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1

VCSEL Polarization Control for Chip-Scale Atomic Clocks.  

National Technical Information Service (NTIS)

Sandia National Laboratories and Mytek, LLC have collaborated to develop a monolithically-integrated vertical-cavity surface-emitting laser (VCSEL) assembly with controllable polarization states suitable for use in chip-scale atomic clocks. During the cou...

D. K. Serkland G. A. Keeler G. M. Peake J. R. Wendt K. M. Geib

2007-01-01

2

VCSEL polarization control for chip-scale atomic clocks.  

SciTech Connect

Sandia National Laboratories and Mytek, LLC have collaborated to develop a monolithically-integrated vertical-cavity surface-emitting laser (VCSEL) assembly with controllable polarization states suitable for use in chip-scale atomic clocks. During the course of this work, a robust technique to provide polarization control was modeled and demonstrated. The technique uses deeply-etched surface gratings oriented at several different rotational angles to provide VCSEL polarization stability. A rigorous coupled-wave analysis (RCWA) model was used to optimize the design for high polarization selectivity and fabrication tolerance. The new approach to VCSEL polarization control may be useful in a number of defense and commercial applications, including chip-scale atomic clocks and other low-power atomic sensors.

Geib, Kent Martin; Peake, Gregory Merwin; Wendt, Joel Robert; Serkland, Darwin Keith; Keeler, Gordon Arthur

2007-01-01

3

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

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

Polarization-stable single-mode VCSELs for Cs-based MEMS atomic clock applications  

NASA Astrophysics Data System (ADS)

Vertical-cavity surface-emitting lasers (VCSELs) emitting at 894.6 nm wavelength have been fabricated for Cs-based atomic clock applications. For polarization control, a previously developed technique relying on the integration of a semiconducting surface grating in the top Bragg mirror of the VCSEL structure is employed. More specifically, we use a so-called inverted grating. The VCSELs are polarized orthogonal to the grating lines with no far-field diffraction side-lobes for sub-wavelength grating periods. Orthogonal polarization suppression ratios exceed 20 dB. The polarization stability has been investigated at different elevated substrate temperatures up to 80 °C, where the VCSEL remains polarization-stable even well above thermal roll-over. For the purpose of integration with the atomic clock microsystem, flip-chip-bondable VCSEL chips have been realized. Sub-mA threshold currents and sufficient output powers in the milliwatt range are achieved. The required modulation bandwidth of more than 5 GHz is reached at only 0.5mA bias. Maximum bandwidths above 10 GHz have been measured even at elevated temperatures up to 80 °C. Modulation current efficiency factors larger than 12 GHz/?mA are achieved at room temperature. Moreover, the intrinsic modulation characteristics of the VCSELs are investigated by precise curve fitting of measured small-signal modulation response curves and relative intensity noise spectra. A K-factor of less than 0.4 ns and a maximum 3 dB bandwidth exceeding 22 GHz are obtained.

Al-Samaneh, Ahmed; Renz, Simeon; Strodl, Andreas; Schwarz, Wolfgang; Wahl, Dietmar; Michalzik, Rainer

2010-04-01

6

10-Gb/s Optical Buffer Memory Using a Polarization Bistable VCSEL  

NASA Astrophysics Data System (ADS)

Optical buffer memory for 10-Gb/s data signal is demonstrated experimentally using a polarization bistable vertical-cavity surface-emitting laser (VCSEL). The optical buffer memory is based on an optical AND gate function and the polarization bistability of the VCSEL. Fast AND gate operation responsive to 50-ps-width optical pulses is achieved experimentally by increasing the detuning frequency between an injection light into the VCSEL and a lasing light from the VCSEL. A specified bit is extracted from the 10-Gb/s data signal by the fast AND gate operation and is stored as the polarization state of the VCSEL by the polarization bistability. The corresponding numerical simulations are also performed using two-mode rate equations taking into account the detuning frequency. The simulation results confirm the fast AND gate operation by increasing the detuning frequency as well as the experimental results.

Mori, Takashi; Sato, Yuuki; Kawaguchi, Hitoshi

7

Polarization and Time-Resolved Dynamics of a 1550-nm VCSEL Subject to Orthogonally Polarized Optical Injection  

Microsoft Academic Search

We report a first experimental study of the simultaneous temporal and polarization-resolved dynamics of a 1550-nm vertical-cavity surface-emitting laser (VCSEL) subject to orthogonally polarized optical injection. A novel technique is used to reveal the behavior of both polarizations at the VCSEL's output. In general, the same type of dynamics can be seen in both polarizations of the fundamental transverse mode

Kevin Schires; Antonio Hurtado; Ian D. Henning; Michael J. Adams

2011-01-01

8

Polarization bistability in long-wavelength multitransverse-mode VCSELs induced by orthogonal optical injection  

NASA Astrophysics Data System (ADS)

In this work we report on an experimental investigation of the bistability found in 1550 nm multitransverse-mode VCSELs subject to orthogonal optical injection. The VCSEL emits in two transverse modes that are linearly polarized in a direction referred as parallel. We study the dependence of the bistable behaviour on the detuning between the frequency of the externally injected signal and the frequency of the subsidiary orthogonal linear polarization of the fundamental mode of the VCSEL. Different qualitative behaviors of the power of each polarized transverse mode versus the optically injected power appear depending on the value of the frequency detuning. Bistable regions are very narrow for positive and small negative values of the frequency detuning. However very wide hysteresis cycles are obtained for large and negative values of the frequency detuning. Bistability is found for both the fundamental and the high-order transverse mode. The shape of the hysteresis cycle depends on the transverse mode under consideration. The power of the parallel polarized fundamental transverse mode decreases gradually as the injected power is increased. However the behaviour of the parallel polarized high-order transverse mode is different because its power remains constant as the optical injected power is increased until it suddenly drops to low levels. This kind of behaviour is of interest for obtaining good quality all-optical inversion and all-optical regeneration.

Quirce, A.; Cuesta, J. R.; Valle, A.; Hurtado, A.; Pesquera, L.; Adams, M. J.

2010-04-01

9

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

PubMed

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

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

2013-11-18

10

Engineering of angular dependence of high-contrast grating mirror for transverse mode control of VCSELs  

NASA Astrophysics Data System (ADS)

We present our recent activity on highly angular-dependent high contrast grating (HCG) for the transverse mode control of VCSELs. The modeling and the experiment show the design flexibility of HCG to manage the angular dependence of HCG. The optimized angular dependent HCG functions as a spatial frequency filter. We are able to use the engineered angular dependence of HCG for the transverse-mode control of VCSELs by filtering out high-order transverse-modes. We fabricated and characterized amorphous Si HCG mirrors, which clearly show the large angular dependence. We demonstrated single-mode 980nm VCSELs with a HCG mirror functioning as a spatial frequency filter.

Koyama, Fumio

2014-02-01

11

High-Contrast Grating VCSELs  

NASA Astrophysics Data System (ADS)

We review a recent invention of single-layer one-dimensional high-index-contrast subwavelength grating (HCG) and its incorporation into a VCSEL structure. The HCG is approximately 50 times thinner than a conventional distributed Bragg reflector (DBR), but offers higher reflectivity with a much broader spectral width. It provides lithographically defined control of polarization, transverse mode and emission wavelength. Using this ultrathin reflector, the tunable mirror in a micro-mechanical HCG-VCSELs are fabricated with a 104 times volume reduction and more than two orders of magnitude improved tuning speed.

Chang-Hasnain, Connie J.

12

VCSEL-powered and polarization-maintaining fiber-optic grating vector rotation sensor.  

PubMed

A compact fiber-optic vector rotation sensor in which a short section of polarization-maintaining (PM) fiber stub containing a straight fiber Bragg grating (FBG) is spliced to another single mode fiber without any lateral offset is proposed and experimentally demonstrated. Due to the intrinsic birefringence of the PM fiber, two well-defined resonances (i.e. orthogonally polarized FBG core modes) with wavelength separation of 0.5 nm have been achieved in reflection, and they exhibit a high sensitivity to fiber rotation. Both the orientation and the angle of rotation can be determined unambiguously via simple power detection of the relative amplitudes of the orthogonal core reflections. Meanwhile, instead of using a broadband source (BBS), the sensor is powered by a commercial vertical cavity surface emitting laser (VCSEL) with the laser wavelength matched to the PM-FBG core modes, which enables the sensor to work at much higher power levels (~15 dB better than BBS). This improves the signal-to-noise ratio considerably (~50 dB), and makes a demodulation filter unnecessary. Vector rotation measurement with a sensitivity of 0.09 dB/deg has been achieved via cost-effective single detector real time power measurement, and the unwanted power fluctuations and temperature perturbations can be effectively referenced out. PMID:23938824

Guo, Tuan; Liu, Fu; Du, Fa; Zhang, Zhaochuan; Li, Chunjie; Guan, Bai-Ou; Albert, Jacques

2013-08-12

13

Enhanced chaotic communication in VCSELs with variable-polarization optical feedback and polarization-preserved optical injection  

NASA Astrophysics Data System (ADS)

The communication performance and security enhancement in vertical-cavity surface-emitting lasers (VCSELs) subject to variable-polarization optical feedback (VPOF) are investigated numerically. Unidirectional polarization-preserved optical injection (PPOI) scheme is adopted, chaos modulation is utilized for message encryption, and two decoding methods are discussed and compared. The influences of VPOF on the performances of two decoding methods are focused on, and the effects of injection strength and frequency detuning are also considered. The security enhancement is further discussed by analyzing the robustness to mismatched feedback configuration and polarizer angle, as well as the intrinsic parameters. It is shown that, successful message encoding and decoding with Q-factors greater than 6 can be achieved by using unpredictability-enhanced chaotic carrier. In particular, the Q-factors are quite sensitive to the feedback configuration and laser parameters. When an attacker with open-loop is considered, Q-factors are smaller than 3 (6) for division (subtraction) decoding method. Specifically, even when an attacker with close-loop is considered, the Q-factors are lower than 6 when mismatched polarizer angles or intrinsic parameters exceed ±20% for subtraction method, and are more sensitive to parameter mismatch for division method, which enhances significantly the security, and thus is extremely useful for the security-enhanced chaotic communication system.

Xiang, Shuiying; Pan, Wei; Luo, Bin; Yan, Lianshan; Zou, Xihua; Li, Nianqiang; Zhang, Liyue

2012-11-01

14

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

15

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

16

Evolution of VCSELs  

NASA Astrophysics Data System (ADS)

Over the last 20 years, nearly 1 billion VCSELs have been shipped, the vast majority of them emitting at 850nm using GaAs active regions, and primarily used in data communications and optical tracking applications. Looking to the future, the ever increasing speed of data communications is driving the VCSEL to evolve with more complex active regions, optical mode control, and alternate wavelengths to meet the more stringent requirements. We will discuss the current state of VCSELs for 28Gbps, and higher speeds, focusing on evolution to more complex active regions and alternate wavelength approaches, particularly as the market evolves to more active optical cables. Other high volume applications for VCSELs are driving improvements in single mode and optical power characteristics. We will present several evolving market trends and applications, and the specific VCSEL requirements that are imposed. The ubiquitous 850nm, GaAs active region VCSEL is evolving in multiple ways, and will continue to be a viable optical source well in to the future.

Tatum, Jim A.

2014-02-01

17

Nonpolar Gallium Nitride-based VCSELs  

NASA Astrophysics Data System (ADS)

GaN vertical-cavity surface-emitting lasers (VCSELs) are of increasing interest as sources of high-quality coherent light in the visible spectrum, particularly in blue wavelengths. These devices so far suffer from many problems, including low output power, low yield, and high costs. Nonpolar GaN offers many advantages for VCSELs. Anisotropic electric fields in the plane of the emitting quantum wells results in higher gain and crystallographically-oriented polarization of emitted light. This should result in the unique property of polarization locking, whereby the polarization direction of each device is identical, and determined by the crystal structure of the material in the device. Prior demonstrations of GaN VCSELs have relied on epitaxially-grown n-DBR mirrors, or mechanical polishing to remove the substrate to allow for deposition of dielectric DBR mirrors. Epitaxially-grown DBRs give epitaxial control of cavity length, but are very difficult and costly to grow. Mechanical polishing and deposition of dielectric DBRs simplifies fabrication, but gives no control of cavity length. This thesis reports on a novel fabrication method using photoelectrochemical (PEC) etching that gives epitaxial control of cavity length, while still allowing for the use of dielectric DBR mirrors. Using this novel fabrication method, the first nonpolar GaN-based VCSELs are demonstrated. These devices exhibit polarization locking, where each device is highly polarized parallel to the crystallographic a-direction of the wurtzite crystal structure. Electrically-injected lasing under pulsed operation at room temperature is reported, with an output power of approximately 20 uW at a wavelength of 411.9 nm.

Holder, Casey Oliver

18

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

19

High-speed characteristics of VCSELs  

Microsoft Academic Search

The high speed characteristics of Vertical Cavity Surface Emitting Lasers (VCSELs) for use in modern high bandwidth fiber optical networks is presented. An equivalent circuit model based on microwave network analyzer S11 measurements is developed. The dynamic operation of multi- transverse mode VCSELs is also investigated. Experimentally, a laser with two orthogonally polarized modes is examined. We show that each

Jim A. Tatum; David Smith; James K. Guenter; Ralph Johnson

1997-01-01

20

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

21

Control of polarization switching in vertical coupled-cavities surface emitting lasers  

Microsoft Academic Search

We report a novel three-contact vertical-cavity surface-emitting laser (VCSEL) for use in polarization-sensitive optical applications. The device consists of two vertical cavities, coupled by a common mirror. We demonstrate that one can independently choose both the power of the output beam-through the current in the first cavity-and the polarization state-through the bias applied to the second cavity. The control of

V. Badilita; J.-F. Carlin; M. Ilegems; M. Brunner; G. Verschaffelt; K. Panajotov

2004-01-01

22

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

23

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

24

VCSEL Applications and Simulation  

NASA Technical Reports Server (NTRS)

This viewgraph presentation gives an overview of Vertical Cavity Surface Emitting Laser (VCSEL) simulation and its applications. Details are given on the optical interconnection in information technology of VCSEL, the formulation of the simulation, its numeric algorithm, and the computational results.

Cheung, Samson; Goorjian, Peter; Ning, Cun-Zheng; Li, Jian-Zhong

2000-01-01

25

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

26

Noise and signal modeling of various VCSEL structures  

Microsoft Academic Search

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

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

2004-01-01

27

Phase-Controlled Polarization Modulators  

NASA Technical Reports Server (NTRS)

We report technology development of millimeter/submillimeter polarization modulators that operate by introducing a a variable, controlled phase delay between two orthogonal polarization states. The variable-delay polarization modulator (VPM) operates via the introduction of a variable phase delay between two linear orthogonal polarization states, resulting in a variable mapping of a single linear polarization into a combination of that Stokes parameter and circular (Stokes V) polarization. Characterization of a prototype VPM is presented at 350 and 3000 microns. We also describe a modulator in which a variable phase delay is introduced between right- and left- circular polarization states. In this architecture, linear polarization is fully modulated. Each of these devices consists of a polarization diplexer parallel to and in front of a movable mirror. Modulation involves sub-wavelength translations of the mirror that change the magnitude of the phase delay.

Chuss, D. T.; Wollack, E. J.; Novak, G.; Moseley, S. H.; Pisano, G.; Krejny, M.; U-Yen, K.

2012-01-01

28

Growth control and polarization.  

PubMed

Filamentous fungi and yeasts both undergo polar growth. In Saccharomyces cerevisiae, where the mechanisms for polar growth are well-understood, polarity requires three steps: establishment of cortical markers specifying the site of bud emergence; relaying the bud site information via the Cdc42 Rho GTPase module; and recruitment of the morphogenetic machinery needed to remodel the cell surface to the specified site. Comparison of the genomes of Aspergillus fumigatus, A. nidulans and A. oryzae with that of S. cerevisiae show that the cortical markers are absent or poorly conserved, while the RhoGTPase signaling module and the morphogenetic machinery are highly conserved in the aspergilli. Genetic approaches to polarity using A. nidulans polarity mutants with defects in germ tube emergence (swo mutants) or branching (ahb mutants) will also be discussed. PMID:16110788

Momany, M

2005-05-01

29

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

30

Interferometric polarization control  

NASA Technical Reports Server (NTRS)

A signal conditioning module provides a polarimeter capability in a photometric system. The module may include multiple variable delay polarization modulators. Each modulator may include an input port, and a first arm formed to include a first reflector and first rooftop mirror arranged in opposed relationship. The first reflector may direct an input radiation signal to the first rooftop mirror. Each modulator also may include an output port and a second arm formed to include a second reflector and second rooftop mirror arranged in opposed relationship. The second reflector can guide a signal from the second rooftop mirror towards the output port to provide an output radiation signal. A beamsplitting grid may be placed between the first reflector and the first rooftop mirror, and also between the second reflector and the second rooftop mirror. A translation apparatus can provide adjustment relative to optical path length vis-a-vis the first arm, the second arm and the grid.

Wollack, Edward J. (Inventor); Moseley, Samuel H. (Inventor); Novak, Giles A. (Inventor); Chuss, David T. (Inventor)

2009-01-01

31

Recent Advances of VCSEL Technologies  

Microsoft Academic Search

A vertical cavity surface emitting laser (VCSEL) was invented 30 years ago. A lot of unique features have been proven, 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 multi-mode optical fibers. Also,

F. Koyama; T. Miyamoto

2007-01-01

32

Fabrication issues of oxide-confined VCSELs  

Microsoft Academic Search

ABSTRACT To insert high performance,oxide-confined vertical-cavity surface-emittinglasers (VCSELs) into the manufacturing arena, we have examined the critical parameters that must be controlled to establish a repeatable and uniform wet thermal oxidation process for AlGaAs. These parameters include the AlAs mole fraction, the sample temperature, the carrier gas flow and the bubbler water temperature. Knowledge,of these critical parameters has enabled the

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

33

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

34

Dynamic Self-Locking of an OEO Containing a VCSEL  

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

35

LW VCSELs for SFP+ applications  

NASA Astrophysics Data System (ADS)

This article outlines development work at JDSU on InGaNAs based vertical cavity surface emitting lasers (VCSELs) operating at 1270nm and their use in 10Gbps SFP+ modules. DC and AC performance of die and transmit optical subassemblies (TOSAs) will be described. Due to their low power consumption, LW VCSELs are ideal for use in SFP+; module performance will be described as well.

Graham, Luke A.; Jewell, Jack L.; Maranowski, Kevin D.; Crom, Max V.; Feld, Stewart A.; Smith, Joseph M.; Beltran, James G.; Fanning, Thomas R.; Schnoes, Melinda; Gray, Matthew H.; Droege, David; Koleva, Vera; Dudek, Mike; Fiers, John; Patterson, Russ

2008-01-01

36

1550-nm wavelength-tunable HCG VCSELs  

NASA Astrophysics Data System (ADS)

We demonstrate wavelength-tunable VCSELs using high contrast gratings (HCGs) as the top output mirror on VCSELs, operating at 1550 nm. Tunable HCG VCSELs with a ~25 nm mechanical tuning range as well as VCSELs with 2 mW output power were realized. Error-free operation of an optical link using directly-modulated tunable HCG VCSELs transmitting at 1.25 Gbps over 18 channels spaced by 100 GHz and transmitted over 20 km of single mode fiber is demonstrated, showing the suitability of the HCG tunable VCSEL as a low cost source for WDM communications systems.

Chase, Christopher; Rao, Yi; Huang, Michael; Chang-Hasnain, Connie

2014-02-01

37

Nuclear reactivity control using laser induced polarization.  

National Technical Information Service (NTIS)

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 sec...

C. D. Bowman

1989-01-01

38

Modal noise in 2.5 Gbit\\/s data links with oxidized VCSELs  

Microsoft Academic Search

The highest bit rate transmitted to date using VCSELs has been achieved when operating the devices in the transverse single-mode linearly polarized regime. On the other hand it has been shown at 500 Mbit\\/s that transverse multi-mode InGaAs VCSELs are less sensitive to mode selective loss (MSL) due to their low coherence. In this contribution we study the effect of

U. Fiedler; B. Weigl; G. Reiner; R. King; K.-J. Ebeling

1996-01-01

39

Reversible Polarization Control of Single Photon Emission  

Microsoft Academic Search

We present reversible and a-priori control of the polarization of a photon emitted by a single molecule by introducing a nanoscale metal object in its near field. It is experimentally shown that, with the metal close to the emitter, the polarization ratio of the emission can be varied by a factor of 2. The tunability of polarization decays, when the

Robert J. Moerland; Tim H. Taminiau; Lukas Novotny; Hulst van Niek F; Laurens Kuipers

2008-01-01

40

Optical Injection Locking of a VCSEL in an OEO  

NASA Technical Reports Server (NTRS)

Optical injection locking has been demonstrated to be effective as a means of stabilizing the wavelength of light emitted by a vertical-cavity surface- emitting laser (VCSEL) that is an active element in the frequency-control loop of an opto-electronic oscillator (OEO) designed to implement an atomic clock based on an electromagnetically- induced-transparency resonance. This particular optical-injection- locking scheme is expected to enable the development of small, low-power, high-stability atomic clocks that would be suitable for use in applications involving precise navigation and/or communication. In one essential aspect of operation of an OEO of the type described above, a microwave modulation signal is coupled into the VCSEL. Heretofore, it has been well known that the wavelength of light emitted by a VCSEL depends on its temperature and drive current, necessitating thorough stabilization of these operational parameters. Recently, it was discovered that the wavelength also depends on the microwave power coupled into the VCSEL. Inasmuch as the microwave power circulating in the frequency-control loop is a dynamic frequency-control variable (and, hence, cannot be stabilized), there arises a need for another means of stabilizing the wavelength. The present optical-injection-locking scheme satisfies the need for a means to stabilize the wavelength against microwave- power fluctuations. It is also expected to afford stabilization against temperature and current fluctuations. In an experiment performed to demonstrate this scheme, wavelength locking was observed when about 200 W of the output power of a commercial tunable diode laser was injected into a commercial VCSEL, designed to operate in the wavelength range of 795+/-3 nm, that was generating about 200 microW of optical power. (The use of relatively high injection power levels is a usual practice in injection locking of VCSELs.)

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

2009-01-01

41

1060nm 28-Gbps VCSEL developed at Furukawa  

NASA Astrophysics Data System (ADS)

This paper presents recent development results of our 28-Gbps VCSELs featured with double intra-cavity structure and a lasing wavelength of 1060 nm. The double intra-cavity realizes very low cavity loss due to undoped semiconductor bottom DBR and dielectric top DBR layers. Compressively strained InGaAs MQW provides high differential gain that contributes to low power consumption and high reliability. Based on our 10-Gbps VCSEL structure, we carefully optimized MQW, selective oxide structure, cavity length, and doping profile in order to achieve high speed operation while maintaining high reliability and other laser performances. The developed VCSELs exhibit modulation 3 dB-bandwidth exceeding 20 GHz and D-factor of 10 GHz/(mA)1/2. Typical threshold current and slope efficiency are 0.5 mA and 0.5 W/A, respectively. The paper also discusses static and dynamic characteristics of VCSELs with various oxide aperture sizes simultaneously fabricated on the same wafer. For a longer transmission distance and better optical coupling to a multimode fiber, optical lateral confinement is precisely controlled to reduce spectral width as well as far-field pattern. Clearly opened eye diagrams are obtained at a bit rate of 28 Gbps. Bit error rate tests are also performed and 28 Gbps error free transmission has been confirmed over 300 meters of multimode-fiber optimized for 1060 nm with a PRBS pattern length of 231-1.

Suzuki, Toshihito; Funabashi, Masaki; Shimizu, Hitoshi; Nagashima, Kazuya; Kamiya, Shinichi; Kasukawa, Akihiko

2014-02-01

42

VCSELs for exascale computing, computer farms, and green photonics  

NASA Astrophysics Data System (ADS)

The bandwidth-induced communication bottleneck due to the intrinsic limitations of metal interconnects is inhibiting the performance and environmental friendliness of todaýs supercomputers, data centers, and in fact all other modern electrically interconnected and interoperable networks such as data farms and "cloud" fabrics. The same is true for systems of optical interconnects (OIs), where even when the metal interconnects are replaced with OIs the systems remain limited by bandwidth, physical size, and most critically the power consumption and lifecycle operating costs. Vertical-cavity surface-emitting lasers (VCSELs) are ideally suited to solve this dilemma. Global communication providers like Google Inc., Intel Inc., HP Inc., and IBM Inc. are now producing optical interconnects based on VCSELs. The optimal bandwidth per link may be analyzed by by using Amdah?s Law and depends on the architecture of the data center and the performance of the servers within the data center. According to Google Inc., a bandwidth of 40 Gb/s has to be accommodated in the future. IBM Inc. demands 80 Tbps interconnects between solitary server chips in 2020. We recently realized ultrahigh bit rate VCSELs up to 49 Gb/s suited for such optical interconnects emitting at 980 nm. These devices show error-free transmission at temperatures up to 155°C and operate beyond 200°C. Single channel data-rates of 40 Gb/s were achieved up to 75°C. Record high energy efficiencies close to 50 fJ/bit were demonstrated for VCSELs emitting at 850 nm. Our devices are fabricated using a full three-inch wafer process, and the apertures were formed by in-situ controlled selective wet oxidation using stainless steel-based vacuum equipment of our own design. assembly, and operation. All device data are measured, recorded, and evaluated by our proprietary fully automated wafer mapping probe station. The bandwidth density of our present devices is expected to be scalable from about 100 Gbps/mm² to a physical limit of roughly 15 Tbps/mm² based on the current 12.5 Gb/s VCSEL technology. Still more energy-efficient and smaller volume laser diode devices dissipating less heat are mandatory for further up scaling of the bandwidth. Novel metal-clad VCSELs enable a reduction of the device's footprint for potentially ultrashort range interconnects by 1 to 2 orders of magnitude compared to conventional VCSELs thus enabling a similar increase of device density and bandwidth.

Hofmann, Werner; Moser, Philip; Wolf, Philip; Larisch, Gunter; Li, Hui; Li, Wei; Lott, James; Bimberg, Dieter

2012-11-01

43

Reversible polarization control of single photon emission.  

PubMed

We present reversible and a-priori control of the polarization of a photon emitted by a single molecule by introducing a nanoscale metal object in its near field. It is experimentally shown that, with the metal close to the emitter, the polarization ratio of the emission can be varied by a factor of 2. The tunability of polarization decays, when the metal is displaced by typically 30 nm. Calculations based on the multiple multipole method agree well with our experiments and predict even further enhancement with a suitable nanoantenna design. PMID:18193913

Moerland, Robert J; Taminiau, Tim H; Novotny, Lukas; van Hulst, Niek F; Kuipers, Laurens

2008-02-01

44

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

45

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

46

Ultrafast Directional Beam Switching in Coupled VCSELs  

NASA Technical Reports Server (NTRS)

We propose a new approach to performing ultrafast directional beam switching using two coupled Vertical-Cavity Surface-Emitting Lasers (VCSELs). The proposed strategy is demonstrated for two VCSELs of 5.6 microns in diameter placed about 1 micron apart from the edges, showing a switching speed of 42 GHz with a maximum far-field angle span of about 10 degrees.

Ning, Cun-Zheng; Goorjian, Peter

2001-01-01

47

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

48

Polarization synchronization in unidirectionally coupled vertical-cavity surface-emitting lasers with orthogonal optical injection.  

PubMed

We analyze theoretically the polarization dynamics in unidirectionally coupled vertical-cavity surface-emitting lasers (VCSELs). The master VCSEL is subject to an isotropic optical feedback. The slave VCSEL is subject to an orthogonal optical injection from the master VCSEL, i.e., only the linearly polarized mode orthogonal to the dominant linearly polarized mode of the free-running slave VCSEL is injected into the slave VCSEL. This laser configuration may lead the slave VCSEL polarization to switch to that of the injected master laser field. The injected power required for polarization switching depends on the frequency detuning. We identify in the plane of the injection parameters two regions of enhanced synchronization between the injected LP mode and the corresponding slave LP mode. In the so-called region II the slave VCSEL exhibits anticorrelated dynamics in its two LP modes while in the so-called region I the slave VCSEL exhibits dynamics in only one LP mode, which corresponds to the polarization of the injected field. The two regions exhibit different synchronization properties in both the LP mode dynamics and total intensity dynamics. We furthermore analyze the dependency of the synchronization quality on the parameter mismatch between master and slave VCSELs and on the polarization switching properties of each VCSEL. PMID:17677154

Sciamanna, M; Gatare, I; Locquet, A; Panajotov, K

2007-05-01

49

Feedback control of ECRH polarization on LHD  

NASA Astrophysics Data System (ADS)

The polarization of electron cyclotron resonance heating (ECRH) waves, set by the orientation of a pair of corrugated mirror polarizers in the transmission line, determines the degree of coupling to O- and X-modes in the plasma and has an important effect on the first-pass absorption. Existing methods for determining the required polarization have been found adequate in most experiments. However, as the pulse length is increased it becomes increasingly important to maximize the first-pass absorption while the plasma or injection conditions change or when there can be significant O- to X-mode power coupling during propagation, particularly in the edge plasma region of a stellarator. This has motivated the development of a dedicated feedback control system which is able to adjust the polarizers' angles settings during the discharge in order to maintain the highest possible absorption. An extremum seeking controller is shown to successfully recover the optimum polarization setting during long-pulse ECRH experiments on the Large Helical Device (LHD). Corrections were made to this article on 02 September 2010. 'The' was removed before LHD in several places.

Felici, F.; Shimozuma, T.; Kubo, S.; Yoshimura, Y.; Takahashi, H.; Igami, H.; Goodman, T. P.; Seki, T.; Tsuchiya, H.; Ito, S.; Mizuno, Y.; Sauter, O.; Mutoh, T.; LHD Experiment Group

2010-10-01

50

Control of atomic collisions by laser polarization.  

PubMed

Atomic collision pairs in a light field form a microscopic interferometer. The light acts as the beam splitter and controls at the same time the amplitudes and phases of the interfering waves. We demonstrate the complete tunability using linear and elliptic polarization. PMID:14753873

Schmidt, T; Figl, C; Grimpe, A; Grosser, J; Hoffmann, O; Rebentrost, F

2004-01-23

51

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

52

VCSEL`s bonded directly to foundry fabricated GaAs smart pixel arrays  

SciTech Connect

This letter reports the flip-chip bonding of an 8 x 8 array of free standing VCSEL`s to a foundry fabricated GaAs metal-semiconductor field-effect transistor (MESFET) smart pixel array. The VCSEL`s have oxide defined apertures and are co-planar bonded directly to smart pixels which perform the selection function of a data filter. The V{sub th} and series resistance of the VCSEL`s were on average approximately 2.1 V and 250 {Omega}, respectively, which indicates that good electrical contact was obtainable with this process. The I{sub th} ranged between 2--4 mA, with a corresponding output power of between 400 {micro}W and >1.0 mW depending on aperture size.

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

1997-12-01

53

Fast beam steering with full polarization control using a galvanometric optical scanner and polarization controller.  

PubMed

Optical beam steering is a key element in many industrial and scientific applications like in material processing, information technologies, medical imaging and laser display. Even though galvanometer-based scanners offer flexibility, speed and accuracy at a relatively low cost, they still lack the necessary control over the polarization required for certain applications. We report on the development of a polarization steerable system assembled with a fiber polarization controller and a galvanometric scanner, both controlled by a digital signal processor board. The system implements control of the polarization decoupled from the pointing direction through a feed-forward control scheme. This enables to direct optical beams to a desired direction without affecting its initial polarization state. When considering the full working field of view, we are able to compensate polarization angle errors larger than 0.2 rad, in a temporal window of less than ? 20 ms. Given the unification of components to fully control any polarization state while steering an optical beam, the proposed system is potentially integrable and robust. PMID:22714214

Jofre, M; Anzolin, G; Steinlechner, F; Oliverio, N; Torres, J P; Pruneri, V; Mitchell, M W

2012-05-21

54

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

55

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

56

Ultrafast Beam Switching Using Coupled VCSELs  

NASA Technical Reports Server (NTRS)

We propose a new approach to performing ultrafast beam switching using two coupled Vertical-Cavity Surface-Emitting Lasers (VCSELs). The strategy is demonstrated by numerical simulation, showing a beam switching of 10 deg at 42 GHz.

Ning, Cun-Zheng; Goorjian, Peter

2001-01-01

57

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

58

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

59

Properties of small-aperture selectively oxidized VCSELs  

SciTech Connect

We report an analysis of the size dependence of VCSEL threshold which agrees with experimental results. The increasing threshold current density of small area VCSELs arises from both increasing threshold gain and increasing leakage current.

Choquette, K.D.; Chow, W.W.; Hadley, G.R.; Hou, H.Q.; Geib, K.M.

