to optical conversion efficiency of 84%. In this fiber, fundamental mode propagates in an acceptable loss, while the HOMs decay rapidly.

  7. Processing of complex shapes with single-mode resonant frequency microwave applicators

    International Nuclear Information System (INIS)

    Fellows, L.A.; Delgado, R.; Hawley, M.C.

    1994-01-01

    Microwave processing is an alternative to conventional composite processing techniques. Single-mode microwave applicators efficiently couple microwave energy into the composite. The application of the microwave energy is greatly affected by the geometry of the composite. In the single mode microwave applicator, two types of modes are available. These modes are best suited to processing flat planar samples or cylindrical samples with geometries that align with the electric fields. Mode-switching is alternating between different electromagnetic modes with the intelligent selection of the modes to alleviate undesirable temperature profiles. This method has improved the microwave heating profiles of materials with complex shapes that do not align with either type of electric field. Parts with two different complex geometries were fabricated from a vinyl toluene/vinyl ester resin with a continuous glass fiber reinforcement by autoclaving and by microwave techniques. The flexural properties of the microwave processed samples were compared to the flexural properties of autoclaved samples. The trends of the mechanical properties for the complex shapes were consistent with the results of experiments with flat panels. This demonstrated that mode-switching techniques are as applicable for the complex shapes as they are for the simpler flat panel geometry

  8. Single-molecule electronics: Cooling individual vibrational modes by the tunneling current.

    Science.gov (United States)

    Lykkebo, Jacob; Romano, Giuseppe; Gagliardi, Alessio; Pecchia, Alessandro; Solomon, Gemma C

    2016-03-21

    Electronic devices composed of single molecules constitute the ultimate limit in the continued downscaling of electronic components. A key challenge for single-molecule electronics is to control the temperature of these junctions. Controlling heating and cooling effects in individual vibrational modes can, in principle, be utilized to increase stability of single-molecule junctions under bias, to pump energy into particular vibrational modes to perform current-induced reactions, or to increase the resolution in inelastic electron tunneling spectroscopy by controlling the life-times of phonons in a molecule by suppressing absorption and external dissipation processes. Under bias the current and the molecule exchange energy, which typically results in heating of the molecule. However, the opposite process is also possible, where energy is extracted from the molecule by the tunneling current. Designing a molecular "heat sink" where a particular vibrational mode funnels heat out of the molecule and into the leads would be very desirable. It is even possible to imagine how the vibrational energy of the other vibrational modes could be funneled into the "cooling mode," given the right molecular design. Previous efforts to understand heating and cooling mechanisms in single molecule junctions have primarily been concerned with small models, where it is unclear which molecular systems they correspond to. In this paper, our focus is on suppressing heating and obtaining current-induced cooling in certain vibrational modes. Strategies for cooling vibrational modes in single-molecule junctions are presented, together with atomistic calculations based on those strategies. Cooling and reduced heating are observed for two different cooling schemes in calculations of atomistic single-molecule junctions.

  9. A Lifecycle Emissions Model (LEM): Lifecycle Emissions from Transportation Fuels, Motor Vehicles, Transportation Modes, Electricity Use, Heating and Cooking Fuels, and Materials, APPENDIX A: Energy Use and Emissions from the Lifecycle of Diesel-Like Fuels Derived From Biomass

    OpenAIRE

    Delucchi, Mark; Lipman, Timothy

    2003-01-01

    An Appendix to the Report, “A Lifecycle Emissions Model (LEM): Lifecycle Emissions From Transportation Fuels, Motor Vehicles, Transportation Modes, Electricity Use, Heating and Cooking Fuels, and Materialsâ€

  10. Separation of common and differential mode conducted emission: Power combiner/splitters

    DEFF Research Database (Denmark)

    Andersen, Michael A. E.; Nielsen, Dennis; Thomsen, Ole Cornelius

    2012-01-01

    A conducted emission measurement contains a common and a differential mode component. Accurate separation of these two components is critical, when designing the input filter of a switch mode power supply. Many techniques exists for performing such separation. Some authors suggested the use...... of wideband transformers, while other prefer current probes. In this paper the use of commercial power splitters/combiners as noise separators are considered. The performance of the noise separators are analyzed and validated based on scattering parameters (S-parameters). Impedance and rejection ratios...... (common and differential mode) are shown. The results based on S-parameters are used to propose a complete noise separator design. This separator is verified through experimental measurements. Finally an example on how to use the separator, when measuring conducted noise is given....

  11. PERFORMANCE, EMISSION, AND COMBUSTION CHARACTERISTICS OF A CI ENGINE USING LIQUID PETROLEUM GAS AND NEEM OIL IN DUAL FUEL MODE

    Directory of Open Access Journals (Sweden)

    Palanimuthu Vijayabalan

    2010-01-01

    Full Text Available Increased environmental awareness and depletion of resources are driving the industries to develop viable alternative fuels like vegetable oils, compresed natural gas, liquid petroleum gas, producer gas, and biogas in order to provide suitable substitute to diesel for compression ignition engine. In this investigation, a single cylinder, vertical, air-cooled diesel engine was modified to use liquid petroleum gas in dual fuel mode. The liquefied petroleum gas, was mixed with air and supplied through intake manifold. The liquid fuel neem oil or diesel was injected into the combustion chamber. The performance, emission, and combustion characteristics were studied and compared for neat fuel and dual fuel mode. The experimental results on dual fuel engine show a reduction in oxides of nitrogen up to 70% of the rated power and smoke in the entire power range. However the brake thermal efficiency was found decreased in low power range due to lower calorific value of liquid petroleum gas, and increase in higher power range due to the complete burning of liquid petroleum gas. Hydrocarbon and carbon monoxide emissions were increased significantly at lower power range and marginal variation in higher power range.

  12. Experimental Performance of a Single-Mode Ytterbium-doped Fiber Ring Laser with Intracavity Modulator

    Science.gov (United States)

    Numata, Kenji; Camp, Jordan

    2012-01-01

    We have developed a linearly polarized Ytterbium-doped fiber ring laser with a single longitudinal mode output at 1064 run. A fiber-coupled intracavity phase modulator ensured mode-hop free operation and allowed fast frequency tuning. The fiber laser was locked with high stability to an iodine-stabilized laser, showing a frequency noise suppression of a factor approx 10 (exp 5) at 1 mHz

  13. Wavelength-selectable and steady single-mode erbium-doped fiber multiple ring laser

    Science.gov (United States)

    Yeh, Chien-Hung; Yang, Zi-Qing; Huang, Tzu-Jung; Chow, Chi-Wai; Chen, Jing-Heng; Chen, Kun-Huang

    2017-11-01

    To achieve a stable and selectable C-band erbium-doped fiber (EDF) laser with single-longitudinal-mode output, a multiple ring architecture is proposed and demonstrated experimentally. In this work, we design a passively quadruple-ring structure in the cavity of an EDF laser to produce a Vernier effect with a mode filter for suppressing the multimode spikes significantly. In addition, the output performance and stability of the proposed EDF ring laser are discussed.

  14. In-Line Fiber Optic Interferometric Sensors in Single-Mode Fibers

    OpenAIRE

    De-Wen Duan; Min Liu; Di Wu; Tao Zhu

    2012-01-01

    In-line fiber optic interferometers have attracted intensive attention for their potential sensing applications in refractive index, temperature, pressure and strain measurement, etc. Typical in-line fiber-optic interferometers are of two types: Fabry-Perot interferometers and core-cladding-mode interferometers. It’s known that the in-line fiber optic interferometers based on single-mode fibers can exhibit compact structures, easy fabrication and low cost. In this paper, ...

  15. A single mode method for the analysis and identification of nonlinear MDOF systems

    Science.gov (United States)

    Huang, Liping; Iwan, W. D.

    In order to apply mode approach to describe a nonlinear system, the concept of modal response of nonlinear systems is examined, and an amplitude-dependent modal model is presented based on an analysis of a single mode of response. The effectiveness of this model is examined under different types and various levels of excitation. A corresponding identification procedure for cubic systems is proposed and applied to the analysis of a 3DOF soltening nonlinear system.

  16. 70 GeV proton volume capture into channeling mode with a bent Si single crystal

    International Nuclear Information System (INIS)

    Chesnokov, Yu.A.; Galyaev, N.A.; Kotov, V.I.; Tsarik, S.V.; Zapol'skij, V.N.

    1990-01-01

    The existence of the volume capture of 70 GeV protons with a Si bent single crystal of (111) orientation into the channeling mode gas experimentally been proved. The data on the probability of capturing protons into the channeling mode versus the bending radius of the crystal have been obtained together with the information on the dynamics of volume captured particle dechanneling. 10 refs

  17. Development of a 10-decade single-mode reactor flux monitoring system

    Energy Technology Data Exchange (ETDEWEB)

    Valentine, K.H.; Shepard, R.L.; Falter, K.G.; Reese, W.B.

    1988-03-31

    Conventional wide-range neutron channels employ three optional modes to monitor the required flux range from source levels to full power (typically 10 or more decades). Difficult calibrations are necessary to provide a continuous output signal when such a system switches from counting mode in the source range to mean-square voltage mode in the midrange to dc current mode in the power range. In an ORNL proof-of-principle test, a method of extended range counting was implemented with a fission counter and conventional wide-band pulse processing electronics to provide a single-mode, monotonically increasing signal that spanned /approximately 10/ decades of neutron flux. Ongoing work includes design, fabrication, and testing of a comlpete neutron flux monitoring system suitable for advanced liquid metal reactor designs. 6 refs., 4 figs.

  18. Development of a 10-decade single-mode reactor flux monitoring system

    International Nuclear Information System (INIS)

    Valentine, K.H.; Shepard, R.L.; Falter, K.G.; Reese, W.B.

    1988-01-01

    Conventional wide-range neutron channels employ three optional modes to monitor the required flux range from source levels to full power (typically 10 or more decades). Difficult calibrations are necessary to provide a continuous output signal when such a system switches from counting mode in the source range to mean-square voltage mode in the midrange to dc current mode in the power range. In an ORNL proof-of-principle test, a method of extended range counting was implemented with a fission counter and conventional wide-band pulse processing electronics to provide a single-mode, monotonically increasing signal that spanned /approximately 10/ decades of neutron flux. Ongoing work includes design, fabrication, and testing of a comlpete neutron flux monitoring system suitable for advanced liquid metal reactor designs. 6 refs., 4 figs

  19. Technology and engineering aspects of high power pulsed single longitudinal mode dye lasers

    Science.gov (United States)

    Rawat, V. S.; Mukherjee, Jaya; Gantayet, L. M.

    2015-09-01

    Tunable single mode pulsed dye lasers are capable of generating optical radiations in the visible range having very small bandwidths (transform limited), high average power (a few kW) at a high pulse repetition rate (a few tens of kHz), small beam divergence and relatively higher efficiencies. These dye lasers are generally utilized laser dyes dissolved in solvents such as water, heavy water, ethanol, methanol, etc. to provide a rapidly flowing gain medium. The dye laser is a versatile tool, which can lase either in the continuous wave (CW) or in the pulsed mode with pulse duration as small as a few tens of femtoseconds. In this review, we have examined the several cavity designs, various types of gain mediums and numerous types of dye cell geometries for obtaining the single longitudinal mode pulsed dye laser. Different types of cavity configuration, such as very short cavity, short cavity with frequency selective element and relatively longer cavity with multiple frequency selective elements were reviewed. These single mode lasers have been pumped by all kinds of pumping sources such as flash lamps, Excimer, Nitrogen, Ruby, Nd:YAG, Copper Bromide and Copper Vapor Lasers. The single mode dye lasers are either pumped transversely or longitudinally to the resonator axis. The pulse repletion rate of these pump lasers were ranging from a few Hz to a few tens of kHz. Physics technology and engineering aspects of tuning mechanism, mode hop free scanning and dye cell designs are also presented in this review. Tuning of a single mode dye laser with a resolution of a few MHz per step is a technologically challenging task, which is discussed here.

  20. Comparison of Numerical Modelling of Degradation Mechanisms in Single Mode Optical Fibre Using MATLAB and VPIphotonics

    Directory of Open Access Journals (Sweden)

    Jana Sajgalikova

    2015-01-01

    Full Text Available Mathematical models for description of physical phenomena often use the statistical description of the individual phenomena and solve those using suitable methods. If we want to develop numerical model of optical communication system based on transmission through single mode optical fibres, we need to consider whole series of phenomena that affect various parts of the system. In the single-mode optical fibre we often encounter influence of chromatic dispersion and nonlinear Kerr effects. By observing various different degradation mechanisms, every numerical model should have its own limits, which fulfil more detailed specification. It is inevitable to consider them in evaluation. In this paper, we focus on numerical modelling of degradation mechanisms in single-mode optical fibre. Numerical solution of non-linear Schroedinger equation is performed by finite difference method applied in MATLAB environment and split-step Fourier method, which is implemented by VPIphotonics software.

  1. Utilizing wheel-ring architecture for stable and selectable single-longitudinal-mode erbium fiber laser

    Science.gov (United States)

    Yeh, Chien-Hung; Yang, Zi-Qing; Huang, Tzu-Jung; Chow, Chi-Wai

    2018-03-01

    To achieve a steady single-longitudinal-mode (SLM) erbium-doped fiber (EDF) laser, the wheel-ring architecture is proposed in the laser cavity. According to Vernier effect, the proposed wheel-ring can produce three different free spectrum ranges (FSRs) to serve as the mode-filter for suppressing the densely multi-longitudinal-mode (MLM). Here, to complete wavelength-tunable EDF laser, an optical tunable bandpass filter (OTBF) is utilized inside the cavity for tuning arbitrarily. In addition, the entire output performances of the proposed EDF wheel-ring laser are also discussed and analyzed experimentally.

  2. Single-mode hole-assisted fiber as a bending-loss insensitive fiber

    Science.gov (United States)

    Nakajima, Kazuhide; Shimizu, Tomoya; Matsui, Takashi; Fukai, Chisato; Kurashima, Toshio

    2010-12-01

    We investigate the design and characteristics of a single-mode and low bending loss HAF both numerically and experimentally. An air filling fraction S is introduced to enable us to design a HAF with desired characteristics more easily. We show that we can expect to realize a single-mode and low bending loss HAF by considering the S dependence of the bending loss α b and cutoff wavelength λ c as well as their relative index difference Δ dependence. We also show that the mode-field diameter (MFD) and chromatic dispersion characteristics of the single-mode and low bending loss HAF can be tailored by optimizing the distance between the core and the air holes. We also investigate the usefulness of the fabricated HAFs taking the directly modulated transmission and multipath interference (MPI) characteristics into consideration. We show that the designed HAF has sufficient applicability to both analog and digital transmission systems. Our results reveal that the single-mode and low bending loss HAF is beneficial in terms of developing a future fiber to the home (FTTH) network as well as for realizing flexible optical wiring.

  3. Q-switching and efficient harmonic generation from a single-mode LMA photonic bandgap rod fiber laser

    DEFF Research Database (Denmark)

    Laurila, Marko; Saby, Julien; Alkeskjold, Thomas T.

    2011-01-01

    We demonstrate a Single-Mode (SM) Large-Mode-Area (LMA) ytterbium-doped PCF rod fiber laser with stable and close to diffraction limited beam quality with 110W output power. Distributed-Mode-Filtering (DMF) elements integrated in the cladding of the rod fiber provide a robust spatial mode with a ...

  4. Excitation of Contained Modes by High Energy Nuclei and Correlated Cyclotron Emission

    Science.gov (United States)

    Coppi, B.; Penn, G.; Riconda, C.

    1997-12-01

    In experiments with fusing plasmas, enhanced radiation emission at the harmonics of the cyclotron frequency of fusion reaction products has been observed. A theory is presented that explains key features of these observations and indicates the possibility of extracting significant information about the fusion product population distribution, both in velocity space and over the plasma cross section. The considered model is consistent in particular with the fact that, in DT plasmas, the radiation peaks occur at frequencies corresponding to harmonics of the αparticles' cyclotron frequency Δαevaluated at the outer edge of the plasma column, and that a transition to a "continuum" spectrum at high frequencies ( ω≳7 Δ α) can be identified. In this model, the radiation is the result of the excitation of radially "contained" modes which are driven unstable by the fusion products. The modes considered to be responsible for the discrete part of the spectrum are spatially localized near the plasma edge. The radial containment, which is associated mainly with the inhomogeneity of the plasma density, is in fact a fundamental characteristic since only contained modes can grow out of a relatively weak mode-particle interaction and justify the detected emission power levels. The contained mode is a solution to a set of macroscopic equations, in which the electron motion is tied to that of the magnetic field (Hall effect). The growth rate has been evaluated considering the particle orbits in a toroidal confinement configuration and modelling the distribution function of the interacting particles with the energy at birth before slowing down occurs. The growth rate depends linearly on the α-particle density and can be larger than, or of the order of, the bounce frequency of the magnetically trapped α-particles, which can have a resonant interaction with the mode. According to the theoretical model presented, the discrete part of the observed spectrum of emission yields

  5. Non-classical light emission from single conjugated polymers

    Science.gov (United States)

    Hollars, Christopher; Lane, Stephen; Huser, Thomas

    2002-03-01

    Photon-antibunching from single, isolated molecules of collapsed-chain poly[2-methoxy,5-(2’-ethyl-hexyloxy)-p-phenylene-vinylene] (MEH-PPV) has been observed using confocal microscopy techniques. Efficient inter-segment energy transfer in collapsed-chain conjugated polymers leads to emission from an average of only 2-3 active sites on a polymer chain that is composed of hundreds of quasi-chromophores. These few centers consist of the segments with the lowest excitation energy and are supplied by the efficient light-harvesting and energy transfer of the surrounding higher-energy segments. This effect depends on the conformation of the polymer molecules, which is controlled by solvent polarity. These results provide new insight into the controversial photophysics of conjugated polymers and their application in optoelectronic devices.

  6. Single photon emission computed tomography in AIDS dementia complex

    International Nuclear Information System (INIS)

    Pohl, P.; Vogl, G.; Fill, H.; Roessler, H.Z.; Zangerle, R.; Gerstenbrand, F.

    1988-01-01

    Single photon emission computed tomography (SPECT) studies were performed in AIDS dementia complex using IMP in 12 patients (and HM-PAO in four of these same patients). In all patients, SPECT revealed either multiple or focal uptake defects, the latter corresponding with focal signs or symptoms in all but one case. Computerized tomography showed a diffuse cerebral atrophy in eight of 12 patients, magnetic resonance imaging exhibited changes like atrophy and/or leukoencephalopathy in two of five cases. Our data indicate that both disturbance of cerebral amine metabolism and alteration of local perfusion share in the pathogenesis of AIDS dementia complex. SPECT is an important aid in the diagnosis of AIDS dementia complex and contributes to the understanding of the pathophysiological mechanisms of this disorder

  7. Super-resolution from single photon emission: toward biological application

    Science.gov (United States)

    Moreva, E.; Traina, P.; Forneris, J.; Ditalia Tchernij, S.; Guarina, L.; Franchino, C.; Picollo, F.; Ruo Berchera, I.; Brida, G.; Degiovanni, I. P.; Carabelli, V.; Olivero, P.; Genovese, M.

    2017-08-01

    Properties of quantum light represent a tool for overcoming limits of classical optics. Several experiments have demonstrated this advantage ranging from quantum enhanced imaging to quantum illumination. In this work, experimental demonstration of quantum-enhanced resolution in confocal fluorescence microscopy will be presented. This is achieved by exploiting the non-classical photon statistics of fluorescence emission of single nitrogen-vacancy (NV) color centers in diamond. By developing a general model of super-resolution based on the direct sampling of the kth-order autocorrelation function of the photoluminescence signal, we show the possibility to resolve, in principle, arbitrarily close emitting centers. Finally, possible applications of NV-based fluorescent nanodiamonds in biosensing and future developments will be presented.

  8. Single-mode 37-core fiber with a cladding diameter of 248 μm

    DEFF Research Database (Denmark)

    Sasaki, Y.; Takenaga, K.; Aikawa, K.

    2017-01-01

    A heterogeneous single-mode 37-core fiber with a cladding diameter of 248 μm is designed and fabricated. The fiber provides the highest core count and low total-crosstalk less than −20 dB/1000 km in C+L band.......A heterogeneous single-mode 37-core fiber with a cladding diameter of 248 μm is designed and fabricated. The fiber provides the highest core count and low total-crosstalk less than −20 dB/1000 km in C+L band....

  9. A portable optical emission spectroscopy-cavity ringdown spectroscopy dual-mode plasma spectrometer for measurements of environmentally important trace heavy metals: Initial test with elemental Hg

    Science.gov (United States)

    Sahay, Peeyush; Scherrer, Susan T.; Wang, Chuji

    2012-09-01

    A portable optical emission spectroscopy-cavity ringdown spectroscopy (OES-CRDS) dual-mode plasma spectrometer is described. A compact, low-power, atmospheric argon microwave plasma torch (MPT) is utilized as the emission source when the spectrometer is operating in the OES mode. The same MPT serves as the atomization source for ringdown measurements in the CRDS mode. Initial demonstration of the instrument is carried out by observing OES of multiple elements including mercury (Hg) in the OES mode and by measuring absolute concentrations of Hg in the metastable state 6s6p 3P0 in the CRDS mode, in which a palm-size diode laser operating at a single wavelength 405 nm is incorporated in the spectrometer as the light source. In the OES mode, the detection limit for Hg is determined to be 44 parts per 109 (ppb). A strong radiation trapping effect on emission measurements of Hg at 254 nm is observed when the Hg solution concentration is higher than 50 parts per 106 (ppm). The radiation trapping effect suggests that two different transition lines of Hg at 253.65 nm and 365.01 nm be selected for emission measurements in lower (50 ppm), respectively. In the CRDS mode, the detection limit of Hg in the metastable state 6s6p 3P0 is achieved to be 2.24 parts per 1012 (ppt) when the plasma is operating at 150 W with sample gas flow rate of 480 mL min-1; the detection limit corresponds to 50 ppm in Hg sample solution. Advantage of this novel spectrometer has two-fold, it has a large measurement dynamic range, from a few ppt to hundreds ppm and the CRDS mode can serve as calibration for the OES mode as well as high sensitivity measurements. Measurements of seven other elements, As, Cd, Mn, Ni, P, Pb, and Sr, using the OES mode are also carried out with detection limits of 1100, 33, 30, 144, 576, 94, and 2 ppb, respectively. Matrix effect in the presence of other elements on Hg measurements has been found to increase the detection limit to 131 ppb. These elements in lower

  10. Proceedings of clinical SPECT [single photon emission computed tomography] symposium

    International Nuclear Information System (INIS)

    1986-09-01

    It has been five years since the last in-depth American College of Nuclear Physicians/Society of Nuclear Medicine Symposium on the subject of single photon emission computed tomography (SPECT) was held. Because this subject was nominated as the single most desired topic we have selected SPECT imaging as the basis for this year's program. The objectives of this symposium are to survey the progress of SPECT clinical applications that have taken place over the last five years and to provide practical and timely guidelines to users of SPECT so that this exciting imaging modality can be fully integrated into the evaluation of pathologic processes. The first half was devoted to a consideration of technical factors important in SPECT acquisition and the second half was devoted to those organ systems about which sufficient clinical SPECT imaging data are available. With respect to the technical aspect of the program we have selected the key areas which demand awareness and attention in order to make SPECT operational in clinical practice. These include selection of equipment, details of uniformity correction, utilization of phantoms for equipment acceptance and quality assurance, the major aspect of algorithms, an understanding of filtered back projection and appropriate choice of filters and an awareness of the most commonly generated artifacts and how to recognize them. With respect to the acquisition and interpretation of organ images, the faculty will present information on the major aspects of hepatic, brain, cardiac, skeletal, and immunologic imaging techniques. Individual papers are processed separately for the data base

  11. Computational investigation of single mode vs multimode Rayleigh endash Taylor seeding in Z-pinch implosions

    International Nuclear Information System (INIS)

    Douglas, M.R.; Deeney, C.; Roderick, N.F.

    1998-01-01

    A series of two-dimensional magnetohydrodynamic calculations have been carried out to investigate single and multimode growth and mode coupling for magnetically-driven Rayleigh endash Taylor instabilities in Z pinches. Wavelengths ranging from 5.0 mm down to 1.25 mm were considered. Such wavelengths are comparable to those observed at stagnation using a random density open-quotes seedingclose quotes method. The calculations show that wavelengths resolved by less than 10 cells exhibit an artificial decrease in initial Fourier spectrum amplitudes and a reduction in the corresponding amplitude growth. Single mode evolution exhibits linear exponential growth and the development of higher harmonics as the mode transitions into the nonlinear phase. The mode growth continues to exponentiate but at a slower rate than determined by linear hydrodynamic theory. In the two and three mode case, there is clear evidence of mode coupling and inverse cascade. In addition, distinct modal patterns are observed late in the implosion, resulting from finite shell thickness and magnetic field effects. copyright 1998 American Institute of Physics. thinsp

  12. Single mode fiber array for planet detection using a visible nulling interferometer

    Science.gov (United States)

    Liu, Duncan; Levine, B. Martin; Shao, Michael; Aguayo, Franciso

    2005-01-01

    We report the design, fabrication, and testing of a coherent large mode field diameter fiber array to be used as a spatial filter in a planet finding visible nulling interferometer. The array is a key component of a space instrument for visible-light detection and spectroscopy of Earth like extrasolar planets. In this concept, a nulling interferometer is synthesized from a pupil image of a single aperture which is then spatially filtered by a coherent array of single mode fibers to suppress the residual scattered star light. The use of the fiber array preserves spatial information between the star and planet. The fiber array uses a custom commercial large mode field or low NA step-index single mode fiber to relax alignment tolerances. A matching custom micro lens array is used to couple light into the fibers, and to recollimate the light out of the fiber array. The use of large mode field diameter fiber makes the fabrication of a large spatial filter array with 300 to 1000 elements feasible.

  13. Single-Phase Microgrid with Seamless Transition Capabilities between Modes of Operation

    DEFF Research Database (Denmark)

    Micallef, Alexander; Apap, Maurice; Spiteri-Staines, Cyril

    2015-01-01

    Microgrids are an effective way to increase the penetration of DG into the grid. They are capable of operating either in grid-connected or in islanded mode thereby increasing the supply reliability for the end user. This paper focuses on achieving seamless transitions from islanded to grid......-connected and vice versa for a single phase microgrid made up from voltage controlled voltage source inverters (VC-VSIs) and current controlled voltage source inverters (CC-VSIs) working together in both modes of operation. The primary control structures for the VC-VSIs and CC-VSIs is considered together...... with the secondary control loops that are used to synchronize the microgrid as a single unit to the grid. Simulation results are given that show the seamless transitions between the two modes without any disconnection times for the CC-VSIs and VC-VSIs connected to the microgrid....

  14. Thermal Effects on the Single-Mode Regime of Distributed Modal Filtering Rod Fiber

    DEFF Research Database (Denmark)

    Coscelli, Enrico; Poli, Federica; Alkeskjold, Thomas Tanggaard

    2012-01-01

    Power scaling of fiber laser systems requires the development of innovative active fibers, capable of providing high pump absorption, ultralarge effective area, high-order mode suppression, and resilience to thermal effects. Thermally induced refractive index change has been recently appointed...... rod-type photonic crystal fiber, which exploits resonant coupling with high-index elements to suppress high-order modes, are thoroughly investigated. A computationally efficient model has been developed to calculate the refractive index change due to the thermo-optical effect, and it has been...... integrated into a full-vector modal solver based on the finite-element method to obtain the guided modes, considering different heating conditions. Results have shown that the single-mode regime of the distributed modal filtering fiber is less sensitive to thermal effects with respect to index-guiding fibers...

  15. Practical Considerations Concerning the Interleaved Transition Mode Single-stage Ballast

    DEFF Research Database (Denmark)

    Teodorescu, Remus; Kjær, Søren Bækhøj; Munk-Nielsen, Stig

    2002-01-01

    The aim of this paper is to present a novel single-stage interleaved ballast focusing on practical design aspects like: key current expression, overall losses, harmonic analysis of the differential-mode EMI current and preheating ballast function. A new preheating method is also presented. A PSPI...

  16. Single mode chalcogenide glass fiber as wavefront filter for the DARWIN planet finding misson

    NARCIS (Netherlands)

    Faber, A.J.; Cheng, L.K.; Gielesen, W.L.M.; Boussard-Plédel, C.; Houizot, P.; Danto, S.; Lucas, J.; Pereira Do Carmo, J.

    2017-01-01

    The development of single mode chalcogenide glass fibers as wavefront filter for the DARWIN mission is reported. Melting procedures and different preform techniques for manufacturing core-cladding chalcogenide fibers are described. Bulk glass samples on the basis of Te-As-Se- and high

  17. Experimental detection of nonclassicality of single-mode fields via intensity moments

    Czech Academy of Sciences Publication Activity Database

    Arkhipov, Ie.I.; Peřina, Jan; Haderka, O.; Michálek, Václav

    2016-01-01

    Roč. 24, č. 26 (2016), s. 29496-29505 ISSN 1094-4087 R&D Projects: GA ČR GAP205/12/0382 Institutional support: RVO:68378271 Keywords : experimental detection of nonclassicality * single-mode fields * intensity moments Subject RIV: BH - Optics , Masers, Lasers Impact factor: 3.307, year: 2016

  18. Cantilever-based sensor with integrated optical read-out using single mode waveguides

    DEFF Research Database (Denmark)

    Nordström, Maria; Zauner, Dan; Calleja, Montserrat

    2007-01-01

    surface. Here, we present a novel integrated optical read-out scheme based on single-mode waveguides that enables the fabrication of a compact system. The complete system is fabricated in the polymer SU-8. This manuscript shows the principle of operation and the design well as the fabrication...

  19. Single-mode waveguides with SU-8 polymer core and cladding for MOEMS applications

    DEFF Research Database (Denmark)

    Nordström, Maria; Zauner, Dan; Boisen, Anja

    2007-01-01

    Fabrication and optical characterization of singlemode polymeric embedded waveguides are performed. A specific material combination (SU-8 2005 as core and the modified SU-8 mr-L 6050XP as cladding) is chosen in order to obtain a small refractive index difference for single-mode propagation combin...

  20. 870nm Bragg grating in single mode TOPAS microstructured polymer optical fibre

    DEFF Research Database (Denmark)

    Yuan, Wu; Webb, David J.; Kalli, Kyriacos

    2011-01-01

    We report the fabrication and characterization of a fiber Bragg grating (FBG) with 870 nm resonance wavelength in a single-mode TOPAS microstructured polymer optical fiber (mPOF). The grating has been UV-written with the phase-mask technique using a 325 nm HeCd laser. The static tensile strain...

  1. Analytical Expression for the Electric Field of the Single Mode Laser ...

    African Journals Online (AJOL)

    The simplest model of the laser is that of a single mode system homogenously broadened. The dynamical behavior of this laser is described by three differential equations, called Haken-Lorenz equations[1], similar to the Lorenz model [1] already known to predict deterministic chaos. In previous recent work [5-7] we have ...

  2. Current Mode Full-Wave Rectifier Based on a Single MZC-CDTA

    Directory of Open Access Journals (Sweden)

    Neeta Pandey

    2013-01-01

    Full Text Available This paper presents a current mode full-wave rectifier based on single modified Z copy current difference transconductance amplifier (MZC-CDTA and two switches. The circuit is simple and is suitable for IC implementation. The functionality of the circuit is verified with SPICE simulation using 0.35 μm TSMC CMOS technology parameters.

  3. Intrinsic pressure response of a single mode cyclo olefin polymer fiber bragg grating

    DEFF Research Database (Denmark)

    Pedersen, Jens Kristian Mølgaard; Woyessa, Getinet; Nielsen, Kristian

    2016-01-01

    The intrinsic pressure response of a Fibre Bragg Grating (FBG) inscribed in a single-mode cyclo olefin polymer (COP) microstructured polymer optical fibre (mPOF) in the range 0-200 bar is investigated for the first time. In order to efficiently suppress the effects from changes in temperature...

  4. Investigation of bending loss in a single-mode optical fibre

    Indian Academy of Sciences (India)

    Abstract. Loss of optical power in a single-mode optical fibre due to bending has been investigated for a wavelength of 1550 nm. In this experiment, the effects of bending radius (4–15 mm, with steps of 1 mm), and wrapping turns (up to 40 turns) on loss have been studied. Twisting the optical fibre and its influence on power ...

  5. Efficient coupling of a single diamond color center to propagating plasmonic gap modes

    DEFF Research Database (Denmark)

    Kumar, Shailesh; Huck, Alexander; Andersen, Ulrik L

    2013-01-01

    We report on coupling of a single nitrogen-vacancy (NV) center in a nanodiamond to the propagating gap mode of two parallel placed chemically grown silver nanowires. The coupled NV-center nanowire system is made by manipulating nanodiamonds and nanowires with the tip of an atomic force microscope...

  6. Image properties of list mode likelihood reconstruction for a rectangular positron emission mammography with DOI measurements

    International Nuclear Information System (INIS)

    Qi, Jinyi; Klein, Gregory J.; Huesman, Ronald H.

    2000-01-01

    A positron emission mammography scanner is under development at our Laboratory. The tomograph has a rectangular geometry consisting of four banks of detector modules. For each detector, the system can measure the depth of interaction information inside the crystal. The rectangular geometry leads to irregular radial and angular sampling and spatially variant sensitivity that are different from conventional PET systems. Therefore, it is of importance to study the image properties of the reconstructions. We adapted the theoretical analysis that we had developed for conventional PET systems to the list mode likelihood reconstruction for this tomograph. The local impulse response and covariance of the reconstruction can be easily computed using FFT. These theoretical results are also used with computer observer models to compute the signal-to-noise ratio for lesion detection. The analysis reveals the spatially variant resolution and noise properties of the list mode likelihood reconstruction. The theoretical predictions are in good agreement with Monte Carlo results

  7. Image properties of list mode likelihood reconstruction for a rectangular positron emission mammography with DOI measurements

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Jinyi; Klein, Gregory J.; Huesman, Ronald H.

    2000-10-01

    A positron emission mammography scanner is under development at our Laboratory. The tomograph has a rectangular geometry consisting of four banks of detector modules. For each detector, the system can measure the depth of interaction information inside the crystal. The rectangular geometry leads to irregular radial and angular sampling and spatially variant sensitivity that are different from conventional PET systems. Therefore, it is of importance to study the image properties of the reconstructions. We adapted the theoretical analysis that we had developed for conventional PET systems to the list mode likelihood reconstruction for this tomograph. The local impulse response and covariance of the reconstruction can be easily computed using FFT. These theoretical results are also used with computer observer models to compute the signal-to-noise ratio for lesion detection. The analysis reveals the spatially variant resolution and noise properties of the list mode likelihood reconstruction. The theoretical predictions are in good agreement with Monte Carlo results.

  8. Optical measuring system with an interrogator and a polymer-based single-mode fibre optic sensor system

    DEFF Research Database (Denmark)

    2017-01-01

    The present invention relates to an optical measuring system comprising a polymer-based single-mode fibre-optic sensor system (102), an optical interrogator (101), and an optical arrangement (103) interconnecting the optical interrogator (101) and the polymer-based single-mode fibre-optic sensor...... system (102). The invention further relates to an optical interrogator adapted to be connected to a polymer-based single-mode fibre-optic sensor system via an optical arrangement. The interrogator comprises a broadband light source arrangement (104) and a spectrum analysing arrangement which receives...... and analyses light reflected from the polymer-based single- mode fibre-optic sensor system....

  9. Mode division multiplexing technology for single-fiber optical trapping axial-position adjustment.

    Science.gov (United States)

    Liu, Zhihai; Wang, Lei; Liang, Peibo; Zhang, Yu; Yang, Jun; Yuan, Libo

    2013-07-15

    We demonstrate trapped yeast cell axial-position adjustment without moving the optical fiber in a single-fiber optical trapping system. The dynamic axial-position adjustment is realized by controlling the power ratio of the fundamental mode beam (LP01) and the low-order mode beam (LP11) generated in a normal single-core fiber. In order to separate the trapping positions produced by the two mode beams, we fabricate a special fiber tapered tip with a selective two-step method. A yeast cell of 6 μm diameter is moved along the optical axis direction for a distance of ~3 μm. To the best of our knowledge, this is the first demonstration of the trapping position adjustment without moving the fiber for single-fiber optical tweezers. The excitation and utilization of multimode beams in a single fiber constitutes a new development for single-fiber optical trapping and makes possible more practical applications in biomedical research fields.

  10. Large Mode Area Single Trench Fiber for 2 mu m Operation

    DEFF Research Database (Denmark)

    Jain, Deepak; Sahu, Jayanta K.

    2016-01-01

    to 25 cm bend radius, respectively, by exploiting high delocalization of the higher order modes. Achievement of a large effective-area can be very useful to address nonlinear effects. Moreover, single trench fiber offers certain advantages such as low-cost fabrication and easy postprocessing (such......Performance of single trench fibers has been investigated using finite-element method at 2 mu m wavelength. Numerical investigations show that an effective single mode operation for large effective area between 3000-4000 mu m(2) and 2000-3000 mu m(2) can be achieved at similar to 40 and similar...... as cleaving and splicing) thanks to the all-solid fiber design....

  11. Benchmarking of grid fault modes in single-phase grid-connected photovoltaic systems

    DEFF Research Database (Denmark)

    Yang, Yongheng; Blaabjerg, Frede; Zou, Zhixiang

    2012-01-01

    Pushed by the booming installations of single-phase photovoltaic (PV) systems, the grid demands regarding the integration of PV systems are expected to be modified. Hence, the future PV systems should become more active with functionalities of low voltage ride-through (LVRT) and the grid support...... capability. The control methods, together with grid synchronization techniques, are responsible for the generation of appropriate reference signals in order to handle ride-through grid faults. Thus, it is necessary to evaluate the behaviors of grid synchronization methods and control possibilities in single...... phase systems under grid faults. The intent of this paper is to present a benchmarking of grid fault modes that might come in future single-phase PV systems. In order to map future challenges, the relevant detection and control strategies are discussed. Some faulty modes are studied experimentally...

  12. Proceedings of clinical SPECT (single photon emission computed tomography) symposium

    Energy Technology Data Exchange (ETDEWEB)

    1986-09-01

    It has been five years since the last in-depth American College of Nuclear Physicians/Society of Nuclear Medicine Symposium on the subject of single photon emission computed tomography (SPECT) was held. Because this subject was nominated as the single most desired topic we have selected SPECT imaging as the basis for this year's program. The objectives of this symposium are to survey the progress of SPECT clinical applications that have taken place over the last five years and to provide practical and timely guidelines to users of SPECT so that this exciting imaging modality can be fully integrated into the evaluation of pathologic processes. The first half was devoted to a consideration of technical factors important in SPECT acquisition and the second half was devoted to those organ systems about which sufficient clinical SPECT imaging data are available. With respect to the technical aspect of the program we have selected the key areas which demand awareness and attention in order to make SPECT operational in clinical practice. These include selection of equipment, details of uniformity correction, utilization of phantoms for equipment acceptance and quality assurance, the major aspect of algorithms, an understanding of filtered back projection and appropriate choice of filters and an awareness of the most commonly generated artifacts and how to recognize them. With respect to the acquisition and interpretation of organ images, the faculty will present information on the major aspects of hepatic, brain, cardiac, skeletal, and immunologic imaging techniques. Individual papers are processed separately for the data base. (TEM)

  13. Single photon emission computed tomography in lumbar degenerative spondylolisthesis

    International Nuclear Information System (INIS)

    Ito, S.; Muro, T.; Eisenstein, S.

    1998-01-01

    Analysis of single photon emission computed tomographic images and plain X-ray films of the lumbar vertebrae was performed in 15 patients with lumbar spondylosis and 15 patients with lumbar degenerative spondylolisthesis. The facet joint and osteophyte images were observed in particular, and the slipping ratio of spondylolisthetic vertebrae was determined. The slipping ratio of degenerative spondylolisthesis ranged from 11.8 % to 22.3 %. Hot uptake of 99mTc-HMDP by both L4-5 facet joints was significantly greater in the patients with degenerative spondylolisthesis than in those with lumbar spondylosis. The hot uptake by the osteophytes in lumbar spondylosis was nearly uniform among the three inferior segments, L3-4, L4-5 and L5-S, but was localized to the spondylolisthetic vertebrae, L4-5, or L5-S, in the patients with spondylolisthesis. Half of the osteophytes with hot uptake were assigned to the 3rd degree of Nathan's grading. It was suggested that stress was localized to the slipping vertebrae and their facet joints in patients with lumbar degenerative spondylolisthesis. (author)

  14. Brain single photon emission computed tomography in neonates

    Energy Technology Data Exchange (ETDEWEB)

    Denays, R.; Van Pachterbeke, T.; Tondeur, M.; Spehl, M.; Toppet, V.; Ham, H.; Piepsz, A.; Rubinstein, M.; Nol, P.H.; Haumont, D. (Free Universities of Brussels (Belgium))

    1989-08-01

    This study was designed to rate the clinical value of ({sup 123}I)iodoamphetamine (IMP) or ({sup 99m}Tc) hexamethyl propylene amine oxyme (HM-PAO) brain single photon emission computed tomography (SPECT) in neonates, especially in those likely to develop cerebral palsy. The results showed that SPECT abnormalities were congruent in most cases with structural lesions demonstrated by ultrasonography. However, mild bilateral ventricular dilatation and bilateral subependymal porencephalic cysts diagnosed by ultrasound were not associated with an abnormal SPECT finding. In contrast, some cortical periventricular and sylvian lesions and all the parasagittal lesions well visualized in SPECT studies were not diagnosed by ultrasound scans. In neonates with subependymal and/or intraventricular hemorrhage the existence of a parenchymal abnormality was only diagnosed by SPECT. These results indicate that ({sup 123}I)IMP or ({sup 99m}Tc)HM-PAO brain SPECT shows a potential clinical value as the neurodevelopmental outcome is clearly related to the site, the extent, and the number of cerebral lesions. Long-term clinical follow-up is, however, mandatory in order to define which SPECT abnormality is associated with neurologic deficit.

  15. Single-Photon Emission Computed Tomography (SPECT) in childhood epilepsy

    International Nuclear Information System (INIS)

    Gulati, Sheffali; Kalra, Veena; Bal, C.S.

    2000-01-01

    The success of epilepsy surgery is determined strongly by the precise location of the epileptogenic focus. The information from clinical electrophysiological data needs to be strengthened by functional neuroimaging techniques. Single photon emission computed tomography (SPECT) available locally has proved useful as a localising investigation. It evaluates the regional cerebral blood flow and the comparison between ictal and interictal blood flow on SPECT has proved to be a sensitive nuclear marker for the site of seizure onset. Many studies justify the utility of SPECT in localising lesions to possess greater precision than interictal scalp EEG or anatomic neuroimaging. SPECT is of definitive value in temporal lobe epilepsy. Its role in extratemporal lobe epilepsy is less clearly defined. It is useful in various other generalized and partial seizure disorders including epileptic syndromes and helps in differentiating pseudoseizures from true seizures. The need for newer radiopharmaceutical agents with specific neurochemical properties and longer shelf life are under investigation. Subtraction ictal SPECT co-registered to MRI is a promising new modality. (author)

  16. Effects of underwater turbulence on laser beam propagation and coupling into single-mode optical fiber.

    Science.gov (United States)

    Hanson, Frank; Lasher, Mark

    2010-06-01

    We characterize and compare the effects of turbulence on underwater laser propagation with theory. Measurements of the coupling efficiency of the focused beam into a single-mode fiber are reported. A simple tip-tilt control system, based on the position of the image centroid in the focal plane, was shown to maintain good coupling efficiency for a beam radius equal to the transverse coherence length, r(0). These results are relevant to high bandwidth communication technology that requires good spatial mode quality.

  17. Excitation of surface plasmon polariton modes with multiple nitrogen vacancy centers in single nanodiamonds

    Science.gov (United States)

    Kumar, Shailesh; Lausen, Jens L.; Garcia-Ortiz, Cesar E.; Andersen, Sebastian K. H.; Roberts, Alexander S.; Radko, Ilya P.; Smith, Cameron L. C.; Kristensen, Anders; Bozhevolnyi, Sergey I.

    2016-02-01

    Nitrogen-vacancy (NV) centers in diamonds are interesting due to their remarkable characteristics that are well suited to applications in quantum-information processing and magnetic field sensing, as well as representing stable fluorescent sources. Multiple NV centers in nanodiamonds (NDs) are especially useful as biological fluorophores due to their chemical neutrality, brightness and room-temperature photostability. Furthermore, NDs containing multiple NV centers also have potential in high-precision magnetic field and temperature sensing. Coupling NV centers to propagating surface plasmon polariton (SPP) modes gives a base for lab-on-a-chip sensing devices, allows enhanced fluorescence emission and collection which can further enhance the precision of NV-based sensors. Here, we investigate coupling of multiple NV centers in individual NDs to the SPP modes supported by silver surfaces protected by thin dielectric layers and by gold V-grooves (VGs) produced via the self-terminated silicon etching. In the first case, we concentrate on monitoring differences in fluorescence spectra obtained from a source ND, which is illuminated by a pump laser, and from a scattering ND illuminated only by the fluorescence-excited SPP radiation. In the second case, we observe changes in the average NV lifetime when the same ND is characterized outside and inside a VG. Fluorescence emission from the VG terminations is also observed, which confirms the NV coupling to the VG-supported SPP modes.

  18. Three-dimensional single-mode nonlinear ablative Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Yan, R.; Aluie, H.; Betti, R.; Sanz, J.; Liu, B.; Frank, A.

    2016-01-01

    The nonlinear evolution of the single-mode ablative Rayleigh-Taylor instability is studied in three dimensions. As the mode wavelength approaches the cutoff of the linear spectrum (short-wavelength modes), it is found that the three-dimensional (3D) terminal bubble velocity greatly exceeds both the two-dimensional (2D) value and the classical 3D bubble velocity. Unlike in 2D, the 3D short-wavelength bubble velocity does not saturate. The growing 3D bubble acceleration is driven by the unbounded accumulation of vorticity inside the bubble. The vorticity is transferred by mass ablation from the Rayleigh-Taylor spikes to the ablated plasma filling the bubble volume

  19. Optimizing single mode robustness of the distributed modal filtering rod fiber amplifier

    DEFF Research Database (Denmark)

    Jørgensen, Mette Marie; Petersen, Sidsel Rübner; Laurila, Marko

    2012-01-01

    High-power fiber amplifiers for pulsed applications require large mode area (LMA) fibers having high pump absorption and near diffraction limited output. Photonic crystal fibers allow realization of short LMA fiber amplifiers having high pump absorption through a pump cladding that is decoupled...... from the outer fiber diameter. However, achieving ultra low NA for single mode (SM) guidance is challenging, thus different design strategies must be applied. The distributed modal filtering (DMF) design enables SM guidance in ultra low NA fibers with very large cores, where large preform tolerances...... can be compensated during the fiber draw. Design optimization of the SM bandwidth of the DMF rod fiber is presented. Analysis of band gap properties results in a fourfold increase of the SM bandwidth compared to previous results, achieved by utilizing the first band of cladding modes, which can cover...

