WorldWideScience

Sample records for resonance spatial modulation

  1. Spatial Terahertz Modulator

    Science.gov (United States)

    Xie, Zhenwei; Wang, Xinke; Ye, Jiasheng; Feng, Shengfei; Sun, Wenfeng; Akalin, Tahsin; Zhang, Yan

    2013-11-01

    Terahertz (THz) technology is a developing and promising candidate for biological imaging, security inspection and communications, due to the low photon energy, the high transparency and the broad band properties of the THz radiation. However, a major encountered bottleneck is lack of efficient devices to manipulate the THz wave, especially to modulate the THz wave front. A wave front modulator should allow the optical or electrical control of the spatial transmission (or reflection) of an input THz wave and hence the ability to encode the information in a wave front. Here we propose a spatial THz modulator (STM) to dynamically control the THz wave front with photo-generated carriers. A computer generated THz hologram is projected onto a silicon wafer by a conventional spatial light modulator (SLM). The corresponding photo-generated carrier spatial distribution will be induced, which forms an amplitude hologram to modulate the wave front of the input THz beam. Some special intensity patterns and vortex beams are generated by using this method. This all-optical controllable STM is structure free, high resolution and broadband. It is expected to be widely used in future THz imaging and communication systems.

  2. Integrated unaligned resonant modulator tuning

    Energy Technology Data Exchange (ETDEWEB)

    Zortman, William A.; Lentine, Anthony L.

    2017-10-03

    Methods and systems for tuning a resonant modulator are disclosed. One method includes receiving a carrier signal modulated by the resonant modulator with a stream of data having an approximately equal number of high and low bits, determining an average power of the modulated carrier signal, comparing the average power to a predetermined threshold, and operating a tuning device coupled to the resonant modulator based on the comparison of the average power and the predetermined threshold. One system includes an input structure, a plurality of processing elements, and a digital control element. The input structure is configured to receive, from the resonant modulator, a modulated carrier signal. The plurality of processing elements are configured to determine an average power of the modulated carrier signal. The digital control element is configured to operate a tuning device coupled to the resonant modulator based on the average power of the modulated carrier signal.

  3. Mie Resonance-Modulated Spatial Distributions of Photogenerated Carriers in Poly(3-hexylthiophene-2,5-diyl)/Silicon Nanopillars

    Science.gov (United States)

    Kim, Eunah; Cho, Yunae; Sohn, Ahrum; Hwang, Heewon; Lee, Y. U.; Kim, Kyungkon; Park, Hyeong-Ho; Kim, Joondong; Wu, J. W.; Kim, Dong-Wook

    2016-07-01

    Organic/silicon hybrid solar cells have great potential as low-cost, high-efficiency photovoltaic devices. The superior light trapping capability, mediated by the optical resonances, of the organic/silicon hybrid nanostructure-based cells enhances their optical performance. In this work, we fabricated Si nanopillar (NP) arrays coated with organic semiconductor, poly(3-hexylthiophene-2,5-diyl), layers. Experimental and calculated optical properties of the samples showed that Mie-resonance strongly concentrated incoming light in the NPs. Spatial mapping of surface photovoltage, i.e., changes in the surface potential under illumination, using Kelvin probe force microscopy enabled us to visualize the local behavior of the photogenerated carriers in our samples. Under red light, surface photovoltage was much larger (63 meV) on the top surface of a NP than on a planar sample (13 meV), which demonstrated that the confined light in the NPs produced numerous carriers within the NPs. Since the silicon NPs provide pathways for efficient carrier transportation, high collection probability of the photogenerated carriers near the NPs can be expected. This suggests that the optical resonance in organic/silicon hybrid nanostructures benefits not only broad-band light trapping but also efficient carrier collection.

  4. Regional left ventricular myocardial contraction abnormalities and asynchrony in patients with hypertrophic cardiomyopathy evaluated by magnetic resonance spatial modulation of magnetization myocardial tagging

    Energy Technology Data Exchange (ETDEWEB)

    Mishiro, Yuichiro; Oki, Takashi [Tokushima Univ. (Japan). School of Medicine; Iuchi, Arata [and others

    1999-06-01

    Global left ventricular (LV) pump function is generally preserved in patients with hypertrophic cardiomyopathy (HCM). However, it is unknown whether regional myocardial contractility is impaired, especially in nonhypertrophied regions. The purpose of this study was to evaluate regional LV myocardial contraction in patients with HCM using magnetic resonance (MR) spatial modulation of magnetization (SPAMM) myocardial tagging. The study group comprised 20 patients with asymmetric septal hypertrophy (HCM group) and 16 age-matched normal patients (control group), and data were collected using transthoracic M-mode and 2-dimensional echocardiography, and MR SPAMM myocardial tagging. The systolic strain ratio, maximum systolic strain velocity, and time from end-diastole to maximum systolic strain ({Delta}T) in the anterior, ventricular septal, inferior and lateral regions for 2 LV short-axis sections at the levels of the chordae tendineae and papillary muscles were measured at 50-ms intervals by MR myocardial tagging. The end-diastolic anterior and ventricular septal wall thicknesses and LV mass index were significantly different between the HCM and control groups. The systolic strain ratio for all 4 walls, particularly the anterior and ventricular septal regions, was significantly lower in the HCM group. In the HCM group, the maximum systolic strain velocity was significantly lower and {Delta}T was significantly shorter for all 4 walls, particularly the anterior and ventricular septal regions. The standard deviation for the {Delta}T, calculated from the {Delta}T for the 8 regions of the 2 LV short-axis sections, was significantly greater in the HCM group. In conclusion, regional LV myocardial contraction is impaired in both hypertrophied and nonhypertrophied regions, and systolic LV wall asynchrony occurs in patients with HCM. (author)

  5. Fast Resonance Frequency Modulation in Superconducting Stripline Resonator

    OpenAIRE

    Segev, Eran; Abdo, Baleegh; Shtempluck, Oleg; Buks, Eyal

    2006-01-01

    Fast resonance frequency modulation of a superconducting stripline resonator is investigated. The experiments are performed using a novel device which integrates a hot electron detector (HED) into a superconducting stripline ring resonator. Frequency modulation is demonstrated by both applying dc current or voltage to the HED, and by applying optical illumination, with modulation frequencies of up to 4.2GHz. Potential applications for such a device are in telecommunication, quantum cryptograp...

  6. Ultrafast Imaging using Spectral Resonance Modulation.

    Science.gov (United States)

    Huang, Eric; Ma, Qian; Liu, Zhaowei

    2016-04-28

    CCD cameras are ubiquitous in research labs, industry, and hospitals for a huge variety of applications, but there are many dynamic processes in nature that unfold too quickly to be captured. Although tradeoffs can be made between exposure time, sensitivity, and area of interest, ultimately the speed limit of a CCD camera is constrained by the electronic readout rate of the sensors. One potential way to improve the imaging speed is with compressive sensing (CS), a technique that allows for a reduction in the number of measurements needed to record an image. However, most CS imaging methods require spatial light modulators (SLMs), which are subject to mechanical speed limitations. Here, we demonstrate an etalon array based SLM without any moving elements that is unconstrained by either mechanical or electronic speed limitations. This novel spectral resonance modulator (SRM) shows great potential in an ultrafast compressive single pixel camera.

  7. Spatial filtering with surface plasmon resonance systems

    Science.gov (United States)

    Ghosh, A. K.; Siddharth, V.; Bhagat, M.; Aggarwal, S.; Anurag, P.; Jain, M.

    2007-09-01

    Surface plasmon resonance based sensors are most useful in measuring the refractive indices of biochemicals. In such sensors a beam of light obliquely incident at an interface of glass and metallic thin film excites resonant plasmon waves in the metal if the angle of incidence or the wavelength is selected properly. The resonance conditions are changed by the refractive indices of any material in contact with the metal film. When resonance occurs the light beam is absorbed strongly. We can easily show that the phenomenon of surface plasmon resonance in such a system acts as a high quality spatial notch or band rejection filter.

  8. Pulse shaping using a spatial light modulator

    CSIR Research Space (South Africa)

    Botha, N

    2009-07-01

    Full Text Available Femtosecond pulse shaping can be done by different kinds of pulse shapers, such as liquid crystal spatial light modulators (LC SLM), acousto optic modulators (AOM) and deformable and movable mirrors. A few applications where pulse shaping...

  9. Spatially coherent surface resonance states derived from magnetic resonances

    CERN Document Server

    Wei, Zeyong; Cao, Yang; Wu, Chao; Ren, Jinzhi; Hang, Zhihong; Chen, Hong; Zhang, Daozhong; Chan, C T

    2010-01-01

    A thin metamaterial slab comprising a dielectric spacer sandwiched between a metallic grating and a ground plane is shown to possess spatially coherent surface resonance states that span a large frequency range and can be tuned by structural and material parameters. They give rise to nearly perfect angle-selective absorption and thus exhibit directional thermal emissivity. Direct numerical simulations show that the metamaterial slab supports spatially coherent thermal emission in a wide frequency range that is robust against structural disorder.

  10. The combination of micro-resonators with spatially resolved ferromagnetic resonance

    Science.gov (United States)

    Schaffers, T.; Meckenstock, R.; Spoddig, D.; Feggeler, T.; Ollefs, K.; Schöppner, C.; Bonetti, S.; Ohldag, H.; Farle, M.; Ney, A.

    2017-09-01

    We present two new and complementary approaches to realize spatial resolution for ferromagnetic resonance (FMR) on the 100 nm-scale. Both experimental setups utilize lithographically fabricated micro-resonators. They offer a detection sensitivity that is increased by four orders of magnitude compared with resonator-based FMR. In the first setup, the magnetic properties are thermally modulated via the thermal near-field effect generated by the thermal probe of an atomic force microscope. In combination with lock-in detection of the absorbed microwave power in the micro-resonator, a spatial resolution of less than 100 nm is achieved. The second setup is a combination of a micro-resonator with a scanning transmission x-ray microscope (STXM). Here a conventional FMR is excited by the micro-resonator while focused x-rays are used for a time-resolved snap-shot detection of the FMR excitations via the x-ray magnetic circular dichroism effect. This technique allows a lateral resolution of nominally 35 nm given by the STXM. Both experimental setups combine the advantage of low-power FMR excitation in the linear regime with high spatial resolution to study single and coupled nanomagnets. As proof-of-principle experiments, two perpendicular magnetic micro-stripes (5 μ m × 1 μ m) were grown and their FMR excitations were investigated using both setups.

  11. Spatial light modulation in compound semiconductor materials

    Science.gov (United States)

    Cheng, Li-Jen (Inventor); Gheen, Gregory O. (Inventor); Partovi, Afshin (Inventor)

    1990-01-01

    Spatial light modulation (22) in a III-V single crystal (12), e.g., gallium arsenide, is achieved using the photorefractive effect. Polarization rotation created by beam coupling is utilized in one embodiment. In particular, information (16)on a control beam (14) incident on the crystal is transferred to an input beam (10), also incident on the crystal. An output beam (18) modulated in intensity is obtained by passing the polarization-modulated input beam through a polarizer (20).

  12. On the mechanism of electrochemical modulation of plasmonic resonances

    Science.gov (United States)

    Shao, L.-H.; Ruther, M.; Linden, S.; Wegener, M.; Weissmüller, J.

    2012-09-01

    Recent electrochemical experiments on gold-based photonic metamaterials have shown a sizable reversible tuning and modulation of plasmonic resonances. Here, we study the mechanism of the electrochemical modulation by measuring the change of the resonance transmittance and resonance frequency during underpotential deposition of Pb, Cu, and electrosorption of OH. The electric resistance change of the resonators is identified as decisive for the resonance transmittance change, while the space-charge layer at the metal surface shifts the resonance frequency.

  13. Spatial light modulation for mode conditioning

    DEFF Research Database (Denmark)

    Glückstad, Jesper; Palima, Darwin

    We demonstrate patented techniques for generating tuneable complex field distributions for controllable coupling to high-order guided modes of micro-structured fibres. The optical Fourier transform of binary phase-only patterns which are encoded on a computer-controlled spatial light modulator...

  14. Gestalt factors modulate basic spatial vision.

    Science.gov (United States)

    Sayim, B; Westheimer, G; Herzog, M H

    2010-05-01

    Human perception of a stimulus varies depending on the context in which the stimulus is presented. Such contextual modulation has often been explained by two basic neural mechanisms: lateral inhibition and spatial pooling. In the present study, we presented observers with a vernier stimulus flanked by single lines; observers' ability to discriminate the offset direction of the vernier stimulus deteriorated in accordance with both explanations. However, when the flanking lines were part of a geometric shape (i.e., a good Gestalt), this deterioration strongly diminished. These findings cannot be explained by lateral inhibition or spatial pooling. It seems that Gestalt factors play an important role in contextual modulation. We propose that contextual modulation can be used as a quantitative measure to investigate the rules governing the grouping of elements into meaningful wholes.

  15. Spatial Modulation for MIMO Communication Systems

    Directory of Open Access Journals (Sweden)

    Reginaldo Nunes

    2012-11-01

    Full Text Available This work provides a review on the main spatial modulation (SM schemes, suitable to wireless communication systems. Performance, complexity and diversity gain of the three new spatial SM schemes suitable for multiple-input-multiple-output (MIMO communication systems are analyzed: a transmission scheme for spatial modulation (SM scheme; b space shift keying (SSK scheme; c generalized space shift keying (GSSK scheme. These three schemes offer low complexity, higher data rate when compared to single-input-single-output (SISO communication systems, as well as design flexibility, while exploits randomness characteristics of wireless communication channel for data transmission. The paper aims to explore the main features of those three SM schemes and to evaluate the inherent performance-complexity trade-off in order to determine which of those schemes results in a higher energy and spectral efficiencies.

  16. Cell culture device using spatial light modulator

    Science.gov (United States)

    Ou, Chung-Jen; Shen, Ching-I.; Ou, Chung-Ming

    2009-07-01

    Spatial light modulator is introduced for cell culturing and related illumination experiment. Two kinds of designs were used. The first type put the cell along with the bio-medium directly on top of the analyzer of the microdisplay and set a cover glass on it to retain the medium environment, which turned the microdisplay into a bio-container. The second type introduced an optical lens system placed below the spatial light modulator to focus the light spots on specific position. Details of the advantages and drawbacks for the two different approaches are discussed, and the human melanocyte cell (HMC) is introduced to prove the feasibility of the concept. Results indicate that the second type is much more suitable than the first for precision required application.

  17. Spatial Light Modulator for wavefront correction

    CERN Document Server

    Vyas, Akondi; Banyal, Ravinder Kumar; Prasad, B Raghavendra

    2009-01-01

    We present a liquid crystal method of correcting the phase of an aberrated wavefront using a spatial light modulator. A simple and efficient lab model has been demonstrated for wavefront correction. The crux of a wavefront correcting system in an adaptive optics system lies in the speed and the image quality that can be achieved. The speeds and the accuracy of wavefront representation using Zernike polynomials have been presented using a very fast method of computation.

  18. Electrothermal Frequency Modulated Resonator for Mechanical Memory

    KAUST Repository

    Hafiz, Md Abdullah Al

    2016-08-18

    In this paper, we experimentally demonstrate a mechanical memory device based on the nonlinear dynamics of an electrostatically actuated microelectromechanical resonator utilizing an electrothermal frequency modulation scheme. The microstructure is deliberately fabricated as an in-plane shallow arch to achieve geometric quadratic nonlinearity. We exploit this inherent nonlinearity of the arch and drive it at resonance with minimal actuation voltage into the nonlinear regime, thereby creating softening behavior, hysteresis, and coexistence of states. The hysteretic frequency band is controlled by the electrothermal actuation voltage. Binary values are assigned to the two allowed dynamical states on the hysteretic response curve of the arch resonator with respect to the electrothermal actuation voltage. Set-and-reset operations of the memory states are performed by applying controlled dc pulses provided through the electrothermal actuation scheme, while the read-out operation is performed simultaneously by measuring the motional current through a capacitive detection technique. This novel memory device has the advantages of operating at low voltages and under room temperature. [2016-0043

  19. Wave propagation in spatially modulated tubes

    CERN Document Server

    Ziepke, A; Engel, H

    2016-01-01

    We investigate wave propagation in rotationally symmetric tubes with a periodic spatial modulation of cross section. Using an asymptotic perturbation analysis, the governing quasi two-dimensional reaction-diffusion equation can be reduced into a one-dimensional reaction-diffusion-advection equation. Assuming a weak perturbation by the advection term and using projection method, in a second step, an equation of motion for traveling waves within such tubes can be derived. Both methods predict properly the nonlinear dependence of the propagation velocity on the ratio of the modulation period of the geometry to the intrinsic width of the front, or pulse. As a main feature, we can observe finite intervals of propagation failure of waves induced by the tube's modulation. In addition, using the Fick-Jacobs approach for the highly diffusive limit we show that wave velocities within tubes are governed by an effective diffusion coefficient. Furthermore, we discuss the effects of a single bottleneck on the period of pul...

  20. Wave propagation in spatially modulated tubes.

    Science.gov (United States)

    Ziepke, A; Martens, S; Engel, H

    2016-09-07

    We investigate wave propagation in rotationally symmetric tubes with a periodic spatial modulation of cross section. Using an asymptotic perturbation analysis, the governing quasi-two-dimensional reaction-diffusion equation can be reduced into a one-dimensional reaction-diffusion-advection equation. Assuming a weak perturbation by the advection term and using projection method, in a second step, an equation of motion for traveling waves within such tubes can be derived. Both methods predict properly the nonlinear dependence of the propagation velocity on the ratio of the modulation period of the geometry to the intrinsic width of the front, or pulse. As a main feature, we observe finite intervals of propagation failure of waves induced by the tube's modulation and derive an analytically tractable condition for their occurrence. For the highly diffusive limit, using the Fick-Jacobs approach, we show that wave velocities within modulated tubes are governed by an effective diffusion coefficient. Furthermore, we discuss the effects of a single bottleneck on the period of pulse trains. We observe period changes by integer fractions dependent on the bottleneck width and the period of the entering pulse train.

  1. Wave propagation in spatially modulated tubes

    Science.gov (United States)

    Ziepke, A.; Martens, S.; Engel, H.

    2016-09-01

    We investigate wave propagation in rotationally symmetric tubes with a periodic spatial modulation of cross section. Using an asymptotic perturbation analysis, the governing quasi-two-dimensional reaction-diffusion equation can be reduced into a one-dimensional reaction-diffusion-advection equation. Assuming a weak perturbation by the advection term and using projection method, in a second step, an equation of motion for traveling waves within such tubes can be derived. Both methods predict properly the nonlinear dependence of the propagation velocity on the ratio of the modulation period of the geometry to the intrinsic width of the front, or pulse. As a main feature, we observe finite intervals of propagation failure of waves induced by the tube's modulation and derive an analytically tractable condition for their occurrence. For the highly diffusive limit, using the Fick-Jacobs approach, we show that wave velocities within modulated tubes are governed by an effective diffusion coefficient. Furthermore, we discuss the effects of a single bottleneck on the period of pulse trains. We observe period changes by integer fractions dependent on the bottleneck width and the period of the entering pulse train.

  2. Method and apparatus for resonant frequency waveform modulation

    Science.gov (United States)

    Taubman, Matthew S [Richland, WA

    2011-06-07

    A resonant modulator device and process are described that provide enhanced resonant frequency waveforms to electrical devices including, e.g., laser devices. Faster, larger, and more complex modulation waveforms are obtained than can be obtained by use of conventional current controllers alone.

  3. Nonlinear Resonance Islands and Modulational Effects in a Proton Synchrotron

    Energy Technology Data Exchange (ETDEWEB)

    Satogata, Todd Jeffrey [Northwestern Univ., Evanston, IL (United States)

    1993-01-01

    We examine both one-dimensional and two-dimensional nonlinear resonance islands created in the transverse phase space of a proton synchrotron by nonlinear magnets. We also examine application of the theoretical framework constructed to the phenomenon of modulational diffusion in a collider model of the Fermilab Tevatron. For the one-dimensional resonance island system, we examine the effects of two types of modulational perturbations on the stability of these resonance islands: tune modulation and beta function modulation. Hamiltonian models are presented which predict stability boundaries that depend on only three paramders: the strength and frequency of the modulation and the frequency of small oscillations inside the resonance island. These. models are compared to particle tracking with excellent agreement. The tune modulation model is also successfully tested in experiment, where frequency domain analysis coupled with tune modulation is demonstrated to be useful in measuring the strength of a nonlinear resonance. Nonlinear resonance islands are also examined in two transverse dimensions in the presence of coupling and linearly independent crossing resonances. We present a first-order Hamiltonian model which predicts fixed point locations, but does not reproduce small oscillation frequencies seen in tracking; therefore in this circumstance such a model is inadequate. Particle tracking is presented which shows evidence of two-dimensional persistent signals, and we make suggestions on methods for observing such signals in future experiment.

  4. Modulation Speed Enhancement of Directly Modulated Lasers Using a Micro-ring Resonator

    DEFF Research Database (Denmark)

    An, Yi; Lorences Riesgo, Abel; Seoane, Jorge;

    2012-01-01

    A silicon micro-ring resonator is used to enhance the modulation speed of a 10-Gbit/s directly modulated laser to 40 Gbit/s, demonstrating a potentially integratable transmitter design for high-speed optical interconnects....

  5. Competing Turing and Faraday Instabilities in Longitudinally Modulated Passive Resonators.

    Science.gov (United States)

    Copie, François; Conforti, Matteo; Kudlinski, Alexandre; Mussot, Arnaud; Trillo, Stefano

    2016-04-08

    We experimentally investigate the interplay of Turing (modulational) and Faraday (parametric) instabilities in a bistable passive nonlinear resonator. The Faraday branch is induced via parametric resonance owing to a periodic modulation of the resonator dispersion. We show that the bistable switching dynamics is dramatically affected by the competition between the two instability mechanisms, which dictates two completely novel scenarios. At low detunings from resonance, switching occurs between the stable stationary lower branch and the Faraday-unstable upper branch, whereas at high detunings we observe the crossover between the Turing and Faraday periodic structures. The results are well explained in terms of the universal Lugiato-Lefever model.

  6. Resonant indirect exchange via spatially separated two-dimensional channel

    Energy Technology Data Exchange (ETDEWEB)

    Rozhansky, I. V., E-mail: rozhansky@gmail.com [Ioffe Institute, 194021 St. Petersburg (Russian Federation); Lappeenranta University of Technology, FI-53851 Lappeenranta (Finland); Peter the Great Saint-Petersburg Polytechnic University, 195251 St. Petersburg (Russian Federation); Krainov, I. V.; Averkiev, N. S. [Ioffe Institute, 194021 St. Petersburg (Russian Federation); Aronzon, B. A. [P.N. Lebedev Physical Institute, 119991 Moscow (Russian Federation); National Research Centre “Kurchatov Institute,” 123182 Moscow (Russian Federation); Davydov, A. B. [P.N. Lebedev Physical Institute, 119991 Moscow (Russian Federation); Kugel, K. I. [Institute for Theoretical and Applied Electrodynamics, Russian Academy of Sciences, 125412 Moscow (Russian Federation); Tripathi, V. [Tata Institute of Fundamental Research, Mumbai 400005 (India); Lähderanta, E. [Lappeenranta University of Technology, FI-53851 Lappeenranta (Finland)

    2015-06-22

    We apply the resonant indirect exchange interaction theory to explain the ferromagnetic properties of the hybrid heterostructure consisting of a InGaAs-based quantum well (QW) sandwiched between GaAs barriers with spatially separated Mn δ-layer. The experimentally obtained dependence of the Curie temperature on the QW depth exhibits a peak related to the region of resonant indirect exchange. We suggest the theoretical explanation and a fit to this dependence as a result of the two contributions to ferromagnetism—the intralayer contribution and the resonant exchange contribution provided by the QW.

  7. General Theoretical Model for Resonantly Enhanced Optical Modulators

    Institute of Scientific and Technical Information of China (English)

    Yuvaraja; S.; Visagathilagar; Arnan; Mitchell; Michael; W.; Austin

    2003-01-01

    1 IntroductionLiNbO3 optical modulators have become essential transmission devices for current and future wideband fibre-optic communications for both military and telecommunications applications. For many telecommunications applications, only a narrow bandwidth is required and thus resonantly enhancedMach-Zehndermodulators(RE-MZMs)have been developed to improve modulation efficiency at the expense of bandwidth.

  8. Spatial localization in nuclear magnetic resonance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Keevil, Stephen F [Department of Medical Physics, Guy' s and St Thomas' NHS Foundation Trust, Guy' s Hospital, London, SE1 9RT (United Kingdom); Division of Imaging Sciences, King' s College London, Guy' s Campus, London, SE1 9RT (United Kingdom)

    2006-08-21

    The ability to select a discrete region within the body for signal acquisition is a fundamental requirement of in vivo NMR spectroscopy. Ideally, it should be possible to tailor the selected volume to coincide exactly with the lesion or tissue of interest, without loss of signal from within this volume or contamination with extraneous signals. Many techniques have been developed over the past 25 years employing a combination of RF coil properties, static magnetic field gradients and pulse sequence design in an attempt to meet these goals. This review presents a comprehensive survey of these techniques, their various advantages and disadvantages, and implications for clinical applications. Particular emphasis is placed on the reliability of the techniques in terms of signal loss, contamination and the effect of nuclear relaxation and J-coupling. The survey includes techniques based on RF coil and pulse design alone, those using static magnetic field gradients, and magnetic resonance spectroscopic imaging. Although there is an emphasis on techniques currently in widespread use (PRESS, STEAM, ISIS and MRSI), the review also includes earlier techniques, in order to provide historical context, and techniques that are promising for future use in clinical and biomedical applications. (topical review)

  9. Magnetic Resonance Microscopy Spatially Resolved NMR Techniques and Applications

    CERN Document Server

    Codd, Sarah

    2008-01-01

    This handbook and ready reference covers materials science applications as well as microfluidic, biomedical and dental applications and the monitoring of physicochemical processes. It includes the latest in hardware, methodology and applications of spatially resolved magnetic resonance, such as portable imaging and single-sided spectroscopy. For materials scientists, spectroscopists, chemists, physicists, and medicinal chemists.

  10. Spatial attention modulates early face processing.

    Science.gov (United States)

    Feng, Wenfeng; Martinez, Antigona; Pitts, Michael; Luo, Yue-Jia; Hillyard, Steven A

    2012-12-01

    It is widely reported that inverting a face dramatically affects its recognition. Previous studies have shown that face inversion increases the amplitude and delays the latency of the face-specific N170 component of the event-related potential (ERP) and also enhances the amplitude of the occipital P1 component (latency 100-132 ms). The present study investigates whether these effects of face inversion can be modulated by visual spatial attention. Participants viewed two streams of visual stimuli, one to the left and one to the right of fixation. One stream consisted of a sequence of alphanumeric characters at 6.67 Hz, and the other stream consisted of a series of upright and inverted images of faces and houses presented in randomized order. The participants' task was to attend selectively to one or the other of the streams (during different blocks) in order to detect infrequent target stimuli. ERPs elicited by inverted faces showed larger P1 amplitudes compared to upright faces, but only when the faces were attended. In contrast, the N170 amplitude was larger to inverted than to upright faces only when the faces were not attended. The N170 peak latency was delayed to inverted faces regardless of attention condition. These inversion effects were face specific, as similar effects were absent for houses. These results suggest that early stages of face-specific processing can be enhanced by attention, but when faces are not attended the onset of face-specific processing is delayed until the latency range of the N170.

  11. Spatially resolved remote measurement of temperature by neutron resonance absorption

    Energy Technology Data Exchange (ETDEWEB)

    Tremsin, A.S., E-mail: ast@ssl.berkeley.edu [Space Sciences Laboratory, University of California at Berkeley, 7 Gauss Way, Berkeley, CA 94720 (United States); Kockelmann, W.; Pooley, D.E. [STFC, Rutherford Appleton Laboratory, ISIS Facility, Didcot OX11 0QX (United Kingdom); Feller, W.B. [NOVA Scientific, Inc., 10 Picker Road, Sturbridge, MA 01566 (United States)

    2015-12-11

    Deep penetration of neutrons into most engineering materials enables non-destructive studies of their bulk properties. The existence of sharp resonances in neutron absorption spectra enables isotopically-resolved imaging of elements present in a sample, as demonstrated by previous studies. At the same time the Doppler broadening of resonance peaks provides a method of remote measurement of temperature distributions within the same sample. This technique can be implemented at a pulsed neutron source with a short initial pulse allowing for the measurement of the energy of each registered neutron by the time of flight technique. A neutron counting detector with relatively high timing and spatial resolution is used to demonstrate the possibility to obtain temperature distributions across a 100 µm Ta foil with ~millimeter spatial resolution. Moreover, a neutron transmission measurement over a wide energy range can provide spatially resolved sample information such as temperature, elemental composition and microstructure properties simultaneously.

  12. Power meter ratio method of stabilizing a resonant modulator

    Science.gov (United States)

    Lentine, Anthony L.; Cox, Jonathan Albert

    2016-10-11

    Methods and systems for stabilizing a resonant modulator include receiving pre-modulation and post-modulation portions of a carrier signal, determining the average power from these portions, comparing an average input power to the average output power, and operating a heater coupled to the modulator based on the comparison. One system includes a pair of input structures, one or more processing elements, a comparator, and a control element. The input structures are configured to extract pre-modulation and post-modulation portions of a carrier signal. The processing elements are configured to determine average powers from the extracted portions. The comparator is configured to compare the average input power and the average output power. The control element operates a heater coupled to the modulator based on the comparison.

  13. High-speed FSK Modulator Using Switched-capacitor Resonators

    CERN Document Server

    Salehi, Mohsen

    2015-01-01

    In this paper, an ultra-fast frequency shift-keying (FSK) modulation technique based on switched capacitor resonators is presented. It is demonstrated that switching a reactive component such as a capacitor, in a high-Q resonator with proper switching signal can preserve the stored energy and shift it to a different frequency. Switching boundaries are found by continuity of electric charge and magnetic flux. It is shown that if switching time is synchronous with zero crossing of the voltage signal across the switched capacitor, impulsive components can be avoided and continuity of electric charge is satisfied without energy dissipation. We use this property to realize a fast binary frequency-shift keying (FSK) modulator with only a single RF source. In this technique, the modulation rate is independent of the resonator bandwidth and can be as high as the lower carrier frequency. Experimental results are presented to validate the simulations.

  14. Modulation scheme for electron-electron double resonance spectroscopy

    Science.gov (United States)

    Mehlkopf, A. F.; Kuiper, F. G.; Smidt, J.; Tiggelman, T. A.

    1983-06-01

    A modulation scheme for electron-electron double resonance (ELDOR) spectrometers is presented. With this scheme an optimum stabilization signal for locking the pump microwave generator to the pumped electron paramagnetic resonance (EPR) line is generated. A separate pump power level and a separate magnetic field modulation amplitude are used for the purpose of locking. In general, such a modulation scheme introduces false ELDOR lines. These false lines disturb the real ELDOR signals, or introduce an ELDOR signal in the absence of any communication between the observed EPR line and the pumped EPR line. With the described modulation scheme the frequencies of the false ELDOR signals are limited to even multiples of the frequency of the wanted ELDOR signals. This makes a suppression of the false ELDOR lines easy.

  15. Backward Masked Snakes and Guns Modulate Spatial Attention

    Directory of Open Access Journals (Sweden)

    Joshua M. Carlson

    2009-10-01

    Full Text Available Fearful faces are important social cues that alert others of potential threat. Even backward masked fearful faces facilitate spatial attention. However, visual stimuli other than fearful faces can signal potential threat. Indeed, unmasked snakes and spiders modulate spatial attention. Yet, it is unclear if the rapid threat-related facilitation of spatial attention to backward masked stimuli is elicited by non-face threat cues. Evolutionary theories claim that phylogenetic threats (i.e. snakes and spiders should preferentially elicit an automatic fear response, but it is untested as to whether this response extends to enhancements in spatial attention under restricted processing conditions. Thirty individuals completed a backward masking dot-probe task with both evolutionary relevant and irrelevant threat cues. The results suggest that backward masked visual fear stimuli modulate spatial attention. Both evolutionary relevant (snake and irrelevant (gun threat cues facilitated spatial attention.

  16. Observation of quantum entanglement using spatial light modulators.

    Science.gov (United States)

    Yao, Eric; Franke-Arnold, Sonja; Courtial, Johannes; Padgett, Miles J; Barnett, Stephen M

    2006-12-25

    We use spatial light modulators to observe the quantum entanglement of down-converted photon pairs. Acting as diffractive optical elements within one of the beams, they can be reconfigured in real time to set the spatial profile of the measured mode. Such configurations are highly applicable to the measurement of orbital angular momentum states or other spatial modes, such as those associated with quantum imaging.

  17. Efficient colored silicon solar modules using integrated resonant dielectric nanoscatterers

    Science.gov (United States)

    Neder, Verena; Luxembourg, Stefan L.; Polman, Albert

    2017-08-01

    We demonstrate photovoltaic modules with a bright green color based on silicon heterojunction solar cells integrated with arrays of light scattering dielectric nanoscatterers. Dense arrays of crystalline silicon nanocylinders, 100-120 nm wide, 240 nm tall, and 325 nm pitch, are made onto module cover slides using substrate-conformal soft-imprint lithography. Strong electric and magnetic dipolar Mie resonances with a narrow linewidth (Q ˜ 30) cause strong (35%-40%) specular light scattering on resonance (˜540 nm). The green color is observed over a wide range of angles (8°-75°). As the resonant nanoscatterers are transparent for the major fraction of the incident solar spectrum, the relative loss in short-circuit current is only 10%-11%. The soft-imprinted nanopatterns can be applied on full-size solar modules and integrated with conventional module encapsulation. The dielectric Mie resonances can be controlled by geometry, opening up a road for designing efficient colorful or white building-integrated photovoltaics.

  18. Time-of-flight detection of ultra-cold atoms using resonant frequency modulation imaging.

    Science.gov (United States)

    Hardman, K S; Wigley, P B; Everitt, P J; Manju, P; Kuhn, C C N; Robins, N P

    2016-06-01

    Resonant frequency modulation imaging is used to detect free falling ultra-cold atoms. A theoretical comparison of fluorescence imaging (FI) and frequency modulation imaging (FMI) is made, indicating that for low optical depth clouds, FMI accomplished a higher signal-to-noise ratio under conditions necessary for a 200 μm spatially resolved atom interferometer. A 750 ms time-of-flight measurement reveals near atom shot-noise limited number measurements of 2×106 Bose-condensed Rb87 atoms. The detection system is applied to high precision spinor BEC based atom interferometer.

  19. All-Optical Photochromic Spatial Light Modulators

    Science.gov (United States)

    Beratan, David N.; Perry, Joseph W.

    1989-01-01

    Photochemical transfer of electrons enables fast reading and writing. New concept based on transfer of electrons between donor and acceptor molecules randomly distributed or covalently linked and dispersed in glassy-polymer host material. Transfer causes significant changes in optical-transmission characteristics of material and used to modulate transmission of reading beam of light impinging on material.

  20. A low-voltage high-speed terahertz spatial light modulator using active metamaterial

    Science.gov (United States)

    Rout, Saroj; Sonkusale, Sameer R.

    2016-11-01

    An all solid-state metamaterial based terahertz (THz) spatial light modulator (SLM) is presented which uses high mobility 2DEG to manipulate the metamaterial resonant frequency (0.45 THz) leading to terahertz wave modulation. The 2DEG is created by embedding pseudomorphic high-electron mobility transistors in the capacitive gap of each electrical-LC resonator, allowing the charge density to be controlled with very low voltage (1 V) and modulating speeds up to 10 MHz while consuming sub-milliwatt power. We have demonstrated our SLM as a 2 × 2 pixel array operating around 0.45 THz by raster scanning a 6 × 6 image of an occluded metal object behind a thick polystyrene screen using a single-pixel THz imaging setup.

  1. Dynamic behavior and complexity of modulated optical micro ring resonator

    Institute of Scientific and Technical Information of China (English)

    Lei Yang; Wei Pan; Bin Luo; ShuiYing Xiang; Ning Jiang

    2011-01-01

    @@ The dynamic behavior of an optical micro ring resonator (OMRR) with an amplitude modulator positioned in the micro ring is investigated quantitatively by adopting a recently introduced quantifier, the permutation entropy (PE).The effects of modulation depth are focused on, and the roles of input power are considered.The two-dimensional (2D) maps of PE showing dependence on both modulation depth and input power are presented as well.PE values nearly increase with modulation depth.On the other hand, the optimal value of input power is achieved when the PE reaches its maximum.Thus, PE can successfully quantify the dynamics of modulated OMRR.Selecting the parameters in the region with high PE values would contribute to the complexity-enhanced OMRR-based chaotic communication systems.%The dynamic behavior of an optical micro ring resonator (OMRR) with an amplitude modulator positioned in the micro ring is investigated quantitatively by adopting a recently introduced quantifier, the permutation entropy (PE). The effects of modulation depth are focused on, and the roles of input power are considered. The two-dimensional (2D) maps of PE showing dependence on both modulation depth and input power are presented as well. PE values nearly increase with modulation depth. On the other hand, the optimal value of input power is achieved when the PE reaches its maximum. Thus, PE can successfully quantify the dynamics of modulated OMRR. Selecting the parameters in the region with high PE values would contribute to the complexity-enhanced OMRR-based chaotic communication systems.

  2. Control of resonant weak-light solitons via a periodic modulated control field.

    Science.gov (United States)

    Qi, Yihong; Niu, Yueping; Xiang, Yang; Jin, Shiqi; Gong, Shangqing

    2010-07-01

    We investigate propagation and control of weak-light spatial solitons in a resonant three-level atomic system with a periodic modulated control field. It is shown that the periodic modulation acts like periodic potential which resists the propagation of the soliton in transverse direction. The soliton could be trapped by the periodic potential in the input channel. When the modulation is canceled, the soliton propagates in its initial incident direction. The periodic modulation of control field could be used to control the propagation of the weak-light probe soliton. Due to the good localization efficiency of the periodic potential, an excellent switching is realized for the probe soliton. These properties may have potential applications in all-optical switching, optical information processing and other fields.

  3. The effect of spatial light modulator (SLM) dependent dispersion on spatial beam shaping

    CSIR Research Space (South Africa)

    Spangenberg, D-M

    2013-08-01

    Full Text Available SLMs used for spatial modulation of lasers are often used in conjunction with very narrow bandwidth laser light where diffractive dispersion could be approximated as a constant. It is known that diffractive dispersion is inversely proportional...

  4. Modulation of the Object/Background Interaction by Spatial Frequency

    Directory of Open Access Journals (Sweden)

    Yanju Ren

    2011-05-01

    Full Text Available With regard to the relationship between object and background perception in the natural scene images, functional isolation hypothesis and interactive hypothesis were proposed. Based on previous studies, the present study investigated the role of spatial frequency in the relationship between object and background perception in the natural scene images. In three experiments, participants reported the object, background, or both after seeing each picture for 500 ms followed by a mask. The authors found that (a backgrounds were identified more accurately when they contained a consistent rather than an inconsistent object, independently of spatial frequency; (b objects were identified more accurately in a consistent than an inconsistent background under the condition of low spatial frequencies but not high spatial frequencies; (c spatial frequency modulation remained when both objects and backgrounds were reported simultaneously. The authors conclude that object/background interaction is partially dependent on spatial frequency.

  5. Spatially modulated laser pulses for printing electronics.

    Science.gov (United States)

    Auyeung, Raymond C Y; Kim, Heungsoo; Mathews, Scott; Piqué, Alberto

    2015-11-01

    The use of a digital micromirror device (DMD) in laser-induced forward transfer (LIFT) is reviewed. Combining this technique with high-viscosity donor ink (silver nanopaste) results in laser-printed features that are highly congruent in shape and size to the incident laser beam spatial profile. The DMD empowers LIFT to become a highly parallel, rapidly reconfigurable direct-write technology. By adapting half-toning techniques to the DMD bitmap image, the laser transfer threshold fluence for 10 μm features can be reduced using an edge-enhanced beam profile. The integration of LIFT with this beam-shaping technique allows the printing of complex large-area patterns with a single laser pulse.

  6. Spatiotemporal structure of femtosecond Bessel beams from spatial light modulators.

    Science.gov (United States)

    Froehly, L; Jacquot, M; Lacourt, P A; Dudley, J M; Courvoisier, F

    2014-04-01

    We numerically investigate the spatiotemporal structure of Bessel beams generated with spatial light modulators (SLMs). Grating-like phase masks enable the spatial filtering of undesired diffraction orders produced by SLMs. Pulse front tilt and temporal broadening effects are investigated. In addition, we explore the influence of phase wrapping and show that the spatiotemporal structure of SLM-generated femtosecond Bessel beams is similar to Bessel X-pulses at short propagation distance and to subluminal pulsed Bessel beams at long propagation distance.

  7. Modulation of attosecond beating in resonant two-photon ionization

    CERN Document Server

    Galán, Álvaro J; Martín, Fernando

    2014-01-01

    We present a theoretical study of the photoelectron attosecond beating at the basis of RABBIT (Reconstruction of Attosecond Beating By Interference of Two-photon transitions) in the presence of autoionizing states. We show that, as a harmonic traverses a resonance, its sidebands exhibit a peaked phase shift as well as a modulation of the beating frequency itself. Furthermore, the beating between two resonant paths persists even when the pump and the probe pulses do not overlap, thus providing a sensitive non-holographic interferometric means to reconstruct coherent metastable wave packets. We characterize these phenomena quantitatively with a general finite-pulse analytical model that accounts for the effect of both intermediate and final resonances on two-photon processes, at a negligible computational cost. The model predictions are in excellent agreement with those of accurate ab initio calculations for the helium atom in the region of the N=2 doubly excited states.

  8. Transport driven by spatially modulated noise in a periodic tube

    Energy Technology Data Exchange (ETDEWEB)

    Ai Baoquan [Institute for Condensed Matter Physics, School of Physics and Telecommunication Engineering and Laboratory of Photonic Information Technology, South China Normal University, 510006 Guangzhou (China); Liu Lianggang [The Faculty of Information Technology, Macau University of Science and Technology, Macao (China)

    2007-07-04

    This paper investigates a three-dimensional periodic tube driven by spatially modulated Gaussian white noise. We derive an analytical expression for the net current by introducing entropic barriers. It is found that the phase shift between the entirely symmetric tube and noise modulation can break the symmetry of the generalized potential and induce directed transport. The sign of the current is determined by the phase shift. The current is a peaked function of the bottleneck radius. The interplay between the asymmetric tube and noise modulation can also induce a net current.

  9. Diffuserless holographic projection working on twin spatial light modulators.

    Science.gov (United States)

    Siemion, Andrzej; Sypek, Maciej; Suszek, Jarosław; Makowski, Michał; Siemion, Agnieszka; Kolodziejczyk, Andrzej; Jaroszewicz, Zbigniew

    2012-12-15

    An improved efficient projection of holographic images is presented. It uses two phase spatial light modulators (SLMs) with two iteratively optimized Fresnel holograms displayed simultaneously--each for one modulator. The phase distribution on the second modulator is taking into account the light distribution coming from the first one. A pixelated structure of the modulator and fluctuations of liquid-crystal molecules cause a zero-order peak that was separated in experiment. Use of two SLMs gives clear and containing almost no speckles images. Thanks to the compensation of phase distribution from the first modulator, we can abandon diffusers in the iterative process and that is why we can control both amplitude and phase distribution in the image plane independently.

  10. Stochasticity and Spatial Resonance in Interdecadal Climate Fluctuations.

    Science.gov (United States)

    Saravanan, R.; McWilliams, James C.

    1997-09-01

    Ocean-atmosphere interaction plays a key role in climate fluctuations on interdecadal timescales. In this study, different aspects of this interaction are investigated using an idealized ocean-atmosphere model, and a hierarchy of uncoupled and stochastic models derived from it. The atmospheric component is an eddy-resolving two-level global primitive equation model with simplified physical parameterizations. The oceanic component is a zonally averaged sector model of the thermohaline circulation. The coupled model exhibits spontaneous oscillations of the thermohaline circulation on interdecadal timescales. The interdecadal oscillation has qualitatively realistic features, such as dipolar sea surface temperature anomalies in the extratropics. Atmospheric forcing of the ocean plays a dominant role in exciting this oscillation. Although the coupled model is in itself deterministic, it is convenient to conceptualize the atmospheric forcing arising from weather excitation as having stochastic time dependence. Spatial correlations inherent in the atmospheric low-frequency variability play a crucial role in determining the oceanic interdecadal variability, through a form of spatial resonance. Local feedback from the ocean affects the amplitude of the interdecadal variability. The spatial patterns of correlations between the atmospheric flow and the oceanic variability fall into two categories: (i) upstream forcing patterns, and (ii) downstream response patterns. Both categories of patterns are expressible as linear combinations of the dominant modes of variability associated with the uncoupled atmosphere.

  11. High-speed laser modulation beyond the relaxation resonance frequency limit.

    Science.gov (United States)

    Sacher, Wesley D; Zhang, Eric J; Kruger, Brett A; Poon, Joyce K S

    2010-03-29

    We propose and show that for coupling modulated lasers (CMLs), in which the output coupler is modulated rather than the pump rate, the conventional relaxation resonance frequency limit to the laser modulation bandwidth can be circumvented. The modulation response is limited only by the coupler. Although CMLs are best suited to microcavities, as a proof-of-principle, a coupling-modulated erbium-doped fiber laser is modulated at 1 Gb/s, over 10000 times its relaxation resonance frequency.

  12. Spatially resolved resonant tunneling on single atoms in silicon

    Science.gov (United States)

    Voisin, B.; Salfi, J.; Bocquel, J.; Rahman, R.; Rogge, S.

    2015-04-01

    The ability to control single dopants in solid-state devices has opened the way towards reliable quantum computation schemes. In this perspective it is essential to understand the impact of interfaces and electric fields, inherent to address coherent electronic manipulation, on the dopants atomic scale properties. This requires both fine energetic and spatial resolution of the energy spectrum and wave-function, respectively. Here we present an experiment fulfilling both conditions: we perform transport on single donors in silicon close to a vacuum interface using a scanning tunneling microscope (STM) in the single electron tunneling regime. The spatial degrees of freedom of the STM tip provide a versatility allowing a unique understanding of electrostatics. We obtain the absolute energy scale from the thermal broadening of the resonant peaks, allowing us to deduce the charging energies of the donors. Finally we use a rate equations model to derive the current in presence of an excited state, highlighting the benefits of the highly tunable vacuum tunnel rates which should be exploited in further experiments. This work provides a general framework to investigate dopant-based systems at the atomic scale.

  13. Metadevice for intensity modulation with sub-wavelength spatial resolution

    CERN Document Server

    Cencillo-Abad, Pablo; Plum, Eric

    2016-01-01

    Effectively continuous control over propagation of a beam of light requires light modulation with pixelation that is smaller than the optical wavelength. Here we propose a spatial intensity modulator with sub-wavelength resolution in one dimension. The metadevice combines recent advances in reconfigurable nanomembrane metamaterials and coherent all-optical control of metasurfaces. It uses nanomechanical actuation of metasurface absorber strips placed near a mirror in order to control their interaction with light from perfect absorption to negligible loss, promising a path towards dynamic beam diffraction, light focusing and holography without unwanted diffraction artefacts.

  14. Optical particle trapping and dynamic manipulation using spatial light modulation

    DEFF Research Database (Denmark)

    Eriksen, René Lynge

    spots acting as tweezers beams are generated using phase-only spatial light modulation of an incident laser beam together with a generalized phase contrast (GPC) filter. The GPC method acts as a common-path interferometer, which converts encoded phase information into an appropriate intensity pattern...... suitable for optical trapping. A phaseonly spatial light modulator (SLM) is used for the phase encoding of the laser beam. The SLM is controlled directly from a standard computer where phase information is represented as gray-scale image information. Experimentally, both linear and angular movements...... proven capable of generating a phase pattern from an input amplitude distribution. The birefringent nature of liquid crystals in the SLM is utilized for the generation of an arbitrary two-dimensional state of polarization using two-cascaded SLMs. By means of elliptically polarized light, generated by one...

  15. Spatially modulated structures in nematic colloids: Statistical thermodynamics and kinetics.

    Science.gov (United States)

    Kleshchonok, A V; Reshetnyak, V Yu; Tatarenko, V A

    2011-03-01

    We examine the spatial distribution of rigid-sphere-like particles in a nematic host. Using a continuum model we analyse the conditions necessary for the appearance of a modulated lamellar structure. There is a long-range effective interaction between the particles, which can lead to the formation of superstructures. In general, this interaction includes several contributions: van der Waals-type direct interaction and indirect interaction via the director field distortions. The latter depends on the temperature of the sample, the coupling energy between a colloidal particle and a nematic host, and the particle concentration. This effective interaction controls the spatial structure and the kinetic properties of the system. We obtained the analytical expression for the temperature when the system loses the stability with respect to the modulated structure formation. Typical contours of the diffuse light scattering are presented.

  16. Spatially modulated instabilities of geometries with hyperscaling violation

    Energy Technology Data Exchange (ETDEWEB)

    Cremonini, Sera [DAMTP, Centre for Mathematical Sciences, University of Cambridge,Wilberforce Road, Cambridge, CB3 0WA (United Kingdom); George and Cynthia Mitchell Institute for Fundamental Physics and Astronomy,Texas A& M University,College Station, TX 77843-4242 (United States); Sinkovics, Annamaria [Institute of Theoretical Physics, MTA-ELTE Theoretical Physics Research Group,Eötvös Loránd University,1117 Budapest, Pázmány s. 1/A (Hungary)

    2014-01-17

    We perform a study of possible instabilities of the infrared AdS{sub 2}×ℝ{sup 2} region of solutions to Einstein-Maxwell-dilaton systems which exhibit an intermediate regime of hyperscaling violation and Lifshitz scaling. Focusing on solutions that are magnetically charged, we probe the response of the system to spatially modulated fluctuations, and identify regions of parameter space in which the infrared AdS{sub 2} geometry is unstable to perturbations. The conditions for the existence of instabilities translate to restrictions on the structure of the gauge kinetic function and scalar potential. In turn, these can lead to restrictions on the dynamical critical exponent z and on the amount of hyperscaling violation θ. Our analysis thus provides further evidence for the notion that the true ground state of ‘scaling’ solutions with hyperscaling violation may be spatially modulated phases.

