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Sample records for enhanced four-wave mixing

  1. Resonantly enhanced four-wave mixing

    DOEpatents

    Begley, Richard F.; Kurnit, Norman A.

    1978-01-01

    A method and apparatus for achieving large susceptibilities and long interaction lengths in the generation of new wavelengths in the infrared spectral region. A process of resonantly enhanced four-wave mixing is employed, utilizing existing laser sources, such as the CO.sub.2 laser, to irradiate a gaseous media. The gaseous media, comprising NH.sub.3, CH.sub.3 F, D.sub.2, HCl, HF, CO, and H.sub.2 or some combination thereof, are of particular interest since they are capable of providing high repetition rate operation at high flux densities where crystal damage problems become a limitation.

  2. Signal enhancement in collinear four-wave mixing

    SciTech Connect

    McKinstrie, C.J.; Luther, G.G.; Batha, S. )

    1990-03-01

    The solitary-wave solutions of the four-wave equations are studied, and their relevance to four-wave mixing in finite media is discussed. In general, the transfer of action from the pump waves to the probe and signal waves is limited by nonlinear phase shifts that detune the interaction. However, by controlling the linear phase mismatch judiciously, it is often possible to effect a complete transfer of action from the pump waves to the probe and signal waves.

  3. Enhanced four-wave mixing with nonlinear plasmonic metasurfaces

    PubMed Central

    Jin, Boyuan; Argyropoulos, Christos

    2016-01-01

    Plasmonic metasurfaces provide an effective way to increase the efficiency of several nonlinear processes while maintaining nanoscale dimensions. In this work, nonlinear metasurfaces based on film-coupled silver nanostripes loaded with Kerr nonlinear material are proposed to achieve efficient four-wave mixing (FWM). Highly localized plasmon resonances are formed in the nanogap between the metallic film and nanostripes. The local electric field is dramatically enhanced in this subwavelength nanoregion. These properties combined with the relaxed phase matching condition due to the ultrathin area lead to a giant FWM efficiency, which is enhanced by nineteen orders of magnitude compared to a bare silver screen. In addition, efficient visible and low-THz sources can be constructed based on the proposed nonlinear metasurfaces. The FWM generated coherent wave has a directional radiation pattern and its output power is relatively insensitive to the incident angles of the excitation sources. This radiated power can be further enhanced by increasing the excitation power. The dielectric nonlinear material placed in the nanogap is mainly responsible for the ultrastrong FWM response. Compact and efficient wave mixers and optical sources spanning different frequency ranges are envisioned to be designed based on the proposed nonlinear metasurface designs. PMID:27345755

  4. Enhanced four-wave mixing with nonlinear plasmonic metasurfaces.

    PubMed

    Jin, Boyuan; Argyropoulos, Christos

    2016-06-27

    Plasmonic metasurfaces provide an effective way to increase the efficiency of several nonlinear processes while maintaining nanoscale dimensions. In this work, nonlinear metasurfaces based on film-coupled silver nanostripes loaded with Kerr nonlinear material are proposed to achieve efficient four-wave mixing (FWM). Highly localized plasmon resonances are formed in the nanogap between the metallic film and nanostripes. The local electric field is dramatically enhanced in this subwavelength nanoregion. These properties combined with the relaxed phase matching condition due to the ultrathin area lead to a giant FWM efficiency, which is enhanced by nineteen orders of magnitude compared to a bare silver screen. In addition, efficient visible and low-THz sources can be constructed based on the proposed nonlinear metasurfaces. The FWM generated coherent wave has a directional radiation pattern and its output power is relatively insensitive to the incident angles of the excitation sources. This radiated power can be further enhanced by increasing the excitation power. The dielectric nonlinear material placed in the nanogap is mainly responsible for the ultrastrong FWM response. Compact and efficient wave mixers and optical sources spanning different frequency ranges are envisioned to be designed based on the proposed nonlinear metasurface designs.

  5. Enhancing four-wave-mixing processes by nanowire arrays coupled to a gold film.

    PubMed

    Poutrina, Ekaterina; Ciracì, Cristian; Gauthier, Daniel J; Smith, David R

    2012-05-07

    We consider the process of four-wave mixing in an array of gold nanowires strongly coupled to a gold film. Using full-wave simulations, we perform a quantitative comparison of the four-wave mixing efficiency associated with a bare film and films with nanowire arrays. We find that the strongly localized surface plasmon resonances of the coupled nanowires provide an additional local field enhancement that, along with the delocalized surface plasmon of the film, produces an overall four-wave mixing efficiency enhancement of up to six orders of magnitude over that of the bare film. The enhancement occurs over a wide range of excitation angles. The film-coupled nanowire array is easily amenable to nanofabrication, and could find application as an ultra-compact component for integrated photonic and quantum optic systems.

  6. Four-wave mixing analysis of quantum dot semiconductor lasers for linewidth enhancement factor extraction.

    PubMed

    Lin, Chih-Hao; Lin, Hung-Hsin; Lin, Fan-Yi

    2012-01-02

    We apply a four-wave mixing analysis on a quantum dot laser to simultaneously obtain the linewidth enhancement factor α and other intrinsic laser parameters. By fitting the experimentally obtained regenerative signals and power spectra at different detuning frequencies with the respective curves analytically calculated from the rate equations, parameters including the linewidth enhancement factor, the carrier decay rate in the dots, the differential gain, and the photon decay rate can be determined all at once under the same operating conditions. In this paper, a theoretical model for the four-wave mixing analysis of the QD lasers is derived and verified. The sensitivity and accuracy of the parameter extraction using the four-wave mixing method are presented. Moreover, how each each parameters alter the shapes of the regenerative signals and the power spectra are also discussed.

  7. Waveguide Four-Wave Mixing

    DTIC Science & Technology

    1991-10-01

    PL-TR--91-1045 /’--"PL-TR-- AD-A243 555 91-1045 WAVEGUIDE FOUR -WAVE MIXING Thomas B. Simpson Jia-ming Liu JAYCOR San Diego, CA 92186-5154 October...Final Report; May 88 - Mar 91 4. TITLE AND SUBTITLE 5. FUNDING NUMBERS WAVEGUIDE FOUR -WAVE MIXING C: F29601-88-C-0023 PE: 62601F PR: 3326 6. AUTHOR(S...for public release; distribution unlimited. 13. ABSTRACT (Maximum 200 words) This program has investigated four -wave mixing (4-win) in non- linear

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

    PubMed

    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.

  9. Optical cavity for enhanced parametric four-wave mixing in rubidium

    NASA Astrophysics Data System (ADS)

    Brekke, E.; Potier, S.

    2017-01-01

    We demonstrate the implementation of a ring cavity to enhance the efficiency of parametric four-wave mixing in rubidium. Using an input coupler with 95% reflectance, a finesse of 19.6$\\pm$0.5 is achieved with a rubidium cell inside. This increases the circulating intensity by a factor of 5.6$\\pm$0.5, and through two-photon excitation on the $5s_{1/2}\\rightarrow5d_{5/2}$ transition with a single excitation laser, up to 1.9$\\pm$0.3 mW of power at 420 nm is generated, 50 times what was previously generated with this scheme. The dependence of the output on Rb density and input power has been explored, suggesting the process may be approaching saturation. The blue output of the cavity also shows greatly improved spatial quality, combining to make this a promising source of 420 nm light for future experiments.

  10. Enhanced four-wave mixing in a hollow-core photonic-crystal fiber.

    PubMed

    Konorov, S O; Fedotov, A B; Zheltikov, A M

    2003-08-15

    Hollow-core photonic-crystal fibers are shown to substantially enhance four-wave mixing (FWM) of laser pulses in a gas filling the fiber core. Picosecond pulses of Nd:YAG fundamental radiation and its second harmonic are used to generate a signal at the frequency of the third harmonic by the FWM process 3omega = 2omega + 2omega - omega. The efficiency achieved for this process in a 9-cm-long, 13-microm-hollow-core-diameter photonic-crystal fiber, designed to simultaneously transmit a two-color pump and the FWM signal, is shown to be approximately 800 times higher than the maximum FWM efficiency attainable with the same laser pulses in the tight-focusing regime.

  11. Enhanced four-wave mixing via photonic bandgap coupled defect resonances.

    PubMed

    Blair, S

    2005-05-16

    Frequency conversion efficiency via four-wave mixing in coupled 1-D photonic crystal defect structures is studied numerically. In structures where all interacting frequencies coincide with intraband defect resonances, energy conversion efficiencies greater than 5% are predicted. Because the frequency spacings are determined by the free-spectral range, thereby requiring long defects for small spacings using intraband resonances, four-wave mixing using coupled-defect miniband resonances in more compact structures is also studied. Conversion efficiencies of greater than 1% are obtained in this case.

  12. Rational design of metallic nanocavities for resonantly enhanced four-wave mixing

    PubMed Central

    Almeida, Euclides; Prior, Yehiam

    2015-01-01

    Optimizing the shape of nanostructures and nano-antennas for specific optical properties has evolved to be a very fruitful activity. With modern fabrication tools a large variety of possibilities is available for shaping both nanoparticles and nanocavities; in particular nanocavities in thin metal films have emerged as attractive candidates for new metamaterials and strong linear and nonlinear optical systems. Here we rationally design metallic nanocavities to boost their Four-Wave Mixing response by resonating the optical plasmonic resonances with the incoming and generated beams. The linear and nonlinear optical responses as well as the propagation of the electric fields inside the cavities are derived from the solution of Maxwell’s equations by using the 3D finite-differences time domain method. The observed conversion-efficiency of near-infrared to visible light equals or surpasses that of BBO of equivalent thickness. Implications to further optimization for efficient and broadband ultrathin nonlinear optical materials are discussed. PMID:25974175

  13. Rational design of metallic nanocavities for resonantly enhanced four-wave mixing.

    PubMed

    Almeida, Euclides; Prior, Yehiam

    2015-05-14

    Optimizing the shape of nanostructures and nano-antennas for specific optical properties has evolved to be a very fruitful activity. With modern fabrication tools a large variety of possibilities is available for shaping both nanoparticles and nanocavities; in particular nanocavities in thin metal films have emerged as attractive candidates for new metamaterials and strong linear and nonlinear optical systems. Here we rationally design metallic nanocavities to boost their Four-Wave Mixing response by resonating the optical plasmonic resonances with the incoming and generated beams. The linear and nonlinear optical responses as well as the propagation of the electric fields inside the cavities are derived from the solution of Maxwell's equations by using the 3D finite-differences time domain method. The observed conversion-efficiency of near-infrared to visible light equals or surpasses that of BBO of equivalent thickness. Implications to further optimization for efficient and broadband ultrathin nonlinear optical materials are discussed.

  14. Four-wave mixing in photonic crystal waveguides: slow light enhancement and limitations.

    PubMed

    Li, Juntao; O'Faolain, Liam; Rey, Isabella H; Krauss, Thomas F

    2011-02-28

    We demonstrate continuous wave four-wave mixing in silicon photonic crystal waveguides of 396 μm length with a group index of ng=30. The highest observed conversion efficiency is -24 dB for 90 mW coupled input pump power. The key question we address is whether the predicted fourth power dependence of the conversion efficiency on the slowdown factor (η≈S4) can indeed be observed in this system, and how the conversion efficiency depends on device length in the presence of propagation losses. We find that the expected dependencies hold as long as both realistic losses and the variation of mode shape with slowdown factor are taken into account. Having achieved a good agreement between a simple analytical model and the experiment, we also predict structures that can achieve the same conversion efficiency as already observed in nanowires for the same input power, yet for a device length that is 50 times shorter.

  15. Enhanced four-wave-mixing effects by large group indices of one-dimensional silicon photonic crystal waveguides.

    PubMed

    Kim, Dong Wook; Kim, Seung Hwan; Lee, Seoung Hun; Jong, Heung Sun; Lee, Jong-Moo; Lee, El-Hang; Kim, Kyong Hon

    2013-12-02

    Enhanced four-wave-mixing (FWM) effects have been observed with the help of large group-indices near the band edges in one-dimensional (1-D) silicon photonic crystal waveguides (Si PhCWs). A significant increase of the FWM conversion efficiency of about 17 dB was measured near the transmission band edge of the 1-D PhCW through an approximate 3.2 times increase of the group index from 8 to 24 with respect to the central transmission band region despite a large group-velocity dispersion. Numerical analyses based on the coupled-mode equations for the degenerated FWM process describe the experimentally measured results well. Our results indicate that the 1-D PhCWs are good candidates for large group-index enhanced nonlinearity devices even without having any special dispersion engineering.

  16. Enhanced intermodal four-wave mixing for visible and near-infrared wavelength generation in a photonic crystal fiber.

    PubMed

    Yuan, Jinhui; Sang, Xinzhu; Wu, Qiang; Zhou, Guiyao; Li, Feng; Zhou, Xian; Yu, Chongxiu; Wang, Kuiru; Yan, Binbin; Han, Ying; Tam, Hwa Yaw; Wai, P K A

    2015-04-01

    We demonstrate experimentally an enhanced intermodal four-wave mixing (FWM) process through coupling positively chirped femtosecond pulses into the deeply normal dispersion region of the fundamental mode of an in-house fabricated photonic crystal fiber (PCF). In the intermodal phase-matching scheme, the energy of the pump waves at 800 nm in the fundamental mode is efficiently converted into the anti-Stokes waves around 553 nm and the Stokes waves within the wavelength range of 1445-1586 nm in the second-order mode. The maximum conversion efficiency of η(as) and η(s) of anti-Stokes and Stokes waves can be up to 21% and 16%, respectively. The Stokes frequency shift Ω is 5580  cm(-1). The fiber bending and intermodal walk-off effect of pulses do not have significant influence on the nonlinear optical process.

  17. Imaging the uptake of gold nanoshells in live cells using plasmon resonance enhanced four wave mixing microscopy.

    PubMed

    Garrett, Natalie; Whiteman, Matt; Moger, Julian

    2011-08-29

    Gold nanoshells (GNS) are novel metal nanoparticles exhibiting attractive optical properties which make them highly suitable for biophotonics applications. We present a novel investigation using plasmon-enhanced four wave mixing microscopy combined with coherent anti-Stokes Raman scattering (CARS) microscopy to visualize the distribution of 75 nm radius GNS within live cells. During a laser tolerance study we found that cells containing nanoshells could be exposed to < 2.5 mJ each with no photo-thermally induced necrosis detected, while cell death was linearly proportional to the power over this threshold. The majority of the GNS signal detected was from plasmon-enhanced four wave mixing (FWM) that we detected in the epi-direction with the incident lasers tuned to the silent region of the Raman spectrum. The cellular GNS distribution was visualized by combining the epi-detected signal with forwards-detected CARS at the CH2 resonance. The applicability of this technique to real-world nanoparticle dosing problems was demonstrated in a study of the effect of H2S on nanoshell uptake using two donor molecules, NaHS and GYY4137. As GYY4137 concentration was increased from 10 µM to 1 mM, the nanoshell pixel percentage as a function of cell volume (PPCV) increased from 2.15% to 3.77%. As NaHS concentration was increased over the same range, the nanoshell PPCV decreased from 12.67% to 11.47%. The most important factor affecting uptake in this study was found to be the rate of H2S release, with rapid-release from NaHS resulting in significantly greater uptake.

  18. Diffraction manipulation by four-wave mixing.

    PubMed

    Katzir, Itay; Ron, Amiram; Firstenberg, Ofer

    2015-03-09

    We suggest a scheme to manipulate paraxial diffraction by utilizing the dependency of a four-wave mixing process on the relative angle between the light fields. A microscopic model for four-wave mixing in a Λ-type level structure is introduced and compared to recent experimental data. We show that images with feature size as low as 10 μm can propagate with very little or even negative diffraction. The mechanism is completely different from that conserving the shape of spatial solitons in nonlinear media, as here diffraction is suppressed for arbitrary spatial profiles. At the same time, the gain inherent to the nonlinear process prevents loss and allows for operating at high optical depths. Our scheme does not rely on atomic motion and is thus applicable to both gaseous and solid media.

  19. Four-wave-mixing gap solitons

    SciTech Connect

    Zhang Yanpeng; Wang Zhiguo; Zheng Huaibin; Yuan Chenzhi; Li Changbiao; Lu Keqing; Xiao Min

    2010-11-15

    We report an experimental demonstration of generating gap soliton trains in a four-wave-mixing (FWM) signal. Such spatial FWM surfacelike gap soliton trains are induced in a periodically modulated self-defocusing atomic medium by the cross-phase modulation, which can be reshaped under different experimental conditions, such as different atomic densities, nonlinear dispersions, and dressing fields. Controlling spatial gap solitons can have important applications in image memory, processing, and communication.

  20. Four-wave mixing in alexandrite crystals

    NASA Astrophysics Data System (ADS)

    Ghazzawi, Ali M.; Tyminski, Jacek K.; Powell, Richard C.; Walling, John C.

    1984-12-01

    Degenerate four-wave mixing was observed in alexandrite crystals (BeAl2O4: Cr3+), and the signal beam efficiency and decay rate were measured as functions of pump beam-crossing angle, wavelength, and power. The results are consistent with scattering from excited-state population gratings related to the difference in dispersion of the Cr3+ ions in the ground and metastable states. These gratings can be selectively established with Cr3+ ions in the inversion or mirror sites depending on the excitation wavelength. Strong scattering occurs only for pump beams polarized parallel to the b direction of the crystal.

  1. Geometric interpretation of four-wave mixing

    NASA Astrophysics Data System (ADS)

    Ott, J. R.; Steffensen, H.; Rottwitt, K.; McKinstrie, C. J.

    2013-10-01

    The nonlinear phenomenon of four-wave mixing (FWM) is investigated using a method, where, without the need of calculus, both phase and amplitudes of the mixing fields are visualized simultaneously, giving a complete overview of the FWM dynamics. This is done by introducing a set of Stokes-like coordinates of the electric fields, which reduce the FWM dynamics to a closed two-dimensional surface, similar to the Bloch sphere of quantum electrodynamics or the Pointcaré sphere in polarization dynamics. The coordinates are chosen so as to use the gauge invariance symmetries of the FWM equations which also give the conservation of action flux known as the Manley-Rowe relations. This reduces the dynamics of FWM to the one-dimensional intersection between the closed two-dimensional surface and the phase-plane given by the conserved Hamiltonian. The analysis is advantageous for visualizing phase-dependent FWM phenomena which are found in a large variety of nonlinear systems and even in various optical communication schemes.

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

    PubMed

    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.

  3. Signal Processing with Degenrate Four-Wave Mixing.

    DTIC Science & Technology

    1987-03-17

    which mann geometry, the four -wave mixing signal observed limits the process to pulses of 100 ps or less. Note also was due to heating of the metal film... four -wave mixing to produced grating. With pulses 28 ps long. 0.6 ns decay real-time processing is time reversal of an optical wave- times were...34’Continuous backward-wave generation by degenerate four -wave the heating effects which dominated their experiment.miigiopca bes--prLt.-vl. 4p .4--419

  4. Four-Wave Mixing in Landau-Quantized Graphene.

    PubMed

    König-Otto, Jacob C; Wang, Yongrui; Belyanin, Alexey; Berger, Claire; de Heer, Walter A; Orlita, Milan; Pashkin, Alexej; Schneider, Harald; Helm, Manfred; Winnerl, Stephan

    2017-04-12

    For Landau-quantized graphene, featuring an energy spectrum consisting of nonequidistant Landau levels, theory predicts a giant resonantly enhanced optical nonlinearity. We verify the nonlinearity in a time-integrated degenerate four-wave mixing (FWM) experiment in the mid-infrared spectral range, involving the Landau levels LL-1, LL0 and LL1. A rapid dephasing of the optically induced microscopic polarization on a time scale shorter than the pulse duration (∼4 ps) is observed, while a complementary pump-probe experiment under the same experimental conditions reveals a much longer lifetime of the induced population. The FWM signal shows the expected field dependence with respect to lowest order perturbation theory for low fields. Saturation sets in for fields above ∼6 kV/cm. Furthermore, the resonant behavior and the order of magnitude of the third-order susceptibility are in agreement with our theoretical calculations.

  5. Four-wave mixing in nanosecond pulsed fiber amplifiers.

    PubMed

    Fève, Jean-Philippe; Schrader, Paul E; Farrow, Roger L; Kliner, Dahv A V

    2007-04-16

    We present an experimental and theoretical analysis of four-wave mixing in nanosecond pulsed amplifiers based on double-clad ytterbium-doped fibers. This process leads to saturation of the amplified pulse energy at 1064 nm and to distortion of the spectral and temporal profiles. These behaviours are well described by a simple model considering both Raman and four-wave-mixing contributions. The role of seed laser polarization in birefringent fibers is also presented. These results point out the critical parameters and possible tradeoffs for optimization.

  6. Parametric four-wave mixing using a single cw laser.

    PubMed

    Brekke, E; Alderson, L

    2013-06-15

    Four-wave mixing can be used to generate coherent output beams, with frequencies difficult to acquire in commercial lasers. Here, a single narrow external cavity diode laser locked to the two photon 5s-5d transition in rubidium is combined with a tapered amplifier system to produce a high power cw beam at 778 nm and used to generate coherent light at 420 nm through parametric four-wave mixing. This process is analyzed in terms of the intensity and frequency of the incoming beam as well as the atomic density of the sample. The efficiency of the process is currently limited when on resonance due to the absorption of the 420 nm beam, and modifications should allow a significant increase in output power.

  7. [Study on phase-matching of four-wave mixing spectrum in photonic crystal fiber].

    PubMed

    Liu, Xiao-xu; Wang, Shu-tao; Zhao, Xing-tao; Chen, Shuang; Zhou, Gui-yao; Wu, Xi-jun; Li, Shu-guang; Hou, Lan-Tian

    2014-06-01

    In the present paper, the four-wave mixing principle of fiber was analyzed, and the high-gain phase-matching conditions were shown. The nonlinear coefficient and dispersion characteristics of photonic crystal fibers were calculated by multipole method. The phase mismatch characteristics of fibers with multiple zero-dispersion wavelengths were analyzed for the first time. The changing rules of phase matching wavelength with the pump wavelength and the pump power were obtained, and the phase matching curves were shown. The characteristics of phase matching wavelengths for different dispersion curves were analyzed. There are four new excitation wavelengths of four-wave mixing spectrum in two zero-dispersion wavelength photonic crystal fiers. Four-wave mixing spectroscopy of photonic crystal fibers with two zero-dispersion wavelengths was obtained in the experi-ent, which is consistent with the theoretical analysis, and verified the reliability of the phase matching theory. The fiber with multiple zero-dispersion wavelengths can create a ricbhphase-matching topology, excite more four-wave mixing wavelengths, ena-ling enhanced control over the spectral locations of the four-wave mixing and resonant-radiation bands emitted by solitons and short pulses. These provide theoretical guidance for photonic crystal fiber wavelength conversion and supercontinoum generation based on four-wave mixing.

  8. Spontaneous four-wave mixing in lossy microring resonators

    NASA Astrophysics Data System (ADS)

    Vernon, Z.; Sipe, J. E.

    2015-05-01

    We develop a general Hamiltonian treatment of spontaneous four-wave mixing in a microring resonator side-coupled to a channel waveguide. The effect of scattering losses in the ring is included, as well as parasitic nonlinear effects including self- and cross-phase modulation. A procedure for computing the output of such a system for arbitrary parameters and pump states is presented. For the limit of weak pumping an expression for the joint spectral intensity of generated photon pairs, as well as the singles-to-coincidences ratio, is derived.

  9. Autoresonant four-wave mixing in optical fibers

    SciTech Connect

    Yaakobi, O.; Friedland, L.

    2010-08-15

    A theory of autoresonant four-wave mixing in tapered fibers is developed in application to optical parametric amplification (OPA). In autoresonance, the interacting waves (two pump waves, a signal, and an idler) stay phase-locked continuously despite variation of system parameters (spatial tapering). This spatially extended phase-locking allows complete pump depletion in the system and uniform amplification spectrum in a wide frequency band. Different aspects of autoresonant OPA are described including the automatic initial phase-locking, conditions for autoresonant transition, stability, and spatial range of the autoresonant interaction.

  10. Optimization of Quantum Correlation in Cascaded Four-Wave Mixing

    NASA Astrophysics Data System (ADS)

    Feng, Jingliang; Jing, Jietai

    2016-12-01

    We propose a measurement strategy that can be used to optimize quantum correlation for a cascaded four-wave mixing (FWM) structure. By calculating the covariance matrix of a cascaded FWM structure, we can get all the correlations between any two parties in the outputs. We then calculate the eigenvalues and corresponding eigenmodes of the covariance matrix to find the squeezing degrees of the squeezed modes. Our theoretical model can explain our previous experimental results very well and is useful to optimize the squeezing degree in the cascaded FWM structure.

  11. Indirect precise angular control using four-wave mixing

    SciTech Connect

    Zhang, Wei; Ding, Dong-Sheng; Shi, Bao-Sen Guo, Guang-Can; Jiang, Yun-Kun

    2014-04-28

    Here, we show indirect precise angular control using a four-wave mixing (FWM) process. This was performed with a superposition of light with orbital angular momentum in an M-Type configuration of a hot {sup 85}Rb atomic ensemble. A gear-shaped interference pattern is observed at FWM light with a donut-shaped input signal. The gear could be rotated and is controlled through the change of the polarization of the pump laser. Our experimental results that are based on nonlinear coherent interactions have applications in image processing and precise angular control.

  12. Optimization of Quantum Correlation in Cascaded Four-Wave Mixing

    NASA Astrophysics Data System (ADS)

    Feng, Jingliang; Jing, Jietai

    2017-03-01

    We propose a measurement strategy that can be used to optimize quantum correlation for a cascaded four-wave mixing (FWM) structure. By calculating the covariance matrix of a cascaded FWM structure, we can get all the correlations between any two parties in the outputs. We then calculate the eigenvalues and corresponding eigenmodes of the covariance matrix to find the squeezing degrees of the squeezed modes. Our theoretical model can explain our previous experimental results very well and is useful to optimize the squeezing degree in the cascaded FWM structure.

  13. Propagation analysis of forward degenerate four-wave mixing

    NASA Astrophysics Data System (ADS)

    Maruani, A.

    1980-05-01

    The problem of forward degenerate four-wave mixing in one- and two-photon absorbing media is shown to be analytically solvable for all current experimental conditions. The resonant interaction is studied in detail, and optical Kerr effect, auto and induced two-photon absorption, and nonlinear gain are taken explicitly into account. It is demonstrated how the Kerr effect limits the efficiency of the process. Around a two-photon resonance, the problem of the nearly parallel propagation of two beams undergoing auto and induced two-photon absorption is solved. The solutions are obtained in a form simple enough to allow numerical computations on a programmable calculator.

  14. Image processing by four-wave mixing in photorefractive GaAs

    NASA Technical Reports Server (NTRS)

    Gheen, Gregory; Cheng, Li-Jen

    1987-01-01

    Three image processing experiments were performed by degenerate four-wave mixing in photorefractive GaAs. The experiments were imaging by phase conjugation, edge enhancement, and autocorrelation. The results show that undoped, semiinsulating, liquid-encapsulated Czochralski-grown GaAs crystals can be used as effective optical processing media despite their small electrooptic coefficient.

  15. Degenerate four-wave mixing in silicon hybrid plasmonic waveguides.

    PubMed

    Duffin, Thorin J; Nielsen, Michael P; Diaz, Fernando; Palomba, Stefano; Maier, Stefan A; Oulton, Rupert F

    2016-01-01

    Silicon-based plasmonic waveguides show high confinement well beyond the diffraction limit. Various devices have been demonstrated to outperform their dielectric counterparts at micrometer scales, such as linear modulators, capable of generating high field confinement and improving device efficiency by increasing access to nonlinear processes, limited by ohmic losses. By using hybridized plasmonic waveguide architectures and nonlinear materials, silicon-based plasmonic waveguides can generate strong nonlinear effects over just a few wavelengths. We have theoretically investigated the nonlinear optical performance of two hybrid plasmonic waveguides (HPWG) with three different nonlinear materials. Based on this analysis, the hybrid gap plasmon waveguide (HGPW), combined with the DDMEBT nonlinear polymer, shows a four-wave mixing (FWM) conversion efficiency of -16.4  dB over a 1 μm propagation length, demonstrating that plasmonic waveguides can be competitive with standard silicon photonics structures over distances three orders of magnitude shorter.

  16. Nondegenerate four-wave mixing in rubidium vapor: Transient regime

    SciTech Connect

    Becerra, F. E.; Willis, R. T.; Rolston, S. L.; Orozco, L. A.; Carmichael, H. J.

    2010-10-15

    We investigate the transient response of the generated light from four-wave mixing (FWM) in the diamond configuration using a step-down field excitation. The transients show fast decay times and oscillations that depend on the detunings and intensities of the fields. A simplified model taking into account the thermal motion of the atoms, propagation, absorption, and dispersion effects shows qualitative agreement with the experimental observations with the energy levels in rubidium (5S{sub 1/2}, 5P{sub 1/2}, 5P{sub 3/2}, and 6S{sub 1/2}). The atomic polarization comes from all the contributions of different velocity classes of atoms in the ensemble modifying dramatically the total transient behavior of the light from FWM.

  17. Degenerate four-wave mixing in equilibrium argon arc plasma

    NASA Astrophysics Data System (ADS)

    Musiol, K.; Dzierzega, K.; Pawelec, E.; Pokrzywka, B.; Pellerin, S.; Labuz, S.

    1997-12-01

    The non-intrusive degenerate four-wave mixing (DFWM) method was used to study the local thermal equilibrium atmospheric-pressure argon arc plasma. The laser wavelength was in resonance with the 0022-3727/30/24/013/img10 - 0022-3727/30/24/013/img11 ArI transition, corresponding to the 696.5 nm emission line. The Abrams - Lind theory was verified and proved to be valid under the conditions of our plasma. In the high-laser-intensity limit, the DFWM signals were shown to be exclusively dependent on the population difference between the relevant argon states. Well resolved axial and radial profiles of the plasma temperature and the electron density were determined.

  18. Stimulated degenerate four-wave mixing in Si nanocrystal waveguides

    NASA Astrophysics Data System (ADS)

    Manna, Santanu; Bernard, Martino; Biasi, Stefano; Ramiro Manzano, Fernando; Mancinelli, Mattia; Ghulinyan, Mher; Pucker, George; Pavesi, Lorenzo

    2016-07-01

    Parametric frequency conversion via four-wave mixing (FWM) in silicon nanocrystal (Si NC) waveguides is observed at 1550 nm. To investigate the role of Si NC, different types of waveguides containing Si NC in a SiO2 matrix were fabricated. Owing to the increase of the dipole oscillator strength mediated by the quantum confinement effect, the non-linear refractive index ({n}2) of Si NCs is found to be more than one order of magnitude larger than the one of bulk Si. Coupled differential equations for the degenerate FWM process taking into account the role of Si NC were numerically solved to model the experimental data. The modeling yields an effective {n}2 for Si NCs in SiO2 waveguides which is similar to the one of Si waveguides. We also measured a large signal to idler conversion bandwidth of ∼22 nm. The large non-linear refractive index is joined with a large two photon absorption coefficient which makes the use of Si NC in non-linear optical devices mostly suitable for mid-infrared applications.

  19. Degenerate four-wave mixing in triply resonant Kerr cavities

    NASA Astrophysics Data System (ADS)

    Ramirez, David M.; Rodriguez, Alejandro W.; Hashemi, Hila; Joannopoulos, J. D.; Soljačić, Marin; Johnson, Steven G.

    2011-03-01

    We demonstrate theoretical conditions for highly efficient degenerate four-wave mixing in triply resonant nonlinear (Kerr) cavities. We employ a general and accurate temporal coupled-mode analysis in which the interaction of light in arbitrary microcavities is expressed in terms of a set of coupling coefficients that we rigorously derive from the full Maxwell equations. Using the coupled-mode theory, we show that light consisting of an input signal of frequency ω0-Δω can, in the presence of pump light at ω0, be converted with quantum-limited efficiency into an output shifted signal of frequency ω0+Δω, and we derive expressions for the critical input powers at which this occurs. We find the critical powers in the order of 10 mW, assuming very conservative cavity parameters (modal volumes ~10 cubic wavelengths and quality factors ~1000). The standard Manley-Rowe efficiency limits are obtained from the solution of the classical coupled-mode equations, although we also derive them from simple photon-counting “quantum” arguments. Finally, using a linear stability analysis, we demonstrate that maximal conversion efficiency can be retained even in the presence of self- and cross-phase modulation effects that generally act to disrupt the resonance condition.

  20. Four wave mixing experiments with extreme ultraviolet transient gratings

    PubMed Central

    Bencivenga, F.; Cucini, R.; Capotondi, F.; Battistoni, A.; Mincigrucci, R.; Giangrisostomi, E.; Gessini, A.; Manfredda, M.; Nikolov, I. P.; Pedersoli, E.; Principi, E.; Svetina, C.; Parisse, P.; Casolari, F.; Danailov, M. B.; Kiskinova, M.; Masciovecchio, C.

    2015-01-01

    Four wave mixing (FWM) processes, based on third-order non-linear light-matter interactions, can combine ultrafast time resolution with energy and wavevector selectivity, and enables to explore dynamics inaccessible by linear methods.1-7 The coherent and multi-wave nature of FWM approach has been crucial in the development of cutting edge technologies, such as silicon photonics,8 sub-wavelength imaging9 and quantum communications.10 All these technologies operate with optical wavelengths, which limit the spatial resolution and do not allow probing excitations with energy in the eV range. The extension to shorter wavelengths, that is the extreme ultraviolet (EUV) and soft-x-ray (SXR) range, will allow to improve the spatial resolution and to expand the excitation energy range, as well as to achieve elemental selectivity by exploiting core resonances.5-7,11-14 So far FWM applications at these wavelengths have been prevented by the absence of coherent sources of sufficient brightness and suitable experimental setups. Our results show how transient gratings, generated by the interference of coherent EUV pulses delivered by the FERMI free electron laser (FEL),15 can be used to stimulate FWM processes at sub-optical wavelengths. Furthermore, we have demonstrated the possibility to read the time evolution of the FWM signal, which embodies the dynamics of coherent excitations as molecular vibrations. This result opens the perspective for FWM with nanometer spatial resolution and elemental selectivity, which, for example, would enable the investigation of charge-transfer dynamics.5-7 The theoretical possibility to realize these applications have already stimulated dedicated and ongoing FEL developments;16-20 today our results show that FWM at sub-optical wavelengths is feasible and would be the spark to the further advancements of the present and new sources. PMID:25855456

  1. Four-wave mixing experiments with extreme ultraviolet transient gratings

    NASA Astrophysics Data System (ADS)

    Bencivenga, F.; Cucini, R.; Capotondi, F.; Battistoni, A.; Mincigrucci, R.; Giangrisostomi, E.; Gessini, A.; Manfredda, M.; Nikolov, I. P.; Pedersoli, E.; Principi, E.; Svetina, C.; Parisse, P.; Casolari, F.; Danailov, M. B.; Kiskinova, M.; Masciovecchio, C.

    2015-04-01

    Four-wave mixing (FWM) processes, based on third-order nonlinear light-matter interactions, can combine ultrafast time resolution with energy and wavevector selectivity, and enable the exploration of dynamics inaccessible by linear methods. The coherent and multi-wave nature of the FWM approach has been crucial in the development of advanced technologies, such as silicon photonics, subwavelength imaging and quantum communications. All these technologies operate at optical wavelengths, which limits the spatial resolution and does not allow the probing of excitations with energy in the electronvolt range. Extension to shorter wavelengths--that is, the extreme ultraviolet and soft-X-ray ranges--would allow the spatial resolution to be improved and the excitation energy range to be expanded, as well as enabling elemental selectivity to be achieved by exploiting core resonances. So far, FWM applications at such wavelengths have been prevented by the absence of coherent sources of sufficient brightness and of suitable experimental set-ups. Here we show how transient gratings, generated by the interference of coherent extreme-ultraviolet pulses delivered by the FERMI free-electron laser, can be used to stimulate FWM processes at suboptical wavelengths. Furthermore, we have demonstrated the possibility of observing the time evolution of the FWM signal, which shows the dynamics of coherent excitations as molecular vibrations. This result opens the way to FWM with nanometre spatial resolution and elemental selectivity, which, for example, would enable the investigation of charge-transfer dynamics. The theoretical possibility of realizing these applications has already stimulated ongoing developments of free-electron lasers: our results show that FWM at suboptical wavelengths is feasible, and we hope that they will enable advances in present and future photon sources.

  2. Four-wave mixing experiments with extreme ultraviolet transient gratings.

    PubMed

    Bencivenga, F; Cucini, R; Capotondi, F; Battistoni, A; Mincigrucci, R; Giangrisostomi, E; Gessini, A; Manfredda, M; Nikolov, I P; Pedersoli, E; Principi, E; Svetina, C; Parisse, P; Casolari, F; Danailov, M B; Kiskinova, M; Masciovecchio, C

    2015-04-09

    Four-wave mixing (FWM) processes, based on third-order nonlinear light-matter interactions, can combine ultrafast time resolution with energy and wavevector selectivity, and enable the exploration of dynamics inaccessible by linear methods. The coherent and multi-wave nature of the FWM approach has been crucial in the development of advanced technologies, such as silicon photonics, subwavelength imaging and quantum communications. All these technologies operate at optical wavelengths, which limits the spatial resolution and does not allow the probing of excitations with energy in the electronvolt range. Extension to shorter wavelengths--that is, the extreme ultraviolet and soft-X-ray ranges--would allow the spatial resolution to be improved and the excitation energy range to be expanded, as well as enabling elemental selectivity to be achieved by exploiting core resonances. So far, FWM applications at such wavelengths have been prevented by the absence of coherent sources of sufficient brightness and of suitable experimental set-ups. Here we show how transient gratings, generated by the interference of coherent extreme-ultraviolet pulses delivered by the FERMI free-electron laser, can be used to stimulate FWM processes at suboptical wavelengths. Furthermore, we have demonstrated the possibility of observing the time evolution of the FWM signal, which shows the dynamics of coherent excitations as molecular vibrations. This result opens the way to FWM with nanometre spatial resolution and elemental selectivity, which, for example, would enable the investigation of charge-transfer dynamics. The theoretical possibility of realizing these applications has already stimulated ongoing developments of free-electron lasers: our results show that FWM at suboptical wavelengths is feasible, and we hope that they will enable advances in present and future photon sources.

  3. Femtosecond Degenerate Four-Wave-Mixing in ZnO Microcrystallite Thin Films

    NASA Astrophysics Data System (ADS)

    Zhang, Wei-li; Wang, Qing-yue; Chai, Lu; Xing, Qi-rong; K, Wong S.; H, Wang; Z, Tang K.; G, Wong K. L.; R, Jain

    1999-06-01

    Transient third-order optical nonlinearity χ(3) of ZnO microcrystallite thin films is measured at various temperatures by using femtosecond degenerate four-wave-mixing. Room-temperature excitonic enhancement of χ(3) is observed. The magnitude of χ(3) ranges between 10-4 to 10-6 esu from 4.2 K to room temperature. The measured χ(3) response time ranging from 200 to 300 fs is ultrafast for temperature down to 4.2 K.

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

    PubMed

    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.

  5. Nonlinear Optical Studies of Rydberg Atoms Using Degenerate Four-Wave Mixing.

    DTIC Science & Technology

    1984-08-01

    AD-Ai46 827 NONLINEAR OPTICAL STUDIES OF RYDBERG ATOMS USING 1/2 DEGENERATE FOUR -WAVE MIXING(U) HUGHES RESEARCH LABS MALIBU CA J F LAM ET AL. AUG 84...146 827 NONLINEAR OPTICAL STUDIES OF RYDBERG ATOMS USING DEGENERATE FOUR -WAVE MIXING J.F. Lam, R.A. McFarlane, and D.G. StMel Hughes Research...techniques were developed nearly degenerate four -wave mixing, polarization nearly degenerate four -wave mixing, fre- quency domain three-state

  6. Influence of stimulated Raman scattering on the conversion efficiency in four wave mixing

    SciTech Connect

    Wunderlich, R.; Moore, M.A.; Garrett, W.R.; Payne, M.G.

    1988-01-01

    Secondary nonlinear optical effects following parametric four wave mixing in sodium vapor are investigated. The generated ultraviolet radiation induces stimulated Raman scattering and other four wave mixing process. Population transfer due to Raman transitions strongly influences the phase matching conditions for the primary mixing process. Pulse shortening and a reduction in conversion efficiency are observed. 8 refs., 3 figs.

  7. Studies of degenerate and nearly degenerate four wave mixing of laser radiation in plasmas

    SciTech Connect

    Joshi, Chan . Dept. of Electrical Engineering)

    1990-12-01

    Optical Phase Conjugation is an area of nonlinear optics with a wide variety of potential applications. One method of generating as phase conjugate signal is with four wave mixing (FWM). In FWM, three input beams interact in a nonlinear medium, and a fourth beam is produced that is the phase conjugate of one of the input waves. Degeneate Four Wave Mixing (DFWM) is a special case of FWM in which all of the beams are at the same frequency. In a plasma, DFWM is an effective technique for phase conjugation in high density, low temperature plasmas. One way of enhancing the phase conjugate signal over and above the DFWM level is with Resonant Four Wave Mixing (RFWM), in which two of the input beams beat at a plasma resonance. In addition to enhancing the generated wave, RFWM can also serve as a diagnostic for many plasma parameters, such as the electron and ion temperatures, the ion acoustic velocity, and the damping rate. In this report, experimental evidence of RFWM with CO{sub 2} laser radiation (10.6 {mu}m) is presented, and the data is compared with theoretical predictions.

  8. Degenerate Four-Wave Mixing Measurements of High Order Nonlinearities in Semiconductors

    DTIC Science & Technology

    1991-10-01

    2274 IEEE JOURNAL OF QUANTUM ELECTRONICS. VOL. 27, NO. IO. OCTOBER 1991 Degenerate Four -Wave Mixing Measurements of High Order Nonlinearities in... four -wave mixing experi- ments on ZnSe and CdTe semiconductor samples with pico- second laser pulses at wavelengths below the bandgap. Nonlin- earities...three-photon absorption. I. INTRODUCTION WE repo~ ~ series of picose~ond degenerate four -wave mixmg (DFWM) studies conducted in ZnSe and CdTe at

  9. Silicon-on-Sapphire Waveguides: Mode-converting Couplers and Four-wave Mixing

    DTIC Science & Technology

    2014-09-01

    TECHNICAL DOCUMENT 3283 September 2014 Silicon-on-Sapphire Waveguides: Mode-converting Couplers and Four-Wave Mixing Sanja...fabrication and performance of mode-converting couplers and silicon-on-sapphire waveguides  Measurements of four-wave mixing in silicon-on-sapphire...2  2.2.  WAVEGUIDE COUPLERS

  10. Collinear Four-Wave Mixing of Two-Component Matter Waves

    SciTech Connect

    Pertot, Daniel; Gadway, Bryce; Schneble, Dominik

    2010-05-21

    We demonstrate atomic four-wave mixing of two-component matter waves in a collinear geometry. Starting from a single-species Bose-Einstein condensate, seed and pump modes are prepared through microwave state transfer and state-selective Kapitza-Dirac diffraction. Four-wave mixing then populates the initially empty output modes. Simulations based on a coupled-mode expansion of the Gross-Pitaevskii equation are in very good agreement with the experimental data. We show that four-wave mixing can play an important role in studies of bosonic mixtures in optical lattices. Moreover, our system should be of interest in the context of quantum atom optics.

  11. Collinear four-wave mixing of two-component matter waves.

    PubMed

    Pertot, Daniel; Gadway, Bryce; Schneble, Dominik

    2010-05-21

    We demonstrate atomic four-wave mixing of two-component matter waves in a collinear geometry. Starting from a single-species Bose-Einstein condensate, seed and pump modes are prepared through microwave state transfer and state-selective Kapitza-Dirac diffraction. Four-wave mixing then populates the initially empty output modes. Simulations based on a coupled-mode expansion of the Gross-Pitaevskii equation are in very good agreement with the experimental data. We show that four-wave mixing can play an important role in studies of bosonic mixtures in optical lattices. Moreover, our system should be of interest in the context of quantum atom optics.

  12. Transient Gratings, Four-Wave Mixing and Polariton Effects in Nonlinear Optics

    DTIC Science & Technology

    1991-06-01

    AD-A251 947 m’NAIO lim oi iTrnsiene Gracn as Four -Wave Mixing and PDlariton EffecS. U~~ ua J. Knoester and S. Mukamel 7. P(OPWO ,~ O*tGANIZAflNM...restricted geometries. The transient grating and it$ fequency-oan analogue (dbgfat four wave mixing) awe used 10 iluste the formalm in both the sucag and...acid-free paper. TRANSIENT GRATINGS, FOUR -WAVE MIXING AND POLARITON EFFECTS IN NONLINEAR OPTICS Jasper KNOESTER Unive’rsitY o1 (roningen. Department of

  13. Polarization switch of four-wave mixing in large mode area hybrid photonic crystal fibers.

    PubMed

    Petersen, Sidsel R; Alkeskjold, Thomas T; Olausson, Christina B; Lægsgaard, Jesper

    2015-02-15

    Degenerate spontaneous four-wave mixing is considered in a large mode area hybrid photonic crystal fiber. Numerical and experimental results show birefringence assisted four-wave mixing for a certain polarization state of the pump field. The parametric gain can be turned on and off by switching the polarization state of the pump field between the two principal axis of the hybrid photonic crystal fiber.

  14. Optical gyroscope with controllable dispersion in four wave mixing regime.

    NASA Astrophysics Data System (ADS)

    Mikhailov, Eugeniy; Wolfe, Owen; Du, Shuangli; Rochester, Simon; Budker, Dmitry; Novikova, Irina

    2016-05-01

    We present our work towards realization of the fast-light gyroscope prototype, in which the sensitivity enhancement (compared to a regular laser gyroscopes) is achieved by adjusting the intra-cavity dispersion. We discuss schematics and underlying nonlinear effects leading to the negative dispersion in Rb vapor: level structure, optically addressed transitions, and configuration of the resonant cavity. We investigate dependence of the pulling factor (i.e., the ratio of the lasing frequency shift with the change of the cavity length to the equivalent resonance frequency shift in the empty cavity) on pump lasers detunings, power, and density of the atomic vapor. The observation of the pulling factor exceeding unity implies the gyroscope sensitivity improvement over the regular system This work is supported by Naval Air Warfare Center STTR program N68335-11-C-0428.

  15. Four-wave mixing microscopy: a high potential nonlinear imaging method

    NASA Astrophysics Data System (ADS)

    Ehmke, Tobias; Knebl, Andreas; Heisterkamp, Alexander

    2015-03-01

    In this work we present non-resonant four-wave mixing microscopy as an additional contrast mechanism in nonlinear microscopy. The setup for this technique was based on a commercially available multiphoton microscope setup equipped with a titanium:sapphire-laser and an optical parametric oscillator as light sources. Fundamental system characteristics with respect to the spatio-temporal pulse overlap and the influence of aberrations on the process are presented. Experiments regarding the directionality of the four-wave mixing signal performed on fresh porcine meat showed an average ratio of the backward to forward signal mean intensity of 0.16 +/- 0.01. Nevertheless, structural information is comparable for both detection modalities. This highlights the potential of four-wave mixing microscopy for in vivo applications. Furthermore, results on porcine meat show the additional contrast generated by four-wave mixing. In summary, the results show a great potential of non-resonant four-wave mixing microscopy as label-free imaging modality in the biomedical sciences.

  16. Inverse four-wave-mixing and self-parametric amplification effect in optical fibre

    PubMed Central

    Turitsyn, Sergei K.; Bednyakova, Anastasia E.; Fedoruk, Mikhail P.; Papernyi, Serguei B.; Clements, Wallace R.L.

    2015-01-01

    An important group of nonlinear processes in optical fibre involves the mixing of four waves due to the intensity dependence of the refractive index. It is customary to distinguish between nonlinear effects that require external/pumping waves (cross-phase modulation and parametric processes such as four-wave mixing) and self-action of the propagating optical field (self-phase modulation and modulation instability). Here, we present a new nonlinear self-action effect, self-parametric amplification (SPA), which manifests itself as optical spectrum narrowing in normal dispersion fibre, leading to very stable propagation with a distinctive spectral distribution. The narrowing results from an inverse four-wave mixing, resembling an effective parametric amplification of the central part of the spectrum by energy transfer from the spectral tails. SPA and the observed stable nonlinear spectral propagation with random temporal waveform can find applications in optical communications and high power fibre lasers with nonlinear intra-cavity dynamics. PMID:26345290

  17. Strongly modified four-wave mixing in a coupled semiconductor quantum dot-metal nanoparticle system

    NASA Astrophysics Data System (ADS)

    Paspalakis, Emmanuel; Evangelou, Sofia; Kosionis, Spyridon G.; Terzis, Andreas F.

    2014-02-01

    We study the four-wave mixing effect in a coupled semiconductor quantum dot-spherical metal nanoparticle structure. Depending on the values of the pump field intensity and frequency, we find that there is a critical distance that changes the form of the spectrum. Above this distance, the four-wave mixing spectrum shows an ordinary three-peaked form and the effect of controlling its magnitude by changing the interparticle distance can be obtained. Below this critical distance, the four-wave mixing spectrum becomes single-peaked; and as the interparticle distance decreases, the spectrum is strongly suppressed. The behavior of the system is explained using the effective Rabi frequency that creates plasmonic metaresonances in the hybrid structure. In addition, the behavior of the effective Rabi frequency is explained via an analytical solution of the density matrix equations.

  18. Four-wave mixing instabilities in photonic-crystal and tapered fibers.

    PubMed

    Biancalana, F; Skryabin, D V; Russell, P St J

    2003-10-01

    Four-wave mixing instabilities are theoretically studied for continuous wave propagation in ultrasmall core photonic-crystal and tapered fibers. The waveguide, or geometrical, contribution to the overall dispersion of these structures is much stronger than in conventional fibers. This leads to the appearance of unstable frequency bands that are qualitatively and quantitatively different from those seen in conventional fibers. The four-wave mixing theory developed here is based on the full wave equation, which allows rigorous study of the unstable bands even when the detunings are of the order of the pump frequency itself. Solutions obtained using the generalized nonlinear Schrödinger equation, which is an approximate version of the full wave equation, reveal that it suffers from several deficiencies when used to describe four-wave mixing processes.

  19. Entangled photon generation using four-wave mixing in azimuthally symmetric microresonators.

    PubMed

    Camacho, Ryan M

    2012-09-24

    A novel quantum mechanical formulation of the bi-photon wavefunction and spectra resulting from four-wave mixing is developed for azimuthally symmetric systems. Numerical calculations are performed verifying the use of the angular group velocity and angular group velocity dispersion in such systems, as opposed their commonly used linear counterparts. The dispersion profile and bi-photon spectra of two illustrative examples are given, emphasizing the physical origin of the effects leading to the conditions for angular momentum and energy conservation. A scheme is proposed in which widely spaced narrowband entangled photons may be produced through a four-wave mixing process in a chip-scale ring resonator. The entangled photon pairs are found to conserve energy and momentum in the four-wave mixing interaction, even though both photon modes lie in spectral regions of steep angular group velocity dispersion.

  20. Intermodal four-wave mixing in a higher-order-mode fiber.

    PubMed

    Cheng, Ji; Pedersen, Martin E V; Charan, Kriti; Wang, Ke; Xu, Chris; Grüner-Nielsen, Lars; Jakobsen, Dan

    2012-10-15

    We demonstrate a high-efficiency intermodal four-wave-mixing process in an all-fiber system, comprising a picosecond fiber laser and a high-order-mode (HOM) fiber. Two pump photons in the LP(01) mode of the fiber can generate an anti-Stokes photon in the LP(01) mode and a Stokes photon in the LP(02) mode. The wavelength dependent mode profiles of the HOM fiber produce significant spatial overlap between the modes involved. The anti-Stokes wave at 941 nm is generated with 20% conversion efficiency with input pulse energy of 20 nJ. The guidance of the anti-Stokes and Stokes waves in the HOM fiber enhances system stability.

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

    PubMed

    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.

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

    PubMed

    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.

  3. Four-wave mixing analysis on injection-locked quantum dot semiconductor lasers.

    PubMed

    Lin, Chih-Hao; Lin, Fan-Yi

    2013-09-09

    We derive a simplified rate equation model for the four-wave mixing (FWM) analysis on quantum dot (QD) semiconductor lasers subject to optical injection. The regenerative and the amplitude modulation spectra of the FWM signals with different intrinsic laser parameters and external injection conditions are investigated. By curve fitting the regenerative and the amplitude modulation spectra obtained experimentally, the intrinsic parameters of a commercial single-mode QD laser under different injection conditions are extracted. The linewidth enhancement factor α at different injection levels and detunings are shown, where a reduction of up to 39% from its free-running value is demonstrated. By increasing the injection strength, the α can be further reduced to minimized the chirp in optical communications.

  4. Multi-photon microscopy based on resonant four-wave mixing of colloidal quantum dots

    NASA Astrophysics Data System (ADS)

    Masia, F.; Langbein, W.; Borri, P.

    2009-02-01

    We demonstrate a novel multi-photon imaging modality based on the detection of four-wave mixing (FWM) from colloidal nanoparticles. Four-wave mixing is a third-order signal which can be excited and detected in resonance with the ground-state excitonic transition of CdSe/ZnS quantum dots. The coherent FWM signal is detected interferometrically to reject incoherent backgrounds for improved image contrast compared to fluorescence methods. We measure transversal and axial resolutions of 140nm and 590nm respectively, significantly beating the one-photon diffraction limit. We also demonstrate optical imaging of quantum-dot-labeled Golgi structures of HepG2 cells.

  5. Interference between Raman gain and four-wave mixing in cold atoms

    SciTech Connect

    Michaud, Franck; Kaiser, Robin; Gattobigio, Giovanni-Luca; Tabosa, Jose W. R.

    2007-10-15

    Using a pump-probe scheme with a large cloud of cold rubidium atoms, we observe very large double-pass gain (1800%) due to interference between Raman gain and four-wave mixing. A simple model explains the main features observed.

  6. Correlation coefficient measurement of the mode-locked laser tones using four-wave mixing.

    PubMed

    Anthur, Aravind P; Panapakkam, Vivek; Vujicic, Vidak; Merghem, Kamel; Lelarge, Francois; Ramdane, Abderrahim; Barry, Liam P

    2016-06-01

    We use four-wave mixing to measure the correlation coefficient of comb tones in a quantum-dash mode-locked laser under passive and active locked regimes. We study the uncertainty in the measurement of the correlation coefficient of the proposed method.

  7. Four-wave mixing for clock recovery of phase modulated optical OFDM superchannel.

    PubMed

    Power, Mark J; Jia, Wei; Webb, Roderick P; Manning, Robert J; Gunning, Fatima C Garcia

    2014-03-24

    We simulate and experimentally demonstrate a novel all-optical clock recovery technique for a BPSK OFDM superchannel. Four-wave mixing in SOAs is used to strip the modulation from the superchannel sub-carriers, two of which are filtered and beat together in a photodiode to recover the clock.

  8. Two-photon-state generation via four-wave mixing in optical fibers

    SciTech Connect

    Chen Jun; Li Xiaoying; Kumar, Prem

    2005-09-15

    A quantum theory of two-photon-state generation via four-wave mixing in optical fibers is studied, with emphasis on the case where the pump is a classical, narrow (picosecond-duration) pulse. One of the experiments performed in our lab is discussed and analyzed. Numerical predictions from the theory are shown to be in good agreement with the experimental results.

  9. Intermodal and cross-polarization four-wave mixing in large-core hybrid photonic crystal fibers.

    PubMed

    Petersen, Sidsel R; Alkeskjold, Thomas T; Olausson, Christina B; Lægsgaard, Jesper

    2015-03-09

    Degenerate four-wave mixing is considered in large mode area hybrid photonic crystal fibers, combining photonic bandgap guidance and index guidance. Co- and orthogonally polarized pump, signal and idler fields are considered numerically by calculating the parametric gain and experimentally by spontaneous degenerate four-wave mixing. Intermodal and birefringence assisted intramodal phase matching is observed. Good agreement between calculations and experimental observations is obtained. Intermodal four-wave mixing is achieved experimentally with a conversion efficiency of 17%.

  10. High resolution spectroscopy and spectral simulation of C2 using degenerate four-wave mixing

    NASA Astrophysics Data System (ADS)

    Lloyd, G. M.; Ewart, P.

    1999-01-01

    Degenerate four-wave mixing in the sub-Doppler phase conjugate geometry was used to record high resolution spectra of the d 3Πg-a3Πu (0-0) Swan band of C2 produced in an oxy-acetylene flame. The line positions of isolated transitions were measured to an accuracy of ˜3×10-3 cm-1 and calibrated using a Fizeau interferometer system. The data obtained from these spectra was used to calculate rotational constants and lambda doubling parameters for the 3Π states from which the line positions for the whole band were calculated. Noticeable improvements between experimental and calculated line positions are seen when compared to previously published values. The effect of inaccuracies in line positions on the simulation of degenerate four-wave mixing spectra is discussed and some examples of the improvement in simulation using the newly calculated line positions are presented.

  11. Optical imaging through turbid media with a degenerate four-wave mixing correlation time gate

    DOEpatents

    Sappey, Andrew D.

    1998-04-14

    Optical imaging through turbid media is demonstrated using a degenerate four-wave mixing correlation time gate. An apparatus and method for detecting ballistic and/or snake light while rejecting unwanted diffusive light for imaging structures within highly scattering media are described. Degenerate four-wave mixing (DFWM) of a doubled YAG laser in rhodamine 590 is used to provide an ultrafast correlation time gate to discriminate against light that has undergone multiple scattering and therefore has lost memory of the structures within the scattering medium. Images have been obtained of a test cross-hair pattern through highly turbid suspensions of whole milk in water that are opaque to the naked eye, which demonstrates the utility of DFWM for imaging through turbid media. Use of DFWM as an ultrafast time gate for the detection of ballistic and/or snake light in optical mammography is discussed.

  12. Monitoring Gold Nanoparticle Growth in Situ via the Acoustic Vibrations Probed by Four-Wave Mixing.

    PubMed

    Wu, Jian; Xiang, Dao; Gordon, Reuven

    2017-02-21

    We monitor in situ gold nanoparticle growth in aqueous solution by probing the acoustic vibrations with four-wave mixing. We observe two acoustic vibrational modes of gold nanoparticles from the nonlinear optical response: an extensional mode with longitudinal expansion and transverse contraction and a breathing mode with radial expansion and contraction. The mode frequencies, which show an inverse dependence on the nanoparticle diameter, allow one to monitor the nanoparticle size and size distribution during synthesis. The information about the nanoparticle size and size distribution calculated on the basis of the mode frequencies agrees well with the results obtained from the electron microscopy analysis, validating the four-wave mixing technique as an accurate and effective tool for in situ monitoring of colloidal growth.

  13. Bunching-induced asymmetry in degenerate four-wave mixing with cold atoms

    SciTech Connect

    Gattobigio, G. L.; Michaud, F.; Kaiser, R.; Javaloyes, J.

    2006-10-15

    We have investigated degenerate four-wave mixing in a sample of cold rubidium atoms. A red-blue asymmetry is observed for high intensities of the pumping beams. This asymmetry is explained by the spatial bunching of the atoms in the nodes or antinodes of the strong standing wave of the pump beams. This explanation is confirmed by different experimental configurations and by numerical simulations.

  14. Experimental demonstration of optical switching and routing via four-wave mixing spatial shift.

    PubMed

    Nie, Zhiqiang; Zheng, Huaibin; Zhang, Yanpeng; Zhao, Yan; Zuo, Cuicui; Li, Changbiao; Chang, Hong; Xiao, Min

    2010-01-18

    We demonstrate the shift characteristics of four-wave mixing (FWM) beam spots which are controlled by the strong laser fields via the large cross-Kerr nonlinearity. The shift distances and directions are determined by the nonlinear dispersions. Based on such spatial displacements of the FWM beams, as well as the probe beam, we experimentally demonstrate spatial optical switching for one beam or multiple optical beams, which can be used for all-optical switching, switching arrays and routers.

  15. Robust and compact entanglement generation from diode-laser-pumped four-wave mixing

    SciTech Connect

    Lawrie, B. J.; Yang, Y.; Eaton, M.; Black, A. N.; Pooser, R. C.

    2016-04-11

    Four-wave-mixing processes are now routinely used to demonstrate multi-spatial-mode Einstein- Podolsky-Rosen entanglement and intensity difference squeezing. Recently, diode-laser-pumped four-wave mixing processes have been shown to provide an affordable, compact, and stable source for intensity difference squeezing, but it was unknown if excess phase noise present in power amplifier pump configurations would be an impediment to achieving quadrature entanglement. Here, we demonstrate the operating regimes under which these systems are capable of producing entanglement and under which excess phase noise produced by the amplifier contaminates the output state. We show that Einstein-Podolsky-Rosen entanglement in two mode squeezed states can be generated by a four-wave-mixing source deriving both the pump field and the local oscillators from a tapered-amplifier diode-laser. In conclusion, this robust continuous variable entanglement source is highly scalable and amenable to miniaturization, making it a critical step toward the development of integrated quantum sensors and scalable quantum information processors, such as spatial comb cluster states.

  16. Robust and compact entanglement generation from diode-laser-pumped four-wave mixing

    DOE PAGES

    Lawrie, B. J.; Yang, Y.; Eaton, M.; ...

    2016-04-11

    Four-wave-mixing processes are now routinely used to demonstrate multi-spatial-mode Einstein- Podolsky-Rosen entanglement and intensity difference squeezing. Recently, diode-laser-pumped four-wave mixing processes have been shown to provide an affordable, compact, and stable source for intensity difference squeezing, but it was unknown if excess phase noise present in power amplifier pump configurations would be an impediment to achieving quadrature entanglement. Here, we demonstrate the operating regimes under which these systems are capable of producing entanglement and under which excess phase noise produced by the amplifier contaminates the output state. We show that Einstein-Podolsky-Rosen entanglement in two mode squeezed states can be generatedmore » by a four-wave-mixing source deriving both the pump field and the local oscillators from a tapered-amplifier diode-laser. In conclusion, this robust continuous variable entanglement source is highly scalable and amenable to miniaturization, making it a critical step toward the development of integrated quantum sensors and scalable quantum information processors, such as spatial comb cluster states.« less

  17. Measurement of Coherence Decay in GaMnAs Using Femtosecond Four-wave Mixing

    PubMed Central

    Webber, Daniel; de Boer, Tristan; Yildirim, Murat; March, Sam; Mathew, Reuble; Gamouras, Angela; Liu, Xinyu; Dobrowolska, Margaret; Furdyna, Jacek; Hall, Kimberley

    2013-01-01

    The application of femtosecond four-wave mixing to the study of fundamental properties of diluted magnetic semiconductors ((s,p)-d hybridization, spin-flip scattering) is described, using experiments on GaMnAs as a prototype III-Mn-V system.  Spectrally-resolved and time-resolved experimental configurations are described, including the use of zero-background autocorrelation techniques for pulse optimization.  The etching process used to prepare GaMnAs samples for four-wave mixing experiments is also highlighted.  The high temporal resolution of this technique, afforded by the use of short (20 fsec) optical pulses, permits the rapid spin-flip scattering process in this system to be studied directly in the time domain, providing new insight into the strong exchange coupling responsible for carrier-mediated ferromagnetism.  We also show that spectral resolution of the four-wave mixing signal allows one to extract clear signatures of (s,p)-d hybridization in this system, unlike linear spectroscopy techniques.   This increased sensitivity is due to the nonlinearity of the technique, which suppresses defect-related contributions to the optical response. This method may be used to measure the time scale for coherence decay (tied to the fastest scattering processes) in a wide variety of semiconductor systems of interest for next generation electronics and optoelectronics. PMID:24326982

  18. A theory for non-degenerate four-wave mixing in doped graphene

    NASA Astrophysics Data System (ADS)

    Margulis, Vl. A.; Muryumin, E. E.; Gaiduk, E. A.

    2017-03-01

    We present a theoretical study of the nonlinear optical (NLO) response of doped graphene to two coherent laser beams, of frequencies ω1 and ω2, resulting in the generation of radiation at frequency ωσ = 2ω1 -ω2 . The two main ingredients of the developed theory are the interplay of interband and intraband electron motion, induced by the incident light waves, and the finite lifetime of excited electronic states, caused by electron scattering. Adopting a tight-binding approximation for the π-electronic band structure of graphene and the Genkin-Mednis formalism of the nonlinear conductivity theory of semiconductors, we calculate the third-order NLO susceptibility χ (3) (-ωσ ;ω1 ,ω1 , -ω2) responsible for the non-degenerate four-wave mixing process under consideration. Our calculations show the resonant enhancement of the |χ (3) | (up to a value of 2.8 ×10-7 esu) when the frequencies ω1 and ω2 of the input beams are mat"ched to provide a resonance for the output photon energy ℏωσ with an effective optical gap of 2EF in the π-electronic band structure of doped graphene (EF is the Fermi energy of charge carriers in the graphene, tunable by an external gate voltage). The results obtained may be of practical interest for generating mid-infrared radiation from doped graphene pumped with two near-infrared laser beams.

  19. Degenerate four-wave mixing and phase conjugation in a collisional plasma

    SciTech Connect

    Federici, J.F.; Mansfield, D.K.

    1986-06-01

    Although degenerate four-wave mixing (DFWM) has many practical applications in the visible regime, no successful attempt has been made to study or demonstrate DFWM for wavelengths longer than 10..mu..m. Recently, Steel and Lam established plasma as a viable DFWM and phase conjugation (PC) medium for infrared, far-infrared, and microwaves. However, their analysis is incomplete since collisional effects were not included. Using a fluid description, our results demonstrate that when collisional absorption is small and the collisional mean-free path is shorter than the nonlinear density grating scale length, collisional heating generates a thermal force which substantially enhances the phase conjugate reflectivity. When the collisional attenuation length becomes comparable to the length of the plasma, the dominant effect is collisional absorption of the pump waves. Numerical estimates of the phase conjugate reflectivity indicate that for modest power levels, gains greater than or equal to1 are possible in the submillimeter to centimeter wavelength range. This suggests that a plasma is a viable PC medium at those long wavelengths. In addition, doubly DFWM is discussed.

