Sample records for vcsel polarization control

  1. Reliable polarization control of VCSELs through monolithically integrated surface gratings: a comparative theoretical and experimental study

    Microsoft Academic Search

    Pierluigi Debernardi; Johannes Michael Ostermann; Martin Feneberg; Christof Jalics; Rainer Michalzik

    2005-01-01

    Vertical cavity surface-emitting lasers (VCSELs) with a well-defined and predictable polarization of the emitted light are sought for a number of applications. In this paper, we show that one can define and stabilize the polarization of single- and multimode oxide-confined VCSELs with a monolithically integrated dielectric surface grating. In recent years, we have developed a three-dimensional, fully vectorial model for

  2. Analysis of nonlinear dynamics and spin-flip parameters on elliptically polarized injection-locked VCSELs

    NASA Astrophysics Data System (ADS)

    Homayounfar, A.; Adams, Michael J.

    2008-08-01

    Using spin-flip model (SFM) of vertical-cavity surface-emitting lasers (VCSELs) subject to polarized injection, it is found that reducing the spin relaxation, or increasing the birefringence and pumping terms, can increase elliptically polarized injection locking (EPIL) stability for the slave VCSEL. The nonlinear dynamic is investigated in optically injected VCSELs with numerical simulation techniques for six fundamental VCSEL rate equations. A novel phenomenon as quasi stability which affects the EPIL is analyzed.

  3. Polymer MEMS for the active control of VCSEL beam

    Microsoft Academic Search

    B. Reig; T. Camps; V. Bardinal; D. Barat; E. Daran; J. B. Doucet

    2011-01-01

    Beam control of VCSELs (Vertical Cavity Surface Emitting Lasers) is a key topic to integrate these laser diodes in microsystems for instrumentation or biomedical application [I]. We report here on a simple method to control dynamically the beam shape of VCSELs devices. Our approach is based on an electro-thermal actuator including a polymer membrane, a heating electrode and a polymer

  4. Single-mode, single-polarization VCSELs via elliptical surface etching: experiments and theory

    Microsoft Academic Search

    Pierluigi Debernardi; Heiko J. Unold; Juergen Maehnss; Rainer Michalzik; Gian Paolo Bava; Karl Joachim Ebeling

    2003-01-01

    Polarization control in vertical-cavity surface-emitting lasers (VCSELs) has attracted a lot of interest and different techniques have been proposed to achieve it. Among them, one of the most attractive relies on slight modifications of existing and well-behaving devices, i.e., by introducing a noncircular transverse section layer somewhere in the device. Even though experimental verifications of this principle have already been

  5. 1.55-?m VCSEL with polarization-independent HCG mirror on SOI.

    PubMed

    Tsunemi, Yoshihiro; Yokota, Nobuhide; Majima, Shota; Ikeda, Kazuhiro; Katayama, Takeo; Kawaguchi, Hitoshi

    2013-11-18

    We designed and fabricated a vertical-cavity surface-emitting laser (VCSEL) incorporating a polarization-independent high-index-contrast subwavelength grating (HCG) mirror on silicon-on-insulator (SOI) for a novel polarization-bistable device on a silicon substrate. The VCSEL consists of the HCG mirror, an active layer with InGaAsP quantum wells having optical gain around 1.55 ?m, and an Al0.9Ga0.1As/Al0.16Ga0.84As DBR. We used direct wafer bonding for the bonding between the active layer and the AlGaAs DBR, and benzocyclobutene (BCB) bonding for the bonding between the active layer and the polarization-independent HCG mirror. The reflectivity of the HCG embedded with BCB was measured, resulting in a 200-nm-high reflectivity band with reflectivity higher than 99% and a small polarization dependence of ± 1%. We achieved lasing of the fabricated HCG-VCSEL at 1527 nm under an optical short pulse excitation with an average power of 50 mW (~0.2 mJ/cm2) at 240 K. PMID:24514380

  6. Study on differences between high contrast grating reflectors for TM and TE polarizations and their impact on VCSEL designs

    NASA Astrophysics Data System (ADS)

    Chung, Il-Sug

    2015-06-01

    A theoretical study of differences in broadband high-index-contrast grating (HCG) reflectors for TM and TE polarizations is presented, covering various grating parameters and properties of HCGs. It is shown that the HCG reflectors for TM polarization (TM HCG reflectors) have much thicker grating thicknesses and smaller grating periods than the TE HCG reflectors. This difference is found to originate from the different boundary conditions met for the electric field of each polarization. Due to this difference, the TM HCG reflectors have much shorter evanescent extension of HCG modes into low-refractive-index media surrounding the HCG. This enables to achieve a very short effective cavity length for VCSELs, which is essential for ultrahigh speed VCSELs and MEMS-tunable VCSELs. The obtained understandings on polarization dependences will be able to serve as important design guidelines for various HCG-based devices.

  7. Improved performance of polarization-stable VCSELs by monolithic sub-wavelength gratings produced by soft nano-imprint lithography

    NASA Astrophysics Data System (ADS)

    Verschuuren, M. A.; Gerlach, P.; van Sprang, H. A.; Polman, A.

    2011-12-01

    We present a novel method for fabricating polarization-stable oxide-confined single-mode GaAs based vertical cavity surface emitting lasers (VCSELs) emitting at 850 nm using a new soft-lithography nano-imprint technique. A monolithic surface grating is etched in the output mirror of the laser cavity using a directly imprinted silica-based sol-gel imprint resist as an etch mask. The opto-electronic performance of these devices is compared to VCSELs fabricated by state-of-the-art electron-beam lithography. The lasers made using the soft nano-imprint technique show single-mode TM lasing at a threshold and laser slope similar to that of devices made by e-beam lithography. The soft nano-imprint technique also enables the fabrication of gratings with sub-wavelength pitch, which avoids diffraction losses in the laser cavity. The resulting single-mode VCSEL devices exhibit 29% enhanced efficiency compared to devices equipped with diffractive gratings.

  8. Control of emitted light polarization in a 1310 nm dilute nitride spin-vertical cavity surface emitting laser subject to circularly polarized optical injection

    NASA Astrophysics Data System (ADS)

    Alharthi, S. S.; Hurtado, A.; Al Seyab, R. K.; Korpijarvi, V.-M.; Guina, M.; Henning, I. D.; Adams, M. J.

    2014-11-01

    We experimentally demonstrate the control of the light polarization emitted by a 1310 nm dilute nitride spin-Vertical Cavity Surface Emitting Laser (VCSEL) at room temperature. This is achieved by means of a combination of polarized optical pumping and polarized optical injection. Without external injection, the polarization of the optical pump controls that of the spin-VCSEL. However, the addition of the externally injected signal polarized with either left- (LCP) or right-circular polarization (RCP) is able to control the polarization of the spin-VCSEL switching it at will to left- or right-circular polarization. A numerical model has been developed showing a very high degree of agreement with the experimental findings.

  9. Ultrafast polarization dynamics with controlled polarization oscillations in vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Lindemann, Markus; Höpfner, Henning; Gerhardt, Nils C.; Hofmann, Martin R.; Pusch, Tobias; Michalzik, Rainer

    2015-03-01

    Spintronic lasers offer promising perspectives for new concepts superior to options of purely charge-based devices. Especially spin-polarized vertical-cavity surface-emitting lasers (spin-VCSELs) exhibit ultrafast spin and polarization dynamics. Using pulsed spin-injection, oscillations in the circular polarization degree can be generated, which have the potential to exceed frequencies of 100 GHz. The oscillations evolve due to coupling of the carrier-spin-photon system for linear modes via birefringence in the VCSEL's cavity. They are independent of the conventional relaxation oscillations and thus their usage can be the cornerstone for ultrafast directly modulated spin-VCSELs in the near future. After giving a short overview of the state of scientific and technical knowledge we will outline a method to control the polarization oscillations by multiple spin-injection pulses. It is possible to switch these oscillations on and off, depending on phase and amplitude conditions of two consecutive excitation pulses. Even half-cycles can be generated, which is the basis for short polarization pulses, only limited by the polarization oscillation resonance frequency. We investigate influences of the birefringence, which directly determines the oscillation frequency, by means of calculations with the spin-flip-model and experimental verification using 850 nm VCSELs. Furthermore we discuss experimental possibilities of increasing the birefringence and therefore the oscillation frequency, such that ultrashort pulses come into reach.

  10. VCSEL beam control with collective and self-aligned polymer technologies

    NASA Astrophysics Data System (ADS)

    Bardinal, Véronique; Camps, Thierry; Reig, Benjamin; Debernardi, Pierluigi; Soppera, Olivier; Barat, David; Doucet, Jean-Baptiste; Daran, Emmanuelle

    2012-03-01

    We present recent results on the integration of polymer microlenses on single mode Vertical-Cavity Surface-Emitting Lasers (VCSELs) to achieve output beam control. We describe in particular low cost and collective fabrication methods developed to allow for a self-alignment of the lens with the laser source. These approaches are based either on surface tension effects or on a self-writing process using novel Near Infra-Red (NIR) photopolymers. Results on beam collimation at 850nm are presented and compared to a fully vectorial and three-dimensional optical model that takes into account the complete geometry of laser resonator is used. Results on short distance focusing using self-aligned microtips are presented. Considerations to achieve an active beam control by means of polymer-based MEMS (Micro-electro-mechanical System) are also discussed. Potential applications may concern the improvement of VCSEL insertion in optical interconnects or sensing systems, as well as the fabrication of optical micro-probes for near-field microscopy.

  11. High-power VCSEL systems and applications

    NASA Astrophysics Data System (ADS)

    Moench, Holger; Conrads, Ralf; Deppe, Carsten; Derra, Guenther; Gronenborn, Stephan; Gu, Xi; Heusler, Gero; Kolb, Johanna; Miller, Michael; Pekarski, Pavel; Pollmann-Retsch, Jens; Pruijmboom, Armand; Weichmann, Ulrich

    2015-03-01

    Easy system design, compactness and a uniform power distribution define the basic advantages of high power VCSEL systems. Full addressability in space and time add new dimensions for optimization and enable "digital photonic production". Many thermal processes benefit from the improved control i.e. heat is applied exactly where and when it is needed. The compact VCSEL systems can be integrated into most manufacturing equipment, replacing batch processes using large furnaces and reducing energy consumption. This paper will present how recent technological development of high power VCSEL systems will extend efficiency and flexibility of thermal processes and replace not only laser systems, lamps and furnaces but enable new ways of production. High power VCSEL systems are made from many VCSEL chips, each comprising thousands of low power VCSELs. Systems scalable in power from watts to multiple ten kilowatts and with various form factors utilize a common modular building block concept. Designs for reliable high power VCSEL arrays and systems can be developed and tested on each building block level and benefit from the low power density and excellent reliability of the VCSELs. Furthermore advanced assembly concepts aim to reduce the number of individual processes and components and make the whole system even more simple and reliable.

  12. Interferometric polarization control

    SciTech Connect

    Chuss, David T.; Wollack, Edward J.; Moseley, S. Harvey; Novak, Giles

    2006-07-20

    We develop the Jones and Mueller matrices for structures that allow control of the path length difference between two linear orthogonal polarizations and consider the effect of placing multiple devices in series. Specifically, we find that full polarization modulation (measurement of Stokes Q, U, and V) can be achieved by placing two such modulators in series if the relative angles of the beam-splitting grids with respect to the analyzer orientation are appropriately chosen. Such a device has several potential advantages over a spinning wave plate modulator for measuring astronomical polarization in the far infrared through millimeter: (i) The use of small, linear motions eliminates the need for cryogenic rotational bearings; (ii) the phase flexibility allows measurement of circular as well as linear polarization; and (iii) this architecture allows for both multiwavelength and broadband modulation. We also present initial laboratory results.

  13. Noise and signal modeling of various VCSEL structures

    Microsoft Academic Search

    Angelique Rissons; Julien Perchoux; Jean-Claude Mollier; Martin Grabherr

    2004-01-01

    Current evolution in Datacoms and Gigabit Ethernet have made 850nm Vertical Cavity Surface Emitting Lasers (VCSEL) the most important and promising emitter. Numerous different structures have been growth, to obtain best current confinement and then to control the emitted light modal behavior. We have developed a small signal equivalent electrical model of VCSEL including Bragg reflectors, active area, chip connection

  14. Red Emitting VCSEL

    NASA Astrophysics Data System (ADS)

    Jetter, Michael; Roßbach, Robert; Michler, Peter

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

  15. Materials issues for VCSEL operation and reliability

    NASA Astrophysics Data System (ADS)

    Mathes, David Todd

    Significant advancements have been made in the characterization and understanding of the behavior of III-V semiconductor materials employed in Vertical Cavity Surface Emitting Laser (VCSEL) diodes. For the first time a technique has been developed whereby it is possible to view the entire active region of a solid state laser in a TEM using a novel plan-view sample geometry. This, in conjunction with cross-section samples enables a three-dimensional characterization of the degradation mechanisms that lead to laser failure. Additionally, proof of concept has been established for an in-situ TEM experiment in which electrical current is passed through a sectioned VCSEL diode and for which it is possible to correlate experimental parameters, such as electrical bias, current flow, and membrane temperature to diode degradation. Finally, due to the fact that layers of laterally grown AlxGa1-xAs oxide (which are commonly employed in VCSEL designs) are possible initiation sites for laser degradation, the oxidation behaviors of a range of III-V materials in the AlxGa1-xAsyP1-y and AlxIn1-xASyP1-y systems have been investigated. For a subset of the studied degraded VCSELs that consists of a single, rapidly failing oxide-confined laser operated for different periods of time, the degradation proceeds as follows. There is an initial drop in laser power output due to the development of cracks in the upper mirror layers (leading to a loss of the resonance cavity) and also, possibly due to a mechanism whereby the resistivity of the active region increases. In order that material degradation in VCSEL devices can be observed in real-time, an electrical in-situ experiment has been designed whereby it is possible to pass electrical current through a TEM-transparent, sectioned VCSEL. Methods have been designed to account for current losses from parallel current paths and for potential drops across series resistances, thereby determining the precise currents and potential drops experienced by the sectioned VCSEL diode. Finally, oxidation of III-V quaternary compounds in the AlxGa 1-xAsyP1-y and InxAl 1-xAsyP1-y systems was studied. The controlled parameters in these studies were composition and epitaxial strain, although it is found that pressures induced during the oxidation and the microstructure of the oxide also likely influence the oxidation. For lateral oxidation of AlxGa1-xAsyP1-y (y ? 0.78) it was found that increased phosphorous content led to slower oxidation rates and higher activation energies. (Abstract shortened by UMI.)

  16. Dynamic Self-Locking of an OEO Containing a VCSEL

    NASA Technical Reports Server (NTRS)

    Strekalov, Dmitry; Matsko, Andrey; Yu, Nan; Savchenkov, Anatoliy; Maleki, Lute

    2009-01-01

    A method of dynamic self-locking has been demonstrated to be effective as a means of stabilizing the wavelength of light emitted by a vertical-cavity surface-emitting laser (VCSEL) that is an active element in the frequency-control loop of an optoelectronic oscillator (OEO) designed to implement an atomic clock based on an electromagnetically- induced-transparency (EIT) resonance. This scheme can be considered an alternative to the one described in Optical Injection Locking of a VCSEL in an OEO (NPO-43454), NASA Tech Briefs, Vol. 33, No. 7 (July 2009), page 33. Both schemes are expected to enable the development of small, low-power, high-stability atomic clocks that would be suitable for use in applications involving precise navigation and/or communication. To recapitulate from the cited prior article: In one essential aspect of operation of an OEO of the type described above, a microwave modulation signal is coupled into the VCSEL. Heretofore, it has been well known that the wavelength of light emitted by a VCSEL depends on its temperature and drive current, necessitating thorough stabilization of these operational parameters. Recently, it was discovered that the wavelength also depends on the microwave power coupled into the VCSEL. This concludes the background information. From the perspective that led to the conception of the optical injection-locking scheme described in the cited prior article, the variation of the VCSEL wavelength with the microwave power circulating in the frequency-control loop is regarded as a disadvantage and optical injection locking is a solution of the problem of stabilizing the wavelength in the presence of uncontrolled fluctuations in the microwave power. The present scheme for dynamic self-locking emerges from a different perspective, in which the dependence of VCSEL wavelength on microwave power is regarded as an advantageous phenomenon that can be exploited as a means of controlling the wavelength. The figure schematically depicts an atomic-clock OEO of the type in question, wherein (1) the light from the VCSEL is used to excite an EIT resonance in selected atoms in a gas cell (e.g., 87Rb atoms in a low-pressure mixture of Ar and Ne) and (2) the power supplied to the VCSEL is modulated by a microwave signal that includes components at beat frequencies among the VCSEL wavelength and modulation sidebands. As the VCSEL wavelength changes, it moves closer to or farther from a nearby absorption spectral line, and the optical power transmitted through the cell (and thus the loop gain) changes accordingly. A change in the loop gain causes a change in the microwave power and, thus, in the VCSEL wavelength. It is possible to choose a set of design and operational parameters (most importantly, the electronic part of the loop gain) such that the OEO stabilizes itself in the sense that an increase in circulating microwave power causes the VCSEL wavelength to change in a direction that results in an increase in optical absorption and thus a decrease in circulating microwave power. Typically, such an appropriate choice of operational parameters involves setting the nominal VCSEL wavelength to a point on the shorter-wavelength wing of an absorption spectral line.

  17. Electrically controlling the polarizing direction of a graphene polarizer

    SciTech Connect

    Zhu, Z. H., E-mail: zzhwcx@163.com; Qin, S. Q. [College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073 (China); State Key Laboratory of High Performance Computing, National University of Defense Technology, Changsha 410073 (China); Guo, C. C.; Liu, K.; Zhang, J. F.; Ye, W. M.; Yuan, X. D. [College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073 (China)

    2014-09-14

    We theoretically demonstrate a polarizer with an electrically controllable polarizing direction in the far infrared range using two orthogonal periodic arrays of graphene ribbons, which have different widths and are supported on a dielectric film placed on a thick piece of metal. The operation mechanism originates from the polarization-dependent resonant absorption of the two orthogonal graphene ribbons, which can be respectively controlled with different external bias voltages. The operation wavelength can be expanded to terahertz (THz) radiation.

  18. Electrically controlling the polarizing direction of a graphene polarizer

    NASA Astrophysics Data System (ADS)

    Zhu, Z. H.; Guo, C. C.; Liu, K.; Zhang, J. F.; Ye, W. M.; Yuan, X. D.; Qin, S. Q.

    2014-09-01

    We theoretically demonstrate a polarizer with an electrically controllable polarizing direction in the far infrared range using two orthogonal periodic arrays of graphene ribbons, which have different widths and are supported on a dielectric film placed on a thick piece of metal. The operation mechanism originates from the polarization-dependent resonant absorption of the two orthogonal graphene ribbons, which can be respectively controlled with different external bias voltages. The operation wavelength can be expanded to terahertz (THz) radiation.

  19. High-speed VCSELs and VCSEL arrays for single- and multi-core fiber interconnects

    NASA Astrophysics Data System (ADS)

    Larsson, Anders; Westbergh, Petter; Gustavsson, Johan S.; Haglund, Erik; Haglund, Emanuel P.

    2015-03-01

    Our recent work on high speed 850 nm VCSELs and VCSEL arrays is reviewed. With a modulation bandwidth approaching 30 GHz, our VCSELs have enabled transmitters and links operating at data rates in excess of 70 Gbps (at IBM) and transmission over onboard polymer waveguides at 40 Gbps (at University of Cambridge). VCSELs with an integrated mode filter for single mode emission have enabled transmission at 25 Gbps over >1 km of multimode fiber and a speed-distance product of 40 Gbps·km. Dense VCSEL arrays for multicore fiber interconnects have demonstrated 240 Gbps aggregate capacity with excellent uniformity and low crosstalk between the 40 Gbps channels.

  20. Multiphysics modeling of intracavity-contacted VCSELs

    Microsoft Academic Search

    Brian P. Riely; J. Jiang Liu; Hongen Shen; Gerard Dang; Wayne H. Chang; Y. Jiang; Z. Sikorski; T. Czyszanowski; Andrzej J. Przekwas

    2003-01-01

    The design of the next generation of vertical-cavity surface-emitting lasers (VCSELs) will greatly depend on the availability of accurate modeling tools. Comprehensive models of semiconductor lasers are needed to predict realistic behavior of various laser devices, such as the spatially nonuniform gain that results from current crowding. Advanced physics models for VCSELs require benchmark quality experimental data for model validation.

  1. Fabrication issues of oxide-confined VCSELs

    NASA Astrophysics Data System (ADS)

    Geib, Kent M.; Choquette, Kent D.; Hou, Hong Q.; Hammons, B. E.

    1997-04-01

    To insert high performance oxide-confined vertical-cavity surface-emitting lasers (VCSELs) into the manufacturing arena, we have examined the critical parameters that must be controlled to establish a repeatable and uniform wet thermal oxidation process for AlGaAs. These parameters include the AlAs mole fraction, the sample temperature, the carrier gas flow and the bubbler water temperature. Knowledge of these critical parameters has enabled the compilation of oxidation rate data for AlGaAs which exhibits an Arrhenius rate dependence. The compositionally dependent activation energies for AlxGa1-xAs layers of x equals 1.00, 0.98 and 0.92 are found to be 1.24, 1.75, and 1.88 eV, respectively.

  2. Organic photovoltaic cells with controlled polarization sensitivity

    SciTech Connect

    Awartani, Omar; O'Connor, Brendan T., E-mail: btoconno@ncsu.edu [Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Kudenov, Michael W. [Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2014-03-03

    In this study, we demonstrate linearly polarized organic photovoltaic cells with a well-controlled level of polarization sensitivity. The polarized devices were created through the application of a large uniaxial strain to the bulk heterojunction poly(3-hexylthiophene):Phenyl-C61-butyric acid methyl ester (P3HT:PCBM) film and printing the plastically deformed active layer onto a PEDOT:PSS and indium tin oxide coated glass substrate. The P3HT:PCBM layer is processed such that it is able to accommodate high strains (over 100%) without fracture. After printing the strained films, thermal annealing is used to optimize solar cell performance while maintaining polarization sensitivity. A dichroic ratio and short circuit current ratio of ?6.1 and ?1.6 were achieved, respectively.

  3. Cold-cavity vectorial eigenmodes of VCSELs

    Microsoft Academic Search

    D. Burak; R. Binder

    1997-01-01

    An analytical approximate solution of Maxwell's equations for the cold-cavity eigenmodes of cylindrical etched air-post vertical-cavity surface-emitting lasers (VCSELs) is presented. In radial and azimuthal directions, the modes correspond to the hybrid modes of cylindrical optical waveguides. A vectorial transform matrix approach is derived which takes into account coupling of bound eigenmodes in VCSEL structures. The method is illustrated for

  4. Multiphysics modeling of intracavity-contacted VCSELs

    NASA Astrophysics Data System (ADS)

    Riely, Brian P.; Liu, J. Jiang; Shen, Hongen; Dang, Gerard; Chang, Wayne H.; Jiang, Y.; Sikorski, Z.; Czyszanowski, T.; Przekwas, Andrzej J.

    2003-07-01

    The design of the next generation of vertical-cavity surface-emitting lasers (VCSELs) will greatly depend on the availability of accurate modeling tools. Comprehensive models of semiconductor lasers are needed to predict realistic behavior of various laser devices, such as the spatially nonuniform gain that results from current crowding. Advanced physics models for VCSELs require benchmark quality experimental data for model validation. This paper presents preliminary results of a collaborative effort at ARL to fabricate and experimentally characterize test optoelectronic structures and VCSEL devices, and at CFDRC to develop comprehensive multiphysics modeling, design and optimization tools for semiconductor lasers and photodetectors. Experimental characterization procedure and measurements of optical and electrical data for oxide-confined intracavity VCSELs are presented. A comprehensive multiphysics modeling tools CFD-ACE+ O"SEMI has been developed. The modeling tool integrates electronic, optical, thermal, and material gain data models for the design of VCSELs and edge emitting lasers (EELs). This paper presents multidimensional simulation analysis of current crowding in oxide-confined intracavity VCSELs. Computational results helped design the test structures and devices and are used as a guide for experimental measurements performed at ARL.

  5. Computer control of the SMC polarized target

    NASA Astrophysics Data System (ADS)

    Le Goff, J.-M.; Azoulay, R.; Berglund, P.; Dulya, C.; Gournay, J. F.; Hayashi, N.; Kyynäräinen, J.; Magnon, A.; Matichard, G.; Niinikoski, T. O.; Trentalange, S.

    1995-02-01

    The SMC polarized target is controlled through VME crates driven by CPUs working under the VxWorks operating system. The CPUs are connected to a SUN workstation which provides the user interface due to a graphical package named SL-GMS. This results in user friendliness, high modularity and flexibility. The system allows the control of: (1) the superconductive solenoid and the transverse dipole: control of the power supplies; automatic reversal of the spin direction by field rotation; acquisition, display and storage of the electric and cryogenic parameters; generation of alarms; and (2) the dilution refrigerator: evaporator level control; acquisition, display and storage of ? 100 cryogenic parameters; and generation of alarms.

  6. Modular VCSEL solution for uniform line illumination in the kW range

    NASA Astrophysics Data System (ADS)

    Moench, Holger; Deppe, Carsten; Dumoulin, Raimond; Gronenborn, Stephan; Gu, Xi; Heusler, Gero; Miller, Michael; Pekarski, Pavel; Pruijmboom, Armand

    2012-03-01

    High power VCSEL arrays can be used as a versatile illumination and heating source. They are widely scalable in power and offer a robust and economic solution for many new applications with moderate brightness requirements. The use of VCSEL arrays for high power laser diode applications enables multiple benefits: Full wafer level production of VCSELs including the combination with micro-optics; assembly technologies allowing large synergy with LED assembly thus profiting from the rapid development in solid state lighting; an outstanding reliability and a modular approach on all levels. A high power VCSEL array module for a very uniform line illumination is described in detail which offers >150W/cm optical output and enables less than 1% non-uniformities per mm along the line. The applied optical principle of near field imaging and massively superposing many thousand VCSELs by arrays of micro-lenses gives perfect control over the intensity distribution and is inherently robust. A specific array of parallelogram shaped VCSELs has been developed in combination with an appropriate micro-lens design and an alignment strategy. The concept uses parallel and serial connection of VCSEL arrays on sub-mounts on water coolers in order to realize a good combination of moderate operating currents and reliability. Lines of any desired length can be built from modules of 1cm length because this optical concept allows large mounting tolerances between individual modules. Therefore the concept is scalable for a wide range of applications. A demonstrator system with an optical output of 3.5kW and a line length of 20cm has been realized.

  7. Interface control of bulk ferroelectric polarization

    SciTech Connect

    Yu, P [University of California, Berkeley; Luo, Weidong [ORNL; Yi, D. [University of California, Berkeley; Zhang, J.-X. [University of California, Berkeley; Rossell, M.D. [Lawrence Berkeley National Laboratory (LBNL); Yang, C.-H. [Korea Advanced Institute of Science and Technology; You, L. [University of California, Berkeley; Singh-Bhalla, G. B. [University of California, Berkeley & LBNL; Yang, S.Y [University of California, Berkeley; He, Q [University of California, Berkeley; Ramasse, Q. M. [Lawrence Berkeley National Laboratory (LBNL); Erni, R. [Lawrence Berkeley National Laboratory (LBNL); Martin, L. W. [University of Illinois, Urbana-Champaign; Chu, Y. H. [University of California, Berkeley; Pantelides, Sokrates T [ORNL; Pennycook, Stephen J [ORNL; Ramesh, R. [University of California, Berkeley

    2012-01-01

    The control of material interfaces at the atomic level has led to no- vel interfacial properties and functionalities. In particular, the study of polar discontinuities at interfaces between complex oxides lies at the frontier of modern condensed matter research. Here we em- ploy a combination of experimental measurements and theoretical calculations to demonstrate the control of a bulk property, namely ferroelectric polarization, of a heteroepitaxial bilayer by precise atomic-scale interface engineering. More specifically, the control is achieved by exploiting the interfacial valence mismatch to influence the electrostatic potential step across the interface, which manifests itself as the biased-voltage in ferroelectric hysteresis loops and determines the ferroelectric state. A broad study of diverse systems comprising different ferroelectrics and conducting perovskite un- derlayers extends the generality of this phenomenon.

  8. Monolithic wavelength-graded VCSEL and wavelength-selective photodetector arrays for WDM applications

    NASA Astrophysics Data System (ADS)

    Cheng, Julian; Luong, Sanh Q.; Ortiz, Gerry G.; Zhou, Yuxin; Lu, Jun; Hou, Hong Q.; Hammons, B. E.; Vawter, G. Allen

    1997-12-01

    Monolithic, multiple-wavelength VCSEL arrays have been obtained by using the surface-controlled enhancement and reduction of the MOCVD epitaxial growth rate to produce a periodic and repeatable grading of the resonance wavelength over a span of greater than 30 nm. Room temperature, electrically-injected, cw lasing has also been achieved with a wavelength span of greater than 20 nm. We show here both the enhancement and the reduction of the growth rate of the entire VCSEL structure and demonstrate the controlled variation of the VCSEL lasing wavelength over a widened spectral range by exploiting both of these effects. Using the same growth techniques, wavelength-selective, resonance-enhanced photodetector arrays with closely-matched resonance wavelengths can be monolithically integrated on the same epilayer structure. We demonstrate the repeatability of this technique using different arrays from the same growth run.

  9. Progress in extended wavelength VCSEL technology

    NASA Astrophysics Data System (ADS)

    Johnson, Klein; Dummer, Matthew; Hibbs-Brenner, Mary; Hogan, William; Steidl, Charles

    2013-03-01

    Vixar has been developing VCSELs at both shorter (680nm) and longer (1850nm) wavelengths. This paper reports on advances in technology at both of these wavelengths. 680nm VCSELs based upon the AlGaAs/AlGaInP materials system were designed and fabricated for high speed operation for plastic optical fiber (POF) based links for industrial, automotive and consumer applications. High speed testing was performed in a "back-to-back" configuration over short lengths of glass fiber, over 42 meters of POF, with and without I.C. drivers and preamps, and over temperature. Performance to 90°C, 10 Gbps and over 40 meters of plastic optical fiber has been demonstrated. Reliability testing has been performed over a range of temperatures and currents. Preliminary results predict a TT1% failure of at least 240,000 hours at 40°C and an average current modulation of 4mA. In addition, the VCSELs survive 1000 hours at 85% humidity 85°C in a non-hermetic package. 1850nm InP based VCSELs are being developed for optical neurostimulation. The goals are to optimize the output power and power conversion efficiency. 7mW of DC output power has been demonstrated at room temperature, as well as a power conversion efficiency of 12%. Devices operate to 85°C. Over 70mW of pulsed power has been achieved from a 35 VCSEL array, with a pulse width of 10?sec.

  10. Broadband laser polarization control with aligned carbon nanotubes

    E-print Network

    Yang, He; Lia, Diao; Chen, Ya; Mattila, Marco; Tian, Ying; Yong, Zhenzhong; Yang, Changxi; Tittonen, Ilkka; Ren, Zhaoyu; Bai, Jingtao; Li, Qingwen; Kauppinen, Esko I; Lipsanen, Harri; Sun, Zhipei

    2015-01-01

    We introduce a simple approach to fabricate aligned carbon nanotube (ACNT) device for broadband polarization control in fiber laser systems. The ACNT device was fabricated by pulling from as-fabricated vertically-aligned carbon nanotube arrays. Their anisotropic property is confirmed with optical and scanning electron microscopy, and with polarized Raman and absorption spectroscopy. The device was then integrated into fiber laser systems (at two technologically important wavelengths of 1 and 1.5 um) for polarization control. We obtained a linearly-polarized light output with the maximum extinction ratio of ~12 dB. The output polarization direction could be fully controlled by the ACNT alignment direction in both lasers. To the best of our knowledge, this is the first time that ACNT device is applied to polarization control in laser systems. Our results exhibit that the ACNT device is a simple, low-cost, and broadband polarizer to control laser polarization dynamics, for various photonic applications (such as ...

  11. VCSEL Intrinsic Response Extraction Using Matrix Formalism

    Microsoft Academic Search

    Alexandre Bacou; Ahmad Hayat; Angélique Rissons; Vladimir Iakovlev; Alexei Syrbu; Jean-Claude Mollier; Eli Kapon

    2009-01-01

    We present a new method to remove the parasitics contribution to the vertical-cavity surface-emitting laser (VCSEL) chip response, in order to obtain the intrinsic S 21 behavior. We demonstrate that the chip can be split into two cascaded subsystems representing the electrical access and the optical cavity, respectively. An equivalent electrical circuit defining the behavior of the electrical access is

  12. VCSEL reliability research at Gore Photonics

    Microsoft Academic Search

    Ted D. Lowes

    2002-01-01

    Reliability of the oxide confined VCSEL used in the Gore nLIGHTENTM parallel optic interconnect is discussed. The Gore reliability program for oxide confined devices has been active for approximately five years. The excellent long term reliability results have been obtained through an approach centered upon fundamental reliability research. The details of the device lifetime measurements and projections are presented along

  13. Temperature dependence of the threshold electric field in a hot electron VCSEL (Invited Paper)

    Microsoft Academic Search

    Ali Serpenguzel; Naci Balkan; Ayse Erol; M. Cetin Arikan; John Roberts

    2005-01-01

    The operation of the Hot Electron Light Emitting and Lasing in Semiconductor Heterostructure -- Vertical Cavity Surface Emitting Laser (HELLISH-VCSEL) devices is based on hot carrier transport parallel to the layers of Ga1-xAlxAs p-n junction. It is therefore a field - effect device and the light emission from the device is independent of the polarity of the applied voltage. In

  14. Development of polarization-mode controllable CARS microscope

    NASA Astrophysics Data System (ADS)

    Hashimoto, Mamoru; Takagi, Tatsuro; Minamikawa, Takeo; Niioka, Hirohiko; Araki, Tsutomu

    2011-03-01

    We developed a polarization-mode controllable coherent anti-Stokes Raman scattering microscope. The polarizationmode of excitations beams such as linear, radial, or azimuth polarization were switched with compact polarization mode converters made of eight-segmented liquid-crystal spatial-light-modulators. The polarization-mode of the excitation beams is electrically controllable without any mechanical operation. We demonstrated the detection of the molecular orientation of liquid crystals with the developed microscope.

  15. Optical power of VCSELs stabilized to 35 ppm/°C without a TEC

    NASA Astrophysics Data System (ADS)

    Downing, John

    2015-03-01

    This paper reports a method and system comprising a light source, an electronic method, and a calibration procedure for stabilizing the optical power of vertical-cavity surface-emitting lasers (VCSELs) and laser diodes (LDs) without the use thermoelectric coolers (TECs). The system eliminates the needs for custom interference coatings, polarization adjustments, and the exact alignment required by the optical method reported in 2013 [1]. It can precisely compensate for the effects of temperature and wavelength drift on photodiode responsivity as well as changes in VCSEL beam quality and polarization angle over a 50°C temperature range. Data obtained from light sources built with single-mode polarization-locked VCSELs demonstrate that 30 ppm/°C stability can be readily obtained. The system has advantages over TECstabilized laser modules that include: 1) 90% lower relative RMS optical power and temperature sensitivity, 2) a five-fold enhancement of wall-plug efficiency, 3) less component testing and sorting, 4) lower manufacturing costs, and 5) automated calibration in batches at time of manufacture is practical. The system is ideally suited for battery-powered environmental and in-home medical monitoring applications.

  16. Coherent optical control of polarization with a critical metasurface

    E-print Network

    Kang, Ming

    2015-01-01

    We describe the mechanism by which a metamaterial surface can act as an ideal phase-controlled rotatable linear polarizer. With equal-power linearly polarized beams incident on each side of the surface, varying the relative phase rotates the polarization angles of the output beams, while keeping the polarization exactly linear. The explanation is based on coupled-mode theory and the idea of coherent perfect absorption into auxiliary polarization channels. The polarization-rotating behavior occurs at a critical point of the coupled-mode theory, which can be associated with the exceptional point of a parity-time (PT) symmetric effective Hamiltonian.

  17. Broadband laser polarization control with aligned carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Yang, He; Fu, Bo; Li, Diao; Tian, Ying; Chen, Ya; Mattila, Marco; Yong, Zhenzhong; Li, Ru; Hassanien, Abdou; Yang, Changxi; Tittonen, Ilkka; Ren, Zhaoyu; Bai, Jintao; Li, Qingwen; Kauppinen, Esko I.; Lipsanen, Harri; Sun, Zhipei

    2015-06-01

    We introduce a simple approach to fabricate an aligned carbon nanotube (ACNT) device for broadband polarization control in fiber laser systems. The ACNT device was fabricated by pulling from as-fabricated vertically-aligned carbon nanotube arrays. Their anisotropic properties are confirmed with various microscopy techniques. The device was then integrated into fiber laser systems (at two technologically important wavelengths of 1 and 1.5 ?m) for polarization control. We obtained a linearly-polarized light output with the maximum extinction ratio of ~12 dB. The output polarization direction could be fully controlled by the ACNT alignment direction in both lasers. To the best of our knowledge, this is the first time that the ACNT device is applied to polarization control in laser systems. Our results exhibit that the ACNT device is a simple, low-cost, and broadband polarizer to control laser polarization dynamics, for various photonic applications (such as material processing, polarization diversity detection in communications etc.), where linear polarization control is necessary.We introduce a simple approach to fabricate an aligned carbon nanotube (ACNT) device for broadband polarization control in fiber laser systems. The ACNT device was fabricated by pulling from as-fabricated vertically-aligned carbon nanotube arrays. Their anisotropic properties are confirmed with various microscopy techniques. The device was then integrated into fiber laser systems (at two technologically important wavelengths of 1 and 1.5 ?m) for polarization control. We obtained a linearly-polarized light output with the maximum extinction ratio of ~12 dB. The output polarization direction could be fully controlled by the ACNT alignment direction in both lasers. To the best of our knowledge, this is the first time that the ACNT device is applied to polarization control in laser systems. Our results exhibit that the ACNT device is a simple, low-cost, and broadband polarizer to control laser polarization dynamics, for various photonic applications (such as material processing, polarization diversity detection in communications etc.), where linear polarization control is necessary. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01904d

  18. Micro-optics on VCSELs using NIR photopolymers

    Microsoft Academic Search

    V. Bardinal; B. Reig; T. Camps; D. Barat; E. Daran; J. B. Doucet; C. Turck; J. P. Malval; D. J. Lougnot; O. Soppera

    2010-01-01

    Laser beam shaping is a key issue for the photonic integration of VCSEL sources. Most of the techniques proposed to integrate micro-optics elements onto VCSEL devices imply either a hybrid assembly or a photolithography step, whose precision limits the accuracy of lens alignment relatively to the VCSEL source. We present here a new method for self-fabrication of microtips on Vertical-Cavity

  19. Using VCSELs and multicore fiber for multi-channel transmission

    Microsoft Academic Search

    B. Rosinski; J. Chi; P. Grosso; J. Le Bihan

    1997-01-01

    In conclusion, two channel simultaneous transmission is realized using direct coupling between pitch-matched VCSEL array and multicore fiber. The transmission capacity can be upgraded by using specifically designed VCSELs and fibers (e.g. 3×3 or 4×4 arrays) or possibly by 1.3-1.6 ?m light sources. These results show that the combination of VCSELs and multicore fiber may be a promising candidate in

  20. VCSEL fault location apparatus and method

    DOEpatents

    Keeler, Gordon A. (Albuquerque, NM); Serkland, Darwin K. (Albuquerque, NM)

    2007-05-15

    An apparatus for locating a fault within an optical fiber is disclosed. The apparatus, which can be formed as a part of a fiber-optic transmitter or as a stand-alone instrument, utilizes a vertical-cavity surface-emitting laser (VCSEL) to generate a test pulse of light which is coupled into an optical fiber under test. The VCSEL is subsequently reconfigured by changing a bias voltage thereto and is used as a resonant-cavity photodetector (RCPD) to detect a portion of the test light pulse which is reflected or scattered from any fault within the optical fiber. A time interval .DELTA.t between an instant in time when the test light pulse is generated and the time the reflected or scattered portion is detected can then be used to determine the location of the fault within the optical fiber.

  1. Single frequency stable VCSEL as a compact source for interferometry and vibrometry

    SciTech Connect

    Dudzik, Grzegorz; Rzepka, Janusz [Department of Field Theory, Electronic Systems and Optoelectronics, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50320 Wroclaw (Poland)

    2010-05-28

    Developing an innovative PS-DAVLL (Polarization Switching DAVLL) method of frequency stabilization, which used a ferroelectric liquid crystal cell as quarter wave plate, rubidium cell and developed ultra-stable current source, allowed to obtain a frequency stability of 10{sup -9}(frequency reproducibility of 1,2centre dot10{sup -8}) and reductions in external dimensions of laser source. The total power consumption is only 1,5 Watt. Because stabilization method used in the frequency standard is insensitive to vibration, the semiconductor laser interferometer was built for measuring range over one meter, which can also be used in industry for the accurate measurement of displacements with an accuracy of 1[mum/m]. Measurements of the VCSEL laser parameters are important from the standpoint of its use in laser interferometry or vibrometry, like narrow emission line DELTAnu{sub FWHM} = 70[MHz] equivalent of this laser type and stability of linear polarization of VCSEL laser. The undoubted advantage of the constructed laser source is the lack of mode-hopping effect during continuous work of VCSEL.

  2. Frequency tuning of long-wavelength VCSELs

    NASA Astrophysics Data System (ADS)

    Lytkine, A.; Jäger, W.; Tulip, J.

    2006-04-01

    Tuning properties of long-wavelength VCSELs have been studied experimentally, for the first time to our knowledge. Injection current and temperature tuning rates of two VCSELs operating near 1512 and 1577 nm have been measured using a Fabry-Perot etalon with free spectral range 0.056 cm -1. A 100-Hz saw-tooth modulation with depths of modulation of ˜10% or less was superimposed on a direct injection current (dc bias) to tune lasers in narrow spectral intervals (0.3-1.2 cm -1) around a central frequency set by the dc bias. The lasers have been found to be capable of being tuned faster at higher levels of dc bias. The enhancement factors were up to ˜2 and ˜3 for the 1512- and 1577-nm lasers, respectively, as compared with their tuning rates measured at the levels of the dc bias close to the threshold of lasing. A linear dependence between injection current tuning rates and the levels of dc bias has been observed. Temperature tuning coefficients have been proved to be independent of the laser heat sink temperature and of the dc bias. Frequency tuning curves were approximated with a second-order polynomial. The frequencies of more than 40 absorption lines of CO, CO 2, H 2O and NH 3 known from spectral databases were compared with the calculated frequencies. The accuracy of the approximation was found to be within 0.2 cm -1 for spectral intervals up to 38 cm -1. The dependence of current tuning rates of the VCSELs on dc bias was shown to be taken into account for accurate analysis of absorption line profiles. The results obtained can be used for precise spectroscopic measurements with long-wavelength VCSELs.

  3. Studying the VCSEL to VCSEL injection locking for enhanced chromatic dispersion compensation

    NASA Astrophysics Data System (ADS)

    Li, Linfu

    2010-11-01

    In order to supply a theoretical guide for digital chaotic telecommunication, the technique of Optical injection locking (OIL) of semiconductor lasers on the chaotic communication have been investigated based on the theoretical models used to describe the dynamics of solitary VCSEL subjected to the external optical injection and signal transmission in fiber. The numerical simulation results show that, the frequency chirp and time-resolved chirp are reduced in magnitude, using a VCSEL laser as master and another VCSEL as slave, it leads to a no-penalty transmission over 50 km of uncompensated in SSMF at 10Gb/s, and it could be higher rate and more remote if there were appropriate compensation.

  4. Broadband laser polarization control with aligned carbon nanotubes.

    PubMed

    Yang, He; Fu, Bo; Li, Diao; Tian, Ying; Chen, Ya; Mattila, Marco; Yong, Zhenzhong; Li, Ru; Hassanien, Abdou; Yang, Changxi; Tittonen, Ilkka; Ren, Zhaoyu; Bai, Jintao; Li, Qingwen; Kauppinen, Esko I; Lipsanen, Harri; Sun, Zhipei

    2015-07-01

    We introduce a simple approach to fabricate an aligned carbon nanotube (ACNT) device for broadband polarization control in fiber laser systems. The ACNT device was fabricated by pulling from as-fabricated vertically-aligned carbon nanotube arrays. Their anisotropic properties are confirmed with various microscopy techniques. The device was then integrated into fiber laser systems (at two technologically important wavelengths of 1 and 1.5 ?m) for polarization control. We obtained a linearly-polarized light output with the maximum extinction ratio of ?12 dB. The output polarization direction could be fully controlled by the ACNT alignment direction in both lasers. To the best of our knowledge, this is the first time that the ACNT device is applied to polarization control in laser systems. Our results exhibit that the ACNT device is a simple, low-cost, and broadband polarizer to control laser polarization dynamics, for various photonic applications (such as material processing, polarization diversity detection in communications etc.), where linear polarization control is necessary. PMID:26060940

  5. Electrical control of terahertz polarization by graphene microstructure

    NASA Astrophysics Data System (ADS)

    Zhu, Ling; Fan, Yunhui; Wu, Shan; Yu, Lizhi; Zhang, Kaiyin; Zhang, Yi

    2015-07-01

    In this letter, we proposed and numerically analyzed an electric controlling polarization modulator of the terahertz wave, which is composed of a graphene monolayer microstructure with an L-shaped nanoholes array. The graphene microstructure is employed to excite the plasmonic dipolar and quadrupolar resonances in terahertz region. Through the superposition of the cross-polarized wave radiated by these plasmonic resonances, the polarization rotation effect can be obtained. Utilizing the capacitor doping, the rotation angle can be controlled by the external applied voltage, thus achieving a tunable polarization modulator.

  6. Full polarization control for fiber optical quantum communication systems using polarization encoding.

    PubMed

    Xavier, G B; Vilela de Faria, G; Temporão, G P; von der Weid, J P

    2008-02-01

    A real-time polarization control system employing two non-orthogonal reference signals multiplexed in either time or wavelength with the data signal is presented. It is shown, theoretically and experimentally, that complete control of multiple polarization states can be attained employing polarization controllers in closed-loop configuration. Experimental results on the wavelength multiplexing setup show that negligible added penalties, corresponding to an average added optical Quantum Bit Error Rate of 0.044%, can be achieved with response times smaller than 10 ms, without significant introduction of noise counts in the quantum channel. PMID:18542265

  7. Electrochemical control of cell and tissue polarity.

    PubMed

    Chang, Fred; Minc, Nicolas

    2014-01-01

    Localized ion fluxes at the plasma membrane provide electrochemical gradients at the cell surface that contribute to cell polarization, migration, and division. Ion transporters, local pH gradients, membrane potential, and organization are emerging as important factors in cell polarization mechanisms. The power of electrochemical effects is illustrated by the ability of exogenous electric fields to redirect polarization in cells ranging from bacteria, fungi, and amoebas to keratocytes and neurons. Electric fields normally surround cells and tissues and thus have been proposed to guide cell polarity in development, cancer, and wound healing. Recent studies on electric field responses in model systems and development of new biosensors provide new avenues to dissect molecular mechanisms. Here, we review recent advances that bring molecular understanding of how electrochemistry contributes to cell polarity in various contexts. PMID:25062359

  8. Light-current characterization of dual-wavelength VCSELs

    Microsoft Academic Search

    Vlad Badilita; Jean-Francois Carlin; Marcel Brunner; Marc Ilegems

    2002-01-01

    The purpose of this paper is to present a detailed characterization of a dual-wavelength VCSEL - the BiVCSEL. This device consists of two active optical cavities, which share a coupling mirror and can be independently electrically pumped. We present the output powers for the two emitted wavelengths (short - (lambda) S, long - (lambda) L versus the currents in the

  9. Mode confinement in VCSEL-based photonic heterostructures

    Microsoft Academic Search

    C.-A. Berseth; G. Guerrero; E. Kapon; M. Moser; R. Hoevel

    2000-01-01

    Arrays of coupled vertical cavity surface emitting lasers (VCSELs) were previously shown to have a coherent photonic mode with high immunity against structural imperfections. In such periodic arrays the photonic mode stability depends on disorder in the position or size of the pixels, injection current, and boundary conditions. In the present work, we show that nonuniform VCSEL arrays with a

  10. Reliability of proton-implanted VCSELs for data communications

    Microsoft Academic Search

    James K. Guenter; R. A. Hawthorne; D. N. Granville; Mary K. Hibbs-Brenner; Robert A. Morgan

    1996-01-01

    We describe vertical cavity surface emitting laser (VCSEL) reliability tests comprising hundreds of parts and more than a million device hours. The VCSELs studied were of a previously described production design intended for local-area network data communication at 850 nm. Devices were operated at temperatures of 35, 80, 100, 125, and 150 degrees C and at currents of 5, 10,

  11. Scaling VCSEL performance for 100Terabits/s systems

    NASA Astrophysics Data System (ADS)

    Cunningham, J. E.; Beckman, D.; Zheng, Xuezhe; Krishnamoorthy, A. V.

    2006-02-01

    We evaluate VCSEL interconnects for next-generation High Productivity Computers in which hundreds of terabits of bandwidth are envisioned. We present results for VCSEL based links operating PAM-4 signaling using a commercial 0.13?m CMOS technology. We perform a complete link analysis of the Bit Error Rate, Q factor, random and deterministic jitter by measuring waterfall curves versus margins in time and amplitude. We demonstrate that VCSEL based PAM-4 can match or even improve performance over binary signaling under conditions of bandwidth limited 100meter multi-mode optical link at 5Gbps. We present the first sensitivity measurements for optical PAM-4 and compare it with binary signaling. An empirical relationship for VCSEL scaling versus bit rate and aperture is presented in order to explore reliability of VCSEL-based links. Reliability is found to degrade with aperture with a fourth order power law dependence.

  12. Commercialized VCSEL components fabricated at TrueLight Corporation

    NASA Astrophysics Data System (ADS)

    Pan, Jin-Shan; Lin, Yung-Sen; Li, Chao-Fang A.; Chang, C. H.; Wu, Jack; Lee, Bor-Lin; Chuang, Y. H.; Tu, S. L.; Wu, Calvin; Huang, Kai-Feng

    2001-05-01

    TrueLight Corporation was found in 1997 and it is the pioneer of VCSEL components supplier in Taiwan. We specialize in the production and distribution of VCSEL (Vertical Cavity Surface Emitting Laser) and other high-speed PIN-detector devices and components. Our core technology is developed to meet blooming demand of fiber optic transmission. Our intention is to diverse the device application into data communication, telecommunication and industrial markets. One mission is to provide the high performance, highly reliable and low-cost VCSEL components for data communication and sensing applications. For the past three years, TrueLight Corporation has entered successfully into the Gigabit Ethernet and the Fiber Channel data communication area. In this paper, we will focus on the fabrication of VCSEL components. We will present you the evolution of implanted and oxide-confined VCSEL process, device characterization, also performance in Gigabit data communication and the most important reliability issue

  13. Cavity structures for low-loss oxide-confined VCSELs

    NASA Astrophysics Data System (ADS)

    Choquette, Kent D.; Hadley, H. R.; Chow, Weng W.; Hou, Hong Q.; Geib, Kent M.; Hammons, B. E.; Mathes, D.; Hull, Robert

    1997-04-01

    We examine the threshold characteristics of selectively oxidized VCSELs as a function of the number, thickness, and placement of the buried oxide apertures. The threshold current density for small area VCSELs is shown to increase with the number of oxide apertures in the cavity due to increased optical loss, while the threshold current density for broad area VCSELs decreases with increasing number of apertures due to more uniform current injection. Reductions of the threshold gain and optical loss are achieved for small area VCSELs using thin oxide apertures which are displaced longitudinally away from the optical cavity. We show that the optical loss can be sufficiency reduced to allow lasing in VCSELs with aperture area as small as 0.25 micrometer2.

  14. VCSELs with two-sided beam emission for pressure sensor applications

    NASA Astrophysics Data System (ADS)

    Fischer, Balthasar; Strodl, Andreas; Hein, Alexander; Wintner, Ernst; Michalzik, Rainer

    2012-06-01

    A novel type of all-optical pressure sensor has been developed. In this context, a vertical-cavity surface-emitting laser (VCSEL) has been modified in its design to provide simultaneous light emission from both facets. One beam serves as measuring signal while the other establishes a reference; and both paths lie on the same optical axis. The VCSELs are based on active InGaAs quantum wells for laser output close to 960 nm wavelength where the GaAs substrate is transparent. From both top and bottom facet, single-polarization and single-mode beams are observed, having a power ratio of 1:2 to 1:4. In this paper we give insight into this new sensing application for VCSELs, describe the laser fabrication and the static operation characteristics as well as the noise properties which have paramount importance for high performance of the sensor. With regard to the sensor application in acoustics, the focus of the noise measurements is put on the low-frequency, i.e. kHz, regime. While laser diode noise performance is readily available for the MHz to GHz frequency range, only very limited data exists in the Hz to kHz domain. The relative intensity noise of both beams is measured and compared and the mutual correlation properties are investigated. The frequency noise is quantified.

  15. Thermal and Optoelectronic Model of VCSEL Arrays for Short Range Communications

    Microsoft Academic Search

    Angelique Rissons; Jean-Claude Mollier; Zeno Toffano; Alain Destrez; Mathias Pez

    2003-01-01

    The integration of different components in optoelectronics modules, such as VCSEL and photodiode arrays, optical guides and electronics, introduces optoelectronical, thermal and mechanical interactions. In this context, a thermal and optoelectronic model of VCSEL array is proposed. The self and cross heating of VCSEL arrays have been simulated. The thermal behavior of VCSEL in the array can be modeled by

  16. Coherent control of polarized neutron interferometry

    E-print Network

    Abutaleb, Mohamed Osama

    2012-01-01

    In this thesis, we describe two sets of experiments using a single crystal neutron interferometer. First, we explore applications of quantum information processing (QIP) to magnetic materials characterization using polarized ...

  17. A Quasioptical Vector Interferometer for Polarization Control

    NASA Technical Reports Server (NTRS)

    Chuss, David T.; Wollack, Edward J.; Moseley, Harvey S.; Novak, Giles

    2005-01-01

    We present a mathematical description of a Quasioptical Vector Interferometer (QVI), a device that maps an input polarization state to an output polarization state by introducing a phase delay between two linear orthogonal components of the input polarization. The advantages of such a device over a spinning wave-plate modulator for measuring astronomical polarization in the far-infrared through millimeter are: 1. The use of small, linear motions eliminates the need for cryogenic rotational bearings, 2. The phase flexibility allows measurement of Stokes V as well as Q and U, and 3. The QVI allows for both multi-wavelength and broadband modulation. We suggest two implementations of this device as an astronomical polarization modulator. The first involves two such modulators placed in series. By adjusting the two phase delays, it is possible to use such a modulator to measure Stokes Q, U, and V for passbands that are not too large. Conversely, a single QVI may be used to measure Q and V independent of frequency. In this implementation, Stokes U must be measured by rotating the instrument. We conclude this paper by presenting initial laboratory results.

  18. High-speed and scalable high-power VCSEL arrays and their applications

    NASA Astrophysics Data System (ADS)

    Warren, Mial E.; Carson, Richard F.; Joseph, John R.; Wilcox, Thomas; Dacha, Preethi; Abell, David J.; Otis, Kirk J.

    2015-03-01

    A unique architecture for two-dimensional arrays of VCSELs that allow for simultaneous high-power output and highbandwidth modulation has been developed for a variety of applications. The arrays use integrated micro-lenses for beam shaping and control, and to enable incoherent beam combining to make compact, high-brightness sources with low coherence noise. The fabrication and performance of the laser arrays are reviewed and sample applications are discussed.

  19. Electrically pumped semiconductor laser with monolithic control of circular polarization

    PubMed Central

    Rauter, Patrick; Lin, Jiao; Genevet, Patrice; Khanna, Suraj P.; Lachab, Mohammad; Giles Davies, A.; Linfield, Edmund H.; Capasso, Federico

    2014-01-01

    We demonstrate surface emission of terahertz (THz) frequency radiation from a monolithic quantum cascade laser with built-in control over the degree of circular polarization by “fishbone” gratings composed of orthogonally oriented aperture antennas. Different grating concepts for circularly polarized emission are introduced along with the presentation of simulations and experimental results. Fifth-order gratings achieve a degree of circular polarization of up to 86% within a 12°-wide core region of their emission lobes in the far field. For devices based on an alternative transverse grating design, degrees of circular polarization as high as 98% are demonstrated for selected far-field regions of the outcoupled THz radiation and within a collection half-angle of about 6°. Potential and limitations of integrated antenna gratings for polarization-controlled emission are discussed. PMID:25512515

  20. Thermal packaging of piggyback VCSELs for GBd optical communications modules

    NASA Astrophysics Data System (ADS)

    Simon, Jonathan; Giboney, Kirk S.; Buckman, Lisa A.

    2001-05-01

    Agilent Laboratories, in a DARPA supported effort, has been developing a series of low-cost VCSEL based, high- performance, surface mount, parallel channel optical communications modules. Separate transmit and receive modules with 12 channels operating at 1.25 and 2.5 GBd per channel have been demonstrated with a datacom application target. Current designs have Vertical Cavity Surface Emitting Lasers (VCSELs) located in tandem with a driver IC on a copper base, which performs both a mechanical and thermal function. A flex circuit substrate laminated on the base provides signal interconnects. As channel speeds increase, the need for co-locating the VCSEL array and its associated output drivers to minimize inductance becomes more important. One solution is to piggyback the VCSELs on the transmitter IC. However, the design is constrained by the need to maintain the VCSEL junction temperature at an acceptable level. Finite element thermal modeling of the tandem mounted and piggybacked VCSELs are discussed, with a focus on comparison of the two schemes at current and projected future power levels, the effect of wirebonds on IC to VCSEL heat transfer, and performance issues related to temperature. Thermal imaging data are used to validate models. The overall module packaging scheme is also discussed.

  1. Polarization-controlled images based on double-exposure polarization holography in an azobenzene liquid-crystalline polymer.

    PubMed

    Zeng, Pengfei; Wang, Changshun; Zhao, Fuli; Cai, Peng; Qin, Mu

    2015-01-01

    Polarization-controlled optical image operations were demonstrated based on the double-exposure polarization holographic method. Two images were stored in the same volume of an azobenzene liquid-crystalline polymer by recording superimposed holograms, a pair of polarization gratings with one spatial frequency, using two orthogonal circularly polarized 532 nm beams and were reconstructed with a 650 nm laser. The recorded polarization holographic gratings were investigated to show distinctive polarization selectivity, high diffraction efficiency, and good stability. The brightness and the polarization of the diffracted images were found to be dependent on the polarization of the readout beam, and two images could be reconstructed individually or simultaneously. PMID:25967006

  2. Polar auxin transport: controlling where and how much

    NASA Technical Reports Server (NTRS)

    Muday, G. K.; DeLong, A.; Brown, C. S. (Principal Investigator)

    2001-01-01

    Auxin is transported through plant tissues, moving from cell to cell in a unique polar manner. Polar auxin transport controls important growth and developmental processes in higher plants. Recent studies have identified several proteins that mediate polar auxin transport and have shown that some of these proteins are asymmetrically localized, paving the way for studies of the mechanisms that regulate auxin transport. New data indicate that reversible protein phosphorylation can control the amount of auxin transport, whereas protein secretion through Golgi-derived vesicles and interactions with the actin cytoskeleton might regulate the localization of auxin efflux complexes.

  3. ?-Tubulin controls neuronal microtubule polarity independently of Golgi outposts

    PubMed Central

    Nguyen, Michelle M.; McCracken, Christie J.; Milner, E. S.; Goetschius, Daniel J.; Weiner, Alexis T.; Long, Melissa K.; Michael, Nick L.; Munro, Sean; Rolls, Melissa M.