  17. Data reconstructed of ultraviolet spatially modulated imaging spectrometer

    Science.gov (United States)

    Yuan, Xiaochun; Yu, Chunchao; Yang, Zhixiong; Yan, Min; Zeng, Yi

    2016-10-01

    With the advantages of fluorescence excitation and environmental adaptability simultaneously, Ultraviolet Image Spectroscopy has shown irreplaceable features in the field of latent target detection and become a current research focus. A design of Large Aperture Ultraviolet Spatially Modulated Imaging Spectrometer (LAUV-SMIS) based on image plane interferometer and offner system was first proposed in this paper. The data processing technology of time-spatial modulation FTIS in UV band has been studied. The latent fingerprint could be recognized clearly from the image since which is capable to meet the need of latent target detection. The spectral curve of the target could distinguish the emission peak at 253.7nm and 365nm when the low pressure and high pressure mercury lamp were used as the illuminator. Accurate spectral data of the target can be collected on the short and long wave ends of the working band.

  18. High contrast ratio, high uniformity multiple quantum well spatial light modulators

    Energy Technology Data Exchange (ETDEWEB)

    Huang Yuyang; Yang Chen; Yang Hui [Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Liu, H C; Cui Guoxin; Bian Lifeng; Zhang Yaohui [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215125 (China); Wasilewski, Z R; Buchanan, M; Laframboise, S R, E-mail: yhzhang2006@sinano.ac.c [Institute for Microstructural Sciences, National Research Council, Ottawa K1A 0R6 (Canada)

    2010-03-15

    Our latest research results on GaAs-AlGaAs multiple quantum well spatial light modulators are presented. The thickness uniformity of the epitaxial layers across the 3-inch wafer grown by our molecular beam epitaxy is better than 0.1% and the variation of cavity resonance wavelength within the wafer is only 0.9 nm. A contrast ratio (CR) of 102 by varying bias voltage from 0 to 6.7 V is achieved after fine tuning the cavity by etching an adjust layer. Both theoretical and experimental results demonstrate that incorporating an adjust layer is an effective tuning method for obtaining high CR. (semiconductor integrated circuits)

  19. Method to measure the phase modulation characteristics of a liquid crystal spatial light modulator.

    Science.gov (United States)

    Wu, Yunlong; Nie, Jinsong; Shao, Li

    2016-11-01

    The universal liquid crystal spatial light modulator (LC-SLM) is widely used in many aspects of optical studies. The working principles and applications of LC-SLM were introduced briefly. The traditional Twyman-Green interference method, which was used to measure the phase modulation characteristics of a liquid spatial light modulator, had some obvious disadvantages in practice. To avoid these issues, the traditional Twyman-Green interference method was improved. Also, a new method to process interference fringes and measure the shift distances and cycles automatically by computers was proposed. The phase modulation characteristics of P512-1064 LC-SLM produced by the Meadowlark Company were measured to verify the validity of the newly proposed method. In addition, in order to compensate and correct the nonlinear characteristics of the phase modulation curve, three universal inverse interpolation methods were utilized. The root mean squared error and residual sum of squares between the calibrated phase modulation curve and the ideal phase modulation curve were reduced obviously by taking advantage of the inverse interpolation methods. Subsequently, the method of shape-preserving subsection cubic interpolation had acquired the best performance with high computation efficiency. Experiments have been performed to verify the validity of the interpolation method. The experimental results showed that the phase modulation characteristics of LC-LSM could be acquired and calibrated automatically with convenience and high efficiency by utilizing the newly proposed processing method.

  20. Preparing arbitrary pure states of spatial qudits with a single phase-only spatial light modulator

    Science.gov (United States)

    Varga, J. J. M.; Solís-Prosser, A. M. A.; Rebón, L.; Arias, A.; Neves, L.; Iemmi, C.; Ledesma, S.

    2015-04-01

    We present a new method for preparing multidimensional spatial qudits by means of a single phase-only spatial light modulator (SLM). This method improves previous ones that use two SLMs, one working in amplitude regime and the other in phase regime. To that end, we addressed diffraction gratings on the slits that define the state and then we performed a spatial filtering in the Fourier plane. The amplitude of the coefficients of the quantum state are determined by the modulation deep of the diffraction gratings, and the relative phase is the mean phase value of the diffraction gratings. This encoding result to be more compact, less expensive and use the photons more efficiently.

  1. Residual intensity modulation in resonator fiber optic gyros with sinusoidal wave phase modulation

    Institute of Scientific and Technical Information of China (English)

    Di-qing YING; Qiang LI; Hui-lian MA; Zhong-he JIN

    2014-01-01

    We present how residual intensity modulation (RIM) affects the performance of a resonator fiber optic gyro (R-FOG) through a sinusoidal wave phase modulation technique. The expression for the R-FOG system’s demodulation curve under RIM is obtained. Through numerical simulation with different RIM coefficients and modulation frequencies, we find that a zero deviation is induced by the RIM effect on the demodulation curve, and this zero deviation varies with the RIM coefficient and modulation frequency. The expression for the system error due to this zero deviation is derived. Simulation results show that the RIM-induced error varies with the RIM coefficient and modulation frequency. There also exists optimum values for the RIM coefficient and modulation frequency to totally eliminate the RIM-induced error, and the error increases as the RIM coefficient or modulation frequency deviates from its optimum value;however, in practical situations, these two parameters would not be exactly fixed but fluctuate from their respective optimum values, and a large system error is induced even if there exists a very small deviation of these two critical parameters from their optimum values. Simulation results indicate that the RIM-induced error should be con-sidered when designing and evaluating an R-FOG system.

  2. Modulation of mechanical resonance by chemical potential oscillation in graphene

    Science.gov (United States)

    Chen, Changyao; Deshpande, Vikram V.; Koshino, Mikito; Lee, Sunwoo; Gondarenko, Alexander; MacDonald, Allan H.; Kim, Philip; Hone, James

    2016-03-01

    The classical picture of the force on a capacitor assumes a large density of electronic states, such that the electrochemical potential of charges added to the capacitor is given by the external electrostatic potential and the capacitance is determined purely by geometry. Here we consider capacitively driven motion of a nano-mechanical resonator with a low density of states, in which these assumptions can break down. We find three leading-order corrections to the classical picture: the first of which is a modulation in the static force due to variation in the internal chemical potential; the second and third are changes in the static force and dynamic spring constant due to the rate of change of chemical potential, expressed as the quantum (density of states) capacitance. As a demonstration, we study capacitively driven graphene mechanical resonators, where the chemical potential is modulated independently of the gate voltage using an applied magnetic field to manipulate the energy of electrons residing in discrete Landau levels. In these devices, we observe large periodic frequency shifts consistent with the three corrections to the classical picture. In devices with extremely low strain and disorder, the first correction term dominates and the resonant frequency closely follows the chemical potential. The theoretical model fits the data with only one adjustable parameter representing disorder-broadening of the Landau levels. The underlying electromechanical coupling mechanism is not limited by the particular choice of material, geometry, or mechanism for variation in the chemical potential, and can thus be extended to other low-dimensional systems.

  3. The study of disk resonators diode modules, solid-state generators active

    Directory of Open Access Journals (Sweden)

    B. A. Kotserzhinskii

    1987-12-01

    Full Text Available The results of an experimental study of disk resonators diode modules, solid-state active microwave generators. The effect of current leads, as well as errors in the manufacture of resonators their characteristics.

  4. Frequency and Spatial Selectivity in Nuclear Magnetic Resonance Spectroscopy.

    Science.gov (United States)

    Friedrich, Jan O.

    1988-12-01

    Available from UMI in association with The British Library. Requires signed TDF. The techniques presented in this thesis are concerned with the high resolution nuclear magnetic resonance spectra of liquids. A selective pulse, shaped according to the first half of a Gaussian curve, is developed; it gives a very narrow absorption-mode excitation profile. This characteristics is used in developing selective coherence transfer experiments in which an individual transition is irradiated by the selective pulse followed by irradiation with an intense non-selective pulse. By stepping the irradiation frequency of the selective pulse along in small increments, this experiment produces results similar to conventional two-dimensional homonuclear correlation spectroscopy. Such a method allows selected spectral regions of a conventional two-dimensional spectrum to be examined under higher resolution while avoiding the restrictions imposed by the sampling theorem. The technique is also extended to a third frequency dimension by irradiating two transitions simultaneously before applying a non-selective pulse which yields correlations between three coupled nuclei. The remainder of this thesis introduces a spatial localisation method based on a "straddle coil": two parallel coaxial surface coils, one on each side of the sample and supplied with radiofrequency pulses of opposite phase. This configuration can be used for spatial localisation experiments by applying a sequence of equal and opposite prepulses before acquiring the signal. The prepulses saturate the nuclear spins in all sample regions except the sensitive volume close to the median plane where the radiofrequency fields from the two coils cancel. Pulse sequences are proposed that are insensitive to radiofrequency offset over an appreciable range. The location of the sensitive volume can be tracked across the sample in the axial dimension by changing the ratio of the radiofrequency currents in the two coils.

  5. Phase-only spatial light modulation by the reverse phase contrast method

    DEFF Research Database (Denmark)

    Glückstad, J.; Mogensen, P.C.; Eriksen, R.L.

    2002-01-01

    A new approach to phase-only spatial light modulation is proposed in which a given amplitude pattern can be converted into a spatially identical binary phase pattern. A spatial filtering approach is applied to transform spatial amplitude modulation into spatial phase modulation using the Reverse...... Phase Contrast (RPC) method. The analytical method for achieving this is outlined and experimental results are shown for the generation of a binary phase-only distribution using an amplitude spatial light modulator and a phase-only spatial filter....

  6. Phase modulation spectroscopy of space-charge wave resonances in Bi12SiO20

    DEFF Research Database (Denmark)

    Vasnetsov, M.; Buchhave, Preben; Lyuksyutov, S.

    1997-01-01

    A new experimental method for the study of resonance effects and space-charge wave excitation in photorefractive Bi12SiO20 crystals by using a combination of frequency detuning and phase modulation technique has been developed. The accuracy of the method allows a detection of resonance peaks...... and revealed its resonance dependence. A minimum of electric current through the sample corresponds to the main resonance detected by phase modulation technique....

  7. Free electromagnetic radiation from the graphene monolayer with spatially modulated conductivity in THz range

    Science.gov (United States)

    Gerasik, Vladimir; Wartak, Marek S.; Zhukov, Alexander V.; Belonenko, Mikhail B.

    2016-03-01

    An infinite graphene layer is known to support graphene surface plasmon polariton (GSP) confined at the interface between the two dielectric half-spaces. In the case of finite width graphene stripe, the termination of the graphene layer acts both as a scattering source and as a “mirror”, thus producing Fabry-Perot (FP)-type resonance. These resonant wavelengths in the presence of free-standing graphene stripe are investigated using the homogeneous convolution-type integral equation approach. The capabilities of the suggested numerical method are illustrated with the results for the transmission spectrum of TM electromagnetic waves travelling in the direction perpendicular to the graphene stripe. Special attention is paid to the case of spatially modulated conductivity of the graphene monolayer, and thus the feasibility of controlling the GSP response.

  8. The modulation of somatosensory resonance by psychopathic traits and empathy.

    Science.gov (United States)

    Marcoux, Louis-Alexandre; Michon, Pierre-Emmanuel; Voisin, Julien I A; Lemelin, Sophie; Vachon-Presseau, Etienne; Jackson, Philip L

    2013-01-01

    A large number of neuroimaging studies have shown neural overlaps between first-hand experiences of pain and the perception of pain in others. This shared neural representation of vicarious pain is thought to involve both affective and sensorimotor systems. A number of individual factors are thought to modulate the cerebral response to other's pain. The goal of this study was to investigate the impact of psychopathic traits on the relation between sensorimotor resonance to other's pain and self-reported empathy. Our group has previously shown that a steady-state response to non-painful stimulation is modulated by the observation of other people's bodily pain. This change in somatosensory response was interpreted as a form of somatosensory gating (SG). Here, using the same technique, SG was compared between two groups of 15 young adult males: one scoring very high on a self-reported measure of psychopathic traits [60.8 ± 4.98; Levenson's Self-Report Psychopathy Scale (LSRP)] and one scoring very low (42.7 ± 2.94). The results showed a significantly greater reduction of SG to pain observation for the high psychopathic traits group compared to the low psychopathic traits group. SG to pain observation was positively correlated with affective and interpersonal facet of psychopathy in the whole sample. The high psychopathic traits group also reported lower empathic concern (EC) scores than the low psychopathic traits group. Importantly, primary psychopathy, as assessed by the LSRP, mediated the relation between EC and SG to pain observation. Together, these results suggest that increase somatosensory resonance to other's pain is not exclusively explained by trait empathy and may be linked to other personality dimensions, such as psychopathic traits.

  9. A novel approach to probing in vivo metabolite relaxation: Linear quantification of spatially modulated magnetization.

    Science.gov (United States)

    Li, Linqing; Li, Ningzhi; An, Li; Shen, Jun

    2017-09-23

    Conventional sequences for metabolite transverse relaxation quantification all generally measure signal changes at different echo times (TEs). However, quantification results obtained via these conventional methods can be very different and are highly dependent on the type of sequence being applied. TE-dependent effects such as diffusion, macromolecule baseline, and J-coupling modulation contribute significantly to these differences. Here, we propose a novel technique-multiple flip angle pulse-driven ratio of longitudinal steady states (MARzss)-for preparing magnetization with T2 /T1 weighting. Using premeasured T1 values, T2 values for metabolites can thereby be determined. The measurement procedure does not require varying TE and is TE independent; T2 , diffusion, and J-coupling effects induced by the readout sequence are cancelled. Longitudinal steady states at different flip angles were prepared with trains of radio frequency pulses interspersed with field gradients. The resulting spatially modulated longitudinal magnetization was acquired with a PRESS readout module. A new linear equation for quantification of MARzss was derived from Bloch equations. By implementing this readout-independent method, T2 measurement of brain metabolites at 7T was demonstrated through Bloch simulations, phantom, and in vivo experiments. The proposed MARzss technique can be used to largely avoid multi-TE associated interference, including diffusion, macromolecules, and J modulation. This MARzss technology, which is uniquely insensitive to readout sequence type and TE, is a promising technique for more accurately probing in vivo metabolite relaxation. Magn Reson Med, 2017. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  10. Calculating potential fields using microchannel spatial light modulators

    Science.gov (United States)

    Reid, Max B.

    1993-01-01

    We describe and present experimental results of the optical calculation of potential field maps suitable for mobile robot navigation. The optical computation employs two write modes of a microchannel spatial light modulator (MSLM). In one mode, written patterns expand spatially, and this characteristic is used to create an extended two dimensional function representing the influence of the goal in a robot's workspace. Distinct obstacle patterns are written in a second, non-expanding, mode. A model of the mechanisms determining MSLM write mode characteristics is developed and used to derive the optical calculation time for full potential field maps. Field calculations at a few hertz are possible with current technology, and calculation time vs. map size scales favorably in comparison to digital electronic computation.

  11. Ferroelectrically driven spatial carrier density modulation in graphene.

    Science.gov (United States)

    Baeumer, Christoph; Saldana-Greco, Diomedes; Martirez, John Mark P; Rappe, Andrew M; Shim, Moonsub; Martin, Lane W

    2015-01-22

    The next technological leap forward will be enabled by new materials and inventive means of manipulating them. Among the array of candidate materials, graphene has garnered much attention; however, due to the absence of a semiconducting gap, the realization of graphene-based devices often requires complex processing and design. Spatially controlled local potentials, for example, achieved through lithographically defined split-gate configurations, present a possible route to take advantage of this exciting two-dimensional material. Here we demonstrate carrier density modulation in graphene through coupling to an adjacent ferroelectric polarization to create spatially defined potential steps at 180°-domain walls rather than fabrication of local gate electrodes. Periodic arrays of p-i junctions are demonstrated in air (gate tunable to p-n junctions) and density functional theory reveals that the origin of the potential steps is a complex interplay between polarization, chemistry, and defect structures in the graphene/ferroelectric couple.

  12. Preparing arbitrary pure states of spatial qudits with a single phase-only spatial light modulator

    CERN Document Server

    Solís-Prosser, M A; Varga, J J M; Rebón, L; Ledesma, S; Iemmi, C; Neves, L

    2013-01-01

    Spatial qudits are D-dimensional ($D\\geq 2$) quantum systems carrying information encoded in the discretized transverse momentum and position of single photons. We present a proof-of-principle demonstration of a method for preparing arbitrary pure states of such systems by using a single phase-only spatial light modulator (SLM). The method relies on the encoding of the complex transmission function corresponding to a given spatial qudit state onto a preset diffraction order of a phase-only grating function addressed at the SLM. Fidelities of preparation above 94% were obtained with this method, which is simpler, less costly, and more efficient than those that require two SLMs for the same purpose.

  13. High-resolution TFT-LCD for spatial light modulator

    Science.gov (United States)

    Lee, JaeWon; Kim, Yong-Hae; Byun, Chun-Won; Pi, Jae-Eun; Oh, Himchan; Kim, GiHeon; Lee, Myung-Lae; Chu, Hye-Yong; Hwang, Chi-Sun

    2014-06-01

    SLM with very fine pixel pitch is needed for the holographic display system. Among various kinds of SLMs, commercially available high resolution LCoS has been widely used as a spatial light modulator. But the size of commercially available LCoS SLM is limited because the manufacturing technology of LCoS is based on the semiconductor process developed on small size Si wafer. Recently very high resolution flat panel display panel (~500ppi) was developed as a "retina display". Until now, the pixel pitch of flat panel display is several times larger than the pixel pitch of LCoS. But considering the possibility of shrink down the pixel pitch with advanced lithographic tools, the application of flat panel display will make it possible to build a SLM with high spatial bandwidth product. We simulated High resolution TFT-LCD panel on glass substrate using oxide semiconductor TFT with pixel pitch of 20um. And we considered phase modulation behavior of LC(ECB) mode. The TFT-LCD panel is reflective type with 4-metal structure with organic planarization layers. The technical challenge for high resolution large area SLM will be discussed with very fine pixel.

  14. Spiral Waves and Multiple Spatial Coherence Resonances Induced by Colored Noise in Neuronal Network

    Institute of Scientific and Technical Information of China (English)

    唐昭; 李玉叶; 惠磊; 贾冰; 吉华光

    2012-01-01

    Gaussian colored noise induced spatial patterns and spatial coherence resonances in a square lattice neuronal network composed of Morris-Lecar neurons are studied. Each neuron is at resting state near a saddle-node bifurcation on invariant circle, coupled to its nearest neighbors by electronic coupling. Spiral waves with different structures and disordered spatial structures can be alternately induced within a large range of noise intensity. By calculating spatial structure function and signal-to-noise ratio (SNR), it is found that SNR values are higher when the spiral structures are simple and are lower when the spatial patterns are complex or disordered, respectively. SNR manifest multiple local maximal peaks, indicating that the colored noise can induce multiple spatial coherence resonances. The maximal SNR values decrease as the correlation time of the noise increases. These results not only provide an example of multiple resonances, but also show that Gaussian colored noise play constructive roles in neuronal network.

  15. Note: A frequency modulated wireless interrogation system exploiting narrowband acoustic resonator for remote physical quantity measurement.

    Science.gov (United States)

    Droit, C; Martin, G; Ballandras, S; Friedt, J-M

    2010-05-01

    We demonstrate the wireless conversion of frequency modulation to amplitude modulation by radio frequency resonators as means of accurately determining the resonance frequency of passive acoustoelectronic sensors. The emitted frequency modulated radio frequency pulses are generated by a pulsed radar for probing a surface acoustic wave based sensor. The sharp sign transition of the amplitude modulated received signal provides a signal on which a feedback loop is locked to monitor the resonance signal. The strategy is demonstrated using a full software implementation on a generic hardware, resulting in 2 Hz resolution at 1 s integration time limited by the proportional feedback loop.

  16. Modulating the Near Field Coupling through Resonator Displacement in Planar Terahertz Metamaterials

    Science.gov (United States)

    Mohan Rao, S. Jagan; Kumar, Deepak; Kumar, Gagan; Chowdhury, Dibakar Roy

    2016-10-01

    We present the effect of vertical displacements between the resonators inside the unit cell of planar coupled metamaterials on their near field coupling and hence on the terahertz (THz) wave modulation. The metamolecule design consists of two planar split- ring resonators (SRRs) in a unit cell which are coupled through their near fields. The numerically simulated transmission spectrum is found to have split resonances due to the resonance mode hybridization effect. With the increase in displacement between the near field coupled SRRs, this metamaterial system shows a transition from coupled to uncoupled state through merging of the split resonances to the single intrinsic resonance. We have used a semi-analytical model describing the effect of displacements between the resonators and determine that it can predict the numerically simulated results. The outcome could be useful in modulating the terahertz waves employing near field coupled metamaterials, hence, can be useful in the development of terahertz modulators and frequency tunable devices in future.

  17. Modulating the Near Field Coupling through Resonator Displacement in Planar Terahertz Metamaterials

    Science.gov (United States)

    Mohan Rao, S. Jagan; Kumar, Deepak; Kumar, Gagan; Chowdhury, Dibakar Roy

    2017-01-01

    We present the effect of vertical displacements between the resonators inside the unit cell of planar coupled metamaterials on their near field coupling and hence on the terahertz (THz) wave modulation. The metamolecule design consists of two planar split- ring resonators (SRRs) in a unit cell which are coupled through their near fields. The numerically simulated transmission spectrum is found to have split resonances due to the resonance mode hybridization effect. With the increase in displacement between the near field coupled SRRs, this metamaterial system shows a transition from coupled to uncoupled state through merging of the split resonances to the single intrinsic resonance. We have used a semi-analytical model describing the effect of displacements between the resonators and determine that it can predict the numerically simulated results. The outcome could be useful in modulating the terahertz waves employing near field coupled metamaterials, hence, can be useful in the development of terahertz modulators and frequency tunable devices in future.

  18. Nonlinear resonance phenomena of a doped fibre laser under cavity-loss modulation: Experimental demonstrations

    Indian Academy of Sciences (India)

    A Ghosh; B K Goswami; R Vijaya

    2010-11-01

    Our experiments with an erbium-doped fibre ring laser (CW, single transverse mode and multiaxial mode) with an intracavity LiNbO3 electro-optic modulator (EOM) display the characteristic features of a nonlinear oscillator (e.g., harmonic and period-2 sub-harmonic resonances) when the EOM driver voltage is modulated periodically. Harmonic resonance leads to period-1 bistability and hysteresis. Inside the period-2 sub-harmonic resonance region, the laser exhibits Feigenbaum sequence and generalized bistability.

  19. Optimized generation of spatial qudits by using a pure phase spatial light modulator

    Science.gov (United States)

    Varga, J. J. M.; Rebón, L.; Solís-Prosser, M. A.; Neves, L.; Ledesma, S.; Iemmi, C.

    2014-11-01

    We present a method for preparing arbitrary pure states of spatial qudits, namely, D-dimensional (D≥slant 2) quantum systems carrying information in the transverse momentum and position of single photons. For this purpose, a set of D slits with complex transmission are displayed on a spatial light modulator (SLM). In a recent work we have shown a method that requires a single phase-only SLM to control independently the complex coefficients which define the quantum state of dimension D. The amplitude information was codified by introducing phase gratings inside each slit, and the phase value of the complex transmission was added to the phase gratings. After a spatial filtering process, we obtained in the image plane the desired qudit state. Although this method has proven to be a good alternative to compact the previously reported architectures, it presents some features that could be improved. In this paper we present an alternative scheme to codify the required phase values that minimizes the effects of temporal phase fluctuations associated to the SLM where the codification is carried out. In this scheme, the amplitudes are set by appropriate phase gratings addressed at the SLM, while the relative phases are obtained by a lateral displacement of these phase gratings. We show that this method improves the quality of the prepared state and provides very high fidelities of preparation for any state. An additional advantage of this scheme is that a complete 2π modulation is obtained by shifting the grating by one period; hence the encoding is not limited by the phase modulation range achieved by the SLM. Numerical simulations, that take into account the phase fluctuations, show high fidelities for thousands of qubit states covering the whole Bloch sphere surface. Similar analyses are performed for qudits with D = 3 and D = 7.

  20. Spatial fluorescence cross correlation spectroscopy by means of a spatial light modulator

    CERN Document Server

    Blancquaert, Yoann; Derouard, Jacques; Delon, Antoine

    2008-01-01

    Spatial Fluorescence Cross Correlation Spectroscopy is a rarely investigated version of Fluorescence Correlation Spectroscopy, in which the fluorescence signals from differ-ent observation volumes are cross-correlated. In the reported experiments, two observation volumes, typically shifted by a few $\\mu$m, are produced, with a Spatial Light Modulator and two adjustable pinholes. We illustrated the feasibility and potentiality of this technique by: i) measuring molecular flows, in the range 0.2 - 1.5 $\\mu$m/ms, of solutions seeded with fluorescent nanobeads or rhodamine molecules (simulating active transport phenomenons); ii) investigating the perme-ability of phospholipidic membrane of Giant Unilamellar Vesicles versus hydrophilic or hydrophobic molecules (in that case the laser spots were set on both sides of the mem-brane). Theoretical descriptions are proposed together with a discussion about FCS based, alternative methods.

  1. Vanadium dioxide spatial light modulator for applications beyond 1200 nm

    Science.gov (United States)

    Anh Do, Phuong; Hendaoui, Ali; Mortazy, Ebrahim; Chaker, Mohamed; Haché, Alain

    2013-02-01

    Spatial light modulators based on vanadium dioxide are used to demonstrate all-optical spectral filtering in the near infrared, up to 1700 nm, with potential to application into the mid-infrared. By spectrally dispersing the shaped beam and transmitting the beam through a vanadium dioxide thin film, the transmission is modified by optically pumping the film locally with a laser beam. Heating causes the film to undergo an insulator-to-metal transition, along with a drop in transmission. The spectrum can be shaped by pumping with a beam at different location and/or different intensity profiles. The method is promising for longer wavelength since the film is more efficient further in the infrared.

  2. The tempo-spatially modulated polarization atmosphere Michelson interferometer.

    Science.gov (United States)

    Zhang, ChunMin; Zhu, HuaChun; Zhao, Baochang

    2011-05-09

    A space-based tempo-spatially modulated polarization atmosphere Michelson interferometer (TSMPAMI) is described. It uses the relative movement between the TSMPAMI and the measured target to change optical path difference. The acquisition method of interferogram is presented. The atmospheric temperatures and horizontal winds can be derived from the optical observations. The measurement errors of the winds and temperatures are discussed through simulations. In the presence of small-scale structures of the atmospheric fields, the errors are found to be significantly influenced by the mismatch of the scenes observed by the adjacent CCD sub-areas aligned along the orbiter's track during successive measurements due to the orbital velocity and the exposure time. For most realistic conditions of the orbit and atmosphere, however, the instrument is proven suitable for measuring the atmospheric parameters.

  3. Parallel optical interconnects utilizing VLSI/FLC spatial light modulators

    Science.gov (United States)

    Genco, Sheryl M.

    1991-12-01

    Interconnection architectures are a cornerstone of parallel computing systems. However, interconnections can be a bottleneck in conventional computer architectures because of queuing structures that are necessary to handle the traffic through a switch at very high data rates and bandwidths. These issues must find new solutions to advance the state of the art in computing beyond the fundamental limit of silicon logic technology. Today's optoelectronic (OE) technology in particular VLSI/FLC spatial light modulators (SLMs) can provide a unique and innovative solution to these issues. This paper reports on the motivations for the system, describes the major areas of architectural requirements, discusses interconnection topologies and processor element alternatives, and documents an optical arbitration (i.e., control) scheme using `smart' SLMs and optical logic gates. The network topology is given in section 2.1 `Architectural Requirements -- Networks,' but it should be noted that the emphasis is on the optical control scheme (section 2.4) and the system.

  4. Optimisation of arbitrary light beam generation with spatial light modulators

    Science.gov (United States)

    Radwell, Neal; Offer, Rachel F.; Selyem, Adam; Franke-Arnold, Sonja

    2017-09-01

    Phase only spatial light modulators (SLMs) have become the tool of choice for shaped light generation, allowing the creation of arbitrary amplitude and phase patterns. These patterns are generated using digital holograms and are useful for a wide range of applications as well as for fundamental research. There have been many proposed methods for optimal generation of the digital holograms, all of which perform well under ideal conditions. Here we test a range of these methods under specific experimental constraints, by varying grating period, filter size, hologram resolution, number of phase levels, phase throw and phase nonlinearity. We model beam generation accuracy and efficiency and show that our results are not limited to the specific beam shapes, but should hold for general beam shaping. Our aim is to demonstrate how to optimise and improve the performance of phase-only SLMs for experimentally relevant implementations.

  5. Soliton Formation in Whispering-Gallery-Mode Resonators via Input Phase Modulation

    CERN Document Server

    Taheri, Hossein; Wiesenfeld, Kurt; Adibi, Ali

    2014-01-01

    We propose a method for soliton formation in whispering-gallery-mode (WGM) resonators through input phase modulation. Our numerical simulations of a variant of the Lugiato-Lefever equation suggest that modulating the input phase at a frequency equal to the resonator free-spectral-range and at modest modulation depths provides a deterministic route towards soliton formation in WGM resonators without undergoing a chaotic phase. We show that the generated solitonic state is sustained when the modulation is turned off adiabatically. Our results support parametric seeding as a powerful means of control, besides input pump power and pump-resonance detuning, over frequency comb generation in WGM resonators. Our findings also help pave the path towards ultra-short pulse formation on a chip.

  6. Transillumination spatially modulated illumination microscopy for human chromosome imaging

    Science.gov (United States)

    Pitris, Costas; Heracleous, Peter; Patsalis, Philippos

    2005-03-01

    Human chromosome analysis is an essential task in cytogenetics, especially in prenatal screening, genetic syndrome diagnosis, cancer pathology research and mutagen dosimetry. Chromosomal analysis begins with the creation of a karyotype, which is a layout of chromosome images organized by decreasing size in pairs. Both manual and automatic classification of chromosomes are limited by the resolution of the microscope and imaging system used. One way to improve the results of classification and even detect subtleties now remaining undetected, is to enhance the resolution of the images. It is possible to achieve lateral resolution beyond the classical limit, by using spatially modulated illumination (SMI) in a wide-field, non-confocal microscope. In this case, the sample is illuminated with spatially modulated light, which makes normally inaccessible high-resolution information visible in the observed image by shifting higher frequencies within the OTF limits of the microscope. Although, SMI microscopes have been reported in the past, this manuscript reports the development of a transillumination microscope for opaque, non-fluorescent samples. The illumination path consisted of a light source illuminating a ruled grating which was subsequently imaged on the sample. The grating was mounted on a rotating and translating stage so that the magnification and rotation of the pattern could be adjusted. The imaging lens was a 1.25 NA oil immersion objective. Test samples showed resolution improvement, as judged from a comparison of the experimentally obtained FWHM. Further studies using smaller fringe distance or laser interference pattern illumination will be evaluated to further optimize the SMI results.

  7. Diffractive characteristics of the liquid crystal spatial light modulator

    Institute of Scientific and Technical Information of China (English)

    Cao Zhao-Liang; Mu Quan-Quan; Hu Li-Fa; Liu Yong-Gang; Xuan Li

    2007-01-01

    The liquid crystal spatial light modulator (LC SLM) is very suitable for wavefront correction and optical testing and can produce a wavefront with large phase change and high accuracy. The LC SLM is composed of thousands of pixels and the pixel size and shape have effects on the diffractive characteristics of the LC SLM. This paper investigates the pixel effect on the phase of the wavefront with the scalar diffractive theory. The results show that the maximum optical path difference modulation is 41 μm to produce the paraboloid wavefront with the peak to valley accuracy better than λ/10. Effects of the mismatch between the pixel and the period, and black matrix on the diffraction efficiency of the LC SLM are also analysed with the Fresnel phase lens model. The ability of the LC SLM is discussed for optical testing and wavefront correction based on the calculated results. It shows that the LC SLM can be used as a wavefront corrector and a compensator.

  8. Modulation properties of spatial three-waveguide system using weakly coupled mode theory

    Institute of Scientific and Technical Information of China (English)

    Yiling Sun; Jianxia Pan

    2007-01-01

    Based on the weakly coupled mode theory, the modulation properties of three-waveguide system are analyzed in general. We examine the modulation behavior for two cases that a voltage is applied on the beamlaunched waveguide or non-beam-launched waveguide. The analytical intensity distributions in both cases are given. Applications of the spatial multi-waveguide coupling systems include spatial light modulators,optical switches, optical interconnection, and spatial optical signal processing.

  9. Spatial confinement of ferromagnetic resonances in honeycomb antidot lattices

    Energy Technology Data Exchange (ETDEWEB)

    Krivoruchko, V.N., E-mail: krivoruc@gmail.com [Donetsk Physics and Technology Institute NAS of Ukraine, 72 R. Luxemburg Str., 83114 Donetsk (Ukraine); Marchenko, A.I., E-mail: marchalexx@gmail.com [Donetsk Physics and Technology Institute NAS of Ukraine, 72 R. Luxemburg Str., 83114 Donetsk (Ukraine)

    2012-09-15

    We report on a theoretical investigation of the magnetic static and dynamic properties of a thin ferromagnetic film with honeycomb lattice of circular antidots using micromagnetic simulations and analytical calculations. The theoretical model is based on the Landau-Lifshitz equations and directly accounts for the effects of the magnetic state nonuniformity. A direct calculation of local dynamic susceptibility tensor yields that the resonance spectra consist of four different quasi-uniform modes of the magnetization precession related to the confinement of magnetic domains by the hole mesh. Three of four resonant modes follow a two-fold variation with respect to the in-plane orientation of the applied magnetic field. The easy axes of these modes are mutually rotated by 60 Degree-Sign and combine to yield the apparent six-fold configurational anisotropy. Additionally, a mode with intrinsic six-fold symmetry behavior exists, as well. Micromagnetic calculations of the local dynamic susceptibility tensor allow identifying the magnetic unit cell areas/domains responsible for each resonance mode. - Highlights: Black-Right-Pointing-Pointer We study the magnetic static and dynamic properties of honeycomb antidot lattices. Black-Right-Pointing-Pointer Micromagnetic simulation and analytical calculation were used. Black-Right-Pointing-Pointer Four quasi-uniform precession modes exist in resonance spectra. Black-Right-Pointing-Pointer The antidot unit cell areas responsible for each resonance mode were identified.

  10. Stochastic resonance in a single-mode laser driven by frequency modulated signal and coloured noises

    Institute of Scientific and Technical Information of China (English)

    Jin Guo-Xiang; Zhang Liang-Ying; Cao Li

    2009-01-01

    By adding frequency modulated signals to the intensity equation of gain-noise model of the single-mode laser driven by two coloured noises which are correlated, this paper uses the linear approximation method to calculate the power spectrum and signal-to-noise ratio (SNR) of the laser intensity. The results show that the SNR appears typical stochastic resonance with the variation of intensity of the pump noise and quantum noise. As the amplitude of a modulated signal has effects on the SNR, it shows suppression, monotone increasing, stochastic resonance, and multiple stochastic resonance with the variation of the frequency of a carrier signal and modulated signal.

  11. Non-monotonic resonance in a spatially forced Lengyel-Epstein model

    Energy Technology Data Exchange (ETDEWEB)

    Haim, Lev [Physics Department, Ben-Gurion University of the Negev, Beer-Sheva 84105 (Israel); Department of Oncology, Soroka University Medical Center, Beer-Sheva 84101 (Israel); Hagberg, Aric [Center for Nonlinear Studies, Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Meron, Ehud [Physics Department, Ben-Gurion University of the Negev, Beer-Sheva 84105 (Israel); Department of Solar Energy and Environmental Physics, BIDR, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion 84990 (Israel)

    2015-06-15

    We study resonant spatially periodic solutions of the Lengyel-Epstein model modified to describe the chlorine dioxide-iodine-malonic acid reaction under spatially periodic illumination. Using multiple-scale analysis and numerical simulations, we obtain the stability ranges of 2:1 resonant solutions, i.e., solutions with wavenumbers that are exactly half of the forcing wavenumber. We show that the width of resonant wavenumber response is a non-monotonic function of the forcing strength, and diminishes to zero at sufficiently strong forcing. We further show that strong forcing may result in a π/2 phase shift of the resonant solutions, and argue that the nonequilibrium Ising-Bloch front bifurcation can be reversed. We attribute these behaviors to an inherent property of forcing by periodic illumination, namely, the increase of the mean spatial illumination as the forcing amplitude is increased.

  12. Transmission Property of Directly Modulated Signals Enhanced by a Micro-ring Resonator

    DEFF Research Database (Denmark)

    An, Yi; Lorences Riesgo, Abel; Seoane, Jorge;

    2012-01-01

    A silicon micro-ring resonator is used to enhance the modulation speed of a 10-Gbit/s directly modulated laser to 40 Gbit/s. The generated signal is transmitted error free over 4.5 km SSMF. Dispersion tolerance is also studied.......A silicon micro-ring resonator is used to enhance the modulation speed of a 10-Gbit/s directly modulated laser to 40 Gbit/s. The generated signal is transmitted error free over 4.5 km SSMF. Dispersion tolerance is also studied....

  13. Frequency Modulation Induced by using the Linear Phase Modulation Method used in a Resonator Micro-optic Gyro

    Institute of Scientific and Technical Information of China (English)

    HONG Ling-Fei; ZHANG Chun-Xi; FENG Li-Shuang; YU Huai-Yong; LEI Ming

    2012-01-01

    Resonator micro-optic gyro (R-MOG) sensing rotation angular-velocity is based on Sagnac effect.We present a frequency modulation (FM) induced by the analog triangle-waveform phase modulation (ATAW-PM) technique in an R-MOG.Compared with the traditional serrodyne phase modulation or digital phase modulation methods,the proposed modulation technique has the intrinsic advantage in free of sweeping-back or step-effect induced pulse noise.The influence on dynamic range and resolution of the R-MOG by the parameters of analog trianglewaveform is theoretically analyzed.Experiments are carried out on an R-MOG composed of an integrated optic resonator with a free spectral range (FSR) and a fitness (F) of 1.6GHz and 61,respectively.Dynamic range of ±500 deg/s and bias drift of 0.6 deg/s over 1 h and 0.05 deg/s for 60 s are reliably obtained.%Resonator micro-optic gyro (R-MOG) sensing rotation angular-velocity is based on Sagnac effect. We present a frequency modulation (FM) induced by the analog triangle-waveform phase modulation (ATAW-PM) technique in an R-MOG. Compared with the traditional serrodyne phase modulation or digital phase modulation methods, the proposed modulation technique has the intrinsic advantage in free of sweeping-back or step-effect induced pulse noise. The influence on dynamic range and resolution of the R-MOG by the parameters of analog triangle-waveform is theoretically analyzed. Experiments are carried out on an R-MOG composed of an integrated optic resonator with a free spectral range (FSR) and a Btness (F) of 1.6 GHz and 61, respectively. Dynamic range of ±500 deg/s and bias drift of 0.6deg/s over 1 h and 0.05deg/s for 60s are reliably obtained.

  14. Spatial Modulation Microscopy for Real-Time Imaging of Plasmonic Nanoparticles and Cells

    CERN Document Server

    Fairbairn, N; Carter, R; Fernandes, R; Kanaras, A G; Elliott, T J; Somekh, M G; Pitter, M C; Muskens, O L

    2012-01-01

    Spatial modulation microscopy is a technique originally developed for quantitative spectroscopy of individual nano-objects. Here, a parallel implementation of the spatial modulation microscopy technique is demonstrated based on a line detector capable of demodulation at kHz frequencies. The capabilities of the imaging system are shown using an array of plasmonic nanoantennas and dendritic cells incubated with gold nanoparticles.

  15. UV Microstereolithography System that uses Spatial Light Modulator Technology.

    Science.gov (United States)

    Chatwin, C; Farsari, M; Huang, S; Heywood, M; Birch, P; Young, R; Richardson, J

    1998-11-10

    A new stereophotolithography technique utilizing a spatial light modulator (SLM) to create three-dimensional components with a planar, layer-by-layer process of exposure is described. With this procedure it is possible to build components with dimensions in the range of 50 mum-50 mm and feature sizes as small as 5 mum with a resolution of 1 mum. A polysilicon thin-film twisted nematic SVGA SLM is used as the dynamic photolithographic mask. The system consists of eight elements: a UV laser light source, an optical shutter, beam-conditioning optics, a SLM, a multielement reduction lens system, a high-resolution translation stage, a control system, and a computer-aided-design system. Each of these system components is briefly described. In addition, the optical characteristics of commercially available UV curable resins are investigated with nondegenerate four-wave mixing. Holographic gratings were written at a wavelength of 351.1 nm and read at 632.8 nm to compare the reactivity, curing speed, shrinkage, and resolution of the resins. These experiments were carried out to prove the suitability of these photopolymerization systems for microstereolithography.

  16. Creating Airy beams employing a transmissive spatial light modulator

    CERN Document Server

    Latychevskaia, Tatiana; Fink, Hans-Werner

    2016-01-01

    We present a detailed study of two novel methods for shaping the light optical wavefront by employing a transmissive spatial light modulator (SLM). Conventionally, optical Airy beams are created by employing SLMs in the so-called all phase mode. In this mode, a cubic phase distribution is transferred onto an SLM and its Fourier transform generates an Airy beam. The Fourier transform is obtained at the back focal plane of the lens, by employing a physical lens behind the SLM. We show that such an approach fails when a transmissive SLM is used; we present an alternative method for creating Airy beams. In our method, a numerically simulated lens phase distribution is transferred directly onto the SLM, together with the cubic phase distribution. An Airy beam is obtained by the Fourier transform of the cubic phase distribution and is generated behind the SLM, at the focal plane of the numerical lens. We study the deflection properties of the so formed Airy beam and derive the formula for deflection of the intensit...

  17. Spatial Modulation Concept for Massive Multiuser MIMO Systems

    Directory of Open Access Journals (Sweden)

    Khaled M. Humadi

    2014-01-01

    Full Text Available This paper presents the concept of spatial modulation (SM scheme for massive multiuser MIMO (MU-MIMO system. We consider a MU-MIMO system where K users, each equipped with multiple antennas, are jointly serviced by a multiantenna base station transmitter (BSTx using appropriate precoding scheme at the BSTx. The main idea introduced here is the utilization of the user’s subchannel index corresponding to the precoding matrix used at the BSTx, to convey extra useful information. This idea has not been explored, and it provides significant throughput enhancements in a multiuser system with large number of users. We examine the performance of the proposed scheme by numerical simulations. The results show that as the number of users and the receiving antennas for each user increase, the overall system throughput gets better, albeit at the cost of some degradation in the BER performance due to interantenna interference (IAI experienced at the receiver. We then explore zero-padding approach that helps to remove these IAI, in order to alleviate the BER degradations.

  18. Calibration of spatial light modulators suffering from spatially varying phase response.

    Science.gov (United States)

    Engström, David; Persson, Martin; Bengtsson, Jörgen; Goksör, Mattias

    2013-07-01

    We present a method for converting the desired phase values of a hologram to the correct pixel addressing values of a spatial light modulator (SLM), taking into account detailed spatial variations in the phase response of the SLM. In addition to thickness variations in the liquid crystal layer of the SLM, we also show that these variations in phase response can be caused by a non-uniform electric drive scheme in the SLM or by local heating caused by the incident laser beam. We demonstrate that the use of a global look-up table (LUT), even in combination with a spatially varying scale factor, generally does not yield sufficiently accurate conversion for applications requiring highly controllable output fields, such as holographic optical trapping (HOT). We therefore propose a method where the pixel addressing values are given by a three-dimensional polynomial, with two of the variables being the (x, y)-positions of the pixels, and the third their desired phase values. The coefficients of the polynomial are determined by measuring the phase response in 8 × 8 sub-sections of the SLM surface; the degree of the polynomial is optimized so that the polynomial expression nearly replicates the measurement in the measurement points, while still showing a good interpolation behavior in between. The polynomial evaluation increases the total computation time for hologram generation by only a few percent. Compared to conventional phase conversion methods, for an SLM with varying phase response, we found that the proposed method increases the control of the trap intensities in HOT, and efficiently prevents the appearance of strong unwanted 0th order diffraction that commonly occurs in SLM systems.

  19. Angle-Resolved Resonant Photoemission as a Probe of Spatial Localization and Character of Electron States

    Science.gov (United States)

    Molodtsov, S. L.; Richter, M.; Danzenbächer, S.; Wieling, S.; Steinbeck, L.; Laubschat, C.

    1997-01-01

    Resonant photoemission (PE) in the angle-resolved mode is proposed as a method to determine the spatial localization and the angular momentum character of valence band states from on-resonance PE signals across the Brillouin zone. This technique is applied to study ordered films of La metal. The obtained experimental data agree well with the results of band-structure calculations and related eigenvector analysis.

  20. Spatial and spectral beam shaping with space-variant guided mode resonance filters.

    Science.gov (United States)

    Srinivasan, Pradeep; Poutous, Menelaos K; Roth, Zachary A; Yilmaz, Yigit O; Rumpf, Raymond C; Johnson, Eric G

    2009-10-26

    Novel all-dielectric beam shaping elements were developed based on guided mode resonance (GMR) filters. This was achieved by spatially varying the duty cycle of a hexagonal-cell GMR filter, to locally detune from the resonant condition, which resulted in modified wavelength dependent reflection and transmission profiles, across the device aperture. This paper presents the design, fabrication, and characterization of the device and compares simulations to experimental results.

  1. Modulation of attosecond beating by resonant two-photon transition

    CERN Document Server

    Galán, Álvaro Jiménez; Martín, Fernando

    2015-01-01

    We present an analytical model that characterizes two-photon transitions in the presence of autoionising states. We applied this model to interpret resonant RABITT spectra, and show that, as a harmonic traverses a resonance, the phase of the sideband beating significantly varies with photon energy. This phase variation is generally very different from the $\\pi$ jump observed in previous works, in which the direct path contribution was negligible. We illustrate the possible phase profiles arising in resonant two-photon transitions with an intuitive geometrical representation.

  2. Polymeric microring resonator based electro-optic modulator

    NARCIS (Netherlands)

    Leinse, Arne

    2005-01-01

    This thesis will describe the design, realization and characterization of an EO polymeric MR resonator, which was fabricated in the framework of a MESA+ Strategic Research Orientation TeraHertz and an IST project NAIS.

  3. Resonant delocalization and Bloch oscillations in modulated lattices.

    Science.gov (United States)

    El-Ganainy, R; Christodoulides, D N; Rüter, C E; Kip, D

    2011-04-15

    We study the propagation of light in Bloch waveguide arrays exhibiting periodic coupling interactions. Intriguing wave packet revival patterns as well as beating Bloch oscillations are demonstrated. A new resonant delocalization phase transition is also predicted.

  4. Electrical Modulation of Fano Resonance in Plasmonic Nanostructures Using Graphene

    DEFF Research Database (Denmark)

    Emani, Naresh K.; Chung, Ting-Fung; Kildishev, Alexander V.;

    2014-01-01

    Pauli blocking of interband transistions gives rise to tunable optical properties in single layer graphene (SLG). This effect is exploited in a graphene-nanoantenna hybrid device where Fano resonant plasmonic nanostructures are fabricated on top of a graphene sheet. The use of Fano resonant......-element simulations. Our approach can be used for development of next generation of tunable plasmonic and hybrid nanophotonic devices....

  5. Stochastic resonance at a subharmonic of a periodic modulation signal in solid-state lasers

    Energy Technology Data Exchange (ETDEWEB)

    Kravtsov, N V; Lariontsev, E G; Chekina, S N [D.V. Skobel' tsyn Institute of Nuclear Physics, M.V. Lomonosov Moscow State University, Moscow (Russian Federation)

    2013-10-31

    The stochastic excitation of a subharmonic of a periodic modulation signal in the intensity spectrum of a solid-state laser is experimentally studied upon modulation of the pump rate by the noise and periodic signal. The stochastic resonance (SR) is observed in the presence of bistability in the laser. The conditions for SR at a subharmonic of the periodic modulation signal are determined. (control of laser radiation parameters)

  6. Photo-generated metasurfaces for resonant and high modulation of terahertz signals.

    Science.gov (United States)

    Smaali, R; Taliercio, T; Centeno, E

    2016-08-15

    We theoretically demonstrate resonant modulation of terahertz (THz) waves with photo-designed metasurfaces. Our approach bypasses the short penetration length issue of the optical pump that prevents photo-generated thick metamaterials. We propose a three-layer semiconductor system of subwavelength thickness that presents 100% modulation of the reflection (or absorption) spectra at around 1 THz when optically actuated. This resonant modulation can be dynamically monitored at high frequency by the optical pump on a broad range of frequencies of Δν/ν=100%. Appropriate 2D photo-printed patterns make the system polarization insensitive and operational for a wide range of incident angles up to 65°.

  7. Off-resonant vibrational excitation: Orientational dependence and spatial control of photofragments

    DEFF Research Database (Denmark)

    Machholm, Mette; Henriksen, Niels Engholm

    2000-01-01

    -dependent response to the IR fields is due to the anharmonicity of the potential. A subsequent ultraviolet laser pulse in resonance at the outer turning point of the vibrational motion can then dissociate the oscillating molecules, all with the same orientation, leading to spatial control of the photofragment......Off-resonant and resonant vibrational excitation with short intense infrared (IR) laser pulses creates localized oscillating wave packets, but differs by the efficiency of the excitation and surprisingly by the orientational dependence. Orientational selectivity of the vibrational excitation...... of randomly oriented heteronuclear diatomic molecules can be obtained under simultaneous irradiation by a resonant and an off-resonant intense IR laser pulse: Molecules with one initial orientation will be vibrationally excited, while those with the opposite orientation will be at rest. The orientation...

  8. Improvement of the Spatial Amplitude Isotropy of a ^4He Magnetometer Using a Modulated Pumping Beam

    Science.gov (United States)

    Chéron, B.; Gilles, H.; Hamel, J.; Moreau, O.; Noël, E.

    1997-08-01

    Optically pumped magnetometers are scalar magnetometers. Contrary to vectoriel magnetometers, they measure the total magnetic field whatever the direction of the sensor. However, for some orientations of the magnetometer with respect to the magnetic field direction, the resonant signal vanishes and the measurement is impossible. In this paper we present a simple solution to reduce the amplitude spatial anisotropy and apply it to a ^4He magnetometer developed in our Laboratory. Les magnétomètres à pompage optique sont des magnétomètres scalaires. Contrairement aux magnétomètres vectoriels, ils mesurent le module du champ magnétique quelle que soit l'orientation du capteur dans l'espace. Cependant, pour certaines orientations du magnétomètre par rapport à la direction du champ à mesurer, l'amplitude du signal de résonance s'annule et la mesure devient impossible. Dans cet article, nous présentons une solution simple pour réduire l'anisotropie spatiale d'amplitude et nous l'appliquons à un magnétomètre à hélium-4 développé dans notre Laboratoire.

