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1

Control of VCSEL polarization using deeply etched surface gratings  

Microsoft Academic Search

We demonstrate a robust approach to VCSEL polarization control using deeply-etched surface gratings oriented at several different rotational angles. A RCWA model is used to optimize the design for high polarization selectivity and fabrication tolerance.

Gordon A. Keeler; Kent M. Geib; Darwin K. Serkland; Gregory M. Peake; Joel R. Wendt

2006-01-01

2

Polarization Dynamics of VCSELs  

NASA Astrophysics Data System (ADS)

In this chapter we wrap up the experimental and theoretical results on polarization dynamics of solitary vertical-cavity surface-emitting lasers. Experiments have shown that VCSELs emit a linearly polarized fundamental transverse mode either along the [110] or [1overline 10] crystallographic direction. Polarization switching between these modes can occur when the injection current is increased, showing either a frequency shift from the higher to the lower frequency mode (type I) or the reverse (type II). The two modes of linear polarization are strongly anti-correlated. The switching can happen through a region of mode hopping, with a dwell time scaling over eight orders of magnitude with the switching current, or through a region of hysteresis. Thermal (carrier) effects influence the polarization behavior of VCSELs through a red (blue) shift of the gain maximum. Also, in-plane anisotropic strain can strongly modify the polarization behavior of VCSELs. All these experimental results call for explanations, as there is no a priori intrinsic polarization selection mechanism in VCSELs. We present different gain equalization models to explain type I, type II or double polarization switching. Alternatively, the spin-flip model can explain both types polarization switching by involving a microscopic spin-flip relaxation mechanism. Its predictive power has been experimentally established as, e.g., polarization switching through elliptically polarized states and dynamical instabilities. Finally, we highlight some perspective applications using polarization dynamics of VCSELs.

Panajotov, Krassimir; Prati, Franco

3

Polarization correlations in pulsed VCSELs  

Microsoft Academic Search

Summary form only given. Vertical-cavity surface-emitting lasers (VCSELs) exhibit very interesting physical properties and have great potential for use in optical communications. However, the physical mechanisms that lead to polarization selection in VCSELs are not completely understood, despite much research. We have measured polarization correlations in a pulsed VCSEL. We apply short (3-30 ns) current pulses to the laser and

D. R. Shelly; T. W. S. Garrison; M. Beck; D. H. Christensen

2000-01-01

4

Temperature-Dependent Multi-Polarization Switching in VCSELs  

NASA Astrophysics Data System (ADS)

The multi-polarization switching (MPS) in vertical-cavity surface-emitting lasers (VCSELs) at constant temperature was investigated. The experiment was performed by triangular modulation signal at 100 Hz under 10 ^oC and 7 ^oC. The results show that the number of polarization switching (PS) was varied from single PS to five PSs and seven PSs at 10 ^oC and 7 ^oC, respectively. It also observed that the variation of PS in VCSEL was sensitive to the increasing and decreasing process of temperature. Rich results concluded that the substrate temperature play an significant role in MPS.

Chen, Yu-Fong; Chin, Pei-Hou; Hsu, Cheng; Quadir, Shaham; Li, Yueh-Chen; Wu, Yu-Heng; Yen, Tsu-Chiang

2013-03-01

5

Parametric Analysis of Spin-Polarized VCSELs  

Microsoft Academic Search

Calculations of spin-injected vertical-cavity surface- emitting lasers (VCSELs) are presented using an efficient algorithm for solution of the steady-state rate equations in the spin-flip model. The effects of spin relaxation, birefringence, electron and photon lifetimes, linewidth factor and the magnitude and ellipticity of the pumping are investigated. After a review of published values for spin relaxation rates in semiconductors of

Michael J. Adams; Dimitris Alexandropoulos

2009-01-01

6

Stochastic logic gate that exploits noise and polarization bistability in an optically injected VCSEL.  

PubMed

We study numerically the dynamics of a vertical-cavity surface-emitting laser (VCSEL) with optical injection and show that the interplay of polarization bistability and noise yields a reliable logic output to two logic inputs. Specifically, by encoding the logic inputs in the strength of the light injected into the suppressed polarization mode of the VCSEL (the so-called 'orthogonal' injection), and by decoding the output logic response from the polarization state of the emitted light, we demonstrate an all-optical stochastic logic gate that exploits the ubiquitous presence of noise. It gives the correct logic output response for as short as 5 ns bit times when the dimensionless spontaneous emission coefficient, ?(sp), is within the range 10(-4)-10(-1). Considering that typical values of ?(sp) in semiconductor lasers are in the range 10(-5)-10(-4), the VCSEL-based logic gate can be implemented with nowadays commercially available VCSELs, exploiting either their intrinsic noise, or external and background noise sources. PMID:23037419

Perrone, Sandro; Vilaseca, Ramon; Masoller, Cristina

2012-09-24

7

Polarization investigation of a tunable high-speed short-wavelength bulk-micromachined MEMS-VCSEL  

NASA Astrophysics Data System (ADS)

We report the investigation of the state of polarization (SOP) of a tunable vertical-cavity surface-emitting laser (VCSEL) operating near 850 nm with a mode-hop free single-mode tuning range of about 12 nm and an amplitude modulation bandwidth of about 5 GHz. In addition, the effect of a sub-wavelength grating on the device and its influence on the polarization stability and polarization switching has been investigated. The VCSEL with an integrated sub-wavelength grating shows a stable SOP with a polarization mode suppression ratio (PMSR) more than 35 dB during the tuning.

Davani, H. A.; Kögel, B.; Debernardi, P.; Grasse, C.; Gierl, C.; Zogal, K.; Haglund, Å.; Gustavsson, J.; Westbergh, P.; Gründl, T.; Komissinskiy, P.; Bitsch, T.; Alff, L.; Küppers, F.; Larsson, A.; Amann, M.-C.; Meissner, P.

2012-02-01

8

VCSELs at Honeywell: The story continues  

NASA Astrophysics Data System (ADS)

Honeywell continues to be the world"s leading supplier of VCSELs operating at 850 nm. This paper will cover new commercial application areas for 850-nm VCSELs, and will present new findings in VCSEL reliability science. In particular, newly-developing applications drive requirements for ever more reliable VCSEL design and fabrication, and for improvements in controls for ESD (electrostatic discharge) and EOS (electrical overstress) at manufacturing facilities both for VCSEL components and for higher-level assemblies employing VCSEL components. Honeywell efforts toward improvement of reliability and toward reduction of ESD exposure are described, as is an alternative approach to improving reliability of systems containing VCSELs without compromising their performance.

Guenter, James K.; Tatum, Jim A.; Hawthorne, Robert A., III; Hawkins, Bobby M.; Mathes, David T.

2004-06-01

9

VCSEL proliferation  

NASA Astrophysics Data System (ADS)

Since the commercialization of Vertical Cavity Surface Emitting Lasers (VCSELs) in 1996, Finisar's Advanced Optical Components Division has shipped well over 50 Million VCSELs. The vast majority of these were shipped into the data communications industry, which was essentially the only volume application until 2005. The driver for VCSEL manufacturing might well shift to the increasingly popular laser based optical mouse. The advantages of the laser based mouse over traditional LED mice include operation on a wider range of surfaces, higher resolution, and increased battery lifetime. What is the next application that will drive growth in VCSELs? This paper will offer a historical perspective on the emergence of VCSELs from the laboratory to reality, and the companies that have played key roles in VCSEL commercialization. Furthermore, a perspective on the market needs of future VCSEL development and applications is described.

Tatum, Jim

2007-03-01

10

Scaling properties of lithographic VCSELs  

NASA Astrophysics Data System (ADS)

Data are presented demonstrating lithographic vertical-cavity surface-emitting lasers (VCSELs) and their scaling properties. Lithographic VCSELs have simultaneous mode- and current-confinement defined only by lithography and epitaxial crystal growth. The lithographic process of these devices allows getting uniform device size throughout a wafer and easy scaling to manufacture very small lasers. The semiconductor's high thermal conductivity enables the small lithographic VCSEL to have lower thermal resistance than an oxide-aperture VCSEL, while the lithographic fabrication produces high VCSEL uniformity even at small size. Very dense packing is also possible. Devices of 3 ?m to 20 ?m diameters are fabricated and scaling properties are characterized. 3 ?m lithographic VCSELs produce output power of 4.1 mW, with threshold current of 260 ?A and slope efficiency of 0.76 W/A at emission wavelength of ~980 nm. These VCSELs also have single-mode single-polarization lasing without the use of a surface grating, and have >25 dB sidemode- suppression-ratio up to 1 mW of output power. Lifetime tests demonstrate that 3 ?m VCSEL operates for hundreds of hours at high injection current level of 85 kA/cm2 with 3.7 mW output power without degradation. Scaling properties and low thermal resistance of the lithographic VCSELs can extend the VCSEL technology to manufacturable and reliable small size lasers and densely packed arrays with long device lifetime.

Demir, Abdullah; Zhao, Guowei; Freisem, Sabine; Liu, Xiaohang; Deppe, Dennis G.

2011-02-01

11

Recent Advances of VCSEL Photonics  

NASA Astrophysics Data System (ADS)

A vertical-cavity surface emitting laser (VCSEL) was invented 30 years ago. A lot of unique features can be expected, such as low-power consumption, wafer-level testing, small packaging capability, and so on. The market of VCSELs has been growing up rapidly in recent years, and they are now key devices in local area networks using multimode optical fibers. Also, long wavelength VCSELs are currently attracting much interest for use in single-mode fiber metropolitan area and wide area network applications. In addition, a VCSEL-based disruptive technology enables various consumer applications such as a laser mouse and laser printers. In this paper, the recent advance of VCSEL photonics will be reviewed, which include the wavelength extension of single-mode VCSELs and their wavelength integration/control. Also, this paper explores the potential and challenges for new functions of VCSELs toward optical signal processing.

Koyama, Fumio

2006-12-01

12

Polarization control of 1.15 ?m vertical-cavity surface-emitting lasers using autocloned photonic crystal polarizer  

NASA Astrophysics Data System (ADS)

The authors propose and demonstrate the polarization control of 1.15 ?m, single-mode vertical-cavity surface-emitting lasers (VCSELs) with the hybrid integration of autocloned photonic crystal polarizer (PCP). The authors experimentally found that transverse electric (TE) and transverse magnetic (TM) modes of polarizations of the PCP can be selected for the in-phase and the out-of-phase conditions with respect to the positioning of PCP on the top surface of VCSELs. The lasing spectrum of TE (TM) mode in the in-phase (the out-of-phase) condition shows polarization suppression ratio of 18 (14) dB. This simple method offers stable polarization operation of VCSELs without penalties in laser performances.

Babu Dayal, P.; Kitabayashi, N.; Miyamoto, T.; Koyama, F.; Kawashima, T.; Kawakami, S.

2007-07-01

13

High contrast grating for spatial mode filtering and mode control of VCSELs  

NASA Astrophysics Data System (ADS)

High contrast gratings (HCG) have various unique features such as broadband high reflections, high-Q resonance, spatial control of optical phase and so on. We focus on the angular dependence of HCG, which can be managed by designing grating parameters. The angular dependence of HCG is much larger than that of conventional quarter-wavelength stack mirrors while keeping their broadband high reflections. The engineered angular dependence can be useful for spatial mode MUX/DEMUX devices. A possibility of spatial mode demultiplexer based on HCG hollow waveguides is suggested for use in optical interconnects with spatial mode multiplexing. Also, we discuss the transverse mode control of HCG-loaded VCSELs.

Koyama, Fumio

2012-02-01

14

VCSEL beam control with collective and self-aligned polymer technologies  

NASA Astrophysics Data System (ADS)

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.

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

2012-02-01

15

VCSEL Fundamentals  

NASA Astrophysics Data System (ADS)

In this chapter we outline major principles of vertical-cavity surface-emitting laser (VCSEL) design and operation. Basic device properties and generally applicable cavity design rules are introduced. Characteristic parameters like threshold gain and current, differential quantum efficiency and power conversion efficiency, as well as thermal resistance are discussed. We describe the design of Bragg reflectors and explain the transfer matrix method as a convenient tool to compute VCSEL resonator properties in a one-dimensional approximation. Experimental results illustrate the emission characteristics of high-efficiency VCSELs that apply selective oxidation for current and photon confinement. Both the 850 and 980 nm wavelength regions are considered. The basic treatment of laser dynamics and noise behavior is presented in terms of the small-signal modulation response as well as the relative intensity noise. Finally we give some examples of VCSEL applications in fiber-based optical interconnects, i.e., optical data transmission over short distances.

Michalzik, Rainer

16

Speed enhancement in VCSELs employing grating mirrors  

NASA Astrophysics Data System (ADS)

In recent years, various approaches to improve the speed of directly modulated vertical-cavity surface-emitting lasers (VCSELs) have been reported and demonstrated good improvement. In this paper, we propose and numerically investigate a new possibility of using high-index-contrast grating (HCG) as mirror for VCSELs. By changing the grating design, one can control the reflection delay of the grating mirror, enabling the control of cavity photon lifetime. On the other hand, short energy penetration depth of the HCG results in smaller modal volume, compared to DBR VCSELs. An example structure shows that the HCG VCSEL has a 30-% higher 3-dB bandwidth than the DBR VCSEL.

Chung, Il-Sug; Mørk, Jesper

2013-03-01

17

VCSELs with nematic and cholesteric liquid crystal overlays  

NASA Astrophysics Data System (ADS)

We study theoretically the spectral and polarization threshold characteristics of Vertical-Cavity Surface-Emitting Lasers with nematic and cholesteric liquid crystal overlay: LC-VCSELs. In the first case, we demonstrate the possibility of selecting between two orthogonal directions of linear polarization (LP) of the fundamental mode (x or y LP) by choosing appropriate NLC length and to achieve strong polarization discrimination: threshold gain difference as large as several times the threshold gain. We also demonstrate an active control of light polarization by electro-optically tuning the LC director and show that either polarization switching between x and y LP modes or continuous change of the LP direction is possible. For cholesteric LC-VCSEL we show that it becomes a coupled system with different spectral, threshold and polarization characteristics than the ones of the stand-alone VCSEL. Due to the existence of a band gap for circularly polarized light in the liquid crystal, lasing occurs in almost circularly polarized modes at the LC side.

Panajotov, K.; Dems, M.; Belmonte, C.; Thienpont, H.; Xie, Y.; Beeckman, J.; Neyts, K.

2013-03-01

18

The VCSELS are coming  

NASA Astrophysics Data System (ADS)

The paper addresses the current status of 850nm VCSELs in data communications systems, and the outlook for adoption of VCSELs in other applications. In particular, recent experimental results obtained by research and development activities at Honeywell are discussed.

Tatum, Jim A.; Guenter, James K.

2003-06-01

19

VCSELs: A Research Review  

NASA Astrophysics Data System (ADS)

This chapter attempts to briefly review the research history of vertical-cavity surface-emitting lasers (VCSELs). Based on the contents of previous monographs on VCSELs written in English, we motivate the selection of topics in the present book and give an introduction to the individual chapters. Moreover, we mention some other research that is not covered in a dedicated chapter in order to provide the readers with even deeper insights into VCSEL research. Future directions and opportunities are also indicated.

Michalzik, Rainer

20

Very High Frequency Mode-Stabilized VCSELs for Linear/RF Photonic Applications.  

National Technical Information Service (NTIS)

Vertical cavity surface emitting lasers (VCSELs) have emerged as a key optical source in digital and RF photonics systems. Investigation to date has involved VCSELs of 'standard' DBR construction. However, incorporation of a controllable saturable absorbe...

C. Chang-Hasnain K. Lau

2000-01-01

21

VCSELs in optical networking  

NASA Astrophysics Data System (ADS)

Vertical Cavity Surface Emitting Lasers (VCSELs) are now essentially the only source used in short distance high bit rate data communications over multimode optical fiber. First commercially realized in 1996 by Honeywell, the primary application has been single channel links operating Ethernet or Fibre Channel protocols in the LAN and SAN environments. Today, the total bandwidth throughput is being raised to more than 10Gbps per channel, with the potential of several channel operation to yield more than 100Gbps. 850nm VCSELs are beginning to emerge in relatively new application arenas and wavelengths. This paper describes the market readiness for VCSELS in a wide variety of optical networking applications.

Tatum, Jim A.

2003-08-01

22

Control of vertically polarized glare.  

PubMed

Reflected glare often interferes with vision. Since such glare is usually polarized it can be controlled with polarizers. The use of polarized filters to eliminate vertically polarized glare from blackboards and glossy printed material is presented. Practical means for the construction of such filters are discussed. PMID:6863803

Peli, E

1983-05-01

23

850nm VCSEL with a liquid crystal overlay  

NASA Astrophysics Data System (ADS)

We developed an in- house technology to overlay liquid crystal (LC) on top of a 850nm Vertical Cavity Surface Emitting Laser (VCSEL) creating a so-called LC-VCSEL. Prior to this, the effect of the cell thickness on the planar alignment of the E7 LC is investigated. It is observed that the LC orientation is planar, uniformly aligned over the whole cell with an average pre-tilt of 22.50 in a thin a cell of 13?m thickness; such alignment uniformity is not observed in a thick cell of 125?m. Nevertheless, several domains of good uniformity are still present. Further, the polarization resolved LI characteristics of LC-VCSEL are investigated with and without the insertion of LC in a cell glued directly onto VCSEL package. Before filling in the LC, the VCSEL emits linearly polarized light and this linear polarization is lost after LC filling. The output intensity as a function of polarizer angle shows partial planar alignment of the E7 LC, which is very important for the further advancement of the LC-VCSEL integrated system.

Nair, Veena M.; Panajotov, Krassimir; Petrov, Mikov; Thienpont, Hugo; Xie, Yi; Beeckman, Jeroen; Neyts, Kristiaan

2012-05-01

24

Red Emitting VCSEL  

NASA Astrophysics Data System (ADS)

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.

Jetter, Michael; Roßbach, Robert; Michler, Peter

25

A high-density multi-point LAPS set-up using a VCSEL array and FPGA control  

Microsoft Academic Search

A new LAPS (light-addressable potentiometric sensor) set-up will be introduced, in which the light sources are miniaturised by the utilisation of a VCSEL (vertical-cavity surface-emitting laser) array to increase the measurement spot density. An FPGA (field-programmable gate array) is used to generate modulation signals for an individual illumination of each measurement spot of the LAPS. The new set-up can operate

T. Wagner; C. F. Werner; K. Miyamoto; M. J. Schöning; T. Yoshinobu

2009-01-01

26

Quantum noise in VCSELs  

NASA Astrophysics Data System (ADS)

In this paper, we study in detail the intensity noise characteristics of vertical-cavity surface-emitting lasers (VCSELs). We demonstrate the possibility of generating intensity squeezed light with free-running or injection-locked VCSELs. Sub-shot noise operation results from very strong anticorrelations between the transverse modes. These anticorrelations have also been analysed through the transverse spatial distribution of the intensity noise. In the case of two transverse modes above threshold, our experimental results are found to be in good agreement with the predictions of a phenomenological model.

Hermier, J.-P.; Maurin, I.; Giacobino, E.; Schnitzer, P.; Michalzik, R.; Ebeling, K. J.; Bramati, A.; Khoury, A. Z.

2000-10-01

27

Thermal Properties of Polarization Switching in Vertical-Cavity Surface-Emitting Lasers  

NASA Astrophysics Data System (ADS)

This investigation studied the thermal properties of the polarization switching (PS) in vertical-cavity surface-emitting lasers (VCSELs). The studies were performed by experiments. In experiments, the current modulation frequency and ambient temperature of VCSELs were varied to study their thermal effects on PS. The hysteresis loop of polarization switching broadens as the modulation frequency increased and narrows as the modulation frequency decreased. We assumed that PS is activated as the temperature in the active region reaches a certain temperature. The PS of the VCSEL controlled by continuously varied ambient temperature is also studied. The experiments results show that the thermal effect plays a major role in PS and the hysteresis of PS. These results contribute to the understanding of the mechanism of VCSEL's polarization switching.

Wu, Yu-Heng; Li, Yueh-Chen; Kuo, Wang-Chuang; Yen, Tsu-Chiang

2012-02-01

28

VCSEL reliability: a user's perspective  

NASA Astrophysics Data System (ADS)

VCSEL arrays are being considered for use in interconnect applications that require high speed, high bandwidth, high density, and high reliability. In order to better understand the reliability of VCSEL arrays, we initiated an internal project at SUN Microsystems, Inc. In this paper, we present preliminary results of an ongoing accelerated temperature-humidity-bias stress test on VCSEL arrays from several manufacturers. This test revealed no significant differences between the reliability of AlGaAs, oxide confined VCSEL arrays constructed with a trench oxide and mesa for isolation. This test did find that the reliability of arrays needs to be measured on arrays and not be estimated with the data from singulated VCSELs as is a common practice.

McElfresh, David K.; Lopez, Leoncio D.; Melanson, Robert; Vacar, Dan

2005-03-01

29

Nonlinear dynamics in VCSELs driven by a sinusoidally modulated current and Rössler oscillator  

NASA Astrophysics Data System (ADS)

We firstly investigate the dynamics of vertical-cavity surface-emitting lasers (VCSELs) subject to sinusoidally modulated current using numerical simulations. For a few-hundred MHz frequency of injection current, the VCSELs emit a single pulse or a package of pulses when the injection current fluctuates around the threshold current. By varying the amplitude of the modulation, we show that the width of the bistability hysteresis loop can be suppressed and replaced by smooth single or multiple switching. For a few GHz frequency of injection current, the polarization modes of VCSELs exhibit a period-doubling transition to chaotic behavior. Then by modulating the VCSELs pump current by one of the outputs of a Rössler oscillator, we generate dynamical behaviors found in VCSELs subject to a sinusoidally modulated current. This new way of modulation of semiconductor lasers would bring a general benefit in the physical equipment, and reduce their cost.

Kingni, S. T.; Talla Mbé, J. H.; Woafo, P.

2012-05-01

30

1.3 and 1.55-?m InP-based VCSELs for digital and radio signal transmission  

Microsoft Academic Search

High performance InP-based LW-VCSELs have been realized. 10-Gbit\\/s error-free transmission was achieved up to 85°C as well as under high reflection. Polarization-stable operation was achieved using misoriented substrates. LW-VCSELs can be used for radio-over-fiber application.

N. Nishiyama; C. Caneau; A. Kobyakov; J. D. Downie; M. Sauer; C. Zah

2007-01-01

31

High-Power VCSEL Arrays  

NASA Astrophysics Data System (ADS)

We review recent developments on high-power , high-efficiency two-dimensional vertical-cavity surface-emitting laser (VCSEL) arrays emitting around 808 and 980 nm. Selectively oxidized, bottom-emitting single VCSEL emitters with 50% power conversion efficiency were developed as the basic building block of these arrays . More than 230 W of continuous-wave (CW) power is demonstrated from a 5 mm {×} 5 mm array chip. In quasi-CW mode, smaller array chips exhibit 100 W output power, corresponding to more than 3.5 kW/cm2 of power-density. High-brightness VCSEL pumps have been developed, delivering a fiber output power of 40 W, corresponding to a brightness close to 50 kW/(cm2 sr). High-energy VCSEL arrays in the milli-Joule range have also been developed. Many of the advantages of low-power single VCSEL devices such as reliability , wavelength stability, low-divergence circular beam, and low-cost manufacturing are preserved for these high-power arrays . VCSELs thus offer an attractive alternative to the dominant edge-emitter technology for many applications requiring compact high-power laser sources.

Seurin, Jean-François P.

32

Interface Controlled Tunneling Spin Polarization  

NASA Astrophysics Data System (ADS)

In recent years spin-dependent tunneling in magnetic tunnel junctions has aroused enormous interest and developed into a vigorous field of research. However, despite extensive efforts to elucidate the mechanisms of spin-dependent tunneling, a complete understanding of this phenomenon is still lacking. In this talk we will consider various factors controlling the spin polarization of the tunneling current and emphasize the decisive role of interface bonding. We will show that the tunneling spin polarization is primarily determined by the electronic and atomic structure of ferromagnet/insulator interfaces rather than bulk properties. Starting from a simple tight-binding model which demonstrates the importance of interface states that are controlled by the hybridization between the atoms at the interface, we will, then, consider spin-dependent tunneling from the oxidized Co surface through vacuum [1] and in Co/Al2O3/Co tunnel junctions [2], where the cobalt-oxygen bonding at the interfaces play a crucial role. Our results indicate that the common argument of the dominant s-electron tunneling which is often used to explain positive values of the spin polarization in alumina-based tunnel junctions might be qualitatively incorrect. Moreover, oxygen atoms adsorbed by cobalt at the Co/Al2O3 interface may be a prerequisite for the positive spin polarization. The importance of the interface bonding and structure in spin-dependent tunneling makes the quantitative description of transport characteristics much more complicated; however, it broadens dramatically the possibility to engineer magnetic tunnel junctions with properties desirable for device applications. [1] K.D. Belashchenko, E.Y. Tsymbal, M. van Schilfgaarde, D. Stewart, I.I. Oleynik, and S.S. Jaswal, Phys. Rev. B 69, 174408 (2004). [2] K.D. Belashchenko, E.Y. Tsymbal, I.I. Oleynik, and M. van Schilfgaarde, submitted paper.

Tsymbal, Evgeny Y.

2005-03-01

33

VCSEL arrays with integrated optics  

NASA Astrophysics Data System (ADS)

Systems with arrays of VCSELs can realize multi kilowatt output power. The inherent simplicity of VCSELs enables a performance and cost breakthrough in solutions for thermal processing and the pumping of solid state lasers. The use of an array of micro-optics i.e. one micro-lens per VCSEL enables multiple advantages: firstly it can function as a collimating lens in order to realize a brightness of an array which is similar to the brightness of a single VCSEL. Secondly the micro-lens can be part of an imaging system for tailored intensity distributions. Last but not least the microlens with moderate feedback into the VCSEL can help to select laser modes in order to increase brightness and mode stability. Wafer-level integrated micro-optics allow keeping the VCSEL advantage of realizing complete and operational lasers on wafer level including the micro-optics. This paper presents our approach to bond a 3" GaAs wafer with a micro-optics wafer of the same size. The type of glass used for the optics wafer has been selected to match the coefficient of thermal expansion of GaAs and is suitable for hot pressing of the lens structures. An alignment strategy with corresponding markers on both wafers is used to allow the alignment on a standard mask aligner thus realizing many thousand lens adjustments in a single process step. The technology can be combined with VCSEL wafers with thinned substrate as well as with complete substrate removal. The basic technology and illustrative prototype systems are described here.

Moench, Holger; Gronenborn, Stephan; Gu, Xi; Kolb, Johanna; Miller, Michael; Pekarski, Pavel; Weichmann, Ulrich

2013-03-01

34

VCSEL array-based light exposure system for laser printing  

NASA Astrophysics Data System (ADS)

Improving the image quality and speed is an endless demand for printer applications. To meet the market requirements, we have launched the world first laser printer (DocuColor 1256 GA) introducing 780-nm single-mode 8×4 VCSEL arrays in the light exposure system in 2003. The DocuColor 1256 GA features 2400 dots per inch (dpi) resolution which is the highest in the industry and a speed of 50 pages per minute (ppm). A VCSEL array design has an advantage that it can increase the pixel density and also increase the printing speed by simultaneously scanning the 32-beam to the photoconductor in the exposure process. Adopting VCSELs as a light source also contributes to the reduction of the machine's power consumption. The VCSELs are industrially manufactured based on the original in-situ monitored oxidation process to control the oxide aperture size. As a result, uniform characteristics with a less than 5% variation in both output power and divergence angle are obtained. Special care is also taken in the assembly process to avoid additional degradation in performance and quality. This technology is currently extended to high-end tandem color machines (2400 dpi, 80 ppm) to grasp on-demand publishing market. This paper will cover the key technologies of the VCSEL based light exposure system as well as its manufacturing process to assure its quality.

Mukoyama, Naotaka; Otoma, Hiromi; Sakurai, Jun; Ueki, Nobuaki; Nakayama, Hideo

2008-01-01

35

High-index-contrast subwavelength grating VCSEL  

NASA Astrophysics Data System (ADS)

In this article, we report our results on 980nm high-index-contrast subwavelength grating (HCG) VCSELs for optical interconnection applications. In our structure, a thin undoped HCG layer replaces a thick p-type Bragg mirror. The HCG mirror can feasibly achieve polarization-selective reflectivities close to 100%. The investigated structure consists of a HCG mirror with an underneath ?/4-thick oxide gap, four p-type GaAlAs/GaAs pairs for current spreading, three InGaAs/GaAs quantum wells, and an n-type GaAlAs/GaAs Bragg mirror. The HCG structure was defined by e-beam lithography and dry etching. The current oxide aperture and the oxide gap underneath the HCG were simultaneously formed by the selective wet oxidation process. Compared to air-gap high contrast grating mirrors demonstrated elsewhere, our grating mirrors are particular since they are supported by thinner ?/4 aluminium oxide layer, and thus are mechanically robust and thinner than usual designs. Sub-milliamp threshold currents and single-transverse-mode operation was obtained. A hero device exhibited maximum singlemode output power of more than 4 mW at room temperature and 1 mw at 70°C, which are the highest values ever reported from the HCG structures. These results build a bridge between a standard VCSEL and a hybrid laser on silicon, making them of potential use for the realization of silicon photonics.

Gilet, Philippe; Olivier, Nicolas; Grosse, Philippe; Gilbert, Karen; Chelnokov, Alexei; Chung, Il-Sug; Mørk, Jesper

2010-02-01

36

Ultrafast spin-polarized vertical-cavity surface-emitting lasers  

NASA Astrophysics Data System (ADS)

Spin-polarized lasers are highly attractive spintronic devices providing characteristics superior to their conventional purely charge-based counterparts. Spin-polarized vertical-cavity surface emitting lasers (spin-VCSELs) promise to offer lower thresholds, enhanced emission intensity, spin amplification, full polarization control, chirp control and ultrafast dynamics. In particular, the ability to control and modulate the polarization state of the laser emission with extraordinarily high frequencies is very attractive for many applications like broadband optical communication and ultrafast optical switches. After briefly reviewing the state of research in this emerging field of spintronics, we present a novel concept for ultrafast spin-VCSELs which has the potential to overcome the conventional speed limitation for directly modulated lasers and to reach modulation frequencies significantly above 100 GHz. The concept is based on the coupled spin-photon dynamics in birefringent micro-cavity lasers. By injecting spin-polarized carriers in the VCSEL, oscillations of the coupled spin-photon system can by induced which lead to oscillations of the polarization state of the laser emission. These oscillations are decoupled from conventional relaxation oscillations of the carrier-photon system and can be much faster than those. Utilizing these polarization oscillations is thus a very promising approach to develop ultrafast spin-VCSELs for high speed optical data communication in the near future.

Gerhardt, Nils C.; Höpfner, Henning; Lindemann, Markus; Li, Mingyuan; Jähme, Hendrik; Ackemann, Thorsten; Hofmann, Martin R.

2013-09-01

37

Commercial VCSELs and VCSEL arrays designed for FDR (14 Gbps) optical links  

NASA Astrophysics Data System (ADS)

Philips recently released a new VCSEL and photodiode product family for the fast growing FDR InfiniBandTM generation. In this work we review the influence of production process variations on VCSEL characteristics, the FDR VCSEL transmission behavior as well as wear-out reliability characteristics. Data collected during an initial 15 wafers pilot production batch verify that FDR VCSEL manufacturing reached mature volume production level. The VCSEL for the next EDR (26Gbps) InfiniBandTM generation is currently being developed at Philips. The paper presents characteristics of the first EDR VCSEL iteration.

King, Roger; Intemann, Steffan; Wabra, Stefan

2012-02-01

38

Nuclear reactivity control using laser induced polarization  

DOEpatents

A control element for reactivity control of a fission source provides an atomic density of {sup 3}He in a control volume which is effective to control criticality as the {sup 3}He is spin-polarized. Spin-polarization of the {sup 3}He affects the cross section of the control volume for fission neutrons and hence, the reactivity. An irradiation source is directed within the {sup 3}He for spin-polarizing the {sup 3}He. An alkali-metal vapor may be included with the {sup 3}He where a laser spin-polarizes the alkali-metal atoms which in turn, spin-couple with {sup 3}He to spin-polarize the {sup 3}He atoms. 5 figs.

Bowman, C.D.

1989-05-26

39

Spectral shifts with polarization control  

NASA Astrophysics Data System (ADS)

The spectral behavior of a limited bandwidth light with different polarization states reflected from an air-water interface near the absorption band of water is theoretically investigated. The results indicate that, at oblique incidence, the reflected wave’s spectral change is blue- or red-shifted for different polarizations and the shift is most obvious when the angle is close to the Brewster angle. This phenomenon can be used as a polarization spectrum selector, and a data transmission scheme utilizing this effect is also proposed.

Han, Pin

2013-10-01

40

Research on voltage-controlled polarization controller in the polarization mode dispersion compensation experiment  

NASA Astrophysics Data System (ADS)

A kind of voltage-controlled polarization controller made in electro-optic materials is studied in the experiment. By changing voltages added on the different plates, the corresponding out states of polarization are gotten which spread all over the Poincare. Results show that the phase retardation angle in each plate is a quadratic function of the applied voltages. And the degrees of polarization ellipsoids are obtained with the same the principal state of polarization. PC, a key element in the communication system, has great advantage for Polarization mode dispersion compensation and accurate controlling to the states of polarization.

Duan, Gaoyan; Zhang, Lan; Zhang, Xiaoguang; Yang, Bojun

2007-11-01

41

VCSEL collimation using self-aligned integrated polymer microlenses  

NASA Astrophysics Data System (ADS)

We report on the design and fabrication of polymer microlenses fabricated on patterned SU-8 layers in view of integrating microlenses on VCSEL arrays for laser beam shaping. For a standard top-emitting VCSEL, the lens has to be fabricated on a thick intermediate layer (pedestal) whose optimal thickness can be modelled as a function of the initial and of the aimed optical properties of the VCSEL beam. In this work, pedestals are fabricated with SU-8, which is a negative-tone photoresist transparent at the lasing wavelength. Lens deposition is realized using a robotized silicon microcantilever spotter technique after a simple SU-8 photolithography step in order to define high aspect ratio cylindrical pedestals with wide range diameters [30-140?m]. The effect of pedestal diameter on the final contact angle and curvature radius has been investigated using non contact optical profilometry and scanning electron microscopy. We show that this technique leads to a complete delimitation of the polymer droplets and to a better control of the final lens size. Moreover, lens positioning is fully ensured by the self-alignment of the droplet with the pillar center and consequently with the VCSEL source, and allows for meeting the stringent requirements on alignments.

Levallois, Christophe; Bardinal, Véronique; Vergnenègre, Corinne; Leïchlé, Thierry; Camps, Thierry; Daran, Emmanuelle; Doucet, Jean-Baptiste

2008-05-01

42

VCSEL technology for medical diagnostics and therapeutics  

NASA Astrophysics Data System (ADS)

In the 1990's a new laser technology, Vertical Cavity Surface Emitting Lasers, or VCSELs, emerged and transformed the data communication industry. The combination of performance characteristics, reliability and performance/cost ratio allowed high data rate communication to occur over short distances at a commercially viable price. VCSELs have not been widely used outside of this application space, but with the development of new attributes, such as a wider range of available wavelengths, the demonstration of arrays of VCSELs on a single chip, and a variety of package form factors, VCSELs can have a significant impact on medical diagnostic and therapeutic applications. One area of potential application is neurostimulation. Researchers have previously demonstrated the feasibility of using 1850nm light for nerve stimulation. The ability to create an array of VCSELs emitting at this wavelength would allow significantly improved spatial resolution, and multiple parallel channels of stimulation. For instance, 2D arrays of 100 lasers or more can be integrated on a single chip less than 2mm on a side. A second area of interest is non-invasive sensing. Performance attributes such as the narrow spectral width, low power consumption, and packaging flexibility open up new possibilities in non-invasive and/or continuous sensing. This paper will suggest ways in which VCSELs can be implemented within these application areas, and the advantages provided by the unique performance characteristics of the VCSEL. The status of VCSEL technology as a function of available wavelength and array size and form factors will be summarized.

Hibbs-Brenner, M. K.; Johnson, K. L.; Bendett, M.

2009-02-01

43

VCSEL-based parallel optical transmission module  

Microsoft Academic Search

This paper describes the design process and performance of the optimized parallel optical transmission module. Based on 1×12 VCSEL (Vertical Cavity Surface Emitting Laser) array, we designed and fabricated the high speed parallel optical modules. Our parallel optical module contains a 1×12 VCSEL array, a 12 channel CMOS laser driver circuit, a high speed PCB (Printed Circuit Board), a MT

Rongxuan Shen; Hongda Chen; Chao Zuo; Weihua Pei; Yi Zhou; Jun Tang

2005-01-01

44

Analysis of waveguiding properties of VCSEL structures  

SciTech Connect

In this paper, the authors explore the feasibility of using the distributed Bragg reflector, grown on the substrate for a VCSEL (Vertical Cavity Surface Emitting Laser), to provide waveguiding within the substrate. This waveguiding could serve as an interconnection among VCSELs in an array. Before determining the feasibility of waveguide interconnected VCSELs, two analysis methods are presented and evaluated for their applicability to this problem. The implementations in Mathematica of both these methods are included. Results of the analysis show that waveguiding in VCSEL structures is feasible. Some of the many possible uses of waveguide interconnected VCSELs are also briefly discussed. The tools and analysis presented in this report can be used to evaluate such system concepts and to do detailed design calculations.

Erteza, I.A. [Sandia National Labs., Albuquerque, NM (United States). Exploratory Systems Development Center

1996-09-01

45

SASE FEL Polarization Control Using Crossed Undulator  

SciTech Connect

There is a growing interest in producing intense, coherent x-ray radiation with an adjustable and arbitrary polarization state. In this paper, we study the crossed undulator scheme for rapid polarization control in a self-amplified spontaneous emission (SASE) free electron laser (FEL). Because a SASE source is a temporally chaotic light, we perform a statistical analysis on the state of polarization using FEL theory and simulations. We show that by adding a small phase shifter and a short (about 1.3 times the FEL power gain length), 90{sup o} rotated planar undulator after the main SASE planar undulator, one can obtain circularly polarized light--with over 80% polarization--near the FEL saturation.

Ding, Yuantao; Huang, Zhirong; /SLAC

2008-09-30

46

Fabrication issues of oxide-confined VCSELs  

SciTech Connect

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, sample temperature, carrier gas flow, and bubbler water temperature. Knowledge of these parameters has enable the compilation of oxidation rate data for AlGaAs which exhibits an Arrhenius rate dependence. The compositionally dependent activation energies for Al{sub x}Ga{sub 1-x}As layers of x=1.00, 0.98, and 0.92 are found to be 1.24, 1.75, and 1.88 eV, respectively. 7 figs, 1 tab, 14 refs.

Geib, K.M.; Choquette, K.D.; Hou, H.Q.; Hammons, B.E.

1997-04-01

47

Advanced Concepts for High-Power VCSELS and 2-Dimensional VCSEL Arrays  

SciTech Connect

We have developed high power vertical cavity surface emitting lasers (VCSELS) for multimode or single mode operation. We have characterized new cavity designs for individual lasers and 2-dimensional VCSEL arrays to maximize output power. Using broad area high power VCSELS under pulsed excitation, we have demonstrated the triggering of a photoconductive semiconductor switch (PCSS) with a VCSEL. We also have developed designs for high output power in a single mode. The first approach is to engineer the oxide aperture profile to influence the optical confinement and thus modal properties. A second approach focuses on "leaky-mode" concepts using lateral modification of the cavity resonance to provide the lateral refractive index difference. To this end, we have developed a regrowth process to fabricate single-mode VCSELS. The overall objective of this work was to develop high-power single-mode or multimode sources appropriate for many applications leveraging the many inherent advantages of VCSELS.

Allerman, A.A.; Choquette, Kent D.; Chow, W.W.; Geib, K.M.; Hadley, R.; Hou, H.Q.; Mar, A.

1999-04-01

48

Design of high power VCSEL arrays  

NASA Astrophysics Data System (ADS)

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 design of high power VCSEL arrays requires a concurrent consideration of mechanical, thermal, optical and electrical aspects. Especially the heat dissipation from the loss regions in the VCSEL mesas into the surrounding materials and finally towards the heat sink is discussed in detail using analytical and finite element calculations. Basic VCSEL properties can be separated from the calculation of thermal resistivity and only the latter depends on the details of array design. Guidelines are derived for shape, size and pitch of the VCSEL mesas in an array and optimized designs are presented. The electro-optical efficiency of the VCSELs and the material properties determine the operation point. A specific VCSEL design with the shape of elongated rectangles is discussed in more depth. The theoretical predictions are confirmed by measurements on practical modules of top-emitting structures as well as of bottom-emitting structures.

Moench, Holger; Dumoulin, Raimond; Gronenborn, Stephan; Gu, Xi; Heusler, Gero; Kolb, Johanna; Miller, Michael; Pekarski, Pavel; Pollmann-Retsch, Jens; Pruijmboom, Armand; Stroesser, Martin

2012-02-01

49

Long-wavelength VCSELs at Honeywell  

NASA Astrophysics Data System (ADS)

In this paper we describe both the 1310 and 1550 nm VCSEL development work at Honeywell using both InP and GaAs substrates, and using both MOCVD and MBE. We describe the material systems, the designs, the growth techniques, and the promising results obtained and compare them to the needs of the communications industry. InGaAsN quantum well based VCSELs have been demonstrated to 1338 nm lasing at temperatures up to 90 C. Continuous wave InP based 1550 nm VCSELs have also been demonstrated.

Johnson, Ralph H.; Blasingame, Virgil; Tatum, Jim A.; Chen, Bo-Su; Mathes, David T.; Orenstein, James D.; Wang, Tzu-Yu; Kim, Jin K.; Kwon, Ho-Ki; Ryou, Jae-Hyun; Park, Gyoungwon; Kalweit, Edith; Chanhvongsak, Helen; Ringle, Mike D.; Marta, Terry; Gieske, Joe

2003-06-01

50

Solar wind control of the polar cusp  

NASA Astrophysics Data System (ADS)

Observations of the distribution of particles, electric fields, and currents in the polar cusp, particularly aspects which enable a comparison between ground-based and space-based observations are discussed. The cusp is characterized by intense fluxes of very low energy electrons, but a definition of the cusp based upon this characteristic is insufficient to exclude other sources like the dayside extension of the plasma-sheet boundary layer. The location of the cusp is partly controlled by Bz. For northward interplanetary magnetic field (IMF), observations support a polar cusp and polar cap convection pattern dominated by an extra two-cell pattern for all By. The relative sizes of the two cells, however, is related to the sign and magnitude of By. For southward IMF the prenoon sector shows a double convection reversal for By 0 compared to a single for By 0. Space and ground-based observations support models of two IMF controlled convection cells.

Friis-Christensen, E.

51

The red light VCSEL for network communication  

NASA Astrophysics Data System (ADS)

Compared with the edge emission laser, the vertical-cavity surface-emitting laser (VCSEL) with better beam quality can be performed more efficiently coupling with optical fiber. The 650nm~670nm wavelength VCSEL can be widely used in plastic optical fiber (POF) network source. This paper introduces a new kind VCSEL with new structure, of which the thermal characteristic is better than tradition device. In the special structure of the laser, the thickness of the substrate under the active region is lower, the heat generated by the laser can be faster transferred to the heat sink and the cooling effect is enhanced. In addition, the series resistance of the device is smaller and the heat produced by the device is further reduced. Through comparative test with the traditional VCSEL, the light output power of the device with new structure is increased by more than 20%.

Deng, Yun; Yan, Changling; Shi, Jianwei; Xu, Li; Feng, Yuan; Hao, Yongqin; Zhao, Yingjie

2013-08-01

52

VCSEL-Based Transceivers for Data Communications  

NASA Astrophysics Data System (ADS)

The data communications (datacom) transceiver market has experienced tremendous growth over the last fifteen years due in large part to the use of vertical-cavity surface-emitting lasers (VCSELs) and multimode optical fibers. This chapter reviews the evolution of 850 nm laser-based datacom transceivers beginning with the early use of AlGaAs edge-emitters to the adoption of VCSELs where their unique attributes have enabled significant performance enhancements and cost reductions in transceiver designs.

Jackson, Kenneth P.; Schow, Clint L.

53

Long-wavelength VCSELs at Honeywell  

Microsoft Academic Search

In this paper we describe both the 1310 and 1550 nm VCSEL development work at Honeywell using both InP and GaAs substrates, and using both MOCVD and MBE. We describe the material systems, the designs, the growth techniques, and the promising results obtained and compare them to the needs of the communications industry. InGaAsN quantum well based VCSELs have been

Ralph H. Johnson; Virgil Blasingame; Jim A. Tatum; Bo-Su Chen; David T. Mathes; James D. Orenstein; Tzu-Yu Wang; Jin K. Kim; Ho-Ki Kwon; Jae-Hyun Ryou; Edith Kalweit; Helen Chanhvongsak; Mike D. Ringle; Terry Marta; Joe Gieske

2003-01-01

54

RCE photodetectors based on VCSEL structures  

Microsoft Academic Search

We have fabricated top illuminated resonant cavity enhanced (RCE) detectors by partially removing top-mirror pairs of a vertical-cavity surface-emitting laser (VCSEL) structure by etching. The observed maximum quantum efficiency is 73% with a spectral full-width at half-maximum (FWHM) of about 1.7 nm. This particular RCE detector was fabricated by etching away 8 top-mirror pairs of a VCSEL structure, with 15.5

T. Knodl; H. K. H. Choy; J. L. Pan; R. King; R. Jager; G. Lullo; J. F. Ahadian; R. J. Ram; K. J. Ebeling

1999-01-01

55

Signaling pathways controlling cell polarity and chemotaxis  

Microsoft Academic Search

Many important biological processes, including chemotaxis (directional cell movement up a chemoattractant gradient), require a clearly established cell polarity and the ability of the cell to respond to a directional signal. Recent advances using Dictyostelium cells and mammalian leukocytes have provided insights into the biochemical and molecular pathways that control chemotaxis. Phosphoinositide 3-kinase plays a central and possibly pivotal role

Chang Y Chung; Satoru Funamoto; Richard A Firtel

2001-01-01

56

Multiphysics modeling of intracavity-contacted VCSELs  

NASA Astrophysics Data System (ADS)

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.

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

57

Interface control of bulk ferroelectric polarization  

SciTech Connect

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.