1996-12-31

60

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

61

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

62

Controlling polar molecules in optical lattices  

SciTech Connect

We theoretically investigate the interaction of polar molecules with optical lattices and microwave fields. We demonstrate the existence of frequency windows in the optical domain where the complex internal structure of the molecule does not influence the trapping potential of the lattice. In such frequency windows the Franck-Condon factors are so small that near-resonant interaction of vibrational levels of the molecule with the lattice fields have a negligible contribution to the polarizability, and light-induced decoherences are kept to a minimum. In addition, we show that microwave fields can induce a tunable dipole-dipole interaction between ground-state rotationally symmetric (J=0) molecules. A combination of a carefully chosen lattice frequency and microwave-controlled interaction between molecules will enable trapping of polar molecules in a lattice and possibly realize molecular quantum logic gates. Our results are based on ab initio relativistic electronic structure calculations of the polar KRb and RbCs molecules combined with calculations of their rovibrational motion.

Kotochigova, S. [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States); National Institute of Standards and Technology, 100 Bureau Drive, Stop 8423, Gaithersburg, Maryland 20899 (United States); Tiesinga, E. [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States)

2006-04-15

63

Progress in extended wavelength VCSEL technology  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

64

Optical reversibility theorems for polarization: Application to remote control of polarization  

Microsoft Academic Search

The authors prove three optical reversibility theorems that relate the polarization ellipticity at the output of an optical system to the polarization of the retroreflected light at the input by using Jones's formalism. How these theorems can be used to measure the ellipticity of a polarization remotely and to control it remotely is described. To create a linear or a

N. Vansteenkiste; P. Vignolo; A. Aspect

1993-01-01

65

VCSEL based, wearable, continuously monitoring pulse oximeter.  

PubMed

We present the development of a novel pulse oximeter based on low power, low cost, Vertical Cavity Surface Emitting Laser (VCSEL) technology. This new design will help address a need to perform regular measurements of pulse oximetry for patients with chronic obstructive pulmonary disease. VCSELs with wavelengths suitable for pulse oximetry were developed and packaged in a PLCC package for a low cost solution that is easy to integrate into a pulse oximeter design. The VCSELs were integrated into a prototype pulse oximeter that is unobtrusive and suitable for long term wearable use. The prototype achieved good performance compared the Nonin Onyx II pulse oximeter at less than one fifth the weight in a design that can be worn behind the ear like a hearing aid. PMID:24110647

Kollmann, Daniel; Hogan, William K; Steidl, Charles; Hibbs-Brenner, Mary K; Hedin, Daniel S; Lichter, Patrick A

2013-01-01

66

Optical Injection-Induced Polarization Switching Dynamics in 1.5- m Wavelength Single-Mode Vertical-Cavity Surface-Emitting Lasers  

Microsoft Academic Search

We report the first experimental invetigation of the polarization-mode switching dynamics and injection-wavelength-dependent polarization-mode bistability of a 1.5-m wavelength single-mode vertical-cavity surface-emitting lasers (VCSELs) under external laser beam injection. An injection beam with polarization orthogonal to that of the stand-alone VCSEL caused polarization-mode instability and switching of the VCSEL output. By varying the optical injection detuning for fixed injection power

Kyu Hyeon Jeong; Kyong Hon Kim; Seoung Hun Lee; Min Hee Lee; Byeung-Soo Yoo; K. Alan Shore

2008-01-01

67

A semiconductor laser with monolithically integrated dynamic polarization control.  

PubMed

We report the first demonstration of a semiconductor laser monolithically integrated with an active polarization controller, which consists of a polarization mode converter followed by an active, differential phase shifter. High speed modulation of the device output polarization is demonstrated via current injection to the phase shifter section. PMID:23037101

Holmes, B M; Naeem, M A; Hutchings, D C; Marsh, J H; Kelly, A E

2012-08-27

68

VCSEL Intrinsic Response Extraction Using Matrix Formalism  

Microsoft Academic Search

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

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

2009-01-01

69

VCSEL-based parallel optical transmission module  

NASA Astrophysics Data System (ADS)

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 fiber connector and a packaging housing. The L-I-V characteristics of the 850nm VCSEL was measured at the operating current 8mA, 3dB frequency bandwidth more than 3GHz and the optical output 1mW. The transmission rate of all 12 channels is 30Gbit/s, with a single channel 2.5Gbit/s. By adopting the integration of the 1×12 VCSEL array and the driver array, we make a high speed PCB (Printed Circuit Board) to provide the optoelectronic chip with the operating voltage and high speed signals current. The LVDS (Low-Voltage Differential Signals) was set as the input signal to achieve better high frequency performance. The active coupling was adopted with a MT connector (8° slant fiber array). We used the Small Form Factor Pluggable (SFP) packaging. With the edge connector, the module could be inserted into the system dispense with bonding process.

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

2005-02-01

70

Optimized VCSELs for high-power arrays  

NASA Astrophysics Data System (ADS)

High-power VCSEL systems with multi kilowatt output power require a good electro-optical efficiency at the point of operation i.e. at elevated temperature. The large number of optimization parameters can be structured in a way that separates system and assembly considerations from the minimization of electrical and optical losses in the epitaxially grown structure. Temperature dependent functions for gain parameters, internal losses and injection efficiency are derived from a fit to experimental data. The empirical description takes into account diameter dependent effects like current spreading or temperature dependent ones like voltage drops over hetero-interfaces in the DBR mirrors. By evaluating experimental measurements of the light output and voltage characteristics over a large range of temperature and diameter, wafer-characteristic parameters are extracted allowing to predict the performance of VCSELs made from this material in any array and assembly configuration. This approach has several beneficial outcomes: Firstly, it gives a general description of a VCSEL independent of its geometry, mounting and detuning, secondly, insights into the structure and the underlying physics can be gained that lead to the improvement potential of the structure and thirdly the performance of the structure in arrays and modules can be predicted. Experimental results validate the approach and demonstrate the significantly improved VCSEL efficiency and the benefit in high power systems.

Moench, Holger; Kolb, Johanna S.; Engelhardt, Andreas P.; Gerlach, Philipp; Jaeger, Roland; Pollmann-Retsch, Jens; Weichmann, Ulrich; Witzigmann, Bernd

2014-02-01

71

Process control system using polarizing interferometer  

DOEpatents

A system for non-destructively 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.

Schultz, Thomas J. (Maumee, OH); Kotidis, Petros A. (Waban, MA); Woodroffe, Jaime A. (North Reading, MA); Rostler, Peter S. (Newton, MA)

1994-01-01

72

Furnace control apparatus using polarizing interferometer  

DOEpatents

A system for non-destructively 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.

Schultz, Thomas J. (Maumee, OH); Kotidis, Petros A. (Waban, MA); Woodroffe, Jaime A. (North Reading, MA); Rostler, Peter S. (Newton, MA)

1995-01-01

73

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

74

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

75

Broadband adaptively-controlled polarization-separation network  

NASA Technical Reports Server (NTRS)

A broadband adaptively-controlled frequency-reuse system has been developed and demonstrated. The system is designed to operate at 11 GHz and above, where polarization deorthogonalization due to rain effects is a problem. Direct analog control is used to continually correct for varying cross polarization conditions. Two cancellation networks are presented; an electro-mechanical RF waveguide network, and an all-electronic IF network; each adaptively controlled using pilot signals, detecting the amount of cross polarized pilot in each channel, and nulling the signal. Cancellations of cross polarization to greater than 35 dB below the copolarized signal are demonstrated.

Gianatasio, A. J.

1978-01-01

76

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

77

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

PubMed

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

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

2008-02-01

78

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

79

Self-Sustained Ultrafast Pulsation in Coupled VCSELs  

NASA Technical Reports Server (NTRS)

High frequency, narrow-band self-pulsating operation is demonstrated in two coupled vertical-cavity surface-emitting lasers (VCSELs). The coupled VCSELs provide an ideal source for high-repetition rate (over 40 GHz), sinusoidal-like modulated laser source with Gaussian-like near- and far-field profiles. We also show that the frequency of the modulation can be tuned by the inter-VCSEL separation or by DC-bias level.

Ning, Cun-Zheng

2001-01-01

80

Quantum confined Stark effect in coupled-cavity VCSELs  

Microsoft Academic Search

We present a comprehensive study of coupled-cavity VCSEL structure (or CC-VCSEL), i.e. two optical cavities that share a coupling mirror and that can be independently biased using three electrical contacts. Each cavity contains multi-quantum-wells (MQW) serving as a gain or absorbing medium. We perform a thorough theoretical modeling of the CC-VCSELs taking into account the modification of the MQW optical

Krassimir Panajotov; Vlad Badilita; Jean-Francois Carlin; Hugo Thienpont; Irina Veretennicoff

2004-01-01

81

Coherent Terahertz Polarization Control through Manipulation of Electron Trajectories  

SciTech Connect

The dynamics of ionized electrons in a plasma can be controlled by synthetic optical fields composed of the fundamental and the second harmonic of femtosecond optical pulses with an arbitrary phase and polarization. We show here that the plasma-emitted half-cycle THz radiation directly reflects the two-dimensional trajectories of the electrons through polarization sensitive THz emission spectroscopy. As a result, we find that the THz polarization smoothly rotates through 2pi radians as the relative phase between the two pulses is adjusted, providing a new means of coherently controlling the polarization of light at THz frequencies.

Wen Haidan [PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California, 94025 (United States); Lindenberg, Aaron M. [PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California, 94025 (United States); Department of Materials Science and Engineering, Stanford University, Stanford, California, 94305 (United States)

2009-07-10

82

Analysis of Multi-Polarization Switching in Vertical-Cavity Surface-Emitting Lasers Using Multi-peak gain model  

NASA Astrophysics Data System (ADS)

This research investigated the mulit-polarization switching (MPS) in vertical-cavity surface-emitting lasers (VCSELs) at constant temperature by simple multi-peak gain model.In experimental results, the phenomenon of the polarization switching (PS) in the VCSEL were arduous to definite quantitative analysis. A simple multi-peak gain model which included the temperature effect and current effect was established to match the MPS in the VCSEL. Simulation results match the experimental results well and shoe that the variation of temperature is a affecting factor of MPS. Therefore, the simple multi-peak gain model contributed a good understanding of multi-polarization switching in VCSELs.

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

2013-03-01

83

Influence of polarization mode competition on the synchronization of two unidirectionally coupled vertical-cavity surface-emitting lasers.  

PubMed

We analyze theoretically the effect of polarization mode competition on the synchronization of two unidirectionally coupled vertical-cavity surface-emitting lasers (VCSELs). Chaos in the master laser is induced by delayed optical feedback, and the slave laser is subject to isotropic optical injection from the master VCSEL. We show that the synchronization quality can be enhanced when the chaotic regime in the master VCSEL involves both fundamental orthogonal linearly polarized modes. PMID:17572728

Gatare, Ignace; Sciamanna, Marc; Locquet, Alexandre; Panajotov, Krassimir

2007-06-15

84

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

85

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

86

Generalized Principal-State-of-Polarization Analysis and Matrix Model for Piezoelectric Polarization Controllers  

NASA Astrophysics Data System (ADS)

We introduce a generalized concept of principal state of polarization (PSP) to analyse the piezoelectric polarization controller (PPC) and find each PPC unit can be described by a rotation matrix determined by the PSP. Our PPC has three components, each made of a jaw and a piezoelectric actuator with the squeezing direction tilted 0°, 45° and 0°, which are driven by a tunable power supply. We demonstrate that all the polarization rotation angles are linear to driving voltages and the PSP of unit 2 is nearly orthogonal to others which are almost equal. Taking some approximate treatments we obtain the matrix model of our PPC with respect to three driving voltages. The average error of our theoretical model is 1.51°, and the polarization response time is < 50 ?s, which is promising to realize an open-loop control of polarization.

Li, Zheng-Yong; Wu, Chong-Qing; Yang, Shuang-Shou; Tian, Chang-Yong; Zhao, Shuang; Wang, Yong-Jun

2008-04-01

87

Electrostatic Gate Control of Optically-Induced Nuclear Polarization  

Microsoft Academic Search

We report initial experiments on optically-induced nuclear spin polarization in gated GaAs 2D electron gas structures, detected via transport. We investigate how polarization depends on gate-controlled depletion, with the ultimate goal of creating submicron regions of polarized nuclei. These regions are expected to yield strong local effective magnetic fields through hyperfine coupling, and may provide a means of manipulating electron

A. A. Houck; J. A. Folk; C. M. Marcus; M. Shayegan

2001-01-01

88

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

NASA Astrophysics Data System (ADS)

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

Li, Linfu

2010-11-01

89

Versatile endless optical polarization controller/tracker/demultiplexer.  

PubMed

Following an initial discussion of control error signal generation, we present new developments and applications of automatic endless optical polarization control based on a commercial electrooptic LiNbO3 polarization transformer: (i) Fast tracking and subsequent demultiplexing of DPSK/DQPSK/QAM polarization channels was hitherto limited to a fairly fixed optical input power. With APD photoreceivers used for residual interference detection, we demonstrate here an optical level tolerance of at least 7 dB, compared to only 3 dB for PIN photoreceivers. DPSK channel polarizations are tracked at up to 40 krad/s and higher speed on the Poincaré sphere. (ii) High-order optical modulation schemes require increased accuracy of the polarization controller in the demultiplexer. This is possible at the expense of a reduced tracking speed. We achieve a mean polarization extinction ratio of >40 dB or <0.02 rad error while tracking arbitrary endless polarization changes of up to 1000 rad/s. (iii) While electronic polarization tracking in coherent receivers is currently limited to a symbol rate of about 28 GBaud we show optical polarization tracking of a signal with 1 THz bandwidth. PMID:24718201

Koch, Benjamin; Noé, Reinhold; Sandel, David; Mirvoda, Vitali

2014-04-01

90

Light polarization control during free-space propagation using coherence  

SciTech Connect

We report an experimental demonstration of light polarization degree control during free propagation via manipulation of the coherent properties of the source. These experimental results corroborate the theory that polarization and coherence are both related to the same statistical properties of the electromagnetic field.

Vidal, Itamar; Fonseca, Eduardo J. S.; Hickmann, Jandir M. [Optics and Materials Group-Optma, Universidade Federal de Alagoas, Caixa Postal 2051, Maceio, AL, 57061-970 (Brazil)

2011-09-15

91

Guided-mode resonant polarization-controlled tunable color filters.  

PubMed

We demonstrate efficient guided-mode resonant polarization-controlled tunable color filters. The devices consist of subwavelength gratings that are partially etched into a thin silicon-nitride film deposited on a glass substrate. Two color filters with grating periods of 300 nm and 370 nm are designed and fabricated. The 300-nm device exhibits green and blue colors and the 370-nm device generates red and yellow colors for TE and TM polarization, respectively. The pixels have a spectral bandwidth of ~12 nm with efficiencies exceeding 90% for TE polarization and 80% for TM polarization. The devices may find application in displays, image sensors, and biomedical imaging technologies. PMID:24921349

Uddin, Mohammad Jalal; Khaleque, Tanzina; Magnusson, Robert

2014-05-19

92

Tapered hollow waveguide multiplexer for multi-wavelength VCSEL array  

Microsoft Academic Search

A tapered hollow waveguide multiplexer is proposed to combine the output of a multi-wavelength VCSEL array. The design of the proposed hollow waveguide is presented based on ray optics. We demonstrated the multiplexing of 4- channel output of a VCSEL array for coupling into a multi-mode fiber with the tapered hollow waveguide. The wavelength of each channel was allocated with

Akihiro Imamura; Koichi Hasebe; Akihiro Matsutani; Fumio Koyama

2009-01-01

93

Reliability of proton-implanted VCSELs for data communications  

Microsoft Academic Search

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

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

1996-01-01

94

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

95

Statistics of transverse mode turn-on dynamics in VCSELs  

Microsoft Academic Search

The turn-on process of a multimode VCSEL is investigated from a statistical point of view. Special attention Is paid to quantities such as time jitter and bit error rate. The single-mode performance of VCSELs during current modulation is compared to that of edge-emitting lasers

J. Dellunde; M. C. Torrent; J. M. Sancho; K. A. Shore

1997-01-01

96

Polar auxin transport: controlling where and how much  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

97

Thermal and Optoelectronic Model of VCSEL Arrays for Short Range Communications  

Microsoft Academic Search

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

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

2003-01-01

98

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

Microsoft Academic Search

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

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

2007-01-01

99

25 Gbps and beyond: VCSEL development at Philips  

NASA Astrophysics Data System (ADS)

In comparison to widely used InGaAs Quantum Wells (QW) in high speed VCSELs operating at 25 Gbps and beyond, we present an investigation on the use of GaAs QWs, which have proven their ability to serve reliably in 10 Gbps and 14 Gbps VCSEL products and allow for an evolutionary extension of data rates based on mature technology. As data centers continuously increase in size, the demand for longer reach optical links within these data centers is addressed by the proposal of using small spectral width single-mode VCSELs that offer the potential of significantly reduced chromatic dispersion along optical fibers of several 100 m length. Performance and modeling parameters of single-mode VCSELs are being compared to those of typical multi-mode VCSELs built from identical epitaxy and process technology.

Grabherr, Martin; Intemann, Steffan; Wabra, Stefan; Gerlach, Philipp; Riedl, Michael; King, Roger

2013-02-01

100

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

101

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

102

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

103

Directive excitation of guided electromagnetic waves through polarization control  

NASA Astrophysics Data System (ADS)

Experimental evidence is reported on the control of the directionality of guided electromagnetic microwaves by the polarization of the exciting wave. Experiments are conducted using a two-dimensional waveguide made of two parallel aluminum plates. The upper plate, which has a linear array of holes, is externally illuminated by a polarized wave whose incident wavevector is contained within the mirror-symmetry plane defined by the linear array. Surprisingly, the measurements show that the propagation inside the waveguide is highly asymmetrical, and it is controlled by the polarization of the incoming wave. This extraordinary phenomenon is explained in terms of a simple model involving a set of dipoles that are excited at the hole positions. Our finding provides a powerful method to sort different polarizations of a free-space beam to different propagation directions of guided electromagnetic waves.

Carbonell, Jorge; Rodríguez-Fortuño, Francisco J.; Díaz-Rubio, Ana; Martínez, Alejandro; Cervera, Francisco; Sánchez-Dehesa, José

2014-04-01

104

Active control of light based on polarization-coupling cascading  

NASA Astrophysics Data System (ADS)

In this letter, we proposed a novel method for optical manipulation based on polarization-coupling cascading in MgO-doped periodically poled lithium niobate crystal. Polarization-coupling cascading, a series of energy exchanges between two orthogonally polarized beams close to phase matching condition, can also lead to phase shifts, in analogy with that in cascaded second-order nonlinearities. In addition, the parameters of light such as phase, amplitude, and group velocity can be modulated by changing the relative power ratio of the incident continuous wave beams. The phase control was demonstrated by Newton's rings experiment, which was in good agreement with the theoretical prediction.

Huo, Juan; Zheng, Yuanlin; Chen, Xianfeng

2014-02-01

105

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

106

Multilevel data storage memory using deterministic polarization control.  

PubMed

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. PMID:22162010

Lee, Daesu; Yang, Sang Mo; Kim, Tae Heon; Jeon, Byung Chul; Kim, Yong Su; Yoon, Jong-Gul; Lee, Ho Nyung; Baek, Seung Hyup; Eom, Chang Beom; Noh, Tae Won

2012-01-17

107

Henko jotai no kosoku seigyo hoshiki no kento. (Study of fast control of optical polarization).  

National Technical Information Service (NTIS)

To develop a control method of SOP (state of optical polarization) for coping with the polarization fluctuation velocity of OPGW (optical ground wire), fast control techniques of optical polarization was investigated using electro-optic devices. Based on ...

M. Kurono

1996-01-01

108

Polarization aberration control for ArF projection lenses  

NASA Astrophysics Data System (ADS)

High NA imaging or/and polarization illumination imaging for exposure tool requires not only scalar aberration performance but also vectorial aberration (so called polarization aberration) control. There are several methods to explain vectorial aberrations such as, Jones Matrix Pupil, Pauli spin matrix, etc. Pauli spin matrix may be intuitively easier to understand and suitable to show scalar wavefront. However, direct use of Pauli spin matrix method may not express physical meaning of vectorial aberration exactly, especially when the amount of polarization aberration is large. In this paper we would like to propose a new explanation method, which is natural expansion of scalar aberration explanation to vectorial aberration explanation and physically mostly exact form. Furthermore useful approximation of the form makes it possible to make vectorial aberration sum-operant from productoperant. Using this method, it is possible to use scalar aberration control technique, such as wavefront control, Zernike sensitivity analysis, Zernike linear combination method, etc. to vectorial aberration control.

Matsuyama, Tomoyuki; Kita, Naonori

2009-03-01

109

Computer aided control of the bonn penning polarized ion source  

Microsoft Academic Search

A CBM computer system is described which has been set up to control the Bonn Polarized Ion Source. The controlling program, besides setting and logging parameters, performs an optimization of the ion source output. A free definable figure of merit, being composed of the current of the ionizer and its variance, has proven to be an effective means in directing

N. W. He; P. von Rossen; P. D. Eversheim; R. Busch

1984-01-01

110

Computer aided control of the bonn penning polarized ion source  

Microsoft Academic Search

A CBM computer system is described which has been set up to control the Bonn Polarized Ion Source. The controlling program, besides setting and logging parameters, performs an optimization of the ion source output. A free definable figure of merit, being composed of the current of the ionizer and its variance, has proven to be an effective means in directing

N. He; P. von Rossen; P. Eversheim; R. Busch

111

Integrated photodiodes complement the VCSEL platform  

NASA Astrophysics Data System (ADS)

Many VCSEL based applications require optical feedback of the emitted light. E.g. light output monitor functions in transceivers are used to compensate for thermally induced power variation, power degradation, or even breakdown of pixels if logic for redundancy is available. In this case integrated photodiodes offer less complex assembly compared to widely used hybrid solutions, e.g. known in LC-TOSA assemblies. Especially for chip-on-board (COB) assembly and array configurations, integrated monitor diodes offer a simple and compact power monitoring possibility. For 850 nm VCSELs the integrated photodiodes can be placed between substrate and bottom-DBR, on top of the top-DBR, or inbetween the layer sequence of one DBR. Integrated intra-cavity photodiodes offer superior characteristics in terms of reduced sensitivity for spontaneously emitted light [1] and thus are very well suited for power monitoring or even endof- life (EOL) detection. We present an advanced device design for an intra-cavity photodiode and according performance data in comparison with competing approaches.

Grabherr, Martin; Gerlach, Philipp; King, Roger; Jäger, Roland

2009-02-01

112

Automated control of optical polarization for nonlinear microscopy  

NASA Astrophysics Data System (ADS)

Laser-scanning non-linear optical techniques such as multi-photon fluorescence excitation microscopy (MPM), Second/ Third Harmonic Generation (SHG/THG), and Coherent Anti-Stokes Raman Scattering (CARS) are being utilized in research laboratories worldwide. The efficiencies of these non-linear effects are dependent on the polarization state of the excitation light relative to the orientation of the sample being imaged. In highly ordered anisotropic biological samples this effect can become pronounced and the excitation polarization can have a dramatic impact on imaging experiments. Therefore, controlling the polarization state of the exciting light is important; however this is challenging when the excitation light passes through a complex optical system. In a typical laser-scanning microscope, components such as the dichroic filters, lenses, and even mirrors can alter the polarization state of a laser beam before it reaches the sample. We present an opto-mechanical solution to compensate for the polarization effects of an optical path, and to precisely program the polarization state of the exciting laser light. The device and accompanying procedures allow the delivery of precise laser polarization states at constant average power levels to a sample during an imaging experiment.

Brideau, Craig; Stys, Peter K.

2012-02-01

113

Tapered hollow waveguide multiplexer for multi-wavelength VCSEL array  

NASA Astrophysics Data System (ADS)

A tapered hollow waveguide multiplexer is proposed to combine the output of a multi-wavelength VCSEL array. The design of the proposed hollow waveguide is presented based on ray optics. We demonstrated the multiplexing of 4- channel output of a VCSEL array for coupling into a multi-mode fiber with the tapered hollow waveguide. The wavelength of each channel was allocated with adjusting driving current. The proposed hollow waveguide multiplexer is useful for realizing compact and low-cost WDM transceivers with a multi-wavelength VCSEL array for high capacity short reach optical networks.

Imamura, Akihiro; Hasebe, Koichi; Matsutani, Akihiro; Koyama, Fumio

2009-02-01

114

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

115

FEL polarization control studies on Dalian coherent light source  

NASA Astrophysics Data System (ADS)

The polarization switch of a free-electron laser (FEL) is of great importance to the user scientific community. In this paper, we investigate the generation of controllable polarization FEL from two well-known approaches for Dalian coherent light source, i.e., crossed planar undulator and elliptical permanent undulator. In order to perform a fair comparative study, a one-dimensional time-dependent FEL code has been developed, in which the imperfection effects of an elliptical permanent undulator are taken into account. Comprehensive simulation results indicate that the residual beam energy chirp and the intrinsic FEL gain may contribute to the degradation of the polarization performance for the crossed planar undulator. The elliptical permanent undulator is not very sensitive to the undulator errors and beam imperfections. Meanwhile, with proper configurations of the main planar undulators and additional elliptical permanent undulator section, circular polarized FEL with pulse energy exceeding 100 ?J could be achieved at Dalian coherent light source.

Zhang, Tong; Deng, Hai-Xiao; Zhang, Wei-Qing; Wu, Guo-Rong; Dai, Dong-Xu; Wang, Dong; Yang, Xue-Ming; Zhao, Zhen-Tang

2013-11-01

116

Classical cadherins control nucleus and centrosome position and cell polarity  

PubMed Central

Control of cell polarity is crucial during tissue morphogenesis and renewal, and depends on spatial cues provided by the extracellular environment. Using micropatterned substrates to impose reproducible cell–cell interactions, we show that in the absence of other polarizing cues, cell–cell contacts are the main regulator of nucleus and centrosome positioning, and intracellular polarized organization. In a variety of cell types, including astrocytes, epithelial cells, and endothelial cells, calcium-dependent cadherin-mediated cell–cell interactions induce nucleus and centrosome off-centering toward cell–cell contacts, and promote orientation of the nucleus–centrosome axis toward free cell edges. Nucleus and centrosome off-centering is controlled by N-cadherin through the regulation of cell interactions with the extracellular matrix, whereas the orientation of the nucleus–centrosome axis is determined by the geometry of N-cadherin–mediated contacts. Our results demonstrate that in addition to the specific function of E-cadherin in regulating baso-apical epithelial polarity, classical cadherins control cell polarization in otherwise nonpolarized cells.

Dupin, Isabelle; Camand, Emeline

2009-01-01

117

Genetic Control of Organ Shape and Tissue Polarity  

PubMed Central

The mechanisms by which genes control organ shape are poorly understood. In principle, genes may control shape by modifying local rates and/or orientations of deformation. Distinguishing between these possibilities has been difficult because of interactions between patterns, orientations, and mechanical constraints during growth. Here we show how a combination of growth analysis, molecular genetics, and modelling can be used to dissect the factors contributing to shape. Using the Snapdragon (Antirrhinum) flower as an example, we show how shape development reflects local rates and orientations of tissue growth that vary spatially and temporally to form a dynamic growth field. This growth field is under the control of several dorsoventral genes that influence flower shape. The action of these genes can be modelled by assuming they modulate specified growth rates parallel or perpendicular to local orientations, established by a few key organisers of tissue polarity. Models in which dorsoventral genes only influence specified growth rates do not fully account for the observed growth fields and shapes. However, the data can be readily explained by a model in which dorsoventral genes also modify organisers of tissue polarity. In particular, genetic control of tissue polarity organisers at ventral petal junctions and distal boundaries allows both the shape and growth field of the flower to be accounted for in wild type and mutants. The results suggest that genetic control of tissue polarity organisers has played a key role in the development and evolution of shape.

Green, Amelia A.; Kennaway, J. Richard; Hanna, Andrew I.; Bangham, J. Andrew; Coen, Enrico

2010-01-01

118

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

119

850nm VCSELs for 10Gb\\/s operation  

Microsoft Academic Search

Summary form only given. 850nm VCSELs are finding escalating markets in fiber optical communication applications, such as 10Gbit-Ethenet, OC-192 VSR and so on. It offers significant advantages for realizing cost-effective, high speed data links. Our progress towards achieving 10Gb\\/s VCSEL is reviewed. In this report, we investigated the optimization of oxide aperture size for 10Gb\\/s operation. And also, we demonstrated

N. Iwai; N. Yokouchi; A. Kasukawa

2002-01-01

120

The next generation of high speed VCSELs at Finisar  

NASA Astrophysics Data System (ADS)

Commercial demand for optical transceivers operating at 14Gbps is now a reality. It is further expected that communications standards utilizing 850nm VCSELs at speeds up to 28Gbps will be ratified in the near future. We report on the development and productization of 850nm VCSELs for several applications, including high speed (both 14Gbps and 28Gbps) operation to support the continued fulfillment of data communication demand.

Graham, Luke A.; Chen, Hao; Gazula, Deepa; Gray, Timo; Guenter, James K.; Hawkins, Bobby; Johnson, Ralph; Kocot, Chris; Macinnes, Andrew N.; Landry, Gary D.; Tatum, Jim A.

2012-02-01

121

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

SciTech Connect

The gain-dependent polarization properties of vertical-cavity surface emitting lasers and methods for polarization control and modulation are discussed. The partitioning of power between the two orthogonal eigen polarizations is shown to depend upon the relative spectral alignment of the nondegenerate polarization cavity resonances with the laser gain spectrum. A dominant polarization can thus be maintained by employing a blue-shifted offset of the peak laser gain relative to the cavity resonance wavelength. Alternatively, the polarization can be controlled through use of anisotropic transverse cavity geometries. The orthogonal eigen polarizations are also shown to enable polarization modulation. By exploiting polarization switching transitions in cruciform lasers, polarization modulation of the fundamental mode up to 50 MHz is demonstrated. At lower modulation frequencies, complementary digital polarized output or frequency doubling of the polarized output is obtained. Control and manipulation of vertical-cavity laser polarization may prove valuable for present and future applications.

Choquette, K.D.; Lear, K.L.; Schneider, R.P. Jr.; Figiel, J.J.; Kilcoyne, S.P.; Hagerott-Crawford, M.; Zolper, J.C. [Sandia National Labs., Albuquerque, NM (United States). Photonics Research Dept.; Leibenguth, R.E. [AT and T Bell Labs., Breinigsville, PA (United States)

1995-03-01

122

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

National Technical Information Service (NTIS)

The gain-dependent polarization properties of vertical-cavity surface emitting lasers and methods for polarization control and modulation are discussed. The partitioning of power between the two orthogonal eigen polarizations is shown to depend upon the r...

K. D. Choquette K. L. Lear R. P. Schneider J. J. Figiel S. P. Kilcoyne

1995-01-01

123

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

SciTech Connect

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

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

1998-05-01

124

Coherent beam combining of fiber amplifier based on adaptive polarization and active phase control  

NASA Astrophysics Data System (ADS)

Coherent beam combining (CBC) of a polarization-maintaining fiber amplifier and a non-polarization-maintaining fiber amplifier is presented. The experiment is based on adaptive polarization control and active phase control. The stochastic parallel gradient decent (SPGD) algorithm is used for the adaptive polarization control in the non-polarization-maintaining fiber amplifier and the active phase control is realized by single frequency dithering (SFD) algorithm. When the adaptive polarization control system and the phase control system go into closed loop, the fringe contrast of far-field intensity pattern is improved to more than 87.7%. A scalable architecture for CBC of two styles fiber amplifiers is also proposed.

Xiong, Y. P.; Li, X.; Su, R. T.; Ma, Y. X.; Wang, X. L.; Zhou, P.; Xu, X. J.

2012-10-01

125

Widely continuous-tuning single-wavelength laser based on commercial multimode VCSELs  

Microsoft Academic Search

The conventional vertical-cavity surface-emitting lasers (VCSELs) are designed to have a very short resonant cavity. Therefore, the longitudinal mode of the VCSELs is intrinsically single; and the VCSELs are expected to be an excellent instrument for many precision measurements that demand high-purity single-wavelength light sources. However, the laser facet of the conventional VCSELs is relatively large, around 10 mum, which

Tsu-Chiang Yen; Chuan-Pi Hsu; Yu-Heng Wu; Da-Long Cheng; Wang-Chuang Kuo

2010-01-01

126

Photonenergy-controlled symmetry breaking with circularly polarized light.  

PubMed

Circularly polarized light (CPL) is known to be a true chiral entity capable of generating absolute molecular asymmetry. However, the degree of inducible optical activity depends on the ? of the incident CPL. Exposure of amorphous films of rac-alanine to tunable CPL led to enantiomeric excesses (ee) which not only follow the helicity but also the energy of driving electromagnetic radiation. Postirradiation analyses using enantioselective multidimensional GC revealed energy-controlled ee?values of up to 4.2?%, which correlate with theoretical predictions based on newly recorded anisotropy spectra g(?). The tunability of asymmetric photochemical induction implies that both magnitude and sign can be fully controlled by CPL. Such stereocontrol provides novel insights into the wavelength and polarization dependence of asymmetric photochemical reactions and are highly relevant for absolute asymmetric molecular synthesis and for understanding the origins of homochirality in living matter. PMID:24227543

Meinert, Cornelia; Hoffmann, Søren V; Cassam-Chenaï, Patrick; Evans, Amanda C; Giri, Chaitanya; Nahon, Laurent; Meierhenrich, Uwe J

2014-01-01

127

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

128

Hemin controls T cell polarization in sickle cell alloimmunization.  

