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Sample records for light slow light

  1. Slow light beam splitter.

    Science.gov (United States)

    Xiao, Yanhong; Klein, Mason; Hohensee, Michael; Jiang, Liang; Phillips, David F; Lukin, Mikhail D; Walsworth, Ronald L

    2008-07-25

    We demonstrate a slow light beam splitter using rapid coherence transport in a wall-coated atomic vapor cell. We show that particles undergoing random and undirected classical motion can mediate coherent interactions between two or more optical modes. Coherence, written into atoms via electromagnetically induced transparency using an input optical signal at one transverse position, spreads out via ballistic atomic motion, is preserved by an antirelaxation wall coating, and is then retrieved in outgoing slow light signals in both the input channel and a spatially-separated second channel. The splitting ratio between the two output channels can be tuned by adjusting the laser power. The slow light beam splitter may improve quantum repeater performance and be useful as an all-optical dynamically reconfigurable router.

  2. Slow light in flight imaging

    CERN Document Server

    Wilson, Kali; Gariepy, Genevieve; Henderson, Robert; Howell, John; Faccio, Daniele

    2016-01-01

    Slow-light media are of interest in the context of quantum computing and enhanced measurement of quantum effects, with particular emphasis on using slow-light with single photons. We use light-in-flight imaging with a single photon avalanche diode camera-array to image in situ pulse propagation through a slow light medium consisting of heated rubidium vapour. Light-in-flight imaging of slow light propagation enables direct visualisation of a series of physical effects including simultaneous observation of spatial pulse compression and temporal pulse dispersion. Additionally, the single-photon nature of the camera allows for observation of the group velocity of single photons with measured single-photon fractional delays greater than 1 over 1 cm of propagation.

  3. Slow Light Semiconductor Laser

    Science.gov (United States)

    2015-02-02

    we demonstrate a semiconductor laser with a spectral linewidth of 18 kHz in the telecom band around 1:55um. The views, opinions and/or findings...we demonstrate a semiconductor laser with a spectral linewidth of 18 kHz in the telecom band around 1:55um. Further, the large intracavity field...hybrid Si/III- V platforms Abstract The semiconductor laser is the principal light source powering the world-wide optical fiber network . Ever

  4. Liquid crystal light valves for slow light and applications

    Energy Technology Data Exchange (ETDEWEB)

    Residori, S; Bortolozzo, U [INLN, CNRS, University de Nice Sophia-Antipolis, 1361 route des Lucioles, 06560 Valbonne (France); Huignard, J P, E-mail: jean-pierre.huignard@thalesgroup.co [Thales Research and Technology, RD 128 91767, Palaiseau Cedex (France)

    2010-02-01

    The large dispersive properties of wave mixing in liquid crystal light-valves allow obtaining fast and slow light with tunable group velocities. A slow light interferometer is shown by using this interaction.

  5. Integrated Photonics Enabled by Slow Light

    DEFF Research Database (Denmark)

    Mørk, Jesper; Chen, Yuntian; Ek, Sara;

    2012-01-01

    In this talk we will discuss the physics of slow light in semiconductor materials and in particular the possibilities offered for integrated photonics. This includes ultra-compact slow light enabled optical amplifiers, lasers and pulse sources.......In this talk we will discuss the physics of slow light in semiconductor materials and in particular the possibilities offered for integrated photonics. This includes ultra-compact slow light enabled optical amplifiers, lasers and pulse sources....

  6. Enhancing the light-matter interaction using slow light: towards the concept of dense light

    OpenAIRE

    Thévenaz, Luc; Dicaire, Isabelle; Chin, Sang Hoon

    2012-01-01

    A couple of experiments are here presented to clarify the impact of slow light on light-matter interaction. The experiments are designed, so that the process generating slow light and the probed light-matter interaction only present a marginal cross-effect. The impact of slow light on simple molecular absorption could be separately evaluated under either material or structural slow light propagation in the same medium and led to an entirely different response.

  7. Slow light invisibility, teleportation, and other mysteries of light

    CERN Document Server

    Perkowitz, Sidney

    2011-01-01

    Slow Light is a popular treatment of today's astonishing breakthroughs in the science of light. Even though we don't understand light's quantum mysteries, we can slow it to a stop and speed it up beyond its Einsteinian speed limit, 186,000 miles/sec; use it for quantum telecommunications; teleport it; manipulate it to create invisibility; and perhaps generate hydrogen fusion power with it. All this is lucidly presented for non-scientists who wonder about teleportation, Harry Potter invisibility cloaks, and other fantastic outcomes. Slow Light shows how the real science and the fantasy inspire

  8. Experimental demonstration of spinor slow light

    CERN Document Server

    Lee, Meng-Jung; Lee, Chin-Yuan; Kudriasov, Viaceslav; Chang, Kao-Fang; Cho, Hung-Wen; Juzeliunas, Gediminas; Yu, Ite A

    2014-01-01

    Over the last decade the developments of slow, stored and stationary light based on the electromagnetically induced transparency effect have attracted a great deal of attention, stimulated by potential applications such as low-light-level nonlinear optics and quantum information manipulation. The previous experiments all dealt with the single-component slow light. Here we report the first experimental demonstration of two-component or spinor slow light using a double tripod (DT) atom-light coupling scheme which involves two atomic ground state coherences. We observe the neutrino-type oscillations between the two slow light components controlled by the two-photon detuning. We show that the DT scheme for the light storage behaves like the two outcomes of a Mach-Zehnder interferometer enabling high precision measurements of the frequency detuning. Finally, we experimentally demonstrate a possible application of the DT scheme as quantum memory/rotator for the two-color qubits.

  9. Slow light Mach-Zehnder fiber interferometer

    Institute of Scientific and Technical Information of China (English)

    Yundong Zhang; Jinfang Wang; Xuenan Zhang; Hao Wu; Yuanxue Cai; Jing Zhang; Ping Yuan

    2012-01-01

    A slow light structure Mach-Zehnder fiber interferometer is theoretically demonstrated.The sensitivity of the interferometer is significantly enhanced by the dispersion of the slow light structure.The numerical results show that the sensitivity enhancement factor varies with the coupling coefficient and reaches its maximum under critical coupling conditions.Interferometers have been investigated in relation to their applications in fields such as metrology[1],optical sensing[2],optical communication[3,4],quantum information processing[5],and biomedical engineering[6].A number of schemes have been proposed to improve the performance of interferometers[7],such as using photonic crystal structures to minimize the size of on-chip devices[8],utilizing the dispersive property of semiconductor to enhance the spectral sensitivity of interferometers[9,10],utilizing slow light medium to enhance the resolution of Fourier transform interferometer[11],exploiting fast light medium or slow light structure to increase the rotation sensitivity of a Sagnac interferometer[12,13],enhancing the transmittance of the Mach-Zehnder interferometer (MZI) in the slow light region by gratings[14],and using liquid crystal light valve to derive high sensitivity interferometers[15].%A slow light structure Mach-Zehnder fiber interferometer is theoretically demonstrated. The sensitivity of the interferometer is significantly enhanced by the dispersion of the slow light structure. The numerical results show that the sensitivity enhancement factor varies with the coupling coefficient and reaches its maximum under critical coupling conditions.

  10. Slow-light pulses in moving media

    OpenAIRE

    Fiurasek, J.; Leonhardt, U.; Parentani, R.

    2000-01-01

    Slow light in moving media reaches a paradoxical regime when the flow speed of the medium approaches the group velocity of light. Pulses can penetrate a region where a counter-propagating flow exceeds the group velocity. When the counter-flow slows down pulses are reflected.

  11. Slow light vortices in periodic waveguides

    DEFF Research Database (Denmark)

    Sukhorukov, Andrey A.; Ha, Sangwoo; Desyatnikov, Anton S.

    2009-01-01

    We reveal that the reduction of the group velocity of light in periodic waveguides is generically associated with the presence of vortex energy flows. We show that the energy flows are gradually frozen for slow-light at the Brillouin zone edge, whereas vortices persist for slow-light states havin...... non-vanishing phase velocity inside the Brillouin zone. We also demonstrate that presence of vortices can be linked to the absence of slow-light at the zone edge, and present calculations illustrating these general results....

  12. Slow-light vortices in periodic waveguides

    DEFF Research Database (Denmark)

    Sukhorukov, Andrey A.; Ha, Sangwoo; Desyatnikov, Anton S.

    2009-01-01

    We reveal that the reduction of the group velocity of light in periodic waveguides is generically associated with the presence of vortex energy flows. We show that the energy flows are gradually frozen for slow-light at the Brillouin zone edge, whereas vortices persist for slow-light states havin...... non-vanishing phase velocity inside the Brillouin zone. We also demonstrate that presence of vortices can be linked to the absence of slow-light at the zone edge, and present calculations illustrating these general results....

  13. Systematic Design of Slow Light Waveguides

    DEFF Research Database (Denmark)

    Wang, Fengwen

    Light can propagate much slower in photonic crystal waveguides and plasmonic waveguides than in vacuum. Slow light propagation in waveguides shows broad prospects in the terabit communication systems. However, it causes severe signal distortions and displays large propagation loss. Moreover...... two different parameterizations. Detailed comparisons show that the bandwidth of slow light propagation can be significantly enhanced by allowing irregular geometries in the waveguides. To mitigate the propagation loss due to scattering in the photonic crystal waveg- uides, an optimization problem...... is formulated to minimize the average propagation loss of the designed modes. The presented approach is employed to design a free-topology slow light waveguide. Numerical result illustrates that slow light propagation in the optimized waveguide displays significantly suppressed propagation loss while keeping...

  14. Ultrafast Faraday Rotation of Slow Light

    Science.gov (United States)

    Musorin, A. I.; Sharipova, M. I.; Dolgova, T. V.; Inoue, M.; Fedyanin, A. A.

    2016-08-01

    The active control of optical signals in the time domain is what science and technology demand in fast all-optical information processing. Nanostructured materials can modify the group velocity and slow the light down, as the artificial light dispersion emerges. We observe the ultrafast temporal behavior of the Faraday rotation within a single femtosecond laser pulse under conditions of slow light in a one-dimensional magnetophotonic crystal. The Faraday effect changes by 20% over the time of 150 fs. This might be applicable to the fast control of light in high-capacity photonic devices.

  15. Slow light and slow acoustic phonons in optophononic resonators

    Science.gov (United States)

    Villafañe, V.; Soubelet, P.; Bruchhausen, A. E.; Lanzillotti-Kimura, N. D.; Jusserand, B.; Lemaître, A.; Fainstein, A.

    2016-11-01

    Slow and confined light have been exploited in optoelectronics to enhance light-matter interactions. Here we describe the GaAs/AlAs semiconductor microcavity as a device that, depending on the excitation conditions, either confines or slows down both light and optically generated acoustic phonons. The localization of photons and phonons in the same place of space amplifies optomechanical processes. Picosecond laser pulses are used to study through time-resolved reflectivity experiments the coupling between photons and both confined and slow acoustic phonons when the laser is tuned either with the cavity (confined) optical mode or with the stop-band edge (slow) optical modes. A model that fully takes into account the modified propagation of the acoustic phonons and light in these resonant structures is used to describe the laser detuning dependence of the coherently generated phonon spectra and amplitude under these different modes of laser excitation. We observe that confined light couples only to confined mechanical vibrations, while slow light can generate both confined and slow coherent vibrations. A strong enhancement of the optomechanical coupling using confined photons and vibrations, and also with properly designed slow photon and phonon modes, is demonstrated. The prospects for the use of these optoelectronic devices in confined and slow optomechanics are addressed.

  16. Fractal THz slow light metamaterial devices

    Science.gov (United States)

    Ito, Shoichi

    Scope and Method of Study: The goal of this study is to investigate the time delay of the fractal H metamaterials in the terahertz regime. This metamaterial contains resonators with two different sizes of H structures which mimic Electromagnetically Induced Transparency and create a transmission window and the corresponding phase dispersion, thus producing slow light. The Al structures were fabricated on silicon wafer and Mylar by using microelectronic lithography and thermal evaporation technique. By using terahertz time-domain spectroscopy, the phase change caused by the slow light system and the actual time delay were obtained. Numerical simulations were carried out to systematize the effect of permittivity and structure dimensions on the optical properties. Findings and Conclusions: We experimentally demonstrated the numerical time delay of the fractal H metamaterial as a slow light device. When permittivity of the substrates increases, the peak position of the transmission window shifts to lower frequency and the bandwidth becomes broader. As a result, silicon performed larger time delay than that of Mylar. By changing the length of the resonator, the bandwidth and the peak position of the transmission window is controllable. At the edges of the transmission window, the negative time delays (fast light) were also observed. Mylar acts as a quaci-free standing structure and allows higher spectral measurement. Moreover, metamaterials fabricated on multiple Mylar films can potentially act as a more effective slow light device. As applications, slow light metamaterials are expected to be used for high-capacity terahertz communication networks, all-optical information processing and sensing devices.

  17. Slow light on a printed circuit board.

    Science.gov (United States)

    Lanin, Aleksandr A; Voronin, Aleksandr A; Sokolov, Viktor I; Fedotov, Ilya V; Fedotov, Andrei B; Akhmanov, Aleksandr S; Panchenko, Vladislav Ya; Zheltikov, Aleksei M

    2011-05-15

    Slow-light effects induced by stimulated Raman scattering in polymer waveguides on a printed circuit board are shown to enable a widely tunable delay of broadband optical signals, suggesting an advantageous platform for optical information processing and ultrafast optical waveform transformation. © 2011 Optical Society of America

  18. Nonlinear light propagation in chalcogenide photonic crystal slow light waveguides.

    Science.gov (United States)

    Suzuki, Keijiro; Baba, Toshihiko

    2010-12-06

    Optical nonlinearity can be enhanced by the combination of highly nonlinear chalcogenide glass and photonic crystal waveguides (PCWs) providing strong optical confinement and slow-light effects. In a Ag-As(2)Se(3) chalcogenide PCW, the effective nonlinear parameter γeff reaches 6.3 × 10(4) W(-1)m(-1), which is 200 times larger than that in Si photonic wire waveguides. In this paper, we report the detailed design, fabrication process, and the linear and nonlinear characteristics of this waveguide at silica fiber communication wavelengths. We show that the waveguide exhibits negligible two-photon absorption, and also high-efficiency self-phase modulation and four-wave mixing, which are assisted by low-dispersion slow light.

  19. Synchronized ion acceleration by ultraintense slow light

    CERN Document Server

    Brantov, A V; Kovalev, V F; Bychenkov, V Yu

    2015-01-01

    An effective scheme of synchronized laser-triggered ion acceleration and the corresponding theoretical model are proposed for a slow light pulse of relativistic intensity, which penetrates into a near-critical-density plasma, strongly slows, and then increases its group velocity during propagation within a target. The 3D PIC simulations confirm this concept for proton acceleration by a femtosecond petawatt-class laser pulse experiencing relativistic self-focusing, quantify the characteristics of the generated protons, and demonstrate a significant increase of their energy compared with the proton energy generated from optimized ultrathin solid dense foils.

  20. Slow light based optical frequency shifter

    CERN Document Server

    Li, Qian; Thuresson, Axel; Nilsson, Adam N; Rippe, Lars; Kröll, Stefan

    2016-01-01

    We demonstrate experimentally and theoretically a controllable way of shifting the frequency of an optical pulse by using a combination of spectral hole burning, slow light effect, and linear Stark effect in a rare-earth-ion doped crystal. We claim that the solid angle of acceptance of a frequency shift structure can be close to $2\\pi$, which means that the frequency shifter could work not only for optical pulses propagating in a specific spatial mode but also for randomly scattered light. As the frequency shift is controlled solely by an external electric field, it works also for weak coherent light fields, and can e.g. be used as a frequency shifter for quantum memory devices in quantum communication.

  1. Slow-light effects in photonic crystal membrane lasers

    DEFF Research Database (Denmark)

    Xue, Weiqi; Yu, Yi; Ottaviano, Luisa

    2015-01-01

    In this paper, we present a systematic investigation of photonic crystal cavity laser operating in the slow-light regime. The dependence of lasing threshold on the effect of slow-light will be particularly highlighted.......In this paper, we present a systematic investigation of photonic crystal cavity laser operating in the slow-light regime. The dependence of lasing threshold on the effect of slow-light will be particularly highlighted....

  2. Nonlinear Gain Saturation in Active Slow Light Photonic Crystal Waveguides

    DEFF Research Database (Denmark)

    Chen, Yaohui; Mørk, Jesper

    2013-01-01

    We present a quantitative three-dimensional analysis of slow-light enhanced traveling wave amplification in an active semiconductor photonic crystal waveguides. The impact of slow-light propagation on the nonlinear gain saturation of the device is investigated.......We present a quantitative three-dimensional analysis of slow-light enhanced traveling wave amplification in an active semiconductor photonic crystal waveguides. The impact of slow-light propagation on the nonlinear gain saturation of the device is investigated....

  3. Slow and fast light in semiconductor waveguides

    DEFF Research Database (Denmark)

    Mørk, Jesper; Hansen, Per Lunnemann; Xue, Weiqi

    2010-01-01

    Investigations of slow and fast light effects in semiconductor waveguides entail interesting physics and point to a number of promising applications. In this review we give an overview of recent progress in the field, in particular focusing on the physical mechanisms of electromagnetically induced...... transparency and coherent population oscillations. While electromagnetically induced transparency has been the most important effect in realizing slowdown effects in atomic gasses, progress has been comparatively slow in semiconductors due to inherent problems of fast dephasing times and inhomogeneous...... broadening in quantum dots. The physics of electromagnetically induced transparency in semiconductors is discussed, emphasizing these limitations and recent suggestions for overcoming them. On the other hand, the mechanism of coherent population oscillations relies on wave mixing effects and is well suited...

  4. Slow light pulse propagation in dispersive media

    DEFF Research Database (Denmark)

    Nielsen, Torben Roland; Mørk, Jesper; Lavrinenko, Andrei

    2009-01-01

    -difference-time-domain Maxwell-Bloch simulations and compared to analytic results. For long pulses the group index (transmission) for the combined system is significantly enhanced (reduced) relative to slow light based on purely material or waveguide dispersion. Shorter pulses are strongly distorted and depending on parameters......We present a theoretical and numerical analysis of pulse propagation in a semiconductor photonic crystal waveguide with embedded quantum dots in a regime where the pulse is subjected to both waveguide and material dispersion. The group index and the transmission are investigated by finite...... broadening or break-up of the pulse may be observed. The transition from linear to nonlinear pulse propagation is quantified in terms of the spectral width of the pulse. To cite this article: T.R. Nielsen et al., C. R. Physique 10 (2009). (C) 2009 Academie des sciences. Published by Elsevier Masson SAS. All...

  5. Slow light in tapered slot photonic crystal waveguide

    Institute of Scientific and Technical Information of China (English)

    WU Jun; LI YanPing; YANG ChuanChuan; PENG Chao; WANG ZiYu

    2009-01-01

    A slotted single-mode photonic crystal waveguide with a linear tapered slot is presented to realize slow light, whose dispersion curve is shifted by changing the slot width. When the slot width is reduced, the band curve shifts in the tapered structure, and the group velocity of light approach zero at the cut-off frequency. Therefore, different frequency components of the guided light are slowed down even loca-lized along the propagation direction inside a tapered slot photonic crystal waveguide. Furthermore, this structure can confine slow light-wave in a narrow slot waveguide, which may effectively enhance the interaction between slow light and the low-index wave-guiding materials filled in the slot. In addition, this tapered slot structure can be used to compensate group velocity dispersion of slow light by mod-ifying the structure, thus opening the opportunity for ultra-wide bandwidth slow light.

  6. Slow-light enhanced gain in active photonic crystal waveguides

    CERN Document Server

    Ek, Sara; Chen, Yaohui; Semenova, Elizaveta; Yvind, Kresten; Mørk, Jesper

    2014-01-01

    Slow light is a fascinating physical effect, raising fundamental questions related to our understanding of light-matter interactions as well as offering new possibilities for photonic devices. From the first demonstrations of slow light propagation in ultra-cold atomic gasses, solid-state Ruby and photonic crystal structures, focus has shifted to applications, with slow light offering the ability to enhance and control light-matter interactions. The demonstration of tuneable delay lines, enhanced nonlinearities and spontaneous emission, enlarged spectral sensitivity and increased phase shifts illustrate the possibilities enabled by slow light propagation, with microwave photonics emerging as one of the promising applications. Here, we demonstrate that slow light can be used to control and increase the gain coefficient of an active semiconductor waveguide. The effect was theoretically predicted but not yet experimentally demonstrated. These results show a route towards realizing ultra-compact optical amplifier...

  7. Slow and fast light in semiconductor structures: physics and applications

    DEFF Research Database (Denmark)

    Mørk, Jesper; Nielsen, Torben Roland; Xue, Weiqi;

    We discuss the physics and applications of slow light in semiconductor waveguides. In particular we introduce methods for enhancing the degree of light speed control considering both electromagnetically induced transparency as well as coherent population oscillations.......We discuss the physics and applications of slow light in semiconductor waveguides. In particular we introduce methods for enhancing the degree of light speed control considering both electromagnetically induced transparency as well as coherent population oscillations....

  8. Slow-light enhancement of Beer-Lambert-Bouguer absorption

    DEFF Research Database (Denmark)

    Mortensen, Asger; Xiao, Sanshui

    2007-01-01

    We theoretically show how slow light in an optofluidic environment facilitates enhanced light-matter interactions, by orders of magnitude. The proposed concept provides strong opportunities for improving existing miniaturized chemical absorbance cells for Beer-Lambert-Bouguer absorption measureme......We theoretically show how slow light in an optofluidic environment facilitates enhanced light-matter interactions, by orders of magnitude. The proposed concept provides strong opportunities for improving existing miniaturized chemical absorbance cells for Beer-Lambert-Bouguer absorption...

  9. Threshold Characteristics of Slow-Light Photonic Crystal Lasers

    DEFF Research Database (Denmark)

    Xue, Weiqi; Yu, Yi; Ottaviano, Luisa

    2016-01-01

    The threshold properties of photonic crystal quantum dot lasers operating in the slow-light regime are investigated experimentally and theoretically. Measurements show that, in contrast to conventional lasers, the threshold gain attains a minimum value for a specific cavity length. The experimental...... results are explained by an analytical theory for the laser threshold that takes into account the effects of slow light and random disorder due to unavoidable fabrication imperfections. Longer lasers are found to operate deeper into the slow-light region, leading to a trade-off between slow-light induced...

  10. Slow light in photonic crystal waveguides

    DEFF Research Database (Denmark)

    Moulin, G.; Jacobsen, Rune Shim; Lavrinenko, Andrei;

    report on the first experiments where a direct measure of the group velocity is performed; this is done by measuring the time delay of modulated light propagating through a photonic crystal waveguide. The structure is fabricated in silicon-on-insulator (SOI). A group index (c/vg) of up to almost 200 has...... been measured. Such a high group index makes the light-matter interaction extremely efficient, opening for new opportunities in micrometer-sized integrated lightwave circuits....

  11. Lighting

    Data.gov (United States)

    Federal Laboratory Consortium — Lighting Systems Test Facilities aid research that improves the energy efficiency of lighting systems. • Gonio-Photometer: Measures illuminance from each portion of...

  12. Slow Light at High Frequencies in an Amplifying Semiconductor Waveguide

    DEFF Research Database (Denmark)

    Öhman, Filip; Yvind, Kresten; Mørk, Jesper

    2006-01-01

    We demonstrate slow-down of a modulated light signal in a semiconductor waveguide. Concatenated amplifying and absorbing sections simultaneously achieve both amplification and a controllable time delay at 15 GHz.......We demonstrate slow-down of a modulated light signal in a semiconductor waveguide. Concatenated amplifying and absorbing sections simultaneously achieve both amplification and a controllable time delay at 15 GHz....

  13. Enhanced parametric amplification in slow-light photonic crystal waveguides

    Institute of Scientific and Technical Information of China (English)

    LIU Yang; JIANG Chun

    2009-01-01

    We demonstrate both theoretically and numerically that slow light can enhance the parametric process of silicon in photonic crystal line-defect waveguides.Specifically,to get the desired gain,the pump power for a given gain medium length or the gain medium length for given pump power can be reduced by (c/vgn)2 when slow light waveguides are used,where n is the material index of conventional waveguide,vg is the group velocity of the slow light waveguide and c is the light velocity in vacuum.

  14. Light

    DEFF Research Database (Denmark)

    Prescott, N.B.; Kristensen, Helle Halkjær; Wathes, C.M.

    2004-01-01

    This chapter presents the effect of artificial light environments (light levels, colour, photoperiod and flicker) on the welfare of broilers in terms of vision, behaviour, lameness and mortality......This chapter presents the effect of artificial light environments (light levels, colour, photoperiod and flicker) on the welfare of broilers in terms of vision, behaviour, lameness and mortality...

  15. On the use of slow light for enhancing waveguide properties

    DEFF Research Database (Denmark)

    Mørk, Jesper; Nielsen, Torben Roland

    2010-01-01

    On the basis of a general analysis of waveguides containing a dispersive material, we identify conditions under which slow-light propagation may enhance the gain, absorption, or phase change. The enhancement is shown to depend on the slow-light mechanism and the translational symmetry...... of the waveguide. A combination of material and waveguide dispersion may strongly enhance the control of light speed, e.g., using electromagnetically induced transparency in quantum dots embedded in a photonic crystal waveguide....

  16. Slow light enhancement and limitations in periodic media

    DEFF Research Database (Denmark)

    Grgic, Jure

    to longer interaction time in the periodic media. Due to this reason, weak light-matter interaction is enhanced. The enhancement due to slow light has been studied for loss and gain. By introducing gain/loss, dispersive properties, in the slow light region, are severely influenced. The minimum attainable......Properties of periodic dielectric media have attracted a big interest in the last two decades due to numerous exciting physical phenomena that cannot occur in homogeneous media. Due to their strong dispersive properties, the speed of light can be significantly slowed down in periodic structures...... and significant structures with numerical and analytical methods. By analyzing different structures, we show very general properties for limitation and enhancement in the slow light regime. Inherent imperfections of fabricated structures such as a material loss and structural disorder have a strong influence...

  17. Simultaneous slow and fast light involving Faraday effect

    CERN Document Server

    Macke, Bruno

    2016-01-01

    We theoretically study the linear transmission of linearly polarized light pulses in an ensemble of cold atoms submitted to a static magnetic field parallel to the direction of propagation. The carrier frequency of the incident pulses coincides with a resonance frequency of the atoms in absence of magnetic field and the light transmitted in presence of magnetic field is examined in the polarizations parallel and perpendicular to that of the incident pulses. We give explicit analytic expressions of the transfer functions of the system for both polarizations. We demonstrate that slow light can be observed in a polarization whereas fast light is simultaneously observed in the perpendicular polarization. Moreover we point out that, due to the polarization post-selection, the system is not necessarily minimum-phase-shift. Slow light can then be obtained in situations where an irrelevant application of the Kramers-Kronig relations leads to expect fast light. When the incident light is step-modulated, we finally sho...

  18. On Slow Light as a Black Hole Analogue

    CERN Document Server

    Unruh, W G

    2003-01-01

    Although slow light (electromagnetically induced transparency) would seem an ideal medium in which to institute a ``dumb hole'' (black hole analog), it suffers from a number of problems. We show that the high phase velocity in the slow light regime ensures that the system cannot be used as an analog displaying Hawking radiation. Even though an appropriately designed slow-light set-up may simulate classical features of black holes -- such as horizon, mode mixing, Bogoliubov coefficients, etc. -- it does not reproduce the related quantum effects. PACS: 04.70.Dy, 04.80.-y, 42.50.Gy, 04.60.-m.

  19. Slow light in photonic crystal waveguides

    DEFF Research Database (Denmark)

    Moulin, G.; Jacobsen, Rune Shim; Lavrinenko, Andrei

    report on the first experiments where a direct measure of the group velocity is performed; this is done by measuring the time delay of modulated light propagating through a photonic crystal waveguide. The structure is fabricated in silicon-on-insulator (SOI). A group index (c/vg) of up to almost 200 has......In photonic crystal waveguides the group velocity vg of the fundamental guided mode generally decreases at wavelengths close to the cut-off of the mode. This can be inferred from the calculated band diagram (frequency vs. wavevector) since the slope of the mode corresponds to its group velocity. We...

  20. Ultrabroad Bandwidth Slow Light in Semiconductor Nanostructures

    Science.gov (United States)

    2008-12-31

    an EDFA before entering the cross- correlator. Cross-correlation with the reference enables recording of pulse amplitude and advance as the SOA...including SOA and EDFA . However, pulse broadening due to fast light effect varies only by 50% as the SOA current is varied. Pulse peak amplitude...from lfl to lpJ. A large ABP of 1.5 is observed in this case. An EDFA at the output of SOA can be used to maintain a constant output power as the

  1. Exploring carrier dynamics in semiconductors for slow light

    DEFF Research Database (Denmark)

    Mørk, Jesper; Xue, Weiqi; Chen, Yaohui

    2009-01-01

    We give an overview of recent results on slow and fast light in active semiconductor waveguides. The cases of coherent population oscillations as well as electromagnetically induced transparency are covered, emphasizing the physics and fundamental limitations.......We give an overview of recent results on slow and fast light in active semiconductor waveguides. The cases of coherent population oscillations as well as electromagnetically induced transparency are covered, emphasizing the physics and fundamental limitations....

  2. Slow light in semiconductor waveguides: Theory and experiment

    DEFF Research Database (Denmark)

    Mørk, Jesper; Öhman, Filip; Poel, Mike van der;

    2007-01-01

    Slow light in multi-section quantum well waveguide structure is realized using either coherent population oscillations (CPO) and electromagnetically induced transparency (EIT) is studied. The properties of the two schemes are compared and discussed.......Slow light in multi-section quantum well waveguide structure is realized using either coherent population oscillations (CPO) and electromagnetically induced transparency (EIT) is studied. The properties of the two schemes are compared and discussed....

  3. Efficient tunable switch from slow light to fast light in quantum opto-electromechanical system

    CERN Document Server

    Akram, M Javed; Saif, Farhan

    2015-01-01

    The control of slow and fast light propagation, in the probe transmission in a single experiment, is a challenging task. This type of control can only be achieved through highly nonlinear interactions and additional interfering pathway(s), which is therefore seldom reported. Here, we devise a scheme in which slow light, and a tunable switch from slow light to fast light can be achieved in the probe transmission based on a hybrid setup, which is composed of an optical cavity with two charged nano mechanical resonators (MRs). The two MRs are electrostatically coupled via tunable Coulomb coupling strength ($g_{c}$) making a quantum opto-electromechanical system (QOEMS). The parameter $g_{c}$ that couples the two MRs can be switched on and off by controlling the bias voltages on the MRs, and acts as a tunable switch that allows the propagation of transmitted probe field as slow light ($g_{c} \

  4. Slowing down light using a dendritic cell cluster metasurface waveguide

    Science.gov (United States)

    Fang, Z. H.; Chen, H.; Yang, F. S.; Luo, C. R.; Zhao, X. P.

    2016-11-01

    Slowing down or even stopping light is the first task to realising optical information transmission and storage. Theoretical studies have revealed that metamaterials can slow down or even stop light; however, the difficulty of preparing metamaterials that operate in visible light hinders progress in the research of slowing or stopping light. Metasurfaces provide a new opportunity to make progress in such research. In this paper, we propose a dendritic cell cluster metasurface consisting of dendritic structures. The simulation results show that dendritic structure can realise abnormal reflection and refraction effects. Single- and double-layer dendritic metasurfaces that respond in visible light were prepared by electrochemical deposition. Abnormal Goos-Hänchen (GH) shifts were experimentally obtained. The rainbow trapping effect was observed in a waveguide constructed using the dendritic metasurface sample. The incident white light was separated into seven colours ranging from blue to red light. The measured transmission energy in the waveguide showed that the energy escaping from the waveguide was zero at the resonant frequency of the sample under a certain amount of incident light. The proposed metasurface has a simple preparation process, functions in visible light, and can be readily extended to the infrared band and communication wavelengths.

  5. Theory of carrier depletion and light amplification in active slow light photonic crystal waveguides

    DEFF Research Database (Denmark)

    Chen, Yaohui; Mørk, Jesper

    2013-01-01

    Using a perturbative approach, we perform a quantitative three-dimensional analysis of slow-light enhanced traveling wave amplification in an active semiconductor photonic crystal waveguide. The impact of slow-light propagation on the carrier-depletion-induced nonlinear gain saturation...... of the device is investigated. An effective rate-equation-based model is presented. It is shown that it well accounts for the three-dimensional simulation results. Simulations indicate that a slow-light-enhanced photonic crystal traveling-wave amplifier has a high small-signal modal gain and low saturation...

  6. Light

    CERN Document Server

    Robertson, William C

    2003-01-01

    Why is left right and right left in the mirror? Baffled by the basics of reflection and refraction? Wondering just how the eye works? If you have trouble teaching concepts about light that you don t fully grasp yourself, get help from a book that s both scientifically accurate and entertaining with Light. By combining clear explanations, clever drawings, and activities that use easy-to-find materials, this book covers what science teachers and parents need to know to teach about light with confidence. It uses ray, wave, and particle models of light to explain the basics of reflection and refraction, optical instruments, polarization of light, and interference and diffraction. There s also an entire chapter on how the eye works. Each chapter ends with a Summary and Applications section that reinforces concepts with everyday examples. Whether you need a deeper understanding of how light bends or a good explanation of why the sky is blue, you ll find Light more illuminating and accessible than a college textbook...

  7. Efficient coupling to slow light photonic crystal waveguide

    Science.gov (United States)

    Khan, Md Shofiqul Islam; Devarapu, Ganga Chinna Rao; O'Faolain, Liam

    2016-04-01

    Slow light photonic crystal waveguides (PCWs) have been the subject of intensive study due to their potential for on-chip applications such as optical buffers and the enhancement of nonlinear phenomenon. However, due to high group velocity mismatch between the strip waveguide and the slow light waveguide efficient coupling of light is challenging. The coupling efficiency is also very sensitive to the truncation at the interface between the two waveguides. This sensitivity can be removed and light can efficiently be coupled from the strip waveguide to the slow light waveguide by adding an intermediate photonic crystal waveguide (or coupler) that operates at a group index of ˜ 5. Several designs have been proposed for couplers to obtain higher coupling efficiency within the desired group index range. We have studied uniaxial stretched couplers in which the lattice constant is stretched in the direction of propagation by 10-50 nm in the coupler region. Using a Finite Difference Time Domain (FDTD) Simulation Method that allows the extraction of the group index, we have observed 8.5 dB improvement in the coupling efficiency at the group index of 30. Efficient coupling is dominantly determined by the band edge position of the coupler region and maximum transmission efficiency is limited by the maximum transmission of the coupler PCW. If the band edge of coupler PCW is sufficiently red shifted relative to the band edge of the slow light PCW then higher coupling efficiency can be achieved.

  8. Slow and fast light: Controlling the speed of light using semiconductor waveguides

    DEFF Research Database (Denmark)

    Mørk, Jesper; Öhman, Filip; Poel, Mike van der

    2009-01-01

    We give an overview of slow- and fast-light effects in semiconductor active waveguides. Experimental and theoretical results are presented, emphasizing the physics of these phenomena and the limitations imposed by the carried dynamical processes.......We give an overview of slow- and fast-light effects in semiconductor active waveguides. Experimental and theoretical results are presented, emphasizing the physics of these phenomena and the limitations imposed by the carried dynamical processes....

  9. Peculiarities of Light Propagation in Photonic Crystal Waveguides in the Slow Light Regime

    DEFF Research Database (Denmark)

    Lavrinenko, Andrei; Borel, Peter Ingo; Frandsen, Lars Hagedorn;

    2006-01-01

    We report on transmission, field mapping, and spectral dependence of the group index in the slow light regime, obtained by numerical modelling. The influence of a finite number of lattice periods on the observed properties is pointed out.......We report on transmission, field mapping, and spectral dependence of the group index in the slow light regime, obtained by numerical modelling. The influence of a finite number of lattice periods on the observed properties is pointed out....

  10. Pecularities of Light Propagation in Photonic Crystal Waveguides in the Slow Light Regime

    DEFF Research Database (Denmark)

    Lavrinenko, Andrei; Borel, Peter Ingo; Frandsen, Lars Hagedorn;

    2006-01-01

    We report on transmission, fied mapping, and spectral dependence of the group index in the slow light regime, obtained by numerical modelling. The influence of a finite number of lattice periods on the observed properties is pointed out.......We report on transmission, fied mapping, and spectral dependence of the group index in the slow light regime, obtained by numerical modelling. The influence of a finite number of lattice periods on the observed properties is pointed out....

  11. Spatial Switching of Slow Light in Periodic Photonic Structures

    Science.gov (United States)

    Sukhorukov, Andrey A.

    The speed of light sets the maximum possible rate for transmission of information, in excess of 108 meters per second. Light pulses in optical fibers carry bits of data around the world in sub-second time frame, enabling interactive global communications. There is a constant demand for increasing the network performance in view of steadily growing information flows. It is envisioned that the presently required multiple conversions between optical pulses and electronic signals at network hubs may be eliminated in future when routing and switching of data flows is performed all-optically. This vision can be realized if the speed of light is dynamically controlled, allowing for synchronization and multiplexing of signals. Furthermore, by temporarily making the light slower it becomes possible to compress optical signals and perform their manipulation in compact photonic chips. Additionally, in the regime of slow light the photon-matter interactions are dramatically enhanced, enabling the active control of light and nonlinear transformations of signals. Slowing down the light is a challenging physical problem. In conventional dielectrics, the speed of light can only be reduced by a factor less than four which is limited by the optical refractive index of available materials. The most dramatic slowing down of light to a complete stop was reported in the regime of electromagnetically induced transparency [1]. This phenomenon is based on a resonant interaction of light with an atomic system and accordingly the speed of light is very sensitive to the frequency detuning. This restricts the effect to narrow frequency ranges limiting its applicability to communication networks with demands for data rates in excess of 100Gb per second. In contrast, dielectric photonic structures with a periodic modulation of the optical refractive index at a sub-micrometer scale can be engineered to operate at any frequency range. Periodic modulation results in resonant light scattering, and

  12. Limits of slow light in photonic crystals

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Xiao, Sanshui; Mortensen, N. Asger

    2008-01-01

    in the group velocity acquiring a finite value above zero at the band-gap edges while attaining uperluminal values within the band gap. Simple scalings of the minimum and maximum group velocities with the imaginary part of the dielectric function or, equivalently, the linewidth of the broadened states......While ideal photonic crystals would support modes with a vanishing group velocity, state-of-the-art structures have still only provided a slow down by roughly two orders of magnitude. We find that the induced density of states caused by lifetime broadening of the electromagnetic modes results...... are presented. The results obtained are entirely general and may be applied to any effect which results in a broadening of the electromagnetic states, such as loss, disorder, and finite-size effects. This significantly limits the reduction in group velocity attainable via photonic crystals....

  13. Slow light with electromagnetically induced transparency in cylindrical waveguide

    CERN Document Server

    Hatta, Agus Muhamad; Al-Hagan, Ola A; Moiseev, Sergey A

    2014-01-01

    Slow light with electromagnetically induced transparency (EIT) in the core of cylindrical waveguide (CW) for an optical fiber system containing three-level atoms is investigated. The CW modes are treated in the weakly guiding approximation which renders the analysis into manageable form. The transparency window and permittivity profile of the waveguide due to the strong pump field in the EIT scheme is calculated. For a specific permittivity profile of the waveguide due to EIT, the propagation constant of the weak signal field and spatial shape of fundamental guided mode are calculated by solving the vector wave equation using the finite difference method. It is found that the transparency window and slow light field can be controlled via the CW parameters. The reduced group velocity of slow light in this configuration is useful for many technological applications such as optical memories, effective control of single photon fields, optical buffer and delay line.

  14. Light

    CERN Document Server

    Ditchburn, R W

    2011-01-01

    This classic study, available for the first time in paperback, clearly demonstrates how quantum theory is a natural development of wave theory, and how these two theories, once thought to be irreconcilable, together comprise a single valid theory of light. Aimed at students with an intermediate-level knowledge of physics, the book first offers a historical introduction to the subject, then covers topics such as wave theory, interference, diffraction, Huygens' Principle, Fermat's Principle, and the accuracy of optical measurements. Additional topics include the velocity of light, relativistic o

  15. Optical signal processing using slow and fast light technologies

    DEFF Research Database (Denmark)

    Capmany, J.; Sales, Salvador; Xue, Weiqi;

    2009-01-01

    microwave or millimeter-wave frequency bands, we present one scheme to increase the achievable RF phase shift by enhancing light slow-down or speed-up. As a real application in microwave photonics, a widely tunable microwave photonic notch filter with 100% fractional tuning range is also proposed......We review the theory of slow and fat light effects due to coherent population oscillations in semiconductor waveguides, which can be potentially applied in microwave photonic systems as a RF phase shifters. In order to satisfy the application requirement of 360 degrees RF phase shift at different...

  16. Entangled photons from on-chip slow light

    CERN Document Server

    Takesue, Hiroki; Kuramochi, Eiichi; Notomi, Masaya

    2014-01-01

    We report the first entanglement generation experiment using an on-chip slow light device. With highly efficient spontaneous four-wave mixing enhanced by the slow light effect in a coupled resonator optical waveguide based on a silicon photonic crystal, we generated 1.5-$\\mu$m-band high-dimensional time-bin entangled photon pairs. We undertook two-photon interference experiments and observed the coincidence fringes with visibilities $>74\\%$. The present result enables us to realize an on-chip entanglement source with a very small footprint, which is an essential function for quantum information processing based on integrated quantum photonics.

  17. All-optical slow-light on a photonic chip.

    Science.gov (United States)

    Okawachi, Yoshitomo; Foster, Mark; Sharping, Jay; Gaeta, Alexander; Xu, Qianfan; Lipson, Michal

    2006-03-20

    We demonstrate optically tunable delays in a silicon-on-insulator planar waveguide based on slow light induced by stimulated Raman scattering (SRS). Inside an 8-mm-long nanoscale waveguide, we produce a group-index change of 0.15 and generate controllable delays as large as 4 ps for signal pulses as short as 3 ps. The scheme can be implemented at bandwidths exceeding 100 GHz for wavelengths spanning the entire low-loss fiber-optics communications window and thus represents an important step in the development of chip-scale photonics devices that process light with light.

  18. Engineering chiral light--matter interaction in photonic crystal waveguides with slow light

    CERN Document Server

    Mahmoodian, Sahand; Söllner, Immo; Stobbe, Søren; Lodahl, Peter

    2016-01-01

    We design photonic crystal waveguides with efficient chiral light--matter interfaces that can be integrated with solid-state quantum emitters. By using glide-plane-symmetric waveguides, we show that chiral light-matter interaction can exist even in the presence of slow light with slow-down factors of up to $100$ and therefore the light--matter interaction exhibits both strong Purcell enhancement and chirality. This allows for near-unity directional $\\beta$-factors for a range of emitter positions and frequencies. Additionally, we design an efficient mode adapter to couple light from a standard nanobeam waveguide to the glide-plane symmetric photonic crystal waveguide. Our work sets the stage for performing future experiments on a solid-state platform.

  19. Slow light in quantum dot photonic crystal waveguides

    DEFF Research Database (Denmark)

    Nielsen, Torben Roland; Lavrinenko, Andrei; Mørk, Jesper

    2009-01-01

    A theoretical analysis of pulse propagation in a semiconductor quantum dot photonic crystal waveguide in the regime of electromagnetically induced transparency is presented. The slow light mechanism considered here is based on both material and waveguide dispersion. The group index n...

  20. Slow light based on material and waveguide dispersion

    DEFF Research Database (Denmark)

    Nielsen, Torben Roland; Lavrinenko, Andrei; Mørk, Jesper

    2009-01-01

    We study slow light pulse propagation in a photonic crystal structure consisting of a dispersive and absorptive dielectric material and compare it with the constant wave case. The group index and the trasmission are investigated for the example of an ensemble of semiconductor quantum dots embedded...

  1. Enhanced circular dichroism via slow light in dispersive structured media

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Mortensen, Asger

    2007-01-01

    Circular dichroism (CD) is in widespread use as a means of determining enantiomeric excess. We show how slow-light phenomena in dispersive structured media allow for a reduction in the required optical path length of an order of magnitude. The same ideas may be used to enhance the sensitivity of CD...

  2. Slow Light by Two-Dimensional Photonic Crystal Waveguides

    Institute of Scientific and Technical Information of China (English)

    ZHANG Chao; HUANG Yan; MAO Xiao-Yu; CUI Kai-Yu; HUANG Yi-Dong; ZHANG Wei; PENG Jiang-De

    2009-01-01

    A simple and effective way to measure the group velocity of photonic crystal waveguides (PCWGs) is developed by using a fiber Mach-Zehnder interferometer. A PCWG with perfect air-bridge structure is fabricated and slow light with group velocity slower than c/80 is demonstrated.

  3. Systematic design of slow-light photonic waveguides

    DEFF Research Database (Denmark)

    Matzen, René; Jensen, Jakob Søndergaard; Sigmund, Ole

    2011-01-01

    A pulse-delaying optimization scheme based on topology optimization for transient response of photonic crystal structures (PhCs) is formulated to obtain slow-light devices. The optimization process is started from a qualified W1 PhC waveguide design with group index ng≈40 obtained from a simple E...

  4. Characterizing micro-macro transitions with slow light

    CERN Document Server

    Zhou, Zhifan; Glasser, Ryan T; Qin, Zhongzhong; Fang, Yami; Jing, Jietai; Zhang, Weiping

    2016-01-01

    The transition between the microscopic to the macroscopic world is of broad fundamental and technological significance. Optical parametric amplifiers allow for amplifying single photons to the macroscopic level, but the underlying temporal dynamics are still not well understood. Slow light, in which the group velocity is delayed via quantum interference, is an effective tool to interrogate the temporal dynamics of light-matter interactions. Here, we demonstrate a scheme to characterize micro-macro transitions with slow light based on a four-wave mixing linear amplification process in a hot rubidium vapour. The scheme exhibits strong dispersion which is sensitive to the input's change at the single-photon level, resulting in a nonlinear decay of the micro-macro transition time with the increased microscopic input. The present system is suitable for the study of the relevant time scale of quantum-to-classical transitions and the potential impact from fundamental effects such as gravity, as indicated by recent p...

  5. Cascaded passive silicon microrings for large bandwidth slow light device

    Energy Technology Data Exchange (ETDEWEB)

    Li Yuntao; Hu Yingtao; Xiao Xi; Li Zhiyong; Yu Yude; Yu Jinzhong, E-mail: ytli@semi.ac.cn [State Key Laboratory of integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, P. O. Box 912, Beijing 100083 (China)

    2011-02-01

    Slow light devices have important applications in the areas of data buffering, signal processing, and phased array antenna. Cascaded microring resonators structure can obtain large delay and also enhance the bandwidth, which was considered as a potential approach for future on-chip optical buffer. In this paper, we demonstrated a large bandwidth slow light device using cascaded Silicon-on-insulator (SOI) based microring resonators. With carefully designed the gap between the bus and the ring waveguides and the distances between the adjacent rings, a 57 ps group delay was observed and 83 Gbps maximum allowable bit rate is suggested according the measured 3 dB spectral bandwidth in the 8-stage cascaded microrings.