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

58

The next generation high data rate VCSEL development at SEDU  

NASA Astrophysics Data System (ADS)

In May of 2012, Emcore's VCSEL FAB and VCSEL based transceiver business joined Sumitomo Electric Device Innovations USA (SEDU). After this change of ownership, our high speed VCSEL development effort continues. In this paper, we will report the progress we made in the past year in our 25Gbps to 28Gbps VCSEL. This next generation device is targeted for EDR, 32GFC as well as other optical interconnect applications.

Xie, Chuan; Li, Neinyi; Huang, Shenghong; Liu, Chiyu; Wang, Li; Jackson, Kenneth P.

2013-03-01

59

High finesse external cavity VCSELs: from very low noise lasers to dual frequency lasers  

NASA Astrophysics Data System (ADS)

Low noise-level optical sources are required for numerous applications such as microwave photonics, fiber-optic sensing and time/frequency references distribution. In this paper, we demonstrate how inserting a SC active medium into a centimetric high-Q external cavity is a simple way to obtain a shot-noise-limited laser source over a very wide frequency bandwidth. This approach ensures, with a compact design, a sufficiently long photon lifetime to reach the oscillation-relaxation- free class-A regime. This concept has been illustrated by inserting a 1/2-VCSEL in an external cavity including an etalon filter. A -156dB/Hz relative intensity noise level is obtained over the 100 MHz to 18 GHz bandwidth of interest. This is several orders of magnitude better than the noise, previously observed in VCSELs, belonging to the class-B regime. The optimization, in terms of noise, is shown to be a trade-off between the cavity length and the laser mode filtering. The transition between the class-B and class-A dynamical behaviors is directly observed by continuously controlling the photon lifetime is a sub-millimetric to a centimetric cavity length. It's proven that the transition occurs progressively, without any discontinuity. Based on the same laser architecture, tunable dual-frequency oscillation is demonstrated by reducing the polarized eigenstates overlap in the gain medium. The class-A dynamics of such a laser, free of relaxation oscillations, enables to suppress the electrical phase noise in excess, usually observed in the vicinity of the beat note. An original technique for jitter reduction in mode-locked VECSELs is also investigated. Such lasers are needed for photonic analog to digital converters.

Baili, Ghaya; Alouini, Medhi; Morvan, Loic; Bretenaker, Fabien; Sagnes, Isabelle; Garnache, Arnaud; Dolfi, Daniel

2011-01-01

60

Control of polarization in integrated optics  

NASA Astrophysics Data System (ADS)

Integrated optical devices have attracted considerable attention in recent years with the rapid progress in optical communications, and the emergence of dense wavelength division multiplexing systems. The control over the state of polarization of the optical signal is an important issue that needs to be addressed due to the structure-induced anisotropy in these devices. In this thesis, two different types of integrated optical devices, with distinct approaches to address their polarization sensitivity, have been explored. The first device investigated was a semiconductor optical amplifier based on multi-quantum wells, where the gain depends on the state of polarization of the optical signal. To realize amplifiers with polarization insensitive gain, tensile-strained quantum wells structures were utilized as active regions in these devices. Optical gain calculations were performed using k.p method to calculate the tensile stress that needs to be introduced for gain equalization. These devices were then fabricated and tested to demonstrate the concept of gain equalization in InGaAsP/InP based material system at 1300 nm wavelength window and in AlInGaAs/InP based material system at both 1300 nm and 1550 run wavelength windows. In the second device, polarization sensitivity of integrated optical devices, combined with the linear electro-optic effect in III-V semiconductor materials, is exploited to manipulate the state of polarization of the optical signal. A phase modulator, combined with a TE <--> TM converter, may be used to obtain a device that converts the arbitrary elliptical input state of polarization to either the TE or the TM mode of the structure. Finite element methods have been developed to model the propagation and loss characteristics, and calculate the switching voltages of these devices based on AlGaAs/GaAs material system. The fabricated devices were then investigated for their I-V characteristics and propagations losses with and without the metal electrodes. These measurements reveal high losses for the optical signal in the presence of the metal electrodes with a higher attenuation for the TM mode as compared to the TE mode. A complete measurement of the polarization characteristics of these devices requires modified waveguide/electrode structure to minimize the excess losses encountered by the optical signal.

Koonath, Prakash Vijayan

61

Low-Cost Optical Video Links Based on VCSELs  

NASA Astrophysics Data System (ADS)

The history of introduction and current status of VCSEL based optical video link modules which have emerged as one of the main applications of VCSELs are described. The structure and characteristics of VCSELs in optical video links are summarized. The technical issues of the next generation optical video links for the mass market are discussed.

Shin, Hyun-Kuk

62

Polarization switching induced by phase change in extremely short external cavity vertical-cavity surface-emitting lasers  

Microsoft Academic Search

We experimentally investigate the spectral and polarization properties of vertical-cavity surface-emitting lasers (VCSELs) subject to polarization insensitive optical feedback from an extremely short external cavity (few microns) and find that the wavelength and the current at which the light polarization switches between the two linearly polarized fundamental modes of the VCSEL are periodically modulated with the length of the external

Krassimir Panajotov; Mikel Arizaleta; Miren Camarena; Hugo Thienpont; Heiko J. Unold; Johannes Michael Ostermann; Rainer Michalzik

2004-01-01

63

Fiber polarization control based on a fast locating algorithm.  

PubMed

In this article, currently used feedback control algorithms used in the polarization controller, including a simulated annealing algorithm and a gradient algorithm, are analyzed. On this basis, a new method of polarization control feedback algorithm based on a fast locating algorithm is proposed to solve the defects of the original algorithm, such as poor convergence and an extensive time consuming search. It can reduce convergence time and improve the response speed of the polarization controllers. This new endless polarization control algorithm utilizing a four-plate polarization controller is proposed and demonstrated. The results have shown that the response time of the polarization controller is less than 1 ms. The control of polarization is achieved and the output polarization state is stable, while the light intensity fluctuated less than 2%, which can run endless resets freely. PMID:24085164

Huang, Zhimeng; Liu, Cangli; Li, Jianfeng; Zhang, Dayong; Cheng, Heping; Luo, Yongquan; Hu, Qiqi; Han, Mei

2013-09-20

64

Optical fiber polarization control system based on fast locating algorithm  

NASA Astrophysics Data System (ADS)

In this thesis, the currently feedback control algorithms used in the polarization controller, including simulated annealing algorithm and gradient algorithm were analyzed. On this basis, a new method of polarization control feedback algorithm based on fast locating algorithm was proposed to solve the defects of the original algorithm, such as poor convergence and long time consuming search. It can reduce convergence time and improve the response speed of the polarization controllers. This new endless polarization control algorithm using 4-plate polarization controller was proposed and demonstrated. The results showed that the response time of the polarization controller was less than 1ms. The control of polarization was achieved and the output polarization state was stable while the light intensity fluctuated less than 2%, which could run endless reset freely.

Huang, Zhi-meng; Zhang, Da-yong; Cheng, He-ping; Luo, Yong-quan; Han, Mei; Li, Jian-feng; Liu, Cang-li

2013-09-01

65

High-power red VCSEL arrays  

NASA Astrophysics Data System (ADS)

High-power red laser sources are used in many applications such as cosmetics, cancer photodynamic therapy, and DNA sequencing in the medical field, laser-based RGB projection display, and bar-code scanning to name a few. Verticalcavity surface-emitting lasers (VCSELs) can be used as high-power laser sources, as efficient single devices can be configured into high-power two-dimensional arrays and scaled into modules of arrays. VCSELs emit in a circular, uniform beam which can greatly reduce the complexity and cost of optics. Other advantages include a narrow and stable emission spectrum, low speckle of the far-field emission, and good reliability. However, developing efficient red VCSEL sources presents some challenges because of the reduced quantum-well carrier confinement and the increased Aluminum content (to avoid absorption) which increases thermal impedance, and also decreases the DBR index contrast resulting in increased penetration length and cavity losses. We have recently developed VCSEL devices lasing in the visible 6xx nm wavelength band, and reaching 30% power conversion efficiency. We fabricated high-power 2D arrays by removing the GaAs substrate entirely and soldered the chips on high thermal conductivity submounts. Such arrays have demonstrated several Watts of output power at room temperature, in continuous-wave (CW) operation. Several tens of Watts are obtained in QCW operation. Results and challenges of these high-power visible VCSEL arrays will be discussed.

Seurin, Jean-Francois; Khalfin, Viktor; Xu, Guoyang; Miglo, Alexander; Li, Daizong; Zhou, Delai; Sundaresh, Mukta; Zou, Wei-Xiong; Lu, Chien-Yao; Wynn, James D.; Ghosh, Chuni

2013-03-01

66

RSFQ electronics for controlling superconducting polarity switches  

NASA Astrophysics Data System (ADS)

Superconducting radiation sensors are of particular interest for imaging applications in the sub-mm wavelength band because of their extraordinary sensitivity. The rising number of sensors integrated in one array entails the requirement of multiplexing techniques in order to reduce the number of wires leading into the cryogenic stage and thus reduce the thermal losses. One kind of promising code division multiplexing technique is based on a current steering switch (CSS), which is composed of two identical superconducting quantum interference devices (SQUIDs) in parallel current paths. One of them is switched from the superconducting into the normal state controlled by the applied magnetic flux. In this way the signal path can be altered and they can act as a polarity switch for analogue signals. We pursue this concept to use rapid single flux quantum (RSFQ) electronics for controlling these switches. As a first step, the SQUIDs of the CSS are inductively coupled to the storing loops of two delay flip flops (DFFs). Thus, one is able to toggle the polarity of the analogue switch by controlling the state of the DFF by RSFQ control signals. The results of simulations and measurements and also margin analyses are discussed.

Brandel, O.; Wetzstein, O.; May, T.; Toepfer, H.; Ortlepp, T.; Meyer, H.-G.

2012-12-01

67

Nonlinear Dynamics in Semiconductor Lasers and VCSELs  

Microsoft Academic Search

The studies of dynamics properties for these lasers are important not only from a fundamental physical aspect of nonlinear dynamics and chaos but also applications. Both edge-emitting semiconductor lasers with external perturbations and VCSELs with and without external perturbations are excellent models for chaos systems, since a rich variety of nonlinear dynamics can be observed. Also these chaotic lasers are

Junji Ohtsubo

2007-01-01

68

VCSEL-based micro-optical systems  

Microsoft Academic Search

This is a brief description of work at Sandia National Laboratories to build miniature systems that incorporate VCSELs, micro-optics and other optoelectronic components to realize sensing systems for unique applications. Miniaturization is the primary driver for these designs. The systems are fabricated with a combination of hybrid circuit assembly techniques and advanced electronic packaging technologies, including flip-chip bonding

M. E. Warren; J. R. Wendt; W. C. Sweatt; J. A. Nevers; C. G. Bailey; D. W. Arnold; C. M. Matzke; A. A. Allerman; R. E. Asbill; T. R. Carter; S. Samora

1998-01-01

69

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

SciTech Connect

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.

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

70

Comparison of Techniques for Bonding VCSELs Directly to Ics  

SciTech Connect

This paper reports the successful bonding of 8 x 8 and 4 x 4 VCSEL arrays to Si CMOS and GaAs MESFET integrated circuits and to GaAs substrates. Three different bonding techniques are demonstrated and their electrical, optical and mechanical characteristics are compared. All three techniques remove the substrate from the VCSEL wafer, leaving individual VCSELs bonded directly to locations within the integrated circuit.

Choquette, K.D.; Geib, K.M.; Hayes, E.M. Wilmsen, C.W.; Hou, H.Q.; Pu, R.

1999-03-26

71

High-power VCSELs with a rectangular aperture  

NASA Astrophysics Data System (ADS)

We show how VCSELs with elongated shapes of the emission area can achieve higher output powers and wall-plug efficiency compared to standard circular or quadratic VCSELs. We identified an improved homogeneity of the carrier concentration in the quantum wells as well as a reduced thermal resistance as the main reasons for the better performance of the rectangular shaped VCSELs presented in this article.

Gronenborn, S.; Pollmann-Retsch, J.; Pekarski, P.; Miller, M.; Strösser, M.; Kolb, J.; Mönch, H.; Loosen, P.

2011-12-01

72

Process control system using polarizing interferometer  

DOEpatents

A system for nondestructively measuring an object and controlling industrial processes in response to the measurement is disclosed in which an impulse laser generates a plurality of sound waves over timed increments in an object. A polarizing interferometer is used to measure surface movement of the object caused by the sound waves and sensed by phase shifts in the signal beam. A photon multiplier senses the phase shift and develops an electrical signal. A signal conditioning arrangement modifies the electrical signals to generate an average signal correlated to the sound waves which in turn is correlated to a physical or metallurgical property of the object, such as temperature, which property may then be used to control the process. External, random vibrations of the workpiece are utilized to develop discernible signals which can be sensed in the interferometer by only one photon multiplier. In addition the interferometer includes an arrangement for optimizing its sensitivity so that movement attributed to various waves can be detected in opaque objects. The interferometer also includes a mechanism for sensing objects with rough surfaces which produce speckle light patterns. Finally the interferometer per se, with the addition of a second photon multiplier is capable of accurately recording beam length distance differences with only one reading. 38 figures.

Schultz, T.J.; Kotidis, P.A.; Woodroffe, J.A.; Rostler, P.S.

1994-02-15

73

Furnace control apparatus using polarizing interferometer  

DOEpatents

A system for nondestructively measuring an object and controlling industrial processes in response to the measurement is disclosed in which an impulse laser generates a plurality of sound waves over timed increments in an object. A polarizing interferometer is used to measure surface movement of the object caused by the sound waves and sensed by phase shifts in the signal beam. A photon multiplier senses the phase shift and develops an electrical signal. A signal conditioning arrangement modifies the electrical signals to generate an average signal correlated to the sound waves which in turn is correlated to a physical or metallurgical property of the object, such as temperature, which property may then be used to control the process. External, random vibrations of the workpiece are utilized to develop discernible signals which can be sensed in the interferometer by only one photon multiplier. In addition the interferometer includes an arrangement for optimizing its sensitivity so that movement attributed to various waves can be detected in opaque objects. The interferometer also includes a mechanism for sensing objects with rough surfaces which produce speckle light patterns. Finally the interferometer per se, with the addition of a second photon multiplier is capable of accurately recording beam length distance differences with only one reading. 38 figures.

Schultz, T.J.; Kotidis, P.A.; Woodroffe, J.A.; Rostler, P.S.

1995-03-28

74

Advancements in the design and production of VCSELs at AXL  

NASA Astrophysics Data System (ADS)

Aiming at various blooming demands of optical communication, AXT provides high performance and highly reliable VCSELs, including implant, oxide, single mode and array devices. The push toward higher modulation rates, from 1 to 10 Gbps, has led to advances in VCSEL design and production techniques. The reliability of VCSEL devices is of prime importance for all new design and is an integral part of the development process. In this paper, we will overview the development activities of high speed VCSELs at AXT and the corresponding device characterization and reliability results.

Zhang, Xiaobo; Xiong, Frank; Sun, Wei; Zhu, Donghai; Yang, Zhihong; Liu, Jeff; Ou, Antoni; Liang, Bing

2002-06-01

75

VCSEL fault location apparatus and method  

DOEpatents

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.

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

2007-05-15

76

Advanced characterization techniques for high power VCSELs  

NASA Astrophysics Data System (ADS)

The performance of high power VCSELs in a specific application depends on the geometrical and thermal design as well as on the quality of the epitaxially grown material. Due to the relatively high heat load in densely packed high power arrays the temperature in the active zone and the DBR mirrors changes significantly with the applied current and the traditional characterization methods become less meaningful than for low power devices. This paper presents a method to measure temperature independent power curves with the help of short pulse techniques and data mapping at different heat sink temperatures. In addition the internal quantum efficiency, the transparency current and the gain coefficient are measured by a novel method which operates the VCSEL material as an edge emitter and applies a cut-back technique. The optical losses in the DBR mirrors are determined using external feedback. In summary all relevant parameters which determine the quality of an epitaxial design are measured independently and can be directly compared with modeling and help to optimize the high power VCSEL performance.

Moench, Holger; Baier, Johannes; Gronenborn, Stephan; Kolb, Johanna; Miller, Michael; Pekarski, Pavel; Schemmann, Marcel; Valster, Adriaan

2010-02-01

77

Stokes vector characterization of the polarization behavior of vertical-cavity surface-emitting lasers.  

PubMed

We demonstrate that a full polarization analysis in terms of the Stokes vector parameters is necessary to determine the polarization state of light emitted by vertical-cavity surface-emitting lasers (VCSELs). For three selected representative VCSEL devices, we measured the injection current dependence of the three Stokes parameters and compared these results with linearly selected polarization P-I curves, clearly demonstrating that a complete polarization analysis is required to unveil the full polarization behavior. PMID:23164918

Molitor, Andreas; Hartmann, Sébastien; Elsässer, Wolfgang

2012-11-15

78

The Design of A Ship's Control Space for Polar Icebreakers.  

National Technical Information Service (NTIS)

This paper presents the design of the ship control space for medium size polar icebreaker presently scheduled for construction award in the early 1970's. The ship control space (in past designs designated as pilothouse) is where navigation surveillance an...

R. P. Voelker E. Koch

1968-01-01

79

Protein complexes that control renal epithelial polarity  

PubMed Central

Establishment of epithelial apicobasal polarity is crucial for proper kidney development and function. In recent years, there have been important advances in our understanding of the factors that mediate the initiation of apicobasal polarization. Key among these are the polarity complexes that are evolutionarily conserved from simple organisms to humans. Three of these complexes are discussed in this review: the Crumbs complex, the Par complex, and the Scribble complex. The apical Crumbs complex consists of three proteins, Crumbs, PALS1, and PATJ, whereas the apical Par complex consists of Par-3, Par-6, and atypical protein kinase C. The lateral Scribble complex consists of Scribble, discs large, and lethal giant larvae. These complexes modulate kinase and small G protein activity such that the apical and basolateral complexes signal antagonistically, leading to the segregation of the apical and basolateral membranes. The polarity complexes also serve as scaffolds to direct and retain proteins at the apical membrane, the basolateral membrane, or the intervening tight junction. There is plasticity in apicobasal polarity, and this is best seen in the processes of epithelial-to-mesenchymal transition and the converse mesenchymal-to-epithelial transition. These transitions are important in kidney disease as well as kidney development, and modulation of the polarity complexes are critical for these transitions.

Pieczynski, Jay

2011-01-01

80

850 nm oxide high speed VCSEL development at Avago  

Microsoft Academic Search

In this paper we will discuss 14 Gb\\/s 850 nm oxide VCSEL performance and reliability. The device is targeted for the 16G Fibre Channel standard. The 14 Gb\\/s 850 nm oxide VCSEL meets the standard's specifications over the extended temperature range to support transceiver module operation from 0C to 85C.

Jingyi Wang; Chen Ji; David Soderstrom; Tong Jian; Laura Giovane; Sumon Ray; Zheng-Wen Feng; Friedhelm Hopfer; Jeong-Ki Hwang; Terry Sale; Sumitro Joyo Taslim; Chen Chu

2011-01-01

81

Antimonide-based approaches for long-wavelength VCSELs  

SciTech Connect

Mixed arsenide/antimonide materials have unique properties which make them potentially valuable for use in VCSELs operating at wavelengths longer than 1 {micro}m. The authors present their progress in applying these materials to VCSEL designs for 1--1.55 {micro}m.

Klem, J.F.; Blum, O. [Sandia National Labs., Albuquerque, NM (United States); Lear, K. [MicroOptical Devices, Albuquerque, NM (United States)

1998-08-01

82

VCSEL Arrays as Micromanipulators in Chip-Based Biosystems  

Microsoft Academic Search

The potential use of vertical cavity surface emitting laser (VCSEL) arrays for applications in cell analysis and tissue engineering is investigated by means of parallel optical trapping and active manipulation of biological cells on microfluidic chips. The simultaneous and independent transport of nine cells using a 3×3 array of VCSELs has been demonstrated experimentally; indicating that larger 2-dimensional array transport

Aaron L. Birkbeck; Richard A. Flynn; Mihrimah Ozkan; Deqiang Song; Matthias Gross; Sadik C. Esener

2003-01-01

83

Cavity structures for low loss oxide-confined VCSELs  

SciTech Connect

The authors 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 te optical cavity. They show that the optical loss can be sufficiently reduced to allow lasing in VCSELs with aperture area as small as 0.25 {micro}m{sup 2}.

Choquette, K.D.; Hadley, G.R.; Chow, W.W.; Hou, H.Q.; Geib, K.M.; Hammons, B.E. [Sandia National Labs., Albuquerque, NM (United States). Center for Compound Semiconductor Science and Technology; Mathes, D.; Hull, R. [Univ. of Virginia, Charlottesville, VA (United States). Dept. of Materials Science

1997-05-01

84

Reset-free integrated polarization controller using phase shifters  

Microsoft Academic Search

An endless, reset-free polarization controller implemented with planar lightwave circuits using phase shifters for tuning is proposed and demonstrated. By avoiding the need for tunable polarization mode converters, simple fabrication processes and a large range of material systems can be used, since neither the electrooptic effect nor a rotatable birefringence axis are necessary for device operation. The proof of concept

C. K. Madsen; P. Oswald; M. Cappuzzo; E. Chen; L. Gomez; A. Griffin; A. Kasper; E. Laskowski; L. Stulz; A. Wong-Foy

2005-01-01

85

Multiplexed gas spectroscopy using tunable VCSELs  

SciTech Connect

Detection and identification of gas species using tunable laser diode laser absorption spectroscopy has been performed using vertical cavity surface emitting lasers (VCSEL). Two detection methods are compared: direct absorbance and wavelength modulation spectroscopy (WMS). In the first, the output of a DC-based laser is directly monitored to detect for any quench at the targeted specie wavelength. In the latter, the emission wavelength of the laser is modulated by applying a sinusoidal component on the drive current of frequency {omega}, and measuring the harmonics component (2{omega}) of the photo-detected current. This method shows a better sensitivity measured as signal to noise ratio, and is less susceptible to interference effects such as scattering or fouling. Gas detection was initially performed at room temperature and atmospheric conditions using VCSELs of emission wavelength 763 nm for oxygen and 1392 nm for water, scanning over a range of approximately 10 nm, sufficient to cover 5-10 gas specific absorption lines that enable identification and quantization of gas composition. The amplitude and frequency modulation parameters were optimized for each detected gas species, by performing two dimensional sweeps for both tuning current and either amplitude or frequency, respectively. We found that the highest detected signal is observed for a wavelength modulation amplitude equal to the width of the gas absorbance lines, in good agreement with theoretical calculations, and for modulation frequencies below the time response of the lasers (<50KHz). In conclusion, we will discuss limit of detection studies and further implementation and packaging of VCSELs in diode arrays for continuous and simultaneous monitoring of multiple species in gaseous mixtures.

Bond, T; Bond, S; McCarrick, J; Zumstein, J; Chang, A; Moran, B; Benett, W J

2012-04-10

86

Polarization-controlled tunable directional coupling of surface plasmon polaritons.  

PubMed

Light can be coupled into propagating electromagnetic surface waves at a metal-dielectric interface known as surface plasmon polaritons (SPPs). This process has traditionally faced challenges in the polarization sensitivity of the coupling efficiency and in controlling the directionality of the SPPs. We designed and demonstrated plasmonic couplers that overcome these limits using polarization-sensitive apertures in a gold film. Our devices enable polarization-controlled tunable directional coupling with polarization-invariant total conversion efficiency and preserve the incident polarization information. Both bidirectional and unidirectional launching of SPPs are demonstrated. The design is further applied to circular structures that create radially convergent and divergent SPPs, illustrating that this concept can be extended to a broad range of applications. PMID:23599488

Lin, Jiao; Mueller, J P Balthasar; Wang, Qian; Yuan, Guanghui; Antoniou, Nicholas; Yuan, Xiao-Cong; Capasso, Federico

2013-04-19

87

Controlled Polar Mosaics of the Moon for LMMP by USGS  

NASA Astrophysics Data System (ADS)

Controlled polar mosaics of the Moon were produced by USGS in support of the Lunar Mapping and Modeling Project for lunar exploration activities. Mosaics consist of images taken by Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Cameras.

Lee, E. M.; Weller, L. A.; Richie, J. O.; Redding, B. L.; Shinaman, J. R.; Edmundson, K. L.; Archinal, B. A.; Hare, T. M.; Fergason, R. L.; Astrogeology Science Center Programming Team

2012-03-01

88

Ultrafast polarization modulation in vertical cavity surface emitting lasers with frequency dependent current injection  

NASA Astrophysics Data System (ADS)

We report on a polarization modulation in vertical cavity surface emitting lasers (VCSEL), based on RF electrical injection. Complex polarization dynamics in the single mode regime is studied as a function of RF frequency and power at different bias currents. It has been observed that the polarization state of the VCSEL can be altered by changing the frequency of RF current modulation. Time resolved measurements show that by injecting periodic bursts of RF modulation in the VCSEL, it is possible to change the dominant polarization between the two orthogonal modes at gigahertz rates.

Barve, A. V.; Zheng, Y.; Johansson, L.; Mehta, A.; Husain, A.; Coldren, L.

2012-12-01

89

Heat assisted magnetic recording (HAMR) with nano-aperture VCSELs for 10 Tb/in2 magnetic storage density  

NASA Astrophysics Data System (ADS)

We have conducted a thorough experimental analysis of nano-aperture VCSELs for use in heat-assisted magnetic recording (HAMR). To the best of our knowledge, this is the first study to both explore the impact of magnetic media proximity on VCSEL aperture power throughput and to use statistical methods to simultaneously characterize thousands of aperture designs. To achieve areal recording densities beyond 1 Tb/in2, high anisotropy magnetic materials are required to overcome the super-paramagnetic effect. These require high switching fields which are not conventionally available. Heat assisted magnetic recording (HAMR) is a potential technology to reduce the coercivity of the media and thus the required switching field by localized heating to enable writing of bits. The challenges being faced by this technology are to develop a precise method of delivering light to a very small, sub wavelength bit area with sufficient power through a near field aperture, and the fabrication of a laser source which can be integrated with current write heads used in hard disk drives. The focus of our work is to characterize nano-aperture VCSELs and test their potential application to HAMR. We have fabricated 850 nm VCSELs with large arrays of differently shaped nano-apertures in the gold layer on top of each VCSEL. The focusing and transmission characteristics of differently shaped nano-apertures are compared by simulations and experiments. C-shaped and H-shaped nano-apertures have also been fabricated in a gold layer deposited on a SiO2 substrate to observe the effect of close proximity of magnetic media (FePt) on the performance of nano-apertures, and polarization effects have also been characterized.

Hussain, Sajid; Kundu, Shreya; Bhatia, C. S.; Yang, Hyunsoo; Danner, Aaron J.

2013-03-01

90

Polarization Bistable Characteristics of Mesa Structure 980 nm Vertical-Cavity Surface-Emitting Lasers  

Microsoft Academic Search

The polarization bistable characteristics of 980 nm vertical-cavity surface-emitting lasers (VCSELs) with a mesa structure were experimentally studied. To achieve this, a distributed Bragg reflector mirror was processed into a rectangular mesa structure waveguide using inductively coupled plasma reactive ion etching and was buried with a polyimide layer. The VCSELs oscillated with single frequency and the lowest order transverse mode

Yuuki Sato; Takashi Mori; Yasuhiro Yamayoshi; Hitoshi Kawaguchi

2006-01-01

91

Terahertz polarization pulse shaping with arbitrary field control  

NASA Astrophysics Data System (ADS)

Polarization shaping of terahertz pulses enables us to manipulate the temporal evolution of the amplitude and direction of electric-field vectors in a prescribed manner. Such arbitrary control of terahertz waves has great potential in expanding the scope of terahertz spectroscopy, the manipulation of terahertz nonlinear phenomena and coherent control. This is analogous to the use of pulse-shaping techniques for optical frequencies that involve light's polarization states as a controllable degree of freedom. Here, we propose and demonstrate a method for generating a prescribed terahertz polarization-shaped waveform by the optical rectification of a laser pulse whose instantaneous polarization state and intensity are controlled by an optical pulse shaper. We have developed a deterministic procedure to derive input parameters for the pulse shaper that are adequate to generate the desired terahertz polarization-shaped waveform, with the benefit of simple polarization selection rules for the rectification process of light waves propagating along the three-fold axis of a nonlinear optical crystal.

Sato, Masaaki; Higuchi, Takuya; Kanda, Natsuki; Konishi, Kuniaki; Yoshioka, Kosuke; Suzuki, Takayuki; Misawa, Kazuhiko; Kuwata-Gonokami, Makoto

2013-09-01

92

Dynamic properties and performance of vertical cavity surface-emitting lasers in polarization-selective free-space optical links  

NASA Astrophysics Data System (ADS)

In the work presented here we study polarization-related dynamic and noise properties of vertical-cavity surface-emitting lasers (VCSELs) and analyze their performance in polarization-selective free-space optical data transmission links.

Kuksenkov, Dmitri V.; Temkin, Henryk

1996-05-01

93

Integrated-optic polarization controllers based on polymer waveguide  

NASA Astrophysics Data System (ADS)

Polarization controllers are demonstrated by integrated polymer waveguide technology. The integrated-optic polarization controllers consist of three birefringence modulators and 45°-inclined quarter-wave plates inserted between them. The birefringence modulator by incorporating highly birefringent polymer material exhibits the difference in phase retardation for TE and TM guided modes in proportion to the heating power. Thin-film quarter-wave plates are fabricated by using a reactive mesogen, and inserted between the birefringence modulators to produce static phase retardation and polarization coupling. By applying a triangular AC signal to one birefringence modulator and a DC signal to another, general polarization conversion covering the entire surface of the Poincaré sphere is demonstrated.

Kim, Jun-Whee; Park, Su-Hyun; Chu, Woo-Sung; Oh, Min-Cheol

2013-03-01

94

Multilevel Data Storage Memory Using Deterministic Polarization Control  

SciTech Connect

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.

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

95

Folded Free-Space Polarization-Controlled Multistage Interconnection Network  

Microsoft Academic Search

We present a folded free-space polarization-controlled optical multistage interconnection network (MIN) based on a dilated bypass exchange switch (DBS) design that uses compact polarization-selective diffractive optical elements (PDOE s). The folded MIN design has several advantages over that of the traditional transparent MIN, including compactness, spatial filtering of unwanted higher-order diffraction terms leading to an improved signal-to-noise ratio (SNR), and

Dan M. Marom; Paul E. Shames; Fang Xu; Yeshaiahu Fainman

1998-01-01

96

An 850 nm dielectric guide VCSEL for data communication links  

Microsoft Academic Search

An 850 nm VCSEL with a lithographically defined aperture and a dielectric index guide has been fabricated with low threshold current and bandwidth for operation at 10 Gb\\/s and beyond. The device structure and characteristics are described.

M. V. R. Murty; K.-L. Chen; Chu Chen; S. T. Joyo; T. E. Sale; Chung Yi Su; L. Giovane

2010-01-01

97

A plot twist: the continuing story of VCSELs at AOC  

NASA Astrophysics Data System (ADS)

During a year of substantial consolidation in the VCSEL industry, Honeywell sold their VCSEL Optical Products Division, which has now officially changed its name to Advanced Optical Components (AOC). Both manufacture and applied research continue, however. Some of the developments of the past year are discussed in this paper. They include advances in the understanding of VCSEL degradation physics, substantial improvements in long-wavelength VCSEL performance, and continuing progress in manufacturing technology. In addition, higher speed serial communications products, at 10 gigabits and particularly at 4 gigabits per second, have shown faster than predicted growth. We place these technologies and AOC's approach to them in a market perspective, along with other emerging applications.

Guenter, James K.; Tatum, Jim A.; Hawthorne, Robert A., III; Johnson, Ralph H.; Mathes, David T.; Hawkins, Bobby M.

2005-03-01

98

Record high temperature high output power red VCSELs  

NASA Astrophysics Data System (ADS)

Red VCSELs are of interest for medical and industrial sensing, printing, scanning, and consumer electronics applications. This paper will describe the optimization of red VCSEL design to achieve improved output power and a broader temperature range of operation. We will also discuss alternative packaging approaches and in particular will describe non-hermetic packages and performance of the VCSELs in a humid environment. Record output power of 14mW CW and a record maximum temperature of operation of 105°C have been achieved at an emission wavelength of 680nm. The achievement is the result of attention to many details including resonance cavitygain peak offset, material choices, current and mode confinement approaches, and metal aperture design. We have also demonstrated lifetimes >1000 hours for non-hermetic packages in an 85% humidity environment. A chip on board approach has been used to create a large scale linear array of VCSELs for a scanning application.

Johnson, Klein; Hibbs-Brenner, Mary; Hogan, William; Dummer, Matthew; Dogubo, Kabir; Berg, Garrett

2011-02-01

99

High-brightness pump sources using 2D VCSEL arrays  

Microsoft Academic Search

Many applications require laser pump sources with high output power (tens to hundreds of Watts) in the smallest spot, with the smallest divergence. Such high-brightness pump sources typically use edge-emitting semiconductor lasers. However, it is also possible to use high-power two-dimensional vertical-cavity surfaceemitting laser (VCSEL) arrays for this purpose. Using a single 976nm 2D VCSEL array chip in an external

Jean-Francois Seurin; Guoyang Xu; Qing Wang; Baiming Guo; Robert van Leeuwen; Alexander Miglo; Prachi Pradhan; James D. Wynn; Viktor Khalfin; Chuni Ghosh

2010-01-01

100

Thermal packaging of piggyback VCSELs for GBd optical communications modules  

Microsoft Academic Search

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

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

2001-01-01

101

Progress in high-power high-efficiency VCSEL arrays  

Microsoft Academic Search

We present recent results on high-power, high-efficiency two-dimensional vertical-cavity surface-emitting laser (VCSEL) arrays emitting around 808nm. Selectively oxidized, top-emitting single VCSEL emitters with 49% power conversion efficiency were developed as the basic building block of these arrays. Because of the strong GaAs absorption at the 808nm wavelength, the traditional bottom-emitting, substrate-emission configuration is not possible for large arrays that require

Jean-Francois Seurin; Guoyang Xu; Viktor Khalfin; Alexander Miglo; James D. Wynn; Prachi Pradhan; Chuni L. Ghosh; L. Arthur D'Asaro

2009-01-01

102

Analysis of the modulation behavior of red VCSELs  

NASA Astrophysics Data System (ADS)

This talk focuses on the high frequency characteristics of red VCSELs. After a short description of important fabrication issues the modulation behaviour of GaInP surface emitting lasers is discussed on the basis of the laser rate equations. The influence of the geometric dimensions of the laser structure and of the operating conditions is investigated. From the S-parameter analysis a modulation coefficient of 3 GHz/(mA)1/2 for VCSELs with a 7 µm aperture and a differential gain of 1.15•10-16 cm2 are deduced. A more detailed analysis reveals, that the modulation behaviour of red VCSELs nearly solely depends on their photon density inside the quantum wells as expected from the rate equations. These results imply that for a certain range of geometries diffusion and diffraction have a second order influence on the high frequency characteristics of red VCSELs. The K-factor analysis indicates very short carrier transfer and relaxation times around 5 ps and a maximum frequency of 25 GHz. Large signal modulation issues such as the properties of the eye diagram are also addressed. From the device characteristics it is concluded that the GaInP-VCSEL is suitable for data communication applications. Low cost fabrication makes the red VCSEL an attractive candidate for both automotive and high-speed data communication.

Ballmann, Tabitha; Rossbach, Robert; Jetter, Michael; Jutzi, Michael; Berroth, Manfred; Schweizer, Heinz C.

2004-10-01

103

Design and Performance of High-Speed VCSELs  

NASA Astrophysics Data System (ADS)

Over the past several years, high-speed vertical-cavity surface-emitting lasers (VCSELs) have been the subject of intensive worldwide research due to their applications in optical interconnects and optical data networks. The performance of VCSELs, especially with respect to their high-speed characteristics, has made significant progress. In this chapter, we first present the basic theory for current-modulated VCSELs using rate equations and small-signal analysis. Factors that affect the modulation bandwidth, including the intrinsic laser responses and extrinsic parasitics, are identified. Once these limitations are known, we discuss various designs that have been implemented in VCSELs to specifically address them, followed by a review of the current high-speed VCSEL performance based on these designs at several different wavelengths, including 850 nm, 980 nm, 1.1 ?m, and 1.3-1.6?m. Finally, we consider new modulation schemes based on loss modulation in coupled-cavity VCSELs, which has the potential to reach even higher speeds.

Chang, Yu-Chia; Coldren, Larry A.

104

Superconducting microwave cavity towards controlling the motion of polar molecules  

NASA Astrophysics Data System (ADS)

We propose the use of superconducting microwave cavities for the focusing and deceleration of cold polar molecular beams. A superconducting cavity with a high quality factor produces a large ac Stark shift in polar molecules, which allow us to efficiently control molecular motion. Our discussion is based on the experimental characterization of a prototype cavity: a lead-tin-coated cylindrical copper cavity, which has a quality factor of 106 and tolerates several watts of input power. Such a microwave device provides a powerful way to control molecules not only in low-field-seeking states, but also in high-field-seeking states such as the ground rotational state.

Enomoto, Katsunari; Djuricanin, Pavle; Gerhardt, Ilja; Nourbakhsh, Omid; Moriwaki, Yoshiki; Hardy, Walter; Momose, Takamasa

2012-10-01

105

Polarization Control of Optical Bistability in Coupled Microdisks  

NASA Astrophysics Data System (ADS)

Semiconductor microcavities are powerful systems both for the study of fundamental light-matter interactions and for applications in photonics. Microdisks composed of GaAs/(Al,GaAs) containing interface-fluctuation quantum dots for gain have been shown to offer low threshold lasing and cavity-induced electron spin coherence modulationfootnotetextS. Ghosh et al. Nature Materials 5, 261 (2006).. More recently, the control of lasing emission bistability by means of pump polarization was measured to occur under non-uniform illumination in elliptical microdisk pairs coupled evanescently along their semi-major axis footnotetextS. N. Ghosh, et al., submitted (2009).. Hysteretic bistability is present when the pump light polarization is perpendicular to the evanescent coupling axis and disappears when the pump polarization is parallel to the coupling axis. This lasing bistability control is a unique functionality which may find use in optical logic devices.

Buckley, B. B.; Awschalom, D. D.; Ghosh, S. N.; Ferri, C. G. L.; Verma, Y. K.; Ghosh, S.; Li, X.; Samarth, N.

2010-03-01

106

Chirp and polarization control of femtosecond molecular fragmentation  

PubMed Central

We explore the simultaneous effect of chirp and polarization as the two control parameters for non-resonant photo-dissociation of n-propyl benzene. Experiments performed over a wide range of laser intensities show that these two control knobs behave mutually exclusively. Specifically, for the coherently enhanced fragments (C3H3+, C5H5+) with negatively chirped pulses and C6H5+ with positively chirped pulses, polarization effect is the same as compared to that in the case of transform-limited pulses. Though a change in polarization affects the overall fragmentation efficiency, the fragmentation pattern of n-propyl benzene molecule remains unaffected in contrast to the chirp case.

Goswami, T; Das, D K; Kumar, S K Karthick; Goswami, D

2013-01-01

107

Polarization Control of Electron Tunneling into Ferroelectric Surfaces  

SciTech Connect

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.

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

108

Independent control of polar and azimuthal anchoring  

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

109

Polarization control method for ultraviolet writing of advanced Bragg gratings.  

PubMed

We present a flexible and simple method for UV writing of Bragg gratings with advanced apodization profiles including discrete phase shifts. The method is based on a p phase shift between the refractive-index modulation profiles induced by s and p polarization of UV light. By changing the ratio of UV intensity in the two polarizations we are able to control the modulation strength and to induce phase shifts while keeping a constant effective refractive index throughout the Bragg grating. We demonstrate strong UV-written Bragg gratings with Gaussian or sinc apodizations with spectral shapes, in good agreement with theoretical predictions. PMID:18026346

Jensen, Jesper Bo; Plougmann, Nikolai; Deyerl, Hans-Jã Rgen; Varming, Poul; Hã Bner, Jã Rg; Kristensen, Martin

2002-06-15

110

Comparison of fabrication approaches for selectively oxidized VCSEL arrays  

SciTech Connect

The impressive performance improvements of laterally oxidized VCSELs come at the expense of increased fabrication complexity for 2-dimensional arrays. Since the epitaxial layers to be wet-thermally oxidized must be exposed, non-planarity can be an issue. This is particularly important in that electrical contact to both the anode and cathode of the diode must be brought out to a package. They have investigated four fabrication sequences suitable for the fabrication of 2-dimensional VCSEL arrays. These techniques include: mesa etched polymer planarized, mesa etched bridge contacted, mesa etched oxide isolated (where the electrical trace is isolated from the substrate during the oxidation) and oxide/implant isolation (oxidation through small via holes) all of which result in VCSELs with outstanding performance. The suitability of these processes for manufacturing are assessed relative to oxidation uniformity, device capacitance, and structural ruggedness for packaging.

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

2000-04-18

111

2D VCSEL arrays for chip-level optical interconnects  

NASA Astrophysics Data System (ADS)

Oxide-confined vertical cavity surface-emitting laser diodes (VCSELs) are fabricated for applications in chip-level optical interconnects. 980 nm wavelength devices in arrays with 4 by 8 elements are investigated. Threshold voltages of 1.5 V and operation voltages below 2V of submilliamp threshold current lasers are fully comparable to 3.3 V CMOS technology. Modulation bandwidths of 9.5 GHz at 1.8 mA laser current with a modulation current efficiency factor of 10 GHz/(root)mA is demonstrated for 3 micrometers diameter VCSELs. No error floors are observed down to bit error rates of 10-11 at 12.5 Gb/s data transmission. VCSEL based top illuminated resonant cavity enhanced photodetectors show peak efficiencies of 50 percent combined with full spectral half-widths of 5 nm.

King, Roger; Michalzik, Rainer; Wiedenmann, Dieter; Jaeger, Roland; Schnitzer, P.; Knoedl, T.; Ebeling, Karl J.

1999-04-01

112

Thermal resistance of VCSEL's bonded to integrated circuits  

SciTech Connect

The thermal resistance of vertical-cavity surface-emitting lasers (VCSEL's) flip chip bonded to GaAs substrates and CMOS integrated circuits has been measured. The measurements on GaAs show that if the bonding is done properly, the bonding does not add significantly to the thermal resistance. However, the SiO{sub 2} under the CMOS bonding pad can double the thermal resistance unless measures are taken to improve the thermal conductance of these layers. Finite element simulations indicate that the thermal resistance of bonded VCSEL's increases rapidly as the solder bond size and the aperture size decrease below {approximately}10 {micro}m.

Pu, R.; Wilmsen, C.W.; Geib, K.M.; Choquette, K.D.

1999-12-01

113

Size dependence of selectively oxidized VCSEL transverse mode structure  

SciTech Connect

The performance of vertical cavity surface emitting lasers (VCSELs) has improved greatly in recent years. Much of this improvement can be attributed to the use of native oxide layers within the laser structure, providing both electrical and optical transverse confinement. Understanding this optical confinement will be vital for the future realization of yet smaller lasers with ultralow threshold currents. Here the authors report the spectral and modal properties of small (0.5 {micro}m to 5 {micro}m current aperture) VCSELs and identify Joule heating as a dominant effect in the resonator properties of the smallest lasers.

Hegarty, S.P.; Huyet, G. [University College, Cork (Ireland). Physics Dept.; McInerney, J.G. [University College, Cork (Ireland). Physics Dept.]|[Univ. of Arizona, Tucson, AZ (United States). Optical Sciences Center; Choquette, K.D.; Hou, H.Q.; Geib, K.M. [Sandia National Labs., Albuquerque, NM (United States). Center for Compound Semiconductor Science and Technology

1998-05-01

114

The Control Performance of Elliptically Polarizing Undulator at SRRC  

Microsoft Academic Search

There are two elliptically polarizing undulators (EPUs) with a period length of 56 mm at SRRC. One is a engineering prototype 1-meter-long EPU which is being installed for beam test. The other is a final version 4- meters-long EPU ( EPU5.6) which will be installed in the end of this year. The requirements of the control performance are a fast

C. S. CHEN; JENNY CHEN; K. T. HSU; K. T. PAN

115

Quantum phase gate and controlled entanglement with polar molecules  

SciTech Connect

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.

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

116

High frequency resonance-free loss modulation in a duo-cavity VCSEL  

NASA Astrophysics Data System (ADS)

We have proposed and demonstrated the principle of optical decoupling of the AC modulation component in a lossmodulated Vertical Cavity Surface Emitting Laser (VCSEL) using a detuned duo-cavity device. This approach allows the VCSEL power to be modulated without changing the photon density in the active region. Analysis of reflectivity spectra of a Fabri-Perot cavity with absorber shows that at a certain detuning from the resonance wavelength, reflectivity is almost independent of absorption magnitude. At this spectral detuning between the active region cavity and modulator cavity, a feedback-free transmission modulation of the VCSEL output is possible. The use a multiple-double-QW (MDQW) electroabsorption modulator allows absorption swing between 0.2% and 2% per pass. Optical power modulation of transmission with contrasts up to 40% and chirp of less than 0.05 nm at 930 nm was demonstrated with our design. Initial cavity resonance detuning is controlled through growth and was determined to be ideally ~0.7 nm from analysis of stand-alone absorber cavities. Resonance coupling (splitting) was calculated to be less than 0.3 nm in case of matching resonances. Applying bias at the MDQW modulator section allows adjustment of detuning between cavities by changing the top cavity resonance wavelength mainly via Kramers-Kronig relations. The high frequency modulation characteristics can be tuned in this manner to show little or no sign of resonance, in which case the high frequency roll-off of the modulation response is entirely determined by parasitics of the modulator section. We have demonstrated a flat (+/-3db) response up to 20 GHz.

van Eisden, J.; Yakimov, M.; Tokranov, V.; Varanasi, M.; Rumyantsev, O.; Mohammed, E. M.; Young, I. A.; Oktyabrsky, S. R.

2008-01-01

117

180 to +80°C CW lasing in visible VCSELs  

Microsoft Academic Search

Electron leakage into the p-DBR is the major process limiting the performance of visible VCSELs. It can be reduced by improving electron confinement, or made less important by reducing the mirror reflectivity. By doing this we would then expect to measure even higher output powers at room temperature, comparable to our low temperature results

T. E. Sale; G. C. Knowles; S. J. Sweeney; A. Onischenko; J. E. F. Frost; S. M. Pinches; J. Woodhead

2000-01-01

118

Numerical Investigation of Leaky-Mode Coupling in VCSELs  

SciTech Connect

We investigate various aspects of leaky-mode coupling behavior in Vertical-Cavity Surface-Emitting Lasers (VCSELs) using a 2D finite difference model to simulate two coupled pixels. Phase-locking is shown to occur in a manner consistent with previous simple models.