PubMed

Patients with sickle cell disease (SCD) often require transfusions to treat and prevent worsening anemia and other SCD complications. However, transfusions can trigger alloimmunization against transfused RBCs with serious clinical sequelae. Risk factors for alloimmunization in SCD remain poorly understood. We recently reported altered regulatory T cell (Treg) and Th responses with higher circulating Th1 (IFN-?(+)) cytokines in chronically transfused SCD patients with alloantibodies as compared with those without alloantibodies. Because monocytes play a critical role in polarization of T cell subsets and participate in clearance of transfused RBCs, we tested the hypothesis that in response to the RBC breakdown product hemin, monocyte control of T cell polarization will differ between alloimmunized and non-alloimmunized SCD patients. Exogenous hemin induced Treg polarization in purified T cell/monocyte cocultures from healthy volunteers through the monocyte anti-inflammatory heme-degrading enzyme heme oxygenase-1. Importantly, hemin primarily through its effect on CD16(+) monocytes induced an anti-inflammatory (higher Treg/lower Th1) polarization state in the non-alloimmunized SCD group, whereas it had little effect in the alloimmunized group. Non-alloimmunized SCD CD16(+) monocytes expressed higher basal levels of heme oxygenase-1. Furthermore, IL-12, which contributed to a proinflammatory polarization state (low Treg/high Th1) in SCD, was dampened in hemin-treated stimulated monocytes from non-alloimmunized SCD patients, but not in the alloimmunized group. These data suggest that unlike alloimmunized patients, non-alloimmunized SCD CD16(+) monocytes in response to transfused RBC breakdown products promote an anti-inflammatory state that is less conducive to alloimmunization. PMID:24879794

Zhong, Hui; Bao, Weili; Friedman, David; Yazdanbakhsh, Karina

2014-07-01

129

Complete Photoionization Experiments via Ultrafast Coherent Control with Polarization Multiplexing  

NASA Astrophysics Data System (ADS)

Photoelectron angular distributions (PADs) obtained from ionization of potassium atoms using moderately intense femtosecond IR fields (˜1012 W cm-2) of various polarization states are shown to provide a route to "complete" photoionization experiments. Ionization occurs by a net three-photon absorption process, driven via the 4s?4p resonance at the one-photon level. A theoretical treatment incorporating the intrapulse electronic dynamics allows for a full set of ionization matrix elements to be extracted from 2D imaging data. 3D PADs generated from the extracted matrix elements are also compared to experimental, tomographically reconstructed, 3D photoelectron distributions, providing a sensitive test of their validity. Finally, application of the determined matrix elements to ionization via more complex, polarization-shaped, pulses is demonstrated, illustrating the utility of this methodology towards detailed understanding of complex ionization control schemes and suggesting the utility of such "multiplexed" intrapulse processes as powerful tools for measurement.

Hockett, P.; Wollenhaupt, M.; Lux, C.; Baumert, T.

2014-06-01

130

Complete Photoionization Experiments via Ultrafast Coherent Control with Polarization Multiplexing.  

PubMed

Photoelectron angular distributions (PADs) obtained from ionization of potassium atoms using moderately intense femtosecond IR fields (?10^{12}??W?cm^{-2}) of various polarization states are shown to provide a route to "complete" photoionization experiments. Ionization occurs by a net three-photon absorption process, driven via the 4s?4p resonance at the one-photon level. A theoretical treatment incorporating the intrapulse electronic dynamics allows for a full set of ionization matrix elements to be extracted from 2D imaging data. 3D PADs generated from the extracted matrix elements are also compared to experimental, tomographically reconstructed, 3D photoelectron distributions, providing a sensitive test of their validity. Finally, application of the determined matrix elements to ionization via more complex, polarization-shaped, pulses is demonstrated, illustrating the utility of this methodology towards detailed understanding of complex ionization control schemes and suggesting the utility of such "multiplexed" intrapulse processes as powerful tools for measurement. PMID:24949763

Hockett, P; Wollenhaupt, M; Lux, C; Baumert, T

2014-06-01

131

Polarization control of plasmonic modes in single nanoparticles and nanostructures  

NASA Astrophysics Data System (ADS)

This thesis investigates the fundamental nanoscale near-field light matter interaction between a probe tip and plasmonic antenna nanostructures. The thesis is focused on polarization control of metallic plasmon modes using scattering-type scanning near-field optical microscopy (s-SNOM). Part of the thesis is dedicated to spectroscopic near-field comparison of coated and bare single plasmonic particles in the infrared wavelength range (lambda= 9--11 microm) using s-SNOM. By tuning the wavelength of the incident light, we have acquired information on the spectral polarization dependence plasmon modes and plasmon/phonon--polariton resonant near-field interactions. The enhanced near-field coupling between the probe tip and high index Au nanostructures and Au-core thin silica coating (thickness ?10 nm) is described and quantified.

Damato, Ralph

132

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

133

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

134

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

135

Study of the Radiation Hardness of Vcsel and Pin Arrays  

NASA Astrophysics Data System (ADS)

The silicon trackers of the ATLAS experiment at LHC (CERN) use optical links for data transmission. VCSEL arrays operating at 850 nm are used to transmit optical signals while PIN arrays are used to convert the optical signals into electrical signals. We investigate the feasibility of using the devices at the Super LHC (SLHC). We irradiated VCSEL and GaAs PIN arrays from three vendors and silicon PIN arrays from one vendor. All arrays can be operated up to the SLHC dosage except the GaAs PIN arrays which have very low responsivities after irradiation and hence are probably not suitable for the SLHC application.

Gan, K. K.; Fernando, W.; Kagan, H. P.; Kass, R. D.; Law, A.; Rau, A.; Smith, D. S.; Lebbai, M. R. M.; Skubic, P. L.; Abi, B.; Rizardinova, F.

2008-06-01

136

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

2013-01-01

137

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

138

Prickle/spiny-legs isoforms control the polarity of the apical microtubule network in planar cell polarity.  

PubMed

Microtubules (MTs) are substrates upon which plus- and minus-end directed motors control the directional movement of cargos that are essential for generating cell polarity. Although centrosomal MTs are organized with plus-ends away from the MT organizing center, the regulation of non-centrosomal MT polarity is poorly understood. Increasing evidence supports the model that directional information for planar polarization is derived from the alignment of a parallel apical network of MTs and the directional MT-dependent trafficking of downstream signaling components. The Fat/Dachsous/Four-jointed (Ft/Ds/Fj) signaling system contributes to orienting those MTs. In addition to previously defined functions in promoting asymmetric subcellular localization of 'core' planar cell polarity (PCP) proteins, we find that alternative Prickle (Pk-Sple) protein isoforms control the polarity of this MT network. This function allows the isoforms of Pk-Sple to differentially determine the direction in which asymmetry is established and therefore, ultimately, the direction of tissue polarity. Oppositely oriented signals that are encoded by oppositely oriented Fj and Ds gradients produce the same polarity outcome in different tissues or compartments, and the tissue-specific activity of alternative Pk-Sple protein isoforms has been observed to rectify the interpretation of opposite upstream directional signals. The control of MT polarity, and thus the directionality of apical vesicle traffic, by Pk-Sple provides a mechanism for this rectification. PMID:25005476

Olofsson, Jessica; Sharp, Katherine A; Matis, Maja; Cho, Bomsoo; Axelrod, Jeffrey D

2014-07-01

139

Polarization controlled tunable Yb3+-doped fiber lasers  

NASA Astrophysics Data System (ADS)

Ytterbium absorbs at 915 and 976nm. It also emits at 976nm and from 1060nm to even 1150nm, showing a quantum efficiency of up to 86%. In this experimental work, our novel inner cavity structures were firstly characterized and studied as free-running lasers from the 4% Fresnel reflection from the flat-cleaved fiber facets. The available pump source, a commercially available laser diode, had a maximum power of 0.5W at 915nm from which a coupled power (into the inner cladding) of 1W was reached; fiber laser efficiency reached, in our best case, 55% with respect to launched pump power. For the second part of the work, polarization controlled Yb-doped fiber laser cavities were studied by way of inserting a polarized beam splitter and a ?/4 wave-plate into de cavity. From this, 177mW of single polarization output were obtained by rotating the wave-plate until the maximum points were identified on a wave-plate angle vs. output power plot. The maximum output power was 200mW from 60° to 90° aprox. Now, based on the data obtained, one can claim that at least 40% of the maximum output power available from the laser was linearly polarized. Finally, a 600 lines/mm bulk grating was employed in order to obtain laser tuning results on a traditional way. i.e. by reflecting lasing into the cavity and selecting output from the close end. The tuning range was measured to be from 1088nm up to 1097nm. All these results and possible applications will be discussed in detail.

Alvarez-Chavez, Jose; Martinez-Rios, Alejandro; Torres-Gomez, Ismael; Villegas-Garcia, Irma; Rosas, Roberto; Mercado Uribe, Hilda

2007-06-01

140

Polarization control of the nonlinear emission of semiconductor microcavities.  

PubMed

The degree of circular polarization ( Weierstrass p ) of the nonlinear emission in semiconductor microcavities is controlled by changing the exciton-cavity detuning. The polariton relaxation towards K approximately 0 cavitylike states is governed by final-state stimulated scattering. The helicity of the emission is selected due to the lifting of the degeneracy of the +/-1 spin levels at K approximately 0. At short times after a pulsed excitation Weierstrass p reaches very large values, either positive or negative, as a result of stimulated scattering to the spin level of lowest energy (+1/-1 spin for positive/negative detuning). PMID:12190556

Martín, M D; Aichmayr, G; Viña, L; André, R

2002-08-12

141

Performance evaluation of VCSEL through single and multi mode fibers  

Microsoft Academic Search

This paper presents influence of the change in temperature of a vertical cavity surface emitting laser (VCSEL) on its output power. It is observed that with increase in temperature of laser its output power decrease. It is also observed that with decrease in threshold voltage of the laser output power increase. Decrease in output power due to increase in temperature

R. S. Kaler

142

Research on VCSEL of single-mode multilayer photonic crystal  

NASA Astrophysics Data System (ADS)

Vertical-Cavity Surface-Emitting Lasers (VCSEL) of single mode have the potential advantage in the domains of optical information network, routing interactions, optical information storage and data transmission for their excellent performance. However, operating on the single-mode model in the whole pumped area is not solved, which impacts the technologies and applications. In this paper, a new research on VCSEL of single mode multilayer photonic crystal is presented. In the structure of photonic crystal, defects in the horizontal direction are provided by the micro-cavity, while the AIR-KTP interface on the top and the KTP-DBR (Distributed Bragg Reflection) interface at the bottom of cavity provide the defects in the vertical direction, which form quantum defects of electron-hole pairs. The PC-VCSEL in the paper has excellent mode-selection characteristics, which can operate continuously at 850nm in single mode. The single-mode suppression ratio (SMSR) of 45dB is obtained in a wide dynamic range. The PC-VCSEL is expected to become a high-power single-mode light in the future.

Li, Wenchao; Liu, Zhengjun; Sha, Xiaopeng

2010-05-01

143

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

144

Current spreading modification to enhance single-fundamental-mode VCSEL operation at higher temperatures  

NASA Astrophysics Data System (ADS)

Continuous-wave (CW) performance of modern oxide-confined (OC) vertical-cavity surface-emitting diode lasers (VCSELs) at room and elevated temperatures is investigated with the aid of the comprehensive fully self-consistent optical-electrical-thermal-gain model. A standard OC GaInNAs/GaAs double-quantum-well VCSEL emitting the 1.3-?m radiation is used as a typical modern VCSEL structure. The oxide aperture is placed at the anti-node position of an optical standing wave within a VCSEL cavity. The desired single-fundamental-mode (SFM) operation has been found to be expected only in VCSELs equipped with relatively small active regions of diameters equal or smaller than 10 ?m. Therefore a proton implantation used as an radial additional confinement of the current spreading from the upper annular contact towards the centrally located active region is proposed and its impact on the VCSEL performance is investigated. The above structure modification has been found to enable a radical improvement in the VCSEL performance. In particular, in this case, the SFM VCSEL operation is possible even in VCSELs with quite large active regions and for much wider ambient-temperature range than in the standard OC VCSELs.

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

2011-06-01

145

VCSEL-based optical trapping for microparticle manipulation  

NASA Astrophysics Data System (ADS)

In recent years, research into microfluidic devices has attracted much interest in the fields of biology and medicine, since they promise cheap and fast sample analysis with drastically reduced volume requirements. The combination of various analysis steps on one chip forms a small-sized biomedical system, where handling, fixing, and sorting of particles are major components. Here, it was demonstrated that optical manipulation is an efficient tool; in particular it is accurate, contactless, and biocompatible. However, the commonly required extensive optical setup contradicts the concept of a miniaturized system. We present a novel particle manipulation concept based on vertical-cavity surface-emitting lasers (VCSELs) as light sources. The small dimensions and the low power consumption of these devices enable a direct integration with microfluidic systems. The symmetric geometry of VCSELs leads to a high-quality, circular output beam, which we additionally shape by an etched surface relief in the laser output facet and an integrated photoresist microlens. Thus, a weakly focused output beam with a beam waist of some micrometers is generated in the microfluidic channel. With this configuration we were able to demonstrate particle deflection, trapping, and sorting with a solitary VCSEL with output powers of only 5mW. Furthermore, the surface emission of VCSELs allows a comparatively easy fabrication of two-dimensional laser arrays with arbitrary arrangement of pixels. Smart particle sorting and switching schemes can thus be realized. We have fabricated densely packed VCSEL arrays with center-to-center spacings of only 24 ?m. Equipped with integrated microlenses, these arrays are integrated with microfluidic chips based on polydimethylsiloxane (PDMS), enabling ultra-compact particle sorting and fractionation.

Michalzik, Rainer; Kroner, Andrea; Bergmann, Anna; Rinaldi, Fernando

2009-02-01

146

Doubling direct-detection data rate by polarization multiplexing of 16-QAM without active polarization control.  

PubMed

We introduce and simulate a technique enabling to utilize the polarization dimension in direct-detection optical transmission, supporting polarization multiplexing (POL-MUX) over direct-detection (DD) methods previously demonstrated for a single polarization such as direct-detection OFDM. POL-MUX is currently precluded in self-coherent DD with remotely transmitted pilot, as signal x pilot components may randomly fade out. We propose POL-MUX transmission of advanced modulation formats, such as 16-QAM and higher, by means of a novel low-complexity photonic integrated optical front-end and adaptive 3x2 MIMO DSP. The principle of operation is as follows: an additional X x Y cross-polarizations signal is generated, providing three projections onto an over-complete frame of three dependent vectors. This enables to resiliently reconstruct the received state of polarization even when the remotely transmitted pilot fades along one of the received polarization axes. PMID:24514795

Nazarathy, Moshe; Agmon, Amos

2013-12-30

147

Polarization and polarization control of random lasers from dye-doped nematic liquid crystals.  

PubMed

A polarimetric study of random laser (RL) emitted from dye-doped nematic liquid crystals (NLCs) is presented. We observed linearly polarized light, the orientation of which is in proximity to the bisection between the polarization direction at the maximal scattering in NLCs and the nematic director. Any arbitrary linear polarization of RLs can be obtained by rotating the NLC sample. The efficiency and output uniformity over the complete direction angle of 2? can be optimized by choosing a proper pump polarization. PMID:23632550

Yao, Fengfeng; Zhou, Wenlong; Bian, Huanting; Zhang, Yu; Pei, Yanbo; Sun, Xiudong; Lv, Zhiwei

2013-05-01

148

Room-temperature threshold reduction in vertical-cavity surface-emitting lasers by injection of spin-polarized electrons  

Microsoft Academic Search

We experimentally demonstrate the reduction of the laser threshold of a commercial GaAs\\/(AlGa)As vertical-cavity surface-emitting laser (VCSEL) by optical injection of spin-polarized electrons at room temperature. Calculations with a rate-equation model reproduce the measured reduction of 2.5% for injected electrons with 50% spin polarization. The model predicts an improved threshold reduction of 50% in otherwise identical VCSELs grown on a

J. Rudolph; S. Döhrmann; D. Hägele; M. Oestreich; W. Stolz

2005-01-01

149

Amplitude, phase, and polarization control with a single spatial light modulator  

NASA Astrophysics Data System (ADS)

Point spread function engineering is usually accomplished by controlling the amplitude, phase and/or polarization of the pupil fields. We analyze and test an optical design for full amplitude, phase, and polarization control of the pupil fields using a single spatial light modulator. In our scheme, the beam is spatially split into four components whose relative phases provide the four degrees of freedom necessary for amplitude, phase, and polarization control.

Theisen, Michael J.; Head, Stephen T.; Brown, Thomas G.; Gillmer, Steven R.; Ellis, Jonathan D.

2014-03-01

150

Active inductor shunt peaking in high-speed VCSEL driver design  

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

151

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

152

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

153

Temporal evolution of high-order transverse modes in a multi-mode VCSEL induced by a beam-profile optical feedback  

NASA Astrophysics Data System (ADS)

This work studied the dynamics of the transverse modes in a multitransverse mode VCSEL when the later was conducted to lase the fundamental transverse mode by a Gaussian-beam-profile optical feedback. The multitransverse-mode beam profile of the solitary VCSEL was emitted into a single-mode fiber to achieve the Gaussian-beam-profile optical feedback. Afterward, a quasi-Gaussian beam fed back into the cavity of laser. The feedback beam irradiated on the facet of the fundamental mode of the laser chip, the photons were stimulated to lase and contribute to the fundamental transverse mode. Some high-order transverse modes were observed out of the above mentioned area. The interaction and evolution between the high-order modes and the fundamental mode of the VCSEL could be controlled by the spot of the feedback beam on the facet of laser. More experimental details will be presented and these results will help to expand the application of VCSELs.

Hsu, Chuan-Pi; Cheng, Da-Long; Kuo, Wang-Chuang; Yen, Tsu Chiang

2010-03-01

154

Electrical package impact on VCSEL-based optical interconnects  

NASA Astrophysics Data System (ADS)

A new CAD tool fREEDA ® based on state variable approach and universal error concept is presented for modelling and simulating systems where physical domains such as electrical, thermal, and optical interact with each other. A single implementation of device equations in fREEDA ® can be used with different analysis types such as transient and harmonic balance, etc. To demonstrate the multi-physics capabilities of fREEDA ®, we present a study of the impact of electrical packages on the source module performance in multi-gigabit per second vertical cavity surface emitting laser (VCSEL)-based optical interconnects. The effect of various operating conditions such as bias/drive level and driver configuration are studied. We consider electrical packages such as printed wire board, thin-film and flip-chip in our study. A comparison of VCSELs with stripe lasers is also presented.

Pant, Ravi; Neifeld, Mark A.; Steer, Michael B.; Kanj, Houssam; Cangellaris, Andreas

2005-01-01

155

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

156

Free-Space Optical Interconnect Employing VCSEL Diodes  

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

157

VCSEL-based optical interconnections at interbox distances and shorter  

Microsoft Academic Search

Optics will soon be established as the mainstay for data-intensive communications at distances about 100 meters or less between workstations, displays and peripherals. The datacom hardware includes arrays of multi-mode vertical-cavity surface-emitting lasers (VCSELs) emitting in the 650 - 1000 nm range and parallel channels of multi-mode optical fiber, which are major departures from the already-established long-distance optical fiber communications

Jack L. Jewell

1996-01-01

158

780nm VCSELs for home networks and printers  

Microsoft Academic Search

A 780 nm multi-mode VCSEL, to meet the requirements for a new GI plastic optical fiber, are reported. It has 4 spots driven simultaneously like a single spot and hence the optical power needed from each spot is reduced to 1\\/4. As a result, the MTTF obtained is well over 200,000 hr at 60°C under 3 mW operation, with a

Hideo Nakayama; Takeshi Nakamura; Masao Funada; Yuichi Ohashi; Mikihiko Kato

2004-01-01

159

Multimode photonic crystal fibers for VCSEL based data transmission  

Microsoft Academic Search

Quasi error-free 10Gbit\\/s data transmission is demonstrated over a novel type of 50 µm core diameter photonic crystal fiber with as much as 100m length. Combined with 850 nm VCSEL sources, this fiber is an attractive alternative to graded-index multi-mode fibers for datacom applications. A comparison to numerical simulations suggests that the high bit-rate may be partly explained by inter-modal

N. A. Mortensen; M. Stach; J. Broeng; A. Petersson; H. R. Simonsen; R. Michalzik

2003-01-01

160

Thermal resistance of VCSELs bonded to integrated circuits  

Microsoft Academic Search

The thermal resistance of vertical-cavity surface-emitting lasers (VCSELs) 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 SiO2 under the CMOS bonding pad can double the thermal resistance unless measures are taken

Rui Pu; Carl W. Wilmsen; Kent M. Geib; Kent D. Choquette

1999-01-01

161

VCSEL-based microsensors for photonic proximity fuzing of munitions  

Microsoft Academic Search

This paper describes technologies developed at Sandia National Laboratories to support a joint DoD\\/DoE initiative to create a compact, robust, and affordable photonic proximity sensor for munitions fuzing. The proximity fuze employs high-power vertical-cavity surface-emitting laser (VCSEL) arrays, resonant-cavity photodetectors (RCPDs), and refractive micro-optics that are integrated within a microsensor whose volume is approximately 0.01 cm3. Successful development and integration

G. A. Keeler; A. Mar; K. M. Geib; A. Y. Hsu; D. K. Serkland; G. M. Peake

2008-01-01

162

Albedo control of seasonal South Polar cap recession on Mars  

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

163

Polarization Sensitive CARS Investigations of Controlled Molecular Rotations  

NASA Astrophysics Data System (ADS)

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, e.g., tuned to initiate certain nuclear motions of well studied photo active proteins (e.g. PYP or Rhodopsin) or engineered larger molecular structures. Measuring nuclear motions requires structurally sensitive spectroscopy methods, and therefore spontaneous Raman and coherent Raman spectroscopies can be applied to qualitatively test and quantitatively measure such motions. Polarization Sensitive Resonance Coherent anti-Stokes Raman Spectroscopy (PSCARS), steady state or time-resolved, can measure controlled dipole moment reorientation through the anisotropic third order nonlinear optical susceptibility. The measured vibrational spectra are sensitive to photo induced isomerization or internal molecular rotation if the rotating chemical group is coupled to or interacting with internal normal modes or to the surrounding molecules e.g. in solutions. In our study, the method was applied to measure the vibrational manifold and reorientation of DCVJ for the first time. DCVJ is a charge transfer molecular rotor showing a viscosity dependent fluorescence quantum yield. This dependence is attributed to the ``friction'' type interaction between the 90 degree internal rotation of the molecule upon photo-excitation and the solvent cage surrounding it. Quantum chemical studies using DFT and normal mode calculations support our findings related to the conformational evolution of the molecule. Theoretical and experimental principles associated with CARS with an emphasis on points relevant to the interpretation of the results will be presented. The design and operation of an all solid-state broadband nanosecond CARS system will be also presented. Finally, an overview of applications of molecular rotors in biology, nanotechnology and perhaps information technology will be outlined.

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

2010-08-01

164

Polarization and phase control of two-photon absorption in an isotropic molecular system  

NASA Astrophysics Data System (ADS)

We theoretically and experimentally study the polarization and phase control of two-photon absorption in an isotropic molecular system. We theoretically show that the two-photon transition probability decreases when the laser polarization changes from linear through elliptical to circular, and the laser polarization does not affect the control efficiency of two-photon transition probability by shaping the spectral phase. These theoretical results are experimentally confirmed in coumarin 480. Furthermore, we propose that the combination of the laser polarization with the spectral phase modulation can further increase the control efficiency of the two-photon absorption.

Lu, Chen-Hui; Zhang, Hui; Zhang, Shi-An; Sun, Zhen-Rong

2012-12-01

165

Mini environment control for the elliptical polarization undulator  

Microsoft Academic Search

The elliptical polarization undulator (EPU) has been constructed at SRRC for creating a high quality and high photon flux. The EPU consists of two fixed diagonal magnet arrays and the other free diagonal arrays to create the right\\/left circular polarization. The magnetic field uniformity of the magnet blocks will influence on the storage beam orbit, the beam lifetime, light source

D. S. Lee; Z. D. Tsai; J. R. Chen

2001-01-01

166

UMTS radio-over-fiber pico-cell interconnection employing low-cost VCSELs and multi-mode fibre  

Microsoft Academic Search

This paper investigates experimentally the suitability of low-cost vertical cavity surface emitting lasers (VCSEL) for radio-over-fibre transmission of UMTS signals. Three directly-modulated VCSEL configurations are investigated: Multi-mode VCSELs operating at 850 nm and 1300 nm respectively in multi-mode fibres (MMF), and single-mode VCSELs operating at 1310 nm with standard single-mode fibre (SSMF). In the later case, the performance of directly-modulated

Rubén Alemany; Roberto Llorente

2009-01-01

167

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

168

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

2012-12-14

169

1.1-?m-range tunnel junction VCSELs with 27GHz relaxation oscillation frequency  

Microsoft Academic Search

We have developed novel 1.1-?m-range InGaAs VCSELs with buried type-II tunnel junctions for high-speed optical interconnections. A relaxation oscillation frequency of 27 GHz was achieved. Error-free 30-Gbps operations were demonstrated using directly modulated multi-mode VCSELs.

K. Yashiki; N. Suzuki; K. Fukatsu; T. Anan; H. Hatakeyama; M. Tsuji

2007-01-01

170

Multi-wavelength 1060nm-band VCSEL array with tapered hollow waveguide multiplexer  

Microsoft Academic Search

We demonstrate a 1060nm-band multi-wavelength VCSEL array with a compact (200?m long) hollow waveguide multiplexer. We show a potential of 12-channel array VCSEL output multiplexed in multi-mode fiber by shifting the lateral position of the array.

A. Imamura; A. Matsutani; F. Koyama

2010-01-01

171

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

172

Analysis of vector LP modes in VCSELs using the effective frequency method  

Microsoft Academic Search

The effective frequency method (EFM) is generalized to the case of vector analysis of LP modes in VCSELs and applied to proton-implanted and oxide-confined VCSEL structures. Resonant wavelengths and mode profiles of a number of vector LP modes are calculated for different values of active region radius. The vector EFM is shown to provide important information about the vertical and

Gennady A. Smolyakov; Peter G. Eliseev; Marek Osinski

2001-01-01

173

VCSEL arrays for high-aggregate bandwidth of up to 1.34 Tbps  

NASA Astrophysics Data System (ADS)

Even though the lane speed of VCSEL based AOC and transceivers has reached 25 Gbps and beyond [1-7], parallel optics are getting even more important in order to meet the increasing demand for aggregate bandwidths in upcoming applications, among others, 100 Gigabit Ethernet, Infiniband EDR, or EOM (embedded optical modules). As 100 Gbps can be achieved by, e.g., 4 times 25 Gbps using standard QSFP form factor, different approaches are using large scale 2D VCSEL arrays operating at lower lane speeds. Early work on 2D VCSEL based transceivers has already been presented beginning of this century [8] and recent work also addressed the potential of this technology [9,10]. In 2013, Compass EOS has introduced a 1.34 Tbps core router solution [11,12,13] that incorporates 2D VCSEL arrays of 14x12 emitters designed and manufactured by Philips U-L-M Photonics. The VCSEL array is mounted face down onto a CMOS ASIC, directly on top of the analog area. The emission wavelength of 1000 nm allows for substrate side emission and thus for flip-chip mounting as well as the possibility of integrating 2D microlens arrays onto the stack of CMOS and VCSEL array. After briefly introducing the router with regard to the incorporated VCSEL technology we discuss the design and performance of the VCSEL array. Finally, the assembly solution for this most compact and dense transceiver solution is presented.

Grabherr, Martin; Intemann, Steffan; King, Roger; Wabra, Stefan; Jäger, Roland; Riedl, Michael

2014-02-01

174

90-deg splicing error control in polarization maintaining fiber resonator based on white-light interferometry  

NASA Astrophysics Data System (ADS)

Polarization fluctuation in polarization maintaining fiber (PMF) resonator is one of the major noise sources in resonant fiber optic gyroscope (R-FOG). 90-deg polarization-axis rotated splicing in R-FOG is an effective way to suppress the polarization-fluctuation induced noise. 90-deg polarization-axis rotated splicing error influences the noise suppression effect. Here, a polarization-coupling testing system based on white-light interferometry is designed to control 90-deg splicing error in double-coupler PMF resonator first time and a result of 0.37-deg splicing error is obtained for the first time. Then the resonant characteristics of the double-coupler PMF resonator are tested using the saw-tooth waveform scanning method. The finesse of this double-coupler PMF resonator is 24.0 and the phase interval of the two eigenstates of polarization (ESOPs) is ?.

Lin, Huizu; Yao, Qiong; Hu, Yongming; Ma, Lina

2012-05-01

175

Polarization-controlled Ohmic to Schottky transition at a metal/ferroelectric interface  

NASA Astrophysics Data System (ADS)

Ferroelectric polar displacements have recently been observed in conducting electron-doped BaTiO3 (n-BTO). The coexistence of a ferroelectric phase and conductivity opens the door to new functionalities that may provide a unique route for novel device applications. Using first-principles methods and electrostatic modeling, we explore the effect that the switchable polarization of n-BTO has on the electronic properties of the SrRuO3/n-BTO (001) interface. Ferroelectric polarization controls the accumulation or depletion of electron charge at the interface, and the associated bending of the n-BTO conduction band determines the transport regime across the interface. The interface exhibits a Schottky tunnel barrier for one polarization orientation, whereas an Ohmic contact is present for the opposite polarization orientation, leading to a large change in interface resistance associated with polarization reversal. Our calculations reveal a five orders of magnitude change in the interface resistance because of polarization switching.

Liu, Xiaohui; Wang, Yong; Burton, J. D.; Tsymbal, Evgeny Y.

2013-10-01

176

Complete polarization controller based on magneto-optic crystals and fixed quarter wave plates.  

PubMed

We propose and demonstrate a polarization controller, which is a concatenation of three Faraday rotators based on magneto-optic crystals separated by two fixed quarter wave plates. Comparing with former schemes, this polarization controller is fast, accurate and stable because it is completely driven by electric signals and has no mechanically moving parts.It is simple-structured and low-cost. Moreover, it is programmable to convert an arbitrary state of polarization (SOP) from the input to any designated SOP at the output. It can also be used as a polarization scrambler. It has potential applications in the research of the polarization dependence of optical communication systems or the compensation of polarization mode dispersion (PMD), etc. PMID:19516494

Zhang, Yang; Yang, Changxi; Li, Shiguang; Yan, He; Yin, Jingchan; Gu, Claire; Jin, Guofan

2006-04-17

177

Selective Area Growth of Well-Ordered ZnO Nanowire Arrays with Controllable Polarity.  

PubMed

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

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

2014-05-27

178

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.

179

Principal State Analysis for a Compact in-Line Fiber Polarization Controller  

NASA Astrophysics Data System (ADS)

A compact in-line fiber-based polarization controller (FPC) made of a rotatable fiber squeezer is investigated in detail with the Mueller matrix model established based on the generalized principal state of polarization (PSP). The PSP caused by the fiber squeezing is in the equator plane, which turns around S3 axis on the Poincaré sphere when rotating the squeezer. Subsequently, a programmable polarization control method is proposed to realize the polarization conversion between arbitrary polarization states, in which only two parameters of phase shift and rotation angle need to be controlled. This type of FPC, which has a highly compact structure, lower insertion loss, and can be directly embedded into any fiber devices without any extra delay, will be an ideal PC for high-speed optical communication and all-optical signal processing.

Li, Zheng-Yong; Wu, Chong-Qing; Wang, Zhi-Hao; Qin, Tao; Wang, Yi-Xu

2013-01-01

180

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

181

High Efficacy Green LEDs by Polarization Controlled MOVPE  

SciTech Connect

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

Wetzel, Christian

2013-03-31

182

Photonic spin Hall effect in hyperbolic metamaterials for polarization-controlled routing of subwavelength modes.  

PubMed

The routing of light in a deep subwavelength regime enables a variety of important applications in photonics, quantum information technologies, imaging and biosensing. Here we describe and experimentally demonstrate the selective excitation of spatially confined, subwavelength electromagnetic modes in anisotropic metamaterials with hyperbolic dispersion. A localized, circularly polarized emitter placed at the boundary of a hyperbolic metamaterial is shown to excite extraordinary waves propagating in a prescribed direction controlled by the polarization handedness. Thus, a metamaterial slab acts as an extremely broadband, nearly ideal polarization beam splitter for circularly polarized light. We perform a proof of concept experiment with a uniaxial hyperbolic metamaterial at radio-frequencies revealing the directional routing effect and strong subwavelength ?/300 confinement. The proposed concept of metamaterial-based subwavelength interconnection and polarization-controlled signal routing is based on the photonic spin Hall effect and may serve as an ultimate platform for either conventional or quantum electromagnetic signal processing. PMID:24526135

Kapitanova, Polina V; Ginzburg, Pavel; Rodríguez-Fortuño, Francisco J; Filonov, Dmitry S; Voroshilov, Pavel M; Belov, Pavel A; Poddubny, Alexander N; Kivshar, Yuri S; Wurtz, Gregory A; Zayats, Anatoly V

2014-01-01

183

Photoelectron spin-polarization control in the topological insulator Bi2Se3.  