  6. Coupled-cavity-based slow light metamaterials with antireflection structures

    Science.gov (United States)

    Lee, Sun-Goo; Kim, Seong-Han; Jung, Soo-Yong; Lee, Jongjin; Park, Jong-Moon; Kee, Chul-Sik

    2016-11-01

    A slow light metamaterial based on a coupled Fabry-Pérot cavity is proposed and numerically studied using finite-difference time-domain simulations. The coupled cavity-based slow light metamaterial is composed of a periodic array of partial mirrors with low transmittance, i.e., thin metal films perforated with a subwavelength hole array. The tight-binding model is employed to investigate the transmission properties of the coupled-cavity-based metamaterial. It is shown that the group velocities of the slowly propagating modes can be controlled by adjusting the radius of holes in the mirrors. We also show that undesirable reflections at the boundaries of the finite-size metamaterial can be minimized by introducing optimized antireflection structures.

  7. Systematic design of loss-engineered slow-light waveguides

    DEFF Research Database (Denmark)

    Wang, Fengwen; Jensen, Jakob Søndergaard; Mørk, Jesper

    2012-01-01

    , where the scattering losses due to manufacturing imperfections are represented by an edge-related effective dissipation. The loss engineering of slow-light waveguides is realized by minimizing the propagation losses of design modes. Numerical examples illustrate that the propagation losses of free......This paper employs topology optimization to systematically design free-topology loss-engineered slow-light waveguides with enlarged group index bandwidth product (GBP). The propagation losses of guided modes are evaluated by the imaginary part of eigenvalues in complex band structure calculations......-topology dispersion-engineered waveguides can be significantly suppressed by loss engineering. Comparisons between fixed- and free-topology loss-engineered waveguides demonstrate that the GBP can be enhanced significantly by the free-topology loss-engineered waveguides with a small increase of the propagation losses....

  8. Slow light and pulse propagation in semiconductor waveguides

    DEFF Research Database (Denmark)

    Hansen, Per Lunnemann

    This thesis concerns the propagation of optical pulses in semiconductor waveguide structures with particular focus on methods for achieving slow light or signal delays. Experimental pulse propagation measurements of pulses with a duration of 180 fs, transmitted through quantum well based waveguide...... structures, are presented. Simultaneous measurements of the pulse transmission and delay are measured as a function of input pulse energy for various applied electrical potentials. Electrically controlled pulse delay and advancement are demonstrated and compared with a theoretical model. The limits...... of the model as well as the underlying physical mechanisms are analysed and discussed. A method to achieve slow light by electromagnetically induced transparency (EIT) in an inhomogeneously broadened quantum dot medium is proposed. The basic principles of EIT are assessed and the main dissimilarities between...

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

    Science.gov (United States)

    Kondo, K; Baba, T

    2014-06-06

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

  10. Passive integrated circuits utilizing slow light in photonic crystal waveguides

    DEFF Research Database (Denmark)

    Lavrinenko, Andrei; Têtu, Amélie; Yang, Lirong;

    2006-01-01

    We report thorough investigations of photonic crystal waveguide properties in the slow light regime. The transmission and the group index near the cutoff wavelengths oscillate in phase in close analogy with the ID photonic crystal behavior. The influence of having a finite number of periods...... in the photonic crystal waveguide is addressed to explain the spiky character of both the transmission and group index spectra. The profile of the slow-light modes is stretched out into the first and second rows of the holes closest to the waveguide channel. One of our strategies to ameliorate the design...... of photonic crystal devices is to engineer the radii of holes in these rows. A topology optimization approach is also utilized to make further improvements. The results of the numerical simulations and the optical characterization of fabricated devices such as straight waveguides with bends and couplers...

  11. Sagnac Interferometry in a Slow-Light Medium

    CERN Document Server

    Purves, G T; Hughes, I G; Adams, Charles S.; Hughes, Ifan G.; Purves, Graham T.

    2005-01-01

    We use a Sagnac interferometer to measure the dispersive and absorptive properties of room temperature Rubidium vapor on the D_2 line at 780.2 nm. We apply a pump beam such that the resulting Lambda system exhibits Electromagnetically Induced Transparency. Using a "biased alignment" technique we demonstrate a direct and robust method of measuring the rapid variation in the refractive index. Such a "slow-light" Sagnac interferometer is ideally suited to precision measurement applications such as magnetometry and inertial sensing.

  12. Using Nonuniform Fiber to Generate Slow Light via SBS

    Directory of Open Access Journals (Sweden)

    Wenhai Li

    2008-01-01

    Full Text Available The data pulse delay based on slow light induced by stimulated Brillouin scattering (SBS in a nonuniform dispersion decreasing fiber (DDF is demonstrated experimentally, and the distortions of data pulses at different beat frequencies are studied. We found that a delay exceeding a pulse width can be achieved at particular beat frequency, and the DDF has larger delay versus gain slope coefficient with much better output pulse quality than single-mode fiber.

  13. Dirac-graphene quasiparticles in strong slow-light pulse

    Science.gov (United States)

    Golovinski, P. A.; Astapenko, V. A.; Yakovets, A. V.

    2017-02-01

    An analytical Volkov's solution of the massless Dirac equation for graphene in the field of slow-light pulse with arbitrary time dependence is obtained. Exact solutions are presented for special cases of monochromatic field and a single-cycle pulse. Following the Fock-Schwinger proper time method, the Green's function for quasiparticles is derived with the account of the influence an external classical electromagnetic wave field.

  14. Tailoring the slow light behavior in terahertz metasurfaces

    CERN Document Server

    Manjappa, Manukumara; Cong, Longqing; Bettiol, Andrew A; Zhang, Weili; Singh, Ranjan

    2015-01-01

    We experimentally study the effect of near field coupling on the transmission of light in terahertz metasurfaces, possessing slightly distinctive SRR resonances. Our results show that the interplay between the strengths of electric and magnetic dipoles, modulates the amplitude of resulting electromagnetically induced transmission, probed under different types of asymmetries in the coupled system. We employ a two-particle model to theoretically study the influence of the near field coupling between bright and quasi-dark modes on the transmission properties of the coupled system and we find an excellent agreement with our observed results. Adding to the enhanced transmission characteristics, our results provide a deeper insight into the metamaterial analogues of atomic electromagnetically induced transparency and offer an approach to engineer slow light devices, broadband filters and attenuators at terahertz frequencies.

  15. Slow light in a semiconductor waveguide at gigahertz frequencies

    DEFF Research Database (Denmark)

    Mørk, Jesper; Kjær, Rasmus; Poel, Mike van der;

    2005-01-01

    We experimentally demonstrate slow-down of light by a factor of three in a 100 µm long semiconductor waveguide at room temperature and at a record-high frequency of 16.7 GHz. It is shown that the group velocity can be controlled all-optically as well as through an applied bias voltage. A semi......-analytical model based on the effect of coherent population oscillations and taking into account propagation effects is derived and is shown to well account for the experimental results. It is shown that the carrier lifetime limits the maximum achievable delay. Based on the general model we analyze fundamental...... limitations in the application of light slowdown due to coherent population oscillations....

  16. Tailoring the slow light behavior in terahertz metasurfaces

    Energy Technology Data Exchange (ETDEWEB)

    Manjappa, Manukumara; Cong, Longqing; Singh, Ranjan, E-mail: ranjans@ntu.edu.sg [Center for Disruptive Photonic Technologies, Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371 (Singapore); Chiam, Sher-Yi [NUS High School of Math and Science, 20 Clementi Avenue 1, Singapore, Singapore 129957 (Singapore); Bettiol, Andrew A. [Department of Physics, National University of Singapore, Science Drive 3, Singapore, Singapore 117542 (Singapore); Zhang, Weili [School of Electrical and Computer Engineering, Oklahoma State University, 202 Engineering South, Stillwater, Oklahoma 74078 (United States)

    2015-05-04

    We experimentally study the effect of near field coupling on the transmission of light in terahertz metasurfaces. Our results show that tailoring the coupling between the resonators modulates the amplitude of resulting electromagnetically induced transmission, probed under different types of asymmetries in the coupled system. Observed change in the transmission amplitude is attributed to the change in the amount of destructive interference between the resonators in the vicinity of strong near field coupling. We employ a two-particle model to theoretically study the influence of the coupling between bright and quasi-dark modes on the transmission properties of the system and we find an excellent agreement with our observed results. Adding to the enhanced transmission characteristics, our results provide a deeper insight into the metamaterial analogues of atomic electromagnetically induced transparency and offer an approach to engineer slow light devices, broadband filters, and attenuators at terahertz frequencies.

  17. An exact solution of the slow-light problem

    CERN Document Server

    Rybin, A V; Bishop, A R

    2004-01-01

    We investigate propagation of a slow-light soliton in atomic vapors and Bose-Einstein condensates described by the nonlinear Lambda-model. We show that the group velocity of the soliton monotonically decreases with the intensity of the controlling laser field, which decays exponentially after the laser is switched off. The shock wave of the vanishing controlling field overtakes the slow soliton and stops it, while the optical information is recorded in the medium in the form of spatially localized polarization. We find an explicit exact solution describing the whole process within the slowly varying amplitude and phase approximation. Our results point to the possibility of addressing spatially localized memory formations and moving these memory bits along the medium in a controllable fashion.

  18. Slow light in fiber Bragg gratings and its applications

    Science.gov (United States)

    Skolianos, George; Arora, Arushi; Bernier, Martin; Digonnet, Michel

    2016-11-01

    Slow-light fiber Bragg gratings (FBGs) belong to a class of gratings designed to exhibit one or more narrow resonances in their reflection and transmission spectra, produced either by introducing a π phase shift near the middle of the grating, or by increasing the index modulation so that the grating behaves like a Fabry-Perot interferometer. These resonances can have very narrow linewidths (optics, optical switching, optical delay lines, and sensing. This paper reviews the principle of these gratings, in particular the more recent slow-light gratings relying on a strong index modulation. It discusses in particular the requirements for achieving large group delays and high sensitivities in sensors, and the fabrication and annealing techniques used to meet these requirements (high index modulation, low loss, index-profile apodization, and optimized length). Several applications are presented, including record-breaking FBGs that exhibit a group delay of 42 ns and Q-factor of ~30 million over a 12.5 mm length, robust acoustic sensors with pressure resolution of ~50 µPa (√Hz)-1 in the few-kHz, and a strain sensor capable of resolving as little as 30 femtostrain (√Hz)-1.

  19. Light transmission through and its complete stoppage in an ultra slow wave optical medium

    CERN Document Server

    V., Ranjith

    2013-01-01

    Light Wave transmission -- its compression, amplification, and the optical energy storage -- in an Ultra Slow Wave Medium (USWM) is studied analytically. Our phenomenological treatment is based entirely on the continuity equation for the optical energy flux, and the well known distribution-product property of Dirac delta-function. The results so obtained provide a clear understanding of some recent experiments on light transmission and its complete stoppage in an USWM. Keywords : Ultra slow light, stopped light, slow wave medium, EIT.

  20. Electromagnetically Induced Transparency and Slow Light with Optomechanics

    CERN Document Server

    Safavi-Naeini, Amir H; Chan, Jasper; Eichenfield, Matt; Winger, Martin; Lin, Qiang; Hill, Jeffrey T; Chang, Darrick; Painter, Oskar

    2010-01-01

    Controlling the interaction between localized optical and mechanical excitations has recently become possible following advances in micro- and nano-fabrication techniques. To date, most experimental studies of optomechanics have focused on measurement and control of the mechanical subsystem through its interaction with optics, and have led to the experimental demonstration of dynamical back-action cooling and optical rigidity of the mechanical system. Converseley, the optical response of these systems is also modified in the presence of mechanical interactions, leading to strong nonlinear optical effects such as Electromagnetically Induced Transparency (EIT) and parametric normal-mode splitting. In atomic systems, seminal experiments and proposals to slow and stop the propagation of light, and their applicability to modern optical networks, and future quantum networks, have thrust EIT to the forefront of experimental study during the last two decades. In a similar fashion, here we use the optomechanical nonli...

  1. Experimental GVD engineering in slow light slot photonic crystal waveguides

    Science.gov (United States)

    Serna, Samuel; Colman, Pierre; Zhang, Weiwei; Le Roux, Xavier; Caer, Charles; Vivien, Laurent; Cassan, Eric

    2016-05-01

    The use in silicon photonics of the new optical materials developed in soft matter science (e.g. polymers, liquids) is delicate because their low refractive index weakens the confinement of light and prevents an efficient control of the dispersion properties through the geometry. We experimentally demonstrate that such materials can be incorporated in 700 μm long slot photonic crystal waveguides, and hence can benefit from both slow-light field enhancement effect and slot-induced ultra-small effective areas. Additionally, we show that their dispersion can be engineered from anomalous to normal regions, along with the presence of multiple zero group velocity dispersion (ZGVD) points exhibiting Normalized Delay Bandwidth Product as high as 0.156. The reported results provide experimental evidence for an accurate control of the dispersion properties of fillable periodical slotted structures in silicon photonics, which is of direct interest for on-chip all-optical data treatment using nonlinear optical effects in hybrid-on-silicon technologies.

  2. Does the Speed of Light Slow Down Over Time?

    Science.gov (United States)

    Ebert, Ronald

    1997-01-01

    The speed of light is a fundamental characteristic of the universe. So many processes are related to and dependent upon it that, if creationist claims were true, the universe would be far different from the way it is now. The speed of light has never been shown to vary based on the direction from which it was measured. (PVD)

  3. Slow-light effect in dual-periodic photonic lattice

    CERN Document Server

    Yamilov, Alexey G; Bertino, Massimo F

    2007-01-01

    We present analytical and numerical study of photonic lattice with short- and long-range harmonic modulations of the refractive index. Such structures can be prepared experimentally with holographic photolithography. In the spectral region of photonic bandgap of the underlying single-periodic crystal, we observe a series of bands with anomalously small dispersion. The related slow-light effect is attributed to the long-range modulation in the photonic lattice, that leads to formation of an array of evanescently-coupled high-$Q$ cavities. The band structure of the lattice is studied with several techniques: (i) transfer matrix approach; (ii) analysis of resonant coupling in process of band folding; (iii) effective medium approach based on coupled-mode theory; and (iv) Bogolyubov-Mitropolsky approach. The latter method, commonly used in the studies of nonlinear oscillators, was employed to investigate the behavior of the eigen-function envelopes and the band structure of our dual-periodic photonic lattice. We s...

  4. Generation and storage of double slow light pulses in a solid

    Institute of Scientific and Technical Information of China (English)

    Fan Yun-Fei; Wang Hai-Hua; Wang Rong; Zhang Xiao-Jun; Kang Zhi-Hui; Wu Jin-Hui; Zhang Han-Zhuang; Gao Jin-Yue

    2012-01-01

    We experimentally study the generation and storage of double slow light pulses in a Pr3+:Y2SiO5 crystal.Under electromagnetically induced transparency,a single signal pulse is stored in the spin coherence of the crystal. By simultaneously switching on two control fields to recall the stored information,the spin coherence is converted into two slow light pulses with distinct frequencies.Furthermore,the storage and controlled retrieval of double slow light pulses are obtained by manipulating the control fields.This study of double slow light pulses may have practical applications in information processing and all-optical networks.

  5. Slow and fast light effects in semiconductor optical amplifiers for applications in microwave photonics

    DEFF Research Database (Denmark)

    Xue, Weiqi

    This thesis analyzes semiconductor optical amplifiers based slow and fast light effects with particular focus on the applications in microwave photonics. We conceive novel ideas and demonstrate a great enhancement of light slow down. Furthermore, by cascading several slow light stages, >360 degree...... microwave phase shifts over a bandwidth of several tens of gigahertz are achieved. These also satisfy the basic requirements of microwave photonic systems. As an application demonstration, a tunable microwave notch filter is realized, where slow light based phase shifters provide 100% fractional tuning over...

  6. Reducing disorder-induced losses for slow light photonic crystal waveguides through Bloch mode engineering

    DEFF Research Database (Denmark)

    Mann, Nishan; Combrié, Sylvian; Colman, Pierre

    2013-01-01

    We present theory and measurements ofdisorder-induced losses for low loss 1.5 mmlong slow light photonic crystal waveguides. A recent class of dispersion engineered waveguides increases the bandwidth of slow light and shows lower propagation losses for the same group index. Our theory and experim...

  7. Enhancing slow and fast light effects in quantum dot semiconductor waveguides through ultrafast dynamics

    DEFF Research Database (Denmark)

    Chen, Yaohui; Mørk, Jesper

    2010-01-01

    We show that ultrafast carrier dynamics plays an important role on slow and fast light effects based on coherent population oscillations in quantum dot semiconductor waveguides. Fast light in the gain regime and slow light in the absorption regime are found to be enhanced at frequencies beyond th...... the usual limits of the carrier lifetime. The effects are investigated by a comprehensive model and shown to originate from non-equilibrium dynamics within the quantum dot carrier populations....

  8. Dynamics of slow light and light storage in a Doppler-broadened electromagnetically-induced-transparency medium: A numerical approach

    CERN Document Server

    Su, Shih-Wei; Gou, Shih-Chuan; Horng, Tzyy-Leng; Yu, Ite A

    2011-01-01

    We present a numerical scheme to study the dynamics of slow light and light storage in an electromagneticallyinduced- transparency (EIT) medium at finite temperatures. Allowing for the motional coupling, we derive a set of coupled Schr\\"{o}dinger equations describing a boosted closed three-level EIT system according to the principle of Galilean relativity. The dynamics of a uniformly moving EIT medium can thus be determined by numerically integrating the coupled Schr\\"odinger equations for atoms plus one ancillary Maxwell-Schr\\"odinger equation for the probe pulse. The central idea of this work rests on the assumption that the loss of ground-state coherence at finite temperatures can be ascribed to the incoherent superposition of density matrices representing the EIT systems with various velocities. Close agreements are demonstrated in comparing the numerical results with the experimental data for both slow light and light storage. In particular, the distinct characters featuring the decay of ground-state coh...

  9. Group-index limitations in slow-light photonic crystals

    DEFF Research Database (Denmark)

    Grgic, Jure; Pedersen, Jesper Goor; Xiao, Sanshui;

    2010-01-01

    In photonic crystals the speed of light can be significantly reduced due to band-structure effects associated with the spatially periodic dielectric function, rather than originating from strong material dispersion. In the ideal and loss-less structures it is possible even to completely stop...... the light near frequency band edges associated with symmetry points in the Brillouin zone. Unfortunately, despite the impressive progress in fabrication of photonic crystals, real structures differ from the ideal structures in several ways including structural disorder, material absorption, out of plane......-valued dielectric function. Perturbation theory predicts that the group index scales as 1/ϵ″ which we find to be in complete agreement with the full solutions for various examples. As a consequence, the group index remains finite in real photonic crystals, with its value depending on the damping parameter...

  10. Topology-optimized slow-light couplers for ring-shaped photonic crystal waveguide

    DEFF Research Database (Denmark)

    Pu, Minhao; Yang, Lirong; Frandsen, L. H.;

    2010-01-01

    We demonstrate a topology-optimized coupler for a ring-shaped photonic crystal waveguide to improve the coupling of light located in the slow-light regime. An enhancement of the coupling efficiency of up to 2.5 dB is experimentally demonstrated.......We demonstrate a topology-optimized coupler for a ring-shaped photonic crystal waveguide to improve the coupling of light located in the slow-light regime. An enhancement of the coupling efficiency of up to 2.5 dB is experimentally demonstrated....

  11. Rapidly reconfigurable slow-light system based on off-resonant Raman absorption

    Science.gov (United States)

    Vudyasetu, Praveen K.; Camacho, Ryan M.; Howell, John C.

    2010-11-01

    We present a slow-light system based on dual Raman absorption resonances in warm rubidium vapor. Each Raman absorption resonance is produced by a control beam in an off-resonant Λ system. This system combines all optical control of the Raman absorption and the low-dispersion broadening properties of the double Lorentzian absorption slow light. The bandwidth, group delay, and central frequency of the slow-light system can all be tuned dynamically by changing the properties of the control beam. We demonstrate multiple pulse delays with low distortion and show that such a system has fast switching dynamics and thus fast reconfiguration rates.

  12. Enhanced spectral sensitivity of a chip-scale photonic-crystal slow-light interferometer

    CERN Document Server

    Magaña-Loaiza, Omar S; Schulz, Sebastian A; Awan, Kashif; Upham, Jeremy; Dolgaleva, Ksenia; Boyd, Robert W

    2016-01-01

    We experimentally demonstrate that the spectral sensitivity of a Mach-Zehnder (MZ) interferometer can be enhanced through structural slow light. We observe a 20 times enhancement by placing a dispersion-engineered-slow-light photonic-crystal waveguide in one arm of a fibre-based MZ interferometer. The spectral sensitivity of the interferometer increases roughly linearly with the group index, and we have quantified the resolution in terms of the spectral density of interference fringes. These results show promise for the use of slow-light methods for developing novel tools for optical metrology and, specifically, for compact high-resolution spectrometers.

  13. Simulation and measurement of slow light in photonic crystal waveguides

    DEFF Research Database (Denmark)

    Lavrinenko, Andrei; Jacobsen, Rune Shim; Fage-Pedersen, Jacob

    Planar photonic crystals offer a fascinating means of manipulation of light in integrated,optical circuits. Such waveguides can be realized, as in the present investigations, byfabricating arrays of holes with sub-micrometer distance in the top layer of a silicon-oninsulatorwafer. The waveguides...... can be tailored such that the propagating mode achievesextreme dispersion as well as a low group velocity, allowing for realization of ultracompact, functional devices. Here, we present numerical modeling and measurements ofthe time-of-flight propagation of optical pulses. Near the cut...

  14. Interaction between atoms and slow light: a design study

    CERN Document Server

    Zang, Xiaorun; Faggiani, Rémi; Gill, Christopher; Petrov, Plamen G; Hugonin, Jean-Paul; Bernon, Simon; Bouyer, Philippe; Boyer, Vincent; Lalanne, Philippe

    2015-01-01

    The emerging field of on-chip integration of nanophotonic devices and cold atoms offers extremely-strong and pure light-matter interaction schemes, which may have profound impact on quantum information science. In this context, a longstanding obstacle is to achieve strong interaction between single atoms and single photons, while at the same time trap atoms in vacuum at large separation distances from dielectric surfaces. In this letter, we study new waveguide geometries that challenge these conflicting objectives. The designed photonic crystal waveguide is expected to offer a good compromise, which additionally allow for easy manipulation of atomic clouds around the structure.

  15. Comments on "Slowing of Bessel light beam group velocity"

    CERN Document Server

    Saari, Peeter

    2016-01-01

    In a recent article [R. R. Alfano and D. A. Nolan, Opt. Commun. 361 (2016) 25] the group velocity reduction below the speed of light in the case of certain Bessel beam pulses has been considered and an idea of its application for a natural optical buffer presented. However, the authors treat the problem as if only one type of Bessel pulse existed, no matter how it is generated. The deficiencies of the article stem from not being familiar with an extensive literature on Bessel pulses, in particular, with a couple of papers published much earlier in the J. Opt. Soc. Am. A, which have studied exactly the same problem more thoroughly.

  16. Few photon switching with slow light in hollow fiber

    DEFF Research Database (Denmark)

    Bajcsy, Michal; Hofferberth, S.; Balic, Vlatko

    2009-01-01

    Cold atoms confined inside a hollow-core photonic-crystal fiber with core diameters of a few photon wavelengths are a promising medium for studying nonlinear optical interactions at extremely low light levels. The high electric field intensity per photon and interaction lengths not limited...... by diffraction are some of the unique features of this system. Here, we present the results of our first nonlinear optics experiments in this system including a demonstration of an all-optical switch that is activated at energies corresponding to few hundred optical photons per pulse....

  17. Simulation and measurement of slow light in photonic crystal waveguides

    DEFF Research Database (Denmark)

    Lavrinenko, Andrei; Jacobsen, Rune Shim; Fage-Pedersen, Jacob;

    Planar photonic crystals offer a fascinating means of manipulation of light in integrated,optical circuits. Such waveguides can be realized, as in the present investigations, byfabricating arrays of holes with sub-micrometer distance in the top layer of a silicon-oninsulatorwafer. The waveguides...... can be tailored such that the propagating mode achievesextreme dispersion as well as a low group velocity, allowing for realization of ultracompact, functional devices. Here, we present numerical modeling and measurements ofthe time-of-flight propagation of optical pulses. Near the cut...

  18. Time reversal constraint limits unidirectional photon emission in slow-light photonic crystals

    CERN Document Server

    Lang, Ben; Oulton, Ruth

    2016-01-01

    Photonic crystal waveguides are known to support C-points - point-like polarisation singularities with local chirality. Such points can couple with dipole-like emitters to produce highly directional emission, from which spin-photon entanglers can be built. Much is made of the promise of using slow-light modes to enhance this light-matter coupling. Here we explore the transition from travelling to standing waves for two different photonic crystal waveguide designs. We find that time-reversal symmetry and the reciprocal nature of light places constraints on using C-points in the slow-light regime. We observe two distinctly different mechanisms through which this condition is satisfied in the two waveguides. In the waveguide designs we consider, a modest group-velocity of $v_g \\approx c/10$ is found to be the optimum for slow-light coupling to the C-points.

  19. Slow light in the GaAs-rod-loaded metallic waveguide for terahertz wave.

    Science.gov (United States)

    Wang, Wei; He, Jinlong; Li, Xiangjun; Hong, Zhi

    2010-05-24

    The modes in a circular metallic waveguide loaded with a high permittivity dielectric rod may possess similar dispersion relations to the modes in the left-handed metamaterial (LHM) waveguide. Therefore such dielectric-loaded metallic waveguide may also support slow light with parameters properly selected. The slow light in the GaAs-rod-loaded metallic waveguide is numerically studied. The results show that the wavelength of slow light varies with the parameters of the waveguide. A linearly tapered waveguide and other realizable simple structures are proposed accordingly to realize the "trapped rainbow" phenomena. Moreover, the practical lossy tapered waveguide is also investigated in the terahertz region. It is shown that the slow light with low loss can be achieved in a realistic GaAs-loaded metallic waveguide.

  20. Experimental demonstration of 360 tunable RF phase shift using slow and fast light effects

    DEFF Research Database (Denmark)

    Xue, Weiqi; Sales, Salvador; Capmany, Jose;

    2009-01-01

    A microwave photonic phase shifter realizing 360º phase shift over a RF bandwidth of more than 10 GHz is demonstrated using optical filtering assisted slow and fast light effects in a cascaded structure of semiconductor optical amplifiers....

  1. Physics and applications of slow and fast light in semiconductor optical waveguides

    DEFF Research Database (Denmark)

    Mørk, Jesper; Chen, Yaohui; Ek, Sara;

    We review the physics of slow and fast light based on coherent population oscillations in active semiconductor waveguides. Exploiting these effects, microwave phase shifters realizing 360 degree phase shift and operating at tens of GHz have been realized.......We review the physics of slow and fast light based on coherent population oscillations in active semiconductor waveguides. Exploiting these effects, microwave phase shifters realizing 360 degree phase shift and operating at tens of GHz have been realized....

  2. Optimization of Photonic Crystal 60o Waveguide Bends in the Slow Light Regime for Broadband Transmission

    DEFF Research Database (Denmark)

    Lavrinenko, Andrei; Têtu, Amélie; Frandsen, Lars Hagedorn

    2006-01-01

    We present results for broadband transmission through photonic crystal waveguide bends optimized for slow-light modes. Theoretical analysis is complemented by experimental verification of designs including topology optimized ones fabricated in SOI material.......We present results for broadband transmission through photonic crystal waveguide bends optimized for slow-light modes. Theoretical analysis is complemented by experimental verification of designs including topology optimized ones fabricated in SOI material....

  3. Slow and fast light in SOA-EA structures for phased-array antennas

    DEFF Research Database (Denmark)

    Sales, S.; Öhman, Filip; Bermejo, A.;

    We present an SOA-EA structure for controlling the phase and amplitude of optically fed phased-array antennas. Phase shifts of 40 degrees are obtained through slow and fast light effects by changing only the reverse voltage.......We present an SOA-EA structure for controlling the phase and amplitude of optically fed phased-array antennas. Phase shifts of 40 degrees are obtained through slow and fast light effects by changing only the reverse voltage....

  4. Effect of loss on slow-light enhanced absorption in liquid-infiltrated photonic crystals

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Xiao, Sanshui; Mortensen, Asger

    2008-01-01

    We study slow-light enhancement of absorption measurements in photonic crystals composed of lossy dielectrics. We find that the material loss has an unexpected limited drawback and may even increase the bandwidth for low-index contrast systems.......We study slow-light enhancement of absorption measurements in photonic crystals composed of lossy dielectrics. We find that the material loss has an unexpected limited drawback and may even increase the bandwidth for low-index contrast systems....

  5. Experimental investigation of slow light propagation in degenerate two-level system

    Institute of Scientific and Technical Information of China (English)

    Wang Li-Rong; Zhao Yan-Ting; Ma Jie; Zhao Jian-Ming; Xiao Lian-Tuan; Jia Suo-Tang

    2006-01-01

    Slowing a light pulse in a degenerate two-level system is observed with a double-frequency sweeping technique. The effects of coupling beam intensity, cell temperature and frequency detunings of the coupling and probe beams in resonance, on the slowing of light propagation in such a system are investigated. It is found that group velocities depend strongly on polarization combinations. A group velocity υg=6760m/s of light pulses in caesium vapour is obtained under the optimal parameters.

  6. Direct observation of surface mode excitation and slow light coupling in photonic crystal waveguides

    DEFF Research Database (Denmark)

    Volkov, V.S.; Bozhevolnyi, Sergey I.; Frandsen, Lars Hagedorn;

    2007-01-01

    are obtained for light at telecom wavelengths propagating in the PhCW, demonstrating directly, for the first time to our knowledge, drastic widening of the PhCW guided mode in the slow-light regime and excitation of surface waves at the PhCW interface along with their feeding into the guided mode......A scanning near-field optical microscope (SNOM) is used to systematically study the properties of guided modes in linear and slow-light regimes of silicon-on-insulator (SOI)-based photonic crystal waveguides (PhCWs) with different terminations of the photonic lattice. High quality SNOM images...

  7. Slow light and band gaps in metallodielectric cylinder arrays.

    Science.gov (United States)

    Shainline, Jeffrey M; Xu, Jimmy

    2009-05-25

    We consider two-dimensional three-component photonic crystals wherein one component is modeled as a drude-dispersive metal. It is found that the dispersion relation of light in this environment depends critically on the configuration of the metallic and dielectric components. In particular, for the case of an incident electromagnetic wave with electric field vector parallel to the axis of the cylinders it is shown that the presence of dielectric shells covering the metallic cylinders leads to a closing of the structural band gap with increased filling factor, as would be expected for a purely dielectric photonic crystal. For the same polarization, the photonic band structure of an array of metallic shell cylinders with dielectric cores do not show the closing of the structural band gap with increased filling factor of the metallic component. In this geometry, the photonic band structure contains bands with very small values of group velocity with some bands having a maximum of group velocity as small as .05c.

  8. Third-harmonic generation in slow-light chalcogenide glass photonic crystal waveguides

    Science.gov (United States)

    Monat, Christelle; Spurny, Marcel; Grillet, Christian; O'Faolain, Liam; Krauss, Thomas F.; Eggleton, Benjamin J.; Bulla, Douglas; Madden, Steve; Luther-Davies, Barry

    2011-08-01

    We demonstrate third-harmonic generation (THG) in a dispersion-engineered slow-light photonic crystal waveguide fabricated in AMTIR-1 chalcogenide glass. Owing to the relatively low loss and low dispersion in the slow-light (c/30) regime, combined with the high nonlinear figure of merit of the material (˜2), we obtain a relatively large conversion efficiency (1.4×10-8/W2), which is 30× higher than in comparable silicon waveguides, and observe a uniform visible light pattern along the waveguide. These results widen the number of applications underpinned by THG in slow-light platforms, such as the direct observation of the spatial evolution of the propagating mode.

  9. Slow light enhanced atomic frequency comb quantum memories in photonic crystal waveguides

    Science.gov (United States)

    Yuan, Chenzhi; Zhang, Wei; Huang, Yidong; Peng, Jiangde

    2016-09-01

    In this paper, we propose a slow light-enhanced quantum memory with high efficiency based on atomic frequency comb (AFC) in ion-doped photonic crystal waveguide (PCW). The performance of the quantum memory is investigated theoretically, considering the impact of the signal bandwidth. Both the forward and backward retrieval schemes are analyzed. In the forward retrieval scheme, the analysis shows that a moderate slow light effect can improve the retrieval efficiency to above 50% with very high fidelity, even when the intrinsic optical depth is very low and the signal bandwidth is comparable with the AFC bandwidth. In the backward retrieval scheme, retrieval efficiency larger than 90% can be obtained and fidelity can remain above 90% for signal with bandwidth much narrower than AFC bandwidth, when moderate slow light is introduced into waveguide with low intrinsic optical depth. Although the phase mismatching effect limits the slow light enhancement on retrieval efficiency and decreases the fidelity for signal with bandwidth approaching AFC bandwidth, we design a modified atomic frequency comb structure (MAFC) based on which a moderate slow light can make the retrieval efficiency larger than 85% and keep the fidelity above 80%. Our calculations show that the proposed scheme provides a promising way to realize high efficiency on-chip quantum memory.

  10. Slow light hierarchy and tunable switching in fractal wave guide

    Science.gov (United States)

    Nandy, Atanu; Chakrabarti, Arunava

    2017-05-01

    An exact analytical description of unraveling hierarchical distribution of slow optical modes in the context of propagation of classical waves through a fractal wave guide is reported using the scale invariance of the underlying geometry in the tight-binding formalism. The flat photonic modes are localized with finite support in the fractal system and getting trapped over clusters of increasing spans displaying the existence of multitude of localization area. The onset of localization can in principal be delayed in space by a suitable choice of the frequency of the incoming radiation. The length scale at which the onset of localization for each bounded optical mode occurs can be tuned at will following real space renormalization group method. Scanning over arbitrary small range of frequency may lead to the possibility of inter-modal switching behavior.

  11. Slow and fast light effects in semiconductor waveguides for applications in microwave photonics

    DEFF Research Database (Denmark)

    Xue, Weiqi; Chen, Yaohui; Öhman, Filip

    2009-01-01

    We review the theory of slow and fast light effects due to coherent population oscillations in semiconductor waveguides, and potential applications of these effects in microwave photonic systems as RF phase shifters. In order to satisfy the application requirement of 360º RF phase shift at differ......We review the theory of slow and fast light effects due to coherent population oscillations in semiconductor waveguides, and potential applications of these effects in microwave photonic systems as RF phase shifters. In order to satisfy the application requirement of 360º RF phase shift...... at different microwave or millimeter-wave frequency bands, we present several schemes to increase the achievable RF phase shift by enhancing light slow-down or speed-up. These schemes include integrating gain and absorption sections, optical filtering and the exploitation of the initial chirp effects...

  12. Modal theory of slow light enhanced third-order nonlinear effects in photonic crystal waveguides.

    Science.gov (United States)

    Chen, Tao; Sun, Junqiang; Li, Linsen

    2012-08-27

    In this paper, we derive the couple-mode equations for third-order nonlinear effects in photonic crystal waveguides by employing the modal theory. These nonlinear interactions include self-phase modulation, cross-phase modulation and degenerate four-wave mixing. The equations similar to that in nonlinear fiber optics could be expanded and applied for third-order nonlinear processes in other periodic waveguides. Based on the equations, we systematically analyze the group-velocity dispersion, optical propagation loss, effective interaction area, slow light enhanced factor and phase mismatch for a slow light engineered silicon photonic crystal waveguide. Considering the two-photon and free-carrier absorptions, the wavelength conversion efficiencies in two low-dispersion regions are numerically simulated by utilizing finite difference method. Finally, we investigate the influence of slow light enhanced multiple four-wave-mixing process on the conversion efficiency.

  13. Nonlinear enhancement in photonic crystal slow light waveguides fabricated using CMOS-compatible process.

    Science.gov (United States)

    Shinkawa, Mizuki; Ishikura, Norihiro; Hama, Yosuke; Suzuki, Keijiro; Baba, Toshihiko

    2011-10-24

    We have studied low-dispersion slow light and its nonlinear enhancement in photonic crystal waveguides. In this work, we fabricated the waveguides using Si CMOS-compatible process. It enables us to integrate spotsize converters, which greatly simplifies the optical coupling from fibers as well as demonstration of the nonlinear enhancement. Two-photon absorption, self-phase modulation and four-wave mixing were observed clearly for picosecond pulses in a 200-μm-long device. In comparison with Si wire waveguides, a 60-120 fold higher nonlinearity was evaluated for a group index of 51. Unique intensity response also occurred due to the specific transmission spectrum and enhanced nonlinearities. Such slow light may add various functionalities in Si photonics, while loss reduction is desired for ensuring the advantage of slow light.

  14. Four-wave mixing in slow light engineered silicon photonic crystal waveguides.

    Science.gov (United States)

    Monat, C; Ebnali-Heidari, M; Grillet, C; Corcoran, B; Eggleton, B J; White, T P; O'Faolain, L; Li, J; Krauss, T F

    2010-10-25

    We experimentally investigate four-wave mixing (FWM) in short (80 μm) dispersion-engineered slow light silicon photonic crystal waveguides. The pump, probe and idler signals all lie in a 14 nm wide low dispersion region with a near-constant group velocity of c/30. We measure an instantaneous conversion efficiency of up to -9dB between the idler and the continuous-wave probe, with 1W peak pump power and 6 nm pump-probe detuning. This conversion efficiency is found to be considerably higher (>10 × ) than that of a Si nanowire with a group velocity ten times larger. In addition, we estimate the FWM bandwidth to be at least that of the flat band slow light window. These results, supported by numerical simulations, emphasize the importance of engineering the dispersion of PhC waveguides to exploit the slow light enhancement of FWM efficiency, even for short device lengths.

  15. Atomic Interaction Effects on Electromagnetically Induced Transparency and Slow Light in Ultracold Bose Gas

    Institute of Scientific and Technical Information of China (English)

    胡正峰; 杜春光; 李代军; 李师群

    2002-01-01

    We investigate electromagnetically induced transparency and slow group velocity of light in ultracold Bose gas with a two-photon Raman process. The properties of electromagnetically induced transparency and light speed can be changed by controlling the atomic interaction. Atomic interaction can be used as a knob to control the optical properties of atomic media. This can be realized in experiment by using the Feshbach resonance technique.

  16. Slow light enhanced optical nonlinearity in a silicon photonic crystal coupled-resonator optical waveguide.

    Science.gov (United States)

    Matsuda, Nobuyuki; Kato, Takumi; Harada, Ken-Ichi; Takesue, Hiroki; Kuramochi, Eiichi; Taniyama, Hideaki; Notomi, Masaya

    2011-10-10

    We demonstrate highly enhanced optical nonlinearity in a coupled-resonator optical waveguide (CROW) in a four-wave mixing experiment. Using a CROW consisting of 200 coupled resonators based on width-modulated photonic crystal nanocavities in a line defect, we obtained an effective nonlinear constant exceeding 10,000 /W/m, thanks to slow light propagation combined with a strong spatial confinement of light achieved by the wavelength-sized cavities.

  17. Time-reversal constraint limits unidirectional photon emission in slow-light photonic crystals.

    Science.gov (United States)

    Lang, Ben; Beggs, Daryl M; Oulton, Ruth

    2016-08-28

    Photonic crystal waveguides are known to support C-points-point-like polarization singularities with local chirality. Such points can couple with dipole-like emitters to produce highly directional emission, from which spin-photon entanglers can be built. Much is made of the promise of using slow-light modes to enhance this light-matter coupling. Here we explore the transition from travelling to standing waves for two different photonic crystal waveguide designs. We find that time-reversal symmetry and the reciprocal nature of light places constraints on using C-points in the slow-light regime. We observe two distinctly different mechanisms through which this condition is satisfied in the two waveguides. In the waveguide designs, we consider a modest group velocity of vg≈c/10 is found to be the optimum for slow-light coupling to the C-points.This article is part of the themed issue 'Unifying physics and technology in light of Maxwell's equations'.

  18. Enhanced four-wave mixing in graphene-silicon slow-light photonic crystal waveguides

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Hao, E-mail: hz2299@columbia.edu, E-mail: tg2342@columbia.edu, E-mail: cww2104@columbia.edu [College of Electronic Information, Sichuan University, Chengdu 610064 (China); Optical Nanostructures Laboratory, Columbia University, New York, New York 10027 (United States); Gu, Tingyi, E-mail: hz2299@columbia.edu, E-mail: tg2342@columbia.edu, E-mail: cww2104@columbia.edu; McMillan, James F.; Wong, Chee Wei, E-mail: hz2299@columbia.edu, E-mail: tg2342@columbia.edu, E-mail: cww2104@columbia.edu [Optical Nanostructures Laboratory, Columbia University, New York, New York 10027 (United States); Petrone, Nicholas; Zande, Arend van der; Hone, James C. [Mechanical Engineering, Columbia University, New York, New York 10027 (United States); Yu, Mingbin; Lo, Guoqiang; Kwong, Dim-Lee [The Institute of Microelectronics, Singapore 117685 (Singapore); Feng, Guoying [College of Electronic Information, Sichuan University, Chengdu 610064 (China); Zhou, Shouhuan [College of Electronic Information, Sichuan University, Chengdu 610064 (China); North China Research Institute of Electro-Optics, Beijing 100015 (China)

    2014-09-01

    We demonstrate the enhanced four-wave mixing of monolayer graphene on slow-light silicon photonic crystal waveguides. 200-μm interaction length, a four-wave mixing conversion efficiency of −23 dB is achieved in the graphene-silicon slow-light hybrid, with an enhanced 3-dB conversion bandwidth of about 17 nm. Our measurements match well with nonlinear coupled-mode theory simulations based on the measured waveguide dispersion, and provide an effective way for all-optical signal processing in chip-scale integrated optics.

  19. Slow light enhanced correlated photon pair generation in photonic-crystal coupled-resonator optical waveguides

    CERN Document Server

    Matsuda, Nobuyuki; Shimizu, Kaoru; Tokura, Yasuhiro; Kuramochi, Eiichi; Notomi, Masaya; 10.1364/OE.21.008596

    2013-01-01

    We demonstrate the generation of quantum-correlated photon pairs from a Si photonic-crystal coupled-resonator optical waveguide. A slow-light supermode realized by the collective resonance of high-Q and small-mode-volume photonic-crystal cavities successfully enhanced the efficiency of the spontaneous four-wave mixing process. The generation rate of photon pairs was improved by two orders of magnitude compared with that of a photonic-crystal line defect waveguide without a slow-light effect.

  20. Slow light enhanced correlated photon pair generation in photonic-crystal coupled-resonator optical waveguides.

    Science.gov (United States)

    Matsuda, Nobuyuki; Takesue, Hiroki; Shimizu, Kaoru; Tokura, Yasuhiro; Kuramochi, Eiichi; Notomi, Masaya

    2013-04-08

    We demonstrate the generation of quantum-correlated photon pairs from a Si photonic-crystal coupled-resonator optical waveguide. A slow-light supermode realized by the collective resonance of high-Q and small-mode-volume photonic-crystal cavities successfully enhanced the efficiency of the spontaneous four-wave mixing process. The generation rate of photon pairs was improved by two orders of magnitude compared with that of a photonic-crystal line defect waveguide without a slow-light effect.

  1. Slow-light enhanced optical detection in liquid-infiltrated photonic crystals

    DEFF Research Database (Denmark)

    Pedersen, Martin Erland Vestergaard; Rishøj, Lars Søgaard; Steffensen, Henrik;

    2007-01-01

    Slow-light enhanced optical detection in liquid-infiltrated photonic crystals is theoretically studied. Using a scattering-matrix approach and the Wigner–Smith delay time concept, we show that optical absorbance benefits both from slow-light phenomena as well as a high filling factor of the energy...... residing in the liquid. Utilizing strongly dispersive photonic crystal structures, we numerically demonstrate how liquid-infiltrated photonic crystals facilitate enhanced light–matter interactions, by potentially up to an order of magnitude. The proposed concept provides strong opportunities for improving...... existing miniaturized absorbance cells for optical detection in lab-on-a-chip systems....

  2. Effect of loss on slow-light-enhanced second-harmonic generation in periodic nanostructures

    DEFF Research Database (Denmark)

    Saravi, Sina; Quintero-Bermudez, Rafael; Setzpfandt, Frank;

    2016-01-01

    We theoretically analyze the dependence of second-harmonic generation efficiency on the group index in periodic optical waveguides with loss. We investigate different possible scenarios of using slow light to enhance the efficiency of this process and show that in some cases there exists a maxima......We theoretically analyze the dependence of second-harmonic generation efficiency on the group index in periodic optical waveguides with loss. We investigate different possible scenarios of using slow light to enhance the efficiency of this process and show that in some cases there exists...... of second-harmonic generation in periodic nanobeam waveguides with loss. (C) 2016 Optical Society of America...

  3. Robust photonic differentiator employing slow light effect in photonic crystal waveguide

    DEFF Research Database (Denmark)

    Yan, Siqi; Cheng, Ziwei; Frandsen, Lars Hagedorn

    2017-01-01

    A robust photonic DIFF exploiting the slow light effect in a photonic crystal waveguide is proposed and experimentally demonstrated. Input Gaussian pulses with full-width halfmaximums ranging from 2.7 ps to 81.4 ps can be accurately differentiated.......A robust photonic DIFF exploiting the slow light effect in a photonic crystal waveguide is proposed and experimentally demonstrated. Input Gaussian pulses with full-width halfmaximums ranging from 2.7 ps to 81.4 ps can be accurately differentiated....

  4. Design of Slow and Fast Light Photonic Crystal Waveguides for Single-photon Emission Using a Bloch Mode Expansion Technique

    DEFF Research Database (Denmark)

    de Lasson, Jakob Rosenkrantz; Rigal, B.; Kapon, E.;

    We design slow and fast light photonic crystal waveguides for single-photon emission using a Bloch mode expansion and scattering matrix technique. We propose slow light designs that increase the group index-waveguide mode volume ratio for larger Purcell enhancement, and address efficient slow...

  5. Fibre Optical Parametric Amplification in Defect Bragg Fibres with Zero Dispersion Slow Light Effect

    Institute of Scientific and Technical Information of China (English)

    XIAO Li; ZHANG Wei; HUANG Yi-Dong; PENG Jiang-De; ZHAO Hong; YANG Ke-Wu

    2008-01-01

    Nonfinearity enhancement by slow light effect and strong light confinement in defect Bragg fibres is demonstrated and analysed in applications of fibre optical parametric amplifiers. Broadband low group velocity and zero dispersion as well as the strong light confinement by band gap enhances the nonlinear coefficient up to more than one order than the conventional high nonlinear fibres.Moreover,the zero dispersion wavelength of coupled core mode can be designed arbitrarily,under which the phase-matching bandwidth of the nonlinear process can be extended.

  6. Light-induced responses of slow oscillatory neurons of the rat olivary pretectal nucleus.

    Directory of Open Access Journals (Sweden)

    Hanna J Szkudlarek

    Full Text Available BACKGROUND: The olivary pretectal nucleus (OPN is a small midbrain structure responsible for pupil constriction in response to eye illumination. Previous electrophysiological studies have shown that OPN neurons code light intensity levels and therefore are called luminance detectors. Recently, we described an additional population of OPN neurons, characterized by a slow rhythmic pattern of action potentials in light-on conditions. Rhythmic patterns generated by these cells last for a period of approximately 2 minutes. METHODOLOGY: To answer whether oscillatory OPN cells are light responsive and whether oscillatory activity depends on retinal afferents, we performed in vivo electrophysiology experiments on urethane anaesthetized Wistar rats. Extracellular recordings were combined with changes in light conditions (light-dark-light transitions, brief light stimulations of the contralateral eye (diverse illuminances or intraocular injections of tetrodotoxin (TTX. CONCLUSIONS: We found that oscillatory neurons were able to fire rhythmically in darkness and were responsive to eye illumination in a manner resembling that of luminance detectors. Their firing rate increased together with the strength of the light stimulation. In addition, during the train of light pulses, we observed two profiles of responses: oscillation-preserving and oscillation-disrupting, which occurred during low- and high-illuminance stimuli presentation respectively. Moreover, we have shown that contralateral retina inactivation eliminated oscillation and significantly reduced the firing rate of oscillatory cells. These results suggest that contralateral retinal innervation is crucial for the generation of an oscillatory pattern in addition to its role in driving responses to visual stimuli.