    2014-01-01

    Neurons have highly polarized arrangements of microtubules, but it is incompletely understood how microtubule polarity is controlled in either axons or dendrites. To explore whether microtubule nucleation by ?-tubulin might contribute to polarity, we analyzed neuronal microtubules in Drosophila containing gain- or loss-of-function alleles of ?-tubulin. Both increased and decreased activity of ?-tubulin, the core microtubule nucleation protein, altered microtubule polarity in axons and dendrites, suggesting a close link between regulation of nucleation and polarity. To test whether nucleation might locally regulate polarity in axons and dendrites, we examined the distribution of ?-tubulin. Consistent with local nucleation, tagged and endogenous ?-tubulins were found in specific positions in dendrites and axons. Because the Golgi complex can house nucleation sites, we explored whether microtubule nucleation might occur at dendritic Golgi outposts. However, distinct Golgi outposts were not present in all dendrites that required regulated nucleation for polarity. Moreover, when we dragged the Golgi out of dendrites with an activated kinesin, ?-tubulin remained in dendrites. We conclude that regulated microtubule nucleation controls neuronal microtubule polarity but that the Golgi complex is not directly involved in housing nucleation sites. PMID:24807906

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

    PubMed

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

    2015-03-23

    A system framework is proposed and analyzed for generating polarization-resolved wideband unpredictability-enhanced chaotic signals based on a slave vertical-cavity surface-emitting laser (S-VCSEL) driven by an injected optical chaos signal from a master VCSEL (M-VCSEL) under optical feedback. After calculating the time series outputs from the M-VCSEL under optical feedback and the S-VCSEL under chaotic optical injection by using the spin-flip model (SFM), the unpredictability degree (UD) is evaluated by permutation entropy (PE), and the bandwidth of the polarization-resolved outputs from the M-VCSEL and S-VCSEL are numerically investigated. The results show that, under suitable parameters, both the bandwidth and UD of two polarization components (PCs) outputs from the S-VCSEL can be enhanced significantly compared with that of the driving chaotic signals output from the M-VCSEL. By simulating the influences of the feedback and injection parameters on the bandwidth and UD of the polarization-resolved outputs from S-VCSEL, related operating parameters can be optimized. PMID:25837062

  5. New applications boost VCSEL quantities: recent developments at Philips

    NASA Astrophysics Data System (ADS)

    Grabherr, Martin

    2015-03-01

    Besides the mature and steadily growing datacom market for which VCSELs are key components in Transceivers, Active Optical Cables (AOC), Mid Board Optical Modules (MBOM) or Embedded Optical Modules (EOM), VCSELs have proven to be key components also for other volume applications. Laser mice emerged 2004, just after the burst of the dotcom bubble and the related downturn in the Datacom industry, and dominated the shipped quantities for some years, accompanied by various smaller applications like atomic clock, oxygen sensing, encoders, and many more. Over the past years, two other major applications came into focus: optical interconnects in high performance computers or datacenters and smart sensors for mobile devices. In addition, VCSELs are penetrating into more and more power applications, primarily for illumination or IR heating. We present recent developments in technology, products, and addressed market segments that will have a major impact on the VCSEL industry.

  6. A theoretical model for ferroelectric polarization-controlled superconductor devices

    NASA Astrophysics Data System (ADS)

    Wang, J. T.; Tang, F.; Chinkhota, M.; Tashakkori, R.; Bagayoko, D.

    1998-02-01

    Polarization-controlled superconductor devices could be used as a logic gate or other electronic units such as acoustic sensors, electro-optical transducers and image detectors. Lin and Wu (Appl. Phys. Lett. 65 (8) (1994) 1) have experimentally investigated the I-V characteristics of such a device. In this paper, we propose a theoretical model to calculate the polarization effect on the I-V curves. The polarization effects include the cause of the superconducting-normal state switching and exponential time dependence of the source-drain voltage. We fit the experimental data with the theoretical model. They agree quite well.

  7. Multilevel Data Storage Memory Using Deterministic Polarization Control

    SciTech Connect

    Lee, Daesu [Seoul National University; Yang, Sang Mo [Seoul National University; Kim, T. H. [Seoul National University; Jeon, B. C. [Seoul National University; Kim, Yong su [Seoul National University; Yoon, J. -G. [University of Suwon; Lee, Ho Nyung [ORNL; Baek, Seung Hyup [University of Wisconsin, Madison; Eom, Chang-Beom [University of Wisconsin, Madison; Noh, Tae Won [Seoul National University

    2012-01-01

    Multilevel non-volatile memory for high-density date storage is achieved by using the deterministic control of ferroelectric polarization. In a real ferroelectric thin-film system, eight stable and reproducible polarization states are realized (i.e., 3-bit data storage) by adjusting the displacement current. This approach can be used to triple or quadruple the memory density, even at existing feature scales.

  8. VCSEL structures used to suppress higher-order transverse modes

    Microsoft Academic Search

    W. Nakwaski

    2011-01-01

    Currently unwanted excitation of higher-order transverse modes is the most serious drawback of vertical-cavity surface-emitting\\u000a diode lasers (VCSELs) limiting their possible applications. In the present paper, various methods used to suppress those modes\\u000a are described and their effectiveness is compared. It is well known that, because of a nearly uniform current injection into\\u000a their active regions, small-aperture VCSELs without any

  9. Brain metabolism dictates the polarity of astrocyte control over arterioles

    E-print Network

    Newman, Eric A.

    ARTICLES Brain metabolism dictates the polarity of astrocyte control over arterioles Grant R. J for differential astrocyte control over cerebrovascular diameter during different states of brain activation in cerebral blood flow. Brain metabolism then shifts, whereby glycolysis is enhanced20,21 in astrocytes14

  10. Fabrication and performance of tuneable single-mode VCSELs emitting in the 750- to 1000-nm range

    NASA Astrophysics Data System (ADS)

    Grabherr, Martin; Wiedenmann, Dieter; Jaeger, Roland; King, Roger

    2005-03-01

    The growing demand on low cost high spectral purity laser sources at specific wavelengths for applications like tuneable diode laser absorption spectroscopy (TDLAS) and optical pumping of atomic clocks can be met by sophisticated single-mode VCSELs in the 760 to 980 nm wavelength range. Equipped with micro thermo electrical cooler (TEC) and thermistor inside a small standard TO46 package, the resulting wavelength tuning range is larger than +/- 2.5 nm. U-L-M photonics presents manufacturing aspects, device performance and reliability data on tuneable single-mode VCSELs at 760, 780, 794, 852, and 948 nm lately introduced to the market. According applications are O2 sensing, Rb pumping, Cs pumping, and moisture sensing, respectively. The first part of the paper dealing with manufacturing aspects focuses on control of resonance wavelength during epitaxial growth and process control during selective oxidation for current confinement. Acceptable resonance wavelength tolerance is as small as +/- 1nm and typical aperture size of oxide confined single-mode VCSELs is 3 &mum with only few hundred nm tolerance. Both of these major production steps significantly contribute to yield on wafer values. Key performance data for the presented single-mode VCSELs are: >0.5 mW of optical output power, >30 dB side mode suppression ratio, and extrapolated 10E7 h MTTF at room temperature based on several millions of real test hours. Finally, appropriate fiber coupling solutions will be presented and discussed.

  11. Spectrally resolved imaging of the transverse modes in multimode VCSELs

    NASA Astrophysics Data System (ADS)

    Misak, Stephen M.; Dugmore, Dan G.; Middleton, Kirsten A.; Hale, Evan R.; Farner, Kelly R.; Choquette, Kent D.; Leisher, Paul O.

    2015-03-01

    Vertical-cavity surface-emitting lasers (VCSELs) enable a range of applications such as data transmission, trace sensing, atomic clocks, and optical mice. For many of these applications, the output power and beam quality are both critical (i.e. high output power with good beam quality is desired). Multi-mode VCSELs offer much higher power than single-mode devices, but this comes at the expense of lower beam quality. Directly observing the resolved mode structure of multi-mode VCSELs would enable engineers to better understand the underlying physics and help them to develop multi-mode devices with improved beam quality. In this work, a low-cost, high-resolution (<3 pm) Echelle grating spectrometer system is used to map the two-dimensional VCSEL near-field emission profile. The system spectrally disperses the VCSEL beam and images it with high magnification onto a CMOS camera. The narrow spectral content of each LP mode allows direct observation of the modal content of the VCSEL.

  12. Geomagnetic control of polar mesosphere summer echoes

    NASA Astrophysics Data System (ADS)

    Bremer, J.; Hoffmann, P.; Hansen, T. L.

    2000-02-01

    Using observations with the ALOMAR SOUSY radar near Andenes (69.3°N, 16.0°E) from 1994 until 1997 polar mesosphere summer echoes (PMSE) have been investigated in dependence on geomagnetic K indices derived at the Auroral Observatory Tromsø (69.66°N, 18.94°E). During night-time and morning hours a significant correlation between the signal-to-noise ratio (SNR) of the radar results and the geomagnetic K indices could be detected with a maximum correlation near midnight. The correlation becomes markedly smaller in the afternoon and early evening hours with a minimum near 17 UT. This diurnal variation is in reasonable agreement with riometer absorption at Ivalo (68.55°N, 27.28°E) and can be explained by the diurnal variation of ionization due to precipitating high energetic particles. Therefore, a part of the diurnal PMSE variation is caused by this particle precipitation. The variability of the solar EUV variation, however, has no significant influence on the PMSE during the observation period.

  13. Polarization Control of Electron Tunneling into Ferroelectric Surfaces

    SciTech Connect

    Maksymovych, Petro [ORNL; Jesse, Stephen [ORNL; Yu, Pu [University of California, Berkeley; Ramesh, R. [University of California, Berkeley; Baddorf, Arthur P [ORNL; Kalinin, Sergei V [ORNL

    2009-01-01

    We demonstrate a highly reproducible control of local electron transport through a ferroelectric oxide via its spontaneous polarization. Electrons are injected from the tip of an atomic force microscope into a thin film of lead-zirconate titanate, Pb(Zr0.2Ti0.8)O3, in the regime of electron tunneling assisted by a high electric field (Fowler-Nordheim tunneling). The tunneling current exhibits a pronounced hysteresis with abrupt switching events that coincide, within experimental resolution, with the local switching of ferroelectric polarization. The large spontaneous polarization of the PZT film results in up to 500-fold amplification of the tunneling current upon ferroelectric switching. The magnitude of the effect is subject to electrostatic control via ferroelectric switching, suggesting possible applications in ultrahigh-density data storage and spintronics.

  14. Does albedo control predominantly the Seasonal South Polar Cap recession ?

    E-print Network

    Paris-Sud XI, Université de

    of the Seasonal South Polar Cap (SSPC) crocus line, defining the edge of the SSPC. This crocus line the local structure of the SSPC edge. Both crocus line and snowdrop distance should now be used to calibrate by topography, we show that the SSPC asymmetry in the crocus line is controlled by albedo. At local scale, we

  15. Polarization control of single photon quantum orbital angular momentum

    E-print Network

    Roma "La Sapienza", Università di

    Polarization control of single photon quantum orbital angular momentum states E. Nagali1, F, Italy Abstract: The orbital angular momentum of photons, being defined in an infinite angular momentum of single photons and vice versa. All our schemes exploit a newly developed optical

  16. Micro-optics on VCSELs using NIR photopolymers

    NASA Astrophysics Data System (ADS)

    Bardinal, V.; Reig, B.; Camps, T.; Barat, D.; Daran, E.; Doucet, J. B.; Turck, C.; Malval, J. P.; Lougnot, D. J.; Soppera, O.

    2010-05-01

    Laser beam shaping is a key issue for the photonic integration of VCSEL sources. Most of the techniques proposed to integrate micro-optics elements onto VCSEL devices imply either a hybrid assembly or a photolithography step, whose precision limits the accuracy of lens alignment relatively to the VCSEL source. We present here a new method for self-fabrication of microtips on Vertical-Cavity Surface-Emitting Lasers (VCSELs) by means of Near Infra- Red (NIR) photo-polymerization. This approach is based on a single fabrication step, implementing novel photopolymers sensitive at the lasing wavelength. Consequently the process is triggered by the laser source itself and can be applied easily to VCSEL devices during their electro-optic characterization. The method we have developed for tips fabrication is detailed as well as corresponding optical properties. The applications of this new and simple method concern laser light focusing and collimation for integrated micro-systems, coupling to fibers for optical communications as well as novel micro-probes fabrication for near-field optical microscopy.

  17. Electrically and optically controlled cross-polarized wave conversion.

    PubMed

    Cada, Michael; Qasymeh, Montasir; Pistora, Jaromir

    2008-03-01

    Light wave propagation in third-order nonlinear media with applied external electric field is investigated. Interplay between the nonlinear electro-optic and all-optical effects is examined theoretically. Energy exchange between the orthogonal light polarizations, the cross polarization conversion, results. The assisting external field acts as either the effect-enhancing or functionality-controlling parameter. Various materials such as silica glass, silicon, other bulk and quantum well semiconductors, organic materials, and particle-doped nanostructures are referred to as possible candidates for device implementations. Numerical estimates of achievable parameters in a selected suitable material are discussed. PMID:18542395

  18. Independent control of polar and azimuthal anchoring.

    PubMed

    Anquetil-Deck, C; Cleaver, D J; Bramble, J P; Atherton, T J

    2013-07-01

    Monte Carlo simulation, experiment, and continuum theory are used to examine the anchoring exhibited by a nematic liquid crystal at a patterned substrate comprising a periodic array of rectangles that, respectively, promote vertical and planar alignment. It is shown that the easy axis and effective anchoring energy promoted by such surfaces can be readily controlled by adjusting the design of the pattern. The calculations reveal rich behavior: for strong anchoring, as exhibited by the simulated system, for rectangle ratios ?2 the nematic aligns in the direction of the long edge of the rectangles, the azimuthal anchoring coefficient changing with pattern shape. In weak anchoring scenarios, however, including our experimental systems, preferential anchoring is degenerate between the two rectangle diagonals. Bistability between diagonally aligned and edge-aligned arrangement is predicted for intermediate combinations of anchoring coefficient and system length scale. PMID:23944468

  19. Coherent control of optical polarization effects in metamaterials

    PubMed Central

    Mousavi, Seyedmohammad A.; Plum, Eric; Shi, Jinhui; Zheludev, Nikolay I.

    2015-01-01

    Processing of photonic information usually relies on electronics. Aiming to avoid the conversion between photonic and electronic signals, modulation of light with light based on optical nonlinearity has become a major research field and coherent optical effects on the nanoscale are emerging as new means of handling and distributing signals. Here we demonstrate that in slabs of linear material of sub-wavelength thickness optical manifestations of birefringence and optical activity (linear and circular birefringence and dichroism) can be controlled by a wave coherent with the wave probing the polarization effect. We demonstrate this in proof-of-principle experiments for chiral and anisotropic microwave metamaterials, where we show that the large parameter space of polarization characteristics may be accessed at will by coherent control. Such control can be exerted at arbitrarily low intensities, thus arguably allowing for fast handling of electromagnetic signals without facing thermal management and energy challenges. PMID:25755071

  20. Coherent control of optical polarization effects in metamaterials.

    PubMed

    Mousavi, Seyedmohammad A; Plum, Eric; Shi, Jinhui; Zheludev, Nikolay I

    2015-01-01

    Processing of photonic information usually relies on electronics. Aiming to avoid the conversion between photonic and electronic signals, modulation of light with light based on optical nonlinearity has become a major research field and coherent optical effects on the nanoscale are emerging as new means of handling and distributing signals. Here we demonstrate that in slabs of linear material of sub-wavelength thickness optical manifestations of birefringence and optical activity (linear and circular birefringence and dichroism) can be controlled by a wave coherent with the wave probing the polarization effect. We demonstrate this in proof-of-principle experiments for chiral and anisotropic microwave metamaterials, where we show that the large parameter space of polarization characteristics may be accessed at will by coherent control. Such control can be exerted at arbitrarily low intensities, thus arguably allowing for fast handling of electromagnetic signals without facing thermal management and energy challenges. PMID:25755071

  1. Coherent control of optical polarization effects in metamaterials

    NASA Astrophysics Data System (ADS)

    Mousavi, Seyedmohammad A.; Plum, Eric; Shi, Jinhui; Zheludev, Nikolay I.

    2015-03-01

    Processing of photonic information usually relies on electronics. Aiming to avoid the conversion between photonic and electronic signals, modulation of light with light based on optical nonlinearity has become a major research field and coherent optical effects on the nanoscale are emerging as new means of handling and distributing signals. Here we demonstrate that in slabs of linear material of sub-wavelength thickness optical manifestations of birefringence and optical activity (linear and circular birefringence and dichroism) can be controlled by a wave coherent with the wave probing the polarization effect. We demonstrate this in proof-of-principle experiments for chiral and anisotropic microwave metamaterials, where we show that the large parameter space of polarization characteristics may be accessed at will by coherent control. Such control can be exerted at arbitrarily low intensities, thus arguably allowing for fast handling of electromagnetic signals without facing thermal management and energy challenges.

  2. Free space ranging based on a chaotic long-wavelength VCSEL with optical feedback

    NASA Astrophysics Data System (ADS)

    Quirce, Ana; Perez, Pablo; Valle, Angel; Pesquera, Luis; Esquivias, Ignacio; Panajotov, Krassimir; Thienpont, Hugo

    2015-03-01

    Chaotic Lidar systems (CLIDAR) are used for high-resolution ranging. They are based on the correlation of a chaotic signal waveform with the signal that is reflected back from the target. We report a novel CLIDAR system based on the autocorrelation of the signal obtained by the superposition of the chaotic signal waveform and the signal that is reflected from the target. A simplified set-up with just one detector is required in contrast to the two detectors used in standard CLIDAR systems. Our experimental results are obtained with a 1550-nm vertical-cavity surface-emitting laser (VCSEL) with chaotic dynamics due to optical feedback. Our CLIDAR system provides an autocorrelation function with several sharp minima. The position of the target is obtained from the location of those minima. A theoretical analysis of the CLIDAR system is also presented. A rate equation model for the polarization of a VCSEL subject to optical feedback is the basis for the simulation of the CLIDAR system. A comparison between our theoretical and experimental results is performed, resulting in a good agreement in the chaotic signal but in a different sign of the CLIDAR signal.

  3. Stable polarization self-modulation in vertical-cavity surface-emitting lasers

    SciTech Connect

    Li, H.; Hohl, A.; Gavrielides, A. [Air Force Research Laboratory DELO, Nonlinear Optics Group, Phillips Research Site, 3550 Aberdeen Avenue, Kirtland Air Force Base, New Mexico 87117-5776 (United States)] [Air Force Research Laboratory DELO, Nonlinear Optics Group, Phillips Research Site, 3550 Aberdeen Avenue, Kirtland Air Force Base, New Mexico 87117-5776 (United States); Hou, H.; Choquette, K.D. [Center of Compound Semiconductor Science and Technology, Sandia National Laboratories MS0603, Albuquerque, New Mexico 87185-1603 (United States)] [Center of Compound Semiconductor Science and Technology, Sandia National Laboratories MS0603, Albuquerque, New Mexico 87185-1603 (United States)

    1998-05-01

    The characteristics of polarization self-modulation in a vertical-cavity surface-emitting laser (VCSEL) were studied for frequencies up to {approx}9 GHz both experimentally and theoretically. Polarization self-modulation was obtained by rotating the linearly polarized output of the VCSEL by 90{degree} and reinjecting it into the laser. Experimentally we simultaneously recorded time traces, optical and radio-frequency spectra. We found for increasing modulation frequencies that the output characteristics changed from square-wave to sinusoidal and the VCSEL system assumed new polarization eigenstates that are different from the free-running VCSEL eigenstates. We modeled polarization self-modulation as an interband process and found a good qualitative agreement between our experimental and numerical results. {copyright} {ital 1998 American Institute of Physics.}

  4. High-power VCSEL arrays for consumer electronics

    NASA Astrophysics Data System (ADS)

    Graham, Luke A.; Chen, Hao; Cruel, Jonathan; Guenter, James; Hawkins, Bobby; Hawthorne, Bobby; Kelly, David Q.; Melgar, Alirio; Martinez, Mario; Shaw, Edward; Tatum, Jim A.

    2015-03-01

    Finisar has developed a line of high power, high efficiency VCSEL arrays. They are fabricated at 860nm as traditional P side up top emitting devices, leveraging Finisar's existing VCSEL fab and test processes for low cost, high volume capability. A thermal camera is used to accurately measure temperature profiles across the arrays at a variety of operating conditions and further allowing development of a full reliability model. The arrays are shown to demonstrate wear out reliability suitable for a wide range of applications. Typical 1/e^2 beam divergence is near 16 degrees under CW operating conditions at peak wall plug efficiency, narrowing further under pulsed drive conditions.

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  6. Quantum phase gate and controlled entanglement with polar molecules

    SciTech Connect

    Charron, Eric; Keller, Arne; Atabek, Osman [Laboratoire de Photophysique Moleculaire du CNRS, Universite Paris-Sud, Batiment 210, 91405 Orsay Cedex (France); Milman, Perola [Laboratoire de Photophysique Moleculaire du CNRS, Universite Paris-Sud, Batiment 210, 91405 Orsay Cedex (France); CERMICS, Ecole Nationale des Ponts et Chaussees, 6 et 8 av. Blaise Pascal, Cite Descartes, Champs-sur-Marne, 77455 Marne-la-Vallee (France)

    2007-03-15

    We propose an alternative scenario for the generation of entanglement between rotational quantum states of two polar molecules. This entanglement arises from dipole-dipole interaction, and is controlled by a sequence of laser pulses simultaneously exciting both molecules. We study the efficiency of the process, and discuss possible experimental implementations with cold molecules trapped in optical lattices or in solid matrices. Finally, various entanglement detection procedures are presented, and their suitability for these two physical situations is analyzed.

  7. Uniformity and performance of selectively oxidized VCSEL arrays

    NASA Astrophysics Data System (ADS)

    Geib, Kent M.; Choquette, Kent D.; Hou, Hong Q.; Hammons, B. E.

    1998-04-01

    We report the uniformity characteristics of low threshold of 1060 nm and high power 850 nm 8 X 8 individually addressable oxide-confined VCSEL arrays. Uniformity of lasing thresholds and operating characteristics are described, as well as thermal issues for 2D laser arrays.

  8. Field Trial of 160-Gbit\\/s, Polarization-Division Multiplexed RZ-DQPSK Transmission System using Automatic Polarization Control

    Microsoft Academic Search

    Mikio Yagi; Shuichi Satomi; Shiro Ryu

    2008-01-01

    We have successfully demonstrated a field trial of 160-Gbit\\/s, RZ-DQPSK polarization-division multiplexed transmission system over 214 km using automatic polarization control. Q-factors of the signals have been kept stable for more than five days.

  9. A long-range polarization-controlled optical tractor beam

    NASA Astrophysics Data System (ADS)

    Shvedov, Vladlen; Davoyan, Arthur R.; Hnatovsky, Cyril; Engheta, Nader; Krolikowski, Wieslaw

    2014-11-01

    The laser beam has become an indispensable tool for the controllable manipulation and transport of microscopic objects in biology, physical chemistry and condensed matter physics. In particular, ‘tractor’ laser beams can draw matter towards a laser source and perform, for instance, all-optical remote sampling. Recent advances in lightwave technology have already led to small-scale experimental demonstrations of tractor beams. However, the realization of long-range tractor beams has not gone beyond the realm of theoretical investigations. Here, we demonstrate the stable transfer of gold-coated hollow glass spheres against the power flow of a single inhomogeneously polarized laser beam over tens of centimetres. Additionally, by varying the polarization state of the beam we can stop the spheres or reverse the direction of their motion at will.

  10. Polarization characteristics, control, and modulation of vertical-cavity surface emitting lasers

    Microsoft Academic Search

    Kent D. Choquette; Kevin L. Lear; Richard P. Schneider; R. E. Leibenguth; J. J. Figiel; S. P. Kilcoyne; Mary Hagerott Crawford; John C. Zolper

    1995-01-01

    The gain-dependent polarization properties of vertical-cavity surface emitting lasers and methods for polarization control and modulation are discussed. The partitioning of power between the two orthogonal eigen polarizations is shown to depend upon the relative spectral alignment of the nondegenerate polarization cavity resonances with the laser gain spectrum. A dominant polarization can thus be maintained by employing a blue-shifted offset

  11. Active inductor shunt peaking in high-speed VCSEL driver design

    E-print Network

    Futian Liang; Datao Gong; Suen Hou; Chonghan Liu; Tiankuan Liu; Da-Shung Su; Ping-Kun Teng; Annie Xiang; Jingbo Ye; Ge Jin

    2013-06-04

    An all transistor active inductor shunt peaking structure has been used in a prototype of 8-Gbps high-speed VCSEL driver which is designed for the optical link in ATLAS liquid Argon calorimeter upgrade. The VCSEL driver is fabricated in a commercial 0.25-um Silicon-on-Sapphire (SoS) CMOS process for radiation tolerant purpose. The all transistor active inductor shunt peaking is used to overcome the bandwidth limitation from the CMOS process. The peaking structure has the same peaking effect as the passive one, but takes a small area, does not need linear resistors and can overcome the process variation by adjust the peaking strength via an external control. The design has been tapped out, and the prototype has been proofed by the preliminary electrical test results and bit error ratio test results. The driver achieves 8-Gbps data rate as simulated with the peaking. We present the all transistor active inductor shunt peaking structure, simulation and test results in this paper.

  12. Planar cell polarity genes control the connectivity of enteric neurons

    PubMed Central

    Sasselli, Valentina; Boesmans, Werend; Vanden Berghe, Pieter; Tissir, Fadel; Goffinet, André M.; Pachnis, Vassilis

    2013-01-01

    A highly complex network of intrinsic enteric neurons is required for the digestive and homeostatic functions of the gut. Nevertheless, the genetic and molecular mechanisms that regulate their assembly into functional neuronal circuits are currently unknown. Here we report that the planar cell polarity (PCP) genes Celsr3 and Fzd3 are required during murine embryogenesis to specifically control the guidance and growth of enteric neuronal projections relative to the longitudinal and radial gut axes. Ablation of these genes disrupts the normal organization of nascent neuronal projections, leading to subtle changes of axonal tract configuration in the mature enteric nervous system (ENS), but profound abnormalities in gastrointestinal motility. Our data argue that PCP-dependent modules of connectivity established at early stages of enteric neurogenesis control gastrointestinal function in adult animals and provide the first evidence that developmental deficits in ENS wiring may contribute to the pathogenesis of idiopathic bowel disorders. PMID:23478408

  13. A narrow-spectrum long-wavelength VCSEL using a fiber Bragg grating

    Microsoft Academic Search

    Toru Mizunami; Syuiti Kojima; Takahiro Kudo

    2006-01-01

    A 1.3-mum vertical-cavity surface-emitting laser (VCSEL) with a fiber Bragg grating (FBG) as an external cavity was developed. VCSELs emit light vertically from the semiconductor substrate. They have a circular output beam and therefore have a merit of easy coupling with optical fibers. Long-wavelength VCSELs in the 1.3 or 1.55-mum bands have recently been developed, which are suitable for long-distance

  14. Free-Space Optical Interconnect Employing VCSEL Diodes

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Savich, Gregory R.; Torres, Heidi

    2009-01-01

    Sensor signal processing is widely used on aircraft and spacecraft. The scheme employs multiple input/output nodes for data acquisition and CPU (central processing unit) nodes for data processing. To connect 110 nodes and CPU nodes, scalable interconnections such as backplanes are desired because the number of nodes depends on requirements of each mission. An optical backplane consisting of vertical-cavity surface-emitting lasers (VCSELs), VCSEL drivers, photodetectors, and transimpedance amplifiers is the preferred approach since it can handle several hundred megabits per second data throughput.The next generation of satellite-borne systems will require transceivers and processors that can handle several Gb/s of data. Optical interconnects have been praised for both their speed and functionality with hopes that light can relieve the electrical bottleneck predicted for the near future. Optoelectronic interconnects provide a factor of ten improvement over electrical interconnects.

  15. Polarization control of a Q-switched, diode-pumped Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Lowrie, Christopher; Zygmunt, Aaron; Crout, Amy; Liu, Yongsong; Thompson, John R.

    1995-07-01

    We describe control of the polarization state of a diode-pumped Nd:YAG laser that is Q switched with an acousto-optic modulator (AOM). One of two orthogonal linear polarization states can be made dominant, depending on the amount of loss introduced by the AOM. Heterodyne beating indicates that the two polarization states are of slightly different frequencies.

  16. Applications of controlled-flow laser-polarized xenon gas to porous and granular media study

    E-print Network

    Walsworth, Ronald L.

    Applications of controlled-flow laser-polarized xenon gas to porous and granular media study R. W of continuous flow laser-polarized xenon gas, both in unrestricted tubing, and in a model porous media of continuous flow laser-polarized xenon gas in unrestricted tubing indicate clear diffraction minima resulting

  17. Conceal time-delay signature of chaotic vertical-cavity surface-emitting lasers by variable-polarization optical feedback

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    Time-delay (TD) signatures of chaotic outputs generated by vertical-cavity surface-emitting lasers (VCSELs) are investigated quantitatively by using two proposed estimators, the peak signal to mean ratio (PSMR) calculated based on the auto-correlation function, and the valley signal to mean ratio (VSMR) calculated based on an information-theory-based estimator, the permutation entropy (PE) function. The VCSELs subject to variable-polarization optical feedback (VPOF) are considered, and the effects of polarizer angle, feedback strength, feedback delay and injection current are discussed. When the feedback strength is small, the TD signatures for the fully developed chaotic outputs of VCSELs can be well concealed for all polarizer angles. While for large feedback strength, the TD signatures cannot be concealed for any polarizer angle. However, for moderate feedback strength, the TD signatures of VCSELs with VPOF at intermediate polarizer angles can be better concealed than those of VCSELs with conventional polarization-selected optical feedback. Thus, the VCSELs with VPOF are extremely interesting for the security-enhanced chaotic optical communication systems.

  18. Polarization control of multiply-scattered light through random media by wavefront shaping

    E-print Network

    Guan, Yefeng; Small, Eran; Zhou, Jianying; Silberberg, Yaron

    2015-01-01

    We show that the polarization state of coherent light propagating through an optically thick multiple-scattering medium, can be controlled by wavefront shaping, i.e. by controlling only the spatial phase of the incoming field with a spatial light modulator. Any polarization state of light at any spatial position behind the scattering medium can be attained with this technique. Thus, transforming the random medium to an arbitrary optical polarization component becomes possible.

  19. Reliability and failure mechanisms of oxide VCSELs in non-hermetic enviroments

    Microsoft Academic Search

    Suning Xie; Robert W. Herrick; Gregory N. De Brabander; Wilson H. Widjaja; Uli Koelle; An-Nien Cheng; Laura M. Giovane; Frank Z. Hu; Mark R. Keever; Tim Osentowski; Scott A. McHugo; Myrna S. Mayonte; Seongsin M. Kim; Danielle R. Chamberlin; S. Jeffrey Rosner; Grant Girolami

    2003-01-01

    High speed fiber optic transceiver modules using parallel optics require that oxide-confined vertical-cavity surface-emitting lasers (VCSELs) be moisture resistant in non-hermetic environments. Conventional storage 85\\/85 (85°C and 85% relative humidity) testing without a bias does not adequately characterize oxide VCSEL\\

  20. Ultra high-speed electro-optically modulated VCSELs: modeling and experimental results

    Microsoft Academic Search

    V. A. Shchukin; N. N. Ledentsov; J. A. Lott; H. Quast; F. Hopfer; L. Ya. Karachinsky; M. Kuntz; P. Moser; A. Mutig; A. Strittmatter; V. P. Kalosha; D. Bimberg

    2008-01-01

    We have studied the modulation properties of a vertical cavity surface-emitting laser (VCSEL) coupled to an electrooptical modulator. It is shown that, if the modulator is placed in a resonant cavity, the modulation of the light output power is governed predominantly by electrooptic, or electrorefraction effect rather than by electroabsorption. A novel concept of electrooptically modulated (EOM) VCSEL based on

  1. Polarization control of microwave ionization of H atoms

    SciTech Connect

    Koch, P.M.; Bellermann, M.R.W.; Richards, D.

    1996-05-01

    At scaled frequencies {Omega}{sub o} = n{sub o}{sup 3}{omega}{much_lt} 1, extreme sensitivity to elliptical polarization (EStoEP) occurs (9.904 GHz, half-sine pulse, 154 field osc.) for certain ranges of n{sub o}, the principal quantum number; n{sub o}=43,42,41 ({Omega}{sub o}=0.1197 to 1.1038), show EStoEP close to circular polarization (CP), while n{sub o} = 33,32,31 ({Omega}{sub o} = 0.0541 to 0.0449) show it farther from CP. Coherent control schemes usually exploit interference of quantal amplitudes, but here 3d classical Monte Carlo calculations (3dCL) are quantitatively accurate. Approximate classical theory reveals underlying resonance physics. In the corotating frame (CRF), a low-{Omega}{sub o} CP/g field of amplitude F induces (Stark) motion at {omega}{sub s} = 1.5n{sub o}F. For {Omega}{sub o} {much_lt} 1, classical ionization requires F{sub o} = n{sub o}{sup 4}F {ge} F{sub cl} = 0.13. In CRF, EP near CP gives driving terms at 2{omega}; EStoEP at n{sub o}=43-41 occurs when this resonates with the {omega}{sub s} motion and F{sub o} {ge}F{sub cl} EStoEP at n{sub o}=33-31 occurs when 4{omega} is close to {omega}{sub s}. At even larger F{sub o}, n{sub o}=31 data show yet more EStoEP reproduced by 3dCL. This is likely the 6{omega} resonance.

  2. Albedo control of seasonal South Polar cap recession on Mars

    NASA Astrophysics Data System (ADS)

    Schmidt, Frédéric; Douté, Sylvain; Schmitt, Bernard; Vincendon, Mathieu; Bibring, Jean-Pierre; Langevin, Yves; Omega Team

    2009-04-01

    Over the last few decades, General Circulation Models (GCM) have been used to simulate the current martian climate. The calibration of these GCMs with the current seasonal cycle is a crucial step in understanding the climate history of Mars. One of the main climatic signals currently used to validate GCMs is the annual atmospheric pressure cycle. It is difficult to use changes in seasonal deposits on the surface of Mars to calibrate the GCMs given the spectral ambiguities between CO 2 and H 2O ice in the visible range. With the OMEGA imaging spectrometer covering the near infra-red range, it is now possible to monitor both types of ice at a spatial resolution of about 1 km. At global scale, we determine the change with time of the Seasonal South Polar Cap (SSPC) crocus line, defining the edge of CO 2 deposits. This crocus line is not symmetric around the geographic South Pole. At local scale, we introduce the snowdrop distance, describing the local structure of the SSPC edge. Crocus line and snowdrop distance changes can now be used to calibrate GCMs. The albedo of the seasonal deposits is usually assumed to be a uniform and constant parameter of the GCMs. In this study, albedo is found to be the main parameter controlling the SSPC recession at both global and local scale. Using a defrost mass balance model (referred to as D-frost) that incorporates the effect of shadowing induced by topography, we show that the global SSPC asymmetry in the crocus line is controlled by albedo variations. At local scale, we show that the snowdrop distance is correlated with the albedo variability. Further GCM improvements should take into account these two results. We propose several possibilities for the origin of the asymmetric albedo control. The next step will be to identify and model the physical processes that create the albedo differences.

  3. Laser polarization and phase control of up-conversion fluorescence in rare-earth ions.

    PubMed

    Yao, Yunhua; Zhang, Shian; Zhang, Hui; Ding, Jingxin; Jia, Tianqing; Qiu, Jianrong; Sun, Zhenrong

    2014-01-01

    We theoretically and experimentally demonstrate the up-conversion fluorescence control via resonance-mediated two-photon absorption in rare-earth ions by varying both the laser polarization and phase. We show that both the laser polarization and phase can control the up-conversion fluorescence, and the up-conversion fluorescence intensity is decreased when the laser polarization changes from linear through elliptical to circular. We also show that the laser polarization will affect the control efficiency of the up-conversion fluorescence by varying the laser phase, and the circular polarization will reduce the control efficiency. Furthermore, we suggest that the control efficiency by varying the laser polarization and the effect of the laser polarization on the control efficiency by varying the laser phase can be artificially manipulated by controlling the laser spectral bandwidth. This optical control method opens a new opportunity to control the up-conversion fluorescence of rare-earth ions, which may have significant impact on the related applications of rare-earth ions. PMID:25465401

  4. Laser polarization and phase control of up-conversion fluorescence in rare-earth ions

    PubMed Central

    Yao, Yunhua; Zhang, Shian; Zhang, Hui; Ding, Jingxin; Jia, Tianqing; Qiu, Jianrong; Sun, Zhenrong

    2014-01-01

    We theoretically and experimentally demonstrate the up-conversion fluorescence control via resonance-mediated two-photon absorption in rare-earth ions by varying both the laser polarization and phase. We show that both the laser polarization and phase can control the up-conversion fluorescence, and the up-conversion fluorescence intensity is decreased when the laser polarization changes from linear through elliptical to circular. We also show that the laser polarization will affect the control efficiency of the up-conversion fluorescence by varying the laser phase, and the circular polarization will reduce the control efficiency. Furthermore, we suggest that the control efficiency by varying the laser polarization and the effect of the laser polarization on the control efficiency by varying the laser phase can be artificially manipulated by controlling the laser spectral bandwidth. This optical control method opens a new opportunity to control the up-conversion fluorescence of rare-earth ions, which may have significant impact on the related applications of rare-earth ions. PMID:25465401

  5. Adaptive polarization control of molecular T. Brixner1

    E-print Network

    Kassel, Universität

    Eµ with )(tE a vectorial quantity. If the momentary polarization state of the applied electromagnetic field involved electronic transitions require electromagnetic fields with polarizations parallel of the potassium dimer system. b) Section of pump­probe transients with mutually parallel (solid line) and crossed

  6. Distributed Algorithm for Signal Polarity Adjustment of Air-Conditioner Control Network

    NASA Astrophysics Data System (ADS)

    Ninagawa, Chuzo; Aoi, Fumio; Yokohama, Koji; Yoneda, Tomohiro

    This paper proposes a distributed algorithm for adjusting the signal polarity of the control networks for building air-conditioners. As field connection work of the two wires to the controller may be straight or cross, each controller has both plus and minus polarity circuits. It starts the algorithm in the arbitary sequence, and then negociates each other to select the plus/minus polarity circuits in order to adjust the signal polarity. A Time Petri Net model was constructed for verification of the proposed algorithm. The model describes the required specification of the system, straight/cross connection of the controller to the network bus line and the polarity adjustment algorithm. The efficient Time Petri Net verification tool made it possible to verify the model.

  7. Full control of polarization states and phase distributions of light with dual-metasurfaces

    E-print Network

    Li, Jianxiong; Yang, Haifang; Li, Junjie; Yu, Ping; Cheng, Hua; Gu, Changzhi; Tian, Jianguo

    2014-01-01

    Control of the phase and polarization states of light is an important goal for nearly all optical research. The development of an efficient optical component that allows the simultaneous manipulation of the polarization and phase distribution is needed. Traditional methods require the combination of multiple optical devices, and a single optical device cannot easily realize full control of light. We theoretically predict and experimentally verify that our proposed dual-metasurfaces provide an excellent means to simultaneously manipulate the phase and polarization of transmission light at the nanoscale. By introducing a phase gradient along the interface, we achieved a near-perfect anomalous refraction with controllable polarization in the near-infrared region. On the basis of these properties, we created a dual-metasurface capable of generating radially polarized beam, demonstrating the power of full control of light. This work opens exciting avenues toward improving the degrees of freedom in the manipulation...

  8. Depth-encoded all-fiber swept source polarization sensitive OCT

    PubMed Central

    Wang, Zhao; Lee, Hsiang-Chieh; Ahsen, Osman Oguz; Lee, ByungKun; Choi, WooJhon; Potsaid, Benjamin; Liu, Jonathan; Jayaraman, Vijaysekhar; Cable, Alex; Kraus, Martin F.; Liang, Kaicheng; Hornegger, Joachim; Fujimoto, James G.

    2014-01-01

    Polarization sensitive optical coherence tomography (PS-OCT) is a functional extension of conventional OCT and can assess depth-resolved tissue birefringence in addition to intensity. Most existing PS-OCT systems are relatively complex and their clinical translation remains difficult. We present a simple and robust all-fiber PS-OCT system based on swept source technology and polarization depth-encoding. Polarization multiplexing was achieved using a polarization maintaining fiber. Polarization sensitive signals were detected using fiber based polarization beam splitters and polarization controllers were used to remove the polarization ambiguity. A simplified post-processing algorithm was proposed for speckle noise reduction relaxing the demand for phase stability. We demonstrated systems design for both ophthalmic and catheter-based PS-OCT. For ophthalmic imaging, we used an optical clock frequency doubling method to extend the imaging range of a commercially available short cavity light source to improve polarization depth-encoding. For catheter based imaging, we demonstrated 200 kHz PS-OCT imaging using a MEMS-tunable vertical cavity surface emitting laser (VCSEL) and a high speed micromotor imaging catheter. The system was demonstrated in human retina, finger and lip imaging, as well as ex vivo swine esophagus and cardiovascular imaging. The all-fiber PS-OCT is easier to implement and maintain compared to previous PS-OCT systems and can be more easily translated to clinical applications due to its robust design. PMID:25401008

  9. Bianisotropic Metasurfaces for Optimal Polarization Control: Analysis and Synthesis

    NASA Astrophysics Data System (ADS)

    Pfeiffer, Carl; Grbic, Anthony

    2014-10-01

    Methods to analyze and synthesize two-dimensional, bianisotropic metamaterials (metasurfaces) are presented. First, a general bianisotropic metasurface is analyzed by using closed-form expressions that relate the reflection and transmission coefficients to its constituent surface parameters. Next, a systematic method to synthesize bianisotropic metasurfaces is outlined. It is analytically shown that bianisotropic metasurfaces can be realized by cascading anisotropic, patterned metallic sheets (electric sheet admittances). This geometry allows for straightforward design and fabrication from microwave to optical wavelengths. To demonstrate the utility of the proposed method, four devices exhibiting exotic polarization transformations are presented: a polarization rotator, an asymmetric circular polarizer, an asymmetric linear polarizer, and a symmetric circular polarizer. The optimal performance at centimeter, millimeter, and micrometer wavelengths highlights the versatility of the design process.

  10. The Hippo pathway controls polar cell fate through Notch signaling during Drosophila oogenesis.

    PubMed

    Chen, Hsi-Ju; Wang, Chi-Ming; Wang, Tsu-Wei; Liaw, Gwo-Jen; Hsu, Ta-Hsing; Lin, Tzu-Huai; Yu, Jenn-Yah

    2011-09-15

    During Drosophila oogenesis, the somatic follicle cells form an epithelial layer surrounding the germline cells to form egg chambers. In this process, follicle cell precursors are specified into polar cells, stalk cells, and main-body follicle cells. Proper specification of these three cell types ensures correct egg chamber formation and polarization of the anterior-posterior axis of the germline cells. Multiple signaling cascades coordinate to control the follicle cell fate determination, including Notch, JAK/STAT, and Hedgehog signaling pathways. Here, we show that the Hippo pathway also participates in polar cell specification. Over-activation of yorkie (yki) leads to egg chamber fusion, possibly through attenuation of polar cell specification. Loss-of-function experiments using RNAi knockdown or generation of mutant clones by mitotic recombination demonstrates that reduction of yki expression promotes polar cell formation in a cell-autonomous manner. Consistently, polar cells mutant for hippo (hpo) or warts (wts) are not properly specified, leading to egg chamber fusion. Furthermore, Notch activity is increased in yki mutant cells and reduction of Notch activity suppresses polar cell formation in yki mutant clones. These results demonstrate that yki represses polar cell fate through Notch signaling. Collectively, our data reveal that the Hippo pathway controls polar cell specification. Through repressing Notch activity, Yki serves as a key repressor in specifying polar cells during Drosophila oogenesis. PMID:21781961

  11. Final report on LDRD project :leaky-mode VCSELs for photonic logic circuits.

    SciTech Connect

    Hargett, Terry W.; Hadley, G. Ronald; Serkland, Darwin Keith; Blansett, Ethan L.; Geib, Kent Martin; Sullivan, Charles Thomas; Keeler, Gordon Arthur; Bauer, Thomas; Ongstand, Andrea; Medrano, Melissa R.; Peake, Gregory Merwin; Montano, Victoria A.

    2005-11-01

    This report describes the research accomplishments achieved under the LDRD Project ''Leaky-mode VCSELs for photonic logic circuits''. Leaky-mode vertical-cavity surface-emitting lasers (VCSELs) offer new possibilities for integration of microcavity lasers to create optical microsystems. A leaky-mode VCSEL output-couples light laterally, in the plane of the semiconductor wafer, which allows the light to interact with adjacent lasers, modulators, and detectors on the same wafer. The fabrication of leaky-mode VCSELs based on effective index modification was proposed and demonstrated at Sandia in 1999 but was not adequately developed for use in applications. The aim of this LDRD has been to advance the design and fabrication of leaky-mode VCSELs to the point where initial applications can be attempted. In the first and second years of this LDRD we concentrated on overcoming previous difficulties in the epitaxial growth and fabrication of these advanced VCSELs. In the third year, we focused on applications of leaky-mode VCSELs, such as all-optical processing circuits based on gain quenching.

  12. Accurate modelling of VCSEL distributed Bragg reflectors by Floquet-Bloch theory

    NASA Astrophysics Data System (ADS)

    De Leonardis, Francesco; Magno, Francesca; Rizzato, Alessandro; Passaro, Vittorio M. N.

    2006-04-01

    Nowadays, vertical cavity surface emitting lasers (VCSELs) provide a very exciting area of research. The unique geometry of VCSELs results in several significant advantages over their edge-emitting counterparts, including low threshold current, single-longitudinal-mode operation, circular output-beam profile. The optimization of the DBR structure is of fundamental importance to increase the performance of optical systems based on the VCSEL technology. To this aim, sophisticated modelling techniques are needed, where only negligible or no approximations are included in the calculations. Therefore, we have used the Floquet-Bloch theory (FBT) formalism to simulate the DBR performance of VCSEL structures. In this paper we explain the general VCSEL theory and propose a number of simulations to individuate the optimal configuration of DBR mirrors with the aim to maximise the output power laser and reduce the threshold current density. The VCSEL optimization is carried out by considering the best trade off among various parameters, including period number, materials, and doping concentration and profile. It is clearly shown the superiority of the FBT approach in the prediction of the best DBR performance and VCSEL properties by comparing results (reflectivity, spectrum, peak wavelength, gain) with other well-known methods, such as the transfer matrix method (TMM) and coupled-mode theory (CMT).

  13. Narrowband polarization entangled paired photons with controllable temporal length

    NASA Astrophysics Data System (ADS)

    Yan, Hui; Chen, JieFei

    2015-04-01

    Quantum networks strongly depend on the efficient interactions between flying photonic quantum bits and local long-lived atomic matter nodes. To achieve the efficient quantum interfaces between polarization-encoding photons and spin-encoding atoms, polarization-entangled paired photons with a bandwidth narrower than the natural linewidth of the atoms are highly required. In this paper, we review the generation of subnatural-linewidth polarization-entangled paired photons through spontaneous four-wave mixing with cold atoms, which is very suitable for the application of quantum networks.

  14. Narrowband polarization entangled paired photons with controllable temporal length

    NASA Astrophysics Data System (ADS)

    Yan, Hui; Chen, JieFei

    2015-07-01

    Quantum networks strongly depend on the efficient interactions between flying photonic quantum bits and local long-lived atomic matter nodes. To achieve the efficient quantum interfaces between polarization-encoding photons and spin-encoding atoms, polarization-entangled paired photons with a bandwidth narrower than the natural linewidth of the atoms are highly required. In this paper, we review the generation of subnatural-linewidth polarization-entangled paired photons through spontaneous four-wave mixing with cold atoms, which is very suitable for the application of quantum networks.

  15. Selective area growth of well-ordered ZnO nanowire arrays with controllable polarity.

    PubMed

    Consonni, Vincent; Sarigiannidou, Eirini; Appert, Estelle; Bocheux, Amandine; Guillemin, Sophie; Donatini, Fabrice; Robin, Ivan-Christophe; Kioseoglou, Joseph; Robaut, Florence

    2014-05-27

    Controlling the polarity of ZnO nanowires in addition to the uniformity of their structural morphology in terms of position, vertical alignment, length, diameter, and period is still a technological and fundamental challenge for real-world device integration. In order to tackle this issue, we specifically combine the selective area growth on prepatterned polar c-plane ZnO single crystals using electron-beam lithography, with the chemical bath deposition. The formation of ZnO nanowires with a highly controlled structural morphology and a high optical quality is demonstrated over large surface areas on both polar c-plane ZnO single crystals. Importantly, the polarity of ZnO nanowires can be switched from O- to Zn-polar, depending on the polarity of prepatterned ZnO single crystals. This indicates that no fundamental limitations prevent ZnO nanowires from being O- or Zn-polar. In contrast to their catalyst-free growth by vapor-phase deposition techniques, the possibility to control the polarity of ZnO nanowires grown in solution is remarkable, further showing the strong interest in the chemical bath deposition and hydrothermal techniques. The single O- and Zn-polar ZnO nanowires additionally exhibit distinctive cathodoluminescence spectra. To a broader extent, these findings open the way to the ultimate fabrication of well-organized heterostructures made from ZnO nanowires, which can act as building blocks in a large number of electronic, optoelectronic, and photovoltaic devices. PMID:24720628

  16. Coherent Polarization Control of Terahertz Waves Generated from Two-Color Laser-Induced Gas Plasma

    SciTech Connect

    Dai Jianming; Karpowicz, Nicholas; Zhang, X.-C. [Center for Terahertz Research, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

    2009-07-10

    Electrons ionized from an atom or molecule by circularly or elliptically polarized femtosecond omega and 2omega pulses exhibit different trajectory orientations as the relative phase between the two pulses changes. Macroscopically, the polarization of the terahertz wave emitted during the ionization process was found to be coherently controllable through the optical phase. This new finding can be completely reproduced by numerical simulation and may enable fast terahertz wave modulation and coherent control of nonlinear responses excited by intense terahertz waves with controllable polarization.

  17. High power 808 nm VCSEL arrays for pumping of compact pulsed high energy Nd:YAG lasers operating at 946 nm and 1064 nm for blue and UV light generation

    Microsoft Academic Search

    Robert van Leeuwen; Yihan Xiong; Laurence S. Watkins; Jean-Francois Seurin; Guoyang Xu; Qing Wang; Chuni Ghosh

    2011-01-01

    High power 808 nm VCSEL arrays were developed to pump compact pulsed Nd:YAG lasers. A QCW side-pumped passively Q-switched Nd:YAG laser operating at 1064 nm produced linearly polarized 4 ns IR pulses with 4.7 mJ pulse energy. These pulses were externally frequency doubled and quadrupled resulting in 2.5 mJ pulse energy at 532 nm and 0.8 mJ at 266 nm

  18. 482 Research Paper CDC-42 controls early cell polarity and spindle orientation

    E-print Network

    Ahringe, Julie

    482 Research Paper CDC-42 controls early cell polarity and spindle orientation in C. elegans Monica of this early E-mail: jaa@mole.bio.cam.ac.uk asymmetry. The small G protein Cdc42 is a key regulator of polarity homolog of PAR-6. The function of Cdc42 in C. elegans had not yet been Revised: 2 February 2001 Accepted

  19. Polarized Secretion of Drosophila EGFR Ligand from Photoreceptor Neurons Is Controlled by ER Localization

    E-print Network

    Shilo, Benny

    Drosophila visual system, photoreceptor neurons secrete the epidermal growth factor receptor ligand SpitzPolarized Secretion of Drosophila EGFR Ligand from Photoreceptor Neurons Is Controlled by ER molecules from neurons must be regulated, to accommodate their highly polarized structure. In the developing

  20. Independent controls of differently-polarized reflected waves by anisotropic metasurfaces.

    PubMed

    Ma, Hui Feng; Wang, Gui Zhen; Kong, Gu Sheng; Cui, Tie Jun

    2015-01-01

    We propose a kind of anisotropic planar metasurface, which has capacity to manipulate the orthogonally-polarized electromagnetic waves independently in the reflection mode. The metasurface is composed of orthogonally I-shaped structures and a metal-grounded plane spaced by a dielectric isolator, with the thickness of about 1/15 wavelength. The normally incident linear-polarized waves will be totally reflected by the metal plane, but the reflected phases of x- and y-polarized waves can be controlled independently by the orthogonally I-shaped structures. Based on this principle, we design four functional devices using the anisotropic metasurfaces to realize polarization beam splitting, beam deflection, and linear-to-circular polarization conversion with a deflection angle, respectively. Good performances have been observed from both simulation and measurement results, which show good capacity of the anisotropic metasurfaces to manipulate the x- and y-polarized reflected waves independently. PMID:25873323

  1. Independent Controls of Differently-Polarized Reflected Waves by Anisotropic Metasurfaces

    PubMed Central

    Ma, Hui Feng; Wang, Gui Zhen; Kong, Gu Sheng; Cui, Tie Jun

    2015-01-01

    We propose a kind of anisotropic planar metasurface, which has capacity to manipulate the orthogonally-polarized electromagnetic waves independently in the reflection mode. The metasurface is composed of orthogonally I-shaped structures and a metal-grounded plane spaced by a dielectric isolator, with the thickness of about 1/15 wavelength. The normally incident linear-polarized waves will be totally reflected by the metal plane, but the reflected phases of x- and y-polarized waves can be controlled independently by the orthogonally I-shaped structures. Based on this principle, we design four functional devices using the anisotropic metasurfaces to realize polarization beam splitting, beam deflection, and linear-to-circular polarization conversion with a deflection angle, respectively. Good performances have been observed from both simulation and measurement results, which show good capacity of the anisotropic metasurfaces to manipulate the x- and y-polarized reflected waves independently. PMID:25873323

  2. Independent Controls of Differently-Polarized Reflected Waves by Anisotropic Metasurfaces

    NASA Astrophysics Data System (ADS)

    Ma, Hui Feng; Wang, Gui Zhen; Kong, Gu Sheng; Cui, Tie Jun

    2015-04-01

    We propose a kind of anisotropic planar metasurface, which has capacity to manipulate the orthogonally-polarized electromagnetic waves independently in the reflection mode. The metasurface is composed of orthogonally I-shaped structures and a metal-grounded plane spaced by a dielectric isolator, with the thickness of about 1/15 wavelength. The normally incident linear-polarized waves will be totally reflected by the metal plane, but the reflected phases of x- and y-polarized waves can be controlled independently by the orthogonally I-shaped structures. Based on this principle, we design four functional devices using the anisotropic metasurfaces to realize polarization beam splitting, beam deflection, and linear-to-circular polarization conversion with a deflection angle, respectively. Good performances have been observed from both simulation and measurement results, which show good capacity of the anisotropic metasurfaces to manipulate the x- and y-polarized reflected waves independently.

  3. TSC1 controls macrophage polarization to prevent inflammatory disease.

    PubMed

    Zhu, Linnan; Yang, Tao; Li, Longjie; Sun, Lina; Hou, Yuzhu; Hu, Xuelian; Zhang, Lianjun; Tian, Hongling; Zhao, Qingjie; Peng, Jianxia; Zhang, Hongbing; Wang, Ruoyu; Yang, Zhongzhou; Zhang, Lianfeng; Zhao, Yong

    2014-01-01

    Macrophages acquire distinct phenotypes during tissue stress and inflammatory responses, but the mechanisms that regulate the macrophage polarization are poorly defined. Here we show that tuberous sclerosis complex 1 (TSC1) is a critical regulator of M1 and M2 phenotypes of macrophages. Mice with myeloid-specific deletion of TSC1 exhibit enhanced M1 response and spontaneously develop M1-related inflammatory disorders. However, TSC1-deficient mice are highly resistant to M2-polarized allergic asthma. Inhibition of the mammalian target of rapamycin (mTOR) fails to reverse the hypersensitive M1 response of TSC1-deficient macrophages, but efficiently rescues the defective M2 polarization. Deletion of mTOR also fails to reverse the enhanced inflammatory response of TSC1-deficient macrophages. Molecular studies indicate that TSC1 inhibits M1 polarization by suppressing the Ras GTPase-Raf1-MEK-ERK pathway in mTOR-independent manner, whereas TSC1 promotes M2 properties by mTOR-dependent CCAAT/enhancer-binding protein-? pathways. Overall, these findings define a key role for TSC1 in orchestrating macrophage polarization via mTOR-dependent and independent pathways. PMID:25175012

  4. Optical implementation of polarization-independent, bidirectional, nonblocking Clos network using polarization control technique in free space

    NASA Astrophysics Data System (ADS)

    Yang, Junbo; Yang, Jiankun; Li, Xiujian; Chang, Shengli; Su, Xianyu; Ping, Xu

    2011-04-01

    The clos network is one of the earliest multistage interconnection networks. Recently, it has been widely studied in parallel optical information processing systems, and there have been many efforts to develop this network. In this paper, a smart and compact Clos network, including Clos(2,3,2) and Clos(2,4,2), is proposed by using polarizing beam-splitters (PBS), phase spatial light modulators (PSLM), and mirrors. PBS features that are s-component (perpendicular to the incident plane) of the incident light beam is reflected, and the p-component (parallel to the incident plane) passes through it. According to switching logic, under control of external electrical signals, PSLM functions to control routing paths of the signal beams, i.e., the polarization of each optical signal is rotated or not rotated 90° by a programmable PSLM. This new type of configuration grants the features of less optical components, compact in structure, efficient in performance, and insensitive to polarization of signal beam. In addition, the straight, the exchange, and the broadcast functions of the basic switch element are implemented bidirectionally in free-space. Furthermore, the new optical experimental module of 2×3 and 2×4 optical switch is also presented by a cascading polarization-independent bidirectional 2×2 optical switch. Simultaneously, the routing state-table of 2×3 and 2×4 optical switch to perform all permutation output and nonblocking switch for the input signal beam, is achieved. Since the proposed optical setup consists of only optical polarization elements, it is compact in structure, and possesses a low energy loss, a high signal-to-ratio, and an available large number of optical channels. Finally, the discussions and the experimental results show that the Clos network proposed here should be helpful in the design of large-scale network matrix, and may be used in optical communication and optical information processing.

  5. Investigation of a Polarization Controller in Titanium Diffused Lithium Niobate Waveguide near 1530 nm Wavelength 

    E-print Network

    Sung, Won Ju

    2013-12-10

    Optical polarization control in Ti diffused channel waveguides onto LiNbO_(3) substrates have been investigated near 1530 nm wavelength regime by utilizing electro-optic effects of the substrate material. A device configuration composed of two...

  6. Photoelectron spin-polarization control in the topological insulator Bi2Se3.

    PubMed

    Zhu, Z-H; Veenstra, C N; Zhdanovich, S; Schneider, M P; Okuda, T; Miyamoto, K; Zhu, S-Y; Namatame, H; Taniguchi, M; Haverkort, M W; Elfimov, I S; Damascelli, A

    2014-02-21

    We study the manipulation of the spin polarization of photoemitted electrons in Bi2Se3 by spin- and angle-resolved photoemission spectroscopy. General rules are established that enable controlling the photoelectron spin-polarization. We demonstrate the ±?100% reversal of a single component of the measured spin-polarization vector upon the rotation of light polarization, as well as full three-dimensional manipulation by varying experimental configuration and photon energy. While a material-specific density-functional theory analysis is needed for the quantitative description, a minimal yet fully generalized two-atomic-layer model qualitatively accounts for the spin response based on the interplay of optical selection rules, photoelectron interference, and topological surface-state complex structure. It follows that photoelectron spin-polarization control is generically achievable in systems with a layer-dependent, entangled spin-orbital texture. PMID:24579623

  7. Fiber Fabry-Perot interferometer (FFPI) sensor using vertical cavity surface emitting laser (VCSEL

    E-print Network

    Lee, Kyung-Woo

    2006-10-30

    to determine the combination of dc bias current, modulation current amplitude and modulation frequency for which single mode VCSEL operation and regular fringe patterns are achieved. The response characteristics of FFPI sensors were determined experimentally...

  8. 1060-nm VCSEL-based parallel-optical modules for short link application

    Microsoft Academic Search

    H. Nasu; Y. Ishikawa; Y. Nekado; M. Yoshihara; A. Izawa; T. Uemura; K. Takahashi

    2010-01-01

    This paper describes advantages of 1060-nm optical interconnect employing parallel-optical modules. 1060-nm optical signals contribute to power budget increase and excellent transmission performance with existing MMFs. 1060-nm VCSELs also contribute to reducing optical link power.

  9. High-speed ultra-broad tuning MEMS-VCSELs for imaging and spectroscopy

    E-print Network

    Jayaraman, V.

    In the last 2 years, the field of micro-electro-mechanical systems tunable vertical cavity surface-emitting lasers (MEMS-VCSELs) has seen dramatic improvements in laser tuning range and tuning speed, along with expansion ...

  10. 1.3-µm wavelength coupled VCSEL arrays employing patterned tunnel junction

    Microsoft Academic Search

    Lukas Mutter; Vladimir Iakovlev; Andrei Caliman; Alexandru Mereuta; Alexei Sirbu; Eli Kapon

    2009-01-01

    Using tunnel junction patterning and double wafer fusion, we demonstrate phase-locked arrays of VCSELs emitting at the 1300 nm waveband. CW powers as high as 10 mW and coherent beams are demonstrated for various array configurations.