  9. Composite modulation of Fano resonance in plasmonic microstructures by electric-field and microcavity

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Fan; Wu, Chenyun; Yang, Hong [State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871 (China); Hu, Xiaoyong, E-mail: xiaoyonghu@pku.edu.cn; Gong, Qihuang [State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter, Beijing 100871 (China)

    2014-11-03

    Composite modulation of Fano resonance by using electric-field and microcavity simultaneously is realized in a plasmonic microstructure, which consists of a gold nanowire grating inserted into a Fabry-Perot microcavity composited of a liquid crystal layer sandwiched between two indium tin oxide layers. The Fano resonance wavelength varies with the applied voltage and the microcavity resonance. A large shift of 48 nm in the Fano resonance wavelength is achieved when the applied voltage is 20 V. This may provide a new way for the study of multi-functional integrated photonic circuits and chips based on plasmonic microstructures.

  10. Spatially resolved chemical reaction monitoring using magnetic resonance imaging.

    Science.gov (United States)

    Feindel, Kirk W

    2016-06-01

    Over the previous three decades, the use of MRI for studying dynamic physical and chemical processes of materials systems has grown significantly. This mini-review provides a brief introduction to relevant principles of MRI, including methods of spatial localization, factors contributing to image contrast, and chemical shift imaging. A few historical examples of (1) H MRI for reaction monitoring will be presented, followed by a review of recent research including (1) H MRI studies of gelation and biofilms, (1) H, (7) Li, and (11) B MRI studies of electrochemical systems, in vivo glucose metabolism monitored with (19) F MRI, and in situ temperature monitoring with (27) Al MRI. Copyright © 2015 John Wiley & Sons, Ltd.

  11. Internal resonances in periodically modulated long Josephson junctions

    DEFF Research Database (Denmark)

    Larsen, Britt Hvolbæk; Mygind, Jesper; Ustinov, Alexey V.

    1995-01-01

    Current-voltage (I-V) characteristics of long Josephson junctions with a periodic lattice of localized inhomogeneities are studied. The interaction between the moving fluxons and the inhomogeneities causes resonant steps in the IV-curve. Some of these steps are due to a synchronization to resonan...... into account the interaction between the resonance in the sub-junction and the magnetic flux density waves excited in the whole junction is given....... Fiske modes in the sub-junctions formed between the inhomogeneities. The voltage positions of the resonant steps oscillate as function of the applied magnetic field with a period corresponding to the inclusion of one magnetic flux quantum, Φ0=h/2e, per sub-junction. A qualitative explanation that takes...

  12. Localized one-dimensional single voxel magnetic resonance spectroscopy without J coupling modulations.

    Science.gov (United States)

    Lin, Yanqin; Lin, Liangjie; Wei, Zhiliang; Zhong, Jianhui; Chen, Zhong

    2016-12-01

    To acquire single voxel localized one-dimensional (1) H magnetic resonance spectroscopy (MRS) without J coupling modulations, free from amplitude and phase distortions. A pulse sequence, named PRESSIR, is developed for volume localized MRS without J modulations at arbitrary echo time (TE). The J coupling evolution is suppressed by the J-refocused module that uses a 90° pulse at the midpoint of a double spin echo. The localization performance of the PRESSIR sequence was tested with a two-compartment phantom. The proposed sequence shows similar voxel localization accuracy as PRESS. Both PRESSIR and PRESS sequences were performed on MRS brain phantom and pig brain tissue. PRESS spectra suffer from amplitude and phase distortions due to J modulations, especially under moderate and long TEs, while PRESSIR spectra are almost free from distortions. The PRESSIR sequence proposed herein enables the acquisition of single voxel in-phase MRS within a single scan. It allows an enhanced signal intensity of J coupling metabolites and reducing undesired broad resonances with short T2s while suppressing J modulations. Moreover, it provides an approach for direct measurement of nonoverlapping J coupling peaks and of transverse relaxation times T2s. Magn Reson Med 76:1661-1667, 2016. © 2015 International Society for Magnetic Resonance in Medicine. © 2015 International Society for Magnetic Resonance in Medicine.

  13. Transformation of the frequency-modulated continuous-wave field into a train of short pulses by resonant filters

    CERN Document Server

    Shakhmuratov, R N

    2016-01-01

    The resonant filtering method transforming frequency modulated radiation field into a train of short pulses is proposed to apply in optical domain. Effective frequency modulation can be achieved by electro-optic modulator or by resonant frequency modulation of the filter with a narrow absorption line. Due to frequency modulation narrow-spectrum CW radiation field is seen by the resonant filter as a comb of equidistant spectral components separated by the modulation frequency. Tuning narrow-bandwidth filter in resonance with $n$-th spectral component of the comb transforms the radiation field into bunches of pulses with $n$ pulses in each bunch. The transformation is explained by the interference of the coherently scattered resonant component of the field with the whole comb. Constructive interference results in formation of pulses, while destructive interference is seen as dark windows between pulses. It is found that the optimal thickness of the resonant filter is several orders of magnitude smaller than the...

  14. Spatial confinement of acoustic and optical waves in stubbed slab structure as optomechanical resonator

    Energy Technology Data Exchange (ETDEWEB)

    Li, Changsheng, E-mail: lcs135@163.com; Huang, Dan; Guo, Jierong

    2015-02-20

    We theoretically demonstrate that acoustic waves and optical waves can be spatially confined in the same micro-cavity by specially designed stubbed slab structure. The proposed structure presents both phononic and photonic band gaps from finite element calculation. The creation of cavity mode inside the band gap region provides strong localization of phonon and photon in the defect region. The practical parameters to inject cavity and work experimentally at telecommunication range are discussed. This structure can be precisely fabricated, hold promises to enhance acousto-optical interactions and design new applications as optomechanical resonator. - Highlights: • A resonator simultaneously supports acoustic and optical modes. • Strong spatial confinement and slow group velocity. • Potential to work as active optomechanical resonator.

  15. Spatial Damping of Propagating Kink Waves Due to Resonant Absorption: Effect of Background Flow

    CERN Document Server

    Soler, Roberto; Goossens, Marcel

    2011-01-01

    Observations show the ubiquitous presence of propagating magnetohydrodynamic (MHD) kink waves in the solar atmosphere. Waves and flows are often observed simultaneously. Due to plasma inhomogeneity in the perpendicular direction to the magnetic field, kink waves are spatially damped by resonant absorption. The presence of flow may affect the wave spatial damping. Here, we investigate the effect of longitudinal background flow on the propagation and spatial damping of resonant kink waves in transversely nonuniform magnetic flux tubes. We combine approximate analytical theory with numerical investigation. The analytical theory uses the thin tube (TT) and thin boundary (TB) approximations to obtain expressions for the wavelength and the damping length. Numerically, we verify the previously obtained analytical expressions by means of the full solution of the resistive MHD eigenvalue problem beyond the TT and TB approximations. We find that the backward and forward propagating waves have different wavelengths and ...

  16. Shaping and detecting mid-IR light with a spatial light modulator

    CSIR Research Space (South Africa)

    Maweza, Elijah L

    2016-10-01

    Full Text Available We demonstrate the operation and calibration of a spatial light modulator in the mid-IR region by creating and measuring the modal content and wavefront of structured light fields at 2um for the first time....

  17. Optimization of the sinusoidal phase modulation technique in resonant fiber optic gyro

    Science.gov (United States)

    Wang, Linglan; Li, Hanzhao; Zhang, Jianjie; Ma, Huilian; Jin, Zhonghe

    2017-03-01

    The sinusoidal wave phase modulation and demodulation have been widely used in the signal processing system of the resonant fiber optic gyro (RFOG). An appropriate selection of the modulation frequency is of great importance, for the frequency value directly affects the slope of the demodulation curve at the resonance point which carries the gyro output information. A large demodulation slope is pursued in a high-performance RFOG. In this paper, an analytical expression of the demodulation slope is for the first time deduced in both transmission-type and reflection-type fiber ring resonators without any approximation. The relationship between the slope value and the modulation frequency at the resonance point is accurately calculated. The calculated best modulation frequency maximizing the demodulation slope at the resonance point is different from previous widely used optimal frequency given by the Lorentzian approximation method. More importantly, both theoretical and experimental results indicate that the achieved maximal demodulation slope from the proposed analytical expression method is double of that obtaining from the Lorentzian approximation method.

  18. Characterization of mode group transfer matrix in multimode couplers using spatial light modulation

    Science.gov (United States)

    Stepniak, G.; Bunge, C. A.

    2016-09-01

    In this paper, spatial light modulation is applied to investigate the selective mode properties of multimode fibers (MMF) and MMF couplers. Spatial light modulator is applied only on the MMF input to excite a selected linearly polarized eigenmode of the MMF. At the system output the impulse and frequency response is studied. By an additional time separation of mode groups achieved during propagation in the MMF, a mode group to mode group transfer matrix of the MMF coupler can be obtained.

  19. Spatial Frequency Modulates the Degree of Illusory Second Flash Perception.

    Science.gov (United States)

    Takeshima, Yasuhiro; Gyoba, Jiro

    2015-01-01

    When a brief single flash is presented simultaneously with two brief beeps, the number of presented flashes is often perceived as two. This phenomenon is referred to as the fission illusion. Several effects related to the fission illusion have been investigated using both psychophysical and neurophysiological methods. The present study examined the effects of spatial frequency on the fission illusion. At a low spatial frequency, transient channels respond preferably; conversely, sustained channels respond preferably at a high spatial frequency. Sustained channels differ in temporal properties from transient channels and are characterized by poor temporal resolution and slow-onset responses. In our previous study, visual stimuli presented at a slow processing speed were not conducive to the fission illusion. Therefore, we hypothesized that the fission illusion would not be difficult to observe when using high spatial frequencies. The results indicated that the degree of the perceived illusory second flash was reduced when spatial frequency was high as compared to when it was is low. Furthermore, according to signal detection theory, this difference between high and low spatial frequencies was not attributed to participants' response biases. Therefore, the fission illusion likely will not occur in conditions of slow processing speed and long response latencies in sustained channels, which respond preferably to high spatial frequency stimuli. Overall, the results indicated that the fission illusion was affected by temporal characteristics of lower-order sensory processing stages.

  20. Signal Quality Enhancement of Directly- Modulated VCSELs Using a Micro-Ring Resonator Transfer Function

    DEFF Research Database (Denmark)

    An, Yi; Muller, M.; Estaran Tolosa, Jose Manuel

    2013-01-01

    A micro-ring resonator transfer function is used to enhance the quality of signals generated using directly modulated VCSELs. The scheme is demonstrated up to 25 Gbit/s with a 17.6-GHz VCSEL, with up to 10 dB sensitivity improvement.......A micro-ring resonator transfer function is used to enhance the quality of signals generated using directly modulated VCSELs. The scheme is demonstrated up to 25 Gbit/s with a 17.6-GHz VCSEL, with up to 10 dB sensitivity improvement....

  1. Strong Modulation of Infrared Light using Graphene Integration with Plasmonic Fano-Resonant Metasurfaces

    CERN Document Server

    Dabidian, Nima; Khanikaev, Alexander B; Tatar, Kaya; Trendafilov, Simeon; Mousavi, S Hossein; Magnuson, Carl; Ruoff, Rodney S; Shvets, Gennady

    2014-01-01

    Plasmonic metasurfaces represent a promising platform for enhancing light-matter interaction. Active control of the optical response of metasurfaces is desirable for applications such as beam-steering, modulators and switches, biochemical sensors, and compact optoelectronic devices. Here we use a plasmonic metasurface with two Fano resonances to enhance the interaction of infrared light with electrically controllable single layer graphene. It is experimentally shown that the narrow spectral width of these resonances, combined with strong light/graphene coupling, enables reflectivity modulation by nearly an order of magnitude leading to a modulation depth as large as 90%. . Numerical simulations demonstrate the possibility of strong active modulation of the phase of the reflected light while keeping the reflectivity nearly constant, thereby paving the way to tunable infrared lensing and beam steering

  2. Identify Dynamic Network Modules with Temporal and Spatial Constraints

    Energy Technology Data Exchange (ETDEWEB)

    Jin, R; McCallen, S; Liu, C; Almaas, E; Zhou, X J

    2007-09-24

    Despite the rapid accumulation of systems-level biological data, understanding the dynamic nature of cellular activity remains a difficult task. The reason is that most biological data are static, or only correspond to snapshots of cellular activity. In this study, we explicitly attempt to detangle the temporal complexity of biological networks by using compilations of time-series gene expression profiling data.We define a dynamic network module to be a set of proteins satisfying two conditions: (1) they form a connected component in the protein-protein interaction (PPI) network; and (2) their expression profiles form certain structures in the temporal domain. We develop the first efficient mining algorithm to discover dynamic modules in a temporal network, as well as frequently occurring dynamic modules across many temporal networks. Using yeast as a model system, we demonstrate that the majority of the identified dynamic modules are functionally homogeneous. Additionally, many of them provide insight into the sequential ordering of molecular events in cellular systems. We further demonstrate that identifying frequent dynamic network modules can significantly increase the signal to noise separation, despite the fact that most dynamic network modules are highly condition-specific. Finally, we note that the applicability of our algorithm is not limited to the study of PPI systems, instead it is generally applicable to the combination of any type of network and time-series data.

  3. Resonance of a Metal Drop under the Effect of Amplitude-Modulated High Frequency Magnetic Field

    Science.gov (United States)

    Guo, Jiahong; Lei, Zuosheng; Zhu, Hongda; Zhang, Lijie; Magnetic Hydrodynamics(Siamm) Team; Magnetic Mechanics; Engineering(Smse) Team

    2016-11-01

    The resonance of a sessile and a levitated drop under the effect of high frequency amplitude-modulated magnetic field (AMMF) is investigated experimentally and numerically. It is a new method to excite resonance of a metal drop, which is different from the case in the presence of a low-frequency magnetic field. The transient contour of the drop is obtained in the experiment and the simulation. The numerical results agree with the experimental results fairly well. At a given frequency and magnetic flux density of the high frequency AMMF, the edge deformations of the drop with an azimuthal wave numbers were excited. A stability diagram of the shape oscillation of the drop and its resonance frequency spectrum are obtained by analysis of the experimental and the numerical data. The results show that the resonance of the drop has a typical character of parametric resonance. The National Natural Science Foundation of China (No. 51274237 and 11372174).

  4. Beam splitter and combiner based on Bloch oscillations in spatially modulated waveguide arrays

    CERN Document Server

    Zhang, Yiqi; Zhong, Weiping; Wen, Feng; Guo, Yang; Guo, Yao; Lu, Keqing; Zhang, Yanpeng

    2014-01-01

    We numerically investigate the light beam propagation in periodic waveguide arrays which are elaborately modulated with certain structures. We find that the light beam may split, coalesce, deflect, and be localized during propagation in these spatially modulated waveguide arrays. All the phenomena originate from Bloch oscillations, and supply possible method for fabricating on-chip beam splitters and beam combiners.

  5. Light-induced spatial gratings created by unipolar attosecond pulses coherently interacting with a resonant medium

    Science.gov (United States)

    Arkhipov, R. M.; Arkhipov, M. V.; Pakhomov, A. V.; Babushkin, I.; Rosanov, N. N.

    2017-09-01

    Recently, the possibility of the creation, erasing and ultrafast control of polarization and population inversion gratings by sequences of few-cycle bipolar pulses interacting with a medium in a resonant and coherent way was predicted. In this case, the overlapping of pulses in the medium is not needed for the creation of gratings. In this paper, we study the possibility of the ultrafast creation and control of spatial periodic gratings in a resonant medium when subcycle unipolar pulses (that is ones containing the constant spectral component of an electric field) propagate in the coherent regime.

  6. Characterization of a High Efficiency, Ultrashort Pulse Shaper Incorporating a Reflective 4096-Element Spatial Light Modulator.

    Science.gov (United States)

    Field, Jeffrey J; Planchon, Thomas A; Amir, Wafa; Durfee, Charles G; Squier, Jeff A

    2007-10-15

    We demonstrate pulse shaping via arbitrary phase modulation with a reflective, 1×4096 element, liquid crystal spatial light modulator (SLM). The unique construction of this device provides a very high efficiency when the device is used for phase modulation only in a prism based pulse shaper, namely 85%. We also present a single shot characterization of the SLM in the spatial domain and a single shot characterization of the pulse shaper in the spectral domain. These characterization methods provide a detailed picture of how the SLM modifies the spectral phase of an ultrashort pulse.

  7. "Chess-board pattern" spatial modulation of magnetization. Assessment of myocardial function

    DEFF Research Database (Denmark)

    Thomsen, C

    1992-01-01

    Heart motion is a complex combination of translation, rotation, and concentric contraction. Evaluation of these complex motions has been difficult using conventional slice-selective methods. Noninvasive tagging of the heart has been obtained by the use of slice-selective radiofrequency pulses....... Through spatial modulation of the magnetization the entire image can be labeled in different patterns. Two new pulse sequences are presented, giving a chess-board like spatial modulation. These pulse sequences have several advantages compared with the previously published methods, as the modulation time...

  8. Rewards modulate saccade latency but not exogenous spatial attention.

    Directory of Open Access Journals (Sweden)

    Stephen eDunne

    2015-07-01

    Full Text Available The eye movement system is sensitive to reward. However, whilst the eye movement system is extremely flexible, the extent to which changes to oculomotor behaviour induced by reward paradigms persist beyond the training period or transfer to other oculomotor tasks is unclear. To address these issues we examined the effects of presenting feedback that represented small monetary rewards to spatial locations on the latency of saccadic eye movements, the time-course of learning and extinction of the effects of rewarding saccades on exogenous spatial attention and oculomotor IOR. Reward feedback produced a relative facilitation of saccadic latency in a stimulus driven saccade task which persisted for 3 blocks of extinction trials. However this hemifield-specific effect failed to transfer to peripheral cueing tasks. We conclude that rewarding specific spatial locations is unlikely to induce long-term, systemic changes to the human oculomotor or attention systems.

  9. Theory of Electro-optic Modulation via a Quantum Dot Coupled to a Nano-resonator

    CERN Document Server

    Majumdar, Arka; Faraon, Andrei; Vuckovic, Jelena

    2009-01-01

    In this paper, we analyze the performance of an electro-optic modulator based on a single quantum dot strongly coupled to a nano-resonator, where electrical control of the quantum dot frequency is achieved via quantum confined Stark effect. Using realistic system parameters, we show that modulation speeds of a few tens of GHz are achievable with this system, while the energy per switching operation can be as small as 0.5 fJ. In addition, we study the non-linear distortion, and the effect of pure quantum dot dephasing on the performance of the modulator.

  10. Laterally vibrating resonator based elasto-optic modulation in aluminum nitride

    Science.gov (United States)

    Ghosh, Siddhartha; Piazza, Gianluca

    2016-06-01

    An integrated strain-based optical modulator driven by a piezoelectric laterally vibrating resonator is demonstrated. The composite structure consists of an acoustic Lamb wave resonator, in which a photonic racetrack resonator is internally embedded to enable overlap of the guided optical mode with the induced strain field. Both types of resonators are defined in an aluminum nitride (AlN) thin film, which rests upon a layer of silicon dioxide in order to simultaneously define optical waveguides, and the structure is released from a silicon substrate. Lateral vibrations produced by the acoustic resonator are transferred through a partially etched layer of AlN, producing a change in the effective index of the guided wave through the interaction of the strain components with the AlN elasto-optic (p) coefficients. Optical modulation through the elasto-optic effect is demonstrated at electromechanically actuated frequencies of 173 MHz and 843 MHz. This device geometry further enables the development of MEMS-based optical modulators in addition to studying elasto-optic interactions in suspended piezoelectric thin films.

  11. Design and implementation of FPGA-based phase modulation control for series resonant inverters

    Indian Academy of Sciences (India)

    N Gayathri; M C Chandorkar

    2008-10-01

    Owing to the tremendous advances in the digital technology, and improved reliability and performance of the digital control mechanisms, this paper focuses on design and implementation of digital controller using FPGA-based circuit design approach. The digital controller proposed is designed for series resonant inverter used in DC–DC converter applications. Phase modulation technique is proposed for the realization of digital controller on FPGA. The Series Resonant Converter (SRC) is considered in this paper as a preferred converter topology for high power, high voltage power supplies. This paper studies the implementation of phase shift modulation technique using FPGA. The inverter designed, is IGBT based, and Zero Voltage Switching (ZVS) technique is implemented due to reduced stresses on devices and increased efficiency. The phase modulated series resonant inverters (PM-SRC) promotes ZVS operation when its switching frequency is greater than resonant frequency. The designed PM controller is realized using FPGA on which control algorithm and other features of a controller are developed. The series resonant inverter is built and tested for full load under open loop and closed loop conditions at a switching frequency of 20 kHz. The results are presented under varying load conditions. The simulation and the experimental results were found to match closely.

  12. Laterally vibrating resonator based elasto-optic modulation in aluminum nitride

    Directory of Open Access Journals (Sweden)

    Siddhartha Ghosh

    2016-06-01

    Full Text Available An integrated strain-based optical modulator driven by a piezoelectric laterally vibrating resonator is demonstrated. The composite structure consists of an acoustic Lamb wave resonator, in which a photonic racetrack resonator is internally embedded to enable overlap of the guided optical mode with the induced strain field. Both types of resonators are defined in an aluminum nitride (AlN thin film, which rests upon a layer of silicon dioxide in order to simultaneously define optical waveguides, and the structure is released from a silicon substrate. Lateral vibrations produced by the acoustic resonator are transferred through a partially etched layer of AlN, producing a change in the effective index of the guided wave through the interaction of the strain components with the AlN elasto-optic (p coefficients. Optical modulation through the elasto-optic effect is demonstrated at electromechanically actuated frequencies of 173 MHz and 843 MHz. This device geometry further enables the development of MEMS-based optical modulators in addition to studying elasto-optic interactions in suspended piezoelectric thin films.

  13. High speed polymer E-O modulator consisting of a MZI with a microring resonator

    NARCIS (Netherlands)

    Leinse, A.; Diemeer, M.B.J.; Rousseau, A.; Driessen, A.

    2005-01-01

    A Mach-Zehnder interferometer with an polymer electro-optic micro-ring resonator on one of its branches is realized in a polymer layerstack and characterized. Electro-optic coefficients of 10 pm/V and modulation frequencies of 1 GHz were measured.

  14. Suppression of electron spin-echo envelope modulation peaks in double quantum coherence electron spin resonance.

    Science.gov (United States)

    Bonora, Marco; Becker, James; Saxena, Sunil

    2004-10-01

    We show the use of the observer blind spots effect for the elimination of electron spin-echo envelope modulation (ESEEM) peaks in double quantum coherence (DQC) electron spin resonance (ESR). The suppression of ESEEM facilitates the routine and unambiguous extraction of distances from DQC-ESR spectra. This is also the first demonstration of this challenging methodology on commercial instrumentation.

  15. Enhanced spatial near-infrared modulation of graphene-loaded perfect absorbers using plasmonic nanoslits.

    Science.gov (United States)

    Cai, Yijun; Zhu, Jinfeng; Liu, Qing Huo; Lin, Timothy; Zhou, Jianyang; Ye, Longfang; Cai, Zhiping

    2015-12-14

    Modulating spatial near-infrared light for ultra-compact electro-optic devices is a critical issue in optical communication and imaging applications. To date, spatial near-infrared modulators based on graphene have been reported, but they showed limited modulation effects due to the relatively weak light-graphene interaction. In combination with graphene and metallic nanoslits, we design a kind of ultrathin near-infrared perfect absorber with enhanced spatial modulation effects and independence on a wide range of incident angles. The modulated spectral shift of central wavelength is up to 258.2 nm in the near-infrared range, which is more promising in applications than state-of-the-art devices. The modulation enhancement is attributed to the plasmonic nanoslit mode, in which the optical electric field is highly concentrated in the deep subwavelength scale and the light-graphene interaction is significantly strengthened. The physical insight is deeply revealed by a combination of equivalent circuit and electromagnetic field analysis. The design principles are not only crucial for spatial near-infrared modulators, but also provide a key guide for developing active near-infrared patch nanoantennas based on graphene.

  16. Parallel-coupled dual racetrack silicon micro-resonators for quadrature amplitude modulation.

    Science.gov (United States)

    Integlia, Ryan A; Yin, Lianghong; Ding, Duo; Pan, David Z; Gill, Douglas M; Jiang, Wei

    2011-08-01

    A parallel-coupled dual racetrack silicon micro-resonator structure is proposed and analyzed for M-ary quadrature amplitude modulation. The over-coupled, critically coupled, and under-coupled scenarios are systematically studied. Simulations indicate that only the over-coupled structures can generate arbitrary M-ary quadrature signals. Analytic study shows that the large dynamic range of amplitude and phase of a modulated over-coupled structure stems from the strong cross-coupling between two resonators, which can be understood through a delicate balance between the direct sum and the "interaction" terms. Potential asymmetries in the coupling constants and quality factors of the resonators are systematically studied. Compensations for these asymmetries by phase adjustment are shown feasible.

  17. Modulation equations for spatially periodic systems: derivation and solutions

    NARCIS (Netherlands)

    Schielen, R.; Doelman, A.

    2001-01-01

    We study a class of partial dierential equations in one spatial dimension, which can be seen as model equations for the analysis of pattern formation in physical systems dened on unbounded, weakly oscillating domains. We perform a linear and weakly nonlinear stability analysis for solutions that bif

  18. Modulation equations for spatially periodic systems: derivation and solutions

    NARCIS (Netherlands)

    Schielen, R.; Doelman, A.

    1996-01-01

    We study a class of partial dierential equations in one spatial dimension, which can be seen as model equations for the analysis of pattern formation in physical systems dened on unbounded, weakly oscillating domains. We perform a linear and weakly nonlinear stability analysis for solutions that bif

  19. Folded-Cavity Resonators as Key Elements for Optical Filtering and Low-Voltage Electroabsorption Modulation

    Science.gov (United States)

    Djordjev, Kostadin D.; Lin, Chao-Kun; Zhu, Jintian; Bour, David; Tan, Michael R.

    2006-09-01

    Folded-cavity (FC) resonators, which are based on shallow-etched ridge waveguides combined with four deeply etched turning mirrors, are designed and fabricated. The device consists of a resonant FC and a bus waveguide coupled to it through a directional coupler. Optical passive filters, based on this technology, exhibit quality factors in the excess of 5000, with a low insertion loss of 5 dB (including the input coupling loss to a fiber) and more than 15-dB extinction at resonance. When the filter is combined with an electroabsorption active region and is designed to operate in the overcoupled regime, a low-voltage/high-extinction-ratio resonant modulation becomes feasible. The resonant modulator exhibits a low insertion loss (greater than 22-dB extinction at resonance) and offers a low-voltage operation. A change in the applied voltage by 0.7 V (close to the critically coupled conditions) leads to a transmission change of more than 16 dB. Open eye diagrams at 12 Gb/s are presented. To decrease the insertion loss, multiple material bangaps are further monolithically integrated across the wafer by utilizing the quantum-well-intermixing techniques.

  20. POLIDENT: A Module for Generating Continuous-Energy Cross Sections from ENDF Resonance Data

    Energy Technology Data Exchange (ETDEWEB)

    Dunn, M.E.; Greene, N.M.

    2000-12-01

    POLIDENT (Point Libraries of Data from ENDF/B Tapes) is an AMPX module that accesses the resonance parameters from File 2 of an ENDF/B library and constructs the continuous-energy cross sections in the resonance energy region. The cross sections in the resonance range are subsequently combined with the File 3 background data to construct the cross-section representation over the complete energy range. POLIDENT has the capability to process all resonance reactions that are identified in File 2 of the ENDF/B library. In addition, the code has the capability to process the single- and multi-level Breit-Wigner, Reich-Moore and Adler-Adler resonance formalisms that are identified in File 2. POLIDENT uses a robust energy-mesh-generation scheme that determines the minimum, maximum and points of inflection in the cross-section function in the resolved-resonance region. Furthermore, POLIDENT processes all continuous-energy cross-section reactions that are identified in File 3 of the ENDF/B library and outputs all reactions in an ENDF/B TAB1 format that can be accessed by other AMPX modules.

  1. POLIDENT: A Module for Generating Continuous-Energy Cross Sections from ENDF Resonance Data

    Energy Technology Data Exchange (ETDEWEB)

    Dunn, M.E.

    2000-10-20

    POLIDENT (POint LIbraries of Data from ENDF/B Tapes) is an AMPX module that accesses the resonance parameters from File 2 of an ENDF/B library and constructs the continuous-energy cross sections in the resonance energy region. The cross sections in the resonance range are subsequently combined with the File 3 background data to construct the cross-section representation over the complete energy range. POLIDENT has the capability to process all resonance reactions that are identified in File 2 of the ENDF/B library. In addition, the code has the capability to process the single- and multi-level Breit-Wigner, Reich-Moore and Adler-Adler resonance formalisms that are identified in File 2. POLIDENT uses a robust energy-mesh-generation scheme that determines the minimum, maximum and points of inflection in the cross-section function in the resolved-resonance region. Furthermore, POLIDENT processes all continuous-energy cross-section reactions that are identified in File 3 of the ENDF/B library and outputs all reactions in an ENDF/B TAB1 format that can be accessed by other AMPX modules.

  2. Low-voltage high-speed coupling modulation in silicon racetrack ring resonators.

    Science.gov (United States)

    Yang, Rui; Zhou, Linjie; Zhu, Haike; Chen, Jianping

    2015-11-02

    We demonstrate a low-voltage high-speed modulator based on a silicon racetrack resonator with a tunable Mach-Zehnder interferometer coupler. Both static measurement and dynamic modulation experiment are carried out. The 3-dB electro-optic bandwidth is measured to be >30 GHz beyond the limit by the cavity photon lifetime. A 32 Gb/s on-off keying (OOK) modulation is realized under a peak-to-peak drive voltage as low as 0.4 V, and a 28 Gb/s binary phase-shift-keying (BPSK) modulation is realized with a drive voltage of 3 V. The low drive voltages results in low energy consumptions of ~13.3 fJ/bit and ~1.2 pJ/bit for OOK and BPSK modulations, respectively.

  3. Decoupling of excitation and receive coils in pulsed magnetic resonance using sinusoidal magnetic field modulation

    Science.gov (United States)

    Tseytlin, Mark; Epel, Boris; Sundramoorthy, Subramanian; Tipikin, Dmitriy; Halpern, Howard J.

    2016-11-01

    In pulsed magnetic resonance, the excitation power is many orders of magnitude larger than that induced by the spin system in the receiving coil or resonator. The receiver must be protected during and immediately after the excitation pulse to allow for the energy stored in the resonator to dissipate to a safe level. The time during which the signal is not detected, the instrumental dead-time, can be shortened by using magnetically decoupled excitation and receive coils. Such coils are oriented, with respect to each other, in a way that minimizes the total magnetic flux produced by one coil in the other. We suggest that magnetically decoupled coils can be isolated to a larger degree by tuning them to separate frequencies. Spins are excited at one frequency, and the echo signal is detected at another. Sinusoidal magnetic field modulation that rapidly changes the Larmor frequency of the spins between the excitation and detection events is used to ensure the resonance conditions for both coils. In this study, the relaxation times of trityl-CD3 were measured in a field-modulated pulsed EPR experiment and compared to results obtained using a standard spin echo method. The excitation and receive coils were tuned to 245 and 256.7 MHz, respectively. Using an available rapid-scan, cross-loop EPR resonator, we demonstrated an isolation improvement of approximately 20-30 dB due to frequency decoupling. Theoretical analysis, numerical simulations, and proof-of-concept experiments demonstrated that substantial excitation-detection decoupling can be achieved. A pulsed L-band system, including a small volume bi-modal resonator equipped with modulation coils, was constructed to demonstrate fivefold dead-time reduction in comparison with the standard EPR experiment. This was achieved by detuning of the excitation and receive coils by 26 MHz and using sinusoidal modulation at 480 kHz.

  4. Design and optimization of optical modulators based on graphene-on-silicon nitride microring resonators

    CERN Document Server

    Wu, Zeru; Zhang, Tianyou; Shao, Zengkai; Wen, Yuanhui; Xu, Pengfei; Zhang, Yanfeng; Yu, Siyuan

    2016-01-01

    In order to overcome the challenge of obtaining high modulation depth due to weak graphene-light interaction, a graphene-on-silicon nitride (SiNx) microring resonator based on graphene's gate-tunable optical conductivity is proposed and studied. Geometrical parameters of graphene-on-SiNx waveguide are systematically analyzed and optimized, yielding a loss tunability of 0.04 dB/{\\mu}m and an effective index variation of 0.0022. We explicitly study the interaction between graphene and a 40-{\\mu}m-radius microring resonator, where electro-absorptive and electro-refractive modulation are both taken into account. By choosing appropriate graphene coverage and coupling coefficient, a high modulation depth of over 40 dB with large fabrication tolerance is obtained.

  5. Design and optimization of optical modulators based on graphene-on-silicon nitride microring resonators

    Science.gov (United States)

    Wu, Zeru; Chen, Yujie; Zhang, Tianyou; Shao, Zengkai; Wen, Yuanhui; Xu, Pengfei; Zhang, Yanfeng; Yu, Siyuan

    2017-04-01

    In order to overcome the challenge of obtaining high modulation depth due to weak graphene–light interaction, a graphene-on-silicon nitride (SiNx) microring resonator based on graphene’s gate-tunable optical conductivity is proposed and studied. Geometrical parameters of graphene-on-SiNx waveguide are systematically analyzed and optimized, yielding a loss tunability of 0.04 dB μm‑1 and an effective index variation of 0.0022. We explicitly study the interaction between graphene and a 40 μm-radius microring resonator, where electro-absorptive and electro-refractive modulation are both taken into account. By choosing appropriate graphene coverage and coupling coefficient, a high modulation depth of over 40 dB with large fabrication tolerance is obtained.

  6. Signal modulating noise effect in bistable stochastic resonance systems and its analog simulation

    Institute of Scientific and Technical Information of China (English)

    XIAO Fang-hong; YAN Gui-rong; XIE Shi-cheng

    2006-01-01

    The effect of signal modulating noise in bistable stochastic resonance systems was studied theoretically and experimentally. A mathematical analysis was made on the bistable stochastic resonance model with small system parameters. An analogue circuit was designed to perform the effect. The effect of signal modulating noise was shown in the analog simulation experiment. The analog experiment was conducted for two sinusoidal signals with different frequencies. The results show that there are a sinusoidal component corresponding to the input sinusoidal signal and a noise component presented as a Wiener process corresponding to the input white noise in the system output. By properly selecting system parameters, the effect of signal modulating noise can be manifested in the system output.

  7. Exact solution to the steady-state dynamics of a periodically modulated resonator

    Directory of Open Access Journals (Sweden)

    Momchil Minkov

    2017-07-01

    Full Text Available We provide an analytic solution to the coupled-mode equations describing the steady-state of a single periodically modulated optical resonator driven by a monochromatic input. The phenomenology of this system was qualitatively understood only in the adiabatic limit, i.e., for low modulation speed. However, both in and out of this regime, we find highly non-trivial effects for specific parameters of the modulation. For example, we show complete suppression of the transmission even with zero detuning between the input and the static resonator frequency. We also demonstrate the possibility for complete, lossless frequency conversion of the input into the sideband frequencies, as well as for optimizing the transmitted signal towards a given target temporal waveform. The analytic results are validated by first-principle simulations.

  8. Astrocytic modulation of neuronal excitability through K(+) spatial buffering.

    Science.gov (United States)

    Bellot-Saez, Alba; Kékesi, Orsolya; Morley, John W; Buskila, Yossi

    2017-03-06

    The human brain contains two major cell populations, neurons and glia. While neurons are electrically excitable and capable of discharging short voltage pulses known as action potentials, glial cells are not. However, astrocytes, the prevailing subtype of glia in the cortex, are highly connected and can modulate the excitability of neurons by changing the concentration of potassium ions in the extracellular environment, a process called K(+) clearance. During the past decade, astrocytes have been the focus of much research, mainly due to their close association with synapses and their modulatory impact on neuronal activity. It has been shown that astrocytes play an essential role in normal brain function including: nitrosative regulation of synaptic release in the neocortex, synaptogenesis, synaptic transmission and plasticity. Here, we discuss the role of astrocytes in network modulation through their K(+) clearance capabilities, a theory that was first raised 50 years ago by Orkand and Kuffler. We will discuss the functional alterations in astrocytic activity that leads to aberrant modulation of network oscillations and synchronous activity.

  9. Collective oscillations in spatially modulated exciton-polariton condensate arrays

    Science.gov (United States)

    Tikhomirov, Andrey A.; Kanakov, Oleg I.; Altshuler, Boris L.; Ivanchenko, Mikhail V.

    2015-02-01

    We study collective dynamics of interacting centers of exciton-polariton condensation in presence of spatial inhomogeneity, as modeled by diatomic active oscillator lattices. The mode formalism is developed and employed to derive existence and stability criteria of plane wave solutions. It is demonstrated that k0 = 0 wave number mode with the binary elementary cell on a diatomic lattice possesses superior existence and stability properties. Decreasing net on-site losses (balance of dissipation and pumping) or conservative nonlinearity favors multistability of modes, while increasing frequency mismatch between adjacent oscillators detriments it. On the other hand, spatial inhomogeneity may recover stability of modes at high nonlinearities. Entering the region where all single-mode solutions are unstable we discover subsequent transitions between localized quasiperiodic, chaotic and global chaotic dynamics in the mode space, as nonlinearity increases. Importantly, the last transition evokes the loss of synchronization. These effects may determine lasing dynamics of interacting exciton-polariton condensation centers.

  10. Spatial coincidence modulates interaction between visual and somatosensory evoked potentials.

    Science.gov (United States)

    Schürmann, Martin; Kolev, Vasil; Menzel, Kristina; Yordanova, Juliana

    2002-05-07

    The time course of interaction between concurrently applied visual and somatosensory stimulation with respect to evoked potentials (EPs) was studied. Visual stimuli, either in the left or right hemifield, and electric stimuli to the left wrist were delivered either alone or simultaneously. Visual and somatosensory EPs were summed and compared to bimodal EPs (BiEP, response to actual combination of both modalities). Temporal coincidence of stimuli lead to sub-additive or over-additive amplitudes in BiEPs in several time windows between 75 and 275 ms. Additional effects of spatial coincidence (left wrist with left hemifield) were found between 75 and 300 ms and beyond 450 ms. These interaction effects hint at a temporo-spatial pattern of multiple brain areas participating in the process of multimodal integration.

  11. Ecologically relevant spatial memory use modulates hippocampal neurogenesis

    OpenAIRE

    LaDage, Lara D.; Roth, Timothy C.; Fox, Rebecca A.; Pravosudov, Vladimir V.

    2009-01-01

    The adult hippocampus in birds and mammals undergoes neurogenesis and the resulting new neurons appear to integrate structurally and functionally into the existing neural architecture. However, the factors underlying the regulation of new neuron production is still under scrutiny. In recent years, the concept that spatial memory affects adult hippocampal neurogenesis has gained acceptance, although results attempting to causally link memory use to neurogenesis remain inconclusive, possibly ow...

  12. Factors modulating social influence on spatial choice in rats.

    Science.gov (United States)

    Bisbing, Teagan A; Saxon, Marie; Sayde, Justin M; Brown, Michael F

    2015-07-01

    Three experiments examined the conditions under which the spatial choices of rats searching for food are influenced by the choices made by other rats. Model rats learned a consistent set of baited locations in a 5 × 5 matrix of locations, some of which contained food. In Experiment 1, subject rats could determine the baited locations after choosing 1 location because all of the baited locations were on the same side of the matrix during each trial (the baited side varied over trials). Under these conditions, the social cues provided by the model rats had little or no effect on the choices made by the subject rats. The lack of social influence on choices occurred despite a simultaneous social influence on rats' location in the testing arena (Experiment 2). When the outcome of the subject rats' own choices provided no information about the positions of other baited locations, on the other hand, social cues strongly controlled spatial choices (Experiment 3). These results indicate that social information about the location of food influences spatial choices only when those cues provide valid information that is not redundant with the information provided by other cues. This suggests that social information is learned about, processed, and controls behavior via the same mechanisms as other kinds of stimuli. (c) 2015 APA, all rights reserved).

  13. How to "hear" visual disparities: real-time stereoscopic spatial depth analysis using temporal resonance.

    Science.gov (United States)

    Porr, B; Cozzi, A; Wörgötter, F

    1998-05-01

    In a stereoscopic system, both eyes or cameras have a slightly different view. As a consequence, small variations between the projected images exist ('disparities') which are spatially evaluated in order to retrieve depth information (Sanger 1988; Fleet et al. 1991). A strong similarity exists between the analysis of visual disparities and the determination of the azimuth of a sound source (Wagner and Frost 1993). The direction of the sound is thereby determined from the temporal delay between the left and right ear signals (Konishi and Sullivan 1986). Similarly, here we transpose the spatially defined problem of disparity analysis into the temporal domain and utilize two resonators implemented in the form of causal (electronic) filters to determine the disparity as local temporal phase differences between the left and right filter responses. This approach permits real-time analysis and can be solved analytically for a step function contrast change, which is an important case in all real-world applications. The proposed theoretical framework for spatial depth retrieval directly utilizes a temporal algorithm borrowed from auditory signal analysis. Thus, the suggested similarity between the visual and the auditory system in the brain (Wagner and Frost 1993) finds its analogy here at the algorithmical level. We will compare the results from the temporal resonance algorithm with those obtained from several other techniques like cross-correlation or spatial phase-based disparity estimation showing that the novel algorithm achieves performances similar to the 'classical' approaches using much lower computational resources.

  14. Bi-Frequency Modulated Quasi-Resonant Converters: Theory and Applications

    Science.gov (United States)

    Zhang, Yuefeng

    1995-01-01

    To avoid the variable frequency operation of quasi -resonant converters, many soft-switching PWM converters have been proposed, all of them require an auxiliary switch, which will increase the cost and complexity of the power supply system. In this thesis, a new kind of technique for quasi -resonant converters has been proposed, which is called the bi-frequency modulation technique. By operating the quasi-resonant converters at two switching frequencies, this technique enables quasi-resonant converters to achieve the soft-switching, at fixed switching frequencies, without an auxiliary switch. The steady-state analysis of four commonly used quasi-resonant converters, namely, ZVS buck, ZCS buck, ZVS boost, and ZCS boost converter has been presented. Using the concepts of equivalent sources, equivalent sinks, and resonant tank, the large signal models of these four quasi -resonant converters were developed. Based on these models, the steady-state control characteristics of BFM ZVS buck, BFM ZCS buck, BFM ZVS boost, and BFM ZCS boost converter have been derived. The functional block and design consideration of the bi-frequency controller were presented, and one of the implementations of the bi-frequency controller was given. A complete design example has been presented. Both computer simulations and experimental results have verified that the bi-frequency modulated quasi-resonant converters can achieve soft-switching, at fixed switching frequencies, without an auxiliary switch. One of the application of bi-frequency modulation technique is for EMI reduction. The basic principle of using BFM technique for EMI reduction was introduced. Based on the spectral analysis, the EMI performances of the PWM, variable-frequency, and bi-frequency modulated control signals was evaluated, and the BFM control signals show the lowest EMI emission. The bi-frequency modulated technique has also been applied to the power factor correction. A BFM zero -current switching boost converter has

  15. The use of impedance matching capillaries for reducing resonance in rosette infrasonic spatial filters.

    Science.gov (United States)

    Hedlin, Michael A H; Alcoverro, Benoit

    2005-04-01

    Rosette spatial filters are used at International Monitoring System infrasound array sites to reduce noise due to atmospheric turbulence. A rosette filter consists of several clusters, or rosettes, of low-impedance inlets. Acoustic energy entering each rosette of inlets is summed, acoustically, at a secondary summing manifold. Acoustic energy from the secondary manifolds are summed acoustically at a primary summing manifold before entering the microbarometer. Although rosette filters have been found to be effective at reducing infrasonic noise across a broad frequency band, resonance inside the filters reduces the effectiveness of the filters at high frequencies. This paper presents theoretical and observational evidence that the resonance inside these filters that is seen below 10 Hz is due to reflections occuring at impedance discontinuities at the primary and secondary summing manifolds. Resonance involving reflections at the inlets amplifies noise levels at frequencies above 10 Hz. This paper further reports results from theoretical and observational tests of impedance matching capillaries for removing the resonance problem. Almost total removal of resonant energy below 5 Hz was found by placing impedance matching capillaries adjacent to the secondary summing manifolds in the pipes leading to the primary summing manifold and the microbarometer. Theory and recorded data indicate that capillaries with resistance equal to the characteristic impedance of the pipe connecting the secondary and primary summing manifolds suppresses resonance but does not degrade the reception of acoustic signals. Capillaries at the inlets can be used to remove resonant energy at higher frequencies but are found to be less effective due to the high frequency of this energy outside the frequency band of interest.

  16. Encoding complex values using two DLP spatial light modulators

    Science.gov (United States)

    Becker, Michael F.; Wu, Sih-Ying; Liang, Jinyang

    2013-03-01

    We present a method to encode complex values into three or four quantized complex values for wavefront modulation using two digital micromirror devices (DMDs). This encoding offers advantages to eliminate the twin image or suppress the zero order diffraction as well to improve hologram fidelity. The optical architecture utilizes a Michelson interferometer with a DMD in Littrow configuration replacing the mirrors to combine the two holograms with the desired phase shift. System performance was examined using numerical simulations and experimental measurements to explore different encoding methods for hologram reconstruction. Both ZOD and conjugate image suppression were demonstrated for different encoding schemes.

  17. Stochastic resonance modulates neural synchronization within and between cortical sources.

    Directory of Open Access Journals (Sweden)

    Lawrence M Ward

    Full Text Available Neural synchronization is a mechanism whereby functionally specific brain regions establish transient networks for perception, cognition, and action. Direct addition of weak noise (fast random fluctuations to various neural systems enhances synchronization through the mechanism of stochastic resonance (SR. Moreover, SR also occurs in human perception, cognition, and action. Perception, cognition, and action are closely correlated with, and may depend upon, synchronized oscillations within specialized brain networks. We tested the hypothesis that SR-mediated neural synchronization occurs within and between functionally relevant brain areas and thus could be responsible for behavioral SR. We measured the 40-Hz transient response of the human auditory cortex to brief pure tones. This response arises when the ongoing, random-phase, 40-Hz activity of a group of tuned neurons in the auditory cortex becomes synchronized in response to the onset of an above-threshold sound at its "preferred" frequency. We presented a stream of near-threshold standard sounds in various levels of added broadband noise and measured subjects' 40-Hz response to the standards in a deviant-detection paradigm using high-density EEG. We used independent component analysis and dipole fitting to locate neural sources of the 40-Hz response in bilateral auditory cortex, left posterior cingulate cortex and left superior frontal gyrus. We found that added noise enhanced the 40-Hz response in all these areas. Moreover, added noise also increased the synchronization between these regions in alpha and gamma frequency bands both during and after the 40-Hz response. Our results demonstrate neural SR in several functionally specific brain regions, including areas not traditionally thought to contribute to the auditory 40-Hz transient response. In addition, we demonstrated SR in the synchronization between these brain regions. Thus, both intra- and inter-regional synchronization of neural

  18. The Modulation of Ionospheric Alfven Resonator on Heating HF Waves and the Doppler Effect

    Institute of Scientific and Technical Information of China (English)

    NiBin-bin; ZhaoZheng-yu; XieShu-guo

    2003-01-01

    The propagation of HF waves in IAR can produce many nonlinear effects, including the modulation effect of IAR on HF waves and the Doppler effect. To start with the dependence of the ionospheric electron temperature varia-tions on the Alfven resonant field, We discuss the mechanism of the modulation effect and lucubrate possible reasons for the Doppler effect. The results show that the Alfven resonant field can have an observable modulation effect on HF waves while its mechanism is quite different from that of Schumann resonant field on HF waves. The depth of modulation of IAR on HF waves has a quasi-quadratic relation with the Alfven field, which directly inspires the formation of cross-spectrum between ULF waves and HF waves and results in spectral peaks at some gyro-frequencies of IAR. With respect to the Doppler effect during the propagation of HF waves in IAR, it is mainly caused by the motion of the high-speed flyer and the drifting electrons and the frequency shift from the phase vari-ation of the reflected waves can be neglected when the frequency of HF incident wave is high enough.

  19. Progress in fabrication of waveguide spatial light modulators via femtosecond laser micromachining

    Science.gov (United States)

    Savidis, Nickolaos; Jolly, Sundeep; Datta, Bianca; Moebius, Michael; Karydis, Thrasyvoulos; Mazur, Eric; Gershenfeld, Neil; Bove, V. Michael

    2017-02-01

    We have previously introduced a femtosecond laser micromachining-based scheme for the fabrication of anisotropic waveguides in lithium niobate for use in a guided-wave acousto-optic spatial light modulator. This spatial light modulation scheme is extensible to off-plane waveguide holography via the integration of a Bragg reflection grating. In this paper, we present femtosecond laser-based direct-write approaches for the fabrication of (1) waveguide in-coupling gratings and (2) volume Bragg reflection gratings via permanent refractive index changes within the lithium niobate substrate. In combination with metal surface-acoustic-wave transducers, these direct-write approaches allow for complete fabrication of a functional spatial light modulator via femtosecond laser direct writing.

  20. Optical generation of a spatially variant two-dimensional lattice structure by using a phase only spatial light modulator

    CERN Document Server

    Kumar, Manish

    2016-01-01

    We propose a simple and straightforward method to generate a spatially variant lattice structures by optical interference lithography method. Using this method, it is possible to independently vary the orientation and period of the two-dimensional lattice. The method consists of two steps which are: numerical synthesis of corresponding phase mask by employing a two-dimensional integrated gradient calculations and experimental implementation of synthesized phase mask by making use of a phase only spatial light modulator in an optical 4f Fourier filtering setup. As a working example, we provide the experimental fabrication of a spatially variant square lattice structure which has the possibility to guide a Gaussian beam through a 90{\\deg} bend by photonic crystal self-collimation phenomena. The method is digitally reconfigurable, is completely scalable and could be extended to other kind of lattices as well.

  1. Optical generation of a spatially variant two-dimensional lattice structure by using a phase only spatial light modulator

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Manish, E-mail: manishk@physics.iitd.ac.in; Joseph, Joby, E-mail: joby@physics.iitd.ac.in [Photonics Research Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016 (India)

    2014-08-04

    We propose a simple and straightforward method to generate spatially variant lattice structures by optical interference lithography method. Using this method, it is possible to independently vary the orientation and period of the two-dimensional lattice. The method consists of two steps which are: numerical synthesis of corresponding phase mask by employing a two-dimensional integrated gradient calculations and experimental implementation of synthesized phase mask by making use of a phase only spatial light modulator in an optical 4f Fourier filtering setup. As a working example, we provide the experimental fabrication of a spatially variant square lattice structure which has the possibility to guide a Gaussian beam through a 90° bend by photonic crystal self-collimation phenomena. The method is digitally reconfigurable, is completely scalable, and could be extended to other kind of lattices as well.