  7. Observation of four-wave mixing in slow-light silicon photonic crystal waveguides.

    Science.gov (United States)

    McMillan, James F; Yu, Mingbin; Kwong, Dim-Lee; Wong, Chee Wei

    2010-07-19

    Four-wave mixing is observed in a silicon W1 photonic crystal waveguide. The dispersion dependence of the idler conversion efficiency is measured and shown to be enhanced at wavelengths exhibiting slow group velocities. A 12-dB increase in the conversion efficiency is observed. Concurrently, a decrease in the conversion bandwidth is observed due to the increase in group velocity dispersion in the slow-light regime. The experimentally observed conversion efficiencies agree with the numerically modeled results.

  8. Observations of four-wave mixing in slow-light silicon photonic crystal waveguides

    CERN Document Server

    McMillan, James F; Kwong, Dim-Lee; Wong, Chee Wei

    2010-01-01

    Four-wave mixing is observed in a silicon W1 photonic crystal waveguide. The dispersion dependence of the idler conversion efficiency is measured and shown to be enhanced at wavelengths exhibiting slow group velocities. A 12-dB increase in the conversion efficiency is observed. Concurrently, a decrease in the conversion bandwidth is observed due to the increase in group velocity dispersion in the slow-light regime. The experimentally observed conversion efficiencies agree with the numerically modeled results.

  9. Slow light in dual-periodic photonic crystals based slotted-waveguide coupled cavity

    Science.gov (United States)

    Zhu, Na; Li, Yuanyuan; Chen, Cheng; Yan, Shu

    2016-09-01

    Considering the capacity of the nanoscale width area with the low-refractive index can confine light waves, the dual-periodic slotted photonic crystals, which is constructed by coupling low-refractive index's slotted-waveguide with high-refractive index's cavity is proposed in this paper. The best slow light properties and the optimal slotted-waveguide coupled cavity are achieved by adjusting the slotted-width and the period of cavity respectively. In this structure, the slow-light properties are simulated by Plane Wave Expansion (PWE), the result reveals that the group velocities are all three orders of magnitude smaller than the speed of light in vacuum, the slowest value is 7.96 ×10-4 c when the slotted-width is 0.54a and the period of cavity is 0.95a. Moreover, the corresponding Normalized Delay-Bandwidth Product (NDBP) values are larger than 0.24. Besides, the slotted-waveguide coupled cavity can be reconfigured, which accordingly changes the corresponding slow-light property. At last, the numerical results provide a new thought and method for decreasing group velocity and potential application for optical buffer in photonic crystals field.

  10. Tunable flat band slow light in reconfigurable photonic crystal waveguides based on magnetic fluids

    DEFF Research Database (Denmark)

    Pu, Shengli; Wang, Haotian; Wang, Ning;

    2013-01-01

    A kind of two-dimensional photonic crystal line-defect waveguide with 45 -rotated square lattice is proposed to present slow light phenomena. Infiltrating the photonic crystal waveguide with appropriate magnetic fluids can generate very wide flat bands of guided modes, which give rise...

  11. Experimental demonstration of enhanced slow and fast light by forced coherent population oscillations in a SOA

    CERN Document Server

    Berger, Perrine; Alouini, Mehdi; de Valicourt, Guilhem; Brenot, \\linebreak Romain; Bretenaker, Fabien; Dolfi, Daniel

    2010-01-01

    We experimentally demonstrate enhanced slow and fast light by forced coherent population oscillations (CPOs) in a SOA. This approach is shown to rely on the interference between two different contributions. This opens the possibility to conceive a controllable RF phase shifter based on this set-up.

  12. Slow-light enhanced absorption in a hollow-core fiber

    DEFF Research Database (Denmark)

    Grgic, Jure; Xiao, Sanshui; Mørk, Jesper;

    2010-01-01

    Light traversing a hollow-core photonic band-gap fiber may experience multiple reflections and thereby a slow-down and enhanced optical path length. This offers a technologically interesting way of increasing the optical absorption of an otherwise weakly absorbing material which can infiltrate...

  13. Photonic crystal waveguides with semi-slow light and tailored dispersion properties

    DEFF Research Database (Denmark)

    Frandsen, Lars Hagedorn; Lavrinenko, Andrei; Fage-Pedersen, Jacob

    2006-01-01

    waveguide with either vanishing, positive, or negative group velocity dispersion and semi-slow light. We realize experimentally a silicon-on-insulator photonic crystal waveguide having nearly constant group velocity [similar to]c$-0$//34 in an 11-nm bandwidth below the silica-line. $CPY@2006 Optical Society...

  14. Extremely large bandwidth and ultralow-dispersion slow light in photonic crystal waveguides with magnetically controllability

    DEFF Research Database (Denmark)

    Pu, Shengli; Wang, Haotian; Wang, Ning;

    2013-01-01

    A line-defect waveguide within a two-dimensional magnetic-fluid-based photonic crystal with 45o-rotated square lattice is presented to have excellent slow light properties. The bandwidth centered at $$ \\lambda_{0} $$ = 1,550 nm of our designed W1 waveguide is around 66 nm, which is very large tha...

  15. Theory of Optical-Filtering Enhanced Slow and Fast Light Effects in Semiconductor Optical Waveguides

    DEFF Research Database (Denmark)

    Chen, Yaohui; Xue, Weiqi; Öhman, Filip;

    2008-01-01

    A theoretical analysis of slow and fast light effects in semiconductor optical amplifiers based on coherent population oscillations and including the influence of optical filtering is presented. Optical filtering is shown to enable a significant increase of the controllable phase shift experienced...

  16. Bandwidth-adaptable silicon photonic differentiator employing a slow light effect

    DEFF Research Database (Denmark)

    Yan, Siqi; Cheng, Ziwei; Frandsen, Lars Hagedorn

    2017-01-01

    exploits the slow light effect in a photonic crystal waveguide (PhCW) to overcome the inherent bandwidth limitation of current photonic DIFFs. We fabricated a PhCW Mach-Zehnder interferometer (PhCW-MZI) on the silicon-onisolator material platform to validate our concept. Input Gaussian pulses with full...

  17. Slow-light enhancement of spontaneous emission in active photonic crystal waveguides

    DEFF Research Database (Denmark)

    Ek, Sara; Chen, Yaohui; Semenova, Elizaveta;

    2012-01-01

    Photonic crystal defect waveguides with embedded active layers containing single or multiple quantum wells or quantum dots have been fabricated. Spontaneous emission spectra are enhanced close to the bandedge, consistently with the enhancement of gain by slow light effects. These are promising...... results for future compact devices for terabit/s communication, such as miniaturised semiconductor optical amplifiers and mode-locked lasers....

  18. Controlling microwave signals by means of slow and fast light effects in SOA-EA structures

    DEFF Research Database (Denmark)

    Sales, Salvador; Öhman, Filip; Capmany, José

    2007-01-01

    We present a novel scheme for the control of microwave signals in the optical domain. We propose the use of alternating amplifying and absorbing sections to implement phase control by using fast and slow light effects in semiconductors. The potential benefits from the proposed semiconductor optic...... microwave photonic filters....

  19. Optimization of an integrated-optical ring-resonator slow-light-based sensor

    NARCIS (Netherlands)

    Uranus, H.P.; Hoekman, M.; Dijkstra, M.; Hoekstra, H.J.W.M.; stoffer, R.

    2008-01-01

    A 3-D, vectorial, and multimodal model that incorporates realistic losses was developed to study the performance of Si3N4 based integrated-optical ring-resonator slow-light-based refractometric sensor. Efficient optimization of the coupler gap and tolerance analysis were also performed using the mod

  20. Study of an integrated-optical slow light ring-resonator for sensing applications

    NARCIS (Netherlands)

    Uranus, H.P.; Dijkstra, M.; Hoekman, M.; Hoekstra, H.J.W.M.

    2008-01-01

    Integrated-optical (IO) micro-ring, -disk, and -sphere resonators have been long considered as a good candidate to enhance optical sensor performance. To the best of our knowledge, none of previous reported works has explicitly attributed such (expected) enhancement to slow-light phenomenon, i.e. a

  1. Band gap characterization and slow light effects in periodic and quasiperiodic one dimensional photonic crystal

    Science.gov (United States)

    Zaghdoudi, J.; Kuszelewicz, R.; Kanzari, M.; Rezig, B.

    2008-04-01

    Slow light offers many opportunities for photonic devices by increasing the effective interaction length of imposed refractive index changes. The slow wave effect in photonic crystals is based on their unique dispersive properties and thus entirely dielectric in nature. In this work we demonstrate an interesting opportunity to decrease drastically the group velocity of light in one-dimensional photonic crystals constructed form materials with large dielectric constant without dispersion). We use numerical analysis to study the photonic properties of periodic (Bragg mirror) and quasiperiodic one dimensional photonic crystals realized to engineer slow light effects. Various geometries of the photonic pattern have been characterized and their photonic band-gap structure analyzed. Indeed, one dimensional quasi periodic photonic multilayer structure based on Fibonacci, Thue-Morse, and Cantor sequences were studied. Quasiperiodic structures have a rich and highly fragmented reflectivity spectrum with many sharp resonant peaks that could be exploited in a microcavity system. A comparison of group velocity through periodic and quasiperiodic photonic crystals was discussed in the context of slow light propagation. The velocity control of pulses in materials is one of the promising applications of photonic crystals. The material systems used for the numerical analysis are TiO II/SiO II and Te/SiO II which have a refractive index contrast of approximately 1.59 and 3.17 respectively. The proposed structures were modelled using the Transfer Matrix Method.

  2. Widely tunable microwave photonic notch filter based on slow and fast light effects

    DEFF Research Database (Denmark)

    Xue, Weiqi; Sales, Salvador; Mørk, Jesper;

    2009-01-01

    A continuously tunable microwave photonic notch filter at around 30 GHz is experimentally demonstrated and 100% fractional tuning over 360 range is achieved without changing the shape of the spectral response. The tuning mechanism is based on the use of slow and fast light effects in semiconductor...

  3. Photon drag enhancement by a slow-light moving medium via electromagnetically-induced transparency amplification

    Science.gov (United States)

    Iqbal, Azmat; Khan, Naveed; Bacha, Bakht Amin; Rahman, Amin Ur; Ahmad, Afaq

    2017-09-01

    Recently, a considerable enhancement has been observed in the celebrated Fresnel-Fizeau light drag by innovative experimental and theoretical approaches because of its fundamental and practical interest in the emerging technology of quantum optics and photonics. We present a semiclassical density matrix approach on the demonstration of light drag in a slow-light moving medium comprising five-level single tripod atomic configuration. To accomplish this, we introduce Kerr-type nonlinearity that leads to electromagnetically-induced transparency amplification under resonance conditions. By switching ON Kerr-type nonlinearity effect, we observe a prominent transparency window in probe field's absorption spectrum whose width and amplitude can be controlled further by the intensity of Kerr field and control field. The incorporation of Kerr field also switches light propagation from superluminal to subluminal domain. We predict a significant enhancement both in the lateral and the rotary photon drag owing to drag of light linear polarization state subjected to translation and rotation of the host medium, respectively. Consistent with earlier results, light drag considerably depends on both transverse and angular velocity of the host medium. In regime of subluminal propagation, light polarization state drags along the medium motion while in the superluminal propagation region it drags opposite to the medium motion.

  4. Slow-light Airy wave packets and their active control via electromagnetically induced transparency

    CERN Document Server

    Hang, Chao

    2014-01-01

    We propose a scheme to generate (3+1)-dimensional slow-light Airy wave packets in a resonant $\\Lambda$-type three-level atomic gas via electromagnetically induced transparency. We show that in the absence of dispersion the Airy wave packets formed by a probe field consist of two Airy wave packets accelerated in transverse directions and a longitudinal Gaussian pulse with a constant propagating velocity lowered to $10^{-5}\\,c$ ($c$ is the light speed in vacuum). We also show that in the presence of dispersion it is possible to generate another type of slow-light Airy wave packets consisting of two Airy beams in transverse directions and an Airy wave packet in the longitudinal direction. In this case, the longitudinal velocity of the Airy wave packet can be further reduced during propagation. Additionally, we further show that the transverse accelerations (or bending) of the both types of slow-light Airy wave packets can be completely eliminated and the motional trajectories of them can be actively manipulated ...

  5. Hollow core photonic bandgap fiber with microfluid-infiltrated air holes for slow-light propagation

    Science.gov (United States)

    Ren, Liyong; Liang, Jian; Yun, Maojin

    2012-10-01

    Slow light plays an important role in the fields of all-optical signal processing and integration photonics. It has shown many potential applications, such as realizing optical delay lines or buffers, enhancing linear and nonlinear light-matter interactions, as well as increasing the sensitivity of the interferometers and transducers. In this paper, hollow-core photonic bandgap fibers made from high index glasses are designed by infiltrating microfluid into the air-holes to tailor the fiber dispersion for slow-light propagation under low pulse distortion. In such a fiber made from Si material, group index ng~8 is obtained with a bandwidth up to 30 nm, where the group index fluctuation is restricted in ±10 % of the ng, while ng~6 is obtained with a bandwidth over 100 nm when the chalcogenide material is selected instead. Such a ±10 % criterion determines a regarded flatland region accordingly, and in this region the group velocity dispersion can be negligible. It is found that for the same fiber length the slow-light time delay in the photonic bandgap fiber is much larger as compared with that in the single mode fiber. This kind of photonic bandgap fiber may have many potential applications in short-distance fiber communications and delay lines.

  6. Photonic band-gap properties for two-component slow light

    CERN Document Server

    Ruseckas, J; Juzeliunas, G; Unanyan, R G; Otterbach, J; Fleischhauer, M

    2011-01-01

    We consider two-component "spinor" slow light in an ensemble of atoms coherently driven by two pairs of counterpropagating control laser fields in a double tripod-type linkage scheme. We derive an equation of motion for the spinor slow light (SSL) representing an effective Dirac equation for a massive particle with the mass determined by the two-photon detuning. By changing the detuning the atomic medium acts as a photonic crystal with a controllable band gap. If the frequency of the incident probe light lies within the band gap, the light tunnels through the sample. For frequencies outside the band gap, the transmission probability oscillates with increasing length of the sample. In both cases the reflection takes place into the complementary mode of the probe field. We investigate the influence of the finite excited state lifetime on the transmission and reflection coefficients of the probe light. We discuss possible experimental implementations of the SSL using alkali atoms such as Rubidium or Sodium.

  7. Topology-optimized and dispersion-tailored photonic crystal slow-light devices

    DEFF Research Database (Denmark)

    Frandsen, Lars Hagedorn; Lavrinenko, Andrei; Borel, Peter Ingo

    2007-01-01

    Within the last few years, photonic crystal waveguides (PhCWs) with low propagation losses and exotic dispersion properties have been realized and, presently, there is a strong movement towards the deployment of such structures in integrated circuits. Effective passive components such as bends...... sophisticated possibilities for realizing complex nanophotonic circuits. Potentially,PhCWs may facilitate delay lines for package synchronization, dispersion compensation, and enhanced light-matter interactions in nanophotonic circuits by exploiting slow-light phenomena. The practical utilization of ultra...

  8. Electromagnetic field manipulation in planar nanorod antennas metamaterial for slow light application

    Science.gov (United States)

    Wang, Junqiao; Zhang, Jia; Fan, Chunzhen; Mu, Kaijun; Liang, Erjun; Ding, Pei

    2017-01-01

    We numerically investigated the optical properties of planar nanorod antennas metamaterial that exhibits plasmon-induced transparency (PIT) effect. The designed metamaterial is made of a silver nanorod dimer antenna surrounded by two parallel silver nanorods. The interaction between two parallel nanorods and middle nanorod dimer antenna leads to a single PIT band in the transmission spectrum. Moreover, the double PIT windows and slow light can be realized by breaking the structure symmetry. The multi-bands PIT effect offers an excellent potential to manipulate the light speed at multi-frequencies.

  9. Diffraction as a reason for slowing down light pulses in vacuum

    Science.gov (United States)

    Fedorov, M. V.; Vintskevich, S. V.; Grigoriev, D. A.

    2017-03-01

    The mean velocity of a finite-size short light pulse in a far zone is defined as the vectorial sum of velocities of all rays forming the pulse. Because of diffraction, the mean pulse velocity defined in this way is always somewhat smaller than the speed of light. The conditions are found when this slowing-down effect is sufficiently pronounced to be experimentally measurable. Under these conditions the original Gaussian shape of a pulse is found to be strongly modified with significant lengthening of the rear wing of the field envelope. Schemes for measuring these effects are suggested and discussed.

  10. Reversible Fano resonance by transition from fast light to slow light in a coupled-resonator-induced transparency structure.

    Science.gov (United States)

    Zhang, Yundong; Zhang, Xuenan; Wang, Ying; Zhu, Ruidong; Gai, Yulong; Liu, Xiaoqi; Yuan, Ping

    2013-04-08

    We theoretically propose and experimentally perform a novel dispersion tuning scheme to realize a tunable Fano resonance in a coupled-resonator-induced transparency (CRIT) structure coupled Mach-Zehnder interferometer. We reveal that the profile of the Fano resonance in the resonator coupled Mach-Zehnder interferometers (RCMZI) is determined not only by the phase shift difference between the two arms of the RCMZI but also by the dispersion (group delay) of the CRIT structure. Furthermore, it is theoretically predicted and experimentally demonstrated that the slope and the asymmetry parameter (q) describing the Fano resonance spectral line shape of the RCMZI experience a sign reversal when the dispersion of the CRIT structure is tuned from abnormal dispersion (fast light) to normal dispersion (slow light). These theoretical and experimental results indicate that the reversible Fano resonance which holds significant implications for some attractive device applications such as highly sensitive biochemical sensors, ultrafast optical switches and routers can be realized by the dispersion tuning scheme in the RCMZI.

  11. Slow light with large group index - bandwidth product in lattice-shifted photonic crystal waveguides

    Science.gov (United States)

    Tang, Jian; Li, Wenhui; Wu, Jun; Xu, Zhonghui

    2016-10-01

    This study presents a systematic optimization procedure to generate slow light with large group index, wideband, and low dispersion in an lattice-shifted photonic crystal waveguide. The waveguide is based on triangular lattice photonic crystal imposed by selectively altering the locations of the holes adjacent to the line defect. Under a constant group index criterion of ± 10% variation, when group indices are nearly constants of 24, 33, 46, 57, and 66, their corresponding bandwidths of flat band reach 24.2, 17.6, 12.8, 10.1 and 8.6 nm around 1550 nm, respectively. A nearly constant large group index - bandwidth product (GBP) of 0.37 is achieved for all cases. Low dispersion slow light propagation is confirmed by studying the relative temporal pulse-width spreading with the 2-D finite-difference time-domain method.

  12. Optical performance monitoring at 640Gb/s via slow-light in a silicon nanowire

    CERN Document Server

    Corcoran, B; Pelusi, M; Grillet, C; White, T P; Faolain, L O; Krauss, T F; Eggleton, B J; Moss, David J

    2015-01-01

    We demonstrate optical performance monitoring of in-band optical signal to noise ratio (OSNR) and residual dispersion, at bit rates of 40Gb/s, 160Gb/s and 640Gb/s, using slow-light enhanced optical third harmonic generation (THG) in a compact (80 micron) dispersion engineered 2D silicon photonic crystal waveguide. We show that there is no intrinsic degradation in the enhancement of the signal processing at 640 Gb/s relative to that at 40Gb/s, and that this device should operate well above 1Tb/s. This work represents a record 16-fold increase in processing speed for a silicon device, and opens the door for slow light to play a key role in ultra-high bandwidth telecommunications systems.

  13. Four-wave mixing in slow light photonic crystal waveguides with very high group index.

    Science.gov (United States)

    Li, Juntao; O'Faolain, Liam; Krauss, Thomas F

    2012-07-30

    We report efficient four-wave mixing in dispersion engineered slow light silicon photonic crystal waveguides with a flat band group index of n(g) = 60. Using only 15 mW continuous wave coupled input power, we observe a conversion efficiency of -28 dB. This efficiency represents a 30 dB enhancement compared to a silicon nanowire of the same length. At higher powers, thermal redshifting due to linear absorption was found to detune the slow light regime preventing the expected improvement in efficiency. We then overcome this thermal limitation by using oxide-clad waveguides, which we demonstrate for group indices of ng = 30. Higher group indices may be achieved with oxide clad-waveguides, and we predict conversion efficiencies approaching -10 dB, which is equivalent to that already achieved in silicon nanowires but for a 50x shorter length.

  14. Strongly coupled slow-light polaritons in one-dimensional disordered localized states

    CERN Document Server

    Gao, Jie; Liang, Baolai; Schmitteckert, Peter; Lehoucq, Gaelle; Xavier, Stephane; Xu, Xinan; Busch, Kurt; Huffaker, Diana L; De Rossi, Alfredo; Wong, Chee Wei

    2013-01-01

    Cavity quantum electrodynamics advances the coherent control of a single quantum emitter with a quantized radiation field mode, typically piecewise engineered for the highest finesse and confinement in the cavity field. This enables the possibility of strong coupling for chip-scale quantum processing, but till now is limited to few research groups that can achieve the precision and deterministic requirements for these polariton states. Here we observe for the first time coherent polariton states of strong coupled single quantum dot excitons in inherently disordered one-dimensional localized modes in slow-light photonic crystals. Large vacuum Rabi splittings up to 311 {\\mu}eV are observed, one of the largest avoided crossings in the solid-state. Our tight-binding models with quantum impurities detail these strong localized polaritons, spanning different disorder strengths, complementary to model-extracted pure dephasing and incoherent pumping rates. Such disorder-induced slow-light polaritons provide a platfor...

  15. Slow and fast light effects and their applications to microwave photonics using semiconductor optical amplifiers

    DEFF Research Database (Denmark)

    Sales, Salvador; Xue, Weiqi; Mørk, Jesper;

    2010-01-01

    We provide a comprehensive review of the application of slow and fast light (SFL) techniques to the field of microwave photonics. Basic principles leading to the implementation of phase shifting and true time delay operations which are instrumental in this field are first considered. We then focu....... Finally, the main results obtained for several microwave photonic applications such as filtering, arbitrary waveform generation and optoelectronic scillators (OEOs)are reviewed, and other directions for future research in the field are discussed.......We provide a comprehensive review of the application of slow and fast light (SFL) techniques to the field of microwave photonics. Basic principles leading to the implementation of phase shifting and true time delay operations which are instrumental in this field are first considered. We then focus...

  16. Broadband Slow Light Metamaterial Based on a Double-Continuum Fano Resonance

    CERN Document Server

    Wu, Chihhui; Shvets, Gennady

    2010-01-01

    We propose a concept of a low-symmetry three-dimensional metamaterial exhibiting a Double- Continuum Fano (DCF) optical resonance. Such metamaterial is described as a birefringent medium supporting a discrete “dark” electromagnetic state weakly coupled to the continua of two nondegen- erate “bright” bands of orthogonal polarizations. It is demonstrated that light propagation through such DCF metamaterial can be slowed down over a broad frequency range when the medium param- eters (e.g. frequency of the “dark” mode) are adiabatically changed along the optical path. Using a specific metamaterial implementation, we demonstrate that the DCF approach to slow light (SL) is superior to that of the EIT because it enables spectrally uniform group velocity and transmission coefficient.

  17. Information-theoretic analysis of a stimulated-Brillouin-scattering-based slow-light system.

    Science.gov (United States)

    Lee, Myungjun; Zhu, Yunhui; Gauthier, Daniel J; Gehm, Michael E; Neifeld, Mark A

    2011-11-10

    We use an information-theoretic method developed by Neifeld and Lee [J. Opt. Soc. Am. A 25, C31 (2008)] to analyze the performance of a slow-light system. Slow-light is realized in this system via stimulated Brillouin scattering in a 2 km-long, room-temperature, highly nonlinear fiber pumped by a laser whose spectrum is tailored and broadened to 5 GHz. We compute the information throughput (IT), which quantifies the fraction of information transferred from the source to the receiver and the information delay (ID), which quantifies the delay of a data stream at which the information transfer is largest, for a range of experimental parameters. We also measure the eye-opening (EO) and signal-to-noise ratio (SNR) of the transmitted data stream and find that they scale in a similar fashion to the information-theoretic method. Our experimental findings are compared to a model of the slow-light system that accounts for all pertinent noise sources in the system as well as data-pulse distortion due to the filtering effect of the SBS process. The agreement between our observations and the predictions of our model is very good. Furthermore, we compare measurements of the IT for an optimal flattop gain profile and for a Gaussian-shaped gain profile. For a given pump-beam power, we find that the optimal profile gives a 36% larger ID and somewhat higher IT compared to the Gaussian profile. Specifically, the optimal (Gaussian) profile produces a fractional slow-light ID of 0.94 (0.69) and an IT of 0.86 (0.86) at a pump-beam power of 450 mW and a data rate of 2.5 Gbps. Thus, the optimal profile better utilizes the available pump-beam power, which is often a valuable resource in a system design.

  18. Theory of slow light enhanced four-wave mixing in photonic crystal waveguides

    OpenAIRE

    Santagiustina M.; Someda C.G.; Vadala G.; Combrie S.; Rossi A.

    2010-01-01

    The equations for Four-Wave-Mixing in a Photonic Crystal waveguide are derived accurately. The dispersive nature of slow-light enhancement, the impact of Bloch mode reshaping in the nonlinear overlap integrals and the tensor nature of the third order polarization are therefore taken into account. Numerical calculations reveal substantial differences with simpler models, which increase with decreasing group velocity. We predict that the gain for a 1.3 mm long, unoptimized GaInP waveguide will ...

  19. Enhancing slow- and fast-light effects in quantum dot semiconductor waveguides through ultrafast dynamics

    DEFF Research Database (Denmark)

    Chen, Yaohui; Mørk, Jesper

    2011-01-01

    In this paper we review our theoretical work on slow and fast light effects in quantum dot semiconductor optical amplifiers (QD SOAs), in particular we investigate the carrier dynamical contributions to the dynamic gain grating and cross gain modulation induced by unique ultrafast inter...... in microwave photonics, especially targeting the millimeter wave range, we propose that quantum dot devices might be used to realize an optically fed microwave phase shifter in the frequency range of 100GHz....

  20. Slow light in metal-insulator-metal waveguide by negative Goos-Hänchen shift

    Science.gov (United States)

    Oh, Geum-Yoon; Chheang, Vuthy; Kim, Doo-Gun; Kim, Tae-Ryong; Jun, Li; Kim, Hong-Seung; Choi, Young-Wan

    2014-12-01

    We demonstrated group velocity delay using a metal-insulator-metal structure for slow light that would be very simple to fabricate. A negative Goos-Hänchen shift of the surface plasmon resonance can be caused by incident radiation while reflecting, resulting in a general group delay. Using this phenomenon, we induced a group delay of 70 fs using a very simple 20-μm-long waveguide.

  1. Mesoscopic self-collimation and slow light in all-positive index layered photonic crystals

    CERN Document Server

    Arlandis, Julien; Pollès, Rémi; Moreau, Antoine; Campos, Julien; Gauthier-Lafaye, Olivier; Monmayrant, Antoine

    2011-01-01

    We demonstrate a mesoscopic self-collimation effect in photonic crystal superlattices consisting of a periodic set of all-positive index 2D photonic crystal and homogeneous layers. We develop an electromagnetic theory showing that diffraction-free beams are observed when the curvature of the optical dispersion relation is properly compensated for. This approach allows to combine slow light regime together with self-collimation in photonic crystal superlattices presenting an extremely low filling ratio in air.

  2. Slow light engineering in polyatomic photonic crystal waveguides based on square lattice

    Science.gov (United States)

    Wang, Daobin; Zhang, Jie; Yuan, Lihua; Lei, Jingli; Chen, Sai; Han, Jiawei; Hou, Shanglin

    2011-12-01

    In this paper, the slow light properties of the polyatomic Photonic Crystal (PhC) which has multiple different air holes in each primitive cell are investigated. A slow light waveguide with "U-type" group index-frequency curve, which results in nearly constant group index over large bandwidth, is achieved using this new photonic crystal geometry based on the square lattice. Also, the radius and position of the innermost rows of small air holes have been modified to investigate the feasibility of controlling the dispersion relation by subtle structural modification. Numerical results demonstrate that decreasing the group velocity effectively and meanwhile maintaining a large Normalized Delay-Bandwidth Product ( NDBP) can be achieved by only modifying the radius of the innermost rows of small air holes. Shifting the innermost rows of small air holes toward the waveguide core is highly beneficial to enlarge the slow light bandwidth, but it contributes nothing to the promotion of NDBP. Our results provide important theoretical basis for the potential application offered by the polyatomic photonic crystal in future optical networks.

  3. Slow Light with Photonic Crystals for On-Chip Optical Interconnects

    Directory of Open Access Journals (Sweden)

    Sean P. Anderson

    2008-01-01

    Full Text Available Transistor scaling alone can no longer be relied upon to yield the exponential speed increases we have come to expect from the microprocessor industry. The principle reason for this is the interconnect bottleneck, where the electrical connections between and within microprocessors are becoming, and in some cases have already become, the limiting factor in overall microprocessor performance. Optical interconnects have the potential to address this shortcoming directly, by providing an inter- and intrachip communication infrastructure that has both greater bandwidth and lower latency than electrical interconnects, while remaining safely within size and power constraints. In this paper, we review the requirements that a successful optical interconnect must meet, as well as some of the recent work in our group in the area of slow-light photonic crystal devices for on-chip optical interconnects. We show that slow-light interferometric optical modulators in photonic crystal can have not only high bandwidth, but also extremely compact size. We also introduce the first example of a multichannel slow light platform, upon which a new class of ultracompact optical devices can be built.

  4. Theoretical study of ultra-wideband slow light in dual-stub-coupled plasmonic waveguide

    Science.gov (United States)

    Li, Chunlei; Su, Runzhou; Wang, Yuxiao; Zhang, Xueru

    2016-10-01

    We propose and demonstrate a metal-insulator-metal (MIM) waveguide side coupled double stubs to realize broadband slow surface plasmon polaritons (SPPs) around the telecom frequency 193.5 THz. When the depth of single stub is approximately equal to integral multiple of half plasmon wavelength, owing to the constructive interferences between the electromagnetic wave propagating through the MIM waveguide and that reflected from the stubs, wideband slow light effect appears. The improved transmission line theory calculation indicates that the group velocity of SPPs in the plasmonic waveguide system for stub depth 1111 nm is 0.1c (c is light speed in vacuum.) over a broad bandwidth of 69 THz. Exploiting the finite-difference time-domain (FDTD) numerical simulation, the group velocity of pulse for width 20 fs (Full width at half high) is calculated. The result agrees well with that predicted by the transmission line theory. This plasmonic waveguide for slow light effect has important potential application in optical delay lines.

  5. Ultracompact all-optical XOR logic gate in a slow-light silicon photonic crystal waveguide.

    Science.gov (United States)

    Husko, C; Vo, T D; Corcoran, B; Li, J; Krauss, T F; Eggleton, B J

    2011-10-10

    We demonstrate an ultracompact, chip-based, all-optical exclusive-OR (XOR) logic gate via slow-light enhanced four-wave mixing (FWM) in a silicon photonic crystal waveguide (PhCWG). We achieve error-free operation (<10⁻⁹) for 40 Gbit/s differential phase-shift keying (DPSK) signals with a 2.8 dB power penalty. Slowing the light to vg = c/32 enables a FWM conversion efficiency, η, of -30 dB for a 396 μm device. The nonlinear FWM process is enhanced by 20 dB compared to a relatively fast mode of vg = c/5. The XOR operation requires ≈ 41 mW, corresponding to a switching energy of 1 pJ/bit. We compare the slow-light PhCWG device performance with experimentally demonstrated XOR DPSK logic gates in other platforms and discuss scaling the device operation to higher bit-rates. The ultracompact structure suggests the potential for device integration.

  6. High sensitivity electro-optic modulation of slow light in ellipse rods PC-CROW

    Science.gov (United States)

    Li, Changhong; Wan, Yong; Zong, Weihua

    2017-07-01

    A tunable slow light with low group velocity, high buffer performance and high sensitivity is realized in photonic crystal coupled resonator optical waveguide (PC-CROW) with elliptical rod around cavity. By adjusting the long axis and short axis of the elliptical rods, the slow light and buffer performance of PC-CROW are optimized. As ae=0.42a, be=0.20a, the group velocity is below 2.3053×10-4c, simultaneously, the buffer capacity C and delay time Ts reach the optimum value of 9.8214 bit and 354.8 ps. Then the dynamic modulation of the slow light and buffer performance based on this optimized structure has been discussed systematically. Thanks to the electro-optic effect of the polystyrene substrate, the guided mode shifts linearly to short wavelength in sensitivity of 3.0 nm/mV around 1550 nm, as the applied voltage increases. The modulation sensitivities of delay time and buffer capacity are 0.445 ns/mV and 0.051 bit/mV, respectively. These results show a considerable potential for this structure that can be dynamically controlled according to the practical requirements by electro-optic effect in PC-CROW.

  7. Slow and fast light using nonlinear processes in semiconductor optical amplifiers

    Science.gov (United States)

    Pesala, Bala Subrahmanyam

    Ability to control the velocity of light is usually referred to as slow or fast light depending on whether the group velocity of light is reduced or increased. The slowing of light as it passes through the glass to 2/3rd its original value is a well known phenomenon. This slowing down happens due to the interaction of light with the electrons in the medium. As a general principle, stronger the interaction, larger is the reduction in velocity. Recently, a fascinating field has emerged with the objective of not only slowing down the velocity of light but also speeding it up as it goes through the medium by enhancing light-matter interaction. This unprecedented control opens up several exciting applications in various scientific disciplines ranging from nonlinear science, RF photonics to all-optical networks. Initial experiments succeeded in reducing the velocity of light more than a million times to a very impressive 17 m/s. This speed reduction is extremely useful to enhance various nonlinear processes. For RF photonic applications including phased array antennas and tunable filters, control of phase velocity of light is required while control of group velocity serves various functionalities including packet synchronization and contention resolution in an optical buffer. Within the last 10 years, several material systems have been proposed and investigated for this purpose. Schemes based on semiconductor systems for achieving slow and fast light has the advantage of extremely high speed and electrical control. In addition, they are compact, operate at room temperature and can be easily integrated with other optical subsystems. In this work, we propose to use nonlinear processes in semiconductor optical amplifiers (SOAs) for the purpose of controlling the velocity of light. The versatility of the physical processes present in SOAs enables the control of optical signals ranging from 1GHz to larger than 1000 GHz (1 THz). First, we experimentally demonstrate both

  8. Slow-light-enhanced energy efficiency for graphene microheaters on silicon photonic crystal waveguides

    Science.gov (United States)

    Yan, Siqi; Zhu, Xiaolong; Frandsen, Lars Hagedorn; Xiao, Sanshui; Mortensen, N. Asger; Dong, Jianji; Ding, Yunhong

    2017-02-01

    Slow light has been widely utilized to obtain enhanced nonlinearities, enhanced spontaneous emissions and increased phase shifts owing to its ability to promote light-matter interactions. By incorporating a graphene on a slow-light silicon photonic crystal waveguide, here we experimentally demonstrate an energy-efficient graphene microheater with a tuning efficiency of 1.07 nmmW-1 and power consumption per free spectral range of 3.99 mW. The rise and decay times (10-90%) are only 750 and 525 ns, which, to the best of our knowledge, are the fastest reported response times for microheaters in silicon photonics. The corresponding figure of merit of the device is 2.543 nW s, one order of magnitude better than results reported in previous studies. The influence of the length and shape of the graphene heater to the tuning efficiency is further investigated, providing valuable guidelines for enhancing the tuning efficiency of the graphene microheater.

  9. Slow-light-enhanced energy efficiency for the graphene microheater on silicon photonic crystal waveguides

    CERN Document Server

    Yan, Siqi; Frandsen, Lars Hagedorn; Xiao, Sanshui; Mortensen, N Asger; Dong, Jianji; Ding, Yunhong

    2016-01-01

    Slow light has been widely utilized to obtain enhanced nonlinearities, enhanced spontaneous emissions, and increased phase shifts owing to its ability to promote light-matter interactions. By incorporating a graphene microheater on a slow-light silicon photonic crystal waveguide, we experimentally demonstrated an energy-efficient graphene microheater with a tuning efficiency of 1.07 nm/mW and power consumption per free spectral range of 3.99 mW. The rise and decay times (10% to 90%) were only 750 ns and 525 ns, which, to the best of our knowledge, are the fastest reported response times for microheaters in silicon photonics. The corresponding record-low figure of merit of the device was 2.543 nW.s, which is one order of magnitude lower than results reported in previous studies. The influences of the graphene-photonic crystal waveguide interaction length and the shape of the graphene heater were also investigated, providing valuable guidelines for enhancing the graphene microheater tuning efficiency.

  10. Ultrahigh sensitivity of rotation sensing beyond the trade-off between sensitivity and linewidth by the storage of light in a dynamic slow-light resonator

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Xuenan; Zhang Yundong; Tian He; Wu Hao; Li Geng; Zhu Ruidong; Yuan Ping [National Key Laboratory of Tunable Laser Technology, Institute of Opto-Electronics, Harbin Institute of Technology, Harbin 150080 (China)

    2011-12-15

    We propose to employ the storage of light in a dynamically tuned add-drop resonator to realize an optical gyroscope of ultrahigh sensitivity and compact size. Taking the impact of the linewidth of incident light on the sensitivity into account, we investigate the effect of rotation on the propagation of a partially coherent light field in this dynamically tuned slow-light structure. It is demonstrated that the fundamental trade-off between the rotation-detection sensitivity and the linewidth will be overcome and the sensitivity-linewidth product will be enhanced by two orders of magnitude in comparison to that of the corresponding static slow-light structure. Furthermore, the optical gyroscope employing the storage of light in the dynamically tuned add-drop resonator can acquire ultrahigh sensitivity by extremely short fiber length without a high-performance laser source of narrow linewidth and a complex laser frequency stabilization system. Thus the proposal in this paper provides a promising and feasible scheme to realize highly sensitive and compact integrated optical gyroscopes by slow-light structures.

  11. Optimization of slow light one-dimensional Bragg structures for photocurrent enhancement in solar cells.

    Science.gov (United States)

    Deparis, Olivier; El Daif, Ounsi

    2012-10-15

    In 1D photonic crystal Bragg structures, strong localization of the light occurs in the high refractive index layers at wavelengths on the red edge of the photonic bandgap. We exploit this slow light effect for thin film solar cells in order to increase the absorption of light in silicon, as the latter has a high refractive index. Amorphous silicon and a transparent conductive oxide are chosen as high-index and low-index materials, respectively. Reference thin film cells have equivalent total thickness of amorphous silicon, plus antireflection coating and optional metallic back mirror. Through transfer-matrix calculations, we demonstrate that the spectrally integrated photon flux absorbed in active layers, hence the photocurrent, is enhanced by at least 10% with respect to reference using only a few periods. The enhancement is robust with respect to the light incidence angle. The key of such an enhancement is the tuning of the red edge to both the solar irradiance spectrum and the intrinsic material absorption spectrum, which is achieved by suitably selecting the layer thicknesses.

  12. Slow-light plasmonic metamaterial based on dressed-state analog of electromagnetically-induced transparency

    CERN Document Server

    Raza, Søren

    2015-01-01

    We consider a simple configuration for realizing one-dimensional slow-light metamaterials with large bandwidth-delay products using stub-shaped Fabry-Perot resonators as building blocks. Each metaatom gives rise to large group indices due to a classical analog of the dressed-state picture of electromagnetically-induced transparency. By connecting up to eight metaatoms, we find bandwidth-delay products over unity and group indices approaching 100. Our approach is quite general and can be applied to any type of Fabry-Perot resonators and tuned to different operating wavelengths.

  13. Zero-Dispersion Slow Light with Wide Bandwidth in Photonic Crystal Coupled Waveguides

    Institute of Scientific and Technical Information of China (English)

    MAO Xiao-Yu; ZHANG Geng-Yan; HUANG Yi-Dong; ZHANG Wei; PENG Jiang-De

    2008-01-01

    @@ By introducing an adjustment waveguide besides the incident waveguide, zero-dispersion slow light with wide bandwidth can be realized due to anticrossing of the incident waveguide mode and the adjustment waveguide mode.The width of the adjustment waveguide (W2) and the hole radii of the coupling region (r') will change the dispersion of incident waveguide mode.Theoretical investigation reveals that zero dispersion at various low group velocity v9 in incident waveguide can be achieved.In particular, proper W2 and r' can lead to the lowest v9 of 0.0085c at 1550nm with wide bandwidth of 202 GHz for zero dispersion.

  14. Slow to superluminal light waves in thin 3D photonic crystals.

    Science.gov (United States)

    Galisteo-López, J F; Galli, M; Balestreri, A; Patrini, M; Andreani, L C; López, C

    2007-11-12

    Phase measurements on self-assembled three-dimensional photonic crystals show that the group velocity of light can flip from small positive (slow) to negative (superluminal) values in samples of a few mum size. This phenomenon takes place in a narrow spectral range around the second-order stop band and follows from coupling to weakly dispersive photonic bands associated with multiple Bragg diffraction. The observations are well accounted for by theoretical calculations of the phase delay and of photonic states in the finite-sized systems.

  15. Theory of slow light enhanced four-wave mixing in photonic crystal waveguides.

    Science.gov (United States)

    Santagiustina, M; Someda, C G; Vadalà, G; Combrié, S; De Rossi, A

    2010-09-27

    The equations for Four-Wave-Mixing in a Photonic Crystal waveguide are derived accurately. The dispersive nature of slow-light enhancement, the impact of Bloch mode reshaping in the nonlinear overlap integrals and the tensor nature of the third order polarization are therefore taken into account. Numerical calculations reveal substantial differences with simpler models, which increase with decreasing group velocity. We predict that the gain for a 1.3 mm long, unoptimized GaInP waveguide will exceed 10 dB if the pump power exceeds 1 W.

  16. Slow-light enhanced correlated photon pair generation in a silicon photonic crystal waveguide.

    Science.gov (United States)

    Xiong, C; Monat, Christelle; Clark, Alex S; Grillet, Christian; Marshall, Graham D; Steel, M J; Li, Juntao; O'Faolain, Liam; Krauss, Thomas F; Rarity, John G; Eggleton, Benjamin J

    2011-09-01

    We report the generation of correlated photon pairs in the telecom C-band at room temperature from a dispersion-engineered silicon photonic crystal waveguide. The spontaneous four-wave mixing process producing the photon pairs is enhanced by slow-light propagation enabling an active device length of less than 100 μm. With a coincidence to accidental ratio of 12.8 at a pair generation rate of 0.006 per pulse, this ultracompact photon pair source paves the way toward scalable quantum information processing realized on-chip.

  17. Theory of Slow Light Enhanced Four-Wave Mixing in Photonic Crystal Waveguides

    CERN Document Server

    Santagiustina, M; Vadalà, G; Combrié, S; De Rossi, A

    2010-01-01

    The equations for Four-Wave-Mixing in a Photonic Crystal waveguide are derived accurately. The dispersive nature of slow-light enhancement, the impact of Bloch mode reshaping in the nonlinear overlap integrals and the tensor nature of the third order polarization are therefore taken into account. Numerical calculations reveal substantial differences with simpler models, which increase with decreasing group velocity. We predict that the gain for a 1.3 mm long, unoptimized GaInP waveguide will exceed 10 dB if the pump power exceeds 1 W.

  18. Slow-light Enhanced Correlated Photon-Pair Generation in Silicon

    CERN Document Server

    Xiong, C; Clark, Alex S; Grillet, Christian; Marshall, Graham D; Steel, M J; Li, Juntao; O'Faolain, Liam; Krauss, Thomas F; Rarity, John G; Eggleton, Benjamin J

    2011-01-01

    We report the generation of correlated photon pairs in the telecom C-band, at room temperature, from a dispersion-engineered silicon photonic crystal waveguide. The spontaneous four-wave mixing process producing the photon pairs is enhanced by slow-light propagation enabling an active device length of less than 100 {\\mu}m. With a coincidence to accidental ratio of 12.8, at a pair generation rate of 0.006 per pulse, this ultra-compact photon pair source is immediately applicable towards scalable quantum information processing realized on-chip.

  19. Slow light with symmetric gap plasmon guides with finite width metal claddings

    Indian Academy of Sciences (India)

    S Dutta Gupta

    2009-02-01

    We study the dispersion relation and the modes of a symmetric gap plasmon guide, where a dielectric planar slab is coated with finite metallic layers on both top and bottom. The finite conductivity of the metal is taken into account. The modes of the structure exhibit significant differences from those of dielectric waveguides with air or metal as the bounding media. Avoided level crossing phenomenon between the plasmon and the guided modes is shown to exist, leading to leaky modes. The structure sandwiched between two high index media is shown to lead to slow light in transmission. The group delay is shown to be larger for higher order modes.

  20. Preservation of Energy-Time Entanglement in a Slow Light Medium

    Science.gov (United States)

    Broadbent, Curtis J.; Camacho, Ryan M.; Xin, Ran; Howell, John C.

    2008-04-01

    We demonstrate the preservation of entanglement of an energy-time entangled biphoton through a slow light medium. Using the D1 and D2 fine structure resonances of Rubidium, we delay one photon of the 1.5 THz biphoton by ˜1.3 correlation lengths and measure the fourth order correlation fringes. After the group delay the fringe visibility is reduced from 97.0±4.4% to 80.0±4.8%, but is still sufficient to violate a Bell inequality. We show that temporal broadening is the primary mechanism for reducing the fringe visibility and that smaller bandwidths lead to greatly reduced broadening.

  1. True-time delay by slow light in a semiconductor waveguide with alternating amplifying and absorbing sections

    DEFF Research Database (Denmark)

    Öhman, Filip; Mørk, Jesper

    2006-01-01

    Modeling of slow light in a semiconductor waveguide with alternating gain and absorption sections demonstrate an increase in time delay by concatenating segments. A true-time delay is predicted over a large bandwidth at high frequency.......Modeling of slow light in a semiconductor waveguide with alternating gain and absorption sections demonstrate an increase in time delay by concatenating segments. A true-time delay is predicted over a large bandwidth at high frequency....

  2. Analysis of an effective optical filtering technique to enhance microwave phase shifts based on slow and fast light effects

    DEFF Research Database (Denmark)

    Chen, Yaohui; Öhman, Filip; Xue, Weiqi

    2008-01-01

    We theoretically analyze and interpret an effective mechanism, which employs optical filtering to enhance the microwave phase shift that can be achieved in semiconductor optical amplifiers based on slow and fast light effects.......We theoretically analyze and interpret an effective mechanism, which employs optical filtering to enhance the microwave phase shift that can be achieved in semiconductor optical amplifiers based on slow and fast light effects....