  11. Design and analysis of anti-resonant reflecting photonic crystal VCSEL lasers

    Microsoft Academic Search

    Hairong Liu; Min Yan; Ping Shum; H. Ghafouri-Shiraz; Deming Liu

    2004-01-01

    Anti-resonant reflecting photonic crystal structure is employed in vertical cavity surface emitting lasers (VCSELs) to achieve photon confinement in lateral direction. Such a design is promising in supporting large-aperture single-mode emission. In the configuration, hexagonal arrays of high-index cylinders which run vertically in the cladding region are introduced in the VCSEL's top DBR (p-DBR) mirror region. The transverse modal property

  12. Recorded Low Power Dissipation in Highly Reliable 1060-nm VCSELs for “Green” Optical Interconnection

    Microsoft Academic Search

    Suguru Imai; Keishi Takaki; Shinichi Kamiya; Hitoshi Shimizu; Junji Yoshida; Yasumasa Kawakita; Tomohiro Takagi; Koji Hiraiwa; Hiroshi Shimizu; Toshihito Suzuki; Norihiro Iwai; Takuya Ishikawa; Naoki Tsukiji; Akihiko Kasukawa

    2011-01-01

    1060-nm VCSELs with low power dissipation and high reliability are demonstrated. We designed 1060-nm VCSELs with double intracavity structure to achieve high reliability and low power dissipation for the optical interconnection. We performed evaluations of an error-free 10-Gbps operation at low bias current, and the recorded low power dissipation per data rate of 0.14 mW\\/Gbps was achieved. Even though the

  13. Optimization of VCSEL spatiotemporal operation in MMF links for 10-gb ethernet

    Microsoft Academic Search

    Asghar Gholami; Zeno Toffano; Alain Destrez; S. Pellevrault; M. Pez; F. Quentel

    2006-01-01

    A complete model of the spatiotemporal behavior of multimode vertical-cavity surface-emitting lasers (VCSELs), through static and dynamic response, noise, thermal effects, and its coupling to multimode fibers (MMF) has been investigated in low-cost 10-Gb Ethernet (10-Gb E) prototype optoelectronic packages using GaAs VCSEL arrays coupled to MMF ribbons for short-distance optical links. Eye diagram simulations compared to measurements allow the

  14. High performance selectively oxidized VCSELs and arrays for parallel high-speed optical interconnects

    Microsoft Academic Search

    F. Mederer; M. Grabherr; F. Eberhard; I. Ecker; R. Jager; J. Joos; C. Jung; M. Kicherer; R. King; P. Schnitzer; H. Unold; D. Wiedenmann; K. J. Ebeling

    2000-01-01

    We introduce a new layout for high-bandwidth single-mode selectively oxidized vertical-cavity surface-emitting laser (VCSEL) arrays operating at 980 nm or 850 nm emission wavelength for substrate or epitaxial side emission. Coplanar feeding lines and polyimide passivation are used to reduce electrical parasitics in top-emitting GaAs and bottom-emitting InGaAs VCSELs. In order to enhance fundamental single-mode emission for larger devices of

  15. Design and fabrication of power-efficient VCSEL-based optical transceiver

    Microsoft Academic Search

    S. M. Mitani; M. S. Alias; M. F. Maulud; A. A. Manaf; M. R. Yahya; A. F. A. Mat

    2008-01-01

    This communication presents an analysis of the design and fabrication of power-efficient, low cost VCSEL-based optical transceiver proposed for emerging fiber data distributed interface (FDDI) and fiber channel local-area network (FCLANpsilas). This transceiver has been designed to meet the increasing amount of information transmitted through communication networks. The proposed optical transceiver consists of Tx that contains VCSEL driver and power

  16. Ultra high-speed electro-optically modulated VCSELs: modeling and experimental results

    NASA Astrophysics Data System (ADS)

    Shchukin, V. A.; Ledentsov, N. N.; Lott, J. A.; Quast, H.; Hopfer, F.; Karachinsky, L. Ya.; Kuntz, M.; Moser, P.; Mutig, A.; Strittmatter, A.; Kalosha, V. P.; Bimberg, D.

    2008-02-01

    We have studied the modulation properties of a vertical cavity surface-emitting laser (VCSEL) coupled to an electrooptical modulator. It is shown that, if the modulator is placed in a resonant cavity, the modulation of the light output power is governed predominantly by electrooptic, or electrorefraction effect rather than by electroabsorption. A novel concept of electrooptically modulated (EOM) VCSEL based on the stopband edge-tunable distributed Bragg reflector (DBR) is proposed which allows overcoming the limitations of the first-generation EOM VCSEL based on resonantly coupled cavities. A new class of electrooptic (EO) media is proposed based on type-II heterostructures, in which the exciton oscillator strength increases from a zero or a small value at zero bias to a large value at an applied bias. A EOM VCSEL based on a stopband-edge tunable DBR including a type-II EO medium is to show the most temperature-robust operation. Modeling of a high-frequency response of a VCSEL light output against large signal modulation of the mirror transmittance has demonstrated the feasibility to reach 40 Gb/s operation at low bit error rate. EOM VCSEL showing 60 GHz electrical and ~35 GHz optical (limited by the photodetector response) bandwidths is realized.

  17. Optimization of an avionic VCSEL-based optical link through large signal characterization

    NASA Astrophysics Data System (ADS)

    Ly, Khadijetou S.; Rissons, A.; Gambardella, E.; Mollier, J.-C.

    2008-04-01

    Optical communication systems have been widely preferred for network communications, especially for Datacoms Local Area Network links. The optical technology is an excellent candidate for on-board systems due to the potential weight saving and EMC immunity. According to the short length of the link and a cost saving, Vertical Cavity Surface Emitting Laser (VCSEL) and multimode fiber are the best solution for gigabit systems. In this context, we propose a modeling of 850nm VCSEL based on the rate equations analysis to predict the optical interconnect performances (jitter, bit error rate). Our aim is to define the operation conditions of VCSEL under large signal modulation in order to maximize the Extinction Ratio (current I OFF below threshold) without affecting link performances. The VCSEL model is developed to provide large signal modulation response. Biasing below threshold causes stochastic turn-on delay. Fluctuations of this delay occur, due to the spontaneous emission. This leads to additional turn-on jitter. These stochastic effects are included in the model by adding the Langevin photon and electron noise sources. The VCSEL behavior under high-speed modulation is studied to observe the transient response and extract the resonance frequency, overshoot and turn-on delay. The associated jitter is evaluated with the standard deviation of the turn-on delay probability density function. Simulations of stochastic and deterministic jitters are realized under different conditions of modulation (OFF current levels). Comparing simulations with measurement results carried out on VCSEL and a short haul gigabit link validates the approach.

  18. High Efficacy Green LEDs by Polarization Controlled MOVPE

    SciTech Connect

    Wetzel, Christian

    2013-03-31

    Amazing performance in GaInN/GaN based LEDs has become possible by advanced epitaxial growth on a wide variety of substrates over the last decade. An immediate push towards product development and worldwide competition for market share have effectively reduced production cost and generated substantial primary energy savings on a worldwide scale. At all times of the development, this economic pressure forced very fundamental decisions that would shape huge industrial investment. One of those major aspects is the choice of epitaxial growth substrate. The natural questions are to what extend a decision for a certain substrate will limit the ultimate performance and to what extent, the choice of a currently more expensive substrate such as native GaN could overcome any of the remaining performance limitations. Therefore, this project has set out to explore what performance characteristic could be achieved under the utilization of bulk GaN substrate. Our work was guided by the hypotheses that line defects such as threading dislocations in the active region should be avoided and the huge piezoelectric polarization needs to be attenuated – if not turned off – for higher performing LEDs, particularly in the longer wavelength green and deep green portions of the visible spectrum. At their relatively lower performance level, deep green LEDs are a stronger indicator of relative performance improvements and seem particular sensitive to the challenges at hand. The project therefore made use of recently developed non-polar and semipolar bulk GaN substrates that were made available at Kyma Technologies by crystallographic cuts from thick polar growth of GaN. This approach naturally leads to rather small pieces of substrates, cm along the long side while mm along the short one. Small size and limited volume of sample material therefore set the limits of the ensuing development work. During the course of the project we achieved green and deep green LEDs in all those crystal growth orientations: polar c-plane, non- polar a-plane, non-polar m-plane, and semipolar planes. The active region in those structures shows dramatically reduced densities of threading dislocations unless the wavelength was extended as far as 510 nm and beyond. With the appearance of such defects, the light output power dropped precipitously supporting the necessity to avoid any and all of such defects to reach the active region. Further aspects of the non-polar growth orientation proved extremely promising for the development of such structures. Chief among them is our success to achieve extremely uniform quantum wells in these various crystal orientations that prove devoid of any alloy fluctuation beyond the theoretical limit of a binominal distribution. This became very Rensselaer Wetzel DE?EE0000627 3 directly apparent in highly advanced atom probe tomography performed in collaboration at Northwestern University. Furthermore, under reduced or absence of piezoelectric polarization, green emitters in those growth geometries exhibit an unsurpassed wavelength stability over very wide excitation and drive current ranges. Such a performance had not been possible in any polar c-plane growth and now places green LEDs in terms of wavelength stability up par with typical 450 nm blue emitters. The project also incorporated enabling opportunities in the development of micro and nano- patterned substrate technologies. Originally developped as a means to enhance generated light extraction we have demonstrated that the method of nano-patterning, in contrast to micro- patterning also results in a substantial reduction of threading dislocation generation. In green LEDs, we thereby see equal contributions of enhanced light extraction and reduced defect generation to a threefold enhancement of the green light output power. These results have opened entirely new approaches for future rapid and low cost epitaxial material development by avoidance of thick defect accommodation layers. All methods developed within this project have meanwhile widely been publicized by the members o

  19. Observation and explanation of polarization-controlled focusing of terahertz surface plasmon polaritons

    NASA Astrophysics Data System (ADS)

    Wang, Sen; Wang, Xinke; Zhao, Feng; Qu, Shiliang; Zhang, Yan

    2015-05-01

    Polarization-controlled focusing of surface plasmon polaritons (SPPs) is experimentally and theoretically investigated in the terahertz (THz) frequency range. The spiral phase distribution and the phase singularities, which, respectively, lead to the transverse shift of the focal spot for the circularly polarized THz radiation and the split of the focal spot for the linearly polarized THz radiation, are experimentally observed. Furthermore, an alternative theoretical model based on the Huygens-Fresnel principle and Fourier transformation of THz SPPs is proposed to analyze the transverse shift of the focal spot, which provides a simple way to understand the polarization-related SPP phenomena. This research is instructive for the design of polarization-based plasmonic devices.

  20. Polarization control of an X-ray free-electron laser with a diamond phase retarder.

    PubMed

    Suzuki, Motohiro; Inubushi, Yuichi; Yabashi, Makina; Ishikawa, Tetsuya

    2014-05-01

    A diamond phase retarder was applied to control the polarization states of a hard X-ray free-electron laser (XFEL) in the photon energy range 5-20 keV. The horizontal polarization of the XFEL beam generated from the planar undulators of the SPring-8 Angstrom Compact Free-Electron Laser (SACLA) was converted into vertical or circular polarization of either helicity by adjusting the angular offset of the diamond crystal from the exact Bragg condition. Using a 1.5 mm-thick crystal, a high degree of circular polarization, 97%, was obtained for 11.56 keV monochromatic X-rays, whereas the degree of vertical polarization was 67%, both of which agreed with the estimations including the energy bandwidth of the Si 111 beamline monochromator. PMID:24763633

  1. Cryogenic control system of the large COMPASS polarized target

    Microsoft Academic Search

    F. Gautheron; J. Ball; G. Baum; P. Berglund; N. Doshita; St. Goertz; K. Gustafsson; N. Horikawa; Y. Kisselev; J. Koivuniemi; K. Kondo; W. Meyer; G. Reicherz

    2004-01-01

    The dilution refrigerator used to cool the large COMPASS polarized target is monitored through a PC running LabVIEWTM 6.1 under Windows 2000TM. About 60 parameters of the target (temperatures, pressures, flow rates) are continuously plotted and checked. They are periodically recorded in an OracleTM database and in a data file. An alarm for every parameter can be individually activated and

  2. Magnetic control of large room-temperature polarization.

    PubMed

    Kumar, Ashok; Sharma, G L; Katiyar, R S; Pirc, R; Blinc, R; Scott, J F

    2009-09-23

    Numerous authors have referred to room-temperature magnetic switching of large electric polarizations as 'the Holy Grail' of magnetoelectricity. We report this long-sought effect, obtained using a new physical process of coupling between magnetic and ferroelectric nanoregions. Solid state solutions of PFW [Pb(Fe(2/3)W(1/3))O(3)] and PZT [Pb(Zr(0.53)Ti(0.47))O(3)] exhibit some bi-relaxor qualities, with both ferroelectric relaxor characteristics and magnetic relaxor phenomena. Near 20% PFW the ferroelectric relaxor state is nearly unstable at room temperature against long-range ferroelectricity. Here we report magnetic switching between the normal ferroelectric state and a magnetically quenched ferroelectric state that resembles relaxors. This gives both a new room-temperature, single-phase, multiferroic magnetoelectric, (PbFe(0.67)W(0.33)O(3))(0.2)(PbZr(0.53)Ti(0.47)O(3))(0.8) ('0.2PFW/0.8PZT'), with polarization, loss (<1%), and resistivity (typically 10(8)-10(9) ? cm) equal to or superior to those of BiFeO(3), and also a new and very large magnetoelectric effect: switching not from +P(r) to -P(r) with applied H, but from P(r) to zero with applied H of less than a tesla. This switching of the polarization occurs not because of a conventional magnetically induced phase transition, but because of dynamic effects: increasing H lengthens the relaxation time by 500 × from<200 ns to>100 µs, and it strongly couples the polarization relaxation and spin relaxations. The diverging polarization relaxation time accurately fits a modified Vogel-Fulcher equation in which the freezing temperature T(f) is replaced by a critical freezing field H(f) that is 0.92 ± 0.07 T. This field dependence and the critical field H(c) are derived analytically from the spherical random bond random field model with no adjustable parameters and an E(2)H(2) coupling. This device permits three-state logic (+P(r),0,-P(r)) and a condenser with >5000% magnetic field change in its capacitance; for H = 0 the coercive voltage is 1.4 V across 300 nm for +P(r) to -P(r) switching, and the coercive magnetic field is 0.5 T for +P(r) to zero switching. PMID:21832364

  3. Full control of magnetism in a manganite bilayer by ferroelectric polarization

    SciTech Connect

    Dong, Shuai [Southeast University, Nanjing, China] [Southeast University, Nanjing, China; Dagotto, Elbio R [ORNL] [ORNL

    2013-01-01

    An oxide heterostructure made of manganite bilayers and ferroelectric perovskites is predicted to lead to the full control of magnetism when switching the ferroelectric polarizations. By using asymmetric polar interfaces in the superlattices, more electrons occupy the Mn layer at the n-type interface side than at the p-type side. This charge disproportionation can be enhanced or suppressed by the ferroelectric polarization. Quantum model and density functional theory calculations reach the same conclusion: a ferromagnetic-ferrimagnetic phase transition with maximal change >90% of the total magnetization can be achieved by switching the polarization s direction. This function is robust and provides full control of the magnetization s magnitude, not only its direction, via electrical methods.

  4. A Polarization Control System for Intensity-Resolved Guided Mode Resonance Sensors

    PubMed Central

    Lin, Sheng-Fu; Chang, Fu-Chen; Chen, Zhi-Heng; Wang, Chih-Ming; Yang, Tsung-Hsun; Chen, Wen-Yih; Chang, Jenq-Yang

    2014-01-01

    In this study, a polarization-control setup for intensity-resolved guided mode resonance sensors is proposed and demonstrated experimentally. The experimental results are in good agreement with the simulation data based on rigorous coupled wave approach calculations. The proposed intensity-resolved measurement setup transfers polarization ellipses, which are produced from guided mode resonance to a linear polarization state under a buffer solution condition, and then suppresses the signals to dark using a polarization-control set. Hence, any changes in the refractive index results in an increase in the intensity signals. Furthermore, no wavelength-resolved or angular-resolved measurement is needed in this scheme. According to the experimental results, a wide linear detection range of 0.014 refractive index units is achieved and the limit of detection is 1.62E-4 RIU. PMID:24625743

  5. Control of magnetic domain-wall polarization by means of angled Oersted field writing

    NASA Astrophysics Data System (ADS)

    Kim, Kab-Jin; Moon, Kyoung-Woong; Lee, Kang-Soo; Choe, Sug-Bong

    2011-01-01

    We propose a method to control the polarization of the magnetic domain walls (DWs) in ferromagnetic nanowires. Two neighboring DWs with antiparallel polarization alignment rather than parallel alignment are found to exhibit better stability with a helical magnetic structure that can be hardly be detangled. To achieve such an antiparallel alignment, two co-planar current lines with an angle to the nanowire are designed, from which the Oersted field creates a domain in between the current lines while keeping the polarization of the DWs beneath the current lines, as confirmed by a micromagnetic calculation for ferromagnetic nanowires with perpendicular magnetic anisotropy.

  6. Intense THz radiation from laser plasma with controllable waveform and polarization

    NASA Astrophysics Data System (ADS)

    Bai, Ya; Liu, Peng; Song, Liwei; Li, Ruxin; Xu, Zhizhan

    2015-03-01

    We demonstrate the generation of waveform-controlled THz radiation from air plasma that is produced when carrier envelope phase (CEP) stabilized few-cycle laser pulses undergoes filamentation in ambient air. Elliptically polarized THz waves are generated from air plasma induced by circularly polarized few-cycle laser pulses. Our results reveal that electric field asymmetry in rotating directions of the circularly polarized few-cycle laser pulses produces the enhanced broadband transient currents, and the phase difference of perpendicular laser field components is partially inherited in the generation process of THz emission.

  7. Demonstration of spectral correlation control in a source of polarization entangled photon pairs at telecom wavelength

    E-print Network

    Lutz, Thomas; Jennewein, Thomas

    2013-01-01

    Spectrally correlated photon pairs can be used to improve performance of long range fiber based quantum communication protocols. We present a source based on spontaneous parametric down-conversion producing polarization entangled photons without spectral filtering. In addition, the spectral correlation within the photon pair can be controlled by changing the pump pulse duration or coupled spatial modes characteristics. The spectral and polarization correlations were characterized. The generated photon pairs feature both positive spectral correlations, no correlations, or negative correlations and polarization entanglement with the fidelity as high as 0.97 (no background subtraction) with the expected Bell state.

  8. Propagation of light in serially coupled plasmonic nanowire dimer: Geometry dependence and polarization control

    SciTech Connect

    Singh, Danveer; Raghuwanshi, Mohit; Pavan Kumar, G. V. [Photonics and Optical Nanoscopy Laboratory, Department of Physics and Department of Chemistry, Indian Institute of Science Education and Research (IISER), Pune 411008 (India)

    2012-09-10

    We experimentally studied plasmon-polariton-assisted light propagation in serially coupled silver nanowire (Ag-NW) dimers and probed their dependence on bending-angle between the nanowires and polarization of incident light. From the angle-dependence study, we observed that obtuse angles between the nanowires resulted in better transmission than acute angles. From the polarization studies, we inferred that light emission from junction and distal ends of Ag-NW dimers can be systematically controlled. Further, we applied this property to show light routing and polarization beam splitting in obtuse-angled Ag-NW dimer. The studied geometry can be an excellent test-bed for plasmonic circuitry.

  9. Electric field control of terahertz polarization in a multiferroic manganite with electromagnons.

    PubMed

    Shuvaev, A; Dziom, V; Pimenov, Anna; Schiebl, M; Mukhin, A A; Komarek, A C; Finger, T; Braden, M; Pimenov, A

    2013-11-27

    All-electrical control of a dynamic magnetoelectric effect is demonstrated in a classical multiferroic manganite DyMnO3, a material containing coupled antiferromagnetic and ferroelectric orders. Because of intrinsic magnetoelectric coupling with electromagnons a linearly polarized terahertz light rotates upon passing through the sample. The amplitude and the direction of the polarization rotation are defined by the orientation of ferroelectric domains and can be switched by static voltage. These experiments allow the terahertz polarization to be tuned using the dynamic magnetoelectric effect. PMID:24329467

  10. Control of Fibrinogen Assembly by Changing a Polarity of Surfaces

    NASA Astrophysics Data System (ADS)

    Koo, Jaseung; Liu, Ying; Snow, Sara; Rambhia, Pooja; Koga, Tadanori; Rafailovich, Miriam; Galanakis, Dennis

    2009-03-01

    Thrombogenesis causes various problems associated with an interruption in the blood flow (e.g., myocardial and cerebral infarction), and a hindrance to use of blood-contact vascular biomaterials (e.g., hemodialysis and cardiopulmonary bypass) with long-term patency since undesired adsorption of blood components occurs on vessels or biomaterials, such as surface-induced thrombosis. we showed that this clotting procedure can be occurred on hydrophobic polymeric surfaces without thrombin cleavage. However, the fibrinogen fibers were not formed on the polar surface such as spun-cast polymer film with pyridine and phenol groups. We also found that ?C domains play an important role in initiation of polymerization on surface. Therefore, molecular association was inhibited on the polar surfaces due to confinement of ?C chains on the surfaces. These findings were directly applied to stent surface modification. The commercial stent consist of Co-Cr alloy forms undesired fiber formation. However, PS-r-PVPh (13% phenol) coated stent surfaces completely prevent fiber formation.

  11. Wide temperature operation of 850-nm VCSEL and isolator-free operation of 1300-nm VCSEL for a variety of applications

    Microsoft Academic Search

    Kevin Nishikata; Maiko Ariga; Norihiro Iwai; Yoshihiko Ikenaga; Casimirus Setiagung; Takeo Kageyama; Hitoshi Shimizu; Noriyuki Yokouchi; Akihiko Kasukawa; Fumio Koyama

    2005-01-01

    Furukawa Electric is looking at a variety of applications using VCSEL. New applications such as sensors, automobile, and home electric appliances require new characteristics of stable CW operation, higher modulation, wider temperature range, and higher density array. Automobile Local Area Network called MOST (Media Orientated System Transport) is now popular using 650 nm LED plus Plastic Optical Fiber with a

  12. The control system of the polarized internal target of ANKE at COSY

    NASA Astrophysics Data System (ADS)

    Kleines, H.; Sarkadi, J.; Zwoll, K.; Engels, R.; Grigoryev, K.; Mikirtychyants, M.; Nekipelov, M.; Rathmann, F.; Seyfarth, H.; Kravtsov, P.; Vasilyev, A.

    2006-05-01

    The polarized internal target for the ANKE experiment at the Cooler Synchrotron COSY of the Forschungszentrum Jülich utilizes a polarized atomic beam source to feed a storage cell with polarized hydrogen or deuterium atoms. The nuclear polarization is measured with a Lamb-shift polarimeter. For common control of the two systems, industrial equipment was selected providing reliable, long-term support and remote control of the target as well as measurement and optimization of its operating parameters. The interlock system has been implemented on the basis of SIEMENS SIMATIC S7-300 family of programmable logic controllers. In order to unify the interfacing to the control computer, all front-end equipment is connected via the PROFIBUS DP fieldbus. The process control software was implemented using the Windows-based WinCC toolkit from SIEMENS. The variety of components, to be controlled, and the logical structure of the control and interlock system are described. Finally, a number of applications derived from the present development to other, new installations are briefly mentioned.

  13. Investigations on spatio-spectrally resolved Stokes polarization parameters of oxide-confined vertical-cavity surface-emitting lasers.

    PubMed

    Molitor, Andreas; Hartmann, Sébastien; Elsäßer, Wolfgang

    2015-07-01

    Recently, we have shown [Opt. Lett.37, 4799 (2012)OPLEDP0146-959210.1364/OL.37.004799] that the amount of unpolarized light, quantified by the degree of polarization (DOP), is strongly enhanced by increasing the oxide aperture of vertical-cavity surface-emitting lasers (VCSELs). Here, we reveal the physical mechanism of the DOP reduction when investigating spatio-spectrally resolved Stokes polarization parameters of transverse multi-mode VCSELs. These results uncover a complementary polarization behavior of each particular transverse mode contributing to the total emission, resulting in the observed unpolarized state of light. PMID:26125382

  14. Wide temperature operation of 850-nm VCSEL and isolator-free operation of 1300-nm VCSEL for a variety of applications

    NASA Astrophysics Data System (ADS)

    Nishikata, Kevin; Ariga, Maiko; Iwai, Norihiro; Ikenaga, Yoshihiko; Setiagung, Casimirus; Kageyama, Takeo; Shimizu, Hitoshi; Yokouchi, Noriyuki; Kasukawa, Akihiko; Koyama, Fumio

    2005-03-01

    Furukawa Electric is looking at a variety of applications using VCSEL. New applications such as sensors, automobile, and home electric appliances require new characteristics of stable CW operation, higher modulation, wider temperature range, and higher density array. Automobile Local Area Network called MOST (Media Orientated System Transport) is now popular using 650 nm LED plus Plastic Optical Fiber with a 1 mm core. For higher operation temperature and higher transmission speed, the system with 850 nm VCSEL plus HCS (Hard Clad Silica) fiber with a core of 200 microns Silica has been investigating. We investigated 850 nm oxide VCSEL performances of LI, RIN, Eye, BERT and reliability in a wide temperature range from -40 to 125°C In order to obtain low-cost modules for data-communication, it is critical to eliminate high-cost components such as an isolator and a lens containing in the module. We confirmed 2.5 Gbps stable operation without the isolator for 1300 nm GaInNAsSb oxide VCSEL experimentally and theoretically. The RIN was stable around -145 dB/Hz with an optical feedback light less than -30 dB and drastically increased at this point. It was -110 dB/Hz with -13 dB. For an increasing demand of high bandwidth for the interconnection between computers and routers, it is important to investigate the maximum frequency of an existing 1300 nm GaInNAsSb VCSEL. We showed the intrinsic maximum modulation frequency of 23 GHz by fitting K-factor that was 0.385 nsec.

  15. Attitude Control of Asymmetric Satellites on Polar Near-Circular

    Microsoft Academic Search

    Wei Zhao; Weiwei Yang; Xiaoqian Chen; Yong Zhao

    2009-01-01

    In this paper, a general problem about the attitude dynamics and control of asymmetric satellites is discussed. Due to the asymmetric structure, the properties of such satellites are different from symmetric ones. Perturbation moments accumulate with time, and the attitude angles increase periodically with time. Furthermore, chaos could be happened. Traditional linear controller can not compensate enough for asymmetric satellite

  16. Lateral Carrier Injection with n-type Modulation-doped Quantum Wells in VCSELs Chin-Han Lin1

    E-print Network

    Rodwell, Mark J. W.

    Lateral Carrier Injection with n-type Modulation-doped Quantum Wells in VCSELs Chin-Han Lin1 , Yan on the novel lateral charge injection structure as well as the advanced bandgap engineering involved lasers. In conventional diode VCSELs, carriers are typically injected into the quantum wells from

  17. Polarization controlled colorful images reconstructed by reflective meta-hologram

    NASA Astrophysics Data System (ADS)

    Huang, Yao-Wei; Chen, Wei Ting; Yang, Kuang-Yu; Wang, Chih-Ming; Wu, Pin Chieh; Sun, Greg; Sun, Shulin; Zhou, Lei; Liu, Ai Qun; Tsai, Din Ping

    2014-09-01

    Holograms, the optical devices to reconstruct pre-designed images, have been evolved dramatically since the advances in today's nanotechnology [1-4]. Metamaterials, the sub-wavelength artificial structures with tailored refraction index, enable us to design the meta-hologram working in arbitrary frequency region. Here we demonstrated the first reflective type, dual image and high efficient meta-hologram with the incident angle as well as the coherence of incident wave insensitivity in visible region at least from ? = 632.8 nm to ? = 850 nm. The meta-hologram is composed of 50-nm-thick gold cross nano-antenna coupled with 130-nm-thick gold mirror with a 50-nm-thick MgF2 as spacer. It shows different images "RCAS" and "NTU" with high image contract under x- and y-polarized illumination, respectively. Making use of the characteristic of meta-materials, these optical properties of proposed meta-hologram can be transferred to arbitrary electromagnetic region by scale-up the size of the unit cell of meta-hologram, leading to more compact, efficient and promising electromagnetic components.

  18. Cytoskeletal control of polar growth in plant cells.

    PubMed

    Kropf, D L; Bisgrove, S R; Hable, W E

    1998-02-01

    There are two quite different modes of polar cell expansion in plant cells, namely, diffuse growth and tip growth. The direction of diffuse growth is determined by the orientation of cellulose microfibrils in the cell wall, which in turn are aligned by microtubules in the cell cortex. The orientation of the cortical microtubule array changes in response to developmental and environmental signals, and recent evidence indicates that microtubule disassembly/reassembly and microtubule translocation participate in reorientation of the array. Tip growth, in contrast, is governed mainly by F-actin, which has several putative forms and functions in elongating cells. Longitudinal cables are involved in vesicle transport to the expanding apical dome and, in some tip growers, a subapical ring of F-actin may participate in wall-membrane adhesions. The structure and function of F-actin within the apical dome may be variable, ranging from a dense meshwork to sparse single filaments. The presence of multiple F-actin structures in elongating tips suggests extensive regulation of this cytoskeletal array. PMID:9484603

  19. Light polarization-controlled shape-memory polymer/gold nanorod composite.

    PubMed

    Zhang, Hongji; Zhang, Jianming; Tong, Xia; Ma, Dongling; Zhao, Yue

    2013-10-01

    It is demonstrated that light polarization can be used to control photothermal effect-based shape-memory polymers (SMPs). Gold nanorods (AuNRs) are embedded in poly(vinyl alcohol) (PVA) and aligned by stretching the composite film. By changing the polarization direction of the incident laser at 785 nm with respect to the film stretching direction, the magnitude of the longitudinal surface plasmon resonance of AuNRs can be varied continuously, which determines the amount of heat generated upon laser exposure and thus the local temperature rise in the composite relative to the glass transition of the PVA matrix. Consequently, the temporary-to-permanent shape recovery process of the composite can be made to occur to different extents by tuning the polarization of laser while keeping all other conditions unchanged. This finding enhances the toolbox for controlling light-triggered SMPs. PMID:24092559

  20. Design of broadband transmission quarter-wave plates for polarization control of isolated attosecond pulses

    NASA Astrophysics Data System (ADS)

    Chen, Shujing; Lin, Chengyou; Gao, Hua

    2015-07-01

    Using a standard Levenberg–Marquardt algorithm, broadband quarter-wave plates (QWPs) with bandwidth from 3 to 18 eV in the extreme ultraviolet (EUV) region were designed using aperiodic Mo/Si multilayers. By analyzing the design results of the Mo/Si multiayers with different bilayer numbers, we found that a Mo/Si multilayer with more bilayers can achieve broader phase control, but suffers from lower total throughput and a degree of circular polarization. In addition, the pulse broadenings caused by the group delay dispersions of the designed broadband QWPs were studied, and their layer distributions were investigated. The oscillating distribution of bilayer thickness in optimized multilayers was observed, which is considered to be the reason for forming the broadband phase control. Such broadband QWPs can be applied to generate a circularly polarized broadband EUV source, such as isolated attosecond pulse, directly from a linearly polarized source.

  1. Transverse Mode Selection and Bistability in Vertical-Cavity Surface-Emitting Lasers Induced by Parallel Polarized Optical Injection

    Microsoft Academic Search

    Matias Fernando Salvide; Maria Susana Torre; Angel Valle; Luis Pesquera

    2011-01-01

    Modal selection induced by parallel polarized opti- cal injection in a vertical-cavity surface-emitting laser (VCSEL) emitting in two transverse modes is analyzed from a theoretical point of view. We show that the selection of the fundamental transverse mode can be achieved when the two transverse modes have parallel polarizations. This selection is accompanied by locking of the fundamental mode to

  2. Polar vortex concentricity as a controlling factor in Arctic denitrification

    NASA Astrophysics Data System (ADS)

    Mann, G. W.; Davies, S.; Carslaw, K. S.; Chipperfield, M. P.; Kettleborough, J.

    2002-11-01

    Recent in situ observations in the Arctic stratosphere have detected nitric acid-containing particles with sizes up to 10-?m radius and number concentrations between 10-5 and 10-3 cm-3. Here we quantify the effect of these particles on Arctic denitrification by using a new three-dimensional (3-D) model which can couple particle growth and sedimentation with the full dynamics of the Arctic polar vortex. We show that the very long growth times of large nitric acid trihydrate (NAT) particles lead to a highly nonlinear dependence of Arctic denitrification on the growth and evaporation cycles of individual particles, thus making denitrification dependent on the precise meteorological conditions in a given winter. Using 3-D wind and temperature fields from December 1999, we identify a period that was optimum for denitrification, in which the cold pool and vortex were nearly concentric and in which a large proportion of the particles were able to sediment over about 8 days through the full depth of the cold pool without evaporating. We then show that small departures from concentric conditions can lead to substantial reductions in denitrification. A case is presented in which denitrification was completely shut off even with over half of the cold pool area remaining within the vortex. Under the same conditions, a model in which the particles were assumed to be in continuous equilibrium with the gas phase caused extensive denitrification. Our results show that low Arctic vortex temperatures in themselves are unlikely to be a reliable indicator of potential denitrification if large NAT particles are involved.

  3. Developments in Polarization and Energy Control of APPLE-II Undulators at Diamond Light Source

    NASA Astrophysics Data System (ADS)

    Longhi, E. C.; Bencok, P.; Dobrynin, A.; Rial, E. C. M.; Rose, A.; Steadman, P.; Thompson, C.; Thomson, A.; Wang, H.

    2013-03-01

    A pair of 2m long APPLE-II type undulators have been built for the I10 BLADE beamline at Diamond Light Source. These 48mm period devices have gap as well as four moveable phase axes which provide the possibility to produce the full range of elliptical polarizations as well as linear polarization tilted through a full 180deg. The mechanical layout chosen has a 'master and slave' arrangement of the phase axes on the top and bottom. This arrangement allows the use of symmetries to provide operational ease for both changing energy using only the master phase while keeping fixed linear horizontal or circular polarization, as well as changing linear polarization angle while keeping fixed energy [1]. The design allows very fast motion of the master phase arrays, without sacrifice of accuracy, allowing the possibility of mechanical polarization switching at 1Hz for dichroism experiments. We present the mechanical design features of these devices, as well as the results of magnetic measurements and shimming from before installation. Finally, we present the results of characterization of these devices by the beamline, including polarimetry, which has been done on the various modes of motion to control energy and polarization. These modes of operation have been available to users since 2011.

  4. Fibroblast polarization is a matrix-rigidity-dependent process controlled by focal adhesion mechanosensing.

    PubMed

    Prager-Khoutorsky, Masha; Lichtenstein, Alexandra; Krishnan, Ramaswamy; Rajendran, Kavitha; Mayo, Avi; Kam, Zvi; Geiger, Benjamin; Bershadsky, Alexander D

    2011-12-01

    Cell elongation and polarization are basic morphogenetic responses to extracellular matrix adhesion. We demonstrate here that human cultured fibroblasts readily polarize when plated on rigid, but not on compliant, substrates. On rigid surfaces, large and uniformly oriented focal adhesions are formed, whereas cells plated on compliant substrates form numerous small and radially oriented adhesions. Live-cell monitoring showed that focal adhesion alignment precedes the overall elongation of the cell, indicating that focal adhesion orientation may direct cell polarization. siRNA-mediated knockdown of 85 human protein tyrosine kinases (PTKs) induced distinct alterations in the cell polarization response, as well as diverse changes in cell traction force generation and focal adhesion formation. Remarkably, changes in rigidity-dependent traction force development, or focal adhesion mechanosensing, were consistently accompanied by abnormalities in the cell polarization response. We propose that the different stages of cell polarization are regulated by multiple, PTK-dependent molecular checkpoints that jointly control cell contractility and focal-adhesion-mediated mechanosensing. PMID:22081092

  5. Adaptive Compensation of Multimode Fiber Dispersion by Control of Launched Amplitude, Phase, and Polarization

    Microsoft Academic Search

    Mahdieh B. Shemirani; Jeffrey P. Wilde; Joseph M. Kahn

    2010-01-01

    In previous work, we studied the compensation of modal dispersion in multimode fiber (MMF) using several different configurations of optical systems that can control the amplitude, phase and polarization of the launched field. In that work, we assumed knowledge of a fiber's principal modes (PMs) and their group delays (GDs), enabling us to compute the optimal settings of the optical

  6. Coherent control of pump-probe signals of helical structures by adaptive pulse polarizations

    E-print Network

    Mukamel, Shaul

    excitons in multidimensional spectroscopy.11­14 Shaping the polarization state of the electric field-Stokes Raman spectroscopy CARS .18 Multipolar- ization optimal control two-dimensional 2D and three with a sequence of laser pulses Fig. 1 , whose electric field is given by E r, = j=1 4 Aj -¯j exp ikjr - i¯ j -¯j

  7. PAM-4 Signaling over VCSELs with 0.13µm CMOS Chip Technology

    NASA Astrophysics Data System (ADS)

    Cunningham, J. E.; Beckman, D.; Zheng, Xuezhe; Huang, Dawei; Sze, T.; Krishnamoorthy, A. V.

    2006-12-01

    We present results for VCSEL based links operating PAM-4 signaling using a commercial 0.13µm CMOS technology. We perform a complete link analysis of the Bit Error Rate, Q factor, random and deterministic jitter by measuring waterfall curves versus margins in time and amplitude. We demonstrate that VCSEL based PAM 4 can match or even improve performance over binary signaling under conditions of a bandwidth limited, 100meter multi-mode optical link at 5Gbps. We present the first sensitivity measurements for optical PAM-4 and compare it with binary signaling. Measured benefits are reconciled with information theory predictions.

  8. Vertical-cavity surface-emitting laser (VCSEL) sources for frequency domain photon migration

    NASA Astrophysics Data System (ADS)

    O'Sullivan, Thomas D.; No, Keun-Sik; Matlock, Alex; Hill, Brian; Cerussi, Albert E.; Tromberg, Bruce J.

    2015-03-01

    Frequency domain photon migration (FDPM) uses modulated laser light to measure the bulk optical properties of turbid media and is increasingly being applied for noninvasive functional medical imaging. Though semiconductor edge emitting laser diodes (EELs) have been traditionally used for this application, we show that VCSELs exhibit performance characteristics suitable for FDPM measurements of tissue optical properties. Their output power and modulation characteristics are more than sufficient for optical property recovery. In addition, their small size, high efficiency, low cost, and simple packaging make them an attractive choice as components in clinical FDPM systems. We demonstrate a unique, compact optical probe that was enabled by VCSEL technology.

  9. Polarization-sensitive coherent control of atomic collisions with nonclassical light

    Microsoft Academic Search

    D. V. Kupriyanov; I. M. Sokolov; A. V. Slavgorodskii

    2002-01-01

    In this paper we consider the mechanism of coherent control of atomic collisions by two-photon excitation of colliding atoms with nonclassical light characterized by polarization entanglement. Such modification of the well-known optical-collision method is proposed as a possible spectroscopic application of nonclassical light for study of collisional dynamics. We show that quantum correlations allow one to have a deeper control

  10. Controlling enhancement and suppression of four-wave mixing via polarized light

    NASA Astrophysics Data System (ADS)

    Li, Changbiao; Zhang, Yanpeng; Nie, Zhiqiang; Du, Yigang; Wang, Ruimin; Song, Jianping; Xiao, Min

    2010-03-01

    We show that the four-wave mixing (FWM) processes in a multi-Zeeman level atomic system can be enhanced and suppressed by changing the polarization of one of the pump beams. Different polarization states of the pump beams will act on different transition pathways among the multi-Zeeman levels with different transition strengths, which affect the FWM efficiencies. An additional dress field applied to the adjacent transition can cause energy level splitting and therefore control the enhancement and suppression of the FWM processes in the system. The experimental results are in good agreement with our theoretical calculations.

  11. Controlling enhancement and suppression of four-wave mixing via polarized light

    SciTech Connect

    Li Changbiao; Zhang Yanpeng; Nie Zhiqiang; Du Yigang; Wang Ruimin; Song Jianping [Key Laboratory for Physical Electronics and Devices of the Ministry of Education and Shaanxi Key Lab of Information Photonic Technique, Xi'an Jiaotong University, Xi'an 710049 (China); Xiao Min [Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701 (United States)

    2010-03-15

    We show that the four-wave mixing (FWM) processes in a multi-Zeeman level atomic system can be enhanced and suppressed by changing the polarization of one of the pump beams. Different polarization states of the pump beams will act on different transition pathways among the multi-Zeeman levels with different transition strengths, which affect the FWM efficiencies. An additional dress field applied to the adjacent transition can cause energy level splitting and therefore control the enhancement and suppression of the FWM processes in the system. The experimental results are in good agreement with our theoretical calculations.

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

    NASA Astrophysics Data System (ADS)

    Frougier, J.; Baili, G.; Alouini, M.; Sagnes, I.; Jaffrès, H.; Garnache, A.; Deranlot, C.; Dolfi, D.; George, J.-M.

    2013-12-01

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

  13. Control of polarization and dipole moment in low-dimensional semiconductor nanostructures

    SciTech Connect

    Li, L. H.; Ridha, P. [Ecole Polytechnique Federale de Lausanne, Institute of Photonics and Quantum Electronics, Station 3, CH-1015 Lausanne (Switzerland); Mexis, M.; Smowton, P. M.; Blood, P. [Cardiff University, The Parade, Cardiff CF24 3AA (United Kingdom); Bozkurt, M.; Koenraad, P. M. [COBRA Research Institute, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Patriarche, G. [LPN/CNRS, Route de Nozay, 91460 Marcoussis (France); Fiore, A. [Ecole Polytechnique Federale de Lausanne, Institute of Photonics and Quantum Electronics, Station 3, CH-1015 Lausanne (Switzerland); COBRA Research Institute, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands)

    2009-11-30

    We demonstrate the control of polarization and dipole moment in semiconductor nanostructures, through nanoscale engineering of shape and composition. Rodlike nanostructures, elongated along the growth direction, are obtained by molecular beam epitaxial growth. By varying the aspect ratio and compositional contrast between the rod and the surrounding matrix, we rotate the polarization of the dominant interband transition from transverse-electric to transverse-magnetic, and modify the dipole moment producing a radical change in the voltage dependence of absorption spectra. This opens the way to the optimization of quantum dot amplifiers and electro-optical modulators.

  14. Frequency-induced polarization bistability in vertical-cavity surface-emitting lasers with orthogonal optical injection

    SciTech Connect

    Gatare, I. [Supelec, LMOPS CNRS UMR-7132, Unite de Recherche Commune Supelec et Universite de Metz, Rue Edouard Belin 2, F-57070 Metz (France); Department of Applied Physics and Photonics, (TW-TONA), Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels (Belgium); Panajotov, K. [Department of Applied Physics and Photonics, (TW-TONA), Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels (Belgium); Sciamanna, M. [Supelec, LMOPS CNRS UMR-7132, Unite de Recherche Commune Supelec et Universite de Metz, Rue Edouard Belin 2, F-57070 Metz (France)

    2007-02-15

    We report theoretically on a pure frequency-induced polarization bistability in a vertical-cavity surface-emitting laser (VCSEL) subject to orthogonal optical injection, i.e., the master laser light polarization is orthogonal to that of the slave VCSEL. As the frequency detuning is scanned from negative to positive values and for a fixed injected power, the VCSEL exhibits two successive and possibly bistable polarization switchings. The first switching (from the slave laser polarization to the injected light polarization) exhibits a bistable region whose width is maximum for a given value of the injected power. Such a dependency of hysteresis width on the injected power is similar to that recently found experimentally by Hong et al.[Electron. Lett. 36, 2019 (2000)]. The bistability accompanying the second switching (from the injected light polarization back to the slave laser free-running polarization) exhibits, however, significantly different features related to the occurrence of optical chaos. Interestingly, the width of the bistable region can be tuned over a large range not only by modifying the injection parameters but also by modifying the device parameters, in particular the VCSEL linewidth enhancement factor.

  15. Optical implementation of tree-type interconnection network using polarization control method

    NASA Astrophysics Data System (ADS)

    Yang, Junbo; Yang, Jiankun; Liu, Ju; Li, Xiujian

    2010-10-01

    Tree-type network composed of optical splitters and optical combiners, according to the corresponding link rule, plays an important role in the all-optical communication and optical information processing. Based on the matured polarization control technology to realize routing and switching of signal beams, a novel tree-type interconnection network using phase spatial light modulator (PSLM), polarizing beam-splitter (PBS) and mirror, is proposed, including 1×2, 1×4, and 2×1, 4×1 switch elements. It is able to perform any arbitrary interconnection pattern, which has the advantages of compact in structure, efficient in performance, small size, and polarization-independent due to exploiting the building block pattern. The theoretical analysis shows the functional experimental prototype with large number of input/output ports should be helpful in the optimization and design of large-scale optical switch matrix.

  16. Microfluidic directional emission control of an azimuthally polarized radial fibre laser

    NASA Astrophysics Data System (ADS)

    Stolyarov, Alexander M.; Wei, Lei; Shapira, Ofer; Sorin, Fabien; Chua, Song L.; Joannopoulos, John D.; Fink, Yoel

    2012-04-01

    Lasers with cylindrically symmetric polarization states are predominantly based on whispering-gallery modes, characterized by high angular momentum and dominated by azimuthal emission. Here, a zero-angular-momentum laser with purely radial emission is demonstrated. An axially invariant, cylindrical photonic-bandgap fibre cavity filled with a microfluidic gain medium plug is axially pumped, resulting in a unique radiating field pattern characterized by cylindrical symmetry and a fixed polarization pointed in the azimuthal direction. Encircling the fibre core is an array of electrically contacted and independently addressable liquid-crystal microchannels embedded in the fibre cladding. These channels modulate the polarized wavefront emanating from the fibre core, leading to a laser with a dynamically controlled intensity distribution spanning the full azimuthal angular range. This new capability, implemented monolithically within a single fibre, presents opportunities ranging from flexible multidirectional displays to minimally invasive directed light delivery systems for medical applications.

  17. Oscillatory dynamics of Cdc42 GTPase in the control of polarized growth

    PubMed Central

    Das, Maitreyi; Drake, Tyler; Wiley, David; Buchwald, Peter; Vavylonis, Dimitrios; Verde, Fulvia

    2013-01-01

    Cells promote polarized growth by activation of Rho-family protein Cdc42 at the cell membrane. We combined experiments and modeling to study bipolar growth initiation in fission yeast. Concentrations of a fluorescent marker for active Cdc42, Cdc42 protein, Cdc42-activator Scd1, and scaffold protein Scd2, exhibited anti-correlated fluctuations and oscillations with a five-minute average period at polarized cell tips. These dynamics indicate competition for active Cdc42, or its regulators, and the presence of positive and delayed negative feedbacks. Cdc42 oscillations and spatial distribution were sensitive to the amounts of Cdc42-activator Gef1 and to the activity of Cdc42-dependent kinase Pak1, a negative regulator. Feedbacks regulating Cdc42 oscillations and spatial self-organization appear to provide a flexible mechanism for fission yeast cells to explore polarization states and control their morphology. PMID:22604726

  18. Electrostatic control of polarity of ?-MoTe2 transistors with dual top gates

    NASA Astrophysics Data System (ADS)

    Nakaharai, Shu; Yamamoto, Mahito; Ueno, Keiji; Lin, Yen-Fu; Li, Song-Lin; Tsukagoshi, Kazuhito

    2015-03-01

    Transition metal dichalcogenides have been expected for future applications in nanoelectronics due to their unique features of the atomically-thin structure. Using semiconducting ?-molybdenum ditelluride (?-MoTe2) , we realized field effect transistors (FETs) in which the polarity (n- or p-type) can be electrostatically controlled without impurity doping. The fabricated device had a pair of top gates (aluminum electrode on silicon dioxide) attached in series with a gap length of 100 nm in between. We experimentally performed transistor operations in both n-FET and p-FET modes in a single device by changing the voltage applied to one of the two top gates, which determined the transistor polarity, and sweeping the bias of the other gate. The demonstrated reversibility of the transistor polarity will contribute to the renovated architecture of logic circuits with lower numbers of transistors and hence the lower power consumption than the conventional technology.

  19. Efficient, High-Speed VCSELs for Optical Interconnects Larry A. Coldren*

    E-print Network

    Coldren, Larry A.

    ] together with accelerated aging data for 1060 nm VCSELs from Furukawa via IBM[1] Co 850 nm to the 950 ­ 1100 nm range. Unfortunately, this has caused some heartburn amongst both users and suppliers as the old standards for datacom fixed the wavelength at 850 nm. Many would like to continue

  20. Low power consumption and highly reliable 1060 nm VCSELs for parallel optical interconnection

    Microsoft Academic Search

    Naoki Tsukiji; Suguru Imai; Keishi Takaki; Hitoshi Shimizu; Yasumasa Kawakita; Tomohiro Takagi; Koji Hiraiwa; Junji Yoshida; Hiroshi Shimizu; Akihiko Kasukawa

    2010-01-01

    1060nm VCSELs with InGaAs\\/GaAs strained quantum wells have been reviewed in terms of power consumption and reliability. Clear eye opening was confirmed at 10Gbps with bias current of as low as 1.4mA.

  1. Resolution and field of view improvement in digital holography using a VCSEL source array

    Microsoft Academic Search

    Luis Granero; Zeev Zalevsky; Vicente Mico

    2011-01-01

    We describe a new implementation capable to produce superresolution (SR) and object field of view (FOV) improvement in digital lensless Fourier holography. The method provides synthetic aperture (SA) generation using angular multiplexing incoming from a Vertical Cavity Surface Emitting Laser (VCSEL) source array. SR imaging in a single exposure is obtained after proper digital processing of a multiplexed hologram coming

  2. Optical injection locking of transverse modes in 1.3-µm wavelength coupled-VCSEL arrays.

    PubMed

    Long, C M; Mutter, L; Dwir, B; Mereuta, A; Caliman, A; Sirbu, A; Iakovlev, V; Kapon, E

    2014-09-01

    Optical injection locking of 1.3-µm phase-locked VCSEL arrays defined by patterned tunnel junctions and wafer fusion is investigated experimentally and theoretically. The impact of the overlap between the master laser injection beam and the injected modes is demonstrated and explained with a rate equation model that incorporates the spatial variations. PMID:25321494

  3. Improved PHIP polarization using a precision, low noise, voltage controlled current source

    NASA Astrophysics Data System (ADS)

    Agraz, Jose; Grunfeld, Alexander; Cunningham, Karl; Li, Debiao; Wagner, Shawn

    2013-10-01

    Existing para-hydrogen induced polarization (PHIP) instrumentation relies on magnetic fields to hyperpolarize substances. These hyperpolarized substances have enhanced magnetic resonance imaging (MRI) signals over 10,000 fold, allowing for MRI at the molecular level. Required magnetic fields are generated by energizing a solenoid coil with current produced by a voltage controlled voltage source (VCVS), also known as a power supply. A VCVS lacks the current regulation necessary to keep magnetic field fluctuations to a minimum, which results in low PHIP polarization. A voltage controlled current source (VCCS) is an electric circuit that generates a steady flow of electrons proportional to an input voltage. A low noise VCCS provides the solenoid current flow regulation necessary to generate a stable static magnetic field (Bo). We discuss the design and implementation of a low noise, high stability, VCCS for magnetic field generation with minimum variations. We show that a precision, low noise, voltage reference driving a metal oxide semiconductor field effect transistor (MOSFET) based current sink, results in the current flow control necessary for generating a low noise and high stability Bo. In addition, this work: (1) compares current stability for ideal VCVS and VCCS models using transfer functions (TF), (2) develops our VCCS design's TF, (3) measures our VCCS design's thermal & 1/f noise, and (4) measures and compares hydroxyethyl-propionate (HEP) polarization obtained using a VCVS and our VCCS. The hyperpolarization of HEP was done using a PHIP instrument developed in our lab. Using our VCCS design, HEP polarization magnitude data show a statistically significant increase in polarization over using a VCVS. Circuit schematic, bill of materials, board layout, TF derivation, and Matlab simulations code are included as supplemental files.

  4. Injection moulding integration of a red VCSEL illuminator module for a hologram reader sensor

    NASA Astrophysics Data System (ADS)

    Keränen, Kimmo; Saastamoinen, Toni; Mäkinen, Jukka-Tapani; Silvennoinen, Mikko; Mustonen, Ilpo; Vahimaa, Pasi; Jääskeläinen, Timo; Lehto, Ari; Ojapalo, Anneli; Schorpp, Marcus; Hoskio, Pekka; Karioja, Pentti

    2007-05-01

    A red VCSEL illuminator module demonstrator was manufactured by injection moulding integration. A red VCSEL chip was first attached to a simple FR4 substrate, which contains bonding pads and conducting wires for the VCSEL chip attachment and electrical driving. The substrate was then placed as an insert in an injection mould. The VCSEL chip shielding and optics formation was made in a one-step injection moulding process. The used optical thermoplastic in the processing was polycarbonate (PC). The pursued optical function of the single spherical surface attained in the moulding was to collimate the emitted red light (?=664.5 nm) from the VCSEL chip. The main critical issue related to the manufacturing of the illuminator module in the injection moulding process was the durability of bonding wire contacts. A single 25 ?m diameter gold wire was used in wire bonding in order to create the upper contact to the chip. The lower contact was processed by attaching the chip to the substrate using conductive epoxy. A test series of 20 modules using FR4 substrate materials were produced. The number of fully operative modules was 12 resulting total module yield of 60%. The main reason for a non-operative module was loosening of the bonding wire during the injection moulding process. The bonding wire durability in the moulding process can be improved by using glob-top shielding of the VCSEL device before injection moulding and using a lower holding pressure in the injection moulding process. A diamond turned insert was used in the mould in order to create a high quality lens surface on the top of the VCSEL chip. The tower average length after one iteration round by mould modification was 8.676 ?m, so the measured value was on average 20 ?m larger than nominal value. The measured RMS roughness of the processed lens surface was 5 ... 7 nm and the radius -3.23 ... 3.83 mm. The radius of the lens and the length of the tower varied depending of the used process parameters. The manufactured illumination module can be integrated with a CMOS image matrix sensor in order to form a compact hologram reader system. The injection moulding integration principle seems to be very promising method to manufacture intelligently integrated and cost-effective optoelectronic products according to experience with this demonstrator.

  5. In situ optical time-domain reflectometry (OTDR) for VCSEL-based communication systems

    NASA Astrophysics Data System (ADS)

    Keeler, Gordon A.; Serkland, Darwin K.; Geib, Kent M.; Klem, John F.; Peake, Gregory M.

    2006-02-01

    Optical time-domain reflectometry (OTDR) is an effective technique for locating faults in fiber communication links. The fact that most OTDR measurements are performed manually is a significant drawback, because it makes them too costly for use in many short-distance networks and too slow for use in military avionic platforms. Here we describe and demonstrate an automated, low-cost, real-time approach to fault monitoring that can be achieved by integrating OTDR functionality directly into VCSEL-based transceivers. This built-in test capability is straightforward to implement and relevant to both multimode and single mode networks. In-situ OTDR uses the transmitter VCSEL already present in data transceivers. Fault monitoring is performed by emitting a brief optical pulse into the fiber and then turning the VCSEL off. If a fault exists, a portion of the optical pulse returns to the transceiver after a time equal to the round-trip delay through the fiber. In multimode OTDR, the signal is detected by an integrated photodetector, while in single mode OTDR the VCSEL itself can be used as a detector. Modified driver electronics perform the measurement and analysis. We demonstrate that VCSEL-based OTDR has sufficient sensitivity to determine the location of most faults commonly seen in short-haul networks (i.e., the Fresnel reflections from improperly terminated fibers and scattering from raggedly-broken fibers). Results are described for single mode and multimode experiments, at both 850 nm and 1.3 ?m. We discuss the resolution and sensitivity that have been achieved, as well as expected limitations for this novel approach to network monitoring.

  6. Controlled polarization of two-dimensional quantum turbulence in atomic Bose-Einstein condensates

    E-print Network

    A. Cidrim; F. E. A. dos Santos; V. S. Bagnato; C. F. Barenghi

    2015-07-11

    We propose a scheme for generating two-dimensional turbulence in harmonically trapped atomic condensates with the novelty of controlling the polarization (net rotation) of the turbulence. Our scheme is based on an initial giant (multicharged) vortex which induces a large-scale circular flow. Two thin obstacles, created by blue-detuned laser beams, speed up the decay of the giant vortex into many singly-quantized vortices of the same circulation; at the same time, vortex-antivortex pairs are created by the decaying circular flow past the obstacles. Rotation of the obstacles against the circular flow controls the relative proportion of positive and negative vortices, from the limit of strongly anisotropic turbulence (almost all vortices having the same sign) to that of isotropic turbulence (equal number of vortices and antivortices). Using the new scheme, we numerically study quantum turbulence and report on its decay as a function of the polarization.

  7. Polarization control in GaN nanowire lasers Huiwen Xu,1

    E-print Network

    New Mexico, University of

    : what's next?" Nano Lett. 10(5), 1529­1536 (2010). 6. Q. Li, J. B. Wright, W. W. Chow, T. S. Luk, I. Cross, L. F. Lester, G. Balakrishnan, G. T. Wang, I. Brener, and Q. Li, "Single-mode lasing of GaPolarization control in GaN nanowire lasers Huiwen Xu,1 Antonio Hurtado,1,2 Jeremy B. Wright,1

  8. Polarization Mode Control of Two-Dimensional Photonic Crystal Laser by Unit Cell Structure Design

    Microsoft Academic Search

    Susumu Noda; Mitsuru Yokoyama; Masahiro Imada; Alongkarn Chutinan; Masamitsu Mochizuki

    2001-01-01

    We demonstrate polarization mode selection in a two-dimensional (2D) photonic crystal laser by controlling the geometry of the unit cell structure. As the band diagram of the square-lattice photonic crystal is influenced by the unit cell structure, calculations reveal that changing the structure from a circular to an elliptical geometry should result in a strong modification of the electromagnetic field

  9. LKB1/AMPK and PKA Control ABCB11 Trafficking and Polarization in Hepatocytes

    PubMed Central

    Homolya, László; Fu, Dong; Sengupta, Prabuddha; Jarnik, Michal; Gillet, Jean-Pierre; Vitale-Cross, Lynn; Gutkind, J. Silvio; Lippincott-Schwartz, Jennifer; Arias, Irwin M.

    2014-01-01

    Polarization of hepatocytes is manifested by bile canalicular network formation and activation of LKB1 and AMPK, which control cellular energy metabolism. The bile acid, taurocholate, also regulates development of the canalicular network through activation of AMPK. In the present study, we used collagen sandwich hepatocyte cultures from control and liver-specific LKB1 knockout mice to examine the role of LKB1 in trafficking of ABCB11, the canalicular bile acid transporter. In polarized hepatocytes, ABCB11 traffics from Golgi to the apical plasma membrane and endogenously cycles through the rab 11a-myosin Vb recycling endosomal system. LKB1 knockout mice were jaundiced, lost weight and manifested impaired bile canalicular formation and intracellular trafficking of ABCB11, and died within three weeks. Using live cell imaging, fluorescence recovery after photobleaching (FRAP), particle tracking, and biochemistry, we found that LKB1 activity is required for microtubule-dependent trafficking of ABCB11 to the canalicular membrane. In control hepatocytes, ABCB11 trafficking was accelerated by taurocholate and cAMP; however, in LKB1 knockout hepatocytes, ABCB11 trafficking to the apical membrane was greatly reduced and restored only by cAMP, but not taurocholate. cAMP acted through a PKA-mediated pathway which did not activate AMPK. Our studies establish a regulatory role for LKB1 in ABCB11 trafficking to the canalicular membrane, hepatocyte polarization, and canalicular network formation. PMID:24643070

  10. PHYSICAL REVIEW B 84, 125305 (2011) Polarity control of carrier injection at ferroelectric/metal interfaces for electrically switchable diode

    E-print Network

    Eom, Chang Beom

    2011-01-01

    /metal interfaces for electrically switchable diode and photovoltaic effects D. Lee,1 S. H. Baek,2 T. H. Kim,1 J received 9 August 2011; published 8 September 2011) We investigated a switchable ferroelectric diode effect training process to obtain ferroelectric control of the diode polarity where, by changing the polarization

  11. Novel Cdc42-binding proteins Gic1 and Gic2 control cell polarity in?yeast

    PubMed Central

    Brown, Jeffrey L.; Jaquenoud, Malika; Gulli, Marie-Pierre; Chant, John; Peter, Matthias

    1997-01-01

    Cdc42p, a Rho-related GTP-binding protein, regulates cytoskeletal polarization and rearrangements in eukaryotic cells, but the effectors mediating this control remain unknown. Through the use of the complete yeast genomic sequence, we have identified two novel Cdc42p targets, Gic1p and Gic2p, which contain consensus Cdc42/Rac interactive–binding (CRIB) domains and bind specifically to Cdc42p–GTP. Gic1p and Gic2p colocalize with Cdc42p as cell polarity is established during the cell cycle and during mating in response to pheromones. Cells deleted for both GIC genes exhibit defects in actin and microtubule polarization similar to those observed in cdc42 mutants. Finally, the interaction of the Gic proteins and Cdc42p is essential, as mutations in the CRIB domain of Gic2p that eliminate Cdc42p binding disrupt Gic2p localization and function. Thus, Gic1p and Gic2p define a novel class of Cdc42p targets that are specifically required for cytoskeletal polarization in vivo. PMID:9367980

  12. 'Downward control' of the mean meridional circulation and temperature distribution of the polar winter stratosphere

    NASA Technical Reports Server (NTRS)

    Garcia, Rolando R.; Boville, Byron A.