Hadley, G. R.

1997-12-31

119

Synaptic polarity of the interneuron circuit controlling C. elegans locomotion  

PubMed Central

Caenorhabditis elegans is the only animal for which a detailed neural connectivity diagram has been constructed. However, synaptic polarities in this diagram, and thus, circuit functions are largely unknown. Here, we deciphered the likely polarities of seven pre-motor neurons implicated in the control of worm's locomotion, using a combination of experimental and computational tools. We performed single and multiple laser ablations in the locomotor interneuron circuit and recorded times the worms spent in forward and backward locomotion. We constructed a theoretical model of the locomotor circuit and searched its all possible synaptic polarity combinations and sensory input patterns in order to find the best match to the timing data. The optimal solution is when either all or most of the interneurons are inhibitory and forward interneurons receive the strongest input, which suggests that inhibition governs the dynamics of the locomotor interneuron circuit. From the five pre-motor interneurons, only AVB and AVD are equally likely to be excitatory, i.e., they have probably similar number of inhibitory and excitatory connections to distant targets. The method used here has a general character and thus can be also applied to other neural systems consisting of small functional networks.

Rakowski, Franciszek; Srinivasan, Jagan; Sternberg, Paul W.; Karbowski, Jan

2013-01-01

120

Synaptic polarity of the interneuron circuit controlling C. elegans locomotion.  

PubMed

Caenorhabditis elegans is the only animal for which a detailed neural connectivity diagram has been constructed. However, synaptic polarities in this diagram, and thus, circuit functions are largely unknown. Here, we deciphered the likely polarities of seven pre-motor neurons implicated in the control of worm's locomotion, using a combination of experimental and computational tools. We performed single and multiple laser ablations in the locomotor interneuron circuit and recorded times the worms spent in forward and backward locomotion. We constructed a theoretical model of the locomotor circuit and searched its all possible synaptic polarity combinations and sensory input patterns in order to find the best match to the timing data. The optimal solution is when either all or most of the interneurons are inhibitory and forward interneurons receive the strongest input, which suggests that inhibition governs the dynamics of the locomotor interneuron circuit. From the five pre-motor interneurons, only AVB and AVD are equally likely to be excitatory, i.e., they have probably similar number of inhibitory and excitatory connections to distant targets. The method used here has a general character and thus can be also applied to other neural systems consisting of small functional networks. PMID:24106473

Rakowski, Franciszek; Srinivasan, Jagan; Sternberg, Paul W; Karbowski, Jan

2013-10-02

121

Optimizing 10Gbps VCSEL for real-world laser driver in parallel optical transceiver  

NASA Astrophysics Data System (ADS)

Recent VCSEL drivers for high data rate parallel transceivers are designed to DC couple to the VCSELs. These drivers normally include no back termination to save power. Due to mechanical restrictions, the wire bond between the driver's output and the laser is usually quite long. Such laser drivers in a transceiver can cause excessive optical eye distortions (overshoot, pattern dependent jitter, etc.) to a VCSEL which performs well when driven by a 50Ohm source. Therefore more careful design optimizations (of the VCSEL's intrinsic laser behavior and its parasitic elements) are needed for such applications. In most cases, this is the only way to achieve good transceiver performance for a given VCSEL driver IC. In this talk, we present Emcore's recent effort to optimize the 850nm 10G VCSEL array for the real world laser drivers used in parallel transceivers and active cables.

Xie, Chuan; Li, Neinyi; Lei, Chun; Sun, Xinyu; Luo, Wenlin

2010-02-01

122

Detection of Water Pollutant Using Surface-Polarity Controlled Sensor  

NASA Astrophysics Data System (ADS)

Aldehyde and carboxylic acid compounds are known as volatile substances with bad smell. It is also said to cause bad smell of tap water. In this study, we tried to detect and analyse aldehyde and carboxylic acid dissolved in water, using a surface-polarity controlled sensor. The sensor measures electrochemical impedance of the electrode surface whose electric potential is dynamically controlled. Adsorption and desorption of target chemicals cause changes in impedance which has constant phase element (CPE) characteristics. The impedance changes depending on the electrode potential are used as a chemical sensor output. As a result, we could detect and distinguish many kinds of aldehyde and carboxylic acids. Furthermore various water pollutant can be detected with high sensitivity. The results suggest that a simple and multi-purposed sensor can be constructed for environmental analysis using the proposed method.

Hayashi, Kenshi; Tanaka, Hiroki; Hayama, Kosuke; Izumi, Ryosuke; Toko, Kiyoshi

123

Planar cell polarity genes control the connectivity of enteric neurons  

PubMed Central

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.

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

2013-01-01

124

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

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

125

Novel concepts for ultrahigh-speed quantum-dot VCSELs and edge-emitters  

Microsoft Academic Search

Advanced types of QD media allow an ultrahigh modal gain, avoid temperature depletion and gain saturation effects, when used in high-speed quantum dot (QD) vertical-cavity surface-emitting lasers (VCSELs). An anti-guiding VCSEL design reduces gain depletion and radiative leakage, caused by parasitic whispering gallery VCSEL modes. Temperature robustness up to 100°C for 0.96 - 1.25 mum range devices is realized in

N. N. Ledentsov; F. Hopfer; A. Mutig; V. A. Shchukin; A. V. Savel'ev; G. Fiol; M. Kuntz; V. A. Haisler; E. Stock; S. S. Mikhrin; A. R. Kovsh; C. Bornholdt; A. Lenz; H. Eisele; M. Dähne; N. D. Zakharov; P. Werner; D. Bimberg

2007-01-01

126

VCSELs bonded directly to foundry fabricated GaAs smart pixel arrays  

Microsoft Academic Search

This letter reports the flip-chip bonding of an 8×8 array of free standing VCSELs to a foundry fabricated GaAs metal-semiconductor field-effect transistor (MESFET) smart pixel array. The VCSELs have oxide defined apertures and are co-planar bonded directly to smart pixels which perform the selection function of a data filter. The Vth and series resistance of the VCSELs were on average

Rui Pu; E. M. Hayes; R. Jurrat; C. W. Wilmsen; K. D. Choquette; H. Q. Hou; K. M. Geib

1997-01-01

127

Widely tunable MEMS-VCSELs operating at > 70 °C  

NASA Astrophysics Data System (ADS)

A mode hop free single mode tuning < 90nm at 40°C and 45nm at 70°C is demonstrated with a MEMS tunable VCSEL for the first time. The device shows a fiber-coupled output power of 2.9mW at 20°C and 0.5mW at 70°C. The side mode suppression ratio is larger than 40 dB over the entire tuning and temperature range of up to 70°C. The presented technology is cost effective and thus capable for mass production. It is applicable for tuneable VCSELs operating in different wavelength regimes, which are limited by the absorption of the DBR materials only.

Gierl, Christian; Gründl, Tobias; Zogal, Karolina; Paul, Sujoy; Grasse, Christian; Böhm, Gerhard; Meissner, Peter; Amann, Markus-Christian; Küppers, Franko

2013-03-01

128

Progress in high-power high-efficiency VCSEL arrays  

NASA Astrophysics Data System (ADS)

We present recent results on high-power, high-efficiency two-dimensional vertical-cavity surface-emitting laser (VCSEL) arrays emitting around 808nm. Selectively oxidized, top-emitting single VCSEL emitters with 49% power conversion efficiency were developed as the basic building block of these arrays. Because of the strong GaAs absorption at the 808nm wavelength, the traditional bottom-emitting, substrate-emission configuration is not possible for large arrays that require efficient heat dissipation. The processing and packaging challenges are discussed. We demonstrate 3mm x 3mm arrays and 5mm x 5mm arrays with the GaAs substrate completely removed and mounted on diamond submounts. These arrays emit more than 50W and 120W, respectively, and exhibit a maximum powerconversion efficiency of 42%.

Seurin, Jean-Francois; Xu, Guoyang; Khalfin, Viktor; Miglo, Alexander; Wynn, James D.; Pradhan, Prachi; Ghosh, Chuni L.; D'Asaro, L. Arthur

2009-02-01

129

Research on polarization control in the long distance fiber-optic sensing  

NASA Astrophysics Data System (ADS)

The long distance fiber-optic sensing system based on Mach-Zehnder interferometer has been widely used in many fields. We discussed the polarization signal fading caused by the birefringence property of the fiber. Research results show that, due to the birefringence effect of long distance fiber-optic sensing, when incident light polarization state changes, the output power will change which causing interference signal changes. This phenomenon is called "polarization-induced signal fading ". In order to eliminate polarization fading in long distance fiber-optic sensing, add the system with polarization controller to adjust light polarization state, can get a good visibility of interference signal.

Wang, Dong-bing; Zhou, Jin-feng

2013-08-01

130

Sensitivity of proton implanted VCSELs to electrostatic discharge pulses  

Microsoft Academic Search

The sensitivity of vertical cavity surface-emitting lasers to electrostatic discharge (ESD) pulses has been investigated under human body model test conditions. Very similar degradation behavior has been found for vertical-cavity surface-emitting lasers (VCSELs) from two different manufacturers, both with proton-implantation for lateral current confinement. For all investigated devices we observed during forward bias stress that the optical degradation precedes the

Heinz-Christoph Neitzert; Agnese Piccirillo; Barbara Gobbi

2001-01-01

131

A simple rate-equation-based thermal VCSEL model  

Microsoft Academic Search

Motivated by the potentially large number of devices and simulations involved in optoelectronic system design, and the associated need for compact optoelectronic device models, we present a simple thermal model of vertical-cavity surface-emitting laser (VCSEL) light-current (LI) characteristics based on the laser rate equations and a thermal offset current. The model was implemented in conventional SPICE-like circuit simulators, including HSPICE,

P. V. Mena; J. J. Morikuni; S.-M. Kang; A. V. Harton; K. W. Wyatt

1999-01-01

132

Feedback in close-coupled axial VCSEL-photodiode pairs  

Microsoft Academic Search

We have been investigating the use of coaxial multimode VCSEL\\/PD (vertical cavity surface emitting laser\\/photodiode) pairs for positional sensing with emitter to target mirror distances on the order of 1mm. We have observed large variations in signal levels due to the strong optical feedback in these close-coupled systems, employing either heterogeneously integrated commercial components or our own monolithically integrated devices.

Kent M. Geib; Darwin K. Serkland; Gregory M. Peake; Victoria M. Sanchez

2011-01-01

133

VCSEL based detection of water vapor near 940 nm  

Microsoft Academic Search

A vertical-cavity surface-emitting laser (VCSEL) was used to study the absorption spectrum of water vapor in the 940nm region. Measurements were performed in ambient air at room temperature and in a hydrogen–oxygen flame over the temperature range of 1500–1800K. Several rotational absorption lines within the 2?1+?3 vibrational band were measured. The absorption spectra were well resolved, which demonstrates the feasibility

Heidi Cattaneo; Toni Laurila; Rolf Hernberg

2004-01-01

134

A TCAD-based yield and reliability analysis for VCSELs  

NASA Astrophysics Data System (ADS)

Yield enhancement and reliability improvement are main requirements in todays industrial VCSEL manufacturing. This requires a thorough understanding of process tolerances and the effects resulting from design variations. So far, this has been done by statistical analysis of experimental data. In this work, we use a state-of-the art technology computer aided design (TCAD) tool to analyze device reliability and yield for multiple VCSEL designs. The starting point is a physics-based simulation model that is calibrated to temperature-dependent static and dynamic measurements for a set of single- and multi-mode VCSELs lasing at 850 nm. Applying statistical variations that result from design modifications and process fluctuations, yield and reliability data are extracted by means of simulation. The yield will be derived by compliance to selected device specifications (such available single-mode power), and the device reliability is determined from an analysis of the internal device properties. As example, the oxide aperture and metal aperture design will be discussed, and a robust design will be presented.

Odermatt, Stefan; Eitel, Sven; Hövel, Rainer; Letay, Gergoe; Witzigmann, Bernd

2006-03-01

135

VCSELs and silicon light sources exploiting SOI grating mirrors  

NASA Astrophysics Data System (ADS)

In this talk, novel vertical-cavity laser structure consisting of a dielectric Bragg reflector, a III-V active region, and a high-index-contrast grating made in the Si layer of a silicon-on-insulator (SOI) wafer will be presented. In the Si light source version of this laser structure, the SOI grating works as a highly-reflective mirror as well as routes light into a Si in-plane output waveguide connected to the grating. In the vertical-cavity surface-emitting laser (VCSEL) version, there is no in-plane output waveguide connected to the grating. Thus, light is vertically emitted through the Bragg reflector. Numerical simulations show that both the silicon light source and the VCSEL exploiting SOI grating mirrors have superior performances, compared to existing silicon light sources and long wavelength VCSELs. These devices are highly adequate for chip-level optical interconnects as well as conventional short-distance optical connections. In the talk, device physics will be discussed in detail.

Chung, Il-Sug; Mørk, Jesper

2012-02-01

136

Twisted hi-bi fiber distributed-feedback lasers with controllable output state of polarization.  

PubMed

We demonstrate that single polarization, hi-bi fiber DFB lasers are, in general, characterized by elliptical state of polarization (SOP), due to the in-built fiber birefringence axis rotation. Externally applied birefringence axis twist is shown to provide accurate control of the output SOP. Continuous tuning from circular to linear polarization, with polarization extinction ratio of ~40 dB, has been demonstrated. PMID:23632542

Zervas, Michalis N; Wilmshurst, Richard; Walker, Louise M B

2013-05-01

137

Polarization control of microwave ionization of H atoms  

SciTech Connect

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.

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

1996-05-01

138

Single spins in diamond: polarization, readout, and coherent control  

NASA Astrophysics Data System (ADS)

The Nitrogen-Vacancy (N-V) color center in diamond is well suited for studying electronic and nuclear spin phenomena, since its spin state can be both initialized and read out optically. Moreover, N-V center spins may allow for quantum information processing, as measurements have shown long room- temperature electron spin coherence times well into the microsecond regime. Here, we report on recent experimental progress towards coherent control and coupling of single spins in diamond. Using magneto-photoluminescence imaging and electron spin resonance (ESR) measurements at room temperature, we have investigated single N-V center spins that are coupled to electron spins of nearby nitrogen (N) defects. These N spins are optically inactive (`dark'), but can be detected via the N-V center, as the N-V and the N spins are coupled via the magnetic dipolar interaction. Some of the N-V centers are strongly coupled to only one single N spin, allowing the controlled polarization and readout of this single `dark' N spin. From time-resolved pump-probe measurements we find the relaxation time of the single N electron spin to be 75 microseconds at room temperature. More recently, we have demonstrated the coherent control of the N-V center spin using optical detection of pulsed ESR and spin echo techniques. Using these tools at different static magnetic fields, we have found that the main source of decoherence for the N-V center spins in our sample is the dipolar coupling to the surrounding bath of N spins. These results pave the way towards room-temperature coherent control of coupled spin states in diamond. R. Hanson, F. M. Mendoza, R. J. Epstein and D. D. Awschalom, Phys. Rev. Lett. 97, 087601 (2006). R. Hanson, O. Gywat and D.D. Awschalom, Phys. Rev. B 74, 161203(R) (2006).

Gywat, Oliver

2007-03-01

139

A FOXO-Pak1 transcriptional pathway controls neuronal polarity  

PubMed Central

Neuronal polarity is essential for normal brain development and function. However, cell-intrinsic mechanisms that govern the establishment of neuronal polarity remain to be identified. Here, we report that knockdown of endogenous FOXO proteins in hippocampal and cerebellar granule neurons, including in the rat cerebellar cortex in vivo, reveals a requirement for the FOXO transcription factors in the establishment of neuronal polarity. The FOXO transcription factors, including the brain-enriched protein FOXO6, play a critical role in axo–dendritic polarization of undifferentiated neurites, and hence in a switch from unpolarized to polarized neuronal morphology. We also identify the gene encoding the protein kinase Pak1, which acts locally in neuronal processes to induce polarity, as a critical direct target gene of the FOXO transcription factors. Knockdown of endogenous Pak1 phenocopies the effect of FOXO knockdown on neuronal polarity. Importantly, exogenous expression of Pak1 in the background of FOXO knockdown in both primary neurons and postnatal rat pups in vivo restores the polarized morphology of neurons. These findings define the FOXO proteins and Pak1 as components of a cell-intrinsic transcriptional pathway that orchestrates neuronal polarity, thus identifying a novel function for the FOXO transcription factors in a unique aspect of neural development.

de la Torre-Ubieta, Luis; Gaudilliere, Brice; Yang, Yue; Ikeuchi, Yoshiho; Yamada, Tomoko; DiBacco, Sara; Stegmuller, Judith; Schuller, Ulrich; Salih, Dervis A.; Rowitch, David; Brunet, Anne; Bonni, Azad

2010-01-01

140

10 Gb\\/s, 850 nm VCSEL based large core POF links  

Microsoft Academic Search

We demonstrate 10 Gb\\/s VCSEL based transmission over 100 m of larger core (120 mum) graded-index perfluorinated plastic optical fiber, thus establishing that multi-transverse-mode VCSELs are compatible with highly alignment tolerant plastic optical fiber.

Arup Polley; Patrick J. Decker; Stephen E. Ralph

2008-01-01

141

Parallel transport of biological cells using individually addressable VCSEL arrays as optical tweezers  

Microsoft Academic Search

We have demonstrated the use of vertical cavity surface emitting lasers (VCSELs) for optical trapping and active manipulation of live biological cells and microspheres. We have experimentally verified that the Laguerre–Gaussian laser mode output from the VCSEL functions just as well as the traditional Gaussian fundamental laser mode for optically trapping biological cells and may be preferable since the highest

Richard A. Flynn; Aaron L. Birkbeck; Matthias Gross; Mihrimah Ozkan; Bing Shao; Mark M. Wang; Sadik C. Esener

2002-01-01

142

Design and fabrication of polymer microlenses arrays for VCSELs using a cantilever based microsystem  

NASA Astrophysics Data System (ADS)

We report on the design and the fabrication of refractive microlenses using a polymer droplet deposition microsystem. The principle of this original technique consists in monomer droplets deposition using a robotized silicon-microcantilevers array. The advantages of this technique rely on the control of droplets dimensions and the positioning accuracy. Microlenses have been first modelled to optimize their geometrical parameters for VCSEL collimation. Results of lens optimization as well as the influence of the fabrication parameters fluctuations on the final divergence are detailed. First results on droplets deposition are presented, demonstrating the technique feasibility. Finally, the possibility of the modification of the surface energy to obtain the most suited contact angle before deposition is also discussed.

Bardinal, Véronique; Daran, Emmanuelle; Vergnenègre, Corinne; Leïchlé, Thierry; Segui, Yvan; Camps, Thierry; Pourciel, Jean-Bernard; Conedera, Véronique; Gavin-Djidina, Léonard; Guirardel, Mathieu

2006-04-01

143

Epitaxy of spin injectors and their application toward spin-polarized lasers  

NASA Astrophysics Data System (ADS)

Spintronics is an emerging; multidisciplinary field which examines the role of electron and nuclear spin in solid-state physics. Recent experiments suggest that the spin degree of freedom may be exploited to enhance the functionality of conventional semi conductor devices. Such endeavors require methods for efficient spin injection; spin transport, and spin detection in semiconductor heterostructures. This dissertation investigates the molecular-beam epitaxial growth and properties of ferromagnetic materials for electrical spin injection. Spin-injecting contacts are incorporated into prototype spintronic devices and their performance is examined. Two classes of materials may be used for spin injection into semiconductors: dilute magnetic semiconductor and ferromagnetic metals. The low-temperature growth and properties of (Al)Gal4nAs and In(Ga)MnAs epilayers and nanostructures are investigated, and a technique for the self-organized growth of Mn-doped InAs quantum dots is developed. The epitaxial growth of (Fe,MnAs)/(Al)GaAs Schottky tunnel barriers for electron spin injection is also investigated. The spin-injection efficiency of these contacts is assessed using a spin-valve or spin-polarized light-emitting diode. Lateral MnAs/GaAs spin-valves where Schottky tunnel barriers enable all-electrical spin injection and detection are grown, fabricated, and characterized. The Rowell criteria confirm that tunneling is the dominant, transport mechanism for the Schottky tunnel contacts. A peak magnetoresistance of 3.6% at 10 K and 1.1% at 125 K are observed for a 0.5 pin channel length spin-valve. Measurements using non-local spin-valves and other control devices verify that spurious contributions from anisotropic magnetoresistance and local Hall effects are negligible. Spin-polarized lasers offer inherent polarization control, reduced chirp, and lower threshold currents and are expected to outperform their charge-based counterparts. Initial efforts to realize a spin-VCSEL utilize (Ga,Mn)As spin aligners for hole spin injection. The polarization of the laser emission is dominated by dichroic absorption in the ferromagnetic (Ga,Mn)As spin-aligner layer, which greatly complicates the verification of spin injection. Significant spin-dependent effects are observed in a spin-VCSEL utilizing epitaxially regrown Fe/AlGaAs Schottky tunnel barriers. A maximum degree of circular polarization of 23% and corresponding threshold current reduction of 11% are measured for a 15 mum Fe spin-VCSEL at 50 K. A cavity spin polarization of 16.8% is estimated from rate equation analysis.

Holub, Michael A.

144

Polarization-Controlled Photoswitching Resolves Dipole Directions with Subwavelength Resolution  

NASA Astrophysics Data System (ADS)

We present that modulation of fluorescence emission by linearly polarized excitation light can allow us to resolve spatially two fluorescent molecules within a diffraction limit and to determine simultaneously their precise dipole directions. Using polarization-dependent photoswitching, we imaged the 2D geometry of the DNA Holliday junction in a 10-nm length scale by measuring both the distance and the in-plane dipole angle between Cy3 emitters stacked onto the ends of two adjacent branches of the Holliday junction. The proposed polarization-modulated imaging technique provides a simple and nonstochastic imaging process to visualize the nanostructure, including directional information, of biomolecules beyond the diffraction limit.

Lee, Seongsil; Oh, Jungsic; Kim, Dohyeon; Kim, Samuel; Lee, Jong-Bong; Nam, Hong Gil

2012-12-01

145

Polarization-controlled photoswitching resolves dipole directions with subwavelength resolution.  

PubMed

We present that modulation of fluorescence emission by linearly polarized excitation light can allow us to resolve spatially two fluorescent molecules within a diffraction limit and to determine simultaneously their precise dipole directions. Using polarization-dependent photoswitching, we imaged the 2D geometry of the DNA Holliday junction in a 10-nm length scale by measuring both the distance and the in-plane dipole angle between Cy3 emitters stacked onto the ends of two adjacent branches of the Holliday junction. The proposed polarization-modulated imaging technique provides a simple and nonstochastic imaging process to visualize the nanostructure, including directional information, of biomolecules beyond the diffraction limit. PMID:23368384

Lee, Seongsil; Oh, Jungsic; Kim, Dohyeon; Kim, Samuel; Lee, Jong-Bong; Nam, Hong Gil

2012-12-10

146

Small-Pitch Flip-Chip-Bonded VCSEL Arrays Enabling Transmitter Redundancy and Monitoring in 2-D 10-Gbit\\/s Space-Parallel Fiber Transmission  

Microsoft Academic Search

We demonstrate novel pixel architectures in 2-D vertical-cavity surface-emitting laser (VCSEL) arrays offering additional functionality without sacrificing efficient fabrication, compactness, and low module cost. Very high flip chip VCSEL packing densities enable both a built-in 3-per-channel VCSEL redundancy as well as simple intracell VCSEL monitoring. Each pixel has three individually addressable oxide-confined and substrate- removed 850-nm-wavelength VCSELs directly flip bonded

Hendrik Roscher; Fernando Rinaldi; Rainer Michalzik

2007-01-01

147

Controlling the polarization eigenstate of a quantum dot exciton with light.  

PubMed

We demonstrate optical control of the polarization eigenstates of a neutral quantum dot exciton without any external fields. By varying the excitation power of a circularly polarized laser in microphotoluminescence experiments on individual InGaAs quantum dots we control the magnitude and direction of an effective internal magnetic field created via optical pumping of nuclear spins. The adjustable nuclear magnetic field allows us to tune the linear and circular polarization degree of the neutral exciton emission. The quantum dot can thus act as a tunable light polarization converter. PMID:19792745

Belhadj, Thomas; Simon, Claire-Marie; Amand, Thierry; Renucci, Pierre; Chatel, Beatrice; Krebs, Olivier; Lemaître, Aristide; Voisin, Paul; Marie, Xavier; Urbaszek, Bernhard

2009-08-18

148

Electron-beam-pumped VCSEL light source for projection display  

NASA Astrophysics Data System (ADS)

An electron beam pumped vertical cavity laser, or an "eVCSEL", has been developed as a low-cost light source for LCOS and DLP based consumer television. 1000 lumens directed towards the spatial light modulator requires a total power of 144 watts for lasers in the three primary colors. This power surplus allows for high screen brightness for rear projection televisions of diagonals greater than 50 inches and eliminates the need for high gain screens with the benefit of larger viewing angles. Because of the high saturation of laser light, a color gamut approaching that of the human visual system is possible, creating superior image reproduction.

Tiberi, Michael D.; Kozlovsky, Vladimir I.

2005-04-01

149

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

SciTech Connect

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.

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

150

Final report on LDRD project : narrow-linewidth VCSELs for atomic microsystems.  

SciTech Connect

Vertical-cavity surface-emitting lasers (VCSELs) are well suited for emerging photonic microsystems due to their low power consumption, ease of integration with other optical components, and single frequency operation. However, the typical VCSEL linewidth of 100 MHz is approximately ten times wider than the natural linewidth of atoms used in atomic beam clocks and trapped atom research, which degrades or completely destroys performance in those systems. This report documents our efforts to reduce VCSEL linewidths below 10 MHz to meet the needs of advanced sub-Doppler atomic microsystems, such as cold-atom traps. We have investigated two complementary approaches to reduce VCSEL linewidth: (A) increasing the laser-cavity quality factor, and (B) decreasing the linewidth enhancement factor (alpha) of the optical gain medium. We have developed two new VCSEL devices that achieved increased cavity quality factors: (1) all-semiconductor extended-cavity VCSELs, and (2) micro-external-cavity surface-emitting lasers (MECSELs). These new VCSEL devices have demonstrated linewidths below 10 MHz, and linewidths below 1 MHz seem feasible with further optimization.

Chow, Weng Wah; Geib, Kent Martin; Peake, Gregory Merwin; Serkland, Darwin Keith

2011-09-01

151

Polarization properties of vertical-cavity surface-emitting lasers  

Microsoft Academic Search

Polarization-state selection, polarization-state dynamics, and polarization switching of a quantum-well vertical-cavity surface-emitting laser (VCSEL) for the lowest order transverse spatial mode of the laser is explored using a recently developed model that incorporates material birefringence, the saturable dispersion characteristic of semiconductor physics, and the sensitivity of the transitions in the material to the vector character of the electric field amplitude.

J. Martin-Regalado; F. Prati; M. San Miguel; N. B. Abraham

1997-01-01

152

Polarization-controlled excitation of multilevel plasmonic nano-circuits using single silicon nanowire.  

PubMed

We propose a surface plasmon polarization-controlled beam splitter based on plasmonic slot waveguides (PSWs). It couples light of different polarizations from a silicon nanowire into multilevel plasmonic networks. Two orthogonal PSWs are utilized as the guiding waveguides for each polarization. The proposed structure overcomes inherent polarization limitation in plasmonic structures by providing multilevel optical signal processing. This ability of controlling polarization can be exploited to achieve 3-D multilevel plasmonic circuits and polarization controlled chip to chip channel. Our device is of a compact size and a wide band operation. The device utilizes both quasi-TE and quasi-TM polarizations to allow for increased optical processing capability. The crosstalk is minimal between the two polarizations propagating in two different levels. We achieve good transmission efficiency at a wavelength of 1.55 µm for different polarizations. We analyze and simulate the structure using the FDTD method. The proposed device can be utilized in integrated chips for optical signal processing and optical computations. PMID:22714235

El Sherif, Mohamed H; Ahmed, Osman S; Bakr, Mohamed H; Swillam, Mohamed A

2012-05-21

153

Polarization control of a high power laser by adjoint feedback control  

Microsoft Academic Search

A novel technique of polarizing a high power laser with unstable resonator optics is described which places the polarizing elements in a low power feedback path external to the parent resonator structure. The technique has been used to polarize a high power industrial CO2 laser. Rejection ratios for the unwanted polarization can exceed 20 dB. The polarization vector can be

Paul R. Blaszuk; John A. Benda; James L. Forgham; Harold L. Cohen

1993-01-01

154

VCSEL-array-based angle-multiplexed optoelectronic crossbar interconnects.  

PubMed

A large crossbar switch, which is a desirable building block for any low-latency interconnect network, is difficult to implement because of many practical problems associated with digital electronics. We propose a new method for implementing a large optoelectronic crossbar interconnect to take advantage of a unique principle of optics. Based on an emerging vertical-cavity surface-emitting laser (VCSEL) technology, a passive angle-multiplexed beam-steering architecture is proposed as a key component of the optoelectronic crossbar. Various optical system parameters are evaluated. Because there is no optical fan-out power loss, the interconnect capacity of the proposed system is determined by the diffraction-limited receiver power cutoff, and therefore interconnection of more than 1000 nodes with a per node bandwidth of 1 GHz is possible with today's technology. A 64-element VCSEL-array-based proof-of-principle optical system for studying the interconnect scalability has been built. Details of the features of the proposed system, its advantages and limitations, demonstration experimental results, and their analyses are presented. PMID:21085241

Li, Y; Wang, T; Linke, R A

1996-03-10

155

1060nm VCSEL for inter-chip optical interconnection  

NASA Astrophysics Data System (ADS)

The demand for the on board intra-chip optical interconnection as the "Green interconnect" have been growing so rapidly in order to catch up the speed of the performance development of high performance computing systems. In this report, our continuous study results expanding to intra-chip application in terms with power consumption and reliability are shown for the "Green" 1060nm VCSEL arrays developed by Furukawa Electric1. As the basic performance level, the clear eye opening up to 20Gbps was achieved with low power dissipation level of 160fJ/bit with voltage swing level of 130mVpp. This value would be considered as the same level of the 140fJ/bit in 10Gbps operation with 75mVpp. In the reliability test, our large scale FIT rate test had been reached up to 7.8E7 device hours and the estimated FIT rate of 30FIT/ch was obtained from no failure sample and confidence level of 90%. Our wear-out study was performed with high stress test of 170°C ambient temperature and estimated failure rate for 10years service time was 0.3FIT/ch for this mode. Our 1060nm VCSEL with low power consumption level of 140fJ/bit and high reliability of 30FIT/ch would be projected to a light source for intra-chip application.

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

2011-02-01

156

FDTD calculations of the divergence angle of multi-mode VCSELs  

NASA Astrophysics Data System (ADS)

We describe and demonstrate a method of decreasing the divergence angle of multi-mode VCSELs, and show how we can obtain a low and stable divergence angle. We first explain the relationship between the lateral wave-vectors of resonant modes and the divergence angle. Then we attempt to optimize the oxide aperture and the electrode structure. Here, we calculate the electro-magnetic field of the VCSELs by the Finite Difference Time Domain (FDTD) method and the far-field pattern by combining the diffraction integral and the FDTD. Finally, we compare the theoretical and experimental results of the divergence angle of the VCSELs.

Mochizuki, Masamitsu; Nishida, Tetsuo; Kakinuma, Satoshi; Kaneko, Takeo

2005-04-01

157

Blazed vector gratings fabricated using photosensitive polymer liquid crystals and control of polarization diffraction  

NASA Astrophysics Data System (ADS)

The blazed vector grating possessing antisymmetric distributions of the birefringence were fabricated by exposing the line-focused linearly polarized ultraviolet light on the photosensitive polymer liquid crystals. The polarization states of the diffraction beams can be highly and widely controlled by designing the blazed structures, and the diffraction properties were well-explained by Jones calculus.

Ono, Hiroshi; Kuzuwata, Mitsuru; Sasaki, Tomoyuki; Noda, Kohei; Kawatsuki, Nobuhiro

2013-06-01

158

Control of the chirality and polarity of magnetic vortices in triangular nanodots  

Microsoft Academic Search

Magnetic vortex dynamics in lithographically prepared nanodots is currently a subject of intensive research, particularly after recent demonstration that the vortex polarity can be controlled by in-plane magnetic field. This has stimulated the proposals of nonvolatile vortex magnetic random access memories. In this work, we demonstrate that triangular nanodots offer a real alternative where vortex chirality, in addition to polarity,

M. Jaafar; R. Yanes; D. Perez de Lara; O. Chubykalo-Fesenko; A. Asenjo; E. M. Gonzalez; J. V. Anguita; M. Vazquez; J. L. Vicent

2010-01-01

159

Integrin-Mediated Activation of Cdc42 Controls Cell Polarity in Migrating Astrocytes through PKC?  

Microsoft Academic Search

We describe here a signal transduction pathway controlling the establishment of mammalian cell polarity. Scratching a confluent monolayer of primary rat astrocytes leads to polarization of cells at the leading edge. The microtubule organizing center, the microtubule cytoskeleton, and the Golgi reorganize to face the new free space, and directed cell protrusion and migration specifically occur perpendicularly to the scratch.

Sandrine Etienne-Manneville; Alan Hall

2001-01-01

160

Multi-polarization quantum control of rotational motion through dipole coupling  

Microsoft Academic Search

In this work we analyze the quantum controllability of rotational motion under the influence of an external laser field coupled through a permanent dipole moment. The analysis takes into consideration up to three polarization fields, but we also discuss the consequences for working with fewer polarized fields.

Gabriel Turinici; Herschel Rabitz

2010-01-01

161

Polymer microlens array with tunable focal intensity by the polarization control of the incident light  

Microsoft Academic Search

This paper proposes an optically tunable focal intensity microlens array (MLA) by using a focusing unit with birefringent liquid crystalline polymer (LCP) and a tuning unit with photoalignment for controlling the polarization state of the incident light. Due to the different refractive indices of LCP, it acts as a positive or negative microlens with respect to the polarization state. The

San-Yi Huang; Tung-Chen Tung; Shin-Wei Ko; Chi-Lun Ting; Hung-Chang Jau; Ming-Shian Li; Hui-Chi Lin; Andy Ying-Guey Fuh

2010-01-01

162

Folded Free-Space Polarization-Controlled Multistage Interconnection Network  

Microsoft Academic Search

this paper we describe the design and implementationof a free-space optical MIN by use of a novelfolded dilated bypass--exchange switch #DBS# built ofPDOE's that addresses these limitations. The use ofa DBS allows for the elimination of the first-order crosstalk that results from inaccuracies of polarization rotation11

Dan M. Marom; Paul E. Shames; Fang Xu; Yeshaiahu Fainman

1998-01-01

163

Remote state preparation: arbitrary remote control of photon polarization.  

PubMed

We experimentally demonstrate the first remote state preparation of arbitrary single-qubit states, encoded in the polarization of photons generated by spontaneous parametric down-conversion. Utilizing degenerate and nondegenerate wavelength entangled sources, we remotely prepare arbitrary states at two wavelengths. Further, we derive theoretical bounds on the states that may be remotely prepared for given two-qubit resources. PMID:15904126

Peters, Nicholas A; Barreiro, Julio T; Goggin, Michael E; Wei, Tzu-Chieh; Kwiat, Paul G

2005-04-20

164

Remote State Preparation: Arbitrary Remote Control of Photon Polarization  

Microsoft Academic Search

We experimentally demonstrate the first remote state preparation of arbitrary single-qubit states, encoded in the polarization of photons generated by spontaneous parametric down-conversion. Utilizing degenerate and nondegenerate wavelength entangled sources, we remotely prepare arbitrary states at two wavelengths. Further, we derive theoretical bounds on the states that may be remotely prepared for given two-qubit resources.

Nicholas A. Peters; Julio T. Barreiro; Michael E. Goggin; Tzu-Chieh Wei; Paul G. Kwiat

2005-01-01

165

Polar Lunar Orbits: controlling the eccentricity with low thrust propulsion  

Microsoft Academic Search

Recently, several nations presented plans to reach the Moon. Satellites have been launched and many more are planned for following years. The expectations are that in the near future there will be a lunar base. The lunar poles are particularly of interest since seems to be where water can be found. Therefore, satellites in polar orbits will be needed. It

Othon Winter; Décio Mourão; Silvia Maria Giuliatti Winter; Jose Leonardo Ferreira

2008-01-01

166

Radiation polarization control of the turnstile antenna with impedance vibrators  

Microsoft Academic Search

The problem concerning the creation of the radiation field with circular polarization in the certain direction by turnstile antenna, consisting of the impedance vibrators, excited cophasedly, has been solved on the basis of the solution of the problem about radiation of the thin impedance vibrator over the perfectly conducting plane. The length and the value of the surface impedance of

V. M. Dakhov; V. A. Katrich; M. V. Nesterenko; S. L. Berdnik

2011-01-01

167

Magmatism During Rifting Controls the Polarity of Tilted Blocks  

NASA Astrophysics Data System (ADS)

Magma-poor rifts, such as non-volcanic passive continental margins (e.g. Galicia) and slow-spreading oceanic ridges (e.g. Mid-Atlantic Ridge), are composed of faulted crustal blocks that dip generally away from the rift axis. By contrast, magma-rich rifts, such as volcanic passive margins (e.g. Norway, Namibia and the obducted paleo-volcanic margin of Oman) and hotspot-influenced slow-spreading oceanic ridges (e.g. Iceland), are composed of faulted crustal blocks that dip generally towards the rift axis. At volcanic passive margins, these tilted blocks are overlain by syn-tectonic volcano-sedimentary sequences that appear on seismic profiles as packages of seaward-dipping reflectors (SDRs). They are associated with swarms of magmatic dikes and sills. On the basis of a detailed structural study of Iceland (Bourgeois et al. 2005, Geodinamica Acta 18:59-80), we demonstrate that, in magma-rich rifts, lithospheric stretching is accomodated in a long-term deformation strip, n x 100 km wide, by the development of successive roll-over structures controlled by growth-faults and underlain by shallow magma chambers. As a given roll-over structure progressively develops and tilts in response to lithospheric stretching, it is continuously covered by lavas erupted from the associated magma chamber and reaching the surface through dike swarms dominantly located along the growth fault. After a lifetime of a few My, this roll-over structure dies at the expense of the activation of a new, laterally offset, one. Correspondingly, such roll-over structures form successively at different places within a diffuse plate boundary n x 100 km wide. After several roll-over structures have developed and died, the overall structure of the long-term deformation strip is composed of faulted crustal blocks that generally dip towards the rift axis and that are covered by volcano-sedimentary sequences. Physical laboratory experiments conducted with analogue materials demonstrate that this peculiar mode of rifting and the polarity of tilted blocks are controlled by the ratio between the rate of lithospheric stretching and the rate of magma supply. When the rate of crustal thickening by magmatism is smaller than (or equal to) the rate of crustal thinning by lithospheric stretching (as in non-volcanic passive margins and in slow-spreading oceanic ridges) the resulting rift zone is composed of outward-tilted blocks. By contrast, when the rate of crustal thickening by magmatism is bigger than the rate of crustal thinning by lithospheric stretching (as in volcanic passive margins and in hotspot-influenced slow-spreading oceanic ridges), the resulting rift zone is composed of inward-tilted blocks.

Chauvet, F.; Bourgeois, O.; Dauteuil, O.

2009-12-01

168

Parallel Transport of Biological Cells using Individually Addressable VCSEL Arrays as Optical Tweezers.  

National Technical Information Service (NTIS)

We have demonstrated the use of vertical cavity surface emitting lasers (VCSELs) for optical trapping and active manipulation of live biological cells and microspheres.We have experimentally verified that the Laguerre Gaussian laser mode output from the V...

A. L. Birkbeck B. Shao M. Gross M. Ozhan R. A. Flynn

2005-01-01

169

Reliability and degradation of oxide VCSELs due to reaction to atmospheric water vapor  

NASA Astrophysics Data System (ADS)

850nm oxide-aperture VCSELs are susceptible to premature failure if operated while exposed to atmospheric water vapor, and not protected by hermetic packaging. The ATLAS detector in CERN's Large Hadron Collider (LHC) has had approximately 6000 channels of Parallel Optic VCSELs fielded under well-documented ambient conditions. Exact time-to-failure data has been collected on this large sample, providing for the first time actual failure data at use conditions. In addition, the same VCSELs were tested under a variety of accelerated conditions to allow us to construct a more accurate acceleration model. Failure analysis information will also be presented to show what we believe causes corrosion-related failure for such VCSELs.

Dafinca, Alexandru; Weidberg, Anthony R.; McMahon, Steven J.; Grillo, Alexander A.; Farthouat, Philippe; Ziolkowski, Michael; Herrick, Robert W.

2013-03-01

170

Rigorous, highly-efficient optical tools for HCG-VCSEL design  

NASA Astrophysics Data System (ADS)

High Contrast Gratings (HCG) have become a hot research topic, because of their new functionalities at very small volumes. However no efficient 3D VCSEL model capable to account for HCG has been reported so far. HCG design is therefore mainly based on 1D simulations. For realistic structures usually FDTD is the most popular approach, with its well known cumbersome computation drawbacks. VELM code,1 the well established VCSEL electromagnetic solver developed in the last ten years in the Torino group, has now been upgraded to rigorously handle HCG layers. The efficiency of the tool is preserved, and an entire set of HCG VCSEL modes can be computed in minutes on an ordinary desktop. A full set of design tools and guidelines, starting from 1D HCG properties up to 3D simulations which include HCG in the VCSEL design, will be presented and applied to the design of a structure that is in fabrication.

Debernardi, Pierluigi; Orta, Renato; Hofmann, Werner

2013-03-01

171

Remote State Preparation: Arbitrary Remote Control of Photon Polarization  

Microsoft Academic Search

We experimentally demonstrate the first remote state preparation of arbitrary\\u000asingle-qubit states, encoded in the polarization of photons generated by\\u000aspontaneous parametric downconversion. Utilizing degenerate and nondegenerate\\u000awavelength entangled sources, we remotely prepare arbitrary states at two\\u000awavelengths. Further, we derive theoretical bounds on the states that may be\\u000aremotely prepared for given two-qubit resources.

Nicholas A. Peters; Julio T. Barreiro; Michael E. Goggin; Tzu-Chieh Wei; Paul G. Kwiat

2005-01-01

172

Controlling Aggregation in Non-Polar Asphaltene Suspensions Through Electrostatics  

NASA Astrophysics Data System (ADS)

Asphaltenes, the most aromatic and largest molecular weight components of petroleum fluids, can undergo a liquid-liquid phase transition in conditions including highly non-polar environments. Phase separation begins with molecular association and proceeds to and through the colloidal length-scale until complete sedimentation or deposition. Non-ionic polymeric dispersants can stabilize asphaltenes at the colloidal scale in non-polar suspensions. We perform a variety of experiments which suggest that stabilization occurs by adsorption of dispersant onto the asphaltenes, truncating the progress of precipitation. In particular, dynamic light scattering (DLS) and phase-analysis light scattering (PALS) measurements indicate that electrostatic repulsion is responsible for stabilizing asphaltene colloids against further aggregation. Aggregation time increases exponentially with dispersant concentration, as expected for particles interacting through a combination of attractive dispersion forces and repulsive electrostatics. However, contrary to current understandings of electrostatic stabilization in non-polar systems, the charges in colloidal asphaltene suspensions seem to arise from the asphaltene colloids themselves rather than from dispersant micelles.

Hashmi, Sara; Firoozabadi, Abbas

2012-02-01

173

Polarization control of a high power laser by adjoint feedback control  

Microsoft Academic Search

A technique for polarizing a high-power laser with unstable resonator optics that places the polarizing elements in a low power feedback path external to the parent resonator structure is described. The technique has been used to polarize a high-power industrial CO2 laser. Rejection ratios for the unwanted polarizations can exceed 20 dB. The polarization vector can be rotated at will

Paul R. Blaszuk; John A. Benda; James L. Forgham; Harold L. Cohen

1993-01-01

174

Fabrication and performance of large (64x64) arrays of integrated VCSELs and detectors  

Microsoft Academic Search

Vertical-cavity surface-emitting lasers (VCSELs) are uniquely suited for applications requiring high-density 2-dimensional arrays of lasers, such as massively parallel interconnects or imaging applications. We have successfully fabricated 64x64 arrays containing alternating rows of selectively-oxidized 850 nm VCSELs and resonant-cavity photodetectors (RCPDs) on semi-insulating GaAs. In order to reduce the input\\/output pin count, we employed a matrix addressable architecture, where all

Kent M. Geib; Kent D. Choquette; Darwin Serkland; Andrew A. Allerman; Terry W. Hargett

2002-01-01

175

Effects of native oxides and optical confinement on microactivity VCSEL spontaneous emission  

Microsoft Academic Search

Threshold currents in small-aperture VCSELs are likely to be dominated by diffraction losses. We have developed a semianalytic technique to estimate the lasing mode energies, field profiles and cavity losses--including absorption, mirror, and diffraction losses--in oxide-apertured VCSELs. By coupling these modes to the full, nonparabolic electronic bandstructure, and by solving the resulting multimode related rate equations, we can model the

John P. Loehr; Michael J. Noble; James A. Lott

1998-01-01

176

The fabrication and characterization of nano-aperture VCSEL array head for high density near-field optical data storage  

Microsoft Academic Search

A 2D nano-aperture VCSEL array head of near-field optics was studied with the formation of small aperture on the VCSEL surface after the deposition of dielectric and metal films. Its optical properties were also characterized to apply the VCSEL array for the near-field optical memory system of higher data capacity and speed. In this study, we could produce very small

Young-Joo Kim; Kazuma Kurihara; Kazuhiro Suzuki; Akihito Yamaguchi

2000-01-01

177

Simulation of polarization switching of Vertical-Cavity Surface-Emitting Lasers at constant current  

NASA Astrophysics Data System (ADS)

The polarization switching (PS) in Vertical-Cavity Surface-Emitting Lasers (VCSELs) at constant bias current was investigated by numerical simulation in this research. The simulation was performed by Linear Current Gain model. The PS with a delay time at constant bias current was observed in the experiment which was performed by quasi-step current. The simulation results show that the PS delay time depends on the constant bias current and these results are matching well with experimental results. These results contribute to the understanding of the mechanism of VCSEL's polarization switching.