  20. Kerr-lens mode-locked Ti:Sapphire laser pumped by a single laser diode

    Science.gov (United States)

    Kopylov, D. A.; Esaulkov, M. N.; Kuritsyn, I. I.; Mavritskiy, A. O.; Perminov, B. E.; Konyashchenko, A. V.; Murzina, T. V.; Maydykovskiy, A. I.

    2018-04-01

    The performance of a Ti:sapphire laser pumped by a single 461 nm laser diode is presented for both the continuous-wave and the mode-locked regimes of operation. We introduce a simple astigmatism correction scheme for the laser diode beam consisting of two cylindrical lenses affecting the pump beam along the fast axis of the laser diode, which provides the mode-matching between the nearly square-shaped pump beam and the cavity mode. The resulting efficiency of the suggested Ti:Sapphire oscillator pumped by such a laser diode is analyzed for the Ti:sapphire crystals of 3 mm, 5 mm and 10 mm in length. We demonstrate that such a system provides the generation of ultrashort pulses up to 15 fs in duration with the repetition rate of 87 MHz, the average power being 170 mW.

  1. Single mode operation of a tea CO2 laser by a CW CO2 laser radiation injection

    International Nuclear Information System (INIS)

    Silakhori, K.; Soltanmoradi, F.; Behjat, A.; Montazerghaem, M.; Sadr, R.

    2005-01-01

    In this research work, single mode operation based on injection of a CW laser beam into TEA CO 2 laser cavity has been demonstrated. The technique has vast applications in research programs for laser spectroscopy and optical pumping. The observed smooth pulse shapes indicated that the system is operating in a single mode of operation, where no additional PZT mounted elements or other cavity stabilizing devices have been used. In addition, it have been observed that the output energy has not been reduced when the laser was operating in a single mode of operation, compared with the case when the laser is operating in the multi-mode regime

  2. Coherent properties of single quantum dot transitions and single photon emission

    Energy Technology Data Exchange (ETDEWEB)

    Ester, Patrick

    2008-04-23

    of the first laser pulse. The relative phase of the QDs exciton can be controlled externally via the bias voltage. This effect is the basis for the observation of RAMSEY-fringes, which are presented in this work. The coherent manipulation of the p-shell is the basis for a novel excitation scheme for single photon emission. In this work it is shown that the first excited state can be coherently manipulated, similar to the ground state. (orig.)

  3. Bend-insensitive single-mode photonic crystal fiber with ultralarge effective area for dual applications

    Science.gov (United States)

    Islam, Md. Asiful; Alam, M. Shah

    2013-05-01

    A novel photonic crystal fiber (PCF) having circular arrangement of cladding air holes has been designed and numerically optimized to obtain a bend insensitive single mode fiber with large mode area for both wavelength division multiplexing (WDM) communication and fiber-to-the-home (FTTH) application. The bending loss of the proposed bent PCF lies in the range of 10-3 to 10-4 dB/turn or lower over 1300 to 1700 nm, and 2 × 10-4 dB/turn at the wavelength of 1550 nm for a 30-mm bend radius with a higher order mode (HOM) cut-off frequency below 1200 nm for WDM application. When the whole structure of the PCF is scaled down, a bending loss of 6.78×10-4 dB/turn at 1550 nm for a 4-mm bend radius is obtained, and the loss remains in the order of 10-4 dB/turn over the same range of wavelength with an HOM cut-off frequency below 700 nm, and makes the fiber useful for FTTH applications. Furthermore, this structure is also optimized to show a splice loss near zero for fusion-splicing to a conventional single-mode fiber (SMF).

  4. BEND-INDUCED LOSSES IN A SINGLE-MODE MICROSTRUCTURED FIBER WITH A LARGE CORE

    Directory of Open Access Journals (Sweden)

    Y. A. Gatchin

    2015-03-01

    Full Text Available A study of bend-induced losses in a silica-based single-mode microstructured fiber with a core diameter ranging from 20 to 35 microns and increased relative air content in the holey cladding has been conducted. With the use of the equivalent step-index profile method in approximation of waveguide parameters of microstructured fiber (normalized frequency and normalized transverse attenuation constant the effect of bending on the spectral position of the fundamentalmode short-wavelength leakage boundary has been analyzed. Upon measurement of spectral characteristics of attenuation in the considered fibers good accordance of numerical and experimental data has been found out. It is shown that increase of the air content in the holey cladding leads to expansion of the mentioned boundary to lower wavelengths for the value from 150 to 800 nm depending on the core size and bending conditions. A single-transverse-mode propagation is achieved on fiber length of 5-10 meters due to a substantial difference in losses of fundamental and higher-order guided modes attained by bending. Optical losses in all studied samples are less than 10 dB/km at the wavelength λ = 1550 nm. The results of the study can be applied in the design of high-power laser systems having such basic requirements as a relatively large mode spot and high beam quality.

  5. Extremely low-loss single-mode photonic crystal fiber in the terahertz regime

    DEFF Research Database (Denmark)

    Islam, Raonaqul; Hasanuzzaman, G. K M; Sadath, Md Anwar

    2015-01-01

    This paper presents an updated design and numerical characterization of a rotated porous-core hexagonal photonic crystal fiber (PCF) for single-mode terahertz (THz) wave guidance. The simulation results are found using an efficient finite element method (FEM) which show a better and ultra......-low effective absorption loss of 0.045 cm-1 at 1 THz and a more flattened dispersion of 0.74±0.07ps/THz/cm in a wider bandwidth (0.54-1.36 THz) than the previously reported results. Besides, the single-mode region has been extended up to 1.74 THz (previously up to 1.3 THz) which is advantageous for wideband THz...

  6. Highly optimized tunable Er3+-doped single longitudinal mode fiber ring laser, experiment and model

    DEFF Research Database (Denmark)

    Poulsen, Christian; Sejka, Milan

    1993-01-01

    A continuous wave (CW) tunable diode-pumped Er3+-doped fiber ring laser, pumped by diode laser at wavelengths around 1480 nm, is discussed. Wavelength tuning range of 42 nm, maximum slope efficiency of 48% and output power of 14.4 mW have been achieved. Single longitudinal mode lasing with a line...... with a linewidth of 6 kHz has been measured. A fast model of erbium-doped fiber laser was developed and used to optimize output parameters of the laser......A continuous wave (CW) tunable diode-pumped Er3+-doped fiber ring laser, pumped by diode laser at wavelengths around 1480 nm, is discussed. Wavelength tuning range of 42 nm, maximum slope efficiency of 48% and output power of 14.4 mW have been achieved. Single longitudinal mode lasing...

  7. Stability of the single-mode output of a laser diode array with phase conjugate feedback

    DEFF Research Database (Denmark)

    Juul Jensen, S.; Løbel, M.; Petersen, P.M.

    2000-01-01

    . The output power and the center wavelength are found to be extremely stable in a 100 h stability measurement. External feedback of the output beam into the laser is seen to decrease both the spatial and the temporal coherence of the output significantly. We outline an approach to obtain a stable single......The stability of the output of a single-mode laser diode array with frequency selective phase conjugate feedback has been investigated experimentally. Both the long-term stability of the laser output and the sensitivity to feedback generated by external reflection of the output beam are examined......-mode output when external feedback is present using spatial filtering in the path of the output beam. (C) 2000 American Institute of Physics....

  8. Whispering-gallery-mode microlaser based on self-assembled organic single-crystalline hexagonal microdisks.

    Science.gov (United States)

    Wang, Xuedong; Liao, Qing; Kong, Qinghua; Zhang, Yi; Xu, Zhenzhen; Lu, Xiaomei; Fu, Hongbing

    2014-06-02

    Whispering-gallery-mode (WGM) resonators of semiconductor microdisks have been applied for achieving low-threshold and narrow-linewidth microlasers, but require sophisticated top-down processing technology. Organic single-crystalline hexagonal microdisks (HMDs) of p-distyrylbenzene (DSB) self-assembled from solution can function as WGM microresonators with a cavity quality factor (Q) of 210. Both multiple- and single-mode lasing had been achieved using DSB HMDs with an edge length of 4.3 and 1.2 μm, respectively. These organic microdisks fabricated by bottom-up self-assembly approach may offer potential applications as low-threshold microlaser sources for photonic circuit integration. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Benchmarking of Grid Fault Modes in Single-Phase Grid-Connected Photovoltaic Systems

    DEFF Research Database (Denmark)

    Yang, Yongheng; Blaabjerg, Frede; Zou, Zhixiang

    2013-01-01

    Pushed by the booming installations of singlephase photovoltaic (PV) systems, the grid demands regarding the integration of PV systems are expected to be modified. Hence, the future PV systems should become more active with functionalities of Low Voltage Ride-Through (LVRT) and grid support...... capability. The control methods, together with grid synchronization techniques, are responsible for the generation of appropriate reference signals in order to handle ride-through grid faults. Thus, it is necessary to evaluate the behaviors of grid synchronization methods and control possibilities in single...... phase systems under grid faults. The intent of this paper is to present a benchmarking of grid fault modes that might come in future single-phase PV systems. In order to map future challenges, the relevant synchronization and control strategies are discussed. Some faulty modes are studied experimentally...

  10. Quantum discord dynamics of two qubits in single-mode cavities

    International Nuclear Information System (INIS)

    Wang Chen; Chen Qing-Hu

    2013-01-01

    The dynamics of quantum discord for two identical qubits in two independent single-mode cavities and a common single-mode cavity are discussed. For the initial Bell state with correlated spins, while the entanglement sudden death can occur, the quantum discord vanishes only at discrete moments in the independent cavities and never vanishes in the common cavity. Interestingly, quantum discord and entanglement show opposite behavior in the common cavity, unlike in the independent cavities. For the initial Bell state with anti-correlated spins, quantum discord and entanglement behave in the same way for both independent cavities and a common cavity. It is found that the detunings always stabilize the quantum discord. (general)

  11. BRIEF COMMUNICATIONS: Investigation of the state of polarization of light in a single-mode fiber waveguide

    Science.gov (United States)

    Kozel, S. M.; Kreopalov, V. I.; Listvin, V. N.; Glavatskikh, N. A.

    1983-01-01

    An analysis is made of the polarization anisotropy of a single-mode fiber with a twisted elliptic core. The Jones matrix is obtained and the complex function of the state of polarization of light in a fiber is investigated. The results are reported of measurements of the linear and circular birefringence of a borosilicate single-mode glass fiber.

  12. Comparison of emissions from on-road sources using a mobile laboratory under various driving and operational sampling modes

    Directory of Open Access Journals (Sweden)

    M. Zavala

    2009-01-01

    Full Text Available Mobile sources produce a significant fraction of the total anthropogenic emissions burden in large cities and have harmful effects on air quality at multiple spatial scales. Mobile emissions are intrinsically difficult to estimate due to the large number of parameters affecting the emissions variability within and across vehicles types. The MCMA-2003 Campaign in Mexico City has showed the utility of using a mobile laboratory to sample and characterize specific classes of motor vehicles to better quantify their emissions characteristics as a function of their driving cycles. The technique clearly identifies "high emitter" vehicles via individual exhaust plumes, and also provides fleet average emission rates. We have applied this technique to Mexicali during the Border Ozone Reduction and Air Quality Improvement Program (BORAQIP for the Mexicali-Imperial Valley in 2005. We analyze the variability of measured emission ratios for emitted NOx, CO, specific VOCs, NH3, and some primary fine particle components and properties by deploying a mobile laboratory in roadside stationary sampling, chase and fleet average operational sampling modes. The measurements reflect various driving modes characteristic of the urban fleets. The observed variability for all measured gases and particle emission ratios is greater for the chase and roadside stationary sampling than for fleet average measurements. The fleet average sampling mode captured the effects of traffic conditions on the measured on-road emission ratios, allowing the use of fuel-based emission ratios to assess the validity of traditional "bottom-up" emissions inventories. Using the measured on-road emission ratios, we estimate CO and NOx mobile emissions of 175±62 and 10.4±1.3 metric tons/day, respectively, for the gasoline vehicle fleet in Mexicali. Comparisons with similar on-road emissions data from Mexico City indicated that fleet average NO emission ratios were

  13. Diode-end-pumped single-longitudinal-mode passively Q-switched Nd:GGG laser

    Science.gov (United States)

    Xue, Feng; Zhang, Sasa; Cong, Zhenhua; Huang, Qingjie; Guan, Chen; Wu, Qianwen; Chen, Hui; Bai, Fen; Liu, Zhaojun

    2018-03-01

    Diode-end-pumped passively Q-switched Nd:GGG laser in a ring cavity at 1062 nm was demonstrated. Single-longitudinal-mode laser linewidth less than 0.5 pm was accomplished by unidirectional operation. The maximum output pulse energy was 437 µJ and the pulse width was 43 ns when Cr4+:YAG with an initial transmission of 61% was used.

  14. Investigation of bending loss in a single-mode optical fibre

    Indian Academy of Sciences (India)

    (glass) used for making optical fibres is about 26.211 Pa. Since radii of the core and cladding in the single-mode fibre used were 4.5 and 62.5 µm respectively, by changing θ/l, loss due to torsion stress on the core and the clad was investigated. Variation of loss against torsion stress is given in figures 10 and 11 for the core ...

  15. Combined effect of viscosity and vorticity on single mode Rayleigh-Taylor instability bubble growth

    International Nuclear Information System (INIS)

    Banerjee, Rahul; Mandal, Labakanta; Roy, S.; Khan, M.; Gupta, M. R.

    2011-01-01

    The combined effect of viscosity and vorticity on the growth rate of the bubble associated with single mode Rayleigh-Taylor instability is investigated. It is shown that the effect of viscosity on the motion of the lighter fluid associated with vorticity accumulated inside the bubble due to mass ablation may be such as to reduce the net viscous drag on the bubble exerted by the upper heavier fluid as the former rises through it.

  16. Single Longitudinal Mode, High Repetition Rate, Q-switched Ho:YLF Laser for Remote Sensing

    Science.gov (United States)

    Bai, Yingxin; Yu, Jirong; Petzar, Paul; Petros, M.; Chen, Songsheng; Trieu, Bo; Lee, Nyung; Singh, U.

    2009-01-01

    Ho:YLF/LuLiF lasers have specific applications for remote sensing such as wind-speed measurement and carbon dioxide (CO2) concentration measurement in the atmosphere because the operating wavelength (around 2 m) is located in the eye-safe range and can be tuned to the characteristic lines of CO2 absorption and there is strong backward scattering signal from aerosol (Mie scattering). Experimentally, a diode pumped Ho:Tm:YLF laser has been successfully used as the transmitter of coherent differential absorption lidar for the measurement of with a repetition rate of 5 Hz and pulse energy of 75 mJ [1]. For highly precise CO2 measurements with coherent detection technique, a laser with high repetition rate is required to averaging out the speckle effect [2]. In addition, laser efficiency is critically important for the air/space borne lidar applications, because of the limited power supply. A diode pumped Ho:Tm:YLF laser is difficult to efficiently operate in high repetition rate due to the large heat loading and up-conversion. However, a Tm:fiber laser pumped Ho:YLF laser with low heat loading can be operated at high repetition rates efficiently [3]. No matter whether wind-speed or carbon dioxide (CO2) concentration measurement is the goal, a Ho:YLF/LuLiF laser as the transmitter should operate in a single longitudinal mode. Injection seeding is a valid technique for a Q-switched laser to obtain single longitudinal mode operation. In this paper, we will report the new results for a single longitudinal mode, high repetition rate, Q-switched Ho:YLF laser. In order to avoid spectral hole burning and make injection seeding easier, a four mirror ring cavity is designed for single longitudinal mode, high repetition rate Q-switched Ho:YLF laser. The ramp-fire technique is chosen for injection seeding.

  17. Single frequency Nd:YLF and Nd:YVO4 laser in the red emission

    International Nuclear Information System (INIS)

    Camargo, Fabiola de Almeida

    2010-01-01

    All solid-state continuous-wave (cw) narrow emission linewidth and tunable red lasers are convenient alternative sources to bulky and expensive dye-lasers for high precision laser spectroscopy. Single-frequency operation of diode-pumped Nd:YLiF 4 and Nd:YVO 4 cw ring lasers were investigated in the 1.32 - 1.34μm range, together with their intracavity second-harmonic generation (SHG) to the red spectral range (0.65 - 0.67μm) using either BiB 3 O 6 (BiBO) or periodically-poled KTiOPO 4 (ppKTP) crystals. We report on such a single-end diode-pumped Nd:YVO 4 unidirectional red ring laser containing a type-I cut BiBO nonlinear crystal, yielding a record of 680 mW of single-longitudinal mode (SLM) red output power at 671.1nm without any intra-cavity etalon. For smooth SLM wavelength tuning over the full gain bandwidth (∼4 nm), a partially-coated (R = 40%) 100μm-thin etalon was found necessary, reducing the maximum SLM power (at 671.15 nm) to 380 mW. At 1342.5nm and with a T = 2% transmission output coupler, the laser provided an optimal 1.5W of single-frequency power. We demonstrate also optimal intracavity SHG of a Nd:YLF ring laser in the π- polarization (λ = 1321.5nm) using a ppKTP. The laser yielded 1.4 W of single frequency red power at 660.5 nm, as much as the maximum fundamental power that can be extracted from the resonator using an optimal output coupler. With a partially coated (R = 25%) thin etalon, the laser was tunable over Δλ∼ 1.6nm. (author)

  18. Three-Input Single-Output Voltage-Mode Multifunction Filter with Electronic Controllability Based on Single Commercially Available IC

    Directory of Open Access Journals (Sweden)

    Supachai Klungtong

    2017-01-01

    Full Text Available This paper presents a second-order voltage-mode filter with three inputs and single-output voltage using single commercially available IC, one resistor, and two capacitors. The used commercially available IC, called LT1228, is manufactured by Linear Technology Corporation. The proposed filter is based on parallel RLC circuit. The filter provides five output filter responses, namely, band-pass (BP, band-reject (BR, low-pass (LP, high-pass (HP, and all-pass (AP functions. The selection of each filter response can be done without the requirement of active and passive component matching condition. Furthermore, the natural frequency and quality factor are electronically controlled. Besides, the nonideal case is also investigated. The output voltage node exhibits low impedance. The experimental results can validate the theoretical analyses.

  19. Relativistic electron acceleration by whistler-mode chorus emissions associated with substorms

    Science.gov (United States)

    Omura, Yoshiharu

    Whistler-mode chorus emissions are generated at the geomagnetic equator by injection of energetic electrons into the inner magnetosphere during geomagnetically disturbed periods of substorms[1]. We perform test particle simulations assuming whistler-mode chorus wave packets that are generated at the geomagnetic equator propagate away from the equator in both poleward directions. While electrons in the energy range 10 - 100 keV are primarily responsible for the generation of chorus waves through pitch angle diffusion into the loss cone, it has been found that a fraction of the higher-energy electrons from a few hundred keV to a few MeV are effectively accelerated by chorus due to special nonlinear trapping processes called relativistic turning acceleration (RTA)[2] and ultra-relativistic acceleration (URA)[3]. In the present study we confirm that the RTA and URA processes take place for a wave packet with variable frequency such as that occurring in a rising tone of chorus emissions. We study the efficiency of the RTA and URA processes for different particle energies. A Green's function method is used to describe the evolution of the particle energy distribution function. The RTA and URA processes due to chorus emissions create a high-energy tail in the electron energy distribution function[4]. The shape of the high-energy tail is determined by the distribution function of the seed electrons in the lower-energy range. The RTA and URA can accelerate electrons in a much shorter timescale than that estimated by quasi-linear diffusion theory, e.g., it typically takes tens of minutes to hours for a few keV seed electrons to be accelerated to energies of a few MeV by RTA and URA. References 1. Y. Omura, Y. Katoh, and D. Summers, Theory and simulation of the generation of whistlermode chorus, J. Geophys. Res., in press. 2. Y. Omura, N. Furuya, D. Summers, J Geophys. Res., Vol. 112, A06236, doi:10.1029/2006JA012243, 2007. 3. D. Summers and Y. Omura, Geophys. Res. Lett., 34

  20. Effects of breathing and oblong mode phonons on transport properties in a single-electron transistor.

    Science.gov (United States)

    Nishiguchi, Norihiko; Wybourne, Martin N

    2010-02-17

    We investigate theoretically the transport characteristics of a single-electron transistor affected by the dynamic deformation of the device configuration due to phonons. By considering changes in capacitances and tunnel resistances caused by the breathing and oblong vibrations of the island that forms part of the transistor, we formulate the electron-phonon interaction peculiar to the device and derive its transport properties by means of the master equation. For a single electron transistor with a gold nanoparticle island of radius 1 nm, we demonstrate the contribution to the transport properties that originates from tunneling channels associated with THz phonon emission and absorption.

  1. Towards simultaneous single emission microscopy and magnetic resonance imaging

    Science.gov (United States)

    Cai, Liang

    In recent years, the combined nuclear imaging and magnetic resonance imaging (MRI) has drawn extensive research effort. They can provide simultaneously acquired anatomical and functional information inside the human/small animal body in vivo. In this dissertation, the development of an ultrahigh resolution MR-compatible SPECT (Single Photon Emission Computed Tomography) system that can be operated inside a pre-existing clinical MR scanner for simultaneous dual-modality imaging of small animals will be discussed. This system is constructed with 40 small pixel CdTe detector modules assembled in a fully stationary ring SPECT geometry. Series of experiments have demonstrated that this system is capable of providing an imaging resolution of CdTe detector module that we recently developed. Each module consists of CdTe detectors having an overall size of 2.2 cm x 1.1 cm, divided into 64 x 32 pixels of 350 mum in size. A novel hybrid pixel-waveform (HPWF) readout system is also designed to alleviate several challenges for using small-pixel CdTe detectors in ultrahigh-resolution SPECT imaging applications. The HPWF system utilizes a modified version of a 2048-channel 2-D CMOS ASIC to readout the anode pixel, and a digitizing circuitry to sample the signal waveform induced on the cathode. The cathode waveform acquired with the HPWF circuitry offers excellent spatial resolution, energy resolution and depth of interaction (DOI) information, even with the presence of excessive charge-sharing/charge-loss between the small anode pixels. The HPWF CdTe detector is designed and constructed with a minimum amount of ferromagnetic materials, to ensure the MR-compatibility. To achieve sub-500?m imaging resolution, two special designed SPECT apertures have been constructed with different pinhole sizes of 300?m and 500?m respectively. It has 40 pinhole inserts that are made of cast platinum (90%)-iridium (10%) alloy, which provides the maximum stopping power and are compatible with MR

  2. Discharge Modes Suggested by Emission Spectra of Nitrogen Dielectric Barrier Discharge with Wire-Cylinder Electrodes

    International Nuclear Information System (INIS)

    Yang Fuxiang; Mu Zongxin; Zhang Jialiang

    2016-01-01

    In this paper, nitrogen dielectric barrier discharge (DBD) plasma was generated in a quartz tube with coaxial wire-cylinder electrodes at atmospheric pressure. By varying the nitrogen gas flow (F N ) in the range of 0-1 m 3 /h, the plasma optical emission spectra (OES) were measured and studied. The vibration (T vib ) and rotation temperature (T rot ) of nitrogen were obtained, by fitting the rovibronic bands of N 2 (C 3 Π u – B 3 Π g , 0-1), and by the Boltzmann plot method for purposes of comparison. T vib increased up to 2481 K with increasing nitrogen flow till 0.2 m 3 /h, and then decreased with further increasing F N , while T rot decreased monotonously and approached to ∼350 K for F N ≥ 0.6 m 3 /h. The intensity of N 2 (C 3 Π u – B 3 Π g , 0-0, 1-0, 0-3) and N 2 + (B 2 Σ u + – X 2 Σ + g , 0-0) exhibited similar evolution with increasing F N to those of the T vib and T rot , respectively. The discharge photos revealed that the discharge filaments gradually decreased with increasing F N , and eventually disappeared, which implied that a discharge mode transition emerged with increasing F N . The possible mechanism for the discharge mode transition is studied in detail according to the vibration (T vib ) and rotation temperature (T rot ) of nitrogen. (paper)

  3. A novel L-shaped linear ultrasonic motor operating in a single resonance mode

    Science.gov (United States)

    Zhang, Bailiang; Yao, Zhiyuan; Liu, Zhen; Li, Xiaoniu

    2018-01-01

    In this study, a large thrust linear ultrasonic motor using an L-shaped stator is described. The stator is constructed by two mutually perpendicular rectangular plate vibrators, one of which is mounted in parallel with the slider to make the motor structure to be more compact. The symmetric and antisymmetric modes of the stator based on the first order bending vibration of two vibrators are adopted, in which each resonance mode is assigned to drive the slider in one direction. The placement of piezoelectric ceramics in a stator could be determined by finite element analysis, and the influence of slots in the head block on the vibration amplitudes of driving foot was studied as well. Three types of prototypes (non-slotted, dual-slot, and single-slot) were fabricated and experimentally investigated. Experimental results demonstrated that the prototype with one slot exhibited the best mechanical output performance. The maximum loads under the excitation of symmetric mode and antisymmetric mode were 65 and 90 N, respectively.

  4. Impact of quantum–classical correspondence on entanglement enhancement by single-mode squeezing

    International Nuclear Information System (INIS)

    Joseph, Sijo K.; Chew, Lock Yue; Sanjuán, Miguel A.F.

    2014-01-01

    Quantum entanglement between two field modes can be achieved through the collective squeezing of the two respective modes. If single-mode squeezing is performed prior to such a two-mode squeezing, an enhancement of entanglement production can happen. Interestingly, the occurrence of this enhancement can be implicitly linked to the local classical dynamical behavior via the paradigm of quantum–classical correspondence. In particular, the entanglement generated through quantum chaos is found to be hardly enhanced by prior squeezing, since it is bounded by the saturation value of the maximally entangled Schmidt state with fixed energy. These results illustrate that entanglement enhancement via initial squeezing can serve as a useful indicator of quantum chaotic behaviour. - Highlights: • Continuous-variable entanglement is explored in the Pullen–Edmonds Hamiltonian. • The local phase-space structure and the entanglement enhancement are related. • Entanglement enhancement via squeezing is smaller for the chaotic orbit. • Entanglement enhancement via squeezing is higher for the regular orbit. • The magnitude of the entanglement enhancement serves as a quantum-chaos indicator

  5. Excimer emission properties on pyrene-labeled protein surface: correlation between emission spectra, ring stacking modes, and flexibilities of pyrene probes.

    Science.gov (United States)

    Fujii, Akira; Sekiguchi, Yutaka; Matsumura, Hiroyoshi; Inoue, Tsuyoshi; Chung, Wen-Sheng; Hirota, Shun; Matsuo, Takashi

    2015-03-18

    The excimer emission of pyrene is popularly employed for investigating the association between pyrene-labeled biomolecules or between pyrene-labeled places in a biomolecule. The property of pyrene excimer emission is affected by the fluctuation in ring stacking modes, which originates from the structural flexibilities of pyrene probes and/or of labeled places. Investigations of the excimer emission in terms of dynamics of pyrene stacking modes provide the detailed spatial information between pyrene-labeled places. In order to evaluate the effects of probe structures and fluctuation in pyrene-pyrene association modes on their emission properties on protein surface, three types of pyrene probe with different linker lengths were synthesized and conjugated to two cysteine residues in the A55C/C77S/V169C mutant of adenylate kinase (Adk), an enzyme that shows a structural transition between OPEN and CLOSED forms. In the CLOSED form of Adk labeled by a pyrene probe with a short linker, excimer emission was found to be predominated by the ground-state association of pyrenes. The pyrene stacking structure on the protein surface was successfully determined by an X-ray crystallographic analysis. However, the emission decay in the protein suggested the existence of several stacking orientations in solution. With the increase in the linker length, the effect of fluctuation in pyrene association modes on the spectral properties distinctly emerged at both ground and excited states. The combination of steady-state and time-resolved spectroscopic analyses is useful for differentiation in the origin of the excimer emission, which is essential for precisely understanding the interaction fashions between pyrene-labeled biomolecules.

  6. Fine structure of the stimulated Raman spectrum in compressed hydrogen. The relaxation-oscillation mode of backscattered Stokes emission

    International Nuclear Information System (INIS)

    Bespalov, V.G.; Efimov, Yu.N.; Staselko, D.I.

    1992-01-01

    This paper studies the emission spectra of backscattered stimulated Raman scattering (SRS) in compressed hydrogen in the relaxation-oscillation mode and the compression SRS mode for the minimum width of the spontaneous scattering spectrum (in the region of the Dicke dip). It is shown that the generation of a train of Stokes-emission subpulses results in the appearance of fine structure in the backscattered SRS spectrum. The influence of the temporal structure of reflected Stokes pulses on this spectrum and on the appearance of fine structure in it is analyzed. The conditions for generating spectrally limited (without phase modulation), extremely coherent Stokes pulses are explained. 18 refs., 3 figs

  7. Study of the impact of board orientation on radiated emissions due to common-mode currents on attached cables

    DEFF Research Database (Denmark)

    Sørensen, Morten; Hubing, Todd H.; Jensen, Kim

    2016-01-01

    Common-mode current on attached cables is a typical source for radiated emission. Several models have been made for conversion of the intended differential signal to unwanted common-mode current on cables. In this paper we refine a method for identifying the radiation sources arising from a long...... microstrip. This method is used to show that the radiated emission from a PCB with attached cable(s) caused by a long trace depends on whether the trace is facing up or down with different result for voltage and current sources....

  8. Single mode operation in a pulsed Ti:sapphire laser oscillator with a grazing-incidence four-mirror cavity

    CERN Document Server

    Ko, D K; Binks, D J; Gloster, L A W; King, T A

    1998-01-01

    We demonstrate stable single mode operation in a pulsed Ti:sapphire laser oscillator with a novel grazing-incidence four-mirror coupled cavity. This cavity consists of a grating, a gain medium, and four mirrors and, therefore, has a four-arm interferometer configuration. Through the interferometric effect, we could suppress the adjacent modes and obtain stable single mode operation with a bandwidth of < 200 MHz. We also have developed a general analysis of the laser modes and the threshold conditions for configuration and the experimental results agree well with the theoretical predictions.

  9. Single photon emissions from InAs/GaAs quantum dots embedded in GaAs/SiO2 hybrid microdisks

    Science.gov (United States)

    Yue, P. Y.; Dou, X. M.; Wang, H. Y.; Ma, B.; Niu, Z. C.; Sun, B. Q.

    2018-03-01

    An approach to integrate InAs/GaAs quantum dots (QDs) active layer on SiO2/Si chip for single photon emitter is demonstrated. The QDs are embedded in GaAs/SiO2 hybrid whispering gallery mode microdisks with the diameters of 10 and 5 μm, corresponding to the quality factors (Q) of 2287 ± 167 and 4366 ± 208, respectively. Temperature tuning QD-cavity resonance is observed. The cavity-enhanced exciton spontaneous emission and single photon emission characteristics are studied.

  10. Response of microchannel plates in ionization mode to single particles and electromagnetic showers

    Science.gov (United States)

    Barnyakov, A. Yu.; Barnyakov, M. Yu.; Brianza, L.; Cavallari, F.; Cipriani, M.; Ciriolo, V.; del Re, D.; Gelli, S.; Ghezzi, A.; Gotti, C.; Govoni, P.; Katcin, A. A.; Malberti, M.; Martelli, A.; Marzocchi, B.; Meridiani, P.; Organtini, G.; Paramatti, R.; Pigazzini, S.; Preiato, F.; Prisekin, V. G.; Rahatlou, S.; Rovelli, C.; Santanastasio, F.; Tabarelli de Fatis, T.

    2018-01-01

    Hundreds of concurrent collisions per bunch crossing are expected at future hadron colliders. Precision timing calorimetry has been advocated as a way to mitigate the pileup effects and, thanks to their excellent time resolution, microchannel plates (MCPs) are good candidate detectors for this goal. We report on the response of MCPs, used as secondary emission detectors, to single relativistic particles and to electromagnetic showers. Several prototypes, with different geometries and characteristics, were exposed to particle beams at the INFN-LNF Beam Test Facility and at CERN. Their time resolution and efficiency are measured for single particles and as a function of the multiplicity of particles. Efficiencies between 50% and 90% to single relativistic particles are reached, and up to 100% in presence of a large number of particles. Time resolutions between 20 ps and 30 ps are obtained.

  11. Microwave measurements of energy lost to longitudinal modes by single electron bunches traversing periodic structures

    International Nuclear Information System (INIS)

    Wang, J.W.; Loew, G.A.; Weaver, J.N.; Wilson, P.B.

    1981-10-01

    In the design of future linear colliders, it will be important to minimize the loss of beam energy due to the excitation of higher-order modes in the accelerator structure by single bunches of electrons or positrons. This loss is not only detrimental in itself but also gives rise to energy spectrum widening and transverse emittance growth. Microwave measurements made on disk-loaded and alternating-spoke structures to determine the loss to the longitudinal modes are described. In these measurements the Gaussian bunch is simulated by a current pulse of the same shape transmitted through the structure on an axial center conductor. Results to date are presented for the total longitudinal loss parameter per period K in volts per picocoulomb

  12. Electrically tunable Brillouin fiber laser based on a metal-coated single-mode optical fiber

    Directory of Open Access Journals (Sweden)

    S.M. Popov

    Full Text Available We explore tunability of the Brillouin fiber laser employing Joule heating. For this purpose, 10-m-length of a metal-coated single-mode optical cavity fiber has been directly included into an electrical circuit, like a conductor wire. With the current up to ∼3.5 A the laser tuning is demonstrated over a spectrum range of ∼400 MHz. The observed laser line broadening up to ∼2 MHz is explained by frequency drift and mode-hoping in the laser caused by thermal noise. Keywords: Brillouin fiber laser, Metal-coated optical fiber, Laser tuning, Fiber sensors

  13. Evaluation of single photon and Geiger mode Lidar for the 3D Elevation Program

    Science.gov (United States)

    Stoker, Jason M.; Abdullah, Qassim; Nayegandhi, Amar; Winehouse, Jayna

    2016-01-01

    Data acquired by Harris Corporation’s (Melbourne, FL, USA) Geiger-mode IntelliEarth™ sensor and Sigma Space Corporation’s (Lanham-Seabrook, MD, USA) Single Photon HRQLS sensor were evaluated and compared to accepted 3D Elevation Program (3DEP) data and survey ground control to assess the suitability of these new technologies for the 3DEP. While not able to collect data currently to meet USGS lidar base specification, this is partially due to the fact that the specification was written for linear-mode systems specifically. With little effort on part of the manufacturers of the new lidar systems and the USGS Lidar specifications team, data from these systems could soon serve the 3DEP program and its users. Many of the shortcomings noted in this study have been reported to have been corrected or improved upon in the next generation sensors.

  14. Report on first masing and single mode locking in a prebunched beam FEM oscillator

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, M.; Eichenbaum, A.; Kleinman, H. [Tel-Aviv Univ., Ramat-Aviv (Israel)] [and others

    1995-12-31

    Radiation characteristics of a table-top free electron maser (FEM) are described in this paper. The FEM employs a prebunched electron beam and is operated as an oscillator in the low-gain collective (Raman) regime. Using electron beam prebunching single mode locking at any one of the possible oscillation modes was obtained. The electron beam is prebunched by a microwave tube section before it is injected into the wiggler. By tuning the electron beam bunching frequency, the FEM oscillation frequency can be locked to any eigen frequency of the resonant waveguide cavity which is within the frequency band of net gain of the FEM. The oscillation build up process is sped up, when the FEM operates with a prebunched electron beam, and the build-up time of radiation is shortened significantly. First measurements of masing with and without prebunching and characterization of the emitted radiation are reported.

  15. Harmonics Suppression for Single-Phase Grid-Connected Photovoltaic Systems in Different Operation Modes

    DEFF Research Database (Denmark)

    Yang, Yongheng; Zhou, Keliang; Blaabjerg, Frede

    2013-01-01

    -connected PV inverters may be severely affected in different operation modes. In this paper, a detailed analysis is conducted to reveal the relationship between the harmonics level with the power factor and the current level in the PV systems. A current control solution which employs an Internal Model...... Principle (IMP) is proposed to suppress the harmonic currents injected into the grid. Experiments are carried out to verify the analysis and the performance of the proposed control method. It is demonstrated that the proposed method presents an effective solution to harmonics suppression for single......-phase grid-connected PV systems in different operation modes. Especially, it can remove higher order harmonics effectively leading to a better power quality compared to the Proportional plus Multi-Resonant Controller, and it has less computational burden....

  16. Differential modal delay measurements in a graded-index multimode fibre waveguide, using a single-mode fibre pro mode selection

    International Nuclear Information System (INIS)

    Sunak, H.R.D.; Soares, S.M.

    1981-01-01

    Differential model delay (DMD) measurements in graded-index multimode optical fibre waveguides, which are very promising for many types of communication system were carried out. These DMD measurements give a direct indication of the deviation of the refractive index profile, from the optimum value, at a given wavelength. For the first time, by using a single-mode fibre, a few guided modes in the graded-index fibre were selected, in two different ways: launching a few modes at the input end or selecting a few modes at the output end. By doing so important features of propagation in the fibre were revealed, especially the intermodal coupling that may exist. The importance of this determination of intermodal coupling or mode mixing, particularly when many fibres are joined together in a link, and the merits of DMD measurements in general and their importance for the production of high bandwidth graded-index fibres are discussed. (Author) [pt

  17. Dynamics of Nonlinear Excitation of the High-Order Mode in a Single-Mode Step-Index Optical Fiber

    Science.gov (United States)

    Burdin, V.; Bourdine, A.

    2018-04-01

    This work is concerned with approximate model of higher-order mode nonlinear excitation in a singlemode silica optical fiber. We present some results of simulation for step-index optical fiber under femtosecond optical pulse launching, which confirm ability of relatively stable higher-order mode excitation in such singlemode optical fiber over sufficiently narrow range of launched optical power variation.

  18. Tunable single photonic defect-mode in cholesteric liquid crystals with laser-induced local modifications of helix

    International Nuclear Information System (INIS)

    Yoshida, Hiroyuki; Lee, Chee Heng; Fujii, Akihiko; Ozaki, Masanori

    2006-01-01

    The authors demonstrate a tunable single photonic defect-mode in a single cholesteric liquid crystal material based on a structural defect introduced by local modification of the helix. An unpolymerized region of cholesteric liquid crystal acting as the defect was left between two polymerized regions via a two-photon excitation laser-lithography process. Upon polymerization, the cholesteric liquid crystal helix elongated and became thermally stable, and a single photonic defect mode was exhibited due to the contrast in the helix pitch at the defect. The defect mode showed tunability upon heating, and a 36 nm redshift was seen over a temperature range of 30 deg. C

  19. High energy nanosecond laser pulses delivered single-mode through hollow-core PBG fibers.

    Science.gov (United States)

    Shephard, Jonathan; Jones, J; Hand, D; Bouwmans, G; Knight, J; Russell, P; Mangan, B

    2004-02-23

    We report on the development of hollow-core photonic bandgap fibers for the delivery of high energy pulses for precision micromachining applications. Short pulses of (65ns pulse width) and energies of the order of 0.37mJ have been delivered in a single spatial mode through hollow-core photonic bandgap fibers at 1064nm using a high repetition rate (15kHz) Nd:YAG laser. The ultimate laser-induced damage threshold and practical limitations of current hollow-core fibers for the delivery of short optical pulses are discussed.

  20. Plasma-implantation-based surface modification of metals with single-implantation mode

    Science.gov (United States)

    Tian, X. B.; Cui, J. T.; Yang, S. Q.; Fu, Ricky K. Y.; Chu, Paul K.

    2004-12-01

    Plasma ion implantation has proven to be an effective surface modification technique. Its biggest advantage is the capability to treat the objects with irregular shapes without complex manipulation of target holder. Many metal materials such as aluminum, stainless steel, tool steel, titanium, magnesium etc, has been treated using this technique to improve their wear-resistance, corrosion-resistance, fatigue-resistance, oxidation-resistance, bio-compatiblity etc. However in order to achieve thicker modified layers, hybrid processes combining plasma ion implantation with other techniques have been frequently employed. In this paper plasma implantation based surface modification of metals using single-implantation mode is reviewed.

  1. Single-longitudinal-mode BEFL incorporating a Bragg grating written in EDF

    Science.gov (United States)

    Gao, Ya; Sun, Junqiang; Chen, Guodong; Xie, Heng

    2015-06-01

    A stable and tunable single-longitudinal-mode (SLM) Brillouin/Erbium fiber laser (BEFL) with narrow linewidth is proposed and experimentally demonstrated. A uniform Bragg grating written in a segment of unpumped Erbium-doped fiber (EDF) is incorporated as an auto-tracking filter to achieve SLM operation. A length of 5 m pumped EDF is used to provide both Brillouin and linear gain in the cavity. The linewidth is measured to be 18 kHz and the lasing peak power fluctuation and wavelength shift are monitored less than 0.027 dB and 2 pm respectively.

  2. Highly damped quasinormal modes of generic single-horizon black holes

    Energy Technology Data Exchange (ETDEWEB)

    Daghigh, Ramin G [Physics Department, University of Winnipeg, Winnipeg, Manitoba R3B 2E9 (Canada); Kunstatter, Gabor [Winnipeg Institute for Theoretical Physics, Winnipeg, Manitoba (Canada)

    2005-10-07

    We calculate analytically the highly damped quasinormal mode spectra of generic single-horizon black holes using the rigorous WKB techniques of Andersson and Howls (2004 Class. Quantum Grav. 21 1623). We thereby provide a firm foundation for previous analysis, and point out some of their possible limitations. The numerical coefficient in the real part of the highly damped frequency is generically determined by the behaviour of coupling of the perturbation to the gravitational field near the origin, as expressed in tortoise coordinates. This fact makes it difficult to understand how the famous ln(3) could be related to the quantum gravitational microstates near the horizon.

  3. Investigation of the glide modes of single crystals of beryllium; Etude des modes de glissement de monocristaux de beryllium

    Energy Technology Data Exchange (ETDEWEB)

    Regnier, P. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-05-01

    The flow characteristics of single crystals of beryllium specially oriented for slip along a single plane and a single direction have been thoroughly investigated. The elastic limit and the strain hardening in basal glide have been investigated in the temperature range (-195 deg. C, 400 deg. C) in tension as well as in compression. Observation of the slip lines and of the dislocation configurations have also been made in addition to the mechanical tests. The prismatic slip has been studied in greater detail: tensile tests have been performed on specimens carefully oriented at different temperatures, strain rates and with varying orientations of the basal and of the prism planes. Tests have also been made in the micro-strain range; the slip lines and the dislocation arrangements were observed in detail. The very unusual variation of the elastic limit with temperature is not due to impurities but to a cross slip mechanism. A model of dislocation locking is proposed to account for the experimental results. This mechanism assumes that the a-bar dislocations may also dissociate on the prism planes [101-bar 0]. Various possible dissociations are suggested, the most probable of which corresponds to the phase transformation: Hexagonal close packed to body centered cubic. This proposal can be extended to account for the relative ease of glide on the different systems in the hexagonal close packed metals. (author) [French] L' ecoulement de monocristaux de berylliurn deformes en glissement basal et en glissement prismatique a ete etudie sur des echantillons orientes de maniere a favoriser au maximum la deformation suivant une seule direction d'un seul systeme de glissement. L'influence de la temperature sur la limite elastique et la consolidation en glissement basal a ete etudie depuis -195 deg. C jusqu' 400 deg. C sur des echantillons deformes en tension et sur d'autres deformes en compression. Ces essais mecaniques ont ete completes par l

  4. Single top quarks at the Tevatron and observation of the s-channel production mode

    CERN Multimedia

    CERN. Geneva

    2014-01-01

    The presentation gives an overview of single-top-quark production at the Tevatron proton-antiproton collider. The talk covers measurements of the total s+t channel production cross section and the extraction of the CKM matrix element |V_tb|. Furthermore, separate analyses of the s-channel and t-channel production modes are discussed. The data correspond to total integrated luminosities of up to 9.7 fb-1 per experiment and represent in most cases the full Run-II dataset. Through a combination of the CDF and D0 measurements the first observation of single-top-quark production in the s-channel is claimed. This is particularly highlighted in the seminar.

  5. Single-photon emission computed tomography and early death in acute ischemic stroke

    NARCIS (Netherlands)

    Limburg, M.; van Royen, E. A.; Hijdra, A.; de Bruïne, J. F.; Verbeeten, B. W.

    1990-01-01

    Single-photon emission computed tomography with thallium-201-labeled diethyldithiocarbamate was performed in 26 consecutive patients less than or equal to 24 hours after a supratentorial brain infarction. Computed tomography excluded other relevant pathology. Two observers assessed the initial

  6. Single-Mode Deceleration Stage Rayleigh-Taylor Instability Growth in Cylindrical Implosions

    Science.gov (United States)

    Sauppe, J. P.; Palaniyappan, S.; Bradley, P. A.; Batha, S. H.; Loomis, E. N.; Kline, J. L.; Srinivasan, B.; Bose, A.; Malka, E.; Shvarts, D.

    2017-10-01

    We present design calculations demonstrating the feasibility of measuring single-mode deceleration stage Rayleigh-Taylor instability (RTI) growth at a factor of four convergence. RTI growth rates are modified as a result of convergence [Bell LA-1321, 1951], and cylindrical targets are considered here, as they allow direct diagnostic access along the interface. The 2D computations, performed with the radiation-hydrodynamics code xRAGE [Gittings et al., CSD 2008] utilizing a new laser ray-tracing package, predict growth factors of 6 to 10 for mode 10 and 4 to 6 for mode 4, both of high interest in evaluating inertial confinement fusion capsule degradation mechanisms [Bose et al., this conference]. These results compare favorably to a linear theory [Epstein, PoP 2004] and to a buoyancy-drag model [Srebro et al., LPB 2003], which accounts for the linear and non-linear stages. Synthetic radiographs, produced by combining 2D computations of axial and transverse cross-sections, indicate this growth will be observable, and these will be compared to experimental data obtained at the OMEGA laser facility. Work performed by Los Alamos National Laboratory under contract DE-AC52-06NA25396 for the National Nuclear Security Administration of the U.S. Department of Energy. (LA-UR-17-25608).