    1994-01-01

    According to the 'downward control' principle, the extratropical mean vertical velocity on a given pressure level is approximately proportional to the meridional gradient of the vertically integrated zonal force per unit mass exerted by waves above that level. In this paper, a simple numerical model that includes parameterizations of both planetary and gravity wave breaking is used to explore the influence of gravity wave breaking in the mesosphere on the mean meridional circulation and temperature distribution at lower levels in the polar winter stratosphere. The results of these calculations suggest that gravity wave drag in the mesosphere can affect the state of the polar winter stratosphere down to altitudes below 30 km. The effect is most important when planetary wave driving is relatively weak: that is, during southern winter and in early northern winter. In southern winter, downwelling weakens by a factor of 2 near the stratospause and by 20% at 30 km when gravity wave drag is not included in the calculations. As a consequence, temperatures decrease considerably throughout the polar winter stratosphere (over 20 K above 40 km and as much as 8 K at 30 km, where the effect is enhanced by the long radiative relaxation timescale). The polar winter states obtained when gravity wave drag is omitted in this simple model resemble the results of simulations with some general circulation models and suggest that some of the shortcomings of the latter may be due to a deficit in mesospheric momentum deposition by small-scale gravity waves.

  13. 40 GHz Bandwidth and 64 GHz Resonance Frequency in Injection-Locked 1.55 ?m VCSELs

    Microsoft Academic Search

    Lukas Chrostowski; Behnam Faraji; Werner Hofmann; Markus-Christian Amann; Sebastian Wieczorek; Weng W. Chow

    2007-01-01

    Injection locking is shown to greatly enhance the resonance frequency of 1.55 mum vertical-cavity surface-emitting lasers (VCSELs), from 10 to 60 GHz, under ultrahigh injection locking conditions. Using injection locking to increase the laser resonance frequency, together with a low parasitic VCSEL design, a 3 dB bandwidth of over 40 GHz was attained, a record broadband performance for directly modulated

  14. Effects of Thermal-Via Structures on Thin-Film VCSELs for Fully Embedded Board-LevelOptical Interconnection System

    Microsoft Academic Search

    J. H. Choi; L. Wang; H. Bi; R. T. Chen

    2006-01-01

    The thermal characteristics of a thin-film vertical-cavity surface-emitting laser (VCSEL) are studied both theoretically and experimentally. The thermal resistances of the VCSEL with variable thickness, ranging from 10 to 200 mum, have been determined by measuring the output wavelength shift as a function of the dissipated power. The thermal simulation results agree reasonably well with the experimentally measured data. From

  15. Linearly polarized single photon antibunching from a site-controlled InGaN quantum dot

    SciTech Connect

    Jemsson, Tomas; Machhadani, Houssaine; Karlsson, K. Fredrik; Hsu, Chih-Wei; Holtz, Per-Olof [Department of Physics, Chemistry, and Biology (IFM), Semiconductor Materials, Linköping University, S-58183 Linköping (Sweden)

    2014-08-25

    We report on the observation of linearly polarized single photon antibunching in the excitonic emission from a site-controlled InGaN quantum dot. The measured second order coherence function exhibits a significant dip at zero time difference, corresponding to g{sub m}{sup 2}(0)=0.90 under continuous laser excitation. This relatively high value of g{sub m}{sup 2}(0) is well understood by a model as the combination of short exciton life time (320 ps), limited experimental timing resolution and the presence of an uncorrelated broadband background emission from the sample. Our result provides the first rigorous evidence of InGaN quantum dot formation on hexagonal GaN pyramids, and it highlights a great potential in these dots as fast polarized single photon emitters if the background emission can be eliminated.

  16. Linearly polarized single photon antibunching from a site-controlled InGaN quantum dot

    NASA Astrophysics Data System (ADS)

    Jemsson, Tomas; Machhadani, Houssaine; Karlsson, K. Fredrik; Hsu, Chih-Wei; Holtz, Per-Olof

    2014-08-01

    We report on the observation of linearly polarized single photon antibunching in the excitonic emission from a site-controlled InGaN quantum dot. The measured second order coherence function exhibits a significant dip at zero time difference, corresponding to g m 2 ( 0 ) = 0.90 under continuous laser excitation. This relatively high value of g m 2 ( 0 ) is well understood by a model as the combination of short exciton life time (320 ps), limited experimental timing resolution and the presence of an uncorrelated broadband background emission from the sample. Our result provides the first rigorous evidence of InGaN quantum dot formation on hexagonal GaN pyramids, and it highlights a great potential in these dots as fast polarized single photon emitters if the background emission can be eliminated.

  17. Dynamic control of spin wave spectra using spin-polarized currents

    SciTech Connect

    Wang, Qi; Zhang, Huaiwu, E-mail: hwzhang@uestc.edu.cn; Tang, Xiaoli; Bai, Feiming; Zhong, Zhiyong, E-mail: zzy@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Fangohr, Hans [Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom)

    2014-09-15

    We describe a method of controlling the spin wave spectra dynamically in a uniform nanostripe waveguide through spin-polarized currents. A stable periodic magnetization structure is observed when the current flows vertically through the center of nanostripe waveguide. After being excited, the spin wave is transmitted at the sides of the waveguide. Numerical simulations of spin-wave transmission and dispersion curves reveal a single, pronounced band gap. Moreover, the periodic magnetization structure can be turned on and off by the spin-polarized current. The switching process from full rejection to full transmission takes place within less than 3?ns. Thus, this type magnonic waveguide can be utilized for low-dissipation spin wave based filters.

  18. Long-range Neural and Gap Junction Protein-mediated Cues Control Polarity During Planarian Regeneration

    PubMed Central

    Oviedo, Néstor J.; Morokuma, Junji; Walentek, Peter; Kema, Ido P.; Gu, Man Bock; Ahn, Joo-Myung; Hwang, Jung Shan; Gojobori, Takashi; Levin, Michael

    2010-01-01

    SUMMARY Having the ability to coordinate the behavior of stem cells to induce regeneration of specific large-scale structures would have far reaching consequences in the treatment of degenerative diseases, acute injury, and aging. Thus, identifying and learning to manipulate the sequential steps that determine the fate of new tissue within the overall morphogenetic program of the organism is fundamental. We identified novel early signals, mediated by the central nervous system and 3 innexin proteins, which determine the fate and axial polarity of regenerated tissue in planarians. Modulation of gap junction-dependent and neural signals specifically induces ectopic anterior regeneration blastemas in posterior and lateral wounds. These ectopic anterior blastemas differentiate new brains that establish permanent primary axes re-established during subsequent rounds of unperturbed regeneration. These data reveal powerful novel controls of pattern formation and suggest a constructive model linking nervous inputs and polarity determination in early stages of regeneration. PMID:20026026

  19. Serrano (Sano) Functions with the Planar Cell Polarity Genes to Control Tracheal Tube Length

    PubMed Central

    Chung, SeYeon; Vining, Melissa S.; Bradley, Pamela L.; Chan, Chih-Chiang; Wharton, Keith A.; Andrew, Deborah J.

    2009-01-01

    Epithelial tubes are the functional units of many organs, and proper tube geometry is crucial for organ function. Here, we characterize serrano (sano), a novel cytoplasmic protein that is apically enriched in several tube-forming epithelia in Drosophila, including the tracheal system. Loss of sano results in elongated tracheae, whereas Sano overexpression causes shortened tracheae with reduced apical boundaries. Sano overexpression during larval and pupal stages causes planar cell polarity (PCP) defects in several adult tissues. In Sano-overexpressing pupal wing cells, core PCP proteins are mislocalized and prehairs are misoriented; sano loss or overexpression in the eye disrupts ommatidial polarity and rotation. Importantly, Sano binds the PCP regulator Dishevelled (Dsh), and loss or ectopic expression of many known PCP proteins in the trachea gives rise to similar defects observed with loss or gain of sano, revealing a previously unrecognized role for PCP pathway components in tube size control. PMID:19956736

  20. Polarization control of intermediate state absorption in resonance-mediated multi-photon absorption process

    NASA Astrophysics Data System (ADS)

    Xu, Shuwu; Huang, Yunxia; Yao, Yunhua; Jia, Tianqing; Ding, Jingxin; Zhang, Shian; Sun, Zhenrong

    2015-07-01

    We theoretically and experimentally demonstrate the control of the intermediate state absorption in an (n + m) resonance-mediated multi-photon absorption process by the polarization-modulated femtosecond laser pulse. An analytical solution of the intermediate state absorption in a resonance-mediated multi-photon absorption process is obtained based on the time-dependent perturbation theory. Our theoretical results show that the control efficiency of the intermediate state absorption by the polarization modulation is independent of the laser intensity when the transition from the intermediate state to the final state is coupled by the single-photon absorption, but will be affected by the laser intensity when this transition is coupled by the non-resonant multi-photon absorption. These theoretical results are experimentally confirmed via a two-photon fluorescence control in (2 + 1) resonance-mediated three-photon absorption of Coumarin 480 dye and a single-photon fluorescence control in (1 + 2) resonance-mediated three-photon absorption of IR 125 dye.

  1. Complete Control of Polarization and Phase of Light with High Efficiency and Sub-wavelength Spatial Resolution

    E-print Network

    Arbabi, Amir; Bagheri, Mahmood; Faraon, Andrei

    2014-01-01

    Meta-surfaces are planar structures that locally change polarization, phase, and amplitude of light, thus enabling flat, lithographically patterned free-space optical components with functionalities controlled by design. Several types of meta-surfaces have been reported, but low efficiency and the inability to provide simultaneous phase and polarization control have limited their applications. Here we demonstrate a platform based on high-contrast dielectric elliptical nano-posts providing complete and efficient control of polarization and phase with sub-wavelength spatial resolution. The unprecedented freedom in manipulating light not only enables realization of conventional free-space transmissive optical elements such as phase-plates, wave-plates and beam-splitters, but also elements with novel functionalities such as general polarization switchable phase holograms and arbitrary vector beam generators which will change the design paradigms for free-space optical systems.

  2. 1W frequency-doubled VCSEL-pumped blue laser with high pulse energy

    NASA Astrophysics Data System (ADS)

    Van Leeuwen, Robert; Chen, Tong; Watkins, Laurence; Xu, Guoyang; Seurin, Jean-Francois; Wang, Qing; Zhou, Delai; Ghosh, Chuni

    2015-02-01

    We report on a Q-switched VCSEL side-pumped 946 nm Nd:YAG laser that produces high average power blue light with high pulse energy after frequency doubling in BBO. The gain medium was water cooled and symmetrically pumped by three 1 kW 808 nm VCSEL pump modules. More than 1 W blue output was achieved at 210 Hz with 4.9 mJ pulse energy and at 340 Hz with 3.2 mJ pulse energy, with 42% and 36% second harmonic conversion efficiency respectively. Higher pulse energy was obtained at lower repetition frequencies, up to 9.3 mJ at 70 Hz with 52% conversion efficiency.

  3. Optimization of mode numbers of VCSELs for small-cell backhaul applications

    NASA Astrophysics Data System (ADS)

    Lu, I.-Cheng; Wei, Chia-Chien; Shi, Jin-Wei; Chen, Hsing-Yu; Tsai, Sheng-Fan; Hsu, Dar-Zu; Wei, Zhi-Rui; Wun, Jhih-Min; Chen, Jyehong

    2015-07-01

    This paper reports optical orthogonal frequency-division multiplexing (OFDM) transmission using 850 nm Zn-diffusion Vertical-Cavity Surface-Emitting Lasers (VCSELs) and multimode fiber (MMF) for small-cell backhaul applications. We also investigated the influence of side mode suppression ratio (SMSR) on the performance of OFDM modulation. By further optimizing the Zn-diffusion conditions and oxide aperture size, a high-power (6.7 mW) SM (SMSR>30 dB) VCSEL is demonstrated. By using OFDM modulation and bit-loading algorithm, record-high BRDP (91 Gb/s km) at 26 Gb/s transmission under FEC threshold (bit error rate (BER)<3.8×10-3) across 3.5 km OM4 fiber has been successfully demonstrated.

  4. Temperature-dependent operation of GaInAsP\\/InP VCSELs

    Microsoft Academic Search

    Carl J. Hepburn; Russell Sceats; Adrian Boland-Thoms; Naci Balkan; A. J. Dann; Simon D. Perrin; Ian Read; J. Reed; P. Cannard; Michael A. Fisher; D. J. Elton; M. Harlow

    2001-01-01

    We present the results of our studies concerning the pulsed operation of a bulk GaInAsP\\/InP vertical cavity surface emitting laser (VCSEL). The device is tailored to emit at around 1.5 micrometers at room temperature. The structure has a 45-period n-doped GaInAsP\\/InP bottom Distributed Bragg Reflector (DBR), and a 4 period Si\\/Al2O3 dielectric top reflector defining a 3-(lambda) cavity. Electroluminescence from

  5. Proton Irradiation Effects in Oxide-Confined Vertical Cavity Surface Emitting Laser (VCSEL) Diodes

    SciTech Connect

    Armendariz, M.G.; Barnes, C.E.; Choquette, K.D.; Guertin, S.; Hash, G.L.; Schwank, J.R.; Swift, G.M.

    1999-03-11

    Recent space experience has shown that the use of commercial optocouplers can be problematic in spacecraft, such as TOPEX/Poseidon, that must operate in significant radiation environments. Radiation--induced failures of these devices have been observed in space and have been further documented at similar radiation doses in the laboratory. The ubiquitous use of optocouplers in spacecraft systems for a variety of applications, such as electrical isolation, switching and power transfer, is indicative of the need for optocouplers that can withstand the space radiation environment. In addition, the distributed nature of their use implies that it is not particularly desirable to shield optocouplers for use in radiation environments. Thus, it will be important for the space community to have access to radiation hardened/tolerant optocouplers. For many microelectronic and photonic devices, it is difficult to achieve radiation hardness without sacrificing performance. However, in the case of optocouplers, one should be able to achieve both superior radiation hardness and performance for such characteristics as switching speed, current transfer ratio (CTR), minimum power usage and array power transfer, if standard light emitting diodes (LEDs), such as those in the commercial optocouplers mentioned above, are avoided, and VCSELs are employed as the emitter portion of the optocoupler. The physical configuration of VCSELs allows one to achieve parallel use of an array of devices and construct a multichannel optocoupler in the standard fashion with the emitters and detectors looking at each other. In addition, detectors similar in structure to the VCSELs can be fabricated which allows bidirectional functionality of the optocoupler. Recent discussions suggest that VCSELs will enjoy widespread applications in the telecommunications and data transfer fields.

  6. Progress on high-power high-brightness VCSELs and applications

    NASA Astrophysics Data System (ADS)

    Zhou, Delai; Seurin, Jean-Francois; Xu, Guoyang; Zhao, Pu; Xu, Bing; Chen, Tong; Van Leeuwen, Robert; Matheussen, Joseph; Wang, Qing; Ghosh, Chuni

    2015-03-01

    Vertical-cavity surface-emitting lasers (VCSELs) are attractive for many pumping and direct-diode applications due to combined advantages in low cost, high reliability, narrow and thermally stable spectrum, high power scalability, and easy system integration, etc. We report our progress on electrically pumped, GaAs-based, high- power high-brightness VCSELs and 2D arrays in the infrared wavelength range. At 976nm, over 5.5W peak CW output and 60% peak power conversion efficiency (PCE) were demonstrated with 225um oxide-confined device. For 5x5mm arrays, peak PCE of 54% and peak power of >450W at 976nm, peak PCE of 46% and peak power of >110W at 808nm were achieved respectively under QCW conditions. External cavity configuration was used to improve the VCSEL brightness. Single mode output of 280mW and 37% PCE were realized from 80um device. For large 325um device, we obtained single mode (M2=1.1) CW output of 2.1W, corresponding to a brightness of 160MW/cm2*sr. Three major areas of applications using such VCSELs are discussed: 1. High brightness fiber output; 2. High power, high efficiency green lasers from 2nd harmonic generation. 3.34W green output with 21.2% PCE were achieved; 3. Pumping solid state lasers for high energy pulse generation. We have demonstrated Q-switched pulses with 16.1mJ at 1064nm and 4.9mJ with 1W average power at 473nm.

  7. Low thermal resistance high-speed top-emitting 980-nm VCSELs

    Microsoft Academic Search

    A. N. Al-Omari; G. P. Carey; S. Hallstein; J. P. Watson; G. Dang; K. L. Lear

    2006-01-01

    Increasing copper plated heatsink radii from 0 to 4 mum greater than the mesa in vertical-cavity surface-emitting lasers (VCSELs) reduced the measured thermal resistance for a range of device sizes to values 50% lower than previously reported over a range of device sizes. For a 9-mum diameter oxide aperture, the larger heatsink increases output power and bandwidth by 131% and

  8. VCSEL-based oxygen spectroscopy for structural analysis of pharmaceutical solids

    Microsoft Academic Search

    T. Svensson; M. Andersson; L. Rippe; S. Svanberg; S. Andersson-Engels; J. Johansson; S. Folestad

    2008-01-01

    We present a minimalistic and flexible single-beam instrumentation based on sensitive tunable diode laser absorption spectroscopy\\u000a (TDLAS) and its use in structural analysis of highly scattering pharmaceutical solids. By utilising a vertical cavity surface\\u000a emitting laser (VCSEL) for sensing of molecular oxygen dispersed in tablets, we address structural properties such as porosity.\\u000a Experiments involve working with unknown path lengths, severe

  9. In Situ Detection of PHIP at 48 mT: Demonstration Using a Centrally Controlled Polarizer

    PubMed Central

    Waddell, Kevin W.; Coffey, Aaron M.; Chekmenev, Eduard Y.

    2011-01-01

    Presented here is a centrally controlled, automated parahydrogen-based polarizer with in situ detection capability. A 20% polarization, corresponding to a 5 000 000-fold signal enhancement at 48 mT, is demonstrated on 2-hydroxyethyl-1-13C-propionate-d2,3,3 using a double-tuned antenna and pulsed polarization transfer. In situ detection is a refinement of first-generation devices enabling fast calibration of rf pulses and B0, quality assurance of hyperpolarized contrast agents, and stand-alone operation without the necessity of high-field MR spectrometers. These features are essential for biomedical applications of parahydrogen-based hyperpolarization and for clinical translation. We demonstrate the flexibility of the device by recording 13C signal decay due to longitudinal relaxation of a hyperpolarized contrast agent at 48 mT corresponding to 2 MHz proton frequency. This appears to be the longest recorded T1 (101 ± 7 s) for a 13C hyperpolarized contrast agent in water. PMID:21141960

  10. Long-wavelength VCSELs for optical networks and trace-gas monitoring

    NASA Astrophysics Data System (ADS)

    Hofmann, W.; Böhm, G.; Ortsiefer, M.; Görblich, M.; Lauer, C.; Zhu, N. H.; Amann, M.-C.

    2007-09-01

    Long-wavelength InGaAlAs-InP vertical-cavity surface-emitting lasers (LW-VCSELs), designed for applications in gas sensing and for optical interconnects are presented. These lasers cover the wavelength-range from 1.3 to 2.3 ?m. With 2.3 ?m, this is the longest wavelength ever achieved with an InP-based interband laser. Fabricated with a novel highspeed design with reduced parasitics, bandwidths in excess of 11 GHz at 1.55 ?m have been achieved. To the best of our knowledge, this is the best dynamic characteristic for a 1.55 ?m VCSEL ever presented. As a proof-of-concept one- and two-dimensional arrays have been fabricated with high yield. All devices use for current confinement a buried tunnel junction (BTJ). This concept, together with a dielectric backside reflector with integrated electroplated gold heat sink for thermal management enables continuous wave (CW) operation at room-temperature with typical single-mode output powers above 1 mW. The operation voltage is around 1 V and power consumption is as low as 10 - 20 mW. Error-free data-transmission at 10 Gbit/s over 20 km is demonstrated, which can be readily applied in uncooled Coarse Wavelength Division Multiplex Passive Optical Networks (CWDM PONs). The functionality of tunable diode laser spectroscopy (TDLS) systems is verified by presenting a laser hygrometer using a 1.84 ?m wavelength VCSEL.

  11. Bidirectional hybrid PM-based RoF and VCSEL-based VLLC system.

    PubMed

    Li, Chung-Yi; Lu, Hai-Han; Chang, Ching-Hung; Lin, Chun-Yu; Wu, Po-Yi; Zheng, Jun-Ren; Lin, Chia-Rung

    2014-06-30

    A bidirectional hybrid phase modulation (PM)-based radio-over-fiber (RoF) and vertical cavity surface emitting laser (VCSEL)-based visible laser light communication (VLLC) systems employing injection-locked VCSEL-based PM-to-intensity modulation (IM) converters and optical interleavers (ILs) is proposed and demonstrated. To be the first one of using injection-locked VCSEL-based PM-to-IM converters and optical ILs in such bidirectional hybrid RoF and VLLC systems, the downstream light is successfully phase-remodulated with RoF signal for up-link transmission. Through a serious investigation in systems, bit error rate (BER) and eye diagram perform brilliantly over a 40-km single-mode fiber (SMF) transport and a 12-m free-space transmission. Such a bidirectional hybrid RoF and VLLC system would be very attractive for the integration of fiber backbone and in-door networks to provide broadband integrated services, including Internet and telecommunication services. PMID:24977870

  12. Do large impact basins in the southern hemisphere of Mars control the distribution of polar structures and deposits?

    NASA Technical Reports Server (NTRS)

    Frey, Herbert; Reidy, Anne-Marie

    1993-01-01

    Among the outstanding problems in Martian geology are the cause of the off-axis and asymmetric distribution of the southern polar layered terrain and residual ice deposits and the cause of the orientation of scarps, valleys, and re-entrant canyons which occur there. A perhaps related problem region is the apparently small number of large (D greater than 500 km) impact basins seen in the relatively well-preserved cratered terrain of the south polar region. Previously only the 850 km wide South Polar Basin was easily recognized. The south polar region was mapped in detail, searching for evidence of ancient, highly degraded impact basins that may have escaped earlier notice, for two reasons: (1) to determine whether the apparent absence of large impact basins is due to incomplete mapping and recognition or a fundamental characteristic of the Martian crust related to the origin of the Martian crustal dichotomy, and (2) to determine whether ancient impact basins, if they exist, exert some control on the distribution of volcanic and polar deposits in the southern hemisphere and on the topography on which these deposits lie. Several promising candidates, including a large pre-Hellas basin in the Malea Planum region and an older but comparably sized basin overlapping South Polar, were previously described. Concentration is on the possible influence of the candidate basins in localizing the asymmetric distribution of polar deposits and in controlling the orientation of structures found within these deposits.

  13. Optical control of hard X-ray polarization by electron injection in a laser wakefield accelerator

    PubMed Central

    Schnell, Michael; Sävert, Alexander; Uschmann, Ingo; Reuter, Maria; Nicolai, Maria; Kämpfer, Tino; Landgraf, Björn; Jäckel, Oliver; Jansen, Oliver; Pukhov, Alexander; Kaluza, Malte Christoph; Spielmann, Christian

    2013-01-01

    Laser-plasma particle accelerators could provide more compact sources of high-energy radiation than conventional accelerators. Moreover, because they deliver radiation in femtosecond pulses, they could improve the time resolution of X-ray absorption techniques. Here we show that we can measure and control the polarization of ultra-short, broad-band keV photon pulses emitted from a laser-plasma-based betatron source. The electron trajectories and hence the polarization of the emitted X-rays are experimentally controlled by the pulse-front tilt of the driving laser pulses. Particle-in-cell simulations show that an asymmetric plasma wave can be driven by a tilted pulse front and a non-symmetric intensity distribution of the focal spot. Both lead to a notable off-axis electron injection followed by collective electron–betatron oscillations. We expect that our method for an all-optical steering is not only useful for plasma-based X-ray sources but also has significance for future laser-based particle accelerators. PMID:24026068

  14. Radial polar histogram: obstacle avoidance and path planning for robotic cognition and motion control

    NASA Astrophysics Data System (ADS)

    Wang, Po-Jen; Keyawa, Nicholas R.; Euler, Craig

    2012-01-01

    In order to achieve highly accurate motion control and path planning for a mobile robot, an obstacle avoidance algorithm that provided a desired instantaneous turning radius and velocity was generated. This type of obstacle avoidance algorithm, which has been implemented in California State University Northridge's Intelligent Ground Vehicle (IGV), is known as Radial Polar Histogram (RPH). The RPH algorithm utilizes raw data in the form of a polar histogram that is read from a Laser Range Finder (LRF) and a camera. A desired open block is determined from the raw data utilizing a navigational heading and an elliptical approximation. The left and right most radii are determined from the calculated edges of the open block and provide the range of possible radial paths the IGV can travel through. In addition, the calculated obstacle edge positions allow the IGV to recognize complex obstacle arrangements and to slow down accordingly. A radial path optimization function calculates the best radial path between the left and right most radii and is sent to motion control for speed determination. Overall, the RPH algorithm allows the IGV to autonomously travel at average speeds of 3mph while avoiding all obstacles, with a processing time of approximately 10ms.

  15. Controllably interfacing with metal: a strategy for enhancing CO oxidation on oxide catalysts by surface polarization.

    PubMed

    Bai, Yu; Zhang, Wenhua; Zhang, Zhenhua; Zhou, Jie; Wang, Xijun; Wang, Chengming; Huang, Weixin; Jiang, Jun; Xiong, Yujie

    2014-10-22

    Heterogeneous catalysis often involves charge transfer from catalyst surface to adsorbed molecules, whose activity thus depends on the surface charge density of catalysts. Here, we demonstrate a unique solution-phase approach to achieve controllable interfacial lengths in oxide-metal hybrid structures. Resulting from their different work functions, surface polarization is induced by the Ag-CuO interface and acts to tailor the surface charge state of CuO. As a result, the designed hybrid catalysts exhibit enhanced intrinsic activities in catalyzing CO oxidation in terms of apparent activation energy, as compared with their counterparts. Moreover, the CO conversion rate can be enhanced by maximizing the Ag-CuO interfacial length and thus the number of active sites on the CuO. This work provides a new strategy for tuning catalytic performance by controlling interface in hybrid catalysts. PMID:25296380

  16. Low-Magnetic-Field Control of Electric Polarization Vector in a Helimagnet

    NASA Astrophysics Data System (ADS)

    Ishiwata, Shintaro; Taguchi, Yasujiro; Murakawa, Hiroshi; Onose, Yoshinori; Tokura, Yoshinori

    2008-03-01

    The mutual control of the electric and magnetic properties of a solid is currently of great interest because of the possible application for novel electronic devices. We report on the low-magnetic-field (for example, B values of ±30 milliteslas) control of the polarization (P) vector in a hexaferrite, Ba2Mg2Fe12O22, which shows the helimagnetic spin structure with the propagation vector k0 parallel to [001]. The B-induced transverse conical spin structure carries the P vector directing perpendicular to both B and k0, in accord with the recently proposed spin-current model. Then, the oscillating or multidirectionally rotating B produces the cyclic displacement current via the flexible handling of the magnetic cone axis.

  17. Control of exciton spin statistics through spin polarization in organic optoelectronic devices

    PubMed Central

    Wang, Jianpu; Chepelianskii, Alexei; Gao, Feng; Greenham, Neil C.

    2012-01-01

    Spintronics based on organic semiconductor materials is attractive because of its rich fundamental physics and potential for device applications. Manipulating spins is obviously important for spintronics, and is usually achieved by using magnetic electrodes. Here we show a new approach where spin populations can be controlled primarily by energetics rather than kinetics. We find that exciton spin statistics can be substantially controlled by spin-polarizing carriers after injection using high magnetic fields and low temperatures, where the Zeeman energy is comparable with the thermal energy. By using this method, we demonstrate that singlet exciton formation can be suppressed by up to 53% in organic light-emitting diodes, and the dark conductance of organic photovoltaic devices can be increased by up to 45% due to enhanced formation of triplet charge-transfer states, leading to less recombination to the ground state. PMID:23149736

  18. Muscle stem cell fate is controlled by the cell-polarity protein Scrib.

    PubMed

    Ono, Yusuke; Urata, Yoshishige; Goto, Shinji; Nakagawa, Shunsuke; Humbert, Patrick O; Li, Tao-Sheng; Zammit, Peter S

    2015-02-24

    Satellite cells are resident skeletal muscle stem cells that supply myonuclei for homeostasis, hypertrophy, and repair in adult muscle. Scrib is one of the major cell-polarity proteins, acting as a potent tumor suppressor in epithelial cells. Here, we show that Scrib also controls satellite-cell-fate decisions in adult mice. Scrib is undetectable in quiescent cells but becomes expressed during activation. Scrib is asymmetrically distributed in dividing daughter cells, with robust accumulation in cells committed to myogenic differentiation. Low Scrib expression is associated with the proliferative state and preventing self-renewal, whereas high Scrib levels reduce satellite cell proliferation. Satellite-cell-specific knockout of Scrib in mice causes a drastic and insurmountable defect in muscle regeneration. Thus, Scrib is a regulator of tissue stem cells, controlling population expansion and self-renewal with Scrib expression dynamics directing satellite cell fate. PMID:25704816

  19. Theory of spin-polarized semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Oszwaldowski, Rafal; Gothgen, Christian; Zutic, Igor

    2008-03-01

    In semiconductor systems spin-polarized electrons couple to photons with definite angular momentum. This effect is the basis for numerous existing and proposed devices [1]. Quantum-well based Vertical Cavity Surface Emitting Lasers (VCSELs) take advantage of this phenomenon to produce circularly-polarized light by using either optical or electrical pumping [2]. We describe the VCSEL system employing Semiconductor Bloch Equations. We include the influence of spin-orbit coupling and the dependence of dipole matrix elements on carrier's wavevectors. We reduce this description to an effective four-level model, incorporating such effects as different spin lifetimes for electrons/holes and laser-cavity birefringence. Applying this approach to a spin-polarized system, we calculate the threshold current, the polarization of the emitted light and other relevant quantities. [1] I. Zutic, J. Fabian, S. Das Sarma, Rev. Mod. Phys. 76, 323 (2004). [2] M. Holub et al., Phys. Rev. Lett. 98, 146603 (2007); J. Rudolph et al., Appl. Phys. Lett. 82, 4516 (2003).

  20. Control of visible harmonic generation using polarization in photonic crystal fibers

    Microsoft Academic Search

    F. G. Omenetto; Anatoly Efimov; Antoinette I. Taylor; J. C. Knight; W. Wadsworth; P. S. J. Russell

    2002-01-01

    We present the dependence of the generated visible radiation on the polarization state of the input pulse coupled into the photonic crystal fiber. We experimentally observe that the propagation of a pulse of fixed energy, yet polarized along different directions, yields different visible components at the output, suggesting polarization-dependent selectivity for phase-matching according to the input polarization state.

  1. Birefringence control of silica waveguides on Si and its application to a polarization-beam splitter\\/switch

    Microsoft Academic Search

    Masayuki Okuno; Akio Sugita; Kaname Jinguji; Masao Kawachi

    1994-01-01

    A novel polarization-beam splitter\\/switch with a Mach-Zehnder interferometer configuration was fabricated using a silica-based planar lightwave circuit (PLC) on a silicon substrate. The polarization-beam splitter\\/switch was realized by accurately controlling the waveguide birefringence and the phase state by laser trimming two kinds of stress-applying amorphous silicon film with widths of 50 ?m and 95 ?m. Fiber-waveguide-fiber insertion loss of 0.5

  2. Optically controlled polarizer using a ladder transition for high speed Stokesmetric Imaging and Quantum Zeno Effect based optical logic.

    PubMed

    Krishnamurthy, Subramanian; Wang, Y; Tu, Y; Tseng, S; Shahriar, M S

    2013-10-21

    We demonstrate an optically controlled polarizer at ~1323 nm using a ladder transition in a Rb vapor cell. The lower leg of the 5S(1/2),F = 1->5P(1/2),F = 1,2->6S(1/2),F = 1,2 transitions is excited by a Ti:Sapphire laser locked to a saturated absorption signal, representing the control beam. A tunable fiber laser at ~1323 nm is used to excite the upper leg of the transitions, representing the signal beam. When the control beam is linearly polarized, it produces an excitation of the intermediate level with a particular orientation of the angular momentum. Under ideal conditions, this orientation is transparent to the signal beam if it has the same polarization as the control beam and is absorbed when it is polarized orthogonally. We also present numerical simulations of the system using a comprehensive model which incorporates all the relevant Zeeman sub-levels in the system, and identify means to improve the performance of the polarizer. A novel algorithm to compute the evolution of large scale quantum system enabled us to perform this computation, which may have been considered too cumbersome to carry out previously. We describe how such a polarizer may serve as a key component for high-speed Stokesmetric imaging. We also show how such a polarizer, combined with an optically controlled waveplate, recently demonstrated by us, can be used to realize a high speed optical logic gate by making use of the Quantum Zeno Effect. Finally, we describe how such a logic gate can be realized at an ultra-low power level using a tapered nanofiber embedded in a vapor cell. PMID:24150297

  3. EB1, p150Glued, and Clasp1 control endothelial tubulogenesis through microtubule assembly, acetylation, and apical polarization.

    PubMed

    Kim, Dae Joong; Martinez-Lemus, Luis A; Davis, George E

    2013-04-25

    Vascular tube morphogenesis requires the establishment of endothelial cell (EC) apical-basal polarity in three-dimensional (3D) extracellular matrices. To date, there is little understanding of how EC polarity is controlled during these highly dynamic and rapid morphogenic events. We show that the microtubule tip complex proteins, end binding 1 (EB1), p150(Glued), and Clasp1, control human EC tube formation by (1) inducing microtubule assembly and asymmetric cytoskeletal polarization, whereby acetylated and detyrosinated tubulins distribute in a subapical membrane location and filamentous actin distributes basally; (2) increasing tubulin posttranslational modifications, including required acetylation events; and (3) regulating an EC lumen signaling cascade that involves membrane type 1 matrix metallopatrinase (MT1-MMP)-dependent proteolysis as well as Pak, Raf, and Erk kinases. Another regulator of this process is the microtubule stabilizing protein, tau, which binds p150(Glued) and similarly affects EC lumen formation by controlling the levels of acetylated and detyrosinated tubulins. Increased expression of the tubulin deacetylases, sirtuin 2, and histone deacetylase 6 (HDAC6), blocks EC tube formation and cytoskeletal polarization, while siRNA suppression of these deacetylases stimulates these events. Overall, this work reveals a fundamental role for microtubule tip complex proteins in coordinating microtubule assembly, posttranslational modifications including acetylation, and apical-basal cytoskeletal polarization to control the developing apical membrane surface during blood vessel tubulogenesis in 3D matrix environments. PMID:23444400

  4. Miro-1 Links Mitochondria and Microtubule Dynein Motors To Control Lymphocyte Migration and Polarity

    PubMed Central

    Morlino, Giulia; Barreiro, Olga; Baixauli, Francesc; Robles-Valero, Javier; González-Granado, José M.; Villa-Bellosta, Ricardo; Cuenca, Jesús; Sánchez-Sorzano, Carlos O.; Veiga, Esteban; Martín-Cófreces, Noa B.

    2014-01-01

    The recruitment of leukocytes to sites of inflammation is crucial for a functional immune response. In the present work, we explored the role of mitochondria in lymphocyte adhesion, polarity, and migration. We show that during adhesion to the activated endothelium under physiological flow conditions, lymphocyte mitochondria redistribute to the adhesion zone together with the microtubule-organizing center (MTOC) in an integrin-dependent manner. Mitochondrial redistribution and efficient lymphocyte adhesion to the endothelium require the function of Miro-1, an adaptor molecule that couples mitochondria to microtubules. Our data demonstrate that Miro-1 associates with the dynein complex. Moreover, mitochondria accumulate around the MTOC in response to the chemokine CXCL12/SDF-1?; this redistribution is regulated by Miro-1. CXCL12-dependent cell polarization and migration are reduced in Miro-1-silenced cells, due to impaired myosin II activation at the cell uropod and diminished actin polymerization. These data point to a key role of Miro-1 in the control of lymphocyte adhesion and migration through the regulation of mitochondrial redistribution. PMID:24492963

  5. Phosphorylation of LKB1/Par-4 Establishes Schwann Cell Polarity to Initiate and Control Myelin Extent

    PubMed Central

    Shen, Yun-An A.; Chen, Yan; Dao, Dang Q.; Mayoral, Sonia R.; Wu, Laiman; Meijer, Dies; Ullian, Erik M.; Chan, Jonah R.; Lu, Q. Richard

    2014-01-01

    The Schwann cell (SC)-axon interface represents a membrane specialization that integrates axonal signals to coordinate cytoskeletal dynamics resulting in myelination. Here we show that LKB1/Par-4 is asymmetrically localized to the SC-axon interface and colocalizes with the polarity protein Par-3. Using purified SCs and myelinating cocultures, we demonstrate that localization is dependent on the phosphorylation of LKB1 at serine-431. SC-specific deletion of LKB1 significantly attenuates developmental myelination, delaying the initiation and altering the myelin extent into adulthood, resulting in a 30% reduction in the conduction velocity along adult sciatic nerves. Phosphorylation of LKB1 by protein kinase A is essential to establish the asymmetric localization of LKB1 and Par-3 and rescues the delay in myelination observed in the SC-specific knockout of LKB1. Our findings suggest that SC polarity may coordinate multiple signaling complexes that couple SC-axon contact to the redistribution of specific membrane components necessary to initiate and control myelin extent. PMID:25255972

  6. Midline 1 controls polarization and migration of murine cytotoxic T cells

    PubMed Central

    Boding, Lasse; Hansen, Ann K; Nielsen, Morten M; Meroni, Germana; Braunstein, Thomas H; Woetmann, Anders; Ødum, Niels; Bonefeld, Charlotte M; Geisler, Carsten

    2014-01-01

    Midline 1 (MID1) is a microtubule-associated ubiquitin ligase that regulates protein phosphatase 2?A levels. Loss-of-function mutations in MID1 lead to the human X-linked Opitz G/BBB (OS) syndrome characterized by defective midline development during embryogenesis. We have recently shown that MID1 is strongly up-regulated in murine cytotoxic T lymphocytes (CTLs), and that it has a significant impact on exocytosis of lytic granules and the killing capacity of CTLs. The aims of the present study were to determine the localization of MID1 in migrating CTLs, and to investigate whether MID1 affects CTL polarization and migration. We found that MID1 mainly localizes to the uropod of migrating CTLs and that it has a substantial impact on CTL polarization and migration in vitro. Furthermore, analysis of contact hypersensitivity responses supported that MID1 controls effector functions of CTLs in hapten-challenged skin in vivo. These results provide significant new knowledge on the role of MID1 in CTL biology. PMID:25866633

  7. Polarization control in high power microwaves from a rectangular cross section gyrotron

    SciTech Connect

    Hochman, J.M.; Gilgenbach, R.M.; Jaynes, R.J.; Rintamaki, J.I.; Lau, Y.Y.; Spencer, T.A. [Univ. of Michigan, Ann Arbor, MI (United States)

    1997-12-31

    The authors summarize the results of experiments on a gyrotron utilizing rectangular-cross-section (RCS) interaction cavities. Current issues under investigation include polarization control as a function of magnetic field, power versus pulselength of microwave emission, and mode competition. The electron beam driver producing an annular beam is the Michigan Electron Long Beam Accelerator (MELBA). The annular e-beam is spun up into an axis-encircling beam by passing it through a magnetic cusp prior to entering the RCS interaction cavity. Initial experimental results show a high degree of polarization [P(TE{sub 10})/P(TE{sub 01}) = 30 or 1/30] as a function of cavity fields. Megawatt microwave output shifts from the fundamental mode, which dominates the next order mode by an order of magnitude, to the next order mode as the field is raised from 1.4 to 1.7 kGauss. Frequency measurements using microstrip bandpass filters and a superheterodyne mixer support this result as well as MAGIC simulations. MAGIC code simulations using various magnetic fields will be presented as well as results utilizing the E-gun code.

  8. Miro-1 links mitochondria and microtubule Dynein motors to control lymphocyte migration and polarity.

    PubMed

    Morlino, Giulia; Barreiro, Olga; Baixauli, Francesc; Robles-Valero, Javier; González-Granado, José M; Villa-Bellosta, Ricardo; Cuenca, Jesús; Sánchez-Sorzano, Carlos O; Veiga, Esteban; Martín-Cófreces, Noa B; Sánchez-Madrid, Francisco

    2014-04-01

    The recruitment of leukocytes to sites of inflammation is crucial for a functional immune response. In the present work, we explored the role of mitochondria in lymphocyte adhesion, polarity, and migration. We show that during adhesion to the activated endothelium under physiological flow conditions, lymphocyte mitochondria redistribute to the adhesion zone together with the microtubule-organizing center (MTOC) in an integrin-dependent manner. Mitochondrial redistribution and efficient lymphocyte adhesion to the endothelium require the function of Miro-1, an adaptor molecule that couples mitochondria to microtubules. Our data demonstrate that Miro-1 associates with the dynein complex. Moreover, mitochondria accumulate around the MTOC in response to the chemokine CXCL12/SDF-1?; this redistribution is regulated by Miro-1. CXCL12-dependent cell polarization and migration are reduced in Miro-1-silenced cells, due to impaired myosin II activation at the cell uropod and diminished actin polymerization. These data point to a key role of Miro-1 in the control of lymphocyte adhesion and migration through the regulation of mitochondrial redistribution. PMID:24492963

  9. Beam control of a 2D polarization maintaining fiber optic phased array with high-fiber count

    Microsoft Academic Search

    Jan E. Kansky; Charles X. Yu; Daniel V. Murphy; Scot E. J. Shaw; Ryan C. Lawrence; Charles Higgs

    2006-01-01

    We demonstrate, for the first time to our knowledge, successful beam control of a fiber optic phased array containing a large number of polarization maintaining fibers. As many as forty-eight fibers have been coherently combined via individual all-fiber phase modulators. The residual phase error is less than 1\\/30th of a wave. Results with both near-field interferometric control and target-in-the-loop control

  10. Highly efficient scheme for the implementation of optical controlled-Z gate via two-qubit polarization parity detector

    NASA Astrophysics Data System (ADS)

    Zhu, Meng-Zheng; Zhao, Chun-Ran; Ye, Liu

    2012-03-01

    A new scheme is proposed to direct implement the optical two-qubit controlled-Z gate with the two-qubit polarization parity detector [Lin, et al., Phys. Rev. A. 80 (2009) 042311] based on weak cross-Kerr nonlinearity. The distinct advantage of the present scheme in contrast with the existing schemes is that the two-qubit polarization parity detector with classical information feed-forward allows the efficiency of our optical controlled-Z gate to be enormously enhanced due to avoiding effectively the photon bunching effects. Therefore, the present scheme is more efficient and more convenient than others in the applications of quantum communication.

  11. Coherent Electronic Wave Packet Motion in C60 Controlled by the Waveform and Polarization of Few-Cycle Laser Fields

    NASA Astrophysics Data System (ADS)

    Li, H.; Mignolet, B.; Wachter, G.; Skruszewicz, S.; Zherebtsov, S.; Süßmann, F.; Kessel, A.; Trushin, S. A.; Kling, Nora G.; Kübel, M.; Ahn, B.; Kim, D.; Ben-Itzhak, I.; Cocke, C. L.; Fennel, T.; Tiggesbäumker, J.; Meiwes-Broer, K.-H.; Lemell, C.; Burgdörfer, J.; Levine, R. D.; Remacle, F.; Kling, M. F.

    2015-03-01

    Strong laser fields can be used to trigger an ultrafast molecular response that involves electronic excitation and ionization dynamics. Here, we report on the experimental control of the spatial localization of the electronic excitation in the C60 fullerene exerted by an intense few-cycle (4 fs) pulse at 720 nm. The control is achieved by tailoring the carrier-envelope phase and the polarization of the laser pulse. We find that the maxima and minima of the photoemission-asymmetry parameter along the laser-polarization axis are synchronized with the localization of the coherent electronic wave packet at around the time of ionization.

  12. 0.9W compact UV pulsed lasers using high-power VCSEL array side-pumping

    NASA Astrophysics Data System (ADS)

    Chen, Tong; Xu, Bing; Van Leeuwen, Robert; Zhao, Pu; Seurin, Jean-Francois; Xu, Guoyang; Miglo, Alexander; Wang, Qing; Ghosh, Chuni

    2013-02-01

    A compact UV pulsed laser pumped by high-power two-dimensional arrays of vertical-cavity surface-emitting lasers (VCSELs) was presented. A passively Q-switched 1064-nm Nd:YAG laser was side-pumped by kW-class 808-nm VCSEL pump modules and the output pulses were frequency quadrupled to 266-nm. 10-ns, 0.68-mJ UV pulsed output was obtained at 1.33k-Hz repetition rate. The average UV power is < 0.9-W. This VCSEL pumped high power UV laser source provides a reliable, low-cost and low-profile solution for military and commercial applications including remote sensing, laser processing and spectroscopy.

  13. Control of tumourigenesis by the Scribble/Dlg/Lgl polarity module.

    PubMed

    Humbert, P O; Grzeschik, N A; Brumby, A M; Galea, R; Elsum, I; Richardson, H E

    2008-11-24

    The neoplastic tumour suppressors, Scribble, Dlg and Lgl, originally discovered in the vinegar fly Drosophila melanogaster, are currently being actively studied for their potential role in mammalian tumourigenesis. In Drosophila, these tumour suppressors function in a common genetic pathway to regulate apicobasal cell polarity and also play important roles in the control of cell proliferation, survival, differentiation and in cell migration/invasion. The precise mechanism by which Scribble, Dlg and Lgl function is not clear; however, they have been implicated in the regulation of signalling pathways, vesicle trafficking and in the Myosin II-actin cytoskeleton. We review the evidence for the involvement of Scribble, Dlg, and Lgl in cancer, and how the various functions ascribed to these tumour suppressors in Drosophila and mammalian systems may impact on the process of tumourigenesis. PMID:19029932

  14. A Permanent Magnet Hall Thruster for Pulsed Orbit Control of Lunar Polar Satellites

    NASA Astrophysics Data System (ADS)

    Silva Moraes, Brunno; Ferreira, José Leonardo; Soares Ferreira, Ivan; Cabo Winter, Othon; Cardozo Mourão, Décio

    2014-05-01

    Future Moon missions devoted to Lunar surface remote sensing, for example, will require very fine and accurate orbit control. It is well known that Lunar satellites in polar orbits will suffer a high increase on the eccentricity due to the gravitational perturbation of the Earth. Without proper orbit correction the satellite lifetime will decrease and end up in a collision with the Moon surface. It is pointed out by many authors that this effect is a natural consequence of the Lidov-Kozai resonance. We studied different arcs of active lunar satellite propulsion, centered on the orbit apoapsis or periapsis, in order to be able to introduce a correction of the eccentricity at each cycle. The proposed method is based on an approach intended to keep the orbital eccentricity of the satellite at low values.

  15. Blending of reactive prepolymers to control the morphology and polarity of polyglycidol based microgels.

    PubMed

    Schulte, B; Rahimi, K; Keul, H; Demco, D E; Walther, A; Möller, M

    2015-02-01

    The compartmentalization of microgels is a challenging task for synthetic polymer chemistry. Although the complexation with low molecular weight compounds or the use of microfluidic techniques offer attractive possibilities for other length scales, it is difficult to implement compartments in the mesoscale range of 10-100 nm. Herein we show how simple blending of reactive prepolymers is suitable to design new microgel morphologies with tailored compartments. We use poly(EEGE)-block-poly(AGE) as crosslinkable, pro-hydrophilic prepolymer in blends with varying amounts of crosslinkable, yet hydrophobic poly(THF-stat-AllylEHO) or inert and hydrophobic polystyrene, and crosslink the allyl functional prepolymer(s) in a thiol-ene click-type reaction after miniemulsification. Our strategy shows how arrested versus free nanophase separation can be used to control easily the morphology and polarity of microgel particles. PMID:25515704

  16. Electric field-induced coherent control in GaAs: polarization dependence and electrical measurement [Invited].

    PubMed

    Wahlstrand, J K; Zhang, H; Choi, S B; Sipe, J E; Cundiff, S T

    2011-11-01

    A static electric field enables coherent control of the photoexcited carrier density in a semiconductor through the interference of one- and two-photon absorption. An experiment using optical detection is described. The polarization dependence of the signal is consistent with a calculation using a 14-band k · p model for GaAs. We also describe an electrical measurement. A strong enhancement of the phase-dependent photocurrent through a metal-semiconductor-metal structure is observed when a bias of a few volts is applied. The dependence of the signal on bias and laser spot position is studied. The field-induced enhancement of the signal could increase the sensitivity of semiconductor-based carrier-envelope phase detectors, useful in stabilizing mode-locked lasers for use in frequency combs. PMID:22109135

  17. Electrical and polarization controlled bistability and oscillations in photorefractive birefringent Fabry-Perot resonators

    NASA Astrophysics Data System (ADS)

    Tenev, T. K.; Zartov, G. D.; Peyeva, R. A.; Thienpont, H.; Veretennicoff, I.; Panajotov, K. P.

    2004-02-01

    We theoretically investigate polarization and intensity all-optical bi- and tri-stability in interference structures that include both a birefringent LiNbO 3 layer of varying crystallographic orientation and an absorbing layer. The origin of this bi- and multistability is the thermo-optical nonlinearity present in the structures. Electrically induced bistable response, electrical control of the bi- and tristable action and regenerative oscillations are demonstrated using the electro-optical and the photorefractive properties of the LiNbO 3 crystal. The unstable dynamical behaviour is explained heuristically as the result of competing nonlinearities. We also observed a mirror image of the multistable curve for specific angles of the obliquely incident input beam.

  18. Polarization control and sensing with two-dimensional coupled photonic crystal microcavity arrays

    E-print Network

    Altug, H; Altug, Hatice; Vuckovic, Jelena

    2004-01-01

    We have experimentally studied polarization properties of the two-dimensional coupled photonic crystal microcavity arrays and observed a strong polarization dependence of the reflection and transmission of light from the structure, as well as a strong polarization conversion. These effects can be employed in building miniaturized polarizing optical components and bio-chemical sensors. Our preliminary experimental results on chemical sensing with these structures are also presented.

  19. Design and analysis of VCSEL-based two-dimension wavelength converter by using developed TLLM

    NASA Astrophysics Data System (ADS)

    Liu, Hairong; Shum, Ping; Kao, Ming-Seng

    2004-05-01

    We develop a complete two-dimension transmission line laser model (TLLM) to analyze the proposed twodimension vertical cavity surface emission laser (VCSEL) based wavelength converter. Modified connecting matrices are used to model the Bragg reflectors. The longitudinal variations of carrier density, photon density and the amplified spontaneous emission noise are taken into account. Therefore, extinction ratio, frequency chirping, optical pulse patterns and dynamic characteristics can be accurately estimated. In this paper, extinction ratio and frequency chirp of the output signal have been calculated for various parameters such as wavelength, input signal power, cavity diameter and facet reflectivity.

  20. Two-channels MGDM transmission over GI-MMF with using low-cost VCSEL lasers

    NASA Astrophysics Data System (ADS)

    Kowalczyk, Marcin

    2014-05-01

    The paper presents the experimental and theoretical investigations for a 2 x 2 MIMO optical communication system based on mode group diversion multiplexing over the 200m GI-MM fiber. As light sources at the system the low-cost VCSEL lasers were used. A coupling of the optical signals into the fiber at the transmitter side was done by using only a commercial optical coupler. In analogical way a `combined' optical signal which was present on the fiber output was divided into two separate optical paths by using second optical coupler acting as a splitter.

  1. Distinct Roles for Two G?–G? Interfaces in Cell Polarity Control by a Yeast Heterotrimeric G Protein

    PubMed Central

    Strickfaden, Shelly C.

    2008-01-01

    Saccharomyces cerevisiae mating pheromones trigger dissociation of a heterotrimeric G protein (G???) into G?-guanosine triphosphate (GTP) and G??. The G?? dimer regulates both mitogen-activated protein (MAP) kinase cascade signaling and cell polarization. Here, by independently activating the MAP kinase pathway, we studied the polarity role of G?? in isolation from its signaling role. MAP kinase signaling alone could induce cell asymmetry but not directional growth. Surprisingly, active G??, either alone or with G?-GTP, could not organize a persistent polarization axis. Instead, following pheromone gradients (chemotropism) or directional growth without pheromone gradients (de novo polarization) required an intact receptor–G??? module and GTP hydrolysis by G?. Our results indicate that chemoattractant-induced cell polarization requires continuous receptor–G??? communication but not modulation of MAP kinase signaling. To explore regulation of G?? by G?, we mutated G? residues in two structurally distinct G?–G? binding interfaces. Polarity control was disrupted only by mutations in the N-terminal interface, and not the Switch interface. Incorporation of these mutations into a G?–G? fusion protein, which enforces subunit proximity, revealed that Switch interface dissociation regulates signaling, whereas the N-terminal interface may govern receptor–G??? coupling. These findings raise the possibility that the G??? heterotrimer can function in a partially dissociated state, tethered by the N-terminal interface. PMID:17978098

  2. DOI: 10.1002/adma.200801190 Surface Polarity and Shape-Controlled Synthesis of ZnO

    E-print Network

    Rogers, John A.

    DOI: 10.1002/adma.200801190 Surface Polarity and Shape-Controlled Synthesis of ZnO Nanostructures in nanotechnology, there has been tremendous interest in ZnO-related nanomaterials because ZnO is a wide band electronics,[4] sensors,[5] and transdu- cers.[6] ZnO crystals have a noncentral symmetric wurtzite structure

  3. Collective Coherent Control: Synchronization of Polarization in Ferroelectric PbTiO3 by Shaped THz Fields

    E-print Network

    Rappe, Andrew M.

    Collective Coherent Control: Synchronization of Polarization in Ferroelectric PbTiO3 by Shaped THz terahertz (THz) fields can be used to move ions in ferroelectric crystals from their positions in an initial structural change. We show through numerical simulations that tem- porally shaped THz fields can be used

  4. Poldip2 controls vascular smooth muscle cell migration by regulating focal adhesion turnover and force polarization.

    PubMed

    Datla, Srinivasa Raju; McGrail, Daniel J; Vukelic, Sasa; Huff, Lauren P; Lyle, Alicia N; Pounkova, Lily; Lee, Minyoung; Seidel-Rogol, Bonnie; Khalil, Mazen K; Hilenski, Lula L; Terada, Lance S; Dawson, Michelle R; Lassègue, Bernard; Griendling, Kathy K

    2014-10-01

    Polymerase-?-interacting protein 2 (Poldip2) interacts with NADPH oxidase 4 (Nox4) and regulates migration; however, the precise underlying mechanisms are unclear. Here, we investigated the role of Poldip2 in focal adhesion turnover, as well as traction force generation and polarization. Poldip2 overexpression (AdPoldip2) in vascular smooth muscle cells (VSMCs) impairs PDGF-induced migration and induces a characteristic phenotype of long cytoplasmic extensions. AdPoldip2 also prevents the decrease in spreading and increased aspect ratio observed in response to PDGF and slightly impairs cell contraction. Moreover, AdPoldip2 blocks focal adhesion dissolution and sustains H2O2 levels in focal adhesions, whereas Poldip2 knockdown (siPoldip2) significantly decreases the number of focal adhesions. RhoA activity is unchanged when focal adhesion dissolution is stimulated in control cells but increases in AdPoldip2-treated cells. Inhibition of RhoA blocks Poldip2-mediated attenuation of focal adhesion dissolution, and overexpression of RhoA or focal adhesion kinase (FAK) reverses the loss of focal adhesions induced by siPoldip2, indicating that RhoA and FAK mediate the effect of Poldip2 on focal adhesions. Nox4 silencing prevents focal adhesion stabilization by AdPoldip2 and induces a phenotype similar to siPoldip2, suggesting a role for Nox4 in Poldip2-induced focal adhesion stability. As a consequence of impaired focal adhesion turnover, PDGF-treated AdPoldip2 cells are unable to reduce and polarize traction forces, a necessary first step in migration. These results implicate Poldip2 in VSMC migration via regulation of focal adhesion turnover and traction force generation in a Nox4/RhoA/FAK-dependent manner. PMID:25063792

  5. Ferroelectricity and polarity control in solid-state flip-flop supramolecular rotators

    NASA Astrophysics Data System (ADS)

    Akutagawa, Tomoyuki; Koshinaka, Hiroyuki; Sato, Daisuke; Takeda, Sadamu; Noro, Shin-Ichiro; Takahashi, Hiroyuki; Kumai, Reiji; Tokura, Yoshinori; Nakamura, Takayoshi

    2009-04-01

    Molecular rotation has attracted much attention with respect to the development of artificial molecular motors, in an attempt to mimic the intelligent and useful functions of biological molecular motors. Random motion of molecular rotators-for example the 180? flip-flop motion of a rotatory unit-causes a rotation of the local structure. Here, we show that such motion is controllable using an external electric field and demonstrate how such molecular rotators can be used as polarization rotation units in ferroelectric molecules. In particular, m-fluoroanilinium forms a hydrogen-bonding assembly with dibenzo[18]crown-6, which was introduced as the counter cation of [Ni(dmit)2]- anions (dmit2-=2-thioxo-1,3-dithiole-4,5-dithiolate). The supramolecular rotator of m-fluoroanilinium exhibited dipole rotation by the application of an electric field, and the crystal showed a ferroelectric transition at 348K. These findings will open up new strategies for ferroelectric molecules where a chemically designed dipole unit enables control of the nature of the ferroelectric transition temperature.

  6. Solar wind control of the open magnetosphere: Comparison of GGS/polar images and theory

    NASA Astrophysics Data System (ADS)

    Urquhart, Andrew Lee

    This investigation explores the connection between the open polar cap magnetic flux ?PCF and interplanetary conditions. ? PCF is determined from GGS/Polar VIS Earth Camera far ultraviolet observations of the aurora borealis. Observations from the GGS/Wind SWE and MFI instruments are used to characterize the interplanetary conditions. Additional observations from the IMP-8 PLA and MAG instruments are used to evaluate solar wind propagation time delay estimation methods so that the GGS/Wind observations can be better associated with the GGS/Polar observations. This allows the GGS/Wind observations to be used to estimate the polar cap potential ?PCP values associated with the GGS/Polar ?PCF values. Statistical methods are applied to determine a proxy relationship between ?PCP and ?PCF. The Rice Field Model (RFM) is modified to accept ? PCF as a configuration parameter, and RFM polar caps are produced using ? PCF determined both directly from the GGS/Polar images and by the proxy relationship from the GGS/Wind data. The RFM is able to produce polar caps with the same areas and open magnetic fluxes as the GGS/Polar observations, but the agreement in the polar cap shapes and locations leaves opportunities for further improvements.

  7. /III-V semiconductor broadband distributed Bragg reflectors for long-wavelength VCSEL and SESAM devices

    NASA Astrophysics Data System (ADS)

    Koeninger, Anna; Boehm, Gerhard; Meyer, Ralf; Amann, Markus-Christian

    2014-12-01

    Semiconductor devices such as vertical-cavity surface-emitting lasers (VCSELs) or semiconductor-saturable absorber mirrors (SESAMs) require high-reflection mirrors. Moreover, in VCSELs, it is beneficial to have a crystalline mirror, which is as thin as possible in order to ensure a high thermal conductivity for efficient heat-sinking of the laser. On the other hand, the wavelength tuning range of a SESAM is limited by the reflection bandwidth of its distributed Bragg reflector (DBR). Thus, broadband mirrors are preferable here. This paper reports a three-pair DBR grown by molecular beam epitaxy (MBE) using BaCaF2 and GaAs on a GaAs (100) substrate. Due to the high ratio in refractive indices of GaAs and the group-IIa-fluorides, high-reflectivity mirrors and wide bandwidths can be obtained with low total thicknesses. We also investigated growth and stability of the material BaCaF2, as well as its thermal conductivity both as single layer and Bragg reflector. Observed peeling of the layers could be avoided by implementing a fluorine treatment previous to the BaCaF2 growth.

  8. Polar — a potent Polyoxin B compound for controlling powdery mildews in apple and nectarine trees, and grapevines

    Microsoft Academic Search

    M Reuveni; H Cohen; T Zahavi; A Venezian

    2000-01-01

    The efficacy of Polar, a polyoxin B compound, in controlling powdery mildews was evaluated in commercial orchards and a vineyard in 1997–1999 in the Golan region of Israel. Foliar sprays of 0.0125–0.05% (v\\/v) suspensions of Polar [1-{5-N-(5-O-carbomonyl-2-amino-2-deoxy-l-xylonyl)-5-amino-5-deoxy-?-d-allofur anosyl uronic acid}-5-hydroxymethyluracil], sulfur, the new strobilurin fungicide Kresoxim-methyl, and sterol inhibitor (SI) fungicides inhibited the development of the powdery mildew fungi on

  9. Parametric polarization pulse shaping demonstrated for optimal control of NaK.

    PubMed

    Weber, Stefan M; Plewicki, Mateusz; Weise, Fabian; Lindinger, Albrecht

    2008-05-01

    We present a routine for calculating and producing customized/parametric femtosecond laser pulses for investigating molecular processes involving the polarization. It is applied on the ionization of NaK molecules by feedback-loop optimization using the recently introduced double-pass "serial setup" that is capable of phase, amplitude, and polarization modulation. The temporal subpulse encoding uses the parameters distance, intensity, zero order spectral phase, and polarization state. PMID:18465921

  10. The planar cell polarity effector protein Wdpcp (Fritz) controls epithelial cell cortex dynamics via septins and actomyosin.

