WorldWideScience

Sample records for cavity surface emitting

  1. Vertical-Cavity Surface-Emitting Lasers

    Science.gov (United States)

    Wilmsen, Carl W.; Temkin, Henryk; Coldren, Larry A.

    2002-01-01

    1. Introduction to VCSELs L. A. Coldren, C. W. Wilmsen and H. Temkin; 2. Fundamental issues in VCSEL design L. A. Coldren and Eric R. Hegblom; 3. Enhancement of spontaneous emission in microcavities E. F. Schubert and N. E. J. Hunt; 4. Epitaxy of vertical-cavity lasers R. P. Schneider Jr and Y. H. Young; 5. Fabrication and performance of vertical-cavity surface-emitting lasers Kent D. Choquette and Kent Geib; 6. Polarization related properties of vertical cavity lasers Dmitri Kuksenkov and Henryk Temkin; 7. Visible light emitting vertical cavity lasers Robert L. Thornton; 8. Long-wavelength vertical-cavity lasers Dubrakovo I. Babic, Joachim Piprek and John E. Bowers; 9. Overview of VCSEL applications Richard C. Williamson; 10. Optical interconnection applications and required characteristics Kenichi Kasahara; 11. VCSEL-based fiber-optic data communications Kenneth Hahn and Kirk Giboney; 12. VCSEL-based smart pixels for free space optoelectronic processing C. W. Wilmsen.

  2. Long wavelength vertical cavity surface emitting laser

    Science.gov (United States)

    Choquette, Kent D.; Klem, John F.

    2005-08-16

    Selectively oxidized vertical cavity lasers emitting near 1300 nm using InGaAsN quantum wells are reported for the first time which operate continuous wave below, at and above room temperature. The lasers employ two n-type Al.sub.0.94 Ga.sub.0.06 As/GaAs distributed Bragg reflectors each with a selectively oxidized current aperture adjacent to the active region, and the top output mirror contains a tunnel junction to inject holes into the active region. Continuous wave single mode lasing is observed up to 55.degree. C.

  3. Cavity solitons in vertical-cavity surface-emitting lasers

    CERN Document Server

    Vladimirov, A G; Gurevich, S V; Panajotov, K; Averlant, E; Tlidi, M

    2014-01-01

    We investigate a control of the motion of localized structures of light by means of delay feedback in the transverse section of a broad area nonlinear optical system. The delayed feedback is found to induce a spontaneous motion of a solitary localized structure that is stationary and stable in the absence of feedback. We focus our analysis on an experimentally relevant system namely the Vertical-Cavity Surface-Emitting Laser (VCSEL). In the absence of the delay feedback we present experimental evidence of stationary localized structures in a 80 $\\mu$m aperture VCSEL. The spontaneous formation of localized structures takes place above the lasing threshold and under optical injection. Then, we consider the effect of the time-delayed optical feedback and investigate analytically the role of the phase of the feedback and the carrier lifetime on the self-mobility properties of the localized structures. We show that these two parameters affect strongly the space time dynamics of two-dimensional localized structures...

  4. Vertical external cavity surface emitting semiconductor lasers

    CERN Document Server

    Holm, M

    2001-01-01

    Active stabilisation showed a relative locked linewidth of approx 3 kHz. Coarse tuning over 7 nm was achieved using a 3-plate birefingent filter plate while fine-tuning using cavity length change allowed tuning over 250 MHz. Vertical external cavity semiconductor lasers have emerged as an interesting technology based on current vertical cavity semiconductor laser knowledge. High power output into a single transverse mode has attracted companies requiring good fibre coupling for telecommunications systems. The structure comprises of a grown semiconductor Bragg reflector topped with a multiple quantum well gain region. This is then included in an external cavity. This device is then optically pumped to promote laser action. Theoretical modelling of AIGaAs based VECSEL structures was undertaken, showing the effect of device design on laser characteristics. A simple 3-mirror cavity was constructed to assess the static characteristics of the structure. Up to 153 mW of output power was achieved in a single transver...

  5. Analysis and Design of Vertical Cavity Surface Emitting Lasers

    Science.gov (United States)

    Yu, S. F.

    2003-08-01

    A practical, hands-on guidebook for the efficient modeling of VCSELs Vertical Cavity Surface Emitting Lasers (VCSELs) are a unique type of semiconductor laser whose optical output is vertically emitted from the surface as opposed to conventional edge-emitting semiconductor lasers. Complex in design and expensive to produce, VCSELs nevertheless represent an already widely used laser technology that promises to have even more significant applications in the future. Although the research has accelerated, there have been relatively few books written on this important topic. Analysis and Design of Vertical Cavity Surface Emitting Lasers seeks to encapsulate this growing body of knowledge into a single, comprehensive reference that will be of equal value for both professionals and academics in the field. The author, a recognized expert in the field of VCSELs, attempts to clarify often conflicting assumptions in order to help readers achieve the simplest and most efficient VCSEL models for any given problem. Highlights of the text include: * A clear and comprehensive theoretical treatment of VCSELs * Detailed derivations for understanding the operational principles of VCSELs * Mathematical models for the investigation of electrical, optical, and thermal properties of VCSELs * Case studies on the mathematical modeling of VCSELs and the implementation of simulation programs

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

    DEFF Research Database (Denmark)

    Ansbæk, Thor

    This thesis deals with the design and fabrication of tunable Vertical-Cavity Surface-Emitting Lasers (VCSELs). The focus has been the application of tunable VCSELs in medical diagnostics, specifically OCT. VCSELs are candidates as light sources for swept-source OCT where their high sweep rate, wide...... sweep range and high degree of coherence enable deep probing of tissue at acquisition rates that will eliminate the effects of rapid involuntary eye movements. The main achievement of the dissertation work has been the development of an electro-statically tunable VCSEL at 1060 nm with wide tuning range...

  7. Ultralow Threshold Red Vertical-Cavity Surface-Emitting Lasers

    Institute of Scientific and Technical Information of China (English)

    程澎; 高俊华; 康学军; 林世鸣; 张光斌; 刘世安; 胡国新

    2000-01-01

    Visible Vertical-cavity Surface-emitting Lasers (VCSELs) have been designed and fabricated by using metalorganic vapor phase epitaxy. Using the 8λ optical cavities with 3 quan tum wells in A1GaInP/AlGaAs VCSEL's to reduce the drift leakage current and enhance the model gain, the device can operate continuous wave at wavelength of 670nm. For better performance, a misoriented (100) substrate (6~10° to (110)) has been used to reduce the ordering of AlGaInP. However, as the angle of misorientation increased, the symmetry of the structure became worse. This made it difficult to achieve little aperture device. By using 45° rotated selective oxidation method, a little aperture (1 × 1μm2) device with low threshold of 0.25mA can operate continuous wave at room temperature.

  8. Transverse-mode-selectable microlens vertical-cavity surface-emitting laser

    DEFF Research Database (Denmark)

    Chung, Il-Sug; Debernardi, Pierluigi; Lee, Yong Tak

    2010-01-01

    A new vertical-cavity surface-emitting laser structure employing a thin microlens is suggested and numerically investigated. The laser can be made to emit in either a high-power Gaussian-shaped single-fundamental mode or a high-power doughnut-shaped higher-order mode. The physical origin of the m...

  9. Intracavity frequency-doubled green vertical external cavity surface emitting laser

    Institute of Scientific and Technical Information of China (English)

    Yanrong Song; Peng Zhang; Xinping Zhang; Boxia Yan; Yi Zhou; Yong Bi; Zhigang Zhang

    2008-01-01

    @@ An intracavity frequency-doubled vertical external cavity surface emitting laser (VECSEL) with green light is demonstrated. The fundamental frequency laser cavity consists of a distributed Bragg reflector (DBR) of the gain chip and an external mirror. A 12-mW frequency-doubled output has been reached at 540 nm with a nonlinear crystal LBO when the fundamental frequency output is 44 mW at 1080 nm. The frequency doubling efficiency is about 30%.

  10. Polymer-coated vertical-cavity surface-emitting laser diode vapor sensor

    DEFF Research Database (Denmark)

    Ansbæk, Thor; Nielsen, Claus Højgaard; Larsen, Niels Bent

    2010-01-01

    We report a new method for monitoring vapor concentration of volatile organic compounds using a vertical-cavity surface-emitting laser (VCSEL). The VCSEL is coated with a polymer thin film on the top distributed Bragg reflector (DBR). The analyte absorption is transduced to the electrical domain ...

  11. Integrated optoelectronic probe including a vertical cavity surface emitting laser for laser Doppler perfusion monitoring

    NARCIS (Netherlands)

    Serov, Alexander N.; Nieland, Janharm; Oosterbaan, Sjoerd; Mul, de Frits F.M.; Kranenburg, van Herma; Bekman, Herman H.P.Th.; Steenbergen, Wiendelt

    2006-01-01

    An integrated optoelectronic probe with small dimensions, for direct-contact laser Doppler blood flow monitoring has been realized. A vertical cavity surface emitting laser (VCSEL), and a chip with photodetectors and all necessary electronics are integrated in a miniature probe head connected to a l

  12. Integrated Optoelectronic Probe Including a Vertical Cavity Surface Emitting Laser for Laser Doppler Perfusion Monitoring

    NARCIS (Netherlands)

    Serov, A.N.; Nieland, J.; Oosterbaan, S.; Steenbergen, W.; Bekman, H.H.P.T.; Mul, F.F.M. de; Kranenburg, H. van

    2006-01-01

    An integrated optoelectronic probe with small dimensions, for direct-contact laser Doppler blood flow monitoring has been realized. A vertical cavity surface emitting laser (VCSEL), and a chip with photodetectors and all necessary electronics are integrated in a miniature probe head connected to a l

  13. Acetone vapor sensing using a vertical cavity surface emitting laser diode coated with polystyrene

    DEFF Research Database (Denmark)

    Ansbæk, Thor; Nielsen, Claus Højgaard; Larsen, Niels Bent

    2009-01-01

    We report theoretical and experimental on a new vapor sensor, using a single-mode vertical-cavity surface-emitting laser (VCSEL) coated with a polymer sensor coating, which can detect acetone vapor at a volume fraction of 2.5%. The sensor provides the advantage of standard packaging, small form...

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

    DEFF Research Database (Denmark)

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

    2009-01-01

    We have experimentally investigated self-mixing interference produced by the feedback of light from a polymer micrometer-sized cantilever into a vertical-cavity surface-emitting laser for sensing applications. In particular we have investigated how the visibility of the optical output power and t...

  15. Polarization switching in vertical-cavity surface emitting lasers observed at constant active region temperature

    Science.gov (United States)

    Martín-Regalado, J.; Chilla, J. L. A.; Rocca, J. J.; Brusenbach, P.

    1997-06-01

    Polarization switching in gain-guided, vertical-cavity, surface-emitting lasers was studied as a function of the active region temperature. We show that polarization switching occurs even when the active region temperature is kept constant during fast pulse low duty cycle operation. This temperature independent polarization switching phenomenon is explained in terms of a recently developed model.

  16. Sub-gigahertz beam switching of vertical-cavity surface-emitting laser with transverse coupled cavity

    Energy Technology Data Exchange (ETDEWEB)

    Nakahama, M.; Gu, X.; Sakaguchi, T. [Photonics Integration System Research Center, Tokyo Institute of Technology, 4259-R2-22, Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Matsutani, A. [Semiconductor and MEMS Processing Center, Tokyo Institute of Technology, 4259-R2-22, Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Ahmed, M.; Bakry, A. [Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia); Koyama, F. [Photonics Integration System Research Center, Tokyo Institute of Technology, 4259-R2-22, Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)

    2015-08-17

    We report a high-speed electrical beam switching of vertical cavity surface emitting laser with a transverse coupled cavity. A high speed (sub-gigahertz) and large deflection angle (>30°) beam switching is demonstrated by employing the transverse mode switching. The angular switching speed of 900 MHz is achieved with narrow beam divergence of below 4° and extinction ratio of 8 dB. We also measured the near- and far-field patterns to clarify the origin of the beam switching. We present a simple one-dimensional Bragg reflector waveguide model, which well predicts the beam switching characteristic.

  17. High-energy terahertz wave parametric oscillator with a surface-emitted ring-cavity configuration.

    Science.gov (United States)

    Yang, Zhen; Wang, Yuye; Xu, Degang; Xu, Wentao; Duan, Pan; Yan, Chao; Tang, Longhuang; Yao, Jianquan

    2016-05-15

    A surface-emitted ring-cavity terahertz (THz) wave parametric oscillator has been demonstrated for high-energy THz output and fast frequency tuning in a wide frequency range. Through the special optical design with a galvano-optical scanner and four-mirror ring-cavity structure, the maximum THz wave output energy of 12.9 μJ/pulse is achieved at 1.359 THz under the pump energy of 172.8 mJ. The fast THz frequency tuning in the range of 0.7-2.8 THz can be accessed with the step response of 600 μs. Moreover, the maximum THz wave output energy from this configuration is 3.29 times as large as that obtained from the conventional surface-emitted THz wave parametric oscillator with the same experimental conditions.

  18. Dynamic Range of Vertical Cavity Surface Emitting Lasers in Multimode Links

    Energy Technology Data Exchange (ETDEWEB)

    Lee, H.L.T.; Dalal, R.V.; Ram, R.J.; Choquette, K.D.

    1999-07-07

    The authors report spurious free dynamic range measurements of 850nm vertical cavity surface emitting lasers in short multimode links for radio frequency communication. For a 27m fiber link, the dynamic range at optimal bias was greater than 95dB-Hz{sup 2/3} for modulation frequencies between 1 and 5.5 GHz, which exceeds the requirements for antenna remoting in microcellular networks. In a free space link, they have measured the highest dynamic range in an 850nm vertical cavity surface emitting laser of 113dB-Hz{sup 2/3} at 900MHz. We have also investigated the effects of modal noise and differential mode delay on the dynamic range for longer lengths of fiber.

  19. Photonic crystal vertical-cavity surface-emitting laser based on GaAs material

    Institute of Scientific and Technical Information of China (English)

    XU XingSheng; WANG ChunXia; SONG Qian; DU Wei; HU HaiYang; ZHAO ZhiMin; LU Lin; KAN Qiang; CHEN HongDa

    2007-01-01

    A photonic crystal vertical-cavity-surface-emitting laser (PC-VCSEL) with a wavelength of about 850 nm was realized. The direct-current electrically-driven PC-VCSELs with a minimum threshold current of 2 mA and a maximum threshold current of 13.5 mA were obtained. We fabricated a series of PC-VCSEL chips whose lattice constants are in the range from 0.5 to 3 ?m with different filling factors, and found that the laser characterization depends on the lattice constant, the filling factor, the size of cavity, etc.

  20. Control of light polarization using optically spin-injected vertical external cavity surface emitting lasers

    Energy Technology Data Exchange (ETDEWEB)

    Frougier, J., E-mail: julien.frougier@thalesgroup.com; Jaffrès, H.; Deranlot, C.; George, J.-M. [Unité Mixte de Physique CNRS-Thales and Université Paris Sud 11, 1 av. Fresnel, 91767 Palaiseau (France); Baili, G.; Dolfi, D. [Thales Research and Technology, 1 av. Fresnel, 91767 Palaiseau (France); Alouini, M. [Institut de Physique de Rennes, 263 Avenue Général Leclerc, 35042 Rennes (France); Sagnes, I. [Laboratoire de Photonique et de Nanostructures, Route de Nozay, 91460 Marcoussis (France); Garnache, A. [Institut d' électronique du Sud CNRS UMR5214, Université Montpellier 2 Place Eugene Bataillon, 34095 Montpellier (France)

    2013-12-16

    We fabricated and characterized an optically pumped (100)-oriented InGaAs/GaAsP multiple quantum well Vertical External Cavity Surface Emitting Laser (VECSEL). The structure is designed to allow the integration of a Metal-Tunnel-Junction ferromagnetic spin-injector for future electrical injection. We report here the control at room temperature of the electromagnetic field polarization using optical spin injection in the active medium of the VECSEL. The switching between two highly circular polarization states had been demonstrated using an M-shaped extended cavity in multi-modes lasing. This result witnesses an efficient spin-injection in the active medium of the LASER.

  1. Tunable Vertical-Cavity Surface-Emitting Lasers Integrated with Two Wafers

    Institute of Scientific and Technical Information of China (English)

    REN Xiu-Juan; GUAN Bao-Lu; GUO Shuai; LI Shuo; LI Chuan-Chuan; HAO Cong-Xia; ZHOU Hong-Yi; GUO Xiao

    2011-01-01

    A novel two-wafer concept for micro-electro-mechanically tunable vertical cavity surface emitting lasers (VCSELs)is presented. The VCSEL is composed by two wafers: one micro-electromechanical-system membrane wafer with four arms to adjust the cavity length through electrostatic actuation and a "half-VCSEL" wafer consisting of a fixed bottom mirror and an amplifying active region. The measurement results of the electricity pumped tunable VCSEL with more than 9mW output power at room temperature over the tuning range prove the feasibility of the proposition.%@@ A novel two-wafer concept for micro-electro-mechanically tunable vertical cavity surface emitting lasers (VCSELs) is presented.The VCSEL is composed by two wafers: one micro-electromechanical-system membrane wafer with four arms to adjust the cavity length through electrostatic actuation and a "half-VCSEL" wafer consisting of a fixed bottom mirror and an amplifying active region.The measurement results of the electricity pumped tunable VCSEL with more than 9mW output power at room temperature over the tuning range prove the feasibility of the proposition.

  2. Buried heterostructure vertical-cavity surface-emitting laser with semiconductor mirrors

    CERN Document Server

    Zhao, G; Deppe, D G; Konthasinghe, K; Muller, A

    2012-01-01

    We report a buried heterostructure vertical-cavity surface-emitting laser fabricated by epitaxial regrowth over an InGaAs quantum well gain medium. The regrowth technique enables microscale lateral confinement that preserves a high cavity quality factor (loaded $Q\\approx$ 4000) and eliminates parasitic charging effects found in existing approaches. Under optimal spectral overlap between gain medium and cavity mode (achieved here at $T$ = 40 K) lasing was obtained with an incident optical power as low as $P_{\\rm th}$ = 10 mW ($\\lambda_{\\rm p}$ = 808 nm). The laser linewidth was found to be $\\approx$3 GHz at $P_{\\rm p}\\approx$ 5 $P_{\\rm th}$.

  3. The pressure and temperature dependence of vertical cavity surface emitting semiconductor lasers

    CERN Document Server

    Knowles, G

    2002-01-01

    The factors affecting the performance of GalnP/AIGalnP vertical-cavity surface-emitting lasers (VCSELs) emitting at an attenuation minimum of PMMA plastic optical fibres (650nm) have been investigated. Using wide temperature-range and high pressure measurement techniques on equivalent (i.e the same active region) edge emitting lasers (EELs), emitting at 672nm, the temperature sensitive leakage current into the indirect X-minima is shown to be approx 20% of the total threshold current at room temperature. This is then estimated to rise to approx 70% for 655nm emission, but may be reduced to approx 50% by using a graded-index separate confinement heterostructure (GRINSCH). By making the same measurements on the full VCSEL structures and using a combination of thermal and gain spectrum models the performance modifying effect of the Bragg stacks have then been evaluated. It is found that temperature dependent tuning/detuning of the gain-peak and the cavity mode is significant at low temperature due to the relativ...

  4. Phase-locked arrays of vertical-cavity surface-emitting lasers

    Energy Technology Data Exchange (ETDEWEB)

    Warren, M.E.; Lear, K.L.; Gourley, P.L.; Hadley, G.R.; Vawter, G.A.; Brennan, T.M.; Hammons, B.E.; Zolper, J.C. [Sandia National Labs., Albuquerque, NM (United States); Lott, J.A. [Air Force Institute of Technology, Wright Patterson Air Force Base, OH (United States); Chalmers, S.A. [Optical Solutions, Albany, CA (United States)

    1994-04-01

    Vertical-Cavity Surface-Emitting Lasers (VCSELS) are of increasing interest to the photonics community because of their surface-emitting structure, simple fabrication and packaging, wafer-level testability, and potential for low cost manufacture. Scaling VCSELs to higher power outputs requires increasing the device area, which leads to transverse mode control difficulties if devices become larger than about 5 microns. One approach to increasing the device size while maintaining a well controlled transverse mode profile is formation of coupled or phase-locked two-dimensional arrays of VCSELs that are individually single-transverse mode. Such arrays have unique optical properties, not all of which are desirable. This paper covers some of the basic principles of these devices and reviews recent work on device designs, fabrication and operation. A technique for improving the far-field properties of the arrays is demonstrated and performance limitations are discussed.

  5. Controllable spiking patterns in long-wavelength vertical cavity surface emitting lasers for neuromorphic photonics systems

    Energy Technology Data Exchange (ETDEWEB)

    Hurtado, Antonio, E-mail: antonio.hurtado@strath.ac.uk [Institute of Photonics, SUPA Department of Physics, University of Strathclyde, TIC Centre, 99 George Street, Glasgow G1 1RD (United Kingdom); Javaloyes, Julien [Departament de Fisica, Universitat de les Illes Balears, c/Valldemossa km 7.5, 07122 Mallorca (Spain)

    2015-12-14

    Multiple controllable spiking patterns are achieved in a 1310 nm Vertical-Cavity Surface Emitting Laser (VCSEL) in response to induced perturbations and for two different cases of polarized optical injection, namely, parallel and orthogonal. Furthermore, reproducible spiking responses are demonstrated experimentally at sub-nanosecond speed resolution and with a controlled number of spikes fired. This work opens therefore exciting research avenues for the use of VCSELs in ultrafast neuromorphic photonic systems for non-traditional computing applications, such as all-optical binary-to-spiking format conversion and spiking information encoding.

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

    DEFF Research Database (Denmark)

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

    2012-01-01

    Vapor detection using a low-refractive index polymer for reflection modulation of the top mirror in a vertical-cavity surface-emitting laser (VCSEL) is demonstrated. The VCSEL sensor concept presents a simple method to detect the response of a sensor polymer in the presence of volatile organic co...... compounds. We model the physics as a change in the top mirror loss caused by swelling of the polymer upon absorbing the target volatile organic compound. Further we show how acetone vapors at 82 000 ppm concentration can change the polymer coated VCSEL output power by 20 mu W....

  7. Stable anticipation synchronization in mutually coupled vertical-cavity surface-emitting lasers system

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Two vertical-cavity surface-emitting lasers(VCSELs) are mutually coupled through a partially transparent mirror (PTM) placed in the pathway. The PTM plays the role of external mirror,which controls the feedback strength and coupling strength.We numerically simulate this system by establishing a visible SIMULINK model.The results demonstrate that the anticipation synchronization is achieved and it can tolerate some extent frequency detuning.Moreover,the system shows similar chaos-pass filtering effect on unidirectionally coupled system even both VCSELs are modulated.This system allows simultaneously bidirectional secure message transmission on public channels.

  8. Temperature characteristics of InGaAs/GaAs vertical cavity surface emitting laser

    Institute of Scientific and Technical Information of China (English)

    QU Hong-wei; GUO Xia; DONG Li-min; WANG Hong-hang; DENG Jun; LIAN Peng; ZHOU De-shu; SHEN Guang-di

    2005-01-01

    The temperature characteristics for the different lasing modes at 300 K of intracavity contacted InGaAs/GaAs Vertical Cavity Surface Emitting Lasers(VCSELs) have been investigated experimentally by using the SV-32 cryostat and LD2002C5 test system.In combination with the simulation results of the reflective spectrum and the gain peak at different temperatures,the measurement results have been analyzed.In addition,the dependence of device size on temperature characteristics is discussed.The experimental data can be used to optimally design of VCSEL at high or cryogenic temperature.

  9. VCSELs Fundamentals, Technology and Applications of Vertical-Cavity Surface-Emitting Lasers

    CERN Document Server

    2013-01-01

    The huge progress which has been achieved in the field is covered here, in the first comprehensive monograph on vertical-cavity surface-emitting lasers (VCSELs) since eight years. Apart from chapters reviewing the research field and the laser fundamentals, there are comprehensive updates on red and blue emitting VCSELs, telecommunication VCSELs, optical transceivers, and parallel-optical links for computer interconnects. Entirely new contributions are made to the fields of vectorial three-dimensional optical modeling, single-mode VCSELs, polarization control, polarization dynamics, very-high-speed design, high-power emission, use of high-contrast gratings, GaInNAsSb long-wavelength VCSELs, optical video links, VCSELs for optical mice and sensing, as well as VCSEL-based laser printing. The book appeals to researchers, optical engineers and graduate students.

  10. Ultrafast circular polarization oscillations in spin-polarized vertical-cavity surface-emitting laser devices

    Science.gov (United States)

    Gerhardt, N. C.; Li, M.; Jaehme, H.; Soldat, H.; Hofmann, M. R.; Ackemann, T.

    2010-02-01

    Spin-polarized lasers offer new encouraging possibilities for future devices. We investigate the polarization dynamics of electrically pumped vertical-cavity surface-emitting lasers after additional spin injection at room temperature. We find that the circular polarization degree exhibits faster dynamics than the emitted light. Moreover the experimental results demonstrate a strongly damped ultrafast circular polarization oscillation due to spin injection with an oscillation frequency of approximately 11GHz depending on the birefringence in the VCSEL device. We compare our experimental results with theoretical calculations based on rate-equations. This allows us to predict undamped long persisting ultrafast polarization oscillations, which reveal the potential of spin-VCSELs for ultrafast modulation applications.

  11. Theoretical study on phase conjugation in weakly injected vertical-cavity surface-emitting lasers

    Institute of Scientific and Technical Information of China (English)

    Zhang Wei-Li; Pan Wei; Luo Bin; Li Xiao-Feng; Zou Xi-Hua; Wang Meng-Yao

    2008-01-01

    This paper gives a detailed theoretical investigation on phase conjugation induced by nearly degenerate fourwave mixing in single mode vertical-cavity surface-emitting lasers (VCSELs) with~weak optical injection.Considering VCSELs that can work in linearly polarized or elliptically polarized states,it derives the theoretical expression of the conjugated field by small signal analysis based on the vectoral rate equations--the spin-flip model.For linearly polarized state,VCSELs show similar conjugate spectra to edge-emitting semiconductor lasers.For the eUiptically polarized state,dichroism and birefringence parameters as well as the spin-flip rate can change the conjugate spectra.Especially,when frequency detuning of the probe and pump waves is between the positive and negative relaxation oscillation frequency,changes are evident.For specific values of parameters,conjugate efficiency between 20 dB to 40 dB are obtained.

  12. Comparative analysis of energy-efficient long wavebands vertical cavity surface emitting lasers

    Science.gov (United States)

    Dahiya, Sandeep; Mishra, Hemant Kumar; Kumar, Suresh; Kaushik, Brajesh Kumar

    2016-10-01

    Vertical cavity surface emitting laser (VCSEL) is an important laser source for their evident plentiful applications in optical communication. The present investigation reports a comparison of the modeling and optimization of long wavelengths 1310 nm and 1550 nm high speed short cavity VCSEL for continuous wave operation at various temperature (283-3230K) for various diameters. The continuous wave lasing is demonstrated for the device diameter from 2 to 5 μm with threshold current of 1.07-1.33 mA with threshold power consumption of 1.86-2.57 mW for 1310 nm and threshold current of 0.94-1.24 mA and threshold power consumption 1.67-2.1 mW for 1550 nm VCSEL. The results demonstrate that the threshold current, peak emitted power and power consumption increases with the increase in device diameter. The results confirm that VCSELs with 2 μm diameter is most suitable to achieve energy-efficient operation. Although rollover current increases with the diameter, but, due to the advantage of lower threshold current and power consumption, VCSEL having smaller diameter is best suited. The power conversion efficiency for proposed long wavelength VCSELs is approximately 50% which is extremely useful for low power applications. The proposed VCSELs are suitable for very short reach (communication in high performance computers.

  13. Quantum modeling of semiconductor gain materials and vertical-external-cavity surface-emitting laser systems

    Energy Technology Data Exchange (ETDEWEB)

    Bueckers, Christina; Kuehn, Eckhard; Schlichenmaier, Christoph; Koch, Stephan W. [Department of Physics and Material Sciences Center, Philipps-University Marburg (Germany); Imhof, Sebastian; Thraenhardt, Angela [Faculty of Natural Sciences, Chemnitz University of Technology, Chemnitz (Germany); Hader, Joerg; Moloney, Jerome V. [Nonlinear Control Strategies, Inc., Tucson, AZ (United States); College of Optical Sciences, University of Arizona, Tucson, AZ (United States); Rubel, Oleg [Thunder Bay Regional Research Institute, Thunder Bay, ON (Canada); Department of Physics, Lakehead University, Thunder Bay, ON (Canada); Zhang, Wei [Centre for Biophotonics, SIPBS, University of Strathclyde, Glasgow, Scotland (United Kingdom); Ackemann, Thorsten [SUPA and Department of Physics, University of Strathclyde, Glasgow, Scotland (United Kingdom)

    2010-04-15

    This article gives an overview of the microscopic theory used to quantitatively model a wide range of semiconductor laser gain materials. As a snapshot of the current state of research, applications to a variety of actual quantum-well systems are presented. Detailed theory-experiment comparisons are shown and it is analyzed how the theory can be used to extract poorly known material parameters. The intrinsic laser loss processes due to radiative and nonradiative Auger recombination are evaluated microscopically. The results are used for realistic simulations of vertical-external-cavity surface-emitting laser systems. To account for nonequilibrium effects, a simplified model is presented using pre-computed microscopic scattering and dephasing rates. Prominent deviations from quasi-equilibrium carrier distributions are obtained under strong in-well pumping conditions. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  14. Spin induced gigahertz polarization oscillations in vertical-cavity surface-emitting laser devices

    Science.gov (United States)

    Li, M. Y.; Jaehme, H.; Soldat, H.; Gerhardt, N. C.; Hofmann, M. R.; Ackemann, T.

    2011-03-01

    Spin-controlled vertical-cavity surface-emitting lasers (VCSELs) have been intensively studied in recent years because of the low threshold feasibility and the nonlinearity above threshold, which make spin-VCSELs very promising for spintronic devices. Here we investigate the circular polarization dynamics of VCSELs on a picosecond time scale after pulsed optical spin injection at room temperature. A hybrid excitation technique combining continuous-wave (cw) unpolarized electrical excitation slightly above threshold and pulsed polarized optical excitation is applied. The experimental results demonstrate ultrafast circular polarization oscillations with a frequency of about 11 GHz. The oscillations last inside the first undulation of the intensity relaxation oscillations. Via theoretical calculations based on a rate equation model we analyze these oscillations as well as the underlying physical mechanisms.

  15. Vertical-Cavity Surface-Emitting Lasers: Advanced Modulation Formats and Coherent Detection

    DEFF Research Database (Denmark)

    Rodes Lopez, Roberto

    transmission link with real-time demodulation. Furthermore, advanced modulation formats are considered in this thesis to expand the state-of-the-art in high-speed short-range data transmission system based on VCSELs. First, directly modulation of a VCSEL with a 4-level pulse amplitude modulation (PAM-4) signal......This thesis expands the state-of-the-art in coherent detection for optical fiber access networks employing vertical-cavity surface-emitting lasers (VCSELs) as light sources. Bit rates up to 10 Gb/s over 25 km single-mode fibre (SMF) transmission distance have been achieved supporting a passive...... generation optical fiber access networks regarding long reach, high splitting ratio, no optical amplification, no external modulation, and use of a single fiber for upstream and downstream transmission. An important contribution of this thesis is the novel concept of chirpassisted coherent detection...

  16. Phase-locked arrays of vertical-cavity surface-emitting lasers

    Energy Technology Data Exchange (ETDEWEB)

    Warren, M.E.; Hadley, G.R.; Lear, K.L.; Gourley, P.L.; Vawter, G.A.; Zolper, J.C.; Brennan, T.M.; Hammons, B.E.

    1994-05-01

    Vertical Cavity Surface-Emitting Lasers (VCSELs) are of increasing interest to the photonics community because of their surface-emitting structure, simple fabrication and packaging, wafer-level testability and potential for low cost. Scaling VCSELs to higher power outputs requires increasing the device area, which leads to transverse mode control difficulties if devices become larger than 10-15 microns. One approach to increasing the device size while maintaining a well controlled transverse mode profile is to form coupled or phase-locked, two-dimensional arrays of VCSELs that are individually single-transverse mode. The authors have fabricated and characterized both photopumped and electrically injected two-dimensional VCSEL arrays with apertures over 100 microns wide. Their work has led to an increased understanding of these devices and they have developed new types of devices, including hybrid semiconductor/dielectric mirror VCSEL arrays, VCSEL arrays with etched trench, self-aligned, gold grid contacts and arrays with integrated phase-shifters to correct the far-field pattern.

  17. Single-mode low threshold current multi-hole vertical-cavity surface-emitting lasers

    Institute of Scientific and Technical Information of China (English)

    Zhao Zhen-Bo; Xu Chen; Xie Yi-Yang; Zhou Kang; Liu Fa; Shen Guang-Di

    2012-01-01

    A multi-hole vertical-cavity surface-emitting laser (VCSEL) operating in stable single mode with a low threshold current was produced by introducing multi-leaf scallop holes on the top distributed Bragg-reflector of an oxidationconfined 850 nm VCSEL.The single-mode output power of 2.6 mW,threshold current of 0.6 mA,full width of half maximum lasing spectrum of less than 0.1 nm,side mode suppression ratio of 28.4 dB,and far-field divergence angle of about 10° are obtained.The effects of different hole depths on the optical characteristics are simulated and analysed,including far-field divergence,spectrum and lateral cavity mode.The single-mode performance of this multi-hole device is attributed to the large radiation loss from the inter-hole spacing and the scattering loss at the bottom of the holes,particularly for higher order modes.

  18. Nonpolar III-nitride vertical-cavity surface-emitting lasers incorporating an ion implanted aperture

    KAUST Repository

    Leonard, J. T.

    2015-07-06

    © 2015 AIP Publishing LLC. We report on our recent progress in improving the performance of nonpolar III-nitride vertical-cavity surface-emitting lasers (VCSELs) by using an Al ion implanted aperture and employing a multi-layer electron-beam evaporated ITO intracavity contact. The use of an ion implanted aperture improves the lateral confinement over SiNx apertures by enabling a planar ITO design, while the multi-layer ITO contact minimizes scattering losses due to its epitaxially smooth morphology. The reported VCSEL has 10 QWs, with a 3nm quantum well width, 1nm barriers, a 5nm electron-blocking layer, and a 6.95- λ total cavity thickness. These advances yield a single longitudinal mode 406nm nonpolar VCSEL with a low threshold current density (∼16kA/cm2), a peak output power of ∼12μW, and a 100% polarization ratio. The lasing in the current aperture is observed to be spatially non-uniform, which is likely a result of filamentation caused by non-uniform current spreading, lateral optical confinement, contact resistance, and absorption loss.

  19. Integrated plasmonic circuitry on a vertical-cavity surface-emitting semiconductor laser platform

    Science.gov (United States)

    McPolin, Cillian P. T.; Bouillard, Jean-Sebastien; Vilain, Sebastien; Krasavin, Alexey V.; Dickson, Wayne; O'Connor, Daniel; Wurtz, Gregory A.; Justice, John; Corbett, Brian; Zayats, Anatoly V.

    2016-08-01

    Integrated plasmonic sources and detectors are imperative in the practical development of plasmonic circuitry for bio- and chemical sensing, nanoscale optical information processing, as well as transducers for high-density optical data storage. Here we show that vertical-cavity surface-emitting lasers (VCSELs) can be employed as an on-chip, electrically pumped source or detector of plasmonic signals, when operated in forward or reverse bias, respectively. To this end, we experimentally demonstrate surface plasmon polariton excitation, waveguiding, frequency conversion and detection on a VCSEL-based plasmonic platform. The coupling efficiency of the VCSEL emission to waveguided surface plasmon polariton modes has been optimized using asymmetric plasmonic nanostructures. The plasmonic VCSEL platform validated here is a viable solution for practical realizations of plasmonic functionalities for various applications, such as those requiring sub-wavelength field confinement, refractive index sensitivity or optical near-field transduction with electrically driven sources, thus enabling the realization of on-chip optical communication and lab-on-a-chip devices.

  20. Operation of a novel hot-electron vertical-cavity surface-emitting laser

    Science.gov (United States)

    Balkan, Naci; O'Brien-Davies, Angela; Thoms, A. B.; Potter, Richard J.; Poolton, Nigel; Adams, Michael J.; Masum, J.; Bek, Alpan; Serpenguzel, Ali; Aydinli, Atilla; Roberts, John S.

    1998-07-01

    The hot Electron Light Emission and Lasing in Semiconductor Heterostructures devices (HELLISH-1) is novel surface emitter consisting of a GaAs quantum well, within the depletion region, on the n side of Ga1-xAlxAs p- n junction. It utilizes hot electron transport parallel to the layers and injection of hot electron hole pairs into the quantum well through a combination of mechanisms including tunnelling, thermionic emission and diffusion of `lucky' carriers. Super Radiant HELLISH-1 is an advanced structure incorporating a lower distributed Bragg reflector (DBR). Combined with the finite reflectivity of the upper semiconductor-air interface reflectivity it defines a quasi- resonant cavity enabling emission output from the top surface with a higher spectral purity. The output power has increased by two orders of magnitude and reduced the full width at half maximum (FWHM) to 20 nm. An upper DBR added to the structure defines HELLISH-VCSEL which is currently the first operational hot electron surface emitting laser and lases at room temperature with a 1.5 nm FWHM. In this work we demonstrate and compare the operation of UB-HELLISH-1 and HELLISH-VCSEL using experimental and theoretical reflectivity spectra over an extensive temperature range.

  1. Towards monolithic integration of mode-locked vertical cavity surface emitting laser

    Science.gov (United States)

    Aldaz, Rafael I.

    2007-12-01

    The speed and performance of today's high end computing and communications systems have placed difficult but still feasible demands on off-chip electrical interconnects. However, future interconnect systems may need aggregate bandwidths well into the terahertz range thereby making electrical bandwidth, density, and power targets impossible to meet. Optical interconnects, and specifically compact semiconductor mode-locked lasers, could alleviate this problem by providing short pulses in time at 10s of GHz repetition rates for Optical Time Division Multiplexing (OTDM) and clock distribution applications. Furthermore, the characteristic spectral comb of frequencies of these lasers could also serve as a multi-wavelength source for Wavelength Division Multiplexing (WDM) applications. A fully integrated mode-locked Vertical Cavity Surface Emitting Laser (VCSEL) is proposed as a low-cost high-speed source for these applications. The fundamental laser platform for such a device has been developed and a continuous-wave version of these lasers has been fabricated and demonstrated excellent results. Output powers close to 60mW have been obtained with very high beam quality factor of M2 unassisted ultrafast QD saturable absorbers, without the need to incorporate high concentrations of non radiative recombination centers by either ion-implantation or low temperature growth.

  2. Polarization switching and synchronization of mutually coupled vertical-cavity surface-emitting semiconductor lasers

    Institute of Scientific and Technical Information of China (English)

    Zhang Wei-Li; Pan Wei; Luo Bin; Li Xiao-Feng; Zou Xi-Hua; Wang Meng-Yao

    2007-01-01

    Polarization switching (PS) dynamics and synchronization performances of two mutually coupled vertical-cavity surface-emitting lasers (VCSELs) are studied theoretically in this paper. A group of dimensionless rate equations is derived to describe our model. While analysing the PS characteristics, we focus on the effects of coupling rate and frequency detuning regarding different mutual injection types. The results indicate that the x-mode injection defers the occurrence of PS, while the y-mode injection leads the PS to occur at a lower current. Strong enough polarizationselective injection can suppress the PS. Moreover, if frequency detuning is considered, the effects of polarization-selective mutual injection will be weakened. To evaluate the synchronization performance, the correlation coefficients and output dynamics of VCSELs with both pure mode and mixed mode polarizations are given. It is found that performance of complete synchronization is sensitive to the frequency mismatch but it is little affected by mixed mode polarizations,which is opposite to the case of injection-locking synchronization.

  3. High-power single-mode vertical-cavity surface-emitting lasers

    Science.gov (United States)

    Samal, Nigamananda

    High-power single-mode vertical-cavity surface-emitting lasers (VCSEL) have a great potential to replace the distributed feedback (DFB) and Fabry-Perot (FP) edge emitting lasers that are currently used in optical communication. VCSELs also have tremendous potential in many niche applications such as "optical read and write," laser printing, bar code scanning and sensing. Despite many of their inherent advantages over its rivals, VCSELs still suffer from some outstanding issues. Most prominent are "limited power" and "multi-mode behavior" at higher injection. This work aims at a few solutions for these fundamental issues. Using strain-compensated GaAsSb as an active material and a standard single-aperture design, 1.3 mum VCSELs are demonstrated and characterized. These devices face basic issues such as "limited output power" and "multi-mode behavior." These VCSELs achieved room temperature CW operation with power outputs from 50--200 muW for wavelengths ranging from 1245 to 1290 nm. To resolve the issue of limited power, several on-wafer thermal-management schemes are proposed. One of the schemes is pursued in this work. To resolve the issue of multi-mode behavior, a novel device design using asymmetric double oxide-apertures is proposed, theoretically modeled, and implemented in this work. The optical mode behavior of this novel design is compared with a traditional single-aperture design using fabricated devices and theoretical modeling. A clear trend of spectral purity in the modal behavior of the devices, under both continuous wave (CW) and pulsed conditions, is demonstrated and is in good agreement with theoretical predictions. One of the novel designs tested on an InGaAs VCSEL has shown a multi-mode power more than 23 mW with maximum wall plug efficiency of 32%, threshold current of 2.5 mA, threshold voltage of 1.2 V, and a slope efficiency of 0.83 W/A. The best design demonstrated a room temperature CW single-mode output power of more than 7 mW with a side

  4. Optical Injection Locking of Vertical Cavity Surface-Emitting Lasers: Digital and Analog Applications

    Science.gov (United States)

    Parekh, Devang

    With the rise of mobile (cellphones, tablets, notebooks, etc.) and broadband wireline communications (Fiber to the Home), there are increasing demands being placed on transmitters for moving data from device to device and around the world. Digital and analog fiber-optic communications have been the key technology to meet this challenge, ushering in ubiquitous Internet and cable TV over the past 20 years. At the physical layer, high-volume low-cost manufacturing of semiconductor optoelectronic devices has played an integral role in allowing for deployment of high-speed communication links. In particular, vertical cavity surface emitting lasers (VCSEL) have revolutionized short reach communications and are poised to enter more markets due to their low cost, small size, and performance. However, VCSELs have disadvantages such as limited modulation performance and large frequency chirp which limits fiber transmission speed and distance, key parameters for many fiber-optic communication systems. Optical injection locking is one method to overcome these limitations without re-engineering the VCSEL at the device level. By locking the frequency and phase of the VCSEL by the direct injection of light from another laser oscillator, improved device performance is achieved in a post-fabrication method. In this dissertation, optical injection locking of VCSELs is investigated from an applications perspective. Optical injection locking of VCSELs can be used as a pathway to reduce complexity, cost, and size of both digital and analog fiber-optic communications. On the digital front, reduction of frequency chirp via bit pattern inversion for large-signal modulation is experimentally demonstrated showing up to 10 times reduction in frequency chirp and over 90 times increase in fiber transmission distance. Based on these results, a new reflection-based interferometric model for optical injection locking was established to explain this phenomenon. On the analog side, the resonance

  5. Evolution of the Novalux extended cavity surface-emitting semiconductor laser (NECSEL)

    Science.gov (United States)

    McInerney, John G.

    2016-03-01

    Novalux Inc was an enterprise founded by Aram Mooradian in 1998 to commercialise a novel electrically pumped vertical extended cavity semiconductor laser platform, initially aiming to produce pump lasers for optical fiber telecommunication networks. Following successful major investment in 2000, the company developed a range of single- and multi-mode 980 nm pump lasers emitting from 100-500 mW with excellent beam quality and efficiency. This rapid development required solution of several significant problems in chip and external cavity design, substrate and DBR mirror optimization, thermal engineering and mode selection. Output coupling to single mode fiber was exceptional. Following the collapse of the long haul telecom market in late 2001, a major reorientation of effort was undertaken, initially to develop compact 60-100 mW hybrid monolithically integrated pumplets for metro/local amplified networks, then to frequency-doubled blue light emitters for biotech, reprographics and general scientific applications. During 2001-3 I worked at Novalux on a career break from University College Cork, first as R&D Director managing a small group tasked with producing new capabilities and product options based on the NECSEL platform, including high power, pulsed and frequency doubled versions, then in 2002 as Director of New Product Realization managing the full engineering team, leading the transition to frequency doubled products.

  6. Graded index profiles and loss-induced single-mode characteristics in vertical-cavity surface-emitting lasers with petal-shape holey structure

    Institute of Scientific and Technical Information of China (English)

    Liu An-Jin; Qu Hong-Wei; Chen Wei; Jiang Bin; Zhou Wen-Jun; Xing Ming-Xin; Zheng Wan-Hua

    2011-01-01

    The 850-nm oxide-confined vertical-cavity surface-emitting lasers with petal-shape holey structures are presented. An area-weighted average refractive index model is given to analyse their effective index profiles, and the graded index distribution in the holey region is demonstrated. The index step between the optical aperture and the holey region is obtained which is related merely to the etching depth. Four types of holey vertical-cavity surface-emitting lasers with different parameters are fabricated as well as the conventional oxide-confined vertical-cavity surface-emitting laser. Compared with the conventional oxide-confined vertical-cavity surface-emitting laser without etched holes, the holey vertical-cavity surface-emitting laser possesses an improved beam quality due to its graded index distribution, but has a lower output power, higher threshold current and lower slope efficiency. With the hole number increased, the holey vertical-cavity surface-emitting laser can realize the single-mode operation throughout the entire current range, and reduces the beam divergence further. The loss mechanism is used to explain the single-mode characteristic, and the reduced beam divergence is attributed to the shallow etching. High coupling efficiency of 86% to a multi-mode fibre is achieved for the single-mode device in the experiment.

  7. Flip-chip bonding of vertical-cavity surface-emitting lasers using laser-induced forward transfer

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, K. S., E-mail: Kaur.Kamalpreet@elis.ugent.be; Missinne, J.; Van Steenberge, G. [Centre for Microsystems Technology, imec/Ghent University, Technologiepark 914A, B-9052 Gent (Belgium)

    2014-02-10

    This letter reports the use of the Laser-Induced Forward Transfer (LIFT) technique for the fabrication of indium micro-bumps for the flip-chip (FC) bonding of single vertical-cavity surface-emitting laser chips. The FC bonded chips were electrically and optically characterized, and the successful functioning of the devices post-bonding is demonstrated. The die shear and life-time tests carried out on the bonded chips confirmed the mechanical reliability of the LIFT-assisted FC bonded assemblies.

  8. Impact of unpredictability on chaos synchronization of vertical-cavity surface-emitting lasers with variable-polarization optical feedback.

    Science.gov (United States)

    Xiang, Shuiying; Pan, Wei; Yan, Lianshan; Luo, Bin; Zou, Xihua; Jiang, Ning; Yang, Lei

    2011-09-01

    The effects of unpredictability degree on the chaos synchronization properties of vertical-cavity surface-emitting lasers with variable-polarization optical feedback are investigated numerically. For variable-polarization optical injection, only low-unpredictability chaos can be well synchronized, while high-unpredictability chaos cannot be synchronized even with large injection strength. On the other hand, for the polarization-preserved optical injection, the synchronization quality is hardly affected by the unpredictability degree, and high-quality synchronization can be achieved for both low- and high-unpredictability chaos due to injection locking.

  9. 1300 nm optically pumped quantum dot spin vertical external-cavity surface-emitting laser

    Energy Technology Data Exchange (ETDEWEB)

    Alharthi, S. S., E-mail: ssmalh@essex.ac.uk; Henning, I. D.; Adams, M. J. [School of Computer Science and Electronic Engineering, University of Essex, Wivenhoe Park, Colchester CO4 3SQ (United Kingdom); Orchard, J. [Department of Physics and Astronomy, University of Sheffield, Hounsfield Road, Sheffield S3 7RH (United Kingdom); Clarke, E. [EPSRC National Centre for III-V Technologies, University of Sheffield, Mappin Street, S1 3JD Sheffield (United Kingdom)

    2015-10-12

    We report a room temperature optically pumped Quantum Dot-based Spin-Vertical-External-Cavity Surface-Emitting laser (QD Spin-VECSEL) operating at the telecom wavelength of 1.3 μm. The active medium was composed of 5 × 3 QD layers; each threefold group was positioned at an antinode of the standing wave of the optical field. Circularly polarized lasing in the QD-VECSEL under Continuous-Wave optical pumping has been realized with a threshold pump power of 11 mW. We further demonstrate at room temperature control of the QD-VECSEL output polarization ellipticity via the pump polarization.

  10. High-sensitivity time-resolved intracavity laser Fourier transform spectroscopy with vertical cavity surface emitting multiple quantum well lasers

    CERN Document Server

    Picqué, N; Kachanov, A A; Picqu\\'e, Nathalie; Guelachvili, Guy; Kachanov, Alexander A.

    2003-01-01

    Spectra comprised of hundreds of time-components for absorption path lengths up to 130 km have been recorded around 1050 nm by combining two recent techniques, intracavity laser spectroscopy with vertical external cavity surface emitting multiple-quantum-well lasers and time-resolved Fourier transform spectroscopy. A sensitivity of 1 10^{-10} cm^{-1}.Hz^{-1/2} is achieved, for simultaneously acquired 10^4 spectral elements, three orders of magnitude better than the sensitivity obtained in previous similar experiments. Specific advantages of the method, especially for frequency and intensity metrology of weak absorption transitions, are discussed.

  11. Temperature stable mid-infrared GaInAsSb/GaSb Vertical Cavity Surface Emitting Lasers (VCSELs)

    Science.gov (United States)

    Ikyo, A. B.; Marko, I. P.; Hild, K.; Adams, A. R.; Arafin, S.; Amann, M.-C.; Sweeney, S. J.

    2016-01-01

    GaInAsSb/GaSb based quantum well vertical cavity surface emitting lasers (VCSELs) operating in mid-infrared spectral range between 2 and 3 micrometres are of great importance for low cost gas monitoring applications. This paper discusses the efficiency and temperature sensitivity of the VCSELs emitting at 2.6 μm and the processes that must be controlled to provide temperature stable operation. We show that non-radiative Auger recombination dominates the threshold current and limits the device performance at room temperature. Critically, we demonstrate that the combined influence of non-radiative recombination and gain peak – cavity mode de-tuning determines the overall temperature sensitivity of the VCSELs. The results show that improved temperature stable operation around room temperature can only be achieved with a larger gain peak – cavity mode de-tuning, offsetting the significant effect of increasing non-radiative recombination with increasing temperature, a physical effect which must be accounted for in mid-infrared VCSEL design.

  12. Lead-chalcogenide mid-infrared vertical external cavity surface emitting lasers with improved threshold: Theory and experiment

    Energy Technology Data Exchange (ETDEWEB)

    Fill, Matthias [ETH Zurich, Laser Spectroscopy and Sensing Lab, 8093 Zurich (Switzerland); Phocone AG, 8005 Zurich (Switzerland); Debernardi, Pierluigi [IEIIT-CNR, Torino 10129 (Italy); Felder, Ferdinand [Phocone AG, 8005 Zurich (Switzerland); Zogg, Hans [ETH Zurich (Switzerland)

    2013-11-11

    Mid-infrared Vertical External Cavity Surface Emitting Lasers (VECSEL) based on narrow gap lead-chalcogenide (IV-VI) semiconductors exhibit strongly reduced threshold powers if the active layers are structured laterally for improved optical confinement. This is predicted by 3-d optical calculations; they show that lateral optical confinement is needed to counteract the anti-guiding features of IV-VIs due to their negative temperature dependence of the refractive index. An experimental proof is performed with PbSe quantum well based VECSEL grown on a Si-substrate by molecular beam epitaxy and emitting around 3.3 μm. With proper mesa-etching, the threshold intensity is about 8-times reduced.

  13. Polarization switching and injection locking in vertical-cavity surface-emitting lasers subject to parallel optical injection.

    Science.gov (United States)

    Quirce, Ana; Pérez, Pablo; Popp, Alexandra; Valle, Ángel; Pesquera, Luis; Hong, Yanhua; Thienpont, Hugo; Panajotov, Krassimir

    2016-06-01

    Polarization switching in a long-wavelength vertical-cavity surface-emitting laser (VCSEL) under parallel optical injection is analyzed in a theoretical and experimental way. For the first time, to our knowledge, we report experimentally a state in which injection locking of the parallel polarization and excitation of the free-running orthogonal polarization of the VCSEL are simultaneously obtained. We obtain very simple analytical expressions that describe both linear polarizations. We show that the power of both linear polarizations depend linearly on the injected power in such a way that the total power emitted by the VCSEL is constant. We perform a linear stability analysis of this solution to characterize the region of parameters in which it can be observed. Our measurements qualitatively confirm the previous theoretical predictions.

  14. Design of Synthesized DBRs for Long-Wavelength InP-Based Vertical-Cavity Surface-Emitting Lasers

    Institute of Scientific and Technical Information of China (English)

    HUANG Zhan-Chao; WU Hui-Zhen

    2004-01-01

    @@ We report applications of a metallic film and a phase matching layer (PML) to increase the reflectivity of the cavity mirror in a long-wavelength InP-based vertical-cavity surface-emitting laser (VCSEL). The synthesis of the InGaAsP/InP distributed-Bragg reflector (DBR) with an Au fllm and the InP PML leads to the decrease of periods of the DBR multilayer stacks from 33 to 20 while keeping the reflectivity of the structure over 99%.The reflectivity over the whole forbidden band is significantly increased and become flatter compared to the bare DBR. The use of smaller DBR periods in a long wavelength VCSEL makes the epitaxial growth well controllable,decrease of the heat resistance, and decrease of the in-series electrical resistance of the devices. This can improve the reliability of the VCSEL growth and possibly cut down the cost of VCSEL devices.

  15. Comparison of nonpolar III-nitride vertical-cavity surface-emitting lasers with tunnel junction and ITO intracavity contacts

    KAUST Repository

    Leonard, J. T.

    2016-03-01

    We report on the lasing of III-nitride nonpolar, violet, vertical-cavity surface-emitting lasers (VCSELs) with III-nitride tunnel-junction (TJ) intracavity contacts and ion implanted apertures (IIAs). The TJ VCSELs are compared to similar VCSELs with tin-doped indium oxide (ITO) intracavity contacts. Prior to analyzing device results, we consider the relative advantages of III-nitride TJs for blue and green emitting VCSELs. The TJs are shown to be most advantageous for violet and UV VCSELs, operating near or above the absorption edge for ITO, as they significantly reduce the total internal loss in the cavity. However, for longer wavelength III-nitride VCSELs, TJs primarily offer the advantage of improved cavity design flexibility, allowing one to make the p-side thicker using a thick n-type III-nitride TJ intracavity contact. This offers improved lateral current spreading and lower loss, compare to using ITO and p-GaN, respectively. These aspects are particularly important for achieving high-power CW VCSELs, making TJs the ideal intracavity contact for any III-nitride VCSEL. A brief overview of III-nitride TJ growth methods is also given, highlighting the molecular-beam epitaxy (MBE) technique used here. Following this overview, we compare 12 mu m aperture diameter, violet emitting, TJ and ITO VCSEL experimental results, which demonstrate the significant improvement in differential efficiency and peak power resulting from the reduced loss in the TJ design. Specifically, the TJ VCSEL shows a peak power of similar to 550 mu W with a threshold current density of similar to 3.5 kA/cm(2), while the ITO VCSELs show peak powers of similar to 80 mu W and threshold current densities of similar to 7 kA/cm

  16. Lateral carrier confinement of GaN-based vertical-cavity surface-emitting diodes using boron ion implantation

    Science.gov (United States)

    Hamaguchi, Tatsushi; Nakajima, Hiroshi; Ito, Masamichi; Mitomo, Jugo; Satou, Susumu; Fuutagawa, Noriyuki; Narui, Hironobu

    2016-12-01

    Boron ion implantation, which is used for confining carriers in gallium nitride (GaN)-based vertical-cavity surface-emitting laser diodes (VCSELs), was studied. Detailed analysis indicated that boron ion implantation of GaN increases GaN’s absorption coefficient from zero to 800 cm-1 and its refractive index from 2.45 to 2.51 at the surface of the wafer at a wavelength of 453 nm. The depth profile of boron obtained by secondary ion mass spectroscopy (SIMS) showed an exponential decrease toward the bottom of the wafer. Assuming that the changes in optical parameters caused by implantation are proportional to the concentration of boron in GaN, the boron ion implantation applied to GaN-VCSELs causes optical absorption of 0.04% per round trip in the cavity and extends the light path of the cavity by 2.2 nm, both of which apparently have negligible impact on the operation of GaN-VCSELs. The implanted boron ions pass through the active regions, introducing non-radiative recombination centers at the edges of those active regions made of InGaN multi-quantum wells, which, however, does not cause significant current injection loss.

  17. Highly-efficient, diffraction-limited laser emission from a Vertical External Cavity Surface-emitting Organic Laser

    CERN Document Server

    Rabbani-Haghighi, Hadi; Chenais, Sebastien; Siove, Alain

    2010-01-01

    We report on a solid-state laser structure being the organic counterpart of the Vertical External-Cavity Surface-Emitting Laser (VECSEL) design. The gain medium is a poly (methyl methacrylate) film doped with Rhodamine 640, spin-casted onto the High-Reflectivity mirror of a plano-concave resonator. Upon pumping by 7-ns pulses at 532 nm, a diffraction-limited beam (M^2=1) was obtained, with a conversion efficiency of 43%; higher peak powers (2kW) could be attained when resorting to shorter (0.5 ns) pump pulses. The spectrum was controlled by the thickness of the active layer playing the role of an intracavity etalon; tunability is demonstrated over up to 20 nm.

  18. A precision fiber bragg grating interrogation system using long-wavelength vertical-cavity surface-emitting laser

    Science.gov (United States)

    Hu, Binxin; Jin, Guangxian; Liu, Tongyu; Wang, Jinyu

    2016-09-01

    This paper presents the development of a cost-effective precision fiber Bragg grating (FBG) interrogation system using long-wavelength vertical-cavity surface-emitting laser (VCSEL). Tuning properties of a long-wavelength VCSEL have been studied experimentally. An approximately quadratic dependence of its wavelength on the injection current has been observed. The overall design and key operations of this system including intensity normalization, peak detection, and quadratic curve fitting are introduced in detail. The results show that the system achieves an accuracy of 1.2 pm with a tuning range of 3 nm and a tuning rate of 1 kHz. It is demonstrated that this system is practical and effective by applied in the FBG transformer temperature monitoring.

  19. Circular polarization switching and bistability in an optically injected 1300 nm spin-vertical cavity surface emitting laser

    Energy Technology Data Exchange (ETDEWEB)

    Alharthi, S. S., E-mail: ssmalh@essex.ac.uk; Henning, I. D.; Adams, M. J. [School of Computer Science and Electronic Engineering, University of Essex, Wivenhoe Park, Colchester CO4 3SQ (United Kingdom); Hurtado, A. [School of Computer Science and Electronic Engineering, University of Essex, Wivenhoe Park, Colchester CO4 3SQ (United Kingdom); Institute of Photonics, Physics Department, University of Strathclyde, Wolfson Centre, 106 Rottenrow East, Glasgow G4 0NW, Scotland (United Kingdom); Korpijarvi, V.-M.; Guina, M. [Optoelectronics Research Centre (ORC), Tampere University of Technology, P.O. Box 692, FIN-33101 Tampere (Finland)

    2015-01-12

    We report the experimental observation of circular polarization switching (PS) and polarization bistability (PB) in a 1300 nm dilute nitride spin-vertical cavity surface emitting laser (VCSEL). We demonstrate that the circularly polarized optical signal at 1300 nm can gradually or abruptly switch the polarization ellipticity of the spin-VCSEL from right-to-left circular polarization and vice versa. Moreover, different forms of PS and PB between right- and left-circular polarizations are observed by controlling the injection strength and the initial wavelength detuning. These results obtained at the telecom wavelength of 1300 nm open the door for novel uses of spin-VCSELs in polarization sensitive applications in future optical systems.

  20. Single-exposure two-dimensional superresolution in digital holography using a vertical cavity surface-emitting laser source array.

    Science.gov (United States)

    Granero, Luis; Zalevsky, Zeev; Micó, Vicente

    2011-04-01

    We present a new implementation capable of producing two-dimensional (2D) superresolution (SR) imaging in a single exposure by aperture synthesis in digital lensless Fourier holography when using angular multiplexing provided by a vertical cavity surface-emitting laser source array. The system performs the recording in a single CCD snapshot of a multiplexed hologram coming from the incoherent addition of multiple subholograms, where each contains information about a different 2D spatial frequency band of the object's spectrum. Thus, a set of nonoverlapping bandpass images of the input object can be recovered by Fourier transformation (FT) of the multiplexed hologram. The SR is obtained by coherent addition of the information contained in each bandpass image while generating an enlarged synthetic aperture. Experimental results demonstrate improvement in resolution and image quality.

  1. Design concepts of monolithic metamorphic vertical-cavity surface-emitting lasers for the 1300–1550 nm spectral range

    Energy Technology Data Exchange (ETDEWEB)

    Egorov, A. Yu., E-mail: anton@beam.ioffe.ru; Karachinsky, L. Ya.; Novikov, I. I.; Babichev, A. V.; Nevedomskiy, V. N. [Russian Academy of Sciences, Ioffe Institute (Russian Federation); Bugrov, V. E. [ITMO University (Russian Federation)

    2015-11-15

    Possible design concepts for long-wavelength vertical-cavity surface-emitting lasers for the 1300–1550 nm spectral range on GaAs substrates are suggested. It is shown that a metamorphic GaAs–InGaAs heterostructure with a thin buffer layer providing rapid transition from the lattice constant of GaAs to that of In{sub x}Ga{sub 1–x}As with an indium fraction of x < 0.3 can be formed by molecular-beam epitaxy. Analysis by transmission electron microscopy demonstrated the effective localization of mismatch dislocations in the thin buffer layer and full suppression of their penetration into the overlying InGaAs metamorphic layer.

  2. High brightness imaging system using vertical cavity surface-emitting laser micro-arrays- results and proposed enhancements

    Science.gov (United States)

    Mentzer, Mark A.; Ghosh, Chuni L.

    2011-05-01

    Laser illumination systems for high brightness imaging through the self-luminosity of explosive events, at Aberdeen Proving Ground and elsewhere, required complex pulse timing, extensive cooling, large-scale laser systems (frequencydoubled flash-pumped Nd:YAG, Cu-vapor, Q-switched ruby), making them difficult to implement for range test illumination in high speed videography. A Vertical Cavity Surface-Emitting Laser (VCSEL) array was designed and implemented with spectral filtering to effectively remove self-luminosity and the fireball from the image, providing excellent background discrimination in a variety of range test scenarios. Further improvements to the system are proposed for applications such as imaging through murky water or dust clouds with optimal penetration of obscurants.

  3. Time-Delay Signature of Chaotic Vertical-Cavity Surface-Emitting Lasers with Polarization-Rotated Optical Feedback

    Institute of Scientific and Technical Information of China (English)

    XIANG Shui-Ying; PAN Wei; YAN Lian-Shan; LUO Bin; ZOU Xi-Hua; JIANG Ning; WEN Kun-Hua

    2011-01-01

    To quantitatively evaluate the time-delay (TD) signatures of chaotic signals generated by vertical-cavity surface-emitting lasers (VCSELs) with polarization-rotated optical feedback (PROF), we propose four cases of resolution coefficients R based on correlation functions. The resolution coefficient characteristics for the x-polarization (XP) mode, y-polarization (YP) mode and the total output are considered. The dependences of R on the feedback strength and feedback delay are discussed and compared carefully. The two-dimensional maps of R show that the TD signatures for the single polarization mode (I.e., XP or YP mode) are much more difficult to retrieve than those for the total output in the entire parameter space. Thus, by using single polarization mode as a chaotic carrier, the TD signatures are extremely difficult to be identified, which contributes a lot in the security-enhanced VCSELs-based chaotic optical communication systems.

  4. Self-Mixing Fringes of Vertical-Cavity Surface-Emitting Lasers under Dual Reflector Feedback

    Institute of Scientific and Technical Information of China (English)

    CHENG Xiang; ZHANG Shu-Lian; ZHANG Lian-Qing; TAN Yi-Dong

    2006-01-01

    The self-mixing fringes which shift due to every one-twentieth wavelength displacement of the target are observed.Taking advantage of the dual reflectors in the external cavity of lasers, the resolution of the sensors has been improved by 10 times. The role of the each reflector has been discussed in detail.