  20. Plasmonic nanofocused four-wave mixing for femtosecond near-field imaging

    NASA Astrophysics Data System (ADS)

    Kravtsov, Vasily; Ulbricht, Ronald; Atkin, Joanna M.; Raschke, Markus B.

    2016-05-01

    Femtosecond nonlinear optical imaging with nanoscale spatial resolution would provide access to coupled degrees of freedom and ultrafast response functions on the characteristic length scales of electronic and vibrational excitations. Although near-field microscopy provides the desired spatial resolution, the design of a broadband high-contrast nanoprobe for ultrafast temporal resolution is challenging due to the inherently weak nonlinear optical signals generated in subwavelength volumes. Here, we demonstrate broadband four-wave mixing with enhanced nonlinear frequency conversion efficiency at the apex of a nanometre conical tip. Far-field light is coupled through a grating at the shaft of the tip, generating plasmons that propagate to the apex while undergoing asymptotic compression and amplification, resulting in a nonlinear conversion efficiency of up to 1 × 10-5. We apply this nonlinear nanoprobe to image the few-femtosecond coherent dynamics of plasmonic hotspots on a nanostructured gold surface with spatial resolution of a few tens of nanometres. The approach can be generalized towards spatiotemporal imaging and control of coherent dynamics on the nanoscale, including the extension to multidimensional spectroscopy and imaging.

  1. Low-power continuous-wave four-wave mixing wavelength conversion in AlGaAs-nanowaveguide microresonators.

    PubMed

    Kultavewuti, Pisek; Pusino, Vincenzo; Sorel, Marc; Stewart Aitchison, J

    2015-07-01

    We experimentally demonstrate enhanced wavelength conversion in a Q∼7500 deeply etched AlGaAs-nanowaveguide microresonator via degenerate continuous-wave four-wave mixing with a pump power of 24 mW. The maximum conversion efficiency is -43  dB and accounts for 12 dB enhancement compared to that of a straight nanowaveguide. The experimental results and theoretical predictions agree very well and show optimized conversion efficiency of -15  dB. This work represents a step toward realizing a fully integrated optical devices for generating new optical frequencies.

  2. Vortex algebra by multiply cascaded four-wave mixing of femtosecond optical beams.

    PubMed

    Hansinger, Peter; Maleshkov, Georgi; Garanovich, Ivan L; Skryabin, Dmitry V; Neshev, Dragomir N; Dreischuh, Alexander; Paulus, Gerhard G

    2014-05-05

    Experiments performed with different vortex pump beams show for the first time the algebra of the vortex topological charge cascade, that evolves in the process of nonlinear wave mixing of optical vortex beams in Kerr media due to competition of four-wave mixing with self-and cross-phase modulation. This leads to the coherent generation of complex singular beams within a spectral bandwidth larger than 200nm. Our experimental results are in good agreement with frequency-domain numerical calculations that describe the newly generated spectral satellites.

  3. Ultrasonic probes of aqueous particle suspensions: Collinear four-wave mixing and resonator detuning

    NASA Astrophysics Data System (ADS)

    Kwiatkowski, Christopher Scott

    The interaction of sound with sound in a suspension can be mediated by the suspension's response to acoustic radiation pressure. The current investigations involve acoustical four-wave mixing mediated by a suspension with collinear pump and probe waves, and the effects of sound on the resonant frequency of a system. The suspension includes hollow glass or polystyrene microparticles in a deionized water/sugar or water/salt mixture designed to make the particles neutrally buoyant. Radiation pressure from counter propagating pump beams induces a periodic grating in the number density of the microspheres, due to the particles difference in compressibility from that of the host solution. The pump beams are formed by the transmission and repeated reverberations of a wave produced by a single ceramic pump transducer that is reflected off a receiver. The pump wave is in the stopband. In the case of four-wave mixing, the Bragg scattering amplitude was measured using the pump transducer as the probe source and a piezoelectric thin film hydrophone as a receiver, with both parallel to the standing pump wave nodal planes. Reflection coefficients as a function of time and frequency are calculated by comparing the reflected and transmitted probe waves. By increasing the particle concentration, total Bragg reflectivities from the established grating reaching 20% have been seen, which is still in the region of agreement between the Born approximation and transfer matrix theory. Bragg scattering by gratings of gas bubbles caused by cavitation was also detected. The redistribution of the suspended particles in the standing wavefield shifts the resonant frequency of the chamber. Adiabatic invariance theory and a transfer matrix approach agree with the experimental results. Some interesting results, including a form of mode-hopping, were also observed. The dynamics of the grating formation and dissolution have been studied using both four-wave mixing and frequency shift measurements

  4. All-optical wavelength conversion by four-wave mixing in a semiconductor optical amplifier

    NASA Astrophysics Data System (ADS)

    Lee, Robert Bumju

    1997-11-01

    Wavelength division multiplexed optical communication systems will soon become an integral part of commercial optical networks. A crucial new function required in WDM networks is wavelength conversion, the spectral translation of information-laden optical carriers, which enhances wavelength routing options and greatly improves network reconfigurability. One of several techniques for implementing this function is four-wave mixing utilizing ultra-fast intraband nonlinearities in semiconductor optical amplifiers. The effects of input power, noise prefiltering and semiconductor optical amplifier length on the conversion efficiency and optical signal-to-noise ratio were examined. Systems experiments have been conducted in which several important performance characteristics of the wavelength converter were studied. A bit-error-rate performance of <10-9 at 10 Gb/s was achieved for a record shift of 18 nm down in wavelength and 10 nm up in wavelength. Two cascaded conversions spanning a 40 km fiber link at 10 Gb/s are also demonstrated for conversions of up to 9 nm down and up in wavelength. The dynamic range of input signal power and its impact on the BER performance were studied at 2.5 Gb/s for both a single-channel conversion and a simultaneous 2-channel conversion. The crosstalk penalty induced by parasitic cross-gain modulation in 2-channel conversion is quantified. The spectral inversion which results from the conversion process is studied by time-resolved spectral analysis, and its application as a technique for dispersion compensation is demonstrated. Finally, the application of selective organometallic vapor-phase epitaxy for the formation of highly-uniform and densely-packed arrays of GaAs quantum dots is demonstrated. GaAs dots of 15-20 nm in base diameter and 8-10 nm in height terminated by slow-growth crystallographic planes were grown within dielectric-mask openings and characterized by atomic force microscopy.

  5. Phase-matching and mitigation of four-wave mixing in fibers with positive gain.

    PubMed

    Fève, Jean-Philippe

    2007-01-22

    We present a theoretical study of four-wave mixing interactions in fibers in the presence of gain. In contrast to passive fibers, positive gain at the pump wavelength leads to constructive generation of the signal and idler waves, even in the case of large phase-mismatch, so that FWM processes can be very efficient even in isotropic single-mode fibers with normal dispersion. We also propose simple ways to mitigate these parametric interactions by applying a controlled variation of the phase-mismatch along the fiber. These concepts apply to all optical amplifiers.

  6. Degenerate four-wave mixing from layered semiconductor clusters in the quantum size regime

    NASA Astrophysics Data System (ADS)

    Sarid, Dror; Rhee, Bum Ku; McGinnis, Brian P.; Sandroff, Claude J.

    1986-11-01

    We report the first measurement of the third-order nonlinear susceptibility χ(3) in layered semiconductor clusters exhibiting pronounced quantum size effects at room temperature. BiI3 clusters prepared in colloidal form in acetonitrile had a thickness of ≂7 Å and lateral dimensions between 60 and 90 Å. Using degenerate four-wave mixing, we observed that the conjugate pulses from the small and the large gratings had comparable intensities, verifying the electronic origin of the nonlinearity. The nonlinear susceptibility was found to be 2.3×10-11 esu for a colloid with a cluster volume fraction of 10-5.

  7. Optical imaging through turbid media using a degenerate-four-wave mixing correlation time gate

    SciTech Connect

    Bigio, I.J.; Strauss, C.E.M.; Zerkle, D.K.

    1998-11-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The authors have demonstrated the use of a degenerate-four-wave-mixing time gate to allow imaging through turbid media, with potential application to tissue imaging. A near infrared (NIR), long-pulse Cr{sup +3}:Li{sub 2}SrAlF{sub 6} laser was used as the light source (during most the project) for imaging through clear and turbid media. Preliminary experiments were also carried out with a continuous diode laser.

  8. Spectrally resolved four-wave mixing experiments on bulk GaAs with 14-fs pulses

    SciTech Connect

    Wehner, M.U.; Steinbach, D.; Wegener, M.; Marschner, T.; Stolz, W.

    1996-05-01

    We investigate the coherent dynamics at the band edge of GaAs at low temperatures for carrier densities ranging from 4.3{times}10{sup 14} cm{sup {minus}3} to 4.4{times}10{sup 17} cm{sup {minus}3} by means of spectrally resolved transient four-wave mixing with 14-fs pulses. At large nonequilibrium carrier densities we observe oscillations with an energy-dependent oscillation period related to interference among continuum states. The experimental findings are compared with a simple model. This comparison delivers a weak energy dependence of dephasing in the initial buildup phase of screening. {copyright} {ital 1996 Optical Society of America.}

  9. Four-wave-mixing-assisted Brillouin fiber laser with double-Brillouin-frequency spacing

    NASA Astrophysics Data System (ADS)

    Gan, G. K. W.; Yeo, K. S.; Adikan, F. R. Mahamd; Shee, Y. G.

    2015-01-01

    The generation of multiwavelength Brillouin fiber laser assisted by four wave mixing has been demonstrated. A maximum of 18 channels of laser Stokes lines are generated at a Brillouin Pump (BP) of 190 mW (∼22.5 dBm). The multiple peaks have a wavelength spacing of 0.176 nm (∼20 GHz). A tunable optical bandpass filter is incorporated to the design to suppress up to 6 dB of the noise floor hump exhibited at the multiwavelength laser spectrum while limiting the laser peaks attenuation thereby providing a much cleaner and better OSNR.

  10. Saturation effects and inhomogeneous broadening in Doppler-free degenerate four-wave mixing

    NASA Astrophysics Data System (ADS)

    Steel, D. G.; Lam, J. F.

    1981-12-01

    We have performed experiments to study the saturation properties of degenerate four-wave mixing (DFWM) in inhomogeneously broadened material. The experiments were performed on line-center in SF 6 using a CW CO 2 laser on the P16 line at 10.6 μm. Measured peak reflectivities of 1.7 x 10 -4 are in reasonable agreement with a simple two-level model. This model also appears to correctly account for the observed saturation effects. While the material is clearly inhomogeneously broadened, both the experimental and theoretical reflectivity scale as though the material was homogeneously broadened.

  11. Real-time monitoring of graphene patterning with wide-field four-wave mixing microscopy

    NASA Astrophysics Data System (ADS)

    Koivistoinen, Juha; Aumanen, Jukka; Hiltunen, Vesa-Matti; Myllyperkiö, Pasi; Johansson, Andreas; Pettersson, Mika

    2016-04-01

    The single atom thick two-dimensional graphene is a promising material for various applications due to its extraordinary electronic, optical, optoelectronic, and mechanical properties. The demand for developing graphene based applications has entailed a requirement for development of methods for fast imaging techniques for graphene. Here, we demonstrate imaging of graphene with femtosecond wide-field four-wave mixing microscopy. The method provides a sensitive, non-destructive approach for rapid large area characterization of graphene. We show that the method is suitable for online following of a laser patterning process of microscale structures on single-layer graphene.

  12. Demonstration of almost octave-spanning cascaded four-wave mixing in optical microfibers.

    PubMed

    Li, Y H; Zhao, Y Y; Wang, L J

    2012-08-15

    We demonstrate almost octave-spanning cascaded four-wave mixing (CFWM) in optical microfibers. Pumped by two synchronized picosecond lasers at about 850 nm, microfibers with a length of 10-20 cm can generate CFWM spanning from a few hundred nanometers to almost one octave, depending on the diameter of the microfibers and the detuning between the two pumps. CFWM in microfibers, which has the advantages of easy fabrication, highly efficient coupling, relatively short length, and easy integration with fiber systems, can be used for applications in widely tunable multiline phase-sensitive amplification, multiwavelength coherent sources, and ultrashort pulse synthesis.

  13. Designing slow-light photonic crystal waveguides for four-wave mixing applications.

    PubMed

    Kanakis, Panagiotis; Kamalakis, Thomas; Sphicopoulos, Thomas

    2014-02-15

    We discuss the optimization of photonic crystal waveguides for four-wave mixing (FWM) applications, taking into account linear loss and free-carrier effects. Suitable figures of merit are introduced in order to guide us through the choice of practical, high-efficiency designs requiring relatively low pump power and small waveguide length. In order to realistically perform the waveguide optimization process, we propose and validate an approximate expression for the FWM efficiency, which significantly alleviates our numerical calculations. Promising waveguide designs are identified by means of an exhaustive search, altering some structural parameters. Our approach aims to optimize the waveguides for nonlinear signal-processing applications based on the FWM.

  14. Intermodal four-wave mixing from femtosecond pulse-pumped photonic crystal fiber.

    PubMed

    Tu, H; Jiang, Z; Marks, D L; Boppart, S A

    2009-03-09

    Large Stokes-shift ( approximately 4700 cm(-1)) four-wave mixing is generated in a deeply normal dispersion regime from a 20 cm commercial large-mode-area photonic crystal fiber pumped by amplified approximately 800 nm femtosecond pulses. The phase-matching condition is realized through an intermodal scheme involving two pump photons in the fundamental fiber mode and a pair of Stokesanti-Stokes photons in a higher-order fiber mode. Over 7% conversion efficiency from the pump input to 586 nm anti-Stokes signal has been attained.

  15. Four-wave mixing stability in hybrid photonic crystal fibers with two zero-dispersion wavelengths.

    PubMed

    Sévigny, Benoit; Vanvincq, Olivier; Valentin, Constance; Chen, Na; Quiquempois, Yves; Bouwmans, Géraud

    2013-12-16

    The four-wave mixing process in optical fibers is generally sensitive to dispersion uniformity along the fiber length. However, some specific phase matching conditions show increased robustness to longitudinal fluctuations in fiber dimensions, which affect the dispersion, even for signal and idler wavelengths far from the pump. In this paper, we present the method by which this point is found, how the fiber design characteristics impact on the stable point and demonstrate the stability through propagation simulations using the non-linear Schrödinger equation.

  16. Designing photonic crystal waveguides for broadband four-wave mixing applications.

    PubMed

    Kanakis, Panagiotis; Kamalakis, Thomas; Sphicopoulos, Thomas

    2015-03-15

    We present photonic crystal waveguide designs which exhibit large four-wave mixing efficiencies over a wide wavelength region. These designs are identified using an optimization process taking into account sophisticated figure-of-merits that depend on the pump bandwidth and the signal/pump tunability. The obtained designs achieve up to -18.9  dB conversion efficiency, tunable over a 10 nm tunability range. We also present alternative designs that are less efficient but have smaller power requirements and are far more compact.

  17. Polarization properties of degenerate four-wave mixing in GaAs

    NASA Technical Reports Server (NTRS)

    Liu, Duncan T.; Cheng, Li-Jen

    1989-01-01

    The effect of an applied dc electric field on beam-polarization properties of degenerate four-wave mixing in GaAs is investigated. The results can be interpreted in terms of the phase retardation arising from the applied electric field and the light-induced periodic space-charge field. The conditions for attaining a cross-polarized diffracted beam and read beam are discussed. The experimental results agree reasonably well with the theoretical calculations for an applied voltage of 6 kV.

  18. Highly efficient picosecond degenerate four-wave mixing in a tellurite microstructured optical fiber

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Hoang Tuan, Tong; Kawamura, Harutaka; Nagasaka, Kenshiro; Suzuki, Takenobu; Ohishi, Yasutake

    2016-06-01

    Wavelength-tunable picosecond degenerate four-wave mixing was demonstrated in a tellurite microstructured optical fiber (TMOF). The zero-dispersion wavelength of the TMOF was shifted to 1570 nm by introducing a single ring of air holes in the cladding. The anti-Stokes signal sideband can be generated from 1490 to 1500 nm, and the Stokes idler sideband can emit from 1595 to 1645 nm. Because of the high nonlinearity of the TMOF and the large peak power of the picosecond pump, a maximal signal gain of 31.2 dB and an idler conversion efficiency of +35 dB were achieved.

  19. Superradiant cascade emissions in an atomic ensemble via four-wave mixing

    SciTech Connect

    Jen, H.H.

    2015-09-15

    We investigate superradiant cascade emissions from an atomic ensemble driven by two-color classical fields. The correlated pair of photons (signal and idler) is generated by adiabatically driving the system with large-detuned light fields via four-wave mixing. The signal photon from the upper transition of the diamond-type atomic levels is followed by the idler one which can be superradiant due to light-induced dipole–dipole interactions. We then calculate the cooperative Lamb shift (CLS) of the idler photon, which is a cumulative effect of interaction energy. We study its dependence on a cylindrical geometry, a conventional setup in cold atom experiments, and estimate the maximum CLS which can be significant and observable. Manipulating the CLS of cascade emissions enables frequency qubits that provide alternative robust elements in quantum network. - Highlights: • Superradiance from a cascade atomic transition. • Correlated photon pair generation via four-wave mixing. • Dynamical light–matter couplings in a phased symmetrical state. • Cooperative Lamb shift in a cylindrical atomic ensemble.

  20. Polarization resolved electric field measurements on plasma bullets in N2 using four-wave mixing

    NASA Astrophysics Data System (ADS)

    van der Schans, Marc; Boehm, Patrick; Nijdam, Sander; Ijzerman, Wilbert; Czarnetzki, Uwe

    2016-09-01

    Atmospheric pressure plasma jets generated by kHz AC or pulsed DC voltages typically consist of discrete guided ionization waves called plasma bullets. In this work, the electric field of plasma bullets generated in a pulsed DC jet with N2 as feed gas is investigated using the four-wave mixing method. In this diagnostic two laser beams, where one is Stokes shifted from the other, non-linearly interact with the N2 molecules and the bullet's electric field. As a result of the interaction a coherent anti-Stokes Raman scattered (CARS) beam and an infrared beam are generated from which the electric field can be determined. Compared to emission-based methods, this technique has the advantage of being able to also probe the electric field in regions around the plasma bullet where no photons are emitted. The four-wave mixing method and its analysis have been adapted to work with the non-uniform electric field of plasma bullets. In addition, an ex-situ calibration procedure using an electrode geometry different from the discharge geometry has been developed. An experimentally obtained radial profile of the axial electric field component of a plasma bullet in N2 is presented. The position of this profile is related to the location of the propagating bullet from temporally resolved images.

  1. Highly efficient four wave mixing in GaInP photonic crystal waveguides.

    PubMed

    Eckhouse, V; Cestier, I; Eisenstein, G; Combrié, S; Colman, P; De Rossi, A; Santagiustina, M; Someda, C G; Vadalà, G

    2010-05-01

    We report highly efficient four wave mixing in a GaInP photonic crystal waveguide. Owing to its large bandgap, the ultrafast Kerr nonlinearity of GaInP is not diminished by two photon absorption and related carrier effects for photons in the 1550 nm range. A four-wave-mixing efficiency of -49 dB was demonstrated for cw pump and probe signals in the milliwatt range, while for pulsed pumps with a peak power of 25 mW the conversion efficiency increased to -36 dB. Measured conversion efficiency dependencies on pump probe detuning and on pump power are in excellent agreement with a simple analytical model from which the nonlinear parameter gamma is extracted. Gamma scales approximately with the square of the slow down factor and varies from 800 W(-1) m(-1) at a pump wavelength lambda(p)=1532 nm to 2900 W(-1) m(-1) at lambda(p)=1550 nm. These values are consistent with those obtained from self phase modulation experiments in similar devices.

  2. Final Report: Investigation of Polarization Spectroscopy and Degenerate Four-Wave Mixing for Quantitative Concentration Measurements

    SciTech Connect

    Robert P. Lucht

    2005-03-09

    Laser-induced polarization spectroscopy (LIPS), degenerate four-wave mixing (DFWM), and electronic-resonance-enhanced (ERE) coherent anti-Stokes Raman scattering (CARS) are techniques that shows great promise for sensitive measurements of transient gas-phase species, and diagnostic applications of these techniques are being pursued actively at laboratories throughout the world. However, significant questions remain regarding strategies for quantitative concentration measurements using these techniques. The primary objective of this research program is to develop and test strategies for quantitative concentration measurements in flames and plasmas using these nonlinear optical techniques. Theoretically, we are investigating the physics of these processes by direct numerical integration (DNI) of the time-dependent density matrix equations that describe the wave-mixing interaction. Significantly fewer restrictive assumptions are required when the density matrix equations are solved using this DNI approach compared with the assumptions required to obtain analytical solutions. For example, for LIPS calculations, the Zeeman state structure and hyperfine structure of the resonance and effects such as Doppler broadening can be included. There is no restriction on the intensity of the pump and probe beams in these nonperturbative calculations, and both the pump and probe beam intensities can be high enough to saturate the resonance. As computer processing speeds have increased, we have incorporated more complicated physical models into our DNI codes. During the last project period we developed numerical methods for nonperturbative calculations of the two-photon absorption process. Experimentally, diagnostic techniques are developed and demonstrated in gas cells and/or well-characterized flames for ease of comparison with model results. The techniques of two-photon, two-color H-atom LIPS and three-laser ERE CARS for NO and C{sub 2}H{sub 2} were demonstrated during the

  3. Analysis of four-wave mixing between pulses in high-data-rate quasi-linear subchannel-multiplexed systems.

    PubMed

    Zweck, John; Menyuk, Curtis R

    2002-07-15

    We study four-wave mixing between pulses in two subchannels of a quasi-linear 40-Gbit/s subchannel-multiplexed system. For a pseudorandom bit string there are resonances in the mean of the ghost pulse energy and in the jitter of the energy in the marks as functions of the subchannel frequency spacing. However, away from these resonances the effect of four-wave mixing decreases as the subchannel spacing increases, permitting propagation over longer distances.

  4. All-optical switching via four-wave mixing Bragg scattering in a silicon platform

    NASA Astrophysics Data System (ADS)

    Zhao, Yun; Lombardo, David; Mathews, Jay; Agha, Imad

    2017-02-01

    We employ the process of non-degenerate four-wave mixing Bragg scattering to demonstrate all-optical control in a silicon platform. In our configuration, a strong, non-information-carrying pump is mixed with a weak control pump and an input signal in a silicon-on-insulator waveguide. Through the optical nonlinearity of this highly confining waveguide, the weak pump controls the wavelength conversion process from the signal to an idler, leading to a controlled depletion of the signal. The strong pump, on the other hand, plays the role of a constant bias. In this work, we show experimentally that it is possible to implement this low-power switching technique as a first step towards universal optical logic gates, and test the performance with random binary data. Even at very low powers, where the signal and control pump levels are almost equal, the eye-diagrams remain open, indicating a successful operation of the logic gates.

  5. Microwave photonic notch filter with complex coefficient based on four wave mixing

    NASA Astrophysics Data System (ADS)

    Xu, Dong; Cao, Ye; Tong, Zheng-rong; Yang, Jing-peng

    2016-11-01

    A microwave photonic notch filter with a complex coefficient is proposed and demonstrated based on four wave mixing (FWM). FWM effect of two single-frequency laser beams occurs in a highly nonlinear fiber (HNLF), and multi-wavelength optical signals are generated and used to generate the multi-tap of microwave photonic filter (MPF). The complex coefficient is generated by using a Fourier-domain optical processor (FD-OP) to control the amplitude and phase of the optical carrier and phase modulation sidebands. The results show that this filter can be changed from bandpass filter to notch filter by controlling the FD-OP. The center frequency of the notch filter can be continuously tuned from 5.853 GHz to 29.311 GHz with free spectral range ( FSR) of 11.729 GHz. The shape of the frequency response keeps unchanged when the phase is tuned.

  6. Quantitative degenerate four-wave mixing spectroscopy: Probes for molecular species

    SciTech Connect

    Farrow, R.; Rakestraw, D.; Paul, P.; Lucht, R.; Danehy, P.; Friedman-Hill, E.; Germann, G.

    1993-12-01

    Resonant degenerate four-wave mixing (DFWM) is currently the subject of intensive investigation as a sensitive diagnostic tool for molecular species. DFWM has the advantage of generating a coherent (beam-like) signal which results in null-background detection and provides excellent immunity to background-light interference. Since multiple one-photon resonances are involved in the signal generation process, the DFWM technique can allow sensitive detection of molecules via electronic, vibrational or rotational transitions. These properties combine to make DFWM a widely applicable diagnostic technique for the probing of molecular species. The authors are conducting fundamental and applied investigations of DFWM for quantitative measurements of trace species in reacting gases. During the past year, efforts have been focussed in two areas: (1) understanding the effects of collisional processes on the DFWM signal generation process, and (2) exploring the applicability of infrared DFWM to detect polyatomic molecules via rovibrational transitions.

  7. Intense terahertz-pulse generation by four-wave mixing process in induced gas plasma

    NASA Astrophysics Data System (ADS)

    Wicharn, S.; Buranasiri, P.

    2015-08-01

    In this article, we have numerically investigated an intense terahertz (THz) pulses generation in gaseous plasma based on the third-order nonlinear effect, four-wave mixing rectification (FWMR). We have proposed that the fundamental fields and second-harmonic field of ultra-short pulse lasers are combined and focused into a very small gas chamber to induce a gaseous plasma, which intense THz pulse is produced. To understand the THz generation process, the first-order multiple-scale perturbation method (MSPM) has been utilized to derive a set of nonlinear coupled-mode equations for interacting fields such as two fundamental fields, a second-harmonic field, and a THz field. Then, we have simulate the intense THz-pulse generation by using split step-beam propagation method (SS-BPM) and calculated output THz intensities. Finally, the output THz intensities generated from induced air, nitrogen, and argon plasma have been compared.

  8. Conversion efficiency in the process of copolarized spontaneous four-wave mixing

    SciTech Connect

    Garay-Palmett, Karina; U'Ren, Alfred B.; Rangel-Rojo, Raul

    2010-10-15

    We study the process of copolarized spontaneous four-wave mixing in single-mode optical fibers, with an emphasis on an analysis of the conversion efficiency. We consider both the monochromatic-pump and pulsed-pump regimes, as well as both the degenerate-pump and nondegenerate-pump configurations. We present analytical expressions for the conversion efficiency, which are given in terms of double integrals. In the case of pulsed pumps we take these expressions to closed analytical form with the help of certain approximations. We present results of numerical simulations, and compare them to values obtained from our analytical expressions, for the conversion efficiency as a function of several key experimental parameters.

  9. Freely designable optical frequency conversion in Raman-resonant four-wave-mixing process

    PubMed Central

    Zheng, Jian; Katsuragawa, Masayuki

    2015-01-01

    Nonlinear optical processes are governed by the relative-phase relationships among the relevant electromagnetic fields in these processes. In this Report, we describe the physics of arbitrary manipulation of Raman-resonant four-wave-mixing process by artificial control of relative phases. As a typical example, we show freely designable optical-frequency conversions to extreme spectral regions, mid-infrared and vacuum-ultraviolet, with near-unity quantum efficiencies. Furthermore, we show that such optical-frequency conversions can be realized by using a surprisingly simple technology where transparent plates are placed in a nonlinear optical medium and their positions and thicknesses are adjusted precisely. In a numerical simulation assuming practically applicable parameters in detail, we demonstrate a single-frequency tunable laser that covers the whole vacuum-ultraviolet spectral range of 120 to 200 nm. PMID:25748023

  10. Performance evaluation of four-wave mixing in a graphene-covered tapered fiber

    NASA Astrophysics Data System (ADS)

    Jin, Qiang; Lu, Jiamei; Li, Xibin; Yan, Qiang; Gao, Qianyu; Gao, Shiming

    2016-07-01

    Four-wave mixing in a monolayer graphene-covered tapered fiber is theoretically analyzed by taking into account the influence of the graphene layer on the light-field distribution. A figure-of-merit (FOM) coefficient, considering both the high nonlinearity and the heavy absorption, is redefined to evaluate nonlinear performance. The fiber diameter and length are optimized to acquire a higher FOM. Using such a graphene-covered tapered fiber with an optimal diameter of 0.736 μm, a maximum conversion efficiency of -38.07 dB is numerically obtained for the 1.55 μm pump when the graphene length is 34.4 μm and the peak pump power is 10 W. Moreover, a 3 dB bandwidth as broad as 430 nm can be realized in the 1.55 μm telecommunication band.

  11. Infrared pulse characterization using four-wave mixing inside a few cycle pulse filament in air

    SciTech Connect

    Marceau, Claude Thomas, Steven; Kassimi, Yacine; Gingras, Guillaume; Witzel, Bernd

    2014-02-03

    We demonstrate a four-wave mixing (FWM) technique to measure near- and mid-infrared (IR) laser pulse shapes in time domain. Few cycle 800 nm laser pulses were synchronized with the IR pulse and focused colinearly to generate a plasma filament in air. Second harmonic radiation around 400 nm was generated through FWM, with a yield proportional to the IR pulse intensity. Excellent signal to noise ratio was observed from 2.1 μm to 18 μm. With proper phase stabilization of the IR beam, this technique is a promising step toward direct electric field sensing of near-IR pulses in air.

  12. Broadband photon pair generation in green fluorescent proteins through spontaneous four-wave mixing

    PubMed Central

    Shi, Siyuan; Thomas, Abu; Corzo, Neil V.; Kumar, Prem; Huang, Yuping; Lee, Kim Fook

    2016-01-01

    Recent studies in quantum biology suggest that quantum mechanics help us to explore quantum processes in biological system. Here, we demonstrate generation of photon pairs through spontaneous four-wave mixing process in naturally occurring fluorescent proteins. We develop a general empirical method for analyzing the relative strength of nonlinear optical interaction processes in five different organic fluorophores. Our results indicate that the generation of photon pairs in green fluorescent proteins is subject to less background noises than in other fluorophores, leading to a coincidence-to-accidental ratio ~145. As such proteins can be genetically engineered and fused to many biological cells, our experiment enables a new platform for quantum information processing in a biological environment such as biomimetic quantum networks and quantum sensors. PMID:27076032

  13. Methods and apparatus of entangled photon generation using four-wave mixing

    SciTech Connect

    Camacho, Ryan

    2016-02-23

    A non-linear optical device is provided. The device comprises an optical disk or ring microresonator fabricated from a material that exhibits an optical nonlinearity able to produce degenerate four-wave mixing (FWM) in response to a pump beam having a pump frequency in a specified effective range. The microresonator is conformed to exhibit an angular group velocity minimum at a pump frequency within the specified effective range such that there is zero angular group velocity dispersion at the pump frequency. We refer to such a pump frequency as the "zero dispersion frequency". In embodiments, excitation of the resonator by a pump beam of sufficient intensity at the zero-dispersion frequency causes the resonator to emit a frequency comb of entangled photon pairs wherein the respective frequencies in each pair are symmetrically placed about the zero-dispersion frequency.

  14. Scanning nonreciprocity spatial four-wave mixing process in moving photonic band gap

    NASA Astrophysics Data System (ADS)

    Wang, Hang; Zhang, Yunzhe; Li, Mingyue; Ma, Danmeng; Guo, Ji; Zhang, Dan; Zhang, Yanpeng

    2017-03-01

    We experimentally investigate the scanning nonreciprocity of four-wave mixing process induced by optical parametric amplification in moving photonic band gap, which is different from the propagation nonreciprocity in the optical diode. Meanwhile the frequency offset and the intensity difference are observed when we scan the frequency of the beams on two arm ramps of one round trip. Such scanning nonreciprocities can be controlled by changing the frequency detuning of the dressing beams. For the first time, we find that the intensity difference can cause the nonreciprocity in spatial image. In the nonreciprocity process, the focusing or defocusing is resulted from the feedback dressing self-phase modulation while shift and split is attributed to feedback dressing cross-phase modulation. Our study could have a potential application in the controllable optical diode.

  15. Experimental characterization of quantum correlated triple beams generated by cascaded four-wave mixing processes

    SciTech Connect

    Qin, Zhongzhong; Cao, Leiming; Jing, Jietai

    2015-05-25

    Quantum correlations and entanglement shared among multiple modes are fundamental ingredients of most continuous-variable quantum technologies. Recently, a method used to generate multiple quantum correlated beams using cascaded four-wave mixing (FWM) processes was theoretically proposed and experimentally realized by our group [Z. Qin et al., Phys. Rev. Lett. 113, 023602 (2014)]. Our study of triple-beam quantum correlation paves the way to showing the tripartite entanglement in our system. Our system also promises to find applications in quantum information and precision measurement such as the controlled quantum communications, the generation of multiple quantum correlated images, and the realization of a multiport nonlinear interferometer. For its applications, the degree of quantum correlation is a crucial figure of merit. In this letter, we experimentally study how various parameters, such as the cell temperatures, one-photon, and two-photon detunings, influence the degree of quantum correlation between the triple beams generated from the cascaded two-FWM configuration.

  16. Broadband photon pair generation in green fluorescent proteins through spontaneous four-wave mixing

    NASA Astrophysics Data System (ADS)

    Shi, Siyuan; Thomas, Abu; Corzo, Neil V.; Kumar, Prem; Huang, Yuping; Lee, Kim Fook

    2016-04-01

    Recent studies in quantum biology suggest that quantum mechanics help us to explore quantum processes in biological system. Here, we demonstrate generation of photon pairs through spontaneous four-wave mixing process in naturally occurring fluorescent proteins. We develop a general empirical method for analyzing the relative strength of nonlinear optical interaction processes in five different organic fluorophores. Our results indicate that the generation of photon pairs in green fluorescent proteins is subject to less background noises than in other fluorophores, leading to a coincidence-to-accidental ratio ~145. As such proteins can be genetically engineered and fused to many biological cells, our experiment enables a new platform for quantum information processing in a biological environment such as biomimetic quantum networks and quantum sensors.

  17. Picosecond phase-conjugation by degenerate four-wave mixing in sodium vapour

    NASA Astrophysics Data System (ADS)

    Cefalas, A. C.; Mikropoulos, T.; Simon, P.; Hebling, J.; Nicolaides, C. A.

    1988-08-01

    Phase-conjugated waves (PCW), via degenerate four-wave mixing (DFWM) with picosecond laser pulses having a FWHM of 80 ps have been obtained in sodium vapour on both sides of the D 2(32 S 1/2→32 P 3/2) transition at 589 nm. The maximum reflectivity of the PCW signals was 60%. The reflectivity of the PCW has been measured as a function of the temperature, the detuning and the pump and probe intensities. Because of the very strong nonlinear behaviour of the D 2 transition the appearance of the PCW is accompanied by strong self-focusing and defocusing of the beams, which give a rather complicated line-shape of the detuning curve of the PCW. By varying the delay between the beams, the lifetime of the transient volume grating has been, measured to be 7.4 ns. The results are in qualitative agreement with the theoretical model of Abrams and Lind.

  18. Triply surface-plasmon resonant four-wave mixing imaging of gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Masia, Francesco; Langbein, Wolfgang; Watson, Peter; Borri, Paola

    2011-03-01

    We have developed a novel multiphoton microscopy technique not relying on (and hence not limited by) fluorescence emission, which exploits the third-order nonlinearity called four-wave mixing of gold nanoparticles in resonance with their surface Plasmon. The coherent, transient and resonant nature of this signal allows its detection free from backgrounds that limit other contrast methods for gold nanoparticles. We show detection of single 10nm gold nanoparticles with low excitation intensities, corresponding to negligible average thermal heating. Owing to the the third-order nonlinearity we measure a transversal and axial resolution of 140nm and 470nm respectively, better than the one-photon diffraction limit. We also show high-contrast imaging of gold-labels down to 5nm size in Golgi structures of HepG2 cells at useful imaging speeds (10 kHz pixel rate). Thermal dissociation of gold nanoparticles from their bonding sites when varying the excitation intensity is also investigated.

  19. Vibrational-coherence measurement of nonequilibrium quantum systems by four-wave mixing

    NASA Astrophysics Data System (ADS)

    Schubert, Alexander; Falvo, Cyril; Meier, Christoph

    2015-11-01

    We show theoretically that a quantum system in a nonequilibrium state interacting with a set of laser pulses in a four-wave-mixing setup leads to signal emission in directions opposite to the ones usually considered. When combined with a pump mechanism which sets a time origin for the nonequilibrium state creation, this particular optical response can be utilized to directly follow decoherence processes in real time. By varying the time delays within the probe sequence, signals in these unconventional directions can also be used to detect two-dimensional spectra determined by the dynamics of up to three-quantum coherences, revealing energetical anharmonicities and environmental influences. As a numerical example, these findings are demonstrated by considering a model of vibrational decoherence of carbon monoxide after photolysis from a hemeprotein.

  20. Four-wave mixing using polarization grating induced thermal grating in liquids exhibiting circular dichroism

    SciTech Connect

    Nunes, J.A.; Tong, W.G.; Chandler, D.W.; Rahn, L.A.

    1995-04-01

    A novel four-wave mixing technique for the detection of circular dichroism in optically active liquid samples is demonstrated. When two cross-polarized laser beams are crossed at a small angle in a circular dichroic liquid a weak thermal grating is produced with a phase depending on the sign of the circular dichroism. The authors show that the polarization of one of the beams can be modified to allow coherent interference with an intensity-grating induced thermal grating. A probe beam scattering from the composite grating results in a signal that reveals the sign and magnitude of the circular dichroism. The use of this technique to optimize the signal-to-noise ratio in the presence of scattered light and laser intensity noise is discussed.

  1. Degenerate four wave mixing in large mode area hybrid photonic crystal fibers.

    PubMed

    Petersen, Sidsel R; Alkeskjold, Thomas T; Lægsgaard, Jesper

    2013-07-29

    Spontaneous degenerate four wave mixing (FWM) is investigated in large mode area hybrid photonic crystal fibers, in which photonic bandgap guidance and index guidance is combined. Calculations show the parametric gain is maximum on the edge of a photonic bandgap, for a large range of pump wavelengths. The FWM products are observed on the edges of a transmission band experimentally, in good agreement with the numerical results. Thereby the bandedges can be used to control the spectral positions of FWM products through a proper fiber design. The parametric gain control combined with a large mode area fiber design potentially allows for power scaling of light at wavelengths not easily accessible with e.g. rare earth ions.

  2. Broadband wavelength converter based on four-wave mixing in a highly nonlinear photonic crystal fiber.

    PubMed

    Zhang, Ailing; Demokan, M S

    2005-09-15

    We demonstrate a 10 Gbit/s nonreturn-to-zero wavelength converter based on four-wave mixing in a 20 m highly nonlinear photonic crystal fiber. The tunable wavelength conversion bandwidth (3 dB) is about 100 nm. The conversion efficiency is -16 dB when the pump power is 22.5 dBm. Phase modulation was not used to suppress the stimulated Brillouin scattering; thus the linewidth of the converted wavelength remained very narrow. The eye diagrams show that there is no additional noise during wavelength conversion. The measured power penalty at a 10(-9) bit-error-rate level is about 0.7 dB.

  3. Multi-channel entanglement distribution using spatial multiplexing from four-wave mixing in atomic vapor

    NASA Astrophysics Data System (ADS)

    Gupta, Prasoon; Horrom, Travis; Anderson, Brian E.; Glasser, Ryan; Lett, Paul D.

    2016-02-01

    Four-wave mixing in atomic vapor allows for the generation of multi-spatial-mode states of light containing many pairs of two-mode entangled vacuum beams. This in principle can be used to send independent secure keys to multiple parties simultaneously using a single light source. In our experiment, we demonstrate this spatial multiplexing of information by selecting three independent pairs of entangled modes and performing continuous-variable measurements to verify the correlations between entangled partners. In this way, we generate three independent pairs of correlated random bit streams that could be used as secure keys. We then demonstrate a classical four-party secret sharing scheme as an example for how this spatially multiplexed source could be used.

  4. Exploitation of transverse spatial modes in spontaneous four wave mixing photon-pair sources

    NASA Astrophysics Data System (ADS)

    Cruz-Ramirez, Hector; Ramirez-Alarcon, Roberto; Cruz-Delgado, Daniel; Monroy-Ruz, Jorge; Ortiz-Ricardo, Erasto; Dominguez-Serna, Francisco; Garay-Palmett, Karina; U'Ren, Alfred B.

    2016-09-01

    We present a source for which multiple spontaneous four-wave mixing (SFWM) processes are supported in a few mode birefringent fiber, each process associated with a particular combination of transverse modes for the four participating waves. Within the weakly guiding regime, for which the propagation modes may be well approximated by linearly polarized (LP) modes, the departure from circular symmetry due to the fiber birefringence translates into orbital angular momentum (OAM) and parity conservation rules, i.e. reflecting elements from both azimuthal and rectangular symmetries. In our source: i) each process is group-velocity-matched so that it is, by design, nearly-factorable, and ii) the spectral separation between neighboring processes is greater than the marginal spectral width of each process. Consequently, there is a direct correspondence between the joint amplitude of each process and each of the Schmidt mode pairs of the overall two-photon state. The present paper covers work presented in Refs.1 and.2

  5. Highly efficient generation of broadband cascaded four-wave mixing products.

    PubMed

    Cerqueira S, Arismar; Boggio, J M Chavez; Rieznik, A A; Hernandez-Figueroa, H E; Fragnito, H L; Knight, J C

    2008-02-18

    We propose a novel way to efficiently generate broadband cascaded Four-Wave Mixing (FWM) products. It consists of launching two strong pump waves near the zero-dispersion wavelength of a very short (of order a few meters) optical fiber. Simulations based on Split Step Fourier Method (SSFM) and experimental data demonstrate the efficiency of our new approach. Multiple FWM products have been investigated by using conventional fibers and ultra-flattened dispersion photonic crystal fibers (UFD-PCFs). Measured results present bandwidths of 300 nm with up to 118 FWM products. We have also demonstrated a flat bandwidth of 110 nm covering the C and L bands, with a small variation of only 1.2 dB between the powers of FWM products, has been achieved using highly nonlinear fibers (HNLFs). The use of UFD-PCFs has been shown interesting for improving the multiple FWM efficiency and reducing the separation between the pump wavelengths.

  6. Filamentation assisted generation of tunable multicolored femtosecond sidebands based on cascaded four-wave mixing

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Liu, Jun; Li, Fangjia; Shen, Xiong; Li, Ruxin

    2015-05-01

    Tunable intense multicolored femtosecond sidebands are generated in a 0.1 mm-thick sapphire plate based on cascaded four-wave mixing (CFWM) by using a spectrally broadened pulse from filamentation in air and a 806 nm fundamental pulse from a Ti:sapphire laser amplifier. By using the filamentation to extend the spectrum of one incident pulse, the experimental setup is compact and inexpensive. Furthermore, the spectra of the sidebands can be conveniently tuned by varying the input power for the filamentation generation, and even the second-order frequency upconversion sideband can maintain its output power higher than 0.2 mW during the process of tuning. The generated sidebands are observed with a spectral range from 500 to 950 nm, and each spectrum has a full width half maximum (FWHM) bandwidth above 37 nm, which have potential applications in ultrafast spectroscopy and microscopy.

  7. Nonlinear Sagnac interferometer based on the four-wave mixing process.

    PubMed

    Xin, Jun; Liu, Jinming; Jing, Jietai

    2017-01-23

    A new nonlinear Sagnac interferometer (NSI) is proposed by replacing the beam-splitter in the traditional Sagnac interferometer (TSI) with a four-wave mixing process. Such a NSI has better angular velocity sensitivity than the one of the TSI. The standard quantum limit can be beaten and the Heisenberg Limit can even be reached for the ideal case by the NSI. We study the effect of the losses on the angular velocity sensitivity of the NSI and find that the optimal angular velocity, where the best angular velocity sensitivity can be obtained, of the NSI may be dependent on the losses inside the interferometer. Such a NSI has its advantages compared with the TSI and may find its potential applications in quantum metrology.

  8. Photon statistics of pulse-pumped four-wave mixing in fiber with weak signal injection

    NASA Astrophysics Data System (ADS)

    Nan-Nan, Liu; Yu-Hong, Liu; Jia-Min, Li; Xiao-Ying, Li

    2016-07-01

    We study the photon statistics of pulse-pumped four-wave mixing in fibers with weak coherent signal injection by measuring the intensity correlation functions of individual signal and idler fields. The experimental results show that the intensity correlation function of individual signal (idler) field decreases with the intensity of signal injection. After applying narrow band filter in signal (idler) band, the value of decreases from 1.9 ± 0.02 (1.9 ± 0.02) to 1.03 ± 0.02 (1.05 ± 0.02) when the intensity of signal injection varies from 0 to 120 photons/pulse. The results indicate that the photon statistics changes from Bose-Einstein distribution to Poisson distribution. We calculate the intensity correlation functions by using the multi-mode theory of four-wave mixing in fibers. The theoretical curves well fit the experimental results. Our investigation will be useful for mitigating the crosstalk between quantum and classical channels in a dense wavelength division multiplexing network. Project supported by the National Natural Science Foundation of China (Grant No. 11527808), the State Key Development Program for Basic Research of China (Grant No. 2014CB340103), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120032110055), the Natural Science Foundation of Tianjin, China (Grant No. 14JCQNJC02300), the Program for Changjiang Scholars and Innovative Research Team in University, China, and the Program of Introducing Talents of Discipline to Universities, China (Grant No. B07014).

  9. Electric Field Measurements in Non-Equilibrium Electric Discharge Plasmas Using Picosecond Four-Wave Mixing

    NASA Astrophysics Data System (ADS)

    Goldberg, Benjamin M.

    This dissertation presents the results of development of a picosecond four wave mixing technique and its use for electric field measurements in nanosecond pulse discharges. This technique is similar to coherent anti-Stokes Raman spectroscopy and is well suited for electric field measurements in high pressure plasmas with high spatial and temporal resolution. The results show that the signal intensity scales proportionally to the square of the electric field, the signal is emitted as a coherent beam, and is polarized parallel to the electric field vector, making possible electric field vector component measurements. The signal is generated when a collinear pair of pump and Stokes beams, which are generated in a stimulated Raman shifting cell (SRS), generate coherent excitation of molecules into a higher energy level, hydrogen for the present work. The coherent excitation mixes with a dipole moment induced by an external electric field. The mixing of these three "waves'" allows the molecules to radiate at their Raman frequency, producing a fourth, signal, wave which is proportional to the square of the electric field. The time resolution of this technique is limited by the coherence decay time of the molecules, which is a few hundred picoseconds.

  10. Two-Photon Absorption and Two-Photon Four-Wave Mixing for the Terbium Ion in Insulators.

    NASA Astrophysics Data System (ADS)

    Huang, Jin

    Resonant enhancement of over two orders of magnitude of direct two-photon absorption from the ground state ^7F_6 to the excited state ^5G_6 of the 4f^8 configuration of Tb^{3+} at 40,200 cm ^{-1} has been observed in time resolved experiments with two separate lasers. The results provide clear evidence for resonant enhancement of two-photon absorption in rare earth compounds and imply the same for Raman scattering. Two separate transition mechanisms have been observed. When a single laser frequency was used, the intermediate states making the largest contribution were from excited configurations of opposite parity which were far from resonance. Detailed two-frequency experiments showed, however, that near the single photon resonance, there was a much stronger contribution from the 4f ^8 configuration ^5D _4 intermediate state. The phase-matching-induced frequency selectivity in the single-photon-resonant four-wave mixing has been observed in further rare earth compounds. These observations provide additional evidence that the phase matching effects, resulting from anomalous dispersion associated with the single-photon resonance, play a major role in determining both the intensity and the line narrowing of the mixing signal, and that similar effects will be observable in any rare earth compound. An effect of two-photon-resonant four-wave mixing has been observed for a transition to the 4f^8 configuration ^5K _8 state of the Tb^{3+ } ion in LiYF_4. The strength of the resonance is comparable to that of single -photon resonances. This technique holds promise as a new spectroscopic tool, especially for studies of two-photon transitions in non-fluorescent materials.

  11. Line-space description of resonant four-wave mixing: theory for isotropic molecular states.

    PubMed

    Kouzov, A; Radi, P

    2014-05-21

    Based on the quantum Liouville formalism, a theory of the two-color, triply resonant four-wave mixing is developed for molecules with isotropically oriented angular momenta. The approach allows to strictly incorporate the relaxation matrices Γ((r)) (r = 0, 1, 2) into the third-order susceptibility χ((3)) whose expression acquires therewith the form of a scalar product in the line space. Thanks to this representation, isolation of all resonance terms from χ((3)) becomes a routine task. Some of these terms correspond to the case when a molecule initially interacts with two pump photons of the same frequency. Such interactions give rise to the grating line-space vectors which have the same (zero) eigenfrequency. Due to this degeneracy, the latter are easily mixed by rotationally inelastic collisions which shows up in a state-resolved coherence transfer. The satellite signals induced thereby provide a great scope to study the state-to-state inelastic rates in situ by purely optical means. If the diagonal form of Γ is assumed, the satellites become forbidden and our results reduce to conventional expressions for the main resonances. Polarization configurations are designed for direct measurements of the population (r = 0), orientation (r = 1), and alignment (r = 2) contributions to χ((3)). Finally, depending on the photon-molecule interaction sequence, the resonance terms of χ((3)) are shown to be differently affected by velocity averaging, the effect which conspicuously manifests itself when Doppler broadening becomes paramount.

  12. THz generation by two-color femtosecond filaments with complex polarization states: four-wave mixing versus photocurrent contributions

    NASA Astrophysics Data System (ADS)

    Fedorov, V. Yu; Koulouklidis, A. D.; Tzortzakis, S.

    2017-01-01

    Two-color filamenation in gases is known to produce intense and broadband THz radiation. There are two physical mechanisms responsible for the THz generation in this scheme: four-wave mixing and emission from the induced plasma currents. The case when the main and second harmonic are linearly polarized is well studied including the impact from each of the above mechanisms. However, for the cases when the two-color fields have complex polarization states the role of the four-wave mixing and plasma mechanisms in the formation of the THz polarization is still under-explored. Here we use both the four-wave mixing and photocurrent models in order to consider the THz generation by two-color fields with arbitrary polarizations. We show that under specific polarizations of the two-color field components it is possible to determine which of the mechanisms is responsible for the THz polarization formation.

  13. Efficient reflection via four-wave mixing in a Doppler-free electromagnetically-induced-transparency gas system

    SciTech Connect

    Zhou, Hai-Tao; Wang, Dan; Zhang, Jun-Xiang; Wang, Da-Wei; Zhu, Shi-Yao

    2011-11-15

    We experimentally demonstrate the high-efficiency reflection of a probe field in {Lambda}-type three-level atoms of cesium vapor driven by two counterpropagating coupling fields. More than 60% of reflection efficiency is observed at the phase-matching angle. The underlying mechanism theoretically is investigated as the four-wave mixing is enhanced by the electromagnetically-induced transparency. Both of the two Doppler-free two-photon resonances (one for the probe and co-propagating fields, the other for the reflected and the counterpropagation fields) play an important role in satisfying the phase matching in the reflection direction. The phase compensation due to the anomalous dispersion and the decrease of effective absorption length in the atomic system allow the efficient reflection to be observed in a wide range of incident angles of the probe field and detunings of the coupling field.

  14. Optical encryption of parallel quadrature phase shift keying signals based on nondegenerate four-wave mixing in highly nonlinear fiber

    NASA Astrophysics Data System (ADS)

    Cui, Yue; Zhang, Min; Zhan, Yueying; Wang, Danshi; Huang, Shanguo

    2016-08-01

    A scheme for optical parallel encryption/decryption of quadrature phase shift keying (QPSK) signals is proposed, in which three QPSK signals at 10 Gb/s are encrypted and decrypted simultaneously in the optical domain through nondegenerate four-wave mixing in a highly nonlinear fiber. The results of theoretical analysis and simulations show that the scheme can perform high-speed wiretapping against the encryption of parallel signals and receiver sensitivities of encrypted signal and the decrypted signal are -25.9 and -23.8 dBm, respectively, at the forward error correction threshold. The results are useful for designing high-speed encryption/decryption of advanced modulated signals and thus enhancing the physical layer security of optical networks.

  15. Frequency shift in three-photon resonant four-wave mixing by internal atom-field interaction

    NASA Astrophysics Data System (ADS)

    de Melo, Natalia R.; Vianna, Sandra S.

    2015-11-01

    We report on experimental results of four-wave mixing processes in rubidium vapor where coherence is induced on the three-photon resonant transition from 5 s to 6 p states via intermediate Rydberg levels. It is shown that the use of two beams in a noncollinear configuration, i.e., θ ≠0 , and high atomic density unveil new features. First, the θ =0 (collinear configuration) odd-photon destructive interference between the incident and generated fields is strongly inhibited for θ ≠0 . Second, most importantly, the observed cooperative frequency shift of the three-photon transition is strongly enhanced for small, but nonzero, values of θ due to the factor (1-cosθ ) -1, which is not present if the generated radiation field is not considered self-consistently in the Maxwell-Bloch equations.

  16. Stimulated and spontaneous four-wave mixing in silicon-on-insulator coupled photonic wire nano-cavities

    NASA Astrophysics Data System (ADS)

    Azzini, Stefano; Grassani, Davide; Galli, Matteo; Gerace, Dario; Patrini, Maddalena; Liscidini, Marco; Velha, Philippe; Bajoni, Daniele

    2013-07-01

    We report on four-wave mixing in coupled photonic crystal nano-cavities on a silicon-on-insulator platform. Three photonic wire cavities are side-coupled to obtain three modes equally separated in energy. The structure is designed to be self-filtering, and we show that the pump is rejected by almost two orders of magnitude. We study both the stimulated and the spontaneous four-wave mixing processes: owing to the small modal volume, we find that signal and idler photons are generated with a hundred-fold increase in efficiency as compared to silicon micro-ring resonators.

  17. Quantum correlations by four-wave mixing in an atomic vapor in a nonamplifying regime: Quantum beam splitter for photons

    SciTech Connect

    Glorieux, Quentin; Guidoni, Luca; Guibal, Samuel; Likforman, Jean-Pierre; Coudreau, Thomas

    2011-11-15

    We study the generation of intensity quantum correlations using four-wave mixing in a rubidium vapor. The absence of cavities in these experiments allows to deal with several spatial modes simultaneously. In the standard amplifying configuration, we measure relative intensity squeezing up to 9.2 dB below the standard quantum limit. We also theoretically identify and experimentally demonstrate an original regime where, despite no overall amplification, quantum correlations are generated. In this regime, a four-wave mixing setup can play the role of a photonic beam splitter with nonclassical properties, that is, a device that splits a coherent state input into two quantum-correlated beams.

  18. Nonlinear photonic crystal fiber with a structured multi-component glass core for four-wave mixing and supercontinuum generation.

    PubMed

    Tombelaine, Vincent; Labruyère, Alexis; Kobelke, Jens; Schuster, Kay; Reichel, Volker; Leproux, Philippe; Couderc, Vincent; Jamier, Raphaël; Bartelt, Hartmut

    2009-08-31

    We report about a new type of nonlinear photonic crystal fibers allowing broadband four-wave mixing and supercontinuum generation. The microstructured optical fiber has a structured core consisting of a rod of highly nonlinear glass material inserted in a silica tube. This particular structure enables four wave mixing processes with very large frequency detuning (>135 THz), which permitted the generation of a wide supercontinuum spectrum extending over 1650 nm after 2.15 m of propagation length. The comparison with results obtained from germanium-doped holey fibers confirms the important role of the rod material properties regarding nonlinear process and dispersion.

  19. Wideband tuning of four-wave mixing in solid-core liquid-filled photonic crystal fibers.

    PubMed

    Velázquez-Ibarra, Lorena; Díez, Antonio; Silvestre, Enrique; Andrés, Miguel V

    2016-06-01

    We present an experimental study of parametric four-wave mixing generation in photonic crystal fibers that have been infiltrated with ethanol. A silica photonic crystal fiber was designed to have the proper dispersion properties after ethanol infiltration for the generation of widely spaced four-wave mixing (FWM) bands under 1064 nm pumping. We demonstrate that the FWM bands can be tuned in a wide wavelength range through the thermo-optic effect. Band shifts of 175 and over 500 nm for the signal and idler bands, respectively, are reported. The reported results can be of interest in many applications, such as CARS microscopy.

  20. Four-wave mixing in Bose-Einstein condensate systems with multiple spin states

    SciTech Connect

    Burke, J.P. Jr.; Julienne, P. S.; Williams, C.J.; Band, Y.B.; Trippenbach, M.

    2004-09-01

    We calculate the four-wave mixing (FWM) in a Bose-Einstein condensate system having multiple spin wave packets that are initially overlapping in physical space, but have nonvanishing relative momentum that causes them to recede from one another. Three receding condensate atom wave packets can result in production of a fourth wave packet by the process of FWM due to atom-atom interactions. We consider cases where the four final wave packets are composed of one, two, three, and four different internal spin components. FWM with one or two-spin state wave packets is much stronger than three- or four-spin state FWM, wherein two of the coherent moving Bose-Einstein condensate wave packets form a spin-polarization grating that rotates the spin projection of the third wave into that of the fourth diffracted wave (as opposed to the one- or two-spin state case where a regular density grating is responsible for the diffraction). Calculations of FWM for {sup 87}Rb and {sup 23}Na condensate systems are presented.

  1. Theoretical Analysis of the Resonance Four-Wave Mixing Amplitudes: a Fully Non-Degenerate Case.

    NASA Astrophysics Data System (ADS)

    Kouzov, Alexander

    2015-06-01

    Degenerate (one-color) and two-color variants of the resonant four-wave mixing (RFWM) have developed into a sensitive and nonintrusive spectroscopic tool to study molecules in different gaseous environments. Yet, the fully non-degenerate (four-color, 4C) RFWM was scrutinized and implemented only for the Coherent AntiStokes Raman Scattering (CARS) excitation scheme. Here, by using the line-space approach, we analyze other 4C-RFWM schemes potentially interesting for the efficient up- and down-frequency conversion as well as for studies of molecular states. Decoupled expressions of the 4C-RFWM amplitudes are derived which allows to predict their polarization dependence. B. Attal-Trétout, P. Berlemont, and J. P. Taran, Mol. Phys. 70, 1 (1990). J.P. Kuehner, S.V. Naik, W.D. Kulatilaka, N. Chai, N.M. Laurendeau, R.P. Lucht, M.O. Scully, S. Roy, A.K. Patnaik, and J.R. Gord, J. Chem. Phys. 128, 174308 (2008). A. Kouzov and P. Radi, J. Chem. Phys. 140, 194302 (2014).

  2. Optical negative refraction by four-wave mixing in thin metallic nanostructures

    NASA Astrophysics Data System (ADS)

    Palomba, Stefano; Zhang, Shuang; Park, Yongshik; Bartal, Guy; Yin, Xiaobo; Zhang, Xiang

    2012-01-01

    The law of refraction first derived by Snellius and later introduced as the Huygens-Fermat principle, states that the incidence and refracted angles of a light wave at the interface of two different materials are related to the ratio of the refractive indices in each medium. Whereas all natural materials have a positive refractive index and therefore exhibit refraction in the positive direction, artificially engineered negative index metamaterials have been shown capable of bending light waves negatively. Such a negative refractive index is the key to achieving a perfect lens that is capable of imaging well below the diffraction limit. However, negative index metamaterials are typically lossy, narrow band, and require complicated fabrication processes. Recently, an alternative approach to obtain negative refraction from a very thin nonlinear film has been proposed and experimentally demonstrated in the microwave region. However, such approaches use phase conjugation, which makes optical implementations difficult. Here, we report a simple but different scheme to demonstrate experimentally nonlinear negative refraction at optical frequencies using four-wave mixing in nanostructured metal films. The refractive index can be designed at will by simply tuning the wavelengths of the interacting waves, which could have potential impact on many important applications, such as superlens imaging.

  3. Phase-locking and Pulse Generation in Multi-Frequency Brillouin Oscillator via Four Wave Mixing

    NASA Astrophysics Data System (ADS)

    Büttner, Thomas F. S.; Kabakova, Irina V.; Hudson, Darren D.; Pant, Ravi; Poulton, Christopher G.; Judge, Alexander C.; Eggleton, Benjamin J.

    2014-05-01

    There is an increasing demand for pulsed all-fibre lasers with gigahertz repetition rates for applications in telecommunications and metrology. The repetition rate of conventional passively mode-locked fibre lasers is fundamentally linked to the laser cavity length and is therefore typically ~10-100 MHz, which is orders of magnitude lower than required. Cascading stimulated Brillouin scattering (SBS) in nonlinear resonators, however, enables the formation of Brillouin frequency combs (BFCs) with GHz line spacing, which is determined by the acoustic properties of the medium and is independent of the resonator length. Phase-locking of such combs therefore holds a promise to achieve gigahertz repetition rate lasers. The interplay of SBS and Kerr-nonlinear four-wave mixing (FWM) in nonlinear resonators has been previously investigated, yet the phase relationship of the waves has not been considered. Here, we present for the first time experimental and numerical results that demonstrate phase-locking of BFCs generated in a nonlinear waveguide cavity. Using real-time measurements we demonstrate stable 40 ps pulse trains with 8 GHz repetition rate based on a chalcogenide fibre cavity, without the aid of any additional phase-locking element. Detailed numerical modelling, which is in agreement with the experimental results, highlight the essential role of FWM in phase-locking of the BFC.

  4. Phase-sensitive cascaded four-wave-mixing processes for generating three quantum correlated beams

    NASA Astrophysics Data System (ADS)

    Wang, Li; Wang, Hailong; Li, Sijin; Wang, Yaxian; Jing, Jietai

    2017-01-01

    Theoretical studies and experimental implementations of quantum correlation are the important contents of continuous variables quantum optics and quantum information science. There are various systems for the study of quantum correlation. Here, we study an experimental scheme for generating three quantum correlated beams based on phase-sensitive cascaded four-wave-mixing (FWM) processes in rubidium vapor. Quantum correlation including intensity difference or sum squeezing, two other combinatorial squeezing, and quantum entanglement among the three output light fields are theoretically analyzed in this paper. Also, the comparison of the quantum correlations have been made between the phase-sensitive cascaded FWM processes and the phase-insensitive cascaded FWM processes. By changing the phases and intensities of the input beams, it is interesting to find that the maximum degrees of various combinatorial squeezing are equal when the two FWM processes share a common intensity gain. When the common intensity gain of the two FWM processes changes, the maximum degrees of different combinatorial squeezing will be synchronously controlled. At last we discuss the genuine tripartite entanglement and steering in our phase-sensitive cascaded scheme, and compare them with the cases of the phase-insensitive cascaded scheme.

  5. Nondegenerate Four-Wave Mixing in Gold Nanocomposites Formed by Ion Implantation

    SciTech Connect

    Saonov, V.P.; Zhu, J.G.; Lepeshkin, N.N.; Armstrong, R.L.; Shalaev, V.M.; Ying, Z.C.; White, C.W.; Zuhr, R.A.

    1999-07-01

    Nondegenerate four-wave mixing technique has been used to investigate the third-order nonlinear susceptibility for nanocomposite material with Au nanocrystals formed inside a SiO{sub 2} glass matrix. High concentrations of encapsulated Au nanocrystals are formed by implantation of Au ions into fused silica glass substrates and thermal annealing. The size distribution and the depth profiles of the Au nanoparticles can be controlled by the implantation dose, energy and annealing temperatures. The high value of the third-order susceptibility - (0.26--1.3)x10{sup -7} esu was found in the range of the frequency detunings near the surface plasmon resonance. Two characteristic relaxation times, 0.66 ps and 5.3 ps, have been extracted from the detuning curve of the third-order susceptibility as the probe-beam frequency changes and the pump-beam frequency fixed at the plasmon resonance. The first relaxation time was attributed to electron-phonon relaxation, and the second to thermal diffusion to the host medium. The efficient nondegenerate conversion is attractive for optical processing.

  6. Light storage based on four-wave mixing and electromagnetically induced transparency in cold atoms

    NASA Astrophysics Data System (ADS)

    Wu, Jinghui; Liu, Yang; Ding, Dong-Sheng; Zhou, Zhi-Yuan; Shi, Bao-Sen; Guo, Guang-Can

    2013-01-01

    We performed an experiment to observe the storage of an input probe field and an idler field generated through an off-axis four-wave mixing (FWM) process via a double-Λ configuration in a cold atomic ensemble. We analyzed the underlying physics in detail and found that the retrieved idler field came from two parts if there was no single-photon detuning for the pump pulse: Part 1 was from the collective atomic spin (the input probe field, the coupling field, and the pump field combined to generate the idler field through FWM; then the idler was stored through electromagnetically induced transparency). Part 2 was from the generated new FWM process during the retrieval process (the retrieved probe field, the coupling field, and the pump field combined to generate a new FWM signal). If there was single-photon detuning for the pump pulse, then the retrieved idler was mainly from part 2. The retrieved two fields exhibited damped oscillations with the same oscillatory period when a homogeneous external magnetic field was applied, which was caused by the Larmor spin precession. We also experimentally realized the storage and retrieval of an image of light using FWM, in which an image was added into the input signal. After the storage, the retrieved idler beams and input signal carried the same image. This image storage technique holds promise for applications in image processing, remote sensing, and quantum communication.