    PubMed

    Park, Tae Joo; Kim, Su Kyoung; Wallingford, John B

    2015-01-01

    Planar cell polarity (PCP) signaling controls polarized behaviors in diverse tissues, including the collective cell movements of gastrulation and the planar polarized beating of motile cilia. A major question in PCP signaling concerns the mechanisms linking this signaling cascade with more general cytoskeletal elements to drive polarized behavior. Previously, we reported that the PCP effector protein Wdpcp (formerly known as Fritz) interacts with septins and is critical for collective cell migration and cilia formation. Here, we report that Wdpcp is broadly involved in maintaining cortical tension in epithelial cells. In vivo 3D time-lapse imaging revealed that Wdpcp is necessary for basolateral plasma membrane stability in epithelial tissues, and we further show that Wdpcp controls cortical septin localization to maintain cortical rigidity in mucociliary epithelial cells. Finally, we show that Wdpcp acts via actomyosin to maintain balanced cortical tension in the epithelium. These data suggest that, in addition to its role in controlling plasma membrane dynamics in collective mesenchymal cell movements, Wdpcp is also essential for normal cell cortex stability during epithelial homeostasis. PMID:25436430

  11. Carrierless amplitude phase modulation of VCSEL with 4 bit/s/Hz spectral efficiency for use in WDM-PON.

    PubMed

    Rodes, Roberto; Wieckowski, Marcin; Pham, Thang Tien; Jensen, Jesper Bevensee; Turkiewicz, Jarek; Siuzdak, Jerzy; Monroy, Idelfonso Tafur

    2011-12-19

    We experimentally demonstrate successful performance of VCSEL-based WDM link supporting advanced 16-level carrierless amplitude/phase modulation up to 1.25 Gbps, over 26 km SSMF with spectral efficiency of 4 bit/s/Hz for application in high capacity PONs. PMID:22274239

  12. A fundamental mode Nd:GdVO4 laser pumped by a large aperture 808 nm VCSEL

    NASA Astrophysics Data System (ADS)

    Hao, Y. Q.; Ma, J. L.; Yan, C. L.; Liu, G. J.; Ma, X. H.; Gong, J. F.; Feng, Y.; Wei, Z. P.; Wang, Y. X.; Zhao, Y. J.

    2013-05-01

    A fundamental mode Nd:GdVO4 laser pumped by a vertical cavity surface emitting laser (VCSEL) is experimentally demonstrated. The VCSEL has a circular output-beam which makes it easier for it to be directly coupled to a Nd:GdVO4 microcrystal. In our research, a large aperture 808 nm VCSEL, with a multi-ring-shaped aperture (MRSA) and an almost Gaussian-shaped far-field profile, is used as the pumping source. Experimental results for the Nd:GdVO4 laser pumped by the VCSEL are presented. The maximum output peak power of 0.754 W is obtained under a pump peak power of 1.3 W, and the corresponding opto-optic conversion efficiency is 58.1%. The average slope efficiency is 65.8% from the threshold pump power of 0.2 W to the pump power of 1.3 W. The laser beam quality factors are measured to be {M}x2=1.2 0 and {M}y2=1.1 5.

  13. Recorded low power dissipation of 0.14 mW\\/Gbps in 1060 nm VCSELs for “Green” optical interconnection

    Microsoft Academic Search

    Suguru Imai; Keishi Takaki; Hitoshi Shimizu; Yasumasa Kawakita; Tomohiro Takagi; Koji Hiraiwa; Hiroshi Shimizu; Norihiro Iwai; Naoki Tsukiji; Akihiko Kasukawa

    2010-01-01

    Extremely low power dissipation of 0.14 mW\\/Gbps at 10 Gbps operation with as small as 75 mVp-p of modulation amplitude has been achieved in carefully designed InGaAs\\/GaAs-MQW 1060 nm VCSELs employed double intra-cavity structure.

  14. Polarization-independent electro-optic modulator based on PMNT electrically-controlled birefringence effect and Sagnac interferometer

    NASA Astrophysics Data System (ADS)

    Zhang, Xuejiao; Ye, Qing; Cai, Haiwen; Qu, Ronghui

    2014-04-01

    A novel polarization-independent electro-optic modulator is proposed and investigated by using the electrically-controlled birefringence effect of transparent lead magnesium niobate titanate (PMNT) electro-optic ceramic and a Sagnac interferometer structure. The PMNT electro-optic ceramic is used as a phase retarder for two counter-propagating waves in which their polarization directions are adjusted to parallel and vertical to the electrical-field vector respectively. Then the output light intensity from the Sagnac interferometer will be modulated completely with the driven electrical signal and it is independent with the polarization direction of incident light. The extinction ratio is more than 21 dB. This modulated device will be very appropriate as a Q-switch or optical attenuator in the high power laser system.

  15. Quantitative analysis of polarization-controlled tip-enhanced Raman imaging through the evaluation of the tip dipole.

    PubMed

    Mino, Toshihiro; Saito, Yuika; Verma, Prabhat

    2014-10-28

    Polarization analysis in tip-enhanced Raman spectroscopy (TERS) is of tremendous advantage, as it allows one to study highly directional intrinsic properties of a sample at the nanoscale. However, neither evaluation nor control of the polarization properties of near-field light in TERS is as straightforward as in usual far-field illumination, because of the random metallic nanostructure attached to the tip apex. In this study, we have developed a method to successfully analyze the polarization of near-field light in TERS from the scattering pattern produced by the induced dipole in the metallic tip. Under dipole approximation, we measured the image of the dipole at a plane away from the focal plane, where the information about the direction of the dipole oscillation was intact. The direction of the dipole oscillation was determined from the defocused pattern, and then the polarization of near-field light was evaluated from the oscillation direction by calculating the intensity distribution of near-field light through Green's function. After evaluating the polarization of some fabricated tips, we used those tips to measure TERS images from single-walled carbon nanotubes and confirmed that the contrast of the TERS image depended on the oscillation direction of the dipole, which were also found in excellent agreement with the calculated TERS images, verifying that the polarization of the near-field was quantitatively estimated by our technique. Our technique would lead to better quantitative analysis in TERS imaging with consideration of polarization impact, giving a better understanding of the behavior of nanomaterials. PMID:25171468

  16. High-efficiency broadband meta-hologram with polarization-controlled dual images.

    PubMed

    Chen, Wei Ting; Yang, Kuang-Yu; Wang, Chih-Ming; Huang, Yao-Wei; Sun, Greg; Chiang, I-Da; Liao, Chun Yen; Hsu, Wei-Lun; Lin, Hao Tsun; Sun, Shulin; Zhou, Lei; Liu, Ai Qun; Tsai, Din Ping

    2014-01-01

    Holograms, the optical devices to reconstruct predesigned images, show many applications in our daily life. However, applications of hologram are still limited by the constituent materials and therefore their working range is trapped at a particular electromagnetic region. In recent years, the metasurfaces, an array of subwavelength antenna with varying sizes, show the abilities to manipulate the phase of incident electromagnetic wave from visible to microwave frequencies. Here, we present a reflective-type and high-efficiency meta-hologram fabricated by metasurface for visible wavelength. Using gold cross nanoantennas as building blocks to construct our meta-hologram devices with thickness ? ?/4, the reconstructed images of meta-hologram show polarization-controlled dual images with high contrast, functioning for both coherent and incoherent light sources within a broad spectral range and under a wide range of incidence angles. The flexibility demonstrated here for our meta-hologram paves the road to a wide range of applications related to holographic images at arbitrary electromagnetic wave region. PMID:24329425

  17. Efficiency optimization and analysis of 808nm VCSELs with a full electro-thermal-optical numerical model

    NASA Astrophysics Data System (ADS)

    Engelhardt, Andreas P.; Kolb, Johanna S.; Roemer, Friedhard; Weichmann, Ulrich; Moench, Holger; Witzigmann, Bernd

    2015-03-01

    A high electro-optical conversion efficiency of a VCSEL (Vertical-Cavity Surface-Emitting Lasers) is one of the key requirements for their application in high power systems for heating, illumination and pumping applications. The substantial amount of degrees of freedom in the epitaxial and structural design of a VCSEL demands numerical guidance in form of technology computer aided design (TCAD) modeling for a straight forward and successful optimization of the devices. We set up a full electro-thermal optical model for the simulation of VCSEL devices. The electro-thermal part of the simulation follows a drift-diffusion model complemented by a customized, energy resolved, semi-classical carrier capture theory in the QW regions. Optical modes, eigensolutions of the vectorial electromagnetic wave equation, stem from a finite element vectorial solver. The electro-thermal and optical models are linked via the photon-rate equation using QW gain spectra (screened Hartree-Fock approximation) and iterated to self-consistency in a Gummel-type iteration scheme. For comparison and calibration, experimental reference data was extracted from oxide-confined, top-emitting VCSEL devices with an emission wavelength of 808 nm. Our simulations are in good agreement with the electro-optical characteristics of the experimental reference. With the calibrated, microscopic model, routes of design adjustment for efficiency optimization are explored. Exemplarily, the maximum VCSEL efficiency of the simulated reference design increases by 10% (absolute) when free hole absorption is switched off. Accordingly, with the combination of an electro-thermal and optical description, a balancing of the tradeoffs of pDBR doping towards reduced free carrier absorption results in a noteworthy efficiency improvement which is validated with experimental data.

  18. The Hippo pathway controls polar cell fate through Notch signaling during Drosophila oogenesis

    Microsoft Academic Search

    Hsi-Ju Chen; Chi-Ming Wang; Tsu-Wei Wang; Gwo-Jen Liaw; Ta-Hsing Hsu; Tzu-Huai Lin; Jenn-Yah Yu

    2011-01-01

    During Drosophila oogenesis, the somatic follicle cells form an epithelial layer surrounding the germline cells to form egg chambers. In this process, follicle cell precursors are specified into polar cells, stalk cells, and main-body follicle cells. Proper specification of these three cell types ensures correct egg chamber formation and polarization of the anterior–posterior axis of the germline cells. Multiple signaling

  19. Control of the Polarization of a Vacuum-Ultraviolet, High-Gain, Free-Electron Laser

    NASA Astrophysics Data System (ADS)

    Allaria, Enrico; Diviacco, Bruno; Callegari, Carlo; Finetti, Paola; Mahieu, Benoît; Viefhaus, Jens; Zangrando, Marco; De Ninno, Giovanni; Lambert, Guillaume; Ferrari, Eugenio; Buck, Jens; Ilchen, Markus; Vodungbo, Boris; Mahne, Nicola; Svetina, Cristian; Spezzani, Carlo; Di Mitri, Simone; Penco, Giuseppe; Trovó, Mauro; Fawley, William M.; Rebernik, Primoz R.; Gauthier, David; Grazioli, Cesare; Coreno, Marcello; Ressel, Barbara; Kivimäki, Antti; Mazza, Tommaso; Glaser, Leif; Scholz, Frank; Seltmann, Joern; Gessler, Patrick; Grünert, Jan; De Fanis, Alberto; Meyer, Michael; Knie, André; Moeller, Stefan P.; Raimondi, Lorenzo; Capotondi, Flavio; Pedersoli, Emanuele; Plekan, Oksana; Danailov, Miltcho B.; Demidovich, Alexander; Nikolov, Ivaylo; Abrami, Alessandro; Gautier, Julien; Lüning, Jan; Zeitoun, Philippe; Giannessi, Luca

    2014-10-01

    The two single-pass, externally seeded free-electron lasers (FELs) of the FERMI user facility are designed around Apple-II-type undulators that can operate at arbitrary polarization in the vacuum ultraviolet-to-soft x-ray spectral range. Furthermore, within each FEL tuning range, any output wavelength and polarization can be set in less than a minute of routine operations. We report the first demonstration of the full output polarization capabilities of FERMI FEL-1 in a campaign of experiments where the wavelength and nominal polarization are set to a series of representative values, and the polarization of the emitted intense pulses is thoroughly characterized by three independent instruments and methods, expressly developed for the task. The measured radiation polarization is consistently >90 % and is not significantly spoiled by the transport optics; differing, relative transport losses for horizontal and vertical polarization become more prominent at longer wavelengths and lead to a non-negligible ellipticity for an originally circularly polarized state. The results from the different polarimeter setups validate each other, allow a cross-calibration of the instruments, and constitute a benchmark for user experiments.

  20. Vesicular sorting controls the polarity of expanding membranes in the C. elegans intestine

    PubMed Central

    Zhang, Hongjie; Kim, Ahlee; Abraham, Nessy; Khan, Liakot A.; Göbel, Verena

    2013-01-01

    Biological tubes consist of polarized epithelial cells with apical membranes building the central lumen and basolateral membranes contacting adjacent cells or the extracellular matrix. Cellular polarity requires distinct inputs from outside the cell, e.g., the matrix, inside the cell, e.g., vesicular trafficking and the plasma membrane and its junctions.1 Many highly conserved polarity cues have been identified, but their integration during the complex process of polarized tissue and organ morphogenesis is not well understood. It is assumed that plasma-membrane-associated polarity determinants, such as the partitioning-defective (PAR) complex, define plasma membrane domain identities, whereas vesicular trafficking delivers membrane components to these domains, but lacks the ability to define them. In vitro studies on lumenal membrane biogenesis in mammalian cell lines now indicate that trafficking could contribute to defining membrane domains by targeting the polarity determinants, e.g., the PARs, themselves.2 This possibility suggests a mechanism for PARs’ asymmetric distribution on membranes and places vesicle-associated polarity cues upstream of membrane-associated polarity determinants. In such an upstream position, trafficking might even direct multiple membrane components, not only polarity determinants, an original concept of polarized plasma membrane biogenesis3,4that was largely abandoned due to the failure to identify a molecularly defined intrinsic vesicular sorting mechanism. Our two recent studies on C. elegans intestinal tubulogenesis reveal that glycosphingolipids (GSLs) and the well-recognized vesicle components clathrin and its AP-1 adaptor are required for targeting multiple apical molecules, including polarity regulators, to the expanding apical/lumenal membrane.5,6 These findings support GSLs’ long-proposed role in in vivo polarized epithelial membrane biogenesis and development and identify a novel function in apical polarity for classical post-Golgi vesicle components. They are also compatible with a vesicle-intrinsic sorting mechanism during membrane biogenesis and suggest a model for how vesicles could acquire apical directionality during the assembly of the functionally critical polarized lumenal surfaces of epithelial tubes. PMID:24058862

  1. Controlled quantum key distribution with three-photon polarization-entangled states via the collective noise channel

    SciTech Connect

    Dong Li; Xiu Xiaoming, E-mail: xiuxiaomingdl@126.com [Dalian University of Technology, School of Physics and Optoelectronic Technology (China); Gao Yajun [Bohai University, Department of Physics, College of Mathematics and Physics (China); Yi, X. X., E-mail: yixx@dlut.edu.cn [Dalian University of Technology, School of Physics and Optoelectronic Technology (China)

    2011-10-15

    Using three-photon polarization-entangled GHZ states or W states, we propose controlled quantum key distribution protocols for circumventing two main types of collective noise, collective dephasing noise, or collective rotation noise. Irrespective of the number of controllers, a three-photon state can generate a one-bit secret key. The storage technique of quantum states is dispensable for the controller and the receiver, and it therefore allows performing the process in a more convenient mode. If the photon cost in a security check is disregarded, then the efficiency theoretically approaches unity.

  2. Do large impact basins in the Southern Hemisphere of Mars control the distribution of polar structures and deposits?

    NASA Technical Reports Server (NTRS)

    Frey, Herbert; Reidy, Anne-Marie

    1992-01-01

    Among the problems in Martian geology are the cause of the off-axis and asymmetric distribution of the southern polar layered terrain and residual ice deposits and the cause of the orientation of scarps, valleys, and reentrant canyons that occur. A problem region is the small number of large (D greater than 500) impact basins seen in the relatively well preserved cratered terrain of the south polar region. This region was mapped in detail, searching for evidence of ancient, highly degraded impact basins for two reasons: To determine whether the apparent absence of large impact basins is due to incomplete mapping and recognition or a fundamental characteristic of the Martian crust related to the origin of the Martian crustal dichotomy, and whether ancient impact basins exert some control on the distribution of volcanic and polar deposits in the Southern Hemisphere and on the topography on which these deposits lie. The possible influence is examined of the candidate basins in localizing the asymmetric distribution of polar deposits and in controlling the orientation of structures found within these deposits.

  3. Small signal and noise circuit model of vertical-cavity surface-emitting laser (VCSEL) arrays for short range optomicrowave links

    Microsoft Academic Search

    A. Rissons; J. Perchoux; J.-C. Mollier

    2003-01-01

    A circuit model of a vertical-cavity surface-emitting laser (VCSEL) array and its experimental validation are presented in this paper. This model describes all optoelectronic phenomena including relative intensity noise (RIN) and electrical crosstalk.

  4. Optimal radii of photonic crystal holes within DBR mirrors in long wavelength VCSEL.

    PubMed

    Czyszanowski, Tomasz; Dems, Maciej; Thienpont, Hugo; Panajotov, Krassimir

    2007-02-01

    The modal characteristics of a Photonic-Crystal Vertical-Cavity Surface-Emitting diode Laser (PC-VCSEL) have been investigated. Photonic crystal structure, realized by a regular net of air holes within the layers, has been etched in the upper DBR mirror. An advanced three-dimensional, vectorial electromagnetic model has been applied to a phosphide - based device design featuring InGaAlAs active region, AlGaAs/GaAs mirrors and a tunnel junction to confine the current flow. For the structure under consideration a single mode operation has been found for the hole diameter over photonic crystal lattice constant ratio between 0.1 - 0.3. PMID:19532360

  5. 1060-nm VCSEL-based parallel-optical modules for optical interconnects

    NASA Astrophysics Data System (ADS)

    Nishimura, N.; Nagashima, K.; Kise, T.; Rizky, A. F.; Uemura, T.; Nekado, Y.; Ishikawa, Y.; Nasu, H.

    2015-03-01

    The capability of mounting a parallel-optical module onto a PCB through solder-reflow process contributes to reduce the number of piece parts, simplify its assembly process, and minimize a foot print for both AOC and on-board applications. We introduce solder-reflow-capable parallel-optical modules employing 1060-nm InGaAs/GaAs VCSEL which leads to the advantages of realizing wider modulation bandwidth, longer transmission distance, and higher reliability. We demonstrate 4-channel parallel optical link performance operated at a bit stream of 28 Gb/s 231-1 PRBS for each channel and transmitted through a 50-?m-core MMF beyond 500 m. We also introduce a new mounting technology of paralleloptical module to realize maintaining good coupling and robust electrical connection during solder-reflow process between an optical module and a polymer-waveguide-embedded PCB.

  6. Full recess integration of small diameter low threshold VCSELs within Si-CMOS ICs.

    PubMed

    Perkins, James M; Simpkins, Travis L; Warde, Cardinal; Fonstad, Clifton G

    2008-09-01

    Oxide-aperture vertical-cavity surface-emitting lasers (VCSELs) have been integrated as individual device pills within the dielectric stacks of commercially produced silicon integrated circuits and monolithically connected electrically with the underlying circuitry using technology compatible with wafer-scale processing. The 55 microm diameter, 8 microm tall device pills were bonded in recesses etched to reveal buried contact/bond pads included in the IC layout; the surface was replanarized, contact vias formed, and interconnect metal deposited and patterned. The typical CW threshold current, 1 to 2.5 mA, was the same before and after integration, and integrated devices had thermal impedances similar to devices on their native GaAs substrates. PMID:18773006

  7. Volumetric cutaneous microangiography of human skin in vivo by VCSEL swept-source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Choi, Woo June; Wang, R. K.

    2014-08-01

    We demonstrate volumetric cutaneous microangiography of the human skin in vivo that utilises 1.3-?m high-speed sweptsource optical coherence tomography (SS-OCT). The swept source is based on a micro-electro-mechanical (MEMS)-tunable vertical cavity surface emission laser (VCSEL) that is advantageous in terms of long coherence length over 50 mm and 100 nm spectral bandwidth, which enables the visualisation of microstructures within a few mm from the skin surface. We show that the skin microvasculature can be delineated in 3D SS-OCT images using ultrahigh-sensitive optical microangiography (UHS-OMAG) with a correlation mapping mask, providing a contrast enhanced blood perfusion map with capillary flow sensitivity. 3D microangiograms of a healthy human finger are shown with distinct cutaneous vessel architectures from different dermal layers and even within hypodermis. These findings suggest that the OCT microangiography could be a beneficial biomedical assay to assess cutaneous vascular functions in clinic.

  8. Polarity control of carrier injection at ferroelectric\\/metal interfaces for electrically switchable diode and photovoltaic effects

    Microsoft Academic Search

    D. Lee; S. H. Baek; T. H. Kim; J.-G. Yoon; C. M. Folkman; C. B. Eom; T. W. Noh

    2011-01-01

    We investigated a switchable ferroelectric diode effect and its physical mechanism in Pt\\/BiFeO3\\/SrRuO3 thin-film capacitors. Our results of electrical measurements support that, near the Pt\\/BiFeO3 interface of as-grown samples, a defective layer (possibly an oxygen-vacancy-rich layer) becomes formed and disturbs carrier injection. We therefore used an electrical training process to obtain ferroelectric control of the diode polarity where, by changing

  9. Dishevelled controls apical docking and planar polarization of basal bodies in ciliated epithelial cells

    PubMed Central

    Park, Tae Joo; Mitchell, Brian J.; Abitua, Philip B.; Kintner, Chris; Wallingford, John B.

    2009-01-01

    The planar cell polarity (PCP) signaling system governs many aspects of polarized cell behavior. Here, we use an in vivo model of vertebrate mucociliary epithelial development to show that Dishevelled (Dvl) is essential for the apical positioning of basal bodies. We find that Dvl and Inturned mediate the activation of the Rho GTPase specifically at basal bodies, and that these three proteins together mediate the docking of basal bodies to the apical plasma membrane. Moreover, we find that the docking involves a Dvl-dependent association of basal bodies with membrane-bound vesicles and with the vesicle-trafficking protein, Sec8. Once docked, Dvl and Rho are once again required for the planar polarization of basal bodies that underlies directional beating of cilia. These results demonstrate novel functions for PCP signaling components and suggest that a common signaling appratus governs both apical docking and planar polarization of basal bodies. PMID:18552847

  10. Electrostatic control of spin polarization in a quantum Hall ferromagnet: a new platform to realize non-Abelian excitations

    NASA Astrophysics Data System (ADS)

    Kazakov, Alexander; Kolkovsky, V.; Adamus, Z.; Karczewski, G.; Wojtowicz, T.; Rokhinson, Leonid

    2015-03-01

    Several experiments detected signatures of Majorana fermions in nanowires, and the focus of current research is shifting toward systems where non-Abelian statistics of excitations can be demonstrated. To achieve this goal we are developing a new platform where non-Abelian excitations can be created and manipulated in a two-dimensional plane, with support for Majorana and higher order non-Abelian excitations. The system is based on CdTe quantum wells non-uniformly doped with paramagnetic impurities, which result in a complicate field-dependence of Zeeman splitting. A unique property of the system is that at high fields we can form a quantum Hall ferromagnet with gate-controllable spin polarization. Helical 1D edge channels formed along the edges of electrostatic gates may support generalized non-Abelian excitations in the fractional qunatum Hall regime, and Majorana and parafermion excitations in the presence of induced superconductivity. We will present results on the gate control of s-d exchange in specially designed heterostructures, demonstrate gate control of spin polarization at filling factor ? = 2 , and show spatial separation of quantum Hall states with different spin polarization using lithographically defined gates.

  11. Route to polarization switching induced by optical injection in vertical-cavity surface-emitting lasers

    SciTech Connect

    Sciamanna, M. [Supelec, Laboratoire Materiaux Optiques, Photonique et Systemes (LMOPS), CNRS UMR-7132, Unite de Recherche Commune Supelec et Universite de Metz, 2 Rue Edouard Belin, F-57070 Metz (France); Panajotov, K. [Department of Applied Physics and Photonics (TW-TONA), Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels (Belgium)

    2006-02-15

    We perform a theoretical investigation of the polarization dynamics in a vertical-cavity surface-emitting laser (VCSEL) subject to orthogonal optical injection, i.e., the injected field has a linear polarization (LP) orthogonal to that of the free-running VCSEL. In agreement with previous experiments [Z. G. Pan et al., Appl. Phys. Lett. 63, 2999 (1993)], an increase of the injection strength may lead to a polarization switching accompanied by an injection locking. We find that this route to polarization switching is typically accompanied by a cascade of bifurcations to wave-mixing dynamics and time-periodic and possibly chaotic regimes. A detailed mapping of the polarization dynamics in the plane of the injection parameters (detuning, injection strength) unveils a large richness of dynamical scenarios. Of particular interest is the existence of another injection-locked solution for which the two LP modes both lock to the master laser frequency, i.e., an elliptically polarized injection-locked (EPIL) steady state. Modern continuation techniques allow us to unveil an unfolding mechanism of the EPIL solution as the detuning varies and also to link the existence of the EPIL solution to a resonance condition between the master laser frequency and the free-running frequency of the normally depressed LP mode in the slave laser. We furthermore report an additional case of bistability, in which the EPIL solution may coexist with the second injection-locked solution (the one being locked to the master polarization). This case of bistability is a result of the interaction between optical injection and the two-polarization-mode characteristics of VCSEL devices.

  12. Route to polarization switching induced by optical injection in vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Sciamanna, M.; Panajotov, K.

    2006-02-01

    We perform a theoretical investigation of the polarization dynamics in a vertical-cavity surface-emitting laser (VCSEL) subject to orthogonal optical injection, i.e., the injected field has a linear polarization (LP) orthogonal to that of the free-running VCSEL. In agreement with previous experiments [Z. G. Pan , Appl. Phys. Lett. 63, 2999 (1993)], an increase of the injection strength may lead to a polarization switching accompanied by an injection locking. We find that this route to polarization switching is typically accompanied by a cascade of bifurcations to wave-mixing dynamics and time-periodic and possibly chaotic regimes. A detailed mapping of the polarization dynamics in the plane of the injection parameters (detuning, injection strength) unveils a large richness of dynamical scenarios. Of particular interest is the existence of another injection-locked solution for which the two LP modes both lock to the master laser frequency, i.e., an elliptically polarized injection-locked (EPIL) steady state. Modern continuation techniques allow us to unveil an unfolding mechanism of the EPIL solution as the detuning varies and also to link the existence of the EPIL solution to a resonance condition between the master laser frequency and the free-running frequency of the normally depressed LP mode in the slave laser. We furthermore report an additional case of bistability, in which the EPIL solution may coexist with the second injection-locked solution (the one being locked to the master polarization). This case of bistability is a result of the interaction between optical injection and the two-polarization-mode characteristics of VCSEL devices.

  13. Applications of controlled-flow laser-polarized xenon gas to porous and granular media study

    Microsoft Academic Search

    R. W. Maira; R. Wang; M. S. Rosen; D. Candela; D. G. Cory; R. L. Walsworth

    We report initial NMR studies of continuous flow laser-polarized xenon gas, both in unrestricted tubing, and in a model porous media. The study uses Pulsed Gradient Spin Echo-based techniques in the gas-phase, with the aim of obtaining more sophisticated information than just translational self-diffusion coefficients. Pulsed Gradient Echo studies of continuous flow laser-polarized xenon gas in unrestricted tubing indicate clear

  14. Adaptive polarization separation

    NASA Technical Reports Server (NTRS)

    Pelchat, G. M.; Rassweiler, G. G.; Gianatasio, A.; Young, L. R. (inventors)

    1981-01-01

    A broadband adaptively controlled polarization separation network is discussed. Two transmitted signals vertically and horizontally polarized are received as elliptically polarized signals. If there is any vertical polarization on the other signal the separation network provides two signals. The separation is done automatically by the use of two sets of crosscouplers which couple a single line to the other line to complete the polarization decoupling operation.

  15. Magnetic-field control of electric polarization in a helimagnetic haxaferrite Ba2Mg2Fe12O22

    NASA Astrophysics Data System (ADS)

    Ishiwata, S.; Taguchi, Y.; Murakawa, H.; Onose, Y.; Tokura, Y.

    2009-03-01

    A Y-type hexaferrite Ba2Mg2Fe12O22 undergoes a transition to a proper-screw type helimagnetic structure with a propagation vector k0 parallel [001] at 195 K, below which the system shows field-induced successive transitions under magnetic fields up to 1 T. Magnetization measurements also indicate the presence of the conical spin structure at low magnetic fields (~ 10 mT) below about 50 K. We report on the magnetic control of the electric polarization in Ba2Mg2Fe12O22 with using the linearly oscillating fields up to ± 1 T at 5 K. The polarization vector can be cyclically reversed by weak magnetic fields of ± 30 mT. In addition, the polarization vector is repeatedly reversed without significant decay even by applying fields of ± 1 T, which suggests that the sense of the spin helix is somehow conserved in the process of the field-induced phase transitions. We propose that the conical spin structure carries the polarization vector upon the reversal of magnetic field.

  16. 850 nm single mode VCSEL-based 25Gx16 transmitter/receiver boards for parallel signal transmission over 1 km of multimode fiber

    NASA Astrophysics Data System (ADS)

    Kropp, J.-R.; Shchukin, V. A.; Ledentsov, N. N.; Schaefer, G.; Ledentsov, N. N.; Wu, Bo; Shaofeng, Qiu; Yanan, Ma; Zhiyong, Feng; Turkiewicz, J. P.

    2015-03-01

    We manufacture and compare parallel optical transceiver and receiver assemblies on test boards for parallel data transmission over multimode fiber using single mode (SM) and multimode (MM) vertical-cavity surface-emitting laser (VCSEL) arrays. VCSELs, GaAs PIN photodetector arrays, commercially-available 12 channel VCSEL driver arrays and 12 channel limiting amplifier arrays were assembled into multi-channel transceiver and receiver assemblies on testboards designed to operate up to 16 channels and coupled to multimode fiber ribbon through industrial connectors. MM VCSEL arrays easily allow 25 Gb/s error-free data transmission over 100m of OM4 fiber with only a minor penalty in the sensitivity (0.5 dB). As opposite increasing the distance to 150-200 m causes a strong increase in the noise level making the error free transmission at 200 m impossible. Using of single mode SM VCSEL arrays allows error-free 25 Gbit/s NRZ PRBS 215-1 transmission over 1 km distances over OM4 fiber and above 600 m over OM3 fiber. In a different set of experiments PAM4 transmission up to 50 Gbit/s using SM VCSEL arrays is studied.

  17. Linearly polarized emission from an embedded quantum dot using nanowire morphology control.

    PubMed

    Foster, Andrew P; Bradley, John P; Gardner, Kirsty; Krysa, Andrey B; Royall, Ben; Skolnick, Maurice S; Wilson, Luke R

    2015-03-11

    GaAs nanowires with elongated cross sections are formed using a catalyst-free growth technique. This is achieved by patterning elongated nanoscale openings within a silicon dioxide growth mask on a (111)B GaAs substrate. It is observed that MOVPE-grown vertical nanowires with cross section elongated in the [21?1?] and [1?12] directions remain faithful to the geometry of the openings. An InGaAs quantum dot with weak radial confinement is realized within each nanowire by briefly introducing indium into the reactor during nanowire growth. Photoluminescence emission from an embedded nanowire quantum dot is strongly linearly polarized (typically >90%) with the polarization direction coincident with the axis of elongation. Linearly polarized PL emission is a result of embedding the quantum dot in an anisotropic nanowire structure that supports a single strongly confined, linearly polarized optical mode. This research provides a route to the bottom-up growth of linearly polarized single photon sources of interest for quantum information applications. PMID:25674919

  18. Fast deterministic switching in orthogonal spin torque devices via the control of the relative spin polarizations

    SciTech Connect

    Park, Junbo; Buhrman, R. A. [Cornell University, Ithaca, New York 14853 (United States)] [Cornell University, Ithaca, New York 14853 (United States); Ralph, D. C. [Cornell University, Ithaca, New York 14853 (United States) [Cornell University, Ithaca, New York 14853 (United States); Kavli Institute at Cornell, Ithaca, New York 14853 (United States)

    2013-12-16

    We model 100 ps pulse switching dynamics of orthogonal spin transfer (OST) devices that employ an out-of-plane polarizer and an in-plane polarizer. Simulation results indicate that increasing the spin polarization ratio, C{sub P}?=?P{sub IPP}/P{sub OPP}, results in deterministic switching of the free layer without over-rotation (360° rotation). By using spin torque asymmetry to realize an enhanced effective P{sub IPP}, we experimentally demonstrate this behavior in OST devices in parallel to anti-parallel switching. Modeling predicts that decreasing the effective demagnetization field can substantially reduce the minimum C{sub P} required to attain deterministic switching, while retaining low critical switching current, I{sub p}???500??A.

  19. Numerical modeling of undercut ridge VCSELs designed for CW operation at 1.3 ?m: design optimization

    Microsoft Academic Search

    Andreas Tsigopoulos; Vassilis Paschos; Constantinos Caroubalos; Paul Salet; Joel Jacquet

    1997-01-01

    Optimized undercut ridge long-wavelength vertical-cavity surface-emitting semiconductor lasers (LW-VCSEL's) are investigated and the influence of thermal effects on the light versus current characteristics is analyzed by thermal-electric, optical, and electronic modeling. The model includes nonuniform current injection, carrier diffusion, stimulated emission, distributed heat sources, and active material band structure calculations. Device parameters such as thermal resistance, threshold current, and external

  20. Modeling and optimization of 1.54 um double-fused VCSELs for cw operation above room temperature

    Microsoft Academic Search

    Joachim Piprek; Dubravko I. Babic; John E. Bowers

    1996-01-01

    Recently, continuous wave (cw) operation of 1.54 micrometer vertical-cavity surface-emitting lasers (VCSELs) up to 33 degrees Celsius ambient temperature has been demonstrated for the first time. These devices employ strain-compensated InGaAsP multi-quantum wells and GaAs\\/AlGaAs distributed Bragg reflectors that are fused on both sides of the InP spacer. Lasing operation of those double-fused lasers is analyzed using a comprehensive numerical

  1. All-epitaxial VCSELs with tunnel QW-QD InGaAs-InAs gain medium

    Microsoft Academic Search

    V. Tokranov; M. Yakimov; J. van Eisden; S. Oktyabrsky

    2007-01-01

    Quantum dot (QD) size distribution and limitations in carrier capture and thermalization rates are still limiting the maximum saturation gain in QD-based laser diodes and the utilization of QD-medium in all-epitaxial vertical cavity surface emitting lasers (VCSELs). To overcome these problems structures of tunnel coupled pairs consisting of InGaAs quantum wells grown on top of self-assembled InAs QDs (QW-on-QDs) were

  2. Improved VCSEL structures for 10 gigabit-Ethernet and next generation optical-integrated PC-boards

    Microsoft Academic Search

    F. Mederer; R. Jager; J. Joos; M. Kicherer; R. King; R. Michalzik; M. Riedl; H. Unold; K. J. Ebeling; S. Lehmacher; B. Wittmann; A. Neyer

    2001-01-01

    We have investigated direct optical interconnection between processor ICs on chip-to-chip level using VCSELs and 2-D 17 cm long, 120 ?m diameter step-index polymer optical fiber (POF) bundles. Their bandwidth-length-product of 2 GHz·m makes them well suited for low-cost high-speed parallel optical interconnects on a board level. We have demonstrated 10 Gbit\\/s PRBS NRZ data transmission over four channels of

  3. Applications of 1.55 ?m optically injection-locked VCSELs in wavelength division multiplexed passive optical networks

    NASA Astrophysics Data System (ADS)

    Wong, Elaine; Zhao, Xiaoxue; Chang-Hasnain, Connie J.; Hofmann, Werner; Amann, Marcus C.

    2007-11-01

    In this paper, we will discuss the utilization of optically injection-locked (OIL) 1.55 ?m vertical-cavity surface-emitting lasers (VCSELs) for operation as low-cost, stable, directly modulated, and potentially uncooled transmitters, whereby the injection-locking master source is furnished by modulated downstream signals. Such a transmitter will find useful application in wavelength division multiplexed passive optical networks (WDM-PONs) which is actively being developed to meet the ever-increasing bandwidth demands of end users. Our scheme eliminates the need for external injection locking optical sources, external modulators, and wavelength stabilization circuitry. We show through experiments that the injection-locked VCSEL favors low injection powers and responds only strongly to the carrier but not the modulated data of the downstream signal. Further, we will discuss results from experimental studies performed on the dependence of OIL-VCSELs in bidirectional networks on the degree of Rayleigh backscattered signal and extinction ratio. We show that error-free upstream performance can be achieved when the upstream signal to Rayleigh backscattering ratio is greater than 13.4 dB, and with minimal dependence on the downstream extinction ratio. We will also review a fault monitoring and localization scheme based on a highly-sensitive yet low-cost monitor comprising a low output power broadband source and low bandwidth detectors. The proposed scheme benefits from the high reflectivity top distributed Bragg reflector mirror of the OIL-VCSEL, incurring only a minimal penalty on the upstream transmissions of the existing infrastructure. Such a scheme provides fault monitoring without having to further invest in the upgrade of customer premises.

  4. Electrical control of the spin polarization of a current in ``pure-carbon'' systems based on partially hydrogenated graphene nanoribbon

    NASA Astrophysics Data System (ADS)

    Guo, Yan-Dong; Yan, Xiao-Hong; Xiao, Yang

    2013-06-01

    Controlling a spin current by electrical means and eliminating the use of ferromagnetic contacts becomes a focus of research in spintronics, as compared with conventional magnetic control methods, electrical one could reduce the dimensions and energy consumption of integrated devices. Inspired by recent progress of controlling the hydrogenation on graphene [Xie et al., Appl. Phys. Lett. 98, 193113 (2011)], we investigate the electronic structure and spin-current transport of partially hydrogenated zigzag graphene nanoribbon (ZGNR) with various hydrogenation geometries, through first-principles calculations. It is found that for ZGNR in ferromagnetic edge-coupling state, near-edge hydrogenation would suppress the magnetization on the edge of ZGNR, and lower down the transmission around EF to zero except two peaks, which reside discretely on both sides of EF with opposite spins. Based on this feature, we propose and demonstrate a three-terminal device, where the spin polarization of the current can be modulated by gate voltage (Vg) to vary from (almost) 100% to -100%, which could serve as a perfect electrically-controlled "pure-carbon" dual-spin filter. Especially, the spin polarization varies gradually with Vg, so a current with any ratio of spin-up to spin-down electron numbers can be achieved. Moreover, the influences of ZGNR width and hydrogenation-region length on the system's performance are also discussed and a large range of ZGNR configurations are found to be suitable for the application of such a device.

  5. Controlling the excitation process of free electrons by a femtosecond elliptically polarized laser

    NASA Astrophysics Data System (ADS)

    Gao, Lili; Wang, Feng; Jiang, Lan; Qu, Liangti; Lu, Yongfeng

    2015-11-01

    This paper is focused on the excitation rates of free electrons of an aluminum (Al) bulk irradiated by an elliptically polarized laser in simulation, using time-dependent density functional theory (TDDFT). The polarized 400 nm, 10 fs laser pulse consisted of two elementary sinusoidal beams, and is adjusted by changing the phase difference ? and the intersection angle ? of the polarization directions between the two beams. The simulation includes cases of ? = ?/2 with ? = 30°, ? = 45°, ? = 60°, ? = 90°, ? = 120°, ? = 135°, ? = 150°, and cases of ? = 90° with ? = ?/4, ? = ?/3, ? = ?/2, ? = 2?/3, ? = 3?/4. The absorbed energy, the excitation rates and the density distributions of free electrons after laser termination are investigated. At the given power intensity (1×1014Wcm-2), pulse width (10 fs) and wavelength (400 nm) of each elementary laser beam, computational results indicate that the excitation rate of free electrons is impacted by three major factors: the long axis direction of the laser projected profile, the amplitude difference of the first main oscillation (1st AD), and the total amplitude difference of main oscillations (TAD) of the external electric field. Among the aforementioned three factors for the excitation rate of free electrons, the direction of long axis plays the most significant role. The screen effect is crucial to compare the importance of the remaining two factors. The analysis approach to investigate the electron dynamics under an elliptically polarized laser is both pioneering and effective.

  6. Elevation beam profile control with bias polarity patterns applied to microfabricated ultrasound transducers

    Microsoft Academic Search

    Chris Daft; Paul Wagner; Satchi Panda; Igal Ladabaum

    2003-01-01

    In contrast to PZT probes, capacitive microfabricated ultrasonic transducers (cMUTs) require a DC bias. We investigate elevation beam profile shaping by spatially varying this bias polarity. Such a scheme introduces a 180° phase shift in the device's impulse response. A Fresnel zone plate is realized which is capable of generating tight elevation foci using a large aperture. This paper presents

  7. Polarization State Control of Light by Single-Walled Carbon Nanotubes

    E-print Network

    Maruyama, Shigeo

    components I. Introduction Single-walled carbon nano-tubes (SWCNTs) have been the subject of focused multi of carbon nano tube (CNT) growth direction has been recently achieved and polarization dependent optical and anisotropic carbon nano tube films would serve the purpose. In this paper we report the optical activity

  8. Cross-control of magnetization and polarization by electric and magnetic fields with competing multiferroic and weak-ferromagnetic phases.

    PubMed

    Choi, Y J; Zhang, C L; Lee, N; Cheong, S-W

    2010-08-27

    From our investigation of magnetoelectric properties of a multiferroic phase in Eu0.75Y0.25MnO3 competing with a weak-ferromagnetic phase in magnetic fields, we found intriguing hysteretic behaviors of physical properties with variation of temperature and magnetic field. These hysteretic behaviors arise from the kinetic arrest (dearrest) processes of the first-order multiferroic-weak-ferromagnetic transition, resulting in frozen (melted) magnetoelectric glass states with coexisting two phases. Tipping the delicate balance of two competing phases by applying electric and magnetic fields leads to a remarkable control of magnetization and electric polarization. PMID:20868188

  9. Magnetochiral control of the light phase II: Proposal for a polarization-independent phase shifter

    NASA Astrophysics Data System (ADS)

    Wagnière, Georges H.

    2014-07-01

    We here propose a fiber-optic device with which the phase of a guided light mode may be continuously changed without modifying the light polarization in any way. The fiber should be chiral, the core containing randomly oriented optically active molecules absorbing in the near-UV-vis region of the electromagnetic spectrum. The fiber would lengthwise be subdivided into two equal halves. One half should contain a given chiral molecular species, the other half the corresponding enantiomer. The guided light would run collinearly to an applied magnetic field generated by an electric coil. The polarization-insensitive phase modulation of the light inside the fiber would be due to the induced magnetochiral birefringence. Natural and magnetic optical activity would be compensated to zero.

  10. Polarization control of ultrabroadband supercontinuum generation from midinfrared laser-induced harmonic emission

    NASA Astrophysics Data System (ADS)

    Jiao, Zhi-Hong; Wang, Guo-Li; Li, Peng-Cheng; Zhou, Xiao-Xin

    2014-08-01

    We present an efficient scheme for generation of an isolated attosecond (as) pulse based on the combination of two well-known methods: polarization gating method plus a method based on using two colors (? +?/2). The first uses a pulse whose ellipticity is small within a very short time interval (called a polarization gating). By adding a second pulse whose frequency is a half-frequency (midinfrared) of the first pulse, we extend significantly the cutoff frequency, as well as the width of the supercontinuum harmonic spectrum. The high-order harmonic generation is calculated using the strong-field approximation theory. As a result, an isolated 42-as pulse is generated directly by superposing the hundreds of harmonics. To explain the mechanism of the ultrashort attosecond generation, we perform the semiclassical three-step model simulation and wavelet time-frequency transform of the harmonic spectra.

  11. Conceptual design of the Space Station polar platform thermal control subsystem

    Microsoft Academic Search

    H. E. Bond; D. J. Benko; D. R. Chalmers; S. D. Pergament

    1989-01-01

    NASA's Space Station Freedom Program encompasses unmanned polar-orbiting platforms (POPs) in low-earth orbit (LEO) designed to support a variety of scientific and earth-observation missions. The platforms are modular in design, permitting in-orbit maintenance and replacement of limited-life subsystem and payload components. Such in-orbit servicing can extend the platform's useful life to 15 years or more, far exceeding that of a

  12. Cdc50p, a Conserved Endosomal Membrane Protein, Controls Polarized Growth in Saccharomyces cerevisiae

    Microsoft Academic Search

    Kenjiro Misu; Konomi Fujimura-Kamada; Takashi Ueda; Akihiko Nakano; Hiroyuki Katoh; Kazuma Tanaka

    2003-01-01

    During the cell cycle of the yeast Saccharomyces cerevisiae, the actin cytoskeleton and the growth of cell surface are polarized, mediating bud emergence, bud growth, and cytokinesis. We identified CDC50 as a multicopy suppressor of the myo3 myo5-360 temperature-sensitive mutant, which is defective in organization of cortical actin patches. The cdc50 null mutant showed cold-sensitive cell cycle arrest with a

  13. Control of Arabidopsis apical-basal embryo polarity by antagonistic transcription factors

    Microsoft Academic Search

    Zachery R. Smith; Jeff A. Long

    2010-01-01

    Plants, similarly to animals, form polarized axes during embryogenesis on which cell differentiation and organ patterning programs are orchestrated. During Arabidopsis embryogenesis, establishment of the shoot and root stem cell populations occurs at opposite ends of an apical-basal axis. Recent work has identified the PLETHORA (PLT) genes as master regulators of basal\\/root fate, whereas the master regulators of apical\\/shoot fate

  14. Applications of controlled-flow laser-polarized xenon gas to porous and granular media study

    E-print Network

    R. W. Mair; R. Wang; M. S. Rosen; D. Candela; D. G. Cory; R. L. Walsworth

    2002-11-09

    We report initial NMR studies of continuous flow laser-polarized xenon gas, both in unrestricted tubing, and in a model porous media. The study uses Pulsed Gradient Spin Echo-based techniques in the gas-phase, with the aim of obtaining more sophisticated information than just translational self-diffusion coefficients. Pulsed Gradient Echo studies of continuous flow laser-polarized xenon gas in unrestricted tubing indicate clear diffraction minima resulting from a wide distribution of velocities in the flow field. The maximum velocity experienced in the flow can be calculated from this minimum, and is seen to agree with the information from the complete velocity spectrum, or motion propagator, as well as previously published images. The susceptibility of gas flows to parameters such as gas mixture content, and hence viscosity, are observed in experiments aimed at identifying clear structural features from echo attenuation plots of gas flow in porous media. Gas-phase NMR scattering, or position correlation flow-diffraction, previously clearly seen in the echo attenuation data from laser-polarized xenon flowing through a 2 mm glass bead pack is not so clear in experiments using a different gas mixture. A propagator analysis shows most gas in the sample remains close to static, while a small portion moves through a presumably near-unimpeded path at high velocities.

  15. Cdc50p, a Conserved Endosomal Membrane Protein, Controls Polarized Growth in Saccharomyces cerevisiae

    PubMed Central

    Misu, Kenjiro; Fujimura-Kamada, Konomi; Ueda, Takashi; Nakano, Akihiko; Katoh, Hiroyuki; Tanaka, Kazuma

    2003-01-01

    During the cell cycle of the yeast Saccharomyces cerevisiae, the actin cytoskeleton and the growth of cell surface are polarized, mediating bud emergence, bud growth, and cytokinesis. We identified CDC50 as a multicopy suppressor of the myo3 myo5-360 temperature-sensitive mutant, which is defective in organization of cortical actin patches. The cdc50 null mutant showed cold-sensitive cell cycle arrest with a small bud as reported previously. Cortical actin patches and Myo5p, which are normally localized to polarization sites, were depolarized in the cdc50 mutant. Furthermore, actin cables disappeared, and Bni1p and Gic1p, effectors of the Cdc42p small GTPase, were mislocalized in the cdc50 mutant. As predicted by its amino acid sequence, Cdc50p appears to be a transmembrane protein because it was solubilized from the membranes by detergent treatment. Cdc50p colocalized with Vps21p in endosomal compartments and was also localized to the class E compartment in the vps27 mutant. The cdc50 mutant showed defects in a late stage of endocytosis but not in the internalization step. It showed, however, only modest defects in vacuolar protein sorting. Our results indicate that Cdc50p is a novel endosomal protein that regulates polarized cell growth. PMID:12589066

  16. Three-dimensional simulation of 1300-nm AlGaInAs VCSEL arrays

    NASA Astrophysics Data System (ADS)

    Czyszanowski, Tomasz; Dems, Maciej; Wasiak, Michal; Sarzala, Robert P.

    2012-06-01

    We present the optimization of the carrier injection, heat flow and optical confinement aimed for single mode operation. The analyzed structure incorporates InAlGaAs quantum wells within InP cavity. The cavity is bounded by AlGaAs/GaAs DBRs The tunnel junction is responsible for carrier funneling into the active region. The air-gap etched at the interface between cavity and top DBR provides the confinement of the lateral modes. To rigorously simulate the physical phenomena taking place in the device we used multi-physical model, which comprises three-dimensional models of optical (Plane Wave Admittance Method), thermal and electrical (Finite Element Method) phenomena. We perform the exhaustive modal analysis of the 1x3, 1x4 and 2x4 VCSEL arrays. In the analysis we investigate the influence of the distance between emitters. The analysis is performed for broad range of injected currents from threshold to the rollover. As the result we illustrate the complex competition of the modes, influence of the optical confinement on structure of the modes and determine the geometrical parameters, which favor the array modes in the considered array designs.

  17. Large-area single-mode selectively oxidized VCSELs: approaches and experimental

    NASA Astrophysics Data System (ADS)

    Unold, Heiko J.; Mahmoud, Sawat W. Z.; Eberhard, Franz; Jaeger, Roland; Kicherer, Max; Mederer, Felix; Riedl, Michael C.; Ebeling, Karl J.

    2000-05-01

    We present the investigation of several methods to increase the active diameter of single transverse mode oxide confined VCSELs in both the 850 and 980 nm wavelength regimes. Among the concepts considered are mode intensity specific shallow surface etched reliefs, monolithically increased cavity lengths, current confinement matching the fundamental mode intensity distribution and saturable absorbers. All approaches are introduced in theoretical considerations and corresponding measurement results are presented. Additionally, numerical simulations are performed to gain an increased understanding of some of the mode selection mechanisms. The considered concepts are evaluated in terms of decrease of the series resistance (for impedance matching/driving reasons) and device lifetime (as derived from maximum current densities). The results obtained are also compared to other approaches found in literature (e.g. metal apertures, photocurrent feedback, Fabry-Perot etalon, half-symmetric cavity). Conventional devices with optimized thin oxide aperture location have shown single-mode output powers above 4 mW with an active diameter of 3.5 micrometer. A record high single-transverse mode output power of 5 mW at a series resistance of 98 (Omega) is obtained for a 7 micrometer aperture device by increasing the cavity length monolithically by 4 micrometer.

  18. Optical coupling structure made by imprinting between single-mode polymer waveguide and embedded VCSEL

    NASA Astrophysics Data System (ADS)

    Karppinen, Mikko; Salminen, Noora; Korhonen, Tia; Alajoki, Teemu; Petäjä, Jarno; Bosman, Erwin; Van Steenberge, Geert; Justice, John; Khan, Umar; Corbett, Brian; Boersma, Arjen

    2015-03-01

    Polymer-based integrated optics is attractive for inter-chip optical interconnection applications, for instance, for coupling photonic devices to fibers in high density packaging. In such a hybrid integration scheme, a key challenge is to achieve efficient optical coupling between the photonic chips and waveguides. With the single-mode polymer waveguides, the alignment tolerances become especially critical as compared to the typical accuracies of the patterning processes. We study novel techniques for such coupling requirements. In this paper, we present a waveguide-embedded micro-mirror structure, which can be aligned with high precision, even active alignment method is possible. The structure enables 90 degree bend coupling between a single-mode waveguide and a vertical-emitting/detecting chip, such as, a VCSEL or photodiode, which is embedded under the waveguide layer. Both the mirror structure and low-loss polymer waveguides are fabricated in a process based mainly on the direct-pattern UV nanoimprinting technology and on the use of UVcurable polymeric materials. Fabrication results of the coupling structure with waveguides are presented, and the critical alignment tolerances and manufacturability issues are discussed.

  19. Ultrahigh speed endoscopic swept source optical coherence tomography using a VCSEL light source and micromotor catheter

    NASA Astrophysics Data System (ADS)

    Tsai, Tsung-Han; Ahsen, Osman O.; Lee, Hsiang-Chieh; Liang, Kaicheng; Giacomelli, Michael G.; Potsaid, Benjamin M.; Tao, Yuankai K.; Jayaraman, Vijaysekhar; Kraus, Martin F.; Hornegger, Joachim; Figueiredo, Marisa; Huang, Qin; Mashimo, Hiroshi; Cable, Alex E.; Fujimoto, James G.

    2014-03-01

    We developed an ultrahigh speed endoscopic swept source optical coherence tomography (OCT) system for clinical gastroenterology using a vertical-cavity surface-emitting laser (VCSEL) and micromotor based imaging catheter, which provided an imaging speed of 600 kHz axial scan rate and 8 ?m axial resolution in tissue. The micromotor catheter was 3.2 mm in diameter and could be introduced through the 3.7 mm accessory port of an endoscope. Imaging was performed at 400 frames per second with an 8 ?m spot size using a pullback to generate volumetric data over 16 mm with a pixel spacing of 5 ?m in the longitudinal direction. Three-dimensional OCT (3D-OCT) imaging was performed in patients with a cross section of pathologies undergoing standard upper and lower endoscopy at the Veterans Affairs Boston Healthcare System (VABHS). Patients with Barrett's esophagus, dysplasia, and inflammatory bowel disease were imaged. The use of distally actuated imaging catheters allowed OCT imaging with more flexibility such as volumetric imaging in the terminal ileum and the assessment of the hiatal hernia using retroflex imaging. The high rotational stability of the micromotor enabled 3D volumetric imaging with micron scale volumetric accuracy for both en face and cross-sectional imaging. The ability to perform 3D OCT imaging in the GI tract with microscopic accuracy should enable a wide range of studies to investigate the ability of OCT to detect pathology as well as assess treatment response.

  20. Volumetric cutaneous microangiography of human skin in vivo by VCSEL swept-source optical coherence tomography

    PubMed Central

    Choi, Woo June; Wang, Ruikang K.

    2015-01-01

    Three-dimensional (3D) assessment of cutaneous microcirculation in human skin is essential in the identification of disease states in skin or other organs. Few 3D imaging techniques have revealed the skin micro-vasculatures non-invasively and with sufficient imaging depth. Here, we demonstrate volumetric cutaneous microangiography of the human skin in vivo that utilizes a 1.3 µm high-speed swept-source optical coherence tomography (SS-OCT). The swept source is based on a MEMS tunable vertical cavity surface emission laser (VCSEL) that is advantageous in terms of long coherence length over 50 mm and 100 nm spectral bandwidth that enables the visualization of microstructures within a few mm from the skin surface. We show that skin microvasculature can be delineated in 3D SS-OCT images using ultrahigh-sensitive optical microangiography (UHS-OMAG) with a correlation mapping mask, providing a contrast enhanced blood perfusion map with capillary flow sensitivity. 3D microangiograms of a healthy human finger are shown with distinct cutaneous vessel architectures from different dermal layers and even within hypodermis. These findings suggest that the OCT microangiography could be a beneficial biomedical assay to assess cutaneous vascular functions in clinic. PMID:25635163

  1. The Hippo pathway controls border cell migration through distinct mechanisms in outer border cells and polar cells of the Drosophila ovary.

    PubMed

    Lin, Tzu-Huai; Yeh, Tsung-Han; Wang, Tsu-Wei; Yu, Jenn-Yah

    2014-11-01

    The Hippo pathway is a key signaling cascade in controlling organ size. The core components of this pathway are two kinases, Hippo (Hpo) and Warts (Wts), and a transcriptional coactivator, Yorkie (Yki). Yes-associated protein (YAP, a Yki homolog in mammals) promotes epithelial-mesenchymal transition and cell migration in vitro. Here, we use border cells in the Drosophila ovary as a model to study Hippo pathway functions in cell migration in vivo. During oogenesis, polar cells secrete Unpaired (Upd), which activates JAK/STAT signaling of neighboring cells and specifies them into outer border cells. The outer border cells form a cluster with polar cells and undergo migration. We find that hpo and wts are required for migration of the border cell cluster. In outer border cells, overexpression of hpo disrupts polarization of the actin cytoskeleton and attenuates migration. In polar cells, knockdown of hpo and wts or overexpression of yki impairs border cell induction and disrupts migration. These manipulations in polar cells reduce JAK/STAT activity in outer border cells. Expression of upd-lacZ is increased and decreased in yki and hpo mutant polar cells, respectively. Furthermore, forced expression of upd in polar cells rescues defects of border cell induction and migration caused by wts knockdown. These results suggest that Yki negatively regulates border cell induction by inhibiting JAK/STAT signaling. Together, our data elucidate two distinct mechanisms of the Hippo pathway in controlling border cell migration: (1) in outer border cells, it regulates polarized distribution of the actin cytoskeleton; (2) in polar cells, it regulates upd expression to control border cell induction and migration. PMID:25161211

  2. Extraction and analysis of high-frequency response and impedance of 980-nm VCSELs as a function of temperature and oxide aperture diameter

    NASA Astrophysics Data System (ADS)

    Wolf, Philip; Li, Hui; Moser, Philip; Larisch, Gunter; Lott, James A.; Bimberg, Dieter

    2015-03-01

    Vertical-cavity surface-emitting lasers (VCSELs) are decisive cost-effective, energy-efficient, and reliable light sources for short-reach (up to ~300 m) optical interconnects in data centers and supercomputers. To viably replace copper interconnects and advance to on-chip integrated photonics, reliable VCSELs ideally must be able to operate highly energy efficient, but at large bit rates and without cooling up to 85 °C, with immunity to temperature variations. Our 980 nm VCSELs achieve such temperature-stable, energy-efficient, and high-speed operation coincidently. Record low 139 fJ/bit of dissipated heat for 35 Gbit/s error-free data transmission at 85 °C is reported. Careful design of both the VCSEL's epitaxial structure and device geometry is of essence. Introducing a suitable gain-to-etalon wavelength offset simultaneously improves the temperature-stability, the maximum bit rate at high temperatures, and the energy efficiency. Tuning the photon lifetime additionally increases the bandwidth by changing the relation between damping and resonance relaxation frequency. Systematic temperature-dependent and oxide aperture-diameter-dependent measurements, including static L-I-V curves and emission spectra, small signal analysis, and data transmission experiments are reported. The modulation bandwidth, the parasitic cut-off frequency, the relaxation resonance frequency, lumped-circuit elements, and the K- and D-factors are derived, useful for energy-efficient optical interconnects based on 980 nm VCSELs.

  3. The heparan sulfate-modifying enzyme glucuronyl C5-epimerase HSE-5 controls Caenorhabditis elegans Q neuroblast polarization during migration.

    PubMed

    Wang, Xiangming; Liu, Jianhong; Zhu, Zhiwen; Ou, Guangshuo

    2015-03-15

    Directional cell migration is fundamental for neural development, and extracellular factors are pivotal for this process. Heparan sulfate proteoglycans (HSPGs) that carry long chains of differentially modified sugar residues contribute to extracellular matrix; however, the functions of HSPG in guiding cell migration remain elusive. Here, we used the Caenorhabditis elegans mutant pool from the Million Mutation Project and isolated a mutant allele of the heparan sulfate-modifying enzyme glucuronyl C5-epimerase HSE-5. Loss-of-function of this enzyme resulted in defective Q neuroblast migration. We showed that hse-5 controlled Q cell migration in a cell non-autonomous manner. By performing live cell imaging in hse-5 mutant animals, we found that hse-5 controlled initial polarization during Q neuroblast migration. Furthermore, our genetic epistasis analysis demonstrated that lon-2 might act downstream of hse-5. Finally, rescue of the hse-5 mutant phenotype by expression of human and mouse hse-5 homologs suggested a conserved function for this gene in neural development. Taken together, our results indicated that proper HSPG modification in the extracellular matrix by HSE-5 is essential for neuroblast polarity during migration. PMID:25614236

  4. Electro-optically generating and controlling right- and left-handed circularly polarized multiring modes of light beams.

    PubMed

    Zhu, Wenguo; She, Weilong

    2012-07-15

    We propose a simple method for generating and controlling right- and left-handed circularly polarized (RHP and LHP) multiring modes of light beams by means of Pockels effect in a single strontium barium niobate (SBN) crystal. The numerical results show that an LHP Laguerre-Gaussian LG(0l) beam, propagating along the optical axis of the crystal, will partly turn into an RHP vortex light field of order l+2. Moreover, a pair of the LHP and RHP components of the output light field is LG-like modes sharing an identically radial index, which is electro-optically controllable. The power ratio between these two components depends on the applied electric field and the mode of input beam. PMID:22825146

  5. Arbitrary-to-linear or linear-to-arbitrary polarization controller based on Faraday and Pockels effects in a single BGO crystal.