  2. Information transfer with rate-modulated Poisson processes: a simple model for nonstationary stochastic resonance.

    Science.gov (United States)

    Goychuk, I

    2001-08-01

    Stochastic resonance in a simple model of information transfer is studied for sensory neurons and ensembles of ion channels. An exact expression for the information gain is obtained for the Poisson process with the signal-modulated spiking rate. This result allows one to generalize the conventional stochastic resonance (SR) problem (with periodic input signal) to the arbitrary signals of finite duration (nonstationary SR). Moreover, in the case of a periodic signal, the rate of information gain is compared with the conventional signal-to-noise ratio. The paper establishes the general nonequivalence between both measures notwithstanding their apparent similarity in the limit of weak signals.

  3. Information transfer with rate-modulated Poisson processes: A simple model for nonstationary stochastic resonance

    Science.gov (United States)

    Goychuk, Igor

    2001-08-01

    Stochastic resonance in a simple model of information transfer is studied for sensory neurons and ensembles of ion channels. An exact expression for the information gain is obtained for the Poisson process with the signal-modulated spiking rate. This result allows one to generalize the conventional stochastic resonance (SR) problem (with periodic input signal) to the arbitrary signals of finite duration (nonstationary SR). Moreover, in the case of a periodic signal, the rate of information gain is compared with the conventional signal-to-noise ratio. The paper establishes the general nonequivalence between both measures notwithstanding their apparent similarity in the limit of weak signals.

  4. Magneto-optic transmittance modulation observed in a hybrid graphene–split ring resonator terahertz metasurface

    Energy Technology Data Exchange (ETDEWEB)

    Zanotto, Simone; Pitanti, Alessandro [NEST, Istituto Nanoscienze–CNR and Scuola Normale Superiore, Piazza San Silvestro 12, 56127 Pisa (Italy); Lange, Christoph; Maag, Thomas; Huber, Rupert [Department of Physics, University of Regensburg, 93040 Regensburg (Germany); Miseikis, Vaidotas; Coletti, Camilla [CNI@NEST, Istituto Italiano di Tecnologia, P.za S. Silvestro 12, 56127 Pisa (Italy); Degl' Innocenti, Riccardo [Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Baldacci, Lorenzo [Scuola Superiore Sant' Anna, Institute of Life Sciences, P.za Martiri della Libertà 33, 56127 Pisa (Italy); Tredicucci, Alessandro [NEST, Istituto Nanoscienze-CNR and Dipartimento di Fisica “E. Fermi,” Università di Pisa, L.go Pontecorvo 3, 56127 Pisa (Italy)

    2015-09-21

    By placing a material in close vicinity of a resonant optical element, its intrinsic optical response can be tuned, possibly to a wide extent. Here, we show that a graphene monolayer, spaced a few tenths of nanometers from a split ring resonator metasurface, exhibits a magneto-optical response which is strongly influenced by the presence of the metasurface itself. This hybrid system holds promises in view of thin optical modulators, polarization rotators, and nonreciprocal devices, in the technologically relevant terahertz spectral range. Moreover, it could be chosen as the playground for investigating the cavity electrodynamics of Dirac fermions in the quantum regime.

  5. Resonant Peak Splitting for Ballistic Conductance in Two-Dimensional Electron Gas Under Electromagnetic Modulation

    Institute of Scientific and Technical Information of China (English)

    WANG Ru-Zhi; YAN Xiao-Hong

    2000-01-01

    By developing a transfer-matrix method, the resonant peaks splitting of ballistic conductance are investigated into the two-dimensional electron gas system with both electric and magnetic modulations of nanoscale periods. It is found that there exists the n-fold resonant peak splitting for ballistic conductance through n perpendicular magnetic barriers to n electric barriers. With a combination of m magnetic barriers and n electric barriers by increasing the amplitude of electric field, the folds of the splitting would shift from m - 1 to n - 1.

  6. Grating-coupled surface plasmon resonance in conical mounting with polarization modulation.

    Science.gov (United States)

    Ruffato, G; Romanato, F

    2012-07-01

    A grating-coupled surface plasmon resonance (GCSPR) technique based on polarization modulation in conical mounting is presented. A metallic grating is azimuthally rotated to support double-surface plasmon polariton excitation and exploit the consequent sensitivity enhancement. Corresponding to the resonance polar angle, a polarization scan of incident light is performed, and reflectivity data are collected before and after functionalization with a dodecanethiol self-assembled monolayer. The output signal exhibits a harmonic dependence on polarization, and the phase term is used as a parameter for sensing. This technique offers the possibility of designing extremely compact, fast, and cheap high-resolution plasmonic sensors based on GCSPR.

  7. Effective electro-optical modulation with high extinction ratio by a graphene-silicon microring resonator

    DEFF Research Database (Denmark)

    Ding, Yunhong; Zhu, Xiaolong; Xiao, Sanshui

    2015-01-01

    comprehensively study the interaction between graphene and a microring resonator, and its influence on the optical modulation depth. We demonstrate graphene-silicon microring devices showing a high modulation depth of 12.5 dB with a relatively low bias voltage of 8.8 V. On-off electro-optical switching......Graphene opens up for novel optoelectronic applications thanks to its high carrier mobility, ultra-large absorption bandwidth, and extremely fast material response. In particular, the opportunity to control optoelectronic properties through tuning of the Fermi level enables electro-optical...... modulation, optical-optical switching, and other optoelectronics applications. However, achieving a high modulation depth remains a challenge because of the modest graphene-light interaction in the graphene-silicon devices, typically, utilizing only a monolayer or few layers of graphene. Here, we...

  8. Three-Wave Resonance Modulation and Fine Structures in the Solar Short Centimeter Wave Bursts

    Institute of Scientific and Technical Information of China (English)

    王德焴; 吴洪敖; 秦至海

    1994-01-01

    A theoretical model is presented. We propose that when the radiation of solar radio bursts propagates outward as a pump wave through the conora, the three-wave resonance interaction would occur if the radio emission interacts with the MHD wave and scattering wave in the conora. This process induces a nonlinear modulation in the emission flux S. The statistical relations between the repetition rates R and S and between the modulation amplitude △S and S, observed from 1.36cm, 2cm and 3.2cm solar radio bursts could be well interpreted by this model under the conditions of imperfect matching and k2≠0. The appreciable difference in the modulation periods among the 2cm, 3.2cm and 1.36cm waves might be caused by the differences in the MHD waves joining in the modulation. Several theoretical expectations have been made from this model, which may be inspected in further observation.

  9. Spatial modulation and conductivities in effective holographic theories

    Science.gov (United States)

    Rangamani, Mukund; Rozali, Moshe; Smyth, Darren

    2015-07-01

    We analyze a class of bottom-up holographic models for low energy thermo-electric transport. The models we focus on belong to a family of Einstein-Maxwell-dilaton theories parameterized by two scalar functions, characterizing the dilaton self-interaction and the gauge coupling function. We impose spatially inhomogeneous lattice boundary conditions for the dilaton on the AdS boundary and study the resulting phase structure attained at low energies. We find that as we dial the scalar functions at our disposal (changing thus the theory under consideration), we obtain either (i) coherent metallic, or (ii) insulating, or (iii) incoherent metallic phases. We chart out the domain where the incoherent metals appear in a restricted parameter space of theories. We also analyze the optical conductivity, noting that non-trivial scaling behaviour at intermediate frequencies appears to only be possible for very narrow regions of parameter space.

  10. Spatial Modulation and Conductivities in Effective Holographic Theories

    CERN Document Server

    Rangamani, Mukund; Smyth, Darren

    2015-01-01

    We analyze a class of bottom-up holographic models for low energy thermo-electric transport. The models we focus on belong to a family of Einstein-Maxwell-dilaton theories parameterized by two scalar functions, characterizing the dilaton self-interaction and the gauge coupling function. We impose spatially inhomogeneous lattice boundary conditions for the dilaton on the AdS boundary and study the resulting phase structure attained at low energies. We find that as we dial the scalar functions at our disposal (changing thus the theory under consideration), we obtain either (i) coherent metallic, or (ii) insulating, or (iii) incoherent metallic phases. We chart out the domain where the incoherent metals appear in a restricted parameter space of theories. We also analyze the optical conductivity, noting that non-trivial scaling behaviour at intermediate frequencies appears to only be possible for very narrow regions of parameter space.

  11. Optical particle trapping and dynamic manipulation using spatial light modulation

    DEFF Research Database (Denmark)

    Eriksen, René Lynge

    This thesis deals with the spatial phase-control of light and its application for optical trapping and manipulation of micron-scale objects. Utilizing the radiation pressure, light exerts on dielectric micron-scale particles, functionality of optical tweezers can be obtained. Multiple intensity...... of trapped colloidal micron-sized polystyrene particles and cell structures were accomplished. Furthermore, fixed arrays consisting of up to 25-trapped particles have been generated. Experimentally, ternary phase encoding has been demonstrated, supporting the GPC theory. Binary intensity patterns having...... proven capable of generating a phase pattern from an input amplitude distribution. The birefringent nature of liquid crystals in the SLM is utilized for the generation of an arbitrary two-dimensional state of polarization using two-cascaded SLMs. By means of elliptically polarized light, generated by one...

  12. Design and optimization of polymer ring resonator modulators for analog microwave photonic applications

    Science.gov (United States)

    Hosseinzadeh, Arash; Middlebrook, Christopher T.

    2016-02-01

    Efficient modulation of electrical signals onto an optical carrier remains the main challenge in full implementation of microwave photonic links (MPLs) for applications such as antenna remoting and wireless access networks. Current MPLs utilize Mach-Zehnder Interferometers (MZI) with sinusoidal transfer function as electro-optic modulators causing nonlinear distortions in the link. Recently ring resonator modulators (RRM) consisting of a ring resonator coupled to a base waveguide attracted interest to enhance linearity, reduce the size and power consumption in MPLs. Fabrication of a RRM is more challenging than the MZI not only in fabrication process but also in designing and optimization steps. Although RRM can be analyzed theoretically for MPLs, physical structures need to be designed and optimized utilizing simulation techniques in both optical and microwave regimes with consideration of specific material properties. Designing and optimization steps are conducted utilizing full-wave simulation software package and RRM function analyzed in both passive and active forms and confirmed through theoretical analysis. It is shown that RRM can be completely designed and analyzed utilizing full-wave simulation techniques and as a result linearity effect of the modulator on MPLs can be studied and optimized. The material nonlinearity response can be determined computationally and included in modulator design and readily adaptable for analyzing other materials such as silicon or structures where theoretical analysis is not easily achieved.

  13. Stochastic resonance of bias signal-modulated noise in a single-mode laser

    Institute of Scientific and Technical Information of China (English)

    Wang Jun; Cao Li; Wu Da-Jin

    2004-01-01

    Stochastic resonance (SR) for bias signal modulation is studied in a single-mode laser system. By investigating a gain-noise model driven by correlated pump noise and quantum noir, we find that, whether the correlation coefficient between both the noises is positive or negative, SR always appears in the dependence of signal-to-noise ratio (SNR) upon the noise correlation time and the frequency of the modulation signal. However, only when the correlation coefficient between both noises is negative can SR occur in the dependence of SNR upon the quantum noise intensity and pump noise intensity, while when the correlation coefficient between both noises is positive, it shows monotonically.

  14. Selective attention modulates human auditory brainstem responses: relative contributions of frequency and spatial cues.

    Science.gov (United States)

    Lehmann, Alexandre; Schönwiesner, Marc

    2014-01-01

    Selective attention is the mechanism that allows focusing one's attention on a particular stimulus while filtering out a range of other stimuli, for instance, on a single conversation in a noisy room. Attending to one sound source rather than another changes activity in the human auditory cortex, but it is unclear whether attention to different acoustic features, such as voice pitch and speaker location, modulates subcortical activity. Studies using a dichotic listening paradigm indicated that auditory brainstem processing may be modulated by the direction of attention. We investigated whether endogenous selective attention to one of two speech signals affects amplitude and phase locking in auditory brainstem responses when the signals were either discriminable by frequency content alone, or by frequency content and spatial location. Frequency-following responses to the speech sounds were significantly modulated in both conditions. The modulation was specific to the task-relevant frequency band. The effect was stronger when both frequency and spatial information were available. Patterns of response were variable between participants, and were correlated with psychophysical discriminability of the stimuli, suggesting that the modulation was biologically relevant. Our results demonstrate that auditory brainstem responses are susceptible to efferent modulation related to behavioral goals. Furthermore they suggest that mechanisms of selective attention actively shape activity at early subcortical processing stages according to task relevance and based on frequency and spatial cues.

  15. Selective attention modulates human auditory brainstem responses: relative contributions of frequency and spatial cues.

    Directory of Open Access Journals (Sweden)

    Alexandre Lehmann

    Full Text Available Selective attention is the mechanism that allows focusing one's attention on a particular stimulus while filtering out a range of other stimuli, for instance, on a single conversation in a noisy room. Attending to one sound source rather than another changes activity in the human auditory cortex, but it is unclear whether attention to different acoustic features, such as voice pitch and speaker location, modulates subcortical activity. Studies using a dichotic listening paradigm indicated that auditory brainstem processing may be modulated by the direction of attention. We investigated whether endogenous selective attention to one of two speech signals affects amplitude and phase locking in auditory brainstem responses when the signals were either discriminable by frequency content alone, or by frequency content and spatial location. Frequency-following responses to the speech sounds were significantly modulated in both conditions. The modulation was specific to the task-relevant frequency band. The effect was stronger when both frequency and spatial information were available. Patterns of response were variable between participants, and were correlated with psychophysical discriminability of the stimuli, suggesting that the modulation was biologically relevant. Our results demonstrate that auditory brainstem responses are susceptible to efferent modulation related to behavioral goals. Furthermore they suggest that mechanisms of selective attention actively shape activity at early subcortical processing stages according to task relevance and based on frequency and spatial cues.

  16. Frequency modulated weak signal detection based on stochastic resonance and genetic algorithm

    Institute of Scientific and Technical Information of China (English)

    XING; Hongyan; LU; Chunxia; ZHANG; Qiang

    2016-01-01

    Stochastic resonance system is subject to the restriction of small frequency parameter in weak signal detection,in order to solve this problem,a frequency modulated weak signal detection method based on stochastic resonance and genetic algorithm is presented in this paper. The frequency limit of stochastic resonance is eliminated by introducing carrier signal,which is multiplied with the measured signal to be injected in the stochastic resonance system,meanwhile,using genetic algorithm to optimize the carrier signal frequency,which determine the generated difference-frequency signal in the lowfrequency range,so as to achieve the stochastic resonance weak signal detection. Results showthat the proposed method is feasible and effective,which can significantly improve the output SNR of stochastic resonance,in addition,the system has the better self-adaptability,according to the operation result and output phenomenon,the unknown frequency of the signal to be measured can be obtained,so as to realize the weak signal detection of arbitrary frequency.

  17. Sub-optical wavelength acoustic wave modulation of integrated photonic resonators at microwave frequencies

    CERN Document Server

    Tadesse, Semere Ayalew

    2014-01-01

    Light-sound interactions have long been exploited in various acousto-optic devices based on bulk crystalline materials. Conventionally these devices operate in megahertz frequency range where the acoustic wavelength is much longer than the optical wavelength and a long interaction length is required to attain significant coupling. With nanoscale transducers, acoustic waves with sub-optical wavelengths can now be excited to induce strong acousto-optic coupling in nanophotonic devices. Here we demonstrate microwave frequency surface acoustic wave transducers co-integrated with nanophotonic resonators on piezoelectric aluminum nitride substrates. Acousto-optic modulation of the resonance modes at above 10 GHz with the acoustic wavelength significantly below the optical wavelength is achieved. The phase and modal matching conditions in this scheme are investigated for efficient modulation. The new acousto-optic platform can lead to novel optical devices based on nonlinear Brillouin processes and provides a direct...

  18. Solitons supported by singular spatial modulation of the Kerr nonlinearity

    CERN Document Server

    Borovkova, Olga V; Malomed, Boris A

    2012-01-01

    We introduce a setting based on the one-dimensional (1D) nonlinear Schroedinger equation (NLSE) with the self-focusing (SF) cubic term modulated by a singular function of the coordinate, |x|^{-a}. It may be additionally combined with the uniform self-defocusing (SDF) nonlinear background, and with a similar singular repulsive linear potential. The setting, which can be implemented in optics and BEC, aims to extend the general analysis of the existence and stability of solitons in NLSEs. Results for fundamental solitons are obtained analytically and verified numerically. The solitons feature a quasi-cuspon shape, with the second derivative diverging at the center, and are stable in the entire existence range, which is 0 < a < 1. Dipole (odd) solitons are found too. They are unstable in the infinite domain, but stable in the semi-infinite one. In the presence of the SDF background, there are two subfamilies of fundamental solitons, one stable and one unstable, which exist together above a threshold value ...

  19. Hyperresolving phase-only filters with an optically addressable liquid crystal spatial light modulator.

    Science.gov (United States)

    McOrist, J; Sharma, M D; Sheppard, C J R; West, E; Matsuda, K

    2003-01-01

    Hyperresolving (sometimes called 'superresolving' or 'ultraresolving') phase-only filters can be generated using an optically addressable liquid crystal spatial light modulator. This approach avoids the problems of low efficiency, and coupling between amplitude and phase modulation, that arise when using conventional liquid crystal modulators. When addressed by a programmed light intensity distribution, it allows filters to be changed rapidly to modify the response of a system or permit the investigation of different filter designs. In this paper we present experimental hyperresolved images obtained using an optically addressable parallel-aligned nematic LCD with two zone Toraldo type phase-only filters. The images are compared with theoretical predictions.

  20. Direct spatial resonance in the laminar boundary layer due to a rotating-disk

    Indian Academy of Sciences (India)

    M Turkyilmazoglu; J S B Gajjar

    2000-12-01

    Numerical treatment of the linear stability equations is undertaken to investigate the occurrence of direct spatial resonance events in the boundary layer flow due to a rotating-disk. A spectral solution of the eigenvalue problem indicates that algebraic growth of the perturbations shows up, prior to the amplification of exponentially growing instability waves. This phenomenon takes place while the flow is still in the laminar state and it also tends to persist further even if the non-parallelism is taken into account. As a result, there exists the high possibility of this instability mechanism giving rise to nonlinearity and transition, long before the unboundedly growing time-amplified waves.

  1. Modulating resonance behaviors by noise recycling in bistable systems with time delay

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Zhongkui, E-mail: sunzk2008@gmail.com; Xu, Wei [Department of Applied Mathematics, Northwestern Polytechnical University, Xi' an 710072 (China); Yang, Xiaoli [College of Mathematics and Information Science, Shaan' xi Normal University, Xi' an 710062 (China); Xiao, Yuzhu [Department of Mathematics and Information Science, Chang' an University, Xi' an 710086 (China)

    2014-06-01

    In this paper, the impact of noise recycling on resonance behaviors is studied theoretically and numerically in a prototypical bistable system with delayed feedback. According to the interior cooperating and interacting activity of noise recycling, a theory has been proposed by reducing the non-Markovian problem into a two-state model, wherein both the master equation and the transition rates depend on not only the current state but also the earlier two states due to the recycling lag and the feedback delay. By virtue of this theory, the formulae of the power spectrum density and the linear response function have been found analytically. And the theoretical results are well verified by numerical simulations. It has been demonstrated that both the recycling lag and the feedback delay play a crucial role in the resonance behaviors. In addition, the results also suggest an alternative scheme to modulate or control the coherence or stochastic resonance in bistable systems with time delay.

  2. Evolutions of matter-wave bright soliton with spatially modulated nonlinearity

    Institute of Scientific and Technical Information of China (English)

    Yongshan Cheng; Fei Liu

    2009-01-01

    The evolution characteristics of a matter-wave bright soliton are investigated by means of the variational approach in the presence of spatially varying nonlinearity.It is found that the atom density envelope of the soliton is changed as a result of the spatial variation of the s-wave scattering length.The stable soliton can exist in appropriate initial conditions.The movement of the soliton depends on the sign and value of the coefficient of spatially modulated nonlinearity.These theoretical predictions are confirmed by the full numerical simulations of the one-dimensional Gross-Pitaevskii equation.

  3. Attention modulates visual-tactile interaction in spatial pattern matching.

    Directory of Open Access Journals (Sweden)

    Florian Göschl

    Full Text Available Factors influencing crossmodal interactions are manifold and operate in a stimulus-driven, bottom-up fashion, as well as via top-down control. Here, we evaluate the interplay of stimulus congruence and attention in a visual-tactile task. To this end, we used a matching paradigm requiring the identification of spatial patterns that were concurrently presented visually on a computer screen and haptically to the fingertips by means of a Braille stimulator. Stimulation in our paradigm was always bimodal with only the allocation of attention being manipulated between conditions. In separate blocks of the experiment, participants were instructed to (a focus on a single modality to detect a specific target pattern, (b pay attention to both modalities to detect a specific target pattern, or (c to explicitly evaluate if the patterns in both modalities were congruent or not. For visual as well as tactile targets, congruent stimulus pairs led to quicker and more accurate detection compared to incongruent stimulation. This congruence facilitation effect was more prominent under divided attention. Incongruent stimulation led to behavioral decrements under divided attention as compared to selectively attending a single sensory channel. Additionally, when participants were asked to evaluate congruence explicitly, congruent stimulation was associated with better performance than incongruent stimulation. Our results extend previous findings from audiovisual studies, showing that stimulus congruence also resulted in behavioral improvements in visuotactile pattern matching. The interplay of stimulus processing and attentional control seems to be organized in a highly flexible fashion, with the integration of signals depending on both bottom-up and top-down factors, rather than occurring in an 'all-or-nothing' manner.

  4. Attention modulates visual-tactile interaction in spatial pattern matching.

    Science.gov (United States)

    Göschl, Florian; Engel, Andreas K; Friese, Uwe

    2014-01-01

    Factors influencing crossmodal interactions are manifold and operate in a stimulus-driven, bottom-up fashion, as well as via top-down control. Here, we evaluate the interplay of stimulus congruence and attention in a visual-tactile task. To this end, we used a matching paradigm requiring the identification of spatial patterns that were concurrently presented visually on a computer screen and haptically to the fingertips by means of a Braille stimulator. Stimulation in our paradigm was always bimodal with only the allocation of attention being manipulated between conditions. In separate blocks of the experiment, participants were instructed to (a) focus on a single modality to detect a specific target pattern, (b) pay attention to both modalities to detect a specific target pattern, or (c) to explicitly evaluate if the patterns in both modalities were congruent or not. For visual as well as tactile targets, congruent stimulus pairs led to quicker and more accurate detection compared to incongruent stimulation. This congruence facilitation effect was more prominent under divided attention. Incongruent stimulation led to behavioral decrements under divided attention as compared to selectively attending a single sensory channel. Additionally, when participants were asked to evaluate congruence explicitly, congruent stimulation was associated with better performance than incongruent stimulation. Our results extend previous findings from audiovisual studies, showing that stimulus congruence also resulted in behavioral improvements in visuotactile pattern matching. The interplay of stimulus processing and attentional control seems to be organized in a highly flexible fashion, with the integration of signals depending on both bottom-up and top-down factors, rather than occurring in an 'all-or-nothing' manner.

  5. Experimental Generation of non-Kolmogorov Turbulence using a Liquid Crystal Spatial Light Modulator

    Science.gov (United States)

    2011-01-01

    Experimental generation of non-Kolmogorov Turbulence using a Liquid Crystal Spatial Light Modulator * Italo Tosellia, Brij N. Agrawala...performance evaluations. ACKNOWLEDGEMENTS This research was performed while the author Italo Toselli holds a National Research Council Research...REFERENCES 1. Larry C. Andrews, Ronald L. Phillips. Laser Beam Propagation through Random Media, 2nd ed. (SPIE, 2005). 2. Italo Toselli, Larry C

  6. Digital control of laser modes with an intra-cavity spatial light modulator

    CSIR Research Space (South Africa)

    Ngcobo, S

    2014-02-01

    Full Text Available In this paper we outline a simple laser cavity which produces customised on-demand digitally controlled laser modes by replacing the end-mirror of the cavity with an electrically addressed reflective phase-only spatial light modulator as a digital...

  7. Two-Dimensional GaAs/AlGaAs Multiple Quantum Well Spatial Light Modulators

    Institute of Scientific and Technical Information of China (English)

    Qin Wang; Jan Borglind; Smilja Becanovic; Stéphane Junique; Daniel (A)gren; Bertrand Noharet; Linda H(o)glund; Olof (O)berg; Erik Petrini; Jan Y. Andersson; Hedda Malm

    2003-01-01

    Multiple quantum well spatial light modulators with 128x128 array in 38μm pitch are fabricated using two pproaches, one with an attachment of an optical substrate and another one without. These two fabrication processes are described and compared.

  8. Modulation instability, solitons and beam propagation in spatially nonlocal nonlinear media

    DEFF Research Database (Denmark)

    Krolikowski, Wieslaw; Bang, Ole; Nikolov, Nikola Ivanov

    2004-01-01

    We present an overview of recent advances in the understanding of optical beams in nonlinear media with a spatially nonlocal nonlinear response. We discuss the impact of nonlocality on the modulational instability of plane waves, the collapse of finite-size beams, and the formation and interaction...

  9. Development of Instrumentation for Spin-Echo Induced Spatial Beam Modulations

    DEFF Research Database (Denmark)

    Sales, Morten

    Institute Delft, TUDelft, and resolve the modulation using absorption gratings in front of a detector without spatial resolution, i.e. a simple counting detector. Combining this with a virtual copy of the instrument, built using the Monte Carlo Ray-Tracing simulation package McStas, we were able to expand...

  10. Vibration suppression for strings with distributed loading using spatial cross-section modulation

    DEFF Research Database (Denmark)

    Sorokin, Vladislav; Thomsen, Jon Juel

    2015-01-01

    A problem of vibration suppression in any preassigned region of a bounded structure subjected to action of an external time-periodic load which is distributed over its domain is considered. A passive control is applied, in which continuous spatially periodic modulations of structural parameters a...

  11. A process to control light in a micro resonator through a coupling modulation by surface acoustic waves

    Science.gov (United States)

    Fan, Guofang; Li, Yuan; Hu, Chunguang; Lei, Lihua; Guo, Yanchuan

    2016-08-01

    A novel process to control light through the coupling modulation by surface acoustic wave (SAW) is presented in an optical micro resonator. An optical waveguide modulator of a racetrack resonator on silicon-on-insulator (SOI) technology is took as an example to explore the mechanism. A finite-difference time-domain (FDTD) is developed to simulate the acousto-optical (AO) modulator using the mechanism. An analytical method is presented to verify our proposal. The results show that the process can work well as an optical modulator by SAW.

  12. A digital receiver module with direct data acquisition for magnetic resonance imaging systems.

    Science.gov (United States)

    Tang, Weinan; Sun, Hongyu; Wang, Weimin

    2012-10-01

    A digital receiver module for magnetic resonance imaging (MRI) with detailed hardware implementations is presented. The module is based on a direct sampling scheme using the latest mixed-signal circuit design techniques. A single field-programmable gate array chip is employed to perform software-based digital down conversion for radio frequency signals. The modular architecture of the receiver allows multiple acquisition channels to be implemented on a highly integrated printed circuit board. To maintain the phase coherence of the receiver and the exciter in the context of direct sampling, an effective phase synchronization method was proposed to achieve a phase deviation as small as 0.09°. The performance of the described receiver module was verified in the experiments for both low- and high-field (0.5 T and 1.5 T) MRI scanners and was compared to a modern commercial MRI receiver system.

  13. Resonator-Based Silicon Electro-Optic Modulator with Low Power Consumption

    Science.gov (United States)

    Xin, Maoqing; Danner, Aaron J.; Eng Png, Ching; Thor Lim, Soon

    2009-04-01

    This paper demonstrates, via simulation, an electro-optic modulator based on a subwavelength Fabry-Perot resonator cavity with low power consumption of 86 µW/µm. This is, to the best of our knowledge, the lowest power reported for silicon photonic bandgap modulators. The device is modulated at a doped p-i-n junction overlapping the cavity in a silicon waveguide perforated with etched holes, with the doping area optimized for minimum power consumption. The surface area of the entire device is only 2.1 µm2, which compares favorably to other silicon-based modulators. A modulation speed of at least 300 MHz is detected from the electrical simulator after sidewall doping is introduced which is suitable for sensing or fiber to the home (FTTH) technologies, where speed can be traded for low cost and power consumption. The device does not rely on ultra-high Q, and could serve as a sensor, modulator, or passive filter with built-in calibration.

  14. Multi-wavelength holography with a single spatial light modulator for ultracold atom experiments.

    Science.gov (United States)

    Bowman, David; Ireland, Philip; Bruce, Graham D; Cassettari, Donatella

    2015-04-06

    We demonstrate a method to independently and arbitrarily tailor the spatial profile of light of multiple wavelengths and we show possible applications to ultracold atoms experiments. A single spatial light modulator is programmed to create a pattern containing multiple spatially separated structures in the Fourier plane when illuminated with a single wavelength. When the modulator is illuminated with overlapped laser beams of different wavelengths, the position of the structures is wavelength-dependent. Hence, by designing their separations appropriately, a desired overlap of different structures at different wavelengths is obtained. We employ regional phase calculation algorithms and demonstrate several possible experimental scenarios by generating light patterns with 670 nm, 780 nm and 1064 nm laser light which are accurate to the level of a few percent. This technique is easily integrated into cold atom experiments, requiring little optical access.

  15. Resonant Laser-SNMS on actinides for spatially resolved ultra-trace analysis

    Energy Technology Data Exchange (ETDEWEB)

    Franzmann, Michael [Institut fuer Radiooekologie und Strahlenschutz, Leibniz Universitaet Hannover (Germany); Institut fuer Physik, Johannes Gutenberg Universitaet Mainz (Germany); Bosco, Hauke; Hamann, Linda; Walther, Clemens [Institut fuer Radiooekologie und Strahlenschutz, Leibniz Universitaet Hannover (Germany); Wendt, Klaus [Institut fuer Physik, Johannes Gutenberg Universitaet Mainz (Germany)

    2016-07-01

    The transport mechanisms and geochemical behavior of actinides in natural systems is of major importance to evaluate their distribution in geological formations at contaminated areas and storage sites. The composition analysis of hot particles, sorption on mineral surfaces and migration of trace concentrations of radionuclides requires an excellent suppression of organic background and isobaric contamination in combination with high spatial resolution while maintaining the natural structure of the sample. The new resonant Laser-SNMS system at the IRS Hannover was developed to cover those specifications by combining the high element selectivity of resonance ionization with the non-destructive spatially resolved analysis of a static TOF-SIMS. After the setup of a Ti:Sa laser system and the adaption of an IONTOF TOF.SIMS 5 for laser post-ionization we achieved a platform for a broad range of radioecological measurements. This talk presents the results of characterization and simulation based optimization of the system as well as latest measurements on artificial and environmental samples containing uranium, plutonium and other radionuclides.

  16. Programmable liquid-crystal TV spatial light modulator: modified drive electronics to improve device performance for spatial-light-modulation operation.

    Science.gov (United States)

    Aiken, J; Bates, B; Catney, M G; Miller, P C

    1991-11-10

    Liquid crystal television (LCTV) continues to play a useful role as a spatial light modulator in the development and evaluation of systems for optical image processing. We outline new addressing electronics developed for a commercially available LCTV that permit writing to individual pixels at an improved display up-date rate and allow the input video signal to cover a much greater transmittance range of the TV display for black and white pixels. We illustrate this by measuring the diffraction efficiency for gratings written onto the display. For vertical gratings written along the display columns the diffraction efficiency is increased significantly, but there is no improvement for horizontal gratings. Some merits of the modified LCTV modulator for optical processing applications are considered briefly.

  17. Ultrafast optical modulation of magneto-optical terahertz effects occurring in a graphene-loaded resonant metasurface

    Science.gov (United States)

    Zanotto, S.; Lange, C.; Maag, T.; Pitanti, A.; Miseikis, V.; Coletti, C.; Degl'Innocenti, R.; Baldacci, L.; Huber, R.; Tredicucci, A.

    2016-09-01

    In this paper we investigate the effect of a static magnetic field and of optical pumping on the transmittance of a hybrid graphene-split ring resonator metasurface. A significant modulation of the transmitted spectra is obtained, both by optical pumping, and by a combination of optical pumping and magnetostatic biasing. The transmittance modulation features spectral fingerprints that are characteristic of a non-trivial interplay between the bare graphene response and the split ring resonance.

  18. Optimize the modulation response of twisted-nematic liquid crystal displays as pure phase spatial light modulators

    Science.gov (United States)

    Ma, Baiheng; Peng, Fei; Kang, Mingwu; Zhou, Jiawu

    2014-11-01

    Twisted-nematic liquid crystal displays (TN-LCD) are widely used in numerous research fields of optics working as spatial light modulators. Approaches to obtaining desired intensity or phase modulation by TN-LCD have been extensively studied based on the knowledge of TN-LCD's internal structure parameters, e.g., the orientation of LC molecules at the surfaces, the twist angle, the thickness of the LC layer, and the birefringence of the material. Generally TN-LCD placed between two linear polarizers (P) produces coupled intensity and phase modulation. To obtain the commonly used pure phase modulation, quarter wave plates (QWP) are often used in front of and/or behind the LCD. In this paper, we present a method to optimize the optical modulation properties of the TN-LCD to obtain pure phase modulation in the configuration of P-QWP-LCD-QWP-P each with proper orientation. Firstly an improved method for determining the Jones matrix of the TN-LCD without knowing its internal parameters is presented, which is based on the macroscopical Jones matrix descriptions for TN-LCD, linear polarizer and QWP. Only three sets of intensity measurements are needed for the complete determination of the TN-LCD's Jones matrix for a single wavelength. Then Jones matrix calculations are carried out to determine the orientations of the polarizers and QWPs for pure phase modulation response. In addition, we prove that the phase modulation depth (PMD) of the TN-LCD can be further increased provided that the mean intensity transmission is decreased to a lower level, which is very useful when the TN-LCD is used as a phase modulator and the ratio between the intensities of the desired diffracted order relative to the other diffracted orders is required higher. Experimental results coincide well with the optical modulation properties of the TN-LCD predicted by our determined Jones matrix. In contrast to the traditional method which requires knowledge of the TN-LCD's internal structure parameters

  19. Design, status and first operations of the spallation neutron source polyphase resonant converter modulator system

    Energy Technology Data Exchange (ETDEWEB)

    Reass, W. A. (William A.); Apgar, S. E. (Sean E.); Baca, D. M. (David M.); Doss, James D.; Gonzales, J. (Jacqueline); Gribble, R. F. (Robert F.); Hardek, T. W. (Thomas W.); Lynch, M. T. (Michael T.); Rees, D. E. (Daniel E.); Tallerico, P. J. (Paul J.); Trujillo, P. B. (Pete B.); Anderson, D. E. (David E.); Heidenreich, D. A. (Dale A.); Hicks, J. D. (Jim D.); Leontiev, V. N.

    2003-01-01

    The Spallation Neutron Source (SNS) is a new 1.4 MW average power beam, 1 GeV accelerator being built at Oak Ridge National Laboratory. The accelerator requires 15 converter-modulator stations each providing between 9 and 11 MW pulses with up to a 1 .I MW average power. The converter-modulator can be described as a resonant 20 kHz polyphase boost inverter. Each converter modulator derives its buss voltage from a standard substation cast-core transformer. Each substation is followed by an SCR pre-regulator to accommodate voltage changes from no load to full load, in addition to providing a soft-start function. Energy storage is provided by self-clearing metallized hazy polypropylene traction capacitors. These capacitors do not fail short, but clear any internal anomaly. Three 'H-Bridge' IGBT transistor networks are used to generate the polyphase 20 kHz transformer primary drive waveforms. The 20 kHz drive waveforms are time-gated to generate the desired klystron pulse width. Pulse width modulation of the individual 20 lcHz pulses is utilized to provide regulated output waveforms with DSP based adaptive feedforward and feedback techniques. The boost transformer design utilizes nanocrystalline alloy that provides low core loss at design flux levels and switching frequencies. Capacitors are used on the transformer secondary networks to resonate the leakage inductance. The transformers are wound for a specific leakage inductance, not turns ratio. This design technique generates multiple secondary volts per turn as compared to the primary. With the appropriate tuning conditions, switching losses are minimized. The resonant topology has the added benefit of being deQed in a klystron fault condition, with little energy deposited in the arc. This obviates the need of crowbars or other related networks. A review of these design parameters, operational performance, production status, and OWL installation and performance to date will be presented.

  20. Multilevel Spatial Multiplexing -Space Time Trellis Coded Modulation System for Fast Fading MIMO Channel

    Directory of Open Access Journals (Sweden)

    K.Kavitha

    2014-03-01

    Full Text Available Multilevel Space Time Trellis Coded Modulation with antenna grouping, which has been proposed recently, has coding gain and diversity gain, which in turn provide high throughput with considerable low computational complexity. However its performance is limited by predefining the antenna groups per component codes. In this paper Multilevel Spatial Multiplexing-Space Time Trellis Coded Modulation (ML-SM-STTCM has been proposed, in which antenna group selection is made based on spatial modulation based on trellis coding proposed by Ertugrul Basar and team. This idea maximizes the spatial diversity. Since only selected antennas are used to transmit the signal, and also the antennas with less cross correlation are in the selected groups, we could able to achieve improved BER performance even in the fast fading channel. Since the antenna selection is based on the component code in the system, at the decoder without increase in the computational complexity, we could achieve better error performance. The performance of the proposed system is analysed with Viterbi decoding algorithm and sub optimal sequential decoding algorithm. In this system, the antenna groups are non-overlapping, hence, it needs Nt, the number transmitter antennas, more than what is required at time t. The computer simulation reveals that the proposed system gives better BER performance compared to Multilevel Space Time Trellis Coded Modulation (ML STTCM over fast fading channel with the same computational complexity both at the transmitter and receiver.

  1. Radiofrequency field inhomogeneity compensation in high spatial resolution magnetic resonance spectroscopic imaging

    Science.gov (United States)

    Passeri, Alessandro; Mazzuca, Stefano; Del Bene, Veronica

    2014-06-01

    Clinical magnetic resonance spectroscopy imaging (MRSI) is a non-invasive functional technique, whose mathematical framework falls into the category of linear inverse problems. However, its use in medical diagnostics is hampered by two main problems, both linked to the Fourier-based technique usually implemented for spectra reconstruction: poor spatial resolution and severe blurring in the spatial localization of the reconstructed spectra. Moreover, the intrinsic ill-posedness of the MRSI problem might be worsened by (i) spatially dependent distortions of the static magnetic field (B0) distribution, as well as by (ii) inhomogeneity in the power deposition distribution of the radiofrequency magnetic field (B1). Among several alternative methods, slim (Spectral Localization by IMaging) and bslim (B0 compensated slim) are reconstruction algorithms in which a priori information concerning the spectroscopic target is introduced into the reconstruction kernel. Nonetheless, the influence of the B1 field, particularly when its operating wavelength is close to the size of the human organs being studied, continues to be disregarded. starslim (STAtic and Radiofrequency-compensated slim), an evolution of the slim and bslim methods, is therefore proposed, in which the transformation kernel also includes the B1 field inhomogeneity map, thus allowing almost complete 3D modelling of the MRSI problem. Moreover, an original method for the experimental determination of the B1 field inhomogeneity map specific to the target under evaluation is also included. The compensation capabilities of the proposed method have been tested and illustrated using synthetic raw data reproducing the human brain.

  2. Electron Paramagnetic Resonance Imaging of the Spatial Distribution of Free Radicals in PMR-15 Polyimide Resins

    Science.gov (United States)

    Ahn, Myong K.; Eaton, Sandra S.; Eaton, Gareth R.; Meador, Mary Ann B.

    1997-01-01

    Prior studies have shown that free radicals generated by heating polyimides above 300 C are stable at room temperature and are involved in thermo-oxidative degradation in the presence of oxygen gas. Electron Paramagnetic Resonance Imaging (EPRI) is a technique to determine the spatial distribution of free radicals. X-band (9.5 GHz) EPR images of PMR-15 polyimide were obtained with a spatial resolution of about 0.18 mm along a 2 mm dimension of the sample. In a polyimide sample that was not thermocycled, the radical distribution was uniform along the 2 mm dimension of the sample. For a polyimide sample that was exposed to thermocycling in air for 300 one-hour cycles at 335 C, one-dimensional EPRI showed a higher concentration of free radicals in the surface layers than in the bulk sample. A spectral-spatial two-dimensional image showed that the EPR lineshape of the surface layer remained the same as that of the bulk. These EPRI results suggest that the thermo-oxidative degradation of PMR-15 resin involves free radicals present in the oxygen-rich surface layer.

  3. The modulation of simple reaction time by the spatial probability of a visual stimulus

    Directory of Open Access Journals (Sweden)

    Carreiro L.R.R.

    2003-01-01

    Full Text Available Simple reaction time (SRT in response to visual stimuli can be influenced by many stimulus features. The speed and accuracy with which observers respond to a visual stimulus may be improved by prior knowledge about the stimulus location, which can be obtained by manipulating the spatial probability of the stimulus. However, when higher spatial probability is achieved by holding constant the stimulus location throughout successive trials, the resulting improvement in performance can also be due to local sensory facilitation caused by the recurrent spatial location of a visual target (position priming. The main objective of the present investigation was to quantitatively evaluate the modulation of SRT by the spatial probability structure of a visual stimulus. In two experiments the volunteers had to respond as quickly as possible to the visual target presented on a computer screen by pressing an optic key with the index finger of the dominant hand. Experiment 1 (N = 14 investigated how SRT changed as a function of both the different levels of spatial probability and the subject's explicit knowledge about the precise probability structure of visual stimulation. We found a gradual decrease in SRT with increasing spatial probability of a visual target regardless of the observer's previous knowledge concerning the spatial probability of the stimulus. Error rates, below 2%, were independent of the spatial probability structure of the visual stimulus, suggesting the absence of a speed-accuracy trade-off. Experiment 2 (N = 12 examined whether changes in SRT in response to a spatially recurrent visual target might be accounted for simply by sensory and temporally local facilitation. The findings indicated that the decrease in SRT brought about by a spatially recurrent target was associated with its spatial predictability, and could not be accounted for solely in terms of sensory priming.

  4. Aging effects of regional activation in a spatial task A functional magnetic resonance imaging study

    Institute of Scientific and Technical Information of China (English)

    Jong-Rak Park; Dae-Woon Lim; Mi-Hyun Choi; Su-Jeong Lee; Jin-Seung Choi; Hyung-Sik Kim; Jeong-Han Yi; Gye-Rae Tack; Soon-Cheol Chung

    2009-01-01

    BACKGROUND: An increasing number of studies have shown the effects of aging in basic cognitive processing and higher cognitive functions using functional magnetic resonance imaging (fMRI). However, little is known about the aging effects in diverse cognitive abilities, such as spatial learning and reasoning. OBJECTIVE: To investigate the effect of aging on spatial cognitive performance and regional brain activation based on fMRI. DESIGN, TIME, AND SETTING: A block design for fMRI observation. This study was performed at the fMRI Laboratory, Brain Science Research Center, Korea Advanced Institute of Science and Technology from March 2006 to May 2009.PARTICIPANTS: Eight right-handed, male, college students in their 20s (mean age 21.5 years) and six right-handed, male, adults in their 40s (mean age 45.7 years), who graduated from college, participated in the study. All subjects were healthy and had no prior history of psychiatric or neurological disorders. METHODS: A spatial task was presented while brain images were acquired using a 3T fMRI system (ISOL Technology, Korea). The spatial tasks involved selecting a shape that corresponded to a given figure using four examples, as well as selecting a development figure of a diagram. MAIN OUTCOME MEASURES: The accuracy rate (number of correct answers/total number of items×100%) of spatial tasks was calculated. Using the subtraction procedure, the activated areas in the brain during spatial tasks were color-coded by T-score. The double subtraction method was used to analyze the effect of aging between the two age groups (20s versus 40s). RESULTS: The cerebellum, occipital lobe, parietal lobe, and frontal lobe were similarly activated in the two age groups. Increased brain activations, however, were observed in bilateral parietal and superior frontal lobes of the younger group. More activation was observed in bilateral middle frontal and right inferior frontal lobes in the older group. Compared with the older group, the

  5. Laser Recrystallized Silicon/plzt Smart Spatial Light Modulators for Optoelectronic Computing

    Science.gov (United States)

    Ersen, Ali

    By integrating materials for electronic processing with light modulating materials, the computational power of electronics can be combined with the communication power of optics. These light modulating devices integrated with silicon (Smart Spatial Light Modulators or S-SLMs) form a key component of highly parallel fine grain optoelectronic computers. Spatial light modulators developed using the combination of silicon with PLZT (a ferroelectric light modulating ceramic) meet the system requirements for optoelectronic computing. PLZT can be integrated with silicon by depositing a thin layer of polysilicon on the top. However, the quality of polysilicon does not allow the fabrication of circuits of high complexity. It is possible to enlarge polysilicon grain size by melting and solidifying it in a controlled manner. A dual beam laser recrystallization technique has been developed for this purpose. This thesis involves the development and the application of this technique to fabrication of S-SLMs. The goal is to increase the number of transistors in an S-SLM while keeping the array yield of such devices above acceptable levels for optoelectronic computer systems. For this purpose, a NMOS process in laser recrystallized silicon on PLZT has been developed. Arrays with up to 12 transistor unit cell complexity have been fabricated using this technology.

  6. Modification of the reconstruction distance of Fresnel holograms for display with multiple spatial light modulators

    Science.gov (United States)

    Leportier, Thibault; Park, Min-Chul; Kim, Taegeun

    2016-06-01

    In digital holography, spatial light modulators (SLMs) devices are used to display the holographic patterns. However, modulation is imperfect because SLMs cannot modulate phase and amplitude at the same time. Then undesired terms such as twin image can be observed in the image plane. One solution to remove twin image contribution without physical spatial filter is to perform complex modulation. Phase and amplitude modulation can be performed sequentially with two different SLMs. Similarly, real and imaginary part of hologram can be displayed and combined in an additive configuration through a polarizing beam splitter. In both case, a major problem is the alignment of the two display devices since misalignment as small as one pixel may degrade significantly quality of the reconstruction. For our experiment, we used data computed numerically to obtain separately real and imaginary part of hologram. Then, we focused on additive configuration where two SLMs are displaying real and imaginary part of hologram respectively. Reconstruction distance of hologram is fixed and distance between SLM and beam splitter should be the same for the two devices. In this paper, we study the effect of having different reconstruction distance for the real and imaginary hologram. We performed simulations and explained the result with the scalar diffraction theory. A method to compensate numerically the reconstruction distance is proposed for on-axis configuration. This method can also be applied to modify reconstruction distance of Fresnel hologram displayed with a single SLM and has potential application in RGB holographic reconstruction

  7. New generation polyphase resonant converter-modulators for the Korean atomic energy research institute

    Energy Technology Data Exchange (ETDEWEB)

    Reass, William A [Los Alamos National Laboratory; Baca, David M [Los Alamos National Laboratory; Gribble, Robert F [Los Alamos National Laboratory

    2009-01-01

    This paper will present operational data and performance parameters of the newest generation polyphase resonant high voltage converter modulator (HVCM) as developed and delivered to the KAERI 100 MeV ''PEFP'' accelerator [1]. The KAERI design realizes improvements from the SNS and SLAC designs [2]. To improve the IGBT switching performance at 20 kHz for the KAERI system, the HVCM utilizes the typical zero-voltage-switching (ZVS) at turn on and as well as artificial zero-current-switching (ZCS) at turn-off. The new technique of artificial ZCS technique should result in a 6 fold reduction of IGBT switching losses (3). This improves the HCVM conversion efficiency to better than 95% at full average power, which is 500 kW for the KAERI two klystron 105 kV, 50 A application. The artificial ZCS is accomplished by placing a resonant RLC circuit across the input busswork to the resonant boost transformer. This secondary resonant circuit provides a damped ''kick-back'' to assist in IGBT commutation. As the transformer input busswork is extremely low inductance (< 10 nH), the single RLC network acts like it is across each of the four IGBT collector-emitter terminals of the H-bridge switching network. We will review these topological improvements and the overall system as delivered to the KAERI accelerator and provide details of the operational results.

  8. Nonlinearity management of photonic composites and observation of spatial-modulation instability due to quintic nonlinearity

    CERN Document Server

    Reyna, Albert S

    2014-01-01

    We present a procedure for nonlinearity management of metal-dielectric composites. Varying the volume fraction occupied by silver nanoparticles suspended in acetone we could cancel the refractive index related to the third-order susceptibility, $\\chi_{eff}^{(3)}$, and the nonlinear refraction behavior was due to the fifth-order susceptibility, $\\chi_{eff}^{(5)}$. Hence, in a cross-phase modulation experiment, we demonstrated for the first time the effect of spatial-modulation- instability due to $\\chi_{eff}^{(5)}$. The results are corroborated with numerical calculations based on a generalized Maxwell-Garnet model.

  9. Development of Instrumentation for Spin-Echo Induced Spatial Beam Modulations

    DEFF Research Database (Denmark)

    Sales, Morten

    Spin-Echo Modulated Small Angle Neutron Scattering in Time-of-Flight mode (ToF SEMSANS) is an emerging technique extending the measurable phase space covered by neutron scattering. Using inclined magnetic field surfaces, (very) small angle scattering from a sample can be mapped into the spin...... Institute Delft, TUDelft, and resolve the modulation using absorption gratings in front of a detector without spatial resolution, i.e. a simple counting detector. Combining this with a virtual copy of the instrument, built using the Monte Carlo Ray-Tracing simulation package McStas, we were able to expand...

  10. Nonlinear response studies and corrections for a liquid crystal spatial light modulator

    Indian Academy of Sciences (India)

    Ravinder Kumar Banyal; B Raghavendra Prasad

    2010-06-01

    The nonlinear response of light transmission characteristics of a liquid crystal (LC) spatial light modulator (SLM) is studied. The results show that the device exhibits a wide range of variations with different control parameters and input settings. Experiments were performed to obtain intensity modulation that is best described by either power-law or sigmoidal functions. Based on the inverse transformation, an appropriate pre-processing scheme for electrically addressed input gray-scale images, particularly important in several optical processing and imaging applications, is suggested. Further, the necessity to compensate the SLM image nonlinearities in a volume holographic data storage and retrieval system is demonstrated.