  7. Experimental setups for FEL-based four-wave mixing experiments at FERMI

    SciTech Connect

    Bencivenga, Filippo; Zangrando, Marco; Svetina, Cristian; Abrami, Alessandro; Battistoni, Andrea; Borghes, Roberto; Capotondi, Flavio; Cucini, Riccardo; Dallari, Francesco; Danailov, Miltcho; Demidovich, Alexander; Fava, Claudio; Gaio, Giulio; Gerusina, Simone; Gessini, Alessandro; Giacuzzo, Fabio; Gobessi, Riccardo; Godnig, Roberto; Grisonich, Riccardo; Kiskinova, Maya; Kurdi, Gabor; Loda, Giorgio; Lonza, Marco; Mahne, Nicola; Manfredda, Michele; Mincigrucci, Riccardo; Pangon, Gianpiero; Parisse, Pietro; Passuello, Roberto; Pedersoli, Emanuele; Pivetta, Lorenzo; Prica, Milan; Principi, Emiliano; Rago, Ilaria; Raimondi, Lorenzo; Sauro, Roberto; Scarcia, Martin; Sigalotti, Paolo; Zaccaria, Maurizio; Masciovecchio, Claudio

    2016-01-01

    The recent advent of free-electron laser (FEL) sources is driving the scientific community to extend table-top laser research to shorter wavelengths adding elemental selectivity and chemical state specificity. Both a compact setup (mini-TIMER) and a separate instrument (EIS-TIMER) dedicated to four-wave-mixing (FWM) experiments has been designed and constructed, to be operated as a branch of the Elastic and Inelastic Scattering beamline: EIS. The FWM experiments that are planned at EIS-TIMER are based on the transient grating approach, where two crossed FEL pulses create a controlled modulation of the sample excitations while a third time-delayed pulse is used to monitor the dynamics of the excited state. This manuscript describes such experimental facilities, showing the preliminary results of the commissioning of the EIS-TIMER beamline, and discusses original experimental strategies being developed to study the dynamics of matter at the fs–nm time–length scales. In the near future such experimental tools will allow more sophisticated FEL-based FWM applications, that also include the use of multiple and multi-color FEL pulses.

  8. Superluminal reflection and transmission of light pulses via resonant four-wave mixing in cesium vapor.

    PubMed

    Jiang, Qichang; Zhang, Yan; Wang, Dan; Ahrens, Sven; Zhang, Junxiang; Zhu, Shiyao

    2016-10-17

    We report the experimental manipulation of the group velocities of reflected and transmitted light pulses in a degenerate two-level atomic system driven by a standing wave, which is created by two counter-propagating light beams of equal frequencies but variable amplitudes. It is shown that the light pulse is reflected with superluminal group velocity while the transmitted pulse propagates from subluminal to superluminal velocities via changing the power of the backward coupling field. We find that the simultaneous superluminal light reflection and transmission can be reached when the power of the backward field becomes closer or equal to the forward power, in this case the periodical absorption modulation for photonic structure is established in atoms. The theoretical discussion shows that the anomalous dispersion associated with a resonant absorption dip within the gain peak due to four-wave mixing leads to the superluminal reflection, while the varying dispersion from normal to anomalous at transparency, transparency within absorption, and electromagnetically induced absorption windows leads to the subluminal to superluminal transmission.

  9. Optical imaging through turbid media with a degenerate four wave mixing correlation time gate

    SciTech Connect

    Sappey, A.D. )

    1994-12-20

    A novel method for detection of ballistic light and rejection of unwanted diffusive light to image structures inside highly scattering media is demonstrated. Degenerate four wave mixing (DFWM) of a doubled YAG laser in Rhodamine 6G is used to provide an ultrafast correlation time gate to discriminate against light that has undergone multiple scattering and therefore lost memory of the structures inside the scattering medium. We present preliminary results that determine the nature of the DFWM grating, confirm the coherence time of the laser, prove the phase-conjugate nature of the signal beam, and determine the dependence of the signal (reflectivity) on dye concentration and laser intensity. Finally, we have obtained images of a test cross-hair pattern through highly turbid suspensions of whole milk in water that are opaque to the naked eye. These imaging experiments demonstrate the utility of DFWM for imaging through turbid media. Based on our results, the use of DFWM as an ultrafast time gate for the detection of ballistic light in optical mammography appears to hold great promise for improving the current state of the art.

  10. Low-frequency four-wave mixing spectroscopy of biomolecules in aqueous solutions

    SciTech Connect

    Bunkin, Aleksei F; Pershin, S M

    2011-01-24

    Four-wave mixing (FWM) spectroscopy is used to detect the rotational resonances of H{sub 2}O and H{sub 2}O{sub 2} molecules in DNA and denatured DNA aqueous solutions in the range {+-}10 cm{sup -1} with a spectral resolution of 3 GHz. It is found that the resonance contribution of the rotational transitions of these molecules increases significantly in solutions rather than in distilled water. This fact is interpreted as a manifestation of specific properties of a hydration layer at DNA-water and denatured DNA-water interfaces. Analysis of the FWM spectra shows that the concentration of H{sub 2}O{sub 2} molecules in the hydration layer of the DNA solution increases by a factor of 3 after denaturation. The FWM spectra of aqueous solutions of {alpha}-chymotrypsin protein are obtained in the range {+-}7cm{sup -1} at the protein concentrations between 0 and 20 mg cm{sup -3}. It is found that the hypersound velocity in the protein aqueous solution, measured by the shift of Brillouin components in the scattering spectrum, obeys a cubic dependence on the protein concentration and reaches a value of about 3000 m s{sup -1} at 20 mg cm{sup -3}. (application of lasers and laser-optical methods in life sciences)

  11. Power dependence of transient degenerate four-wave mixing in molecular systems

    NASA Astrophysics Data System (ADS)

    Pakhomov, A.; Wu, Chung-Jen; Chen, Yit-Tsong; Lin, S. H.

    1997-04-01

    The object of this study is to quantitatively elucidate the laser-power dependence in transient degenerate four-wave mixing (DFWM) with an emphasis on the high laser-pump intensity region. We discuss our investigation on the power dependence of transient DFWM by taking gas-phase iodine (I2) molecules as a testing example. The distinct physical feature is that in the high-power laser pump, where both laser-pulse duration and the inverse of pump rate are much shorter than the molecular population relaxation time, the steady-state DFWM theory of Abrams and Lind [Optical Phase Conjugation, edited by R. A. Fisher (Academic, New York, 1983), Chap. 8, pp. 211-284 Opt. Lett. 2, 94 (1978); 3, 205 (1978)] is not appropriate. The prediction by the steady-state theory has shown the DFWM to decrease with increasing laser-pump intensity as a function of 1/Ilaser, which disagrees with the saturation behavior observed in the experiment. To elucidate the dependence of DFWM on the laser pump intensity, a non-steady-state extension of the nonperturbative theory of Abrams and Lind is required. The non-steady-state theoretical result will be shown to be in good agreement with the experimental power dependence at resonance transient DFWM especially in the high-power pump region.

  12. Investigation of a four-wave mixing signal generated in fiber-delivered CARS microscopy.

    PubMed

    Jun, Chang Su; Kim, Byoung Yoon; Park, Ju Hyun; Lee, Jae Yong; Lee, Eun Seong; Yeom, Dong-Il

    2010-07-10

    We studied the nonlinear signal generated in the fiber at an anti-Stokes wavelength during the delivery of the picosecond (ps) pump and Stokes beams in coherent anti-Stokes Raman scattering (CARS) microscopy. A small non-phase-matched four-wave mixing (FWM) signal was prevalently observed in the fiber at the power level where other nonlinear processes, including self-phase modulation and cross-phase modulation, were well suppressed. We analyzed the features of the FWM signal generation by varying the location of temporal overlap between two input pulses in the fiber to compare this to the CARS signal generated in the sample. Numerical modeling based on the nonlinear Schrödinger equation was also conducted and clearly explains the results in the experiment. In addition, we experimentally verified the interferometric feature of this FWM signal with the CARS signal by employing a phase-shifting unit, which potentially suggests the use of the FWM signal as a local oscillator for the interferometric CARS system.

  13. Non-intrusive detection of methanol in gas phase using infrared degenerate four-wave mixing

    NASA Astrophysics Data System (ADS)

    Zhou, J.; Sahlberg, A. L.; Nilsson, H.; Lundgren, E.; Zetterberg, J.

    2015-11-01

    Sensitive and non-intrusive detection of gas-phase methanol with high spatial and temporal resolution has for the first time been reported using mid-infrared degenerate four-wave mixing (IR-DFWM). IR-DFWM spectra of methanol have been successfully recorded in nitrogen-diluted gas flows at room temperature and at 300 °C, by probing ro-vibrational transitions belonging to the fundamental C-H stretching modes, ν 2 and ν 9, and the O-H stretching mode, ν 1. The detection limit of methanol vapor at room temperature and atmospheric pressure is estimated to be 250 ppm with the present setup. Potential interference from CH4 and CO2 is discussed from recorded IR-DFWM spectra of CH4 and CO2, and it was found that detection of methanol free from CH4 and CO2 interference is possible. These results show the potential of the detection of methanol with IR-DFWM for applications in both combustion and catalytic environments, such as CO2 hydrogenation and CH4 oxidation.

  14. Fiber-based source for multiplex-CARS microscopy based on degenerate four-wave mixing.

    PubMed

    Gottschall, Thomas; Baumgartl, Martin; Sagnier, Aude; Rothhardt, Jan; Jauregui, Cesar; Limpert, Jens; Tünnermann, Andreas

    2012-05-21

    We present a fiber-based laser source for multiplex coherent anti-Stokes Raman scattering (CARS) microscopy. This source is very compact and potentially alignment-free. The corresponding pump and Stokes pulses for the CARS process are generated by degenerate four-wave mixing (FWM) in photonic-crystal fibers. In addition, an ytterbium-doped fiber laser emitting spectrally narrow 100 ps pulses at 1035 nm wavelength serves as pump for the FWM frequency conversion. The FWM process delivers narrow-band pulses at 648 nm and drives a continuum-like spectrum ranging from 700 to 820 nm. With the presented source vibrational resonances with energies between 1200 cm-1 and 3200 cm-1 can be accessed with a resolution of 10 cm-1. Additionally, the temporal characteristics of the FWM output have been investigated by a cross-correlation setup, revealing the suitability of the emitted pulses for CARS microscopy. This work marks a significant step towards a simple and powerful all-fiber, maintenance-free multiplex-CARS source for real-world applications outside a laboratory environment.

  15. Electric field strength determination in filamentary DBDs by CARS-based four-wave mixing

    NASA Astrophysics Data System (ADS)

    Boehm, Patrick; Kettlitz, Manfred; Brandenburg, Ronny; Hoeft, Hans; Czarnetzki, Uwe

    2016-09-01

    The electric field strength is a basic parameter of non-thermal plasmas. Therefore, a profound knowledge of the electric field distribution is crucial. In this contribution a four wave mixing technique based on Coherent Anti-Stokes Raman spectroscopy (CARS) is used to measure electric field strengths in filamentary dielectric barrier discharges (DBDs). The discharges are operated with a pulsed voltage in nitrogen at atmospheric pressure. Small amounts hydrogen (10 vol%) are admixed as tracer gas to evaluate the electric field strength in the 1 mm discharge gap. Absolute values of the electric field strength are determined by calibration of the CARS setup with high voltage amplitudes below the ignition threshold of the arrangement. Alteration of the electric field strength has been observed during the internal polarity reversal and the breakdown process. In this case the major advantage over emission based methods is that this technique can be used independently from emission, e.g. in the pre-phase and in between two consecutive, opposite discharge pulses where no emission occurs at all. This work was supported by the Deutsche Forschungsgemeinschaft, Forschergruppe FOR 1123 and Sonderforschungsbereich TRR 24 ``Fundamentals of complex plasmas''.

  16. Theory of pulsed four-wave mixing in one-dimensional silicon photonic crystal slab waveguides

    NASA Astrophysics Data System (ADS)

    Lavdas, Spyros; Panoiu, Nicolae C.

    2016-03-01

    We present a comprehensive theoretical analysis and computational study of four-wave mixing (FWM) of optical pulses co-propagating in one-dimensional silicon photonic crystal waveguides (Si-PhCWGs). Our theoretical analysis describes a very general setup of the interacting optical pulses, namely we consider nondegenerate FWM in a configuration in which at each frequency there exists a superposition of guiding modes. We incorporate in our theoretical model all relevant linear optical effects, including waveguide loss, free-carrier (FC) dispersion and FC absorption, nonlinear optical effects such as self- and cross-phase modulation (SPM, XPM), two-photon absorption (TPA), and cross-absorption modulation (XAM), as well as the coupled dynamics of free-carriers FCs and optical field. In particular, our theoretical analysis based on the coupled-mode theory provides rigorously derived formulas for linear dispersion coefficients of the guiding modes, linear coupling coefficients between these modes, as well as the nonlinear waveguide coefficients describing SPM, XPM, TPA, XAM, and FWM. In addition, our theoretical analysis and numerical simulations reveal key differences between the characteristics of FWM in the slow- and fast-light regimes, which could potentially have important implications to the design of ultracompact active photonic devices.

  17. Dressed Gain from the Parametrically Amplified Four-Wave Mixing Process in an Atomic Vapor

    NASA Astrophysics Data System (ADS)

    Zhang, Zhaoyang; Wen, Feng; Che, Junling; Zhang, Dan; Li, Changbiao; Zhang, Yanpeng; Xiao, Min

    2015-10-01

    With a forward cone emitting from the strong pump laser in a thermal rubidium atomic vapor, we investigate the non-degenerate parametrically amplified four-wave mixing (PA-FWM) process with dressing effects in a three-level “double-Λ” configuration both theoretically and experimentally. By seeding a weak probe field into the Stokes or anti-Stokes channel of the FWM, the gain processes are generated in the bright twin beams which are called conjugate and probe beams, respectively. However, the strong dressing effect of the pump beam will dramatically affect the gain factors both in the probe and conjugate channels, and can inevitably impose an influence on the quantum effects such as entangled degree and the quantum noise reduction between the two channels. We systematically investigate the intensity evolution of the dressed gain processes by manipulating the atomic density, the Rabi frequency and the frequency detuning. Such dressing effects are also visually evidenced by the observation of Autler-Townes splitting of the gain peaks. The investigation can contribute to the development of quantum information processing and quantum communications.

  18. Study of degenerate four-wave mixing in germanium and rhenate-doped potassium chloride at carbon dioxide laser wavelengths

    SciTech Connect

    Watkins, D.E.

    1982-02-01

    Theoretical and experimental studies of degenerate four-wave mixing (DFWM) by three different mechanisms are presented. These are the nonlinear index of refraction of a lossless, Kerr-like medium, the saturable absorption of a resonant optical transition, and the formation of a free-carrier grating.

  19. Higher-Order Squeezing of Quantum Field and the Generalized Uncertainty Relations in Non-Degenerate Four-Wave Mixing

    NASA Technical Reports Server (NTRS)

    Li, Xi-Zeng; Su, Bao-Xia

    1996-01-01

    It is found that the field of the combined mode of the probe wave and the phase-conjugate wave in the process of non-degenerate four-wave mixing exhibits higher-order squeezing to all even orders. And the generalized uncertainty relations in this process are also presented.

  20. Efficiency of four-wave mixing between orthogonally polarized linear waves and solitons in a birefringent fiber

    NASA Astrophysics Data System (ADS)

    Mas Arabí, C.; Bessin, F.; Kudlinski, A.; Mussot, A.; Skryabin, D.; Conforti, M.

    2016-12-01

    We analyze the interaction between orthogonally polarized solitons and dispersive waves via four-wave mixing in a birefringent fiber. We calculate analytically the efficiency of the phase-sensitive scattering between orthogonally polarized solitons and dispersive waves. Experiments performed by using a photonic crystal fiber perfectly match the analytical predictions.

  1. Optical limiting and degenerate four-wave mixing in novel fullerenes

    NASA Astrophysics Data System (ADS)

    Marciu, Daniela

    1999-09-01

    Two experimental methods, optical limiting and degenerate four-wave mixing, are employed to study the nonlinear optical properties of various novel fullerenes structures. Optical limiting refers to decreased transmittance of a material with increased incident light intensity. Detailed measurements of the wavelength- dependence of fullerene optical limiters have illustrated several key features of reverse saturable absorption. Most important among these is the requirement of weak but non-negligible ground state absorption. We have shown that the optical limiting performance of C60 can be extended into the near infrared range by appropriate modifications of the structure such as higher cage fullerenes or derivatization of the basic C60 molecule. The higher cage fullerene C76 shows improved optical limiting behavior compared to C60, for wavelengths higher than 650 nm, but becomes a weak limiter in the 800 nm range. C84, even at high concentrations in α- chloronaphthalene, does not reach the good performance of C 60, but instead shows weak optical limiting in the 800 nm range. We also demonstrate that by attaching various groups to the C60 molecule, we can extend the optical limiting performance in the near infrared regime. The C60 derivatives studied, (C60 cyclic ketone, C60 secondary amine, C60CHC6H 4CO2H, and C60C4H4(CH 3)CH2O2C(CH2)CO2H), have a similar characteristic: the attached groups cause a symmetry-breaking of the C60 sphere and, therefore, there are new allowed transitions that appear as absorption features up to 750 nm. The optical limiting measurements show that these materials, even for low input energies, have an exceptionally strong optical limiting response in the 640 to 750 nm spectral region. For wavelengths higher than 800 nm, however, they become transparent and no optical limiting is observed. Excited state absorption cross-sections obtained from analysis of the optical limiting data reveal that the C60 derivatives have a maximum triplet

  2. Heralded single-photon source from spontaneous four-wave mixing process in lossy waveguides

    NASA Astrophysics Data System (ADS)

    Silva, Nuno A.; Pinto, Armando N.

    2015-10-01

    We investigate theoretically the spontaneous four-wave mixing (FWM) process that occurs in optical waveguides, as a source of quantum correlated photon-pairs. We consider that the waveguide used to implement the spontaneous FWM process presents a high value of nonlinear parameter, γ = 93.4 W-1m-1, and a non-negligible value of loss coefficient, α = 133.3 dB/m. Moreover, the theoretical model also consider the Raman scattering that inevitably accompanies the FWM process, and generates time-uncorrelated (noise) photon pairs. We use the coincident-to-accidental ratio (CAR) as a figure of merit of the photon pair source, and we were able to observe a CAR of the order of 65 in a high loss regime. After, we use the time-correlated photon pairs generated by the spontaneous FWM process to implement a heralded single photon source at waveguide output. In this scenario, the detection of one photon of the pair heralds the presence of the other photon. The quality of the source was studied by the evaluation of the second order coherence function for one photon of the pair conditioned by the detection of its twin photon. We observe that the presence of a high loss coefficient tends to improve the quality of the photon source, when compared with the lossless regime, even considering the Raman noise photons. We obtain a value for the conditional second order coherence function of the order of 0.11 in absence of loss, and a value of 0.03 for a loss coefficient of 133.3 dB/m.

  3. Effect of Doppler broadening on quantitative concentration measurements with degenerate four-wave mixing spectroscopy

    NASA Astrophysics Data System (ADS)

    Reichardt, Thomas A.; Lucht, Robert P.

    1996-06-01

    The effect of Doppler broadening on degenerate four-wave mixing (DFWM) signal intensities in the regime of high pump and probe laser intensities is investigated theoretically. DFWM reflectivities are calculated by solving the time-dependent density-matrix equations for a two-level system interacting with three laser fields. The density-matrix equations are integrated directly in the time domain on a grid of spatial locations along the phase-matching axis; the DFWM signal level is then calculated by summation of the polarization contribution (with the appropriate phase factor) from each of the spatial grid points. For the case in which the Doppler and the collisional linewidths are comparable, the DFWM reflectivity is found to be inversely proportional to the factor 1+(b Delta omega D/ Delta omega C ) 2 , where Delta omega D is the Doppler width, Delta omega C is the collisional width, and b is weakly dependent on the pump and the probe laser powers. We developed an analytical expression for the reflectivity of a line that is both collision and Doppler broadened by dividing the widely used Abrams and Lind expression for homogeneous reflectivity Rhom by the factor 1+(b Delta omega D/ Delta omega C )2 . This modified reflectivity expression is found to give accurate results for the DFWM reflectivity over a wide range of values for the ratio of Doppler to collisional width. With this modified Abrams-Lind expression, strategies for quantitative DFWM concentration measurements in flames and plasmas are proposed and analyzed. We conclude that, by selection of the appropriate rotational transition, a DFWM reflectivity that is directly proportional to the square of the total species number density can be obtained over a wide range of temperature for constant-laser-intensity spatial profile mapping in flames.

  4. Energy correlations of photon pairs generated by a silicon microring resonator probed by Stimulated Four Wave Mixing.

    PubMed

    Grassani, Davide; Simbula, Angelica; Pirotta, Stefano; Galli, Matteo; Menotti, Matteo; Harris, Nicholas C; Baehr-Jones, Tom; Hochberg, Michael; Galland, Christophe; Liscidini, Marco; Bajoni, Daniele

    2016-04-01

    Compact silicon integrated devices, such as micro-ring resonators, have recently been demonstrated as efficient sources of quantum correlated photon pairs. The mass production of integrated devices demands the implementation of fast and reliable techniques to monitor the device performances. In the case of time-energy correlations, this is particularly challenging, as it requires high spectral resolution that is not currently achievable in coincidence measurements. Here we reconstruct the joint spectral density of photons pairs generated by spontaneous four-wave mixing in a silicon ring resonator by studying the corresponding stimulated process, namely stimulated four wave mixing. We show that this approach, featuring high spectral resolution and short measurement times, allows one to discriminate between nearly-uncorrelated and highly-correlated photon pairs.

  5. Four-wave mixing parametric oscillation and frequency comb generation at visible wavelengths in a silica microbubble resonator

    NASA Astrophysics Data System (ADS)

    Yang, Yong; Jiang, Xuefeng; Kasumie, Sho; Zhao, Guangming; Xu, Linhua; Ward, Jonathan M.; Yang, Lan; Chormaic, Síle Nic

    2016-11-01

    Frequency comb generation in microresonators at visible wavelengths has found applications in a variety of areas such as metrology, sensing, and imaging. To achieve Kerr combs based on four-wave mixing in a microresonator, dispersion must be in the anomalous regime. In this work, we demonstrate dispersion engineering in a microbubble resonator (MBR) fabricated by a two-CO$_2$ laser beam technique. By decreasing the wall thickness of the MBR down to 1.4 $\\mu$m, the zero dispersion wavelength shifts to values shorter than 764 nm, making phase matching possible around 765 nm. With the optical \\textit{Q}-factor of the MBR modes being greater than $10^7$, four-wave mixing is observed at 765 nm for a pump power of 3 mW. By increasing the pump power, parametric oscillation is achieved, and a frequency comb with 14 comb lines is generated at visible wavelengths.

  6. Energy correlations of photon pairs generated by a silicon microring resonator probed by Stimulated Four Wave Mixing

    PubMed Central

    Grassani, Davide; Simbula, Angelica; Pirotta, Stefano; Galli, Matteo; Menotti, Matteo; Harris, Nicholas C.; Baehr-Jones, Tom; Hochberg, Michael; Galland, Christophe; Liscidini, Marco; Bajoni, Daniele

    2016-01-01

    Compact silicon integrated devices, such as micro-ring resonators, have recently been demonstrated as efficient sources of quantum correlated photon pairs. The mass production of integrated devices demands the implementation of fast and reliable techniques to monitor the device performances. In the case of time-energy correlations, this is particularly challenging, as it requires high spectral resolution that is not currently achievable in coincidence measurements. Here we reconstruct the joint spectral density of photons pairs generated by spontaneous four-wave mixing in a silicon ring resonator by studying the corresponding stimulated process, namely stimulated four wave mixing. We show that this approach, featuring high spectral resolution and short measurement times, allows one to discriminate between nearly-uncorrelated and highly-correlated photon pairs. PMID:27032688

  7. Four-wave-mixing spectroscopy of localized excitons in CdS 1- xSe x

    NASA Astrophysics Data System (ADS)

    Dinger, A.; Ell, R.; Reznitsky, A.; Klingshirn, C.

    2000-06-01

    We investigated the dephasing properties of excitons in CdS 1- xSe x in the compositional range 0.07≲ x≲0.80 by means of transient four-wave-mixing experiments. For 0.35≲ x≲0.80, the dephasing times of localized excitons are in the order of a few 100 ps up to 1 ns. Thereby, we observe a strong dependence of the dephasing times on the composition x, the localization depth and the spectral excitation width. For very short delay times (a few ps), a beat phenomenon is presented which is interpreted by multiple reflections of propagating exciton-polariton wave packets. In the compositional range 0.07≲ x≲0.35 the four-wave-mixing signal is strongly suppressed and the slowly dephasing signal is hardly observable or as in the most cases not measureable at all.

  8. Photon pair-state preparation with tailored spectral properties by spontaneous four-wave mixing in photonic-crystal fiber.

    PubMed

    Garay-Palmett, K; McGuinness, H J; Cohen, Offir; Lundeen, J S; Rangel-Rojo, R; U'ren, A B; Raymer, M G; McKinstrie, C J; Radic, S; Walmsley, I A

    2007-10-29

    We study theoretically the generation of photon pairs by spontaneous four-wave mixing (SFWM) in photonic crystal optical fiber. We show that it is possible to engineer two-photon states with specific spectral correlation ("entanglement") properties suitable for quantum information processing applications. We focus on the case exhibiting no spectral correlations in the two-photon component of the state, which we call factorability, and which allows heralding of single-photon pure-state wave packets without the need for spectral post filtering. We show that spontaneous four wave mixing exhibits a remarkable flexibility, permitting a wider class of two-photon states, including ultra-broadband, highly-anticorrelated states.

  9. Design and optimization of highly nonlinear low-dispersion crystal fiber with high birefringence for four-wave mixing.

    PubMed

    Zhang, Ya-Ni; Ren, Li-Yong; Gong, Yong-Kang; Li, Xiao-Hui; Wang, Lei-Ran; Sun, Chuan-Dong

    2010-06-01

    We have proposed a novel type of photonic crystal fiber (PCF) with low dispersion and high nonlinearity for four-wave mixing. This type of fiber is composed of a solid silica core and a cladding with a squeezed hexagonal lattice elliptical airhole along the fiber length. Its dispersion and nonlinearity coefficient are investigated simultaneously by using the full vectorial finite element method. Numerical results show that the proposed highly nonlinear low-dispersion fiber has a total dispersion as low as +/-2.5 ps nm(-1) km(-1) over an ultrabroad wavelength range from 1.43 to 1.8 microm, and the corresponding nonlinearity coefficient and birefringence are about 150 W(-1) km(-1) and 2.5x10(-3) at 1.55 microm, respectively. The proposed PCF with low ultraflattened dispersion, high nonlinearity, and high birefringence can have important application in four-wave mixing.

  10. Buffer gas-assisted four-wave mixing resonances in alkali vapor excited by a single cw laser

    NASA Astrophysics Data System (ADS)

    Shmavonyan, Svetlana; Khanbekyan, Aleksandr; Khanbekyan, Alen; Mariotti, Emilio; Papoyan, Aram V.

    2016-12-01

    We report the observation of a fluorescence peak appearing in dilute alkali (Rb, Cs) vapor in the presence of a buffer gas when the cw laser radiation frequency is tuned between the Doppler-broadened hyperfine transition groups of an atomic D2 line. Based on steep laser radiation intensity dependence above the threshold and spectral composition of the observed features corresponding to atomic resonance transitions, we have attributed these features to the buffer gas-assisted four-wave mixing process.

  11. Observation of parametric gain due to four-wave mixing in dispersion engineered GaInP photonic crystal waveguides.

    PubMed

    Colman, Pierre; Cestier, Isabelle; Willinger, Amnon; Combrié, Sylvain; Lehoucq, Gaëlle; Eisenstein, Gadi; De Rossi, Alfredo

    2011-07-15

    We investigate four-wave mixing (FWM) in GaInP 1.5 mm long dispersion engineered photonic crystal waveguides. We demonstrate an 11 nm FWM bandwidth in the CW mode and a conversion efficiency of -24 dB in the quasi-CW mode. For picosecond pump and probe pulses, we report a 3 dB parametric gain and nearly a -5 dB conversion efficiency at watt-level peak pump powers.

  12. Extinction ratio improvement by pump-modulated four-wave mixing in a dispersion-flattened nonlinear photonic crystal fiber.

    PubMed

    Chow, K K; Shu, C; Lin, Chinlon; Bjarklev, A

    2005-10-31

    We demonstrate extinction ratio improvement by using pump-modulated four-wave mixing in a dispersion-flattened nonlinear photonic crystal fiber. A 6-dB improvement in the extinction ratio of a degraded return-to-zero signal has been achieved. A power penalty improvement of 3 dB at 10(-9) bit-error-rate level is obtained in the 10 Gb/s bit-error-rate measurements.

  13. Efficiency of four-wave mixing in injection-locked InAs/GaAs quantum-dot lasers

    NASA Astrophysics Data System (ADS)

    Huang, H.; Arsenijević, D.; Schires, K.; Sadeev, T.; Erasme, D.; Bimberg, D.; Grillot, F.

    2016-12-01

    Frequency conversion using highly non-degenerate four-wave mixing is investigated in optically injection-locked InAs/GaAs quantum-dot Fabry-Perot lasers with different ridge waveguide dimensions. Conversion efficiencies up to -16 dB with a large optical signal-to-noise ratios of 36 dB are unveiled. The conversion bandwidth is extended to 4 THz with a quasi-symmetrical response between up- and down-converted signals.

  14. Experimental investigation of combined four-wave mixing and Raman effect in the normal dispersion regime of a photonic crystal fiber.

    PubMed

    Kudlinski, A; Pureur, V; Bouwmans, G; Mussot, A

    2008-11-01

    We study the effect of stimulated Raman scattering on four-wave mixing sidebands generated by pumping in the normal dispersion regime of a photonic crystal fiber. Q-switch nanosecond pulses at 1064 nm are used to generate signal and idler wavelengths by degenerate four-wave mixing. These three waves generate their own Raman Stokes orders, leading to a broadband supercontinuum.

  15. Synthesis, z-scan and degenerate four wave mixing characterization of certain functionalized photosensitive polyesters containing ortho-hydroxyazo chromophores

    NASA Astrophysics Data System (ADS)

    Jayakrishnan, K.; Siji Narendran, N. K.; Sreejith, P.; Joseph, Antony; Chandrasekharan, K.; Purushothaman, E.

    2015-07-01

    The preparation and NLO characterization of photosensitive polyesters containing azoaromatic residues in the molecular backbone, functionalized with orthohydroxy chromophores is presented. Samples were studied for its UV-vis absorption, FT-IR and intensity dependent nonlinear absorption properties. Nonlinear characterization was carried out with z-scan using frequency doubled, Q-switched Nd:YAG laser operating at 532 nm. The closed aperture z-scan spectra reveal the self defocusing effects of the samples with negative nonlinearity coefficient (n2) showing values as high as -1.28 × 10-10 (esu) for certain samples and the corresponding third order susceptibility coefficient of the order of 29.9 × 10-12 (esu). Degenerate four wave mixing technique was employed to substantiate the findings. The numerical fits show that the molecules exhibit reverse saturable absorption. A study of beam fluence dependence of nonlinear absorption coefficient (βeff) has been presented. All phenomena indicate that molecules are reverse saturable absorbers whose optical limiting property gets enhanced with increasing conjugation length.

  16. High Efficiency Four-Wave Mixing with Relaxation Coupling of Longitude-Optical Phonons in Semiconductor Quantum Wells

    NASA Astrophysics Data System (ADS)

    She, Yan-Chao; Zheng, Xue-Jun; Wang, Deng-Long; Ding, Jian-Wen

    2015-05-01

    The time-dependent analysis of four-wave mixing (FWM) has been performed in four-level double semiconductor quantum wells (SQWs) considering the cross-coupling of the longitude-optical phonons (LOP) relaxation. It is shown that both the amplitude and the conversion efficiency of the FWM field enhance greatly with the increasing strength of cross-coupling of LOP relaxation. Interestingly, a double peak value of the conversion efficiency is obtained under a relatively weak single-photon detuning considering the LOP coupling. When the detuning becomes stronger, the double peaks turn into one peak appearing at the line respect to the about equality two control fields. The results can be interpreted by the effect of electromagnetically induced transparency and the indirect transition. Such controlled high efficiency FWM based on the cross-coupling LOP may have potential applications in quantum control and communications. Supported by Program for Changjiang Scholars and Innovative Research Team in University under Grant (IRT1080), National Natural Science Foundation of China under Grant Nos. 51272158, 11374252, and 51372214, Changjiang Scholar Incentive Program under Grant No. [2009] 17, Scientific Research Fund of Hunan Provincial Education Department of China under Grant No. 12A140, the Science and Technology Foundation of Guizhou Province of China under Grant No. J20122314

  17. Polarization rotation of light propagating through a medium with efficient four-wave mixing and cross-phase modulation

    NASA Astrophysics Data System (ADS)

    Sahoo, Sushree S.; Bhowmick, Arup; Mohapatra, Ashok K.

    2017-03-01

    We have studied the rotation of an elliptically polarized light propagating through thermal rubidium vapor with efficient four-wave mixing (FWM) and cross-phase modulation (XPM). These nonlinear processes are enhanced by Zeeman coherence within the degenerate sub-levels of the two-level atomic system. The elliptically polarized light with small ellipticity is considered as the superposition of a strong-linearly-polarized pump beam and a weak-orthogonal-polarized probe beam. The interference of the probe and the newly generated light field due to degenerate FWM and their gain in the medium due to a large XPM induced by the pump beam leads to the rotation of the elliptical polarized light. A theoretical analysis of the probe propagation through the nonlinear medium was used to explain the experimental observation and the fitting of the experimental data gives the estimates of the third-order non-linear susceptibilities associated with FWM and XPM. Our study can provide useful parameters for the generation of efficient squeezed vacuum states and squeezed polarization states of light. Furthermore our study finds application in controlling the diffraction of a linearly-polarized light beam traversing the medium.

  18. Phase-matched waveguide four-wave mixing scaled to higher peak powers with large-core-area hollow photonic-crystal fibers.

    PubMed

    Konorov, S O; Serebryannikov, E E; Fedotov, A B; Miles, R B; Zheltikov, A M

    2005-05-01

    Hollow photonic-crystal fibers with large core diameters are shown to allow waveguide nonlinear-optical interactions to be scaled to higher pulse peak powers. Phase-matched four-wave mixing is predicted theoretically and demonstrated experimentally for millijoule nanosecond pulses propagating in a hollow photonic-crystal fiber with a core diameter of about 50 microm , suggesting the way to substantially enhance the efficiency of nonlinear-optical spectral transformations and wave mixing of high-power laser pulses in the gas phase.

  19. Kinetic Temperature and Electron Density Measurement in an Inductively Coupled Plasma Torch using Degenerate Four-Wave Mixing

    NASA Technical Reports Server (NTRS)

    Schafer, Julia; Lyons, Wendy; Tong, WIlliam G.; Danehy, Paul M.

    2008-01-01

    Laser wave mixing is presented as an effective technique for spatially resolved kinetic temperature measurements in an atmospheric-pressure radio-frequency inductively-coupled plasma. Measurements are performed in a 1 kW, 27 MHz RF plasma using a continuous-wave, tunable 811.5-nm diode laser to excite the 4s(sup 3)P2 approaches 4p(sup 3)D3 argon transition. Kinetic temperature measurements are made at five radial steps from the center of the torch and at four different torch heights. The kinetic temperature is determined by measuring simultaneously the line shape of the sub-Doppler backward phase-conjugate degenerate four-wave mixing and the Doppler-broadened forward-scattering degenerate four-wave mixing. The temperature measurements result in a range of 3,500 to 14,000 K+/-150 K. Electron densities measured range from 6.1 (+/-0.3) x 10(exp 15)/cu cm to 10.1 (+/-0.3) x 10(exp 15)/cu cm. The experimental spectra are analyzed using a perturbative treatment of the backward phase-conjugate and forward-geometry wave-mixing theory. Stark width is determined from the collisional broadening measured in the phase-conjugate geometry. Electron density measurements are made based on the Stark width. The kinetic temperature of the plasma was found to be more than halved by adding deionized water through the nebulizer.

  20. Ultrafast optical transistor and router of multi-order fluorescence and spontaneous parametric four-wave mixing in Pr³⁺:YSO.

    PubMed

    Wen, Feng; Ali, Imran; Hasan, Abdulkhaleq; Li, Changbiao; Tang, Haijun; Zhang, Yufei; Zhang, Yanpeng

    2015-10-15

    We study the realization of an optical transistor (switch and amplifier) and router in multi-order fluorescence (FL) and spontaneous parametric four-wave mixing (SP-FWM). We estimate that the switching speed is about 15 ns. The router action results from the Autler-Townes splitting in spectral or time domain. The switch and amplifier are realized by dressing suppression and enhancement in FL and SP-FWM. The optical transistor and router can be controlled by multi-parameters (i.e., power, detuning, or polarization).

  1. Characterization of Pairwise Correlations from Multiple Quantum Correlated Beams Generated from Cascaded Four-Wave Mixing Processes

    PubMed Central

    Wang, Hailong; Cao, Leiming; Jing, Jietai

    2017-01-01

    We theoretically characterize the performance of the pairwise correlations (PCs) from multiple quantum correlated beams based on the cascaded four-wave mixing (FWM) processes. The presence of the PCs with quantum corre- lation in these systems can be verified by calculating the degree of intensity difference squeezing for any pair of all the output fields. The quantum correlation characteristics of all the PCs under different cascaded schemes are also discussed in detail and the repulsion effect between PCs in these cascaded FWM processes is theoretically predicted. Our results open the way for the classification and application of quantum states generated from the cascaded FWM processes. PMID:28071759

  2. Realization of low frequency and controllable-bandwidth squeezing based on a four-wave-mixing amplifer in rubidium vapor

    SciTech Connect

    Liu, Cunjin; Jing, Jietai; Zhou, Zhifan; Pooser, Raphael C; Hudelist, Florian; Zhang, Weiping

    2011-01-01

    We experimentally demonstrate the creation of two correlated beams generated by a nondegenerate four-wave-mixing amplifier at {lambda} = 795 nm in hot rubidium vapor. We achieve intensity difference squeezing at frequencies as low as 1.5 kHz which is so far the lowest frequency to observe squeezing in an atomic system. The squeezing spans from 5.5 to 16.5 MHz with a maximum squeezing of {approx}5 dB at 1 MHz. We can control the squeezing bandwidth by changing the pump power. Both low frequency and controllable bandwidth squeezing show great potential in sensitivity detection and precise control of the atom optics measurement.

  3. Optical parametric oscillator based on degenerate four-wave mixing in suspended core tellurite microstructured optical fiber.

    PubMed

    Zhang, Lei; Tuan, Tong Hoang; Kawamura, Harutaka; Suzuki, Takenobu; Ohishi, Yasutake

    2015-10-05

    We report on a suspended core tellurite microstructured optical fiber (TMOF) based optical parametric oscillator (OPO). The intracavity gain is provided by the degenerate four-wave mixing (DFWM) occurred in a 1.5-m-long TMOF synchronously pumped by a mode-locked picosecond erbium-doped fiber laser. The oscillated signal can be generated from 1606 nm to 1743.5 nm, and the idler can be emited from 1526.8 nm to 1395 nm by adjusting the pump wavelength from 1565.4 nm to 1551 nm. A total intenal conversion efficiency of -17.2 dB has been achieved.

  4. Optimisation of 40 Gb/s wavelength converters based on four-wave mixing in a semiconductor optical amplifier

    NASA Astrophysics Data System (ADS)

    Schulze, K.; Petersen, M. N.; Herrera, J.; Ramos, F.; Marti, J.

    2007-08-01

    The optimum operating powers and wavelengths for a 40 Gb/s wavelength converter based on four-wave mixing in a semiconductor optical amplifier are inferred from experimental results. From these measurements, some general rules of thumb are derived for this kind of devices. Generally, the optimum signal power should be 10 dB lower than the pump power (-16 dB conversion efficiency) whereas the wavelength separation between the signal and the pump carrier should not be lower than about four times the signal bitrate (1.3 nm for 40 Gb/s RZ signals).

  5. Wavelength conversion of 28 GBaud 16-QAM signals based on four-wave mixing in a silicon nanowire.

    PubMed

    Adams, Rhys; Spasojevic, Mina; Chagnon, Mathieu; Malekiha, Mahdi; Li, Jia; Plant, David V; Chen, Lawrence R

    2014-02-24

    We demonstrate error-free wavelength conversion of 28 GBaud 16-QAM single polarization (112 Gb/s) signals based on four-wave mixing in a dispersion engineered silicon nanowire (SNW). Wavelength conversion covering the entire C-band is achieved using a single pump. We characterize the performance of the wavelength converter subsystem through the electrical signal to noise ratio penalty as well as the bit error rate of the converted signal as a function of input signal power. Moreover, we evaluate the degradation of the optical signal to noise ratio due to wavelength conversion in the SNW.

  6. Phase-matched four wave mixing and quantum beam splitting of matter waves in a periodic potential

    SciTech Connect

    Hilligsoee, Karen Marie; Moelmer, Klaus

    2005-04-01

    We show that the dispersion properties imposed by an external periodic potential ensure both energy and quasimomentum conservation such that correlated pairs of atoms can be generated by four wave mixing from a Bose-Einstein condensate moving in an optical lattice potential. In our numerical solution of the Gross-Pitaevskii equation, a condensate with initial quasimomentum k{sub 0} is transferred almost completely (>95%) into a pair of correlated atomic components with quasimomenta k{sub 1} and k{sub 2}, if the system is seeded with a smaller number of atoms with the appropriate quasimomentum k{sub 1}.

  7. Optical four-wave mixing and generation of squeezed light in an optomechanical cavity driven by a bichromatic field

    NASA Astrophysics Data System (ADS)

    Garcés, Rafael; de Valcárcel, Germán. J.

    2014-05-01

    We show that an optomechanical cavity pumped by a bichromatic light beam can generate a signal whose frequency lies halfway between the two driving frequencies. This process can be understood as a degenerate four-wave mixing, in which two pump photons (one from each frequency) are combined to yield two identical signal photons. This process takes place between a lower and an upper threshold in terms of the pump intensity, which depend on the pump frequency difference. Close to the signal oscillation threshold a clear noise reduction in one of its quadratures is shown numerically.

  8. Line space theory of Resonant Four-Wave Mixing: New prospects for all-optical studies of photofragment states

    NASA Astrophysics Data System (ADS)

    Kouzov, A. P.; Radi, P. P.

    2017-04-01

    Based on the line-space quantum formalism, the potential of Resonant Four-Wave Mixing spectroscopy as a new tool to study rotational and translational anisotropy of photofragments produced by absorption of plane-polarized photons is theoretically addressed. Synergy of the flexible polarization setup, fine quantum state resolution and of the possibility to study translational recoil distributions, makes the tool unsurpassed among the all-optical means to interrogate the photofragment states. It allows to directly separate signals induced by the rotational anisotropy which remain silent in the most of laser-induced fluorescence responses and thus opens new ways to study rotational helicity, a crucial signature of the photolysis pathway.

  9. Depolarization technique for wavelength conversion using four-wave mixing in a dispersion-flattened photonic crystal fiber.

    PubMed

    Yang, Taotao; Shu, Chester; Lin, Chinlon

    2005-07-11

    We have developed a depolarization technique to achieve polarization-insensitive wavelength conversion using four-wave mixing in an optical fiber. A maximum conversion efficiency of -11.79 dB was achieved over a 3 dB bandwidth of 26 nm in a 100-m-long dispersion-flattened photonic crystal fiber. The polarization-dependent conversion efficiency was less than 0.38 dB and the measured power penalty for a 10 Gbit/s NRZ signal was 1.9 dB. The relation between the conversion efficiency and the degree of polarization of the pump was also formulated.

  10. Time domain switching/demultiplexing using four wave mixing in GaInP photonic crystal waveguides.

    PubMed

    Cestier, I; Willinger, A; Eckhouse, V; Eisenstein, G; Combrié, S; Colman, P; Lehoucq, G; De Rossi, A

    2011-03-28

    We describe dynamical four wave mixing (FWM) functionalities of an GaInP photonic crystal waveguide. A W1 waveguide was used to wavelength convert 100 ps pulses and for sampling a 10.56 Gbit/s data stream so as to time demultiplex it into 16 or 32 channels. In all cases, the extracted pulses at the idler wavelength are undistorted and have a high signal to noise ratio proving the high efficiency and the versatility of the FWM process in the GaInP PhC waveguides we used.

  11. Four-wave mixing parametric oscillation and frequency comb generation at visible wavelengths in a silica microbubble resonator.

    PubMed

    Yang, Yong; Jiang, Xuefeng; Kasumie, Sho; Zhao, Guangming; Xu, Linhua; Ward, Jonathan M; Yang, Lan; Chormaic, Síle Nic

    2016-11-15

    Frequency comb generation in microresonators at visible wavelengths has found applications in a variety of areas such as metrology, sensing, and imaging. To achieve Kerr combs based on four-wave mixing in a microresonator, dispersion must be in the anomalous regime. In this Letter, we demonstrate dispersion engineering in a microbubble resonator (MBR) fabricated by a two-CO2 laser beam technique. By decreasing the wall thickness of the MBR to 1.4 μm, the zero dispersion wavelength shifts to values shorter than 764 nm, making phase matching possible around 765 nm. With the optical Q-factor of the MBR modes being greater than 107, four-wave mixing is observed at 765 nm for a pump power of 3 mW. By increasing the pump power, parametric oscillation is achieved, and a frequency comb with 14 comb lines is generated at visible wavelengths.

  12. Impact of signal-ASE four-wave mixing on the effectiveness of digital back-propagation in 112 Gb/s PM-QPSK systems.

    PubMed

    Rafique, Danish; Ellis, Andrew D

    2011-02-14

    Limitations in the performance of coherent transmission systems employing digital back-propagation due to four-wave mixing impairments are reported for the first time. A significant performance constraint is identified, originating from four-wave mixing between signals and amplified spontaneous emission noise which induces a linear increase in the standard deviation of the received field with signal power, and linear dependence on transmission distance.

  13. Dual-pumped nondegenerate four-wave mixing in semiconductor laser with a built-in external cavity

    NASA Astrophysics Data System (ADS)

    Wu, Jian-Wei; Qiu, Qi; Hyub Won, Yong

    2017-04-01

    In this paper, a semiconductor laser system consisting of a conventional multimode Fabry–Pérot laser diode with a built-in external cavity is presented and demonstrated. More than two resonance modes, whose peak levels are significantly higher than other residual modes, are simultaneously supported and output by adjusting the bias current and operating temperature of the active region. Based on this device, dual-pumped nondegenerate four-wave mixing—in which two pump waves and a single signal wave are simultaneously fed into the laser, and the injection power and wavelength of the injected pump and signal waves are changed—is observed and discussed thoroughly. The results show that while the wavelengths of pump wave A and signal wave S are kept constant, the other pump wave B jumps from about 1535 nm to 1578 nm, generating conversion signals with changed wavelengths. The achieved conversion bandwidth between the primary signal and the converted signal waves is broadly tunable in the range of several terahertz frequencies. Both the conversion efficiency and optical signal-to-noise ratio of the newly generated conversion signals are adopted to evaluate the performance of the proposed four-wave mixing process, and are strongly dependent on the wavelength and power of the injected waves. Here, the attained maximum conversion efficiency and optical signal-to-noise ratio are close to ‑22 dB and 15 dB, respectively.

  14. Photon-pair generation by intermodal spontaneous four-wave mixing in birefringent, weakly guiding optical fibers

    NASA Astrophysics Data System (ADS)

    Garay-Palmett, K.; Cruz-Delgado, D.; Dominguez-Serna, F.; Ortiz-Ricardo, E.; Monroy-Ruz, J.; Cruz-Ramirez, H.; Ramirez-Alarcon, R.; U'Ren, A. B.

    2016-03-01

    We present a theoretical and experimental study of the generation of photon pairs through the process of spontaneous four-wave mixing (SFWM) in a few-mode, birefringent fiber. Under these conditions, multiple SFWM processes are in fact possible, each associated with a different combination of transverse modes for the four waves involved. We show that in the weakly guiding regime, for which the propagation modes may be well approximated by linearly polarized modes, the departure from circular symmetry due to the fiber birefringence translates into conservation rules, which retain elements from azimuthal and rectangular symmetries: both OAM and parity must be conserved for a process to be viable. We have implemented a SFWM source based on a bowtie birefringent fiber, and have measured for a collection of pump wavelengths the SFWM spectra of each of the signal and idler photons in coincidence with its partner photon. We have used this information, together with knowledge of the transverse modes into which the signal and idler photons are emitted, as input for a genetic algorithm, which accomplishes two tasks: (i) the identification of the particular SFWM processes that are present in the source, and (ii) the characterization of the fiber used.

  15. FOUR WAVE MIXING SPECTROSCOPY OF THE NO_3 tilde{B} ^2E' - tilde{X} ^2A_2' transition

    NASA Astrophysics Data System (ADS)

    Fukushima, Masaru; Ishiwata, Takashi

    2014-06-01

    The tilde{B} ^2E' - tilde{X} ^2A_2' electronic transition of NO_3 generated in a supersonic free jet expansion was investigated by four wave mixing ( 4WM ) spectroscopy. The degenerated 4WM and laser induced fluorescence ( LIF ) spectra around the 0_0^0 band region were measured simultaneously. The D4WM spectrum shows broad band features for the 0_0^0 band similar to that of the LIF spectrum. The broad 0_0^0 band does not consist of one sub-band, but of several bands. The intensity distribution of the sub-bands of the D4WM spectrum is similar, but not identical to that of the LIF spectrum.

  16. Diagnostic study of four-wave-mixing-based electric-field measurements in high-pressure nitrogen plasmas.

    PubMed

    Lempert, Walter R; Kearney, Sean P; Barnat, Edward V

    2011-10-10

    We present the results of a diagnostic study of the use of coherent four wave mixing for in situ measurement of an electric field in air or in nitrogen-containing plasmas. Static electric fields in air at a nominal pressure of 625 Torr and temperature of 300 K are detected using vibrational CARS of nitrogen. It is shown that the ratio of the infrared signal to the vibrational N(2) CARS signal is equal to approximately 10(-8) at 8.33 kV/cm, a factor of approximately 50 less than that predicted assuming equal third-order nonlinear susceptibilities. It is also shown that the spatial resolution of a typical collinear geometry measurement is approximately 1 cm. Finally, it is shown that achieving sensitivities of the order of 1 kV/cm requires that the coherent Raman pumping be performed in the highly saturated and Stark broadened regime.

  17. Thermometry of an oxy-acetylene flame using multiplex degenerate four-wave mixing of C2

    NASA Astrophysics Data System (ADS)

    Kaminski, C. F.; Hughes, I. G.; Lloyd, G. M.; Ewart, P.

    1996-01-01

    Thermometry of an oxy-acetylene flame using multiplex Degenerate Four-Wave Mixing (DFWM) of C2 is demonstrated. More than 100 rotational transitions in the d 3 Π g ← a 3 Π u (0,0) Swan band of C2 could be recorded simultaneously by use of a pulsed, broad bandwidth “modeless” laser. Temperatures were inferred by fitting temperature-dependent synthetic spectra of single- or multiple-shot averaged spectra. The strength and reliability of recorded signals together with the large number of rotational lines observed suggest that multiplex DFWM is a promising technique for minor species detection and for temporally resolved temperature measurements in luminous environments. Factors influencing the accuracy and precision of single-shot thermometry using the technique are discussed.

  18. Graphene-assisted nonlinear optical device for four-wave mixing based tunable wavelength conversion of QPSK signal.

    PubMed

    Hu, Xiao; Zeng, Mengqi; Wang, Andong; Zhu, Long; Fu, Lei; Wang, Jian

    2015-10-05

    We fabricate a nonlinear optical device based on a fiber pigtail cross-section coated with a single-layer graphene grown by chemical vapor deposition (CVD) method. Using such graphene-assisted nonlinear optical device, we experimentally demonstrate tunable wavelength conversion of a 10 Gbaud quadrature phase-shift keying (QPSK) signal by exploiting degenerate four-wave mixing (FWM) progress in graphene. We study the conversion efficiency as functions of the pump power and pump wavelength and evaluate the bit-error rate (BER) performance. The observed optical signal-to-noise ratio (OSNR) penalties for tunable QPSK wavelength conversion are less than 2.2 dB at a BER of 1 × 10(-3).

  19. High-power picosecond terahertz-wave generation in photonic crystal fiber via four-wave mixing.

    PubMed

    Wu, Huihui; Liu, Hongjun; Huang, Nan; Sun, Qibing; Wen, Jin

    2011-09-20

    We demonstrate picosecond terahertz (THz)-wave generation via four-wave mixing in an octagonal photonic crystal fiber (O-PCF). Perfect phase-matching is obtained at the pump wavelength of 1.55 μm and a generation scheme is proposed. Using this method, THz waves can be generated in the frequency range of 7.07-7.74 THz. Moreover, peak power of 2.55 W, average power of 1.53 mW, and peak conversion efficiency of more than -66.65 dB at 7.42 THz in a 6.25 cm long fiber are realized with a pump peak power of 2 kW.

  20. Optical frequency combs generated by four-wave mixing in optical fibers for astrophysical spectrometer calibration and metrology.

    PubMed

    Cruz, Flavio C

    2008-08-18

    Optical frequency combs generated by multiple four-wave mixing in short and highly nonlinear optical fibers are proposed for use as high precision frequency markers, calibration of astrophysical spectrometers, broadband spectroscopy and metrology. Implementations can involve two optical frequency standards as input lasers, or one standard and a second laser phase-locked to it using a stable microwave reference oscillator. Energy and momentum conservation required by the parametric generation assures phase coherence among comb frequencies, while fibers with short lengths can avoid linewidth broadening and stimulated Brillouin scattering. In contrast to combs from mode-locked lasers or microcavities, the absence of a resonator allows large tuning of the frequency spacing from tens of gigahertz to beyond teraHertz.

  1. Four-wave-mixing-based optical parametric oscillator delivering energetic, tunable, chirped femtosecond pulses for non-linear biomedical applications.

    PubMed

    Gottschall, Thomas; Meyer, Tobias; Schmitt, Michael; Popp, Jürgen; Limpert, Jens; Tünnermann, Andreas

    2015-09-07

    A novel concept for an optical parametric oscillator based on four-wave mixing (FOPO) in an optical fiber is presented. This setup has the ability of generating highly chirped signal and idler pulses with compressed pulse durations below 600 fs and pulse energies of up to 250 nJ. At a fixed pump wavelength of 1040 nm, the emerging signal and idler wavelengths can be easily tuned between 867 to 918 nm and 1200 to 1300 nm, respectively, only by altering the cavity length. With compressed peak powers >100 kW and a repetition rate of only 785 kHz, this source provides tunable intense ultra-short pulses at moderate average powers. This setup constitutes a stable, simple and in many ways superior alternative to bulk state-of-the-art OPO light converters for demanding biomedical applications and non-linear microspectroscopy.

  2. High-quality ultraviolet beam generation in multimode photonic crystal fiber through nondegenerate four-wave mixing at 532 nm.

    PubMed

    Sévigny, Benoit; Cassez, Andy; Vanvincq, Olivier; Quiquempois, Yves; Bouwmans, Géraud

    2015-05-15

    All-fiber ultraviolet (UV) light sources are of great practical interest for a multitude of applications spanned across different sectors, from industrial processes such as nonthermal, high-resolution materials processing, to biomedical applications such as eye surgery, to name a few. However, production of UV light sources with high beam quality has been a problem to this day as the fiber designs required to reach UV wavelengths by four-wave mixing with widely available pumps (i.e., 532 nm) are challenging because of their small size and increased risk of material damage. In this Letter, a specific pumping scheme is presented that allows the conversion of two pump photons in different modes to UV light in the fundamental mode and the corresponding idler in a higher order mode. The process has also been shown to work experimentally, and UV light at 390.5 nm in the fundamental mode was successfully generated.

  3. Electromagnetically induced transparency and four-wave mixing in a cold atomic ensemble with large optical depth

    NASA Astrophysics Data System (ADS)

    Geng, J.; Campbell, G. T.; Bernu, J.; Higginbottom, D. B.; Sparkes, B. M.; Assad, S. M.; Zhang, W. P.; Robins, N. P.; Lam, P. K.; Buchler, B. C.

    2014-11-01

    We report on the delay of optical pulses using electromagnetically induced transparency (EIT) in an ensemble of cold atoms with an optical depth exceeding 500. To identify the regimes in which four-wave mixing (4WM) impacts on EIT behaviour, we conduct the experiment in both 85Rb and 87Rb. Comparison with theory shows excellent agreement in both isotopes. In 87Rb negligible 4WM was observed and we obtained one pulse-width of delay with 50% efficiency. In 85Rb 4WM contributes to the output. In this regime we achieve a delay-bandwidth product of 3.7 at 50% efficiency, allowing temporally multimode delay, which we demonstrate by compressing two pulses into the memory medium.

  4. Response functions for dimers and square-symmetric molecules in four-wave-mixing experiments with polarized light.

    PubMed

    Smith, Eric Ryan; Farrow, Darcie A; Jonas, David M

    2005-07-22

    Four-wave-mixing nonlinear-response functions are given for intermolecular and intramolecular vibrations of a perpendicular dimer and intramolecular vibrations of a square-symmetric molecule containing a doubly degenerate state. A two-dimensional particle-in-a-box model is used to approximate the electronic wave functions and obtain harmonic potentials for nuclear motion. Vibronic interactions due to symmetry-lowering distortions along Jahn-Teller active normal modes are discussed. Electronic dephasing due to nuclear motion along both symmetric and asymmetric normal modes is included in these response functions, but population transfer between states is not. As an illustration, these response functions are used to predict the pump-probe polarization anisotropy in the limit of impulsive excitation.

  5. Wavelength conversion for polarization multiplexing signal using four-wave mixing in semiconductor optical amplifier with reduced polarization crosstalk

    NASA Astrophysics Data System (ADS)

    Zhou, Hui; Chen, Ming; Wan, Qiuzhen; Zheng, Zhiwei

    2016-06-01

    We investigated wavelength conversion for polarization multiplexing signal based on four-wave mixing in a semiconductor optical amplifier. We found that the converted signals endured crosstalk among the pol-muxed channels. We also proposed and demonstrated a wavelength conversion scheme with polarization diversity technique. By utilizing the technique, the converted polarization multiplexing signal can be received without crosstalk. In addition, the performance of the proposed system is numerically analyzed with respect to the bit error rate of the converted signal, different frequency spacing between signal and pump and modulated data rate. The simulation results show that the proposed scheme may be a promising method to realize transparent wavelength conversion for polarization multiplexing signals.

  6. Degenerate four-wave mixing in room-temperature GaAs/GaAlAs multiple quantum well structures

    NASA Astrophysics Data System (ADS)

    Miller, D. A. B.; Chemla, D. S.; Eilenberger, D. J.; Smith, P. W.; Gossard, A. C.; Wiegman, W.

    1983-06-01

    Degenerate four-wave mixing (DFWM) is of current interest both for practical applications (e.g., phase conjugation) and as a physical probe. DFWM makes it possible to detect very small nonlinear changes in refraction. In connection with the present investigation, the first observations of DFWM in GaAs/GaAlAs multiple quantum well structures (MQW's) at room temperature are reported. By combining DFWM and nonlinear absorption results, a direct measurement of the nonlinear refraction near the band gap of the MQW is conducted. The obtained value is compared with previous estimates. The measurements are of practical importance for possible low-power optical devices compatible with laser diodes based either on DFWM, nonlinear refraction (such as optical bistability) of nonlinear absorption. The MQW samples were grown by molecular beam epitaxy (MBE) on GaAs substrates, with the MQW layers sandwiched between GaAlAs cap layers which are transparent at the considered wavelengths.

  7. Nonlinear optical properties of porphyrin and chlorophyll dimers studied by degenerated four wave mixing

    SciTech Connect

    Chen, L.X.Q.

    1992-01-01

    As one of the important elements in natural and artificial electron transfer and energy transfer processes, porphyrin and its derivatives have received much attention in photoelectronics and photoelectronic materials. As our first attempt to relate the [pi]-[pi] electronic couplings between porphyrin macrocycles to apparent third order nonlinear susceptibilities, we measured [chi]([sup 3]) for several porphyrin and chlorophyll a derivatives, including dimers with different configurations. Our preliminary results show that the dimers have enhanced [chi]([sup 3]) compared to those of the monomer. This enhancement is related to the relative orientations between the two macrocycles in the dimers. The parallel dimers with close face-to-face distances seem to have the highest enhancement in [chi]([sup 3]). Thus, we believe that [chi]([sup 3]) is strongly related to the [pi]-[pi] electronic coupling between the two conjugated ring systems.

  8. Nonlinear optical properties of porphyrin and chlorophyll dimers studied by degenerated four wave mixing

    SciTech Connect

    Chen, L.X.Q.

    1992-12-31

    As one of the important elements in natural and artificial electron transfer and energy transfer processes, porphyrin and its derivatives have received much attention in photoelectronics and photoelectronic materials. As our first attempt to relate the {pi}-{pi} electronic couplings between porphyrin macrocycles to apparent third order nonlinear susceptibilities, we measured {chi}({sup 3}) for several porphyrin and chlorophyll a derivatives, including dimers with different configurations. Our preliminary results show that the dimers have enhanced {chi}({sup 3}) compared to those of the monomer. This enhancement is related to the relative orientations between the two macrocycles in the dimers. The parallel dimers with close face-to-face distances seem to have the highest enhancement in {chi}({sup 3}). Thus, we believe that {chi}({sup 3}) is strongly related to the {pi}-{pi} electronic coupling between the two conjugated ring systems.

  9. All-optical logic circuits based on the polarization properties of non-degenerate four-wave mixing

    NASA Astrophysics Data System (ADS)

    Bhardwaj, Ashish Ishwar Singh

    2001-10-01

    This thesis investigates a new class of all-optical logic circuits that are based on the polarization properties of non-degenerate Four-Wave Mixing. Such circuits would be used in conjunction with a data modulation format where the information is coded on the states of polarization of the electric field. Schemes to perform multiple triple- product logic functions are discussed and it is shown that higher-level Boolean operations involving several bits can be implemented without resorting to the standard 2-input gates that are based on some form of switching. Instead, an entire hierarchy of more complex Boolean functions can be derived based on the selection rules of multi-photon scattering processes that can form a new classes of primitive building blocks for digital circuits. Possible applications of these circuits could involve some front-end signal processing to be performed all- optically in shared computer back-planes. As a simple illustration of this idea, a circuit performing error correction on a (3,1) Hamming Code is demonstrated. Error-free performance (Bit Error Rate of <10-9) at 2.5 Gbit/s is achieved after single-error correction on the Hamming word with 50 percent errors. The bit-rate is only limited by the bandwidth of available resources. Since Four-Wave Mixing is an ultrafast nonlinearity, these circuits offer the potential of computing at several terabits per second. Furthermore, it is shown that several Boolean functions can be performed in parallel in the same set of devices using different multi-photon scattering processes. The main objective of this thesis is to motivate a new paradigm of thought in digital circuit design. Challenges pertaining to the feasibility of these ideas are discussed.

  10. Four-Wave Mixing and Optical Phase Conjugation in Vertical Cavity Surface Emitting Devices

    DTIC Science & Technology

    1997-01-01

    1990). Osinski , Marek and Jens Buus. "Linewidth Broadening Factor in Semiconductor Lasers- An Overview," IEEE Journal of Quantum Electronics QE-23(1): 9...above threshold. But as pointed out in the definitive document on the linewidth enhancement factor ( Osinski , 1987), for low carrier densities one can

  11. Generation and Amplification of Tunable Multicolored Femtosecond Laser Pulses by Using Cascaded Four-Wave Mixing in Transparent Bulk Media

    PubMed Central

    Liu, Jun; Kobayashi, Takayoshi

    2010-01-01

    We have reviewed the generation and amplification of wavelength-tunable multicolored femtosecond laser pulses using cascaded four-wave mixing (CFWM) in transparent bulk media, mainly concentrating on our recent work. Theoretical analysis and calculations based on the phase-matching condition could explain well the process semi-quantitatively. The experimental studies showed: (1) as many as fifteen spectral up-shifted and two spectral down-shifted sidebands were obtained simultaneously with spectral bandwidth broader than 1.8 octaves from near ultraviolet (360 nm) to near infrared (1.2 μm); (2) the obtained sidebands were spatially separated well and had extremely high beam quality with M2 factor better than 1.1; (3) the wavelengths of the generated multicolor sidebands could be conveniently tuned by changing the crossing angle or simply replacing with different media; (4) as short as 15-fs negatively chirped or nearly transform limited 20-fs multicolored femtosecond pulses were obtained when one of the two input beams was negatively chirped and the other was positively chirped; (5) the pulse energy of the sideband can reach a μJ level with power stability better than 1% RMS; (6) broadband two-dimensional (2-D) multicolored arrays with more than ten periodic columns and more than ten rows were generated in a sapphire plate; (7) the obtained sidebands could be simultaneously spectra broadened and power amplified in another bulk medium by using cross-phase modulation (XPM) in conjunction with four-wave optical parametric amplification (FOPA). The characterization showed that this is interesting and the CFWM sidebands generated by this novel method have good enough qualities in terms of power stability, beam quality, and temporal features suited to various experiments such as ultrafast multicolor time-resolved spectroscopy and multicolor-excitation nonlinear microscopy. PMID:22399882

  12. Effects of refractive index changes on four-wave mixing bands in Er-doped photonic crystal fibers pumped at 976 nm.

    PubMed

    Velázquez-Ibarra, L; Díez, A; Andrés, M V; Lucio, J L

    2012-04-01

    An experimental study of the effects of an auxiliary 976 nm pump signal on the four-wave mixing parametric bands generated with a 1064 nm pump in a normal dispersion Er-doped photonic crystal fiber is presented. The four-wave mixing signal and idler bands shift to shorter and longer wavelengths, respectively, with increasing 976 nm pump power. It is shown that the wavelength-dependent resonant refractive index change in the erbium-doped core under 976 nm pumping is at the origin of the effect.