  7. Tuning the dispersion and single/multi-modeness of a hole-assisted fiber by the hole's geometrical parameters

    NARCIS (Netherlands)

    Uranus, H.P.; Hoekstra, Hugo; van Groesen, Embrecht W.C.

    2008-01-01

    Using a vectorial finite element mode solver developed earlier, we studied a hole-assisted multi-ring fiber. We report the role of the hole’s geometrical parameters in tuning the waveguide dispersion and the single/multi-modeness of the particular fiber. By correctly selecting the hole’s size and

  8. Simple immunoglobulin G sensor based on thin core single-mode fiber

    Science.gov (United States)

    Zheng, Yingfang; Lang, Tingting; Shen, Tingting; Shen, Changyu

    2018-03-01

    In this paper, a simple fiber biosensor (FOB) for immunoglobulin G (IgG) detection is designed and experimentally verified. The FOB is constructed by a 20 mm long thin core single-mode fiber (TCSMF) sandwiched between two single-mode optical fibers (SMFs). First, the refractive index (RI) sensitivity of the fiber structures is calculated by the beam propagation method. The refractive index sensing experiment is performed using different concentrations of glycerol solutions, and the experimental results are mostly consistent with the simulation predictions. The experimental RI sensitivity increases with the surrounding RI and reaches 82.7 nm/RIU. Then the surface of the FOB is functionalized by APTES for covalent bonding. The human IgG and goat anti-human IgG are chosen as a bioconjugated pair to examine the bio-sensing effectiveness of this FOB. The sensitivity of IgG detection is determined to be 10.4 nm/(mg/ml). And the serum IgG concentration in normal adults lies within the range of 6-16 mg/ml (Worsfold et al., 1985), so the sensor is applicable to human IgG monitoring. The specificity of the FOB is also verified by a contrast experiment conducted using rabbit immunoglobulin G. The proposed FOB is simple, low loss, cost-effective, and can be used for various biological and chemical applications.

  9. Optical access network using centralized light source, single-mode fiber + broad wavelength window multimode fiber

    Science.gov (United States)

    Yam, Scott S.-H.; Kim, Jaedon; Gutierrez, David; Achten, Frank

    2006-08-01

    Access networks based on a single-mode fiber (SMF) using a centralized light source (CLS) have attracted much attention recently due to their wavelength management flexibility and potential for cost reduction at customers' premises. Future networks, in addition, are likely to contain segments of multimode fiber (MMF), whose core dimension is relatively large in comparison with its single-mode counterpart, substantially reducing fiber alignment constraints and the subsequent network construction and installation cost. In this study, a CLS-based passive optical network (PON) is proposed, which will use a new generation of high-performance MMF optimized for a broad wavelength transmission window spanning from 1300to1550 nm, with a bandwidth distance product (BDP) of 40 Gbit/s-km. The proposed architecture is implemented in a test bed, and its performance is verified by bit error ratio (BER) measurement. Results show that we can implement high-performance CLS-based PONs containing both an SMF and an MMF infrastructure, simultaneously.

  10. Feasibility study to damp power system multi-mode oscillations by using a single FACTS device

    Energy Technology Data Exchange (ETDEWEB)

    Du, W.; Wu, X. [School of Electrical Engineering, Southeast University, Nanjing (China); Wang, H.F. [School of Electronics, Electrical Engineering and Computer Science, The Queen' s University of Belfast, Belfast BT7 1NN (United Kingdom); Dunn, R. [University of Bath, Bath (United Kingdom)

    2010-07-15

    To damp power system multi-mode oscillations, the commonly-used method is to arrange multiple decentralized stabilizers, such as PSS (Power System Stabilizer) and FACTS (Flexible AC Transmission Systems) stabilizers. In order to overcome the problem of interactions between stabilizers, coordinated design of multiple decentralized stabilizers has been proposed to simultaneously set parameters of all stabilizers. However, in practice it could be very difficult to implement the coordinated design of multiple stabilizers. This is because those stabilizers are often at different geographical locations in a power system and cross-location simultaneous field tuning of stabilizers' parameters is a tremendous task due to their interactions. Hence this paper proposes a novel scheme of damping power system multi-mode oscillations by using a single FACTS device and presents the results of feasibility study of the proposed scheme. It is demonstrated that multiple stabilizers can be arranged in a single FACTS device to effectively damp power system multi-mode oscillations. Under this scheme, multiple stabilizers are at a same geographical location in the power system and hence their parameters can be tuned simultaneously in coordination in the field. In the paper, three examples of multi-machine power systems installed with a UPFC (Unified Power Flow Controller), a STATCOM (Static Synchronous Compensator)/BESS (Battery Energy Storage System) and a MUPFC (Multiple-terminal UPFC) respectively are presented. Parameters of multiple stabilizers are designed in coordination by using a newly appeared method of optimisation-artificial fish swarm algorithm. Simulation results in the paper are compared with those obtained from applying the conventional scheme of decentralized control involving multiple PSSs. They demonstrate and confirm the feasibility of proposed scheme in the paper. (author)

  11. A new mode of acoustic NDT via resonant air-coupled emission

    Science.gov (United States)

    Solodov, Igor; Dillenz, Alexander; Kreutzbruck, Marc

    2017-06-01

    Resonant modes of non-destructive testing (NDT) which make use of local damage resonance (LDR) have been developed recently and demonstrated a significant increase in efficiency and sensitivity of hybrid inspection techniques by laser vibrometry, ultrasonic thermography, and shearography. In this paper, a new fully acoustic version of resonant NDT is demonstrated for defects in composite materials relevant to automotive and aviation applications. This technique is based on an efficient activation of defect vibrations by using a sonic/ultrasonic wave matched to a fundamental LDR frequency of the defect. On this condition, all points of the faulty area get involved in synchronous out-of-plane vibrations which produce a similar in-phase wave motion in ambient air. This effect of resonant air-coupled emission results in airborne waves emanating from the defect area, which can be received by a commercial microphone (low LDR frequency) or an air-coupled ultrasonic transducer (high frequency LDR). A series of experiments confirm the feasibility of both contact and non-contact versions of the technique for NDT and imaging of simulated and realistic defects (impacts, delaminations, and disbonds) in composites.

  12. List-mode maximum-likelihood reconstruction applied to positron emission mammography (PEM) with irregular sampling.

    Science.gov (United States)

    Huesman, R H; Klein, G J; Moses, W W; Qi, J; Reutter, B W; Virador, P R

    2000-05-01

    We present a preliminary study of list-mode likelihood reconstruction of images for a rectangular positron emission tomograph (PET) specifically designed to image the human breast. The prospective device consists of small arrays of scintillation crystals for which depth of interaction is estimated. Except in very rare instances, the number of annihilation events detected is expected to be far less than the number of distinguishable events. If one were to histogram the acquired data, most histogram bins would remain vacant. Therefore, it seems natural to investigate the efficacy of processing events one at a time rather than processing the data in histogram format. From a reconstruction perspective, the new tomograph presents a challenge in that the rectangular geometry leads to irregular radial and angular sampling, and the field of view extends completely to the detector faces. Simulations are presented that indicate that the proposed tomograph can detect 8-mm-diameter spherical tumors with a tumor-to-background tracer density ratio of 3:1 using realistic image acquisition parameters. Spherical tumors of 4-mm diameter are near the limit of detectability with the image acquisition parameters used. Expressions are presented to estimate the loss of image contrast due to Compton scattering.

  13. List-mode maximum-likelihood reconstruction applied to positron emission mammography (PEM) with irregular sampling

    Energy Technology Data Exchange (ETDEWEB)

    Huesman, Ronald H.; Klein, Gregory J.; Moses, William W.; Qi, Jinyi; Reutter, Bryan W.; Virador, Patrick R.G.

    2000-02-01

    We present a preliminary study of list mode likelihood reconstruction of images for a rectangular positron emission tomograph (PET) specifically designed to image the human breast. The prospective device consists of small arrays of scintillation crystals for which depth of interaction is estimated. Except in very rare instances the number of annihilation events detected is expected to be far less than the number of distinguishable events. If one were to histogram the acquired data, most histogram bins would remain vacant. It therefore seems natural to investigate the efficacy of processing events one at a time rather than processing the data in histogram format. From a reconstruction perspective, the new tomograph presents a challenge in that the rectangular geometry leads to irregular radial and angular sampling, and the field of view extends completely to the detector faces. Simulations are presented which indicate that the proposed tomograph can detect 8{approximately}mm diameter spherical tumors with a tumor to background tracer density ratio of 3:1 using realistic image acquisition parameters. Spherical tumors of 4{approximately}mm diameter are near the limit of detectability with the image acquisition parameters used. Expressions are presented to estimate the loss of image contrast due to Compton scattering.

  14. Single-Phase Full-Wave Rectifier as an Effective Example to Teach Normalization, Conduction Modes, and Circuit Analysis Methods

    Directory of Open Access Journals (Sweden)

    Predrag Pejovic

    2013-12-01

    Full Text Available Application of a single phase rectifier as an example in teaching circuit modeling, normalization, operating modes of nonlinear circuits, and circuit analysis methods is proposed.The rectifier supplied from a voltage source by an inductive impedance is analyzed in the discontinuous as well as in the continuous conduction mode. Completely analytical solution for the continuous conduction mode is derived. Appropriate numerical methods are proposed to obtain the circuit waveforms in both of the operating modes, and to compute the performance parameters. Source code of the program that performs such computation is provided.

  15. Modulation Analysis of Whistler Mode Sidebands in VLF-Triggered Emissions and Implications for Conditions of Nonlinear Growth

    Science.gov (United States)

    Costabile, Jamie D.; Gołkowski, Mark; Wall, Randall E.

    2017-12-01

    Experimental observations of very low frequency (VLF) triggered emissions are an important resource in investigation of nonlinear wave-particle interactions between whistler mode waves and energetic electrons in the Earth's radiation belts. Magnetospherically generated whistler mode sidebands observed during the Siple Station wave injection experiment are analyzed using a mixed modulation model and the MINUIT minimization package. The observed sidebands are found to exhibit features of both amplitude and frequency modulation of the input carrier wave with frequency modulation becoming more prominent as the observed amplitudes of the carrier and sidebands increase. A nonlinear whistler mode wave growth formulation based on phase bunching of counterstreaming electrons within a well-defined phase trap is shown to reproduce the salient features of the sideband observations. Whistler mode sideband amplitude is shown to be affected by the shape and uniformity of the trap.

  16. Effects of sulfur-metabolizing bacterial community diversity on H2S emission behavior in landfills with different operation modes.

    Science.gov (United States)

    Fang, Yuan; Du, Yao; Hu, Lifang; Xu, Jing; Long, Yuyang; Shen, Dongsheng

    2016-11-01

    Hydrogen sulfide (H 2 S) is one of the major contributors to offensive odors from landfills, and its concentration differs under different operation modes. This study examined the distribution of H 2 S emission from different landfill depths under different operation modes (anaerobic, semi-aerobic, semi-aerobic transformation, and the three operation modes with additional leachate recirculation). The microbial community (especially the sulfur-metabolizing bacterial community) was investigated using high-throughput sequencing technology. The results showed that the semi-aerobic mode could substantially lower the risks of H 2 S pollution in landfills, which might be because of the difference in biological processes related to sulfur metabolism driven by functional microbes. A myriad of factors are responsible for mutually shaping the sulfur-metabolizing bacterial community composition in landfills that might subsequently affect the behavior of H 2 S emission in landfills. The differences in abundance of the genera Acinetobacter and Paracoccus (phylum Proteobacteria) caused by environmental factors might explain the differences in H 2 S emission. H 2 S odor control could be realized if the related functional microbe diversity can be influenced by adjustments to landfill operation.

  17. Tuning Single Quantum Dot Emission with a Micromirror.

    Science.gov (United States)

    Yuan, Gangcheng; Gómez, Daniel; Kirkwood, Nicholas; Mulvaney, Paul

    2018-02-14

    The photoluminescence of single quantum dots fluctuates between bright (on) and dark (off) states, also termed fluorescence intermittency or blinking. This blinking limits the performance of quantum dot-based devices such as light-emitting diodes and solar cells. However, the origins of the blinking remain unresolved. Here, we use a movable gold micromirror to determine both the quantum yield of the bright state and the orientation of the excited state dipole of single quantum dots. We observe that the quantum yield of the bright state is close to unity for these single QDs. Furthermore, we also study the effect of a micromirror on blinking, and then evaluate excitation efficiency, biexciton quantum yield, and detection efficiency. The mirror does not modify the off-time statistics, but it does change the density of optical states available to the quantum dot and hence the on times. The duration of the on times can be lengthened due to an increase in the radiative recombination rate.

  18. Trapped-ion anomalous diffusion coefficient on the basis of single mode saturation

    International Nuclear Information System (INIS)

    Koshi, Yuji; Hatayama, Akiyoshi; Ogasawara, Masatada.

    1982-03-01

    Expressions of the anomalous diffusion coefficient due to the dissipative trapped ion instability (DTII) are derived for the case with and without the effect of magnetic shear. Derivation is made by taking into account of the single mode saturation of the DTII previously obtained numerically. In the absence of the shear effect, the diffusion coefficient is proportional to #betta#sub(i)a 2 (#betta#sub(i) is the effective collision frequency of the trapped ions and a is the minor radius of a torus) and is much larger than the neoclassical ion heat conductivity. In the presence of the shear effect, the diffusion coefficient is much smaller than the Kadomtsev and Pogutse's value and is the same order of magnitude as the neoclassical ion heat conductivity. Dependences of the diffusion coefficient on the temperature and on the total particle number density are rather complicated due to the additional spectral cut-off, which is introduced to regularize the short wavelength modes in the numerical analysis. (author)

  19. High energy, single frequency, tunable laser source operating in burst mode for space based lidar applications

    Science.gov (United States)

    Cosentino, Alberto; Mondello, Alessia; Sapia, Adalberto; D'Ottavi, Alessandro; Brotini, Mauro; Gironi, Gianna; Suetta, Enrico

    2017-11-01

    This paper describes energetic, spatial, temporal and spectral characterization measurements of the Engineering Qualification Model (EQM) of the Laser Transmitter Assembly (TXA) used in the ALADIN instrument currently under development for the ESA ADM-AEOLUS mission (EADS Astrium as prime contractor for the satellite and the instrument). The EQM is equivalent to the Flight Model, with the exception of some engineering grade components. The Laser Transmitter Assembly, based on a diode pumped tripled Nd:YAG laser, is used to generate laser pulses at a nominal wavelength of 355 nm. This laser is operated in burst mode, with a pulse repetition cycle of 100 Hz during bursts. It is capable to operate in Single Longitudinal Mode and to be tuned over 25 GHz range. An internal "network" of sensors has been implemented inside the laser architecture to allow "in flight" monitoring of transmitter. Energy in excess of 100 mJ, with a spatial beam quality factor (M2) lower than 3, a spectral linewidth less than 50 MHz with a frequency stability better than 4 MHz on short term period have been measured on the EQM. Most of the obtained results are well within the expected values and match the Instrument requirements. They constitute an important achievement, showing the absence of major critical areas in terms of performance and the capability to obtain them in a rugged and compact structure suitable for space applications. The EQM will be submitted in the near future to an Environmental test campaign.

  20. Geometric characterization of separability and entanglement in pure Gaussian states by single-mode unitary operations

    International Nuclear Information System (INIS)

    Adesso, Gerardo; Giampaolo, Salvatore M.; Illuminati, Fabrizio

    2007-01-01

    We present a geometric approach to the characterization of separability and entanglement in pure Gaussian states of an arbitrary number of modes. The analysis is performed adapting to continuous variables a formalism based on single subsystem unitary transformations that has been recently introduced to characterize separability and entanglement in pure states of qubits and qutrits [S. M. Giampaolo and F. Illuminati, Phys. Rev. A 76, 042301 (2007)]. In analogy with the finite-dimensional case, we demonstrate that the 1xM bipartite entanglement of a multimode pure Gaussian state can be quantified by the minimum squared Euclidean distance between the state itself and the set of states obtained by transforming it via suitable local symplectic (unitary) operations. This minimum distance, corresponding to a, uniquely determined, extremal local operation, defines an entanglement monotone equivalent to the entropy of entanglement, and amenable to direct experimental measurement with linear optical schemes

  1. Fibre-Bragg-grating writing in single-mode optical fibres by UV femtosecond pulses

    International Nuclear Information System (INIS)

    Zagorul'ko, K A; Kryukov, P G; Dianov, Evgenii M; Dragomir, A; Nikogosyan, D N

    2003-01-01

    Fibre-Bragg-grating writing in single-mode optical fibres by the phase-mask method using 220-fs, 264-nm UV pulses of intensity 31 - 77 GW cm -2 is reported for the first time. The achieved degree of modulation of the photoinduced refractive index was 1.9 x 10 -3 in an H 2 -loaded SMF-28 telecommunication fibre and 1.1 x 10 -3 in a H 2 -free Nufern GF1 fibre. The dependence of the induced refractive index on the intensity for the same irradiation fluences in the case of the H 2 -loaded SMF-28 fibre shows that the refractive index is induced due to nonlinear absorption. (letters)

  2. Semiconductor laser engineering, reliability and diagnostics a practical approach to high power and single mode devices

    CERN Document Server

    Epperlein, Peter W

    2013-01-01

    This reference book provides a fully integrated novel approach to the development of high-power, single-transverse mode, edge-emitting diode lasers by addressing the complementary topics of device engineering, reliability engineering and device diagnostics in the same book, and thus closes the gap in the current book literature. Diode laser fundamentals are discussed, followed by an elaborate discussion of problem-oriented design guidelines and techniques, and by a systematic treatment of the origins of laser degradation and a thorough exploration of the engineering means to enhance the optical strength of the laser. Stability criteria of critical laser characteristics and key laser robustness factors are discussed along with clear design considerations in the context of reliability engineering approaches and models, and typical programs for reliability tests and laser product qualifications. Novel, advanced diagnostic methods are reviewed to discuss, for the first time in detail in book literature, performa...

  3. Remarks on the stabilization of the systems a single unstable leading mode

    International Nuclear Information System (INIS)

    Cotsaftis, M.

    1978-07-01

    Different types of stabilization were proposed for cancelling the plasma motion due to instabilities. The problem of the conventional feedback systems of 'passive' type currently used is rediscussed. The analysis is dealing with the simple case of a plasma with a single leading unstable mode. It is shown that whereas the usual passive feedback cannot achieve a compplete stability on the full interval some other type of more convenient control loops can be used in such a way that the plasma comes back to its original state after a given time, with a power consumption much weaker than in the first case. These properties are also shown to be saved under rather large assumptions in more general situations including the adjunction of delay terms, nonlinear or decoupling terms in the evolution equations of the plasma system [fr

  4. 2-kW single-mode fiber laser employing bidirectional-pump scheme

    Science.gov (United States)

    Zhang, Fan; Zheng, Wenyou; Shi, Pengyang; Zhang, Xinhai

    2018-01-01

    2kW single-mode fiber laser with two cascade home-made cladding light strippers (CLSs) by employing bidirectionalpump scheme has been demonstrated. 2.009 kW signal power is obtained when pump power is 2.63 kW and the slope efficiency is 76.6%. Raman Stokes light is less than -47 dB at 2.009 kW even with a 10-m delivery fiber with core/inner cladding diameter of 20/400um. The beam quality M2stability of +/-0.14% is achieved by special thermal management for a more uniform temperature distribution on the Yb-doped gain fiber.

  5. A long-baseline interferometer employing single-mode fiber optics

    Science.gov (United States)

    Shaklan, Stuart

    The idea of the Fiber-Linked Optical Array Telescope proposed by Connes (1987) is to mount several small optical telescopes around the perimeter of a radio dish or other large steerable structure, couple the light into single-mode (SM) fibers, and use the fibers to coherently combine the beams at the output. This paper examines the important properties of SM fibers and then discusses the whole system in general terms, starting with the telescopes and following the light through to the detectors, along with the results of laboratory experiments evaluating the performance of SM fibers. The imaging capabilities of the array were simulated, and it was found that, using 10 telescopes on a 440-m dish, the array obtains images with resolution of the order of 2 milliarc seconds in the visible range.

  6. Interaction of a single mode field cavity with the 1D XY model: Energy spectrum

    International Nuclear Information System (INIS)

    Tonchev, H; Donkov, A A; Chamati, H

    2016-01-01

    In this work we use the fundamental in quantum optics Jaynes-Cummings model to study the response of spin 1/2chain to a single mode of a laser light falling on one of the spins, a focused interaction model between the light and the spin chain. For the spin-spin interaction along the chain we use the XY model. We report here the exact analytical results, obtained with the help of a computer algebra system, for the energy spectrum in this model for chains of up to 4 spins with nearest neighbors interactions, either for open or cyclic chain configurations. Varying the sign and magnitude of the spin exchange coupling relative to the light-spin interaction we have investigated both cases of ferromagnetic or antiferromagnetic spin chains. (paper)

  7. Laser direct micro-machining with top-hat-converted single mode lasers

    Science.gov (United States)

    Homburg, O.; Toennissen, F.; Mitra, T.; Lissotschenko, V.

    2008-02-01

    Laser direct micro-machining processes are used in a variety of industries like inkjet printing, semiconductor processing, solar technology, flat-panel display production and medicine. Various kinds of materials, e.g. ceramics, metals, isolators, oxides, organics and semiconductors are being structured. In most cases pulsed single mode solid state lasers with an inhomogeneous Gaussian beam profile are employed, like YAG lasers and their harmonics. However, the quality and functionality of the generated structures and micro-systems as well as the speed of the process can be improved by the utilization of homogeneous top hat profiles. The beam shaping principle of refractive Gaussian-to-top-hat converters is shown. Compact beam shaper modules based on this principle have been developed - supporting most direct laser micro-machining applications. The resulting process advantages are demonstrated by selected application results, namely the drilling of holes and patterning of trenches for different kinds of materials.

  8. A single-spatial-mode semiconductor laser based on InAs/InGaAs quantum dots with a diffraction filter of optical modes

    International Nuclear Information System (INIS)

    Gordeev, N. Yu.; Novikov, I. I.; Kuznetsov, A. M.; Shernyakov, Yu. M.; Maximov, M. V.; Zhukov, A. E.; Chunareva, A. V.; Payusov, A. S.; Livshits, D. A.; Kovsh, A. R.

    2010-01-01

    The concept of a diffraction optical filter is used for prevention of high-order mode oscillation in a design of stripe laser diodes with an active region based on InAs/InGaAs quantum dots emitting in the 1.3-μm wavelength range grown on GaAs substrates. Incorporation of such a filter made it possible to increase the width of the stripe and obtain an output power as high as 700 mW with retention of a single-spatial-mode character of lasing.

  9. Interferometric measurement of refractive index modification in a single mode microfiber

    Science.gov (United States)

    Ahmed, Farid; Ahsani, Vahid; Jun, Martin B. G.

    2017-02-01

    Efficient and cost effective measurement of the refractive index profile in an optical fiber is a significant technical job to design and manufacture in-fiber photonic devices and communication systems. For instance, to design fiber gratings, it is required to estimate the refractive index modulation to be inscribed by the fabrication apparatus such as ultraviolet or infrared lasers. Mach-Zehnder interferometer (MZI) based quantification of refractive index change written in single mode microfiber by femtosecond laser radiation is presented in this study. The MZI is constructed by splicing a microfiber (core diameter: 3.75 μm, cladding diameter: 40 μm) between standard single mode fibers. To measure the RI inscribed by infrared femtosecond laser, 200 μm length of the core within the MZI was scanned with laser radiation. As the higher index was written within 200 μm length of the core, the transmission spectrum of the interferometer displayed a corresponding red shift. The observed spectral shift was used to calculate the amount of refractive index change inscribed by the femtosecond irradiation. For the MZI length of 3.25 mm, and spectral shift of 0.8 nm, the calculated refractive index was found to be 0.00022. The reported results display excellent agreement between theory and experimental findings. Demonstrated method provides simple yet very effective on-site measurement of index change in optical fibers. Since the MZI can be constructed in diverse fiber types, this technique offers flexibility to quantify index change in various optical fibers.

  10. Interpreting Adaptation to Concurrent Compared with Single-Mode Exercise Training: Some Methodological Considerations.

    Science.gov (United States)

    Fyfe, Jackson J; Loenneke, Jeremy P

    2018-02-01

    Incorporating both endurance and resistance training into an exercise regime is termed concurrent training. While there is evidence that concurrent training can attenuate resistance training-induced improvements in maximal strength and muscle hypertrophy, research findings are often equivocal, with some suggesting short-term concurrent training may instead further enhance muscle hypertrophy versus resistance training alone. These observations have questioned the validity of the purported 'interference effect' on muscle hypertrophy with concurrent versus single-mode resistance training. This article aims to highlight some methodological considerations when interpreting the concurrent training literature, and, in particular, the degree of changes in strength and muscle hypertrophy observed with concurrent versus single-mode resistance training. Individual training status clearly influences the relative magnitude and specificity of both training adaptation and post-exercise molecular responses in skeletal muscle. The training status of participants is therefore likely a key modulator of the degree of adaptation and interference seen with concurrent training interventions. The divergent magnitudes of strength gain versus muscle hypertrophy induced by resistance training also suggests most concurrent training studies are likely to observe more substantial changes in (and in turn, any potential interference to) strength compared with muscle hypertrophy. Both the specificity and sensitivity of measures used to assess training-induced changes in strength and muscle hypertrophy also likely influence the interpretation of concurrent training outcomes. Finally, the relative importance of any modulation of hypertrophic versus strength adaptation with concurrent training should be considered in context with the relevance of training-induced changes in these variables for enhancing athletic performance and/or functional capacity. Taken together, these observations suggest that

  11. Data driven modeling of the low-Atwood single-mode Rayleigh-Taylor instability

    Science.gov (United States)

    Hutchinson, Maxwell

    The Rayleigh-Taylor instability is one of the most common and well studied phenomena in fluid dynamics. Despite research dating to the late 19th century, the non-linear dynamics of the interfacial instability are still not fully understood, particularly in the case when the two fluids have nearly the same density. It was recently demonstrated in this, the low-Atwood regime, that the idealized single-mode problem departs from established potential flow models in the form of a re-acceleration beyond the predicted terminal interface velocity. This thesis is an attempt to model that re-acceleration and, more broadly, the late time dynamics of the single-mode low-Atwood Rayleigh-Taylor instability. The approach taken here is based on buoyancy-drag models, which express a force balance between buoyancy and parasitic drag. The dynamical buoyancy-drag model is supplemented with a mixing model that dilutes the buoyant force over time. These models are written deliberately generally, with 8 unique coefficients. Three of these coefficients are solved for by equating the early time behavior with that of well established linear theories. The remaining 5 coefficients are estimated by relating them to drag coefficients, friction factors, and geometric ratios in the interface shape. To evaluate the model and compute the 5 unknown coefficients more precisely, a set of direct numerical simulations are performed over the relevant parameter space. These simulations are first validated against experimental data. Then they are shown to converge and their resolutions are chosen such as to minimize computational cost given the accuracy scale of the model. The 5 coefficients are fit to the resulting data set, and the model achieves better than 2% error in the bubble height and 4% error in the volume of mixed fluid. Three coefficients are nominally independent of the parameterization of the problem, while two are shown to vary with the Rayleigh number and the diffusivity.

  12. Coupling single NV-centres to high-Q whispering gallery modes of a preselected frequency-matched microresonator

    International Nuclear Information System (INIS)

    Schietinger, Stefan; Benson, Oliver

    2009-01-01

    In this paper, we report the controlled coupling of fluorescence from a single NV-centre in a single nanodiamond to the high-Q modes of a preselected microsphere. Microspheres from an ensemble with a finite size distribution can be characterized precisely via white light Mie-scattering. The mode spectrum of individual spheres can be determined with high precision. A sphere with an appropriate spectrum can be selected, and a nanodiamond containing a single NV-centre can be coupled to it. The spectral position of the calculated lowest order whispering gallery modes are found to be in very good agreement with the experimentally observed resonances of the coupled fluorescence from the single NV-re.

  13. Field electron emission characteristics and physical mechanism of individual single-layer graphene.

    Science.gov (United States)

    Xiao, Zhiming; She, Juncong; Deng, Shaozhi; Tang, Zikang; Li, Zhibing; Lu, Jianming; Xu, Ningsheng

    2010-11-23

    Due to its difficulty, experimental measurement of field emission from a single-layer graphene has not been reported, although field emission from a two-dimensional (2D) regime has been an attractive topic. The open surface and sharp edge of graphene are beneficial for field electron emission. A 2D geometrical effect, such as massless Dirac fermion, can lead to new mechanisms in field emission. Here, we report our findings from in situ field electron emission characterization on an individual singe-layer graphene and the understanding of the related mechanism. The measurement of field emission from the edges was done using a microanode probe equipped in a scanning electron microscope. We show that repeatable stable field emission current can be obtained after a careful conditioning process. This enables us to examine experimentally the typical features of the field emission from a 2D regime. We plot current versus applied field data, respectively, in ln(I/E(3/2)) ∼ 1/E and ln(I/E(3)) ∼ 1/E(2) coordinates, which have recently been proposed for field emission from graphene in high- and low-field regimes. It is observed that the plots all exhibit an upward bending feature, revealing that the field emission processes undergo from a low- to high-field transition. We discuss with theoretical analysis the physical mechanism responsible for the new phenomena.

  14. Systematic analysis of whistler-mode emissions below the lower hybrid frequency based on the data of the Cluster project.

    Science.gov (United States)

    Nemec, F.; Santolik, O.; Gereova, K.; Macusova, E.; Cornilleau-Wehrlin, N.

    2003-12-01

    We report results of a systematic analysis of equatorial noise below the local lower hybrid frequency. Our analysis is based on the entire data set collected by the STAFF-SA instruments on board the Cluster spacecraft during the first two years of operation (2001 - 2002). We compare intensities of equatorial noise with other whistler-mode emissions, for example with chorus or hiss. The results indicate that these emissions can play a significant role in the dynamics of the inner magnetosphere. Using the multipoint measurement we show considerable spatio-temporal variations of the wave intensity.

  15. A tuneable, power efficient and narrow single longitudinal mode fibre ring laser using an inline dual-taper fibre Mach–Zehnder filter

    International Nuclear Information System (INIS)

    Ahmad, H; Dernaika, M; Alimadad, M; Ibrahim, M F; Lim, K S; Harun, S W; Kharraz, O M

    2014-01-01

    A tuneable single longitudinal mode fibre ring laser with dual-taper fibre filter is proposed and experimentally demonstrated in this paper. The single longitudinal mode operation, and power limitations for a Mach–Zehnder interferometer filter generated from a single mode fibre, are verified for the first time. Incorporating an in-line taper fibre Mach–Zehnder interferometer filter inside the laser ring cavity causes a spatial mode beating interference, resulting in a passive narrow band filter with the ability to generate stable single longitudinal modes. The single longitudinal mode achieves a side mode suppression ratio of more than 60 dB using low pump power. The tuneability of the fibre laser ranges from 1525 to 1562 nm using a passive band pass filter. A study of the stability and limitation of the single longitudinal mode in the Mach–Zehnder tapered fibre is also presented. (paper)

  16. Single-input Multiple-output Tunable Log-domain Current-mode Universal Filter

    Directory of Open Access Journals (Sweden)

    P. Prommee

    2013-06-01

    Full Text Available This paper describes the design of a current-mode single-input multiple-output (SIMO universal filter based on the log-domain filtering concept. The circuit is a direct realization of a first-order differential equation for obtaining the lossy integrator circuit. Lossless integrators are realized by log-domain lossy integrators. The proposed filter comprises only two grounded capacitors and twenty-four transistors. This filter suits to operate in very high frequency (VHF applications. The pole-frequency of the proposed filter can be controlled over five decade frequency range through bias currents. The pole-Q can be independently controlled with the pole-frequency. Non-ideal effects on the filter are studied in detail. A validated BJT model is used in the simulations operated by a single power supply, as low as 2.5 V. The simulation results using PSpice are included to confirm the good performances and are in agreement with the theory.

  17. Dual-mode optical microscope based on single-pixel imaging

    Science.gov (United States)

    Rodríguez, A. D.; Clemente, P.; Tajahuerce, E.; Lancis, J.

    2016-07-01

    We demonstrate an inverted microscope that can image specimens in both reflection and transmission modes simultaneously with a single light source. The microscope utilizes a digital micromirror device (DMD) for patterned illumination altogether with two single-pixel photosensors for efficient light detection. The system, a scan-less device with no moving parts, works by sequential projection of a set of binary intensity patterns onto the sample that are codified onto a modified commercial DMD. Data to be displayed are geometrically transformed before written into a memory cell to cancel optical artifacts coming from the diamond-like shaped structure of the micromirror array. The 24-bit color depth of the display is fully exploited to increase the frame rate by a factor of 24, which makes the technique practicable for real samples. Our commercial DMD-based LED-illumination is cost effective and can be easily coupled as an add-on module for already existing inverted microscopes. The reflection and transmission information provided by our dual microscope complement each other and can be useful for imaging non-uniform samples and to prevent self-shadowing effects.

  18. Performance of Single Electrode-Supported Cells Operating in the Electrolysis Mode

    Energy Technology Data Exchange (ETDEWEB)

    J. E. O' Brien; G. K. Housley; D. G. Milobar

    2009-11-01

    An experimental study is under way to assess the performance of electrode-supported solid-oxide cells operating in the steam electrolysis mode for hydrogen production over a temperature range of 800 to 900ºC. Results presented in this paper were obtained from single cells, with an active area of 16 cm2 per cell. The electrolysis cells are electrode-supported, with yttria-stabilized zirconia (YSZ) electrolytes (~10 µm thick), nickel-YSZ steam/hydrogen electrodes (~1400 µm thick), and manganite (LSM) air-side electrodes. The experiments were performed over a range of steam inlet mole fractions (0.1 – 0.6), gas flow rates, and current densities (0 to 0.6 A/cm2). Steam consumption rates associated with electrolysis were measured directly using inlet and outlet dewpoint instrumentation. On a molar basis, the steam consumption rate is equal to the hydrogen production rate. Cell performance was evaluated by performing DC potential sweeps at 800, 850, and 900°C. The voltage-current characteristics are presented, along with values of area-specific resistance as a function of current density. Long-term cell performance is also assessed to evaluate cell degradation. Details of the custom single-cell test apparatus developed for these experiments are also presented.

  19. Design and Characterization of 64K Pixels Chips Working in Single Photon Processing Mode

    CERN Document Server

    Llopart Cudie, Xavier; Campbell, M

    2007-01-01

    Progress in CMOS technology and in fine pitch bump bonding has made possible the development of high granularity single photon counting detectors for X-ray imaging. This thesis studies the design and characterization of three pulse processing chips with 65536 square pixels of 55 µm x 55 µm designed in a commercial 0.25 µm 6-metal CMOS technology. The 3 chips share the same architecture and dimensions and are named Medipix2, Mpix2MXR20 and Timepix. The Medipix2 chip is a pixel detector readout chip consisting of 256 x 256 identical elements, each working in single photon counting mode for positive or negative input charge signals. The preamplifier feedback provides compensation for detector leakage current on a pixel by pixel basis. Two identical pulse height discriminators are used to define an energy window. Every event falling inside the energy window is counted with a 13 bit pseudo-random counter. The counter logic, based in a shift register, also behaves as the input/output register for the pixel. Each...

  20. Tunable room-temperature single photon emission from atomic defects in hexagonal boron nitride

    Science.gov (United States)

    Grosso, Gabriele; Moon, Hyowon; Lienhard, Benjamin; Efetov, Dmitri; Furchi, Marco; Jarillo-Herrero, Pablo; Ali, Sajid; Ford, Michael; Aharonovich, Igor; Englund, Dirk

    Two-dimensional van der Waals materials have emerged as promising platforms for solid-state quantum information processing devices with unusual potential for heterogeneous assembly. Recently, bright and photostable single photon emitters were reported from atomic defects in layered hexagonal boron nitride (hBN), but controlling inhomogeneous spectral distribution and reducing multi-photon emission presented open challenges. We demonstrate that strain control allows spectral tunability of hBN single photon emitters, and material processing sharply improves the single-photon purity. Our sample fabrication process relies on ion irradiation and high temperature annealing to isolate individual defects for single photon emission. Spectroscopy on this emitter reports high single photon purity of g(2)(0) =0.07, and high count rates exceeding 107 counts/sec at saturation. Furthermore, these emitters are stable to material transfer to other substrates, including a bendable beam that allows us to controllably apply strain. Our experiments indicate a maximum tuning of 6 meV and emission energy dependencies ranging from -3 to 6 meV/%. High-purity and photostable single photon emission at room temperature, together with spectral tunability and transferability, opens the door to scalable integration of high-quality quantum emitters in photonic quantum technologies.

  1. Geiger-mode APD camera system for single-photon 3D LADAR imaging

    Science.gov (United States)

    Entwistle, Mark; Itzler, Mark A.; Chen, Jim; Owens, Mark; Patel, Ketan; Jiang, Xudong; Slomkowski, Krystyna; Rangwala, Sabbir

    2012-06-01

    The unparalleled sensitivity of 3D LADAR imaging sensors based on single photon detection provides substantial benefits for imaging at long stand-off distances and minimizing laser pulse energy requirements. To obtain 3D LADAR images with single photon sensitivity, we have demonstrated focal plane arrays (FPAs) based on InGaAsP Geiger-mode avalanche photodiodes (GmAPDs) optimized for use at either 1.06 μm or 1.55 μm. These state-of-the-art FPAs exhibit excellent pixel-level performance and the capability for 100% pixel yield on a 32 x 32 format. To realize the full potential of these FPAs, we have recently developed an integrated camera system providing turnkey operation based on FPGA control. This system implementation enables the extremely high frame-rate capability of the GmAPD FPA, and frame rates in excess of 250 kHz (for 0.4 μs range gates) can be accommodated using an industry-standard CameraLink interface in full configuration. Real-time data streaming for continuous acquisition of 2 μs range gate point cloud data with 13-bit time-stamp resolution at 186 kHz frame rates has been established using multiple solid-state storage drives. Range gate durations spanning 4 ns to 10 μs provide broad operational flexibility. The camera also provides real-time signal processing in the form of multi-frame gray-scale contrast images and single-frame time-stamp histograms, and automated bias control has been implemented to maintain a constant photon detection efficiency in the presence of ambient temperature changes. A comprehensive graphical user interface has been developed to provide complete camera control using a simple serial command set, and this command set supports highly flexible end-user customization.

  2. Aeration Strategies To Mitigate Nitrous Oxide Emissions from Single-Stage Nitritation/Anammox Reactors

    DEFF Research Database (Denmark)

    Domingo Felez, Carlos; Mutlu, A. Gizem; Jensen, Marlene Mark

    2014-01-01

    Autotrophic nitrogen removal is regarded as a resource efficient process to manage nitrogen-rich residual streams. However, nitrous oxide emissions of these processes are poorly documented and strategies to mitigate emissions unknown. In this study, two sequencing batch reactors performing single......-stage nitritation/anammox were operated under different aeration strategies, gradually adjusted over six months. At constant but limiting oxygen loading, synthetic reject water was fed (0.75g-N/L.d) and high nitrogen removal efficiencies (83 +/- 5 and 88 +/- 2%) obtained. Dynamics of liquid phase nitrous (N2O......) and nitric oxide (NO) concentrations were monitored and N2O emissions calculated. Significant decreases in N2O emissions were obtained when the frequency of aeration was increased while maintaining a constant air flow rate (from >6 to 1.7% Delta N2O/Delta TN). However, no significant effect on the emissions...

  3. Field emission of carbon quantum dots synthesized from a single organic solvent.

    Science.gov (United States)

    Liu, Xiahui; Yang, Bingjun; Yang, Juan; Yu, Shengxue; Chen, Jiangtao

    2016-11-04

    In this paper, a facile synthesis of carbon quantum dots (CQDs) and its field emission performance are reported. The CQDs are prepared from a single N, N-dimethylformamide acting as carbon and nitrogen-doping sources simultaneously. The CQDs are investigated by photoluminescence, transmission electron microscopy and x-ray photoelectron spectroscopy. The CQDs have an average size of 3 nm and are doped with N atoms. CQD dispersion shows strong fluorescence under UV illumination. For the first time, the field emission behavior of CQDs coated on Si substrate is studied. As a candidate of cold cathode, the CQDs display good field emission performance. The CQD emitter reaches the current density of 1.1 mA cm(-2) at 7.0 V μm(-1) and exhibits good long-term emission stability, suggesting promising application in field emission devices.

  4. Super-Resolution Imaging of Molecular Emission Spectra and Single Molecule Spectral Fluctuations.

    Science.gov (United States)

    Mlodzianoski, Michael J; Curthoys, Nikki M; Gunewardene, Mudalige S; Carter, Sean; Hess, Samuel T

    2016-01-01

    Localization microscopy can image nanoscale cellular details. To address biological questions, the ability to distinguish multiple molecular species simultaneously is invaluable. Here, we present a new version of fluorescence photoactivation localization microscopy (FPALM) which detects the emission spectrum of each localized molecule, and can quantify changes in emission spectrum of individual molecules over time. This information can allow for a dramatic increase in the number of different species simultaneously imaged in a sample, and can create super-resolution maps showing how single molecule emission spectra vary with position and time in a sample.

  5. Pyroelectric electron emissions and domain inversion of LiNbO3 single crystals

    International Nuclear Information System (INIS)

    Kim, Dong-Wook; Bourim, E.M.; Jeong, Soo-Hwan; Yoo, In K.

    2004-01-01

    We investigated the electron emissions from a congruent LiNbO 3 single crystal with variation in temperature. When there was a small gap between the crystal and detector (<2 mm), we observed abrupt drops in the emission current and polarization domain inversion of the crystal. The current burst was distributed in tree-like patterns that suggested plasma generation. A sufficient gap and a crystal with a high coercive field appear to be factors that allow reproducible electron emissions from pyroelectric materials

  6. Single mode wavelength control of modulated AlGaAs lasers with external and internal etalon feedback

    Science.gov (United States)

    Maynard, William L.

    1989-01-01

    Single mode lasing without mode hops has been obtained for VSIS and CSP laser diodes with an external etalon attached to the laser's front facet for up to an 8 C range CW and a 4 C range pulsed, with .07 nm/C tuning. Tests of thin tapered-thickness (TTT) laser diodes show CW and pulsed single mode lasing over 10 C and 2 C ranges, respectively, with .08 nm/C tuning. An analysis of the TTT structure reveals the equivalent of an internal etalon. The time-resolved pulsed behavior for both types of lasers show single mode lasing within the proper temperature ranges with minor modes present only early in the optical pulse, if at all. The external etalon produces noticeable interference fringes in the farfield pattern, while those of the TTT lasers are smooth. Ongoing CW lifetest results indicate stability to within one longitudinal mode after a few hundred hours of operation, along with at least several thousand hours lifetime.

  7. 26 nJ picosecond solitons from thulium-doped single-mode master oscillator power fiber amplifier.

    Science.gov (United States)

    Renard, William; Canat, Guillaume; Bourdon, Pierre

    2012-02-01

    We report on an all single-mode master oscillator power fiber amplifier delivering high energy picosecond solitons at 1960 nm. The Bragg stabilized and self-starting oscillator delivers 62 pJ transform-limited pulses at 11.2 MHz pulse repetition frequency. Solitons are amplified in a core-pumped single-mode heavily thulium-doped fiber up to 26 nJ. The average and peak power are 291 mW and 7.4 kW, respectively. Pulses remain transform limited without significant self-phase-modulation distortion. We discuss the limitations of picosecond pulse amplification in a core-pumped single-mode fiber amplifier.

  8. Toward single-mode random lasing within a submicrometre-sized spherical ZnO particle film

    International Nuclear Information System (INIS)

    Niyuki, Ryo; Fujiwara, Hideki; Sasaki, Keiji; Ishikawa, Yoshie; Koshizaki, Naoto; Tsuji, Takeshi

    2016-01-01

    We had recently reported unique random laser action such as quasi-single-mode and low-threshold lasing from a submicrometre-sized spherical ZnO nanoparticle film with polymer particles as defects. The present study demonstrates a novel approach to realize single-mode random lasing by adjusting the sizes of the defect particles. From the dependence of random lasing properties on defect size, we find that the average number of lasing peaks can be modified by the defect size, while other lasing properties such as lasing wavelengths and thresholds remain unchanged. These results suggest that lasing wavelengths and thresholds are determined by the resonant properties of the surrounding scatterers, while the defect size stochastically determines the number of lasing peaks. Therefore, if we optimize the sizes of the defects and scatterers, we can intentionally induce single-mode lasing even in a random structure (Fujiwara et al 2013 Appl. Phys. Lett. 102 061110). (paper)

  9. A Comparison between Boundary and Continuous Conduction Modes in Single Phase PFC Using 600V Range Devices

    DEFF Research Database (Denmark)

    Hernandez Botella, Juan Carlos; Petersen, Lars Press; Andersen, Michael A. E.

    2015-01-01

    This paper presents an analysis and comparison of boundary conduction mode (BCM) and continuous conduction mode (CCM) in single phase power factor correction (PFC) applications. The comparison is based on double pulse tester (DPT) characterization results of state-of-the-art superjunction devices...... in the 600V range. The measured switching energy is used to evaluate the devices performance in a conventional PFC. This data is used together with a mathematical model for prediction of the conducted electromagnetic interference (EMI). This allows comparing the different devices in BCM and CCM operation...... modes and evaluating the performance as a function of the PFC power density and efficiency....