  5. Absorber and gain chip optimization to improve performance from a passively modelocked electrically pumped vertical external cavity surface emitting laser

    Energy Technology Data Exchange (ETDEWEB)

    Zaugg, C. A., E-mail: zauggc@phys.ethz.ch; Mangold, M.; Pallmann, W. P.; Golling, M.; Tilma, B. W.; Keller, U. [Department of Physics, Institute for Quantum Electronics, ETH Zürich, 8093 Zürich (Switzerland); Gronenborn, S.; Moench, H.; Weichmann, U. [Philips Technologie GmbH Photonics Aachen, Steinbachstrasse 15, 52074 Aachen (Germany); Miller, M. [Philips Technologie GmbH U-L-M Photonics, Lise-Meitner-Strasse 13, 89081 Ulm (Germany)

    2014-03-24

    We present an electrically pumped vertical-external-cavity surface-emitting laser (EP-VECSEL) modelocked with a semiconductor saturable absorber mirror (SESAM) with significantly improved performance. In different cavity configurations, we present the shortest pulses (2.5 ps), highest average output power (53.2 mW), highest repetition rate (18.2 GHz), and highest peak power (4.7 W) to date. The simple and low-cost concept of EP-VECSELs is very attractive for mass-market applications such as optical communication and clocking. The improvements result from an optimized gain chip from Philips Technologie GmbH and a SESAM, specifically designed for EP-VECSELs. For the gain chip, we found a better trade-off between electrical and optical losses with an optimized doping scheme in the substrate to increase the average output power. Furthermore, the device's bottom contact diameter (60 μm) is smaller than the oxide aperture diameter (100 μm), which favors electro-optical conversion into a TEM{sub 00} mode. Compared to optically pumped VECSELs we have to increase the field enhancement in the active region of an EP-VECSEL which requires a SESAM with lower saturation fluence and higher modulation depth for modelocking. We therefore used a resonant quantum well SESAM with a 3.5-pair dielectric top-coating (SiN{sub x} and SiO{sub 2}) to enhance the field in the absorber at the lasing wavelength of 980 nm. The absorption bandedge at room temperature is detuned (965 nm) compared to the resonance (980 nm), which enables temperature-tuning of the modulation depth and saturation fluence from approximately 2.5% up to 15% and from 20 μJ/cm{sup 2} to 1.1 μJ/cm{sup 2}, respectively.

  6. Absorber and gain chip optimization to improve performance from a passively modelocked electrically pumped vertical external cavity surface emitting laser

    Science.gov (United States)

    Zaugg, C. A.; Gronenborn, S.; Moench, H.; Mangold, M.; Miller, M.; Weichmann, U.; Pallmann, W. P.; Golling, M.; Tilma, B. W.; Keller, U.

    2014-03-01

    We present an electrically pumped vertical-external-cavity surface-emitting laser (EP-VECSEL) modelocked with a semiconductor saturable absorber mirror (SESAM) with significantly improved performance. In different cavity configurations, we present the shortest pulses (2.5 ps), highest average output power (53.2 mW), highest repetition rate (18.2 GHz), and highest peak power (4.7 W) to date. The simple and low-cost concept of EP-VECSELs is very attractive for mass-market applications such as optical communication and clocking. The improvements result from an optimized gain chip from Philips Technologie GmbH and a SESAM, specifically designed for EP-VECSELs. For the gain chip, we found a better trade-off between electrical and optical losses with an optimized doping scheme in the substrate to increase the average output power. Furthermore, the device's bottom contact diameter (60 μm) is smaller than the oxide aperture diameter (100 μm), which favors electro-optical conversion into a TEM00 mode. Compared to optically pumped VECSELs we have to increase the field enhancement in the active region of an EP-VECSEL which requires a SESAM with lower saturation fluence and higher modulation depth for modelocking. We therefore used a resonant quantum well SESAM with a 3.5-pair dielectric top-coating (SiNx and SiO2) to enhance the field in the absorber at the lasing wavelength of 980 nm. The absorption bandedge at room temperature is detuned (965 nm) compared to the resonance (980 nm), which enables temperature-tuning of the modulation depth and saturation fluence from approximately 2.5% up to 15% and from 20 μJ/cm2 to 1.1 μJ/cm2, respectively.

  7. Research of the use of silver nanowires as a current spreading layer on vertical-cavity surface-emitting lasers

    Science.gov (United States)

    Guo, Xia; Shi, Lei; Li, Chong; Dong, Jian; Liu, Bai; Hu, Shuai; He, Yan

    2016-11-01

    Silver nanowire (AgNW) film was proposed to apply on the surface of the vertical-cavity surface-emitting lasers (VCSELs) with large aperture in order to obtain a uniform current distribution in the active region and a better optical beam quality. Optimization of the AgNW film was carried out with the sheet resistance of 28.4 Ω/sq and the optical transmission of 94.8% at 850 nm. The performance of VCSELs with and without AgNW film was studied. When the AgNW film was applied to the surface of VCSELs, due to its better current spreading effect, the maximum output optical power increased from 23.4 mW to 24.4 mW, the lasing wavelength redshift decreased from 0.085 nm/mA to 0.077 nm/mA, the differential resistance decreased from 23.95 Ω to 21.13 Ω, and the far field pattern at 50 mA decreased from 21.6° to 19.2°. At the same time, the near field test results showed that the light in the aperture was more uniform, and the far field exhibited a better single peak characteristic. Various results showed that VCSELs with AgNW on the surface showed better beam quality. Project supported by the National Natural Science Foundation of China (Grant Nos. 61335004 and 61505003), the National High Technology Research and Development Program of China (Grant No. 2015AA017101), and the National Key Research and Development of China (Grant No. 2016YFB0400603).

  8. Chaos synchronization in vertical-cavity surface-emitting laser based on rotated polarization-preserved optical feedback

    Energy Technology Data Exchange (ETDEWEB)

    Nazhan, Salam; Ghassemlooy, Zabih; Busawon, Krishna [Optical Communications Research Group, NCRLab, Faculty of Engineering and Environment, Northumbria University, Newcastle upon Tyne (United Kingdom)

    2016-01-15

    In this paper, the influence of the rotating polarization-preserved optical feedback on the chaos synchronization of a vertical-cavity surface-emitting laser (VCSEL) is investigated experimentally. Two VCSELs' polarization modes (XP) and (YP) are gradually rotated and re-injected back into the VCSEL. The anti-phase dynamics synchronization of the two polarization modes is evaluated using the cross-correlation function. For a fixed optical feedback, a clear relationship is found between the cross-correlation coefficient and the polarization angle θ{sub p}. It is shown that high-quality anti-phase polarization-resolved chaos synchronization is achieved at higher values of θ{sub p}. The maximum value of the cross-correlation coefficient achieved is −0.99 with a zero time delay over a wide range of θ{sub p} beyond 65° with a poor synchronization dynamic at θ{sub p} less than 65°. Furthermore, it is observed that the antiphase irregular oscillation of the XP and YP modes changes with θ{sub p}. VCSEL under the rotating polarization optical feedback can be a good candidate as a chaotic synchronization source for a secure communication system.

  9. Chaos synchronization in vertical-cavity surface-emitting laser based on rotated polarization-preserved optical feedback

    Science.gov (United States)

    Nazhan, Salam; Ghassemlooy, Zabih; Busawon, Krishna

    2016-01-01

    In this paper, the influence of the rotating polarization-preserved optical feedback on the chaos synchronization of a vertical-cavity surface-emitting laser (VCSEL) is investigated experimentally. Two VCSELs' polarization modes (XP) and (YP) are gradually rotated and re-injected back into the VCSEL. The anti-phase dynamics synchronization of the two polarization modes is evaluated using the cross-correlation function. For a fixed optical feedback, a clear relationship is found between the cross-correlation coefficient and the polarization angle θp. It is shown that high-quality anti-phase polarization-resolved chaos synchronization is achieved at higher values of θp. The maximum value of the cross-correlation coefficient achieved is -0.99 with a zero time delay over a wide range of θp beyond 65° with a poor synchronization dynamic at θp less than 65°. Furthermore, it is observed that the antiphase irregular oscillation of the XP and YP modes changes with θp. VCSEL under the rotating polarization optical feedback can be a good candidate as a chaotic synchronization source for a secure communication system.

  10. Mapping of two-polarization-mode dynamics in vertical-cavity surface-emitting lasers with optical injection.

    Science.gov (United States)

    Gatare, I; Sciamanna, M; Nizette, M; Thienpont, H; Panajotov, K

    2009-08-01

    We report theoretically on the interplay between polarization switching and bifurcations to nonlinear dynamics in a vertical-cavity surface-emitting laser (VCSEL) subject to orthogonal optical injection. Qualitatively different bifurcation scenarios leading to polarization switching are found and mapped out in the plane of the injection parameters, i.e., the frequency detuning vs injection strength plane. A Hopf bifurcation mechanism on the two-polarization-mode solution determines the injection-locking boundaries and influences polarization switching induced by optical injection. We furthermore report on a torus bifurcation emerging from a two-linearly polarized (LP) mode time-periodic dynamics before polarization switching and injection locking appear. It corresponds to an interesting combination of relaxation oscillation dynamics in the x -LP mode together with wave mixing dynamics in the injected y -LP mode. In agreement with recent experiments, we unveil a period-doubling route to chaos that involves both VCSEL orthogonal LP modes. The corresponding region of chaotic dynamics coincides with abrupt changes in the polarization switching boundaries in the plane of the injection parameters.

  11. Nonpolar III-nitride vertical-cavity surface-emitting laser with a photoelectrochemically etched air-gap aperture

    Energy Technology Data Exchange (ETDEWEB)

    Leonard, J. T., E-mail: jtleona01@gmail.com; Yonkee, B. P.; Cohen, D. A.; Megalini, L.; Speck, J. S. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Lee, S. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); DenBaars, S. P.; Nakamura, S. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States)

    2016-01-18

    We demonstrate a III-nitride nonpolar vertical-cavity surface-emitting laser (VCSEL) with a photoelectrochemically (PEC) etched aperture. The PEC lateral undercut etch is used to selectively remove the multi-quantum well (MQW) region outside the aperture area, defined by an opaque metal mask. This PEC aperture (PECA) creates an air-gap in the passive area of the device, allowing one to achieve efficient electrical confinement within the aperture, while simultaneously achieving a large index contrast between core of the device (the MQW within the aperture) and the lateral cladding of the device (the air-gap formed by the PEC etch), leading to strong lateral confinement. Scanning electron microscopy and focused ion-beam analysis is used to investigate the precision of the PEC etch technique in defining the aperture. The fabricated single mode PECA VCSEL shows a threshold current density of ∼22 kA/cm{sup 2} (25 mA), with a peak output power of ∼180 μW, at an emission wavelength of 417 nm. The near-field emission profile shows a clearly defined single linearly polarized (LP) mode profile (LP{sub 12,1}), which is in contrast to the filamentary lasing that is often observed in III-nitride VCSELs. 2D mode profile simulations, carried out using COMSOL, give insight into the different mode profiles that one would expect to be displayed in such a device. The experimentally observed single mode operation is proposed to be predominantly a result of poor current spreading in the device. This non-uniform current spreading results in a higher injected current at the periphery of the aperture, which favors LP modes with high intensities near the edge of the aperture.

  12. Coupling of polarization and spatial degrees of freedom of highly divergent emission in broad-area square vertical-cavity surface-emitting lasers.

    Science.gov (United States)

    Babushkin, I V; Schulz-Ruhtenberg, M; Loiko, N A; Huang, K F; Ackemann, T

    2008-05-30

    The polarization of highly divergent modes of broad-area square vertical-cavity surface-emitting lasers is shown to be only marginally affected by material anisotropies but determined by an interplay of the polarization properties of the Bragg cavity mirrors and of the transverse boundary conditions. This leads to a locking of the polarization direction to the boundaries and its indeterminacy for wave vectors oriented along the diagonal. We point out a non-Poissonian character of nearest-neighbor frequency spacing distribution and the impossibility of single-wave number solutions.

  13. Birefringence controlled room-temperature picosecond spin dynamics close to the threshold of vertical-cavity surface-emitting laser devices

    Science.gov (United States)

    Li, M. Y.; Jähme, H.; Soldat, H.; Gerhardt, N. C.; Hofmann, M. R.; Ackemann, T.

    2010-11-01

    We analyze the spin-induced circular polarization dynamics at the threshold of vertical-cavity surface-emitting lasers at room-temperature using a hybrid excitation combining electrically pumping without spin preference and spin-polarized optical injection. After a short pulse of spin-polarized excitation, fast oscillations of the circular polarization degree (CPD) are observed within the relaxation oscillations. A theoretical investigation of this behavior on the basis of a rate equation model shows that these fast oscillations of CPD could be suppressed by means of a reduction of the birefringence of the laser cavity.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-01-07

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

  15. Time-resolved spectral characterization of ring cavity surface emitting and ridge-type distributed feedback quantum cascade lasers by step-scan FT-IR spectroscopy.

    Science.gov (United States)

    Brandstetter, Markus; Genner, Andreas; Schwarzer, Clemens; Mujagic, Elvis; Strasser, Gottfried; Lendl, Bernhard

    2014-02-10

    We present the time-resolved comparison of pulsed 2nd order ring cavity surface emitting (RCSE) quantum cascade lasers (QCLs) and pulsed 1st order ridge-type distributed feedback (DFB) QCLs using a step-scan Fourier transform infrared (FT-IR) spectrometer. Laser devices were part of QCL arrays and fabricated from the same laser material. Required grating periods were adjusted to account for the grating order. The step-scan technique provided a spectral resolution of 0.1 cm(-1) and a time resolution of 2 ns. As a result, it was possible to gain information about the tuning behavior and potential mode-hops of the investigated lasers. Different cavity-lengths were compared, including 0.9 mm and 3.2 mm long ridge-type and 0.97 mm (circumference) ring-type cavities. RCSE QCLs were found to have improved emission properties in terms of line-stability, tuning rate and maximum emission time compared to ridge-type lasers.

  16. Frequency-modulated continuous-wave laser radar using dual vertical-cavity surface-emitting laser diodes for real-time measurements of distance and radial velocity

    Science.gov (United States)

    Kakuma, Seiichi

    2017-02-01

    A frequency-modulated continuous-wave (FMCW) laser radar capable of real-time displaying the distance to a target object and its radial velocity as their corresponding frequency spectra is developed. The system employs a pair of oppositely frequency-swept vertical-cavity surface-emitting laser diodes (VCSELs). This makes possible simultaneous detection of beat signals induced by the increment (up-ramp) and decrement (down-ramp) in laser frequencies. By mixing these two beat signals, their sum and difference frequencies are directly obtained without arithmetic processing such as averaging and subtraction. Results of the test experiments adopting axially moving block gauges as target objects show that both the distance and given velocities are accurately determined from the spectrum of the frequency mixer.

  17. AlGaAs/GaAs/InGaAs pnp-type vertical-cavity surface-emitting transistor-lasers.

    Science.gov (United States)

    Xiang, Y; Reuterskiöld-Hedlund, C; Yu, X; Yang, C; Zabel, T; Hammar, M; Akram, M N

    2015-06-15

    We report on the design, fabrication and analysis of vertical-cavity surface-emitting transistor-lasers (T-VCSELs) based on the homogeneous integration of an InGaAs/GaAs VCSEL and an AlGaAs/GaAs pnp-heterojunction bipolar transistor (HBT). Epitaxial regrowth confinement, modulation doping, intracavity contacting and non-conducting mirrors are used to ensure a low-loss structure, and a variety of design variations are investigated for a proper internal biasing and current injection to ensure a wide operating range. Optimized devices show mW-range output power, mA-range base threshold current and high-temperature operation to at least 60°C with the transistor in its active mode of operation for base currents well beyond threshold. Current confinement schemes based on pnp-blocking layers or a buried tunnel junction are investigated as well as asymmetric current injection for reduced extrinsic resistances.

  18. Gain-switching dynamics in optically pumped single-mode InGaN vertical-cavity surface-emitting lasers.

    Science.gov (United States)

    Chen, Shaoqiang; Asahara, Akifumi; Ito, Takashi; Zhang, Jiangyong; Zhang, Baoping; Suemoto, Tohru; Yoshita, Masahiro; Akiyama, Hidefumi

    2014-02-24

    The gain-switching dynamics of single-mode pulses were studied in blue InGaN multiple-quantum-well vertical-cavity surface-emitting lasers (VCSELs) through impulsive optical pumping. We measured the shortest single-mode pulses of 6.0 ps in width with a method of up-conversion, and also obtained the pulse width and the delay time as functions of pump powers from streak-camera measurements. Single-mode rate-equation calculations quantitatively and consistently explained the observed data. The calculations indicated that the pulse width in the present VCSELs was mostly limited by modal gain, and suggested that subpicosecond pulses should be possible within feasible device parameters.

  19. Ultrafast and widely tuneable vertical-external-cavity surface-emitting laser, mode-locked by a graphene-integrated distributed Bragg reflector.

    Science.gov (United States)

    Zaugg, C A; Sun, Z; Wittwer, V J; Popa, D; Milana, S; Kulmala, T S; Sundaram, R S; Mangold, M; Sieber, O D; Golling, M; Lee, Y; Ahn, J H; Ferrari, A C; Keller, U

    2013-12-16

    We report a versatile way of controlling the unsaturated loss, modulation depth and saturation fluence of graphene-based saturable absorbers (GSAs), by changing the thickness of a spacer between a single layer graphene (SLG) and a high-reflection mirror. This allows us to modulate the electric field intensity enhancement at the GSA from 0 up to 400%, due to the interference of incident and reflected light at the mirror. The unsaturated loss of the SLG-mirror-assembly can be reduced to ∼0. We use this to mode-lock a vertical-external-cavity surface-emitting laser (VECSEL) from 935 to 981 nm. This approach can be applied to integrate SLG into various optical components, such as output coupler mirrors, dispersive mirrors or dielectric coatings on gain materials. Conversely, it can also be used to increase the absorption (up to 10%) in various graphene based photonics and optoelectronics devices, such as photodetectors.

  20. Feasibility analysis and demonstration of high-speed digital imaging using micro-arrays of vertical cavity surface-emitting lasers

    Science.gov (United States)

    Mentzer, Mark A.; Ghosh, Chuni L.; Guo, Baiming; Brewer, Kristopher; Nicolai, Robin; Herr, Douglas; Lubking, Carl; Ojason, Neil; Tangradi, Edward; Tarpine, Howard

    2011-04-01

    Previous laser illumination systems at Aberdeen Proving Ground and elsewhere required complex pulse timing, extensive cooling, large-scale laser systems (frequency-doubled flash-pumped Nd:YAG, Cu-vapor, Q-switched ruby), making them difficult to implement for range test illumination in high speed videography. Requirements to illuminate through the self-luminosity of explosive events motivate the development of a high brightness imaging technique obviating the limitations of previous attempts. A lensed vertical cavity surface-emitting laser array is proposed and implemented with spectral filtering to effectively remove self-luminosity and the fireball from the image, providing excellent background discrimination in a variety of range test scenarios.

  1. Dynamics of 1.55 μm Wavelength Single-Mode Vertical-Cavity Surface-Emitting Laser Output under External Optical Injection

    Directory of Open Access Journals (Sweden)

    Kyong Hon Kim

    2012-01-01

    Full Text Available We review the temporal dynamics of the laser output spectrum and polarization state of 1.55 μm wavelength single-mode (SM vertical-cavity surface-emitting lasers (VCSELs induced by external optical beam injection. Injection of an external continuous-wave laser beam to a gain-switched SM VCSEL near the resonance wavelength corresponding to its main polarization-mode output was critical for improvement of its laser pulse generation characteristics, such as pulse timing-jitter reduction, linewidth narrowing, pulse amplitude enhancement, and pulse width shortening. Pulse injection of pulse width shorter than the cavity photon lifetime into the SM VCSEL in the orthogonal polarization direction with respect to its main polarization mode caused temporal delay of the polarization recovery after polarization switching (PS, and its delay was found to be the minimum at an optimized bias current. Polarization-mode bistability was observed even in the laser output of an SM VCSEL of a standard circularly cylindrical shape and used for all-optical flip-flop operations with set and reset injection pulses of very low pulse energy of order of the 3.5~4.5 fJ.

  2. Electron beam pumped III-V nitride vertical cavity surface emitting lasers grown by molecular beam epitaxy

    Science.gov (United States)

    Ng, Hock Min

    The design and fabrication by molecular beam epitaxy of a prototype vertical cavity laser based on the III-V nitrides were investigated in this work. The bottom mirror of the laser consists of distributed Bragg reflectors (DBRs) based on quarterwave AlN (or AlxGa1-xN) and GaN layers. Such DBRs were designed for maximum reflectivity in the spectral region from 390--600 nm. The epitaxial growth of these two binaries on each other revealed that while AlN grows on GaN in a two-dimensional mode (Frank-van der Merwe mode), GaN grows on AlN in a three-dimensional mode (Stranski-Krastanov mode). In spite of that, DBRs with peak reflectance up to 99% and bandwidths of 45nm were fabricated. The measured reflectance spectra were compared with simulations using the transmission matrix method. The mechanical stability of these DBR structures due to non-uniform distribution of strain arising from lattice or thermal mismatch of the various components were also addressed. The active region of the laser consists of InGaN/GaN multiple quantum wells (MQWs). The existence of up to the third order diffraction peaks in the x-ray diffraction spectra suggests that the interfaces between InGaN and GaN are sharp with little interdiffusion at the growth temperature. The photoluminescence and cathodoluminescence spectra were analyzed to determine the optical quality of the MQWs. The best MQWs were shown to have a single emission peak at 397nm with full width half maximum (FWHM) of 11nm. Cathodoluminescence studies showed that there are spatially localized areas of intense light emission. The complete device was formed on (0001) sapphire substrates using the previously described DBRs as bottom mirrors and the MQWs as the active region. The top mirror of the device consists of metallic silver. The device was pumped by an electron beam from the top mirror side and the light output was collected from the sapphire side. Measurements at 100K showed narrowing of the linewidth with increasing pump

  3. Phase noise analysis of a 10-GHz optical injection-locked vertical-cavity surface-emitting laser-based optoelectronic oscillator

    Science.gov (United States)

    Coronel, Juan; Varón, Margarita; Rissons, Angélique

    2016-09-01

    The optical injection locking (OIL) technique is proposed to reduce the phase noise of a carrier generated for a vertical-cavity surface-emitting laser (VCSEL)-based optoelectronic oscillator. The OIL technique permits the enhancement of the VCSEL direct modulation bandwidth as well as the stabilization of the optical noise of the laser. A 2-km delay line, 10-GHz optical injection-locked VCSEL-based optoelectronic oscillator (OILVBO) was implemented. The internal noise sources of the optoelectronic oscillator components were characterized and analyzed to understand the noise conversion of the system into phase noise in the oscillator carrier. The implemented OILVBO phase noise was -105.7 dBc/Hz at 10 kHz from the carrier; this value agrees well with the performed simulated analysis. From the computed and measured phase noise curves, it is possible to infer the noise processes that take place inside the OILVBO. As a second measurement of the oscillation quality, a time-domain analysis was done through the Allan's standard deviation measurement, reported for first time for an optoelectronic oscillator using the OIL technique.

  4. The study of temperature effect on the performance characteristics of the InGaN-based vertical cavity surface emitting laser (VCSEL) by solving the rate equations

    Science.gov (United States)

    Goharrizi, A. Zandi; Alahyarizadeh, Gh.

    2016-08-01

    The use of semiconductor lasers is beneficial in long-distance communications. Practical communication systems based on these lasers need high ambient temperature, with temperature changes between 40∘C and 85∘C. The study of the temperature-dependent response of these lasers is important to improve them. This study investigates the effect of temperature on InGaN-based vertical cavity surface emitting lasers (VCSEL). The active region in this structure includes a single quantum well (SQW). The rate equations of carriers and densities are numerically solved. The time variations of carrier density, photon density and output power (N, S and P) at 25∘C and the current injection of 0.04 A are obtained. Values obtained for threshold current and output power include 7 mA and 44 mW, respectively. The effect of temperature on the time variations of N, S and P from 10∘C to 35∘C is studied. Results show that these parameters decrease and the threshold current increases with an increase in temperature. Furthermore, the investigation of the effect of injection current on N, S and P shows that raising the injection current can increase these parameters. Moreover, an increase in the injection current reduces the time response.

  5. Generation of polarization-resolved wideband unpredictability-enhanced chaotic signals based on vertical-cavity surface-emitting lasers subject to chaotic optical injection.

    Science.gov (United States)

    Chen, Jian-Jun; Wu, Zheng-Mao; Tang, Xi; Deng, Tao; Fan, Li; Zhong, Zhu-Qiang; Xia, Guang-Qiong

    2015-03-23

    A system framework is proposed and analyzed for generating polarization-resolved wideband unpredictability-enhanced chaotic signals based on a slave vertical-cavity surface-emitting laser (S-VCSEL) driven by an injected optical chaos signal from a master VCSEL (M-VCSEL) under optical feedback. After calculating the time series outputs from the M-VCSEL under optical feedback and the S-VCSEL under chaotic optical injection by using the spin-flip model (SFM), the unpredictability degree (UD) is evaluated by permutation entropy (PE), and the bandwidth of the polarization-resolved outputs from the M-VCSEL and S-VCSEL are numerically investigated. The results show that, under suitable parameters, both the bandwidth and UD of two polarization components (PCs) outputs from the S-VCSEL can be enhanced significantly compared with that of the driving chaotic signals output from the M-VCSEL. By simulating the influences of the feedback and injection parameters on the bandwidth and UD of the polarization-resolved outputs from S-VCSEL, related operating parameters can be optimized.

  6. The improved output performance of a broad-area vertical-cavity surface-emitting laser with an optimized electrode diameter

    Institute of Scientific and Technical Information of China (English)

    Zhang Xing; Ning Yong-Qiang; Qin Li; Tong Cun-Zhu; Liu Yun; Wang Li-Jun

    2013-01-01

    The output performance of a 980-nm broad-area vertical-cavity surface-emitting laser (VCSEL) is improved by optimizing the p-electrode diameter in this study.Based on a three-dimensional finite-element method,the current density distribution within the active region of the VCSEL is optimized through the appropriate adjustment of the p-electrode diameter,and uniform current-density distribution is achieved.Then,the effects of this optimization are studied experimentally.The L-I-V characteristics under different temperatures of the VCSELs with different p-electrode diameters are investigated,and better temperature stability is demonstrated in the VCSEL with an optimized p-electrode diameter.The far-field measurements show that with an injected current of 2 A,the far-field divergence angle of the VCSEL with an optimized p-electrode diameter is 9°,which is much lower than the far-field angle of the VCSEL without this optimization.Also the VCSEL with an optimized p-electrode diameter shows a better near-field distribution.

  7. Intensity- and phase-noise correlations in a dual-frequency vertical-external-cavity surface-emitting laser operating at telecom wavelength

    Science.gov (United States)

    De, Syamsundar; Baili, Ghaya; Bouchoule, Sophie; Alouini, Mehdi; Bretenaker, Fabien

    2015-05-01

    The amplitude and phase noises of a dual-frequency vertical-external-cavity surface-emitting laser (DF-VECSEL) operating at telecom wavelength are theoretically and experimentally investigated in detail. In particular, the spectral behavior of the correlation between the intensity noises of the two modes of the DF-VECSEL is measured. Moreover, the correlation between the phase noise of the radio-frequency beat note generated by optical mixing of the two laser modes with the intensity noises of the two modes is investigated. All these spectral behaviors of noise correlations are analyzed for two different values of the nonlinear coupling between the laser modes. We find that to describe the spectral behavior of noise correlations between the laser modes, it is of utmost importance to have precise knowledge about the spectral behavior of the pump noise, which is the dominant source of noise in the frequency range of interest (10 kHz to 35 MHz). Moreover, it is found that the noise correlation also depends on how the spatially separated laser modes of the DF-VECSEL intercept the noise from a multimode fiber-coupled laser diode used for pumping both the laser modes. To this aim, a specific experiment is reported which aims at measuring the correlations between different spatial regions of the pump beam. The experimental results are in excellent agreement with a theoretical model based on modified rate equations.

  8. Demonstration of a III-nitride vertical-cavity surface-emitting laser with a III-nitride tunnel junction intracavity contact

    Energy Technology Data Exchange (ETDEWEB)

    Leonard, J. T., E-mail: jtleona01@gmail.com; Young, E. C.; Yonkee, B. P.; Cohen, D. A.; Margalith, T.; Speck, J. S. [Materials Department, University of California, Santa Barbara, California 93106 (United States); DenBaars, S. P.; Nakamura, S. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States)

    2015-08-31

    We report on a III-nitride vertical-cavity surface-emitting laser (VCSEL) with a III-nitride tunnel junction (TJ) intracavity contact. The violet nonpolar VCSEL employing the TJ is compared to an equivalent VCSEL with a tin-doped indium oxide (ITO) intracavity contact. The TJ VCSEL shows a threshold current density (J{sub th}) of ∼3.5 kA/cm{sup 2}, compared to the ITO VCSEL J{sub th} of 8 kA/cm{sup 2}. The differential efficiency of the TJ VCSEL is also observed to be significantly higher than that of the ITO VCSEL, reaching a peak power of ∼550 μW, compared to ∼80 μW for the ITO VCSEL. Both VCSELs display filamentary lasing in the current aperture, which we believe to be predominantly a result of local variations in contact resistance, which may induce local variations in refractive index and free carrier absorption. Beyond the analyses of the lasing characteristics, we discuss the molecular-beam epitaxy (MBE) regrowth of the TJ, as well as its unexpected performance based on band-diagram simulations. Furthermore, we investigate the intrinsic advantages of using a TJ intracavity contact in a VCSEL using a 1D mode profile analysis to approximate the threshold modal gain and general loss contributions in the TJ and ITO VCSEL.

  9. Mode-locking of an InAs Quantum Dot Based Vertical External Cavity Surface Emitting Laser Using Atomic Layer Graphene

    Science.gov (United States)

    2015-07-16

    disperse the graphene by physical adsorption on its surface. The dispersions are mixed with poly vinyl alcohol (PVA) in a polymer mixer. The...is a more bring color . The bottom structure shows the image of the structure after the incorporation of the GSAM in the VECSEL cavity. The single

  10. Room-temperature continuous-wave operation of GaN-based vertical-cavity surface-emitting lasers with n-type conducting AlInN/GaN distributed Bragg reflectors

    Science.gov (United States)

    Ikeyama, Kazuki; Kozuka, Yugo; Matsui, Kenjo; Yoshida, Shotaro; Akagi, Takanobu; Akatsuka, Yasuto; Koide, Norikatsu; Takeuchi, Tetsuya; Kamiyama, Satoshi; Iwaya, Motoaki; Akasaki, Isamu

    2016-10-01

    The room-temperature continuous-wave operation of a 1.5λ-cavity GaN-based vertical-cavity surface-emitting laser with an n-type conducting AlInN/GaN distributed Bragg reflector (DBR) was achieved. A peak reflectivity of over 99.9% was obtained in the n-type conducting AlInN/GaN DBR so that the current was injected through the DBR for the operation. The threshold current was 2.6 mA, corresponding to the threshold current density of 5.2 kA/cm2, and the operating voltage was 4.7 V. A lasing spectrum with a peak wavelength of 405.1 nm and a full-width at half maximum of 0.08 nm was also observed.

  11. Composite Resonator Surface Emitting Lasers

    Energy Technology Data Exchange (ETDEWEB)

    FISCHER,ARTHUR J.; CHOQUETTE,KENT D.; CHOW,WENG W.; ALLERMAN,ANDREW A.; GEIB,KENT M.

    2000-05-01

    The authors have developed electrically-injected coupled-resonator vertical-cavity lasers and have studied their novel properties. These monolithically grown coupled-cavity structures have been fabricated with either one active and one passive cavity or with two active cavities. All devices use a selectively oxidized current aperture in the lower cavity, while a proton implant was used in the active-active structures to confine current in the top active cavity. They have demonstrated optical modulation from active-passive devices where the modulation arises from dynamic changes in the coupling between the active and passive cavities. The laser intensity can be modulated by either forward or reverse biasing the passive cavity. They have also observed Q-switched pulses from active-passive devices with pulses as short as 150 ps. A rate equation approach is used to model the Q-switched operation yielding good agreement between the experimental and theoretical pulseshape. They have designed and demonstrated the operation of active-active devices which la.se simultaneously at both longitudinal cavity resonances. Extremely large bistable regions have also been observed in the light-current curves for active-active coupled resonator devices. This bistability can be used for high contrast switching with contrast ratios as high as 100:1. Coupled-resonator vertical-cavity lasers have shown enhanced mode selectivity which has allowed devices to lase with fundamental-mode output powers as high as 5.2 mW.

  12. Spectrum study of top-emitting organic light-emitting devices with micro-cavity structure

    Institute of Scientific and Technical Information of China (English)

    Liu Xiang; Wei Fuxiang; Liu Hui

    2009-01-01

    Blue and white top-emitting organic light-emitting devices OLEDs with cavity effect have been fabricated.TBADN:3%DSAPh and Alq3:DCJTB/TBADN:TBPe/Alq3:C545 were used as emitting materials of microcavity OLEDs.On a patterned glass substrate,silver was deposited as reflective anode,and copper phthalocyanine (CuPc)layer as HIL and 4'-bis[N-(1-Naphthyl)-N-phenyl-amino]biphenyl(NPB)layer as HTL were made.Al/Ag thin films were made as semi-transparent cathode with a transmittance of about 30%.By changing the thickness of indium tin oxide ITO,deep blue with Commission Internationale de L'Eclairage chromaticity coordinates(CIEx,y)of(0.141,0.049)was obtained on TBADN:3%DSAPh devices,and different color(red,blue and green)was obrained on Alq3:DCJTB/TBADN:TBPe/Alq3:C545 devices,full width at half maxima(FWHM)was only 17 nm.The spectral intensity and FWHM of emission in cavity devices have also been studied.

  13. Binary arithmetic using optical symbolic substitution and integrated phototransistor surface-emitting laser logic

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, J. (Center for High Technology, University of New Mexico, Albuquerque, New Mexico (USA)); Olbright, G.R.; Bryan, R.P. (Sandia National Laboratories, Albuquerque, New Mexico (USA))

    1991-10-20

    We outline an architecture for performing binary addition by using optical symbolic substitution and optical logic gates based on heterojunction phototransistors and vertical-cavity surface-emitting lasers.

  14. Substrate-etched high power external-cavity surface-emitting lasers%基质刻蚀的高功率外腔面发射激光器

    Institute of Scientific and Technical Information of China (English)

    伍瑜; 倪演海; 戴特力; 周勇; 秦莉; 梁一平; 范嗣强; 张鹏

    2012-01-01

    为了降低光抽运外腔面发射激光器的热效应,提高激光器的输出功率,采用液体毛细键合方法将逆序生长的半导体外延片与高热导率的碳化硅散热窗口键合,并用化学刻蚀方法去除外延片的基质.实验研究了用基质刻蚀的外延片搭建的外腔面发射激光器的性能.当增益介质的有源区为InGaAs/AlGaAs多量子阱、抽运源为808nm的光纤耦合输出半导体激光器,输出镜对激光波长透过率为3%时,在室温下获得TEM00模的最大输出功率0.52W,激光波长1018nm,光谱线宽2nm(半峰全宽),激光器的光光转换效率约为20%.测得x方向与y方向的M2因子分别为1.01和1.00,说明输出光束为质量优良的近衍射极限高斯光束.结果表明,基质刻蚀技术可明显改善外腔面发射激光器的热性能,获得高功率、高光束质量的激光输出.%To decrease the thermal effect of a vertical-external-cavity surface-emitting laser and increase its output power, a high thermal conductivity SiC heatspreader was bond on the reverse-order semiconductor wafer with the capillary method, and then the substrate was removed by means of chemical etch. The characteristics of the laser formed by the substrate-etched wafer were experimentally studied. When the active region in the gain structure is InGaAs/AlGaAs multiple quantum wells, the pump source is a fiber-coupled 808nm diode laser, and the transmission of the output coupler is 3% at laser wavelength, the TEM00 mode output power of 0. 52W and the optical-to-optical conversion efficiency of 20% are obtained at room temperature. The laser wavelength is 1018nm, and the spectrum width is 2nm(full width half maximum) . The measured M2 factor in x and y direction of 1. 01 and 1. 00 demonstrate the near diffraction-limited Gaussian beam of the laser. It can be concluded that the substrate-etching technology can significantly improve the thermal property of vertical-external-cavity surface-emitting

  15. Plasmonic Coupled Cavities on Moire Surfaces

    Science.gov (United States)

    Balci, Sinan; Kocabas, Askin; Karabiyik, Mustafa; Kocabas, Coskun; Aydinli, Atilla

    2010-03-01

    We investigate surface plasmon polariton (SPP) coupled cavity modes on Moire surfaces. An experimental study has been made of the propagation of SPPs on a thin silver surface that is textured with Moire surface pattern using interference lithography. The Moire surface contains periodic array of one dimensional cavities. The distance between the cavities can be controlled by changing the periodicities of Moire surface. When the SPP cavity separation is sufficiently small, we show splitting of strongly coupled plasmonic cavity modes through numerical simulations. Conversely, when the SPP cavity separation is sufficiently large, SPP cavity modes are found to be localized and do not show splitting of SPP cavity modes . This splitting of SPP cavity modes are well explained with a tight binding model that has been succesfully applied in photonic coupled cavities. Reflection measurements and numerical simulation of a large number of adjacent SPP cavities have shown a coupled resonator optical waveguide (CROW) type plasmonic waveguide band formation within the band gap region of unperturbed uniform grating.

  16. Room temperature continuous wave InGaAsN quantum well vertical cavity lasers emitting at 1.3 um

    Energy Technology Data Exchange (ETDEWEB)

    CHOQUETTE,KENT D.; KLEM,JOHN F.; FISCHER,ARTHUR J.; SPAHN,OLGA B.; ALLERMAN,ANDREW A.; FRITZ,IAN J.; KURTZ,STEVEN R.; BREILAND,WILLIAM G.; SIEG,ROBERT M.; GEIB,KENT M.; SCOTT,J.W.; NAONE,R.L.

    2000-06-05

    Selectively oxidized vertical cavity lasers emitting at 1294 nm using InGaAsN quantum wells are reported for the first time which operate continuous wave at and above room temperature. The lasers employ two n-type Al{sub 0.94}Ga{sub 0.06}As/GaAs distributed Bragg reflectors each with a selectively oxidized current aperture adjacent to the optical cavity, and the top output mirror contains a tunnel junction to inject holes into the active region. Continuous wave single mode lasing is observed up to 55 C. These lasers exhibit the longest wavelength reported to date for vertical cavity surface emitting lasers grown on GaAs substrates.

  17. Submonolayer Quantum Dots for High Speed Surface Emitting Lasers

    Directory of Open Access Journals (Sweden)

    Zakharov ND

    2007-01-01

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

  18. Optical cavity integrated surface ion trap for enhanced light collection

    Science.gov (United States)

    Benito, Francisco M.

    Ion trap systems allow the faithful storage and manipulation of qubits encoded in the energy levels of the ions, and can be interfaced with photonic qubits that can be transmitted to connect remote quantum systems. Single photons transmitted from two remote sites, each entangled with one quantum memory, can be used to entangle distant quantum memories by interfering on a beam splitter. Efficient remote entanglement generation relies upon efficient light collection from single ions into a single mode fiber. This can be realized by integrating an ion trap with an optical cavity and employing the Purcell effect for enhancing the light collection. Remote entanglement can be used as a resource for a quantum repeater for provably secure long-distance communication or as a method for communicating within a distributed quantum information processor. We present the integration of a 1 mm optical cavity with a micro-fabricated surface ion trap. The plano-concave cavity is oriented normal to the chip surface where the planar mirror is attached underneath the trap chip. The cavity is locked using a 780 nm laser which is stabilized to Rubidium and shifted to match the 369 nm Doppler transition in Ytterbium. The linear ion trap allows ions to be shuttled in and out of the cavity mode. The Purcell enhancement of spontaneous emission into the cavity mode would then allow efficient collection of the emitted photons, enabling faster remote entanglement generation.

  19. Two Dimensional Plasmonic Cavities on Moire Surfaces

    Science.gov (United States)

    Balci, Sinan; Kocabas, Askin; Karabiyik, Mustafa; Kocabas, Coskun; Aydinli, Atilla

    2010-03-01

    We investigate surface plasmon polariton (SPP) cavitiy modes on two dimensional Moire surfaces in the visible spectrum. Two dimensional hexagonal Moire surface can be recorded on a photoresist layer using Interference lithography (IL). Two sequential exposures at slightly different angles in IL generate one dimensional Moire surfaces. Further sequential exposure for the same sample at slightly different angles after turning the sample 60 degrees around its own axis generates two dimensional hexagonal Moire cavity. Spectroscopic reflection measurements have shown plasmonic band gaps and cavity states at all the azimuthal angles (omnidirectional cavity and band gap formation) investigated. The plasmonic band gap edge and the cavity states energies show six fold symmetry on the two dimensional Moire surface as measured in reflection measurements.

  20. Spontaneous Emission and Light Extraction Enhancement of Light Emitting Diode Using Partially-Reflecting Metasurface Cavity (PRMC)

    CERN Document Server

    Chen, Luzhou; Kallos, Themos; Caloz, Christophe

    2016-01-01

    The enhancement of the power conversion efficiency (PCE), and subsequent reduction of cost, of light emitting diodes (LEDs) is of crucial importance in the current lightening market. For this reason, we propose here a PCE-enhanced LED architecture, based on a partially-reflecting metasurface cavity (PRMC) structure. This structure simultaneously enhances the light extraction efficiency (LEE) and the spontaneous emission rate (SER) of the LED by enforcing the emitted light to radiate perpendicularly to the device, so as to suppress wave trapping and enhance lateral field confinement, while ensuring cavity resonance matching and maximal constructive field interference. The PRMC structure is designed using a recent surface susceptibility metasurface synthesis technique. A PRMC blue LED design is presented and demonstrated by full-wave simulation to provide LEE and SER enhancements by factors 4.0 and 1.9, respectively, corresponding to a PCE enhancement factor of 7.6, suggesting that the PRMC concept has a promis...

  1. Near-infrared broad-band cavity enhanced absorption spectroscopy using a superluminescent light emitting diode.

    Science.gov (United States)

    Denzer, W; Hamilton, M L; Hancock, G; Islam, M; Langley, C E; Peverall, R; Ritchie, G A D

    2009-11-01

    A fibre coupled near-infrared superluminescent light emitting diode that emits approximately 10 mW of radiation between 1.62 and 1.7 microm is employed in combination with a broad-band cavity enhanced spectrometer consisting of a linear optical cavity with mirrors of reflectivity approximately 99.98% and either a dispersive near-infrared spectrometer or a Fourier transform interferometer. Results are presented on the absorption of 1,3-butadiene, and sensitivities are achieved of 6.1 x 10(-8) cm(-1) using the dispersive spectrometer in combination with phase-sensitive detection, and 1.5 x 10(-8) cm(-1) using the Fourier transform interferometer (expressed as a minimum detectable absorption coefficient) over several minutes of acquisition time.

  2. High-quality distributed Bragg reflectors for resonant-cavity light-emitting diode applications

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, S.; Naranjo, F.B.; Calle, F.; Sanchez-Garcia, M.A.; Calleja, E. [ISOM, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain); Departamento de Ingenieria Electronica, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain); Vennegues, P. [CHREA-CNRS, Rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France)

    2002-08-16

    Efficient distributed Bragg reflectors based on Al{sub x}Ga{sub 1} {sub -} {sub x}N/GaN multilayer stacks have been grown by plasma-assisted molecular-beam epitaxy on GaN/Al{sub 2}O{sub 3} templates. The final goal is to incorporate these reflectors as bottom mirrors in a backside (sapphire) resonant-cavity light-emitting diode at 510 nm. The reflectors have been characterised by atomic force microscopy, high-resolution X-ray diffraction and high-resolution transmission electron microscopy. Reflectivity measurements have also been performed, obtaining values between 30% and 50%, depending on the Al content used. The incorporation of the Al{sub x}Ga{sub 1} {sub -} {sub x}N/GaN Bragg reflector as bottom mirror in a RCLED structure improves the output power by a factor of 12 compared with conventional light-emitting diodes. (Abstract Copyright[2002], Wiley Periodicals, Inc.)

  3. Device Fabrication of 60 μm Resonant Cavity Light-Emitting Diode

    Directory of Open Access Journals (Sweden)

    J. J. C. Reyes

    2004-12-01

    Full Text Available An array of 60-mm-diameter resonant cavity light-emitting diodes suited for coupling with fiber opticwere fabricated using standard device fabrication technique. I-V characterization was used to determinethe viability of the device fabricating process. Under forward bias, the turn-on voltage of the devices is1.95–2.45 V with a series resistance of 17–14 kW. Under reverse bias, the devices showed a breakdownvoltage of 35 V.

  4. High-power diode-pumped AlGaAs surface-emitting laser.

    Science.gov (United States)

    Holm, M A; Burns, D; Cusumano, P; Ferguson, A I; Dawson, M D

    1999-09-20

    We report the development and characterization of an efficient diode-pumped surface-emitting semiconductor laser operating at approximately 870 nm. By using a semiconductor Bragg reflector stack/multiple GaAs quantum well structure, mounted within a conventional laser cavity, we achieved single transverse mode laser output powers of 153 mW. Self-tuning over a 15-nm spectral range has been obtained.

  5. Application in Secret Communication of Chaos Driving Synchronization of Vertical Cavity Surface Emitting Lasers with Optical Feedback%光反馈垂直腔面发射半导体激光器的混沌驱动同步在保密通信中的应用

    Institute of Scientific and Technical Information of China (English)

    刘玉金; 张胜海; 杨华; 谭建锋

    2012-01-01

    基于光反馈垂直腔面发射半导体激光器(VCSELs)混沌驱动同步,提出了一种光反馈VCSELs混沌保密通信系统.通过模拟信号和数字信号在该系统的混沌保密通信的实现,验证了该系统的可行性.进一步利用该方案实现了对文字和数字图像的保密通信,并对解密图像及原始图像灰度值的差值做了相关计算.数值模拟结果说明该通信方案具有良好的解密效果.%Based on the chaos driving synchronization of vertical cavity surface emitting lasers (VCSELs) with optical feedback, the chaotic secure communication system of VCSELs with optical feedback is designed. Through the realizations of simulation signal and digital signal in the chaotic secure communication system, the feasibility of this system is verified. Besides, the secret communications of text and digital image can be well achieved by this scheme. Furthermore, the difference of image grey value between their histograms of encryption image and decryption image is calculated. Numerical simulation results show that the secret communication system has a good decryption effect.

  6. Geometrically induced surface polaritons in planar nanostructured metallic cavities

    Energy Technology Data Exchange (ETDEWEB)

    Davids, P. S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Intravia, F [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dalvit, Diego A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-01-14

    We examine the modal structure and dispersion of periodically nanostructured planar metallic cavities within the scattering matrix formulation. By nanostructuring a metallic grating in a planar cavity, artificial surface excitations or spoof plasmon modes are induced with dispersion determined by the periodicity and geometric characteristics of the grating. These spoof surface plasmon modes are shown to give rise to new cavity polaritonic modes at short mirror separations that modify the density of modes in nanostructured cavities. The increased modal density of states form cavity polarirons have a large impact on the fluctuation induced electromagnetic forces and enhanced hear transfer at short separations.

  7. SRF Cavity Surface Topography Characterization Using Replica Techniques

    Energy Technology Data Exchange (ETDEWEB)

    C. Xu, M.J. Kelley, C.E. Reece

    2012-07-01

    To better understand the roll of topography on SRF cavity performance, we seek to obtain detailed topographic information from the curved practical cavity surfaces. Replicas taken from a cavity interior surface provide internal surface molds for fine Atomic Force Microscopy (AFM) and stylus profilometry. In this study, we confirm the replica resolution both on surface local defects such as grain boundary and etching pits and compare the surface uniform roughness with the aid of Power Spectral Density (PSD) where we can statistically obtain roughness parameters at different scales. A series of sampling locations are at the same magnetic field chosen at the same latitude on a single cell cavity to confirm the uniformity. Another series of sampling locations at different magnetic field amplitudes are chosen for this replica on the same cavity for later power loss calculation. We also show that application of the replica followed by rinsing does not adversely affect the cavity performance.

  8. Frustrated total internal reflection in organic light-emitting diodes employing sphere cavity embedded in polystyrene

    Science.gov (United States)

    Zhu, Peifen

    2016-02-01

    The light extraction efficiency of top-emitting organic light-emitting diodes (OLEDs) is numerically investigated employing the finite-difference time-domain method. The periodic nanostructures formed by embedding the sphere arrays in polystyrene (PS) are placed on top of OLED to frustrate the total internal reflection at the interface between OLED and free space. These nanostructures serve as an intermediate medium to extract the light out of OLED devices. Efficiently coupling both evanescent waves and propagation waves into spheres and subsequently extracting these light waves out of the sphere is key to achieving high extraction efficiency. By tuning the thickness of PS layer, both of the in-coupling efficiency and out-coupling efficiency are optimized for achieving high light extraction efficiency. Thicker PS layer results in higher in-coupling efficiency in sphere while the thinner PS layer leads to higher out-coupling efficiency. Thus the maximum light extraction is a trade-off between the in-coupling efficiency and out-coupling efficiency. The study shows that light extraction efficiency of 89% can be achieved by embedding 0.90 μm TiO2 sphere in 0.30 μm PS layer with optimized in-coupling efficiency, out-coupling efficiency and cavity effect.

  9. Near Field and Far Field Effects in the Taguchi-Optimized Design of AN InP/GaAs-BASED Double Wafer-Fused Mqw Long-Wavelength Vertical-Cavity Surface-Emitting Laser

    Science.gov (United States)

    Menon, P. S.; Kandiah, K.; Mandeep, J. S.; Shaari, S.; Apte, P. R.

    Long-wavelength VCSELs (LW-VCSEL) operating in the 1.55 μm wavelength regime offer the advantages of low dispersion and optical loss in fiber optic transmission systems which are crucial in increasing data transmission speed and reducing implementation cost of fiber-to-the-home (FTTH) access networks. LW-VCSELs are attractive light sources because they offer unique features such as low power consumption, narrow beam divergence and ease of fabrication for two-dimensional arrays. This paper compares the near field and far field effects of the numerically investigated LW-VCSEL for various design parameters of the device. The optical intensity profile far from the device surface, in the Fraunhofer region, is important for the optical coupling of the laser with other optical components. The near field pattern is obtained from the structure output whereas the far-field pattern is essentially a two-dimensional fast Fourier Transform (FFT) of the near-field pattern. Design parameters such as the number of wells in the multi-quantum-well (MQW) region, the thickness of the MQW and the effect of using Taguchi's orthogonal array method to optimize the device design parameters on the near/far field patterns are evaluated in this paper. We have successfully increased the peak lasing power from an initial 4.84 mW to 12.38 mW at a bias voltage of 2 V and optical wavelength of 1.55 μm using Taguchi's orthogonal array. As a result of the Taguchi optimization and fine tuning, the device threshold current is found to increase along with a slight decrease in the modulation speed due to increased device widths.

  10. Electrically driven surface plasmon light-emitting diodes

    DEFF Research Database (Denmark)

    Fadil, Ahmed; Ou, Yiyu; Iida, Daisuke;

    We investigate device performance of GaN light-emitting diodes (LEDs) with a 30-nm p-GaN layer. The metallization used to separate the p-contact from plasmonic metals, reveals limitations on current spreading which reduces surface plasmonic enhancement.......We investigate device performance of GaN light-emitting diodes (LEDs) with a 30-nm p-GaN layer. The metallization used to separate the p-contact from plasmonic metals, reveals limitations on current spreading which reduces surface plasmonic enhancement....

  11. Improved surface treatment of the superconducting TESLA cavities

    Energy Technology Data Exchange (ETDEWEB)

    Lilje, L. E-mail: lutz.lilje@desy.de; Antoine, C.; Benvenuti, C.; Bloess, D.; Charrier, J.-P.; Chiaveri, E.; Ferreira, L.; Losito, R.; Matheisen, A.; Preis, H.; Proch, D.; Reschke, D.; Safa, H.; Schmueser, P.; Trines, D.; Visentin, B.; Wenninger, H

    2004-01-11

    The proposed linear electron-positron collider TESLA is based on 1.3 GHz superconducting niobium cavities for particle acceleration. For a centre-of-mass energy of 500 GeV, an accelerating field of 23.4 MV/m is required which is reliably achieved with a niobium surface preparation by chemical etching. An upgrade of the collider to 800 GeV requires an improved cavity preparation technique. In this paper, results are presented on single-cell cavities which demonstrate that fields of up to 40 MV/m are accessible by electrolytic polishing of the inner surface of the cavity.

  12. Improved surface treatment of the superconducting TESLA cavities

    Science.gov (United States)

    Lilje, L.; Antoine, C.; Benvenuti, C.; Bloess, D.; Charrier, J.-P.; Chiaveri, E.; Ferreira, L.; Losito, R.; Matheisen, A.; Preis, H.; Proch, D.; Reschke, D.; Safa, H.; Schmüser, P.; Trines, D.; Visentin, B.; Wenninger, H.

    2004-01-01

    The proposed linear electron-positron collider TESLA is based on 1.3 GHz superconducting niobium cavities for particle acceleration. For a centre-of-mass energy of 500 GeV, an accelerating field of 23.4 MV/m is required which is reliably achieved with a niobium surface preparation by chemical etching. An upgrade of the collider to 800 GeV requires an improved cavity preparation technique. In this paper, results are presented on single-cell cavities which demonstrate that fields of up to 40 MV/m are accessible by electrolytic polishing of the inner surface of the cavity.

  13. Improved surface treatment of the superconducting TESLA cavities

    Energy Technology Data Exchange (ETDEWEB)

    Lilje, L.; Matheisen, A.; Proch, D.; Reschke, D.; Trines, D.; Antoine, C.; Charrier, J.P.; Safa, H.; Visentin, B. [CEA Saclay, DAPHNIA, Gif-sur-Yvette (France); Benvenuti, C.; Bloess, D.; Chiaveri, E.; Ferreira, L.; Losito, R.; Preis, H.; Wenninger, H. [CERN, Geneva (Switzerland); Schmueser, P. [Hamburg Univ. (Germany)

    2004-01-01

    The proposed linear electron-positron collider TESLA is based on 1.3 GHz superconducting niobium cavities for particle acceleration. For a center-of-mass energy of 500 GeV an accelerating field of 23.4 MV/m is required which is reliably achieved with a niobium surface preparation by chemical etching. An upgrade of the collider to 800 GeV requires an improved cavity preparation technique. In this paper results are presented on single-cell cavities which demonstrate that fields of up to 40 MV/m are accessible by electrolytic polishing of the inner surface of the cavity. (orig.)

  14. AZO/Ag/AZO anode for resonant cavity red, blue, and yellow organic light emitting diodes

    Science.gov (United States)

    Gentle, A. R.; Yambem, S. D.; Burn, P. L.; Meredith, P.; Smith, G. B.

    2016-06-01

    Indium tin oxide (ITO) is the transparent electrode of choice for organic light-emitting diodes (OLEDs). Replacing ITO for cost and performance reasons is a major drive across optoelectronics. In this work, we show that changing the transparent electrode on red, blue, and yellow OLEDs from ITO to a multilayer buffered aluminium zinc oxide/silver/aluminium zinc oxide (AZO/Ag/AZO) substantially enhances total output intensity, with better control of colour, its constancy, and intensity over the full exit hemisphere. The thin Ag containing layer induces a resonant cavity optical response of the complete device. This is tuned to the emission spectra of the emissive material while minimizing internally trapped light. A complete set of spectral intensity data is presented across the full exit hemisphere for each electrode type and each OLED colour. Emission zone modelling of output spectra at a wide range of exit angles to the normal was in excellent agreement with the experimental data and hence could, in principle, be used to check and adjust production settings. These multilayer transparent electrodes show significant potential for both eliminating indium from OLEDs and spectrally shaping the emission.

  15. Surface processing for bulk niobium superconducting radio frequency cavities

    Science.gov (United States)

    Kelly, M. P.; Reid, T.

    2017-04-01

    The majority of niobium cavities for superconducting particle accelerators continue to be fabricated from thin-walled (2–4 mm) polycrystalline niobium sheet and, as a final step, require material removal from the radio frequency (RF) surface in order to achieve performance needed for use as practical accelerator devices. More recently bulk niobium in the form of, single- or large-grain slices cut from an ingot has become a viable alternative for some cavity types. In both cases the so-called damaged layer must be chemically etched or electrochemically polished away. The methods for doing this date back at least four decades, however, vigorous empirical studies on real cavities and more fundamental studies on niobium samples at laboratories worldwide have led to seemingly modest improvements that, when taken together, constitute a substantial advance in the reproducibility for surface processing techniques and overall cavity performance. This article reviews the development of niobium cavity surface processing, and summarizes results of recent studies. We place some emphasis on practical details for real cavity processing systems which are difficult to find in the literature but are, nonetheless, crucial for achieving the good and reproducible cavity performance. New approaches for bulk niobium surface treatment which aim to reduce cost or increase performance, including alternate chemical recipes, barrel polishing and ‘nitrogen doping’ of the RF surface, continue to be pursued and are closely linked to the requirements for surface processing.

  16. Modulation of cavity-polaritons by surface acoustic waves

    DEFF Research Database (Denmark)

    de Lima, M. M.; Poel, Mike van der; Hey, R.;

    2006-01-01

    We modulate cavity-polaritons using surface acoustic waves. The corresponding formation of a mini-Brillouin zone and band folding of the polariton dispersion is demonstrated for the first time. Results are in good agreement with model calculations.......We modulate cavity-polaritons using surface acoustic waves. The corresponding formation of a mini-Brillouin zone and band folding of the polariton dispersion is demonstrated for the first time. Results are in good agreement with model calculations....

  17. Localization of surface plasmon polaritons in hexagonal arrays of Moiré cavities

    Science.gov (United States)

    Balci, Sinan; Kocabas, Askin; Kocabas, Coskun; Aydinli, Atilla

    2011-01-01

    In view of the progress on the confinement of light, we report on the dispersion characteristics of surface plasmon polaritons (SPPs) on two-dimensional Moiré surfaces in the visible part of the electromagnetic spectrum. Polarization dependent spectroscopic reflection measurements show omnidirectional confinement of SPPs. The resonance wavelength of SPP cavity modes can be adjusted by tuning the propagation direction of SPPs. The results may have an impact on the control of spontaneous emission and absorption with applications in light emitting diodes and solar cells, as well as in quantum electrodynamics experiments.

  18. Gain chip design, power scaling and intra-cavity frequency doubling with LBO of optically pumped red-emitting AlGaInP-VECSELs

    Science.gov (United States)

    Kahle, Hermann; Mateo, Cherry M. N.; Brauch, Uwe; Bek, Roman; Schwarzbäck, Thomas; Jetter, Michael; Graf, Thomas; Michler, Peter

    2016-03-01

    The wide range of applications in biophotonics, television or projectors, spectroscopy and lithography made the optically-pumped semiconductor (OPS) vertical external cavity surface-emitting lasers (VECSELs) an important category of power scalable lasers. The possibility of bandgap engineering, inserting frequency selective and converting elements into the open laser cavity and laser emission in the fundamental Gaussian mode leads to ongoing growth of the area of applications for tuneable laser sources. We present an AlGaInP-VECSEL system with a multi quantum well structure consisting of compressively strained GaInP quantum wells in an AlxGa1-xInP separate confinement heterostructure with an emission wavelength around 665 nm. The VECSEL chip with its n-λ cavity is pumped by a 532nm Nd:YAG laser under an angle to the normal incidence of 50°. In comparison, a gain chip design for high absorption values at pump wavelengths around 640nm with the use of quantum dot layers as active material is also presented. Frequency doubling is now realized with an antireflection coated lithium borate crystal, while a birefringent filter, placed inside the laser cavity under Brewster's angle, is used for frequency tuning. Further, power-scaling methods like in-well pumping as well as embedding the active region of a VECSEL between two transparent ic heaspreaders are under investigation.

  19. Laser polishing for topography management of accelerator cavity surfaces

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-07-20

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

  20. Optical cavity coupled surface plasmon resonance sensing for enhanced sensitivity

    Institute of Scientific and Technical Information of China (English)

    Zheng Zheng; Xin Zhao; Jinsong Zhu; Jim Diamond

    2008-01-01

    A surface plasmon resonance (SPR) sensing system based on the optical cavity enhanced detection tech-nique is experimentally demonstrated. A fiber-optic laser cavity is built with a SPR sensor inside. By measuring the laser output power when the cavity is biased near the threshold point, the sensitivity, defined as the dependence of the output optical intensity on the sample variations, can be increased by about one order of magnitude compared to that of the SPR sensor alone under the intensity interrogation scheme. This could facilitate ultra-high sensitivity SPR biosensing applications. Further system miniaturization is possible by using integrated optical components and waveguide SPR sensors.

  1. Plasma Processing of Large Curved Surfaces for SRF Cavity Modification

    CERN Document Server

    Upadhyay, J; Popović, S; Valente-Feliciano, A -M; Phillips, L; Vušković, L

    2014-01-01

    Plasma based surface modification of niobium is a promising alternative to wet etching of superconducting radio frequency (SRF) cavities. The development of the technology based on Cl2/Ar plasma etching has to address several crucial parameters which influence the etching rate and surface roughness, and eventually, determine cavity performance. This includes dependence of the process on the frequency of the RF generator, gas pressure, power level, the driven (inner) electrode configuration, and the chlorine concentration in the gas mixture during plasma processing. To demonstrate surface layer removal in the asymmetric non-planar geometry, we are using a simple cylindrical cavity with 8 ports symmetrically distributed over the cylinder. The ports are used for diagnosing the plasma parameters and as holders for the samples to be etched. The etching rate is highly correlated with the shape of the inner electrode, radio-frequency (RF) circuit elements, chlorine concentration in the Cl2/Ar gas mixtures, residence...

  2. Microstructured Air Cavities as High-Index Contrast Substrates with Strong Diffraction for Light-Emitting Diodes.

    Science.gov (United States)

    Moon, Yoon-Jong; Moon, Daeyoung; Jang, Jeonghwan; Na, Jin-Young; Song, Jung-Hwan; Seo, Min-Kyo; Kim, Sunghee; Bae, Dukkyu; Park, Eun Hyun; Park, Yongjo; Kim, Sun-Kyung; Yoon, Euijoon

    2016-05-11

    Two-dimensional high-index-contrast dielectric gratings exhibit unconventional transmission and reflection due to their morphologies. For light-emitting devices, these characteristics help guided modes defeat total internal reflections, thereby enhancing the outcoupling efficiency into an ambient medium. However, the outcoupling ability is typically impeded by the limited index contrast given by pattern media. Here, we report strong-diffraction, high-index-contrast cavity engineered substrates (CESs) in which hexagonally arranged hemispherical air cavities are covered with a 80 nm thick crystallized alumina shell. Wavelength-resolved diffraction measurements and Fourier analysis on GaN-grown CESs reveal that the high-index-contrast air/alumina core/shell patterns lead to dramatic excitation of the low-order diffraction modes. Large-area (1075 × 750 μm(2)) blue-emitting InGaN/GaN light-emitting diodes (LEDs) fabricated on a 3 μm pitch CES exhibit ∼39% enhancement in the optical power compared to state-of-the-art, patterned-sapphire-substrate LEDs, while preserving all of the electrical metrics that are relevant to LED devices. Full-vectorial simulations quantitatively demonstrate the enhanced optical power of CES LEDs and show a progressive increase in the extraction efficiency as the air cavity volume is expanded. This trend in light extraction is observed for both lateral- and flip-chip-geometry LEDs. Measurements of far-field profiles indicate a substantial beaming effect for CES LEDs, despite their few-micron-pitch pattern. Near-to-far-field transformation simulations and polarization analysis demonstrate that the improved extraction efficiency of CES LEDs is ascribed to the increase in emissions via the top escape route and to the extraction of transverse-magnetic polarized light.