Chin, Pei-Hou; Kuo, Wang-Chuang; Quadir, Shaham; Wu, Yu-Heng; Yen, Tsu-Chiang

2013-03-01

178

Control of Fibrinogen Assembly by Changing a Polarity of Surfaces  

NASA Astrophysics Data System (ADS)

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.

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

2009-03-01

179

Tissue polarity-dependent control of mammary epithelial homeostasis and cancer development: an epigenetic perspective.  

PubMed

The basoapical organization of monolayered epithelia is defined by the presence of hemidesmosomes at the basal cellular pole, where the cell makes contacts with the basement membrane, and tight junctions at the opposite apical pole. In the mammary gland, tight junctions seal cell-cell contacts against the lumen and separate the apical and basolateral cell membranes. This separation is critical to organize intracellular signaling pathways and the cytoskeleton. The study of the impact of the highly organized apical pole, and notably apical polarity regulators (Crb complex, Par complex, and Scrib, Dlg, Lgl proteins) and tight junction proteins on cell phenotype and gene expression has revealed an intricate relationship between apical polarity and the cell nucleus. The goal of this review is to highlight the role of the apical pole of the tissue polarity axis in the epigenetic control of tissue phenotype. The organization of the apical pole and its importance in mammary homeostasis and tumorigenesis will be emphasized before presenting how apical polarity proteins impact gene expression indirectly, by influencing signal transduction and the location of transcription regulators, and directly, by participating in chromatin-associated complexes. The relationship between apical polarity and cell nucleus organizations might explain how apical polarity proteins could switch from nuclear repressors to nuclear promoters of cancerous behavior following alterations in the apical pole. The impact of apical polarity proteins on epigenetic mechanisms of gene expression will be discussed in light of increased evidence supporting a role for apical polarity in the fate of breast neoplasms. PMID:20101444

Lelièvre, Sophie A

2010-01-27

180

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

SciTech Connect

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.

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

181

Full control of magnetism in a manganite bilayer by ferroelectric polarization  

NASA Astrophysics Data System (ADS)

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.

Dong, Shuai; Dagotto, Elbio

2013-10-01

182

Controllable surface electrostatic velocity filter for polar molecules  

NASA Astrophysics Data System (ADS)

We propose a scheme of a surface electrostatic velocity filter capable of preparing cold polar molecules on the surface of a substrate by selecting a low-velocity component of an effusive beam from a thermal gas reservoir. Using ND3 as a molecular sample, the dependence of the performance of the filter on the parameters of both the filter setup and the incident molecular beam is investigated by using a theoretical model and Monte Carlo simulations. A detailed study of the guiding process of molecules, including the evolution of phase space density of the packet in the filter, is carried out and shows that the beam selection process is mainly completed in the front part of the filter.

Hou, Shunyong; Wang, Qin; Deng, Lianzhong; Yin, Jianping

2013-07-01

183

Cellular networks controlling Th2 polarization in allergy and immunity  

PubMed Central

In contrast to the development of Th1 (type 1 T helper cells), Th17 and Treg (regulatory T cells), little is known of the mechanisms governing Th2 development, which is important for immunity to helminths and for us to understand the pathogenesis of allergy. A picture is emerging in which mucosal epithelial cells instruct dendritic cells to promote Th2 responses in the absence of IL-12 (interleukin 12) production and provide instruction through thymic stromal lymphopoieitin (TSLP) or granulocyte-macrophage colony stimulating factor (GM-CSF). At the same time, allergens, helminths and chemical adjuvants elicit the response of innate immune cells like basophils, which provide more polarizing cytokines and IL-4 and reinforce Th2 immunity. This unique communication between cells will only be fully appreciated if we study Th2 immunity in vivo and in a tissue-specific context, and can only be fully understood if we compare several models of Th2 immune response induction.

Kool, Mirjam; Hammad, Hamida

2012-01-01

184

Magnetic field controlled reversal of ferroelectric polarization in conical spin ordered multiferroics: Monte Carlo simulation  

Microsoft Academic Search

To understand the fascinating multiferroicity observed in CoCr2O4, Monte Carlo simulation is performed on a three-dimensional spinel lattice with classical Heisenberg spins. The conical spin order is confirmed to be the origin of the peculiar magnetoelectric behavior with coexisting magnetization and ferroelectric polarization. Furthermore, the simultaneous reversals of magnetization and polarization controlled by the external magnetic field are reproduced, consisting

Xiaoyan Yao; Veng Cheong Lo; Jun-Ming Liu

2009-01-01

185

Polymer microlens array with tunable focal intensity by the polarization control of the incident light  

NASA Astrophysics Data System (ADS)

This paper proposes an optically tunable focal intensity microlens array (MLA) by using a focusing unit with birefringent liquid crystalline polymer (LCP) and a tuning unit with photoalignment for controlling the polarization state of the incident light. Due to the different refractive indices of LCP, it acts as a positive or negative microlens with respect to the polarization state. The resultant tunable focal intensity MLA shows the fast optical switching time without voltage and the multi-stable characteristics.

Huang, San-Yi; Tung, Tung-Chen; Ko, Shin-Wei; Ting, Chi-Lun; Jau, Hung-Chang; Li, Ming-Shian; Lin, Hui-Chi; Fuh, Andy Ying-Guey

2010-02-01

186

A Spin-Polarized Current Direction Controller Based on a Nonuniform Rashba Quantum Wire  

NASA Astrophysics Data System (ADS)

A spin-polarized current direction controller scheme is proposed based on a nonuniform Rashba quantum wire. It is shown that |PLRz| = |PRLz|, whereas their signs are opposite, and the effect of this phenomenon is due to the two broken symmetries and the unbroken C2-rotation symmetry of the investigated system. In addition, the spin-polarized current is nonzero even with a strong disorder strength, which demonstrates that this structure may be utilized for potential applications.

Xu, Zhong-Hui; Xiao, Wen; Chen, Yu-Guang

2013-05-01

187

Polarization caging in diffusion-controlled electron transfer reactions in solution.  

PubMed

In some bimolecular diffusion-controlled electron transfer (ET) reactions such as ion recombination (IR), both solvent polarization relaxation and the mutual diffusion of the reacting ion pair may determine the rate and even the yield of the reaction. However, a full treatment with these two reaction coordinates is a challenging task and has been left mostly unsolved. In this work, we address this problem by developing a dynamic theory by combining the ideas from ET reaction literature and barrierless chemical reactions. Two-dimensional coupled Smoluchowski equations are employed to compute the time evolution of joint probability distribution for the reactant (P((1))(X,R,t)) and the product (P((2))(X,R,t)), where X, as is usual in ET reactions, describes the solvent polarization coordinate and R is the distance between the reacting ion pair. The reaction is described by a reaction line (sink) which is a function of X and R obtained by imposing a condition of equal energy on the initial and final states of a reacting ion pair. The resulting two-dimensional coupled equations of motion have been solved numerically using an alternate direction implicit (ADI) scheme (Peaceman and Rachford, J. Soc. Ind. Appl. Math. 1955, 3, 28). The results reveal interesting interplay between polarization relaxation and translational dynamics. The following new results have been obtained. (i) For solvents with slow longitudinal polarization relaxation, the escape probability decreases drastically as the polarization relaxation time increases. We attribute this to caging by polarization of the surrounding solvent. As expected, for the solvents having fast polarization relaxation, the escape probability is independent of the polarization relaxation time. (ii) In the slow relaxation limit, there is a significant dependence of escape probability and average rate on the initial solvent polarization, again displaying the effects of polarization caging. Escape probability increases, and the average rate decreases on increasing the initial polarization. Again, in the fast polarization relaxation limit, there is no effect of initial polarization on the escape probability and the average rate of IR. (iii) For normal and barrierless regions the dependence of escape probability and the rate of IR on initial polarization is stronger than in the inverted region. (iv) Because of the involvement of dynamics along R coordinate, the asymmetrical parabolic (that is, non-Marcus) energy gap dependence of the rate is observed. PMID:20809586

Singh, Rakesh Sharan; Tachiya, Masanori; Bagchi, Biman

2010-09-30

188

Polarization readout characteristics of electric-controlled holographic Bragg grating in photorefractive crystal  

NASA Astrophysics Data System (ADS)

In the paraelectric phase photorefractive crystal, the quadratic electro-optic effect can result in Bragg gratings in the volume of the crystal. The reconstruction process and the diffractive properties of the grating can be governed by the externally applied electric field. The measurement of the diffraction efficiency as a function of the applied electric field during recording is described. Dependence of electrically controlled Bragg grating in paraelectric phase KLTN: Cu crystals on readout illumination beam polarization were experimentally investigated. The results of experiments show that the diffraction efficiency of electric-controlled volume grating can also be controlled by the polarization of readout light. All these results would offer an possibility for a photorefractive optical switch by adjusting the polarization of the readout beam to control the diffraction efficiency.

Wan, Yuhong; Lin, Lin; Man, Tianlong; Zhai, Qianli; Liu, Guoqing; Tao, Shiquan

2010-11-01

189

Control of polarized iodine atom branching ratio in NaI photodissociation  

SciTech Connect

We report branching ratios between the ground and excited states of iodine atoms in the photodissociation of sodium iodide. We employ wave packet propagation techniques to study the optimal production of polarized iodine atoms and find experimentally realizable laser parameters to control the outcome. Application of a learning algorithm shows that the product branching can be controlled by suitably varying the time delay, the chirp, and the relative phase of the pump and control laser pulses. Periodic modulation of the polarized iodine atom branching ratio as a function of the delay between the firing of the two ultrashort laser pulses provides interesting insights into the photodissociation process.

Hosseini, Babak H. [ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138 (United States); Fakultaet fuer Physik und Astronomie, Universitaet Heidelberg, Heidelberg (Germany); Sadeghpour, H.R. [ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138 (United States); Balakrishnan, N. [Department of Chemistry, University of Nevada Las Vegas, Las Vegas, Nevada 89154 (United States)

2005-02-01

190

Increasing the focused response of impulse radiating antennas through polarization control of aperture fields  

Microsoft Academic Search

Wide-band, focused aperture antennas like impulse radiating antennas (IRAs) can see improved aperture efficiency through control of the aperture shape and aperture field distribution. The shape of the aperture fields is largely dictated by the transverse electromagnetic mode distribution on the nondispersive feed of the IRA. In this paper we consider reshaping the aperture field by controlling the polarization of

J. Scott Tyo; M. Dogan; J. H. Boddeker; C. J. Buchenauer

2006-01-01

191

USING LOW THRUST PROPULSION TO ORBIT CONTROL OF THE LUNAR POLAR SATELLITES  

Microsoft Academic Search

It is well known that lunar satellites in polar orbits suffer a high increase on the eccentricity due to the gravitational perturbation of the Earth. That effect is a natural consequence of the Lidov-Kozai resonance. The final fate of such satellites is the collision with the Moon. Therefore, the control of the orbital eccentricity leads to the control of the

Othon Cabo Winter; Décio Cardozo Mourão; Cristiano Fiorillo Melo; José Leonardo Ferreira

2009-01-01

192

Complete chaotic synchronization characteristics of the linear-polarization mode of vertical-cavity surface-emitting semiconductor lasers with isotropic optical feedback  

NASA Astrophysics Data System (ADS)

Based on the SFM model [M. San Miguel, Q. Feng, J.V. Moloney, Phys. Rev. A. 52 (1995) 1728.], complete chaotic synchronization characteristics of linear-polarization (LP) Mode of the vertical-cavity surface-emitting semiconductor lasers (VCSELs) with isotropic optical feedback are numerically investigated. When the propagation time ?c of light from the transmitter to the receiver equals to the external cavity round-trip time ?, and the central frequency of the T_VCSEL matches that of the R_VCSEL, in large scale region of the feedback coefficient and the injection current where the x-polarization mode as well as the y-polarization mode obtains high synchronization quality at the same time. However, in the central frequency mismatch regions where the x- and y-polarization mode can obtain inferior synchronization quality at same time. But for ?c ? ?, each LP mode of the mixed polarization modes achieved inferior synchronization quality at the same time. Besides, with big enough injection current, the output of the system with the same central frequency in two lasers is entirely governed by the y-polarization mode when the feedback coefficient and ??(=?c - ?) fixed at a certain value. So the system can realize steadily good synchronization of the completely dominant y-polarization mode. But the synchronization quality of the completely dominated y-polarization mode can be deteriorated by increasing absolute frequency detuning value. Besides, in positive frequency mismatch regions where the influence of the same frequency detuning value on the synchronization quality of the entirely governed y-polarization mode becomes smaller than in negative frequency detuning regions. At last, when ? is given and the central frequency of the T_VCSEL matches that of the R_VCSEL, the influence of the ?c is not a simple time-shift in the time-evolution of the receiver VCSEL, which has serious influence on the complete synchronization quality of each LP mode.

Zhong, Dong-Zhou; Xia, Guang-Qiong; Wu, Zheng-Mao; Jia, Xin-Hong

2008-03-01

193

Polarization Sensitive CARS Investigations of Controlled Molecular Rotations  

Microsoft Academic Search

The emerging field of nanotechnology requires new methodologies to be developed in order to address the needs of fabrication, manipulation, control, and measurement of motions of molecules and devices on the nanoscale. Optical excitation and control of translational, vibrational, and rotational motions can offer a unique way to achieve the desired goals by using a sequence of short laser pulses,

Laszlo Ujj; Ferenc Bartha; Zengjun Chen; Chandra Prayaga; Timothy Royappa; Charles Amos; Mauricio Tsukuda

2010-01-01

194

Transverse and polarization effects in index-guided vertical-cavity surface-emitting lasers  

NASA Astrophysics Data System (ADS)

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 LP01 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 [Opt. Lett. 29, 53 (2004)], based on a rate-equation model that takes into account transverse inhomogeneities through an intensity-dependent confinement factor.

Torre, M. S.; Masoller, C.; Mandel, Paul

2006-10-01

195

Real-time feedback control of millimeter-wave polarization for LHD  

SciTech Connect

Electron cyclotron heating (ECH) is widely used in magnetic fusion devices, and the polarization of the injected millimeter-wave beams plays a crucial role in the propagation and absorption of the beam energy by the plasma. This polarization can be adjusted by grating mirror polarizers placed in the transmission lines which carry the microwaves from the power source to the plasma. In long-pulse devices such as the Large Helical Device (LHD) and ITER, it is desirable to track changes in the plasma and adjust the polarization of the ECH in real time such as to keep the absorption as high as possible and avoid shine-through which may lead to overheating of vessel components. For this purpose a real-time feedback control scheme is envisioned in which a measure of the absorption efficiency can be used to adjust the orientation of the polarizing mirrors toward an optimum. Such a setup has been tested in a low-power test stand as preparation for future implementation in the LHD ECH system. It is shown that a simple search algorithm is efficient and can in principle be used to control either the absorption efficiency or the linear polarization angle.

Felici, F.; Goodman, T.; Sauter, O. [Centre de Recherches en Physique des Plasmas, Association EURATOM-Suisse, Ecole Polytechnique Federale de Lausanne (EPFL), 1015 Lausanne (Switzerland); Shimozuma, T.; Ito, S.; Mizuno, Y.; Kubo, S.; Mutoh, T. [National Institite for Fusion Science (NIFS), Oroshi-cho, Toki 509-5292 (Japan)

2009-01-15

196

Real-time feedback control of millimeter-wave polarization for LHD.  

PubMed

Electron cyclotron heating (ECH) is widely used in magnetic fusion devices, and the polarization of the injected millimeter-wave beams plays a crucial role in the propagation and absorption of the beam energy by the plasma. This polarization can be adjusted by grating mirror polarizers placed in the transmission lines which carry the microwaves from the power source to the plasma. In long-pulse devices such as the Large Helical Device (LHD) and ITER, it is desirable to track changes in the plasma and adjust the polarization of the ECH in real time such as to keep the absorption as high as possible and avoid shine-through which may lead to overheating of vessel components. For this purpose a real-time feedback control scheme is envisioned in which a measure of the absorption efficiency can be used to adjust the orientation of the polarizing mirrors toward an optimum. Such a setup has been tested in a low-power test stand as preparation for future implementation in the LHD ECH system. It is shown that a simple search algorithm is efficient and can in principle be used to control either the absorption efficiency or the linear polarization angle. PMID:19191434

Felici, F; Goodman, T; Sauter, O; Shimozuma, T; Ito, S; Mizuno, Y; Kubo, S; Mutoh, T

2009-01-01

197

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

NASA Astrophysics Data System (ADS)

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.

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

198

Complete wavefront and polarization control for ultrashort-pulse laser microprocessing.  

PubMed

We report on new developments in wavefront and polarization control for ultrashort-pulse laser microprocessing. We use two Spatial Light Modulators in combination to structure the optical fields of a picosecond-pulse laser beam, producing vortex wavefronts and radial or azimuthal polarization states. We also carry out the first demonstration of multiple first-order beams with vortex wavefronts and radial or azimuthal polarization states, produced using Computer Generated Holograms. The beams produced are used to nano-structure a highly polished metal surface. Laser Induced Periodic Surface Structures are observed and used to directly verify the state of polarization in the focal plane and help to characterize the optical properties of the setup. PMID:24103993

Allegre, O J; Jin, Y; Perrie, W; Ouyang, J; Fearon, E; Edwardson, S P; Dearden, G

2013-09-01

199

Light-by-light polarization control and stabilization in optical fibers for telecommunication applications  

NASA Astrophysics Data System (ADS)

In this work, we experimentally demonstrate light-by-light polarization control for Telecom applications via a nonlinear interaction occurring in single mode fiber between a signal beam and a counter-propagating control pump wave. In particular, we observe an attraction and stabilization process of the state of polarization (SOP) of a 10-Gbit/s optical telecommunication signal around 1550 nm for either on/off keying (OOK) and non return-to-zero (NRZ) modulation formats. In a second section, we extend our device to 40-Gbit/s by experimentally combining an all-optical regeneration of both the polarization state and the intensity profile of a 40-Gbit/s OOK signal in a single segment of fiber. These experimental results confirm yet another fascinating way to all-optical control light features within optical fibers.

Morin, Philippe; Pitois, Stéphane; Finot, Christophe; Fatome, Julien

2012-05-01

200

Hybrid integration approach of VCSELs for miniaturized optical deflection of microparticles  

NASA Astrophysics Data System (ADS)

In recent years, optical manipulation has gained increasing interest, especially in combination with microfluidics. This combination offers promising tools for a fast and cost-effective sample analysis and manipulation. The contamination-free handling of micrometer-sized particles without any mechanical contact is an attractive tool for biology and medicine. VCSELs (vertical-cavity surface-emitting lasers) are an excellent choice for the trapping lasers, offering the opportunity of parallel particle manipulation by using two-dimensional VCSEL arrays, and of miniaturization by means of integration. In this paper, we present two novel concepts for the realization of the so-called integrated optical trap, resembling a strongly miniaturized version of the typically bulky setup of an optical trap. For this purpose, AlGaAs-GaAs-based VCSEL arrays with a very small device pitch were fabricated. We show the realization of integration-ready particle manipulation devices, both with top-emitting and with bottom-emitting densely packed VCSEL arrays. The smallest pitch of 18 ?m is achieved with bottom-emitting VCSEL arrays, having mesa diameters of only 16 ?m.

Bergmann, Anna; Khan, Niazul Islam; Martos Calahorro, Jose Antonio; Wahl, Dietmar; Michalzik, Rainer

2012-05-01

201

Novel concepts for ultrahigh-speed quantum-dot VCSELs and edge-emitters  

NASA Astrophysics Data System (ADS)

Advanced types of QD media allow an ultrahigh modal gain, avoid temperature depletion and gain saturation effects, when used in high-speed quantum dot (QD) vertical-cavity surface-emitting lasers (VCSELs). An anti-guiding VCSEL design reduces gain depletion and radiative leakage, caused by parasitic whispering gallery VCSEL modes. Temperature robustness up to 100°C for 0.96 - 1.25 ?m range devices is realized in the continuous wave (cw) regime. An open eye 20 Gb/s operation with bit error rates better than 10-12 has been achieved in a temperature range 25-85°C without current adjustment. A different approach for ultrahigh-speed operation is based on a combination of the VCSEL section, operating in the CW mode with an additional section of the device, which is electrooptically modulated under a reverse bias. The tuning of a resonance wavelength of the second section, caused by the electrooptic effect, affects the transmission of the system. The second cavity mode, resonant to the VCSEL mode, or the stopband edge of the second Bragg reflector can be used for intensity modulation. The approach enables ultrahigh speed signal modulation. 60GHz electrical and ~35GHz optical (limited by the photodetector response) bandwidths are realized.

Ledentsov, N. N.; Hopfer, F.; Mutig, A.; Shchukin, V. A.; Savel'ev, A. V.; Fiol, G.; Kuntz, M.; Haisler, V. A.; Warming, T.; Stock, E.; Mikhrin, S. S.; Kovsh, A. R.; Bornholdt, C.; Lenz, A.; Eisele, H.; Dähne, M.; Zakharov, N. D.; Werner, P.; Bimberg, D.

2007-02-01

202

Wafer-scale replication and testing of micro-optical components for VCSELs  

NASA Astrophysics Data System (ADS)

VCSELs (Vertical-Cavity Surface-Emitting Lasers) emit circularly symmetric beams vertical to the substrate; the small footprint of the active area (around 400 um2) enables the simultaneous fabrication of several thousand devices on a single wafer. Micro-optical components can modify the free-space optical properties of VCSELs for applications such as fiber-coupling in transceiver modules, illumination purposes, or beam profiling in sensing applications. However, the alignment of a laser towards a lens, for example, is expensive when performed separately for each device. Here we demonstrate a wafer-scale replication process to realise microlenses directly on top of the undiced VCSEL wafers. The process combines uv-casting and lithography to achieve material-free bonding pads and dicing lines. Several examples of lenses and gratings are given. An organically modified sol-gel material (ORMOCER) has been used as lens material. The micro-optical components on the wafer show good stability while sawing and bonding, where temperatures up to 220°C may occur. We have compared refractive lenses on top of the VCSELs with lenses on glass substrates. The lenses on the glass wafers were illuminated from the back-side by a planar wave. Spot diameters around 1.2 um and focal lengths of 30 um to 100 um were measured depending on the radii of curvature. On the VCSELs the lenses showed a strong influence on the transversal mode behaviour.

Gimkiewicz, Christiane; Moser, Michael; Obi, Samuel; Urban, Claus; Pedersen, Joern S.; Thiele, Hans; Zschokke, Christian; Gale, Michael T.

2004-09-01

203

Oxide confined 850-nm VCSELs for high-speed datacom applications  

NASA Astrophysics Data System (ADS)

Vertical cavity surface emitting lasers (VCSELs) are low cost and reliable light sources for high-speed local area and storage area network (LAN/SAN) optical fiber data communication systems and all other short-reach high-speed data transfer applications. The intrinsic limitations of copper-based electrical links at data rates exceeding 10 Gbit/s leads to a progressive movement wherein optical communication links replace traditional short-reach (300 m or shorter) copper interconnects. The wavelength of 850 nm is the standard for LAN/SAN applications as well as for several other evolving short-reach application areas including Fibre Channel, InfiniBand, Universal Serial Bus (optical USB), and active optical cables. Here we present our recent results on 850 nm oxide-confined VCSELs operating at data bit rates up to 40 Gbit/s at low current densities of ~10 kA/cm2 ensuring device reliability and long-term stability based on conventional industry certification specifications. The relaxation resonance frequencies, damping factors, and parasitic cut-off frequencies are determined for VCSELs with oxide-confined apertures of various diameters. At the highest optical modulation rates the VCSELs' high speed operation is limited by parasitic cut-off frequencies of 24-28 GHz. We believe that by further reducing device parasitics we will produce current modulated VCSELs with optical modulation bandwidths larger than 30 GHz and data bit rates beyond 40 Gbit/s.

Moser, Philip; Mutig, Alex; Lott, James A.; Blokhin, Sergey; Fiol, Gerrit; Nadtochiy, Alexey M.; Ledentsov, Nikolai N.; Bimberg, Dieter

2010-04-01

204

Modeling and characterization of VCSEL-based avionics full-duplex ethernet (AFDX) gigabit links  

NASA Astrophysics Data System (ADS)

Low cost and intrinsic performances of 850 nm Vertical Cavity Surface Emitting Lasers (VCSELs) compared to Light Emitting Diodes make them very attractive for high speed and short distances data communication links through optical fibers. Weight saving and Electromagnetic Interference withstanding requirements have led to the need of a reliable solution to improve existing avionics high speed buses (e.g. AFDX) up to 1Gbps over 100m. To predict and optimize the performance of the link, the physical behavior of the VCSEL must be well understood. First, a theoretical study is performed through the rate equations adapted to VCSEL in large signal modulation. Averaged turn-on delays and oscillation effects are analytically computed and analyzed for different values of the on- and off state currents. This will affect the eye pattern, timing jitter and Bit Error Rate (BER) of the signal that must remain within IEEE 802.3 standard limits. In particular, the off-state current is minimized below the threshold to allow the highest possible Extinction Ratio. At this level, the spontaneous emission is dominating and leads to significant turn-on delay, turn-on jitter and bit pattern effects. Also, the transverse multimode behavior of VCSELs, caused by Spatial Hole Burning leads to some dispersion in the fiber and degradation of BER. VCSEL to Multimode Fiber coupling model is provided for prediction and optimization of modal dispersion. Lastly, turn-on delay measurements are performed on a real mock-up and results are compared with calculations.

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

2008-01-01

205

Laser diode based oxygen sensing: A comparison of VCSEL and DFB laser diodes emitting in the 762 nm region  

Microsoft Academic Search

The performance of VCSEL and DFB laser diodes for spectroscopic based high sensitivity oxygen sensing is compared. Detectivities of < 20 ppm m using the DFB laser diode and < 7 × 103 ppm m using the VCSEL were determined utilising wavelength modulation spectroscopy and harmonic detection. We assess factors influencing the relative performance of these devices, including spectral resolution,

V. Weldon; J. O'Gorman; J. J. Pérez-Camacho; D. McDonald; J. Hegarty; J. C. Connolly; N. A. Morris; R. U. Martinelli; J. H. Abeles

1997-01-01

206

Fabrication of advanced Bragg gratings with complex apodization profiles by use of the polarization control method.  

PubMed

The polarization control method offers a flexible, robust, and low-cost route for the parallel fabrication of gratings with complex apodization profiles including several discrete phase shifts and chirp. The performance of several test gratings is evaluated in terms of their spectral response and compared with theoretical predictions. Short gratings with sidelobe-suppression levels in excess of 32 dB and transmission dips lower than 80 dB have been realized. Finally, most of the devices fabricated by the polarization control method show comparable quality to gratings manufactured by far more complex methods. PMID:15219034

Deyerl, Hans-Jürgen; Plougmann, Nikolai; Jensen, Jesper Bo; Floreani, Filip; Sörensen, Henrik Rokkjaer; Kristensen, Martin

2004-06-10

207

Polarization mode structure in long-wavelength wafer-fused vertical-cavity surface-emitting lasers  

NASA Astrophysics Data System (ADS)

Applications of long-wavelength (? > 1 ?m) vertical-cavity surface-emitting lasers (VCSELs) generally require close control over wavelength and polarization of the emitted light. In most cases, single mode and polarization stable lasing is desired. We report here on the detailed modal analysis of wafer-fused 1550-nm wavelength VCSELs incorporating an AlGaInAs/InP active region, a re-grown circular tunnel junction (TJ) and undoped AlGaAs/GaAs distributed Bragg reflectors (DBRs). We experimentally determined the diameter of the TJ that optimizes the output power and threshold current, finding a value between 7.0 ?m and 9.5 ?m depending on the temperature. Moreover, we investigated the impact of the TJ aperture diameter on the mode structure. A large batch of devices was investigated, allowing drawing conclusions on typical behavior of these devices. The measured emission spectra show that the fundamental spatial mode is split into two orthogonal polarization modes, which are spectrally separated in wavelength by ?, used as a birefringence parameter. We observed that this parameter is independent of current but depends on the particular chip, suggesting that it is caused by stress, growth inhomogeneities, or etched mesa shape. The higher order spatial modes show similar polarization doublets with a splitting also equal to ?. This suggests that the birefringence results from effects not particular to the mechanism of mode confinement. Finally, the spectral separation ?01 between the fundamental mode and the first-order transverse mode increases linearly with current, with a slope that depends only on the TJ aperture diameter. This confirms that the mode confinement is induced by the structured TJ, and possibly also by the temperature distribution induced by the current injection.

Volet, N.; Iakovlev, V.; Sirbu, A.; Caliman, A.; Suruceanu, G.; Mereuta, A.; Kapon, E.

2012-05-01

208

Polarization dynamics in vertical-cavity surface-emitting lasers with optical feedback through a quarter-wave plate  

NASA Astrophysics Data System (ADS)

Square-wave switching of the intensities of the orthogonal linearly polarized components of the output of a vertical-cavity surface-emitting laser (VCSEL) found previously in experiments with polarization-changing optical feedback, is not found in rate equation models incorporating only birefringence and gain anisotropy, but is found in the model for VCSELs developed by San Miguel, Feng, and Moloney [M. San Miguel, Q. Feng, and J. V. Moloney, Phys. Rev. A 52, 1729 (1995)]. The dynamics is sensitive to both the feedback strength and the relaxation rate of the magnetization in the quantum well sublevels.

Masoller, C.; Abraham, N. B.

1999-02-01

209

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

NASA Astrophysics Data System (ADS)

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.

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

2013-03-01

210

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

PubMed

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

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

2013-09-20

211

Giant tunnel electroresistance and electrical control of spin polarization with ferroelectric tunnel barriers  

NASA Astrophysics Data System (ADS)

At room temperature, we use piezoresponse force microscopy to show robust ferroelectricity in BaTiO3 ultrathin films, and conductive-tip atomic force microscopy to demonstrate the resistive readout of the polarization state via its influence on the tunnel current [1]. This giant electroresistance nondestructive readout paves the way for ferroelectric memories with simplified architectures, higher densities and faster operation. Additionally, ferroelectric tunnel junctions with ferromagnetic electrodes were engineered to demonstrate local, large and non-volatile control of carrier spin polarization by switching ferroelectric polarization [2]. Our results represent a giant interfacial type of magnetoelectric coupling and suggest a new low-power approach for spin-based information control. [4pt] [1] V. Garcia et al., Nature 460, 81 (2009) [0pt] [2] V. Garcia et al., Science 327, 1106 (2010)

Garcia, Vincent

2011-03-01

212

Optical phase modulation based on directly modulated reflection-mode OIL-VCSEL.  

PubMed

Optical phase modulation based on directly modulated reflection-mode optically injection-locked VCSEL is investigated based on standard OIL rate equations and reflection-mode OIL model. The phase information of both static and dynamic state is simulated. The difference of static state phase information between transmission- and reflection-mode OIL is numerically analyzed. With specific OIL parameters, the output power of directly modulated OIL-VCSEL remains constant and phase deviation of 0.934? rad is obtained. Results show that a directly modulated OIL-VCSEL can function as a key component in QPSK or 8PSK transmitters. Preliminary 2.5 Gb/s PSK modulation characteristic is demonstrated experimentally. PMID:24104103

Guo, Peng; Sun, Tao; Yang, Weijian; Parekh, Devang; Zhang, Cheng; Xie, Xiaopeng; Chang-Hasnain, Connie J; Xu, Anshi; Chen, Zhangyuan

2013-09-23

213

VCSELs based on arrays of sub-monolayer InGaAs quantum dots  

SciTech Connect

Vertical-cavity surface-emitting lasers (VCSELs) with an active region based on sub-monolayer InGaAs quantum dots and doped AlGaAs/GaAs distributed Bragg reflectors were grown by MBE. VCSELs with current aperture of 3 {mu}m in diameter demonstrate single-mode lasing in 980-nm range with the threshold current of 0.6 mA, maximum output power up to 4 mW, and external differential efficiency of 68%. Multimode VCSELs with a (10-12)-{mu}m aperture demonstrate ultralow internal optical loss of 0.09% per pass, which compares favorably with the best results obtained in similar lasers with undoped distributed Bragg reflectors.

Blokhin, S. A., E-mail: blokh@mail.ioffe.ru; Maleev, N. A.; Kuz'menkov, A. G.; Shernyakov, Yu. M.; Novikov, I. I.; Gordeev, N. Yu.; Dyudelev, V. V.; Sokolovskii, G. S.; Kuchinskii, V. I.; Kulagina, M. M.; Maximov, M. V.; Ustinov, V. M. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation); Kovsh, A. R.; Mikhrin, S. S.; Ledentsov, N. N. [NL-Nanosemiconductors GmbH (Germany)

2006-05-15

214

First-order polarization mode dispersion compensator using two independent feedback signals enabling separation of principal states of polarization and differential group delay controls.  

PubMed

We propose and demonstrate a novel first-order polarization mode dispersion (PMD) compensator separating principal-states-of-polarization (PSP) control from differential-group-delay (DGD) control by using two independent feedback monitoring signals. To verify the proposed operating principle, we fabricated an automatically adaptive module-type 40-Gb/s PMD compensator on printed circuit boards. The results show that unlike previous typical compensation method of controlling alternately PSP and DGD, the proposed scheme provides independent continuous PSP tracking regardless of DGD control by delay line under rapidly varying PSP condition, thus resulting in stable compensated signal with reduction in compensation time. PMID:22418113

Han, Ki Ho; Lee, Wang Joo

2012-02-13

215

High-speed single-mode quantum dot and quantum well VCSELs  

NASA Astrophysics Data System (ADS)

As the density of transistors in CMOS integrated circuits continues to roughly double each two years the processor computational power also roughly doubles. Since the number of input/output (I/O) devices can not increase without bound I/O speed must analogously approximately double each two years. In the Infiniband EDR standard (2011) a single channel bit rate of 26 Gb/s is foreseen. The maximum reliable and efficient copper link length shrinks at bit rates above 10 Gb/s to a few meters at best. At higher bit rates the length of a given multimode fiber link must also shrink, due to both modal and wavelength dispersions. Although the modal dispersion in modern multimode OM3 and OM4 fibers that are optimized for 850 nm vertical-cavity surface-emitting lasers (VCSELs) is reduced, the wavelength dispersion remains a serious issue for standard multimode VCSELs. An ultimate solution to overcome this problem is to apply single-mode VCSELs to extend and ultimately maximize the link length. In this paper we demonstrate recent results for single-mode VCSELs with very high relaxation resonance frequencies. Quantum well 850 nm VCSELs with record high 30 GHz resonance frequencies are demonstrated. Additionally single-mode data transmission at 35 Gb/s over multimode fiber is demonstrated. For comparison we also present specific device modeling parameters and performance characteristics of 850 nm single-mode quantum dot (QD) VCSELs. Despite a significant spectral broadening of the QD photoluminescence and gain due to QD size dispersion we obtain relaxation resonance frequencies as high as 17 GHz.

Ledentsov, Nikolay N.; Lott, James A.; Bimberg, Dieter; Mutig, Alex; Fiol, Gerrit; Blokhin, Sergey A.; Nadtochiy, Alexey M.; Shchukin, Vitaly A.; Kropp, Jörg; Novikov, Innokenty I.; Karachinsky, Leonid Y.; Maximov, Mikhail V.

2011-02-01

216

Multidimensional VCSEL-array push\\/pull module fabricated using the self-alignment mounting technique  

Microsoft Academic Search

We have developed plastic-molded receptacle-lope vertical-cavity surface-emitting laser (VCSEL)-array modules directly push\\/pull connectable with the one-dimensional (1-D) conventional mechanically-transferable multifiber push-on (MPO) fiber connector and with a new two-dimensional (2-D) MPO-compatible fiber connector developed for this module. The VCSEL was mounted on the plastic-molded package using a highly precise completely alignment-free process using flip-chip solder bonding and ball-guide die bonding.

Hideo Kosaka; Mikihiro Kajita; Yoshimasa Sugimoto

1998-01-01

217

Effect of the spectral width on mode partition noise in multimode VCSELs  

NASA Astrophysics Data System (ADS)

The dependence of the mode partition noise (MPN) and the power penalty associated with it can be measured from the source spectral width. Our findings show that there is strong dependence of the carrier lifetime on the bit error rate degradation caused by MPN on the spectral width of the vertical cavity surface emitting laser (VCSEL). VCSELs with smaller spectral width (shorter carrier lifetime) exhibited smaller MPN induced power penalty. We found that the theoretical calculation of the power penalties caused by MPN from the carrier lifetime and the spectral width is in good agreement with the measured system penalties.

Tayahi, Moncef B.; Lanka, Sivakumar; Carstens, Jan; Hoffmann, Lutz

2005-03-01

218

Experimental study of the scintillation index of a radially polarized beam with controllable spatial coherence  

NASA Astrophysics Data System (ADS)

Radially polarized (RP) beam with controllable spatial coherence (i.e., partially coherent RP beam) was generated in experiment recently [Appl. Phys. Lett. 100, 051108 (2012)]. In this letter, we report experimental study of the scintillation index of a partially coherent RP beam propagating through thermally induced turbulence. Our results show that a partially coherent RP beam has advantage over a linearly polarized partially coherent beam for reducing turbulence-induced scintillation, which will be useful in free-space optical communications, remote sensing and laser radar systems.

Wang, Fei; Liu, Xianlong; Liu, Lin; Yuan, Yangsheng; Cai, Yangjian

2013-08-01

219

Microfluidic directional emission control of an azimuthally polarized radial fibre laser  

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

220

Reversal construction of polarization-controlled focusing field with multiple focal spots  

NASA Astrophysics Data System (ADS)

We propose an approach to control the polarization and intensity of the focusing field with multiple focal spots in a high-numerical-aperture imaging system. This focused field is explained as the reversal radiation of the dipole array with presupposed oscillating direction in the focal volume. By engineering the structure of the electric dipole array and reversing the radiation from this dipole array, the local manipulation of intensity and polarization in the focal region is achieved, and the required field at the pupil plane is derived. A focusing field with six vectorial focal spots is created as an example to verify this method. This multifocal field will meet potential application in polarization-dependent optical microscope and optical trapping for multiple particles.

Wang, Jiming; Liu, Qingliang; He, Chongjun; Liu, Youwen

2013-04-01

221

Coupling strength can control the polarization twist of a plasmonic antenna.  

PubMed

The far-field polarization of the optical response of a plasmonic antenna can be tuned by subtly engineering of its geometry. In this paper, we develop design rules for nano antennas which enable the generation of circular polarized light via the excitation of circular plasmonic modes in the structure. Two initially orthogonal plasmonic modes are coupled in such a way that a rotational current is excited in the structure. Modifying this coupling strength from a weak to a strong regime controls the helicity of the scattered field. Finally, we introduce an original sensing approach that relies on the rotation of the incident polarization and demonstrates a sensitivity of 0.23 deg·nm(-1) or 33 deg·RIU(-1), related to changes of mechanical dimensions and the refractive index, respectively. PMID:23987803

Abasahl, Banafsheh; Dutta-Gupta, Shourya; Santschi, Christian; Martin, Olivier J F

2013-09-03

222

Laser-polarization-dependent and magnetically controlled optical bistability in diamond nitrogen-vacancy centers  

NASA Astrophysics Data System (ADS)

We explore laser-polarization-dependent and magnetically controlled optical bistability (OB) in an optical ring cavity filled with diamond nitrogen-vacancy (NV) defect centers under optical excitation. The shape of the OB curve can be significantly modified in a new operating regime from the previously studied OB case, namely, by adjusting the intensity of the external magnetic field and the polarization of the control beam. The influences of the intensity of the control beam, the frequency detuning, and the cooperation parameter on the OB behavior are also discussed in detail. These results are useful in real experiments for realizing an all-optical bistate switching or coding element in a solid-state platform.

Zhang, Duo; Yu, Rong; Li, Jiahua; Ding, Chunling; Yang, Xiaoxue

2013-11-01

223

Second-Harmonic-Generation Microscopy Using Excitation Beam with Controlled Polarization Pattern to Determine Three-Dimensional Molecular Orientation  

NASA Astrophysics Data System (ADS)

We have developed a second-harmonic-generation (SHG) microscope using an excitation beam with a controlled polarization pattern in order to detect three-dimensional molecular orientation. The electric field at the focus is controlled three-dimensionally by modifying the polarization distribution with a parallel-aligned nematic-liquid-crystal spatial-light-modulator without any mechanical moving parts. We demonstrated that the SHG signal from an Achilles tendon, sliced so that collagen fibers were aligned parallel to the optical axis, excited by a radially polarized beam was higher than those excited by linearly polarized beams. The possibility of determinating three-dimensional molecular orientation was thus shown.

Yoshiki, Keisuke; Hashimoto, Mamoru; Araki, Tsutomu

2005-08-01

224

Control of valley polarization in monolayer MoS2 by optical helicity.  

PubMed

Electronic and spintronic devices rely on the fact that free charge carriers in solids carry electric charge and spin. There are, however, other properties of charge carriers that might be exploited in new families of devices. In particular, if there are two or more minima in the conduction band (or maxima in the valence band) in momentum space, and if it is possible to confine charge carriers in one of these valleys, then it should be possible to make a valleytronic device. Valley polarization, as the selective population of one valley is designated, has been demonstrated using strain and magnetic fields, but neither of these approaches allows dynamic control. Here, we demonstrate that optical pumping with circularly polarized light can achieve complete dynamic valley polarization in monolayer MoS(2) (refs 11, 12), a two-dimensional non-centrosymmetric crystal with direct energy gaps at two valleys. Moreover, this polarization is retained for longer than 1 ns. Our results, and similar results by Zeng et al., demonstrate the viability of optical valley control and suggest the possibility of valley-based electronic and optoelectronic applications in MoS(2) monolayers. PMID:22706698

Mak, Kin Fai; He, Keliang; Shan, Jie; Heinz, Tony F

2012-06-17

225

Control of valley polarization in monolayer MoS2 by optical helicity  

NASA Astrophysics Data System (ADS)

Electronic and spintronic devices rely on the fact that free charge carriers in solids carry electric charge and spin. There are, however, other properties of charge carriers that might be exploited in new families of devices. In particular, if there are two or more minima in the conduction band (or maxima in the valence band) in momentum space, and if it is possible to confine charge carriers in one of these valleys, then it should be possible to make a valleytronic device. Valley polarization, as the selective population of one valley is designated, has been demonstrated using strain and magnetic fields, but neither of these approaches allows dynamic control. Here, we demonstrate that optical pumping with circularly polarized light can achieve complete dynamic valley polarization in monolayer MoS2 (refs 11, 12), a two-dimensional non-centrosymmetric crystal with direct energy gaps at two valleys. Moreover, this polarization is retained for longer than 1 ns. Our results, and similar results by Zeng et al., demonstrate the viability of optical valley control and suggest the possibility of valley-based electronic and optoelectronic applications in MoS2 monolayers.

Mak, Kin Fai; He, Keliang; Shan, Jie; Heinz, Tony F.

2012-08-01

226

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

PubMed

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. PMID:23988431

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

2013-08-12

227

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

NASA Astrophysics Data System (ADS)

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.

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

2013-10-01

228

Impact of optical feedback on current-induced polarization behavior of 1550 nm vertical-cavity surface-emitting lasers.  

PubMed

Polarization switching (PS) between two orthogonal linearly polarized fundamental modes is experimentally observed in commercial free-running 1550 nm vertical-cavity surface-emitting lasers (VCSELs) (Raycan). The characteristics of this PS are strongly modified after introducing a polarization-preserved (PP) or polarization-orthogonal (PO) optical feedback. Under the case that the external cavity is approximately 30 cm, the PP optical feedback results in the PS point shifting toward a lower injection current, and the region within which the two polarization modes coexist is enlarged with the increase of the PP feedback strength. Under too-strong PP feedback levels, the PS disappears. The impact of PO optical feedback on VCSEL polarization behavior is quite similar to that of PP optical feedback, but larger feedback strength is needed to obtain similar results. PMID:23736341

Deng, Tao; Wu, Zheng-Mao; Xie, Yi-Yuan; Wu, Jia-Gui; Tang, Xi; Fan, Li; Panajotov, Krassimir; Xia, Guang-Qiong

2013-06-01

229

Push-pull modulation of lateral coupling of dual VCSEL cavities using a bow-tie shape  

NASA Astrophysics Data System (ADS)

We propose the lateral coupling of dual VCSEL cavities using a bow-tie shape connection for increasing the modulation bandwidth. The 3-D modeling shows no-noticeable radiation loss when two oxide-defined VCSEL cavities are coherently coupled. Transverse-mode switching offers a unique modulation concept that makes intensity modulation while total photon density inside the coupled cavities is unchanged under push-pull current modulation. Large modulation bandwidth free from relaxation oscillation frequencies can be expected. We fabricated 980nm laterally coupled cavity VCSELs with a bow-tie shape oxide aperture and demonstrated the transverse-mode switching under push-pull operations.

Dalir, Hamed; Matsutani, Akihiro; Koyama, Fumio

2013-03-01

230

Studies of ESD-related failure patterns of Agilent oxide VCSELs  

NASA Astrophysics Data System (ADS)

Electrostatic Discharge (ESD) damage is considered to be the leading cause for IC field failures. With increasing integration densities, devices tend to become more and more sensitive to ESD events. This observation holds in particular true for 850nm VCSELs, as the quest for higher modulation frequencies calls for shrinking device dimensions and aperture sizes in particular. This publication is geared towards an understanding of the various factors that lead to ESD-related failures of oxide VCSELs. A broad variety of current VCSEL product lines at Agilent have been investigated in respect to their ESD resistance and related long-term reliability. Intentionally stressed devices have been characterized in terms of their electrical, optical and visual failure patterns as well as the medium time-to-failure. Cross-sectional and plan-view TEM have been employed to localize ESD damage and its propagation. For the first time, emission microscopy has been used to study the electroluminescence pattern of damaged VCSELs at very low currents. The paper will conclude by listing experimental signatures allowing for differentiation between ESD and other failure modes. Based upon these, effective screening methods are proposed.

Krueger, Joachim J.; Sabharwal, Reena; McHugo, Scott A.; Nguyen, Kimanh; Tan, Ningxia; Janda, Naginder; Mayonte, Myrna S.; Heidecker, Mike; Eastley, David; Keever, Mark R.; Kocot, Christopher P.