  10. Load bearing capacity, fracture mode, and wear performance of digitally veneered full-ceramic single crowns.

    Science.gov (United States)

    Schubert, Oliver; Nold, Ephraim; Obermeier, Matthias; Erdelt, Kurt; Stimmelmayr, Michael; Beuer, Florian

    Computer-aided technologies can help to minimize clinical complications of zirconia-based restorations such as veneering porcelain fractures. The aim of this study was to evaluate different veneering approaches for zirconia single crowns regarding contact wear, fracture strength, and failure mode. Six different types of computer-aided design (CAD) crowns were manufactured and conventionally cemented on 10 metal dies each: three groups with a zirconia framework and a CAD/CAM-fabricated veneering cap ("digital veneering system": DVS, CAD-on, Infix CAD), zirconia-based crowns with pressed veneering caps (Infix Press), zirconia framework containing the dentin layer with only the incisal enamel material added (dentin-core), and conventional substructure with powder buildup veneering porcelain (layering technique). All specimens were submitted to artificial aging (120,000 mechanical cycles, 50 N load, 0.7-mm sliding movement, 320 thermocycles). After contact wear was measured with a laser scanning system, fracture resistance and failure mode were examined using a universal testing machine and a scanning electron microscope. Statistical analysis was performed at a significance level of 5%. No statistical difference was revealed regarding the contact wear of the restorations (P = 0.171; ANOVA). No significant difference was found regarding the fracture resistance of the crowns (P = 0.112; ANOVA). Failure analysis revealed three different failure patterns: cohesive veneering fracture, adhesive delamination, and total fracture, with a characteristic distribution between the groups. All tested specimens survived artificial aging and exhibited clinically acceptable wear resistance and fracture resistance. Digital veneering techniques offer a promising, time- and cost-effective manufacturing process for all-ceramic restorations and may usefully complement the digital workflow.

  11. Electro-opto-mechanical radio-frequency oscillator driven by guided acoustic waves in standard single-mode fiber

    Directory of Open Access Journals (Sweden)

    Yosef London

    2017-04-01

    Full Text Available An opto-electronic radio-frequency oscillator that is based on forward scattering by the guided acoustic modes of a standard single-mode optical fiber is proposed and demonstrated. An optical pump wave is used to stimulate narrowband, resonant guided acoustic modes, which introduce phase modulation to a co-propagating optical probe wave. The phase modulation is converted to an intensity signal at the output of a Sagnac interferometer loop. The intensity waveform is detected, amplified, and driven back to modulate the optical pump. Oscillations are achieved at a frequency of 319 MHz, which matches the resonance of the acoustic mode that provides the largest phase modulation of the probe wave. Oscillations at the frequencies of competing acoustic modes are suppressed by at least 40 dB. The linewidth of the acoustic resonance is sufficiently narrow to provide oscillations at a single longitudinal mode of the hybrid cavity. Competing longitudinal modes are suppressed by at least 38 dB as well. Unlike other opto-electronic oscillators, no radio-frequency filtering is required within the hybrid cavity. The frequency of oscillations is entirely determined by the fiber opto-mechanics.

  12. Multi-wavelength emission from a single InGaN/GaN nanorod analyzed by cathodoluminescence hyperspectral imaging

    KAUST Repository

    Kusch, Gunnar

    2018-01-23

    Multiple luminescence peaks emitted by a single InGaN/GaN quantum-well(QW) nanorod, extending from the blue to the red, were analysed by a combination of electron microscope based imaging techniques. Utilizing the capability of cathodoluminescence hyperspectral imaging it was possible to investigate spatial variations in the luminescence properties on a nanoscale. The high optical quality of a single GaN nanorod was demonstrated, evidenced by a narrow band-edge peak and the absence of any luminescence associated with the yellow defect band. Additionally two spatially confined broad luminescence bands were observed, consisting of multiple peaks ranging from 395 nm to 480 nm and 490 nm to 650 nm. The lower energy band originates from broad c-plane QWs located at the apex of the nanorod and the higher energy band from the semipolar QWs on the pyramidal nanorod tip. Comparing the experimentally observed peak positions with peak positions obtained from plane wave modelling and 3D finite difference time domain(FDTD) modelling shows modulation of the nanorod luminescence by cavity modes. By studying the influence of these modes we demonstrate that this can be exploited as an additional parameter in engineering the emission profile of LEDs.

  13. Application of Single-Mode Fiber-Coupled Receivers in Optical Satellite to High-Altitude Platform Communications

    Directory of Open Access Journals (Sweden)

    Fidler Franz

    2008-01-01

    Full Text Available Abstract In a free-space optical communication system employing fiber-optic components, the phasefront distortions induced by atmospheric turbulence limit the efficiency with which the laser beam is coupled into a single-mode fiber. We analyze different link scenarios including a geostationary (GEO satellite, a high-altitude platform (HAP, and an optical ground station (OGS. Single-mode coupled optically preamplified receivers allow for efficient suppression of background noise and highly sensitive detection. While GEO-to-OGS communication suffers from atmospheric turbulence, we demonstrate that GEO-to-HAP communication allows for close to diffraction-limited performance when applying tip-tilt correction.

  14. Application of Single-Mode Fiber-Coupled Receivers in Optical Satellite to High-Altitude Platform Communications

    Directory of Open Access Journals (Sweden)

    Oswald Wallner

    2008-05-01

    Full Text Available In a free-space optical communication system employing fiber-optic components, the phasefront distortions induced by atmospheric turbulence limit the efficiency with which the laser beam is coupled into a single-mode fiber. We analyze different link scenarios including a geostationary (GEO satellite, a high-altitude platform (HAP, and an optical ground station (OGS. Single-mode coupled optically preamplified receivers allow for efficient suppression of background noise and highly sensitive detection. While GEO-to-OGS communication suffers from atmospheric turbulence, we demonstrate that GEO-to-HAP communication allows for close to diffraction-limited performance when applying tip-tilt correction.

  15. Single mode step-index polymer optical fiber for humidity insensitive high temperature fiber Bragg grating sensors

    OpenAIRE

    Woyessa, Getinet; Fasano, Andrea; Stefani, Alessio; Markos, Christos; Nielsen, Kristian; Rasmussen, Henrik K.; Bang, Ole

    2016-01-01

    We have fabricated the first single-mode step-index and humidity insensitive polymer optical fiber operating in the 850 nm wavelength ranges. The step-index preform is fabricated using injection molding, which is an efficient method for cost effective, flexible and fast preparation of the fiber preform. The fabricated single-mode step-index (SI) polymer optical fiber (POF) has a 4.8µm core made from TOPAS grade 5013S-04 with a glass transition temperature of 134°C and a 150 µm cladding made f...

  16. Wavefront Analysis of Nonlinear Self-Amplified Spontaneous-Emission Free-Electron Laser Harmonics in the Single-Shot Regime

    Energy Technology Data Exchange (ETDEWEB)

    Bachelard, R.; Chubar, O.; Mercere, P.; Idir, M.; Couprie, M.E.; Lambert, G.; Zeitoun, Ph.; Kimura, H.; Ohashi, H.; Higashiya, A.; Yabashi, M.; Nagasono, M.; Hara, T. and Ishikawa, T.

    2011-06-08

    The single-shot spatial characteristics of the vacuum ultraviolet self-amplified spontaneous emission of a free electron laser (FEL) is measured at different stages of amplification up to saturation with a Hartmann wavefront sensor. We show that the fundamental radiation at 61.5 nm tends towards a single-mode behavior as getting closer to saturation. The measurements are found in good agreement with simulations and theory. A near diffraction limited wavefront was measured. The analysis of Fresnel diffraction through the Hartmann wavefront sensor hole array also provides some further insight for the evaluation of the FEL transverse coherence, of high importance for various applications.

  17. Controlling light emission from single-photon sources using photonic nanowires

    DEFF Research Database (Denmark)

    Gregersen, Niels; Chen, Yuntian; Mørk, Jesper

    2012-01-01

    The photonic nanowire has recently emerged as an promising alternative to microcavity-based single-photon source designs. In this simple structure, a geometrical effect ensures a strong coupling between an embedded emitter and the optical mode of interest and a combination of tapers and mirrors a...... designs allowing for electrical contacting, polarization control, improved efficiency and simplified fabrication....

  18. Single-photon-sensitive linear-mode APD ladar receiver developments

    Science.gov (United States)

    Williams, George M.; Compton, Madison A.; Huntington, Andrew S.

    2008-04-01

    New measurements are presented for multi-stage InGaAs avalanche photodiodes (APDs) which have the potential to perform GHz-rate single photon counting in linear mode. No increase in dark current was measured for an 11-device sample of 5-stage APDs following 717 hours of accelerated aging under bias at 50°C, during an initial lifetime study. Impulse response times of 0.45 ns, 0.9 ns, and 1.1 ns were measured directly for 6-, 8-, and 10-stage APDs, respectively, operated at a nominal gain of M=10. To assess the suitability of the technology for a NASA optical communications application, separate samples of 5-stage APDs were irradiated by 1- and 2-MeV protons at the University of Washington's Center for Experimental Nuclear Physics and Astrophysics (UW CENPA) and by 63.5-MeV protons at the University of California Davis, Crocker Nuclear Laboratory (UCD CNL). Good agreement between calculated non-ionizing energy loss (NIEL) and observed damage was found for the low-energy protons at fluences of 10 10 and 10 11 cm -2. A NIEL calculation successfully predicted the damage observed following a 5×10 10 cm -2 dose of 63.5-MeV protons by extrapolating from 2 MeV data, which suggests that displacement damage is the dominant mechanism.

  19. Influence of photo- and thermal bleaching on pre-irradiation low water peak single mode fibers

    Science.gov (United States)

    Yin, Jianchong; Wen, Jianxiang; Luo, Wenyun; Xiao, Zhongyin; Chen, Zhenyi; Wang, Tingyun

    2011-12-01

    Reducing the radiation-induced transmission loss in low water peak single mode fiber (LWP SMF) has been investigated by using photo-bleaching method with 980nm pump light source and using thermal-bleaching method with temperature control system. The results show that the radiation-induced loss of pre-irradiation optical fiber can be reduced effectively with the help of photo-bleaching or thermal-bleaching. Although the effort of photo-bleaching is not as significant as thermal-bleaching, by using photo-bleaching method, the loss of fiber caused by radiation-induced defects can be reduced best up to 49% at 1310nm and 28% at 1550nm in low pre-irradiation condition, the coating of the fiber are not destroyed, and the rehabilitating time is just several hours, while self-annealing usually costs months' time. What's more, the typical high power LASER for photo-bleaching can be 980nm pump Laser Diode, which is very accessible.

  20. Artificially controlled backscattering in single mode fibers based on femtosecond laser fabricated reflectors

    Science.gov (United States)

    Wang, Xiaoliang; Chen, Daru; Li, Haitao; Wu, Qiong

    2018-04-01

    A novel method to artificially control the backscattering of the single-mode fiber (SMF) is proposed and investigated for the first time. This method can help to fabricate a high backscattering fiber (HBSF), such as by fabricating reflectors in every one meter interval of an SMF based on the exposure of the femtosecond laser beam. The artificially controlled backscattering (ACBS) can be much higher than the natural Rayleigh backscattering (RB) of the SMF. The RB power and ACBS power in the unit length fiber are derived according to the theory of the RBS. The total relative power and the relative back power reflected in the unit length of the HBSF have been simulated and presented. The simulated results show that the HBSF has the characteristics of both low optical attenuation and high backscattering. The relative back power reflected in the unit length of the HBSF is 25dB larger than the RB power of the SMF when the refractive index modulation quantity of the reflectors is 0.009. Some preliminary experiments also indicate that the method fabricating reflectors to increase the backscattering power of the SMF is practical and promising.

  1. Large-Area High Aspect Ratio Plasmonic Interference Lithography Utilizing a Single High-k Mode.

    Science.gov (United States)

    Chen, Xi; Yang, Fan; Zhang, Cheng; Zhou, Jing; Guo, L Jay

    2016-04-26

    Plasmonic lithography, which utilizes subwavelength confinement of surface plasmon polartion (SPP) waves, has the capability of breaking the diffraction limit and delivering high resolution. However, all previously reported results suffer from critical issues, such as shallow pattern depth and pattern nonuniformity even over small exposure areas, which limit the application of the technology. In this work, periodic patterns with high aspect ratios and a half-pitch of about 1/6 of the wavelength were achieved with pattern uniformity in square centimeter areas. This was accomplished by designing a special mask and photoresist (PR) system to select a single high spatial frequency mode and incorporating the PR into a waveguide configuration to ensure uniform light exposure over the entire depth of the photoresist layer. In addition to the experimental progress toward large-scale applications of plasmonic interference lithography, the general criteria of designing such an exposure system is also discussed, which can be used for nanoscale fabrication in this fashion for various applications with different requirements for wavelength, pitch, aspect ratio, and structure.

  2. Single-mode Rayleigh-Taylor growth-rate measurements with the OMEGA laser system

    International Nuclear Information System (INIS)

    Knauer, J.P.; Verdon, C.P.; Meyerhofer, D.D.; Boehly, T.R.; Bradley, D.K.; Smalyuk, V.A.; Ofer, D.; McKenty, P.W.; Glendinning, S.G.; Kalantar, D.H.; Watt, R.G.; Gobby, P.L.; Willi, O.; Taylor, R.J.

    1997-01-01

    The results from a series of single-mode Rayleigh-Taylor (RT) instability growth experiments performed on the OMEGA laser system using planar targets are reported. Planar targets with imposed mass perturbations were accelerated using five to six 351-nm laser beams overlapped with total intensities up to 2.5x10 14 W/cm 2 . Experiments were performed with both 3-ns ramp and 3-ns flat-topped temporal pulse shapes. The use of distributed phase plates and smoothing by spectral dispersion resulted in a laser-irradiation nonuniformity of 4%endash 7% over a 600-μm-diam region defined by the 90% intensity contour. The temporal growth of the modulation in optical depth was measured using through-foil radiography and was detected with an x-ray framing camera for CH targets with and without a foam buffer. The growth of both 31-μm and 60-μm wavelength perturbations was found to be in good agreement with ORCHID simulations when the experimental details, including noise, were included. The addition of a 30-mg/cc, 100-μm-thick polystyrene foam buffer layer resulted in reduced growth of the 31-μm perturbation and essentially unchanged growth for the 60-μm case when compared to targets without foam. copyright 1997 American Institute of Physics

  3. All-fiber single-mode high modulation rate pseudorandom-coded laser

    Science.gov (United States)

    Zhang, Xin; Yang, Fang; Liu, Yuan; He, Yan; Hou, Xia; Chen, Weibiao

    2013-12-01

    An all-fiber high modulation speed pseudorandom-coded laser based on master oscillator power amplifier configuration is proposed. We use a high modulation rate distributed feedback laser diode as the seed laser to generate the original pseudorandom pulse train. The modulation rate is 1 Gb/s, which corresponds to a minimum pulse interval of 1 ns. A 1 kHz repetition frequency of 10-order M-sequence pseudorandom pulse train is chosen to balance on-line data processing speed and laser ranging resolution. Then, the pseudorandom pulse train is amplified by two-stage amplifiers to boost the output power. All components used in the amplifiers are built in single mode (SM) fiber, so the final output laser is SM with excellent beam quality. Finally, the peak power of pseudorandom code laser is amplified to 23.6 W from 1.5 mW without wave distortion, corresponding to a gain of 42 dB. The ranging experiment of using the optical fiber delay method indoors shows the transmitter of combining modulated laser diode and multistage fiber amplifiers as a promising solution for developing laser for pseudorandom-coded laser ranging.

  4. Role of third-order dispersion in chirped Airy pulse propagation in single-mode fibers

    Science.gov (United States)

    Cai, Wangyang; Wang, Lei; Wen, Shuangchun

    2018-04-01

    The dynamic propagation of the initial chirped Airy pulse in single-mode fibers is studied numerically, special attention being paid to the role of the third-order dispersion (TOD). It is shown that for the positive TOD, the Airy pulse experiences inversion irrespective of the sign of initial chirp. The role of TOD in the dynamic propagation of the initial chirped Airy pulse depends on the combined sign of the group-velocity dispersion (GVD) and the initial chirp. If the GVD and chirp have the opposite signs, the chirped Airy pulse compresses first and passes through a breakdown area, then reconstructs a new Airy pattern with opposite acceleration, with the breakdown area becoming small and the main peak of the new Airy pattern becoming asymmetric with an oscillatory structure due to the positive TOD. If the GVD and chirp have the same signs, the finite-energy Airy pulse compresses to a focal point and then inverses its acceleration, in the case of positive TOD, the distance to the focal point becoming smaller. At zero-dispersion point, the finite-energy Airy pulse inverses to the opposite acceleration at a focal point, with the tight-focusing effect being reduced by initial chirp. Under the effect of negative TOD, the initial chirped Airy pulse disperses and the lobes split. In addition, in the anomalous dispersion region, for strong nonlinearity, the initial chirped Airy pulse splits and enters a soliton shedding regime.

  5. Experimental demonstration of single-mode fiber coupling over relatively strong turbulence with adaptive optics.

    Science.gov (United States)

    Chen, Mo; Liu, Chao; Xian, Hao

    2015-10-10

    High-speed free-space optical communication systems using fiber-optic components can greatly improve the stability of the system and simplify the structure. However, propagation through atmospheric turbulence degrades the spatial coherence of the signal beam and limits the single-mode fiber (SMF) coupling efficiency. In this paper, we analyze the influence of the atmospheric turbulence on the SMF coupling efficiency over various turbulences. The results show that the SMF coupling efficiency drops from 81% without phase distortion to 10% when phase root mean square value equals 0.3λ. The simulations of SMF coupling with adaptive optics (AO) indicate that it is inevitable to compensate the high-order aberrations for SMF coupling over relatively strong turbulence. The SMF coupling efficiency experiments, using an AO system with a 137-element deformable mirror and a Hartmann-Shack wavefront sensor, obtain average coupling efficiency increasing from 1.3% in open loop to 46.1% in closed loop under a relatively strong turbulence, D/r0=15.1.

  6. Capacitive deionization of arsenic-contaminated groundwater in a single-pass mode.

    Science.gov (United States)

    Fan, Chen-Shiuan; Liou, Sofia Ya Hsuan; Hou, Chia-Hung

    2017-10-01

    A single-pass-mode capacitive deionization (CDI) reactor was used to remove arsenic from groundwater in the presence of multiple ions. The CDI reactor involved an applied voltage of 1.2 V and six cell pairs of activated carbon electrodes, each of which was 20 × 30 cm 2 . The results indicate that this method achieved an effluent arsenic concentration of 0.03 mg L -1 , which is lower than the arsenic concentration standard for drinking water and irrigation sources in Taiwan, during the charging stage. Additionally, the ability of the CDI to remove other coexisting ions was studied. The presence of other ions has a significant influence on the removal of arsenic from groundwater. From the analysis of the electrosorption selectivity, the preference for anion removal could be ordered as follows: NO 3 -  > SO 4 2-  > F -  > Cl - >As. The electrosorption selectivity for cations could be ordered as follows: Ca 2+  > Mg 2+  > Na +  ∼ K + . Moreover, monovalent cations can be replaced by divalent cations at the electrode surface in the later period of the electrosorption stage. Consequently, activated carbon-based capacitive deionization is demonstrated to be a high-potential technology for remediation of arsenic-contaminated groundwater. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Development of distributed temperature sensor based on single-mode fiber

    Science.gov (United States)

    Jiang, Mingshun; Wang, Jing; Feng, Dejun; Sui, Qingmei

    2008-12-01

    The distributed optical fiber temperature measurement system (DTS) is a kind of sensing system, which is applied to the real-time measurement of the temperature field in space. It is widely used in monitoring of production process: fire alarm of coal mine and fuel depots, heat detection and temperature monitor of underground cable, seepage and leakage of dam. Through analyzing temperature effect of optical fiber Raman backscattering theoretically, a distributed temperature sensor based on single-mode fiber was designed, which overcame the inadequacies of multimode fiber. The narrow pulse width laser, excellent InGaAS PIN, low noise precision difet operational amplifier and high speed data acquisition card in order to improve the stability of this system were selected. The demodulation method based on ratio of Anti-Stokes and Stokes Raman backscattering intensity was adopted. Both hardware composition and software implementation of the system were introduced in detail. It is proved that its distinguishing ability of temperature and space are 1 m and 2 m, respectively. The system response time is about 180 s, with a sensing range of 5 km and the temperature measurement range 0~100 °C.

  8. A Novel Technique for Sterilization Using a Power Self-Regulated Single-Mode Microwave Cavity

    Directory of Open Access Journals (Sweden)

    Juan D. Reverte-Ors

    2017-06-01

    Full Text Available In this paper, a novel technique to achieve precise temperatures in food sterilization has been proposed. An accurate temperature profile is needed in order to reach a commitment between the total removal of pathogens inside the product and the preservation of nutritional and organoleptic characteristics. The minimal variation of the target temperature in the sample by means of a monitoring and control software platform, allowing temperature stabilization over 100 °C, is the main goal of this work. A cylindrical microwave oven, under pressure conditions and continuous control of the microwave supply power as function of the final temperature inside the sample, has been designed and developed with conditions of single-mode resonance. The uniform heating in the product is achieved by means of sample movement and the self-regulated power control using the measured temperature. Finally, for testing the sterilization of food with this technology, specific biological validation based on Bacillus cereus as a biosensor of heat inactivation has been incorporated as a distribution along the sample in the experimental process to measure the colony-forming units (CFUs for different food samples (laboratory medium, soup, or fish-based animal by-products. The obtained results allow the validation of this new technology for food sterilization with precise control of the microwave system to ensure the uniform elimination of pathogens using high temperatures.

  9. Imaging of the dopaminergic neurotransmission system using single-photon emission tomography and positron emission tomography in patients with parkinsonism

    International Nuclear Information System (INIS)

    Booij, J.; Tissingh, G.; Winogrodzka, A.; Royen, E.A. van

    1999-01-01

    Parkinsonism is a feature of a number of neurodegenerative diseases, including Parkinson's disease, multiple system atrophy and progressive supranuclear palsy. The results of post-mortem studies point to dysfunction of the dopaminergic neurotransmitter system in patients with parkinsonism. Nowadays, by using single-photon emission tomography (SPET) and positron emission tomography (PET) it is possible to visualise both the nigrostriatal dopaminergic neurons and the striatal dopamine D 2 receptors in vivo. Consequently, SPET and PET imaging of elements of the dopaminergic system can play an important role in the diagnosis of several parkinsonian syndromes. This review concentrates on findings of SPET and PET studies of the dopaminergic neurotransmitter system in various parkinsonian syndromes. (orig.)

  10. Acoustic emission evolution during sliding friction of Hadfield steel single crystal

    Science.gov (United States)

    Lychagin, D. V.; Novitskaya, O. S.; Kolubaev, A. V.; Sizova, O. V.

    2017-12-01

    Friction is a complex dynamic process. Direct observation of processes occurring in the friction zone is impossible due to a small size of a real contact area and, as a consequence, requires various additional methods applicable to monitor a tribological contact state. One of such methods consists in the analysis of acoustic emission data of a tribological contact. The use of acoustic emission entails the problem of interpreting physical sources of signals. In this paper, we analyze the evolution of acoustic emission signal frames in friction of Hadfield steel single crystals. The chosen crystallographic orientation of single crystals enables to identify four stages related to friction development as well as acoustic emission signals inherent in these stages. Acoustic emission signal parameters are studied in more detail by the short-time Fourier transform used to determine the time variation of the median frequency and its power spectrum. The results obtained will facilitate the development of a more precise method to monitor the tribological contact based on the acoustic emission method.

  11. Characterization of microwave plasma in a multicusp using 2D emission based tomography: Bessel modes and wave absorption

    Science.gov (United States)

    Rathore, Kavita; Bhattacharjee, Sudeep; Munshi, Prabhat

    2017-06-01

    A tomographic method based on the Fourier transform is used for characterizing a microwave plasma in a multicusp (MC), in order to obtain 2D distribution of plasma emissions, plasma (electron) density (Ne) and temperature (Te). The microwave plasma in the MC is characterized as a function of microwave power, gas pressure, and axial distance. The experimentally obtained 2D emission profiles show that the plasma emissions are generated in a circular ring shape. There are usually two bright rings, one at the plasma core and another near the boundary. The experimental results are validated using a numerical code that solves Maxwell's equations inside a waveguide filled with a plasma in a magnetic field, with collisions included. It is inferred that the dark and bright circular ring patterns are a result of superposition of Bessel modes (TE11 and TE21) of the wave electric field inside the plasma filled MC, which are in reasonable agreement with the plasma emission profiles. The tomographically obtained Ne and Te profiles indicate higher densities in the plasma core (˜1010 cm-3) and enhanced electron temperature in the ECR region (˜13 eV), which are in agreement with earlier results using a Langmuir probe and optical emission spectroscopy (OES) diagnostics.

  12. Ag-protein plasmonic architectures for surface plasmon-coupled emission enhancements and Fabry-Perot mode-coupled directional fluorescence emission

    Science.gov (United States)

    Badiya, Pradeep Kumar; Patnaik, Sai Gourang; Srinivasan, Venkatesh; Reddy, Narendra; Manohar, Chelli Sai; Vedarajan, Raman; Mastumi, Noriyoshi; Belliraj, Siva Kumar; Ramamurthy, Sai Sathish

    2017-10-01

    We report the use of silver decorated plant proteins as spacer material for augmented surface plasmon-coupled emission (120-fold enhancement) and plasmon-enhanced Raman scattering. We extracted several proteins from different plant sources [Triticum aestivum (TA), Aegle marmelos (AM), Ricinus communis (RC), Jatropha curcas (JC) and Simarouba glauca (SG)] followed by evaluation of their optical properties and simulations to rationalize observed surface plasmon resonance. Since the properties exhibited by protein thin films is currently gaining research interest, we have also carried out simulation studies with Ag-protein biocomposites as spacer materials in metal-dielectric-metal planar microcavity architecture for guided emission of Fabry-Perot mode-coupled fluorescence.

  13. Fingerprinting of traditional Chinese medicines on the C18-Diol mixed-mode column in online or offline two-dimensional liquid chromatography on the single column modes.

    Science.gov (United States)

    Wang, Qing; Tong, Ling; Yao, Lin; Zhang, Peng; Xu, Li

    2016-06-05

    In the present study, a mixed-mode stationary phase, C18-Diol, was applied for fingerprint analysis of traditional Chinese medicines. Hydrophobic, hydrogen bonding and electrostatic interactions were demonstrated to contribute the retention separately or jointly, which endowed the C18-Diol stationary phase with distinct selectivity compared to the bare C18 one. The separation of total alkaloids extracted from Fritillaria hupehensis was compared on the C18-Diol and conventional C18 column with the greater resolving power and better symmetry responses on the former one. Besides, a novel two-dimensional liquid chromatography on the single column (2D-LC-1C) was realized on C18-Diol with the offline mode for the alcohol extract of Fritillaria hupehensis and online mode for Ligusticum chuanxiong Hort. The early co-eluted extracted components with great polarity on the first dimension were reinjected on the same column and well separated on the second dimension. The results exhibited that the two complementary RPLC and HILIC modes on C18-Diol stationary phase enhanced the separation capacity and revealed more abundant chemical information of the sample, which was a powerful tool in analyzing complex herbal medicines. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Monitoring CBF in clinical routine by dynamic single photon emission tomography (SPECT) of inhaled xenon-133

    DEFF Research Database (Denmark)

    Sugiyama, H; Christensen, J; Skyhøj Olsen, T

    1986-01-01

    A very simple and low-cost brain dedicated, rapidly rotating Single Photon Emission Tomograph SPECT is described. Its use in following patients with ischemic stroke is illustrated by two middle cerebral artery occlusion cases, one with persistent occlusion and low CBF in MCA territory, and one wi...

  15. Evaluation of a 99Tcm bound brain scanning agent for single photon emission computed tomography

    DEFF Research Database (Denmark)

    Andersen, A R; Hasselbalch, S G; Paulson, O B

    1986-01-01

    D,L HM-PAO-99Tcm (PAO) is a lipophilic tracer complex which is avidly taken up by the brain. We have compared the regional distribution of PAO with regional cerebral blood flow (CBF). CBF was measured by single photon emission computed tomography (SPECT) by Tomomatic 64 after 133Xe inhalation in 41...

  16. Single photon emission computed tomography in motor neuron disease with dementia

    Energy Technology Data Exchange (ETDEWEB)

    Sawada, H.; Udaka, F.; Kishi, Y.; Seriu, N.; Ohtani, S.; Abe, K.; Mezaki, T.; Kameyama, M.; Honda, M.; Tomonobu, M.

    1988-12-01

    Single photon emission computed tomography with (123 I) isopropylamphetamine was carried out on a patient with motor neutron disease with dementia. (123 I) uptake was decreased in the frontal lobes. This would reflect the histopathological findings such as neuronal loss and gliosis in the frontal lobes.

  17. Single photon emission computed tomography in motor neuron disease with dementia.

    Science.gov (United States)

    Sawada, H; Udaka, F; Kishi, Y; Seriu, N; Mezaki, T; Kameyama, M; Honda, M; Tomonobu, M

    1988-01-01

    Single photon emission computed tomography with [123 I] isopropylamphetamine was carried out on a patient with motor neuron disease with dementia. [123 I] uptake was decreased in the frontal lobes. This would reflect the histopathological findings such as neuronal loss and gliosis in the frontal lobes.

  18. Tailoring surface plasmon resonance and dipole cavity plasmon modes of scattering cross section spectra on the single solid-gold/gold-shell nanorod

    International Nuclear Information System (INIS)

    Chou Chau, Yuan-Fong; Lim, Chee Ming; Kumara, N. T. R. N.; Yoong, Voo Nyuk; Lee, Chuanyo; Huang, Hung Ji; Lin, Chun-Ting; Chiang, Hai-Pang

    2016-01-01

    Tunable surface plasmon resonance (SPR) and dipole cavity plasmon modes of the scattering cross section (SCS) spectra on the single solid-gold/gold-shell nanorod have been numerically investigated by using the finite element method. Various effects, such as the influence of SCS spectra under x- and y-polarizations on the surface of the single solid-gold/gold-shell nanorod, are discussed in detail. With the single gold-shell nanorod, one can independently tune the relative SCS spectrum width by controlling the rod length and rod diameter, and the surface scattering by varying the shell thickness and polarization direction, as well as the dipole peak energy. These behaviors are consistent with the properties of localized SPRs and offer a way to optically control and produce selected emission wavelengths from the single solid-gold/gold-shell nanorod. The electric field and magnetic distributions provide us a qualitative idea of the geometrical properties of the single solid-gold/gold-shell nanorod on plasmon resonance.

  19. National emission standards for hazardous air pollutants application for approval to construct rotary mode core-sampling truck and exhauster

    International Nuclear Information System (INIS)

    1993-05-01

    Characterization of wastes in the underground single-shell tanks and double-shell tanks on the Hanford Site is crucial in developing the final disposal options for the waste and closure strategy for the Hanford Site. Additionally, characterization of tank waste is important for the waste tank safety programs. The Hanford Federal Facility Agreement and Consent Order (also referred to as the Tri-Party Agreement) Milestone M-10-00 requires the obtaining and analyzing of at least two samples from each single-shell tank, and Milestone M-10-13 specifically requires the ability to sample hard saltcake. Existing equipment does not allow sampling of all single-shell tanks within established tank safety limits. Consequently, the US Department of Energy, Richland Operations Office has developed a rotary mode core-sampling system that uses nitrogen gas to cool and clear the drill bit. A rotary mode core-sampling truck will be used on approximately 80 single-shell tanks which contain saltcake wastes, and will provide crucial information on the contents of the tanks. This application is a request for approval to construct and operate the rotary mode core-sampling truck and exhauster in the 200 East and 200 West Area Tank Farms of the Hanford Site. This request is being made pursuant to 40 CFR 61, Subpart H

  20. Tunable single-longitudinal-mode operation of an injection-locked TEA CO2 laser. [ozone absorption spectroscopy

    Science.gov (United States)

    Megie, G.; Menzies, R. T.

    1979-01-01

    The tunable single-longitudinal-mode operation of a TEA CO2 laser by an injection technique using a CW waveguide laser as the master oscillator is reported. With the experimental arrangement described, in which the waveguide laser frequency is tuned to correspond to one of the oscillating longitudinal modes of the TEA laser, single-longitudinal-mode operation was achieved with no apparent reduction in the TEA output energy, on various CO2 lines with frequency offsets from the line center as large as 300 MHz. The capability of this technique for high-resolution spectroscopy or atmospheric lidar studies is demonstrated by the recording of the absorption spectrum of a strong ozone line.

  1. Tunable single-polarization single-longitudinal-mode erbium-doped fiber ring laser employing a CMFBG filter and saturable absorber

    Science.gov (United States)

    Feng, Suchun; Lu, Shaohua; Peng, Wanjing; Li, Qi; Feng, Ting; Jian, Shuisheng

    2013-04-01

    A tunable single-polarization single-longitudinal-mode (SLM) erbium-doped fiber ring laser is proposed and demonstrated. For the first time as we know, a chirped moiré fiber Bragg grating (CMFBG) filter with ultra-narrow transmission band and a uniform fiber Bragg grating (UFBG) are used to select the laser longitudinal mode. The stable SLM operation of the fiber laser is guaranteed by the combination of the CMFBG filter and 3 m unpumped erbium-doped fiber acting as a saturable absorber. The single polarization operation of the fiber laser is obtained by using an inline broadband polarizer. A tuning range of about 0.7 nm with about 0.1 nm step is achieved by stretching the uniform FBG.

  2. Realization of Current Mode Universal Filter and a Dual-Mode Single Resistance Controlled Quadrature Oscillator Employing VDCC and Only Grounded Passive Elements

    Directory of Open Access Journals (Sweden)

    Manish Gupta

    2017-01-01

    Full Text Available The manuscript presents a circuit that can act as a universal filter as well as a single resistence controlled oscillator by unpretentiously changing the switch positions. The circuit employs only two active devices and all grounded passive elements. The utilization of only grounded passive components makes this circuit a better choice for integrated circuit implementation. The current mode biquadratic filter offers all the five basic responses along with independent tunability of its quality factor. The dual-mode quadrature sinusoidal oscillator offers explicit current outputs along with voltage outputs. The circuit also offers a simple and uncoupled condition of oscillation and frequency of oscillation. The typical analysis such as non-ideal, sensitivity and parasitic analysis along with the regular simulation results as well as experimental results are exposed here, to strengthen the design idea.

  3. Study on performance and emission characteristics of a single cylinder diesel engine using exhaust gas recirculation

    Directory of Open Access Journals (Sweden)

    Anantha Raman Lakshmipathi

    2017-01-01

    Full Text Available Exhaust gas re-circulation is a method used in compression ignition engines to control and reduce NOx emission. These emissions are controlled by reducing the oxygen concentration inside the cylinder and thereby reducing the flame temperature of the charge mixture inside the combustion chamber. In the present investigation, experiments were performed to study the effect of exhaust gas re-circulation on performance and emission characteristics in a four stroke single cylinder, water cooled and constant speed diesel engine. The experiments were performed to study the performance and emissions for different exhaust gas re-circulation ratios of the engine. Performance parameters such as brake thermal efficiency, indicated thermal efficiency, specific fuel consumption, total fuel consumption and emission parameters such as oxides of nitrogen, unburned hydrocarbons, carbon monoxide, carbon dioxide and smoke opacity were measured. Reductions in NOx and CO2 were observed but other emissions like HC, CO, and smoke opacity were found to have increased with the usage of exhaust gas re-circulation. The 15% exhaust gas re-circulation was found optimum for the engine in the aspects of performance and emission.

  4. Comparative investigation of methods to determine the group velocity dispersion of an endlessly single-mode photonic crystal fiber

    Science.gov (United States)

    Baselt, Tobias; Popp, Tobias; Nelsen, Bryan; Lasagni, Andrés. Fabián.; Hartmann, Peter

    2017-05-01

    Endlessly single-mode fibers, which enable single mode guidance over a wide spectral range, are indispensable in the field of fiber technology. A two-dimensional photonic crystal with a silica central core and a micrometer-spaced hexagonal array of air holes is an established method to achieve endless single-mode guidance. There are two possible ways to determine the dispersion: measurement and calculation. We calculate the group velocity dispersion GVD based on the measurement of the fiber structure parameters, the hole diameter and the pitch of a presumed homogeneous hexagonal array and compare the calculation with two methods to measure the wavelength-dependent time delay. We measure the time delay on a three hundred meter test fiber with a homemade supercontinuum light source, a set of bandpass filters and a fast detector and compare the results with a white light interferometric setup. To measure the dispersion of optical fibers with high accuracy, a time-frequency-domain setup based on a Mach-Zehnder interferometer is used. The experimental setup allows the determination of the wavelength dependent differential group delay of light travelling through a thirty centimeter piece of test fiber in the wavelength range from VIS to NIR. The determination of the GVD using different methods enables the evaluation of the individual methods for characterizing the endlessly single-mode fiber.

  5. Single-Mode, High Repetition Rate, Compact Ho:YLF Laser for Space-Borne Lidar Applications

    Science.gov (United States)

    Bai, Yingxin; Yu, Jirong; Wong, Teh-Hwa; Chen, Songsheng; Petros, Mulugeta; Singh, Upendra N.

    2014-01-01

    A single transverse/longitudinal mode, compact Q-switched Ho:YLF laser has been designed and demonstrated for space-borne lidar applications. The pulse energy is between 34-40 mJ for 100-200 Hz operation. The corresponding peak power is >1 MW.

  6. Open quantum systems and the two-level atom interacting with a single mode of the electromagnetic field

    International Nuclear Information System (INIS)

    Sandulescu, A.; Stefanescu, E.

    1987-07-01

    On the basis of Lindblad theory of open quantum systems we obtain new optical equations for the system of two-level atom interacting with a single mode of the electromagnetic field. The conventional Block equations in a generalized form with field phases are obtained in the hypothesis that all the terms are slowly varying in the rotating frame.(authors)

  7. A passive micromachined device for alignment of arrays of single-mode fibers for hermetic photonic packaging - the CLASP concept

    Energy Technology Data Exchange (ETDEWEB)

    Seigal, P.K.; Kravitz, S.H.; Word, J.C.; Bauer, T.M. [and others

    1997-02-01

    A micro-machined fiber alignment device, called CLASP (Capture and Locking Alignment Spring Positioner) has been fabricated. It uses a nickel leaf spring to passively capture vertical arrays of single-mode fibers with {approximately} 2 {mu}m accuracy.

  8. A method to synchronize signals from multiple patient monitoring devices through a single input channel for inclusion in list-mode acquisitions

    Energy Technology Data Exchange (ETDEWEB)

    O’Connor, J. Michael; Pretorius, P. Hendrik; Johnson, Karen; King, Michael A., E-mail: Michael.King@umassmed.edu [Department of Radiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655 (United States)

    2013-12-15

    Purpose: This technical note documents a method that the authors developed for combining a signal to synchronize a patient-monitoring device with a second physiological signal for inclusion into list-mode acquisition. Our specific application requires synchronizing an external patient motion-tracking system with a medical imaging system by multiplexing the tracking input with the ECG input. The authors believe that their methodology can be adapted for use in a variety of medical imaging modalities including single photon emission computed tomography (SPECT) and positron emission tomography (PET). Methods: The authors insert a unique pulse sequence into a single physiological input channel. This sequence is then recorded in the list-mode acquisition along with the R-wave pulse used for ECG gating. The specific form of our pulse sequence allows for recognition of the time point being synchronized even when portions of the pulse sequence are lost due to collisions with R-wave pulses. This was achieved by altering our software used in binning the list-mode data to recognize even a portion of our pulse sequence. Limitations on heart rates at which our pulse sequence could be reliably detected were investigated by simulating the mixing of the two signals as a function of heart rate and time point during the cardiac cycle at which our pulse sequence is mixed with the cardiac signal. Results: The authors have successfully achieved accurate temporal synchronization of our motion-tracking system with acquisition of SPECT projections used in 17 recent clinical research cases. In our simulation analysis the authors determined that synchronization to enable compensation for body and respiratory motion could be achieved for heart rates up to 125 beats-per-minute (bpm). Conclusions: Synchronization of list-mode acquisition with external patient monitoring devices such as those employed in motion-tracking can reliably be achieved using a simple method that can be implemented using

  9. Measurement of peripheral electron temperature by electron cyclotron emission during the H-mode transition in JFT-2M tokamak

    International Nuclear Information System (INIS)

    Hoshino, Katsumichi; Yamamoto, Takumi; Kawashima, Hisato

    1987-01-01

    Time evolution and profile of peripheral electron temperature during the H-mode like transition in a tokamak plasma is measured using the second and third harmonic of electron cyclotron emission (ECE). The so called ''H-mode'' state which has good particle/energy confinement is characterized by sudden decrease in the spectral line intensity of deuterium molecule. Such a sudden decrease in the line intensity of D α with good energy confinement is found not only in divertor discharges, but also in limiter dischargs in JFT-2M tokamak. It is found by the measurement of ECE that the peripheral electron temperature suddenly increases in both of such phases. The relation between H-transition and the peripheral electron temperature or its profile is investigated. (author)

  10. Model of a single mode energy harvester and properties for optimal power generation

    International Nuclear Information System (INIS)

    Liao Yabin; Sodano, Henry A

    2008-01-01

    The process of acquiring the energy surrounding a system and converting it into usable electrical energy is termed power harvesting. In the last few years, the field of power harvesting has experienced significant growth due to the ever increasing desire to produce portable and wireless electronics with extended life. Current portable and wireless devices must be designed to include electrochemical batteries as the power source. The use of batteries can be troublesome due to their finite energy supply, which necessitates their periodic replacement. In the case of wireless sensors that are to be placed in remote locations, the sensor must be easily accessible or of disposable nature to allow the device to function over extended periods of time. Energy scavenging devices are designed to capture the ambient energy surrounding the electronics and covert it into usable electrical energy. The concept of power harvesting works towards developing self-powered devices that do not require replaceable power supplies. The development of energy harvesting systems is greatly facilitated by an accurate model to assist in the design of the system. This paper will describe a theoretical model of a piezoelectric based energy harvesting system that is simple to apply yet provides an accurate prediction of the power generated around a single mode of vibration. Furthermore, this model will allow optimization of system parameters to be studied such that maximal performance can be achieved. Using this model an expression for the optimal resistance and a parameter describing the energy harvesting efficiency will be presented and evaluated through numerical simulations. The second part of this paper will present an experimental validation of the model and optimal parameters

  11. Single-mode, Rayleigh-Taylor growth-rate measurements on the OMEGA laser system

    International Nuclear Information System (INIS)

    Knauer, J. P.; Betti, R.; Bradley, D. K.; Boehly, T. R.; Collins, T. J. B.; Goncharov, V. N.; McKenty, P. W.; Meyerhofer, D. D.; Smalyuk, V. A.; Verdon, C. P.

    2000-01-01

    The results from a series of single-mode, Rayleigh-Taylor (RT) instability growth experiments performed on the OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] using planar targets are reported. Planar targets with imposed mass perturbations were accelerated using five or six 351 nm laser beams overlapped with total intensities up to 2.5x10 14 W/cm 2 . Experiments were performed with both 3 ns ramp and 3 ns flat-topped temporal pulse shapes. The use of distributed phase plates and smoothing by spectral dispersion resulted in a laser-irradiation nonuniformity of 4%-7% over a 600 μm diam region defined by the 90% intensity contour. The temporal growth of the modulation in optical depth was measured using throughfoil radiography and was detected with an x-ray framing camera for CH targets. Two-dimensional (2-D) hydrodynamic simulations (ORCHID) [R. L. McCrory and C. P. Verdon, in Inertial Confinement Fusion (Editrice Compositori, Bologna, 1989), pp. 83-124] of the growth of 20, 31, and 60 μm wavelength perturbations were in good agreement with the experimental data when the experimental details, including noise, were included. The amplitude of the simulation optical depth is in good agreement with the experimental optical depth; therefore, great care must be taken when the growth rates are compared to dispersion formulas. Since the foil's initial condition just before it is accelerated is not that of a uniformly compressed foil, the optical density measurement does not accurately reflect the amplitude of the ablation surface but is affected by the initial nonuniform density profile. (c) 2000 American Institute of Physics

  12. ESTABLISHED MODES AND STATIC CHARACTERISTICS OF THREE-PHASE ASYNCHRONOUS MOTOR POWERED WITH SINGLE PHASE NETWORK

    Directory of Open Access Journals (Sweden)

    V. S. Malyar

    2016-01-01

    Full Text Available A mathematical model is developed to study the operation of three-phase asynchronous motor with squirrel-cage rotor when the stator winding is powered from a single phase network. To create a rotating magnetic field one of the phases is fed through the capacitor. Due to the asymmetry of power feed not only transients, but the steady-state regimes are dynamic, so they are described by differential equations in any coordinate system. Their study cannot be carried out with sufficient adequacy on the basis of known equivalent circuits and require the use of dynamic parameters. In the mathematical model the state equations of the circuits of the stator and rotor are composed in the stationary three phase coordinate system. Calculation of the established mode is performed by solving the boundary problem that makes it possible to obtain the coordinate dependences over the period, without calculation of the transient process. In order to perform it, the original nonlinear differential equations are algebraized by approximating the variables with the use of cubic splines. The resulting nonlinear system of algebraic equations is a discrete analogue of the initial system of differential equations. It is solved by parameter continuation method. To calculate the static characteristics as a function of a certain variable, the system is analytically differentiated, and then numerically integrated over this variable. In the process of integration, Newton's refinement is performed at each step or at every few steps, making it possible to implement the integration in just a few steps using Euler's method. Jacobi matrices in both cases are the same. To account for the current displacement in the rods of the squirrel-cage rotor, each of them, along with the squirrel-cage rings, is divided in height into several elements. This results in several squirrel-cage rotor windings which are represented by three-phase windings with magnetic coupling between them.

  13. A comparative study of the single-mode Richtmyer-Meshkov instability

    Science.gov (United States)

    Bai, X.; Deng, X.-L.; Jiang, L.