  13. Phase correlation between four-wave mixing and optical fields in double Λ-type atomic system.

    PubMed

    Jeong, Taek; Moon, Han Seb

    2016-12-12

    We study the spectral features and phase of four-wave mixing (FWM) light according to the relative phase-noise of the optical fields coupled to a double Λ-type atomic system of the 5S1/2-5P1/2 transition of 87Rb atoms. We observe that the spectral shape of the FWM spectrum is identical to that of the two-photon absorption (TPA) spectrum due to two-photon coherence and that it is independent of the relative phase-noise of the pump light. From these results, we clarify that the two-photon coherence plays a very important role in the FWM process. Furthermore, we measure the relative linewidth of the FWM signal to the probe and pump lasers by means of a beat interferometer. We confirmed that the phase of the FWM signal is strongly correlated with that of the pump laser under the condition of phase-locked probe and coupling lasers for two-photon coherence.

  14. [Study of the effect of light source stability on the signal to noise ratio in degenerate four wave mixing experiment].

    PubMed

    Wang, Wei-Bo; Chen, De-Ying; Fan, Rong-Wei; Xia, Yuan-Qin

    2010-02-01

    The effects of the stability of dye laser on the signal to noise ratio in degenerate four-wave mixing (DFWM) were first investigated in iodine vapor using forward geometries. Frequency-doubled outputs from a multi-mode Nd : YAG laser pumped dye laser with laser dye PM580 dissolved in ethanol was used. With the help of forward compensated beam-split technique and imaging detecting system, the saturation intensity of DFWM spectrum in the iodine vapor at 5 554.013 nm was first measured to be 290 microJ under the condition of atmospheric pressure and room temperature. The features of the dye laser such as wavelength ranges, beam quality and energy conversion efficiency decreased gradually with increasing pumping service use, pulse number and intensity. Additionally, with the comparison of the stable and unstable dye laser output, it was found that the instability of dye laser output had greatly influenced the DFWM signal and decreased the signal to background noise ratio. Shot to shot jitter and the broadening in the output frequency leads to an effective broadening of the recorded spectrum and loss of the DFWM signal to noise ratio under the same pumping intensity at different time. The study is of importance to the detection of trace atom, molecule and radical in combustion diagnosis.

  15. Direct generation of graphene plasmonic polaritons at THz frequencies via four wave mixing in the hybrid graphene sheets waveguides.

    PubMed

    Sun, Yu; Qiao, Guofu; Sun, Guodong

    2014-11-17

    A compact waveguide incorporating a high-index nano-ridge sandwiched between graphene sheets is proposed for the direct generation of graphene plasmonic polaritons (GSPs) via four wave mixing (FWM). The proposed waveguide supports GSP modes at the THz frequencies and photonic modes at the infrared wavelengths. Due to the strong confinement of coupled graphene sheets, the GSP modes concentrate in the high-index nano-ridge far below the diffraction limit, which improves integral overlap with the photonic modes and greatly facilitates the FWM process. To cope with the ultra-high effective refractive of the GSP modes, an alternative energy conservation diagram is selected for the degenerated FWM, which corresponds to one pump photon transfers its energy to two signal photons and one GSP photon. The single mode condition of the generated symmetric GSP modes is analyzed by the effective index method to suppress the undesired conversion. Due to the unique tunability of GSPs, the phase matching condition can be satisfied by tuning the chemical potential of the graphene sheets employing external gates. The FWM pumped at 1,550 nm with a peak power of 1 kW is theoretically investigated by solving the modified coupled mode equations. The generated GSP power reaches its maximum up to 67 W at a propagation distance of only 43.7 μm. The proposed waveguide have a great potential for integrated chip-scale GSP source.

  16. Four-wave mixing based light sources for real-world biomedical applications of coherent Raman microscopy

    NASA Astrophysics Data System (ADS)

    Gottschall, Thomas; Meyer, Tobias; Jauregui, Cesar; Schmitt, Michael; Popp, Jürgen; Limpert, Jens; Tünnermann, Andreas

    2016-03-01

    Stimulated Raman Scattering requires an extremely quiet, widely wavelength tunable laser, which, up to now, is unheard of in fiber lasers. We present a compact and maintenance-free optical parametric oscillator based on degenerate four-wave mixing in a photonic crystal fiber. By employing an all-fiber frequency and repetition rate tunable laser as a seed source, we are able to generate tunable light between 1015 and 1065 nm. After amplification and subsequent conversion in the fiber OPO, signal and idler radiation between 785 and 960 nm and 1177 and 1500 nm may be generated with a repetition rate of 9 MHz. Therefore, we are able to address Raman shifts between 910 and 3030 cm-1. An additional output provides the Stokes radiation at 18 MHz required for the SRS process, which is passively synchronized to the tunable radiation. We measure the relative intensity noise of the Stokes beam at 9 MHz to be -150 dBc enabling high speed SRS imaging with a good signal-to-noise ratio. The combination of FWM based conversion, coupled with all-fiber Yb-based fiber lasers allows for the first turn-key, widely tunable and extremely compact laser systems developed for applications of CRS microscopy in clinics. This source could very well be the missing key instrument that CRS imaging requires for its real world transition.

  17. Spectrally-isolated violet to blue wavelength generation by cascaded degenerate four-wave mixing in a photonic crystal fiber.

    PubMed

    Yuan, Jinhui; Kang, Zhe; Li, Feng; Zhang, Xianting; Zhou, Guiyao; Sang, Xinzhu; Wu, Qiang; Yan, Binbin; Zhou, Xian; Wang, Liang; Zhong, Kangping; Wang, Kuiru; Yu, Chongxiu; Tam, Hwa Yaw; Wai, P K A

    2016-06-01

    Generation of spectrally-isolated wavelengths in the violet to blue region based on cascaded degenerate four-wave mixing (FWM) is experimentally demonstrated for the first time in a tailor-made photonic crystal fiber, which has two adjacent zero dispersion wavelengths (ZDWs) at 696 and 852 nm in the fundamental mode. The influences of the wavelength λp and the input average power Pav of the femtosecond pump pulses on the phase-matched frequency conversion process are studied. When femtosecond pump pulses at λp of 880, 870, and 860 nm and Pav of 500 mW are coupled into the normal dispersion region close to the second ZDW, the first anti-Stokes waves generated near the first ZDW act as a secondary pump for the next FWM process. The conversion efficiency ηas2 of the second anti-Stokes waves, which are generated at the violet to blue wavelengths of 430, 456, and 472 nm, are 4.8, 6.48, and 9.66%, for λp equalling 880, 870, and 860 nm, respectively.

  18. Realisation of four-wave mixing phase matching for frequency components at intracavity stimulated Raman scattering in a calcite crystal

    SciTech Connect

    Smetanin, Sergei N; Fedin, Aleksandr V; Shurygin, Anton S

    2013-06-30

    The possibilities of implementing four-wave mixing (FWM) phase matching at stimulated Raman scattering (SRS) in a birefringent SRS-active crystal placed in a cavity with highly reflecting mirrors have been theoretically and experimentally investigated. Phase-matching angles providing conditions for five types of phase matching are determined for a calcite crystal. These types are characterised by different combinations of polarisation directions for the interacting waves and ensure FWM generation of either an anti-Stokes wave or the second Stokes SRS component. In agreement with the calculation results, low-threshold generation of the second Stokes SRS component with a wavelength 0.602 {mu}m was observed at angles of incidence on a calcite crystal of 4.8 Degree-Sign and 18.2 Degree-Sign , under SRS pumping at a wavelength of 0.532 {mu}m. This generation is due to the FWM coupling of the first and second Stokes SRS components with the SRS-pump wave. (nonlinear optical phenomena)

  19. Modeling interchannel four-wave mixing for 8-Ary modulated dense wavelength division multiplexing systems over dispersion map

    NASA Astrophysics Data System (ADS)

    Du, Jianxin; Shen, Ninghang; Xu, Yue

    2016-08-01

    Semianalytic models are developed to deterministically calculate the variances of degenerate and nondegenerate four-wave mixing (FWM) noises for dispersion-managed dense wavelength division multiplexing (DWDM) systems with 8-Ary modulations [i.e., 8-level amplitude- and differential phase-shift keying (8APSK) and constant-amplitude optical differential 8-level phase-shift keying (D8PSK)]. The semianalytic models include various important propagation effects for exact numerical results. A 5.28-Tb/s (40-Gs/s/ch) 100-GHz-spaced 33-channel DWDM system with a dispersion map is then numerically analyzed by using the newly derived semianalytic models. It is numerically validated that FWM impacts coming from 8APSK pump channels are more severe than those coming from D8PSK ones, where pump channels denote the channels whose energies are transferred to a probe channel through the FWM process. The numerical results show that although FWM tolerance of a central channel with 8APSK is worse than that with D8PSK, a central channel with 8APSK is still superior to that with D8PSK when some linear noises and FWM noise are simultaneously taken into account for our given system conditions, which is mainly attributed to a relatively larger minimum Euclidean distance for the 8APSK constellation than the D8PSK one.

  20. Generation of optical frequency combs via four-wave mixing processes for low- and medium-resolution astronomy

    NASA Astrophysics Data System (ADS)

    Zajnulina, M.; Boggio, J. M. Chavez; Böhm, M.; Rieznik, A. A.; Fremberg, T.; Haynes, R.; Roth, M. M.

    2015-07-01

    We investigate the generation of optical frequency combs through a cascade of four-wave mixing processes in nonlinear fibres with optimised parameters. The initial optical field consists of two continuous-wave lasers with frequency separation larger than 40 GHz (312.7 pm at 1531 nm). It propagates through three nonlinear fibres. The first fibre serves to pulse shape the initial sinusoidal-square pulse, while a strong pulse compression down to sub-100 fs takes place in the second fibre which is an amplifying erbium-doped fibre. The last stage is a low-dispersion highly nonlinear fibre where the frequency comb bandwidth is increased and the line intensity is equalised. We model this system using the generalised nonlinear Schrödinger equation and investigate it in terms of fibre lengths, fibre dispersion, laser frequency separation and input powers with the aim to minimise the frequency comb noise. With the support of the numerical results, a frequency comb is experimentally generated, first in the near infra-red and then it is frequency-doubled into the visible spectral range. Using a MUSE-type spectrograph, we evaluate the comb performance for astronomical wavelength calibration in terms of equidistancy of the comb lines and their stability.

  1. Characterization of a deep-level compensation ratio through picosecond four-wave mixing on a transient reflection grating

    NASA Astrophysics Data System (ADS)

    Kadys, A.; Delaye, Ph; Roosen, G.; Jarasiunas, K.

    2007-09-01

    We demonstrate a novel application of a time-resolved four-wave mixing technique for the determination of a deep-level compensation ratio in a semi-insulating crystal. The approach is based on photoexcitation of carriers from deep impurity levels, formation of a space-charge electric field in deep traps, and monitoring dynamics of photorefractive, free- carrier and absorption gratings by light diffraction. The analysis of anisotropic diffraction features on the reflection grating provided requirements for crystal orientation in order to discriminate contribution of amplitude grating from the photorefractive phase grating, both being related to deep-trap occupation. Contributions of these optical nonlinearities were studied experimentally in (0 0 1)-oriented GaAs wafers by using a transient reflection grating configuration with a very small grating period (150 nm). Comparison of the reflection grating picosecond kinetics and its diffraction efficiency with modeling curves allowed us to ascribe the slow decay component to amplitude grating in recharged deep traps and determine their compensation ratio. The proposed technique allowed the determination of the compensation ratio of a deep EL2 donor, equal to 0.6 ± 0.05 in the given GaAs crystal.

  2. Generation of octave-spanning supercontinuum by Raman-assisted four-wave mixing in single-crystal diamond.

    PubMed

    Lu, Chih-Hsuan; Yang, Li-Fan; Zhi, Miaochan; Sokolov, Alexei V; Yang, Shang-Da; Hsu, Chia-Chen; Kung, A H

    2014-02-24

    An octave-spanning coherent supercontinuum is generated by non-collinear Raman-assisted four-wave mixing in single-crystal diamond using 7.7 fs laser pulses that have been chirped to about 420 fs in duration. The use of ultrabroad bandwidth pulses as input results in substantial overlap of the generated spectrum of the anti-Stokes sidebands, creating a phase-locked supercontinuum when all the sidebands are combined to overlap in time and space. The overall bandwidth of the generated supercontinuum is sufficient to support its compression to isolated few-to-single cycle attosecond transients. The significant spectral overlap of adjacent anti-Stokes sidebands allows the utilization of straight-forward spectral interferometry to test the relative phase coherence of the anti-Stokes outputs and is demonstrated here for two adjacent pairs of sidebands. The method can subsequently be employed to set the relative phase of the sidebands for pulse compression and for the synthesis of arbitrary field transients.

  3. Analysis of degenerate four-wave mixing spectra of NO in a CH4/N2/O2 flame

    NASA Astrophysics Data System (ADS)

    Farrow, R. L.; Rakestraw, D. J.

    We report comparisons of degenerate four-wave mixing (DFWM) spectra of NO measured in a CH4/N2/O2 flame to spectral simulations based on a two-level theory for stationary, saturable absorbers by Abrams et al. Temperatures determined from least-squares fits of simulations to experimental spectra in the A2Σ+?X2Π+(0,0) band are compared to temperatures obtained from OH absorption spectroscopy and a radiation-corrected thermocouple. We find that DFWM rotational temperatures derived from Q-branch spectra agree with thermocouple and are independent of pump laser intensity for low to moderate saturation (I Isat). However, the temperatures are systematically low and depend on pump intensity if the analysis neglects saturation effects. We demonstrate a method for obtaining an effective pump saturation intensity for use with the two-level model. This approach for analyzing saturated DFWM line intensities differs from previous work in that the use of the theory of Abrams et al. rather than a transition-dipole-moment power law allows treatment of a much wider range of saturation. Based on the observed signal-to-noise ratio an NO detection sensitivity of 25 ppm is projected, limited by a DFWM background interference specific to hydrocarbon flames.

  4. Two-photon resonances in femtosecond time-resolved four-wave mixing spectroscopy: {beta}-carotene

    SciTech Connect

    Namboodiri, V.; Namboodiri, M.; Flachenecker, G.; Materny, A.

    2010-08-07

    Femtosecond time-resolved pump-degenerate four-wave mixing (pump-DFWM) spectroscopy has been used to study the ultrafast dynamics of {beta}-carotene involving several electronic and vibrational states. An initial pump pulse, resonant with the S{sub 0}-to-S{sub 2} transition, excites the molecular system and a DFWM process, resonant with the S{sub 1}-to-S{sub n} transition, is used to probe the relaxation pathways. The transient shows a peculiar decay behavior, which is due to the contributions of resonant DFWM signal of the excited S{sub 1} state, nonresonant DFWM signal of the ground S{sub 0} state and vibrational hot S{sub 0}{sup *} state, and the two-photon resonant DFWM signal of the ground S{sub 0} state. We have used a kinetic model including all the signal contributions to successfully fit the transient. The time constants extracted are in very good agreement with the known values for {beta}-carotene. For comparison, a two-pulse pump-probe experiment was performed measuring the transient absorption at the wavelength of the DFWM experiment.

  5. Determination of the electric field strength of filamentary DBDs by CARS-based four-wave mixing

    NASA Astrophysics Data System (ADS)

    Böhm, P.; Kettlitz, M.; Brandenburg, R.; Höft, H.; Czarnetzki, U.

    2016-10-01

    It is demonstrated that a four-wave mixing technique based on coherent anti-Stokes Raman spectroscopy (CARS) can determine the electric field strength of a pulsed-driven filamentary dielectric barrier discharge (DBD) of 1 mm gap, using hydrogen as a tracer medium in nitrogen at atmospheric pressure. The measurements are presented for a hydrogen admixture of 10%, but even 5% H2 admixture delivers sufficient infrared signals. The lasers do not affect the discharge by photoionization or by other radiation-induced processes. The absolute values of the electric field strength can be determined by the calibration of the CARS setup with high voltage amplitudes below the ignition threshold of the arrangement. This procedure also enables the determination of the applied breakdown voltage. The alteration of the electric field is observed during the internal polarity reversal and the breakdown process. One advantage of the CARS technique over emission-based methods is that it can be used independently of emission, e.g. in the pre-phase and in between two consecutive discharges, where no emission occurs at all.

  6. Detection and Interpretation of Collisional Transfer and Rotational Anisotropy Fingerprints in Resonant Four-Wave Mixing Spectra.

    NASA Astrophysics Data System (ADS)

    Kouzov, A.; Radi, P.; Maksyutenko, P.; Kozlov, D.

    2013-06-01

    Coherent responses produced by resonant four-wave mixing (RFWM) in a weakly absorbing medium carry valuable information on the intrinsic properties and dynamics of the quantum states involved. Here, two aspects of RFWM applications are highlighted. First, the Two-Color (TC) version of RFWM was found to be a unique spectroscopic tool to directly trace collisional state-to-state transfer in isotropic gaseous media, both in the frequency% and time domains. Second, the RFWM techniques appeared to be very useful for studies of the rotational anisotropy. Here we report new experimental one-color RFWM spectra of the OH radicals produced by laser photolysis of H_{2}O_{2} at 266 nm. Polarization dependence and Doppler line structure of the spectra show clear evidence of the pronounced anisotropy of angular momentum (j) and velocity (% v) distributions as well as on the j-v correlation. The obtained results directly point to the pronounced OH helicity (i.e. j% ∥ v) which yet remained beyound the reach of purely optical means. For all mentioned cases, the line-shape theory is an optimal tool to derive compact expressions for the RFWM signals. The work was supported by the Swiss Federal Office of Energy, the Swiss National Science Foundation (200020_124542/1), and by the Russian Foundation for Basic Research, grants 11-02-01296 and 11-03-00448. P. P. Radi, H.-M. Frey, B. Mischler, A. P. Tzannis, P. Beaud, and T. Gerber, Chem. Phys. Lett. 265, 271 (1997). X. Chen and T. B. Settersten, Appl. Opt. 46, 3911 (2007). T. A. W. Wasserman, P. H. Vaccaro, and B. R. Johnson, J. Chem. Phys. 106, 6314 (1997). A.P. Kouzov and P.P. Radi, Phys. Rev. A 63, 010701 (2000).

  7. Optical phase conjugation by four-wave mixing in Nd:YAG laser oscillator for optical energy transfer to a remote target

    NASA Astrophysics Data System (ADS)

    Kawakami, K.; Okamura, H.; Komurasaki, K.

    2015-02-01

    A self-starting phase conjugator was designed for optical energy transfer to a remote target. Saturable-gain four-wave mixing in a laser resonator was achieved using a flash-lamp pumped Nd:YAG crystal and phase-conjugate light (PCL) generation were verified. Wavefront correction experimentation revealed that beam wander caused by air turbulence is compensated. Tracking capability was demonstrated in the range of 9 mrad with tracking accuracy of ±0.04 mrad. The maximum field of view was measured to be 4.7°. Dependence of phase-conjugate light energy on reference light energy was investigated. The maximum output of 320 mJ was obtained. The temporal behavior of PCL is discussed based on the four-wave mixing mechanism. Unlike a conventional loop resonator type phase conjugator, this system is applicable for wireless energy transfer to a remote target.

  8. Generation of femtosecond anti-stokes pulses through phase-matched parametric four-wave mixing in a photonic crystal fiber.

    PubMed

    Konorov, S O; Serebryannikov, E E; Zheltikov, A M; Zhou, Ping; Tarasevitch, A P; von der Linde, D

    2004-07-01

    Phase-matched parametric four-wave mixing in higher-order guided modes of a photonic crystal fiber is shown to result in an efficient decay of 40-fs 800-nm Ti:sapphire laser pump pulses into an anti-Stokes signal with a central wavelength around 590-600 nm and a Stokes signal centered at 1.25 microm. The photonic crystal fiber is designed in such a way as to minimize the group-velocity dispersion at the pump wavelength, phase match the parametric four-wave-mixing process, and reduce the group delay between the pump and the anti-Stokes pulses. The duration of the anti-Stokes pulse under these conditions, as shown by cross-correlation frequency-resolved optical gating measurements, is less than 200 fs.

  9. Experimental generation of quadruple quantum-correlated beams from hot rubidium vapor by cascaded four-wave mixing using spatial multiplexing

    NASA Astrophysics Data System (ADS)

    Cao, Leiming; Qi, Jian; Du, Jinjian; Jing, Jietai

    2017-02-01

    Multimode quantum states, such as multipartite quantum entanglement or quantum correlations, are important for both fundamental science and the future development of quantum technologies. Here we theoretically propose and experimentally realize a scheme that can fully exploit the multi-spatial-mode nature of the four-wave-mixing (FWM) process, i.e., spatial multiplexing, and thus integrates multiple FWM processes into a single cell at each stage of the cascaded process. The number of generated quantum-correlated beams 2n is exponentially dependent on the number of vapor cells n . In addition, the quantum correlations between the multiple beams also increase as the number of vapor cell increases. For the case of n =2 , we experimentally show that the degree of intensity-difference squeezing between the four quantum-correlated beams in our scheme is enhanced to -8.2 ±0.2 dB from -5.6 ±0.3 and -6.5 ±0.2 dB of squeezing obtained with a single FWM process. Our system may find applications in quantum information and precision measurement.

  10. Photoionization pathways and thresholds in generation of Lyman-α radiation by resonant four-wave mixing in Kr-Ar mixture

    NASA Astrophysics Data System (ADS)

    Louchev, Oleg A.; Saito, Norihito; Oishi, Yu; Miyazaki, Koji; Okamura, Kotaro; Nakamura, Jumpei; Iwasaki, Masahiko; Wada, Satoshi

    2016-09-01

    We develop a set of analytical approximations for the estimation of the combined effect of various photoionization processes involved in the resonant four-wave mixing generation of ns pulsed Lyman-α (L-α ) radiation by using 212.556 nm and 820-845 nm laser radiation pulses in Kr-Ar mixture: (i) multi-photon ionization, (ii) step-wise (2+1)-photon ionization via the resonant 2-photon excitation of Kr followed by 1-photon ionization and (iii) laser-induced avalanche ionization produced by generated free electrons. Developed expressions validated by order of magnitude estimations and available experimental data allow us to identify the area for the operation under high input laser intensities avoiding the onset of full-scale discharge, loss of efficiency and inhibition of generated L-α radiation. Calculations made reveal an opportunity for scaling up the output energy of the experimentally generated pulsed L-α radiation without significant enhancement of photoionization.

  11. [Characteristics of rubidium forward degenerate four-wave mixing (FDFWM) influenced by the matrix effect of chloride brine in graphite furnace].

    PubMed

    Wang, Jian; Ren, Zhao-Yu; Cheng, Xue-Mei; Miao, Yi-Zhu; Chen, Hao-Wei; Yin, Xun-Li; Wang, Li-Qin; Bai, Jin-Tao

    2012-06-01

    Rb is mainly extracted from brine. The authors studied the matrix effect of chloride brine (NaCl, CaCl2, KCl and MgCl2) on FDFWM (Forward phase-matching degenerate four-wave mixing) of Rb in the graphite furnace. The Rb and other chloride brine concentrations dependences of FDFWM were investigated respectively. The results indicate that with the increase in Rb concentration, FDFWM increases and reaches the highest at 80 ng x mL(-1). With the concentration of Rb sample further increasing, the FDFWM intensity drops. It was also found that when the Rb concentration is low, FDFWM signal is suppressed by the chloride brine, and the suppressing effect gets stronger with the increase in the chloride brine concentration. However, when the Rb concentration is high, FDFWM signal is first enhanced and then suppressed with the increase in the chloride brine concentration. The Cl- interference and Rb ionization in the graphite furnace were employed to explain the experimental results. This work is of important meaning in extracting and analyzing Rb in brine.

  12. Electrically Tunable Microlens via Photopolymerization-Induced Phase Separation of Liquid Crystal/Monomer Mixtures Based on Four-Wave Mixing

    NASA Astrophysics Data System (ADS)

    Kyu, Thein; Nwabunma, Domasius

    2001-03-01

    We introduce a new method of fabricating electrically tunable liquid crystal (LC) microlens via photopolymerization-induced phase separation of LC/monomer mixtures using four-wave mixing technique, i.e., interference of two horizontal and two vertical waves. The microlens forming process was simulated based on a spatially modulated photopolymerization reaction coupled with the time-dependent Ginzburg-Landau (TDGL) Model C equations, which incorporate free energy densities due to isotropic mixing, LC ordering, and polymer network elasticity. Our simulation revealed that the calculated LC microlens are similar to the compound eyes found in the eyes of insects such as flies, ants, and wasps.

  13. Spectral phase transfer from near IR to deep UV by broadband phase-matched four-wave mixing in an argon-filled hollow core waveguide

    NASA Astrophysics Data System (ADS)

    Siqueira, J. P.; Mendonça, C. R.; Zilio, S. C.; Misoguti, L.

    2016-10-01

    We report on the implementation of a spectral phase transfer scheme from near IR to deep UV, in which the frequency conversion step is based on the broadband phase-matched four-wave mixing in a gas-filled hollow core waveguide. Micro joule level femtosecond pulses at 260 nm were generated by nonlinear mixing of a Ti:sapphire laser and its second-harmonic. The transfer of a π-step phase in a controllable manner was proposed and confirmed by a modulation observed in the generated deep UV femtosecond pulse spectrum due to an interference process. Numerical simulations confirmed our results.

  14. Generation of sub-two-cycle mid-infrared pulses by four-wave mixing through filamentation in air.

    PubMed

    Fuji, Takao; Suzuki, Toshinori

    2007-11-15

    Generation of sub-two-cycle, microjoule pulses in the mid-infrared region is demonstrated. Fundamental and second-harmonic pulses of 25 fs Ti:sapphire amplifier output were focused into the air to produce extremely broadband mid-infrared pulses by four-wave difference-frequency generation through the filamentation. The full width at half-maximum of the spectral bandwidth reaches one octave (2.5-5.5 microm), which is sufficiently broad for sub-single-cycle pulse generation. The pulse width was estimated to be 13 fs, without any compressors, by cross-correlation frequency resolved optical gating. The output energy of more than a few microjoule is sufficient for spectroscopy.

  15. Chalcogenide As2S3 suspended core fiber for mid-IR wavelength conversion based on degenerate four-wave mixing

    NASA Astrophysics Data System (ADS)

    Szpulak, M.; Février, Sébastien

    2009-05-01

    A chalcogenide optical fiber of special design is proposed to convert a short-wavelength IR radiation (around 2 μm) up to second transparency window of atmospheric air (around 4.5 μm) by degenerate four-wave mixing. The fiber supports a small core surrounded by three large air holes. The zero-dispersion wavelength is shifted down to 2 μm in this fiber by properly tailoring geometry of the fiber core. We demonstrate by solving the nonlinear Schrödinger equation that efficient wavelength-conversion can be obtained by pumping the fiber with a Tm:SiO2 pulsed fiber laser.

  16. Generation of polarization-entangled photon pairs and violation of Bell's inequality using spontaneous four-wave mixing in a fiber loop

    SciTech Connect

    Takesue, Hiroki; Inoue, Kyo

    2004-09-01

    We report the generation of polarization entangled photon pairs in the 1550-nm wavelength band using spontaneous four-wave mixing in a dispersion-shifted fiber loop. The use of the fiber-loop configuration made it possible to generate polarization entangled states very stably. With accidental coincidences subtracted, we obtained coincidence fringes with >90% visibilities, and observed a violation of Bell's inequality by seven standard deviations. We also confirmed the preservation of the quantum correlation between the photons even after they had been separated by 20 km of optical fiber.

  17. Four-wave mixing based widely tunable wavelength conversion using 1-m dispersion-shifted bismuth-oxide photonic crystal fiber.

    PubMed

    Chow, K K; Kikuchi, K; Nagashima, T; Hasegawa, T; Ohara, S; Sugimoto, N

    2007-11-12

    We demonstrate widely tunable wavelength conversion based on four-wave mixing using a dispersion-shifted bismuth-oxide photonic crystal fiber (Bi-PCF). A 1-meter-long Bi-PCF is used as the nonlinear medium for wavelength conversion of a 10 Gb/s non-return-to-zero (NRZ) signal. A 3- dB working range of the converted signal over 35 nm is obtained with around 1-dB power penalty in the bit-error-rate measurements.

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

    PubMed

    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.

  19. Synthesis of optical standard frequencies in the S, C and L telecommunication bands by use of four-wave mixing in semiconductor optical amplifiers

    NASA Astrophysics Data System (ADS)

    Carrasco-Sanz, Ana; Martín-López, Sonia; González-Herráez, Miguel; Corredera, Pedro; Hernanz, María Luisa

    2006-08-01

    The generation of standard reference frequencies close to the ITU channels is essential for the calibration and maintenance of DWDM systems. This work describes a method to synthesize frequency references in the range from 187.1 to 205.1 THz (1462-1602 nm). The method is based on the generation of four equispaced frequencies (by the process of four-wave mixing in a semiconductor amplifier) of which two are locked to absorption lines of the acetylene 12C 2H 2 (1511-1542 nm).

  20. Mechanism and computational model for Lyman-{alpha}-radiation generation by high-intensity-laser four-wave mixing in Kr-Ar gas

    SciTech Connect

    Louchev, Oleg A.; Saito, Norihito; Wada, Satoshi; Bakule, Pavel; Yokoyama, Koji; Ishida, Katsuhiko; Iwasaki, Masahiko

    2011-09-15

    We present a theoretical model combined with a computational study of a laser four-wave mixing process under optical discharge in which the non-steady-state four-wave amplitude equations are integrated with the kinetic equations of initial optical discharge and electron avalanche ionization in Kr-Ar gas. The model is validated by earlier experimental data showing strong inhibition of the generation of pulsed, tunable Lyman-{alpha} (Ly-{alpha}) radiation when using sum-difference frequency mixing of 212.6 nm and tunable infrared radiation (820-850 nm). The rigorous computational approach to the problem reveals the possibility and mechanism of strong auto-oscillations in sum-difference resonant Ly-{alpha} generation due to the combined effect of (i) 212.6-nm (2+1)-photon ionization producing initial electrons, followed by (ii) the electron avalanche dominated by 843-nm radiation, and (iii) the final breakdown of the phase matching condition. The model shows that the final efficiency of Ly-{alpha} radiation generation can achieve a value of {approx}5x10{sup -4} which is restricted by the total combined absorption of the fundamental and generated radiation.

  1. Mechanism and computational model for Lyman-α-radiation generation by high-intensity-laser four-wave mixing in Kr-Ar gas

    NASA Astrophysics Data System (ADS)

    Louchev, Oleg A.; Bakule, Pavel; Saito, Norihito; Wada, Satoshi; Yokoyama, Koji; Ishida, Katsuhiko; Iwasaki, Masahiko

    2011-09-01

    We present a theoretical model combined with a computational study of a laser four-wave mixing process under optical discharge in which the non-steady-state four-wave amplitude equations are integrated with the kinetic equations of initial optical discharge and electron avalanche ionization in Kr-Ar gas. The model is validated by earlier experimental data showing strong inhibition of the generation of pulsed, tunable Lyman-α (Ly-α) radiation when using sum-difference frequency mixing of 212.6 nm and tunable infrared radiation (820-850 nm). The rigorous computational approach to the problem reveals the possibility and mechanism of strong auto-oscillations in sum-difference resonant Ly-α generation due to the combined effect of (i) 212.6-nm (2+1)-photon ionization producing initial electrons, followed by (ii) the electron avalanche dominated by 843-nm radiation, and (iii) the final breakdown of the phase matching condition. The model shows that the final efficiency of Ly-α radiation generation can achieve a value of ˜5×10-4 which is restricted by the total combined absorption of the fundamental and generated radiation.

  2. The first search for sub-eV scalar fields via four-wave mixing at a quasi-parallel laser collider

    NASA Astrophysics Data System (ADS)

    Homma, Kensuke; Hasebe, Takashi; Kume, Kazuki

    2014-08-01

    A search for sub-eV scalar fields coupling to two photons has been performed via four-wave mixing at a quasi-parallel laser collider for the first time. The experiment demonstrates the novel approach of searching for resonantly produced sub-eV scalar fields by combining two-color laser fields in the vacuum. The aim of this paper is to provide the concrete experimental setup and the analysis method based on specific combinations of polarization states between incoming and outgoing photons, which is extendable to higher-intensity laser systems operated at high repetition rates. No significant signal of four-wave mixing was observed by combining a 0.2 μ J/0.75 ns pulse laser and a 2 mW CW laser on the same optical axis. Based on the prescription developed for this particular experimental approach, we obtained the upper limit at a confidence level of 95% on the coupling-mass relation.

  3. Optical bistability and four-wave mixing with a single nitrogen-vacancy center coupled to a photonic crystal nanocavity in the weak-coupling regime.

    PubMed

    Li, Jiahua; Yu, Rong; Ding, Chunling; Wu, Ying

    2014-06-16

    We explore optical bistability and degenerate four-wave mixing of a hybrid optical system composed of a photonic crystal nanocavity, a single nitrogen-vacancy center embedded in the cavity, and a nearby photonic waveguide serving for in- and outcoupling of light into the cavity in the weak-coupling regime. Here the hybrid system is coherently driven by a continuous-wave bichromatic laser field consisting of a strong control field and a weak probe field. We take account of the nonlinear nature of the nitrogen-vacancy center in the Heisenberg-Langevin equations and give an effective perturbation method to deal with such problems in the continuous-wave-operation regime. The results clearly show that the bistability region of the population inversion and the intensity of the generated four-wave mixing field can be well controlled by properly adjusting the system practical parameters. The nanophotonic platform can be used to implement our proposal. This investigation may be useful for gaining further insight into the properties of solid-state cavity quantum electrodynamics system and find applications in all-optical wavelength converter and switch in a photonic crystal platform.

  4. All-optical ultrafast wavelength and mode converter based on inter-modal four-wave mixing in few-mode fibers

    NASA Astrophysics Data System (ADS)

    Weng, Yi; He, Xuan; Wang, Junyi; Pan, Zhongqi

    2015-08-01

    An ultrafast all-optical simultaneous wavelength and mode conversion scheme is purposed based on intermodal four-wave mixing (IM-FWM), with the capability of switching state of polarization (SOP) and mode degeneracy orientation (MDO) in few-mode fibers (FMF). The relation among the conversion efficiency, pump power and phase matching conditions is investigated in theory analysis and simulation. Using this scheme, cross-polarization modulation (XPolM) and cross-mode modulation (XMM) can be achieved, by in the best case up to 50% conversion efficiency. Furthermore, numerical results further indicate that the proposed configuration has the potential application for generating doughnut modes by the mixing of three characteristic spatial frequencies.

  5. Broadband optical parametric amplifier formed by two pairs of adjacent four-wave mixing sidebands in a tellurite microstructured optical fibre

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Tuan, Tong-Hoang; Kawamura, Harutaka; Nagasaka, Kenshiro; Suzuki, Takenobu; Ohishi, Yasutake

    2016-05-01

    A broadband fibre-optical parametric amplifier (FOPA) operating at a novel wavelength region that is far from the pump wavelength has been demonstrated by exploiting two pairs of adjacent four-wave mixing (FWM) sidebands generated simultaneously in a tellurite microstructured optical fibre (TMOF). Owing to the large nonlinearity of the TMOF and the high pump peak power provided by a picosecond laser, a maximal average gain of 65.1 dB has been obtained. When the FOPA is operated in a saturated state, a flat-gain amplification from 1424 nm to 1459 nm can be achieved. This broadband and high-gain FOPA operating at new wavelength regions far from the pump offers the prospect of all-optical signal processing.

  6. QPSK-to-2×BPSK wavelength and modulation format conversion through phase-sensitive four-wave mixing in a highly nonlinear optical fiber.

    PubMed

    Da Ros, Francesco; Dalgaard, Kjeld; Lei, Lei; Xu, Jing; Peucheret, Christophe

    2013-11-18

    A phase-sensitive four-wave mixing (FWM) scheme enabling the simultaneous conversion of the two orthogonal quadratures of an optical signal to different wavelengths is demonstrated for the first time under dynamic operation using a highly nonlinear optical fiber (HNLF) as the nonlinear medium. The scheme is first optimized with respect to the power levels and phases of the four phase-coherent pumps. The successful modulation and wavelength conversion of the two complex quadratures of a quadrature phase-shift keying (QPSK) signal to two binary phase-shift keying (BPSK) signals is then demonstrated experimentally with no power penalty at a bit-error-ratio (BER) of 10(-9) compared to direct interferometric demodulation of the QPSK signal.

  7. Stable power multi-wavelength fibre laser based on four-wave mixing in a short length of highly non-linear fibre

    NASA Astrophysics Data System (ADS)

    Awang, N. A.; Zulkifli, M. Z.; Latif, A. A.; Harun, S. W.; Ahmad, H.

    2011-07-01

    A multi-wavelength fibre laser utilizing the four-wave mixing (FWM) effect in a 100 m long highly non-linear fibre (HNLF) is proposed and demonstrated. The multi-wavelength fibre laser is configured in a ring cavity and only needs a low power erbium doped fibre amplifier (EDFA) as the gain medium to generate 11 lines in the range of 1582-1600 nm with a signal-to-noise ratio (SNR) of 43 dB. The proposed system is very stable, with only minor fluctuations of 0.1 dB in the output power of the generated multi-wavelengths observed for a test period of more than an hour. The multi-wavelength fibre laser has many potential applications in optical communications and optical sensing systems.

  8. Microjoule sub-10 fs VUV pulse generation by MW pump pulses using highly efficient chirped four-wave mixing in hollow-core photonic crystal fibers

    NASA Astrophysics Data System (ADS)

    Im, Song-Jin

    2015-03-01

    We theoretically study chirped four-wave mixing for VUV pulse generation in hollow-core photonic crystal fibers. We predict the generation of sub-10 fs VUV pulses with energy of up to hundreds of µJ by broad-band chirped idler pulses at 830 nm and MW pump pulses with narrow-band at 277 nm. The MW pump could be desirable to reduce the complexity of the laser system or use a high repetition rate laser system. The energy conversion efficiency from pump pulse to VUV pulse reaches to 30% . This generation can be realized in a kagome-lattice hollow-core PCF filled with noble gas of high pressure with core diameter less than 40 µm, which would enable technically simple or highly efficient coupling to the fundamental mode of the fiber.

  9. Non-degenerate four-wave mixing in an optically injection-locked InAs/InP quantum dot Fabry–Perot laser

    SciTech Connect

    Huang, H.; Schires, K.; Grillot, F.; Poole, P. J.

    2015-04-06

    Non-degenerate four-wave mixing in an InAs/InP quantum dot Fabry–Perot laser is investigated with an optical injection-locking scheme. Wavelength conversion is obtained for frequency detunings ranging from +2.5 THz to −3.5 THz. The normalized conversion efficiency is maintained above −40 dB between −1.5 and +0.5 THz with an optical signal-to-noise ratio above 20 dB and a maximal third-order nonlinear susceptibility normalized to material gain of 2 × 10{sup −19} m{sup 3}/V{sup 2}. In addition, we show that injection-locking at different positions in the gain spectrum has an impact on the nonlinear conversion process and the symmetry between up- and down- converted signals.

  10. Performance investigation of suppression of four wave mixing using optical phase conjugation with different modulation format in DWDM soliton communication system

    NASA Astrophysics Data System (ADS)

    Kaur, G.; Kaler, R. S.; Singh, S.

    2017-03-01

    In this paper, the performance of dense wavelength division multiplexed (DWDM) soliton transmission system for return-to-zero (RZ) and non-return-to-zero (NRZ) modulation formats have been investigated. The main aim of this paper is to estimate and mitigate the four wave mixing (FWM) power by using in-line optical phase conjugator (OPC). The effect of FWM has been estimated using real fiber link having non-linear and attenuation losses. The FWM power is strongly suppressed by introducing destructive interference between the first and second halves of in-line OPC. It has been indicated that RZ with OPC yields the better performance with FWM power suppression (more than 20 dBm in certain cases) with reasonable bit error rate and Q-factor.

  11. Four-wave mixing and octave-spanning supercontinuum generation in a small core hydrogenated amorphous silicon fiber pumped in the mid-infrared.

    PubMed

    Shen, L; Healy, N; Xu, L; Cheng, H Y; Day, T D; Price, J H V; Badding, J V; Peacock, A C

    2014-10-01

    An octave-spanning supercontinuum is generated in a hydrogenated amorphous silicon core fiber when pumped in the mid-infrared regime. The broadband wavelength conversion which extends from the edge of the telecommunications band into the mid-infrared (1.64-3.37 μm) is generated by four-wave mixing (FWM) and subsequent pulse break-up, facilitated by the high material nonlinear figure of merit and the anomalous dispersion of the relatively small 1.7 μm diameter core fiber. The FWM sidebands and corresponding supercontinuum can be tuned through the pump parameters, and show good agreement with the predicted phase-matching curves for the fiber.

  12. Efficient high-power generation of visible and mid-infrared light by degenerate four-wave-mixing in a large-mode-area photonic-crystal fiber.

    PubMed

    Nodop, D; Jauregui, C; Schimpf, D; Limpert, J; Tünnermann, A

    2009-11-15

    An efficient and simple approach for converting pulsed near-IR laser radiation into visible and mid-IR light by exploiting degenerate four-wave-mixing in an endlessly single-mode, large-mode-area photonic-crystal fiber is presented. Coupling a 1 MHz, 200 ps, 8 W average power pulsed source emitting at 1064 nm into this fiber results in average powers of 3 W at 673 nm signal wavelength and of 450 mW at 2539 nm idler wavelength, respectively. The excellent pulse energy conversion efficiencies of 35% for the signal and 6% for the idler wavelength are due to the unique combination of characteristics of this type of fiber.

  13. χ{sup (3)} measurements of axial ligand modified high valent tin(IV) porphyrins using degenarete four wave mixing at 532nm

    SciTech Connect

    Narendran, N. K. Siji Chandrasekharan, K.; Soman, Rahul; Arunkumar, Chellaiah; Sudheesh, P.

    2014-10-15

    Porphyrins and metalloporphyrins are unique class of molecules for Nonlinear Optical applications because of their unique structure of altering the central metal atom, large extended π-system, high thermal stability, tunable shape, symmetry and synthetic versatility Here, we report χ{sup (3)} Measurements of a simple phenyl porphyrins and its highvalent tin(IV) porphyrins with Bromination characterized by UV-Visible spectroscopic method. In this study, we employed the Degenerate Four Wave Mixing technique using forward Boxcar geometry with an Nd:YAG nano second pulsed laser as source and it was found that the tin(IV) porphyrin with Bromination exhibits good χ{sup (3)} value and figure of merit.

  14. Measurements of exciton diffusion by degenerate four-wave mixing in CdS1-xSex

    NASA Astrophysics Data System (ADS)

    Schwab, H.; Pantke, K.-H.; Hvam, J. M.; Klingshirn, C.

    1992-09-01

    We performed transient-grating experiments to study the diffusion of excitons in CdS1-xSex mixed crystals. The decay of the initially created exciton density grating is well described for t<=1 ns by a stretched-exponential function. For later times this decay changes over to a behavior that is well fitted by a simple exponential function. During resonant excitation of the localized states, we find the diffusion coefficient (D) to be considerably smaller than in the binary compounds CdSe and CdS. At 4.2 K, D is below our experimental resolution which is about 0.025 cm2/s. With increasing lattice temperature (Tlattice) the diffusion coefficient increases. It was therefore possible to prove, in a diffusion experiment, that at Tlattice<=5 K the excitons are localized, while the exciton-phonon interaction leads to a delocalization and thus to the onset of diffusion. It was possible to deduce the diffusion coefficient of the extended excitons as well as the energetic position of the mobility edge.

  15. All-optical frequency downconversion technique utilizing a four-wave mixing effect in a single semiconductor optical amplifier for wavelength division multiplexing radio-over-fiber applications.

    PubMed

    Kim, Hyoung-Jun; Song, Jong-In

    2012-03-26

    An all-optical frequency downconversion utilizing a four-wave mixing effect in a single semiconductor optical amplifier (SOA) was experimentally demonstrated for wavelength division multiplexing (WDM) radio-over-fiber (RoF) applications. Two WDM optical radio frequency (RF) signals having 155 Mbps differential phase shift keying (DPSK) data at 28.5 GHz were simultaneously down-converted to two WDM optical intermediate frequency (IF) signals having an IF frequency of 4.5 GHz by mixing with an optical local oscillator (LO) signal having a LO frequency of 24 GHz in the SOA. The bit-error-rate (BER) performance of the RoF up-links with different optical fiber lengths employing all-optical frequency downconversion was investigated. The receiver sensitivity of the RoF up-link with a 6 km single mode fiber and an optical IF signal in an optical double-sideband format was approximately -8.5 dBm and the power penalty for simultaneous frequency downconversion was approximately 0.63 dB. The BER performance showed a strong dependence on the fiber length due to the fiber dispersion. The receiver sensitivity of the RoF up-link with the optical IF signal in the optical single-sideband format was reduced to approximately -17.4 dBm and showed negligible dependence on the fiber length.

  16. Synthesis, Z-Scan and Degenerate Four Wave Mixing characterization of certain novel thiocoumarin derivatives for third order nonlinear optical applications

    NASA Astrophysics Data System (ADS)

    Jayakrishnan, K.; Joseph, Antony; Mathew, K. Paulson; Siji, T. B.; Chandrasekharan, K.; Narendran, N. K. Siji; Jaseela, M. A.; Muraleedharan, K.

    2016-08-01

    The third order nonlinear optical features of certain novel thiocoumarin derivatives have been studied. Single beam Z-scan study on these compounds reveals that the compounds exhibit self defocusing effect upon irradiation with 532 nm, 7 ns pulses of Nd:YAG laser. Nonlinear absorption coefficient, nonlinear refractive index and second-order molecular hyperpolarizability values were estimated. The optical power limiting properties of the compounds are found to be attributable to both two-photon and excited state absorption. Some of the samples show nonlinear absorption coefficient (βeff) as high as 24.5 cm/GW. UV-Visible and photoluminescence outputs of these compounds reveal remarkable absorptive and emissive properties. This article also reports extraordinary growth of third order optical nonlinearity in pure coumarin upon certain donor substitutions in lieu of hydrogen. Degenerate Four Wave Mixing (DFWM) signals of the compounds were analyzed to verify the Z-scan results. Electrostatic Surface Potential (ESP) mapping and structure optimization techniques have been employed to interpret the structure-property relationship of each molecule.

  17. Simultaneous observation of free and defect-bound excitons in CH3NH3PbI3 using four-wave mixing spectroscopy

    PubMed Central

    March, Samuel A.; Clegg, Charlotte; Riley, Drew B.; Webber, Daniel; Hill, Ian G.; Hall, Kimberley C.

    2016-01-01

    Solar cells incorporating organic-inorganic perovskite, which may be fabricated using low-cost solution-based processing, have witnessed a dramatic rise in efficiencies yet their fundamental photophysical properties are not well understood. The exciton binding energy, central to the charge collection process, has been the subject of considerable controversy due to subtleties in extracting it from conventional linear spectroscopy techniques due to strong broadening tied to disorder. Here we report the simultaneous observation of free and defect-bound excitons in CH3NH3PbI3 films using four-wave mixing (FWM) spectroscopy. Due to the high sensitivity of FWM to excitons, tied to their longer coherence decay times than unbound electron- hole pairs, we show that the exciton resonance energies can be directly observed from the nonlinear optical spectra. Our results indicate low-temperature binding energies of 13 meV (29 meV) for the free (defect-bound) exciton, with the 16 meV localization energy for excitons attributed to binding to point defects. Our findings shed light on the wide range of binding energies (2–55 meV) reported in recent years. PMID:27974815

  18. Influence of four-wave mixing in short- and medium-range 1310  nm dense wavelength division multiplexing systems.

    PubMed

    Markowski, Konrad; Chorchos, Łukasz; Turkiewicz, Jarosław Piotr

    2016-04-10

    In this paper, we demonstrate a comprehensive analysis of the impact of four-wave mixing (FWM) on the quality of transmission in short- and medium-range dense wavelength division multiplexing (DWDM) systems in the 1310 nm wavelength domain. The presented analysis proves that, for the system with uniform power per channel assignment, setting proper input channel power can substantially reduce the influence of the FWM effect on bit error rate in low channel spaced short-range systems, despite the position of the DWDM grid around the zero-dispersion wavelength. Simulations and experimental analysis of the possibility of FWM suppression have been provided. The power penalty measurements show that the influence of FWM on system performance may be as low as 0.3 dB with reasonable input power (i.e., -11  dBm per channel), making possible the transmission of data by fiber over distances of 25 km. Finally, we demonstrate that, for channel spacing as low as 120 GHz, error-free transmission in the 1310 nm wavelength domain is possible, despite high efficiency of FWM generation. The results prove that utilization of the 1310 nm wavelength domain in a system with low channel spacing, i.e., with better bandwidth allocation, is an interesting solution for data storage and processing center applications.

  19. Dynamic characteristics of a multi-wavelength Brillouin-Raman fiber laser assisted by multiple four-wave mixing processes in a ring cavity

    NASA Astrophysics Data System (ADS)

    Shirazi, M. R.; Mohamed Taib, J.; De La Rue, R. M.; Harun, S. W.; Ahmad, H.

    2015-03-01

    Dynamic characteristics of a multi-wavelength Brillouin-Raman fiber laser (MBRFL) assisted by four-wave mixing have been investigated through the development of Stokes and anti-Stokes lines under different combinations of Brillouin and Raman pump power levels and different Raman pumping schemes in a ring cavity. For a Stokes line of order higher than three, the threshold power was less than the saturation power of its last-order Stokes line. By increasing the Brillouin pump power, the nth order anti-Stokes and the (n+4)th order Stokes power levels were unexpectedly increased almost the same before the Stokes line threshold power. It was also found out that the SBS threshold reduction (SBSTR) depended linearly on the gain factor for the 1st and 2nd Stokes lines, as the first set. This relation for the 3rd and 4th Stokes lines as the second set, however, was almost linear with the same slope before SBSTR -6 dB, then, it approached to the linear relation in the first set when the gain factor was increased to 50 dB. Therefore, the threshold power levels of Stokes lines for a given Raman gain can be readily estimated only by knowing the threshold power levels in which there is no Raman amplification.

  20. APPLICATION OF LASERS AND LASER-OPTICAL METHODS IN LIFE SCIENCES Low-frequency four-wave mixing spectroscopy of biomolecules in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Bunkin, Aleksei F.; Pershin, S. M.

    2011-01-01

    Four-wave mixing (FWM) spectroscopy is used to detect the rotational resonances of H2O and H2O2 molecules in DNA and denatured DNA aqueous solutions in the range ±10 cm-1 with a spectral resolution of 3 GHz. It is found that the resonance contribution of the rotational transitions of these molecules increases significantly in solutions rather than in distilled water. This fact is interpreted as a manifestation of specific properties of a hydration layer at DNA—water and denatured DNA—water interfaces. Analysis of the FWM spectra shows that the concentration of H2O2 molecules in the hydration layer of the DNA solution increases by a factor of 3 after denaturation. The FWM spectra of aqueous solutions of α-chymotrypsin protein are obtained in the range ±7cm-1 at the protein concentrations between 0 and 20 mg cm-3. It is found that the hypersound velocity in the protein aqueous solution, measured by the shift of Brillouin components in the scattering spectrum, obeys a cubic dependence on the protein concentration and reaches a value of about 3000 m s-1 at 20 mg cm-3.

  1. Demonstration and optimisation of an ultrafast all-optical AND logic gate using four-wave mixing in a semiconductor optical amplifier

    SciTech Connect

    Razaghi, M; Nosratpour, A; Das, N K

    2013-02-28

    We have proposed an all-optical AND logic gate based on four-wave mixing (FWM) in a semiconductor optical amplifier (SOA) integrated with an optical filter. In the scheme proposed, the preferred logical function can be performed without using a continuous-wave (cw) signal. The modified nonlinear Schroedinger equation (MNLSE) is used for the modelling wave propagation in a SOA. The MNLSE takes into account all nonlinear effects relevant to pico- and sub-picosecond pulse durations and is solved by the finite-difference beam-propagation method (FD-BPM). Based on the simulation results, the optimal output signal with a 40-fJ energy can be obtained at a bit rate of 50 Gb s{sup -1}. In the simulations, besides the nonlinearities included in the model, the pattern effect of the signals propagating in the SOA medium and the effect of the input signal bit rate are extensively investigated to optimise the system performance. (optical logic elements)

  2. Simultaneous observation of free and defect-bound excitons in CH3NH3PbI3 using four-wave mixing spectroscopy.

    PubMed

    March, Samuel A; Clegg, Charlotte; Riley, Drew B; Webber, Daniel; Hill, Ian G; Hall, Kimberley C

    2016-12-15

    Solar cells incorporating organic-inorganic perovskite, which may be fabricated using low-cost solution-based processing, have witnessed a dramatic rise in efficiencies yet their fundamental photophysical properties are not well understood. The exciton binding energy, central to the charge collection process, has been the subject of considerable controversy due to subtleties in extracting it from conventional linear spectroscopy techniques due to strong broadening tied to disorder. Here we report the simultaneous observation of free and defect-bound excitons in CH3NH3PbI3 films using four-wave mixing (FWM) spectroscopy. Due to the high sensitivity of FWM to excitons, tied to their longer coherence decay times than unbound electron- hole pairs, we show that the exciton resonance energies can be directly observed from the nonlinear optical spectra. Our results indicate low-temperature binding energies of 13 meV (29 meV) for the free (defect-bound) exciton, with the 16 meV localization energy for excitons attributed to binding to point defects. Our findings shed light on the wide range of binding energies (2-55 meV) reported in recent years.

  3. Effect of chromatic-dispersion-induced chirp on the temporal coherence properties of individual beams from spontaneous four-wave mixing

    SciTech Connect

    Ma Xiaoxin; Li Xiaoying; Cui Liang; Guo Xueshi; Yang Lei

    2011-08-15

    Temporal coherence of individual signal or idler beam, determined by the spectral correlation property of photon pairs, is important for realizing quantum interference among independent sources. Based on spontaneous four-wave mixing in optical fibers, we study the effect of chirp on the temporal coherence property by introducing a different amount of chirp into either the pulsed pump or individual signal (idler) beam. The investigation shows that the pump chirp induces additional frequency correlation into photon pairs; the mutual spectral correlation of photon pairs and the coherence of individual beam can be characterized by measuring the intensity correlation function g{sup (2)} of the individual beam. To improve the coherence degree, the pump chirp should be minimized. Moreover, a Hong-Ou-Mandel-type two-photon interference experiment with the signal beams generated in two different fibers illustrates that the chirp of the individual signal (idler) beam does not change the temporal coherence degree, but affects the temporal mode matching. To achieve high visibility among multiple sources, apart from improving the coherence degree, mode matching should be optimized by managing the chirps of individual beams.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  5. Efficient and broadband Stokes wave generation by degenerate four-wave mixing at the mid-infrared wavelength in a silica photonic crystal fiber.

    PubMed

    Yuan, Jinhui; Sang, Xinzhu; Wu, Qiang; Zhou, Guiyao; Yu, Chongxiu; Wang, Kuiru; Yan, Binbin; Han, Ying; Farrell, Gerald; Hou, Lantian

    2013-12-15

    Based on degenerate four-wave mixing (FWM), the broadband Stokes waves are efficiently generated at the mid-infrared wavelength above 2 μm, for the first time to our knowledge, by coupling the femtosecond pulses into the fundamental mode of a silica photonic crystal fiber designed and fabricated in our laboratory. Influences of the power and wavelength of pump pulses on the phase-matched frequency conversion process are discussed. When pump pulses with central wavelength of 815 nm and average power of 300 mW are used, the output power ratio of the Stokes wave generated at 2226 nm and the residual pump wave P(s)/P(res) is estimated to be 10.8:1, and the corresponding conversion efficiency η(s) and bandwidth B(s) of the Stokes wave can be up to 26% and 33 nm, respectively. The efficient and broadband Stokes waves can be used as the ultrashort pulse sources for mid-infrared photonics and spectroscopy.

  6. Simultaneous observation of free and defect-bound excitons in CH3NH3PbI3 using four-wave mixing spectroscopy

    NASA Astrophysics Data System (ADS)

    March, Samuel A.; Clegg, Charlotte; Riley, Drew B.; Webber, Daniel; Hill, Ian G.; Hall, Kimberley C.

    2016-12-01

    Solar cells incorporating organic-inorganic perovskite, which may be fabricated using low-cost solution-based processing, have witnessed a dramatic rise in efficiencies yet their fundamental photophysical properties are not well understood. The exciton binding energy, central to the charge collection process, has been the subject of considerable controversy due to subtleties in extracting it from conventional linear spectroscopy techniques due to strong broadening tied to disorder. Here we report the simultaneous observation of free and defect-bound excitons in CH3NH3PbI3 films using four-wave mixing (FWM) spectroscopy. Due to the high sensitivity of FWM to excitons, tied to their longer coherence decay times than unbound electron- hole pairs, we show that the exciton resonance energies can be directly observed from the nonlinear optical spectra. Our results indicate low-temperature binding energies of 13 meV (29 meV) for the free (defect-bound) exciton, with the 16 meV localization energy for excitons attributed to binding to point defects. Our findings shed light on the wide range of binding energies (2–55 meV) reported in recent years.

  7. Quantum dynamics of Kerr optical frequency combs below and above threshold: Spontaneous four-wave mixing, entanglement, and squeezed states of light

    NASA Astrophysics Data System (ADS)

    Chembo, Yanne K.

    2016-03-01

    The dynamical behavior of Kerr optical frequency combs is very well understood today from the perspective of the semiclassical approximation. These combs are obtained by pumping an ultrahigh-Q whispering-gallery mode resonator with a continuous-wave laser. The long-lifetime photons are trapped within the toruslike eigenmodes of the resonator, where they interact nonlinearly via the Kerr effect. In this article, we use quantum Langevin equations to provide a theoretical understanding of the nonclassical behavior of these combs when pumped below and above threshold. In the configuration where the system is under threshold, the pump field is the unique oscillating mode inside the resonator, and it triggers the phenomenon of spontaneous four-wave mixing, where two photons from the pump are symmetrically up- and down-converted in the Fourier domain. This phenomenon, also referred to as parametric fluorescence, can only be understood and analyzed from a fully quantum perspective as a consequence of the coupling between the field of the central (pumped) mode and the vacuum fluctuations of the various side modes. We analytically calculate the power spectra of the spontaneous emission noise, and we show that these spectra can be either single- or double-peaked depending on the value of the laser frequency, chromatic dispersion, pump power, and spectral distance between the central mode and the side mode of interest. We also calculate as well the overall spontaneous noise power per side mode and propose simplified analytical expressions for some particular cases. In the configuration where the system is pumped above threshold, we investigate the phenomena of quantum correlations and multimode squeezed states of light that can occur in the Kerr frequency combs originating from stimulated four-wave mixing. We show that for all stationary spatiotemporal patterns, the side modes that are symmetrical relative to the pumped mode in the frequency domain display quantum correlations

  8. Tunable error-free optical frequency conversion of a 4ps optical short pulse over 25 nm by four-wave mixing in a polarisation-maintaining optical fibre

    NASA Astrophysics Data System (ADS)

    Morioka, T.; Kawanishi, S.; Saruwatari, M.

    1994-05-01

    Error-free, tunable optical frequency conversion of a transform-limited 4.0 ps optical pulse signalis demonstrated at 6.3 Gbit/s using four-wave mixing in a polarization-maintaining optical fibre. The process generates 4.0-4.6 ps pulses over a 25nm range with time-bandwidth products of 0.31-0.43 and conversion power penalties of less than 1.5 dB.

  9. Highly efficient non-degenerate four-wave mixing under dual-mode injection in InP/InAs quantum-dash and quantum-dot lasers at 1.55 μm

    SciTech Connect

    Sadeev, T. Arsenijević, D.; Huang, H.; Schires, K.; Grillot, F.; Bimberg, D.

    2015-11-09

    This work reports on non-degenerate four-wave mixing under dual-mode injection in metalorganic vapor phase epitaxy grown InP/InAs quantum-dash and quantum dot Fabry-Perot laser operating at 1550 nm. High values of normalized conversion efficiency of −18.6 dB, optical signal-to-noise ratio of 37 dB, and third order optical susceptibility normalized to material gain χ{sup (3)}/g{sub 0} of ∼4 × 10{sup −19} m{sup 3}/V{sup 3} are measured for 1490 μm long quantum-dash lasers. These values are similar to those obtained with distributed-feedback lasers and semiconductor optical amplifiers, which are much more complicated to fabricate. On the other hand, due to the faster gain saturation and enhanced modulation of carrier populations, quantum-dot lasers demonstrate 12 dB lower conversion efficiency and 4 times lower χ{sup (3)}/g{sub 0} compared to quantum dash lasers.

  10. Measurements of the nonlinear refractive index of air, N2, and O2 at 10 μm using four-wave mixing.

    PubMed

    Pigeon, J J; Tochitsky, S Ya; Welch, E C; Joshi, C

    2016-09-01

    We report on measurements of the nonlinear index of refraction of air, N2, and O2 at a wavelength close to 10 μm by collinear four-wave mixing of a 200 MW CO2 laser beat-wave. The use of a 200 ps long beat-wave comprising radiation amplified on the 10P20 and 10R16 lines of the CO2 laser provides a sensitive method to measure the small nonlinearities characteristic of the gas phase in a spectral region where no such data exists.

  11. Mass-analyzed threshold ionization study of vinyl bromide cation in the first excited electronic state using vacuum-ultraviolet radiation generated by four-wave mixing in Hg

    NASA Astrophysics Data System (ADS)

    Lee, Mina; Kim, Myung Soo

    2005-11-01

    The vibrational spectrum of the vinyl bromide cation in the first excited electronic state ÃA'2 was obtained by one-photon mass-analyzed threshold ionization (MATI) spectroscopy. The use of an improved vacuum-ultraviolet radiation source based on four-wave sum frequency mixing in Hg resulted in excellent sensitivity for MATI signals. From the MATI spectrum, the ionization energy to the ÃA'2 state of the cation was determined to be 10.9150±0.0006eV. Nearly complete vibrational assignments for the MATI peaks were possible by utilizing the vibrational frequencies and Franck-Condon factors calculated at the density-functional theory (DFT) and time-dependent DFT/B3LYP levels with the 6-311+G(df,p) basis set.

  12. Phase-matched four-wave mixing of sub-100-TW/ cm2 femtosecond laser pulses in isolated air-guided modes of a hollow photonic-crystal fiber.

    PubMed

    Konorov, S O; Serebryannikov, E E; Akimov, D A; Ivanov, A A; Alfimov, M V; Zheltikov, A M

    2004-12-01

    Hollow-core photonic-crystal fibers are shown to allow propagation and nonlinear-optical frequency conversion of high-intensity ultrashort laser pulses in the regime of isolated guided modes confined in the hollow gas-filled fiber core. With a specially designed dispersion of such modes, the 3omega=2omega+2omega-omega four-wave mixing of fundamental (omega) and second-harmonic (2omega) sub-100- TW/ cm(2) femtosecond pulses of a Cr:forsterite laser can be phase matched in a hollow photonic-crystal fiber within a spectral band of more than 10 nm, resulting in the efficient generation of femtosecond pulses in a well-resolved higher-order air-guided mode of 417-nm radiation.

  13. Design of optical time-division multiplexed systems using the cascaded four-wave mixing in a highly nonlinear photonic crystal fiber for simultaneous time demultiplexing and wavelength multicasting

    NASA Astrophysics Data System (ADS)

    Hui, Zhan-Qiang; Zhang, Jian-Guo

    2015-07-01

    This paper reports a new design of optical time-division multiplexed (OTDM) systems that possess a functionality of simultaneous time demultiplexing and wavelength multicasting based on the cascaded four-wave mixing in a dispersion-flattened highly nonlinear photonic crystal fiber (DF-HNL-PCF). A module of OTDM demultiplexing and wavelength multicasting can be feasibly implemented by using a 3 dB optical coupler, a high-power erbium-doped fiber amplifier, a short-length DF-HNL-PCF, and a wavelength demultiplexer in the simple configuration. We also carry out an experiment on the proposed system to demonstrate the 100-10 Gbit s-1 OTDM demultiplexing with wavelength conversion simultaneously at 4 multicast wavelengths. It is shown that error-free wavelength multicasting is achieved on two wavelength channels with the minimum power penalty of 3.2 dB relative to the 10 Gbit s-1 back-to-back measurement, whereas the bit error rates of other two multicasting channels are measured to be about 10-6-10-5. Moreover, we propose the use of a proper error-correcting code to improve the multicasting performance of such an OTDM system, and our work reveals that the resulting system can theoretically support error-free multicasting of the OTDM-demultiplexed signal on four wavelength channels.

  14. All-optical NRZ-to-RZ format conversion at 10 Gbit/s with 1-to-4 wavelength multicasting exploiting cross-phase modulation & four-wave-mixing in single dispersion-flattened highly nonlinear photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Hui, Zhan-Qiang; Zhang, Bo; Zhang, Jian-Guo

    2016-04-01

    All-optical NRZ-to-RZ format conversion with a function of wavelength multicasting is proposed in this paper, which is realized by exploiting cross-phase modulation (XPM) and four-wave-mixing (FWM) in a dispersion-flattened highly nonlinear photonic crystal fiber (DF-HNL-PCF). The designed format converter is experimentally demonstrated, for which the 1-to-4 wavelength multicasting is achieved simultaneously by filtering out two FWM idler waves and both blue-chirped and red-chirped components of the broadened NRZ spectrum induced by XPM. Moreover, the wavelength tunability and dynamic characteristics of the proposed NRZ-to-RZ format converter are also exploited using the different central wavelengths of an optical clock signal and varying the input optical power at a DF-HNL-PCF in our experiment. It is shown that the designed format converter can possess a wide range of operational wavelength over 17 nm, an optimal extinction ratio of 11.6 dB, and a Q-factor of 7.1, respectively. Since the proposed scheme uses an optical fiber-based configuration and is easy for implementation, it can be very useful for future applications in advanced fiber-optic communication networks.