    PubMed

    Chen, Lixiang; She, Weilong

    2007-11-12

    We propose an arbitrary-to-linear or linear-to-arbitrary polarization controller based on the mutual action of Faraday and Pockels effects in a single Bi(4)Ge(3)O(12) (BGO) crystal after the wave coupling theory describing these two effects. It is demonstrated that, the expected conversion of arbitrary-to-linear or linear-to-arbitrary polarization state of light can be realized by adjusting the applied electric and magnetic fields. PMID:19550846

  6. Position- and orientation-controlled polarized light interaction of individual indium tin oxide nanorods

    SciTech Connect

    Choi, Daniel S.; Joh, Daniel Y.; Lee, Thomas; Milchak, Marissa; Zhou, Hebing; Kang, Yongkoo; Hahm, Jong-in, E-mail: jh583@georgetown.edu [Department of Chemistry, Georgetown University, 37th and O Sts. N.W., Washington, DC 20057 (United States)

    2014-02-24

    We have systematically investigated the position, orientation, and polarization angle dependence of scattered light from well-characterized, indium tin oxide nanorods (ITO NRs) upon illumination with monochromatic light. Scattering signals from individual ITO NRs of horizontal and vertical configurations are probed quantitatively by examining signal response with respect to the analyzer angle and position along the length of the NR. Our efforts can be highly beneficial in providing fundamental understanding for the light interaction behavior of ITO NRs. Our results can provide valuable bases for comprehending optical emission from individual NRs, with their ever-growing applications in optoelectronics, photonics, and biosensing.

  7. Multiscale structures for polarization control by using imprint and UV lithography

    NASA Astrophysics Data System (ADS)

    Deng, Xuegong; Wang, Jian; Liu, Feng; Sciortino, Paul F., Jr.; Liu, Xiaoming; Graham, Alan

    2005-11-01

    We investigate a viable manufacture method of large area transmission only polarizers (TOPOL). A multilayer, mixed-scale (nanostructures and microstructrures) design is presented to accomplish the required functional integration. The effective domain of the device is less than 2 ?m in thickness. Nanoimprint and UV lithography is combined to demonstrate the viable fabrication processes with 100 mm diameter wafers. The proposed structures can be further integrated. We also present detailed comparisons of the integrated devices with high-performance commercial-grade bulk optics.

  8. Plasmonic Nanoantennas for Efficient Control of Polarization-Entangled Photon Pairs

    E-print Network

    Ivan S. Maksymov; Andrey E. Miroshnichenko; Yuri S. Kivshar

    2012-06-22

    We suggest a novel source of polarization-entangled photon pairs based on a cross-shaped plasmonic nanoantenna driven by a single quantum dot. The integration of the nanoantenna with a metal mirror overcomes the fundamental tradeoff between the spontaneous emission (SE) enhancement and the extraction efficiency typical of microcavity and nanowire-based architectures. With a very-high extraction efficiency of entangled photons (~90%) at 1.55 um and large SE enhancement (~90) over a broad 330 nm spectral range, the proposed design will pave the way toward reliable integrated sources of nonclassical light.

  9. Position- and orientation-controlled polarized light interaction of individual indium tin oxide nanorods

    PubMed Central

    Choi, Daniel S.; Joh, Daniel Y.; Lee, Thomas; Milchak, Marissa; Zhou, Hebing; Kang, Yongkoo; Hahm, Jong-in

    2014-01-01

    We have systematically investigated the position, orientation, and polarization angle dependence of scattered light from well-characterized, indium tin oxide nanorods (ITO NRs) upon illumination with monochromatic light. Scattering signals from individual ITO NRs of horizontal and vertical configurations are probed quantitatively by examining signal response with respect to the analyzer angle and position along the length of the NR. Our efforts can be highly beneficial in providing fundamental understanding for the light interaction behavior of ITO NRs. Our results can provide valuable bases for comprehending optical emission from individual NRs, with their ever-growing applications in optoelectronics, photonics, and biosensing. PMID:24753625

  10. Control of atomic single and double ionization dynamics using orthogonally polarized two-color laser pulses

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Xie, X.; Roither, S.; Kartashov, D.; Schöffler, M.; Shafir, D.; Corkum, P. B.; Baltuška, A.; Staudte, A.; Kitzler, M.

    2014-04-01

    Single- and double-ionization of neon with orthogonally polarized two-color (OTC) laser fields is investigated using the COLTRIMS method. We study the influence of the long range Coulomb potential of the parent ion on the final momentum distribution of electrons emitted during single ionization. Furthermore, we investigate nonsequential double ionization in OTC fields and demonstrate that the electron-electron correlation is highly sensitive to the sub-cycle field shape of the OTC pulses, in agreement with recent theoretical predictions.

  11. NHERF1/EBP50 controls lactation by establishing basal membrane polarity complexes with prolactin receptor

    PubMed Central

    Morales, F C; Hayashi, Y; van Pelt, C S; Georgescu, M-M

    2012-01-01

    The development of the lactating mammary gland is a complex multifactorial process occurring in mammals during pregnancy. We show here that this process requires NHERF1/EBP50 (Na/H exchanger regulatory factor 1/ERM-binding phosphoprotein 50) expression and that successful lactation depends on NHERF1 allele copy number, with rates of 50 and 20% in NHERF1(+/?) and (?/?) mice, respectively. The prolactin receptor (PRLR)-STAT5 signaling provides the central axis triggering the differentiation of secretory mammary alveolar cells. In successfully lactating glands, NHERF1 is massively upregulated and forms complexes with PRLR, but also with ?-catenin, E-cadherin and ezrin at the alveolar basal membrane, establishing basal polarity. In NHERF1-deficient glands, the basal polarity is disrupted, the PRLR levels and basal membrane localization are abolished, and the downstream STAT5 activation collapses with consequent reduction of milk protein synthesis. NHERF1/EBP50, a protein deregulated in breast cancer, thus emerges as an important physiological mediator of milk secretion, by engagement of PRLR in multimeric complexes at the alveolar basal membrane with subsequent network activation leading to cell differentiation. PMID:22992649

  12. Controllable fully spin-polarized transport in a ferromagnetically doped topological insulator junction

    SciTech Connect

    Zhou, Benliang; Tang, Dongsheng; Zhou, Guanghui, E-mail: ghzhou@hunnu.edu.cn [Department of Physics and Key Laboratory for Low-Dimensional Quantum Structures and Manipulation (Ministry of Education), Hunan Normal University, Changsha 410081 (China); Zhou, Benhu [Department of Physics, Shaoyang University, Shaoyang 422001 (China)

    2014-04-21

    We investigate the energy band structure and the spin-dependent transport for a normal/ferromagnetic/normal two-dimension topological insulator (TI) junction. By diagonalizing Hamiltonian for the system, the band structure shows that the edge states on two sides are coupled resulting in a gap opening due to the transverse spatial confinement. Further, the exchange field induced by magnetic impurities can also modulate the band structure with two spin degenerate bands splitting. By using the nonequilibrium Green's function method, the dependence of spin-dependent conductance and spin-polarization on the Fermi energy, the exchange field strength and the ferromagnetic TI (FTI) length are also analyzed, respectively. Interestingly, the degenerate conductance plateaus for spin-up and -down channels are broken, and both the conductances are suppressed by magnetic impurities due to the time-reversal symmetry broken and inelastic scattering. The spin-dependent conductance shows different behaviors when the Fermi energy is tuned into different ranges. Moreover, the conductance can be fully spin polarized by tuning the Fermi energy and the exchange field strength, or by tuning the Fermi energy and the FTI length. Consequently, the junction can transform from a quantum spin Hall state to a quantum anomalous Hall state, which is very important to enable dissipationless charge current for designing perfect spin filter.

  13. Theory and characterization of elliptically polarized modes in vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Volet, Nicolas

    2015-03-01

    The polarization of the beam emitted from telecom-wavelength vertical-cavity surface-emitting lasers (VCSELs) is studied in detail. Stokes parameters are extracted separately for the two polarization submodes of the fundamental spatial mode LP01. This characterization was performed at room temperature and for a significant number of devices. This led to the discovery of stable optical modes with a polarization that differs from the linear case. This crucial result was obtained without immersing the devices in an external magnetic field or driving them under external optical injection. In addition, the polarization can be tuned directly with the drive current. Moreover, the polarization handedness can be switched electrically. A theoretical investigation shows that some of the equations forming the basis of the spin-flip model should be reconsidered. In particular, a generalization of this theory is discussed and fantastic agreement is found with the experimental results. This work paves the way for a broad range of novel applications with the VCSEL technology, in particular for spintronics, bio-chemical sensing and telecommunication.

  14. Golgi-derived CLASP-dependent Microtubules Control Golgi Organization and Polarized Trafficking in Motile Cells

    PubMed Central

    Miller, Paul M.; Folkmann, Andrew W.; Maia, Ana R.R.; Efimova, Nadia; Efimov, Andrey; Kaverina, Irina

    2009-01-01

    Microtubules are indispensable for Golgi complex assembly and maintenance that is an integral part of cytoplasm organization in interphase mammalian cells. Here, we show that two discrete microtubule subsets drive two distinct, yet simultaneous, stages of Golgi assembly. In addition to the radial centrosomal microtubule array, which positions the Golgi in the cell center, we identify a role for microtubules that form at the Golgi membranes in a manner dependent on microtubule regulators CLASPs. These Golgi-derived microtubules draw Golgi mini-stacks together in tangential fashion and are critical for establishing continuity and proper morphology of the Golgi complex. We propose that specialized functions of these two microtubule arrays arise from their specific geometries. Further, we demonstrate that directional post-Golgi trafficking and cell migration depend on Golgi-associated CLASPs suggesting that correct organization of the Golgi complex by microtubules is essential for cell polarization and motility. PMID:19701196

  15. A quantum dot single-photon source with on-the-fly all-optical polarization control and timed emission

    E-print Network

    Dirk Heinze; Artur Zrenner; Stefan Schumacher

    2014-12-02

    Sources of single photons are key elements in the study of basic quantum optical concepts and applications in quantum information science. Among the different sources available, semiconductor quantum dots excel with their straight forward integrability in semiconductor based on-chip solutions and the potential that photon emission can be triggered on demand. Usually, the photon emission event is part of a cascaded biexciton-exciton emission scheme. Important properties of the emitted photon such as polarization and time of emission are either probabilistic in nature or pre-determined by electronic properties of the system. In this work, we study the direct two-photon emission from the biexciton. We show that emission through this higher-order transition provides a much more versatile approach to generate a single photon. In the scheme we propose, the two-photon emission from the biexciton is enabled by a laser field (or laser pulse) driving the system into a virtual state inside the band gap. From this intermediate virtual state, the single photon of interest is then spontaneously emitted. Its properties are determined by the driving laser pulse, enabling all-optical on-the-fly control of polarization state, frequency, and time of emission of the photon.

  16. Reducing multiphoton ionization in a linearly polarized microwave field by local control

    E-print Network

    S. Huang; C. Chandre; T. Uzer

    2006-10-27

    We present a control procedure to reduce the stochastic ionization of hydrogen atom in a strong microwave field by adding to the original Hamiltonian a comparatively small control term which might consist of an additional set of microwave fields. This modification restores select invariant tori in the dynamics and prevents ionization. We demonstrate the procedure on the one-dimensional model of microwave ionization.

  17. Highly birefringent silicate glass photonic-crystal fiber with polarization-controlled frequency-shifted output: A promising fiber light source for nonlinear Raman microspectroscopy.

    PubMed

    Mitrofanov, Aleksandr V; Linik, Yaroslav M; Buczynski, Ryszard; Pysz, Dariusz; Lorenc, Dusan; Bugar, Ignac; Ivanov, Anatoly A; Alfimov, Mikhail V; Fedotov, Andrei B; Zheltikov, Aleksei M

    2006-10-30

    A highly birefringent silicate glass photonic-crystal fiber (PCF) is employed for polarization-controlled nonlinear-optical frequency conversion of femtosecond Cr: forsterite laser pulses with a central wavelength of 1.24 mum to the 530--720-nm wavelength range through soliton dispersion-wave emission. The fiber exhibits a modal birefringence of 1.2.10(-3) at the wavelength of 1.24 mum due to a strong form anisotropy of its core, allowing polarization switching of the central wavelength of its blue-shifted output by 75 nm. Polarization properties and the beam quality of the blue-shifted PCF output are shown to be ideally suited for polarization-sensitive nonlinear Raman microspectroscopy. PMID:19529469

  18. Sea ice dynamics as a control for halogen deposition in polar regions

    NASA Astrophysics Data System (ADS)

    Spolaor, Andrea; Plane, John M. C.; Vallelonga, Paul; Gabrieli, Jacopo; Cozzi, Giulio; Turetta, Clara; Kohler, Jack; Isaksson, Elisabeth; Barbante, Carlo

    2013-04-01

    Bromine and iodine chemistry is extremely active at the sea ice margins of both polar regions, with enhanced concentrations of BrO and IO in the air column compared to the open ocean surface or snow-covered land. So-called "Bromine explosions" occur principally over first-year sea ice close to the sea ice edge, and are the major source of reactive bromine in the polar atmosphere. This results in an increase of bromide (Br-) deposited to the snowpack, compared with the Br-Na sea water mass ratio. The main source of iodine is phytoplankton, which colonize the underside of sea ice, producing iodocarbons and probably I2. Though it has been discovered that atmospheric iodine around Antarctica is produced from algae growing on the underside of the relatively thin/seasonal sea ice, satellite measurements do not show exceptional iodine activity above Arctic sea ice. However, in opposition to Antarctica, boundary layer observations show relatively small atmospheric IO concentrations downwind of ice-free open ocean, including leads and polynias. Analysis of bromine and iodine has been carried out in the Talos Dome ice core (Antarctica) which covers the last 215 ky, and in a shallow/firn core drilled at the summit of the Holtedahlfonna glacier (Northern Spitsbergen, Svalbard), covering the last 10 years. Talos Dome Br- is positively correlated with temperature and negatively correlated with sodium (Na). Based on the Br-/Na seawater ratio, bromide is depleted in the ice during glacial periods and enriched during interglacial periods. Total iodine, consisting of iodide (I-) and iodate (IO3-), peaks during glacials with lower values during interglacial periods. Although iodate is believed to be the most stable iodine species in atmospheric aerosols, it was present only in the ice core only during glacial maxima. Glacial-interglacial changes in the multi-year sea ice extent will almost certainly alter the distance between the sea ice edge and Antarctic plateau, which will influence the total bromide flux (arising both from sea salt and Br- from bromine explosions) and its ratio with sodium. A simple 1-D transport model of this scenario is able to reproduce the measured fluxes of bromine and sodium. The seasonal sea ice extent will also alter the surface area available to algal colonization, and hence iodine emission. In support of the Antarctic results, analysis of iodine and bromine in the Svalbard shallow/firn core appears to confirm the linkage between sea ice and these halogens. In particular, changes in I concentration are associated with the extent of sea ice at spring time, while Br, evaluated as enrichment relative to the Br/Na sea water mass ratio, is influenced by changes in the seasonal sea ice area. The Arctic and Antarctic ice core results suggest that sea ice dynamics are arguably the primary driver of halogen fluxes in polar regions and that both halogens could be used to understand the past variability of sea ice.

  19. Transverse and polarization effects in index-guided vertical-cavity surface-emitting lasers

    SciTech Connect

    Torre, M. S.; Masoller, C.; Mandel, Paul [Instituto de Fisica Arroyo Seco, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pinto 399 (7000) Tandil (Argentina); Departament de Fisica i Enginyeria Nuclear, Universitat Politecnica de Catalunya, Colom 11, E-08222 Terrassa (Spain); Universite Libre de Bruxelles, Optique Nonlineaire Theorique, Campus Plaine C. P. 231, B-1050 Bruxelles (Belgium)

    2006-10-15

    We study numerically the polarization dynamics of vertical-cavity surface-emitting lasers (VCSEL's) operating in the fundamental transverse mode. We use an extension of the spin-flip model that not only accounts for the vector nature of the laser field, but also considers spatial transverse effects. The model assumes two orthogonal, linearly polarized fields, which are coupled to two carrier populations, associated with different spin sublevels of the conduction and valence bands in the quantum-well active region. Spatial effects are taken into account by considering transverse profiles for the two polarizations, for the two carrier populations, and for the carrier diffusion. The optical profile is the LP{sub 01} mode, suitable for describing index-guided VCSEL's with cylindrical symmetry emitting on the fundamental transverse mode for both polarizations. We find that in small-active-region VCSEL's, fast carrier diffusion induces self-sustained oscillations of the total laser output, which are not present in larger-area devices or with slow carrier diffusion. These self-pulsations appear close to threshold, and, as the injection current increases, they grow in amplitude; however, there is saturation and the self-pulsations disappear at higher injection levels. The dependence of the oscillation amplitude on various laser parameters is investigated, and the results are found to be in good qualitative agreement with those reported by Van der Sande et al. [Opt. Lett. 29, 53 (2004)], based on a rate-equation model that takes into account transverse inhomogeneities through an intensity-dependent confinement factor.

  20. Spacecraft Potential Control by the Plasma Source Instrument on the POLAR Satellite

    NASA Technical Reports Server (NTRS)

    Comfort, R. H.; Moore, T. E.; Craven, P. D.; Pollock, C. J.; Mozer, F. S.; Williamson, W. S.

    1998-01-01

    This increasingly recognized that the low-energy core plasma is a critically important part of magnetospheric plasma transport, yet this plasma cannot be accurately measured from spacecraft at potentials much different from that of the ambient plasma. In low-density regions such as the polar cap and lobes, spacecraft charge positively, excluding core ions from the spacecraft and accelerating core electrons so much that their velocities cannot be measured with any accuracy. In regions of high electron pressure and temperature, spacecraft charge negatively, excluding the ambient core electrons and accelerating the core ions so much that their velocity cannot be accurately measured. Plasma contactors have been used on a number of spacecraft operating in low-plasma-density regions to prevent charging of spacecraft to high potentials, particularly when exposed to high fluxes of energetic particles. This concern has prompted extensive studies by NASA for use of plasma contractors on the international space station where solar arrays may significantly affect the spacecraft potential.

  1. Inducible Costimulator Protein (Icos) Controls T Helper Cell Subset Polarization after Virus and Parasite Infection

    PubMed Central

    Kopf, Manfred; Coyle, Anthony J.; Schmitz, Nicole; Barner, Marijke; Oxenius, Annette; Gallimore, Awen; Gutierrez-Ramos, Jose-Carlos; Bachmann, Martin F.

    2000-01-01

    It has been shown that certain pathogens can trigger efficient T cell responses in the absence of CD28, a key costimulatory receptor expressed on resting T cells. Inducible costimulator protein (ICOS) is an inducible costimulator structurally and functionally related to CD28. Here, we show that in the absence of CD28 both T helper cell type 1 (Th1) and Th2 responses were impaired but not abrogated after infection with lymphocytic choriomeningitis virus (LCMV), vesicular stomatitis virus (VSV), and the nematode Nippostrongylus brasiliensis. Inhibition of ICOS in CD28-deficient mice further reduced Th1/Th2 polarization. Blocking of ICOS alone had a limited but significant capacity to downregulate Th subset development. In contrast, cytotoxic T lymphocyte (CTL) responses, which are regulated to a minor and major extent by CD28 after LCMV and VSV infection, respectively, remained unaffected by blocking ICOS. Together, our results demonstrate that ICOS regulates both CD28-dependent and CD28-independent CD4+ subset (Th1 and Th2) responses but not CTL responses in vivo. PMID:10880526

  2. Polar Bears

    NSDL National Science Digital Library

    Mr. Thomas

    2010-09-27

    Use the following websites to answer questions about the rapid disappearance of polar bears in the Arctic region. Polar Bear picture Polar Bear Tracker 1: What region in the world has the fewest polar bears? 2: Using the internet as a resource, provide some reasons as to why this region is suffering from the most polar bear differences? Polar Bears Change Diet 1: Why are polar bears having to change their diets? 2: List some other factors (besides diet) in the ...

  3. Parallel interconnect components for optical modules utilizing flip-chip VCSEL on ultra-thin silicon-on-sapphire substrate

    NASA Astrophysics Data System (ADS)

    Thai, Serey; Kuznia, Charles; Divakar, M. P.; Albares, Donald J.; Pendleton, Mike; Le, Tri; Bachta, Paul M.; Hagan, Rick; Pommer, Dick; Cable, Jim; Reedy, Ronald E.

    2002-06-01

    We report on optical components for parallel transmit and receive module, operating at 850nm, designed for short haul optical multimode fiber networks. The component is realized by flip-chip bonding of arrayed optoelectronic devices, i.e., VCSEL and PIN detector array, onto ultra-thin silicon- on-sapphire (UTSi) substrate, which is optically transparent and electrically insulated. Flip-chipped assemblies provide several advantages over conventional wire bond techniques, such as extremely low interconnection parasitics that enable high data rates at low power. Using UTSi technology further improves performance by minimizing crosstalk through its insulating substrate while providing the means for a reliable, low cost optical assembly directly onto the substrate. In addition, applying UTSi technology to optical modules allows a higher degree of functional integration within the module. The insulating substrate provides excellent isolation between mixed signal circuitry, enabling the integration of high performance transmitters, receivers and other sensitive analog circuits with digital circuitry on the same substrate. Furthermore, the integration of VCSEL and photodetector array with UTSi circuits for parallel optical interconnects yields several packaging advantages, such as parallelism, scalability, compactness and simplicity.

  4. Polarization-controlled TIRFM with focal drift and spatial field intensity correction.

    PubMed

    Johnson, Daniel S; Toledo-Crow, Ricardo; Mattheyses, Alexa L; Simon, Sanford M

    2014-03-01

    Total internal reflection fluorescence microscopy (TIRFM) is becoming an increasingly common methodology to narrow the illumination excitation thickness to study cellular process such as exocytosis, endocytosis, and membrane dynamics. It is also frequently used as a method to improve signal/noise in other techniques such as in vitro single-molecule imaging, stochastic optical reconstruction microscopy/photoactivated localization microscopy imaging, and fluorescence resonance energy transfer imaging. The unique illumination geometry of TIRFM also enables a distinct method to create an excitation field for selectively exciting fluorophores that are aligned either parallel or perpendicular to the optical axis. This selectivity has been used to study orientation of cell membranes and cellular proteins. Unfortunately, the coherent nature of laser light, the typical excitation source in TIRFM, often creates spatial interference fringes across the illuminated area. These fringes are particularly problematic when imaging large cellular areas or when accurate quantification is necessary. Methods have been developed to minimize these fringes by modulating the TIRFM field during a frame capture period; however, these approaches eliminate the possibility to simultaneously excite with a specific polarization. A new, to our knowledge, technique is presented, which compensates for spatial fringes while simultaneously permitting rapid image acquisition of both parallel and perpendicular excitation directions in ~25 ms. In addition, a back reflection detection scheme was developed that enables quick and accurate alignment of the excitation laser. The detector also facilitates focus drift compensation, a common problem in TIRFM due to the narrow excitation depth, particularly when imaging over long time courses or when using a perfusion flow chamber. The capabilities of this instrument were demonstrated by imaging membrane orientation using DiO on live cells and on lipid bilayers that were supported on a glass slide (supported lipid bilayer). The use of the approach to biological problems was illustrated by examining the temporal and spatial dynamics of exocytic vesicles. PMID:24606926

  5. Polar-localised poplar K + channel capable of controlling electrical properties of wood-forming cells

    Microsoft Academic Search

    Matthias Arend; Andrea Stinzing; Christa Wind; Katharina Langer; Andreas Latz; Peter Ache; Jörg Fromm; Rainer Hedrich

    2005-01-01

    In previous studies, we have shown that annual expression profiles of cambial and wood tissue with respect to the Shaker K+ channel PTORK correlate with cambial activity. To follow PTORK-gene activity on the cellular level, we isolated the respective promoter regions and generated transgenic Arabidopsis plants expressing the GUS gene under the control of the PTORK promoter. Cross-sections of petioles

  6. `Downward Control' of the Mean Meridional Circulation and Temperature Distribution of the Polar Winter Stratosphere

    Microsoft Academic Search

    Rolando R. Garcia; Byron A. Boville

    1994-01-01

    According to the `downward control' principle, the extratropical mean vertical velocity on a given pressure level is approximately proportional to the meridional gradient of the vertically integrated zonal force per unit mass exerted by waves above that level. In this paper, a simple numerical model that includes parameterizations of both planetary and gravity wave breaking is used to explore the

  7. Factors controlling the distribution of anaerobic methanotrophic communities in marine environments: Evidence from intact polar membrane lipids

    NASA Astrophysics Data System (ADS)

    Rossel, Pamela E.; Elvert, Marcus; Ramette, Alban; Boetius, Antje; Hinrichs, Kai-Uwe

    2011-01-01

    Three distinct types of microbial consortia appear to mediate the anaerobic oxidation of methane with sulfate as electron acceptor in marine sediments and are distributed ubiquitously. These consortia consist of ANerobic MEthanotrophic (ANME) archaea of the ANME-1, ANME-2 and ANME-3 clades and their sulfate-reducing bacterial partners either of the Desulfosarcina- Desulfococcus (ANME-1/DSS and ANME-2/DSS) or Desulfobulbus spp. (ANME-3/DBB) branches. Frequently one consortium type dominates the community, but the selective factors are not well constrained. Here we analyzed patterns in the composition of intact polar lipids extracted from bacterial and archaeal communities of different marine seep environments. Further, we investigated if different environmental and geographical factors were responsible for the observed patterns, and hence could be important in the selection of seep communities. Intact polar lipids (IPLs) provide a more robust distinction of the composition of extant communities than their less polar derivatives. In ANME-1/DSS-dominated communities, glycosidic- and phospho-glyceroldialkylglyceroltetraethers were abundant, while ANME-2/DSS and ANME-3/DBB-dominated communities showed abundant archaeol-based IPLs, either with glycosidic and phospho-headgroups or only phospho-headgroups, respectively. The relative proportion of bacterial IPLs varied widely from 0% to 93% and was generally lower in samples of the ANME-1 type, suggesting lower bacterial biomasses in the respective communities. In addition to these lipid signatures, distinctive features were related to the habitat characteristics of these communities: lower amounts of phosphate-based IPLs were generally observed in communities from calcified microbial mats compared to sediments, which may reflect phosphate limitation. Based on statistical analyses of IPLs and environmental data this study constrained for the first time the occurrence of three environmental factors controlling the distribution of different ANME-associated communities in a wide range of hydrocarbon seep systems. Habitats dominated by ANME-1/DSS communities were characterized by high temperature and low oxygen content in bottom waters (or even anoxia), while ANME-2/DSS and ANME-3/DBB-dominated sediments were located in settings with lower temperatures and higher oxygen content in bottom waters. Furthermore, ANME-2/DSS communities were particularly prominent in environments in which a relatively high supply of sulfate was sustained.

  8. Subcellular localization of Cdc42p, a Saccharomyces cerevisiae GTP-binding protein involved in the control of cell polarity.

    PubMed Central

    Ziman, M; Preuss, D; Mulholland, J; O'Brien, J M; Botstein, D; Johnson, D I

    1993-01-01

    The Saccharomyces cerevisiae Cdc42 protein, a member of the Ras superfamily of low-molecular-weight GTP-binding proteins, is involved in the control of cell polarity during the yeast cell cycle. This protein has a consensus sequence (CAAX) for geranylgeranyl modification and is likely to be associated, at least in part, with cell membranes. Using cell fractionation and immunolocalization techniques, we have investigated the subcellular localization of Cdc42p. Cdc42p was found in both soluble and particulate pools, and neither its abundance nor its distribution varied through the cell cycle. The particulate form of Cdc42p could be solubilized with detergents but not with NaCl or urea, suggesting that it is tightly associated with membranes. An increase in soluble Cdc42p was observed in a geranylgeranyltransferase mutant strain (cdc43-2ts) grown at the restrictive temperature. In addition, Cdc42p from a cdc42C188S mutant strain (that has an alteration at the prenylation consensus site) was almost exclusively in the soluble fraction, suggesting that membrane localization is dependent on geranylgeranyl modification at Cys-188. Immunofluorescence and immunoelectron microscopy experiments demonstrated that Cdc42p localizes to the plasma membrane in the vicinity of secretory vesicles that were found at the site of bud emergence, at the tips and sides of enlarging buds, and within mating projections (shmoo tips) in alpha-factor-arrested cells. These results indicate that Cdc42p is localized to the bud site early in the cell cycle and suggest that this localization is critical for the selection of the proper site for bud emergence and for polarized cell growth. Images PMID:8167411

  9. In-situ weak-beam and polarization control of multidimensional laser sidebands for ultrafast optical switching

    NASA Astrophysics Data System (ADS)

    Liu, Weimin; Wang, Liang; Fang, Chong

    2014-03-01

    All-optical switching has myriad applications in optoelectronics, optical communications, and quantum information technology. To achieve ultrafast optical switching in a compact yet versatile setup, we demonstrate distinct sets of two-dimensional (2D) broadband up-converted multicolor arrays (BUMAs) in a thin type-I ?-barium-borate crystal with two noncollinear near-IR femtosecond pulses at various phase-matching conditions. The unique interaction mechanism is revealed as quadratic spatial solitons (QSSs)-coupled cascaded four-wave mixing (CFWM), corroborated by numerical calculations of the governing phase-matching conditions. Broad and continuous spectral-spatial tunability of the 2D BUMAs are achieved by varying the time delay between the two incident pulses that undergo CFWM interaction, rooted in the chirped nature of the weak white light and the QSSs generation of the intense fundamental beam. The control of 2D BUMAs is accomplished via seeding a weak second-harmonic pulse in situ to suppress the 2D arrays with polarization dependence on the femtosecond timescale that matches the control pulse duration of ˜35 fs. A potential application is proposed on femtosecond all-optical switching in an integrated wavelength-time division multiplexing device.

  10. Multiple-color GaAs\\/AlGaAs superlattice infrared photodetector controlled by the polarity and magnitude of the bias voltage

    Microsoft Academic Search

    M. C. Hsu; C. H. Kaun; S. Y. Wang; C. P. Lee

    1999-01-01

    We present a voltage-controlled multi-color infrared photodetector consisting of two stacks of GaAs\\/AlGaAs superlattices with main absorption peaks at 10.7 ?m and 6.7 ?m respectively. The switching in response wavelengths is achieved by using the opposite polarity dependence of responsivity in each stack. Compared with traditional voltage-controlled designs, the detector achieves better switching in response colors and lower operating bias

  11. Polarization feedback laser stabilization

    DOEpatents

    Esherick, P.; Owyoung, A.

    1987-09-28

    A system for locking two Nd:YAG laser oscillators includes an optical path for feeding the output of one laser into the other with different polarizations. Elliptical polarization is incorporated into the optical path so that the change in polarization that occurs when the frequencies coincide may be detected to provide a feedback signal to control one laser relative to the other. 4 figs.

  12. Single-atom polarizer

    E-print Network

    W. A. Li; L. F. Wei

    2013-06-17

    Traditional polarizer provides a way to convert an unknown polarization into a specified polarization. According to Malus, the intensity of the transmission is directly proportional to the square of the cosine of angle between the transmission axes of the polarizer and the incident polarization. There, the intensity refers to the collective behavior of many photons. Here we propose a novel approach to realizing polarization-filtering at single-photon level. We discuss how a single planepolarized photon transports through a polarized analyzer generated by a single atom (the so-called "single-atom polarizer"), and provide a single quantum version of Malus's law. We investigate the quantum scattering of a single photon by a controllable four-level atom inside a one-dimensional waveguide. By using real-space theoretical approach, we obtain analytic expressions of the transmission spectrum of the photon. Then, our numerical experiments show that the transmitted probability of the incident photon can be controlled by selecting the polarized-dependent transition configuration of the driven atom. The application of such a single-atom polarizer to linear optical quantum information processing is also discussed.

  13. High-contrast coherent population trapping based on crossed polarizers method.

    PubMed

    Yano, Yuichiro; Goka, Shigeyoshi

    2014-12-01

    A method based on crossed polarizers to observe high-contrast coherent population trapping (CPT) resonance has been developed. Because crossed polarizers have a simple optical system, our method is suitable for chip-scale atomic clocks (CSACs). In CPT, the Faraday rotation in a linearly polarized light field (lin||lin) was calculated using two pairs of ?-system models; the spectrum of the Faraday rotation is also estimated. After measuring the contrast and linewidth with the crossed-polarizer method, a comparison of the theoretical model and experimental data showed they were in good agreement. Moreover, the experimental results showed that a high contrast (88.4%) and narrow linewidth (1.15 kHz) resonance could be observed using a Cs gas cell and D1-line verticalcavity surface-emitting laser (VCSEL). PMID:25474771

  14. Vanin-1 controls granuloma formation and macrophage polarization in Coxiella burnetii infection.

    PubMed

    Meghari, Soraya; Berruyer, Carole; Lepidi, Hubert; Galland, Franck; Naquet, Philippe; Mege, Jean-Louis

    2007-01-01

    Q fever is caused by Coxiella burnetii, a bacterium that survives in MPhi. Vanin-1 is a membrane-anchored pantetheinase that controls tissue inflammation. Consequently, Vanin-1-deficient mice represent a unique mouse model in which stress-induced inflammation is limited by the reaction of resident tissue cells. To investigate the contribution of host tissues in the control of a bacterial infection, we infected Vanin-1-deficient mice with C. burnetii. Mortality and morbidity of mice were not affected. The lack of Vanin-1 had no effect on C. burnetii clearance but decreased the formation of granulomas in spleen and liver. Granuloma formation depends upon MPhi recruitment and activation in these tissues. Whereas the former was slightly impaired in mutant mice, the lack of Vanin-1 significantly affected the activation pattern of BM-derived MPhi stimulated by C. burnetii. While their microbicidal activity against C. burnetii was moderately impaired, they exhibited decreased inducible nitric oxide synthase (iNOS) and MCP-1 gene expression, and increased IL-10 and arginase expression. In liver from mutant mice, increased arginase expression and decreased expression of MCP-1 and iNOS were reminiscent of MPhi data. These results suggest a role of Vanin-1 in granuloma formation in response to C. burnetii by skewing MPhi activation toward an M2 program. PMID:17163446

  15. Control of the electric polarization flop direction by a canted magnetic field in a magnetoelectric multiferroic MnWO4

    Microsoft Academic Search

    K. Taniguchi; N. Abe; H. Umetsu; T. Arima

    2010-01-01

    The relationship between the magnetic field direction and the flopped ferroelectric polarization has been investigated for multiferroic MnWO4. We have observed that the ferroelectric polarization flop direction is switched without applying an electric field, when the direction of an applied magnetic field slightly deviates from the b axis within the ab-plane. The polarization flop direction during the phase transition between

  16. The Importance of Age Control in Defining Apparent Polar Wander Paths of Fast Moving Plates: The Jurassic Case Study

    NASA Astrophysics Data System (ADS)

    Muttoni, G.

    2014-12-01

    During periods of fast plate motion (e.g. Cambrian, Jurassic), plate velocities in excess of ~20 cm/yr (200 km/Myr) relative to the Earth's spin axis have been suggested. Pinning down the position of fast moving plates requires paleomagnetic poles (paleopoles) with age resolution of a few million years. Modern generations of apparent polar wander paths (APWPs) are becoming increasingly sophisticated in handling ever-growing volumes of data, usually by applying moving windows (e.g., 10 Myr) to the available paleopoles. Averaging paleopoles of fast moving plates may however result in loss of resolution whereby abrupt (but real) changes in APWP may appear subdued when a multimillion-year moving window is applied. Episodes of fast motion are better captured by using paleopoles with best age resolution (coupled with good structural control and provided with inclination flattening estimates) grouped within discrete and independent time windows. Best age control is attained when paleopoles are retrieved from laterally reproducible magnetostratigraphic sections calibrated with biostratigraphy and/or radiometric dating and correlated with reference timescales. This approach was recently applied to the construction of the Adria-Africa APWP (Muttoni et al. 2013). Paleopoles from parautochthonous regions of Adria and obtained either from biostratigraphically dated sedimentary rocks, corrected for inclination shallowing, or from radiometrically dated igneous rocks that are regarded as free from inclination shallowing, were compared with coeval, and inclination flattening-free, paleopoles from stable Africa. The resulting composite APWP shows a remarkable agreement with the Kent and Irving (2010) APWP, and displays a rapid polar shift of ~40° during the Jurassic that other APWPs tend to underestimate. This Jurassic monster shift is also predicted for Eurasia. Paleomagnetic data from the Kimmeridgian-Tithonian Garedu Formation of Iran, which was part of Eurasia since the Triassic, indicate a paleolatitude of deposition that is in excellent agreement with the latitude drop predicted by the monster shift (Mattei et al. 2014), which stands as a major and generalized plate motion event of vast and as yet unexplored paleogeographic implications.

  17. Polarization and polar climate

    NASA Astrophysics Data System (ADS)

    Overland, James; Schweitzer, Peter

    2012-10-01

    International Polar Year 2012 Conference: From Knowledge to Action;Montreal, Quebec, Canada, 22-27 April 2012 As a follow- up to the 2007-2008 International Polar Year (IPY), more than 3000 international participants came together in April 2012 at a conference entitled “From Knowledge to Action.” The conference addressed a broad scope of topics beyond academic science to include challenges of globalization, climate change, and social and economic issues. Participants included researchers and others with expertise in multiple fields: policy and decision making, law, industry, nongovernmental organizations, circumpolar communities, and indigenous peoples. The challenge of translating academic and other forms of knowledge into societal benefits dominated the event.

  18. Controlled suppression of superconductivity by the generation of polarized Cooper pairs in spin-valve structures

    NASA Astrophysics Data System (ADS)

    Flokstra, M. G.; Cunningham, T. C.; Kim, J.; Satchell, N.; Burnell, G.; Curran, P. J.; Bending, S. J.; Kinane, C. J.; Cooper, J. F. K.; Langridge, S.; Isidori, A.; Pugach, N.; Eschrig, M.; Lee, S. L.

    2015-02-01

    Transport measurements are presented on thin-film superconducting spin-valve systems, where the controlled noncollinear arrangement of two ferromagnetic Co layers can be used to influence the superconducting state of Nb. We observe a very clear oscillation of the superconducting transition temperature with the relative orientation of the two ferromagnetic layers. Our measurements allow us to distinguish between the competing influences of domain averaging, stray dipolar fields, and the formation of superconducting spin triplets. Domain averaging is shown to lead to a weak enhancement of transition temperature for the antiparallel configuration of exchange fields, while much larger changes are observed for other configurations, which can be attributed to drainage currents due to spin triplet formation.

  19. Polarization Manipulation via Orientation Control in Polycrystalline BiFeO3 Thin Films on Biaxially Textured, Flexible Metallic Tapes

    SciTech Connect

    Shin, Junsoo [ORNL; Goyal, Amit [ORNL; Jesse, Stephen [ORNL; Heatherly Jr, Lee [ORNL

    2011-01-01

    (111)-, (101)-, and (001)-oriented polycrystalline BiFeO3 films were fabricated on rolling-assisted biaxially textured substrates (RABiTS) with appropriate, buffer layer engineering of heteroepitaxially grown buffer multilayers on RABiTS. The crystallographic orientation and polarization direction were confirmed using X-ray diffraction and piezoresponse force microscopy (PFM), respectively. All the films exhibited excellent ferroelectric properties. Switching spectroscopy PFM demonstrated that the switching polarization in (111)-oriented polycrystalline BiFeO3 films is higher than (101) or (001) oriented films. These high-quality, BiFeO3 films on low-cost, flexible, biaxially textured metallic tapes with controllable orientation and polarization are attractive for application in flexible ferroelectric devices.

  20. Controlling the polarity of metalorganic vapor phase epitaxy-grown GaP on Si(111) for subsequent III-V nanowire growth

    NASA Astrophysics Data System (ADS)

    Paszuk, A.; Brückner, S.; Steidl, M.; Zhao, W.; Dobrich, A.; Supplie, O.; Kleinschmidt, P.; Prost, W.; Hannappel, T.

    2015-06-01

    Nanowire growth on heteroepitaxial GaP/Si(111) by metalorganic vapor phase epitaxy requires the [-1-1-1] face, i.e., GaP(111) material with B-type polarity. Low-energy electron diffraction (LEED) allows us to identify the polarity of GaP grown on Si(111), since (2×2) and (1×1) surface reconstructions are associated with GaP(111)A and GaP(111)B, respectively. In dependence on the pre-growth treatment of the Si(111) substrates, we were able to control the polarity of the GaP buffers. GaP films grown on the H-terminated Si(111) surface exhibited A-type polarity, while GaP grown on Si surfaces terminated with arsenic exhibited a (1×1) LEED pattern, indicating B-type polarity. We obtained vertical GaAs nanowire growth on heteroepitaxial GaP with (1×1) surface reconstruction only, in agreement with growth experiments on homoepitaxially grown GaP(111).

  1. Polar Bear Polar Bear

    NSDL National Science Digital Library

    Kelly Burgess

    2012-09-11

    In this lesson, students will listen for key details in a nonfiction text about polar bears. They will work at completing a graphic organizer with the teacher to help organize their thinking and understanding of key details about a text. They will also complete an independent assignment where they will draw or write two things that they learned about the topic.

  2. Cell polarity and hyphal morphogenesis are controlled by multiple rho-protein modules in the filamentous ascomycete Ashbya gossypii.

    PubMed Central

    Wendland, J; Philippsen, P

    2001-01-01

    Polarized cell growth requires a polarized organization of the actin cytoskeleton. Small GTP-binding proteins of the Rho-family have been shown to be involved in the regulation of actin polarization as well as other processes. Hyphal growth in filamentous fungi represents an ideal model to investigate mechanisms involved in generating cell polarity and establishing polarized cell growth. Since a potential role of Rho-proteins has not been studied so far in filamentous fungi we isolated and characterized the Ashbya gossypii homologs of the Saccharomyces cerevisiae CDC42, CDC24, RHO1, and RHO3 genes. The AgCDC42 and AgCDC24 genes can both complement conditional mutations in the S. cerevisiae CDC42 and CDC24 genes and both proteins are required for the establishment of actin polarization in A. gossypii germ cells. Agrho1 mutants show a cell lysis phenotype. Null mutant strains of Agrho3 show periodic swelling of hyphal tips that is overcome by repolarization and polar hyphal growth in a manner resembling the germination pattern of spores. Thus different Rho-protein modules are required for distinct steps during polarized hyphal growth of A. gossypii. PMID:11156982

  3. The ecological controls on the prevalence of candidate division TM7 in polar regions

    PubMed Central

    Winsley, Tristrom J.; Snape, Ian; McKinlay, John; Stark, Jonny; van Dorst, Josie M.; Ji, Mukan; Ferrari, Belinda C.; Siciliano, Steven D.

    2014-01-01

    The candidate division TM7 is ubiquitous and yet uncultured phylum of the Bacteria that encompasses a commonly environmental associated clade, TM7-1, and a “host-associated” clade, TM7-3. However, as members of the TM7 phylum have not been cultured, little is known about what differs between these two clades. We hypothesized that these clades would have different environmental niches. To test this, we used a large-scale global soil dataset, encompassing 223 soil samples, their environmental parameters and associated bacterial 16S rRNA gene sequence data. We correlated chemical, physical and biological parameters of each soil with the relative abundance of the two major classes of the phylum to deduce factors that influence the groups' seemingly ubiquitous nature. The two classes of the phylum (TM7-1 and TM7-3) were indeed distinct from each other in their habitat requirements. A key determinant of each class' prevalence appears to be the pH of the soil. The class TM7-1 displays a facultative anaerobic nature with correlations to more acidic soils with total iron, silicon, titanium and copper indicating a potential for siderophore production. However, the TM7-3 class shows a more classical oligotrophic, heterotroph nature with a preference for more alkaline soils, and a probable pathogenic role with correlations to extractable iron, sodium and phosphate. In addition, the TM7-3 was abundant in diesel contaminated soils highlighting a resilient nature along with a possible carbon source. In addition to this both classes had unique co-occurrence relationships with other bacterial phyla. In particular, both groups had opposing correlations to the Gemmatimonadetes phylum, with the TM7-3 class seemingly being outcompeted by this phylum to result in a negative correlation. These ecological controls allow the characteristics of a TM7 phylum preferred niche to be defined and give insight into possible avenues for cultivation of this previously uncultured group. PMID:25076941

  4. Phase-controlled polarization coherent anti-Stokes Raman scattering microscopy for high-sensitivity and high-contrast molecular imaging

    Microsoft Academic Search

    Fake Lu; Wei Zheng; Zhiwei Huang

    2008-01-01

    We report on a phase-controlled polarization coherent anti-Stokes Raman scattering (CARS) microscopy for high-sensitivity and high-contrast molecule vibrational imaging. By changing the phase difference between the two CARS signals (i.e., a weak resonant CARS and a strong nonresonant CARS signal) simultaneously gen- erated from the same focal volume of the sample, the complete constructive (in-phase) and destructive (out-of- phase) interference

  5. Phosphatidylinositol 4,5-Bisphosphate Influences PIN Polarization by Controlling Clathrin-Mediated Membrane Trafficking in Arabidopsis[C][W

    PubMed Central

    Ischebeck, Till; Werner, Stephanie; Krishnamoorthy, Praveen; Lerche, Jennifer; Meijón, Mónica; Stenzel, Irene; Löfke, Christian; Wiessner, Theresa; Im, Yang Ju; Perera, Imara Y.; Iven, Tim; Feussner, Ivo; Busch, Wolfgang; Boss, Wendy F.; Teichmann, Thomas; Hause, Bettina; Persson, Staffan; Heilmann, Ingo

    2013-01-01

    The functions of the minor phospholipid phosphatidylinositol-4,5-bisphosphate [PtdIns(4,5)P2] during vegetative plant growth remain obscure. Here, we targeted two related phosphatidylinositol 4-phosphate 5-kinases (PI4P 5-kinases) PIP5K1 and PIP5K2, which are expressed ubiquitously in Arabidopsis thaliana. A pip5k1 pip5k2 double mutant with reduced PtdIns(4,5)P2 levels showed dwarf stature and phenotypes suggesting defects in auxin distribution. The roots of the pip5k1 pip5k2 double mutant had normal auxin levels but reduced auxin transport and altered distribution. Fluorescence-tagged auxin efflux carriers PIN-FORMED (PIN1)–green fluorescent protein (GFP) and PIN2-GFP displayed abnormal, partially apolar distribution. Furthermore, fewer brefeldin A–induced endosomal bodies decorated by PIN1-GFP or PIN2-GFP formed in pip5k1 pip5k2 mutants. Inducible overexpressor lines for PIP5K1 or PIP5K2 also exhibited phenotypes indicating misregulation of auxin-dependent processes, and immunolocalization showed reduced membrane association of PIN1 and PIN2. PIN cycling and polarization require clathrin-mediated endocytosis and labeled clathrin light chain also displayed altered localization patterns in the pip5k1 pip5k2 double mutant, consistent with a role for PtdIns(4,5)P2 in the regulation of clathrin-mediated endocytosis. Further biochemical tests on subcellular fractions enriched for clathrin-coated vesicles (CCVs) indicated that pip5k1 and pip5k2 mutants have reduced CCV-associated PI4P 5-kinase activity. Together, the data indicate an important role for PtdIns(4,5)P2 in the control of clathrin dynamics and in auxin distribution in Arabidopsis. PMID:24326589

  6. Dynamic nuclear self-polarization with circularly polarized light

    NASA Astrophysics Data System (ADS)

    Koizumi, M.; Goto, J.; Matsuki, S.

    2011-07-01

    Lattice nuclei of III-V type semiconductors can be self-polarized through the contact hyperfine interaction with artificially excited conduction electrons at extremely low temperatures. In the self-polarization process, a positive feedback between the nuclear magnetization and the expansion of the energy splitting of the conduction electron states due to this nuclear magnetization takes an essential role. Extending the original theoretical work on the self-polarization with linearly polarized (LP) light by Dyakonov and Perel,1 we examined the effect of the circularly polarized (CP) light on the phenomenon of the nuclear self-polarization. While no polarization is obtained with LP light above the critical temperature, the nuclear polarization is enhanced also above the critical temperatures with CP light. More important finding in the application of CP light is that the direction of the nuclear polarization can be controlled by the orientation of the excited conduction-electron polarization, which is easily manipulated by changing the degree of polarization of the excitation light. Related to this polarization change, it is also remarked that the nuclear polarization shows a hysteresis phenomenon below the critical temperature when the degree of the electron polarization is swept up and down.

  7. High-temperature operating 894.6nm-VCSELs with extremely low threshold for Cs-based chip scale atomic clocks.

    PubMed

    Zhang, Jianwei; Zhang, Xing; Zhu, Hongbo; Zhang, Jian; Ning, Yongqiang; Qin, Li; Wang, Lijun

    2015-06-01

    We report on the design and fabrication of 894.6nm vertical-cavity surface-emitting lasers (VCSELs) with extremely low threshold at high temperatures, for use in chip-scale Cs atomic clocks. A new design method based on the analysis of the threshold gain and the desired carrier density for different active region structures was proposed to gain the low transparent current density. The increase of the threshold current at higher temperatures was successfully suppressed by introducing the large gain-cavity detuning of VCSEL. By detuning the gain-cavity mode to be -11nm, the minimum threshold current of only 0.23mA at 70 °C was achieved. The operating temperature for emitting the wavelength of 894.6nm was 110 °C, with the single mode suppression ratio (SMSR) of more than 25dB and the threshold current of only 0.32mA. PMID:26072835

  8. 2.49 GHz low phase-noise optoelectronic oscillator using 1.55?m VCSEL for avionics and aerospace applications

    Microsoft Academic Search

    Ahmad Hayat; Margarita Varon; Alexandre Bacou; A. Rissons; J.-C. Mollier

    2008-01-01

    We present here a 1.55 mum single mode vertical-cavity surface-emitting laser (VCSEL) based low phase-noise ring optoelectronic (OEO) oscillator operating at 2.49 GHz for aerospace, avionics and embedded systems applications. Experiments using optical fibers of different lengths have been carried out to obtain optimal results. A phase-noise measurement of -107 dBc\\/Hz at an offset of 10 kHz from the carrier

  9. Quad 14 Gbps L-band VCSEL-based system for WDM migration of 4-lanes 56 Gbps optical data links.

    PubMed

    Estaran, Jose; Rodes, Roberto; Pham, Tien Thang; Ortsiefer, Markus; Neumeyr, Christian; Rosskopf, Jürgen; Monroy, Idelfonso Tafur

    2012-12-17

    We report on migrating multiple-lane link into an L-band VCSEL-based WDM system. Experimental validation achieves successful transmission over 10 km of SMF at 4x14Gbps. Inter-channel crosstalk penalty is observed to be less than 0.5 dB and a transmission penalty around 1 dB. The power budget margin ranges within 6 dB and 7 dB. PMID:23263089

  10. Multigigabit\\/s perfluorinated graded-index plastic-optical-fiber data links with butt-coupled single-mode InGaAs VCSEL

    Microsoft Academic Search

    Felix Mederer; Roland Jaeger; Peter Schnitzer; Heiko J. Unold; Max Kicherer; Karl J. Ebeling; Masaki Naritomi; Ryouta Yoshida

    1999-01-01

    Vertical-cavity surface-emitting lasers (VCSELs) with emission wavelengths in the range from 850 nm to 950 nm are highly attractive light sources for low-cost, high-speed data transmission over several hundred meters of perfluorinated graded-index plastic-optical fibers (GI- POFs). Multi-Gigabit\\/s data transmission over common PMA- based step-index POFs is generally limited to several meters predominantly due to dispersion. Here, we demonstrate 3

  11. Performance comparison of 850-nm and 1550-nm VCSELs exploiting OOK, OFDM, and 4-PAM over SMF/MMF links for low-cost optical interconnects

    NASA Astrophysics Data System (ADS)

    Karinou, Fotini; Deng, Lei; Lopez, Roberto Rodes; Prince, Kamau; Jensen, Jesper Bevensee; Monroy, Idelfonso Tafur

    2013-06-01

    We experimentally compare the performance of two commercially available vertical-cavity surface-emitting laser diodes (VCSELs), a multi-mode 850-nm and a single-mode 1550-nm, exploiting on-off keying/direct detection (OOK/DD), and orthogonal frequency division multiplexed (OFDM) quadrature phase-shift keying (QPSK)/16-ary quadrature amplitude modulation (16QAM) with direct detection, over SMF (100 m and 5 km) and MMF (100 m and 1 km) short-range links, for their potential application in low-cost rack-to-rack optical interconnects. Moreover, we assess the performance of quaternary-pulse amplitude modulation (4-PAM), for the 1550-nm transmitter over SMF and MMF links and we compare it to the data-rate equivalent NRZ-OOK. The extensive performance comparison under various transmission scenarios shows the superiority of 1550-nm single-mode VCSEL compared to its multi-mode 850-nm counterpart. Moreover, OFDM/DD and 4-PAM in conjunction with low-cost, inexpensive VCSELs as transmitters prove to be an enabling technology for next-generation WDM, point-to-point, short-reach, SMF/MMF optical interconnects and potential candidates to substitute NRZ-OOK. Nevertheless, the sensitivity requirements are higher in that case, whereas these advanced, spectrally-efficient modulation formats become severely degraded when transmitted over MMF links, especially, when employing the inexpensive 850-nm VCSELs as transmitter. Finally, we compare the performance of the point-to-point links under investigation to the performance of a semiconductor optical amplifier (SOA)- based, scalable permutation switch fabric, the Optical Shared MemOry Supercomputer Interconnect System (OSMOSIS).

  12. Wavelength tuning and controlled temperature dependence in vertical-cavity surface-emitting lasers with a thermally and electrostatically actuated cantilever structure

    NASA Astrophysics Data System (ADS)

    Nakahama, Masanori; Sano, Hayato; Inoue, Shunya; Sakaguchi, Takahiro; Matsutani, Akihiro; Ahmed, Moustafa; Bakry, Ahmed; Koyama, Fumio

    2014-01-01

    We demonstrate the wavelength tuning and the control of its temperature dependence in 850 nm GaAs vertical cavity surface emitting lasers (VCSELs) using a thermally and electrostatically actuated cantilever structure. The temperature dependence can be controlled from +0.035 to -0.14 nm/K by changing the length of a micromachined cantilever, which can be electrostatically actuated for wavelength tuning. Continuous wavelength tuning over 36 nm was obtained keeping almost constant temperature dependence. The result indicates a possibility of realizing widely-tunable VCSELs with engineered temperature dependence.

  13. Polarized Sunglasses

    NSDL National Science Digital Library

    2011-12-05

    In this activity, learners explore how polarizing sunglasses can help diminish road glare. By rotating a pair of polarizing sunglass lenses or other polarizing materials, learners will discover that some angles are better at reducing glare than others. Learners observe light from the sky, reflected from a mirror, or reflected from the surface of a pond. Use this activity to introduce learners to principles of light and polarization.

  14. RHIC Polarized proton operation

    SciTech Connect

    Huang, H.; Ahrens, L.; Alekseev, I.G.; Aschenauer, E.; Atoian, G.; Bai, M.; Bazilevsky, A.; Blaskiewicz, M.; Brennan, J.M.; Brown, K.A.; Bruno, D.; Connolly, R.; Dion, A.; D'Ottavio, T.; Drees, K.A.; Fischer, W.; Gardner, C.; Glenn, J.W.; Gu, X.; Harvey, M.; Hayes, T.; Hoff, L.; Hulsart, R.L.; Laster, J.; Liu, C.; Luo, Y.; MacKay, W.W.; Makdisi, Y.; Marr, G.J.; Marusic, A.; Meot, F.; Mernick, K.; Michnoff, R,; Minty, M.; Montag, C.; Morris, J.; Nemesure, S.; Poblaguev, A.; Ptitsyn, V.; Ranjibar, V.; Robert-Demolaize, G.; Roser, T.; J.; Severino, F.; Schmidke, B.; Schoefer, V.; Severino, F.; Smirnov, D.; Smith, K.; Steski, D.; Svirida, D.; Tepikian, S.; Trbojevic, D.; Tsoupas, N.; Tuozzolo, J. Wang, G.; Wilinski, M.; Yip, K.; Zaltsman, A.; Zelenski, A.; Zeno, K.; Zhang, S.Y.

    2011-03-28

    The Relativistic Heavy Ion Collider (RHIC) operation as the polarized proton collider presents unique challenges since both luminosity(L) and spin polarization(P) are important. With longitudinally polarized beams at the experiments, the figure of merit is LP{sup 4}. A lot of upgrades and modifications have been made since last polarized proton operation. A 9 MHz rf system is installed to improve longitudinal match at injection and to increase luminosity. The beam dump was upgraded to increase bunch intensity. A vertical survey of RHIC was performed before the run to get better magnet alignment. The orbit control is also improved this year. Additional efforts are put in to improve source polarization and AGS polarization transfer efficiency. To preserve polarization on the ramp, a new working point is chosen such that the vertical tune is near a third order resonance. The overview of the changes and the operation results are presented in this paper. Siberian snakes are essential tools to preserve polarization when accelerating polarized beams to higher energy. At the same time, the higher order resonances still can cause polarization loss. As seen in RHIC, the betatron tune has to be carefully set and maintained on the ramp and during the store to avoid polarization loss. In addition, the orbit control is also critical to preserve polarization. The higher polarization during this run comes from several improvements over last run. First we have a much better orbit on the ramp. The orbit feedback brings down the vertical rms orbit error to 0.1mm, much better than the 0.5mm last run. With correct BPM offset and vertical realignment, this rms orbit error is indeed small. Second, the jump quads in the AGS improved input polarization for RHIC. Third, the vertical tune was pushed further away from 7/10 snake resonance. The tune feedback maintained the tune at the desired value through the ramp. To calibrate the analyzing power of RHIC polarimeters at any energy above injection, the polarized hydrogen jet target runs for every fill with both beams. Based on the known analyzing power, there is very little polarization loss between injection and 100 GeV. An alternative way is to measure the asymmetry at 100 GeV followed by ramping up to 250 GeV and back down to 100 GeV and then to measure the asymmetry again at 100 GeV. If the asymmetry after the down ramp is similar to the measurement before the up ramp, polarization was also preserved during the ramp to 250 GeV. The analyzing power at storage energy can then be extracted from the asymmetries measured at 100 GeV and 250 GeV. The tune and orbit feedbacks are essential for the down ramp to be possible. The polarized proton operation is still going on. We will push bunch intensity higher until reaching the beam-beam limit. The even higher intensity will have to wait for the electron lenses to compensate the beam-beam effect. To understand the details of spin dynamics in RHIC with two snakes, spin simulation with the real magnet fields have been developed recently. The study will provide guidance for possible polarization loss schemes. Further polarization gain will requires a polarized source upgrade; more careful setup jump quads in the AGS to get full benefit; and control emittance in the whole accelerator chain.

  15. aPKC Phosphorylates p27Xic1, Providing a Mechanistic Link between Apicobasal Polarity and Cell-Cycle Control

    PubMed Central

    Sabherwal, Nitin; Thuret, Raphael; Lea, Robert; Stanley, Peter; Papalopulu, Nancy

    2014-01-01

    Summary During the development of the nervous system, apicobasally polarized stem cells are characterized by a shorter cell cycle than nonpolar progenitors, leading to a lower differentiation potential of these cells. However, how polarization might be directly linked to the kinetics of the cell cycle is not understood. Here, we report that apicobasally polarized neuroepithelial cells in Xenopus laevis have a shorter cell cycle than nonpolar progenitors, consistent with mammalian systems. We show that the apically localized serine/threonine kinase aPKC directly phosphorylates an N-terminal site of the cell-cycle inhibitor p27Xic1 and reduces its ability to inhibit the cyclin-dependent kinase 2 (Cdk2), leading to shortening of G1 and S phases. Overexpression of activated aPKC blocks the neuronal differentiation-promoting activity of p27Xic1. These findings provide a direct mechanistic link between apicobasal polarity and the cell cycle, which may explain how proliferation is favored over differentiation in polarized neural stem cells. PMID:25490266

  16. Polarized Electrons for Polarized Positrons

    NASA Astrophysics Data System (ADS)

    Fanchini, Erica

    2012-03-01

    Recently, the nuclear and high-energy physics communities have shown a growing interest in the availability of high current, highly spin-polarized positron beams. The Polarized Electrons for Polarized Positrons (PEPPo) experiment at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) aims to measure the transfer of polarization from a low energy 10 MeV highly spin polarized electron beam to positrons. A sufficiently energetic polarized photon or lepton may generate, via bremsstrahlung and pair creation processes within a target foil, electron-positron pairs that will carry a fraction of the initial polarization. This approach has been successfully tested using polarized photons created with a multi-GeV unpolarized electron beam, resulting in positrons with polarization of 80%. Although pair creation yield is reduced at lower energy, recent advances in high current milliampere spin-polarized electron sources at Jefferson Lab offer the perspective of creating polarized positrons using a low energy electron beam. A successful demonstration of this technique would provide an alternative scheme to produce low energy polarized positrons, as well as useful information to optimize the design of a polarized positron source using sub-GeV electron beam. An overview and status of the PEPPo experiment will be presented, along with some of the motivations in the context of the Jefferson Lab nuclear physics program.

  17. Spatial-mode control of vertical-cavity lasers with micromirrors fabricated and replicated in semiconductor materials.