    2017-11-01

    In this work, the single-mode Richtmyer-Meshkov instability is studied numerically to find a reasonable nonlinear theoretical model which can be applied to predict the interface evolution from the linear stage to the early nonlinear stage. The cut-cell-based sharp-interface methods MuSiC+ (Chang et al. in J Comput Phys 242:946-990, 2013) and CCGF (Bai and Deng in Adv Appl Math Mech 9(5):1052-1075, 2017) are applied to generate numerical results for comparisons. Classical Air-SF6 and Air-Helium conditions are applied in this study, and initial amplitude and Atwood number are varied for comparison. Comparisons to the simulation results from the literature show the applicability of MuSiC+ and CCGF. Comparisons to the nonlinear theoretical models show that ZS (Zhang and Sohn in Phys Lett A 212:149-155, 1996; Phys Fluids 9:1106-1124, 1997), SEA (Sadot et al. in Phys Rev Lett 80:1654-1657, 1998), and DR (Dimonte and Ramaprabhu in Phys Fluids 22:014104, 2010) models are valid for both spike and bubble growth rates, and MIK (Mikaelian in Phys Rev E 67:026319, 2003) and ZG (Zhang and Guo in J Fluid Mech 786:47-61, 2016) models are valid for bubble growth rate, when the initial perturbation is small and the Atwood number is low, but only the DR model is applicable for both spike and bubble growth rates when the initial perturbation amplitude and the Atwood number are large. A new term of non-dimensional initial perturbation amplitude is presented and multiplied to the DR model to get a unified fitted DR model, which gives consistent results to the simulation ones for small and large initial amplitudes.

  14. Toward photostable multiplex analyte detection on a single mode planar optical waveguide

    Energy Technology Data Exchange (ETDEWEB)

    Mukundan, Harshini [Los Alamos National Laboratory; Xei, Hongshi [Los Alamos National Laboratory; Anderson, Aaron S [Los Alamos National Laboratory; Grace, Wynne K [Los Alamos National Laboratory; Martinez, Jennifer S [NON LANL; Swanson, Basil [Los Alamos National Laboratory

    2009-01-01

    We have developed a waveguide-based optical biosensor for the sensitive and specific detection of biomarkers associated with disease. Our technology combines the superior optical properties of single-mode planar waveguides, the robust nature of functionalized self-assembled monolayer sensing films and the specificity of fluorescence sandwich immunoassays to detect biomarkers in complex biological samples such as serum, urine and sputum. We have previously reported the adaptation of our technology to the detection of biomarkers associated with breast cancer and anthrax. However, these approaches primarily used phospholipid bilayers as the functional film and organic dyes (ex: AlexaFluors) as the fluorescence reporter. Organic dyes are easily photodegraded and are not amenable to multiplexing because of their narrow Stokes' shift. Here we have developed strategies for conjugation of the detector antibodies with quantum dots for use in a multiplex detection platform. We have previously evaluated dihydroxylipoic acid quantum dots for the detection of a breast cancer biomarker. In this manuscript, we investigate the detection of the Bacillus anthracis protective antigen using antibodies conjugated with polymer-coated quantum dots. Kinetics of binding on the waveguide-based biosensor is reported. We compare the sensitivity of quantum dot labeled antibodies to those labeled with AlexaFluor and demonstrate the photostability of the former in our assay platform. In addition, we compare sulfydryl labeling of the antibody in the hinge region to that of nonspecific amine labeling. This is but the first step in developing a multiplex assay for such biomarkers on our waveguide platform.

  15. Characterization of continuous and pulsed emission modes of a hybrid micro focus x-ray source for medical imaging applications

    Energy Technology Data Exchange (ETDEWEB)

    Ghani, Muhammad U.; Wong, Molly D.; Ren, Liqiang; Wu, Di; Zheng, Bin [Center for Biomedical Engineering and School of Electrical and Computer Engineering, University of Oklahoma, Norman, OK 73019 (United States); Rong, John X. [Department of Imaging Physics, University of Texas MD Anderson Cancer Center, Houston, TX 77030 (United States); Wu, Xizeng [Department of Radiology, University of Alabama at Birmingham, Birmingham, AL 35249 (United States); Liu, Hong, E-mail: liu@ou.edu [Center for Biomedical Engineering and School of Electrical and Computer Engineering, University of Oklahoma, Norman, OK 73019 (United States)

    2017-05-01

    The aim of this study was to quantitatively characterize a micro focus x-ray tube that can operate in both continuous and pulsed emission modes. The micro focus x-ray source (Model L9181-06, Hamamatsu Photonics, Japan) has a varying focal spot size ranging from 16 µm to 50 µm as the source output power changes from 10 to 39 W. We measured the source output, beam quality, focal spot sizes, kV accuracy, spectra shapes and spatial resolution. Source output was measured using an ionization chamber for various tube voltages (kVs) with varying current (µA) and distances. The beam quality was measured in terms of half value layer (HVL), kV accuracy was measured with a non-invasive kV meter, and the spectra was measured using a compact integrated spectrometer system. The focal spot sizes were measured using a slit method with a CCD detector with a pixel pitch of 22 µm. The spatial resolution was quantitatively measured using the slit method with a CMOS flat panel detector with a 50 µm pixel pitch, and compared to the qualitative results obtained by imaging a contrast bar pattern. The focal spot sizes in the vertical direction were smaller than that of the horizontal direction, the impact of which was visible when comparing the spatial resolution values. Our analyses revealed that both emission modes yield comparable imaging performances in terms of beam quality, spectra shape and spatial resolution effects. There were no significantly large differences, thus providing the motivation for future studies to design and develop stable and robust cone beam imaging systems for various diagnostic applications. - Highlights: • A micro focus x-ray source that operates in both continuous and pulse emission modes was quantitatively characterized. • The source output, beam quality, focal spot measurements, kV accuracy, spectra analyses and spatial resolution were measured. • Our analyses revealed that both emission modes yield comparable imaging performances in terms of beam

  16. Near-roadway monitoring of vehicle emissions as a function of mode of operation for light-duty vehicles.

    Science.gov (United States)

    Wen, Dongqi; Zhai, Wenjuan; Xiang, Sheng; Hu, Zhice; Wei, Tongchuan; Noll, Kenneth E

    2017-11-01

    Determination of the effect of vehicle emissions on air quality near roadways is important because vehicles are a major source of air pollution. A near-roadway monitoring program was undertaken in Chicago between August 4 and October 30, 2014, to measure ultrafine particles, carbon dioxide, carbon monoxide, traffic volume and speed, and wind direction and speed. The objective of this study was to develop a method to relate short-term changes in traffic mode of operation to air quality near roadways using data averaged over 5-min intervals to provide a better understanding of the processes controlling air pollution concentrations near roadways. Three different types of data analysis are provided to demonstrate the type of results that can be obtained from a near-roadway sampling program based on 5-min measurements: (1) development of vehicle emission factors (EFs) for ultrafine particles as a function of vehicle mode of operation, (2) comparison of measured and modeled CO 2 concentrations, and (3) application of dispersion models to determine concentrations near roadways. EFs for ultrafine particles are developed that are a function of traffic volume and mode of operation (free flow and congestion) for light-duty vehicles (LDVs) under real-world conditions. Two air quality models-CALINE4 (California Line Source Dispersion Model, version 4) and AERMOD (American Meteorological Society/U.S. Environmental Protection Agency Regulatory Model)-are used to predict the ultrafine particulate concentrations near roadways for comparison with measured concentrations. When using CALINE4 to predict air quality levels in the mixing cell, changes in surface roughness and stability class have no effect on the predicted concentrations. However, when using AERMOD to predict air quality in the mixing cell, changes in surface roughness have a significant impact on the predicted concentrations. The paper provides emission factors (EFs) that are a function of traffic volume and mode of

  17. Single-mode cavities at frequencies of 172 and 178 MHz

    CERN Document Server

    Volkov, V N; Fomin, N G; Kurkin, G Ya; Tribendis, A G

    2001-01-01

    In the report presented here the projects of two accelerating cavities with strong damping of higher modes (HOM) with special vacuum loads are presented.The designs of the cavities and loads are described.The design parameters of cavities,their spectra of higher modes and calculation results of the beam phase motion stability are given for the VEPP-2000 and NANOHANA Projects.

  18. High core count single-mode multicore fiber for dense space division multiplexing

    DEFF Research Database (Denmark)

    Aikawa, K.; Sasaki, Y.; Amma, Y.

    2016-01-01

    Multicore fibers and few-mode fibers have the potential to realize dense-space-division multiplexing systems. Several dense-space-division multiplexing system transmission experiments over multicore fibers and few-mode fibers have been demonstrated so far. Multicore fibers, including recent resul...

  19. Single-Photon Emission Computerized Tomography (SPECT in Neuropsychiatry: A Review

    Directory of Open Access Journals (Sweden)

    B. K. Puri

    1992-01-01

    Full Text Available Cranial single-photon emission computerized tomography (SPECT or SPET can now give regional cerebral blood flow images with a resolution approaching that of positron emission tomography (PET. In this paper, the use of high resolution SPECT neuroimaging in neuropsychiatric disorders, including Alzheimer's disease, multi-infarct dementia, Pick's disease, progressive supranuclear palsy, Korsakoff's psychosis, Creutzfeld-Jakob disease, Parkinson's disease, Huntington's disease, schizophrenia, mood disorders, obsessive–compulsive disorder, HIV infection and AIDS is reviewed. Finally, further potential research and clinical uses, based on ligand studies, are outlined.

  20. Nanometer-scale discernment of field emission from tungsten surface with single carbon monoxide molecule

    Science.gov (United States)

    Matsunaga, Soichiro; Suwa, Yuji; Katagiri, Souichi

    2017-12-01

    Unusual quantized beam fluctuations were found in the emission current from a cold-field emitter (CFE) operating in an extremely high vacuum of 10-10 Pa. To clarify the microscopic mechanism behind these fluctuations, we developed a new calculation method to evaluate the field emission from a heterogeneous surface under a strong electric field of 4 × 109 V/m by using the local potential distribution obtained by a first-principles calculation, instead of by using the work function. As a result of the first-principles calculations of a single molecule adsorbed on a tungsten surface, we found that dissociative adsorption of a carbon monoxide (CO) molecule enhances the emission current by changing the potential barrier in the area surrounding the C and O adatoms when these two atoms are placed at their most stable positions. It is also found that the migration of the O atom from the most stable position reduces the emission current. These types of enhancement and reduction of the emission current quantitatively explain the observed quantized fluctuations of the CFE emission current.

  1. Aphasia following left thalamic hemorrhage. A study by Western Aphasia Battery and single photon emission CT

    Energy Technology Data Exchange (ETDEWEB)

    Makishita, Hideo; Miyasaka, Motomaro; Tanizaki, Yoshio; Yanagisawa, Nobuo; Sugishita, Morihiro

    1984-07-01

    A report is given of 7 patients with left thalamic hemorrhage in the chronic stage (from 1.5 months to 4.5 months) in which language disorders were examined by Western Aphasia Battery (WAB) and cerebral blood flow was measured by single photon emission CT. Examination of language by WAB revealed 4 aphasics out of 7 cases, and 3 patients had no language deficit. The patient with Wernicke's aphasia showed low density area only in the left posterior thalamus in X-ray CT, and revealed severe low blood flow area extending to left temporal lobe in emission CT. In the case with transcortical sensory aphasia, although X-ray CT showed no obvious low density area, emission CT revealed moderate low flow area in the left temporooccipital region and low blood flow at the left thalamus. In one of the two patients classified as anomic aphasia, emission CT showed slight low flow area at the temporo-occipital region similar to the case with transcortical sensory aphasia. In another case with anomic aphasia there was a wide low density area all over the left thalamus and midline shift to the right in X-ray CT, and emission CT showed severe low blood flow in the same region spreading widely toward the cerebral surface. In all of the 3 patients without aphasia, emission CT showed low flow region restricted to the left thalamus.

  2. Strong coupling between a single nitrogen-vacancy spin and the rotational mode of diamonds levitating in an ion trap

    Science.gov (United States)

    Delord, T.; Nicolas, L.; Chassagneux, Y.; Hétet, G.

    2017-12-01

    A scheme for strong coupling between a single atomic spin and the rotational mode of levitating nanoparticles is proposed. The idea is based on spin readout of nitrogen-vacancy centers embedded in aspherical nanodiamonds levitating in an ion trap. We show that the asymmetry of the diamond induces a rotational confinement in the ion trap. Using a weak homogeneous magnetic field and a strong microwave driving we then demonstrate that the spin of the nitrogen-vacancy center can be strongly coupled to the rotational mode of the diamond.

  3. Thermal field emission observation of single-crystal LaB6

    International Nuclear Information System (INIS)

    Nagata, H.; Harada, K.; Shimizu, R.

    1990-01-01

    TFE (thermal field emission) properties of LaB 6 left-angle 100 right-angle and left-angle 310 right-angle single crystals were investigated by emission pattern observation. It was found that field evaporation with the tip temperature held at ∼1500 degree C is very useful to get a clean pattern of fourfold symmetry. Each of four bright spots in the clean pattern was presumed to correspond to left-angle 310 right-angle emission. It is proposed, as the most appropriate operating condition, to use the left-angle 310 right-angle LaB 6 tip at a temperature ∼1000 degree C in vacuum of 10 -9 Torr region, promising a new TF emitter of high brightness and stability for practical use

  4. Baseline performance and emissions data for a single-cylinder, direct-injected diesel engine

    Science.gov (United States)

    Dezelick, R. A.; Mcfadden, J. J.; Ream, L. W.; Barrows, R. F.

    1983-01-01

    Comprehensive fuel consumption, mean effective cylinder pressure, and emission test results for a supercharged, single-cylinder, direct-injected, four-stroke-cycle, diesel test engine are documented. Inlet air-to-exhaust pressure ratios were varied from 1.25 to 3.35 in order to establish the potential effects of turbocharging techniques on engine performance. Inlet air temperatures and pressures were adjusted from 34 to 107 C and from 193 to 414 kPa to determine the effects on engine performance and emissions. Engine output ranged from 300 to 2100 kPa (brake mean effective pressure) in the speed range of 1000 to 3000 rpm. Gaseous and particulate emission rates were measured. Real-time values of engine friction and pumping loop losses were measured independently and compared with motored engine values.

  5. Strong coupling and stimulated emission in single parabolic quantum well microcavity for terahertz cascade

    International Nuclear Information System (INIS)

    Tzimis, A.; Savvidis, P. G.; Trifonov, A. V.; Ignatiev, I. V.; Christmann, G.; Tsintzos, S. I.; Hatzopoulos, Z.; Kavokin, A. V.

    2015-01-01

    We report observation of strong light-matter coupling in an AlGaAs microcavity (MC) with an embedded single parabolic quantum well. The parabolic potential is achieved by varying aluminum concentration along the growth direction providing equally spaced energy levels, as confirmed by Brewster angle reflectivity from a reference sample without MC. It acts as an active region of the structure which potentially allows cascaded emission of terahertz (THz) light. Spectrally and time resolved pump-probe spectroscopy reveals characteristic quantum beats whose frequencies range from 0.9 to 4.5 THz, corresponding to energy separation between relevant excitonic levels. The structure exhibits strong stimulated nonlinear emission with simultaneous transition to weak coupling regime. The present study highlights the potential of such devices for creating cascaded relaxation of bosons, which could be utilized for THz emission

  6. The contribution of single photon emission computed tomography in the clinical assessment of Alzheimer type dementia

    International Nuclear Information System (INIS)

    Boudousq, V.; Collombier, L.; Kotzki, P.O.

    1999-01-01

    Interest of brain single-photon emission computed tomography to support clinical diagnosis of Alzheimer-type dementia is now established. Numerous studies have reported a decreased perfusion in the association cortex of the parietal lobe and the posterior temporal regions. In patients with mild cognitive complaints, the presence of focal hypoperfusion may increase substantially the probability of the disease. In addition, emission tomography emerges as a helpful tool in situation in which there is diagnostic doubt. In this case, the presence of temporo-parietal perfusion deficit associated with hippocampal atrophy on MRI or X-ray computed tomography contributes to diagnostic accuracy. However, some studies suggest that emission tomography may be useful for preclinical prediction of Alzheimer's disease and to predict cognitive decline. (author)

  7. Shock-induced optical emission from yttria-doped cubic zircon single crystal: crystal orientation effects

    Science.gov (United States)

    Cao, Xiuxia; Zhou, Xianming; Meng, Chuanmin

    2015-06-01

    The shock-induced optical emission from yttria (Y2O3) -doped cubic zircon single crystal ( and crystal orientations) under the pressure range from 30 to 52 GPa was measured by the time-resolved 40-channel optical pyrometer at discrete wavelengths ranging from 400 to 800 nm. Clear periodic fluctuation was observed in spectral radiance history of ZrO2, while a noise fluctuation was found in ZrO2. The gray-body function was used to fit the spectral radiance histories. We found that the obtained apparent temperature varied slightly with time, but the emissivity history showed a fluctuate increase with time. Moreover, all the temperature data were independent of shock stress and were well above the calculated Lindeman melting temperature. Present result suggests that the optical emission relates to the shock-induced local hot spots, and its crystal orientation effect is attributed to the different dynamic deformation response between and ZrO2.

  8. Measurement of direct photon emission in the K(L) ---> pi+ pi- gamma decay mode

    Energy Technology Data Exchange (ETDEWEB)

    Abouzaid, E.; /Chicago U., EFI; Arenton, M.; /Virginia U.; Barker, A.R.; /Colorado U.; Bellantoni, L.; /Fermilab; Bellavance, A.; /Rice U.; Blucher, E.; /Chicago U., EFI; Bock,; /Fermilab; Cheu, E.; /Arizona U.; Coleman, R.; /Fermilab; Corcoran, M.D.; /Rice U.; Corti, G.; /Virginia U. /Wisconsin U., Madison

    2006-04-01

    In this paper the KTeV collaboration reports the analysis of 112.1 x 10{sup 3} candidate K{sub L} {yields} {pi}{sup +}{pi}{sup -}{gamma} decays including a background of 671 {+-} 41 events with the objective of determining the photon production mechanisms intrinsic to the decay process. These decays have been analyzed to extract the relative contributions of the Cp violating bremsstrahlung process and the CP conserving M1 and CP violating E1 direct photon emission processes. The M1 direct photon emission amplitude and its associated vector form factor parameterized as |{bar g}{sub M1}|(1 + a{sub 1}/a{sub 2}/(M{sub {rho}}{sup 2}-M{sub K}{sup 2}) + 2M{sub K}E{sub {gamma}}) have been measured to be |{bar g}{sub M1}| = 1.198 {+-} 0.035(stat) {+-} 0.086(syst) and a{sub 1}/a{sub 2} = =0.738 {+-} 0.007(stat) {+-} 0.018(syst) GeV{sup 2}/c{sup 2} respectively. An upper limit for the CP violating E1 direct emission amplitude |g{sub E1}| {le} 0.1 (90%CL) has been found. The overall ratio of direct photon emission (DE) to total photon emission including the bremsstrahlung process (IB) has been determined to be DE/(DE + IB) = 0.689 {+-} 0.021 for E{sub {gamma}} {ge} 20 MeV.

  9. Design and prototyping of self-centering optical single-mode fiber alignment structures

    International Nuclear Information System (INIS)

    Ebraert, Evert; Gao, Fei; Thienpont, Hugo; Van Erps, Jürgen; Beri, Stefano; Watté, Jan

    2016-01-01

    The European Commission’s goal of providing each European household with at least a 30 Mb s −1 Internet connection by 2020 would be facilitated by a widespread deployment of fibre-to-the-home, which would in turn be sped up by the development of connector essential components, such as high-precision alignment features. Currently, the performance of state-of-the-art physical contact optical fiber connectors is limited by the tolerance on the cladding of standard telecom-grade single-mode fiber (SMF), which is typically smaller than  ±1 μ m. We propose to overcome this limit by developing micro-spring-based self-centering alignment structures (SCAS) for SMF-connectors. We design these alignment structures with robustness and low-cost replication in mind, allowing for large-scale deployment. Both theoretical and finite element analysis (FEA) models are used to determine the optimal dimensions of the beams of which the micro-springs of the SCAS are comprised. Two topologies of the SCAS, consisting of three and four micro-springs respectively, are investigated for two materials: polysulfone (PSU) and polyetherimide (PEI). These materials hold great potential for high-performance fiber connectors while being compatible with low-cost production and with the harsh environmental operation conditions of those connectors. The theory and FEA agree well (<3% difference) for a simple micro-spring. When including a pedestal on the micro-spring (to bring it further away from the fiber) and for shorter spring lengths the agreement worsens. This is due to spring compression effects not being taken into account in our theoretical model. Prototypes are successfully fabricated using deep proton writing and subsequently characterized. The controlled insertion of an SMF in the SCAS is investigated and we determine that a force of 0.11 N is required. The fiber insertion also causes an out-of-plane deformation of the micro-springs in the SCAS of about 7 μ m, which is no

  10. Modal analysis and dispersion curves of an elliptical W-type single mode fiber

    Science.gov (United States)

    Prajapati, Y.; Maurya, Jitendra Bahadur; Singh, Vivek; Saini, J. P.

    2015-05-01

    In this paper, the propagation of electromagnetic waves in W-type elliptical dielectric optical fiber having various cladding layers is presented. The presented fiber has concentric core and cladding which have elliptical cross section and the refractive index of one of the inner cladding (the cladding between first clad and last clad) maximum. Using elliptic cylindrical coordinates, boundary conditions are derived and longitudinal field components for the even and odd modes are obtained. The characteristic equation for the fiber to be studied is determined by solving the Mathieu ( q > 0) and the modified Mathieu functions ( q < 0). In order to study the fundamental mode, the modal index m is put as m = 1. Finally, the cutoff frequencies for several lower order modes have been calculated and their dispersion characteristics are plotted. The effects of elliptical eccentricity e on the mode cutoff frequencies and mode transmissions are also addressed. The analysis shows that one can control the propagation property of optical fiber by increasing the number of inner claddings. These claddings provide additional degree of freedom to control the modes.

  11. The entanglement of two moving atoms interacting with a single-mode field via a three-photon process

    International Nuclear Information System (INIS)

    Chao, Wu; Mao-Fa, Fang

    2010-01-01

    In this paper, the entanglement of two moving atoms induced by a single-mode field via a three-photon process is investigated. It is shown that the entanglement is dependent on the category of the field, the average photon number N, the number p of half-wave lengths of the field mode and the atomic initial state. Also, the sudden death and the sudden birth of the entanglement are detected in this model and the results show that the existence of the sudden death and the sudden birth depends on the parameter and the category of the mode field. In addition, the three-photon process is a higher order nonlinear process. (general)

  12. Optical frequency comb generation for DWDM transmission over 25- to 50-km standard single-mode fiber

    Science.gov (United States)

    Ullah, Rahat; Bo, Liu; Yaya, Mao; Ullah, Sibghat; Khan, Muhammad Saad; Tian, Feng; Ali, Amjad; Ahmad, Ibrar; Xiangjun, Xin

    2018-01-01

    Dense wavelength division multiplexed (DWDM) transmission equal to 1.2 Tbps over 25 to 50 km across standard single-mode fiber (SSMF) in the C band is performed based on an optical frequency comb generator. Sixty-one flattened optical frequency tones were realized with 30-GHz frequency spacing, high side-mode suppression ratio over 35 dB, and minimum amplitude difference was realized using amplitude modulator for first time in cascade mode with two Mach-Zehnder modulators (MZMs) where all the modulators were tailored by RF signals. 20×61 Gbps DWDM-based differential quadrature phase shift keying modulated signals were successfully transmitted over SSMF and analyze its transmission capability for range of 25 to 50 km with acceptable power penalties and bit error rates.

  13. Single-photon emission correlated to double-electron capture by bare ions: background processes

    Science.gov (United States)

    Elkafrawy, T.; Warczak, A.; Simon, A.; Tanis, J. A.

    2013-09-01

    Radiative single- and double-electron capture are one-step processes where a single target electron or two target electrons, respectively, are captured to a bound state of a highly charged projectile with the simultaneous emission of a single photon. In ion-atom collisions, several background processes are likely to contribute to these processes and may interfere with the measured x-rays due to radiative single and double capture. In this study, possible contributions from radiative electron capture to the continuum, secondary electron bremsstrahlung, the two-step process of independent double radiative electron capture, as well as radiative- combined with nonradiative-electron capture are taken into account based on our analysis of the data for 2.21 MeV u-1 F9+ ions colliding with a thin carbon foil.

  14. Single photon emission from charged excitons in CdTe/ZnTe quantum dots

    Science.gov (United States)

    Belyaev, K. G.; Rakhlin, M. V.; Sorokin, S. V.; Klimko, G. V.; Gronin, S. V.; Sedova, I. V.; Mukhin, I. S.; Ivanov, S. V.; Toropov, A. A.

    2017-11-01

    We report on micro-photoluminescence studies of individual self-organized CdTe/ZnTe quantum dots intended for single-photon-source applications in a visible spectral range. The quantum dots surface density below 1010 per cm2 was achieved by using a thermally activated regime of molecular beam epitaxy that allowed fabrication of etched mesa-structures containing only a few emitting quantum dots. The single photon emission with the autocorrelation function g(2)(0)<0.2 was detected and identified as recombination of charged excitons in the individual quantum dot.

  15. Degenerative dementia: nosological aspects and results of single photon emission computed tomography

    International Nuclear Information System (INIS)

    Dubois, B.; Habert, M.O.

    1999-01-01

    Ten years ago, the diagnosis discussion of a dementia case for the old patient was limited to two pathologies: the Alzheimer illness and the Pick illness. During these last years, the frame of these primary degenerative dementia has fallen into pieces. The different diseases and the results got with single photon emission computed tomography are discussed. for example: fronto-temporal dementia, primary progressive aphasia, progressive apraxia, visio-spatial dysfunction, dementia at Lewy's bodies, or cortico-basal degeneration. (N.C.)

  16. Evaluation of a 99Tcm bound brain scanning agent for single photon emission computed tomography

    DEFF Research Database (Denmark)

    Andersen, A R; Hasselbalch, S G; Paulson, O B

    1986-01-01

    D,L HM-PAO-99Tcm (PAO) is a lipophilic tracer complex which is avidly taken up by the brain. We have compared the regional distribution of PAO with regional cerebral blood flow (CBF). CBF was measured by single photon emission computed tomography (SPECT) by Tomomatic 64 after 133Xe inhalation in ...... of the (decay corrected) brain counts were lost during 24 hours....

  17. Bidirectional single-longitudinal mode SOA-fiber ring laser based on optical filter assisted gain starvation

    Science.gov (United States)

    Khalil, Kamal; Al-Arifi, Fares; Al-Otaibi, Mohammed; Sabry, Yasser M.; Khalil, Diaa

    2015-03-01

    Generation of a single-longitudinal mode (SLM) in bidirectional ring lasers has direct impact on the laser linewidth and dynamic range of operation, when used in rotation sensing applications. Besides, operating at a specific wavelength helps in optimizing the performance of the system components. In this work, we report a novel method for generating SLM in bidirectional SOA-fiber ring laser using mechanically tunable Fabry-Perot filter with 1-nm bandwidth. The method is based on gain starvation by tuning the central wavelength of the filter in the blue edge of the gain-wavelength response. By adjusting the SOA driving current, the oscillation condition is satisfied mainly for single mode and bidirectional operation can be achieved simultaneously. The SLM operation is verified by monitoring the beating signal between the modes on an RF spectrum analyzer. Using an SOA with a small-signal gain of 20 dB at 300 mA pumping current and a gain bandwidth of 100 nm centered around 1490 nm; the central wavelength of the ring laser could be tuned from 1440 nm to 1480 nm with a side-mode suppression ratio of 25 dB.

  18. Single and two-mode mechanical squeezing of an optically levitated nanodiamond via dressed-state coherence

    Science.gov (United States)

    Ge, Wenchao; Bhattacharya, M.

    2016-10-01

    Nonclassical states of macroscopic objects are promising for ultrasensitive metrology as well as testing quantum mechanics. In this work, we investigate dissipative mechanical quantum state engineering in an optically levitated nanodiamond. First, we study single-mode mechanical squeezed states by magnetically coupling the mechanical motion to a dressed three-level system provided by a nitrogen-vacancy center in the nanoparticle. Quantum coherence between the dressed levels is created via microwave fields to induce a two-phonon transition, which results in mechanical squeezing. Remarkably, we find that in ultrahigh vacuum quantum squeezing is achievable at room temperature with feedback cooling. For moderate vacuum, quantum squeezing is possible with cryogenic temperature. Second, we present a setup for two mechanical modes coupled to the dressed three levels, which results in two-mode squeezing analogous to the mechanism of the single-mode case. In contrast to previous works, our study provides a deterministic method for engineering macroscopic squeezed states without the requirement for a cavity.

  19. Single-longitudinal-mode Er:GGG microchip laser operating at 2.7  μm.

    Science.gov (United States)

    You, Zhenyu; Wang, Yan; Xu, Jinlong; Zhu, Zhaojie; Li, Jianfu; Wang, Hongyan; Tu, Chaoyang

    2015-08-15

    We reported on a diode-end-pumped single-longitudinal-mode microchip laser using a 600-μm-thick Er:GGG crystal at ∼2.7  μm, generating a maximum output power of 50.8 mW and the maximum pulsed energy of 0.306 mJ, with repetition rates of pumping light of 300, 200, and 100 Hz, respectively. The maximum slope efficiency of the laser was 20.1%. The laser was operated in a single-longitudinal mode centered at about 2704 nm with a FWHM of 0.42 nm. The laser had a fundamental beam profile and the beam quality parameter M(2) was measured as 1.46. These results indicate that the Er:GGG microchip laser is a potential compact mid-infrared laser source.

  20. Investigation of single-mode vertical-cavity surface-emitting lasers with graphene-bubble dielectric DBR

    Science.gov (United States)

    Guan, Baolu; Li, Pengtao; Arafin, Shamsul; Alaskar, Yazeed; Wang, Kang L.

    2018-02-01

    An inter-cavty contact single mode 850 nm VCSEL was fabricated with a graphene assisted self-assembly curved dielectric bubble Bragg mirror for the first time. Taking the advantage of graphene's uniform low surface energy, the low cost dielectric bubble DBR (Si3N4/SiO2) was deposited on top of the graphene/half-VCSEL structure via van der Waals Force (vdWF) without using any additional spacing elements and sacrificial layer release-etch process. The continuous-wave operating VCSELs with an aperture diameter of 7 μm exhibit single-mode output power of more than 1 mW with a slope efficiency of 0.2 W/A. The sidemode suppression ratios are >40 dB. This novel modification into the lasers can also be applied to a variety of other optoelectronic devices, such as resonance photodetecter and super narrow linewidth VCSEL.

  1. Single mode step-index polymer optical fiber for humidity insensitive high temperature fiber Bragg grating sensors

    DEFF Research Database (Denmark)

    Woyessa, Getinet; Fasano, Andrea; Stefani, Alessio

    2016-01-01

    We have fabricated the first single-mode step-index and humidity insensitive polymer optical fiber operating in the 850 nm wavelength ranges. The step-index preform is fabricated using injection molding, which is an efficient method for cost effective, flexible and fast preparation of the fiber...... preform. The fabricated single-mode step-index (SI) polymer optical fiber (POF) has a 4.8µm core made from TOPAS grade 5013S-04 with a glass transition temperature of 134°C and a 150 µm cladding made from ZEONEX grade 480R with a glass transition temperature of 138°C. The key advantages of the proposed...... SIPOF are low water absorption, high operating temperature and chemical inertness to acids and bases and many polar solvents as compared to the conventional poly-methyl-methacrylate (PMMA) and polystyrene based POFs. In addition, the fiber Bragg grating writing time is short compared to microstructured...

  2. The use of Lorentz group formalism in solving polarization effects of a birefringent single mode optical fiber

    International Nuclear Information System (INIS)

    Ishiekwene, G.C.; Brown, C.S.; Mensah, S.Y.; Bak, A.E.

    2000-07-01

    A theoretical analysis on the polarization effects of a light beam propagating in a birefringent single-mode fiber is presented. We derive a system of differential equations representing the evolution of Stokes parameters and illustrate their application to polarization effects in a straight birefringent single mode optical fiber. The solutions to the set of equations are obtained using specifically the methods of the unified formalism for polarization optics which adopt the use of the Stokes-Mueller equation and the Lorentz group to model polarization phenomena in media such as optical fibers. The analytical results presented using this approach are identical to results obtained from other conventional methods. We observe the characteristic exponential decrease in the total intensity of the input light due to attenuation by the fiber. (author)

  3. Sub-micrometre accurate free-form optics by three-dimensional printing on single-mode fibres

    Science.gov (United States)

    Gissibl, Timo; Thiele, Simon; Herkommer, Alois; Giessen, Harald

    2016-01-01

    Micro-optics are widely used in numerous applications, such as beam shaping, collimation, focusing and imaging. We use femtosecond 3D printing to manufacture free-form micro-optical elements. Our method gives sub-micrometre accuracy so that direct manufacturing even on single-mode fibres is possible. We demonstrate the potential of our method by writing different collimation optics, toric lenses, free-form surfaces with polynomials of up to 10th order for intensity beam shaping, as well as chiral photonic crystals for circular polarization filtering, all aligned onto the core of the single-mode fibres. We determine the accuracy of our optics by analysing the output patterns as well as interferometrically characterizing the surfaces. We find excellent agreement with numerical calculations. 3D printing of microoptics can achieve sufficient performance that will allow for rapid prototyping and production of beam-shaping and imaging devices. PMID:27339700

  4. Single-shot photonic time-stretch digitizer using a dissipative soliton-based passively mode-locked fiber laser.

    Science.gov (United States)

    Peng, Di; Zhang, Zhiyao; Zeng, Zhen; Zhang, Lingjie; Lyu, Yanjia; Liu, Yong; Xie, Kang

    2018-03-19

    We demonstrate a single-shot photonic time-stretch digitizer using a dissipative soliton-based passively mode-locked fiber laser. The theoretical analysis and simulation results indicate that the dissipative soliton-based optical source with a flat spectrum relieves the envelope-induced signal distortion, and its high energy spectral density helps to improve the signal-to-noise ratio, both of which are favorable for simplifying the optical front-end architecture of a photonic time-stretch digitizer. By employing a homemade dissipative soliton-based passively mode-locked erbium-doped fiber laser in a single-shot photonic time-stretch digitizer, an effective number of bits of 4.11 bits under an effective sampling rate of 100 GS/s is experimentally obtained without optical amplification in the link and pulse envelope removing process.

  5. Single mode step-index polymer optical fiber for humidity insensitive high temperature fiber Bragg grating sensors.

    Science.gov (United States)

    Woyessa, Getinet; Fasano, Andrea; Stefani, Alessio; Markos, Christos; Nielsen, Kristian; Rasmussen, Henrik K; Bang, Ole

    2016-01-25

    We have fabricated the first single-mode step-index and humidity insensitive polymer optical fiber operating in the 850 nm wavelength ranges. The step-index preform is fabricated using injection molding, which is an efficient method for cost effective, flexible and fast preparation of the fiber preform. The fabricated single-mode step-index (SI) polymer optical fiber (POF) has a 4.8µm core made from TOPAS grade 5013S-04 with a glass transition temperature of 134°C and a 150 µm cladding made from ZEONEX grade 480R with a glass transition temperature of 138°C. The key advantages of the proposed SIPOF are low water absorption, high operating temperature and chemical inertness to acids and bases and many polar solvents as compared to the conventional poly-methyl-methacrylate (PMMA) and polystyrene based POFs. In addition, the fiber Bragg grating writing time is short compared to microstructured POFs.

  6. A tunable and switchable single-longitudinal-mode dual-wavelength fiber laser with a simple linear cavity.

    Science.gov (United States)

    He, Xiaoying; Fang, Xia; Liao, Changrui; Wang, D N; Sun, Junqiang

    2009-11-23

    A simple linear cavity erbium-doped fiber laser based on a Fabry-Perot filter which consists of a pair of fiber Bragg gratings is proposed for tunable and switchable single-longitudinal-mode dual-wavelength operation. The single-longitudinal-mode is obtained by the saturable absorption of an unpumed erbium-doped fiber together with a narrow-band fiber Bragg grating. Under the high pump power (>166 mW) condition, the stable dual-wavelength oscillation with uniform amplitude can be realized by carefully adjusting the polarization controller in the cavity. Wavelength selection and switching are achieved by tuning the narrow-band fiber Bragg grating in the system. The spacing of the dual-wavelength can be selected at 0.20 nm (approximately 25.62 GHz), 0.22 nm (approximately 28.19 GHz) and 0.54 nm (approximately 69.19 GHz).

  7. Combined single-mode/multimode fiber link supporting simplified in-building 60-GHz gigabit wireless access

    DEFF Research Database (Denmark)

    Pham, Tien Thang; Lebedev, Alexander; Beltrán, Marta

    2012-01-01

    In this paper, we propose and experimentally demonstrate a simple, cost-effective hybrid gigabit fiber-wireless system for in-building wireless access. Simplicity and cost-effectiveness are achieved in all parts of the system by utilizing direct laser modulation, optical frequency up-conversion, ......In this paper, we propose and experimentally demonstrate a simple, cost-effective hybrid gigabit fiber-wireless system for in-building wireless access. Simplicity and cost-effectiveness are achieved in all parts of the system by utilizing direct laser modulation, optical frequency up......-conversion, combined single mode/multimode fiber transmission and envelope detection. Error-free transmission of 2-Gbps data in 60-GHz band over a composite channel including 10-km standard single-mode fiber (SSMF)/1-km multimode fiber (MMF) and 6.5-m air transmission was successfully achieved....

  8. Sub-micrometre accurate free-form optics by three-dimensional printing on single-mode fibres

    Science.gov (United States)

    Gissibl, Timo; Thiele, Simon; Herkommer, Alois; Giessen, Harald

    2016-06-01

    Micro-optics are widely used in numerous applications, such as beam shaping, collimation, focusing and imaging. We use femtosecond 3D printing to manufacture free-form micro-optical elements. Our method gives sub-micrometre accuracy so that direct manufacturing even on single-mode fibres is possible. We demonstrate the potential of our method by writing different collimation optics, toric lenses, free-form surfaces with polynomials of up to 10th order for intensity beam shaping, as well as chiral photonic crystals for circular polarization filtering, all aligned onto the core of the single-mode fibres. We determine the accuracy of our optics by analysing the output patterns as well as interferometrically characterizing the surfaces. We find excellent agreement with numerical calculations. 3D printing of microoptics can achieve sufficient performance that will allow for rapid prototyping and production of beam-shaping and imaging devices.

  9. Single Mode Theory for Impedance Eduction in Large-Scale Ducts with Grazing Flow

    Science.gov (United States)

    Watson, Willie R.; Gerhold, Carl H.; Jones, Michael G.; June, Jason C.

    2014-01-01

    An impedance eduction theory for a rigid wall duct containing an acoustic liner with an unknown impedance and uniform grazing flow is presented. The unique features of the theory are: 1) non-planar waves propagate in the hard wall sections of the duct, 2) input data consist solely of complex acoustic pressures acquired on a wall adjacent to the liner, and 3) multiple higher-order modes may exist in the direction perpendicular to the liner and the opposite rigid wall. The approach is to first measure the axial propagation constant of a dominant higher-order mode in the liner sample section. This axial propagation constant is then used in conjunction with a closed-form solution to a reduced form of the convected Helmholtz equation and the wall impedance boundary condition to educe the liner impedance. The theory is validated on a conventional liner whose impedance spectrum is educed in two flow ducts with different cross sections. For the frequencies and Mach numbers of interest, no higher-order modes propagate in the hard wall sections of the smaller duct. A benchmark method is used to educe the impedance spectrum in this duct. A dominant higher-order vertical mode propagates in the larger duct for similar test conditions, and the current theory is applied to educe the impedance spectrum. Results show that when the theory is applied to data acquired in the larger duct with a dominant higher-order vertical mode, the same impedance spectra is educed as that obtained in the small duct where only the plane wave mode is present and the benchmark method is used. This result holds for each higher-order vertical mode that is considered.

  10. Plasmon modes in light emission from silver nanoparticles induced by a scanning tunneling microscope

    Czech Academy of Sciences Publication Activity Database

    Kůsová, Kateřina; Charra, F.; Schull, G.; Pelant, Ivan

    2008-01-01

    Roč. 602, č. 1 (2008), s. 345-348 ISSN 0039-6028 R&D Projects: GA AV ČR IAA1010316; GA MŠk LC510; GA AV ČR IAA1010413 Institutional research plan: CEZ:AV0Z10100521 Keywords : scanning tunneling microscopy * photon emission * plasmons * silver nanoparticles Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.731, year: 2008

  11. Source region and growth analysis of narrowband Z-mode emission

    Czech Academy of Sciences Publication Activity Database

    Menietti, J. D.; Yoon, P. H.; Píša, David; Ye, S.; Y.; Santolík, Ondřej; Arridge, C. S.; Gurnett, D. A.; Coates, A. J.

    2016-01-01

    Roč. 121, č. 12 (2016), s. 11929-11942 ISSN 2169-9380 Grant - others:AV ČR(CZ) AP1401 Program:Akademická prémie - Praemium Academiae Institutional support: RVO:68378289 Keywords : auroral radio emissions * magnetic-field * plasma * magnetosphere * radiation * acceleration * pectrometer * electrons * density Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.733, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/2016JA022913/abstract

  12. Single-mode optical fiber design with wide-band ultra low bending-loss for FTTH application.

    Science.gov (United States)

    Watekar, Pramod R; Ju, Seongmin; Han, Won-Taek

    2008-01-21

    We propose a new design of a single-mode optical fiber (SMF) which exhibits ultra low bend sensitivity over a wide communication band (1.3 microm to 1.65 microm). A five-cladding fiber structure has been proposed to minimize the bending loss, estimated to be as low as 4.4x10(-10) dB/turn for the bend radius of 10 mm.

  13. Modulational instability and localized modes in Heisenberg ferromagnetic chains with single-ion easy-axis anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Bing, E-mail: bingtangphy@jsu.edu.cn; Li, Guang-Ling; Fu, Mei

    2017-03-15

    A semiclassical theoretical study on the property of the modulational instability of corresponding linear spin-waves and the presence of nonlinear localized excitations in a discrete quantum ferromagnetic spin chain with single-ion easy-axis anisotropy is reported. We consider the Glauber coherent-state representation combined with the Dyson-Maleev transformation for local spin operators as the basic representation of the system, and derive the equation of motion by means of the Ehrenfest theorem. Using a modulational instability analysis of plane waves, we predict the existence regions of bright envelope solitons and intrinsic localized spin-wave modes. Besides, with the help of a semidiscrete multi-scale method, we obtain analytical solutions for the bright envelope soliton and intrinsic localized spin-wave mode. Moreover, we analyze their existence conditions, which agree with the results of modulational instability analysis. - Highlights: • The anisotropy plays significant role in both the property of the modulational instability and the existence conditions for localized modes in ferromagnetic chains. • The analytical solutions of localized modes are obtained. • The appearance conditions for such localized modes agree with the modulational instability analysis.

  14. Thermal Optimized Operation of the Single-Phase Full-Bridge PV Inverter under Low Voltage Ride-Through Mode

    DEFF Research Database (Denmark)

    Wang, Huai; Yang, Yongheng; Blaabjerg, Frede

    2013-01-01

    . At the same time, the target of a long service time (25 years or more) imposes new challenges to grid-connected transformer-less PV systems. Achieving more reliable PV inverters is of intense interest in recent research. As one of the most critical stresses that induce failures, the thermal stresses...... on the power devices of a single-phase full-bridge PV inverter are analyzed in different operational modes in this paper. The low voltage grid condition is specially taken into account in this paper. The analysis is demonstrated by a 3 kW single-phase full-bridge grid-connected PV system by simulations...

  15. Toward single-mode UV to near-IR guidance using hollow-core anti-resonant silica fiber

    DEFF Research Database (Denmark)

    Habib, Md Selim; Antonio-Lopez, Jose Enrique; Van Newkirk, Amy

    2017-01-01

    Hollow-core anti-resonant (HC-AR) fibers with a “negative-curvature” of the core-cladding boundary have been extensively studied over the past few years owing to their low loss and wide transmission bandwidths. The key unique feature of the HC-AR fiber is that the coupling between the core and cl...... a silica HC-AR fiber having a single ring of 7 non-touching capillaries, designed to have effectively single-mode operation and low loss from UV to near-IR....

  16. Enhancement of single mode operation in coaxial optical waveguide using DB boundary conditions

    Science.gov (United States)

    Lohia, Pooja; Prajapati, Y.; Saini, J. P.; Rai, B. S.

    2014-11-01

    In this study, a competent numerical strategy to compute the dispersion of optical waveguides is presented and propagation of electromagnetic waves in a coaxial optical waveguide with DB boundary conditions is instigated. For this intend, cylindrical coordinates are here being used to derive the DB boundary conditions and to obtain field components for the modes. The propagation constant for the waveguide to be studied is determined by solving the Bessel and the modified Bessel functions. The cutoff frequencies for various lower order modes have been calculated and their dispersion characteristics are plotted correspondingly. The behavior of the coaxial optical waveguide under DB boundary conditions is shown to be significantly different from that of coaxial optical waveguide and conventional optical waveguide under traditional or tangential boundary conditions. Finally, the effect of waveguide dimensions on the mode cutoff frequencies and fabrication issues are also addressed.

  17. Reduction of NOx emission in tangential fired - furnace by changing the, mode of operation

    International Nuclear Information System (INIS)

    Chudnovsky, B.; Talanker, A.; Levin, L.; Kahana, S

    1998-01-01

    The present work analyses tile results of tests on 575 MW units with tangential firing furnace arrangement in sub-stoichiometric combustion. Tangential firing provides good conditions for implementing sub-stoichiometric combustion owing to the delivery scheme of pulverized coal and air. The furnace was tested in several different modes of operation (Over Fire Air, Bunkers Out Of Service, Excess air, Tilt etc.) to achieve low cost NOx reduction. Actual performance data are presented based on experiments made on lEC's boiler in M.D. 'B' power station

  18. Fracture mode during cyclic loading of implant-supported single-tooth restorations

    DEFF Research Database (Denmark)

    Hosseini, Mandana; Kleven, Erik; Gotfredsen, Klaus

    2012-01-01

    restorations of zirconia abutment-retained crowns with zirconia copings veneered with glass-ceramics (n=8) and feldspathic ceramics (n=8). The control group was composed of 16 metal ceramic restorations of titanium abutment-retained crowns with gold alloy copings veneered with glass (n=8) and feldspathic......STATEMENT OF PROBLEM: Fracture of veneering ceramics in zirconia-based restorations has frequently been reported. Investigation of the fracture mode of implant-supported ceramic restorations by using clinically relevant laboratory protocols is needed. PURPOSE: This study compared the mode...... and resisted more cyclic loads than the ceramic restorations, particularly when the metal ceramic crowns were veneered with glass-ceramics....