  3. Demonstration of tunable microwave photonic notch filters using slow and fast light effects in semiconductor optical amplifiers

    DEFF Research Database (Denmark)

    Xue, Weiqi; Sales, Salvador; Mørk, Jesper

    2009-01-01

    We introduce a novel scheme based on slow and fast light effects in semiconductor optical amplifiers, to implement a microwave photonic notch filter with ~100% fractional tuning range at a microwave frequency of 30 GHz.......We introduce a novel scheme based on slow and fast light effects in semiconductor optical amplifiers, to implement a microwave photonic notch filter with ~100% fractional tuning range at a microwave frequency of 30 GHz....

  4. Large Signal Modulation and Distortion in a Microwave Phase Shifter Based on Slow Light in a Semiconductor Waveguide

    DEFF Research Database (Denmark)

    Chen, Yaohui; Öhman, Filip; Mørk, Jesper

    2006-01-01

    We model slow/light propagation in an active semiconductor waveguide in the large modulation depth regime. Distortion from higher harmonics is countered by filtering and the regenerating properties of the device further increase the modulation depth.......We model slow/light propagation in an active semiconductor waveguide in the large modulation depth regime. Distortion from higher harmonics is countered by filtering and the regenerating properties of the device further increase the modulation depth....

  5. Demonstration of tunable microwave photonic notch filters using slow and fast light effects in semiconductor optical amplifiers

    DEFF Research Database (Denmark)

    Xue, Weiqi; Sales, Salvador; Mørk, Jesper;

    2009-01-01

    We introduce a novel scheme based on slow and fast light effects in semiconductor optical amplifiers, to implement a microwave photonic notch filter with ~100% fractional tuning range at a microwave frequency of 30 GHz.......We introduce a novel scheme based on slow and fast light effects in semiconductor optical amplifiers, to implement a microwave photonic notch filter with ~100% fractional tuning range at a microwave frequency of 30 GHz....

  6. Slow-light Mach–Zehnder modulators based on Si photonic crystals

    Directory of Open Access Journals (Sweden)

    Toshihiko Baba

    2014-04-01

    Full Text Available Mach–Zehnder optical modulators are the key devices for high-speed electrical-to-optical conversion in Si photonics. Si rib waveguides with a p–n diode structure operated in the carrier depletion mode have mainly been developed as their phase shifters. Their length is usually longer than millimeters due to the limited change in the refractive index due to the carrier depletion in a Si p–n diode. This length is shorter than commercial LiNbO3 modulators, but still much shorter devices are desired for large-scale integration and for simplifying the high-speed RF modulation. A promising solution is to use slow light in photonic crystal waveguides, which enhances the modulation efficiency in proportion to the group-velocity refractive index n g. In particular, dispersion-engineered slow light allows more than five-fold enhancement, maintaining a wide working spectrum as well as large temperature tolerance. The devices with a phase shifter length of around 100 μm are fabricated by a standard process compatible with complementary metal-oxide semiconductors. The operation at 10 Gbps and higher speeds are obtained in the wavelength range of 16.9 nm and temperature range of 105 K.

  7. Slow-light-enhanced energy efficiency for graphene microheaters on silicon photonic crystal waveguides

    Science.gov (United States)

    Yan, Siqi; Zhu, Xiaolong; Frandsen, Lars Hagedorn; Xiao, Sanshui; Mortensen, N. Asger; Dong, Jianji; Ding, Yunhong

    2017-01-01

    Slow light has been widely utilized to obtain enhanced nonlinearities, enhanced spontaneous emissions and increased phase shifts owing to its ability to promote light–matter interactions. By incorporating a graphene on a slow-light silicon photonic crystal waveguide, here we experimentally demonstrate an energy-efficient graphene microheater with a tuning efficiency of 1.07 nmmW−1 and power consumption per free spectral range of 3.99 mW. The rise and decay times (10–90%) are only 750 and 525 ns, which, to the best of our knowledge, are the fastest reported response times for microheaters in silicon photonics. The corresponding figure of merit of the device is 2.543 nW s, one order of magnitude better than results reported in previous studies. The influence of the length and shape of the graphene heater to the tuning efficiency is further investigated, providing valuable guidelines for enhancing the tuning efficiency of the graphene microheater. PMID:28181531

  8. A simple and tunable switch between slow- and fast-light in two signal modes with an optomechanical system

    Science.gov (United States)

    Ma, Peng-Cheng; Yan, Lei-Lei; Chen, Gui-Bin; Li, Xiao-Wei; Zhan, You-Bang

    2016-12-01

    The control of slow and fast light propagation is a challenging task. Here, we theoretically study the dynamics of a driven optomechanical cavity coupled to a charged nanomechanical resonator (NR) via Coulomb interaction. We find that the tunable switch between slow- and fast-light for two signal modes can be observed from the output field by adjusting the laser-cavity detuning in this system. Moreover, the frequencies of two signal light can be tuned by Coulomb coupling strength. In comparison with previous schemes, the clear advantage of our scheme is that we can simply switch from fast- to slow-light in two signal modes by only adjusting the laser-cavity deturning from Δ ={ω1} to Δ =-{ω1} . The proposal may have potential application in optical router and quantum optomechanical memory.

  9. Multiple electromagnetically induced transparency, slow and fast light in hybrid optomechanics

    CERN Document Server

    Akram, M Javed; Saif, Farhan

    2015-01-01

    We theoretically investigate the phenomenon of electromagnetically induced transparency (EIT) of a weak probe field in hybrid optomechanics with a single three-level ($\\Lambda$-type) atomic system. We report that, in the presence of optomechanical coupling and two transition coupling parameters of three-level atom (TLA), there occurs three distinct multiple EIT windows in the probe absorption spectrum. Moreover, the switching of multiple windows into double and single EIT windows can be obtained by suitably tuning the system parameters. Furthermore, the probe transmission spectrum have been studied. Based on our analytical and numerical work, we explain the occurrence of slow and fast light (superluminal) regimes, and enhancement of superluminal behaviour in the probe field transmission. This work demonstrates great potential in multi-channel waveguide, fiber optics and classical communication networks, multi-channel quantum information processing, real quality imaging, cloaking devices and delay lines & ...

  10. Slow light in a dielectric waveguide with negative-refractive-index photonic crystal cladding.

    Science.gov (United States)

    He, Jinlong; Jin, Yi; Hong, Zhi; He, Sailing

    2008-07-21

    A slow light waveguide made of a dielectric slab inserted in a two-dimensional photonic crystal with a negative effective refractive index is proposed and numerically studied. The waveguide may possess modes with zero group velocity, and its frequency varies with the thickness of the waveguide. A linearly tapered left-handed photonic crystal waveguide is also proposed and studied. It is shown that the so-called 'trapped rainbow' proposed by Tsakmakidis, Boardman, and Hess [1] is difficult to realize due to a coupling of forward- and backward-propagating modes near zero group velocity. However, different frequency components of a broadband excitation can still be separated through partial accumulation at waveguide sections of different thicknesses.

  11. High Purcell factor in fiber Bragg gratings utilizing the fundamental slow-light mode.

    Science.gov (United States)

    Skolianos, George; Arora, Arushi; Bernier, Martin; Digonnet, Michel J F

    2015-08-01

    We demonstrate through numerical simulations that the slow-light resonances that exist in strong, apodized fiber Bragg gratings (FBGs) fabricated with femtosecond pulses in deuterium-loaded fibers can exhibit very large intensity enhancements and Purcell factors with the proper optimization of their length. This potential is illustrated with two saturated FBGs that are less than 5 mm long and have been annealed to reduce their internal loss. The first one exhibits the largest measured Purcell factor in an all-fiber device (38.7), and the second one exhibits the largest intensity enhancement (1525). These devices are anticipated to have significant applications in quantum-dot lasers, nonlinear fiber devices, and cavity quantum-electrodynamics experiments.

  12. Coupled plasmon-exciton induced transparency and slow light in plexcitonic metamaterials

    DEFF Research Database (Denmark)

    Panahpour, Ali; Silani, Yaser; Farrokhian, Marzieh

    2012-01-01

    effects in low-loss nanostructures, and development of low-loss metamaterials. A large variety of plasmonic structures has been proposed for producing classical EIT-like effects in different spectral ranges. The current approach for producing plasmon-induced transparency is usually based on precise design...... effects in metamaterials composed of such coupled NPs. To reveal more details of the wave-particle and particle-particle interactions, the electric field distribution and field lines of Poynting vector inside and around the NPs are calculated using the finite element method. Finally, using extended...... Maxwell Garnett theory, we study the coupled-NP-induced transparency and slow light effects in a metamaterial comprising random mixture of silver and copper chloride (CuCl) NPs, and more effectively in a metamaterial consisting of random distribution of coated NPs with CuCl cores and aluminum shells...

  13. Impact of slow-light enhancement on optical propagation in active semiconductor photonic crystal waveguides

    DEFF Research Database (Denmark)

    Chen, Yaohui; de Lasson, Jakob Rosenkrantz; Gregersen, Niels

    2015-01-01

    We derive and validate a set of coupled Bloch wave equations for analyzing the reflection and transmission properties of active semiconductor photonic crystal waveguides. In such devices, slow-light propagation can be used to enhance the material gain per unit length, enabling, for example......, the realization of short optical amplifiers compatible with photonic integration. The coupled wave analysis is compared to numerical approaches based on the Fourier modal method and a frequency domain finite element technique. The presence of material gain leads to the build-up of a backscattered field, which...... is interpreted as distributed feedback effects or reflection at passive-active interfaces, depending on the approach taken. For very large material gain values, the band structure of the waveguide is perturbed, and deviations from the simple coupled Bloch wave model are found....

  14. Slow light engineering in a photonic crystal slab waveguide through optofluidic infiltration and geometric modulation

    Science.gov (United States)

    Khodamohammadi, A.; Khoshsima, H.; Fallahi, V.

    2017-05-01

    In this paper, a new type of flat-band slow light structure with high group index ( n g) and large normalized delay-bandwidth product (NDBP) in a silicon on insulator (SOI) based photonic crystal (PC) slab waveguide with a triangular lattice of circular holes is demonstrated. The dispersion engineering is performed by infiltrating optical fluids with different refractive indices n f in the first row and shifting the second row of air holes adjacent to the PC waveguide (PCW) in the longitudinal direction. In the optimized case, a high NDBP of 0.32 with a group index of 54.55 and a bandwidth of 9.13 nm could be obtained. Furthermore, an ultra-low group velocity dispersion (GVD) in the range of 10-20 s2/m is achieved in all of the structures. These results are obtained by numerical simulations based on three-dimensional (3D) plane wave expansion (PWE) method.

  15. Slow-Light Propagation in a Tapered Dielectric Periodic Waveguide over Broad Frequency Range

    Institute of Scientific and Technical Information of China (English)

    FANG Yi-Jiao; CHEN Zhuo; WANG Zhen-Lin

    2011-01-01

    @@ A tapered waveguide composed of a one-dimensional periodic arrangement of dielectric materialis proposed for light trapping.The equifrequency contours(EFC) of silicon-air multilayer photonic crystals within the first bandgap region are first studied.A zero-group-velocity at the first Brillouin zone boundary along the grating vector is predicted.The propagation constants and eigenfrequencies of the first-order guiding modes are numerically investigated for photonic crystal waveguide structures with a finite thickness.Different frequency components of the guiding modes are found to slov and stop at different thicknesses inside such a tapered waveguide structure.In addition,the time-evolution of a femto-second pulse propagating in the tapered waveguide is also demonstrated.%A tapered waveguide composed of a one-dimensional periodic arrangement of dielectric material is proposed for light trapping. The equifrequency contours (EFC) of silicon-air multilayer photonic crystals within the first bandgap region are first studied. A zero-group-velocity at the first Brillouin zone boundary along the grating vector is predicted. The propagation constants and eigenfrequencies of the first-order guiding modes are numerically investigated for photonic crystal waveguide structures with a finite thickness. Different frequency components of the guiding modes are found to slow and stop at different thicknesses inside such a tapered waveguide structure. In addition, the time-evolution of a femto-second pulse propagating in the tapered waveguide is also demonstrated.

  16. Implementing structural slow light on short length scales: the photonic speed-bump

    CERN Document Server

    Faggiani, Remi; Hostein, Richard; Lalanne, Philippe

    2016-01-01

    One-dimensional (1D) infinite periodic systems exhibit vanishing group velocity and diverging density of states (DOS) near band edges. However, in practice, systems have finite sizes and inevitably this prompts the question of whether helpful physical quantities related to infinite systems, such as the group velocity that is deduced from the band structure, remain relevant in finite systems. For instance, one may wonder how the DOS divergence can be approached with finite systems. Intuitively, one may expect that the implementation of larger and larger DOS, or equivalently smaller and smaller group velocities, would critically increase the system length. Based on general 1D-wave-physics arguments, we demonstrate that the large slow-light DOS enhancement of periodic systems can be observed with very short systems, whose lengths scale with the logarithm of the inverse of the group velocities. The understanding obtained for 1D systems leads us to propose a novel sort of microstructure to enhance light-matter int...

  17. Efficient light coupling into a photonic crystal waveguide with flatband slow mode

    CERN Document Server

    Säynätjoki, A; Mulot, M; Cassagne, D; Ahopelto, J; Lipsanen, H

    2008-01-01

    We design an efficient coupler to transmit light from a strip waveguide into the flatband slow mode of a photonic crystal waveguide with ring-shaped holes. The coupler is a section of a photonic crystal waveguide with a higher group velocity, obtained by different ring dimensions. We demonstrate coupling efficiency in excess of 95% over the 8 nm wavelength range where the photonic crystal waveguide exhibits a quasi constant group velocity vg = c/37. An analysis based on the small Fabry-P\\'erot resonances in the simulated transmission spectra is introduced and used for studying the effect of the coupler length and for evaluating the coupling efficiency in different parts of the coupler. The mode conversion efficiency within the coupler is more than 99.7% over the wavelength range of interest. The parasitic reflectance in the coupler, which depends on the propagation constant mismatch between the slow mode and the coupler mode, is lower than 0.6% within this wavelength range.

  18. Large delay tunable slow-light based on high-gain stimulated-Brillouin-scattering amplification in optical fibers

    Institute of Scientific and Technical Information of China (English)

    XING Liang; ZHAN Li; XIA YuXing

    2009-01-01

    Tunable stimulated-Brillouin-scattering (SBS)-based slow-light in optical fibers has potential applications in optical buffering in the future all-optical router commutation systems.However,due to the low SBS threshold and relatively high realistic signal power,the gain in the usual SBS systems is limited at~30 dB.This paper presents a high-gain SBS scheme to realize large delay slow-light,which benefits from avoiding the depletion of the pump power in a short fiber as SBS media.The experiment demon strates that,up to 50 dB non-saturated gain has been observed in the single-stage 591.8 m fiber SBS amplification.The slow-light delay can be obtained 52 ns,and the fractional delay can exceed 1.

  19. Complete compensation of pulse broadening in an amplifier-based slow light system using a nonlinear regeneration element.

    Science.gov (United States)

    Chin, Sanghooon; Gonzalez-Herraez, Miguel; Thévenaz, Luc

    2009-11-23

    We experimentally demonstrate complete compensation of pulse broadening in an amplifier-based slow light system. The configuration of the delay line basically consists of two stages: a conventional Brillouin slow light system and a nonlinear regeneration element. Signal pulses experienced both time delay and temporal broadening through the Brillouin delay line and then the delayed pulses were delivered into a nonlinear optical loop mirror. Due to the nonlinear response of the transmission of the fiber loop, the inevitably broadened pulses were moderately compressed in the output of the loop, without loss in the capacity to delay the pulses. The overall result is that, for the maximum delay, the width of the pulse could be kept below the input width while the time delays introduced by the slow light element were preserved. Using this delay line, a signal pulse with duration of 27 ns at full width at half maximum was delayed up to 1.3-bits without suffering from signal distortion.

  20. Alignment dynamics of slow light diffusion in ultracold atomic $^{85}$Rb

    CERN Document Server

    Balik, S; Sukenik, C I; Havey, M D; Datsyuk, V M; Sokolov, I M; Kupriyanov, D V

    2014-01-01

    A combined experimental and theoretical investigation of time- and alignment-dependent propagation of light in an ultracold atomic gas of atomic $^{85}$Rb is reported. Coherences among the scattering amplitudes for light scattering off excited hyperfine levels produce strong variations of the light polarization in the vicinity of atomic resonance. Measurements are in excellent agreement with Monte-Carlo simulations of the multiple scattering process.

  1. Synchronized ion acceleration by ultraintense slow light and electron source for x-ray production from low-density targets

    Science.gov (United States)

    Brantov, A. V.; Bychenkov, V. Yu

    2017-03-01

    Synchronized proton acceleration by ultraintense slow light in a low-density target Brantov et al (2016 Phys. Rev. Lett. 116 085004) is studied for a circularly polarized laser pulse. This study demonstrates the advantage of circularly polarized light compared with linearly polarized light used for high-energy proton generation. At the same time, high-energy electron production for gamma-ray generation is not sensitive to the polarization of the laser pulse. Both the proton and the electron sources are considered in application to petawatt-class lasers.

  2. Lighting: Green Light.

    Science.gov (United States)

    Maniccia, Dorine

    2003-01-01

    Explains that by using sustainable (green) building practices, schools and universities can make their lighting systems more efficient, noting that embracing green design principles can help schools attract students. Discusses lighting-control technologies (occupancy sensing technology, daylighting technology, and scheduling based technologies),…

  3. Effect of color temperature of light sources on slow-wave sleep.

    Science.gov (United States)

    Kozaki, Tomoaki; Kitamura, Shingo; Higashihara, Yuichi; Ishibashi, Keita; Noguchi, Hiroki; Yasukouchi, Akira

    2005-03-01

    In order to examine whether the spectral compositions of light source may affect sleep quality, sleep architecture under different color temperatures of light sources was evaluated. Seven healthy males were exposed to the light sources of different color temperatures (3000 K, 5000 K and 6700 K) for 6.5 h before sleep. The horizontal illuminance level was kept at 1000 lux. Subjects slept on a bed in near darkness (light, and polysomnograms recorded the sleep parameters. In the early phase of the sleep period, the amount of stage-4 sleep (S4-sleep) was significantly attenuated under the higher color temperature of 6700 K compared with the lower color temperature of 3000 K. Present findings suggest that light sources with higher color temperatures may affect sleep quality in a view that S4-sleep period is important for sleep quality.

  4. Numerical Investigation and Optimization of SBS-Based Slow-Light Using Filtered Incoherent Pump

    Institute of Scientific and Technical Information of China (English)

    ZHENG Di; PAN Wei; YAN Lian-Shan; LUO Bin; ZOU Xi-Hua; WEN Kun-Hua; JIANG Ning

    2009-01-01

    The performance of stimulated Brillouin scattering(SBS)-based slow light using a novel spectrally-sliced broad band incoherent pump source is numerically studied.The profile of the pump-power spectrum is determined by the transmission spectra of the optical filter followed by the polarized broadband incoherent pump source.We also investigate the performance of Gaussian-type and super-Gaussian-type filtering under different spectrally-sliced bandwidths and pump power levels for 2.5 Gbit/s return-to-zero pulse(50% duty-cycle).The pulse broadening is characterized by the full width of half maximum(FWHM)and the rms pulse width,respectively.However,the results obtained by the two kinds of measurement methods deviate from each other with increasing pump power.Compared with the regular Gaussian-type filtering,the pulse broadening can be significantly reduced using super-Gaussian-type filtering at the cost of a small reduction in delay time.Furthermore,the maximum improvement in pulse broadening of △B_(FWHM) = 28.4% and △B_(RMS)= 10.4% is achieved by using a five-order super-Gaussian-type filter and a pump power of 500mw.

  5. Control of Fano resonances and slow light using Bose-Einstein condensates in a nanocavity

    Science.gov (United States)

    Akram, M. Javed; Ghafoor, Fazal; Khan, M. Miskeen; Saif, Farhan

    2017-02-01

    In this study, a standing wave in an optical nanocavity with Bose-Einstein condensate (BEC) constitutes a one-dimensional optical lattice potential in the presence of a finite two bodies atomic interaction. We report that the interaction of a BEC with a standing field in an optical cavity coherently evolves to exhibit Fano resonances in the output field at the probe frequency. The behavior of the reported resonance shows an excellent compatibility with the original formulation of asymmetric resonance as discovered by Fano [U. Fano, Phys. Rev. 124, 1866 (1961), 10.1103/PhysRev.124.1866]. Based on our analytical and numerical results, we find that the Fano resonances and subsequently electromagnetically induced transparency of the probe pulse can be controlled through the intensity of the cavity standing wave field and the strength of the atom-atom interaction in the BEC. In addition, enhancement of the slow light effect by the strength of the atom-atom interaction and its robustness against the condensate fluctuations are realizable using presently available technology.

  6. Compared propagation characteristics of superluminal and slow light in SOA and EDFA based on rectangle signals

    Science.gov (United States)

    Wang, Fu; Wang, Zhi; Wu, Chongqing; Sun, Zhenchao; Mao, Yaya; Liu, Lanlan; Li, Qiang

    2015-10-01

    Based on the general mechanism of the coherent population oscillations (CPO) in the Semiconductor optical amplifiers (SOA) and Erbium doped fiber amplifiers (EDFA), the group time delay of rectangle signal propagating in the active media is deduced. Compared with the sinusoidal signal, the time delay difference between the fundamental harmonics (FHFD: fundamental harmonic fractional delay) is first investigated in detail for the rectangle signal which is more popularly used in the digital signal systems. The plenty of simulations based on the propagation equations and some experiments for the sinusoidal and rectangle signals are used to analyze the differences and evaluate the slow and superluminal light effects. Furthermore, the time delay/advance always takes place accompanying with the signal distortion, which is evaluated by the total harmonic distortion (THD). The distortion caused by the SOA is smaller than that by the EDFA. A factor Q which is defined to evaluate the trade-off between the FHFD and the THD, shows that higher input power or higher optical gain is better for optical signal processing and optical telecommunications, and the SOA is more suitable for the higher modulation frequency (>10 GHz).

  7. Control of slow light in a ring-out-ring structure

    Institute of Scientific and Technical Information of China (English)

    Wang Nan; Zhang Yun-Dong; Yuan Ping

    2011-01-01

    This paper proposes a ring-out-ring structure of coupled optical resonators to yield coupled-resonator-induced transparency(GRIT). Considering the insertion loss of the coupler, it theoretically deduces the transmission and the effective phase shift. The influences of the insertion loss of the coupler on the transmittance, the effective phase shift,the group index and the CRIT linewidth are fully studied. We find that the increase in multiple m can effectively enhance the normal dispersion and the group index of the proposed structure. Moreover, the specific expression of the group index at resonance is theoretically deduced and discussed for the proposed structure with two rings. The result shows that the multiple m between the lengths of ring 1 and ring 2 can enhance the group index to m times that of the structure with two equal-sized rings at resonance. The control of slow light in the proposed structure is important for applications of highly sensitivity gyroscopes, optical delay lines and optical buffers, etc.

  8. Slow-light enhanced absorption for bio-chemical sensing applications: potential of low-contrast lossy materials

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Xiao, Sanshui; Mortensen, Niels Asger

    2008-01-01

    Slow-light enhanced absorption in liquid-infiltrated photonic crystals has recently been proposed as a route to compensate for the reduced optical path in typical lab-on-a-chip systems for bio-chemical sensing applications. A simple perturbative expression has been applied to ideal structures...

  9. Microwave phase shifter with controllable power response based on slow-and fast-light effects in semiconductor optical amplifiers

    DEFF Research Database (Denmark)

    Xue, Weiqi; Sales, Salvador; Capmany, Jose

    2009-01-01

    We suggest and experimentally demonstrate a method for increasing the tunable rf phase shift of semiconductor waveguides while at the same time enabling control of the rf power. This method is based on the use of slow- and fast-light effects in a cascade of semiconductor optical amplifiers combined...

  10. Graphene based silicon–air grating structure to realize electromagnetically-induced-transparency and slow light effect

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Buzheng; Liu, Huaiqing [Key Lab of All Optical Network & Advanced Telecommunication Network of EMC, Beijing Jiaotong University, Beijing 100044 (China); Institute of Lightwave Technology, Beijing Jiaotong University, Beijing 100044 (China); Ren, Guobin, E-mail: gbren@bjtu.edu.cn [Key Lab of All Optical Network & Advanced Telecommunication Network of EMC, Beijing Jiaotong University, Beijing 100044 (China); Institute of Lightwave Technology, Beijing Jiaotong University, Beijing 100044 (China); Yang, Yuguang; Ye, Shen; Pei, Li; Jian, Shuisheng [Key Lab of All Optical Network & Advanced Telecommunication Network of EMC, Beijing Jiaotong University, Beijing 100044 (China); Institute of Lightwave Technology, Beijing Jiaotong University, Beijing 100044 (China)

    2017-01-23

    Highlights: • The EIT and slow light effect are achieved by our novel graphene based structure. • Excellent tunability of wide wavelength range can be obtained only by a small change in Fermi energy level. • The group velocity of incident light is reduced to more than 1/600 of that in vacuum. • Position control is realized by designing a graded period grating. - Abstract: A broad band tunable graphene based silicon–air grating structure is proposed. Electromagnetically-induced-transparency (EIT) window can be successfully tuned by virtually setting the desired Fermi energy levels on graphene sheets. Carrier mobility plays an important role in modulating the resonant depth. Furthermore, by changing the grating periods, light can be trapped at corresponding resonant positions where slow down factor is relatively larger than in the previous works. This structure can be used as a highly tunable optoelectronic device such as optical filter, broad-band modulator, plasmonic switches and buffers.

  11. Large dynamic light-matter entanglement from driving neither too fast nor too slow

    Science.gov (United States)

    Acevedo, O. L.; Quiroga, L.; Rodríguez, F. J.; Johnson, N. F.

    2015-09-01

    A significant problem facing next-generation quantum technologies is how to generate and manipulate macroscopic entanglement in light and matter systems. Here we report a regime of dynamical light-matter behavior in which a giant, system-wide entanglement is generated by varying the light-matter coupling at intermediate velocities. This enhancement is far larger, broader ranged, and more experimentally accessible than that occurring near the quantum phase transition of the same model under adiabatic conditions. By appropriate choices of the coupling within this intermediate regime, the enhanced entanglement can be made to spread system-wide or to reside in each subsystem separately.

  12. Slow light performance enhancement of Bragg slot photonic crystal waveguide with particle swarm optimization algorithm

    Science.gov (United States)

    Abedi, Kambiz; Mirjalili, Seyed Mohammad

    2015-03-01

    Recently, majority of current research in the field of designing Phonic Crystal Waveguides (PCW) focus in extracting the relations between output slow light properties of PCW and structural parameters through a huge number of tedious non-systematic simulations in order to introduce better designs. This paper proposes a novel systematic approach which can be considered as a shortcut to alleviate the difficulties and human involvements in designing PCWs. In the proposed method, the problem of PCW design is first formulated as an optimization problem. Then, an optimizer is employed in order to automatically find the optimum design for the formulated PCWs. Meanwhile, different constraints are also considered during optimization with the purpose of applying physical limitations to the final optimum structure. As a case study, the structure of a Bragg-like Corrugation Slotted PCWs (BCSPCW) is optimized by using the proposed method. One of the most computationally powerful techniques in Computational Intelligence (CI) called Particle Swarm Optimization (PSO) is employed as an optimizer to automatically find the optimum structure for BCSPCW. The optimization process is done by considering five constraints to guarantee the feasibility of the final optimized structures and avoid band mixing. Numerical results demonstrate that the proposed method is able to find an optimum structure for BCSPCW with 172% and 100% substantial improvements in the bandwidth and Normalized Delay-Bandwidth Product (NDBP) respectively compared to the best current structure in the literature. Moreover, there is a time domain analysis at the end of the paper which verifies the performance of the optimized structure and proves that this structure has low distortion and attenuation simultaneously.

  13. Slow and fast light in metal/dielectric composites with passive and active host matrices

    Energy Technology Data Exchange (ETDEWEB)

    Mal' nev, V.N., E-mail: vadimmalnev@yahoo.com; Shewamare, Sisay, E-mail: sisayshewa20@yahoo.com

    2013-10-01

    The optical properties of metal/dielectric composites (metal with dielectric core and pure metal inclusions) in passive and active host matrices are studied. It is shown that the real and imaginary parts of the refractive index of the composites with metal covered inclusions have two maxima at two resonant frequencies. Both types of composites show strong anomalous dispersion of the real part of refractive index. The active host matrices can considerably reduce the absorption and provide the conditions for the propagation of weakly damping light waves at the resonant frequencies. The weakly spreading wave packets of light with negative group velocity can be experimentally observed in these composites.

  14. High-performance slow light photonic crystal waveguides with topology optimized or circular-hole based material layouts

    DEFF Research Database (Denmark)

    Wang, Fengwen; Jensen, Jakob Søndergaard; Sigmund, Ole

    2012-01-01

    Photonic crystal waveguides are optimized for modal confinement and loss related to slow light with high group index. A detailed comparison between optimized circular-hole based waveguides and optimized waveguides with free topology is performed. Design robustness with respect to manufacturing...... imperfections is enforced by considering different design realizations generated from under-, standard- and over-etching processes in the optimization procedure. A constraint ensures a certain modal confinement, and loss related to slow light with high group index is indirectly treated by penalizing field...... of 0.48 or above. The comparisons between circular-hole based designs and topology optimized designs illustrate that the former can be efficient for dispersion engineering but that larger improvements are possible if irregular geometries are allowed....

  15. Slowing light down by low magnetic fields: pulse delay by transient spectral hole-burning in ruby.

    Science.gov (United States)

    Riesen, Hans; Rebane, Aleksander K; Szabo, Alex; Carceller, Ivana

    2012-08-13

    We report on the observation of slow light induced by transient spectral hole-burning in a solid, that is based on excited-state population storage. Experiments were conducted in the R1-line (2E←4A2 transition) of a 2.3 mm thick pink ruby (Al2O3:Cr(III) 130 ppm). Importantly, the pulse delay can be controlled by the application of a low external magnetic field B||c≤9 mT and delays of up to 11 ns with minimal pulse distortion are observed for ~55 ns Gaussian pulses. The delay corresponds to a group velocity value of ~c/1400. The experiment is very well modelled by linear spectral filter theory and the results indicate the possibility of using transient hole-burning based slow light experiments as a spectroscopic technique.

  16. Improved slow-light performance of 10 Gb/s NRZ, PSBT and DPSK signals in fiber broadband SBS.

    Science.gov (United States)

    Yi, Lilin; Jaouen, Yves; Hu, Weisheng; Su, Yikai; Bigo, Sébastien

    2007-12-10

    We have demonstrated error-free operations of slow-light via stimulated Brillouin scattering (SBS) in optical fiber for 10-Gb/s signals with different modulation formats, including non-return-to-zero (NRZ), phase-shaped binary transmission (PSBT) and differential phase-shiftkeying (DPSK). The SBS gain bandwidth is broadened by using current noise modulation of the pump laser diode. The gain shape is simply controlled by the noise density function. Super-Gaussian noise modulation of the Brillouin pump allows a flat-top and sharp-edge SBS gain spectrum, which can reduce slow-light induced distortion in case of 10-Gb/s NRZ signal. The corresponding maximal delay-time with error-free operation is 35 ps. Then we propose the PSBT format to minimize distortions resulting from SBS filtering effect and dispersion accompanied with slow light because of its high spectral efficiency and strong dispersion tolerance. The sensitivity of the 10-Gb/s PSBT signal is 5.2 dB better than the NRZ case with a same 35-ps delay. The maximal delay of 51 ps with error-free operation has been achieved. Futhermore, the DPSK format is directly demodulated through a Gaussian-shaped SBS gain, which is achieved using Gaussian-noise modulation of the Brillouin pump. The maximal error-free time delay after demodulation of a 10-Gb/s DPSK signal is as high as 81.5 ps, which is the best demonstrated result for 10-Gb/s slow-light.

  17. Slow and fast light via two-wave mixing in the rare-earth doped optical fibers (Conference Presentation)

    Science.gov (United States)

    Stepanov, Serguei I.; Plata Sánchez, Marcos; Hernández, Eliseo

    2017-02-01

    Dynamic population Bragg gratings can be recorded in the rare-earth-doped (e.g. doped with erbium or ytterbium) optical fibers with mWatt-scale cw laser power. Two-wave mixing (TWM) via such gratings is utilized in single-frequency fiber lasers and in adaptive interferometric fiber sensors with automatic stabilization of the operation point. Slow and fast light propagation can also be observed in the vicinity of narrow ( 20-200Hz) spectral profile of stationary no-degenerate TWM. In particular, slow light propagation is observed for the purely amplitude grating, recorded in the erbium-doped fiber in spectral range 1510-1550nm. In its turn, in ytterbium-doped fibers at 1064nm (or in erbium-doped fiber at the wavelength below 1500nm) the dynamic grating has significant contribution of the phase component, the TWM profile has essentially asymmetric form, and both slow and fast (superluminal) light propagation is possible at different frequency off-sets between the counter-propagating interacting waves.

  18. The effect of higher-order dispersion on slow light propagation in photonic crystal waveguides

    NARCIS (Netherlands)

    Engelen, R.J.P.; Engelen, R.J.P.; Sugimoto, Y.; Watanabe, Y.; Korterik, Jeroen P.; Ikeda, N.; van Hulst, N.F.; Asakawa, K.; Kuipers, L.

    2006-01-01

    We have studied the dispersion of ultrafast pulses in a photonic crystal waveguide as a function of optical frequency, in both experiment and theory. With phase-sensitive and time-resolved near-field microscopy, the light was probed inside the waveguide in a non-invasive manner. The effect of

  19. Public lighting.

    NARCIS (Netherlands)

    Schreuder, D.A.

    1986-01-01

    The function of public lighting and the relationship between public lighting and accidents are considered briefly as aspects of effective countermeasures. Research needs and recent developments in installation and operational described. Public lighting is an efficient accident countermeasure, but

  20. Light sleep versus slow wave sleep in memory consolidation: a question of global versus local processes?

    Science.gov (United States)

    Genzel, Lisa; Kroes, Marijn C W; Dresler, Martin; Battaglia, Francesco P

    2014-01-01

    Sleep is strongly involved in memory consolidation, but its role remains unclear. 'Sleep replay', the active potentiation of relevant synaptic connections via reactivation of patterns of network activity that occurred during previous experience, has received considerable attention. Alternatively, sleep has been suggested to regulate synaptic weights homeostatically and nonspecifically, thereby improving the signal:noise ratio of memory traces. Here, we reconcile these theories by highlighting the distinction between light and deep nonrapid eye movement (NREM) sleep. Specifically, we draw on recent studies to suggest a link between light NREM and active potentiation, and between deep NREM and homeostatic regulation. This framework could serve as a key for interpreting the physiology of sleep stages and reconciling inconsistencies in terminology in this field.

  1. Slow light in a semiconductor waveguide for true-time delay applications in microwave photonics

    DEFF Research Database (Denmark)

    Öhman, Filip; Yvind, Kresten; Mørk, Jesper

    2007-01-01

    We have investigated the slowand fast light properties of a semiconductor waveguide device employing concatenated gain and absorber sections. This letter presents the experimental results as well as theoretical modeling. A large phase shift of 110 and a true-time delay of more than 150 ps are dem...... are demonstrated. The combination of amplitude and phase control of the modulated signal shows great promise for applications within microwave photonics....

  2. WOW: light print, light propel, light point

    DEFF Research Database (Denmark)

    Glückstad, Jesper; Bañas, Andrew Rafael; Aabo, Thomas

    2012-01-01

    anywhere in a sample at any orientation using real-time 3D optical micromanipulation with six degrees of freedom. One of the key aspects of our demonstrated WOWs is the change in direction of in-coupled light and the marked increase in numerical aperture of the out-coupled light. Hence, each light...... propelled WOW can tap from a relatively broad incident beam and generate a much more tightly confined light at its tip. The presentation contains both numerical simulations related to the propagation of light through a WOW and preliminary experimental demonstrations on our BioPhotonics Workstation...

  3. Reduced irradiation time in slow-curing of resin composite using an intensity-changeable light source.

    Science.gov (United States)

    Abo, Tomoko; Uno, Shigeru; Tagami, Junji

    2005-06-01

    Possibility to shorten the total irradiation time in slow-curing with an intensity-changeable light source, Curetron 7 (CT-7), was investigated for four hybrid-type resin composites. Irradiation condition with CT-7 was assigned as 10 or 20 seconds at low light intensity (230 mW/cm2) and followed by 20 or 10 seconds at high intensity (600 mW/cm2) respectively (i.e., a total of 30 seconds). For a reference, irradiation was carried out for 30 seconds using a halogen lamp (900 mW/cm2). After irradiation, mechanical properties of the cured composites--in terms of microhardness and flexural strength--were evaluated. Also, cavity adaptation was examined in standardized, cylindrical dentin cavities treated with an adhesive system. Compared to the reference irradiation, slow-curing with CT-7 produced acceptable mechanical properties and better adaptation. These results suggested that total exposure time of slow-curing with CT-7 could be shortened to 30 seconds.

  4. Infrared light irradiation diminishes effective charge transfer in slow sodium channel gating system

    Science.gov (United States)

    Plakhova, Vera B.; Bagraev, Nikolai T.; Klyachkin, Leonid E.; Malyarenko, Anna M.; Romanov, Vladimir V.; Krylov, Boris V.

    2001-02-01

    Effects of infrared light irradiation (IR) on cultured dorsal root ganglia cells were studied by the whole-cell patch-clamp technique. The IR field is demonstrated to diminish the effective charge transfer in the activation system from 6.2 +-0.6 to 4.5 +-0.4 in units of electron charge per e-fold change in membrane potential. The effects was blocked with ouabain. Our data is the first indication that sodium pump might be the molecular sensor of infrared irradiation in animal kingdom.

  5. Magnetic field protects plants against high light by slowing down production of singlet oxygen.

    Science.gov (United States)

    Hakala-Yatkin, Marja; Sarvikas, Päivi; Paturi, Petriina; Mäntysaari, Mika; Mattila, Heta; Tyystjärvi, Taina; Nedbal, Ladislav; Tyystjärvi, Esa

    2011-05-01

    Recombination of the primary radical pair of photosystem II (PSII) of photosynthesis may produce the triplet state of the primary donor of PSII. Triplet formation is potentially harmful because chlorophyll triplets can react with molecular oxygen to produce the reactive singlet oxygen (¹O₂). The yield of ¹O₂ is expected to be directly proportional to the triplet yield and the triplet yield of charge recombination can be lowered with a magnetic field of 100-300 mT. In this study, we illuminated intact pumpkin leaves with strong light in the presence and absence of a magnetic field and found that the magnetic field protects against photoinhibition of PSII. The result suggests that radical pair recombination is responsible for significant part of ¹O₂ production in the chloroplast. The magnetic field effect vanished if leaves were illuminated in the presence of lincomycin, an inhibitor of chloroplast protein synthesis, or if isolated thylakoid membranes were exposed to light. These data, in turn, indicate that ¹O₂ produced by the recombination of the primary charge pair is not directly involved in photoinactivation of PSII but instead damages PSII by inhibiting the repair of photoinhibited PSII. We also found that an Arabidopsis thaliana mutant lacking α-tocopherol, a scavenger of ¹O₂, is more sensitive to photoinhibition than the wild-type in the absence but not in the presence of lincomycin, confirming that the target of ¹O₂ is the repair mechanism.

  6. Ultracompact 160 Gbaud all-optical demultiplexing exploiting slow light in an engineered silicon photonic crystal waveguide.

    Science.gov (United States)

    Corcoran, Bill; Pelusi, Mark D; Monat, Christelle; Li, Juntao; O'Faolain, Liam; Krauss, Thomas F; Eggleton, Benjamin J

    2011-05-01

    We demonstrate all-optical demultiplexing of a high-bandwidth, time-division multiplexed 160 Gbit/s signal to 10 Gbit/s channels, exploiting slow light enhanced four-wave mixing in a dispersion engineered, 96 μm long planar photonic crystal waveguide. We report error-free (bit error rate<10⁻⁹) operation of all 16 demultiplexed channels, with a power penalty of 2.2-2.4 dB, highlighting the potential of these structures as a platform for ultracompact all-optical nonlinear processes.

  7. Graphene based silicon-air grating structure to realize electromagnetically-induced-transparency and slow light effect

    Science.gov (United States)

    Wei, Buzheng; Liu, Huaiqing; Ren, Guobin; Yang, Yuguang; Ye, Shen; Pei, Li; Jian, Shuisheng

    2017-01-01

    A broad band tunable graphene based silicon-air grating structure is proposed. Electromagnetically-induced-transparency (EIT) window can be successfully tuned by virtually setting the desired Fermi energy levels on graphene sheets. Carrier mobility plays an important role in modulating the resonant depth. Furthermore, by changing the grating periods, light can be trapped at corresponding resonant positions where slow down factor is relatively larger than in the previous works. This structure can be used as a highly tunable optoelectronic device such as optical filter, broad-band modulator, plasmonic switches and buffers.

  8. Controlling slow and fast light and dynamic pulse-splitting with tunable optical gain in a whispering-gallery-mode microcavity

    Science.gov (United States)

    Asano, M.; Özdemir, Ş. K.; Chen, W.; Ikuta, R.; Yang, L.; Imoto, N.; Yamamoto, T.

    2016-05-01

    We report controllable manipulation of slow and fast light in a whispering-gallery-mode microtoroid resonator fabricated from Erbium (Er3+) doped silica. We observe continuous transition of the coupling between the fiber-taper waveguide and the microresonator from undercoupling to critical coupling and then to overcoupling regimes by increasing the pump power even though the spatial distance between the resonator and the waveguide was kept fixed. This, in turn, enables switching from fast to slow light and vice versa just by increasing the optical gain. An enhancement of delay of two-fold over the passive silica resonator (no optical gain) was observed in the slow light regime. Moreover, we show dynamic pulse splitting and its control in slow/fast light systems using optical gain.

  9. Controlling slow and fast light and dynamic pulse-splitting with tunable optical gain in a whispering-gallery-mode microcavity

    CERN Document Server

    Asano, Motoki; Chen, Weijian; Ikuta, Rikizo; Yang, Lan; Imoto, Nobuyuki; Yamamoto, Takashi

    2016-01-01

    We report controllable manipulation of slow and fast light in a whispering-gallery-mode (WGM) microtoroid resonator fabricated from Erbium (Er3+) doped silica. We observe continuous transition of the coupling between the fiber-taper waveguide and the microresonator from undercoupling to critical coupling and then to overcoupling regimes by increasing the pump power even though the spatial distance between the resonator and the waveguide was kept fixed. This, in turn, enables switching from fast to slow light and vice versa just by increasing the optical gain. An enhancement of delay of two-fold over the passive silica resonator (no optical gain) was observed in the slow light regime. Moreover, we show dynamic pulse splitting and its control in slow/fast light systems using optical gain.

  10. Slow pupillary light responses in infants at high risk of cerebral palsy were associated with periventricular leukomalacia and neurological outcome.

    Science.gov (United States)

    Hamer, Elisa G; Vermeulen, R Jeroen; Dijkstra, Linze J; Hielkema, Tjitske; Kos, Claire; Bos, Arend F; Hadders-Algra, Mijna

    2016-12-01

    Having observed slow pupillary light responses (PLRs) in infants at high risk of cerebral palsy, we retrospectively evaluated whether these were associated with specific brain lesions or unfavourable outcomes. We carried out neurological examinations on 30 infants at very high risk of cerebral palsy five times until the corrected age of 21 months, classifying each PLR assessment as normal or slow. The predominant reaction during development was determined for each infant. Neonatal brain scans were classified based on the type of brain lesion. Developmental outcome was evaluated at 21 months of corrected age with a neurological examination, the Bayley Scales of Infant Development Second Edition and the Infant Motor Profile. Of the 30 infants, 16 developed cerebral palsy. Predominantly slow PLRs were observed in eight infants and were associated with periventricular leukomalacia (p = 0.007), cerebral palsy (p = 0.039), bilateral cerebral palsy (p = 0.001), poorer quality of motor behaviour (p cerebral palsy were associated with periventricular leukomalacia and poorer developmental outcome. Slow PLR might be an expression of white matter damage, resulting in dysfunction of the complex cortico-subcortical circuitries. ©2016 Foundation Acta Paediatrica. Published by John Wiley & Sons Ltd.

  11. "Tangible Lights"

    DEFF Research Database (Denmark)

    Sørensen, Tor; Merritt, Timothy; Andersen, Oskar

    2015-01-01

    While there has been much focus on tangible lighting interfaces embedded in physical objects and smartphones as remote control, there has not been sufficient attention on how the expressivity of bodily movement can be used when designing interactions with light. Therefore, we investigate interact...... knowledge from the tangible world. Tangible Lights has been subject to initial evaluations.......While there has been much focus on tangible lighting interfaces embedded in physical objects and smartphones as remote control, there has not been sufficient attention on how the expressivity of bodily movement can be used when designing interactions with light. Therefore, we investigate...... interaction with lighting technology beyond the smartphone and physical controllers. We examine the usefulness of the in-air gestural interaction style for lighting control. We bring forward "Tangible Lights", which serves as a novel interface for in-air interaction with lighting, drawing on existing...

  12. Light Robotics

    DEFF Research Database (Denmark)

    Glückstad, Jesper; Palima, Darwin

    Light Robotics - Structure-Mediated Nanobiophotonics covers the latest means of sculpting of both light and matter for achieving bioprobing and manipulation at the smallest scales. The synergy between photonics, nanotechnology and biotechnology spans the rapidly growing field of nanobiophotonics...

  13. Twisted light

    CSIR Research Space (South Africa)

    Forbes, A

    2010-12-01

    Full Text Available Research at the Mathematical Optics Group uses "twisted" light to study new quatum-based information security systems. In order to understand the structure of "twisted" light, it is useful to start with an ordinary light beam with zero twist, namely...

  14. Public lighting.

    NARCIS (Netherlands)

    2011-01-01

    Visual perception is very important for road users and in the dark it can be facilitated by public lighting. Public lighting has a mostly positive road safety effect. Installing public lighting on roads that were previously unlit generally results in fewer and less serious crashes. This effect seems

  15. Slow and stored light under conditions of electromagnetically induced transparency and four wave mixing in an atomic vapor

    Science.gov (United States)

    Phillips, Nathaniel Blair

    The recent prospect of efficient, reliable, and secure quantum communication relies on the ability to coherently and reversibly map nonclassical states of light onto long-lived atomic states. A promising technique that accomplishes this employs Electromagnetically Induced Transparency (EIT), in which a strong classical control field modifies the optical properties of a weak signal field in such a way that a previously opaque medium becomes transparent to the signal field. The accompanying steep dispersion in the index of refraction allows for pulses of light to be decelerated, then stored as an atomic excitation, and later retrieved as a photonic mode. This dissertation presents the results of investigations into methods for optimizing the memory efficiency of this process in an ensemble of hot Rb atoms. We have experimentally demonstrated the effectiveness of two protocols for yielding the best memory efficiency possible at a given atomic density. Improving memory efficiency requires operation at higher optical depths, where undesired effects such as four-wave mixing (FWM) become enhanced and can spontaneously produce a new optical mode (Stokes field). We present the results of experimental and theoretical investigations of the FWM-EIT interaction under continuous-wave (cw), slow light, and stored light conditions. In particular, we provide evidence that indicates that while a Stokes field is generated upon retrieval of the signal field, any information originally encoded in a seeded Stokes field is not independently preserved during the storage process. We present a simple model that describes the propagation dynamics and provides an intuitive description of the EIT-FWM process.