PubMed

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

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

2014-02-21

184

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

185

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

186

New markets for VCSELS: pulsed operation of high-power devices  

NASA Astrophysics Data System (ADS)

Driving basic VCSEL technology in the '90, datacom has been the first volume market for various VCSEL products. The downturn in 2001 can be regarded as a point in time, when engineers both from VCSEL manufacturers and nondatacom users started to identify VCSEL technology as a very promising laser source platform for many other applications. Dedicated spectroscopy laser sources based on VCSEL technology, e.g. for oxygen sensing [1], have proven their competitiveness in industrial applications. The most prosepective consumer market of human-machineinterfaces like laser mice has shown the huge potential of the VCSEL technology in low costs, high volume applications, even given extreme technical performance specifications [2]. Just as a consequence, VCSELs are now penetrating into the next potential volume markets, where unique properties of this technology is requested: High power pulsed laser applications, where low cost is a key factor for market entry. In this paper we discuss a suitable semiconductor technology platform, assembly solutions, selected applications and their market potential as well as performance and reliability data. From small footprint of 0.3 mm2 and 0.11 mm2 peak output powers of 0.7 W and more than 6 W at 850 nm wavelength are shown at 30 ?s and 30 ns pulse widths, respectively.

Grabherr, Martin; Miller, Michael; Wiedenmann, Dieter; Jäger, Roland; King, Roger

2007-03-01

187

An optically controlled phased array antenna based on single sideband polarization modulation.  

PubMed

A novel optically controlled phased array antenna consisting a simple optical beamforming network and an N element linear patch antenna array is proposed and demonstrated. The optical beamforming network is realized by N independent phase shifters using a shared optical single sideband (OSSB) polarization modulator together with N polarization controllers (PCs), N polarization beam splitters (PBSs) and N photodetectors (PDs). An experiment is carried out. A 4-element linear patch antenna array operating at 14 GHz and a 1 × 4 optical beamforming network (OBFN) is employed to realize the phased array antenna. The radiation patterns of the phased array antenna at -30°, 0° and 30° are achieved. PMID:24663694

Zhang, Yamei; Wu, Huan; Zhu, Dan; Pan, Shilong

2014-02-24

188

VCSEL-based optical interconnections at interbox distances and shorter  

NASA Astrophysics Data System (ADS)

Optics will soon be established as the mainstay for data-intensive communications at distances about 100 meters or less between workstations, displays and peripherals. The datacom hardware includes arrays of multi-mode vertical-cavity surface-emitting lasers (VCSELs) emitting in the 650 - 1000 nm range and parallel channels of multi-mode optical fiber, which are major departures from the already-established long-distance optical fiber communications for telecom. These radical departures are brought about by two major forces. (1) They are forced by the driving need to reduce costs for datacom links to the consumer affordability level, as opposed to the network provider level in telecom links. (2) They are allowed by the different requirements of the shorter communication distances. In the future, optics is expected to replace traditional communication links at even shorter distances. If optical communications extends down to the inter-chip level, it is likely that the 'chipcom' links will require technologies as different from datacom technologies as VCSEL arrays and fiber ribbons are from distributed feedback lasers and single-mode fibers. In this paper are reviewed the forces which shape the emerging datacom hardware, current state of datacom links, and a crude forecast of what will be required for chipcom links.

Jewell, Jack L.

1996-01-01

189

Hybrid VCSEL modules with integrated amorphous silicon power monitors  

NASA Astrophysics Data System (ADS)

We present a novel optoelectronic package incorporating Vertical-Cavity Surface-Emitting Laser (VCSEL) arrays with built-in power monitors. The power monitor consists of a thin film amorphous silicon p-i-n photodetector that is fabricated on glass. Sets of micro-machined springs for electrical contacting are also fabricated in the same process on the same glass substrate. The springs are made by sputtering, masking, and releasing a stress-engineered conductive thin film. The stress-engineered film is patterned into electrical routing wires whose ends curl up into compliant springs when released from the substrate. Hybrid packages are formed by pressing the micro-machined springs against individual contact pads of the GaAs VCSEL array in a flip-chip assembly process. The power monitor is designed so it lies directly in front of the laser array in the path of the light after module assembly. Although only about 2% of the laser power is absorbed by the sensor, a large signal to noise ratio is retained because of the sensor"s extremely low dark current. Our typical laser output powers of about 1 mW at wavelengths of 811 nm produces power monitor photocurrents of 0.5 to 1 ?A, which, for our detectors, correspond to dynamic ranges of over five orders of magnitude.

Chua, Christopher L.; Lemmi, Francesco; Lu, Jeng-Ping

2004-06-01

190

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

191

Transverse Mode Dynamics of VCSELs Undergoing Current Modulation  

NASA Technical Reports Server (NTRS)

Transverse mode dynamics of a 20-micron-diameter vertical-cavity surface-emitting laser (VCSEL) undergoing gain switching by deep current modulation is studied numerically. The direct current (dc) level is set slightly below threshold and is modulated by a large alternating current (ac). The resulting optical pulse train and transverse-mode patterns are obtained numerically. The ac frequency is varied from 2.5 GHz to 10 GHz, and the ac amplitude is varied from one-half to four times that of the dc level. At high modulation frequencies, a regular pulse train is not generated unless the ac amplitude is large enough. At all modulation frequencies, the transverse spatial profile switches from single-mode to multiple-mode pattern as the ac pumping level is increased. Optical pulse widths vary in the range 5-30 ps. with the pulse width decreasing when either the frequency is increased or the ac amplitude is decreased. The numerical modeling uses an approximation form of the semiconductor Maxwell-Bloch equations. Temporal evolution of the spatial profiles of the laser (and of carrier density) is determined without any assumptions about the type or number of modes. Keywords: VCSELs, current modulation, gain switching, transverse mode dynamics, computational modeling

Goorjian, Peter M.; Ning, C. Z.; Agrawal, Govind

2000-01-01

192

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

193

960-km SSMF transmission of 105.7-Gb/s PDM 3-PAM using directly modulated VCSELs and coherent detection.  

PubMed

We generate a 105.7-Gb/s signal by directly modulating a 1.5-µm VCSEL with a 33.35-Gbaud 3-level signal and polarization multiplexing. By using digital coherent detection, we successfully transmit the 105.7-Gb/s line rate (88.10 Gb/s net bit rate) signal over 960-km standard single-mode-fiber (SSMF) at a 20% hard-decision forward-error correction (FEC) threshold, which is at bit-error ratio (BER) of 1.5 x 10(-2) PMID:23670015

Xie, Chongjin; Dong, Po; Winzer, Peter; Gréus, C; Ortsiefer, M; Neumeyr, C; Spiga, Silvia; Müller, Michael; Amann, M-C

2013-05-01

194

Magnetic control of large room-temperature polarization.  

PubMed

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

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

2009-09-23

195

Highly efficient oxide-confined VCSEL arrays for parallel optical interconnects  

Microsoft Academic Search

We have designed and fabricated 1464-4258\\/1\\/2\\/030\\/img1 and 1464-4258\\/1\\/2\\/030\\/img2 VCSEL arrays at 850 and 980 nm operation wavelength, respectively, which are designed for maximum single-mode output power and high-frequency applications. GaAs VCSELs in the 1464-4258\\/1\\/2\\/030\\/img1 array show record high single-mode CW powers up to 4.8 mW. Individual devices of the 1464-4258\\/1\\/2\\/030\\/img2 InGaAs VCSEL array exhibit small-signal modulation bandwidths exceeding 10 GHz.

C. Jung; R. King; R. Jäger; M. Grabherr; F. Eberhard; R. Michalzik; K. J. Ebeling

1999-01-01

196

Development of GaInNAs-based 1.3-?m VCSEL  

NASA Astrophysics Data System (ADS)

In this paper the realization, development and production of 1.3?m vertical cavity surface emitting lasers (VCSEL) with datacom suitable performance are presented. These low cost laser diodes are well suited for optical interconnect applications for LAN and MAN with transmission distances up to 15 km. The possibilities as well as the advantages and limits of shifting the wavelength from commercially available VCSEL emitting at 850nm to 1300nm are discussed. 1300nm VCSELs in a low cost SMD plastic package assembled into an intelligent SFP-module developed by Infineon Technologies are demonstrated.

Ramakrishnan, Arun; Ebbinghaus, G.; Lima, A.; Supper, D.; Kristen, Guenter; Popp, M.; Degen, C.; Althaus, H.-L.; Killer, T.; Scholz, R.; Melinde, M.; Sauter, M.; Weigert, M.; Riechert, Henning; Steinle, Gunther

2003-12-01

197

Triggering of guiding and antiguiding effects in GaN-based VCSELs  

NASA Astrophysics Data System (ADS)

We show numerically that many recently proposed GaN-based VCSEL cavities, with DBR mirrors deposited onto the current aperture, balance dangerously close to the border between the guided and antiguided regime. A guided cavity is often preferred because of its lower optical loss, but a strongly antiguided cavity offers built-in modal discrimination favoring single fundamental mode operation. We show that very small changes in the VCSEL structure are sufficient to strongly change the guiding character of the VCSEL cavity, and that thermal lensing caused by device self-heating under operation can dramatically reduce the optical loss but not the modal discrimination in the antiguided cavities.

Hashemi, Ehsan; Bengtsson, Jörgen; Gustavsson, Johan; Stattin, Martin; Glauser, Marlene; Cosendey, Gatien; Grandjean, Nicolas; Calciati, Marco; Goano, Michele; Haglund, Åsa

2014-02-01

198

Polarization bistability in 1.5 micron wavelength single-mode vertical-cavity surface-emitting lasers induced by orthogonal optical injection  

NASA Astrophysics Data System (ADS)

We study experimentally the polarization bistability of a single transverse and polarization mode vertical-cavity surface-emitting laser (VCSEL) induced by orthogonal optical injection. As the master laser frequency is scanned near the resonance frequency of the depressed linearly polarized fundamental-mode, and for a fixed master laser power, the VCSEL exhibits two successive polarization switchings. Pure frequency-induced polarization bistability is found because both polarization switchings exhibit bistable regions. The width of both bistable regions is analyzed as a function of the master laser power and for different values of the VCSEL current. The hysteresis width fluctuates around a constant level while the injected power is smaller than a certain value. Further increase of the master laser power leads to a smaller constant value of the hysteresis width. The value of that transition value is independent on the VCSEL current. Power-induced polarization bistability - by fixing the frequency of the injected light- is found near that transition value. The character of the power-hysteresis cycles change from clockwise to anticlockwise as the master laser frequency moves away from the frequency of the depressed linearly polarized fundamental-mode. Qualitatively similar results are found for different VCSELs with wavelength around 1550 nm.

Valle, A.; Gómez-Molina, M.; Pesquera, L.

2008-05-01

199

Defect-mediated polarization switching in ferroelectrics and related materials: from mesoscopic mechanisms to atomistic control  

SciTech Connect

The plethora of lattice and electronic behaviors in ferroelectric and multiferroic materials and heterostructures opens vistas into novel physical phenomena including magnetoelectric coupling and ferroelectric tunneling. The development of new classes of electronic, energy-storage, and information-technology devices depends critically on understanding and controlling field-induced polarization switching. Polarization reversal is controlled by defects that determine activation energy, critical switching bias, and the selection between thermodynamically equivalent polarization states in multiaxial ferroelectrics. Understanding and controlling defect functionality in ferroelectric materials is as critical to the future of oxide electronics and solid-state electrochemistry as defects in semiconductors are for semiconductor electronics. Here, recent advances in understanding the defect-mediated switching mechanisms, enabled by recent advances in electron and scanning probe microscopy, are discussed. The synergy between local probes and structural methods offers a pathway to decipher deterministic polarization switching mechanisms on the level of a single atomically defined defect.

Kalinin, Sergei V [ORNL; Rodriguez, Brian J [ORNL; Baddorf, Arthur P [ORNL; Balke, Nina [ORNL; Borisevich, Albina Y [ORNL; Chang, Hye Jung [ORNL; Chen, Long-Qing [Pennsylvania State University; Jesse, Stephen [ORNL; Maksymovych, Petro [ORNL; Nikiforov, Maxim [ORNL; Pennycook, Stephen J [ORNL

2010-01-01

200

Optical metasurfaces for polarization-controlled beam shaping.  

PubMed

We have developed multifunctional optical beam shapers based on plasmonic metasurfaces. The metasurfaces are composed of subwavelength-spaced polarization- and wavelength-selective optical nanoantennas that allow encoding several beam shapers on a single element. We demonstrate numerically and experimentally beam shapers that can be used to switch between arbitrary beam shapes. We specifically demonstrate switching between one-dimensional Airy and Gaussian beams, Hermite-Gaussian beams of different orders, and two-dimensional Airy and Bessel beams. These beam shapers can be used as integrated optical elements in applications that require more than one laser beam shape. PMID:24978764

Avayu, Ori; Eisenbach, Omri; Ditcovski, Ran; Ellenbogen, Tal

2014-07-01

201

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

PubMed

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

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

2014-05-01

202

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

203

Recent progress in short-wavelength VCSEL-based optical interconnections  

NASA Astrophysics Data System (ADS)

We report on recent progress in the design and application of vertical-cavity surface-emitting lasers (VCSELs) for optical interconnect applications in the 850 nm emission wavelength regime. Ongoing work toward parallel optical interconnect modules with channel data rates of 10 Gbit/s is reviewed and performance results of flip-chip integrated two-dimensional VCSEL arrays are presented. 10 Gbit/s speed as well as low thermal resistance of the lasers has been achieved. As a possible alternative to graded-index multimode fibers, we show 10 Gbit/s data transmission over 100 m length of a novel, entirely undoped multimode photonic crystal fiber. The use of VCSELs with output powers in the 10 mW range is demonstrated in a 16-channel free-space optical (FSO) module and VCSELs with even higher output power are shown to provide possible FSO connectivity up to data rates of 2.5 Gbit/s.

Michalzik, Rainer; Roscher, Hendrik; Stach, Martin; Wiedenmann, Dieter; Miller, Michael; Broeng, Jes; Petersson, Anders; Mortensen, Niels A.; Simonsen, Harald R.; Kube, Erhard

2003-12-01

204

A passively aligned VCSEL transmitter operating at fixed current over a wide temperature range.  

PubMed

We have investigated low-current operation characteristics of a passively aligned VCSEL transmitter driven at fixed "on" and "off" current over a wide temperature range. GaAs/AlGaAs-based 850-nm oxide VCSELs with the minimum threshold current of 0.79 mA at 50 masculineC and small temperature dependence of the threshold current, d(2)I(th)/dT(2), as low as 0.114 muA/ masculineC(2) have been fabricated and used for the transmitter module. The superior temperature characteristics enable fixed-current operation of the VCSEL transmitter that complies with Gigabit Ethernet standard over a wide temperature range from -20 to 120 masculineC. This result paves the way to a VCSEL transmitter featured by low-power consumption, low-cost with a simple driving circuit and passive alignment, and a wide operation temperature range. PMID:19333278

Park, Jonghyun; Kim, Taeyong; Kim, Sung-Han; Kim, Sang-Bae

2009-03-30

205

The range of VCSEL wearout reliability acceleration behavior and its effects on applications  

NASA Astrophysics Data System (ADS)

For nearly twenty years most models of VCSEL wearout reliability have incorporated Arrhenius activation energy near 0.7 eV, usually with a modest current exponent in addition. As VCSEL production extends into more wavelength, power, and speed regimes new active regions, mirror designs, and growth conditions have become necessary. Even at more traditional VCSEL 850-nm wavelengths instances of very different reliability acceleration factors have arisen. In some cases these have profound effects on the expected reliability under normal use conditions, resulting in wearout lifetimes that can vary more than an order of magnitude. These differences enable the extension of VCSELs in communications applications to even greater speeds with reliability equal to or even greater than the previous lowerspeed devices. This paper discusses some of the new applications, different wearout behaviors, and their implications in real-life operation. The effect of different acceleration behaviors on reliability testing is also addressed.

Guenter, James; Graham, Luke; Hawkins, Bobby; Hawthorne, Robert; Johnson, Ralph; Landry, Gary; Tatum, Jim

2013-03-01

206

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

207

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

208

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

PubMed Central

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

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

2014-01-01

209

A polarization control system for intensity-resolved guided mode resonance sensors.  

PubMed

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

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

2014-01-01

210

Full control of magnetism in a manganite bilayer by ferroelectric polarization  

SciTech Connect

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

2013-01-01

211

Control of polarization and mode mapping of small volume high Q micropillars  

SciTech Connect

We show that the polarization of the emission of a single quantum dot embedded within a microcavity pillar of elliptical cross section can be completely controlled and even switched between two orthogonal linear polarizations by changing the coupling of the dot emission with the polarized photonic modes. We also measure the spatial profile of the emission of a series of pillars with different ellipticities and show that the results can be well described by simple theoretical modeling of the modes of an infinite length elliptical cylinder.

Daraei, A.; Sanvitto, D.; Timpson, J. A.; Fox, A. M.; Whittaker, D. M.; Skolnick, M. S.; Guimaraes, P. S. S.; Vinck, H.; Tahraoui, A.; Fry, P. W.; Liew, S. L.; Hopkinson, M. [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom); Departamento de Fisica, Universidade Federal de Minas Gerais, 30123-970, Belo Horizonte, Minas Gerais (Brazil); Instituto de Fisica, Universidad de Antioquia, AA 1226 Medellin (Colombia); Department of Electronic and Electrical Engineering, University of Sheffield, Sheffield S1 3JD (United Kingdom)

2007-08-15

212

Electric control of state of polarization in index-guiding photonic liquid crystal fibers  

NASA Astrophysics Data System (ADS)

Photonic liquid crystal fibers allow for dynamic modification of their guiding and polarization properties. In particular it is possible to dynamically tune phase delay between two orthogonal polarization of the guided mode. In this work an index-guiding photonic liquid crystal fiber with highly tunable retardation, reaching value of 15? (or 30? in terms of phase difference) is presented. Electric tuning with two sets of electrodes is also discussed and demonstrated proving that photonic liquid crystal fibers can be utilized as a all-in-fiber polarization controllers.

Ertman, Slawomir; Siarkowska, Agata; Pysz, Dariusz; Buczy?ski, Ryszard; Nowinowski-Kruszelnicki, Edward; DÄ browski, Roman; Woli?ski, Tomasz R.

2013-05-01

213

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

NASA Astrophysics Data System (ADS)

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 with the experimental observation qualitatively. It is revealed that, from the microscopic structures of spins, the axis of spin cone provides a ``handle,'' with which the magnetization and polarization can be reversed by the magnetic field easily.

Yao, Xiaoyan; Lo, Veng Cheong; Liu, Jun-Ming

2009-10-01

214

Polarized-light-controlled holographic recording in an azobenzene-doped polymer film  

NASA Astrophysics Data System (ADS)

A new polarized-light-controlled holographic recording based on the optical enhancement/restraint of self-diffraction has been demonstrated in an azobenzene-doped polymer film. It is found that a continuous variation of the polarization status as well as of the intensity of the pumping light results in a continuous variation of self-diffraction efficiency. The mechanism originates from the photo-induced anisotropy and polarization-dependent absorption. Both positive and negative replicas of an incident image were presented in real time by means of this incoherent-coherent optical conversion technique.

Yang, Q.; Wei, Z.; Zhang, Y.; Sun, G.; Li, F.

215

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

PubMed

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

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

2013-11-27

216

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

Microsoft Academic Search

High-bandwidth single-mode selectively oxidized vertical-cavity surface-emitting laser (VCSEL) arrays operate at 980 nm or 850 nm emission wavelength for substrate or epitaxial side emission. Coplanar feeding lines and polyimide passivation are used to reduce electrical parasitics in top-emitting GaAs and bottom-emitting InGaAs VCSELs. To enhance fundamental single-mode emission for larger devices of reduced series resistance a surface relief transverse mode

Felix Mederer; Irene Ecker; Jürgen Joos; Max Kicherer; Heiko J. Unold; Karl Joachim Ebeling; Martin Grabherr; Roland Jäger; Roger King; Dieter Wiedenmann

2001-01-01

217

Room temperature continuous-wave operation of GaInNAs long wavelength VCSELs  

Microsoft Academic Search

Vertical cavity surface-emitting lasers (VCSELs) are becoming increasingly important for short-haul optical fiber transmission systems. Given the commercial success of GaAs-based 850 nm VCSELs, dramatic enhancements in transmission bandwidth and distance can be achieved in conventional single- and multi-mode fiber by extending the emission wavelength to the 1300 nm-1550 nm range. GaInNAs is a promising active layer material grown on

M. C. Larson; C. W. Coldren; S. G. Spruytte; H. E. Petersen; J. S. Harris

2000-01-01

218

Spatiotemporal and Thermal Analysis of VCSEL for Short-range Gigabit Optical Links  

Microsoft Academic Search

High-speed Optoelectronic Modules using Vertical Cavity Surface Emitting Lasers (VCSEL) coupled to Multi Mode Fibers (MMF)\\u000a are a performing and low-cost solution for 10 Gigabit Ethernet (10 GbE) in short-distance optical links. A complete model\\u000a of the spatiotemporal behavior of multimode VCSELs, through static and dynamic response, noise, thermal effects, and its coupling\\u000a to MMF has been investigated. Relative Intensity

A. Gholami; Z. Toffano; A. Destrez; M. Pez; F. Quentel

2006-01-01

219

120 Gb\\/s-level VCSEL array optical subassembly using passive alignment technique  

Microsoft Academic Search

Our suggested VCSEL array optical subassembly (OSA) for 120 Gb\\/s-level parallel optical interconnect modules was composed of a 12 channel VCSEL array chip, a SiOB, two silicon spacers, and a molded microlens with accurate guide pin holes. For high speed operation above 10 Gb\\/s per a channel, we carefully designed transmission lines on the SiOB. The results of the transmission

Sung Hwan Hwang; Jung Woon Lim; Byung Sup Rho

2008-01-01

220

1.3 micron InGaAsN oxide-confined VCSELs grown by MOCVD  

Microsoft Academic Search

Summary form only given. An Emcore D 180 metalorganic chemical vapor deposition (MOCVD) system was used to develop 1.3 micron InGaAsN\\/GaAs vertical cavity surface emitting lasers (VCSELs). The InGaAsN VCSELs are dry etched to form a 42 micron mesa that is subsequently wet oxidized to form apertures ranging from 6.0 to 8.5 microns. The quasi-single mode laser was modulated with

C. S. Murray; F. D. Newman; Shangzhu Sun; J. B. Clevenger; D. J. Bossert; C. X. Wang; H. Q. Hou; R. Stall

2002-01-01

221

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

NASA Astrophysics Data System (ADS)

In the last 2 years, the field of micro-electro-mechanical systems tunable vertical cavity surface-emitting lasers (MEMS-VCSELs) has seen dramatic improvements in laser tuning range and tuning speed, along with expansion into unexplored wavelength bands, enabling new applications. This paper describes the design and performance of high-speed ultra-broad tuning range 1050nm and 1310nm MEMS-VCSELs for medical imaging and spectroscopy. Key results include achievement of the first MEMS-VCSELs at 1050nm and 1310nm, with 100nm tuning demonstrated at 1050nm and 150nm tuning at shown at 1310nm. The latter result represents the widest tuning range of any MEMS-VCSEL at any wavelength. Wide tuning range has been achieved in conjunction with high-speed wavelength scanning at rates beyond 1 MHz. These advances, coupled with recent demonstrations of very long MEMS-VCSEL dynamic coherence length, have enabled advancements in both swept source optical coherence tomography (SS-OCT) and gas spectroscopy. VCSEL-based SS-OCT at 1050nm has enabled human eye imaging from the anterior eye through retinal and choroid layers using a single instrument for the first time. VCSEL-based SS-OCT at 1310nm has enabled real-time 3-D SS-OCT imaging of large tissue volumes in endoscopic settings. The long coherence length of the VCSEL has also enabled, for the first time, meter-scale SS-OCT applicable to industrial metrology. With respect to gas spectroscopy, narrow dynamic line-width has allowed accurate high-speed measurement of multiple water vapor and HF absorption lines in the 1310nm wavelength range, useful in gas thermometry of dynamic combustion engines.

Jayaraman, V.; Potsaid, B.; Jiang, J.; Cole, G. D.; Robertson, M. E.; Burgner, C. B.; John, D. D.; Grulkowski, I.; Choi, W.; Tsai, T. H.; Liu, J.; Stein, B. A.; Sanders, S. T.; Fujimoto, J. G.; Cable, A. E.

2013-05-01

222

Calculation and measurement of resonant-mode blueshifts in oxide-apertured VCSELs  

Microsoft Academic Search

As the aperture size of oxide-apertured vertical-cavity surface-emitting lasers (VCSELs) shrinks, the lasing wavelength blueshifts. We have calculated this effect using both a scalar effective index model and a full-vector weighted index model. Results were compared against experimental data for two different VCSEL designs emitting near 780 and 850 nm. We find that the full-vector weighted index calculation matches the

Michael J. Noble; Jae-Heon Shin; Kent D. Choquette; J. A. Lott; Yong-Hee Lee

1998-01-01

223

Direct coupling of VCSELs to plastic optical fibers using guide holes patterned in a thick photoresist  

Microsoft Academic Search

In this letter, we report a simple passive alignment method to couple plastic optical fibers (POFs) to vertical-cavity surface-emitting lasers (VCSELs) for use in parallel optical interconnects. Polymer guide holes were fabricated directly on the top of VCSELs by means of standard photolithography using SU-8 epoxy-based thick photoresist. Perfluorinated graded-index POFs were inserted and fixed in the guide holes to

T. Ouchi; A. Imada; T. Sato; H. Sakata

2002-01-01

224

CONTROL OF LASER RADIATION PARAMETERS: Phase-polarization control of the emission spectra of ring dye lasers  

NASA Astrophysics Data System (ADS)

A ring dye laser with a three-mirror resonator and phase-polarization control of the emission spectrum was constructed and investigated. A resonator mirror performed the function of a nonresonant rotator of the plane of polarization of the light wave. Such a system subjected to single-pulse laser pumping was capable of generating narrow-band radiation with a spectral width 2-4 pm and a high signal/noise ratio in a fairly wide range of pump energies.

Smirnov, A. Ya; Teplyashin, L. L.

1988-05-01

225

VCSEL-based microsensors for photonic proximity fuzing of munitions  

NASA Astrophysics Data System (ADS)

This paper describes technologies developed at Sandia National Laboratories to support a joint DoD/DoE initiative to create a compact, robust, and affordable photonic proximity sensor for munitions fuzing. The proximity fuze employs high-power vertical-cavity surface-emitting laser (VCSEL) arrays, resonant-cavity photodetectors (RCPDs), and refractive micro-optics that are integrated within a microsensor whose volume is approximately 0.01 cm3. Successful development and integration of these custom photonic components should enable a g-hard photonic proximity fuze that replaces costly assemblies of discrete lasers, photodetectors, and bulk optics. Additional applications of this technology include void sensing, ladar and short-range 3-D imaging.

Keeler, G. A.; Mar, A.; Geib, K. M.; Hsu, A. Y.; Serkland, D. K.; Peake, G. M.

2008-08-01

226

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

NASA Astrophysics Data System (ADS)

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

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

2008-05-01

227

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

NASA Astrophysics Data System (ADS)

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

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

2008-03-01

228

An optically controlled microwave phase stabilizer based on polarization interference technique using semiconductor optical amplifier  

NASA Astrophysics Data System (ADS)

We introduce an optically controlled microwave phase stabilizer based on polarization interference technique using single semiconductor optical amplifier (SOA). A prototype with a frequency of 10 GHz is experimentally demonstrated. It provides a stable phase drift that can be linearly compensated over 10 km single-mode fiber by controlling the SOA injection current.

Chen, Han; Sun, Mingming; Sun, Xiaohan

2014-03-01

229

Uniform wafer-bonded oxide-confined bottom-emitting 850-nm VCSEL arrays on sapphire substrates  

Microsoft Academic Search

Uniform bottom-emitting 850-nm vertical-cavity surface-emitting laser (VCSEL) arrays on sapphire substrates have been demonstrated using wafer bonding technology to transfer the epitaxially-grown VCSEL structures from GaAs substrates onto sapphire substrates. The uniformity of the VCSEL arrays were improved by placing thin oxide aperture at the standing wave node to reduce scattering loss for small aperture devices. The averaged threshold current

Chao-Kun Lin; P. Daniel Dapkus

2001-01-01

230

A 54-mW 8-Gbit/s VCSEL driver in a 65-nm CMOS technology  

NASA Astrophysics Data System (ADS)

We report a VCSEL driver ASIC designed and fabricated in a commercial 65-nm CMOS process. At 8 Gbps, the eye diagram passes the eye mask test and the bit-error-rate is less than 10-12 at the 95% confidence level. The total power consumption (including VCSEL) is about 54 mW, less than 1/4 of our previous VCSEL driver ASIC in a silicon-on-sapphire CMOS technology. The VCSEL driver has been tested in a neutron beam with the maximum energy of 800 MeV and the cross section has been estimated to be less than 3.14 × 10-11 cm2.

Liang, F.; Lu, W.; Chen, J.; Deng, B.; Gong, D.; Guo, D.; Jin, G.; Li, X.; Liang, H.; Liu, C.; Liu, G.; Wang, Z.; Xiang, A.; Xu, T.; Ye, J.; Liu, T.

2014-01-01

231

Universal time control of the south polar F layer during the IGY  

NASA Astrophysics Data System (ADS)

A reexamination of south polar F layer data from the International Geophysical Year has been made, and these results were compared with recent satellite measurements of low-energy electrons. The ionospheric data were plotted so that they would show more clearly the dominance of universal time in the control of polar F layer electron densities. This plot of the data also establishes the clear dependence of polar F layer electron densities on corrected geomagnetic latitude. Comparison between the latitudinal dependence of the F layer electron densities and that of the low-energy electron measurements shows close agreement. This agreement suggests that influxes of low-energy electrons into the ionosphere may be responsible for maintaining or enhancing the south polar F layer. Thus, if universal time control of the F layer is due to precipitation of low-energy electron fluxes, one could say that electron precipitation itself must be dependent on universal time. The latitudinal dependence of south polar F layer electron densities indicates that in winter the area of universal time control is restricted to corrected geomagnetic latitudes greater than 50°. Other workers have indicated that in summer universal time control existed at midlatitudes, but only in the South American sector. Present satellite measurements do not support an intrusion of these low-energy electrons down to midlatitudes. Thus, an unknown process confined to this area in summer appears to be operating.

Pike, C. P.

232

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

233

What controls the polarity change of decollement reflection along the Nankai Trough?  

NASA Astrophysics Data System (ADS)

Understanding of the structure and physical properties of the decollement, which is a plate boundary fault in a subduction zone, is important to elucidate a mechanism of megathrust earthquake generation. Variation of reflection polairty, which is one of the key natures of the decollement, appears to be closely related to fluid flow process in the subduction. In spite of previous seismic reflection studies to show a locality of polarity change of the decollement reflection in the Nankai Trough, its general pattern and causes are still controversial. In this study, we aim to figure out what controls the polarity change of decollement reflection along the entire Nankai Trough. We interpreted multichannel seismic reflection profiles that have been acquired in the Nankai Trough margin by Japan Agency for Marine-Earth Science and Technology (JAMSTEC) since the year of 1997. We focus on three features of the decollement reflection: regional distribution, polarity, and seismic stratigraphy. We separated the Nankai subduction zone into "stable sliding" and "stick slip" zones, based on location of the decollement step-down to the subducting oceanic crust. According to the reflection polarity (i.e., normal or reverse) of the decollement, we divided the entire Nankai subduction zone into 6 different regions along Trough. Assuming that the reflection polarity is closely related to incoming sediments, we could recognize 5 different cases in relationship between the decollement reflection polarity and seismic facies: (1) normal polarity on the top of turbidites, (2) reverse polarity in hemipelagic mud, (3) normal polarity on the volcaniclastic layer with a turbidites below, (4) reverse polarity on the volcaniclastic layer without turbidites below, and (5) normal polarity off Kumano basin. Since bedding planes of tubidites may be used as fluid paths, fluid supply to the docollement zone is quite restricted, producing the normal polarity of docollement reflection on the top of turbidites. When the decollement is developed within hemipelagic muddy sediments, it shows reverse polarity. For the vocaniclastic layer with high porosity, the decollement may be easily formed. In this talk, we will present results of the decollement reflection study, and discuss its implications for subduction processes in the Nankai Trough margin.