2003-06-01

231

A TCAD approach to robust ESD design in oxide-confined VCSELs  

NASA Astrophysics Data System (ADS)

Electrostatic Discharge (ESD) events can cause irreversible damage during production, packaging and application of Vertical-Cavity Surface Emitting Lasers (VCSELs). Experimental investigation of those damage patterns inside a real device is a complex and expensive task. Simulation tools can provide insight into the physics during an actual discharge event. This paper aims to analyze ESD events in VCSELs with a microscopic simulation. With the help of a state-of-the art Technology Computer Aided Design (TCAD) virtual ESD tests are performed on oxide-confined VCSELs. The 2-D simulation model takes into account high-field effects and self-heating in a hydrodynamic framework that allows time-dependent spatially resolved monitoring of critical quantities (such as electric field across the oxide, temperature profile, current densities) during the ESD events. Human Body Model (HBM), Machine Model (MM) and Charged Device Model (CDM) show typical local heating and current crowding effects which may lead to irreversible damaging of the device. For slow ESD events the temperature peak is found near the center of the device. Faster pulses show maximum temperature at the interface between oxide and aperture. Physics-based explanations in terms of local electric field, heat generation and heat transport are given. Oxide aperture, thickness and its position relative to the intrinsic region strongly influence self-heating, electric fields, current density profiles and the dielectric breakdown conditions. The impact of those factors on ESD robustness are analyzed and guidelines for robust ESD design in VCSELs are presented.

Meier, Hektor; Santschi, Rafael; Odermatt, Stefan; Witzigmann, Bernd; Eitel, Sven; Nallet, Franck; Letay, Gergö

2007-03-01

232

The oxide defined VCSEL-based smart pixels for the optical database filter  

SciTech Connect

This paper presents the construction of the smart pixel arrays which perform AND and XOR functions with three-input and one-output optical signals for the application of an optical database filter. The device is based on oxide confined VCSELs bump bonded to GaAs MESFET pixels. The MSM photodetectors are monolithically integrated with MESFETs.

Pu, R.; Hayes, E.; Jurrat, R.; Stanko, P.J.; Wilmsen, C.W. [Colorado State Univ., Ft. Collins, CO (United States). Dept. of Electrical Engineering; Choquette, K.; Geib, K.; Hou, H.Q. [Sandia National Labs., Albuquerque, NM (United States)

1997-04-01

233

Laser-based micro-bonding of VCSELs using arrayed beams from a fiber laser  

NASA Astrophysics Data System (ADS)

We demonstrate a laser-based micro-bonding method for Vertical Cavity Surface Emitting Lasers (VCSELs) that enables practically sufficient joint strength, while securing the output power before bonding. VCSELs have great potential for optical interconnects because of their low threshold current and high-speed modulation capability. As for packaging of VCSELs, flip-chip bonding (FCB), among others, has been investigated because it facilitates the coupling of laser emission into fibers and waveguides. Conventional schemes for FCB, however, entail thermo-compressing stages and therefore the thermal and mechanical stresses involved are prone to cause defects in the lasing media, leading to quality defects. To overcome this problem, we have come up with a modified FCB method that can reduce such stress by employing laser irradiation to efficiently heat joints minimizing heat-affected regions. A micro-bonding system used in the experiments has an infrared fiber laser for heating, a diffractive beam splitter for parallel processing, a mounting head, and a slider for precise alignment and translation. VCSEL pads are kept in contact with counter pads on a substrate with AuSn solder placed between them. The split and focused beams by the element are guided to strike the joining points through the substrate, heating and melting the solder to attain a tight joint.

Nagasaka, Kimio; Amako, Jun; Fujii, Eiichi

2008-03-01

234

Modeling of ultrawidely tunable vertical cavity air-gap filters and VCSELs  

Microsoft Academic Search

Tunable vertical cavity devices including an air-gap integrated in the cavity have been designed, fabricated, and investigated. The ultrawide wavelength tuning is realized by micromechanical actuation of Bragg mirror membranes. Based on optical and mechanical model calculations, the air-gap filters and vertical cavity surface emitting lasers (VCSELs) are designed for investigating mainly the optical tuning efficiency. In our research, we

Cornelia Prott; F. Romer; E. O. Ataro; J. Daleiden; S. Irmer; A. Tarraf; H. Hillmer

2003-01-01

235

Reliability study of 1060nm 25Gbps VCSEL in terms of high speed modulation  

NASA Astrophysics Data System (ADS)

Furukawa's 1060nm VCSELs with double-intra-cavity structure and Al-free InGaAs/GaAs QWs enable us to realize low power consumption, high speed operation and high reliability simultaneously. The power dissipation was as low as 140fJ/bit. Clear eye opening up to 20Gbps was achieved. Random failure rate and wear-out lifetime were evaluated as 30FIT/channel and 300 years. For higher speed operation, thickness of oxidation layer was increased for lower parasitic capacitance of device. Preliminary reliability test was performed on those devices. In high speed operation faster than 10Gbps, conventional lifetime definition as 2dB down of output power is not sufficient due to smaller margin of modulation characteristics. We suggest threshold current as a barometer for degradation of modulation characteristics. The threshold currents of our VCSELs degrade small enough during accelerated aging test. We also observed no remarkable change in 25Gbps eye diagram after aging test. The definition of life time for high speed VCSEL is discussed from the change in threshold current and so on in addition to the conventional power degradation during aging. It is experimentally verified that our VCSELs are promising candidate for highly reliable light source including long term stable high speed operation.

Suzuki, Toshihito; Imai, Suguru; Kamiya, Shinichi; Hiraiwa, Koji; Funabashi, Masaki; Kawakita, Yasumasa; Shimizu, Hitoshi; Ishikawa, Takuya; Kasukawa, Akihiko

2012-02-01

236

Comparative Study of QD and Nitrogen-Based 1.3 mu m VCSELs.  

National Technical Information Service (NTIS)

We study two types of GaAs-based heterostructures (InAs/InGaAs quantum dots and InGaAsN quantum wells) designed for 1.3 micrometers vertical- cavity surface-emitting lasers (VCSELs) and compare different device designs. A correlation between properties of...

A. E. Zhukov A. P. Vasil'ev A. R. Kovsh A. Y. Egorov N. A. Maleev

2001-01-01

237

Shot-noise-limited VCSELs for high-speed fiber optic data transmission  

NASA Astrophysics Data System (ADS)

Oxide-confined vertical-cavity surface-emitting laser diodes (VCSELs) are optimized for multi-Gbit/s data rate optical transmission systems. Noise characteristics and small-signal modulation response of high-performance transverse single- and multi-mode devices under different operation conditions are investigated. We demonstrate for the first time 12.5 Gbit/s data rate fiber transmission with a bit-error rate of better than 10-11 for pseudo-random bit sequence signals over 100m multimode fiber and 1 km single-mode fiber. Maximum electrical and optical bandwidths obtained at 3 mA driving current are 12 GHz and 13 GHz, respectively. For pumping levels above 2.8 times threshold current, the relative intensity noise is below -150 dB/Hz up to 5 GHz for output powers of about 1mW. In detail, we investigate the low frequency intensity noise of high efficiency small area selectively oxidized VCSELs emitting in the fundamental transverse mode up to 7 times threshold current at room temperature and in multiple transverse modes up to 20 times threshold current. For low temperature operation quantum efficiency of the VCSEL is increased leading to photon- number fluctuations 1.4 dB below the shot noise limit. This is to our best knowledge the largest amount of squeezing ever reported for VCSELs.

Jaeger, Roland; Wiedenmann, Dieter; Grabherr, Martin; Jung, Christian; Kicherer, Max; King, Roger; Mederer, Felix; Miller, Michael; Schnitzer, Peter; Ebeling, Karl J.

1999-11-01

238

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

NASA Astrophysics Data System (ADS)

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.

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

2007-06-01

239

Improved uniformity of target irradiation by combining an orthogonal cylindrical lens array and the polarization control  

NASA Astrophysics Data System (ADS)

A scheme of combining technology of orthogonal cylindrical lens array (OCLA) and polarization control plate (PCP) is introduced to improve target irradiation uniformity in laser fusion. The feasibility of the scheme is also analyzed by detailed two-dimensional simulation. It shows that a focal pattern with flat-top and sharp-edge profile could be obtained with an OCLA, while interference stripes inside the pattern are smoothed out by the use of the polarization control plate (PCP) technique. Moving the target slightly from the exact focal plane of the principal focusing lens can eliminate middle-scale-length intensity fluctuation further. And a well-irradiated laser spot with small nonuniformity and great energy efficiency can be obtained in this scheme.

Zheng, Jianzhou; Zheng, Wenyang; Yu, Qingxu; Dong, Bin; Guan, Shouhua; Wu, Yunfeng

2010-05-01

240

Studies concerning the temporal and genetic control of cell polarity in Saccharomyces cerevisiae  

PubMed Central

The establishment of cell polarity was examined in the budding yeast, S. cerevisiae. The distribution of a polarized protein, the SPA2 protein, was followed throughout the yeast cell cycle using synchronized cells and cdc mutants. The SPA2 protein localizes to a patch at the presumptive bud site of G1 cells. Later it concentrates at the bud tip in budded cells. At cytokinesis, the SPA2 protein is at the neck between the mother and daughter cells. Analysis of unbudded haploid cells has suggested a series of events that occurs during G1. The SPA2 patch is established very early in G1, while the spindle pole body residues on the distal side of the nucleus. Later, microtubules emanating from the spindle pole body intersect the SPA2 crescent, and the nucleus probably rotates towards the SPA2 patch. By middle G1, most cells contain the SPB on the side of the nucleus proximal to the SPA2 patch, and a long extranuclear microtubule bundle intersects this patch. We suggest that a microtubule capture site exists in the SPA2 staining region that stabilizes the long microtubule bundle; this capture site may be responsible for rotation of the nucleus. Cells containing a polarized distribution of the SPA2 protein also possess a polarized distribution of actin spots in the same region, although the actin staining is much more diffuse. Moreover, cdc4 mutants, which form multiple buds at the restrictive temperature, exhibit simultaneous staining of the SPA2 protein and actin spots in a subset of the bud tips. spa2 mutants contain a polarized distribution of actin spots, and act1-1 and act1-2 mutants often contain a polarized distribution of the SPA2 protein suggesting that the SPA2 protein is not required for localization of the actin spots and the actin spots are not required for localization of the SPA2 protein. cdc24 mutants, which fail to form buds at the restrictive temperature, fail to exhibit polarized localization of the SPA2 protein and actin spots, indicating that the CDC24 protein is directly or indirectly responsible for controlling the polarity of these proteins. Based on the cell cycle distribution of the SPA2 protein, a "cytokinesis tag" model is proposed to explain the mechanism of the non-random positioning of bud sites in haploid yeast cells.

1991-01-01

241

Monolithic 2D high-power arrays of long-wavelength VCSELs  

NASA Astrophysics Data System (ADS)

InP-based, long-wavelength vertical-cavity surface-emitting lasers (LW-VCSELs) with buried tunnel junction are presented for high-power applications. Various studies of single-devices with large apertures and monolithically integrated two-dimensional VCSEL arrays are shown. The influence of aperture and array size on laser power, efficiency and divergence angle is investigated in detail. Unlike GaAs-based devices, large apertures are not favorable due to thermal issues. Accordingly, we focused on VCSEL arrays and derived scaling rules for optimum performance. This allows manufacturing high-power devices achieving continuous-wave (CW) optical powers in excess of 3 W at -11°C heat-sink temperature, circular far-field, low divergence angles around 20° and power densities of 130 W/cm2 at 1.55 ?m. To the best of our knowledge, this is the highest power ever reported for a monolithic VCSEL array. At room temperature, more than 2 W is still available and high-temperature operation up to 70°C is applicable. The driving voltages around 1.2 V are significantly low, enabling single battery mobile operation. The wall-plug efficiency at room temperature exceeds 20% in a wide range. Addressing the array in sectors, we found that the array is very homogenous in performance with a standard deviation of less than 2.8%. Therefore, high-power applications can also be accomplished by VCSEL technology. As these novel devices with emission wavelengths beyond 1400 nm are less restrictive with respect to eye-safety, they are also favorable for free-space applications. Additionally, the devices may be used as concealed infra-red headlights that are invisible for all silicon-based detectors.

Hofmann, W.; Görblich, M.; Ortsiefer, M.; Böhm, G.; Amann, M.-C.

2008-01-01

242

On-chip replication of micro-optical structures for VCSEL to fiber coupling  

NASA Astrophysics Data System (ADS)

We present an approach towards design and fabrication of optical microsystems based on UV-replication techniques using Ormocer materials. An integration of the structures on chip level is demonstrated for Vertical Surface Emitting Lasers (VCSEL). VCSEL's are of increasing interest for various fields such as telecommunications, optical sensing and optical interconnects. In terms of optical system integration, high technological requirements are imposed. UV-replication techniques using Ormocer materials offer a cost-effective way of integrating micro-optical elements directly on the chip with reduced assembly effort. Structures up to several hundred microns thickness and alignment tolerances in the order of few microns can be produced. The method is suitable for the fabrication of single elements, arrays and is extendable to wafer-scale processing. Here, we give an example for the coupling of VCSEL arrays into multimode optical fibers using two different approaches: Focusing of the VCSEL output into the fiber using replicated microlenses and fiber butt-coupling of the VCSEL lasers with help of replicated fiber alignment/guiding structures. Origination of the structure elements is accomplished by direct laser writing into photoresist and resist reflow techniques, respectively. Specific limitations of the corresponding fabrication method are already taken into account during element design and modeling. Results for the replicated lenses show a total fiber launch efficiency better than 70% over the laser operational range with alignment tolerances of approximately +/- 10 micrometers , which can be met by passive fiber alignment. In case of the replicated fiber alignment/guiding structures, fiber launch efficiencies better than 50% over the operation range and peak values better than 80% are reported.

Ammer, Thomas; Gale, Michael T.; Rossi, Markus

2001-11-01

243

Hybrid Improper Ferroelectricity: A Mechanism for Controllable Polarization-Magnetization Coupling  

NASA Astrophysics Data System (ADS)

First-principles calculations are presented for the layered perovskite Ca3Mn2O7. The results reveal a rich set of coupled structural, magnetic, and polar domains in which oxygen octahedron rotations induce ferroelectricity, magnetoelectricity, and weak ferromagnetism. The key point is that the rotation distortion is a combination of two nonpolar modes with different symmetries. We use the term “hybrid” improper ferroelectricity to describe this phenomenon and discuss how control over magnetism is achieved through these functional antiferrodistortive octahedron rotations.

Benedek, Nicole A.; Fennie, Craig J.

2011-03-01

244

Polarity controlled by the composition of inorganic recording materials in Al-Si binary system  

Microsoft Academic Search

A technique was introduced to control the polarity of discs. Inorganic materials of binary Al-Si were used as recording layers in our study. By adjusting the layer thickness of Al and Si individually, we found that over a certain thickness ratio of Al-Si double layers, the reflectivity shift measured by a static tester altered from high-to-low into low-to-high. By using

Ru-Lin Yeh; Hsun-Hao Chang; Bing-Mau Chen; Teng-Chien Yu

2004-01-01

245

Drosophila Atypical Protein Kinase C Associates with Bazooka and Controls Polarity of Epithelia and Neuroblasts  

PubMed Central

The establishment and maintenance of polarity is of fundamental importance for the function of epithelial and neuronal cells. In Drosophila, the multi-PDZ domain protein Bazooka (Baz) is required for establishment of apico-basal polarity in epithelia and in neuroblasts, the stem cells of the central nervous system. In the latter, Baz anchors Inscuteable in the apical cytocortex, which is essential for asymmetric localization of cell fate determinants and for proper orientation of the mitotic spindle. Here we show that Baz directly binds to the Drosophila atypical isoform of protein kinase C and that both proteins are mutually dependent on each other for correct apical localization. Loss-of-function mutants of the Drosophila atypical isoform of PKC show loss of apico-basal polarity, multilayering of epithelia, mislocalization of Inscuteable and abnormal spindle orientation in neuroblasts. Together, these data provide strong evidence for the existence of an evolutionary conserved mechanism that controls apico-basal polarity in epithelia and neuronal stem cells. This study is the first functional analysis of an atypical protein kinase C isoform using a loss-of-function allele in a genetically tractable organism.

Wodarz, Andreas; Ramrath, Andreas; Grimm, Alexandra; Knust, Elisabeth

2000-01-01

246

Planar Cell Polarity Controls Pancreatic Beta Cell Differentiation and Glucose Homeostasis  

PubMed Central

Summary Planar cell polarity (PCP) refers to the collective orientation of cells within the epithelial plane. We show that progenitor cells forming the ducts of the embryonic pancreas express PCP proteins and exhibit an active PCP pathway. Planar polarity proteins are acquired at embryonic day 11.5 synchronously to apicobasal polarization of pancreas progenitors. Loss of function of the two PCP core components Celsr2 and Celsr3 shows that they control the differentiation of endocrine cells from polarized progenitors, with a prevalent effect on insulin-producing beta cells. This results in a decreased glucose clearance. Loss of Celsr2 and 3 leads to a reduction of Jun phosphorylation in progenitors, which, in turn, reduces beta cell differentiation from endocrine progenitors. These results highlight the importance of the PCP pathway in cell differentiation in vertebrates. In addition, they reveal that tridimensional organization and collective communication of cells are needed in the pancreatic epithelium in order to generate appropriate numbers of endocrine cells.

Cortijo, Cedric; Gouzi, Mathieu; Tissir, Fadel; Grapin-Botton, Anne

2013-01-01

247

Control of the electric polarization flop direction by a canted magnetic field in a magnetoelectric multiferroic MnWO4  

NASA Astrophysics Data System (ADS)

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 P//a and P//b phase in a canted magnetic fields has been experimentally determined. The stability of magnetoelectric domain walls in a canted magnetic field would play a key role in the directional control of the electric polarization flop phenomenon.

Taniguchi, K.; Abe, N.; Umetsu, H.; Arima, T.

2010-01-01

248

FGF signaling regulates Wnt ligand expression to control vulval cell lineage polarity in C. elegans.  

PubMed

The interpretation of extracellular cues leading to the polarization of intracellular components and asymmetric cell divisions is a fundamental part of metazoan organogenesis. The Caenorhabditis elegans vulva, with its invariant cell lineage and interaction of multiple cell signaling pathways, provides an excellent model for the study of cell polarity within an organized epithelial tissue. Here, we show that the fibroblast growth factor (FGF) pathway acts in concert with the Frizzled homolog LIN-17 to influence the localization of SYS-1, a component of the Wnt/?-catenin asymmetry pathway, indirectly through the regulation of cwn-1. The source of the FGF ligand is the primary vulval precursor cell (VPC) P6.p, which controls the orientation of the neighboring secondary VPC P7.p by signaling through the sex myoblasts (SMs), activating the FGF pathway. The Wnt CWN-1 is expressed in the posterior body wall muscle of the worm as well as in the SMs, making it the only Wnt expressed on the posterior and anterior sides of P7.p at the time of the polarity decision. Both sources of cwn-1 act instructively to influence P7.p polarity in the direction of the highest Wnt signal. Using single molecule fluorescence in situ hybridization, we show that the FGF pathway regulates the expression of cwn-1 in the SMs. These results demonstrate an interaction between FGF and Wnt in C. elegans development and vulval cell lineage polarity, and highlight the promiscuous nature of Wnts and the importance of Wnt gradient directionality within C. elegans. PMID:23946444

Minor, Paul J; He, Ting-Fang; Sohn, Chang Ho; Asthagiri, Anand R; Sternberg, Paul W

2013-08-14

249

Controlled growth of carbon nanotubes on electrodes under different bias polarity  

NASA Astrophysics Data System (ADS)

Carbon nanotubes (CNTs) of different alignments, such as surface-bounded and vertically aligned arrays, enable applications in different fields. In this study, controlled growth of CNTs with different alignments was achieved by electrically biasing catalyzed electrodes with different polarities in a laser-assisted chemical vapor deposition process. CNT growth was suggested to be guided by the movement of electrically charged catalyst-nanoparticles under the influence of an external electric field. This discovery provides a convenient approach to control the alignment of CNT arrays for different applications.

Gao, Y.; Zhou, Y. S.; Xiong, W.; Mahjouri-Samani, M.; Mitchell, M.; Lu, Y. F.

2009-10-01

250

Tunable and rotatable polarization controller using photonic crystal fiber filled with liquid crystal  

NASA Astrophysics Data System (ADS)

We design and fabricate a compact tunable and rotatable polarization controller using liquid crystal photonic band gap fibers. The electrically and thermally induced phase shift in the Poincaré sphere and corresponding birefringence change are measured. The direction of the electric field is managed by connecting four electrodes in different electrode configurations, and the thermal tunability is controlled by on-chip heaters. According to the results, a quarter-wave plate and a half-wave plate working in the wavelength range of 1520-1600 nm are experimentally demonstrated.

Wei, Lei; Alkeskjold, Thomas Tanggaard; Bjarklev, Anders

2010-06-01

251

Precise, motion-free polarization control in Second Harmonic Generation microscopy using a liquid crystal modulator in the infinity space  

PubMed Central

Second Harmonic Generation (SHG) microscopy coupled with polarization analysis has great potential for use in tissue characterization, as molecular and supramolecular structural details can be extracted. Such measurements are difficult to perform quickly and accurately. Here we present a new method that uses a liquid crystal modulator (LCM) located in the infinity space of a SHG laser scanning microscope that allows the generation of any desired linear or circular polarization state. As the device contains no moving parts, polarization can be rotated accurately and faster than by manual or motorized control. The performance in terms of polarization purity was validated using Stokes vector polarimetry, and found to have minimal residual polarization ellipticity. SHG polarization imaging characteristics were validated against well-characterized specimens having cylindrical and/or linear symmetries. The LCM has a small footprint and can be implemented easily in any standard microscope and is cost effective relative to other technologies.

Lien, Chi-Hsiang; Tilbury, Karissa; Chen, Shean-Jen; Campagnola, Paul J.

2013-01-01

252

10Gb\\/s data transmission experiments over polymeric waveguides with 850-nm wavelength multimode VCSEL array  

Microsoft Academic Search

A practical transmitter module was demonstrated, using a metal optical bench (MOB) and a tapered polymeric waveguide. The transmitter module was prepared for optical printed circuit board, which consists of the MOB, the driver chips, the vertical-cavity surface-emitting laser (VCSEL), and a tapered polymeric waveguide. We report a 10-Gb\\/s 223-1 pseudorandom bit sequence nonreturn-to-zero of data transmission from VCSEL to

Keun Byoung Yoon; In-Kui Cho; Seung-Ho Ahn

2004-01-01

253

Dynamic nuclear polarization of {sup 29}Si nuclei in isotopically controlled phosphorus doped silicon  

SciTech Connect

Dynamic nuclear polarization (DNP) of {sup 29}Si nuclei in isotopically controlled silicon single crystals with the {sup 29}Si isotope abundance f{sub 29Si} varied from 1.2% to 99.2% is reported. It was found that both the DNP enhancement and {sup 29}Si nuclear spin-lattice relaxation time under saturation of the electron paramagnetic resonance transitions of phosphorus donors increase with the decrease in the {sup 29}Si abundance. A remarkably large steady-state DNP enhancement, E{sup ss}=2680 which is comparable to the theoretical upper limit of 3310, has been achieved through the ''resolved'' solid effect that has been identified clearly in the f{sub 29Si}=1.2% sample. The DNP enhancement depends not only on the {sup 29}Si abundance but also on the electron spin-lattice relaxation time that can be controlled by temperature and/or illumination. The linewidth of {sup 29}Si NMR spectra after DNP shows a linear dependence on f{sub 29Si} for f{sub 29Si}{<=}10% and changes to a square-root dependence for f{sub 29Si}{>=}50%. Comparison of experimentally determined nuclear polarization time with nuclear spin diffusion coefficients indicates that the rate of DNP is limited by the polarization transfer rather than by spin diffusion.

Hayashi, Hiroshi; Itahashi, Tatsumasa; Itoh, Kohei M.; Vlasenko, Leonid S.; Vlasenko, Marina P. [School of Fundamental Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); A. F. Ioffe Physico-Technical Institute, 194021 Saint Petersburg (Russian Federation)

2009-07-15

254

Polarization-resolved SHG microscopy of rat-tail tendon with controlled mechanical strain  

NASA Astrophysics Data System (ADS)

We combined polarization-resolved SHG microscopy with mechanical assays in rat-tail-tendon and measured collagen remodeling upon controlled stretching. This approach aimed to analyze the relationship between macroscopic response and sub-micrometer scale organization of collagen fibrils. We observed a straightening of the crimps followed by a sliding of the fibrils with increasing stretching of the tendon fascicles. Polarization resolution of the SHG images provided complementary information about the orientation dispersion of collagen fibrils within the focal volume and enabled monitoring of collagen remodeling at the sub-micrometer scale. Our approach can be readily generalized to other tissues and should bring new valuable information about biomechanics of microstructured tissues.

Gusachenko, I.; Goulam Houssen, Y.; Tran, V.; Allain, J.-M.; Schanne-Klein, M.-C.

2013-06-01

255

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

PubMed Central

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.

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

2010-01-01

256

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

NASA Astrophysics Data System (ADS)

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

Xiang, Shui-Ying; Pan, Wei; Yan, Lian-Shan; Luo, Bin; Zou, Xi-Hua; Jiang, Ning; Wen, Kun-Hua

2011-01-01

257

Laser trapping in anisotropic fluids and polarization-controlled particle dynamics  

PubMed Central

Anisotropic fluids are widespread, ranging from liquid crystals used in displays to ordered states of a biological cell interior. Optical trapping is potentially a powerful technique in the fundamental studies and applications of anisotropic fluids. We demonstrate that laser beams in these fluids can generate anisotropic optical trapping forces, even for particles larger than the trapping beam wavelength. Immersed colloidal particles modify the fluid's ordered molecular structures and locally distort its optic axis. This distortion produces a refractive index “corona” around the particles that depends on their surface characteristics. The laser beam can trap such particles not only at their center but also at the high-index corona. Trapping forces in the beam's lateral plane mimic the corona and are polarization-controlled. This control allows the optical forces to be reversed and cause the particle to follow a prescribed trajectory. Anisotropic particle dynamics in the trap varies with laser power because of the anisotropy of both viscous drag and trapping forces. Using thermotropic liquid crystals and biological materials, we show that these phenomena are quite general for all anisotropic fluids and impinge broadly on their quantitative studies using laser tweezers. Potential applications include modeling thermodynamic systems with anisotropic polarization-controlled potential wells, producing optically tunable photonic crystals, and fabricating light-controlled nano- and micropumps.

Smalyukh, Ivan I.; Kachynski, Aliaksandr V.; Kuzmin, Andrey N.; Prasad, Paras N.

2006-01-01

258

Enhanced Scattered Light Imaging of Nanoparticles by Controlling the Polarization Distribution with Photonic Crystals  

NASA Astrophysics Data System (ADS)

An optical microscopy with a high sensitivity and resolution is required for observing semiconductor wafers and biological cells for nanotechnology and biotechnology applications. However, it is difficult to observe samples that are small compared with the optical wavelength since the signal is swamped by background noise such as dark noise and electrical noise and other signals besides that from the sample. Furthermore, light scattered from the sample cannot be focused into a spot in the image plane due to interference of polarized light, resulting in a blurred image that has a low resolution. This study proposes a method for removing the background noise and for improving the image resolution of nanoparticles by controlling the polarization direction. This method can be used to perform optical microscopy with a high sensitivity and resolution. We verify the effectiveness of this method by performing simulations and experiments. Simulations predict that the peak intensity obtained using this method will be 3.4 times higher than that obtained using a conventional microscope and that the resolution of this technique will be 0.43 times smaller than that of conventional microscopy. Experiments show that this method with a photonic crystal utilized as a radial polarization converter is capable of detecting 23-nm-diameter PSLs on a silicon wafer.

Otani, Yuko; Urano, Yuta; Honda, Toshifumi; Watanabe, Masahiro

2013-05-01

259

Polarization control of microwave emission from high power rectangular cross-section gyrotron devices  

Microsoft Academic Search

Results are summarized of experiments on a gyrotron utilizing a rectangular-cross-section (RCS) cavity region. The major issue under investigation is polarization control of microwave emission as a function of magnetic field. The electron beam driver is the Michigan Electron Long Beam Accelerator (MELBA) at parameters: V=0.8 MV, Idiode=1-10 kA, Itube=0.1=0.5 kA, and te-beam=0.4-1.0 ?s. The annular e-beam is spun up

Jonathan M. Hochman; Ronald M. Gilgenbach; Reginald L. Jaynes; Joshua I. Rintamaki; Y. Y. Lau; William E. Cohen; Chris W. Peters; Thomas A. Spencer

1998-01-01

260

Metal Controlled Diastereoselective Self-assembly and Circularly Polarized Luminescence of a Chiral Heptanuclear Europium Wheel  

PubMed Central

The chiral dissymmetric tetradentate ligand SPhbipox (6’-(4-phenyloxazolin-2-yl)-2,2’-bipyridine-6-carboxylic acid) leads to the diastereoselective assembly of a homochiral Eu(III) triangle and of a highly emissive (QY=27%) heptanuclear wheel which is the largest example of chiral luminescent complex of Eu(III) reported to date. We show that the nuclearity of the assembly is controlled by the solvent and the europium cation. All the compounds show large circularly polarized luminescence with an activity which varies with the nature of the assembly (highest for the homochiral trimer).

Bozoklu, Gulay; Gateau, Christelle; Imbert, Daniel; Pecaut, Jacques; Robeyns, Koen; Filinchuk, Yaroslav; Memon, Farah; Muller, Gilles

2012-01-01

261

Polarity controlled by the composition of inorganic recording materials in Al-Si binary system  

NASA Astrophysics Data System (ADS)

A technique was introduced to control the polarity of discs. Inorganic materials of binary Al-Si were used as recording layers in our study. By adjusting the layer thickness of Al and Si individually, we found that over a certain thickness ratio of Al-Si double layers, the reflectivity shift measured by a static tester altered from high-to-low into low-to-high. By using this technique, the feasibility for making both types of discs has been proved according to good testing results from dynamic tester.

Yeh, Ru-Lin; Chang, Hsun-Hao; Chen, Bing-Mau; Yu, Teng-Chien

2004-09-01

262

Self-polarization phenomenon and control of dispersion of synthetic antiferromagnetic nanoparticles for biological applications  

NASA Astrophysics Data System (ADS)

Using a top-down approach, synthetic antiferromagnetic micro/nanoparticles usable for biological applications were prepared. These particles exhibit ``superparamagneticlike'' properties. Their magnetic susceptibility can be accurately controlled by the thickness of the constituting layers. When dispersed in solution, striking differences in their interactions are observed depending on their susceptibility. Above a susceptibility threshold, a phenomenon of self-polarization is observed in zero applied field, resulting in a gradual agglomeration of the particles. In contrast, below the susceptibility threshold, the particles get redispersed in zero field. This is interpreted by a self-consistent model taking into account dipolar interactions between particles and their magnetic susceptibility.

Joisten, H.; Courcier, T.; Balint, P.; Sabon, P.; Faure-Vincent, J.; Auffret, S.; Dieny, B.

2010-12-01

263

Rapidly swept, ultra-widely-tunable 1060 nm MEMS-VCSELs.  

PubMed

Demonstrated are 1060 nm microelectromechanical-systems-based tunable vertical-cavity surface-emitting lasers (MEMS-VCSELs) with a 100 nm continuous tuning range under repetitively scanned operation at rates beyond 500 kHz and a 90 nm continuous tuning range under static operation. These devices employ a thin strained InGaAs multiple quantum well active region integrated with a fully oxidised GaAs/AlxOy bottom mirror and a suspended dielectric top mirror. The devices are optically pumped via 850 nm light. These ultra-widely tunable lasers represent the first MEMS-VCSELs reported in this wavelength range, and are ideally suited for application in ophthalmic swept-source optical coherence tomography. PMID:23520409

Jayaraman, V; Cole, G D; Robertson, M; Burgner, C; John, D; Uddin, A; Cable, A

2012-10-11

264

Widely tunable singlemode surface micro-machined MEMS-VCSELs operating at 1.95-?m  

NASA Astrophysics Data System (ADS)

We present surface micro-machined micro-electro mechanical-system (MEMS) tunable vertical-cavity surfaceemitting lasers (VCSEL) with rectangular and triangular shaped quantum wells (QWs) emitting around 1:95 ?m predestined for broadband tunable diode laser absorption spectroscopy. The VCSELs show single-mode operation and high side-mode suppression-ratio SMSR < 50 dB within the whole tuning range of 50nm and 35 nm, the fibre-coupled optical power of 1:0mW and 1:76mW and the threshold current of 2:5mA and 2:0mA for the rectangular and triangular shaped QWs respectively. The 3 dB modulation frequency of the MEMS is 110 Hz.

Zogal, Karolina; Gruendl, Tobias; Gierl, Christian; Paul, Sujoy; Grasse, Christian; Meissner, Peter; Amann, Marcus-Christian; Kueppers, Franko

2013-03-01

265

Quantum control of molecular motion including electronic polarization effects with a two-stage toolkit.  

PubMed

A method for incorporating strong electric field polarization effects into optimal control calculations is presented. A Born-Oppenheimer-type separation, referred to as the electric-nuclear Born-Oppenheimer (ENBO) approximation, is introduced in which variations of both the nuclear geometry and the external electric field are assumed to be slow compared with the speed at which the electronic degrees of freedom respond to these changes. This assumption permits the generation of a potential energy surface that depends not only on the relative geometry of the nuclei but also on the electric field strength and on the orientation of the molecule with respect to the electric field. The range of validity of the ENBO approximation is discussed in the paper. A two-stage toolkit implementation is presented to incorporate the polarization effects and reduce the cost of the optimal control dynamics calculations. As an illustration of the method, it is applied to optimal control of vibrational excitation in a hydrogen molecule aligned along the field direction. Ab initio configuration interaction calculations with a large orbital basis set are used to compute the H-H interaction potential in the presence of the electric field. The significant computational cost reduction afforded by the toolkit implementation is demonstrated. PMID:15836023

Balint-Kurti, Gabriel G; Manby, Frederick R; Ren, Qinghua; Artamonov, Maxim; Ho, Tak-San; Rabitz, Herschel

2005-02-22

266

High-total-dose gamma and neutron radiation tolerance of VCSEL assemblies  

NASA Astrophysics Data System (ADS)

Optical fiber technology is seriously considered for communication and monitoring applications during the operation and maintenance of future thermonuclear fusion reactors. Their environment is characterized, in particular, by possibly high gamma dose-rates and total doses in excess of 10 MGy. In addition, the maintenance equipment might be stored in close vicinity of the reactor during its operation and therefore the communication devices might also be exposed to a substantial neutron fluence. The feasibility of applying photonic technology in these radiation fields therefore needs to be assessed. Whereas many reports deal with the radiation behavior of a variety of fiber-optic devices, only little information is available on the radiation tolerance at high total dose (e.g. > 1 MGy). We describe our recent results obtained on vertical-cavity surface-emitting laser (VCSEL) assemblies. We have conducted high total dose (up to 20 MGy) irradiation experiments on such devices, which confirmed their excellent gamma radiation hardness. The optical power loss at nominal forward current was less than 2 dB and the threshold current remained unaltered. We have also irradiated these devices with neutrons inside the BR1 reactor (SCK•CEN, Mol, Belgium) up to a total fluence on the order of 1015 n×cm-2. The response of VCSELs to neutrons is, as expected, different from that to gamma radiation. VCSELs previously exposed to gamma rays exhibited an accelerated degradation under neutron radiation compared to not pre-irradiated devices. The beneficial effect of applying a continuous forward bias to the VCSELs is also evidenced.

Berghmans, Francis; Van Uffelen, Marco; Decréton, Marc C.

2002-09-01

267

A microwave frequency reference based on VCSEL-driven dark line resonances in Cs vapor  

Microsoft Academic Search

Dark line resonances, narrowed with a buffer gas to less than 100 Hz width, are observed in a Cs vapor cell using a directly modulated vertical-cavity surface-emitting laser (VCSEL). An external oscillator locked to one of these resonances exhibits a short-term stability of ?y(?)=9.3×10-12\\/??, which drops to 1.6×10-12 at 100 s. A physics package for a frequency-reference based on this

J. Kitching; S. Knappe; M. Vukicevic; L. Hollberg; R. Wynands; W. Weidmann

2000-01-01

268

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

Microsoft Academic Search

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

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

2006-01-01

269

VCSELs with a high-index-contrast grating for mode-division multiplexing  

NASA Astrophysics Data System (ADS)

Novel VCSEL structure with a high-index-contrast grating (HCG) mirror that can selectively choose one of two LP01 and four LP11 modes is proposed and numerically investigated. This can be achieved by designing the spatial reflectivity profile of the HCG so that the HCG gives a LP mode of interest the highest modal reflectivity among six LP modes. This approach may considerably miniaturize the light source module for mode-division multiplexing.

Ran, Qijiang; Mørk, Jesper

2013-03-01

270

Design and Assessment of a Circuit and Layout Level Radiation Hardened CMOS VCSEL Driver  

Microsoft Academic Search

The radiation hard design of a 155 Mb\\/s, 0.7 mum CMOS driver for a vertical-cavity surface-emitting laser (VCSEL) is presented. The circuit features enhanced tolerance to radiation induced shifts in the device characteristics by employing a replica-based feedback mechanism. The layout was achieved using an in-house developed radiation hardened component library. At a low dose rate of 4.5 Gy\\/h or

Paul Leroux; Steven Lens; Reinhard Voorspoels; Marco Van Uffelen; Wouter De Cock; Michiel Steyaert; Francis Berghmans

2007-01-01

271

Remote State Preparation: Arbitrary remote control of photon polarizations for quantum communication  

Microsoft Academic Search

By using a partial polarizer to apply a generalized polarization measurement to one photon of a polarization- entangled pair, we remotely prepare single photons in arbitrary polarization qubits. Specifically, we are able to produce a range of states of any desired degree of mixedness or purity, over (and within) the entire Poincare sphere, with a typical fidelity exceeding 99.5%. Moreover,

N. A. Peters; T.-C. Wei; P. G. Kwiat

272

Remote state preparation: arbitrary remote control of photon polarizations for quantum communication  

Microsoft Academic Search

By using a partial polarizer to apply a generalized polarization measurement to one photon of a polarization entangled pair, we remotely prepare single photons in arbitrary polarization qubits. Specifically, we are able to produce a range of states of any desired degree of mixedness or purity, over (and within) the entire Poincare sphere, with a typical fidelity exceeding 99.5%. Moreover,

N. A. Peters; J. T. Barreiro; M. E. Goggin; T.-C. Wei; P. G. Kwiat

2005-01-01

273

Fabrication, Packaging, and Performance of VCSELs and Photodetectors for Space Applications  

SciTech Connect

Optocouplers are used for a variety of applications aboard spacecraft including electrical isolation, switching and power transfer. Commercially available light emitting diode (LED)-based optocouplers have experienced severe degradation of light output due to extensive displacement damage occurring in the semiconductor lattice caused by energetic proton bombardment. A new optocoupler has been designed and fabricated which utilizes vertical cavity surface emitting laser (VCSEL) and resonant cavity photodetector (RCPD) technologies for the optocoupler emitter and detector, respectively. Linear arrays of selectively oxidized GaAs/AlGaAs VCSELS and RCPDS, each designed to operate at a wavelength of 850nm, were fabricated using an airbridge contacting scheme. The airbridged contacts were designed to improve packaging yields and device reliability by eliminating the use of a polyimide planarizing layer which provided poor adhesion to the bond pad metallization. Details of the airbridged optocoupler fabrication process are reported. Discrete VCSEL and RCPD devices were characterized at temperatures between {minus}100 to 100 C. Devices were packaged in a face-to-face configuration to form a single channel optocoupler and its performance was evaluated under conditions of high-energy proton bombardment.

Armendariz, M.G.; Briggs, R.D.; Choquette, K.D.; Geib, K.M.; Serkland, D.K.

1999-03-09

274

Development of a Compact Optical-MEMS Scanner with Integrated VCSEL Light Source and Diffractive Optics  

SciTech Connect

In this work the design and initial fabrication results are reported for the components of a compact optical-MEMS laser scanning system. This system integrates a silicon MEMS laser scanner, a Vertical Cavity Surface Emitting Laser (VCSEL) and passive optical components. The MEMS scanner and VCSEL are mounted onto a fused silica substrate which serves as an optical interconnect between the devices. Two Diffractive Optical Elements (DOEs) are etched into the fused silica substrate to focus the VCSEL beam and increase the scan range. The silicon MEMS scanner consists of an actuator that continuously scans the position of a large polysilicon gold-coated shuttle containing a third DOE. Interferometric measurements show that the residual stress in the 500 {micro}m x 1000 {micro}m shuttle is extremely low, with a maximum deflection of only 0.18{micro}m over an 800 {micro}m span for an unmetallized case and a deflection of 0.56{micro}m for the metallized case. A conservative estimate for the scan range is {approximately}{+-}4{degree}, with a spot size of about 0.5 mm, producing 50 resolvable spots. The basic system architecture, optical and MEMS design is reported in this paper, with an emphasis on the design and fabrication of the silicon MEMS scanner portion of the system.

Krygowski, Thomas W.; Reyes, David; Rodgers, M. Steven; Smith, James H.; Warren, Mial; Sweatt, William; Blum-Spahn, Olga; Wendt, Joel R.; Asbill, Randy

1999-06-30

275

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

NASA Astrophysics Data System (ADS)

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 the polarization direction using an external bias, we could switch the transport characteristics between forward and reverse diodes. Our system is characterized with a rectangular polarization-hysteresis loop with which we confirmed that the diode-polarity switching occurred at the ferroelectric coercive voltage. Moreover, we observed a simultaneous switching of the diode polarity and the associated photovoltaic response dependent on the ferroelectric domain configurations. Our detailed study suggests that the polarization charge can affect the Schottky barrier at the ferroelectric/metal interfaces, resulting in a modulation of the interfacial carrier injection. The amount of polarization-modulated carrier injection can affect the transition voltage value at which a space-charge-limited bulk current-voltage (J-V) behavior is changed from Ohmic (i.e., J ? V) to nonlinear (i.e., J ? Vn with n ? 2). This combination of bulk conduction and polarization-modulated carrier injection explains the detailed physical mechanism underlying the switchable diode effect in ferroelectric capacitors.

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

2011-09-01

276

Polarity, cell division, and out-of-equilibrium dynamics control the growth of epithelial structures.  

PubMed

The growth of a well-formed epithelial structure is governed by mechanical constraints, cellular apico-basal polarity, and spatially controlled cell division. Here we compared the predictions of a mathematical model of epithelial growth with the morphological analysis of 3D epithelial structures. In both in vitro cyst models and in developing epithelial structures in vivo, epithelial growth could take place close to or far from mechanical equilibrium, and was determined by the hierarchy of time-scales of cell division, cell-cell rearrangements, and lumen dynamics. Equilibrium properties could be inferred by the analysis of cell-cell contact topologies, and the nonequilibrium phenotype was altered by inhibiting ROCK activity. The occurrence of an aberrant multilumen phenotype was linked to fast nonequilibrium growth, even when geometric control of cell division was correctly enforced. We predicted and verified experimentally that slowing down cell division partially rescued a multilumen phenotype induced by altered polarity. These results improve our understanding of the development of epithelial organs and, ultimately, of carcinogenesis. PMID:24145168

Cerruti, Benedetta; Puliafito, Alberto; Shewan, Annette M; Yu, Wei; Combes, Alexander N; Little, Melissa H; Chianale, Federica; Primo, Luca; Serini, Guido; Mostov, Keith E; Celani, Antonio; Gamba, Andrea

2013-10-21

277

Dynamic nuclear polarization and optimal control spatial-selective 13C MRI and MRS  

NASA Astrophysics Data System (ADS)

Aimed at 13C metabolic magnetic resonance imaging (MRI) and spectroscopy (MRS) applications, we demonstrate that dynamic nuclear polarization (DNP) may be combined with optimal control 2D spatial selection to simultaneously obtain high sensitivity and well-defined spatial restriction. This is achieved through the development of spatial-selective single-shot spiral-readout MRI and MRS experiments combined with dynamic nuclear polarization hyperpolarized [1-13C]pyruvate on a 4.7 T pre-clinical MR scanner. The method stands out from related techniques by facilitating anatomic shaped region-of-interest (ROI) single metabolite signals available for higher image resolution or single-peak spectra. The 2D spatial-selective rf pulses were designed using a novel Krotov-based optimal control approach capable of iteratively fast providing successful pulse sequences in the absence of qualified initial guesses. The technique may be important for early detection of abnormal metabolism, monitoring disease progression, and drug research.

Vinding, Mads S.; Laustsen, Christoffer; Maximov, Ivan I.; Søgaard, Lise Vejby; Ardenkjær-Larsen, Jan H.; Nielsen, Niels Chr.

2013-02-01

278

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

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

279

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

PubMed

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

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

280

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

PubMed Central

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.

Schnell, Michael; Savert, Alexander; Uschmann, Ingo; Reuter, Maria; Nicolai, Maria; Kampfer, Tino; Landgraf, Bjorn; Jackel, Oliver; Jansen, Oliver; Pukhov, Alexander; Kaluza, Malte Christoph; Spielmann, Christian

2013-01-01

281

Simulation of Polarization Switching in Vertical-Cavity Surface-Emitting Lasers under Quasi-Decreasing Step Current Operation  

NASA Astrophysics Data System (ADS)

Numerical simulation of the polarization switching (PS) in vertical-cavity surface-emitting lasers (VCSELs) induced by quasi-decreasing step current was investigated in this research. Linear Current Gain model (LCG) was used to simulate the polarization switching delay phenomena and these numerical simulation results show a good match to the experimental results. The initial current and the intrinsic PS current were set at 10 mA and 8 mA respectively and the target current was less than the intrinsic PS current. It is observed that the polarization switched to orthogonal direction with a delay time as the bias current is a quasi-decreasing step current. These simulation results help us to give a precise understanding of polarization switching in VCSEL driven by quasi-decreasing step current.

Quadir, Shaham; Chin, Pei-Hou; Kuo, Wang-Chuang; Wu, Yu-Heng; Yen, Tsu-Chiang

2013-03-01

282

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

PubMed

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

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

2012-01-01

283

Extended Lagrangian formalism applied to temperature control and electronic polarization effects in molecular dynamics simulations  

NASA Astrophysics Data System (ADS)

This paper describes the implementation of the extended Lagrangian method to control the temperature, and to compute electronic polarization effects in molecular dynamics simulations of complex systems. Temperature control is achieved by introducing an extra variable coupled to the velocities, whereas induced dipoles are represented as Drude oscillators that respond to the electric field produced by the surrounding particles. Computing the contribution from the induced dipoles therefore requires no iteration or matrix inversion procedures and is as fast as evaluating classical non-bonded interactions. It is shown how a judicious choice of the integration algorithm makes the implementation of both procedures straightforward. The application in a molecular dynamics procedure, which integrates both methods, is illustrated in the constant-temperature simulations of pure water and methane-water mixtures, in which the solvent is represented by the mean-field SPC or by the polarizable PSPC water models.

van Belle, D.; Wodak, S. J.