  3. Printed Large-Area Single-Mode Photonic Crystal Bandedge Surface-Emitting Lasers on Silicon.

    Science.gov (United States)

    Zhao, Deyin; Liu, Shihchia; Yang, Hongjun; Ma, Zhenqiang; Reuterskiöld-Hedlund, Carl; Hammar, Mattias; Zhou, Weidong

    2016-01-04

    We report here an optically pumped hybrid III-V/Si photoic crystal surface emitting laser (PCSEL), consisting of a heterogeneously integrated III-V InGaAsP quantum well heterostructure gain medium, printed on a patterned defect-free Si photonic crystal (PC) bandedge cavity. Single mode lasing was achieved for a large area laser, with a side-mode suppression ratio of 28 dB, for lasing operation temperature ~ 200 K. Two types of lasers were demonstrated operating at different temperatures. Detailed modal analysis reveals the lasing mode matches with the estimated lasing gain threshold conditions. Our demonstration promises a hybrid laser sources on Si towards three-dimensional (3D) integrated Si photonics for on-chip wavelength-division multiplex (3D WDM) systems for a wide range of volume photonic/electronic applications in computing, communication, sensing, imaging, etc.

  4. Analytical modelling of end thermal coupling in a solid-state laser longitudinally bonded by a vertical-cavity top-emitting laser diode

    Institute of Scientific and Technical Information of China (English)

    Wu Jian; H.D.Summers

    2009-01-01

    The intrinsic features involving a circularly symmetric beam profile with low divergence, planar geometry as well as the increasingly enhanced power of vertical-cavity surface-emitting lasers (VCSELs) have made the VCSEL a promising pump source in direct end bonding to a solid-state laser medium to form the minimized, on-wafer integrated laser system. This scheme will generate a surface contact pump configuration and thus additional end thermal coupling to the laser medium through the joint interface of both materials, apart from pump beam heating. This paper analytically models temperature distributions in both VCSEL and the laser medium from the end thermal coupling regarding surface contact pump configuration using a top-emitting VCSEL as the pump source for the first time. The analytical solutions are derived by introducing relative temperature and mean temperature expressions. The results show that the end contact heating by the VCSEL could lead to considerable temperature variations associated with thermal phase shift and thermal lensing in the laser medium. However, if the central temperature of the interface is increased by less than 20 K, the end contact heating does not have a significant thermal influence on the laser medium. In this case, the thermal effect should be dominated by pump beam heating. This work provides useful analytical results for further analysis of hybrid thermal effects on those lasers pumped by a direct VCSEL bond.

  5. Investigation Of Breakdown Induced Surface Damage On 805 Mhz Pillbox Cavity Interior Surfaces

    CERN Document Server

    Jana, M R; Leonova, M; Moretti, A; Tollestrup, A; Yonehara, K; Freemire, B; Torun, Y; Bowring, D; Flanagan, G

    2014-01-01

    The MuCool Test Area (MTA) at Fermilab is a facility to develop the technology required for ionization cooling for a future Muon Collider and/or Neutrino Factory. As part of this research program, we have tested two 805 MHz vacuum RF cavities in a multi-Tesla magnetic field to study the effects of the static magnetic field on the cavity operation. This study gives useful information on field emitters in the cavity, dark current, surface conditioning, breakdown mechanisms and material properties of the cavity. All these factors determine the maximum accelerating gradient in the cavity. This paper discusses the image processing technique for quantitative estimation of spark damage spot distribution on cavity interior surfaces. The distribution is compared with the electric field distribution predicted by a computer code calculation. The local spark density is proportional to probability of surface breakdown and shows a power law dependence on the maximum electric field (E). This E dependence is consistent with ...

  6. The role of phonon scattering in the indistinguishability of photons emitted from semiconductor cavity QED systems

    DEFF Research Database (Denmark)

    Nielsen, Per Kær; Gregersen, Niels; Mørk, Jesper

    2013-01-01

    A solid-state single-photon source emitting indistinguishable photons on-demand is an essential component of linear optics quantum computing schemes. However, the emitter will inevitably interact with the solid-state environment causing decoherence and loss of indistinguishability. In this paper......, we present a comprehensive theoretical treatment of the influence of phonon scattering on the coherence properties of single photons emitted from semiconductor quantum dots. We model decoherence using a full microscopic theory and compare with standard Markovian approximations employing Lindblad...

  7. Influence of Er:YAG laser ablation on cavity surface and cavity shape

    Science.gov (United States)

    Jelinkova, Helena; Dostalova, Tatjana; Krejsa, Otakar; Hamal, Karel; Kubelka, Jiri; Prochazka, Stanislav

    1996-04-01

    The cavity surface and shape after Er:YAG laser ablation at different energies, number of pulses and at a different repetition rate were observed. Longitudinal sections of extracted human incisors and transverse sections of ivory tusk were cut and polished to flat and glazed surfaces. The samples thickness was from 3 to 5 mm. The Er:YAG laser was operating in a free-running (long pulse) mode. The laser radiation was focused onto the tooth surface by CaF2 lens (f equals 55 mm). During the experiment, the teeth were steady and the radiation was delivered by a special mechanical arm fixed in a special holder; fine water mist was also used (water-mJ/min, a pressure of two atm, air-pressure three atm). The shapes of the prepared cavities were studied either by using a varying laser energies (from 70 mJ to 500 mJ) for a constant number of pulses, or a varying number of pulses (from one to thirty) for constant laser energy. The repetition rate was changed from 1 to 2 Hz. For evaluating the surfaces, shapes, and profiles, scanning electron microscopy and photographs from a light microscope were used. The results were analyzed both quantitatively and qualitatively. It is seen that there is no linear relation between the radiation pulse energy and the size of the prepared holes. With increasing the incident energy the cavity depth growth is limited. There exists some saturation not only in the enamel and dentin but especially in the homogeneous ivory.

  8. Continuous-wave 1.55 $\\mu$m diode-pumped surface emitting semiconductor laser for broadband multiplex spectroscopy

    CERN Document Server

    Jacquemet, M; Guelachvili, G; Picqué, N; Sagnes, I; Strassner, M; Symonds, C; Garnache, Arnaud; Guelachvili, Guy; Jacquemet, Mathieu; Picqu\\'{e}, Nathalie; Sagnes, Isabelle; Strassner, Martin; Symonds, Cl\\'{e}mentine

    2007-01-01

    A room temperature operating Vertical External Cavity Surface Emitting Laser is applied around 1550 nm to intracavity laser absorption spectroscopy analyzed by time-resolved Fourier transform interferometry. At an equivalent pathlength of 15 km, the high resolution spectrum of the semiconductor disk laser emission covers 17 nm simultaneously. A noise equivalent absorption coefficient at one second averaging equal to 1.5 10^{-10} cm^{-1}.Hz^{-1/2} per spectral element is reported for the 65 km longest path length employed.

  9. Investigations on the p olarization switching and bistability in a 1550 nm vertical-cavity surface-emitting laser under variable-p olarization optical injection%可变偏振光注入下1550 nm垂直腔面发射激光器的偏振开关及双稳特性∗

    Institute of Scientific and Technical Information of China (English)

    陈俊; 陈建军; 吴正茂; 蒋波; 夏光琼

    2016-01-01

    基于自旋反转模型,研究了可变偏振光注入1550 nm垂直腔面发射激光器(VPOI-1550 nm-VCSEL)的偏振开关(PS)及双稳(PB)特性。研究结果表明:对于一自由运行的1550 nm-VCSEL,在给定电流下,激光器中的平行偏振模式(Y偏振模式)激射,而正交偏振模式(X偏振模式)被抑制。引入可变偏振光注入后,在给定频率失谐∆ν(定义为注入光与X偏振模式之间的频率差异)的条件下,当注入光偏振角θp(定义为注入光的偏振方向与自由运行1550 nm-VCSEL中主导偏振模式的夹角)足够大时,正向扫描(逐渐增加)注入光功率可观察到1550 nm-VCSEL发生I类PS,反向扫描(逐渐减小)注入光功率可使1550 nm-VCSEL产生II类PS,且两类PS 的开关点要求的注入功率不一致,即出现PB现象。对于一确定的频率失谐∆ν,随着θp的增加, I类、II类PS开关点对应的注入功率以及PB区宽度都呈现减小的趋势,且|∆ν|值越大,尽管I类PS的开关点所需注入功率更大,但PB区域更宽;在给定注入功率,对于特定∆ν,通过正向及反向扫描θp也可观察到VPOI-1550 nm-VCSEL输出功率呈现的PS以及PB现象。当|∆ν|较小时,发生I类和II 类PS所要求的θp近似相同,因此PB区宽度较窄,而当|∆ν|较大时,发生两类PS所需的θp以及PB宽度随∆ν的变化曲线均呈现较大波动。因此,在1550 nm-VCSEL 工作参数给定的条件下,通过调节可变偏振光注入的注入参量,可优化1550 nm-VCSEL呈现的PS及PB特性。%Due to the potential applications in optical storage, optical logic gates and all-optical signal shaping, the polarization switching (PS) and bistability (PB) of vertical-cavity surface-emitting lasers (VCSELs) under external disturbance have attracted much attention. In this work, based on the spin-flip model, the characteristics of PS and PB in a variable-polarization optical injection 1550 nm VCSEL (VPOI-1550 nm-VCSEL) are investigated numerically

  10. Water entry without surface seal: Extended cavity formation

    KAUST Repository

    Mansoor, Mohammad M.

    2014-03-01

    We report results from an experimental study of cavity formation during the impact of superhydrophobic spheres onto water. Using a simple splash-guard mechanism, we block the spray emerging during initial contact from closing thus eliminating the phenomenon known as \\'surface seal\\', which typically occurs at Froude numbers Fr= V0 2/(gR0) = O(100). As such, we are able to observe the evolution of a smooth cavity in a more extended parameter space than has been achieved in previous studies. Furthermore, by systematically varying the tank size and sphere diameter, we examine the influence of increasing wall effects on these guarded impact cavities and note the formation of surface undulations with wavelength λ =O(10)cm and acoustic waves λa=O(D0) along the cavity interface, which produce multiple pinch-off points. Acoustic waves are initiated by pressure perturbations, which themselves are generated by the primary cavity pinch-off. Using high-speed particle image velocimetry (PIV) techniques we study the bulk fluid flow for the most constrained geometry and show the larger undulations ( λ =O (10cm)) have a fixed nature with respect to the lab frame. We show that previously deduced scalings for the normalized (primary) pinch-off location (ratio of pinch-off depth to sphere depth at pinch-off time), Hp/H = 1/2, and pinch-off time, τ α (R0/g) 1/2, do not hold for these extended cavities in the presence of strong wall effects (sphere-to-tank diameter ratio), ε = D 0/Dtank 1/16. Instead, we find multiple distinct regimes for values of Hp/H as the observed undulations are induced above the first pinch-off point as the impact speed increases. We also report observations of \\'kinked\\' pinch-off points and the suppression of downward facing jets in the presence of wall effects. Surprisingly, upward facing jets emanating from first cavity pinch-off points evolve into a \\'flat\\' structure at high impact speeds, both in the presence and absence of wall effects.

  11. From ultraviolet to green InGaN-based conventional and resonant-cavity light-emitting diodes grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Naranjo, F.B.; Fernandez, S.; Calle, F.; Sanchez-Garcia, M.A.; Calleja, E. [ISOM, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria, 28040 Madrid (Spain); Dpto. Ingenieria Electronica, ETSI Telecomunicacion, Universidad Polittecnica de Madrid (Spain)

    2002-08-16

    InGaN/GaN multiple quantum wells grown by molecular beam epitaxy were used as the active layer of standard and resonant-cavity light emitting diodes. Varying the In content in the wells from 1% to 35% and the well thickness from 1 to 2.5 nm, the room temperature electroluminescence can be tuned from 370 nm (ultraviolet) to 510 nm (green). The main factor that determines the emission energy in the well is the exciton localization for narrow wells, whereas for well thicknesses larger than 3 nm the piezoelectric field is the key factor, even for high In contents. Green resonant-cavity light emitting diodes have been successfully fabricated with a semitransparent AlGaN/GaN-based distributed bragg reflector as bottom mirror and an Al coating as top mirror. The external efficiency of those devices is increased by a factor of 10 compared to standard light emitting diodes. (Abstract Copyright[2002], Wiley Periodicals, Inc.)

  12. Surface Plasmon Enhanced Phosphorescent Organic Light Emitting Diodes

    Energy Technology Data Exchange (ETDEWEB)

    Guillermo Bazan; Alexander Mikhailovsky

    2008-08-01

    The objective of the proposed work was to develop the fundamental understanding and practical techniques for enhancement of Phosphorescent Organic Light Emitting Diodes (PhOLEDs) performance by utilizing radiative decay control technology. Briefly, the main technical goal is the acceleration of radiative recombination rate in organometallic triplet emitters by using the interaction with surface plasmon resonances in noble metal nanostructures. Increased photonic output will enable one to eliminate constraints imposed on PhOLED efficiency by triplet-triplet annihilation, triplet-polaron annihilation, and saturation of chromophores with long radiative decay times. Surface plasmon enhanced (SPE) PhOLEDs will operate more efficiently at high injection current densities and will be less prone to degradation mechanisms. Additionally, introduction of metal nanostructures into PhOLEDs may improve their performance due to the improvement of the charge transport through organic layers via multiple possible mechanisms ('electrical bridging' effects, doping-like phenomena, etc.). SPE PhOLED technology is particularly beneficial for solution-fabricated electrophosphorescent devices. Small transition moment of triplet emitters allows achieving a significant enhancement of the emission rate while keeping undesirable quenching processes introduced by the metal nanostructures at a reasonably low level. Plasmonic structures can be introduced easily into solution-fabricated PhOLEDs by blending and spin coating techniques and can be used for enhancement of performance in existing device architectures. This constitutes a significant benefit for a large scale fabrication of PhOLEDs, e.g. by roll-to-roll fabrication techniques. Besides multieexciton annihilation, the power efficacy of PhOLEDs is often limited by high operational bias voltages required for overcoming built-in potential barriers to injection and transport of electrical charges through a device. This problem is

  13. 基于椭圆偏振光注入垂直腔表面发射激光器的正交偏振模式单周期振荡产生两路光子微波∗%Two channel photonic microwave generation based on period-one oscillations of two orthogonally polar-ized modes in a vertical-cavity surface-emitting laser subjected to an elliptically polarized optical injection

    Institute of Scientific and Technical Information of China (English)

    周娅; 吴正茂; 樊利; 孙波; 何洋; 夏光琼

    2015-01-01

    Previous investigations demonstrated that a semiconductor laser subjected to optical injection can realize period-one (P1) oscillation output under suitable operational parameters, which can be used to obtain high quality photonic microwave. In this paper, we propose a scheme for simultaneously generating two channel photonic microwave based on the P1 oscillations of two orthogonally polarization modes in a vertical-cavity surface-emitting laser (VCSEL) subjected to an elliptical polarization optical injection, and the relevant characteristics of obtained photonic microwave are numerically simulated and analyzed. The results show that under suitable operational parameters, a free-running VCSEL (named master VCSEL, M-VCSEL) can output an elliptical polarization light in which both X and Y polarization components of the elliptical polarization light oscillate at the same frequency. By using the elliptical polarization light from the M-VCSEL as an injection light into another VCSEL (named slave VCSEL, S-VCSEL), both two polarization components of the S-VCSEL can be driven into P1 oscillation through selecting suitable injection strength under a fixed frequency detuning between the M-VCSEL and the S-VCSEL. Based on the P1 oscillation, two orthogonally photonic microwave signals can be obtained. With the increase of the injection strength from the M-VCSEL, the frequency of photonic microwave shows a gradually increasing trend while the power of photonic microwave displays an increasing process accompanied by slight ripples. Combining the distribution mappings of the frequency, the power, and the amplitude difference between the first sideband and the second sideband of the photonic microwave in the parameter space of the injection strength and the frequency detuning, certain regions with optimally operational parameters can be determined for acquiring high quality photonic microwave.

  14. Some Estimations for Correlation Between the RF Cavity Surface Temperature and Electrical Breakdown Possibility

    CERN Document Server

    Paramonov, V V

    2004-01-01

    The electrical breakdown in accelerating cavities is the complicated phenomenon and depends on many parameters. Some reasons for breakdown can be avoided by appropriate vacuum system design and the cavity surface cleaning. This case, for normal conducting accelerating cavities free electrons - the dark currents due to Fowler-Nordheim emission can be considered as the main reason of possible electrical breakdown. It is known from the practice - the combination of the high electric field at the cavity surface with high surface temperature is the subject for risk in the cavity operation. In this paper the dependence on the surface temperature is considered and 'effective' electric field enhancement is discussed.

  15. Electrically Pumped Vertical-Cavity Amplifiers

    DEFF Research Database (Denmark)

    Greibe, Tine

    2007-01-01

    In this work, the design of electrically pumped vertical cavity semiconductor optical amplifiers (eVCAs) for use in a mode-locked external-cavity laser has been developed, investigated and analysed. Four different eVCAs, one top-emitting and three bottom emitting structures, have been designed...... and discussed. The thesis concludes with recommendations for further work towards the realisation of compact electrically pumped mode-locked vertical externalcavity surface emitting lasers....

  16. Enhanced light emission from top-emitting organic light-emitting diodes by optimizing surface plasmon polariton losses

    CERN Document Server

    Fuchs, Cornelius; Wieczorek, Martin; Gather, Malte C; Hofmann, Simone; Reineke, Sebastian; Leo, Karl; Scholz, Reinhard

    2015-01-01

    We demonstrate enhanced light extraction for monochrome top-emitting organic light-emitting diodes (OLEDs). The enhancement by a factor of 1.2 compared to a reference sample is caused by the use of a hole transport layer (HTL) material possessing a low refractive index (1.52). The low refractive index reduces the in-plane wave vector of the surface plasmon polariton (SPP) excited at the interface between the bottom opaque metallic electrode (anode) and the HTL. The shift of the SPP dispersion relation decreases the power dissipated into lost evanescent excitations and thus increases the outcoupling efficiency, although the SPP remains constant in intensity. The proposed method is suitable for emitter materials owning isotropic orientation of the transition dipole moments as well as anisotropic, preferentially horizontal orientation, resulting in comparable enhancement factors. Furthermore, for sufficiently low refractive indices of the HTL material, the SPP can be modeled as a propagating plane wave within ot...

  17. Final report on LDRD project: Semiconductor surface-emitting microcavity laser spectroscopy for analysis of biological cells and microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Gourley, P.L.; McDonald, A.E. [Sandia National Labs., Albuquerque, NM (United States). Nanostructure and Semiconductor Physics Dept.; Gourley, M.F. [Washington Hospital Center, DC (United States); Bellum, J. [Coherent Technologies, Boulder, CO (United States)

    1997-08-01

    This article discusses a new intracavity laser technique that uses living or fixed cells as an integral part of the laser. The cells are placed on a GaAs based semiconductor wafer comprising one half of a vertical cavity surface-emitting laser. After placement, the cells are covered with a dielectric mirror to close the laser cavity. When photo-pumped with an external laser, this hybrid laser emits coherent light images and spectra that depend sensitively on the cell size, shape, and dielectric properties. The light spectra can be used to identify different cell types and distinguish normal and abnormal cells. The laser can be used to study single cells in real time as a cell-biology lab-on-a-chip, or to study large populations of cells by scanning the pump laser at high speed. The laser is well-suited to be integrated with other micro-optical or micro-fluidic components to lead to micro-optical-mechanical systems for analysis of fluids, particulates, and biological cells.

  18. Negative plasma potential relative to electron-emitting surfaces.

    Science.gov (United States)

    Campanell, M D

    2013-09-01

    Most works on plasma-wall interaction predict that with strong electron emission, a nonmonotonic "space-charge-limited" (SCL) sheath forms where the plasma potential is positive relative to the wall. We show that a fundamentally different sheath structure is possible where the potential monotonically increases toward a positively charged wall that is shielded by a single layer of negative charge. No ion-accelerating presheath exists in the plasma and the ion wall flux is zero. An analytical solution of the "inverse sheath" regime is demonstrated for a general plasma-wall system where the plasma electrons and emitted electrons are Maxwellian with different temperatures. Implications of the inverse sheath effect are that (a) the plasma potential is negative, (b) ion sputtering vanishes, (c) no charge is lost at the wall, and (d) the electron energy flux is thermal. To test empirically what type of sheath structure forms under strong emission, a full plasma bounded by strongly emitting walls is simulated. It is found that inverse sheaths form at the walls and ions are confined in the plasma. This result differs from past particle-in-cell simulation studies of emission which contain an artificial "source sheath" that accelerates ions to the wall, leading to a SCL sheath at high emission intensity.

  19. Theoretical and exp erimental investigation on the narrow-linewidth photonic microwave generation based on parallel polarized optically injected 1550 nm vertical-cavity surface-emitting laser%基于平行偏振光注入的1550 nm波段垂直腔表面发射激光器获取窄线宽光子微波的理论和实验研究∗

    Institute of Scientific and Technical Information of China (English)

    孙波; 吴加贵; 王顺天; 吴正茂; 夏光琼

    2016-01-01

    Photonic microwave generation has attracted much attention in recent years due to its potential applications in various fields such as radio-over-fiber communication, signal processing and radar systems. So far, different photonic microwave generation schemes have been proposed and investigated, such as the optical heterodyne method based on the beat of two independent lasers with a certain wavelength difference, the external modulation method based on electro-optical modulator, the dual-mode beat method based on the monolithic dual-mode semiconductor lasers, and the optoelectronic microwave oscillator method based on optoelectronic feedback loops. These schemes have their own advantages and deficiencies. Unlike the above schemes, in this paper we propose an all optical scheme for generating high-quality microwave based on a 1550 nm vertical-cavity surface-emitting laser (1550 nm-VCSEL). For such a scheme, high frequency microwave can be obtained based on a 1550 nm-VCSEL subjected to external optical injection, where the polarization of the injected light is the same as that of the dominant mode of the free-running 1550 nm-VCSEL (named parallel-polarized optical injection) and its wavelength is adjusted to being close to the wavelength of the suppressed polarization mode of the free-running 1550 nm-VCSEL. With the aid of double optical feedback, the linewidth of the obtained microwave can be narrowed. In this work, firstly, the feasibility of microwave generation based on parallel-polarized optically injected 1550 nm-VCSEL is analyzed theoretically by using the spin-flip model. Next, a corresponding experimental system is constructed, and the performance of microwave generation is preliminarily investigated experi-mentally. The experimental results show that 30 GHz microwave signals could be obtained based on a parallel-polarized, optically injected 1550 nm-VCSEL under suitable injection parameters, but the linewidth of microwave signal is relatively wide (hundreds

  20. Defect Detection in Superconducting Radiofrequency Cavity Surface Using C + + and OpenCV

    Science.gov (United States)

    Oswald, Samantha; Thomas Jefferson National Accelerator Facility Collaboration

    2014-03-01

    Thomas Jefferson National Accelerator Facility (TJNAF) uses superconducting radiofrequency (SRF) cavities to accelerate an electron beam. If theses cavities have a small particle or defect, it can degrade the performance of the cavity. The problem at hand is inspecting the cavity for defects, little bubbles of niobium on the surface of the cavity. Thousands of pictures have to be taken of a single cavity and then looked through to see how many defects were found. A C + + program with Open Source Computer Vision (OpenCV) was constructed to reduce the number of hours searching through the images and finds all the defects. Using this code, the SRF group is now able to use the code to identify defects in on-going tests of SRF cavities. Real time detection is the next step so that instead of taking pictures when looking at the cavity, the camera will detect all the defects.

  1. One Innovation of Mechanical Polishing Apparatus for Surface Treatment of 6 GHz TESLA Superconducting Cavity

    Institute of Scientific and Technical Information of China (English)

    YU; Guo-long; A.A.Rossi; R.K.Thakur; V.Palmieri

    2013-01-01

    6 GHz spinning seamless superconducting radio frequency(SRF)cavities are a very useful tool for testing alternative surface treatments in the fabrication of TESLA cavity.However,the surface is damaged in internal part for the using of the collapsible mandrel during spinning.The first important step of the

  2. Convective Heat Transfer Between the Wall Surface of a Cavity and the External Main Stream

    Science.gov (United States)

    Yoshiwara, Masahiro; Katto, Yoshiro; Yokoyama, Masanori

    An experimental study has been made under the following conditions for convective heat transfer between the wall surface of a cavity of which both width and depth are 25 mm and the external main stream; the range of Reynolds numbers is from 104 to 105, and the ratio of tripping wire diameter to cavity width is 0.08. The oncoming boundary layer to a cavity is turbulent by the tripping wire with the existing study. Convective heat transfer between a cavity wall surface and the external main stream is treated by the following two phenomena; one is the heat transfer which is related to the temperature difference between the wall surface and the fluid in the cavity, and the other the heat transfer which is related to the temperature difference between the fluid in a cavity and the external mainstream. Experimental data obtained for the foregoing conditions is almost coincide with the existing dimensionless correlations of two of the authors.

  3. Effects of Surface Emitting and Cumulative Collisions on Elliptic Flow

    Institute of Scientific and Technical Information of China (English)

    LIU Jian-Li; WU Feng-Juan; ZHANG Jing-Bo; TANG Gui-Xin; HUO Lei

    2008-01-01

    @@ The integral and differential elliptic flow of partons is calculated using the multiphase transport model for Au+Au collisions at centre-of-mass energy √SNN=200 GeV.It is shown that elliptic flow of partons freezing out at early time,which is affected mainly by surface emittance,decreases with time and elliptic flow of partons freezing out at late time,which is dominated by cumulative collisions,increases with time.The elliptic flow of partons freezing out early has a large contribution to the flatting of curve of final differential elliptic flow at large transverse momentum.It is argued that the effect of surface emittance is not neglectable.

  4. Laterally emitted surface second harmonic generation in a single ZnTe nanowire

    CERN Document Server

    Liu, Weiwei; Liu, Zhe; Shen, Guozhen; Lu, Peixiang

    2012-01-01

    We report a direct observation on the unique laterally emitted surface second harmonic generation (SHG) in a single ZnTe nanowire. The highly directional surface SHG signal that polarizes along the direction vertical to the nanowire growth axis, is significantly larger than the bulk SHG contribution, indicating a high efficiency of surface SHG. Two strong SHG peaks are observed on both sides of the nanowire surfaces in the far-field scanning images, which is further supported by FDTD simulations, demonstrating that the unique laterally emitted signal is ascribed to surface SHG in the ZnTe nanowire. The surface SHG in a single ZnTe nanowire with unique lateral emission and high conversion efficiency shows great potential applications in short-wavelength nanolasers, nonlinear microscopy and polarization dependent photonic integrating.

  5. Automated Surface Classification of SRF Cavities for the Investigation of the Influence of Surface Properties onto the Operational Performance

    Energy Technology Data Exchange (ETDEWEB)

    Wenskat, Marc

    2015-07-15

    Superconducting niobium radio-frequency cavities are fundamental for the European XFEL and the International Linear Collider. To use the operational advantages of superconducting cavities, the inner surface has to fulfill quite demanding requirements. The surface roughness and cleanliness improved over the last decades and with them, the achieved maximal accelerating field. Still, limitations of the maximal achieved accelerating field are observed, which are not explained by localized geometrical defects or impurities. The scope of this thesis is a better understanding of these limitations in defect free cavities based on global, rather than local, surface properties. For this goal, more than 30 cavities underwent subsequent surface treatments, cold RF tests and optical inspections within the ILC-HiGrade research program and the XFEL cavity production. An algorithm was developed which allows an automated surface characterization based on an optical inspection robot. This algorithm delivers a set of optical surface properties, which describes the inner cavity surface. These optical surface properties deliver a framework for a quality assurance of the fabrication procedures. Furthermore, they shows promising results for a better understanding of the observed limitations in defect free cavities.

  6. Surface Emitting Distributed Feedback Quantum Cascade Laser around 8.3μm

    Institute of Scientific and Technical Information of China (English)

    GUO Wan-Hong; LIU Jun-Qi; LU Quan-Yong; ZHANG Wei; JIANG Yu-Chao; LI Lu; WANG Li-Jun; LIU Feng-Qi; WANG Zhan-Guo

    2010-01-01

    @@ We demonstrate surface emitting distributed feedback quantum cascade lasers emitting at wavelengths from8.1 μm at 90 K to 8.4 μm at 210K.The second-order metalized grating is carefully designed using a modified coupled-mode theory and fabricated by contact lithography.The devices show single mode behavior with a side mode suppression ratio above 18dB at all working temperatures.At 90K,the device emits an optical power of 101 mW from the surface and 199mW from the edge.In addition,a double-lobe far-field pattern with a separation of 2.2° is obtained in the direction along the waveguide.

  7. Mode-locking external-cavity laser-diode sensor for displacement measurements of technical surfaces

    Science.gov (United States)

    Czarske, Jürgen; Möbius, Jasper; Moldenhauer, Karsten

    2005-09-01

    A novel laser sensor for position measurements of technical solid-state surfaces is proposed. An external Fabry-Perot laser cavity is assembled by use of an antireflection-coated laser diode together with the technical surface. Mode locking results from pumping the laser diode synchronously to the mode spacing of the cavity. The laser cavity length, i.e., the distance to the measurement object, is determined by evaluation of the modulation transfer function of the cavity by means of a phase-locked loop. The mode-locking external-cavity laser sensor incorporates a resonance effect that results in highly resolving position and displacement measurements. More than a factor-of-10 higher resolution than with conventional nonresonant sensing principles is achieved. Results of the displacement measurements of various technical surfaces are reported. Experimental and theoretical investigations are in good agreement.

  8. Binary arithmetic using optical symbolic substitution and integrated phototransistor surface-emitting laser logic

    Science.gov (United States)

    Cheng, Julian; Olbright, G. R.; Bryan, R. P.

    1991-10-01

    The architecture described in the paper supports binary addition by means of optical logic gates and symbolic substitution utilizing heterojunction phototransistors and lasers. The high-speed optical switches are compatible with surface-normal architecture, require low-input optical energies, and afford high optical gain. A highly compact binary half-adder is described to demonstrate the implementation of the binary arithmetic with heterojunction-phototransistor optical logic gates and surface emitting lasers.

  9. A method for cleaning optical precision surface of laser gyro cavity

    Science.gov (United States)

    Cui, Ying; Jiao, Ling Yan; Lin, Na Na; Zhang, Dong

    2016-10-01

    Laser gyro is the only one non-electromechanical high-precision inertial sensitive instruments in aircraft inertial guidance systems. Ultra high vacuum acquisition is a key segment during the manufacturing process of laser gyro. The surface cleanliness and integrity have decisive influence on the sealing performance of ultra-high vacuum. A cleaning technology for the optical surface of laser gyro cavity was found by experiment. Meanwhile, the analysis of the adsorption mechanism of contaminant on the laser gyro cavity surface and overview of common optical element cleaning technology were given. The result showed that the new cleaning technology improved the cleanliness of the cavity optical surface without any damage and provided a reliable solution for chronic leak of high precision laser gyro cavity.

  10. Electrical excitation of waveguided surface plasmons by a light-emitting tunneling optical gap antenna.

    Science.gov (United States)

    Cazier, N; Buret, M; Uskov, A V; Markey, L; Arocas, J; Colas Des Francs, G; Bouhelier, A

    2016-02-22

    We introduce a new type of electroplasmonic interfacing component to electrically generate surface plasmons. Specifically, an electron-fed optical tunneling gap antenna is integrated on a plasmonic waveguiding platform. When electrical charges are injected in the tunneling barrier of the gap antenna, a broad-band radiation is emitted from the feed area by a process identified as a thermal emission of hot electrons. Part of the emitted photons couples to surface plasmon modes sustained by the waveguide geometry. The transducing optical antenna is thus acting as a localized electrical source of surface plasmon polaritons. The integration of electrically-activated optical antennas into a plasmonic architecture mitigates the need for complex coupling scheme and proposes a solution for realizing nanoscale units at the interface between nano-electronics and photonics.

  11. Laser heating of a cavity versus a plane surface for metal targets utilizing photothermal deflection measurements

    Science.gov (United States)

    Jeong, S. H.; Greif, R.; Russo, R. E.

    1996-08-01

    The effects of a cylindrical cavity in a metal surface on the energy coupling of a laser beam with the solid were investigated by using a photothermal deflection technique. The photothermal deflection of a probe beam over the cavity was measured while the bottom of the cavity was heated with a Nd-YAG laser with a wavelength of 1064 nm. Cavities in three different materials and with two different aspect ratios were used for the experiment. Temperature distributions in the solid and the surrounding air were computed numerically and used to calculate photothermal deflections for cavity heating and for plane surface heating. Reflection of the heating laser beam inside the cavity increased the photothermal deflection amplitude significantly with larger increases for materials with larger thermal diffusivity. The computed photothermal deflections agreed more closely with the experimental results when reflection of the heating laser beam inside the cavity was included in the numerical model. The overall energy coupling between a heating laser and a solid is enhanced by a cavity.

  12. Ultimate Cavity Dynamics of Hydrophobic Spheres Impacting on Free Water Surfaces

    KAUST Repository

    Mansoor, Mohammad M.

    2012-12-01

    Cavity formation resulting from the water-entry of solid objects has been the subject of extensive research owing to its practical relevance in naval, military, industrial, sports and biological applications. The cavity formed by an impacting hydrophobic sphere normally seals at two places, one below (deep seal) and the other above the water surface (surface seal). For Froude numbers , the air flow into the resulting cavity is strong enough to suck the splash crown above the surface and disrupt the cavity dynamics before it deep seals. In this research work we eliminate surface seals by means of a novel practice of using cone splash-guards and examine the undisturbed transient cavity dynamics by impact of hydrophobic spheres for Froude numbers ranging . This enabled the measurement of extremely accurate pinch-off heights, pinch-off times, radial cavity collapse rates, and jet speeds in an extended range of Froude numbers compared to the previous work of Duclaux et al. (2007). Results in the extended regime were in remarkable agreement with the theoretical prediction of scaled pinch-off depth, and experimentally derived pinch-off time for . Furthermore, we investigated the influence of confinement on cavity formation by varying the cross-sectional area of the tank of liquid. In conjunction with surface seal elimination we observed the formation of multiple pinch-off points where a maximum of four deep seals were obtained in a sequential order for the Froude number range investigated. The presence of an elongated cavity beneath the first pinch-off point 5 resulted in evident "kinks" primarily related to the greatly diminished air pressure at the necking region caused by supersonic air flows (Gekle et al. 2010). Such flows passing through second pinch-offs were also found to choke the cavities beneath the first pinch- off depths causing radial expansion and hence disappearance of downward jets.

  13. A study on surface roughness and microleakage test in cavities prepared by Er:YAG laser irradiation and etched bur cavities.

    Science.gov (United States)

    Hossain, M; Yamada, Y; Nakamura, Y; Murakami, Y; Tamaki, Y; Matsumoto, K

    2003-01-01

    The purposes of this study were to investigate the surface morphology, suface roughness of cavities prepared by Er:YAG laser irradiation, and compared the microleakage degree after composite resin restoration with etched bur cavities, in vitro. In each of the 30 human extracted teeth, two shallow cavities were prepared; one prepared with the Er:YAG laser system on the buccal surface, and one produced on the lingual (palatal) surface with a high-speed turbine. Five cavities from each group were investigated by scanning electron microscopy (SEM), and five were subjected to surface roughness analysis by a colour laser three-dimensional (3D) microscope. The remaining cavities were filled with a composite resin and subjected to a microleakage test under thermocycling. Only bur cavities were acid-etched before filling. Statistical analysis was performed using the Mann-Whitney U test; a value of p roughness was significantly increased with the laser system. Microleakage test revealed no significant differences between the laser and bur cavities. Crosscut sections of the cavities with no microleakage showed no gap at the interface. Laser cavity may facilitate good adaptation of composite resin with enamel and dentine, because an increase of surface roughness and the openings of dentinal tubules may facilitate the formation of a hybrid zone, since a primer and an adhesive can penetrate the surface better when the smear layer is removed. It can be concluded that shallow cavity prepared by Er:YAG laser is capable of decreasing microleakage of composite resin restorations, and its efficiency is similar to etched bur cavities.

  14. Observation of Stable Low Surface Resistance in Large-Grain Niobium SRF Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Geng, Rongli [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Huang, Shichun [Institute of Modern Physics (IMP)/Chinese Academy of Sciences (CAS), Lanzhou (China)

    2016-05-01

    Low surface resistance, or high unloaded quality factor (Q0), superconducting radio frequency (SRF) cavities are being pursued actively nowadays as their application in large-scale CW SRF accelerators can save capital and operational cost in cryogenics. There are different options in realization of such cavities. One of them is the large-grain (LG) niobium cavity. In this contribution, we present new experimental results in evaluation of LG niobium cavities cooled down in the presence of an external magnetic field. High Q0 values are achieved even with an ambient magnetic field of up to 100 mG. More over, it is observed that these high Q0 values are super-robust against repeated quench, literally not affected at all after the cavity being deliberately quenched for hundreds of times in the presence of an ambient magnetic field of up to 200 mG.

  15. Effect of non-uniform surface resistance on the quality factor of superconducting niobium cavity

    Science.gov (United States)

    Tan, Weiwei; Lu, Xiangyang; Yang, Ziqin; Zhao, Jifei; Yang, Deyu; Yang, Yujia

    2016-08-01

    The formula Rs = G /Q0 is commonly used in the calculation of the surface resistance of radio frequency niobium superconducting cavities. The applying of such equation is under the assumption that surface resistance is consistent over the cavity. However, the distribution of the magnetic field varies over the cavity. The magnetic field in the equator is much higher than that in the iris. According to Thermal Feedback Theory, it leads non-uniform distribution of the density of heat flux, which results in a different temperature distribution along the cavity inter surface. The BCS surface resistance, which depends largely on the temperature, is different in each local inner surface. In this paper, the effect of surface non-uniform resistance on the quality factor has been studied, through the calculation of Q0 in the original definition of it. The results show that it is necessary to consider the non-uniform distribution of magnetic field when the accelerating field is above 20 MV/m for TESLA cavities. Also, the effect of inhomogeneity of residual resistance on the quality factor is discussed. Its distribution barely affects the quality factor.

  16. Pulp response to a composite resin inserted in deep cavities with and without a surface seal.

    Science.gov (United States)

    Fuks, A B; Funnell, B; Cleaton-Jones, P

    1990-02-01

    The objective of the present investigation was to observe pulp response to a composite material (Occlusin) placed in deep cavities with and without a zinc oxide-eugenol covering. Deep cavities were prepared in 116 teeth of four young baboons and divided into four groups. In group 1, Occlusin material was placed directly into the cavity, without etching, to approximately half the depth, cured, and covered to the surface with zinc oxide-eugenol. In group 2, the cavities were etched, a bonding agent was applied, and Occlusin material was used and cured in two increments to fill the cavities up to the surface. In group 3, the composite resin was placed in two increments as in group 2, but without etching and bonding; and in group 4 (control), the cavities were filled up to the surface with zinc oxide-eugenol. Follow-up times were 5, 30, and 90 days. Light microscopy revealed that, although some differences were observed, a good pulp response was evident in all groups.

  17. 底部出光纳米孔径面发射激光器的研究%Study of bottom-emitting nano-aperture vertical-cavity surfaceemitting laser

    Institute of Scientific and Technical Information of China (English)

    高建霞; 王岭娥

    2012-01-01

    在普通大功率垂直腔面发射激光器(VCSEI。)基础上,制备出了底部出光纳米孔径VCSEL。利用聚焦离子束刻蚀技术完成纳米孔径的制作。当小孔直径为480nm×480nm时,测量得到器件的远场输出光功率为0.07mw。并分析了温度的变化对该器件远场输出光功率的影响。%Bottom-emitting nano-aperture vertical-cavity surface-emitting lasers (VCSELs) were fabrica- ted based on common high-power VCSELs. The major fabrication steps and the structure of the device were briefly introduced. The nano-aperture was etched by the focused ion beam system and the far field output power of the device can be measured by the NA-VCSEL far field power measurement setup. When the size of the aperture is 480 nm×480 nm,the far-field output power is 0.07 mW. The fabrication process is introduced and the temperature characteristics are also analyzed.

  18. Recent Vertical External Cavity Surface Emitting Lasers (VECSELs) Developments for Sensor Applications (POSTPRINT)

    Science.gov (United States)

    2013-02-01

    and Nanotechnology Sensors, Systems, and Applications III, SPIE, ed., Proc. SPIE 8031(1), p. 803126, SPIE, 2011. [7] S. Masui, Y. Matsuyama, T...Tuning and brightness optimization of high-performance GaSb-based semiconductor disk lasers from 1.86 to 2.80 μm,” CLEO Europe 09, p. 1, june 2009

  19. Theory and Modeling of Lasing Modes in Vertical Cavity Surface Emitting Lasers

    Directory of Open Access Journals (Sweden)

    Benjamin Klein

    1998-01-01

    modes that the VCSEL can support are then determined by matching the gain necessary for the optical system in both magnitude and phase to the gain available from the laser's electronic system. Examples are provided.

  20. On the field dependent surface resistance of niobium on copper cavities

    CERN Document Server

    Junginger, Tobias

    2015-01-01

    The surface resistance Rs of superconducting cavities prepared by sputter coating a thin niobium film on a copper substrate increases significantly stronger with the applied RF field compared to cavities of bulk material. A possible cause is that due to the thermal boundary resistance between the copper substrate and the niobium film Rs is enhanced due to global heating of the inner cavity wall. Introducing helium gas in the cavity and measuring its pressure as a function of applied field allowed to conclude that the inner surface of the cavity is heated up by only 60+/-60 mK when Rs increases with Eacc by 100 nOhm. This is more than one order of magnitude less than what one would expect from global heating. Additionally the effect of cooldown speed and low temperature baking have been investigated in the framework of these experiments. It is shown that for current state of the art niobium on copper cavities there is only a detrimental effect of low temperature baking. A fast cooldown results in a lowered Rs.

  1. Slowing surface plasmon polaritons on plasmonic coupled cavities by tuning grating grooves

    Science.gov (United States)

    Balci, Sinan; Kocabas, Askin; Kocabas, Coskun; Aydinli, Atilla

    2010-09-01

    We investigate slow surface plasmon polaritons (SPPs) in plasmonic waveguiding bands formed by coupled plasmonic cavities on Moiré surfaces. We demonstrate controlling the group velocity and dispersion of the SPPs by varying the depth of the plasmonic Bragg grating groove. Changing the grating depth results in modification of coupling coefficients between the cavities and hence the SPPs group velocity is altered. Variation in the group velocity and dispersion of SPPs can be measured with polarization dependent spectroscopic reflection measurements. Dispersion of SPPs has been calculated by finite-difference time-domain method in agreement with the experimental data.

  2. Controlled impact of a disk on a water surface: Cavity dynamics

    CERN Document Server

    Bergmann, Raymond; Gekle, Stephan; van der Bos, Arjan; Lohse, Detlef

    2008-01-01

    In this paper we study the transient surface cavity which is created by the controlled impact of a disk of radius h0 on a water surface at Froude numbers below 200. The dynamics of the transient free surface is recorded by high speed imaging and compared to boundary integral simulations. An excellent agreement is found between both. The flow surrounding the cavity is measured with high speed particle image velocimetry and is found to also agree perfectly with the flow field obtained from the simulations. We present a simple model for the radial dynamics of the cavity based on the collapse of an infinite cylinder. This model accounts for the observed asymmetry of the radial dynamics between the expansion and contraction phase of the cavity. It reproduces the scaling of the closure depth and total depth of the cavity which are both found to scale roughly proportional to Fr^{1/2} with a weakly Froude number dependent prefactor. In addition, the model accurately captures the dynamics of the minimal radius of the ...

  3. Measurement of Frequency, Temperature, RF Field Dependence of Surface Resistance of Superconductors Using a Half Wave Cavity

    Science.gov (United States)

    Park, Hyekyoung; Delayen, Jean

    2017-01-01

    A theory of surface resistance of superconductor was rigorously formulated by Bardeen, Cooper, Schrieffer more than 50 years ago. Since then the accelerator community has been used the theory as a guideline to improve the surface resistance of the superconducting cavity. It has been observed that the surface resistance is dependent on frequency, temperature and rf field strength, and surface preparation. To verify these dependences, a well-controlled study is required. Although many different types of cavities have been tested, the typical superconducting cavities are built for specific frequencies of their application. They do not provide data other than at its own frequency. A superconducting half wave cavity is a cavity that enables us to collect the surface resistance data across frequencies of interest for particle accelerators and evaluate preparation techniques. This paper will present the design of the half wave cavity, its electromagnetic mode characteristics and experimental results. Research supported by NSF Award PHY-1416051.

  4. A novel approach to characterizing the surface topography of niobium superconducting radio frequency (SRF) accelerator cavities

    Energy Technology Data Exchange (ETDEWEB)

    Tian Hui [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Applied Sci. Dept., College of William and Mary, Williamsburg, VA 23185 (United States); Ribeill, Guilhem [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Dept. of Physics, North Carolina State University, Raleigh, NC 27695 (United States); Xu Chen [Applied Sci. Dept., College of William and Mary, Williamsburg, VA 23185 (United States); Reece, Charles E. [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Kelley, Michael J., E-mail: mkelley@jlab.org [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Applied Sci. Dept., College of William and Mary, Williamsburg, VA 23185 (United States)

    2011-03-15

    As superconducting niobium radio-frequency (SRF) cavities approach fundamental material limits, there is increased interest in understanding the details of topographical influences on realized performance limitations. Micro- and nano-roughness are implicated in both direct geometrical field enhancements as well as complications of the composition of the 50 nm surface layer in which the super-currents typically flow. Interior surface chemical treatments such as buffered chemical polishing (BCP) and electropolishing (EP) used to remove mechanical damage leave surface topography, including pits and protrusions of varying sharpness. These may promote RF magnetic field entry, locally quenching superconductivity, so as to degrade cavity performance. A more incisive analysis of surface topography than the widely used average roughness is needed. In this study, a power spectral density (PSD) approach based on Fourier analysis of surface topography data acquired by both stylus profilometry and atomic force microscopy (AFM) is introduced to distinguish the scale-dependent smoothing effects, resulting in a novel qualitative and quantitative description of Nb surface topography. The topographical evolution of the Nb surface as a function of different steps of well-controlled EP is discussed. This study will greatly help to identify optimum EP parameter sets for controlled and reproducible surface levelling of Nb for cavity production.

  5. A novel approach to characterizing the surface topography of niobium superconducting radio frequency (SRF) accelerator cavities

    Energy Technology Data Exchange (ETDEWEB)

    Hui Tian, Guilhem Ribeill, Chen Xu, Charles E. Reece, Michael J. Kelley

    2011-03-01

    As superconducting niobium radio-frequency (SRF) cavities approach fundamental material limits, there is increased interest in understanding the details of topographical influences on realized performance limitations. Micro- and nano-roughness are implicated in both direct geometrical field enhancements as well as complications of the composition of the 50 nm surface layer in which the super-currents typically flow. Interior surface chemical treatments such as buffered chemical polishing (BCP) and electropolishing (EP) used to remove mechanical damage leave surface topography, including pits and protrusions of varying sharpness. These may promote RF magnetic field entry, locally quenching superconductivity, so as to degrade cavity performance. A more incisive analysis of surface topography than the widely used average roughness is needed. In this study, a power spectral density (PSD) approach based on Fourier analysis of surface topography data acquired by both stylus profilometry and atomic force microscopy (AFM) is introduced to distinguish the scale-dependent smoothing effects, resulting in a novel qualitative and quantitative description of Nb surface topography. The topographical evolution of the Nb surface as a function of different steps of well-controlled EP is discussed. This study will greatly help to identify optimum EP parameter sets for controlled and reproducible surface levelling of Nb for cavity production.

  6. Protection of enamel surfaces in the oral cavity

    DEFF Research Database (Denmark)

    Lazovic, Maja Bruvo

    and foodstuffs or gastric juice can cause dental erosion. During a lifetime the enamel surface is also exposed to fluids that can have protective effects against dental caries and erosion such as saliva, various foodstuffs, drinking water and many types of drinks. However, little is still known about simple...... inorganic interactions between different fluids and dental caries and little is also known about which saliva proteins are able to protect the enamel surface against dental erosion. Therefore, the overall aim of this thesis was to examine simple inorganic and protein related protective effects with dental...... caries and erosion. Drinking water was used as a model system to test previously undetermined inorganic effects with importance for dental caries and the pellicle forming properties of the saliva proteins were used to test organic effects of importance for dental erosion. Inorganic effects on enamel...

  7. Magnetohydrodynamic motion of a colloidal sphere with self-electrochemical surface reactions in a spherical cavity.

    Science.gov (United States)

    Hsieh, Tzu H; Keh, Huan J

    2013-02-21

    An analytical study is presented for the magnetic-field-induced motion of a colloidal sphere with spontaneous electrochemical reactions on its surface situated at the center of a spherical cavity filled with an electrolyte solution at the quasi-steady state. The zeta potential associated with the particle surface may have an arbitrary distribution, whereas the electric double layers adjoining the particle and cavity surfaces are taken to be thin relative to the particle size and the spacing between the solid surfaces. The electric current and magnetic flux density distributions are solved for the particle and fluid phases of arbitrary electric conductivities and magnetic permeabilities. Applying a generalized reciprocal theorem to the Stokes equations with a Lorentz force term resulting from these density distributions for the fluid motion, we obtain explicit formulas for the translational and angular velocities of the colloidal sphere valid for all values of the particle-to-cavity size ratio. The particle velocities decrease monotonically with an increase in this size ratio. For the limiting case of an infinitely large cavity, our result reduces to the relevant solution for an unconfined spherical particle. The boundary effect on the movement of the particle with interfacial self-electrochemical reactions induced by the magnetohydrodynamic force is equivalent to that in sedimentation and much stronger than that in general phoretic motions.

  8. Terahertz-wave generation by surface-emitted four-wave mixing in optical fiber

    Institute of Scientific and Technical Information of China (English)

    Ping Zhou; Dianyuan Fan

    2011-01-01

    We propose a novel terahertz-wave source through the four-wave mixing effect in a conventional singlemode optical fiber pumped by a dual-wavelength laser whose difference frequency lies in the terahertz range.Surface-emitted geometry is employed to decrease absorption loss.A detailed derivation of the terahertz-wave power expression is presented using the coupled-wave theory.This is a promising way for realizing a reasonable narrow-band terahert-wave source.%@@ We propose a novel terahertz-wave source through the four-wave mixing effect in a conventional singlemode optical fiber pumped by a dual-wavelength laser whose difference frequency lies in the terahertz range.Surface-emitted geometry is employed to decrease absorption loss.A detailed derivation of the terahertz-wave power expression is presented using the coupled-wave theory.This is a promising way for realizing a reasonable narrow-band terahertz-wave source.

  9. Extracting superconducting parameters from surface resistivity by using inside temperatures of SRF cavities

    CERN Document Server

    Ge, M; Padamsee, H; Shemelin, V

    2014-01-01

    The surface resistance of an RF superconductor depends on the surface temperature, the residual resistance and various superconductor parameters, e.g. the energy gap, and the electron mean free path. These parameters can be determined by measuring the quality factor Q0 of a SRF cavity in helium-baths of different temperatures. The surface resistance can be computed from Q0 for any cavity geometry, but it is not trivial to determine the temperature of the surface when only the temperature of the helium bath is known. Traditionally, it was approximated that the surface temperature on the inner surface of the cavity was the same as the temperature of the helium bath. This is a good approximation at small RF-fields on the surface, but to determine the field dependence of Rs, one cannot be restricted to small field losses. Here we show the following: (1) How computer simulations can be used to determine the inside temperature Tin so that Rs(Tin) can then be used to extract the superconducting parameters. The compu...

  10. Optical investigations of InGaN heterostructures and GeSn nanocrystals for photonic and phononic applications: light emitting diodes and phonon cavities

    Science.gov (United States)

    Hafiz, Shopan din Ahmad

    InGaN heterostructures are at the core of blue light emitting diodes (LEDs) which are the basic building blocks for energy efficient and environment friendly modern white light generating sources. Through quantum confinement and electronic band structure tuning on the opposite end of the spectrum, Ge1-xSnx alloys have recently attracted significant interest due to its potential role as a silicon compatible infra-red (IR) optical material for photodetectors and LEDs owing to transition to direct bandgap with increasing Sn. This thesis is dedicated to establishing an understanding of the optical processes and carrier dynamics in InGaN heterostructures for achieving more efficient visible light emitters and terahertz generating nanocavities and in colloidal Ge1-xSnx quantum dots (QDs) for developing efficient silicon compatible optoelectronics. To alleviate the electron overflow, which through strong experimental evidence is revealed to be the dominating mechanism responsible for efficiency degradation at high injection in InGaN based blue LEDs, different strategies involving electron injectors and optimized active regions have been developed. Effectiveness of optimum electron injector (EI) layers in reducing electron overflow and increasing quantum efficiency of InGaN based LEDs was demonstrated by photoluminescence (PL) and electroluminescence spectroscopy along with numerical simulations. Increasing the two-layer EI thickness in double heterostructure LEDs substantially reduced the electron overflow and increased external quantum efficiency (EQE) by three fold. By incorporating delta p-doped InGaN barriers in multiple quantum well (MQW) LEDs, 20% enhancement in EQE was achieved due to improved hole injection without degrading the layer quality. Carrier diffusion length, an important physical parameter that directly affects the performance of optoelectronic devices, was measured in epitaxial GaN using PL spectroscopy. The obtained diffusion lengths at room

  11. Red Emitting VCSEL

    Science.gov (United States)

    Jetter, Michael; Roßbach, Robert; Michler, Peter

    This chapter describes the progress in development of vertical-cavity surface-emitting lasers (VCSEL) emitting in the red spectral region around 650 nm for data transmission over polymer optical fibers (POF). First, growth issues of red VCSEL using two different material systems, namely AlGaAs and AlGaInP, are introduced. In particular, the optical and electrical state-of-the-art characteristics as low threshold currents ({≤} 1 mA) and high output powers (several mW) are presented with a special focus on emission wavelength. Also the thermal budget and heat removal in the devices are pointed out with regard to the geometry of the VCSEL. Small-signal modulation response in terms of maximum resonance frequency in dependance on temperature behavior are discussed. Applications of these devices in optical interconnects are described and digital data transmission at data rates up to 2.1 Gbit/s over step-index POF is reported. These properties make red emitting VCSEL perfectly suited for high-speed low power consuming light sources for optical data communication via POF. By introducing InP quantum dots as gain material in red emitting VCSEL nearly temperature independent record low threshold current densities of around 10 A/cm2 could be observed.

  12. Imaging of sub-surface nanostructures by dielectric planer cavity coupled microsphere lens

    Science.gov (United States)

    Guo, Minglei; Ye, Yong-Hong; Hou, Jinglei; Du, Bintao; Wang, Tian

    2017-01-01

    In this paper, a dielectric planar cavity between an object and a microsphere lens is fabricated and its effects on the imaging of sub-surface nanostructures have been studied. Using the dielectric planar cavity combined (DPCC) silica microsphere lens, our experimental results illustrate that the nanostructures of data-recorded Blu-ray disc can be clearly resolved. Optical images of the object with higher contrast and larger field of view (FOV) can be obtained, compared to the case when only a microsphere lens is used. For the 3.4 μm diameter microsphere lens combing a planar cavity with a thickness about 2.2 μm, the FOV is about 2.4 μm and the magnification is about 1.6. With the 3.4 μm diameter microsphere lens only, the FOV and magnification is 1.5 μm and 1.4 respectively. Theoretical analysis of the imaging properties is carried out by the characteristics of electric field distribution of microsphere lenses. The simulated results indicate that the dielectric planar cavity working as a Fabry-Pérot cavity can effectively enhance the coupling of optical information.

  13. Metasurface external cavity laser

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Luyao, E-mail: luyaoxu.ee@ucla.edu; Curwen, Christopher A.; Williams, Benjamin S. [Department of Electrical Engineering, University of California, Los Angeles, California 90095 (United States); California NanoSystems Institute, University of California, Los Angeles, California 90095 (United States); Hon, Philip W. C.; Itoh, Tatsuo [Department of Electrical Engineering, University of California, Los Angeles, California 90095 (United States); Chen, Qi-Sheng [Northrop Grumman Aerospace Systems, Redondo Beach, California 90278 (United States)

    2015-11-30

    A vertical-external-cavity surface-emitting-laser is demonstrated in the terahertz range, which is based upon an amplifying metasurface reflector composed of a sub-wavelength array of antenna-coupled quantum-cascade sub-cavities. Lasing is possible when the metasurface reflector is placed into a low-loss external cavity such that the external cavity—not the sub-cavities—determines the beam properties. A near-Gaussian beam of 4.3° × 5.1° divergence is observed and an output power level >5 mW is achieved. The polarized response of the metasurface allows the use of a wire-grid polarizer as an output coupler that is continuously tunable.

  14. Surface-emitting superconductor laser spectroscopy for characterizing normal and sickled red blood cells

    Energy Technology Data Exchange (ETDEWEB)

    Gourley, P.L.; Meissner, K.E.; Brennan, T.M.; Hammons, B.E. [Sandia National Labs., Albuquerque, NM (United States); Gourley, M.F. [National Institutes of Health, Bethesda, MD (United States)

    1995-02-01

    We have developed a new intracavity laser technique that uses a living or a fixed cell as an integral component of the laser. The cells are placed on an AlGaAs/GaAs surface-emitting semiconductor wafer and covered with a glass dielectric mirror to form a laser resonator. In this arrangement, the cells serve as optical waveguides (or lens elements) to confine (or focus) light generated in the resonator by the semiconductor. Because of the high transparency, the cells aid the lasing process to generate laser light. This ultra sensitive laser provides a novel imaging/spectroscopic technique for histologic examination which we demonstrate with normal and sickled human red blood cells. Extremely high contrast microscopic images of the cells are observed near 830-850 nm. These images correspond to electromagnetic modes of cell structures and are sensitive to shape of the cell. Using a high resolution spectrometer, we resolve the light emitted from these images into very narrow spectral peaks associated with the lasing modes. Analysis of the spectra reveals that the distribution of peaks is quite different for normal and sickled red blood cells. This technique, in a more developed form, may be useful for the rapid analysis of other kinds of normal and abnormal cells.

  15. Surface-Plasmon-Polariton Laser based on an Open-Cavity Fabry-Perot Resonator

    CERN Document Server

    Zhu, Wenqi; Agrawal, Amit; Lezec, Henri J

    2016-01-01

    Recent years have witnessed growing interest in the development of small-footprint lasers for potential applications in small-volume sensing and on-chip optical communications. Surface-plasmons, electromagnetic modes evanescently confined to metal-dielectric interfaces, offer an effective route to achieving lasing at nanometer-scale dimensions when resonantly amplified in contact with a gain-medium. Here, we achieve visible frequency ultra-narrow linewidth lasing at room-temperature by leveraging surface plasmons propagating in an open Fabry-Perot cavity formed by a flat metal surface coated with a subwavelength-thick layer of optically-pumped gain medium and orthogonally bound by a pair of flat metal sidewalls. Low perturbation transmission-configuration sampling of the lasing plasmon mode is achieved via an evanescently coupled recessed nanoslit, opening the way to high-figure-of-merit refractive-index sensing of analytes interacting with the open cavity.

  16. Light-Emitting Diodes with Hierarchical and Multifunctional Surface Structures for High Light Extraction and an Antifouling Effect.

    Science.gov (United States)

    Leem, Young-Chul; Park, Jung Su; Kim, Joon Heon; Myoung, NoSoung; Yim, Sang-Youp; Jeong, Sehee; Lim, Wantae; Kim, Sung-Tae; Park, Seong-Ju

    2016-01-13

    Bioinspired hierarchical structures on the surface of vertical light-emitting diodes (VLEDs) are demonstrated by combining a self-assembled dip-coating process and nanopatterning transfer method using thermal release tape. This versatile surface structure can efficiently reduce the total internal reflection and add functions, such as superhydrophobicity and high oleophobicity, to achieve an antifouling effect for VLEDs.

  17. High-power terahertz radiation from surface-emitted THz-wave parametric oscillator

    Institute of Scientific and Technical Information of China (English)

    Li Zhong-Yang; Yao Jian-Quan; Xu De-Gang; Zhong Kai; Wang Jing-Li; Bing Pi-Bin

    2011-01-01

    We report a pulsed surface-emitted THz-wave parametric oscillator based on two MgO:LiNbC>3 crystals pumped by a multi-longitudinal mode Q-switched Nd:YAG laser. Through varying the phase matching angle, the tunable THz wave output from 0.79 THz to 2.84 THz is realized. The maximum THz-wave output was 193.2 nJ/pulse at 1.84 THz as the pump power density was 212.5 MW/cm2, corresponding to the energy conversion efficiency of 2.42 ×10-6 and the photon conversion efficiency of about 0.037%. When the pump power density changed from 123 MW/cm2 to 148 MW/cm2 and 164 MW/cm2, the maximum output of the THz-wave moved to the high frequency band. We give a reasonable explanation for this phenomenon.

  18. Polarized light emitting diode by long-range nanorod self-assembling on a water surface.

    Science.gov (United States)

    Rizzo, Aurora; Nobile, Concetta; Mazzeo, Marco; De Giorgi, Milena; Fiore, Angela; Carbone, Luigi; Cingolani, Roberto; Manna, Liberato; Gigli, Giuseppe

    2009-06-23

    We demonstrate a straightforward strategy to fabricate a multilayer inorganic/organic polarized light-emitting diode device based on highly ordered arrays of rod-shaped nanocrystals as the active species. We have developed a simple and effective method that allows colloidal CdSe/CdS core/shell nanorods to be laterally aligned in smectic or nematic phases on the surface of water. A floating film of such ordered nanorods has been collected by a poly(dimethylsiloxane) (PDMS) stamp pad and transferred by contact printing onto previously evaporated organic layers. Thanks to the lateral nanorod alignment the as-prepared film exhibited strong polarized photoluminescence and it has been used as emissive layer in the polarized electroluminescent device.

  19. Microleakage in conservative cavities varying the preparation method and surface treatment

    Directory of Open Access Journals (Sweden)

    Juliana Abdallah Atoui

    2010-08-01

    Full Text Available OBJECTIVE: To assess microleakage in conservative class V cavities prepared with aluminum-oxide air abrasion or turbine and restored with self-etching or etch-and-rinse adhesive systems. Materials and Methods: Forty premolars were randomly assigned to 4 groups (I and II: air abrasion; III and IV: turbine and class V cavities were prepared on the buccal surfaces. Conditioning approaches were: groups I/III - 37% phosphoric acid; groups II/IV - self-priming etchant (Tyrian-SPE. Cavities were restored with One Step Plus/Filtek Z250. After finishing, specimens were thermocycled, immersed in 50% silver nitrate, and serially sectioned. Microleakage at the occlusal and cervical interfaces was measured in mm and calculated by a software. Data were subjected to ANOVA and Tukey's test (α=0.05. RESULTS: Marginal seal provided by air abrasion was similar to high-speed handpiece, except for group I. There was SIGNIFICANT difference between enamel and dentin/cementum margins for to group I and II: air abrasion. The etch-and-rinse adhesive system promoted a better marginal seal. At enamel and dentin/cementum margins, the highest microleakage values were found in cavities treated with the self-etching adhesive system. At dentin/cementum margins, high-speed handpiece preparations associated with etch-and-rinse system provided the least dye penetration. CONCLUSION: Marginal seal of cavities prepared with aluminum-oxide air abrasion was different from that of conventionally prepared cavities, and the etch-and-rinse system promoted higher marginal seal at both enamel and dentin margins.

  20. Analysis of Nb{sub 3}Sn surface layers for superconducting radio frequency cavity applications

    Energy Technology Data Exchange (ETDEWEB)

    Becker, Chaoyue [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); High Energy Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Department of Physics, Illinois Institute of Technology, Chicago, Illinois 60616 (United States); Posen, Sam; Hall, Daniel Leslie [Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York 14853 (United States); Groll, Nickolas; Proslier, Thomas, E-mail: prolier@anl.gov [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); High Energy Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Cook, Russell [Nanoscience and Technology Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Schlepütz, Christian M. [X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Liepe, Matthias [Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York 14853 (United States); Department of Physics, Cornell University, Ithaca, New York 14853 (United States); Pellin, Michael [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Zasadzinski, John [Department of Physics, Illinois Institute of Technology, Chicago, Illinois 60616 (United States)

    2015-02-23

    We present an analysis of Nb{sub 3}Sn surface layers grown on a bulk Niobium (Nb) coupon prepared at the same time and by the same vapor diffusion process used to make Nb{sub 3}Sn coatings on 1.3 GHz Nb cavities. Tunneling spectroscopy reveals a well-developed, homogeneous superconducting density of states at the surface with a gap value distribution centered around 2.7 ± 0.4 meV and superconducting critical temperatures (T{sub c}) up to 16.3 K. Scanning transmission electron microscopy performed on cross sections of the sample's surface region shows an ∼2 μm thick Nb{sub 3}Sn surface layer. The elemental composition map exhibits a Nb:Sn ratio of 3:1 and reveals the presence of buried sub-stoichiometric regions that have a ratio of 5:1. Synchrotron x-ray diffraction experiments indicate a polycrystalline Nb{sub 3}Sn film and confirm the presence of Nb rich regions that occupy about a third of the coating volume. These low T{sub c} regions could play an important role in the dissipation mechanisms occurring during RF tests of Nb{sub 3}Sn-coated Nb cavities and open the way for further improving a very promising alternative to pure Nb cavities for particle accelerators.