  11. Multichannel mode conversion and multiplexing based on a single spatial light modulator for optical communication

    Science.gov (United States)

    Nie, Song; Yu, Song; Cai, Shanyong; Lan, Mingying; Gu, Wanyi

    2016-07-01

    A method is proposed to achieve multichannel mode conversion and multiplexing by dividing a single spatial light modulator into several blocks with the mode conversion pattern and blazed grating loaded on each block. The conversion patterns realize the precise excitation of higher order modes using combined amplitude and phase modulation. The blazed gratings bring together incident beams, so these beams can be coupled into few-mode fiber (FMF). In the experiment, four higher order modes are precisely excited and converge with a tilt angle. Through the simulation method, these beams can be coupled into FMF with small tilt angles (0.0344 deg for LP11 mode).

  12. Discontinuous conduction mode analysis of phase-modulated series resonant converter

    Indian Academy of Sciences (India)

    UTSAB KUNDU; PARTHASARATHI SENSARMA

    2017-08-01

    This paper proposes an analytical approach to derive voltage gain for phase-modulated dc–dc series resonant converter (SRC) operating in discontinuous conduction mode (DCM). The conventional fundamental harmonic approximation technique is extended for a non-ideal series resonant tank to clarify the limitations of SRC operating in continuous conduction mode (CCM). The DCM analysis is described in a normalized form defining appropriate base quantities. The converter is analysed both in time and frequency domain to derive a non-linear algebraic function of diode rectifier extinction angle. The root of this function is numericallydetermined using MATLAB and used to predict the dc bus voltage. Analytical derivation of critical load resistance is discussed, which indicates the CCM–DCM boundary condition. Experimental results are presented to validate the analysis

  13. Optically detected electron paramagnetic resonance by microwave modulated magnetic circular dichroism

    Science.gov (United States)

    Börger, Birgit; Bingham, Stephen J.; Gutschank, Jörg; Schweika, Marc Oliver; Suter, Dieter; Thomson, Andrew J.

    1999-11-01

    Electron paramagnetic resonance (EPR) can be detected optically, with a laser beam propagating perpendicular to the static magnetic field. As in conventional EPR, excitation uses a resonant microwave field. The detection process can be interpreted as coherent Raman scattering or as a modulation of the laser beam by the circular dichroism of the sample oscillating at the microwave frequency. The latter model suggests that the signal should show the same dependence on the optical wavelength as the MCD signal. We check this for two different samples [cytochrome c-551, a metalloprotein, and ruby (Cr3+:Al2O3)]. In both cases, the observed wavelength dependence is almost identical to that of the MCD signal. A quantitative estimate of the amplitude of the optically detected EPR signal from the MCD also shows good agreement with the experimental results.

  14. Design and implementation of a risk assessment module in a spatial decision support system

    Science.gov (United States)

    Zhang, Kaixi; van Westen, Cees; Bakker, Wim

    2014-05-01

    The spatial decision support system named 'Changes SDSS' is currently under development. The goal of this system is to analyze changing hydro-meteorological hazards and the effect of risk reduction alternatives to support decision makers in choosing the best alternatives. The risk assessment module within the system is to assess the current risk, analyze the risk after implementations of risk reduction alternatives, and analyze the risk in different future years when considering scenarios such as climate change, land use change and population growth. The objective of this work is to present the detailed design and implementation plan of the risk assessment module. The main challenges faced consist of how to shift the risk assessment from traditional desktop software to an open source web-based platform, the availability of input data and the inclusion of uncertainties in the risk analysis. The risk assessment module is developed using Ext JS library for the implementation of user interface on the client side, using Python for scripting, as well as PostGIS spatial functions for complex computations on the server side. The comprehensive consideration of the underlying uncertainties in input data can lead to a better quantification of risk assessment and a more reliable Changes SDSS, since the outputs of risk assessment module are the basis for decision making module within the system. The implementation of this module will contribute to the development of open source web-based modules for multi-hazard risk assessment in the future. This work is part of the "CHANGES SDSS" project, funded by the European Community's 7th Framework Program.

  15. In Vivo Assessment of Neurotransmitters and Modulators with Magnetic Resonance Spectroscopy: Application to Schizophrenia

    Science.gov (United States)

    Wijtenburg, S. Andrea; Yang, Shaolin; Fischer, Bernard A.; Rowland, Laura M.

    2015-01-01

    In vivo measurement of neurotransmitters and modulators is now feasible with advanced proton magnetic resonance spectroscopy (1H-MRS) techniques. This review provides a basic tutorial of MRS, describes the methods available to measure brain glutamate, glutamine, γ-aminobutyric acid, glutathione, N-acetylaspartylglutamate, glycine, and serine at magnetic field strengths of 3Tesla or higher, and summarizes the neurochemical findings in schizophrenia. Overall, 1H-MRS holds great promise for producing biomarkers that can serve as treatment targets, prediction of disease onset, or illness exacerbation in schizophrenia and other brain diseases. PMID:25614132

  16. Angle modulated surface plasmon resonance spectrometer for refractive index sensing with enhanced detection resolution

    Science.gov (United States)

    Zhou, Xinlei; Chen, Ke; Li, Li; Peng, Wei; Yu, Qingxu

    2017-01-01

    We design and manufacture an angle modulated surface plasmon resonance (SPR) spectrometer with high detection resolution for refractive index sensing. The presented SPR spectrometer is based on a five-layer Kretchmann configuration. To enhance the sensitivity and resolution of the SPR spectrometer, we introduce a reference beam into the system, which has improved the stability of the system by nearly one order of magnitude. Numerical simulation and experimental study are presented and the results show that a sensitivity of 85 degrees/RIU (refractive index unit) and a good repeatability (standard deviation=3.7×10-6 RIU) have been achieved.

  17. Stochastic resonance in a fractional harmonic oscillator subject to random mass and signal-modulated noise

    Science.gov (United States)

    Guo, Feng; Zhu, Cheng-Yin; Cheng, Xiao-Feng; Li, Heng

    2016-10-01

    Stochastic resonance in a fractional harmonic oscillator with random mass and signal-modulated noise is investigated. Applying linear system theory and the characteristics of the noises, the analysis expression of the mean output-amplitude-gain (OAG) is obtained. It is shown that the OAG varies non-monotonically with the increase of the intensity of the multiplicative dichotomous noise, with the increase of the frequency of the driving force, as well as with the increase of the system frequency. In addition, the OAG is a non-monotonic function of the system friction coefficient, as a function of the viscous damping coefficient, as a function of the fractional exponent.

  18. Compound cavity theory of resonant phase modulation in laser self-mixing ultrasonic vibration measurement

    Science.gov (United States)

    Tao, Yufeng; Wang, Ming; Guo, Dongmei

    2016-07-01

    The theoretical basis of self-mixing interference (SMI) employing a resonant phase modulator is explored to prove its tempting advantages. The adopted method induces a pure phase carrier without increasing system complexity. A simple time-domain signal process is used to estimate modulation depth and precisely track vibrating trail, which promises the flexibility of measuring ultrasonic vibration regardless of the constraint of the Bessel functions. The broad bandwidth, low speckle noise, compact, safe, and easy operating SMI system obtains the best resolution of a poor reflection environment. Numerical simulation discusses the spectrum broadening and errors due to multiple reflections. Experimental results agree with theory coherently and are compared with laser Doppler vibration meter showing a dynamical error better than 20 nm in ultrasonic vibration measurement.

  19. Helical electric potential modulation via zonal-flow coupling to resonant magnetic perturbations

    Science.gov (United States)

    Leconte, M.; Kim, J.-H.

    2017-08-01

    Helical modulations of the electric potential were observed in several devices during application of resonant magnetic perturbations (RMPs). To address the implication of the helical modulation on RMP-induced transport, we derive a system of 1D equations for zonal flows (ZFs) and helical potential in the presence of RMPs. As ZFs are turbulence-driven, turbulence plays a major role in this plasma self-organization towards a quasi-equilibrium with 3D helical potential. The model reveals how RMPs modify an initially given a saturated-state of coexisting turbulence and ZFs. It is shown that RMPs trigger a transport bifurcation by allowing energy-transfer out of turbulence-driven ZFs into ZF-driven helical potential.

  20. Vibration suppression for strings with distributed loading using spatial cross-section modulation

    DEFF Research Database (Denmark)

    Sorokin, Vladislav; Thomsen, Jon Juel

    2015-01-01

    of rain and wind, and dynamics of suspension bridges and stay cables. Suppression of vibration in predefined regions of the string is performed by continuous spatial modulation of its cross-section. For analyzing the problem considered a novel approach named the method of varying amplitudes is employed......A problem of vibration suppression in any preassigned region of a bounded structure subjected to action of an external time-periodic load which is distributed over its domain is considered. A passive control is applied, in which continuous spatially periodic modulations of structural parameters...... are used as a means for vibration suppression. As an example, stationary vibrations of a string under action of a distributed time-periodic load are studied. This system in a simplified form models such processes as interaction between membranes and colloids, oscillations of transmission lines under action...

  1. Measuring the size of biological nanostructures with spatially modulated illumination microscopy.

    Science.gov (United States)

    Martin, Sonya; Failla, Antonio Virgilio; Spöri, Udo; Cremer, Christoph; Pombo, Ana

    2004-05-01

    Spatially modulated illumination fluorescence microscopy can in theory measure the sizes of objects with a diameter ranging between 10 and 200 nm and has allowed accurate size measurement of subresolution fluorescent beads ( approximately 40-100 nm). Biological structures in this size range have so far been measured by electron microscopy. Here, we have labeled sites containing the active, hyperphosphorylated form of RNA polymerase II in the nucleus of HeLa cells by using the antibody H5. The spatially modulated illumination-microscope was compared with confocal laser scanning and electron microscopes and found to be suitable for measuring the size of cellular nanostructures in a biological setting. The hyperphosphorylated form of polymerase II was found in structures with a diameter of approximately 70 nm, well below the 200-nm resolution limit of standard fluorescence microscopes.

  2. Note: Laser beam scanning using a ferroelectric liquid crystal spatial light modulator

    Energy Technology Data Exchange (ETDEWEB)

    Das, Abhijit [Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781039, Assam (India); Department of Physics, Gauhati University, Guwahati 781014, Assam (India); Boruah, Bosanta R., E-mail: brboruah@iitg.ernet.in [Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781039, Assam (India)

    2014-04-15

    In this work we describe laser beam scanning using a ferroelectric liquid crystal spatial light modulator. Commercially available ferroelectric liquid crystal spatial light modulators are capable of displaying 85 colored images in 1 s using a time dithering technique. Each colored image, in fact, comprises 24 single bit (black and white) images displayed sequentially. We have used each single bit image to write a binary phase hologram. For a collimated laser beam incident on the hologram, one of the diffracted beams can be made to travel along a user defined direction. We have constructed a beam scanner employing the above arrangement and demonstrated its use to scan a single laser beam in a laser scanning optical sectioning microscope setup.

  3. A position sensor based on grating projection with spatial filtering and polarization modulation

    Institute of Scientific and Technical Information of China (English)

    Jianming Hu; Aijun Zeng; Xiangzhao Wang

    2006-01-01

    A position sensor based on grating projection with spatial filtering and polarization modulation is presented. A grating is projected onto the object to be measured through a 4f optical system with a spatial filter. After reflected by the object, the grating projection is imaged on a detection grating through an other 4f optical system to form moit(e) fringes.The polarization modulated moir(e) signal is deteted to obtain the position of object.The measurement is independent of the incident intensity on the projection grating and the reflectivity of the object to be measured. In experiments, the effectiveness of the position sensor is proved, and the root mean square (RMS) error at each measurement position is less than 13 nm.

  4. A high-end mask writer using a spatial light modulator

    Science.gov (United States)

    Ljungblad, Ulric B.; Askebjer, Per; Karlin, Tord; Sandstrom, Tor; Sjoeberg, Henrik

    2005-01-01

    This paper presents the properties of the Sigma7300 which is a commercial DUV laser pattern generator based on spatial light modulator (SLM) technology designed to meet the requirements of the 65-nm technology node and below. The introduction of spatial light modulators provides a possibility for optical mask writers to combine high resolution and accuracy with short write time making it possible to write most of the high end mask layers in a cost effective way. The Sigma7300 mask writer is developed by Micronic Laser Systems whereas the SLM, which is a combined MEMS and CMOS component with individually controllable movable micromirrors, is developed by the Fraunhofer-IPMS institute in Dresden. The SLM allows parallel writing of one million pixels with a frame rate of up to 2 kHz. The technology offers resolution enhancement advantages from stepper technology not available in other mask patterning tools.

  5. High-speed and compact silicon modulator based on a racetrack resonator with a 1 V drive voltage.

    Science.gov (United States)

    Dong, Po; Liao, Shirong; Liang, Hong; Qian, Wei; Wang, Xin; Shafiiha, Roshanak; Feng, Dazeng; Li, Guoliang; Zheng, Xuezhe; Krishnamoorthy, Ashok V; Asghari, Mehdi

    2010-10-01

    Fast, compact, and power-efficient silicon microcavity electro-optic modulators are expected to be critical components for chip-level optical interconnects. It is highly desirable that these modulators can be driven by voltage swings of 1 V or less to reduce power dissipation and make them compatible with voltage supply levels associated with current and future complementary metal-oxide-semiconductor technology nodes. Here, we present a silicon racetrack resonator modulator that achieves over 8 dB modulation depth at 12.5 Gbps with a 1 V swing. In addition, the use of a racetrack resonator geometry relaxes the tight lithography resolution requirements typically associated with microring resonators and enhances the ability to use common lithographic optical techniques for their fabrication.

  6. Fast two-photon neuronal imaging and control using a spatial light modulator and ruthenium compounds

    Science.gov (United States)

    Peterka, Darcy S.; Nikolenko, Volodymyr; Fino, Elodie; Araya, Roberto; Etchenique, Roberto; Yuste, Rafael

    2010-02-01

    We have developed a spatial light modulator (SLM) based microscope that uses diffraction to shape the incoming two-photon laser source to any arbitrary light pattern. This allows the simultaneous imaging or photostimulation of different regions of a sample with three-dimensional precision at high frame rates. Additionally, we have combined this microscope with a new class of two photon active neuromodulators with Ruthenium BiPyridine (RuBi) based cages that offer great flexibility for neuronal control.

  7. Pixel size and pitch measurements of liquid crystal spatial light modulator by optical diffraction

    Indian Academy of Sciences (India)

    Ravinder Kumar Banyal; B Raghavendra Prasad

    2005-08-01

    We present a simple technique for the determination of pixel size and pitch of liquid crystal (LC) based spatial light modulator (SLM). The proposed method is based on optical diffraction from pixelated LC panel that has been modeled as a two-dimensional array of rectangular apertures. A novel yet simple, two-plane measurement technique is implemented to circumvent the difficulty in absolute distance measurement. Experimental results are presented for electrically addressed twisted nematic LC-SLM removed from the display projector.

  8. Two spatial light modulator system for laboratory simulation of random beam propagation in random media.

    Science.gov (United States)

    Wang, Fei; Toselli, Italo; Korotkova, Olga

    2016-02-10

    An optical system consisting of a laser source and two independent consecutive phase-only spatial light modulators (SLMs) is shown to accurately simulate a generated random beam (first SLM) after interaction with a stationary random medium (second SLM). To illustrate the range of possibilities, a recently introduced class of random optical frames is examined on propagation in free space and several weak turbulent channels with Kolmogorov and non-Kolmogorov statistics.

  9. Contextual modulation of motor resonance during the observation of everyday actions.

    Science.gov (United States)

    Amoruso, Lucia; Urgesi, Cosimo

    2016-07-01

    Neuroimaging studies on action observation suggest that context plays a key role in coding high-level components of motor behavior, including the short-term and the end-goal of an action. However, little is known about the possible role of context in shaping lower-levels of action processing such as reading action kinematics and simulating muscular activity. Here, we combined single-pulse TMS and motor-evoked potentials (MEPs) recording to explore whether top-down contextual information is capable of modulating low-level motor representations. We recorded MEPs from FDI and FCR muscles while participants watched videos about everyday actions embedded in congruent, incongruent or ambiguous contexts. Videos were interrupted before action ending, and participants were requested to predict the course of the observed action. A contextual modulation of corticospinal excitability was observed only for the FDI muscle, which is specifically involved in the execution of reaching-to-grasping movements, and whose corticospinal pathway is influenced by the observation of the very same movements. This modulation was reflected in a selective decrease of corticospinal excitability during the observation of actions embedded in incongruent as compared to congruent and ambiguous contexts. These findings indicate that motor resonance is not an entirely automatic process, but it can be modulated by high-level contextual representations.

  10. Modulation of the pupil function of microscope objective lens for multifocal multi-photon microscopy using a spatial light modulator

    Science.gov (United States)

    Matsumoto, Naoya; Okazaki, Shigetoshi; Takamoto, Hisayoshi; Inoue, Takashi; Terakawa, Susumu

    2014-02-01

    We propose a method for high precision modulation of the pupil function of a microscope objective lens to improve the performance of multifocal multi-photon microscopy (MMM). To modulate the pupil function, we adopt a spatial light modulator (SLM) and place it at the conjugate position of the objective lens. The SLM can generate an arbitrary number of spots to excite the multiple fluorescence spots (MFS) at the desired positions and intensities by applying an appropriate computer-generated hologram (CGH). This flexibility allows us to control the MFS according to the photobleaching level of a fluorescent protein and phototoxicity of a specimen. However, when a large number of excitation spots are generated, the intensity distribution of the MFS is significantly different from the one originally designed due to misalignment of the optical setup and characteristics of the SLM. As a result, the image of a specimen obtained using laser scanning for the MFS has block noise segments because the SLM could not generate a uniform MFS. To improve the intensity distribution of the MFS, we adaptively redesigned the CGH based on the observed MFS. We experimentally demonstrate an improvement in the uniformity of a 10 × 10 MFS grid using a dye solution. The simplicity of the proposed method will allow it to be applied for calibration of MMM before observing living tissue. After the MMM calibration, we performed laser scanning with two-photon excitation to observe a real specimen without detecting block noise segments.

  11. Localization of massless Dirac particles via spatial modulations of the Fermi velocity

    Science.gov (United States)

    Downing, C. A.; Portnoi, M. E.

    2017-08-01

    The electrons found in Dirac materials are notorious for being difficult to manipulate due to the Klein phenomenon and absence of backscattering. Here we investigate how spatial modulations of the Fermi velocity in two-dimensional Dirac materials can give rise to localization effects, with either full (zero-dimensional) confinement or partial (one-dimensional) confinement possible depending on the geometry of the velocity modulation. We present several exactly solvable models illustrating the nature of the bound states which arise, revealing how the gradient of the Fermi velocity is crucial for determining fundamental properties of the bound states such as the zero-point energy. We discuss the implications for guiding electronic waves in few-mode waveguides formed by Fermi velocity modulation.

  12. Magnetic resonance image restoration via dictionary learning under spatially adaptive constraints.

    Science.gov (United States)

    Wang, Shanshan; Xia, Yong; Dong, Pei; Feng, David Dagan; Luo, Jianhua; Huang, Qiu

    2013-01-01

    This paper proposes a spatially adaptive constrained dictionary learning (SAC-DL) algorithm for Rician noise removal in magnitude magnetic resonance (MR) images. This algorithm explores both the strength of dictionary learning to preserve image structures and the robustness of local variance estimation to remove signal-dependent Rician noise. The magnitude image is first separated into a number of partly overlapping image patches. The statistics of each patch are collected and analyzed to obtain a local noise variance. To better adapt to Rician noise, a correction factor is formulated with the local signal-to-noise ratio (SNR). Finally, the trained dictionary is used to denoise each image patch under spatially adaptive constraints. The proposed algorithm has been compared to the popular nonlocal means (NLM) filtering and unbiased NLM (UNLM) algorithm on simulated T1-weighted, T2-weighted and PD-weighted MR images. Our results suggest that the SAC-DL algorithm preserves more image structures while effectively removing the noise than NLM and it is also superior to UNLM at low noise levels.

  13. Doubling the resolution of spatial-light-modulator-based differential interference contrast microscopy by structured illumination.

    Science.gov (United States)

    Chen, Jianling; Lv, Xiaohua; Zeng, Shaoqun

    2013-09-01

    Recently developed spatial light modulator (SLM)-based differential interference contrast (DIC) microscopy [Opt. Lett. 34, 2988 (2009)] reveals flexibility on the implementation of DIC imaging. However, its numerical aperture (spatial resolution) is limited to maintain sufficient interference contrast, because it requires two beams to interfere. We present a structured illumination (SI) SLM-based DIC microscopy to effectively improve the lateral resolution of the SLM-based DIC microscopy. The SI field is generated and controlled by an adjustable grating displayed on an SLM. The SI SLM-based DIC expands the bandwidth of the coherent transfer function of the SLM-based DIC imaging system, thus improving the spatial resolution. The reconstructed SI SLM-based DIC image exhibits lateral resolution of approximately 208 nm, doubling that of the common SLM-based DIC image (approximately 415 nm). SI SLM-based DIC microscopy has the potential for achieving high-resolution quantitative phase images.

  14. Magnetic-free non-reciprocity and isolation based on parametrically modulated coupled-resonator loops

    Science.gov (United States)

    Estep, Nicholas A.; Sounas, Dimitrios L.; Soric, Jason; Alù, Andrea

    2014-12-01

    Non-reciprocal components, which are essential to many modern communication systems, are almost exclusively based on magneto-optical materials, severely limiting their applicability. A practical and inexpensive route to magnetic-free non-reciprocity could revolutionize radio-frequency and nanophotonic communication networks. Angular-momentum biasing was recently proposed as a means of realizing isolation for sound waves travelling in a rotating medium, and envisaged as a path towards compact, linear integrated non-reciprocal electromagnetic components. Inspired by this concept, here we demonstrate a subwavelength, linear radio-frequency non-reciprocal circulator free from magnetic materials and bias. The scheme is based on the parametric modulation of three identical, strongly and symmetrically coupled resonators. Their resonant frequencies are modulated by external signals with the same amplitude and a relative phase difference of 120°, imparting an effective electronic angular momentum to the system. We observe giant non-reciprocity, with up to six orders of magnitude difference in transmission for opposite directions. Furthermore, the device topology is tunable in real time, and can be directly embedded in a conventional integrated circuit.

  15. Double-Slot Hybrid Plasmonic Ring Resonator Used for Optical Sensors and Modulators

    Directory of Open Access Journals (Sweden)

    Xu Sun

    2015-11-01

    Full Text Available An ultra-high sensitivity double-slot hybrid plasmonic (DSHP ring resonator, used for optical sensors and modulators, is developed. Due to high index contrast, as well as plasmonic enhancement, a considerable part of the optical energy is concentrated in the narrow slots between Si and plasmonic materials (silver is used in this paper, which leads to high sensitivity to the infiltrating materials. By partial opening of the outer plasmonic circular sheet of the DSHP ring, a conventional side-coupled silicon on insulator (SOI bus waveguide can be used. Experimental results demonstrate ultra-high sensitivity (687.5 nm/RIU of the developed DSHP ring resonator, which is about five-times higher than for the conventional Si ring with the same geometry. Further discussions show that a very low detection limit (5.37 × 10−6 RIU can be achieved after loaded Q factor modifications. In addition, the plasmonic metal structures offer also the way to process optical and electronic signals along the same hybrid plasmonic circuits with small capacitance (~0.275 fF and large electric field, which leads to possible applications in compact high-efficiency electro-optic modulators, where no extra electrodes for electronic signals are required.

  16. The Stochastic Resonance Behaviors of a Generalized Harmonic Oscillator Subject to Multiplicative and Periodically Modulated Noises

    Directory of Open Access Journals (Sweden)

    Suchuan Zhong

    2016-01-01

    Full Text Available The stochastic resonance (SR characteristics of a generalized Langevin linear system driven by a multiplicative noise and a periodically modulated noise are studied (the two noises are correlated. In this paper, we consider a generalized Langevin equation (GLE driven by an internal noise with long-memory and long-range dependence, such as fractional Gaussian noise (fGn and Mittag-Leffler noise (M-Ln. Such a model is appropriate to characterize the chemical and biological solutions as well as to some nanotechnological devices. An exact analytic expression of the output amplitude is obtained. Based on it, some characteristic features of stochastic resonance phenomenon are revealed. On the other hand, by the use of the exact expression, we obtain the phase diagram for the resonant behaviors of the output amplitude versus noise intensity under different values of system parameters. These useful results presented in this paper can give the theoretical basis for practical use and control of the SR phenomenon of this mathematical model in future works.

  17. Dimensional metrology of smooth micro structures utilizing the spatial modulation of white-light interference fringes

    Science.gov (United States)

    Zhou, Yi; Tang, Yan; Deng, Qinyuan; Liu, Junbo; Wang, Jian; Zhao, Lixin

    2017-08-01

    Dimensional metrology for micro structure plays an important role in addressing quality issues and observing the performance of micro-fabricated products. In white light interferometry, the proposed method is expected to measure three-dimensional topography through modulation depth in spatial frequency domain. A normalized modulation depth is first obtained in the xy plane (image plane) for each CCD image individually. After that, the modulation depth of each pixel is analyzed along the scanning direction (z-axis) to reshape the topography of micro samples. Owing to the characteristics of modulation depth in broadband light interferometry, the method could effectively suppress the negative influences caused by light fluctuations and external irradiance disturbance. Both theory and experiments are elaborated in detail to verify that the modulation depth-based method can greatly level up the stability and sensitivity with satisfied precision in the measurement system. This technique can achieve an improved robustness in a complex measurement environment with the potential to be applied in online topography measurement such as chemistry and medical domains.

  18. Equilibrium configurations of director in a planar nematic cell with one spatially modulated surface

    Directory of Open Access Journals (Sweden)

    M.F. Ledney

    2016-09-01

    Full Text Available We study two-dimensional equilibrium configurations of nematic liquid crystal (NLC director in a cell confined between two parallel surfaces: a planar surface and a spatially modulated one. The relief of the modulated surface is described by a smooth periodic sine-like function. The director easy axis orientation is homeotropic at one of the bounding surfaces and is planar at the other one. Strong NLC anchoring with both surfaces is assumed. We consider the case where disclination lines occur in the bulk of NLC strictly above local extrema of the modulated surface. These disclination lines run along the crests and troughs of the relief waves. In the approximation of planar director deformations we obtain analytical expressions describing a director distribution in the bulk of the cell. Equilibrium distances from disclination lines to the modulated surface are calculated and their dependences on the cell thickness and the period and depth of the surface relief are studied. It is shown that the distances from disclination lines to the modulated surface decrease as the depth of the relief increases.

  19. Spatial normalization of ultrahigh resolution 7 T magnetic resonance imaging data of the postmortem human subthalamic nucleus: a multistage approach

    NARCIS (Netherlands)

    Weiss, M; Alkemade, A.; Keuken, M.C.; Müller-Axt, C.; Geyer, S.; Turner, R.; Forstmann, B.U.

    2015-01-01

    In this paper, we describe a novel processing strategy for the spatial normalization of ultrahigh resolution magnetic resonance imaging (MRI) data of small ex vivo samples into MNI standard space. We present a multistage scanning and registration method for data of the subthalamic nucleus (STN) obta

  20. Spatial normalization of ultrahigh resolution 7 T magnetic resonance imaging data of the postmortem human subthalamic nucleus: a multistage approach

    NARCIS (Netherlands)

    Weiss, M; Alkemade, A.; Keuken, M.C.; Müller-Axt, C.; Geyer, S.; Turner, R.; Forstmann, B.U.

    2015-01-01

    In this paper, we describe a novel processing strategy for the spatial normalization of ultrahigh resolution magnetic resonance imaging (MRI) data of small ex vivo samples into MNI standard space. We present a multistage scanning and registration method for data of the subthalamic nucleus (STN) obta

  1. Longitudinal stratified liquid crystal structures to enable practical spatial light modulators in the terahertz regime

    Science.gov (United States)

    Tareki, Abubaker M.; Kim, Wonkyu; Guo, Junpeng; Lindquist, Robert G.

    2016-09-01

    Electro-optic (EO) modulation of the amplitude and phase of electromagnetic waves using liquid crystals (LCs) is commonplace in the optical and infrared regions. This effort has led to commercially available components used in spectral filtering, polarization management, beam steering, transmitters, displays, etc. However, electro-optic techniques have had limited success in the terahertz (THz) region due to several practical design challenges. The growth in applications has led to an interest in the development of a spatial light modulator (SLM) for the terahertz region. In the visible region, the most common SLMs use electro-optic materials such as liquid crystals to spatially modulate a beam. However, this approach to achieve a practical SLM in the terahertz regime has been difficult. The primary barrier for components is the long interaction lengths required to modulate a THz wave. Since the EO modulation depth is directly proportional to the multiplication of the change of permittivity and the ratio of interaction length over wavelength, THz systems with wavelengths ranging from 150 μm to 1mm pose a challenge. To overcome this barrier, longitudinal stratified sub-wavelength liquid crystal structures have been engineered and fabricated. The stratified structures introduce the challenge in the selection and design of the electrodes. By using multiple layers the tunable films can be maintained at manageable thicknesses (25 to 200 μm). The reduced individual film thickness will significantly improve the requisite drive voltage and response time. However, the layered structure with multiple conducting layers adds considerable challenges to the design of the transparent electrode. Both simulation and experimental data will be presented.

  2. Linear and nonlinear resonance features of an erbium-doped fibre ring laser under cavity-loss modulation

    Indian Academy of Sciences (India)

    Aditi Ghosh; R Vijaya

    2014-07-01

    The continuous-wave output of a single-mode erbium-doped fibre ring laser when subjected to cavity-loss modulation is found to exhibit linear as well as nonlinear resonances. At sufficiently low driving amplitude, the system resembles a linear damped oscillator. At higher amplitudes, the dynamical study of these resonances shows that the behaviour of the system exhibits features of a nonlinear damped oscillator under harmonic modulation. These nonlinear dynamical features, including harmonic and subharmonic resonances, have been studied experimentally and analysed with the help of a simple time-domain and frequency-domain information obtained from the output of the laser. All the studies are restricted to the modulation frequency lying in a regime near the relaxation oscillation frequency.

  3. Laser beam shaping limitations for laboratory simulation of turbulence using a phase-only spatial light modulator

    CSIR Research Space (South Africa)

    Litvin, IA

    2007-09-01

    Full Text Available Recent approaches to demonstrating adaptive optics and atmospheric turbulence have made use of spatial light modulators (SLMs) as the active phase element. However, there are limitations in using SLMs as an accurate method of simulating turbulence...

  4. Comparison of gold- and graphene-based resonant nanostructures for terahertz metamaterials and an ultrathin graphene-based modulator

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Nian-Hai [Ames Laboratory; Tassin, Philippe [Ames Laboratory; Koschny, Thomas [Ames Laboratory; Soukoulis, Costas M [Ames Laboratory

    2014-09-01

    Graphene exhibits unique material properties, and in electromagnetic wave technology it raises the prospect of devices miniaturized down to the atomic length scale. Here we study split-ring resonator metamaterials made from graphene and we compare them to gold-based metamaterials. We find that graphene's huge reactive response derived from its large kinetic inductance allows for deeply subwavelength resonances, although its resonance strength is reduced due to higher dissipative loss damping and smaller dipole coupling. Nevertheless, tightly stacked graphene rings may provide for negative permeability and the electric dipole resonance of graphene meta-atoms turns out to be surprisingly strong. Based on these findings, we present a terahertz modulator based on a metamaterial with a multilayer stack of alternating patterned graphene sheets separated by dielectric spacers. Neighboring graphene flakes are biased against each other, resulting in modulation depths of over 75% at a transmission level of around 90%.

  5. Comparison of gold- and graphene-based resonant nanostructures for terahertz metamaterials and an ultrathin graphene-based modulator

    Science.gov (United States)

    Shen, Nian-Hai; Tassin, Philippe; Koschny, Thomas; Soukoulis, Costas M.

    2014-09-01

    Graphene exhibits unique material properties, and in electromagnetic wave technology it raises the prospect of devices miniaturized down to the atomic length scale. Here we study split-ring resonator metamaterials made from graphene and we compare them to gold-based metamaterials. We find that graphene's huge reactive response derived from its large kinetic inductance allows for deeply subwavelength resonances, although its resonance strength is reduced due to higher dissipative loss damping and smaller dipole coupling. Nevertheless, tightly stacked graphene rings may provide for negative permeability and the electric dipole resonance of graphene meta-atoms turns out to be surprisingly strong. Based on these findings, we present a terahertz modulator based on a metamaterial with a multilayer stack of alternating patterned graphene sheets separated by dielectric spacers. Neighboring graphene flakes are biased against each other, resulting in modulation depths of over 75% at a transmission level of around 90%.

  6. Sleep modulates the neural substrates of both spatial and contextual memory consolidation.

    Directory of Open Access Journals (Sweden)

    Géraldine Rauchs

    -training sleep modulates the neural substrates of the consolidation of both the spatial and contextual memories acquired during virtual navigation.

  7. APPLICATION OF SPATIAL LIGHT MODULATORS FOR GENERATION OF LASER BEAMS WITH A SPIRAL PHASE DISTRIBUTION

    Directory of Open Access Journals (Sweden)

    A. A. Zinchik

    2015-09-01

    Full Text Available Subject of Research. This paper discusses numerical simulation of spiral beams. Spiral beams have been experimentally obtained with the use of liquid crystal spatial light modulators (LCD SLM. The ability of dynamical change for the laser beam parameters has been studied. Method. Spiral beams are traditionally obtained by means of static masks defining the amplitude and phase distribution of the beam. The paper deals with modernized method with the use of two LCD SLMs. Modulators form separately the amplitude and phase distribution of the laser beam. Main Results. Numerical modeling of space spiral beams with different amplitude and phase characteristics has been carried out with the use of VirtualLab 5.0 software package manufactured by LightTrans GmbH. Simulation results are compared to the results of a natural experiment. Experimental results are in good agreement with computer simulation. It is shown that LCD SLMs application gives the possibility for dynamical change of the spiral beam parameters, their structure and the dependence of rotation angle on the distance. Distribution phase inversion leads to a change in the rotation direction of the laser beam and, therefore, to a change in the direction of its orbital angular momentum. Practical Relevance. The use of spatial modulators makes it possible to change dynamically the beam parameters, including rotation direction change. The results can be applied for solution of problems related to laser manipulating of microparticles, as well as the problems of determining the phase inhomogeneities of transparent objects.

  8. Adaptive imaging system with spatial light modulator for robust shape measurement of partially specular objects.

    Science.gov (United States)

    Jeong, Joongki; Kim, Min Young

    2010-12-20

    In imaging systems, when specular surfaces responding sensitively to varying illumination conditions are imaged on groups of CCD pixels using imaging optics, the obtained image usually suffers from pixel saturation, resulting in smearing or blooming phenomena. These problems are then serious obstacles when applying structured light-based optical profiling methods to the shape measurement of general objects with partially specular surfaces. Therefore, this paper combines a phase-based profiling system with an with an adaptive spatial light modulator in the imaging part for measuring the three-dimensional shapes of objects with an advanced dynamic range. The use of a spatial light modulator in front of a CCD camera prevents the image sensor from being saturated, as the pixel transmittance is controlled by monitoring the input images and providing modulator feedback signals over time and space. When using the proposed system, since the projected fringes are effectively imaged on the CCD without any pixel saturation, phase information according to the object's shape can be correctly extracted from non-saturated images. The configuration of the proposed system and transmittance control scheme are explained in detail, plus the performance is verified through a series of experiments, in which phase information was successfully extracted from areas that are not normally measurable due to saturation. Based on the results, the proposed shape measurement system showed a more advanced adaptive dynamic range when compared with a conventional system.

  9. Nonlinear resonance converse magnetoelectric effect modulated by voltage for the symmetrical magnetoelectric laminates under magnetic and thermal loadings

    Science.gov (United States)

    Zhou, Hao-Miao; Liu, Hui; Zhou, Yun; Hu, Wen-Wen

    2016-12-01

    Based on the tri-layer symmetrical magnetoelectric laminates, a equivalent circuit for the nonlinear resonance converse magnetoelectric coupling effect is established. Because the nonlinear thermo-magneto-mechanical constitutive equations of magnetostrictive material were introduced, a converse magnetoelectric coefficient model was derived from the equivalent circuit, which can describe the influence of bias electric field, bias magnetic field and ambient temperature on the resonance converse magnetoelectric coupling effect. Especially, the model can well predict the modulation effect of bias electric field/voltage on the magnetism of magnetoelectric composite or the converse magnetoelectric coefficient, which is absolutely vital in applications. Both of the converse magnetoelectric coefficient and the resonance frequency predicted by the model have good agreements with the existing experimental results in qualitatively and quantitatively, and the validity of the model is confirmed. On this basis, according to the model, the nonlinear trends of the resonance converse magnetoelectric effect under different bias voltages, bias magnetic fields and ambient temperatures are predicted. From the results, it can be found that the bias voltage can effectively modulate the curve of the resonance converse magnetoelectric coefficient versus bias magnetic field, and then change the corresponding optimal bias magnetic field of the maximum converse magnetoelectric coefficient; with the increasing volume ratio of piezoelectric layers, the modulation effect of bias voltage becomes more obvious; under different bias magnetic fields, the modulation effect of bias voltage on the converse magnetoelectric effect has nonvolatility in a wide temperature region.

  10. Spatial Modulation and Filtering of Diffusion Patterns for Inverse Analysis of Heat Deposition

    Science.gov (United States)

    Lambrakos, S. G.

    2010-11-01

    General parameterizations are constructed for spatial modulation and filtering of heat diffusion patterns according to general energy deposition characteristics occurring within a volume of material resulting from a volumetrically coupled energy source. These parameterizations include previously constructed models of energy deposition as special cases. The construction of a general parameterization of energy deposition processes is necessary for their inverse analysis. The structure of such a parameterization follows from the concepts of model and data spaces that imply the existence of an optimal parametric representation for a given class of inverse problems. Accordingly, the optimal parametric representation is determined by the characteristics of the available data, which in principle can contain both experimental measurements and numerical simulation data. Parameterizations for spatial modulation and filtering of heat diffusion follow from the observation that many different types of energy deposition processes can be represented by weighted sums of basis functions whose general forms are that of spatially modulated or filtered diffusion. A significant aspect of the parameterizations presented is that the definition of the inverse heat deposition problem, which is adopted for their construction, provides a rigorous foundation for a highly flexible and general parameterization of energy deposition processes, which is essential for their inverse analysis. A preliminary proof is presented that shows the significance of these parameterizations for the application of similarity transformations to the inverse analysis of energy deposition processes. The applicability of similarity transforms to the inverse analysis of heat deposition is another property that follows from the specific definition of the inverse heat deposition problem considered here.

  11. Modulated Pulses Based High Spatial Resolution Distributed Fiber System for Multi-Parameter Sensing

    CERN Document Server

    Zhang, Jingdong; Zhou, Huan; Li, Yang; Liu, Min; Huang, Wei

    2016-01-01

    We demonstrate a hybrid distributed fiber sensing system for multi-parameter detection. The integration of phase-sensitive optical time domain reflectometry ({\\Phi}-OTDR) and Brillouin optical time domain reflectometry (B-OTDR) enables measurement of vibration, temperature and strain. Exploiting the fast changing property of vibration and the static property of temperature and strain, the laser pulse width and intensity are modulated and then injected into the single-mode sensing fiber proportionally, so that the three concerned parameters can be extracted simultaneously by only one photo-detector and data acquisition channel. Combining with advanced data processing methods, the modulation of laser pulse brings additional advantages because of trade and balance between the backscattering light power and nonlinear effect noise, which enhances the signal-to-noise ratio, and enables sub-meter level spatial resolution together with long sensing distance. The proposed method realizes up to 4.8 kHz vibration sensin...

  12. A Polymer Film Dye Laser with Spatially Modulated Emission Controlled by Transversely Distributed Pumping

    Directory of Open Access Journals (Sweden)

    Zurab V. Wardosanidze

    2016-01-01

    Full Text Available Spatial modulation of laser emission controlled by the structure of excitation light field was demonstrated. A dye doped polymer film as an active medium was sandwiched between two laser mirrors forming a laser cell. The pumping was performed by an interference pattern formed with two mutually coherent beams of the second harmonic of a Q-switched Nd:YAG laser (532 nm and located in the plane of the laser cell. The laser emission was observed normally on the plane of the cell. The cross section of the obtained laser emission was modulated in intensity with an interval between maximums depending on the period of the pumping interference pattern. Thus, the emitted light field qualitatively looks like diffraction from an elementary dynamic hologram, that is, a holographic diffraction grating.

  13. Non-resonant wavelength modulation saturation spectroscopy in acetylene-filled hollow-core photonic bandgap fibres applied to modulation-free laser diode stabilisation.

    Science.gov (United States)

    Pineda-Vadillo, Pablo; Lynch, Michael; Charlton, Christy; Donegan, John F; Weldon, Vincent

    2009-12-07

    In this paper the application of Wavelength Modulation (WM) techniques to non-resonant saturation spectroscopy in acetylene-filled Hollow-Core Photonic Bandgap Fibres (HC-PBFs) and modulation-free Laser Diode (LD) frequency stabilisation is investigated. In the first part WM techniques are applied to non-resonant pump-probe saturation of acetylene overtone rotational transitions in a HC-PBF. A high-power DFB chip-on-carrier mounted LD is used in conjunction with a tuneable External Cavity Laser (ECL) and the main saturation parameters are characterized. In the second part a novel feedback system to stabilize the DFB emission wavelength based on the WM saturation results is implemented. Modulation-free locking of the DFB laser frequency to the narrow linewidth saturation feature is achieved for both constant and variable LD temperatures.

  14. Spatiotemporal soliton clusters in the $(3+1)$-dimensional nonlinear Schrödinger equation with spatially modulated nonlinearity

    Indian Academy of Sciences (India)

    HONG-YU WU; LI-HONG JIANG

    2017-09-01

    From a generic transformation, a $(3+1)$-dimensional nonlinear Schrödinger equation with spatially modulated nonlinearity is studied and exact spatiotemporal soliton cluster solutions are derived. When the azimuthal parameter $m = 0$, Gaussian solitons are constructed. For the modulation depth $q = 1$ and the azimuthal parameter $m \

  15. Spatiotemporal soliton clusters in the (3+1)-dimensional nonlinear Schrödinger equation with spatially modulated nonlinearity

    Science.gov (United States)

    Wu, Hong-Yu; Jiang, Li-Hong

    2017-09-01

    From a generic transformation, a (3+1)-dimensional nonlinear Schrödinger equation with spatially modulated nonlinearity is studied and exact spatiotemporal soliton cluster solutions are derived. When the azimuthal parameter m = 0, Gaussian solitons are constructed. For the modulation depth q = 1 and the azimuthal parameter m\

  16. Stochastic resonance in a single-mode laser driven by quadratic Pump noise and amplitude-modulated signal

    Institute of Scientific and Technical Information of China (English)

    Zhang Li

    2009-01-01

    This paper investigates the phenomenon of stochastic resonance in a single-mode laser driven by quadratic pump noise and amplitude-modulated signal.A new linear approximation approach is advanced to calculate the signal-to-noise ratio.In the linear approximation only the drift term is linearized,the multiplicative noise term is unchangeable.It is found that there appears not only the standard form of stochastic resonance but also the broad sense of stochastic resonance,especially stochastic multiresonance appears in the curve of signal-to-noise ratio as a function of coupling strength λ between the real and imaginary parts of the pump noise.

  17. Mycobacterium tuberculosis DNA detection using surface plasmon resonance modulated by telecommunication wavelength.

    Science.gov (United States)

    Hsu, Shih-Hsiang; Lin, Yan-Yu; Lu, Shao-Hsi; Tsai, I-Fang; Lu, Yen-Ta; Ho, Hsin-Tsung

    2013-12-27

    A surface plasmon resonance sensor for Mycobacterium tuberculosis (MTB) deoxyribonucleic acid (DNA) is developed using repeatable telecommunication wavelength modulation based on optical fiber communications laser wavelength and stability. MTB DNA concentrations of 1 μg/mL and 10 μg/mL were successfully demonstrated to have the same spectral half-width in the dip for optimum coupling. The sensitivity was shown to be -0.087 dB/(μg/mL) at all applied telecommunication wavelengths and the highest sensitivity achieved was 115 ng/mL without thiolated DNA immobilization onto a gold plate, which is better than the sensor limit of 400 ng/mL possible with commercial biosensor equipment.

  18. All-optical photochromic spatial light modulators based on photoinduced electron transfer in rigid matrices

    Science.gov (United States)

    Beratan, David N. (Inventor); Perry, Joseph W. (Inventor)

    1991-01-01

    A single material (not a multi-element structure) spatial light modulator may be written to, as well as read out from, using light. The device has tailorable rise and hold times dependent on the composition and concentration of the molecular species used as the active components. The spatial resolution of this device is limited only by light diffraction as in volume holograms. The device may function as a two-dimensional mask (transmission or reflection) or as a three-dimensional volume holographic medium. This device, based on optically-induced electron transfer, is able to perform incoherent to coherent image conversion or wavelength conversion over a wide spectral range (ultraviolet, visible, or near-infrared regions).

  19. Extended depth of field using a liquid crystal annular spatial light modulator.

    Science.gov (United States)

    Klapp, Iftach; Solodar, Asi; Abdulhalim, Ibrahim

    2014-07-01

    A detailed investigation is presented on the tunable extended depth of field (EDOF) method, proposed recently by Klapp et al. [Opt. Lett.39, 1414 (2014)]. This method is based on temporal multiplexing of phase masks, using an annular liquid crystal spatial light modulator possessing a small number of rings. Examples of 3D simulations used to determine the phase profiles in the pupil plane are presented, as well as more detailed experimental results. Both the experimental and numerical results include comprehensive analysis of contrast dependence on both the spatial spectrum of the object and the amount of defocus. In addition, for the first time, we present the EDOF order inversion in the experimental and simulated data. The results show a profound performance of the proposed system and method.

  20. Simple structured illumination microscope setup with high acquisition speed by using a spatial light modulator

    CERN Document Server

    Förster, Ronny; Jost, Aurélie; Kielhorn, Martin; Wicker, Kai; Heintzmann, Rainer

    2014-01-01

    We describe a two-beam interference structured illumination fluorescence microscope. The novelty of the presented system lies in its simplicity. A programmable electro-optical spatial light modulator in an intermediate image plane enables precise and rapid control of the excitation pattern in the specimen. The contrast of the projected light pattern is strongly influenced by the polarization state of the light entering the high NA objective. To achieve high contrast, we use a segmented polarizer. Furthermore, a mask with six holes blocks unwanted components in the spatial frequency spectrum of the illumination grating. Both these passive components serve their purpose in a simpler and almost as efficient way as active components. We demonstrate a lateral resolution of 114.2 +- 9.5 nm at a frame rate of 7.6 fps per reconstructed 2D slice.

  1. An all-optical spatial light modulator for field-programmable silicon photonic circuits

    CERN Document Server

    Bruck, Roman; Lalanne, Philippe; Mills, Ben; Thomson, David J; Mashanovich, Goran Z; Reed, Graham T; Muskens, Otto L

    2016-01-01

    Reconfigurable photonic devices capable of routing the flow of light enable flexible integrated-optic circuits that are not hard-wired but can be externally controlled. Analogous to free-space spatial light modulators, we demonstrate all-optical wavefront shaping in integrated silicon-on-insulator photonic devices by modifying the spatial refractive index profile of the device employing ultraviolet pulsed laser excitation. Applying appropriate excitation patterns grants us full control over the optical transfer function of telecommunication-wavelength light travelling through the device, thus allowing us to redefine its functionalities. As a proof-of-concept, we experimentally demonstrate routing of light between the ports of a multimode interference power splitter with more than 97% total efficiency and negligible losses. Wavefront shaping in integrated photonic circuits provides a conceptually new approach toward achieving highly adaptable and field-programmable photonic circuits with applications in optica...

  2. Simple structured illumination microscope setup with high acquisition speed by using a spatial light modulator.

    Science.gov (United States)

    Förster, Ronny; Lu-Walther, Hui-Wen; Jost, Aurélie; Kielhorn, Martin; Wicker, Kai; Heintzmann, Rainer

    2014-08-25

    We describe a two-beam interference structured illumination fluorescence microscope. The novelty of the presented system lies in its simplicity. A programmable spatial light modulator (ferroelectric LCoS) in an intermediate image plane enables precise and rapid control of the excitation pattern in the specimen. The contrast of the projected light pattern is strongly influenced by the polarization state of the light entering the high NA objective. To achieve high contrast, we use a segmented polarizer. Furthermore, a mask with six holes blocks unwanted components in the spatial frequency spectrum of the illumination grating. Both these passive components serve their purpose in a simpler and almost as efficient way as active components. We demonstrate a lateral resolution of 114.2 ± 9.5 nm at a frame rate of 7.6 fps per reconstructed 2D slice.

  3. Micro mirror arrays as high-resolution spatial light modulators for photoactivation and optogenetics

    Science.gov (United States)

    Rückerl, F.; Kielhorn, Martin; Tinevez, J.-Y.; Heber, J.; Heintzmann, R.; Shorte, S.

    2013-03-01

    The ability to control the illumination and imaging paths of optical microscopes is an essential part of advanced fluorescence microscopy, and a powerful tool for optogenetics. In order to maximize the visualization and the image quality of the objects under observation we use programmable, fast Micro Mirror Arrays (MMAs) as high-resolution Spatial Light Modulators (SLMs). Using two 256x256 MMAs in a mirror-based illumination setup allows for fast angular-spatial control at a wide range of wavelengths (300-1000nm). Additionally, the illumination intensity can be controlled at 10-bit resolution. The setup allows selective illumination of subcellular regions of interest enabling the precise, localized activation of fluorescent probes and the activation and deactivation of subcellular and cellular signaling cascades using photo-activated ion-channels. Furthermore, inasmuch as phototoxicity is dependent on the rate of photo illumination [1] we show that our system, which provides fast, compartmentalized illumination is minimally phototoxic.

  4. Design and Analysis of Enhanced Modulation Response in Integrated Coupled Cavities DBR Lasers Using Photon-Photon Resonance

    OpenAIRE

    Paolo Bardella; Chow, Weng W.; Ivo Montrosset

    2016-01-01

    In the last few decades, various solutions have been proposed to increase the modulation bandwidth and, consequently, the transmission bit-rate of semiconductor lasers. In this manuscript, we discuss a design procedure for a recently proposed laser cavity realized with the monolithic integration of two distributed Bragg reflector (DBR) lasers allowing one to extend the modulation bandwidth. Such an extension is obtained introducing in the dynamic response a photon-photon resonance (PPR) at a ...