1995-09-01

284

Controlled generation of four-photon polarization-entangled decoherence-free states with conventional photon detectors  

SciTech Connect

We propose a protocol for the controlled generation of four-photon polarization-entangled decoherence-free states with a certain success probability. The proposed setup involves simple linear optical elements, two single-photon polarzaition entangled states, a pair of two-photon polarization entangled states, and conventional photon detectors that only distinguish the vacuum and nonvacuum Fock number states. This makes the protocol more realizable in experiments.

Xia Yan [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Department of Physics, College of Science, Yanbian University, Yanji, Jilin 133002 (China); Song Jie; Song Heshan [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Zhang Shou [Department of Physics, College of Science, Yanbian University, Yanji, Jilin 133002 (China)

2009-01-15

285

Optical beam steering using MEMS-controllable microlens array  

Microsoft Academic Search

Novel, two-dimensional MEMS-controllable microlens array has been integrated with a vertical cavity surface emitting laser (VCSEL) array using flip-chip assembly. The MEMS\\/VCSEL hybrid system is built as an efficient and reliable smart pixel array for board-to-board or chip-to-chip optical interconnects in digital systems. Theory including geometrical and Fourier transform analysis and beam steering experimental results are presented. By translating polymer

Adisorn Tuantranont; V. M. Bright; J. Zhang; W. Zhang; J. A. Neff; Y. C. Lee

2001-01-01

286

Polarization-Controlled Differentiation of Human Neural Stem Cells Using Synergistic Cues from the Patterns of Carbon Nanotube Monolayer Coating  

PubMed Central

We report a method for selective growth and structural-polarization-controlled neuronal differentiation of human neural stem cells (hNSCs) into neurons using carbon nanotube network patterns. The CNT patterns provide synergistic cues for the differentiation of hNSCs in physiological solution and an optimal nanotopography at the same time with good biocompatibility. We demonstrated a polarized-controlled neuronal differentiation at the level of individual NSCs. This result should provide a stable and versatile platform for controlling the hNSC growth because CNT patterns are known to be stable in time unlike commonly-used organic molecular patterns.

Park, Sung Young; Choi, Dong Shin; Jin, Hye Jun; Park, Juhun; Byun, Kyung-Eun; Lee, Ki-Bum; Hong, Seunghun

2011-01-01

287

New optical disk system of ultra high density and high data rate using 2D VCSEL array: nanofabrication for evanescent light enhancement by surface plasmon polariton  

Microsoft Academic Search

Higher density optical disk system of super parallel optical heads using a two dimensional VCSEL array are described for the higher data transfer rate and technological capability. Optical heads of the VCSEL array and microlens array play a key role to get higher evanescent light from a small aperture for the optical disk system, of which disk surface is coated

Yoshiki Masuda; Takayuki Kirigaya; Kazuma Kurihara; Satoshi Mitsugi

2004-01-01

288

Topographical control over seasonal sublimation of the Mars North polar cap  

NASA Astrophysics Data System (ADS)

Spectroscopic analysis of the Mars permanent North polar cap (NPC) by MEX/OMEGA and MRO/CRISM instruments reveal apparent seasonal changes in the ice morphology during the summer season, implying that ice surface becomes increasingly coarse during the progression of season. This general trend is non-uniform in space, being particularly strong near inner edges of the spiral terraces. The comparison of spectroscopic data with high-resolution images returned by MRO/HiRISE camera shows that the extent of NPC apparent seasonal change revealed by NIR spectroscopy correlates with the orientation of dunes on the ice surface. In the inner edges of the spiral terraces, dunes are aligned preferentially in zonal direction, implying their formation under control of the meridional winds. In turn at the outer edges, where seasonal changes are less evident, dunes are aligned mostly in the meridional direction, assuming impact of the zonal atmospheric flow. Indeed, zonally aligned dunes have better conditions in terms of sunlight exposure, and their surface is expected to reveal faster aging. However the question arises what processes are responsible for this alignment. We hypothesize that the dunes are formed under strong control of the local meteorology, dominated with competing mesoscale zonal circulation and local katabatic winds. In most cases the latter have meridional direction and maximize near the steepest relief, i.e. southward of the boundary between neighboring terraces. In some cases katabatic winds directions are in the strong interconnection with certain local and mesoscale topography features. Thus seasonal changes of the ice surface microstructure are connected with the relief on the scale of tens of meters, which in turn may be formed under influence of the local wind pattern controlled by large-scale relief of the North polar cap.

Evdokimova, N. A.; Rodin, A. V.; Appere, T.

2012-09-01

289

Control parameters for polar ionospheric convection patterns during northward interplanetary magnetic field  

SciTech Connect

Using the DE 2 electric field data from 191 dawn-dusk passes, the authors have sought parameters that distinguish between the various polar ionospheric convection patterns for northward IMF. The passes were divided into the daytime and nightime sectors, and categorized the convection into three convection patterns for each sector by focusing on flow having a horizontal scale of > 150 km. The three daytime sector patterns are convection of reverse polarity, i.e., sunward at the highest latitudes and antisunward on both sides of the sunward flow region, irregular convection having a single antisunward flow region at the highest latitude, which is similiar to the pattern for southward IMF. The IMF clock (B{sub y}/B{sub z}) angle, the Earth`s dipole tilt angle, and the IMF B{sub x}/B{sub z} angle measured from the dipole axis are the patterns that cause the difference in the three convection pattern. In the nighttime sector three similar convection patterns are identified. The occurrence of these patterns is controlled by the IMF clock angle. Thus, the convection pattern for northward IMF is very sensitive to the direction of the IMF. The magnetospheric sources for the convection patterns are discussed. 18 refs., 5 fig.

Taguchi, S.; Hoffman, R.A. [NASA Goddard Space Flight Center, Greenbelt, MD (United States)

1996-03-15

290

Development and characterization of controlled release polar lipid microparticles of candesartan cilexetil by solid dispersion  

PubMed Central

Candesartan cilexetil (CC) is a newer class of angiotensin II receptor antagonist used for the treatment of hypertension. The solubility of the CC is very poor and its oral bioavailability is only 15%. The controlledrelease polar lipid microparticles of CC (formulations F1, F2, F3 and F4) were prepared using variable erodible lipophilic excipients like hydrogenated castor oil, stearic acid, cetostearyl alcohol and carnauba wax by fusion method. The particle sizes of polar lipid microparticles were less than 50 microns and they were irregular in shape. Drug content ranged between 98.96 ± 2.1 and 101.9 ± 1.6% were present in all the formulations. The formulation F3 showed better drug release throughout the study period in a controlled release manner. Moreover, the in vitro release showed that all the formulations were best fitted to Higuchi model. Accelerated stability studies indicated that there was no significant changes in the chemical and physical characteristics of the formulated drug product during initial and at the end of the study period. The FTIR and DSC studies showed that there was no interaction between the drug and lipophilic excipients and no polymorphic transitions in all formulations. The X-ray diffraction peak of solid dispersion indicated that the crystalline nature of CC disappeared and no new peaks could be observed, suggesting the absence of interaction between drug and excipients.

Kamalakkannan, V; Puratchikody, A; Ramanathan, L

2013-01-01

291

Shot noise and s-o coherent control of entangled and spin polarized electrons.  

NASA Astrophysics Data System (ADS)

We extend our previous work on shot noise for entangled and spin polarized electrons in a beam-splitter geometry with spin-orbit (s-o) interaction in the incoming leads. Besides accounting for both the Dresselhaus and the Rashba spin-orbit terms, we present general formulas for the shot noise of singlet and triplets states derived within the scattering approach. We determine the full scattering matrix of the system for the case of leads with two orbital channels coupled via a weak s-o interaction inducing channel anti-crossings. We show that this interband coupling gives rise to an additional modulation angle which allows for further coherent control of the electrons. We also derive explicit shot noise formulas for a variety of correlated pairs (e.g., Bell states) and lead spin polarizations. Interestingly, the singlet and textiteach of the triplets defined along the quantization axis perpendicular to lead 1 and in the plane of the beam splitter display distinctive shot noise for injection energies near the channel anti-crossings -- one can tell apart all the triplets through noise measurements. Finally, we find that backscattering within lead 1 reduces the visibility of the noise oscillations. This work was supported by NCCR Nanoscale Science, EU-Spintronics, CNPq, Swiss NSF, DARPA, ARO, and ONR (to appear in PRB).

Egues, J. Carlos; Burkard, Guido; Saraga, Daniel; Schliemann, John; Loss, Daniel

2006-03-01

292

Polarity controls forces governing asymmetric spindle positioning in the Caenorhabditis elegans embryo.  

PubMed

Cell divisions that create daughter cells of different sizes are crucial for the generation of cell diversity during animal development. In such asymmetric divisions, the mitotic spindle must be asymmetrically positioned at the end of anaphase. The mechanisms by which cell polarity translates to asymmetric spindle positioning remain unclear. Here we examine the nature of the forces governing asymmetric spindle positioning in the single-cell-stage Caenorhabditis elegans embryo. To reveal the forces that act on each spindle pole, we removed the central spindle in living embryos either physically with an ultraviolet laser microbeam, or genetically by RNA-mediated interference of a kinesin. We show that pulling forces external to the spindle act on the two spindle poles. A stronger net force acts on the posterior pole, thereby explaining the overall posterior displacement seen in wild-type embryos. We also show that the net force acting on each spindle pole is under control of the par genes that are required for cell polarity along the anterior-posterior embryonic axis. Finally, we discuss simple mathematical models that describe the main features of spindle pole behaviour. Our work suggests a mechanism for generating asymmetry in spindle positioning by varying the net pulling force that acts on each spindle pole, thus allowing for the generation of daughter cells with different sizes. PMID:11214323

Grill, S W; Gönczy, P; Stelzer, E H; Hyman, A A

2001-02-01

293

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

PubMed

We demonstrate an optically controlled polarizer at ~1323 nm using a ladder transition in a Rb vapor cell. The lower leg of the 5S1/2,F = 1->5P1/2,F = 1,2->6S1/2,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

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

2013-10-21

294

Universal quantum control of two-electron spin quantum bits using dynamic nuclear polarization  

NASA Astrophysics Data System (ADS)

One fundamental requirement for quantum computation is to carry out universal manipulations of quantum bits at rates much faster than the qubit's rate of decoherence. Recently, fast gate operations have been demonstrated in logical spin qubits composed of two electron spins where the rapid exchange of the two electrons permits electrically controllable rotations around one axis of the qubit. However, universal control of the qubit requires arbitrary rotations around at least two axes. Here, we show that by subjecting each electron spin to a magnetic field of different magnitude, we achieve full quantum control of the two-electron logical spin qubit with nanosecond operation times. Using a single device, a magnetic-field gradient of several hundred millitesla is generated and sustained using dynamic nuclear polarization of the underlying Ga and As nuclei. Universal control of the two-electron qubit is then demonstrated using quantum state tomography. The presented technique provides the basis for single- and potentially multiple-qubit operations with gate times that approach the threshold required for quantum error correction.

Foletti, Sandra; Bluhm, Hendrik; Mahalu, Diana; Umansky, Vladimir; Yacoby, Amir

2009-12-01

295

Polarized linewidth-controllable double-trapping electromagnetically induced transparency spectra in a resonant plasmon nanocavity  

NASA Astrophysics Data System (ADS)

Surface plasmons with ultrasmall optical mode volume and strong near field enhancement can be used to realize nanoscale light-matter interaction. Combining surface plasmons with the quantum system provides the possibility of nanoscale realization of important quantum optical phenomena, including the electromagnetically induced transparency (EIT), which has many applications in nonlinear quantum optics and quantum information processing. Here, using a custom-designed resonant plasmon nanocavity, we demonstrate polarized position-dependent linewidth-controllable EIT spectra at the nanoscale. We analytically obtain the double coherent population trapping conditions in a double-? quantum system with crossing damping, which give two transparent points in the EIT spectra. The linewidths of the three peaks are extremely sensitive to the level spacing of the excited states, the Rabi frequencies and detunings of pump fields, and the Purcell factors. In particular the linewidth of the central peak is exceptionally narrow. The hybrid system may have potential applications in ultra-compact plasmon-quantum devices.

Wang, Luojia; Gu, Ying; Chen, Hongyi; Zhang, Jia-Yu; Cui, Yiping; Gerardot, Brian D.; Gong, Qihuang

2013-10-01

296

Implementing quantum algorithms in hyperfine levels of ultracold polar molecules by optimal control.  

PubMed

We numerically implement quantum algorithms in hyperfine levels of ultracold polar molecules. Logical operations are driven by pulses optimized by optimal control theory. All implementations take place in the lowest two rotational levels of the ground vibrational state of the ground (1)?(+) electronic state, exploiting the richness of the hyperfine energy structure and state mixing in static external fields. We show that it is possible to realize high fidelity complex logical operations with microsecond pulses. The possibility to run algorithms implemented on two interacting molecules is also demonstrated. (41)K(85)Rb and (41)K(87)Rb molecules are considered for the numerical simulations but the results are general and can be extended to other species. PMID:21766136

Pellegrini, Philippe; Vranckx, Stéphane; Desouter-Lecomte, Michèle

2011-07-18

297

Controlling the Hyperfine State of Rovibronic Ground-State Polar Molecules  

SciTech Connect

We report the preparation of a rovibronic ground-state molecular quantum gas in a single hyperfine state and, in particular, the absolute lowest quantum state. This addresses the last internal degree of freedom remaining after the recent production of a near quantum degenerate gas of molecules in their rovibronic ground state, and provides a crucial step towards full control over molecular quantum gases. We demonstrate a scheme that is general for bialkali polar molecules and allows the preparation of molecules in a single hyperfine state or in an arbitrary coherent superposition of hyperfine states. The scheme relies on electric-dipole, two-photon microwave transitions through rotationally excited states and makes use of electric nuclear quadrupole interactions to transfer molecular population between different hyperfine states.

Ospelkaus, S.; Ni, K.-K.; Quemener, G.; Neyenhuis, B.; Wang, D.; Miranda, M. H. G. de; Bohn, J. L.; Ye, J.; Jin, D. S. [JILA, National Institute of Standards and Technology and University of Colorado, and Department of Physics, University of Colorado, Boulder, Colorado 80309-0440 (United States)

2010-01-22

298

Polarized linewidth-controllable double-trapping electromagnetically induced transparency spectra in a resonant plasmon nanocavity  

PubMed Central

Surface plasmons with ultrasmall optical mode volume and strong near field enhancement can be used to realize nanoscale light-matter interaction. Combining surface plasmons with the quantum system provides the possibility of nanoscale realization of important quantum optical phenomena, including the electromagnetically induced transparency (EIT), which has many applications in nonlinear quantum optics and quantum information processing. Here, using a custom-designed resonant plasmon nanocavity, we demonstrate polarized position-dependent linewidth-controllable EIT spectra at the nanoscale. We analytically obtain the double coherent population trapping conditions in a double-? quantum system with crossing damping, which give two transparent points in the EIT spectra. The linewidths of the three peaks are extremely sensitive to the level spacing of the excited states, the Rabi frequencies and detunings of pump fields, and the Purcell factors. In particular the linewidth of the central peak is exceptionally narrow. The hybrid system may have potential applications in ultra-compact plasmon-quantum devices.

Wang, Luojia; Gu, Ying; Chen, Hongyi; Zhang, Jia-Yu; Cui, Yiping; Gerardot, Brian D.; Gong, Qihuang

2013-01-01

299

High temperature operating (>80°C) 795-nm VCSEL based on InAlGaAs MQWs active region  

NASA Astrophysics Data System (ADS)

Design of the active region and analysis of temperature sensitivity of high-temperature operating 795-nm special VCSELs for Chip-Scale Atomic Clock (CSAC) are presented. Composition and thickness of the InAlGaAs multiple quantum wells (MQWs) are optimized at room and elevated temperatures. Temperature sensitivity of the threshold current is analyzed by calculating the temperature dependence of cavity-mode gain over a broad temperature range (25°C-150°C). A self-consistent VCSEL model based on quasi 3D finite element analysis is employed to investigate selfheating effects and temperature distribution in the proposed structure. Output power of 2.5mW is expected from 10?m aperture VCSELs at 10mA current at ambient temperature of 358K.

Zhang, Jian; Ning, Yongqiang; Zhang, Jianwei; Zhang, Xing; Wang, Lijun

2013-09-01

300

Impact of the aperture diameter on the energy efficiency of oxide-confined 850 nm high speed VCSELs  

NASA Astrophysics Data System (ADS)

A new record for energy-efficient oxide-confined 850 nm vertical-cavity surface-emitting lasers (VCSELs) particularly suited for optical interconnects is presented. Error-free performance at 25 Gb/s is achieved with only 56 fJ/bit of dissipated energy per quantum of information. The influence of the oxide-aperture diameter on the energy-efficiency of our VCSELs is determined by comparing the total and dissipated power versus the modulation bandwidth of devices with different aperture diameters. Trade-offs between various parameters such as threshold current, differential quantum efficiency, wall plug efficiency and differential resistance are investigated with respect to energy-efficiency. We show that our present single-mode VCSELs are more energy-efficient than our multimode ones.

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

2013-03-01

301

Mode Control of Vertical-Cavity Surface-Emitting Lasers by Germanium Coating  

Microsoft Academic Search

We have successfully developed a selective surface coating technique to control the modal behavior of the ion-implanted vertical-cavity surface-emitting laser (VCSEL). With selective deposition of a germanium coating by the lift-off process, we could spatially control the threshold gain condition of the VCSEL to support the single transverse mode. The threshold current is 7 mA and single transverse mode operation

Shu-Woei Chiou; Gray Lin; Chien-Ping Lee; Hung-Pin Yang; Chia-Pin Sung

2001-01-01

302

RAB-5 Controls the Cortical Organization and Dynamics of PAR Proteins to Maintain C. elegans Early Embryonic Polarity  

PubMed Central

In all organisms, cell polarity is fundamental for most aspects of cell physiology. In many species and cell types, it is controlled by the evolutionarily conserved PAR-3, PAR-6 and aPKC proteins, which are asymmetrically localized at the cell cortex where they define specific domains. While PAR proteins define the antero-posterior axis of the early C. elegans embryo, the mechanism controlling their asymmetric localization is not fully understood. Here we studied the role of endocytic regulators in embryonic polarization and asymmetric division. We found that depleting the early endosome regulator RAB-5 results in polarity-related phenotypes in the early embryo. Using Total Internal Reflection Fluorescence (TIRF) microscopy, we observed that PAR-6 is localized at the cell cortex in highly dynamic puncta and depleting RAB-5 decreased PAR-6 cortical dynamics during the polarity maintenance phase. Depletion of RAB-5 also increased PAR-6 association with clathrin heavy chain (CHC-1) and this increase depended on the presence of the GTPase dynamin, an upstream regulator of endocytosis. Interestingly, further analysis indicated that loss of RAB-5 leads to a disorganization of the actin cytoskeleton and that this occurs independently of dynamin activity. Our results indicate that RAB-5 promotes C. elegans embryonic polarity in both dynamin-dependent and -independent manners, by controlling PAR-6 localization and cortical dynamics through the regulation of its association with the cell cortex and the organization of the actin cytoskeleton.

Hyenne, Vincent; Tremblay-Boudreault, Thierry; Velmurugan, Ramraj; Grant, Barth D.; Loerke, Dinah; Labbe, Jean-Claude

2012-01-01

303

a Permanent Magnet Hall Thruster for Orbit Control of Lunar Polar Satellites  

NASA Astrophysics Data System (ADS)

Future moon missions devoted to lunar surface remote sensing and to many others scientific exploration topics will require more fine and higher precision 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 life time 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. In the present work, we propose a precise method of orbit eccentricity control based on the use of a low thrust Hall plasma thruster. The proposed method is based on an approach intended to keep the orbital eccentricity of the satellite at low values. A previous work on this subject was made using numerical integration considering two systems: the 3-body problem, Moon-Earth-satellite and the 4-body problem, Moon-Earth-Sun-satellite (??). In such simulation it is possible to follow the evolution of the satellite's eccentricity and find empirical expressions for the length of time needed to occur the collision with the moon. In this work, a satellite orbit eccentricity control maneuvering is proposed. It is based on working parameters of a low thrust propulsion permanent magnet Hall plasma thruster (PMHT), which is been developed at University of Brasilia, Brazil. We studied different arcs of active lunar satellite propulsion in order to be able to introduce a correction of the eccentricity at each cycle. The calculations were made considering a set of different thrust values, from 0.1N up to 0.4N which can be obtained by using the PMHT. In each calculation procedure we measured the length of eccentricity correction provided by active propulsion. From these results we obtained empirical expressions of the time needed for the corrections as a function of the initial altitude and as a function of the thrust value. 1. Winter, O. C. et all in Controlling the Eccentricity of Polar Lunar Orbits with Low Thrust Propulsion, Mathematical Problems in Engineering, vol. on Space Dynamics, 2009.

Ferreira, Jose Leonardo; Silva Moraes, Bruno; Soares Ferreira, Ivan; Cardozo Mour, Decio; Winter, Othon

304

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

NASA Astrophysics Data System (ADS)

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.

Urquhart, Andrew Lee

305

Highly-integrated VCSEL-based optoelectronics for fault-tolerant self-routing optical networks  

NASA Astrophysics Data System (ADS)

The demand for bandwidth and interconnectivity in aerospace and other defense networks and systems continues to expand. To meet this demand while still satisfying the unique requirements of these systems, innovative approaches are needed. For future networks to meet these goals, they will need to have high bandwidths that are scalable to the requirements of particular applications. In addition, the networks need to be very fault tolerant, protocol independent, non-blocking, low latency, and have low power consumption and small size. OptiComp Corporation has developed a unique network architecture where the hardware is distributed across the network, allowing the network to be self routing and highly fault tolerant. This network architecture is enabled by OptiComp's integrated optoelectronic technologies including waveguide coupled VCSELs and detectors, compact WDM, SOAs, and hybrid integration. Waveguide grating couplers that enable a VCSEL to be coupled bidirectionally into an internal waveguide and allow a portion of the light in a waveguide to be tapped off to a detector comprise the core of OptiComp's integrated optoelectronics. This on-chip coupling into and out of a waveguide enables coarse WDM multiplexing and demultiplexing to be accomplished in a very small area with no additional packaging, making the structure more compact and rugged. Waveguide coupled device results will be presented, including high-speed data transmission between waveguide coupled VCSELs and detectors. Preliminary results on waveguide coupled WDM components will also be discussed. In addition to the enabling components, the implementation of the network architecture will also be presented.

Guilfoyle, Peter S.; Cheng, J.; Yang, K.; Patel, K. M.; Louderback, D. A.; Jin, X. J.

2007-04-01

306

Plastic packaging of VCSEL-based fiber optic transceivers for PCS fiber systems  

NASA Astrophysics Data System (ADS)

We have developed VCSEL based fiber optics transceivers for PCS fiber systems. The PCS fiber has a core diameter of 200?m. The relatively large diameter enables the usage of low cost optical connectors for the fiber link and provides wide alignment tolerances. The measured lateral and longitudinal 3dB coupling tolerances are +/-100?m and 500?m, respectively. The VCSEL is integrated with an electronics driver chip and some passive electronics components on a leadframe structure before plastic encapsulation. The hybrid integration on the leadframe enables batch processing to increase throughput and lower manufacturing cost. No full-hermetic sealing is required for the VCSEL chosen. The variation of optical output power is less than 0.2dB from -40°C to 105°C. Eye diagrams show wide open eyes at a data rate of 500Mbit/s at wide temperature range up to 105°C. The technology can go up to data rates in the Gbit/s range, but this is currently not required for the target applications. The module is reliable over 1000 temperature cycles from -40°C to 125°C. For the receiver side we developed high speed MSM photodetectors. The large area MSM photodetectors relax the coupling alignment tolerance to the core of the optical fiber for 80?m and 4000?m in lateral axis and longitudinal axis, respectively. The MSM photodetector is capable of data rates of 3.2Gb/s. At this high speed the sensitivity is better than -18dBm for the MSM photodetector co-packaged with a suitable transimpedance amplifier (TIA).

Ho, Flora; Lui, Ben; Hung, Vincent; Tong, Eric; Yau, Kin; Choi, Thomas; Egnisaban, Gomer; Mangente, Tony; Ng, Steven; Ng, Amy; Cheng, Sing; Cheung, Edwin; Wipiejewski, Torsten

2005-03-01

307

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

PubMed Central

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.

Strickfaden, Shelly C.

2008-01-01

308

Shot noise and spin-orbit coherent control of entangled and spin-polarized electrons  

NASA Astrophysics Data System (ADS)

We extend our previous work on shot noise for entangled and spin polarized electrons in a beam-splitter geometry with spin-orbit (SO) interaction in one of the incoming leads (lead 1). In addition to accounting for both the Dresselhaus and the Rashba spin-orbit terms, we present general formulas for the shot noise of singlet and triplets states derived within the scattering approach. We determine the full scattering matrix of the system for the case of leads with two orbital channels coupled via weak SO interactions inducing channel anticrossings. We show that this interband coupling coherently transfers electrons between the channels and gives rise to an additional modulation angle—dependent on both the Rashba and Dresselhaus interaction strengths—which allows for further independent coherent control of the electrons traversing the incoming leads. We derive explicit shot noise formulas for a variety of correlated pairs (e.g., Bell states) and lead spin polarizations. Interestingly, the singlet and each of the triplets defined along the quantization axis perpendicular to lead 1 (with the local SO interaction) and in the plane of the beam splitter display distinctive shot noise for injection energies near the channel anticrossings; hence, one can tell apart all the triplets, in addition to the singlet, through noise measurements. We also find that spin-orbit induced backscattering within lead 1 reduces the visibility of the noise oscillations, due to the additional partition noise in this lead. Finally, we consider injection of two-particle wavepackets into leads with multiple discrete states and find that two-particle entanglement can still be observed via noise bunching and antibunching.

Egues, J. Carlos; Burkard, Guido; Saraga, D. S.; Schliemann, John; Loss, Daniel

2005-12-01

309

Control of electron localization in the dissociation of H2+ using orthogonally polarized two-color sequential laser pulses  

NASA Astrophysics Data System (ADS)

Orthogonally polarized two-color sequential laser pulses are used to control the electron localization in the dissociation of H2+. The first single attosecond pulse, whose polarization axis is perpendicular to the molecular axis, excites H2+ from 1s?g to 2p?u, and the time-delayed infrared pulse, whose polarization axis is parallel to the molecular axis, steers the electron between two nuclei. The simulation of the time-dependent Schrödinger equation predicts the control degree of the electron localization can be up to 90% with the current laser technology. In this article, we reveal that the mechanism for this asymmetric localization is due to the mixture of 2p?g and 2p?u, instead of 1s?gand 2p?u in the previous studies.

He, Feng

2012-12-01

310

Manipulation of operation states by polarization control in an erbium-doped fiber laser with a hybrid saturable absorber.  

PubMed

We propose an operation switchable ring-cavity erbium-doped fiber laser (EDFL) via intra-cavity polarization control. By using a semiconductor saturable absorber mirror in the EDFL cavity, stable Q-switching, Q-switched mode-locking, continuous-wave mode-locking, pulse splitting, and harmonic mode-locking pulses can be manipulated simply by detuning a polarization controller while keeping the pump power at the same level. All EDFL operation states can be obtained under the polarization angles detuning within 180 degrees. Continuous-wave mode-locking of EDFL with 800-fs pulsewidth repeated at 4 MHz has been obtained, for which the output pulse energy is 0.5 nJ and the peak power is 625 W. Interaction between solitons and the accompanied non-soliton component will lead to either pulse splitting or 5th-order harmonic mode-locking at repetition rate of 20 MHz. PMID:19293911

Lin, Kuei-Huei; Kang, Jung-Jui; Wu, Hsiao-Hua; Lee, Chao-Kuei; Lin, Gong-Ru

2009-03-16

311

Sub-cycle QAM modulation for VCSEL-based optical fiber links.  

PubMed

QAM modulation utilizing subcarrier frequency lower than the symbol rate is both theoretically and experimentally investigated. High spectral efficiency and concentration of power in low frequencies make sub-cycle QAM signals attractive for optical fiber links with direct modulated light sources. Real-time generated 10-Gbps 4-level QAM signal in a 7.5-GHz bandwidth utilizing subcarrier frequency at a half symbol rate was successfully transmitted over 20-km SMF using an un-cooled 1.5-µm VCSEL. Only 2.5-dB fiber transmission power penalty was observed with no equalization applied. PMID:23389167

Pham, Tien-Thang; Rodes, Roberto; Jensen, Jesper Bevensee; Chang-Hasnain, Connie J; Monroy, Idelfonso Tafur

2013-01-28

312

Quantum image control through polarization entanglement in parametric down-conversion  

Microsoft Academic Search

We demonstrate both theoretically and experimentally the manipulation of quantum entangled images, using the coupling between polarization entanglement and the entanglement for the transverse degrees of freedom. Starting from a two-crystal bright source of polarization-entangled photons, we arrive at a configuration in which we are able to prepare superposition states for the down-converted angular spectrum while the polarization superposition state

D. P. Caetano; P. H. Souto Ribeiro; J. T. Pardal; A. Z. Khoury

2003-01-01

313

Microchip-laser polarization control by destructive-interference resonant-grating mirror  

Microsoft Academic Search

An output coupler comprising a resonant grating submirror monolithically associated with a standard multilayer submirror polarizes the emission of a Nd:YAG microchip laser linearly over its full emission bandwidth by intra-mirror destructive interference for the undesired polarization. A polarization extinction ratio of more than 25 dB is obtained up to 6.1µJ pulse energy. This passively Q-switched laser performance is almost

F. Pigeon; J. C. Pommier; S. Reynaud; O. Parriaux; M. Abdou Ahmed; S. Tonchev; N. Landru; J. P. Fève

2007-01-01

314

Square-wave switching in vertical-cavity surface-emitting lasers with polarization-rotated optical feedback: Experiments and simulations  

NASA Astrophysics Data System (ADS)

We study experimentally the dynamics of vertical-cavity surface-emitting lasers (VCSELs) with polarization-rotated (PR) optical feedback, such that the natural lasing polarization of a VCSEL is rotated by 90 deg and then is reinjected into the laser. We observe noisy, square-wave-like polarization switchings with periodicity slightly longer than twice the delay time, which degrade to (or alternate with) bursts of irregular oscillations. We present results of simulations that are in good agreement with the observations. The simulations demonstrate that close to threshold the regular switching is very sensitive to noise, while well above threshold is less affected by the noise strength. The frequency splitting between the two polarizations plays a key role in the switching regularity, and we identify wide parameter regions where deterministic and robust switching can be observed.

Sukow, David W.; Gilfillan, Taylor; Pope, Brenton; Torre, Maria S.; Gavrielides, Athanasios; Masoller, Cristina

2012-09-01

315

Polarity Therapy for Cancer-Related Fatigue in Patients With Breast Cancer Receiving Radiation Therapy: A Randomized Controlled Pilot Study  

Microsoft Academic Search

Background. Cancer-related fatigue (CRF) is the most frequently reported side effect of cancer and its treatment. In previous research, Polarity Therapy (PT), an energy therapy, was shown to reduce CRF in patients receiving radiation. This study reports on a small randomized clinical trial designed to collect preliminary data on the efficacy of PT compared with an active control (massage) and

Karen M. Mustian; Joseph A. Roscoe; Oxana G. Palesh; Lisa K. Sprod; Charles E. Heckler; Luke J. Peppone; Kenneth Y. Usuki; Marilyn N. Ling; Ralph A. Brasacchio; Gary R. Morrow

2011-01-01

316

Design and performance of broadly tunable, narrow line-width, high repetition rate 1310nm VCSELs for swept source optical coherence tomography  

NASA Astrophysics Data System (ADS)

MEMS tunable vertical cavity surface emitting laser (MEMS-VCSEL) development, over the past two decades, has primarily focused on communications and spectroscopic applications. Because of the narrow line-width, single-mode operation, monolithic fabrication, and high-speed capability of these devices, MEMS-VCSELs also present an attractive optical source for emerging swept source optical coherence tomography (SSOCT) systems. In this paper, we describe the design and performance of broadly tunable MEMS-VCSELs targeted for SSOCT, emphasizing 1310nm operation for cancer and vascular imaging. We describe the VCSEL structure and fabrication, employing a fully oxidized GaAs/AlxOy mirrors in conjunction with dielectric mirrors and InP-based multi-quantum well active regions. We also describe the optimization of MEMs speed and frequency response for SSOCT. Key results include 1310 nm VCSELs with >120nm dynamic tuning range and imaging rates near 1MHz, representing the widest VCSEL tuning range and some of the fastest swept source imaging rates thus far obtained. We also describe how low-noise semiconductor optical amplification boosts average optical power to the required levels, while maintaining superior OCT imaging quality and state of the art system sensitivity. Finally, we present measured multi-centimeter dynamic coherence length, and discuss the implications of VCSELs for OCT.

Jayaraman, V.; Jiang, J.; Potsaid, B.; Cole, G.; Fujimoto, J.; Cable, A.

2012-02-01

317

Drosophila Stardust interacts with Crumbs to control polarity of epithelia but not neuroblasts  

Microsoft Academic Search

Establishing cellular polarity is critical for tissue organization and function. Initially discovered in the landmark genetic screen for Drosophila developmental mutants, bazooka, crumbs, shotgun and stardust mutants exhibit severe disruption in apicobasal polarity in embryonic epithelia, resulting in multilayered epithelia, tissue disintegration, and defects in cuticle formation. Here we report that stardust encodes single PDZ domain MAGUK (membrane-associated guanylate kinase)

Yang Hong; Beth Stronach; Norbert Perrimon; Lily Yeh Jan; Yuh Nung Jan

2001-01-01

318

Organic field effect transistors with dipole-polarized polymer gate dielectrics for control of threshold voltage  

NASA Astrophysics Data System (ADS)

The authors demonstrate organic field effect transistors (OFETs) with a dipole-polarized polyurea for the gate dielectrics. In the dielectrics, the internal electric field induces the mobile charge carrier in the semiconductor layer to the semiconductor-dielectric interface. OFETs with dipole-polarized gate dielectrics exhibit lower threshold voltage. With nonpolarized gate dielectrics, the threshold voltage was -11.4 V, whereas that decreased to -5.3 V with polarized gate dielectrics. In addition to the threshold voltage, polarized gate dielectrics reduced subthreshold swing from 4.1 to 2.4 V/decade at the gate voltage of -20 V. These results show that dipole-polarized polyurea gate dielectrics allow us to operate OFETs with lower power consumption.

Sakai, Heisuke; Takahashi, Yoshikazu; Murata, Hideyuki

2007-09-01

319

Collimating diode laser beams from a large-area VCSEL-array using microlens array  

SciTech Connect

In this letter, the authors demonstrate the fabrication and bonding of a 1 cm {times} 1 cm monolithic two-dimensional (2-D) vertical-cavity surface-emitting laser (VCSEL) array. They coupled the array to a matched microlens array to individually collimate light from each laser. They found the beam divergence of the collimated array to be 1.6{degree} (1/e{sup 2}) for the entire array. Using a 1-cm diameter F2 lens, they were able to focus the collimated beams to a spot of 400 {micro}m in diameter and to couple more than 75% of the array power into a 1-mm core fiber. The results show that it is possible to uniformly bond large area VCSEL arrays to heat sinks, and to collimate light from each element into parallel beams using a single 2-D microlens array. The results also show that the brightness of the focused beam can be further increased with a lens to near 10{sup 5}-W/cm{sup 2} Steradian, a level that is useful for many high-power applications.

Chen, H.L. [Lawrence Livermore National Lab., CA (United States); Francis, D.; Nguyen, T.; Yuen, W.; Li, G.; Chang-Hasnain, C. [Univ. of California, Berkeley, CA (United States)

1999-05-01

320

InAlGaP vertical cavity surface emitting lasers (VCSELs): Processing and performance  

SciTech Connect

(Al{sub y}Ga{sub 1{minus}y}){sup 1{minus}x}In{sub x}P semiconductor alloys lattice-matched to GaAs are widely used in visible optoelectronic devices. One of the most recent developments in this area is the AlGaInP-based red vertical cavity surface emitting laser (VCSEL). These lasers, which employ AlGaInP active regions and AlGaAs distributed Bragg reflectors (DBRs), have demonstrated continuous-wave (CW) lasing over the 630--690 nm region of the spectrum. Applications for these lasers include plastic fiber data communications, laser printing and bar code scanning. In this paper, the authors present an overview of recent developments in the processing and performance of AlGaInP based VCSELs. This overview will include a review of the general heterostructure designs that have been employed, as well as the performance of lasers fabricated by both ion implantation and selective oxidation.

Crawford, M.H.; Choquette, K.D.; Hickman, R.J.; Geib, K.M.

1997-06-01

321

Investigation of temperature characteristics of modern InAsP\\/InGaAsP multi-quantum-well TJ-VCSELs for optical fibre communication  

Microsoft Academic Search

Continuous-wave (CW) performance of modern 1.3-?m InAsP\\/InGaAsP multi-quantum-well (MQW) tunnel-junction vertical-cavity surface-emitting\\u000a diode lasers (TJ-VCSELs) is investigated using our comprehensive self-consistent simulation model to suggest their optimal\\u000a design for room and elevated temperatures. For increasing ambient temperatures, an increase in the VCSEL threshold current\\u000a has happened to be mostly associated with the Auger recombination. Nevertheless, the InAsP\\/InGaAsP VCSELs have been

?. Piskorski; R. P. Sarza?a; W. Nakwaski

2011-01-01

322

Equilibrium polarization of ultrathin PbTiO{<_3} with surface compensation controlled by oxygen partial pressure.  

SciTech Connect

We present a synchrotron x-ray study of the equilibrium polarization structure of ultrathin PbTiO{sub 3} films on SrRuO{sub 3} electrodes epitaxially grown on SrTiO{sub 3} (001) substrates, as a function of temperature and the external oxygen partial pressure (pO{sub 2}) controlling their surface charge compensation. We find that the ferroelectric Curie temperature (T{sub c}) varies with pO{sub 2} and has a minimum at the intermediate pO{sub 2}, where the polarization below T{sub c} changes sign. The experiments are in qualitative agreement with a model based on Landau theory that takes into account the interaction of the phase transition with the electrochemical equilibria for charged surface species. The paraelectric phase is stabilized at intermediate pO2 when the concentrations of surface species are insufficient to compensate either polar orientation.

Highland, M. J.; Fister, T. T.; Fong, D. D.; Fuoss, P. H.; Thompson, C.; Eastman, J. A.; Streiffer, S. K.; Stephenson, G. B. (Chemical Sciences and Engineering Division); ( MSD); ( OTD-PSE); (Northern Illinois Univ.)

2011-01-01

323

Polarized linewidth-controllable double-trapping electromagnetically induced transparency spectra in a resonant plasmon nanocavity.  

PubMed

Surface plasmons with ultrasmall optical mode volume and strong near field enhancement can be used to realize nanoscale light-matter interaction. Combining surface plasmons with the quantum system provides the possibility of nanoscale realization of important quantum optical phenomena, including the electromagnetically induced transparency (EIT), which has many applications in nonlinear quantum optics and quantum information processing. Here, using a custom-designed resonant plasmon nanocavity, we demonstrate polarized position-dependent linewidth-controllable EIT spectra at the nanoscale. We analytically obtain the double coherent population trapping conditions in a double-? quantum system with crossing damping, which give two transparent points in the EIT spectra. The linewidths of the three peaks are extremely sensitive to the level spacing of the excited states, the Rabi frequencies and detunings of pump fields, and the Purcell factors. In particular the linewidth of the central peak is exceptionally narrow. The hybrid system may have potential applications in ultra-compact plasmon-quantum devices. PMID:24096943

Wang, Luojia; Gu, Ying; Chen, Hongyi; Zhang, Jia-Yu; Cui, Yiping; Gerardot, Brian D; Gong, Qihuang

2013-10-07

324

Temperature-controllable spin-polarized current and spin polarization in a Rashba three-terminal double-quantum-dot device  

NASA Astrophysics Data System (ADS)

We propose a Rashba three-terminal double-quantum-dot device to generate a spin-polarized current and manipulate the electron spin in each quantum dot by utilizing the temperature gradient instead of the electric bias voltage. This device possesses a nonresonant tunneling channel and two resonant tunneling channels. The Keldysh nonequilibrium Green's function techniques are employed to determinate the spin-polarized current flowing from the electrodes and the spin accumulation in each quantum dot. We find that their signs and magnitudes are well controllable by the gate voltage or the temperature gradient. This result is attributed to the change in the slope of the transmission probability at the Fermi levels in the low-temperature region. Importantly, an obviously pure spin current can be injected into or extracted from one of the three electrodes by properly choosing the temperature gradient and the gate voltages. Therefore, the device can be used as an ideal thermal generator to produce a pure spin current and manipulate the electron spin in the quantum dot.

Hong, Xue-Kun; Yang, Xi-Feng; Feng, Jin-Fu; Liu, Yu-Shen

2013-05-01

325

Vertical cavity surface emitting laser with nematic and chiral liquid crystals overlay  

NASA Astrophysics Data System (ADS)

A technological platform for a vertical cavity surface emitting laser (VCSEL) with tunable polarization is presented. It is realized by integrating an 850nm VCSEL chip in a liquid crystal (LC) cell that uses photo-alignment (PA) to orient the LC. Two kinds of LC are filled in and form a thin layer over the emitter of the VCSEL: nematic LC or chiral nematic LC (cLC). The VCSEL and the nematic LC layer can be electrically driven with separate electrodes. The polarization state of the laser emission can be controlled by applying an appropriate voltage over the nematic LC layer. The chiral nematic LC has a reflection band that contains the VCSEL emission wavelength, so that one circular polarized mode of the laser emission is reflected as a feedback into the VCSEL. We found that the emission from the VCSEL with cLC overlay is circularly polarized.

Xie, Y.; Beeckman, J.; Woestenborghs, W.; Panajotov, K.; Neyts, K.

2013-03-01

326

Photoelectron emission control with polarized light in plasmonic metal random structures  

SciTech Connect

We report on the possibility of switching the emission rate of photoelectrons by polarization changes in the plasmon excitation light. Photoelectron emission is strongly enhanced in the near-field of localized surface plasmons and occurs from areas with typical diameters of 20-70 nm. The underlying physical process involves excitation of a localized surface plasmon polariton with a femtosecond laser pulse, and a subsequent multi-photon photoemission process. The non-linearity of this process leads to a sharp polarization dependence that allows efficient switching of the emission. We demonstrate that a 90 deg. polarization change can result in on/off ratios of {approx}100 for electron emission.

Word, R. C.; Fitzgerald, J.; Koenenkamp, R. [Physics Department, Portland State University, Portland, Oregon 97201 (United States)

2011-07-25

327

How many molecular layers of polar solvent molecules control chemistry? The concept of compensating dipoles.  

PubMed

The extension of the solvent influence of the shell into the volume of a polar medium was examined by means of anti-collinear dipoles on the basis of the ET (30) solvent polarity scale (i.e., the molar energy of excitation of a pyridinium-N-phenolatebetaine dye; generally: ET =28?591?nm?kcal?mol(-1) /?max ) where no compensation effects were found. As a consequence, solvent polarity effects are concentrated to a very thin layer of a few thousand picometres around the solute where extensions into the bulk solvent become unimportant. A parallelism to the thin surface layer of water to the gas phase is discussed. PMID:23939588

Langhals, Heinz; Braun, Patricia; Dietl, Christian; Mayer, Peter

2013-08-12

328

SHG microscopy excited by polarization controlled beam for three-dimensional molecular orientation measurement  

NASA Astrophysics Data System (ADS)

We have developed a second-harmonic-generation (SGH) microscope to observe the three-dimensional molecular orientation with three-dimensional high spatial resolution using a polarization mode converter. The mode converter consists of a parallel-aligned nematic-liquid-crystal spatial-light-modulator (PAL-SLM) and quarter-waveplates, and converts a incident linearly polarized beam to orthogonal linearly polarized beams or radially polarized beam. We combined the mode converter with SHG microscope to obtain the local information of the three-dimensional molecular orientation. We demonstrated the detection of three-dimensional molecular orientation of collagen fiber in human Achilles' tendon. For high precision three-dimensional molecular orientation measurement, we propose a technique to calibrate the dependence of SHG detection efficiencies on molecular orientation using a liposome.

Yoshiki, K.; Hashimoto, M.; Araki, T.

2006-08-01

329

Magnetic field control of the ferroelectric polarization in multiferroic MnWO4  

NASA Astrophysics Data System (ADS)

The relationship between magnetic order and ferroelectric properties has been investigated for MnWO4. Spontaneous electric polarization is observed in a cycloidal spiral spin phase. The magnetic-field dependence of electric polarization indicates that the noncollinear spin configuration plays a key role for the appearance of ferroelectric phase. Destabilization of the ferroelectric phase and an electric polarization flop from the b direction to the a direction have been observed when a magnetic field is applied along the b axis. On the other hand, the ferroelectric phase is stabilized when a magnetic field is applied along the a-, c- and the spin easy axes. We have also found that the magnetic field induced ferroelectric polarization disappears in a high magnetic field above 12T along the spin easy axis. Theses phenomena provide us useful information for gigantic magnetoelectric effects because MnWO4 is a simple system without rare-earth f-moments.

Taniguchi, Kouji; Abe, Nobuyuki; Arima, Takahisa; Takenobu, Taishi; Iwasa, Yoshihiro

2008-03-01

330

Effective all-optical polarization control induced by Raman nonlinear amplification  

Microsoft Academic Search

An effective all-optical Raman-based stabilization of any input polarization into a single state is experimentally proved exploiting an optimal combination of pump power, fibre PMD and fibre length, identified through systematic numerical simulations.