Lim, J.; Sasaki, T.; Higashi, M.; Park, J.

2010-12-01

234

Controllable directive radiation of a circularly polarized dipole above planar metal surface.  

PubMed

We report unidirectional radiation of a circularly polarized dipole above planar metal surface, the radiation direction can be manipulated via changing the distance between the dipole and the surface. This phenomenon is unique for the combination of circularly polarized dipole and metal surface and does not happen for linearly polarized dipole on metal surface or circularly polarized dipole on dielectric surface. The underlying physics is analytically disclosed by the interference of two orthogonally-oriented dipole component with ?/2 phase lag. A substantially different mechanism of introducing the vectorial nature of the dipole itself to control light emission distinguishes the present scheme from nanoantenna and provides a new degree of freedom in light emission engineering. PMID:24514611

Xi, Zheng; Lu, Yonghua; Yao, Peijun; Yu, Wenhai; Wang, Pei; Ming, Hai

2013-12-16

235

High-speed endless optical polarization stabilization using calibrated waveplates and field-programmable gate array-based digital controller.  

PubMed

A truly endless polarization stabilization experiment with a tracking speed of 15 krad/s is presented. The high-speed polarization tracking is realized by using calibrated lithium niobate linear retardation waveplates as the polarization transformers combined with a very fast digital controller running on a field-programmable gate array (FPGA). PMID:19581991

Hidayat, Ariya; Koch, Benjamin; Zhang, Hongbin; Mirvoda, Vitali; Lichtinger, Manfred; Sandel, David; Noé, Reinhold

2008-11-10

236

Role of Cdc42 dynamics in the control of fission yeast cell polarization.  

PubMed

Cell polarization is fundamental to many cellular processes, including cell differentiation, cell motility and cell fate determination. A key regulatory enzyme in the control of cell morphogenesis is the conserved Rho GTPase Cdc42, which breaks symmetry via self-amplifying positive-feedback mechanisms. Additional mechanisms of control, including competition between different sites of polarized cell growth and time-delayed negative feedback, define a cellular-level system that promotes Cdc42 oscillatory dynamics and modulates activated Cdc42 intracellular distribution. PMID:24256285

Das, Maitreyi; Verde, Fulvia

2013-12-01

237

Cytokinin controls polarity of PIN1-dependent auxin transport during lateral root organogenesis.  

PubMed

The plant hormones auxin and cytokinin mutually coordinate their activities to control various aspects of development [1-9], and their crosstalk occurs at multiple levels [10, 11]. Cytokinin-mediated modulation of auxin transport provides an efficient means to regulate auxin distribution in plant organs. Here, we demonstrate that cytokinin does not merely control the overall auxin flow capacity, but might also act as a polarizing cue and control the auxin stream directionality during plant organogenesis. Cytokinin enhances the PIN-FORMED1 (PIN1) auxin transporter depletion at specific polar domains, thus rearranging the cellular PIN polarities and directly regulating the auxin flow direction. This selective cytokinin sensitivity correlates with the PIN protein phosphorylation degree. PIN1 phosphomimicking mutations, as well as enhanced phosphorylation in plants with modulated activities of PIN-specific kinases and phosphatases, desensitize PIN1 to cytokinin. Our results reveal conceptually novel, cytokinin-driven polarization mechanism that operates in developmental processes involving rapid auxin stream redirection, such as lateral root organogenesis, in which a gradual PIN polarity switch defines the growth axis of the newly formed organ. PMID:24768050

Marhavý, Peter; Duclercq, Jérôme; Weller, Benjamin; Feraru, Elena; Bielach, Agnieszka; Offringa, Remko; Friml, Ji?í; Schwechheimer, Claus; Murphy, Angus; Benková, Eva

2014-05-01

238

Analysis of broadcasting satellite service feeder link power control and polarization  

NASA Technical Reports Server (NTRS)

Statistical analyses of carrier to interference power ratios (C/Is) were performed in assessing 17.5 GHz feeder links using (1) fixed power and power control, and (2) orthogonal linear and orthogonal circular polarizations. The analysis methods and attenuation/depolarization data base were based on CCIR findings to the greatest possible extent. Feeder links using adaptive power control were found to neither cause or suffer significant C/I degradation relative to that for fixed power feeder links having similar or less stringent availability objectives. The C/Is for sharing between orthogonal linearly polarized feeder links were found to be significantly higher than those for circular polarization only in links to nominally colocated satellites from nominally colocated Earth stations in high attenuation environments.

Sullivan, T. M.

1982-01-01

239

Oscillatory spin-polarized tunnelling from silicon quantum wells controlled by electric field  

NASA Astrophysics Data System (ADS)

Spin-dependent electronic transport is widely used to probe and manipulate magnetic materials and develop spin-based devices. Spin-polarized tunnelling, successful in ferromagnetic metal junctions, was recently used to inject and detect electron spins in organics and bulk GaAs or Si. Electric field control of spin precession was studied in III-V semiconductors relying on spin-orbit interaction, which makes this approach inefficient for Si, the mainstream semiconductor. Methods to control spin other than through precession are thus desired. Here we demonstrate electrostatic modification of the magnitude of spin polarization in a silicon quantum well, and detection thereof by means of tunnelling to a ferromagnet, producing prominent oscillations of tunnel magnetoresistance of up to 8%. The electric modification of the spin polarization relies on discrete states in the Si with a Zeeman spin splitting, an approach that is also applicable to organic, carbon-based and other materials with weak spin-orbit interaction.

Jansen, Ron; Min, Byoung-Chul; Dash, Saroj P.

2010-02-01

240

Analysis of broadcasting satellite service feeder link power control and polarization  

NASA Astrophysics Data System (ADS)

Statistical analyses of carrier to interference power ratios (C/Is) were performed in assessing 17.5 GHz feeder links using (1) fixed power and power control, and (2) orthogonal linear and orthogonal circular polarizations. The analysis methods and attenuation/depolarization data base were based on CCIR findings to the greatest possible extent. Feeder links using adaptive power control were found to neither cause or suffer significant C/I degradation relative to that for fixed power feeder links having similar or less stringent availability objectives. The C/Is for sharing between orthogonal linearly polarized feeder links were found to be significantly higher than those for circular polarization only in links to nominally colocated satellites from nominally colocated Earth stations in high attenuation environments.

Sullivan, T. M.

1982-11-01

241

CANMET residuum hydrocracking: Advances through the control of polar aromatics  

SciTech Connect

The beginnings of the CANMET hydrocracking process took root in the mid 1970`s. An ongoing program of development has broadened this novel hydrocracking process for upgrading Canadian oil sands bitumen to successfully process a wide range of refinery residues from conventional crudes as well as residues from refinery conversion units. FCCU slurry, visbreaker vacuum tower bottoms, deasphalter bottoms residue, and poor quality gas oils from cokers and visbreakers are all upgradable in the CANMET process. This paper gives an overview of the process, describes its demonstrated performance, and outlines recent technology improvements. The CANMET slurry hydrocracking process utilizes a solid additive to inhibit coke formation and is capable of 975+ F conversion levels in excess of 90%. Typical hydrogen partial pressures are in the range of 1,500 psi. Demonstration in a 5,000 BPD unit over a seven-year period has shown that operation is easier to control than a conventional gas oil hydrocracker. The absence of an active catalyst combined with the auto-cooling effect of the well back mixed upflow reactor leads to an extremely stable reactor operation. The reactor is stable even if reactor quenches are not used for control.

Benham, N.K. [Petro-Canada, Calgary, Alberta (Canada); Pruden, B.B. [Univ. of Calgary, Alberta (Canada). Dept. of Chemical and Petroleum Engineering

1996-12-01

242

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

Microsoft Academic Search

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

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

2005-01-01

243

A novel multipath dispersion reduction technique based on controlled-polarization optical wireless link setup  

Microsoft Academic Search

The detection characteristics of an indoor-optical communication system, which utilizes infrared radiation as carrier has been explored and enhanced for telemedicine, and wireless local area network applications. The novelty of the presented technique consists in the fact that multipath dispersion can be reduced under controlled polarization link setup. The design of such a network is based on the specifications set

G. C. Giakos; N. Patnekar; S. Sumrain; L. Fraiwan; V. Kumar; G. B. Mertzios

2003-01-01

244

Analysis of Broadcasting Satellite Service Feeder Link Power Control and Polarization.  

National Technical Information Service (NTIS)

Statistical analyses of carrier to interference power ratios (C/Is) were performed in assessing 17.5 GHz feeder links using (1) fixed power and power control, and (2) orthogonal linear and orthogonal circular polarizations. The analysis methods and attenu...

T. M. Sullivan

1982-01-01

245

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

NASA Astrophysics Data System (ADS)

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

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

2005-03-01

246

Phase control of semi-polar (112¯2) and non-polar (112¯0) GaN on cone shaped r-plane patterned sapphire substrates  

NASA Astrophysics Data System (ADS)

The control of formation of semi-polar (112¯2) and nonpolar a-plane (112¯0) GaN phases on r-plane cone shaped patterned sapphire substrates (CPSS) by metalorganic vapor-phase epitaxy has been investigated. With a nucleation layer grown at 535 °C and 200 mbar, only semi-polar (112¯2) GaN is formed. Increasing the nucleation layer temperature to 965 °C, only (112¯0) GaN is grown at 200 mbar. At reduced reactor pressure of 60 mbar, phase selectivity breaks down and semi-polar (112¯2) and non-polar (112¯0) GaN exist simultaneously. The crystalline quality of a-plane GaN on r-plane CPSS can be effectively improved using optimized growth direction control.

Wang, Mei-Tan; Brunner, Frank; Liao, Kuan-Yung; Li, Yun-Li; Tseng, Snow H.; Weyers, Markus

2013-05-01

247

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

248

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

249

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

SciTech Connect

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

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

2007-02-15

250

Coherent optical control of the ultrafast dephasing and mobility in a polar semiconductor  

Microsoft Academic Search

Using the nonperturbative many-body time-dependent approach, we investigate the nonequilibrium dynamics of the coherent longitudinal optical phonon-plasmon coupled (LOPC) modes in a polar semiconductor and explore their coherent optical control and eventually the carrier mobility of the semiconductor. The basic idea for a control of the carrier mobility is to manipulate the ultrafast dephasing of the coherent carrier-relevant LOPC mode.

J. D. Lee; H. Gomi; Muneaki Hase

2009-01-01

251

Control of temporal mapping and harmonic intensity modulation using two-color orthogonally polarized fields  

NASA Astrophysics Data System (ADS)

We demonstrate theoretically control over the time-frequency mapping in two-color high-order harmonic generation. By changing the temporal delay between a driving field and its orthogonally polarized second harmonic we are able to preferentially select between the short- and long-orbit contributions to the harmonic emission along both polarization axes. This trajectory selection is interpreted through use of classical and quantum orbit models. We further observe, and explain, different modulations in intensity of odd and even order harmonic emission modeled via a full macroscopic propagation model coupled to a single-atom quantum orbit treatment.

Hoffmann, David J.; Hutchison, Chris; Zaïr, Amelle; Marangos, Jonathan P.

2014-02-01

252

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

SciTech Connect

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

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

2009-11-30

253

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

254

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

255

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

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

256

Transcriptional control of polarity in Escherichia coli by cAMP.  

PubMed

In Escherichia coli, 3'5'-adenosine cyclic monophosphate (cAMP) and its receptor protein (CAP) are known to be involved in the control of transcription initiation of catabolic operons. In previous papers we have shown that the cAMP-CAP complex is also involved as a modulator of polarity in polycistronic transcription units. Furthermore we showed that there exists a functional relationship between this complex and the transcription termination protein, Rho. In this work, we measured mRNA synthesis corresponding to the promoter proximal and distal parts of the lac and gal operons by DNA-RNA hybridization. We show that in these operons the main polarity effect is essentially transcriptional and the cAMP-CAP complex decreases polarity by interfering with premature transcription termination. PMID:6092868

Guidi-Rontani, C; Danchin, A; Ullmann, A

1984-01-01

257

Ionospheric control of polarization of low-latitude geomagnetic micropulsations at sunrise  

NASA Astrophysics Data System (ADS)

The ionospheric control of low latitude pulsation polarization characteristics suggested by Saka et al. (1980) has been confirmed through continuous low latitude Pc3 and Pc4 geomagnetic micropulsation observations. The D-component amplitude increases as much as that of the H-component after sunrise, effecting the tilting of the major polarization ellipse axis from north to northwest. This coincides with the appearance of the E-layer in the ionosphere within an hour, and the time of the coincidence shifts from season to season in parallel with changes of sunrise. The ellipticity of the horizontal plane polarization is not appreciably affected by sunrise. It is suggested that the Hall conductivity increment associated with the E-layer sunrise enhancement affects the characteristics of the D-component on the ground.

Saka, O.; Itonaga, M.; Kitamura, T.

1982-08-01

258

Oscillatory dynamics of Cdc42 GTPase in the control of polarized growth  

PubMed Central

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

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

2013-01-01

259

Ultrafast direct modulation of transverse-mode coupled-cavity VCSELs far beyond the relaxation oscillation frequency  

NASA Astrophysics Data System (ADS)

A novel approach for bandwidth augmentation for direct modulation of VCSELs using transverse-coupled-cavity (TCC) scheme is raised, which enables us to tailor the modulation-transfer function. The base structure is similar to that of 3QW VCSELs with 980 nm wavelength operation. While the bandwidth of conventional VCSELs was limited by 9-10 GHz, the 3-dB bandwidth of TCC VCSEL with aperture diameters of 8.5×8.5?m2 and 3×3?m2 are increased by a factor of 3 far beyond the relaxation-oscillation frequency. Our current bandwidth achievement on the larger aperture size is 29 GHz which is limited by the used photo-detector. To the best of our knowledge this is the fastest 980 nm VCSEL.

Dalir, Hamed; Koyama, Fumio

2014-02-01

260

Stable Circularly Polarized Emission from a Vertical-Cavity Surface-Emitting Laser with a Chiral Reflector  

NASA Astrophysics Data System (ADS)

An optically pumped vertical-cavity surface-emitting laser (VCSEL) was conceived, fabricated, and characterized for stable circularly polarized (CP) emission. This laser includes a columnar thin film as a quarter-wave plate and a chiral sculptured thin film as a chiral mirror for its microcavity. Pure CP lasing with a high degree of CP (˜0.97) was observed when the VCSEL was optically pumped. The polarization of the laser output exhibits the same handedness as that of the chiral mirror.

Zhu, YiMing; Zhang, Fan; You, GuanJun; Liu, Jie; Zhang, John D.; Lakhtakia, Akhlesh; Xu, Jian

2012-03-01

261

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

262

Suppressing the turn-off-induced pulsations in VCSELs using an elevated oxide-layer structure.  

PubMed

We have demonstrated that, in elevated oxide-layer vertical-cavity surface-emitting lasers (VCSELs) where the spacing between 1-lambda cavity and oxide layer is 9lambda/4, a variety of turn-off-induced abnormalities such as secondary pulsations, bumps and tails is effectively suppressed. Compared are turn-off transient responses of conventional and elevated oxide-layer VCSELs with the oxide-aperture diameter of approximately 6.6 microm. The "on"- and "off"-current dependence of the turn-off-induced transient responses and bit rate dependence of the timing jitters show that the elevated oxide-layer structure effectively suppresses the turn-off-induced pulsations to less than half of the conventional one, which enables the VCSEL transmitter to operate without deleterious effects by the turnoff-induced pulsation. PMID:20173951

Kim, Taeyong; Kim, Sang-Bae

2010-01-18

263

Coherent laser control in attosecond sum-frequency polarization beats using twin noisy driving fields  

SciTech Connect

Based on the phase-conjugate polarization interference between two-pathway excitations, we obtained an analytic closed form for the second-order or fourth-order Markovian stochastic correlation of the V three-level sum-frequency polarization beat (SFPB) in attosecond scale. Novel interferometric oscillatory behavior is exposed in terms of radiation-radiation, radiation-matter, and matter-matter polarization beats. The phase-coherent control of the light beams in the SFPB is subtle. When the laser has broadband linewidth, the homodyne detected SFPB signal shows resonant-nonresonant cross correlation, a drastic difference for three Markovian stochastic fields, and the autocorrelation of the SFPB exhibits hybrid radiation-matter detuning terahertz damping oscillation. As an attosecond ultrafast modulation process, it can be extended intrinsically to any sum frequency of energy levels. It has been also found that the asymmetric behaviors of the polarization beat signals due to the unbalanced controllable dispersion effects between the two arms of interferometer do not affect the overall accuracy in case using the SFPB to measure the Doppler-free energy-level sum of two excited states.

Zhang Yanpeng; Song Jianping; Yu Xiaojun; Ma Ruiqiong; Ge Hao; Li Chuangshe [Department of Electronic Science and Technology, Xi'an Jiaotong University, Xi'an 710049 (China); Gan Chenli [Department of Physics, P.O. Box 311427, University of North Texas, Denton, Texas 76203-1427 (United States); Lu Keqing [State Key Laboratory of Transient Optics and Technology, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an 710068 (China)

2005-02-01

264

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

2013-10-01

265

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

266

High-speed 850 nm oxide-confined VCSELs for 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 short-reach computer interconnects. The continuing rapid increase of serial transmission data rates driven by multi-core microprocessor's bandwidth upgrades cannot be sustained via conventional copper-based links as bit rates move beyond 10 Gbit/s and distances greater than 1 m. The intrinsic limitation of copper at high single-channel data rates facilitates the need to transition to optical fiberbased links at ever shorter distances. For LAN/SAN applications the 850 nm wavelength is standard. This same wavelength is also the standard for several other evolving short-reach application areas including Fibre Channel, CEI, USB, InfiniBand, and HDMI optical link systems. Herein we present our recent results on 850 nm oxide-confined VCSELs operating at data bit rates up to 40 Gbit/s. The low operational current density in the range of ~10 kA/cm2 ensures viable device reliability and long-term stability based on well-known industry certification specifications. Key VCSEL device parameters including the relaxation resonance frequency, damping, and parasitic cut-off frequency are determined for VCSELs with oxide-confined apertures of various diameters. We find that a parasitic cut-off frequency of 24-28 GHz limits the VCSEL's high speed operation at the highest optical modulation rates. We believe that with some effort the device parasitics can be further reduced such that current modulated VCSELs can be realized with larger than 30 GHz optical modulation bandwidth and reliable and practical operation beyond 40 Gbit/s.

Mutig, Alex; Blokhin, Sergey; Nadtochiy, Alexey M.; Fiol, Gerrit; Lott, James A.; Shchukin, Vitaly A.; Ledenstov, Nikolai N.; Bimberg, Dieter

2010-02-01

267

Polarization-rotation resonances with subnatural widths using a control laser  

NASA Astrophysics Data System (ADS)

We demonstrate extremely narrow resonances for polarization rotation in an atomic vapor. The resonances are created using a strong control laser on the same transition, which polarizes the atoms due to optical pumping among the magnetic sublevels. As the power in the control laser is increased, successively higher-order nested polarization-rotation resonances are created, with progressively narrower linewidths. We study these resonances in the D2 line of Rb in a room temperature vapor cell, and demonstrate a width of 0.14~\\Gamma for the third-order rotation. The physical basis for the observed resonances is that optical pumping results in a simplified ?V-type level structure with differential dressing of the levels by the control laser, which is why the control power has to be sufficiently high for each resonance to appear. This explanation is borne out by a density-matrix analysis of the system. The dispersive lineshape and subnatural width of the resonance lends itself naturally to applications such as laser locking to atomic transitions and precision measurements.

Ranjita Chanu, Sapam; Pandey, Kanhaiya; Bharti, Vineet; Wasan, Ajay; Natarajan, Vasant

2014-05-01

268

Electrically pumped fluidic cavity (EPFC) VCSEL for the detection of biologic agents  

NASA Astrophysics Data System (ADS)

A fluidic cavity vertical-cavity surface-emitting laser (VCSEL) is presented for the detection of biological agents via introducing the analytic biofluid into the high finesse laser cavity. The optical properties of the fluid as modified by the biological cells they contain are sensed by monitoring the output optical intensity and wavelength of the laser. As a preliminary study, our first generation electrically pumped GaAs/AlGaAs based fluidic cavity VCSEL is described, with emphasis on the system design and techniques for the system construction. The device shows a strong spontaneous emission and a considerable wavelength shift when DI water is capillarily fed into the fluidic cavity.

Yu, Tao; Ao, Tao; Hartinger, Klaus; Shao, Hua; Wilmsen, Carl W.; Lear, Kevin L.; Geib, Kent M.; Feld, Stewart A.

2003-06-01

269

Electrical characterization and application of very high speed vertical cavity surface emitting lasers (VCSELs)  

SciTech Connect

Vertical Cavity Surface Emitting Lasers (VCSELs) offer many benefits over conventional edge-emitting lasers including economical microelectronic batch processing, easy extension to 2-D arrays, and of interest here, very large intrinsic bandwidths due to reduced cavity volume. Results of electrical characterization of a 19 GHz bandwidth 850 nm VCSEL are presented. Small-signal characterization and modeling of the frequency response and device impedance is presented. Large signal performance is studied using two-tone RF and high-speed digital measurements. Appropriate drive conditions for high-speed digital applications are demonstrated.

Hietala, V.M.; Lear, K.L.; Armendariz, M.G. [and others

1997-04-01

270

Chaos synchronization and encrypted communication systems as an application of VCSELs  

NASA Astrophysics Data System (ADS)

In this work we have proposed chaotic synchronization system using two identical electro-optical nonlinear delayed feedback systems (NDFS) utilizing VCSEL. This first time proposal has high potential to perform more sensitive chaotic dynamics for improvement of encrypted communications quality. In this system we have demonstrated the reduction of robustness to prevent tapping by someone else attaining higher correlation but only if the feedback gain is the same value. We have also demonstrated the variations of correlation if feedback gain has the slight difference. Moreover, we have demonstrated applications to encrypted communications using VCSEL.

Hisatomi, Masanori; Sasaki, Wakao

2014-02-01

271

Dynamic modulation of spatially structured polarization fields for real-time control of ultrafast laser-material interactions.  

PubMed

The polarization state of an ultrafast laser is dynamically controlled using two Spatial Light Modulators and additional waveplates. Consequently, four states of polarization, linear horizontal and vertical, radial and azimuthal, all with a ring intensity distribution, were dynamically switched at a frequency ? = 12.5 Hz while synchronized with a motion control system. This technique, demonstrated here for the first time, enables a remarkable level of real-time control of the properties of light waves and applied to real-time surface patterning, shows that highly controlled nanostructuring is possible. Laser ablation of Induced Periodic Surface Structures is used to directly verify the state of polarization at the focal plane. PMID:24150374

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

2013-10-21

272

Ferroelectric control of the spin polarization in an organic spin valve  

NASA Astrophysics Data System (ADS)

Recently engineering the spin propagation in organic spin valves has shown increasingly interesting properties. In this work we demonstrate novel ferroelectric control of the spin polarization in an organic spin valve. By inserting a thin ferroelectric buffer layer between a bottom La0.67Sr0.33MnO3 (LSMO) electrode and the organic Alq3 layer, a controlled spin polarization through the ferroelectric interface is achieved. The spin valve exhibits both positive and negative magnetoresistance depending on the applied bias. We conclude that this results from the energy level shift by the ferroelectric dipoles between Alq3 and LSMO (Research sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. Department of Energy).

Sun, Dali; Xu, Xiaoshan; Jiang, Lu; Lee, Ho Nyung; Guo, Hangwen; Snijders, Paul C.; Zac Ward, T.; Gai, Zheng; Zhang, X.-G.; Shen, Jian

2012-02-01

273

Harnessing randomness to control the polarization of light transmitted through highly scattering media.  

PubMed

We show that the multiple scattering events taking place inside a highly scattering medium, in conjunction with wavefront shaping, can be used to control the state of polarization of the light transmitted through a highly scattering medium. This control is achieved by using the intensity, phase, and polarization changing behavior of a scattering medium captured by a vector transmission matrix (VTM). We use a single beam incident upon a scattering medium to measure the absolute value of the VTM elements, in contrast to the multiple beams required in our previously reported approach. Further, the phase-only spatial light modulator based on a low-cost (< US$600) deformable micro-mirror array used in our work will make similar experiments accessible to other researchers. PMID:24663764

Tripathi, Santosh; Toussaint, Kimani C

2014-02-24

274

Role of external cavity reflectivity for achieving polarization control and stabilization of vertical cavity surface emitting laser  

NASA Astrophysics Data System (ADS)

The authors present the experimental results showing how the external mirror reflectivity affects the polarization properties of a vertical cavity surface emitting laser subject to optical feedback from an extremely short external cavity. The amplitude of modulation of the polarization switching current with the external cavity length is found to be proportional to the external mirror reflectivity, confirming its key role in achieving polarization control and stabilization of such lasers using optical feedback. Numerical simulations presented here show good agreement with experiments.

Arizaleta Arteaga, Mikel; López-Amo, Manuel; Thienpont, Hugo; Panajotov, Krassimir

2007-01-01

275

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

Microsoft Academic Search

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

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

2001-01-01

276

The nano-gap and the emitting molecule: Control of polarization and spectral shape  

NASA Astrophysics Data System (ADS)

The realization of single-molecule surface-enhanced Raman scattering (SERS) from molecules positioned within nano-gaps between metallic nanopraticles has opened up exciting opportunities for studying plasmonic fields and their effects on quantum emitters. We recently showed that constructs made of pairs of nanoparticles with an individual molecules bridging their gap can be systematically formed and studied [1]. By changing the size of the particles, we were able to tune the position of the plasmon resonance spectrum, so that the overlap with different parts of the molecular Raman spectrum changed, leading to significant modulation of its shape. More intricate control over molecular properties can be achieved if a third particle is added to the contstruct. It was found that by breaking the dimer symmetry, a third particle can couple strongly to the emitted Raman field and modulate its polarization in a wavelength-dependent fashion [2]. This surprising experimental result was backed up by a series of Generalized Mie calculations, showing the effect of the distance of the third particle, its size and position [3]. Interestingly, the refractive index of the surrounding medium serves as another control parameter that allows changing the coupling between the particles and modulating the polarization of emitted light. [4pt] [1] Dadosh T, et al. (2009) Plasmonic Control of the Shape of the Raman Spectrum of a Single Molecule in a Silver Nanoparticle Dimer. Acs Nano 3:1988-1994. [0pt] [2] Shegai T, et al. (2008) Managing light polarization via plasmon-molecule interactions within an asymmetric metal nanoparticle trimer. Proc Natl Acad Sci USA 105:16448-16453. [0pt] [3] Li ZP, Shegai T, Haran G, Xu HX (2009) Multiple-Particle Nanoantennas for Enormous Enhancement and Polarization Control of Light Emission. Acs Nano 3:637-642.

Haran, Gilad

2010-03-01

277

Polarity control of ZnO on c-plane sapphire by plasma-assisted MBE  

Microsoft Academic Search

Polarity-controlled ZnO films with an MgO buffer layer were grown on c-plane sapphire by plasma-assisted molecular beam epitaxy (MBE). The effect of the thickness of the MgO buffer layer on the MBE growth of ZnO was investigated. The growth rate of ZnO increased from 250 to 500nm\\/h when the MgO layer thickness was increased from 1 to 3nm. Convergent beam

Hiroyuki Kato; Michihiro Sano; Kazuhiro Miyamoto; Takafumi Yao

2005-01-01

278

Use of polar organic solvents to control SOâ emissions: a study of solubilities and conceptual designs  

Microsoft Academic Search

Vapor-liquid equilibrium (VLE) data for SOâ in eight polar organic solvents and three mixtures of organic solvents were investigated over the temperature range of 30 to 95°C and over a concentration range of 0.02 to 0.16 weight fraction of SOâ. Process designs were evaluated for controlling SOâ emissions from sulfuric acid plants and for flue gas desulfurization (FGD) of electric

Demyanovich

1984-01-01

279

Selective control of polarized luminescence from GaN/AlN self-assembled quantum dots  

NASA Astrophysics Data System (ADS)

GaN/AlN self-assembled quantum dots (QDs) were grown by the Stranski-Krastanov method on Si(111) using molecular beam epitaxy. During the subsequent cooling from growth temperatures, the thermal expansion coefficient mismatch between the Si substrate and GaN/AlN film containing vertically stacked QDs leads to an additional biaxial tensile stress at the Si/III-Nitride interface. We have modified the thermal stress in the QD layers by etching stripes of varying widths using inductively coupled Cl/Ar plasma reactive ion etching. The results show that a suitable choice of stripe width and orientation can create regions of in-plane uniaxial stress ranging from 20-30 kbar which enables a selective and local control of polarized emission from the QDs. Localized cathodoluminescence (CL) spectroscopy of the QDs exhibits emissions from both the ground and excited states, whose relative contributions depend on the level of excitation and temperature. We have studied these emissions using time- and polarization-resolved CL for ensembles of QDs. The effects of screening of the polarization field in the QD, state-filling, changes in the polarization anisotropy and lifetime with varying excitation were studied experimentally and modeled with a self-consistent 6x6 k.p calculation method.

Rich, Daniel; Moshe, Ofer; Damilano, Benjamin; Massies, Jean

2011-03-01

280

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

281

Optically controlled microwave phase shifter based on nonlinear polarization rotation in a highly nonlinear fiber.  

PubMed

This Letter reports an optically controlled microwave phase shifter with an ultra-wideband working bandwidth and a full 360° phase shifting range based on nonlinear polarization rotation (NPR) in a highly nonlinear fiber (HNLF). A continuous wave probe light is modulated by a polarization modulator (PolM) that is driven by a microwave signal to be phase shifted. The optical carrier and the first-order sidebands of the probe light experience different phase shifts due to the NPR induced by the control light in the HNLF. An optical bandpass filter is used to realize single-sideband modulation of the probe light by removing one of the first-order sidebands, as well as to reject the control light. After detecting by a photodetector, the phase of the recovered microwave signal is continuously tunable by adjusting the power of the control light. The proposed approach is theoretically analyzed and experimentally verified. A full 360° tunable phase shift is realized over an ultra-wideband frequency range from 8 to 38 GHz when the power of the control light is tuned from 0 to 570 mW. PMID:24876035

Li, Wei; Sun, Wen Hui; Wang, Wen Ting; Zhu, Ning Hua

2014-06-01

282

Demonstration of Repeater-Based Access Network Using VCSEL Transmitters and Multimode Fibers  

Microsoft Academic Search

We experimentally demonstrate a repeater-based optical access network using VCSEL-based transmitters and multi-mode fibers. Our system uses back-to-back connection of standard transceivers for the upstream repeater. The system shows similar performance compared with standard PON.

An Vu Tran; Chang-Joon Chae; R. S. Tucker

2006-01-01

283

Extremely Low-Noise High-Speed VCSELs for Optical Interconnects  

Microsoft Academic Search

wavelength are characterised for this purpose. Relative intensity noise (RIN) and small signal modulation measurements have been performed and re- sulting spectra are fitted to theoretical curves in order to obtain internal device parameters. Different operation regimes, where transverse single- or multi-mode emission occurs, are in- vestigated. At low temperatures the quantum efficiency of the VCSEL is increased, leading to

Max Kicherer

1999-01-01

284

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

285

1.55-µm VCSEL arrays for optical multiple-input multiple-output (MIMO)  

Microsoft Academic Search

We present a monolithically integrated, individually addressable 2D VCSEL array of five lasers which can be coupled into the core of a multi-mode fiber. This device, emitting at 1.55 mum with a perchannel modulation bandwidth in excess of 10 GHz, is especially designed for optical multiple-input multiple-output (MIMO) data transmission.

W. Hofmann; N. H. Zhu; M. Gorblich; L. Xie; G. Bohm; M. Ortsiefer; M.-C. Amann

2009-01-01

286

Far-field emission characteristics and linewidth measurements of surface micro-machined MEMS tunable VCSELs  

NASA Astrophysics Data System (ADS)

In this paper, we demonstrate for the first time the far-field experimental results and the linewidth characteris- tics for widely tunable surface-micromachined micro-electro-mechanical system (MEMS) vertical-cavity surface- emitting lasers (VCSELs) operating at 1550 nm. The fundamental Gaussian mode emission is confirmed by optimizing the radius of curvature of top distributed Bragg reflector (DBR) membrane and by choosing an ap- propriate diameter of circular buried tunnel junctions (BTJs) so that only the fundamental Gaussian mode can sustain. For these VCSELs, a mode-hop free continuous tuning over 100 nm has already been demonstrated, which is achieved by electro-thermal tuning of the MEMS mirror. The fiber-coupled optical power of 2mW over the entire tuning range has been reported. The singlemode laser emission has more than 40 dB of side-mode suppression ratio (SMSR). The smallest linewidth achieved with these of MEMS tunable VCSELs is 98MHz which is one order of magnitude higher than that of fixed-wavelength VCSELs.