  5. Nanosizing by spatially modulated illumination (SMI) microscopy and applications to the nucleus.

    Science.gov (United States)

    Birk, Udo J; Baddeley, David; Cremer, Christoph

    2009-01-01

    In this chapter we present the method of spatially modulated illumination (SMI) microscopy, a (far-field) fluorescence microscopy technique featuring structured illumination obtained via a standing wave field laser excitation pattern. While this method does not provide higher optical resolution, it has been proven a highly valuable tool to access structural parameters of fluorescently labeled macromolecular structures in cells. SMI microscopy has been used to measure relative positions with a reproducibility of SMI microscope over other (ultra-)high resolution light microscopes are its easy sample preparation and microscope handling as well as the comparably fast acquisition times and large fields of view.

  6. Simulating atmospheric turbulence using a phase-only spatial light modulator

    CSIR Research Space (South Africa)

    Burger, L

    2008-04-01

    Full Text Available intensity, called scintillation (see Fig. 1). These two artifacts are also observed with the naked eye in the case of starlight: the so-called twinkling of the stars is precisely this randomness in path and intensity. It is now well understood... and military applications (see refs 1 and 2 for a good overview of the field). A modern optical element in the form of a spatial light modulator (SLM) has allowed new approaches to adaptive optics, and has already been recommended and used...

  7. Optical phase encryption by phase contrast using electrically addressed spatial light modulator

    Science.gov (United States)

    Nishchal, Naveen Kumar; Joseph, Joby; Singh, Kehar

    2003-03-01

    We report the use of an electrically addressed liquid crystal spatial light modulator (EALCSLM) operating in the phase mode as a phase-contrast filter (PCF). As an application, an optical phase encryption system has been implemented. We encrypt and decrypt a two-dimensional phase image obtained from an amplitude image. Encrypted image is holographically recorded in a Barium titanate crystal and is then decrypted by generating through phase conjugation, a conjugate of the encrypted image. The decrypted phase image is converted into an amplitude image using an EASLM as a PCF. The idea has been supported by the experimental results.

  8. Development and control of kilo-pixel MEMS deformable mirrors and spatial light modulators

    Science.gov (United States)

    Perreault, Julie Ann

    This dissertation describes the development of kilo-pixel micro-electro-mechanical optical-quality surface-micromachined deformable mirrors and spatial light modulators along with scalable control electronics. These silicon-based deformable mirrors have the potential to modulate spatial and temporal features of an optical wavefront with applications in imaging, beam-forming, and optical communication systems. Techniques to improve the manufacturing, quality, and capability of these mirrors are detailed. The new mirror system was characterized and a scalable control system was developed to coordinate and control a large array of mirrors. Three types of kilo-pixel deformable mirrors were created: continuous membrane, segmented membrane, and a hybrid stress-relieved membrane mirrors. This new class of mirrors, deformed using electrostatically actuated surface-normal actuators, have an aperature of 10 mm, a stroke of 2 mum, position repeatability of 3 nm, surface roughness of 12 nm, reflectivity of 91%, and a bandwidth in air of 7 kHz. A custom fabrication process was developed in tandem with a new mirror design to address design and layout issues including packaging, residual stress, reliability, yield, fill factor, and surface topography. A chemo-mechanical polishing process improved the surface quality of the mirrors by decreasing surface roughness from an RMS value of 46nm to 12nm. A gold coating process increased reflectivity from 42% to greater than 91% without introducing a significant amount of stress in the mirror membrane. An alternative actuator design and layout was also developed that achieved an increased stroke of 6 mum, with the potential for even longer stroke with stress reduction. The long stroke capability was realized through introduction of split electrodes, actuation membrane cuts, and a double stacked anchor architecture. A computer-driven electronic system was developed to aid in the electro-mechanical testing of these deformable mirrors. Quasi

  9. The Pocketscope: a spatial light modulator based epi-fluorescence microscope for optogenetics

    Science.gov (United States)

    Linnenberger, Anna; Peterka, Darcy S.; Quirin, Sean; Yuste, Rafael

    2014-09-01

    Microscopy incorporating spatial light modulators (SLMs) enables three dimensional (3D) excitation and monitoring of the activity of neuronal ensembles, enabling studies of neuronal circuit activity both in vitro and in vivo. In this paper we present a portable (22 cm x 42.5 cm x 30 cm), SLM-based epi-fluorescence upright microscope ("Pocketscope") that enables 3D calcium imaging and photoactivation of neurons in brain slices. Here we describe the implementation of the instrument; quantify the volume over which neural activity can be excited; and demonstrate the use of the system for mapping neural circuits in brain slices.

  10. Modulation of spatial and stimulus-response learning strategies by exogenous cortisol in healthy young women.

    Science.gov (United States)

    Schwabe, Lars; Oitzl, Melly S; Richter, Steffen; Schächinger, Hartmut

    2009-04-01

    Glucocorticoids (GCs) are known to influence learning and memory processes. While most studies focus on the effects of GCs on the performance within a single memory system, we asked whether GCs modulate also the transition between hippocampus-dependent spatial and caudate nucleus-dependent stimulus-response memory systems. Eighty-four young healthy women received a placebo, 5 or 30 mg hydrocortisone orally. One hour later, participants were asked to locate a win-card in a 3D model of a room. The card could be located via two strategies: spatial (multiple distal cues) and stimulus-response (a single proximal cue). Relocation of the proximal cue after 12 trials revealed the strategy, number of trials to learning criterion the performance. As expected, more trials were needed to acquire the task with hydrocortisone. Remarkably, hydrocortisone switched the use of learning strategies towards more spatial learning (dose-dependently: placebo 4% learning curves of spatial and stimulus-response learners were comparable. Our results demonstrate that exogenous GCs prior to learning affect the performance within a memory system and also coordinate the use of multiple memory systems. Taking into account this dual action of GCs will contribute to a better understanding of stress (hormone) effects on learning and memory.

  11. Investigating the spatial and temporal modulation of visuotactile interactions in older adults.

    Science.gov (United States)

    Couth, Samuel; Gowen, Emma; Poliakoff, Ellen

    2016-05-01

    Previous research has shown that spatially and temporally disparate multisensory events are more likely to interact for older adults. For visuotactile interactions, this suggests that the representation of peripersonal space is expanded and temporal perception within this space is less precise. Previously, visuotactile space has been found to expand horizontally into the opposite hemispace, and here we sought to replicate and extend this by exploring both horizontal and vertical space from the hand. Moreover, we investigated whether both spatial and temporal domains are affected for an individual, which have previously been measured using distinct tasks and different participants. We presented a modified cross-modal congruency task (Poole et al. in Multisens Res. doi: 10.1163/22134808-00002475 , 2015a) to thirty older participants (age range 65-85 years), with unisensory tactile performance equated for each individual. For the temporal manipulation, the timings of visual distractors and tactile targets were offset. For the spatial manipulation, visual distractors were presented from multiple positions in ipsilateral and contralateral hemispaces. Whilst the temporal modulation of visuotactile interactions for older adults was equivalent to that observed in young adults, spatial modulation was reduced; significant visuotactile interactions were observed for visual distractors presented in the same and opposite hemispace to the stimulated hand, in the lower visual field. This suggests an expanded representation of visuotactile space surrounding the hand in older adults, which occurs horizontally into the contralateral hemispace only, rather than expanding both vertically and horizontally. This is likely to have consequences for perception of space and goal-directed action in ageing.

  12. Entrainment of visual steady-state responses is modulated by global spatial statistics.

    Science.gov (United States)

    Nguyen, Thomas; Kuntzelman, Karl; Miskovic, Vladimir

    2017-07-01

    The rhythmic delivery of visual stimuli evokes large-scale neuronal entrainment in the form of steady-state oscillatory field potentials. The spatiotemporal properties of stimulus drive appear to constrain the relative degrees of neuronal entrainment. Specific frequency ranges, for example, are uniquely suited for enhancing the strength of stimulus-driven brain oscillations. When it comes to the nature of the visual stimulus itself, studies have used a plethora of inputs ranging from spatially unstructured empty fields to simple contrast patterns (checkerboards, gratings, stripes) and complex arrays (human faces, houses, natural scenes). At present, little is known about how the global spatial statistics of the input stimulus influence entrainment of scalp-recorded electrophysiological signals. In this study, we used rhythmic entrainment source separation of scalp EEG to compare stimulus-driven phase alignment for distinct classes of visual inputs, including broadband spatial noise ensembles with varying second-order statistics, natural scenes, and narrowband sine-wave gratings delivered at a constant flicker frequency. The relative magnitude of visual entrainment was modulated by the global properties of the driving stimulus. Entrainment was strongest for pseudo-naturalistic broadband visual noise patterns in which luminance contrast is greatest at low spatial frequencies (a power spectrum slope characterized by 1/ƒ(-2)).NEW & NOTEWORTHY Rhythmically modulated visual stimuli entrain the activity of neuronal populations, but the effect of global stimulus statistics on this entrainment is unknown. We assessed entrainment evoked by 1) visual noise ensembles with different spectral slopes, 2) complex natural scenes, and 3) narrowband sinusoidal gratings. Entrainment was most effective for broadband noise with naturalistic luminance contrast. This reveals some global properties shaping stimulus-driven brain oscillations in the human visual system. Copyright © 2017

  13. Polarization control efficiency manipulation in resonance-mediated two-photon absorption by femtosecond spectral frequency modulation

    Science.gov (United States)

    Yao, Yunhua; Cheng, Wenjing; Zheng, Ye; Xu, Cheng; Liu, Pei; Jia, Tianqing; Qiu, Jianrong; Sun, Zhenrong; Zhang, Shian

    2017-04-01

    The femtosecond laser polarization modulation is considered as a very simple and efficient method to control the multi-photon absorption process. In this work, we theoretically and experimentally show that the polarization control efficiency in the resonance-mediated two-photon absorption can be artificially manipulated by modulating the femtosecond spectral frequency components. We theoretically demonstrate that the on- and near-resonant parts in the resonance-mediated two-photon absorption process depend on the different femtosecond spectral frequency components, and therefore their contributions in the whole excitation process can be controlled by properly designing the femtosecond spectral frequency components. The near-resonant two-photon absorption is correlated with the femtosecond laser polarization while the on-resonant two-photon absorption is independent of it, and thus the polarization control efficiency in the resonance-mediated two-photon absorption can be manipulated by the femtosecond spectral frequency modulation. We experimentally verify these theoretical results by performing the laser polarization control experiment in the Dy3+-doped glass sample under the modulated femtosecond spectral frequency components, and the experimental results show that the polarization control efficiency can be increased when the central spectral frequency components are cut off, while it is decreased when both the low and high spectral frequency components are cut off, which is in good agreement with the theoretical predictions. Our works can provide a feasible pathway to understand and control the resonance-mediated multi-photon absorption process under the femtosecond laser field excitation, and also may open a new opportunity to the related application areas.

  14. LCD-based digital eyeglass for modulating spatial-angular information.

    Science.gov (United States)

    Bian, Zichao; Liao, Jun; Guo, Kaikai; Heng, Xin; Zheng, Guoan

    2015-05-04

    Using programmable aperture to modulate spatial-angular information of light field is well-known in computational photography and microscopy. Inspired by this concept, we report a digital eyeglass design that adaptively modulates light field entering human eyes. The main hardware includes a transparent liquid crystal display (LCD) and a mini-camera. The device analyzes the spatial-angular information of the camera image in real time and subsequently sends a command to form a certain pattern on the LCD. We show that, the eyeglass prototype can adaptively reduce light transmission from bright sources by ~80% and retain transparency to other dim objects meanwhile. One application of the reported device is to reduce discomforting glare caused by vehicle headlamps. To this end, we report the preliminary result of using the reported device in a road test. The reported device may also find applications in military operations (sniper scope), laser counter measure, STEM education, and enhancing visual contrast for visually impaired patients and elderly people with low vision.

  15. Fabricating micro embossments on the metal surface through spatially modulating laser-induced shock wave

    Science.gov (United States)

    Ye, Y. X.; Xuan, T.; Lian, Z. C.; Hua, X. J.; Fu, Y. H.

    2015-12-01

    In this paper, we propose one improved method to fabricate micro embossments on the metal surface through laser shock processing. One mapping layer with holes must be actively designed and produced on the metal surface, with which, laser-induced shock wave will be spatially modulated. Laser shock experiments were conducted. Then the surface morphologies, and metallographic microstructures were characterized. The forming process of the micro embossments was simulated with ABAQUS. The results show that under the spatially modulated shock loading, the surface material flows from the high-pressure zone to the low-pressure zone, which is responsible for forming the micro embossments. The shapes, sizes and arrangements of the micro embossments conform to those of the mapping holes. The hardnesses on the entire laser-shocked zones improve remarkably due to the plastic deformation at a high strain rate. The influences of the laser energy and mask pattern on the embossed structures are presented. Within certain limits, increasing laser energy is beneficial for making the embossment more convex. However, further excessively increasing the laser energy, the embossment will exhibit the height saturation due to the pressure rise within the closed mapping hole. The transverse sizes of the mapping holes also can influence the embossment heights significantly. Process parameters need to be chosen carefully to suppress the severe adiabatic compression of the gas within the mapping holes, and then avoid weakening the mechanical properties of the micro embossments. This method has a potential application in manufacturing protruded structures on the metal surface.

  16. Spatial profile and differential recruitment of GABAB modulate oscillatory activity in auditory cortex.

    Science.gov (United States)

    Oswald, Anne-Marie M; Doiron, Brent; Rinzel, John; Reyes, Alex D

    2009-08-19

    The interplay between inhibition and excitation is at the core of cortical network activity. In many cortices, including auditory cortex (ACx), interactions between excitatory and inhibitory neurons generate synchronous network gamma oscillations (30-70 Hz). Here, we show that differences in the connection patterns and synaptic properties of excitatory-inhibitory microcircuits permit the spatial extent of network inputs to modulate the magnitude of gamma oscillations. Simultaneous multiple whole-cell recordings from connected fast-spiking interneurons and pyramidal cells in L2/3 of mouse ACx slices revealed that for intersomatic distances <50 microm, most inhibitory connections occurred in reciprocally connected (RC) pairs; at greater distances, inhibitory connections were equally likely in RC and nonreciprocally connected (nRC) pairs. Furthermore, the GABA(B)-mediated inhibition in RC pairs was weaker than in nRC pairs. Simulations with a network model that incorporated these features showed strong, gamma band oscillations only when the network inputs were confined to a small area. These findings suggest a novel mechanism by which oscillatory activity can be modulated by adjusting the spatial distribution of afferent input.

  17. Japanese quail's genetic background modulates effects of chronic stress on emotional reactivity but not spatial learning.

    Directory of Open Access Journals (Sweden)

    Agathe Laurence

    Full Text Available Chronic stress is known to enhance mammals' emotional reactivity and alters several of their cognitive functions, especially spatial learning. Few studies have investigated such effects in birds. We investigated the impact of a two-week stress on Japanese quail's emotional reactivity and spatial learning. Quail is an avian model widely used in laboratory studies and for extrapolation of data to other poultry species. As sensitivity to chronic stress can be modulated by intrinsic factors, we tested juvenile female Japanese quail from three lines, two of them divergently selected on tonic immobility duration, an indicator of general fearfulness. The different emotional reactivity levels of quail belonging to these lines can be revealed by a large variety of tests. Half of the birds were submitted to repeated unpredictable aversive events for two weeks, whereas the other half were left undisturbed. After this procedure, two tests (open field and emergence tests evaluated the emotional reactivity of treated and control quails. They were then trained in a T-maze for seven days and their spatial learning was tested. The chronic stress protocol had an impact on resting, preening and foraging in the home cage. As predicted, the emotional reactivity of treated quails, especially those selected for long tonic immobility duration, was higher. Our spatial learning data showed that the treatment enhanced acquisition but not memorization. However, intrinsic fearfulness did not seem to interact with the treatment in this test. According to an inverted U-shaped relationship between stress and cognition, chronic stress can improve the adaptability of birds to a stressful environment. We discussed the mechanisms possibly implied in the increase of emotional reactivity and spatial abilities.

  18. Electron paramagnetic resonance-based pH mapping using spectral-spatial imaging of sequentially scanned spectra

    OpenAIRE

    Koda, Shunichi; Goodwin, Jonathan; Khramtsov, Valery V.; Fujii, Hirotada; Hirata, Hiroshi

    2012-01-01

    The development of electron paramagnetic resonance (EPR)-based mapping of pH is an important advancement for the field of diagnostic imaging. The ability to accurately quantify pH change in vivo and monitor spatial distribution is desirable for the assessment of a number of pathological conditions in the human body as well as the monitoring of treatment response. In this work we introduce a method for EPR-based pH mapping, utilizing a method of spectral-spatial imaging of sequentially scanned...

  19. Proof of principle of a high-spatial-resolution, resonant-response gamma-ray detector for Gamma Resonance Absorption in 14N

    CERN Document Server

    Brandis, M; Vartsky, D; Friedman, E; Kreslo, I; Mardor, I; Dangendorf, V; Levi, S; Mor, I; Bar, D

    2011-01-01

    The development of a mm-spatial-resolution, resonant-response detector based on a micrometric glass capillary array filled with liquid scintillator is described. This detector was developed for Gamma Resonance Absorption (GRA) in 14N. GRA is an automatic-decision radiographic screening technique that combines high radiation penetration (the probe is a 9.17 MeV gamma ray) with very good sensitivity and specificity to nitrogenous explosives. Detailed simulation of the detector response to electrons and protons generated by the 9.17 MeV gamma-rays was followed by a proof-of-principle experiment, using a mixed gamma-ray and neutron source. Towards this, a prototype capillary detector was assembled, including the associated filling and readout systems. Simulations and experimental results indeed show that proton tracks are distinguishable from electron tracks at relevant energies, on the basis of a criterion that combines track length and light intensity per unit length.

  20. Proof of principle of a high-spatial-resolution, resonant-response γ-ray detector for Gamma Resonance Absorption in 14N

    Science.gov (United States)

    Brandis, M.; Goldberg, M. B.; Vartsky, D.; Friedman, E.; Kreslo, I.; Mardor, I.; Dangendorf, V.; Levi, S.; Mor, I.; Bar, D.

    2011-02-01

    The development of a mm-spatial-resolution, resonant-response detector based on a micrometric glass capillary array filled with liquid scintillator is described. This detector was developed for Gamma Resonance Absorption (GRA) in 14N. GRA is an automatic-decision radiographic screening technique that combines high radiation penetration (the probe is a 9.17 MeV γ-ray) with very good sensitivity and specificity to nitrogenous explosives. Detailed simulation of the detector response to electrons and protons generated by the 9.17 MeV γ-rays was followed by a proof-of-principle experiment, using a mixed γ-ray and neutron source. Towards this, a prototype capillary detector was assembled, including the associated filling and readout systems. Simulations and experimental results indeed show that proton tracks are distinguishable from electron tracks at relevant energies, based on a criterion that combines track length and light intensity per unit length.

  1. Spatially and spectrally resolved ultra-narrowband TE-polarization absorber based on the guide-mode resonance

    Science.gov (United States)

    Liao, Yan-Lin; Zhao, Yan; Zhang, Xingfang; Zhang, Wen; Wang, Zhongzhu

    2017-08-01

    A spatially and spectrally resolved ultra-narrowband absorber with a dielectric grating and metal substrate has been reported. The absorber shows that the absorption rate is more than 0.99 with the absorption bandwidth less than 1.5 nm at normal incidence for TE polarization (electric field is parallel to grating grooves). The angular width of the absorption is about 0.27∘. The wavelength-angle sensitivity and absorption-angle sensitivity are 13.4 nm per degree and 296.3% per degree, respectively. The simulation results also show the spatially and spectrally resolved ultra-narrowband absorption is originated from the guide-mode resonance. In addition, the wavelength-angle sensitivity can be improved by enlarging the grating period according to the guide-mode resonance mechanism. The proposed absorber has potential applications in optical filters, angle measurement and thermal emitters.

  2. Spatially resolved confocal resonant Raman microscopic analysis of anode-grown Geobacter sulfurreducens biofilms.

    Science.gov (United States)

    Lebedev, Nikolai; Strycharz-Glaven, Sarah M; Tender, Leonard M

    2014-02-03

    When grown on the surface of an anode electrode, Geobacter sulfurreducens forms a multi-cell thick biofilm in which all cells appear to couple the oxidation of acetate with electron transport to the anode, which serves as the terminal metabolic electron acceptor. Just how electrons are transported through such a biofilm from cells to the underlying anode surface over distances that can exceed 20 microns remains unresolved. Current evidence suggests it may occur by electron hopping through a proposed network of redox cofactors composed of immobile outer membrane and/or extracellular multi-heme c-type cytochromes. In the present work, we perform a spatially resolved confocal resonant Raman (CRR) microscopic analysis to investigate anode-grown Geobacter biofilms. The results confirm the presence of an intra-biofilm redox gradient whereby the probability that a heme is in the reduced state increases with increasing distance from the anode surface. Such a gradient is required to drive electron transport toward the anode surface by electron hopping via cytochromes. The results also indicate that at open circuit, when electrons are expected to accumulate in redox cofactors involved in electron transport due to the inability of the anode to accept electrons, nearly all c-type cytochrome hemes detected in the biofilm are oxidized. The same outcome occurs when a comparable potential to that measured at open circuit (-0.30 V vs. SHE) is applied to the anode, whereas nearly all hemes are reduced when an exceedingly negative potential (-0.50 V vs. SHE) is applied to the anode. These results suggest that nearly all c-type cytochrome hemes detected in the biofilm can be electrochemically accessed by the electrode, but most have oxidation potentials too negative to transport electrons originating from acetate metabolism. The results also reveal a lateral heterogeneity (x-y dimensions) in the type of c-type cytochromes within the biofilm that may affect electron transport to the

  3. Spatial optical modulator (SOM): high-density diffractive laser projection display

    Science.gov (United States)

    Yun, SangKyeong; Song, JongHyeong; Yeo, InJae; Choi, YoonJoon; Yurlov, Victor; An, SeungDo; Park, HeungWoo; Yang, HaengSeok; Lee, YeongGyu; Han, KyuBum; Shyshkin, Ihar; Lapchuk, Anatoliy; Oh, KwanYoung; Ryu, SeungWon; Jang, JaeWook; Park, ChangSu; Kim, ChunGi; Kim, SunKi; Kim, EungJu; Woo, KiSuk; Yang, JeongSuong; Kim, EuiJoong; Kim, JooHong; Byun, SungHo; Lee, SeungWoo; Lim, OhkKun; Cheong, JongPil; Hwang, YoungNam; Byun, GiYoung; Kyoung, JeHong; Yoon, SangKee; Lee, JaeKwang; Lee, TaeWon; Hong, SeokKee; Hong, YoonShik; Park, DongHyun; Kang, JungChul; Shin, WooChul; Lee, SungIl; Oh, SungKyung; Song, ByungKi; Kim, HeeYeoun; Koh, ChongMann; Ryu, YungHo; Lee, HyunKee; Baek, YoungKi

    2007-02-01

    A new type of diffractive spatial optical modulators, named SOM, has been developed by Samsung Electro-Mechanics for laser projection display. It exhibit inherent advantages of fast response time and high-performance light modulation, suitable for high quality embedded laser projection displays. The calculated efficiency and contrast ratio are 75 % and 800:1 respectively in case of 0 th order, 67 % and 1000:1 respectively in case of +/-1st order. The response time is as fast as 0.7 μs. Also we get the displacement of 400 nm enough to display full color with single panel in VGA format, as being 10 V driven. Optical module with VGA was successfully demonstrated for its potential applications in mobile laser projection display such as cellular phone, digital still camera and note PC product. Electrical power consumption is less than 2 W, volume is less than 13 cc. Brightness is enough to watch TV and movie in the open air, being variable up to 6 lm. Even if it's optimal diagonal image size is 10 inch, image quality does not deteriorate in the range of 5 to 50 inch because of the merit of focus-free. Due to 100 % fill factor, the image is seamless so as to be unpleasant to see the every pixel's partition. High speed of response time can make full color display with 24-bit gray scale and cause no scan line artifact, better than any other devices.

  4. Two-component vector solitons in defocusing Kerr-type media with spatially modulated nonlinearity

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Wei-Ping, E-mail: zhongwp6@126.com [Department of Electronic and Information Engineering, Shunde Polytechnic, Guangdong Province, Shunde 528300 (China); Texas A and M University at Qatar, P.O. Box 23874 Doha (Qatar); Belić, Milivoj [Texas A and M University at Qatar, P.O. Box 23874 Doha (Qatar); Institute of Physics, University of Belgrade, P.O. Box 57, 11001 Belgrade (Serbia)

    2014-12-15

    We present a class of exact solutions to the coupled (2+1)-dimensional nonlinear Schrödinger equation with spatially modulated nonlinearity and a special external potential, which describe the evolution of two-component vector solitons in defocusing Kerr-type media. We find a robust soliton solution, constructed with the help of Whittaker functions. For specific choices of the topological charge, the radial mode number and the modulation depth, the solitons may exist in various forms, such as the half-moon, necklace-ring, and sawtooth vortex-ring patterns. Our results show that the profile of such solitons can be effectively controlled by the topological charge, the radial mode number, and the modulation depth. - Highlights: • Two-component vector soliton clusters in defocusing Kerr-type media are reported. • These soliton clusters are constructed with the help of Whittaker functions. • The half-moon, necklace-ring and vortex-ring patterns are found. • The profile of these solitons can be effectively controlled by three soliton parameters.

  5. Neutron resonance transmission spectroscopy with high spatial and energy resolution at the J-PARC pulsed neutron source

    Energy Technology Data Exchange (ETDEWEB)

    Tremsin, A.S., E-mail: ast@ssl.berkeley.edu [University of California at Berkeley, 7 Gauss Way, Berkeley, CA 94720 (United States); Shinohara, T.; Kai, T.; Ooi, M. [Japan Atomic Energy Agency, 2–4 Shirakata-shirane, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Kamiyama, T.; Kiyanagi, Y.; Shiota, Y. [Hokkaido University, Kita 13 Nishi 8 Kita-ku, Sapporo-shi, Hokkaido 060-8628 (Japan); McPhate, J.B.; Vallerga, J.V.; Siegmund, O.H.W. [University of California at Berkeley, 7 Gauss Way, Berkeley, CA 94720 (United States); Feller, W.B. [NOVA Scientific, Inc., 10 Picker Rd., Sturbridge, MA 01566 (United States)

    2014-05-11

    The sharp variation of neutron attenuation at certain energies specific to particular nuclides (the lower range being from ∼1 eV up to ∼1 keV), can be exploited for the remote mapping of element and/or isotope distributions, as well as temperature probing, within relatively thick samples. Intense pulsed neutron beam-lines at spallation sources combined with a high spatial, high-timing resolution neutron counting detector, provide a unique opportunity to measure neutron transmission spectra through the time-of-flight technique. We present the results of experiments where spatially resolved neutron resonances were measured, at energies up to 50 keV. These experiments were performed with the intense flux low background NOBORU neutron beamline at the J-PARC neutron source and the high timing resolution (∼20 ns at epithermal neutron energies) and spatial resolution (∼55 µm) neutron counting detector using microchannel plates coupled to a Timepix electronic readout. Simultaneous element-specific imaging was carried out for several materials, at a spatial resolution of ∼150 µm. The high timing resolution of our detector combined with the low background beamline, also enabled characterization of the neutron pulse itself – specifically its pulse width, which varies with neutron energy. The results of our measurements are in good agreement with the predicted results for the double pulse structure of the J-PARC facility, which provides two 100 ns-wide proton pulses separated by 600 ns, broadened by the neutron energy moderation process. Thermal neutron radiography can be conducted simultaneously with resonance transmission spectroscopy, and can reveal the internal structure of the samples. The transmission spectra measured in our experiments demonstrate the feasibility of mapping elemental distributions using this non-destructive technique, for those elements (and in certain cases, specific isotopes), which have resonance energies below a few keV, and with lower

  6. Image Processing and control of a programmable spatial light modulator for optic damage protection

    Energy Technology Data Exchange (ETDEWEB)

    Awwal, A; Leach, R; Brunton, G; Tse, E; Matone, J; Heebner, J

    2010-12-06

    The heart of the National Ignition Facility is a megajoule-class laser system consisting of 192 beams used to drive inertial confinement fusion reactions. A recently installed system of programmable, liquid-crystal-based spatial light modulators adds the capability of arbitrarily shaping the spatial beam profiles in order to enhance operational flexibility. Its primary intended use is for introducing 'blocker' obscurations shadowing isolated flaws on downstream optical elements that would otherwise be damaged by high fluence laser illumination. Because an improperly shaped blocker pattern can lead to equipment damage, both the position and shape of the obscurations must be carefully verified prior to high-fluence operations. An automatic alignment algorithm is used to perform detection and estimation of the imposed blocker centroid positions compared to their intended locations. Furthermore, in order to minimize the spatially-varying nonlinear response of the device, a calibration of the local magnification is performed at multiple sub-image locations. In this paper, we describe the control and associated image processing of this device that helps to enhance the safety and longevity of the overall system.

  7. How does experience modulate auditory spatial processing in individuals with blindness?

    Science.gov (United States)

    Tao, Qian; Chan, Chetwyn C H; Luo, Yue-jia; Li, Jian-jun; Ting, Kin-hung; Wang, Jun; Lee, Tatia M C

    2015-05-01

    Comparing early- and late-onset blindness in individuals offers a unique model for studying the influence of visual experience on neural processing. This study investigated how prior visual experience would modulate auditory spatial processing among blind individuals. BOLD responses of early- and late-onset blind participants were captured while performing a sound localization task. The task required participants to listen to novel "Bat-ears" sounds, analyze the spatial information embedded in the sounds, and specify out of 15 locations where the sound would have been emitted. In addition to sound localization, participants were assessed on visuospatial working memory and general intellectual abilities. The results revealed common increases in BOLD responses in the middle occipital gyrus, superior frontal gyrus, precuneus, and precentral gyrus during sound localization for both groups. Between-group dissociations, however, were found in the right middle occipital gyrus and left superior frontal gyrus. The BOLD responses in the left superior frontal gyrus were significantly correlated with accuracy on sound localization and visuospatial working memory abilities among the late-onset blind participants. In contrast, the accuracy on sound localization only correlated with BOLD responses in the right middle occipital gyrus among the early-onset counterpart. The findings support the notion that early-onset blind individuals rely more on the occipital areas as a result of cross-modal plasticity for auditory spatial processing, while late-onset blind individuals rely more on the prefrontal areas which subserve visuospatial working memory.

  8. The Importance of Facial Features and Their Spatial Organization for Attractiveness is Modulated by Gender

    Directory of Open Access Journals (Sweden)

    D Gill

    2011-04-01

    Full Text Available Many studies suggest that facial attractiveness signals mate quality. Fewer studies argue that the preference criteria emerge as a by-product of cortical processes. One way or the other, preference criteria should not be necessarily identical between female and male observers because either their preferences may have different evolutionary roles or they may even be due to known differences in visiospatial skills and brain function lateralization (ie, advantages favoring males' inability to determine spatial relations despite distracting information. The goal of this study was to assess sex differences in face attractiveness judgments by estimating the importance of facial features and their spatial organization. To this end, semipartial correlations were measured between intact-face preferences and preferences based on specific facial parts (eyes, nose, mouth, and hairstyle or preferences based more on configuration (as reflected by low spatial frequency images. The results show strategy modulations by both observers' and faces' genders. In general, the association between intact-face preferences and parts-based preferences was significantly higher for female compared with male participants. For female faces, males' preferences were more strongly associated with their low spatial frequency preferences than were those of females. The two genders' strategies were more similar when judging male faces, and males performed more criteria modifications across face gender. The similarities between sexes regarding male faces are in line with previous studies that showed higher assignment of importance among men to attractiveness. Moreover, the results may suggest that men adjust their strategy to assess the danger of other males as potential rivals for mates.

  9. A review of in vitro experimental evidence for the effect of spatial and temporal modulation of radiation dose on response

    Energy Technology Data Exchange (ETDEWEB)

    Suchowerska, Natalka (Dept. of Radiation Oncology, Royal Prince Alfred Hospital, New South Wales (Australia)), E-mail: Natalka@email.cs.nsw.gov.au; McKenzie, David R. (School of Physics, Univ. of Sydney, New South Wales (Australia)); Ebert, Martin A. (Dept. of Radiation Oncology, Sir Charles Gairdner Hospital, Western Australia (Australia)); Jackson, Michael (Dept. of Radiation Oncology, Prince of Wales Hospital, Randwick, New South Wales (Australia))

    2010-11-15

    Background. Intensity modulated radiation therapy introduces strong spatial and temporal modulation of the dose delivery that may have therapeutic benefits, as yet unrealized. Material and methods. Experimental evidence for spatial and temporal modulation affecting the cell survival following in vitro irradiation has been derived using clonogenic assays. Results and discussion. The experimental results show that the survival status of a cell is strongly influenced by the spatial dose modulation. The classical bystander effect of decreased survival has now been supplemented by observations of increased survival, which may result from the same or different signaling mechanisms. Temporal dose modulation experiments show that dose protraction significantly increases cell survival. An appropriate choice of temporal dose modulation pattern enables cell death to be maximized or minimized for a constant dose and delivery time. Conclusion. Bystander effects challenge the assumption that outcome is solely dependent on local dose. Intra-fractional temporal modulation via protracted treatments and time varying dose delivery both affect the cell survival. The presence of bystander and temporal effects emphasize the need for a mathematical framework which incorporates their influence on cell survival

  10. Resonances

    DEFF Research Database (Denmark)

    an impetus or drive to that account: change, innovation, rupture, or discontinuity. Resonances: Historical Essays on Continuity and Change explores the historiographical question of the modes of interrelation between these motifs in historical narratives. The essays in the collection attempt to realize...... theoretical consciousness through historical narrative ‘in practice’, by discussing selected historical topics from Western cultural history, within the disciplines of history, literature, visual arts, musicology, archaeology, philosophy, and theology. The title Resonances indicates the overall perspective...

  11. Modulation of human global/local perception by low spatial frequency filtering

    Institute of Scientific and Technical Information of China (English)

    HAN Shihui; J. A. Weaver; S. O. Murray; KANG Xiaojian; E. W. Yund; D. L. Woods

    2003-01-01

    We investigated the effect of low spatial frequency (SF) filtering on neural substrates underlying global and local processing in the peripheral vision by measuring hemodynamic responses with functional magnetic resonance imaging (fMRI). Subjects identified global or local shapes of compound letters that were either broadband in spatial- frequency spectrum or contrast balanced (CB) to removed low SFs and displayed randomly in the left or right visual fields. Attention to both broadband and CB global shapes generated stronger activation over the medial occipital cortex relative to local attention. Lateralized activations in association with global processing were observed over the right temporal-parietal junction for broadband stimuli whereas over the right fusiform gyrus for CB stimuli. Attention to CB local shapes resulted in activations in the medial frontal cortex, bilateral inferior frontal and superior temporal cortices. The results were discussed in terms of the competition between global and local information in determining brain activations in association with global/local processing of compound stimuli.

  12. Spatial Coherence Properties of Organic Molecules Coupled to Plasmonic Surface Lattice Resonances in the Weak and Strong Coupling Regimes

    CERN Document Server

    Shi, L; Rekola, H T; Martikainen, J -P; Moerland, R J; Törmä, P

    2014-01-01

    We study spatial coherence properties of a system composed of periodic silver nanoparticle arrays covered with a fluorescent organic molecule (DiD) film. The evolution of spatial coherence of this composite structure from the weak to the strong coupling regime is investigated by systematically varying the coupling strength between the localized DiD excitons and the collective, delocalized modes of the nanoparticle array known as surface lattice resonances. A gradual evolution of coherence from the weak to the strong coupling regime is observed, with the strong coupling features clearly visible in interference fringes. A high degree of spatial coherence is demonstrated in the strong coupling regime, even when the mode is very excitonlike (80%), in contrast to the purely localized nature of molecular excitons. We show that coherence appears in proportion to the weight of the plasmonic component of the mode throughout the weak-to-strong coupling crossover, providing evidence for the hybrid nature of the normal m...

  13. Programmable apodizer to compensate chromatic aberration effects using a liquid crystal spatial light modulator.

    Science.gov (United States)

    Márquez, A; Iemmi, C; Campos, J; Escalera, J; Yzuel, M

    2005-02-07

    Programmable apodizers written on a liquid crystal spatial light modulator (LCSLM) offer the possibility of modifying the point spread function (PSF) of an optical system in monochromatic light with a high degree of flexibility. Extension to polychromatic light has to take into account the liquid crystal response dependence on the wavelength. Proper control of the chromatic properties of the LCSLM in combination with the design of the correct apodizer is necessary for this new range of applications. In this paper we report a successful application of a programmable amplitude apodizer illuminated with polychromatic light. We use an axial apodizing filter to compensate the longitudinal secondary axial color (LSAC) effects of a refractive optical system on the polychromatic PSF. The configuration of the LCSLM has been optimized to obtain a good amplitude transmission in polychromatic light. Agreement between experimental and simulated results shows the feasibility of our proposal.

  14. Efficient and accurate laser shaping with liquid crystal spatial light modulators

    Energy Technology Data Exchange (ETDEWEB)

    Maxson, Jared M.; Bartnik, Adam C.; Bazarov, Ivan V. [Cornell Laboratory for Accelerator-Based Sciences and Education, Cornell University, Ithaca, New York 14853 (United States)

    2014-10-27

    A phase-only spatial light modulator (SLM) is capable of precise transverse laser shaping by either functioning as a variable phase grating or by serving as a variable mask via polarization rotation. As a phase grating, the highest accuracy algorithms, based on computer generated holograms (CGHs), have been shown to yield extended laser shapes with <10% rms error, but conversely little is known about the experimental efficiency of the method in general. In this work, we compare the experimental tradeoff between error and efficiency for both the best known CGH method and polarization rotation-based intensity masking when generating hard-edged flat top beams. We find that the masking method performs comparably with CGHs, both having rms error < 10% with efficiency > 15%. Informed by best practices for high efficiency from a SLM phase grating, we introduce an adaptive refractive algorithm which has high efficiency (92%) but also higher error (16%), for nearly cylindrically symmetric cases.

  15. Effect of optical surface flatness performance on spatial-light-modulator-based imaging system

    Science.gov (United States)

    Zhou, Hongqiang; Wan, Yuhong; Man, Tianlong; Han, Ying

    2016-10-01

    Spatial light modulator (SLM) has various of applications in the field of imaging, beam shaping, adaptive optics and so on. While SLM is used as an aberration correction element in super-resolution microscopy, the surface flatness of SLM could affect the imaging performance of the system due to the higher sensitivity to aberrations of these kind microscopic techniques. In this paper, the optical surface flatness of SLM is measured experimentally by employing the image plane digital holography. The topography of SLM is retrieved from the captured hologram. Aiming to the application of SLM as an adaptive correction element in super resolution microscopy, the aberrations introduced by the surface flatness of SLM are further evaluated and corrected in the same optical system.

  16. Two-dimensional gain cross-grating based on spatial modulation of active Raman gain

    Science.gov (United States)

    Wang, Li; Zhou, Feng-Xue; Guo, Hong-Ju; Niu, Yue-Ping; Gong, Shang-Qing

    2016-11-01

    Based on the spatial modulation of active Raman gain, a two-dimensional gain cross-grating is theoretically proposed. As the probe field propagates along the z direction and passes through the intersectant region of the two orthogonal standing-wave fields in the x-y plane, it can be effectively diffracted into the high-order directions, and the zero-order diffraction intensity is amplified at the same time. In comparison with the two-dimensional electromagnetically induced cross-grating based on electromagnetically induced transparency, the two-dimensional gain cross-grating has much higher diffraction intensities in the first-order and the high-order directions. Hence, it is more suitable to be utilized as all-optical switching and routing in optical networking and communication. Project supported by the National Natural Science Foundation of China (Grant Nos. 11274112 and 11347133).

  17. Generation of Vector Partially Coherent Optical Sources Using Phase-Only Spatial Light Modulators

    Science.gov (United States)

    Hyde, Milo W.; Bose-Pillai, Santasri; Voelz, David G.; Xiao, Xifeng

    2016-12-01

    A simple and flexible optical system for generating electromagnetic or vector partially coherent sources or beams is presented. The alternative design controls field amplitude (beam shape), coherence, and polarization using only spatial light modulators. This improvement makes the apparatus simpler to construct and significantly increases the flexibility of vector partially coherent source generators by allowing many different types of sources to be produced without changing the physical setup. The system's layout and theoretical foundations are thoroughly discussed. The utility and flexibility of the proposed system are demonstrated by producing a vector Schell-model and non-Schell-model source. The experimental results are compared to theoretical predictions to validate the design. Lastly, design aspects, which must be considered when building a vector partially coherent source generator for a specific application, are discussed.

  18. Efficient illumination of spatial light modulators for optical trapping and manipulation

    DEFF Research Database (Denmark)

    Bañas, Andrew Rafael; Kopylov, Oleksii; Raaby, Peter

    Energy efficiency is always desirable. This is particularly true with lasers that find many applications in research and industry. Combined with spatial light modulators (SLMs) lasers are used for optical trapping and manipulation, sorting, microscopy or biological stimulation1. Besides efficiency......, one wants to uniformly illuminate a specific shape such as the addressable area of an SLM. The common practice of truncating an expanded Gaussian source, however, is inefficient2. The Generalized Phase Contrast (GPC) enables illumination that inherits the efficiency advantages of phase-only light...... be addressed. This allows better response or increased parallel addressing for e.g. optical manipulation and sorting. Simple yet effective, a GPC-LS could save substantial power in applications that truncate lasers to a specific shape....

  19. Compact Holographic Projection Display Using Liquid-Crystal-on-Silicon Spatial Light Modulator

    Directory of Open Access Journals (Sweden)

    Wei-Feng Hsu

    2016-09-01

    Full Text Available This paper presents a holographic projection display in which a phase-only spatial light modulator (SLM performs three functions: beam shaping, image display, and speckle reduction. The functions of beam shaping and image display are performed by dividing the SLM window into four sub-windows loaded with different diffractive phase elements (DPEs. The DPEs are calculated using a modified iterative Fourier transform algorithm (IFTA. The function of speckle reduction is performed using temporal integration of display images containing speckles. The speckle contrast ratio of the display image is 0.39 due to the integration of eight speckled images. The system can be extended to display full-color images also by using temporal addition of elementary color images. Because the system configuration needs only an SLM, a Fourier transform lens, and two mirrors, the system volume is very small, becoming a potential candidate for micro projectors.

  20. Two-photon microscopy with diffractive optical elements and spatial light modulators

    Directory of Open Access Journals (Sweden)

    Brendon O Watson

    2010-09-01

    Full Text Available Two-photon microscopy is often performed at slow frame rates, due to the need to serially scan all points in a field of view with a single laser beam. To overcome this problem, we have developed two optical methods that split and multiplex a laser beam across the sample. In the first method a diffractive optical element (DOE generates a fixed number of beamlets that are scanned in parallel, resulting in a corresponding increase in speed, or in signal-to-noise ratio, in time-lapse measurements. The second method uses a computer-controlled spatial light modulator (SLM, to generate any arbitrary spatio-temporal light pattern. With an SLM one can image or photostimulate any predefined region of the image, such as neurons or dendritic spines. In addition, SLMs can be used to mimic a large number of optical transfer functions, including light path corrections or as adaptive optical devices.

  1. Phase Quantization Study of Spatial Light Modulator for Extreme High contrast Imaging

    CERN Document Server

    Dou, Jiangpei

    2016-01-01

    Direct imaging of exoplanets by reflected starlight is extremely challenging due to the large luminosity ratio to the primary star. Wave front control is a critical technique to attenuate the speckle noise in order to achieve an extreme high contrast. We present the phase quantization study of spatial light modulator for wave front control to meet the contrast requirement of detection of a terrestrial planet in the habitable zone of a solar-type star. We perform the numerical simulation by employing the SLM with different phase accuracy and actuator numbers, which are related to the achievable contrast. We use an optimization algorithm to solve the quantization problems that is matched to the controllable phase step of the SLM. Two optical configurations are discussed with the SLM located before and after the coronagraph focal plane mask, respectively. The simulation result has constrained the specification for phase accuracy of SLM in above two optical configurations. Finally, we have demonstrated that the S...

  2. Super-resolution imaging in digital holography by using dynamic grating with a spatial light modulator

    Science.gov (United States)

    Lin, Qiaowen; Wang, Dayong; Wang, Yunxin; Rong, Lu; Chang, Shifeng

    2015-03-01

    A super-resolution imaging method using dynamic grating based on liquid-crystal spatial light modulator (SLM) is developed to improve the resolution of a digital holographic system. The one-dimensional amplitude cosine grating is loaded on the SLM, which is placed between the object and hologram plane in order to collect more high-frequency components towards CCD plane. The point spread function of the system is given to confirm the separation condition of reconstructed images for multiple diffraction orders. The simulation and experiments are carried out for a standard resolution test target as a sample, which confirms that the imaging resolution is improved from 55.7 μm to 31.3 μm compared with traditional lensless Fourier transform digital holography. The unique advantage of the proposed method is that the period of the grating can be programmably adjusted according to the separation condition.

  3. Adaptive electron beam shaping using a photoemission gun and spatial light modulator

    Science.gov (United States)

    Maxson, Jared; Lee, Hyeri; Bartnik, Adam C.; Kiefer, Jacob; Bazarov, Ivan

    2015-02-01

    The need for precisely defined beam shapes in photoelectron sources has been well established. In this paper, we use a spatial light modulator and simple shaping algorithm to create arbitrary, detailed transverse laser shapes with high fidelity. We transmit this shaped laser to the photocathode of a high voltage dc gun. Using beam currents where space charge is negligible, and using an imaging solenoid and fluorescent viewscreen, we show that the resultant beam shape preserves these detailed features with similar fidelity. Next, instead of transmitting a shaped laser profile, we use an active feedback on the unshaped electron beam image to create equally accurate and detailed shapes. We demonstrate that this electron beam feedback has the added advantage of correcting for electron optical aberrations, yielding shapes without skew. The method may serve to provide precisely defined electron beams for low current target experiments, space-charge dominated beam commissioning, as well as for online adaptive correction of photocathode quantum efficiency degradation.

  4. Ultrafast laser parallel microdrilling using multiple annular beams generated by a spatial light modulator

    Science.gov (United States)

    Kuang, Zheng; Perrie, Walter; Edwardson, Stuart P.; Fearon, Eamonn; Dearden, Geoff

    2014-03-01

    Ultrafast laser parallel microdrilling using diffractive multiple annular beam patterns is demonstrated in this paper. The annular beam was generated by diffractive axicon computer generated holograms (CGHs) using a spatial light modulator. The diameter of the annular beam can be easily adjusted by varying the radius of the smallest ring in the axicon. Multiple annular beams with arbitrary arrangement and multiple annular beam arrays were generated by superimposing an axicon CGH onto a grating and lenses algorithm calculated multi-beam CGH and a binary Dammann grating CGH, respectively. Microholes were drilled through a 0.03 mm thick stainless steel foil using the multiple annular beams. By avoiding huge laser output attenuation and mechanical annular scanning, the processing is ˜200 times faster than the normal single beam processing.

  5. The effects of molecular diffusion in spatially encoded magnetic resonance imaging

    Science.gov (United States)

    Marhabaie, Sina; Bodenhausen, Geoffrey; Pelupessy, Philippe

    2016-12-01

    In spatially encoded MRI, the signal is acquired sequentially for different coordinates. In particular for single-scan acquisitions in inhomogeneous fields, spatially encoded methods improve the image quality compared to traditional k-space encoding. Previously, much attention has been paid in order to homogenize T2 losses across the sample. In this work, we investigate the effects of diffusion on the image quality in spatially encoded MRI. We show that losses due to diffusion are often not uniform along the spatially encoded dimension, and how to adapt spatially encoded sequences in order to obtain uniformly diffusion-weighted images.

  6. Influence of Spatial Resolution in Three-dimensional Cine Phase Contrast Magnetic Resonance Imaging on the Accuracy of Hemodynamic Analysis.

    Science.gov (United States)

    Fukuyama, Atsushi; Isoda, Haruo; Morita, Kento; Mori, Marika; Watanabe, Tomoya; Ishiguro, Kenta; Komori, Yoshiaki; Kosugi, Takafumi

    2017-10-10

    We aim to elucidate the effect of spatial resolution of three-dimensional cine phase contrast magnetic resonance (3D cine PC MR) imaging on the accuracy of the blood flow analysis, and examine the optimal setting for spatial resolution using flow phantoms. The flow phantom has five types of acrylic pipes that represent human blood vessels (inner diameters: 15, 12, 9, 6, and 3 mm). The pipes were fixed with 1% agarose containing 0.025 mol/L gadolinium contrast agent. A blood-mimicking fluid with human blood property values was circulated through the pipes at a steady flow. Magnetic resonance (MR) images (three-directional phase images with speed information and magnitude images for information of shape) were acquired using the 3-Tesla MR system and receiving coil. Temporal changes in spatially-averaged velocity and maximum velocity were calculated using hemodynamic analysis software. We calculated the error rates of the flow velocities based on the volume flow rates measured with a flowmeter and examined measurement accuracy. When the acrylic pipe was the size of the thoracicoabdominal or cervical artery and the ratio of pixel size for the pipe was set at 30% or lower, spatially-averaged velocity measurements were highly accurate. When the pixel size ratio was set at 10% or lower, maximum velocity could be measured with high accuracy. It was difficult to accurately measure maximum velocity of the 3-mm pipe, which was the size of an intracranial major artery, but the error for spatially-averaged velocity was 20% or less. Flow velocity measurement accuracy of 3D cine PC MR imaging for pipes with inner sizes equivalent to vessels in the cervical and thoracicoabdominal arteries is good. The flow velocity accuracy for the pipe with a 3-mm-diameter that is equivalent to major intracranial arteries is poor for maximum velocity, but it is relatively good for spatially-averaged velocity.

  7. The amygdala modulates neuronal activation in the hippocampus in response to spatial novelty.

    Science.gov (United States)

    Sheth, Archana; Berretta, Sabina; Lange, Nicholas; Eichenbaum, Howard

    2008-01-01

    Emerging evidence indicates that the amygdala and the hippocampus play an important role in the pathophysiology of major psychotic disorders. Consistent with this evidence, and with data indicating amygdala modulation of hippocampal activity, animal model investigations have shown that a disruption of amygdala activity induces neurochemical changes in the hippocampus that are similar to those detected in subjects with schizophrenia. With the present study, we used induction of the immediate early gene Fos, to test the hypothesis that the amygdala may affect neuronal activation of the hippocampus in response to different spatial environments (familiar, modified, and novel). Exploratory and anxiety related behaviors were also assessed. In vehicle-treated rats, exposure to a modified version of the familiar environment was associated with an increase of numerical densities of Fos-immunoreactive nuclei in sectors CA1 and CA2, while exposure to a completely novel environment was associated with an increase in sectors CA1, CA4, and DG, compared with the familiar environment. Pharmacological disruption of amygdala activity resulted in a failure to increase Fos induction in the hippocampus in response to these environments. Exploratory behavior in response to the different environments was not altered by manipulation of amygdala activity. These findings support the idea that the amygdala modulates spatial information processing in the hippocampus and may affect encoding of specific environmental features, while complex behavioral responses to environment may be the result of broader neural circuits. These findings also raise the possibility that amygdala abnormalities may contribute to impairments in cognitive information processing in subjects with major psychoses.