  1. Energetic neutral atoms emitted from ice by ion bombardment under Ganymede surface conditions

    Science.gov (United States)

    Wieser, Martin; Barabash, Stas; Futaana, Yoshifumi; Wurz, Peter

    2013-04-01

    Magnetospheric or solar wind ions directly interacting with a planetary surface result in backscattering or sputtering of energetic neutral atoms. One example is the solar wind interaction with the surface of the Moon, where the produced energetic neutral atoms were observed by the Sub-keV Atom Reflecting Analyzer instrument (SARA) on Chandrayaan-1. At Jupiter, magnetospheric plasma interacts in a similar way with the surface of the Galilean moons. However, the emission of energetic neutral atoms from "dirty" ices as found e.g. on Ganymede's surface is poorly understood. We set up an experiment to study the ion to surface interaction under Ganymede surface environment conditions using the unique capabilities of the MEFISTO test facility at University of Bern. Ions of various species and energies up to 33 keV/q were impacted on a block of ice made from a mixture of water, NaCl and dry ice. The energetic neutral atoms produced by the interaction were detected with the prototype of the Jovian Neutrals Analyzer instrument (JNA.) JNA is proposed as part of the Particle Environment Package (PEP) for ESA's JUICE mission to Jupiter and instrument is based on the Energetic Energetic Neutral Atom instrument (ENA) built for the BepiColombo Magnetospheric Orbiter. We present energy spectra for different ion beam species and energetic neutral atom species combinations. The data show high yields for energetic neutral atoms up to the upper end of the instrument energy range of 3.3 keV. The energy spectra of the neutral atom flux emitted from the ice could only partially be fitted by the Sigmund-Thompson formula. In some cases, but not all, a Maxwellian distribution provides a reasonable description of the data.

  2. Efficient semiconductor light-emitting device and method

    Science.gov (United States)

    Choquette, Kent D.; Lear, Kevin L.; Schneider, Jr., Richard P.

    1996-01-01

    A semiconductor light-emitting device and method. The semiconductor light-emitting device is provided with at least one control layer or control region which includes an annular oxidized portion thereof to channel an injection current into the active region, and to provide a lateral refractive index profile for index guiding the light generated within the device. A periodic composition grading of at least one of the mirror stacks in the device provides a reduced operating voltage of the device. The semiconductor light-emitting device has a high efficiency for light generation, and may be formed either as a resonant-cavity light-emitting diode (RCLED) or as a vertical-cavity surface-emitting laser (VCSEL).

  3. Surface polishing of niobium for superconducting radio frequency (SRF) cavity applications

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Liang [College of William and Mary, Williamsburg, VA (United States)

    2014-08-01

    Niobium cavities are important components in modern particle accelerators based on superconducting radio frequency (SRF) technology. The interior of SRF cavities are cleaned and polished in order to produce high accelerating field and low power dissipation on the cavity wall. Current polishing methods, buffered chemical polishing (BCP) and electro-polishing (EP), have their advantages and limitations. We seek to improve current methods and explore laser polishing (LP) as a greener alternative of chemical methods. The topography and removal rate of BCP at different conditions (duration, temperature, sample orientation, flow rate) was studied with optical microscopy, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). Differential etching on different crystal orientations is the main contributor to fine grain niobium BCP topography, with gas evolution playing a secondary role. The surface of single crystal and bi-crystal niobium is smooth even after heavy BCP. The topography of fine grain niobium depends on total removal. The removal rate increases with temperature and surface acid flow rate within the rage of 0~20 °C, with chemical reaction being the possible dominate rate control mechanism. Surface flow helps to regulate temperature and avoid gas accumulation on the surface. The effect of surface flow rate on niobium EP was studied with optical microscopy, atomic force microscopy (AFM), and power spectral density (PSD) analysis. Within the range of 0~3.7 cm/s, no significant difference was found on the removal rate and the macro roughness. Possible improvement on the micro roughness with increased surface flow rate was observed. The effect of fluence and pulse accumulation on niobium topography during LP was studied with optical microscopy, SEM, AFM, and PSD analysis. Polishing on micro scale was achieved within fluence range of 0.57~0.90 J/cm2, with pulse accumulation adjusted accordingly. Larger area treatment was proved possible by

  4. Interfacial Cavity Filling To Optimize CD4-Mimetic Miniprotein Interactions with HIV-1 Surface Glycoprotein

    Energy Technology Data Exchange (ETDEWEB)

    Morellato-Castillo, Laurence; Acharya, Priyamvada; Combes, Olivier; Michiels, Johan; Descours, Anne; Ramos, Oscar H.P.; Yang, Yongping; Vanham, Guido; Ariën, Kevin K.; Kwong, Peter D.; Martin, Loïc; Kessler, Pascal [ITM-Antwerp; (CEA-CNRS); (NIH)

    2013-08-05

    Ligand affinities can be optimized by interfacial cavity filling. A hollow (Phe43 cavity) between HIV-1 surface glycoprotein (gp120) and cluster of differentiation 4 (CD4) receptor extends beyond residue phenylalanine 43 of CD4 and cannot be fully accessed by natural amino acids. To increase HIV-1 gp120 affinity for a family of CD4-mimetic miniproteins (miniCD4s), we targeted the gp120 Phe43 cavity with 11 non-natural phenylalanine derivatives, introduced into a miniCD4 named M48 (1). The best derivative, named M48U12 (13), bound HIV-1 YU2 gp120 with 8 pM affinity and showed potent HIV-1 neutralization. It contained a methylcyclohexyl derivative of 4-aminophenylalanine, and its cocrystal structure with gp120 revealed the cyclohexane ring buried within the gp120 hydrophobic core but able to assume multiple orientations in the binding pocket, and the aniline nitrogen potentially providing a focus for further improvement. Altogether, the results provide a framework for filling the interfacial Phe43 cavity to enhance miniCD4 affinity.

  5. Cavity formation and surface modeling of laser milling process under a thin-flowing water layer

    Science.gov (United States)

    Tangwarodomnukun, Viboon

    2016-11-01

    Laser milling process normally involves a number of laser scans over a workpiece to selectively remove the material and then to form cavities with shape and dimensions required. However, this process adversely causes a heat accumulation in work material, which can in turn damage the laser-milled area and vicinity in terms of recast deposition and change of material properties. Laser milling process performing in a thin-flowing water layer is a promising method that can overcome such damage. With the use of this technique, water can flush away the cut debris and at the same time cool the workpiece during the ablation. To understand the potential of this technique for milling application, the effects of process parameters on cavity dimensions and surface roughness were experimentally examined in this study. Titanium sheet was used as a workpiece to be milled by a nanosecond pulse laser under different water flow velocities. A smooth and uniform cut feature can be obtained when the metal was ablated under the high laser pulse frequency and high water flow velocity. Furthermore, a surface model based on the energy balance was developed in this study to predict the cavity profile and surface roughness. By comparing to the experiments, the predicted profiles had a good agreement with the measured ones.

  6. Detection of near-surface cavities by generalized S-transform of Rayleigh waves

    Science.gov (United States)

    Shao, Guang-zhou; Tsoflias, George P.; Li, Chang-jiang

    2016-06-01

    The near-surface cavities can cause a huge hidden trouble for urban infrastructure construction, such as, foundation settlement and roadbed subsidence, and so on. So, it is an important task to detect the underground cavities effectively for many engineering projects. At the same time, because of the complexity of near-surface materials and the limited resolution of geophysical methods, detecting the location of the hidden cavities quantitatively is still a technical challenge which needs to be studied further. Base on the study of Xia et al. (Xia et al., 2007), we performed a little modification to the travel time equation for the Rayleigh-wave diffraction. We put forward another way to detect the shallow subsurface voids. The generalized S-transform was adopted to extract the arrival times of the diffracted Rayleigh waves from the near and far-offset boundaries of the void at a certain receiver. Then the arrival times were used to calculate the boundary locations of the void. Three half-space void models and a two-layered void model were used to demonstrate the feasibility and effect of detecting a void with the generalized S-transform. A rotated staggered-grid finite-difference method was adopted in wave field modeling to obtain the synthetic seismic record. Finally, a real world field data was used to verify the detecting effect. The theoretical models and the real world example showed that it is feasible and effective to use the generalized S-transform to detect the near-surface cavities.

  7. Binary Arithmetic Using Optical Symbolic Substitution and Cascadable Surface-Emitting Laser Logic Devices,

    Science.gov (United States)

    LOGIC DEVICES, *OPTICAL CIRCUITS, *OPTICAL SWITCHING, HETEROJUNCTIONS, PHOTOTRANSISTORS, ELECTROOPTICS, LASER CAVITIES, OPTICAL PROCESSING, PARALLEL PROCESSING, BISTABLE DEVICES, GATES(CIRCUITS), VOLTAGE, BINARY ARITHMETIC .

  8. Simultaneous 60-GHz RoF Transmission of Lightwaves Emitted by ECL, DFB, and VCSEL

    DEFF Research Database (Denmark)

    Lebedev, Alexander; Pang, Xiaodan; Vegas Olmos, Juan José;

    2014-01-01

    Simultaneous 60-GHz radio over fiber upconversion and fiber transmission of lightwaves produced by an external cavity laser, a distributed feedback laser, and a $C$ -band vertical cavity surface emitting laser are demonstrated. The 1.25-Gb/s data are transmitted concurrently on each...

  9. Plasma Processing of Large Surfaces with Application to SRF Cavity Modification

    Energy Technology Data Exchange (ETDEWEB)

    Upadhyay, Janardan; Popovic, Svetozar; Vuskovic, Leposova; Im, Do; Valente, Anne-Marie; Phillips, H

    2013-09-01

    Plasma based surface modifications of SRF cavities present promising alternatives to the wet etching technology currently applied. To understand and characterize the plasma properties and chemical kinetics of plasma etching processes inside a single cell cavity, we have built a specially-designed cylindrical cavity with 8 observation ports. These ports can be used for holding niobium samples and diagnostic purposes simultaneously. Two frequencies (13.56 MHz and 2.45 GHz) of power source are used for different pressure, power and gas compositions. The plasma parameters were evaluated by a Langmuir probe and by an optical emission spectroscopy technique based on the relative intensity of two Ar 5p-4s lines at 419.8 and 420.07 nm. Argon 5p-4s transition is chosen to determine electron temperature in order to optimize parameters for plasma processing. Chemical kinetics of the process was observed using real-time mass spectroscopy. The effect of these parameters on niobium surface would be measured, presented at this conference, and used as guidelines for optimal design of SRF etching process.

  10. Thoracic cavity segmentation algorithm using multiorgan extraction and surface fitting in volumetric CT

    Energy Technology Data Exchange (ETDEWEB)

    Bae, JangPyo [Interdisciplinary Program, Bioengineering Major, Graduate School, Seoul National University, Seoul 110-744, South Korea and Department of Radiology, University of Ulsan College of Medicine, 388-1 Pungnap2-dong, Songpa-gu, Seoul 138-736 (Korea, Republic of); Kim, Namkug, E-mail: namkugkim@gmail.com; Lee, Sang Min; Seo, Joon Beom [Department of Radiology, University of Ulsan College of Medicine, 388-1 Pungnap2-dong, Songpa-gu, Seoul 138-736 (Korea, Republic of); Kim, Hee Chan [Department of Biomedical Engineering, College of Medicine and Institute of Medical and Biological Engineering, Medical Research Center, Seoul National University, Seoul 110-744 (Korea, Republic of)

    2014-04-15

    Purpose: To develop and validate a semiautomatic segmentation method for thoracic cavity volumetry and mediastinum fat quantification of patients with chronic obstructive pulmonary disease. Methods: The thoracic cavity region was separated by segmenting multiorgans, namely, the rib, lung, heart, and diaphragm. To encompass various lung disease-induced variations, the inner thoracic wall and diaphragm were modeled by using a three-dimensional surface-fitting method. To improve the accuracy of the diaphragm surface model, the heart and its surrounding tissue were segmented by a two-stage level set method using a shape prior. To assess the accuracy of the proposed algorithm, the algorithm results of 50 patients were compared to the manual segmentation results of two experts with more than 5 years of experience (these manual results were confirmed by an expert thoracic radiologist). The proposed method was also compared to three state-of-the-art segmentation methods. The metrics used to evaluate segmentation accuracy were volumetric overlap ratio (VOR), false positive ratio on VOR (FPRV), false negative ratio on VOR (FNRV), average symmetric absolute surface distance (ASASD), average symmetric squared surface distance (ASSSD), and maximum symmetric surface distance (MSSD). Results: In terms of thoracic cavity volumetry, the mean ± SD VOR, FPRV, and FNRV of the proposed method were (98.17 ± 0.84)%, (0.49 ± 0.23)%, and (1.34 ± 0.83)%, respectively. The ASASD, ASSSD, and MSSD for the thoracic wall were 0.28 ± 0.12, 1.28 ± 0.53, and 23.91 ± 7.64 mm, respectively. The ASASD, ASSSD, and MSSD for the diaphragm surface were 1.73 ± 0.91, 3.92 ± 1.68, and 27.80 ± 10.63 mm, respectively. The proposed method performed significantly better than the other three methods in terms of VOR, ASASD, and ASSSD. Conclusions: The proposed semiautomatic thoracic cavity segmentation method, which extracts multiple organs (namely, the rib, thoracic wall, diaphragm, and heart

  11. Light extraction enhancement from organic light-emitting diodes with randomly scattered surface fixture

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Dong-Ying; Shi, Xiao-Bo; Gao, Chun-Hong; Cai, Shi-Duan; Jin, Yue; Liao, Liang-Sheng, E-mail: lsliao@suda.edu.cn

    2014-09-30

    Graphical abstract: - Highlights: • A combination of scattering layer and roughened substrate is used for light extraction from OLEDs. • The scattering layer is readily achieved by spin-coating the TiO{sub 2} sol. • The enhancement relying scattering depends on the size of TiO{sub 2} nano particles. • With the light extraction techniques the uniform emission is achieved. - Abstract: A combination of a scattering medium layer and a roughened substrate was proposed to enhance the light extraction efficiency of organic light-emitting diodes (OLEDs). Comparing with a reference OLED without any scattering layer, 65% improvement in the forward emission has been achieved with a scattering layer formed on an intentionally roughened external substrate surface of the OLED by spin-coating a sol–gel fabricated matrix containing well dispersed titania (TiO{sub 2}) particles. Such a combination method not only demonstrated efficient extraction of the light trapped in the glass substrate but also achieved homogenous emission from the OLED panel. The proposed technique, convenient and inexpensive, is believed to be suitable for the large area OLED production in lighting applications.

  12. Self-assembled large-area annular cavity arrays with tunable cylindrical surface plasmons for sensing.

    Science.gov (United States)

    Ni, Haibin; Wang, Ming; Shen, Tianyi; Zhou, Jing

    2015-02-24

    Surface plasmons that propagate along cylindrical metal/dielectric interfaces in annular apertures in metal films, called cylindrical surface plasmons (CSPs), exhibit attractive optical characteristics. However, it is challenging to fabricate these nanocoaxial structures. Here, we demonstrate a practical low-cost route to manufacture highly ordered, large-area annular cavity arrays (ACAs) that can support CSPs with great tunability. By employing a sol-gel coassembly method, reactive ion etching and metal sputtering techniques, regular, highly ordered ACAs in square-centimeter-scale with a gap width tunable in the range of several to hundreds of nanometers have been produced with good reproducibility. Ag ACAs with a gap width of 12 nm and a gap height of 635 nm are demonstrated. By finite-difference time-domain simulation, we confirm that the pronounced dips in the reflectance spectra of ACAs are attributable to CSP resonances excited in the annular gaps. By adjusting etching time and Ag film thickness, the CSP dips can be tuned to sweep the entire optical range of 360 to 1800 nm without changing sphere size, which makes them a promising candidate for forming integrated plasmonic sensing arrays. The high tunability of the CSP resonant frequencies together with strong electric field enhancement in the cavities make the ACAs promising candidates for surface plasmon sensors and SERS substrates, as, for example, they have been used in liquid refractive index (RI) sensing, demonstrating a sensitivity of 1505 nm/RIU and a figure of merit of 9. One of the CSP dips of ACAs with a certain geometry size is angle- (0-70 degrees) and polarization-independent and can be used as a narrow-band absorber. Furthermore, the nano annular cavity arrays can be used to construct solar cells, nanolasers and nanoparticle plasmonic tweezers.

  13. Initial bioadhesion on surfaces in the oral cavity investigated by scanning force microscopy

    Science.gov (United States)

    Schwender, N.; Huber, K.; Marrawi, F. Al; Hannig, M.; Ziegler, Ch.

    2005-09-01

    Scanning force microscopy (SFM) was used to measure the adhesion forces between BSA, a saliva protein, and two dental surfaces, natural enamel and a filling material (Dyract AP™). Measurements were taken in phosphate buffered aqueous solutions (PBS). Forces were resolved down to the piconewton regime. The dependency of the adhesion force on the interaction time, pH-value and substrate surface was monitored. In a further step, surface samples were fixed on an enamel brace and carried for a defined time in the oral cavity. The formed biofilm, called pellicle, shows a different morphology on the different substrates. This can be explained by the above-mentioned substrate dependence of the adhesion force.

  14. Comparison of two tooth-saving preparation techniques for one-surface cavities.

    Science.gov (United States)

    Rahimtoola, Salim; van Amerongen, Evert

    2002-01-01

    The atraumatic restorative treatment technique (ART) is based on removing infected tooth material using only hand instruments and filling the subsequently cleaned cavity with adhesive material such as glass ionomer. As its name suggests, the ART technique should be atraumatic during treatment, as well as for the tooth itself as for the patient. It was primarily developed for treating people living in underserved areas of the world where resources and facilities such as electricity and trained manpower are limited. Many studies have evaluated the ART technique and the results have supported its application. However, a very limited number of studies have compared ART with more conventional techniques. For that reason, a study was conducted in Pakistan, to compare the ART technique with another more conventional treatment technique. The results of this study show that the preparations with hand instruments resulted in smaller sized cavities and therefore may be less traumatic to the tooth. It was also associated with less pain reactions compared to the more conventional technique. Although preparations with hand instruments required more time, this did not seem to affect the survival of restorations. The survival of glass ionomer cement restorations made with hand instruments was comparable with single surface amalgam restorations made with a more conventional technique. Recurrent caries was not associated with any glass ionomer cement restorations made with hand instruments. The retention rate of glass ionomer sealants was low, however one dentist had a sealant retention rate of 81.5 percent that suggests that this procedure can be performed satisfactorily in conjunction with a glass ionomer cement restoration. Operator variances did seem to affect the restorations. Survival of glass ionomer restorations made with both hand and rotary instruments varied for different operators. Similarly, the retention of fissure sealant also varied amongst operators. Operator

  15. Temperature variation on root surface with three root-end cavity preparation techniques

    Directory of Open Access Journals (Sweden)

    Bodrumlu Emre

    2013-01-01

    Full Text Available Introduction. Thermal changes can occur on the external root surface when root-end cavity preparation is performed, which may damage periodontal ligament cells and alveolar bone. Objective. The purpose of this study was to evaluate the temperature changes during preparation of the root-end cavities at 1 and 3 mm to the sectioned apical root surfaces when either tungsten carbide round bur, diamond round bur or ultrasonic diamond tip was used. Methods. Root-end resection was performed at 90° to the long axis of the root, 3 mm from the apex. Specimens were randomly divided into three groups of 12 teeth each for three different root-end cavity preparation techniques to be used, i.e. tungsten carbide bur, diamond bur and ultrasonic diamond retro tip. Thermocouples were used to measure temperature changes at 1 mm (T1 and 3 mm (T2 to the cutting plane during the preparations. Results. For T1, the lowest and the highest mean temperature increases of 3.53°C and 4.34°C were recorded for the carbide and diamond burs, respectively. For T2, the lowest and the highest mean temperature increases of 2.62°C and 4.39°C where recorded for the carbide and diamond burs, respectively. The mean temperatures with the ultrasonic tip were 3.68 and 3.04 ºC at T1 and T2 region, respectively. For root-end preparation, the ultrasonic preparation technique took the shortest preparation time (10.25 sec and the diamond bur took the longest time (28.17 sec. Conclusion. Ultrasonic retro tips and burs caused temperature to rise from 2.62° to 4.39°C, and these rises were within safety levels.

  16. Surface studies of niobium chemically polished under conditions for superconducting radiofrequency cavity production

    Energy Technology Data Exchange (ETDEWEB)

    Hui Tian; Michael Kelley; Charles Reece

    2005-11-14

    The performance of niobium superconducting radiofrequency accelerator cavities is strongly impacted by the topmost several nanometers of the active (interior) surface, especially by the final surface conditioning treatments. We examined the effect of the most commonly employed treatment, buffered chemical polishing (BCP), on polycrystalline niobium sheet over a range of realistic solution flow rates using electron back scatter diffraction (EBSD), stylus profilometry, atomic force microscopy, laboratory XPS and synchrotron (variable photon energy) XPS, seeking to collect statistically significant data sets. We found that the predominant general surface orientation is (100), but others are also present and at the atomic-level details of surface plane orientation are more complex. The post-etch surface exhibits micron-scale roughness, whose extent does not change with treatment conditions. The outermost surface consists of a few-nm thick layer of niobium pentoxide, whose thickness increases with solution flow rate to a maximum of 1.3 - 1.4 times that resulting from static solution. The standard deviation of the roughness measurements is ?? 30% and that of the surface composition is ?? 5%.

  17. Surface studies of niobium chemically polished under conditions for superconducting radio frequency (SRF) cavity production

    Energy Technology Data Exchange (ETDEWEB)

    Tian Hui [Thomas Jefferson National Accelerator Facility and College of William and Mary (United States); Reece, Charles E. [Thomas Jefferson National Accelerator Facility and College of William and Mary (United States); Kelley, Michael J. [Thomas Jefferson National Accelerator Facility and College of William and Mary (United States)]. E-mail: mkelley@jlab.org; Wang Shancai [Department of Physics, Boston University (United States); Plucinski, Lukasz [Department of Physics, Boston University (United States); Smith, Kevin E. [Department of Physics, Boston University (United States); Nowell, Matthew M. [EDAX TSL (United States)

    2006-11-30

    The performance of niobium superconducting radiofrequency (SRF) accelerator cavities is strongly impacted by the topmost several nanometers of the active (interior) surface, especially as influenced by the final surface conditioning treatments. We examined the effect of the most commonly employed treatment, buffered chemical polishing (BCP), on polycrystalline niobium sheet over a range of realistic solution flow rates using electron back scatter diffraction (EBSD), stylus profilometry, atomic force microscopy, laboratory XPS and synchrotron (variable photon energy) XPS, seeking to collect statistically significant datasets. We found that the predominant general surface orientation is (1 0 0), but others are also present and at the atomic-level details of surface plane orientation are more complex. The post-etch surface exhibits micron-scale roughness, whose extent does not change with treatment conditions. The outermost surface consists of a few-nm thick layer of niobium pentoxide, whose thickness increases with solution flow rate to a maximum of 1.3-1.4 times that resulting from static solution. The standard deviation of the roughness measurements is {+-}30% and that of the surface composition is {+-}5%.

  18. Evaluation of micromorphological changes in tooth enamel after mechanical and ultrafast laser preparation of surface cavities.

    Science.gov (United States)

    Luengo, Ma Cruz Lorenzo; Portillo, M; Sánchez, J M; Peix, M; Moreno, P; García, A; Montero, J; Albaladejo, A

    2013-01-01

    The aim of this in vitro study was to evaluate the morphological changes that occur in tooth enamel after mechanical instrumentation and after femtosecond laser irradiation with different parameters via light and scanning electron microscopy (SEM). Twelve totally impacted third molars were collected and sectioned to provide several cut surfaces. These surfaces were exposed to infrared (λ = 795 nm, 120 fs, 1-kHz repetition rate, maximum mean power 1 W) laser pulses and machined by means of a conventional mechanical technique. Two very different geometrical patterns were performed with femtosecond laser pulses: shallow rectangular cavities and deep cylindrical ones. The results of both machining procedures were examined using light and scanning electron microscopy. The SEM images show the femtosecond laser ability to produce high-precision cavities in tooth enamel. No signs of collateral damage, burning, melting, or cracks were observed despite the far different laser pulse energies used (ranging from 7 to 400 μJ), unlike what is seen with conventional mechanical techniques. The femtosecond laser has the potential to become an optimal tool for the treatment of dental decay and as an alternative to the conventional drill to reduce mechanical damage during removal of the hard dental tissue.

  19. Spectral investigation of hot-spot and cavity resonance effects on the terahertz radiation emitted from high-Tc superconducting Bi2Sr2CaCu2O8+δ single crystal mesa structures

    Science.gov (United States)

    Kadowaki, Kazuo; Watanabe, Chiharu; Minami, Hidetoshi; Yamamoto, Takashi; Kashiwagi, Takanari; Klemm, Richard

    2014-03-01

    Terahertz (THz) electromagnetic radiation emitted from high-Tc superconducting Bi2Sr2CaCu2O8+δ mesa structures in the case of single mesa and series-connected mesas is investigated by the FTIR spectroscopic technique while observing its temperature distribution simultaneously by a SiC photoluminescence technique. Changing the bias level, sudden jumps of the hot-spot position were clearly observed. Although the radiation intensity changes drastically associated with the jump of the hot spot position, the frequency is unaffected as long as the voltage per junction is kept constant. Since the frequency of the intense radiation satisfies the cavity resonance condition, we confirmed that the cavity resonance is of primarily importance for the synchronization of whole intrinsic Josephson junctions in the mesa for high power radiation. This work was supported in part by the Grant-in-Aid for challenging Exploratory Research, the Ministry of Education, Culture, Sports, Science & Technology (MEXT).

  20. Study of the surface resistance of niobium sputter-coated copper cavities

    CERN Document Server

    Benvenuti, Cristoforo; Campisi, I E; Darriulat, Pierre; Peck, M A; Russo, R; Valente, A M

    1999-01-01

    A systematic study of the superconducting properties of niobium films deposited on the inner wall of copper radiofrequency cavities is presented. Films are grown by sputtering with different discharge gases (Xe, Kr, Ar and Ar/Ne mixtures) on substrates prepared under different conditions. The measured quantities include the surface resistance at 1.5 GHz, the critical temperature and the penetration depth. The surface resistance is analyzed in terms of its dependence on temperature, RF field and the density of trapped fluxons. Once allowance for electron scattering is made by means of a single mean free path parameter, good agreement with BCS theory is observed. The residual resistance is observed to be essentially noncorrelated with the superconducting properties, although influenced by specific coating conditions. On occasions, very low residual resistances, in the nano-ohm range, have been maintained over a broad range of RF field, indicating the absence of fundamental limitations specific to the film techn...

  1. Accoustic Localization of Breakdown in Radio Frequency Accelerating Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Lane, Peter Gwin [IIT, Chicago

    2016-07-01

    Current designs for muon accelerators require high-gradient radio frequency (RF) cavities to be placed in solenoidal magnetic fields. These fields help contain and efficiently reduce the phase space volume of source muons in order to create a usable muon beam for collider and neutrino experiments. In this context and in general, the use of RF cavities in strong magnetic fields has its challenges. It has been found that placing normal conducting RF cavities in strong magnetic fields reduces the threshold at which RF cavity breakdown occurs. To aid the effort to study RF cavity breakdown in magnetic fields, it would be helpful to have a diagnostic tool which can localize the source of breakdown sparks inside the cavity. These sparks generate thermal shocks to small regions of the inner cavity wall that can be detected and localized using microphones attached to the outer cavity surface. Details on RF cavity sound sources as well as the hardware, software, and algorithms used to localize the source of sound emitted from breakdown thermal shocks are presented. In addition, results from simulations and experiments on three RF cavities, namely the Aluminum Mock Cavity, the High-Pressure Cavity, and the Modular Cavity, are also given. These results demonstrate the validity and effectiveness of the described technique for acoustic localization of breakdown.

  2. Estimation of Time Dependent Properties from Surface Pressure in Open Cavities

    Science.gov (United States)

    2008-02-01

    the aft wall when the shear layer enters the cavity. More recently, schlieren images of a cavity in transonic flow by Heller and Delfs (1996) have... Delfs , J., "Cavity Pressure Oscillations: The Generating Mechanisms Visualized," Journal of Sound and Vibration, Vol. 196, No. 2, 1996

  3. Highly Efficient Perovskite-Quantum-Dot Light-Emitting Diodes by Surface Engineering

    KAUST Repository

    Pan, Jun

    2016-08-16

    A two-step ligand-exchange strategy is developed, in which the long-carbon-chain ligands on all-inorganic perovskite (CsPbX3, X = Br, Cl) quantum dots (QDs) are replaced with halide-ion-pair ligands. Green and blue light-emitting diodes made from the halide-ion-paircapped quantum dots exhibit high external quantum efficiencies compared with the untreated QDs.

  4. Single-mode surface-emitting distributed feedback quantum-cascade lasers based on hybrid waveguide structure

    Institute of Scientific and Technical Information of China (English)

    Wanhong Guo; Junqi Liu; Jianyan Chen; Lu Li; Lijun Wang; Fengqi Liu; Zhanguo Wang

    2011-01-01

    Surface-emitting distributed feedback quantum-cascade lasers operating at λ≈7.8 μm are demonstrated.The metal-covered second-order grating is shallow-etched into the surface of a thin InGaAs contact and cladding layer. This forms a hybrid waveguide and used to achieve relatively low waveguide losses and high coupling strengths. The devices exhibit stable single-mode operation from 90 to 130 K with a side mode suppression ratio above 20 dB. A slope efficiency of 194 mW/A is obtained at 90 K, which is twice higher than that of the Fabry-Perot counterpart.%@@ Surface-emitting distributed feedback quantum-cascade lasers operating at λ≈7.8 μm are demonstrated.The metal-covered second-order grating is shallow-etched into the surface of a thin InGaAs contact and cladding layer.This forms a hybrid waveguide and used to achieve relatively low waveguide losses and high coupling strengths.The devices exhibit stable single-mode operation from 90 to 130 K with a side mode suppression ratio above 20 dB.A slope efficiency of 194 mW/A is obtained at 90 K, which is twice higher than that of the Fabry-Perot counterpart.

  5. Etching of Niobium Sample Placed on Superconducting Radio Frequency Cavity Surface in Ar/CL2 Plasma

    Energy Technology Data Exchange (ETDEWEB)

    Janardan Upadhyay, Larry Phillips, Anne-Marie Valente

    2011-09-01

    Plasma based surface modification is a promising alternative to wet etching of superconducting radio frequency (SRF) cavities. It has been proven with flat samples that the bulk Niobium (Nb) removal rate and the surface roughness after the plasma etchings are equal to or better than wet etching processes. To optimize the plasma parameters, we are using a single cell cavity with 20 sample holders symmetrically distributed over the cell. These holders serve the purpose of diagnostic ports for the measurement of the plasma parameters and for the holding of the Nb sample to be etched. The plasma properties at RF (100 MHz) and MW (2.45 GHz) frequencies are being measured with the help of electrical and optical probes at different pressures and RF power levels inside of this cavity. The niobium coupons placed on several holders around the cell are being etched simultaneously. The etching results will be presented at this conference.

  6. Impact of nitrogen doping of niobium superconducting cavities on the sensitivity of surface resistance to trapped magnetic flux

    Science.gov (United States)

    Gonnella, Dan; Kaufman, John; Liepe, Matthias

    2016-02-01

    Future particle accelerators such as the SLAC "Linac Coherent Light Source-II" (LCLS-II) and the proposed Cornell Energy Recovery Linac require hundreds of superconducting radio-frequency (SRF) niobium cavities operating in continuous wave mode. In order to achieve economic feasibility of projects such as these, the cavities must achieve a very high intrinsic quality factor (Q0) to keep cryogenic losses within feasible limits. To reach these high Q0's in the case of LCLS-II, nitrogen-doping of niobium cavities has been selected as the cavity preparation technique. When dealing with Q0's greater than 1 × 1010, the effects of ambient magnetic field on Q0 become significant. Here, we show that the sensitivity to RF losses from trapped magnetic field in a cavity's walls is strongly dependent on the cavity preparation. Specifically, standard electropolished and 120 °C baked cavities show a sensitivity of residual resistance from trapped magnetic flux of ˜0.6 and ˜0.8 nΩ/mG trapped, respectively, while nitrogen-doped cavities show a higher sensitivity of residual resistance from trapped magnetic flux of ˜1 to 5 nΩ/mG trapped. We show that this difference in sensitivities is directly related to the mean free path of the RF surface layer of the niobium: shorter mean free paths lead to less sensitivity of residual resistance to trapped magnetic flux in the dirty limit (ℓ ≪ ξ0), while longer mean free paths lead to lower sensitivity of residual resistance to trapped magnetic flux in the clean limit (ℓ ≫ ξ0). These experimental results are also shown to have good agreement with recent theoretical predictions for pinned vortex lines oscillating in RF fields.

  7. Guyana dolphins (Sotalia guianensis) from Costa Rica emit whistles that vary with surface behaviors.

    Science.gov (United States)

    May-Collado, Laura J

    2013-10-01

    Guyana dolphins show remarkable intraspecific whistle variation. This variation has been largely explained in terms of distance among populations; however, other factors such as behavior may also be important. A broadband recording system recorded the whistles of Guyana dolphins under three behavioral states. A discriminant analysis found that during social and travel events, dolphins emit whistles with high delta and minimum frequency, respectively. Whistle duration was also important in discriminating behaviors. This study indicates that behavior is an important factor contributing to whistle variation of Guyana dolphins. Understanding how dolphin whistles vary with behavioral context will advance our understanding of dolphin communication and enable appropriate comparative studies.

  8. Self-assembly surface modified indium-tin oxide anodes for single-layer light-emitting diodes

    CERN Document Server

    Morgado, J; Charas, A; Matos, M; Alcacer, L; Cacialli, F

    2003-01-01

    We study the effect of indium-tin oxide surface modification by self assembling of highly polar molecules on the performance of single-layer light-emitting diodes (LEDs) fabricated with polyfluorene blends and aluminium cathodes. We find that the efficiency and light-output of such LEDs is comparable to, and sometimes better than, the values obtained for LEDs incorporating a hole injection layer of poly(3,4-ethylene dioxythiophene) doped with polystyrene sulphonic acid. This effect is attributed to the dipole-induced work function modification of indium-tin oxide.

  9. Photoelectron emission from metal surfaces induced by radiation emitted by a 14 GHz electron cyclotron resonance ion source

    Science.gov (United States)

    Laulainen, Janne; Kalvas, Taneli; Koivisto, Hannu; Komppula, Jani; Kronholm, Risto; Tarvainen, Olli

    2016-02-01

    Photoelectron emission measurements have been performed using a room-temperature 14 GHz ECR ion source. It is shown that the photoelectron emission from Al, Cu, and stainless steel (SAE 304) surfaces, which are common plasma chamber materials, is predominantly caused by radiation emitted from plasma with energies between 8 eV and 1 keV. Characteristic X-ray emission and bremsstrahlung from plasma have a negligible contribution to the photoelectron emission. It is estimated from the measured data that the maximum conceivable photoelectron flux from plasma chamber walls is on the order of 10% of the estimated total electron losses from the plasma.

  10. Photoelectron emission from metal surfaces induced by radiation emitted by a 14 GHz electron cyclotron resonance ion source

    Energy Technology Data Exchange (ETDEWEB)

    Laulainen, Janne, E-mail: janne.p.laulainen@student.jyu.fi; Kalvas, Taneli; Koivisto, Hannu; Komppula, Jani; Kronholm, Risto; Tarvainen, Olli [Department of Physics, University of Jyvaskyla, P.O. Box 35, FI-40014 Jyvaskyla (Finland)

    2016-02-15

    Photoelectron emission measurements have been performed using a room-temperature 14 GHz ECR ion source. It is shown that the photoelectron emission from Al, Cu, and stainless steel (SAE 304) surfaces, which are common plasma chamber materials, is predominantly caused by radiation emitted from plasma with energies between 8 eV and 1 keV. Characteristic X-ray emission and bremsstrahlung from plasma have a negligible contribution to the photoelectron emission. It is estimated from the measured data that the maximum conceivable photoelectron flux from plasma chamber walls is on the order of 10% of the estimated total electron losses from the plasma.

  11. Photoelectron Emission from Metal Surfaces Induced by Radiation Emitted by a 14 GHz Electron Cyclotron Resonance Ion Source

    CERN Document Server

    Laulainen, Janne; Koivisto, Hannu; Komppula, Jani; Kronholm, Risto; Tarvainen, Olli

    2015-01-01

    Photoelectron emission measurements have been performed using a room-temperature 14 GHz ECR ion source. It is shown that the photoelectron emission from Al, Cu, and stainless steel (SAE 304) surfaces, which are common plasma chamber materials, is predominantly caused by radiation emitted from plasma with energies between 8 eV and 1 keV. Characteristic X-ray emission and bremsstrahlung from plasma have a negligible contribution to the photoelectron emission. It is estimated from the measured data that the maximum conceivable photoelectron flux from plasma chamber walls is on the order of 10 % of the estimated total electron losses from the plasma.

  12. Stacking and translation of microscopic particles by means of 2×2 beams emitted from a vertical-cavity surface-emitting laser array

    OpenAIRE

    Sumiyama, Fumika; Ogura, Yusuke; Tanida, Jun

    2003-01-01

    Copyright 2003 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Applied Physics Letters, 82(18), 2969-2971, 2003 and may be found at http://dx.doi.org/10.1063/1.1570939

  13. Horizontally assembled green InGaN nanorod LEDs: scalable polarized surface emitting LEDs using electric-field assisted assembly

    Science.gov (United States)

    Park, Hoo Keun; Yoon, Seong Woong; Eo, Yun Jae; Chung, Won Woo; Yoo, Gang Yeol; Oh, Ji Hye; Lee, Keyong Nam; Kim, Woong; Do, Young Rag

    2016-01-01

    In this study, we report the concerted fabrication process, which is easy to transform the size of active emitting area and produce polarized surface light, using the electric-field-assisted assembly for horizontally assembled many tiny nanorod LEDs between two metal electrodes. We fabricate the millions of individually separated 1D nanorod LEDs from 2D nanorod arrays using nanosphere lithography, etching and cutting process of InGaN/GaN LED structure on a flat sapphire substrate. The horizontally assembled InGaN-based nanorods LED device shows bright (~2,130 cd/m2) and uniform polarized (polarization ratio, ρ = ~0.61) green emissions from large area (0.7 cm × 0.6 cm) planar surface. The realization of a horizontally assembled nanorod LED device can prove the concept of an innovative idea to fabricate formable and scalable polarized surface LED lighting. PMID:27324568

  14. R&D Status for In-Situ Plasma Surface Cleaning of SRF Cavities at Spallation Neutron Source

    Energy Technology Data Exchange (ETDEWEB)

    S.-H. Kim, M.T. Crofford, M. Doleans, J.D. Mammosser, J. Saunders

    2011-03-01

    The SNS SCL is reliably operating at 0.93 GeV output energy with an energy reserve of 10MeV with high availability. Most of the cavities exhibit field emission, which directly or indirectly (through heating of end groups) limits the gradients achievable in the high beta cavities in normal operation with the beam. One of the field emission sources would be surface contaminations during surface processing for which mild surface cleaning, if any, will help in reducing field emission. An R&D effort is in progress to develop in-situ surface processing for the cryomodules in the tunnel without disassembly. As the first attempt, in-situ plasma processing has been applied to the CM12 in the SNS SRF facility after the repair work with a promising result. This paper will report the R&D status of plasma processing in the SNS.

  15. Reconstruction of energy and angle distribution function of surface-emitted negative ions in hydrogen plasmas using mass spectrometry

    Science.gov (United States)

    Kogut, D.; Achkasov, K.; Dubois, J. P. J.; Moussaoui, R.; Faure, J. B.; Layet, J. M.; Simonin, A.; Cartry, G.

    2017-04-01

    A new method involving mass spectrometry and modeling is described in this work, which may highlight the production mechanisms of negative ions (NIs) on surface in low pressure plasmas. Positive hydrogen ions from plasma impact a sample which is biased negatively with respect to the plasma potential. NIs are produced on the surface through the ionization of sputtered and backscattered particles and detected according to their energy and mass by a mass spectrometer (MS) placed in front of the sample. The shape of the measured negative-ion energy distribution function (NIEDF) strongly differs from the NIEDF of the ions emitted by the sample because of the limited acceptance angle of the MS. The reconstruction method proposed here allows to compute the distribution function in energy and angle (NIEADF) of the NIs emitted by the sample based on the NIEDF measurements at different tilt angles of the sample. The reconstruction algorithm does not depend on the NI surface production mechanism, so it can be applied to any type of surface and/or NI. The NIEADFs for highly oriented pyrolitic graphite (HOPG) and gadolinium (low work-function metal) are presented and compared with the SRIM modeling. HOPG and Gd show comparable integrated NI yields, however the key differences in mechanisms of NI production can be identified. While for Gd the major process is backscattering of ions with the peak of NIEDF at 36 eV, in case of HOPG the sputtering contribution due to adsorbed H on the surface is also important and the NIEDF peak is found at 5 eV.

  16. The use of Erbium: Yttrium-aluminum-garnet laser in cavity preparation and surface treatment: 3-year follow-up.

    Science.gov (United States)

    Buyukhatipoglu, Isil; Secilmis, Asli

    2015-01-01

    From the currently available choices, esthetic restorative materials for posterior teeth are limited to composite and ceramic restoration. Ceramic inlays/onlays are reliable solutions for both of these treatments. For successful treatment planning, usable ceramic and adhesive systems should be chosen by the dentist. Since the Federal Drug Administration approval of the erbium: Yttrium-aluminum-garnet (Er:YAG) laser-for caries removal, cavity preparation and the conditioning of tooth substance-in 1997, there have been many reports on the use of this technique in combination with composite resins. In addition, cavity pretreatment with the Er:YAG laser (laser etching) has been proposed as an alternative to acid etching of enamel and dentin. This case report presents the use of the Er:YAG in cavity preparation for composite resin restoration and surface treatment for ceramic onlay restoration of adjacent permanent molars.

  17. The use of Erbium: Yttrium-aluminum-garnet laser in cavity preparation and surface treatment: 3-year follow-up

    Science.gov (United States)

    Buyukhatipoglu, Isil; Secilmis, Asli

    2015-01-01

    From the currently available choices, esthetic restorative materials for posterior teeth are limited to composite and ceramic restoration. Ceramic inlays/onlays are reliable solutions for both of these treatments. For successful treatment planning, usable ceramic and adhesive systems should be chosen by the dentist. Since the Federal Drug Administration approval of the erbium: Yttrium-aluminum-garnet (Er:YAG) laser-for caries removal, cavity preparation and the conditioning of tooth substance-in 1997, there have been many reports on the use of this technique in combination with composite resins. In addition, cavity pretreatment with the Er:YAG laser (laser etching) has been proposed as an alternative to acid etching of enamel and dentin. This case report presents the use of the Er:YAG in cavity preparation for composite resin restoration and surface treatment for ceramic onlay restoration of adjacent permanent molars. PMID:26038665

  18. Failure of man-made cavities in salt and surface subsidence due to sulfur mining

    Energy Technology Data Exchange (ETDEWEB)

    Coates, G.K.; Lee, C.A.; McClain, W.C.; Senseny, P.E.

    1981-01-01

    An engineering data base relevant to subsidence due to sulfur mining and to structural failure of cavities in salt is established, evaluated and documented. Nineteen failure events are discussed. Based on these documented failure events, capabilities of and inputs to a mathematical model of cavity failure are determined. Two failure events are adequately documented for use in model verification studies. A conclusion of this study that is pertinent to the Strategic Petroleum Reserve is that cavity failures in dome salt are fairly rare, but that as the number of large cavities (especially those having large roof spans) increases, failures will probably be more common unless stability and failure mechanisms of cavities are better understood.

  19. Increasing the extraction efficiency of blue light emitting diodes via laser patterned Ga-polar p-GaN surface

    Energy Technology Data Exchange (ETDEWEB)

    Zuo, Zhiyuan; Liu, Duo; Zhang, Baitao; He, Jingliang; Liu, Hong; Xu, Xiangang [State Key Laboratory of Crystal Materials, Shandong University, Jinan, Shandong 250100 (China)

    2011-09-15

    We report here the laser patterned Ga-polar p-GaN surface to improve the light extraction efficiency of GaN based blue light emitting diodes (LEDs) by using a pulsed UV laser in combination with a mirror scanner. The patterns created on p-GaN are confirmed to be suitable for light extraction and a 34.9% enhancement of the electroluminescent (EL) emission intensity has been obtained. Detailed discussions on the effects of laser on LEDs and the angular dependence of the emission profile are also provided. This method could be extended to other III-V LEDs and LEDs on SiC for fabricating highly efficient LEDs. The schematic of laser fabrication equipment, SEM image of patterned p-GaN surface and guided-modes extraction photograph of patterned GaN epilayer. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Materials and surface aspects in the development of SRF Niobium cavities

    CERN Document Server

    Antoine, C

    2012-01-01

    Foreword from author; When I joined the CEA Saclay SRF group in 1989, my initial background was physical chemistry and surface science, which I completed later on with solid state physics and metallurgy. Most accelerator physicists at that time had training in RF, plasma physics, nuclear or particle physics. We were very few with a background in material science. Working with people with a different background than yours reveals to be both challenging and funny: you can impress them with things you consider basic while they simply do not believe you for other things you consider so well admitted that you do not even remember where it comes from. At the end it obliges you to reconsider your basics and re-question many results, which opens many new and sometimes unexpected paths. Like usual in science, answering one question rises many new ones, and trying to improve cavities performance led to fascinating physics problems. Exploring some of these problems often requires techniques and expertise that are far be...

  1. Selection of Optical Cavity Surface Coatings for 1micron Laser Based Missions

    Science.gov (United States)

    Hedgeland, Randy J.; Straka, Sharon; Matsumura, Mark; Hammerbacher, Joseph

    2004-01-01

    The particulate surface cleanliness level on several coatings for aluminum and beryllium substrates were examined for use in the optical cavities of high pulse energy Nd:YAG Q-switched, diode-pumped lasers for space flight applications. Because of the high intensity of the lasers, any contaminants in the laser beam path could damage optical coatings and limit the instrument mission objectives at the operating wavelength of 1 micron (micrometer). Our goal was to achieve an EST-STD-CC1246D Level 100 particulate distribution or better to ensure particulate redistribution during launch would not adversely affect the performance objectives. Tapelifts were performed to quantify the amount of particles using in-house developed procedures. The primary candidate coatings included chromate conversion coating aluminum (Al), uncoated Al electroless Nickel (Ni) on Al, Ni-gold (Au) on Al, anodized Al, and gold (Au)/Ni on Beryllium (Be). The results indicate that there were advantages in Ni and Au coating applications for the two major substrates, Al and Be, when considering applications that need to meet launch environments.

  2. Effects of A Top SiO2 Surface Layer on Cavity Formation and Helium Desorption in Silicon

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Cz n-type Si (100) samples with and without a top SiO2 layer were implanted with 40 keV helium ions at the same dose of 5×1016 cm-2. Cross-sectional transmission electron microscopy (XTEM) and thermal desorption spectroscopy (THDS) were used to study the thermal evolution of cavities upon and helium thermal release, respectively. XTEM results show that the presence of the top SiO2 layer could suppress the thermal growth of cavities mainly formed in the region close to the SiO2/Si interface, which leads to the reduction in both the cavity band and cavity density. THDS results reveal that the top oxide layer could act as an effective barrier for the migration of helium atoms to the surface, and it thus gives rise to the formation of more overpresurrized bubbles and to the occurrence of a third release peak located at about 1100 K. The results were qualitively discussed by considering the role of the oxide surface layer in defect migration and evolution upon annealing.

  3. WAFER TEST CAVITY -Linking Surface Microstructure to RF Performance: a ‘Short-­Sample Test Facility’ for characterizing superconducting materials for SRF cavities.

    Energy Technology Data Exchange (ETDEWEB)

    Pogue, Nathaniel; Comeaux, Justin; McIntyre, Peter

    2014-05-30

    The Wafer Test cavity was designed to create a short sample test system to determine the properties of the superconducting materials and S-I-S hetero-structures. The project, funded by ARRA, was successful in accomplishing several goals to achieving a high gradient test system for SRF research and development. The project led to the design and construction of the two unique cavities that each severed unique purposes: the Wafer test Cavity and the Sapphire Test cavity. The Sapphire Cavity was constructed first to determine the properties of large single crystal sapphires in an SRF environment. The data obtained from the cavity greatly altered the design of the Wafer Cavity and provided the necessary information to ascertain the Wafer Test cavity’s performance.

  4. Effect of surface radiation on the breakdown of steady natural convection flows in a square, air-filled cavity containing a centered inner body

    OpenAIRE

    Sun, H; Chénier, Eric; Lauriat, Guy

    2011-01-01

    Abstract The physical model considered in the present numerical work is a square air-filled cavity cooled from below and above, with a heated square body located at the cavity center. The aim is to establish the effects of radiation interchanges amongst surfaces on the transition from steady, symmetric flows about the cavity centerline to complex periodic flows. Owing to the low temperature differences involved (1 K ? ?T ? 5 K), the two-dimensional model is based on the Boussinesq ...

  5. Breakdown study based on direct in situ observation of inner surfaces of an rf accelerating cavity during a high-gradient test

    Science.gov (United States)

    Abe, Tetsuo; Kageyama, Tatsuya; Sakai, Hiroshi; Takeuchi, Yasunao; Yoshino, Kazuo

    2016-10-01

    We have developed normal-conducting accelerating single-cell cavities with a complete higher-order-mode (HOM) heavily damped structure, into which we feed a 508.9-MHz continuous wave. During a high-gradient test of the second production version of the cavity, we performed a breakdown study based on direct in situ observation of the inner surfaces of the cavity. This paper presents our experimental findings obtained from this observation.

  6. RF surface resistance of copper-on-beryllium at cryogenic temperatures measured by a 22-GHZ demountable cavity

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jianfei; Krawczyk, F. L. (Frank L.); Kurennoy, S. (Sergey); Schrage, D. L. (Dale L.); Shapiro, A. H. (Alan H.); Tajima, T. (Tsuyoshi); Wood R. L. (Richard L.)

    2003-01-01

    A 22-GHz demountable cavity on the cold head of a compact refrigerator system was used to measure the RF performance of several coppt:r-plated Beryllium samples. The cavity inner surfce was treated by chemical polishing and heat treatment., as well as an OFE copper coupon to provide a baseline for comparison. The measured surhce resistance was reasonable and repeatable during either cooling or warming. Materials tested included four grades of Beryllium, OFE copper, alumina-dispersion strengthened copper (Glidcop), and Cu-plated versions of all of the above. Two coupons, Cuplated on Beryllium 0-30 and 1-70, offered comparable surface resistance to pure OFE copper or Cu-plated Glidcop. The RF surface resistance of Cu-on-Beryllium samples at cryogenic temperatures is reported together with that of other reference materials.

  7. Near Infrared Cavity Ring-Down Spectroscopy for Isotopic Analyses of CH4 on Future Martian Surface Missions

    Science.gov (United States)

    Chen, Y.; Mahaffy P.; Holmes, V.; Burris, J.; Morey, P.; Lehmann, K.K.; Lollar, B. Sherwood; Lacrampe-Couloume, G.; Onstott, T.C.

    2014-01-01

    A compact Near Infrared Continuous Wave Cavity Ring-Down Spectrometer (near-IR-cw-CRDS) was developed as a candidate for future planetary surface missions. The optical cavity was made of titanium with rugged quartz windows to protect the delicate super cavity from the harsh environmental changes that it would experience during space flight and a Martian surface mission. This design assured the long-term stability of the system. The system applied three distributed feedback laser diodes (DFB-LD), two of which were tuned to the absorption line peaks of (sup 12)CH4 and (sup 13)CH4 at 6046.954 inverse centimeters and 6049.121 inverse centimeters, respectively. The third laser was tuned to a spectral-lines-free region for measuring the baseline cavity loss. The multiple laser design compensated for typical baseline drift of a CRDS system and, thus, improved the overall precision. A semiconductor optical amplifier (SOA) was used instead of an Acousto-Optic Module (AOM) to initiate the cavity ring-down events. It maintained high acquisition rates such as AOM, but consumed less power. High data acquisition rates combined with improved long-term stability yielded precise isotopic measurements in this near-IR region even though the strongest CH4 absorption line in this region is 140 times weaker than that of the strongest mid-IR absorption band. The current system has a detection limit of 1.4 times 10( sup –12) inverse centimeters for (sup 13)CH4. This limit corresponds to approximately 7 parts per trillion volume of CH4 at 100 Torrs. With no further improvements the detection limit of our current near IR-cw-CRDS at an ambient Martian pressure of approximately 6 Torrs (8 millibars) would be 0.25 parts per billion volume for one 3.3 minute long analysis.

  8. Localized surface plasmon enhanced emission of organic light emitting diode coupled to DBR-cathode microcavity by using silver nanoclusters.

    Science.gov (United States)

    Khadir, Samira; Chakaroun, Mahmoud; Belkhir, Abderrahmane; Fischer, Alexis; Lamrous, Omar; Boudrioua, Azzedine

    2015-09-01

    In this work, we aim to increase the emission of the standard guest-host organic light emitting diode (OLED) thanks to localized surface plasmon and to investigate this effect in a microcavity. As a first step, we consider thermal deposition of silver clusters within an OLED guest-host stack. We investigate both the influence of the size of silver nanoparticles (Ag-NPs) and their position within the OLED heterostructure. Secondly, we study the optimized OLED within a microcavity formed by Al-cathode top mirror and a Distributed Bragg Reflector (DBR) bottom mirror. The experimental results show a substantial enhancement of the electroluminescence (EL) intensity as well as a reduction of the spectral width at a half maximum.

  9. Therapy of estrogen receptor-positive micrometastases in the peritoneal cavity with Auger electron-emitting estrogens--Theoretical and practical considerations

    Energy Technology Data Exchange (ETDEWEB)

    DeSombre, E.R.; Hughes, A.; Hanson, R.N.; Kearney, T. [Univ. of Chicago, IL (United States). Ben May Inst. for Cancer Research

    2000-11-01

    Previous studies have demonstrated that Auger electron-emitting estrogens, when associated with the estrogen receptor (ER), can effect breaks in DNA and ER-dependent radiotoxicity. To evaluate the potential of {sup 123}I-iodoestrogens, ({sup 123}I-IE) to treat ER-positive human cancer cells, we have studied the effect of incubation of {sup 123}I-IE with ER-positive MCF-7 breast cancer cells on cell survival in vitro and found that subnanomolar concentrations of {sup 123}I-IE effectively reduce survival, with a mean lethal dose of about 800 decays per cell. MCF-7 cells incubated 30 min with 2 nM {sup 123}I-IE (13 MBq/ml) showed a 2 log reduction in the ability to form tumors in immunodeficient mice. Evaluation of a mathematical model for {sup 123}I-IE therapy for intraperitoneal micrometastases in vivo in the mouse, based on variables related to the (a) specific activity of {sup 123}I-IE; (b) its affinity for ER; (c) the characteristics of the uptake and retention of {sup 123}I-IE by the target cells; (d) the concentration of ER in the tumor cells and (e) the tumor weight suggest that such therapy may be feasible.

  10. Strong Coupling of the Cyclotron Motion of Surface Electrons on Liquid Helium to a Microwave Cavity

    Science.gov (United States)

    Abdurakhimov, L. V.; Yamashiro, R.; Badrutdinov, A. O.; Konstantinov, D.

    2016-07-01

    The strong coupling regime is observed in a system of two-dimensional electrons whose cyclotron motion is coupled to an electromagnetic mode in a Fabry-Perot cavity resonator. Rabi splitting of eigenfrequencies of the coupled motion is observed both in the cavity reflection spectrum and ac current of the electrons, the latter probed by measuring their bolometric photoresponse. Despite the fact that similar observations of Rabi splitting in many-particle systems have been described as a quantum-mechanical effect, we show that the observed splitting can be explained completely by a model based on classical electrodynamics.

  11. accelerating cavity

    CERN Multimedia

    On the inside of the cavitytThere is a layer of niobium. Operating at 4.2 degrees above absolute zero, the niobium is superconducting and carries an accelerating field of 6 million volts per metre with negligible losses. Each cavity has a surface of 6 m2. The niobium layer is only 1.2 microns thick, ten times thinner than a hair. Such a large area had never been coated to such a high accuracy. A speck of dust could ruin the performance of the whole cavity so the work had to be done in an extremely clean environment.

  12. Gamma emitting fission products in surface sediments of the Ravenglass estuary

    Energy Technology Data Exchange (ETDEWEB)

    Aston, S.R.; Stanners, D.A. (Lancaster Univ. (UK))

    1982-04-01

    The occurrence of some fission products from the Sellafield (formerly Windscale) nuclear fuel reprocessing facility has been determined for surface sediments from forty locations in the Ravenglass estuary, North-West England. The influence of the silt-sized fraction in the sediments on the geographic distribution of /sup 137/Cs is clearly important, and to a lesser extent also influences the distributions of /sup 106/Ru, /sup 134/Cs + /sup 95/Zr/Nb and /sup 144/Ce. The data are compared with recently published results reported by the Ministry of Agriculture, Fisheries and Food for a monitoring site in this estuary.

  13. Experimental Study on Fundamental Phenomena of Nucleate-Boiling by Using Heat Transfer Surface with Artificial Cavities Created by MEMS Technology

    Science.gov (United States)

    Sato, Takato; Koizumi, Yasuo; Ohtake, Hiroyasu

    Pool nucleate boiling heat transfer experiments were performed for water by using a well-controlled and -defined heat transfer surfaces in the range of the surface heat flux of ˜ 4.54×104 W⁄m2. One or three cavities were created on a mirror-finished silicon plate of 0.525 mm thickness by utilizing the Micro-Electro Mechanical Systems (MEMS) technology. In present experiments, the cavities were arranged in a straight line. The silicon plate was placed facing up at the bottom of the test container filled with distilled water. The back side of the silicon plate was irradiated by a laser beam to heat up the test heat transfer surface. The back side temperature was measured with a radiation thermometer. A boiling state was recorded with a high speed video camera. Thermal interaction between neighboring cavities became weak as the cavity spacing became wide and it disappeared when S⁄Lc = 1.6 in present experimental range. Four bubble coalescence patterns; vertical, horizontal and declining coalescence and vertical lift (no coalescence), were confirmed. When S⁄Lc ≥ 1.6, horizontal and declining coalescence disappeared. When the cavity spacing was narrow, hydraulic interaction between neighboring cavities played an important role in heat transfer. It became less important as the cavity spacing became wide. When S⁄Lc ≥ 1.2, the hydraulic interaction between neighboring cavities became negligible and phase change heat transfer took a main part.

  14. Field limit and nano-scale surface topography of superconducting radio-frequency cavity made of extreme type II superconductor

    CERN Document Server

    Kubo, Takayuki

    2014-01-01

    The field limit of superconducting radio-frequency cavity made of type II superconductor with a large Ginzburg-Landau parameter is studied with taking effects of nano-scale surface topography into account. If the surface is ideally flat, the field limit is imposed by the superheating field. On the surface of cavity, however, nano-defects almost continuously distribute and suppress the superheating field everywhere. The field limit is imposed by an effective superheating field given by the product of the superheating field for ideal flat surface and a suppression factor that contains effects of nano-defects. A nano-defect is modeled by a triangular groove with a depth smaller than the penetration depth. An analytical formula for the suppression factor of bulk and multilayer superconductors are derived in the framework of the London theory. As an immediate application, the suppression factor of the dirty Nb processed by the electropolishing is evaluated by using results of surface topographic study. The estimat...

  15. Atmospheric and Surface Biosignatures in the reflected, emitted and transmitted Spectra of Terrestrial Exoplanets

    Science.gov (United States)

    Tinetti, G.; Liang, M. C.; Schneider, J.; Rashby, S.; Ehrenreich, D.; Riaud, P.; Yung, Y. L.

    NASA and ESA are planning missions to directly detect and characterize terrestrial planets outside our solar system. These missions will provide our first opportunity to spectroscopically study the global characteristics of those planets, and search for signs of habitability and life. We have used spatially and spectrally-resolved models to explore the observational sensitivity to changes in atmospheric and surface properties, and the detectability of surface biosignatures, in the globally averaged spectra and light-curves of Earth-like planets (Tinetti et al., 2006a,b) and more exotic but plausible terrestrial planets (Tinetti et al. 2005;2006c,d). These simulations are presented as a function of viewing geometry and phase at both VIS and IR wavelength ranges, applicable to the next generation of terrestrial planet exploration missions. Sensitivity studies we performed on the detectability of the red-edge -a sharp discontinuity in outgoing near-IR radiation representing a combined effect of plant leaf structure and tuning of photosynthetic pigments-show that Earth's land vegetation could potentially be seen in disk-averaged spectra, even with cloud cover, and when the signal is averaged over the daily time scale. For a terrestrial planet orbiting a later type star, this signature might be red-shifted (due to the adaptation of the extraterrestrial phototrophs to their planetary environment over the course of their evolution) but, depending on the atmospheric composition, better detectable. We evaluate also the possibility to detect atmospheric signatures of different kind of Earth-size exoplanets by stellar occultation, as function of the planet's size, atmospheric composition, cloud cover and parent-star type (Ehrenreich, Tinetti et al. 2006).

  16. Distribution of gamma-emitting radionuclides in surface subtidal sediments near the Sellafield plant

    Energy Technology Data Exchange (ETDEWEB)

    Jones, D.G.; Roberts, P.D.; Miller, J.M.

    1988-08-01

    Detailed distributions of total gamma activity, /sup 137/Cs, /sup 106/Ru and /sup 95/Zr + /sup 95/Nb in surface seabed sediments near the Sellafield plant are presented. The results are derived from a towed seabed gamma-ray spectrometer survey in September, 1982. All the distributions are similar, with contours of equal activity parallel to the coast defining a 'ridge' of higher activity which is displaced northwards relative to the outfall. Nuclide concentrations decrease with increasing distance from Sellafield; rates of decrease being in the order Zr + Nb > Ru > Cs. This can be related to the levels of the nuclides discharged, their sorption characteristics and their half lives. The pattern of seabed activity seems to have been fairly stable over the period 1978-85, but there is evidence of a small northward shift. Concentrations of /sup 137/Cs and /sup 106/Ru in 1985 were considerably lower than in 1978 or 1982. This is explicable in terms of the fall in discharge levels allied, in the case of Ru, to its short half life and, for Cs, the desorption observed in laboratory experiments. Nuclide ratios in sediment samples yield apparent transit times for the transport of nuclides in the survey area of 1.7-3.7 years. These times are generally greater than those obtained from sediments in the more distant Solway Firth and Ravenglass Estuary. It is suggested that they reflect fairly intense bioturbation causing mixing of relatively recent effluent with that from earlier discharges. This is supported by structures observed in X-radiographs of box cores, an abundant burrowing benthos and by interpretations of nuclide profiles and radiocarbon dating of sediment cores by other workers. A lag effect, of up to two years across the survey area, appears to be superimposed on that due to mixing.

  17. Buffered Electropolishing – A New Way for Achieving Extremely Smooth Surface Finish on Nb SRF Cavities to be Used in Particle Accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Hui Tian, Charles Reece, Michael Kelley

    2009-05-01

    Future accelerators require unprecedented cavity performance, which is strongly influenced by interior surface nano-smoothness. Electropolishing (EP) is the technique of choice to be developed for high-field superconducting radio frequency (SRF) cavities. Electrochemical impedance spectroscopy (EIS) and related techniques point to the electropolishing mechanism of Nb in a sulphuric and hydrofluoric acid electrolyte controlled by a compact surface salt film under F- diffusion-limited mass transport control. These and other findings are guiding a systematic characterization to form the basis for cavities process optimization.