  15. Nonlinear Optics Technology, Area 1: FWM (Four Wave Mixing) Technology

    DTIC Science & Technology

    1986-09-22

    41 0 u Q)Co o 0 0. >1- o 0 41 -A $4 P4 38 paths to insure a high degree of copolarization at the Na cell. Turning mirrors (M) were visible dielectric...or MAXBRIte coated Zerodur substrate optics with twentieth wave or better surface figures. A 50-50 beamsplitter (BSl) served to generate the two pump...retroreflecting mirror . The signal beam, which essentially constituted a very bright glint, was split off of the pump leg by a beamsplitter and directed to a

  16. Mixing in microfluidic devices and enhancement methods

    PubMed Central

    Ward, Kevin; Fan, Z Hugh

    2015-01-01

    Mixing in microfluidic devices presents a challenge due to laminar flows in microchannels, which result from low Reynolds numbers determined by the channel’s hydraulic diameter, flow velocity, and solution’s kinetic viscosity. To address this challenge, novel methods of mixing enhancement within microfluidic devices have been explored for a variety of applications. Passive mixing methods have been created, including those using ridges or slanted wells within the microchannels, as well as their variations with improved performance by varying geometry and patterns, by changing the properties of channel surfaces, and by optimization via simulations. In addition, active mixing methods including microstirrers, acoustic mixers, and flow pulsation have been investigated and integrated into microfluidic devices to enhance mixing in a more controllable manner. In general, passive mixers are easy to integrate, but difficult to control externally by users after fabrication. Active mixers usually take efforts to integrate within a device and they require external components (e.g. power sources) to operate. However, they can be controlled by users to a certain degree for tuned mixing. In this article, we provide a general overview of a number of passive and active mixers, discuss their advantages and disadvantages, and make suggestions on choosing a mixing method for a specific need as well as advocate possible integration of key elements of passive and active mixers to harness the advantages of both types. PMID:26549938

  17. Mixing in microfluidic devices and enhancement methods.

    PubMed

    Ward, Kevin; Fan, Z Hugh

    2015-09-01

    Mixing in microfluidic devices presents a challenge due to laminar flows in microchannels, which result from low Reynolds numbers determined by the channel's hydraulic diameter, flow velocity, and solution's kinetic viscosity. To address this challenge, novel methods of mixing enhancement within microfluidic devices have been explored for a variety of applications. Passive mixing methods have been created, including those using ridges or slanted wells within the microchannels, as well as their variations with improved performance by varying geometry and patterns, by changing the properties of channel surfaces, and by optimization via simulations. In addition, active mixing methods including microstirrers, acoustic mixers, and flow pulsation have been investigated and integrated into microfluidic devices to enhance mixing in a more controllable manner. In general, passive mixers are easy to integrate, but difficult to control externally by users after fabrication. Active mixers usually take efforts to integrate within a device and they require external components (e.g. power sources) to operate. However, they can be controlled by users to a certain degree for tuned mixing. In this article, we provide a general overview of a number of passive and active mixers, discuss their advantages and disadvantages, and make suggestions on choosing a mixing method for a specific need as well as advocate possible integration of key elements of passive and active mixers to harness the advantages of both types.

  18. Mixing in microfluidic devices and enhancement methods

    NASA Astrophysics Data System (ADS)

    Ward, Kevin; Fan, Z. Hugh

    2015-09-01

    Mixing in microfluidic devices presents a challenge due to laminar flows in microchannels, which result from low Reynolds numbers determined by the channel’s hydraulic diameter, flow velocity, and solution’s kinetic viscosity. To address this challenge, novel methods of mixing enhancement within microfluidic devices have been explored for a variety of applications. Passive mixing methods have been created, including those using ridges or slanted wells within the microchannels, as well as their variations with improved performance by varying geometry and patterns, by changing the properties of channel surfaces, and by optimization via simulations. In addition, active mixing methods including microstirrers, acoustic mixers, and flow pulsation have been investigated and integrated into microfluidic devices to enhance mixing in a more controllable manner. In general, passive mixers are easy to integrate, but difficult to control externally by users after fabrication. Active mixers usually take efforts to integrate within a device and they require external components (e.g. power sources) to operate. However, they can be controlled by users to a certain degree for tuned mixing. In this article, we provide a general overview of a number of passive and active mixers, discuss their advantages and disadvantages, and make suggestions on choosing a mixing method for a specific need as well as advocate possible integration of key elements of passive and active mixers to harness the advantages of both types.

  19. Control of Jet Noise Through Mixing Enhancement

    NASA Technical Reports Server (NTRS)

    Bridges, James; Wernet, Mark; Brown, Cliff

    2003-01-01

    The idea of using mixing enhancement to reduce jet noise is not new. Lobed mixers have been around since shortly after jet noise became a problem. However, these designs were often a post-design fix that rarely was worth its weight and thrust loss from a system perspective. Recent advances in CFD and some inspired concepts involving chevrons have shown how mixing enhancement can be successfully employed in noise reduction by subtle manipulation of the nozzle geometry. At NASA Glenn Research Center, this recent success has provided an opportunity to explore our paradigms of jet noise understanding, prediction, and reduction. Recent advances in turbulence measurement technology for hot jets have also greatly aided our ability to explore the cause and effect relationships of nozzle geometry, plume turbulence, and acoustic far field. By studying the flow and sound fields of jets with various degrees of mixing enhancement and subsequent noise manipulation, we are able to explore our intuition regarding how jets make noise, test our prediction codes, and pursue advanced noise reduction concepts. The paper will cover some of the existing paradigms of jet noise as they relate to mixing enhancement for jet noise reduction, and present experimental and analytical observations that support these paradigms.

  20. Mixing Enhancement in a Lobed Injector

    NASA Technical Reports Server (NTRS)

    Smith, L. L.; Majamaki, A. J.; Lam, I. T.; Delabroy, O.; Karagozian, A. R.; Marble, F. E.; Smith, O. I.

    1997-01-01

    An experimental investigation of the non-reactive mixing processes associated with a lobed fuel injector in a coflowing air stream is presented. The lobed fuel injector is a device which generates streamwise vorticity, producing high strain rates which can enhance the mixing of reactants while delaying ignition in a controlled manner. The lobed injectors examined in the present study consist of two corrugated plates between which a fuel surrogate, CO2, is injected into coflowing air. Acetone is seeded in the CO2 supply as a fuel marker. Comparison of two alternative lobed injector geometries is made with a straight fuel injector to determine net differences in mixing and strain fields due to streamwise vorticity generation. Planar laser-induced fluorescence (PLIF) of the seeded acetone yields two-dimensional images of the scalar concentration field at various downstream locations, from which local mixing and scalar dissipation rates are computed. It is found that the lobed injector geometry can enhance molecular mixing and create a highly strained flowfield, and that the strain rates generated by scalar energy dissipation can potentially delay ignition in a reacting flowfield.

  1. Mixed surfactant systems for enhanced oil recovery

    SciTech Connect

    Llave, F.M.; Gall, B.L.; Noll, L.A.

    1990-12-01

    The results of an evaluation of mixed surfactant systems for enhanced oil recovery are described. Several surfactant combinations have been studied. These include alkyl aryl sulfonates as primary surfactants and carboxymethylated ethoxylated (CME) surfactants and ethoxylated sulfonates (ES) as secondary surfactants. The ethoxylated surfactants increase the salinity tolerance of the primary surfactants and, in theory, allow tailoring of the surfactant system to match selected reservoir conditions. The experiments conducted included interfacial tension (IFT) measurements, phase behavior measurements, adsorption and/or chromatographic separation of mixed surfactant systems, measurements of solution properties such as the critical micelle concentration (CMC) of surfactant mixtures, and crude oil displacement experiments. The effects of temperature, surfactant concentration, salinity, presence of divalent ions, hydrocarbon type, and component proportions in the mixed surfactant combinations, and injection strategies on the performance potential of the targeted surfactant/hydrocarbon systems were studied. 40 refs., 37 figs., 8 tabs.

  2. Enhanced Mixing in a Rectangular Duct

    NASA Technical Reports Server (NTRS)

    Liscinsky, D. S.; True, B.

    2003-01-01

    An experimental investigation of the mixing of non-reacting opposed rows of jets injected normal to a confined rectangular crossflow has been conducted. Planar Mie-scattering was used to measure the time-average concentration distribution of the jet fluid in planes perpendicular to the duct axis. Particular emphasis was placed on the study of closely spaced orifice configurations applicable to the mixing zone of an RQL combustor. Baseline studies were performed of mixing under "ideal" conditions, i.e., plenum fed jets injecting into a crossflow uniform in velocity and turbulence intensity. In addition, more practical ("non-ideal") issues encountered during hardware design were also studied. As in other studies, mixing effectiveness, determined using a spatial unmixedness parameter based on the variance of mean jet concentration distributions, was found to be optimum when the spacing-to-duct-height ratio was inversely proportional to the square root of the jet-to-mainstream momentum-flux ratio. This relationship is suitable for design under ideal flow conditions. Inlet flow boundary conditions of the jet and approach flow (mainstream) were found to strongly influence mixing performance, but no attempt was made to determine optimum performance under non-ideal conditions. The tests performed do offer some guidance as to expected mixing behavior for several common variables likely to be imposed by hardware constraints. Additionally, in this study it was found that for rows of orifices with opposite centerlines inline, mixing was similar for blockages up to 89 percent (previous crossflow mixing studies concerned with dilution zone configurations, blockages were typically less than 50 percent). Lower levels of unmixedness were obtained as a function of downstream location when axial injection length was minimized. Mixing may be enhanced if orifice centerlines of opposed rows are staggered, but blockage must be =50 percent in this configuration. Round hole and "square

  3. Magma mixing enhanced by bubble segregation

    NASA Astrophysics Data System (ADS)

    Wiesmaier, S.; Morgavi, D.; Renggli, C. J.; Perugini, D.; De Campos, C. P.; Hess, K.-U.; Ertel-Ingrisch, W.; Lavallée, Y.; Dingwell, D. B.

    2015-08-01

    In order to explore the materials' complexity induced by bubbles rising through mixing magmas, bubble-advection experiments have been performed, employing natural silicate melts at magmatic temperatures. A cylinder of basaltic glass was placed below a cylinder of rhyolitic glass. Upon melting, bubbles formed from interstitial air. During the course of the experimental runs, those bubbles rose via buoyancy forces into the rhyolitic melt, thereby entraining tails of basaltic liquid. In the experimental run products, these plume-like filaments of advected basalt within rhyolite were clearly visible and were characterised by microCT and high-resolution EMP analyses. The entrained filaments of mafic material have been hybridised. Their post-experimental compositions range from the originally basaltic composition through andesitic to rhyolitic composition. Rheological modelling of the compositions of these hybridised filaments yield viscosities up to 2 orders of magnitude lower than that of the host rhyolitic liquid. Importantly, such lowered viscosities inside the filaments implies that rising bubbles can ascend more efficiently through pre-existing filaments that have been generated by earlier ascending bubbles. MicroCT imaging of the run products provides textural confirmation of the phenomenon of bubbles trailing one another through filaments. This phenomenon enhances the relevance of bubble advection in magma mixing scenarios, implying as it does so, an acceleration of bubble ascent due to the decreased viscous resistance facing bubbles inside filaments and yielding enhanced mass flux of mafic melt into felsic melt via entrainment. In magma mixing events involving melts of high volatile content, bubbles may be an essential catalyst for magma mixing. Moreover, the reduced viscosity contrast within filaments implies repeated replenishment of filaments with fresh end-member melt. As a result, complex compositional gradients and therefore diffusion systematics can be

  4. Undulated Nozzle for Enhanced Exit Area Mixing

    NASA Technical Reports Server (NTRS)

    Seiner, John M. (Inventor); Gilinsky, Mikhail M. (Inventor)

    2000-01-01

    A nozzle having an undulating surface for enhancing the mixing of a primary flow with a secondary flow or ambient air, without requiring an ejector. The nozzle includes a nozzle structure and design for introducing counter-rotating vorticity into the primary flow either through (i) internal surface corrugations where an axisymmetric line through each corrugation is coincident with an axisymmetric line through the center of the flow passageway or (ii) through one or more sets of alternating convexities and cavities in the internal surface of the nozzle where an axisymmetric line through each convexity and cavity is coincident with an axisymmetric line through the center of the flow passageway, and where the convexities contract from the entrance end towards the exit end. Exit area mixing is also enhanced by one or more chevrons attached to the exit edge of the nozzle. The nozzle is ideally suited for application as a jet engine nozzle. When used as a jet engine nozzle, noise suppression with simultaneous thrust augmentation/minimal thrust loss is achieved.

  5. Mixed Hydrotropy: Novel Science of Solubility Enhancement

    PubMed Central

    Maheshwari, R. K.; Jagwani, Y.

    2011-01-01

    Conventional furosemide tablets are practically insoluble in water, have slow onset of action (45-60 min) and poor bioavailability (39-53%), and therefore cannot be given in emergency clinical situations like hypertension or pulmonary edema. So purpose of research was to provide a fast dissolving oral dosage form of furosemide, which can provide quick onset of action by using concept of mixed hydrotropy. Initially solubility of furosemide was determined individually in 4 hydrotropic agents namely urea, sodium acetate, sodium benzoate, sodium citrate at concentration of 10, 20, 30 and 40% w/v solutions using purified water as solvent. Highest solubility was obtained in 40% sodium benzoate solution. Then different combinations of 2, 3 and 4 hydrotropic agents in different ratios were used to determine solubility, so that total concentration of hydrotropic agents was always 40%. Highest solubility was obtained in solution of urea+sodium benzoate+sodium citrate at optimum ratio of 15:20:5. This optimized combination was utilized in preparing solid dispersions by common solvent technique using distilled water as solvent. Solid dispersions were evaluated for flow properties, XRD, DSC, SEM and were also compressed to form tablets. Dissolution studies of conventional and prepared tablets were done using USP Type II apparatus. It was concluded that the concept of mixed hydrotropic solid dispersion is novel, safe and cost-effective technique for enhancing bioavailability of poorly water-soluble drugs by dissolving drug in nonionized form. The magical enhancement in solubility of furosemide is clear indication of its potential to be used in future for other poorly water-soluble drugs in which low bioavailability is major concern. PMID:22303061

  6. On the mixing enhancement in annular flows

    NASA Astrophysics Data System (ADS)

    Moradi, H. V.; Floryan, J. M.

    2017-02-01

    The potential for mixing enhancement associated with the use of axisymmetric ribs in annular flows has been analyzed. The enhancement relies on the use of streamwise vortices produced by the centrifugal instability. Conditions leading to the formation of such vortices have been established for a wide range of geometric parameters of interest using linear stability theory. It has been demonstrated that vortices can be formed only in the presence of ribs with O(1) wavelengths. Slopes of the bounding walls in the case of the long wavelength ribs are too small to create centrifugal forces sufficient for flow destabilization. In the case of short wavelength ribs, the slopes become excessively large, resulting in the stream moving away from the wall and becoming rectilinear and, thus, reducing the magnitude of the centrifugal force field. It has been shown that decreasing the annulus' radius reduces the critical Reynolds number when ribs are placed at the inner cylinder but increases when the ribs are placed at the outer cylinder. The onset of the shear-driven instability has been investigated as the resulting travelling waves may interfere with the formation of vortices. It has been shown that the axisymmetric waves play the critical role for annuli with large radii while the spiral waves play the critical role for annuli with small radii. The ribs always reduce the critical Reynolds number for the travelling waves when compared with the onset conditions for smooth annuli. The conduit geometries giving preference to the formation of vortices while avoiding creation of the travelling waves have been identified. It is demonstrated that predictions of flow characteristics determined through the analysis of sinusoidal ribs provide a good approximation of the flow response to ribs of arbitrary shape.

  7. Turbulence Measurements of Separate Flow Nozzles with Mixing Enhancement Features

    NASA Technical Reports Server (NTRS)

    Bridges, James; Wernet, Mark P.

    2002-01-01

    Comparison of turbulence data taken in three separate flow nozzles, two with mixing enhancement features on their core nozzle, shows how the mixing enhancement features modify turbulence to reduce jet noise. The three nozzles measured were the baseline axisymmetric nozzle 3BB, the alternating chevron nozzle, 3A12B, with 6-fold symmetry, and the flipper tab nozzle 3T24B also with 6-fold symmetry. The data presented show the differences in turbulence characteristics produced by the geometric differences in the nozzles, with emphasis on those characteristics of interest in jet noise. Among the significant findings: the enhanced mixing devices reduce turbulence in the jet mixing region while increasing it in the fan/core shear layer, the ratios of turbulence components are significantly altered by the mixing devices, and the integral lengthscales do not conform to any turbulence model yet proposed. These findings should provide guidance for modeling the statistical properties of turbulence to improve jet noise prediction.

  8. Magma mixing enhanced by bubble segregation

    NASA Astrophysics Data System (ADS)

    Wiesmaier, S.; Daniele, M.; Renggli, C.; Perugini, D.; De Campos, C.; Hess, K. U.; Ertel-Ingrisch, W.; Lavallée, Y.; Dingwell, D. B.

    2014-12-01

    Rising bubbles may significantly affect magma mixing paths as has been demonstrated by analogue experiments in the past. Here, bubble-advection experiments are performed for the first time employing natural materials at magmatic temperatures. Cylinders of basaltic glass were placed below cylinders of rhyolite glass. Upon melting, interstitial air formed bubbles that rose into the rhyolite melt, thereby entraining tails of basaltic liquid. The formation of plume-like filaments of advected basalt within the rhyolite was characterized by microCT and subsequent high-resolution EMP analyses. Melt entrainment by bubble ascent appears as efficient mechanism to mingle contrasting melt compositions. MicroCT imaging shows bubbles trailing each other and trails of multiple bubbles having converged. Rheological modelling of the filaments yields viscosities of up to 2 orders of magnitude lower than for the surrounding rhyolitic liquid. Such a viscosity contrast implies that subsequent bubbles rising are likely to follow the same pathways that previously ascending bubbles have generated. Filaments formed by multiple bubbles would thus experience episodic replenishment with mafic material. Fundamental implications for the concept of bubble advection in magma mixing are thus a) an acceleration of mixing because of decreased viscous resistance for bubbles inside filaments and b) non-conventional diffusion systematics because of intermittent supply of mafic material (instead of a single pulse) inside a filament. Inside these filaments, the mafic material was variably hybridised to andesitic through rhyolitic composition. Compositional profiles alone are ambiguous, however, to determine whether single or multiple bubbles were involved during formation of a filament. Statistical analysis, employing concentration variance as measure of homogenisation, demonstrates that also filaments appearing as single-bubble filaments are likely to have experienced multiple bubbles passing through

  9. Magma mixing enhanced by bubble segregation

    NASA Astrophysics Data System (ADS)

    Wiesmaier, S.; Morgavi, D.; Renggli, C.; Perugini, D.; De Campos, C. P.; Hess, K.-U.; Ertel-Ingrisch, W.; Lavallée, Y.; Dingwell, D. B.

    2015-04-01

    That rising bubbles may significantly affect magma mixing paths has already been demon strated by analogue experiments. Here, for the first time, bubble-advection experiments are performed employing volcanic melts at magmatic temperatures. Cylinders of basaltic glass were placed below cylinders of rhyolite glass. Upon melting, interstitial air formed bubbles that rose into the rhyolite melt, thereby entraining tails of basaltic liquid. The formation of plume-like filaments of advected basalt within the rhyolite was characterized by microCT and subsequent high-resolution EMP analyses. Melt entrainment by bubble ascent appears to be an efficient mechanism for mingling volcanic melts of highly contrasting compositions and properties. MicroCT imaging reveals bubbles trailing each other and multiple filaments coalescing into bigger ones. Rheological modelling of the filaments yields viscosities of up to 2 orders of magnitude lower than for the surrounding rhyolitic liquid. Such a viscosity contrast implies that bubbles rising successively are likely to follow this pathway of low resistance that previously ascending bubbles have generated. Filaments formed by multiple bubbles would thus experience episodic replenishment with mafic material. Inevitable implications for the concept of bubble advection in magma mixing include thereby both an acceleration of mixing because of decreased viscous resistance for bubbles inside filaments and non-conventional diffusion systematics because of intermittent supply of mafic material (instead of a single pulse) inside a material. Inside the filaments, the mafic material was variably hybridised to andesitic through rhyolitic composition. Compositional profiles alone are ambiguous, however, to determine whether single or multiple bubbles were involved during formation of a filament. Statistical analysis, employing concentration variance as measure of homogenisation, demonstrates that also filaments appearing as single-bubble filaments

  10. Supersonic jet mixing enhancement by vortex generators

    NASA Technical Reports Server (NTRS)

    Samimy, M.; Reeder, M. F.; Zaman, K. B. M. Q.

    1991-01-01

    Experiments were conducted to explore the effects of vortex generators, in the form of tabs projecting normally into the jet, on the mixing and the far-field noise characteristics of a jet. A converging-diverging nozzle with a design Mach number of 1.36 was used in the experiments. The flow regimes from subsonic to highly underexpanded supersonic conditions were studied. One, two, and four tabs were used and some of the findings of previous investigators were examined and confirmed. The tabs eliminated screech noise from moderately overexpanded cases to highly underexpanded cases. Detailed flow visualizations and measurements showed that two tabs bifurcated the jet at all Mach numbers. While the effect of two tabs was persistent and the jet remained bifurcated, the distortions produced by one and four tabs disappeared by a streamwise distance of approximately 16 jet diameters. Two and four tabs significantly increased the entrainment of ambient air into the jet.

  11. Supersonic mixing enhancement by vorticity for high-speed propulsion

    NASA Technical Reports Server (NTRS)

    Settles, Gary S.

    1991-01-01

    The results of a three year study on vortex enhancement of supersonic mixing are discussed. Recent interests in compressible mixing has spurred research in the field of high speed shear layers. It was established that shear layer growth diminishes with increasing convective Mach number; this Mach number is the relative Mach number of the large scale structures in the shear layer with respect to the Mach numbers on either side of the shear layer. The purpose was to evaluate the effect of swirl on compressible mixing rates. Previously analytical and experimental results seem to indicate that swirling flow may significantly modify the shear layer, in some cases resulting in enhanced mixing. Previous studies of the effect of swirl on compressible mixing were incomplete since the amount of swirl in the flowfield was not quantified. This study was undertaken to conclusively determine the effect of swirl on supersonic mixing, including the quantification of the swirl. Preliminary results indicate that the swirl modestly enhances the mixing rates.

  12. Numerical analysis of mixing enhancement for micro-electroosmotic flow

    NASA Astrophysics Data System (ADS)

    Tang, G. H.; He, Y. L.; Tao, W. Q.

    2010-05-01

    Micro-electroosmotic flow is usually slow with negligible inertial effects and diffusion-based mixing can be problematic. To gain an improved understanding of electroosmotic mixing in microchannels, a numerical study has been carried out for channels patterned with wall blocks, and channels patterned with heterogeneous surfaces. The lattice Boltzmann method has been employed to obtain the external electric field, electric potential distribution in the electrolyte, the flow field, and the species concentration distribution within the same framework. The simulation results show that wall blocks and heterogeneous surfaces can significantly disturb the streamlines by fluid folding and stretching leading to apparently substantial improvements in mixing. However, the results show that the introduction of such features can substantially reduce the mass flow rate and thus effectively prolongs the available mixing time when the flow passes through the channel. This is a non-negligible factor on the effectiveness of the observed improvements in mixing efficiency. Compared with the heterogeneous surface distribution, the wall block cases can achieve more effective enhancement in the same mixing time. In addition, the field synergy theory is extended to analyze the mixing enhancement in electroosmotic flow. The distribution of the local synergy angle in the channel aids to evaluate the effectiveness of enhancement method.

  13. Shock enhancement and control of hypersonic mixing and combustion

    NASA Technical Reports Server (NTRS)

    Marble, Frank E.; Zukoski, Edward E.; Jacobs, Jeffrey; Hendricks, Gavin; Waitz, Ian

    1990-01-01

    Experimental and computational analyses of the possibility that shock-enhanced mixing can substantially increase the rate of mixing between coflowing streams of hydrogen and air are discussed. Numerical computations indicate that the steady interaction between a weak shock in air with a coflowing hydrogen jet can be approximated by the two-dimensional time-dependent interaction between a weak shock and an initially circular region filled with hydrogen imbedded in air. Experimental results obtained in a shock tube and contoured wall injector are presented. It is shown that the shock impinging process causes the light gas cylinder to split into two parts; one of these mixes rapidly with air and the other forms a stably stratified vortex pair which mixes more slowly. The geometry of the flow field and the mixing process and scaling parameters are assessed.

  14. Enhanced solubilization of curcumin in mixed surfactant vesicles.

    PubMed

    Kumar, Arun; Kaur, Gurpreet; Kansal, S K; Chaudhary, Ganga Ram; Mehta, S K

    2016-05-15

    Self-assemblies of equimolar double and single chain mixed ionic surfactants, with increasing numbers of carbon atoms of double chain surfactant, were analyzed on the basis of fluorescence and conductivity results. Attempts were also made to enhance the solubilization of curcumin in aqueous equimolar mixed surfactant systems. Mixed surfactant assembly was successful in retarding the degradation of curcumin in alkaline media (only 25-28 40% degraded in 10h at pH 13). Fluorescence spectroscopy and fluorescence quenching methods were employed to predict the binding position and mechanism of curcumin with self-assemblies. Results indicate that the interactions take place according to both dynamic and static quenching mechanisms and curcumin was distributed in a palisade layer of mixed aggregates. Antioxidant activity (using DPPH radical) and biocompatibility (using calf-thymus DNA) of curcumin-loaded mixed surfactant formulations were also evaluated. The prepared systems improved the stability, solubility and antioxidant activity of curcumin and additionally are biocompatible.

  15. Comparative analysis of the use of various solid-state laser media for the self-starting of four-wave PCW generation in a loop laser resonator

    NASA Astrophysics Data System (ADS)

    Smetanin, Sergei N.

    2013-01-01

    A generalised theory has been used to carry out a comparative analysis of the use of various four-level and quasi-threelevel media for the self-starting of degenerate four-wave mixing PCW generation directly in a laser medium placed in a loop resonator. It has been shown that quasi-three-level media can compete with four-level media at long upper laser level lifetimes and increased pump intensities. The most attractive solid-state laser media for four-wave PCW generation have been identified that have the highest deposited energy at a given pump intensity. In addition to neodymium-doped crystals, which are already widely used for four-wave PCW generation, promising materials are fourlevel chromium-doped media, e.g. alexandrite and Cr : LiCAF, and quasi-three-level media with the longest upper laser level lifetime, such as Yb : YAG and Tm, Ho : YAG, at high pump intensities.

  16. Recent Enhancements to the National Transonic Facility (Mixed Mode Operations)

    NASA Technical Reports Server (NTRS)

    Kilgore, W. Allen; Chan, David; Balakrishna, S.; Wahls, Richard A.

    2006-01-01

    The U.S. National Transonic Facility continues to make enhancements to provide quality data in a safe, efficient and cost effective method for aerodynamic ground testing. Recent enhancements discussed in this paper include the development of a Mixed-mode of operations that combine Air-mode operations with Nitrogen-mode operations. This implementation and operational results of this new Mixed-mode expands the ambient temperature transonic region of testing beyond the Air-mode limitations at a significantly reduced cost over Nitrogen Mode operation.

  17. Mixing enhancement for high viscous fluids in a microfluidic chamber.

    PubMed

    Wang, Shasha; Huang, Xiaoyang; Yang, Chun

    2011-06-21

    Due to small channel dimensions and laminar flows, mixing in microfluidic systems is always a challenging task, especially for high viscous fluids. Here we report a method of enhancing microfluidic mixing for high viscous fluids using acoustically induced bubbles. The bubbles can be generated in an acoustically profiled microfluidic structure by using a piezoelectric disk activated at a working frequency range between 1.5 kHz and 2 kHz. The mixing enhancement is achieved through interactions between the oscillating bubbles and fluids. Both experimental studies and numerical simulations are conducted. In the experiments, DI water-glycerol mixture solutions with various viscosities were used. The results, based on the mixing efficiency calculated from experimentally acquired fluorescent images, showed that good mixing can occur in the DI water-glycerol solutions with their maximum viscosity up to 44.75 mPa s, which to our best knowledge is the highest viscosity of fluids in microfluidic mixing experiments. To explain the mechanisms of bubble generation, the numerical simulation results show that, corresponding to the actuations at the working frequency range used in the experiment, there exists a low pressure region where the pressure is lower than the water vapor pressure in the DI water-glycerol solutions, resulting in the generation of bubbles.

  18. Enhanced disinfection efficiency of mechanically mixed oxidants with free chlorine.

    PubMed

    Son, Hyunju; Cho, Min; Kim, Jaeeun; Oh, Byungtaek; Chung, Hyenmi; Yoon, Jeyong

    2005-02-01

    To the best of our knowledge, this study is the first investigation to be performed into the potential benefits of mechanically mixed disinfectants in controlling bacterial inactivation. The purpose of this study was to evaluate the disinfection efficiency of mechanically mixed oxidants with identical oxidant concentrations, which were made by adding small amounts of subsidiary oxidants, namely ozone (O3), chlorine dioxide (ClO2), hydrogen peroxide (H2O2) and chlorite (ClO2(-)), to free available chlorine (Cl2), using Bacillus subtilis spores as the indicator microorganisms. The mechanically mixed oxidants containing Cl2/O3, Cl2/ClO2 and Cl2/ClO2(-) showed enhanced efficiencies (of up to 52%) in comparison with Cl2 alone, whereas no significant difference was observed between the mixed oxidant, Cl2/H2O2, and Cl2 alone. This enhanced disinfection efficiency can be explained by the synergistic effect of the mixed oxidant itself and the effect of intermediates such as ClO2(-)/ClO2, which are generated from the reaction between an excess of Cl2 and a small amount of O3/ClO2(-). Overall, this study suggests that mechanically mixed oxidants incorporating excess chlorine can constitute a new and moderately efficient method of disinfection.

  19. Jet Nozzle Having Centerbody for Enhanced Exit Area Mixing

    NASA Technical Reports Server (NTRS)

    Seiner, John M. (Inventor); Gilinsky, Mikhail M. (Inventor)

    1999-01-01

    A nozzle arrangement includes a nozzle and a centerbody. The longitudinal axis of the centerbody is coaxially aligned with the nozzle. The centerbody has a free end portion shaped to create vortices in exhaust exiting the exit area. The vortices enhance mixing action in the exhaust and reduce exhaust noise while augmenting thrust.

  20. Mixing in wicking structures and the use of enhanced mixing within wicks in microchannel devices

    DOEpatents

    Stenkamp, Victoria S.; TeGrotenhuis, Ward E.; Wegeng, Robert S.

    2009-06-02

    Advanced wicking structures and methods utilizing these structures are described. The use of advanced wicking structures can promote rapid mass transfer while maintaining high capillary pressure through the use of small pores. Particularly improved results in fluid contacting processes can be achieved by enhanced mixing within a wicking layer within a microchannel.

  1. Mixing in wicking structures and the use of enhanced mixing within wicks in microchannel devices

    DOEpatents

    Stenkamp, Victoria S [Richland, WA; TeGrotenhuis, Ward E [Kennewick, WA; Wegeng, Robert S [Richland, WA

    2011-04-19

    Advanced wicking structures and methods utilizing these structures are described. The use of advanced wicking structures can promote rapid mass transfer while maintaining high capillary pressure through the use of small pores. Particularly improved results in fluid contacting processes can be achieved by enhanced mixing within a wicking layer within a microchannel.

  2. Topographic enhancement of vertical turbulent mixing in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Mashayek, A.; Ferrari, R.; Merrifield, S.; Ledwell, J. R.; St Laurent, L.; Garabato, A. Naveira

    2017-03-01

    It is an open question whether turbulent mixing across density surfaces is sufficiently large to play a dominant role in closing the deep branch of the ocean meridional overturning circulation. The diapycnal and isopycnal mixing experiment in the Southern Ocean found the turbulent diffusivity inferred from the vertical spreading of a tracer to be an order of magnitude larger than that inferred from the microstructure profiles at the mean tracer depth of 1,500 m in the Drake Passage. Using a high-resolution ocean model, it is shown that the fast vertical spreading of tracer occurs when it comes in contact with mixing hotspots over rough topography. The sparsity of such hotspots is made up for by enhanced tracer residence time in their vicinity due to diffusion toward weak bottom flows. The increased tracer residence time may explain the large vertical fluxes of heat and salt required to close the abyssal circulation.

  3. Topographic enhancement of vertical turbulent mixing in the Southern Ocean

    PubMed Central

    Mashayek, A.; Ferrari, R.; Merrifield, S.; Ledwell, J. R.; St Laurent, L.; Garabato, A. Naveira

    2017-01-01

    It is an open question whether turbulent mixing across density surfaces is sufficiently large to play a dominant role in closing the deep branch of the ocean meridional overturning circulation. The diapycnal and isopycnal mixing experiment in the Southern Ocean found the turbulent diffusivity inferred from the vertical spreading of a tracer to be an order of magnitude larger than that inferred from the microstructure profiles at the mean tracer depth of 1,500 m in the Drake Passage. Using a high-resolution ocean model, it is shown that the fast vertical spreading of tracer occurs when it comes in contact with mixing hotspots over rough topography. The sparsity of such hotspots is made up for by enhanced tracer residence time in their vicinity due to diffusion toward weak bottom flows. The increased tracer residence time may explain the large vertical fluxes of heat and salt required to close the abyssal circulation. PMID:28262808

  4. MIX and match: mobile T6SS MIX-effectors enhance bacterial fitness.

    PubMed

    Salomon, Dor

    2016-01-01

    Protein secretion systems that mediate interbacterial competition secret a wide repertoire of antibacterial toxins. A major player in these competitions is the newly discovered bacterial type VI secretion system (T6SS). We recently found that a subset of polymorphic MIX-effectors, which are a widespread class of effectors secreted by T6SSs, are horizontally shared between marine bacteria and are used to diversify their T6SS effector repertoires, thus enhancing their environmental fitness. In this commentary, I expand on the ideas that were introduced in the previous report, and further speculate on the possible mobility of other MIX-effectors. In addition, I discuss the possible role of horizontal gene transfer in the dissemination of MIX-effectors through bacterial genomes, as well as its possible role in diversifying the T6SS effector repertoire.

  5. Evidence for enhanced boundary mixing in the Santa Monica Basin

    NASA Astrophysics Data System (ADS)

    Ledwell, James R.; Hickey, Barbara M.

    1995-10-01

    Transients in the heat content in Santa Monica and San Pedro Basins imply a basin-wide diapycnal eddy diffusivity greater than 1 cm2/s. This is significantly larger than the value for SF6 of 0.25±0.08 cm2/s determined for the interior of Santa Monica Basin for September 1985 to February 1986 by Ledwell and Watson (1991). However, the exodus of SF6 from Santa Monica Basin after February 1986, by which time the tracer had mixed to the boundaries of the basin, was fast enough to be consistent with a greatly enhanced vertical flux. Since the kinetic energy in the basin had not changed significantly, it is unlikely that a temporal increase in forcing resulted in enhanced fluxes in the interior of the basin. The most likely interpretation is that diapycnal fluxes in the basin are dominated by processes in the boundary regions. Temperature and SF6 profiles from near the edges of the basin do not give conclusive evidence either for or against such enhanced mixing.

  6. Solubility enhancement studies on lurasidone hydrochloride using mixed hydrotropy

    PubMed Central

    Madan, Jyotsana R.; Pawar, Kiran T.; Dua, Kamal

    2015-01-01

    Low aqueous solubility is a major problem faced during formulation development of new drug molecules. Lurasidone HCl (LRD) is an antipsychotic agent specially used in the treatments of schizophrenia and is a good example of the problems associated with low aqueous solubility. Lurasidone is practically insoluble in water, has poor bioavailability and slow onset of action and therefore cannot be given in emergency clinical situations like schizophrenia. Hence, purpose of this research was to provide a fast dissolving oral dosage form of Lurasidone. This dosage form can provide quick onset of action by using the concept of mixed hydrotropy. Initially, solubility of LRD was determined individually in nicotinamide, sodium citrate, urea and sodium benzoate at concentration of 10, 20, 30 and 40% w/v solutions using purified water as a solvent. Highest solubility was obtained in 40% sodium benzoate solution. In order to decrease the individual hydrotrope concentration mixed hydrotropic agents were used. Highest solubility was obtained in 15:20:5 ratio of Nicotinamide + sodium benzoate + sodium citrate. This optimized combination was utilized in the preparation of solid dispersions by using distilled water as a solvent. Solid dispersions were evaluated for X-ray diffraction, differential scanning calorimetry and Fourier-transform infrared to show no drug-hydrotropes interaction has occurred. This solid dispersion was compressed to form fast dissolving tablets. Dissolution studies of prepared tablets were done using USP Type II apparatus. The batch L3 tablets show 88% cumulative drug release within 14 min and in vitro dispersion time was 32 min. It was concluded that the concept of mixed hydrotropic solid dispersion is novel, safe and cost-effective technique for enhancing the bioavailability of poorly water-soluble drugs. The miraculous enhancement in solubility and bioavailability of Lurasidone is clear indication of the potential of mixed hydrotropy to be used in future

  7. Four-Wave Mixing And Scanning Tunneling Microscopy Of Semiconductor Clusters

    NASA Astrophysics Data System (ADS)

    Sarid, Dror; McGinnis, B. P.; Henson, Tammy D.

    1988-05-01

    Semiconductor structures in lower dimensions, dubbed quantum dots, exhibit novel properties which result from size quantization of their charge carriers, as well as from their large surface-to-volume ratio. Optical measurements, combined with scanning tunneling microscopy, can provide the detailed information required to model the nonlinear optical response of these clusters.

  8. Probe gain via four-wave mixing based on spontaneously generated coherence

    NASA Astrophysics Data System (ADS)

    Yang, Hong; Zhang, Ting-gui; Zhang, Yan

    2017-02-01

    Not Available Project supported by the Natural Science Foundation of Hainan Province, China (Grant Nos. 20151005, 20151015, and 20161006), the National Natural Science Foundation of China (Grant Nos. 11247005, 51262007, 11501153, and 41564006), the Postdoctoral Scientific Research Program of Jilin Province, China (Grant No. RB201330), the Project Sponsored by Science Research Foundation for Returned Overseas Chinese Scholars, and the Fundamental Research Funds for the Central Universities, China (Grant No. 12QNJJ006).

  9. Geometries for the coherent control of four-wave mixing in graphene multilayers

    PubMed Central

    Rao, Shraddha M.; Lyons, Ashley; Roger, Thomas; Clerici, Matteo; Zheludev, Nikolay I.; Faccio, Daniele

    2015-01-01

    Deeply sub-wavelength two-dimensional films may exhibit extraordinarily strong nonlinear effects. Here we show that 2D films exhibit the remarkable property of a phase-controllable nonlinearity, i.e., the amplitude of the nonlinear polarisation wave in the medium can be controlled via the pump beam phase and determines whether a probe beam will “feel” or not the nonlinearity. This is in stark contrast to bulk nonlinearities where propagation in the medium averages out any such phase dependence. We perform a series of experiments in multilayer graphene that highlight some of the consequences of the optical nonlinearity phase-dependence, such as the coherent control of nonlinearly diffracted beams, single-pump-beam induced phase-conjugation and the demonstration of a nonlinear mirror characterised by negative reflection. The observed phase sensitivity is not specific to graphene but rather is solely a result of the dimensionality and is therefore expected in all 2D materials. PMID:26486075

  10. Degenerate four-wave mixing in a mercury-argon discharge

    NASA Technical Reports Server (NTRS)

    Richardson, W.; Maleki, L.; Garmire, E.

    1986-01-01

    Phase conjugation has been obtained with pump powers as low as 0.5 mW on the 546.1-nm line of atomic mercury. Collisional processes that oppose the effects of optical pumping sustain the signal. Line splittings observed in the Doppler regime are compared with theory. Reflectivities agree with those obtained from a model that includes pump absorption.

  11. Effect of Mixing Enhancement Devices on Turbulence in Separate Flow Nozzles

    NASA Technical Reports Server (NTRS)

    Bridges, James

    2001-01-01

    This paper presents the effects of several mixing enhancement devices on turbulence in jet nozzles. The topics include: 1) The Advanced Subsonic Technology (AST) Program; 2) Test Programs SFNT97 and SFNT2K; 3) Facility; 4) Mixing Enhancement Nozzles; 5) IR reductions; 6) Schlieren of Chevrons; and 7) Aeroacoustics of Enhanced Mixing-Paradigm. This paper is presented in viewgraph form.

  12. Investigation of ramp injectors for supersonic mixing enhancement

    NASA Technical Reports Server (NTRS)

    Haimovitch, Y.; Gartenberg, E.; Roberts, A. S., Jr.

    1994-01-01

    A comparative study of wall mounted swept ramp injectors fitted with injector nozzles of different shape has been conducted in a constant area duct to explore mixing enhancement techniques for scramjet combustors. Six different injector nozzle inserts, all having equal exit and throat areas, were tested to explore the interaction between the preconditioned fuel jet and the vortical flowfield produced by the ramp: circular nozzle (baseline), nozzle with three downstream facing steps, nozzle with four vortex generators, elliptical nozzle, tapered-slot nozzle, and trapezoidal nozzle. The main flow was air at Mach 2, and the fuel was simulated by air injected at Mach 1.63 or by helium injected at Mach 1.7. Pressure and temperature surveys, combined with Mie and Rayleigh scattering visualization, were used to investigate the flow field. The experiments were compared with three dimensional Navier-Stokes computations. The results indicate that the mixing process is dominated by the streamwise vorticity generated by the ramp, the injectors' inner geometry having a minor effect. It was also found that the injectant/air mixing in the far-field is nearly independent of the injector geometry, molecular weight of the injectant, and the initial convective Mach number.

  13. Application of DPIV to Enhanced Mixing Heated Nozzle Flows

    NASA Technical Reports Server (NTRS)

    Wernet, Mark P.; Bridges, James

    2002-01-01

    Digital Particle Imaging Velocimetry (DPIV) is a planar velocity measurement technique that continues to be applied to new and challenging engineering research facilities while significantly reducing facility test time. DPIV was used in the GRC Nozzle Acoustic Test Rig (NATR) to characterize the high temperature (560 C), high speed (is greater than 500 m/s) flow field properties of mixing enhanced jet engine nozzles. The instantaneous velocity maps obtained using DPIV were used to determine mean velocity, rms velocity and two-point correlation statistics to verify the true turbulence characteristics of the flow. These measurements will ultimately be used to properly validate aeroacoustic model predictions by verifying CFD input to these models. These turbulence measurements have previously not been possible in hot supersonic jets. Mapping the nozzle velocity field using point based techniques requires over 60 hours of test time, compared to less than 45 minutes using DPIV, yielding a significant reduction in testing time. A dual camera DPIV configuration was used to maximize the field of view and further minimize the testing time required to map the nozzle flow. The DPIV system field of view covered 127 by 267 mm. Data were acquired at 19 axial stations providing coverage of the flow from the nozzle exit to 2.37 in downstream. At each measurement station, 400 image frame pairs were acquired from each camera. The DPIV measurements of the mixing enhanced nozzle designs illustrate the changes in the flow field resulting in the reduced noise signature.

  14. Phase Coupling in Langmuir Wave Packets: Evidence for Four Wave Interactions in Solar Type III Radio Bursts

    NASA Technical Reports Server (NTRS)

    Thejappa, G.; MacDowall, R. J.; Bergamo, M.

    2012-01-01

    The four wave interaction process, known as the oscillating two stream instability (OTSI) is considered as one of the mechanisms responsible for stabilizing the electron beams associated with solar type III radio bursts. It has been reported that (1) an intense localized Langmuir wave packet associated with a type III burst contains the spectral characteristics of the OTSI: (a) a resonant peak at the local electron plasma frequency, f(sub pe), (b) a Stokes peak at a frequency slightly lower than f(sub pe), (c) anti-Stokes peak at a frequency slightly higher than f(sub pe), and (d) a low frequency enhancement below a few hundred Hz, (2) the frequencies and wave numbers of these spectral components satisfy the resonance conditions of the OTSI, and (3) the peak intensity of the wave packet is well above the thresholds for the OTSI as well as spatial collapse of envelope solitons. Here, for the first time, applying the trispectral analysis on this wave packet, we show that the tricoherence, which measures the degree of coherent four-wave coupling amongst the observed spectral components exhibits a peak. This provides an additional evidence for the OTSI and related spatial collapse of Langmuir envelope solitons in type III burst sources.

  15. Mixing Enhancement by Tabs in Round Supersonic Jets

    NASA Technical Reports Server (NTRS)

    Seiner, John M.; Grosch, C. E.

    1998-01-01

    The objective of this study was to analyze jet plume mass flow entrainment rates associated with the introduction of counter-rotating streamwise vorticity by prism shaped devices (tabs) located at the lip of the nozzle. We have examined the resulting mixing process through coordinated experimental tests and numerical simulations of the supersonic flow from a model axisymmetric nozzle. In the numerical simulations, the total induced vorticity was held constant while varying the distribution of counter-rotating vorticity around the nozzle lip training edge. In the experiment, the number of tabs applied was varied while holding the total projected area constant. Evaluations were also conducted on initial vortex strength. The results of this work show that the initial growth rate of the jet shear layer is increasingly enhanced as more tabs are added, but that the lowest tab count results in the largest entrained mass flow. The numerical simulations confirm these results.

  16. Comparative analysis of the use of various solid-state laser media for the self-starting of four-wave PCW generation in a loop laser resonator

    SciTech Connect

    Smetanin, Sergei N

    2013-01-31

    A generalised theory has been used to carry out a comparative analysis of the use of various four-level and quasi-threelevel media for the self-starting of degenerate four-wave mixing PCW generation directly in a laser medium placed in a loop resonator. It has been shown that quasi-three-level media can compete with four-level media at long upper laser level lifetimes and increased pump intensities. The most attractive solid-state laser media for four-wave PCW generation have been identified that have the highest deposited energy at a given pump intensity. In addition to neodymium-doped crystals, which are already widely used for four-wave PCW generation, promising materials are fourlevel chromium-doped media, e.g. alexandrite and Cr : LiCAF, and quasi-three-level media with the longest upper laser level lifetime, such as Yb : YAG and Tm, Ho : YAG, at high pump intensities. (nonlinear optical phenomena)

  17. Enhanced Mixed Electronic-Ionic Conductors through Cation Ordering

    SciTech Connect

    Jacobson, Allan J.; Morgan, Dane; Grey, Clare

    2014-08-31

    The performance of many energy conversion and storage devices depend on the properties of mixed ionic-electronic conducting (miec) materials. Mixed or ambipolar conductors simultaneously transport ions and electrons and provide the critical interface between chemical and electrical energy in devices such as fuel cells, ion transport membranes, and batteries. Enhancements in storage capacity, reversibility, power density and device lifetime all require new materials and a better understanding of the fundamentals of ambipolar conductivity and surface reactivity.The high temperature properties of the ordered perovksites AA’B2O5+x, where A = rare earth ion, Y and B = Ba, Sr were studied. The work was motivated by the high oxygen transport and surface exchange rates observed for members of this class of mixed ionic and electronic conductors. A combined experimental and computational approach, including structural, electrochemical, and transport characterization and modeling was used. The approach attacks the problem simultaneously at global (e.g., neutron diffraction and impedance spectroscopy), local (e.g., pair distribution function, nuclear magnetic resonance) and molecular (ab initio thermokinetic modeling) length scales. The objectives of the work were to understand how the cation and associated anion order lead to exceptional ionic and electronic transport properties and surface reactivity in AA’B2O5+x perovskites. A variety of compounds were studied by X-ray and neutron diffraction, measurements of thermodynamics and transport and theoretically. These included PrBaCo2O5+x and NdBaCo2O5+x, PrBaCo2-xFexO6- δ (x = 0, 0.5, 1.0, 1.5 and 2) and LnBaCoFeO6- δ (Ln = La, Pr, Nd, Sm, Eu and Gd), Sr3YCo4O10.5, YBaMn2O5+x. A0.5A’0.5BO3 (where A=Y, Sc, La, Ce, Pr, Nd, Pm, Sm; A’= Sr

  18. Heat transfer enhancement with mixing vane spacers using the field synergy principle

    NASA Astrophysics Data System (ADS)

    Yang, Lixin; Zhou, Mengjun; Tian, Zihao

    2017-01-01

    The single-phase heat transfer characteristics in a PWR fuel assembly are important. Many investigations attempt to obtain the heat transfer characteristics by studying the flow features in a 5 × 5 rod bundle with a spacer grid. The field synergy principle is used to discuss the mechanism of heat transfer enhancement using mixing vanes according to computational fluid dynamics results, including a spacer grid without mixing vanes, one with a split mixing vane, and one with a separate mixing vane. The results show that the field synergy principle is feasible to explain the mechanism of heat transfer enhancement in a fuel assembly. The enhancement in subchannels is more effective than on the rod's surface. If the pressure loss is ignored, the performance of the split mixing vane is superior to the separate mixing vane based on the enhanced heat transfer. Increasing the blending angle of the split mixing vane improves heat transfer enhancement, the maximum of which is 7.1%. Increasing the blending angle of the separate mixing vane did not significantly enhance heat transfer in the rod bundle, and even prevented heat transfer at a blending angle of 50°. This finding testifies to the feasibility of predicting heat transfer in a rod bundle with a spacer grid by field synergy, and upon comparison with analyzed flow features only, the field synergy method may provide more accurate guidance for optimizing the use of mixing vanes.

  19. Supersonic Jet Mixing Enhancement due to Natural and Induced Screech

    NASA Technical Reports Server (NTRS)

    Rice, E. J.; Raman, G.

    1999-01-01

    Outline of presentation are: (1) Review of experimental apparatus. (2) Effect of natural screech of jet mixing; converging nozzle, underexpanded jet and converging-diverging nozzle, design pressure.(3) Effect of induced screech on jet mixing: produced by paddles in shear layers, similar to edge tones, and converging-diverging nozzle, design pressure. (4) Effect of paddles on near-field jet noise. and (5) Concluding remarks.

  20. A Generalized Multiple Discrete Interaction Approximation for resonant four-wave interactions in wind wave models

    NASA Astrophysics Data System (ADS)

    Tolman, Hendrik L.

    2013-10-01

    For several decades, the Discrete Interaction Approximation (DIA) for nonlinear resonant four-wave interactions has been the engine of third-generation wind-wave models. The present study presents a Generalized Multiple DIA (GMD) which expands upon the DIA by (i) expanding the definition of the representative quadruplet, (ii) formulating the DIA for arbitrary water depths, (iii) providing complimentary deep and shallow water scaling terms and (iv) allowing for multiple representative quadruplets. The GMD is rigorously derived to be an extension of the DIA, and is backward compatible with it. The free parameters of the GMD are optimized holistically, by optimizing full model behavior in the WAVEWATCH III® wave model as reported in a companion paper. Here, a cascade of GMD configurations with increasing complexity, accuracy and cost is presented. First, the performance of these configurations is discussed using idealized test cases used to optimize the GMD. It is shown that in deep water, GMD configurations can be found which remove most of the errors of the DIA. The GMD is also capable of representing four-wave interactions in extremely shallow water, although some remaining spurious behavior makes applications of this part of the GMD less suitable for operational wave models. Finally, several GMD configurations are applied to an idealized hurricane case, showing that results from idealized test cases indeed are representative for real-world applications, and confirming that such GMD configurations are economically feasible in operational wind wave models. Finally, the DIA results in surprisingly large model errors in hurricane conditions.

  1. Enhancing Health-Care Services with Mixed Reality Systems

    NASA Astrophysics Data System (ADS)

    Stantchev, Vladimir

    This work presents a development approach for mixed reality systems in health care. Although health-care service costs account for 5-15% of GDP in developed countries the sector has been remarkably resistant to the introduction of technology-supported optimizations. Digitalization of data storing and processing in the form of electronic patient records (EPR) and hospital information systems (HIS) is a first necessary step. Contrary to typical business functions (e.g., accounting or CRM) a health-care service is characterized by a knowledge intensive decision process and usage of specialized devices ranging from stethoscopes to complex surgical systems. Mixed reality systems can help fill the gap between highly patient-specific health-care services that need a variety of technical resources on the one side and the streamlined process flow that typical process supporting information systems expect on the other side. To achieve this task, we present a development approach that includes an evaluation of existing tasks and processes within the health-care service and the information systems that currently support the service, as well as identification of decision paths and actions that can benefit from mixed reality systems. The result is a mixed reality system that allows a clinician to monitor the elements of the physical world and to blend them with virtual information provided by the systems. He or she can also plan and schedule treatments and operations in the digital world depending on status information from this mixed reality.

  2. Experimental study of mixing enhancement using pylon in supersonic flow

    NASA Astrophysics Data System (ADS)

    Vishwakarma, Manmohan; Vaidyanathan, Aravind

    2016-01-01

    The Supersonic Combustion Ramjet (SCRAMJET) engine has been recognized as one of the most promising air breathing propulsion system for the supersonic/hypersonic flight mission requirements. Mixing and combustion of fuel inside scramjet engine is one of the major challenging tasks. In the current study the main focus has been to increase the penetration and mixing of the secondary jet inside the test chamber at supersonic speeds. In view of this, experiments are conducted to evaluate the effect of pylon on the mixing of secondary jet injection into supersonic mainstream flow at Mach 1.65. Two different pylons are investigated and the results are compared with those obtained by normal injection from a flat plate. The mixing studies are performed by varying the height of the pylon while keeping all other parameters the same. The study mainly focused on analyzing the area of spread and penetration depth achieved by different injection schemes based on the respective parameters. The measurements involved Mie scattering visualization and the flow features are analyzed using Schlieren images. The penetration height and spread area are the two parameters that are used for analyzing and comparing the performance of the pylons. It is observed that the secondary jet injection carried out from behind the big pylon resulted in maximum penetration and spread area of the jet as compared to the small pylon geometry. Moreover it is also evident that for obtaining maximum spreading and penetration of the jet, the same needs to be achieved at the injection location.

  3. Plasma-enhanced mixing and flameholding in supersonic flow

    PubMed Central

    Firsov, Alexander; Savelkin, Konstantin V.; Yarantsev, Dmitry A.; Leonov, Sergey B.

    2015-01-01

    The results of experimental study of plasma-based mixing, ignition and flameholding in a supersonic model combustor are presented in the paper. The model combustor has a length of 600 mm and cross section of 72 mm width and 60 mm height. The fuel is directly injected into supersonic airflow (Mach number M=2, static pressure Pst=160–250 Torr) through wall orifices. Two series of tests are focused on flameholding and mixing correspondingly. In the first series, the near-surface quasi-DC electrical discharge is generated by flush-mounted electrodes at electrical power deposition of Wpl=3–24 kW. The scope includes parametric study of ignition and flame front dynamics, and comparison of three schemes of plasma generation: the first and the second layouts examine the location of plasma generators upstream and downstream from the fuel injectors. The third pattern follows a novel approach of combined mixing/ignition technique, where the electrical discharge distributes along the fuel jet. The last pattern demonstrates a significant advantage in terms of flameholding limit. In the second series of tests, a long discharge of submicrosecond duration is generated across the flow and along the fuel jet. A gasdynamic instability of thermal cavity developed after a deposition of high-power density in a thin plasma filament promotes the air–fuel mixing. The technique studied in this work has weighty potential for high-speed combustion applications, including cold start/restart of scramjet engines and support of transition regime in dual-mode scramjet and at off-design operation. PMID:26170434

  4. Plasma-enhanced mixing and flameholding in supersonic flow.

    PubMed

    Firsov, Alexander; Savelkin, Konstantin V; Yarantsev, Dmitry A; Leonov, Sergey B

    2015-08-13

    The results of experimental study of plasma-based mixing, ignition and flameholding in a supersonic model combustor are presented in the paper. The model combustor has a length of 600 mm and cross section of 72 mm width and 60 mm height. The fuel is directly injected into supersonic airflow (Mach number M=2, static pressure P(st)=160-250 Torr) through wall orifices. Two series of tests are focused on flameholding and mixing correspondingly. In the first series, the near-surface quasi-DC electrical discharge is generated by flush-mounted electrodes at electrical power deposition of W(pl)=3-24 kW. The scope includes parametric study of ignition and flame front dynamics, and comparison of three schemes of plasma generation: the first and the second layouts examine the location of plasma generators upstream and downstream from the fuel injectors. The third pattern follows a novel approach of combined mixing/ignition technique, where the electrical discharge distributes along the fuel jet. The last pattern demonstrates a significant advantage in terms of flameholding limit. In the second series of tests, a long discharge of submicrosecond duration is generated across the flow and along the fuel jet. A gasdynamic instability of thermal cavity developed after a deposition of high-power density in a thin plasma filament promotes the air-fuel mixing. The technique studied in this work has weighty potential for high-speed combustion applications, including cold start/restart of scramjet engines and support of transition regime in dual-mode scramjet and at off-design operation.

  5. Ocean science. Enhanced: internal tides and ocean mixing.

    PubMed

    Garrett, Chris

    2003-09-26

    Recent satellite and in situ observations have shown that at ocean ridges and other seafloor topographic features, a substantial amount of energy is transferred from the main ocean tides into "internal tides." In his Perspective, Garrett explains how these internal waves with tidal periods propagate through the density-stratified deep ocean and eventually break down into turbulence. The resulting mixing affects ocean stratification and ocean circulation. It thus influences climate as well as biological production. The energy for the internal tides is derived from the rotational energy of the Earth-Moon system changes of the length of the day and the distance to the Moon.

  6. Surfactant mixing rules applied to surfactant enhanced alkaline flooding

    SciTech Connect

    Taylor, K.C. )

    1992-01-01

    This paper discusses surfactant mixing rules which have been used to describe crude oil/alkali/surfactant phase behavior, using David Lloydminster crude oil and the surfactant Neodol 25-3S. It was found that at a fixed salinity and alkali concentration, a specific mole fraction of synthetic surfactant to petroleum soap was required to produce optimal phase behavior as the water-to-oil ratio varied. This methodology is useful in understanding the relationship between the variables of water-to-oil ratio and synthetic surfactant concentration in phase behavior systems that produce a petroleum soap.

  7. Numerical Simulations of Jet Mixing Enhancement in a Round Jet Exhaust Using SJA

    NASA Astrophysics Data System (ADS)

    Hong, Liang; Zhang, Rubing; Liu, Zheng

    2017-03-01

    Symmetric synthetic jet is used to stimulate a Mach number 0.9 and high temperature jet for the mixing enhancement. The movement of the piston-type synthetic jet is simulated by dynamic mesh based on URANS numerical methods. Jet flapping, streamwise vortex and geometric axis transformation are the jet mixing mechanism. However, the jet mixing enhancement effect depends on penetration area, which consists of penetration depth and spanwise. And the penetration area is determined by actuator nozzle diameter and blowing jet momentum. In addition, a 54% reduction in potential core length and maximum 45.8K decrease in potential temperature are achieved.

  8. Efficiency enhancement of blue phosphorescent organic light-emitting diodes using mixed electron transport layer

    NASA Astrophysics Data System (ADS)

    Yoo, Seung Il; Yoon, Ju-An; Kim, Nam Ho; Kim, Jin Wook; Lee, Ho Won; Kim, Young Kwan; He, Gufeng; Kim, Woo Young

    2015-01-01

    Blue phosphorescent organic light-emitting diodes (OLED) using mixed electron transport layer (ETL) were fabricated with the device structure of ITO/NPB/mCP:Firpic-8%/TPBi:BCP or TPBi:3TPYMB/Liq/Al to observe mixed ETL's influence on their electrical and optical characteristics. OLED device with mixed ETL of TPBi with BCP or 3TPYMB significantly improved its current efficiency to 30.4 and 34.2 cd/A comparing to 19.8 cd/A of single ETL with BCP only. We examined mixed ETL's capability of electron transport and triplet exciton confinement enhancing phosphorescent OLED's luminance and luminous efficiency.

  9. Supersonic jet mixing enhancement by delta-tabs

    NASA Technical Reports Server (NTRS)

    Zaman, K. B. M. Q.; Reeder, M. F.; Samimy, M.

    1992-01-01

    The results of a continuing investigation of the effect of vortex generators, in the form of small tabs at the nozzle exit, on the evolution of a jet are reported. Primarily, tabs of triangular shape are considered, and the effect is studied up to an equivalent jet Mach number of 1.8. By changing the orientation of the tab with respect to the nozzle exit plane, streamwise vortex pairs of opposite sign were generated. This resulted in either an outward election of jet core fluid into the ambient or an inward indentation of the mixing layer into the core of the jet. A triangular shaped tab with its apex leaning downstream, referred to as a delta tab, was found to be the most effective in influencing the jet evolution. Two delta tabs, spaced 180 degrees apart, completely bifurcated the jet. Four delta tabs increased jet mixing substantially, more than by various other methods tried previously; the mass flux at fourteen jet diameters downstream from the nozzle increased by about 50 percent over that for the no tab case. The tabs were found to be effective in jets with laminar or turbulent boundary layers as well as in jets with low or high core turbulence intensities.

  10. Aquifer/aquitard interfaces: mixing zones that enhance biogeochemical reactions

    NASA Astrophysics Data System (ADS)

    McMahon, P. B.

    2001-01-01

    Several important biogeochemical reactions are known to occur near the interface between aquifer and aquitard sediments. These reactions include O2 reduction; denitrification; and Fe3+, SO42-, and CO2 (methanogenesis) reduction. In some settings, these reactions occur on the aquitard side of the interface as electron acceptors move from the aquifer into the electron-donor-enriched aquitard. In other settings, these reactions occur on the aquifer side of the interface as electron donors move from the aquitard into the electron-acceptor-enriched, or microorganism-enriched, aquifer. Thus, the aquifer/aquitard interface represents a mixing zone capable of supporting greater microbial activity than either hydrogeologic unit alone. The extent to which biogeochemical reactions proceed in the mixing zone and the width of the mixing zone depend on several factors, including the abundance and solubility of electron acceptors and donors on either side of the interface and the rate at which electron acceptors and donors react and move across the interface. Biogeochemical reactions near the aquifer/aquitard interface can have a substantial influence on the chemistry of water in aquifers and on the chemistry of sediments near the interface. Résumé. Il se produit au voisinage de l'interface entre les aquifères et les imperméables plusieurs réactions biogéochimiques importantes. Il s'agit des réactions de réduction de l'oxygène, de la dénitrification et de la réduction de Fe3+, SO42- et CO2 (méthanogenèse). Dans certaines situations, ces réactions se produisent du côté imperméable de l'interface, avec des accepteurs d'électrons qui vont de l'aquifère vers l'imperméable riche en donneurs d'électrons. Dans d'autres situations, ces réactions se produisent du côté aquifère de l'interface, avec des donneurs d'électrons qui se déplacent de l'imperméable vers l'aquifère riche en accepteurs d'électrons ou en microorganismes. Ainsi, l'interface aquif

  11. Enhanced pinning in mixed rare earth-123 films

    DOEpatents

    Driscoll, Judith L.; Foltyn, Stephen R.

    2009-06-16

    An superconductive article and method of forming such an article is disclosed, the article including a substrate and a layer of a rare earth barium cuprate film upon the substrate, the rare earth barium cuprate film including two or more rare earth metals capable of yielding a superconductive composition where ion size variance between the two or more rare earth metals is characterized as greater than zero and less than about 10.times.10.sup.-4, and the rare earth barium cuprate film including two or more rare earth metals is further characterized as having an enhanced critical current density in comparison to a standard YBa.sub.2Cu.sub.3O.sub.y composition under identical testing conditions.

  12. Enhanced mixing and spatial instability in concentrated bacterial suspensions.

    SciTech Connect

    Sokolov, A.; Goldstein, R. E.; Feldchtein, F. I.; Aranson, I. S.; Materials Science Division; Illinois Inst. of Tech.; Univ. of Cambridge; Imalux Corp.

    2009-09-01

    High-resolution optical coherence tomography is used to study the onset of a large-scale convective motion in free-standing thin films of adjustable thickness containing suspensions of swimming aerobic bacteria. Clear evidence is found that beyond a threshold film thickness there exists a transition from quasi-two-dimensional collective swimming to three-dimensional turbulent behavior. The latter state, qualitatively different from bioconvection in dilute bacterial suspensions, is characterized by enhanced diffusivities of oxygen and bacteria. These results emphasize the impact of self-organized bacterial locomotion on the onset of three-dimensional dynamics, and suggest key ingredients necessary to extend standard models of bioconvection to incorporate effects of large-scale collective motion.

  13. Enhanced harmonic emission from a polar molecule medium driven by few-cycle laser pulses.

    PubMed

    Zhang, Chaojin; Yao, Jinping; Ni, Jielei; Umran, Fadhil A

    2012-11-19

    We investigate theoretically the enhancement of the low-order harmonic emission from a polar molecular medium. The results show that, by using a control laser field, the intensity of the spectral signals near fourth-order harmonics will increase over 25 times as a result of the four-wave mixing process. Moreover, the enhancement effects depend strongly on the carrier-envelope phase of the initial laser fields, which cannot be found in a symmetric system.

  14. Condensate enhancement and D-meson mixing in technicolor theories

    SciTech Connect

    Chivukula, R. Sekhar; Simmons, Elizabeth H.