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

2013-03-01

287

Optical modelling of photonic crystals and VCSELs using eigenmode expansion and perfectly matched layers  

Microsoft Academic Search

We present a modelling approach for photonic crystal structures and vertical-cavity surface-emitting lasers (VCSELs). This method is based on vectorial eigenmode expansion combined with perfectly matched layer (PML) boundary conditions. Compared to other methods, a relatively small computational effort is required, while at the same time accurate results are obtained, even in the presence of strong scattering and diffraction losses.

P. Bienstman; R. Baets

2001-01-01

288

Energy-efficient oxide-confined high-speed VCSELs for optical interconnects  

NASA Astrophysics Data System (ADS)

Principles of energy-efficient high speed operation of oxide-confined VCSELs are presented. Trade-offs between oxideaperture diameter, current-density, and energy consumption per bit are demonstrated and discussed. Record energyefficient error-free data transmission up to 40 Gb/s, across up to 1000 m of multimode optical fiber and at up to 85 °C is reviewed.

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

2014-02-01

289

Coupled mode theory: a powerful tool for analyzing complex VCSELs and designing advanced device features  

Microsoft Academic Search

Vertical-cavity surface-emitting lasers (VCSELs) have become leading light sources in plenty of applications due to their good characteristics and low costs. There are, however, some features that need improvements; therefore, optimized or new designs ideas are necessary. To this aim, an electromagnetic simulation tool, which is fast and precise at the same time, is desirable; to cover all the possible

Pierluigi Debernardi; Gian Paolo Bava

2003-01-01

290

Multichannel parallel free-space VCSEL optoelectronic interconnects for digital data transmission and processing  

NASA Astrophysics Data System (ADS)

A free-space integrated optoelectronic interconnect was built to explore parallel data transmission and processing. This interconnect comprises an 8 X 8 substrate-emitting 980-nm InGaAs/GaAs quantum-well vertical-cavity surface- emitting laser (VCSEL) array and an 8 X 8 InGaAs/InP P-I- N photodetector array. Both VCSEL and detector arrays were flip-chip bonded onto the complimentary metal-oxide- semiconductor (CMOS) circuitry, packaged in pin-grid array packages, and mounted on customized printed circuit boards. Individual data rates as high as 1.2 Gb/s on the VCSEL/CMOS transmitter array were measured. After the optical alignment, we carried out serial and parallel transmissions of digital data and live video scenes through this interconnect between two computers. Images captured by CCD camera were digitized to 8-bit data signals and transferred in serial bit-stream through multiple channels in this parallel VCSEL-detector optical interconnect. A data processing algorithm of edge detection was attempted during the data transfer. Final images were reconstructed back from optically transmitted and processed digital data. Although the transmitter and detector offered much higher data rates, we found that the overall image transfer rate was limited by the CMOS receiver circuits. A new design for the receiver circuitry was accomplished and submitted for fabrication.

Liu, J. Jiang; Lawler, William B.; Riely, Brian P.; Chang, Wayne H.; Shen, Paul H.; Newman, Peter G.; Taysing-Lara, Monica A.; Olver, Kimberly; Koley, Bikash; Dagenais, Mario; Simonis, George J.

2000-07-01

291

High single mode operation from hybrid ion implanted\\/selectively oxidized VCSELs  

Microsoft Academic Search

Summary form only given. The modal discrimination can be augmented by creating a central region of gain surrounded by a region of optical loss. We report single mode output of more than 5 mW for 850 nm VCSELs fabricated using a hybrid ion implantation and selective oxidation device structure designed to achieve this end

K. D. Choquette; A. J. Fischer; K. M. Geib; G. R. Hadley; A. A. Allerman; J. J. Hindi

2000-01-01

292

Transverse Mode Dynamics of VCSELs Through Space-Time Domain Simulation  

NASA Technical Reports Server (NTRS)

Modeling and simulation are important to understand laser operation and to optimize and design device functions. Numerical simulation of VCSEL (Vertical Cavity Surface Emitting Lasers) has been largely based on solving time-independent Helmholtz equation or time dependent coupled mode equations. There are various advantages for choosing these approaches. However, the disadvantages are also apparent. The former cannot handle dynamical mode competition seen in VCSELs, while the latter assumes a given type and number of modes a priori. Furthermore, the microscopic physics of heterstructures and electron-hole plasma is very often represented by a few parameters such as linear gain coefficients and the linewidth enhancement factor. These are over simplification of space and frequency (wavelength) dependent gain and refractive index functions. When the space-time dynamical operation of VCSELs becomes important, these simple approximations become questionable. In this paper, we apply a recently developed model for edge-emitting lasers to a gain guided VCSEL for space-time domain simulation. This model takes into account the actual nonlinear dependence of gain and refractive index on frequency and carrier density within the frame work of the effective Bloch equations. The corresponding partial differential equations are solved directly by finite difference methods. Laser behavior with increasing pumping current is investigated in detail. Special attention is paid to the dynamical competition of the transverse modes.

Goorjian, Peter M.; Ning, Cun-Zheng; Saini, Subhash (Technical Monitor)

1999-01-01

293

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

294

Novel VCSEL driving technique with virtual back termination for high-speed optical interconnection  

NASA Astrophysics Data System (ADS)

In this work, we develop a simple and high-speed VCSEL driving technique with "virtual back termination" for optical interconnect applications. For achieving compact and high-speed optical interconnects, an optical module with the flipchip bonding structure is effective. To realize flip-chip mounting, the development of the VCSEL driving technique, which can perform impedance matching with the transmission line, is a critical issue. Back termination has to be implemented to reduce signal reflection via the transmission line. Additionally, back termination must have a simple dc coupling. Introducing a virtual GND to the circuit ensures that these requirements are met. The virtual GND is made by a dummy load connected to a complementary output and dc-coupled 50-? resisters between output and complementary output. The dummy load has characteristics similar to the load VCSEL. As a result of the virtual GND, the resisters act as the back termination. When we drove the VCSEL with this technique, clear eye opening without the reflectance effects was obtained up to 28-Gb/s despite using a 10-cm transmission These results show that our driving technique is suitable for high-speed optical interconnect applications.

Sugawara, Mariko; Tsunoda, Yukito; Oku, Hideki; Ide, Satoshi; Tanaka, Kazuhiro

2012-02-01

295

In-situ OTDR for low-cost optical networks using a single-mode 850-nm VCSEL.  

SciTech Connect

A new approach to optical time-domain reflectometry (OTDR) is proposed that will enable distributed fault monitoring in singlemode VCSEL-based networks. In situ OTDR uses the transmitter VCSEL already resident in data transceivers as both emitter and resonant-cavity photodiode for fault location measurements. Also valuable at longer wavelengths, the concept is demonstrated here using an 850 nm oxide-confined VCSEL and simple electronics. The dead times and sensitivity obtained are adequate to detect the majority of faults anticipated in local- and metropolitan-area networks.

Geib, Kent Martin; Peake, Gregory Merwin; Serkland, Darwin Keith; Keeler, Gordon Arthur

2005-04-01

296

Polarization Control in Silicon Photonic Waveguide Components Using Cladding Stress Engineering  

NASA Astrophysics Data System (ADS)

This chapter reviews the characteristics of SOI ridge waveguide birefringence, as governed by the waveguide cross-section geometry, the cladding stress level, and cladding thickness. Typical stress levels in dielectric cladding films such as silicon dioxide and silicon nitride are such that the stress-induced birefringence is of comparable magnitude to the waveguide geometrical birefringence. Therefore the total waveguide birefringence can be precisely controlled by counter-balancing these two factors. The application of this technique for achieving polarization independence in a variety of photonic components is described, as well as an example of polarization splitting. Passive and active tuning of the stress-induced birefringence is discussed. The use of birefringence tuning to enhance the efficiency in optical parametric processes and stress-induced Pockels electro-optic effect are also briefly addressed.

Xu, Dan-Xia

297

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

298

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

299

2.7-?m single-frequency TEM00 operation of Sb-based diode-pumped external-cavity VCSEL  

NASA Astrophysics Data System (ADS)

We present the design, technology and performances of a tunable Sb-based diode-pumped type-I quantum-well vertical-external-cavity surface-emitting lasers emitting at 2.7?m. The half VCSEL structure was grown by MBE with quantum-well growth temperature of 440 °C. The sample was thermally annealed to optimize the QW gain design. We report on room-temperature continuous-wave laser with 0.17mW output power and low threshold incident pump intensity of 0.7kW/cm2 while pumping at 830nm with a commercial diode laser. The external cavity provides a circular TEM00 beam with a low divergence of 3.6°. The short mm-long optical cavity laser exhibits tunable single frequency operation, with a side mode suppression ratio 23 dB, a linewidth 4GHz and a linear light polarization. Thermal and optical properties are studied.

Laurain, Alexandre; Cerutti, Laurent; Myara, Mikhael; Garnache, Arnaud

2012-02-01

300

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

301

Nano-structured magnetic photonic crystals for magneto-optic polarization controllers at the communication-band wavelengths  

Microsoft Academic Search

We investigate the properties of optimized 1-D magnetic photonic crystal structures using doped iron garnet layers as magnetic\\u000a constituents, for use in integrated-optics polarization controllers. We engineer the enhancement of Faraday rotation near\\u000a 1,550 nm and describe a novel hysteresis-based driving scheme suitable for implementing ultra-fast polarization controllers.

Mohammad Nur-E-Alam; Mikhail Vasiliev; Kamal Alameh

2009-01-01

302

Effect of polarization controlling on coherent beam combining of two-fiber laser arrays of interferometric configuration.  

PubMed

The effect of polarization controlling on coherent beam combining of two-fiber laser arrays of interferometric configuration is researched. Three kinds of arrays, built on the basis of Michelson and Mach-Zehnder interferometers, are investigated experimentally. It is found that polarization controlling is not necessary for coherent beam combining of the Michelson interferometric array but necessary for that of Mach-Zehnder interferometric arrays. These results reveal the important role of polarization in the self-organization process of interferometric laser arrays. PMID:19148232

Cao, Jianqiu; Lu, Qisheng; Chen, Sheng-Ping; Hou, Jing; Xu, Xiaojun

2009-01-15

303

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

304

GDI-Mediated Cell Polarization in Yeast Provides Precise Spatial and Temporal Control of Cdc42 Signaling  

PubMed Central

Cell polarization is a prerequisite for essential processes such as cell migration, proliferation or differentiation. The yeast Saccharomyces cerevisiae under control of the GTPase Cdc42 is able to polarize without the help of cytoskeletal structures and spatial cues through a pathway depending on its guanine nucleotide dissociation inhibitor (GDI) Rdi1. To develop a fundamental understanding of yeast polarization we establish a detailed mechanistic model of GDI-mediated polarization. We show that GDI-mediated polarization provides precise spatial and temporal control of Cdc42 signaling and give experimental evidence for our findings. Cell cycle induced changes of Cdc42 regulation enhance positive feedback loops of active Cdc42 production, and thereby allow simultaneous switch-like regulation of focused polarity and Cdc42 activation. This regulation drives the direct formation of a unique polarity cluster with characteristic narrowing dynamics, as opposed to the previously proposed competition between transient clusters. As the key components of the studied system are conserved among eukaryotes, we expect our findings also to apply to cell polarization in other organisms.

Wedlich-Soldner, Roland; Frey, Erwin

2013-01-01

305

Generation of single transverse modes in a commercial multimode VCSEL by the beam-profile adapted optical feedback  

Microsoft Academic Search

This research investigated the feasibility of applying beam-profile adapted optical feedback to generate single high-order transverse modes in a commercial multi-transverse mode vertical-cavity surface-emitting laser (VCSEL). The beam-profile adaption was achieved by launching the multi-transverse-mode beam profile of the solitary VCSEL into a single-mode fiber. At the fiber's exit, a quasi-Gaussian beam profile was easily obtained. Afterward, the beam was

Yu-Heng Wu; Chuan-Pi Hsu; Da-Long Cheng; Wang-Chuang Kuo; Tsu-Chiang Yen

2010-01-01

306

Silicon oxide-planarized single-mode 850-nm VCSELs with TO package for 10 Gb\\/s data transmission  

Microsoft Academic Search

In this letter, we report on an alternative method to fabricate a high-efficiency planar-type oxide-confined 850-nm vertical-cavity surface-emitting lasers (VCSELs). The planarized process of VCSELs was to use the silicon oxide as the buried layer. As a result, these devices with an oxidized aperture of 3 ?m in diameter exhibit a single-transverse mode behavior throughout the operation current range. In

Chia-Lung Tsai; Feng-Ming Lee; Fu-Yi Cheng; Meng-Chyi Wu; Sum-Chien Ko; Hai-Lin Wang; Wen-Jeng Ho

2005-01-01

307

Design and simulation of array lens for coupling of a 4×4 VCSEL array to a single mode fiber  

Microsoft Academic Search

A 4×4 nano-scale VCSEL array simultaneously collimated on a single mode fiber (SMF) has been demonstrated. Through the proposed 4×4 BK7 microlens array, every laser beam can be conveyed simultaneously, from 360 nm to 2000 nm, into a 1000 mm long SMF. These results show that it is possible to bond multi-element VCSEL arrays to a SMF, and to simultaneously

Wen-Ming Cheng; Hen-Wai Tsao; Shyh-Lin Tsao

2004-01-01

308

Photonic-plasmonic-coupled nanoantennas for polarization-controlled multispectral nanofocusing.  

PubMed

We report on the design and experimental demonstration of array-enhanced nanoantennas for polarization-controlled multispectral nanofocusing in the near-IR spectral range. We design plasmonic double bow-tie nanoantennas-coupled to multiple-periodic nanoparticle arrays to harvest radiation of designed wavelengths from a large spatial area and to focus it into a targeted nanoscale region. Near-field calculations were performed on a gold nanoantenna array using three-dimensional finite difference time domain simulations. Cross-shaped optical nanoantennas were fabricated on glass substrates using electron beam lithography. The optical characterization of the fabricated nanoantennas was performed using second harmonic excitation spectroscopy that demonstrates multiwavelength photonic coupling in good agreement with the antenna modeling. The nanoantenna structures introduced in this Letter provide the ability to focus optical energy into deep subwavelength areas and to address multiple spectral regions with polarization control. Such attributes are highly desirable in optical biosensing, enhanced Raman scattering, and for nonlinear plasmonic applications. PMID:24322151

Trevino, J; Walsh, G F; Pecora, E F; Boriskina, S V; Dal Negro, L

2013-11-15

309

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

PubMed Central

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.

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

2013-01-01

310

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

311

Fast control of nuclear spin polarization in an optically pumped single quantum dot  

NASA Astrophysics Data System (ADS)

Highly polarized nuclear spins within a semiconductor quantum dot induce effective magnetic (Overhauser) fields of up to several Tesla acting on the electron spin, or up to a few hundred mT for the hole spin. Recently this has been recognized as a resource for intrinsic control of quantum-dot-based spin quantum bits. However, only static long-lived Overhauser fields could be used. Here we demonstrate fast redirection on the microsecond timescale of Overhauser fields on the order of 0.5 T experienced by a single electron spin in an optically pumped GaAs quantum dot. This has been achieved using coherent control of an ensemble of 105 optically polarized nuclear spins by sequences of short radiofrequency pulses. These results open the way to a new class of experiments using radiofrequency techniques to achieve highly correlated nuclear spins in quantum dots, such as adiabatic demagnetization in the rotating frame leading to sub-?K nuclear spin temperatures, rapid adiabatic passage, and spin squeezing.

Makhonin, M. N.; Kavokin, K. V.; Senellart, P.; Lemaître, A.; Ramsay, A. J.; Skolnick, M. S.; Tartakovskii, A. I.

2011-11-01

312

Stable zirconia-erbium doped multiwavelength fiber laser by precise control of polarization states  

NASA Astrophysics Data System (ADS)

A compact zirconium-erbium doped fiber (Zr-EDF) based multiwavelength fiber laser (MWFL) with stable output comb is proposed and demonstrated. The MWFL utilizes a 3 m long Zr-EDF with an erbium concentration of 3000 ppm and pumped by a 1480 nm laser diode (LD) as the active gain medium. A fiber based multimode polarization controller (PC) is used to precisely control the polarization states of the oscillating modes in the MWFL, distributing the total energy of the system among the lasing wavelengths in order to overcome the mode-suppression and mode-competition that arises from homogenous line broadening. The MWFL is capable of generating up to four lasing wavelengths with average peak powers of 0.08 dBm in the extended L-band of 1600 nm. The lasing wavelengths have a 3-dB linewidth of 0.1 and an extinction ratio of 40 dB as well as highly stable, with minimal fluctuations of less than 0.6 dB observed in the peak powers of the lasing wavelengths over a period of 1 h. The proposed system allows for the realization of a compact, cost-effective and stable erbium based MWFL capable of operating at room temperature.

Ahmad, H.; Thambiratnam, K.; Awang, N. A.; Jemangin, M. H.; Harun, S. W.

2012-05-01

313

Low-magnetic-field control of electric polarization vector in a helimagnet.  

PubMed

The mutual control of the electric and magnetic properties of a solid is currently of great interest because of the possible application for novel electronic devices. We report on the low-magnetic-field (for example, B values of +/-30 milliteslas) control of the polarization (P) vector in a hexaferrite, Ba2Mg2Fe12O22, which shows the helimagnetic spin structure with the propagation vector k0 parallel to [001]. The B-induced transverse conical spin structure carries the P vector directing perpendicular to both B and k0, in accord with the recently proposed spin-current model. Then, the oscillating or multidirectionally rotating B produces the cyclic displacement current via the flexible handling of the magnetic cone axis. PMID:18356519

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

2008-03-21

314

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

NASA Astrophysics Data System (ADS)

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

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

2008-03-01

315

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

PubMed Central

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.

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

2012-01-01

316

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

Microsoft Academic Search

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

Mohsen Ghali; Keita Ohtani; Yuzo Ohno; Hideo Ohno

2012-01-01

317

LabVIEW-based control software for para-hydrogen induced polarization instrumentation.  

PubMed

The elucidation of cell metabolic mechanisms is the modern underpinning of the diagnosis, treatment, and in some cases the prevention of disease. Para-Hydrogen induced polarization (PHIP) enhances magnetic resonance imaging (MRI) signals over 10 000 fold, allowing for the MRI of cell metabolic mechanisms. This signal enhancement is the result of hyperpolarizing endogenous substances used as contrast agents during imaging. PHIP instrumentation hyperpolarizes Carbon-13 ((13)C) based substances using a process requiring control of a number of factors: chemical reaction timing, gas flow, monitoring of a static magnetic field (Bo), radio frequency (RF) irradiation timing, reaction temperature, and gas pressures. Current PHIP instruments manually control the hyperpolarization process resulting in the lack of the precise control of factors listed above, resulting in non-reproducible results. We discuss the design and implementation of a LabVIEW based computer program that automatically and precisely controls the delivery and manipulation of gases and samples, monitoring gas pressures, environmental temperature, and RF sample irradiation. We show that the automated control over the hyperpolarization process results in the hyperpolarization of hydroxyethylpropionate. The implementation of this software provides the fast prototyping of PHIP instrumentation for the evaluation of a myriad of (13)C based endogenous contrast agents used in molecular imaging. PMID:24784636

Agraz, Jose; Grunfeld, Alexander; Li, Debiao; Cunningham, Karl; Willey, Cindy; Pozos, Robert; Wagner, Shawn

2014-04-01

318

The PTEN Phosphatase Controls Intestinal Epithelial Cell Polarity and Barrier Function: Role in Colorectal Cancer Progression  

PubMed Central

Background The PTEN phosphatase acts on phosphatidylinositol 3,4,5-triphosphates resulting from phosphatidylinositol 3-kinase (PI3K) activation. PTEN expression has been shown to be decreased in colorectal cancer. Little is known however as to the specific cellular role of PTEN in human intestinal epithelial cells. The aim of this study was to investigate the role of PTEN in human colorectal cancer cells. Methodology/Principal Findings Caco-2/15, HCT116 and CT26 cells were infected with recombinant lentiviruses expressing a shRNA specifically designed to knock-down PTEN. The impact of PTEN downregulation was analyzed on cell polarization and differentiation, intercellular junction integrity (expression of cell-cell adhesion proteins, barrier function), migration (wound assay), invasion (matrigel-coated transwells) and on tumor and metastasis formation in mice. Electron microscopy analysis showed that lentiviral infection of PTEN shRNA significantly inhibited Caco-2/15 cell polarization, functional differentiation and brush border development. A strong reduction in claudin 1, 3, 4 and 8 was also observed as well as a decrease in transepithelial resistance. Loss of PTEN expression increased the spreading, migration and invasion capacities of colorectal cancer cells in vitro. PTEN downregulation also increased tumor size following subcutaneous injection of colorectal cancer cells in nude mice. Finally, loss of PTEN expression in HCT116 and CT26, but not in Caco-2/15, led to an increase in their metastatic potential following tail-vein injections in mice. Conclusions/Significance Altogether, these results indicate that PTEN controls cellular polarity, establishment of cell-cell junctions, paracellular permeability, migration and tumorigenic/metastatic potential of human colorectal cancer cells.

Langlois, Marie-Josee; Bergeron, Sebastien; Bernatchez, Gerald; Boudreau, Francois; Saucier, Caroline; Perreault, Nathalie; Carrier, Julie C.; Rivard, Nathalie

2010-01-01

319

High-sweep-rate 1310 nm MEMS-VCSEL with 150 nm continuous tuning range  

PubMed Central

Microelectromechanical-systems-based vertical-cavity surface-emitting lasers (MEMS-VCSELs) capable of a 150 nm continuous tuning range near 1310 nm are demonstrated. These devices employ a thin optically pumped active region structure with large free-spectral range, which promotes wide and continuous tuning. To achieve VCSEL emission at 1310 nm, a wide-gain-bandwidth indium phosphide-based multiple quantum well active region is combined with a wide-bandwidth fully oxidised GaAs-based mirror through wafer bonding, with tuning enabled by a suspended dielectric top mirror. These devices are capable of being scanned over the entire tuning range at frequencies up to 500 kHz, making them ideal for applications such as swept source optical coherence tomography and high-speed transient spectroscopy.

Jayaraman, V.; Cole, G.D.; Robertson, M.; Uddin, A.; Cable, A.

2013-01-01

320

Dynamics of 980 nm VCSELs Characterized Using Temperature Dependent RIN Spectra  

NASA Astrophysics Data System (ADS)

High speed optical interconnects are replacing copper connections in ever shorter link distance, low cost, high speed communication systems employing directly modulated laser diodes. In very short distance systems (<1 m), laser diode bandwidth is a major limitation. Laser intensity noise spectra contain valuable information on laser dynamics including resonant frequency and damping. In this work, vertical cavity surface emitting lasers (VCSELs) are fabricated from a metal-organic chemical vapor deposition (MOCVD) grown AlGaAs structure on an n-type substrate. The intrinsic resonance frequency and damping constant of 980 nm VCSELs are measured. Two methods are used: constant temperature and varying injection current and constant injection current with varying temperature. After fitting the spectra to the conventional damped oscillator model to extract resonance frequency and damping, K-factor analysis is performed both on the conventional constant temperature data as well as the constant current data. The results of the two approaches are compared.

Safaisini, Rashid; Al-Omari, Ahmad N.; Joseph, John R.; Lear, Kevin L.

2007-03-01

321

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

322

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

PubMed Central

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.

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

2013-01-01

323

Multi-mode photonic crystal fibers for VCSEL based data transmission  

NASA Astrophysics Data System (ADS)

Quasi error-free 10Gbit/s data transmission is demonstrated over a novel type of 50 µm core diameter photonic crystal fiber with as much as 100m length. Combined with 850 nm VCSEL sources, this fiber is an attractive alternative to graded-index multi-mode fibers for datacom applications. A comparison to numerical simulations suggests that the high bit-rate may be partly explained by inter-modal diffusion.

Mortensen, N. A.; Stach, M.; Broeng, J.; Petersson, A.; Simonsen, H. R.; Michalzik, R.

2003-08-01

324

Peak power and wavelength optimization of a double-fused LW-VCSEL  

Microsoft Academic Search

Long-wavelength vertical-cavity surface-emitting lasers (LW-VCSELs) have profound advantages over the traditional edge-emitting lasers offering improved properties with respect to mode selectivity, fiber coupling, threshold currents and integration into 2D arrays or with other electronic devices. Its commercialization is gaining momentum as the local and access network in optical communication system expands. This paper reports the optimization of the peak lasing

P. S. Menon; K. Kumarajah; B. Bais; H. Abdullah; B. Y. Majlis; P. R. Apte

2010-01-01

325

Low threshold current continuous-wave GaInNAs\\/GaAs VCSELs  

Microsoft Academic Search

Vertical cavity surface-emitting lasers (VCSELs) emitting near 0.85 ?m are becoming increasingly important for short-haul optical fiber transmission systems. These devices benefit from highly reflective and thermally conductive all-epitaxial GaAs-based mirrors and efficient transverse confinement through AlAs-oxide dielectric apertures. Extending this commercially-established technology to wavelengths in the 1.3-1.6 ?m range allows for dramatically increased transmission bandwidth and distance in conventional

M. C. Larson; C. W. Coldren; S. G. Spruytte; H. E. Petersen; J. S. Harris

2000-01-01

326

Single and multi-mode VCSELs for 12.5 Gb\\/s data links  

Microsoft Academic Search

Summary form only given. Single channel as well as one-dimensional fiber ribbonized parallel interconnect modules for data rates up to a few Gb\\/s per channel using vertical-cavity surface-emitting lasers (VCSELs) are already on the market. For very high speed data transmission at data rates above 10 Gb\\/s per channel the noise behavior of the transmitter becomes more and more important.

M. Kicherer; R. Jager; R. King; F. Mederer; H. J. Unold; K. J. Ebeling

2000-01-01

327

2.5 Gbit\\/s data link using oxidized sub mA threshold VCSELs  

Microsoft Academic Search

Intensity modulated laterally oxidized InGaAs strained QW vertical cavity surface emitting lasers (VCSELs) with threshold current as low as 0.45 mA are investigated as light source for optical interconnection. Data transmission at 2.5 Gbit\\/s with a BER of less than 10\\/sup -11\\/ is reported for transmission over 500 m of graded index multi-mode fiber.

U. Fiedler; B. Weigl; G. Reiner; B. Lehmann; K. J. Ebeling

1996-01-01

328

Full 3D FDTD analysis of modal characteristics in VCSELs with holey structure  

Microsoft Academic Search

We analyzed lateral mode characteristics in 850-nm GaAs-based VCSELs with holey structures by FDTD method. Full three-dimensional analysis, which requires huge computer resources, was carried out using cluster computer. As a result, we estimated the good mode selectivity in circular and triangular holey structures, which cannot be obtained in a simple oxide aperture structure. It is explained by the large

Kosuke Morito; Daisuke Mori; Eichi Mizuta; Toshihiko Baba

2005-01-01

329

Large-area single-mode VCSELs and the self-aligned surface relief  

Microsoft Academic Search

The effect of mode-profile specific etching of the top layer in selectively oxidized vertical-cavity surface-emitting laser (VCSEL) structures at 850-nm emission wavelength is examined. For high reproducibility, a self-aligned etching technique is demonstrated which aligns surface etch and oxide aperture by only one additional photoresist step. By optimizing layer structure and etch spot size, completely single-mode devices with aperture diameters

Heiko J. Unold; Safwat W. Z. Mahmoud; Roland Jäger; Martin Grabherr; Rainer Michalzik; Karl Joachim Ebeling

2001-01-01

330

Intracavity-contacted resonant cavity enhanced photodetectors based on VCSEL structure  

Microsoft Academic Search

Intracavity-contacted resonant cavity enhanced photodetectors (IC RCEPDs) have been fabricated for monolithic integration with IC VCSELs. A low parasitic capacitance of 0.39 pF and an extrinsic 3-dB bandwidth of 9 GHz are demonstrated by using coplanar metal contacts. Optimization issues on device and epi designs are discussed. The largest frequency saturation photocurrent below which the extrinsic 3-dB bandwidth exceeds 6.5

Il-Sug Chung; Jin-Kyung Choi; Ki-Soo Chang; Kamal Alameh; Yong Tak Lee

2006-01-01

331

GaAs/AlOx high contrast gratings for 980nm VCSELs  

NASA Astrophysics Data System (ADS)

In this paper we present results of computer optical simulations of VCSEL with modified high refractive index contrast grating (HCG) as a top mirror. We consider the HCG of two different designs which determine the lateral aperture. Such HCG mirror provides selective guiding effect. We show that proper design of aperture of HCG results in almost sixfold increase in cavity Q-factor for zero order mode and a discrimination of higher order modes.

Gebski, M.; Dems, M.; Chen, J.; Qijie, W.; Dao Hua, Z.; Czyszanowski, T.

2014-02-01

332

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

333

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

SciTech Connect

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

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

1999-03-11

334

VCSEL-based smart pixels for free-space optical interconnection  

Microsoft Academic Search

High speed smart pixel arrays (SPAs) hold great promise as an enabling technology for board-to-board interconnections in digital systems. The SPAs are arrays of optoelectronic circuits for which each circuit possesses the property of signal processing and has an optical transmitter and receiver for I\\/O. This paper describes a VCSEL\\/Si smart pixel array technology developed at the University of Colorado,

J. A. Neff

1997-01-01

335

256-channel bidirectional optical interconnect using VCSELs and photodiodes on CMOS  

Microsoft Academic Search

Two-dimensional parallel optical interconnects (2-D-POIs) are capable of providing large connectivity between elements in computing and switching systems. Using this technology we have demonstrated a bidirectional optical interconnect between two printed circuit boards containing optoelectronic (OE) very large scale integration (VLSI) circuits. The OE-VLSI circuits were constructed using vertical cavity surface emitting lasers (VCSELs) and photodiodes (PDs) flip-chip bump-bonded to

David V. Plant; Michael B. Venditti; Emmanuelle Laprise; Julien Faucher; K. Razavi; M. Chateauneuf; A. G. Kirk; J. S. Ahearn

2001-01-01

336

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)] [NASA Goddard Space Flight Center, Greenbelt, MD (United States)

1996-03-15

337

Dynamic nuclear polarization of 29Si via spin S=1 centers in isotopically controlled silicon  

NASA Astrophysics Data System (ADS)

We report the results of the experiments on dynamic nuclear polarization (DNP) of 29Si nuclei under saturation the electron paramagnetic resonance (EPR) transitions of the photoexcited spin S=1 states of the oxygen+vacancy complexes in irradiated 29Si isotopically controlled silicon. The effect of isotope 29Si abundance on the line width and hyperfine structure of the Si-SL1 EPR spectra was observed. It was shown clearly that the decrease of the 29Si abundance leads to the transformation the DNP mechanism from the “differential” to “resolved” solid-effect accompanied with the increase of DNP degree. High steady-state 29Si nuclear polarization of 6% due to “resolved” solid-effect was achieved in silicon crystals with the 29Si isotope abundance below 4.7%. It was found that the DNP induced by saturation the hyperfine structure EPR lines of triplet centers does not follow the symmetric first derivative EPR line shape, showing the additional contribution to the DNP process.

Itahashi, T.; Hayashi, H.; Itoh, K. M.; Poloskin, D. S.; Vlasenko, L. S.; Vlasenko, M. P.

2009-12-01

338

The RPG gene of Medicago truncatula controls Rhizobium-directed polar growth during infection  

PubMed Central

Rhizobia can infect roots of host legume plants and induce new organs called nodules, in which they fix atmospheric nitrogen. Infection generally starts with root hair curling, then proceeds inside newly formed, intracellular tubular structures called infection threads. A successful symbiotic interaction relies on infection threads advancing rapidly at their tips by polar growth through successive cell layers of the root toward developing nodule primordia. To identify a plant component that controls this tip growth process, we characterized a symbiotic mutant of Medicago truncatula, called rpg for rhizobium-directed polar growth. In this mutant, nitrogen-fixing nodules were rarely formed due to abnormally thick and slowly progressing infection threads. Root hair curling was also abnormal, indicating that the RPG gene fulfils an essential function in the process whereby rhizobia manage to dominate the process of induced tip growth for root hair infection. Map-based cloning of RPG revealed a member of a previously unknown plant-specific gene family encoding putative long coiled-coil proteins we have called RRPs (RPG-related proteins) and characterized by an “RRP domain” specific to this family. RPG expression was strongly associated with rhizobial infection, and the RPG protein showed a nuclear localization, indicating that this symbiotic gene constitutes an important component of symbiotic signaling.

Arrighi, Jean-Francois; Godfroy, Olivier; de Billy, Francoise; Saurat, Olivier; Jauneau, Alain; Gough, Clare

2008-01-01

339

Electrically controlled spin polarization and selection in a topological insulator sandwiched between ferromagnetic electrodes  

NASA Astrophysics Data System (ADS)

We theoretically investigate the electrically controllable spin polarization and selective efficiency of the edge state Dirac electron in a two-dimensional topological insulator (TI) sandwiched between ferromagnetic (FM) electrodes by using the method of Keldysh nonequilibrium Green's function. A nearly full spin polarization of the topological edge state with giant inversion of ˜80% is observed, which is much higher than the value previously reported. Moreover, the selective efficiency for spin-up electrons under the modulation of the parallel configuration of FM electrodes has been demonstrated to be larger than 95% for the first time, while that for spin-down electrons in the antiparallel case is higher than 90% in a wide energy range, owing to the inter-edge spin tunneling induced backscattering and spin dephasing effect. The obtained results may provide a deeper understanding of the TI edge states and a valuable guidance to design spin switch and filter with high on-off speed and selective efficiency based on TIs.