    PubMed

    Nikolajeff, F; Ballen, T A; Leger, J R; Gopinath, A; Lee, T C; Williams, R C

    1999-05-10

    Micromirrors were fabricated in gallium phosphide by mass transport to provide spatial-mode control of vertical-cavity surface-emitting lasers (VCSEL's). The concave mirrors were used in an external-cavity configuration to provide spatial filtering in the far field. Single-mode cw lasing was demonstrated in 15-microm-diameter VCSEL's with currents as high as 6 times threshold. The fabrication process was extended to micromirrors in gallium arsenide by use of a replication and dry-etch transfer process. PMID:18319888

  18. Gravity and light control of the developmental polarity of regenerating protoplasts isolated from prothallial cells of the fern Ceratopteris richardii

    NASA Technical Reports Server (NTRS)

    Edwards, E. S.; Roux, S. J.

    1998-01-01

    A procedure has been developed for isolating protoplasts from prothalli of Ceratopteris richardii which can be cultured and are capable of regeneration. Protoplasts were isolated from 2-week-old gametophytes in a medium containing wall-digesting enzymes in 0.5 M sucrose, followed by purification of the released protoplasts by floating them up into a 0.5 M sorbitol layer. Regeneration occurred over a period of 10-24 days, and, under optimal osmotic conditions, followed the developmental pattern seen during spore germination, in that the first division gave rise to a primary rhizoid. Thus, prothallial protoplasts are comparable to germinating spores as suitable models for studies of developmental polarity in single cells. As in germinating spores, the polarity of development in regenerating protoplasts is influenced by the vectors of gravity and unilateral light. However, the relative influence of light in fixing this polarity is greater in regenerating protoplasts, while in germinating spores, the influence of gravity is greater.

  19. Polarization Effects in Optical Free Space Communications

    Microsoft Academic Search

    E. B. Gindele; T. L. Miller

    1986-01-01

    Polarization control in free space laser communications systems plays a critical role in systems modeling, design and configuration. The key issues of transmit\\/receive isolation and transmitted beam polarization form the basis of the discussion. Optical systems utilizing polarization effects differ from conventional optical systems in both design and analytical treatment. Starting with a review of polarization definitions and concepts, the

  20. Polarization effects in optical free space communications

    Microsoft Academic Search

    E. B. Gindele; T. L. Miller

    1986-01-01

    Polarization control in free space laser communications systems plays a critical role in systems modeling, design, and configuration. The key issues of transmit\\/receive isolation and transmitted beam polarization form the basis of the discussion. Optical systems utilizing polarization effects differ from conventional optical systems in both design and analytical treatment. Starting with a review of polarization definitions and concepts, the

  1. Planar polarization of Vangl2 in the vertebrate neural plate is controlled by Wnt and Myosin II signaling

    PubMed Central

    Ossipova, Olga; Kim, Kyeongmi; Sokol, Sergei Y.

    2015-01-01

    The vertebrate neural tube forms as a result of complex morphogenetic movements, which require the functions of several core planar cell polarity (PCP) proteins, including Vangl2 and Prickle. Despite the importance of these proteins for neurulation, their subcellular localization and the mode of action have remained largely unknown. Here we describe the anteroposterior planar cell polarity (AP-PCP) of the cells in the Xenopus neural plate. At the neural midline, the Vangl2 protein is enriched at anterior cell edges and that this localization is directed by Prickle, a Vangl2-interacting protein. Our further analysis is consistent with the model, in which Vangl2 AP-PCP is established in the neural plate as a consequence of Wnt-dependent phosphorylation. Additionally, we uncover feedback regulation of Vangl2 polarity by Myosin II, reiterating a role for mechanical forces in PCP. These observations indicate that both Wnt signaling and Myosin II activity regulate cell polarity and cell behaviors during vertebrate neurulation. PMID:25910938

  2. IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 23, NO. 5, MARCH 1, 2011 305 Control of Polarization Phase Offset in Low

    E-print Network

    Coldren, Larry A.

    ; date of current version February 24, 2011. This work was supported by the Defense Advanced Research Projects Agency (DARPA) through an STTR with ZIVA Corp. The authors are with the University of California polarization states is demonstrated. A novel dual intracavity contacted vertical-cavity surface-emitting laser

  3. Numerical simulation of temperature-dependence on distributed Bragg reflector (DBR) and performance analyses for proton-implant/oxide confined VCSEL: comparison with transmission matrix, matrix calculating methods, and Macleod model

    NASA Astrophysics Data System (ADS)

    Tsai, Hong-Mau; Tang, Shiang-Feng; Sua, Shih-Tsang; Chen, Tzu-Chiang; Chiang, Cheng-Der

    2007-02-01

    This paper mainly focuses on the simulation for temperature-dependent Distributed Bragg Reflector (DBR) of 850nm vertical cavity surface emitting laser (VCSEL) with Transmission Matrix (TMM), Matrix Calculating Methods (MCM) and Macleod Model and performance for comparison with proton-implant/oxide confined process on VCSEL. Using well-developed temperature-dependent DBR-reflectivity solver with Mathcad simulator, we have successfully compared the Macleod Model simulator with theoretical self-developed solution based on the Transmission Matrix (TMM), Matrix Calculating Methods (MCM) and find very good agreement with previous results while accounting for influences of conjugated part of refractive index and graded Al compositions of DBR materials. Moreover, optoelectronic performance of Proton-Implant/Oxide Confined 850nm VCSEL have been demonstrated on this paper using temperature-dependent power output, voltage/injection current, transverse operating wavelengths, optical spectral characteristics, slope efficiency and transverse optical modes with an approximated Marcatili's method extracted and measurement from systematically measuring experiments. Through adequate and precise LD device design and processes, we have proposed the high performance single-mode proton implanted in contrast to the oxide confined 850 nm VCSEL. Under nominal temperature-variety and keeping operating temperature of 30°C,the threshold voltage, injecting current, peak-wavelength and differential resistance of the proton implanted VCSEL with the optical aperture in the dimension of 10 ?m are 1.8 V, 3.2 mA, 851 nm and 36.8 ohm, respectively.

  4. Polarization developments

    SciTech Connect

    Prescott, C.Y.

    1993-07-01

    Recent developments in laser-driven photoemission sources of polarized electrons have made prospects for highly polarized electron beams in a future linear collider very promising. This talk discusses the experiences with the SLC polarized electron source, the recent progress with research into gallium arsenide and strained gallium arsenide as a photocathode material, and the suitability of these cathode materials for a future linear collider based on the parameters of the several linear collider designs that exist.

  5. Neuronal polarization.

    PubMed

    Takano, Tetsuya; Xu, Chundi; Funahashi, Yasuhiro; Namba, Takashi; Kaibuchi, Kozo

    2015-06-15

    Neurons are highly polarized cells with structurally and functionally distinct processes called axons and dendrites. This polarization underlies the directional flow of information in the central nervous system, so the establishment and maintenance of neuronal polarization is crucial for correct development and function. Great progress in our understanding of how neurons establish their polarity has been made through the use of cultured hippocampal neurons, while recent technological advances have enabled in vivo analysis of axon specification and elongation. This short review and accompanying poster highlight recent advances in this fascinating field, with an emphasis on the signaling mechanisms underlying axon and dendrite specification in vitro and in vivo. PMID:26081570

  6. "A" cation polarity control in ACuTe2O7 (A = Sr2+, Ba2+, or Pb2+).

    PubMed

    Yeon, Jeongho; Kim, Sang-Hwan; Hayward, Michael A; Halasyamani, P Shiv

    2011-09-01

    The synthesis and characterization of ACuTe(2)O(7) (A = Sr(2+), Ba(2+), or Pb(2+)) have been carried out. Interestingly, SrCuTe(2)O(7) and PbCuTe(2)O(7) are centrosymmetric and isostructural, whereas BaCuTe(2)O(7) is noncentrosymmetric and polar. All of the materials contain [CuTe(2)O(7)](2-) layers stacked along the b-axis direction that are separated by the "A" cations. The layers are composed of corner-shared CuO(5), TeO(6), and TeO(4) polyhedra. The influence of the "A" cation on the polarity is described by bond valence concepts, including the bond strain index and global instability index. Infrared, UV-vis, thermogravimetric, differential thermal analysis, and magnetic measurements were performed on all three materials. For BaCuTe(2)O(7), second-harmonic generation (SHG), piezoelectric, and polarization measurements were performed. A moderate SHG efficiency of approximately 70 × ?-SiO(2) was measured. In addition, we determined that BaCuTe(2)O(7) is not ferroelectric; that is, the macroscopic polarization is not reversible. For BaCuTe(2)O(7), a pyroelectric coefficient of -9.5 ?C/m(2)·K at 90 °C and a piezoelectric charge coefficient of 49 pm/V were determined. Crystal data are the following: SrCuTe(2)O(7), orthorhombic, space group Pbcm (No. 57), a = 7.1464(7) Å, b = 15.0609(15) Å, c = 5.4380(5) Å, V = 585.30(10) Å(3), and Z = 4; PbCuTe(2)O(7), orthorhombic, space group Pbcm (No. 57), a = 7.2033(5) Å, b = 15.0468(10) Å, c = 5.4691(4) Å, V = 592.78(7) Å(3), and Z = 4. PMID:21800873

  7. Electric-field control of the chiral magnetism of multiferroic MnWO4 as seen via polarized neutron diffraction

    Microsoft Academic Search

    T. Finger; D. Senff; K. Schmalzl; W. Schmidt; L. P. Regnault; P. Becker; L. Bohaty; M. Braden

    2010-01-01

    The chiral components in the magnetic order in multiferroic MnWO4 have been studied by neutron diffraction using spherical polarization analysis as a function of temperature and of external electric field. We show that sufficiently close to the ferroelectric transition at T=12.3K it is possible to switch the chiral component by applying moderate electric fields at constant temperature. Full hysteresis cycles

  8. Interference of polarized waves at the exit of crystal prisms and their use to control the wavefront flatness

    Microsoft Academic Search

    V. Yu. Osipov; Yu. V. Osipov; V. N. Popov; A. A. Buznikov

    2011-01-01

    A theoretical and experimental study was performed of the interference of polarized e- and o-waves generated by passing a laser beam (collimated, convergent or divergent) through a variable-splitting-angle birefringent\\u000a prism (VSABP) with inclined optical axes in the crystalline components of the prism. The VSABP-2 modification is suitable\\u000a for measuring the radius of curvature of the incident wavefront from the deflection

  9. Polarity and proliferation are controlled by distinct signaling pathways downstream of PI3-kinase in breast epithelial tumor cells

    Microsoft Academic Search

    Hong Liu; Derek C. Radisky; Fei Wang; Mina J. Bissell

    2004-01-01

    oss of tissue polarity and increased proliferation are the characteristic alterations of the breast tumor phenotype. To investigate these processes, we used a three-dimensional (3D) culture system in which malignant human breast cells can be reverted to a normal phenotype by exposure to inhibitors of phosphatidylinositol 3-kinase (PI3K). Using this assay, we find that Akt and Rac1 act as downstream

  10. Micellar and Biochemical Properties of (Hemi)Fluorinated Surfactants Are Controlled by the Size of the Polar Head

    PubMed Central

    Breyton, Cécile; Gabel, Frank; Abla, Maher; Pierre, Yves; Lebaupain, Florence; Durand, Grégory; Popot, Jean-Luc; Ebel, Christine; Pucci, Bernard

    2009-01-01

    Abstract Surfactants with fluorinated and hemifluorinated alkyl chains have yielded encouraging results in terms of membrane protein stability; however, the molecules used hitherto have either been chemically heterogeneous or formed heterogeneous micelles. A new series of surfactants whose polar head size is modulated by the presence of one, two, or three glucose moieties has been synthesized. Analytical ultracentrifugation and small-angle neutron scattering show that fluorinated surfactants whose polar head bears a single glucosyl group form very large cylindrical micelles, whereas those with two or three glucose moieties form small, homogeneous, globular micelles. We studied the homogeneity and stability of the complexes formed between membrane proteins and these surfactants by using bacteriorhodopsin and cytochrome b6f as models. Homogeneous complexes were obtained only with surfactants that form homogeneous micelles. Surfactants bearing one or two glucose moieties were found to be stabilizing, whereas those with three moieties were destabilizing. Fluorinated and hemifluorinated surfactants with a two-glucose polar head thus appear to be very promising molecules for biochemical applications and structural studies. They were successfully used for cell-free synthesis of the ion channel MscL. PMID:19686655

  11. Polarity protein Par3 controls B-cell receptor dynamics and antigen extraction at the immune synapse

    PubMed Central

    Reversat, Anne; Yuseff, Maria-Isabel; Lankar, Danielle; Malbec, Odile; Obino, Dorian; Maurin, Mathieu; Penmatcha, Naga Venkata Gayathri; Amoroso, Alejandro; Sengmanivong, Lucie; Gundersen, Gregg G.; Mellman, Ira; Darchen, François; Desnos, Claire; Pierobon, Paolo; Lennon-Duménil, Ana-Maria

    2015-01-01

    B-cell receptor (BCR) engagement with surface-tethered antigens leads to the formation of an immune synapse, which facilitates antigen uptake for presentation to T-lymphocytes. Antigen internalization and processing rely on the early dynein-dependent transport of BCR–antigen microclusters to the synapse center, as well as on the later polarization of the microtubule-organizing center (MTOC). MTOC repositioning allows the release of proteases and the delivery of MHC class II molecules at the synapse. Whether and how these events are coordinated have not been addressed. Here we show that the ancestral polarity protein Par3 promotes BCR–antigen microcluster gathering, as well as MTOC polarization and lysosome exocytosis, at the synapse by facilitating local dynein recruitment. Par3 is also required for antigen presentation to T-lymphocytes. Par3 therefore emerges as a key molecule in the coupling of the early and late events needed for efficient extraction and processing of immobilized antigen by B-cells. PMID:25631815

  12. Polar Bear

    USGS Publications Warehouse

    Amstrup, S.D.; DeMaster

    1988-01-01

    Polar bears are long-lived, late-maturing carnivores that have relatively low rates of reproduction and natural mortality. Their populations are susceptible to disturbance from human activities, such as the exploration and development of mineral resources or hunting. Polar bear populations have been an important renewable resource available to coastal communities throughout the Arctic for thousands of years.

  13. EDITORIAL: Polarization Optics

    NASA Astrophysics Data System (ADS)

    Turunen, Jari; Friesem, Asher A.; Friberg, Ari T.

    2004-03-01

    This special issue on Polarization Optics contains one review article and 23 research papers, many of which are based on presentations at the International Commission for Optics Topical Meeting on Polarization Optics, held in Polvijärvi, Finland, between 30 June and 3 July 2003. While this issue should not in any sense be considered as a `proceedings' of this meeting, the possibility of submitting papers to it was widely advertised during the meeting, which was attended by a large fraction of prominent scientists in the field of polarization optics. Thus the quality of papers in this special issue is high. In announcing both the meeting and this special issue, we emphasized that the concept of `polarization optics' should be understood in a wide sense. In fact, all contributions dealing with the vectorial nature of light were welcome. As a result, the papers included here cover a wide range of different aspects of linear and nonlinear polarization optics. Both theoretical and experimental features are discussed. We are pleased to see that the conference and this special issue both reflect the wide diversity of important and novel polarization phenomena in optics. The papers in this special issue, and other recently published works, demonstrate that even though polarization is a fundamental property of electromagnetic fields, interest in it is rapidly increasing. The fundamental relations between partial coherence and partial polarization are currently under vigorous research in electromagnetic coherence theory. In diffractive optics it has been found that the exploitation of the vectorial nature of light can be of great benefit. Fabrication of sophisticated, spatially variable polarization-control elements is becoming possible with the aid of nanolithography. Polarization singularities and the interplay of bulk properties and topology in nanoscale systems have created much enthusiasm. In nonlinear optics, the second harmonic waves generated on reflection and transmission of intense light enable research into the chirality of nanogratings. Pump-probe techniques allow one to visualize the effects of the nanostructure topology on the surface mode excitation. In quantum optics the coherent control of polarization may lead to new and fascinating applications. Some authors of invited papers at the conference have written review-type introductory sections—they were encouraged to do so—but all contributions are genuine research papers with original results, and were judged according to the normal publication criteria of the journal. It is our pleasure to thank all authors for making this a splendid special issue of Journal of Optics A: Pure and Applied Optics.

  14. Polarization Imaging Apparatus

    NASA Technical Reports Server (NTRS)

    Zou, Yingyin K.; Chen, Qiushui

    2010-01-01

    A polarization imaging apparatus has shown promise as a prototype of instruments for medical imaging with contrast greater than that achievable by use of non-polarized light. The underlying principles of design and operation are derived from observations that light interacts with tissue ultrastructures that affect reflectance, scattering, absorption, and polarization of light. The apparatus utilizes high-speed electro-optical components for generating light properties and acquiring polarization images through aligned polarizers. These components include phase retarders made of OptoCeramic (registered TradeMark) material - a ceramic that has a high electro-optical coefficient. The apparatus includes a computer running a program that implements a novel algorithm for controlling the phase retarders, capturing image data, and computing the Stokes polarization images. Potential applications include imaging of superficial cancers and other skin lesions, early detection of diseased cells, and microscopic analysis of tissues. The high imaging speed of this apparatus could be beneficial for observing live cells or tissues, and could enable rapid identification of moving targets in astronomy and national defense. The apparatus could also be used as an analysis tool in material research and industrial processing.

  15. Molecule Polarity

    NSDL National Science Digital Library

    The PhET project at the University of Colorado creates "fun, interactive, research-based simulations of physical phenomena." This particular one deals with molecular polarity. When is a molecule polar? Change the electronegativity of atoms in a molecule to see how it affects polarity. This simulation will allow visitors to see how molecules behave in an electric field, and change the bond angle to see how shape affects polarity for real molecules in 3D. The simulation is also paired with teaching tips and user-contirubed Teaching Ideas, lessons using the simulation in context, that can be found near the bottom of the page. The simulation is also available in multiple languages.

  16. Statistical study of Subauroral Polarization Streams (SAPS): Solar wind, ionospheric control and its effect on the thermosphere

    NASA Astrophysics Data System (ADS)

    Wang, H.; Luhr, H.; Ridley, A. J.; Ma, S.

    2011-12-01

    The effects of cross-polar cap potential (CPCP) and subauroral flux tube-integrated conductivity on the spatial distribution of Subauroral Polarization Streams (SAPS) have been investigated by using DMSP observations. For higher flux tube-integrated conductivity the SAPS tend to occur more poleward than for lower conductivity. The CPCP averaged over 15 min prior to the SAPS correlates best with the SAPS peak velocities. The high-latitude CPCP has a stronger effect on SAPS velocities for low integrated conductivity than for high conductivity. With coordinated CHAMP and DMSP observations we have further investigated the relationship between SAPS, ionospheric Hall current (electrojet), upper thermospheric zonal wind, and mass density at subauroral regions in the dusk and premidnight sectors. For comparison, we have also analyzed the same parameters as a function of magnetic latitude (30°-80° magnetic latitude) during nonSAPS periods. Both neutral and plasma velocities peak at the same latitude regardless of SAPS occurrence. The neutral wind during SAPS events gets enhanced by a factor of 1.5/1.2 for Kp<4 and 1.3/1.9 for Kp?4 in the Northern/Southern Hemisphere, respectively, as compared to nonSAPS time. The velocity difference between plasma drift and neutral wind is also larger during SAPS period than during nonSAPS period, and the difference tends to increase with increasing geomagnetic activity. The peak latitude of the eastward auroral electrojet appears 1.5° poleward of SAPS during SAPS events, confirming the formation of SAPS equatorward of the high conductivity channel. The upper thermosphere is heated during SAPS periods. As a result we observe a 10% enhanced mass density at 400 km altitude with respect to periods without SAPS. In addition a density anomaly peak occurs collocated with the SAPS, displaced from the electrojet peak. We regard this as an indication for efficient thermospheric heating by ion neutral friction.

  17. Comparison of InP- and GaSb-based VCSELs emitting at 2.3 ?m suitable for carbon monoxide detection

    NASA Astrophysics Data System (ADS)

    Boehm, Gerhard; Bachmann, Alexander; Rosskopf, Jürgen; Ortsiefer, Markus; Chen, Jia; Hangauer, Andreas; Meyer, Ralf; Strzoda, Rainer; Amann, Markus-Christian

    2011-05-01

    Carbon monoxide (CO) is a prominent and toxic gas mainly generated by imperfect burning in fires or ovens. For trace gas monitoring and fire detection a compact, long term stable and calibration-free CO sensor is desirable. One very interesting measuring method is Tuneable Diode Laser Absorption Spectroscopy (TDLAS), which utilizes the unique properties of Vertical-Cavity Surface-Emitting Lasers (VCSELs). Two approaches to reach the required wavelength range for the absorption lines of CO at around 2350 nm are discussed in this paper. The first approach is an expansion of the emission wavelength range of the now well-established lasers based on InP and a second and new one is fabricating VCSELs based on GaSb. From the epitaxial point of view the gain of the active material and the realization of a tunnel junction as well as optical, thermal and electrical characteristics of the mirror materials are important issues. For a proper choice of the device design the structuring of the used materials also plays a fundamental role- in particular the substrate removal. With simultaneous considerations of all these crucial issues, devices on InP and GaSb substrates have been fabricated. Both types work in continuous-wave mode, generating light in single-mode emission at the desired wavelength of the CO absorption line, which enables CO measurements down to a concentration limit of 2 ppm.

  18. Correlation of Martian South Polar CO2 Seasonal Cap Retreat With Low Altitude Clouds: A Control On Annual Accumulation

    NASA Astrophysics Data System (ADS)

    Smith, Isaac; Spiga, Aymeric

    2014-05-01

    Both the north and south polar layered deposits (NPLD and SPLD) comprise the majority of surface ice on Mars and offer a historical record for understanding recent climate. Of importance, the deposits undergo seasonal variability, between winter (when CO2 ice frost covers the polar regions) and summer (when the CO2 ice has sublimed). Recent evidence has shown that winds and atmospheric deposition played major roles for forming the spiral troughs that cover the NPLD. Observations of low altitude clouds (or visible expressions of katabatic jumps), radar stratigraphy, and surface morphology, in combination with high resolution mesoscale simulations from the Laboratoire de Météorologie Dynamique, demonstrate that ice is transported across the NPLD by wind to form and modify the troughs [Smith et al., 2013]. We employ the same techniques on the SPLD to find that the processes affecting southern spiral troughs are very similar, although there is an additional seasonal component not detected on the NPLD. Clouds, as mechanisms of deposition, retreat pole-ward during southern spring and summer. The retreat is matched spatially to modeled high speed winds near the CO2 seasonal ice cap boundary. Our mesoscale simulations reveal that topographic heights of the SPLD primarily drive slope-wind (katabatic) circulations. This existing circulation is reinforced by an additional thermally-direct circulation driven by the retreating CO2 ice in proximity to nearby exposed low albedo deposits, explaining why enhanced winds (and trough clouds) are mostly found in the vicinity of the CO2 seasonal ice boundary. In one simulation, at Ls 290°, the ice line is located so that the slope winds produced by the SPLD topography are optimally enhanced (up to 20 ms-1) by thermally directed circulations caused by a nearly 100 K thermal contrast. This work, in combination with detailed stratigraphic analysis from ground penetrating radar indicates that sites of deposition and retention of ice on the pole coincide with where clouds form. Thus clouds influenced by the retreating CO2 seasonal cap tell us where annual and long-term accumulation occurs. Regions with many clouds have thicker recent deposits, while those with no clouds have little or no recent accumulation. It is possible, and eventually testable with adequate modeling, that trough morphology is dependent on a seasonal CO2 ice cap and that the troughs themselves may require a seasonal cap to initiate.

  19. Configuration Manual Polarized Proton Collider at RHIC

    SciTech Connect

    Alekseev, I.; Allgower, C.; Bai, M.; Batygin, Y.; Bozano, L.; Brown, K.; Bunce, G.; Cameron, P.; Courant, E.; Erin, S.; Escallier, J.; Fischer, W.; Gupta, R.; Hatanka, K.; Huang, H.; Imai, K.; Ishihara, M.; Jain, A.; Kanavets, V.; Katayama, T.; Kawaguchi, T.; Kelly, E.; Kurita, K.; Lee, S. Y.; Luccio, A.; MacKay, W. W.; Mahler, G.; Makdisi, Y.; Mariam, F.; McGahern, W.; Morgan, G.; Muratore, J.; Okamura, M.; Peggs, S.; Pilat, F.; Ptitsin, V.; Ratner, L.; Roser, T.; Saito, N.; Satoh, H.; Shatunov, Y.; Spinka, H.; Svirida, D.; Syphers, M.; Tepikian, S.; Tominaka, T.; Tsoupas, N.; Underwood, D.; Vasiliev, A.; Wanderer, P.; Willen, E.; Wu, H.; Yokosawa, A.; Zelenski, A.

    2006-01-01

    In this report we present our design to accelerate and store polarized protons in RHIC, with the level of polarization, luminosity, and control of systematic errors required by the approved RHIC spin physics program. We provide an overview of the physics to be studied using RHIC with polarized proton beams, and a brief description of the accelerator systems required for the project.

  20. An ultra-bright white LED based non-contact skin cancer imaging system with polarization control

    NASA Astrophysics Data System (ADS)

    Günther, A.; Basu, C.; Roth, B.; Meinhardt-Wollweber, M.

    2013-06-01

    Early detection and excision of melanoma skin cancer is crucial for a successful therapy. Dermoscopy in direct contact with the skin is routinely used for inspection, but screening is time consuming for high-risk patients with a large number of nevi. Features like symmetry, border, color and most importantly changes like growth or depigmentation of a nevus may indicate malignancy. We present a non-contact remote imaging system for human melanocytic nevi with homogenous illumination by an ultra-bright white LED. The advantage compared to established dermoscopy systems requiring direct skin contact is that deformation of raised nevi is avoided and full-body scans of the patients may time-efficiently be obtained while they are in a lying, comfortable position. This will ultimately allow for automated screening in the future. In addition, calibration of true color rendering, which is essential for distinguishing between benign and malignant lesions and to ensure reproducibility and comparison between individual check-ups in order to follow nevi evolution is implemented as well as suppression of specular highlights on the skin surface by integration of polarizing filters. Important features of the system which will be crucial for future integration into automated systems are the possibility to record images without artifacts in combination with short exposure times which both reduce image blurring caused by patient motion.

  1. Reduction of phase-induced intensity noise in a fiber-based coherent Doppler lidar using polarization control.

    PubMed

    Rodrigo, Peter John; Pedersen, Christian

    2010-03-01

    Optimization of signal-to-noise ratio is an important aspect in the design of optical heterodyne detection systems such as a coherent Doppler lidar (CDL). In a CDL, optimal performance is achieved when the noise in the detector signal is dominated by local oscillator shot-noise. Most modern CDL systems are built using rugged and cost-efficient fiber optic components. Unfortunately, leakage signals such as residual reflections inherent within fiber components (e.g. circulator) can introduce phase-induced intensity noise (PIIN) to the Doppler spectrum in a CDL. Such excess noise may be a few orders of magnitude above the shot-noise level within the relevant CDL frequency bandwidth--corrupting the measurement of typically weak backscattered signals. In this study, observation of PIIN in a fiber-based CDL with a master-oscillator power-amplifier tapered semiconductor laser source is reported. Furthermore, we experimentally demonstrate what we believe is a newly proposed method using a simple polarization scheme to reduce PIIN by more than an order of magnitude. PMID:20389545

  2. Polar wandering of Mars

    NASA Astrophysics Data System (ADS)

    Schultz, P.; Lutz, A. B.

    1988-01-01

    The present study focuses on large regions of layered and stripped terrain that bear many morphologic similarities to the present polar deposits. They occur, however, near the present Martian equator and are proposed to represent locations of ancient Martian poles. The authors first review the morphologies and distributions of these terrains. Second, they review previous explanations for their origin and offer an alternative based on their distribution and similarity with processes presently active in the polar regions. Third, the authors propose a scenario that traces the migration of the poles through time. Finally, they review changes in latitude-controlled climates resulting from polar wandering and compare the inferred climate histories with the global distributions of relevant features.

  3. Polar Bear

    NSDL National Science Digital Library

    2009-01-01

    In this episode of the Podcast of Life, host Ari Daniel Shapiro relates two close calls with polar bears. Listen as Heather Cray recalls how, dumped by a storm on a small Arctic island without a shotgun, she got an unexpected wake-up call. And when researcher Steve Amstrup accidentally crashed through the roof of a polar bear’s den, no one could predict what happened next. Also included is a Learn More section that provides background information on the scientists recorded in the podcast, lessons, images, and cool facts.

  4. Strategic Polarization

    Microsoft Academic Search

    Adam Kalai; Ehud Kalai

    2001-01-01

    In joint decision making, similarly minded people may take opposite positions. Consider the example of a marriage in which one spouse gives generously to charity while the other donates nothing. Such “polarization” may misrepresent what is, in actuality, a small discrepancy in preferences. It may be that the donating spouse would like to see 10% of their combined income go

  5. Controlling the stoichiometry and strand polarity of a tetramolecular G-quadruplex structure by using a DNA origami frame.

    PubMed

    Rajendran, Arivazhagan; Endo, Masayuki; Hidaka, Kumi; Tran, Phong Lan Thao; Mergny, Jean-Louis; Sugiyama, Hiroshi

    2013-10-01

    Guanine-rich oligonucleotides often show a strong tendency to form supramolecular architecture, the so-called G-quadruplex structure. Because of the biological significance, it is now considered to be one of the most important conformations of DNA. Here, we describe the direct visualization and single-molecule analysis of the formation of a tetramolecular G-quadruplex in KCl solution. The conformational changes were carried out by incorporating two duplex DNAs, with G-G mismatch repeats in the middle, inside a DNA origami frame and monitoring the topology change of the strands. In the absence of KCl, incorporated duplexes had no interaction and laid parallel to each other. Addition of KCl induced the formation of a G-quadruplex structure by stably binding the duplexes to each other in the middle. Such a quadruplex formation allowed the DNA synapsis without disturbing the duplex regions of the participating sequences, and resulted in an X-shaped structure that was monitored by atomic force microscopy. Further, the G-quadruplex formation in KCl solution and its disruption in KCl-free buffer were analyzed in real-time. The orientation of the G-quadruplex is often difficult to control and investigate using traditional biochemical methods. However, our method using DNA origami could successfully control the strand orientations, topology and stoichiometry of the G-quadruplex. PMID:23863846

  6. Focusing through turbid media by polarization modulation

    NASA Astrophysics Data System (ADS)

    Park, Jongchan; Park, Jung-Hoon; Yu, Hyeonseung; Park, YongKeun

    2015-04-01

    We demonstrate that polarization modulation of an illumination beam can effectively control the spatial profile of the light transmitted through turbid media. Since the transmitted electric fields are completely mingled in turbid media, polarization states of an illumination beam can be effectively used to control the propagation of light through turbid media. Numerical simulations were performed which agree with experimental results obtained using a commercial in-plane switching liquid-crystal display for modulating the input polarization states.

  7. Controls on Soil Moisture Wicking Extent Away From Lake Fryxell (Constant Boundary Condition) in the Dry Valleys Polar Desert, Antarctica

    NASA Astrophysics Data System (ADS)

    Gooseff, M. N.; Barrett, J. E.; Hill, K. R.; Bate, D. B.; Northcott, M. L.; Zeglin, L. H.; Bobb, M.; Vesbach, C. D.

    2005-12-01

    The extreme conditions of the Antarctic Dry Valleys, are accentuated by the lack of available water across the landscape. In general, the majority of soils are wetted only briefly after infrequent, small snowfall events. However, adjacent to glacial meltwater streams and closed-basin lakes, soils wick water from these sources and wetted fronts at the soil surface are visually conspicuous, extending several meters from shoreline. We postulate that this wicking of surface water is responsible for unique solute transport and microbial diversity within the Dry Valley landscape. We performed synoptic sampling and topographic surveys around Lake Fryxell, Taylor Valley, to quantify the influence of two geomorphic controls on the scaling of these wetting fronts: 1) near-shore topography (slope), and 2) soil grain size distribution. The topographic survey was carried out with a GPS RTK unit (>10,000 points), and in the synoptic sampling campaign we collected 120 samples (4 samples from wet to dry sediments at 30 transects around the lake) for gravimetric soil moisture and particle size analysis, and made measurements of surface soil moisture, depth to permafrost at an additional 114 transects. We found that wetted fronts range in distance from 1.4 to 22.2 m and depth to resistance of penetration (taken as depth of active layer) ranged from 12 to 63.5 cm, generally decreasing with distance from shore. Our results suggest that near-lake soils are fairly homogeneous in particle size distribution; therefore slope has a greater control on wicking front distance, explaining 54% of the variance as a power-law function.

  8. Polar Textures

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Context image for PIA03646 Polar Textures

    This VIS image shows part of the south polar region. The ejecta from the relatively young crater covers the rougher textured polar surface.

    Image information: VIS instrument. Latitude 81S, Longitude 54.5E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  9. Expansion of CAG Repeats in Escherichia coli Is Controlled by Single-Strand DNA Exonucleases of Both Polarities

    PubMed Central

    Jackson, Adam; Okely, Ewa A.

    2014-01-01

    The expansion of CAG·CTG repeat tracts is responsible for several neurodegenerative diseases, including Huntington disease and myotonic dystrophy. Understanding the molecular mechanism of CAG·CTG repeat tract expansion is therefore important if we are to develop medical interventions limiting expansion rates. Escherichia coli provides a simple and tractable model system to understand the fundamental properties of these DNA sequences, with the potential to suggest pathways that might be conserved in humans or to highlight differences in behavior that could signal the existence of human-specific factors affecting repeat array processing. We have addressed the genetics of CAG·CTG repeat expansion in E. coli and shown that these repeat arrays expand via an orientation-independent mechanism that contrasts with the orientation dependence of CAG·CTG repeat tract contraction. The helicase Rep contributes to the orientation dependence of repeat tract contraction and limits repeat tract expansion in both orientations. However, RuvAB-dependent fork reversal, which occurs in a rep mutant, is not responsible for the observed increase in expansions. The frequency of repeat tract expansion is controlled by both the 5?–3? exonuclease RecJ and the 3?–5? exonuclease ExoI, observations that suggest the importance of both 3?and 5? single-strand ends in the pathway of CAG·CTG repeat tract expansion. We discuss the relevance of our results to two competing models of repeat tract expansion. PMID:25081568

  10. EAT-2, a SAP-like adaptor, controls NK cell activation through phospholipase C?, Ca++, and Erk, leading to granule polarization

    PubMed Central

    Pérez-Quintero, Luis-Alberto; Roncagalli, Romain; Guo, Huaijian; Latour, Sylvain; Davidson, Dominique

    2014-01-01

    Ewing’s sarcoma-associated transcript 2 (EAT-2) is an Src homology 2 domain-containing intracellular adaptor related to signaling lymphocytic activation molecule (SLAM)–associated protein (SAP), the X-linked lymphoproliferative gene product. Both EAT-2 and SAP are expressed in natural killer (NK) cells, and their combined expression is essential for NK cells to kill abnormal hematopoietic cells. SAP mediates this function by coupling SLAM family receptors to the protein tyrosine kinase Fyn and the exchange factor Vav, thereby promoting conjugate formation between NK cells and target cells. We used a variety of genetic, biochemical, and imaging approaches to define the molecular and cellular mechanisms by which EAT-2 controls NK cell activation. We found that EAT-2 mediates its effects in NK cells by linking SLAM family receptors to phospholipase C?, calcium fluxes, and Erk kinase. These signals are triggered by one or two tyrosines located in the carboxyl-terminal tail of EAT-2 but not found in SAP. Unlike SAP, EAT-2 does not enhance conjugate formation. Rather, it accelerates polarization and exocytosis of cytotoxic granules toward hematopoietic target cells. Hence, EAT-2 promotes NK cell activation by molecular and cellular mechanisms distinct from those of SAP. These findings explain the cooperative and essential function of these two adaptors in NK cell activation. PMID:24687958

  11. EAT-2, a SAP-like adaptor, controls NK cell activation through phospholipase C?, Ca++, and Erk, leading to granule polarization.

    PubMed

    Pérez-Quintero, Luis-Alberto; Roncagalli, Romain; Guo, Huaijian; Latour, Sylvain; Davidson, Dominique; Veillette, André

    2014-04-01

    Ewing's sarcoma-associated transcript 2 (EAT-2) is an Src homology 2 domain-containing intracellular adaptor related to signaling lymphocytic activation molecule (SLAM)-associated protein (SAP), the X-linked lymphoproliferative gene product. Both EAT-2 and SAP are expressed in natural killer (NK) cells, and their combined expression is essential for NK cells to kill abnormal hematopoietic cells. SAP mediates this function by coupling SLAM family receptors to the protein tyrosine kinase Fyn and the exchange factor Vav, thereby promoting conjugate formation between NK cells and target cells. We used a variety of genetic, biochemical, and imaging approaches to define the molecular and cellular mechanisms by which EAT-2 controls NK cell activation. We found that EAT-2 mediates its effects in NK cells by linking SLAM family receptors to phospholipase C?, calcium fluxes, and Erk kinase. These signals are triggered by one or two tyrosines located in the carboxyl-terminal tail of EAT-2 but not found in SAP. Unlike SAP, EAT-2 does not enhance conjugate formation. Rather, it accelerates polarization and exocytosis of cytotoxic granules toward hematopoietic target cells. Hence, EAT-2 promotes NK cell activation by molecular and cellular mechanisms distinct from those of SAP. These findings explain the cooperative and essential function of these two adaptors in NK cell activation. PMID:24687958

  12. Cell Polarization and Cytokinesis in Budding Yeast

    PubMed Central

    Bi, Erfei; Park, Hay-Oak

    2012-01-01

    Asymmetric cell division, which includes cell polarization and cytokinesis, is essential for generating cell diversity during development. The budding yeast Saccharomyces cerevisiae reproduces by asymmetric cell division, and has thus served as an attractive model for unraveling the general principles of eukaryotic cell polarization and cytokinesis. Polarity development requires G-protein signaling, cytoskeletal polarization, and exocytosis, whereas cytokinesis requires concerted actions of a contractile actomyosin ring and targeted membrane deposition. In this chapter, we discuss the mechanics and spatial control of polarity development and cytokinesis, emphasizing the key concepts, mechanisms, and emerging questions in the field. PMID:22701052

  13. Adaptive shaping of femtosecond polarization profiles

    NASA Astrophysics Data System (ADS)

    Brixner, T.; Damrauer, N. H.; Krampert, G.; Niklaus, P.; Gerber, G.

    2003-05-01

    We report the experimental implementation of femtosecond polarization pulse shaping within an adaptive learning loop. This technique makes it possible to optimally and automatically generate light fields in which intensity, momentary frequency, and light polarization (i.e., ellipticity and orientation) change as a function of time within a single femtosecond laser pulse. By use of second-harmonic generation as a feedback signal in an evolutionary algorithm, specific phase- and polarization-modulated laser pulses are generated. Material dispersion and time-dependent modulations of the polarization state can be compensated. These experiments demonstrate the feasibility of adaptive quantum control experiments with polarization-shaped femtosecond laser pulses.

  14. Multichannel polarization stabilization for coherently combined fiber laser arrays.

    PubMed

    Goodno, Gregory D; McNaught, Stuart J; Weber, Mark E; Weiss, S Benjamin

    2012-10-15

    We demonstrate a simplified approach toward active polarization control in coherently combined laser architectures. By leveraging optical phase dithers applied by a phase controller, polarization error signals are generated for an entire laser array from a single beam sample of the combined output, enabling closed-loop polarization locking of non-polarization-maintaining fibers. The concept is shown to be compatible with both hill-climbing and synchronous multidither phase control methods. Simultaneous phase locking and polarization locking was demonstrated for a five-fiber array with >99% phasing efficiency and >20 dB polarization extinction ratio. PMID:23073434

  15. INJECTION ELECTRODE POLARIZATION RESISTIVITY AND INDUCED POLARIZATION

    E-print Network

    Merriam, James

    INJECTION ELECTRODE POLARIZATION IN RESISTIVITY AND INDUCED POLARIZATION J.B. Merriam University.merriam@usask.ca Abstract Polarization of injection electrodes in resistivity and induced polarization may reach several elsewhere that this may present a problem for programmable switching resistivity meters because

  16. Mutational analysis of CDC42Sc, a Saccharomyces cerevisiae gene that encodes a putative GTP-binding protein involved in the control of cell polarity.

    PubMed Central

    Ziman, M; O'Brien, J M; Ouellette, L A; Church, W R; Johnson, D I

    1991-01-01

    The Saccharomyces cerevisiae CDC42 gene product, a member of the ras superfamily of low-molecular-weight GTP-binding proteins, is involved in the control of cell polarity. We have analyzed the effects of three CDC42 mutations (Gly to Val-12, Gln to Leu-61, and Asp to Ala-118) in the putative GTP-binding and hydrolysis domains and one mutation (Cys to Ser-188) in the putative isoprenylation site. The first three mutations resulted in either a dominant-lethal or dose-dependent dominant-lethal phenotype when present on plasmids in haploid cdc42-1ts or wild-type strains. Both wild-type and cdc42-1ts cells carrying plasmids (pGAL) with either the CDC42Val-12 or CDC42Leu-61 alleles under the control of a GAL promoter were arrested with a novel phenotype of large cells with elongated or multiple buds. Cells carrying pGAL-CDC42Ala-118 were arrested as large, round, unbudded cells reminiscent of cdc42-1ts arrested cells. The different phenotype of the CDC42Ala-118 mutant versus the CDC42Val-12 and CDC42Leu-61 mutants was unexpected since the phenotypes of all three analogous ras mutants were similar to each other. This suggests that aspects of the biochemical properties of the Cdc42 protein differ from those of the Ras protein. The cdc42Ser-188 mutant gene was incapable of complementing the cdc42-1ts mutation and was recessive to both wild-type and cdc42-1ts. In double-mutant alleles, the cdc42Ser-188 mutation was capable of suppressing the dominant lethality associated with the three putative GTP-binding and hydrolysis mutations, suggesting that isoprenylation is necessary for the activity of the wild-type and mutant proteins. Images PMID:1904541

  17. Polar Shells

    NASA Technical Reports Server (NTRS)

    2006-01-01

    21 May 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows sand dunes overlain by a layer of seasonal carbon dioxide frost in the north polar region of Mars. Sunlight illuminates the scene from the lower left, but slopes facing toward the upper right seem illuminated because of the thicker accumulation of frost on the slopes facing away from the sunlight.

    Location near: 76.3oN, 264.3oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Winter

  18. Counteractive Control of Polarized Morphogenesis during Mating by Mitogen-activated Protein Kinase Fus3 and G1 Cyclin-dependent Kinase

    PubMed Central

    Yu, Lu; Qi, Maosong; Sheff, Mark A.

    2008-01-01

    Cell polarization in response to external cues is critical to many eukaryotic cells. During pheromone-induced mating in Saccharomyces cerevisiae, the mitogen-activated protein kinase (MAPK) Fus3 induces polarization of the actin cytoskeleton toward a landmark generated by the pheromone receptor. Here, we analyze the role of Fus3 activation and cell cycle arrest in mating morphogenesis. The MAPK scaffold Ste5 is initially recruited to the plasma membrane in random patches that polarize before shmoo emergence. Polarized localization of Ste5 is important for shmooing. In fus3 mutants, Ste5 is recruited to significantly more of the plasma membrane, whereas recruitment of Bni1 formin, Cdc24 guanine exchange factor, and Ste20 p21-activated protein kinase are inhibited. In contrast, polarized recruitment still occurs in a far1 mutant that is also defective in G1 arrest. Remarkably, loss of Cln2 or Cdc28 cyclin-dependent kinase restores polarized localization of Bni1, Ste5, and Ste20 to a fus3 mutant. These and other findings suggest Fus3 induces polarized growth in G1 phase cells by down-regulating Ste5 recruitment and by inhibiting Cln/Cdc28 kinase, which prevents basal recruitment of Ste5, Cdc42-mediated asymmetry, and mating morphogenesis. PMID:18256288

  19. Polar ozone

    NASA Technical Reports Server (NTRS)

    Solomon, S.; Grose, W. L.; Jones, R. L.; Mccormick, M. P.; Molina, Mario J.; Oneill, A.; Poole, L. R.; Shine, K. P.; Plumb, R. A.; Pope, V.

    1990-01-01

    The observation and interpretation of a large, unexpected ozone depletion over Antarctica has changed the international scientific view of stratospheric chemistry. The observations which show the veracity, seasonal nature, and vertical structure of the Antarctic ozone hole are presented. Evidence for Arctic and midlatitude ozone loss is also discussed. The chemical theory for Antarctic ozone depletion centers around the occurrence of polar stratospheric clouds (PSCs) in Antarctic winter and spring; the climatology and radiative properties of these clouds are presented. Lab studies of the physical properties of PSCs and the chemical processes that subsequently influence ozone depletion are discussed. Observations and interpretation of the chemical composition of the Antarctic stratosphere are described. It is shown that the observed, greatly enhanced abundances of chlorine monoxide in the lower stratosphere are sufficient to explain much if not all of the ozone decrease. The dynamic meteorology of both polar regions is given, interannual and interhemispheric variations in dynamical processes are outlined, and their likely roles in ozone loss are discussed.

  20. Polar Lines

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Context image for PIA03597 Polar Lines

    This linear features near the South Polar Cap appeared during the height of southern summer.

    Image information: VIS instrument. Latitude 79.7S, Longitude 249.1E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  1. Polar Layers

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Context image for PIA03083 Polar Layers

    This VIS image illlustrates how distinct polar layers appear with no frost cover. This image was collected during the height of summer at the south pole of Mars.

    Image information: VIS instrument. Latitude 80.7S, Longitude 295.6E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  2. Polar Layers

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Context image for PIA03288 Polar Layers

    Late in the summer season, the numerous polar layers are free of frost and easily visible.

    Image information: VIS instrument. Latitude -84.9N, Longitude 135.9E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  3. Polar Variety

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Context image for PIA03599 Polar Variety

    This VIS image of the south polar region contains a variety of features including mesas, craters, surfaces with different textures and a couple of windstreaks.

    Image information: VIS instrument. Latitude 80.2S, Longitude 323.4E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  4. Polar Ridges

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA03662 Polar Ridges

    This ridge system is located in the south polar region.

    Image information: VIS instrument. Latitude -81.7N, Longitude 296.5E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  5. Polar Terrains

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Context image for PIA03577 Polar Terrains

    The region surrounding the South Polar Cap contains many different terrain types. This image shows both etched terrain and a region of 'mounds'.

    Image information: VIS instrument. Latitude 75S, Longitude 286.5E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  6. Polar Layers

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA02153 Polar Layers

    This image of the south polar region shows layered material. It is not known if the layers are formed yearly or if they form over the period of 10s to 100s of years or more.

    Image information: VIS instrument. Latitude -80.3N, Longitude 296.2E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  7. Polar Markings

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA02155 Polar Markings

    These bright and dark markings occurred near the end of summer in the south polar region. The dark material is likely dust that has been freed of frost cover.

    Image information: VIS instrument. Latitude -76.3N, Longitude 84.9E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  8. Polar Textures

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Context image for PIA03638 Polar Textures

    This image illustrates the variety of textures that appear in the south polar region during late summer.

    Image information: VIS instrument. Latitude 80.5S, Longitude 57.9E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  9. JPL Polar Oceanography Group

    NSDL National Science Digital Library

    The Jet Propulsion Laboratory's Polar Oceanography Group utilizes "satellite microwave remote sensing data and in-situ methods to understand the climate-induced variability in sea-ice and land-ice on seasonal to interannual time scales." Research conducted by the group is mainly concerned with Arctic Sea Ice, Antarctic Sea Ice, and Ice Sheets. "The principal thrust of this research is to understand the role of the polar oceans in controlling or regulating global climate." A data products section includes online data for sea ice melt detection and ice drift and ice motion data. The excellent publications section offers online copies (.pdf) of the group's work dating from 1989 to current publications that are in press. The site also provides news, contacts, and links.

  10. Isotropically polarized speckle patterns.

    PubMed

    Schmidt, Mikolaj K; Aizpurua, Javier; Zambrana-Puyalto, Xavier; Vidal, Xavier; Molina-Terriza, Gabriel; Sáenz, Juan José

    2015-03-20

    The polarization of the light scattered by an optically dense and random solution of dielectric nanoparticles shows peculiar properties when the scatterers exhibit strong electric and magnetic polarizabilities. While the distribution of the scattering intensity in these systems shows the typical irregular speckle patterns, the helicity of the incident light can be fully conserved when the electric and magnetic polarizabilities of the scatterers are equal. We show that the multiple scattering of helical beams by a random dispersion of "dual" dipolar nanospheres leads to a speckle pattern exhibiting a perfect isotropic constant polarization, a situation that could be useful in coherent control of light as well as in lasing in random media. PMID:25839272

  11. Neuronal polarization in the developing cerebral cortex

    PubMed Central

    Sakakibara, Akira; Hatanaka, Yumiko

    2015-01-01

    Cortical neurons consist of excitatory projection neurons and inhibitory GABAergic interneurons, whose connections construct highly organized neuronal circuits that control higher order information processing. Recent progress in live imaging has allowed us to examine how these neurons differentiate during development in vivo or in in vivo-like conditions. These analyses have revealed how the initial steps of polarization, in which neurons establish an axon, occur. Interestingly, both excitatory and inhibitory cortical neurons establish neuronal polarity de novo by undergoing a multipolar stage reminiscent of the manner in which polarity formation occurs in hippocampal neurons in dissociated culture. In this review, we focus on polarity formation in cortical neurons and describe their typical morphology and dynamic behavior during the polarization period. We also discuss cellular and molecular mechanisms underlying polarization, with reference to polarity formation in dissociated hippocampal neurons in vitro. PMID:25904841

  12. Neuronal polarization in the developing cerebral cortex.

    PubMed

    Sakakibara, Akira; Hatanaka, Yumiko

    2015-01-01

    Cortical neurons consist of excitatory projection neurons and inhibitory GABAergic interneurons, whose connections construct highly organized neuronal circuits that control higher order information processing. Recent progress in live imaging has allowed us to examine how these neurons differentiate during development in vivo or in in vivo-like conditions. These analyses have revealed how the initial steps of polarization, in which neurons establish an axon, occur. Interestingly, both excitatory and inhibitory cortical neurons establish neuronal polarity de novo by undergoing a multipolar stage reminiscent of the manner in which polarity formation occurs in hippocampal neurons in dissociated culture. In this review, we focus on polarity formation in cortical neurons and describe their typical morphology and dynamic behavior during the polarization period. We also discuss cellular and molecular mechanisms underlying polarization, with reference to polarity formation in dissociated hippocampal neurons in vitro. PMID:25904841

  13. Anodic Concentration Polarization in SOFCs

    SciTech Connect

    Williford, Rick E.; Chick, Lawrence A.; Maupin, Gary D.; Simner, Steve P.; Stevenson, Jeffry W.; Khaleel, Mohammad A.; Wachsman, ED, et al

    2003-08-01

    Concentration polarization is important because it determines the maximum power output of a solid oxide fuel cell (SOFC) at high fuel utilization. Anodic concentration polarization occurs when the demand for reactants exceeds the capacity of the porous ceramic anode to supply them by gas diffusion mechanisms. High tortuosities (bulk diffusion resistances) are often assumed to explain this behavior. However, recent experiments show that anodic concentration polarization originates in the immediate vicinity of the reactive triple phase boundary (TPB) sites near the anode/electrolyte interface. A model is proposed to describe how concentration polarization is controlled by two localized phenomena: competitive adsorption of reactants in areas adjacent to the reactive TPB sites, followed by relatively slow surface diffusion to the reactive sites. Results suggest that future SOFC design improvements should focus on optimization of the reactive area, adsorption, and surface diffusion at the anode/electrolyte interface.

  14. Polarization in Optical Design

    Microsoft Academic Search

    Daniel J. Reiley

    1993-01-01

    The polarization effects of optical interfaces are important in certain types of optical systems. These systems include polarization microscopes, remote sensing platforms, optical computers, solar magnetographs, and barcode readers. These systems are characterized by their polarization aberration function, which maps a ray's amplitude, phase, and polarization state in the entrance pupil onto its amplitude, phase, and polarization state in the

  15. Planar polarity

    PubMed Central

    Yates, Laura L

    2011-01-01

    The clinical burden of both adult and neonatal lung disease worldwide is substantial; in the UK alone, respiratory disease kills one in four people. It is increasingly recognized that genes and pathways that regulate lung development, may be aberrantly activated in disease and/or reactivated as part of the lungs' intrinsic repair mechanisms. Investigating the genes and signaling pathways that regulate lung growth has led to significant insights into the pathogenesis of congenital and adult lung disease. Recently, the planar cell polarity (PCP) pathway has been shown to be required for normal lung development, and data suggests that this signaling pathway is also involved in the pathogenesis of some lung diseases. In this review, we summarize current evidence indicating that the PCP pathway is required for both lung development and disease. PMID:22030785

  16. Electric field control of multiferroic domains in Ni3V2O8 imaged by x-ray polarization-enhanced topography

    Microsoft Academic Search

    F. Fabrizi; H. C. Walker; L. Paolasini; F. de Bergevin; T. Fennell; N. Rogado; R. J. Cava; Th. Wolf; M. Kenzelmann; D. F. McMorrow

    2010-01-01

    The magnetic structure of multiferroic Ni3V2O8 has been investigated using nonresonant x-ray magnetic scattering. Incident circularly polarized x rays combined with full polarization analysis of the scattered beam is shown to yield high sensitivity to the components of the cycloidal magnetic order, including their relative phases. Information on the magnetic structure in the ferroelectric phase is obtained, where it is

  17. Polar Layers

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Context image for PIA03581 Polar Layers

    This image shows just one example of the bright and dark markings that appear during summer time. The marks are related to the polar layers. If you happen to see a wild-eyed guy sticking his tongue out at you, you'll know why this image qualifies for the old 'art' category of THEMIS releases.

    Image information: VIS instrument. Latitude 80.6S, Longitude 34.1E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  18. Primordial Inflation Polarization Explorer: Status and Plans

    NASA Technical Reports Server (NTRS)

    Kogut, Alan

    2009-01-01

    The Primordial Inflation Polarization Explorer is a balloon-borne instrument to measure the polarization of the cosmic microwave background in order to detect the characteristic signature of gravity waves created during an inflationary epoch in the early universe. PIPER combines cold /I.G K\\ optics, 5120 bolometric detectors, and rapid polarization modulation using VPM grids to achieve both high sensitivity and excellent control of systematic errors. I will discuss the current status and plans for the PIPER instrument.

  19. Element-selective spin polarization analysis of surfaces by spin-polarized ion scattering spectroscopy

    NASA Astrophysics Data System (ADS)

    Suzuki, T. T.; Kuwahara, H.; Yamauchi, Y.

    2010-09-01

    We discuss the validity of surface spin polarization analysis with element selectivity using spin-polarized ion scattering spectroscopy (SP-ISS). We examined the control of the incident 4He+ spins and successfully conducted magnetic hysteresis measurement on an Fe(100) surface. The spin polarization of the Fe(100) surface exposed to O 2 atmosphere measured by spin-polarized ion neutralization spectroscopy was consistent with that reported by spin-polarized metastable de-excitation spectroscopy. The element selectivity of SP-ISS is discussed in terms of ion neutralization, re-ionization, and multiple scattering.

  20. Polar Shapelets

    E-print Network

    Richard Massey; Alexandre Refregier

    2006-08-18

    The shapelets method for image analysis is based upon the decomposition of localised objects into a series of orthogonal components with convenient mathematical properties. We extend the "Cartesian shapelet" formalism from earlier work, and construct "polar shapelet" basis functions that separate an image into components with explicit rotational symmetries. These frequently provide a more compact parameterisation, and can be interpreted in an intuitive way. Image manipulation in shapelet space is simplified by the concise expressions for linear coordinate transformations; and shape measures (including object photometry, astrometry and galaxy morphology estimators) take a naturally elegant form. Particular attention is paid to the analysis of astronomical survey images, and we test shapelet techniques upon real data from the Hubble Space Telescope. We present a practical method to automatically optimise the quality of an arbitrary shapelet decomposition in the presence of observational noise, pixellisation and a Point-Spread Function. A central component of this procedure is the adaptive choice of the shapelet expansion's scale size and truncation order. A complete software package to perform shapelet image analysis is made available on the world-wide web at http://www.astro.caltech.edu/~rjm/shapelets/ .

  1. Broadband graphene polarizer

    NASA Astrophysics Data System (ADS)

    Bao, Qiaoliang; Zhang, Han; Wang, Bing; Ni, Zhenhua; Lim, Candy Haley Yi Xuan; Wang, Yu; Tang, Ding Yuan; Loh, Kian Ping

    2011-07-01

    Conventional polarizers can be classified into three main modes of operation: sheet polarizer using anisotropic absorption media, prism polarizer by refraction and Brewster-angle polarizer by reflection. These polarizing components are not easily integrated with photonic circuits. The in-line fibre polarizer, which relies on polarization-selective coupling between the evanescent field and birefringent crystal or metal, is a promising alternative because of its compatibility with most fibre-optic systems. Here, we demonstrate the operation of a broadband fibre polarizer based on graphene, an ultrathin two-dimensional carbon material. The out-coupled light in the telecommunication band shows a strong s-polarization effect with an extinction ratio of 27 dB. Unlike polarizers made from thin metal film, a graphene polarizer can support transverse-electric-mode surface wave propagation due to its linear dispersion of Dirac electrons.

  2. Topological aspects of polarization structured beams

    NASA Astrophysics Data System (ADS)

    Kumar, Vijay; Viswanathan, Nirmal K.

    2014-02-01

    Polarization structured optical beams have half-integer topological structures: star, lemon, monstar in ?-symmetric polarization ellipse orientation tensor field and integer-index topological structures: saddle, spiral, node in 2?-symmetric Poynting vector field. Topological approach to study the polarization structured optical beams is carried out and presented here in some detail. These polarization structured light beams are demonstrated to be the best platform to explore the topological interdependencies. The dependence of one type of topological structure on the other is used to control the Poynting vector density distribution and locally enhance the angular momentum density as compared to its constituent beam fields.

  3. Cell polarity: intrinsic or externally imposed?

    PubMed

    Bornens, M

    1991-06-01

    A basic question in studies of the genesis of cell polarity is whether the polarity is an intrinsic and permanent property of cells or whether it is externally imposed by signals at the cell periphery. Current models favor the possibility that an external signal selectively imposes a polarized cell morphology. However, recent data from different experimental systems are discussed here that support the idea that an intrinsic polarity in animal cells is maintained through a dynamic process involving specific activities of the cortical microfilament system and the centrosome-microtubule complex. In this view, external signals capable of modulating cell polarity, for example, during chemotaxis or histogenesis, do so by acting on mechanisms that maintain cells permanently polarized. The contribution of the cytoskeleton to the genesis of cell polarity is discussed, with particular reference to experimental evidence for global cytoskeletal dynamics, and it is suggested that critical advances in our understanding of the maintenance of cell polarity will depend on our obtaining further knowledge of the molecular mechanisms controlling interactions between microtubules and microfilaments. Microtubules appear to exert an inhibitory control on the recruitment of cytoplasmic myosin into the cortex, and there are data indicating that the centrosome and centrioles could actively contribute to the establishment of cell polarity. PMID:1911649

  4. Linearly polarized fiber amplifier

    DOEpatents

    Kliner, Dahv A.; Koplow, Jeffery P.

    2004-11-30

    Optically pumped rare-earth-doped polarizing fibers exhibit significantly higher gain for one linear polarization state than for the orthogonal state. Such a fiber can be used to construct a single-polarization fiber laser, amplifier, or amplified-spontaneous-emission (ASE) source without the need for additional optical components to obtain stable, linearly polarized operation.

  5. Polarization of barcode readers

    Microsoft Academic Search

    Daniel J. Reiley

    1998-01-01

    In high-quality barcode readers, specular reflection from shiny barcodes is blocked by using a polarized scan laser and a crossed polarizer in front of the detector. When complex scanning geometries are required, the polarization properties of the mirrors in the system can become a limiting factor in system performance. Polarization raytracing allows systems such as barcode readers, LIDAR systems, and

  6. WebTOP Polarization Tutorial

    NSDL National Science Digital Library

    Behringer, Ernest

    This is an interactive tutorial about Polarization based on two of the WebTOP (http://webtop.msstate.edu/) simulations, Polarization and Scattering. Covered topics include polarized and unpolarized light, waveplates, polarization by reflection and polarization by scattering.

  7. Polarized maser growth

    SciTech Connect

    Melrose, D.B.; Judge, A.C. [School of Physics, University of Sydney, Sydney, NSW 2006 (Australia)

    2004-11-01

    A polarized maser is assumed to operate in an anisotropic medium with natural modes polarized differently to the maser. It is shown that when the spatial growth rate and the generalized Faraday rotation rate are comparable, the polarization of the growing radiation is different from those of the maser and medium. In particular, for a lineary polarized maser operating in a medium with linearly polarized natural modes, the growing radiation is partially circularly polarized. This provides a previously unrecognized source of circular polarization that may be relevant to pulsar radio emission.

  8. Polar Color

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Released 3 May 2004 This nighttime visible color image was collected on January 1, 2003 during the Northern Summer season near the North Polar Troughs.