  19. SISGR: Room Temperature Single-Molecule Detection and Imaging by Stimulated Emission Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Xiaoliang Sunney [Harvard Univ., Cambridge, MA (United States). Dept. of Chemistry and Chemical Biology

    2017-03-13

    Single-molecule spectroscopy has made considerable impact on many disciplines including chemistry, physics, and biology. To date, most single-molecule spectroscopy work is accomplished by detecting fluorescence. On the other hand, many naturally occurring chromophores, such as retinal, hemoglobin and cytochromes, do not have detectable fluorescence. There is an emerging need for single-molecule spectroscopy techniques that do not require fluorescence. In the last proposal period, we have successfully demonstrated stimulated emission microscopy, single molecule absorption, and stimulated Raman microscopy based on a high-frequency modulation transfer technique. These first-of-a- kind new spectroscopy/microscopy methods tremendously improved our ability to observe molecules that fluorescence weakly, even to the limit of single molecule detection for absorption measurement. All of these methods employ two laser beams: one (pump beam) excites a single molecule to a real or virtual excited state, and the other (probe beam) monitors the absorption/emission property of the single. We extract the intensity change of the probe beam with high sensitivity by implementing a high-frequency phase-sensitive detection scheme, which offers orders of magnitude improvement in detection sensitivity over direct absorption/emission measurement. However, single molecule detection based on fluorescence or absorption is fundamentally limited due to their broad spectral response. It is important to explore other avenues in single molecule detection and imaging which provides higher molecular specificity for studying a wide variety of heterogeneous chemical and biological systems. This proposal aimed to achieve single-molecule detection sensitivity with near resonance stimulated Raman scattering (SRS) microscopy. SRS microscopy was developed in our lab as a powerful technique for imaging heterogeneous samples based on their intrinsic vibrational contrasts, which provides much higher molecular

  20. Brain receptor single-photon emission computer tomography with 123I Datscan in Parkinson's disease

    International Nuclear Information System (INIS)

    Minchev, D.; Peshev, N.; Kostadinova, I.; Grigorova, O.; Trindev, P.; Shotekov, P.

    2005-01-01

    Clinical aspects of Parkinson's disease are not enough for the early diagnosis of the disease. Positron emission tomography and the receptor single - photon emission tomography can be used for imaging functional integrity of nigrostriatal dopaminergic structures. 24 patient (17 men and 7 women) were investigated. 20 of them are with Parkinson's disease and 4 are with essential tremor. The radiopharmaceutical - 123I-Datscan (ioflupane, bind with 123I) represent a cocaine analogue with selective affinity to dopamine transporters, located in the dopaminergic nigrostriatal terminals in the striatum. Single - photon emission computer tomography was performed with SPECT gamma camera (ADAC, SH Epic detector). The scintigraphic study was made 3 to 6 hours after intravenous injection of the radiopharmaceutical - 123I- Datscan in dose 185 MBq. 120 frames are registered with duration of each one 22 seconds and gamma camera rotation 360. After generation of transversal slices we generated two composites pictures. The first composite picture image the striatum, the second - the occipital region. Two ratios were calculated representing the uptake of the radiopharmaceutical in the left and right striatum. Qualitative and quantitative criteria were elaborated for evaluating the scintigraphic patterns. Decreased, nonhomogeneous and asymmetric uptake of the radiopharmaceutical coupled with low quantitative parameters in range from 1.44 to 2.87 represents the characteristic scintigraphic pattern for Parkinson's disease with clear clinical picture. Homogenous with high intensity and symmetric uptake of the radiopharmaceutical in the striatum coupled with his clear frontier and with quantitative parameters up to 4.40 represent the scintigraphic pattern in two patients with essential tremor. Receptor single - photon emission computer tomography with 123I - Datscan represents an accurate nuclear-medicine method for precise diagnosis of Parkinson's disease and for its differentiation from

  1. A single source microwave photonic filter using a novel single-mode fiber to multimode fiber coupling technique.

    Science.gov (United States)

    Chang, John; Fok, Mable P; Meister, James; Prucnal, Paul R

    2013-03-11

    In this paper we present a fully tunable and reconfigurable single-laser multi-tap microwave photonic FIR filter that utilizes a special SM-to-MM combiner to sum the taps. The filter requires only a single laser source for all the taps and a passive component, a SM-to-MM combiner, for incoherent summing of signal. The SM-to-MM combiner does not produce optical interference during signal merging and is phase-insensitive. We experimentally demonstrate an eight-tap filter with both positive and negative programmable coefficients with excellent correspondence between predicted and measured values. The magnitude response shows a clean and accurate function across the entire bandwidth, and proves successful operation of the FIR filter using a SM-to-MM combiner.

  2. Divertor power load studies for attached L-mode single-null plasmas in TCV

    NARCIS (Netherlands)

    Maurizio, R.; Elmore, S.; Fedorczak, N.; Gallo, A.; Reimerdes, H.; Labit, B.; Theiler, C.; Tsui, C. K.; Vijvers, W. A. J.; TCV team,; MST1 Team,

    2018-01-01

    This paper investigates the power loads at the inner and outer divertor targets of attached, Ohmic L-mode, deuterium plasmas in the TCV tokamak, in various experimental situations using an Infrared thermography system. The study comprises variations of the outer divertor leg length and target flux

  3. Self-Similar Nanocavity Design with Ultrasmall Mode Volume for Single-Photon Nonlinearities

    DEFF Research Database (Denmark)

    Choi, Hyeongrak; Heuck, Mikkel; Englund, Dirk R.

    2017-01-01

    illustrate the design concept with a silicon-air one-dimensional photon crystal cavity that reaches an ultrasmall mode volume of V-eff similar to 7.01 x 10(-5)lambda(3) at lambda similar to 1550 nm. We show that the extreme light concentration in our design can enable ultrastrong Kerr nonlinearities, even...

  4. Highly tunable large core single-mode liquid crystal photonic bandgap fiber

    DEFF Research Database (Denmark)

    Alkeskjold, Thomas Tanggaard; Lægsgaard, Jesper; Bjarklev, Anders Overgaard

    2006-01-01

    We demonstrate a highly tunable photonic bandgap fiber, which has a large-core diameter of 25 mu m and an effective mode area of 440 mu m(2). The tunability is achieved by infiltrating the air holes of a photonic crystal fiber with an optimized liquid-crystal mixture having a large temperature...

  5. Design optimization of the distributed modal filtering rod fiber for increasing single mode bandwidth

    DEFF Research Database (Denmark)

    Jørgensen, Mette Marie; Petersen, Sidsel Rübner; Laurila, Marko

    2012-01-01

    High-power fiber amplifiers for pulsed applications require large mode area (LMA) fibers having high pump absorption and near diffraction limited output. This improves the limiting factor of nonlinear effects, while maintaining good beam quality. Photonic crystal fibers allow realization of short...

  6. Impact of Reabsorption on the Emission Spectra and Recombination Dynamics of Hybrid Perovskite Single Crystals.

    Science.gov (United States)

    Diab, Hiba; Arnold, Christophe; Lédée, Ferdinand; Trippé-Allard, Gaëlle; Delport, Géraud; Vilar, Christèle; Bretenaker, Fabien; Barjon, Julien; Lauret, Jean-Sébastien; Deleporte, Emmanuelle; Garrot, Damien

    2017-07-06

    Understanding the surface properties of organic-inorganic lead-based perovskites is of high importance to improve the device's performance. Here, we have investigated the differences between surface and bulk optical properties of CH 3 NH 3 PbBr 3 single crystals. Depth-resolved cathodoluminescence was used to probe the near-surface region on a depth of a few microns. In addition, we have studied the transmitted luminescence through thicknesses between 50 and 600 μm. In both experiments, the expected spectral shift due to the reabsorption effect has been precisely calculated. We demonstrate that reabsorption explains the important variations reported for the emission energy of single crystals. Single crystals are partially transparent to their own luminescence, and radiative transport is the dominant mechanism for propagation of the excitation in thick crystals. The transmitted luminescence dynamics are characterized by a long rise time and a lengthening of their decay due to photon recycling and light trapping.

  7. Spectrum of single photon emission computed tomography/computed tomography findings in patients with parathyroid adenomas.

    Science.gov (United States)

    Chakraborty, Dhritiman; Mittal, Bhagwant Rai; Harisankar, Chidambaram Natrajan Balasubramanian; Bhattacharya, Anish; Bhadada, Sanjay

    2011-01-01

    Primary hyperparathyroidism results from excessive parathyroid hormone secretion. Approximately 85% of all cases of primary hyperparathyroidism are caused by a single parathyroid adenoma; 10-15% of the cases are caused by parathyroid hyperplasia. Parathyroid carcinoma accounts for approximately 3-4% of cases of primary disease. Technetium-99m-sestamibi (MIBI), the current scintigraphic procedure of choice for preoperative parathyroid localization, can be performed in various ways. The "single-isotope, double-phase technique" is based on the fact that MIBI washes out more rapidly from the thyroid than from abnormal parathyroid tissue. However, not all parathyroid lesions retain MIBI and not all thyroid tissue washes out quickly, and subtraction imaging is helpful. Single photon emission computed tomography (SPECT) provides information for localizing parathyroid lesions, differentiating thyroid from parathyroid lesions, and detecting and localizing ectopic parathyroid lesions. Addition of CT with SPECT improves the sensitivity. This pictorial assay demonstrates various SPECT/CT patterns observed in parathyroid scintigraphy.

  8. Modification of emission photon statistics from single quantum dots using metal/SiO2 core/shell nanostructures.

    Science.gov (United States)

    Naiki, Hiroyuki; Oikawa, Hidetoshi; Masuo, Sadahiro

    2017-04-12

    Emission photon statistics, i.e., single-photon and multi-photon emissions, of isolated QDs is required for tailoring optoelectronic applications. In this article, we demonstrate that the emission photon statistics can be modified by the control of the spectral overlap of the QDs with the localized surface plasmon resonance (LSPR) of the metal nanoparticle (metal NP) and by the distance between the QD and the metal NP. Moreover, the contribution to the modification of the emission photon statistics, which is the excitation and emission enhancements and the quenching generated by the spectral overlap and the distance, is elucidated. By fabricating well-defined SiO 2 -coated AgNPs and AuNPs (metal/SiO 2 ), the spectral overlap originated from the metal species of Ag and Au and the distance constituted by the thickness of the SiO 2 shell are controlled. The probability of single-photon emission of single QD was increased by the enhancement of the excitation rate via adjusting the distance using Ag/SiO 2 while the single-photon emission was converted to multi-photon emission by the effect of exciton quenching at a short distance and a small spectral overlap. By contrast, the probability of multi-photon emission was increased by enhancement of the multi-photon emission rate and the quenching via the spectral overlap using Au/SiO 2 . These results indicated the fundamental finding to control emission photon statistics in single QDs by controlling the spectral overlap and the distance, and understand the interaction of plasmonic nanostructures and single QD systems.

  9. Color optimization of single emissive white OLEDs via energy transfer between RGB fluorescent dopants

    International Nuclear Information System (INIS)

    Kim, Nam Ho; Kim, You-Hyun; Yoon, Ju-An; Lee, Sang Youn; Ryu, Dae Hyun; Wood, Richard; Moon, C.-B.; Kim, Woo Young

    2013-01-01

    The electroluminescent characteristics of white organic light-emitting diodes (WOLEDs) were investigated including single emitting layer (SEL) with an ADN host and dopants; BCzVBi, C545T, and DCJTB for blue, green and red emission, respectively. The structure of the high efficiency WOLED device was; ITO/NPB(700 Å)/ADN: BCzVBi-7%:C545T-0.05%:DCJTB-0.1%(300 Å)/Bphen(300 Å)/Liq(20 Å)/Al(1200 Å) for mixing three primary colors. Luminous efficiency was 9.08 cd/A at 3.5 V and Commission Intenationale de L’eclairage (CIE x,y ) coordinates of white emission was measured as (0.320, 0.338) at 8 V while simulated CIE x,y coordinates were (0.336, 0.324) via estimation from each dopant's PL spectrum. -- Highlights: • This paper observes single-emissive-layered white OLED using fluorescent dopants. • Electrical and optical properties are analyzed. • Color stability of white OLED is confirmed for new planar light source

  10. Color optimization of single emissive white OLEDs via energy transfer between RGB fluorescent dopants

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Nam Ho; Kim, You-Hyun; Yoon, Ju-An; Lee, Sang Youn [Department of Green Energy and Semiconductor Engineering, Hoseo University, Asan (Korea, Republic of); Ryu, Dae Hyun [Department of Information Technology, Hansei University, Gunpo (Korea, Republic of); Wood, Richard [Department of Engineering Physics, McMaster University, Hamilton, Ontario, Canada L8S 4L7 (Canada); Moon, C.-B. [Department of Green Energy and Semiconductor Engineering, Hoseo University, Asan (Korea, Republic of); Kim, Woo Young, E-mail: wykim@hoseo.edu [Department of Green Energy and Semiconductor Engineering, Hoseo University, Asan (Korea, Republic of); Department of Engineering Physics, McMaster University, Hamilton, Ontario, Canada L8S 4L7 (Canada)

    2013-11-15

    The electroluminescent characteristics of white organic light-emitting diodes (WOLEDs) were investigated including single emitting layer (SEL) with an ADN host and dopants; BCzVBi, C545T, and DCJTB for blue, green and red emission, respectively. The structure of the high efficiency WOLED device was; ITO/NPB(700 Å)/ADN: BCzVBi-7%:C545T-0.05%:DCJTB-0.1%(300 Å)/Bphen(300 Å)/Liq(20 Å)/Al(1200 Å) for mixing three primary colors. Luminous efficiency was 9.08 cd/A at 3.5 V and Commission Intenationale de L’eclairage (CIE{sub x,y}) coordinates of white emission was measured as (0.320, 0.338) at 8 V while simulated CIE{sub x,y} coordinates were (0.336, 0.324) via estimation from each dopant's PL spectrum. -- Highlights: • This paper observes single-emissive-layered white OLED using fluorescent dopants. • Electrical and optical properties are analyzed. • Color stability of white OLED is confirmed for new planar light source.

  11. Enhanced single-photon emission from a diamond–silver aperture

    KAUST Repository

    Choy, Jennifer T.

    2011-10-09

    Solid-state quantum emitters, such as the nitrogen-vacancy centre in diamond, are robust systems for practical realizations of various quantum information processing protocols2-5 and nanoscale magnetometry schemes6,7 at room temperature. Such applications benefit from the high emission efficiency and flux of single photons, which can be achieved by engineering the electromagnetic environment of the emitter. One attractive approach is based on plasmonic resonators8-13, in which sub-wavelength confinement of optical fields can strongly modify the spontaneous emission of a suitably embedded dipole despite having only modest quality factors. Meanwhile, the scalability of solid-state quantum systems critically depends on the ability to control such emitterg-cavity interaction in a number of devices arranged in parallel. Here, we demonstrate a method to enhance the radiative emission rate of single nitrogen-vacancy centres in ordered arrays of plasmonic apertures that promises greater scalability over the previously demonstrated bottom-up approaches for the realization of on-chip quantum networks. © 2011 Macmillan Publishers Limited. All rights reserved.

  12. Single-mode biological distributed feedback lasers based on vitamin B2 doped gelatin

    DEFF Research Database (Denmark)

    Vannahme, Christoph; Maier-Flaig, F.; Lemmer, U.

    Biological second-order distributed feedback (DFB) lasers are presented. Riboflavin (vitamin B2) doped gelatin as active material is spin-coated onto nanoimprinted polymer with low refractive index. DFB grating periods of 368 nm and 384 nm yield laser emission at 543 nm and 562 nm, respectively....

  13. Characterization of Continuous and Pulsed Emission modes of a Hybrid Micro Focus X-ray Source for Medical Imaging Applications.

    Science.gov (United States)

    Ghani, Muhammad U; Wong, Molly D; Ren, Liqiang; Wu, Di; Zheng, Bin; Rong, John X; Wu, Xizeng; Liu, Hong

    2017-05-01

    The aim of this study was to quantitatively characterize a micro focus x-ray tube that can operate in both continuous and pulsed emission modes. The micro focus x-ray source (Model L9181-06, Hamamatsu Photonics, Japan) has a varying focal spot size ranging from 16-50 μm as the source output power changes from 10-39 W. We measured the source output, beam quality, focal spot sizes, kV accuracy, spectra shapes and spatial resolution. Source output was measured using an ionization chamber for various tube voltages (kVs) with varying current (μA) and distances. The beam quality was measured in terms of half value layer (HVL), kV accuracy was measured with a non-invasive kV meter, and the spectra was measured using a compact integrated spectrometer system. The focal spot sizes were measured using a slit method with a CCD detector with a pixel pitch of 22 μm. The spatial resolution was quantitatively measured using the slit method with a CMOS flat panel detector with a 50 μm pixel pitch, and compared to the qualitative results obtained by imaging a contrast bar pattern. The focal spot sizes in the vertical direction were smaller than that of the horizontal direction, the impact of which was visible when comparing the spatial resolution values. Our analyses revealed that both emission modes yield comparable imaging performances in terms of beam quality, spectra shape and spatial resolution effects. There were no significantly large differences, thus providing the motivation for future studies to design and develop stable and robust cone beam imaging systems for various diagnostic applications.

  14. Perturbations of gyrosynchrotron emission polarization from solar flares by sausage modes: forward modeling

    Science.gov (United States)

    Reznikova, V. E.; Van Doorsselaere, T.; Kuznetsov, A. A.

    2015-03-01

    We examined the polarization of the microwave flaring emission and its modulation by the fast sausage standing wave using a linear 3D magnetohydrodynamic model of a plasma cylinder. We analyzed the effects of the line-of-sight angle on the perturbations of the gyrosynchrotron intensity for two models: a base model with strong Razin suppression and a low-density model in which the Razin effect was negligible. The circular polarization (Stokes V) oscillation is in phase with the intensity oscillation, and the polarization degree (Stokes V/I) oscillates in phase with the magnetic field at the examined frequencies in both models. The two quantities experience a periodical reversal of their signs with a period equal to half of the sausage wave period when seen at a 90° viewing angle, in this case, their modulation depth reaches 100%.

  15. Measurements of the evaporation and hygroscopic response of single fine-mode aerosol particles using a Bessel beam optical trap.

    Science.gov (United States)

    Cotterell, Michael I; Mason, Bernard J; Carruthers, Antonia E; Walker, Jim S; Orr-Ewing, Andrew J; Reid, Jonathan P

    2014-02-07

    A single horizontally-propagating zeroth order Bessel laser beam with a counter-propagating gas flow was used to confine single fine-mode aerosol particles over extended periods of time, during which process measurements were performed. Particle sizes were measured by the analysis of the angular variation of light scattered at 532 nm by a particle in the Bessel beam, using either a probe beam at 405 nm or 633 nm. The vapour pressures of glycerol and 1,2,6-hexanetriol particles were determined to be 7.5 ± 2.6 mPa and 0.20 ± 0.02 mPa respectively. The lower volatility of hexanetriol allowed better definition of the trapping environment relative humidity profile over the measurement time period, thus higher precision measurements were obtained compared to those for glycerol. The size evolution of a hexanetriol particle, as well as its refractive index at wavelengths 532 nm and 405 nm, were determined by modelling its position along the Bessel beam propagation length while collecting phase functions with the 405 nm probe beam. Measurements of the hygroscopic growth of sodium chloride and ammonium sulfate have been performed on particles as small as 350 nm in radius, with growth curves well described by widely used equilibrium state models. These are the smallest particles for which single-particle hygroscopicity has been measured and represent the first measurements of hygroscopicity on fine mode and near-accumulation mode aerosols, the size regimes bearing the most atmospheric relevance in terms of loading, light extinction and scattering. Finally, the technique is contrasted with other single particle and ensemble methods, and limitations are assessed.

  16. A safety equipment list for rotary mode core sampling systems operation in single shell flammable gas tanks

    International Nuclear Information System (INIS)

    SMALLEY, J.L.

    1999-01-01

    This document identifies all interim safety equipment to be used for rotary mode core sampling of single-shell flammable gas tanks utilizing Rotary Mode Core Sampling systems (RMCS). This document provides the safety equipment for RMCS trucks HO-68K-4600, HO-68K-4647, trucks three and four respectively, and associated equipment. It is not intended to replace or supersede WHC-SD-WM-SEL-023, (Kelly 1991), or WHC-SD-WM-SEL-032, (Corbett 1994), which classifies 80-68K-4344 and HO-68K-4345 respectively. The term ''safety equipment'' refers to safety class (SC) and safety significant (SS) equipment, where equipment refers to structures, systems and components (SSC's). The identification of safety equipment in this document is based on the credited design safety features and analysis contained in the Authorization Basis (AB) for rotary mode core sampling operations in single-shell flammable gas tanks. This is an interim safety classification since the AB is interim. This document will be updated to reflect the final RMCS equipment safety classification designations upon completion of a final AB which will be implemented with the release of the Final Safety Analysis Report (FSAR)

  17. Medipix3: A 64 k pixel detector readout chip working in single photon counting mode with improved spectrometric performance

    CERN Document Server

    Ballabriga, R; Wong, W; Heijne, E; Campbell, M; Llopart, X

    2011-01-01

    Medipix3 is a 256 x 256 channel hybrid pixel detector readout chip working in a single photon counting mode with a new inter-pixel architecture, which aims to improve the energy resolution in pixelated detectors by mitigating the effects of charge sharing between channels. Charges are summed in all 2 x 2 pixel clusters on the chip and a given hit is allocated locally to the pixel summing circuit with the biggest total charge on an event-by-event basis. Each pixel contains also two 12-bit binary counters with programmable depth and overflow control. The chip is configurable such that either the dimensions of each detector pixel match those of one readout pixel or detector pixels are four times greater in area than the readout pixels. In the latter case, event-by-event summing is still possible between the larger pixels. Each pixel has around 1600 transistors and the analog static power consumption is below 15 mu W in the charge summing mode and 9 mu W in the single pixel mode. The chip has been built in an 8-m...

  18. Single-photon emission associated with double electron capture in F9 ++C collisions

    Science.gov (United States)

    Elkafrawy, T.; Simon, A.; Tanis, J. A.; Warczak, A.

    2016-10-01

    Radiative double electron capture (RDEC), the one-step process occurring in ion-atom collisions, has been investigated for bare fluorine ions colliding with carbon. RDEC is completed when two target electrons are captured to a bound state of a projectile simultaneously with the emission of a single photon. This work is a follow-up to our earlier measurement of RDEC for bare oxygen projectiles, thus providing a recipient system free of electron-related Coulomb fields in both cases and allowing for the comparison between the two collision systems as well as with available theoretical studies. The most significant mechanisms of x-ray emission that may contribute to the RDEC energy region as background processes are also addressed.

  19. Development of radioiodinated receptor ligands for cerebral single photon emission tomography

    International Nuclear Information System (INIS)

    Knapp, F.F. Jr.; McPherson, D.W.

    1992-01-01

    In the last decade the use of radiolabeled ligands for the imaging of cerebral receptors by emission computed tomography (ECT) has seen rapid growth. The opportunity to routinely perform cerebral single photon emission tomography (SPET) with iodine-123-labeled ligands depends on the availability of receptor ligands into which iodine can be introduced without decreasing the required high target receptor specificity. The use of iodine-123-labeled receptor-specific ligands also depends on the availability of high purity iodine-123 at reasonable costs and the necessary imaging instrumentation. In this paper, the development and current stage of evaluation of various iodine-123-labeled ligands for SPET imaging of dopaminergic, serotonergic and muscarinic acetylcholinergic receptor classes are discussed

  20. Single-photon emission associated with double electron capture in F9+ + C collisions

    CERN Document Server

    Elkafrawy, Tamer; Tanis, John A; Warczak, Andrzej

    2016-01-01

    Radiative double electron capture (RDEC), the one-step process occurring in ion-atom collisions, has been investigated for bare fluorine ions colliding with carbon. RDEC is completed when two target electrons are captured to a bound state of a projectile simultaneously with the emission of a single photon. This work is a follow-up to our earlier measurement of RDEC for bare oxygen projectiles, thus providing a recipient system free of electron-related Coulomb fields in both cases and allowing for the comparison between the two collision systems as well as with available theoretical studies. The most significant mechanisms of x-ray emission that may contribute to the RDEC energy region as background processes are also addressed.

  1. Guided wave mode dispersion of transient acoustic emission on copper pipes-Its visualisation and application to source location

    Science.gov (United States)

    Wang, Chao; Joe Au, Y. H.; Li, Lin; Cheng, Kai

    2016-03-01

    In this paper is presented an improved method for locating a transient acoustic emission (AE) source on a pipeline with two broad-band AE sensors. Using Short Time Fourier Transform (STFT), the method identifies a flexural wave mode, F(1,1), in the two AE signals detected, notes its respective arrival times at different frequencies, and determines the location of the AE source based on the arrival times. Due to velocity dispersion, the arrival time of the wave mode varies with frequency. The method has three main advantages: that the wave speed is not required in the calculation, that it is insensitive to threshold setting for arrival time estimation, and that, at least in theory, the accuracy of the source location can be made as high as desired. The paper first demonstrates, by way of an experiment, the inadequacy of threshold-crossing as a method for identifying the first arrival time of the AE wave. The paper then presents the theory of the proposed method and of the estimated error inherent in the theory and an explanation on how the error can be reduced. The method is then verified experimentally using results obtained from a 3-m long copper pipe of 22 mm diameter.

  2. Field emission properties of a DWCNT bundle and a single MWCNT

    Science.gov (United States)

    Fujishige, Masatsugu; Wongwiriyapan, Winadda; Muramatsu, Hiroyuki; Takeuchi, Kenji; Arai, Susumu

    2018-02-01

    The field emission properties of a bundle of double-walled carbon nanotubes (DWCNTs) and a single multiwalled carbon nanotube (MWCNT) were investigated. A DWCNT bundle or a single MWCNT was attached to the head of sharpened tip of tungsten by electrophoresis; the tungsten tip was dipped into a drop of a carbon nanotube/1,2-dichloroethane suspension on a stainless plate, and a high-frequency AC voltage (20 V peak to peak with a frequency of 15 MHz) was applied between the tungsten tip and the stainless steel plate. The turn-on fields of the DWCNT and MWCNT tips for 1 nA/cm2 were 0.05 and 0.48 V/μm, respectively. From the Fowler-Nordheim plots, the field enhancement factor (β) of the tips was estimated to be 109,600 (DWCNT) and 6780 (MWCNT). The present DWCNT emitter is characterized by a very small turn-on field and large β. The field emission performance is discussed in terms of the sizes of the bundle of DWCNTs and a single MWCNT.

  3. Fabry-Perot Microcavity Modes in Single GaP/GaNP Core/Shell Nanowires.

    Science.gov (United States)

    Dobrovolsky, Alexander; Stehr, Jan E; Sukrittanon, Supanee; Kuang, Yanjin; Tu, Charles W; Chen, Weimin M; Buyanova, Irina A

    2015-12-16

    Semiconductor nanowires (NWs) are attracting increasing interest as nanobuilding blocks for optoelectronics and photonics. A novel material system that is highly suitable for these applications are GaNP NWs. In this article, we show that individual GaP/GaNP core/shell nanowires (NWs) grown by molecular beam epitaxy on Si substrates can act as Fabry-Perot (FP) microcavities. This conclusion is based on results of microphotoluminescence (μ-PL) measurements performed on individual NWs, which reveal periodic undulations of the PL intensity that follow an expected pattern of FP cavity modes. The cavity is concluded to be formed along the NW axis with the end facets acting as reflecting mirrors. The formation of the FP modes is shown to be facilitated by an increasing index contrast with the surrounding media. Spectral dependence of the group refractive index is also determined for the studied NWs. The observation of the FP microcavity modes in the GaP/GaNP core/shell NWs can be considered as a first step toward achieving lasing in this quasidirect bandgap semiconductor in the NW geometry. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Cyclotron Acceleration of Relativistic Electrons through Landau Resonance with Obliquely Propagating Whistler Mode Chorus Emissions

    Science.gov (United States)

    Omura, Y.; Hsieh, Y. K.; Foster, J. C.; Erickson, P. J.; Kletzing, C.; Baker, D. N.

    2017-12-01

    A recent test particle simulation of obliquely propagating whistler mode wave-particle interaction [Hsieh and Omura, 2017] shows that the perpendicular wave electric field can play a significant role in trapping and accelerating relativistic electrons through Landau resonance. A further theoretical and numerical investigation verifies that there occurs nonlinear wave trapping of relativistic electrons by the nonlinear Lorentz force of the perpendicular wave magnetic field. An electron moving with a parallel velocity equal to the parallel phase velocity of an obliquely propagating wave basically see a stationary wave phase. Since the electron position is displaced from its gyrocenter by a distance ρ*sin(φ), where ρ is the gyroradius and φ is the gyrophase, the wave phase is modulated with the gyromotion, and the stationary wave fields as seen by the electron are expanded as series of Bessel functions Jn with phase variations n*φ. The J1 components of the wave electric and magnetic fields rotate in the right-hand direction with the gyrofrequency, and they can be in resonance with the electron undergoing the gyromotion, resulting in effective electron acceleration and pitch angle scattering. We have performed a subpacket analysis of chorus waveforms observed by the Van Allen Probes [Foster et al., 2017], and calculated the energy gain by the cyclotron acceleration through Landau resonance. We compare the efficiencies of accelerations by cyclotron and Landau resonances in typical events of rapid electron acceleration observed by the Van Allen Probes.References:[1] Hsieh, Y.-K., and Y. Omura (2017), Nonlinear dynamics of electrons interacting with oblique whistler mode chorus in the magnetosphere, J. Geophys. Res. Space Physics, 122, 675-694, doi:10.1002/2016JA023255.[2] Foster, J. C., P. J. Erickson, Y. Omura, D. N. Baker, C. A. Kletzing, and S. G. Claudepierre (2017), Van Allen Probes observations of prompt MeV radiation belt electron acceleration in nonlinear

  5. Interannual variation in the fine-mode MODIS aerosol optical depth and its relationship to the changes in sulfur dioxide emissions in China between 2000 and 2010

    Directory of Open Access Journals (Sweden)

    S. Itahashi

    2012-03-01

    Full Text Available Anthropogenic SO2 emissions increased alongside economic development in China at a rate of 12.7% yr−1 from 2000 to 2005. However, under new Chinese government policy, SO2 emissions declined by 3.9% yr−1 between 2005 and 2009. Between 2000 and 2010, we found that the variability in the fine-mode (submicron aerosol optical depth (AOD over the oceans adjacent to East Asia increased by 3–8% yr−1 to a peak around 2005–2006 and subsequently decreased by 2–7% yr−1, based on observations by the Moderate Resolution Imaging Spectroradiometer (MODIS on board NASA's Terra satellite and simulations by a chemical transport model. This trend is consistent with ground-based observations of aerosol particles at a mountainous background observation site in central Japan. These fluctuations in SO2 emission intensity and fine-mode AOD are thought to reflect the widespread installation of fuel-gas desulfurization (FGD devices in power plants in China, because aerosol sulfate is a major determinant of the fine-mode AOD in East Asia. Using a chemical transport model, we confirmed that the contribution of particulate sulfate to the fine-mode AOD is more than 70% of the annual mean and that the abovementioned fluctuation in fine-mode AOD is caused mainly by changes in SO2 emission rather than by other factors such as varying meteorological conditions in East Asia. A strong correlation was also found between satellite-retrieved SO2 vertical column density and bottom-up SO2 emissions, both of which were also consistent with observed fine-mode AOD trends. We propose a simplified approach for evaluating changes in SO2 emissions in China, combining the use of modeled sensitivity coefficients that describe the variation of fine-mode AOD with changes in SO2 emissions and satellite retrieval. Satellite measurements of fine-mode AOD

  6. Label free imaging system for measuring blood flow speeds using a single multi-mode optical fiber (Conference Presentation)

    Science.gov (United States)

    Sigal, Iliya; Caravaca Aguirre, Antonio M.; Gad, Raanan; Piestun, Rafael; Levi, Ofer

    2016-03-01

    We demonstrate a single multi-mode fiber-based micro-endoscope for measuring blood flow speeds. We use the transmission-matrix wavefront shaping approach to calibrate the multi-mode fiber and raster-scan a focal spot across the distal fiber facet, imaging the cross-polarized back-reflected light at the proximal facet using a camera. This setup allows assessment of the backscattered photon statistics: by computing the mean speckle contrast values across the proximal fiber facet we show that spatially-resolved flow speed maps can be inferred by selecting an appropriate camera integration time. The proposed system is promising for minimally-invasive studies of neurovascular coupling in deep brain structures.

  7. Photon emission statistics and photon tracking in single-molecule spectroscopy of molecular aggregates : Dimers and trimers

    NARCIS (Netherlands)

    Bloemsma, E. A.; Knoester, J.

    2012-01-01

    Based on the generating function formalism, we investigate broadband photon statistics of emission for single dimers and trimers driven by a continuous monochromatic laser field. In particular, we study the first and second moments of the emission statistics, which are the fluorescence excitation

  8. On the excess photon noise in single-beam measurements with photo-emissive and photo-conductive cells

    NARCIS (Netherlands)

    Alkemade, C.T.J.

    In this paper the so-called excess photon noise is theoretically considered with regard to noise power measurements with a single, illumined photo-emissive or photo-conductive cell. Starting from a modification of Mandel's stochastic association of the emission of photo-electrons with wave

  9. Propagation of Single-Mode Fibre Laser Beams through an Optical ABCD System with Circular Aperture at the Fibre Output End

    International Nuclear Information System (INIS)

    Kai-Liang, Duan; Jian-Feng, Li; Wei, Zhao; Yi-Shan, Wang

    2008-01-01

    Based on the expansion expression of the fundamental mode of a single-mode fibre in terms of Laguerre–Gauss modes, the propagation of a beam of a weakly guiding fibre laser through an optical ABCD system with a circular aperture at the fibre end is studied. The results show that there is much difference between the propagation of the laser beam described by the expansion expression and by the Gaussian mode approximation. The depth of focus of the laser beam is longer than that of the Gaussian modes

  10. Bronchobiliary Fistula Localized by Cholescintigraphy with Single-Photon Emission Computed Tomography

    International Nuclear Information System (INIS)

    Artunduaga, Maddy; Patel, Niraj R.; Wendt, Julie A.; Guy, Elizabeth S.; Nachiappan, Arun C.

    2015-01-01

    Biliptysis is an important clinical feature to recognize as it is associated with bronchobiliary fistula, a rare entity. Bronchobiliary fistulas have been diagnosed with planar cholescintigraphy. However, cholescintigraphy with single-photon emission computed tomography (SPECT) can better spatially localize a bronchobiliary fistula as compared to planar cholescintigraphy alone, and is useful for preoperative planning if surgical treatment is required. Here, we present the case of a 23-year-old male who developed a bronchobiliary fistula in the setting of posttraumatic and postsurgical infection, which was diagnosed and localized by cholescintigraphy with SPECT

  11. Painful spondylolysis or spondylolisthesis studied by radiography and single-photon emission computed tomography

    International Nuclear Information System (INIS)

    Collier, B.D.; Johnson, R.P.; Carrera, G.F.

    1985-01-01

    Planar bone scintigraphy (PBS) and single-photon emission computed tomography (SPECT) were compared in 19 adults with radiographic evidence of spondylolysis and/or spondylolisthesis. SPECT was more sensitive than PBS when used to identify symptomatic patients and sites of painful defects in the pars interarticularis. In addition, SPECT allowed more accurate localization than PBS. In 6 patients, spondylolysis or spondylolisthesis was unrealted to low back pain, and SPECT images of the posterior neural arch were normal. The authors conclude that when spondylolysis or spondylolisthesis is the cause of low back pain, pars defects are frequently heralded by increased scintigraphic activity which is best detected and localized by SPECT

  12. Painful spondylolysis or spondylolisthesis studied by radiography and single-photon emission computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Collier, B.D.; Johnson, R.P.; Carrera, G.F.; Meyer, G.A.; Schwab, J.P.; Flatley, T.J.; Isitman, A.T.; Hellman, R.S.; Zielonka, J.S.; Knobel, J.

    1985-01-01

    Planar bone scintigraphy (PBS) and single-photon emission computed tomography (SPECT) were compared in 19 adults with radiographic evidence of spondylolysis and/or spondylolisthesis. SPECT was more sensitive than PBS when used to identify symptomatic patients and sites of painful defects in the pars interarticularis. In addition, SPECT allowed more accurate localization than PBS. In 6 patients, spondylolysis or spondylolisthesis was unrealted to low back pain, and SPECT images of the posterior neural arch were normal. The authors conclude that when spondylolysis or spondylolisthesis is the cause of low back pain, pars defects are frequently heralded by increased scintigraphic activity which is best detected and localized by SPECT.

  13. Performance assessment of the single photon emission microscope: high spatial resolution SPECT imaging of small animal organs

    OpenAIRE

    Mejia, J.; Reis, M.A.; Miranda, A.C.C.; Batista, I.R.; Barboza, M.R.F.; Shih, M.C.; Fu, G.; Chen, C.T.; Meng, L.J.; Bressan, R.A.; Amaro Jr, E.

    2013-01-01

    The single photon emission microscope (SPEM) is an instrument developed to obtain high spatial resolution single photon emission computed tomography (SPECT) images of small structures inside the mouse brain. SPEM consists of two independent imaging devices, which combine a multipinhole collimator, a high-resolution, thallium-doped cesium iodide [CsI(Tl)] columnar scintillator, a demagnifying/intensifier tube, and an electron-multiplying charge-coupling device (CCD). Collimators have 300- and ...

  14. Multistabilities and symmetry-broken one-color and two-color states in closely coupled single-mode lasers

    Science.gov (United States)

    Clerkin, Eoin; O'Brien, Stephen; Amann, Andreas

    2014-03-01

    We theoretically investigate the dynamics of two mutually coupled, identical single-mode semi-conductor lasers. For small separation and large coupling between the lasers, symmetry-broken one-color states are shown to be stable. In this case the light outputs of the lasers have significantly different intensities while at the same time the lasers are locked to a single common frequency. For intermediate coupling we observe stable symmetry-broken two-color states, where both lasers lase simultaneously at two optical frequencies which are separated by up to 150 GHz. Using a five-dimensional model, we identify the bifurcation structure which is responsible for the appearance of symmetric and symmetry-broken one-color and two-color states. Several of these states give rise to multistabilities and therefore allow for the design of all-optical memory elements on the basis of two coupled single-mode lasers. The switching performance of selected designs of optical memory elements is studied numerically.

  15. Efficient injection from large telescopes into single-mode fibres: Enabling the era of ultra-precision astronomy

    Science.gov (United States)

    Jovanovic, N.; Schwab, C.; Guyon, O.; Lozi, J.; Cvetojevic, N.; Martinache, F.; Leon-Saval, S.; Norris, B.; Gross, S.; Doughty, D.; Currie, T.; Takato, N.

    2017-08-01

    Photonic technologies offer numerous advantages for astronomical instruments such as spectrographs and interferometers owing to their small footprints and diverse range of functionalities. Operating at the diffraction-limit, it is notoriously difficult to efficiently couple such devices directly with large telescopes. We demonstrate that with careful control of both the non-ideal pupil geometry of a telescope and residual wavefront errors, efficient coupling with single-mode devices can indeed be realised. A fibre injection was built within the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument. Light was coupled into a single-mode fibre operating in the near-IR (J - H bands) which was downstream of the extreme adaptive optics system and the pupil apodising optics. A coupling efficiency of 86% of the theoretical maximum limit was achieved at 1550 nm for a diffraction-limited beam in the laboratory, and was linearly correlated with Strehl ratio. The coupling efficiency was constant to within 40% for 84% of the time and >50% for 41% of the time. The laboratory results allow us to forecast that extreme adaptive optics levels of correction (Strehl ratio >90% in H-band) would allow coupling of >67% (of the order of coupling to multimode fibres currently) while standard levels of wavefront correction (Strehl ratio >20% in H-band) would allow coupling of >18%. For Strehl ratios <20%, few-port photonic lanterns become a superior choice but the signal-to-noise, and pixel availability must be considered. These results illustrate a clear path to efficient on-sky coupling into a single-mode fibre, which could be used to realise modal-noise-free radial velocity machines, very-long-baseline optical/near-IR interferometers and/or simply exploit photonic technologies in future instrument design.

  16. Evaluation of scatter correction using a single isotope for simultaneous emission and transmission data

    International Nuclear Information System (INIS)

    Yang, J.; Kuikka, J.T.; Vanninen, E.; Laensimies, E.; Kauppinen, T.; Patomaeki, L.

    1999-01-01

    Photon scatter is one of the most important factors degrading the quantitative accuracy of SPECT images. Many scatter correction methods have been proposed. The single isotope method was proposed by us. Aim: We evaluate the scatter correction method of improving the quality of images by acquiring emission and transmission data simultaneously with single isotope scan. Method: To evaluate the proposed scatter correction method, a contrast and linearity phantom was studied. Four female patients with fibromyalgia (FM) syndrome and four with chronic back pain (BP) were imaged. Grey-to-cerebellum (G/C) and grey-to-white matter (G/W) ratios were determined by one skilled operator for 12 regions of interest (ROIs) in each subject. Results: The linearity of activity response was improved after the scatter correction (r=0.999). The y-intercept value of the regression line was 0.036 (p [de

  17. Characteristics of the Single-Longitudinal-Mode Planar-Waveguide External Cavity Diode Laser at 1064 nm

    Science.gov (United States)

    Numata, Kenji; Alalusi, Mazin; Stolpner, Lew; Margaritis, Georgios; Camp, Jordan; Krainak, Michael

    2014-01-01

    We describe the characteristics of the planar-waveguide external cavity diode laser (PW-ECL). To the best of our knowledge, it is the first butterfly-packaged 1064 nm semiconductor laser that is stable enough to be locked to an external frequency reference. We evaluated its performance from the viewpoint of precision experiments. Using a hyperfine absorption line of iodine, we suppressed its frequency noise by a factor of up to 104 at 10 mHz. The PWECL's compactness and low cost make it a candidate to replace traditional Nd:YAG nonplanar ring oscillators and fiber lasers in applications that require a single longitudinal mode.

  18. High-performance imaging of stem cells using single-photon emissions

    Science.gov (United States)

    Wagenaar, Douglas J.; Moats, Rex A.; Hartsough, Neal E.; Meier, Dirk; Hugg, James W.; Yang, Tang; Gazit, Dan; Pelled, Gadi; Patt, Bradley E.

    2011-10-01

    Radiolabeled cells have been imaged for decades in the field of autoradiography. Recent advances in detector and microelectronics technologies have enabled the new field of "digital autoradiography" which remains limited to ex vivo specimens of thin tissue slices. The 3D field-of-view (FOV) of single cell imaging can be extended to millimeters if the low energy (10-30 keV) photon emissions of radionuclides are used for single-photon nuclear imaging. This new microscope uses a coded aperture foil made of highly attenuating elements such as gold or platinum to form the image as a kind of "lens". The detectors used for single-photon emission microscopy are typically silicon detectors with a pixel pitch less than 60 μm. The goal of this work is to image radiolabeled mesenchymal stem cells in vivo in an animal model of tendon repair processes. Single-photon nuclear imaging is an attractive modality for translational medicine since the labeled cells can be imaged simultaneously with the reparative processes by using the dual-isotope imaging technique. The details our microscope's two-layer gold aperture and the operation of the energy-dispersive, pixellated silicon detector are presented along with the first demonstration of energy discrimination with a 57Co source. Cell labeling techniques have been augmented by genetic engineering with the sodium-iodide symporter, a type of reporter gene imaging method that enables in vivo uptake of free 99mTc or an iodine isotope at a time point days or weeks after the insertion of the genetically modified stem cells into the animal model. This microscopy work in animal research may expand to the imaging of reporter-enabled stem cells simultaneously with the expected biological repair process in human clinical trials of stem cell therapies.

  19. Versatile Gap Mode Plasmon under ATR Geometry towards Single Molecule Raman, Laser Trapping and Photocatalytic Reactions.

    Science.gov (United States)

    Futamata, Masayuki; Akai, Keitaro; Iida, Chiaki; Akiba, Natsumi

    2017-01-01

    We have investigated various aspects of a gap mode plasmon to establish it as an analytical tool. First, markedly large (10 7 - 10 9 ) enhancement factors for the Raman scattering intensity from a thiophenol (TP) monolayer sandwiched by Ag films on a prism and silver nanoparticles (AgNPs) were obtained under attenuated total reflection (ATR) geometry. Second, AgNPs with a radius of ∼20 nm were optically trapped and immobilized on TP-covered Ag films under a gap mode resonance with extremely weak laser power density of ∼1 μW/μm 2 at 532 nm. The observed optical trapping and immobilization were theoretically rationalized using a dipole-dipole coupling and van der Waals interaction between AgNPs and Ag films. Third, p-alkyl TP molecules such as p-methyl TP, p-ethyl TP, p-isopropyl TP, and p-tertiary butyl TP were photocatalytically oxidized into p-carboxyl TP, whereas o- and m-methyl TP did not show such reactions.

  20. Telecommunication Wavelength-Band Single-Photon Emission from Single Large InAs Quantum Dots Nucleated on Low-Density Seed Quantum Dots.

    Science.gov (United States)

    Chen, Ze-Sheng; Ma, Ben; Shang, Xiang-Jun; He, Yu; Zhang, Li-Chun; Ni, Hai-Qiao; Wang, Jin-Liang; Niu, Zhi-Chuan

    2016-12-01

    Single-photon emission in the telecommunication wavelength band is realized with self-assembled strain-coupled bilayer InAs quantum dots (QDs) embedded in a planar microcavity on GaAs substrate. Low-density large QDs in the upper layer active for ~1.3 μm emission are fabricated by precisely controlling the indium deposition amount and applying a gradient indium flux in both QD layers. Time-resolved photoluminescence (PL) intensity suggested that the radiative lifetime of their exciton emission is 1.5~1.6 ns. The second-order correlation function of g (2)(0) < 0.5 which demonstrates a pure single-photon emission.

  1. Spontaneous and stimulated emission in Sm3+-doped YAl3(BO3)4 single crystal

    International Nuclear Information System (INIS)

    Ryba-Romanowski, Witold; Lisiecki, Radosław; Beregi, Elena; Martín, I.R.