  18. Output Enhancement of a THz Wave Based on a Surface-Emitted THz-Wave Parametric Oscillator

    Institute of Scientific and Technical Information of China (English)

    LI Zhong-Yang; YAO Jian-Quan; XU De-Gang; BING Pi-Bin; ZHONG Kai

    2011-01-01

    High-power nanosecond pulsed THz-wave radiation is achieved via a surface-emitted THz-wave parametric oscillator.One MgO:LiNbO3 crystal with large volume is used as the gain medium.THz-wave radiation from 1.084 THz to 2.654 THz is obtained.The maximum THz-wave average power is 5.8 μ W at 1.93 THz when the pump energy is 84 m J,corresponding to a energy conversion efficiency of 6.9 × 10-6.The polarization characteristics of THz wave are analyzed.During the experiments the radiations of the first-order and the second-order Stokes wave are observed.The THz wave has great scientific research value and wide applications in imaging,material detection,environmental monitoring,communication,astronomy,life sciences,national defense security and so on.[1-4] THz-wave parametric oscillators (TPOs)based on stimulated polariton scattering have many advantages,such as high efficient,coherent,tuning,narrow linewidth,compactness and room-temperature operation.[5-7] In recent years,TPOs have been developed rapidly.Stothard et al.[8] reported on a line-narrowed and widely tunable intracavity TPO,in which the linewidth of the THz wave is about 1 GHz,the tunning range is from 1 to 3 THz,and the peak power of the THz wave is about 3W.Wu et al.[9]reported on a TPO with recycled pump beam,and their experiment results show that the THz-wave out-put power increases almost four times in magnitude.%High-power nanosecond pulsed THz-wave radiation is achieved via a surface-emitted THz-wave parametric oscillator. One MgO:LiNbO3 crystal with large volume is used as the gain medium. THz-wave radiation from 1.084THz to 2.654THz is obtained. The maximum THz-wave average power is 5.8μW at 1.93THz when the pump energy is 84mJ, corresponding to a energy conversion efficiency of 6.9×10-6. The polarization characteristics of THz wave are analyzed. During the experiments the radiations of the first-order and the second-order Stokes wave are observed.

  19. The distribution of gamma-emitting radionuclides in surface subtidal sediments near the Sellafield plant

    Science.gov (United States)

    Jones, D. G.; Roberts, P. D.; Miller, J. M.

    1988-08-01

    Detailed distributions of total gamma activity, 137Cs, 106Ru and 95Zr + 95Nb in surface seabed sediments near the Sellafield plant are presented. The results are derived from a towed seabed gamma-ray spectrometer survey in September, 1982. All the distributions are similar, with contours of equal activity parallel to the coast defining a 'ridge' of higher activity which is displaced northwards relative to the outfall. This pattern appears to be largely a response to the transport of particle-associated radioeffluent modified in places by the type of seabed sediment present. At greater distance from Sellafield, the uptake of nuclides from solution seems to be more important. Nuclide concentrations decrease with increasing distance from Sellafield; rates of decrease being in the order Zr + Nb > Ru > Cs. This can be related to the levels of the nuclides discharged, their sorption characteristics and their half lives. The pattern of seabed activity seems to have been fairly stable over the period 1978 - 1985, but there is evidence of a small northward shift. Concentrations of 137Cs and 106Ru in 1985 were considerably lower than in 1978 or 1982. This is explicable in terms of the fall in discharge levels allied, in the case of Ru, to its short half life and, for Cs, the desorption observed in laboratory experiments. Nuclide ratios in sediment samples yield apparent transit times for the transport of nuclides in the survey area of 1·7 - 3·7 years. These times are generally greater than those obtained from sediments in the more distant Solway Firth and Ravenglass Estuary. It is suggested that they reflect fairly intense bioturbation causing mixing of relatively recent effluent with that from earlier discharges. This is supported by structures observed in X-radiographs of box cores, an abundant burrowing benthos and by interpretations of nuclide profiles and radiocarbon dating of sediment cores by other workers. A lag effect, of up to two years across the survey area

  20. Cavity QED by the Numbers

    Science.gov (United States)

    Kimble, H. J.; Boca, A.; Boozer, A. D.; Bowen, W. P.; Buck, J. R.; Chou, C. W.; Duan, L.-M.; Kuzmich, A.; McKeever, J.

    2004-12-01

    Observations of cooling and trapping of N = 1,2,3,... atoms inside a small optical cavity are described. The atom-cavity system operates in a regime of strong coupling for which single photons are sufficient to saturate the atomic response. New theoretical protocols for the efficient engineering of multi-atom entanglement within the setting of cavity QED are described. By trapping a single atom within the cavity mode, a one-atom laser is experimentally realized in a regime of strong coupling. Beyond the setting of cavity QED, quantum correlations have been observed for photon pairs emitted from an atomic ensemble and with a programmable time offset.

  1. Frequency dependence of the microwave surface resistance of MgB{sub 2} by coaxial cavity resonator

    Energy Technology Data Exchange (ETDEWEB)

    Agliolo Gallitto, A., E-mail: aurelio.agliologallitto@unipa.it [CNISM and Dipartimento di Fisica e Chimica, Università di Palermo, via Archirafi 36, 90123 Palermo (Italy); Camarda, P.; Li Vigni, M. [CNISM and Dipartimento di Fisica e Chimica, Università di Palermo, via Archirafi 36, 90123 Palermo (Italy); Figini Albisetti, A. [EDISON SpA Research and Development Division, Foro Buonaparte 31, 20121 Milano (Italy); Giunchi, G. [Freelance Consultant, via Teodosio 8, 20131 Milano (Italy)

    2014-08-15

    Highlights: • We investigate the microwave properties of a bulk MgB{sub 2} rod 94.3 mm long. • The MgB{sub 2} rod is used as inner conductor of a coaxial cavity. • The mw surface resistance vs. frequency is studied in the range 1–9 GHz. • R{sub s} vs. f curves follow a f{sup n} law, with n decreasing with the temperature. • Deviations from the quadratic law are highlighted at relatively low temperatures. - Abstract: We report on the microwave (mw) properties of a cylindrical MgB{sub 2} rod prepared by the reactive liquid Mg infiltration technology. The MgB{sub 2} rod, 94.3 mm long, is used as inner conductor of a coaxial cavity having a Cu tube as external conductor. By analyzing the resonance curves of the cavity in the different resonant modes and at different temperatures, we have determined the temperature dependence of the mw surface resistance, R{sub s}, of the MgB{sub 2} material, at fixed frequencies, and the frequency dependence of R{sub s}, at fixed temperatures. Our results show that the R{sub s}(f) curves follow a f{sup n} law, where n decreases on increasing the temperature, starting from n≈2, at T=4.2K, down to n≈0.7 at T⩾T{sub c}. The double-gap nature of MgB{sub 2} manifests itself in the presence of a wide low-T tail in the R{sub s}(T) curves, which can be ascribed to the quasiparticles thermally excited through the π gap even at relatively low temperatures.

  2. Investigation of surface-plasmon coupled red light emitting InGaN/GaN multi-quantum well with Ag nanostructures coated on GaN surface

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yi; Liu, Bin, E-mail: bliu@nju.edu.cn, E-mail: rzhang@nju.edu.cn; Zhang, Rong, E-mail: bliu@nju.edu.cn, E-mail: rzhang@nju.edu.cn; Xie, Zili; Zhuang, Zhe; Dai, JiangPing; Tao, Tao; Zhi, Ting; Zhang, Guogang; Chen, Peng; Ren, Fangfang; Zhao, Hong; Zheng, Youdou [Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, People' s Republic of China and Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093 (China)

    2015-04-21

    Surface-plasmon (SP) coupled red light emitting InGaN/GaN multiple quantum well (MQW) structure is fabricated and investigated. The centre wavelength of 5-period InGaN/GaN MQW structure is about 620 nm. The intensity of photoluminescence (PL) for InGaN QW with naked Ag nano-structures (NS) is only slightly increased due to the oxidation of Ag NS as compared to that for the InGaN QW. However, InGaN QW with Ag NS/SiO{sub 2} structure can evidently enhance the emission efficiency due to the elimination of surface oxide layer of Ag NS. With increasing the laser excitation power, the PL intensity is enhanced by 25%–53% as compared to that for the SiO{sub 2} coating InGaN QW. The steady-state electric field distribution obtained by the three-dimensional finite-difference time-domain method is different for both structures. The proportion of the field distributed in the Ag NS for the GaN/Ag NS/SiO{sub 2} structure is smaller as compared to that for the GaN/naked Ag NS structure. As a result, the energy loss of localized SP modes for the GaN/naked Ag NS structure will be larger due to the absorption of Ag layer.

  3. Comparison of 3 methods on fabricating micro- /nano- structured surface on 3D mold cavity

    DEFF Research Database (Denmark)

    Zhang, Yang; Hansen, Hans Nørgaard; Bissacco, Giuliano

    2015-01-01

    The methods to manufacture micro- or nano- structures on surfaces have been an area of intense investigation. Demands are shown for technologies for surface structuring on real 3D parts in many fields. However, most technologies for the fabrication of micro-structured functional surfaces are stil...

  4. Experimental Study on Behavior of Bubbles and Heat transfer by Using Heat Transfer Surface with Artificial Cavities Created by MEMS Technology

    Science.gov (United States)

    Sato, Takato; Koizumi, Yasuo; Ohtake, Hiroyasu

    Pool nucleate boiling heat transfer experiments were performed for water using heat transfer surfaces having unified cavities. Cylindrical holes of 10 μm in diameter and 40 μm in depth were formed on a mirror-finished silicon wafer of 0.2 mm in thickness using Micro-Electro Mechanical Systems (MEMS) technology. This silicon plate was used as the heat transfer surface. The test heat transfer surface was heated by a semiconductor laser beam. Experiments were conducted in the range of up to 1.35 × 105 W⁄m2. When a single cavity was formed, the vertical coalescence of bubbles above the cavity was 60 % and no coalescence was 40 %. The ratios of the convection and the phase change were 80 % and 20 %, respectively. When the number of cavities were increased to three, the coalescence of bubbles on the heat transfer surface became important. When the role of the convection and the phase change in nucleate boiling is considered, it is appropriate to examine the bubble departure from the vapor mass on the heat transfer surface not from cavities.

  5. Response-surface models for deterministic effects of localized irradiation of the skin by discrete {beta}/{gamma} -emitting sources

    Energy Technology Data Exchange (ETDEWEB)

    Scott, B.R.

    1995-12-01

    Individuals who work at nuclear reactor facilities can be at risk for deterministic effects in the skin from exposure to discrete {Beta}- and {gamma}-emitting ({Beta}{gamma}E) sources (e.g., {Beta}{gamma}E hot particles) on the skin or clothing. Deterministic effects are non-cancer effects that have a threshold and increase in severity as dose increases (e.g., ulcer in skin). Hot {Beta}{gamma}E particles are {sup 60}Co- or nuclear fuel-derived particles with diameters > 10 {mu}m and < 3 mm and contain at least 3.7 kBq (0.1 {mu}Ci) of radioactivity. For such {Beta}{gamma}E sources on the skin, it is the beta component of the dose that is most important. To develop exposure limitation systems that adequately control exposure of workers to discrete {Beta}{gamma}E sources, models are needed for systems that adequately control exposure of workers to discrete {Beta}{gamma}E sources, models are needed for evaluating the risk of deterministic effects of localized {Beta} irradiation of the skin. The purpose of this study was to develop dose-rate and irradiated-area dependent, response-surface models for evaluating risks of significant deterministic effects of localized irradiation of the skin by discrete {Beta}{gamma}E sources and to use modeling results to recommend approaches to limiting occupational exposure to such sources. The significance of the research results as follows: (1) response-surface models are now available for evaluating the risk of specific deterministic effects of localized irradiation of the skin; (2) modeling results have been used to recommend approaches to limiting occupational exposure of workers to {Beta} radiation from {Beta}{gamma}E sources on the skin or on clothing; and (3) the generic irradiated-volume, weighting-factor approach to limiting exposure can be applied to other organs including the eye, the ear, and organs of the respiratory or gastrointestinal tract and can be used for both deterministic and stochastic effects.

  6. Enhanced chiral response from the Fabry-Perot cavity coupled meta-surfaces

    Science.gov (United States)

    Yang, Ze-Jian; Hu, De-Jiao; Gao, Fu-Hua; Hou, Yi-Dong

    2016-08-01

    The circular dichroism (CD) signal of a two-dimensional (2D) chiral meta-surface is usually weak, where the difference between the transmitted (or reflected) right and left circular polarization is barely small. We present a general method to enhance the reflective CD spectrum, by adding a layer of reflective film behind the meta-surface. The light passes through the chiral meta-surface and propagates towards the reflector, where it is reflected back and further interacts with the chiral meta-surface. The light is reflected back and forth between these two layers, forming a Fabry-Perot type resonance, which interacts with the localized surface plasmonic resonance (LSPR) mode and greatly enhances the CD signal of the light wave leaving the meta-surface. We numerically calculate the CD enhancing effect of an L-shaped chiral meta-surface on a gold film in the visible range. Compared with the single layer meta-surface, the L-shaped chiral meta-surface has a CD maximum that is dramatically increased to 1. The analysis of reflection efficiency reveals that our design can be used to realize a reflective circular polarizer. Corresponding mode analysis shows that the huge CD originates from the hybrid mode comprised of FP mode and LSPR. Our results provide a general approach to enhancing the CD signal of a chiral meta-surface and can be used in areas like biosensing, circular polarizer, integrated photonics, etc. Project supported by the National Natural Science Foundation of China (Grant No. 61377054).

  7. Topographic power spectral density study of the effect of surface treatment processes on niobium for superconducting radio frequency accelerator cavities

    Energy Technology Data Exchange (ETDEWEB)

    Charles Reece, Hui Tian, Michael Kelley, Chen Xu

    2012-04-01

    Microroughness is viewed as a critical issue for attaining optimum performance of superconducting radio frequency accelerator cavities. The principal surface smoothing methods are buffered chemical polish (BCP) and electropolish (EP). The resulting topography is characterized by atomic force microscopy (AFM). The power spectral density (PSD) of AFM data provides a more thorough description of the topography than a single-value roughness measurement. In this work, one dimensional average PSD functions derived from topography of BCP and EP with different controlled starting conditions and durations have been fitted with a combination of power law, K correlation, and shifted Gaussian models to extract characteristic parameters at different spatial harmonic scales. While the simplest characterizations of these data are not new, the systematic tracking of scale-specific roughness as a function of processing is new and offers feedback for tighter process prescriptions more knowledgably targeted at beneficial niobium topography for superconducting radio frequency applications.

  8. 200 nm-1000 nm spectra of light emitted in the impact of 40Ar10+ upon Al and Si solid surfaces

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Xiaoan; (张小安); ZHAO; Yongtao; (赵永涛); LI; Fuli; (李福利); YANG; Zhihu(杨治虎); XIAO; Guoqing(肖国青); ZHAN; Wenlong(詹文龙)

    2003-01-01

    This paper reports the measured results of the 200 nm-1000 nm characteristic spectral lines of Al, Si and Ar atoms when highly charged ions 40Ar10+ are incident upon Al and P-type Si surfaces. The ion 40Ar10+ is provided by the ECR ion source of the National Laboratory of the Heavy Ion Accelerator in Lanzhou. The results show that when the low-speed ions in the highly charged state interact with the solid surfaces, the characteristic spectral lines of the target atoms and ions spurted from the surfaces can be effectively excited. Moreover, because of the competition of the non-radiation de-excitation of the hollow atom by emitting secondary electrons with the de-excitation process by radiating photons, the spectral intensity of the characteristic spectral lines of Ar atoms on the P-type Si surface is, as a whole, greater than that of Ar atoms on the Al surface.

  9. Effect of surface roughness of cavity preparations on the microleakage of Class V resin composite restorations.

    Science.gov (United States)

    Shook, Larry W; Turner, Edgar W; Ross, Judith; Scarbecz, Mark

    2003-01-01

    This study determined whether surface roughness of the internal walls of a Class V resin composite preparation, using a carbide bur, a medium-grit diamond bur and a fine-grit diamond bur, affected the degree of microleakage of the restoration. The facial and lingual surfaces of 45 non-carious extracted human molars provided 90 samples for evaluation. The specimen surfaces were assigned randomly in equal numbers to one of three groups (n = 30). Conservative Class V composite preparations were made using one of three different burs: a 330-carbide bur, a 330 fine-grit diamond bur or a 330 medium-grit diamond bur (Brasseler USA). After acid etching, PQ1 (Ultradent Products Inc) primer/bonding resin and Vitalescence (Ultradent Products Inc) were applied and cured following the manufacturers' instructions. After minor finishing, the apices of all root surfaces were sealed with Vitrebond (3M), and the unprepared external surfaces were sealed with nail polish to within 1 mm of the restoration margins. The specimens were stored in distilled water at room temperature for 24 hours, then subjected to 1,200 thermocycles at 5 degrees C and 55 degrees C with a 30-second dwell time. After cycling, the teeth were immersed in a 5% solution of methylene blue dye for 12 hours. The molars were invested in clear acrylic casting resin, labeled, then sectioned once vertically approximately midway through the facial and lingual surfaces using a diamond coated saw blade. Microleakage was evaluated using a 10x microscope for the enamel and cementum surfaces and blindly scored by two independent examiners. In all cases, regardless of the examiner, at both the enamel and the dentin margins, the analysis revealed no statistically significant differences in microleakage across bur types. Further results show that dentin margins leaked significantly more than enamel margins for all bur types.

  10. SPS accelerating cavity

    CERN Multimedia

    1980-01-01

    One of the SPS acceleration cavities (200 MHz, travelling wave structure). On the ceiling one sees the coaxial transmission line which feeds the power from the amplifier, located in a surface building above, to the upstream end of the cavity. See 7603195 for more details, 7411032 for the travelling wave structure, and also 8104138, 8302397.

  11. Superconducting cavities for LEP

    CERN Multimedia

    1983-01-01

    Above: a 350 MHz superconducting accelerating cavity in niobium of the type envisaged for accelerating electrons and positrons in later phases of LEP. Below: a small 1 GHz cavity used for investigating the surface problems of superconducting niobium. Albert Insomby stays on the right. See Annual Report 1983 p. 51.

  12. Equilibrator-based measurements of dissolved methane in the surface ocean using an integrated cavity output laser absorption spectrometer

    Institute of Scientific and Technical Information of China (English)

    LI Yuhong; ZHAN Liyang; ZHANG Jiexia; CHEN Liqi

    2015-01-01

    A new off-axis integrated cavity output spectroscopy (ICOS) is coupled to Weiss equilibrator for continuous high-resolution dissolved methane measurement in the surface ocean. The time constant for the equilibrator in freshwater at room temperature is determined via dis-equilibration and re-equilibration experiments. The constant for methane is about 40 min. The system is calibrated using a standard gas of 3.980×10–6, and the precision of the ICOS for methane is 0.07%. This system is equipped onboard to measure the spatial distribution in methane concentrations of South Yellow Sea (SYS) along the cruise track from Shanghai to Qingdao. Result shows that the methane concentration varies from 2.79 to 36.36 nmol/L, reveals a significant pattern of methane source in SYS, and a distinct decreasing trend from south to north. The peak value occurs at the coast area outside mouth of the Changjiang River, likely to be affected by the Changjiang diluted water mass dissolving a large amount of rich in methane. Moreover, all the surface waters are oversaturated, air-to-sea fluxes range from 98.59 to 5 485.35 μmol/(m2·d) (average value (1 169.74±1 398.46) μmol/(m2·d)), indicating a source region for methane to the atmosphere.

  13. Vertical cavity lasing from melt-grown crystals of cyano-substituted thiophene/phenylene co-oligomer

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Yosuke; Yanagi, Hisao, E-mail: yanagi@ms.naist.jp [Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama, Ikoma, Nara 630-0192 (Japan); Goto, Kaname; Yamashita, Kenichi; Yamao, Takeshi; Hotta, Shu [Graduate School of Science and Technology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585 (Japan); Sasaki, Fumio [Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan)

    2015-10-19

    Vertical-cavity organic lasers are fabricated with melt-grown crystals of a cyano-substituted thiophene-phenylene co-oligomer. Due to lying molecular orientation, surface-emitting lasing is achieved even in the half-cavity crystal grown on a distributed Bragg reflector (DBR) under optical pumping at room temperature. Anticrossing splits in angle-resolved photoluminescence spectra suggest the formation of exciton-polaritons between the cavity photons and the confined Frenkel excitons. By constructing the full-cavity structure sandwiched between the top and bottom DBRs, the lasing threshold is reduced to one order, which is as low as that of the half cavity. Around the threshold, the time profile of the full-cavity emission is collapsed to a pulsed shape accompanied by a finite turn-on delay. We discuss these observed characteristics in terms of a polariton contribution to the conventional photon lasing.

  14. Surface quality of extruding metal special-shape products and frictional behavior in optimized die cavity

    Institute of Scientific and Technical Information of China (English)

    QI Hong-yuan; ZHU Heng-jun

    2004-01-01

    With the help of Complex Function Mapping theory, the complicated three-dimensional deformation problems are transferred into two-dimensional problems, and the function of strain ratio field is analyzed in the metal plastic extruding deformation. Taking the strain-hardening effect of metal deformation into account, the relationship between friction behavior and optimized mathematical model is analyzed by the numerical analysis friction energy dissipation function. As a result, the method of lowering the material hardening and decreasing the reduction ratio over multi-procedures can be used to improve the surface quality of metal special-shape extrusion products.

  15. Microwave band gap and cavity mode in spoof-insulator-spoof waveguide with multiscale structured surface

    CERN Document Server

    Zhang, Qiang; Han, Dezhuan; Qin, Fei Fei; Zhang, Xiao Ming; Yao, Yong

    2015-01-01

    We propose a multiscale spoof-insulator-spoof (SIS) waveguide by introducing periodic geometry modulation in the wavelength scale to a SIS waveguide made of perfect electric conductor. The MSIS consists of multiple SIS subcells. The dispersion relationship of the fundamental guided mode of the spoof surface plasmon polaritons (SSPPs) is studied analytically within the small gap approximation. It is shown that the multiscale SIS possesses microwave band gap (MBG) due to the Bragg scattering. The "gap maps" in the design parameter space are provided. We demonstrate that the geometry of the subcells can efficiently adjust the effective refraction index of the elementary SIS and therefore further control the width and the position of the MBG. The results are in good agreement with numerical calculations by the finite element method (FEM). For finite-sized MSIS of given geometry in the millimeter scale, FEM calculations show that the first-order symmetric SSPP mode has zero transmission in the MBG within frequency...

  16. Enhanced optical output of InGaN/GaN near-ultraviolet light-emitting diodes by localized surface plasmon of colloidal silver nanoparticles.

    Science.gov (United States)

    Hong, Sang-Hyun; Kim, Jae-Joon; Kang, Jang-Won; Jung, Yen-Sook; Kim, Dong-Yu; Yim, Sang-Youp; Park, Seong-Ju

    2015-09-25

    We report on the characteristics of localized surface plasmon (LSP)-enhanced near-ultraviolet light-emitting diodes (NUV-LEDs) fabricated by using colloidal silver (Ag) nanoparticles (NPs). Colloidal Ag NPs were deposited on the 20 nm thick p-GaN spacer layer using a spray process. The optical output power of NUV-LEDs with colloidal Ag NPs was increased by 48.7% at 20 mA compared with NUV-LEDs without colloidal Ag NPs. The enhancement was attributed to increased internal quantum efficiency caused by the resonance coupling between excitons in the multiple quantum wells and the LSPs in the Ag NPs.

  17. Interactions between nano-TiO{sub 2} and the oral cavity: Impact of nanomaterial surface hydrophilicity/hydrophobicity

    Energy Technology Data Exchange (ETDEWEB)

    Teubl, Birgit J.; Schimpel, Christa [Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology, University of Graz, 8010 (Austria); Leitinger, Gerd [Institute of Cell Biology, Histology and Embryology, Research Unit Electron Microscopic Techniques, Medical University of Graz, 8010 (Austria); Center for Medical Research, Medical University of Graz, 8010 (Austria); BioTechMed, Graz 8010 (Austria); Bauer, Bettina [Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology, University of Graz, 8010 (Austria); Fröhlich, Eleonore [Center for Medical Research, Medical University of Graz, 8010 (Austria); BioTechMed, Graz 8010 (Austria); Zimmer, Andreas [Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology, University of Graz, 8010 (Austria); BioTechMed, Graz 8010 (Austria); Roblegg, Eva, E-mail: eva.roblegg@uni-graz.at [Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology, University of Graz, 8010 (Austria); BioTechMed, Graz 8010 (Austria)

    2015-04-09

    Highlights: • Hydrophilic as well as hydrophobic TiO{sub 2} NPs agglomerated under oral physiological conditions. • Particles penetrated the upper and lower buccal epithelium, independent on the degree of hydrophilicity. • Most of the hydrophobic particles were found in vesicular structures, while hydrophilic particles were freely distributed in the cytoplasm. • Hydrophilic particles had a higher potential to trigger toxic effects (e.g., ROS) than hydrophobic particles. - Abstract: Titanium dioxide (TiO{sub 2}) nanoparticles are available in a variety of oral applications, such as food additives and cosmetic products. Thus, questions about their potential impact on the oro-gastrointestinal route rise. The oral cavity represents the first portal of entry and is known to rapidly interact with nanoparticles. Surface charge and size contribute actively to the particle–cell interactions, but the influence of surface hydrophilicity/hydrophobicity has never been shown before. This study addresses the biological impact of hydrophilic (NM 103, rutile, 20 nm) and hydrophobic (NM 104, rutile, 20 nm) TiO{sub 2} particles within the buccal mucosa. Particle characterization was addressed with dynamic light scattering and laser diffraction. Despite a high agglomeration tendency, 10% of the particles/agglomerates were present in the nanosized range and penetrated into the mucosa, independent of the surface properties. However, significant differences were observed in intracellular particle localization. NM 104 particles were found freely distributed in the cytoplasm, whereas their hydrophobic counterparts were engulfed in vesicular structures. Although cell viability/membrane integrity was not affected negatively, screening assays demonstrated that NM 104 particles showed a higher potential to decrease the physiological mitochondrial membrane potential than NM 103, resulting in a pronounced generation of reactive oxygen species.

  18. Multi circular-cavity surface coil for magnetic resonance imaging of monkey's brain at 4 Tesla

    Science.gov (United States)

    Osorio, A. I.; Solis-Najera, S. E.; Vázquez, F.; Wang, R. L.; Tomasi, D.; Rodriguez, A. O.

    2014-11-01

    Animal models in medical research has been used to study humans diseases for several decades. The use of different imaging techniques together with different animal models offers a great advantage due to the possibility to study some human pathologies without the necessity of chirurgical intervention. The employ of magnetic resonance imaging for the acquisition of anatomical and functional images is an excellent tool because its noninvasive nature. Dedicated coils to perform magnetic resonance imaging experiments are obligatory due to the improvement on the signal-to-noise ratio and reduced specific absorption ratio. A specifically designed surface coil for magnetic resonance imaging of monkey's brain is proposed based on the multi circular-slot coil. Numerical simulations of the magnetic and electric fields were also performed using the Finite Integration Method to solve Maxwell's equations for this particular coil design and, to study the behavior of various vector magnetic field configurations and specific absorption ratio. Monkey's brain images were then acquired with a research-dedicated magnetic resonance imaging system at 4T, to evaluate the anatomical images with conventional imaging sequences. This coil showed good quality images of a monkey's brain and full compatibility with standard pulse sequences implemented in research-dedicated imager.

  19. Polishing Difficult-To-Reach Cavities

    Science.gov (United States)

    Malinzak, R. Michael; Booth, Gary N.

    1990-01-01

    Springy abrasive tool used to finish surfaces of narrow cavities made by electrical-discharge machining. Robot arm moves vibrator around perimeters of cavities, polishing walls of cavities as it does so. Tool needed because such cavities inaccessible or at least difficult to reach with most surface-finishing tools.

  20. Three-dimensional cavity nanoantennas with resonant-enhanced surface plasmons as dynamic color-tuning reflectors.

    Science.gov (United States)

    Fan, J R; Wu, W G; Chen, Z J; Zhu, J; Li, J

    2017-03-09

    As plasmonic antennas for surface-plasmon-assisted control of optical fields at specific frequencies, metallic nanostructures have recently emerged as crucial optical components for fascinating plasmonic color engineering. Particularly, plasmonic resonant nanocavities can concentrate lightwave energy to strongly enhance light-matter interactions, making them ideal candidates as optical elements for fine-tuning color displays. Inspired by the color mixing effect found on butterfly wings, a new type of plasmonic, multiresonant, narrow-band (the minimum is about 45 nm), high-reflectance (the maximum is about 95%), and dynamic color-tuning reflector is developed. This is achieved from periodic patterns of plasmonic resonant nanocavities in free-standing capped-pillar nanostructure arrays. Such cavity-coupling structures exhibit multiple narrow-band selective and continuously tunable reflections via plasmon standing-wave resonances. Consequently, they can produce a variety of dark-field vibrant reflective colors with good quality, strong color signal and fine tonal variation at the optical diffraction limit. This proposed multicolor scheme provides an elegant strategy for realizing personalized and customized applications in ultracompact photonic data storage and steganography, colorimetric sensing, 3D holograms and other plasmon-assisted photonic devices.

  1. Sediment studies at Bikini Atoll part 3. Inventories of some long-lived gamma-emitting radionuclides associated with lagoon surface sediments

    Energy Technology Data Exchange (ETDEWEB)

    Noshkin, V.E.

    1997-12-01

    Surface sediment samples were collected during 1979 from 87 locations in the lagoon at Bikini Atoll. The collections were made to better define the concentrations and distribution of long-lived radionuclides associated with the bottom material and to show what modifications occurred to the composition of the surface sediment from the nuclear testing program conducted by the United States at the Atoll between 1946 and 1958. This is the last of three reports on Bikini sediment studies. In this report, we discuss the concentrations and inventories of the residual long-lived gamma-emitting radionuclides in sediments from the lagoon. The gamma-emitting radionuclides detected most frequently in sediments collected in 1979, in addition to Americium-241 ({sup 241}Am) (discussed in the second report of this series), included Cesium-137 ({sup 137}Cs), Bismuth-207 ({sup 207}Bi), Europium-155 ({sup 155}Eu), and Cobalt-60 ({sup 60}Co). Other man-made, gamma-emitting radionuclides such as Europium-152,154 ({sup 152,154}Eu), Antimony-125 ({sup 125}Sb), and Rhodium-101,102m ({sup 101,102m}Rh) were occasionally measured above detection limits in sediments near test site locations. The mean inventories for {sup 137}Cs, {sup 207}Ei, {sup 155}Eu, and {sup 60}Co in the surface 4 cm of the lagoon sediment to be 1.7, 0.56, 7.76, and 0.74 TBq, respectively. By June 1997, radioactive decay would reduce these values to 1.1, 0.38, 0.62, and 0.07 TBq, respectively. Some additional loss results from a combination of different processes that continuously mobilize and return some amount of the radionuclides to the water column. The water and dissolved constituents are removed from the lagoon through channels and exchange with the surface waters of the north equatorial Pacific Ocean. Highest levels of these radionuclides are found in surface deposits lagoonward of the Bravo Crater. Lowest concentrations and inventories are associated with sediment lagoonward of the eastern reef. The quantities in

  2. Possible influence of surface oxides on the optical response of high-purity niobium material used in the fabrication of superconducting radio frequency cavity

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Nageshwar [Magnetic and Superconducting Materials Section, Raja Ramanna Centre for Advanced Technology, Indore 452013, M.P. (India); Deo, M.N. [High Pressure & Synchrotron Radiation Physics Division, BARC, Mumbai 400085 (India); Roy, S.B. [Magnetic and Superconducting Materials Section, Raja Ramanna Centre for Advanced Technology, Indore 452013, M.P. (India)

    2016-09-11

    We have investigated the possible influence of surface oxides on the optical properties of a high-purity niobium (Nb) material for fabrication of superconducting radio frequency (SCRF) cavities. Various peaks in the infrared region were identified using Fourier transform infrared and Raman spectroscopy. Optical response functions such as complex refractive index, dielectric and conductivity of niobium were compared with the existing results on oxides free Nb and Cu. It was observed that the presence of a mixture of niobium-oxides, and probably near other surface impurities, appreciably influence the conducting properties of the material causing deviation from the typical metallic characteristics. In this way, the key result of this work is the observation, identification of vibrational modes of some of surface complexes and study of its influences on the optical responses of materials. This method of spectroscopic investigation will help in understanding the origin of degradation of performance of SCRF cavities.

  3. Possible influence of surface oxides on the optical response of high-purity niobium material used in the fabrication of superconducting radio frequency cavity

    Science.gov (United States)

    Singh, Nageshwar; Deo, M. N.; Roy, S. B.

    2016-09-01

    We have investigated the possible influence of surface oxides on the optical properties of a high-purity niobium (Nb) material for fabrication of superconducting radio frequency (SCRF) cavities. Various peaks in the infrared region were identified using Fourier transform infrared and Raman spectroscopy. Optical response functions such as complex refractive index, dielectric and conductivity of niobium were compared with the existing results on oxides free Nb and Cu. It was observed that the presence of a mixture of niobium-oxides, and probably near other surface impurities, appreciably influence the conducting properties of the material causing deviation from the typical metallic characteristics. In this way, the key result of this work is the observation, identification of vibrational modes of some of surface complexes and study of its influences on the optical responses of materials. This method of spectroscopic investigation will help in understanding the origin of degradation of performance of SCRF cavities.

  4. Free-Energy Barrier of Filling a Spherical Cavity in the Presence of Line Tension: Implication to the Energy Barrier between the Cassie and Wenzel States on a Superhydrophobic Surface with Spherical Cavities.

    Science.gov (United States)

    Iwamatsu, Masao

    2016-09-20

    The free-energy barrier of filling a spherical cavity having an inner wall of various wettabilities is studied. The morphology and free energy of a lens-shaped droplet are determined from the minimum of the free energy. The effect of line tension on the free energy is also studied. Then, the equilibrium contact angle of the droplet is determined from the generalized Young's equation. By increasing the droplet volume within the spherical cavity, the droplet morphology changes from spherical with an equilibrium contact angle of 180° to a lens with a convex meniscus, where the morphological complete drying transition occurs. By further increasing the droplet volume, the meniscus changes from convex to concave. Then, the lens-shaped droplet with concave meniscus spreads over the whole inner wall, resulting in an equilibrium contact angle of 0° to leave a spherical bubble, where the morphological complete wetting transition occurs. Finally, the whole cavity is filled with liquid. The free energy shows a barrier from complete drying to complete wetting as a function of droplet volume, which corresponds to the energy barrier between the Cassie and Wenzel states of the superhydrophobic surface with spherical cavities. The free-energy maximum occurs when the meniscus of the droplet becomes flat, and it is given by an analytic formula. The effect of line tension is expressed by the scaled line tension, and this effect is largest at the free-energy maximum. The positive line tension increases the free-energy maximum, which thus increases the stability of the Cassie superhydrophobic state, whereas the negative line tension destabilizes the superhydrophobic state.

  5. An enhanced surface passivation effect in InGaN/GaN disk-in-nanowire light emitting diodes for mitigating Shockley–Read–Hall recombination

    KAUST Repository

    Zhao, Chao

    2015-07-24

    We present a detailed study on the effects of dangling bond passivation and the comparison of different sulfides passivation process on the properties of InGaN/GaN quantum-disk (Qdisk)-in-nanowire based light emitting diodes (NW-LEDs). Our results demonstrated the first organic sulfide passivation process for nitride nanowires (NWs). The results from Raman spectroscopy, photoluminescence (PL) measurements, and X-ray photoelectron spectroscopy (XPS) showed octadecylthiol (ODT) effectively passivated the surface states, and altered the surface dynamic charge, thereby recovered the band-edge emission. The effectiveness of the process with passivation duration was also studied. Moreover, we also compared the electro-optical performance of NW-LEDs emitting at green wavelength before and after ODT passivation. We have shown that the Shockley-Read-Hall (SRH) non-radiative recombination of NW-LEDs can be greatly reduced after passivation by ODT, which led to a much faster increasing trend of quantum efficiency, and higher peak efficiency. Our results highlighted the research opportunity in employing this technique for further design and realization of high performance NW-LEDs and NW-lasers.

  6. Improvement of optical and electrical properties of indium tin oxide layer of GaN-based light-emitting diode by surface plasmon in silver nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Chu-Young [Applied Device and Material Department, Korea Advanced Nano fab Center, Suwon 443–270 (Korea, Republic of); Hong, Sang-Hyun [Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology, Gwangju 500–712 (Korea, Republic of); Park, Seong-Ju, E-mail: esjpark@gist.ac.kr [Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology, Gwangju 500–712 (Korea, Republic of)

    2015-09-01

    We report on the effect of silver (Ag) nanoparticles on the optical transmittance and electrical conductivity of indium tin oxide (ITO) transparent conducting layer deposited on p-GaN layer of light-emitting diodes (LEDs). The sheet resistance of ITO and the series resistance of LEDs were decreased due to the increased electrical conductivity of ITO by Ag nanoparticles, compared with those of the LEDs with a bare ITO only. The ITO transmittance was also improved by localized surface plasmon resonance between the incident light and the randomly distributed Ag nanoparticles on ITO. The optical output power of LEDs with Ag nanoparticles on ITO was increased by 16% at 20 mA of injection current. - Highlights: • We studied the effect of Ag nanoparticles deposited on ITO on the properties of LED. • The optical power of LED and transmittance of ITO were improved by Ag surface plasmon. • The electrical conductivity of ITO was increased by Ag nanoparticles.

  7. Pulsed, High Power Microwave Processing of Field Emission in Superconducting Cavities

    Energy Technology Data Exchange (ETDEWEB)

    I.E. Campisi

    1992-08-03

    The phenomenon of field emission is very well known: electrons are extracted from within the solid state potential well of a metal and are emitted from the metal's surface under the presence of an accelerating potential. In many accelerators, electromagnetic energy is delivered to charged particles by means of microwave cavities excited in modes with electric field components aligned along the particles trajectory. If the mode used is of the TM type (most accelerators operate in the TM{sub 010} mode), then a surface electric field inside the cavities exists which can produce field emitted electrons when allowed by the phase of the fields. These field emitted currents can cause considerable current loading and bremsstrahlung radiation in normal conducting cavities (mostly copper), but in superconducting cavities they have the additional effect of locally heating the superconducting material above its transition temperature and causing performance degradation of the cavities and eventually quenches (transition to the normal conducting state). At present this phenomenon constitutes the limiting factor in superconducting cavity performance, and is receiving a great deal of attention. Several diagnostic methods have been developed to detect, locate and characterize the sources of field-emitted electrons. Methods have also been proposed and tested which decrease the incidence of field emission sites on metal surfaces, but the most effective method to date requires high temperature firing of the superconducting structures in an ultra high vacuum. This can be done only if the cavities are completely removed from their cryostat, a lengthy and costly process. In this paper the properties and advantages are examined of a different method for field emission processing, which does not require a cavity disassembly and which can be performed in situ. The method described makes use of short, high peak power RF pulses to reach high electric fields for a short time. At the same

  8. Multiscale Micro-Nano Nested Structures: Engineered Surface Morphology for Efficient Light Escaping in Organic Light-Emitting Diodes.

    Science.gov (United States)

    Zhou, Lei; Dong, Xiaoxuan; Zhou, Yun; Su, Wenming; Chen, Xiaolian; Zhu, Yufu; Shen, Su

    2015-12-01

    Various micro-to-nanometer scale structures are extremely attractive for light escaping in organic light-emitting diodes. To develop and optimize such structures, an innovative approach was demonstrated for the first time to fabricate multiscale micro-nano nested structures by photolithography with a well-designed mask pattern followed by a controllable thermal reflow process. The experimental and theoretical characterizations verify that these unique nested structures hold the capability of light concentration, noticeable low haze, and efficient antireflection. As a proof-of-concept, the incorporation of this pattern onto the glass substrate efficiently facilitates light escaping from the device, resulting in current efficiency 1.60 times and external quantum efficiency 1.63 times that of a control flat device, respectively. Moreover, compared to a hexagonally arranged microlens array and quasi-random biomimetic moth eye nanostructures, the nested structures proposed here can magically tune the spatial emission profile to comply with the Lambertian radiation pattern. Hence, this novel structure is expected to be of great potential in related ubiquitous optoelectronic applications and provide scientific inspiration to other novel multiscale micro-nanostructure research.

  9. Nanofriction in Cavity Quantum Electrodynamics.

    Science.gov (United States)

    Fogarty, T; Cormick, C; Landa, H; Stojanović, Vladimir M; Demler, E; Morigi, Giovanna

    2015-12-01

    The dynamics of cold trapped ions in a high-finesse resonator results from the interplay between the long-range Coulomb repulsion and the cavity-induced interactions. The latter are due to multiple scatterings of laser photons inside the cavity and become relevant when the laser pump is sufficiently strong to overcome photon decay. We study the stationary states of ions coupled with a mode of a standing-wave cavity as a function of the cavity and laser parameters, when the typical length scales of the two self-organizing processes, Coulomb crystallization and photon-mediated interactions, are incommensurate. The dynamics are frustrated and in specific limiting cases can be cast in terms of the Frenkel-Kontorova model, which reproduces features of friction in one dimension. We numerically recover the sliding and pinned phases. For strong cavity nonlinearities, they are in general separated by bistable regions where superlubric and stick-slip dynamics coexist. The cavity, moreover, acts as a thermal reservoir and can cool the chain vibrations to temperatures controlled by the cavity parameters and by the ions' phase. These features are imprinted in the radiation emitted by the cavity, which is readily measurable in state-of-the-art setups of cavity quantum electrodynamics.

  10. Optofluidic Fabry-Pérot Micro-Cavities Comprising Curved Surfaces for Homogeneous Liquid Refractometry—Design, Simulation, and Experimental Performance Assessment

    OpenAIRE

    2016-01-01

    In the scope of miniaturized optical sensors for liquid refractometry, this work details the design, numerical simulation, and experimental characterization of a Fabry-Pérot resonator consisting of two deeply-etched silicon cylindrical mirrors with a micro-tube in between holding the liquid analyte under study. The curved surfaces of the tube and the cylindrical mirrors provide three-dimensional light confinement and enable achieving stability for the cavity illuminated by a Gaussian beam inp...

  11. Design, Construction, and Initial Test of High Spatial Resolution Thermometry Arrays for Detection of Surface Temperature Profiles on SRF Cavities in Super Fluid Helium

    Energy Technology Data Exchange (ETDEWEB)

    Ari Palczewski, Rongli Geng, Grigory Eremeev

    2011-07-01

    We designed and built two high resolution (0.6-0.55mm special resolution [1.1-1.2mm separation]) thermometry arrays prototypes out of the Allen Bradley 90-120 ohm 1/8 watt resistor to measure surface temperature profiles on SRF cavities. One array was designed to be physically flexible and conform to any location on a SRF cavity; the other was modeled after the common G-10/stycast 2850 thermometer and designed to fit on the equator of an ILC (Tesla 1.3GHz) SRF cavity. We will discuss the advantages and disadvantages of each array and their construction. In addition we will present a case study of the arrays performance on a real SRF cavity TB9NR001. TB9NR001 presented a unique opportunity to test the performance of each array as it contained a dual (4mm separation) cat eye defect which conventional methods such as OST (Oscillating Superleak second-sound Transducers) and full coverage thermometry mapping were unable to distinguish between. We will discuss the new arrays ability to distinguish between the two defects and their preheating performance.

  12. Tuning the spectrometric properties of white light by surface plasmon effect using Ag nanoparticles in a colour converting light-emitting diode

    Science.gov (United States)

    Chandramohan, S.; Ryu, Beo Deul; Uthirakumar, P.; Kang, Ji Hye; Kim, Hyun Kyu; Kim, Hyung Gu; Hong, Chang-Hee

    2011-03-01

    We report on the spectral tunability of white light by localized surface plasmon (LSP) effect in a colour converting hybrid device made of CdSe/ZnS quantum dots (QDs) integrated on InGaN/GaN blue light-emitting diodes (LEDs). Silver (Ag) nanoparticles (NPs) are mixed with QDs for generating LSP effect. When the plasmon absorption of Ag NPs is synchronized to the QW emission at 448 nm, the NPs selectively absorb the blue light and subsequently enhance the QD emission. Using this energy transfer scheme, the ( x, y) chromaticity coordinates of the hybrid white LED was tuned from (0.32, 0.17) to (0.43, 0.26), and thereby generated warm white light emission with correlated colour temperature (CCT) around 1800 K. Moreover, a 47% enhancement in the external quantum efficiency (EQE) was realized.

  13. InGaN multiple-quantum-well epifilms on GaN-sillicon substrates for microcavities and surface-emitting lasers

    Energy Technology Data Exchange (ETDEWEB)

    Lee, June Key [Chonnam National University, Gwangju (Korea, Republic of); Cho, Hoon; Kim, Bok Hee; Park, Si Hyun [Chosun University, Gwangju (Korea, Republic of); Gu, Erdan; Watson, Ian; Dawson, Martin [University of Strathclyde, Wolfson Centre, Glasgow (United Kingdom)

    2006-07-15

    We report the processing of InGaN/GaN epifilms on GaN-silicon substrates. High-quality InGaN/GaN multi-quantum wells (MQWs) were grown on GaN-silicon substrates, and their membranes were successfully fabricated using a selective wet etching of silicon followed by a dry etching of the AlGaN buffer layer. With atomic force microscope (AFM) measurements and photoluminescence (PL) measurements, we investigated the physical and the optical properties of the InGaN/GaN MQWs membranes. On the InGaN/GaN MQW membranes, dielectric distributed Bragg reflector (DBRs) were successfully deposited, which give, new possibilities for use in GaN microcavity and surface-emitting laser fabrication.

  14. External-cavity solid-state organic lasers: Design rules and application perspectives (Conference Presentation)

    Science.gov (United States)

    Chénais, Sébastien; Gallinelli, Thomas; Mhibik, Oussama; Blanchard, Cédric; Forget, Sébastien

    2016-09-01

    Among various laser architectures currently used to make lasers out of organic materials (distributed feedback lasers or organic vertical cavity surface-emitting lasers, ....), vertical EXTERNAL cavities have several distinctive features that enable making lasers with a high brightness, resulting from a combination of high efficiency and good beam quality, and also offer a superior flexibility to monitor the laser spectrum. In this talk I will highlight a few recent results on external-cavity organic lasers and reveal their potential through the example of a single mode organic laser device with an ultranarrow linewidth (art). From the material point of view, I will also show how ink-jet printing can be successfully used in vertical external-cavity organic lasers to make thick and optical-quality films that have the potential to be easily produced with a high throughput.

  15. Ultra low-energy switch based on a cavity soliton laser with pump modulation

    Science.gov (United States)

    Eslami, M.; Gandomani, S. Z.; Prati, F.; Tajalli, H.; Kheradmand, R.

    2017-01-01

    We study the effects of pump modulation in a cavity soliton laser consisting of a vertical cavity surface emitting laser with an intra-cavity saturable absorber. We show that a drifting soliton experiences enhanced mobility features by modulating the pump at the resonance frequency, and the effects are even larger below resonance. In particular, pump modulation reduces the rest time of the soliton in the initial stage of the motion and it increases its drift velocity in this regime. Moreover, pump modulation allows a decrease in the switching energy of the soliton to an amount equal to 36 photons. These results indicate that pump modulation is a promising way for the use of a cavity soliton laser as a fast optical buffer and an ultra low-energy optical switch.

  16. 5-W Yellow Laser by Intracavity Frequency Doubling of High-Power Vertical-External-Cavity Surface-Emitting Laser (POSTPRINT)

    Science.gov (United States)

    2008-10-15

    to: The University of Arizona. Downloaded on October 16, 2008 at 14:27 from IEEE Xplore . Restrictions apply. 1 FALLAHI et al.: 5-W YELLOW LASER BY...Authorized licensed use limited to: The University of Arizona. Downloaded on October 16, 2008 at 14:27 from IEEE Xplore . Restrictions apply. 2 1702 IEEE...Theory and Practice, 2nd ed. San Diego, CA: Academic, 1999. Authorized licensed use limited to: The University of Arizona. Downloaded on October 16, 2008 at 14:27 from IEEE Xplore . Restrictions apply. 3

  17. Investigation of GaInNAs/GaAs quantum wells and vertical-cavity surface-emitting laser structures using modulated reflectance spectroscopy

    CERN Document Server

    Choulis, S A

    2001-01-01

    study on a representative InGaAs/GaAs/AlAs/AIGaAs as-grown VCSEL structure, using PR spectroscopy as a function of position on a non-uniform wafer. We also show how temperature dependent PR and the appropriate lineshape model can be used to obtain a full picture of the relative movements between the gain and the CM over the full range of temperature. This information allows calculating the material gain in the temperature range of interest, independent from the effect of the CM and also provides an alternative method for characterising the growth, which can be applied to uniform wafers. PR and non-destructive ER can be used to identify regions suitable for fabrication into devices. For this reason modulation spectroscopy can be very useful for industry to reject wafers where good alignment between the CM and the QW does not occur and can thus save on the time consuming and expensive fabrication procedures. We investigate the electronic band structure of device relevant GaInNAs/GaAs multiple quantum wells (MQW...

  18. Effect of sheath potential on electromagnetic radiation emitted from the rear surface of a metallic foil target

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In ultra-intense laser-matter interactions, intense electric fields formed at the rear surface of a foil target may have strong influences on the motion of energetic electrons, and thereby affect the electromagnetic emissions from the rear surface, usually ascribed to transition radiation. Due to the electric fields, transition radiation occurs twice and bremsstrahlung radiation also happens because the electrons will cross the rear surface twice and have large accelerations.In the optic region, transition radiation is dominant. The radiation spectrum depends on the electric field only when the electrons are monochromatic, and becomes independent of the electric field when the electrons have a broadband momentum distribution. Therefore, in an actual experiment, the electric field at the rear surface of a foil could not be studied just with the measurement of optic emissions. In the terahertz region, both bremsstrahlung and transition radiations should be taken into account, and the radiation power could be enhanced in comparison with that without the inclusion of bremsstrahlung radiation. The frequency at which the maximum terahertz radiation appears depends on the electric field.

  19. High Resolution Trichromatic Road Surface Scanning with a Line Scan Camera and Light Emitting Diode Lighting for Road-Kill Detection

    Directory of Open Access Journals (Sweden)

    Gil Lopes

    2016-04-01

    Full Text Available This paper presents a road surface scanning system that operates with a trichromatic line scan camera with light emitting diode (LED lighting achieving road surface resolution under a millimeter. It was part of a project named Roadkills—Intelligent systems for surveying mortality of amphibians in Portuguese roads, sponsored by the Portuguese Science and Technology Foundation. A trailer was developed in order to accommodate the complete system with standalone power generation, computer image capture and recording, controlled lighting to operate day or night without disturbance, incremental encoder with 5000 pulses per revolution attached to one of the trailer wheels, under a meter Global Positioning System (GPS localization, easy to utilize with any vehicle with a trailer towing system and focused on a complete low cost solution. The paper describes the system architecture of the developed prototype, its calibration procedure, the performed experimentation and some obtained results, along with a discussion and comparison with existing systems. Sustained operating trailer speeds of up to 30 km/h are achievable without loss of quality at 4096 pixels’ image width (1 m width of road surface with 250 µm/pixel resolution. Higher scanning speeds can be achieved by lowering the image resolution (120 km/h with 1 mm/pixel. Computer vision algorithms are under development to operate on the captured images in order to automatically detect road-kills of amphibians.

  20. Surface plasmon dispersion engineering via double-metallic AU/AG layers for nitride light-emitting diodes

    Science.gov (United States)

    Tansu, Nelson; Zhao, Hongping; Zhang, Jing; Liu, Guangyu

    2014-04-01

    A double-metallic deposition process is used whereby adjacent layers of different metals are deposited on a substrate. The surface plasmon frequency of a base layer of a first metal is tuned by the surface plasmon frequency of a second layer of a second metal formed thereon. The amount of tuning is dependent upon the thickness of the metallic layers, and thus tuning can be achieved by varying the thicknesses of one or both of the metallic layers. In a preferred embodiment directed to enhanced LED technology in the green spectrum regime, a double-metallic Au/Ag layer comprising a base layer of gold (Au) followed by a second layer of silver (Ag) formed thereon is deposited on top of InGaN/GaN quantum wells (QWs) on a sapphire/GaN substrate.

  1. Detection of cell surface calreticulin as a potential cancer biomarker using near-infrared emitting gold nanoclusters

    Science.gov (United States)

    Subramaniyam Ramesh, Bala; Giorgakis, Emmanouil; Lopez-Davila, Victor; Kamali Dashtarzheneha, Ashkan; Loizidou, Marilena

    2016-07-01

    Calreticulin (CRT) is a cytoplasmic calcium-binding protein. The aim of this study was to investigate CRT presence in cancer with the use of fluorescent gold nanoclusters (AuNCs) and to explore AuNC synthesis using mercaptosuccinic acid (MSA) as a coating agent. MSA-coated AuNCs conferred well-dispersed, bio-stable, water-soluble nanoparticles with bioconjugation capacity and 800-850 nm fluorescence after broad-band excitation. Cell-viability assay revealed good AuNC tolerability. A native CRT amino-terminus corresponding peptide sequence was synthesised and used to generate rabbit site-specific antibodies. Target specificity was demonstrated with antibody blocking in colorectal and breast cancer cell models; human umbilical vein endothelial cells served as controls. We demonstrated a novel route of AuNC/MSA manufacture and CRT presence on colonic and breast cancerous cell surface. AuNCs served as fluorescent bio-probes specifically recognising surface-bound CRT. These results are promising in terms of AuNC application in cancer theranostics and CRT use as surface biomarker in human cancer.

  2. SPS RF Accelerating Cavity

    CERN Multimedia

    1979-01-01

    This picture shows one of the 2 new cavities installed in 1978-1979. The main RF-system of the SPS comprises four cavities: two of 20 m length and two of 16.5 m length. They are all installed in one long straight section (LSS 3). These cavities are of the travelling-wave type operating at a centre frequency of 200.2 MHz. They are wideband, filling time about 700 ns and untuned. The power amplifiers, using tetrodes are installed in a surface building 200 m from the cavities. Initially only two cavities were installed, a third cavity was installed in 1978 and a forth one in 1979. The number of power amplifiers was also increased: to the first 2 MW plant a second 2 MW plant was added and by end 1979 there were 8 500 kW units combined in pairs to feed each of the 4 cavities with up to about 1 MW RF power, resulting in a total accelerating voltage of about 8 MV. See also 7412016X, 7412017X, 7411048X

  3. SPS RF Cavity

    CERN Multimedia

    1975-01-01

    The picture shows one of the two initially installed cavities. The main RF-system of the SPS comprises four cavities: two of 20 m length and two of 16.5 m length. They are all installed in one long straight section (LSS 3). These cavities are of the travelling-wave type operating at a centre frequency of 200.2 MHz. They are wideband, filling time about 700 ns and untuned. The power amplifiers, using tetrodes are installed in a surface building 200 m from the cavities. Initially only two cavities were installed, a third cavity was installed in 1978 and a forth one in 1979. The number of power amplifiers was also gradually increased: by end 1980 there were 8 500 kW units combined in pairs to feed each of the 4 cavities with up to about 1 MW RF power, resulting in a total accelerating voltage of about 8 MV. See also 7412017X, 7411048X, 7505074.

  4. Progress on a Cavity with Beryllium Walls for Muon Ionization Cooling Channel R&D.

    Energy Technology Data Exchange (ETDEWEB)

    Bowring, D. L.; DeMello, A. J.; Lambert, A. R.; Li, D.; Virostek, S.; Zisman, M.; Kaplan, D.; Palmer, R. B.

    2012-05-20

    The Muon Accelerator Program (MAP) collaboration is working to develop an ionization cooling channel for muon beams. An ionization cooling channel requires the operation of high-gradient, normal-conducting RF cavities in multi-Tesla solenoidal magnetic fields. However, experiments conducted at Fermilab?s MuCool Test Area (MTA) show that increasing the solenoidal field strength reduces the maximum achievable cavity gradient. This gradient limit is characterized by an RF breakdown process that has caused significant damage to copper cavity interiors. The damage may be caused by field-emitted electrons, focused by the solenoidal magnetic field onto small areas of the inner cavity surface. Local heating may then induce material fatigue and surface damage. Fabricating a cavity with beryllium walls would mitigate this damage due to beryllium?s low density, low thermal expansion, and high electrical and thermal conductivity. We address the design and fabrication of a pillbox RF cavity with beryllium walls, in order to evaluate the performance of high-gradient cavities in strong magnetic fields.

  5. accelerating cavity from LEP

    CERN Multimedia

    This is an accelerating cavity from LEP, with a layer of niobium on the inside. Operating at 4.2 degrees above absolute zero, the niobium is superconducting and carries an accelerating field of 6 million volts per metre with negligible losses. Each cavity has a surface of 6 m2. The niobium layer is only 1.2 microns thick, ten times thinner than a hair. Such a large area had never been coated to such a high accuracy. A speck of dust could ruin the performance of the whole cavity so the work had to be done in an extremely clean environment. These challenging requirements pushed European industry to new achievements. 256 of these cavities are now used in LEP to double the energy of the particle beams.

  6. SPS accelerating cavity

    CERN Multimedia

    1976-01-01

    The SPS started up with 2 accelerating cavities (each consisting of 5 tank sections) in LSS3. They have a 200 MHz travelling wave structure (see 7411032 and 7802190) and 750 kW of power is fed to each of the cavities from a 1 MW tetrode power amplifier, located in a surface building above, via a coaxial transmission line. Clemens Zettler, builder of the SPS RF system, is standing at the side of one of the cavities. In 1978 and 1979 another 2 cavities were added and entered service in 1980. These were part of the intensity improvement programme and served well for the new role of the SPS as proton-antiproton collider. See also 7411032, 8011289, 8104138, 8302397.

  7. radiofrequency cavity

    CERN Multimedia

    1988-01-01

    The pulse of a particle accelerator. 128 of these radio frequency cavities were positioned around CERN's 27-kilometre LEP ring to accelerate electrons and positrons. The acceleration was produced by microwave electric oscillations at 352 MHz. The electrons and positrons were grouped into bunches, like beads on a string, and the copper sphere at the top stored the microwave energy between the passage of individual bunches. This made for valuable energy savings as it reduced the heat generated in the cavity.

  8. An Analysis of the Temperature and Field Dependence of the RF Surface Resistance of Nitrogen-Doped Niobium SRF Cavities with Respect to Existing Theoretical Models

    Energy Technology Data Exchange (ETDEWEB)

    Reece, Charles E. [Jefferson Lab, Newport News, VA; Palczewski, Ari D. [Jefferson Lab, Newport News, VA; Xiao, Binping [Brookhaven National Laboratory, Upton, NY

    2015-09-01

    Recent progress with the reduction of rf surface resistance (Rs) of niobium SRF cavities via the use of high temperature surface doping by nitrogen has opened a new regime for energy efficient accelerator applications. For particular doping conditions one observes dramatic decreases in Rs with increasing surface magnetic fields. The observed variations as a function of temperature may be analyzed in the context of recent theoretical treatments in hopes of gaining insight into the underlying beneficial mechanism of the nitrogen treatment. Systematic data sets of Q0 vs. Eacc vs. temperature acquired during the high Q0 R&D work of the past year will be compared with theoretical model predictions..

  9. Surface and spectral studies of green emitting Sr{sub 3}B{sub 2}O{sub 6}:Tb{sup 3+} phosphor

    Energy Technology Data Exchange (ETDEWEB)

    Neharika [School of Physics, Shri Mata Vaishno Devi University, Katra 182320, J& K (India); Kumar, Vinay, E-mail: vinaykumar@smvdu.ac.in [School of Physics, Shri Mata Vaishno Devi University, Katra 182320, J& K (India); Sharma, J.; Singh, Vivek K. [School of Physics, Shri Mata Vaishno Devi University, Katra 182320, J& K (India); Ntwaeaborwa, O.M.; Swart, H.C. [Department of Physics, University of the Free State, PO Box 339, Bloemfontein ZA9300 (South Africa)

    2016-01-15

    Highlights: • XPS technique has been used to study the surface composition of the phosphor. • The phosphor is synthesized by combustion method using urea as fuel. • Multipole–multipole interaction was found to play a key role for concentration quenching of Tb{sup 3+} doped Sr{sub 3}B{sub 2}O{sub 6} phosphor. - Abstract: In this paper, we report the synthesis of trivalent Tb{sup 3+} doped Sr{sub 3}B{sub 2}O{sub 6} phosphor by combustion method using urea as an organic fuel. The structure of the product has been verified by X-ray diffraction study which shows a rhombohedral phase with a space group of R-3c having lattice constants a = 9.064 Å, b = 9.064 Å, c = 12.611 Å. X-ray photoelectron spectroscopy has been used to study the elemental composition and electronic states of the Tb{sup 3+} doped Sr{sub 3}B{sub 2}O{sub 6} phosphor. Photoluminescence spectra showed that the phosphor emits in the greenish region (with the main peak at 544 nm) of color gamut under UV excitation. The diffuse reflectance spectra of the Sr{sub 3}B{sub 2}O{sub 6} phosphor were studied. Lifetime and band gap of the phosphors were calculated to be 2.55 ms and 5.25 ± 0.02 eV, respectively.

  10. Surface-emitting circular DFB, disk-, and ring-Bragg resonator lasers with chirped gratings. II: nonuniform pumping and far-field patterns.

    Science.gov (United States)

    Sun, Xiankai; Yariv, Amnon

    2009-01-05

    This is a continuation of our previous work [Opt. Express 16, 9155 (2008)]. In this paper we investigate the effect of nonuniform pumping on the modal properties of surface-emitting chirped circular grating lasers. By numerically solving the coupled-mode equations and matching the boundaries we compare and discuss the threshold pump levels and frequency detuning factors for three pumping profiles: uniform, Gaussian, and annular. Depending on the overlap of the pumping and modal profiles, Gaussian pumping results in the lowest threshold pump levels except for the fundamental mode of ring Bragg resonator laser, and annular pumping provides larger threshold discrimination between the fundamental and first-order modes of circular DFB and ring Bragg resonator lasers, which is favorable for single-mode operation in these lasers. We also study the far-field patterns of the fundamental modes of circular DFB, disk-, and ring- Bragg resonator lasers. Circular DFB and ring Bragg resonator lasers have the first-order dominating peak, while disk Bragg resonator laser exhibits the zeroth-order dominating peak.

  11. A hybrid soliton-based system: generation and steering of cavity solitons by means of photorefractive soliton electro-activation

    CERN Document Server

    Columbo, Lorenzo; Brambilla, Massimo; Prati, Franco; Tissoni, Giovanna

    2012-01-01

    We propose a hybrid soliton-based system consisting of a centrosymmetric photorefractive crystal, supporting photorefractive solitons, coupled to a vertical cavity surface emitting laser, supporting multistable cavity solitons. The composite nature of the system, which couples a propagative/conservative field dynamics to a stationary/dissipative one, allows to observe a more general and unified system phenomenology and to conceive novel photonic functionalities. The potential of the proposed hybrid system becomes clear when investigating the generation and control of cavity solitons by propagating a plane wave through electro-activated solitonic waveguides in the crystal. By changing the electro-activation voltage of the crystal, we prove that cavity solitons can be turned on and shifted with controlled velocity across the device section. The scheme can be exploited for applications to optical information encoding and processing.

  12. Effect of Eugenol on Cell Surface Hydrophobicity, Adhesion, and Biofilm of Candida tropicalis and Candida dubliniensis Isolated from Oral Cavity of HIV-Infected Patients

    Directory of Open Access Journals (Sweden)

    Suelen Balero de Paula

    2014-01-01

    Full Text Available Most Candida spp. infections are associated with biofilm formation on host surfaces. Cells within these communities display a phenotype resistant to antimicrobials and host defenses, so biofilm-associated infections are difficult to treat, representing a source of reinfections. The present study evaluated the effect of eugenol on the adherence properties and biofilm formation capacity of Candida dubliniensis and Candida tropicalis isolated from the oral cavity of HIV-infected patients. All isolates were able to form biofilms on different substrate surfaces. Eugenol showed inhibitory activity against planktonic and sessile cells of Candida spp. No metabolic activity in biofilm was detected after 24 h of treatment. Scanning electron microscopy demonstrated that eugenol drastically reduced the number of sessile cells on denture material surfaces. Most Candida species showed hydrophobic behavior and a significant difference in cell surface hydrophobicity was observed after exposure of planktonic cells to eugenol for 1 h. Eugenol also caused a significant reduction in adhesion of most Candida spp. to HEp-2 cells and to polystyrene. These findings corroborate the effectiveness of eugenol against Candida species other than C. albicans, reinforcing its potential as an antifungal applied to limit both the growth of planktonic cells and biofilm formation on different surfaces.