Maddalena Ferrario; Valentina Gilardone; Paolo Martelli; Lucia Marazzi; Mario Martinelli

2010-01-01

331

A novel role for retromer in the control of epithelial cell polarity  

PubMed Central

The establishment and maintenance of epithelial cell polarity is essential throughout the development and adult life of all multicellular organisms. A key player in maintaining epithelial polarity is Crumbs (Crb), an evolutionarily conserved type-I transmembrane protein initially identified in Drosophila. Correct Crb levels and apical localization are imperative for its function. However, as is the case for many polarized proteins, the mechanisms of its trafficking and strict apical localization are poorly understood. To address these questions, we developed a liposome-based assay to identify trafficking coats and interaction partners of Crb in a native-like environment. Thereby, we demonstrated that Crb is a cargo for Retromer, a trafficking complex required for transport from endosomes to the trans-Golgi-network. The functional importance of this interaction was revealed by studies in Drosophila epithelia, which established Retromer as a novel regulator of epithelial cell polarity and verified the vast potential of this technique.

Pocha, Shirin Meher

2011-01-01

332

Polarity control of intrinsic ZnO films using substrate bias  

NASA Astrophysics Data System (ADS)

The structures and properties of zinc oxide thin films deposited by radio-frequency magnetron sputtering were investigated for different substrate biases applied during deposition. The electrical bias determined the crystalline polarity of a nominally undoped film on an amorphous substrate: films with a (0001) surface and a (0001) surface were produced under positive and negative biases, respectively. Moreover, the polarity of the films was determined at an early stage of the deposition and could not be reversed by switching the substrate bias.

Williams, Jesse R.; Furukawa, Hirokazu; Adachi, Yutaka; Grachev, Sergey; Sønderga?rd, Elin; Ohashi, Naoki

2013-07-01

333

Flamingo, a Seven-Pass Transmembrane Cadherin, Regulates Planar Cell Polarity under the Control of Frizzled  

Microsoft Academic Search

We identified a seven-pass transmembrane receptor of the cadherin superfamily, designated Flamingo (Fmi), localized at cell–cell boundaries in the Drosophila wing. In the absence of Fmi, planar polarity was distorted. Before morphological polarization of wing cells along the proximal-distal (P-D) axis, Fmi was redistributed predominantly to proximal and distal cell edges. This biased localization of Fmi appears to be driven

Tadao Usui; Yasuyuki Shima; Yuko Shimada; Shinji Hirano; Robert W. Burgess; Thomas L. Schwarz; Masatoshi Takeichi; Tadashi Uemura

1999-01-01

334

Modeling of the laser polarization as control parameter in self-organized surface pattern.  

PubMed

To shed light on nanopattern formation upon femtosecond laser ablation, an adopted surface erosion model is developed, based on the description for ion beam sputtering. In particular, the dependence of generated patterns on the laser polarization is taken into account. We find that an asymmetry in deposition and dissipation of incident laser energy results in a respective dependence of coefficients in a nonlinear equation of the Kuramoto-Sivashinsky type. Surface morphologies obtained by this model for different polarization of the laser beam are presented and the time evolution of the nanopattern is discussed. A comparison of these numerical results with experimental data shows an excellent agreement. Dependence of femtosecond laser induced formation on the polarization of the incident beam within an adopted surface erosion model is considered. A continuum theory of erosion by polarized laser radiation is developed. We exploit the similarity to ion-beam sputtering and extend a corresponding model for laser ablation by including laser polarization. This yields a respective dependence of coefficients in a nonlinear equation of the Kuramoto-Sivashinsky type. We present the surface morphologies obtained by this model for different polarization of the laser beam and discuss a time evolution of the nanopattern. These numerical results are in a good agreement with numerous experimental data. We show that the correlation of ripples orientation with laser polarization can be described within a model where the polarization causes the breaking of symmetry at the surface. Our results support the non-linear self-organization mechanism of pattern formation on the surface of solids. PMID:22400336

Varlamova, Olga; Reif, Juergen; Varlamov, Sergey; Bestehorn, Michael

2011-10-01

335

Solar cycle control of the magnetic cloud polarity and the geoeffectiveness  

NASA Astrophysics Data System (ADS)

Magnetic clouds are surveyed in interplanetary magnetic field (IMF) and solar wind data from ACE, WIND, ISEE3, and IMP8 spacecraft. The annual frequency distribution of the bipolar magnetic clouds combined with PVO results by Mulligan et al. (Geophys. Res. Lett. 25 (1998) 2959) shows that the occurrence of SN magnetic clouds prevails over NS magnetic clouds in an odd solar cycle, and the reverse is true for an even solar cycle. The prevailing polarity cases decrease in number towards the solar minimum, while the secondary polarity clouds start to increase in number, only becoming predominant after the later part of the declining phase. Therefore, the predominance of the magnetic cloud polarity reverses within the later part of the declining phase near the solar minimum, but does not coincide with either the solar minimum when the new polarity sunspots begin to emerge or the solar maximum when the large scale solar polar field reverses. The annual frequency distribution of the total number of bipolar magnetic clouds and total number of unipolar magnetic clouds is not well ordered by the solar cycle. Perhaps both solar polar field cycle and the Hale active region polarity cycle may affect the magnetic cloud polarity. Magnetic clouds from all four spacecraft during 1978-2002 are evaluated for their geoeffectiveness. Overall statistics show that NS and SN magnetic clouds are equally geoeffective. We also found that both the cloud portion and sheath portion during the magnetic cloud period are important in causing geomagnetic storms. The magnetic cloud disturbance periods are the primary cause of one-third of the total number of geomagnetic storms analyzed, but are responsible for the most intense storms.

Li, Yan; Luhmann, Janet

2004-02-01

336

Ultrafast polarization dynamics and noise in pulsed vertical-cavity surface-emitting lasers  

NASA Astrophysics Data System (ADS)

We have measured on ps time scales the temporal behavior of the intensity noise of, and correlations between, orthogonally polarized modes in an optically pumped VCSEL. Measurements were made in both the circular and the linear bases. Sub-ps optical pumping with circular polarization leads to positively correlated intensity noise for emission in orthogonal linear polarizations. Optical pumping with linear polarization leads to anti-correlated intensity noise for emission in orthogonal linear polarizations, due to random orientation of linearly polarized emission. Intensity noise for circularly polarized emission is uncorrelated or anti-correlated depending on spin-flip rates which determine the strength of gain competition. We have generalized the theoretical treatment of San Miguel, Feng, and Moloney to successfully model these phenomena.

Blansett, Ethan; Raymer, Michael G.; Khitrova, Galina; Gibbs, Hyatt M.; Serkland, Darwin Keith; Allerman, A. A.; Geib, Kent M.

2001-09-01

337

Differential Polarization Nonlinear Optical Microscopy with Adaptive Optics Controlled Multiplexed Beams  

PubMed Central

Differential polarization nonlinear optical microscopy has the potential to become an indispensable tool for structural investigations of ordered biological assemblies and microcrystalline aggregates. Their microscopic organization can be probed through fast and sensitive measurements of nonlinear optical signal anisotropy, which can be achieved with microscopic spatial resolution by using time-multiplexed pulsed laser beams with perpendicular polarization orientations and photon-counting detection electronics for signal demultiplexing. In addition, deformable membrane mirrors can be used to correct for optical aberrations in the microscope and simultaneously optimize beam overlap using a genetic algorithm. The beam overlap can be achieved with better accuracy than diffraction limited point-spread function, which allows to perform polarization-resolved measurements on the pixel-by-pixel basis. We describe a newly developed differential polarization microscope and present applications of the differential microscopy technique for structural studies of collagen and cellulose. Both, second harmonic generation, and fluorescence-detected nonlinear absorption anisotropy are used in these investigations. It is shown that the orientation and structural properties of the fibers in biological tissue can be deduced and that the orientation of fluorescent molecules (Congo Red), which label the fibers, can be determined. Differential polarization microscopy sidesteps common issues such as photobleaching and sample movement. Due to tens of megahertz alternating polarization of excitation pulses fast data acquisition can be conveniently applied to measure changes in the nonlinear signal anisotropy in dynamically changing in vivo structures.

Samim, Masood; Sandkuijl, Daaf; Tretyakov, Ian; Cisek, Richard; Barzda, Virginijus

2013-01-01

338

Wave-front-engineered grating mirrors for VCSELs  

NASA Astrophysics Data System (ADS)

High-index-contrast grating mirrors featuring beam steering abilities for the transmitted beam as well as high reflectivity over a broad bandwidth are suggested. Gratings designed to provide control over the wave front of the transmitted beam are numerically investigated. The proposed structures are then fabricated for experimental characterization. The measurements performed show the beam steering ability of the suggested HCG designs and are also in good agreement with the theoretical predictions. General design rules to engineer these HCG structures for different applications are derived. These grating mirrors would have a significant impact on low cost laser sources fabrication, since a more efficient integration of optoelectronic modules can be achieved by avoiding expensive external lens systems.

Carletti, L.; Malureanu, R.; Mørk, J.; Chung, I.-S.

2012-02-01

339

Band model for light-polarization selection in unstrained quantum-well vertical-cavity surface-emitting lasers  

NASA Astrophysics Data System (ADS)

We present a model for light polarization in vertical-cavity surface-emitting lasers (VCSEL's) based on semiconductor Bloch equations, which includes the effects of valence-band mixing and accounts for the possibility of different spin-flip rates for conduction electrons and holes. We calculate the stability boundaries of linearly polarized solutions and compare them with those of the model introduced by San Miguel, Feng, and Moloney [Phys. Rev. A 52, 1728 (1995)], to which our equations reduce under appropriate assumptions. We study the dependence of such boundaries on some physical parameter of the VCSEL, and show how our equations can be used to interpret some measurements of the spin-flip rate performed recently.

Prati, F.; Fratta, L.; Travagnin, M.

2000-09-01

340

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

SciTech Connect

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.

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

341

Physical insight into the polarization dynamics of semiconductor vertical-cavity lasers  

NASA Astrophysics Data System (ADS)

The polarization properties of semiconductor vertical-cavity lasers (VCSELs) are generally described with a model introduced by San Miguel, Feng, and Moloney (SFM) in Phys. Rev. A 52, 1728 (1995). We have analyzed this SFM model from an experimentalist's point of view, using the idea that under certain conditions, which are satisfied by most practical VCSELs, the complicated spin dynamics can be adiabatically eliminated, leading to a managable analytical description. We hereby obtain new physical insight and intuitive pictures. One of the key results is the prediction that, via the spin dynamics, the presence of a strong lasing mode with a certain polarization will effectively lead to a broadening and frequency shift of the weak nonlasing mode with orthogonal polarization. This result gives a simple physical explanation for a polarization switch predicted by the model, and leads to further predictions that can be experimentally verified. The analysis also shows how the relaxation oscillations are related to the polarization dynamics and how they might be of crucial importance to experimentally determine the various parameters in the SFM model. We then discuss how the spin elimination reduces the SFM model to existing models for the polarization dynamics of class A (gas) lasers, with intuitive pictures of the polarization evolution on the Poincaré sphere. Finally we will show how, within the context of adiabatic elimination, the cubic crystalline symmetry plays a special role in possible generalizations of the SFM model.

van Exter, M. P.; Hendriks, R. F. M.; Woerdman, J. P.

1998-03-01

342

480-Mbps, BiDirectional, Ultra-Wideband Radio-Over-Fiber Transmission Using a 1308\\/1564-nm Reflective Electro-Absorption Transducer and Commercially Available VCSELs  

Microsoft Academic Search

We describe 480 Mbps, bi-directional ultra-wideband (UWB) radio signal transmission over 1 km of single-mode optical fiber. Key components are a highly linear, reflective electro absorption transducer (EAT) and commercially available 1308-nm and 1564-nm VCSELs with 4.8-GHz bandwidth. Detailed EAT and 1308-nm VCSEL distortion analyses and measurements are presented highlighting the low intermodulation and harmonic distortion necessary for typical -18-dB

Manoj Prasad Thakur; Terence James Quinlan; Carlos Bock; Stuart D. Walker; Mehmet Toycan; Sandra E. M. Dudley; David W. Smith; Anna Borghesani; David Moodie; Moshe Ran; Yossef Ben-Ezra

2009-01-01

343

Investigation of 1.3-?m GaInNAs vertical-cavity surface-emitting lasers (VCSELs) using temperature, high-pressure, and modeling techniques  

Microsoft Academic Search

We have investigated the temperature and pressure dependence of the threshold current (Ith) of 1.3 ?m emitting GaInNAs vertical-cavity surface-emitting lasers (VCSELs) and the equivalent edge-emitting laser (EEL) devices employing the same active region. Our measurements show that the VCSEL devices have the peak of the gain spectrum on the high-energy side of the cavity mode energy and hence operate

G. Knowles; Robin Fehse; Stanko Tomic; Stephen John Sweeney; T. E. Sale; Alfred R. Adams; E. P. O'Reilly; G. Steinle; H. Riechert

2003-01-01

344

Defect Control for Large Remanent Polarization in Bismuth Titanate Ferroelectrics Doping Effect of Higher-Valent Cations---  

Microsoft Academic Search

The effects of concentration and distribution of defects controlled by quenching and doping of higher-valent cations on the ferroelectric properties of dense Bi4Ti3O12 ceramics were investigated. The remanent polarization (Pr) of non-doped ceramics quenched from 800°C (above the Curie temperature) was twice as large as those of samples subjected to slow cooling to 25°C and quenched from 600°C (below the

Yuji Noguchi; Ichiro Miwa; Yu Goshima; Masaru Miyayama

2000-01-01

345

Bidirectional reflectance distribution function of thermal control coatings and heat-shielding materials illuminated by polarized light  

NASA Astrophysics Data System (ADS)

Stokes parameters were measured for radiation reflected in the range 5° to 80° by silver-colored, white, and black thermal control coatings deposited on an aluminum alloy substrate, by green paint on a phenolic plastic surface, and by uncoated carbon-fiber reinforced plastic illuminated by linearly polarized He-Ne laser radiation at an incident angle of -5°. The bidirectional reflectance distribution function of the investigated samples was determined as a function of the view zenith angle.

Voschula, I. V.; Dlugunovich, V. A.; Zhumar, A. Yu.

2013-05-01

346

Multiple wavelength vertical-cavity surface-emitting laser arrays using surface-controlled MOCVD growth rate enhancement and reduction  

SciTech Connect

Multiple-wavelength VCSEL and photodetector arrays are useful for wavelength-multiplexed fiberoptic networks, and for optical crosstalk isolation in parallel, free-space interconnects. Multiple wavelength VCSEL arrays have been obtained by varying the growth rate using thermal gradients caused by a backside-patterned substrate, by growth enhancement on a patterned substrate, and by varying the cavity length through anodic oxidation and selective etching of the wafer. We show here for the first time both the enhancement and the reduction of the growth rate of the entire VCSEL structure on a topographically patterned substrate, and demonstrate the controlled variation of the lasing wavelengths of a VCSEL array over an extended spectral range.

Ortiz, G.G.; Hains, C.P.; Luong, S.; Cheng, J. [Univ. of New Mexico, Albuquerque, NM (United States). Center for High Technology Materials; Hou, H.Q.; Vawter, G.A. [Sandia National Labs., Albuquerque, NM (United States)

1997-04-01

347

Effects of built-in polarization on InGaN-GaN vertical-cavity surface-emitting lasers  

Microsoft Academic Search

We investigate the effect of built-in spontaneous and piezoelectric polarization on the internal device physics of current-injected GaN-based vertical-cavity surface-emitting lasers (VCSELs) with strained InGaN quantum wells. Advanced device simulation is applied to a previously manufactured device design featuring dielectric mirrors and an indium-tin-oxide current injection layer. Contrary to common perception, we show: 1) that only a small fraction of

Joachim Piprek; Robert Farrell; Steve DenBaars; Shuji Nakamura

2006-01-01

348

Performance evaluation of zero-biased VCSEL for high speed data transmission  

NASA Astrophysics Data System (ADS)

In an optical transceiver, the power consumption related to the operation of the laser device takes a significant parcel of the total consumed power. Thus, in optical networks where a large number of transceiver devices are interconnected, e.g. large distributed sensor networks, it is of great importance to reduce this power consumption. In this work an analysis and simulation results are presented regarding the operation of a bias-free vertical-cavity surface-emitting laser (VCSEL) device, which is based on a previously developed model. The impact on bit-error rate (BER) of the increased turn-on jitter due to the bit-pattern and spontaneous emission is considered. A method for mitigating the eye-diagram distortion penalty based on the received signal equalization is also illustrated.

Silva, S.; Pessoa, L.; Oliveira, J.; Coelho, D.; Castro, J. C. S.; Salgado, H. M.

2010-11-01

349

MIMO-OFDM WDM PON with DM-VCSEL for femtocells application.  

PubMed

We report on experimental demonstration of 2x2 MIMO-OFDM 5.6-GHz radio over fiber signaling over 20 km WDM-PON with directly modulated (DM) VCSELs for femtocells application. MIMO-OFDM algorithms effectively compensate for impairments in the wireless link. Error-free signal demodulation of 64 subcarrier 4-QAM signals modulated at 198.5 Mb/s net data rate is achieved after fiber and 2 m indoor wireless transmission. We report BER of 7x10(-3) at the receiver for 16-QAM signals modulated at 397 Mb/s after 1 m of wireless transmission. Performance dependence on different wireless transmission path lengths, antenna separation, and number of subcarriers have been investigated. PMID:22274067

Othman, M B; Deng, Lei; Pang, Xiaodan; Caminos, J; Kozuch, W; Prince, K; Yu, Xianbin; Jensen, Jesper Bevensee; Monroy, I Tafur

2011-12-12

350

Wide temperature operation of a VCSEL pumped 355nm frequency tripled Nd:YAG laser  

NASA Astrophysics Data System (ADS)

We have fabricated prototype frequency tripled Nd:YAG lasers using 808nm Vertical Cavity Surface emitting laser (VCSEL) arrays for end-pumping. The passively Q-switched Nd:YAG laser generated 15mJ pulses with a duration of 2-4 ns. Used as a source for third harmonic generation, the laser produced in excess of 2mJ at 355nm. Of particular concern was the impact of temperature variation on conversion efficiency, which included effects for both the source laser and non-linear crystals. Various solutions to the temperature effects were explored to enable operation of the frequency tripled laser over a wide temperature range.

Cole, Brian; Hays, Alan; McIntosh, Chris; Goldberg, Lew

2013-03-01

351

Comparison of polarization handling methods in coherent optical systems  

Microsoft Academic Search

The authors compare three polarization handling methods in coherent optical systems. These methods are: endless polarization control, polarization diversity, and data-induced polarization switching. These methods are also compared with active, data-synchronous polarization switching. It is seen that endless polarization control is potentially the most powerful candidate, however, the choice of polarization control devices remain questionable. Polarization diversity is as versatile

Reinhold Noe; H. Rodler; Alfred Ebberg; Gisela Gaukel; Bernd Noll; Julius Wittmann; Franz Auracher

1991-01-01

352

Polarization control of Raman spectroscopy optimizes the assessment of bone tissue.  

PubMed

There is potential for Raman spectroscopy (RS) to complement tools for bone diagnosis due to its ability to assess compositional and organizational characteristics of both collagen and mineral. To aid this potential, the present study assessed specificity of RS peaks to the composition of bone, a birefringent material, for different degrees of instrument polarization. Specifically, relative changes in peaks were quantified as the incident light rotated relative to the orientation of osteonal and interstitial tissue, acquired from cadaveric femurs. In a highly polarized instrument (10(6)?1 extinction ratio), the most prominent mineral peak (?1 Phosphate at 961 cm(-1)) displayed phase similarity with the Proline peak at 856 cm(-1). This sensitivity to relative orientation between bone and light observed in the highly polarized regime persisted for certain sensitive peaks (e.g., Amide I at 1666? cm(-1)) in unaltered instrumentation (200?1 extinction ratio). Though Proline intensity changed with bone rotation, the phase of Proline matched that of ?1 Phosphate. Moreover, when mapping ?1 Phosphate/Proline across osteonal-interstitial borders, the mineralization difference between the tissue types was evident whether using a 20x or 50x objectives. Thus, the polarization bias inherent in commercial RS systems does not preclude the assessment of bone composition when using phase-matched peaks. PMID:23708192

Makowski, Alexander J; Patil, Chetan A; Mahadevan-Jansen, Anita; Nyman, Jeffry S

2013-05-01

353

Drosophila Stardust is a partner of Crumbs in the control of epithelial cell polarity  

Microsoft Academic Search

The polarized architecture of epithelial cells depends on the highly stereotypic distribution of cellular junctions and other membrane-associated protein complexes. In epithelial cells of the Drosophila embryo, three distinct domains subdivide the lateral plasma membrane. The most apical one comprises the subapical complex (SAC). It is followed by the zonula adherens (ZA) and, further basally, by the septate junction. A

André Bachmann; Martina Schneider; Eva Theilenberg; Ferdi Grawe; Elisabeth Knust

2001-01-01

354

Polarity controls forces governing asymmetric spindle positioning in the Caenorhabditis elegans embryo  

Microsoft Academic Search

2,3 . The mechanisms by which cell polarity translates to asymmetric spindle positioning remain unclear. Here we examine the nature of the forces governing asymmetric spindle positioning in the single-cell-stage Caenorhabditis elegans embryo. To reveal the forces that act on each spindle pole, we removed the central spindle in living embryos either physically with an ultraviolet laser microbeam, or genetically

Stephan W. Grill; Pierre Gonczy; Ernst H. K. Stelzer; Anthony A. Hyman

2001-01-01

355

Generation and control of polarization-entangled photons from GaAs island quantum dots by an electric field  

PubMed Central

Semiconductor quantum dots are potential sources for generating polarization-entangled photons efficiently. The main prerequisite for such generation based on biexciton–exciton cascaded emission is to control the exciton fine-structure splitting. Among various techniques investigated for this purpose, an electric field is a promising means to facilitate the integration into optoelectronic devices. Here we demonstrate the generation of polarization-entangled photons from single GaAs quantum dots by an electric field. In contrast to previous studies, which were limited to In(Ga)As quantum dots, GaAs island quantum dots formed by a thickness fluctuation were used because they exhibit a larger oscillator strength and emit light with a shorter wavelength. A forward voltage was applied to a Schottky diode to control the fine-structure splitting. We observed a decrease and suppression in the fine-structure splitting of the studied single quantum dot with the field, which enabled us to generate polarization-entangled photons with a high fidelity of 0.72±0.05.

Ghali, Mohsen; Ohtani, Keita; Ohno, Yuzo; Ohno, Hideo

2012-01-01

356

A pump power controlled 1,060 nm multiwavelength fiber ring laser using nonlinear polarization rotation of SOA  

NASA Astrophysics Data System (ADS)

We propose and experimentally demonstrate a both channel spacing and wavelength-tunable 1,060 nm multiwavelength fiber laser using nonlinear polarization rotation of semiconductor optical amplifier (SOA). The SOA in the cavity can not only provide the gain but also generate a pump power controlled phase-shift between two orthogonal linear states of polarization. The experimental result shows that the fast and continuous wavelength tuning is achieved with external light injection, while the channel spacing of the multiwavelength laser can be varied by adjusting the length of polarization maintaining fiber. When an external laser source with 13 dBm power is injected into the SOA as a control pump, optically tunable operation of up to 20 wavelength channels, from 1,042 to 1,058 nm, with a wavelength spacing of 0.8 nm has been demonstrated with the signal-to-spontaneous-noise ratio over 40 dB at room temperature. The lasers are stable with a maximum power fluctuation per channel of less than 0.5 dB during 2-h test.

Liu, S.; Fu, Songnian; Tang, Ming; Shum, Perry; Liu, Deming

2013-03-01

357

The linear dependence of polar cap index on its controlling factors in solar wind and magnetotail  

NASA Astrophysics Data System (ADS)

The solar wind is coupled to the magnetosphere-ionosphere system through various interactions, e.g., magnetic reconnection at the dayside magnetopause, and viscous interactions at the low latitude boundary layer. The polar cap, a region of open magnetic flux connecting the magnetic field of the Earth to that of the solar wind, is an ideal region in which to investigate how solar wind drives the magnetosphere-ionosphere dynamo. For such studies, the polar cap (PC) index provides a useful characterization of the state of the polar ionosphere. A previous study by Gao et al. (2012a) found that polar cap dynamics, characterized by the PC index, responds to both solar wind driving quantified by the electric field (EK-R) proposed by Kivelson and Ridley (2008) which is a representative of the electric field imposed on the ionosphere by magnetopause reconnection that takes cross polar cap potential saturation into account, and the energy release in the magnetotail, described by a modified AL index (ALU). In that study, the dependence of the PC index on EK-R and ALU was investigated assuming a linear relationship. In this study, we test the assumption that the relationship is linear by performing a similar analysis applying a more general, nonlinear model to the events of the Gao et al. (2012a) study. A nonlinear relationship can be established by use of a statistical approach referred to as the additive model. We find that the more flexible additive model outperforms the linear model. However, the improvement is small. Provided that EK-R is used to characterize the solar wind input, results obtained from the additive model are very similar to those from the linear model. This result indicates that the linear relation between the PC index and EK-R, ALU obtained by Gao et al. (2012a) represents the data within fluctuations.

Gao, Ye; Kivelson, Margaret G.; Walker, Raymond J.

2012-05-01

358

Oxygen rotation driven ferroelectricity enables controllable magnetization-polarization coupling in Ca3Mn2O7  

NASA Astrophysics Data System (ADS)

We show how to achieve the electric field switching of magnetism in a multiferroic with a large polarization by having the ferroelectric state arise from the same lattice instability that modulates the spin system. Oxygen octahedron rotations, ubiquitous in perovskites and related materials, are natural candidates for this lattice instability. First-principles calculations are presented for the layered perovskite Ca3Mn2O7, in which rotations induce both ferroelectricity and weak ferromagnetism. The key point is that this rotation pattern is a combination of two non-polar structural modes with different symmetries. We introduce the term "hybrid" improper ferroelectricity to describe this phenomenon. Our results suggest a new strategy in magnetoelectronics, whereby control over magnetism is achieved through functional antiferrodistortive oxygen octahedron rotations.N. A. Benedek and C. J. Fennie, arXiv:1007.1003 (2010).

Fennie, Craig; Benedek, Nicole

2011-03-01

359

VCSEL-based, high-speed, in situ TDLAS for in-cylinder water vapor measurements in IC engines.  

PubMed

We report the first application of a vertical-cavity surface-emitting laser (VCSEL) for calibration- and sampling-free, high-speed, in situ H2O concentration measurements in IC engines using direct TDLAS (tunable diode laser absorption spectroscopy). Measurements were performed in a single-cylinder research engine operated under motored conditions with a time resolution down to 100 ?s (i.e., 1.2 crank angle degrees at 2000 rpm). Signal-to-noise ratios (1?) up to 29 were achieved, corresponding to a H2O precision of 0.046 vol.% H2O or 39 ppm·m. The modulation frequency dependence of the performance was investigated at different engine operating points in order to quantify the advantages of VCSEL against DFB lasers. PMID:24105541

Witzel, O; Klein, A; Meffert, C; Wagner, S; Kaiser, S; Schulz, C; Ebert, V

2013-08-26

360

Crosstalk and interconnection distance considerations for board-to-board optical interconnects using 2-D VCSEL and microlens array  

Microsoft Academic Search

We describe the design and experimental characterization of a substrate-mode optical backplane using 0.5-, 0.75- and 1-mm spacing two-dimensional (2-D) optical beam arrays. The system uses arrays of multiplexed holograms to implement free space board-to-board interconnects, and employs 250-?m pitch 2-D vertical-cavity surface-emitting lasers (VCSEL) and microlens array as a transmitter to provide 0.5- to 1-mm spacing 2-D beam array,

Gicherl Kim; Xuliang Han; Ray T. Chen

2000-01-01

361

Control of Electronic Conduction at an Oxide Heterointerface using Surface Polar Adsorbates  

SciTech Connect

We study the effect of the surface adsorption of a variety of common laboratory solvents on the conductivity at the interface between LaAlO{sub 3} and SrTiO{sub 3}. This interface possesses a range of intriguing physics, notably a proposed connection between the surface state of the LaAlO{sub 3} and the conductivity buried in the SrTiO{sub 3}. We show that the application of chemicals such as acetone, ethanol, and water can induce a large change (factor of three) in the conductivity. This phenomenon is observed only for polar solvents. These data provide experimental evidence for a general polarization-facilitated electronic transfer mechanism.

Bell, Christopher

2011-08-19

362

Polarization Control in Two-Color Above-Threshold Ionization of Atomic Helium  

SciTech Connect

Two-color multiphoton ionization of atomic helium was investigated by combining extreme ultraviolet (XUV) radiation from the Free Electron Laser in Hamburg with an intense synchronized optical laser. In the photoelectron spectrum, lines associated with direct ionization and above-threshold ionization show strong variations of their amplitudes as a function of both the intensity of the optical dressing field and the relative orientation of the linear polarization vectors of the two fields. The polarization dependence provides direct insight into the symmetry of the outgoing electrons in above-threshold ionization. In the high field regime, the monochromaticity of the XUV radiation enables the unperturbed observation of nonlinear processes in the optical field.

Meyer, M.; Cubaynes, D.; Glijer, D. [LIXAM, UMR 8624, CNRS-Universite Paris Sud, Batiment 350, 91405 Orsay Cedex (France); Dardis, J.; Hayden, P.; Hough, P.; Richardson, V.; Kennedy, E. T.; Costello, J. T. [National Center for Plasma Science and Technology and School of Physical Sciences, Dublin City University, Dublin (Ireland); Radcliffe, P.; Duesterer, S.; Azima, A.; Li, W. B.; Redlin, H.; Feldhaus, J. [HASYLAB at DESY, Notkestr. 85, D-22607 Hamburg (Germany); Taieeb, R.; Maquet, A. [UPMC, Universite Paris 06, CNRS, UMR 7614, LCPMR, 11 Rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); Grum-Grzhimailo, A. N.; Gryzlova, E. V.; Strakhova, S. I. [Institute of Nuclear Physics, Moscow State University, Moscow 119991 (Russian Federation)

2008-11-07

363

Polarization-Control Components and Narrow-Band Filters Based on Subwavelength Grating Structures.  

NASA Astrophysics Data System (ADS)

Theoretical methods for modeling diffraction from grating structures are presented. These methods are used to investigate polarization properties and resonant effects of subwavelength-period grating structures. Applications discussed include a waveplate with high transmission, a partial polarization beamsplitter and a co-directional polarization beamsplitter used in magneto-optical data storage systems, and narrowband filters based on one-dimensional and two-dimensional gratings. Fabrication processes and measured results for the partial polarization beamsplitter and resonant grating filters are reported. The diffraction properties of subwavelength grating structures need to be analyzed through the use of rigorous electromagnetic theory. A computationally efficient implementation of rigorous coupled-wave analysis (RCWA) is presented. Specifically, the eigenvalue problem for a one-dimensional (1-D) grating in a conical mounting is reduced to two eigenvalue problems in the corresponding nonconical mounting. This reduction yields two n x n matrices to solve for eigenvalues and eigenvectors, where n is the number of orders retained in the computation. Computation on a two-dimensional (2 -D) grating is also simplified by reducing the size of the matrix in the eigenvalue problem to 2n x 2n. These simplifications reduce the computation time for the eigenvalue problem by 8 to 32 times compared to the original computation time. Phase retardation and diffraction efficiencies of zeroth-order dielectric gratings are modeled. The investigation emphasizes the transmission properties of these structures. It is found that if a zeroth-order dielectric grating is appropriately coated the transmissions for both orthogonal polarizations can be significantly enhanced. This result is particularly important for applications involving subwavelength grating structures in waveplates and birefringent computer-generated holograms. A co-directional polarization beamsplitter which consists of a subwavelength grating modulated by a coarse grating profile is also discussed. Subwavelength-period metallic gratings formed on transparent substrates are investigated. In particular, a partial polarization beamsplitter used in magneto-optical data storage systems is designed. Using aluminum grating structures, a device was fabricated through the use of holographic exposure and reactive ion etching; the measured results agreed with the theoretical predictions and met the basic system requirements. Detailed analysis of resonance phenomena in diffraction from two-dimensional (2D) gratings is presented. A polarization -independent narrowband reflection filter and a dual-linewidth reflection filter were designed. A 2D-grating structure consisting of a silicon nitride layer and a photoresist grating was fabricated. A symmetric, low-sideband resonant response that is suitable for narrow-band filter applications was achieved. One-dimensional-grating resonant filters, which consist of a silicon nitride waveguide layer and a silicon dioxide grating or a photoresist grating, were fabricated. Sub -nanometer linewidth and high efficiencies (>70%) were achieved.

Peng, Song

364

Polarization control in two-color above-threshold ionization of atomic helium.  

PubMed

Two-color multiphoton ionization of atomic helium was investigated by combining extreme ultraviolet (XUV) radiation from the Free Electron Laser in Hamburg with an intense synchronized optical laser. In the photoelectron spectrum, lines associated with direct ionization and above-threshold ionization show strong variations of their amplitudes as a function of both the intensity of the optical dressing field and the relative orientation of the linear polarization vectors of the two fields. The polarization dependence provides direct insight into the symmetry of the outgoing electrons in above-threshold ionization. In the high field regime, the monochromaticity of the XUV radiation enables the unperturbed observation of nonlinear processes in the optical field. PMID:19113264

Meyer, M; Cubaynes, D; Glijer, D; Dardis, J; Hayden, P; Hough, P; Richardson, V; Kennedy, E T; Costello, J T; Radcliffe, P; Düsterer, S; Azima, A; Li, W B; Redlin, H; Feldhaus, J; Taïeb, R; Maquet, A; Grum-Grzhimailo, A N; Gryzlova, E V; Strakhova, S I

2008-11-07

365

Broadband femtosecond circular dichroism spectrometer with white-light polarization control  

NASA Astrophysics Data System (ADS)

A broadband, femtosecond transient circular dichroism (TRCD) spectrometer has been developed and tested in the wavelength range from 350 to 700 nm. The spectrometer uses a femtosecond probe white light with well-defined circular polarization. The latter is modulated by the polarization of a narrowband seed pulse. We have implemented a dual-beam probe geometry with phase-locked detection technique to increase the signal-to-noise ratio and to reduce optical artifacts. The spectrometer allows the acquisition of TRCD spectra with subpicosecond time resolution and typical noise levels of 10-4 absorbance units. The performance of this instrument has been demonstrated on bis(merocyanine) nanorod aggregates in tetrahydrofurane/methylcyclohexane solution. The case study confirmed that this spectrometer is effective for the investigation of chiral properties in various molecular and nanostructural systems that have transient spectra in the UV-visible spectral range.

Trifonov, Anton; Buchvarov, Ivan; Lohr, Andreas; Würthner, Frank; Fiebig, Torsten

2010-04-01

366

Broadband femtosecond circular dichroism spectrometer with white-light polarization control.  

PubMed

A broadband, femtosecond transient circular dichroism (TRCD) spectrometer has been developed and tested in the wavelength range from 350 to 700 nm. The spectrometer uses a femtosecond probe white light with well-defined circular polarization. The latter is modulated by the polarization of a narrowband seed pulse. We have implemented a dual-beam probe geometry with phase-locked detection technique to increase the signal-to-noise ratio and to reduce optical artifacts. The spectrometer allows the acquisition of TRCD spectra with subpicosecond time resolution and typical noise levels of 10(-4) absorbance units. The performance of this instrument has been demonstrated on bis(merocyanine) nanorod aggregates in tetrahydrofurane/methylcyclohexane solution. The case study confirmed that this spectrometer is effective for the investigation of chiral properties in various molecular and nanostructural systems that have transient spectra in the UV-visible spectral range. PMID:20441322

Trifonov, Anton; Buchvarov, Ivan; Lohr, Andreas; Würthner, Frank; Fiebig, Torsten

2010-04-01

367

Yeast formins regulate cell polarity by controlling the assembly of actin cables  

Microsoft Academic Search

Formins are conserved Rho-GTPase effectors that communicate Rho-GTPase signals to the cytoskeleton. We found that formins were required for the assembly of one of the three budding yeast actin structures: polarized arrays of actin cables. A dominant-active formin induced the assembly of actin cables. The activation and localization of the formin Bni1p required components of the polarisome complex. These findings

Isabelle Sagot; Saskia K. Klee; David Pellman

2001-01-01

368

Study on the Control Strategy of Commutation Process in Variable Polarity Plasma Arc Welding  

Microsoft Academic Search

The peak of resonance current during commutation greatly influences the safety of commutation component in variable polarity\\u000a plasma arc welding (VPPAW). It is necessary to study measure to restrain the current peak. Phenomenon of arc resonance current\\u000a is studied by experiments. Analysis shows that the arc resistance is time variable. Model of commutation circuit is set up\\u000a and simulated. Results

Zhining Li; Dong Du; Li Wang; Baohua Chang; Hua Zhang

369

Photoionization of Synchrotron-Radiation-Excited Atoms: Separating Partial Cross Sections by Full Polarization Control  

SciTech Connect

Resonant atomic excitation by synchrotron radiation and subsequent ionization by a tunable dye laser is used to study the photoionization of short-lived Rydberg states in Xe. By combining circular and linear polarization of the synchrotron as well as of the laser photons the partial photoionization cross sections were separated in the region of overlapping autoionizing resonances of different symmetry and the parameters of the resonances were extracted.

Aloiese, S.; Meyer, M. [LURE, Centre Universitaire Paris-Sud, Ba circumflex timent 209D, F-91898 Orsay Cedex (France); CEA/DRECAM/SPAM, CEN Saclay, F-91105 Gif-sur-Yvette (France); O'Keeffe, P. [LURE, Centre Universitaire Paris-Sud, Ba circumflex timent 209D, F-91898 Orsay Cedex (France); Cubaynes, D. [LURE, Centre Universitaire Paris-Sud, Ba circumflex timent 209D, F-91898 Orsay Cedex (France); LIXAM, Centre Universitaire Paris-Sud, Ba circumflex timent 350, F-91405 Orsay Cedex (France); Grum-Grzhimailo, A. N. [LURE, Centre Universitaire Paris-Sud, Ba circumflex timent 209D, F-91898 Orsay Cedex (France); Institute of Nuclear Physics, Moscow State University, Moscow 119992 (Russian Federation)

2005-06-10

370

Photoionization of synchrotron-radiation-excited atoms: separating partial cross sections by full polarization control.  

PubMed

Resonant atomic excitation by synchrotron radiation and subsequent ionization by a tunable dye laser is used to study the photoionization of short-lived Rydberg states in Xe. By combining circular and linear polarization of the synchrotron as well as of the laser photons the partial photoionization cross sections were separated in the region of overlapping autoionizing resonances of different symmetry and the parameters of the resonances were extracted. PMID:16090387

Aloïse, S; O'Keeffe, P; Cubaynes, D; Meyer, M; Grum-Grzhimailo, A N

2005-06-08

371

Giant tunnel electroresistance and electrical control of spin polarization with ferroelectric tunnel barriers  

Microsoft Academic Search

At room temperature, we use piezoresponse force microscopy to show robust ferroelectricity in BaTiO3 ultrathin films, and conductive-tip atomic force microscopy to demonstrate the resistive readout of the polarization state via its influence on the tunnel current [1]. This giant electroresistance nondestructive readout paves the way for ferroelectric memories with simplified architectures, higher densities and faster operation. Additionally, ferroelectric tunnel

Vincent Garcia

2011-01-01

372

PRC1 controls spindle polarization and recruitment of cytokinetic factors during monopolar cytokinesis  

PubMed Central

The central spindle is a postanaphase array of microtubules that plays an essential role in organizing the signaling machinery for cytokinesis. The model by which the central spindle organizes the cytokinetic apparatus is premised on an antiparallel arrangement of microtubules, yet cells lacking spindle bipolarity are capable of generating a distal domain of ectopic furrowing when forced into mitotic exit. Because protein regulator of cytokinesis (PRC1) and kinesin family member 4A (KIF4A) are believed to play a principal role in organizing the antiparallel midzone array, we sought to clarify their roles in monopolar cytokinesis. Although both factors localized to the distal ends of microtubules during monopolar cytokinesis, depletion of PRC1 and KIF4A displayed different phenotypes. Cells depleted of PRC1 failed to form a polarized microtubule array or ectopic furrows following mitotic exit, and recruitment of Aurora B kinase, male germ cell Rac GTPase-activating protein, and RhoA to the cortex was impaired. In contrast, KIF4A depletion impaired neither polarization nor ectopic furrowing, but it did result in elongated spindles with a diffuse distribution of cytokinetic factors. Thus, even in the absence of spindle bipolarity, PRC1 appears to be essential for polarizing parallel microtubules and concentrating the factors responsible for contractile ring assembly, whereas KIF4A is required for limiting the length of anaphase microtubules.

Shrestha, Sanjay; Wilmeth, Lori Jo; Eyer, Jarrett; Shuster, Charles B.

2012-01-01

373

Second order regulator Collier directly controls intercalary-specific segment polarity gene expression.  

PubMed

In Drosophila, trunk metamerization is established by a cascade of segmentation gene activities: the gap genes, the pair rule genes, and the segment polarity genes. In the anterior head, metamerization requires also gap-like genes and segment polarity genes. However, because the pair rule genes are not active in this part of the embryo, the question on which gene activities are fulfilling the role of the second order regulator genes still remains to be solved. Here we provide first molecular evidence that the Helix-Loop-Helix-COE transcription factor Collier fulfills this role by directly activating the expression of the segment polarity gene hedgehog in the posterior part of the intercalary segment. Collier thereby occupies a newly identified binding site within an intercalary-specific cis-regulatory element. Moreover, we identified a direct physical association between Collier and the basic-leucine-zipper transcription factor Cap'n'collar B, which seems to restrict the activating input of Collier to the posterior part of the intercalary segment and to lead to the attenuation of hedgehog expression in the intercalary lobes at later stages. PMID:22005665

Ntini, Evgenia; Wimmer, Ernst A

2011-10-08

374

A two-step Notch-dependant mechanism controls the selection of the polar cell pair in Drosophila oogenesis.  

PubMed

Organisers control the patterning and growth of many tissues and organs. Correctly regulating the size of these organisers is crucial for proper differentiation to occur. Organiser activity in the epithelium of the Drosophila ovarian follicle resides in a pair of cells called polar cells. It is known that these two cells are selected from a cluster of equivalent cells. However, the mechanisms responsible for this selection are still unclear. Here, we present evidence that the selection of the two cells is not random but, by contrast, depends on an atypical two-step Notch-dependent mechanism. We show that this sequential process begins when one cell becomes refractory to Notch activation and is selected as the initial polar cell. This cell then produces a Delta signal that induces a high level of Notch activation in one other cell within the cluster. This Notch activity prevents elimination by apoptosis, allowing its selection as the second polar cell. Therefore, the mechanism used to select precisely two cells from among an equivalence group involves an inductive Delta signal that originates from one cell, itself unable to respond to Notch activation, and results in one other cell being selected to adopt the same fate. Given its properties, this two-step Notch-dependent mechanism represents a novel aspect of Notch action. PMID:20630949

Vachias, Caroline; Couderc, Jean-Louis; Grammont, Muriel

2010-07-14

375

New speckle control technique using high-speed electro-optic modulators with resonant electrode and polarization-reversed structures  

NASA Astrophysics Data System (ADS)

We propose a new technique for reducing speckle noise in laser displays utilizing a high-speed optical phase modulator for expanding the laser beam spectrum. By adopting standing-wave resonant electrodes and polarization-reversed structures to LiTaO3 electro-optic modulators, high-efficiency phase modulation with a large modulation index at high microwave frequency ranges is obtainable for different color laser beams at the same time. This enables us to expand laser spectra to over 100 GHz and reduce speckle noise. The device design, fabrication, and experimental demonstration for speckle control are reported.

Murata, Hiroshi; Furusho, Keita; Yamamoto, Kazuhisa; Okamura, Yasuyuki

2012-11-01

376

External feedback optimization by means of polarization control in fiber Bragg grating stabilized 980-nm pump lasers  

Microsoft Academic Search

Effects of polarization change in the feedback provided by fiber Bragg gratings that stabilize 980-nm pump lasers are investigated. The effective feedback in the proper transverse-electric polarization is calculated from an easily measured parameter, describing the polarization at the fiber grating. This provides a useful experimental tool to investigate the effect of feedback loss due to polarization change that can

Tomas Pliska; Nicolai Matuschek; Stefan Mohrdiek; Amos Hardy; Christoph Harder

2001-01-01

377

Growth Control by Committee - Intercellular Junctions, Cell Polarity, and the Cytoskeleton Regulate Hippo Signaling  

PubMed Central

Summary Over the past decade, the Hippo tumor suppressor pathway has emerged as a central regulator of growth in epithelial tissues. Research in Drosophila and in mammals has shown that this kinase signaling cascade regulates the activity of the transcriptional coactivator and oncoprotein Yorkie/Yap. In this review, we discuss recent findings that emphasize the cell cortex - specifically the actin cytoskeleton, intercellular junctions and the protein complexes determine cell polarity - as a key site for Hippo pathway regulation. We also highlight where additional research is needed to integrate known functional interactions between Hippo pathway components.

Boggiano, Julian C.; Fehon, Richard G.

2012-01-01

378

FAST TRACK COMMUNICATION: Magnetic control of large room-temperature polarization  

Microsoft Academic Search

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(Fe2\\/3W1\\/3)O3] and PZT [Pb(Zr0.53Ti0.47)O3] exhibit some bi-relaxor qualities, with both ferroelectric relaxor characteristics and magnetic relaxor phenomena. Near 20%

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

2009-01-01

379

Towards atomic unit pulse duration by polarization-controlled few-cycle pulses  

NASA Astrophysics Data System (ADS)

We demonstrate the generation of broadband extreme ultraviolet (XUV) continua by high order harmonic generation in neon using carrier-envelope phase (CEP) stabilized, few-cycle pulses with a time-dependent polarization. The XUV spectra can support isolated attosecond pulses with a duration of about 50 as, opening the possibility of achieving time resolution close to the atomic unit of time. A theoretical model that calculates the spectral and temporal characteristics of the XUV radiation emitted by a single atom is used to interpret the CEP dependence of the harmonic structures.

Sansone, G.; Ferrari, F.; Vozzi, C.; Calegari, F.; Stagira, S.; Nisoli, M.

2009-07-01

380

Rashba control for the spin excitation of a fully spin-polarized vertical quantum dot  

NASA Astrophysics Data System (ADS)

Far-infrared radiation absorption of a quantum dot with few electrons in an orthogonal magnetic field could monitor the crossover to the fully spin-polarized state. A Rashba spin-orbit coupling can tune the energy and the spin density of the first excited state that has a spin texture carrying one extra unit of angular momentum. The spin-orbit coupling can squeeze a flipped spin density at the center of the dot and can increase the gap in the spectrum.