  8. Suggestion-Induced Modulation of Semantic Priming during Functional Magnetic Resonance Imaging

    Science.gov (United States)

    Ulrich, Martin; Kiefer, Markus; Bongartz, Walter; Grön, Georg; Hoenig, Klaus

    2015-01-01

    Using functional magnetic resonance imaging during a primed visual lexical decision task, we investigated the neural and functional mechanisms underlying modulations of semantic word processing through hypnotic suggestions aimed at altering lexical processing of primes. The priming task was to discriminate between target words and pseudowords presented 200 ms after the prime word which was semantically related or unrelated to the target. In a counterbalanced study design, each participant performed the task once at normal wakefulness and once after the administration of hypnotic suggestions to perceive the prime as a meaningless symbol of a foreign language. Neural correlates of priming were defined as significantly lower activations upon semantically related compared to unrelated trials. We found significant suggestive treatment-induced reductions in neural priming, albeit irrespective of the degree of suggestibility. Neural priming was attenuated upon suggestive treatment compared with normal wakefulness in brain regions supporting automatic (fusiform gyrus) and controlled semantic processing (superior and middle temporal gyri, pre- and postcentral gyri, and supplementary motor area). Hence, suggestions reduced semantic word processing by conjointly dampening both automatic and strategic semantic processes. PMID:25923740

  9. Neutron intensity modulation and time-focusing with integrated Larmor and resonant frequency techniques

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Jinkui, E-mail: zhaoj@ornl.gov; Hamilton, William A.; Robertson, J. L.; Crow, Lowell [Instrument and Source Division, Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Lee, Sung-Woo; Kang, Yoon W. [Research Accelerator Division, Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

    2015-09-14

    The analysis of neutron diffraction experiments often assumes that neutrons are elastically scattered from the sample. However, there is growing evidence that a significant fraction of the detected neutrons is in fact inelastically scattered, especially from soft materials and aqueous samples. Ignoring these inelastic contributions gives rise to inaccurate experimental results. To date, there has been no simple method with broad applicability for inelastic signal separation in neutron diffraction experiments. Here, we present a simple and robust method that we believe could be suited for this purpose. We use two radio frequency resonant spin flippers integrated with a Larmor precession field to modulate the neutron intensity and to encode the inelastic scattering information into the neutron data. All three components contribute to the spin encoding. The Larmor field serves several additional purposes. Its usage facilitates neutron time-focusing, eliminates the need for stringent magnetic shielding, and allows for compact setups. The scheme is robust, simple, and flexible. We believe that, with further improvements, it has the potential of adding inelastic signal discrimination capabilities to many existing diffraction instruments in the future.

  10. Fine-pitch high-efficiency spatial optical modulator for mobile display applications

    Science.gov (United States)

    Song, Jong Hyeong; Yun, Sang Kyeong; Kim, Hee Yeoun; An, Seungdo; Park, Heung Woo; Choi, Yoon Joon; Yurlov, Victor; Lapchuk, Anatoliy; Yang, Chung Mo; Lee, Sung Jun; Jang, Jae Wook; Lee, Ki Un; Woo, Ki Suk; Bourim, El M.

    2009-02-01

    Diffractive spatial optical modulators (SOM) with fine pitch pixel array were introduced for the mobile applications of laser projection display which requires the small volume, low power consumption and high optical efficiency. Micromechanical designs of piezoelectric (PZT) actuator and mirror ribbon structure were optimized for small volume, but keeping the same level of the other performance. Even though the same design rule and fabrication equipment were used for 10 um pitch SOM and 16 um pitch SOM, the optical efficiency of the fine pitch SOM was 78 % for the 0th order diffraction and is better than that of 16 um pitch SOM (73%). The full on/off contrast ratio has no difference between 10 um pitch and 16 um pitch SOM. All the optical characteristics coincide well with the theoretical estimations. High displacement of 500nm, which is enough to modulate the three Red, Green and Blue colors were achieved by the control of the thicknesses and stresses of constituent structural layers. It was found that the stress of Pt/PZT/Pt actuating layer was the main parameter affecting the initial gap height of the ribbon and also its displacement. For improving the optical properties of the SOM devices, the required ribbon-flatness could be achieved by applying a stress gradient on the SiN layer to compensate for the stress unbalance between Al mirror and SiN supprting layer. The temperature sensitive characteristics of the SOM device, which degrades the image quality, could be minimized by a mechanical compensation method using a thermal expansion effect of Si substrates. This concept could be applied in most of the bridge type MEMS structure. The most critical parameter which limit the SOM device lifetime was found to be the ribbon displacement degradation. By using a temperature accelerating lifetime measurement method based on the displacement degradation the estimated lifetime was more than 4,000 hrs and is of acceptable level in the mobile application. In short, the

  11. The Modulation of Ionospheric Alfvén Resonator on Heating HF Waves and the Doppler Effect

    Institute of Scientific and Technical Information of China (English)

    Ni Bin-bin; Zhao Zheng-yu; Xie Shu-guo

    2003-01-01

    Abstract: The propagation of HF waves in IAR can produce many nonlinear effects, including the modulation effect of IAR on HF waves and the Doppler effect. To start with the dependence of the ionospheric electron temperature variaof the modulation effect and lucubrate possible reasons for the field can have an observable modulation effect on HF waves while its mechanism is quite different from that of Schumann resonant field on HF waves. The depth of modulation of IAR field, which directly inspires the formation of cross-spectrum between ULF waves and HF waves and results in spectral peaks at some gyro-frequencies of IAR. With respect to the Doppler effect during the propagation of HF waves in IAR, it is mainly caused by the motion of the high-speed flyer and the drifting electrons and the frequency shift from the phase variation of the reflected waves can be neglected when the frequency of HF incident wave is high enough.

  12. DNS of the turbulence modulation by dispersed particles in compressible spatially developing two-phase jets

    Institute of Scientific and Technical Information of China (English)

    LUO Kun; FAN Jianren; CEN Kefa

    2004-01-01

    A new two-way coupled direct numerical simulation (DNS) method is developed to study the turbulence modulation in the compressible and spatial developing particle-laden turbulent jets with higher Reynolds number. The high-resolution solver is performed for the gas phase flow-field and the Lagrangian method is used to trace particles. It is found that the particles with Stokes number of 0.01and 50 advance the evolution of the coherent structures in the flow-field, but the particles with Stokes number of 1 delay it. All particles increase the turbulent kinetic energy and decrease the vorticity thickness, in which the particles with the Stokes number of 1 exhibit the maximum modulation. The jet velocity half-width and the decay of the streamwise mean velocity along the centerline are reduced by particles with Stokes number of 0.01 and 1. The momentum thickness is increased by particles and the larger the Stokes number is, the larger the momentum thickness is.

  13. A low-power high-speed driving circuit for spatial light modulators

    Institute of Scientific and Technical Information of China (English)

    朱明皓; 朱从义; 李文江; 张耀辉

    2012-01-01

    This paper describes the design and test of a novel custom driving circuit for multi-quantum-well (MQW) spatial light modulators (SLMs).Unlike previous solutions,we integrated all blocks in one chip to synchronize the control logic circuit and the driving circuits.Single-slope digital-to-analog converters (DACs) inside each pixel are not adopted because it is difficult to eliminate capacitor mismatch.64 column-shared 8-bit resistorstring DACs are utilized to provide programmable output voltages from 0.5 to 3.8 V.They are located on the top of 64 × 64 driving pixels tightly to match each other with several dummies.Each DAC performs its conversion in 280 ns and draws 80 μA.For a high speed data transfer rate,the system adopts a 2-stage shift register that operates at 50 MHz and the modulating rate achieves 50 K frames/s while dissipating 302 mW from a 5-V supply.The die is fabricated in a 0.35μm CMOS process and its area is 5.5 × 7 mm2.

  14. A low-power high-speed driving circuit for spatial light modulators

    Science.gov (United States)

    Minghao, Zhu; Congyi, Zhu; Wenjiang, Li; Yaohui, Zhang

    2012-02-01

    This paper describes the design and test of a novel custom driving circuit for multi-quantum-well (MQW) spatial light modulators (SLMs). Unlike previous solutions, we integrated all blocks in one chip to synchronize the control logic circuit and the driving circuits. Single-slope digital-to-analog converters (DACs) inside each pixel are not adopted because it is difficult to eliminate capacitor mismatch. 64 column-shared 8-bit resistor-string DACs are utilized to provide programmable output voltages from 0.5 to 3.8 V. They are located on the top of 64 × 64 driving pixels tightly to match each other with several dummies. Each DAC performs its conversion in 280 ns and draws 80 μA. For a high speed data transfer rate, the system adopts a 2-stage shift register that operates at 50 MHz and the modulating rate achieves 50 K frames/s while dissipating 302 mW from a 5-V supply. The die is fabricated in a 0.35 μm CMOS process and its area is 5.5 × 7 mm2.

  15. Non-Contact Surface Roughness Measurement by Implementation of a Spatial Light Modulator

    Directory of Open Access Journals (Sweden)

    Laura Aulbach

    2017-03-01

    Full Text Available The surface structure, especially the roughness, has a significant influence on numerous parameters, such as friction and wear, and therefore estimates the quality of technical systems. In the last decades, a broad variety of surface roughness measurement methods were developed. A destructive measurement procedure or the lack of feasibility of online monitoring are the crucial drawbacks of most of these methods. This article proposes a new non-contact method for measuring the surface roughness that is straightforward to implement and easy to extend to online monitoring processes. The key element is a liquid-crystal-based spatial light modulator, integrated in an interferometric setup. By varying the imprinted phase of the modulator, a correlation between the imprinted phase and the fringe visibility of an interferogram is measured, and the surface roughness can be derived. This paper presents the theoretical approach of the method and first simulation and experimental results for a set of surface roughnesses. The experimental results are compared with values obtained by an atomic force microscope and a stylus profiler.

  16. Analysis of compressive sensing with optical mixing using a spatial light modulator.

    Science.gov (United States)

    Zhu, Zhijing; Chi, Hao; Zheng, Shilie; Jin, Tao; Jin, Xiaofeng; Zhang, Xianmin

    2015-03-10

    Compressive sensing (CS) in a photonic link has a high potential for acquisition of wideband sparse signals. In CS it is necessary to mix the input sparse signal with a pseudorandom sequence prior to subsampling. A pulse shaper with a spatial light modulator (SLM) can be used in photonic CS as an optical mixer to improve the speed of mixing. In this approach, the sparse signal is modulated on a chirped optical pulse and the pseudorandom sequence is recorded on the SLM within the pulse shaper. The optical mixing in the frequency domain is realized based on the principle of frequency-to-time mapping. In this paper, we investigate the performance and limitations of photonic CS with an SLM in detail. A theoretical model to describe optical mixing based on frequency-to-time mapping is presented. We point out that there is an upper limit on the length of the pseudorandom sequence recorded on the SLM that can be mixed with the sparse signal due to the condition of the far-field approximation of the frequency-to-time mapping. Since the length of the pseudorandom sequence is one of the major factors that affect the signal recovery performance in CS, this limitation should be fully considered in the system design of the CS with optical mixing in the frequency domain. We present numerical and experimental results to verify the theoretical findings. Discussion on the performance improvement is also presented.

  17. Affective and contextual values modulate spatial frequency use in object recognition

    Directory of Open Access Journals (Sweden)

    Laurent eCaplette

    2014-05-01

    Full Text Available Visual object recognition is of fundamental importance in our everyday interaction with the environment. Recent models of visual perception emphasize the role of top-down predictions facilitating object recognition via initial guesses that limit the number of object representations that need to be considered. Several results suggest that this rapid and efficient object processing relies on the early extraction and processing of low spatial frequencies (SF. The present study aimed to investigate the SF content of visual object representations and its modulation by contextual and affective values of the perceived object during a picture-name verification task. Stimuli consisted of pictures of objects equalized in SF content and categorised as having low or high affective and contextual values. To access the SF content of stored visual representations of objects, SFs of each image were then randomly sampled on a trial-by-trial basis. Results reveal that intermediate SFs between 14 and 24 cycles per object (2.3 to 4 cycles per degree are correlated with fast and accurate identification for all categories of objects. Moreover, there was a significant interaction between affective and contextual values over the SFs correlating with fast recognition. These results suggest that affective and contextual values of a visual object modulate the SF content of its internal representation, thus highlighting the flexibility of the visual recognition system.

  18. High Spatial Resolution of an Optical Addressing Spatial Light Modulator Made by Photorefractive Semi-Insulting Multiple Quantum Wells

    Institute of Scientific and Technical Information of China (English)

    陈兢; 李春勇; 韩英军; 郭丽伟; 黄绮; 张治国; 汤俊雄; 段明浩

    2002-01-01

    We use nondegenerate four-wave mixing to study the spatial resolution of photorefractive semi-insulating multiple quantum wells grown by molecular beam epitaxy. By optimizing the experimental conditions, we have demonstrated that our sample has spatial resolution up to 2.5μm, which approaches the theoretical limit. We also analyse the factors that affect the spatial resolution of multiple quantum wells.

  19. Super-resolved multimodal multiphoton microscopy with spatial frequency-modulated imaging

    CERN Document Server

    Field, Jeffrey J; Domingue, Scott R; Motz, Alyssa M Allende; DeLuca, Keith F; DeLuca, Jennifer G; Kuciauskas, Darius; Levi, Dean H; Squier, Jeff A; Bartels, Randy A

    2015-01-01

    Super-resolved far-field microscopy has emerged as a powerful tool for investigating the structure of objects with resolution well below the diffraction limit of light. Nearly all super-resolution imaging techniques reported to date rely on real energy states of probe molecules to circumvent the diffraction limit, preventing super-resolved imaging of contrast mechanisms that occur via virtual energy states such as harmonic generation (HG). Here we report a super-resolution technique based on SPatIal Frequency modulated Imaging (SPIFI) that permits super-resolved nonlinear microscopy with any contrast mechanism, and with single-pixel detection. We show multimodal super-resolved images with two-photon excited fluorescence (TPEF) and second-harmonic generation (SHG) from biological and inorganic media. Multiphoton SPIFI (MP-SPIFI) provides spatial resolution up to 2$\\eta$ below the diffraction limit, where $\\eta$ is the highest power of the nonlinear intensity response. MP-SPIFI has the potential to not only pro...

  20. Spatial Location in Brief, Free-Viewing Face Encoding Modulates Contextual Face Recognition

    Directory of Open Access Journals (Sweden)

    Fatima M. Felisberti

    2013-08-01

    Full Text Available The effect of the spatial location of faces in the visual field during brief, free-viewing encoding in subsequent face recognition is not known. This study addressed this question by tagging three groups of faces with cheating, cooperating or neutral behaviours and presenting them for encoding in two visual hemifields (upper vs. lower or left vs. right. Participants then had to indicate if a centrally presented face had been seen before or not. Head and eye movements were free in all phases. Findings showed that the overall recognition of cooperators was significantly better than cheaters, and it was better for faces encoded in the upper hemifield than in the lower hemifield, both in terms of a higher d' and faster reaction time (RT. The d' for any given behaviour in the left and right hemifields was similar. The RT in the left hemifield did not vary with tagged behaviour, whereas the RT in the right hemifield was longer for cheaters than for cooperators. The results showed that memory biases in contextual face recognition were modulated by the spatial location of briefly encoded faces and are discussed in terms of scanning reading habits, top-left bias in lighting preference and peripersonal space.

  1. Idler-resonant intracavity KTA-based OPO pumped by a dual-loss modulated-Q-switched-laser with AOM and Cr4+:YAG

    Science.gov (United States)

    Qiao, Junpeng; Zhao, Shengzhi; Yang, Kejian; Zhao, Jia; Li, Guiqiu; Li, Dechun; Li, Tao; Qiao, Wenchao

    2017-06-01

    An idler-resonant KTiOAsO4 (KTA)-based intracavity optical parametric oscillator (IOPO) pumped by a dual-loss-modulated Q-switched laser with an acousto-optic modulator (AOM) and a Cr4+:YAG saturable absorber (Cr4+:YAG-SA) has been presented. By utilizing a type-II non-critically phase-matched KTA crystal, signal wave at 1535 nm and idler wave at 3467 nm have been generated. Under an incident pump power of 18.3 W, maximum output powers of 615 mW for signal wave and 228 mW for idler wave were obtained at an AOM modulation rate of 10 kHz, corresponding to a whole optical-to-optical conversion efficiency of 4.6%. The shortest pulse widths of signal and idler wave were measured to be 898 ps and 2.9 ns, corresponding to the highest peak powers of 68.4 and 7.9 kW, respectively. In comparison with IOPO pumped by a singly Q-switched laser with an AOM, the IOPO pumped by a doubly Q-switched laser (DIOPO) with an AOM and a Cr4+:YAG-SA can generate signal wave and idler wave with shorter pulse width and higher peak power. By considering the spatial Gaussian distribution of intracavity photon density, a set of coupled rate equations for the idler-resonant DIOPO were built for the first time to the best of our knowledge. The simulation results agreed well with the experimental results.

  2. Microring resonator based modulator made by direct photodefinition of an electro-optic polymer

    NARCIS (Netherlands)

    Balakrishnan, M; Faccini, M.; Diemeer, M.B.J.; Klein, E.J.; Sengo, G.; Driessen, A.; Verboom, W.; Reinhoudt, D.N.

    2008-01-01

    A laterally coupled microring resonator was fabricated by direct photodefinition of negative photoresist SU8, containing tricyanovinylidenediphenylaminobenzene chromophore, by exploiting the low ultraviolet absorption window of this chromophore. The ring resonator was first photodefined by slight cr

  3. Study on Interaction of Ginsenosides with Bovine or Human Serum Albumin Using Wavelength Modulation Surface Plasmon Resonance Biosensor

    Institute of Scientific and Technical Information of China (English)

    LIU Xia; SUN Ying; SONG Da-Qian; LI Xu-Wen; ZHANG Qing-Lin; TIAN Yuan; LIU Zhong-Ying; ZHANG Han-Qi

    2006-01-01

    To use a newly developed wavelength modulation surface plasmon resonance (SPR) biosensor, an experimental protocol was developed to investigate the interaction of ginsenosides with serum albumin. With a known concentration of the ginsenosides, bound percentages of the ginsenosides with human serum albumin (HSA) or bovine serum albumin (BSA) were obtained. SPR technique could require no labeling and this method provided the detailed information on association and disassociation of molecules in real time. The results indicate that the sensitivity of wavelength modulation SPR biosensor is sufficient for detection and characterization of binding events involving low-molecular weight compounds and their immobilized protein targets.

  4. Using Off-Resonance Laser Modulation for Beam Energy Spread Cooling in Generation of Short-Wavelength Radiation

    CERN Document Server

    Deng, Haixiao

    2013-01-01

    Various seeding configurations have being proposed for frequency up-conversion of the electron beam density distribution, in which the energy spread, may however hinder the harmonic generation efficiency. In this Letter, a method for cooling the electron beam energy spread by off-resonance seed laser modulation is described, using a transversely dispersed beam and a modulator undulator with proper transverse gradient. With this novel mechanism, it is shown that the frequency up-conversion efficiency can be significantly enhanced. We present theoretical analysis and numerical simulations for seeded soft x-ray free electron laser and storage ring based coherent harmonic generation in extreme ultraviolet spectral region.

  5. Spatial self-phase modulation in the H2TPP(OH)4 doped in Boric Acid Glass

    CERN Document Server

    Allam, Srinivasa Rao; Venkatramaiah, N; Venkatesan, R; Sharan, Alok

    2015-01-01

    Self-diffraction rings or spatial self-phase modulation (SSPM) was observed in tetra-phenyl porphyrin derivative 5,10,15,20 - meso-tetrakis (4-hydroxyphenyl) porphyrin (H2TPP(OH)4) doped in boric acid glass (BAG) at 671 nm excitation wave-length lying within the absorption band of sample with TEM00 mode profile. Intensity modulated Z-scan was performed on these systems to study the thermal diffusion and to estimate the thermo-optic coefficients. The results obtained from self-diffraction rings experiment and modulated Z-scan are compared and analyzed for different concentration.

  6. Fluorescence Resonance Energy Transfer Imaging Reveals that Chemokine-Binding Modulates Heterodimers of CXCR4 and CCR5 Receptors

    OpenAIRE

    2008-01-01

    BACKGROUND: Dimerization has emerged as an important feature of chemokine G-protein-coupled receptors. CXCR4 and CCR5 regulate leukocyte chemotaxis and also serve as a co-receptor for HIV entry. Both receptors are recruited to the immunological synapse during T-cell activation. However, it is not clear whether they form heterodimers and whether ligand binding modulates the dimer formation. METHODOLOGY/PRINCIPAL FINDINGS: Using a sensitive Fluorescence Resonance Energy Transfer (FRET) imaging ...

  7. Nonlinear magneto-optical rotation of frequency-modulated light resonant with a low-J transition

    CERN Document Server

    Malakyan, Y P; Budker, D; Kimball, D F; Yashchuk, V V; Malakyan, Yu. P.

    2003-01-01

    A low-light-power theory of nonlinear magneto-optical rotation of frequency-modulated light resonant with a J=1->J'=0 transition is presented. The theory is developed for a Doppler-free transition, and then modified to account for Doppler broadening and velocity mixing due to collisions. The results of the theory are shown to be in qualitative agreement with experimental data obtained for the rubidium D1 line.

  8. Magnetic resonance imaging spatial and time study of lung water content in newborn lamb: methods and preliminary results.

    Science.gov (United States)

    Viard, Romain; Tourneux, Pierre; Storme, Laurent; Girard, Julie-Marie; Betrouni, Nacim; Rousseau, Jean

    2008-06-01

    To study the lung liquid clearance in vivo at the time of birth, magnetic resonance experiments were conducted on newborn lambs immediately after uterine incision deliverance. Images obtained with a fast spin echo magnetic resonance imaging sequence enable to quantify lung liquid each 5 minutes for 30 minutes, then each 10 minutes for 1.5 hours. After manually determining lung contours, pulmonary volume, pulmonary water, and spatial gradient of pulmonary water were studied. At 2 hours of life, the total pulmonary water content was still high and the liquid clearance was slower in the lower part of the lung. Air inflation increased the size of the distal airways and shifted liquid from the lung lumen towards the pulmonary interstitial tissue. The lung liquid washout was belated, and the passage to the aerial life was performed by progressive liberation of the superior pulmonary spaces, water flowing out by gravity toward the lower spaces.

  9. Parameter Diversity Induced Multiple Spatial Coherence Resonances and Spiral Waves in Neuronal Network with and Without Noise

    Institute of Scientific and Technical Information of China (English)

    李玉叶; 贾冰; 古华光; 安书成

    2012-01-01

    Diversity in the neurons and noise are inevitable in the real neuronal network.In this paper,parameter diversity induced spiral waves and multiple spatial coherence resonances in a two-dimensional neuronal network without or with noise are simulated.The relationship between the multiple resonances and the multiple transitions between patterns of spiral waves are identified.The coherence degrees induced by the diversity are suppressed when noise is introduced and noise density is increased.The results suggest that natural nervous system might profit from both parameter diversity and noise,provided a possible approach to control formation and transition of spiral wave by the cooperation between the diversity and noise.

  10. Coupling effect combined with incident polarization to modulate double split-ring-resonator in terahertz frequency range

    Science.gov (United States)

    Zhu, Mei; Lin, Yu-Sheng; Lee, Chengkuo

    2014-11-01

    This work examines the coupling effect in concentric double split-ring-resonator devices in terahertz (THz) range when the inner ring changes its relative orientation to the outer ring. Through detailed analysis on the simulation results of surface current and electrical field distributions, we look into the changes of inductance and capacitance in the system caused by structural layouts, and present a set of coherent theory that is solely rooted in the inductance-capacitance circuit analogy to systematically account for the resonance change. Such coupling effect combined with polarization of the incident wave is further explored to demonstrate continuous modulation of THz resonances. A variation range of transmission intensity from 20% to 80% has been successfully achieved. These experimental results demonstrate the promise of realizing future tunable THz filters by means of rotating sub-structures of the device only.

  11. Out-of-plane resonances in terahertz photonic crystal slabs modulated by optical pumping.

    Science.gov (United States)

    Shi, Yulei; Zhou, Qing-Li; Liu, Wei; Zhang, Cunlin

    2011-10-10

    This paper describes detailed optical-pump-terahertz-probe studies of two-dimensional photonic crystal slabs for propagation perpendicular to the slabs. When the slabs are excited by an 800 nm pump pulse and the effect of shielding by photocarriers is removed, we find that the decaying tail in the transmitted terahertz radiation is strikingly enhanced. The photocarriers weaken guided resonances, but they also greatly enhance the excitation efficiency of guided resonances and the ability of the guided resonances to transfer energy back to the radiation field. This increases the resonance-assisted contribution to transmitted field. The photoinduced resonant extremes agree well with the Fano model.

  12. Spatiotemporal vector pulse shaping of femtosecond laser pulses with a multi-pass two-dimensional spatial light modulator.

    Science.gov (United States)

    Esumi, Y; Kabir, M D; Kannari, F

    2009-10-12

    A novel non-interferometric vector pulse-shaping scheme is developed for femtosecond laser pulses using a two-dimensional spatial light modulator (2D-SLM). By utilizing spatiotemporal pulse shaping obtainable by the 2D-SLM, we demonstrate spatiotemporal vector pulse shaping for the first time.

  13. Utilization of a liquid crystal spatial light modulator in a gray scale detour phase method for Fourier holograms.

    Science.gov (United States)

    Makey, Ghaith; El-Daher, Moustafa Sayem; Al-Shufi, Kanj

    2012-11-10

    This paper introduces a new modification for the well-known binary detour phase method, which is largely used to represent Fourier holograms; the modification utilizes gray scale level control provided by a liquid crystal spatial light modulator to improve the traditional binary detour phase. Results are shown by both simulation and experiment.

  14. Spatial Interferer Rejection in a 4-Element Beamforming Receiver Frontend with a Switched-Capacitor Vector Modulator

    NARCIS (Netherlands)

    Soer, Michiel C.M.; Klumperink, Eric A.M.; Nauta, Bram; Vliet, van Frank E.

    2011-01-01

    A 1-4GHz 4-element phased array receiver frontend demonstrates spatial interferer rejection using null steering. Element phase and amplitude control are performed by a switchedcapacitor vector modulator with integrated downconversion, utilizing a rational sine/cosine approximation. The 65nm CMOS rec

  15. Differential modulation of lateral septal vasopressin receptor blockade in spatial learning, social recognition, and anxiety-related behaviors in rats

    NARCIS (Netherlands)

    Everts, HGJ; Koolhaas, JM

    1999-01-01

    The role of lateral septal vasopressin (VP) in the modulation of spatial memory, social memory, and anxiety-related behavior was studied in adult, male Wistar rats. Animals were equipped with osmotic minipumps delivering the VP-antagonist d(CH2)5-D-Tyr(Et)VAVP (1 ng/0.5 mu l per h) bilaterally into

  16. The effects of visual control and distance in modulating peripersonal spatial representation.

    Directory of Open Access Journals (Sweden)

    Chiara Renzi

    Full Text Available In the presence of vision, finalized motor acts can trigger spatial remapping, i.e., reference frames transformations to allow for a better interaction with targets. However, it is yet unclear how the peripersonal space is encoded and remapped depending on the availability of visual feedback and on the target position within the individual's reachable space, and which cerebral areas subserve such processes. Here, functional magnetic resonance imaging (fMRI was used to examine neural activity while healthy young participants performed reach-to-grasp movements with and without visual feedback and at different distances of the target from the effector (near to the hand-about 15 cm from the starting position-vs. far from the hand-about 30 cm from the starting position. Brain response in the superior parietal lobule bilaterally, in the right dorsal premotor cortex, and in the anterior part of the right inferior parietal lobule was significantly greater during visually-guided grasping of targets located at the far distance compared to grasping of targets located near to the hand. In the absence of visual feedback, the inferior parietal lobule exhibited a greater activity during grasping of targets at the near compared to the far distance. Results suggest that in the presence of visual feedback, a visuo-motor circuit integrates visuo-motor information when targets are located farther away. Conversely in the absence of visual feedback, encoding of space may demand multisensory remapping processes, even in the case of more proximal targets.

  17. The effects of visual control and distance in modulating peripersonal spatial representation.

    Science.gov (United States)

    Renzi, Chiara; Ricciardi, Emiliano; Bonino, Daniela; Handjaras, Giacomo; Vecchi, Tomaso; Pietrini, Pietro

    2013-01-01

    In the presence of vision, finalized motor acts can trigger spatial remapping, i.e., reference frames transformations to allow for a better interaction with targets. However, it is yet unclear how the peripersonal space is encoded and remapped depending on the availability of visual feedback and on the target position within the individual's reachable space, and which cerebral areas subserve such processes. Here, functional magnetic resonance imaging (fMRI) was used to examine neural activity while healthy young participants performed reach-to-grasp movements with and without visual feedback and at different distances of the target from the effector (near to the hand-about 15 cm from the starting position-vs. far from the hand-about 30 cm from the starting position). Brain response in the superior parietal lobule bilaterally, in the right dorsal premotor cortex, and in the anterior part of the right inferior parietal lobule was significantly greater during visually-guided grasping of targets located at the far distance compared to grasping of targets located near to the hand. In the absence of visual feedback, the inferior parietal lobule exhibited a greater activity during grasping of targets at the near compared to the far distance. Results suggest that in the presence of visual feedback, a visuo-motor circuit integrates visuo-motor information when targets are located farther away. Conversely in the absence of visual feedback, encoding of space may demand multisensory remapping processes, even in the case of more proximal targets.

  18. A microwave detection way by electromagnetic and elastic resonance: Breaking the bottleneck of spatial resolution in microwave imaging

    Science.gov (United States)

    Ji, Zhong; Lou, Cunguang; Shi, Yujiao; Ding, Wenzheng; Yang, Sihua; Xing, Da

    2015-10-01

    The spatial resolution of microwave imaging depends on the geometrical size of the detector. The existing techniques mainly focus on optimizing the antenna design to achieve high detection sensitivity. However, since the optimal antenna size is closely related to the wavelength to be measured, and the miniaturization of the geometrical size is challenging, this limits the spatial resolution of microwave imaging. In this letter, a microwave detection technique based on the electromagnetic-elastic resonance effect is proposed. The piezoelectric materials can produce mechanical responses under microwave excitation, and the amplitude of the microwave can be detected by measuring these responses. In contrast to conventional microwave detection method, the proposed method has distinct advantages in terms of high sensitivity and wide spectral response. Most importantly, it overcomes the limitation of detector size, thus, significantly improving the detection resolution. Therefore, the proposed method has potential for microwave imaging in biomedical applications.

  19. Serotonergic modulation of spatial working memory: predictions from a computational network model

    Directory of Open Access Journals (Sweden)

    Maria eCano-Colino

    2013-09-01

    Full Text Available Serotonin (5-HT receptors of types 1A and 2A are massively expressed in prefrontal cortex (PFC neurons, an area associated with cognitive function. Hence, 5-HT could be effective in modulating prefrontal-dependent cognitive functions, such as spatial working memory (SWM. However, a direct association between 5-HT and SWM has proved elusive in psycho-pharmacological studies. Recently, a computational network model of the PFC microcircuit was used to explore the relationship between 5‑HT and SWM (Cano-Colino et al. 2013. This study found that both excessive and insufficient 5-HT levels lead to impaired SWM performance in the network, and it concluded that analyzing behavioral responses based on confidence reports could facilitate the experimental identification of SWM behavioral effects of 5‑HT neuromodulation. Such analyses may have confounds based on our limited understanding of metacognitive processes. Here, we extend these results by deriving three additional predictions from the model that do not rely on confidence reports. Firstly, only excessive levels of 5-HT should result in SWM deficits that increase with delay duration. Secondly, excessive 5-HT baseline concentration makes the network vulnerable to distractors at distances that were robust to distraction in control conditions, while the network still ignores distractors efficiently for low 5‑HT levels that impair SWM. Finally, 5-HT modulates neuronal memory fields in neurophysiological experiments: Neurons should be better tuned to the cued stimulus than to the behavioral report for excessive 5-HT levels, while the reverse should happen for low 5-HT concentrations. In all our simulations agonists of 5-HT1A receptors and antagonists of 5-HT2A receptors produced behavioral and physiological effects in line with global 5-HT level increases. Our model makes specific predictions to be tested experimentally and advance our understanding of the neural basis of SWM and its neuromodulation

  20. Correcting the wavefront aberration of membrane mirror based on liquid crystal spatial light modulator

    Science.gov (United States)

    Yang, Bin; Wei, Yin; Chen, Xinhua; Tang, Minxue

    2014-11-01

    Membrane mirror with flexible polymer film substrate is a new-concept ultra lightweight mirror for space applications. Compared with traditional mirrors, membrane mirror has the advantages of lightweight, folding and deployable, low cost and etc. Due to the surface shape of flexible membrane mirror is easy to deviate from the design surface shape, it will bring wavefront aberration to the optical system. In order to solve this problem, a method of membrane mirror wavefront aberration correction based on the liquid crystal spatial light modulator (LCSLM) will be studied in this paper. The wavefront aberration correction principle of LCSLM is described and the phase modulation property of a LCSLM is measured and analyzed firstly. Then the membrane mirror wavefront aberration correction system is designed and established according to the optical properties of a membrane mirror. The LCSLM and a Hartmann-Shack sensor are used as a wavefront corrector and a wavefront detector, respectively. The detected wavefront aberration is calculated and converted into voltage value on LCSLM for the mirror wavefront aberration correction by programming in Matlab. When in experiment, the wavefront aberration of a glass plane mirror with a diameter of 70 mm is measured and corrected for verifying the feasibility of the experiment system and the correctness of the program. The PV value and RMS value of distorted wavefront are reduced and near diffraction limited optical performance is achieved. On this basis, the wavefront aberration of the aperture center Φ25 mm in a membrane mirror with a diameter of 200 mm is corrected and the errors are analyzed. It provides a means of correcting the wavefront aberration of membrane mirror.

  1. Modulating resonance modes and Q value of a CdS nanowire cavity by single Ag nanoparticles.

    Science.gov (United States)

    Zhang, Qing; Shan, Xin-Yan; Feng, Xiao; Wang, Chun-Xiao; Wang, Qu-Quan; Jia, Jin-Feng; Xue, Qi-Kun

    2011-10-12

    Semiconductor nanowire (NW) cavities with tailorable optical modes have been used to develop nanoscale oscillators and amplifiers in microlasers, sensors, and single photon emitters. The resonance modes of NW could be tuned by different boundary conditions. However, continuously and reversibly adjusting resonance modes and improving Q-factor of the cavity remain a great challenge. We report a method to modulate resonance modes continuously and reversibly and improve Q-factor based on surface plasmon-exciton interaction. By placing single Ag nanoparticle (NP) nearby a CdS NW, we show that the wavelength and relative intensity of the resonance modes in the NW cavity can systematically be tuned by adjusting the relative position of the Ag NP. We further demonstrate that a 56% enhancement of Q-factor and an equivalent π-phase shift of the resonance modes can be achieved when the Ag NP is located near the NW end. This hybrid cavity has potential applications in active plasmonic and photonic nanodevices.

  2. Optical pathology of human brain metastasis of lung cancer using combined resonance Raman and spatial frequency spectroscopies

    Science.gov (United States)

    Zhou, Yan; Liu, Cheng-hui; Pu, Yang; Cheng, Gangge; Zhou, Lixin; Chen, Jun; Zhu, Ke; Alfano, Robert R.

    2016-03-01

    Raman spectroscopy has become widely used for diagnostic purpose of breast, lung and brain cancers. This report introduced a new approach based on spatial frequency spectra analysis of the underlying tissue structure at different stages of brain tumor. Combined spatial frequency spectroscopy (SFS), Resonance Raman (RR) spectroscopic method is used to discriminate human brain metastasis of lung cancer from normal tissues for the first time. A total number of thirty-one label-free micrographic images of normal and metastatic brain cancer tissues obtained from a confocal micro- Raman spectroscopic system synchronously with examined RR spectra of the corresponding samples were collected from the identical site of tissue. The difference of the randomness of tissue structures between the micrograph images of metastatic brain tumor tissues and normal tissues can be recognized by analyzing spatial frequency. By fitting the distribution of the spatial frequency spectra of human brain tissues as a Gaussian function, the standard deviation, σ, can be obtained, which was used to generate a criterion to differentiate human brain cancerous tissues from the normal ones using Support Vector Machine (SVM) classifier. This SFS-SVM analysis on micrograph images presents good results with sensitivity (85%), specificity (75%) in comparison with gold standard reports of pathology and immunology. The dual-modal advantages of SFS combined with RR spectroscopy method may open a new way in the neuropathology applications.

  3. UV-modulated one-dimensional photonic-crystal resonator for visible lights

    Science.gov (United States)

    Yang, S. Y.; Yang, P. H.; Liao, C. D.; Chieh, J. J.; Chen, Y. P.; Horng, H. E.; Hong, Chin-Yih; Yang, H. C.

    2006-12-01

    The one-dimensional photonic-crystal (A/SiO2)6/ZnO/(SiO2/A)6 resonators at visible lights are fabricated and characterized, where A may be ZnO or indium tin oxide. Owing to the absorption of ultraviolet (UV) light by the ZnO layers, the refractive index of ZnO layers is changed temporally. This fact led to a temporary shifting of the forbidden band and the resonant mode of the resonator under UV irradiation. Besides, via adjusting the thickness of the ZnO defect layer, the resonant wavelength is manipulated. These experimental data show good consistence with simulated results.

  4. Psychophysical testing of spatial and temporal dimensions of endogenous analgesia: conditioned pain modulation and offset analgesia.

    Science.gov (United States)

    Honigman, Liat; Yarnitsky, David; Sprecher, Elliot; Weissman-Fogel, Irit

    2013-08-01

    The endogenous analgesia (EA) system is psychophysically evaluated using various paradigms, including conditioned pain modulation (CPM) and offset analgesia (OA) testing, respectively, the spatial and temporal filtering processes of noxious information. Though both paradigms assess the function of the EA system, it is still unknown whether they reflect the same aspects of EA and consequently whether they provide additive or equivalent data. Twenty-nine healthy volunteers (15 males) underwent 5 trials of different stimulation conditions in random order including: (1) the classic OA three-temperature stimulus train ('OA'); (2) a three-temperature stimulus train as control for the OA ('OAcon'); (3) a constant temperature stimulus ('constant'); (4) the classic parallel CPM ('CPM'); and (5) a combination of OA and CPM ('OA + CPM'). We found that in males, the pain reduction during the OA + CPM condition was greater than during the OA (P = 0.003) and CPM (P = 0.07) conditions. Furthermore, a correlation was found between OA and CPM (r = 0.62, P = 0.01) at the time of maximum OA effect. The additive effect found suggests that the two paradigms represent at least partially different aspects of EA. The moderate association between the CPM and OA magnitudes indicates, on the other hand, some commonality of their underlying mechanisms.

  5. Spatial resolution characterization of differential phase contrast CT systems via modulation transfer function (MTF) measurements

    Science.gov (United States)

    Li, Ke; Zambelli, Joseph; Bevins, Nicholas; Ge, Yongshuai; Chen, Guang-Hong

    2013-06-01

    By adding a Talbot-Lau interferometer to a conventional x-ray absorption computed tomography (CT) imaging system, both differential phase contrast (DPC) signal and absorption contrast signal can be simultaneously measured from the same set of CT measurements. The imaging performance of such multi-contrast x-ray CT imaging systems can be characterized with standard metrics such as noise variance, noise power spectrum, contrast-to-noise ratio, modulation transfer function (MTF), and task-based detectability index. Among these metrics, the measurement of the MTF can be challenging in DPC-CT systems due to several confounding factors such as phase wrapping and the difficulty of using fine wires as probes. To address these technical challenges, this paper discusses a viable and reliable method to experimentally measure the MTF of DPC-CT. It has been found that the spatial resolution of DPC-CT is degraded, when compared to that of the corresponding absorption CT, due to the presence of a source grating G0 in the Talbot-Lau interferometer. An effective MTF was introduced and experimentally estimated to describe the impact of the Talbot-Lau interferometer on the system MTF.

  6. Alarm calls modulate the spatial structure of a breeding owl community.

    Science.gov (United States)

    Parejo, Deseada; Avilés, Jesús M; Rodríguez, Juan

    2012-06-07

    Animals should continuously assess the threat of predation. Alarm calls inform on predation risk and are often used as cues to shape behavioural responses in birds and mammals. Hitherto, however, the ecological consequences of alarm calls in terms of organization of animal communities have been neglected. Here, we show experimentally that calls of a resident nocturnal raptor, the little owl Athene noctua, triggered a response in terms of breeding habitat selection and investment in current reproduction in conspecifics and heterospecifics. Little owls preferred to settle in territories where calls of conspecifics, irrespective of their type (i.e. alarm versus contact calls), were broadcasted, indicating that either conspecific attraction exists or calls are interpreted as foreign calls, eliciting settlement as a mode of defence against competitors. Also, we found that little owls seemed to invest more in current reproduction in safe territories as revealed by conspecific calls. Innovatively, we reported that a second owl species, the migratory scops owl Otus scops, preferred to breed in safe territories as indicated by little owls' calls. These results evidence that the emission of alarm calls may have, apart from well-known behavioural effects, ecological consequences in natural communities by inducing species-specific biases in breeding habitat selection. This study demonstrates a previously unsuspected informative role of avian alarm calls which may modulate the spatial structure of species within communities.

  7. E-beam addressed Spatial Light Modulator employing electron trapping materials. Phase 1

    Science.gov (United States)

    Lu, Xiaojing; Yang, Xiangyang; Wrigley, Charles Y.; Bradley, Richard; Meszaros, Janos

    1995-03-01

    Spatial light modulators (SLM's) play a critically important role in optical signal processing and optical computing. A novel electron beam addressed emissive SLM which combines high performance polycrystalline electron trapping (ET) materials with an advanced field-emitter array is being developed. The proposed SLM combines high resolution (greater than 100 lplmm), high SBP (greater than 1000 x 1000), high frame rate (greater than or equal 1 KHz), high contrast ratio (greater than l03:l) and low drive voltage (less than 15 V) in a single device. The additional features of the proposed SLM are its wide variety of operation modes and electrical and optical dual-addressability. Such a SLM, if successfully developed, will surely have substantial impact on optical processing technology. During the Phase-1 efforts, a review of field emitter arrays has been done to show that it has the merits of electrical-addressability, high space-bandwidth product (SBP), low drive voltage compatible with IC driving circuitry, and high update speed. The device architecture has been investigated and the design of two prototype devices has been provided.

  8. Adaptive Bessel-autocorrelation of ultrashort pulses with phase-only spatial light modulators

    Science.gov (United States)

    Huferath-von Luepke, Silke; Bock, Martin; Grunwald, Ruediger

    2009-06-01

    Recently, we proposed a new approach of a noncollinear correlation technique for ultrashort-pulsed coherent optical signals which was referred to as Bessel-autocorrelator (BAC). The BAC-principle combines the advantages of Bessellike nondiffracting beams like stable propagation, angular robustness and self-reconstruction with the principle of temporal autocorrelation. In comparison to other phase-sensitive measuring techniques, autocorrelation is most straightforward and time-effective because of non-iterative data processing. The analysis of nonlinearly converted fringe patterns of pulsed Bessel-like beams reveals their temporal signature from details of fringe envelopes. By splitting the beams with axicon arrays into multiple sub-beams, transversal resolution is approximated. Here we report on adaptive implementations of BACs with improved phase resolution realized by phase-only liquid-crystal-on-silicon spatial light modulators (LCoS-SLMs). Programming microaxicon phase functions in gray value maps enables for a flexible variation of phase and geometry. Experiments on the diagnostics of few-cycle pulses emitted by a mode-locked Ti:sapphire laser oscillator at wavelengths around 800 nm with 2D-BAC and angular tuned BAC were performed. All-optical phase shift BAC and fringe free BAC approaches are discussed.

  9. [Study on transmission efficiency of interference system in spatially modulated Fourier transform spectrometer].

    Science.gov (United States)

    Lü, Jin-Guang; Liang, Jing-Qiu; Liang, Zhong-Zhu; Qin, Yu-Xin; Tian, Chao

    2013-03-01

    The reflection of the optic system surface and the absorption of the infrared material could reduce the transmission of the incident light in spatially modulated Fourier transform infrared spectrometer. Through the calculation of the transmission function of the interference system and the simulation of the interferogram image and recovered spectrum affected by transmission function, it was indicated that the contrast of the interferogram image declined and the spectral line intensity weakened. The theoretical analysis shows that the contrast of the interferogram image was related to the intensity reflectance of the anti-reflection film, and the attenuation of the spectrum was determined by transmission efficiency concerned with intensity reflectance R1 of the anti-reflection film, intensity reflectance R2 of the beam splitter film, and the absorption coefficient. By means of the analysis and argumentation, the absorption of the material could be ignored in our investigative wave band. So the transmission efficiency was determined only by R1 and R2. Then taking the transmission efficiency as the design target, according to the transmission required by system, the tolerance of the R1 and R2 could be gained.

  10. [A novel spatial modulation Fourier transform spectrometer with adjustable spectral resolution].

    Science.gov (United States)

    Lian, Yu-Sheng; Liao, Ning-Fang; Lü, Hang; Wu, Wen-Min; Dong, Zhi-Gang

    2014-11-01

    In the premise of fulfilling the application requirement, the adjustment of spectral resolution can improve efficiency of data acquisition, data processing and data saving. So, by adjusting the spectral resolution, the performance of spectrometer can be improved, and its application range can be extended. To avoid the problems of the fixed spectral resolution of classical Fourier transform spectrometer, a novel type of spatial modulation Fourier transform spectrometer with adjustable spectral resolution is proposed in this paper. The principle of the novel spectrometer and its interferometer is described. The general expressions of the optical path difference and the lateral shear are induced by a ray tracing procedure. The equivalent model of the novel interferometer is analyzed. Meanwhile, the principle of the adjustment of spectral resolution is analyzed. The result shows that the novel spectrometer has the merits of adjustable spectral resolution, high stability, easy assemblage and adjustment etc. This theoretical study will provide the theoretical basis for the design of the spectrometer with adjustable spectral resolution and expand the application range of Fourier transform spectrometer.

  11. Holographic Fabrication of Designed Functional Defect Lines in Photonic Crystal Lattice Using a Spatial Light Modulator

    Directory of Open Access Journals (Sweden)

    Jeffrey Lutkenhaus

    2016-04-01

    Full Text Available We report the holographic fabrication of designed defect lines in photonic crystal lattices through phase engineering using a spatial light modulator (SLM. The diffracted beams from the SLM not only carry the defect’s content but also the defect related phase-shifting information. The phase-shifting induced lattice shifting in photonic lattices around the defects in three-beam interference is less than the one produced by five-beam interference due to the alternating shifting in lattice in three beam interference. By designing the defect line at a 45 degree orientation and using three-beam interference, the defect orientation can be aligned with the background photonic lattice, and the shifting is only in one side of the defect line, in agreement with the theory. Finally, a new design for the integration of functional defect lines in a background phase pattern reduces the relative phase shift of the defect and utilizes the different diffraction efficiency between the defect line and background phase pattern. We demonstrate that the desired and functional defect lattice can be registered into the background lattice through the direct imaging of designed phase patterns.

  12. Design of coupled mace filters for optical pattern recognition using practical spatial light modulators

    Science.gov (United States)

    Rajan, P. K.; Khan, Ajmal

    1993-01-01

    Spatial light modulators (SLMs) are being used in correlation-based optical pattern recognition systems to implement the Fourier domain filters. Currently available SLMs have certain limitations with respect to the realizability of these filters. Therefore, it is necessary to incorporate the SLM constraints in the design of the filters. The design of a SLM-constrained minimum average correlation energy (SLM-MACE) filter using the simulated annealing-based optimization technique was investigated. The SLM-MACE filter was synthesized for three different types of constraints. The performance of the filter was evaluated in terms of its recognition (discrimination) capabilities using computer simulations. The correlation plane characteristics of the SLM-MACE filter were found to be reasonably good. The SLM-MACE filter yielded far better results than the analytical MACE filter implemented on practical SLMs using the constrained magnitude technique. Further, the filter performance was evaluated in the presence of noise in the input test images. This work demonstrated the need to include the SLM constraints in the filter design. Finally, a method is suggested to reduce the computation time required for the synthesis of the SLM-MACE filter.

  13. Isotropic image in structured illumination microscopy patterned with a spatial light modulator.

    Science.gov (United States)

    Chang, Bo-Jui; Chou, Li-Jun; Chang, Yun-Ching; Chiang, Su-Yu

    2009-08-17

    We developed a structured illumination microscopy (SIM) system that uses a spatial light modulator (SLM) to generate interference illumination patterns at four orientations - 0 degrees, 45 degrees, 90 degrees, and 135 degrees, to reconstruct a high-resolution image. The use of a SLM for pattern alterations is rapid and precise, without mechanical calibration; moreover, our design of SLM patterns allows generating the four illumination patterns of high contrast and nearly equivalent periods to achieve a near isotropic enhancement in lateral resolution. We compare the conventional image of 100-nm beads with those reconstructed from two (0 degrees +90 degrees or 45 degrees +135 degrees) and four (0 degrees +45 degrees +90 degrees +135 degrees) pattern orientations to show the differences in resolution and image, with the support of simulations. The reconstructed images of 200-nm beads at various depths and fine structures of actin filaments near the edge of a HeLa cell are presented to demonstrate the intensity distributions in the axial direction and the prospective application to biological systems.

  14. Axially uniform magnetic field-modulation excitation for electron paramagnetic resonance in rectangular and cylindrical cavities by slot cutting

    Science.gov (United States)

    Sidabras, Jason W.; Richie, James E.; Hyde, James S.

    2017-01-01

    In continuous-wave (CW) Electron Paramagnetic Resonance (EPR) a low-frequency time-harmonic magnetic field, called field modulation, is applied parallel to the static magnetic field and incident on the sample. Varying amplitude of the field modulation incident on the sample has consequences on spectral line-shape and line-height over the axis of the sample. Here we present a method of coupling magnetic field into the cavity using slots perpendicular to the sample axis where the slot depths are designed in such a way to produce an axially uniform magnetic field along the sample. Previous literature typically assumes a uniform cross-section and axial excitation due to the wavelength of the field modulation being much larger than the cavity. Through numerical analysis and insights obtained from the eigenfunction expansion of dyadic Green's functions, it is shown that evanescent standing-wave modes with complex cross-sections are formed within the cavity. From this analysis, a W-band (94 GHz) cylindrical cavity is designed where modulation slots are optimized to present a uniform 100 kHz field modulation over the length of the sample.