  13. Green (In,Ga,Al)P-GaP light-emitting diodes grown on high-index GaAs surfaces

    Science.gov (United States)

    Ledentsov, N. N.; Shchukin, V. A.; Lyytikäinen, J.; Okhotnikov, O.; Cherkashin, N. A.; Shernyakov, Yu M.; Payusov, A. S.; Gordeev, N. Y.; Maximov, M. V.; Schlichting, S.; Nippert, F.; Hoffmann, A.

    2015-03-01

    We report on green (550-560 nm) electroluminescence (EL) from (Al0.5Ga0.5)0.5In0.5P-(Al0.8Ga0.2)0.5In0.5P double p-i-n heterostructures with monolayer-scale tensile strained GaP insertions in the cladding layers and light-emitting diodes (LEDs) based thereupon. The structures are grown side-by-side on high-index and (100) GaAs substrates by molecular beam epitaxy. Cross-sectional transmission electron microscopy studies indicate that GaP insertions are flat, thus the GaP-barrier substrate orientation-dependent heights should match the predictions of the flat model. At moderate current densities (~500 A/cm2) the EL intensity of the structures is comparable for all substrate orientations. Opposite to the (100)-grown strictures, the EL spectra of (211) and (311)-grown devices are shifted towards shorter wavelengths (~550 nm at room temperature). At high current densities (>1 kA/cm2) a much higher EL intensity is achieved for the devices grown on high-index substrates. The integrated intensity of (311)-grown structures gradually saturates at current densities above 4 kA/cm2, whereas no saturation is revealed for (211)-grown structures up to the current densities above 14 kA/cm2. We attribute the effect to the surface orientation-dependent engineering of the GaP band structure which prevents the escape of the nonequilibrium electrons into the indirect conduction band minima of the p- doped (Al0.8Ga0.2)0.5In0.5P cladding layers.

  14. Optofluidic Fabry-Pérot Micro-Cavities Comprising Curved Surfaces for Homogeneous Liquid Refractometry—Design, Simulation, and Experimental Performance Assessment

    Directory of Open Access Journals (Sweden)

    Noha Gaber

    2016-04-01

    Full Text Available In the scope of miniaturized optical sensors for liquid refractometry, this work details the design, numerical simulation, and experimental characterization of a Fabry-Pérot resonator consisting of two deeply-etched silicon cylindrical mirrors with a micro-tube in between holding the liquid analyte under study. The curved surfaces of the tube and the cylindrical mirrors provide three-dimensional light confinement and enable achieving stability for the cavity illuminated by a Gaussian beam input. The resonant optofluidic cavity attains a high-quality factor (Q—over 2800—which is necessary for a sensitive refractometer, not only by providing a sharp interference spectrum peak that enables accurate tracing of the peak wavelengths shifts, but also by providing steep side peaks, which enables detection of refractive index changes by power level variations when operating at a fixed wavelength. The latter method can achieve refractometry without the need for spectroscopy tools, provided certain criteria explained in the details are met. By experimentally measuring mixtures of acetone-toluene with different ratios, refractive index variations of 0.0005 < Δn < 0.0022 could be detected, with sensitivity as high as 5500 μW/RIU.

  15. Light emitting device having peripheral emissive region

    Science.gov (United States)

    Forrest, Stephen R

    2013-05-28

    Light emitting devices are provided that include one or more OLEDs disposed only on a peripheral region of the substrate. An OLED may be disposed only on a peripheral region of a substantially transparent substrate and configured to emit light into the substrate. Another surface of the substrate may be roughened or include other features to outcouple light from the substrate. The edges of the substrate may be beveled and/or reflective. The area of the OLED(s) may be relatively small compared to the substrate surface area through which light is emitted from the device. One or more OLEDs also or alternatively may be disposed on an edge of the substrate about perpendicular to the surface of the substrate through which light is emitted, such that they emit light into the substrate. A mode expanding region may be included between each such OLED and the substrate.

  16. Matrix approach for modeling of emission from multilayer spin-polarized light-emitting diodes and lasers

    Science.gov (United States)

    Fördös, Tibor; Postava, Kamil; Jaffrès, Henri; Pištora, Jaromír

    2014-06-01

    Spin-polarized light sources such as the spin-polarized light-emitting diodes (spin-LEDs) and spin-polarized lasers (spin-lasers) are prospective devices in which the radiative recombination of spin-polarized carriers results in emission of circularly polarized photons. The main goal of this article is to model emitted radiation and its polarization properties from spin-LED and spin-controlled vertical-cavity surface-emitting laser (spin-VCSEL) solid-state structures. A novel approach based on 4 × 4 transfer matrix formalism is derived for modeling of the interaction of light with matter in active media of resonant multilayer anisotropic structure and enables magneto-optical effects. Quantum transitions, which result in photon emission, are described using general Jones source vectors.

  17. Theory and technology for superconducting cavities

    CERN Document Server

    Lengeler, Herbert

    1993-01-01

    The course will address Physicist and Engineers who are newcomers in the field of accelerators and accelerating cavities. The elements of RF-Superconductivity will be presented with special relevance to accelerating cavities. The present ststus of achievable accelerating fields and RF losses will be given and their link to the special technologies for cavity fabrication and surface treatments will be stressed. Cavity auxiliaries like main couplers, higher order mode couplers and frequency tuners will be described.

  18. Ultrasmall Microfabricated Laser Cavities

    Science.gov (United States)

    2013-10-23

    opinions and/or findings contained in this report are those of the author(s) and should not contrued as an official Department of the Army position...use total internal reflection, which can theoretically exhibit perfect reflectivity. Disk and toroid resonators both operate on this principle...amount of emitted power contained in the 30_ cone from surface normal increases from 6.5% with s = 0 to 33.2% with s = 52 nm, where the center lobe in

  19. Guided access cavity preparation using cone-beam computed tomography and optical surface scans - an ex vivo study

    DEFF Research Database (Denmark)

    Buchgreitz, J; Buchgreitz, M; Mortensen, D

    2016-01-01

    AIM: To evaluate ex vivo, the accuracy of a preparation procedure planned for teeth with pulp canal obliteration (PCO) using a guide rail concept based on a cone-beam computed tomography (CBCT) scan merged with an optical surface scan. METHODOLOGY: A total of 48 teeth were mounted in acrylic bloc...

  20. Sensitivity of surface resistance measurement of HTS thin films by cavity resonator, dielectric resonator and microstrip line resonator

    Indian Academy of Sciences (India)

    N D Kataria; Mukul Misra; R Pinto

    2002-05-01

    Microwave surface resistance s of silver-doped YBa2Cu3O7- (YBCO) thin film, deposited by laser ablation technique on 10 mm × 10 mm LaAlO3 substrate, has been measured by resonant techniques in the frequency range from 5 GHz to 20 GHz. The geometrical factor of the sample and the resonator has been determined theoretically by the knowledge of the electromagnetic field distribution in the resonators. The microwave surface resistance of the superconducting sample is then extracted from the measured value as a function of temperature. The sensitivity of the s measurement, that is, the relative change in the value with the change in the s value is determined for each resonator.

  1. Cavity magnomechanics

    Science.gov (United States)

    Zou, Chang-Ling; Zhang, Xufeng; Jiang, Liang; Tang, Hong

    2016-05-01

    Recently, cavity magnonics has attracted much attention for potential applications of coherent information transduction and hybrid quantum devices. The magnon is a collective spin wave excitation in ferromagnetic material. It is magnetically tunability, with long coherence time and non-reciprocical interaction with electro-magnetic fields. We report the coherent coupling between magnon, microwave photon and phonon. First, we demonstrate strong coupling and ultrastrong coupling between the magnon in YIG sphere and microwave photon in three-dimensional cavity. Then, based on the hybridized magnon-photon modes, we observe the triply resonant magnon-mcirowave photon-phonon coupling, where the ultrahigh-Q mechanical vibration of YIG sphere is dispersively coupled with the magnon via magnetostrictive interaction. We observe interesting phenomena, including electromagnetically induced transparency/absorption and parametric amplification. In particular, benefit from the large tunability of the magnon, we demonstrate a tunable microwave amplifier with gain as high as 30 dB. The single crystal YIG also has excellent optical properties, and thus provide a unique platform bridging MHz, GHz and THz information carriers. Finally, we present the latest progress towards coherent magnon to optical photon conversion.

  2. Secondary electron emission from plasma processed accelerating cavity grade niobium

    Science.gov (United States)

    Basovic, Milos

    Advances in the particle accelerator technology have enabled numerous fundamental discoveries in 20th century physics. Extensive interdisciplinary research has always supported further development of accelerator technology in efforts of reaching each new energy frontier. Accelerating cavities, which are used to transfer energy to accelerated charged particles, have been one of the main focuses of research and development in the particle accelerator field. Over the last fifty years, in the race to break energy barriers, there has been constant improvement of the maximum stable accelerating field achieved in accelerating cavities. Every increase in the maximum attainable accelerating fields allowed for higher energy upgrades of existing accelerators and more compact designs of new accelerators. Each new and improved technology was faced with ever emerging limiting factors. With the standard high accelerating gradients of more than 25 MV/m, free electrons inside the cavities get accelerated by the field, gaining enough energy to produce more electrons in their interactions with the walls of the cavity. The electron production is exponential and the electron energy transfer to the walls of a cavity can trigger detrimental processes, limiting the performance of the cavity. The root cause of the free electron number gain is a phenomenon called Secondary Electron Emission (SEE). Even though the phenomenon has been known and studied over a century, there are still no effective means of controlling it. The ratio between the electrons emitted from the surface and the impacting electrons is defined as the Secondary Electron Yield (SEY). A SEY ratio larger than 1 designates an increase in the total number of electrons. In the design of accelerator cavities, the goal is to reduce the SEY to be as low as possible using any form of surface manipulation. In this dissertation, an experimental setup was developed and used to study the SEY of various sample surfaces that were treated

  3. L-Band Relative Permittivity of Organic Soil Surface Layers—A New Dataset of Resonant Cavity Measurements and Model Evaluation

    Directory of Open Access Journals (Sweden)

    Simone Bircher

    2016-12-01

    Full Text Available Global surface soil moisture products are derived from passive L-band microwave satellite observations. The applied retrieval algorithms include dielectric models (relating soil water content to relative permittivity developed for mineral soils. First efforts to generate equivalent models for areas where organic surface layers are present such as in the high-latitude regions have recently been undertaken. The objective of this study was to improve our still insufficient understanding of L-band emission of organic substrates in prospect of enhancing soil moisture estimations in the high latitudes undergoing most rapid climatic changes. To this end, L-band relative permittivity measurements using a resonant cavity were carried out on a wide range of organic surface layer types collected at different sites. This dataset was used to evaluate two already existing models for organic substrates. Some samples from underlying mineral layers were considered for comparison. In agreement with theory the bulk relative permittivity measured in organic substrate was decreased due to an increased bound water fraction (where water molecules are rotationally hindered compared to the measured mineral material and corresponding output of the dielectric model for mineral soils used in satellite algorithms. No distinct differences in dielectric response were detected in the measurements from various organic layer types, suggesting a generally uniform L-band emission behavior. This made it possible to fit a simple empirical model to the data obtained from all collected organic samples. Outputs of the two existing models both based on only one organic surface layer type were found to lie within the spread of our measured data, and in close proximity to the derived simple model. This general consensus strengthened confidence in the validity of all these models. The simple model should be suitable for satellite soil moisture retrieval applications as it is calibrated on

  4. Equilibrator-based measurements of dissolved nitrous oxide in the surface ocean using an integrated cavity output laser absorption spectrometer

    Directory of Open Access Journals (Sweden)

    I. Grefe

    2013-07-01

    Full Text Available A laser-based analyser for nitrous oxide, carbon monoxide and water vapour was coupled to an equilibrator for continuous high-resolution dissolved gas measurements in the surface ocean. Results for nitrous oxide measurements from laboratory tests and field deployments are presented here. Short-term precision for 10 s-average N2O mole fractions at an acquisition rate of 1 Hz was better than 0.2 nmol mol−1 for standard gases and equilibrator measurements. The same precision was achieved for replicate standard gas analyses within 1 h of each other. The accuracy of the equilibrator measurements was verified by comparison with purge-and-trap GC-MS measurements of N2O concentrations in discrete samples from the Southern Ocean and showed agreement to within the 2% measurement uncertainty of the GC-MS method. Measured atmospheric N2O mole fractions agreed with AGAGE values to within 0.4%. The equilibrator response time to concentration changes in water was 142 to 203 s, depending on the headspace flow rate. The system was tested at sea during a north-to-south transect of the Atlantic Ocean. While the subtropical gyres were slightly undersaturated, the equatorial region was a source of nitrous oxide to the atmosphere. The ability to measure at high temporal and spatial resolution revealed sub-mesoscale variability in dissolved N2O concentrations. The magnitude of the observed saturation is in agreement with published data. Mean sea-to-air fluxes in the tropical and subtropical Atlantic ranged between −1.6 and 0.11 μmol m−2d−1 and confirm that the subtropical Atlantic is not an important source region for N2O to the atmosphere, compared to average global fluxes of 0.6 to 2.4 μmol m−2d−1. The system can be easily modified for autonomous operation on voluntary observing ships (VOS. Further work should include an interlaboratory comparison exercise with other methods of dissolved N2O analyses.

  5. State of the Art SRF Cavity Performance

    CERN Document Server

    Lilje, L

    2004-01-01

    The paper will review superconducting RF cavity performance for β=1 cavities used in both linear and circular accelerators. These superconducting cavities are used in two kinds of applications: High current storage rings and efficient high duty cycle linacs. In recent years the performance of those cavities has been improving steadily. High accelerating gradients have been achieved using advanced surface preparation techniques like electropolishing and surface cleaning methods like high pressure water rinsing. High intensity beams can be handled with advanced higher-order-mode damping schemes.

  6. Niobium LEP 2 accelerating cavities

    CERN Multimedia

    An accelerating cavity from LEP. This could be cut open to show the layer of niobium on the inside. Operating at 4.2 degrees above absolute zero, the niobium is superconducting and carries an accelerating field of 6 million volts per metre with negligible losses. Each cavity has a surface of 6 m2. The niobium layer is only 1.2 microns thick, ten times thinner than a hair. Such a large area had never been coated to such a high accuracy. A speck of dust could ruin the performance of the whole cavity so the work had to be done in an extremely clean environment. These challenging requirements pushed European industry to new achievements. 256 of these cavities were used in an upgrade of the LEP accelerator to double the energy of the particle beams.

  7. SPS RF System an Accelerating Cavity

    CERN Multimedia

    1975-01-01

    The picture shows one of the two initially installed cavities. The main RF-system of the SPS comprises four cavities: two of 20 m length and two of 16.5 m length. They are all installed in one long straight section (LSS 3). These cavities are of the travelling-wave type operating at a centre frequency of 200.2 MHz. They are wideband, filling time about 700 ns and untuned. The power amplifiers, using tetrodes are installed in a surface building 200 m from the cavities. Initially only two cavities were installed, a third cavity was installed in 1978 and a forth one in 1979. The number of power amplifiers was also gradually increased: by end 1980 there were 8 500 kW units combined in pairs to feed each of the 4 cavities with up to about 1 MW RF power, resulting in a total accelerating voltage of about 8 MV. See also 7412017X, 7411048X.

  8. Development mechanism of cavity damage under urban roads and its influence on road surface subsidence%城市道路地下空洞病害发展机理及对路面塌陷的影响

    Institute of Scientific and Technical Information of China (English)

    陶连金; 袁松; 安军海

    2015-01-01

    外界因素作用易引起城市道路地下空洞破坏,甚至向上发展至地面形成地层塌陷。基于离散元软件对城市道路路基下空洞的发展破坏进行数值模拟,分析空洞规模、埋深、施工振动、空洞周围土性对空洞稳定性的影响。结果表明:道路路面沉降随着空洞埋深的减小和尺寸的增大,均出现先急剧增加后趋于平缓的过程。该曲线的拐点为道路安全性预测的关键点。当空洞与扰动土层相距3 m以内时,必须考虑施工扰动的影响。沉降值随空洞所在土层的黏聚力和摩擦角均近似呈线性变化。该研究从颗粒细观角度揭示了地下空洞发展至路面塌陷的破坏机制,为地下病害研究提供了新方法。%This paper is concerned specifically with a deeper study addressing cavity disease—cavity damage more likely to occur under urban roads due to the external factors and even cause road surface subsidence. The study involves simulating the development and damage of cavity under urban road using distinct element software and analyzing the impact of the cavity size, buried depth, the vibration during construction, the property of soil around the cavity on the stability of the cavity. The study demonstrates that, as a result of the decrease of the cavity depth and the increase of size, the road surface is subjected to the typical subsidence tending to sharply increase, followed by a flat increase, suggesting that the point of inflexion holds the key to the road safety prediction; the occurrence of a 3-m-distance between cavity and disturbed soil necessitates the consideration of the influence of vibration during construction;and sur-face has subsidence value approximate to linear variation due to the cohesive force and the friction angle of soil to which the cavity is exposed. The study offers a new insight into failure mechanism behind the underground cavity and the resulting road surface subsidence thanks to

  9. Parity-Time Symmetry in Coherently Coupled Vertical Cavity Laser Arrays

    CERN Document Server

    Gao, Zihe; Thompson, Bradley J; Carney, P Scott; Choquette, Kent D

    2016-01-01

    Parity-time (PT) symmetry in optics has been demonstrated in a variety of passive or optically pumped platforms. Here we discuss the notion of PT symmetry in the context of electrically pumped coherently coupled vertical cavity surface emitting laser arrays. Effects of both asymmetric gain distribution and local frequency detuning are considered using temporal coupled mode theory. It is shown theoretically that beam steering, mode evolution and mode hopping are all related to PT symmetry. Experimentally we observed the predicted mode evolution, mode hopping and PT symmetry breaking with quantitative agreement with the theory.

  10. Decoherence in semiconductor cavity QED systems due to phonon couplings

    DEFF Research Database (Denmark)

    Nielsen, Per Kær; Mørk, Jesper

    2014-01-01

    We investigate the effect of electron-phonon interactions on the coherence properties of single photons emitted from a semiconductor cavity QED (quantum electrodynamics) system, i.e., a quantum dot embedded in an optical cavity. The degree of indistinguishability, governing the quantum mechanical...... interference between two single photons, is calculated as a function of important parameters describing the cavity QED system and the phonon reservoir, e.g., cavity quality factor, light-matter coupling strength, temperature, and phonon lifetime. We show that non-Markovian effects play an important role...

  11. Scanning electron microscope observations on the monogenean parasite Paraquadriacanthus nasalis from the nasal cavities of the freshwater fish Clarias gariepinus in Egypt with a note on some surface features of its microhabitat.

    Science.gov (United States)

    Arafa, Safaa Zaky

    2012-05-01

    Surface features of the monogenean Paraquadriacanthus nasalis Ergens, 1988 (quoted by Kritsky, 1990) inhabiting the nasal cavities of the freshwater fish Clarias gariepinus were studied for the first time using scanning electron microscopy. The anterior adhesive areas possess two slit-like openings. Many small openings were detected on the tegument covering the anterior-most region of the head. Some considerably large openings were also found in the median region between the two slit-like openings of the adhesive sacs. A transverse slit-like mouth opening with two lip-like structures was detected on the ventral surface of the body. Three types of presumed sensory structures were found associated with the tegument of the anterior adhesive area and anterior region of the body. These are surface ciliary sensilla, dome-shaped structures, and many spherical structures. The possible functions of these presumed sensory structures were discussed. The tegument covering the anterior adhesive area lacks microvilli, while the tegument covering the haptor is associated with microvilli. The haptoral sclerites were found in two different positions. Some surface features of the nasal cavities of C. gariepinus (microhabitat of P. nasalis) were also studied using scanning electron microscopy. Many lamellae-like and spine-like structures were recognized. The epithelium lining in some regions of the nasal cavities has small and large openings and covered with mucus. The possible roles of some haptoral sclerites in the attachment of the parasite to the host tissues were discussed.

  12. Cavity and other radial substructures in the disk around HD 97048

    Science.gov (United States)

    van der Plas, G.; Wright, C. M.; Ménard, F.; Casassus, S.; Canovas, H.; Pinte, C.; Maddison, S. T.; Maaskant, K.; Avenhaus, H.; Cieza, L.; Perez, S.; Ubach, C.

    2017-01-01

    Context. Gaps, cavities, and rings in circumstellar disks are signposts of disk evolution and planet-disk interactions. We follow the recent suggestion that Herbig Ae/Be disks with a flared disk harbor a cavity, and investigate the disk around HD 97048. Aims: We aim to resolve the 34 ± 4 AU central cavity that has been predicted and to investigate the structure of the disk. Methods: We imaged the disk around HD 97048 using ALMA at 0.85 mm and 2.94 mm and ATCA (multiple frequency) observations. Our observations also include the 12CO J = 1-0, 12CO J = 3-2 and HCO+ J = 4-3 emission lines. Results: A central cavity in the disk around HD 97048 is resolved with a 40-46 AU radius. Additional radial structure present in the surface brightness profile can be accounted for either by an opacity gap at 90 AU or by an additional emitting ring at 150 AU. The continuum emission tracing the dust in the disk is detected out to 355 AU. The 12CO J = 3-2 disk is detected 2.4 times farther out. The 12CO emission can be traced down to ≈10 AU scales. Apparent non-Keplerian kinematics are detected inside the cavity on the HCO+ J = 4-3 velocity map. The mm spectral index measured from ATCA observations suggests that grain growth has occurred in the HD 97048 disk. Finally, we resolve a highly inclined disk out to 150 AU around the nearby 0.5 M⊙ binary ISO-ChaI 126. Conclusions: The data presented here reveal a cavity in the disk of HD 97048, and prominent radial structure in the surface brightness. The cavity size varies for different continuum frequencies and gas tracers. The gas inside the cavity follows non-Keplerian kinematics seen in HCO+ emission. The variable cavity size along with the kinematical signature suggests the presence of a substellar companion or a massive planet inside the cavity.

  13. Fast Excitation and Photon Emission of a Single-Atom-Cavity System

    OpenAIRE

    Bochmann, J.; Muecke, M.; Langfahl-Klabes, G.; Erbel, C; Weber, B.; Specht, H. P.; Moehring, D L; Rempe, G.

    2008-01-01

    We report on the fast excitation of a single atom coupled to an optical cavity using laser pulses that are much shorter than all other relevant processes. The cavity frequency constitutes a control parameter that allows the creation of single photons in a superposition of two tunable frequencies. Each photon emitted from the cavity thus exhibits a pronounced amplitude modulation determined by the oscillatory energy exchange between the atom and the cavity. Our technique constitutes a versatil...

  14. Single transverse mode selectively oxidized vertical cavity lasers

    Energy Technology Data Exchange (ETDEWEB)

    CHOQUETTE,KENT D.; GEIB,KENT M.; BRIGGS,RONALD D.; ALLERMAN,ANDREW A.; HINDI,JANA JO

    2000-04-26

    Vertical cavity surface emitting lasers (VCSELs) which operate in multiple transverse optical modes have been rapidly adopted into present data communication applications which rely on multi-mode optical fiber. However, operation only in the fundamental mode is required for free space interconnects and numerous other emerging VCSEL applications. Two device design strategies for obtaining single mode lasing in VCSELs based on mode selective loss or mode selective gain are reviewed and compared. Mode discrimination is attained with the use of a thick tapered oxide aperture positioned at a longitudinal field null. Mode selective gain is achieved by defining a gain aperture within the VCSEL active region to preferentially support the fundamental mode. VCSELs which exhibit greater than 3 mW of single mode output power at 850 nm with mode suppression ratio greater than 30 dB are reported.

  15. Intensity correlations near a cavity QED antiresonance

    Science.gov (United States)

    Xu, Qing; Mølmer, Klaus

    2017-02-01

    We explore the antiresonance phenomenon, where a two-level atom is excited inside a single-mode, laser-driven cavity without appreciably exciting the field mode. Antiresonance is well known in classical physics and the excitation of the atomic and field degrees of freedom by a weak laser field can be easily understood in a classical oscillator picture. The temporal intensity correlations in the signal emitted from the atom and from the cavity, however, show strong signs of nonclassical behavior. We calculate these correlations and show how they can be interpreted in terms of a conditional quantum trajectory dynamics of the system.

  16. High-resolution birefringence cartography of a vertical cavity semiconductor laser

    CERN Document Server

    Wang, T

    2015-01-01

    We report on spatially resolved birefringence measurements in a multimode vertical-cavity surface-emitting laser (VCSEL) by using the emission wavelength distribution mapping. The point-by-point, polarization-resolved spectral information lends itself to the identification of anisotropies in the material and enables the estimate of refractive index differences and gradients in the two orthogonal polarization components with high spatial resolution. Compared with classical optical microscopy techniques, we can easily recognize the position of the emission wavelength split (which carefully points to the position of defects) with a much better spectral sensitivity (potentially as low as 3 GHz). The presented method is general and can be used with any bulk, light-emitting source (even passive, if external illumination is added) and may prove very useful for device fabrication, quality checks and process improvements.

  17. Effective index model predicts modal frequencies of vertical-cavity lasers

    Energy Technology Data Exchange (ETDEWEB)

    SERKLAND,DARWIN K.; HADLEY,G. RONALD; CHOQUETTE,KENT D.; GEIB,KENT M.; ALLERMAN,ANDREW A.

    2000-04-18

    Previously, an effective index optical model was introduced for the analysis of lateral waveguiding effects in vertical-cavity surface-emitting lasers. The authors show that the resultant transverse equation is almost identical to the one typically obtained in the analysis of dielectric waveguide problems, such as a step-index optical fiber. The solution to the transverse equation yields the lateral dependence of the optical field and, as is recognized in this paper, the discrete frequencies of the microcavity modes. As an example, they apply this technique to the analysis of vertical-cavity lasers that contain thin-oxide apertures. The model intuitively explains the experimental data and makes quantitative predictions in good agreement with a highly accurate numerical model.

  18. Direct detection of the Josephson radiation emitted from superconducting thin-film microbridges

    DEFF Research Database (Denmark)

    Pedersen, Niels Falsig; Sørensen, O. H.; Mygind, Jesper;

    1976-01-01

    We report direct measurements of the Josephson radiation emitted in X band from a superconducting thin-film microbridge coupled to a resonance cavity. Power is emitted if one of the harmonics of the Josephson frequency is in the bandwidth of the receiver. The maximum power emitted during our expe...... experiment was 10−13 W. The Josephson radiation could easily be detected at frequencies off resonance. Applied Physics Letters is copyrighted by The American Institute of Physics....

  19. Crab Cavity Development

    CERN Document Server

    Calaga, R; Burt, G; Ratti, A

    2015-01-01

    The HL-LHC upgrade will use deflecting (or crab) cavities to compensate for geometric luminosity loss at low β* and non-zero crossing angle. A local scheme with crab cavity pairs across the IPs is used employing compact crab cavities at 400 MHz. Design of the cavities, the cryomodules and the RF system is well advanced. The LHC crab cavities will be validated initially with proton beam in the SPS.

  20. Droplet based cavities and lasers

    DEFF Research Database (Denmark)

    Mølhave, Kristian; Kristensen, Anders; Mortensen, Asger

    2009-01-01

    The self-organized and molecularly smooth surface on liquid microdroplets makes them attractive as optical cavities with very high quality factors. This chapter describes the basic theory of optical modes in spherical droplets. The mechanical properties including vibrational excitation are also d...

  1. The effects of halogen and light-emitting diode light curing on the depth of cure and surface microhardness of composite resins

    Directory of Open Access Journals (Sweden)

    Batu Can Yaman

    2011-01-01

    Full Text Available Aim : Light-emitting diode light curing units (LED LCUs have become more popular than halogen LCUs in routine dental restorative treatment. The aim of the study was to compare the effects of two conventional halogen (Hilux Plus and VIP and two LED (Elipar FreeLight 2 and Smart Lite light curing units on the depth of cure and the microhardness of various esthetic restorative materials. Materials and Methods : The curing depth and microhardness of a compomer (Dyract Extra, a resin-modified glass ionomer (Vitremer, a packable composite (Sculpt It, an ormocer (Admira, a hybrid composite (Tetric Ceram, two microhybrid composites (Miris and Clearfil Photo Posterior and, a nanofil composite (Filtek Supreme were determined using a scraping method and a hardness tester. A total of 320 samples were prepared using the eight different materials (n = 10 samples for each subgroup. The scraping test was based on ISO 4049:2000. Vicker′s microhardness testing was carried out using hardness tester (Zwick 3212. Data were analyzed using one-way analysis of variance (ANOVA, Bonferroni and the Kolmogorov-Smirnov tests. Results : Best microhardness results were obtained with the LED light curing units and Tetric EvoCeram and Filtek Supreme achieved the highest hardness values. The nanofil composite, Filtek Supreme, showed the best curing depth results in all the tested light curing systems. Conclusions : The LEDs were found to be more successful than the halogen units with respect to both curing depth and microhardness properties.

  2. Updating of Optical Inspection System for 6 GHz Superconducting Cavities

    Institute of Scientific and Technical Information of China (English)

    YU; Guo-long

    2013-01-01

    As a validation tool for the material properties and the surface treatment process,6 GHz superconducting cavity needs complex surface treatment process during its manufacture.It is verynecessary to record and monitor the statues of the internal surface of the cavity after each surface treatment,such as ultrasonic washing,mechanical polishing,electronic polishing(EP),buffered chemical

  3. Ratiometric sensing of metabolites using dual-emitting ZnS:Mn(2+) quantum dots as sole luminophore via surface chemistry design.

    Science.gov (United States)

    Gu, Wenliang; Gong, Suqin; Zhou, Yunlong; Xia, Yunsheng

    2017-04-15

    We herein present an effective and versatile platform for ratiometric sensing of metabolites using intrinsically dual-emitting ZnS:Mn(2+) quantum dots (QDs) as sole reporter. To avoid notoriously non-specific interactions, a special triple-layer "filter screen" around the inorganic QD core is rationally constructed, which is made of oleic acid, cetyltrimethyl ammonium bromide and bio-enzymes. In the presence of the analytes, the in-situ enzymatic H2O2 molecules diffuse and pass through the "filter screen" along the molecule interspace, which then reacts with the inorganic core and leads to more dramatically quenching of the Mn(2+) emission. The ratiometric signal readout is so distinct that can be observed by naked eyes (from orange to violet). In contrast, various coexisting bio-molecules, due to larger size, are well prevented from penetrating the filter screen by steric hindrance effect. So, various potential interfering substances do not disturb the assay. Under optimal conditions, five kinds of the corresponding substrates, namely glucose, cholesterol, lactate, xanthine and uric acid are well quantified by the emission intensity ratio of I470/I615, and the linear ranges are 0.1-200µM, 0.1-200µM, 1-200µM, 1-200µM and 1-200µM, respectively. The detection limits can even reach quasi-picomole levels. Because of favorable analytical performances (excellent selectivity, appropriate sensitivity and broad linear range), the proposed system can direct assay the analytes in blood without any sample pre-treatment.

  4. Hydrodynamic Drag on Streamlined Projectiles and Cavities

    KAUST Repository

    Jetly, Aditya

    2016-04-19

    The air cavity formation resulting from the water-entry of solid objects has been the subject of extensive research due to its application in various fields such as biology, marine vehicles, sports and oil and gas industries. Recently we demonstrated that at certain conditions following the closing of the air cavity formed by the initial impact of a superhydrophobic sphere on a free water surface a stable streamlined shape air cavity can remain attached to the sphere. The formation of superhydrophobic sphere and attached air cavity reaches a steady state during the free fall. In this thesis we further explore this novel phenomenon to quantify the drag on streamlined shape cavities. The drag on the sphere-cavity formation is then compared with the drag on solid projectile which were designed to have self-similar shape to that of the cavity. The solid projectiles of adjustable weight were produced using 3D printing technique. In a set of experiments on the free fall of projectile we determined the variation of projectiles drag coefficient as a function of the projectiles length to diameter ratio and the projectiles specific weight, covering a range of intermediate Reynolds number, Re ~ 104 – 105 which are characteristic for our streamlined cavity experiments. Parallel free fall experiment with sphere attached streamlined air cavity and projectile of the same shape and effective weight clearly demonstrated the drag reduction effect due to the stress-free boundary condition at cavity liquid interface. The streamlined cavity experiments can be used as the upper bound estimate of the drag reduction by air layers naturally sustained on superhydrophobic surfaces in contact with water. In the final part of the thesis we design an experiment to test the drag reduction capacity of robust superhydrophobic coatings deposited on the surface of various model vessels.

  5. A cavity and further radial substructures in the disk around HD~97048

    CERN Document Server

    van der Plas, G; Ménard, F; Casassus, S; Canovas, H; Pinte, C; Maddison, S T; Maaskant, K; Avenhaus, H; Cieza, L; Perez, S; Ubach, C

    2016-01-01

    Context: Gaps, cavities and rings in circumstellar disks are signposts of disk evolution and planet-disk interactions. We follow the recent suggestion that Herbig Ae/Be disks with a flared disk harbour a cavity, and investigate the disk around HD~97048. Aims: We aim to resolve the 34$\\pm$ 4 au central cavity predicted by Maaskant et al. (2013) and to investigate the structure of the disk. Methods: We image the disk around HD~97048 using ALMA at 0.85~mm and 2.94~mm, and ATCA (multiple frequencies) observations. Our observations also include the 12CO J=1-0, 12CO J=3-2 and HCO+ J=4-3 emission lines. Results: A central cavity in the disk around HD~97048 is resolved with a 40-46 au radius. Additional radial structure present in the surface brightness profile can be accounted for either by an opacity gap at ~90 au or by an extra emitting ring at ~150 au. The continuum emission tracing the dust in the disk is detected out to 355 au. The 12CO J=3-2 disk is detected 2.4 times farther out. The 12CO emission can be trac...

  6. Parametric study of a side impact dual cavity airbag using the flexible body EUROSID-1 database in a facet surface environment

    NARCIS (Netherlands)

    Kant, A.R.; Tuinenburg, C.; Hellkamp, U.

    1998-01-01

    The numerical optimisation of the thorax & head dual cavity side airbag has been an integrated part of a thorax & head feasibility study for a mid size vehicle. The objective was to minimise injury parameters for the EUROSID-1 due to a side impact deformable barrier crash test. To reach this objecti

  7. SiO2 Nanopillars on Microscale Roughened Surface of GaN-Based Light-Emitting Diodes by SILAR-Based Method

    Directory of Open Access Journals (Sweden)

    X. F. Zeng

    2013-01-01

    Full Text Available We reported the SiO2 nanopillars on microscale roughened surface on GaN-based LED to enhance light-extraction efficiency. ZnO nanoparticles were deposited on SiO2 as an etching mask before ICP etching SiO2 by successive ionic layer adsorption and reaction method (SILAR, and the different heights of SiO2 nanopillars on microroughened ITO/GaN were obtained after etching. Compared to a regular (flat surface GaN-based LED, the light output power for a LED with microroughening was increased by 33%. Furthermore, the proposed LEDs with SiO2 nanopillars on microroughened surface show the enhancement in light output power by 42.7%–49.1% at 20 mA. The increase in light output power is mostly attributed to reduction in Fresnel reflection by rough surface. The height of SiO2 nanopillars was increasing cause resulting in more rough on the microscale surface of GaN-based LEDs.

  8. Light-Emitting Pickles

    Science.gov (United States)

    Vollmer, M.; Mollmann, K-P.

    2015-01-01

    We present experiments giving new insights into the classical light-emitting pickle experiment. In particular, measurements of the spectra and temperatures, as well as high-speed recordings, reveal that light emission is connected to the polarity of the electrodes and the presence of hydrogen.

  9. Superconducting RF cavity R&D for future accelerators

    CERN Document Server

    Ginsburg, C M

    2009-01-01

    High-beta superconducting radiofrequency (SRF) elliptical cavities are being developed for several accelerator projects including Project X, the European XFEL, and the International Linear Collider (ILC). Fermilab has recently established an extensive infrastructure for SRF cavity R&D for future accelerators, including cavity surface processing and testing and cavity assembly into cryomodules. Some highlights of the global effort in SRF R&D toward improving cavity performance, and Fermilab SRF cavity R&D in the context of global projects are reviewed.

  10. 1.3 GHz superconducting RF cavity program at Fermilab

    Energy Technology Data Exchange (ETDEWEB)

    Ginsburg, C.M.; Arkan, T.; Barbanotti, S.; Carter, H.; Champion, M.; Cooley, L.; Cooper, C.; Foley, M.; Ge, M.; Grimm, C.; Harms, E.; /Fermilab

    2011-03-01

    At Fermilab, 9-cell 1.3 GHz superconducting RF (SRF) cavities are prepared, qualified, and assembled into cryomodules (CMs) for Project X, an International Linear Collider (ILC), or other future projects. The 1.3 GHz SRF cavity program includes targeted R&D on 1-cell 1.3 GHz cavities for cavity performance improvement. Production cavity qualification includes cavity inspection, surface processing, clean assembly, and one or more cryogenic low-power CW qualification tests which typically include performance diagnostics. Qualified cavities are welded into helium vessels and are cryogenically tested with pulsed high-power. Well performing cavities are assembled into cryomodules for pulsed high-power testing in a cryomodule test facility, and possible installation into a beamline. The overall goals of the 1.3 GHz SRF cavity program, supporting facilities, and accomplishments are described.

  11. Cavity QED on a nanofiber using a composite photonic crystal cavity

    CERN Document Server

    Yalla, Ramachandrarao; Nayak, Kali P; Hakuta, Kohzo

    2014-01-01

    We demonstrate cavity QED conditions in the Purcell regime for single quantum emitters on the surface of an optical nanofiber. The cavity is formed by combining an optical nanofiber and a nanofabricated grating to create a composite photonic crystal cavity. Using this technique, significant enhancement of the spontaneous emission rate into the nanofiber guided modes is observed for single quantum dots. Our results pave the way for enhanced on-fiber light-matter interfaces with clear applications to quantum networks.

  12. Cavity quantum electrodynamics on a nanofiber using a composite photonic crystal cavity.

    Science.gov (United States)

    Yalla, Ramachandrarao; Sadgrove, Mark; Nayak, Kali P; Hakuta, Kohzo

    2014-10-01

    We demonstrate cavity QED conditions in the Purcell regime for single quantum emitters on the surface of an optical nanofiber. The cavity is formed by combining an optical nanofiber and a nanofabricated grating to create a composite photonic crystal cavity. By using this technique, significant enhancement of the spontaneous emission rate into the nanofiber guided modes is observed for single quantum dots. Our results pave the way for enhanced on-fiber light-matter interfaces with clear applications to quantum networks.

  13. Dawn of Cavity Spintronics

    OpenAIRE

    Hu, Can-Ming

    2015-01-01

    Merging the progress of spintronics with the advancement in cavity quantum electrodynamics and cavity polaritons, a new field of Cavity Spintronics is forming, which connects some of the most exciting modern physics, such as quantum information and quantum optics, with one of the oldest science on the earth, the magnetism.

  14. Inkjet-printed vertically emitting solid-state organic lasers

    Science.gov (United States)

    Mhibik, Oussama; Chénais, Sébastien; Forget, Sébastien; Defranoux, Christophe; Sanaur, Sébastien

    2016-05-01

    In this paper, we show that Inkjet Printing can be successfully applied to external-cavity vertically emitting thin-film organic lasers and can be used to generate a diffraction-limited output beam with an output energy as high as 33.6 μJ with a slope efficiency S of 34%. Laser emission shows to be continuously tunable from 570 to 670 nm using an intracavity polymer-based Fabry-Perot etalon. High-optical quality films with several μm thicknesses are realized, thanks to ink-jet printing. We introduce a new optical material where EMD6415 commercial ink constitutes the optical host matrix and exhibits a refractive index of 1.5 and an absorption coefficient of 0.66 cm-1 at 550-680 nm. Standard laser dyes like Pyrromethene 597 and Rhodamine 640 are incorporated in solution to the EMD6415 ink. Such large size "printed pixels" of 50 mm2 present uniform and flat surfaces, with roughness measured as low as 1.5 nm in different locations of a 50 μm × 50 μm AFM scan. Finally, as the gain capsules fabricated by Inkjet printing are simple and do not incorporate any tuning or cavity element, they are simple to make, have a negligible fabrication cost, and can be used as fully disposable items. This work opens the way towards the fabrication of really low-cost tunable visible lasers with an affordable technology that has the potential to be widely disseminated.

  15. Beam cavity interaction

    CERN Document Server

    Gamp, A

    2011-01-01

    We begin by giving a description of the rf generator-cavity-beam coupled system in terms of basic quantities. Taking beam loading and cavity detuning into account, expressions for the cavity impedance as seen by the generator and as seen by the beam are derived. Subsequently methods of beam-loading compensation by cavity detuning, rf feedback, and feed-forward are described. Examples of digital rf phase and amplitude control for the special case of superconducting cavities are also given. Finally, a dedicated phase loop for damping synchrotron oscillations is discussed.

  16. Supersonic flows over cavities

    Institute of Scientific and Technical Information of China (English)

    Tianwen FANG; Meng DING; Jin ZHOU

    2008-01-01

    The characteristics of supersonic cold flows over cavities were investigated experimentally and numer-ically, and the effects of cavities of different sizes on super-sonic flow field were analyzed. The results indicate that the ratio of length to depth L/D within the range of 5-9 has little relevance to integral structures of cavity flow. The bevel angle of the rear wall does not alter the overall structure of the cavity flow within the range of 30°-60°, but it can exert obvious effect on the evolvement of shear layer and vortexes in cavities.

  17. RESONANT CAVITY EXCITATION SYSTEM

    Science.gov (United States)

    Baker, W.R.; Kerns, Q.A.; Riedel, J.

    1959-01-13

    An apparatus is presented for exciting a cavity resonator with a minimum of difficulty and, more specifically describes a sub-exciter and an amplifier type pre-exciter for the high-frequency cxcitation of large cavities. Instead of applying full voltage to the main oscillator, a sub-excitation voltage is initially used to establish a base level of oscillation in the cavity. A portion of the cavity encrgy is coupled to the input of the pre-exciter where it is amplified and fed back into the cavity when the pre-exciter is energized. After the voltage in the cavity resonator has reached maximum value under excitation by the pre-exciter, full voltage is applied to the oscillator and the pre-exciter is tunned off. The cavity is then excited to the maximum high voltage value of radio frequency by the oscillator.

  18. Cavity turnover and equilibrium cavity densities in a cottonwood bottomland

    Science.gov (United States)

    Sedgwick, James A.; Knopf, Fritz L.

    1992-01-01

    A fundamental factor regulating the numbers of secondary cavity nesting (SCN) birds is the number of extant cavities available for nesting. The number of available cavities may be thought of as being in an approximate equilibrium maintained by a very rough balance between recruitment and loss of cavities. Based on estimates of cavity recruitment and loss, we ascertained equilibrium cavity densities in a mature plains cottonwood (Populus sargentii) bottomland along the South Platte River in northeastern Colorado. Annual cavity recruitment, derived from density estimates of primary cavity nesting (PCN) birds and cavity excavation rates, was estimated to be 71-86 new cavities excavated/100 ha. Of 180 active cavities of 11 species of cavity-nesting birds found in 1985 and 1986, 83 were no longer usable by 1990, giving an average instantaneous rate of cavity loss of r = -0.230. From these values of cavity recruitment and cavity loss, equilibrium cavity density along the South Platte is 238-289 cavities/100 ha. This range of equilibrium cavity density is only slightly above the minimum of 205 cavities/100 ha required by SCN's and suggests that cavity availability may be limiting SCN densities along the South Platte River. We submit that snag management alone does not adequately address SCN habitat needs, and that cavity management, expressed in terms of cavity turnover and cavity densities, may be more useful.

  19. Air flow in a collapsing cavity

    CERN Document Server

    Peters, Ivo R; Lohse, Detlef; van der Meer, Devaraj

    2013-01-01

    We experimentally study the airflow in a collapsing cavity created by the impact of a circular disk on a water surface. We measure the air velocity in the collapsing neck in two ways: Directly, by means of employing particle image velocimetry of smoke injected into the cavity and indirectly, by determining the time rate of change of the volume of the cavity at pinch-off and deducing the air flow in the neck under the assumption that the air is incompressible. We compare our experiments to boundary integral simulations and show that close to the moment of pinch-off, compressibility of the air starts to play a crucial role in the behavior of the cavity. Finally, we measure how the air flow rate at pinch-off depends on the Froude number and explain the observed dependence using a theoretical model of the cavity collapse.

  20. Performance of 3-cell Seamless Niobium cavities

    Energy Technology Data Exchange (ETDEWEB)

    Kneisel, Peter K. [JLAB; Ciovati, Gianluigi [JLBA; Jelezov, I. [DESY, Hamburg; Singer, W. [DESY, Hamburg; Singer, X. [DESY, Hamburg

    2009-11-01

    In the last several months we have surface treated and cryogenically tested three TESLA-type 3-cell cavities, which had been manufactured at DESY as seamless assemblies by hydroforming. The cavities were completed at JLab with beam tube/flange assemblies. All three cavities performed very well after they had been post-purified with titanium at 1250C for 3 hrs. The cavities, two of which consisted of an end cell and 2 center cells and one was a center cell assembly, achieved gradients of Eacc = 32 MV/m, 34 MV/m and 35 MV/m without quenches. The performance was limited by the appearance of the “Q-drop” in the absence of field emission. This contribution reports about the various measurements undertaken with these cavities.

  1. Niobium Cavity Electropolishing Modelling and Optimisation

    CERN Document Server

    Ferreira, L M A; Forel, S; Shirra, J A

    2013-01-01

    It’s widely accepted that electropolishing (EP) is the most suitable surface finishing process to achieve high performance bulk Nb accelerating cavities. At CERN and in preparation for the processing of the 704 MHz high-beta Superconducting Proton Linac (SPL) cavities a new vertical electropolishing facility has been assembled and a study is on-going for the modelling of electropolishing on cavities with COMSOL® software. In a first phase, the electrochemical parameters were taken into account for a fixed process temperature and flow rate, and are presented in this poster as well as the results obtained on a real SPL single cell cavity. The procedure to acquire the data used as input for the simulation is presented. The modelling procedure adopted to optimise the cathode geometry, aimed at a uniform current density distribution in the cavity cell for the minimum working potential and total current is explained. Some preliminary results on fluid dynamics is also briefly described.

  2. Doppler effect for sound emitted by a moving airborne source and received by acoustic sensors located above and below the sea surface.

    Science.gov (United States)

    Ferguson, B G

    1993-12-01

    The acoustic emissions from a propeller-driven aircraft are received by a microphone mounted just above ground level and then by a hydrophone located below the sea surface. The dominant feature in the output spectrum of each acoustic sensor is the spectral line corresponding to the propeller blade rate. A frequency estimation technique is applied to the acoustic data from each sensor so that the Doppler shift in the blade rate can be observed at short time intervals during the aircraft's transit overhead. For each acoustic sensor, the observed variation with time of the Doppler-shifted blade rate is compared with the variation predicted by a simple ray-theory model that assumes the atmosphere and the sea are distinct isospeed sound propagation media separated by a plane boundary. The results of the comparison are shown for an aircraft flying with a speed of about 250 kn at altitudes of 500, 700, and 1000 ft.

  3. Inkjet-printed vertically emitting solid-state organic lasers

    CERN Document Server

    Mhibik, Oussama; Forget, Sébastien; Defranoux, Christophe; Sanaur, Sébastien

    2016-01-01

    In this paper, we show that Inkjet Printing can be successfully applied to external-cavity vertically-emitting thin-film organic lasers, and can be used to generate a diffraction-limited output beam with an output energy as high as 33.6 uJ with a slope efficiency S of 34%. Laser emission shows to be continuously tunable from 570 to 670 nm using an intracavity polymer-based Fabry-Perot etalon. High-optical quality films with several um thicknesses are realized thanks to ink-jet printing. We introduce a new optical material where EMD6415 commercial ink constitutes the optical host matrix and exhibits a refractive index of 1.5 and an absorption coefficient of 0.66 cm-1 at 550-680 nm. Standard laser dyes like Pyromethene 597 and Rhodamine 640 are incorporated in solution to the EMD6415 ink. Such large size " printed pixels " of 50 mm 2 present uniform and flat surfaces, with roughness measured as low as 1.5 nm in different locations of a 50um x 50um AFM scan. Finally, as the gain capsules fabricated by Inkjet pri...

  4. A broadband cavity enhanced absorption spectrometer for aircraft measurements of glyoxal, methylglyoxal, nitrous acid, nitrogen dioxide, and water vapor

    Science.gov (United States)

    Min, K.-E.; Washenfelder, R. A.; Dubé, W. P.; Langford, A. O.; Edwards, P. M.; Zarzana, K. J.; Stutz, J.; Lu, K.; Rohrer, F.; Zhang, Y.; Brown, S. S.

    2016-02-01

    We describe a two-channel broadband cavity enhanced absorption spectrometer (BBCEAS) for aircraft measurements of glyoxal (CHOCHO), methylglyoxal (CH3COCHO), nitrous acid (HONO), nitrogen dioxide (NO2), and water (H2O). The instrument spans 361-389 and 438-468 nm, using two light-emitting diodes (LEDs) and a single grating spectrometer with a charge-coupled device (CCD) detector. Robust performance is achieved using a custom optical mounting system, high-power LEDs with electronic on/off modulation, high-reflectivity cavity mirrors, and materials that minimize analyte surface losses. We have successfully deployed this instrument during two aircraft and two ground-based field campaigns to date. The demonstrated precision (2σ) for retrievals of CHOCHO, HONO and NO2 are 34, 350, and 80 parts per trillion (pptv) in 5 s. The accuracy is 5.8, 9.0, and 5.0 %, limited mainly by the available absorption cross sections.

  5. A broadband cavity enhanced absorption spectrometer for aircraft measurements of glyoxal, methylglyoxal, nitrous acid, nitrogen dioxide, and water vapor

    Directory of Open Access Journals (Sweden)

    K.-E. Min

    2015-10-01

    Full Text Available We describe a two-channel broadband cavity enhanced absorption spectrometer (BBCEAS for aircraft measurements of glyoxal (CHOCHO, methylglyoxal (CH3COCHO, nitrous acid (HONO, nitrogen dioxide (NO2, and water (H2O. The instrument spans 361–389 and 438–468 nm, using two light emitting diodes (LEDs and a grating spectrometer with a charge-coupled device (CCD detector. Robust performance is achieved using a custom optical mounting system, high power LEDs with electronic on/off modulation, state-of-the-art cavity mirrors, and materials that minimize analyte surface losses. We have successfully deployed this instrument during two aircraft and two ground-based field campaigns to date. The demonstrated precision (2σ for retrievals of CHOCHO, HONO and NO2 are 34, 350 and 80 pptv in 5 s. The accuracy is 5.8, 9.0 and 5.0 % limited mainly by the available absorption cross sections.

  6. Research on Field Emission and Dark Current in ILC Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Kexin; Li, Yongming; Palczewski, Ari; Geng, Rongli

    2013-09-01

    Field emission and dark current are issues of concern for SRF cavity performance and SRF linac operation. Complete understanding and reliable control of the issue are still needed, especially in full-scale multi-cell cavities. Our work aims at developing a generic procedure for finding an active field emitter in a multi-cell cavity and benchmarking the procedure through cavity vertical test. Our ultimate goal is to provide feedback to cavity preparation and cavity string assembly in order to reduce or eliminate filed emission in SRF cavities. Systematic analysis of behaviors of field emitted electrons is obtained by ACE3P developed by SLAC. Experimental benchmark of the procedure was carried out in a 9-cell cavity vertical test at JLab. The energy spectrum of Bremsstrahlung X-rays is measured using a NaI(Tl) detector. The end-point energy in the X-ray energy spectrum is taken as the highest kinetic electron energy to predict longitudinal position of the active field emitter. Angular location of the field emitter is determined by an array of silicon diodes around irises of the cavity. High-resolution optical inspection was conducted at the predicted field emitter location.

  7. Light Emitting Porous Silicon

    Science.gov (United States)

    1993-05-01

    ml - mm m lm m ~ m m ThO report Page 14 preparation method which has been originally described by Wohler [23] leads to a bright yellow substance with...Solid State Commun. 81, 307 (1992). [221 H. Kautsky, and H. Zocher, Z. Phys. 9,267 (1992). L TNO report Page 28 [231 F. Wohler , Lieb. Ann. 127, 275 (1863...Netherlands Fax + 31 70 328 09 61 Phone + 31 70 326 42 21 TNO- report copy no. e FEL-93eo047r Lh Emitting Porous Silicon sitho(s): DTICHMi.P.Th

  8. LEP copper accelerating cavities

    CERN Multimedia

    Laurent Guiraud

    1999-01-01

    These copper cavities were used to generate the radio frequency electric field that was used to accelerate electrons and positrons around the 27-km Large Electron-Positron (LEP) collider at CERN, which ran from 1989 to 2000. The copper cavities were gradually replaced from 1996 with new superconducting cavities allowing the collision energy to rise from 90 GeV to 200 GeV by mid-1999.

  9. Cryogenic rf test of the first plasma etched SRF cavity

    CERN Document Server

    Upadhyay, J; Popović, S; Valente-Feliciano, A -M; Im, D; Phillips, L; Vušković, L

    2016-01-01

    Plasma etching has a potential to be an alternative processing technology for superconducting radio frequency (SRF) cavities. An apparatus and a method are developed for plasma etching of the inner surfaces of SRF cavities. To test the effect of the plasma etching on the cavity rf performance, a 1497 MHz single cell SRF cavity is used. The single cell cavity is mechanically polished, buffer chemically etched afterwards and rf tested at cryogenic temperatures for a baseline test. This cavity is then plasma processed. The processing was accomplished by moving axially the inner electrode and the gas flow inlet in a step-wise manner to establish segmented plasma processing. The cavity is rf tested afterwards at cryogenic temperatures. The rf test and surface condition results are presented.

  10. Two-photon gateway in one-atom cavity quantum electrodynamics

    OpenAIRE

    2008-01-01

    Single atoms absorb and emit light from a resonant laser beam photon by photon. We show that a single atom strongly coupled to an optical cavity can absorb and emit resonant photons in pairs. The effect is observed in a photon correlation experiment on the light transmitted through the cavity. We find that the atom-cavity system transforms a random stream of input photons into a correlated stream of output photons, thereby acting as a two-photon gateway. The phenomenon has its origin in the q...

  11. 光子晶体垂直腔型表面发射和接收光电子器件%Photonic Crystal Vertical Cavity Surface Emitting and Detecting Photodiodes

    Institute of Scientific and Technical Information of China (English)

    宋倩; 许兴胜; 胡海洋; 鲁琳; 王春霞; 杜伟; 刘发民; 陈弘达

    2007-01-01

    介绍了制作光子晶体垂直腔面发射激光器实验研究的主要内容,包括材料的光谱测试分析、氧化工艺以及制作光子晶体等,成功制作了波长在980nm附近的光子晶体垂直腔面发射激光器.在此基础上,采用高精度湿法腐蚀和感应耦合等离子体干法刻蚀技术,研究制作了基于垂直腔面发射激光器外延材料的光子晶体谐振腔增强型探测器.

  12. Rapid cavity prototyping using mode matching and globalised scattering matrix

    CERN Document Server

    Shinton, I

    2009-01-01

    Cavity design using traditional mesh based numerical means (such as the finite element or finite difference methods) require large mesh calculations in order to obtain accurate values and cavity optimisation is often not achieved. Here we present a mode matching scheme which utilises a globalised scattering matrix approach that allows cavities with curved surfaces (i.e. cavities with elliptical irises and or equators) to be accurately simulated allowing rapid cavity prototyping and optimisation to be achieved. Results on structures in the CLIC main

  13. Cavity spin optodynamics

    CERN Document Server

    Brahms, N

    2010-01-01

    The dynamics of a large quantum spin coupled parametrically to an optical resonator is treated in analogy with the motion of a cantilever in cavity optomechanics. New spin optodynamic phenonmena are predicted, such as cavity-spin bistability, optodynamic spin-precession frequency shifts, coherent amplification and damping of spin, and the spin optodynamic squeezing of light.

  14. SPS accelerating cavity

    CERN Multimedia

    CERN PhotoLab

    1981-01-01

    One of the SPS accelerating cavities (200 MHz, travelling wave structure). The power that is fed into the upstream end of the cavity is extracted at the downstream end and sent into a dump load. See 7603195 for more details, 7411032 for the travelling wave structure, and also 8011289, 8302397.

  15. Modeling of Coupled Nano-Cavity Lasers

    DEFF Research Database (Denmark)

    Skovgård, Troels Suhr

    Modeling of nanocavity light emitting semiconductor devices is done using the semiconductor laser rate equations with spontaneous and stimulated emission terms modified for Purcell enhanced recombination. The modified terms include details about the optical and electronic density......, coupled photonic crystal nanocavity structures are simulated. The resonance frequencies of in-phase and out-of-phase coupled quadrupole modes in rectangular photonic crystal H1 cavities are extracted and are found to vary non-trivially with the intercavity separation. A qualitative explanation is given...... in terms of the in-plane mode profiles. Fareld emission patterns for the structures are calculated based on the finite-dierence time-domain simulations. It is found that only systems with an even number of holes separating the cavities show clear signs of being coupled. This non-trivial coupling behavior...

  16. Optical Physics of Microcavity Surface Emitting Lasers

    Science.gov (United States)

    2007-11-02

    N.K. Dutta. Long-Wavelength Semiconductor Lasers. Van Nostrand Reinhold, 1986. 3. Arfken , G. Mathematical Methods for Physicists (3rd Edition...Solutions 1-7 1.5 Parasitic Modes 1-9 1.6 Complete Laser Modeling 1-10 II. Vector Weighted Index Method 2-1 2.1 Vector Field Equations 2-1 2.2...The Weighted Index Method 2-3 2.3 Weighted Boundary Conditions and Solutions 2-5 2.3.1 Axial Boundary Conditions and Solutions 2-8 2.3.2

  17. Defects in III-nitride microdisk cavities

    Science.gov (United States)

    Ren, C. X.; Puchtler, T. J.; Zhu, T.; Griffiths, J. T.; Oliver, R. A.

    2017-03-01

    Nitride microcavities offer an exceptional platform for the investigation of light–matter interactions as well as the development of devices such as high efficiency light emitting diodes (LEDs) and low-threshold nanolasers. Microdisk geometries in particular are attractive for low-threshold lasing applications due to their ability to support high finesse whispering gallery modes (WGMs) and small modal volumes. In this article we review the effect of defects on the properties of nitride microdisk cavities fabricated using photoelectrochemical etching of an InGaN sacrificial superlattice (SSL). Threading dislocations originating from either the original GaN pseudosubstrate are shown to hinder the undercutting of microdisk cavities during the photoelectric chemical etching process resulting in whiskers of unetched material on the underside of microdisks. The unetched whiskers provide a pathway for light to escape, reducing microdisk Q-factor if located in the region occupied by the WGMs. Additionally, dislocations can affect the spectral stability of quantum dot emitters, thus hindering their effective integration in microdisk cavities. Though dislocations are clearly undesirable, the limiting factor on nitride microdisk Q-factor is expected to be internal absorption, indicating that the further optimisation of nitride microdisk cavities must incorporate both the elimination of dislocations and careful tailoring of the active region emission wavelength and background doping levels.

  18. Cavity-enhanced laser cooling of solid-state materials in a standing-wave cavity

    Institute of Scientific and Technical Information of China (English)

    Youhua Jia; Biao Zhong; Jianping Yin

    2008-01-01

    We propose a new method to cool the Yba+-doped ZBLANP glass in a standing-wave cavity. There are two advantages of this cavity-enhanced technique: the pumping power is greatly enhanced and the absorption of the cooling material is greatly increased. We introduce the basic principle of the cavity-enhanced laser cooling and discuss the cooling effect of a solid-state material in a cavity. From the theoretical study, it is found that the laser cooling effect is strongly dependent on the reflectivity of the cavity mirrors, the length of the solid material, the surface scattering of the material, and so on. Some optimal parameters for efficient laser cooling are obtained.

  19. Multi-Mode Cavity Accelerator Structure

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Yong [Yale Univ., New Haven, CT (United States); Hirshfield, Jay Leonard [Omega-P R& D, Inc., New Haven, CT (United States)

    2016-11-10

    This project aimed to develop a prototype for a novel accelerator structure comprising coupled cavities that are tuned to support modes with harmonically-related eigenfrequencies, with the goal of reaching an acceleration gradient >200 MeV/m and a breakdown rate <10-7/pulse/meter. Phase I involved computations, design, and preliminary engineering of a prototype multi-harmonic cavity accelerator structure; plus tests of a bimodal cavity. A computational procedure was used to design an optimized profile for a bimodal cavity with high shunt impedance and low surface fields to maximize the reduction in temperature rise ΔT. This cavity supports the TM010 mode and its 2nd harmonic TM011 mode. Its fundamental frequency is at 12 GHz, to benchmark against the empirical criteria proposed within the worldwide High Gradient collaboration for X-band copper structures; namely, a surface electric field Esurmax< 260 MV/m and pulsed surface heating ΔTmax< 56 °K. With optimized geometry, amplitude and relative phase of the two modes, reductions are found in surface pulsed heating, modified Poynting vector, and total RF power—as compared with operation at the same acceleration gradient using only the fundamental mode.

  20. section of an accelerating cavity from LEP

    CERN Multimedia

    This is a section of an accelerating cavity from LEP, cut in half to show the layer of niobium on the inside. Operating at 4.2 degrees above absolute zero, the niobium is superconducting and carries an accelerating field of 6 million volts per metre with negligible losses. Each cavity has a surface of 6 m2. The niobium layer is only 1.2 microns thick, ten times thinner than a hair. Such a large area had never been coated to such a high accuracy. A speck of dust could ruin the performance of the whole cavity so the work had to be done in an extremely clean environment. These challenging requirements pushed European industry to new achievements. 256 of these cavities are now used in LEP to double the energy of the particle beams.

  1. Coupled external cavity photonic crystal enhanced fluorescence.

    Science.gov (United States)

    Pokhriyal, Anusha; Lu, Meng; Ge, Chun; Cunningham, Brian T

    2014-05-01

    We report a fundamentally new approach to enhance fluorescence in which surface adsorbed fluorophore-tagged biomolecules are excited on a photonic crystal surface that functions as a narrow bandwidth and tunable mirror of an external cavity laser. This scheme leads to ∼10× increase in the electromagnetic enhancement factor compared to ordinary photonic crystal enhanced fluorescence. In our experiments, the cavity automatically tunes its lasing wavelength to the resonance wavelength of the photonic crystal, ensuring optimal on-resonance coupling even in the presence of variable device parameters and variations in the density of surface-adsorbed capture molecules. We achieve ∼10(5) × improvement in the limit of detection of a fluorophore-tagged protein compared to its detection on an unpatterned glass substrate. The enhanced fluorescence signal and easy optical alignment make cavity-coupled photonic crystals a viable approach for further reducing detection limits of optically-excited light emitters that are used in biological assays.

  2. Cavity-enhanced spectroscopies

    CERN Document Server

    van Zee, Roger

    2003-01-01

    ""Cavity-Enhanced Spectroscopy"" discusses the use of optical resonators and lasers to make sensitive spectroscopic measurements. This volume is written by the researcchers who pioneered these methods. The book reviews both the theory and practice behind these spectroscopic tools and discusses the scientific discoveries uncovered by these techniques. It begins with a chapter on the use of optical resonators for frequency stabilization of lasers, which is followed by in-depth chapters discussing cavity ring-down spectroscopy, frequency-modulated, cavity-enhanced spectroscopy, intracavity spectr

  3. Tuned optical cavity magnetometer

    Science.gov (United States)

    Okandan, Murat; Schwindt, Peter

    2010-11-02

    An atomic magnetometer is disclosed which utilizes an optical cavity formed from a grating and a mirror, with a vapor cell containing an alkali metal vapor located inside the optical cavity. Lasers are used to magnetically polarize the alkali metal vapor and to probe the vapor and generate a diffracted laser beam which can be used to sense a magnetic field. Electrostatic actuators can be used in the magnetometer for positioning of the mirror, or for modulation thereof. Another optical cavity can also be formed from the mirror and a second grating for sensing, adjusting, or stabilizing the position of the mirror.