  16. Influence of many-particle interactions on slow light phenomena in quantum dots

    DEFF Research Database (Denmark)

    Houmark-Nielsen, Jakob; Jauho, Antti-Pekka; Nielsen, Torben Roland;

    2008-01-01

    We investigate the impact of many-particle interactions on group-velocity slowdown achieved via Electromagnetically Induced Transparency (EIT) in quantum dots. Using a ladder scheme we find in the steady-state an increase in maximum slow-down as compared to the non-interacting case, which can...

  17. Theoretical study of the spurious-free dynamic range of a tunable delay line based on slow light in SOA.

    Science.gov (United States)

    Berger, Perrine; Bourderionnet, Jérôme; Alouini, Mehdi; Bretenaker, Fabien; Dolfi, Daniel

    2009-10-26

    We developed a predictive model describing harmonic generation and intermodulation distortions in semiconductor optical amplifiers (SOAs). This model takes into account the variations of the saturation parameters along the propagation axis inside the SOA, and uses a rigorous expression of the gain oscillations harmonics. We derived the spurious-free dynamic range (SFDR) of a slow light delay line based on coherent population oscillation (CPO) effects, in a frequency range covering radar applications (from 40 kHz up to 30 GHz), and for a large range of injected currents. The influence of the high order distortions in the input microwave spectrum is discussed, and in particular, an interpretation of the SFDR improvement of a Mach-Zehnder modulator by CPOs effects in a SOA is given.

  18. Broadband true time delay for microwave signal processing, using slow light based on stimulated Brillouin scattering in optical fibers.

    Science.gov (United States)

    Chin, Sanghoon; Thévenaz, Luc; Sancho, Juan; Sales, Salvador; Capmany, José; Berger, Perrine; Bourderionnet, Jérôme; Dolfi, Daniel

    2010-10-11

    We experimentally demonstrate a novel technique to process broadband microwave signals, using all-optically tunable true time delay in optical fibers. The configuration to achieve true time delay basically consists of two main stages: photonic RF phase shifter and slow light, based on stimulated Brillouin scattering in fibers. Dispersion properties of fibers are controlled, separately at optical carrier frequency and in the vicinity of microwave signal bandwidth. This way time delay induced within the signal bandwidth can be manipulated to correctly act as true time delay with a proper phase compensation introduced to the optical carrier. We completely analyzed the generated true time delay as a promising solution to feed phased array antenna for radar systems and to develop dynamically reconfigurable microwave photonic filters.

  19. Adaptive Lighting

    DEFF Research Database (Denmark)

    Petersen, Kjell Yngve; Søndergaard, Karin; Kongshaug, Jesper

    2015-01-01

    to be static, and no longer acts as a kind of spatial constancy maintaining stability and order? Moreover, what new potentials open in lighting design? This book is one of four books that is published in connection with the research project entitled LED Lighting; Interdisciplinary LED Lighting Research...... offered by adaptive lighting control are created by the ways that the system components, the network and data flow can be coordinated through software so that the dynamic variations are controlled in ways that meaningfully adapt according to people’s situations and design intentions. This book discusses...... the investigations of lighting scenarios carried out in two test installations: White Cube and White Box. The test installations are discussed as large-scale experiential instruments. In these test installations we examine what could potentially occur when light using LED technology is integrated and distributed...

  20. Adaptive Lighting

    DEFF Research Database (Denmark)

    Petersen, Kjell Yngve; Søndergaard, Karin; Kongshaug, Jesper

    2015-01-01

    Adaptive Lighting Adaptive lighting is based on a partial automation of the possibilities to adjust the colour tone and brightness levels of light in order to adapt to people’s needs and desires. IT support is key to the technical developments that afford adaptive control systems. The possibilities...... offered by adaptive lighting control are created by the ways that the system components, the network and data flow can be coordinated through software so that the dynamic variations are controlled in ways that meaningfully adapt according to people’s situations and design intentions. This book discusses...... differently into an architectural body. We also examine what might occur when light is dynamic and able to change colour, intensity and direction, and when it is adaptive and can be brought into interaction with its surroundings. In short, what happens to an architectural space when artificial lighting ceases...

  1. A versatile and light-weight slow control system for small-scale applications

    CERN Document Server

    Zappa, Philipp; Coderre, Daniel; Kaminsky, Basho; Schumann, Marc; von Sivers, Moritz

    2016-01-01

    We present an open source slow control system for small and medium scale projects. Thanks to its modular and flexible design, where the various instruments are read and controlled by independent plugins, Doberman (Detector OBsERving and Monitoring ApplicatioN) can be quickly adapted for many applications, also making use of existing code or proprietary components. The system uses a SQL database to store the data from the instruments and provides an online application to display and browse through the data. It allows the modification of device settings while the program is running and features a protocol to handle exceptions, including the automated distribution of alarm messages. We present two case studies from astroparticle physics, on which Doberman is successfully deployed: a low-background screening facility installed in a remote underground laboratory and a detector R&D platform using cryogenic liquid xenon.

  2. A versatile and light-weight slow control system for small-scale applications

    Science.gov (United States)

    Zappa, P.; Bütikofer, L.; Coderre, D.; Kaminsky, B.; Schumann, M.; von Sivers, M.

    2016-09-01

    We present an open source slow control system for small and medium scale projects. Thanks to its modular and flexible design, where the various instruments are read and controlled by independent plugins, Doberman (Detector OBsERving and Monitoring ApplicatioN) can be quickly adapted for many applications, also making use of existing code or proprietary components. The system uses a SQL database to store the data from the instruments and provides an online application to display and browse through the data. It allows the modification of device settings while the program is running and features a protocol to handle exceptions, including the automated distribution of alarm messages. We present two case studies from astroparticle physics, on which Doberman is successfully deployed: a low-background screening facility installed in a remote underground laboratory and a detector R&D platform using cryogenic liquid xenon.

  3. A proposal for enhancing four-wave mixing in slow light engineered photonic crystal waveguides and its application to optical regeneration.

    Science.gov (United States)

    Ebnali-Heidari, M; Monat, C; Grillet, C; Moravvej-Farshi, M K

    2009-09-28

    In this paper, we investigate both analytically and numerically four-wave mixing (FWM) in short (80 microm) dispersion engineered slow light photonic crystal waveguides. We demonstrate that both a larger FWM conversion efficiency and an increased FWM bandwidth (approximately 10 nm) can be achieved in these waveguides as compared to dispersive PhC waveguides. This improvement is achieved through the net slow light enhancement of the FWM efficiency (almost 30dB as compared to a fast nanowire of similar length), even in the presence of slow light increased linear and nonlinear losses, and the suitable dispersion profile of these waveguides. We show how such improved FWM operation can be advantageously exploited for designing a compact 2R and 3R regenerator with the appropriate nonlinear power transfer function.

  4. Influence of fast and slow alkali myosin light chain isoforms on the kinetics of stretch-induced force transients of fast-twitch type IIA fibres of rat.

    Science.gov (United States)

    Andruchov, Oleg; Galler, Stefan

    2008-03-01

    This study contributes to understand the physiological role of slow myosin light chain isoforms in fast-twitch type IIA fibres of skeletal muscle. These isoforms are often attached to the myosin necks of rat type IIA fibres, whereby the slow alkali myosin light chain isoform MLC1s is much more frequent and abundant than the slow regulatory myosin light chain isoform MLC2s. In the present study, single-skinned rat type IIA fibres were maximally Ca(2+) activated and subjected to stepwise stretches for causing a perturbation of myosin head pulling cycles. From the time course of the resulting force transients, myosin head kinetics was deduced. Fibres containing MLC1s exhibited slower kinetics independently of the presence or absence of MLC2s. At the maximal MLC1s concentration of about 75%, the slowing was about 40%. The slowing effect of MLC1s is possibly due to differences in the myosin heavy chain binding sites of the fast and slow alkali MLC isoforms, which changes the rigidity of the myosin neck. Compared with the impact of myosin heavy chain isoforms in various fast-twitch fibre types, the influence of MLC1s on myosin head kinetics of type IIA fibres is much smaller. In conclusion, the physiological role of fast and slow MLC isoforms in type IIA fibres is a fine-tuning of the myosin head kinetics.

  5. Deterministic tuning of slow-light in photonic-crystal waveguides through the C and L bands by atomic layer deposition

    CERN Document Server

    Chen, Charlton J; Meric, Inanc; Shepard, Ken L; Wong, Chee Wei; Green, William M J; Vlasov, Yurii A; Assefa, Solomon

    2009-01-01

    We demonstrate digital tuning of the slow-light regime in silicon photonic-crystal waveguides by performing atomic layer deposition of hafnium oxide. The high group-index regime was deterministically controlled (red-shift of 140 +/- 10 pm per atomic layer) without affecting the group-velocity dispersion and third-order dispersion. Additionally, differential tuning of 110 +/- 30 pm per monolayer of the slow-light TE-like and TM-like modes was observed. This passive post-fabrication process has potential applications including the tuning of chip-scale optical interconnects, as well as Raman and parametric amplification.

  6. Baking Light

    DEFF Research Database (Denmark)

    Tamke, Martin

    2005-01-01

    decisions. Display quality, comfortable navigation and realistic illumination are crucial ingredients here. Light is one of the principal elements in architectural design, so design reviews must enable the architect to judge the quality of his design in this respect. Realistic light simulations, e.g. via...... radiosity algorithms, are no longer the domain of high-end graphic workstations. Today’s off-the-shelf hardware and 3D-software provide the architect with high-quality tools to simulate physically correct light distributions. But the quality and impression of light is hard to judge by looking at still...... practical experiences with global-light-simulations. We share results which we think are helpful to others, and we highlight areas where further research is necessary....

  7. Lightness functions

    DEFF Research Database (Denmark)

    Campi, Stefano; Gardner, Richard; Gronchi, Paolo;

    2012-01-01

    Variants of the brightness function of a convex body K in n-dimensional Euclidean are investigated. The Lambertian lightness function L(K; v , w ) gives the total reflected light resulting from illumination by a light source at infinity in the direction w that is visible when looking...... in the direction v . The partial brightness function R( K ; v , w ) gives the area of the projection orthogonal to v of the portion of the surface of K that is both illuminated by a light source from the direction w and visible when looking in the direction v . A class of functions called lightness functions...... is introduced that includes L(K;.) and R(K;.) as special cases. Much of the theory of the brightness function like uniqueness, stability, and the existence and properties of convex bodies of maximal and minimal volume with finitely many function values equal to those of a given convex body, is extended...

  8. Baking Light

    DEFF Research Database (Denmark)

    Tamke, Martin

    2005-01-01

    decisions. Display quality, comfortable navigation and realistic illumination are crucial ingredients here. Light is one of the principal elements in architectural design, so design reviews must enable the architect to judge the quality of his design in this respect. Realistic light simulations, e.g. via...... radiosity algorithms, are no longer the domain of high-end graphic workstations. Today’s off-the-shelf hardware and 3D-software provide the architect with high-quality tools to simulate physically correct light distributions. But the quality and impression of light is hard to judge by looking at still...... practical experiences with global-light-simulations. We share results which we think are helpful to others, and we highlight areas where further research is necessary....

  9. Shaping light

    CSIR Research Space (South Africa)

    Forbes, A

    2010-01-01

    Full Text Available mirrors, a gain medium, and a means to excite the gain medium. Quest 6(3) 2010 11 The excited gain medium has what is called a population inversion (it contains more atoms in an excited state than at a lower energy state). Laser light... of what is known as coherence, a measure of how ?in-step? the emitted photons of light are. Coherent light can be made to interfere with itself, in a way that is similar to the way in which ripples on a pond interact. As a result, it is possible...

  10. Combination Light

    Science.gov (United States)

    1990-01-01

    The Rayovac TANDEM is an advanced technology combination work light and general purpose flashlight that incorporates several NASA technologies. The TANDEM functions as two lights in one. It features a long range spotlight and wide angle floodlight; simple one-hand electrical switching changes the beam from spot to flood. TANDEM developers made particular use of NASA's extensive research in ergonomics in the TANDEM's angled handle, convenient shape and different orientations. The shatterproof, water resistant plastic casing also draws on NASA technology, as does the shape and beam distance of the square diffused flood. TANDEM's heavy duty magnet that permits the light to be affixed to any metal object borrows from NASA research on rare earth magnets that combine strong magnetic capability with low cost. Developers used a NASA-developed ultrasonic welding technique in the light's interior.

  11. Acoustic waves in a Biot-type porous snow model: The fast slow wave in light snow

    CERN Document Server

    Sidler, Rolf

    2015-01-01

    Wave velocities, attenuation and reflection coefficients in snow can not be explained by the widely used elastic or viscoelastic models for wave propagation. Instead, Biot's model of wave propagation in porous materials should be used. However, the application of Biot's model is difficult due to the large property space of the underlying porous material. Here we use the properties of ice and air as well as empirical relationships to define the properties of snow as a function of porosity. This reduction allows to predict phase velocities and attenuation of the shear- and compressional-waves as functions of porosity or density. For light snow the peculiarity was found that the velocity of the compressional wave of the first kind is lower than the compressional wave of the second kind that is commonly referred to as the "slow" wave. The reversal of the velocities comes with an increase of attenuation for the first compressional wave. This is in line with the common observation that sound is strongly absorbed af...

  12. Slow motility in hair cells of the frog amphibian papilla: myosin light chain-mediated shape change.

    Science.gov (United States)

    Farahbakhsh, Nasser A; Narins, Peter M

    2008-07-01

    Using video, fluorescence and confocal microscopy, quantitative analysis and modeling, we investigated intracellular processes mediating the calcium/calmodulin (Ca(2+)/CaM)-dependent slow motility in hair cells dissociated from the rostral region of amphibian papilla, one of the two auditory organs in frogs. The time course of shape changes in these hair cells during the period of pretreatment with several specific inhibitors, as well as their response to the calcium ionophore, ionomycin, were recorded and compared. These cells respond to ionomycin with a tri-phasic shape change: an initial phase of iso-volumetric length decrease; a period of concurrent shortening and swelling; and the final phase of increase in both length and volume. We found that both the myosin light chain kinase inhibitor, ML-7, and antagonists of the multifunctional Ca(2+)/CaM-dependent kinases, KN-62 and KN-93, inhibit the iso-volumetric shortening phase of the response to ionomycin. The type 1 protein phosphatase inhibitors, calyculin A and okadaic acid induce minor shortening on their own, but do not significantly alter phase 1 response. However, they appear to counter effects of the inhibitors of Ca(2+)/CaM-dependent kinases. We hypothesize that an active actomyosin-based process mediates the iso-volumetric shortening in the frog rostral amphibian papillar hair cells.

  13. Dynamic modeling of slow-light in a semiconductor optical amplifier including the effects of forced coherent population oscillations by bias current modulation

    Science.gov (United States)

    Connelly, M. J.

    2014-05-01

    The slow light effect in SOAs has many applications in microwave photonics such as phase shifting and filtering. Models are needed to predict slow light in SOAs and its dependence on the bias current, optical power and modulation index. In this paper we predict the slow light characteristics of a tensile-strained SOA by using a detailed time-domain model. The model includes full band-structure based calculations of the material gain, bimolecular recombination and spontaneous emission, a carrier density rate equation and travelling wave equations for the input signal and amplified spontaneous emission. The slow light effect is caused by coherent population oscillations, whereby beating between the spectral components of an amplitude modulated lightwave causes carrier density oscillations at the beat frequency, leading to changes in the group velocity. The resulting beat signal at the SOA output after photodetection, is phase shifted relative to the SOA input beat signal. The phase shift can be adjusted by controlling the optical power and bias current. However the beat signal gain is low at low frequencies, leading to a poor beat signal output signal-to-noise ratio. If the optical input and SOA drive current are simultaneously modulated, this leads to forced population oscillations that greatly enhance the low frequency beat signal gain. The model is used to determine the improvement in gain and phase response and its dependency on the optical power, bias current and modulation index. Model predictions show good agreement with experimental trends reported in the literature.

  14. Theoretical analysis of multiple quantum-well, slow-light devices under applied external fields using a fully analytical model in fractional dimension

    Energy Technology Data Exchange (ETDEWEB)

    Kohandani, R; Kaatuzian, H [Photonics Research Laboratory, Electrical Engineering Department, AmirKabir University of Technology, Hafez Ave., Tehran (Iran, Islamic Republic of)

    2015-01-31

    We report a theoretical study of optical properties of AlGaAs/GaAs multiple quantum-well (MQW), slow-light devices based on excitonic population oscillations under applied external magnetic and electric fields using an analytical model for complex dielectric constant of Wannier excitons in fractional dimension. The results are shown for quantum wells (QWs) of different width. The significant characteristics of the exciton in QWs such as exciton energy and exciton oscillator strength (EOS) can be varied by application of external magnetic and electric fields. It is found that a higher bandwidth and an appropriate slow-down factor (SDF) can be achieved by changing the QW width during the fabrication process and by applying magnetic and electric fields during device functioning, respectively. It is shown that a SDF of 10{sup 5} is obtained at best. (slowing of light)

  15. Nonlinear phase shifts of modulated light waves with slow and superluminal group delay in stimulated Brillouin scattering.

    Science.gov (United States)

    Arditi, Tal; Granot, Er'el; Sternklar, Shmuel

    2007-09-15

    Brillouin amplification with counterpropagating modulated pump and Stokes light leads to nonlinear modulation-phase shifts of the interacting intensity waves. This is due to a partial transformation of the nonmodulated light component at the input into modulated light at the output as a result of a mixing process with the counterpropagating modulated component of the pump and results in an advance or delay of the input modulation. This occurs for interactions over less than half of a modulation wavelength. Milliwatts of power in a kilometer of standard single-mode fiber give significant tunability of the modulation phase.

  16. Lighting Computer Programs in Lighting Technology

    OpenAIRE

    Ekren, Nazmi; Dursun, Bahtiyar; Ercan AYKUT

    2008-01-01

    It is well known that the computer in lighting technology is a vital component for lighting designers. Lighting computer programs are preferred in preparing architectural projects in lighting techniques, especially in lighting calculations. Lighting computer programs, which arise with the aim of helping lighting designers, gain more interest day by day. The most important property of lighting computer programs is the ability to enable the simulation of lighting projects without requiring any ...

  17. 'Slow'- and 'fast'-light in a single ring-resonator circuit: theory, experimental observations, and sensing applications

    NARCIS (Netherlands)

    Uranus, H.P.; Zhuang, L.; Roeloffzen, C.G.H.; Hoekstra, H.J.W.M.

    2007-01-01

    Transfer matrix method (TMM) was used to study the phenomena of ‘slow’- and ‘fast’-light in a single two-port ring-resonator (TPRR) circuit theoretically. Their classifications into ‘slow’- and ‘fast’-light with negative and positive group velocity (v_g), where ‘slow’ means |v_g|

  18. Lighting and public health.

    NARCIS (Netherlands)

    Ierland, J. van & Schreuder, D.A.

    1969-01-01

    The following topics; are discussed with respect to public health: - the effect of visible and ultraviolet radiation upon man. - vision with respect to lighting. interior lighting. - artificial lighting of work environments. - day light and windows. - recommendations for lighting. public lighting. -

  19. Economic photoprotection in photosystem II that retains a complete light-harvesting system with slow energy traps.

    Science.gov (United States)

    Belgio, Erica; Kapitonova, Ekaterina; Chmeliov, Jevgenij; Duffy, Christopher D P; Ungerer, Petra; Valkunas, Leonas; Ruban, Alexander V

    2014-07-11

    The light-harvesting antenna of higher plant photosystem II has an intrinsic capability for self-defence against intense sunlight. The thermal dissipation of excess energy can be measured as the non-photochemical quenching of chlorophyll fluorescence. It has recently been proposed that the transition between the light-harvesting and self-defensive modes is associated with a reorganization of light-harvesting complexes. Here we show that despite structural changes, the photosystem II cross-section does not decrease. Our study reveals that the efficiency of energy trapping by the non-photochemical quencher(s) is lower than the efficiency of energy capture by the reaction centres. Consequently, the photoprotective mechanism works effectively for closed rather than open centres. This type of defence preserves the exceptional efficiency of electron transport in a broad range of light intensities, simultaneously ensuring high photosynthetic productivity and, under hazardous light conditions, sufficient photoprotection for both the reaction centre and the light-harvesting pigments of the antenna.

  20. Economic photoprotection in photosystem II that retains a complete light-harvesting system with slow energy traps

    Science.gov (United States)

    Belgio, Erica; Kapitonova, Ekaterina; Chmeliov, Jevgenij; Duffy, Christopher D. P.; Ungerer, Petra; Valkunas, Leonas; Ruban, Alexander V.

    2014-07-01

    The light-harvesting antenna of higher plant photosystem II has an intrinsic capability for self-defence against intense sunlight. The thermal dissipation of excess energy can be measured as the non-photochemical quenching of chlorophyll fluorescence. It has recently been proposed that the transition between the light-harvesting and self-defensive modes is associated with a reorganization of light-harvesting complexes. Here we show that despite structural changes, the photosystem II cross-section does not decrease. Our study reveals that the efficiency of energy trapping by the non-photochemical quencher(s) is lower than the efficiency of energy capture by the reaction centres. Consequently, the photoprotective mechanism works effectively for closed rather than open centres. This type of defence preserves the exceptional efficiency of electron transport in a broad range of light intensities, simultaneously ensuring high photosynthetic productivity and, under hazardous light conditions, sufficient photoprotection for both the reaction centre and the light-harvesting pigments of the antenna.

  1. Lighting Design

    DEFF Research Database (Denmark)

    Hansen, Ellen Kathrine; Mullins, Michael

    2014-01-01

    Light as a multi-dimensional design element has fundamental importance for a sustainable environment. The paper discusses the need for an integration of scientific, technical and creative approaches to light and presents theory, methods and applications toward fulfilling this need. A theory...... of design developed from three experiments show how distinct qualitative and quantitative criteria in different disciplinary traditions can be integrated successfully, despite disparate technical/scientific, social scientific and art/humanities backgrounds. The model is applied to a pedagogical curriculum...

  2. Lighting Design

    DEFF Research Database (Denmark)

    Hansen, Ellen Kathrine; Mullins, Michael

    2014-01-01

    of design developed from three experiments show how distinct qualitative and quantitative criteria in different disciplinary traditions can be integrated successfully, despite disparate technical/scientific, social scientific and art/humanities backgrounds. The model is applied to a pedagogical curriculum......Light as a multi-dimensional design element has fundamental importance for a sustainable environment. The paper discusses the need for an integration of scientific, technical and creative approaches to light and presents theory, methods and applications toward fulfilling this need. A theory...

  3. Calculus light

    CERN Document Server

    Friedman, Menahem

    2011-01-01

    Another Calculus book? As long as students find calculus scary, the failure rate in mathematics is higher than in all other subjects, and as long as most people mistakenly believe that only geniuses can learn and understand mathematics, there will always be room for a new book of Calculus. We call it Calculus Light. This book is designed for a one semester course in ""light"" calculus -- mostly single variable, meant to be used by undergraduate students without a wide mathematical background and who do not major in mathematics but study subjects such as engineering, biology or management infor

  4. Green lights

    DEFF Research Database (Denmark)

    Fisker, Peter Kielberg

    This study investigates the effect of drought on economic activity globally using remote sensing data. In particular, predicted variation in greenness is correlated with changes in the density of artificial light observed at night on a grid of 0.25 degree latitude-longitude pixels. I define drought...

  5. Room temperature low-threshold InAs/InP quantum dot single mode photonic crystal microlasers at 1.5 microm using cavity-confined slow light.

    Science.gov (United States)

    Bordas, Frédéric; Seassal, Christian; Dupuy, Emmanuel; Regreny, Philippe; Gendry, Michel; Viktorovitch, Pierre; Steel, M J; Rahmani, Adel

    2009-03-30

    We have designed, fabricated, and characterized an InP photonic crystal slab structure that supports a cavity-confined slow-light mode, i.e. a bandgap-confined valence band-edge mode. Three dimensional finite difference in time domain calculations predict that this type of structure can support electromagnetic modes with large quality factors and small mode volumes. Moreover these modes are robust with respect to fabrication imperfections. In this paper, we demonstrate room-temperature laser operation at 1.5 mum of a cavity-confined slow-light mode under pulsed excitation. The gain medium is a single layer of InAs/InP quantum dots. An effective peak pump power threshold of 80 microW is reported.

  6. Casimir light: field pressure.

    OpenAIRE

    1994-01-01

    The electromagnetic field is assigned a self-consistent role in which abrupt slowing of the collapse produces radiation and the pressure of the radiation produces abrupt slowing. A simple expression is introduced for the photon spectrum. Conditions for light emission are proposed that imply a high degree of spatial localization. Some numerical checks are satisfied. A study of the mechanical equations of motion suggests an explanation of the very short time scale in terms of oppositely directe...

  7. Light Sources and Lighting Circuits

    Science.gov (United States)

    Honda, Hisashi; Suwa, Takumi; Yasuda, Takeo; Ohtani, Yoshihiko; Maehara, Akiyoshi; Okada, Atsunori; Komatsu, Naoki; Mannami, Tomoaki

    According to the Machinery Statistics of the Ministry of Economy, Trade and Industry, the production of incandescent lamps in Japan in 2007 was 990 million units (90.0% of the previous year's total), in which the production of incandescent lamps for general lighting was 110 million units (90.0% of the previous year's total) and of tungsten-halogen lamps was 44 million units (96.6% of the previous year's total). The production of fluorescent lamps was 927 million units (93.9% of the previous year's total), in which general fluorescent lamps, excluding those for LCD back lighting, was 320 million units (87.2% of the previous year's total). Also, the production of HID lamps was 10 million units (101.5% of the previous year's total). On the other hand, when the numbers of sales are compared with the sales of the previous year, incandescent lamps for general use was 99.8%, tungsten-halogen lamps was 96.9%, fluorescent lamps was 95.9%, and HID lamps was 98.9%. Self-ballasted fluorescent lamps alone showed an increase in sales as strong as 29 million units, or 121.7% of the previous year's sales. It is considered that the switchover of incandescent lamps to HID lamps was promoted for energy conservation and carbon dioxide reduction with the problem of global warming in the background. In regard to exhibitions, Lighting Fair 2007 was held in Tokyo in March, and LIGHTFAIR INTERNATIONAL 2007 was held in New York in May. Regarding academic conferences, LS:11 (the 11th International Symposium on the Science & Technology of Light Sources) was held in Shanghai in May, and the First International Conference on White LEDs and Solid State Lighting was held in Tokyo in November. Both conferences suggested that there are strong needs and concerns now about energy conservation, saving natural resources, and restrictions of hazardous materials. In regard to incandescent lamps, the development of products aiming at higher efficacy, electric power savings, and longer life was advanced by

  8. EDITORIAL: Controlling light with light

    Science.gov (United States)

    Hesselink, Lambertus; Feinberg, Jack; Roosen, Gerald

    2008-11-01

    The field of photorefractive physics and optics is mature and, although there is no significant commercial activity using photorefractive media, researchers in the field have had an extraordinary impact on many related areas of research and development. For example, in the late 1990s many of the telecom innovations and products were based on the interaction between light and matter. Examples include optical switches, filters, gratings, routers and light sources. The theory of multiple interacting beams of light inside a photosensitive medium, many of which were developed or further explored in photorefractive media, has found application in medicine, engineering, communication systems, displays and other photonics devices. On the occasions of the 30th anniversary of the theory of coupled wave analysis and the 10th anniversary of the meetings on Photorefractive Effects and Devices, it seemed appropriate to the meeting organizers of PR'07 to broaden the scope to include other related fields. The name of the meeting was changed to Controlling Light with Light: Photorefractive Effects, Photosensitivity, Fiber Gratings, Photonic Materials and More to attract a larger audience than traditionally would attend the more narrowly focused photorefractive meeting. To further disseminate the results of the 2007 meeting, Gerald Roosen proposed a special publication of original full research articles arising from key presentations at the meeting. The selection of papers in this Cluster Issue of Journal of Physics D: Applied Physics is the result of that initiative. We would like to thank all the authors for their contributions, the committee members for their valuable insight and efforts in helping to organize the meeting, and the Optical Society of America for their professional assistance throughout the preparation period of the meeting as well as during the three beautiful days in Lake Tahoe, CA.

  9. Handbook of industrial lighting

    CERN Document Server

    Lyons, Stanley L

    2013-01-01

    Handbook of Industrial Lighting is a practical guide on the specification, design, installation, operation, and maintenance of lighting in industrial premises. Coverage of the book includes the importance of good localized lighting; the different lighting schemes; lighting for difficult visual tasks; lighting in consideration to safety; and emergency lighting. The book also includes the practical, thermal, ventilation, and energy considerations; lighting in different environments; maintenance of lighting installations; and the cost benefits of efficient lighting. Appendices include useful info

  10. Exp erimental study of the effects of two-photon detuning on slow light and light memory%双光子失谐对慢光和光存储影响的实验研究∗

    Institute of Scientific and Technical Information of China (English)

    闫研; 李淑静; 田龙; 王海

    2016-01-01

    Electromagnetically induced transparency (EIT) effect is an effective means to store light field into the atom ensemble. The extra noise introduced in the stored procedure can be suppressed greatly under the condition of large one-photon detuning and proper two-photon detuning. In this paper, we experimentally investigate the slow light and light storage in 87Rb vapor by using EIT effect, and study the effects of the two-photon detuning on light pulse delay and light memory at 650 MHz one-photon red detuning. In order to avoid some unwanted effects under the high optical depth condition, such as four-wave mixing, etc., the temperature of the atomic cell is controlled at 65 degrees Celsius. The experimental results show that the delay and the retrieval signals are significant in a two-photon detuning range from 0 to 0.5 MHz. The pulse delay decreases with the increase of two-photon detuning. The delay is 0.36 µs at two-photon resonance, and it is 0.07 µs at 1 MHz two-photon detuning. We simulate the delayed light pulse by using a three-levelΛ-type EIT model. The shapes of the measured slow light are in agreement with the theoretical results. The retrieval signals are observed at different two-photon detunings. The shapes of the retrieval pulses change with the two-photon detuning. The shape variations of the retrieval pulses cannot be explained by the three-level EIT theoretical model. By considering the atomic Zeeman sublevels interacting with the left-circular and right-circular polarized components of probe and coupling fields, multiple Λ-type EIT systems will be formed. The interference between the retrieval signals from multiple EIT subsystems causes the shape distortions of retrieval pulses. The retrieval efficiency is measured as a function of two-photon detuning. The retrieval efficiency oscillates, and multiple peaks appear with the increase of two-photon detuning. The first peak appears at two-photon resonance, and the second peak appears at 0.48 MHz

  11. Light fantastic

    Science.gov (United States)

    2010-05-01

    The laser has become so ubiquitous that it would be impossible to acknowledge everyone who has played a role in its success. As Roy Glauber said at the 2005 Nobel-prize banquet, when it comes to lasers, "many hands make light work". And he should know: the prize Glauber shared with fellow optics pioneers John Hall and Theodore Hänsch is one of more than 10 Nobels awarded (so far!) for laser-related research. This timeline marking 50 years of the laser contains Physics World's pick of events from laser history, including prizes (gold text), applications (green) and "firsts" (blue).

  12. Green lights

    DEFF Research Database (Denmark)

    Fisker, Peter Kielberg

    as greenness estimated by lagged variation in monthly rainfall and temperature. This definition of drought performs well in identifying self-reported drought events since 2000 compared with measures of drought that do not take greenness into account, and the subsequent analysis indicates that predicted...... variation in greenness is positively associated with year-on-year changes in luminosity: If a unit of observation experiences a predicted variation in greenness that lies 1 standard deviation below the global mean, on average 1.5 - 2.5 light pixels out of 900 are extinguished that year. Finally, an attempt...... is made to estimate the global cost of drought....

  13. Slow light enhanced near infrared luminescence in CeO{sub 2}: Er{sup 3+}, Yb{sup 3+} inverse opal photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Zhengwen, E-mail: yangzw@kmust.edu.cn; Wu, Hangjun; Li, Jun; Shao, Bo; Qiu, Jianbei; Song, Zhiguo

    2015-08-25

    Highlights: • CeO{sub 2}: Er{sup 3+}, Yb{sup 3+} photonic crystals was prepared. • Near infrared emission in the CeO{sub 2}: Er{sup 3+}, Yb{sup 3+} inverse opal was obtained. • Near infrared emission was enhanced by slow light effect of photonic crystals. - Abstract: The surface plasmon resonances of metal nanoparticles and energy transfer between rare earth ions were used widely to enhance the near infrared emission of rare earth ions. In this paper, a new method for near infrared emission enhancement of rare-earth is reported. The CeO{sub 2}: Er{sup 3+}, Yb{sup 3+} inverse opals with the photonic band gaps at the 500 and 450 nm were prepared by using polystyrene colloidal crystal as templates, and their near infrared emission properties were investigated. The results show that the near infrared emission property of the CeO{sub 2}: Er{sup 3+}, Yb{sup 3+} inverse opals depends on the overlapped extend between the excited light and photonic band gap. The near infrared emission located at the 1540 nm of the CeO{sub 2}: Er{sup 3+}, Yb{sup 3+} inverse opals have been enhanced obviously when the wavelength of the excitation light overlapped with photonic band gaps edge, which is attributed to the slow light effect of photonic crystals. The enhancement of near infrared emission may be important for the development of infrared laser and amplifiers for optical communication.

  14. Comparative analysis of four-wave mixing of optical pulses in slow- and fast-light regimes of a silicon photonic crystal waveguide.

    Science.gov (United States)

    Lavdas, Spyros; Panoiu, Nicolae C

    2015-09-15

    We present an in-depth study of four-wave mixing (FWM) of optical pulses in silicon photonic crystal waveguides. Our analysis is based on a rigorous model that includes all relevant linear and nonlinear optical effects and their dependence on the group velocity, as well as the influence of free carriers on pulse dynamics. In particular, we reveal key differences between FWM in the slow- and fast-light regimes and how they are related to the physical parameters of the pulses and waveguide. Finally, we illustrate how these results can be used to design waveguides with optimized FWM conversion efficiency.

  15. Enhancement of the low-frequency response of a reflective semiconductor optical amplifier slow light-based microwave phase shifter by forced coherent population oscillations

    Science.gov (United States)

    Meehan, Aidan; Connelly, Michael J.

    2014-05-01

    The enhancement of the low frequency gain response of a microwave phase shifter based on slow light in a bulk reflective semiconductor optical amplifier (RSOA), by using forced coherent population oscillations (FCPO), is experimentally demonstrated. FCPO is achieved by simultaneously modulating the input optical power and bias current. The beat signal gain improvement ranges from 45 to 0 dB over a frequency range of 0.5 to 2.5 GHz, thereby improving the noise performance of the phase shifter. Tunable phase shifts of up to 40º are possible over this frequency range.

  16. Novel InN/InGaN multiple quantum well structures for slow-light generation at telecommunication wavelengths

    Energy Technology Data Exchange (ETDEWEB)

    Naranjo, F.B.; Valdueza-Felip, S.; Gonzalez-Herraez, M. [Grupo de Ingenieria Fotonica, Departamento de Electronica, Escuela Politecnica Superior, Universidad de Alcala Campus Universitario, 28871 Alcala de Henares, Madrid (Spain); Kandaswamy, P.K.; Lahourcade, L.; Calvo, V.; Monroy, E. [CEA-Grenoble, INAC/SP2M, 17 rue des Martyrs, 38054 Grenoble cedex 9 (France); Martin-Lopez, S.; Corredera, P. [Departamento de Metrologia, Instituto de Fisica Aplicada (CSIC), 28006 Madrid (Spain)

    2010-01-15

    The third order susceptibility is responsible for a variety of optical non-linear phenomena - like self focusing, phase conjugation and four-wave mixing - with applications in coherent control of optical communication. InN is particularly attractive due to its near-IR bandgap and predicted high nonlinear effects. Moreover, the synthesis of InN nanostructures makes possible to taylor the absorption edge in the telecomunication spectral range and enhance nonlinear parameters thanks to carrier confinement. In this work, we assess the nonlinear optical behavior of InN/In{sub x}Ga{sub (1-x)}N (0.9 > x > 0.7) multiple-quantum-well (MQW) structures grown by plasma-assisted MBE on GaN-on-sapphire templates. Low-temperature (5 K) photoluminescence measurements show near-IR emission whose intensity increases with the In content in the barriers, which is explained in terms of the existence of piezoelectric fields in the structures. The nonlinear optical absorption coefficient, {alpha}{sub 2}, were measured at 1.55 {mu}m using the Z-scan method. We observe a strong dependence of the nonlinear absorption coefficient on the In content in the barriers. Saturable absorption is observed for the sample with x = 0.9, with {alpha}{sub 2} {proportional_to} -9 x 10{sub 3} cm/GW. For this sample, an optically controlled reduction of the speed of light by a factor S {proportional_to} 80 is obtained at 1.55 {mu}m (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Residential lighting design

    CERN Document Server

    Steffen, Marcus

    2014-01-01

    Good lighting is essential to a building. An effective design is not just about introducing light into a space, but rather an appreciation of how the space will be used. A good lighting design is so intertwined with the building that it is only noticed in its absence. This book introduces the tools of the lighting designer and explains how to produce a lighting design for a home. Looking at the nature of light and introducing different lamps and light fittings available, it explains the basics of lighting design and how to provide atmosphere through the play of light and shadow. It gives room-

  18. Light up My Life

    Science.gov (United States)

    Kellett, Sarah

    2015-01-01

    Simply stated, light is nature's way of transferring energy through space. Discussions of light usually refer to visible light, which is perceived by the human eye and is responsible for the sense of sight. We see however, only a small part of the light spectrum. Light connects us as we sit and tell yarns around camp fires. Yet, one in every four…

  19. Mobile lighting apparatus

    Science.gov (United States)

    Roe, George Michael; Klebanoff, Leonard Elliott; Rea, Gerald W; Drake, Robert A; Johnson, Terry A; Wingert, Steven John; Damberger, Thomas A; Skradski, Thomas J; Radley, Christopher James; Oros, James M; Schuttinger, Paul G; Grupp, David J; Prey, Stephen Carl

    2013-05-14

    A mobile lighting apparatus includes a portable frame such as a moveable trailer or skid having a light tower thereon. The light tower is moveable from a stowed position to a deployed position. A hydrogen-powered fuel cell is located on the portable frame to provide electrical power to an array of the energy efficient lights located on the light tower.

  20. Next Generation Light Robotics

    DEFF Research Database (Denmark)

    Glückstad, Jesper

    potential of this new ‘drone-like’ light-printed, light-driven, light-actuated micro- and nano-robotics in challenging geometries requires a versatile and real-time reconfigurable light addressing that can dynamically track a plurality of tiny tools in 3D to ensure real-time continuous light...

  1. Light up My Life

    Science.gov (United States)

    Kellett, Sarah

    2015-01-01

    Simply stated, light is nature's way of transferring energy through space. Discussions of light usually refer to visible light, which is perceived by the human eye and is responsible for the sense of sight. We see however, only a small part of the light spectrum. Light connects us as we sit and tell yarns around camp fires. Yet, one in every four…

  2. Label-free antibody detection using band edge fringes in SOI planar photonic crystal waveguides in the slow-light regime.

    Science.gov (United States)

    García-Rupérez, Jaime; Toccafondo, Veronica; Bañuls, María José; Castelló, Javier García; Griol, Amadeu; Peransi-Llopis, Sergio; Maquieira, Ángel

    2010-11-08

    We report experimental results of label-free anti-bovine serum albumin (anti-BSA) antibody detection using a SOI planar photonic crystal waveguide previously bio-functionalized with complementary BSA antigen probes. Sharp fringes appearing in the slow-light regime near the edge of the guided band are used to perform the sensing. We have modeled the presence of these band edge fringes and demonstrated the possibility of using them for sensing purposes by performing refractive index variations detection, achieving a sensitivity of 174.8 nm/RIU. Then, label-free anti-BSA biosensing experiments have been carried out, estimating a surface mass density detection limit below 2.1 pg/mm2 and a total mass detection limit below 0.2 fg.

  3. Energy Efficient Task Light

    DEFF Research Database (Denmark)

    Logadottir, Asta; Ardkapan, Siamak Rahimi; Johnsen, Kjeld

    2014-01-01

    The objectives of this work is to develop a task light for office lighting that fulfils the minimum requirements of the European standard EN12464 - 1 : Light and lightingLighting of work places, Part 1: Indoor workplaces and the Danish standard DS 700 : Lys og belysning I arbejdsrum , or more...... specifically the requirements that apply to the work area and the immediate surrounding area. By providing a task light that fulfils the requirements for task lighting and the immediate surrounding area, the general lighting only needs to provide the illuminance levels required for background lighting...... and thereby a reduction in installed power for general lighting of about 40 % compared to the way illuminance levels are designed in an office environment in Denmark today. This lighting strategy is useful when the placement of the task area is not defined in the space before the lighting is design ed...

  4. Ultra-compact optical auto-correlator based on slow-light enhanced third harmonic generation in a silicon photonic crystal waveguide

    CERN Document Server

    Monat, Christelle; Collins, Matthew; Clark, Alex; Schroeder, Jochen; Xiong, Chunle; Li, Juntao; O'Faolain, Liam; Krauss, Thomas F; Eggleton, Benjamin J; Moss, David J

    2014-01-01

    The ability to use coherent light for material science and applications is directly linked to our ability to measure short optical pulses. While free-space optical methods are well-established, achieving this on a chip would offer the greatest benefit in footprint, performance, flexibility and cost, and allow the integration with complementary signal processing devices. A key goal is to achieve operation at sub-Watt peak power levels and on sub-picosecond timescales. Previous integrated demonstrations require either a temporally synchronized reference pulse, an off-chip spectrometer, or long tunable delay lines. We report the first device capable of achieving single-shot time-domain measurements of near-infrared picosecond pulses based on an ultra-compact integrated CMOS compatible device, with the potential to be fully integrated without any external instrumentation. It relies on optical third-harmonic generation in a slow-light silicon waveguide. Our method can also serve as a powerful in-situ diagnostic to...

  5. PBN (Phenyl-N-Tert-Butylnitrone-Derivatives Are Effective in Slowing the Visual Cycle and Rhodopsin Regeneration and in Protecting the Retina from Light-Induced Damage.

    Directory of Open Access Journals (Sweden)

    Megan Stiles

    Full Text Available A2E and related toxic molecules are part of lipofuscin found in the retinal pigment epithelial (RPE cells in eyes affected by Stargardt's disease, age-related macular degeneration (AMD, and other retinal degenerations. A novel therapeutic approach for treating such degenerations involves slowing down the visual cycle, which could reduce the amount of A2E in the RPE. This can be accomplished by inhibiting RPE65, which produces 11-cis-retinol from all-trans-retinyl esters. We recently showed that phenyl-N-tert-butylnitrone (PBN inhibits RPE65 enzyme activity in RPE cells. In this study we show that like PBN, certain PBN-derivatives (PBNDs such as 4-F-PBN, 4-CF3-PBN, 3,4-di-F-PBN, and 4-CH3-PBN can inhibit RPE65 and synthesis of 11-cis-retinol in in vitro assays using bovine RPE microsomes. We further demonstrate that systemic (intraperitoneal, IP administration of these PBNDs protect the rat retina from light damage. Electroretinography (ERG and histological analysis showed that rats treated with PBNDs retained ~90% of their photoreceptor cells compared to a complete loss of function and 90% loss of photoreceptors in the central retina in rats treated with vehicle/control injections. Topically applied PBN and PBNDs also significantly slowed the rate of the visual cycle in mouse and baboon eyes. One hour dark adaptation resulted in 75-80% recovery of bleachable rhodopsin in control/vehicle treated mice. Eye drops of 5% 4-CH3-PBN were most effective, inhibiting the regeneration of bleachable rhodopsin significantly (60% compared to vehicle control. In addition, a 10% concentration of PBN and 5% concentration of 4-CH3-PBN in baboon eyes inhibited the visual cycle by 60% and by 30%, respectively. We have identified a group of PBN related nitrones that can reach the target tissue (RPE by systemic and topical application and slow the rate of rhodopsin regeneration and therefore the visual cycle in mouse and baboon eyes. PBNDs can also protect the rat

  6. Light as experiential material

    DEFF Research Database (Denmark)

    Petersen, Kjell Yngve; Søndergaard, Karin

    2013-01-01

    'Light as experiential material' is concerned with the development of a psychophysical method of investigation, by which the experience and design of architectural lighting can be approached in research and education......'Light as experiential material' is concerned with the development of a psychophysical method of investigation, by which the experience and design of architectural lighting can be approached in research and education...

  7. Light as experiential material

    DEFF Research Database (Denmark)

    Søndergaard, Karin; Petersen, Kjell Yngve

    2013-01-01

    'Light as experiential material' is concerned with the development of a psychophysical method of investigation, by which we can approach the experience and design of architectural lighting in research and education.......'Light as experiential material' is concerned with the development of a psychophysical method of investigation, by which we can approach the experience and design of architectural lighting in research and education....

  8. Light as experiential material

    DEFF Research Database (Denmark)

    Søndergaard, Karin; Petersen, Kjell Yngve

    2013-01-01

    'Light as experiential material' is concerned with the development of a psychophysical method of investigation, by which we can approach the experience and design of architectural lighting in research and education.......'Light as experiential material' is concerned with the development of a psychophysical method of investigation, by which we can approach the experience and design of architectural lighting in research and education....

  9. Pedestrian Friendly Outdoor Lighting

    Energy Technology Data Exchange (ETDEWEB)

    Miller, N. J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Koltai, R. N. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); McGowan, T. K. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2013-12-01

    The GATEWAY program followed two pedestrian-scale lighting projects that required multiple mockups – one at Stanford University in California and the other at Chautauqua Institution in upstate New York. The report provides insight into pedestrian lighting criteria, how they differ from street and area lighting criteria, and how solid-state lighting can be better applied in pedestrian applications.

  10. Light Rhythms in Architecture

    DEFF Research Database (Denmark)

    Bülow, Katja

    2013-01-01

    On one hand, urban lighting expresses itself in a complex visual environment made by the interplay by between many separate lighting schemes, as street lighting, shop lighting, luminous commercials etc. On the other, a noticeable order of patterns occurs, when lighting is observed as luminous...... formation and rhythm. When integrated into an architectural concept, electrical lighting non-intended for poetic composition has the ability to contribute to place, time, and function-telling aspects of places in urban contexts. Urban environments are information wise challenging to pre-historic human...... instincts, but they can be met by careful selection and adjustment of existing light situations....

  11. Light Rhythms in Architecture

    DEFF Research Database (Denmark)

    Bülow, Katja

    2013-01-01

    On one hand, urban lighting expresses itself in a complex visual environment made by the interplay by between many separate lighting schemes, as street lighting, shop lighting, luminous commercials etc. On the other, a noticeable order of patterns occurs, when lighting is observed as luminous...... formation and rhythm. When integrated into an architectural concept, electrical lighting non-intended for poetic composition has the ability to contribute to place, time, and function-telling aspects of places in urban contexts. Urban environments are information wise challenging to pre-historic human...... instincts, but they can be met by careful selection and adjustment of existing light situations....