    2015-01-01

    Single crystals of YAl 3 (BO 3 ) 4 doped with trivalent samarium were grown by the top-seeded high temperature solution method and their absorption and emission spectra were investigated. Optical pumping into prominent absorption band around 405 nm feeds the 4 G 5/2 metastable level giving rise to intense visible luminescence distributed in several spectral lines with the most intense line around 600 nm characterized by a branching ratio of 0.42 and peak emission cross section of 0.25×10 −20 cm 2 . Optical amplification at 600 nm with a gain coefficient of 2.9 cm −1 was achieved during a pump-and-probe experiment. - Highlights: • YAB:Sm crystal grown by the top-seeded high temperature solution method. • Spectroscopic qualities relevant for visible laser operation. • YAB:Sm single crystal used in a pump-and-probe experiment. • Optical amplification properties of samarium doped YAl 3 (BO 3 ) 4

  2. Shape dependent synthesis and field emission induced rectification in single ZnS nanocrystals.

    Science.gov (United States)

    Thupakula, Umamahesh; Dalui, Amit; Debangshi, Anupam; Bal, Jayanta K; Kumar, Gundam S; Acharya, Somobrata

    2014-05-28

    We report on the synthesis of shape controlled ZnS nanocrystals designed into nanodots, nanorods, and nanowires retaining the same diameter and crystallographic phase. We used UHV scanning tunneling microscopy and spectroscopy to study rectification behavior from single nanocrystals. The nanorod and nanowire show large tunneling current at the negative bias in comparison to the positive bias demonstrating current rectification, while the nanodot shows symmetric current-voltage behavior. We proposed a tunneling mechanism where direct tunneling is followed by resonant tunneling mechanism through ZnS nanocrystal at lower applied bias voltages. Stimulation of field emission in Fowler-Nordheim tunneling regime at higher negative bias voltages enables the rectification behavior from the ZnS nanorod or nanowire. Absence of rectification from the ZnS nanodot is associated with spherical shape where the field emission becomes less significant. Realizing functional electronic component from such shape dependent single ZnS nanocrystal may provide a means in realizing nanocrystal based miniaturized devices.

  3. DE-BLURRING SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY IMAGES USING WAVELET DECOMPOSITION

    Directory of Open Access Journals (Sweden)

    Neethu M. Sasi

    2016-02-01

    Full Text Available Single photon emission computed tomography imaging is a popular nuclear medicine imaging technique which generates images by detecting radiations emitted by radioactive isotopes injected in the human body. Scattering of these emitted radiations introduces blur in this type of images. This paper proposes an image processing technique to enhance cardiac single photon emission computed tomography images by reducing the blur in the image. The algorithm works in two main stages. In the first stage a maximum likelihood estimate of the point spread function and the true image is obtained. In the second stage Lucy Richardson algorithm is applied on the selected wavelet coefficients of the true image estimate. The significant contribution of this paper is that processing of images is done in the wavelet domain. Pre-filtering is also done as a sub stage to avoid unwanted ringing effects. Real cardiac images are used for the quantitative and qualitative evaluations of the algorithm. Blur metric, peak signal to noise ratio and Tenengrad criterion are used as quantitative measures. Comparison against other existing de-blurring algorithms is also done. The simulation results indicate that the proposed method effectively reduces blur present in the image.

  4. DECAY MODES OF HIGH-LYING SINGLE-PARTICLE STATES IN PB-209

    NARCIS (Netherlands)

    BEAUMEL, D; FORTIER, S; GALES, S; GUILLOT, J; LANGEVINJOLIOT, H; LAURENT, H; MAISON, JM; VERNOTTE, J; BORDEWIJK, JA; BRANDENBURG, S; KRASZNAHORKAY, A; CRAWLEY, GM; MASSOLO, CP; RENTERIA, M

    The neutron decay of high-lying single-particle states in Pb-209 excited by means of the (alpha, He-3) reaction has been investigated at 122 MeV incident energy using a multidetector array. The high-spin values of these states, inferred from previous inclusive experiments, are confirmed by the

  5. Approaches to building single-stage AC/AC conversion switch-mode audio power amplifiers

    DEFF Research Database (Denmark)

    Ljusev, Petar; Andersen, Michael Andreas E.

    2004-01-01

    This paper discusses the possible topologies and promising approaches towards direct single-phase AC-AC conversion of the mains voltage for audio applications. When compared to standard Class-D switching audio power amplifiers with a separate power supply, it is expected that direct conversion...

  6. A novel phantom design for emission tomography enabling scatter- and attenuation-''free'' single-photon emission tomography imaging

    International Nuclear Information System (INIS)

    Larsson, S.A.; Johansson, L.; Jonsson, C.; Pagani, M.; Jacobsson, H.

    2000-01-01

    A newly designed technique for experimental single-photon emission tomography (SPET) and positron emission tomography (PET) data acquisition with minor disturbing effects from scatter and attenuation has been developed. In principle, the method is based on discrete sampling of the radioactivity distribution in 3D objects by means of equidistant 2D planes. The starting point is a set of digitised 2D sections representing the radioactivity distribution of the 3D object. Having a radioactivity-related grey scale, the 2D images are printed on paper sheets using radioactive ink. The radioactive sheets can be shaped to the outline of the object and stacked into a 3D structure with air or some arbitrary dense material in between. For this work, equidistantly spaced transverse images of a uniform cylindrical phantom and of the digitised Hoffman rCBF phantom were selected and printed out on paper sheets. The uniform radioactivity sheets were imaged on the surface of a low-energy ultra-high-resolution collimator (4 mm full-width at half-maximum) of a three-headed SPET camera. The reproducibility was 0.7% and the uniformity was 1.2%. Each rCBF sheet, containing between 8.3 and 80 MBq of 99m TcO 4 - depending on size, was first imaged on the collimator and then stacked into a 3D structure with constant 12 mm air spacing between the slices. SPET was performed with the sheets perpendicular to the central axis of the camera. The total weight of the stacked rCBF phantom in air was 63 g, giving a scatter contribution comparable to that of a point source in air. The overall attenuation losses were <20%. A second SPET study was performed with 12-mm polystyrene plates in between the radioactive sheets. With polystyrene plates, the total phantom weight was 2300 g, giving a scatter and attenuation magnitude similar to that of a patient study. With the proposed technique, it is possible to obtain ''ideal'' experimental images (essentially built up by primary photons) for comparison with

  7. Performance of a residential heat pump operating in the cooling mode with single faults imposed

    International Nuclear Information System (INIS)

    Kim, Minsung; Payne, W. Vance; Domanski, Piotr A.; Yoon, Seok Ho; Hermes, Christian J.L.

    2009-01-01

    The system behavior of a R410A residential unitary split heat pump operating in the cooling mode was investigated. Seven artificial faults were implemented: compressor/reversing valve leakage, improper outdoor air flow, improper indoor air flow, liquid line restriction, refrigerant undercharge, refrigerant overcharge, and presence of non-condensable gas in the refrigerant. This study monitored eight fault detection features and identified the most sensitive features for each fault. The effect of the various fault levels on energy efficiency ratio (EER) was also estimated. Since the studied system employed a thermostatic expansion valve (TXV) as an expansion device, it could adapt to some faults making the fault less detectable. The distinctiveness of the fault depended on the TXV status (fully open or not)

  8. Position Control of the Single Spherical Wheel Mobile Robot by Using the Fuzzy Sliding Mode Controller

    Directory of Open Access Journals (Sweden)

    Hamed Navabi

    2017-01-01

    Full Text Available A spherical wheel robot or Ballbot—a robot that balances on an actuated spherical ball—is a new and recent type of robot in the popular area of mobile robotics. This paper focuses on the modeling and control of such a robot. We apply the Lagrangian method to derive the governing dynamic equations of the system. We also describe a novel Fuzzy Sliding Mode Controller (FSMC implemented to control a spherical wheel mobile robot. The nonlinear nature of the equations makes the controller nontrivial. We compare the performance of four different fuzzy controllers: (a regulation with one signal, (b regulation and position control with one signal, (c regulation and position control with two signals, and (d FSMC for regulation and position control with two signals. The system is evaluated in a realistic simulation and the robot parameters are chosen based on a LEGO platform, so the designed controllers have the ability to be implemented on real hardware.

  9. Adaptable Optical Fiber Displacement-Curvature Sensor Based on a Modal Michelson Interferometer with a Tapered Single Mode Fiber.

    Science.gov (United States)

    Salceda-Delgado, G; Martinez-Rios, A; Selvas-Aguilar, R; Álvarez-Tamayo, R I; Castillo-Guzman, A; Ibarra-Escamilla, B; Durán-Ramírez, V M; Enriquez-Gomez, L F

    2017-06-02

    A compact, highly sensitive optical fiber displacement and curvature radius sensor is presented. The device consists of an adiabatic bi-conical fused fiber taper spliced to a single-mode fiber (SMF) segment with a flat face end. The bi-conical taper structure acts as a modal coupling device between core and cladding modes for the SMF segment. When the bi-conical taper is bent by an axial displacement, the symmetrical bi-conical shape of the tapered structure is stressed, causing a change in the refractive index profile which becomes asymmetric. As a result, the taper adiabaticity is lost, and interference between modes appears. As the bending increases, a small change in the fringe visibility and a wavelength shift on the periodical reflection spectrum of the in-fiber interferometer is produced. The displacement sensitivity and the spectral periodicity of the device can be adjusted by the proper selection of the SMF length. Sensitivities from around 1.93 to 3.4 nm/mm were obtained for SMF length between 7.5 and 12.5 cm. Both sensor interrogations, wavelength shift and visibility contrast, can be used to measure displacement and curvature radius magnitudes.

  10. Attenuation correction in pulmonary and myocardial single photon emission computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Almquist, H

    2000-01-01

    The objective was to develop and validate methods for single photon emission computed tomography, SPECT, allowing quantitative physiologic and diagnostic studies of lung and heart. A method for correction of variable attenuation in SPECT, based on transmission measurements before administration of an isotope to the subject, was developed and evaluated. A protocol based upon geometrically well defined phantoms was developed. In a mosaic pattern phantom count rates were corrected from 39-43% to 101-110% of reference. In healthy subjects non-gravitational pulmonary perfusion gradients observed without attenuation correctionwere artefacts caused by attenuation. Pulmonary density in centre of right lung, obtained from the transmission measurement, was 0.28 {+-} 0.03 g/ml in normal subjects. Mean density was lower in large lungs compared to smaller ones. We also showed that regional ventilation/perfusion ratios could be measured with SPECT, using the readily available tracer {sup 133}Xe. Because of the low energy of {sup 133}Xe this relies heavily upon attenuation correction. A commercially available system for attenuation correction with simultaneous emission and transmission, considered to improve myocardial SPECT, performed erroneously. This could lead to clinical misjudgement. We considered that manufacturer-independent pre-clinical tests are required. In a test of two other commercial systems, based on different principles, an adapted variant of our initial protocol was proven useful. Only one of the systems provided correct emission count rates independently on phantom configuration. Errors in the other system were related to inadequate compensation of the influence of emission activity on the transmission study.

  11. Attenuation correction in pulmonary and myocardial single photon emission computed tomography

    International Nuclear Information System (INIS)

    Almquist, H.

    2000-01-01

    The objective was to develop and validate methods for single photon emission computed tomography, SPECT, allowing quantitative physiologic and diagnostic studies of lung and heart. A method for correction of variable attenuation in SPECT, based on transmission measurements before administration of an isotope to the subject, was developed and evaluated. A protocol based upon geometrically well defined phantoms was developed. In a mosaic pattern phantom count rates were corrected from 39-43% to 101-110% of reference. In healthy subjects non-gravitational pulmonary perfusion gradients observed without attenuation correction were artefacts caused by attenuation. Pulmonary density in centre of right lung, obtained from the transmission measurement, was 0.28 ± 0.03 g/ml in normal subjects. Mean density was lower in large lungs compared to smaller ones. We also showed that regional ventilation/perfusion ratios could be measured with SPECT, using the readily available tracer 133 Xe. Because of the low energy of 133 Xe this relies heavily upon attenuation correction. A commercially available system for attenuation correction with simultaneous emission and transmission, considered to improve myocardial SPECT, performed erroneously. This could lead to clinical misjudgement. We considered that manufacturer-independent pre-clinical tests are required. In a test of two other commercial systems, based on different principles, an adapted variant of our initial protocol was proven useful. Only one of the systems provided correct emission count rates independently on phantom configuration. Errors in the other system were related to inadequate compensation of the influence of emission activity on the transmission study

  12. Meterwavelength Single-pulse Polarimetric Emission Survey. IV. The Period Dependence of Component Widths of Pulsars

    Science.gov (United States)

    Skrzypczak, Anna; Basu, Rahul; Mitra, Dipanjan; Melikidze, George I.; Maciesiak, Krzysztof; Koralewska, Olga; Filothodoros, Alexandros

    2018-02-01

    The core component width in normal pulsars, with periods (P) > 0.1 s, measured at the half-power point at 1 GHz, has a lower boundary line (LBL) that closely follows the P ‑0.5 scaling relation. This result is of fundamental importance for understanding the emission process and requires extended studies over a wider frequency range. In this paper we have carried out a detailed study of the profile component widths of 123 normal pulsars observed in the Meterwavelength Single-pulse Polarimetric Emission Survey at 333 and 618 MHz. The components in the pulse profile were separated into core and conal classes. We found that at both frequencies, the core, as well as the conal component widths versus period, had a LBL that followed the P ‑0.5 relation with a similar lower boundary. The radio emission in normal pulsars has been observationally shown to arise from a narrow range of heights around a few hundred kilometers above the stellar surface. In the past the P ‑0.5 relation has been considered as evidence for emission arising from last open dipolar magnetic field lines. We show that the P ‑0.5 dependence only holds if the trailing and leading half-power points of the component are associated with the last open field line. In such a scenario we do not find any physical motivation that can explain the P ‑0.5 dependence for both core and conal components as evidence for dipolar geometry in normal pulsars. We believe the period dependence is a result of a currently unexplained physical phenomenon.

  13. Single-longitudinal mode distributed-feedback fiber laser with low-threshold and high-efficiency

    Science.gov (United States)

    Jiang, Man; Zhou, Pu; Gu, Xijia

    2018-01-01

    Single-frequency fiber laser has attracted a lot of interest in recent years due to its numerous application potentials in telecommunications, LIDAR, high resolution sensing, atom frequency standard, etc. Phosphate glass fiber is one of the candidates for building compact high gain fiber lasers because of its capability of high-concentration of rare-earth ions doping in fiber core. Nevertheless, it is challenging for the integration of UV-written intra-core fiber Bragg gratings into the fiber laser cavity due to the low photosensitivity of phosphate glass fiber. The research presented in this paper will focus on demonstration of UV-written Bragg gratings in phosphate glass fiber and its application in direct-written short monolithic single-frequency fiber lasers. Strong π-phase shift Bragg grating structure is direct-inscribed into the Er/Yb co-doped gain fiber using an excimer laser, and a 5-cm-long phase mask is used to inscribe a laser cavity into the Er/Yb co-doped phosphate glass fibers. The phase mask is a uniform mask with a 50 μm gap in the middle. The fiber laser device emits output power of 10.44 mW with a slope efficiency of 21.5% and the threshold power is about 42.8 mW. Single-longitudinal mode operation is validated by radio frequency spectrum measurement. Moreover, the output spectrum at the highest power shows an excellent optical signal to noise ratio of about 70 dB. These results, to the best of our knowledge, show the lowest power threshold and highest efficiency among the reports that using the same structure to achieve single-longitudinal mode laser output.

  14. 1.5 W high efficiency and tunable single-longitudinal-mode Ho:YLF ring laser based on Faraday effect.

    Science.gov (United States)

    Wu, Jing; Ju, Youlun; Dai, Tongyu; Yao, Baoquan; Wang, Yuezhu

    2017-10-30

    We demonstrated an efficient and tunable single-longitudinal-mode Ho:YLF ring laser based on Faraday effect for application to measure atmospheric carbon dioxide (CO 2 ). Single-longitudinal-mode power at 2051.65 nm achieved 528 mW with the slope efficiency of 39.5% and the M 2 factor of 1.07, and the tunable range of about 178 GHz was obtained by inserting a Fabry-Perot (F-P) etalon with the thickness of 0.5 mm. In addition, the maximum single-longitudinal-mode power reached 1.5 W with the injected power of 528 mW at 2051.65 nm by master oscillator power amplifier (MOPA) technique. High efficiency and tunable single-longitudinal-mode based on Faraday effect around 2 μm has not been reported yet to the best of our knowledge.

  15. Evaluation of an improved atomic data basis for carbon in UEDGE emission modeling for L-mode plasmas in DIII-D

    Energy Technology Data Exchange (ETDEWEB)

    Muñoz Burgos, J.M., E-mail: munozj@fusion.gat.com [Oak Ridge Institute for Science and Education, Oak Ridge, TN 37831-0117 (United States); Leonard, A.W. [General Atomics, P.O. Box 85608, San Diego, CA 92186-5608 (United States); Loch, S.D.; Ballance, C.P. [Auburn University, Auburn, AL 36849 (United States)

    2013-07-15

    New scaled carbon atomic electron-impact excitation data is utilized to evaluate comparisons between experimental measurements and fluid emission modeling of detached plasmas at DIII-D. The C I and C II modeled emission lines for 909.8 and 514.7 nm were overestimated by a factor of 10–20 than observed experimentally for the inner leg, while the outer leg was within a factor of 2. Due to higher modeled emissions, a previous study using the UEDGE code predicted that a higher amount of carbon was required to achieve a detached outboard divertor plasma in L-mode at DIII-D. The line emission predicted by using the new scaled carbon data yields closer results when compared against experiment. We also compare modeling and measurements of D{sub α} emission from neutral deuterium against predictions from newly calculated R-Matrix with pseudostates data available at the ADAS database.

  16. Single-Trial Classification of Bistable Perception by Integrating Empirical Mode Decomposition, Clustering, and Support Vector Machine

    Directory of Open Access Journals (Sweden)

    Hualou Liang

    2008-04-01

    Full Text Available We propose an empirical mode decomposition (EMD- based method to extract features from the multichannel recordings of local field potential (LFP, collected from the middle temporal (MT visual cortex in a macaque monkey, for decoding its bistable structure-from-motion (SFM perception. The feature extraction approach consists of three stages. First, we employ EMD to decompose nonstationary single-trial time series into narrowband components called intrinsic mode functions (IMFs with time scales dependent on the data. Second, we adopt unsupervised K-means clustering to group the IMFs and residues into several clusters across all trials and channels. Third, we use the supervised common spatial patterns (CSP approach to design spatial filters for the clustered spatiotemporal signals. We exploit the support vector machine (SVM classifier on the extracted features to decode the reported perception on a single-trial basis. We demonstrate that the CSP feature of the cluster in the gamma frequency band outperforms the features in other frequency bands and leads to the best decoding performance. We also show that the EMD-based feature extraction can be useful for evoked potential estimation. Our proposed feature extraction approach may have potential for many applications involving nonstationary multivariable time series such as brain-computer interfaces (BCI.

  17. Observing Exoplanets with High-dispersion Coronagraphy. II. Demonstration of an Active Single-mode Fiber Injection Unit

    Energy Technology Data Exchange (ETDEWEB)

    Mawet, D.; Ruane, G.; Xuan, W.; Echeverri, D.; Klimovich, N.; Randolph, M.; Fucik, J.; Wang, J.; Dekany, R.; Delorme, J.-R. [Department of Astronomy, California Institute of Technology, 1200 East California Boulevard, MC 249-17, Pasadena, CA 91125 (United States); Wallace, J. K.; Vasisht, G.; Mennesson, B.; Choquet, E.; Serabyn, E., E-mail: dmawet@astro.caltech.edu [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)

    2017-04-01

    High-dispersion coronagraphy (HDC) optimally combines high-contrast imaging techniques such as adaptive optics/wavefront control plus coronagraphy to high spectral resolution spectroscopy. HDC is a critical pathway toward fully characterizing exoplanet atmospheres across a broad range of masses from giant gaseous planets down to Earth-like planets. In addition to determining the molecular composition of exoplanet atmospheres, HDC also enables Doppler mapping of atmosphere inhomogeneities (temperature, clouds, wind), as well as precise measurements of exoplanet rotational velocities. Here, we demonstrate an innovative concept for injecting the directly imaged planet light into a single-mode fiber, linking a high-contrast adaptively corrected coronagraph to a high-resolution spectrograph (diffraction-limited or not). Our laboratory demonstration includes three key milestones: close-to-theoretical injection efficiency, accurate pointing and tracking, and on-fiber coherent modulation and speckle nulling of spurious starlight signal coupling into the fiber. Using the extreme modal selectivity of single-mode fibers, we also demonstrated speckle suppression gains that outperform conventional image-based speckle nulling by at least two orders of magnitude.

  18. Approaches to building single-stage AC/AC conversion switch-mode audio power amplifiers

    Energy Technology Data Exchange (ETDEWEB)

    Ljusev, P.; Andersen, Michael A.E.

    2005-07-01

    This paper discusses the possible topologies and promising approaches towards direct single-phase AC-AC conversion of the mains voltage for audio applications. When compared to standard Class-D switching audio power amplifiers with a separate power supply, it is expected that direct conversion will provide better efficiency and higher level of integration, leading to lower component count, volume and cost, but at the expense of a minor performance deterioration. (au)

  19. Imaging of dopamine transporters in rats using high-resolution pinhole single-photon emission tomography

    Energy Technology Data Exchange (ETDEWEB)

    Booij, Jan; Bruin, Kora de; Habraken, Jan B.A. [Department of Nuclear Medicine, F2N, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam (Netherlands); Voorn, Pieter [Department of Anatomy, Vrije Universiteit Medical Center, Amsterdam (Netherlands)

    2002-09-01

    To date, the vast majority of investigations on the dopaminergic system in small animals have been in vitro studies. In comparison with in vitro studies, single-photon emission tomography (SPET) or positron emission tomography (PET) imaging of the dopaminergic system in small animals has the advantage of permitting repeated studies within the same group of animals. Dopamine transporter imaging is a valuable non-invasive tool with which to investigate the integrity of dopaminergic neurons. The purpose of this study was to investigate the feasibility of assessing dopamine transporter density semi-quantitatively in rats using a recently developed high-resolution pinhole SPET system. This system was built exclusively for imaging of small animals. In this unique single-pinhole system, the animal rotates instead of the collimated detector. The system has proven to have a high spatial resolution. We performed SPET imaging with [{sup 123}I]FP-CIT to quantify striatal dopamine transporters in rat brain. In all seven studied control rats, symmetrical striatal binding to dopamine transporters was seen 2 h after injection of the radiotracer, with striatal-to-cerebellar binding ratios of approximately 3.5. In addition, test/retest variability of the striatal-to-cerebellar binding ratios was studied and found to be 14.5%. Finally, in unilaterally 6-hydroxydopamine-lesioned rats, striatal binding was only visible on the non-lesioned side. Quantitative analysis revealed that striatal-to-cerebellar SPET ratios were significantly lower on the lesioned (mean binding ratio 2.2{+-}0.2) than on the non-lesioned (mean ratio 3.1{+-}0.4) side. The preliminary results of this study indicate that semi-quantitative assessment of striatal dopamine transporter density using our recently developed high-resolution single-pinhole SPET system is feasible in living rat brain. (orig.)

  20. A Lifecycle Emissions Model (LEM): Lifecycle Emissions from Transportation Fuels, Motor Vehicles, Transportation Modes, Electricity Use, Heating and Cooking Fuels, and Materials

    OpenAIRE

    Delucchi, Mark

    2003-01-01

    This report documents changes to the methods and data in a recently revised version of the greenhouse-gas emissions model originally documented in Emissions of Greenhouse Gases from the Use of Transportation Fuels and Electricity, ANL/ESD/TM-22, Volumes 1 and 2, Center for Transportation Research, Argonne National Laboratory, Argonne (ANL), Illinois (DeLuchi, 1991, 1993). The revised Lifecycle Emissions Model (LEM) calculates energy use, air-pollutant emissions, and CO2-equivalent emissions o...

  1. Single-mode interband cascade laser sources for mid-infrared spectroscopic applications

    Science.gov (United States)

    Scheuermann, J.; von Edlinger, M.; Weih, R.; Becker, S.; Nähle, L.; Fischer, M.; Koeth, J.; Kamp, M.; Höfling, S.

    2016-05-01

    Compared to the near infrared, many technologically and industrially relevant gas species have more than an order of magnitude higher absorption features in the mid-infrared (MIR) wavelength range. These species include for example important hydrocarbons (methane, acetylene), nitrogen oxides and sulfur oxides. Tunable laser absorption spectroscopy (TLAS) has proven to be a versatile tool for gas sensing applications with significant advantages compared to other techniques. These advantages include real time measurement, standoff detection and ruggedness of the sensor. We present interband cascade lasers (ICLs), which have evolved into important laser sources for the MIR spectral range from 3 to 7 μm. ICLs achieve high efficiency by cascading optically active zones whilst using interband transitions, so they combine common diode laser as well as quantum cascade laser based technologies. Our application grade singlemode distributed feedback devices operate continuous wave at room temperature and are offering several features especially useful for high performance TLAS applications like: side mode suppression ratio of > 30 dB, continuous tuning ranges up to 30 nm, low threshold power densities and low overall power consumption. The devices are typically integrated in a thermoelectrically cooled TO-style package, hermetically sealed using a cap with anti-reflection coated window. This low power consumption as well as the compact size and ruggedness of the fabricated laser sources makes them perfectly suited for battery powered portable solutions for in field spectroscopy applications.

  2. High energy, single frequency, tunable laser source operating in burst mode for space based lidar applications

    Science.gov (United States)

    Cosentino, Alberto; Mondello, Alessia; Sapia, Adalberto; D'Ottavi, Alessandro; Brotini, Mauro; Nava, Enzo; Stucchi, Emanuele; Trespidi, Franco; Mariottini, Cristina; Wazen, Paul; Falletto, Nicolas; Fruit, Michel

    2017-11-01

    This paper describes the laser transmitter assembly used in the ALADIN instrument currently in C/D development phase for the ESA ADM-AEOLUS mission (EADS Astrium as prime contractor for the satellite and the instrument). The Laser Transmitter Assembly (TXA), based on a diode pumped tripled Nd:YAG laser, is used to generate tunable laser pulses of 150 mJ at a nominal wavelength of 355 nm. This laser is operated in burst mode, with a pulse repetition cycle of 100 Hz. The TXA is composed of the following units: a diodepumped CW Nd:YAG Laser named Reference Laser Head (RLH), used to inject a diode-pumped, Q-switched, amplified and frequency tripled Nd:YAG Laser working in the third harmonic referred as Power Laser Head (PLH) and a Transmitter Laser Electronics (TLE) containing all the control and power electronics needed for PLH and RLH operation. The TXA is made by an European consortium under the leadership of Galileo Avionica (It), and including CESI (It), Quantel (Fr), TESAT (Ge) and Thales (Fr).

  3. A Plasma Based OES-CRDS Dual-mode Portable Spectrometer for Trace Element Detection: Emission and Ringdown Measurements of Mercury

    Science.gov (United States)

    Sahay, Peeyush; Scherrer, Susan; Wang, Chuji

    2012-10-01

    Design and development of a plasma based optical emission spectroscopy-cavity ringdown spectroscopy (OES-CRDS) dual-mode portable spectrometer for in situ monitoring of trace elements is described. A microwave plasma torch (MPT) has been utilized, which serves both as an atomization and excitation source for the two modes, viz. OES and CRDS, of the spectrometer. Operation of both modes of the instrument is demonstrated with initial measurements of elemental mercury (Hg). A detection limit of 44 ng mL-1 for Hg at 253.65 nm was determined with the emission mode of the instrument. Severe radiation trapping of 253.65 nm line hampers the measurement of Hg in higher concentration region (> 50 μg ml-1). Therefore, a different wavelength, 365.01 nm, is suggested to measure Hg in that region. Ringdown measurements of the metastable 6s6p ^3P0 state of Hg in the plasma using a 404.65 nm palm size diode laser was conducted to demonstrate the CRDS mode of the instrument. Along with being portable, dual-mode, and self-calibrated, the instrument is capable of measuring a wide range of concentration ranging from sub ng mL-1 to several μg ml-1 for a number of elements.

  4. Examples of deletion of single component failure mode on fuelling machine hoist system

    International Nuclear Information System (INIS)

    Arthurs, D.L.

    1986-01-01

    Strachan and Henshaw AGR Fuelling Machine designs have previously used two completely independent hoist chains for reactor component handling. For Heysham II/Torness the concept has been extended to include the headshaft which carries the chain sprockets. The design described in the paper now includes a duplicate load path through all components from the chain/grab attachment through to the emergency headshaft brakes. The machine grab comprises a single main forged body with a very high load factor of safety. Studies are being undertaken to provide a second load path through the grab. (author)

  5. Displacement-enhanced entanglement distillation of single-mode-squeezed entangled states

    DEFF Research Database (Denmark)

    Tipsmark, Anders; Neergaard-Nielsen, Jonas Schou; Andersen, Ulrik Lund

    2013-01-01

    It has been shown that entanglement distillation of Gaussian entangled states by means of local photon subtraction can be improved by local Gaussian transformations. Here we show that a similar effect can be expected for the distillation of an asymmetric Gaussian entangled state that is produced...... by a single squeezed beam. We show that for low initial entanglement, our largely simplified protocol generates more entanglement than previous proposed protocols. Furthermore, we show that the distillation scheme also works efficiently on decohered entangled states as well as with a practical photon...

  6. The frequency of single-bicycle crashes (SBCs) in countries with varying bicycle mode shares

    DEFF Research Database (Denmark)

    Schepers, Paul; Agerholm, Niels; Amoros, Emmanuelle

    In  order  to  encourage  cycling,  we  need  to  reduce  the  hazards  that  cyclists  face. Single-bicycle crashes or ‘bicycle-only crashes’ are falls and obstacle collisions in which only one cyclist is involved. Between 60 and 95% of cyclists admitted to hospital or treated at an emergency...... department are victims of single-bicycle crashes. As proportion of the total number of traffic casualties  the  share  exceeds  20%  in  most  countries  with  medium  to  high  levels  of cycling.  This paper  discusses  the  prevalence  of  the  problem  and  describes  measures  that  may  both reduce...

  7. Characterization of performance-emission indices of a diesel engine using ANFIS operating in dual-fuel mode with LPG

    Science.gov (United States)

    Chakraborty, Amitav; Roy, Sumit; Banerjee, Rahul

    2018-03-01

    This experimental work highlights the inherent capability of an adaptive-neuro fuzzy inference system (ANFIS) based model to act as a robust system identification tool (SIT) in prognosticating the performance and emission parameters of an existing diesel engine running of diesel-LPG dual fuel mode. The developed model proved its adeptness by successfully harnessing the effects of the input parameters of load, injection duration and LPG energy share on output parameters of BSFCEQ, BTE, NOX, SOOT, CO and HC. Successive evaluation of the ANFIS model, revealed high levels of resemblance with the already forecasted ANN results for the same input parameters and it was evident that similar to ANN, ANFIS also has the innate ability to act as a robust SIT. The ANFIS predicted data harmonized the experimental data with high overall accuracy. The correlation coefficient (R) values are stretched in between 0.99207 to 0.999988. The mean absolute percentage error (MAPE) tallies were recorded in the range of 0.02-0.173% with the root mean square errors (RMSE) in acceptable margins. Hence the developed model is capable of emulating the actual engine parameters with commendable ranges of accuracy, which in turn would act as a robust prediction platform in the future domains of optimization.

  8. Enhancement of single particle rare earth doped NaYF4: Yb, Er emission with a gold shell

    International Nuclear Information System (INIS)

    Li, Ling; Green, Kory; Hallen, Hans; Lim, Shuang Fang

    2015-01-01

    Upconversion of infrared light to visible light has important implications for bioimaging. However, the small absorption cross-section of rare earth dopants has limited the efficiency of these anti-Stokes nanomaterials. We present enhanced excitation absorption and single particle fluorescent emission of sodium yttrium fluoride, NaYF 4 : Yb, Er based upconverting nanoparticles coated with a gold nanoshell through surface plasmon resonance. The single gold-shell coated nanoparticles show enhanced absorption in the near infrared, enhanced total emission intensity, and increased green relative to red emission. We also show differences in enhancement between single and aggregated gold shell nanoparticles. The surface plasmon resonance of the gold-shell coated nanoparticle is shown to be dependent on the shell thickness. In contrast to other reported results, our single particle experimental observations are corroborated by finite element calculations that show where the green/red emission enhancement occurs, and what portion of the enhancement is due to electromagnetic effects. We find that the excitation enhancement and green/red emission ratio enhancement occurs at the corners and edges of the doped emissive core. (paper)

  9. Decay modes of high-lying single-particle states in [sup 209]Pb

    Energy Technology Data Exchange (ETDEWEB)

    Beaumel, D.; Fortier, S.; Gales, S.; Guillot, J.; Langevin-Joliot, H.; Laurent, H.; Maison, J.M.; Vernotte, J.; Bordewijk, J.A.; Brandenburg, S.; Krasznahorkay, A.; Crawley, G.M.; Massolo, C.P.; Renteria, M. (Institut de Physique Nucleaire, Institut National de Physique Nucleaire et de Physique des Particules Centre National de la Recherche Scientifique, 91406 Orsay Cedex (France) Kernfysisch Versneller Instituut, 9747AA Groningen (Netherlands) National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824 (United States) Departamento de Fisica, Fac. Cs. Exactas, Universidad Nacional de La Plata, CC No. 67, 1900 La Plata (Argentina))

    1994-05-01

    The neutron decay of high-lying single-particle states in [sup 209]Pb excited by means of the ([alpha],[sup 3]He) reaction has been investigated at 122 MeV incident energy using a multidetector array. The high spin values of these states, inferred from previous inclusive experiments, are confirmed by the present data involving angular correlation measurements and the determination of branching ratios to low lying levels in [sup 208]Pb. The structure located between 8.5 and 12 MeV excitation energy in [sup 209]Pb displays large departures from a pure statistical decay with significant direct feeding of the low-lying collective states (3[sup [minus

  10. Decay modes of high-lying single-particle states in 209Pb

    International Nuclear Information System (INIS)

    Beaumel, D.; Fortier, S.; Gales, S.; Guillot, J.; Crawley, G.M.; Massolo, C.P.; Renteria, M.

    1993-01-01

    The neutron decay of high-lying single-particle states in 209 Pb excited by means of the (α, 3 He) reaction has been investigated at 122 MeV incident energy using the multidetector array EDEN. The high spin values of these states, inferred from previous inclusive experiments, are confirmed by the present data involving angular correlation measurements and the determination of branching ratios to low lying levels in 208 Pb. The structure located between 8.5 and 12 MeV excitation energy in 209 Pb displays large departures from a pure statistical decay with significant direct feeding of the low-lying collective states (3 - ,5 - ) of 208 Pb. At higher excitation energy up to 20 MeV, the measured neutron decay is in agreement with the predictions of the statistical model. (authors). 24 refs., 16 figs., 2 tabs

  11. Depression following intracerebral hemorrhage and the evaluation of cerebral blood flow by single photon emission tomography

    International Nuclear Information System (INIS)

    Masada, Tetsuya; Makabe, Tetsuo; Kunishio, Katsuzo; Matsumoto, Akira

    2007-01-01

    The authors studied patients who presented depression and apathy following intracerebral hemorrhage (ICH). Twelve patients who were admitted in our hospital were divided into two groups according to the presence of post-stroke depression (PSD). Five patients with PSD are in group A, and another seven patients without PSD are in group B. Zung-self depression scale (SDS) and apathy scale were used for screening of depression and apathy. PSD was recognized in 5 (42%) of patients following ICH. Single photon emission tomography (SPECT) suggested the reduction of cerebral blood flow (CBF) in the frontal lobe in all patients of the group A (100%), whereas only 29% of patients of the group B. The reduction of CBF in the frontal lobe might be involved in the mechanism of depression following ICH in subacute stage. (author)

  12. Brain perfusion single photon emission computed tomography in major psychiatric disorders: From basics to clinical practice

    International Nuclear Information System (INIS)

    Santra, Amburanjan; Kumar, Rakesh

    2014-01-01

    Brain single photon emission computed tomography (SPECT) is a well-established and reliable method to assess brain function through measurement of regional cerebral blood flow (rCBF). It can be used to define a patient's pathophysiological status when neurological or psychiatric symptoms cannot be explained by anatomical neuroimaging findings. Though there is ample evidence validating brain SPECT as a technique to track human behavior and correlating psychiatric disorders with dysfunction of specific brain regions, only few psychiatrists have adopted brain SPECT in routine clinical practice. It can be utilized to evaluate the involvement of brain regions in a particular patient, to individualize treatment on basis of SPECT findings, to monitor the treatment response and modify treatment, if necessary. In this article, we have reviewed the available studies in this regard from existing literature and tried to present the evidence for establishing the clinical role of brain SPECT in major psychiatric illnesses

  13. Thallium-201 myocardial imaging with single photon emission CT in Kawasaki disease

    International Nuclear Information System (INIS)

    Matsumoto, Syuhei

    1992-01-01

    Seventy-five patients with Kawasaki disease underwent single photon emission computed tomography (SPECT) and planar imaging with thallium-201 after dipyridamole in order to evaluate the usefulness of detecting the complication of coronary artery disease (CAD). The results of SPECT with a three reconstruction imaging study (short axis, vertical long axis, horizontal long axis) and of planar imaging study with thallium-201 were compared with coronary angiography. The overall sensitivity of detecting CAD was 86.7% with SPECT and 66.7% with planar imaging. The sensitivity in identifying individual vessels was 76.0% with SPECT and 44.0% with planar imaging. SPECT was especially superior to planar imaging in detecting localized stenosis. (53.8% vs 15.4%) The specificity of SPECT did not differ from the planar imaging study. Dipyridamole thallium-201 SPECT is a useful non-invasive method to detect CAD due to Kawasaki disease. (author)

  14. Single excitation-emission fluorescence spectrum (EEF) for determination of cetane improver in diesel fuel.

    Science.gov (United States)

    Insausti, Matías; Fernández Band, Beatriz S

    2015-04-05

    A highly sensitive spectrofluorimetric method has been developed for the determination of 2-ethylhexyl nitrate in diesel fuel. Usually, this compound is used as an additive in order to improve cetane number. The analytical method consists in building the chemometric model as a first step. Then, it is possible to quantify the analyte with only recording a single excitation-emission fluorescence spectrum (EEF), whose data are introduced in the chemometric model above mentioned. Another important characteristic of this method is that the fuel sample was used without any pre-treatment for EEF. This work provides an interest improvement to fluorescence techniques using the rapid and easily applicable EEF approach to analyze such complex matrices. Exploding EEF was the key to a successful determination, obtaining a detection limit of 0.00434% (v/v) and a limit of quantification of 0.01446% (v/v). Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Brain perfusion single photon emission computed tomography in children after acute encephalopathy

    International Nuclear Information System (INIS)

    Kurihara, Mana; Nakae, Yoichiro; Kohagizawa, Toshitaka; Eto, Yoshikatsu

    2005-01-01

    We studied single photon emission computed tomography (SPECT) of 15 children with acute encephalopathy after more than 1 year from the onset, using technetium-99 m-L, L-ethyl cystinate dimer ( 99m Tc-ECD) and a three-dementional stereotaxic region of interest template. Regional cerebral blood flow was evaluated and divided in three groups according to the severity of disability: absent or mild, moderate, and severe. There was no abnormality on SPECT in the patients without disability or with mild disability. Diffuse hypoperfusion was shown in the groups with moderate and severe disability. The patients with severe disability showed hypoperfusion in the pericallosal, frontal and central areas which was more pronounced than in the patients with moderate disability. (author)

  16. Hot water epilepsy: Phenotype and single photon emission computed tomography observations

    Directory of Open Access Journals (Sweden)

    Mehul Patel

    2014-01-01

    Full Text Available We studied the anatomical correlates of reflex hot water epilepsy (HWE using multimodality investigations viz. magnetic resonance imaging (MRI, electroencephalography (EEG, and single photon emission computed tomography (SPECT. Five men (mean age: 27.0 ΁ 5.8 years with HWE were subjected to MRI of brain, video-EEG studies, and SPECT scan. These were correlated with phenotypic presentations. Seizures could be precipitated in three patients with pouring of hot water over the head and semiology of seizures was suggestive of temporal lobe epilepsy. Ictal SPECT showed hyperperfusion in: left medial temporal - one, left lateral temporal - one, and right parietal - one. Interictal SPECT was normal in all five patients and did not help in localization. MRI and interictal EEG was normal in all the patients. The clinical and SPECT studies suggested temporal lobe as the seizure onset zone in some of the patients with HWE.

  17. Single-photon emission computed tomography in human immunodeficiency virus encephalopathy: A preliminary report

    International Nuclear Information System (INIS)

    Masdeu, J.C.; Yudd, A.; Van Heertum, R.L.; Grundman, M.; Hriso, E.; O'Connell, R.A.; Luck, D.; Camli, U.; King, L.N.

    1991-01-01

    Depression or psychosis in a previously asymptomatic individual infected with the human immunodeficiency virus (HIV) may be psychogenic, related to brain involvement by the HIV or both. Although prognosis and treatment differ depending on etiology, computed tomography (CT) and magnetic resonance imaging (MRI) are usually unrevealing in early HIV encephalopathy and therefore cannot differentiate it from psychogenic conditions. Thirty of 32 patients (94%) with HIV encephalopathy had single-photon emission computed tomography (SPECT) findings that differed from the findings in 15 patients with non-HIV psychoses and 6 controls. SPECT showed multifocal cortical and subcortical areas of hypoperfusion. In 4 cases, cognitive improvement after 6-8 weeks of zidovudine (AZT) therapy was reflected in amelioration of SPECT findings. CT remained unchanged. SPECT may be a useful technique for the evaluation of HIV encephalopathy

  18. Statistical evaluation of single-photon emission computed tomography image using smoothed bootstrap method

    International Nuclear Information System (INIS)

    Tsukamoto, Megumi; Hatabu, Asuka; Takahashi, Yoshitake; Matsuda, Hiroshi; Okamoto, Kousuke; Yamashita, Noriyuki; Takagi, Tatsuya

    2013-01-01

    Many of the neurodegenerative diseases associated with a decrease in regional cerebral blood flow (rCBF) are untreatable, and the appropriate therapeutic strategy is to slow the progression of the disease. Therefore, it is important that a definitive diagnosis is made as soon as possible when such diseases are suspected. Diagnostic imaging methods, such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT), play an important role in such a definitive diagnosis. Since several problems arise when evaluating these images visually, a procedure to evaluate them objectively is necessary, and studies of image analyses using statistical evaluations have been suggested. However, the assumed data distribution in a statistical procedure may occasionally be inappropriate. Therefore, to evaluate the decrease of rCBF, it is important to use a statistical procedure without assumptions about the data distribution. In this study, we propose a new procedure that uses nonparametric or smoothed bootstrap methods to calculate a standardized distribution of the Z-score without assumptions about the data distribution. To test whether the judgment of the proposed procedure is equivalent to that of an evaluation based on the Z-score with a fixed threshold, the procedure was applied to a sample data set whose size was large enough to be appropriate for the assumption of the Z-score. As a result, the evaluations of the proposed procedure were equivalent to that of an evaluation based on the Z-score. (author)

  19. Simulation of the single-vibronic-level emission spectrum of HPS.

    Science.gov (United States)

    Mok, Daniel K W; Lee, Edmond P F; Chau, Foo-tim; Dyke, John M

    2014-05-21

    We have computed the potential energy surfaces of the X¹A' and ùA" states of HPS using the explicitly correlated multi-reference configuration interaction (MRCI-F12) method, and Franck-Condon factors between the two states, which include anharmonicity and Duschinsky rotation, with the aim of testing the assignment of the recently reported single-vibronic-level (SVL) emission spectrum of HPS [R. Grimminger, D. J. Clouthier, R. Tarroni, Z. Wang, and T. J. Sears, J. Chem. Phys. 139, 174306 (2013)]. These are the highest level calculations on these states yet reported. It is concluded that our spectral simulation supports the assignments of the molecular carrier, the electronic states involved and the vibrational structure of the experimental laser induced fluorescence, and SVL emission spectra proposed by Grimminger et al. [J. Chem. Phys. 139, 174306 (2013)]. However, there remain questions unanswered regarding the relative electronic energies of the two states and the geometry of the excited state of HPS.

  20. Cone beam tomography of the heart using single-photon emission-computed tomography

    International Nuclear Information System (INIS)

    Gullberg, G.T.; Christian, P.E.; Zeng, G.L.; Datz, F.L.; Morgan, H.T.

    1991-01-01

    The authors evaluated cone beam single-photon emission-computed tomography (SPECT) of the heart. A new cone beam reconstruction algorithm was used to reconstruct data collected from short scan acquisitions (of slightly more than 180 degrees) of a detector anteriorally traversing a noncircular orbit. The less than 360 degrees acquisition was used to minimize the attenuation artifacts that result from reconstructing posterior projections of 201T1 emissions from the heart. The algorithm includes a new method for reconstructing truncated projections of background tissue activity that eliminates reconstruction ring artifacts. Phantom and patient results are presented which compare a high-resolution cone beam collimator (50-cm focal length; 6.0-mm full width at half maximum [FWHM] at 10 cm) to a low-energy general purpose (LEGP) parallel hole collimator (8.2-mm FWHM at 10 cm) which is 1.33 times more sensitive. The cone beam tomographic results are free of reconstruction artifacts and show improved spatial and contrast resolution over that obtained with the LEGP parallel hole collimator. The limited angular sampling restrictions and truncation problems associated with cone beam tomography do not deter from obtaining diagnostic information. However, even though these preliminary results are encouraging, a thorough clinical study is still needed to investigate the specificity and sensitivity of cone beam tomography

  1. Removal of Muscle Artifacts from Single-Channel EEG Based on Ensemble Empirical Mode Decomposition and Multiset Canonical Correlation Analysis

    Directory of Open Access Journals (Sweden)

    Xun Chen

    2014-01-01

    Full Text Available Electroencephalogram (EEG recordings are often contaminated with muscle artifacts. This disturbing muscular activity strongly affects the visual analysis of EEG and impairs the results of EEG signal processing such as brain connectivity analysis. If multichannel EEG recordings are available, then there exist a considerable range of methods which can remove or to some extent suppress the distorting effect of such artifacts. Yet to our knowledge, there is no existing means to remove muscle artifacts from single-channel EEG recordings. Moreover, considering the recently increasing need for biomedical signal processing in ambulatory situations, it is crucially important to develop single-channel techniques. In this work, we propose a simple, yet effective method to achieve the muscle artifact removal from single-channel EEG, by combining ensemble empirical mode decomposition (EEMD with multiset canonical correlation analysis (MCCA. We demonstrate the performance of the proposed method through numerical simulations and application to real EEG recordings contaminated with muscle artifacts. The proposed method can successfully remove muscle artifacts without altering the recorded underlying EEG activity. It is a promising tool for real-world biomedical signal processing applications.