  4. Yeasts Occurring in Surface and Mouth Cavity of Two Chelonian Species, Podocnemis expansa Schweigger and P. unifilis Troschel (Reptilia: Chelonia: Pelomedusidae, in the Javaés River Border of Araguaia National Park in Brazil

    Directory of Open Access Journals (Sweden)

    Paula Benevides de Morais

    2010-01-01

    Full Text Available Thirty-eight specimens of free-ranging Podocnemis expansa (Amazon turtle and 22 of P. unifilis (Tracajá were screened for yeast isolation from surface (plastron, skin, and nails, eye, and mouth cavity. A hundred and eighteen yeast isolates belonging to 39 species were obtained. Debaryomyces hansenii, Candida galli, C. sake, and Rhodotorula mucilaginosa were the most frequent species isolated from these chelonians. Species diversity measured by Shannon's index was shown to be low and a degree of dominance could be detected as species known as potential pathogens were commonly isolated. The effective number of species in plastron of P. expansa was higher than in mouth samples, but not in P. unifilis probably due to dietary factors. P. expansa animals were captured on the beaches, and the superficial yeast populations may include terrestrial species. P. unifilis animals were captured in the water and the yeasts from superficial sites may represent species from river water.

  5. Yeasts Occurring in Surface and Mouth Cavity of Two Chelonian Species, Podocnemis expansa Schweigger and P. unifilis Troschel (Reptilia: Chelonia: Pelomedusidae), in the Javaés River Border of Araguaia National Park in Brazil

    Science.gov (United States)

    de Morais, Paula Benevides; Pimenta, Raphael Sanzio; Tavares, Inara Brito; de Garcia, Virginia; Rosa, Carlos Augusto

    2010-01-01

    Thirty-eight specimens of free-ranging Podocnemis expansa (Amazon turtle) and 22 of P. unifilis (Tracajá) were screened for yeast isolation from surface (plastron, skin, and nails), eye, and mouth cavity. A hundred and eighteen yeast isolates belonging to 39 species were obtained. Debaryomyces hansenii, Candida galli, C. sake, and Rhodotorula mucilaginosa were the most frequent species isolated from these chelonians. Species diversity measured by Shannon's index was shown to be low and a degree of dominance could be detected as species known as potential pathogens were commonly isolated. The effective number of species in plastron of P. expansa was higher than in mouth samples, but not in P. unifilis probably due to dietary factors. P. expansa animals were captured on the beaches, and the superficial yeast populations may include terrestrial species. P. unifilis animals were captured in the water and the yeasts from superficial sites may represent species from river water. PMID:20936145

  6. The influence of MoOx gap states on hole injection from aluminum doped zinc oxide with nanoscale MoOx surface layer anodes for organic light emitting diodes

    Science.gov (United States)

    Jha, Jitendra Kumar; Santos-Ortiz, Reinaldo; Du, Jincheng; Shepherd, Nigel D.

    2015-08-01

    The effective workfunction of Al doped ZnO films (AZO) increased from 4.1 eV to 5.55 eV after surface modification with nanoscale molybdenum sub-oxides (MoOx). Hole only devices with anodes consisting of 3 nm of MoOx on AZO exhibited a lower turn-on voltage (1.5 vs 1.8 V), and larger charge injection (190 vs 118 mA/cm2) at the reference voltage, compared to indium tin oxide (ITO). AZO devices with 10 nm of MoOx exhibited the highest workfunction but performed poorly compared to devices with 3 nm of MoOx, or standard ITO. Ultraviolet photoelectron, X-ray photoelectron, and optical spectroscopies indicate that the 3 nm MoOx films are more reduced and farther away from MoO3 stoichiometry than their 10 nm equivalents. The vacancies associated with non-stoichiometry result in donor-like gap states which we assign to partially occupied Mo 4d levels. We propose that Fowler-Nordheim tunneling from these levels is responsible for the reduction in threshold voltage measured in devices with 3 nm of MoOx. A schematic band diagram is proposed. The thicker MoOx layers are more stoichiometric and resistive, and the voltage drop across these layers dominates their electrical performance, leading to an increase in threshold voltage. The results indicate that AZO with MoOx layers of optimal thickness may be potential candidates for anode use in organic light emitting diodes.

  7. A comparative microleakage evaluation of three different base materials in Class I cavity in deciduous molars in sandwich technique using dye penetration and dentin surface interface by scanning electron microscope

    Directory of Open Access Journals (Sweden)

    Babita Niranjan

    2016-01-01

    Full Text Available Introduction: A major objective in restorative dentistry is the control of marginal leakage, which may occur because of dimensional changes or lack of adaptation of restorative material to the cavity preparation. Numerous techniques have been advocated to overcome polymerization shrinkage in composite restorations. Aim and Objectives: This study investigated microleakage of three different bases under composite resin in sandwich technique using dye penetration and dentin surface interface using scanning electron microscope (SEM. Materials and Methods: Sixty extracted deciduous molars were stored in distilled water and Class I cavities with a width of about one-fourth of intercuspal distance and a depth of 0.5-1 mm below the dentino-enamel junction was prepared without bevels. In Group 1 - glass ionomer cement (GIC; Group 2 - mineral trioxide aggregate (MTA; Group 3 - Biodentine™ was placed as a base under composite. Teeth were longitudinally sectioned in two halves, through the centers of the restoration, immersed in 2% methylene blue and microleakage was evaluated under stereomicroscope and surface interface between base and dentin was evaluated under SEM. Results:Under the condition of in vitro study, less microleakage and less internal gaps were seen in Biodentine™ (0.00 ± 0.00 and 4.00 ± 1.59 group than MTA (0.00 ± 0.00 and 6.08 ± 1.82 and GIC (25.25 ± 6.57 and 14.73 ± 3.72, respectively and showed very strong positive correlation between microleakage and internal gaps. Conclusion: Biodentine™ exhibits superior marginal sealing ability as well as marginal adaptation under composite resin as compared to MTA and GIC.

  8. Different optical properties in different periodic slot cavity geometrical morphologies

    Science.gov (United States)

    Zhou, Jing; Shen, Meng; Du, Lan; Deng, Caisong; Ni, Haibin; Wang, Ming

    2016-09-01

    In this paper, optical properties of two-dimensional periodic annular slot cavity arrays in hexagonal close-packing on a silica substrate are theoretically characterized by finite difference time domain (FDTD) simulation method. By simulating reflectance spectra, electric field distribution, and charge distribution, we confirm that multiple cylindrical surface plasmon resonances can be excited in annular inclined slot cavities by linearly polarized light, in which the four reflectance dips are attributed to Fabry-Perot cavity resonances in the coaxial cavity. A coaxial waveguide mode TE11 will exist in these annular cavities, and the wavelengths of these reflectance dips are effectively tailored by changing the geometrical pattern of slot cavity and the dielectric materials filled in the cavities. These resonant wavelengths are localized in annular cavities with large electric field enhancement and dissipate gradually due to metal loss. The formation of an absorption peak can be explained from the aspect of phase matching conditions. We observed that the proposed structure can be tuned over the broad spectral range of 600-4000 nm by changing the outer and inner radii of the annular gaps, gap surface topography. Meanwhile, different lengths of the cavity may cause the shift of resonance dips. Also, we study the field enhancement at different vertical locations of the slit. In addition, dielectric materials filling in the annular gaps will result in a shift of the resonance wavelengths, which make the annular cavities good candidates for refractive index sensors. The refractive index sensitivity of annular cavities can also be tuned by the geometry size and the media around the cavity. Annular cavities with novel applications can be implied as surface enhanced Raman spectra substrates, refractive index sensors, nano-lasers, and optical trappers. Project supported by the National Natural Science Foundation of China (Grant No. 61178044), the Natural Science Foundation

  9. Temperature Mapping of Nitrogen-doped Niobium Superconducting Radiofrequency Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Makita, Junki [Old Dominion Univ., Norfolk, VA (United States); Ciovati, Gianluigi [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Dhakal, Pashupati [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)

    2015-09-01

    It was recently shown that diffusing nitrogen on the inner surface of superconducting radiofrequency (SRF) cavities at high temperature can improve the quality factor of the niobium cavity. However, a reduction of the quench field is also typically found. To better understand the location of rf losses and quench, we used a thermometry system to map the temperature of the outer surface of ingot Nb cavities after nitrogen doping and electropolishing. Surface temperature of the cavities was recorded while increasing the rf power and also during the quenching. The results of thermal mapping showed no precursor heating on the cavities and quenching to be ignited near the equator where the surface magnetic field is maximum. Hot-spots at the equator area during multipacting were also detected by thermal mapping.

  10. Comparative numerical studies of ion traps with integrated optical cavities

    CERN Document Server

    Podoliak, Nina; Keller, Matthias; Horak, Peter

    2016-01-01

    We study a range of radio-frequency ion trap geometries and investigate the effect of integrating dielectric cavity mirrors on their trapping potential. We aim to identify ion trap and cavity configurations that are best suited for achieving small cavity volumes and thus large ion-photon coupling as required for scalable quantum information networks. In particular, we investigate the trapping potential distortions caused by the dielectric material of the cavity mirrors for different mirror orientations with respect to the trapping electrodes, as well as for mirror misalignment. We also analyze the effect of the mirror material properties such as dielectric constants and surface conductivity, and study the effect of surface charges on the mirrors. The smallest trapping potential distortions are found if the cavities are aligned along the major symmetry axis of the electrode geometries. These cavity configurations also appear to be the most stable with respect to any mirror misalignment.

  11. Facet Reflection Coefficient of Phase-locked Diode Laser Array in an External Cavity

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A diode laser array(DLA)positioned in an external cavity can receive the radiations emitted from its neighboring elements (C1) and that of itself (S) after being reflected at the DLA facet as well as from the external mirror (C0). Considering the fact that|C0/S| should be larger than unity if the external cavity is effective,and|C1/S| should be larger than unity if the phase locking may be established in the external cavity.The requirements on the reflection at the facet of the diode laser array have been specified in terms of the cavity length and reflection coefficient of the external mirror.

  12. Hybrid vertical cavity laser

    DEFF Research Database (Denmark)

    Chung, Il-Sug; Mørk, Jesper

    2010-01-01

    A new hybrid vertical cavity laser structure for silicon photonics is suggested and numerically investigated. It incorporates a silicon subwavelength grating as a mirror and a lateral output coupler to a silicon ridge waveguide.......A new hybrid vertical cavity laser structure for silicon photonics is suggested and numerically investigated. It incorporates a silicon subwavelength grating as a mirror and a lateral output coupler to a silicon ridge waveguide....

  13. Thermal Model of a Dish Stirling Cavity-Receiver

    OpenAIRE

    Rubén Gil; Carlos Monné; Nuria Bernal; Mariano Muñoz; Francisco Moreno

    2015-01-01

    This paper presents a thermal model for a dish Stirling cavity based on the finite differences method. This model is a theoretical tool to optimize the cavity in terms of thermal efficiency. One of the main outcomes of this work is the evaluation of radiative exchange using the radiosity method; for that purpose, the view factors of all surfaces involved have been accurately calculated. Moreover, this model enables the variation of the cavity and receiver dimensions and the materials to deter...

  14. Slow plasmons in grating cavities

    Science.gov (United States)

    Aydinli, Atilla; Karademir, Ertugrul; Balci, Sinan; Kocabas, Coskun

    2016-03-01

    Recent research on surface plasmon polaritons and their applications have brought forward a wealth of information and continues to be of interest to many. In this report, we concentrate on propagating surface plasmon polaritons (SPPs) and their interaction with matter. Using grating based metallic structures, it is possible to control the electrodynamics of propagating SPPs. Biharmonic gratings loaded with periodic Si stripes allow excitation of SPPs that are localized inside the band gap with grating coupling. The cavity state is formed due to periodic effective index modulation obtained by one harmonic of the grating and loaded Si stripes. More complicated grating structures such as metallic Moiré surfaces have also been shown to form a localized state inside the band gap when excited with Kretschmann configuration.

  15. The Superconducting TESLA Cavities

    CERN Document Server

    Aune, B.; Bloess, D.; Bonin, B.; Bosotti, A.; Champion, M.; Crawford, C.; Deppe, G.; Dwersteg, B.; Edwards, D.A.; Edwards, H.T.; Ferrario, M.; Fouaidy, M.; Gall, P-D.; Gamp, A.; Gössel, A.; Graber, J.; Hubert, D.; Hüning, M.; Juillard, M.; Junquera, T.; Kaiser, H.; Kreps, G.; Kuchnir, M.; Lange, R.; Leenen, M.; Liepe, M.; Lilje, L.; Matheisen, A.; Möller, W-D.; Mosnier, A.; Padamsee, H.; Pagani, C.; Pekeler, M.; Peters, H-B.; Peters, O.; Proch, D.; Rehlich, K.; Reschke, D.; Safa, H.; Schilcher, T.; Schmüser, P.; Sekutowicz, J.; Simrock, S.; Singer, W.; Tigner, M.; Trines, D.; Twarowski, K.; Weichert, G.; Weisend, J.; Wojtkiewicz, J.; Wolff, S.; Zapfe, K.

    2000-01-01

    The conceptional design of the proposed linear electron-positron colliderTESLA is based on 9-cell 1.3 GHz superconducting niobium cavities with anaccelerating gradient of Eacc >= 25 MV/m at a quality factor Q0 > 5E+9. Thedesign goal for the cavities of the TESLA Test Facility (TTF) linac was set tothe more moderate value of Eacc >= 15 MV/m. In a first series of 27industrially produced TTF cavities the average gradient at Q0 = 5E+9 wasmeasured to be 20.1 +- 6.2 MV/m, excluding a few cavities suffering fromserious fabrication or material defects. In the second production of 24 TTFcavities additional quality control measures were introduced, in particular aneddy-current scan to eliminate niobium sheets with foreign material inclusionsand stringent prescriptions for carrying out the electron-beam welds. Theaverage gradient of these cavities at Q0 = 5E+9 amounts to 25.0 +- 3.2 MV/mwith the exception of one cavity suffering from a weld defect. Hence only amoderate improvement in production and preparation technique...

  16. RF BREAKDOWN STUDIES USING PRESSURIZED CAVITIES

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Rolland

    2014-09-21

    Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved and mitigation techniques to improve practical maximum accelerating gradients have had only limited success. Part of the problem is that RF breakdown in an evacuated cavity involves a complex mixture of effects, which include the geometry, metallurgy, and surface preparation of the accelerating structures and the make-up and pressure of the residual gas in which plasmas form. Studies showed that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas, as needed for muon cooling channels, without the need for long conditioning times, even in the presence of strong external magnetic fields. This positive result was expected because the dense gas can practically eliminate dark currents and multipacting. In this project we used this high pressure technique to suppress effects of residual vacuum and geometry that are found in evacuated cavities in order to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of magnetic field, frequency, and surface preparation. One of the interesting and useful outcomes of this project was the unanticipated collaborations with LANL and Fermilab that led to new insights as to the operation of evacuated normal-conducting RF cavities in high external magnetic fields. Other accomplishments included: (1) RF breakdown experiments to test the effects of SF6 dopant in H2 and He gases with Sn, Al, and Cu electrodes were carried out in an 805 MHz cavity and compared to calculations and computer simulations. The heavy corrosion caused by the SF6 components led to the suggestion that a small admixture of oxygen, instead of SF6, to the hydrogen would allow the same advantages without the corrosion in a practical muon beam line. (2) A

  17. Plasma processing of superconducting radio frequency cavities

    Science.gov (United States)

    Upadhyay, Janardan

    The development of plasma processing technology of superconducting radio frequency (SRF) cavities not only provides a chemical free and less expensive processing method, but also opens up the possibility for controlled modification of the inner surfaces of the cavity for better superconducting properties. The research was focused on the transition of plasma etching from two dimensional flat surfaces to inner surfaces of three dimensional (3D) structures. The results could be applicable to a variety of inner surfaces of 3D structures other than SRF cavities. Understanding the Ar/Cl2 plasma etching mechanism is crucial for achieving the desired modification of Nb SRF cavities. In the process of developing plasma etching technology, an apparatus was built and a method was developed to plasma etch a single cell Pill Box cavity. The plasma characterization was done with the help of optical emission spectroscopy. The Nb etch rate at various points of this cavity was measured before processing the SRF cavity. Cylindrical ring-type samples of Nb placed on the inner surface of the outer wall were used to measure the dependence of the process parameters on plasma etching. The measured etch rate dependence on the pressure, rf power, dc bias, temperature, Cl2 concentration and diameter of the inner electrode was determined. The etch rate mechanism was studied by varying the temperature of the outer wall, the dc bias on the inner electrode and gas conditions. In a coaxial plasma reactor, uniform plasma etching along the cylindrical structure is a challenging task due to depletion of the active radicals along the gas flow direction. The dependence of etch rate uniformity along the cylindrical axis was determined as a function of process parameters. The formation of dc self-biases due to surface area asymmetry in this type of plasma and its variation on the pressure, rf power and gas composition was measured. Enhancing the surface area of the inner electrode to reduce the

  18. "Fine grain Nb tube for SRF cavities"

    Energy Technology Data Exchange (ETDEWEB)

    Robert E. Barber

    2012-07-08

    Superconducting radio frequency (SRF) cavities used in charged particle linear accelerators, are currently fabricated by deep drawing niobium sheets and welding the drawn dishes together. The Nb sheet has a non-uniform microstructure, which leads to unpredictable cavity shape and surface roughness, and inconsistent "spring-back" during forming. In addition, weld zones cause hot spots during cavity operation. These factors limit linear accelerator performance and increase cavity manufacturing cost. Equal channel angular extrusion (ECAE) can be used to refine and homogenize the microstructure of Nb tube for subsequent hydroforming into SRF cavities. Careful selection of deformation and heat treatment conditions during the processing steps can give a uniform and consistent microstructure in the tube, leading to improved deformability and lower manufacturing costs. Favorable microstructures were achieved in short test samples of RRR Nb tube, which may be particularly suitable for hydroforming into SRF cavity strings. The approach demonstrated could be applicable to microstructure engineering of other tube materials including tantalum, titanium, and zirconium.

  19. Very Bright and Efficient Microcavity Top-Emitting Quantum Dot Light-Emitting Diodes with Ag Electrodes.

    Science.gov (United States)

    Liu, Guohong; Zhou, Xiang; Chen, Shuming

    2016-07-01

    The microcavity effect in top-emitting quantum dot light-emitting diodes (TQLEDs) is theoretically and experimentally investigated. By carefully optimizing the cavity length, the thickness of the top Ag electrode and the thickness of the capping layer, very bright and efficient TQLEDs with external quantum efficiency (EQE) of 12.5% are demonstrated. Strong dependence of luminance and efficiency on cavity length is observed, in good agreement with theoretical calculation. By setting the normal-direction resonant wavelength around the peak wavelength of the intrinsic emission, highest luminance of 112 000 cd/m(2) (at a driving voltage of 7 V) and maximum current efficiency of 27.8 cd/A are achieved, representing a 12-fold and a 2.1-fold enhancement compared to 9000 cd/m(2) and 13.2 cd/A of the conventional bottom emitting devices, respectively, whereas the highest EQE of 12.5% is obtained by setting the resonant wavelength 30 nm longer than the peak wavelength of the intrinsic emission. Benefit from the very narrow spectrum of QDs and the low absorption of silver electrodes, the potential of microcavity effect can be fully exploited in TQLEDs.

  20. Three-dimensional analysis of the pulp cavity on surface models of molar teeth, using X-ray micro-computed tomography

    DEFF Research Database (Denmark)

    Markvart, Merete; Bjørndal, Lars; Darvann, Tron Andre

    2012-01-01

    . In summary, three-dimensional surface models were made with a high precision; an increased accumulation of mineral deposits was noted in molars with small pulp chambers and combined with the consistent pattern of intra-radicular connections, the potential endodontic treatment complexity is underlined...

  1. Emissive Ion Thruster -EMIT Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A propulsion system is proposed that is based on acceleration of ions emitted from a thin, solid-state electrochemical ceramic membrane. This technology would...

  2. Electrochemical Light-Emitting Gel

    Directory of Open Access Journals (Sweden)

    Nobuyuki Itoh

    2010-06-01

    Full Text Available Light-emitting gel, a gel state electroluminescence material, is reported. It is composed of a ruthenium complex as the emitter, an ionic liquid as the electrolyte, and oxide nanoparticles as the gelation filler. Emitted light was produced via electrogenerated chemiluminescence. The light-emitting gel operated at low voltage when an alternating current was passed through it, regardless of its structure, which is quite thick. The luminescence property of the gel is strongly affected by nanoparticle materials. TiO2 nanoparticles were a better gelation filler than silica or ZnO was, with respect to luminescence stability, thus indicating a catalytic effect. It is demonstrated that the light-emitting gel device, with quite a simple fabrication process, flashes with the application of voltage.

  3. Low threshold and room-temperature lasing of electrically pumped red-emitting InP/(Al{sub 0.20}Ga{sub 0.80}){sub 0.51}In{sub 0.49}P quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Eichfelder, Marcus; Schulz, Wolfgang-Michael; Reischle, Matthias; Wiesner, Michael; Rossbach, Robert; Jetter, Michael; Michler, Peter, E-mail: m.eichfelder@ihfg.uni-stuttgart.d [Institut fuer Halbleiteroptik und Funktionelle Grenzflaechen, Universitaet Stuttgart, Allmandring 3, 70569 Stuttgart (Germany)

    2010-02-01

    In this letter, we report on laser light emission in the red spectral range. Self-assembled InP quantum dots being electrically pumped were embedded in a microcavity mesa realized by monolithically grown high-reflectivity AlGaAs distributed Bragg reflectors. Common semiconductor laser processing steps were used to fabricate stand-alone index-guided vertical-cavity surface-emitting lasers with oxide apertures for optical transverse mode confinement and electrical current constriction. Ultra-low threshold current densities of around 10A/cm{sup 2} and room temperature lasing were achieved.

  4. Plasma production by means of discharge in a spherical cavity

    NARCIS (Netherlands)

    Antsiferov, P. S.; Dorokhin, L. A.; Koshelev, K. N.

    2010-01-01

    The work is devoted to the study of plasma, appearing as a result of cumulation of shock wave with form close to spherical. The shock wave was obtained by triggering of fast discharge (dI/dt about 10(12) A/s) on inner surface of cavity, made from insulator. Spherical cavity with radius 4.5 mm was fi

  5. Performance study of cavity-backed dual-band radiators

    NARCIS (Netherlands)

    Amaldoss, S.E.; Yarovoy, A.

    2011-01-01

    The effectiveness of a cavity for dual-band patch radiator with a frequency ratio of 1.65:1 is analysed. The use of cavities can help in maintaining impedance matching, reducing the levels of mutual coupling between the elements as well as in containing the surface waves, aspects vital to array perf

  6. Direct Numerical Simulation of Automobile Cavity Tones

    Science.gov (United States)

    Kurbatskii, Konstantin; Tam, Christopher K. W.

    2000-01-01

    The Navier Stokes equation is solved computationally by the Dispersion-Relation-Preserving (DRP) scheme for the flow and acoustic fields associated with a laminar boundary layer flow over an automobile door cavity. In this work, the flow Reynolds number is restricted to R(sub delta*) < 3400; the range of Reynolds number for which laminar flow may be maintained. This investigation focuses on two aspects of the problem, namely, the effect of boundary layer thickness on the cavity tone frequency and intensity and the effect of the size of the computation domain on the accuracy of the numerical simulation. It is found that the tone frequency decreases with an increase in boundary layer thickness. When the boundary layer is thicker than a certain critical value, depending on the flow speed, no tone is emitted by the cavity. Computationally, solutions of aeroacoustics problems are known to be sensitive to the size of the computation domain. Numerical experiments indicate that the use of a small domain could result in normal mode type acoustic oscillations in the entire computation domain leading to an increase in tone frequency and intensity. When the computation domain is expanded so that the boundaries are at least one wavelength away from the noise source, the computed tone frequency and intensity are found to be computation domain size independent.

  7. Superconducting spoke cavities for high-velocity applications

    Energy Technology Data Exchange (ETDEWEB)

    Hopper, Christopher S. [Old Dominion U.; Delayen, Jean R. [Old Dominion U., JLAB

    2013-10-01

    To date, superconducting spoke cavities have been designed, developed, and tested for particle velocities up to {beta}{sub 0}~0.6, but there is a growing interest in possible applications of multispoke cavities for high-velocity applications. We have explored the design parameter space for low-frequency, high-velocity, double-spoke superconducting cavities in order to determine how each design parameter affects the electromagnetic properties, in particular the surface electromagnetic fields and the shunt impedance. We present detailed design for cavities operating at 325 and 352 MHz and optimized for {beta}{sub 0}~=0.82 and 1.

  8. Design of 162 MHz RF Experimental Cavity

    Institute of Scientific and Technical Information of China (English)

    YIN; Zhi-guo; CAO; Xue-long; GUO; Juan-juan; JI; Bin; FU; Xiao-liang; WEI; Jun-yi

    2015-01-01

    In this paper,a 162MHz RF experimental cavity is designed to study the multipacting multiplier effect of the medium and the metal electrode and its relationship with the plate surface characteristics,and to find out the method for inhibiting multipacting multiplier effects.The

  9. Suppressing Spectral Diffusion of the Emitted Photons with Optical Pulses

    CERN Document Server

    Fotso, H F; Awschalom, D D; Dobrovitski, V V

    2016-01-01

    In many quantum architectures the solid-state qubits, such as quantum dots or color centers, are interfaced via emitted photons. However, the frequency of photons emitted by solid-state systems exhibits slow uncontrollable fluctuations over time (spectral diffusion), creating a serious problem for implementation of the photon-mediated protocols. Here we show that a sequence of optical pulses applied to the solid-state emitter can stabilize the emission line at the desired frequency. We demonstrate efficiency, robustness, and feasibility of the method analytically and numerically. Taking nitrogen-vacancy (NV) center in diamond as an example, we show that only several pulses, with the width of 1 ns, separated by few ns (which is not difficult to achieve) can suppress spectral diffusion. Our method provides a simple and robust way to greatly improve the efficiency of photon-mediated entanglement and/or coupling to photonic cavities for solid-state qubits.

  10. Investigation of top-emitting OLEDs using molybdenum oxide as anode buffer layer

    Institute of Scientific and Technical Information of China (English)

    LIN Hui; YU Jun-sheng; ZHANG Wei

    2012-01-01

    A high-effective bottom anode is essential for high-performance top-emitting organic light-emitting devices (OLEDs).In this paper,Ag-based top-emitting OLEDs are investigated.Ag has the highest reflectivity for visible light among all metals,yet its hole-injection properties are not ideal for anodes of top-emitting OLED.The performance of the devices is significantly improved using the molybdenum oxide as anode buffer layer at the surface of Ag.By introducing the molybdenum oxide,the hole injection from Ag anodes into top-emitting OLED is largely enhanced with rather high reflectivity retained.

  11. The ``Q disease'' in Superconducting Niobium RF Cavities

    Science.gov (United States)

    Knobloch, J.

    2003-07-01

    Superconducting niobium cavities can achieve quality (Q0) factors of 1010-1011, more than six orders of magnitude higher than conventional copper cavities. However, to maintain this performance at high accelerating gradient (20 MV/m) the radio-frequency (rf) surface must be damage and dust free. Cavity preparation techniques therefore routinely include a chemical etch or electropolishing. Under certain conditions, these (and other) treatments can contaminate the niobium with hydrogen. Hydrides may then form when the cavity is cooled through 150 K, even if only a few atomic percent hydrogen are present. If hydrides are formed, the cavity quality can degrade substantially (Q disease). A rapid cooldown often inhibits the hydride formation. Other "cures" include degassing cavities at 900 °C to eliminate the hydrogen. A historical review of the Q disease is provided here, with the emphasis being placed on its discovery, symptoms, mechanism, and cures.

  12. Experimental investigation of cavity flows

    Energy Technology Data Exchange (ETDEWEB)

    Loeland, Tore

    1998-12-31

    This thesis uses LDV (Laser Doppler Velocimetry), PIV (Particle Image Velocimetry) and Laser Sheet flow Visualisation to study flow inside three different cavity configurations. For sloping cavities, the vortex structure inside the cavities is found to depend upon the flow direction past the cavity. The shape of the downstream corner is a key factor in destroying the boundary layer flow entering the cavity. The experimental results agree well with numerical simulations of the same geometrical configurations. The results of the investigations are used to find the influence of the cavity flow on the accuracy of the ultrasonic flowmeter. A method to compensate for the cavity velocities is suggested. It is found that the relative deviation caused by the cavity velocities depend linearly on the pipe flow. It appears that the flow inside the cavities should not be neglected as done in the draft for the ISO technical report on ultrasonic flowmeters. 58 refs., 147 figs., 2 tabs.

  13. Energy Levels of Coupled Plasmonic Cavities

    Institute of Scientific and Technical Information of China (English)

    Chuan-Pu Liu; Xin-Li Zhu; Jia-Sen Zhang; Jun Xu; Yamin Leprince-Wang; Da-Peng Yu

    2016-01-01

    We demonstrate the hybridization of the plasmonic modes in directly coupled whispering gallery cavities fabricated on silver films and present the mode patterns and energy levels using cathodoluminescence spectroscopy.Although the energy of the most antisymmetrically coupled modes is higher than that of the corresponding symmetrically coupled ones,the contrary cases happen for small quantum number modes.We attribute the phenomenon to the different surface plasmon polariton paths between the symmetrically and antisymmetrically coupled modes.These results provide an understanding of the resonant properties in coupled plasmonic cavities,which have potential applications in nanophotonic devices.

  14. Two-photon gateway in one-atom cavity quantum electrodynamics.

    Science.gov (United States)

    Kubanek, A; Ourjoumtsev, A; Schuster, I; Koch, M; Pinkse, P W H; Murr, K; Rempe, G

    2008-11-14

    Single atoms absorb and emit light from a resonant laser beam photon by photon. We show that a single atom strongly coupled to an optical cavity can absorb and emit resonant photons in pairs. The effect is observed in a photon correlation experiment on the light transmitted through the cavity. We find that the atom-cavity system transforms a random stream of input photons into a correlated stream of output photons, thereby acting as a two-photon gateway. The phenomenon has its origin in the quantum anharmonicity of the energy structure of the atom-cavity system. Future applications could include the controlled interaction of two photons by means of one atom.

  15. Turbomachine component having an internal cavity reactivity neutralizer and method of forming the same

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, III, Herbert Chidsey; Meschter, Peter Joel

    2017-03-07

    A turbomachine component includes a body having an exterior surface and an interior surface, an internal cavity defined by the interior surface, and a reactivity neutralizing member arranged within the internal cavity. The reactivity neutralizing member is configured and disposed to neutralize turbomachine combustion products on the interior surface of the body.

  16. Electromigration occurrences and its effects on metallic surfaces submitted to high electromagnetic field : A novel approach to breakdown in accelerators

    CERN Document Server

    Antoine, C; Pimpec, F Le

    2011-01-01

    The application of a high electrical field on metallic surfaces leads to the well described phenomena of breakdown. In the classical scenario, explosive electron emission (EEE), breakdown (BD) originates from an emitting site (surface protrusion). The conditioning process consists of "burning" the emitting sites one after another and numerous observations exhibit surfaces covered with molten craters that more or less overlap. When dealing with RF cavities for accelerators, where increasingly fields are now sought, one can legitimately wonder if other physical phenomena should also be taken into account. In particular, we believe that electromigration, especially at surfaces or grain boundaries cannot be neglected anymore at high field (i.e. 50-100 MV/m). Many publications in the domain of liquid metal emission sources show that very stable and strong emission sources, either ions or electrons, build up on metallic surfaces submitted to electrical fields through a mechanism that is slightly different from the ...

  17. Apparatus and method for plasma processing of SRF cavities

    CERN Document Server

    Upadhyay, J; Peshl, J; Bašović, M; Popović, S; Valente-Feliciano, A -M; Phillips, L; Vuškovića, L

    2015-01-01

    An apparatus and a method are described for plasma etching of the inner surface of superconducting radio frequency (SRF) cavities. Accelerator SRF cavities are formed into a variable-diameter cylindrical structure made of bulk niobium, for resonant generation of the particle accelerating field. The etch rate non-uniformity due to depletion of the radicals has been overcome by the simultaneous movement of the gas flow inlet and the inner electrode. An effective shape of the inner electrode to reduce the plasma asymmetry for the coaxial cylindrical rf plasma reactor is determined and implemented in the cavity processing method. The processing was accomplished by moving axially the inner electrode and the gas flow inlet in a step-wise way to establish segmented plasma columns. The test structure was a pillbox cavity made of steel of similar dimension to the standard SRF cavity. This was adopted to experimentally verify the plasma surface reaction on cylindrical structures with variable diameter using the segment...

  18. Cavity formation by the impact of Leidenfrost spheres

    KAUST Repository

    Marston, Jeremy

    2012-05-01

    We report observations of cavity formation and subsequent collapse when a heated sphere impacts onto a liquid pool. When the sphere temperature is much greater than the boiling point of the liquid, we observe an inverted Leidenfrost effect where the sphere is encompassed by a vapour layer that prevents physical contact with the liquid. This creates the ultimate non-wetting scenario during sphere penetration through a free surface, producing very smooth cavity walls. In some cases during initial entry, however, the liquid contacts the sphere at the equator, leading to the formation of a dual cavity structure. For cold sphere impacts, where a contact line is observed, we reveal details of the contact line pinning, which initially forms a sawtooth pattern. We also observe surface waves on the cavity interface for cold spheres. We compare our experimental results to previous studies of cavity dynamics and, in particular, the influence of hydrophobicity on the entry of the sphere. © 2012 Cambridge University Press.

  19. Niobium superconducting cavity

    CERN Multimedia

    1980-01-01

    This 5-cell superconducting cavity, made from bulk-Nb, stems from the period of general studies, not all directed towards direct use at LEP. This one is dimensioned for 1.5 GHz, the frequency used at CEBAF and also studied at Saclay (LEP RF was 352.2 MHz). See also 7908227, 8007354, 8209255, 8210054, 8312339.

  20. Vertical cavity laser

    DEFF Research Database (Denmark)

    2016-01-01

    The present invention provides a vertical cavity laser comprising a grating layer comprising an in-plane grating, the grating layer having a first side and having a second side opposite the first side and comprising a contiguous core grating region having a grating structure, wherein an index...

  1. LEP superconducting cavity

    CERN Multimedia

    1995-01-01

    Engineers work in a clean room on one of the superconducting cavities for the upgrade to the LEP accelerator, known as LEP-2. The use of superconductors allow higher electric fields to be produced so that higher beam energies can be reached.

  2. Melatonin and oral cavity.

    Science.gov (United States)

    Cengiz, Murat İnanç; Cengiz, Seda; Wang, Hom-Lay

    2012-01-01

    While initially the oral cavity was considered to be mainly a source of various bacteria, their toxins and antigens, recent studies showed that it may also be a location of oxidative stress and periodontal inflammation. Accordingly, this paper focuses on the involvement of melatonin in oxidative stress diseases of oral cavity as well as on potential therapeutic implications of melatonin in dental disorders. Melatonin has immunomodulatory and antioxidant activities, stimulates the proliferation of collagen and osseous tissue, and acts as a protector against cellular degeneration associated with aging and toxin exposure. Arising out of its antioxidant actions, melatonin protects against inflammatory processes and cellular damage caused by the toxic derivates of oxygen. As a result of these actions, melatonin may be useful as a coadjuvant in the treatment of certain conditions of the oral cavity. However, the most important effect of melatonin seems to result from its potent antioxidant, immunomodulatory, protective, and anticancer properties. Thus, melatonin could be used therapeutically for instance, locally, in the oral cavity damage of mechanical, bacterial, fungal, or viral origin, in postsurgical wounds caused by tooth extractions and other oral surgeries. Additionally, it can help bone formation in various autoimmunological disorders such as Sjorgen syndrome, in periodontal diseases, in toxic effects of dental materials, in dental implants, and in oral cancers.

  3. Melatonin and Oral Cavity

    Directory of Open Access Journals (Sweden)

    Murat İnanç Cengiz

    2012-01-01

    Full Text Available While initially the oral cavity was considered to be mainly a source of various bacteria, their toxins and antigens, recent studies showed that it may also be a location of oxidative stress and periodontal inflammation. Accordingly, this paper focuses on the involvement of melatonin in oxidative stress diseases of oral cavity as well as on potential therapeutic implications of melatonin in dental disorders. Melatonin has immunomodulatory and antioxidant activities, stimulates the proliferation of collagen and osseous tissue, and acts as a protector against cellular degeneration associated with aging and toxin exposure. Arising out of its antioxidant actions, melatonin protects against inflammatory processes and cellular damage caused by the toxic derivates of oxygen. As a result of these actions, melatonin may be useful as a coadjuvant in the treatment of certain conditions of the oral cavity. However, the most important effect of melatonin seems to result from its potent antioxidant, immunomodulatory, protective, and anticancer properties. Thus, melatonin could be used therapeutically for instance, locally, in the oral cavity damage of mechanical, bacterial, fungal, or viral origin, in postsurgical wounds caused by tooth extractions and other oral surgeries. Additionally, it can help bone formation in various autoimmunological disorders such as Sjorgen syndrome, in periodontal diseases, in toxic effects of dental materials, in dental implants, and in oral cancers.

  4. Finemet cavity impedance studies

    CERN Document Server

    Persichelli, S; Migliorati, M; Salvant, B

    2013-01-01

    The aim of the study is to evaluate the impedance of the Finemet kicker cavity to be installed in the PS straight section 02 during LS1, under realistic assumptions of bunch length. Time domain simulations with CST Particle Studio have been performed in order to get the impedance of the cavity and make a comparison with the longitudinal impedance measured for a single cell prototype. The study has been performed on simplified 3D geometries imported from a mechanical CATIA drawing, assuming that the simplications have small impact on the nal results. Simulations confirmed that the longitudinal impedance observed with measurements can be excited by bunches circulating in the PS. In the six-cells Finemet cavity, PS bunches circulating in the center can excite a longitudinal impedance, the real part of which has a maximum of 2 kOhm at 4 MHz. This mode does not seem to have any transverse component. All the eigenmodes of the cavity are strongly damped by the Finemet rings: we predict to have no issues regarding tr...

  5. Statistical electromagnetics: Complex cavities

    NARCIS (Netherlands)

    Naus, H.W.L.

    2008-01-01

    A selection of the literature on the statistical description of electromagnetic fields and complex cavities is concisely reviewed. Some essential concepts, for example, the application of the central limit theorem and the maximum entropy principle, are scrutinized. Implicit assumptions, biased choic

  6. Filling a Conical Cavity

    Science.gov (United States)

    Nye, Kyle; Eslam-Panah, Azar

    2016-11-01

    Root canal treatment involves the removal of infected tissue inside the tooth's canal system and filling the space with a dense sealing agent to prevent further infection. A good root canal treatment happens when the canals are filled homogeneously and tightly down to the root apex. Such a tooth is able to provide valuable service for an entire lifetime. However, there are some examples of poorly performed root canals where the anterior and posterior routes are not filled completely. Small packets of air can be trapped in narrow access cavities when restoring with resin composites. Such teeth can cause trouble even after many years and lead the conditions like acute bone infection or abscesses. In this study, the filling of dead-end conical cavities with various liquids is reported. The first case studies included conical cavity models with different angles and lengths to visualize the filling process. In this investigation, the rate and completeness at which a variety of liquids fill the cavity were observed to find ideal conditions for the process. Then, a 3D printed model of the scaled representation of a molar with prepared post spaces was used to simulate the root canal treatment. The results of this study can be used to gain a better understanding of the restoration for endodontically treated teeth.

  7. Nitrogen doping study in ingot niobium cavities

    Energy Technology Data Exchange (ETDEWEB)

    Dhakal, Pashupati [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Ciovati, Gianluigi [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Kneisel, Peter [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Myneni, Ganapati Rao [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Makita, Junki [Old Dominion Univ., Norfolk, VA (United States)

    2015-09-01

    Thermal diffusion of nitrogen in niobium superconducting radio frequency cavities at temperature ~800 °C has resulted in the increase in quality factor with a low-field Q-rise extending to Bp > 90 mT. However, the maximum accelerating gradient of these doped cavities often deteriorates below the values achieved by standard treatments prior to doping. Here, we present the results of the measurements on ingot niobium cavities doped with nitrogen at 800 °C. The rf measurements were carried out after the successive electropolishing to remove small amount of material from the inner surface layer. The result showed higher breakdown field with lower quality factor as material removal increases.

  8. Synchronization of Bloch oscillations by a ring cavity.

    Science.gov (United States)

    Samoylova, M; Piovella, N; Robb, G R M; Bachelard, R; Courteille, Ph W

    2015-06-01

    We consider Bloch oscillations of ultracold atoms stored in a one-dimensional vertical optical lattice and simultaneously interacting with a unidirectionally pumped optical ring cavity whose vertical arm is collinear with the optical lattice. We find that the feedback provided by the cavity field on the atomic motion synchronizes Bloch oscillations via a mode-locking mechanism, steering the atoms to the lowest Bloch band. It also stabilizes Bloch oscillations against noise, and even suppresses dephasing due to atom-atom interactions. Furthermore, it generates periodic bursts of light emitted into the counter-propagating cavity mode, providing a non-destructive monitor of the atomic dynamics. All these features may be crucial for future improvements of the design of atomic gravimeters based on recording Bloch oscillations.

  9. Teleportation of Cavity Field States via Cavity QED

    CERN Document Server

    Guerra, E S

    2004-01-01

    In this article we discuss two schemes of teleportation of cavity field states. In the first scheme we consider cavities prepared in a coherent state and in the second scheme we consider cavities prepared in a superposition of zero and one Fock states.

  10. Plasmonic band gap cavities on biharmonic gratings

    Science.gov (United States)

    Kocabas, Askin; Seckin Senlik, S.; Aydinli, Atilla

    2008-05-01

    In this paper, we have experimentally demonstrated the formation of plasmonic band gap cavities in infrared and visible wavelength range. The cavity structure is based on a biharmonic metallic grating with selective high dielectric loading. A uniform metallic grating structure enables strong surface plasmon polariton (SPP) excitation and a superimposed second harmonic component forms a band gap for the propagating SPPs. We show that a high dielectric superstructure can dramatically perturb the optical properties of SPPs and enables the control of the plasmonic band gap structure. Selective patterning of the high index superstructure results in an index contrast in and outside the patterned region that forms a cavity. This allows us to excite the SPPs that localize inside the cavity at specific wavelengths, satisfying the cavity resonance condition. Experimentally, we observe the formation of a localized state in the band gap and measure the dispersion diagram. Quality factors as high as 37 have been observed in the infrared wavelength. The simplicity of the fabrication and the method of testing make this approach attractive for applications requiring localization of propagating SPPs.

  11. Effects of Electric and Magnetic Fields on the Performance of a Superconducting Cavity

    Energy Technology Data Exchange (ETDEWEB)

    Gianluigi Ciovati; Peter Kneisel; Jacek Sekutowicz; Waldemar Singer

    2005-05-01

    A special two-cell cavity was designed to obtain surface field distributions suitable for investigation of electric and magnetic field effects on cavity performance. The cavity design and preliminary results were presented in a previous contribution. The bulk niobium cavity was heat-treated in a vacuum furnace at 1250 C to improve thermal conductivity. Three seamless hydroformed Nb/Cu cavities of the same design were fabricated to investigate the role of the electron beam welds located in high field areas. This paper will present RF test results at 2 K for the bulk niobium and one of the seamless cavities.

  12. Analysis of mechanical fabrication experience with CEBAF`s production SRF cavities

    Energy Technology Data Exchange (ETDEWEB)

    Mammosser, J.; Kneisel, P.; Benesch, J.

    1993-06-01

    CEBAF has received a total of 360 five-cell niobium cavities, the largest group of industrially fabricated superconducting cavities so far. An extensive data base exists on the fabrication, surface treatment, assembly and cavity performance parameters. Analysis of the mechanical features of the cavities includes the following: the spread in fabrication tolerances of the cells derived from field profiles of the ``as fabricated`` cavities and the ``as fabricated`` external Q-values of the fundamental power coupler compared to dimensional deviations. A comparison is made of the pressure sensitivity of cavities made of materials from different manufacturers between 760 torr (4.2 K) and 23 torr (2 K).

  13. Rationale for designing cavity preparations.

    Science.gov (United States)

    Laswell, H R; Welk, D A

    1985-04-01

    Increased resistance to caries, increased dental awareness, superior diagnostic capabilities, better illumination, optical aids that significantly enhance vision, improved and standardized materials for restoration, and a deeper understanding of the caries process enable a far more conservative approach to tooth preparation. The dentist can concentrate on preserving as much sound tooth structure as possible with less attention being devoted to resistance and retention form that previously demanded in bulk restorations and massive channels and locks that are no longer appropriate. Although caries inhibitory effects have been shown with materials such as silicate cement, glass ionomers, and resins that leach fluoride, in general, dentists should not rely on restorative materials to inhibit the development of future decay. Characteristics of the carious lesion are unique for each tooth according to many factors centering around the plaque pattern for that tooth and not according to zones of natural susceptibility or immunity strictly dictated by morphology. Therefore, no single cavity preparation duplicated from a textbook is likely to be satisfactory for an individual tooth. Furthermore, novices learning the subject of cavity preparation often leave decalcified enamel when they attempt to replicate under clinical conditions that which they have learned in technique courses. This is the major invitation to future caries reappearing adjacent to restorations. Also, failure to duplicate the exact morphology of the tooth surface that has been replaced is likely to alter the pattern of plaque accumulation and create other caries prone areas.(ABSTRACT TRUNCATED AT 250 WORDS)

  14. ORGANIC LIGHT EMITTING DIODE (OLED

    Directory of Open Access Journals (Sweden)

    Aririguzo Marvis Ijeaku

    2015-09-01

    Full Text Available An Organic Light Emitting Diode (OLED is a device composed of an organic layer that emits lights in response to an electrical current. Organic light emitting diodes have advanced tremendously over the past decades. The different manufacturing processes of the OLED itself to several advantages over flat panel displays made with LCD technology which includes its light weight and flexible plastic substrates, wider viewing angles, improved brightness, better power efficiency and quicker response time. However, its drawbacks include shorter life span, poor color balance, poor outdoor performance, susceptibility to water damage etc.The application of OLEDs in electronics is on the increase on daily basics from cameras to cell phones to OLED televisions, etc. Although OLEDs provides prospects for thinner, smarter, lighter and ultraflexible electronics displays, however, due to high cost of manufacturing, it is not yet widely used.

  15. Development of a cryogenic radiation detector for mapping radio frequency superconducting cavity field emissions

    Energy Technology Data Exchange (ETDEWEB)

    Danny Dotson; John Mammosser

    2005-05-01

    Field emissions in a super conducting helium cooled RF cavity and the production of radiation (mostly X-Rays) have been measured externally on cryomodules at Jefferson Lab since 1991. External measurements are limited to radiation energies above 100 keV due to shielding of the stainless steel cryogenic body. To measure the onset of and to map field emissions from a superconducting cavity requires the detecting instrument be inside the shield and within the liquid Helium. Two possible measurement systems are undergoing testing at JLab. A CsI detector array set on photodiodes and an X-Ray film camera with a fixed aperture. Several devices were tested in the cell with liquid Helium without success. The lone survivor, a CsI array, worked but saturated at high power levels due to backscatter. The array was encased in a lead shield with a slit opening set to measure the radiation emitted directly from the cell eliminating a large portion of the backscatter. This is a work in progress and te sting should be complete before the PAC 05. The second system being tested is passive. It is a shielded box with an aperture to expose radiation diagnostic film located inside to direct radiation from the cell. Developing a technique for mapping field emissions in cryogenic cells will assist scientists and engineers in pinpointing any surface imperfections for examination.

  16. Light Emitting Transistors of Organic Single Crystals

    Science.gov (United States)

    Iwasa, Yoshihiro

    2009-03-01

    Organic light emitting transistors (OLETs) are attracting considerable interest as a novel function of organic field effect transistors (OFETs). Besides a smallest integration of light source and current switching devices, OLETs offer a new opportunity in the fundamental research on organic light emitting devices. The OLET device structure allows us to use organic single crystals, in contrast to the organic light emitting diodes (OLEDs), the research of which have been conducted predominantly on polycrystalline or amorphous thin films. In the case of OFETs, use of single crystals have produced a significant amount of benefits in the studies of pursuit for the highest performance limit of FETs, intrinsic transport mechanism in organic semiconductors, and application of the single crystal transistors. The study on OLETs have been made predominantly on polycrystalline films or multicomponent heterojunctions, and single crystal study is still limited to tetracene [1] and rubrene [2], which are materials with relatively high mobility, but with low photoluminescence efficiency. In this paper, we report fabrication of single crystal OLETs of several kinds of highly luminescent molecules, emitting colorful light, ranging from blue to red. Our strategy is single crystallization of monomeric or oligomeric molecules, which are known to have a very high photoluminescence efficiency. Here we report the result on single crystal LETs of rubrene (red), 4,4'-bis(diphenylvinylenyl)-anthracene (green), 1,4-bis(5-phenylthiophene-2-yl)benzene (AC5) (green), and 1,3,6,8-tetraphenylpyrene (TPPy) (blue), all of which displayed ambipolar transport as well as peculiar movement of voltage controlled movement of recombination zone, not only from the surface of the crystal but also from the edges of the crystals, indicting light confinement inside the crystal. Realization of ambipolar OLET with variety of single crystals indicates that the fabrication method is quite versatile to various light

  17. Novel laser machining of optical fibers for long cavities with low birefringence

    CERN Document Server

    Takahashi, Hiroki; Orucevic, Fedja; Noguchi, Atsushi; Kassa, Ezra; Keller, Matthias

    2015-01-01

    We present a novel method of machining optical fiber surfaces with a CO${}_2$ laser for use in Fiber-based Fabry-Perot Cavities (FFPCs). Previously FFPCs were prone to large birefringence and limited to relatively short cavity lengths ($\\le$ 200 $\\mu$m). These characteristics hinder their use in some applications such as cavity quantum electrodynamics with trapped ions. We optimized the laser machining process to produce large, uniform surface structures. This enables the cavities to achieve high finesse even for long cavity lengths. By rotating the fibers around their axis during the laser machining process the asymmetry resulting from the laser's transverse mode profile is eliminated. Consequently we are able to fabricate fiber mirrors with a high degree of rotational symmetry, leading to remarkably low birefringence. Through measurements of the cavity finesse over a range of cavity lengths and the polarization dependence of the cavity linewidth, we confirmed the quality of the produced fiber mirrors for us...

  18. Optimising Blackbody Cavity Shape for Spatially Uniform Integrated Emissivity

    Science.gov (United States)

    Saunders, P.

    2017-01-01

    The emissivity of a blackbody cavity, as seen by a radiation thermometer viewing the cavity, depends on both the field of view of the thermometer and the distribution of local effective emissivity values within the field of view. For cylindro-conical cavities, the local effective emissivity generally attains a maximum value at the apex of the cone and drops along the conical section. Thus, radiation thermometers with different fields of view see different blackbody emissivity values. This impacts, particularly, on the calibration of wide-angle low-temperature radiation thermometers and thermal imaging systems where each pixel responds to a different radiance. The spatial uniformity of the effective emissivity profile depends principally on the cone angle, with a weaker dependence on the length-to-diameter ratio of the cavity, the intrinsic emissivity of the cavity surfaces, and the temperature gradient along the cavity. In this paper, a nonlinear least-squares method is used to determine the optimal cone angle as a function of the cavity parameters. It is concluded that full cone angles close to 160° provide the flattest effective emissivity profile across the conical section of the cavity for typical cavity parameters. A method is also described for calculating the value of integrated emissivity, which includes the umbral and penumbral regions seen by an imaging radiation thermometer.

  19. Theory of RF superconductivity for resonant cavities

    Science.gov (United States)

    Gurevich, Alex

    2017-03-01

    An overview of a theory of electromagnetic response of superconductors in strong radio-frequency (RF) electromagnetic fields is given with the emphasis on applications to superconducting resonant cavities for particle accelerators. The paper addresses fundamentals of the BCS surface resistance, the effect of subgap states and trapped vortices on the residual surface resistance at low RF fields, and a nonlinear surface resistance at strong fields, particularly the effect of the RF field suppression of the surface resistance. These issues are essential for the understanding of the field dependence of high quality factors Q({B}a)∼ {10}10{--}{10}11 achieved on the Nb cavities at 1.3–2 K in strong RF fields B a close to the depairing limit, and the extended Q({B}a) rise which has been observed on Ti and N-treated Nb cavities. Possible ways of further increase of Q({B}a) and the breakdown field by optimizing impurity concentration at the surface and by multilayer nanostructuring with materials other than Nb are discussed.

  20. Hollow waveguide cavity ringdown spectroscopy

    Science.gov (United States)

    Dreyer, Chris (Inventor); Mungas, Greg S. (Inventor)

    2012-01-01

    Laser light is confined in a hollow waveguide between two highly reflective mirrors. This waveguide cavity is used to conduct Cavity Ringdown Absorption Spectroscopy of loss mechanisms in the cavity including absorption or scattering by gases, liquid, solids, and/or optical elements.

  1. Spectral and surface investigations of Ca{sub 2}V{sub 2}O{sub 7}:Eu{sup 3+} nanophosphors prepared by citrate-gel combustion method: a potential red-emitting phosphor for near-UV light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Vinay [Shri Mata Vaishno Devi University, School of Physics, Katra, J and K (India); University of the Free State, Department of Physics, P.O. Box 339, Bloemfontein (South Africa); Bedyal, A.K.; Sharma, J. [Shri Mata Vaishno Devi University, School of Physics, Katra, J and K (India); Kumar, V.; Ntwaeaborwa, O.M.; Swart, H.C. [University of the Free State, Department of Physics, P.O. Box 339, Bloemfontein (South Africa)

    2014-09-15

    In the present work, red-emitting Ca{sub 2}V{sub 2}O{sub 7}:xEu{sup 3+} (x = 0.5-6.0 mol%) nanophosphors, in the form of powders, were synthesized by the citrate-gel combustion method using metal nitrates as precursors and citric acid as fuel. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy, photoluminescence (PL) and cathodoluminescence (CL) spectroscopy were used to study the structure, morphology and spectral properties of the samples. The chemical compositions and electronic states of the powders were analyzed with X-ray photoelectron spectroscopy. The average crystallite sizes estimated using the XRD data were found to be in the range of 30-45 nm, and were cross verified by TEM. The lattice parameters determined by the POWD program were approximated as a = 7.242 Aa, b = 6.674 Aa, c = 6.932 Aa and V = 291.24 Aa{sup 3}, respectively. Under UV (395 nm) (PL) and electron (CL) excitation, the nanophosphors show characteristic emission from the Eu{sup 3+} ion ({sup 5}D{sub 0} → {sup 7}F{sub j}, j = 1-5) with the main peaks at 612 and 616 nm. The maximum emission intensity was recorded from the sample with an Eu{sup 3+} concentration of 4 mol% and a critical energy distance of 19.084 Aa between the donor and the acceptor. Above this concentration, there was a reduction in the intensity due to dipole-dipole induced concentration quenching effects. The potential applications of this phosphor as a high color-purity phosphor in light-emitting diodes are evaluated. (orig.)

  2. Colloquium: cavity optomechanics

    CERN Multimedia

    2011-01-01

    Monday 14 November 2011, 17:00 Ecole de Physique, Auditoire Stueckelberg Université de Genève Cavity optomechanics: controlling micro mechanical oscillators with laser light Prof. Tobias Kippenberg EPFL, Lausanne Laser light can be used to cool and to control trapped ions, atoms and molecules at the quantum level. This has lead to spectacular advances such as the most precise atomic clocks. An outstanding frontier is the control with lasers of nano- and micro-mechancial systems. Recent advances in cavity optomechanics have allowed such elementary control for the first time, enabling mechanical systems to be ground state cooled leading to readout with quantum limited sensitivity and permitting to explore new device concepts resulting from radiation pressure.  

  3. Access cavity preparation.

    Science.gov (United States)

    Adams, N; Tomson, P L

    2014-03-01

    Each stage of root canal treatment should be carried out to the highest possible standard. The access cavity is arguably the most important technical stage, as subsequent preparation of the root canal(s) can be severely comprised if this is not well executed. Inadequate access can lead to canals being left untreated, poorly disinfected, difficult to shape and obturate, and may ultimately lead to the failure of the treatment. This paper highlights common features in root canal anatomy and outlines basic principles for locating root canals and producing a good access cavity. It also explores each phase of the preparation in detail and offers suggestions of instruments that have been specifically designed to overcome potential difficulties in the process. Good access design and preparation will result in an operative environment which will facilitate cleaning, shaping and obturation of the root canal system in order to maximise success.

  4. Cavity enhanced atomic magnetometry

    CERN Document Server

    Crepaz, Herbert; Dumke, Rainer

    2015-01-01

    Atom sensing based on Faraday rotation is an indispensable method for precision measurements, universally suitable for both hot and cold atomic systems. Here we demonstrate an all-optical magnetometer where the optical cell for Faraday rotation spectroscopy is augmented with a low finesse cavity. Unlike in previous experiments, where specifically designed multipass cells had been employed, our scheme allows to use conventional, spherical vapour cells. Spherical shaped cells have the advantage that they can be effectively coated inside with a spin relaxation suppressing layer providing long spin coherence times without addition of a buffer gas. Cavity enhancement shows in an increase in optical polarization rotation and sensitivity compared to single-pass configurations.

  5. Cavity enhanced atomic magnetometry.

    Science.gov (United States)

    Crepaz, Herbert; Ley, Li Yuan; Dumke, Rainer

    2015-10-20

    Atom sensing based on Faraday rotation is an indispensable method for precision measurements, universally suitable for both hot and cold atomic systems. Here we demonstrate an all-optical magnetometer where the optical cell for Faraday rotation spectroscopy is augmented with a low finesse cavity. Unlike in previous experiments, where specifically designed multipass cells had been employed, our scheme allows to use conventional, spherical vapour cells. Spherical shaped cells have the advantage that they can be effectively coated inside with a spin relaxation suppressing layer providing long spin coherence times without addition of a buffer gas. Cavity enhancement shows in an increase in optical polarization rotation and sensitivity compared to single-pass configurations.

  6. Microleakage of composite resin restoration in cavities prepared by Er,Cr:YSGG laser irradiation and etched bur cavities in primary teeth.

    Science.gov (United States)

    Hossain, Mozammal; Nakamura, Yukio; Yamada, Yoshishige; Murakami, Yoshiko; Matsumoto, Koukichi

    2002-01-01

    In this in vitro study, the surface alterations of enamel and dentin in cavities prepared by Er,Cr:YSGG laser irradiation was investigated by scanning electron microscopy and compared to the microleakage degree after composite resin restoration with etched bur cavities in human primary teeth. The results confirmed that laser cavity surface facilitated a good adhesion with the restorative materials; the acid etch step can be easily avoided with the laser treatment.

  7. Cavity enhanced atomic magnetometry

    OpenAIRE

    Herbert Crepaz; Li Yuan Ley; Rainer Dumke

    2015-01-01

    Atom sensing based on Faraday rotation is an indispensable method for precision measurements, universally suitable for both hot and cold atomic systems. Here we demonstrate an all-optical magnetometer where the optical cell for Faraday rotation spectroscopy is augmented with a low finesse cavity. Unlike in previous experiments, where specifically designed multipass cells had been employed, our scheme allows to use conventional, spherical vapour cells. Spherical shaped cells have the advantage...

  8. Crab Cavities for Linear Colliders

    Energy Technology Data Exchange (ETDEWEB)

    Burt, G.; Ambattu, P.; Carter, R.; Dexter, A.; Tahir, I.; /Cockcroft Inst. Accel. Sci. Tech. /Lancaster U.; Beard, C.; Dykes, M.; Goudket, P.; Kalinin, A.; Ma, L.; McIntosh, P.; /Daresbury; Shulte, D.; /CERN; Jones, Roger M.; /Cockcroft Inst. Accel. Sci. Tech. /Manchester U.; Bellantoni, L.; Chase, B.; Church, M.; Khabouline, T.; Latina, A.; /Fermilab; Adolphsen, C.; Li, Z.; Seryi, Andrei; /SLAC

    2011-11-08

    Crab cavities have been proposed for a wide number of accelerators and interest in crab cavities has recently increased after the successful operation of a pair of crab cavities in KEK-B. In particular crab cavities are required for both the ILC and CLIC linear colliders for bunch alignment. Consideration of bunch structure and size constraints favour a 3.9 GHz superconducting, multi-cell cavity as the solution for ILC, whilst bunch structure and beam-loading considerations suggest an X-band copper travelling wave structure for CLIC. These two cavity solutions are very different in design but share complex design issues. Phase stabilisation, beam loading, wakefields and mode damping are fundamental issues for these crab cavities. Requirements and potential design solutions will be discussed for both colliders.

  9. Crab cavities for linear colliders

    CERN Document Server

    Burt, G; Carter, R; Dexter, A; Tahir, I; Beard, C; Dykes, M; Goudket, P; Kalinin, A; Ma, L; McIntosh, P; Shulte, D; Jones, Roger M; Bellantoni, L; Chase, B; Church, M; Khabouline, T; Latina, A; Adolphsen, C; Li, Z; Seryi, Andrei; Xiao, L

    2008-01-01

    Crab cavities have been proposed for a wide number of accelerators and interest in crab cavities has recently increased after the successful operation of a pair of crab cavities in KEK-B. In particular crab cavities are required for both the ILC and CLIC linear colliders for bunch alignment. Consideration of bunch structure and size constraints favour a 3.9 GHz superconducting, multi-cell cavity as the solution for ILC, whilst bunch structure and beam-loading considerations suggest an X-band copper travelling wave structure for CLIC. These two cavity solutions are very different in design but share complex design issues. Phase stabilisation, beam loading, wakefields and mode damping are fundamental issues for these crab cavities. Requirements and potential design solutions will be discussed for both colliders.

  10. High Gradient Accelerator Cavities Using Atomic Layer Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ives, Robert Lawrence [Calabazas Creek Research, Inc., San Mateo, CA (United States); Parsons, Gregory [North Carolina State Univ., Raleigh, NC (United States); Williams, Philip [North Carolina State Univ., Raleigh, NC (United States); Oldham, Christopher [North Carolina State Univ., Raleigh, NC (United States); Mundy, Zach [North Carolina State Univ., Raleigh, NC (United States); Dolgashev, Valery [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2014-12-09

    In the Phase I program, Calabazas Creek Research, Inc. (CCR), in collaboration with North Carolina State University (NCSU), fabricated copper accelerator cavities and used Atomic Layer Deposition (ALD) to apply thin metal coatings of tungsten and platinum. It was hypothesized that a tungsten coating would provide a robust surface more resistant to arcing and arc damage. The platinum coating was predicted to reduce processing time by inhibiting oxides that form on copper surfaces soon after machining. Two sets of cavity parts were fabricated. One was coated with 35 nm of tungsten, and the other with approximately 10 nm of platinum. Only the platinum cavity parts could be high power tested during the Phase I program due to schedule and funding constraints. The platinum coated cavity exhibit poor performance when compared with pure copper cavities. Not only did arcing occur at lower power levels, but the processing time was actually longer. There were several issues that contributed to the poor performance. First, machining of the base copper cavity parts failed to achieve the quality and cleanliness standards specified to SLAC National Accelerator Center. Secondly, the ALD facilities were not configured to provide the high levels of cleanliness required. Finally, the nanometer coating applied was likely far too thin to provide the performance required. The coating was ablated or peeled from the surface in regions of high fields. It was concluded that the current ALD process could not provide improved performance over cavities produced at national laboratories using dedicated facilities.

  11. High Quality RF resonant cavity for high gradient linacs

    CERN Document Server

    TianXiu-fang,; Deguo, Xun; Kun, Liu; yong, Hou; Jian, Cheng

    2015-01-01

    In traditional accelerating structures, maximum amplitudes of accelerating fields are restricted by Joule heating losses in conducting walls and electron breakdown. In this paper, a composite accelerating cavity utilizing a resonant, periodic structure with a dielectric sphere located at a spherical conducting cavity center is presented. The presence of the dielectric in the central part of the resonance cavity shifts the magnetic fields maximum from regions close to the metallic wall towards the dielectric surface, which strongly lowers the skin effect losses in the wall. By using the existing ultra-low loss Sapphire dielectrics, we make theory analyze and numerical calculations by MATLAB, and further make simulated calculation by CST for comparison. The results show that all field components at the metallic wall are either zero or very small, so one can expect the cavity to be less prone to electrical breakdowns than the traditional cavity. And the quality factor Q can be three orders of magnitude higher th...