    2010-08-01

    Since the pioneering work of Eichten and Lane it has been known that the scale of the interactions responsible for the generation of the strange-quark mass in extended technicolor theories must, absent any Glashow-Iliopoulos-Maiani mechanism for suppressing flavor-changing neutral currents, be greater than of order 1000 TeV. In this paper we point out that the constraint from the neutral D-meson system is now equally strong, implying that the charm quark mass must also arise from flavor dynamics at a scale this high. We then quantify the degree to which the technicolor condensate must be enhanced in order to yield the observed quark masses, if the extended technicolor scale is of order 1000 TeV. Our results are intended to provide a framework in which to interpret and apply the results of lattice studies of conformal strongly interacting gauge theories, and the corresponding numerical measurements of the anomalous dimension of the mass operator in candidate theories of walking technicolor.

  15. Liquid mixing enhanced by pulse width modulation in a Y-shaped jet configuration

    NASA Astrophysics Data System (ADS)

    Xia, Qingfeng; Zhong, Shan

    2013-04-01

    In this paper, mixing between two fluid streams, which are injected into a planar mixing channel via a Y-shaped confluence section at the same volume flow rate, is studied experimentally. The injection of the two fluid streams is controlled by two separate solenoid valves, which are operated with a phase difference of 180°, using pulse width modulation. The experiments are conducted using water at a mean Reynolds number between 83 and 250, a range of pulsation frequencies and two duty cycles (25 and 50%). Both particle-image velocimetry and planar laser-induced fluorescence technique are used to visualize the flow patterns and to quantify the mixing degree in the mixing channel. This experiment shows that the pulsation of each jet produces vortical structures, which promotes mixing via vortex entrainment and vortex breakup, and at the same time the mixing is also greatly enhanced by sequential segmentation produced by a 180° out-of-phase pulsation of the two jets. This mixing enhancement method is effective at a Reynolds number greater than 125 with a mixing degree of 0.9 being achieved. For the Reynolds numbers studied in the present experiments, an optimal frequency exists, which corresponds to a Strouhal number in the range of 0.5-2. Furthermore, at a given mean Reynolds number a lower duty cycle is found to produce a better mixing due to the resultant higher instantaneous Reynolds number in the jet flow. It is also found that pulsation of only one jet can produce a similar mixing effect.

  16. Application of a Flip-Flop Nozzle on Plume Mixing Enhancement

    NASA Technical Reports Server (NTRS)

    Schreck, Stefan; Michaelian, Mark; Ho, Chih-Ming

    1999-01-01

    Mach wave radiation is a major source of noise in high speed jets. It is created by turbulent eddies which travel at supersonic speed within the shear layer of the jet. Downstream of the potential core, the convection speed of the eddies decays and noise production is reduced. Once the convection speeds drops below the speed of sound, eddy Mach wave radiation ceases. Mach wave radiation may be reduced by shortening the core length of the jet. This requires a faster growth of the shear layer, i.e. enhanced mixing in the jet. We investigated the possibility of mixing enhancement by the excitation of the instability waves in a supersonic rectangular jet.

  17. Ultrabroadband mid-infrared spectroscopy with four-wave difference frequency generation

    NASA Astrophysics Data System (ADS)

    Fuji, Takao; Shirai, Hideto; Nomura, Yutaka

    2015-09-01

    Four-wave difference frequency generation (FWDFG) is a third-order optical parametric process, which is generally explained as {ω }1+{ω }2-{ω }3\\to {ω }4 or {ω }1-{ω }2-{ω }3\\to {ω }4, where three input frequencies are {ω }1, {ω }2, and {ω }3, and the output frequency is {ω }4. Here we report the use of FWDFG for chirped-pulse upconversion (CPU) of an ultrabroadband mid-infrared (MIR) supercontinuum and the application of the technique for MIR spectroscopy. When the CPU technique is used for MIR spectroscopy, ultrashort MIR pulses are converted into visible ones. This way, the spectra can be recorded with a visible spectrometer, which has much higher performance than MIR spectrometers. In the previous experiments, the CPU has been performed by using sum-frequency generation (SFG) with a solid crystal, and the bandwidth has been limited to less than 1000 cm-1 due to the phase matching condition of the SFG. This limitation can be removed by using FWDFG, which is a third-order nonlinear process that allows us to use centrosymmetric nonlinear media such as gases for the upconversion. Since gaseous media have much less dispersion than solid media, the bandwidth of the phase-matching condition for the upconversion process becomes very broad. In our experiments, the entire spectrum of the MIR supercontinuum spanning from 200 to 5500 cm-1 was upconverted by using a 4.9 ps chirped pulse to visible wavelength radiation, which was detected with a conventional visible dispersive spectrometer. The technique has been applied to attenuated total reflectance MIR spectroscopy. Absorption spectra of liquids in the range from 200 to 5500 cm-1 were measured with a visible spectrometer on a single-shot basis.

  18. Enhanced biogas production by anaerobic co-digestion from a trinary mix substrate over a binary mix substrate.

    PubMed

    Ara, Efath; Sartaj, Majid; Kennedy, Kevin

    2015-06-01

    The synergetic enhancement of mesophilic anaerobic co-digestion of trinary and binary mix of organic fraction of municipal solid waste (OFMSW) + primary sludge (PS) + thickened waste activated sludge (TWAS) as substrates was investigated through batch biological methane potential (BMP) and semi-continuous flow reactor tests. Cumulative biogas yield (CBY) yield for the binary mix of OFMSW:TWAS was 555, 580, and 660 mL/g volatile solids (VS)added for an OFMSW:TWAS ratio of 25:75, 50:50, and 75:25, respectively, which was 48, 78.5, and 140% higher than the calculated expected biogas (CEB) yield from the corresponding individual substrates. The trinary mixture of OFMSW:TWAS:PS at ratios of 25:37.5:375.5, 50:25:25 and 75:12.5:12.5 was able to produce 680, 710 and 780 mL/g VSadded, respectively, which was 25.5, 62.0 and 135.6% more biogas than the calculated expected biogas yield from the corresponding individual substrates. Cumulative methane yield (CMY) of trinary mixtures was also higher than the corresponding binary mixtures (20, 27, and 12 % increase for OFMSW:TWAS:PS at a ratio of 25:37.5:37.5, 50:25:25, and 75:12.5:12.5 compared to the binary mix of OFMSW:TWAS at a ratio of 25:75, 50:50, and 75:25, respectively). Methane content of the biogas varied from 54 to 57%. The results from semi-continuous flow anaerobic reactors under hydraulic retention times (HRT) of 15, 10 and 7 days supported the results of batch biological methane potential tests. The results were conclusive that enhancement in biogas production was noticeably higher from the co-digestion of trinary mix of organic fraction of municipal solid waste+ thickened waste activated sludge + primary sludge than the binary mix organic fraction of municipal solid waste+thickened waste activated sludge or thickened waste activated sludge+primary sludge with concomitant improvements in VS removal and biodegradability for tri-digestion of organic fraction of municipal solid waste, thickened waste activated sludge

  19. Noise characterization in double-heralded generation of two-photon-states by spontaneous four-wave-mixing

    NASA Astrophysics Data System (ADS)

    Smith, Roger A.; Reddy, Dileep V.; Vitullo, Dashiell L. P.; Raymer, Michael G.

    2016-09-01

    In quantum optics experiments, heralding, a form of conditional state preparation, is a useful tool for creating photon-number states from nonlinear optical sources for quantum-information science experiments. Heralding occurs when one photon from a correlated pair is detected to herald the presence of the other photon, labeled the signal photon. However, as heralding is extended to two or more photon pairs, the presence of noise photons in the herald channel quickly degrades the photon statistics of the signal photons. We create two-photon number states from a non-degenerate, third-order nonlinear optical fiber source with double heralding and present a method for verifying these photon-number states. The consequences of noisy heralding on the statistics of states created via third-order nonlinear processes are analyzed. We present a method for estimating the effects of noise photons on the signal photon statistics. Additionally, we prove the equivalence between noise in the herald channel and a loss in the signal channel. We utilize this equivalence to infer the photon statistics of the photon-number states in the signal channel that would be present in the absence of noise in the herald channel. By measuring the statistics of the signal channels with noise in the herald channel and comparing to the inferred, noise-free distribution, we can estimate the potential benefits of additional noise-reducing procedures on the experiment.

  20. Degenerate four-wave mixing spectroscopy and spectral simulation of C2 in an atmospheric pressure oxy-acetylene flame

    NASA Astrophysics Data System (ADS)

    Kaminski, C. F.; Hughes, I. G.; Ewart, P.

    1997-04-01

    The d 3Πg↔a3Πu Swan bands of C2 have been recorded with high resolution using DFWM in the nearly Doppler free, phase conjugate geometry. C2 was probed in a standard oxy-acetylene welding flame with excellent signal-to-noise ratio and spectral resolution. Theoretical spectra were simulated and fitted directly to the complex overlapping spectra. The good agreement obtained shows that DFWM holds promise to become a robust and reliable tool for flame thermometry. Current theories of DFWM are reviewed in context of the present work and advantages and disadvantages of the technique are discussed.

  1. Design of photonic crystal fibers with highly nonlinear glasses for four-wave-mixing based telecom applications.

    PubMed

    Kanka, Jiri

    2008-12-08

    A fully-vectorial mode solver based on the finite element method is employed in a combination with the downhill simplex method the dispersion optimization of photonic crystal fibers made from highly nonlinear glasses. The nonlinear fibers are designed for telecom applications such as parametric amplification, wavelength conversion, ultra-fast switching and regeneration of optical signals. The optimization is carried in terms of the zero dispersion wavelength, dispersion magnitude and nonlinear coefficient and confinement loss in the wavelength range around 1.55 microm. We restrict our work to the index-guiding fiber structures a small number of hexagonally arrayed air holes.

  2. Distinguishing non-resonant four-wave-mixing noise in coherent stokes and anti-stokes Raman scattering

    NASA Technical Reports Server (NTRS)

    Marks, Daniel L. (Inventor); Boppart, Stephen A. (Inventor)

    2009-01-01

    A method of examining a sample comprises exposing the sample to a pump pulse of electromagnetic radiation for a first period of time, exposing the sample to a stimulant pulse of electromagnetic radiation for a second period of time which overlaps in time with at least a portion of the first exposing, to produce a signal pulse of electromagnetic radiation for a third period of time, and interfering the signal pulse with a reference pulse of electromagnetic radiation, to determine which portions of the signal pulse were produced during the exposing of the sample to the stimulant pulse. The first and third periods of time are each greater than the second period of time.

  3. Nonlinear Optics Technology. Phase 2. Area 1. Four Wave Mixing Technology. Area 2. Phase Conjugated Solid State Laser Technology

    DTIC Science & Technology

    1988-01-15

    particle - in - a - box model for MQWs...the system. E GoAsg C 56 c1 irges in the band gap physics. Temporarily ignoring the effects of the e-h Coulomb interaction, simple particle - in - a - box theory...and 0 is the Heaviside step function. Figure 3-17C shows schematically the particle in a box energy levels and wave functions for both the

  4. Interplay of phase-sensitive amplification and cascaded four-wave mixing in dispersion-controlled waveguides

    NASA Astrophysics Data System (ADS)

    Martin, Aude; Combrié, Sylvain; Willinger, Amnon; Eisenstein, Gadi; de Rossi, Alfredo

    2016-08-01

    Phase-sensitive parametric interactions can selectively process the two complex quadratures of the optical field. We implement phase-sensitive amplification in a large band-gap semiconductor photonic crystal waveguide in order to avoid two-photon absorption and free-carrier-related effects. Experimentally, an extinction ratio of 15 dB is achieved in a 1.5-mm-long photonic crystal waveguide, at a peak pump power of about 600 mW. We show that cascaded parametric interaction has a strong impact on squeezing and phase-sensitive extinction ratio and that this depends on the dispersion profile of the waveguide.

  5. Spontaneous four-wave mixing in liquid-core fibers: towards fibered Raman-free correlated photon sources

    NASA Astrophysics Data System (ADS)

    Barbier, M.; Zaquine, I.; Delaye, P.

    2015-05-01

    We experimentally demonstrate, for the first time to our knowledge, the generation of correlated photon pairs in a liquid-core photonic crystal fiber. Moreover, we show that, thanks to the specific Raman properties of liquids, the Raman noise (which is the main limitation of the performance of silica-core fiber-based correlated photon pair sources) is highly reduced. With a demonstrated coincident-to-accidental ratio equal to 63 and a pair generation efficiency of about 10-4 per pump pulse, this work contributes to the development of high-quality correlated photon pair sources for quantum communications.

  6. Supercontinuum and four-wave mixing with Q-switched pulses in endlessly single-mode photonic crystal fibres.

    PubMed

    Wadsworth, W; Joly, N; Knight, J; Birks, T; Biancalana, F; Russell, P

    2004-01-26

    Photonic crystal fibres exhibiting endlessly single-mode operation and dispersion zero in the range 1040 to 1100 nm are demonstrated. A sub-ns pump source at 1064 nm generates a parametric output at 732 nm with an efficiency of 35%, or parametric gain of 55 dB at 1315 nm. A broad, flat supercontinuum extending from 500 nm to beyond 1750 nm is also demonstrated using the same pump source.

  7. Two-color interference effect involving three-photon atomic excitation and four-wave mixing in crossed laser beams

    SciTech Connect

    Peet, V.

    2007-09-15

    Through multiphoton ionization measurements, the polarization effects in destructive quantum interference under three-photon resonant excitation have been studied. Recent observations [V. Peet, Phys. Rev. A 74, 033406 (2006)] have indicated that contrary to the well-known pattern of a total suppression of resonance excitation, the destructive interference becomes incomplete if three-photon transition is driven by crossed beams with orthogonal polarization planes. These observations have been tested for a more general case of two-color excitation and very similar polarization-dependent anomalies in the interference character have been registered. It has been shown that the destructive interference is modified and the resonance excitation does occur if two crossed laser beams have opposite circular polarizations. The pressure-induced evolution of the uncanceled ionization peaks has the ratio of blue shift to width close to 0.5 exactly as it is known for resonance ionization peaks registered under excitation by counterpropagating laser beams.

  8. Switching suppression and enhancement of fluorescence and six-wave mixing by phase modulation.

    PubMed

    Wang, Zhiguo; Ying, Peng; Li, Peiying; Zhang, Dan; Huang, Heqing; Tian, Hao; Zhang, Yanpeng

    2013-12-04

    The conversion between enhancement and suppression in six-wave mixing (SWM) and fluorescence signals by phase modulation has demonstrated for the first time. It is observed in our experiment the suppression of SWM and fluorescence is transformed into enhancement in company with the switch from electromagnetically induced transparency (EIT) to electromagnetically induced absorption (EIA) in the transmitted probe with the relative phase changed from 0 to π/2. Our research could be potentially applied in optical communication and quantum information processing.

  9. The suppression of enhanced bitterness intensity of macrolide dry syrup mixed with an acidic powder.

    PubMed

    Ishizaka, Toshihiko; Okada, Sachie; Takemoto, Eri; Tokuyama, Emi; Tsuji, Eriko; Mukai, Junji; Uchida, Takahiro

    2007-10-01

    The aim of the present study was to identify a medicine which strongly enhanced the bitterness of clarithromycin dry syrup (CAMD) when administered concomitantly and to develop a method to suppress this enhanced bitterness. The bitterness enhancement was evaluated not only by gustatory sensation tests but also using pH and taste sensor measurements of the mixed sample. A remarkable bitterness enhancement was found when CAMD was mixed with the acidic powder L-carbocysteine. The acidic pH (pH 3.40) of the suspension made from these two preparations, seemed to be due to enhanced release of clarithromycin caused by the dissolution of the alkaline polymer film-coating. Several methods for preventing this bitterness enhancement were investigated. Neither increasing the volume of water taken with the mixture, nor changing the ratio of CAMD:L-carbocysteine in the mixture, were effective in reducing the bitterness intensity of the CAMD/L-carbocysteine mixture. The best way to achieve taste masking was to first administer CAMD mixed with chocolate jelly, which has a neutral pH, followed by the L-carbocysteine suspension. Similar results were obtained for the bitterness suppression of azithromycin fine granules with L-carbocysteine. The chocolate jelly will be useful for taste masking of bitter macrolide drug formulations, when they need to be administered together with acidic drug formulations.

  10. The Role of Identity Integration in Enhancing Creativity among Mixed-Race Individuals

    ERIC Educational Resources Information Center

    Tendayi Viki, G.; Williams, May Liang J.

    2014-01-01

    Identity integration among bicultural individuals refers to the perception that their two cultural identities are compatible. Previous research has shown that identity integration is likely to lead to enhanced creativity. However, this research was conducted among first- and second-generation immigrants, but not among mixed-race individuals. The…

  11. Enhanced mixing via alternating injection in radial Hele-Shaw flows.

    PubMed

    Chen, Ching-Yao; Huang, Yi-Cheng; Huang, Yu-Sheng; Miranda, José A

    2015-10-01

    Mixing at low Reynolds numbers, especially in the framework of confined flows occurring in Hele-Shaw cells, porous media, and microfluidic devices, has attracted considerable attention lately. Under such circumstances, enhanced mixing is limited due to the lack of turbulence, and absence of sizable inertial effects. Recent studies, performed in rectangular Hele-Shaw cells, have demonstrated that the combined action of viscous fluid fingering and alternating injection can dramatically improve mixing efficiency. In this work, we revisit this important fluid mechanical problem, and analyze it in the context of radial Hele-Shaw flows. The development of radial fingering instabilities under alternating injection conditions is investigated by intensive numerical simulations. We focus on the impact of the relevant physical parameters of the problem (Péclet number Pe, viscosity contrast A, and injection time interval Δt) on fluid mixing performance.

  12. Cavity-Enhanced Room-Temperature Broadband Raman Memory

    NASA Astrophysics Data System (ADS)

    Saunders, D. J.; Munns, J. H. D.; Champion, T. F. M.; Qiu, C.; Kaczmarek, K. T.; Poem, E.; Ledingham, P. M.; Walmsley, I. A.; Nunn, J.

    2016-03-01

    Broadband quantum memories hold great promise as multiplexing elements in future photonic quantum information protocols. Alkali-vapor Raman memories combine high-bandwidth storage, on-demand readout, and operation at room temperature without collisional fluorescence noise. However, previous implementations have required large control pulse energies and have suffered from four-wave-mixing noise. Here, we present a Raman memory where the storage interaction is enhanced by a low-finesse birefringent cavity tuned into simultaneous resonance with the signal and control fields, dramatically reducing the energy required to drive the memory. By engineering antiresonance for the anti-Stokes field, we also suppress the four-wave-mixing noise and report the lowest unconditional noise floor yet achieved in a Raman-type warm vapor memory, (15 ±2 )×10-3 photons per pulse, with a total efficiency of (9.5 ±0.5 )%.

  13. The golden-mean surface pattern to enhance flow mixing in micro-channel.

    PubMed

    Wang, J F; Liu, Y; Xu, Y S

    2009-04-01

    Mixing of analytes and reagents in microfluidic devices is often crucial to the effective functioning of lab-on-a-chip. It is possible to affect the mixing in microfluidics by intelligently controlling the thermodynamic and chemical properties of the substrate surface. Numerous studies have shown that the phase behavior of mixtures is significantly affected by surface properties of microfluidics. For example, the phase separation between the fluids can be affected by heterogeneous patterns on the substrate. The patterned substrate can offer an effective means to control fluid behavior and in turn to enhance mixing. The golden mean is a ratio that is present in the growth patterns of many biological systems--the spiral formed by a shell or the curve of a fern, for example. The golden mean or golden section was derived by the ancient Greeks. Like "pi" the golden mean ratio is an irrational number 1.618, or (square root{5} + 1) / 2. It was found that the golden mean was an optimum ratio in natural convection heat transfer problem (Liu and Phan-Thien, Numer Heat Transf 37:613-630, 2000). In this study, we numerically studied the effect of optimum surface pattern on mixing in a micro channel and found that the flow oscillation and chaotic mixing were enhanced apparently when the ratio of hydrophobic and hydrophilic boundary follows the golden mean.

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

    PubMed

    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.

  15. Sucrose mixed with spinosad enhances kill and reduces oviposition of Rhagoletis indifferens (Diptera: Tephritidae) under low-food conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Whether sugar mixed with insecticides enhances kill of western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), may depend on insecticide rate and food availability. Here, the hypothesis that sucrose mixed with the insecticide spinosad (in the Entrust® SC formulation) enhance...

  16. Enhancement of Absorption by Micro-Mixing induced by Villi Motion

    NASA Astrophysics Data System (ADS)

    Wang, Yanxing; Brasseur, James; Banco, Gino

    2009-11-01

    Motions of surface villi create microscale flows that can couple with lumen-scale eddies to enhance absorption at the epithelium of the small intestine. Using a multigrid strategy within the lattice-Boltzmann framework, we model a macro-scale cavity flow with microscale ``villi'' in pendular motion on the lower surface and evaluate the couplings between macro and micro-scale fluid motions, scalar mixing, and uptake of passive scalar at the villi surface. We study the influences of pendular frequency, villous length, and villous groupings on absorption rate. The basic mechanism underlying the enhancement of absorption rate by a villous-induced ``micro-mixing layer'' (MML) is the microscale ``pumping'' of low concentration fluid from between groups of villi coupled with the return of high concentration fluid into the villi groups from the macroscale flow. The MML couples with the macrosacle eddies through a diffusion layer that separates micro and macro mixed layers. The absorption rate increases with frequency of villi oscillation due to enhanced vertical pumping. We discover a critical villus length above which absorption rate increases significantly. The absorption is influenced by villus groupings in a complex way due to the interference between vertical and horizontal geometry vs. MML scales. We conclude that optimized villi motility can enhance absorption and may underlie an explanation for the existence of villi in the gut. [Supported by NSF

  17. Mixing in three-phase systems: Implications for enhanced oil recovery and unconventional gas extraction

    NASA Astrophysics Data System (ADS)

    Jimenez-Martinez, J.; Porter, M. L.; Hyman, J.; Carey, J. W.; Viswanathan, H. S.

    2015-12-01

    Although the mixing of fluids within a porous media is a common process in natural and industrial systems, how the degree of mixing depends on the miscibility of multiple phases is poorly characterized. Often, the direct consequence of miscible mixing is the modification of the resident fluid (brine and hydrocarbons) rheological properties. We investigate supercritical (sc)CO2 displacement and mixing processes in a three-phase system (scCO2, oil, and H2O) using a microfluidics experimental system that accommodates the high pressures and temperatures encountered in fossil fuel extraction operations. The miscibility of scCO2 with the resident fluids, low with aqueous solutions and high with hydrocarbons, impacts the mixing processes that control sweep efficiency in enhanced oil recovery (EOR) and the unlocking of the system in unconventional oil and gas extraction. Using standard volume-averaging techniques we upscale the aqueous phase saturation to the field-scale (i.e., Darcy scale) and interpret the results as a simpler two-phase system. This process allows us to perform a statistical analysis to quantify i) the degree of heterogeneity in the system resulting from the immiscible H2O and ii) how that heterogeneity impacts mixing between scCO2 and oil and their displacement. Our results show that when scCO2 is used for miscible displacement, the presence of an aqueous solution, which is common in secondary and tertiary EOR and unconventional oil and gas extraction, strongly impacts the mixing of scCO2 with the hydrocarbons due to low scCO2-H2O miscibility. H2O, which must be displaced advectively by the injected scCO2, introduces spatio-temporal variability into the system that acts as a barrier between the two miscibile fluids. This coupled with the effect of viscosity contrast, i.e., viscous fingering, has an impact on the mixing of the more miscible pair.

  18. Mixed-micellar proliposomal systems for enhanced oral delivery of progesterone.

    PubMed

    Potluri, Praveen; Betageri, Guru V

    2006-01-01

    The objective of our study was to develop a mixed-micellar proliposomal formulation of poorly water-soluble drug progesterone and evaluate the dissolution profile and membrane transport. Several formulations of proliposomes were prepared by mixing different concentrations of lipid, progesterone, polysorbate 80, and microcrystalline cellulose. The mixed-micellar formulation of drug:dimyristoyl-phosphatidycholine:polysorbate 80 (1:20:3.3) exhibited the maximum dissolution (75.27%), while pure progesterone resulted in low dissolution. The above formulation showed a 4-fold increase in transport in Caco-2 cells and a 6-fold increase in transport across the everted rat intestinal sac experiments compared with control. Proliposomal formulations enhance the extent of dissolution and membrane transport of progesterone and serve as ideal carriers for oral delivery of drugs with low water solubility.

  19. Enhanced copper micro/nano-particle mixed paste sintered at low temperature for 3D interconnects

    NASA Astrophysics Data System (ADS)

    Dai, Y. Y.; Ng, M. Z.; Anantha, P.; Lin, Y. D.; Li, Z. G.; Gan, C. L.; Tan, C. S.

    2016-06-01

    An enhanced copper paste, formulated by copper micro- and nano-particles mixture, is reported to prevent paste cracking and obtain an improved packing density. The particle mixture of two different sizes enables reduction in porosity of the micro-paste and resolves the cracking issue in the nano-paste. In-situ temperature and resistance measurements indicate that the mixed paste has a lower densification temperature. Electrical study also shows a ˜12× lower sheet resistance of 0.27 Ω/sq. In addition, scanning electron microscope image analysis confirms a ˜50% lower porosity, which is consistent with the thermal and electrical results. The 3:1 (micro:nano, wt. %) mixed paste is found to have the strongest synergistic effect. This phenomenon is discussed further. Consequently, the mixed paste is a promising material for potential low temperature 3D interconnects fabrication.

  20. Enhancement of Magma Mixing Efficiency by Chaotic Dynamics: an Experimental Study

    NASA Astrophysics Data System (ADS)

    Perugini, D.; de Campos, C. P.; Ertel, W.; Dingwell, D. B.; Poli, G.

    2010-12-01

    Magma mixing is common in the Earth. Understanding the dynamics of the mixing process is necessary for dealing with the likely consequences of mixing events in the petrogenesis of igneous rocks and the physics of volcanic eruptive triggers. We present a new apparatus to perform chaotic mixing experiments in systems of melts with high viscosity contrast. The apparatus consists of an outer and an inner cylinder, which can be independently rotated at finite strains to generate chaotic streamlines. The two cylinder axes are offset. Two end-member silicate melt compositions were synthesized from oxide and carbonate components and used in the experiments: (1) a peralkaline haplogranite and (2) a haplobasalt. The viscosity ratio between these two melts was of the order of 103. Experiments have been performed for ca. 2 h, at 1,400°C under laminar fluid dynamic conditions [Re ~ 10^(-7)]. Optical analysis of post-experimental samples revealed a complex pattern of mingled filaments forming a scale-invariant (i.e. fractal) distribution down to the μm-scale, as commonly observed in natural samples. This is due to the development of stretching and folding of the two melts in space and time. Chemical analysis showed that the original end-member compositions had nearly entirely disappeared from the filaments generated by the chaotic flow field. In addition, strong non-linear correlations in inter-elemental plots were observed. The generation of thin layers of compositionally widely contrasting interfaces strongly enhanced chemical diffusion producing a remarkable modulation of compositional fields over a short-length scale. Notably, diffusive fractionation generated highly heterogeneous pockets of melt, in which depletion or enrichment of chemical elements occurred, depending on their potential to spread within the magma mixing system. Results presented in this work offer new insights into the complexity of processes expected to be operating during magma mixing and may have

  1. Phase behavior and oil recovery investigations using mixed and alkaline-enhanced surfactant systems

    SciTech Connect

    Llave, F.M.; Gall, B.L.; French, T.R.; Noll, L.A.; Munden, S.A.

    1992-03-01

    The results of an evaluation of different mixed surfactant and alkaline-enhanced surfactant systems for enhanced oil recovery are described. Several mixed surfactant systems have been studies to evaluate their oil recovery potential as well as improved adaptability to different ranges of salinity, divalent ion concentrations, and temperature. Several combinations of screening methods were used to help identify potential chemical formulations and determine conditions where particular chemical systems can be applied. The effects of different parameters on the behavior of the overall surfactant system were also studied. Several commercially available surfactants were tested as primary components in the mixtures used in the study. These surfactants were formulated with different secondary as well as tertiary components, including ethoxylated and non-ethoxylated sulfonates and sulfates. Improved salinity and hardness tolerance was achieved for some of these chemical systems. The salinity tolerance of these systems were found to be dependent on the molecular weight, surfactant type, and concentration of the surfactant components.

  2. Enhanced index tracking modeling in portfolio optimization with mixed-integer programming z approach

    NASA Astrophysics Data System (ADS)

    Siew, Lam Weng; Jaaman, Saiful Hafizah Hj.; Ismail, Hamizun bin

    2014-09-01

    Enhanced index tracking is a popular form of portfolio management in stock market investment. Enhanced index tracking aims to construct an optimal portfolio to generate excess return over the return achieved by the stock market index without purchasing all of the stocks that make up the index. The objective of this paper is to construct an optimal portfolio using mixed-integer programming model which adopts regression approach in order to generate higher portfolio mean return than stock market index return. In this study, the data consists of 24 component stocks in Malaysia market index which is FTSE Bursa Malaysia Kuala Lumpur Composite Index from January 2010 until December 2012. The results of this study show that the optimal portfolio of mixed-integer programming model is able to generate higher mean return than FTSE Bursa Malaysia Kuala Lumpur Composite Index return with only selecting 30% out of the total stock market index components.

  3. Suppression of two-photon resonantly enhanced nonlinear processes in extended media

    SciTech Connect

    Garrett, W.R.; Moore, M.A.; Payne, M.G.; Wunderlich, R.K.

    1988-11-01

    On the basis of combined experimental and theoretical studies of nonlinear processes associated with two-photon excitations near 3d and 4d states in Na, we show how resonantly enhanced stimulated hyper-Raman emission, parametric four-wave mixing processes and total resonant two-photon absorption can become severely suppressed through the actions of internally generated fields on the total atomic response in extended media. 7 refs., 3 figs.

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

    PubMed

    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.

  5. Numerical investigation of enhanced dilution zone mixing in a reverse flow gas turbine combustor

    NASA Astrophysics Data System (ADS)

    Crocker, D. S.; Smith, C. E.

    1995-04-01

    An advanced method for dilution zone mixing in a reverse flow gas turbine combustor was numerically investigated. For long mixing lengths associated with reverse flow combustors (X/H greater than 2.0), pattern factor was found to be mainly driven by nozzle-to-nozzle fuel flow and/or circumferential airflow variations; conventional radially injected dilution jets could not effectively mix out circumferential nonuniformities. To enhance circumferential mixing, dilution jets were angled to produce a high circumferential (swirl) velocity component. The jets on the outer liner were angled in one direction while the jets on the inner liner were angled in the opposite direction, thus enhancing turbulent shear at the expense of jet penetration. Three-dimensional CFD calculations were performed on a three-nozzle (90 deg) sector, with different fuel flow from each nozzle (90, 100, and 110% of design fuel flow). The computations showed that the optimum configuration of angled jets reduced the pattern factor by 60% compared to an existing conventional dilution hole configuration. The radial average temperature profile was adequately controlled by the inner-to-outer liner dilution flow split.

  6. Deployment of an innovative thermally enhanced soil mixing process augmented with zero-valent iron.

    SciTech Connect

    Lynch, P. L.

    1999-01-15

    An innovative in-situ soil treatment process, referred to as soil mixing/thermally enhanced soil vapor extraction (SM/TESVE), was used to remediate the 317 Area of Argonne National Laboratory-East (i.e., Argonne), which is contaminated with volatile organic compounds (VOCs). Following the initial soil treatment, polishing was required to reduce residual concentrations of contaminants. A study of polishing methods was conducted. It determined that injecting metallic iron particles into the soil, in conjunction with soil mixing, would reduce residual VOC concentrations more effectively than the original conventional soil ventilation approach. After the effectiveness of iron injection was verified, it replaced the soil ventilation step. The modified process involved mixing the soil while hot air and steam were injected into it. Off-gases were captured in a hood over the treatment area. During this process, an iron slurry, consisting of up to 50% iron particles in water with guar gum added as a thickening agent, was injected and mixed into the soil by the mixing equipment. Approximately 6,246 m{sup 3} (8, 170 yd{sup 3}) of soil was treated during this project. Confirmatory samples were then collected. In these samples, VOC concentrations were usually reduced by more than 80%.

  7. Enhancement of murine mixed lymphocyte response by 1,1-dimethylhydrazine: characterization and possible mechanism.

    PubMed

    Tarr, M J; McKown, B J; Olsen, R G

    1988-01-01

    Treatment of mice with 1,1-dimethylhydrazine (UDMH) resulted in enhancement of the one-way mixed lymphocyte response (MLR); this effect was seen when both responder and stimulator mice were treated as well as when just the stimulator or just the responder mice were treated. Experiments in which splenocytes were exposed to UDMH in vitro indicated that exposure of the stimulator cells alone resulted in an enhanced MLR; exposure of the responder cells alone had no effect; and addition of UDMH to the assay (exposure of both populations) resulted in suppression of the response at higher concentrations. A possible mechanism for the enhancement of the MLR by UDMH was suggested by further experiments showing that UDMH inhibited prostaglandin E2 production by adherent splenocytes.

  8. Experiments on the enhancement of compressible mixing via streamwise vorticity. II - Vortex strength assessment and seed particle dynamics

    NASA Technical Reports Server (NTRS)

    Naughton, J. W.; Cattafesta, L. N.; Settles, G. S.

    1993-01-01

    The effect of streamwise vorticity on compressible axisymmetric mixing layers is examined using vortex strength assessment and seed particle dynamics analysis. Experimental results indicate that the particles faithfully represent the dynamics of the turbulent swirling flow. A comparison of the previously determined mixing layer growth rates with the present vortex strength data reveals that the increase of turbulent mixing up to 60 percent scales with the degree of swirl. The mixing enhancement appears to be independent of the compressibility level of the mixing layer.

  9. Enhancement of nitrate removal at the sediment-water interface by carbon addition plus vertical mixing.

    PubMed

    Chen, Xuechu; He, Shengbing; Zhang, Yueping; Huang, Xiaobo; Huang, Yingying; Chen, Danyue; Huang, Xiaochen; Tang, Jianwu

    2015-10-01

    Wetlands and ponds are frequently used to remove nitrate from effluents or runoffs. However, the efficiency of this approach is limited. Based on the assumption that introducing vertical mixing to water column plus carbon addition would benefit the diffusion across the sediment-water interface, we conducted simulation experiments to identify a method for enhancing nitrate removal. The results suggested that the sediment-water interface has a great potential for nitrate removal, and the potential can be activated after several days of acclimation. Adding additional carbon plus mixing significantly increases the nitrate removal capacity, and the removal of total nitrogen (TN) and nitrate-nitrogen (NO3(-)-N) is well fitted to a first-order reaction model. Adding Hydrilla verticillata debris as a carbon source increased nitrate removal, whereas adding Eichhornia crassipe decreased it. Adding ethanol plus mixing greatly improved the removal performance, with the removal rate of NO3(-)-N and TN reaching 15.0-16.5 g m(-2) d(-1). The feasibility of this enhancement method was further confirmed with a wetland microcosm, and the NO3(-)-N removal rate maintained at 10.0-12.0 g m(-2) d(-1) at a hydraulic loading rate of 0.5 m d(-1).

  10. Enhancement of Exciton Emission in Lead Halide-Based Layered Perovskites by Cation Mixing.

    PubMed

    Era, Masanao; Komatsu, Yumeko; Sakamoto, Naotaka

    2016-04-01

    Spin-coated films of a lead halide, PbX: X = I and Br, layered perovskites having cyclohexenylethyl ammonium molecule as an organic layer, which were mixed with other metal halide-based layered perovskites consisting of various divalent metal halides (for example, Ca2, Cdl2, FeI2, SnBr2 and so on), were prepared. The results of X-ray diffraction measurements exhibited that solid solution formation between PbX-based layered perovskite and other divalent metal halide-based layered perovskites was observed up to very high molar concentration of 50 molar% in the mixed film samples when divalent cations having ionic radius close to that of Pb2+ were employed. In the solid solution films, the exciton emission was much enhanced at room temperature. Exciton emission intensity of Pbl-based layered perovskite mixed with Cal-based layered perovskite (20 molar%) is about 5 times large that of the pristine Pbl-based layered perovskite, and that of PbBr-based layered perovskite mixed with SnBr-based layered perovskite (20 molar%) was also about 5 times large that of the pristine PbBr-based layered perovskite at room temperature.

  11. Relations between Political Violence and Child Adjustment: A Four-Wave Test of the Role of Emotional Insecurity about Community

    PubMed Central

    Cummings, E. Mark; Taylor, Laura K.; Merrilees, Christine E.; Goeke-Morey, Marcie C.; Shirlow, Peter; Cairns, Ed

    2015-01-01

    This study further explored the impact of sectarian violence and children’s emotional insecurity about community on child maladjustment using a four-wave longitudinal design. The study included 999 mother-child dyads in Belfast, Northern Ireland (482 boys, 517 girls). Across the four-waves, child mean age was 12.19 (SD = 1.82), 13.24 (SD = 1.83), 13.61 (SD = 1.99), and 14.66 years (SD = 1.96), respectively. Building on previous studies of the role of emotional insecurity in child adjustment, the current study examines within-person change in emotional insecurity using latent growth curve analyses. The results showed that children’s trajectories of emotional insecurity about community were related to risk for developing conduct and emotion problems. These findings controlled for earlier adjustment problems, age and gender, and took into account the time-varying nature of experience with sectarian violence. Discussion considers the implications for children’s emotional insecurity about community for relations between political violence and children’s adjustment, including the significance of trajectories of emotional insecurity over time. PMID:23527495

  12. Mars' south polar Ar enhancement: a tracer for south polar seasonal meridional mixing.

    PubMed

    Sprague, A L; Boynton, W V; Kerry, K E; Janes, D M; Hunten, D M; Kim, K J; Reedy, R C; Metzger, A E

    2004-11-19

    The gamma ray spectrometer on the Mars Odyssey spacecraft measured an enhancement of atmospheric argon over southern high latitudes during autumn followed by dissipation during winter and spring. Argon does not freeze at temperatures normal for southern winter (approximately 145 kelvin) and is left in the atmosphere, enriched relative to carbon dioxide (CO2), as the southern seasonal cap of CO2 frost accumulates. Calculations of seasonal transport of argon into and out of southern high latitudes point to meridional (north-south) mixing throughout southern winter and spring.

  13. Radiative absorption enhancements due to the mixing state of atmospheric black carbon

    SciTech Connect

    Cappa, Christopher D.; Onasch, Timothy B.; Massoli, Paola; Worsnop, Douglas R.; Bates, Timothy S.; Cross, Eben S.; Davidovits, Paul; Hakala, Jani; Hayden, Katherine; Jobson, Bertram Thomas; Kolesar, K. R.; Lack, D. A.; Lerner, Brian M.; Li, Shao-Meng; Mellon, Daniel; Nuaaman, Ibraheem; Olfert, Jason; Petaja, Tuukka; Quinn, P. K.; Song, Chen; Subramanian, R.; Williams, Eric; Zaveri, Rahul A.

    2012-08-30

    Atmospheric particulate black carbon (BC) leads to warming of the Earth's climate. Many models that include forcing by BC assume that non-BC aerosol species internally mixed with BC enhance BC absorption, often by a factor of {approx}2. However, such model estimates have yet to be clearly validated through atmospheric observations. Here, we report on direct measurements of the absorption enhancement (Eabs) of BC in the atmosphere around California and find that it is negligible at 532 nm and much smaller than predicted from theoretical calculations that are uniquely constrained by observations, suggesting that the warming by BC may be significantly overestimated (factor of 2) in many climate models. Additionally, non-BC particulate matter is found to contribute {approx}10% to the total absorption at 405 nm.

  14. Numerical Investigation of Enhanced Mixing in a Microchannel Using Ferrofluid Using The Lattice Boltzmann Method

    NASA Astrophysics Data System (ADS)

    de, Anindya

    2005-11-01

    Ferrofluids are colloidal suspensions of magnetic nanoparticles in carrier liquids which can be readily maneuvered from a distance using magnetic fields. When functionalized with different antibodies or medicinal compounds the ferrofluid nanoparticles can be used for various purposes, e.g., to detect bacteria or as a carrier of chemotherapeutic agents for targeted drug delivery. Localized magnetic nanoparticle agglomerates can also be remotely moved to create perturbations within a microchannel flow, thereby resulting in better mixing of various fluids. We have numerically investigated ferrofluid agglomeration and its influence on enhancing local mixing in microchannels by using the lattice Boltzmann method. Employing this method, we solve for the one-particle probability distribution function f which denotes the probability density of finding a particle at time t, at the location x, moving with velocity v when a force F is acting on it. (A Chapman-Enskog expansion recreates the continuum relation and the Navier-Stokes equation for weakly compressible flows.) We have simulated ferrofluid agglomeration near a magnetic dipole for flow through a rectangular microchannel. When a number of such magnets are placed across the channel and activated in sequence, they locally perturb the fluid flow to produce better mixing in two initially unmixed fluids.

  15. Gas-Enhanced Ultra-High Shear Mixing: A Concept and Applications

    NASA Astrophysics Data System (ADS)

    Czerwinski, Frank; Birsan, Gabriel

    2017-04-01

    The processes of mixing, homogenizing, and deagglomeration are of paramount importance in many industries for modifying properties of liquids or liquid-based dispersions at room temperature and treatment of molten or semi-molten alloys at high temperatures, prior to their solidification. To implement treatments, a variety of technologies based on mechanical, electromagnetic, and ultrasonic principles are used commercially or tested at the laboratory scale. In a large number of techniques, especially those tailored toward metallurgical applications, the vital role is played by cavitation, generation of gas bubbles, and their interaction with the melt. This paper describes a novel concept exploring an integration of gas injection into the shear zone with ultra-high shear mixing. As revealed via experiments with a prototype of the cylindrical rotor-stator apparatus and transparent media, gases injected radially through the high-speed rotor generate highly refined bubbles of high concentration directly in the shear zone of the mixer. It is believed that an interaction of large volume of fine gas bubbles with the liquid, superimposed on ultra-high shear, will enhance mixing capabilities and cause superior refining and homogenizing of the liquids or solid-liquid slurries, thus allowing their effective property modification.

  16. Gas-Enhanced Ultra-High Shear Mixing: A Concept and Applications

    NASA Astrophysics Data System (ADS)

    Czerwinski, Frank; Birsan, Gabriel

    2016-12-01

    The processes of mixing, homogenizing, and deagglomeration are of paramount importance in many industries for modifying properties of liquids or liquid-based dispersions at room temperature and treatment of molten or semi-molten alloys at high temperatures, prior to their solidification. To implement treatments, a variety of technologies based on mechanical, electromagnetic, and ultrasonic principles are used commercially or tested at the laboratory scale. In a large number of techniques, especially those tailored toward metallurgical applications, the vital role is played by cavitation, generation of gas bubbles, and their interaction with the melt. This paper describes a novel concept exploring an integration of gas injection into the shear zone with ultra-high shear mixing. As revealed via experiments with a prototype of the cylindrical rotor-stator apparatus and transparent media, gases injected radially through the high-speed rotor generate highly refined bubbles of high concentration directly in the shear zone of the mixer. It is believed that an interaction of large volume of fine gas bubbles with the liquid, superimposed on ultra-high shear, will enhance mixing capabilities and cause superior refining and homogenizing of the liquids or solid-liquid slurries, thus allowing their effective property modification.

  17. Mixing enhancement in a scramjet combustor using fuel jet injection swirl

    NASA Astrophysics Data System (ADS)

    Flesberg, Sonja M.

    The scramjet engine has proven to be a viable means of powering a hypersonic vehicle, especially after successful flights of the X-51 WaveRider and various Hy-SHOT test vehicles. The major challenge associated with operating a scramjet engine is the short residence time of the fuel and oxidizer in the combustor. The fuel and oxidizer have only milliseconds to mix, ignite and combust in the combustion chamber. Combustion cannot occur until the fuel and oxidizer are mixed on a molecular level. Therefore the improvement of mixing is of utmost interest since this can increase combustion efficiency. This study investigated mixing enhancement of fuel and oxidizer within the combustion chamber of a scramjet by introducing swirl to the fuel jet. The investigation was accomplished with numerical simulations using STAR-CCM+ computational fluid dynamic software. The geometry of the University of Virginia Supersonic Combustion Facility was used to model the isolator, combustor and nozzle of a scramjet engine for simulation purposes. Experimental data from previous research at the facility was used to verify the simulation model before investigating the effect of fuel jet swirl on mixing. The model used coaxial fuel jet with a swirling annular jet. Single coaxial fuel jet and dual coaxial fuel jet configurations were simulated for the investigation. The coaxial fuel jets were modelled with a swirling annular jet and non-swirling core jet. Numerical analysis showed that fuel jet swirl not only increased mixing and entrainment of the fuel with the oxidizer but the mixing occurred further upstream than without fuel jet swirl. The burning efficiency was calculated for the all the configurations. An increase in burning efficiency indicated an increase in the mixing of H2 with O2. In the case of the single fuel jet models, the maximum burning efficiency increase due to fuel injection jet swirl was 23.3%. The research also investigated the possibility that interaction between two

  18. Enhanced reaction kinetics and reactive mixing scale dynamics in mixing fronts under shear flow for arbitrary Damköhler numbers

    NASA Astrophysics Data System (ADS)

    Bandopadhyay, Aditya; Le Borgne, Tanguy; Méheust, Yves; Dentz, Marco

    2017-02-01

    Mixing fronts, where fluids of different chemical compositions mix with each other, are known to represent hotspots of chemical reaction in hydrological systems. These fronts are typically subjected to velocity gradients, ranging from the pore scale due to no slip boundary conditions at fluid solid interfaces, to the catchment scale due to permeability variations and complex geometry of the Darcy velocity streamlines. A common trait of these processes is that the mixing interface is strained by shear. Depending on the Péclet number Pe , which represents the ratio of the characteristic diffusion time to the characteristic shear time, and the Damköhler number Da , which represents the ratio of the characteristic diffusion time to the characteristic reaction time, the local reaction rates can be strongly impacted by the dynamics of the mixing interface. So far, this impact has been characterized mostly either in kinetics-limited or in mixing-limited conditions, that is, for either low or high Da. Here the coupling of shear flow and chemical reactivity is investigated for arbitrary Damköhler numbers, for a bimolecular reaction and an initial interface with separated reactants. Approximate analytical expressions for the global production rate and reactive mixing scale are derived based on a reactive lamella approach that allows for a general coupling between stretching enhanced mixing and chemical reactions. While for Pe < Da , reaction kinetics and stretching effects are decoupled, a scenario which we name "weak stretching", for Pe > Da , we uncover a "strong stretching" scenario where new scaling laws emerge from the interplay between reaction kinetics, diffusion, and stretching. The analytical results are validated against numerical simulations. These findings shed light on the effect of flow heterogeneity on the enhancement of chemical reaction and the creation of spatially localized hotspots of reactivity for a broad range of systems ranging from kinetic limited

  19. Measurements of Turbulent Flow Field in Separate Flow Nozzles with Enhanced Mixing Devices - Test Report

    NASA Technical Reports Server (NTRS)

    Bridges, James

    2002-01-01

    As part of the Advanced Subsonic Technology Program, a series of experiments was conducted at NASA Glenn Research Center on the effect of mixing enhancement devices on the aeroacoustic performance of separate flow nozzles. Initial acoustic evaluations of the devices showed that they reduced jet noise significantly, while creating very little thrust loss. The explanation for the improvement required that turbulence measurements, namely single point mean and RMS statistics and two-point spatial correlations, be made to determine the change in the turbulence caused by the mixing enhancement devices that lead to the noise reduction. These measurements were made in the summer of 2000 in a test program called Separate Nozzle Flow Test 2000 (SFNT2K) supported by the Aeropropulsion Research Program at NASA Glenn Research Center. Given the hot high-speed flows representative of a contemporary bypass ratio 5 turbofan engine, unsteady flow field measurements required the use of an optical measurement method. To achieve the spatial correlations, the Particle Image Velocimetry technique was employed, acquiring high-density velocity maps of the flows from which the required statistics could be derived. This was the first successful use of this technique for such flows, and shows the utility of this technique for future experimental programs. The extensive statistics obtained were likewise unique and give great insight into the turbulence which produces noise and how the turbulence can be modified to reduce jet noise.

  20. Enhancing grain boundary ionic conductivity in mixed ionic–electronic conductors

    DOE PAGES

    Lin, Ye; Fang, Shumin; Su, Dong; ...

    2015-04-10

    Mixed ionic–electronic conductors are widely used in devices for energy conversion and storage. Grain boundaries in these materials have nanoscale spatial dimensions, which can generate substantial resistance to ionic transport due to dopant segregation. Here, we report the concept of targeted phase formation in a Ce0.8Gd0.2O2₋δ–CoFe2O4 composite that serves to enhance the grain boundary ionic conductivity. Using transmission electron microscopy and spectroscopy approaches, we probe the grain boundary charge distribution and chemical environments altered by the phase reaction between the two constituents. The formation of an emergent phase successfully avoids segregation of the Gd dopant and depletion of oxygen vacanciesmore » at the Ce0.8Gd0.2O2₋δ–Ce0.8Gd0.2O2₋δ grain boundary. This results in superior grain boundary ionic conductivity as demonstrated by the enhanced oxygen permeation flux. Lastly, this work illustrates the control of mesoscale level transport properties in mixed ionic–electronic conductor composites through processing induced modifications of the grain boundary defect distribution.« less

  1. Enhancing grain boundary ionic conductivity in mixed ionic–electronic conductors

    PubMed Central

    Lin, Ye; Fang, Shumin; Su, Dong; Brinkman, Kyle S; Chen, Fanglin

    2015-01-01

    Mixed ionic–electronic conductors are widely used in devices for energy conversion and storage. Grain boundaries in these materials have nanoscale spatial dimensions, which can generate substantial resistance to ionic transport due to dopant segregation. Here, we report the concept of targeted phase formation in a Ce0.8Gd0.2O2−δ–CoFe2O4 composite that serves to enhance the grain boundary ionic conductivity. Using transmission electron microscopy and spectroscopy approaches, we probe the grain boundary charge distribution and chemical environments altered by the phase reaction between the two constituents. The formation of an emergent phase successfully avoids segregation of the Gd dopant and depletion of oxygen vacancies at the Ce0.8Gd0.2O2−δ–Ce0.8Gd0.2O2−δ grain boundary. This results in superior grain boundary ionic conductivity as demonstrated by the enhanced oxygen permeation flux. This work illustrates the control of mesoscale level transport properties in mixed ionic–electronic conductor composites through processing induced modifications of the grain boundary defect distribution. PMID:25857355

  2. Enhancing grain boundary ionic conductivity in mixed ionic–electronic conductors

    SciTech Connect

    Lin, Ye; Fang, Shumin; Su, Dong; Brinkman, Kyle S.; Chen, Fanglin

    2015-04-10

    Mixed ionic–electronic conductors are widely used in devices for energy conversion and storage. Grain boundaries in these materials have nanoscale spatial dimensions, which can generate substantial resistance to ionic transport due to dopant segregation. Here, we report the concept of targeted phase formation in a Ce0.8Gd0.2O2₋δ–CoFe2O4 composite that serves to enhance the grain boundary ionic conductivity. Using transmission electron microscopy and spectroscopy approaches, we probe the grain boundary charge distribution and chemical environments altered by the phase reaction between the two constituents. The formation of an emergent phase successfully avoids segregation of the Gd dopant and depletion of oxygen vacancies at the Ce0.8Gd0.2O2₋δ–Ce0.8Gd0.2O2₋δ grain boundary. This results in superior grain boundary ionic conductivity as demonstrated by the enhanced oxygen permeation flux. Lastly, this work illustrates the control of mesoscale level transport properties in mixed ionic–electronic conductor composites through processing induced modifications of the grain boundary defect distribution.

  3. Unconventional ratiometric-enhanced optical sensing of oxygen by mixed-phase TiO2

    NASA Astrophysics Data System (ADS)

    Lettieri, S.; Pallotti, D. K.; Gesuele, F.; Maddalena, P.

    2016-07-01

    We show that mixed-phase titanium dioxide (TiO2) can be effectively employed as an unconventional, inorganic, dual-emitting, and ratiometric optical sensor of O2. Simultaneous availability of rutile and anatase TiO2 photoluminescence (PL) and their peculiar "anti-correlated" PL responses to O2 allow using their ratio as a measurement parameter associated with the O2 concentration, leading to an experimental responsivity being by construction larger than the one obtainable for single-phase PL detection. A proof of this concept is given, showing a two-fold enhancement of the optical responsivity provided by the ratiometric approach. Besides the peculiar ratiometric-enhanced responsivity, other characteristics of mixed phase TiO2 can be envisaged as favorable for O2 optical probing, namely (a) low production costs, (b) absence of heterogeneous components, and (c) self-supporting properties. These characteristics encourage experimenting with its use for applications requiring high indicator quantities at a competitive price, possibly also tackling the need to develop supporting matrixes that carry the luminescent probes and avoiding issues related to the use of different components for ratiometric sensing.

  4. Real-time edge-enhanced optical correlator

    NASA Technical Reports Server (NTRS)

    Liu, Tsuen-Hsi (Inventor); Cheng, Li-Jen (Inventor)

    1992-01-01

    Edge enhancement of an input image by four-wave mixing a first write beam with a second write beam in a photorefractive crystal, GaAs, was achieved for VanderLugt optical correlation with an edge enhanced reference image by optimizing the power ratio of a second write beam to the first write beam (70:1) and optimizing the power ratio of a read beam, which carries the reference image to the first write beam (100:701). Liquid crystal TV panels are employed as spatial light modulators to change the input and reference images in real time.

  5. Critical thinking instruction and technology enhanced learning from the student perspective: A mixed methods research study.

    PubMed

    Swart, Ruth

    2017-03-01

    Critical thinking is acclaimed as a valuable asset for graduates from higher education programs. Technology has advanced in quantity and quality; recognized as a requirement of 21st century learners. A mixed methods research study was undertaken, examining undergraduate nursing student engagement with critical thinking instruction, platformed on two technology-enhanced learning environments: a classroom response system face-to-face in-class and an online discussion forum out-of-class. The Community of Inquiry framed the study capturing constructivist collaborative inquiry to support learning, and facilitate critical thinking capability. Inclusion of quantitative and qualitative data sources aimed to gather a comprehensive understanding of students' development of critical thinking and engagement with technology-enhanced learning. The findings from the students' perspectives were positive toward the inclusion of technology-enhanced learning, and use in supporting their development of critical thinking. Students considered the use of two forms of technology beneficial in meeting different needs and preferences, offering varied means to actively participate in learning. They valued critical thinking instruction being intentionally aligned with subject-specific content facilitating understanding, application, and relevance of course material. While the findings are limited to student participants, the instructional strategies and technology-enhanced learning identified as beneficial can inform course design for the development of critical thinking.

  6. Enhanced SOA formation from mixed anthropogenic and biogenic emissions during the CARES campaign

    SciTech Connect

    Shilling, John E.; Zaveri, Rahul A.; Fast, Jerome D.; Kleinman, Lawrence I.; Alexander, M. L.; Canagaratna, Manjula R.; Fortner, Edward; Hubbe, John M.; Jayne, John T.; Sedlacek, Art; Setyan, Ari; Springston, S.; Worsnop, Douglas R.; Zhang, Qi

    2013-02-21

    The CARES campaign was conducted during June, 2010 in the vicinity of Sacramento, California to study aerosol formation and aging in a region where anthropogenic and biogenic emissions regularly mix. Here, we describe measurements from an Aerodyne High Resolution Aerosol Mass Spectrometer (AMS), an Ionicon Proton Transfer Reaction Mass Spectrometer (PTR-MS), and trace gas detectors (CO, NO, NOx) deployed on the G-1 research aircraft to investigate ambient gas- and particle-phase chemical composition. AMS measurements showed that the particle phase is dominated by organic aerosol (OA) (85% on average) with smaller concentrations of sulfate (5%), nitrate (6%) and ammonium (3%) observed. PTR-MS data showed that isoprene dominated the biogenic volatile organic compound concentrations (BVOCs), with monoterpene concentrations generally below the detection limit. Using two different metrics, median OA concentrations and the slope of plots of OA vs. CO concentrations (i.e., ΔOA/ΔCO), we contrast organic aerosol evolution on flight days with different prevailing meteorological conditions to elucidate the role of anthropogenic and biogenic emissions on OA formation. Airmasses influenced predominantly by biogenic emissions had median OA concentrations of 2.9 μg/m3 and near zero ΔOA/ΔCO. Those influenced predominantly by anthropogenic emissions had median OA concentrations of 4.7 μg/m3 and ΔOA/ΔCO ratios of 35 - 44 μg/m3ppmv. When biogenic and anthropogenic emissions mix, OA levels are dramatically enhanced with median OA concentrations of 11.4 μg/m3 and ΔOA/ΔCO ratios of 77 - 157 μg/m3ppmv. Taken together, our observations show that production of OA is enhanced when anthropogenic emissions from Sacramento mix with isoprene-rich air from the foothills. A strong, non-linear dependence of SOA yield from isoprene is the mechanistic explanation for this enhancement most consistent with both the gas- and particle-phase data. If these observations are found to be robust

  7. Optimum Mixed-State Discrimination for Noisy Entanglement-Enhanced Sensing

    NASA Astrophysics Data System (ADS)

    Zhuang, Quntao; Zhang, Zheshen; Shapiro, Jeffrey H.

    2017-01-01

    Quantum metrology utilizes nonclassical resources, such as entanglement or squeezed light, to realize sensors whose performance exceeds that afforded by classical-state systems. Environmental loss and noise, however, easily destroy nonclassical resources and, thus, nullify the performance advantages of most quantum-enhanced sensors. Quantum illumination (QI) is different. It is a robust entanglement-enhanced sensing scheme whose 6 dB performance advantage over a coherent-state sensor of the same average transmitted photon number survives the initial entanglement's eradication by loss and noise. Unfortunately, an implementation of the optimum quantum receiver that would reap QI's full performance advantage has remained elusive, owing to its having to deal with a huge number of very noisy optical modes. We show how sum-frequency generation (SFG) can be fruitfully applied to optimum multimode Gaussian-mixed-state discrimination. Applied to QI, our analysis and numerical evaluations demonstrate that our SFG receiver saturates QI's quantum Chernoff bound. Moreover, augmenting our SFG receiver with a feedforward (FF) mechanism pushes its performance to the Helstrom bound in the limit of low signal brightness. The FF-SFG receiver, thus, opens the door to optimum quantum-enhanced imaging, radar detection, state and channel tomography, and communication in practical Gaussian-state situations.

  8. Bandwidth enhancement of electro-optic field sensing using photonic down-mixing with harmonic sidebands.

    PubMed

    Lee, Dong-Joon; Whitaker, John F

    2008-09-15

    We demonstrate that harmonic sidebands of an electro-optic modulator's driving frequency can be used as the local oscillator in a photonic down-mixing process in order to significantly enhance the bandwidth of near-field, electro-optic, microwave measurements. The creation of second- and third-order-harmonic modulation sidebands on a laser-diode output are described, with heterodyne down-conversion of microwave signals taking place within an electro-optic sensor crystal. The measurement bandwidth of an electro-optic microwave probe can thus be enhanced by as much as a factor of three with respect to the use of conventional, fundamental-harmonic sidebands. Carrier-sideband analysis from the measured optical spectrum indicates that millimeter-wave-frequency local-oscillator sidebands can be created using a Ku-band electro-optic modulator and that the electro-optic-signal-modulation depth can be enhanced by suppressing the light-beam carrier component. Transverse near-field distributions from high frequency patch antennas are extracted using both second- and third-order-harmonic sidebands.

  9. Ice Formation and Growth in Orographically-Enhanced Mixed-Phase Clouds

    NASA Astrophysics Data System (ADS)

    David, Robert; Lowenthal, Douglas; Gannet Hallar, A.; McCubbin, Ian; Avallone, Linnea; Mace, Gerald; Wang, Zhien

    2015-04-01

    The formation and evolution of ice in mixed-phase clouds continues to be an active area of research due to the complex interactions between vapor, liquid and ice. Orographically-enhanced clouds are commonly mixed-phase during winter. An airborne study, the Colorado Airborne Mixed-Phase Cloud Study (CAMPS), and a ground-based field campaign, the Storm Peak Lab (SPL) Cloud Property Validation Experiment (StormVEx) were conducted in the Park Range of the Colorado Rockies. The CAMPS study utilized the University of Wyoming King Air (UWKA) to provide airborne cloud microphysical and meteorological data on 29 flights totaling 98 flight hours over the Park Range from December 15, 2010 to February 28, 2011. The UWKA was equipped with instruments that measured both cloud droplet and ice crystal size distributions, liquid water content, total water content (vapor, liquid, and ice), and 3-dimensional wind speed and direction. The Wyoming Cloud Radar and Lidar were also deployed during the campaign. These measurements are used to characterize cloud structure upwind and above the Park Range. StormVEx measured temperature, and cloud droplet and ice crystal size distributions at SPL. The observations from SPL are used to determine mountain top cloud microphysical properties at elevations lower than the UWKA was able to sample in-situ. Comparisons showed that cloud microphysics aloft and at the surface were consistent with respect to snow growth processes. Small ice crystal concentrations were routinely higher at the surface and a relationship between small ice crystal concentrations, large cloud droplet concentrations and temperature was observed, suggesting liquid-dependent ice nucleation near cloud base. Terrain flow effects on cloud microphysics and structure are considered.

  10. Enhanced biodegradation of alkane hydrocarbons and crude oil by mixed strains and bacterial community analysis.

    PubMed

    Chen, Yu; Li, Chen; Zhou, Zhengxi; Wen, Jianping; You, Xueyi; Mao, Youzhi; Lu, Chunzhe; Huo, Guangxin; Jia, Xiaoqiang

    2014-04-01

    In this study, two strains, Acinetobacter sp. XM-02 and Pseudomonas sp. XM-01, were isolated from soil samples polluted by crude oil at Bohai offshore. The former one could degrade alkane hydrocarbons (crude oil and diesel, 1:4 (v/v)) and crude oil efficiently; the latter one failed to grow on alkane hydrocarbons but could produce rhamnolipid (a biosurfactant) with glycerol as sole carbon source. Compared with pure culture, mixed culture of the two strains showed higher capability in degrading alkane hydrocarbons and crude oil of which degradation rate were increased from 89.35 and 74.32 ± 4.09 to 97.41 and 87.29 ± 2.41 %, respectively. In the mixed culture, Acinetobacter sp. XM-02 grew fast with sufficient carbon source and produced intermediates which were subsequently utilized for the growth of Pseudomonas sp. XM-01 and then, rhamnolipid was produced by Pseudomonas sp. XM-01. Till the end of the process, Acinetobacter sp. XM-02 was inhibited by the rapid growth of Pseudomonas sp. XM-01. In addition, alkane hydrocarbon degradation rate of the mixed culture increased by 8.06 to 97.41 % compared with 87.29 % of the pure culture. The surface tension of medium dropping from 73.2 × 10(-3) to 28.6 × 10(-3) N/m. Based on newly found cooperation between the degrader and the coworking strain, rational investigations and optimal strategies to alkane hydrocarbons biodegradation were utilized for enhancing crude oil biodegradation.

  11. Enhanced optical cycling and slowing of YO through rotational state microwave mixing

    NASA Astrophysics Data System (ADS)

    Yan, Bo; Hummon, Matthew; Yeo, Mark; Collopy, Alejandra; Hemmerling, Boerge; Chae, Eunmi; Anderegg, Loic; Ravi, Aakash; Doyle, John; Ye, Jun

    2015-05-01

    In order to address rotational dark states in the molecule yttrium (II) monoxide (YO) and to enhance optical cycling, we demonstrate the remixing of ground electronic state rotational levels using microwave radiation. This mixing technique, in conjunction with a broadband modulated and frequency chirped laser, is used to decelerate a beam of YO from a cryogenic buffer gas cell. The result is a population of molecules with velocities less than 10 m/s, which are sufficiently slow to be loaded into a magneto-optical trap. With two vibrational repump lasers, the cycling transition is closed to the 10-6 level. Additionally, we present progress towards a three dimensional implementation of a magneto-optical trap for YO. This work was supported in part by the Gordon and Betty Moore Foundation through Grant GBMF3852. We also acknowledge support from ARO, AFOSR (MURI), NIST, and NSF.

  12. Enhanced mixing of an axisymmetric jet by aerodynamic excitation. Final Report M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Raman, Ganesh

    1986-01-01

    The main objective of acoustic excitation studies is to gain a high level of control over processes governing free shear flow characteristics. The basic premise is that inherent instability waves in free shear flows are excitable by external perturbations with frequencies close to the natural instability frequency of the flow. An 8.89 cm diameter axisymmetric jet was acoustically excited by four loudspeakers placed upstream of the nozzle exit. Measurements were made at Mach numbers of 0.435 and 0.2. A single hot-wire probe was used to obtain turbulence levels at the nozzle exit and along the centerline, and a microphone at the nozzle exit was used to study the resonance characteristics of the rig. A Pitot probe was stationed at X/D = 9 downstream along the nozzle axis to study the Strouhal number dependence and to look at threshold levels for excitation. The test results were obtained after a preliminary evaluation and facility improvement. Excitation at the correct Strouhal number enhanced mixing significantly. The effects were most prominent in the Strouhal number range between 0.4 and 1.0. The effects of acoustic excitation also depend considerably on the sound pressure level at the nozzle exit and were more pronounced at higher sound levels. Other factors which influenced the excitability were valve noise, exit turbulence levels, extraneous noise, and a flanged nozzle. Analysis of the hot-wire signal, in conditions of optimum jet mixing, showed vortex pairing to occur between 2 and 3 diameters downstream.