Guo, Junji; Liao, Wenhu; Zhao, Heping; Zhou, Guanghui

2014-01-01

340

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

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

2013-10-21

341

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

342

Large-area high-power VCSEL pump arrays optimized for high-energy lasers  

NASA Astrophysics Data System (ADS)

Practical, large-area, high-power diode pumps for one micron (Nd, Yb) as well as eye-safer wavelengths (Er, Tm, Ho) are critical to the success of any high energy diode pumped solid state laser. Diode efficiency, brightness, availability and cost will determine how realizable a fielded high energy diode pumped solid state laser will be. 2-D Vertical-Cavity Surface-Emitting Laser (VCSEL) arrays are uniquely positioned to meet these requirements because of their unique properties, such as low divergence circular output beams, reduced wavelength drift with temperature, scalability to large 2-D arrays through low-cost and high-volume semiconductor photolithographic processes, high reliability, no catastrophic optical damage failure, and radiation and vacuum operation tolerance. Data will be presented on the status of FLIR-EOC's VCSEL pump arrays. Analysis of the key aspects of electrical, thermal and mechanical design that are critical to the design of a VCSEL pump array to achieve high power efficient array performance will be presented.

Wang, Chad; Geske, Jonathan; Garrett, Henry; Cardellino, Terri; Talantov, Fedor; Berdin, Glen; Millenheft, David; Renner, Daniel; Klemer, Daniel

2012-05-01

343

Two dimensional analysis of finite size high-contrast gratings for applications in VCSELs.  

PubMed

2-dimensional simulations of high-contrast gratings (HCGs) of finite size are carried out, targeting at their applications in vertical-cavity surface-emitting lasers (VCSELs). Finite HCGs show a very different behavior from infinite grating ones. The reflectivity of a finite HCG strongly depends on the HCG size and the source size. Our simulation results predict finite reflectivity and transmission values, well consistent with reported experimental results. The band of high reflectivity (>99.5%) of finite HCGs is less broad as compared to the infinite case. Losses into a guided mode excited in the HCG plane are identified as being at the root. This guided mode is excited due to the nonzero angular components in the finite source size, and greatly enhances the transmission and the light leakage from the slab. In addition, the simulation results show that the details of the finite HCG can shape the output beam, whilst a Gaussian-like reflected wave is typically achieved. Our simulations can explain the current discrepancies between numerical predictions of reflectivities approaching 100% and working HCG-VCSELs showing finite reflectivities and nearly Gaussian-like output. Consequently, our analysis of finite HCGs is indispensable for HCG-VCSEL design. PMID:24921302

Liu, Anjin; Hofmann, Werner; Bimberg, Dieter

2014-05-19

344

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

PubMed

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

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

2014-06-30

345

Temperature characteristics of surface micromachined MEMS-VCSEL with large tuning range.  

PubMed

Several Applications for tunable laser diodes have strict constraints in terms of overall power consumption. Furthermore, the implementation in harsh environments with large temperature fluctuations is necessary. Due to the constraint in power consumption, the application of active cooling might not be an option. For this reason we investigate the temperature characteristics of an electrically pumped MEMS-VCSEL with wide continuous wavelength tuning. For the first time, a mode hop free single mode (side mode suppression ratio (SMSR) > 40dB) tuning range of 45nm at 70°C is demonstrated with a MEMS-VCSEL. An increase of the tuning range from 85nm at 20°C to 92nm at 40°C is measured and explained. In contrast to fixed wavelength VCSEL, the investigated device shows a negative temperature induced wavelength shift of -4.5nmK-1, which is caused by the MEMS-mirror. At 1560nm, the fibre-coupled optical output power is above 0.6mW over the entire temperature range between 20°C to 70°C and shows a maximum of > 3mW at 20°C. PMID:24921503

Gierl, C; Gründl, T; Paul, S; Zogal, K; Haidar, M T; Meissner, P; Amann, M-C; Küppers, F

2014-06-01

346

High-speed 2D VCSEL arrays at 990nm for short reach interconnects  

NASA Astrophysics Data System (ADS)

We have demonstrated high density, 2D (4x12) VCSEL arrays operating at an aggregate data rate of over 480Gb/s in an aerial density of 1400x3750 ?m2, or 9.14 Tbs/cm2. These flip-chip, bottom-emitting 990nm VCSELs have low drive voltage, low electrical parasitics, improved thermal impedance and 2D scalability over their wire-bonded top emitting counterparts. Excellent high speed performance was obtained through the use of 1) compressively strained InGaAs MQW active region 2) low parasitic capacitance oxide-confined VCSEL structures and 3) low series resistance, high index contrast AlGaAs/GaAs mirrors. 10Gb/s operation was obtained with low operating current density of ~6kA/cm2 at 70C. Our best results to date have achieved data rates greater than 12.5Gb/s @70C at a current density less than 10kA/cm2. The device results show good agreement with theoretically calculated/simulated values. This work was partially supported by DARPA under contract MDA972-03-3-0004.

Tandon, Ashish; Lin, Chao-Kun; Djordjev, Kostadin; Corzine, Scott; Tan, Michael

2005-03-01

347

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

348

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

PubMed Central

Vascular tube morphogenesis requires the establishment of endothelial cell (EC) apical–basal polarity in three-dimensional (3D) extracellular matrices. To date, there is little understanding of how EC polarity is controlled during these highly dynamic and rapid morphogenic events. We show that the microtubule tip complex proteins, end binding 1 (EB1), p150Glued, and Clasp1, control human EC tube formation by (1) inducing microtubule assembly and asymmetric cytoskeletal polarization, whereby acetylated and detyrosinated tubulins distribute in a subapical membrane location and filamentous actin distributes basally; (2) increasing tubulin posttranslational modifications, including required acetylation events; and (3) regulating an EC lumen signaling cascade that involves membrane type 1 matrix metallopatrinase (MT1-MMP)–dependent proteolysis as well as Pak, Raf, and Erk kinases. Another regulator of this process is the microtubule stabilizing protein, tau, which binds p150Glued and similarly affects EC lumen formation by controlling the levels of acetylated and detyrosinated tubulins. Increased expression of the tubulin deacetylases, sirtuin 2, and histone deacetylase 6 (HDAC6), blocks EC tube formation and cytoskeletal polarization, while siRNA suppression of these deacetylases stimulates these events. Overall, this work reveals a fundamental role for microtubule tip complex proteins in coordinating microtubule assembly, posttranslational modifications including acetylation, and apical–basal cytoskeletal polarization to control the developing apical membrane surface during blood vessel tubulogenesis in 3D matrix environments.

Kim, Dae Joong; Martinez-Lemus, Luis A.

2013-01-01

349

Ferroelectric polarization-controlled two-dimensional electron gas in ferroelectric/AlGaN/GaN heterostructure  

NASA Astrophysics Data System (ADS)

The control effect of the ferroelectric polarization on the two-dimensional electron gas (2DEG) in a ferroelectric/AlGaN/GaN metal-ferroelectric-semiconductor (MFS) structure is theoretically analyzed by a self-consistent approach. With incorporating the hysteresis nature of the ferroelectric into calculation, the nature of the control effect is disclosed, where the 2DEG density is depleted/restored after poling/depoling operation on the MFS structure. The orientation of the ferroelectric polarization is clarified to be parallel to that of the AlGaN barrier, which, based on an electrostatics analysis, is attributed to the pinning effect of the underlying polarization. Reducing the thickness of the AlGaN barrier from 25 nm to 20 nm leads to an improved control modulation of the 2DEG density from 36.7% to 54.1%.

Kong, Y. C.; Xue, F. S.; Zhou, J. J.; Li, L.; Chen, C.; Li, Y. R.

2009-06-01

350

Polarization controlled multiwavelength switchable erbium-doped fiber laser based on high birefringence few-mode fiber loop mirror  

NASA Astrophysics Data System (ADS)

A multiwavelength switchable erbium-doped fiber laser with linear cavity is proposed and experimentally demonstrated. It is based on a fiber loop mirror incorporating a piece of high birefringence few-mode fiber and polarization controller. Due to dependence of its reflection properties on the polarization controllers, the fiber laser can operate in the random combination of three wavelengths by only adjusting the polarization controllers in the linear cavity. The wavelengths involved in the switching operation are determined by the merged Sagnac and intermodal interferences elicited in the fiber loop mirror. The optical signal to noise extinction ratio of every oscillation line is higher than 40 dB and power fluctuation less than 0.5 dB.

Sun, G.; Zhou, Y.; Cui, L.; Chung, Y.

2011-11-01

351

Control of vertical-cavity laser polarization with anisotropic transverse cavity geometries  

SciTech Connect

The authors show the two-fold polarization degeneracy of etched air-post vertical-cavity surface emitting laser diodes can be lifted and a dominant polarization state selected through use of anisotropic transverse laser cavity geometries. For lasers with rhombus-shaped cavities, fundamental mode lasing emission linearly polarized along one specified crystal axis is obtained up to twice the threshold current. For dumbbell-shaped lasers, fundamental mode lasing emission linearly polarized along one specified crystal axis is maintained over the entire operating range of the device producing a maximum orthogonal polarization suppression ratio of 14 dB.

Choquette, K.D. (Sandia National Labs., Albuquerque, NM (United States)); Leibenguth, R.E. (AT T Bell Labs., Breinigsville, PA (United States))

1994-01-01

352

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

353

Experimental study of polarization switching of vertical-cavity surface-emitting lasers as a dynamical bifurcation  

Microsoft Academic Search

We study the role of the bias current sweep rate in measurements of polarization switching (PS) of vertical-cavity surface-emitting lasers (VCSELs). We show that the polarization-resolved L-I (light-intensity) curve depends on the current sweep rate. As the current sweep rate increases, the PS occurs at higher bias currents for upward scans and at lower bias currents for downward scans. We

Jon Paul; Cristina Masoller; Yanhua Hong; Paul S. Spencer; K. Alan Shore

2006-01-01

354

Microoptical Two-Dimensional Devices for the Optical Memory Head of an Ultrahigh Data Transfer Rate and Density Sytem Using a Vertical Cavity Surface Emitting Laser (VCSEL) Array  

Microsoft Academic Search

The parallel optical memory system has important advantages for realizing both a fast data transfer rate and high memory capacity since it is based on multibeam recording and a smaller spot size using the vertical cavity surface emitting laser (VCSEL) and a nanoprobe array. The concept, theoretical analysis and fabrication process for the integrated VCSEL nanoprobe array head are discussed

Young-Joo Kim; Satoshi Mitsugi; Kazuhiro Suzuki; Kazuma Kurihara; Takayuki Horibe

2002-01-01

355

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

356

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. To the best of our knowledge, we first reveal that the new mechanism for this asymmetric localization is due to the mixture of 2p?g and 2p?u, instead of 1s?g and 2p?u in the previous studies.

He, Feng

2014-04-01

357

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

358

Evidence for interlayer electronic coupling in multilayer epitaxial graphene from polarization-dependent coherently controlled photocurrent generation  

NASA Astrophysics Data System (ADS)

Most experimental studies to date of multilayer epitaxial graphene on C-face SiC have indicated that the electronic states of different layers are decoupled as a consequence of rotational stacking. We have measured the third-order nonlinear tensor in epitaxial graphene as a novel approach to probe interlayer electronic coupling, by studying THz emission from coherently controlled photocurrents as a function of the optical pump and THz beam polarizations. We find that the polarization dependence of the coherently controlled THz emission expected from perfectly uncoupled layers, i.e. a single graphene sheet, is not observed. We hypothesize that the observed angular dependence arises from weak coupling between the layers; a model calculation, treating the interlayer coupling as bilayer coupling with variable strength, qualitatively reproduces the polarization angular dependence, providing evidence for coupling.

Sun, Dong; Rioux, Julien; Sipe, J. E.; Zou, Yang; Mihnev, Momchil T.; Berger, Claire; de Heer, Walt A.; First, Phillip N.; Norris, Theodore B.

2012-04-01

359

Polarization controlled deep sub-wavelength periodic features written by femtosecond laser on nanodiamond thin film surface  

NASA Astrophysics Data System (ADS)

Deep sub-wavelength (?/? = ˜0.22) periodic features are induced uniformly on a nanodiamond (ND) thin film surface using femtosecond (fs) laser irradiation (pulse duration = ˜110 fs and central wavelength of ˜800 nm). The topography of the surface features is controlled by the laser polarization. Orientation of features is perpendicular to laser polarization. Periodicity (spatial periodicity of < ?/4) of the surface features is less than the laser wavelength. This work gives an experimental proof of polarization controlled surface plasmon-fs laser coupling mechanism prompting the interaction between fs laser and solid matter (here ND thin film) which in turn is resulting in the periodic surface features. Scanning electron microscopy in conjunction with micro Raman scattering, X-ray diffraction, and atomic force microscopy are carried out to extract surface morphology and phase information of the laser irradiated regions. This work demonstrates an easy and efficient surface fabrication technique.

Kumar Kuntumalla, Mohan; Rajamudili, Kuladeep; Rao Desai, Narayana; Srikanth, Vadali V. S. S.

2014-04-01

360

Polarization control of high order harmonics in the EUV photon energy range.  

PubMed

We report the generation of circularly polarized high order harmonics in the extreme ultraviolet range (18-27 nm) from a linearly polarized infrared laser (40 fs, 0.25 TW) focused into a neon filled gas cell. To circularly polarize the initially linearly polarized harmonics we have implemented a four-reflector phase-shifter. Fully circularly polarized radiation has been obtained with an efficiency of a few percents, thus being significantly more efficient than currently demonstrated direct generation of elliptically polarized harmonics. This demonstration opens up new experimental capabilities based on high order harmonics, for example, in biology and materials science. The inherent femtosecond time resolution of high order harmonic generating table top laser sources renders these an ideal tool for the investigation of ultrafast magnetization dynamics now that the magnetic circular dichroism at the absorption M-edges of transition metals can be exploited. PMID:21369265

Vodungbo, Boris; Barszczak Sardinha, Anna; Gautier, Julien; Lambert, Guillaume; Valentin, Constance; Lozano, Magali; Iaquaniello, Grégory; Delmotte, Franck; Sebban, Stéphane; Lüning, Jan; Zeitoun, Philippe

2011-02-28

361

Control of vertical-cavity laser polarization with anisotropic transverse cavity geometries  

Microsoft Academic Search

We show the two-fold polarization degeneracy of etched air-post vertical-cavity surface emitting laser diodes can be lifted and a dominant polarization state selected through use of anisotropic transverse laser cavity geometries. For lasers with rhombus-shaped cavities, fundamental mode lasing emission linearly polarized along one specified crystal axis is obtained up to twice the threshold current. For dumbbell-shaped lasers, fundamental mode

Kent D. Choquette; R. E. Leibenguth

1994-01-01

362

Polarization-controlled circular second-harmonic generation from metal hole arrays with threefold rotational symmetry.  

PubMed

The discrete rotational symmetry of nanostructures provides a powerful and simple guiding principle for designing the second-harmonic generation process in nonlinear metamaterials. We demonstrate that, in achiral nanostructures with threefold rotational symmetries, a circularly polarized fundamental beam produces a countercircularly polarized second-harmonic beam. In this case, the polarization state of the second harmonic is determined in a very simple manner. We also demonstrate how rotational symmetries in nonlinear metamaterials manifest themselves in SHG selection rules. PMID:24745436

Konishi, Kuniaki; Higuchi, Takuya; Li, Jia; Larsson, Jakob; Ishii, Shuntaro; Kuwata-Gonokami, Makoto

2014-04-01

363

Polarization-Controlled Circular Second-Harmonic Generation from Metal Hole Arrays with Threefold Rotational Symmetry  

NASA Astrophysics Data System (ADS)

The discrete rotational symmetry of nanostructures provides a powerful and simple guiding principle for designing the second-harmonic generation process in nonlinear metamaterials. We demonstrate that, in achiral nanostructures with threefold rotational symmetries, a circularly polarized fundamental beam produces a countercircularly polarized second-harmonic beam. In this case, the polarization state of the second harmonic is determined in a very simple manner. We also demonstrate how rotational symmetries in nonlinear metamaterials manifest themselves in SHG selection rules.

Konishi, Kuniaki; Higuchi, Takuya; Li, Jia; Larsson, Jakob; Ishii, Shuntaro; Kuwata-Gonokami, Makoto

2014-04-01

364

Polarization-Control Components and Narrow-Band Filters Based on Subwavelength Grating Structures  

Microsoft Academic Search

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

Song Peng

1996-01-01

365

CLASSICAL AREAS OF PHENOMENOLOGY: The number of least degrees of freedom required for a polarization controller to transform any state of polarization to any other output covering the entire Poincaré sphere  

Microsoft Academic Search

Using two typical types of polarization controller, this paper analyses theoretically and experimentally the fact that it is necessary to adjust at least three instead of two waveplates in order to transform any state of polarization to any other output covering the entire Poincaré sphere. The experimental results are exactly in accordance with the theory discussed in this paper. It

Xiao-Guang Zhang; Yuan Zheng

2008-01-01

366

Pulse width shaping of passively mode-locked soliton fiber laser via polarization control in carbon nanotube saturable absorber.  

PubMed

We report the continuous control of the pulse width of a passively mode-locked fiber laser via polarization state adjustment in a single-walled carbon nanotube saturable absorber (SWCNT-SA). The SWCNT, coated on the side-polished fiber, was fabricated with optimized conditions and used for stable mode-locking of the fiber laser without Q-switching instabilities for any polarization state of the laser intra-cavity. The 3-dB spectral bandwidth of the mode-locked pulses can be continuously tuned from 1.8 nm to 8.5 nm with the polarization control for a given laser cavity length and applied pump power. A pulse duration varying from 470 fs to 1.6 ps was also observed with a change in the spectral bandwidth. The linear and the nonlinear transmission properties of the SA were analyzed, and found to exhibit different modulation depths depending on the input polarization state in the SA. The largest modulation depth of the SA was observed at the polarization state of the transverse electric mode that delivers shortest pulses at the laser output. PMID:24216924

Jeong, Hwanseong; Choi, Sun Young; Rotermund, Fabian; Yeom, Dong-Il

2013-11-01

367

Local control of spin polarization in a semiconductor by microscale current loops  

NASA Astrophysics Data System (ADS)

We demonstrate a method to electrically manipulate the spin polarization in a semiconductor on a micrometer length scale and a submicrosecond time scale. A variable magnetic field induced by a microscale current loop magnetizes the Mn2+ ions in a CdMnTe/CdMgTe diluted magnetic semiconductor quantum well, and via sp-d exchange interaction polarizes photogenerated electron-hole pairs. A maximum spin polarization degree of +/-8.5% is obtained at 4.2 K without external magnetic field. The induced carrier spin polarization and the thermal heating of Mn2+ spins are resolved spatially and temporally by microphotoluminescence measurements.

Chen, Y. S.; Halm, S.; Neshataeva, E.; Kümmell, T.; Bacher, G.; Wiater, M.; Wojtowicz, T.; Karczewski, G.

2008-10-01

368

A novel multipath light signal dispersion reduction technique based on controlled-polarization optical wireless link setup  

Microsoft Academic Search

The detection characteristics of an indoor-optical communication system, which utilizes infrared radiation as carrier, has been explored and enhanced for telemedicine and wireless local area network applications. The novelty of the presented technique consists of the fact that multipath dispersion can be reduced under controlled polarization link setup. The design of such a network is based on the specifications set

George C. Giakos; N. Patnekar; S. Sumrain; Luay Fraiwan; V. Kumar

2005-01-01

369

Odor sensor with water membrane using surface polarity controlling method and analysis of responses to partial structures of odor molecules  

Microsoft Academic Search

A novel odor sensing system which imitates the process of reception of odorants in biological olfactory system had been developed, utilizing surface polarity controlling method as a transducer of the sensor. In biological system, odorants are received by a large number of receptors, which recognize not whole structures but partial structures of molecules. The present sensor responded partial structures of

Ryosuke Izumi; Kenshi Hayashi; Kiyoshi Toko

2004-01-01

370

Optically and electrically controlled circularly polarized emission from cholesteric liquid crystal materials doped with semiconductor quantum dots.  

PubMed

Novel types of electro- and photoactive quantum dot-doped cholesteric materials have been engineered. UV-irradiation or electric field application allows one to control the degree of circular polarization and intensity of fluorescence emission by prepared quantum dot-doped liquid crystal films. PMID:22972420

Bobrovsky, Alexey; Mochalov, Konstantin; Oleinikov, Vladimir; Sukhanova, Alyona; Prudnikau, Anatol; Artemyev, Mikhail; Shibaev, Valery; Nabiev, Igor

2012-12-01

371

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

372

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

373

Modeling of a CW Nd:YVO4 laser longitudinally pumped by high power VCSEL modules at 808 nm  

NASA Astrophysics Data System (ADS)

In this work longitudinal pumping of a continuous wave (CW) Nd:YVO4 laser by high power VCSEL modules was numerically studied. Two VCSEL pump modules (6 W and 15 W) were compared. The maximum output power from a Nd:YVO4 crystal using these pump modules was calculated to be 2.5 W and 6 W, respectively, using a 10 % output coupler. The slope and optical-to-optical efficiencies in both cases were around 47% and 40%, respectively. The performance of Nd:YVO4 crystal was found to be better than that of Nd:YAG crystal. Our numerical results indicate that VCSELs can serve as efficient pump sources for the end-pumped CW Nd:YVO4 lasers.

Alimohammadian, E.; Major, A.

2014-02-01

374

Catalyst-site-controlled coordination polymerization of polar vinyl monomers to highly syndiotactic polymers.  

PubMed

This contribution reports a combined synthetic, kinetic, mechanistic, and theoretical/computational study of the recently discovered catalyst-site-controlled coordination polymerization of polar vinyl monomers [such as methyl methacrylate (MMA) and N,N-dimethylacrylamide (DMAA)] into highly syndiotactic polymers. Among the 12 C(s)-ligated ansa-cyclopentadienyl (Cp)-R(2)E(C,Si)-fluorenyl (Flu) group 4 metallocene catalyst systems examined-which varied in metal center, anion structure, bridging atom and substituents, and ligand substitution pattern-cationic ansa-metallocene ester enolate catalyst 6(+)[B(C(6)F(5))(4)](-), derived from the activation of the precatalyst [Ph(2)C(Cp)(2,7-(t)Bu(2)-Flu)]Zr[OC(O(i)Pr)=CMe(2)](2) with [Ph(3)C][B(C(6)F(5))(4)], stood out as the best catalyst in all aspects of the MMA polymerization at room temperature, including the highest activity (1554 h(-1) TOF), efficiency (98% I*), syndiotacticity (94% rr), and control (predicted number-average molecular weight and 1.14 molecular weight distribution). Kinetic and mechanistic results are consistent with a catalyst-site-controlled, monometallic coordination-addition mechanism, involving fast intramolecular addition within the catalyst-monomer complex leading to the resting eight-membered ester enolate chelate, followed by the rate-limiting ring-opening of the chelate to regenerate the active species. This work has also uncovered several unique features of this polymerization system that are in marked contrast to the propylene polymerization by analogous C(s)-ligated cationic alkyl catalysts: a constant syndiotacticity of PMMA produced over a wide polymerization temperature range (i.e., from 0 degrees C, 94% rr to 25 degrees C, 94% rr to 50 degrees C, 93% rr); insensitivity of its high activity, degree of control, and stereoselectivity to solvent polarity and structure of weakly coordinating anions; and deviation from a pure site-control mechanism at high [MMA]/[catalyst] ratios. Computational results provide theoretical support for the proposed monomer-assisted, catalyst-site epimerization, after an enantiofacial mistake, to a thermodynamically more stable resting state, which accounts for the observed higher than expected [mr] contents based on a pure site-controlled mechanism. DFT calculations rationalize why the Ph(2)C< bridged catalyst 6 exhibits higher stereoselectivity than other catalysts with the Me(2)C< or Me(2)Si< bridge: the bridge rigidity pushes the eta(3)-bound Flu ligand closer to the growing chain and the monomer, thereby increasing DeltaE(stereo) between the competing transition states for the addition of a monomer molecule to the opposite (correct and wrong) enantiofaces of the enolate growing chain. The relative polymerization activity of this catalyst series is shown to correlate with the relative energetics of the back-biting of the penultimate unit and ion-pair formation. PMID:20121281

Zhang, Yuetao; Ning, Yalan; Caporaso, Lucia; Cavallo, Luigi; Chen, Eugene Y-X

2010-03-01

375

Optimal control design of NMR and dynamic nuclear polarization experiments using monotonically convergent algorithms.  

PubMed

Optimal control theory has recently been introduced to nuclear magnetic resonance (NMR) spectroscopy as a means to systematically design and optimize pulse sequences for liquid- and solid-state applications. This has so far primarily involved numerical optimization using gradient-based methods, which allow for the optimization of a large number of pulse sequence parameters in a concerted way to maximize the efficiency of transfer between given spin states or shape the nuclear spin Hamiltonian to a particular form, both within a given period of time. Using such tools, a variety of new pulse sequences with improved performance have been developed, and the NMR spin engineers have been challenged to consider alternative routes for analytical experiment design to meet similar performance. In addition, it has lead to increasing demands to the numerical procedures used in the optimization process in terms of computational speed and fast convergence. With the latter aspect in mind, here we introduce an alternative approach to numerical experiment design based on the Krotov formulation of optimal control theory. For practical reasons, the overall radio frequency power delivered to the sample should be minimized to facilitate experimental implementation and avoid excessive sample heating. The presented algorithm makes explicit use of this requirement and iteratively solves the stationary conditions making sure that the maximum of the objective is reached. It is shown that this method is faster per iteration and takes different paths within a control space than gradient-based methods. In the present work, the Krotov approach is demonstrated by the optimization of NMR and dynamic nuclear polarization experiments for various spin systems and using different constraints with respect to radio frequency and microwave power consumption. PMID:18532824

Maximov, Ivan I; Tosner, Zden?k; Nielsen, Niels Chr

2008-05-14

376

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

Microsoft Academic Search

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

M Reuveni; H Cohen; T Zahavi; A Venezian

2000-01-01

377

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

PubMed

Spectrally correlated photon pairs can be used to improve the performance of long-range fiber-based quantum communication protocols. We present a source based on spontaneous parametric downconversion, which allows one to control spectral correlations within the entangled photon pair without spectral filtering by changing the pump-pulse duration or the characteristics of the coupled spatial modes. The spectral correlations and polarization entanglement are characterized. We find that the generated photon pairs can feature both positive spectral correlations, decorrelation, or negative correlations at the same time as polarization entanglement with a high fidelity of 0.97 (no background subtraction) with the expected Bell state. PMID:24690818

Lutz, Thomas; Kolenderski, Piotr; Jennewein, Thomas

2014-03-15

378

Spin polarization control by electric stirring: proposal for a spintronic device  

Microsoft Academic Search

We propose a spintronic device to generate spin polarization in a mesoscopic region by purely electric means. We show that the spin Hall effect in combination with the stirring effect are sufficient to induce measurable spin polarization in a closed geometry. Our device structure does not require the application of magnetic fields, external radiation or ferromagnetic leads, and can be

Yu. V. Pershin; N. A. Sinitsyn; A. Kogan; A. Saxena; D. L. Smith

2009-01-01

379

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

Microsoft Academic Search

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

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

2011-01-01

380

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

PubMed

Biological tubes consist of polarized epithelial cells with apical membranes building the central lumen and basolateral membranes contacting adjacent cells or the extracellular matrix. Cellular polarity requires distinct inputs from outside the cell, e.g., the matrix, inside the cell, e.g., vesicular trafficking and the plasma membrane and its junctions.(1) Many highly conserved polarity cues have been identified, but their integration during the complex process of polarized tissue and organ morphogenesis is not well understood. It is assumed that plasma-membrane-associated polarity determinants, such as the partitioning-defective (PAR) complex, define plasma membrane domain identities, whereas vesicular trafficking delivers membrane components to these domains, but lacks the ability to define them. In vitro studies on lumenal membrane biogenesis in mammalian cell lines now indicate that trafficking could contribute to defining membrane domains by targeting the polarity determinants, e.g., the PARs, themselves.(2) This possibility suggests a mechanism for PARs' asymmetric distribution on membranes and places vesicle-associated polarity cues upstream of membrane-associated polarity determinants. In such an upstream position, trafficking might even direct multiple membrane components, not only polarity determinants, an original concept of polarized plasma membrane biogenesis(3) (,) (4)that was largely abandoned due to the failure to identify a molecularly defined intrinsic vesicular sorting mechanism. Our two recent studies on C. elegans intestinal tubulogenesis reveal that glycosphingolipids (GSLs) and the well-recognized vesicle components clathrin and its AP-1 adaptor are required for targeting multiple apical molecules, including polarity regulators, to the expanding apical/lumenal membrane.(5) (,) (6) These findings support GSLs' long-proposed role in in vivo polarized epithelial membrane biogenesis and development and identify a novel function in apical polarity for classical post-Golgi vesicle components. They are also compatible with a vesicle-intrinsic sorting mechanism during membrane biogenesis and suggest a model for how vesicles could acquire apical directionality during the assembly of the functionally critical polarized lumenal surfaces of epithelial tubes. PMID:24058862

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

2013-01-01

381

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

382

Subwavelength polarization beam splitter with controllable splitting ratio based on surface plasmon polaritons.  

PubMed

We propose a novel V-shaped Ag nanowire structure as a subwavelength polarization beam splitter. When an incident light is focused onto the junction of the two branches, two surface plasmon polaritons (SPPs) are launched and propagate along the two branches. The polarizations of the emission light from the two ends are always parallel to the directions of the branches and the splitting ratio can be adjusted by changing the polarization of the incident light. The polarization characteristic originates from the fact that only single plasmonic waveguide mode exists in the thin nanowire and high order modes are cutoff. The near-field coupling between the two branches dominates the SPPs launching and the splitting ratio, which are very different with the single nanowire case. The V-shaped nanowire structure will have many potential applications in the integration of plasmonic devices, such as plasmonic router or polarizer. PMID:23388925

Chen, Yuanyuan; Song, Gang; Xiao, Jinghua; Yu, Li; Zhang, Jiasen

2013-01-14

383

Optical subassembly with 57°-angled fiber array and silicon optical bench for VCSEL array and parallel optical transmitter module  

NASA Astrophysics Data System (ADS)

This paper suggests a passive aligned optical subassembly (OSA) using 54.7° mirrors of a silicon optical bench (SiOB) and a 57° angled fiber array for a vertical cavity surface emitting laser (VCSEL). This OSA is very cost-effective because the OSA was fabricated by only one-axis alignment along the V-groove's direction and flip-chip-bonding the VCSEL. In addition, this paper describes a 2.5-Gbps x 12-channels parallel optical transmitter module fabricated with the OSA.

Hwang, Sung Hwan; Lee, Sang Hwan; Park, Hyo-Hoon

2006-10-01

384

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

2013-01-01

385

X11/Mint Genes Control Polarized Localization of Axonal Membrane Proteins in Vivo  

PubMed Central

Mislocalization of axonal proteins can result in misassembly and/or miswiring of neural circuits, causing disease. To date, only a handful of genes that control polarized localization of axonal membrane proteins have been identified. Here we report that Drosophila X11/Mint proteins are required for targeting several proteins, including human amyloid precursor protein (APP) and Drosophila APP-like protein (APPL), to axonal membranes and for their exclusion from dendrites of the mushroom body in Drosophila, a brain structure involved in learning and memory. Axonal localization of APP is mediated by an endocytic motif, and loss of X11/Mint results in a dramatic increase in cell-surface levels of APPL, especially on dendrites. Mutations in genes required for endocytosis show similar mislocalization of these proteins to dendrites, and strongly enhance defects seen in X11/Mint mutants. These results suggest that X11/Mint-dependent endocytosis in dendrites may serve to promote the axonal localization of membrane proteins. Since X11/Mint binds to APP, and abnormal trafficking of APP contributes to Alzheimer's disease, deregulation of X11/Mint may be important for Alzheimer's disease pathogenesis.

Gross, Garrett G.; Lone, G. Mohiddin; Leung, Lok Kwan; Hartenstein, Volker

2013-01-01

386

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

PubMed

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

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

2014-01-01

387

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

388

Controllable optical steady behavior from nonradiative coherence in GaAs quantum well driven by a single elliptically polarized field  

NASA Astrophysics Data System (ADS)

In this paper, we analyze theoretically the optical steady behavior in GaAs quantum well structure which interacts with a single elliptically polarized field (EPF) and a ?-polarized probe field. Due to the existence of the robust nonradiative coherence, we demonstrate that the controllable optical steady behavior including multi-stability (OM) and optical bistability (OB) can be obtained. More interestingly, our numerical results also illustrate that tuning the phase difference between two components of polarized electric field of the EPF can realize the conversion between OB and OM. Our results illustrate the potential to utilize the optical phase for developing the new all-optical switching devices, as well as a guidance in the design for possible experimental implementations.