  2. A dual-mode single-molecule fluorescence assay for the detection of expanded CGG repeats in Fragile X syndrome.

    Science.gov (United States)

    Cannon, Brian; Pan, Cynthia; Chen, Liangjing; Hadd, Andrew G; Russell, Rick

    2013-01-01

    Fragile X syndrome is the leading cause of inherited mental impairment and is associated with expansions of CGG repeats within the FMR1 gene. To detect expanded CGG repeats, we developed a dual-mode single-molecule fluorescence assay that allows acquisition of two parallel, independent measures of repeat number based on (1) the number of Cy3-labeled probes bound to the repeat region and (2) the physical length of the electric field-linearized repeat region, obtained from the relative position of a single Cy5 dye near the end of the repeat region. Using target strands derived from cell-line DNA with defined numbers of CGG repeats, we show that this assay can rapidly and simultaneously measure the repeats of a collection of individual sample strands within a single field of view. With a low occurrence of false positives, the assay differentiated normal CGG repeat lengths (CGG( N ), N = 23) and expanded CGG repeat lengths (CGG( N ), N = 118), representing a premutation disease state. Further, mixtures of these DNAs gave results that correlated with their relative populations. This strategy may be useful for identifying heterozygosity or for screening collections of individuals, and it is readily adaptable for screening other repeat disorders.

  3. Sensor system for multi-point monitoring using bending loss of single mode optical fiber

    International Nuclear Information System (INIS)

    Kim, Heon Young; Kim, Dae Hyun

    2015-01-01

    Applications of smart sensors have been extended to safety systems in the aerospace, transportation and civil engineering fields. In particular, structural health monitoring techniques using smart sensors have gradually become necessary and have been developed to prevent dangers to human life and damage to assets. Generally, smart sensors are based on electro-magnets and have several weaknesses, including electro-magnetic interference and distortion. Therefore, fiber optic sensors are an outstanding alternative to overcome the weaknesses of electro-magnetic sensors. However, they require expensive devices and complex systems. This paper proposes a new, affordable and simple sensor system that uses a single fiber to monitor pressures at multiple-points. Moreover, a prototype of the sensor system was manufactured and tested for a feasibility study. Based on the results of this experimental test, a relationship was carefully observed between the bend loss conditions and light-intensity. As a result, it was shown that impacts at multiple-points could be monitored.

  4. Whispering Gallery mode ESR spectroscopy and parameters measurement in single crystal SrLaAlO4at millikelvin temperature.

    Science.gov (United States)

    Hosain, M A; Le Floch, J-M; Krupka, J; Tobar, M E

    2017-08-01

    A cylindrical single crystal SrLaAlO 4 Whispering Gallery mode dielectric resonator was cooled to millikelvin temperature using a dilution refrigerator. By controlling a DC-magnetic field, impurity ions' spins were coupled to a variety of modes allowing the measurement of hybrid spin-photon systems. This Electron Spin Resonance mapping technique allowed us to detect Cu 2+ ,Fe 3+ and Mn 4+ impurity ions (at the level of parts per million (ppm) to parts per billion (ppb)), verified by the measurement of the spin parameters along with their site symmetry. Whispering Gallery modes exhibited Q-factors ⩾10 5 at a temperature less than 20mK, allowing sensitive spectroscopy with high precision. Measured hyperfine line constants of the Cu 2+ ion shows different parallel g-factors, g ‖Cu , of 2.526,2.375,2.246 and 2.142. The spin-orbit coupling constant of the Cu 2+ ion was determined to be λ≃-635cm -1 . The low-spin state Fe 3+ ion's measured parallel g-factor, g ‖Fe , of 2.028 reveals tetragonal anisotropy. The Mn 4+ ion is identified in the lattice, producing hyperfine structure with high-valued g-factors,g ‖Mn , of 7.789,7.745,7.688,7.613,7.5304 and 7.446. The hyperfine structures of the Cu 2+ and Mn 4+ ions show broadening of about 79G between 9.072GHz and 10.631GHz, and 24.5G broadening between 9.072GHz and 14.871GHz, respectively. Copyright © 2017 Elsevier Inc. All rights reserved.

  5. Modeling satellite-Earth quantum channel downlinks with adaptive-optics coupling to single-mode fibers

    Science.gov (United States)

    Gruneisen, Mark T.; Flanagan, Michael B.; Sickmiller, Brett A.

    2017-12-01

    The efficient coupling of photons from a free-space quantum channel into a single-mode optical fiber (SMF) has important implications for quantum network concepts involving SMF interfaces to quantum detectors, atomic systems, integrated photonics, and direct coupling to a fiber network. Propagation through atmospheric turbulence, however, leads to wavefront errors that degrade mode matching with SMFs. In a free-space quantum channel, this leads to photon losses in proportion to the severity of the aberration. This is particularly problematic for satellite-Earth quantum channels, where atmospheric turbulence can lead to significant wavefront errors. This report considers propagation from low-Earth orbit to a terrestrial ground station and evaluates the efficiency with which photons couple either through a circular field stop or into an SMF situated in the focal plane of the optical receiver. The effects of atmospheric turbulence on the quantum channel are calculated numerically and quantified through the quantum bit error rate and secure key generation rates in a decoy-state BB84 protocol. Numerical simulations include the statistical nature of Kolmogorov turbulence, sky radiance, and an adaptive-optics system under closed-loop control.

  6. A Simple Differential Mode EMI Suppressor for the LLCL-Filter-Based Single-Phase Grid-Tied Transformerless Inverter

    DEFF Research Database (Denmark)

    Ji, Junhao; Wu, Weimin; He, Yuanbin

    2015-01-01

    The single-phase power converter topologies evolving of photovoltaic applications are still including passive filters, like the LCLor LLCL-filter. Compared with the LCL-filter, the total inductance of the LLCL-filter can be reduced a lot. However, due to the resonant inductor in series...... with the bypass capacitor, the differential mode (DM) electromagnetic interference (EMI) noise attenuation of an LLCL-filter-based grid-tied inverter declines. Conventionally, a capacitor was inserted in parallel with the LC resonant circuit branch of the LLCL-filter to suppress the DM EMI noise. In order...... to achieve a small value of capacitor as well as to minimize the additional reactive power, a novel simple DM EMI suppressor for the LLCL-filter-based system is proposed. The characters of two kinds of DM EMI suppressor are analyzed and compared in detail. Simulations and experiments on a 0.5-kW 110-V/50-Hz...

  7. Transmission of 2.5 Gbit/s Spectrum-sliced WDM System for 50 km Single-mode Fiber

    Science.gov (United States)

    Ahmed, Nasim; Aljunid, Sayed Alwee; Ahmad, R. Badlisha; Fadil, Hilal Adnan; Rashid, Mohd Abdur

    2011-06-01

    The transmission of a spectrum-sliced WDM channel at 2.5 Gbit/s for 50 km of single mode fiber using an system channel spacing only 0.4 nm is reported. We have investigated the system performance using NRZ modulation format. The proposed system is compared with conventional system. The system performance is characterized as the bit-error-rate (BER) received against the system bit rates. Simulation results show that the NRZ modulation format performs well for 2.5 Gbit/s system bit rates. Using this narrow channel spectrum-sliced technique, the total number of multiplexed channels can be increased greatly in WDM system. Therefore, 0.4 nm channel spacing spectrum-sliced WDM system is highly recommended for the long distance optical access networks, like the Metro Area Network (MAN), Fiber-to-the-Building (FTTB) and Fiber-to-the-Home (FTTH).

  8. Statistical properties of single-mode fiber coupling of satellite-to-ground laser links partially corrected by adaptive optics.

    Science.gov (United States)

    Canuet, Lucien; Védrenne, Nicolas; Conan, Jean-Marc; Petit, Cyril; Artaud, Geraldine; Rissons, Angelique; Lacan, Jerome

    2018-01-01

    In the framework of satellite-to-ground laser downlinks, an analytical model describing the variations of the instantaneous coupled flux into a single-mode fiber after correction of the incoming wavefront by partial adaptive optics (AO) is presented. Expressions for the probability density function and the cumulative distribution function as well as for the average fading duration and fading duration distribution of the corrected coupled flux are given. These results are of prime interest for the computation of metrics related to coded transmissions over correlated channels, and they are confronted by end-to-end wave-optics simulations in the case of a geosynchronous satellite (GEO)-to-ground and a low earth orbit satellite (LEO)-to-ground scenario. Eventually, the impact of different AO performances on the aforementioned fading duration distribution is analytically investigated for both scenarios.

  9. ANALYTICAL EXPRESSION FOR THE ELECTRIC FIELD OF THE SINGLE MODE LASER HOMOGENEOUS BROADENING IN THE PULSE REGIME

    Directory of Open Access Journals (Sweden)

    S. Ayadi

    2015-07-01

    Full Text Available The simplest model of the laser is that of a single mode system homogenously broadened. The dynamical behavior of this laser is described by three differential equations, called Haken-Lorenz equations[1],  similar to the Lorenz model [1] already known to predict deterministic chaos. In previous recent work [5-7] we have proposed a simple harmonic expansion method to obtain a series of harmonics terms that yield analytical solutions to the laser equations. ¶This method allows us to derive an analytical expression of the laser field amplitude  when this last  undergoes a  periodic oscillations around zero mean value. We also obtain an analytical expression of the pulsing frequency.

  10. High-temperature sensor based on an abrupt-taper Michelson interferometer in single-mode fiber.

    Science.gov (United States)

    Xu, Le; Jiang, Lan; Wang, Sumei; Li, Benye; Lu, Yongfeng

    2013-04-01

    This study proposes a high-temperature sensor based on an abrupt fiber-taper Michelson interferometer (FTMI) in single-mode fiber fabricated by a fiber-taper machine and electric-arc discharge. The proposed FTMI is applied to measure temperature and refractive index (RI). A high temperature sensitivity of 118.6 pm/°C is obtained in the temperature range of 500°C-800°C. The wavelength variation is only -0.335 nm for the maximum attenuation peak, with the external RI changed from 1.333 to 1.3902, which is desirable for high-temperature sensing to eliminate the cross sensitivity to RI.

  11. Analytical study of nonlinear phase shift through stimulated Brillouin scattering in single mode fiber with the pump power recycling technique

    International Nuclear Information System (INIS)

    Al-Asadi, H A; Mahdi, M A; Bakar, A A A; Adikan, F R Mahamd

    2011-01-01

    We present a theoretical study of nonlinear phase shift through stimulated Brillouin scattering in single mode optical fiber. Analytical expressions describing the nonlinear phase shift for the pump and Stokes waves in the pump power recycling technique have been derived. The dependence of the nonlinear phase shift on the optical fiber length, the reflectivity of the optical mirror and the frequency detuning coefficient have been analyzed for different input pump power values. We found that with the recycling pump technique, the nonlinear phase shift due to stimulated Brillouin scattering reduced to less than 0.1 rad for 5 km optical fiber length and 0.65 reflectivity of the optical mirror, respectively, at an input pump power equal to 30 mW

  12. Efficient selection of a single harmonic emission using a multi-color laser field with an aperture-iris diaphragm

    Science.gov (United States)

    Wei, Pengfei; Tian, Qili; Zeng, Zhinan; Jiang, Jiaming; Miao, Jing; Zheng, Yinghui; Ge, Xiaochun; Li, Chuang; Li, Ruxin; Xu, Zhizhan

    2014-08-01

    The efficient selection of an almost pure single harmonic emission (the 14th harmonic at 57 nm) from the harmonic comb has been experimentally achieved in an argon gas cell using a multi-color laser field with an aperture-iris diaphragm. When compared with the non-diaphragm case, the purity of the selected single harmonic emission (i.e. the contrast ratio) in the case of using the aperture-iris diaphragm is dramatically increased by approximately order of magnitude. Therefore, the modification of the multi-color laser field by using such an aperture-iris diaphragm before focusing is demonstrated to be an effective way of improving the phase-matching conditions for selective enhancement of the single harmonic emission.

  13. Efficient selection of a single harmonic emission using a multi-color laser field with an aperture-iris diaphragm

    International Nuclear Information System (INIS)

    Wei, Pengfei; Tian, Qili; Zeng, Zhinan; Jiang, Jiaming; Miao, Jing; Zheng, Yinghui; Ge, Xiaochun; Li, Chuang; Li, Ruxin; Xu, Zhizhan

    2014-01-01

    The efficient selection of an almost pure single harmonic emission (the 14th harmonic at 57 nm) from the harmonic comb has been experimentally achieved in an argon gas cell using a multi-color laser field with an aperture-iris diaphragm. When compared with the non-diaphragm case, the purity of the selected single harmonic emission (i.e. the contrast ratio) in the case of using the aperture-iris diaphragm is dramatically increased by approximately order of magnitude. Therefore, the modification of the multi-color laser field by using such an aperture-iris diaphragm before focusing is demonstrated to be an effective way of improving the phase-matching conditions for selective enhancement of the single harmonic emission. (paper)

  14. Single Spatial-Mode Room-Temperature-Operated 3.0 to 3.4 micrometer Diode Lasers

    Science.gov (United States)

    Frez, Clifford F.; Soibel, Alexander; Belenky, Gregory; Shterengas, Leon; Kipshidze, Gela

    2010-01-01

    Compact, highly efficient, 3.0 to 3.4 m light emitters are in demand for spectroscopic analysis and identification of chemical substances (including methane and formaldehyde), infrared countermeasures technologies, and development of advanced infrared scene projectors. The need for these light emitters can be currently addressed either by bulky solid-state light emitters with limited power conversion efficiency, or cooled Interband Cascade (IC) semiconductor lasers. Researchers here have developed a breakthrough approach to fabrication of diode mid-IR lasers that have several advantages over IC lasers used for the Mars 2009 mission. This breakthrough is due to a novel design utilizing the strain-engineered quantum-well (QW) active region and quinternary barriers, and due to optimization of device material composition and growth conditions (growth temperatures and rates). However, in their present form, these GaSb-based laser diodes cannot be directly used as a part of sensor systems. The device spectrum is too broad to perform spectroscopic analysis of gas species, and operating currents and voltages are too high. In the current work, the emitters were fabricated as narrow-ridge waveguide index-guided lasers rather than broad stripe-gain guided multimode Fabry-Perot (FP) lasers as was done previously. These narrow-ridge waveguide mid-IR lasers exhibit much lower power consumptions, and can operate in a single spatial mode that is necessary for demonstration of single-mode distributed feedback (DBF) devices for spectroscopic applications. These lasers will enable a new generation of compact, tunable diode laser spectrometers with lower power consumption, reduced complexity, and significantly reduced development costs. These lasers can be used for the detection of HCN, C2H2, methane, and ethane.

  15. Pinhole single-photon emission tomography reconstruction based on median root prior

    International Nuclear Information System (INIS)

    Sohlberg, Antti; Kuikka, Jyrki T.; Ruotsalainen, Ulla

    2003-01-01

    The maximum likelihood expectation maximisation (ML-EM) algorithm can be used to reduce reconstruction artefacts produced by filtered backprojection (FBP) methods in pinhole single-photon emission tomography (SPET). However, ML-EM suffers from noise propagation along iterations, which leads to quantitatively unpleasant reconstruction results. To avoid this increase in noise, the median root prior (MRP) algorithm for pinhole SPET was implemented. Projection data of a line source and Picker's thyroid phantom were collected using a single-head gamma camera with a pinhole collimator. MRP was added to existing pinhole ML-EM reconstruction algorithm and the phantom studies were reconstructed using MRP, ML-EM and FBP for comparison. Coefficients of variation, contrasts and full-widths at half-maximum were calculated and showed a clear reduction in noise without significant loss of resolution or decrease in contrast when MRP was applied. MRP also produced visually pleasing images even with high iteration numbers, free of the checkerboard-type noise patterns which are typical of ML-EM images. (orig.)

  16. Quantitation of postexercise lung thallium-201 uptake during single photon emission computed tomography

    International Nuclear Information System (INIS)

    Kahn, J.K.; Carry, M.M.; McGhie, I.; Pippin, J.J.; Akers, M.S.; Corbett, J.R.

    1989-01-01

    To test the hypothesis that analysis of lung thallium uptake measured during single photon emission computed tomography (SPECT) yields supplementary clinical information as reported for planar imaging, quantitative analysis of lung thallium uptake following maximal exercise was performed in 40 clinically normal subjects (Group 1) and 15 angiographically normal subjects (Group 2). Lung thallium uptake was measured from anterior projection images using a ratio of heart-to-lung activities. Seventy subjects with coronary artery disease (CAD) (Group 3) determined by angiography (greater than or equal to 70% luminal stenosis) underwent thallium perfusion SPECT. Thirty-nine percent of these subjects had multivessel and 61% had single vessel CAD. Lung thallium uptake was elevated in 47 of 70 (67%) Group 3 subjects. Group 3 subjects with elevated lung thallium uptake did not differ from Group 3 subjects with normal lung thallium uptake with respect to extent or distribution of coronary artery disease, left ventricular function, or severity of myocardial ischemia as determined by exercise and redistribution thallium SPECT. Thus, the measurement of thallium lung uptake from anterior projection images obtained during SPECT frequently identifies patients with CAD, but it may not provide supplementary information regarding the extent of myocardial ischemia or ventricular dysfunction

  17. The role of single photon emission computed tomography in bone imaging.

    Science.gov (United States)

    Sarikaya, I; Sarikaya, A; Holder, L E

    2001-01-01

    Single photon emission computed tomography (SPECT) of the bone is the second most frequently performed SPECT examination in routine nuclear medicine practice, with cardiac SPECT being the most frequent. Compared with planar scintigraphy, SPECT increases image contrast and improves lesion detection and localization. Studies have documented the unique diagnostic information provided by SPECT, particularly for avascular necrosis of the femoral head, in patients with back pain, for the differential diagnosis between malignant and benign spinal lesions, in the detection of metastatic cancer in the spine, for the diagnosis of temporomandibular joint internal derangement, and for the evaluation of acute and chronic knee pain. Although less rigorously documented, SPECT is being increasingly used in all types of situations that demand more precise anatomic localization of abnormal tracer uptake. The effectiveness of bone SPECT increases with the selection of the proper collimator, which allows one to acquire adequate counts and minimize the patient-to-detector distance. Low-energy, ultrahigh-resolution or high-resolution collimation is preferred over all-purpose collimators. Multihead gamma cameras can increase the counts obtained or shorten acquisition time, making SPECT acquisitions more practical in busy departments and also increasing image quality compared with single-head cameras. Iterative reconstruction, with the use of ordered subsets estimation maximization, provides better quality images than classical filtered back projection algorithms. Three-dimensional image analysis often aids lesion localization.

  18. Nonlinear Phenomena in the Single-Mode Dynamics in an AFM Cantilever Beam

    KAUST Repository

    Ruzziconi, Laura

    2016-12-05

    This study deals with the nonlinear dynamics arising in an atomic force microscope cantilever beam. After analyzing the static behavior, a single degree of freedom Galerkin reduced order model is introduced, which describes the overall scenario of the structure response in a neighborhood of the primary resonance. Extensive numerical simulations are performed when both the forcing amplitude and frequency are varied, ranging from low up to elevated excitations. The coexistence of competing attractors with different characteristics is analyzed. Both the non-resonant and the resonant behavior are observed, as well as ranges of inevitable escape. Versatility of behavior is highlighted, which may be attractive in applications. Special attention is devoted to the effects of the tip-sample separation distance, since this aspect is of fundamental importance to understand the operation of an AFM. We explore the metamorphoses of the multistability region when the tip-sample separation distance is varied. To have a complete description of the AFM response, comprehensive behavior charts are introduced to detect the theoretical boundaries of appearance and disappearance of the main attractors. Also, extensive numerical simulations investigate the AFM response when both the forcing amplitude and the tip-sample separation distance are considered as control parameters. The main features are analyzed in detail and the obtained results are interpreted in terms of oscillations of the cantilever-tip ensemble. However, we note that all the aforementioned results represent the limit when disturbances are absent, which never occurs in practice. Here comes the importance of overcoming local investigations and exploring dynamics from a global perspective, by introducing dynamical integrity concepts. To extend the AFM results to the practical case where disturbances exist, we develop a dynamical integrity analysis. After performing a systematic basin of attraction analysis, integrity

  19. Sequential Growth of Uniform β-NaYF4@β-NaLnF4 (Ln = Y, Lu, Yb Microcrystals with Luminescent Properties of Multicolor Tuning and Dual-Mode Emission

    Directory of Open Access Journals (Sweden)

    Dandan Ju

    2017-12-01

    Full Text Available We synthesized the uniform core-shell microstructured compounds with hexagonal phase NaYF4:Er/Yb microrods as the core and hexagonal phase NaLnF4 (NaYbF4, NaLuF4:Yb/Tm, NaYF4:Yb/Er, NaYF4:Eu as the shell based on the hydrothermal reaction. These microscale core-shell structures provided a platform for the spatially confining optical process while possessing high luminescence efficiency. The thickness of the shell could be controlled by adjusting the amounts of shell precursor, which significantly affected the intensity of the shell dopant ions emission and the emission color of core-shell upconversion luminescence (UCL. The uniform NaYF4@NaLnF4 (Ln = Y, Lu, Yb microrods, with a series of rare-earth ions doped into the core and shell layer at various doping concentrations, achieved color-tuning of the upconversion (UC emission and dual-mode emission at the single-microcrystal level, thus allowing the efficient utilization of core-shell microcrystals in the photonics and security labeling. This study suggests a new class of luminescent materials in the microscopic field.

  20. Solitary-wave emission fronts, spectral chirping, and coupling to beam acoustic modes in RPIC simulation of SRS backscatter.

    Energy Technology Data Exchange (ETDEWEB)

    DuBois, D. F. (Donald F.); Yin, L. (Lin); Daughton, W. S. (William S.); Bezzerides, B. (Bandel); Dodd, E. S. (Evan S.); Vu, H. X. (Hoanh X.)

    2004-01-01

    Detailed diagnostics of quasi-2D RPIC simulations of backward stimulated Raman scattering (BSRS), from single speckles under putative NIF conditions, reveal a complex spatio-temporal behavior. The scattered light consists of localized packets, tens of microns in width, traveling toward the laser at an appreciable fraction of the speed of light. Sub pico-second reflectivity pulses occur as these packets leave the system. The LW activity consists of a front traveling with the light packets with a wake of free LWs traveling in the laser direction. The parametric coupling occurs in the front where the scattered light and LW overlap and are strongest. As the light leaves the plasma the LW quickly decays, liberating its trapped electrons. The high frequency part of the |n{sub e}(k,{omega})|{sup 2} spectrum, where n{sub e} is the electron density fluctuation, consists of a narrow streak or straight line with a slope that is the velocity of the parametric front. The time dependence of |n{sub e}(k,t)|{sup 2}, shows that during each pulse the most intense value of k also 'chirps' to higher values, consistent with the k excursions seen in the |n{sub e}(k,{omega})|{sup 2} spectrum. But k does not always return, in the subsequent pulses, to the original parametrically matched value, indicating that, in spite of side loss, the electron distribution function does not return to its original Maxwellian form. Liberated pulses of hot electrons result in down-stream, bump on tail distributions that excite LWs and beam acoustic modes deeper in the plasma. The frequency broadened spectra are consistent with Thomson scatter spectra observed in TRIDENT single-hot-spot experiments in the high k{lambda}{sub D}, trapping regime. Further details including a comparison of results from full PIC simulations, and movies of the spatio-temporal behavior, will be given in the poster by L Yin et al.

  1. Single photon emission tomography in neurological studies: Instrumentation and clinical applications

    International Nuclear Information System (INIS)

    Nikkinen, P.

    1999-01-01

    One triple head and two single head gamma camera systems were used for single photon emission tomography (SPET) imaging of both patients and brain phantoms. Studies with an anatomical brain phantom were performed for evaluation of reconstruction and correction methods in brain perfusion SPET studies. The use of the triple head gamma camera system resulted in a significant increase in image contrast and resolution. This was mainly due to better imaging geometry and the use of a high resolution collimator. The conventional Chang attenuation correction was found suitable for the brain perfusion studies. In the brain perfusion studies region of interest (ROI) based semiquantitation methods were used. A ROI map based on anatomical areas was used in 70 elderly persons (age range 55-85 years) without neurological diseases and in patients suffering from encephalitis or having had a cardiac arrest. Semiquantitative reference values are presented. For the 14 patients with encephalitis the right-to-left side differences were calculated. Defect volume indexes were calculated for 64 patients with brain infarcts. For the 30 cardiac arrest patients the defect percentages and the anteroposterior ratios were used for semiquantitation. It is concluded that different semiquantitation methods are needed for the various patient groups. Age-related reference values will improve the interpretation of SPET data. For validation of the basal ganglia receptor studies measurements were performed using a cylindrical and an anatomical striatal phantom. In these measurements conventional and transmission imaging based non-uniform attenuation corrections were compared. A calibration curve was calculated for the determination of the specific receptor uptake ratio. In the phantom studies using the triple head camera the uptake ratio obtained from simultaneous transmission-emission protocol (STEP) acquisition and iterative reconstruction was closest to the true activity ratio. Conventional

  2. Evaluation of scatter correction using a single isotope for simultaneous emission and transmission data

    Energy Technology Data Exchange (ETDEWEB)

    Yang, J.; Kuikka, J.T.; Vanninen, E.; Laensimies, E. [Kuopio Univ. Hospital (Finland). Dept. of Clinical Physiology and Nuclear Medicine; Kauppinen, T.; Patomaeki, L. [Kuopio Univ. (Finland). Dept. of Applied Physics

    1999-05-01

    Photon scatter is one of the most important factors degrading the quantitative accuracy of SPECT images. Many scatter correction methods have been proposed. The single isotope method was proposed by us. Aim: We evaluate the scatter correction method of improving the quality of images by acquiring emission and transmission data simultaneously with single isotope scan. Method: To evaluate the proposed scatter correction method, a contrast and linearity phantom was studied. Four female patients with fibromyalgia (FM) syndrome and four with chronic back pain (BP) were imaged. Grey-to-cerebellum (G/C) and grey-to-white matter (G/W) ratios were determined by one skilled operator for 12 regions of interest (ROIs) in each subject. Results: The linearity of activity response was improved after the scatter correction (r=0.999). The y-intercept value of the regression line was 0.036 (p<0.0001) after scatter correction and the slope was 0.954. Pairwise correlation indicated the agreement between nonscatter corrected and scatter corrected images. Reconstructed slices before and after scatter correction demonstrate a good correlation in the quantitative accuracy of radionuclide concentration. G/C values have significant correlation coefficients between original and corrected data. Conclusion: The transaxial images of human brain studies show that the scatter correction using single isotope in simultaneous transmission and emission tomography provides a good scatter compensation. The contrasts were increased on all 12 ROIs. The scatter compensation enhanced details of physiological lesions. (orig.) [Deutsch] Die Photonenstreuung gehoert zu den wichtigsten Faktoren, die die quantitative Genauigkeit von SPECT-Bildern vermindern. Es wurde eine ganze Reihe von Methoden zur Streuungskorrektur vorgeschlagen. Von uns wurde die Einzelisotopen-Methode empfohlen. Ziel: Wir untersuchten die Streuungskorrektur-Methode zur Verbesserung der Bildqualitaet durch simultane Gewinnung von Emissions

  3. High-power actively Q-switched single-mode 1342 nm Nd:YVO4 ring laser, injection-locked by a cw single-frequency microchip laser.

    Science.gov (United States)

    Koch, Peter; Bartschke, Juergen; L'huillier, Johannes A

    2015-11-30

    In this paper we report on the realization of a single-mode Q-switched Nd:YVO4 ring laser at 1342 nm. Unidirectional and single-mode operation of the ring laser is achieved by injection-locking with a continuous wave Nd:YVO4 microchip laser, emitting a single-frequency power of up to 40 mW. The ring laser provides a single-mode power of 13.9 W at 10 kHz pulse repetition frequency with a pulse duration of 18.2 ns and an excellent beam quality (M2 laser, a power of 8.7 W at 671 nm with a pulse duration of 14.8 ns and a beam propagation factor of M2 < 1.1 is obtained. The 671 nm radiation features a long-term spectral width of 75 MHz.

  4. Semi-guiding high-aspect-ratio core (SHARC) fiber providing single-mode operation and an ultra-large core area in a compact coilable package

    Science.gov (United States)

    Rockwell, David A.; Shkunov, Vladimir V.; Marciante, John R.

    2011-07-01

    A new class of optical fiber is presented that departs from the circular-core symmetry common to conventional fibers. By using a high-aspect-ratio (~30:1) rectangular core, the mode area can be significantly expanded well beyond 10,000 μm2. Moreover, by also specifying a very small refractive-index step at the narrow core edges, the core becomes ``semi-guiding,'' i.e. it guides in the narrow dimension and is effectively un-guiding in the wide mm-scale dimension. The mode dependence of the resulting Fresnel leakage loss in the wide dimension strongly favors the fundamental mode, promoting single-mode operation. Since the modal loss ratios are independent of mode area, this core structure offers nearly unlimited scalability. The implications of using such a fiber in fiber laser and amplifier systems are also discussed.

  5. Precision measurement of single atoms strongly coupled to the higher-order transverse modes of a high-finesse optical cavity

    Energy Technology Data Exchange (ETDEWEB)

    Du, Jinjin; Li, Wenfang; Wen, Ruijuan; Li, Gang; Zhang, Pengfei; Zhang, Tiancai [State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006 (China)

    2013-08-19

    We have experimentally demonstrated the strong coupling between single atoms and the higher-order Hermite-Gaussian transverse modes in a high-finesse optical microcavity. Compared to the usual low-order symmetric transverse modes, multiple lobes and the asymmetric spatial pattern of the titled modes provide more information about the motion of single atoms in the cavity. The motional information can be extracted from the measured transmission spectra, which includes the velocities and the positions of the atoms in vertical and off-axis directions. The scheme has great potential in time-resolved atom-cavity microscopy and in tracking the three-dimensional single atom trajectory in real time.

  6. Selective generation of two pulse modes in a single all normal dispersion fiber laser oscillator and analysis of their optical characteristics

    Science.gov (United States)

    Kim, S.; Choi, M.; Song, J. Y.; Lee, J. H.; Kim, Y.

    2017-02-01

    Fiber ultrafast pulses such as mode-locked and noise-like pulses have useful optical characteristics for high precision metrology applications. In this study, we develop an ytterbium doped fiber laser with all normal dispersion which can selectively generate two pulse modes, mode-locked and noise-like pulses, by a turn-key system including polarization control and selective detection parts. The spectral and temporal characteristics of two pulses generated from the single oscillator are analyzed and compared with each other through optical spectrum, RF spectrum and autocorrelation. Furthermore, spectral coherence characteristics are verified through interference signals generated by balanced and unbalanced arm interferometers.

  7. High Power Test of X-band Single Cell HOM-free Choke-mode Damped Accelerating Structure made by Tsinghua University

    OpenAIRE

    Wu, Xiaowei; Abe, Tetsuo; Chen, Huaibi; Higo, Toshiyasu; Shi, Jiaru; Wuensch, Walter; Zha, Hao

    2016-01-01

    As an alternative design for CLIC main accelerating structures, X-band choke-mode damped structures had been studied for several years. However, the performance of choke-mode cavity under high power is still in lack of research. Two standing wave single cell choke-mode damped accelerating structures with different choke dimensions which are working at 11.424 GHz were designed, manufactured and bench tested by accelerator group in Tsinghua University. High power test was carried out on it to s...

  8. Assessment of endogenous dopamine release by methylphenidate challenge using iodine-123 iodobenzamide single-photon emission tomography

    NARCIS (Netherlands)

    Booij, J.; Korn, P.; Linszen, D. H.; van Royen, E. A.

    1997-01-01

    This double-blind, placebo-controlled study assessed pharmacologically induced endogenous dopamine (DA) release in healthy male volunteers (n=12). Changes in endogenous DA release after injection of the psychostimulant drug methylphenidate were evaluated by single-photon emission tomography (SPET)

  9. Few-view single photon emission computed tomography (SPECT) reconstruction based on a blurred piecewise constant object model

    DEFF Research Database (Denmark)

    Wolf, Paul A.; Jørgensen, Jakob Sauer; Schmidt, Taly G.

    2013-01-01

    A sparsity-exploiting algorithm intended for few-view Single Photon Emission Computed Tomography (SPECT) reconstruction is proposed and characterized. The algorithm models the object as piecewise constant subject to a blurring operation. To validate that the algorithm closely approximates the true...

  10. Diagnosing Alzheimer's disease in elderly, mildly demented patients: the impact of routine single photon emission computed tomography

    NARCIS (Netherlands)

    van Gool, W. A.; Walstra, G. J.; Teunisse, S.; van der Zant, F. M.; Weinstein, H. C.; van Royen, E. A.

    1995-01-01

    Based on the observation of bilateral temporoparietal hypoperfusion in Alzheimer's disease (AD), single photon emission computed tomography (SPECT) is advocated by some as a powerful diagnostic tool in the evaluation of demented patients. We studied whether routine brain SPECT in elderly, mildly

  11. Exercise echocardiography and single photon emission computed tomography in patients with left anterior descending coronary artery stenosis

    NARCIS (Netherlands)

    A. Salustri (Alessandro); M. Pozzoli (M.); B. Ilmer; W.R.M. Hermans (Walter); A.E.M. Reijs (Ambroos); J.H.C. Reiber (Johan); J.R.T.C. Roelandt (Jos); P.M. Fioretti (Paolo)

    1992-01-01

    textabstractTo compare the diagnostic value of exercise echocardiography and perfusion single photon emission computed tomography (SPECT) in the detection of the presence and the severity of coronary artery disease, we studied 21 patients with isolated stenosis of different degree of the left

  12. Investigation of palm methyl-ester bio-diesel with additive on performance and emission characteristics of a diesel engine under 8-mode testing cycle

    Directory of Open Access Journals (Sweden)

    S. Senthilkumar

    2015-09-01

    Full Text Available Biodiesel is receiving increasing attention each passing day because of its same diesel-like fuel properties and compatibility with petroleum-based diesel fueled engines. Therefore, in this paper the prospects and opportunities of using various blends of methyl esters of palm oil as fuel in an engine with and without the effect of multi-functional fuel additive (MFA, Multi DM 32 are studied to arrive at an optimum blend of bio-diesel best suited for low emissions and minimal power drop. Experimental tests were conducted on a four stroke, three cylinder and naturally aspirated D.I. Diesel engine with diesel and various blend percentages of 20%, 40%, 45%, and 50% under the 8 mode testing cycle. The effect of fuel additive was tested out on the optimum blend ratio of the bio-diesel so as to achieve further reduced emissions. Comparison of results shows that, 73% reduction in hydrocarbon emission, 46% reduction in carbon monoxide emission, and around 1% reduction in carbon dioxide emission characteristics. So it is observed that the blend ratio of 40% bio-diesel with MFA fuel additive creates reduced emission and minimal power drop due to effective combustion even when the calorific value is comparatively lower due to its higher cetane number.

  13. Efficient polymer white-light-emitting diodes with a single-emission layer of fluorescent polymer blend

    International Nuclear Information System (INIS)

    Niu Qiaoli; Xu Yunhua; Jiang Jiaxing; Peng Junbiao; Cao Yong

    2007-01-01

    Efficient polymer white-light-emitting diodes (WPLEDs) have been fabricated with a single layer of fluorescent polymer blend. The device structure consists of ITO/PEDOT/PVK/emissive layer/Ba/Al. The emissive layer is a blend of poly(9,9-dioctylfluorene) (PFO), phenyl-substituted PPV derivative (P-PPV) and a copolymer of 9,9-dioctylfluorene and 4,7-di(4-hexylthien-2-yl)-2,1,3-benzothiadiazole (PFO-DHTBT), which, respectively, emits blue, green and red light. The emission of pure and efficient white light was implemented by tuning the blend weight ratio of PFO: P-PPV: PFO-DHTBT to 96:4:0.4. The maximum current efficiency and luminance are, respectively, 7.6 cd/A at 6.7 V and 11930 cd/m 2 at 11.2 V. The CIE coordinates of white-light emission were stable with the drive voltages

  14. Single photon emission computed tomography in the diagnosis of Alzheimer's disease

    International Nuclear Information System (INIS)

    Hanyu, Haruo; Asano, Tetsuichi; Abe, Shin'e; Arai, Hisayuki; Iwamoto, Toshihiko; Takasaki, Masaru; Shindo, Hiroaki; Abe, Kimihiko

    1997-01-01

    Studies with single photon emission computed tomography (SPECT) have shown temporoparietal (TP) hypoperfusion in patients with Alzheimer's disease (AD). We evaluated the utility of this findings in the diagnosis of AD. SPECT images with 123 I-iodoamphetamine were analyzed qualitatively by a rater without knowledge of the subject's clinical status. Sixty-seven of 302 consecutive patients were judged as having TP hypoperfusion by SPECT imaging. This perfusion pattern was observed in 44 of 51 patients with AD, in 5 with mixed dementia, 8 with cerebrovascular disease (including 5 with dementia), 4 with Parkinson's disease (including 2 with dementia), 1 with normal pressure hydrocephalus, 1 with slowly progressive aphasia, 1 with progressive autonomic failure, 2 with age-associated memory impairment, and 1 with unclassified dementia. The sensitivity for AD was 86.3% (44 of 51 AD), and the specificity was 91.2% (229 of 251 non-AD). Next, we looked for differences in perfusion images between patients with AD and without AD. Some patients without AD had additional hypoperfusion beyond TP areas: deep gray matter hypoperfusion and diffuse frontal hypoperfusion, which could be used to differentiate them from the patients with AD. Others could not be distinguished from patients with AD by their perfusion pattern. Although patients with other cerebral disorders occasionally have TP hypoperfusion, this finding makes the diagnosis of AD very likely. (author)

  15. Single photon emission computed tomography in the diagnosis of Alzheimer`s disease

    Energy Technology Data Exchange (ETDEWEB)

    Hanyu, Haruo; Asano, Tetsuichi; Abe, Shin`e; Arai, Hisayuki; Iwamoto, Toshihiko; Takasaki, Masaru; Shindo, Hiroaki; Abe, Kimihiko [Tokyo Medical Coll. (Japan)

    1997-06-01

    Studies with single photon emission computed tomography (SPECT) have shown temporoparietal (TP) hypoperfusion in patients with Alzheimer`s disease (AD). We evaluated the utility of this findings in the diagnosis of AD. SPECT images with {sup 123}I-iodoamphetamine were analyzed qualitatively by a rater without knowledge of the subject`s clinical status. Sixty-seven of 302 consecutive patients were judged as having TP hypoperfusion by SPECT imaging. This perfusion pattern was observed in 44 of 51 patients with AD, in 5 with mixed dementia, 8 with cerebrovascular disease (including 5 with dementia), 4 with Parkinson`s disease (including 2 with dementia), 1 with normal pressure hydrocephalus, 1 with slowly progressive aphasia, 1 with progressive autonomic failure, 2 with age-associated memory impairment, and 1 with unclassified dementia. The sensitivity for AD was 86.3% (44 of 51 AD), and the specificity was 91.2% (229 of 251 non-AD). Next, we looked for differences in perfusion images between patients with AD and without AD. Some patients without AD had additional hypoperfusion beyond TP areas: deep gray matter hypoperfusion and diffuse frontal hypoperfusion, which could be used to differentiate them from the patients with AD. Others could not be distinguished from patients with AD by their perfusion pattern. Although patients with other cerebral disorders occasionally have TP hypoperfusion, this finding makes the diagnosis of AD very likely. (author)

  16. Gated single photon emission computer tomography for the detection of silent myocardial ischemia

    International Nuclear Information System (INIS)

    Pena Q, Yamile; Coca P, Marco Antonio; Batista C, Juan Felipe; Fernandez-Britto, Jose; Quesada P, Rodobaldo; Pena C; Andria

    2009-01-01

    Background: Asymptomatic patients with severe coronary atherosclerosis may have a normal resting electrocardiogram and stress test. Aim: To assess the yield of Gated Single Photon Emission Computer Tomography (SPECT) for the screening of silent myocardial ischemia in type 2 diabetic patients. Material and methods: Electrocardiogram, stress test and gated-SPECT were performed on 102 type 2 diabetic patients aged 60 ± 8 years without cardiovascular symptoms. All subjects were also subjected to a coronary angiography, whose results were used as gold standard. Results: Gated-SPECT showed myocardial ischemia on 26.5% of studied patients. The sensibility, specificity, accuracy, positive predictive value and negative predictive value were 92.3%, 96%, 95%, 88.8%, 97.3%, respectively. In four and six patients ischemia was detected on resting electrocardiogram and stress test, respectively. Eighty percent of patients with doubtful resting electrocardiogram results and 70% with a doubtful stress test had a silent myocardial ischemia detected by gated-SPECT. There was a good agreement between the results of gated-SPECT and coronary angiography (k =0.873). Conclusions: Gated-SPECT was an useful tool for the screening of silent myocardial ischemia

  17. Single-photon emission computed tomographic findings and motor neuron signs in amyotrophic lateral sclerosis

    International Nuclear Information System (INIS)

    Terao, Shin-ichi; Sobue, Gen; Higashi, Naoki; Takahashi, Masahiko; Suga, Hidemichi; Mitsuma, Terunori

    1995-01-01

    123 I-amphetamine-single photon emission computed tomography (SPECT) was performed on 16 patients with amyotrophic lateral sclerosis (ALS) to investigate the correlation between regional cerebral blood flow (rCBF) and upper motor neuron signs. Significant decreased blood flow less than 2 SDs below the mean of controls was observed in the frontal lobe in 4 patients (25%) and in the frontoparietal lobe including the cortical motor area in 4 patients, respectively. The severity of extermity muscular weakness was significantly correlate with decrease in blood flow through the frontal lobe (p<0.05) and through the frontoparietal lobe (p<0.001). A significant correlation was also noted to exist between the severity of bulbar paralysis and decrease in blood flow through the frontoparietal lobe. No correlation, however, was observed between rCBF and severity of spasticity, presence or absence of Babinski's sign and the duration of illness. Although muscular weakness in the limbs and bulbar paralysis are not pure upper motor neuron signs, the observed reduction in blood flow through the frontal or frontoparietal lobes appears to reflect extensive progression of functional or organic lesions of cortical neurons including the motor area. (author)

  18. Musicogenic epilepsy: review of the literature and case report with ictal single photon emission computed tomography.

    Science.gov (United States)

    Wieser, H G; Hungerbühler, H; Siegel, A M; Buck, A

    1997-02-01

    We report a case of musicogenic epilepsy with ictal single photon emission computed tomography (SPECT) study and discuss the findings of this patient in the context of 76 cases with musicogenic epilepsy described in the literature and seven other cases followed in Zurich. We analyzed the 83 patients according to the precipitating musical factors, type of epilepsy, presumed localization of seizure onset, and demographic data. Fourteen of 83 patients (17%) had seizures triggered exclusively by music. At time of examination, music was the only known precipitating stimulus in 65 of 83 patients (78%). Various characteristics of the musical stimulus were significant, e.g., musical category, familiarity, and instruments. Musicogenic epilepsy is a particular form of epilepsy with a strong correlation to the temporal lobe and a right-sided preponderance. A high musial standard might predispose for musicogenic epilepsy. Moreover, the majority of cases do not fall into the category of a strictly defined "reflex epilepsy," but appear to depend on the indermediary of a certain emotional reaction mediated through limbic mesial temporal lobe structures.

  19. Comparison of Ga-67 planar imaging and single photon emission computed tomography in malignant chest disease

    International Nuclear Information System (INIS)

    Tumeh, S.S.; Rosenthal, D.; Kaplan, W.D.; English, R.E.; Holman, B.L.

    1985-01-01

    To determine the value of Ga-67 single photon emission computed tomography (SPECT) in patients (pts) with malignant chest disease, the authors compared Ga-67 planar scans (ps) and SPECT with the medical records in twenty-five consecutive patients. Twenty-three examinations were performed on 17 pts with Hodgkin's disease (HD) and three pts with non-Hodgkin's lymphoma. Five examinations were performed on 5 pts with bronchogenic carcinoma (BC). The two modalities were evaluated for (1) presence or absence of disease, (2) number of foci of abnormal uptake and (3) extent of disease. In pts with lymphoma, SPECT defined the extent of disease better than planar imaging in eight examinations; it demonstrated para-cardial involvement in one pt, separated hilar from mediastinal disease in 4, and demonstrated posterior mediastinal disease in 3. SPECT clarified suspicious foci on planar images in seven examinations, correctly ruled out disease in two pts with equivocal planar images and did not exchange planar image findings in six examinations. In pts with bronchogenic carcinoma, both medalities correctly ruled out mediastinal involvement in three pts. SPECT detected mediastinal lymph node involvement in one pt with equivocal planar images. Both SPECT and planar imaging missed direct tumor extension to the mediastinum in one pt. They conclude that Ga-67 with SPECT is better than planar images for staging of chest lymphoma and BC. Since it defines different lymph node groups it carries a good potential for staging as well as follow up of those pts

  20. Single photon emission computed tomography (SPECT) in seizure disorders in childhood

    International Nuclear Information System (INIS)

    Vles, J.S.H.; Demandt, E.; Ceulemans, B.; de Roo, M.; Casaer, P.J.M.

    1990-01-01

    In 38 children with partial seizures, the EEG, CT and NMR findings were compared to the results obtained with Tc99m HMPAO single photon emission computed tomography (SPECT) in order to determine whether SPECT is a useful adjunct to EEG, CT and NMR in this age group. In 3 out of 7 patients with a normal EEG, SPECT showed focal abnormalities. Nine patients whose EEGs did not show adequate lateralization had an abnormal SPECT which revealed a focus. In 14 out of 21 patients with a normal CT, SPECT showed focal changes in 13 patients and diffuse changes in the other one. In 7 out of 12 patients with a normal NMR, SPECT showed focal abnormalities. Although clinical history and a careful description of the seizures are the most valuable information in partial seizure disorders, SPECT imaging gives valuable additional information, which might target treatment. SPECT was superior to CT and NMR with respect to the depiction of some kind of abnormality. (author)