  13. Vertically oriented Ti-Pd mixed oxynitride nanotube arrays for enhanced photoelectrochemical water splitting.

    PubMed

    Allam, Nageh K; Poncheri, Adam J; El-Sayed, Mostafa A

    2011-06-28

    In recent years, considerable efforts have been made to design and discover photoactive nanostructured materials that can be used as anodes in water photoelectrolysis cells. Herein, we report on the growth of a novel photoanode material composed of self-ordered, vertically oriented nanotube arrays of titanium-palladium mixed oxynitride films via anodization of Ti-Pd alloy in an electrolyte solution of formamide containing NH(4)F at room temperature, followed by annealing in an ammonia atmosphere. The nanostructure topology was found to depend on both the anodization time and the applied voltage. Our results demonstrate the ability to grow mixed oxynitride nanotube array films that are several micrometers thick. The Ti-Pd oxynitride nanotube array films were utilized in solar-spectrum water photoelectrolysis, demonstrating a photocurrent density of 1.9 mA/cm(2) and a ∼5-fold increase in the photoconversion efficiency under AM 1.5 illumination (100 mW/cm(2), 1.0 M KOH) compared to pure TiO(2) nanotubes fabricated and tested under the same conditions. The obtained efficiency is among the highest reported values for a TiO(2) nanotube-based photoelectrochemical cell. This enhancement in the photoconversion efficiency is related to the synergistic effects of Pd alloying, nitrogen doping, and the unique structural properties of the fabricated nanotube arrays.

  14. Mixing enhancement of an axisymmetric jet using flaplets with zero mass-flux excitation

    NASA Astrophysics Data System (ADS)

    Müller-Vahl, Hanns; Nayeri, Christian Navid; Paschereit, Christian Oliver; Greenblatt, David

    2015-02-01

    A novel active control concept aimed at mixing enhancement of an axisymmetric incompressible jet was investigated experimentally. The lip of the jet was equipped with evenly distributed small flaps, or flaplets, deflected away from the stream at an angle of 30°. Controlled attachment of the jet's boundary layer to the flaps was achieved by introducing zero mass-flux perturbations through control slots located at the base of the flaps, yielding a radial deflection of the shear layer. As a result, pairs of strong streamwise vortices of a finite length were periodically generated and shed in phase with the control signal. At a Strouhal number of 0.3 based on the nozzle diameter, the perturbations also regulated the shedding of spanwise vortex rings. Hot-wire measurements in the vicinity of the flaplets as well as phase-averaged stereoscopic PIV measurements at various streamwise locations were employed to elucidate the mechanism of controlled attachment and to map the evolution of the coherent structures. The strength of axial vorticity was strongly dependent upon the control frequency. A semiempirical framework adopted to quantify the overall effect of control predicted a significant increase in mixing in the region close to the nozzle.

  15. Lysophosphatidylcholine enhances carotenoid uptake from mixed micelles by Caco-2 human intestinal cells.

    PubMed

    Sugawara, T; Kushiro, M; Zhang, H; Nara, E; Ono, H; Nagao, A

    2001-11-01

    Despite the interest in the beneficial roles of dietary carotenoids in human health, little is known about their solubilization from foods to mixed bile micelles during digestion and the intestinal uptake from the micelles. We investigated the absorption of carotenoids solubilized in mixed micelles by differentiated Caco-2 human intestinal cells, which is a useful model for studying the absorption of dietary compounds by intestinal cells. The micelles were composed of 1 micromol/L carotenoids, 2 mmol/L sodium taurocholate, 100 micromol/L monoacylglycerol, 33.3 micromol/L fatty acid and phospholipid (0-200 micromol/L). The phospholipid content of micelles had profound effects on the cellular uptake of carotenoids. Uptake of micellar beta-carotene and lutein was greatly suppressed by phosphatidylcholine (PC) in a dose-dependent manner, whereas lysophosphatidylcholine (lysoPC), the lipolysis product of PC by phospholipase A2 (PLA2), markedly enhanced both beta-carotene and lutein uptake. The addition of PLA2 from porcine pancreas to the medium also enhanced the uptake of carotenoids from micelles containing PC. Caco-2 cells could take up 15 dietary carotenoids, including epoxy carotenoids, such as violaxanthin, neoxanthin and fucoxanthin, from micellar carotenoids, and the uptakes showed a linear correlation with their lipophilicity, defined as the distribution coefficient in 1-octanol/water (log P(ow)). These results suggest that pancreatic PLA2 and lysoPC are important in regulating the absorption of carotenoids in the digestive tract and support a simple diffusion mechanism for carotenoid absorption by the intestinal epithelium.

  16. Enhanced nonlinear optical characteristics of copper-ion-doped double crossover DNAs

    NASA Astrophysics Data System (ADS)

    Park, Byeongho; Lee, Byung Jic; Dugasani, Sreekantha Reddy; Cho, Youngho; Kim, Chulki; Seo, Minah; Lee, Taikjin; Jhon, Young Min; Choi, Jaebin; Lee, Seok; Park, Sung Ha; Jun, Seong Chan; Yeom, Dong-Il; Rotermund, Fabian; Kim, Jae Hun

    2015-10-01

    The modification of deoxyribonucleic acid (DNA) samples by sequencing the order of bases and doping copper ions opens the possibility for the design of novel nanomaterials exhibiting large optical nonlinearity. We investigated the nonlinear characteristics of copper-ion doped double crossover DNA samples for the first time to the best of our knowledge by using Z-scan and four-wave mixing methods. To accelerate the nonlinear characteristics, we prepared two types of unique DNA nanostructures composed of 148 base pairs doped with copper ions with a facile annealing method. The outstanding third-order nonlinear optical susceptibility of the copper-ion-doped DNA solution, 1.19 × 10-12 esu, was estimated by the conventional Z-scan measurement, whereas the four-wave mixing experiment was also investigated. In the visible spectral range, the copper-ion-doped DNA solution samples provided competent four-wave mixing signals with a remarkable conversion efficiency of -4.15 dB for the converted signal at 627 nm. The interactions between DNA and copper ions contribute to the enhancement of nonlinearity due to structural and functional changes. The present study signifies that the copper-ion-doped double crossover DNA is a potential candidate as a highly efficient novel material for further nonlinear optical applications.

  17. Culturing oil sands microbes as mixed species communities enhances ex situ model naphthenic acid degradation

    PubMed Central

    Demeter, Marc A.; Lemire, Joseph A.; Yue, Gordon; Ceri, Howard; Turner, Raymond J.

    2015-01-01

    Oil sands surface mining for bitumen results in the formation of oil sands process water (OSPW), containing acutely toxic naphthenic acids (NAs). Potential exists for OSPW toxicity to be mitigated by aerobic degradation of the NAs by microorganisms indigenous to the oil sands tailings ponds, the success of which is dependent on the methods used to exploit the metabolisms of the environmental microbial community. Having hypothesized that the xenobiotic tolerant biofilm mode-of-life may represent a feasible way to harness environmental microbes for ex situ treatment of OSPW NAs, we aerobically grew OSPW microbes as single and mixed species biofilm and planktonic cultures under various conditions for the purpose of assaying their ability to tolerate and degrade NAs. The NAs evaluated were a diverse mixture of eight commercially available model compounds. Confocal microscopy confirmed the ability of mixed and single species OSPW cultures to grow as biofilms in the presence of the NAs evaluated. qPCR enumeration demonstrated that the addition of supplemental nutrients at concentrations of 1 g L-1 resulted in a more numerous population than 0.001 g L-1 supplementation by approximately 1 order of magnitude. GC-FID analysis revealed that mixed species cultures (regardless of the mode of growth) are the most effective at degrading the NAs tested. All constituent NAs evaluated were degraded below detectable limits with the exception of 1-adamantane carboxylic acid (ACA); subsequent experimentation with ACA as the sole NA also failed to exhibit degradation of this compound. Single species cultures degraded select few NA compounds. The degradation trends highlighted many structure-persistence relationships among the eight NAs tested, demonstrating the effect of side chain configuration and alkyl branching on compound recalcitrance. Of all the isolates, the Rhodococcus spp. degraded the greatest number of NA compounds, although still less than the mixed species cultures

  18. Enhanced photodegradation of pentachlorophenol by single and mixed nonionic and anionic surfactants using graphene-TiO₂ as catalyst.

    PubMed

    Zhang, Yaxin; He, Xin; Zeng, Guangming; Chen, Tan; Zhou, Zeyu; Wang, Hongtao; Lu, Wenjing

    2015-11-01

    The photodegradation of pentachlorophenol (PCP) in a surfactant-containing (single and mixed) complex system using graphene-TiO2 (GT) as catalyst was investigated. The objective was to better understand the behavior of surfactants in a GT catalysis system for its possible use in remediation technology of soil contaminated by hydrophobic organic compounds (HOCs). In a single-surfactant system, surfactant molecules aggregated on GT via hydrogen bonding and electrostatic force; nonideal mixing between nonionic and anionic surfactants rendered GT surface with mixed admicelles in a mixed surfactant system. Both effects helped incorporating PCP molecules into surfactant aggregates on catalyst surface. Hence, the targeted pollutants were rendered easily available to photo-yielded oxidative radicals, and photodegradation efficiency was significantly enhanced. Finally, real soil washing-photocatalysis trials proved that anionic-nonionic mixed surfactant soil washing coupled with graphene-TiO2 photocatalysis can be one promising technology for HOC-polluted soil remediation.

  19. Organosilane modified silica/polydimethylsiloxane mixed matrix membranes for enhanced propylene/nitrogen separation

    NASA Astrophysics Data System (ADS)

    Beltran, Arnel B.; Nisola, Grace M.; Cho, Eulsaeng; Lee, Erli Eros D.; Chung, Wook-Jin

    2011-10-01

    Gas transport behaviors of oxygen (O 2), nitrogen (N 2) and propylene (C 3H 6) in polydimethylsiloxane (PDMS) mixed matrix membranes (MMM) containing modified silica (SiO 2) nanoparticles are presented. Two surface modified SiO 2 nanoparticles, silica dimethyloctyl silane (Si-DMOS) and silica dimethylphenyl silane (Si-DMPS), were used as fillers. Surface modification was carried out through silanization, which was confirmed via Fourier transform infrared spectroscopy. From elemental analysis, degrees of modifications on Si-DMOS and Si-DMPS were estimated to be 29.64% and 79.89%, respectively. Field emission scanning electron microscopy showed uniform distribution of the modified SiO 2 fillers in MMMs. Both MMMs exhibited reduced O 2 and N 2 permeabilities as compared to pure PDMS, while enhanced C 3H 6 permeabilities were observed. Consequently, C 3H 6/N 2 permselectivities were increased by 35 and 44% in MMMs filled with Si-DMOS and Si-DMPS, respectively. Results revealed that permeability was dependent on penetrant diffusivities, a parameter related to the structure of MMMs. Density measurements and differential scanning calorimetry were performed to elucidate the changes in MMM properties which affected the permeation behaviors of O 2, N 2 and C 3H 6. Overall, both Si-DMOS and Si-DMPS show potential as fillers for the enhancement of PDMS permeation performance.

  20. Secondary flows enhance mixing in a model of vibration-assisted dialysis

    NASA Astrophysics Data System (ADS)

    Pitre, John; Mueller, Bruce; Lewis, Susan; Bull, Joseph

    2014-11-01

    Hemodialysis is an integral part of treatment for patients with end stage renal disease. While hemodialysis has traditionally been described as a diffusion-dominated process, recent in vitro work has shown that vibration of the dialyzer can enhance the clearance of certain solutes during treatment. We hypothesize that the addition of vibration generates secondary flows in the dialysate compartment. These flows, perpendicular to the longitudinal axis of the dialysis fibers, advect solute away from the fiber walls, thus maintaining a larger concentration gradient and enhancing diffusion. Using the finite element method, we simulated the flow of dialysate through a hexagonally-packed array of cylinders and the transport of solute away from the cylinder walls. The addition of vibration was modeled using sinusoidal body forces of various frequencies and amplitudes. Using the variance of the concentration field as a metric, we found that vibration improves mixing according to a power law dependency on frequency. We will discuss the implications of these computational results on our understanding of the in vitro experiments and propose optimal vibration patterns for improving clearance in dialysis treatments. This work was supported by the Michigan Institute for Clinical and Health Research and NIH Grant UL1TR000433.

  1. Enhancement of passive Q-switching performance with mixed Nd:LuxGd1-xVO4 laser crystals.

    PubMed

    Yu, Haohai; Zhang, Huaijin; Wang, Zhengping; Wang, Jiyang; Yu, Yonggui; Shao, Zongshu; Jiang, Minhua

    2007-08-01

    Passive Q-switching operation has been demonstrated with a class of mixed Nd:Lu(x)Gd(1-x)VO(4) laser crystals. With respect to that obtained with Nd:GdVO(4), the passive Q-switching performance, including threshold, pulse energy, and peak power, was found to be greatly enhanced with the mixed vanadate crystals. The shortest pulse width of 6.2 ns, largest pulse energy of 192.5 microJ, and highest peak power of 31.1 kW were obtained at the incident pump power of 13.75 W with the mixed crystal for x=0.5.

  2. Deoxycholic acid-modified chitooligosaccharide/mPEG-PDLLA mixed micelles loaded with paclitaxel for enhanced antitumor efficacy.

    PubMed

    Jiang, Chengjun; Wang, Hangxiang; Zhang, Xiaomin; Sun, Zhibin; Wang, Feng; Cheng, Jun; Xie, Haiyang; Yu, Bo; Zhou, Lin

    2014-11-20

    Poly(ethylene glycol) (PEG) as a block in polymeric micelles can prolong circulation life and reduce systemic clearance but decrease the cellular uptake. To overcome this limitation, a mixed micelle composed of deoxycholic acid-modified chitooligosaccharide (COS-DOCA) and methoxy poly(ethylene glycol)-polylactide copolymer (mPEG-PDLLA) was designed to load paclitaxel (PTX). The PTX-loaded mixed micelles was prepared by nanoprecipitation method with high drug-loading efficiency of 8.03% and encapsulation efficiency of 97.09% as well as small size (∼40 nm) and narrow size distribution. COS-DOCA/mPEG-PDLLA mixed micelles exhibited the sustained release property. Due to the positive charge and bioadhesive property of COS-DOCA, the cellular uptake of PTX in mixed micelles was higher in cancer cells but lower in macrophage cells compared to the mPEG-PDLLA micelles. The systemic toxicity of PTX in mixed micelles was much lower than Taxol using zebrafish as a toxicological model. Furthermore, the PTX-loaded COS-DOCA/mPEG-PDLLA mixed micelles can prolong the blood circulation time of PTX and enhance the antitumor efficacy in A549 lung xenograft model. Our findings indicate that COS-DOCA/mPEG-PDLLA mixed micelles could be a potential vehicle for enhanced delivery of anticancer drugs.

  3. Enhancing plant-microbe associated bioremediation of phenanthrene and pyrene contaminated soil by SDBS-Tween 80 mixed surfactants.

    PubMed

    Ni, Hewei; Zhou, Wenjun; Zhu, Lizhong

    2014-05-01

    The use of surfactants to enhance plant-microbe associated dissipation in soils contaminated with polycyclic aromatic hydrocarbons (PAHs) is a promising bioremediation technology. This comparative study was conducted on the effects of plant-microbe treatment on the removal of phenanthrene and pyrene from contaminated soil, in the presence of low concentration single anionic, nonionic and anionic-nonionic mixed surfactants. Sodium dodecyl benzene sulfonate (SDBS) and Tween 80 were chosen as representative anionic and nonionic surfactants, respectively. We found that mixed surfactants with concentrations less than 150 mg/kg were more effective in promoting plant-microbe associated bioremediation than the same amount of single surfactants. Only about (m/m) of mixed surfactants was needed to remove the same amount of phenanthrene and pyrene from either the planted or unplanted soils, when compared to Tween 80. Mixed surfactants (< 150 mg/kg) better enhanced the degradation efficiency of phenanthrene and pyrene via microbe or plant-microbe routes in the soils. In the concentration range of 60-150 mg/kg, both ryegrass roots and shoots could accumulate 2-3 times the phenanthrene and pyrene with mixed surfactants than with Tween 80. These results may be explained by the lower sorption loss and reduced interfacial tension of mixed surfactants relative to Tween 80, which enhanced the bioavailability of PAHs in soil and the microbial degradation efficiency. The higher remediation efficiency of low dosage SDBS-Tween 80 mixed surfactants thus advanced the technology of surfactant-enhanced plant-microbe associated bioremediation.

  4. Étalon enhancement of nonlinear optical response in Bi1 - xSbx

    NASA Astrophysics Data System (ADS)

    Youngdale, E. R.; Meyer, J. R.; Hoffman, C. A.; Bartoli, F. J.; Partin, D. L.; Thrush, C. M.; Heremans, J. P.

    1991-08-01

    Measurements of the nondegenerate four-wave mixing of CO2 laser beams in a Bi1-xSbx film have yielded the largest high-power third-order nonlinear susceptibilities ever reported at that wavelength (χ(3)≳6×10-4 esu at P0≳2×105 W/cm2). Furthermore, an étalon effect resulting from the high reflectivity of the Bi1-xSbx films at both the air and substrate interfaces leads to an additional enhancement of the four-wave signal by as much as a factor of 30. A theoretical model based on optical modulation of the free-carrier susceptibility gives results which are in excellent agreement with the data.

  5. Evidence for enhanced mixing on the super-meteoritic Li-rich red giant HD 233517

    NASA Astrophysics Data System (ADS)

    Strassmeier, K. G.; Carroll, T. A.; Weber, M.; Granzer, T.

    2015-02-01

    Context. HD 233517 is among the most Li-rich stars in the sky. It is a rapidly rotating, single K giant thought to be on its first ascent on the red giant branch. The star has also the highest known infrared excess among any of the known first-ascent giants. Aims: We revisit the physical parameters of the system and aim to map its surface temperature distribution. Methods: New time-series photometry and high-resolution spectroscopy were obtained with our robotic facilities STELLA and Amadeus Automatic Photoelectric Telescope (APT) in 2007-2011. Inverse line-profile modelling is performed on a total of 167 échelle spectra and six Doppler images are presented. Results: Light and radial-velocity variations suggest a stellar rotation period of 47.6±0.3 d. The atmospheric parameters agree with previous studies and verify a super-meteoritic log 7Li abundance of 4.29±0.10 with undetected 6Li, while the metals are generally deficient by -0.4 dex with respect to the Sun. We determine a lower than normal isotopic carbon ratio of 12C/13C = 9+4-2. Our Doppler images indicate warm and cool spots with an average temperature contrast of just ±65 K with respect to the effective temperature. Doppler maps from Li i 670.78 reveal practically identical surface morphology, with a higher average contrast of ±160 K and errors that are five times larger. Reconstructions with simultaneously 1617 and 3007 spectral lines showed both a signal degradation with respect to our 56-line final image. An error analysis indicates an average temperature error per surface pixel of just ±4 K. Conclusions: HD 233517 appears to be an old (≈10-Gyr) single 0.95-M⊙ giant currently undergoing mild mass loss in the form of a wind. The cool and warm photospheric features are interpreted to be merely locations of suppressed and enhanced convection, respectively, probably intermingled by a yet undetected weak magnetic field. The low carbon-isotope ratio is indicative of extra mixing rather than of an

  6. Research on identification and determination of mixed pesticides in apples using surface enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhai, Chen; Li, Yongyu; Peng, Yankun; Xu, Tianfeng; Dhakal, Sagar; Chao, Kuanglin; Qin, Jianwei

    2015-05-01

    Residual pesticides in fruits and vegetables have become one of the major food safety concerns around the world. At present, routine analytical methods used for the determination of pesticide residue on the surface of fruits and vegetables are destructive, complex, time-consuming, high cost and not environmentally friendly. In this study, a novel Surface Enhanced Raman Spectroscopy (SERS) method with silver colloid was developed for fast and sensitive nondestructive detection of residual pesticides in fruits and vegetables by using a self-developed Raman system. SERS technology is a combination of Raman spectroscopy and nanotechnology. SERS can greatly enhance the Raman signal intensity, achieve single-molecule detection, and has a simple sample pre-treatment characteristic of high sensitivity and no damage; in recent years it has begun to be used in food safety testing research. In this study a rapid and sensitive method was developed to identify and analyze mixed pesticides of chlorpyrifos, deltamethrin and acetamiprid in apple samples by SERS. Silver colloid was used for SERS measurement by hydroxylamine hydrochloride reduced. The advantages of this method are seen in its fast preparation at room temperature, good reproducibility and immediate applicability. Raman spectrum is highly interfered by noise signals and fluorescence background, which make it too complex to get good result. In this study the noise signals and fluorescence background were removed by Savitzky-Golay filter and min-max signal adaptive zooming method. Under optimal conditions, pesticide residues in apple samples can be detected by SERS at 0.005 μg/cm2 and 0.002 μg/cm2 for individual acetamiprid and thiram, respectively. When mixing the two pesticides at low concentrations, their characteristic peaks can still be identified from the SERS spectrum of the mixture. Based on the synthesized material and its application in SERS operation, the method represents an ultrasensitive SERS performance

  7. Enhanced Solar Energy Absorption by Internally-mixed Black Carbon in Snow Grains

    SciTech Connect

    Flanner, M. G.; Liu, Xiaohong; Zhou, Cheng; Penner, Joyce E.; Jiao, C.

    2012-05-30

    Here we explore light absorption by snowpack containing black carbon (BC) particles residing within ice grains. Basic considerations of particle volumes and BC/snow mass concentrations show that there are generally 0:05-109 BC particles for each ice grain. This suggests that internal BC is likely distributed as multiple inclusions within ice grains, and thus the dynamic effective medium approximation (DEMA) (Chylek and Srivastava, 1983) is a more appropriate optical representation for BC/ice composites than coated-sphere or standard mixing approximations. DEMA calculations show that the 460 nm absorption cross-section of BC/ice composites, normalized to the mass of BC, is typically enhanced by factors of 1.8-2.1 relative to interstitial BC. BC effective radius is the dominant cause of variation in this enhancement, compared with ice grain size and BC volume fraction. We apply two atmospheric aerosol models that simulate interstitial and within-hydrometeor BC lifecycles. Although only {approx}2% of the atmospheric BC burden is cloud-borne, 71-83% of the BC deposited to global snow and sea-ice surfaces occurs within hydrometeors. Key processes responsible for within-snow BC deposition are development of hydrophilic coatings on BC, activation of liquid droplets, and subsequent snow formation through riming or ice nucleation by other species and aggregation/accretion of ice particles. Applying deposition fields from these aerosol models in offline snow and sea-ice simulations, we calculate that 32-73% of BC in global surface snow resides within ice grains. This fraction is smaller than the within-hydrometeor deposition fraction because meltwater flux preferentially removes internal BC, while sublimation and freezing within snowpack expose internal BC. Incorporating the DEMA into a global climate model, we simulate increases in BC/snow radiative forcing of 43-86%, relative to scenarios that apply external optical properties to all BC. We show that snow metamorphism

  8. Possibility of Enhancement of Amplitude-Squared Squeezing in Mixing with Coherent Light Beam Using a Mach-Zehnder Interferometer

    NASA Astrophysics Data System (ADS)

    Mishra, D. K.

    2007-11-01

    Possibility of enhancement of amplitude-squared squeezing for Mach-Zehnder interferometer is investigated and it is found that the maximum amount of amplitude-squared squeezing obtained by the present mixing is not greater than that obtained by Prakash and Mishra.

  9. Evaluation of aroma enhancement for "Ecolly" dry white wines by mixed inoculation of selected Rhodotorula mucilaginosa and Saccharomyces cerevisiae.

    PubMed

    Wang, Xing-Chen; Li, Ai-Hua; Dizy, Marta; Ullah, Niamat; Sun, Wei-Xuan; Tao, Yong-Sheng

    2017-08-01

    To improve the aroma profile of Ecolly dry white wine, the simultaneous and sequential inoculations of selected Rhodotorula mucilaginosa and Saccharomyces cerevisiae were performed in wine making of this work. The two yeasts were mixed in various ratios for making the mixed inoculum. The amount of volatiles and aroma characteristics were determined the following year. Mixed fermentation improved both the varietal and fermentative aroma compound composition, especially that of (Z)-3-hexene-1-ol, nerol oxide, certain acetates and ethyls group compounds. Citrus, sweet fruit, acid fruit, berry, and floral aroma traits were enhanced by mixed fermentation; however, an animal note was introduced upon using higher amounts of R. mucilaginosa. Aroma traits were regressed with volatiles as observed by the partial least-square regression method. Analysis of correlation coefficients revealed that the aroma traits were the multiple interactions of volatile compounds, with the fermentative volatiles having more impact on aroma than varietal compounds.

  10. Increase of fruity aroma during mixed T. delbrueckii/S. cerevisiae wine fermentation is linked to specific esters enhancement.

    PubMed

    Renault, Philippe; Coulon, Joana; de Revel, Gilles; Barbe, Jean-Christophe; Bely, Marina

    2015-08-17

    The aim of this work was to study ester formation and the aromatic impact of Torulaspora delbrueckii when used in association with Saccharomyces cerevisiae during the alcoholic fermentation of must. In order to evaluate the influence of the inoculation procedure, sequential and simultaneous mixed cultures were carried out and compared to pure cultures of T. delbrueckii and S. cerevisiae. Our results showed that mixed inoculations allowed the increase, in comparison to S. cerevisiae pure culture, of some esters specifically produced by T. delbrueckii and significantly correlated to the maximal T. delbrueckii population reached in mixed cultures. Thus, ethyl propanoate, ethyl isobutanoate and ethyl dihydrocinnamate were considered as activity markers of T. delbrueckii. On the other hand, isobutyl acetate and isoamyl acetate concentrations were systematically increased during mixed inoculations although not correlated with the development of either species but were rather due to positive interactions between these species. Favoring T. delbrueckii development when performing sequential inoculation enhanced the concentration of esters linked to T. delbrueckii activity. On the contrary, simultaneous inoculation restricted the growth of T. delbrueckii, limiting the production of its activity markers, but involved a very important production of numerous esters due to more important positive interactions between species. These results suggest that the ester concentrations enhancement via interactions during mixed modalities was due to S. cerevisiae production in response to the presence of T. delbrueckii. Finally, sensory analyses showed that mixed inoculations between T. delbrueckii and S. cerevisiae allowed to enhance the complexity and fruity notes of wine in comparison to S. cerevisiae pure culture. Furthermore, the higher levels of ethyl propanoate, ethyl isobutanoate, ethyl dihydrocinnamate and isobutyl acetate in mixed wines were found responsible for the increase of

  11. Enhancing distributive mixing of immiscible polyethylene/thermoplastic starch blend through zeolite ZSM-5 compounding sequence.

    PubMed

    Thipmanee, Ranumas; Lukubira, Sam; Ogale, Amod A; Sane, Amporn

    2016-01-20

    The aim of this work was to explore the effect of zeolite ZSM-5 (ZSM5) incorporation sequence on the phase morphology, microstructure, and performance of polyethylene/thermoplastic starch (PE/TPS) films. Two processing sequences were used for preparing PE/TPS/ZSM5 composites at a weight ratio of PE to TPS of 70:30 and ZSM5 concentrations of 1-5 wt%: (i) melt compounding of PE with ZSM5 prior to melt blending with TPS (SI); and (ii) TPS was compounded with ZSM5 prior to blending with PE (SII). Distributive mixing and mechanical properties of PE/TPS blend were greatly enhanced when ZSM5 was incorporated via SII. These were caused by both the higher affinity between PE and ZSM5, compared to that of TPS and ZSM5, and the reduction of TPS viscosity after compounding with ZSM5, leading to migration of ZSM5 from TPS dispersed phase toward PE matrix and increase in breakup of TPS droplets during SII sequence.

  12. Enhancement effect of silver nanoparticles on fermentative biohydrogen production using mixed bacteria.

    PubMed

    Zhao, Wei; Zhang, Yongfang; Du, Bin; Wei, Dong; Wei, Qin; Zhao, Yanfang

    2013-08-01

    Silver nanoparticles were added into anaerobic batch reactors to enhance acidogenesis and fermentative hydrogen production simultaneously. The effects of silver nanoparticles concentration (0-200 nmol L(-1)) and inorganic nitrogen concentration (0-4.125 g L(-1)) on cell growth and hydrogen production were investigated using glucose-fed mixed bacteria dominated by Clostridium butyricum. The tests with silver nanoparticles exhibited much higher H2 yields than the blank, and the maximum hydrogen yield (2.48 mol/mol glucose) was obtained at the silver concentration of 20 nmol L(-1). Presence of silver nanoparticles reduced the yield of ethanol, but increased the yield of acetic acid. The high silver nanoparticles had higher cell biomass production rate. Further study using the alkaline pretreated culture as inoculum was carried out to verify the positive effect of silver nanoparticles on H2 production. Results demonstrated that silver nanoparticles could not only increase the hydrogen yield, but reduce the lag phase for hydrogen production simultaneously.

  13. Energy enhancement of mixed Nd:LuYSGG crystal in passively Q-switched lasers.

    PubMed

    Wang, Baolin; Tian, Li; Yu, Haohai; Zhang, Huaijin; Wang, Jiyang

    2015-07-01

    The continuous-wave (cw) and passively Q-switched laser performances of mixed Nd:Lu(2)YSc(1.5)Ga(3.5)O(12) (Nd:LuYSGG) crystal at 1.06 μm were reported for the first time. The cw output power reached 4.39 W at the absorbed pump power of 10.34 W with slope efficiency of 48.0%. With a Cr(4+):YAG crystal as both the saturable absorber and output coupler, a passively Q-switched laser was realized with the maximum average output power of 1.43 W and slope efficiency of 21.0%. The shortest pulse width, largest pulse energy, and highest peak power were 4.1 ns, 157.1 μJ, and 38.3 kW, respectively. Compared with Nd:Lu(3)Sc(1.5)Ga(3.5)O(12) (Nd:LuSGG) crystal, the pulse energy and peak power are enhanced over more than two times for Nd:LuYSGG. The results show that Nd:LuYSGG crystal is a promising laser material with large energy storage capacities and suitable for the application of pulsed lasers with shorter pulses and larger energies.

  14. Closed-loop enhancement of jet mixing with extremum-seeking and physics-based strategies

    NASA Astrophysics Data System (ADS)

    Wu, Z.; Zhou, Y.; Cao, H. L.; Li, W. J.

    2016-06-01

    The closed-loop control of a turbulent round air jet is experimentally investigated based on two unsteady minijets, with a view to enhancing jet mixing. The two minijets are placed at diametrically opposite locations upstream of the nozzle exit. The open-loop control experiments are first performed. Given the mass flow rate ratio C m of the minijets to that of the main jet, the decay rate overline{K} of jet centerline mean velocity exhibits a maximum at the frequency ratio f e/ f 0 ≈ 1.0, where f e and f 0 are the excitation frequency of minijets and the preferred mode frequency of the natural main jet, respectively. An extremum-seeking feedback control has been developed to achieve autonomously the optimal control performance. It has been found that, given C m, this closed-loop control technique may obtain automatically and rapidly the optimal value of f e and the desired or maximum overline{K}, as achieved in the open-loop control. This control technique is robust and adaptable when the Reynolds number and initial excitation frequency are changed separately. A flow-physics-based feedback control strategy has also been investigated, which could achieve the optimal control performance automatically with a shorter convergence time than the extremum-seeking control, not robust though.

  15. Synthesizing mixed phase titania nanocomposites with enhanced photoactivity and redshifted photoresponse by reactive DC magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Chen, Le

    Recent work points out the importance of the solid-solid interface in explaining the high photoactivity of mixed phase TiO2 catalysts. The goal of this research was to probe the synthesis-structure-function relationships of the solid-solid interfaces created by the reactive direct current (DC) magnetron sputtering of titanium dioxide. I hypothesize that the reactive DC magnetron sputtering is a useful method for synthesizing photo-catalysts with unique structure including solid-solid interfaces and surface defects that are associated with enhanced photoreactivity as well as a photoresponse shifted to longer wavelengths of light. I showed that sputter deposition provides excellent control of the phase and interface formation as well as the stoichiometry of the films. I explored the effects exerted by the process parameters of pressure, oxygen partial pressure, target power, substrate bias (RF), deposition incidence angle, and post annealing treatment on the structural and functional characteristics of the catalysts. I have successfully made pure and mixed phase TiO2 films. These films were characterized with UV-Vis, XPS, AFM, SEM, TEM, XRD and EPR, to determine optical properties, elemental stoichiometry, surface morphology, phase distribution and chemical coordination. Bundles of anatase-rutile nano-columns having high densities of dual-scale of interfaces among and within the columns are fabricated. Photocatalytic performance of the sputtered films as measured by the oxidation of the pollutant, acetaldehyde, and the reduction of CO2 for fuel (CH4) production was compared (normalized for surface area) to that of mixed phase TiO2 fabricated by other methods, including flame hydrolysis powders, and solgel deposited TiO 2 films. The sputtered mixed phase materials were far superior to the commercial standard (Degussa P25) and solgel TiO2 based on gas phase reaction of acetaldehyde oxidation under UV light and CO2 reduction under both UV and visible illuminations. The

  16. A two-dimensional numerical simulation of shock-enhanced mixing in a rectangular scramjet flowfield with parallel hydrogen injection

    SciTech Connect

    Domel, N.D.; Thompson, D.S. )

    1991-01-01

    The effect of shock impingement on the mixing and combustion of a reacting shear-layer is numerically simulated. Hydrogen fuel is injected at sonic velocity behind a backward facing step in a direction parallel to a supersonic freestream vitiated with H{sub 2}O. The two-dimensional Navier-Stokes equations are solved and explicitly coupled to a chemistry package employing a global, two-step combustion model. The results show that shock impingement enhances the mixing and combustion. 17 refs.

  17. Mesoporous mixed-phase Ga{sub 2}O{sub 3}: Green synthesis and enhanced photocatalytic activity

    SciTech Connect

    Liu, Jin; Zhang, Gaoke

    2015-08-15

    Highlights: • Mixed-phase Ga{sub 2}O{sub 3} was synthesized by a facile and green method. • Mixed-phase Ga{sub 2}O{sub 3} exhibited good photocatalytic activity and stability. • The reactive species in the photocatalytic process were investigated. - Abstract: Mesoporous mixed-phase Ga{sub 2}O{sub 3} was synthesized by calcining the GaOOH precursor. The composition, crystal phase and microstructures of Ga{sub 2}O{sub 3} were characterized in detail. The phase composition of the as-prepared Ga{sub 2}O{sub 3} depended on the calcination temperature and the mixed-phase Ga{sub 2}O{sub 3} was obtained at 600–700 °C. As compared to the pure-phase α-Ga{sub 2}O{sub 3} and β-Ga{sub 2}O{sub 3}, the mixed-phase Ga{sub 2}O{sub 3} exhibited an enhanced photocatalytic property for the degradation of metronidazole solution. The heterojunction in the mixed-phase Ga{sub 2}O{sub 3} was beneficial to the separation of photogenerated electrons and holes. Moreover, the mixed-phase Ga{sub 2}O{sub 3} possessed mesopore structure, which increased more reaction sites and was in favor of the contact of metronidazole molecules with reaction sites. The recycling experiments show that the mixed-phase Ga{sub 2}O{sub 3} has good stability and can be separated easily from the reaction system.

  18. Mixed-Mode Surveys: A Strategy to Reduce Costs and Enhance Response Rates

    ERIC Educational Resources Information Center

    Tobin, Daniel; Thomson, Joan; Radhakrishna, Rama; LaBorde, Luke

    2012-01-01

    Mixed-mode surveys present one opportunity for Extension to determine program outcomes at lower costs. In order to conduct a follow-up evaluation, we implemented a mixed-mode survey that relied on communication using the Web, postal mailings, and telephone calls. Using multiple modes conserved costs by reducing the number of postal mailings yet…

  19. Molecular organization and mixing in thin solid films of novel perylene tetracarboxylic dianhydride derivatives: Infrared and surface enhanced Raman studies

    NASA Astrophysics Data System (ADS)

    Kam, Alicia Patricia

    The present work focuses on the fabrication and spectroscopic characterization of submicron thin solid films of novel organic dyes. The synthesis, thin film fabrication, electronic and vibrational spectra of neat materials are described. The main group of organic dyes studied here are novel perylene tetracarboxylic derivatives. The fabrication of thin solid films on a variety of substrates is demonstrated and the long-range molecular organization in the films, extracted using mainly infrared techniques, is illustrated. The starting point in using vibrations as structural probes, is the vibrational assignments of the characteristic perylene tetracarboxylic fundamentals for each dye under study. The assigned vibrational spectra are employed as references to extract the molecular organization in the vacuum evaporated films using data from the complementary techniques: transmission infrared and reflection-absorption infrared spectroscopy. The understanding of the molecular organization opens the door to changing and controlling the molecular film structure with thermal annealing, and these studies are illustrated for bis(n-propylimido) perylene films. It is shown that reorientation can be induced in thin films of bisPTCD dye. The factors that may determine reorientation on thermal annealing are investigated. Surface-enhanced spectroscopic studies of metal island films coated with the dyes were carried out. The surface-enbanced vibrational spectroscopy (SEVS) used encompasses spectral data obtained from surface-enhanced Raman scattering (SERS), surface-enhanced-resonance Raman scattering- (SERRS) and surface-enhanced infrared (SEIR). The first systematic study of mixed thin solid films of PTDC materials and phthalocyanines, using vacuum co-evaporation, is presented. Mixed films of Perylene and phthalocyanine derivatives were fabricated and investigated using SERS, SERRS and SERRS imaging. It is demonstrated that SERRS global imaging is a powerful analytical tool that

  20. Helically agitated mixing in dry dilute acid pretreatment enhances the bioconversion of corn stover into ethanol

    PubMed Central

    2014-01-01

    Background Dry dilute acid pretreatment at extremely high solids loading of lignocellulose materials demonstrated promising advantages of no waste water generation, less sugar loss, and low steam consumption while maintaining high hydrolysis yield. However, the routine pretreatment reactor without mixing apparatus was found not suitable for dry pretreatment operation because of poor mixing and mass transfer. In this study, helically agitated mixing was introduced into the dry dilute acid pretreatment of corn stover and its effect on pretreatment efficiency, inhibitor generation, sugar production, and bioconversion efficiency through simultaneous saccharification and ethanol fermentation (SSF) were evaluated. Results The overall cellulose conversion taking account of cellulose loss in pretreatment was used to evaluate the efficiency of pretreatment. The two-phase computational fluid dynamics (CFD) model on dry pretreatment was established and applied to analyze the mixing mechanism. The results showed that the pretreatment efficiency was significantly improved and the inhibitor generation was reduced by the helically agitated mixing, compared to the dry pretreatment without mixing: the ethanol titer and yield from cellulose in the SSF reached 56.20 g/L and 69.43% at the 30% solids loading and 15 FPU/DM cellulase dosage, respectively, corresponding to a 26.5% increase in ethanol titer and 17.2% increase in ethanol yield at the same fermentation conditions. Conclusions The advantage of helically agitated mixing may provide a prototype of dry dilute acid pretreatment processing for future commercial-scale production of cellulosic ethanol. PMID:24387051

  1. Reaction enhancement in an unsteady obstacle wake: Implications for broadcast spawning and other mixing-limited processes in marine environments

    NASA Astrophysics Data System (ADS)

    Crimaldi, J. P.; Kawakami, T. R.

    2015-03-01

    Structured wakes behind flow obstacles are shown to be regions that enhance mixing and reactions between initially distant scalars, with implications for a wide range of mixing-limited biogeochemical processes in marine systems (e.g., broadcast spawning, phytoplankton-nutrient interactions). Reaction of initially distant reactive scalars in the structured laminar wake of a round obstacle is quantified using direct numerical simulations of the 2D Navier-Stokes and reactive transport equations with Reynolds number of 100 and Schmidt number of 1. Scalars are released upstream of the obstacle, initially separated by ambient fluid that acts as a barrier to mixing and reaction. Reaction is computed using second-order kinetics in the low-Damkholer limit. Reaction enhancement is quantified by comparing the obstacle-wake reactions to those in a similar flow but without the obstacle. Integrated reaction rates are shown to be orders of magnitude larger in the obstacle wake for cases with significant initial separation between the scalars. The role of unsteady processes in the reaction enhancement is also investigated by quantifying the scalar covariance in different regions of the wake.

  2. CFD Simulations of a Flow Mixing and Heat Transfer Enhancement in an Advanced LWR Nuclear Fuel Assembly

    SciTech Connect

    In, Wang-Kee; Chun, Tae-Hyun; Shin, Chang-Hwan; Oh, Dong-Seok

    2007-07-01

    A computational fluid dynamics (CFD) analysis has been performed to investigate a flow-mixing and heat-transfer enhancement caused by a mixing-vane spacer in a LWR fuel assembly which is a rod bundle. This paper presents the CFD simulations of a flow mixing and heat transfer in a fully heated 5x5 array of a rod bundle with a split-vane and hybrid-vane spacer. The CFD prediction at a low Reynolds number of 42,000 showed a reasonably good agreement of the initial heat transfer enhancement with the measured one for a partially heated experiment using a similar spacer structure. The CFD simulation also predicted the decay rate of a normalized Nusselt number downstream of the split-vane spacer which agrees fairly well with those of the experiment and the correlation. The CFD calculations for the split vane and hybrid vane at the LWR operating conditions(Re = 500,000) predicted hot fuel spots in a streaky structure downstream of the spacer, which occurs due to the secondary flow occurring in an opposite direction near the fuel rod. However, the split-vane and hybrid-vane spacers are predicted to significantly enhance the overall heat transfer of a LWR nuclear fuel assembly. (authors)

  3. An experimental investigation of mixing enhancement in a simulated scramjet combustor by use of swirling jets. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Kraus, Donna Karen

    1993-01-01

    It is desired to maintain supersonic flow through the combustor of supersonic airbreathing engines to reduce static temperatures and total pressure losses inherent in reducing flow to subsonic speeds. Due to the supersonic speeds through the combustor, mixing of the fuel and air must by rapid for complete combustion to occur within a reasonable streamwise distance. It was proposed that the addition of swirl to the fuel jet prior to injection might enhance the mixing of the fuel with the air. The effects of swirl on the mixing of a 30 deg wall jet into a Mach 2 flow were experimentally investigated. Swirl was introduced into the fuel stream by tangential injection into a cylindrical swirl chamber. The flow was then accelerated through a convergent-divergent nozzle with an area ratio of two, and supersonically injected into the Mach 2 flow such that the static pressure of the fuel matched the effective back pressure of the main flow. Two different cases with swirl and one without swirl were investigated, with both helium and air simulating the fuel. Rayleigh scattering was used to visualize the flow and seeding the fuel with water allowed it to be traced through the main flow. Using histograms of the pure molecular Rayleigh scattering images, the helium concentration in the jet-mixing region of the flow was monitored and found to decrease slightly with swirl, indicating better mixing. Thresholding the water-seeded images allowed the jet-mixing region to be isolated and showed a slight increase in this area with swirl. Penetration, however, was slightly less with swirl. Rescaling the data for equal mass flow rates allowed comparison for a scramjet application of a combustor with a single injector and the desire to fuel to a specified fuel-to-oxidant ratio. These results showed a substantial increase in the spreading area with swirl, an increase in the mixing occurring in this area, and slightly better penetration.

  4. Parametric Study of a Mixer/Ejector Nozzle with Mixing Enhancement Devices

    NASA Technical Reports Server (NTRS)

    DalBello, T.; Steffen, C. J., Jr.

    2001-01-01

    A numerical study employing a simplified model of the High Speed Civil Transport mixer/ejector nozzle has been conducted to investigate the effect of tabs (vortex generators) on the mixing process. More complete mixing of the primary and secondary flows within the confined ejector lowers peak exit velocity resulting in reduced jet noise. Tabs were modeled as vortex pairs and inserted into the computational model. The location, size, and number of tabs were varied and its effect on the mixing process is presented here both quantitatively and qualitatively. A baseline case (no tabs) along with six other cases involving two different vortex strengths at three different orientations have been computed and analyzed. The case with the highest vorticity (six vortices representing large tabs) gives the best mixing. It is shown that the influence of the vorticity acts primarily in the forward or middle portions of the duct, significantly alters the flow structure, and promotes some mixing in the lateral direction. Unmixed pockets were found at the top and bottom of the lobe, and more clever placement of tabs improved mixing in the vertical direction. The technique of replacing tabs with vortices shows promise as an efficient tool for quickly optimizing tab placement in lobed mixers.

  5. Microbiological-enhanced mixing across scales during in-situ bioreduction of metals and radionuclides at Department of Energy Sites

    SciTech Connect

    Valocchi, Albert; Werth, Charles; Liu, Wen-Tso; Sanford, Robert; Nakshatrala, Kalyan

    2015-10-20

    Bioreduction is being actively investigated as an effective strategy for subsurface remediation and long-term management of DOE sites contaminated by metals and radionuclides (i.e. U(VI)). These strategies require manipulation of the subsurface, usually through injection of chemicals (e.g., electron donor) which mix at varying scales with the contaminant to stimulate metal reducing bacteria. There is evidence from DOE field experiments suggesting that mixing limitations of substrates at all scales may affect biological growth and activity for U(VI) reduction. Although current conceptual models hold that biomass growth and reduction activity is limited by physical mixing processes, a growing body of literature suggests that reaction could be enhanced by cell-to-cell interaction occurring over length scales extending tens to thousands of microns. Our project investigated two potential mechanisms of enhanced electron transfer. The first is the formation of single- or multiple-species biofilms that transport electrons via direct electrical connection such as conductive pili (i.e. ‘nanowires’) through biofilms to where the electron acceptor is available. The second is through diffusion of electron carriers from syntrophic bacteria to dissimilatory metal reducing bacteria (DMRB). The specific objectives of this work are (i) to quantify the extent and rate that electrons are transported between microorganisms in physical mixing zones between an electron donor and electron acceptor (e.g. U(IV)), (ii) to quantify the extent that biomass growth and reaction are enhanced by interspecies electron transport, and (iii) to integrate mixing across scales (e.g., microscopic scale of electron transfer and macroscopic scale of diffusion) in an integrated numerical model to quantify these mechanisms on overall U(VI) reduction rates. We tested these hypotheses with five tasks that integrate microbiological experiments, unique micro-fluidics experiments, flow cell experiments, and

  6. Using spatio-temporal asymmetry to enhance mixing in chaotic flows: From maps to stirred tanks

    NASA Astrophysics Data System (ADS)

    Alvarez, Mario Moises

    Under laminar flow conditions, chaos is the only route to achieve effective mixing. Indeed, industrially relevant devices such as static mixers, stirred tanks, and roller bottles work because they create chaotic flows. However, they are generally operated and designed in a symmetric fashion (e.g. symmetric construction, periodic operation). Under such circumstances, chaotic and nonchaotic regions always co-exist, often hindering mixing performance. The introduction of asymmetries (in space or time) has been proposed as a means to improve mixing performance by generating globally chaotic systems in which the entire flow domain is subject to the action of exponential stretching and repeated folding, key features of chaotic flows capable of good mixing. Here we compare mixing performance of symmetric and asymmetric mixing flows from the point of view of the properties of the structure that they generate. In particular, we analyze two classes of systems: We use computer simulations to follow the process of elongation and deformation of interfaces as they are advected by time-periodic and aperiodic protocols in an idealized 2-D flow (the sine flow). The distribution of length scales characteristic of the partially mixed structures in this flow is calculated and their statistical properties are investigated. As the main conclusion, we find that the distribution of length scales is universal (independently on the periodic or aperiodic nature of the flow), and predictable (based on stretching calculations) for any globally chaotic flow. Subsequently, mixing structures and flow patterns in stirred tank systems of geometries encountered in engineering practice and operated in the laminar regime are investigated experimentally using UV visualization techniques, Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (p-LIF). It is experimentally demonstrated that concentric stirred tank configurations achieve partial chaos only by virtue of the small

  7. Enhancing oxygen transport through Mixed-Ionic-and-Electronic-Conducting ceramic membranes

    NASA Astrophysics Data System (ADS)

    Yu, Anthony S.

    Ceramic membranes based on Mixed-Ionic-and-Electronic-Conducting (MIEC) oxides are capable of separating oxygen from air in the presence of an oxygen partial-pressure gradient. These MIEC membranes show great promise for oxygen consuming industrial processes, such as the production of syngas from steam reforming of natural gas (SRM), as well as for electricity generation in Solid Oxide Fuel Cells (SOFC). For both applications, the overall performance is dictated by the rate of oxygen transport across the membrane. Oxygen transport across MIEC membranes is composed of a bulk oxygen-ion diffusion process and surface processes, such as surface reactions and adsorption/desorption of gaseous reactants/products. The main goal of this thesis was to determine which process is rate-limiting in order to significantly enhance the overall rate of oxygen transport in MIEC membrane systems. The rate-limiting step was determined by evaluating the total resistance to oxygen transfer, Rtot. Rtot is the sum of a bulk diffusion resistance in the membrane itself, Rb, and interfacial loss components, Rs. Rb is a function of the membrane's ionic conductivity and thickness, while Rs arises primarily from slow surface-exchange kinetics that cause the P(O2) at the surfaces of the membrane to differ from the P(O 2) in the adjacent gas phases. Rtot can be calculated from the Nernst potential across the membrane and the measured oxygen flux. The rate-limiting process can be determined by evaluating the relative contributions of the various losses, Rs and Rb, to Rtot. Using this method, this thesis demonstrates that for most membrane systems, Rs is the dominating factor. In the development of membrane systems with high oxygen transport rates, thin membranes with high ionic conductivities are required to achieve fast bulk oxygen-ion diffusion. However, as membrane thickness is decreased, surface reaction kinetics become more important in determining the overall transport rate. The two

  8. Critical Performance Enhancement of Ultrahigh-Bandwidth Microwave Photonic Links through Nonlinear Photonic Signal Processing

    DTIC Science & Technology

    2013-04-11

    four-wave mixing (FWM) interaction such that in an amplifier-less link we are thermally noise limited after photodetection due to a low received...link with self-phase modulation based enhancement and balanced detection. optical signal. During this quarter we have constructed the sampling-based...photodetector. Furthermore, 8-dB of signal gain, a 3.6-dB improvement in OIP3, and a 3.1 -dB improvement in OIP2. the use of the balanced detector allows for

  9. Strong nonlinear optical enhancement in MBE-grown Bi 1-xSb x

    NASA Astrophysics Data System (ADS)

    Youngdale, E. R.; Meyer, J. R.; Hoffman, C. A.; Bartoli, F. J.; Partin, D. L.; Thrush, C. M.; Heremans, J. P.

    1991-05-01

    We report an experimental study of the linear and nonlinear optical properties of Bi 1-xSb x alloy layers grown by MBE. Non-degenerate four-wave mixing experiments at CO 2 laser wavelengths yield a large third-order nonlinear susceptibility (χ (3)≈3.5 × 10 -4 esu). Furthermore, due to the high reflectivity of the Bi 1-xSb x films at both the air and substrate interfaces, the etalon formed can enhance the nonlinear optical signal by over an order of magnitude.

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

    PubMed

    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.

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

    PubMed

    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.

  12. The feasibility of enhanced soil washing of p-nitrochlorobenzene (pNCB) with SDBS/Tween80 mixed surfactants.

    PubMed

    Guo, Huiqin; Liu, Zhenyu; Yang, Shaogui; Sun, Cheng

    2009-10-30

    The present study investigated the feasibility of using two mixed surfactants, anionic surfactant sodium dodecylbenzenesulfonate (SDBS) and nonionic surfactant polysorbate 80 (Tween80), for the remediation of p-nitrochlorobenzene (pNCB) contaminated soil. The water solubility, the apparent soil-water distribution constant (K(d)(*)) and the desorption ratio of pNCB, as well as the sorption of surfactants by the soil were significantly affected by the dosage of surfactants and the mass ratio of SDBS/Tween80. Because of the formation of mixed micelles, the presence of SDBS showed more effective than individual Tween80 for increasing the water solubility, decreasing the K(d)(*) and enhancing the desorption ratio of pNCB, as well as inhibiting the sorption of surfactants by the soil. Low dosage of surfactants (Tween80 < 2000 mg L(-1)) increased the K(d)(*) value and inhibited the desorption of pNCB from soil. However, relative high concentration of Tween80 had positive effect on the decrease of the K(d)(*) value and increase of pNCB desorption. In addition, among the tested surfactant systems, mixed SDBS/Tween80 with a 1:1 mass ratio exhibited the highest pNCB desorption. The results indicated that it is feasible to use mixed SDBS/Tween80 surfactants for the remediation of pNCB contaminated soil.

  13. Enhanced blood brain barrier transport of vinpocetine by oral delivery of mixed micelles in combination with a message guider.

    PubMed

    Ding, Jiaojiao; Sun, Yujiao; Li, Jinfeng; Wang, Huimin; Mao, Shirui

    2017-02-02

    The blood brain barrier represents an insurmountable obstacle for the therapy of central nervous system related diseases. Polymeric micelles have many desirable properties for brain targeting by oral delivery but the stability and targeting efficiency needs to be improved. In this study, it was demonstrated that binary micelle system can compensate the drawbacks of mono system by preparing mixed micelles in combination with PEG based copolymers. Here we explored a brain targeting drug delivery system via facile approaches using P123 based mixed micelles in combination with a message guider from traditional Chinese medicine, borneol, for oral delivery. With higher drug-loading, improved stability, prolonged in vitro release profile, increased bioavailability and enhanced brain targeting effect was achieved after peroral delivery of the mixed micelles. More importantly, without extra structure modification for active targeting, it was demonstrated for the first time that oral delivery of vinpocetine loaded mixed micelles together with borneol is an effective way to increase drug concentration in the brain and the targeting efficiency is borneol dose dependent. Such a "simple but effective" modality may shed light on the potential use of polymeric micelles in combination with a message drug to achieve drug brain targeting or other targeting sites via oral delivery.

  14. Enhancing Learning Outcomes through Evaluation of Serious Gaming: A Mixed Methods Study

    ERIC Educational Resources Information Center

    Douglas, Kerrie Anna

    2012-01-01

    This study compared the change in counseling student's self-efficacy and skill related to suicide assessment and intervention through the use of a novel intervention-oriented evaluation method, evaluation focused discussion groups, in an experimental embedded mixed methods design. An innovation counselor pedagogical tool, Suicide Risk Assessment…

  15. Using Bayesian Stable Isotope Mixing Models to Enhance Marine Ecosystem Models

    EPA Science Inventory

    The use of stable isotopes in food web studies has proven to be a valuable tool for ecologists. We investigated the use of Bayesian stable isotope mixing models as constraints for an ecosystem model of a temperate seagrass system on the Atlantic coast of France. δ13C and δ15N i...

  16. Promise for Enhancing Children's Reading Attitudes through Peer Reading: A Mixed Method Approach

    ERIC Educational Resources Information Center

    Lee, Youngju

    2014-01-01

    Peer-Assisted Learning Strategies (PALS) was implemented for supplementary reading classes in a Korean elementary school. The treatment group children were exposed to PALS during 20 min sessions, 4 times a week, for 8 weeks. The impacts of PALS were investigated in 3 aspects using a mixed-methods approach: improvement in reading attitudes, reading…

  17. Adjoint-based approach to Enhancing Mixing in Rayleigh-Taylor Turbulence

    NASA Astrophysics Data System (ADS)

    Kord, Ali; Capecelatro, Jesse

    2016-11-01

    A recently developed adjoint method for multi-component compressible flow is used to measure sensitivity of the mixing rate to initial perturbations in Rayleigh-Taylor (RT) turbulence. Direct numerical simulations (DNS) of RT instabilities are performed at moderate Reynolds numbers. The DNS are used to provide an initial prediction, and the corresponding space-time discrete-exact adjoint provides a sensitivity gradient for a specific quantity of interest (QoI). In this work, a QoI is defined based on the time-integrated scalar field to quantify the mixing rate. Therefore, the adjoint solution is used to measure sensitivity of this QoI to a set of initial perturbations, and inform a gradient-based line search to optimize mixing. We first demonstrate the adjoint approach in the linear regime and compare the optimized initial conditions to the expected values from linear stability analysis. The adjoint method is then used in the high Reynolds number limit where theory is no longer valid. Finally, chaos is known to contaminate the accuracy of the adjoint gradient in turbulent flows when integrated over long time horizons. We assess the influence of chaos on the accuracy of the adjoint gradient to guide the work of future studies on adjoint-based sensitivity of turbulent mixing. PhD Student, Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI.

  18. Enhanced submarine ground water discharge form mixing of pore water and estuarine water

    USGS Publications Warehouse

    Martin, Jonathan B.; Cable, Jaye E.; Swarzenski, Peter W.; Lindenberg, Mary K.

    2004-01-01

    Submarine ground water discharge is suggested to be an important pathway for contaminants from continents to coastal zones, but its significance depends on the volume of water and concentrations of contaminants that originate in continental aquifers. Ground water discharge to the Banana River Lagoon, Florida, was estimated by analyzing the temporal and spatial variations of Cl− concentration profiles in the upper 230 cm of pore waters and was measured directly by seepage meters. Total submarine ground water discharge consists of slow discharge at depths > ∼70 cm below seafloor (cmbsf) of largely marine water combined with rapid discharge of mixed pore water and estuarine water above ∼70 cmbsf. Cl− profiles indicate average linear velocities of ∼0.014 cm/d at depths > ∼70 cmbsf. In contrast, seepage meters indicate water discharges across the sediment-water interface at rates between 3.6 and 6.9 cm/d. The discrepancy appears to be caused by mixing in the shallow sediment, which may result from a combination of bioirrigation, wave and tidal pumping, and convection. Wave and tidal pumping and convection would be minor because the tidal range is small, the short fetch of the lagoon limits wave heights, and large density contacts are lacking between lagoon and pore water. Mixing occurs to ∼70 cmbsf, which represents depths greater than previously reported. Mixing of oxygenated water to these depths could be important for remineralization of organic matter.

  19. Supplemental design requirements document enhanced radioactive and mixed waste storage Phase V Project W-112

    SciTech Connect

    Ocampo, V.P.; Boothe, G.F.; Greager, T.M.; Johnson, K.D.; Kooiker, S.L.; Martin, J.D.

    1994-11-01

    This document provides additional and supplemental information to WHC-SD-W112-FDC-001, Project W-112 for radioactive and mixed waste storage. It provides additional requirements for the design and summarizes Westinghouse Hanford Company key design guidance and establishes the technical baseline agreements to be used for definitive design of the Project W-112 facilities.

  20. The enhancement of the mixing and combustion processes in supersonic flow applied to scramjet engine

    SciTech Connect

    Kopchenov, V.I.; Lomkov, K.E. )

    1992-07-01

    The Reynolds averaged parabolized Navier-Stokes equations are employed for the numerical study of turbulent mixing and combustion of a supersonic hydrogen jet in a supersonic airflow. A one-equation differential turbulence model is utilized. The simplified flame sheet model is employed for the numerical simulation of the supersonic combustion. 24 refs.

  1. High intensity vacuum ultraviolet and extreme ultraviolet production by noncollinear mixing in laser vaporized media

    NASA Astrophysics Data System (ADS)

    Todt, Michael A.; Albert, Daniel R.; Davis, H. Floyd

    2016-06-01

    A method is described for generating intense pulsed vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) laser radiation by resonance enhanced four-wave mixing of commercial pulsed nanosecond lasers in laser vaporized mercury under windowless conditions. By employing noncollinear mixing of the input beams, the need of dispersive elements such as gratings for separating the VUV/XUV from the residual UV and visible beams is eliminated. A number of schemes are described, facilitating access to the 9.9-14.6 eV range. A simple and convenient scheme for generating wavelengths of 125 nm, 112 nm, and 104 nm (10 eV, 11 eV, and 12 eV) using two dye lasers without the need for dye changes is described.

  2. High intensity vacuum ultraviolet and extreme ultraviolet production by noncollinear mixing in laser vaporized media.

    PubMed

    Todt, Michael A; Albert, Daniel R; Davis, H Floyd

    2016-06-01

    A method is described for generating intense pulsed vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) laser radiation by resonance enhanced four-wave mixing of commercial pulsed nanosecond lasers in laser vaporized mercury under windowless conditions. By employing noncollinear mixing of the input beams, the need of dispersive elements such as gratings for separating the VUV/XUV from the residual UV and visible beams is eliminated. A number of schemes are described, facilitating access to the 9.9-14.6 eV range. A simple and convenient scheme for generating wavelengths of 125 nm, 112 nm, and 104 nm (10 eV, 11 eV, and 12 eV) using two dye lasers without the need for dye changes is described.

  3. Enhanced turbulent mixing induced by strong wind on the South China Sea shelf

    NASA Astrophysics Data System (ADS)

    Zhang, Yanwei; Tian, Jiwei

    2014-06-01

    Integrated observations were made on the South China Sea shelf at 19°37' N, 112°04' E, under strong wind and heavy raining weather conditions in August 2005. Current data were obtained using a moored 150-kHz Acoustic Doppler Current Profiler, turbulent kinetic energy dissipation rate were measured with TurboMapII, and temperature was recorded by thermistor chains. Both the mixed layer thickness and the corresponding mean dissipation rate increased after the strong wind bursts. Average surface mixed layer thickness was 13.4 m pre-wind and 22.4 m post-wind, and the average turbulent dissipation rate in the mixed layer pre-wind and post-wind were 4.26 × 10-7 and 1.09 × 10-6 Wkg-1, respectively. The post-wind dissipation rate was 2.5 times larger than the pre-wind dissipation rate in the interior layer and four times larger in the intermediate water column. Spectra and vertical mode analysis revealed that near-inertial motion post-wind, especially with high modes, was strengthened and propagated downward toward the intermediate layer. The downward group velocity of near-inertial current was about 8.1 × 10-5 ms-1 during the strong wind bursts. The mean percentage of wind work transmitted into the intermediate layer is about 4.2 %. The ratio of post-wind high-mode energy to total horizontal kinetic energy increased below the surface mixed layer, which would have caused instabilities and result in turbulent mixing. Based on these data, we discuss a previous parameterization that relates dissipation rate, stratification, and shear variance calculated from baroclinic currents with high modes (higher than mode 1) which concentrate a large fraction of energy.

  4. Pore-scale mechanisms for the enhancement of mixing in unsaturated porous media and implications for chemical reactions

    NASA Astrophysics Data System (ADS)

    Jiménez-Martínez, Joaquín.; Anna, Pietro de; Tabuteau, Hervé; Turuban, Régis; Borgne, Tanguy Le; Méheust, Yves

    2015-07-01

    Porous media in which different fluid phases coexist are common in nature (e.g., vadose zone and gas-oil reservoirs). In partially saturated porous media, the intricate spatial distributions of the wetting and nonwetting phases causes their flow to be focused onto preferential paths. Using a novel 2-D experimental setup allowing pore-scale measurement of concentration fields in a controlled unsaturated flow, we highlight mechanisms by which mixing of an invading fluid with the resident fluid is significantly enhanced when decreasing saturation. The mean scalar dissipation rate is observed to decrease slowly in time, while under saturated conditions it decays rapidly. This slow decrease is due to sustained longitudinal solute fingering, which causes concentration gradients to remain predominantly transverse to the average flow. Consequently, the effective reactivity is found to be much larger than under saturated conditions. These results provide new insights into the role that multiphase flows play on mixing/reaction in porous media.

  5. Enhanced light absorption by mixed source black and brown carbon particles in UK winter

    PubMed Central

    Liu, Shang; Aiken, Allison C.; Gorkowski, Kyle; Dubey, Manvendra K.; Cappa, Christopher D.; Williams, Leah R.; Herndon, Scott C.; Massoli, Paola; Fortner, Edward C.; Chhabra, Puneet S.; Brooks, William A.; Onasch, Timothy B.; Jayne, John T.; Worsnop, Douglas R.; China, Swarup; Sharma, Noopur; Mazzoleni, Claudio; Xu, Lu; Ng, Nga L.; Liu, Dantong; Allan, James D.; Lee, James D.; Fleming, Zoë L.; Mohr, Claudia; Zotter, Peter; Szidat, Sönke; Prévôt, André S. H.

    2015-01-01

    Black carbon (BC) and light-absorbing organic carbon (brown carbon, BrC) play key roles in warming the atmosphere, but the magnitude of their effects remains highly uncertain. Theoretical modelling and laboratory experiments demonstrate that coatings on BC can enhance BC's light absorption, therefore many climate models simply assume enhanced BC absorption by a factor of ∼1.5. However, recent field observations show negligible absorption enhancement, implying models may overestimate BC's warming. Here we report direct evidence of substantial field-measured BC absorption enhancement, with the magnitude strongly depending on BC coating amount. Increases in BC coating result from a combination of changing sources and photochemical aging processes. When the influence of BrC is accounted for, observationally constrained model calculations of the BC absorption enhancement can be reconciled with the observations. We conclude that the influence of coatings on BC absorption should be treated as a source and regionally specific parameter in climate models. PMID:26419204

  6. Enhanced light absorption by mixed source black and brown carbon particles in UK winter.

    PubMed

    Liu, Shang; Aiken, Allison C; Gorkowski, Kyle; Dubey, Manvendra K; Cappa, Christopher D; Williams, Leah R; Herndon, Scott C; Massoli, Paola; Fortner, Edward C; Chhabra, Puneet S; Brooks, William A; Onasch, Timothy B; Jayne, John T; Worsnop, Douglas R; China, Swarup; Sharma, Noopur; Mazzoleni, Claudio; Xu, Lu; Ng, Nga L; Liu, Dantong; Allan, James D; Lee, James D; Fleming, Zoë L; Mohr, Claudia; Zotter, Peter; Szidat, Sönke; Prévôt, André S H

    2015-09-30

    Black carbon (BC) and light-absorbing organic carbon (brown carbon, BrC) play key roles in warming the atmosphere, but the magnitude of their effects remains highly uncertain. Theoretical modelling and laboratory experiments demonstrate that coatings on BC can enhance BC's light absorption, therefore many climate models simply assume enhanced BC absorption by a factor of ∼1.5. However, recent field observations show negligible absorption enhancement, implying models may overestimate BC's warming. Here we report direct evidence of substantial field-measured BC absorption enhancement, with the magnitude strongly depending on BC coating amount. Increases in BC coating result from a combination of changing sources and photochemical aging processes. When the influence of BrC is accounted for, observationally constrained model calculations of the BC absorption enhancement can be reconciled with the observations. We conclude that the influence of coatings on BC absorption should be treated as a source and regionally specific parameter in climate models.