  12. Thermal Model of a Dish Stirling Cavity-Receiver

    Directory of Open Access Journals (Sweden)

    Rubén Gil

    2015-01-01

    Full Text Available This paper presents a thermal model for a dish Stirling cavity based on the finite differences method. This model is a theoretical tool to optimize the cavity in terms of thermal efficiency. One of the main outcomes of this work is the evaluation of radiative exchange using the radiosity method; for that purpose, the view factors of all surfaces involved have been accurately calculated. Moreover, this model enables the variation of the cavity and receiver dimensions and the materials to determine the optimal cavity design. The tool has been used to study the cavity optimization regarding geometry parameters and material properties. Receiver absorptivity has been identified as the most influential property of the materials. The optimal aperture height depends on the minimum focal space.

  13. Ionization wave propagation on a micro cavity plasma array

    CERN Document Server

    Wollny, Alexander; Gebhardt, Markus; Brinkmann, Ralf Peter; Boettner, Henrik; Winter, Joerg; der Gathen, Volker Schulz-von; Mussenbrock, Thomas

    2011-01-01

    Microcavity plasma arrays are regular arrays of inverse pyramidal cavities created on positive doped silicon wafers. Each cavity acts as a microscopic dielectric barrier discharge. Operated at atmospheric pressure in argon and excited with high voltage at about 10 kHz frequency each cavity develops a localized microplasma. Experiments show a strong interaction of the individual cavities, leading to the propagation of wave-like emission structures along the array surface. This paper studies the ignition process of a micro cavity plasma array by means of a numerical simulation and confirms the experimental results. The propagation of an ionization wave is observed. Its propagation speed of 1 km/s matches experimental findings.

  14. Apparatus and process for passivating an SRF cavity

    Science.gov (United States)

    Myneni, Ganapati Rao; Wallace, John P

    2014-12-02

    An apparatus and process for the production of a niobium cavity exhibiting high quality factors at high gradients is provided. The apparatus comprises a first chamber positioned within a second chamber, an RF generator and vacuum pumping systems. The process comprises placing the niobium cavity in a first chamber of the apparatus; thermally treating the cavity by high temperature in the first chamber while maintaining high vacuum in the first and second chambers; and applying a passivating thin film layer to a surface of the cavity in the presence of a gaseous mixture and an RF field. Further a niobium cavity exhibiting high quality factors at high gradients produced by the method of the invention is provided.

  15. Magnetic Flux Expulsion Studies in Niobium SRF Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Posen, Sam [Fermilab; Checchin, Mattia [Fermilab; Crawford, Anthony [Fermilab; Grassellino, Anna [Fermilab; Martinello, Martina [Fermilab; Melnychuk, Oleksandr [Fermilab; Romanenko, Alexander [Fermilab; Sergatskov, Dmitri [Fermilab; Trenikhina, Yulia [Fermilab

    2016-06-01

    With the recent discovery of nitrogen doping treatment for SRF cavities, ultra-high quality factors at medium accelerating fields are regularly achieved in vertical RF tests. To preserve these quality factors into the cryomodule, it is important to consider background magnetic fields, which can become trapped in the surface of the cavity during cooldown and cause Q₀ degradation. Building on the recent discovery that spatial thermal gradients during cooldown can significantly improve expulsion of magnetic flux, a detailed study was performed of flux expulsion on two cavities with different furnace treatments that are cooled in magnetic fields amplitudes representative of what is expected in a realistic cryomodule. In this contribution, we summarize these cavity results, in order to improve understanding of the impact of flux expulsion on cavity performance.

  16. Development of a cavity enhanced aerosol albedometer

    Directory of Open Access Journals (Sweden)

    W. Zhao

    2014-03-01

    Full Text Available We report on the development of a cavity enhanced aerosol single scattering albedometer incorporating incoherent broad-band cavity-enhanced spectroscopy (IBBCEAS approach and an integrating sphere (IS for simultaneous in situ measurements of aerosol scattering and extinction coefficients in the exact same sample volume. The cavity enhanced albedometer employed a blue light-emitting diode (LED based IBBCEAS approach for the measurement of wavelength-resolved aerosol optical extinction over the spectral range of 445–480 nm. An integrating sphere nephelometer coupled to the IBBCEAS setup was used for the measurement of aerosol scattering. The scattering signal was measured with a single channel photomultiplier tube (PMT, providing an integrated value over a narrow bandwidth (FWHM ~ 9 nm in the spectral region of 465–474 nm. A scattering coefficient at a wavelength of 470 nm was deduced as an averaged scattering value and used for data analysis and instrumental performance comparison. Performance evaluation of the albedometer was carried out using laboratory-generated particles and ambient aerosol. The scattering and extinction measurements of monodisperse polystyrene latex (PSL spheres generated in laboratory proved excellent correlation between two channels of the albedometer. The retrieved refractive index (RI from the measured scattering and extinction efficiencies agreed well with the values reported in previously published papers. Aerosol light scattering and extinction coefficients, single scattering albedo (SSA and NO2 concentrations in an ambient sample were directly and simultaneously measured using the developed albedometer. The developed instrument was validated via an intercomparison of the measured aerosol scattering coefficient and NO2 trace concentration against a TSI 3563 integrating nephelometer and a chemiluminescence detector, respectively.

  17. Radiation emission from the "Rhodotron-TT200" cavity

    Institute of Scientific and Technical Information of China (English)

    Farshid Tabbakh; Mahmud Borhani

    2011-01-01

    In this paper, the X-rays emitted from the Rhodotron-TT200 cavity have been studied in depth. We found that the Bremsstrahlung interaction is the only contribution of X-ray generation important to safety. The X-ray dose rate in the Rhodotron vault is calc

  18. Tunable mode-locked semiconductor laser with Bragg mirror external cavity

    DEFF Research Database (Denmark)

    Yvind, Kresten; Jørgensen, T.; Birkedal, Dan

    2002-01-01

    We present a simplified design for a wavelength tunable external cavity mode-locked laser by employing a wedged GaAs/AlGaAs Bragg mirror. The device emits 4-6 ps pulses at 10 GHz and is tunable over 15 nm. Although, in the present configuration, tunability is limited to 15 nm, however, we have...

  19. Study of multipacting effect in superconducting cavity

    Institute of Scientific and Technical Information of China (English)

    ZHANG Meng; ZHAO Ming-Hua

    2008-01-01

    A number of superconducting cavities of axis-symmetric geometry have been considered to study the effect in order to achieve the desired performance.It is shown that the multipacting effect is strongly dependent on the condition of the RF surface and can be suppressed with reconsideration of the geometry.The simulation result is compared with the result of the semi-analytical model in the end.

  20. ISR RF cavities

    CERN Multimedia

    1983-01-01

    In each ISR ring the radiofrequency cavities were installed in one 9 m long straight section. The RF system of the ISR had the main purpose to stack buckets of particles (most of the time protons)coming from the CPS and also to accelerate the stacked beam. The installed RF power per ring was 18 kW giving a peak accelerating voltage of 20 kV. The system had a very fine regulation feature allowing to lower the voltage down to 75 V in a smooth and well controlled fashion.

  1. Cavity Optomechanical Magnetometer

    CERN Document Server

    Forstner, S; Knittel, J; van Ooijen, E D; Swaim, J D; Harris, G I; Szorkovszky, A; Bowen, W P; Rubinsztein-Dunlop, H

    2011-01-01

    A cavity optomechanical magnetometer is demonstrated where the magnetic field induced expansion of a magnetostrictive material is transduced onto the physical structure of a highly compliant optical microresonator. The resulting motion is read out optically with ultra-high sensitivity. Detecting the magnetostrictive deformation of Terfenol-D with a toroidal whispering gallery mode (TWGM) resonator a peak sensitivity of 400 nT/Hz^.5 was achieved with theoretical modelling predicting that sensitivities of up to 500 fT/Hz^.5 may be possible. This chip-based magnetometer combines high-sensitivity and large dynamic range with small size and room temperature operation.

  2. Cavity optomechanical magnetometer.

    Science.gov (United States)

    Forstner, S; Prams, S; Knittel, J; van Ooijen, E D; Swaim, J D; Harris, G I; Szorkovszky, A; Bowen, W P; Rubinsztein-Dunlop, H

    2012-03-23

    A cavity optomechanical magnetometer is demonstrated. The magnetic-field-induced expansion of a magnetostrictive material is resonantly transduced onto the physical structure of a highly compliant optical microresonator and read out optically with ultrahigh sensitivity. A peak magnetic field sensitivity of 400  nT  Hz(-1/2) is achieved, with theoretical modeling predicting the possibility of sensitivities below 1  pT  Hz(-1/2). This chip-based magnetometer combines high sensitivity and large dynamic range with small size and room temperature operation.

  3. Evaluation of Cavity Collapse and Surface Crater Formation at the Norbo Underground Nuclear Test in U8c, Nevada Nuclear Security Site, and the Impact on Stability of the Ground Surface

    Energy Technology Data Exchange (ETDEWEB)

    Pawloski, G A

    2012-06-18

    Lawrence Livermore National Laboratory (LLNL) Containment Program performed a review of nuclear test-related data for the Norbo underground nuclear test in U8c to assist in evaluating this legacy site as a test bed for application technologies for use in On-Site Inspections (OSI) under the Comprehensive Nuclear Test Ban Treaty. This request is similar to one made for the Salut site in U8c (Pawloski, 2012b). Review of the Norbo site is complicated because the test first exhibited subsurface collapse, which was not unusual, but it then collapsed to the surface over one year later, which was unusual. Of particular interest is the stability of the ground surface above the Norbo detonation point. Proposed methods for on-site verification include radiological signatures, artifacts from nuclear testing activities, and imaging to identify alteration to the subsurface hydrogeology due to the nuclear detonation. Aviva Sussman from the Los Alamos National Laboratory (LANL) has also proposed work at this site. Both proposals require physical access at or near the ground surface of specific underground nuclear test locations at the Nevada Nuclear Security Site (NNSS), formerly the Nevada Test Site (NTS), and focus on possible activities such as visual observation, multispectral measurements, and shallow and deep geophysical surveys.

  4. Evaluation of Cavity Collapse and Surface Crater Formation at the Salut Underground Nuclear Test in U20ak, Nevada National Security Site, and the Impact of Stability of the Ground Surface

    Energy Technology Data Exchange (ETDEWEB)

    Pawloski, G A

    2012-04-25

    At the request of Jerry Sweeney, the LLNL Containment Program performed a review of nuclear test-related data for the Salut underground nuclear test in U20ak to assist in evaluating this legacy site as a test bed for application technologies for use in On-Site Inspections (OSI) under the Comprehensive Nuclear Test Ban Treaty. Review of the Salut site is complicated because the test experienced a subsurface, rather than surface, collapse. Of particular interest is the stability of the ground surface above the Salut detonation point. Proposed methods for on-site verification include radiological signatures, artifacts from nuclear testing activities, and imaging to identify alteration to the subsurface hydrogeologogy due to the nuclear detonation. Sweeney's proposal requires physical access at or near the ground surface of specific underground nuclear test locations at the Nevada Nuclear Test Site (NNSS, formerly the Nevada Test Site), and focuses on possible activities such as visual observation, multispectral measurements, and shallow, and deep geophysical surveys.

  5. Centrifugal barrel polishing of 1.3 GHz Nb cavities

    Energy Technology Data Exchange (ETDEWEB)

    Tamashevich, Yegor; Foster, Brian [DESY, Hamburg (Germany); Hamburg Univ. (Germany); Navitski, Aliaksandr; Steder, Lea; Elsen, Eckhard [DESY, Hamburg (Germany)

    2013-07-01

    Superconducting radio-frequency (SRF) cavities are the key components of particle accelerators such as the European X-ray Free Electron Laser (XFEL, under construction) and the planned future International Linear Collider (ILC). Steady progress in surface treatment techniques of SRF cavities in both the achievable quality factor Q and the accelerating electric field Eacc makes new accelerators and ambitious projects feasible. One of the alternative surface preparation techniques which is actually being explored is centrifugal barrel polishing (CBP) pioneered at KEK in Japan in mid-nineties by T. Hiuchi et al. CBP is a mechanical polishing of cavities and results in around 10 x smaller surface roughness and mirror-like surface as compared to chemistry alone. Q and E{sub acc} are expected to be at least as high as for chemically treated cavities. CBP eliminates the bulk chemistry and has the potential to completely replace the chemistry. The University of Hamburg is installing a CBP machine to study it as a cavity preparation and repair technique for 9-cell 1.3 GHz SRF cavities at the Deutsche Elektronen-Synchrotron (DESY). The setup and first commissioning tests will be presented and discussed.

  6. Development of the superconducting 3.9-GHz accelerating cavity at Fermilab

    Energy Technology Data Exchange (ETDEWEB)

    Arkan, T.; Bauer, P.; Bellantoni, L.; Boffo, C.; Borissov, E.; Carter, H.; Edwards, H.; Foley, M.; Gonin, I.; Khabibouline, T.; Mishra, S.; Mitchell, D.; Polubotko, V.; Rowe, A.; Solyak, N.; Terechkine, I.; /Fermilab

    2005-05-01

    A superconducting third harmonic 3.9 GHz accelerating cavity was proposed to improve the beam quality in the TTF-like photoinjector [1]. Fermilab has developed, built and tested several prototypes, including two copper 9-cell cavities, one niobium 3-cell cavity, and one 9-cell cavity. The helium vessel and frequency tuner for the 9-cell cavity was built and tested as well. In cold tests, we achieved a peak surface magnetic field of {approx}100mT, well above the 70mT specification. The accelerating gradient was likely limited by thermal breakdown. Studies of the higher order modes in the cavity revealed that the existing cavity design with two HOM couplers will provide sufficient damping of these modes. In this paper we discuss the cavity design, results of the studies and plans for further development.

  7. Open Microwave Cavity for use in a Purcell Enhancement Cooling Scheme

    CERN Document Server

    Evetts, N; Bizzotto, D; Longuevergne, D; Hardy, W N

    2016-01-01

    A microwave cavity is described which can be used to cool lepton plasmas for potential use in synthesis of antihydrogen. The cooling scheme is an incarnation of the Purcell Effect: when plasmas are coupled to a microwave cavity, the plasma cooling rate is resonantly enhanced through increased spontaneous emission of cyclotron radiation. The cavity forms a three electrode section of a Penning-Malmberg trap and has a bulged cylindrical geometry with open ends aligned with the magnetic trapping axis. This allows plasmas to be injected and removed from the cavity without the need for moving parts while maintaining high quality factors for resonant modes. The cavity includes unique surface preparations for adjusting the cavity quality factor and achieving anti-static shielding using thin layers of nichrome and colloidal graphite respectively. Geometric design considerations for a cavity with strong cooling power and low equilibrium plasma temperatures are discussed. Cavities of this weak-bulge design will be appli...

  8. RF breakdown of 805 MHz cavities in strong magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Bowring, D. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Stratakis, D. [Brookhaven National Lab. (BNL), Upton, NY (United States); Kochemirovskiy, A. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Leonova, M. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Moretti, A. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Palmer, M. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Peterson, D. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Yonehara, K. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Freemire, B. [Illinois Inst. of Technology, Chicago, IL (United States); Lane, P. [Illinois Inst. of Technology, Chicago, IL (United States); Torun, Y. [Illinois Inst. of Technology, Chicago, IL (United States); Haase, A. [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-05-03

    Ionization cooling of intense muon beams requires the operation of high-gradient, normal-conducting RF structures in the presence of strong magnetic fields. We have measured the breakdown rate in several RF cavities operating at several frequencies. Cavities operating within solenoidal magnetic fields B > 0.25 T show an increased RF breakdown rate at lower gradients compared with similar operation when B = 0 T. Ultimately, this breakdown behavior limits the maximum safe operating gradient of the cavity. Beyond ionization cooling, this issue affects the design of photoinjectors and klystrons, among other applications. We have built an 805 MHz pillbox-type RF cavity to serve as an experimental testbed for this phenomenon. This cavity is designed to study the problem of RF breakdown in strong magnetic fields using various cavity materials and surface treatments, and with precise control over sources of systematic error. We present results from tests in which the cavity was run with all copper surfaces in a variety of magnetic fields.

  9. Applications of cavity optomechanics

    Energy Technology Data Exchange (ETDEWEB)

    Metcalfe, Michael [Booz Allen Hamilton, 3811 Fairfax Drive, Arlington, Virginia 22203 (United States)

    2014-09-15

    Cavity-optomechanics” aims to study the quantum properties of mechanical systems. A common strategy implemented in order to achieve this goal couples a high finesse photonic cavity to a high quality factor mechanical resonator. Then, using feedback forces such as radiation pressure, one can cool the mechanical mode of interest into the quantum ground state and create non-classical states of mechanical motion. On the path towards achieving these goals, many near-term applications of this field have emerged. After briefly introducing optomechanical systems and describing the current state-of-the-art experimental results, this article summarizes some of the more exciting practical applications such as ultra-sensitive, high bandwidth accelerometers and force sensors, low phase noise x-band integrated microwave oscillators and optical signal processing such as optical delay-lines, wavelength converters, and tunable optical filters. In this rapidly evolving field, new applications are emerging at a fast pace, but this article concentrates on the aforementioned lab-based applications as these are the most promising avenues for near-term real-world applications. New basic science applications are also becoming apparent such as the generation of squeezed light, testing gravitational theories and for providing a link between disparate quantum systems.

  10. Applications of cavity optomechanics

    Science.gov (United States)

    Metcalfe, Michael

    2014-09-01

    "Cavity-optomechanics" aims to study the quantum properties of mechanical systems. A common strategy implemented in order to achieve this goal couples a high finesse photonic cavity to a high quality factor mechanical resonator. Then, using feedback forces such as radiation pressure, one can cool the mechanical mode of interest into the quantum ground state and create non-classical states of mechanical motion. On the path towards achieving these goals, many near-term applications of this field have emerged. After briefly introducing optomechanical systems and describing the current state-of-the-art experimental results, this article summarizes some of the more exciting practical applications such as ultra-sensitive, high bandwidth accelerometers and force sensors, low phase noise x-band integrated microwave oscillators and optical signal processing such as optical delay-lines, wavelength converters, and tunable optical filters. In this rapidly evolving field, new applications are emerging at a fast pace, but this article concentrates on the aforementioned lab-based applications as these are the most promising avenues for near-term real-world applications. New basic science applications are also becoming apparent such as the generation of squeezed light, testing gravitational theories and for providing a link between disparate quantum systems.

  11. Spectroscopic evaluation of photodynamic therapy of the intraperitoneal cavity

    Science.gov (United States)

    Finlay, Jarod C.; Sandell, Julia L.; Zhu, Timothy C.; Lewis, Robert; Cengel, Keith A.; Hahn, Stephen M.

    2015-01-01

    We present the results of spectroscopic measurements of diffuse reflectance and fluorescence before and after photodynamic therapy of healthy canine peritoneal cavity. Animals were treated intra-operatively after iv injection of the benzoporphyrin derivative (BPD). The small bowel was treated using a uniform light field projected by a microlenstipped fiber. The cavity was then filled with scattering medium and the remaining organs were treated using a moving diffuser. Diffuse reflectance and fluorescence measurements were made using a multi-fiber optical probe positioned on the surface of various tissues within the cavity before and after illumination. The measured data were analyzed to quantify hemoglobin concentration and oxygenation and sensitizer concentration. PMID:26028798

  12. Slotted photonic crystal cavities with integrated microfluidics for biosensing applications.

    Science.gov (United States)

    Scullion, M G; Di Falco, A; Krauss, T F

    2011-09-15

    We demonstrate the detection of dissolved avidin concentrations as low as 15 nM or 1 μg/ml using functionalized slotted photonic crystal cavities with integrated microfluidics. With a cavity sensing surface area of approximately 2.2 μm(2), we are able to detect surface mass densities of order 60 pg/mm(2) corresponding to a bound mass of approximately 100 ag. The ultra-compact size of the sensors makes them attractive for lab-on-a-chip applications where high densities of independent sensing elements are desired within a small area. The high sensitivity over an extremely small area is due to the strong modal overlap with the analyte enabled by the slotted waveguide cavity geometry that we employ. This strong overlap results in larger shifts in the cavity peak wavelength when compared to competing approaches.

  13. Nanostructure surface patterning of GaN thin films and application to AlGaN/AlN multiple quantum wells: A way towards light extraction efficiency enhancement of III-nitride based light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Wei, E-mail: wguo2@ncsu.edu; Kirste, Ronny; Bryan, Zachary; Bryan, Isaac; Collazo, Ramón; Sitar, Zlatko [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7919 (United States); Gerhold, Michael [Engineering Science Directorate, Army Research Office, Research Triangle Park, North Carolina 27703 (United States)

    2015-03-21

    Enhanced light extraction efficiency was demonstrated on nanostructure patterned GaN and AlGaN/AlN Multiple-Quantum-Well (MQW) structures using mass production techniques including natural lithography and interference lithography with feature size as small as 100 nm. Periodic nanostructures showed higher light extraction efficiency and modified emission profile compared to non-periodic structures based on integral reflection and angular-resolved transmission measurement. Light extraction mechanism of macroscopic and microscopic nanopatterning is discussed, and the advantage of using periodic nanostructure patterning is provided. An enhanced photoluminescence emission intensity was observed on nanostructure patterned AlGaN/AlN MQW compared to as-grown structure, demonstrating a large-scale and mass-producible pathway to higher light extraction efficiency in deep-ultra-violet light-emitting diodes.

  14. Synergetic electrode architecture for efficient graphene-based flexible organic light-emitting diodes

    Science.gov (United States)

    Lee, Jaeho; Han, Tae-Hee; Park, Min-Ho; Jung, Dae Yool; Seo, Jeongmin; Seo, Hong-Kyu; Cho, Hyunsu; Kim, Eunhye; Chung, Jin; Choi, Sung-Yool; Kim, Taek-Soo; Lee, Tae-Woo; Yoo, Seunghyup

    2016-06-01

    Graphene-based organic light-emitting diodes (OLEDs) have recently emerged as a key element essential in next-generation displays and lighting, mainly due to their promise for highly flexible light sources. However, their efficiency has been, at best, similar to that of conventional, indium tin oxide-based counterparts. We here propose an ideal electrode structure based on a synergetic interplay of high-index TiO2 layers and low-index hole-injection layers sandwiching graphene electrodes, which results in an ideal situation where enhancement by cavity resonance is maximized yet loss to surface plasmon polariton is mitigated. The proposed approach leads to OLEDs exhibiting ultrahigh external quantum efficiency of 40.8 and 62.1% (64.7 and 103% with a half-ball lens) for single- and multi-junction devices, respectively. The OLEDs made on plastics with those electrodes are repeatedly bendable at a radius of 2.3 mm, partly due to the TiO2 layers withstanding flexural strain up to 4% via crack-deflection toughening.

  15. Light emitting diode with high aspect ratio submicron roughness for light extraction and methods of forming

    Science.gov (United States)

    Li, Ting

    2013-08-13

    The surface morphology of an LED light emitting surface is changed by applying a reactive ion etch (RIE) process to the light emitting surface. High aspect ratio, submicron roughness is formed on the light emitting surface by transferring a thin film metal hard-mask having submicron patterns to the surface prior to applying a reactive ion etch process. The submicron patterns in the metal hard-mask can be formed using a low cost, commercially available nano-patterned template which is transferred to the surface with the mask. After subsequently binding the mask to the surface, the template is removed and the RIE process is applied for time duration sufficient to change the morphology of the surface. The modified surface contains non-symmetric, submicron structures having high aspect ratio which increase the efficiency of the device.

  16. Performance evaluation of the cavities on nucleate boiling at microscale level

    CERN Document Server

    Mu, Yu-Tong; Kang, Qinjun; Tao, Wen-Quan

    2015-01-01

    Nucleate boiling heat transfer (NBHT) from enhanced structures is an effective way to dissipate high heat flux. In the present study, the cavities behaviours for nucleation on roughened surface are numerically studied on the entire ebullition cycle based on a phase-change lattice Boltzmann method without introducing any artificial disturbances. The adopted model is firstly validated with the Laplace law and the two phase coexistence curve, and then applied to investigate the effects of cavity structure on NBHT. The bubble departure diameter, departure frequency and total boiling heat flux of an ebullition cycle are also explored. It is demonstrated that the cavity widths and the cavity grooves show significant influence on the features of NBHT. Cavity with circular groove in the present research shows the best performance for NBHT in terms of the averaged heat flux and bubble release frequency. When a specific cavity is combined with other different cavities on roughened surfaces its nucleation process on dif...

  17. Three-dimensional self-consistent simulations of multipacting in superconducting radio frequency cavities

    Energy Technology Data Exchange (ETDEWEB)

    Chet Nieter

    2010-12-01

    Superconducting radio frequency (SRF) cavities are a popular choice among researchers designing new accelerators because of the reduced power losses due to surface resistance. However, SRF cavities still have unresolved problems, including the loss of power to stray electrons. Sources of these electrons are field emission from the walls and ionization of background gas, but the predominant source is secondary emission yield (SEY) from electron impact. When the electron motion is in resonance with the cavity fields the electrons strike the cavity surface repeatedly creating a resonant build up of electrons referred to as multipacting. Cavity shaping has successfully reduced multipacting for cavities used in very high energy accelerators. However, multipacting is still a concern for the cavity power couplers, where shaping is not possible, and for cavities used to accelerate particles at moderate velocities. This Phase II project built upon existing models in the VORPAL simulation framework to allow for simulations of multipacting behavior in SRF cavities and their associated structures. The technical work involved allowed existing models of secondary electron generation to work with the complex boundary conditions needed to model the cavity structures. The types of data produced by VORPAL were also expanded to include data common used by cavity designers to evaluate cavity performance. Post-processing tools were also modified to provide information directly related to the conditions that produce multipacting. These new methods were demonstrated by running simulations of a cavity design being developed by researchers at Jefferson National Laboratory to attempt to identify the multipacting that would be an issue for the cavity design being considered. These simulations demonstrate that VORPAL now has the capabilities to assist researchers working with SRF cavities to understand and identify possible multipacting issues with their cavity designs.

  18. JLEIC SRF cavity RF Design

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Shaoheng [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Guo, Jiquan [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Wang, Haipeng [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Rimmer, Robert A. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

    2016-05-01

    The initial design of a low higher order modes (HOM) impedance superconducting RF (SRF) cavity is presented in this paper. The design of this SRF cavity is for the proposed Jefferson Lab Electron Ion Collider (JLEIC). The electron ring of JLEIC will operate with electrons of 3 to 10 GeV energy. The ion ring of JLEIC will operate with protons of up to 100 GeV energy. The bunch lengths in both rings are ~12 mm (RMS). In order to maintain the short bunch length in the ion ring, SRF cavities are adopted to provide large enough gradient. In the first phase of JLEIC, the PEP II RF cavities will be reused in the electron ring to lower the initial cost. The frequency of the SRF cavities is chosen to be the second harmonic of PEP II cavities, 952.6 MHz. In the second phase of JLEIC, the same frequency SRF cavities may replace the normal conducting PEP II cavities to achieve higher luminosity at high energy. At low energies, the synchro-tron radiation damping effect is quite weak, to avoid the coupled bunch instability caused by the intense closely-spaced electron bunches, low HOM impedance of the SRF cavities combined with longitudinal feedback sys-tem will be necessary.

  19. Cavity coalescence in superplastic deformation

    Energy Technology Data Exchange (ETDEWEB)

    Stowell, M.J.; Livesey, D.W.; Ridley, N.

    1984-01-01

    An analysis of the probability distribution function of particles randomly dispersed in a solid has been applied to cavitation during superplastic deformation and a method of predicting cavity coalescence developed. Cavity size distribution data were obtained from two microduplex nickel-silver alloys deformed superplastically to various extents at elevated temperature, and compared to theoretical predictions. Excellent agreement occurred for small void sizes but the model underestimated the number of voids in the largest size groups. It is argued that the discrepancy results from a combination of effects due to non-random cavity distributions and to enhanced growth rates and incomplete spheroidization of the largest cavities.

  20. Plasma Processing of SRF Cavities for the next Generation Of Particle Accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Vuskovic, Leposava

    2015-11-23

    The cost-effective production of high frequency accelerating fields are the foundation for the next generation of particle accelerators. The Ar/Cl2 plasma etching technology holds the promise to yield a major reduction in cavity preparation costs. Plasma-based dry niobium surface treatment provides an excellent opportunity to remove bulk niobium, eliminate surface imperfections, increase cavity quality factor, and bring accelerating fields to higher levels. At the same time, the developed technology will be more environmentally friendly than the hydrogen fluoride-based wet etching technology. Plasma etching of inner surfaces of standard multi-cell SRF cavities is the main goal of this research in order to eliminate contaminants, including niobium oxides, in the penetration depth region. Successful plasma processing of multi-cell cavities will establish this method as a viable technique in the quest for more efficient components of next generation particle accelerators. In this project the single-cell pill box cavity plasma etching system is developed and etching conditions are determined. An actual single cell SRF cavity (1497 MHz) is plasma etched based on the pill box cavity results. The first RF test of this plasma etched cavity at cryogenic temperature is obtained. The system can also be used for other surface modifications, including tailoring niobium surface properties, surface passivation or nitriding for better performance of SRF cavities. The results of this plasma processing technology may be applied to most of the current SRF cavity fabrication projects. In the course of this project it has been demonstrated that a capacitively coupled radio-frequency discharge can be successfully used for etching curved niobium surfaces, in particular the inner walls of SRF cavities. The results could also be applicable to the inner or concave surfaces of any 3D structure other than an SRF cavity.

  1. Plasmonic Structures for Sensing and Emitting Devices

    Science.gov (United States)

    Floris, Francesco; Fornasari, Lucia; Patrini, Maddalena; Figus, Cristiana; Mura, Andrea; Bongiovanni, Giovanni; Quochi, Francesco; Pellacani, Paola; Valsesia, Andrea; Marabelli, Franco

    2014-12-01

    We report on the study of a plasmonic nanostructure that could be adopted as platform for emitting and sensing applications. Several devices have been prepared and characterized by atomic force microscopy (AFM) and Fourier transform micro-reflectance (FT- pR) techniques. In addition, a modelling via finite-difference time-domain (FDTD) simulations have been developed in order to interpret the morphological shape and the optical response of the considered structures. Until now, remarkable performances as surface plasmon resonance (SPR) based optical sensor have been founded. Moreover, we are performing preliminary trials in order to establish a coupling between photoluminescence (PL) features of suitable emitters with respect to the plasmonic resonances.

  2. Shock wave diffraction and reflection around a dusty square cavity

    Institute of Scientific and Technical Information of China (English)

    王柏懿; 王超; 戚隆溪

    2001-01-01

    The diffraction and reflection of planar shock wave around a dusty square cavity is investigated nuerically, which is embedded in the flat bottom surface of a two-dimensional channel, and the induced gas-particle twophase flow. The wave patterns at different times are obtained for three different values of the particle diameter. The computational results show that the existence of particles affects appreciably the shock wave diffraction and cavity flow.

  3. Design of EPU oscillator cavity in femtosecond accelerator

    Institute of Scientific and Technical Information of China (English)

    BEI Hua; DENG Hai-Xiao; DAI Zhi-Min

    2009-01-01

    We adopt the groove guide as the cavity of the undulator to reduce the diffraction effect.The groove guide has the advantages of lower surface energy loss,larger power capacity,less modes,and larger structure dimension over the traditional method waveguide.The attenuation calculation is given in this paper including the cavity optimization.And the dispersive character indicates that the oscillator can work in different modes with the change of the electron beam energy.

  4. Result of MHI 2-Cell Seamless Dumb-Bell Cavity Vertical Test

    Energy Technology Data Exchange (ETDEWEB)

    Okihira, K. [Mitsubishi Heavy Industries, Ltd, Mihara, Hiroshima, 729-0393, Japan; Hara, H. [Mitsubishi Heavy Industries, Ltd, Mihara, Hiroshima, 729-0393, Japan; Ikeda, N. [Mitsubishi Heavy Industries, Ltd, Mihara, Hiroshima, 729-0393, Japan; Inoue, F. [Mitsubishi Heavy Industries, Ltd, Mihara, Hiroshima, 729-0393, Japan; Sennyu, K. [Mitsubishi Heavy Industries, Ltd, Mihara, Hiroshima, 729-0393, Japan; Geng, Rongli [JLAB; Rimmer, Robert A. [JLAB; Kako, E. [KEK

    2014-12-01

    MHI have supplied several 9-cell cavities for STF (R&D of ILC project at KEK) and have been considering production method for stable quality and cost reduction, seamless dumb-bell cavity was one of them. We had fabricated a 2 cell seamless dumb-bell cavity for cost reduction and measured RF performance in collaboration with JLab, KEK and MHI. Surface treatment recipe for ILC was applied for MHI 2-cell cavity and vertical test was performed at JLab. The cavity reached Eacc=32.4MV/m after BCP and EP. Details of the result are reported.

  5. Deterioration of polymethyl methacrylate dentures in the oral cavity.

    Science.gov (United States)

    Matsuo, Hiroshi; Suenaga, Hanako; Takahashi, Masatoshi; Suzuki, Osamu; Sasaki, Keiichi; Takahashi, Nobuhiro

    2015-01-01

    Polymethyl methacrylate (PMMA)-made prostheses used in the oral cavity were evaluated by multimodal assessment in order to elucidate the biodeterioration of PMMA. In used dentures (UD), the micro-Vickers hardness of the polished denture surface and denture basal surface was lower than that of the torn surface (pPMMA deteriorated during long-term use in the oral cavity in terms of hardness and volatile content with component alteration, and suggests the involvement of biodeterioration, possibly due to saliva and oral microbiota.

  6. A Scanning Cavity Microscope

    CERN Document Server

    Mader, Matthias; Hänsch, Theodor W; Hunger, David

    2014-01-01

    Imaging of the optical properties of individual nanosystems beyond fluorescence can provide a wealth of information. However, the minute signals for absorption and dispersion are challenging to observe, and only specialized techniques requiring sophisticated noise rejection are available. Here we use signal enhancement in a scanning optical microcavity to demonstrate ultra-sensitive imaging. Harnessing multiple interactions of probe light with a sample within an optical resonator, we achieve a 1700-fold signal enhancement compared to diffraction-limited microscopy. We demonstrate quantitative imaging of the extinction cross section of gold nanoparticles with a sensitivity below 1 nm2, we show a method to improve spatial resolution potentially below the diffraction limit by using higher order cavity modes, and we present measurements of the birefringence and extinction contrast of gold nanorods. The demonstrated simultaneous enhancement of absorptive and dispersive signals promises intriguing potential for opt...

  7. Shock induced cavity collapse

    Science.gov (United States)

    Skidmore, Jonathan; Doyle, Hugo; Tully, Brett; Betney, Matthew; Foster, Peta; Ringrose, Tim; Ramasamy, Rohan; Parkin, James; Edwards, Tom; Hawker, Nicholas

    2016-10-01

    Results from the experimental investigation of cavity collapse driven by a strong planar shock (>6km/s) are presented. Data from high speed framing cameras, laser backlit diagnostics and time-resolved pyromety are used to validate the results of hydrodynamic front-tracking simulations. As a code validation exercise, a 2-stage light gas gun was used to accelerate a 1g Polycarbonate projectile to velocities exceeding 6km/s; impact with a PMMA target containing a gas filled void results in the formation of a strong shockwave with pressures exceeding 1Mbar. The subsequent phenomena associated with the collapse of the void and excitation of the inert gas fill are recorded and compared to simulated data. Variation of the mass density and atomic number of the gas fill is used to alter the plasma parameters furthering the extent of the code validation.

  8. Frequency Tuning for a DQW Crab Cavity

    CERN Document Server

    Verdú-Andrés, Silvia; Ben-Zvi, Ilan; Calaga, Rama; Capatina, Ofelia; Leuxe, Raphael; Skaritka, John; Wu, Qiong; Xiao, Binping; Zanoni, Carlo

    2016-01-01

    The nominal operating frequency for the HL-LHC crab cavities is 400.79 MHz within a bandwidth of ±60kHz. Attaining the required cavity tune implies a good understanding of all the processes that influence the cavity frequency from the moment when the cavity parts are being fabricated until the cavity is installed and under operation. Different tuning options will be available for the DQW crab cavity of LHC. This paper details the different steps in the cavity fabrication and preparation that may introduce a shift in the cavity frequency and introduces the different tuning methods foreseen to bring the cavity frequency to meet the specifications.

  9. Theory of quantum light emission from a strongly-coupled single quantum dot photonic-crystal cavity system.

    Science.gov (United States)

    Hughes, Stephen; Yao, P

    2009-03-02

    We present a rigorous medium-dependent theory for describing the quantum field emitted and detected from a single quantum dot exciton, strongly coupled to a planar photonic crystal nanocavity, from which the exact spectrum is derived. By using simple mode decomposition techniques, this exact spectrum is subsequently reduced to two separate user-friendly forms, in terms of the leaky cavity mode emission and the radiation mode emission. On application to study exciton-cavity coupling in the strong coupling regime, besides a pronounced modification of the usual vacuum Rabi spectral doublet, we predict several new effects associated with the leaky cavity mode emission, including the appearance of an off-resonance cavity mode and a loss-induced on-resonance spectral triplet. The cavity mode emission is shown to completely dominate the emitted spectrum, even for large cavity-exciton detunings, whereby the usual cavity-QED formulas developed for radiation-mode emission drastically fail. These predictions are in qualitative agreement with several "mystery observations" reported in recent experiments, and apply to a wide range of semiconductor cavities.

  10. LEP radio-frequency cavity

    CERN Multimedia

    1991-01-01

    One of the copper radio-frequency accelerating cavities installed for the first phase of LEP (1989-1995). Bunches of electrons and positrons circulated in LEP in opposite directions and were accelerated in eight different sets of 16 cavities (situated on either side of the four experiments), gaining 400 million volts of accelerating power per turn.

  11. Single and Coupled Nanobeam Cavities

    DEFF Research Database (Denmark)

    Ivinskaya, Aliaksandra; Lavrinenko, Andrei; Shyroki, Dzmitry M.

    2013-01-01

    for analysis and design of photonic crystal devices, such as 2D ring resonators for filters, single and coupled nanobeam cavities, birefringence in photonic crystal cavities, threshold analysis in photonic crystal lasers, gap solitons in photonic crystals, novel photonic atolls, dynamic characteristics...

  12. Quantum entanglement purification in cavities

    CERN Document Server

    Romero, J L; Saavedra, C; Retamal, J C

    2002-01-01

    A physical implementation of an entanglement purification protocol is studied using a cavity quantum electrodynamic based proposal, where, the quantum information is stored in quantum field sates inside cavities. Also a procedure is given for quantifying the degree of entanglement between quantum fields. (Author)

  13. Superconducting cavity model for LEP

    CERN Multimedia

    1979-01-01

    A superconducting cavity model is being prepared for testing in a vertical cryostat.At the top of the assembly jig is H.Preis while A.Scharding adjusts some diagnostic equipment to the cavity. See also photo 7912501X.

  14. Dynamics of bouncing droplets in annular cavities

    Science.gov (United States)

    Lentz, Zachary Louis; Jalali, Mir Abbas; Alam, Mohammad-Reza

    2014-11-01

    In a cylindrical bath of silicon oil, vertically excited by a frequency of 45 Hz, we trace the motion of bouncing droplets as they fill an annular region. We compute the mean tangential and radial velocity components of the droplets and show that the maximum tangential velocity is larger than the maximum radial velocity by one order of magnitude. Velocity dispersions have almost equal levels in the radial and tangential directions, and their mean values are 1/4 times smaller than the mean tangential velocity. These results show that bouncing droplets undergo random motions within annular cavities determined by the interference patterns of self-induced circumferential waves. We derive analytical relations between the velocity dispersion and the wavelength of surface waves, and calculate the mean tangential velocity of droplets using the random kicks that they experience at the boundaries of the cavity by inward and outward traveling waves.

  15. Structure of magnetic fields in intracluster cavities

    CERN Document Server

    Gourgouliatos, Konstantinos Nektarios; Lyutikov, Maxim

    2010-01-01

    Observations of clusters of galaxies show ubiquitous presence of X-ray cavities, presumably blown by the AGN jets. We consider magnetic field structures of these cavities. Stability requires that they contain both toroidal and poloidal magnetic fields, while realistic configurations should have vanishing magnetic field on the boundary. For axisymmetric configurations embedded in unmagnetized plasma, the continuity of poloidal and toroidal magnetic field components on the surface of the bubble then requires solving the elliptical Grad-Shafranov equation with both Dirichlet and Neumann boundary conditions. This leads to a double eigenvalue problem, relating the pressure gradients and the toroidal magnetic field to the radius of the bubble. We have found fully analytical stable solutions. This result is confirmed by numerical simulation. We present synthetic X-ray images and synchrotron emission profiles and evaluate the rotation measure for radiation traversing the bubble.

  16. Cavity quantum electrodynamics with Anderson-localized modes.

    Science.gov (United States)

    Sapienza, Luca; Thyrrestrup, Henri; Stobbe, Søren; Garcia, Pedro David; Smolka, Stephan; Lodahl, Peter

    2010-03-12

    A major challenge in quantum optics and quantum information technology is to enhance the interaction between single photons and single quantum emitters. This requires highly engineered optical cavities that are inherently sensitive to fabrication imperfections. We have demonstrated a fundamentally different approach in which disorder is used as a resource rather than a nuisance. We generated strongly confined Anderson-localized cavity modes by deliberately adding disorder to photonic crystal waveguides. The emission rate of a semiconductor quantum dot embedded in the waveguide was enhanced by a factor of 15 on resonance with the Anderson-localized mode, and 94% of the emitted single photons coupled to the mode. Disordered photonic media thus provide an efficient platform for quantum electrodynamics, offering an approach to inherently disorder-robust quantum information devices.

  17. Radiation emission from the "Rhodotron-TT200" cavity

    Institute of Scientific and Technical Information of China (English)

    Farshid Tabbakh; Mahmud Borhani

    2011-01-01

    In this paper, the X-rays emitted from the Rhodotron-TT200 cavity have been studied in depth.We found that the Bremsstrahlung interaction is the only contribution of X-ray generation important to safety.The X-ray dose rate in the Rhodotron vault is calculated for normal conditions based on MCNP4C results.The presented calculation shows good agreement with the experimental measurements, which consequently confirms the reliability of the calculation for use in shielding design and other safety aspects.

  18. Probing biological light-harvesting phenomena by optical cavities

    CERN Document Server

    Caruso, Filippo; Solano, Enrique; Huelga, Susana F; Aspuru-Guzik, Alán; Plenio, Martin B

    2011-01-01

    We propose a driven optical cavity quantum electrodynamics (QED) set up aimed at directly probing energy transport dynamics in photosynthetic biomolecules. We show that detailed information concerning energy transfer paths and delocalization of exciton states can be inferred (and exciton energies estimated) from the statistical properties of the emitted photons. This approach provides us with a novel spectroscopic tool for the interrogation of biological systems in terms of quantum optical phenomena which have been usually studied for atomic or solid-state systems, e.g. trapped atoms and semiconductor quantum dots.

  19. AGN-Induced Cavities in NGC 1399 And NGC 4649

    Energy Technology Data Exchange (ETDEWEB)

    Shurkin, K.; /New Mexico U.; Dunn, R.J.H.; /Southampton U.; Gentile, G.; Taylor, G.B.; /New Mexico U.; Allen, S.W.; /KIPAC, Menlo Park

    2007-11-14

    We present an analysis of archival Chandra and VLA observations of the E0 galaxy NGC1399 and the E2 galaxy NGC4649 in which we investigate cavities in the surrounding X-ray emitting medium caused by the central AGN. We calculate the jet power required for the AGN to evacuate these cavities and find values of {approx} 8x10{sup 41} erg s-1 and {approx} 14x10{sup 41} erg s{sup -1} for the lobes of NGC1399 and {approx} 7x10{sup 41} erg s{sup -1} and {approx} 6x1041 erg s{sup -1} for those of NGC4649. We also calculate the k/f values for each cavity, where k is the ratio of the total particle energy to that of electrons radiating in the range of 10 MHz to 10 GHz, and f is the volume filling factor of the plasma in the cavity. We find that the values of k/f for the lobes of NGC1399 are {approx} 93 and {approx} 190, and those of the lobes of NGC4649 are {approx} 15000 and {approx} 12000. We conclude that the assumed spectrum describes the electron distribution in the lobes of NGC1399 reasonably well, and that there are few entrained particles. For NGC4649, either there are many entrained particles or the model spectrum does not accurately describe the population of electrons.

  20. CMC blade with pressurized internal cavity for erosion control

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Crespo, Andres; Goike, Jerome Walter

    2016-02-02

    A ceramic matrix composite blade for use in a gas turbine engine having an airfoil with leading and trailing edges and pressure and suction side surfaces, a blade shank secured to the lower end of each airfoil, one or more interior fluid cavities within the airfoil having inlet flow passages at the lower end which are in fluid communication with the blade shank, one or more passageways in the blade shank corresponding to each one of the interior fluid cavities and a fluid pump (or compressor) that provides pressurized fluid (nominally cool, dry air) to each one of the interior fluid cavities in each airfoil. The fluid (e.g., air) is sufficient in pressure and volume to maintain a minimum fluid flow to each of the interior fluid cavities in the event of a breach due to foreign object damage.

  1. Quantitative analysis of quantum dot dynamics and emission spectra in cavity quantum electrodynamics

    DEFF Research Database (Denmark)

    Madsen, Kristian Høeg; Lodahl, Peter

    2013-01-01

    –Cummings model, whereas systematic deviations are observed for the emission spectra. The discrepancy for the spectra is attributed to the coupling of other exciton lines to the cavity and interference of different propagation paths toward the detector of the fields emitted by the quantum dot. In contrast......We present detuning-dependent spectral and decay-rate measurements to study the difference between the spectral and dynamical properties of single quantum dots embedded in micropillar and photonic crystal cavities. For the micropillar cavity, the dynamics is well described by the dissipative Jaynes......, quantitative information about the system can readily be extracted from the dynamical measurements. In the case of photonic crystal cavities, we observe an anti-crossing in the spectra when detuning a single quantum dot through resonance, which is the spectral signature of a strong coupling. However, time...

  2. Two-dimensional Josephson junction arrays coupled through a high-Q cavity

    DEFF Research Database (Denmark)

    Filatrella, G.; Pedersen, Niels Falsig; Wiesenfeld, K.

    2001-01-01

    the cavity. The highly resonant cavity induces synchronized behavior, which is qualitatively different than what is familiar from other studies on nonlinear oscillator arrays, for example the Kuramoto model. We also address the effects of disorder, as well as the role of detuning between the spontaneous...... emission frequency of the junctions and the cavity resonant frequency. We show with a simple argument that we can predict the scaling behavior of disorder with the size of the array. The consequences for the design of microwave oscillators in the Gigahertz region are discussed......The problem of disordered two-dimensional arrays of underdamped Josephson junctions is addressed. Our simulations show that when coupled to a high-Q cavity, the array exhibits synchronized behavior, and the power emitted can be considerably increased once enough junctions are activated to pump...

  3. Self-cavity lasing in optically pumped single crystals of p-sexiphenyl

    Directory of Open Access Journals (Sweden)

    Hisao Yanagi

    2016-08-01

    Full Text Available Organic single-crystal self-cavities are prepared by solution growth of p-sexiphenyl (p-6P. Based on Fabry-Pérot feedback inside a quasi-lozenge-shaped platelet crystal, edge-emitting laser is obtained under optical pumping. The multimode lasing band appears at the 0-1 or 0-2 vibronic progressions depending on the excitation conditions which affect the self-absorption effect. Cavity-size dependence of amplified spontaneous emission (ASE is investigated with laser-etched single crystals of p-6P. As the cavity length of square-shaped crystal is reduced from 100 to 10 μm, ASE threshold fluence is decreased probably due to size-dependent light confinement in the crystal cavity.

  4. Morphological evaluation of cavity preparation surface after duraphat and Er:YAG laser treatment by scanning electronic microscopy; Avaliacao das alteracoes morfologicas da superficie do preparo cavitario apos condicionamento com verniz fluoretado a 2,26 % e laser de Er:YAG atraves de microscopia eletronica de varredura

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, Luciane Borelli

    2002-07-01

    The treatment of dental surface using different lasers to prevent dental caries has been studied for several on last years. The purpose of this in vitro study was to evaluate the morphological changes on dentin surface from pulpal wall of cavity preparations performed by high-speed drill, treated with 2,26% fluoride varnish (Duraphat) and Er:YAG laser, and then submitted after receiving or not to EDTA 15% treatment. Twenty Class V cavities were performed on ten humans molars. The specimens were randomly divided in to 4 groups: group 1- treatment with Duraphat followed by Er:YAG laser irradiation (120 mJ/ 4 Hz); group 2: Er:YAG laser irradiation, same parameters, followed by Duraphat treatment; group 3- same group 1 followed by immersion in EDTA (5 min); group 4 - same as group 2 followed by immersion in EDTA (5 min). The specimens were processed for SEM analysis. The micrographs showed that Duraphat treatment promoted morphological changes on dentin, closing dentinal tubules; the specimens treated by Duraphat and Er:YAG laser and immersed in EDTA (group 3) showed homogeneous surface, closed and protected dentinal tubules, maintenance of the fluoride varnish on the dentin surface and around the dentinal tubules, showing feasible and efficiency of these therapies the feasibility.(author)

  5. The Rise of Ingot Niobium as a Material for Superconducting Radiofrequency Accelerating Cavities

    CERN Document Server

    Kneisel, P; Dhakal, P; Saito, K; Singer, W; Singer, X; Myneni, G R

    2013-01-01

    As a result of a collaboration between Jefferson Lab and niobium manufacturer CBMM, ingot niobium was explored as a possible material for superconducting radiofrequency (SRF) cavity fabrication. The first single cell cavity from large grain high purity niobium was fabricated and successfully tested at Jefferson Lab in 2004. This pioneering work triggered research activities in other SRF laboratories around the world. Large grain niobium became not only an interesting alternative material for cavity builders, but also material scientists and surface scientists were eager to participate in the development of this material. Most of the original expectations for this material of being less costly and allowing less expensive fabrication and treatment procedures at the same performance levels in cavities have been met. Many single cell cavities made from material of different suppliers have been tested successfully and several multi-cell cavities have shown the performances comparable to the best cavities made from...

  6. Design of a tandem distributed Bragg reflectors specialized for enhancing the efficiency of GaN-based ultraviolet light-emitting diodes

    Science.gov (United States)

    Yang, Yue; Ji, Qingbin; Zong, Hua; Yan, Tongxing; Li, Junchao; Wei, Tiantian; Hu, Xiaodong

    2016-09-01

    We design a type of "tandem distributed Bragg reflector (DBR)" that shows advantages over normal DBR in ultraviolet region. We apply a tandem DBR centered at 390 nm to a resonant cavity light emitting diodes model, consequently enhancing the extraction efficiency without detuning the cavity while narrowing the spectral width of the emitted light. The extraction efficiency into a numerical aperture exhibits a 36% increase compared to that of the normal structure. We further demonstrate the potential that the tandem DBRs (centered at 343 nm and 246 nm respectively) have for enhancing the efficiency in GaN-based deep UV device.

  7. Photoswitchable NIR-Emitting Gold Nanoparticles.

    Science.gov (United States)

    Bonacchi, Sara; Cantelli, Andrea; Battistelli, Giulia; Guidetti, Gloria; Calvaresi, Matteo; Manzi, Jeannette; Gabrielli, Luca; Ramadori, Federico; Gambarin, Alessandro; Mancin, Fabrizio; Montalti, Marco

    2016-09-05

    Photo-switching of the NIR emission of gold nanoparticles (GNP) upon photo-isomerization of azobenzene ligands, bound to the surface, is demonstrated. Photophysical results confirm the occurrence of an excitation energy transfer process from the ligands to the GNP that produces sensitized NIR emission. Because of this process, the excitation efficiency of the gold core, upon excitation of the ligands, is much higher for the trans form than for the cis one, and t→c photo-isomerization causes a relevant decrease of the GNP NIR emission. As a consequence, photo-isomerization can be monitored by ratiometric detection of the NIR emission upon dual excitation. The photo-isomerization process was followed in real-time through the simultaneous detection of absorbance and luminescence changes using a dedicated setup. Surprisingly, the photo-isomerization rate of the ligands, bound to the GNP surface, was the same as measured for the chromophores in solution. This outcome demonstrated that excitation energy transfer to gold assists photo-isomerization, rather than competing with it. These results pave the road to the development of new, NIR-emitting, stimuli-responsive nanomaterials for theranostics.

  8. Hybrid Light-Emitting Diode Enhanced With Emissive Nanocrystals

    DEFF Research Database (Denmark)

    Kopylov, Oleksii

    This thesis investigates a new type of white light emitting hybrid diode, composed of a light emitting GaN/InGaN LED and a layer of semiconductor nanocrystals for color conversion. Unlike standard white LEDs, the device is configured to achieve high color conversion efficiency via non...... was less than 10nm. Analysis of the results shows that in order to achieve sufficient for the white LED color conversion, better surface passivation and nanocrystals with shorter exciton lifetimes and weaker Auger recombination and needed.......-radiative energy transfer from the primary LED to the nanocrystals. LED structures with sub-10 nm separation the between quantum well and the surface and patterned standard bright LEDs are considered for the hybrid devices, which require close proximity of the nanocrystals to the quantum well. The development...

  9. Light-Emitting Devices with Conjugated Polymers

    Directory of Open Access Journals (Sweden)

    Xian-Yu Deng

    2011-03-01

    Full Text Available This article introduces a previous study and tremendous progress in basic theoretical modeling, material developments and device engineering for polymer light-emitting devices (PLEDs.

  10. Hierarchical Non-Emitting Markov Models

    CERN Document Server

    Ristad, E S; Ristad, Eric Sven; Thomas, Robert G.

    1998-01-01

    We describe a simple variant of the interpolated Markov model with non-emitting state transitions and prove that it is strictly more powerful than any Markov model. More importantly, the non-emitting model outperforms the classic interpolated model on the natural language texts under a wide range of experimental conditions, with only a modest increase in computational requirements. The non-emitting model is also much less prone to overfitting. Keywords: Markov model, interpolated Markov model, hidden Markov model, mixture modeling, non-emitting state transitions, state-conditional interpolation, statistical language model, discrete time series, Brown corpus, Wall Street Journal.

  11. The noise generated by a landing gear wheel with hub and rim cavities

    Science.gov (United States)

    Wang, Meng; Angland, David; Zhang, Xin

    2017-03-01

    Wheels are one of the major noise sources of landing gears. Accurate numerical predictions of wheel noise can provide an insight into the physical mechanism of landing gear noise generation and can aid in the design of noise control devices. The major noise sources of a 33% scaled isolated landing gear wheel are investigated by simulating three different wheel configurations using high-order numerical simulations to compute the flow field and the FW-H equation to obtain the far-field acoustic pressures. The baseline configuration is a wheel with a hub cavity and two rim cavities. Two additional simulations are performed; one with the hub cavity covered (NHC) and the other with both the hub cavity and rim cavities covered (NHCRC). These simulations isolate the effects of the hub cavity and rim cavities on the overall wheel noise. The surface flow patterns are visualised by shear stress lines and show that the flow separations and attachments on the side of the wheel, in both the baseline and the configuration with only the hub cavity covered, are significantly reduced by covering both the hub and rim cavities. A frequency-domain FW-H equation is used to identify the noise source regions on the surface of the wheel. The tyre is the main low frequency noise source and shows a lift dipole and side force dipole pattern depending on the frequency. The hub cavity is identified as the dominant middle frequency noise source and radiates in a frequency range centered around the first and second depth modes of the cylindrical hub cavity. The rim cavities are the main high-frequency noise sources. With the hub cavity and rim cavities covered, the largest reduction in Overall Sound Pressure Level (OASPL) is achieved in the hub side direction. In the other directivities, there is also a reduction in the radiated sound.

  12. Atraumatic restorative treatment in atypical cavities

    Directory of Open Access Journals (Sweden)

    Letícia Simino Carvalho

    2009-10-01

    Full Text Available The atraumatic restorative treatment has been widely divulged among professionals in the area of Pediatric Dentistry. This restorative technique is included in the philosophy of Minimal Intervention and is considered one of the most conservative treatments, because only the layer of infected dentin caries is removed. Moreover, the atraumatic restorative treatment has been shown to be less painful than conventional approaches, and local anesthesia is rarely required. After the removal of the infected dentin, the cavities are filled with glass ionomer cement, a material that has antimicrobial capacity, good marginal sealing and constant fluorine release and recharge. In spite of the increasing number of studies about atraumatic restorative treatment, only studies related to restorations in occlusal cavities have shown scientific evidences about the technique. The aim of this study was to evaluate the feasibility of atraumatic restorative treatment in cavities with 3 or more surfaces involved, by means of a clinical case report of a patient with extensive dstruction in primary teeth, who was submitted to atraumatic restorative treatment, and observe the result of the treatment after one year of clinical and radiographic control.

  13. Surface acoustic wave regulated single photon emission from a coupled quantum dot-nanocavity system

    Science.gov (United States)

    Weiß, M.; Kapfinger, S.; Reichert, T.; Finley, J. J.; Wixforth, A.; Kaniber, M.; Krenner, H. J.

    2016-07-01

    A coupled quantum dot-nanocavity system in the weak coupling regime of cavity-quantumelectrodynamics is dynamically tuned in and out of resonance by the coherent elastic field of a fSAW ≃ 800 MHz surface acoustic wave. When the system is brought to resonance by the sound wave, light-matter interaction is strongly increased by the Purcell effect. This leads to a precisely timed single photon emission as confirmed by the second order photon correlation function, g(2). All relevant frequencies of our experiment are faithfully identified in the Fourier transform of g(2), demonstrating high fidelity regulation of the stream of single photons emitted by the system.

  14. Multi-purpose 805 MHz Pillbox RF Cavity for Muon Acceleration Studies

    Energy Technology Data Exchange (ETDEWEB)

    Kurennoy, Sergey S. [Los Alamos National Laboratory; Chan, Kwok-Chi Dominic [Los Alamos National Laboratory; Jason, Andrew [Los Alamos National Laboratory; Miyadera, Haruo [Los Alamos National Laboratory; Turchi, Peter J. [Los Alamos National Laboratory

    2011-01-01

    An 805 MHz RF pillbox cavity has been designed and constructed to investigate potential muon beam acceleration and cooling techniques. The cavity can operate at vacuum or under pressure to 100 atmospheres, at room temperature or in a liquid nitrogen bath at 77 K. The cavity is designed for easy assembly and disassembly with bolted construction using aluminum seals. The surfaces of the end walls of the cavity can be replaced with different materials such as copper, aluminum, beryllium, or molybdenum, and with different geometries such as shaped windows or grid structures. Different surface treatments such as electro polished, high-pressure water cleaned, and atomic layer deposition are being considered for testing. The cavity has been designed to fit inside the 5-Tesla solenoid in the MuCool Test Area at Fermilab. Current status of the cavity prepared for initial conditioning and operation in the external magnetic field is discussed.

  15. Growth and properties of wide spectral white light emitting diodes

    Institute of Scientific and Technical Information of China (English)

    Xie Zi-Li; Shi Yi; Zheng You-Dou; Zhang Rong; Fu De-Yi; Liu Bin; Xiu Xiang-Qian; Hua Xue-Mei; Zhao Hong; Chen Peng; Han Ping

    2011-01-01

    Wide spectral white light emitting diodes have been designed and grown on a sapphire substrate by using a metal-organic chemical vapor deposition system.Three quantum wells with blue-light-emitting,green-light-emitting and red-light-emitting structures were grown according to the design.The surface morphology of the film was observed by using atomic force microscopy. The films were characterized by their photoluminescence measurements. X-ray diffraction θ/2θ scan spectroscopy was carried out on the multi-quantum wells.The secondary fringes of the symmetric ω/2θ X-ray diffraction scan peaks indicate that the thicknesses and the alloy compositions of the individual quantum wells are repeatable throughout the active region.The room temperature photolumineecence spectra of the structures indicate that the white light emission of the multi-quantum wells is obtained.The light spectrum covers 400-700 nm,which is almost the whole visible light spectrum.

  16. SRF Cavity Fabrication and Materials

    CERN Document Server

    Singer, W

    2014-01-01

    The technological and metallurgical requirements of material for highgradient superconducting cavities are described. High-purity niobium, as the preferred metal for the fabrication of superconducting accelerating cavities, should meet exact specifications. The content of interstitial impurities such as oxygen, nitrogen, and carbon must be below 10μg/g. The hydrogen content should be kept below 2μg/g to prevent degradation of the Q-value under certain cool-down conditions. The material should be free of flaws (foreign material inclusions or cracks and laminations) that can initiate a thermal breakdown. Defects may be detected by quality control methods such as eddy current scanning and identified by a number of special methods. Conventional and alternative cavity fabrication methods are reviewed. Conventionally, niobium cavities are fabricated from sheet niobium by the formation of half-cells by deep drawing, followed by trim machining and Electron-Beam Welding (EBW). The welding of half-cells is a delicate...

  17. Vibration insensitive optical ring cavity

    Institute of Scientific and Technical Information of China (English)

    Miao Jin; Jiang Yan-Yi; Fang Su; Bi Zhi-Yi; Ma Long-Sheng

    2009-01-01

    The mounting configuration of an optical ring cavity is optimized for vibration insensitivity by finite element analysis. A minimum response to vertical accelerations is found by simulations made for different supporting positions.

  18. Nb3Sn SRF Cavities for Nuclear Physics Applications

    Science.gov (United States)

    Eremeev, Grigory

    2017-01-01

    Nuclear physics experiments rely increasingly on accelerators, which employ superconducting RF (SRF) technology. CEBAF, SNS, FRIB, ESS, among others exploit the low surface resistance of SRF cavities to efficiently accelerate particle beams towards experimental targets. Niobium is the cavity material of choice for all current or planned SRF accelerators, but it has been long recognized that other superconductors with high superconducting transition temperatures have the potential to surpass niobium for SRF applications. Among the alternatives, Nb3Sn coated cavities are the most advanced on the path to practical applications: Nb3Sn coatings on R&D cavities have Tc consistently close the optimal 18 K, very low RF surface resistances, and very recently were shown to reach above Hc1 without anomalous RF surface resistance increase. In my talk I will discuss the prospects of Nb3Sn SRF cavities, the research efforts to realize Nb3Sn coatings on practical multi-cell accelerating structures, and the path toward possible inclusion in CEBAF. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics.

  19. Principal Component Analysis reveals correlation of cavities evolution and functional motions in proteins.

    Science.gov (United States)

    Desdouits, Nathan; Nilges, Michael; Blondel, Arnaud

    2015-02-01

    Protein conformation has been recognized as the key feature determining biological function, as it determines the position of the essential groups specifically interacting with substrates. Hence, the shape of the cavities or grooves at the protein surface appears to drive those functions. However, only a few studies describe the geometrical evolution of protein cavities during molecular dynamics simulations (MD), usually with a crude representation. To unveil the dynamics of cavity geometry evolution, we developed an approach combining cavity detection and Principal Component Analysis (PCA). This approach was applied to four systems subjected to MD (lysozyme, sperm whale myoglobin, Dengue envelope protein and EF-CaM complex). PCA on cavities allows us to perform efficient analysis and classification of the geometry diversity explored by a cavity. Additionally, it reveals correlations between the evolutions of the cavities and structures, and can even suggest how to modify the protein conformation to induce a given cavity geometry. It also helps to perform fast and consensual clustering of conformations according to cavity geometry. Finally, using this approach, we show that both carbon monoxide (CO) location and transfer among the different xenon sites of myoglobin are correlated with few cavity evolution modes of high amplitude. This correlation illustrates the link between ligand diffusion and the dynamic network of internal cavities.

  20. Imaging of the oral cavity.

    Science.gov (United States)

    Meesa, Indu Rekha; Srinivasan, Ashok

    2015-01-01

    The oral cavity is a challenging area in head and neck imaging because of its complex anatomy and the numerous pathophysiologies that involve its contents. This challenge is further compounded by the ubiquitous artifacts that arise from the dental amalgam, which compromise image quality. In this article, the anatomy of the oral cavity is discussed in brief, followed by a description of the imaging technique and some common pathologic abnormalities.