Zhu, Zhonghu; Chen, Ai-Xi; Bai, Yanfeng; Yang, Wen-Xing; Lee, Ray-Kuang

2014-05-01

389

Equilibrium Polarization of Ultrathin PbTiO3 with Surface Compensation Controlled by Oxygen Partial Pressure  

NASA Astrophysics Data System (ADS)

We present a synchrotron x-ray study of the equilibrium polarization structure of ultrathin PbTiO3 films on SrRuO3 electrodes epitaxially grown on SrTiO3 (001) substrates, as a function of temperature and the external oxygen partial pressure (pO2) controlling their surface charge compensation. We find that the ferroelectric Curie temperature (TC) varies with pO2 and has a minimum at the intermediate pO2, where the polarization below TC 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, Carol; Eastman, J. A.; Streiffer, S. K.; Stephenson, G. B.

2011-10-01

390

Characteristics of InGa(N)As VCSELs for fiber optic applications  

Microsoft Academic Search

We report our results on InGaNAs\\/GaAs vertical-cavity surface-emitting lasers (VCSELs) for fiber-optic applications in the 1.3 mum range. The epitaxial structures were grown on (100) GaAs substrates by MBE or MOCVD. The nitrogen composition of the InGaNAs\\/GaAs quantum-well (QW) active region is 0 to 0.02. Long-wavelength (up to 1.3 mum) room-temperature continuous-wave (RT CW) lasing operation was achieved for MBE

Hung-Pin D. Yang; Chen-Ming Lu; Ru-Shang Hsiao; Chih-Hung Chiou; Cheng-Hung Lee; Chun-Yuan Huang; Hsin-Chieh Yu; Chin-May Wang; Kuen Fong Lin; Chih-Ming Lai; Li-Chung Wei; Nikolay A. Maleev; Alexey R. Kovsh; Chia-Pin Sung; Jyh-Shyang Wang; Jenn-Fang Chen; Tsin-Dong Lee; Jim Y. Chi

2004-01-01

391

Design and modeling of a vertical-cavity surface-emitting laser (VCSEL)  

Microsoft Academic Search

In this paper, we attempt to design, simulate and characterize an InGaAs-based vertical-cavity surface-emitting laser (VCSEL) employing InGaAsP multi-quantum wells sandwiched between GaAs\\/AlGaAs and GaAs\\/AlAs distributed Bragg reflectors using an industrial-based numerical simulator. We were able to obtain a working model at an optical wavelength of 1.55 mum. This paper provides key results of the device characteristics including the DC

K. Kandiah; P. S. Menon; S. Shaari; B. Y. Majlis

2008-01-01

392

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

Microsoft Academic Search

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

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

1999-01-01

393

Development of an electroabsorption loss-modulated VCSEL for high-speed data transfer  

NASA Astrophysics Data System (ADS)

The possibilities to increase modulation bandwidth for high-speed data transfer using vertical cavity surface emitting lasers (VCSEL) are explored using intracavity loss-modulation instead of the traditional current modulation technique. Theory shows that a larger bandwidth is possible, but at the cost of having a large (+20 dB) resonance peak. The high-frequency roll-off slope of these devices is shown to have an intrinsic slope of -20 dB/decade, and an additional -20 dB/decade is observed due to parasitics. Sources of electrical parasitics were suspected to be one or more of the following: (1) carrier time-of-flight (TOF), (2) carrier accumulation at heterointerfaces, (3) modulator p-i-n junction capacitance and (4) contact metallization capacitance and resistance. An analysis was done to find the sources of the parasitics, and through methods such as (1) variation of modulator i-region thickness, (2) low temperature growth of the i-region, (3) reduction of metallization capacitance and blue shifting of the modulator absorption wavelength. The effects of these measures were estimated by fitting the high frequency roll-off slope of the optical response. Reduction of metallization and junction capacitance have shown to be the most beneficial measures, partly determined by fitting and measurements of frequency dependent S-parameters. A novel type of VCSEL has been proposed and demonstrated based on research done on an intracavity loss-modulated VCSEL. This device uses a duo-cavity architecture to optically decouple the AC modulation component from the VCSEL section. Devices were fabricated and showed a nearly resonance-free high-frequency response up to or beyond 20 GHz. To improve bandwidth and device parasitics, intracavity loss-modulated devices were used as a test-bed for the modulator section. To increase the modulation depth of these devices from the initial 20% shown by the proof-of-concept design, additional multiple quantum well (MQW) sets were added to a modulator i-region of increased thickness. The final duo-cavity device presented in this work shows a 40% modulation depth and a 17 GHz bandwidth at a drive current of 7 mA. In this device, the bandwidth is believed to be limited by a large RC value due to a high modulator junction series resistance.

van Eisden, Jobert

394

In-plane integration of VCSEL with photo-detector by using laterally coupled cavities  

NASA Astrophysics Data System (ADS)

A novel concept to form a photo-detector integrated VCSELs using transverse-coupled-cavity (TCC) scheme is demonstrated. In our configuration one cavity suppressed by the reverse bias voltage at 1volt, while the other cavity used as a laser. Proton-implantation was used in order to prevent the current leakage. The formation aperture diameter of each cavity gives us multimode and quasi-single mode condition. Our preliminary results on L-I indicate the possibility of continues tracking of photocurrent in the range of 0.7- 10 mA, which is limited by the threshold and saturation level of the laser side cavity.

Dalir, Hamed; Koyama, Fumio

2014-02-01

395

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

396

30 Gbps 4-PAM transmission over 200 m of MMF using an 850 nm VCSEL.  

PubMed

We present high speed real time, error free 4-PAM transmission for short range optical links based on a VCSEL operating at 850 nm, a multimode fibre and a simple intensity detector. Transmission speeds of 25 Gbps and 30 Gbps are demonstrated, and the maximum fibre reaches were 300 m and 200 m, respectively. The 4-PAM is also compared with OOK transmission at 25 Gbps, and we find that at this bit rate 4-PAM increases the error free transmission distance in the multimode fibre by 100 m, compared to OOK. PMID:22274020

Szczerba, Krzysztof; Westbergh, Petter; Karout, Johnny; Gustavsson, Johan; Haglund, Åsa; Karlsson, Magnus; Andrekson, Peter; Agrell, Erik; Larsson, Anders

2011-12-12

397

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

398

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

NASA Astrophysics Data System (ADS)

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

Park, Junbo; Ralph, D. C.; Buhrman, R. A.

2013-12-01

399

Enhanced single-fundamental LP01 mode operation of 650-nm GaAs-based GaInP/AlGaInP quantum-well VCSELs  

NASA Astrophysics Data System (ADS)

Minimal optical attenuation of plastic (polymer) optical fibres (POFs) corresponds to the 650-nm wavelength. Currently the GaInP/AlGaInP quantum-well (QW) oxide-confined (OC) vertical-cavity surface-emitting diode lasers (VCSELs) are undoubtedly the laser devices most suited to be used in 650-nm POF optical communication, for which the stable single-fundamental-mode LP01 emission (SFM) is definitely the one most desired. In the present paper, the comprehensive fully self-consistent VCSEL model is used to examine mode selectivity of the above VCSELs. An increase in the VCSEL active-region diameter leads to a gradual modification of the current injection into this region and subsequent carrier radial diffusion within it before their recombination, which is followed by an essential transformation of active-region optical-gain profiles deciding upon an excitation of successive transverse modes. In standard arsenide OC VCSELs, SFM operation is usually limited to relatively small active regions. But for a room-temperature continuous-wave operation of the GaInP/AlGaInP VCSELs, the fundamental LP01 mode remains surprisingly the lowest-threshold one up to relatively large active regions of 9-µm diameters. Nevertheless, in such VCSELs, thresholds of many LP modes become very similar to one another, which leads to their relatively poor mode selectivity and an unwanted multi-mode operation for higher output powers.

Piskorski, ?ukasz; Sarza?a, Robert P.; Nakwaski, W?odzimierz

2010-03-01

400

Control of phonons in semiconductor nanocrystals via femtosecond pulse chirp-influenced wavepacket dynamics and polarization.  

PubMed

The realistic electronic structure of semiconductor nanocrystals is characterized by excitonic fine structure and atomistic symmetry breakings that are challenging to resolve experimentally. Exciton-phonon coupling is one of the most sensitive measures of the excitonic wave functions of the nanocrystals. Here, we exploit this sensitivity via chirped pulse and polarization resolved femtosecond pump/probe spectroscopy of colloidal CdSe nanocrystals. Pulse chirp measurements and simulations are used to explore the contributions of excited- and ground-state vibrational wavepackets to the observed coherent phonons in the pump/probe signals. Polarization resolved pump/probe spectroscopy is used to explore electronic and vibrational polarization anisotropies. We find no electronic polarization anisotropy, whereas vibrational anisotropy is preserved. PMID:24131171

Mooney, Jonathan; Saari, Jonathan I; Kelley, Anne Myers; Krause, Michael M; Walsh, Brenna R; Kambhampati, Patanjali

2013-12-12

401

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

402

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

403

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

404

A top-down design methodology and its implementation for VCSEL-based optical links design  

NASA Astrophysics Data System (ADS)

In order to find the optimal design for a given specification of an optical communication link, an integrated simulation of electronic, optoelectronic, and optical components of a complete system is required. It is very important to be able to simulate at both system level and detailed model level. This kind of model is feasible due to the high potential of Verilog-AMS language. In this paper, we propose an effective top-down design methodology and employ it in the development of a complete VCSEL-based optical links simulation. The principle of top-down methodology is that the development would proceed from the system to device level. To design a hierarchical model for VCSEL based optical links, the design framework is organized in three levels of hierarchy. The models are developed, and implemented in Verilog-AMS. Therefore, the model parameters are fitted to measured data. A sample transient simulation demonstrates the functioning of our implementation. Suggestions for future directions in top-down methodology used for optoelectronic systems technology are also presented.

Li, Jiguang; Cao, Mingcui; Cai, Zilong

2005-01-01

405

MBE growth of active regions for electrically pumped, cw-operating GaSb-based VCSELs  

NASA Astrophysics Data System (ADS)

Electrically pumped, cw-operating, single-mode GaSb-based VCSELs are attractive light sources for trace-gas sensing systems using tunable diode laser absorption spectroscopy (TDLAS) [A. Vicet, D.A. Yarekha, A. Pérona, Y. Rouillard, S. Gaillard, Spectrochimica Acta Part A 58 (2002) 2405-2412]. Only recently, the first electrically pumped (EP) devices emitting at 2.325 ?m in cw-mode at room temperature have been reported [A. Bachmann, T. Lim, K. Kashani-Shirazi, O. Dier, C. Lauer, M.-C. Amann, Electronics Letters 44(3) (2008) 202-203]. The fabrication of these devices employs the molecular beam epitaxy (MBE) growth of GaSb/AlAsSb-distributed Bragg mirrors, a multi-quantum-well active region made of AlGaAsSb/InGaAsSb and an InAsSb/GaSb-buried-tunnel junction. As VCSELs are usually driven under high injection rates, an optimum electrical design of active regions is essential for high-performance devices. In this paper we present an enhanced simulation of current flow in the active region under operation conditions. The calculation includes carrier transport by drift, diffusion and tunneling. We discuss different design criteria and material compositions for active regions. Active regions with various barrier materials were incorporated into edge emitter samples to evaluate their performance. Aluminum-containing barriers show better internal efficiency compared to active regions with GaSb as the barrier material.

Kashani-Shirazi, K.; Bachmann, A.; Boehm, G.; Ziegler, S.; Amann, M.-C.

2009-03-01

406

Ultrahigh speed endoscopic optical coherence tomography using micromotor imaging catheter and VCSEL technology  

PubMed Central

We developed a micromotor based miniature catheter with an outer diameter of 3.2 mm for ultrahigh speed endoscopic swept source optical coherence tomography (OCT) using a vertical cavity surface-emitting laser (VCSEL) at a 1 MHz axial scan rate. The micromotor can rotate a micro-prism at several hundred frames per second with less than 5 V drive voltage to provide fast and stable scanning, which is not sensitive to the bending of the catheter. The side-viewing probe can be pulled back to acquire a three-dimensional (3D) data set covering a large area on the specimen. The VCSEL provides a high axial scan rate to support dense sampling under high frame rate operation. Using a high speed data acquisition system, in vivo 3D-OCT imaging in the rabbit GI tract and ex vivo imaging of a human colon specimen with 8 ?m axial resolution, 8 ?m lateral resolution and 1.2 mm depth range in tissue at a frame rate of 400 fps was demonstrated.

Tsai, Tsung-Han; Potsaid, Benjamin; Tao, Yuankai K.; Jayaraman, Vijaysekhar; Jiang, James; Heim, Peter J. S.; Kraus, Martin F.; Zhou, Chao; Hornegger, Joachim; Mashimo, Hiroshi; Cable, Alex E.; Fujimoto, James G.

2013-01-01

407

Ultrahigh speed endoscopic optical coherence tomography using micromotor imaging catheter and VCSEL technology.  

PubMed

We developed a micromotor based miniature catheter with an outer diameter of 3.2 mm for ultrahigh speed endoscopic swept source optical coherence tomography (OCT) using a vertical cavity surface-emitting laser (VCSEL) at a 1 MHz axial scan rate. The micromotor can rotate a micro-prism at several hundred frames per second with less than 5 V drive voltage to provide fast and stable scanning, which is not sensitive to the bending of the catheter. The side-viewing probe can be pulled back to acquire a three-dimensional (3D) data set covering a large area on the specimen. The VCSEL provides a high axial scan rate to support dense sampling under high frame rate operation. Using a high speed data acquisition system, in vivo 3D-OCT imaging in the rabbit GI tract and ex vivo imaging of a human colon specimen with 8 ?m axial resolution, 8 ?m lateral resolution and 1.2 mm depth range in tissue at a frame rate of 400 fps was demonstrated. PMID:23847737

Tsai, Tsung-Han; Potsaid, Benjamin; Tao, Yuankai K; Jayaraman, Vijaysekhar; Jiang, James; Heim, Peter J S; Kraus, Martin F; Zhou, Chao; Hornegger, Joachim; Mashimo, Hiroshi; Cable, Alex E; Fujimoto, James G

2013-07-01

408

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

SciTech Connect

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

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

2006-02-15

409

Energy efficiency, bit rate, and modal properties of 980 nm VCSELs for very-short-reach optical interconnects  

NASA Astrophysics Data System (ADS)

Via experimental results supported by numerical modeling we report the energy-efficiency, bit rate, and modal properties of GaAs-based 980 nm vertical cavity surface emitting lasers (VCSELs). Using our newly established Principles for the design and operation of energy-efficient VCSELs as reported in the Invited paper by Moser et al. (SPIE 9001-02 ) [1] along with our high bit rate 980 nm VCSEL epitaxial designs that include a relatively large etalonto- quantum well gain-peak wavelength detuning of about 15 nm we demonstrate record error-free (bit error ratio below 10-12) data transmission performance of 38, 40, and 42 Gbit/s at 85, 75, and 25°C, respectively. At 38 Gbit/s in a back-toback test configuration from 45 to 85°C we demonstrate a record low and highly stable dissipated energy of only ~179 to 177 fJ per transmitted bit. We conclude that our 980 nm VCSELs are especially well suited for very-short-reach and ultra-short-reach optical interconnects where the data transmission distances are about 1 m or less, and about 10 mm or less, respectively.

Li, Hui; Moser, Philip; Wolf, Philip; Larisch, Gunter; Frasunkiewicz, Leszek; Dems, Maciej; Czyszanowski, Tomasz; Lott, James A.; Bimberg, Dieter

2014-02-01

410

10 Gbit\\/s photonic crystal fiber transmissions with 1.1 ?m directly-modulated single-mode VCSEL  

Microsoft Academic Search

We demonstrate a 10-Gbit\\/s transmission over a 5-km photonic crystal fiber in the 1.1 ?m band using a directly-modulated single-mode VCSEL. The transmission distance was extended to 14 km by using an ytterbium-doped fiber amplifier.

Kengo Koizumi; Masato Yoshida; Toshihiko Hirooka; M. Nakazawa

2010-01-01

411

Ultrafast Laser Beam Switching and Pulse Train Generation by Using Coupled Vertical-Cavity, Surface-Emitting Lasers (VCSELS)  

NASA Technical Reports Server (NTRS)

Ultrafast directional beam switching is achieved using coupled VCSELs. This approach is demonstrated to achieve beam switching frequencies of 40 GHz and more and switching directions of about eight degrees. This switching scheme is likely to be useful for ultrafast optical networks at frequencies much higher than achievable with other approaches.

Goorjian, Peter M. (Inventor); Ning, Cun-Zheng (Inventor)

2005-01-01

412

A compact, portable and low cost generic interrogation strain sensor system using an embedded VCSEL, detector and fibre Bragg grating  

NASA Astrophysics Data System (ADS)

We present a compact, portable and low cost generic interrogation strain sensor system using a fibre Bragg grating configured in transmission mode with a vertical-cavity surface-emitting laser (VCSEL) light source and a GaAs photodetector embedded in a polymer skin. The photocurrent value is read and stored by a microcontroller. In addition, the photocurrent data is sent via Bluetooth to a computer or tablet device that can present the live data in a real time graph. With a matched grating and VCSEL, the system is able to automatically scan and lock the VCSEL to the most sensitive edge of the grating. Commercially available VCSEL and photodetector chips are thinned down to 20 ?m and integrated in an ultra-thin flexible optical foil using several thin film deposition steps. A dedicated micro mirror plug is fabricated to couple the driving optoelectronics to the fibre sensors. The resulting optoelectronic package can be embedded in a thin, planar sensing sheet and the host material for this sheet is a flexible and stretchable polymer. The result is a fully embedded fibre sensing system - a photonic skin. Further investigations are currently being carried out to determine the stability and robustness of the embedded optoelectronic components.

Lee, Graham C. B.; van Hoe, Bram; Yan, Zhijun; Maskery, Oliver; Sugden, Kate; Webb, David; van Steenberge, Geert

2012-02-01

413

22 Gb/s error-free data transmission beyond 1 km of multi-mode fiber using 850 nm VCSELs  

NASA Astrophysics Data System (ADS)

The first error-free data transmission beyond 1 km of multi-mode fiber at bit-rates exceeding 20 Gb/s is demonstrated using a high modulation bandwidth, quasi-single mode (SMSR~20 dB) 850 nm VCSEL. A VCSEL with small ~3 ?m aperture shows quasi-single mode operation with a narrow spectral width. The top mirror reflectivity of the VCSEL is optimized for high speed and high output power by shallow etching. A combination of narrow spectral width and high optical power reduces the effects of fiber dispersion and fiber and connector losses and enables such a long transmission distance at high bit-rates.

Safaisini, Rashid; Szczerba, Krzysztof; Haglund, Erik; Westbergh, Petter; Gustavsson, Johan S.; Larsson, Anders; Andrekson, Peter A.

2013-03-01

414

A method to control the polarization of random terahertz lasing in two-dimensional disordered ruby medium  

NASA Astrophysics Data System (ADS)

Terahertz (THz) random lasing is studied numerically for two-dimensional disordered media made of ruby grains with a three-level atomic system. A method via the adjustment of the pumping area to control the polarization of the THz wave is proposed. Computed results reveal that transverse electric THz lasing modes could occur if pumping is supplied on the whole medium, while transverse magnetic THz lasing modes could occur if pumping is appropriately supplied on a partial area of the medium.

Liu, Yong; Liu, Jin-Song; Wang, Ke-Jia

2011-09-01

415

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

416

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

417

T-Cell-Receptor-Dependent Signal Intensity Dominantly Controls CD4(+) T Cell Polarization In Vivo.  

PubMed

Polarization of effector CD4(+) T cells can be influenced by both antigen-specific signals and by pathogen- or adjuvant-induced cytokines, with current models attributing a dominant role to the latter. Here we have examined the relationship between these factors in shaping cell-mediated immunity by using intravital imaging of CD4(+) T cell interactions with dendritic cells (DCs) exposed to polarizing adjuvants. These studies revealed a close correspondence between strength of T cell receptor (TCR)-dependent signaling and T helper 1 (Th1) versus Th2 cell fate, with antigen concentration dominating over adjuvant in controlling T cell polarity. Consistent with this finding, at a fixed antigen concentration, adjuvants inducing Th1 cells operated by affecting DC costimulation that amplified TCR signaling. TCR signal strength controlled downstream cytokine receptor expression, linking the two components in a hierarchical fashion. These data reveal how quantitative integration of antigen display and costimulation regulates downstream checkpoints responsible for cytokine-mediated control of effector differentiation. PMID:24981853

van Panhuys, Nicholas; Klauschen, Frederick; Germain, Ronald N

2014-07-17

418

Electrical control of cell polarization in the fission yeast Schizosaccharomyces pombe.  

PubMed

Electric signals surround tissues and cells and have been proposed to participate in directing cell polarity in processes such as development, wound healing, and host invasion [1, 2]. The application of exogenous electric fields (EFs) can direct cell polarization in cell types ranging from bacteria and fungi to neurons and neutrophils [3-7]. The mechanisms by which EFs modulate cell polarity, however, remain poorly understood. Here we introduce the fission yeast Schizosaccharomyces pombe as a model organism to elucidate the mechanisms underlying this process. In these rod-shaped cells, an exogenous EF reorients cell growth in a direction orthogonal to the field, producing cells with a bent morphology. A candidate genetic screen identifies conserved factors involved in this process: an integral membrane proton ATPase pma1p that regulates intracellular pH, the small GTPase cdc42p, and the formin for3p that assembles actin cables. Interestingly, mutants in these genes still respond to the EF but orient in a different direction, toward the anode. In addition, EFs also cause electrophoretic movement of cell wall synthase complex proteins toward the anode. These data suggest molecular models for how the EF reorients cell polarization by modulating intracellular pH and steering cell polarity factors in multiple directions. PMID:20362451

Minc, Nicolas; Chang, Fred

2010-04-27

419

Arabidopsis thaliana Rop GTPases are localized to tips of root hairs and control polar growth.  

PubMed

Plants contain a novel unique subfamily of Rho GTPases, vital components of cellular signalling networks. Here we report a general role for some members of this family in polarized plant growth processes. We show that Arabidopsis AtRop4 and AtRop6 encode functional GTPases with similar intrinsic GTP hydrolysis rates. We localized AtRop proteins in root meristem cells to the cross-wall and cell plate membranes. Polar localization of AtRops in trichoblasts specifies the growth sites for emerging root hairs. These sites were visible before budding and elongation of the Arabidopsis root hair when AtRops accumulated at their tips. Expression of constitutively active AtRop4 and AtRop6 mutant proteins in root hairs of transgenic Arabidopsis plants abolished polarized growth and delocalized the tip-focused Ca2+ gradient. Polar localization of AtRops was inhibited by brefeldin A, but not by other drugs such as latrunculin B, cytochalasin D or caffeine. Our results demonstrate a general function of AtRop GTPases in tip growth and in polar diffuse growth. PMID:11387211

Molendijk, A J; Bischoff, F; Rajendrakumar, C S; Friml, J; Braun, M; Gilroy, S; Palme, K

2001-06-01

420

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

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

421

Controlled synthesis and size-dependent polarization domain structure of colloidal germanium telluride nanocrystals.  

PubMed

Germanium telluride (GeTe) exhibits interesting materials properties, including a reversible amorphous-to-crystalline phase transition and a room-temperature ferroelectric distortion, and has demonstrated potential for nonvolatile memory applications. Here, a colloidal approach to the synthesis of GeTe nanocrystals over a wide range of sizes is demonstrated. These nanocrystals have size distributions of 10-20% and exist in the rhombohedral structure characteristic of the low-temperature polar phase. The production of nanocrystals of widely varying sizes is facilitated by the use of Ge(II) precursors with different reactivities. A transition from a monodomain state to a state with multiple polarization domains is observed with increasing size, leading to the formation of richly faceted nanostructures. These results provide a starting point for deeper investigation into the size-scaling and fundamental nature of polar-ordering and phase-change processes in nanoscale systems. PMID:21280629

Polking, Mark J; Zheng, Haimei; Ramesh, Ramamoorthy; Alivisatos, A Paul

2011-02-23

422

Subnatural-Linewidth Polarization-Entangled Photon Pairs with Controllable Temporal Length  

NASA Astrophysics Data System (ADS)

We demonstrate an efficient experimental scheme for producing polarization-entangled photon pairs from spontaneous four-wave mixing (SFWM) in a laser-cooled Rb85 atomic ensemble, with a bandwidth (as low as 0.8 MHz) much narrower than the rubidium atomic natural linewidth. By stabilizing the relative phase between the two SFWM paths in a Mach-Zehnder interferometer configuration, we are able to produce all four Bell states. These subnatural-linewidth photon pairs with polarization entanglement are ideal quantum information carriers for connecting remote atomic quantum nodes via efficient light-matter interaction in a photon-atom quantum network.

Liao, Kaiyu; Yan, Hui; He, Junyu; Du, Shengwang; Zhang, Zhi-Ming; Zhu, Shi-Liang

2014-06-01

423

Microbial Competition in Polar Soils: A Review of an Understudied but Potentially Important Control on Productivity  

PubMed Central

Intermicrobial competition is known to occur in many natural environments, and can result from direct conflict between organisms, or from differential rates of growth, colonization, and/or nutrient acquisition. It has been difficult to extensively examine intermicrobial competition in situ, but these interactions may play an important role in the regulation of the many biogeochemical processes that are tied to microbial communities in polar soils. A greater understanding of how competition influences productivity will improve projections of gas and nutrient flux as the poles warm, may provide biotechnological opportunities for increasing the degradation of contaminants in polar soil, and will help to predict changes in communities of higher organisms, such as plants.

Bell, Terrence H.; Callender, Katrina L.; Whyte, Lyle G.; Greer, Charles W.

2013-01-01

424

Polarization-controlled contrasted images using dye-doped nematic liquid crystals.  

PubMed

We explore the polarization dependence of the nonlinear response of a planar nematic liquid crystal cell doped with 1% wt of methyl red dye. The results obtained show that the refractive index change can be switched from a positive value to a negative one as the polarization of the beam changes from parallel to perpendicular with respect to the rubbing direction. This property is exploited in a phase contrast system, where a dynamic phase filter is photoinduced in a liquid crystal cell placed in the system's Fourier plane. Real-time contrast inversion in the resulting images is demonstrated. PMID:19259179

Porras Aguilar, R; Ramirez-San-Juan, J C; Baldovino-Pantaleon, O; May-Arrioja, D; Arroyo Carrasco, M L; Iturbe-Castillo, M D; Sánchez-de-la-Llave, D; Ramos-Garcia, R

2009-03-01

425

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

426

Polarized optical feedback from an extremely short external cavity for controlling and stabilizing the polarization of vertical cavity surface emitting lasers  

NASA Astrophysics Data System (ADS)

The authors present experimental results showing that polarization selective optical feedback from an extremely short external cavity induces switching between the two fundamental transverse modes with orthogonal linear polarization of the otherwise (without optical feedback) polarization stable vertical cavity surface emitting laser. Moreover, when properly selecting the external cavity length within a subwavelength range the polarization state of the emitted light can be chosen in either of the two fundamental transverse modes and stabilized against injection current variations. The numerical results reported are in good agreement with experiments.

Arizaleta Arteaga, Mikel; Parriaux, Olivier; López-Amo, Manuel; Thienpont, Hugo; Panajotov, Krassimir

2007-03-01

427

Polarization control of Raman spectroscopy optimizes the assessment of bone tissue  

PubMed Central

Abstract. 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 (106?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.

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

2013-01-01

428

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

429

Conducting the lasing of single transverse modes in a commercial multi-mode VCSEL by the beam-profile adapted optical feedback  

NASA Astrophysics Data System (ADS)

This work studied the generation of single high-order transverse modes in a commercial multi-transverse mode VCSEL by applied beam-profile adapted optical feedback. To adapt the beam profile, the multi-transverse-mode beam profile of the solitary VCSEL was launched into a single-mode fiber, resulting in a quasi-Gaussian beam profile at the exit of fiber. The adapted beam passed through a spatial light modulator (SLM) and was then fed back into the laser's cavity. The SLM was designed to have the beam profile of a high-order transverse mode. The VCSEL would lasing the designated single transverse mode with a side-mode suppression ratio about 20 dB by the optical feedback. More experimental details will be presented and these results will help to expand the application of VCSELs.

Wu, Yu-Heng; Hsu, Chuan-Pi; Cheng, Da-Long; Kuo, Wang-Chuang; Yen, Tsu Chiang

2010-03-01

430

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

Microsoft Academic Search

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

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

2003-01-01

431

Polarization rotator-splitters and controllers in a Si3N4-on-SOI integrated photonics platform.  

PubMed

We demonstrate novel polarization management devices in a custom-designed silicon nitride (Si3N4) on silicon-on-insulator (SOI) integrated photonics platform. In the platform, Si3N4 waveguides are defined atop silicon waveguides. A broadband polarization rotator-splitter using a TM0-TE1 mode converter in a composite Si3N4-silicon waveguide is demonstrated. The polarization crosstalk, insertion loss, and polarization dependent loss are less than -19 dB, 1.5 dB, and 1.0 dB, respectively, over a bandwidth of 80 nm. A polarization controller composed of polarization rotator-splitters, multimode interference couplers, and thin film heaters is also demonstrated. PMID:24921814

Sacher, Wesley D; Huang, Ying; Ding, Liang; Barwicz, Tymon; Mikkelsen, Jared C; Taylor, Benjamin J F; Lo, Guo-Qiang; Poon, Joyce K S

2014-05-01

432

Slmb antagonises the aPKC/Par-6 complex to control oocyte and epithelial polarity.  

PubMed

The Drosophila anterior-posterior axis is specified when the posterior follicle cells signal to polarise the oocyte, leading to the anterior/lateral localisation of the Par-6/aPKC complex and the posterior recruitment of Par-1, which induces a microtubule reorganisation that localises bicoid and oskar mRNAs. Here we show that oocyte polarity requires Slmb, the substrate specificity subunit of the SCF E3 ubiquitin ligase that targets proteins for degradation. The Par-6/aPKC complex is ectopically localised to the posterior of slmb mutant oocytes, and Par-1 and oskar mRNA are mislocalised. Slmb appears to play a related role in epithelial follicle cells, as large slmb mutant clones disrupt epithelial organisation, whereas small clones show an expansion of the apical domain, with increased accumulation of apical polarity factors at the apical cortex. The levels of aPKC and Par-6 are significantly increased in slmb mutants, whereas Baz is slightly reduced. Thus, Slmb may induce the polarisation of the anterior-posterior axis of the oocyte by targeting the Par-6/aPKC complex for degradation at the oocyte posterior. Consistent with this, overexpression of the aPKC antagonist Lgl strongly rescues the polarity defects of slmb mutant germline clones. The role of Slmb in oocyte polarity raises an intriguing parallel with C. elegans axis formation, in which PAR-2 excludes the anterior PAR complex from the posterior cortex to induce polarity, but its function can be substituted by overexpressing Lgl. PMID:25053432

Morais-de-Sá, Eurico; Mukherjee, Avik; Lowe, Nick; St Johnston, Daniel

2014-08-01

433

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

434

Conducting the lasing of single transverse modes in a commercial multi-mode VCSEL by the beam-profile adapted optical feedback  

Microsoft Academic Search

This work studied the generation of single high-order transverse modes in a commercial multi-transverse mode VCSEL by applied beam-profile adapted optical feedback. To adapt the beam profile, the multi-transverse-mode beam profile of the solitary VCSEL was launched into a single-mode fiber, resulting in a quasi-Gaussian beam profile at the exit of fiber. The adapted beam passed through a spatial light

Yu-Heng Wu; Chuan-Pi Hsu; Da-Long Cheng; Wang-Chuang Kuo; Tsu Chiang Yen

2010-01-01

435

Temporal evolution of high-order transverse modes in a multi-mode VCSEL induced by a beam-profile optical feedback  

Microsoft Academic Search

This work studied the dynamics of the transverse modes in a multitransverse mode VCSEL when the later was conducted to lase the fundamental transverse mode by a Gaussian-beam-profile optical feedback. The multitransverse-mode beam profile of the solitary VCSEL was emitted into a single-mode fiber to achieve the Gaussian-beam-profile optical feedback. Afterward, a quasi-Gaussian beam fed back into the cavity of

Chuan-Pi Hsu; Da-Long Cheng; Wang-Chuang Kuo; Tsu Chiang Yen

2010-01-01

436

Optical hitless switches and all-state polarization controller with single-level proximity perturbation for high density photonic integrated circuits  

Microsoft Academic Search

This work demonstrates optical hitless switches and all-state polarization controller with single-level proximity perturbation. Design principles and fabrication steps are also presented. These devices offer practical applications in the field of high density photonic integrated circuits.

Rohit Chatterjee; Jordan Strauss; Xiaodong Yang; Chee Wei Wong

2004-01-01

437