  12. Outdoor lighting guide

    CERN Document Server

    2013-01-01

    As concern grows over environmental issues and light pollution, this book satisfies a need for a straightforward and accessible guide to the use, design and installation of outdoor lighting.This all-inclusive guide to exterior lighting from the Institution of Lighting Engineers, recognized as the pre-eminent professional source in the UK for authoritative guidance on exterior lighting, provides a comprehensive source of information and advice on all forms of exterior lighting, from floodlighting, buildings and road lighting to elaborate Christmas decorations. Useful to practitioners

  13. Light and colours

    DEFF Research Database (Denmark)

    Volf, Carlo

    2011-01-01

    Often a dichotomy between daylight and artificial light is observed, often artificial lighting replaces daylight. In Denmark daylight is characterized partly by being "borrowed" half of the year, partly by having long transitions periods between the light and the dark (nautical and civil twilight......). For these reasons artificial lighting does not complement daylight but provides, coupled with the daylight, the total lighting in the indoor environment. Electric lighting is therefore ‐ in a complex interaction with the daylight ‐ of great importance for both our lighting and our wellbeing. Studying artificial...... lighting without studying daylight seem to be a common procedure of the practice of today in Denmark and other parts of the industrialized world. As a consequence of this artificial lighting suffers from a quantifying tyranny, a tyranny where the quality of light is measured in quantities. This procedure...

  14. Light and colours

    DEFF Research Database (Denmark)

    Volf, Carlo

    2011-01-01

    Often a dichotomy between daylight and artificial light is observed, often artificial lighting replaces daylight. In Denmark daylight is characterized partly by being "borrowed" half of the year, partly by having long transitions periods between the light and the dark (nautical and civil twilight......). For these reasons artificial lighting does not complement daylight but provides, coupled with the daylight, the total lighting in the indoor environment. Electric lighting is therefore ‐ in a complex interaction with the daylight ‐ of great importance for both our lighting and our wellbeing. Studying artificial...... lighting without studying daylight seem to be a common procedure of the practice of today in Denmark and other parts of the industrialized world. As a consequence of this artificial lighting suffers from a quantifying tyranny, a tyranny where the quality of light is measured in quantities. This procedure...

  15. Analysis of the effects of applying external fields and device dimensions alterations on GaAs/AlGaAs multiple quantum well slow light devices based on excitonic population oscillation.

    Science.gov (United States)

    Kohandani, Reza; Zandi, Ashkan; Kaatuzian, Hassan

    2014-02-20

    This paper demonstrates the effects of applying magnetic and electric fields and physical dimensions alterations on AlGaAs/GaAs multiple quantum well (QW) slow light devices. Physical parameters include quantum well sizes and number of quantum wells. To the best of our knowledge, this is the first analysis of the effects of both applying magnetic/electric fields and physical parameters alterations and the first suggestion for matching the prefabrication and post fabrication tuning of the slow light devices based on excitonic population oscillations. The aim of our theoretical analysis is controlling the optical properties such as central frequency, bandwidth, and slow down factor (SDF) in slow light devices based on excitonic population oscillation to achieve better tuning. To reach these purposes, first we investigate the quantum well size and number of quantum wells alteration effects. Next, we analyze the effects of applying magnetic and electric fields to the multiple quantum well structure, separately. Finally, physical parameters and applied external fields are changed for measuring frequency shift and SDF for coherent population oscillation slow light devices. The results show the available central frequency shifts in about 1.6 THz at best. Also the SDF value improvement is about one order of magnitude. These results will be applicable for optical nonlinearity enhancements, all-optical signal processing, optical communications, all-optical switches, optical modulators, and variable true delays.

  16. Occlusion, transparency, and lightness

    OpenAIRE

    2007-01-01

    The lightness of a visual surface is its perceived achromatic reflectance [Adelson, E. H., (2000). Lightness perception and lightness illusions. In M. Gazzaniga (Ed.), The new cognitive neuroscience (2nd ed.) (pp. 339-351) Berlin: Springer; Gilchrist, A. (1999). Lightness perception. In R. W. F. Keil (Ed.), MIT encyclopedia of cognitive science (pp. 471-472). Cambridge: MIT press]. Lightness ranges from black, through various shades of grey, up to white. Anderson and Winawer [Anderson, B., Wi...

  17. The Properties of Light

    Science.gov (United States)

    Haglund, Richard F.

    The mystery of light has formed the core of creation stories in every culture, and attracted the earnest attentions of philosophers since at least the fifth century BCE. Their questions have ranged from how and what we see, to the interaction of light with material bodies, and finally to the nature of light itself. This chapter begins with a brief intellectual history of light from ancient Greece to the end of the 19th century. After introducing the physical parameterization of light in terms of standard units, three concepts of light are introduced: light as a wave, light as a quantum particle, and light as a quantum field. After highlighting the distinctive characteristics of light beams from various sources - thermal radiation, luminescence from atoms and molecules, and synchrotron light sources - the distinctive physical characteristics of light beams are examined in some detail. The chapter concludes with a survey of the statistical and quantum-mechanical properties of light beams. In the appropriate limits, this treatment not only recovers the classical description of light waves and the semiclassical view of light as a stream of quanta, but also forms a consistent description of quantum phenomena - such as interference phenomena generated by single photons - that have no classical analogs.

  18. Lamps and lighting

    CERN Document Server

    Cayless, MA; Marsden, A M

    2012-01-01

    This book is a comprehensive guide to the theory and practice of lighting. Covering the physics of light production, light sources, circuits and a wide variety of lighting applications, it is both suitable as a detailed textbook and as thoroughly practical guide for practising lighting engineers. This fourth edition of Lamps and Lighting has been completely updated with new chapters on the latest lamp technology and applications. The editors ahve called upon a wide range of expertise and as a result many sections have been broadened to include both European and US practice.The book begins with

  19. The design of lighting

    CERN Document Server

    Tregenza, Peter

    2013-01-01

    This fully updated edition of the successful book The Design of Lighting, provides the lighting knowledge needed by the architect in practice, the interior designer and students of both disciplines. The new edition offers a clear structure, carefully selected material and linking of lighting with other subjects, in order to provide the reader with a comprehensive and specifically architectural approach to lighting. Features of this new edition include:technical knowledge of lighting in the context of architectural design;an emphasis on imagination in architectural light and presentation of the

  20. Slow Light in Metamaterial Waveguides

    CERN Document Server

    Lavoie, Benjamin R

    2013-01-01

    Metamaterials, which are materials engineered to possess novel optical properties, have been increasingly studied. The ability to fabricate metamaterials has sparked an interest in determining possible applications. We investigate using a metamaterial for boundary engineering in waveguides. A metamaterial-clad cylindrical waveguide is used to provide confinement for an optical signal, thereby increasing the local electromagnetic energy density. We show that metamaterial-clad waveguides have unique optical properties, including new modes, which we call hybrid modes. These modes have properties of both ordinary guided modes and surface plasmon-polariton modes. We show that for certain metamaterial parameters, the surface plasmon-polariton modes of a metamaterial-clad waveguide have less propagation loss than those of a metal-clad guide with the same permittivity. This low-loss mode is exploited for all-optical control of weak fields. Embedding three-level {\\Lambda} atoms in the dielectric core of a metamaterial...

  1. GPC Light Shaper

    DEFF Research Database (Denmark)

    Bañas, Andrew Rafael; Raaby, Peter; Glückstad, Jesper

    Generalized Phase Contrast is a disruptive light sculpting technology for studying brain functionalities via light-activated neuron control. GPC dynamically reshapes conventional or multiwavelength lasers for precise and efficient neuron targeting. GPC also makes existing laser systems much more...

  2. Spectrally tunable lighting facility

    Data.gov (United States)

    Federal Laboratory Consortium — Solid-state lighting (SSL) is increasingly being introduced into the market and it is expected that many of the light sources currently used for general illumination...

  3. Light Imaging Section

    Data.gov (United States)

    Federal Laboratory Consortium — The mission of the Light Imaging Section is to give NIAMS scientists access to state-of-the-art light imaging equipment and to offer training and assistance at all...

  4. Interference and Polarized Light.

    Science.gov (United States)

    Charas, Seymour

    1988-01-01

    Discusses a demonstration of interference phenomena using three sheets of polaroid material, a light source, and a light meter. Describes instructional procedures with mathematical expressions and a diagram. (YP)

  5. Advanced Light Source (ALS)

    Data.gov (United States)

    Federal Laboratory Consortium — The Advanced Light Source (ALS), a world leader in soft x-ray science, generates light in the wavelengths needed for examining the atomic and electronic structure of...

  6. Lighting detectives forum

    DEFF Research Database (Denmark)

    Bülow, Katja; Skindbjerg Kristensen, Lisbeth

    2003-01-01

    Belysning for boligområder var emnet for lighting detectives forum, der blev afholdt i Stockholm i august 2003.......Belysning for boligområder var emnet for lighting detectives forum, der blev afholdt i Stockholm i august 2003....

  7. The landscape lighting book

    CERN Document Server

    Moyer, Janet Lennox

    2013-01-01

    This richly illustrated, up-to-date guide offers practical coverage of all aspects of lighting design. Written by an award-winning, internationally known lighting designer, it covers lighting practices, materials, and their design applications and offers guidelines for preparing lighting drawings, control and transfer charts, symbol lists, and other technical specifications. This edition provides a new focus on the use of LEDs, as well as new and expanded coverage of renderings, Mesopic Vision, and the latest controls approaches and systems.

  8. OLED displays and lighting

    CERN Document Server

    Koden, Mitsuhiro

    2017-01-01

    Organic light-emitting diodes (OLEDs) have emerged as the leading technology for the new display and lighting market. OLEDs are solid-state devices composed of thin films of organic molecules that create light with the application of electricity. OLEDs can provide brighter, crisper displays on electronic devices and use less power than conventional light-emitting diodes (LEDs) or liquid crystal displays (LCDs) used today. This book covers both the fundamentals and practical applications of flat and flexible OLEDs.

  9. Geolocation by light

    DEFF Research Database (Denmark)

    Lisovski, Simeon; Hewson, Chris M.; Klaassen, Raymond H. G.

    2012-01-01

    1. Geolocation by light allows for tracking animal movements, based on measurements of light intensity over time by a data-logging device (‘geolocator’). Recent developments of ultra-light devices (<2 g) broadened the range of target species and boosted the number of studies using geolocators. Ho...

  10. LEDs for greenhouse lighting

    NARCIS (Netherlands)

    Nederhoff, E.M.

    2010-01-01

    Light Emitting Diodes (LED's) are a promising technology for greenhouse lighting with their efficiency to activate plant photosynthesis potentially higher in red LEDs than in HPS lamps. Due to their particular light colour, LEDs can initiate special effects in plants or steer plant processes and

  11. Simulating Supernova Light Curves

    Energy Technology Data Exchange (ETDEWEB)

    Even, Wesley Paul [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dolence, Joshua C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-05-05

    This report discusses supernova light simulations. A brief review of supernovae, basics of supernova light curves, simulation tools used at LANL, and supernova results are included. Further, it happens that many of the same methods used to generate simulated supernova light curves can also be used to model the emission from fireballs generated by explosions in the earth’s atmosphere.

  12. Light in man's environment.

    Science.gov (United States)

    Marshall, J

    2016-02-01

    Light in the form of solar radiation influenced early civilisations and resulted in the independent development of a number of sun-worshipping dieties. These were of particular importance as hunter gatherers transformed into settled agricultural societies. All artificial light sources were synonymous with fire, and early civilisations began to expand their visual day by burning brands, oil, and candles. Fire-based light sources extended for thousands of years and were still present in the era of gas lighting. Light meant fire risk. The advent of incandescent bulbs and the era of electric lighting really only expanded in the early part of the twentieth century. Fluorescent lighting became available in the 1940s, and today the drive for low energy has resulted in a plethora of novel light sources-in particular, light-emitting diodes (LEDs). Evolution governed the development of the eye in relation to roughly 12 h of light gradually changing to 12 h of darkness. Today almost daylight levels can be achieved abruptly at the flick of a switch. Many studies have demonstrated the spectral dependence of eye health, with the retinal hazard zone associated with wavelengths in the blue, peaking at 441 nm- many of today's low-energy sources peak in this region. Given the increased longevity and artificial light sources emitting at biologically unfriendly wavelengths, attention has to be directed towards light in man's environment as a risk factor in age-related ocular diseases.

  13. Plants under continuous light

    NARCIS (Netherlands)

    Velez Ramirez, A.I.; Ieperen, van W.; Vreugdenhill, D.; Millenaar, F.F.

    2011-01-01

    Continuous light is an essential tool for understanding the plant circadian clock. Additionally, continuous light might increase greenhouse food production. However, using continuous light in research and practice has its challenges. For instance, most of the circadian clock-oriented experiments wer

  14. Seeing the Light

    Science.gov (United States)

    Sportel, Samuel; Bruxvoort, Crystal; Jadrich, James

    2009-01-01

    Conceptually, students are typically introduced to light as a type of wave. However, children struggle to understand this model because it is highly abstract. Light can be represented more concretely using the photon model. According to this scientific model, light emanates from sources as tiny "packets" of energy (called "photons") that move in…

  15. Seeing the Light

    Science.gov (United States)

    Sportel, Samuel; Bruxvoort, Crystal; Jadrich, James

    2009-01-01

    Conceptually, students are typically introduced to light as a type of wave. However, children struggle to understand this model because it is highly abstract. Light can be represented more concretely using the photon model. According to this scientific model, light emanates from sources as tiny "packets" of energy (called "photons") that move in…

  16. Light On the Behavior of Light Bulbs.

    Science.gov (United States)

    Armstrong, H. L.

    1985-01-01

    Discusses a problem (on page 523 of "College Physics," by Sears, Zemansky, and Young, published by Addison-Wesley, 1980) concerning light bulbs and resistance. Shows why the assumption of constant resistance is unrealistic and provides guidelines for revision. (DH)

  17. Light On the Behavior of Light Bulbs.

    Science.gov (United States)

    Armstrong, H. L.

    1985-01-01

    Discusses a problem (on page 523 of "College Physics," by Sears, Zemansky, and Young, published by Addison-Wesley, 1980) concerning light bulbs and resistance. Shows why the assumption of constant resistance is unrealistic and provides guidelines for revision. (DH)

  18. Roadmap on structured light

    Science.gov (United States)

    Rubinsztein-Dunlop, Halina; Forbes, Andrew; Berry, M. V.; Dennis, M. R.; Andrews, David L.; Mansuripur, Masud; Denz, Cornelia; Alpmann, Christina; Banzer, Peter; Bauer, Thomas; Karimi, Ebrahim; Marrucci, Lorenzo; Padgett, Miles; Ritsch-Marte, Monika; Litchinitser, Natalia M.; Bigelow, Nicholas P.; Rosales-Guzmán, C.; Belmonte, A.; Torres, J. P.; Neely, Tyler W.; Baker, Mark; Gordon, Reuven; Stilgoe, Alexander B.; Romero, Jacquiline; White, Andrew G.; Fickler, Robert; Willner, Alan E.; Xie, Guodong; McMorran, Benjamin; Weiner, Andrew M.

    2017-01-01

    Structured light refers to the generation and application of custom light fields. As the tools and technology to create and detect structured light have evolved, steadily the applications have begun to emerge. This roadmap touches on the key fields within structured light from the perspective of experts in those areas, providing insight into the current state and the challenges their respective fields face. Collectively the roadmap outlines the venerable nature of structured light research and the exciting prospects for the future that are yet to be realized.

  19. Traffic Light Options

    DEFF Research Database (Denmark)

    Jørgensen, Peter Løchte

    2006, and supervisory authorities in many other European countries have implemented similar regulation. Traffic light options are therefore likely to attract the attention of a wider audience of pension fund managers in the future. Focusing on the valuation of the traffic light option we set up a Black......This paper introduces, prices, and analyzes traffic light options. The traffic light option is an innovative structured OTC derivative developed independently by several London-based investment banks to suit the needs of Danish life and pension (L&P) companies, which must comply with the traffic...... light scenarios. These stress scenarios entail drops in interest rates as well as in stock prices, and traffic light options are thus designed to pay off and preserve sufficient capital when interest rates and stock prices fall simultaneously. Sweden's FSA implemented a traffic light system in January...

  20. Traffic Light Options

    DEFF Research Database (Denmark)

    Jørgensen, Peter Løchte

    2007-01-01

    2006, and supervisory authorities in many other European countries have implemented similar regulation. Traffic light options are therefore likely to attract the attention of a wider audience of pension fund managers in the future. Focusing on the valuation of the traffic light option we set up a Black......This paper introduces, prices, and analyzes traffic light options. The traffic light option is an innovative structured OTC derivative developed independently by several London-based investment banks to suit the needs of Danish life and pension (L&P) companies, which must comply with the traffic...... light scenarios. These stress scenarios entail drops in interest rates as well as in stock prices, and traffic light options are thus designed to pay off and preserve sufficient capital when interest rates and stock prices fall simultaneously. Sweden's FSA implemented a traffic light system in January...

  1. Light Emitting Diodes (LEDs)

    Science.gov (United States)

    1997-01-01

    A special lighting technology was developed for space-based commercial plant growth research on NASA's Space Shuttle. Surgeons have used this technology to treat brain cancer on Earth, in two successful operations. The treatment technique, called Photodynamic Therapy, requires the surgeon to use tiny, pinhead-size Light Emitting Diodes (LEDs) (a source that releases long wavelengths of light ) to activate light-sensitive, tumor-treating drugs. 'A young woman operated on in May 1999 has fully recovered with no complications and no evidence of the tumor coming back,' said Dr. Harry Whelan, a pediatric neurologist at the Medical Hospital of Wisconsin in Milwaukee. Laser light has been used for this type of surgery in the past, but the LED light illuminates through all nearby tissues, reaching parts of a tumor that shorter wavelengths of laser light carnot. The new probe is safer because the longer wavelengths of light are cooler than the shorter wavelengths of laser light, making the LED less likely to injure normal brain tissue near the tumor. It can be used for hours at a time while still remaining cool to the touch. The LED light source is compact, about the size of a briefcase, and can be purchased for a fraction of the cost of a laser. The LEDs, developed and managed by NASA's Marshall Space Flight Center, have been used on seven Space Shuttle flights inside the Microgravity Astroculture Facility. This technology has also been successfully used to further commercial research in crop growth.

  2. Optical bistability controlling light with light

    CERN Document Server

    Gibbs, Hyatt

    1985-01-01

    Optical Bistability: Controlling Light with Light focuses on optical bistability in nonlinear optical systems. Emphasis is on passive (non-laser) systems that exhibit reversible bistability with input intensity as the hysteresis variable, along with the physics and the potential applications of such systems for nonlinear optical signal processing. This book consists of seven chapters and begins with a historical overview of optical bistability in lasers and passive systems. The next chapter describes steady-state theories of optical bistability, including the Bonifacio-Lugiato model, as we

  3. Traffic Light Options

    DEFF Research Database (Denmark)

    Jørgensen, Peter Løchte

    This paper introduces, prices, and analyzes traffic light options. The traffic light option is an innovative structured OTC derivative developed independently by several London-based investment banks to suit the needs of Danish life and pension (L&P) companies, which must comply with the traffic...... light solvency stress test system introduced by the Danish Financial Supervisory Authority (DFSA) in June 2001. This monitoring system requires L&P companies to submit regular reports documenting the sensitivity of the companies' base capital to certain pre-defined market shocks - the red and yellow...... light scenarios. These stress scenarios entail drops in interest rates as well as in stock prices, and traffic light options are thus designed to pay off and preserve sufficient capital when interest rates and stock prices fall simultaneously. Sweden's FSA implemented a traffic light system in January...

  4. Framing Light Rail Projects

    DEFF Research Database (Denmark)

    Olesen, Mette

    2014-01-01

    In Europe, there has been a strong political will to implement light rail. This article contributes to the knowledge concerning policies around light rail by analysing how local actors frame light rail projects and which rationalities and arguments are present in this decision-making process....... The article draws on the socio-technical approach to mobilities studies in order to reassemble the decision-making process in three European cases: Bergen, Angers, and Bern. This article provides insights into the political, discursive and material production of light rail mobilities in a European context....... It identifies the planning rationales behind the systems and the policies that have been supportive of this light rail vision. Finally, the article identifies the practical challenges and potentials that have been connected to the different local frames of light rail mobility which can be used in future...

  5. Light metal production

    Science.gov (United States)

    Fan, Qinbai

    2016-04-19

    An electrochemical process for the production of light metals, particularly aluminum. Such a process involves contacting a light metal source material with an inorganic acid to form a solution containing the light metal ions in high concentration. The solution is fed to an electrochemical reactor assembly having an anode side containing an anode and a cathode side containing a cathode, with anode side and the cathode side separated by a bipolar membrane, with the solution being fed to the anode side. Light metal ions are electrochemically transferred through the bipolar membrane to the cathode side. The process further involves reducing the light metal ions to light metal powder. An associated processing system is also provided.

  6. 3D light robotics

    DEFF Research Database (Denmark)

    Glückstad, Jesper; Palima, Darwin; Villangca, Mark Jayson

    2016-01-01

    As celebrated by the Nobel Prize 2014 in Chemistry light-based technologies can now overcome the diffraction barrier for imaging with nanoscopic resolution by so-called super-resolution microscopy1. However, interactive investigations coupled with advanced imaging modalities at these small scale...... research discipline that could potentially be able to offer the full packet needed for true "active nanoscopy" by use of so-called light-driven micro-robotics or Light Robotics in short....

  7. 3D light robotics

    DEFF Research Database (Denmark)

    Glückstad, Jesper; Palima, Darwin; Villangca, Mark Jayson;

    2016-01-01

    As celebrated by the Nobel Prize 2014 in Chemistry light-based technologies can now overcome the diffraction barrier for imaging with nanoscopic resolution by so-called super-resolution microscopy1. However, interactive investigations coupled with advanced imaging modalities at these small scale...... research discipline that could potentially be able to offer the full packet needed for true "active nanoscopy" by use of so-called light-driven micro-robotics or Light Robotics in short....

  8. High efficiency incandescent lighting

    Science.gov (United States)

    Bermel, Peter; Ilic, Ognjen; Chan, Walker R.; Musabeyoglu, Ahmet; Cukierman, Aviv Ruben; Harradon, Michael Robert; Celanovic, Ivan; Soljacic, Marin

    2014-09-02

    Incandescent lighting structure. The structure includes a thermal emitter that can, but does not have to, include a first photonic crystal on its surface to tailor thermal emission coupled to, in a high-view-factor geometry, a second photonic filter selected to reflect infrared radiation back to the emitter while passing visible light. This structure is highly efficient as compared to standard incandescent light bulbs.

  9. Berkeley Lighting Cone

    Energy Technology Data Exchange (ETDEWEB)

    Lask, Kathleen [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Gadgil, Ashok [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2016-10-24

    A lighting cone is a simple metal cone placed on the fuel bed of a stove during ignition to act as a chimney, increasing the draft through the fuel bed. Many stoves tend to be difficult to light due to poor draft through the fuel bed, so lighting cones are used in various parts of the world as an inexpensive accessory to help with ignition.

  10. Dissecting a Light Echo

    Science.gov (United States)

    2008-01-01

    [figure removed for brevity, see original site] Click on image for audio animation This animation illustrates how a light echo works, and how an optical illusion of material moving outward is created. A light echo occurs when a star explodes, acting like a cosmic flashbulb. The light from this explosion zips through nearby dust clumps, illuminating and heating them up slightly. This brief period of warming causes them to glow in infrared, like a chain of Christmas bulbs lighting up one by one. The animation starts by showing the explosion of a star, which results in a flash of light that moves outward in all directions. The direction of our line of sight from Earth is indicated by the blue arrow. When the light flash reaches surrounding dust, shown here as three dark clouds, the dust is heated up, creating infrared light that begins to travel toward Earth (indicated by the red arrows). Dust closest to the explosion lights up first, while the explosion's shock wave takes longer to reach more distant material. This results in light from different parts of the cloud reaching Earth at different times, creating the illusion of motion over time. As the animation shows, the inclination of the cloud toward our line of sight can result in the material seeming to move both away from and toward the central star.

  11. Light and Sound

    CERN Document Server

    Karam, P Andrew

    2010-01-01

    Our world is largely defined by what we see and hear-but our uses for light and sound go far beyond simply seeing a photo or hearing a song. A concentrated beam of light, lasers are powerful tools used in industry, research, and medicine, as well as in everyday electronics like DVD and CD players. Ultrasound, sound emitted at a high frequency, helps create images of a developing baby, cleans teeth, and much more. Light and Sound teaches how light and sound work, how they are used in our day-to-day lives, and how they can be used to learn about the universe at large.

  12. Occlusion, transparency, and lightness.

    Science.gov (United States)

    Albert, Marc K

    2007-11-01

    The lightness of a visual surface is its perceived achromatic reflectance [Adelson, E. H., (2000). Lightness perception and lightness illusions. In M. Gazzaniga (Ed.), The new cognitive neuroscience (2nd ed.) (pp. 339-351) Berlin: Springer; Gilchrist, A. (1999). Lightness perception. In R. W. F. Keil (Ed.), MIT encyclopedia of cognitive science (pp. 471-472). Cambridge: MIT press]. Lightness ranges from black, through various shades of grey, up to white. Anderson and Winawer [Anderson, B., Winawer, J. (2005). Image segmentation and lightness perception. Nature, 434, 79-83] suggested that perceptual decomposition of image luminance into multiple sources in different layers (e.g., perceptual transparency) is critical to the their lightness illusions. However, I show that simple perceptual occlusion evoked by T-junctions will work as well, suggesting that perceptual scission of luminance into multiple layers is unnecessary for such effects. I argue that the lightness illusions presented by Anderson and Winawer involve fundamentally different mechanisms than previously studied lightness illusions, including those involving perceptual transparency.

  13. Theodolite Ring Lights

    Science.gov (United States)

    Clark, David

    2006-01-01

    Theodolite ring lights have been invented to ease a difficulty encountered in the well-established optical-metrology practice of using highly reflective spherical tooling balls as position references. A theodolite ring light produces a more easily visible reflection and eliminates the need for an autocollimating device. A theodolite ring light is a very bright light source that is well centered on the optical axis of the instrument. It can be fabricated, easily and inexpensively, for use on a theodolite or telescope of any diameter.

  14. Quantum states of light

    CERN Document Server

    Furusawa, Akira

    2015-01-01

    This book explains what quantum states of light look like. Of special interest, a single photon state is explained by using a wave picture, showing that it corresponds to the complementarity of a quantum. Also explained is how light waves are created by photons, again corresponding to the complementarity of a quantum. The author shows how an optical wave is created by superposition of a "vacuum" and a single photon as a typical example. Moreover, squeezed states of light are explained as "longitudinal" waves of light and Schrödinger's cat states as macroscopic superposition states.

  15. Light source modeling for automotive lighting devices

    Science.gov (United States)

    Zerhau-Dreihoefer, Harald; Haack, Uwe; Weber, Thomas; Wendt, Dierk

    2002-08-01

    Automotive lighting devices generally have to meet high standards. For example to avoid discomfort glare for the oncoming traffic, luminous intensities of a low beam headlight must decrease by more than one order of magnitude within a fraction of a degree along the horizontal cutoff-line. At the same time, a comfortable homogeneous illumination of the road requires slowly varying luminous intensities below the cutoff line. All this has to be realized taking into account both, the legal requirements and the customer's stylistic specifications. In order to be able to simulate and optimize devices with a good optical performance different light source models are required. In the early stage of e.g. reflector development simple unstructured models allow a very fast development of the reflectors shape. On the other hand the final simulation of a complex headlamp or signal light requires a sophisticated model of the spectral luminance. In addition to theoretical models based on the light source's geometry, measured luminance data can also be used in the simulation and optimization process.

  16. Light + Light = Darkness : searching for exoplanets

    NARCIS (Netherlands)

    Hartmann, L.

    2002-01-01

    Arjan Mieremet, a doctorate student in the Optics section at Applied Physics, wants to extinguish stellar light in order to see the planets around it. The idea originated over twenty years ago, but so far nobody has managed to construct the necessary optical equipment. Mieremet tried, and soon ran i

  17. Light + Light = Darkness : searching for exoplanets

    NARCIS (Netherlands)

    Hartmann, L.

    2002-01-01

    Arjan Mieremet, a doctorate student in the Optics section at Applied Physics, wants to extinguish stellar light in order to see the planets around it. The idea originated over twenty years ago, but so far nobody has managed to construct the necessary optical equipment. Mieremet tried, and soon ran

  18. Natural light illumination system.

    Science.gov (United States)

    Whang, Allen Jong-Woei; Chen, Yi-Yung; Yang, Shu-Hua; Pan, Po-Hsuan; Chou, Kao-Hsu; Lee, Yu-Chi; Lee, Zong-Yi; Chen, Chi-An; Chen, Cheng-Nan

    2010-12-10

    In recent years, green energy has undergone a lot of development and has been the subject of many applications. Many research studies have focused on illumination with sunlight as a means of saving energy and creating healthy lighting. Natural light illumination systems have collecting, transmitting, and lighting elements. Today, most daylight collectors use dynamic concentrators; these include Sun tracking systems. However, this design is too expensive to be cost effective. To create a low-cost collector that can be easily installed on a large building, we have designed a static concentrator, which is prismatic and cascadable, to collect sunlight for indoor illumination. The transmission component uses a large number of optical fibers. Because optical fibers are expensive, this means that most of the cost for the system will be related to transmission. In this paper, we also use a prismatic structure to design an optical coupler for coupling n to 1. With the n-to-1 coupler, the number of optical fibers necessary can be greatly reduced. Although this new natural light illumination system can effectively guide collected sunlight and send it to the basement or to other indoor places for healthy lighting, previously there has been no way to manage the collected sunlight when lighting was not desired. To solve this problem, we have designed an optical switch and a beam splitter to control and separate the transmitted light. When replacing traditional sources, the lighting should have similar characteristics, such as intensity distribution and geometric parameters, to those of traditional artificial sources. We have designed, simulated, and optimized an illumination lightpipe with a dot pattern to redistribute the collected sunlight from the natural light illumination system such that it equals the qualities of a traditional lighting system. We also provide an active lighting module that provides lighting from the natural light illumination system or LED auxiliary

  19. Light enhances learned fear.

    Science.gov (United States)

    Warthen, Daniel M; Wiltgen, Brian J; Provencio, Ignacio

    2011-08-16

    The ability to learn, remember, and respond to emotional events is a powerful survival strategy. However, dysregulated behavioral and physiological responses to these memories are maladaptive. To fully understand learned fear and the pathologies that arise during response malfunction we must reveal the environmental variables that influence learned fear responses. Light, a ubiquitous environmental feature, modulates cognition and anxiety. We hypothesized that light modulates responses to learned fear. Using tone-cued fear conditioning, we found that light enhances behavioral responses to learned fear in C57BL/6J mice. Mice in light freeze more in response to a conditioned cue than mice in darkness. The absence of significant freezing during a 2-wk habituation period and during intertrial intervals indicated that light specifically modulates freezing to the learned acoustic cue rather than the context of the experimental chamber. Repeating our assay in two photoreceptor mutant models, Pde6b(rd1/rd1) and Opn4(-/-) mice, revealed that light-dependent enhancement of conditioned fear is driven primarily by the rods and/or cones. By repeating our protocol with an altered lighting regimen, we found that lighting conditions acutely modulate responses when altered between conditioning and testing. This is manifested either as an enhancement of freezing when light is added during testing or as a depression of freezing when light is removed during testing. Acute enhancement, but not depression, requires both rod/cone- and melanopsin-dependent photoreception. Our results demonstrate a modulation by light of behavioral responses to learned fear.

  20. Hydrogen Storage in Nanostructured Light Metal Hydrides

    NARCIS (Netherlands)

    Singh, S.

    2009-01-01

    The global energy issues can be solved by the abundantly available hydrogen on earth. Light metals are a compact and safe medium for storing hydrogen. This makes them attractive for vehicular use. Unfortunately, hydrogen uptake and release is slow in light metals at practical temperature and pressur

  1. Hydrogen Storage in Nanostructured Light Metal Hydrides

    NARCIS (Netherlands)

    Singh, S.

    2009-01-01

    The global energy issues can be solved by the abundantly available hydrogen on earth. Light metals are a compact and safe medium for storing hydrogen. This makes them attractive for vehicular use. Unfortunately, hydrogen uptake and release is slow in light metals at practical temperature and

  2. Architectural Creation of Light

    DEFF Research Database (Denmark)

    Bülow, Katja

    2015-01-01

    Bidraget "Architectural Creation of Light" indgår sammen med 108 andre bidrag i bogen "You Say Light, I Think Shadow". Bogens indhold undersøger: "Hvad er lys". I dette bidrag besvares spørgsmålet gennem iagttagelser af arkitektstuderendes undersøgelser af lyset i deres arbejdsmodeller i...

  3. The visual light field

    NARCIS (Netherlands)

    Koenderink, J.J.; Pont, S.C.; Doorn, A.J. van; Kappers, A.M.L.; Todd, J.T.

    2007-01-01

    Human observers are sensitive to the ‘(physical) light field' in the sense that they have expectations of how a given object would appear if it were introduced in the scene in front of them at some arbitrary location. Thus the ‘visual light field' is defined even in the ‘empty space' between

  4. Light-emitting Diodes

    Science.gov (United States)

    Opel, Daniel R.; Hagstrom, Erika; Pace, Aaron K.; Sisto, Krisanne; Hirano-Ali, Stefanie A.; Desai, Shraddha

    2015-01-01

    Background: In the early 1990s, the biological significance of light-emitting diodes was realized. Since this discovery, various light sources have been investigated for their cutaneous effects. Study design: A Medline search was performed on light-emitting diode lights and their therapeutic effects between 1996 and 2010. Additionally, an open-label, investigator-blinded study was performed using a yellow light-emitting diode device to treat acne, rosacea, photoaging, alopecia areata, and androgenetic alopecia. Results: The authors identified several case-based reports, small case series, and a few randomized controlled trials evaluating the use of four different wavelengths of light-emitting diodes. These devices were classified as red, blue, yellow, or infrared, and covered a wide range of clinical applications. The 21 patients the authors treated had mixed results regarding patient satisfaction and pre- and post-treatment evaluation of improvement in clinical appearance. Conclusion: Review of the literature revealed that differing wavelengths of light-emitting diode devices have many beneficial effects, including wound healing, acne treatment, sunburn prevention, phototherapy for facial rhytides, and skin rejuvenation. The authors’ clinical experience with a specific yellow light-emitting diode device was mixed, depending on the condition being treated, and was likely influenced by the device parameters. PMID:26155326

  5. Enriching lighting design.

    Science.gov (United States)

    Brawley, Elizabeth C

    2009-01-01

    Good lighting is perhaps the most important and least understood element in designing healthcare environments. Both physically and mentally challenged individuals become more vulnerable and dependent on their environment to compensate for sensory impairments, including dimming eyesight, which interferes to some degree with daily activities as well as social and leisure activities - the things that provide emotional and social well-being. Too few building designs today result in lighting that meets the needs of these individuals, regardless of age. Typical lighting in most care environments is inadequate to meet lighting needs affecting both vision and the photobiological (non-visual) needs of synchronization of circadian rhythm, which impacts sleep and depression. Well-designed lighting is one of the most important design elements that will support an individual's ability to perform normal daily activities and decrease the level of disability associated with these impairments. Daylight contains the spectrum to which the circadian clock is most sensitive and provides higher light levels during the day. Easily accessible outdoor gardens encourage individuals outside, providing the necessary regular exposure to direct bright light that sunlight provides. The combination good interior lighting and regular daylight exposure contributes to regaining and maintaining an active and fulfilling lifestyle - greatly improving quality of life.

  6. The Traffic Light Challenge

    Science.gov (United States)

    Roman, Harry T.

    2014-01-01

    Traffic lights are an important part of the transportation infrastructure, regulating traffic flow and maintaining safety when crossing busy streets. When they go awry or become nonfunctional, a great deal of havoc and danger can be present. During power outages, the street lights go out all over the affected area. It would be good to be able to…

  7. Road lighting for safety.

    NARCIS (Netherlands)

    Schreuder, D.A.

    2000-01-01

    This book is aimed at broad readership, not especially at lighting experts. Lighting is presented as a system, as part of the public highway. Much attention is paid to subjects not greatly covered in the specialist literature, such as environmental aspects, traffic safety, crime prevention, and the

  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. Lighting at computer workstations.

    Science.gov (United States)

    Osterhaus, Werner; Hemphälä, Hillevi; Nylén, Per

    2015-01-01

    The visual conditions for computer work are complex and include several factors that need to be well controlled. These factors include the lighting system, the design of the computer and screen itself, the screens position and orientation within the room, the surface reflectances and colours of the room, and the visualability of the worker. The objective was to review the literature (including standards) on lighting for computer work in an accessible summary. This contribution focuses on lighting for computer work, but the reader is reminded of the fact that lighting continuously interacts with the other factors mentioned above. The combined visual conditions shall enable the worker to see and perform the work task without causing unnecessary strain for the eyes or the other parts of the body. The main lighting-related factors in the visual environment to evaluate are: illuminance, luminance, direction of light, glare, correlated colour temperature of the light source (CCT), colour rendering of the light source, and the non-visual effects (such as non-visual flicker). A visual ergonomics checklist is presented as a guide to analyse the visual environment.

  10. Road lighting for safety.

    NARCIS (Netherlands)

    Schreuder, D.A.

    2000-01-01

    This book is aimed at broad readership, not especially at lighting experts. Lighting is presented as a system, as part of the public highway. Much attention is paid to subjects not greatly covered in the specialist literature, such as environmental aspects, traffic safety, crime prevention, and the

  11. Dynamic public lighting (DYNO)

    NARCIS (Netherlands)

    Kaptein, N.A.; Hogema, J.H.; Folles, E.

    1997-01-01

    In The Netherlands the concept of Dynamic Public Lighting (DYNO) has been introduced, which implies that road lighting is continuously adapted to the prevailing conditions, finding a balance between traffic safety and environment. For instance, in case of favourable weather conditions and low

  12. Traffic Light Detection

    DEFF Research Database (Denmark)

    Philipsen, Mark Philip; Jensen, Morten Bornø; Møgelmose, Andreas

    2015-01-01

    database is collected based on footage from US roads. The database consists of both test and training data, totaling 46,418 frames and 112,971 annotated traffic lights, captured in continuous sequences under a varying light and weather conditions. The learning based detector achieves an AUC of 0.4 and 0...

  13. Dynamic lighting design

    DEFF Research Database (Denmark)

    Linnebjerg, Sofie

    and under various weather conditions, creating a multitude of light settings. Humans live in interaction with this dynamic light and consider it as a natural part of our world [Mathiasen, 2015]. Furthermore, it has by the recent discovery of intrinsically photosensitive retinal ganglion cells in 2002...

  14. Light in complex dielectrics

    NARCIS (Netherlands)

    Schuurmans, F.J.P.

    1999-01-01

    In this thesis the properties of light in complex dielectrics are described, with the two general topics of "modification of spontaneous emission" and "Anderson localization of light". The first part focuses on the spontaneous emission rate of an excited atom in a dielectric host with variable refra

  15. Serum Free Light Chains

    Science.gov (United States)

    ... or of one of its component parts – a kappa or lambda light chain, or rarely, a heavy chain. Traditionally, plasma cell ... protein (M-protein) production and to calculate a kappa/lambda free light chain ratio. If the protein electrophoresis test is abnormal, ...

  16. 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.

  17. Architectural Creation of Light

    DEFF Research Database (Denmark)

    Bülow, Katja

    2015-01-01

    Bidraget "Architectural Creation of Light" indgår sammen med 108 andre bidrag i bogen "You Say Light, I Think Shadow". Bogens indhold undersøger: "Hvad er lys". I dette bidrag besvares spørgsmålet gennem iagttagelser af arkitektstuderendes undersøgelser af lyset i deres arbejdsmodeller i...

  18. Autonomous photovoltaic lighting system

    OpenAIRE

    Ahmed A. A. Hafez; Montesinos Miracle, Daniel; Sudrià Andreu, Antoni

    2012-01-01

    This paper introduces a comparison between the conventional and Photovoltaic (PV) lighting systems. A simple sizing procedure for a PV stand-alone system was advised. The paper also proposes a novel PV lighting system. The proposed system is simple, compact and reliable. The system operation was investigated by thoroughly mathematical and simulation work.

  19. Dynamic public lighting (DYNO)

    NARCIS (Netherlands)

    Kaptein, N.A.; Hogema, J.H.; Folles, E.

    1997-01-01

    In The Netherlands the concept of Dynamic Public Lighting (DYNO) has been introduced, which implies that road lighting is continuously adapted to the prevailing conditions, finding a balance between traffic safety and environment. For instance, in case of favourable weather conditions and low traffi

  20. Light and sound

    Institute of Scientific and Technical Information of China (English)

    王佩夫

    2002-01-01

    Light travels at a speed which is about a million times faster than the speed of sound.In one second,light travels about 300,000 km,but sound travels only 314m,you can get some idea of this difference(区别) by watching the start of a race.

  1. Dynamic public lighting (DYNO)

    NARCIS (Netherlands)

    Kaptein, N.A.; Hogema, J.H.; Folles, E.

    1997-01-01

    In The Netherlands the concept of Dynamic Public Lighting (DYNO) has been introduced, which implies that road lighting is continuously adapted to the prevailing conditions, finding a balance between traffic safety and environment. For instance, in case of favourable weather conditions and low traffi

  2. Household transitions to energy efficient lighting

    OpenAIRE

    Mills, Bradford; Schleich, Joachim

    2014-01-01

    New energy efficient lighting technologies have the potential to significantly reduce household electricity consumption. But adoption of many technologies has been slow. This paper employs a unique dataset of German households to examine the factors associated with the replacement of old incandescent lamps (ILs) with new energy efficient compact fluorescent lamps (CFLs) and light emitting diodes (LEDs). The 'rebound' effect of increased light luminosity during the transition to energy efficie...

  3. Light Beam Generation

    DEFF Research Database (Denmark)

    2007-01-01

    The invention relates to a method and a system for synthesizing a set of controllable light beams by provision of a system for synthesizing a set of light beams, comprising a spatially modulated light source for generation of electromagnetic radiation with a set of replicas of a predetermined......(x-xs, y-ys), a Fourier transforming lens for Fourier transforming the electromagnetic radiation, a first spatial light modulator for phase shifting the Fourier transformed electromagnetic radiation with the phase -F(u, v) of S*, S* is the complex conjugate of the Fourier transformed symbol s, a Fourier...... transforming lens for Inverse Fourier transforming the spatially modulated radiation, whereby a set of light beams are formed propagating through the inverse Fourier plane (x', y') at desired positions (x's, y's), and a controller for controlling the position of a replica of the symbol, s, for movement...

  4. Light dispersion in space

    Science.gov (United States)

    Barbosa, L. C.

    2015-09-01

    Considering an idea of F. Arago in 1853 regarding light dispersion through the light ether in the interstellar space, this paper presents a new idea on an alternative interpretation of the cosmological red shift of the galaxies in the universe. The model is based on an analogy with the temporal material dispersion that occurs with light in the optical fiber core. Since intergalactic space is transparent, according to the model, this phenomenon is related to the gravitational potential existing in the whole space. Thus, it is possible to find a new interpretation to Hubble's constant. In space, light undergoes a dispersion process in its path, which is interpreted by a red shift equation of the type Δz = HL, since H = (d2n/dλ2 Δv Δλ), where H means the Hubble constant, n is the refractive index of the intergalactic space, Δλ is the spectral width of the extragalactic source, and Δv is the variation of the speed of light caused by the gravitational potential. We observe that this "constant" is governed by three new parameters. Light traveling the intergalactic space undergoes red shift due to this mechanism, while light amplitude decreases with time, and the wavelength always increases, thus producing the same type of behavior given by Hubble's Law. It can be demonstrated that the dark matter phenomenon is produced by the apparent speed of light of the stars on the periphery of the galaxies, without the existence of dark energy. Based on this new idea, the model of the universe is static, lacking expansion. Other phenomena may be interpreted based on this new model of the universe. We have what we call temporal gravitational dispersion of light in space produced by the variations of the speed of light, due to the presence of the gravitational potential in the whole space.

  5. Face recognition at mesopic light levels and various light spectra

    NARCIS (Netherlands)

    Alferdinck, J.W.A.M.; Hogervorst, M.A.

    2013-01-01

    Light sources that are optimized for mesopic vision contain a relatively high amount of bluish light (high S/P-ratio) and are therefore effective for peripheral visual tasks at mesopic light levels. Since the spectra of these light sources differ strongly from the common public lighting there were d

  6. An effective thermal-parametrization theory for the slow-light dynamics in a Doppler-broadened electomagnetically induced transparency medium

    CERN Document Server

    Su, Shih-Wei; Gou, Shih-Chuan; Yu, Ite A

    2011-01-01

    We model the effects of atomic thermal motion on the propagation of a light pulse in an electromagnetically induced transparency medium by introducing a set of effectively temperature-dependent parameters, including the Rabi frequency of the coupling field, optical density and relaxation rate of the ground state coherence, into the governing equations. The validity of this effective theory is verified by the close agreement between the theoretical results and the experimental data.

  7. Light water reactor safety

    CERN Document Server

    Pershagen, B

    2013-01-01

    This book describes the principles and practices of reactor safety as applied to the design, regulation and operation of light water reactors, combining a historical approach with an up-to-date account of the safety, technology and operating experience of both pressurized water reactors and boiling water reactors. The introductory chapters set out the basic facts upon which the safety of light water reactors depend. The central section is devoted to the methods and results of safety analysis. The accidents at Three Mile Island and Chernobyl are reviewed and their implications for light wate

  8. Green Light Pulse Oximeter

    Energy Technology Data Exchange (ETDEWEB)

    Scharf, John Edward (Oldsmar, FL)

    1998-11-03

    A reflectance pulse oximeter that determines oxygen saturation of hemoglobin using two sources of electromagnetic radiation in the green optical region, which provides the maximum reflectance pulsation spectrum. The use of green light allows placement of an oximetry probe at central body sites (e.g., wrist, thigh, abdomen, forehead, scalp, and back). Preferably, the two green light sources alternately emit light at 560 nm and 577 nm, respectively, which gives the biggest difference in hemoglobin extinction coefficients between deoxyhemoglobin, RHb, and oxyhemoglobin, HbO.sub.2.

  9. Responsive City Lighting

    DEFF Research Database (Denmark)

    Poulsen, Esben Skouboe; Andersen, Hans Jørgen; Jensen, Ole B.

    This paper presents and discusses perspectives extracted from two interviews conducted during the experiments Urban Responsive Lighting. The two experts embody two different fields related to city lighting: architecture & public lighting industry. The representatives were invited to the test......-site, where 15 LED RGB Park lamps, controlled driven by a wind sensor, mobile phone applications or by thermal camera tracking. According to the specialists are the social and aesthetical dimensions more interesting than the energy use cases and efficiency. This motivates an interdisciplinary discussion...

  10. Light on curved backgrounds

    Science.gov (United States)

    Batic, D.; Nelson, S.; Nowakowski, M.

    2015-05-01

    We consider the motion of light on different spacetime manifolds by calculating the deflection angle, lensing properties and by probing into the possibility of bound states. The metrics in which we examine the light motion include, among other items, a general relativistic dark matter metric, a dirty black hole, and a worm hole metric, the last two inspired by noncommutative geometry. The lensing in a holographic screen metric is discussed in detail. We study also the bending of light around naked singularities like, e.g., the Janis-Newman-Winicour metric and include other cases. A generic property of light behavior in these exotic metrics is pointed out. For the standard metric like the Schwarzschild and Schwarzschild-de Sitter cases, we improve the accuracy of the lensing results for the weak and strong regimes.