Lucignano, P.; Jouault, B.; Tagliacozzo, A.; Altshuler, B. L.

2005-03-01

381

A new spore precipitator with polarized dielectric insulators for physical control of tomato powdery mildew.  

PubMed

ABSTRACT In an attempt to physically protect greenhouse tomato plants from the powdery mildew fungus Oidium neolycopersici, we developed a new electrostatic spore precipitator in which a copper wire conductor is linked to an electrostatic generator and covered with a transparent acrylic cylinder (insulator). The conductor was negatively charged by the generator, and the electrostatic field created by the conductor was used to dielectrically polarize the insulator cylinder. The dielectrically polarized cylinder also produced an electrostatic force without a spark discharge. This force was directly proportional to the potential applied to the conductor and was used to attract conidia of the pathogen. The efficacy of this spore precipitator in protecting hydroponically cultured tomato plants from powdery mildew was evaluated in the greenhouse. The hydroponic culture troughs were covered with a cubic frame installed with the spore precipitator, and the disease progress on precipitator-guarded and unguarded seedlings was traced after the conidia were disseminated mechanically from inoculum on tomato plants. Seedlings in the guarded troughs remained uninfected during the entire experiment, in spite of rapid spread of the disease to all leaves of the unguarded seedlings. PMID:18944052

Matsuda, Yoshinori; Ikeda, Hiroki; Moriura, Nobuyuki; Tanaka, Norio; Shimizu, Kunihiko; Oichi, Wataru; Nonomura, Teruo; Kakutani, Koji; Kusakari, Shin-Ichi; Higashi, Katsuhide; Toyoda, Hideyoshi

2006-09-01

382

NHERF1/EBP50 controls lactation by establishing basal membrane polarity complexes with prolactin receptor  

PubMed Central

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.

Morales, F C; Hayashi, Y; van Pelt, C S; Georgescu, M-M

2012-01-01

383

Complete chaotic synchronization characteristics of the linear-polarization mode of vertical-cavity surface-emitting semiconductor lasers with isotropic optical feedback  

Microsoft Academic Search

Based on the SFM model [M. San Miguel, Q. Feng, J.V. Moloney, Phys. Rev. A. 52 (1995) 1728.], complete chaotic synchronization characteristics of linear-polarization (LP) Mode of the vertical-cavity surface-emitting semiconductor lasers (VCSELs) with isotropic optical feedback are numerically investigated. When the propagation time ?c of light from the transmitter to the receiver equals to the external cavity round-trip time

Dong-Zhou Zhong; Guang-Qiong Xia; Zheng-Mao Wu; Xin-Hong Jia

2008-01-01

384

Ferroelectric-Antiferroelectric Phase Control: Interplay Between Octahedral Tilt, Polarization, and Chemistry at BFO-LSMO Interfaces  

NASA Astrophysics Data System (ADS)

Atomically-defined interfaces between complex oxides offer a paradigm of novel electronic and coupled functionalities. Here, we report the stabilization of the ferroelectric and antiferroelectric phases at the BFO-LSMO interface though termination control and reveal associated atomic-scale mechanisms with the help of aberration-corrected scanning transmission electron microscopy combined with Electron Energy Loss Spectroscopy. The BFO thin film grown on MnO2-terminated surface of LSMO exhibits stabilized ferroelectric phase at the interface. The interfacial and bulk polarization are antiparallel, giving rise to head to head ferroelectric domain wall mostly parallel to the interface. In comparison, the film grown on (Sr,La)O-terminated surface of LSMO exhibits antiferroelectric phase in the vicinity of the interface, with associated ferroelectric-antiferroelectric domain wall in the bulk. Details of tilt and polarization behavior, as well as electronic properties at the interfaces including charged domain walls and FE-AFE walls, will be presented. These results imply that the structural parameters such as octahedral tilt and ferroelectricity in BFO can be directly controlled by modifying the interface structure.

Kim, Young-Min; Yu, Pu; Chu, Ying-Hao; Pennycook, Stephen; Kalinin, Sergei; Borisevich, Albina

2012-02-01

385

Transverse and polarization effects in index-guided vertical-cavity surface-emitting lasers  

SciTech Connect

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.

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

386

Optical control of exciton valley polarization in MoS2  

NASA Astrophysics Data System (ADS)

Atomic monolayers of transition metal dichalcogenides have emerged as an interesting class of 2-dimensional (2D) crystals beyond graphene. In particular, the isoelectronic family of MoS2, MoSe2, WS2 and WSe2 monolayers are direct band gap semiconductors.footnotetextMak, K. F., Lee, C., Hone, J., Shan, J. & Heinz, T. F. Phys Rev Lett 105, 136805 (2010); Splendiani, A. et al. Nano Lett 10, 1271-1275 (2010).^,footnotetextXiao, D., Liu, G.-B., Feng, W., Xu, X. & Yao, W. Phys Rev Lett 108, 196802 (2012); Zhu, Z. Y., Cheng, Y. C. & Schwingenschlogl, U. Phys Rev B 84, 153402 (2011). Unlike graphene, because of the lack of inversion symmetry and the presence of strong spin-orbit interactions, the fundamental energy gaps of these compounds are located at two inequivalent high-symmetry valleys in the Brillouin zone (K and K') with coupled valley and spin degrees of freedom.footnotetextIbid. This electronic property makes them unique from conventional semiconductors. In this talk, we will discuss the properties of MoS2 atomic layers as a prototype. Through characterization of the optical properties of the material as a function of thickness, we show that quantum confinement effects lead to a crossover in MoS2 from a bulk indirect gap semiconductor to a direct gap semiconductor at monolayer thickness.footnotetextMak, PRL 105, 2010 With this basic property established, we show that complete valley polarization of the excitons in monolayer MoS2 can be achieved by optical pumping with circularly polarized light.footnotetextMak, K. F., He, K., Shan, J. & Heinz, T. F. Nat Nano 7, 494-498 (2012); Zeng, H., Dai, J., Yao, W., Xiao, D., & Cui, X. Nat Nano 7, 490-493 (2012); Cao, T. et al. Nat Commun 3, 887 (2012); Sallen, G. et al. Phys Rev B 86, 081301(R) (2012). Furthermore, this polarization can be retained for longer than 1ns. Our results thus highlight the great potential of this material family for studies of valley and spin Hall physics.footnotetextXiao, D., Yao, W. & Niu, Q. Phys Rev Lett 99, 236809 (2007); Yao, W., Xiao, D. & Niu, Q. Phys Rev B 77, 235406 (2008); Xiao, D., Chang, M.-C. & Niu, Q. Rev Mod Phys 82, 1959-2007 (2010).

Mak, Kin Fai

2013-03-01

387

Effect of GaN interlayer on polarity control of epitaxial ZnO thin films grown by molecular beam epitaxy  

SciTech Connect

Epitaxial ZnO thin films were grown on nitrided (0001) sapphire substrates with an intervening GaN layer by rf-plasma-assisted molecular beam epitaxy. It was found that polarity of the ZnO epilayer could be controlled by modifying the GaN interlayer. ZnO grown on a distorted 3-nm-thick GaN interlayer has Zn-polarity while ZnO on a 20-nm-thick GaN interlayer with a high structural quality has O-polarity. High resolution transmission electron microscopy analysis indicates that the polarity of ZnO epilayer is controlled by the atomic structure of the interface between the ZnO buffer layer and the intervening GaN layer.

Wang, X. Q. [State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Sun, H. P.; Pan, X. Q. [Department of Materials Science and Engineering, The University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)

2010-10-11

388

Polarity control of ZnO films on (0001) Al{sub 2}O{sub 3} by Cr-compound intermediate layers  

SciTech Connect

This letter presents a reliable and very easy method for selective growth of polarity controlled ZnO films on (0001) Al{sub 2}O{sub 3} substrates by plasma-assisted molecular-beam epitaxy. Cr-compound intermediate layers are used to control the crystal polarity of ZnO films on (0001) Al{sub 2}O{sub 3}. ZnO films grown on rocksalt structure CrN/(0001) Al{sub 2}O{sub 3} shows Zn polarity, while those grown on rhombohedral Cr{sub 2}O{sub 3}/(0001) Al{sub 2}O{sub 3} shows O polarity. Possible interface atomic arrangements for both heterostructures are proposed.

Park, J. S.; Hong, S. K.; Minegishi, T.; Park, S. H.; Im, I. H.; Hanada, T.; Cho, M. W.; Yao, T.; Lee, J. W.; Lee, J. Y. [Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577 (Japan); Department of Nano Information Systems Engineering, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577 (Japan); Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea, Republic of)

2007-05-14

389

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

PubMed

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

Zhu, Wenguo; She, Weilong

2012-07-15

390

A VCSEL based system for on-site monitoring of low level methane emission  

NASA Astrophysics Data System (ADS)

Continuous monitoring of methane emissions has assumed greater significance in the recent past due to increasing focus on global warming issues. Many industries have also identified the need for ppm level methane measurement as a means of gaining carbon credits. Conventional instruments based on NDIR spectroscopy are unable to offer the high selectivity and sensitivity required for such measurements. Here we discuss the development of a robust VCSEL based system for accurate low level measurements of methane. A possible area of application is the measurement of residual methane whilst monitoring the output of flare stacks and exhaust gases from methane combustion engines. The system employs a Wavelength Modulation Spectroscopy (WMS) scheme with second harmonic detection at 1651 nm. Optimum modulation frequency and ramp rates were chosen to maintain high resolution and fast response times which are vital for the intended application. Advanced data processing techniques were used to achieve long term sensitivity of the order of 10-5 in absorbance. The system is immune to cross interference from other gases and its inherent design features makes it ideal for large scale commercial production. The instrument maintains its calibration and offers a completely automated continuous monitoring solution for remote on site deployment.

Kannath, A.; Hodgkinson, J.; Gillard, R. G.; Riley, R. J.; Tatam, R. P.

2011-02-01

391

Control of plasmaspheric dynamics by both convection and sub-auroral polarization stream  

NASA Astrophysics Data System (ADS)

The long-standing hypothesis that plasmaspheric dynamics are described by superposition of corotation and solar-wind-driven sunward convection is tested via direct comparison between plasmasphere observations and simulation output. The observations consist of global plasmasphere images produced by the IMAGE extreme ultraviolet (EUV) imager during plasmasphere erosion on 2 June 2001. The simulation is a plasmapause evolution model driven by a time-varying Volland-Stern (VS) electric potential distribution. On the dawnside and much of the nightside the model matches the EUV plasmapause position to within 0.2-0.5 earth radii (RE). Near dusk the model plasmapause is about 0.7-1.2 RE farther out than the EUV plasmapause, suggesting that an improved model should include the duskside flow enhancement known as the sub-auroral polarization stream (SAPS). We demonstrate that including a simplified ad-hoc SAPS potential can correct the model on the duskside.

Goldstein, J.; Sandel, B. R.; Hairston, M. R.; Reiff, P. H.

2003-12-01

392

Experimental Evidence for Oxygen Sublattice Control in Polar Infinite Layer SrCuO_{2}.  

PubMed

A recent theoretical study [Phys. Rev. B 85, 121411(R) (2012)] predicted a thickness limit below which ideal polar cuprates turn nonpolar driven by the associated electrostatic instability. Here we demonstrate this possibility by inducing a structural transformation from the bulk planar to chainlike structure upon reducing the SrCuO_{2} repeat thickness in SrCuO_{2}/SrTiO_{3} superlattices with unit-cell precision. Our results, based on structural investigation by x-ray diffraction and high resolution scanning transmission electron microscopy, demonstrate that the oxygen sublattice can essentially be built by design. In addition, the electronic structure of the chainlike structure, as studied by x-ray absorption spectroscopy, shows the signature for preferential hole occupation in the Cu 3d_{3z^{2}-r^{2}} orbital, which is different from the planar case. PMID:24033050

Samal, D; Tan, Haiyan; Molegraaf, H; Kuiper, B; Siemons, W; Bals, Sara; Verbeeck, Jo; Van Tendeloo, Gustaaf; Takamura, Y; Arenholz, Elke; Jenkins, Catherine A; Rijnders, G; Koster, Gertjan

2013-08-27

393

Experimental Evidence for Oxygen Sublattice Control in Polar Infinite Layer SrCuO2  

NASA Astrophysics Data System (ADS)

A recent theoretical study [Phys. Rev. B 85, 121411(R) (2012)] predicted a thickness limit below which ideal polar cuprates turn nonpolar driven by the associated electrostatic instability. Here we demonstrate this possibility by inducing a structural transformation from the bulk planar to chainlike structure upon reducing the SrCuO2 repeat thickness in SrCuO2/SrTiO3 superlattices with unit-cell precision. Our results, based on structural investigation by x-ray diffraction and high resolution scanning transmission electron microscopy, demonstrate that the oxygen sublattice can essentially be built by design. In addition, the electronic structure of the chainlike structure, as studied by x-ray absorption spectroscopy, shows the signature for preferential hole occupation in the Cu 3d3z2-r2 orbital, which is different from the planar case.

Samal, D.; Haiyan, Tan; Molegraaf, H.; Kuiper, B.; Siemons, W.; Bals, Sara; Verbeeck, Jo; Van Tendeloo, Gustaaf; Takamura, Y.; Arenholz, Elke; Jenkins, Catherine A.; Rijnders, G.; Koster, Gertjan

2013-08-01

394

Dynamically controllable emission of polymer nanofibers: electrofluorescence chromism and polarized emission of polycarbazole derivatives.  

PubMed

Electrochemical polymerization of a series of N-alkyl-2,7-di(2-thienyl)carbazoles in acetonitrile was performed to obtain conjugated polymers with fluorescence. Scanning electron and atomic force microscopies revealed that the surface morphology of the polymer films significantly depends on the alkyl chain lengths of the polymers. Particularly, a homopolymer bearing hexyl groups and copolymers with an average alkyl chain length of six carbon atoms show nanofiber morphology. The polymer nanofibers were stacked on a substrate electrode. The fluorescence of the polymer nanofiber film was tunable with application of voltage, with good repeatability. The X-ray diffraction pattern of the fibers showed the structural order. The polymer nanofibers thus prepared showed an electrochemically driven change in polarized photoluminescence. PMID:23032793

Kawabata, Kohsuke; Goto, Hiromasa

2012-10-02

395

Control of interplanetary solar wind sector polarity on changes in the ionosphere  

NASA Astrophysics Data System (ADS)

Solar sector polarity effects on the ionosphere may provide some clues in understanding of the ionospheric day-to-day variability. In this study, a solar-terrestrial connection ranging from solar sector boundary (SB) crossings, geomagnetic disturbances and ionospheric perturbations has been demonstrated. Superposed epoch analysis confirms that the increases in interplanetary solar wind speed within three days after SB crossings and the decreases in solar wind dynamic pressure and magnetic field intensity immediately after SB crossings. Furthermore, the interplanetary magnetic field (IMF) Bz component turns from northward to southward in March equinox and June solstice as the Earth passes from a solar sector of outward to inward directed magnetic fields, whereas the reverse situation occurs for the transition from toward to away sectors. For the same solar sector polarity there are opposite IMF Bz components between March and September equinox, and between June and December solstice. The F2 region critical frequency (foF2) covering about four solar cycles and total electron content (TEC) during 1998-2011 are utilized to extract how the ionosphere reacts to the interplanetary solar wind variations linkage of SB crossings. foF2 vary within the range of ±15% on average. The responses of the ionospheric TEC to SB crossings exhibit complex temporal and spatial variations and have strong dependencies on season, latitude, and solar cycle. This effect is more appreciable in equinoctial months than in solstitial months. In September equinox, relative variations of foF2 at noon are depressed at high latitudes and enhanced in low-equatorial latitudes during IMF away sectors. This research was supported by Chinese Academy of Sciences (KZZD-EW-01-3), National Key Basic Research Program of China (2012CB825604) and National Natural Science Foundation of China (41231065).

Liu, Libo; Liu, Jing; Zhao, Biqiang; Wan, Weixing

2013-04-01

396

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

PubMed

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

Chen, Lixiang; She, Weilong

2007-11-12

397

LETTER TO THE EDITOR: High-speed (>10 Gbps) 850 nm oxide-confined vertical cavity surface emitting lasers (VCSELs) with a planar process and reduced parasitic capacitance  

NASA Astrophysics Data System (ADS)

This study reports the high-speed performance of 850 nm oxide-confined vertical cavity surface emitting lasers (VCSELs) with a planar process and reduced parasitic capacitance. The parasitic capacitance of VCSELs was reduced using additional proton implantation. The small signal modulation bandwidth which was restricted by electric parasitic capacitance expanded from 2.3 GHz to 9 GHz after proton implantation. The reflection coefficient showed that the electric parasitic pole exceeded 20 GHz. An eye diagram of VCSEL with reduced parasitic capacitance operating at 10 Gps with 6 mA bias and 6 dB extinction ratio showed a very clean eye with a jitter of less than 20 ps.

Chang, Y. H.; Lai, Fang-I.; Lu, C. Y.; Kuo, H. C.; Yu, H. C.; Sung, C. P.; Yang, H. P.; Wang, S. C.

2004-07-01

398

Sea ice dynamics as a control for halogen deposition in polar regions  

NASA Astrophysics Data System (ADS)

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.

Spolaor, Andrea; Plane, John M. C.; Vallelonga, Paul; Gabrieli, Jacopo; Cozzi, Giulio; Turetta, Clara; Kohler, Jack; Isaksson, Elisabeth; Barbante, Carlo

2013-04-01

399

Interpreting shadows: Arms control and defense planning in a rapidly changing multi-polar world  

Microsoft Academic Search

The focus of arms control is changing. It now deals with issues affecting all nations and not just the super powers. A new framework for approaching non-proliferation of weapons of mass destruction and arms control could focus on a two-fold policy initiative. The first policy would be a new strategic `triad` built around conventional capability including rapidly deployable forces, regional

1999-01-01

400

Controlling helicity-correlated beam asymmetries in a polarized electron source  

SciTech Connect

The control of helicity-correlated changes in the electron beam is a critical issue for the next generation of parity-violating electron scattering measurements. The underlying causes and methods for controlling these changes are reviewed with reference to recent operational experience at Jefferson Lab.

Kent Paschke

2007-07-01

401

Interpreting Shadows: Arms Control and Defense Planning in a Rapidly Changing Multi-Polar World.  

National Technical Information Service (NTIS)

The focus of arms control is changing. It now deals with issues affecting all nations and not just the super powers. A new framework for approaching non-proliferation of weapons of mass destruction and arms control could focus on a two-fold policy initiat...

D. R. King

1999-01-01

402

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

PubMed Central

Plants, similar to animals, form polarized axes during embryogenesis upon 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 fate1–3, while the master regulators of apical/shoot fate have remained elusive. Here we show that the PLT1 and PLT2 genes are direct targets of the transcriptional corepressor TOPLESS (TPL) and that PLT1/2 are necessary for the homeotic conversion of shoots to roots in tpl-1 mutants. Using tpl-1 as a genetic tool, we identify the CLASS III HOMEODOMAIN-LEUCINE ZIPPER (HD-ZIP III) transcription factors as master regulators of embryonic apical fate, and show they are sufficient to drive the conversion of the embryonic root pole into a second shoot pole. Furthermore, genetic and misexpression studies reveal an antagonistic relationship between the PLT and HD-ZIP III genes in specifying the root and shoot pole.

Smith, Zachery R.; Long, Jeff A.

2010-01-01

403

Planar cell polarity controls directional Notch signaling in the Drosophila leg  

PubMed Central

The generation of functional structures during development requires tight spatial regulation of signaling pathways. Thus, in Drosophila legs, in which Notch pathway activity is required to specify joints, only cells distal to ligand-producing cells are capable of responding. Here, we show that the asymmetric distribution of planar cell polarity (PCP) proteins correlates with this spatial restriction of Notch activation. Frizzled and Dishevelled are enriched at distal sides of each cell and hence localize at the interface with ligand-expressing cells in the non-responding cells. Elimination of PCP gene function in cells proximal to ligand-expressing cells is sufficient to alleviate the repression, resulting in ectopic Notch activity and ectopic joint formation. Mutations that compromise a direct interaction between Dishevelled and Notch reduce the efficacy of repression. Likewise, increased Rab5 levels or dominant-negative Deltex can suppress the ectopic joints. Together, these results suggest that PCP coordinates the spatial activity of the Notch pathway by regulating endocytic trafficking of the receptor.

Capilla, Amalia; Johnson, Ruth; Daniels, Maki; Benavente, Maria; Bray, Sarah J.; Galindo, Maximo Ibo

2012-01-01

404

Temperature-Controlled Symmetry of Linear Polarization of Photoluminescence from InGaAs-Buried InAs/GaAs Quantum Dots  

NASA Astrophysics Data System (ADS)

We have succeeded in adjusting the symmetry of the linear polarization of exciton emission from self-assembled InAs/GaAs quantum dots by controlling the combination of temperature and composition of the InGaAs burying layer. The anisotropic shape of the Stranski--Krastanow-type quantum dot is a drawback to the generation of a polarization-entangled photon pair. We found that the polarization symmetry of the intensity and wavelength of photon emission depends on the sample temperature and the composition of the burying layer. The ground-state emission peaks in two linear polarization directions were tuned to overlap by lowering the temperature and using a high indium composition of the burying layer. Our results will aid in the development of an entangled-photon generator using the emission of exciton molecule in self-assembled quantum dots.

Mukai, Kohki; Kikushima, Kousuke; Tanaka, Tomoya; Nakashima, Seisuke

2013-06-01

405

Localized photo-induced voltage with controlled polarity in single K enriched MoO3 nanobundle.  

PubMed

The photo-induced voltage in an individual K enriched MoO(3) nanobundle was studied with localized focused laser beam irradiation. Without an external bias voltage, a significant photo-induced voltage (36.5 mV) was produced in a single nanobundle under low laser power (2.2 mW). Remarkably, the amplitude and polarity of the voltage could be controlled by the location of the focused laser spot. Unlike the common photo-response that comes from metal-semiconductor junction or PN junction in hybrid nanomaterial, the observed photo-induced effect is from the nanobundle itself, attributed to the small band gap of the material. PMID:23117865

Hu, Zhibin; Tok, Eng Soon; Sow, Chorng Haur

2012-11-01

406

Interpreting shadows: Arms control and defense planning in a rapidly changing multi-polar world  

SciTech Connect

The focus of arms control is changing. It now deals with issues affecting all nations and not just the super powers. A new framework for approaching non-proliferation of weapons of mass destruction and arms control could focus on a two-fold policy initiative. The first policy would be a new strategic `triad` built around conventional capability including rapidly deployable forces, regional ballistic missile defense, and long-range precision-strike capability. The second policy would employ an information strategy using the current diplomatic initiatives that appear to be the most productive, or unilateral and multilateral export controls, military assistance in the form of infrastructure, and confidence building measures. Continued success in arms control requires abandoning Cold War policies. Emerging policies will need to appreciate different world views. Good intelligence will be a key factor in the success of any policy orientation and its implementation. The focus needs to change from arms control involving the superpowers to arms control involving everyone.

King, D.R.

1999-06-01

407

Members of a novel class of Arabidopsis Rho guanine nucleotide exchange factors control Rho GTPase-dependent polar growth.  

PubMed

Rho family small GTPases are signaling switches controlling many eukaryotic cellular processes. Conversion from the GDP- to GTP-bound form is catalyzed by guanine nucleotide exchange factors (GEFs). Rho GEFs in animals fall into two structurally distinct classes containing DH and DOCKER catalytic domains. Using a plant Rho GTPase (ROP1) as bait in yeast two-hybrid screens, we identified a family of Rho GEFs, named RopGEFs. The Arabidopsis thaliana RopGEF family of 14 members contains a conserved central domain, the domain of unknown function 315 (DUF315), and variable N- and C-terminal regions. In vitro GEF assays show that DUF315 but not the full-length version of RopGEF1 has high GEF activity toward ROP1. Our data suggest that the variable regions of RopGEF1 are involved in regulation of RopGEF through an autoinhibitory mechanism. RopGEF1 overexpression in pollen tubes produced growth depolarization, as does a constitutively active ROP1 mutant. The RopGEF1 overexpression phenotype was suppressed by expression of a dominant-negative mutant of ROP1, probably by trapping RopGEF1. Deletion mutant analysis suggested a requirement of RopGEF activity for the function of RopGEF1 in polar growth. Green fluorescent protein-tagged RopGEF1 was localized to the tip of pollen tubes where ROP1 is activated. These results provide strong evidence that RopGEF1 activates ROP1 in control of polar growth in pollen tubes. PMID:16415208

Gu, Ying; Li, Shundai; Lord, Elizabeth M; Yang, Zhenbiao

2006-01-13

408

Analysis of filter control polarization mode dispersion in dispersion managed soliton systems  

NASA Astrophysics Data System (ADS)

The effects of the PMD and filter control in DMS system are studied theoretically with variational method. Firstly, the DMS transmission of filtering control in constant birefringence fibers is analyzed by Varitional method, from which the evolving rules of characteristically DMS parameters are obtained. Secondly, the stability of DMS transmission and its timing jitter are investigated in the random varying birefringence fibers. At the last, the mean square of DMS timing jitter is gotten, which can be simplfied to no filtering DMS system and to linear transmission systems in considering the effects of PMD. The results reveal that the condition of stability of filter control in DMS system must be satisfied with the relationship of filter strength kf < 2dyP3 Esol ÷ ??B4C2 + 2yP3 Esol C and DMS's timing jitter can be decreased considerably with help of filter strength.

Xu, Ming; Ji, Jianhua; Yang, Shuwen

2005-12-01

409

Polarity Therapy for Cancer-Related Fatigue in Patients With Breast Cancer Receiving Radiation Therapy: A Randomized Controlled Pilot Study  

PubMed Central

Background Cancer-related fatigue (CRF) is the most frequently reported side effect of cancer and its treatment. In previous research, Polarity Therapy (PT), an energy therapy, was shown to reduce CRF in patients receiving radiation. This study reports on a small randomized clinical trial designed to collect preliminary data on the efficacy of PT compared with an active control (massage) and passive control (standard care) for CRF among cancer patients receiving radiation therapy. Methods Forty-five women undergoing radiation therapy for breast cancer were randomized to I of 3 weekly treatment conditions. Patients received standard clinical care, 3 modified massages, or 3 PT treatments. CRF and healthrelated quality of life (HRQL) were assessed during baseline and the 3 intervention weeks. Results TResults show CRF ratings were reduced after PT. The effect sizes for PT versus modified massage and versus standard care were small when using the primary measure of CRF (Brief Fatigue Inventory) and large when using the secondary measure of CRF (Daily CRF Diaries).The effect size was medium when assessing the benefit of PT on maintaining HRQL compared with standard care with very little difference between the PT and modified massage conditions. Patients’ feedback showed that both the modified massage and PT treatments were deemed useful by radiation patients. Conclusion. The present pilot randomized clinical trial supports previous experimental research showing that PT, a noninvasive and gentle energy therapy, may be effective in controlling CRF. Further confirmatory studies as well as investigations of the possible mechanisms of PT are warranted.

Mustian, Karen M.; Roscoe, Joseph A.; Palesh, Oxana G.; Sprod, Lisa K.; Heckler, Charles E.; Peppone, Luke J.; Usuki, Kenneth Y.; Ling, Marilyn N.; Brasacchio, Ralph A.; Morrow, Gary R.

2011-01-01

410

A Bacterial Ras-Like Small GTP-Binding Protein and Its Cognate GAP Establish a Dynamic Spatial Polarity Axis to Control Directed Motility  

PubMed Central

Regulated cell polarity is central to many cellular processes. We investigated the mechanisms that govern the rapid switching of cell polarity (reversals) during motility of the bacterium Myxococcus xanthus. Cellular reversals are mediated by pole-to-pole oscillations of motility proteins and the frequency of the oscillations is under the control of the Frz chemosensory system. However, the molecular mechanism that creates dynamic polarity remained to be characterized. In this work, we establish that polarization is regulated by the GTP cycle of a Ras-like GTPase, MglA. We initially sought an MglA regulator and purified a protein, MglB, which was found to activate GTP hydrolysis by MglA. Using live fluorescence microscopy, we show that MglA and MglB localize at opposite poles and oscillate oppositely when cells reverse. In absence of MglB, MglA-YFP accumulates at the lagging cell end, leading to a strikingly aberrant reversal cycle. Spatial control of MglA is achieved through the GAP activity of MglB because an MglA mutant that cannot hydrolyze GTP accumulates at the lagging cell end, despite the presence of MglB. Genetic and cell biological studies show that the MglA-GTP cycle controls dynamic polarity and the reversal switch. The study supports a model wherein a chemosensory signal transduction system (Frz) activates reversals by relieving a spatial inhibition at the back pole of the cells: reversals are allowed by Frz-activated switching of MglB to the opposite pole, allowing MglA-GTP to accumulate at the back of the cells and create the polarity switch. In summary, our results provide insight into how bacteria regulate their polarity dynamically, revealing unsuspected conserved regulations with eukaryots.

Zhang, Yong; Franco, Michel; Ducret, Adrien; Mignot, Tam

2010-01-01

411

High-density optical interconnect using polymer waveguides interfaced to a VCSEL array in molded plastic packaging  

NASA Astrophysics Data System (ADS)

The technical approach and progress achieved under the Polymer Optical Interconnect Technology (POINT) program are described in this paper. The POINT program is a collaborative effort among GE, Honeywell, AMP, AlliedSignal, Columbia University, and University of California at San Diego (UCSD), sponsored by DARPA/ETO, to develop affordable optoelectronic packaging and interconnect technologies for board and backplane applications. Specifically, progress is reported on (a) development of a plastic VCSEL array packaging technology using batch and planar fabrication, (b) demonstration of high-density optical interconnects for board and backplane applications using polymer waveguides to a length of 50 cm at an I/O density of 250 channels per inch, (c) development of low-loss optical polymer waveguides with loss less than 0.1 dB/cm at 850 nm, and (d) development of passively alignment processes for efficient coupling between a VCSEL array and polymer waveguides. Significant progress has also been made under the POINT program at Columbia University, in applying CAD tools to simulate multi-mode-guided wave systems and, at UCSD, to assist mechanical and thermal design in optoelectronic packaging. Because of space limitations, these results will be described elsewhere in future publications.

Liu, Yung S.; Wojnarowski, R. J.; Hennessy, W. B.; Piacente, P. A.; Rowlette, John R.; Kadar-Kallen, Michael A.; Stack, Jared D.; Liu, Yue; Peczalski, Andrzej; Nahata, Ajay

1998-05-01

412

Polarization controlled kinetics and composition of trivalent chromium coatings on aluminum.  

PubMed

Combined in situ spectroscopic ellipsometry and electrochemistry have been employed to monitor, in real-time, the formation of trivalent Cr conversion coatings on polished Al substrates at applied sample potentials. It is found that the formation kinetics and chemical composition of the film can be controlled by adjusting the anodic and cathodic reactions. The growth kinetics are accelerated at more positive anodic potentials or more negative cathodic potentials. At more negative potentials, the percentage of chromium in the coating is found to increase, while the zirconium percentage decreases. PMID:21726081

Dardona, Sameh; Chen, Lei; Kryzman, Michael; Goberman, Daniel; Jaworowski, Mark

2011-07-21

413

Progress towards a polarization spectroscopy experiment for quantum control of collective spin  

NASA Astrophysics Data System (ADS)

We report preliminary results from an experiment that will implement quantum control of the collective spin of an atomic ensemble. In our setup, a weak probe laser interacts with a cold, trapped atomic sample of cesium atoms with high optical depth, leading to Faraday rotation of the probe light proportional to the atomic magnetization. If the atom-light coupling is strong enough, polarimetry of the probe light will provide a measurement of the magnetization with resolution better than the spin projection noise, at which point measurement back-action will become significant enough to be used for quantum control of the spin. Thus far, we have loaded cesium atoms into a ˜50 ?K deep optical dipole trap, and we observe Faraday rotation of the probe light as it passes through this cloud of atoms. Work is ongoing to increase the optical depth of the atom sample and to optimize the atom-light coupling by mode-matching the probe beam to the atom sample.

Mickelson, Pascal G.; Montano, Enrique; Hemmer, Daniel; Jessen, Poul S.

2012-06-01

414

Induced morphology control of Ln-asparagine coordination polymers from the macro to nanoscopic regime in polar solvent-water mixtures.  

PubMed

A bottom-up approach is presented here for morphology control of Ln-asparagine (Asn) coordination polymers (CPs) from the macro to nanoscopic regime by tuning solvent polarity based on the ?* solvent polarity scale in polar solvent-water mixed solutions. By a simple hydrothermal treatment, large macroporous spheres with sizes up to millimeters were obtained in ethanol (?*: 0.54)-water mixtures, and their formation mechanism was proved to be particle aggregation together with a hollowing process based on Ostwald ripening. Other solvents with increasing polarity were also used, and submicrometer spheres as well as fine nanoparticles were prepared in acetone (?*: 0.71) and DMF (?*: 0.88), respectively. When dioxane (?*: 0.55) was used here, whose ?* value is similar to ethanol, large macroporous spheres were also prepared. Furthermore, with Ce- and La-Asn CPs large spheres as precursors, after calcination, ceria and lanthana large spheres with hierarchical structures were fabricated, respectively. Considering that many growth media of CPs are single solvent systems, designing certain solvents mixtures and tuning their polarity would bring us new opportunities to achieve morphology and composition control of CPs materials. PMID:23111349

Yang, Ming; Shen, Zhurui; Chen, Tiehong; Bi, Huichao; Yang, Bin; Xu, Wei

2013-01-28

415

Parsing the Polarity Code  

Microsoft Academic Search

Cell polarization is used both to mediate physical fates, as, for example, in orientated cell migration, and to specify differential phenotypic fates, as in the asymmetric division of stem cells. Strikingly, the same sets of conserved proteins are used throughout the Metazoa for these purposes. The PAR proteins organize cell polarization in many contexts, and the PINS proteins control the

Ian G. Macara

2004-01-01

416

Cell polarity and hyphal morphogenesis are controlled by multiple rho-protein modules in the filamentous ascomycete Ashbya gossypii.  

PubMed Central

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.

Wendland, J; Philippsen, P

2001-01-01

417

Polarization Manipulation via Orientation Control in Polycrystalline BiFeO3 Thin Films on Biaxially Textured, Flexible Metallic Tapes  

SciTech Connect

(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.

Shin, Junsoo [ORNL; Goyal, Amit [ORNL; Jesse, Stephen [ORNL; Heatherly Jr, Lee [ORNL

2011-01-01

418

Polarized Electrons for Polarized Positrons  

NASA Astrophysics Data System (ADS)

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.

Fanchini, Erica

2012-03-01

419

Real-time, continuous, fluorescence sensing in a freely-moving subject with an implanted hybrid VCSEL/CMOS biosensor  

PubMed Central

Performance improvements in instrumentation for optical imaging have contributed greatly to molecular imaging in living subjects. In order to advance molecular imaging in freely moving, untethered subjects, we designed a miniature vertical-cavity surface-emitting laser (VCSEL)-based biosensor measuring 1cm3 and weighing 0.7g that accurately detects both fluorophore and tumor-targeted molecular probes in small animals. We integrated a critical enabling component, a complementary metal-oxide semiconductor (CMOS) read-out integrated circuit, which digitized the fluorescence signal to achieve autofluorescence-limited sensitivity. After surgical implantation of the lightweight sensor for two weeks, we obtained continuous and dynamic fluorophore measurements while the subject was un-anesthetized and mobile. The technology demonstrated here represents a critical step in the path toward untethered optical sensing using an integrated optoelectronic implant.

O'Sullivan, Thomas D.; Heitz, Roxana T.; Parashurama, Natesh; Barkin, David B.; Wooley, Bruce A.; Gambhir, Sanjiv S.; Harris, James S.; Levi, Ofer

2013-01-01

420

Real-time, continuous, fluorescence sensing in a freely-moving subject with an implanted hybrid VCSEL/CMOS biosensor.  

PubMed

Performance improvements in instrumentation for optical imaging have contributed greatly to molecular imaging in living subjects. In order to advance molecular imaging in freely moving, untethered subjects, we designed a miniature vertical-cavity surface-emitting laser (VCSEL)-based biosensor measuring 1cm(3) and weighing 0.7g that accurately detects both fluorophore and tumor-targeted molecular probes in small animals. We integrated a critical enabling component, a complementary metal-oxide semiconductor (CMOS) read-out integrated circuit, which digitized the fluorescence signal to achieve autofluorescence-limited sensitivity. After surgical implantation of the lightweight sensor for two weeks, we obtained continuous and dynamic fluorophore measurements while the subject was un-anesthetized and mobile. The technology demonstrated here represents a critical step in the path toward untethered optical sensing using an integrated optoelectronic implant. PMID:24009996

O'Sullivan, Thomas D; Heitz, Roxana T; Parashurama, Natesh; Barkin, David B; Wooley, Bruce A; Gambhir, Sanjiv S; Harris, James S; Levi, Ofer

2013-07-15

421

Surface micromachined tunable 1.55 ?m-VCSEL with 102 nm continuous single-mode tuning.  

PubMed

For the first time a vertical-cavity surface-emitting laser (VCSEL) with a single-mode wavelength-tuning over 102 nm in the range of 1550 nm is demonstrated. The fiber-coupled optical output power has a maximum of 3.5 mW and is > 2 mW over the entire tuning range. The sidemode suppression ratios are > 45 dB. The wavelength tuning is achieved with the micro-electro mechanical actuation of a mirror membrane fabricated with surface micro-machining for on-wafer mass production. The mirror membrane consists of low cost dielectric materials (SiOx/SiNy) deposited with low temperature (< 100°C) Plasma Enhanced Chemical Vapor Deposition (PECVD). PMID:21935097

Gierl, C; Gruendl, T; Debernardi, P; Zogal, K; Grasse, C; Davani, H A; Böhm, G; Jatta, S; Küppers, F; Meissner, P; Amann, M-C

2011-08-29

422

The effect of surface alignment on analog control of director rotation in polarization stiffened SmC* devices  

NASA Astrophysics Data System (ADS)

The effect of surface alignment on the achievement of analog (``V''-shaped) electric field control of director rotation in SmC* liquid crystal devices is investigated experimentally and through numerical modeling. Ferroelectric SmC* liquid crystals are intrinsically analog and thresholdless, i.e. the director can be rotated freely around the tilt cone. Whether or not a SmC* liquid crystal cell exhibits thresholdless switching depends strongly on the influence of the cell's alignment layers, on the magnitude of the liquid crystal's spontaneous polarization, and on whether smectic layers adopt a bookshelf or chevron configuration. To study the effect of the surface alignment layers, we have exploited a technique for the vertical (bookshelf) alignment of the smectic layers that does not depend on surface anisotropy. The alignment technique allows an experimental study of the influence of surfaces spanning a wide range of pretilt angles, azimuthal and zenithal anchoring energies. This technique is used to study the effect of surfaces on the threshold behavior of director rotation in SmC* materials under the influence of an electric field. The alignment technique also allowed us to use a high-PS liquid crystal material having an I-A-C phase sequence and reduced layer shrinkage thought to be well suited to thresholdless switching. We show that the alignment layer has a strong effect, and that excellent analog response can be achieved for the case of alignment layers which promote homeotropic director orientation. We further model and discuss the potential effect of a thin layer of nematic at the surface and the possibility of gliding of the easy axis during switching.

Reznikov, Mitya; Lopatina, Lena M.; O'Callaghan, Michael J.; Bos, Philip J.

2011-03-01

423

Soluble peroxidase gradients in lupin hypocotyls and the control of the level of polarly transported indole-3yl-acetic acid  

Microsoft Academic Search

The distribution of basic soluble isoperoxidases along the growth gradient of lupin hypocotyl was studied in order to establish\\u000a the role of these isoenzymes in controlling polarly transported indole-3yl-acetic acid (IAA) levels. The observation that\\u000a the levels of basic isoperoxidases, which diminish from the young (vascular differentiating) to the older (vascular differentiated)\\u000a tissues, are related with previously reported IAA oxidation

M. A. Ferrer; M. A. Pedrefio; R. Mufioz; A. Ros Barceló

1991-01-01

424

Polarization of barcode readers  

NASA Astrophysics Data System (ADS)

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 other polarization-critical system to be accurately characterized. Polarization raytracing often requires the use of local, ray-based coordinate system for expressing rays' polarization states, yet the choice of coordinate system can have important implications on system analysis. An example is presented in which specular reflection is controlled in a barcode reader by using reflection-enhanced coatings on only one of the four set of the mirrors in the system. The coordinate system used to express rays' polarization states in the example system provides useful lessons for other systems. The other analytical methods used in this example can be applied to a variety of scanning systems.

Reiley, Daniel J.

1998-02-01

425

Polarization-controlled evolution of light transverse modes and associated Pancharatnam geometric phase in orbital angular momentum  

SciTech Connect

We present an easy, efficient, and fast method to generate arbitrary linear combinations of light orbital angular-momentum eigenstates l={+-}2 starting from a linearly polarized TEM{sub 00} laser beam. The method exploits the spin-to-orbital angular-momentum conversion capability of a liquid-crystal-based q plate and a Dove prism inserted into a Sagnac polarizing interferometer. The nominal generation efficiency is 100%, being limited only by reflection and scattering losses in the optical components. When closed paths are followed on the polarization Poincare sphere of the input beam, the associated Pancharatnam geometric phase is transferred unchanged to the orbital angular momentum state of the output beam.

Karimi, Ebrahim; Marrucci, Lorenzo [Dipartimento di Scienze Fisiche, Universita di Napoli 'Federico II', Complesso di Monte S. Angelo, I-80126 Napoli (Italy); CNR-INFM Coherentia, Complesso di Monte S. Angelo, I-80126 Napoli (Italy); Slussarenko, Sergei; Piccirillo, Bruno; Santamato, Enrico [Dipartimento di Scienze Fisiche, Universita di Napoli 'Federico II', Complesso di Monte S. Angelo, I-80126 Napoli (Italy); Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, I-80126 Napoli (Italy)

2010-05-15

426

Multi-Gb\\/s graded-index POF data link with butt-coupled single-mode InGaAs VCSEL  

Microsoft Academic Search

InGaAs quantum-well-based vertical-cavity surface-emitting lasers (VCSEL's) at 935-nm emission wavelength are investigated for perfluorinated graded-index plastic-optical fiber (GI-POF) links. We report a 7-Gb\\/s pseudorandom bit sequence (PRBS) nonreturn-to-zero (NRZ) data transmission over 80-m-long 155-?m-diameter GI-POF at a bit-error rate (BER) of better than 10-11

F. Mederer; R. Jager; P. Schnitzer; H. Unold; M. Kicherer; K. J. Ebeling; M. Naritomi; R. Yoshida

2000-01-01

427

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)

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).

Karinou, Fotini; Deng, Lei; Lopez, Roberto Rodes; Prince, Kamau; Jensen, Jesper Bevensee; Monroy, Idelfonso Tafur

2013-06-01

428

Laser hygrometer using a vertical-cavity surface-emitting laser (VCSEL) with an emission wavelength of 1.84 ?m  

Microsoft Academic Search

This paper presents a hygrometer setup for measuring the concentration of water vapor in air by means of infrared absorption spectroscopy. Recently developed vertical-cavity surface-emitting lasers (VCSELs) emitting near 1.84 ?m are used as source of the infrared light. The laser hygrometer is able to calculate the density of water molecules from the measurement of one single light-current characteristic, without

Christian Lauer; Stefan Szalay; Gerhard Böhm; Chun Lin; Fabian Köhler; Markus-Christian Amann

2005-01-01

429

Simulation studies of a 2 Gb s-1 monolithic integrated smart pixel based on fabricated p-i-n PD, DHBT and a VCSEL  

NASA Astrophysics Data System (ADS)

A smart pixel that can function as a building block of an optical transceiver with circular dimensions is proposed using InGaP/GaAs double heterojunction bipolar transistors (DHBTs) and a GaAs/AlGaAs vertical cavity surface emitting laser (VCSEL). Fabricated DHBT showed a breakdown voltage of 13 V and a cut-off frequency of 35 GHz at Ic = 30 mA. Also a high-performance 850 nm infra-red VCSEL exhibited a threshold current of 3.5 mA with a maximum optical output of 4.8 mW at Ic = 20 mA and forward voltage of 1.8 V. The detector, comprised of the base-to-collector junction of the DHBT as a pin-PD, produced a photocurrent of 180 µA for a given input power of 0.3 mW. The extracted small-signal equivalent circuit parameters from measurement of these devices were used in PSPICE simulations to design an interface drive circuit for high-speed modulation. The overall OEIC circuit performance operates up to data rates of 2 Gb s-1 at 1 mW output power with maximum output voltage of 2 V across the VCSEL and modulation current of 5 mA.

Loga, R.; Vilches, A.

2003-07-01

430

Multigigabit/s perfluorinated graded-index plastic-optical-fiber data links with butt-coupled single-mode InGaAs VCSEL  

NASA Astrophysics Data System (ADS)

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 Gbit/s and 7 Gbit/s pseudo-random-bit-sequence non-return- to-zero data transmission over 80 m perfluorinated GI-POF made of CYTOP using a single mode butt-coupled selectively oxidized InGaAs VCSEL source emitting at 935 nm emission wavelength. For 3 Gbit/s data rather the received optical power for a bit error rate (BER) of 10-11 is -22.5 dBm for back-to-back (BTB). A power penalty of 1 dB is found for transmission over 100 m graded-index multimode glass fiber and 2 dB for 80 m GI-POF for 80 m GI- POF transmission. Reduced power penalty observed at 7 Gbit/s is attributed to the restricted modulation bandwidth of the VCSEL used in the experiment.

Mederer, Felix; Jaeger, Roland; Schnitzer, Peter; Unold, Heiko J.; Kicherer, Max; Ebeling, Karl J.; Naritomi, Masaki; Yoshida, Ryouta

1999-11-01

431

Controlling the delay of 100 Gb\\/s polarization division multiplexed signals through silicon photonics delay lines  

Microsoft Academic Search

We show a direct comparison between silicon reconfigurable delay lines based on coupled resonator optical waveguides and photonic crystal waveguides. The structures are used to selectively delay the two orthogonally polarized channels of a RZ-PolDM-DQPSK format at 100 Gbit\\/s.

F. Morichetti; A. Canciamilla; C. Ferrari; M. Torregiani; M. Ferrario; R. Siano; P. Boffi; L. Marazzi; P. Martelli; P. Parolari; M. Martinelli; A. Samarelli; M. Sorel; R. M. De La Rue; L. O'Faolain; D. M. Beggs; T. F. Krauss; A. Melloni

2010-01-01