    This daytime visible color image was collected on September 4, 2002 during the Northern Spring season in Vastitas Borealis. The THEMIS VIS camera is capable of capturing color images of the martian surface using its five different color filters. In this mode of operation, the spatial resolution and coverage of the image must be reduced to accommodate the additional data volume produced from the use of multiple filters. To make a color image, three of the five filter images (each in grayscale) are selected. Each is contrast enhanced and then converted to a red, green, or blue intensity image. These three images are then combined to produce a full color, single image. Because the THEMIS color filters don't span the full range of colors seen by the human eye, a color THEMIS image does not represent true color. Also, because each single-filter image is contrast enhanced before inclusion in the three-color image, the apparent color variation of the scene is exaggerated. Nevertheless, the color variation that does appear is representative of some change in color, however subtle, in the actual scene. Note that the long edges of THEMIS color images typically contain color artifacts that do not represent surface variation.

    Image information: VIS instrument. Latitude 79, Longitude 346 East (14 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  9. Polarization-balanced beamsplitter

    DOEpatents

    Decker, Derek E. (Livermore, CA)

    1998-01-01

    A beamsplitter assembly that includes several beamsplitter cubes arranged to define a plurality of polarization-balanced light paths. Each polarization-balanced light path contains one or more balanced pairs of light paths, where each balanced pair of light paths includes either two transmission light paths with orthogonal polarization effects or two reflection light paths with orthogonal polarization effects. The orthogonal pairing of said transmission and reflection light paths cancels polarization effects otherwise caused by beamsplitting.

  10. Polarization-balanced beamsplitter

    DOEpatents

    Decker, D.E.

    1998-02-17

    A beamsplitter assembly is disclosed that includes several beamsplitter cubes arranged to define a plurality of polarization-balanced light paths. Each polarization-balanced light path contains one or more balanced pairs of light paths, where each balanced pair of light paths includes either two transmission light paths with orthogonal polarization effects or two reflection light paths with orthogonal polarization effects. The orthogonal pairing of said transmission and reflection light paths cancels polarization effects otherwise caused by beamsplitting. 10 figs.

  11. Polarization of stored beam by spin-filtering at COSY

    NASA Astrophysics Data System (ADS)

    Ciullo, G.

    2014-01-01

    In the challenging aim to achieve polarized antiproton, the PAX collaboration performed dedicated measurements of the spin-dependent polarizing cross section for p- p scattering at COSY. The result, under a very nice control of the process, agrees with the theoretical previsions, and confirms the pursuability of the spin-filtering for polarizing antiprotons.

  12. 1 Lunar Polar Lander: UK Meeting 2011 Simulations

    E-print Network

    Anand, Mahesh

    Lander Phase B1 SAGE; Robust GNC, Precision Landing GNC TF #12;4 Lunar Polar Lander: UK Meeting 20111 Lunar Polar Lander: UK Meeting 2011 Modelling & Simulations Control & Operations On Board #12;2 Lunar Polar Lander: UK Meeting 2011 On Board Software OUR CAPABILITY Embedded software for platforms

  13. Polarization attractors in harmonic mode-locked fiber laser.

    PubMed

    Habruseva, Tatiana; Mou, Chengbo; Rozhin, Alex; Sergeyev, Sergey V

    2014-06-16

    We report on a polarimetry of harmonic mode-locked erbium-doped fiber laser with carbon nanotubes saturable absorber. We find new types of vector solitons with locked, switching and precessing states of polarization. The underlying physics presents interplay between birefringence of a laser cavity created by polarization controller along with light induced anisotropy caused by polarization hole burning. PMID:24977612

  14. Polarization methods for diode laser excitation of solid state lasers

    DOEpatents

    Holtom, Gary R. (Richland, WA)

    2008-11-25

    A mode-locked laser employs a coupled-polarization scheme for efficient longitudinal pumping by reshaped laser diode bars. One or more dielectric polarizers are configured to reflect a pumping wavelength having a first polarization and to reflect a lasing wavelength having a second polarization. A Yb-doped gain medium can be used that absorbs light having a first polarization and emits light having a second polarization. Using such pumping with laser cavity dispersion control, pulse durations of less than 100 fs can be achieved.

  15. Polarized radiation from extended polar caps.

    NASA Astrophysics Data System (ADS)

    Frank, J.

    The values of magnetic moments in magnetic cataclysmic variables expected from theoretical considerations about spin up/down and binary evolution are reviewed. While observational estimates for magnetic fields exist for many AM Her binaries, BG CMi is the only intermediate polar with direct observational evidence of its magnetic nature. The degree of polarization observed in BG CMi and its wavelength dependence can be understood as a combination of polarized free-free and cyclotron emission from a large polar cap with dilution by the thermal radiation from the underlying heated white dwarf surface. Recent theoretical models suggest a value of 4×106G for the polar field in BG CMi. The evolutionary implications for locking and the relationship between AM Her systems and intermediate polars are discussed.

  16. Monolithic, multiple-wavelength vertical-cavity surface-emitting laser arrays by surface-controlled MOCVD growth rate enhancement and reduction

    Microsoft Academic Search

    G. G. Ortiz; S. Q. Luong; S. Z. Sun; Julian Cheng; H. Q. Hou; G. A. Vawter; B. E. Hammons

    1997-01-01

    Monolithic, multiple-wavelength vertical-cavity surface-emitting laser (VCSEL) arrays have been obtained by the surface-controlled enhancement and reduction of the MOCVD epitaxial growth rate, achieving a periodic, graded wavelength span greater than 30 nm. Room-temperature (RT), electrically pumped continuous-wave (CW) lasing is demonstrated, with uniform threshold currents of 5.5±0.5 mA with typical output powers of 0.5 mW. We show here for the

  17. Processing polarity: ERP evidence for differences between positive and negative polarity.

    PubMed

    Yurchenko, Anna; den Ouden, Dirk-Bart; Hoeksema, Jack; Dragoy, Olga; Hoeks, John C J; Stowe, Laurie A

    2013-01-01

    The goal of the present study was to investigate event-related potential (ERP) responses to Dutch negative and positive polarity adverbs of degree presented in licensed and unlicensed contexts with negative and affirmative particles directly preceding the polarity item. To control for effects of the processing of negation as such, neutral adverbs were also presented in negative and affirmative contexts. The results did not show any significant effect of negation for the non-polar adverbs, allowing context effects for polarity items to be interpreted as being due to the appropriateness of the context. Negative polarity violations elicited an N400 response that might reflect the lack of semantic congruity of the negative polarity item in an affirmative context. In contrast, processing positive polarity items in context of negation resulted in a positive effect resembling the P600, which may be considered as a marker of a different sort of integration difficulty caused by violation of licensing conditions and/or a search for a licensor in the wider discourse context. The study presented here is the first to show an unambiguous dissociation between responses to negative and positive polarity violations. This dissociation argues for different mechanisms underlying the processing of these two types of polarity; we propose that positive polarity items are sensitive to wider discourse context, while negative polarity items are more sensitive to local lexical context. PMID:23142350

  18. Stable polarization-encoded quantum key distribution in fiber

    E-print Network

    Guang Wu; Jie Chen; Yao Li; Heping Zeng

    2006-06-13

    Polarizations of single-photon pulses have been controlled with long-term stability of more than 10 hours by using an active feedback technique for auto-compensation of unpredictable polarization scrambling in long-distance fiber. Experimental tests of long-term operations in 50, 75 and 100 km fibers demonstrated that such a single-photon polarization control supported stable polarization encoding in long-distance fibers to facilitate stable one-way fiber system for polarization-encoded quantum key distribution, providing quantum bit error rates below the absolute security threshold.

  19. BLADE-ON-PETIOLE1 and 2 Control Arabidopsis Lateral Organ Fate through Regulation of LOB Domain and Adaxial-Abaxial Polarity Genes

    Microsoft Academic Search

    Chan Man Ha; Ji Hyung Jun; Hong Gil Nam; J. C. Fletcher

    2007-01-01

    We report a novel function for BLADE-ON-PETIOLE1 (BOP1) and BOP2 in regulating Arabidopsis thaliana lateral organ cell fate and polarity, through the analysis of loss-of-function mutants and transgenic plants that ectopically express BOP1 or BOP2. 35S:BOP1 and 35S:BOP2 plants exhibit a very short and compact stature, hyponastic leaves, and downward- orienting siliques. We show that the LATERAL ORGAN BOUNDARIES (LOB)

  20. ACCELERATING POLARIZED PROTONS TO 250 GEV

    SciTech Connect

    BAI,M.; AHRENS, L.; ALEKSEEV, I.G.; ALESSI, J.; BEEBE-WANG, J.; ET AL.

    2007-06-25

    The Relativistic Heavy Ion Collider (RHIC) as the first high energy polarized proton collider was designed t o provide polarized proton collisions a t a maximum beam energy of 250 GeV. I t has been providing collisions a t a beam energy of 100 Gel' since 2001. Equipped with two full Siberian snakes in each ring, polarization is preserved during the acceleration from injection to 100 GeV with careful control of the betatron tunes and the vertical orbit distortions. However, the intrinsic spin resonances beyond 100 GeV are about a factor of two stronger than those below 100 GeV? making it important t o examine the impact of these strong intrinsic spin resonances on polarization survival and the tolerance for vertical orbit distortions. Polarized protons were accelerated t o the record energy of 250 GeV in RHIC with a polarization of 46% measured a t top energy in 2006. The polarization measurement as a function of beam energy also shows some polarization loss around 136 GeV, the first strong intrinsic resonance above 100 GeV. This paper presents the results and discusses the sensitivity of the polarization survival t o orbit distortions.

  1. Tracking Polar Bears

    NSDL National Science Digital Library

    WGBH Educational Foundation

    2008-01-17

    In this interactive activity adapted from the USGS Alaska Science Center, track the movements of a polar bear as it migrates across the changing Arctic sea ice and compare the paths of four different polar bears.

  2. Our Polar Past

    NSDL National Science Digital Library

    James Wandersee

    2009-12-01

    The study of polar exploration is fascinating and offers students insights into the history, culture, and politics that affect the developing sciences at the farthest ends of Earth. Therefore, the authors think there is value in incorporating polar explor

  3. Eigenstate of polarization in a fiber ring resonator and its effect in an optical passive ring-resonator gyro

    SciTech Connect

    Iwatsuki, K.; Hotate, K.; Higashiguchi, M.

    1986-08-01

    Resonance characteristics of an optical fiber ring resonator are derived taking the effect of birefringence into account. We introduce the concept of the eigenstate of polarization to discuss the resonance characteristics resulting from the polarization fluctuation. Using this concept, the polarization problem in an optical passive ring-resonator gyro (OPRG) is discussed to reveal that this causes gyro drift. A way to reduce the drift is to use not polarizers but two polarization controllers. The precision required for polarization control is estimated; it is found difficult to do in practice. We discuss another configuration to solve the polarization problem in an OPRG without polarization controllers.

  4. Optical pumping production of spin polarized hydrogen

    SciTech Connect

    Knize, R.J.; Happer, W.; Cecchi, J.L.

    1984-09-01

    There has been much interest recently in the production of large quantities of spin polarized hydrogen in various fields, including controlled fusion, quantum fluids, high energy, and nuclear physics. One promising method for the development of large quantities of spin polarized hydrogen is the utilization of optical pumping with a laser. Optical pumping is a process in which photon angular momentum is converted into electron and nuclear spin. The advent of tunable CW dye lasers (approx. 1 watt) allows the production of greater than 10/sup 18/ polarized atoms/sec. We have begun a program at Princeton to investigate the physics and technology of using optical pumping to produce large quantities of spin polarized hydrogen. Initial experiments have been done in small closed glass cells. Eventually, a flowing system, open target, or polarized ion source could be constructed.

  5. Probing absolute spin polarization at the nanoscale.

    PubMed

    Eltschka, Matthias; Jäck, Berthold; Assig, Maximilian; Kondrashov, Oleg V; Skvortsov, Mikhail A; Etzkorn, Markus; Ast, Christian R; Kern, Klaus

    2014-12-10

    Probing absolute values of spin polarization at the nanoscale offers insight into the fundamental mechanisms of spin-dependent transport. Employing the Zeeman splitting in superconducting tips (Meservey-Tedrow-Fulde effect), we introduce a novel spin-polarized scanning tunneling microscopy that combines the probing capability of the absolute values of spin polarization with precise control at the atomic scale. We utilize our novel approach to measure the locally resolved spin polarization of magnetic Co nanoislands on Cu(111). We find that the spin polarization is enhanced by 65% when increasing the width of the tunnel barrier by only 2.3 Å due to the different decay of the electron orbitals into vacuum. PMID:25423049

  6. Polar axis solar collector

    Microsoft Academic Search

    Ludlow

    1994-01-01

    A polar column solar collector is described for use in association with a building, the system having a concave mirror located on the exterior of the building and defining a focal point and a central axis, a mounting column secured to the mirror coaxial therewith, a polar axis column, a hinge swingably connecting the mounting column to the polar axis

  7. Playing with Polarizers.

    ERIC Educational Resources Information Center

    Hecht, Jeff

    1991-01-01

    Discussed is how polarized sunglasses block glare, help spot subtle differences in surfaces, and give a clearer view under water. Information on unpolarized and polarized light is provided. The reasons causing glare to occur and how polarizers decrease glare are discussed. (KR)

  8. Silicon Raman polarizer.

    PubMed

    Kozlov, Victor V; Wabnitz, Stefan

    2012-02-15

    We theoretically investigate the polarization properties of Raman amplifiers based on silicon-on-insulator waveguides, and show that it is possible to realize a waveguide Raman polarizer. The Raman polarizer is a special type of Raman amplifier with the property of producing an amplified and highly repolarized beam when it is fed by a relatively weak and unpolarized signal. PMID:22344165

  9. Bumblebees Learn Polarization Patterns

    PubMed Central

    Foster, James J.; Sharkey, Camilla R.; Gaworska, Alicia V.A.; Roberts, Nicholas W.; Whitney, Heather M.; Partridge, Julian C.

    2014-01-01

    Summary Foraging insect pollinators such as bees must find and identify flowers in a complex visual environment. Bees use skylight polarization patterns for navigation [1–3], a capacity mediated by the polarization-sensitive dorsal rim area (DRA) of their eye [4, 5]. While other insects use polarization sensitivity to identify appropriate habitats [6], oviposition sites, and food sources [7], to date no nonnavigational functions of polarization vision have been identified in bees. Here we investigated the ability of bumblebees (Bombus terrestris) to learn polarization patterns on artificial “flowers” in order to obtain a food reward. We show that foraging bumblebees can learn to discriminate between two differently polarized targets, but only when the target artificial “flower” is viewed from below. A context for these results is provided by polarization imaging of bee-pollinated flowers, revealing the potential for polarization patterns in real flowers. Bees may therefore have the ability to use polarization vision, possibly mediated by their polarization-sensitive DRA, both for navigation and to learn polarization patterns on flowers, the latter being the first nonnavigational function for bee polarization vision to be identified. PMID:24909321

  10. Arecibo Upgrade Notes INSTRUMENTAL POLARIZATION

    E-print Network

    Arecibo Upgrade Notes INSTRUMENTAL POLARIZATION: CROSS COUPLING AND HYBRID CONVERSION ISSUES Jim routine measurement of circular polarizations. The linears thus need conversion to circular polarization% polarization. (B) We also consider cross coupling combined with imperfect conversion. Calibration

  11. Polarization switching detection method using a ferroelectric liquid crystal for dichroic atomic vapor laser lock frequency stabilization techniques.

    PubMed

    Dudzik, Grzegorz; Rzepka, Janusz; Abramski, Krzysztof M

    2015-04-01

    We present a concept of the polarization switching detection method implemented for frequency-stabilized lasers, called the polarization switching dichroic atomic vapor laser lock (PSDAVLL) technique. It is a combination of the well-known dichroic atomic vapor laser lock method for laser frequency stabilization with a synchronous detection system based on the surface-stabilized ferroelectric liquid crystal (SSFLC).The SSFLC is a polarization switch and quarter wave-plate component. This technique provides a 9.6 dB better dynamic range ratio (DNR) than the well-known two-photodiode detection configuration known as the balanced polarimeter. This paper describes the proposed method used practically in the VCSEL laser frequency stabilization system. The applied PSDAVLL method has allowed us to obtain a frequency stability of 2.7×10-9 and a reproducibility of 1.2×10-8, with a DNR of detected signals of around 81 dB. It has been shown that PSDAVLL might be successfully used as a method for spectra-stable laser sources. PMID:25967193

  12. Electrostatically Reversible Polarity of Ambipolar ?-MoTe2 Transistors.

    PubMed

    Nakaharai, Shu; Yamamoto, Mahito; Ueno, Keiji; Lin, Yen-Fu; Li, Song-Lin; Tsukagoshi, Kazuhito

    2015-06-23

    A doping-free transistor made of ambipolar ?-phase molybdenum ditelluride (?-MoTe2) is proposed in which the transistor polarity (p-type and n-type) is electrostatically controlled by dual top gates. The voltage signal in one of the gates determines the transistor polarity, while the other gate modulates the drain current. We demonstrate the transistor operation experimentally, with electrostatically controlled polarity of both p- and n-type in a single transistor. PMID:25988597

  13. ATP-binding motifs play key roles in Krp1p, kinesin-related protein 1, function for bi-polar growth control in fission yeast

    SciTech Connect

    Rhee, Dong Keun [School of Life Sciences and Biotechnology, Korea University, Seoul 136-701 (Korea, Republic of); Cho, Bon A [School of Life Sciences and Biotechnology, Korea University, Seoul 136-701 (Korea, Republic of); Kim, Hyong Bai [Department of Bioinformatics, Korea University, Yeongigun, Chungnam 339-700 (Korea, Republic of)]. E-mail: hbkim5212@hotmail.com

    2005-06-03

    Kinesin is a microtubule-based motor protein with various functions related to the cell growth and division. It has been reported that Krp1p, kinesin-related protein 1, which belongs to the kinesin heavy chain superfamily, localizes on microtubules and may play an important role in cytokinesis. However, the function of Krp1p has not been fully elucidated. In this study, we overexpressed an intact form and three different mutant forms of Krp1p in fission yeast constructed by site-directed mutagenesis in two ATP-binding motifs or by truncation of the leucine zipper-like motif (LZiP). We observed hyper-extended microtubules and the aberrant nuclear shape in Krp1p-overexpressed fission yeast. As a functional consequence, a point mutation of ATP-binding domain 1 (G89E) in Krp1p reversed the effect of Krp1p overexpression in fission yeast, whereas the specific mutation in ATP-binding domain 2 (G238E) resulted in the altered cell polarity. Additionally, truncation of the leucine zipper-like domain (LZiP) at the C-terminal of Krp1p showed a normal nuclear division. Taken together, we suggest that krp1p is involved in regulation of cell-polarized growth through ATP-binding motifs in fission yeast.

  14. Profiling Signaling Polarity in Chemotactic Cells

    SciTech Connect

    Wang, Yingchun; Ding, Shi-Jian; Wang, Wei; Jacobs, Jon M.; Qian, Weijun; Moore, Ronald J.; Yang, Feng; Camp, David G.; Smith, Richard D.; Klemke, Richard L.

    2007-05-15

    While directional movement requires morphological polarization characterized by formation of a leading pseudopodium at the front and a trailing rear at the back, little is known about how protein networks are spatially integrated to regulate this process. Here, we utilize a unique pseudopodial purification system and quantitative proteomics and phosphoproteomics to map the spatial relationship of 3509 proteins and 228 distinct sites of phosphorylation in polarized cells. Networks of signaling proteins, metabolic pathways, actin regulatory proteins, and kinase-substrate cascades were found to partition to different poles of the cell including components of the Ras/ERK pathway. Also, several novel proteins were found to be differentially phosphorylated at the front or rear of polarized cells and to localize to distinct subcellular structures. Our findings provide insight into the spatial organization of signaling networks that control cell movement and provide a comprehensive profile of proteins and their sites of phosphorylation that control cell polarization.

  15. Fully automatic fiber optic polarization analyzer

    NASA Astrophysics Data System (ADS)

    Mar?, P.; Jaroszewicz, L. R.; Stasiewicz, K.

    2008-04-01

    Since many years one of the topic our research team are multi-parametric fiber optic polarization sensors. In the paper is presented a new version of the Fiber-Optic Interferometric Polarization Analyzer (FOIPA). This system is based on modified Sagnac interferometer and it was equipped with automatic current driven polarization controllers driven by special analog output card and detection system based on data acquisition card and LabVIEW software. This system was called full automatic fiber optic interferometric polarization analyzer. Used in the system automatic, temperature driven polarization controllers allow working in feedback electronic loop with data acquisition system and they function as calibration and stabilization subsystem. Specially developed detection system allow measuring amplitudes of first three tones of the AC parts of two electric signals as well as they DC voltages. That advantages have given possibility replaced an expensive lock-in amplifier and make data performance and polarization parameters calculation more faster and easier. It was necessary to implement special procedure to proper SOP identification In the paper are presented theoretical and experimental analyzes of the uncertainties, also. Finally a comparison with commercially available polarization analyzer is shown.

  16. Quantum control of electron wave packet during high harmonic process of H2+ in a combination of a circularly polarized laser field and a Terahertz field.

    PubMed

    Ge, Xin-Lei; Du, Hui; Guo, Jing; Liu, Xue-Shen

    2015-04-01

    By solving a two-dimensional time-dependent Schrödinger equation we investigate high harmonic generation (HHG) and isolated attosecond pulse generation for the H2+ molecular ion in a circularly polarized laser pulse combined with a Terahertz (THz) field. The harmonic intensity can be greatly enhanced and a continuum spectrum can be obtained when a THz field is added. The HHG process is studied by the semi-classical three-step model and the time-frequency analysis. Our studies show that only short trajectories contribute to HHG. Furthermore, we present the temporal evolution of the probability density of electron wave packet, which perfectly shows a clear picture of the electron's two-time recombination when a THz field is added, and it is the main mechanism of HHG. By superposing the harmonics in the range of 216-249 eV, an isolated attosecond pulse with a duration of about 69 attoseconds can be generated. PMID:25968721

  17. Hsp70-Hsp40 chaperone complex functions in controlling polarized growth by repressing Hsf1-driven heat stress-associated transcription.

    PubMed

    Vjestica, Aleksandar; Zhang, Dan; Liu, Jianhua; Oliferenko, Snezhana

    2013-01-01

    How the molecular mechanisms of stress response are integrated at the cellular level remains obscure. Here we show that the cellular polarity machinery in the fission yeast Schizosaccharomyces pombe undergoes dynamic adaptation to thermal stress resulting in a period of decreased Cdc42 activity and altered, monopolar growth. Cells where the heat stress-associated transcription was genetically upregulated exhibit similar growth patterning in the absence of temperature insults. We identify the Ssa2-Mas5/Hsp70-Hsp40 chaperone complex as repressor of the heat shock transcription factor Hsf1. Cells lacking this chaperone activity constitutively activate the heat-stress-associated transcriptional program. Interestingly, they also exhibit intermittent monopolar growth within a physiological temperature range and are unable to adapt to heat stress. We propose that by negatively regulating the heat stress-associated transcription, the Ssa2-Mas5 chaperone system could optimize cellular growth under different temperature regiments. PMID:24146635

  18. A tunable comb filter using single-mode/multimode/polarization-maintaining-fiber-based Sagnac fiber loop

    NASA Astrophysics Data System (ADS)

    Ruan, Juan; Zhang, Wei-Gang; Zhang, Hao; Geng, Peng-Cheng; Bai, Zhi-Yong

    2013-06-01

    A novel tunable comb filter composed of a single-mode/multimode/polarization-maintaining-fiber-based Sagnac fiber loop is proposed and experimentally demonstrated. The filter tunability is achieved by rotating the polarization controller. The spectral shift is dependent on rotation direction and the position of the polarization controller. In addition, the adjustable range achieved by rotating the half-wave-plate polarization controller is twice higher than that of the quarter-wave-plate one.

  19. Property evaluation on the spontaneous polarity for nanopowders.

    PubMed

    Meng, Junping; Liang, Jinsheng; Ding, Yan; Han, Yilin; Yuan, Youde

    2011-11-01

    For the tourmaline fine powders, in view of their low polarized charge density and easily occurred neutralization, a new evaluation model on the spontaneous polarity was proposed. By adjusting the temperature and applying electric field, the polarized charge could be measured. On this basis, a portable evaluation device was designed and assembled into four parts: Voltage Input Unit, Temperature Control Unit, Sample Loading Unit, and Charge Detection Unit. Using the designed device, the property evaluation on the spontaneous polarity of tourmaline fine powders was carried out. The spontaneous polarization intensity was finally achieved. After experimental verification, the method had the characteristics of easy operation and high accuracy. PMID:22413324

  20. TSC1 Controls Distribution of Actin Fibers through Its Effect on Function of Rho Family of Small GTPases and Regulates Cell Migration and Polarity

    PubMed Central

    Ohsawa, Maki; Kobayashi, Toshiyuki; Okura, Hidehiro; Igarashi, Takashi; Mizuguchi, Masashi; Hino, Okio

    2013-01-01

    The tumor-suppressor genes TSC1 and TSC2 are mutated in tuberous sclerosis, an autosomal dominant multisystem disorder. The gene products of TSC1 and TSC2 form a protein complex that inhibits the signaling of the mammalian target of rapamycin complex1 (mTORC1) pathway. mTORC1 is a crucial molecule in the regulation of cell growth, proliferation and survival. When the TSC1/TSC2 complex is not functional, uncontrolled mTORC1 activity accelerates the cell cycle and triggers tumorigenesis. Recent studies have suggested that TSC1 and TSC2 also regulate the activities of Rac1 and Rho, members of the Rho family of small GTPases, and thereby influence the ensuing actin cytoskeletal organization at focal adhesions. However, how TSC1 contributes to the establishment of cell polarity is not well understood. Here, the relationship between TSC1 and the formation of the actin cytoskeleton was analyzed in stable TSC1-expressing cell lines originally established from a Tsc1-deficient mouse renal tumor cell line. Our analyses showed that cell proliferation and migration were suppressed when TSC1 was expressed. Rac1 activity in these cells was also decreased as was formation of lamellipodia and filopodia. Furthermore, the number of basal actin stress fibers was reduced; by contrast, apical actin fibers, originating at the level of the tight junction formed a network in TSC1-expressing cells. Treatment with Rho-kinase (ROCK) inhibitor diminished the number of apical actin fibers, but rapamycin had no effect. Thus, the actin fibers were regulated by the Rho-ROCK pathway independently of mTOR. In addition, apical actin fibers appeared in TSC1-deficient cells after inhibition of Rac1 activity. These results suggest that TSC1 regulates cell polarity-associated formation of actin fibers through the spatial regulation of Rho family of small GTPases. PMID:23355874

  1. TSC1 controls distribution of actin fibers through its effect on function of Rho family of small GTPases and regulates cell migration and polarity.

    PubMed

    Ohsawa, Maki; Kobayashi, Toshiyuki; Okura, Hidehiro; Igarashi, Takashi; Mizuguchi, Masashi; Hino, Okio

    2013-01-01

    The tumor-suppressor genes TSC1 and TSC2 are mutated in tuberous sclerosis, an autosomal dominant multisystem disorder. The gene products of TSC1 and TSC2 form a protein complex that inhibits the signaling of the mammalian target of rapamycin complex1 (mTORC1) pathway. mTORC1 is a crucial molecule in the regulation of cell growth, proliferation and survival. When the TSC1/TSC2 complex is not functional, uncontrolled mTORC1 activity accelerates the cell cycle and triggers tumorigenesis. Recent studies have suggested that TSC1 and TSC2 also regulate the activities of Rac1 and Rho, members of the Rho family of small GTPases, and thereby influence the ensuing actin cytoskeletal organization at focal adhesions. However, how TSC1 contributes to the establishment of cell polarity is not well understood. Here, the relationship between TSC1 and the formation of the actin cytoskeleton was analyzed in stable TSC1-expressing cell lines originally established from a Tsc1-deficient mouse renal tumor cell line. Our analyses showed that cell proliferation and migration were suppressed when TSC1 was expressed. Rac1 activity in these cells was also decreased as was formation of lamellipodia and filopodia. Furthermore, the number of basal actin stress fibers was reduced; by contrast, apical actin fibers, originating at the level of the tight junction formed a network in TSC1-expressing cells. Treatment with Rho-kinase (ROCK) inhibitor diminished the number of apical actin fibers, but rapamycin had no effect. Thus, the actin fibers were regulated by the Rho-ROCK pathway independently of mTOR. In addition, apical actin fibers appeared in TSC1-deficient cells after inhibition of Rac1 activity. These results suggest that TSC1 regulates cell polarity-associated formation of actin fibers through the spatial regulation of Rho family of small GTPases. PMID:23355874

  2. Determination of the polarization states of an arbitrary polarized terahertz beam: Vectorial vortex analysis

    NASA Astrophysics Data System (ADS)

    Wakayama, Toshitaka; Higashiguchi, Takeshi; Oikawa, Hiroki; Sakaue, Kazuyuki; Washio, Masakazu; Yonemura, Motoki; Yoshizawa, Toru; Tyo, J. Scott; Otani, Yukitoshi

    2015-03-01

    Vectorial vortex analysis is used to determine the polarization states of an arbitrarily polarized terahertz (0.1-1.6 THz) beam using THz achromatic axially symmetric wave (TAS) plates, which have a phase retardance of ? = 163° and are made of polytetrafluorethylene. Polarized THz beams are converted into THz vectorial vortex beams with no spatial or wavelength dispersion, and the unknown polarization states of the incident THz beams are reconstructed. The polarization determination is also demonstrated at frequencies of 0.16 and 0.36 THz. The results obtained by solving the inverse source problem agree with the values used in the experiments. This vectorial vortex analysis enables a determination of the polarization states of the incident THz beam from the THz image. The polarization states of the beams are estimated after they pass through the TAS plates. The results validate this new approach to polarization detection for intense THz sources. It could find application in such cutting edge areas of physics as nonlinear THz photonics and plasmon excitation, because TAS plates not only instantaneously elucidate the polarization of an enclosed THz beam but can also passively control THz vectorial vortex beams.

  3. Determination of the polarization states of an arbitrary polarized terahertz beam: Vectorial vortex analysis

    PubMed Central

    Wakayama, Toshitaka; Higashiguchi, Takeshi; Oikawa, Hiroki; Sakaue, Kazuyuki; Washio, Masakazu; Yonemura, Motoki; Yoshizawa, Toru; Tyo, J. Scott; Otani, Yukitoshi

    2015-01-01

    Vectorial vortex analysis is used to determine the polarization states of an arbitrarily polarized terahertz (0.1–1.6?THz) beam using THz achromatic axially symmetric wave (TAS) plates, which have a phase retardance of ? = 163° and are made of polytetrafluorethylene. Polarized THz beams are converted into THz vectorial vortex beams with no spatial or wavelength dispersion, and the unknown polarization states of the incident THz beams are reconstructed. The polarization determination is also demonstrated at frequencies of 0.16 and 0.36?THz. The results obtained by solving the inverse source problem agree with the values used in the experiments. This vectorial vortex analysis enables a determination of the polarization states of the incident THz beam from the THz image. The polarization states of the beams are estimated after they pass through the TAS plates. The results validate this new approach to polarization detection for intense THz sources. It could find application in such cutting edge areas of physics as nonlinear THz photonics and plasmon excitation, because TAS plates not only instantaneously elucidate the polarization of an enclosed THz beam but can also passively control THz vectorial vortex beams. PMID:25799965

  4. Polarized confocal theta microscopy

    NASA Astrophysics Data System (ADS)

    Haeberlé, Olivier; Furukawa, Hiromitsu; Tenjimbayashi, Koji

    2002-12-01

    We propose a comprehensive treatment of theta microscopy based on dipole emission, which better describes fluorescence emission than the isotropic emission model, as fluorescence emission is often polarized. Formulas describing the point spread function for polarized confocal fluorescence theta microscopy are given. Examples are given and some advantages of polarized theta fluorescence microscopy are presented. To cite this article: O. Haeberlé et al., C. R. Physique 3 (2002) 1445-1450.

  5. Polarization independent microphotonic circuits

    E-print Network

    Watts, Michael Robert, 1974-

    2005-01-01

    Microphotonic circuits have been proposed for applications ranging from optical switching and routing to optical logic circuits. However many applications require microphotonic circuits to be polarization independent, a ...

  6. Polarization at SLC

    SciTech Connect

    Swartz, M.L.

    1988-07-01

    The SLAC Linear Collider has been designed to readily accommodate polarized electron beams. Considerable effort has been made to implement a polarized source, a spin rotation system, and a system to monitor the beam polarization. Nearly all major components have been fabricated. At the current time, several source and polarimeter components have been installed. The installation and commissioning of the entire system will take place during available machine shutdown periods as the commissioning of SLC progresses. It is expected that a beam polarization of 45% will be achieved with no loss in luminosity. 13 refs., 15 figs.

  7. Vector photochromism in polarization-sensitive materials.

    PubMed

    Chaganava, Irakli; Kakauridze, George; Kilosanidze, Barbara; Mshvenieradze, Yuri

    2014-07-01

    The phenomenon of vector photochromism was observed in some high-efficient polarization-sensitive materials depending on the radiant exposure of the inducing linearly polarized actinic light. The phenomenon has the purely vector nature because the absorption of the irradiated and unirradiated areas of the material is practically identical when we use unpolarized probing light. However, an essential change in the absorption spectrum was observed under probing the sample by linearly polarized nonactinic light when it passes through an analyzer, and this change depends on the value of radiant exposure. The kinetics of the photoanisotropy induced by linearly polarized actinic light at 457 nm was studied in case of wavelengths of 532 and 635 nm of the probing beam. The noticeable difference in absorbance was observed with increase in radiant exposure from 60??J/cm² up to 250??J/cm² for the used wavelengths of the probing beam. The experimental results obtained in polarization-sensitive material based on the ammonium salt of the azodye Mordant pure yellow in a gelatin matrix are presented. The dependence of the effective anisotropy on the material thickness has been investigated. The mechanism of the phenomenon is discussed. The observed effect can be used for creating dynamic polarization spectral filters controlled by light and the spectrally selective dynamic polarization holographic gratings. PMID:24978751

  8. Automated mode locking in nonlinear polarization rotation fiber lasers by detection of a discontinuous jump in the polarization state.

    PubMed

    Olivier, Michel; Gagnon, Marc-Daniel; Piché, Michel

    2015-03-01

    A strategy to align a mode-locked fiber laser with nonlinear polarization rotation is presented. This strategy is based on measurements of the output polarization state. It is shown that, as the angle of a motorized polarization controller inside the cavity is swept, the laser eventually reaches a mode-locked regime and the values of the Stokes parameters undergo an abrupt change. The sensing of this sudden variation is thus used to detect the mode-locking condition and a feedback mechanism drives the alignment of the polarization controller to force mode locking. PMID:25836890

  9. Photometric structure of polar-ring galaxies

    NASA Astrophysics Data System (ADS)

    Reshetnikov, V. P.

    2004-03-01

    The results of B, V, R surface photometry of three polar-ring galaxies (PRGs) - A 0017+2212, UGC 1198, UGC 4385 - are presented. The data were acquired at the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. It was shown that all three galaxies are peculiar late-type spirals in the state of ongoing interaction or merging. We discuss available photometric properties of the PRGs with spiral hosts and consider the Tully-Fisher relation for different types of PRGs. In agreement with Iodice et al. (\\cite{Iodice03}), we have shown that true PRGs demonstrate ˜1/3 larger maximum rotation velocities than spiral galaxies of the same luminosity. Peculiar objects with forming polar structures satisfy, on average, the Tully-Fisher relation for disk galaxies but with large scatter.

  10. Tunable all electric spin polarizer

    NASA Astrophysics Data System (ADS)

    Bhandari, Nikhil K.

    To realize the full potential of spin-based devices, ways must be found to inject, manipulate, and detect the spin of the electron by purely electrical means. Previously, our group has shown that a quantum point contact (QPC) with lateral spin orbit coupling (LSOC) can be used to create a strongly spin-polarized current by purely electrical means. The LSOC results from the lateral in-plane electric field created by the confining potential in QPCs with in-plane side gates (SGs). Strongly spin-polarized currents can be generated by tuning the asymmetric bias voltages on the side gates. A conductance anomaly in the form of a plateau at conductance G ? 0.5G0 (where G 0 = 2e2/h) was observed in the ballistic conductance of a QPC based in the absence of magnetic field - which was established to be a signature of complete spin polarization. A Non-Equilibrium Green's Function (NEGF) analysis was used to model a small QPC and three ingredients were found to be essential to generate a strong spin polarization: (1) LSOC, (2) an asymmetric lateral confinement, and (3) a strong electron-electron (e-e) interaction. We have also shown that all-electric control of spin polarization can be achieved for different materials, electron mobility, heterostructure design, QPC dimensions and strength of LSOC. Our previous experimental and theoretical results have also found the presence of other conductance anomalies (i.e., at values different from 0.5 G0 ) and the main reason for these occurrences was shown to be due to the influence of surface roughness scattering. In this thesis, we address the important technological challenge to better control the location of the conductance anomalies in QPCs and create a tunable all-electric spin polarizer based on a QPC with four gates, i.e., with two in-plane SGs in series. Here, the first pair of SGs, near the source, is asymmetrically biased to create spin polarization in the QPC channel. The second set of gates, near the drain, is symmetrically biased and that bias is varied to maximize the amount of spin polarization in the channel. We have fabricated several InAs based QPCs with four SGs and have shown that the experimental results were in qualitative agreement with our NEGF simulations. Our main finding is that the range of common mode bias on the first set of gates over which maximum spin polarization can be achieved is much broader for the four gate structure compared to the case of a single pair of in-plane SGs. In addition, we have observed both hysteresis and negative differential regions in the conductance for specific biasing conditions. We believe these are evidence of Coulomb and Spin Blockade effects on the conductance of these devices and cannot be explained within the context of a NEGF approach and require a many-body approach to the description of carrier transport. Our studies suggest that the study of spin valve structures composed of a quantum dot or wire coupled to the source and drain via asymmetrically biased QPCs should open a new area in the field of spintronics.

  11. Optimal polarization conversion in coupled dimer plasmonic nanoantennas for metasurfaces.

    PubMed

    Black, Leo-Jay; Wang, Yudong; de Groot, C H; Arbouet, Arnaud; Muskens, Otto L

    2014-06-24

    We demonstrate that polarization conversion in coupled dimer antennas, used in phase discontinuity metasurfaces, can be tuned by careful design. By controlling the gap width, a strong variation of the coupling strength and polarization conversion is found between capacitively and conductively coupled antennas. A theoretical two-oscillator model is proposed, which shows a universal scaling of the degree of polarization conversion with the energy splitting of the symmetric and antisymmetric modes supported by the antennas. Using single antenna spectroscopy, we find good agreement for the scaling of mode splitting and polarization conversion with gap width over the range from capacitive to conductive coupling. Next to linear polarization conversion, we demonstrate single-antenna linear to circular polarization conversion. Our results provide strategies for phase-discontinuity metasurfaces and ultracompact polarization optics. PMID:24805941

  12. Coherent optical communication using polarization multiple-input-multiple-output.

    PubMed

    Han, Yan; Li, Guifang

    2005-09-19

    Polarization-division multiplexed (PDM) optical signals can potentially be demultiplexed by coherent detection and digital signal processing without using optical dynamic polarization control at the receiver. In this paper, we show that optical communications using PDM is analogous to wireless communications using multiple-input-multiple-output (MIMO) antennae and thus algorithms for channel estimation in wireless MIMO can be ready applied to optical polarization MIMO (PMIMO). Combined with frequency offset and phase estimation algorithms, simulations show that PDM quadrature phase-shift keying signals can be coherently detected by the proposed scheme using commercial semiconductor lasers while no optical phase locking and polarization control are required. This analogy further suggests the potential application of space-time coding in wireless communications to optical polarization MIMO systems and relates the problem of polarization-mode dispersion in fiber transmission to the multi-path propagation in wireless communications. PMID:19498778

  13. Coherent optical communication using polarization multiple-input-multiple-output

    NASA Astrophysics Data System (ADS)

    Han, Yan; Li, Guifang

    2005-09-01

    Polarization-division multiplexed (PDM) optical signals can potentially be demultiplexed by coherent detection and digital signal processing without using optical dynamic polarization control at the receiver. In this paper, we show that optical communications using PDM is analogous to wireless communications using multiple-input-multiple-output (MIMO) antennae and thus algorithms for channel estimation in wireless MIMO can be ready applied to optical polarization MIMO (PMIMO). Combined with frequency offset and phase estimation algorithms, simulations show that PDM quadrature phase-shift keying signals can be coherently detected by the proposed scheme using commercial semiconductor lasers while no optical phase locking and polarization control are required. This analogy further suggests the potential application of space-time coding in wireless communications to optical polarization MIMO systems and relates the problem of polarization-mode dispersion in fiber transmission to the multi-path propagation in wireless communications.

  14. Eliptically polarizing optical fiber

    Microsoft Academic Search

    Ian M. Bassett; Margareta Bjarme; Daryl Chan; Ian G. Clarke; Justin Digweed; Tom Ryan; Andrew Michie; Danny W. Wong

    1999-01-01

    Elliptically polarizing optical fiber has been fabricated. Measurements show an extinction of the lossy mode relative to the transmitted mode of around 10 dB\\/m. The preform is spun during drawing and the ellipticity of the transmitted polarization state is as expected from the measured beat length of the unspun fiber and the pitch length of the spun fiber. This fiber

  15. The Polar Insulation Investigation

    ERIC Educational Resources Information Center

    Urban-Rich, Juanita

    2006-01-01

    In this article, the author developed an activity called "The Polar Insulation Investigation." This activity builds on students' natural interest in "things polar" and introduces them to animal adaptations in a unique way. The aim of the exploration is to determine the role of animal coverings (e.g., blubber, fur, and feathers) and to see which is…

  16. TRANSVERSELY POLARIZED L PRODUCTION.

    SciTech Connect

    BORER,D.

    2000-05-22

    Transversely polarized {Lambda} production in hard scattering processes is discussed in terms of a leading twist T-odd fragmentation function which describes the fragmentation of an unpolarized quark into a transversely polarized {Lambda}. We focus on the properties of this function and its relevance for the RHIC and HERMES experiments.

  17. Neutral polar wind

    Microsoft Academic Search

    Larry C. Gardner; Robert W. Schunk

    2004-01-01

    The classical polar wind is an ambipolar outflow of ions from high latitudes along open geomagnetic field lines. The polar wind consists of light thermal ions (H+, He+) and energetic light and heavy ions (H+, He+, O+). The characteristics of these ions have been studied quite extensively since the 1960s. In just the last 20 years, however, energetic neutral atoms

  18. Electromagnetically induced polarization conversion

    NASA Astrophysics Data System (ADS)

    Khanikaev, Alexander B.; Mousavi, S. Hossein; Wu, Chihhui; Dabidian, Nima; Alici, Kamil B.; Shvets, Gennady

    2012-07-01

    Electromagnetically induced transparency and polarization conversion due to interference between two polarization-selective plasmonic resonances coexisting in the same planar metamaterial are studied. The metasurface represents a periodic array of two topologically distinct metamolecules combined on the same substrate: i) monopole antennas connected to wires and supporting a high-Q resonance radiatively coupled to x-polarization, and ii) dipolar antennas supporting a low-Q resonance coupled to y-polarization. We demonstrate that due to the interaction between these modes through a capacitive coupling between the metamolecules, one can observe a circularly-polarized Electromagnetically Induced Transparency (EIT) and thereby achieve an efficient ultra-thin quarter-wave plate.

  19. AGS polarized beam facility

    SciTech Connect

    Ratner, L.G.

    1985-01-01

    On February 23, 1984, 2 ..mu..A of polarized H/sup -/ was accelerated through the linac to 200 MeV with a polarization of 65%. 1 ..mu..A was injected into the AGS and acceleration attempts began. Several short tests were made until June 1984 when full time effort began. By June 26, the AGS polarized beam reached 13.8 GeV/c to eclipse the previous world's high energy of 12.75 GeV/c set at the Argonne ZGS some six years earlier. The polarized beam energy was raised to 16.5 GeV/c at which energy the decision was made to commence high energy physics running. By this time the accelerated beam intensity exceeded 10/sup 10/ protons per pulse with about 40% polarization. The beam was extracted and two experiments began taking data.

  20. Polarization fluctuation in optical fibers based on probability.

    PubMed

    Imai, T; Matsumoto, T

    1987-09-01

    Polarization fluctuations are measured in submarine and underground cables and in long-haul fibers as long as 270 km. The fluctuations are discussed in terms of probabilities using the Poincaré sphere. When the fluctuations are small, the distribution of the polarization state on the Poincaré sphere closely matches a normal two-dimensional distribution. To compensate automatically for the fluctuations, an endlessly rotatable polarization controller is used. PMID:19741852

  1. Arecibo Upgrade Notes INSTRUMENTAL POLARIZATION

    E-print Network

    Arecibo Upgrade Notes INSTRUMENTAL POLARIZATION: CROSS COUPLING AND HYBRID CONVERSION ISSUES Jim require routine measurement of circular polarizations. The linears thus need conversion to circular 1 polarization. B We also consider cross coupling combined with imperfect conversion. Calibration

  2. Control of Polarized Growth by the Rho Family GTPase Rho4 in Budding Yeast: Requirement of the N-Terminal Extension of Rho4 and Regulation by the Rho GTPase-Activating Protein Bem2

    PubMed Central

    Gong, Ting; Liao, Yuan; He, Fei; Yang, Yang; Yang, Dan-Dan; Chen, Xiang-Dong

    2013-01-01

    In the budding yeast Saccharomyces cerevisiae, Rho4 GTPase partially plays a redundant role with Rho3 in the control of polarized growth, as deletion of RHO4 and RHO3 together, but not RHO4 alone, caused lethality and a loss of cell polarity at 30°C. Here, we show that overexpression of the constitutively active rho4Q131L mutant in an rdi1? strain caused a severe growth defect and generated large, round, unbudded cells, suggesting that an excess of Rho4 activity could block bud emergence. We also generated four temperature-sensitive rho4-Ts alleles in a rho3? rho4? strain. These mutants showed growth and morphological defects at 37°C. Interestingly, two rho4-Ts alleles contain mutations that cause amino acid substitutions in the N-terminal region of Rho4. Rho4 possesses a long N-terminal extension that is unique among the six Rho GTPases in the budding yeast but is common in Rho4 homologs in other yeasts and filamentous fungi. We show that the N-terminal extension plays an important role in Rho4 function since rho3? rho4?61 cells expressing truncated Rho4 lacking amino acids (aa) 1 to 61 exhibited morphological defects at 24°C and a growth defect at 37°C. Furthermore, we show that Rho4 interacts with Bem2, a Rho GTPase-activating protein (RhoGAP) for Cdc42 and Rho1, by yeast two-hybrid, bimolecular fluorescence complementation (BiFC), and glutathione S-transferase (GST) pulldown assays. Bem2 specifically interacts with the GTP-bound form of Rho4, and the interaction is mediated by its RhoGAP domain. Overexpression of BEM2 aggravates the defects of rho3? rho4 mutants. These results suggest that Bem2 might be a novel GAP for Rho4. PMID:23264647

  3. High Field Optomagnetic (OM) Polarization-Phase Selective (PPS) Monitoring of Structures and Controlling Reaction Agents Mechanisms in Complex Molecular Systems

    NASA Astrophysics Data System (ADS)

    Rupnik, Kresimir

    2014-03-01

    Using OM techniques, including new high filed 25T Split-Florida magnet at NHMF Laboratory, we have recently observed unusual metal cluster structures and electron transfer patterns in complex molecular systems of biomedical and material science interest. We report here some of the new technological solutions and (many) challenges that face OM and (quantum) control research. Of particular interest is identification of fast (10-100s fs) highly correlated electrons spin and vibrational coupling interpreted using adaptive molecular-photonic interaction models. Our observations question interpretations of previously proposed electron spin structure models and mechanisms and\\ indicate possible new controlling mechanisms through highly selective coupled channels that combine different specific redox and photonic agents. A portion of this work from 2008 to 2013 was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR-1157490, and 0654118 and the U.S. Department of Energy.

  4. A new miniature hydrostatic pressure chamber for microscopy. Strain-free optical glass windows facilitate phase-contrast and polarized-light microscopy of living cells. Optional fixture permits simultaneous control of pressure and temperature.

    PubMed

    Salmon, E D; Ellis, G W

    1975-06-01

    This paper describes the development of a miniature, temperature-controlled, stainless steel pressure chamber which uses strain-free optical glass for windows. It is directly adaptable to standard phase-contrast and polarized-light microscopes and requires a minimum amount of equipment to generate and measure pressure. Birefringence retardation (BR) og 0.1 nm up to 3,000 psi, 0.4 nm up to 5,000 psi and 1.0 nm up to 10,000 psi can be detected over a 0.75-mm central field with two strain-free Leitz 20 times UM objectives, one used as a condenser. In phase-contrast studies a Nikon DML 40 times phase objective and Zeiss model IS long working-distance phase condenser were used, with little deterioration of image quality or contrast at pressures as high as 12,000 psi. The actual design process required a synthesis of various criteria which may be categorized under four main areas of consideration: (a) specimen physiology; (b) constraints imposed by available optical equipment and standard microscope systems; (c) mechanical strength and methods for generating pressure; and (d) optical requirements of the chamber windows. Procedures for using the chambers, as well as methods for shifting and controlling the temperature within the chamber, are included. PMID:1094021

  5. FDTD analysis of 100% efficient polarization-independent liquid crystal polarization grating

    Microsoft Academic Search

    Chulwoo Oh; Ravi Komanduri; Michael J. Escuti

    2006-01-01

    We report a numerical analysis of the liquid crystal polarization grating (LCPG) as an electro-optically controlled, polarization independent light modulator. The 2D finite-difference time-domain (FDTD) modeling for periodic anisotropic structures has been developed as a numerical tool to study optical properties of anisotropic gratings. Both normal and oblique incidence cases are successfully implemented for wide-band analysis. Nematic director profiles of

  6. Research on alignment method of the polarization coupling testing system

    NASA Astrophysics Data System (ADS)

    Yang, Li; Yang, Zhichao; Yang, Jun; Yuan, Libo

    2011-11-01

    The optical coherence domain polarization (OCDP) system based on white light interferometry is used for the detection of distributed polarization mode coupling point in the polarization-maintaining fiber (PMF). Compared with existing OCDP, in order to detect the polarization coupling amplitude between the fast-axis and slow-axis of high precision PM fiber optic gyro ring, this paper presents a method of angular alignment for measuring polarization coupling in PMF used for OCDP. We add a light intensity detector and two alignment devices in the OCDP. We use the light intensity detector to detect the polarization of rotated PM fiber real-timely and use the two align devices to control the polarization of input and output PMF of fiber optic ring respectively. Based on the theory of Jones, we establish the simulation model of the polarization detection system so as to simulate the influence of different input or output polarization on light intensity; we also design the alignment system of PMF. The experimental results show that the above method can effectively achieve the polarization-maintaining fiber alignment, ratio of axial is 1°, measure the polarization coupling of optical fiber ring without optical fiber fusion splicing, and does not destroy the symmetry of sensitive ring. Overall, the method is simple and high precision.

  7. Polarization at the SLC

    SciTech Connect

    Moffeit, K.C.

    1988-10-01

    The Stanford Linear collider was designed to accommodate polarized electron beams. Longitudinally polarized electrons colliding with unpolarized positrons at a center of mass energy near the Z/sup 0/ mass can be used as novel and sensitive probes of the electroweak process. A gallium arsenide based photon emission source will provide a beam of longitudinally polarized electrons of about 45 percent polarization. A system of bend magnets and a superconducting solenoid will be used to rotate the spins so that the polarization is preserved while the 1.21 GeV electrons are stored in the damping ring. Another set of bend magnets and two superconducting solenoids orient the spin vectors so that longitudinal polarization of the electrons is achieved at the collision point with the unpolarized positrons. A system to monitor the polarization based on Moller and Compton scattering will be used. Nearly all major components have been fabricated and tested. Subsystems of the source and polarimeters have been installed, and studies are in progress. The installation and commissioning of the entire system will take place during available machine shutdown periods as the commissioning of SLC progresses. 8 refs., 16 figs., 1 tab.

  8. The Polar Insulation Investigation

    NSDL National Science Digital Library

    Juanita Urban-Rich

    2006-10-01

    In this article an oceanographer discusses her development of an activity to help students explore polar-related questions more fully. "The Polar Insulation Investigation" builds on students' natural interest in "things polar" and introduces them to animal adaptations in a unique way. The aim of the exploration is to determine the role of animal coverings (e.g. blubber, fur, and feathers) and to see which is the best insulator. It also provides an opportunity to develop and practice skills for measuring temperature.

  9. Circular polarization of twilight.

    NASA Technical Reports Server (NTRS)

    Angel, J. R. P.; Illing, R.; Martin, P. G.

    1972-01-01

    Review of observations of circular polarization of twilight performed with a polarimeter which uses an electronically switched Pockels cell operated as a reversible quarter-wave plate to convert circular into linear polarization. The latter was then analyzed by a Wollaston prism followed by two gallium-arsenide photomultipliers. The discovery of a definite natural circular polarization at twilight does suggest that, with increased observation precision, measurements of the small daylight component are possible. These could give useful information about particles in the atmosphere and be valuable in studies of meteorology and air pollution.

  10. A dual-polarized parasitic patch antenna for MIMO systems

    Microsoft Academic Search

    Daniele Pinchera; Fulvio Schettino

    2009-01-01

    A preliminary analysis of a reconfigurable parasitic patch antenna for MIMO applications is presented. The proposed antenna is able to work on two different polarizations, providing a separate control of the antenna pattern of each of the two polarization. A number of numerical results, showing the adaptive capabilities of the antenna, is given.

  11. Polarization dependent guiding in liquid crystal filled photonic crystal fibers

    Microsoft Academic Search

    Guobin Ren; Ping Shum; Xia Yu; Juanjuan Hu; Guanghui Wang; Yandong Gong

    2008-01-01

    A theoretical study of nematic liquid crystal filled photonic crystal fibers (LCPCFs) is presented. Detailed investigations including the polarization dependent bandgap formation and the modal properties are given for LCPCFs, in which alignment of the molecules could be controlled by external static electric field. The polarization dependent bandgap splitting caused by the high index difference between the ordinary and the

  12. Polarization alignment of polarization maintaining fiber using coherent detection

    Microsoft Academic Search

    Roman C. Gutierrez

    1994-01-01

    A new method of polarization alignment into PM fiber based on electronic coherent detection is presented. The electric field resulting from interference between the polarization eigenmodes of a PM fiber at a linear polarizer when the light coupled into the fiber is amplitude modulated is solved for. The results of polarization alignment experiments using a current modulated laser diode are

  13. A CMB Polarization Primer

    E-print Network

    Wayne Hu; Martin White

    1997-06-16

    We present a pedagogical and phenomenological introduction to the study of cosmic microwave background (CMB) polarization to build intuition about the prospects and challenges facing its detection. Thomson scattering of temperature anisotropies on the last scattering surface generates a linear polarization pattern on the sky that can be simply read off from their quadrupole moments. These in turn correspond directly to the fundamental scalar (compressional), vector (vortical), and tensor (gravitational wave) modes of cosmological perturbations. We explain the origin and phenomenology of the geometric distinction between these patterns in terms of the so-called electric and magnetic parity modes, as well as their correlation with the temperature pattern. By its isolation of the last scattering surface and the various perturbation modes, the polarization provides unique information for the phenomenological reconstruction of the cosmological model. Finally we comment on the comparison of theory with experimental data and prospects for the future detection of CMB polarization.

  14. Invariants of polarization transformations.

    PubMed

    Sadjadi, Firooz A

    2007-05-20

    The use of polarization-sensitive sensors is being explored in a variety of applications. Polarization diversity has been shown to improve the performance of the automatic target detection and recognition in a significant way. However, it also brings out the problems associated with processing and storing more data and the problem of polarization distortion during transmission. We present a technique for extracting attributes that are invariant under polarization transformations. The polarimetric signatures are represented in terms of the components of the Stokes vectors. Invariant algebra is then used to extract a set of signature-related attributes that are invariant under linear transformation of the Stokes vectors. Experimental results using polarimetric infrared signatures of a number of manmade and natural objects undergoing systematic linear transformations support the invariancy of these attributes. PMID:17514238

  15. Polarization contrast vision

    NASA Astrophysics Data System (ADS)

    Pugh, Edward N.

    1990-05-01

    An attempt is made to establish the possibility that the geometry of certain classes of vertebrate photoreceptors results in a birefringence that allows the animals to utilize the state of polarization of light striking their retinas as a meaningful stimulus parameter. Simulate the photoreceptors as dielectric waveguides using a simple physical model, and augment this theoretical work with empirical measurements of the light guiding properties of photoreceptors in isolated pieces of retina from a green sunfish (Lepomis cyanellus). With a classical conditioning paradigm, this fish's sensitivity to light is modulated by the orientation of the plane of polarization of linearly polarized light. This functional dependence was predicted by a hypothetical antagonistic mechanism between twin cones of two orientations in the animal's retinal mosaic. Further study is planned for the nature of the stimulus to which the fish is sensitive by creating a camera that will generate images based purely upon the contrast between orthogonal polarizations at each point in space.

  16. PCs and Polar Bears

    NSDL National Science Digital Library

    Jessica Fries-Gaither

    2011-01-01

    This article looks at the growing energy consumption from consumer electronics and the increases it may cause in greenhouse gases and global warming. The article appears in the free, online magazine Beyond Penguins and Polar Bears.

  17. Remanent transmission neutron polarizer

    Microsoft Academic Search

    Jochen Stahn; Daniel Clemens

    2002-01-01

    Our goal is to develop magnetically remanent neutron supermirrors using the material combinations Fe\\/Si and FeCo\\/Si. With these we plan to build compact neutron transmission polarizers and neutron polarizers which can be operated with their magnetization oriented antiparallel to the guide field. In the latter case no spin flipper is necessary to switch to the other spin state. The supermirrors

  18. AGS polarized proton project

    SciTech Connect

    Halama, H.J.

    1983-01-01

    At the end of this year, polarized H/sup -/ beam will be injected into the AGS, where it will be stripped and subsequently accelerated to 26 GeV/c. 20 keV polarized H/sup -/ are produced in an ion source working at ground potential by colliding polarized H/sup 0/ with cesium beams and 12 ..mu..A of H/sup -/ have already been achieved in 0.5 ms pulses. 20 keV beam is transported to an RFQ linac where it is accelerated to 750 keV. 750 keV LEBT line matches the RFQ output emittance to the acceptance of the existing 200 MeV linac to reach the desired AGS injection energy. The degree of polarization will depend critically on how well we can cross some 30 depolarizing resonances in the AGS. They can be divided into two types: (1) intrinsic resonances due to natural periodicity of the AGS will be crossed in less than one revolution (approx. 2 ..mu..s) by a fast tune jump generated by 12 fast quadrupoles and their modulators, and (2) imperfection resonances due to magnet misalignment will be minimized by generating harmonic correction using 96 existing dipole magnets. In addition, all existing AGS multipoles will be programmed to tailor the tune and chromaticity during the acceleration to further facilitate resonance crossing. In order to insure rapid tune up and commissioning of polarized beams, four independent polarimeters will be used to measure polarization.

  19. Ferroelectric domain wall motion induced by polarized light.

    PubMed

    Rubio-Marcos, Fernando; Del Campo, Adolfo; Marchet, Pascal; Fernández, Jose F

    2015-01-01

    Ferroelectric materials exhibit spontaneous and stable polarization, which can usually be reoriented by an applied external electric field. The electrically switchable nature of this polarization is at the core of various ferroelectric devices. The motion of the associated domain walls provides the basis for ferroelectric memory, in which the storage of data bits is achieved by driving domain walls that separate regions with different polarization directions. Here we show the surprising ability to move ferroelectric domain walls of a BaTiO? single crystal by varying the polarization angle of a coherent light source. This unexpected coupling between polarized light and ferroelectric polarization modifies the stress induced in the BaTiO? at the domain wall, which is observed using in situ confocal Raman spectroscopy. This effect potentially leads to the non-contact remote control of ferroelectric domain walls by light. PMID:25779918

  20. Ferroelectric domain wall motion induced by polarized light

    PubMed Central

    Rubio-Marcos, Fernando; Del Campo, Adolfo; Marchet, Pascal; Fernández, Jose F.

    2015-01-01

    Ferroelectric materials exhibit spontaneous and stable polarization, which can usually be reoriented by an applied external electric field. The electrically switchable nature of this polarization is at the core of various ferroelectric devices. The motion of the associated domain walls provides the basis for ferroelectric memory, in which the storage of data bits is achieved by driving domain walls that separate regions with different polarization directions. Here we show the surprising ability to move ferroelectric domain walls of a BaTiO3 single crystal by varying the polarization angle of a coherent light source. This unexpected coupling between polarized light and ferroelectric polarization modifies the stress induced in the BaTiO3 at the domain wall, which is observed using in situ confocal Raman spectroscopy. This effect potentially leads to the non-contact remote control of ferroelectric domain walls by light. PMID:25779918