  7. Co-Al mixed metal oxides/carbon nanotubes nanocomposite prepared via a precursor route and enhanced catalytic property

    SciTech Connect

    Fan Guoli; Wang Hui; Xiang Xu; Li Feng

    2013-01-15

    The present work reported the synthesis of Co-Al mixed metal oxides/carbon nanotubes (CoAl-MMO/CNT) nanocomposite from Co-Al layered double hydroxide/CNTs composite precursor (CoAl-LDH/CNT). The materials were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), low temperature nitrogen adsorption-desorption experiments, thermogravimetric and differential thermal analyses (TG-DTA), Raman spectra and X-ray photoelectron spectroscopy (XPS). The results revealed that in CoAl-MMO/CNT nanocomposite, the nanoparticles of cobalt oxide (CoO) and Co-containing spinel-type complex metal oxides could be well-dispersed on the surface of CNTs, thus forming the heterostructure of CoAl-MMO and CNTs. Furthermore, as-synthesized CoAl-MMO/CNT nanocomposite was utilized as additives for catalytic thermal decomposition of ammonium perchlorate (AP). Compared to those for pure AP and CoAl-MMO, the peak temperature of AP decomposition for CoAl-MMO/CNT was significantly decreased, which is attributed to the novel heterostructure and synergistic effect of multi-component metal oxides of nanocomposite. - Graphical abstract: Hybrid Co-Al mixed metal oxides/carbon nanotubes nanocomposite showed the enhanced catalytic activity in the thermal decomposition of ammonium perchlorate, as compared to carbon nanotubes and pure Co-Al mixed metal oxides. Highlights: Black-Right-Pointing-Pointer Co-Al mixed metal oxides/carbon nanotubes nanocomposite was synthesized. Black-Right-Pointing-Pointer Co-Al mixed metal oxides consisted of cobalt oxide and Co-containing spinels. Black-Right-Pointing-Pointer Nanocomposite exhibited excellent catalytic activity for the decomposition of AP. Black-Right-Pointing-Pointer The superior catalytic property is related to novel heterostructure and composition.

  8. Enhanced diapycnal mixing by salt fingers in the thermocline of the tropical Atlantic.

    PubMed

    Schmitt, R W; Ledwell, J R; Montgomery, E T; Polzin, K L; Toole, J M

    2005-04-29

    Diapycnal mixing plays a significant role in the ocean's circulation and uptake of heat and carbon dioxide, but has not been quantified in salt finger-driven thermohaline staircases. We recently performed a tracer release experiment in the western tropical Atlantic staircase at approximately 400 m depth. The observed dispersion implies an effective diapycnal diffusivity for tracer and salt of 0.8 to 0.9 x 10(-4) m2/s. Temperature microstructure data interpreted in terms of a vertical production-dissipation balance yields a smaller effective diffusivity for heat of 0.45 (+/- 0.2) x 10(-4) m2/s, consistent with salt fingers and well above the mixing ascribable to mechanical turbulence.

  9. Two-phase mixed media dielectric with macro dielectric beads for enhancing resistivity and breakdown strength

    DOEpatents

    Falabella, Steven; Meyer, Glenn A; Tang, Vincent; Guethlein, Gary

    2014-06-10

    A two-phase mixed media insulator having a dielectric fluid filling the interstices between macro-sized dielectric beads packed into a confined volume, so that the packed dielectric beads inhibit electro-hydrodynamically driven current flows of the dielectric liquid and thereby increase the resistivity and breakdown strength of the two-phase insulator over the dielectric liquid alone. In addition, an electrical apparatus incorporates the two-phase mixed media insulator to insulate between electrical components of different electrical potentials. And a method of electrically insulating between electrical components of different electrical potentials fills a confined volume between the electrical components with the two-phase dielectric composite, so that the macro dielectric beads are packed in the confined volume and interstices formed between the macro dielectric beads are filled with the dielectric liquid.

  10. Streamwise vorticity generation and mixing enhancement in free jets by 'delta-tabs'

    NASA Technical Reports Server (NTRS)

    Zaman, K. B. M. Q.

    1993-01-01

    The effect of triangular tabs, placed at the nozzle exit, on the evolution of free jets is investigated. The effect, a large distortion of the jet cross section and a resultant increase in mixing downstream, has been inferred before to be due to a pair of streamwise vortices originating from each tab. In this paper, the generation mechanism of the streamwise vorticity (omega sub x) is considered first. Two sources are postulated. One is the upstream 'pressure hill', produced by the tab, which appears to be the dominant source. Another is due to vortex filaments shed from the sides of the tab and reoriented downstream by the mean shear of the mixing layer. In the case of a 'delta-tab', a triangular tab with its apex leaning downstream, vorticity from the two sources explain the stronger effect in that configuration. Data on the vorticity evolution for the effect of two delta-tabs are presented, up to twelve jet diameters from the exit, which show that the streamwise vortices persist even at the farthest measurement station. The magnitude of omega sub x-maximum decays continually with distance from the nozzle, its ratio to azimuthal vorticity maximum is found to be about 1/5 everywhere. The relative effect of a delta-tab on jets from an axisymmetric nozzle and a 8:1 rectangular nozzle is also studied. The mixing layer distortion is found to be less pronounced in the rectangular case. The jet mixing, as manifested by the mass flux measured at a downstream station, is increased in the axisymmetric jet but it is decreased in the rectangular jet under consideration by the delta-tab.

  11. Quantum-enhanced protocols with mixed states using cold atoms in dipole traps

    NASA Astrophysics Data System (ADS)

    Krzyzanowska, K.; Copley-May, M.; Romain, R.; MacCormick, C.; Bergamini, S.

    2017-01-01

    We discuss the use of cold atoms in dipole traps to demonstrate experimentally a particular class of protocols for computation and metrology based on mixed states. Modelling of the system shows that, for a specific class of problems (tracing, phase estimation), a quantum advantage can be achieved over classical algorithms for very realistic conditions and strong decoherence. We discuss the results of the models and the experimental implementation.

  12. Mixing Effect of Gold and Silver Nanoparticles on Enhancement in Performance of Organic Thin-Film Solar Cells

    NASA Astrophysics Data System (ADS)

    Akiyama, Tsuyoshi; Yamamoto, Tomoki; Oku, Takeo; Yahiro, Masayuki; Kurihara, Takashi; Adachi, Chihaya; Yamada, Sunao

    2013-12-01

    Bulk-heterojunction organic thin-film solar cells incorporating gold and silver nanoparticles were fabricated and evaluated. These nanoparticles were embedded in the hole-transport layer of the solar cells. Plasmonic absorption peaks of isolated gold and silver nanoparticles were confirmed from extinction spectra even in the hole-transport material. The incorporation of gold and silver nanoparticles increased the photoelectric conversion efficiency of organic thin-film solar cells, whose enhancement ratio was further increased by mixing gold and silver nanoparticles.

  13. Evidence for enhanced mixing over rough topography in the abyssal ocean

    PubMed

    Ledwell; Montgomery; Polzin; St. Laurent LC; Schmitt; Toole

    2000-01-13

    The overturning circulation of the ocean plays an important role in modulating the Earth's climate. But whereas the mechanisms for the vertical transport of water into the deep ocean--deep water formation at high latitudes--and horizontal transport in ocean currents have been largely identified, it is not clear how the compensating vertical transport of water from the depths to the surface is accomplished. Turbulent mixing across surfaces of constant density is the only viable mechanism for reducing the density of the water and enabling it to rise. However, measurements of the internal wave field, the main source of energy for mixing, and of turbulent dissipation rates, have typically implied diffusivities across surfaces of equal density of only approximately 0.1 cm2 s(-1), too small to account for the return flow. Here we report measurements of tracer dispersion and turbulent energy dissipation in the Brazil basin that reveal diffusivities of 2-4 cm2 s(-1) at a depth of 500 m above abyssal hills on the flank of the Mid-Atlantic Ridge, and approximately 10 cm2 s(-1) nearer the bottom. This amount of mixing, probably driven by breaking internal waves that are generated by tidal currents flowing over the rough bathymetry, may be large enough to close the buoyancy budget for the Brazil basin and suggests a mechanism for closing the global overturning circulation.

  14. Enhanced hydrogen and 1,3-propanediol production from glycerol by fermentation using mixed cultures.

    PubMed

    Selembo, Priscilla A; Perez, Joe M; Lloyd, Wallis A; Logan, Bruce E

    2009-12-15

    The conversion of glycerol into high value products, such as hydrogen gas and 1,3-propanediol (PD), was examined using anaerobic fermentation with heat-treated mixed cultures. Glycerol fermentation produced 0.28 mol-H(2)/mol-glycerol (72 mL-H(2)/g-COD) and 0.69 mol-PD/mol-glycerol. Glucose fermentation using the same mixed cultures produced more hydrogen gas (1.06 mol-H(2)/mol-glucose) but no PD. Changing the source of inoculum affected gas production likely due to prior acclimation of bacteria to this type of substrate. Fermentation of the glycerol produced from biodiesel fuel production (70% glycerol content) produced 0.31 mol-H(2)/mol-glycerol (43 mL H(2)/g-COD) and 0.59 mol-PD/mol-glycerol. These are the highest yields yet reported for both hydrogen and 1,3-propanediol production from pure glycerol and the glycerol byproduct from biodiesel fuel production by fermentation using mixed cultures. These results demonstrate that production of biodiesel can be combined with production of hydrogen and 1,3-propanediol for maximum utilization of resources and minimization of waste.

  15. Genetic Analysis of Stress Responses in Soil Bacteria for Enhanced Bioremediation of Mixed Contaminants

    SciTech Connect

    Wong, Kwong-Kwok

    2000-12-31

    In order to realize the full potential of bioremediation, an understanding of microbial community and individual bacterial responses to the stresses encountered at contaminated sites is needed. Knowledge about genetic responses of soil and subsurface bacteria to environmental stresses, which include low nutrients, low oxygen, and mixed pollutants, will allow extrapolation of basic principles to field applications, either using indigenous bacteria or genetically engineered microorganisms. Defining bacterial responses to those stresses presents an opportunity for improving bioremediation strategies, both with indigenous populations and genetically-engineered microbes, and should contribute to environmental management and restoration actions that would reduce the cost and time required to achieve OEM's clean up goals. Stress-inducible genes identified in this project can be used as molecular probes for monitoring performance of indigenous bacteria as well as the effectiveness of bioremediation strategies being employed. Knowledge of survival and catabolic plasmid stability of indigenous bacteria will be needed for devising the most effective bioremediation strategy. In addition, stress-inducible regulatory elements identified in this project will be useful for creating genetically-engineered microorganisms which are able to degrade hazardous wastes under stress conditions at contaminated sites. One of the model organisms, Deinococcus radiodurans, is a stress-resistant bacterium. Thus, in addition to serving as a model for gene regulation in Gram-positive organisms, it may have specific application at aerobic DOE sites where combinations of contaminants produce a particularly stressful environment. Similarly, the use of Sphingomonas F199, isolated from a depth of 407 m at the Savannah River site (Fredrickson et al., 1991), may have relevance to deep subsurface bioremediation applications, where indigenous or engineered microorganisms adapted to the that environment are

  16. Black-carbon absorption enhancement in the atmosphere determined by particle mixing state

    NASA Astrophysics Data System (ADS)

    Liu, Dantong; Whitehead, James; Alfarra, M. Rami; Reyes-Villegas, Ernesto; Spracklen, Dominick V.; Reddington, Carly L.; Kong, Shaofei; Williams, Paul I.; Ting, Yu-Chieh; Haslett, Sophie; Taylor, Jonathan W.; Flynn, Michael J.; Morgan, William T.; McFiggans, Gordon; Coe, Hugh; Allan, James D.

    2017-02-01

    Atmospheric black carbon makes an important but poorly quantified contribution to the warming of the global atmosphere. Laboratory and modelling studies have shown that the addition of non-black-carbon materials to black-carbon particles may enhance the particles’ light absorption by 50 to 60% by refracting and reflecting light. Real-world experimental evidence for this `lensing’ effect is scant and conflicting, showing that absorption enhancements can be less than 5% or as large as 140%. Here we present simultaneous quantifications of the composition and optical properties of individual atmospheric black-carbon particles. We show that particles with a mass ratio of non-black carbon to black carbon of less than 1.5, which is typical of fresh traffic sources, are best represented as having no absorption enhancement. In contrast, black-carbon particles with a ratio greater than 3, which is typical of biomass-burning emissions, are best described assuming optical lensing leading to an absorption enhancement. We introduce a generalized hybrid model approach for estimating scattering and absorption enhancements based on laboratory and atmospheric observations. We conclude that the occurrence of the absorption enhancement of black-carbon particles is determined by the particles’ mass ratio of non-black carbon to black carbon.

  17. Enhanced light absorption by mixed source black and brown carbon particles in UK winter

    SciTech Connect

    Liu, Shang; Aiken, Allison C.; Gorkowski, Kyle; Dubey, Manvendra K.; Cappa, Christopher D.; Williams, Leah R.; Herndon, Scott C.; Massoli, Paola; Fortner, Edward C.; Chhabra, Puneet S.; Brooks, William A.; Onasch, Timothy B.; Jayne, John T.; Worsnop, Douglas R.; China, Swarup; Sharma, Noopur; Mazzoleni, Claudio; Xu, Lu; Ng, Nga L.; Liu, Dantong; Allan, James D.; Lee, James D.; Fleming, Zoë L.; Mohr, Claudia; Zotter, Peter; Szidat, Sönke; Prévôt, André S. H.

    2015-09-30

    We report that black carbon (BC) and light-absorbing organic carbon (brown carbon, BrC) play key roles in warming the atmosphere, but the magnitude of their effects remains highly uncertain. Theoretical modelling and laboratory experiments demonstrate that coatings on BC can enhance BC’s light absorption, therefore many climate models simply assume enhanced BC absorption by a factor of ~1.5. However, recent field observations show negligible absorption enhancement, implying models may overestimate BC’s warming. Here we report direct evidence of substantial field-measured BC absorption enhancement, with the magnitude strongly depending on BC coating amount. Increases in BC coating result from a combination of changing sources and photochemical aging processes. When the influence of BrC is accounted for, observationally constrained model calculations of the BC absorption enhancement can be reconciled with the observations. In conclusion, we find that the influence of coatings on BC absorption should be treated as a source and regionally specific parameter in climate models.

  18. Enhanced light absorption by mixed source black and brown carbon particles in UK winter

    DOE PAGES

    Liu, Shang; Aiken, Allison C.; Gorkowski, Kyle; ...

    2015-09-30

    We report that black carbon (BC) and light-absorbing organic carbon (brown carbon, BrC) play key roles in warming the atmosphere, but the magnitude of their effects remains highly uncertain. Theoretical modelling and laboratory experiments demonstrate that coatings on BC can enhance BC’s light absorption, therefore many climate models simply assume enhanced BC absorption by a factor of ~1.5. However, recent field observations show negligible absorption enhancement, implying models may overestimate BC’s warming. Here we report direct evidence of substantial field-measured BC absorption enhancement, with the magnitude strongly depending on BC coating amount. Increases in BC coating result from a combinationmore » of changing sources and photochemical aging processes. When the influence of BrC is accounted for, observationally constrained model calculations of the BC absorption enhancement can be reconciled with the observations. In conclusion, we find that the influence of coatings on BC absorption should be treated as a source and regionally specific parameter in climate models.« less

  19. Enhancing Science Education Instruction: A Mixed-Methods Study on University and Middle School Collaborations

    NASA Astrophysics Data System (ADS)

    Owen-Stone, Deborah S.

    The purpose of this concurrent mixed methods study was to examine the collaborative relationship between scientists and science teachers and to incorporate and advocate scientific literacy based on past and current educational theories such as inquiry based teaching. The scope of this study included archived student standardized test scores, semi-structured interviews, and a Likert scale survey to include open-ended comments. The methodology was based on the guiding research question: To what extent and in what ways does the collaboration and inquiry methodology, with GTF and PT teams, serve toward contributing to a more comprehensive and nuanced understanding of this predicting relationship between student PASS scores, inquiry skills, and increased scientific literacy for GTF's, PT's, and students via an integrative mixed methods analysis? The data analysis considerations were derived from the qualitative data collected from the three GTF/PT teams by the use of recorded interviews and text answered survey comments. The quantitative data of archived student Palmetto Assessment of State Standards (PASS) scores on scientific literacy and inquiry tests and the Likert-scale portion of the survey were support data to the aforementioned qualitative data findings. Limitations of the study were (1) the population of only the GK-12 teachers and their students versus the inclusion of participants that did not experience the GK-12 Fellow partnerships within their classrooms, should they be considered as participants, (2) involved the researcher as a participant for two years of the program and objectivity remained through interpretation and well documented personal reflections and experiences to inform accuracy, and (3) cultural diversity contributed to the relationship formed between the research Fellow and science educator and communication and scientific language did form a barrier between the Fellow, educator, and student rapport within the classroom. This study

  20. Mixing in a three-phase system: Enhanced production of oil-wet reservoirs by CO2 injection

    NASA Astrophysics Data System (ADS)

    Jiménez-Martínez, Joaquín.; Porter, Mark L.; Hyman, Jeffrey D.; Carey, J. William; Viswanathan, Hari S.

    2016-01-01

    We recreate three-phase reservoir conditions (high-pressure/temperature) using a microfluidics system and show that the use of scCO2 for restimulation operations, such as hydraulic fracturing, can enhance mixing and production. The results inform hydrocarbon extraction from deep shale formations, which has recently generated an energy boom that has lowered hydrocarbon costs. However, production decreases rapidly and methods to increase efficiency or allow restimulation of wells are needed. In our experiments, the presence of residual brine from initial production creates spatiotemporal variability in the system that causes the injected scCO2 to more effectively interact-mix with trapped hydrocarbon, thereby increasing recovery. We apply volume-averaging techniques to upscale brine saturation, which allows us to analyze the complex three-phase system in the framework of well characterized two-phase systems. The upscaled three-phase system behaves like a two-phase system: greater mixing with larger non-wetting content and higher heterogeneity. The results are contrary to previous observations in water-wet systems.

  1. Investigate the Metabolic Reprogramming of Saccharomyces cerevisiae for Enhanced Resistance to Mixed Fermentation Inhibitors via 13C Metabolic Flux Analysis

    PubMed Central

    Guo, Weihua; Chen, Yingying; Wei, Na; Feng, Xueyang

    2016-01-01

    The fermentation inhibitors from the pretreatment of lignocellulosic materials, e.g., acetic acid and furfural, are notorious due to their negative effects on the cell growth and chemical production. However, the metabolic reprogramming of the cells under these stress conditions, especially metabolic response for resistance to mixed inhibitors, has not been systematically investigated and remains mysterious. Therefore, in this study, 13C metabolic flux analysis (13C-MFA), a powerful tool to elucidate the intracellular carbon flux distributions, has been applied to two Saccharomyces cerevisiae strains with different tolerances to the inhibitors under acetic acid, furfural, and mixed (i.e., acetic acid and furfural) stress conditions to unravel the key metabolic responses. By analyzing the intracellular carbon fluxes as well as the energy and cofactor utilization under different conditions, we uncovered varied metabolic responses to different inhibitors. Under acetate stress, ATP and NADH production was slightly impaired, while NADPH tended towards overproduction. Under furfural stress, ATP and cofactors (including both NADH and NADPH) tended to be overproduced. However, under dual-stress condition, production of ATP and cofactors was severely impaired due to synergistic stress caused by the simultaneous addition of two fermentation inhibitors. Such phenomenon indicated the pivotal role of the energy and cofactor utilization in resisting the mixed inhibitors of acetic acid and furfural. Based on the discoveries, valuable insights are provided to improve the tolerance of S. cerevisiae strain and further enhance lignocellulosic fermentation. PMID:27532329

  2. Mixed plantations of eucalyptus and leguminous trees enhance biomass production. Forest Service research paper (Final)

    SciTech Connect

    DeBell, D.S.; Whitesell, C.D.; Schubert, T.H.

    1985-07-01

    Two Eucalyptus species--E. Saligna and E. grandis--are especially favored in Hawaii for wood, fiber, and fuel production because of their quick growth and high yields. Their growth is limited, however, on many sites by low levels of available nitrogen. Supplemental nitrogen can be provided by nitrogen-fixing plants, such as legumes. A test was conducted to determine whether planting two leguminous species--Acacia melanoxylon and Albizia falcataria Fosberg--could increase biomass production. Total biomass production was much greater in the mixed-species plantations than in the pure Eucalyptus plantation.

  3. Structural mechanism of the enhanced glass-forming ability in multicomponent alloys with positive heat of mixing

    PubMed Central

    Wu, S. Y.; Wei, S. H.; Guo, G. Q.; Wang, J. G.; Yang, L.

    2016-01-01

    The issue, microalloying certain element with positive heat of mixing leading to the enhanced glass forming ability (GFA) in multicomponent alloys, has been investigated by systematic experimental measurements coupled with theoretical calculations. It is found that in the Nb-doped CuZr alloys, strong interaction between Nb and Zr atoms leads to a shortened pair distance. In addition, fraction of the icosahedral-like local structures increases with Nb addition and Nb solutes are apt to be separated with each other. These factors contribute to an increase of the atomic level efficiency to fill space and formation of the short-to-medium range orderings. As a result, the amorphous structure is stabilized and the GFA is enhanced accordingly. This work provides an in-depth understanding of microalloying-induced high GFAs in multicomponent alloys and is helpful for guiding the development of more metallic glasses with high GFAs via microalloying, despite the positive heat of mixing between the constituent elements. PMID:27897257

  4. Enhanced sub-micron colloidal particle separation with interdigitated microelectrode arrays using mixed AC/DC dielectrophoretic scheme.

    PubMed

    Swaminathan, Vikhram V; Shannon, Mark A; Bashir, Rashid

    2015-04-01

    Dielectrophoretic separation of particles finds a variety of applications in the capture of species such as cells, viruses, proteins, DNA from biological systems, as well as other organic and inorganic contaminants from water. The ability to capture particles is constrained by poor volumetric scaling of separation force with respect to particle diameter, as well as the weak penetration of electric fields in the media. In order to improve the separation of sub-micron colloids, we present a scheme based on multiple interdigitated electrode arrays under mixed AC/DC bias. The use of high frequency longitudinal AC bias breaks the shielding effects through electroosmotic micromixing to enhance electric fields through the electrolyte, while a transverse DC bias between the electrode arrays enables penetration of the separation force to capture particles from the bulk of the microchannel. We determine the favorable biasing conditions for field enhancement with the help of analytical models, and experimentally demonstrate the improved capture from sub-micron colloidal suspensions with the mixed AC/DC electrostatic excitation scheme over conventional AC-DEP methods.

  5. Enhancement of the optical transmission by mixing the metallic and dielectric nanoparticles atop the silicon substrate.

    PubMed

    Yeh, Yung-Ming; Wang, Yu-Sheng; Li, Jia-Han

    2011-03-14

    We propose a structure with the metallic and dielectric nanoparticles on the surface of the silicon material and study its optical transmission properties. The structure with the radiuses of the silver and silica nanoparticles as 50 nm and 100 nm, respectively, with the gap as 8 nm between silver and silica nanoparticles is found to have the largest optical transmission into the silicon material in our simulations. The largest field intensities are on the bottom of the silver nanoparticles and these can result strong field scattering into the silicon material. From the plotting of the average power densities around the gaps and the air regions between the silver and silica nanoparticles, the light power can go thorough these regions and flow downward to the silicon material. It is also found that the light energy rotates around the bottom of the silver nanoparticles due to the strong localized surface plasmons. The rectangular arrangement of the nanoparticle structures with mixing metallic and dielectric nanoparticles are studied, and the cases for the structures with only the metallic nanoparticles or only the dielectric nanoparticles are also simulated and compared. The rectangular or hexagonal structures with mixing metallic and dielectric nanoparticles on the surface of the silicon substrate can have better optical transmission than the cases of the rectangular arrangement with only metallic or dielectric nanoparticles.

  6. Supersonic Inlet with Pylons Set and Star-Shaped Forebody for Mixing, Combustion and Thrust Enhancement

    NASA Technical Reports Server (NTRS)

    Gilinsky, M.; Gonor, A. L.; Khaikine, V. A.; Blankson, I. M.

    2003-01-01

    Two new approaches are discussed in this paper for application in the Scramjet inlet of an air-breathing propulsion system: 1) In the first approach, the pylon set is installed in the rectangular inlet near the cowl front edge. For a quasi-axisymmetric inlet, a similar set is installed along the Star-shaped forebody axis. This set contains 3 - 4 airfoil-shaped strips or cross-sectional rings depending on the type of inlet. The inlets: rectangular, axisymmetric or star-shaped, are located at different distances from the forebody. Fuel injection takes place through these pylons, which provides for uniform mixing downstream. The locations, sizes and angles of these pylons are very important for efficient application. Optimal values of geometrical parameters were determined from multi-parametric NSE-based numerical simulations of the laminar and turbulent external/internal flows. These simulations have shown significant benefits for mixing, combustion and thrust of the proposed approach by comparison with traditional well-known designs. Experimental tests will be conducted soon at the NASA LaRC and Institute of Mechanics at Moscow State University. Preliminary estimates are very promising.

  7. Enhanced nonlinear inspection of diffusion bonded interfaces using reflected non-collinear ultrasonic wave mixing

    NASA Astrophysics Data System (ADS)

    Zhang, Ziyin; Nagy, Peter B.; Hassan, Waled

    2016-02-01

    Ultrasonic wave mixing has shown promising potential for assessing otherwise hidden subtle imperfections in imperfect diffusion bonds between Ti-6Al-4V components. When interrogating a diffusion bonded specimen using non-collinear shear wave mixing, both bulk and interface nonlinearity will contribute to the transmitted nonlinear signal. Although a recent study has shown that changing the transducer alignment can suppress the intrinsic nonlinearity of the surrounding material to some extent so that the interface nonlinearity could be detected more selectively, it is still difficult to distinguish different levels of bond quality based on the detected transmitted signal only. Analytical and numerical studies showed that an imperfect interface generates the same amount of nonlinear displacement in the reflected and transmitted fields. In this study, we used the reflected nonlinear interface signature to characterize diffusion bonded interfaces. Our results indicate that it is better to use the reflected nonlinear interface signature to assess the bond quality, which is in agreement with our previous analytical and numerical predictions. However, the observed random phase of the reflected signature indicates that existing nonlinear interface models are insufficient for accurately describing the nonlinear interaction of shear incident waves with high-quality diffusion bonded interfaces.

  8. Enhancing zero valent iron based natural organic matter removal by mixing with dispersed carbon cathodes.

    PubMed

    Liu, Peng; Keller, Jurg; Gernjak, Wolfgang

    2016-04-15

    Former studies have shown that adding granular activated carbon (GAC) cathodes could enhance the overall performance of the zero valent iron (ZVI) process for organics removal. The present study evaluates for the first time the performance of such an enhanced ZVI process to remove natural organic matter (NOM), an important water quality parameter in drinking water. Lab-scale batch tests were conducted with surface reservoir feed water from a drinking water plant. In the GAC enhanced ZVI process dissolved organic carbon (DOC) and UV254 were reduced by 61±3% and 70±2%, respectively, during 24h treatment corresponding to 1.8min empty bed contact time. The process was superior to ZVI alone, particularly during the earlier stages of the process due to the synergistically increased iron dissolution rate. Besides GAC, graphite and anthracite also prove to be suitable and potentially more cost-effective options as cathode materials for the enhanced ZVI process, whereby electrically conductive graphite clearly outperformed anthracite. The dominant mechanisms in terms of NOM removal from surface water were found to be coagulation following iron dissolution and adsorption in the case of employing GAC. Oxidation was also occurring to a lesser degree, converting some non-biodegradable into biodegradable DOC.

  9. Enhancing Student Engagement in Student Experience Surveys: A Mixed Methods Study

    ERIC Educational Resources Information Center

    Webber, Martin; Lynch, Siobhan; Oluku, Jennifer

    2013-01-01

    Background: Measuring the student experience is becoming increasingly important in higher education in the UK. Student experience surveys are used as indicators of quality and form the basis of rankings of higher education institutions. They are also used by them as tools to assist their quality enhancement initiatives. However, these surveys…

  10. Localized arc filament plasma actuators for noise mitigation and mixing enhancement

    NASA Technical Reports Server (NTRS)

    Samimy, Mohammad (Inventor); Adamovich, Igor (Inventor)

    2010-01-01

    A device for controlling fluid flow. The device includes an arc generator coupled to electrodes. The electrodes are placed adjacent a fluid flowpath such that upon being energized by the arc generator, an arc filament plasma adjacent the electrodes is formed. In turn, this plasma forms a localized high temperature, high pressure perturbation in the adjacent fluid flowpath. The perturbations can be arranged to produce vortices, such as streamwise vortices, in the flowing fluid to control mixing and noise in such flows. The electrodes can further be arranged within a conduit configured to contain the flowing fluid such that when energized in a particular frequency and sequence, can excite flow instabilities in the flowing fluid. The placement of the electrodes is such that they are unobtrusive relative to the fluid flowpath being controlled.

  11. Caffeinated coffee enhances co-operative behavior in the Mixed Motive Game in healthy volunteers.

    PubMed

    Tse, Wai S; Chan, Chi Choi S; Shiu, Shun Yan K; Chung, Pik Yee A; Cheng, Shuk Han

    2009-02-01

    Caffeinated drinks are commonly consumed in social gatherings. However, their effects on social behavior remain unclear. The present study examined the effects of caffeinated coffee on antidepressant-related co-operative behavior. Seventy-seven low-caffeine users took part in a randomized, double-blind, cross-over study of single dose of caffeinated coffee (150 mg caffeine) and decaffeinated coffee (9 mg caffeine) with at least a 3-day washout period. In each session, participants were asked to imagine a fictitious person and play the Mixed Motive Game with that person 45 min after coffee consumption. Heart rate, blood pressure, and state moods were measured at baseline and at 45 min post-coffee consumption. After caffeinated coffee, participants exhibited significantly higher blood pressure. They also allocated significantly fewer scores to themselves and sent significantly more sadness message during the game. These results suggest that caffeinated coffee may help to improve social support and depressive symptoms.

  12. Localized arc filament plasma actuators for noise mitigation and mixing enhancement

    NASA Technical Reports Server (NTRS)

    Samimy, Mohammad (Inventor); Adamovich, Igor (Inventor)

    2008-01-01

    A device for controlling fluid flow. The device includes an arc generator coupled to electrodes. The electrodes are placed adjacent a fluid flowpath such that upon being energized by the arc generator, an arc filament plasma adjacent the electrodes is formed. In turn, this plasma forms a localized high temperature, high pressure perturbation in the adjacent fluid flowpath. The perturbations can be arranged to produce vortices, such as streamwise vortices, in the flowing fluid to control mixing and noise in such flows. The electrodes can further be arranged within a conduit configured to contain the flowing fluid such that when energized in a particular frequency and sequence, can excite flow instabilities in the flowing fluid. The placement of the electrodes is such that they are unobtrusive relative to the fluid flowpath being controlled.

  13. Numerical investigation and optimization on mixing enhancement factors in supersonic jet-to-crossflow flow fields

    NASA Astrophysics Data System (ADS)

    Yan, Li; Huang, Wei; Li, Hao; Zhang, Tian-tian

    2016-10-01

    Sufficient mixing between the supersonic airstream and the injectant is critical for the design of scramjet engines. The information in the two-dimensional supersonic jet-to-crossflow flow field has been explored numerically and theoretically, and the numerical approach has been validated against the available experimental data in the open literature. The obtained results show that the extreme difference analysis approach can obtain deeper information than the variance analysis method, and the optimal strategy can be generated by the extreme difference analysis approach. The jet-to-crossflow pressure ratio is the most important influencing factor for the supersonic jet-to-crossflow flow field, following is the injection angle, and all the design variables have no remarkable impact on the separation length and the height of Mach disk in the range considered in the current study.

  14. 76 FR 67022 - Enhanced-Use Lease (EUL) of Department of Veterans Affairs (VA) Real Property for a Mixed-Use...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-28

    ..., manage, maintain and operate the EUL development. As consideration for the lease, the lessee will be... AFFAIRS Enhanced-Use Lease (EUL) of Department of Veterans Affairs (VA) Real Property for a Mixed-Use.... ACTION: Notice of Intent to Enter into an Enhanced-Use Lease (EUL). SUMMARY: The Secretary of VA...

  15. Mixed-organic-cation perovskite photovoltaics for enhanced solar-light harvesting.

    PubMed

    Pellet, Norman; Gao, Peng; Gregori, Giuliano; Yang, Tae-Youl; Nazeeruddin, Mohammad K; Maier, Joachim; Grätzel, Michael

    2014-03-17

    Hybrid organic-inorganic lead halide perovskite APbX3 pigments, such as methylammonium lead iodide, have recently emerged as excellent light harvesters in solid-state mesoscopic solar cells. An important target for the further improvement of the performance of perovskite-based photovoltaics is to extend their optical-absorption onset further into the red to enhance solar-light harvesting. Herein, we show that this goal can be reached by using a mixture of formamidinium (HN=CHNH3 (+), FA) and methylammonium (CH3 NH3 (+), MA) cations in the A position of the APbI3 perovskite structure. This combination leads to an enhanced short-circuit current and thus superior devices to those based on only CH3 NH3 (+). This concept has not been applied previously in perovskite-based solar cells. It shows great potential as a versatile tool to tune the structural, electrical, and optoelectronic properties of the light-harvesting materials.

  16. Dual-pump wave mixing in semiconductor optical amplifiers: performance enhancement with long amplifiers

    NASA Astrophysics Data System (ADS)

    Tomkos, Ioannis; Zacharopoulos, Ioannis; Syvridis, Dimitrios

    1999-05-01

    We demonstrate experimentally the improvement of the performance of the dual pump wave mixing scheme in semiconductor optical amplifiers, using long amplifier chips and high optical pump powers. The optical amplifiers used in the experiment had a ridge waveguide structure with bulk active layer and antireflective-coated angled facets. Measurements of the conversion efficiency and SBR as a function of wavelength shift are presented for a wavelength shift of more than 40 nm. The above measurements are carried out for three amplifier lengths (500 micrometers , 1000 micrometers , and 1500 micrometers ) and for different levels of the optical power of the two pumps. It will be shown that an increase in the amplifier length from 500 micrometers to 1500 micrometers results to an increase of more than 25 dB for the efficiency and more than 20 dB for the SBR. This improvement combined with the inherent advantages of the dual pump scheme (almost constant SBR and high efficiency for large wavelength shifts) results in a highly performing wavelength converter/phase conjugator, suitable for many applications.

  17. Enhancing the carrier thermalization time in organometallic perovskites by halide mixing.

    PubMed

    Madjet, Mohamed El-Amine; Akimov, Alexey V; El-Mellouhi, Fadwa; Berdiyorov, Golibjon R; Ashhab, Sahel; Tabet, Nouar; Kais, Sabre

    2016-02-21

    Hybrid metal-organic halide perovskites have recently attracted a great deal of attention because of their interesting electronic, optical and transport properties, which make them promising materials for high-performance, low-cost solar cells. Fundamental understanding of the formation mechanisms and dynamics of photoinduced charge carriers is essential for improving the performance of perovskite solar cell devices. For example, a significant amount of absorbed solar energy is lost as a result of carrier thermalization. This energy could be harnessed by extracting hot carriers before they cool down to the band edges. Although such hot carrier collection is experimentally challenging, theoretical investigations based on time-dependent methods can guide future experimental research by providing insights into the thermalization process. Here, we perform ab initio nonadiabatic molecular dynamics simulations to study non-radiative relaxation dynamics of charge carriers in hybrid halide perovskites. We find that the carrier relaxation time can be considerably increased by mixing halogen atoms in the perovskite materials. These findings show that simple approaches could be adopted to slow down the thermalization process of hot carriers in perovskite materials.

  18. Biomimetic nanoparticles with polynucleotide and PEG mixed-monolayers enhance calcium phosphate mineralization

    NASA Astrophysics Data System (ADS)

    Vasconcellos, Kayla B.; McHugh, Sean M.; Dapsis, Katherine J.; Petty, Alexander R.; Gerdon, Aren E.

    2013-09-01

    Biomineralization of hydroxyapatite (Ca10(PO4)6(OH)2) is of significant importance in biomedical applications such as bone and dental repair, and biomimetic control of mineral formation may lead to more effective restorative procedures. Gold nanoparticles are functional scaffolds on which to assemble multi-component monolayers capable of mimicking protein activity in the templated synthesis of calcium phosphate. The goal of this research was to explore nanoparticle templates with mixed-monolayers of uncharged polar polyethylene glycol (PEG) molecules and highly charged polynucleotide and amino acid molecules in their ability to influence mineralization rates and mineral particle size and morphology. This research demonstrates through time-resolved optical density and dynamic light scattering measurements that the combination of tiopronin, PEG, and DNA presented on a nanoparticle surface decreases nanoparticle aggregation from 59 to 21 nm solvated radius, increases mineralization kinetics from 1.5 × 10-3 to 3.1 × 10-3 OD/min, and decreases mineral particle size from 685 to 442 nm average radius. FT-IR and TEM data demonstrate that mineralized material, while initially amorphous, transforms to a semi-crystalline material when guided by template interactions. This demonstrates that surface-tailored monolayer protected cluster scaffolds are successful and controllable mineralization templates with further potential for biomedical applications involving calcium phosphate and other biomaterials.

  19. Noni puree (Morinda citrifolia) mixed in beef patties enhanced color stability.

    PubMed

    Tapp, W Nathan; Yancey, Janeal W S; Apple, Jason K; Dikeman, Michael E; Godbee, Richard G

    2012-06-01

    Ground beef, mixed with 0, 2, 4, and 6% Noni puree, was formed into 150-g patties, aerobically packaged, and displayed in retail for 5d. After 2 and 3d, patties with higher concentrations of Noni were perceived as redder and less discolored (P<0.05) by visual panelists. Noni patties were found to have greater (P<0.05) a* values than controls, even though all patties became less red during display. After 3 and 5d of retail display, patties with higher concentrations of Noni puree also had lower TBARS (were less oxidized; P<0.05). In fresh taste panels, panelists perceived the patties to have less beef flavor and greater incidence of off-flavors (P<0.05) as Noni puree concentration increased. The potential of Noni puree to improve the color stability and shelf life of fresh ground beef is very promising, but the flavors produced by the addition of Noni in ground beef may be detrimental to its use.

  20. Enhancing non-melonic triangulations: A tensor model mixing melonic and planar maps

    NASA Astrophysics Data System (ADS)

    Bonzom, Valentin; Delepouve, Thibault; Rivasseau, Vincent

    2015-06-01

    Ordinary tensor models of rank D ≥ 3 are dominated at large N by tree-like graphs, known as melonic triangulations. We here show that non-melonic contributions can be enhanced consistently, leading to different types of large N limits. We first study the most generic quartic model at D = 4, with maximally enhanced non-melonic interactions. The existence of the 1 / N expansion is proved and we further characterize the dominant triangulations. This combinatorial analysis is then used to define a non-quartic, non-melonic class of models for which the large N free energy and the relevant expectations can be calculated explicitly. They are matched with random matrix models which contain multi-trace invariants in their potentials: they possess a branched polymer phase and a 2D quantum gravity phase, and a transition between them whose entropy exponent is positive. Finally, a non-perturbative analysis of the generic quartic model is performed, which proves analyticity in the coupling constants in cardioid domains.

  1. Study of Mixing Enhancement Observed with a Co-Annular Nozzle Configuration

    NASA Technical Reports Server (NTRS)

    Zaman, K. B. M. Q.; Papamoschou, D.

    2000-01-01

    Jet spreading enhancement with a certain coannular nozzle configuration has been explored. When the outer nozzle is flaired (i.e., made convergent-divergent) the ensuing jet spreads faster than the case where the outer nozzle is convergent. The spreading enhancement is most pronounced when the outer flow is run near 'transonic' condition, in an overexpanded state. Under this condition, the increased spreading takes place regardless of the operating conditions of the inner jet. This observation, first made in a small scale facility, has been confirmed and studied in some detail in a larger-scale facility. Results of the latter experiment are presented in this paper. The spreading increase is shown to be substantial and comparable to or better than that achieved by a lobed nozzle. Estimates based on idealized flow indicate that there is an accompanying thrust penalty - the actual penalty is expected to be less than the estimate but remains undetermined at this time. In both the earlier and the present experiments, the spreading increase has often been found to accompany a flow resonance. The nature of this resonance is addressed in this paper. It is shown that the spreading increase takes place even if the resonance is absent. Thus, flow excitation due to the resonance is ruled out as the underlying mechanism. While the complete mechanism remains unclear, it is conjectured that pressure gradients near the nozzle, characteristic of overexpanded flow, are at the root of the phenomenon.

  2. Genetic analysis of stress responses in soil bacteria for enhanced bioremediation of mixed contaminants. 1998 annual progress report

    SciTech Connect

    Wong, K.K.

    1998-06-01

    'To realize the full potential of bioremediation, the individual bacterial responses to the stresses (lack of nutrients or oxygen; mixed pollutants) encountered at contaminated sites must be understood. This information can then be extrapolated to field applications using indigenous bacteria or genetically engineered micro-organisms. Studying bacterial response to stresses presents an opportunity for improving bioremediation strategies, both with indigenous populations and genetically engineered microbes, and should contribute to environmental management and restoration goals. Enhancing in-situ removal of hazardous wastes by stimulating the growth of indigenous bacteria with nutrients has been demonstrated. But how much and how often to apply these supplements has been difficult to determine, and controlled and reproducible degradation of pollutants in the environment has not yet been achieved. As of May 31st 1998, this report summarizes work after 17 months of a 36 month project.'

  3. [Kinetic model of enhanced biological phosphorus removal with mixed acetic and propionic acids as carbon sources. (I): Model constitution].

    PubMed

    Zhang, Chao; Chen, Yin-Guang

    2013-03-01

    Based on activated sludge model No. 2 (ASM2), the anaerobic/aerobic kinetic model of phosphorus-accumulating organisms (PAO) was established with mixed short-chain fatty acids (SCFAs) as the base substance in enhanced biological phosphorus removal process. The characteristic of the PAO model was that the anaerobic metabolism rates of glycogen degradation, poly-beta-hydroxyalkanoates synthesis and polyphosphate hydrolysis were expressed by SCFAs uptake equation, and the effects of anaerobic maintenance on kinetics and stoichiometry were considered. The PAO kinetic model was composed of 3 soluble components, 4 particulate components and a pH parameter, which constituted the matrix of stoichiometric coefficients. On the basis of PAO model, the GAO kinetic model was established, which included 7 processes, and phosphorus content influenced the aerobic metabolism only.

  4. Enhancement of oxidative electrocatalytic properties of platinum nanoparticles by supporting onto mixed WO3/ZrO2 matrix

    NASA Astrophysics Data System (ADS)

    Rutkowska, Iwona A.; Wadas, Anna; Kulesza, Pawel J.

    2016-12-01

    Nanostructured mixed metal (W, Zr) oxide matrices (in a form of layered intercalated films of WO3 and ZrO2) are considered here for supporting and activating catalytic platinum nanoparticles toward electrooxidation of ethanol. Remarkable increases of electrocatalytic (voltammetric, chronoamperometric) currents measured in 0.5 mol dm-3 H2SO4 (containing 0.5 mol dm-3 ethanol) have been observed. Comparison has been made to the behavior of methanol and acetaldehyde under analogous conditions. The enhancement effects are interpreted in terms of specific interactions between platinum nanoparticles and the metal oxide species, high acidity of the mixed oxide sites, as well as high population of surface hydroxyl groups and high mobility of protons existing in close vicinity of Pt catalytic sites. The metal oxide nanostructures are expected to interact competitively (via the surface hydroxyl groups) with adsorbates of the undesirable reaction intermediates, including CO, facilitating their desorption ("third body effect"), or even oxidative removal (e.g., of CO to CO2). The fact that the partially reduced tungsten oxide (HxWO3) component is characterized by fast electron transfers coupled to proton displacements tends to improve the overall charge propagation at the electrocatalytic interface.

  5. Enhanced photoassisted water electrolysis using vertically oriented anodically fabricated Ti-Nb-Zr-O mixed oxide nanotube arrays.

    PubMed

    Allam, Nageh K; Alamgir, Faisal; El-Sayed, Mostafa A

    2010-10-26

    Self-ordered, highly oriented arrays of titanium-niobium-zirconium mixed oxide nanotube films were fabricated by the anodization of Ti(35)Nb(5)Zr alloy in aqueous and formamide electrolytes containing NH(4)F at room temperature. The nanostructure topology was found to depend on the nature of the electrolyte and the applied voltage. Our results demonstrate the possibility to grow mixed oxide nanotube array films possessing several-micrometer-thick layers by a simple and straightforward electrochemical route. The fabricated Ti-Nb-Zr-O nanotubes showed a ∼17.5% increase in the photoelectrochemical water oxidation efficiency as compared to that measured for pure TiO(2) nanotubes under UV illumination (100 mW/cm(2), 320-400 nm, 1 M KOH). This enhancement could be related to a combination of the effect of the thin wall of the fabricated Ti-Nb-Zr-O nanotubes (10 ± 2 nm) and the formation of Zr oxide and Nb oxide layers on the nanotube surface, which seems to slow down the electron-hole recombination in a way similar to that reported for Grätzel solar cells.

  6. [Dmt(1)]DALDA analogues with enhanced μ opioid agonist potency and with a mixed μ/κ opioid activity profile.

    PubMed

    Bai, Longxiang; Li, Ziyuan; Chen, Jiajia; Chung, Nga N; Wilkes, Brian C; Li, Tingyou; Schiller, Peter W

    2014-04-01

    Analogues of [Dmt(1)]DALDA (H-Dmt-d-Arg-Phe-Lys-NH2; Dmt=2',6'-dimethyltyrosine), a potent μ opioid agonist peptide with mitochondria-targeted antioxidant activity, were prepared by replacing Phe(3) with various 2',6'-dialkylated Phe analogues, including 2',6'-dimethylphenylalanine (Dmp), 2',4',6'-trimethylphenylalanine (Tmp), 2'-isopropyl-6'-methylphenylalanine (Imp) and 2'-ethyl-6'-methylphenylalanine (Emp), or with the bulky amino acids 3'-(1-naphthyl)alanine (1-Nal), 3'-(2-naphthyl)alanine (2-Nal) or Trp. Several compounds showed significantly increased μ agonist potency, retained μ receptor selectivity and are of interest as drug candidates for neuropathic pain treatment. Surprisingly, the Dmp(3)-, Imp(3)-, Emp(3)- and 1-Nal(3)-containing analogues showed much increased κ receptor binding affinity and had mixed μ/κ properties. In these cases, molecular dynamics studies indicated conformational preorganization of the unbound peptide ligands due to rotational restriction around the C(β)C(γ) bond of the Xxx(3) residue, in correlation with the observed κ receptor binding enhancement. Compounds with a mixed μ/κ opioid activity profile are known to have therapeutic potential for treatment of cocaine abuse.

  7. Enhanced Electron Heating and Mixing in a 3D Kinetic Simulation for MMS Magnetopause Crossings with Weak Guide Fields

    NASA Astrophysics Data System (ADS)

    Le, Ari; Daughton, William; Chen, Li-Jen; Egedal, Jan

    2016-10-01

    We present a 3D kinetic simulation of asymmetric reconnection with plasma parameters matching the MMS magetopause diffusion region crossing reported by Burch et al. (Science 2016). The simulation was performed with the code VPIC on LANL's Trinity machine, which enabled relatively high grid resolution and numerical particle numbers to resolve the electron diffusion region dynamics. The simulation not only reproduces the reported crescent distributions but also appears to account for new features observed by MMS in other diffusion region events with weak guide fields. Compared to a 2D simulation with the same plasma parameters, drift turbulence in the 3D simulation substantially enhances the mixing and parallel heating of electrons on the magnetosphere side. This modifies the reconnection rate inferred from a recently introduced electron mixing diagnostic. To the magnetosphere side of the in-plane magnetic null, the parallel electric field exhibits a bipolar structure with polarities opposite to the large-scale parallel electric field. The 3D structure of the X line and the particle signature of the inverted bipolar parallel electric field have been observed by MMS.

  8. Chemically enhanced mixed region vapor stripping of TCE-contaminated saturated peat and silty clay soils

    SciTech Connect

    West, O.R.; Cameron, P.A.; Lucero, A.J.; Koran, L.J. Jr.

    1996-01-01

    The objective of this study was to conduct further testing of MRVS, chemically enhanced with calcium oxide conditioning, on field- contaminated soils collected from beneath the NASA Michoud Rinsewater Impoundment. In this study, residual soil VOC levels as a function of vapor stripping time were measured to quantify VOC removal rates. Physical and chemical soil parameters expected to affect MRVS efficiency were measures. The effects of varying the calcium oxide loadings as well as varying the vapor stripping flow rates on VOC removal were also evaluated. The results of this study will be used to determine whether acceptable removals can be achieved within reasonable treatment times, remediation costs being directly proportional to the latter. The purpose of this report is to document the experimental results of this study, as well as to address issues that were raised after completion of the previous Michoud treatability work.

  9. Enhanced viability of Lactobacillus reuteri for probiotics production in mixed solid-state fermentation in the presence of Bacillus subtilis.

    PubMed

    Zhang, Yi-Ran; Xiong, Hai-Rong; Guo, Xiao-Hua

    2014-01-01

    In order to develop a multi-microbe probiotic preparation of Lactobacillus reuteri G8-5 and Bacillus subtilis MA139 in solid-state fermentation, a series of parameters were optimized sequentially in shake flask culture. The effect of supplementation of B. subtilis MA139 as starters on the viability of L. reuteri G8-5 was also explored. The results showed that the optimized process was as follows: water content, 50 %; initial pH of diluted molasses, 6.5; inocula volume, 2 %; flask dry contents, 30∼35 g/250 g without sterilization; and fermentation time, 2 days. The multi-microbial preparations finally provided the maximum concentration of Lactobacillus of about 9.01 ± 0.15 log CFU/g and spores of Bacillus of about 10.30 ± 0.08 log CFU/g. Compared with pure fermentation of L. reuteri G8-5, significantly high viable cells, low value of pH, and reducing sugar in solid substrates were achieved in mixed fermentation in the presence of B. subtilis MA139 (P < 0.05). Meanwhile, the mixed fermentation showed the significantly higher antimicrobial activity against E. coli K88 (P < 0.05). Based on the overall results, the optimized process enhanced the production of multi-microbe probiotics in solid-state fermentation with low cost. Moreover, the viability of L. reuteri G8-5 could be significantly enhanced in the presence of B. subtilis MA139 in solid-state fermentation, which favored the production of probiotics for animal use.

  10. A mixed alkanethiol based immunosensor for surface plasmon field-enhanced fluorescence spectroscopy in serum.

    PubMed

    Scholten, Andreas; Menges, Bernhard; Juebner, Martin; Rothschild, Markus A; Bender, Katja

    2013-03-21

    This paper describes a simple and sensitive immuno-based biosensor for interference-reduced detection of C-reactive protein (CRP) in serum. The detection was performed by using a non-competitive sandwich immunoassay in combination with surface plasmon field-enhanced fluorescence spectroscopy (SPFS). CRP is an important marker for the diagnosis of inflammatory processes and cardiovascular diseases (CVD). It is nowadays detected by high-sensitivity enzyme-linked immunosorbent assays (ELISA) in blood serum. CRP was used as a model analyte in this work because it is well-characterized. However, interfering effects of matrix components affect the limit of detection (LOD) and quantification (LOQ) in general. Therefore, the availability of fast, sensitive and robust analytical methods is of major interest. A number of biosensor approaches have been described already, but only a few have demonstrated their usefulness in authentic samples such as serum. Thus our aim was to develop a simple and sensitive immunoassay-based biosensor for an interference-reduced detection of CRP in serum with surface plasmon enhanced fluorescence spectroscopy (SPFS). LODs and LOQs were experimentally determined both for CRP spiked buffer and serum. SPFS in combination with our biosensor allows sensitive analysis of CRP, achieving in buffer a LOD of 0.016 μg mL(-1) and a LOQ of 0.049 μg mL(-1). In serum the accomplished LOD was 0.026 μg mL(-1) and the LOQ was found to be 0.08 μg mL(-1). These low LODs and LOQs demonstrate the applicability of the designed biosensor for qualitative and semi-quantitative analysis of trace amounts of substances in very small sample volumes of body fluids.

  11. Surface coverage enhancement of a mixed halide perovskite film by using an UV-ozone treatment

    NASA Astrophysics Data System (ADS)

    Lee, Hyunho; Rhee, Seunghyun; Kim, Jaeyoul; Lee, Changhee; Kim, Hyeok

    2016-08-01

    Recently, a significant breakthrough in emerging photovoltaics occurred. Now, perovskite solar cells, hybrid types of organic and inorganic solar cells, are considered as reliable next-generation solar cells due to their outstanding photovoltaic performance. Records of the National Renewable Energy Laboratory (NREL) on cell efficiency research indicates a prominent growth in the power conversion efficiency (PCE) of a perovskite solar cells which is now approaching 20.1%. Perovskite solar cells are, in general, classified into three types based on their structures; the mesoporous type with TiO2 nanoparticles, the meso-superstructure type with Al2O3 and the planar hetero-junction type. Among them, planar-structured perovskite solar cells have strong advantages due to their easy processibility and flexibility. We can replace the materials in the electron transport layer (ETL) and the hole transport layer (HTL) with common materials that are available in organic solar cells. However, a great challenge is to fabricate a high-quality perovskite film because the perovskite morphology is highly sensitive to its fabrication conditions. For control of the film's morphology, some experiments, such as changing the annealing temperature or time and adding some additives, have been done to increase the surface coverage of perovskite films. In this work, we introduce normal, planar, perovskite solar cells with a hetero-junction structure based on compact TiO2 and a mixed halide perovskite (CH3NH3PbI3- x Cl x ). To enlarge the surface coverage of perovskite film, we used an UV-ozone treatment on top of the compact TiO2, which made the surface of TiO2 hydrophilic. Because a perovskite precursor is hydrophilic, an UV-ozone treatment is expected to improve the wettability between the compact TiO2 and the perovskite film. Here, we present the photovoltaic performance, along with the surface coverage difference, for various UV-ozone treatment time. In addition, the effect of the UV

  12. Graphene immobilized enzyme/polyethersulfone mixed matrix membrane: Enhanced antibacterial, permeable and mechanical properties

    NASA Astrophysics Data System (ADS)

    Duan, Linlin; Wang, Yuanming; Zhang, Yatao; Liu, Jindun

    2015-11-01

    Enzyme immobilization has been developed to address lots of issues of free enzyme, such as instability, low activity and difficult to retain. In this study, graphene was used as an ideal carrier for lysozyme immobilization, including graphene oxide (GO) immobilized lysozyme (GO-Ly) and chemically reduced graphene oxide (CRGO) immobilized lysozyme (CRGO-Ly). Herein, lysozyme as a bio-antibacterial agent has excellent antibacterial performance and the products of its catalysis are safety and nontoxic. Then the immobilized lysozyme materials were blended into polyethersulfone (PES) casting solution to prepare PES ultrafiltration membrane via phase inversion method. GO and CRGO were characterized by Fourier transform infrared spectroscopy (FTIR), Ultraviolet-visible spectrum (UV), X-ray diffraction (XRD), and transmission electron microscopy (TEM) and the immobilized lysozyme composites were observed by fluorescent microscopy. The results revealed that GO and CRGO were successfully synthesized and lysozyme was immobilized on their surfaces. The morphology, hydrophilicity, mechanical properties, separation properties and antibacterial activity of the hybrid membranes were characterized in detail. The hydrophilicity, water flux and mechanical strength of the hybrid membranes were significantly enhanced after adding the immobilized lysozyme. In the antibacterial experiment, the hybrid membranes exhibited an effective antibacterial performance against Escherichia coli (E. coli).

  13. Enhancement mechanism of the additional absorbent on the absorption of the absorbing composite using a type-based mixing rule

    NASA Astrophysics Data System (ADS)

    Xu, Yonggang; Yuan, Liming; Zhang, Deyuan

    2016-04-01

    A silicone rubber composite filled with carbonyl iron particles and four different carbonous materials (carbon black, graphite, carbon fiber or multi-walled carbon nanotubes) was prepared using a two-roller mixture. The complex permittivity and permeability were measured using a vector network analyzer at the frequency of 2-18 GHz. Then a type-based mixing rule based on the dielectric absorbent and magnetic absorbent was proposed to reveal the enhancing mechanism on the permittivity and permeability. The enforcement effect lies in the decreased percolation threshold and the changing pending parameter as the carbonous materials were added. The reflection loss (RL) result showed the added carbonous materials enhanced the absorption in the lower frequency range, the RL decrement value being about 2 dB at 4-5 GHz with a thickness of 1 mm. All the added carbonous materials reinforced the shielding effectiveness (SE) of the composites. The maximum increment value of the SE was about 3.23 dB at 0.5 mm and 4.65 dB at 1 mm, respectively. The added carbonous materials could be effective additives for enforcing the absorption and shielding property of the absorbers.

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

    PubMed

    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.

  15. Capture, Release and Culture of Circulating Tumor Cells from Pancreatic Cancer Patients using an Enhanced Mixing Chip

    PubMed Central

    Sheng, Weian; Ogunwobi, Olorunseun O.; Chen, Tao; Zhang, Jinling; George, Thomas J.; Liu, Chen; Fan, Z. Hugh

    2013-01-01

    Circulating tumor cells (CTCs) from peripheral blood hold important information for cancer diagnosis and disease monitoring. Analysis of this “liquid biopsy” holds the promise to usher in a new era of personalized therapeutic treatments and real-time monitoring for cancer patients. But the extreme rarity of CTCs in blood makes their isolation and characterization technologically challenging. This paper reports the development of a geometrically enhanced mixing (GEM) chip for high-efficiency and high-purity tumor cell capture. We also successfully demonstrated the release and culture of the captured tumor cells, as well as the isolation of CTCs from cancer patients. The high-performance microchip is based on geometrically optimized micromixer structures, which enhance the transverse flow and flow folding, maximizing the interaction between CTCs and antibody-coated surfaces. With the optimized channel geometry and flow rate, the capture efficiency reached >90% with a purity of >84% when capturing spiked tumor cells in buffer. The system was further validated by isolating a wide range of spiked tumor cells (50–50,000) in 1 mL of lysed blood and whole blood. With the combination of trypsinization and high flow rate washing, captured tumor cells were efficiently released. The released cells were viable and able to proliferate, and showed no difference compared with intact cells that were not subjected to the capture and release process. Furthermore, we applied the device for detecting CTCs from metastatic pancreatic cancer patients’ blood; and CTCs were found from 17 out of 18 samples (>94%). We also tested the potential utility of the device in monitoring the response to anti-cancer drug treatment in pancreatic cancer patients, and the CTC numbers correlated with the clinical computed tomograms (CT scans) of tumors. The presented technology shows great promise for accurate CTC enumeration, biological studies of CTCs and cancer metastasis, as well as for cancer

  16. Enhancing the Lithium Ion Conductivity in Lithium Superionic Conductor (LISICON) Solid Electrolytes through a Mixed Polyanion Effect.

    PubMed

    Deng, Yue; Eames, Christopher; Fleutot, Benoit; David, Rénald; Chotard, Jean-Noël; Suard, Emmanuelle; Masquelier, Christian; Islam, M Saiful

    2017-03-01

    Lithium superionic conductor (LISICON)-related compositions Li4±xSi1-xXxO4 (X = P, Al, or Ge) are important materials that have been identified as potential solid electrolytes for all solid state batteries. Here, we show that the room temperature lithium ion conductivity can be improved by several orders of magnitude through substitution on Si sites. We apply a combined computer simulation and experimental approach to a wide range of compositions (Li4SiO4, Li3.75Si0.75P0.25O4, Li4.25Si0.75Al0.25O4, Li4Al0.33Si0.33P0.33O4, and Li4Al1/3Si1/6Ge1/6P1/3O4) which include new doped materials. Depending on the temperature, three different Li(+) ion diffusion mechanisms are observed. The polyanion mixing introduced by substitution lowers the temperature at which the transition to a superionic state with high Li(+) ion conductivity occurs. These insights help to rationalize the mechanism of the lithium ion conductivity enhancement and provide strategies for designing materials with promising transport properties.

  17. Additives enhancing the catalytic properties of lipase from Burkholderia cepacia immobilized on mixed-function-grafted mesoporous silica gel.

    PubMed

    Abaházi, Emese; Boros, Zoltán; Poppe, László

    2014-07-08

    Effects of various additives on the lipase from Burkholderia cepacia (BcL) immobilized on mixed-function-grafted mesoporous silica gel support by hydrophobic adsorption and covalent attachment were investigated. Catalytic properties of the immobilized biocatalysts were characterized in kinetic resolution of racemic 1-phenylethanol (rac-1a) and 1-(thiophen-2-yl)ethan-1-ol (rac-1b). Screening of more than 40 additives showed significantly enhanced productivity of immobilized BcL with several additives such as PEGs, oleic acid and polyvinyl alcohol. Effects of substrate concentration and temperature between 0-100 °C on kinetic resolution of rac-1a were studied with the best adsorbed BcLs containing PEG 20 k or PVA 18-88 additives in continuous-flow packed-bed reactor. The optimum temperature of lipase activity for BcL co-immobilized with PEG 20k found at around 30 °C determined in the continuous-flow system increased remarkably to around 80 °C for BcL co-immobilized with PVA 18-88.

  18. Mixed Substrate Fermentation for Enhanced Phytase Production by Thermophilic Mould Sporotrichum thermophile and Its Application in Beneficiation of Poultry Feed.

    PubMed

    Kumari, Amit; Satyanarayana, T; Singh, Bijender

    2016-01-01

    The optimum values of the critical variables determined by the central composite design of response surface methodology (RSM) for maximum phytase production (1881.26 U g(-1) dry mouldy residue (DMR)) by Sporotrichum thermophile are 2.5 % Tween 80, 1.0 % yeast extract and 48 h of incubation period. Phytase production in the mixed substrate (sugarcane bagasse and wheat bran) fermentation enhanced 11.6-fold over the initial production as a consequence of optimization. Phytase titres are sustainable in flasks, trays and column bioreactor (1796 to 2095 U g(-1) DMR), thus validating the model and the process for large-scale phytase production. When the yeast extract was replaced with corn steep liquor (2 % w/v), a sustained enzyme titre (1890 U g(-1) DMR) was attained, making the process cost-effective. Among all the detergents, Tween 80 supported a higher phytase production than others. The enzyme efficiently liberated nutritional components from poultry feed (inorganic phosphate, soluble protein and reducing sugars) in a time-dependent manner.

  19. Novel Low Temperature Processing for Enhanced Properties of Ion Implanted Thin Films and Amorphous Mixed Oxide Thin Film Transistors

    NASA Astrophysics Data System (ADS)

    Vemuri, Rajitha

    This research emphasizes the use of low energy and low temperature post processing to improve the performance and lifetime of thin films and thin film transistors, by applying the fundamentals of interaction of materials with conductive heating and electromagnetic radiation. Single frequency microwave anneal is used to rapidly recrystallize the damage induced during ion implantation in Si substrates. Volumetric heating of the sample in the presence of the microwave field facilitates quick absorption of radiation to promote recrystallization at the amorphous-crystalline interface, apart from electrical activation of the dopants due to relocation to the substitutional sites. Structural and electrical characterization confirm recrystallization of heavily implanted Si within 40 seconds anneal time with minimum dopant diffusion compared to rapid thermal annealed samples. The use of microwave anneal to improve performance of multilayer thin film devices, e.g. thin film transistors (TFTs) requires extensive study of interaction of individual layers with electromagnetic radiation. This issue has been addressed by developing detail understanding of thin films and interfaces in TFTs by studying reliability and failure mechanisms upon extensive stress test. Electrical and ambient stresses such as illumination, thermal, and mechanical stresses are inflicted on the mixed oxide based thin film transistors, which are explored due to high mobilities of the mixed oxide (indium zinc oxide, indium gallium zinc oxide) channel layer material. Semiconductor parameter analyzer is employed to extract transfer characteristics, useful to derive mobility, subthreshold, and threshold voltage parameters of the transistors. Low temperature post processing anneals compatible with polymer substrates are performed in several ambients (oxygen, forming gas and vacuum) at 150 °C as a preliminary step. The analysis of the results pre and post low temperature anneals using device physics fundamentals

  20. Raman frequency mixing under coherent population trapping conditions

    SciTech Connect

    Arkhipkin, V G; Popov, A K; Manushkin, D V; Myslivets, S A

    1998-07-31

    An investigation is reported of resonant four-wave frequency mixing of the type {omega}{sub 4}={omega}{sub 1}-{omega}{sub 2}+{omega}{sub 3} under coherent population trapping conditions. Such mixing may appear when radiations of frequencies {omega}{sub 1,2} are strong and when {omega}{sub 1}-{omega}{sub 2}={omega}{sub 20} ({omega}{sub 20} is the frequency of a dipole-forbidden transition). The density matrix method is used to calculate (taking quantum interference into account) the absorption coefficients, the refractive indices, and the nonlinear susceptibilities exactly for the strong fields and in the first order of perturbation theory for the weak fields. A study is made of the dependence of the power of nonlinear optical generation on various characteristics of the transitions and of the radiation, subject to the propagation effects. The cases of homogeneous and Doppler broadening of the resonant transitions are considered. The characteristics of transitions in the barium atom are used in numerical illustrations. It is shown that the efficiency of resonant nonlinear-optical conversion of radiation can be enhanced by utilising interference processes in quantum transitions, which represent coherent population trapping. (nonlinear optical phenomena)