  11. Light on curved backgrounds

    CERN Document Server

    Batic, D; Nowakowski, M

    2014-01-01

    We consider the motion of light on different spacetime manifolds by calculating the deflection angle, lensing properties and by probing into the possibility of bound states. The metrics in which we examine the light motion include, among other, a general relativistic Dark Matter metric, a dirty Black Hole and a Worm Hole metric, the last two inspired by non-commutative geometry. The lensing in a Holographic Screen metric is discussed in detail. We study also the bending of light around naked singularities like, e.g., the Janis-Newman-Winicour metric and include other cases. A generic property of light behaviour in these exotic metrics is pointed out. For the standard metric like the Schwarzschild and Schwarzschild-de Sitter cases we improve the accuracy of the lensing results for the weak and strong regime.

  12. Thermoelectricity Light Sources

    Institute of Scientific and Technical Information of China (English)

    SHIYongji

    1997-01-01

    A thermoelectricity light source in a gaseous plasma discharge between two electrodes is described,one of which emits electrons thermoionically.The analytical model describing basic physical phenomena is developed.The results are excellent agreement with simulated test.

  13. Sustainable indoor lighting

    CERN Document Server

    Mercatelli, Luca; Farini, Alessandro

    2015-01-01

    Encompassing a thorough survey of the lighting techniques applied to internal illumination characterized by high efficiency, optimized color and architectural integration, a consolidated summary of the latest scientific, technical and architectural research is presented in order to give the reader an overview of the different themes with their interactions and mutual effects.   This book describes light principles, methodologies and realisations for indoor illumination at low consumption. Power efficiency, color characteristics and architectural aspects are analyzed in terms of their  practical application, with the interactions between scientific, technological and architectural features considered in order to supply a complete overview, which can be read both at technical level and at user level. Introducing photometric and radiometric quantities and laws, the book first discusses tests and measurements assessing lighting and color characteristics before examining in detail artificial light sources with p...

  14. Light shielding apparatus

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Richard Dean; Thom, Robert Anthony

    2017-10-10

    A light shielding apparatus for blocking light from reaching an electronic device, the light shielding apparatus including left and right support assemblies, a cross member, and an opaque shroud. The support assemblies each include primary support structure, a mounting element for removably connecting the apparatus to the electronic device, and a support member depending from the primary support structure for retaining the apparatus in an upright orientation. The cross member couples the left and right support assemblies together and spaces them apart according to the size and shape of the electronic device. The shroud may be removably and adjustably connectable to the left and right support assemblies and configured to take a cylindrical dome shape so as to form a central space covered from above. The opaque shroud prevents light from entering the central space and contacting sensitive elements of the electronic device.

  15. Light composite vector bosons

    CERN Document Server

    Kosower, David A.

    1993-01-01

    In gauge theories with slowly-running coupling constants, it may be possible for four-fermion operators to be nearly marginal. Such operators can possess asymptotically weak couplings, and can plausibly give rise to light composite vector mesons.

  16. Light, Matter, and Geometry

    DEFF Research Database (Denmark)

    Frisvad, Jeppe Revall

    Interaction of light and matter produces the appearance of materials. To deal with the immense complexity of nature, light and matter is modelled at a macroscopic level in computer graphics. This work is the first to provide the link between the microscopic physical theories of light and matter...... of a material and determine the contents of the material. The book is in four parts. Part I provides the link between microscopic and macroscopic theories of light. Part II describes how to use the properties of microscopic particles to compute the macroscopic properties of materials. Part III illustrates...... that we can use geometrical models to handle the large number of variables which appear when we construct appearance models from microscopic theories. Finally, Part IV provides detailed appearance models for natural water, ice, and milk to demonstrate how the theory is applied....

  17. From light to knowledge

    CERN Multimedia

    Globe Info

    2011-01-01

    An evening in two parts with Fabio Barblan. 1/ Light in daily life and what light means for an astronomer (exhibition). 2/ Light in all its states or how to extract information from the heavenly bodies: exploration using telescopes, space probes, spectrometry and imagery. Measuring and modelling using light (physical parameters, distances, etc.) Fabio Barblan is "an external scientific collaborator" and member of the photometry, stellar variability and GAIA group at the Observatoire de Genève. Observatoire de Genève Friday 14 October from 8:30 p.m. to 10:00 p.m. » Suitable for all – Admission free - Lecture in French For further information: +33 (0)4 50 41 96 80

  18. Modeling LED street lighting.

    Science.gov (United States)

    Moreno, Ivan; Avendaño-Alejo, Maximino; Saucedo-A, Tonatiuh; Bugarin, Alejandra

    2014-07-10

    LED luminaires may deliver precise illumination patterns to control light pollution, comfort, visibility, and light utilization efficiency. Here, we provide simple equations to determine how the light distributes in the streets. In particular, we model the illuminance spatial distribution as a function of Cartesian coordinates on a floor, road, or street. The equations show explicit dependence on the luminary position (pole height and arm length), luminary angle (fixture tilt), and the angular intensity profile (radiation pattern) of the LED luminary. To achieve this, we propose two mathematical representations to model the sophisticated intensity profiles of LED luminaries. Furthermore, we model the light utilization efficiency, illumination uniformity, and veiling luminance of glare due to one or several LED streetlamps.

  19. Polarized Light Corridor Demonstrations.

    Science.gov (United States)

    Davies, G. R.

    1990-01-01

    Eleven demonstrations of light polarization are presented. Each includes a brief description of the apparatus and the effect demonstrated. Illustrated are strain patterns, reflection, scattering, the Faraday Effect, interference, double refraction, the polarizing microscope, and optical activity. (CW)

  20. POLARIZED LIGHT IN PHYSIOTHERAPY

    National Research Council Canada - National Science Library

    L. D. Tondiy; O. L. Tondiy; I. V. Kas; O. V. Zemlyana; O. L. Zakrevska; V. O. Zhuravliev

    2015-01-01

    The data on polarized light (PS) - a new promising treatment, rehabilitation and prevention, which took its deserved place among the known therapeutic physical factors and may even compete with laser radiation of low and LED therapy...

  1. Light Detection And Ranging

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — LiDAR (Light Detection and Ranging) discrete-return point cloud data are available in the American Society for Photogrammetry and Remote Sensing (ASPRS) LAS format....

  2. The wonders of light

    CERN Document Server

    García-Matos, Marta

    2015-01-01

    Discover the spectacular power of light with this visually stunning celebration of the multitude of ways in which light-based technology has shaped our society. Be inspired by state-of-the-art science: sixteen beautiful, straightforward chapters demonstrate the science behind the fascinating and surprising ways in which light can be harnessed and used, from displays, solar cells and the Internet to advanced quantum technologies. Be dazzled by brilliant color: dramatic design and radiant color illustrations bring cutting-edge science and groundbreaking innovations to life, clearly explaining the fundamental principles behind them. Be part of something bigger: published in association with the Institute of Photonic Sciences (ICFO) to celebrate the 2015 UNESCO International Year of Light, it is perfect for anyone interested in the frontiers of science, engineering or medicine, and in the phenomenal technological advances that have been made possible by human innovation.

  3. Cosmic Light EDU kit

    Science.gov (United States)

    Doran, Rosa

    2015-08-01

    In 2015 we celebrate the International Year of Light, a great opportunity to promote awareness about the importance of light coming from the Cosmos and what messages it is bringing to mankind. In parallel a unique moment to attract the attention of stakeholders on the dangers of light pollution and its impact in our lives and our pursuit of more knowledge. In this presentation I want to present one of the conrnerstones of IYL2015, a partnership between the Galileo Teacher Training Program, Universe Awareness and Globe at Night, the Cosmic Light EDU kit. The aim of this project is to assemble a core set of tools and resources representing our basic knowledge pilars about the Universe and simple means to preserve our night sky.

  4. Casimir light: a glimpse.

    OpenAIRE

    1993-01-01

    Light emission produced by the reversible collapse of a cavity in a dielectric medium is given an initial, simplified treatment. The agreement between planar and spherical shapes indicates the volume nature of the effect.

  5. Occupant Controlled Lighting

    DEFF Research Database (Denmark)

    Logadóttir, Ásta

    2011-01-01

    of adjustment. Firstly, there was preliminary laboratory study exploring the influence of daylight on occupant controlled dynamic lighting in a laboratory office environment. Secondly, there was non-daylit laboratory study on occupant preferences for illuminance, and thirdly a scale model study on occupant......The studies presented in this thesis explore opportunities and limitations of using the method of adjustment for occupant controlled lighting. The method of adjustment is studied with respect to occupant preferences and energy efficiency. The work presents three types of studies using the method...... preferences for correlated colour temperature (CCT). The results suggest that the method of adjustment, previously used in the lighting literature, is not adequate to generalize about occupant preferences for illuminance or CCT. Factors that influence occupants’ lighting preference when applying the method...

  6. Light Detection And Ranging

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — LiDAR (Light Detection and Ranging) discrete-return point cloud data are available in the American Society for Photogrammetry and Remote Sensing (ASPRS) LAS format....

  7. Indoor Lighting Facilities

    Science.gov (United States)

    Matsushima, Koji; Saito, Yoshinori; Ichikawa, Shigenori; Kawauchi, Takao; Tanaka, Tsuneo; Hirano, Rika; Tazuke, Fuyuki

    According to the statistics by the Ministry of Land, Infrastructure and Transport, the total floor space of all building construction started was 188.87 million m2 (1.5% increase y/y), marking the fourth straight year of increase. Many large-scale buildings under construction in central Tokyo become fully occupied by tenants before completion. As for office buildings, it is required to develop comfortable and functional office spaces as working styles are becoming more and more diversified, and lighting is also an element of such functionalities. The total floor space of construction started for exhibition pavilions, multipurpose halls, conference halls and religious architectures decreased 11.1% against the previous year. This marked a decline for 10 consecutive years and the downward trend continues. In exhibition pavilions, the light radiation is measured and adjusted throughout the year so as not to damage the artworks by lighting. Hospitals, while providing higher quality medical services and enhancing the dwelling environment of patients, are expected to meet various restrictions and requirements, including the respect for privacy. Meanwhile, lighting designs for school classrooms tend to be homogeneous, yet new ideas are being promoted to strike a balance between the economical and functional aspects. The severe economic environment continues to be hampering the growth of theaters and halls in both the private and public sectors. Contrary to the downsizing trend of such facilities, additional installations of lighting equipment were conspicuous, and the adoption of high efficacy lighting appliances and intelligent function control circuits are becoming popular. In the category of stores/commercial facilities, the construction of complex facilities is a continuing trend. Indirect lighting, high luminance discharge lamps with excellent color rendition and LEDs are being effectively used in these facilities, together with the introduction of lighting designs

  8. Cauldron of Light

    Science.gov (United States)

    2008-01-01

    [figure removed for brevity, see original site] Click on image to view the animation In this animation, a seething cauldron of light appears to bubble and ooze around the remains of a giant star that astronomers have been watching tear itself apart for the last 300 years. This movie flips quickly between different observations taken over three years by NASA's Spitzer Space Telescope. Beginning in the center, the well-studied Cassiopeia A supernova remnant is shown. Cassiopeia A is the remnant of a once massive star that died in a violent supernova explosion. It consists of a dead star, called a neutron star, and a surrounding shell of material that was blasted off as the star died. Panning outward, 'light echoes' create the illusion of motion in the clouds, as different areas of the material are lit up in succession by the light flash of the supernova. A light echo occurs when a star explodes, acting like a cosmic flashbulb. The light from this explosion zips through nearby dust clumps, illuminating and heating them up slightly. This brief period of warming causes them to glow in infrared, like a chain of Christmas bulbs lighting up one by one. The result is an optical illusion, in which the dust appears to be flying outward at the speed of light. In reality, the clouds are stationary, at least in the brief time over which these observations were taken. The inclination of the clouds cause some light echoes to appear to expand away from the supernova remnant, while others move towards it or boil in many directions with seeming turbulence.

  9. Painting with light

    DEFF Research Database (Denmark)

    Jensen, Niels Henrik

    The paper describes a method, where Photoshop are used for balancing the different light sources of a rendered CAD-model. The method shortens the work process considerably, and makes it easier to obtain a result of a high quality.......The paper describes a method, where Photoshop are used for balancing the different light sources of a rendered CAD-model. The method shortens the work process considerably, and makes it easier to obtain a result of a high quality....

  10. Light enhances learned fear

    OpenAIRE

    Warthen, Daniel M.; Wiltgen, Brian J.; Provencio, Ignacio

    2011-01-01

    The ability to learn, remember, and respond to emotional events is a powerful survival strategy. However, dysregulated behavioral and physiological responses to these memories are maladaptive. To fully understand learned fear and the pathologies that arise during response malfunction we must reveal the environmental variables that influence learned fear responses. Light, a ubiquitous environmental feature, modulates cognition and anxiety. We hypothesized that light modulates responses to lear...

  11. Light chain nephropathy

    Directory of Open Access Journals (Sweden)

    Sihem Darouich

    2015-01-01

    Full Text Available Light chain deposition disease (LCDD is characterized by the tissue deposition of monotypic immunoglobulin light chains of either kappa or lambda isotype. It is the archetypal systemic disease that is most frequently diagnosed on a kidney biopsy, although the deposits may involve several other organs. This brief review focuses on the clinicopathological features of LCDD-associated nephropathy with an emphasis on the diagnostic and therapeutic difficulties related to this elusive condition.

  12. Lighting Retrofitting: improving energy efficiency and lighting quality

    OpenAIRE

    2015-01-01

    In order to minimize energy consumption for lighting and increasing lighting quality in existing offices old lighting systems can be retrofitted with more efficient luminaires. Additional savings can be achieved by installing a lighting control system. Installation time and costs can be reduced by installing LED luminaires equipped with inbuilt lighting controls. In the case study six rooms were analysed: in two rooms the old lighting system has been retrofitted with LED luminaires with inbui...

  13. Organic light emitting diode with light extracting electrode

    Energy Technology Data Exchange (ETDEWEB)

    Bhandari, Abhinav; Buhay, Harry

    2017-04-18

    An organic light emitting diode (10) includes a substrate (20), a first electrode (12), an emissive active stack (14), and a second electrode (18). At least one of the first and second electrodes (12, 18) is a light extracting electrode (26) having a metallic layer (28). The metallic layer (28) includes light scattering features (29) on and/or in the metallic layer (28). The light extracting features (29) increase light extraction from the organic light emitting diode (10).

  14. [Bright light therapy].

    Science.gov (United States)

    Poirrier, R; Cambron, L

    2007-01-01

    Bright light therapy is a treatment that emerged in the eighties of the last century. It can be used in different pathologies such as seasonal affective disorders, major depressions, and many disorders of the wake-sleep rhythm, whether they are of primary or secondary origin. Important progress made at the basic neuroscience levels, allows today a sound understanding of the bright light mode of action. Moreover, the main indications are now the subject of consensus reports and meta-analyses which show good levels of evidence-based medicine. Bright light therapy constitutes a first choice indication in seasonal affective disorder. It is also perfectly possible to prescribe bright light therapy in the major depression disorders. It has been demonstrated that the effect size is the same as with antidepressants of reference. It is admitted nowadays that bright light therapy may be at least, an adjunct to pharmacotherapy, in order to accelerate the antidepressant effect onset, or to prolong this effect after withdrawal of the drug. Bright light therapy can also be viewed as an alternative to the pharmacological approach especially when this one is impossible, not tolerated or not accepted by the patient. The contraindications are rare.

  15. Fifth generation light sources

    Science.gov (United States)

    Romaniuk, Ryszard S.

    2016-12-01

    Coherent light sources are one of the most fundamental research tools in biology, technology and in other areas. Synchrotron light source consists of a few basic parts: energy source - which is an electron beam accelerator, energy converter between electron and photon beams - which is an undulator, and photon user experimental lines. Each of these parts is separately a complex system, which is currently a subject to fast technological development. Future light sources of the fifth generation are based on completely new solutions of these fundamental parts, in comparison with the sources of the previous generations. Energy source is a new generation laser - plasma accelerator with electrical field in the area of multiple GV/m. A miniature undulator is tested in the MEMS technology from new materials. Classical light beam lines, vacuum, and difficult for management and beam distribution, change their meaning in the case of availability of miniature undulators positioned immediately at or even inside the experimental stations. After an introduction concerning the light sources of the previous generations, the article shows current research efforts on the mentioned key components of the fifth generation light sources. In some cases this is a continuation and modernization of the previous technologies, in the majority it is a brave endeavour to apply completely new technologies, like laser - plasma acceleration.

  16. Lightness and perceptual transparency.

    Science.gov (United States)

    Albert, Marc K

    2006-01-01

    To estimate intrinsic descriptors of objects in the environment, effective biological vision systems must 'discount' extrinsic image properties that arise from changes in viewing conditions. In particular, to estimate the reflectance of surfaces, human vision must discount, or 'take account of', likely differences in the illumination of surfaces between one image region and another. If human vision possesses any significant degree of lightness constancy, then we would expect a target perceived to be in low illumination to appear lighter than an identical target perceived to be in higher illumination. In this paper, I present lightness illusions that run directly counter to this expectation. I suggest that mid-level and higher-level factors such as image junction structure and perceived illumination and transparency, are ineffective for generating strong lightness illusions on their own, and that these factors are not 'stronger' than luminance contrast in determining lightness. I discuss the implications of these results for current models of lightness perception. I also suggest a statistical justification for the highest-luminance anchoring rule for lightness.

  17. Compressive light field sensing.

    Science.gov (United States)

    Babacan, S Derin; Ansorge, Reto; Luessi, Martin; Matarán, Pablo Ruiz; Molina, Rafael; Katsaggelos, Aggelos K

    2012-12-01

    We propose a novel design for light field image acquisition based on compressive sensing principles. By placing a randomly coded mask at the aperture of a camera, incoherent measurements of the light passing through different parts of the lens are encoded in the captured images. Each captured image is a random linear combination of different angular views of a scene. The encoded images are then used to recover the original light field image via a novel Bayesian reconstruction algorithm. Using the principles of compressive sensing, we show that light field images with a large number of angular views can be recovered from only a few acquisitions. Moreover, the proposed acquisition and recovery method provides light field images with high spatial resolution and signal-to-noise-ratio, and therefore is not affected by limitations common to existing light field camera designs. We present a prototype camera design based on the proposed framework by modifying a regular digital camera. Finally, we demonstrate the effectiveness of the proposed system using experimental results with both synthetic and real images.

  18. Light Pollution and Wildlife

    Science.gov (United States)

    Duffek, J.

    2008-12-01

    for Educational Program IYA Dark Skies Education Session Fall American Geophysical Union San Francisco, December 15-19, 2008 Light Pollution and Wildlife This is a very exciting time to be a part of the mission to keep the nighttime skies natural. The International Year of Astronomy (IYA) 2009 is developing programs for all areas of Dark Skies Awareness. For many years the issue of light pollution focused on the impact to the astronomy industry. While this is an important area, research has shown that light pollution negatively impacts wildlife, their habitat, human health, and is a significant waste of energy. Since the message and impact of the effects of light pollution are much broader now, the message conveyed to the public must also be broader. Education programs directed at youth are a new frontier to reach out to a new audience about the adverse effects of too much artificial light at night. The International Dark-Sky Association (IDA) has developed educational presentations using the National Science Teachers Association Education Standards. These programs focus on youth between the ages of 5 to 17exploring new territory in the education of light pollution. The IDA education programs are broken down into three age groups; ages 5-9, 8-13, 12 and older. The presentations come complete with PowerPoint slides, discussion notes for each slide, and workbooks including age appropriate games to keep young audiences involved. A new presentation reflects the growing area of interest regarding the effects of too much artificial light at night on wildlife. This presentation outlines the known problems for ecosystems caused by artificial light at night. Insects are attracted to artificial lights and may stay near that light all night. This attraction interferes with their ability to migrate, mate, and look for food. Such behavior leads to smaller insect populations. Fewer insects in turn affect birds and bats, because they rely on insects as a food source. The IDA

  19. Aircraft Lighting and Transparency Lab

    Data.gov (United States)

    Federal Laboratory Consortium — The Advanced Lighting and Transparencies with Night Combat Lab performs radiometric and photometric measurements of cockpit lighting and displays. Evaluates the day,...

  20. Biomaterials in light amplification

    Science.gov (United States)

    Mysliwiec, Jaroslaw; Cyprych, Konrad; Sznitko, Lech; Miniewicz, Andrzej

    2017-03-01

    Biologically produced or inspired materials can serve as optical gain media, i.e. they can exhibit the phenomenon of light amplification. Some of these materials, under suitable dye-doping and optical pumping conditions, show lasing phenomena. The emerging branch of research focused on obtaining lasing action in highly disordered and highly light scattering materials, i.e. research on random lasing, is perfectly suited for biological materials. The use of biomaterials in light amplification has been extensively reported in the literature. In this review we attempt to report on progress in the development of biologically derived systems able to show the phenomena of light amplification and random lasing together with the contribution of our group to this field. The rich world of biopolymers modified with molecular aggregates and nanocrystals, and self-organized at the nanoscale, offers a multitude of possibilities for tailoring luminescent and light scattering properties that are not easily replicated in conventional organic or inorganic materials. Of particular importance and interest are light amplification and lasing, or random lasing studies in biological cells and tissues. In this review we will describe nucleic acids and their complexes employed as gain media due to their favorable optical properties and ease of manipulation. We will report on research conducted on various biomaterials showing structural analogy to nucleic acids such as fluorescent proteins, gelatins in which the first distributed feedback laser was realized, and also amyloids or silks, which, due to their dye-doped fiber-like structure, allow for light amplification. Other materials that were investigated in that respect include polysaccharides, like starch exhibiting favorable photostability in comparison to other biomaterials, and chitosan, which forms photonic crystals or cellulose. Light amplification and random lasing was not only observed in processed biomaterials but also in living

  1. Indoor Lighting Facilities

    Science.gov (United States)

    Matsushima, Koji; Saito, Yoshinori; Ichikawa, Shigenori; Kawauchi, Takao; Tanaka, Tsuneo; Hirano, Rika; Tazuke, Fuyuki

    According to the statistics on building construction floor area from the Ministry of Land, Infrastructure, Transport and Tourism, the total floor area of building construction started in Japan in 2007 was 160,991 thousand square meters, or 14.8% less than the area of the previous year, and the reduction was the first reduction in the past five years. The office markets in Tokyo and Nagoya were active, as represented by the supplies of skyscrapers, and energy saving measures, such as the adoption of high efficiency lighting equipment, the control for initial stage illuminance, daylight harvesting, and the use of occupancy sensors, were well established. In the field of public construction, including museums, multi-purpose halls, and religious buildings, the total area of the new construction was 10.8% less than the total for the previous year, and this reduction was a continuation of an eleven-year trend. In spaces with high ceiling, the innovation for easy replacement of light sources used with reflection mirror systems and optical fibers was noted. Hospitals adapted to the expectation for improved services in their selection of lighting facilities to improve the residential environment for patients while taking into consideration the needs of the aging population, by their use of devices in corridors to help maintain a continuity of light. In libraries, a pendant system was developed to illuminate both ceilings and book shelves. In the field of theaters and halls, the time limit for repairing existing systems had come for the large facilities that were opened during the theater and hall construction boom of the 1960s through 1980s, and around 26 renovations were done. Almost all the renovations were conversions to intelligent dimming systems and lighting control desks. In the field of stores and commercial facilities, the atmosphere and glitter of the selling floor was produced by new light sources, such as ceramic metal halide lamps and LEDs, which have high

  2. Observation of subluminal twisted light in vacuum

    CERN Document Server

    Bouchard, Frédéric; Mand, Harjaspreet; Boyd, Robert W; Karimi, Ebrahim

    2015-01-01

    Einstein's theory of relativity establishes the speed of light in vacuum, c, as a fundamental constant. However, the speed of light pulses can be altered significantly in dispersive materials. While significant control can be exerted over the speed of light in such media, no experimental demonstration of altered light speeds has hitherto been achieved in vacuum for ``twisted'' optical beams. We show that ``twisted'' light pulses exhibit subluminal velocities in vacuum, being slowed by 0.1\\% relative to c. This work does not challenge relativity theory, but experimentally supports a body of theoretical work on the counterintuitive vacuum group velocities of twisted pulses. These results are particularly important given recent interest in applications of twisted light to quantum information, communication and quantum key distribution.

  3. Lighting system with illuminance control

    DEFF Research Database (Denmark)

    2013-01-01

    The present invention relates to an illumination control system comprising a plurality of outdoor luminaries and a motorized service vehicle. Each luminaire comprises a controllable light source producing a light illuminance. The motorized service vehicle comprises a light sensor configured...... to detect the light illuminance generated by the controllable light source at the motorized service vehicle. The motorized service vehicle computes light illuminance data based on the detected light illuminance and transmits these to the outdoor luminaire through a wireless communication link or stores...... the light illuminance data on a data recording device of the motorized service vehicle. The outdoor luminaire receives may use the light illuminance data to set or adjust a light illuminance of the controllable light source....

  4. Handbook of advanced lighting technology

    CERN Document Server

    Sun, Ching-Cherng; Zissis, Georges; Ma, Ruiqing

    2017-01-01

    The Handbook of Advanced Lighting Technology is a major reference work on the subject of light source science and technology, with particular focus on solid-state light sources – LEDs and OLEDs – and the development of 'smart' or 'intelligent' lighting systems; and the integration of advanced light sources, sensors, and adaptive control architectures to provide tailored illumination which is 'fit to purpose.' The concept of smart lighting goes hand-in-hand with the development of solid-state light sources, which offer levels of control not previously available with conventional lighting systems. This has impact not only at the scale of the individual user, but also at an environmental and wider economic level. These advances have enabled and motivated significant research activity on the human factors of lighting, particularly related to the impact of lighting on healthcare and education, and the Handbook provides detailed reviews of work in these areas. The potential applications for smart lighting span ...

  5. Sneaky light stop

    Directory of Open Access Journals (Sweden)

    Till Eifert

    2015-04-01

    Full Text Available A light supersymmetric top quark partner (stop with a mass nearly degenerate with that of the standard model (SM top quark can evade direct searches. The precise measurement of SM top properties such as the cross-section has been suggested to give a handle for this ‘stealth stop’ scenario. We present an estimate of the potential impact a light stop may have on top quark mass measurements. The results indicate that certain light stop models may induce a bias of up to a few GeV, and that this effect can hide the shift in, and hence sensitivity from, cross-section measurements. Due to the different initial states, the size of the bias is slightly different between the LHC and the Tevatron. The studies make some simplifying assumptions for the top quark measurement technique, and are based on truth-level samples.

  6. Structured light scatteroscopy.

    Science.gov (United States)

    Krishnaswamy, Venkataramanan; Elliott, Jonathan T; McClatchy, David M; Barth, Richard J; Wells, Wendy A; Pogue, Brian W; Paulsen, Keith D

    2014-01-01

    A new imaging approach, structured light scatteroscopy (SLS), is demonstrated, which offers rapid wide-field imaging of microscopic morphological variations in bulk tissue surfaces. Elastic scattering of light offers exquisite sensitivity to ultrastructural changes at multiple size scales ranging from nanometers to millimeters, but in bulk tissues the confounding effects of molecular absorption and strong multiple scattering of light often lead to a dramatic reduction in scatter contrast and specificity. It is demonstrated that the SLS using structured high spatial frequency illumination and detection to probe the tissue achieves direct, absorption-independent, high-resolution maps of the scattering response. The scattering response is observed to be dependent on both the wavelength and spatial frequency of choice, indicating a potential for multiscale probing of ultrastructural changes in superficial tissue layers. This methodology can be easily applied in most wide-field imaging systems.

  7. Pupillary efficient lighting system

    Science.gov (United States)

    Berman, Samuel M.; Jewett, Don L.

    1991-01-01

    A lighting system having at least two independent lighting subsystems each with a different ratio of scotopic illumination to photopic illumination. The radiant energy in the visible region of the spectrum of the lighting subsystems can be adjusted relative to each other so that the total scotopic illumination of the combined system and the total photopic illumination of the combined system can be varied independently. The dilation or contraction of the pupil of an eye is controlled by the level of scotopic illumination and because the scotopic and photopic illumination can be separately controlled, the system allows the pupil size to be varied independently of the level of photopic illumination. Hence, the vision process can be improved for a given level of photopic illumination.

  8. Light sterile neutrinos

    Science.gov (United States)

    Gariazzo, S.; Giunti, C.; Laveder, M.; Li, Y. F.; Zavanin, E. M.

    2016-03-01

    The theory and phenomenology of light sterile neutrinos at the eV mass scale is reviewed. The reactor, gallium and Liquid Scintillator Neutrino Detector anomalies are briefly described and interpreted as indications of the existence of short-baseline oscillations which require the existence of light sterile neutrinos. The global fits of short-baseline oscillation data in 3 + 1 and 3 + 2 schemes are discussed, together with the implications for β-decay and neutrinoless double-β decay. The cosmological effects of light sterile neutrinos are briefly reviewed and the implications of existing cosmological data are discussed. The review concludes with a summary of future perspectives. This review is dedicated to the memory of Hai-Wei Long, our dear friend and collaborator, who passed away on 29 May 2015. He was an exceptionally kind person and an enthusiastic physicist. We deeply miss him.

  9. Radioluminescent lighting technology

    Energy Technology Data Exchange (ETDEWEB)

    1990-01-01

    The glow-in-the-dark stereotype that characterizes the popular image of nuclear materials is not accidental. When the French scientist, Henri Becquerel, first discovered radioactivity in 1896, he was interested in luminescence. Radioluminescence, the production of light from a mixture of energetic and passive materials, is probably the oldest practical application of the unstable nucleus. Tritium-based radioluminescent lighting, in spite of the biologically favorable character of the gaseous tritium isotope, was included in the general tightening of environmental and safety regulations. Tritium light manufacturers would have to meet two fundamental conditions: (1) The benefit clearly outweighed the risk, to the extent that even the perceived risk of a skeptical public would be overcome. (2) The need was significant enough that the customer/user would be willing and able to afford the cost of regulation that was imposed both in the manufacture, use and eventual disposal of nuclear materials. In 1981, researchers at Oak Ridge National Laboratory were investigating larger radioluminescent applications using byproduct nuclear material such as krypton-85, as well as tritium. By 1982, it appeared that large source, (100 Curies or more) tritium gas tube, lights might be useful for marking runways and drop zones for military operations and perhaps even special civilian aviation applications. The successful development of this idea depended on making the light bright enough and demonstrating that large gas tube sources could be used and maintained safely in the environment. This successful DOE program is now in the process of being completed and closed-out. Working closely with the tritium light industry, State governments and other Federal agencies, the basic program goals have been achieved. This is a detailed report of what they have learned, proven, and discovered. 91 refs., 29 figs., 5 tabs. (JF)

  10. [Light and Medicine].

    Science.gov (United States)

    Lemmer, Björn

    2016-12-01

    There would be no life without light. The rotation of the earth around its axis has introduced the development of biological clocks in all living subjects regulating all functions of the body. The rhythms best described are the 24-hour/circadian and the seasonal rhythms. The rhythmic composition around the body clock has great impact on health and disease, both in diagnostics and treatment. Nowadays, bright light, e.g. in seasonal affective disorder, can be regarded as a drug, being even more effective than selective serotonin reuptake inhibitors.

  11. Light is Heavy

    OpenAIRE

    Mark, M.B. van der; Hooft, G. W. 't

    2015-01-01

    Einstein's relativity theory appears to be very accurate, but at times equally puzzling. On the one hand, electromagnetic radiation must have zero rest mass in order to propagate at the speed of light, but on the other hand, since it definitely carries momentum and energy, it has non-zero inertial mass. Hence, by the principle of equivalence, it must have non-zero gravitational mass, and so, light must be heavy. In this paper, no new results will be derived, but a possibly surprising perspect...

  12. Optics, light and lasers

    CERN Document Server

    Meschede, Dieter

    2008-01-01

    Starting from the concepts of classical optics, Optics, Light and Lasers introduces in detail the phenomena of linear and nonlinear light matter interaction, the properties of modern laser sources, and the concepts of quantum optics. Several examples taken from the scope of modern research are provided to emphasize the relevance of optics in current developments within science and technology. The text has been written for newcomers to the topic and benefits from the author's ability to explain difficult sequences and effects in a straightforward and easily comprehensible way. To this second, c

  13. Ions and light

    CERN Document Server

    Bowers, Michael T

    2013-01-01

    Gas Phase Ion Chemistry, Volume 3: Ions and Light discusses how ions are formed by electron impact, ion-molecule reactions, or electrical discharge. This book discusses the use of light emitted by excited molecules to characterize either the chemistry that formed the excited ion, the structure of the excited ion, or both.Organized into 10 chapters, this volume begins with an overview of the extension of the classical flowing afterglow technique to include infrared and chemiluminescence and laser-induced fluorescence detection. This text then examines the experiments involving molecules that ar

  14. Kinematics grounded on light

    CERN Document Server

    Neda, Zoltan

    2015-01-01

    The space-time of modern physics is tailored on light. We rigorously construct the basic entities needed by kinematics: geometry of the physical space and time, using as tool electromagnetic waves, and particularly light-rays. After such a mathematically orthodox construction, the special theory of relativity will result naturally. One will clearly understand and easily accept all those puzzling consequences that makes presently the special theory of relativity hard to digest. Such an approach is extremely rewarding in teaching the main ideas of Einstein's relativity theory for high-school and/or university students. Interesting speculations regarding the fundaments and future of physics are made.

  15. Light is Heavy

    CERN Document Server

    van der Mark, M B

    2015-01-01

    Einstein's relativity theory appears to be very accurate, but at times equally puzzling. On the one hand, electromagnetic radiation must have zero rest mass in order to propagate at the speed of light, but on the other hand, since it definitely carries momentum and energy, it has non-zero inertial mass. Hence, by the principle of equivalence, it must have non-zero gravitational mass, and so, light must be heavy. In this paper, no new results will be derived, but a possibly surprising perspective on the above paradox is given.

  16. Light scattering reviews 8 radiative transfer and light scattering

    CERN Document Server

    Kokhanovsky, Alexander A

    2013-01-01

    Light scattering review (vol 8) is aimed at the presentation of recent advances in radiative transfer and light scattering optics. The topics to be covered include: scattering of light by irregularly shaped particles suspended in atmosphere (dust, ice crystals), light scattering by particles much larger as compared the wavelength of incident radiation, atmospheric radiative forcing, astrophysical radiative transfer, radiative transfer and optical imaging in biological media, radiative transfer of polarized light, numerical aspects of radiative transfer.

  17. Light therapies for acne.

    Science.gov (United States)

    Barbaric, Jelena; Abbott, Rachel; Posadzki, Pawel; Car, Mate; Gunn, Laura H; Layton, Alison M; Majeed, Azeem; Car, Josip

    2016-09-27

    Acne vulgaris is a very common skin problem that presents with blackheads, whiteheads, and inflamed spots. It frequently results in physical scarring and may cause psychological distress. The use of oral and topical treatments can be limited in some people due to ineffectiveness, inconvenience, poor tolerability or side-effects. Some studies have suggested promising results for light therapies. To explore the effects of light treatment of different wavelengths for acne. We searched the following databases up to September 2015: the Cochrane Skin Specialised Register, CENTRAL, MEDLINE, Embase and LILACS. We searched ISI Web of Science and Dissertation Abstracts International (from inception). We also searched five trials registers, and grey literature sources. We checked the reference lists of studies and reviews and consulted study authors and other experts in the field to identify further references to relevant randomised controlled trials (RCTs). We updated these searches in July 2016 but these results have not yet been incorporated into the review. We included RCTs of light for treatment of acne vulgaris, regardless of language or publication status. We used standard methodological procedures expected by Cochrane. We included 71 studies, randomising a total of 4211 participants.Most studies were small (median 31 participants) and included participants with mild to moderate acne of both sexes and with a mean age of 20 to 30 years. Light interventions differed greatly in wavelength, dose, active substances used in photodynamic therapy (PDT), and comparator interventions (most commonly no treatment, placebo, another light intervention, or various topical treatments). Numbers of light sessions varied from one to 112 (most commonly two to four). Frequency of application varied from twice daily to once monthly.Selection and performance bias were unclear in the majority of studies. Detection bias was unclear for participant-assessed outcomes and low for investigator

  18. Light, colour and the eye

    CERN Document Server

    Sylvester, Doug

    1995-01-01

    These illuminating topics include ""Light and Color"", where students are introduced to luminous and illuminated objects, transparent, translucent and opaque objects, and investigate light's property of travelling in straight lines. Refraction, bending light and the use of prisms to ""break"" white light into the colors of the rainbow are also explored.

  19. Coupling light to periodic nanostructures

    NARCIS (Netherlands)

    Driessen, Eduard Frans Clemens

    2009-01-01

    This thesis describes coupling of light to periodic structures. A material is patterned with a regular pattern on a length scale comparable to the wavelength of light. With these structures, light can be manipulated very precisely. The structures find applications in semiconductor lasers, light emit

  20. Freeform reflectors for architectural lighting.

    Science.gov (United States)

    Zhu, Ruidong; Hong, Qi; Zhang, Hongxia; Wu, Shin-Tson

    2015-12-14

    We propose an improved method to design freeform reflectors for architectural lighting: one for accent lighting and another for large area wall washing. The designed freeform reflectors effectively distribute light fluxes over the target surfaces, and generate appropriate illumination patterns for comfortable visual environments, which provides greater flexibility for lighting designs, allows many challenging designs, and improves energy-efficiency simultaneously.

  1. Green light to slaughter

    NARCIS (Netherlands)

    Reinhart, T.

    2000-01-01

    In the Sharm-al-Sheikh summit last week, Barak got from the US his green light to slaughter. To judge by the Israeli media, what we have seen so far is just the prelude. "The most important time will come in the middle of next week, when...Israel will have to consider taking the initiative, rather t

  2. Conceptualization of Light Refraction

    Science.gov (United States)

    Sokolowski, Andrzej

    2013-01-01

    There have been a number of papers dealing quantitatively with light refraction. Yet the conceptualization of the phenomenon that sets the foundation for a more rigorous math analysis is minimized. The purpose of this paper is to fill that gap. (Contains 3 figures.)

  3. Lights and Larvae

    Science.gov (United States)

    TItlow, Josh; Anderson, Heidi; Cooper, Robin

    2014-01-01

    Switching genes between organisms and controlling an animal's brain using lasers may seem like science fiction, but with advancements in a technique called optogenetics, such experiments are now common in neuroscience research. Optogenetics combines recombinant DNA technology with a controlled light source to help researchers address…

  4. Space Made Light

    DEFF Research Database (Denmark)

    Gigone, Fabio

    2009-01-01

    These drawings, published in their first book "Space Made Light", reveal concepts and layouts, physical qualities and technological details, research procedures and origin of the materials, logistics and timetables of planning and realization. The diagrams have been conceived also for several...

  5. Plasmonics light modulators

    DEFF Research Database (Denmark)

    Babicheva, Viktoriia; Malureanu, Radu; Lavrinenko, Andrei

    Surface plasmon polaritons (SPPs) are waves propagating at the interface between a metal and a dielectric and, due to their tight confinement, may be used for nanoscale control of the light propagation. Thus, photonic integrated circuits can benefit from devices using SPPs because of their highly...

  6. Burnout and Light Treatment

    NARCIS (Netherlands)

    Meesters, Y.; Waslander, M.

    The core symptom of the burnout syndrome is emotional exhaustion, which leads to impaired functioning on the job. Studies of sufferers of seasonal affective disorders and of healthy people show that energy levels can be improved by exposing them to bright light. It is hypothesized that energy levels

  7. Faster Than Light Communication

    CERN Document Server

    Michalski, M

    1999-01-01

    If it is possible to measure any photon at arbitrary polarization state with the probability arbitrary close to 1, we can force photon from entangled photon pair to be measured in desired state and project the second photon to the parallel state. Measurement performed on the second photon (which is arbitrary far away from the first) makes possible faster than light communication.

  8. Light element ceramics

    OpenAIRE

    Rao, KJ; Varma, KBR; Raju, AR

    1988-01-01

    An overview of a few structually important light element ceramics is presented. Included in the overview are silicon nitide, sialon, aluminium nitride, boron carbide and silicon carbide. Methods of preparation, characterization and industrial applications of these ceramics are summarized. Mechanical properties, industrial production techniques and principal uses of these ceramics are emphasized.

  9. Light activated bionanodevices

    CSIR Research Space (South Africa)

    Sparrow, RW

    2006-02-27

    Full Text Available The aim of this research is to develop a device that will move a rod in 8 nm controllable steps. The researchers are utilising the biological principles and materials of photosynthetic light (energy) harvesting and transfer, ATPsynthase, ATP...

  10. Burnout and Light Treatment

    NARCIS (Netherlands)

    Meesters, Y.; Waslander, M.

    2010-01-01

    The core symptom of the burnout syndrome is emotional exhaustion, which leads to impaired functioning on the job. Studies of sufferers of seasonal affective disorders and of healthy people show that energy levels can be improved by exposing them to bright light. It is hypothesized that energy levels

  11. Light-Front QCD

    CERN Document Server

    Brodsky, S J

    2004-01-01

    In these lectures, I survey a number of applications of light-front methods to hadron and nuclear physics phenomenology and dynamics, Light-front Fock-state wavefunctions provide a frame-independent representation of hadrons in terms of their fundamental quark and gluon degrees of freedom. Nonperturbative methods for computing LFWFs in QCD are discussed, including string/gauge duality which predicts the power-law fall-off at high momentum transfer of light-front Fock-state hadronic wavefunctions with an arbitrary number of constituents and orbital angular momentum. The AdS/CFT correspondence has important implications for hadron phenomenology in the conformal limit, including an all-orders derivation of counting rules for exclusive processes. One can also compute the hadronic spectrum of near-conformal QCD assuming a truncated AdS/CFT space. The quantum fluctuations represented by the light-front Fock expansion leads to novel QCD phenomena such as color transparency, intrinsic heavy quark distributions, diffr...

  12. Radioluminescent polymer lights

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, G.A.; Nelson, D.A.; Molton, P.M.

    1990-09-01

    The preparation of radioluminescent light sources where the tritium is located on the aryl-ring in a polymer has been demonstrated with deuterium/tritium substitution. This report discusses tests, results, and future applications of radioluminescent polymers. 10 refs. (FI)

  13. Light water reactor program

    Energy Technology Data Exchange (ETDEWEB)

    Franks, S.M.

    1994-12-31

    The US Department of Energy`s Light Water Reactor Program is outlined. The scope of the program consists of: design certification of evolutionary plants; design, development, and design certification of simplified passive plants; first-of-a-kind engineering to achieve commercial standardization; plant lifetime improvement; and advanced reactor severe accident program. These program activities of the Office of Nuclear Energy are discussed.

  14. Polarized Light: Three Demonstrations.

    Science.gov (United States)

    Goehmann, Ruth; Welty, Scott

    1984-01-01

    Describes three demonstrations used in the Chicago Museum of Science and Industry polarized light show. The procedures employed are suitable for the classroom by using smaller polarizers and an overhead projector. Topic areas include properties of cellophane tape, nondisappearing arrows, and rope through a picket fence. (JN)

  15. Green light to slaughter

    NARCIS (Netherlands)

    Reinhart, T.

    2006-01-01

    In the Sharm-al-Sheikh summit last week, Barak got from the US his green light to slaughter. To judge by the Israeli media, what we have seen so far is just the prelude. "The most important time will come in the middle of next week, when...Israel will have to consider taking the initiative, rather t

  16. Photoacoustics with coherent light

    Directory of Open Access Journals (Sweden)

    Emmanuel Bossy

    2016-03-01

    Full Text Available Since its introduction in the mid-nineties, photoacoustic imaging of biological tissue has been one of the fastest growing biomedical imaging modality, and its basic principles are now considered as well established. In particular, light propagation in photoacoustic imaging is generally considered from the perspective of transport theory. However, recent breakthroughs in optics have shown that coherent light propagating through optically scattering medium could be manipulated towards novel imaging approaches. In this article, we first provide an introduction to the relevant concepts in the field, and then review the recent works showing that it is possible to exploit the coherence of light in conjunction with photoacoustics. We illustrate how the photoacoustic effect can be used as a powerful feedback mechanism for optical wavefront shaping in complex media, and conversely show how the coherence of light can be exploited to enhance photoacoustic imaging, for instance in terms of spatial resolution or for designing minimally invasive endoscopic devices. Finally, we discuss the current challenges and perspectives down the road towards practical applications in the field of photoacoustic imaging.

  17. Light in the temples.

    Science.gov (United States)

    Krupp, E. C.

    Contents: 1. The dawn of archaeoastronomy. 2. Stalking Lockyer. 3. Solar connotations at Karnak. 4. Solar sanctuaries at Abu Simbel. 5. Another look at the Sun. 6. The great temple of Amun-Re at Karnak. 7. The solar sanctuary of Hatshepsut's mortuary temple at Deir el-Bahri. 8. The Sun temple of Neuserre' at Abu Ghurab. 9. Shedding light on the temples.

  18. The yellow Light Offensive

    Institute of Scientific and Technical Information of China (English)

    2013-01-01

    Arevised traffic regulation, seen as the harshest ever by many, took effect on January 1. Accordingly, drivers who run yellow lights will have six points deducted from the 12 allocated on their licenses. Those who have any part of their vehicles crossing the line at the time of change will not be punished.

  19. High Brightness OLED Lighting

    Energy Technology Data Exchange (ETDEWEB)

    Spindler, Jeffrey [OLEDWorks LLC; Kondakova, Marina [OLEDWorks LLC; Boroson, Michael [OLEDWorks LLC; Hamer, John [OLEDWorks LLC

    2016-05-25

    In this work we describe the technology developments behind our current and future generations of high brightness OLED lighting panels. We have developed white and amber OLEDs with excellent performance based on the stacking approach. Current products achieve 40-60 lm/W, while future developments focus on achieving 80 lm/W or higher.

  20. Windows and lighting program

    Energy Technology Data Exchange (ETDEWEB)

    1990-06-01

    More than 30% of all energy use in buildings is attributable to two sources: windows and lighting. Together they account for annual consumer energy expenditures of more than $50 billion. Each affects not only energy use by other major building systems, but also comfort and productivity -- factors that influence building economics far more than does direct energy consumption alone. Windows play a unique role in the building envelope, physically separating the conditioned space from the world outside without sacrificing vital visual contact. Throughout the indoor environment, lighting systems facilitate a variety of tasks associated with a wide range of visual requirements while defining the luminous qualities of the indoor environment. Windows and lighting are thus essential components of any comprehensive building science program. Despite important achievements in reducing building energy consumption over the past decade, significant additional savings are still possible. These will come from two complementary strategies: (1) improve building designs so that they effectively apply existing technologies and extend the market penetration of these technologies; and (2) develop advanced technologies that increase the savings potential of each application. Both the Windows and Daylighting Group and the Lighting System Research Group have made substantial contributions in each of these areas, and continue to do so through the ongoing research summarized here. 23 refs., 16 figs.

  1. Angular Accelerating White Light

    CSIR Research Space (South Africa)

    Dudley, Angela L

    2015-08-01

    Full Text Available Shaping XVI, 958104, San Diego, California, United States, 09 August 2015 Angular Accelerating White Light Angela Dudley*a,b, Christian Vetterc , Alexander Szameitc , and Andrew Forbesa,b a CSIR National Laser Centre, PO Box 395, Pretoria 0001...

  2. Polarized Light: Three Demonstrations.

    Science.gov (United States)

    Goehmann, Ruth; Welty, Scott

    1984-01-01

    Describes three demonstrations used in the Chicago Museum of Science and Industry polarized light show. The procedures employed are suitable for the classroom by using smaller polarizers and an overhead projector. Topic areas include properties of cellophane tape, nondisappearing arrows, and rope through a picket fence. (JN)

  3. Light atmosphere in hospital wards

    DEFF Research Database (Denmark)

    Stidsen, Lone Mandrup

    Sociocultural aspects of light are important for the user experience of the atmosphere in a ward. According to the Danish Regulation for light in hospitals (DS703, 1983), a home-like feeling is required to support the patients, as they needa pleasant environment for their recovery. The term ‘Light...... the requirements. What does it mean to create a 'home-like' and 'pleasant or appealing' light in this context? Does the composition of CRI and degree of Kelvin tell it all? Is it enough information to provide a proper illumination in which the patient can have a homely and pleasant experience? The 'Model of Light...... from the Danish interior design magazine BO BEDRE.The findings show that the placement of light atmosphere in Denmark are determined as three horizontal light zones: 'High Lighting Zone', 'Center Lighting Zone' and 'Low Lighting Zone' An experimental study evaluates the experience of the atmosphere...

  4. Radioluminescent lighting technology

    Science.gov (United States)

    The glow-in-the-dark stereotype that characterizes the popular image of nuclear materials is not accidental. When the French scientist, Henri Becquerel, first discovered radioactivity in 1896, he was interested in luminescence. Radioluminescence, the production of light from a mixture of energetic and passive materials, is probably the oldest practical application of the unstable nucleus. Tritium based radioluminescent lighting, in spite of the biologically favorable character of the gaseous tritium isotope, was included in the general tightening of environmental and safety regulations. Tritium light manufacturers would have to meet two fundamental conditions: (1) The benefit clearly outweighed the risk, to the extent that even the perceived risk of a skeptical public would be overcome; and (2) The need was significant enough that the customer/user would be willing and able to afford the cost of regulation that was imposed both in the manufacture, use, and eventual disposal of nuclear materials. In 1981, researchers at Oak Ridge National Laboratory were investigating larger radioluminescent applications using byproduct nuclear material such as krypton-85, as well as tritium. By 1982, it appeared that large source, (100 Curies or more) tritium gas tube, lights might be useful for marking runways and drop zones for military operations and perhaps even special civilian aviation applications. The successful development of this idea depended on making the light bright enough and demonstrating that large gas tube sources could be used and maintained safely in the environment. The basic program goals were achieved. This is a detailed report of what they have learned, proven, and discovered.

  5. Analysis of light regime in continuous light distributions in photobioreactors.

    Science.gov (United States)

    Brindley, Celeste; Fernández, F G Acién; Fernández-Sevilla, J M

    2011-02-01

    Maximum photobioreactor (PBR) efficiency is a must in applications such as the obtention of microalgae-derived fuels. Improving PBR performance requires a better understanding of the "light regime", the varying irradiance that microalgal cells moving in a dense culture are exposed to. We propose a definition of light regime that can be used consistently to describe the continuously varying light patterns in PBRs as well as in light/dark cycles. Equivalent continuous and light/dark regimes have been experimentally compared and the results show that continuous variations are not well represented by light/dark cycles, as had been widely accepted. It has been shown that a correct light regime allows obtaining photosynthetic rates higher than the corresponding to continuous light, the so-called "flashing light effect" and that this is possible in commercial PBRs. A correct PBR operation could result in photosynthetic efficiency close to the optimum eight quanta per O(2).

  6. Light Localization in Slot Photonic Crystal Waveguide

    Institute of Scientific and Technical Information of China (English)

    WU Jun; PENG Chao; LI Yan-Ping; WANG Zi-Yu

    2009-01-01

    A single-mode photonic crystal waveguide with a linear tapered slot is presented, which can localize light spatially by changing the slot width. Its effective bandwidth is 52nm, from 150Onto to 1552nm. Along the tapered structure, the slot width is reduced, and the corresponding band curve shifts. The group velocity of light becomes zero at the band edge. Therefore, different frequency components of the guided light are slowed down and finally localized at correspondingly different widths inside a tapered slot photonic crystal waveguide. Furthermore, this structure can confine light wave in a narrow slot waveguide, which may effectively enhance the interaction between light and the low-index wave-guiding materials filled in the slot.

  7. OLEDS FOR GENERAL LIGHTING

    Energy Technology Data Exchange (ETDEWEB)

    Anil Duggal; Don Foust; Chris Heller; Bill Nealon; Larry Turner; Joe Shiang; Nick Baynes; Tim Butler; Nalin Patel

    2004-02-29

    The goal of this program was to reduce the long term technical risks that were keeping the lighting industry from embracing and developing organic light-emitting diode (OLED) technology for general illumination. The specific goal was to develop OLEDs for lighting to the point where it was possible to demonstrate a large area white light panel with brightness and light quality comparable to a fluorescence source and with an efficacy comparable to that of an incandescent source. it was recognized that achieving this would require significant advances in three area: (1) the improvement of white light quality for illumination, (2) the improvement of OLED energy efficiency at high brightness, and (3) the development of cost-effective large area fabrication techniques. The program was organized such that, each year, a ''deliverable'' device would be fabricated which demonstrated progress in one or more of the three critical research areas. In the first year (2001), effort concentrated on developing an OLED capable of generating high illumination-quality white light. Ultimately, a down-conversion method where a blue OLED was coupled with various down-conversion layers was chosen. Various color and scattering models were developed to aid in material development and device optimization. The first year utilized this approach to deliver a 1 inch x 1 inch OLED with higher illumination-quality than available fluorescent sources. A picture of this device is shown and performance metrics are listed. To their knowledge, this was the first demonstration of true illumination-quality light from an OLED. During the second year, effort concentrated on developing a scalable approach to large area devices. A novel device architecture consisting of dividing the device area into smaller elements that are monolithically connected in series was developed. In the course of this development, it was realized that, in addition to being scalable, this approach made the device

  8. Light, Matter, and Geometry

    DEFF Research Database (Denmark)

    Frisvad, Jeppe Revall

    2008-01-01

    This thesis is about physically-based modelling of the appearance of materials. When a material is graphically rendered, its appearance is computed by considering the interaction of light and matter at a macroscopic level. In particular, the shape and the macroscopic optical properties...... of the material determine how it will interact with incident illumination. In this thesis the macroscopic optical properties are connected to the microscopic physical theories of light and matter. This enables prediction of the macroscopic optical properties of materials, and, consequently, also prediction...... of appearance based on the contents and the physical conditions of the materials. Physically-based appearance models have many potential input and output parameters. There are many choices that must be made: How many material components to include in the model, how many physical conditions to take into account...

  9. Sun light European Project

    Science.gov (United States)

    Soubielle, Marie-Laure

    2015-04-01

    2015 has been declared the year of light. Sunlight plays a major role in the world. From the sunbeams that heat our planet and feed our plants to the optical analysis of the sun or the modern use of sun particles in technologies, sunlight is everywhere and it is vital. This project aims to understand better the light of the Sun in a variety of fields. The experiments are carried out by students aged 15 to 20 in order to share their discoveries with Italian students from primary and secondary schools. The experiments will also be presented to a group of Danish students visiting our school in January. All experiments are carried out in English and involve teams of teachers. This project is 3 folds: part 1: Biological project = what are the mechanisms of photosynthesis? part 2: Optical project= what are the components of sunlight and how to use it? part 3: Technical project= how to use the energy of sunlight for modern devices? Photosynthesis project Biology and English Context:Photosynthesis is a process used by plants and other organisms to convert light energy, normally from the Sun, into chemical energy that can later fuel the organisms' activities. This chemical energy is stored in molecules which are synthesized from carbon dioxide and water. In most cases, oxygen is released as a waste product. Most plants perform photosynthesis. Photosynthesis maintains atmospheric oxygen levels and supplies all of the organic compounds and most of the energy necessary for life on Earth. Outcome: Our project consists in understanding the various steps of photosynthesis. Students will shoot a DVD of the experiments presenting the equipments required, the steps of the experiments and the results they have obtained for a better understanding of photosynthesis Digital pen project Electricity, Optics and English Context: Sunlight is a complex source of light based on white light that can be decomposed to explain light radiations or colours. This light is a precious source to create

  10. Radiative light dark matter

    Science.gov (United States)

    Dedes, A.; Karamitros, D.; Pilaftsis, A.

    2017-06-01

    We present a Peccei-Quinn (PQ)-symmetric two-Higgs doublet model that naturally predicts a fermionic singlet dark matter in the mass range 10 keV-1 GeV. The origin of the smallness of the mass of this light singlet fermion arises predominantly at the one-loop level, upon soft or spontaneous breakdown of the PQ symmetry via a complex scalar field in a fashion similar to the so-called Dine-Fischler-Sredniki-Zhitnitsky axion model. The mass generation of this fermionic radiative light dark matter (RLDM) requires the existence of two heavy vectorlike SU(2) isodoublets, which are not charged under the PQ symmetry. We show how the RLDM can be produced via the freeze-in mechanism, thus accounting for the missing matter in the Universe. Finally, we briefly discuss possible theoretical and phenomenological implications of the RLDM model for the strong C P problem and the CERN Large Hadron Collider (LHC).

  11. [LED lights in dermatology].

    Science.gov (United States)

    Noé, C; Pelletier-Aouizerate, M; Cartier, H

    2017-01-16

    The use in dermatology of light-emitting diodes (LEDs) continues to be surrounded by controversy. This is due mainly to poor knowledge of the physicochemical phases of a wide range of devices that are difficult to compare to one another, and also to divergences between irrefutable published evidence either at the level of in vitro studies or at the cellular level, and discordant clinical results in a variety of different indications: rejuvenation, acne, wound healing, leg ulcers, and cutaneous inflammatory or autoimmune processes. Therapeutic LEDs can emit wavelengths ranging from the ultraviolet, through visible light, to the near infrared (247-1300 nm), but only certain bands have so far demonstrated any real value. We feel certain that if this article remains factual, then readers will have a different, or at least more nuanced, opinion concerning the use of such LED devices in dermatology.

  12. Fundamentals of Polarized Light

    Science.gov (United States)

    Mishchenko, Michael

    2003-01-01

    The analytical and numerical basis for describing scattering properties of media composed of small discrete particles is formed by the classical electromagnetic theory. Although there are several excellent textbooks outlining the fundamentals of this theory, it is convenient for our purposes to begin with a summary of those concepts and equations that are central to the subject of this book and will be used extensively in the following chapters. We start by formulating Maxwell's equations and constitutive relations for time- harmonic macroscopic electromagnetic fields and derive the simplest plane-wave solution that underlies the basic optical idea of a monochromatic parallel beam of light. This solution naturally leads to the introduction of such fundamental quantities as the refractive index and the Stokes parameters. Finally, we define the concept of a quasi-monochromatic beam of light and discuss its implications.

  13. Polarized Light from Jupiter

    Science.gov (United States)

    2001-01-01

    These images taken through the wide angle camera near closest approach in the deep near-infrared methane band, combined with filters which sense electromagnetic radiation of orthogonal polarization, show that the light from the poles is polarized. That is, the poles appear bright in one image, and dark in the other. Polarized light is most readily scattered by aerosols. These images indicate that the aerosol particles at Jupiter's poles are small and likely consist of aggregates of even smaller particles, whereas the particles at the equator and covering the Great Red Spot are larger. Images like these will allow scientists to ascertain the distribution, size and shape of aerosols, and consequently, the distribution of heat, in Jupiter's atmosphere.

  14. EDITORIAL: LED light sources (light for the future) LED light sources (light for the future)

    Science.gov (United States)

    Grandjean, N.

    2010-09-01

    Generating white light from electricity with maximum efficacy has been a long quest since the first incandescent lamp was invented by Edison at the end of the 19th century. Nowadays, semiconductors are making reality the holy grail of converting electrons into photons with 100% efficiency and with colours that can be mixed for white light illumination. The revolution in solid-state lighting (SSL) dates to 1994 when Nakamura reported the first high-brightness blue LED based on GaN semiconductors. Then, white light was produced by simply combining a blue dye with a yellow phosphor. After more than a decade of intensive research the performance of white LEDs is quite impressive, beating by far the luminous efficacy of compact fluorescent lamps. We are likely close to replacing our current lighting devices by SSL lamps. However, there are still technological and fabrication cost issues that could delay large market penetration of white LEDs. Interestingly, SSL may create novel ways of using light that could potentially limit electricity saving. Whatever the impact of SSL, it will be significant on our daily life. The purpose of this special cluster issue is to produce a snapshot of the current situation of SSL from different viewing angles. In an introductory paper, Tsao and co-workers from Sandia National Laboratories, present an energy-economics perspective of SSL considering societal changes and SSL technology evolution. In a second article, Narukawa et al working at Nichia Corporation—the pioneer and still the leading company in SSL—describe the state of the art of current research products. They demonstrate record performance with white LEDs exhibiting luminous efficacy of 183 lm W-1 at high-current injection. Then, a series of topical papers discuss in detail various aspects of the physics and technology of white LEDs Carrier localization in InGaN quantum wells has been considered the key to white LEDs' success despite the huge density of defects. A

  15. Scattering Of Light Nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Quaglioni, S; Navratil, P; Roth, R

    2009-12-15

    The exact treatment of nuclei starting from the constituent nucleons and the fundamental interactions among them has been a long-standing goal in nuclear physics. Above all nuclear scattering and reactions, which require the solution of the many-body quantum-mechanical problem in the continuum, represent an extraordinary theoretical as well as computational challenge for ab initio approaches.We present a new ab initio many-body approach which derives from the combination of the ab initio no-core shell model with the resonating-group method [4]. By complementing a microscopic cluster technique with the use of realistic interactions, and a microscopic and consistent description of the nucleon clusters, this approach is capable of describing simultaneously both bound and scattering states in light nuclei. We will discuss applications to neutron and proton scattering on sand light p-shell nuclei using realistic nucleon-nucleon potentials, and outline the progress toward the treatment of more complex reactions.

  16. Light cone matrix product

    Energy Technology Data Exchange (ETDEWEB)

    Hastings, Matthew B [Los Alamos National Laboratory

    2009-01-01

    We show how to combine the light-cone and matrix product algorithms to simulate quantum systems far from equilibrium for long times. For the case of the XXZ spin chain at {Delta} = 0.5, we simulate to a time of {approx} 22.5. While part of the long simulation time is due to the use of the light-cone method, we also describe a modification of the infinite time-evolving bond decimation algorithm with improved numerical stability, and we describe how to incorporate symmetry into this algorithm. While statistical sampling error means that we are not yet able to make a definite statement, the behavior of the simulation at long times indicates the appearance of either 'revivals' in the order parameter as predicted by Hastings and Levitov (e-print arXiv:0806.4283) or of a distinct shoulder in the decay of the order parameter.

  17. Visualizing stray light

    Science.gov (United States)

    Barron, Don R.

    1996-08-01

    Stray light in optical systems is usually assessed by techniques which are essentially similar to those used in the design synthesis of the system. In general however the dimensionality of the actual build of the system is far higher than that of the design and the traditional 'ray tracing' assessment techniques can become unmanageable. Modern computer graphics software developed for CAD and the entertainment industry has been applied to this problem at Pilkington Optronics as part of the process of integrated optomechanical design. This paper describes the relevant features of the new software packages as applied to the analysis of stray light and presents some results from particular systems. A useful feature of the technique is the use of animation to reduce the dimensionality; these examples cannot be presented here in written form but some simplified examples are available on request on 3.5 inch diskette format.

  18. LCC: Light Curves Classifier

    Science.gov (United States)

    Vo, Martin

    2017-08-01

    Light Curves Classifier uses data mining and machine learning to obtain and classify desired objects. This task can be accomplished by attributes of light curves or any time series, including shapes, histograms, or variograms, or by other available information about the inspected objects, such as color indices, temperatures, and abundances. After specifying features which describe the objects to be searched, the software trains on a given training sample, and can then be used for unsupervised clustering for visualizing the natural separation of the sample. The package can be also used for automatic tuning parameters of used methods (for example, number of hidden neurons or binning ratio). Trained classifiers can be used for filtering outputs from astronomical databases or data stored locally. The Light Curve Classifier can also be used for simple downloading of light curves and all available information of queried stars. It natively can connect to OgleII, OgleIII, ASAS, CoRoT, Kepler, Catalina and MACHO, and new connectors or descriptors can be implemented. In addition to direct usage of the package and command line UI, the program can be used through a web interface. Users can create jobs for ”training” methods on given objects, querying databases and filtering outputs by trained filters. Preimplemented descriptors, classifier and connectors can be picked by simple clicks and their parameters can be tuned by giving ranges of these values. All combinations are then calculated and the best one is used for creating the filter. Natural separation of the data can be visualized by unsupervised clustering.

  19. Faster than Light Neutrinos

    Institute of Scientific and Technical Information of China (English)

    Jarah Evslin

    2011-01-01

    In September, the OPERA experiment in Italy claimed to have observed neutrinos which travel faster than light. Strong experimental constraints are placed by neutrinos observed from the supernova SN1987A and from various terrestrial and astrophysical measurements of synchrotron radiation. I will review the many experimental and theoretical challenges faced by any theory which attempts to explain this result, and speculate on just which theories may succeed.

  20. Radioluminescent lighting program description

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1987-11-01

    For more than 30 years the Department of Energy (DOE) and its predecessor agencies have conducted research and development aimed at beneficial uses of products derived from its nuclear activities. An important and promising element of radiation technology is the Program for Radioluminescent (RL) development. For years simple RL devices, such as aircraft exit signs, have served necessary functions in society. Electrons exciting phosphors and producing light is a fundamental concept to which the layman can immediately relate, while gaining a balanced perspective concerning risk and safety. DOE`s RL lighting development program has advanced the technology with infrared RL markers for helipads which are not detectable without the aid of special viewers. These devices were used to aid in the evacuation of wounded from Grenada. Visible RL airfield lighting has been used to promote aviation safety in remote Eskimo communities in Alaska, and non-electric taxiway signs and markers in the corrosive saline soils of Florida airports. The current plan is to consolidate past accomplishments and develop RL devices and systems using advanced technology for new applications. The potential for improved performance that solid-matrix RL techniques offer has stimulated interest in a variety of innovative applications for which electric lighting has long been the only practical alternative. The program described in this document is intended to provide for an optimum development and application of RL technology while supporting the transfer of this technology to the private sector and providing an institutional perspective from which the longer range applications and ramifications of this technology can be anticipated.

  1. Green light to slaughter

    OpenAIRE

    Reinhart, T.

    2006-01-01

    In the Sharm-al-Sheikh summit last week, Barak got from the US his green light to slaughter. To judge by the Israeli media, what we have seen so far is just the prelude. "The most important time will come in the middle of next week, when...Israel will have to consider taking the initiative, rather than merely responding to events." (Ha'aretz, Amos Harel, Oct 19).

  2. Lighting – laboratory practice

    Directory of Open Access Journals (Sweden)

    Борис Васильевич Дзюндзюк

    2014-10-01

    Full Text Available In this article discussed one of the possible variants of the building study bench for laboratory work and practical lessons on the basic parameters of the study of artificial and natural lighting in the labour protection in accordance with the DBN V.2.5-28-2006. The model is on the latest LED components, which has high reliability, maintainability and eliminates the disadvantages of the existing laboratory stands.

  3. LIGHT*HOUSE

    DEFF Research Database (Denmark)

    Ibsen, Lars Bo; Nielsen, Benjamin; Madsen, Jesper V;

    Med udgangspunkt i det konkrete byggeprojekt Light*house, der skal opføres på Århus havn, er der i projektet foretaget en række analyser til bestemmelse af de geotekniske egenskaber for den fede tertiære ler fra søvindmergel-formationen, som findes på lokaliteten til stor dybde. Søvindmerglens...

  4. Squeezed light in semiconductors

    CERN Document Server

    Ward, M B

    2001-01-01

    Experimental evidence is presented for the generation of photon-number squeezed states of light as a result of multi-photon absorption. Photon-number squeezing as a result of non-linear absorption has long been predicted and results have been obtained utilising two very different material systems: (i) an AIGaAs waveguide in which high optical intensities can be maintained over a relatively long interaction length of 2 mm; (ii) the organic polymer p-toluene sulphonate polydiacetylene that is essentially a one-dimensional semiconductor possessing a highly nonlinear optical susceptibility. The resulting nonlinear absorption is shown to leave the transmitted light in a state that is clearly nonclassical, exhibiting photon-number fluctuations below the shot-noise limit. Tuning the laser wavelength across the half-bandgap energy has enabled a comparison between two- and three-photon processes in the semiconductor waveguide. The correlations created between different spectral components of a pulsed beam of light as ...

  5. Atypical Light Curves

    CERN Document Server

    Steenwyk, Steven D; Molnar, Lawrence A

    2013-01-01

    We have identified some two-hundred new variable stars in a systematic study of a data archive obtained with the Calvin-Rehoboth observatory. Of these, we present five close binaries showing behaviors presumably due to star spots or other magnetic activity. For context, we first present two new RS CVn systems whose behavior can be readily attribute to star spots. Then we present three new close binary systems that are rather atypical, with light curves that are changing over time in ways not easily understood in terms of star spot activity generally associated with magnetically active binary systems called RS CVn systems. Two of these three are contact binaries that exhibit gradual changes in average brightness without noticeable changes in light curve shape. A third system has shown such large changes in light curve morphology that we speculate this may be a rare instance of a system that transitions back and forth between contact and noncontact configurations, perhaps driven by magnetic cycles in at least o...

  6. Light shining through walls

    Energy Technology Data Exchange (ETDEWEB)

    Redondo, Javier [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Max-Planck-Institut fuer Physik, Muenchen (Germany); Ringwald, Andreas [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2010-11-15

    Shining light through walls? At first glance this sounds crazy. However, very feeble gravitational and electroweak effects allow for this exotic possibility. Unfortunately, with present and near future technologies the opportunity to observe light shining through walls via these effects is completely out of question. Nevertheless there are quite a number of experimental collaborations around the globe involved in this quest. Why are they doing it? Are there additional ways of sending photons through opaque matter? Indeed, various extensions of the standard model of particle physics predict the existence of new particles called WISPs - extremely weakly interacting slim particles. Photons can convert into these hypothetical particles, which have no problems to penetrate very dense materials, and these can reconvert into photons after their passage - as if light was effectively traversing walls. We review this exciting field of research, describing the most important WISPs, the present and future experiments, the indirect hints from astrophysics and cosmology pointing to the existence of WISPs, and finally outlining the consequences that the discovery of WISPs would have. (orig.)

  7. Fast Light Optical Gyroscopes

    Science.gov (United States)

    Smith, David D.

    2015-01-01

    Next-generation space missions are currently constrained by existing spacecraft navigation systems which are not fully autonomous. These systems suffer from accumulated dead-reckoning errors and must therefore rely on periodic corrections provided by supplementary technologies that depend on line-of-sight signals from Earth, satellites, or other celestial bodies for absolute attitude and position determination, which can be spoofed, incorrectly identified, occluded, obscured, attenuated, or insufficiently available. These dead-reckoning errors originate in the ring laser gyros themselves, which constitute inertial measurement units. Increasing the time for standalone spacecraft navigation therefore requires fundamental improvements in gyroscope technologies. One promising solution to enhance gyro sensitivity is to place an anomalous dispersion or fast light material inside the gyro cavity. The fast light essentially provides a positive feedback to the gyro response, resulting in a larger measured beat frequency for a given rotation rate as shown in figure 1. Game Changing Development has been investing in this idea through the Fast Light Optical Gyros (FLOG) project, a collaborative effort which began in FY 2013 between NASA Marshall Space Flight Center (MSFC), the U.S. Army Aviation and Missile Research, Development, and Engineering Center (AMRDEC), and Northwestern University. MSFC and AMRDEC are working on the development of a passive FLOG (PFLOG), while Northwestern is developing an active FLOG (AFLOG). The project has demonstrated new benchmarks in the state of the art for scale factor sensitivity enhancement. Recent results show cavity scale factor enhancements of approx.100 for passive cavities.

  8. Value metrics for better lighting

    CERN Document Server

    Rea, Mark S

    2012-01-01

    We often do not fully understand what lighting can do for us. We know that we need lighting, but often that is as far as the thinking goes. We do a really good job, however, of conceptualizing the costs of those lighting systems because we can readily measure those costs. Reducing costs will certainly increase the value ratio for lighting if the benefits of the lighting system are held constant. Without a clear purpose for the lighting system, and no clear idea of benefits, there is little else that can be used in the value engineering process. This book is dedicated to the notion that our s

  9. Imitating Broadband Diurnal Light Variations Using Solid State Light Sources

    Science.gov (United States)

    Ferguson, Ian; Melton, Andrew; Li, Nola; Nicol, David; Park, Eun Hyun; Tosini, Gianluca

    Many studies have documented the success of light therapy in treating disorders of the human internal clock (circadian rhythm). Recent biological research has shown the importance of developing light sources that are tunable in the blue region of the spectrum for treatment to be safe and effective. A novel tunable broadband solid-state light source is presented here that mimics the diurnal variation in sunlight by modulating the intensity of blue light emission.

  10. Pollution-free road lighting

    Science.gov (United States)

    Schreuder, Duco A.

    They relate to reducing road accidents and some forms of crime but also enhance the social safety of residents and pedestrians and the amenity for residents. Road traffic in developing countries is much more hazardous than in industrialized countries. Accident rates in 'low' income countries may be as much as 35 times higher than in 'high' income countries. Thus, it might be much more cost-effective to light roads in the developing world than in the industrialized world. Fighting light pollution is more pressing in developing countries as most of the major high-class astronomical observatories are there. Astronomical observations are disturbed by light from outdoor lighting installations, part of which is scattered in the atmosphere to form 'sky glow'. The International Lighting Commission CIE has published a Technical Report giving general guidance for lighting designers and policy makers on the reduction of the sky glow. Lighting improves visibility, essential for almost all human activity. However, light that hits the road contributes to visibility only if it is reflected. In poorly designed lighting equipment much of the lumen output of the lamps is sent directly upwards. This can be avoided by properly defined light fittings. The light output of fittings is determined by their optical quality and by the installation maintenance factor. Open fittings are to be preferred. If mounted horizontally, they make street lighting with the least light pollution.

  11. Organic light emitting diode with light extracting layer

    Science.gov (United States)

    Lu, Songwei

    2016-06-14

    A light extraction substrate includes a glass substrate having a first surface and a second surface. A light extraction layer is formed on at least one of the surfaces. The light extraction layer is a coating, such as a silicon-containing coating, incorporating nanoparticles.

  12. Dichromatic light halting using double spin coherence gratings

    Science.gov (United States)

    Ham, Byoung S.; Hahn, Joonseong

    2011-08-01

    Light control by another light has drawn much attention in nonlinear quantum optics. Achieving all-optical control of the refractive index has been a key issue in all-optical information processing. Ultraslow light has been a good candidate for this purpose, where a giant phase shift can be achieved. The recent presentation of stationary light utilizing ultraslow light is an advanced example of such research. The stationary light functions as cavity quantum electrodynamics, where no high-Q-factor mirror pair is needed. In this paper, we report on two-color halted light pulses inside a solid medium, where the trapping time is comparable with that of ultraslow light but is much longer than quantum mapping storage time. The observed two-color halted light is achieved by means of double Raman optical field-excited spin coherence gratings, where slow light enhanced backward nondegenerate four-wave mixing processes play a major role.

  13. Optimizing photosynthesis under fluctuating light

    DEFF Research Database (Denmark)

    Pesaresi, Paolo; Hertle, Alexander; Pribil, Mathias

    2010-01-01

    Optimal photosynthetic performance requires that equal amounts of light are absorbed by photosystem II (PSII) and photosystem I (PSi), which are functionally linked through the photosynthetic electron transport chain. However, photosynthetic organisms must cope with light conditions that lead to ...

  14. Issues of Rural Light Pollution

    Science.gov (United States)

    Osborn, W. H.; Hammer, R. L.; Hammer, A.

    2001-12-01

    Light pollution is generally considered mostly an urban problem. Common sources of light pollution are poorly designed lighting of streets, parking lots, businesses and advertizing signs and for security. These sources, and the amount of light pollution generated, increase with population density. Nevertheless, light pollution can also be significant in rural areas. Rural light pollution differs from that in urban settings, both in the types of pollution and in the means that must be employed to control it. In the country the offending sources are often isolated lights such as from farm barns, vacation cottages, radio and cell phone towers, and road intersections. A culture of strong property rights and privacy rights affects attempts to control rural light pollution. We describe how some of these issues may be addressed based on the results from an Eagle Scout project carried out in central Michigan.

  15. Lighting for Today and Tomorrow.

    Science.gov (United States)

    Murphy, Peter

    2000-01-01

    Discusses how technology has contributed to brighter, less expensive, and more efficient lighting. Four key areas where suspended Direct/Indirect lighting out performs parabolic troffers are examined. (GR)

  16. Photodetector with enhanced light absorption

    Science.gov (United States)

    Kane, James

    1985-01-01

    A photodetector including a light transmissive electrically conducting layer having a textured surface with a semiconductor body thereon. This layer traps incident light thereby enhancing the absorption of light by the semiconductor body. A photodetector comprising a textured light transmissive electrically conducting layer of SnO.sub.2 and a body of hydrogenated amorphous silicon has a conversion efficiency about fifty percent greater than that of comparative cells. The invention also includes a method of fabricating the photodetector of the invention.

  17. Tomographic imaging with polarized light.

    Science.gov (United States)

    Soloviev, Vadim Y; Zacharakis, Giannis; Spiliopoulos, George; Favicchio, Rosy; Correia, Teresa; Arridge, Simon R; Ripoll, Jorge

    2012-06-01

    We report three-dimensional tomographic reconstruction of optical parameters for the mesoscopic light scattering regime from experimentally obtained datasets by using polarized light. We present a numerically inexpensive approximation to the radiative transfer equation governing the polarized light transport. This approximation is employed in the reconstruction algorithm, which computes two optical parameters by using parallel and perpendicular polarizations of transmitted light. Datasets were obtained by imaging a scattering phantom embedding highly absorbing inclusions. Reconstruction results are presented and discussed.

  18. LIGHT-PENCIL COORDINATE POSITIONER,

    Science.gov (United States)

    information sources such as radar and IFF PPI repeaters and computer displays. A light pencil which detects and controls a positionand intensity...position the video gate which extracts desired signals from the radar/IFF returns without requiring the operator to hold the pencil in position. The light ...to-one light pencil motion to marker motion. Except for the light detection photomultipler, the entire design is solid state. (Author)

  19. On the photosynthetic responses of crops to intracanopy lighting with light emitting diodes

    NARCIS (Netherlands)

    Trouwborst, G.

    2011-01-01

    Key words: Cucumis sativus, intracanopy lighting, light-emitting diodes (LEDs), light distribution, light interception, light quality, photosynthesis, photosynthetic acclimation Assimilation lighting is a production factor of increasing importance in Dutch greenhouse horticulture. Assimilation

  20. Ultrathin ZnSe nanowires: one-pot synthesis via a heat-triggered precursor slow releasing route, controllable Mn doping and application in UV and near-visible light detection.

    Science.gov (United States)

    Li, Dong; Xing, Guanjie; Tang, Shilin; Li, Xiaohong; Fan, Louzhen; Li, Yunchao

    2017-10-12

    We report herein a heat-triggered precursor slow releasing route for the one-pot synthesis of ultrathin ZnSe nanowires (NWs), which relies on the gradual dissolving of Se powder into oleylamine containing a soluble Zn precursor under heating. This route allows the reaction system to maintain a high monomer concentration throughout the entire reaction process, thus enabling the generation of ZnSe NWs with diameter down to 2.1 nm and length approaching 400 nm. The size-dependent optical properties and band-edge energy levels of the ZnSe NWs were then explored in depth by UV-visible spectroscopy and cyclic voltammetry, respectively. Considering their unique absorption properties, these NWs were specially utilized for fabricating photoelectrochemical-type photodetectors (PDs). Impressively, the PDs based on the ZnSe NWs with diameters of 2.1 and 4.5 nm exhibited excellent responses to UVA and near-visible light, respectively: both possessed ultrahigh on/off ratios (5150 for UVA and 4213 for near-visible light) and ultrawide linear response ranges (from 2.0 to 9000 μW cm(-2) for UVA and 5.0 to 8000 μW cm(-2) for near-visible light). Furthermore, these ZnSe NWs were selectively doped with various amounts of Mn(2+) to tune their emission properties. As a result, ZnSe NW film-based photochromic cards were creatively developed for visually detecting UVA and near-visible radiation.

  1. Neurofilament light chain

    OpenAIRE

    Lu, CH; Macdonald-Wallis, C.; Gray, E; Pearce, N; Petzold, A; Norgren, N.; Giovannoni, G; Fratta, P.; Sidle, K.; Fish, M.; Orrell, R; Howard, R; Talbot, K.; Greensmith, L.; Kuhle, J

    2015-01-01

    OBJECTIVE: To test blood and CSF neurofilament light chain (NfL) levels in relation to disease progression and survival in amyotrophic lateral sclerosis (ALS). METHODS: Using an electrochemiluminescence immunoassay, NfL levels were measured in samples from 2 cohorts of patients with sporadic ALS and healthy controls, recruited in London (ALS/control, plasma: n = 103/42) and Oxford (ALS/control, serum: n = 64/36; paired CSF: n = 38/20). NfL levels in patients were measured at regular intervals...

  2. Light addressable gold electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Khalid, Waqas

    2011-07-01

    The main objective carried out in this dissertation was to fabricate Light Amplified Potentiometric sensors (LAPS) based upon the semiconductor nanoparticles (quantum dots) instead of its bulk form. Quantum dots (QDs) were opted for this device fabrication because of their superior fluorescent, electric and catalytic properties. Also in comparison to their bulk counterparts they will make device small, light weighted and power consumption is much lower. QDs were immobilized on a Au substrate via 1,4 benzene dithiol (BDT) molecule. Initially a self-assembled monolayer (SAM) of BDT was established on Au substrate. Because of SAM, the conductivity of Au substrate decreased dramatically. Furthermore QDs were anchored with the help of BDT molecule on Au substrate. When QDs immobilized on Au substrate (QD/Au) via BDT molecule were irradiated with UV-visible light, electron-hole pairs were generated in QDs. The surface defect states in QDs trapped the excited electrons and long lived electron-hole pairs were formed. By the application of an appropriate bias potential on Au substrate the electrons could be supplied or extracted from the QDs via tunneling through BDT. Thus a cathodic or anodic current could be observed depending upon bias potential under illumination. However without light illumination the QD/Au electrode remained an insulator. To improve the device different modifications were made, including different substrates (Au evaporated on glass, Au evaporated on mica sheets and Au sputtered on SiO{sub 2}/Si) and different dithiol molecules (capped and uncapped biphenyl 4,4' dithiol and capped and uncapped 4,4' dimercaptostilbenes) were tried. Also different QD immobilization techniques (normal incubation, spin coating, layer by layer assembly (LbL) of polyelectrolytes and heat immobilization) were employed. This device was able to detect electrochemically different analytes depending upon the QDs incorporated. For example CdS QDs were able to detect 4

  3. Coherent light microscopy

    CERN Document Server

    Ferraro, Pietro; Zalevsky, Zeev

    2011-01-01

    This book deals with the latest achievements in the field of optical coherent microscopy. While many other books exist on microscopy and imaging, this book provides a unique resource dedicated solely to this subject. Similarly, many books describe applications of holography, interferometry and speckle to metrology but do not focus on their use for microscopy. The coherent light microscopy reference provided here does not focus on the experimental mechanics of such techniques but instead is meant to provide a users manual to illustrate the strengths and capabilities of developing techniques. Th

  4. Experiments with twisted light

    Science.gov (United States)

    Courtial, J.; O'Holleran, K.

    2007-06-01

    The generic that is, stable under perturbations nodes of the field in a monochromatic light beam are optical vortices. We describe here their connection to Chladni's nodal lines in the oscillations of metal plates, as well as a few experiments that have been performed with optical vortices. We will describe how optical vortices can be generated experimentally; how it can be shown that they possess orbital angular momentum; how individual photons can be sorted according to their vortex state; and how optical vortices can be used to demonstrate higher-dimensional quantum entanglement.

  5. Wiring and lighting

    CERN Document Server

    Kitcher, Chris

    2013-01-01

    Wiring and Lighting provides a comprehensive guide to DIY wiring around the home. It sets out the regulations and legal requirements surrounding electrical installation work, giving clear guidelines that will enable the reader to understand what electrical work they are able to carry out, and what the testing and certification requirements are once the work is completed. Topics covered include: Different types of circuits; Types of cables and cable installation under floors and through joists; Isolating, earthing and bonding; Accessory boxes and fixings; Voltage bands; Detailed advice on safe

  6. Lighting with laser diodes

    Science.gov (United States)

    Basu, Chandrajit; Meinhardt-Wollweber, Merve; Roth, Bernhard

    2013-08-01

    Contemporary white light-emitting diodes (LEDs) are much more efficient than compact fluorescent lamps and hence are rapidly capturing the market for general illumination. LEDs are also replacing halogen lamps or even newer xenon based lamps in automotive headlamps. Because laser diodes are inherently much brighter and often more efficient than corresponding LEDs, there is great research interest in developing laser diode based illumination systems. Operating at higher current densities and with smaller form factors, laser diodes may outperform LEDs in the future. This article reviews the possibilities and challenges in the integration of visible laser diodes in future illumination systems.

  7. Light Cone Current Algebra

    CERN Document Server

    Fritzsch, Harald

    2003-01-01

    This talk follows by a few months a talk by the same authors on nearly the same subject at the Coral Gables Conference. The ideas presented here are basically the same, but with some amplification, some change of viewpoint, and a number of new questions for the future. For our own convenience, we have transcribed the Coral Gables paper, but with an added ninth section, entitled "Problems of light cone current algebra", dealing with our present views and emphasizing research topics that require study.

  8. Pedestrian Friendly Outdoor Lighting

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Naomi J.; Koltai, Rita; McGowan, Terry

    2013-12-31

    This GATEWAY report discusses the problems of pedestrian lighting that occur with all technologies with a focus on the unique optical options and opportunities offered by LEDs through the findings from two pedestrian-focused projects, one at Stanford University in California, and one at the Chautauqua Institution in upstate New York. Incorporating user feedback this report reviews the tradeoffs that must be weighed among visual comfort, color, visibility, efficacy and other factors to stimulate discussion among specifiers, users, energy specialists, and in industry in hopes that new approaches, metrics, and standards can be developed to support pedestrian-focused communities, while reducing energy use.

  9. Tunnel of light

    Science.gov (United States)

    Ohlmann, Dietmar

    1998-02-01

    When I made the decision to give up science for becoming a painter I could not imagine that I would paint light. In the 2nd year of my fine art studies I had my first contact with holography, thanks to my former tutor, Roddney Murray at the Liverpool School of Art. During the MA course of the RCA in London I knew that the potential of holography was far beyond our present perception. Since I had the opportunity to work in large scale, doing architectural installation, I have got certain that holography and diffraction media would set new trends into the arts and society.

  10. Light relations in orchard systems

    NARCIS (Netherlands)

    Wagenmakers, P.S.

    1995-01-01

    The optimization of light interception is essential for the production of highquality fruit. High light interception is required for high yields, whereas insufficient light exposure may lead to inferior flowering and a reduction of many characteristics of fruit quality. Orchard

  11. Light, Gravity and Black Holes

    Science.gov (United States)

    Falla, David

    2012-01-01

    The nature of light and how it is affected by gravity is discussed. Einstein's prediction of the deflection of light as it passes near the Sun was verified by observations made during the solar eclipse of 1919. Another prediction was that of gravitational redshift, which occurs when light emitted by a star loses energy in the gravitational field…

  12. Light, Gravity and Black Holes

    Science.gov (United States)

    Falla, David

    2012-01-01

    The nature of light and how it is affected by gravity is discussed. Einstein's prediction of the deflection of light as it passes near the Sun was verified by observations made during the solar eclipse of 1919. Another prediction was that of gravitational redshift, which occurs when light emitted by a star loses energy in the gravitational field…

  13. Measuring Light with Useful Tools

    Science.gov (United States)

    Peek, Gina; Hebert, Paulette; Frazier, Robert Scott; Knag, Mihyun

    2013-01-01

    Lighting, a necessary part of our home and work environment, is often considered as an afterthought. This article describes tools that Extension educators (Agriculture, Family and Consumer Sciences, and 4-H) can use to measure light levels. 4-H youth may also participate. These tools include light meters and Illuminating Engineering Society (IES)…

  14. Light relations in orchard systems

    NARCIS (Netherlands)

    Wagenmakers, P.S.

    1995-01-01

    The optimization of light interception is essential for the production of highquality fruit. High light interception is required for high yields, whereas insufficient light exposure may lead to inferior flowering and a reduction of many characteristics of fruit quality. Orchard configuratio

  15. White Light Heterodyne Interferometry SNR

    Science.gov (United States)

    2015-04-09

    for Research and Engineering under Air Force Contract FA8721-05-C-0002. Approved for public release; distribution is unlimited. White Light ...White Light Heterodyne Interferometry SNR J.B. Ashcom Group 91...public release; distribution is unlimited. ii ABSTRACT White light heterodyne interferometry is a powerful technique for obtaining high-angular

  16. Measuring Light with Useful Tools

    Science.gov (United States)

    Peek, Gina; Hebert, Paulette; Frazier, Robert Scott; Knag, Mihyun

    2013-01-01

    Lighting, a necessary part of our home and work environment, is often considered as an afterthought. This article describes tools that Extension educators (Agriculture, Family and Consumer Sciences, and 4-H) can use to measure light levels. 4-H youth may also participate. These tools include light meters and Illuminating Engineering Society (IES)…

  17. Light Converting Inorganic Phosphors for White Light-Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Chiao-Wen Yeh

    2010-03-01

    Full Text Available White light-emitting diodes (WLEDs have matched the emission efficiency of florescent lights and will rapidly spread as light source for homes and offices in the next 5 to 10 years. WLEDs provide a light element having a semiconductor light emitting layer (blue or near-ultraviolet (nUV LEDs and photoluminescence phosphors. These solid-state LED lamps, rather than organic light emitting diode (OLED or polymer light-emitting diode (PLED, have a number of advantages over conventional incandescent bulbs and halogen lamps, such as high efficiency to convert electrical energy into light, reliability and long operating lifetime. To meet with the further requirement of high color rendering index, warm light with low color temperature, high thermal stability and higher energy efficiency for WLEDs, new phosphors that can absorb excitation energy from blue or nUV LEDs and generate visible emissions efficiently are desired. The criteria of choosing the best phosphors, for blue (450-480 nm and nUV (380-400 nm LEDs, strongly depends on the absorption and emission of the phosphors. Moreover, the balance of light between the emission from blue-nUV LEDs and the emissions from phosphors (such as yellow from Y3Al5O12:Ce3+ is important to obtain white light with proper color rendering index and color temperature. Here, we will review the status of phosphors for LEDs and prospect the future development.

  18. Assessing Light Pollution in China Based on Nighttime Light Imagery

    Directory of Open Access Journals (Sweden)

    Wei Jiang

    2017-02-01

    Full Text Available Rapid urbanization and economic development inevitably lead to light pollution, which has become a universal environmental issue. In order to reveal the spatiotemporal patterns and evolvement rules of light pollution in China, images from 1992 to 2012 were selected from the Defense Meteorological Satellite Program Operational Linescan System (DMSP/OLS and systematically corrected to ensure consistency. Furthermore, we employed a linear regression trend method and nighttime light index method to demonstrate China’s light pollution characteristics across national, regional, and provincial scales, respectively. We found that: (1 China’s light pollution expanded significantly in provincial capital cities over the past 21 years and hot-spots of light pollution were located in the eastern coastal region. The Yangtze River Delta, Pearl River Delta, and Beijing–Tianjin–Hebei regions have formed light pollution stretch areas; (2 China’s light pollution was mainly focused in areas of north China (NC and east China (EC, which, together, accounted for over 50% of the light pollution for the whole country. The fastest growth of light pollution was observed in northwest China (NWC, followed by southwest China (SWC. The growth rates of east China (EC, central China (CC, and northeast China (NEC were stable, while those of north China (NC and south China (SC declined; (3 Light pollution at the provincial scale was mainly located in the Shandong, Guangdong, and Hebei provinces, whereas the fastest growth of light pollution was in Tibet and Hainan. However, light pollution levels in the developed provinces (Hong Kong, Macao, Shanghai, and Tianjin were higher than those of the undeveloped provinces. Similarly, the light pollution heterogeneities of Taiwan, Beijing, and Shanghai were higher than those of undeveloped western provinces.

  19. Slowing and cooling of heavy or light (even with a tiny electric dipole moment) polar molecules using a novel, versatile electrostatic Stark decelerator.

    Science.gov (United States)

    Wang, Qin; Hou, Shunyong; Xu, Liang; Yin, Jianping

    2016-02-21

    To meet some demands for realizing precise measurements of an electric dipole moment of electron (eEDM) and examining cold collisions or cold chemical physics, we have proposed a novel, versatile electrostatic Stark decelerator with an array of true 3D electric potential wells, which are created by a series of horizontally-oriented, U-shaped electrodes with time-sequence controlling high voltages (± HV) and two guiding electrodes with a constant voltage. We have calculated the 2D electric field distribution, the Stark shifts of the four lowest rotational sub-levels of PbF molecules in the X1(2)Π1/2(v = 0) electronic and vibrational ground states as well as the population in the different rotational levels. We have discussed the 2D longitudinal and transverse phase-space acceptances of PbF molecules in our decelerator. Subsequently, we have simulated the dynamic processes of the decelerated PbF molecules using the 3D Monte-Carlo method, and have found that a supersonic PbF beam with a velocity of 300 m s(-1) can be efficiently slowed to about 5 m s(-1), which will greatly enhance the sensitivities to research a parity violation and measure an eEDM. In addition, we have investigated the dependences of the longitudinal velocity spread, longitudinal temperature and bunching efficiency on both the number of guiding stages and high voltages, and found that after bunching, a cold packet of PbF molecules in the J = 7/2, MΩ = -7/4 state with a longitudinal velocity spread of 0.69 m s(-1) (corresponding to a longitudinal temperature of 2.35 mK) will be produced by our high-efficient decelerator, which will generate a high energy-resolution molecular beam for studying cold collision physics. Finally, our novel decelerator can also be used to efficiently slow NO molecules with a tiny electric dipole moment (EDM) of 0.16 D from 315 m s(-1) to 28 m s(-1). It is clear that our proposed new decelerator has a good slowing performance and experimental feasibility as well as wide

  20. GreenLight Model 960.

    Science.gov (United States)

    Fernandes, Richard; Carey, Conn; Hynes, James; Papkovsky, Dmitri

    2013-01-01

    The importance of food safety has resulted in a demand for a more rapid, high-throughput method for total viable count (TVC). The industry standard for TVC determination (ISO 4833:2003) is widely used but presents users with some drawbacks. The method is materials- and labor-intensive, requiring multiple agar plates per sample. More importantly, the method is slow, with 72 h typically required for a definitive result. Luxcel Biosciences has developed the GreenLight Model 960, a microtiter plate-based assay providing a rapid high-throughput method of aerobic bacterial load assessment through analysis of microbial oxygen consumption. Results are generated in 1-12 h, depending on microbial load. The mix and measure procedure allows rapid detection of microbial oxygen consumption and equates oxygen consumption to microbial load (CFU/g), providing a simple, sensitive means of assessing the microbial contamination levels in foods (1). As bacteria in the test sample grow and respire, they deplete O2, which is detected as an increase in the GreenLight probe signal above the baseline level (2). The time required to reach this increase in signal can be used to calculate the CFU/g of the original sample, based on a predetermined calibration. The higher the initial microbial load, the earlier this threshold is reached (1).