  15. Low-energy MOS depletion modulators in silicon-on-insulator micro-donut resonators coupled to bus waveguides.

    Science.gov (United States)

    Soref, Richard; Guo, Junpeng; Sun, Greg

    2011-09-12

    Electrical, optical and electro-optical simulations are presented for a waveguided, resonant, bus-coupled, p-doped Si micro-donut MOS depletion modulator operating at the 1.55 μm wavelength. To minimize the switching voltage and energy, a high-K dielectric film of HfO₂ or ZrO₂ is chosen as the gate dielectric, while a narrow ring-shaped layer of p-doped poly-silicon is selected for the gate electrode, rather than metal, to minimize plasmonic loss loading of the fundamental TE mode. In a 6-μm-diam high-Q resonator, an infrared intensity extinction ratio of 6 dB is predicted for a modulation voltage of 2 V and a switching energy of 4 fJ/bit. A speed-of-response around 1 ps is anticipated. For a modulator scaled to operate at 1.3 μm, the estimated switching energy is 2.5 fJ/bit.

  16. Two-dimensional periodic and quasiperiodic spatial structures in microchip laser resonator

    CERN Document Server

    Okulov, A Yu

    2014-01-01

    The spatially periodic 2D patterns at output mirror of solid state microchip laser with high Fresnel number (100-1000) are discussed in view of numerical modeling with split-step FFT code comprising nonlinear gain, relaxation of inversion and paraxial diffraction.

  17. Performance analysis of free space optical system with spatial modulation and diversity combiners over the Gamma Gamma atmospheric turbulence

    Science.gov (United States)

    Odeyemi, Kehinde O.; Owolawi, Pius A.; Srivastava, Viranjay M.

    2017-01-01

    Atmospheric turbulence is a major impairment that degrades the performance of free space optical (FSO) communication systems. Spatial modulation (SM) with receive spatial diversity is considered as a powerful technique to mitigate the fading effect induced by atmospheric turbulence. In this paper, the performance of free space optical spatial modulation (FSO-SM) system under Gamma-Gamma atmospheric turbulence is presented. We studied the Average Bit Error Rate (ABER) for the system by employing spatial diversity combiners such Maximum Ratio Combining (MRC) and Equal Gain Combining (EGC) at the receiving end. In particular, we provide a theoretical framework for the system error by deriving Average Pairwise Error Probability (APEP) expression using a generalized infinite power series expansion approach and union bounding technique is applied to obtain the ABER for each combiner. Based on this study, it was found that spatial diversity combiner significantly improved the system error rate where MRC outperforms the EGC. The performance of this system is also compared with other well established diversity combiner systems. The proposed system performance is further improved by convolutional coding technique and our analysis confirmed that the system performance of MRC coded system is enhanced by approximately 20 dB while EGC falls within 17 dB.

  18. Spin and valley dependent line-type resonant peaks in electrically and magnetically modulated silicene quantum structures

    Science.gov (United States)

    Zhang, Yuanshan; Guo, Yong

    2017-02-01

    A barrier with a tunable spin-valley dependent energy gap in silicene could be used as a spin and valley filter. Meanwhile, special resonant modes in unique quantum structure can act as energy filters. Hence we investigate valley and spin transport properties in the potential silicene quantum structures, i.e., single ferromagnetic barrier, single electromagnetic barrier and double electric barriers. Our quantum transport calculation indicates that quantum devices of high accuracy and efficiency (100% polarization), based on modulated silicene quantum structures, can be designed for valley, spin and energy filtering. These intriguing features are revealed by the spin, valley dependent line-type resonant peaks. In addition, line-type peaks in different structure depend on spin and valley diversely. The filter we proposed is controllable by electric gating.

  19. Multi-location laser ignition using a spatial light modulator towards improving automotive gasoline engine performance

    Science.gov (United States)

    Kuang, Zheng; Lyon, Elliott; Cheng, Hua; Page, Vincent; Shenton, Tom; Dearden, Geoff

    2017-03-01

    We report on a study into multi-location laser ignition (LI) with a Spatial Light Modulator (SLM), to improve the performance of a single cylinder automotive gasoline engine. Three questions are addressed: i/ How to deliver a multi-beam diffracted pattern into an engine cylinder, through a small opening, while avoiding clipping? ii/ How much incident energy can a SLM handle (optical damage threshold) and how many simultaneous beam foci could thus be created? ; iii/ Would the multi-location sparks created be sufficiently intense and stable to ignite an engine and, if so, what would be their effect on engine performance compared to single-location LI? Answers to these questions were determined as follows. Multi-beam diffracted patterns were created by applying computer generated holograms (CGHs) to the SLM. An optical system for the SLM was developed via modelling in ZEMAX, to cleanly deliver the multi-beam patterns into the combustion chamber without clipping. Optical damage experiments were carried out on Liquid Crystal on Silicon (LCoS) samples provided by the SLM manufacturer and the maximum safe pulse energy to avoid SLM damage found to be 60 mJ. Working within this limit, analysis of the multi-location laser induced sparks showed that diffracting into three identical beams gave slightly insufficient energy to guarantee 100% sparking, so subsequent engine experiments used 2 equal energy beams laterally spaced by 4 mm. The results showed that dual-location LI gave more stable combustion and higher engine power output than single-location LI, for increasingly lean air-fuel mixtures. The paper concludes by a discussion of how these results may be exploited.

  20. Optical Tweezers Array and Nimble Tweezers Probe Generated by Spatial- Light Modulator

    Science.gov (United States)

    Decker, Arthur J.; Jassemnejad, Baha; Seibel, Robin E.; Weiland, Kenneth E.

    2003-01-01

    An optical tweezers is being developed at the NASA Glenn Research Center as a visiblelight interface between ubiquitous laser technologies and the interrogation, visualization, manufacture, control, and energization of nanostructures such as silicon carbide (SiC) nanotubes. The tweezers uses one or more focused laser beams to hold micrometer-sized particles called tools (sometimes called tips in atomic-force-microscope terminology). A strongly focused laser beam has an associated light-pressure gradient that is strong enough to pull small particles to the focus, in spite of the oppositely directed scattering force; "optical tweezers" is the common term for this effect. The objective is to use the tools to create carefully shaped secondary traps to hold and assemble nanostructures that may contain from tens to hundreds of atoms. The interaction between a tool and the nanostructures is to be monitored optically as is done with scanning probe microscopes. One of the initial efforts has been to create, shape, and control multiple tweezers beams. To this end, a programmable spatial-light modulator (SLM) has been used to modify the phase of a laser beam at up to 480 by 480 points. One program creates multiple, independently controllable tweezer beams whose shapes can be tailored by making the SLM an adaptive mirror in an interferometer (ref. 1). The beams leave the SLM at different angles, and an optical Fourier transform maps these beams to different positions in the focal plane of a microscope objective. The following figure shows two arrays of multiple beams created in this manner. The patterns displayed above the beam array control the intensity-to-phase transformation required in programming the SLM. Three of the seven beams displayed can be used as independently controllable beams.

  1. The generation of flat-top beams by complex amplitude modulation with a phase-only spatial light modulator

    CSIR Research Space (South Africa)

    Hendriks, A

    2012-08-01

    Full Text Available amplitude modulation of the light, i.e., in amplitude and phase. We outline the theoretical concept, and then illustrate its use with the example of the laser beam shaping of Gaussian beams into flat-top beams. We quantify the performance of this approach...

  2. Spatial configuration of a plasma bunch formed under gyromagnetic resonance in a magnetic mirror trap

    Science.gov (United States)

    Andreev, V. V.; Novitskii, A. A.; Umnov, A. M.; Chuprov, D. V.

    2016-06-01

    The spatial configuration of a relativistic plasma bunch generated under the gyromagnetic autoresonance and confined in a magnetic mirror trap has been studied experimentally and numerically. The characteristics of bremsstrahlung generated by the plasma bunch from the gas and chamber walls were investigated using X-ray spectroscopy and radiometry, which made it possible to determine the localization of the bunch and analyze the dynamics of its confinement.

  3. Co-integration of a smart CMOS image sensor and a spatial light modulator for real-time optical phase modulation

    Science.gov (United States)

    Laforest, Timothé; Verdant, Arnaud; Dupret, Antoine; Gigan, Sylvain; Ramaz, François; Tessier, Gilles

    2014-03-01

    We present a CMOS light detector-actuator array, in which every pixel combines a spatial light modulator and a photodiode. It will be used in medical imaging based on acousto-optical coherence tomography with a digital holographic detection scheme. Our architecture is able to measure an interference pattern between a scattered beam transmitted through a scattering media and a reference beam. The array of 16 μm pixels pitch has a frame rate of several kfps, which makes this sensor compliant with the correlation time of light in biological tissues. In-pixel analog processing of the interference pattern allows controlling the polarization of a stacked light modulator and thus, to control the phase of the reflected beam. This reflected beam can then be focused on a region of interest, i.e. for therapy. The stacking of a photosensitive element with a spatial light modulator on the same chip brings a significant robustness over the state of the art such as perfect optical matching and reduced delay in controlling light.

  4. Mode-locked semiconductor laser system with intracavity spatial light modulator for linear and nonlinear dispersion management.

    Science.gov (United States)

    Balzer, Jan C; Döpke, Benjamin; Brenner, Carsten; Klehr, Andreas; Erbert, Götz; Tränkle, Günther; Hofmann, Martin R

    2014-07-28

    We analyze the influence of second and third order intracavity dispersion on a passively mode-locked diode laser by introducing a spatial light modulator (SLM) into the external cavity. The dispersion is optimized for chirped pulses with highest possible spectral bandwidth that can be externally compressed to the sub picosecond range. We demonstrate that the highest spectral bandwidth is achieved for a combination of second and third order dispersion. With subsequent external compression pulses with a duration of 437 fs are generated.

  5. Mask-Free Patterning of High-Conductivity Metal Nanowires in Open Air by Spatially Modulated Femtosecond Laser Pulses.

    Science.gov (United States)

    Wang, Andong; Jiang, Lan; Li, Xiaowei; Liu, Yang; Dong, Xianzi; Qu, Liangti; Duan, Xuanming; Lu, Yongfeng

    2015-10-28

    A novel high-resolution nanowire fabrication method is developed by thin-film patterning using a spatially modulated femtosecond laser pulse. Deep subwavelength (≈1/13 of the laser wavelength) and high conductivity (≈1/4 of the bulk gold) nanowires are fabricated in the open air without using masks, which offers a single-step arbitrary direct patterning approach for electronics, plasmonics, and optoelectronics nanodevices.

  6. High power operation of the polyphase resonant converter modulator system for the spallation neutron source linear accelerator

    CERN Document Server

    Reass, W A; Baca, D M; Doss, J D; Gonzáles, J M; Gribble, R F; Trujillo, P G

    2003-01-01

    The spallation neutron source (SNS) is a new 1.4 MW average power beam, 1 GeV accelerator being built at Oak Ridge national laboratory. The accelerator requires 15 "long-pulse" converter-modulator stations each providing a maximum of 11 MW pulses with a 1.1 MW average power. Two variants of the converter-modulator are utilized, an 80 kV and a 140 kV design, the voltage dependant on the type of klystron load. The converter-modulator can be described as a resonant zero-voltage- switching polyphase boost inverter. As noted in Figure 1, each converter modulator derives its buss voltage from a standard 13.8 kV to 2100 Y (1.5 MVA) substation cast-core transformer. The substation also contains harmonic traps and filters to accommodate IEEE 519 and 141 regulations. Each substation is followed by an SCR preregulator to accommodate system voltage changes from no load to full load, in addition to providing a soft-start function. Energy storage and filtering is provided by special low inductance self-clearing metallized ...

  7. Improvement of the sensitivity of the surface plasmon resonance sensors based on multi-layer modulation techniques

    Science.gov (United States)

    Zhao, Xihong; Chu-Su, Yu; Tsai, Woo-Hu; Wang, Ching-Ho; Chuang, Tsung-Liang; Lin, Chii-Wann; Tsao, Yu-Chia; Wu, Mu-Shiang

    2015-01-01

    In this study, a multi-layer modulation technique was used in an SPR optical fiber sensor to enhance the sensitivity of the SPR optical fiber sensor by adjusting the SPR resonant wavelength. The sputtering process deposited 20 nm of TiO2, 11 nm of SiO2 and 30 nm of gold film on the material surface to change the refractive index. Regardless of the different refractive index solutions (1.32 and 1.36), the sensitivities in wavelength interrogation of the SPR optical fiber with the single gold thin film and multi-layers modulation were 1.08×10-5 RIUs and 1.74×10-6 RIUs, respectively. The results showed the significant differences between the different refractive index solutions of 1.32 and 1.36 using the 850 nm light source to analyze the SPR optical fiber sensor in real-time. The sensitivities in intensity interrogation of the SPR optical fiber with the single gold thin film and multi-layers modulation were 1.08×10-3 RIUs and 1.73×10-4 RIUs, respectively, which indicated that the multi-layer modulation techniques could enhance the sensitivity of the SPR optical fiber sensor. The compact size of the multi-layer SPR fiber sensor had a wider detecting range of the refractive index and higher sensitivity, which had the potential for other applications in biological analysis with suitable wavelength.

  8. Spatial distribution of charged particles along the ion-optical axis in electron cyclotron resonance ion sources. Experimental results

    Energy Technology Data Exchange (ETDEWEB)

    Panitzsch, Lauri

    2013-02-08

    The experimental determination of the spatial distribution of charged particles along the ion-optical axis in electron cyclotron resonance ion sources (ECRIS) defines the focus of this thesis. The spatial distributions of different ion species were obtained in the object plane of the bending magnet ({approx}45 cm downstream from the plasma electrode) and in the plane of the plasma electrode itself, both in high spatial resolution. The results show that each of the different ion species forms a bloated, triangular structure in the aperture of the plasma electrode. The geometry and the orientation of these structures are defined by the superposition of the radial and axial magnetic fields. The radial extent of each structure is defined by the charge of the ion. Higher charge states occupy smaller, more concentrated structures. The total current density increases towards the center of the plasma electrode. The circular and star-like structures that can be observed in the beam profiles of strongly focused, extracted ion beams are each dominated by ions of a single charge state. In addition, the spatially resolved current density distribution of charged particles in the plasma chamber that impinge on the plasma electrode was determined, differentiating between ions and electrons. The experimental results of this work show that the electrons of the plasma are strongly connected to the magnetic field lines in the source and thus spatially well confined in a triangular-like structure. The intensity of the electrons increases towards the center of the plasma electrode and the plasma chamber, as well. These electrons are surrounded by a spatially far less confined and less intense ion population. All the findings mentioned above were already predicted in parts by simulations of different groups. However, the results presented within this thesis represent the first (and by now only) direct experimental verification of those predictions and are qualitatively transferable to

  9. A multiple-input-multiple-output visible light communication system based on VCSELs and spatial light modulators.

    Science.gov (United States)

    Lu, Hai-Han; Lin, Ying-Pyng; Wu, Po-Yi; Chen, Chia-Yi; Chen, Min-Chou; Jhang, Tai-Wei

    2014-02-10

    A multiple-input-multiple-output (MIMO) visible light communication (VLC) system employing vertical cavity surface emitting laser (VCSEL) and spatial light modulators (SLMs) with 16-quadrature amplitude modulation (QAM)-orthogonal frequency-division multiplexing (OFDM) modulating signal is proposed and experimentally demonstrated. The transmission capacity of system is significantly increased by space-division demultiplexing scheme. With the assistance of low noise amplifier (LNA) and data comparator, good bit error rate (BER) performance, clear constellation map, and clear eye diagram are achieved for each optical channel. Such a MIMO VLC system would be attractive for providing services including data and telecommunication services. Our proposed system is suitably applicable to the lightwave communication system in wireless transmission.

  10. Improving the spatial resolution of a soft X-ray Charge Coupled Device used for Resonant Inelastic X-ray Scattering

    OpenAIRE

    Soman, M. R.; Hall, D. J. (David John); Tutt, J. H.; Murray, N. J.; Holland, A. D.; Schmitt, T.; Raabe, J.; Schmitt, B.

    2011-01-01

    The Super Advanced X-ray Emission Spectrometer (SAXES) at the Advanced Resonant Scattering (ADRESS) beamline of the Swiss Light Source is a high-resolution X-ray spectrometer used as an end station for Resonant Inelastic X-ray Scattering from 400 eV to 1600 eV. Through the dispersion of photons across a CCD, the energy of scattered photons may be determined by their detected spatial position. The limiting factor of the energy resolution is currently the spatial resolution achieved with the CC...

  11. Retrieving the spatial distribution of cavity modes in dielectric resonators by near-field imaging and electrodynamics simulations.

    Science.gov (United States)

    Goñi, Alejandro R; Güell, Frank; Pérez, Luis A; López-Vidrier, Julian; Ossó, J Oriol; Coronado, Eduardo A; Morante, Joan R

    2012-03-01

    For good performance of photonic devices whose working principle is based on the enhancement of electromagnetic fields obtained by confining light into dielectric resonators with dimensions in the nanometre length scale, a detailed knowledge of the optical mode structure becomes essential. However, this information is usually lacking and can only be indirectly obtained by conventional spectroscopic techniques. Here we unraveled the influence of wire size, incident wavelength, degree of polarization and the presence of a substrate on the optical near fields generated by cavity modes of individual hexagonal ZnO nanowires by combining scanning near-field optical microscopy (SNOM) with electrodynamics calculations within the discrete dipole approximation (DDA). The near-field patterns obtained with very high spatial resolution, better than 50 nm, exhibit striking size and spatial-dispersion effects, which are well accounted for within DDA, using a wavevector-dependent dipolar interaction and considering the dielectric anisotropy of ZnO. Our results show that both SNOM and DDA simulations are powerful tools for the design of optoelectronic devices able to manipulate light at the nanoscale.

  12. OMERACT Rheumatoid Arthritis Magnetic Resonance Imaging Studies. Summary of OMERACT 6 MR Imaging Module

    DEFF Research Database (Denmark)

    McQueen, F; Lassere, M; Edmonds, J;

    2003-01-01

    Magnetic resonance image (MRI) scanning is a new method for imaging and quantifying joint inflammation and damage in rheumatoid arthritis (RA). Over the past 4 years, the OMERACT MR Imaging Group has been developing and testing the RA-MRI scoring system (RAMRIS) for use in RA. The OMERACT filter...

  13. Controlling Spiral Waves by Modulations Resonant with the Intrinsic System Mode

    Institute of Scientific and Technical Information of China (English)

    XIAO Jing-Hua; HU Gang; HU Bam-Bi

    2004-01-01

    We investigate the spiral wave control in the two-dimensional complex Ginzburg-Landau equation. External drivings which are not resonant with spiral waves but with intrinsic system modes are used to successfully annihilate spiral waves and direct the system to various target states. The novel control mechanism is intuitively explained and the richness and flexibility the control results are emphasized.

  14. Optical method to differentiate tequilas based on angular modulation surface plasmon resonance

    Science.gov (United States)

    Martínez-López, G.; Luna-Moreno, D.; Monzón-Hernández, D.; Valdivia-Hernández, R.

    2011-06-01

    We report the use of the prism-based surface plasmon resonance (SPR) technique to differentiate between three types of tequilas white or silver, aged, and extra-aged. We used the angular interrogation method in which the structure is based on prism fabricated with BK7 glass coated with a gold layer as the SPR active layer. Our study was centered in the analysis of the resonant angle of the SPR generated by the three types of tequilas produced by the three major tequila-producing firms. We observed that each tequila sample produced a well-differentiated SPR curve. We found that resonant angle of the SPR curve produced by silver tequilas is larger than that produced by the aged and extra-aged tequilas of the same producer firm. We found that the position of the SPR curve is not exclusively determined by the alcohol contents; we believe that there are other parameters derived from the aging process that should be considered. The refractive index of the tequilas used in this study was estimated using the measured resonant angle.

  15. Thermo-optically driven silicon microring-resonator-loaded Mach-Zehnder modulator for low-power consumption and multiple-wavelength modulation

    Science.gov (United States)

    Gautam, Rajdeep; Kaneshige, Hiroki; Yamada, Hitoshi; Katouf, Redouane; Arakawa, Taro; Kokubun, Yasuo

    2014-02-01

    Low-power-consumption thermo-optically controlled silicon-microring-resonator loaded Mach-Zehnder modulators (MRR-loaded MZMs) are demonstrated. We experimentally characterized a single microring and cascaded-multiple-microring resonators coupled to one arm of a Mach-Zehnder interferometer (MZI). The driving power consumption of the proposed MZM is significantly reduced owing to the enhanced phase shift in the MRR. The device was fabricated on a silicon-on-insulator (SOI) waveguide structure, and each microring is equipped with TiN microheater for thermo-optic tuning. The coupling efficiency between the microring and a busline waveguide was regulated by varying the gap between two waveguides at a directional coupler. The power consumption of single microring and cascaded MRR-loaded MZMs was approximately 0.4 and 1 mW, respectively. The phase-shift enhancement factor of up to 19 with a maximum extinction ratio of 18 dB was obtained experimentally. Multiple-wavelength operation was also demonstrated in the cascaded MRR-loaded MZM.

  16. Superpixel-based spatial amplitude and phase modulation using a digital micromirror device

    NARCIS (Netherlands)

    Goorden, Sebastianus A.; Bertolotti, Jacopo; Mosk, Allard P.

    2014-01-01

    We present a superpixel method for full spatial phase and amplitude control of a light beam using a digital micromirror device (DMD) combined with a spatial filter. We combine square regions of nearby micromirrors into superpixels by low pass filtering in a Fourier plane of the DMD. At each superpix

  17. Spatial Frequency Components of Images Modulate Neuronal Activity in Monkey Amygdala.

    Science.gov (United States)

    Montes-Lourido, Pilar; Bermudez, M A; Romero, M C; Vicente, A F; Gonzalez, F

    2016-04-01

    Processing the spatial frequency components of an image is a crucial feature for visual perception, especially in recognition of faces. Here, we study the correlation between spatial frequency components of images of faces and neuronal activity in monkey amygdala while performing a visual recognition task. The frequency components of the images were analyzed using a fast Fourier transform for 40 spatial frequency ranges. We recorded 65 neurons showing statistically significant responses to at least one of the images used as a stimulus. A total of 37 of these neurons (n = 37) showed significant responses to at least three images, and in eight of them (8/37, 22%), we found a statistically significant correlation between neuron response and the modulus amplitude of at least one frequency range present in the images. Our results indicate that high spatial frequency and low spatial frequency components of images influence the activity of amygdala neurons.

  18. Object-based attentional modulation of biological motion processing: spatiotemporal dynamics using functional magnetic resonance imaging and electroencephalography.

    Science.gov (United States)

    Safford, Ashley S; Hussey, Elizabeth A; Parasuraman, Raja; Thompson, James C

    2010-07-07

    Although it is well documented that the ability to perceive biological motion is mediated by the lateral temporal cortex, whether and when neural activity in this brain region is modulated by attention is unknown. In particular, it is unclear whether the processing of biological motion requires attention or whether such stimuli are processed preattentively. Here, we used functional magnetic resonance imaging, high-density electroencephalography, and cortically constrained source estimation methods to investigate the spatiotemporal effects of attention on the processing of biological motion. Directing attention to tool motion in overlapping movies of biological motion and tool motion suppressed the blood oxygenation level-dependent (BOLD) response of the right superior temporal sulcus (STS)/middle temporal gyrus (MTG), while directing attention to biological motion suppressed the BOLD response of the left inferior temporal sulcus (ITS)/MTG. Similarly, category-based modulation of the cortical current source density estimates from the right STS/MTG and left ITS was observed beginning at approximately 450 ms following stimulus onset. Our results indicate that the cortical processing of biological motion is strongly modulated by attention. These findings argue against preattentive processing of biological motion in the presence of stimuli that compete for attention. Our findings also suggest that the attention-based segregation of motion category-specific responses only emerges relatively late (several hundred milliseconds) in processing.

  19. Giant peak to valley ratio in a GaN based resonant tunnel diode with barrier width modulation

    Science.gov (United States)

    Sankaranarayanan, Sandeep; Saha, Dipankar

    2016-10-01

    A barrier width modulated GaN based resonant tunnel diode is theoretically proposed which exhibits a giant peak to valley current ratio as high as 60 and a high negative differential conductance (NDC) of 1.77 × 106 S/cm2 with very low valley current density of 3 mA/cm2. This is achieved by the unique characteristic of the device current which monotonically decreases for applied voltages greater than the valley voltage in our simulation window. This is in contrast to all the other negative differential conductance based devices which experience an immediate exponential increase in current after the NDC region. The proposed device is also the first bidirectional tunneling diode which shows negative differential conductance for both polarity of the applied bias which is normally not observed with the conventional GaN/AlGaN double barrier structures due to the strong asymmetry arising from the internal electric fields due to polarization. The unique characteristics of the device can be attributed to the use of a modulated barrier width which is made possible by a polarization modulating InGaN layer and efficient utilization of internal electric fields in III-nitrides.

  20. Design and Analysis of Enhanced Modulation Response in Integrated Coupled Cavities DBR Lasers Using Photon-Photon Resonance

    Directory of Open Access Journals (Sweden)

    Paolo Bardella

    2016-01-01

    Full Text Available In the last few decades, various solutions have been proposed to increase the modulation bandwidth and, consequently, the transmission bit-rate of semiconductor lasers. In this manuscript, we discuss a design procedure for a recently proposed laser cavity realized with the monolithic integration of two distributed Bragg reflector (DBR lasers allowing one to extend the modulation bandwidth. Such an extension is obtained introducing in the dynamic response a photon-photon resonance (PPR at a frequency higher than the modulation bandwidth of the corresponding single-section laser. Design guidelines will be proposed, and dynamic small and large signal simulations results, calculated using a finite difference traveling wave (FDTW numerical simulator, will be discussed to confirm the design results. The effectiveness of the design procedure is verified in a structure with PPR frequency at 35 GHz allowing one to obtain an open eye diagram for a non-return-to-zero (NRZ digital signal up to 80 GHz . Furthermore, the investigation of the rich dynamics of this structure shows that with proper bias conditions, it is possible to obtain also a tunable self-pulsating signal in a frequency range related to the PPR design.

  1. Extreme and superextreme events in a loss-modulated CO2 laser: Nonlinear resonance route and precursors

    Science.gov (United States)

    Bonatto, Cristian; Endler, Antonio

    2017-07-01

    We investigate the occurrence of extreme and rare events, i.e., giant and rare light pulses, in a periodically modulated CO2 laser model. Due to nonlinear resonant processes, we show a scenario of interaction between chaotic bands of different orders, which may lead to the formation of extreme and rare events. We identify a crisis line in the modulation parameter space, and we show that, when the modulation amplitude increases, remaining in the vicinity of the crisis, some statistical properties of the laser pulses, such as the average and dispersion of amplitudes, do not change much, whereas the amplitude of extreme events grows enormously, giving rise to extreme events with much larger deviations than usually reported, with a significant probability of occurrence, i.e., with a long-tailed non-Gaussian distribution. We identify recurrent regular patterns, i.e., precursors, that anticipate the emergence of extreme and rare events, and we associate these regular patterns with unstable periodic orbits embedded in a chaotic attractor. We show that the precursors may or may not lead to the emergence of extreme events. Thus, we compute the probability of success or failure (false alarm) in the prediction of the extreme events, once a precursor is identified in the deterministic time series. We show that this probability depends on the accuracy with which the precursor is identified in the laser intensity time series.

  2. Study on measurement accuracy of active optics null test systems based on liquid crystal spatial light modulator and laser interferometer

    Science.gov (United States)

    Liu, Shijie; Xu, Longbo; Ma, Xiao; Zhang, Zhigang; Zhou, You; Lu, Qi; Bai, Yunbo; Shao, Jianda

    2017-06-01

    A common way to test high-quality aspherical lenses is to use a measurement system based on a set of null corrector and a laser interferometer. The null corrector can either be a combination of spherical lenses or be a computer generated hologram (CGH), which compensates the aspheric wave-front being tested. However, the null optics can't be repeatedly used once the shape of tested optics changes. Alternative active null correctors have been proposed based on dynamic phase modulator devices. A typical dynamic phase modulator is liquid crystal spatial light modulator (LCSLM), which can spatially change the refractive index of the liquid crystal and thus modify the phase of the input wave-front. Even though the measurement method based on LCSLM and laser interferometer has been proposed and demonstrated for optical testing several years ago, it still can't be used in the high quality measurement process due to its limited accuracy. In this paper, we systematically study the factors such as LCSLM structure parameters, encoding error and laser interferometer performance, which significantly affect the measurement accuracy. Some solutions will be proposed in order to improve the measurement accuracy based on LCSLM and laser interferometer.

  3. Comparison of gold- and graphene-based resonant nano-structures for terahertz metamaterials and an ultra-thin graphene-based modulator

    CERN Document Server

    Shen, Nian-Hai; Koschny, Thomas; Soukoulis, Costas M

    2014-01-01

    Graphene exhibits unique material properties and in electromagnetic wave technology, it raises the prospect of devices miniaturized down to the atomic length scale. Here we study split-ring resonator metamaterials made from graphene and we compare them to gold-based metamaterials. We find that graphene's huge reactive response derived from its large kinetic inductance allows for deeply subwavelength resonances, although its resonance strength is reduced due to higher dissipative loss damping and smaller dipole coupling. Nevertheless, tightly stacked graphene rings may provide for negative permeability and the electric dipole resonance of graphene meta-atoms turns out to be surprisingly strong. Based on these findings, we present a terahertz modulator based on a metamaterial with a multi-layer stack of alternating patterned graphene sheets separated by dielectric spacers. Neighbouring graphene flakes are biased against each other, resulting in modulation depths of over 75% at a transmission level of around 90%...

  4. Resonant transmission and mode modulation of acoustic waves in H-shaped metallic gratings

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Yu-Qiang; Fan, Ren-Hao; Zhang, Kun; Peng, Ru-Wen, E-mail: rwpeng@nju.edu.cn, E-mail: dongxiang87@gmail.com [National Laboratory of solid State Microstructures and School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); Qi, Dong-Xiang, E-mail: rwpeng@nju.edu.cn, E-mail: dongxiang87@gmail.com [National Laboratory of solid State Microstructures and School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); School of Science, Jiangnan University, Wuxi 214122 (China)

    2015-04-15

    In this work, we demonstrate that resonant full transmission of acoustic waves exists in subwavelength H-shaped metallic gratings, and transmission peaks can be efficiently tuned by adjusting the grating geometry. We investigate this phenomenon through both numerical simulations and theoretical calculations based on rigorous-coupled wave analysis. The transmission peaks are originated from Fabry-Perot resonances together with the couplings between the diffractive wave on the surface and the multiple guided modes in the slits. Moreover, the transmission modes can be efficiently tuned by adjusting the cavity geometry, without changing the grating thickness. The mechanism is analyzed based on an equivalent circuit model and verified by both the theoretical calculations and the numerical simulations. This research has potential application in acoustic-device miniaturization over a wide range of wavelengths.

  5. Spatial mapping of mineralization with manganese-enhanced magnetic resonance imaging

    Science.gov (United States)

    Chesnick, I.E.; Centeno, J.A.; Todorov, T.I.; Koenig, A.E.; Potter, K.

    2011-01-01

    Paramagnetic manganese can be employed as a calcium surrogate to sensitize the magnetic resonance imaging (MRI) technique to the processing of calcium during the bone formation process. At low doses, after just 48h of exposure, osteoblasts take up sufficient quantities of manganese to cause marked reductions in the water proton T1 values compared with untreated cells. After just 24h of exposure, 25??M MnCl2 had no significant effect on cell viability. However, for mineralization studies 100??M MnCl2 was used to avoid issues of manganese depletion in calvarial organ cultures and a post-treatment delay of 48h was implemented to ensure that manganese ions taken up by osteoblasts is deposited as mineral. All specimens were identified by their days in vitro (DIV). Using inductively coupled plasma optical emission spectroscopy (ICP-OES), we confirmed that Mn-treated calvariae continued to deposit mineral in culture and that the mineral composition was similar to that of age-matched controls. Notably there was a significant decrease in the manganese content of DIV18 compared with DIV11 specimens, possibly relating to less manganese sequestration as a result of mineral maturation. More importantly, quantitative T1 maps of Mn-treated calvariae showed localized reductions in T1 values over the calvarial surface, indicative of local variations in the surface manganese content. This result was verified with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). We also found that ??R1 values, calculated by subtracting the relaxation rate of Mn-treated specimens from the relaxation rate of age-matched controls, were proportional to the surface manganese content and thus mineralizing activity. From this analysis, we established that mineralization of DIV4 and DIV11 specimens occurred in all tissue zones, but was reduced for DIV18 specimens because of mineral maturation with less manganese sequestration. In DIV25 specimens, active mineralization was observed for

  6. Symmetry-breaking on-off intermittency under modulation: Robustness of supersensitivity, resonance and information gain

    OpenAIRE

    Hu, Bambi; Zhou, Changsong

    2000-01-01

    Nonlinear dynamical systems possessing an invariant subspace in the phase space and chaotic or stochastic motion within the subspace often display on-off intermittency close to the threshold of stability of the subspace. In a class of symmetric systems, the intermittency is symmetry-breaking [Ying-Cheng Lai, Phys. Rev. E {\\bf 53}. R4267 (1996)]. We report interesting and practically important universal behavior of robustness of supersensitivity, resonance and information gain in this class of...

  7. [Spectra modulated surface plasmon resonance sensor based on side polished multi-mode optical fiber].

    Science.gov (United States)

    Luo, Yun-Han; Chen, Xiao-Long; Xu, Meng-Yun; Ge, Jia; Zhang, Yi-Long; He, Yong-Hong; Tang, Jie-Yuan; Yu, Jian-Hui; Zhang, Jun; Chen, Zhe; Chen, Xing-Dan

    2014-03-01

    Surface plasmon resonance, which utilizes the resonance of optical evanescent wave with the metal surface plasmon wave, has been developed into a high sensitivity, rapid, label-less measurement method for chemical and biological analysis. In order to improve the spectral sensitivity in refractive index for a side polished fiber surface plasmon resonance sensor, the whole cladding layer and part of core of a multimode fiber was polished off. Additionally, an extra chrome layer with relatively high refractive index was coated on the polished zone before a gold film. The results showed that the sensor can measure the refractive index range from 1.333 to 1. 431 RIU, with the average spectral sensitivity of 4.11 x 10(3) nm RIU(-1), which is better than the reported results. Especially, in the refractive index range of 1. 417 1. 431 RIU, the sensitivity reaches to 1.09 x 10(4) nm RIU(-1). The minimum resolution of approximately 3.6 x 10(-5) RIU was estimated by a combination analysis with the sensor sensitivity and stability. The superiorities possessed by the proposed sensor in high sensitivity, wide detection range, small size and good stability and reproducibility, etc., make it a good candidate for food testing, environmental monitoring, biomedical testing and other related fields.

  8. Phase stability in fMRI time series: effect of noise regression, off-resonance correction and spatial filtering techniques.

    Science.gov (United States)

    Hagberg, Gisela E; Bianciardi, Marta; Brainovich, Valentina; Cassara, Antonino Mario; Maraviglia, Bruno

    2012-02-15

    Although the majority of fMRI studies exploit magnitude changes only, there is an increasing interest regarding the potential additive information conveyed by the phase signal. This integrated part of the complex number furnished by the MR scanners can also be used for exploring direct detection of neuronal activity and for thermography. Few studies have explicitly addressed the issue of the available signal stability in the context of phase time-series, and therefore we explored the spatial pattern of frequency specific phase fluctuations, and evaluated the effect of physiological noise components (heart beat and respiration) on the phase signal. Three categories of retrospective noise reduction techniques were explored and the temporal signal stability was evaluated in terms of a physiologic noise model, for seven fMRI measurement protocols in eight healthy subjects at 3T, for segmented CSF, gray and white matter voxels. We confirmed that for most processing methods, an efficient use of the phase information is hampered by the fact that noise from physiological and instrumental sources contributes significantly more to the phase than to the magnitude instability. Noise regression based on the phase evolution of the central k-space point, RETROICOR, or an orthonormalized combination of these were able to reduce their impact, but without bringing phase stability down to levels expected from the magnitude signal. Similar results were obtained after targeted removal of scan-to-scan variations in the bulk magnetic field by the dynamic off-resonance in k-space (DORK) method and by the temporal off-resonance alignment of single-echo time series technique (TOAST). We found that spatial high-pass filtering was necessary, and in vivo a Gaussian filter width of 20mm was sufficient to suppress physiological noise and bring the phase fluctuations to magnitude levels. Stronger filters brought the fluctuations down to levels dictated by thermal noise contributions, and for 62

  9. Analysis and suppression of high-order diffractions in liquid-crystal-based spatial light modulator for photonic switch application

    Science.gov (United States)

    Nakajima, Mitsumasa; Nemoto, Naru; Yamaguchi, Keita; Kudo, Hiroshi; Yamaguchi, Joji; Suzuki, Kenya; Hashimoto, Toshikazu

    2017-09-01

    Spatial light modulators based on liquid crystal on silicon (LCOS) are widely used for large-scale photonic switches in optical telecom network. For this application, high-order diffractions in LCOS is a critical issue because it causes signal crosstalk. In this paper, we analyze the impact of phase inaccuracy due to the fringing electric field in LCOS on the signal crosstalk in optical switches. We also propose a crosstalk reduction method that is analogous to frequency modulation in signal processing. The method is simple and optimized by only using a few parameters of the applied phase pattern without the need to modify the optics or electronics in use. With the proposed method, the worst crosstalk of a photonic switch was decreased from -16.2 to -31.6 dB.

  10. Enhanced spatial stimulus-response mapping near the hands: the Simon effect is modulated by hand-stimulus proximity.

    Science.gov (United States)

    Wang, Xiaotao; Du, Feng; He, Xiaosong; Zhang, Kan

    2014-12-01

    Emerging evidence has revealed that visual processing of objects near the hands is altered. The present study shows that the visuomotor Simon effect when the hands are proximal to stimuli is greater than that observed when the hands are far from stimuli, thereby indicating stronger spatial stimulus-response mapping near the hands. The visuomotor Simon effect is robustly enhanced near the hands even when hand visibility and stimulus-response axis-similarity are controlled. However, the semantic Simon effect with location words is not modulated by hand-stimulus proximity. Thus, consistent with the dimensional overlap model and the known features of the bimodal visuotactile neurons, hand-stimulus proximity enhances spatial stimulus-response mapping but has no effect on semantic processing of location words.

  11. Pulse re-shaping by using a liquid crystal spatial light modulator and deflector for producing a specific waveform

    Institute of Scientific and Technical Information of China (English)

    Jun Kang; Wei Zhang; Hui Wei; Shaohe Chen; Jianqiang Zhu

    2006-01-01

    @@ A new shaping method for producing nanosecond pulses with specific shape is introduced. When a Gaussian laser pulse passes through an electro-optic deflector, it has been scanned as a line on the focal plane according to time precedence. Through controlling the intensity of transmitted light on each pixel of the liquid crystal spatial light modulator (LCSLM), various complicated pulses can be easily produced. Using this method, various specific shaped pulses with pulse duration varying from 750 ps to 5 ns are achieved.

  12. Trinary flip-flops using Savart plate and spatial light modu-lator for optical computation in multivalued logic

    Institute of Scientific and Technical Information of China (English)

    Areal K Ghosh; Amitabha Basuray

    2008-01-01

    The memory devices in multi-valued logic are of most significance in modern research. This paper deals with the imple-mentation of basic memory devices in multi-valued logic using Savart plate and spatial light modulator (SLM) basedoptoelectronic circuits. Photons are used here as the carrier to speed up the operations. Optical tree architecture (OTA) hasbeen also utilized in the optical interconnection network. We have exploited the advantages of Savart plates, SLMs andOTA and proposed the SLM based high speed JK, D-type and T-type flip-flops in a trinary system.

  13. Addressable, large-field second harmonic generation microscopy based on 2D acousto-optical deflector and spatial light modulator.

    Science.gov (United States)

    Shao, Yonghong; Liu, Honghai; Qin, Wan; Qu, Junle; Peng, Xiang; Niu, Hanben; Gao, Bruce Z

    2012-09-01

    We present an addressable, large-field second harmonic generation microscope by combining a 2D acousto-optical deflector with a spatial light modulator. The SLM shapes an incoming mode-locked, near-infrared Ti:Sapphire laser beam into a multifocus array, which can be rapidly scanned by changing the incident angle of the laser beam using a 2D acousto-optical deflector. Compared to the single-beam-scan technique, the multifocus array scan can increase the scanning rate and the field-of-view size with the multi-region imaging ability.

  14. Real-time computer-generated hologram by means of liquid-crystal television spatial light modulator

    Science.gov (United States)

    Mok, Fai; Psaltis, Demetri; Diep, Joseph; Liu, Hua-Kuang

    1986-01-01

    The usefulness of an inexpensive liquid-crystal television) (LCTV) as a spatial light modulator for coherent-optical processing in the writing and reconstruction of a single computer-generated hologram has been demonstrated. The thickness nonuniformities of the LCTV screen were examined in a Mach-Zehnder interferometer, and the phase distortions were successfully removed using a technique in which the LCTV screen was submerged in a liquid gate filled with an index-matching nonconductive mineral oil with refractive index of about 1.45.

  15. Adaptive Optics with a Liquid-Crystal-on-Silicon Spatial Light Modulator and Its Behavior in Retinal Imaging

    Science.gov (United States)

    Shirai, Tomohiro; Takeno, Kohei; Arimoto, Hidenobu; Furukawa, Hiromitsu

    2009-07-01

    An adaptive optics system with a brand-new device of a liquid-crystal-on-silicon (LCOS) spatial light modulator (SLM) and its behavior in in vivo imaging of the human retina are described. We confirmed by experiments that closed-loop correction of ocular aberrations of the subject's eye was successfully achieved at the rate of 16.7 Hz in our system to obtain a clear retinal image in real time. The result suggests that an LCOS SLM is one of the promising candidates for a wavefront corrector in a prospective commercial ophthalmic instrument with adaptive optics.

  16. Preparation of starch stabilized silver nanoparticles with spatial self-phase modulation properties by laser ablation technique

    Energy Technology Data Exchange (ETDEWEB)

    Zamiri, Reza; Azmi, B.Z.; Sadrolhosseini, Amir R.; Husin, M.S.; Zaidan, A.W. [Universiti Putra Malaysia, Department of Physics, Faculty of Science, UPM Serdang, Selangor (Malaysia); Darroudi, Majid [Universiti Putra Malaysia, Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology, UPM Serdang, Selangor (Malaysia); Mahdi, M.A. [Universiti Putra Malaysia, Wireless and Photonics Networks Research Center, Faculty of Engineering, UPM Serdang, Selangor (Malaysia)

    2011-01-15

    Silver nanoparticles inside the starch solution have been successfully fabricated by laser ablation of a silver plate immersed in starch solution. The ablation has been done using a Q-switched Nd:YAG laser at 10 Hz repetition rate. The starch solution allows for the formation of silver nanoparticles with uniform particle diameters and well dispersed. The ablation was performed at different time durations to study the influence of the laser ablation time on efficiency of particle formation and sizes. The Spatial Self-phase modulation phenomena which can determine the nonlinear optical property of the samples were also investigated for starch solutions containing silver nanoparticles. (orig.)

  17. Real-time computer-generated hologram by means of liquid-crystal television spatial light modulator

    Science.gov (United States)

    Mok, Fai; Psaltis, Demetri; Diep, Joseph; Liu, Hua-Kuang

    1986-01-01

    The usefulness of an inexpensive liquid-crystal television) (LCTV) as a spatial light modulator for coherent-optical processing in the writing and reconstruction of a single computer-generated hologram has been demonstrated. The thickness nonuniformities of the LCTV screen were examined in a Mach-Zehnder interferometer, and the phase distortions were successfully removed using a technique in which the LCTV screen was submerged in a liquid gate filled with an index-matching nonconductive mineral oil with refractive index of about 1.45.

  18. Dual-plane in-line digital holography based on liquid crystal on silicon spatial light modulator.

    Science.gov (United States)

    Panezai, Spozmai; Wang, Dayong; Zhao, Jie; Wang, Yunxin; Rong, Lu

    2014-09-20

    A dual-plane in-line digital holographic method is proposed with a liquid crystal on silicon (LCOS) spatial light modulator (SLM) for recording holograms at two slightly displaced planes. The computer-generated chirp-like complex reflectance is displayed on the LCOS SLM to adapt the object beam at two planes for recording two holograms processed to eliminate the DC term and twin image accurately; no mechanical components or manual operation during data acquisition is required. The proposed approach improves the speed, accuracy, and stability of the experiment. Computer simulation and experiments for both amplitude and phase objects are carried out to validate the proposed method.

  19. Wavelength agile nonmechanical laser beam steering from Fresnel zone plates imprinted on a liquid crystal spatial light modulator

    Science.gov (United States)

    Lindle, James R.; Watnik, Abbie T.; Cassella, Vincent A.

    2016-09-01

    Multibeam, multicolor, large-angle beam-steering is demonstrated in the visible spectral region by imprinting Fresnel zone plates (FZP) on a liquid crystal spatial light modulator. Spectral dispersion, both diffractive and refractive, is observed but does not prevent the use of this technology for beam steering applications. The experimental results show that while diffractive dispersion dominates over refractive dispersion, wavelength-specific FZPs can be rendered to direct those beams on target, either simultaneously or consecutively. Only a slight correction in the FZP positon is necessary to compensate for refractive dispersion. The position, intensity, and wavelength of each beam can be controlled independently.

  20. Analysis of spatial diffusion of ferric ions in PVA-GTA gel dosimeters through magnetic resonance imaging

    Energy Technology Data Exchange (ETDEWEB)

    Marrale, Maurizio [Dipartimento di Fisica e Chimica, Universitá di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy); Istituto Nazionale di Fisica Nucleare (INFN) – Gruppo V Sezione di Catania, Via Santa Sofia, 64, 95123 Catania (Italy); ATeN Center, Università di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy); Collura, Giorgio [Dipartimento di Fisica e Chimica, Universitá di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy); Istituto Nazionale di Fisica Nucleare (INFN) – Gruppo V Sezione di Catania, Via Santa Sofia, 64, 95123 Catania (Italy); Gallo, Salvatore, E-mail: salvatore.gallo05@unipa.it [Dipartimento di Fisica e Chimica, Universitá di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy); Istituto Nazionale di Fisica Nucleare (INFN) – Gruppo V Sezione di Catania, Via Santa Sofia, 64, 95123 Catania (Italy); Dipartimento di Fisica, Universitá di Milano, Via Giovanni Celoria 16, 20133 Milano (Italy); Nici, Stefania [Dipartimento di Fisica e Chimica, Universitá di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy); Tranchina, Luigi [ATeN Center, Università di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy); Abbate, Boris Federico [U.O.C. Fisica Sanitaria, A.R.N.A.S., Ospedale Civico Palermo, Piazza Nicola Leotta 4, 90127 Palermo (Italy); Marineo, Sandra; Caracappa, Santo [Istituto Zooprofilattico Sperimentale della Sicilia (IZS), Via Gino Marinuzzi, 3, 90129 Palermo (Italy); and others

    2017-04-01

    Highlights: • Analysis of ferric ions diffusion throughout the gel matrix in PVA-GTA samples. • Measurements with preclinical 7T MRI scanner with spatial resolution of 200 μm. • Diffusion process is much slower for PVA-GTA gels than for agarose ones. - Abstract: This work focused on the analysis of the temporal diffusion of ferric ions through PVA-GTA gel dosimeters. PVA-GTA gel samples, partly exposed with 6 MV X-rays in order to create an initial steep gradient, were mapped using magnetic resonance imaging on a 7T MRI scanner for small animals. Multiple images of the gels were acquired over several hours after irradiation and were analyzed to quantitatively extract the signal profile. The spatial resolution achieved is 200 μm and this makes this technique particularly suitable for the analysis of steep gradients of ferric ion concentration. The results obtained with PVA-GTA gels were compared with those achieved with agarose gels, which is a standard dosimetric gel formulation. The analysis showed that the diffusion process is much slower (more than five times) for PVA-GTA gels than for agarose ones. Furthermore, it is noteworthy that the diffusion coefficient value obtained through MRI analysis is significantly consistent with that obtained in separate study Marini et al. (Submitted for publication) using a totally independent method such as spectrophotometry. This is a valuable result highlighting that the good dosimetric features of this gel matrix not only can be reproduced but also can be measured through independent experimental techniques based on different physical principles.

  1. Exploring the modulation of attentional capture by spatial attentional control settings: converging evidence from event-related potentials.

    Science.gov (United States)

    Ishigami, Yoko; Hamm, Jeff P; Satel, Jason; Klein, Raymond M

    2012-12-01

    Automatic attentional capture by a salient distractor can be prevented by spatial attentional control settings (ACSs) (e.g., Yantis and Jonides in J Exp Psychol Hum Percept Perform 16:121-134, 1990). Earlier, converging evidence for a spatial ACS (Eason et al. 1969) was found in event-related potentials (ERPs). In these studies, the ACS was defined by a single target-relevant location. In an extension, Ishigami et al. (Vis Cogn 17:431-456, 2009) demonstrated a successful ACS in performance that was based on multiple (two) target-relevant locations. The purpose of the current study is to seek converging evidence from ERPs for a spatial ACS defined by multiple (two) target-relevant locations, using the methods in Ishigami et al. (Vis Cogn 17:431-456, 2009). Any one of four figure-8s brightened uninformatively (cue) before presentation of a digit target calling for a speeded identification (2 or 5). A spatial ACS was encouraged because in different blocks, the digit targets appeared only on the horizontal or vertical axis. Performance was more impaired following the invalid-attended cues than following invalid-unattended cues, consistent with Ishigami et al. (Vis Cogn 17:431-456, 2009) and verifying a successful spatial ACS. The direction of attention significantly affected the visual evoked potentials (VEPs) elicited by otherwise identical cues: the amplitudes of early VEPs were greater when the location the cue was presented in was target-relevant than when the location was target-irrelevant. These results re-affirm that attentional capture by irrelevant salient stimuli can be modulated by spatial ACSs defined by multiple target locations in performance and provide converging evidence from ERPs for the previously established behavioral findings.

  2. 12.5 Gbps optical modulation of silicon racetrack resonator based on carrier-depletion in asymmetric p-n diode.

    Science.gov (United States)

    You, Jong-Bum; Park, Miran; Park, Jeong-Woo; Kim, Gyungock

    2008-10-27

    We present a high speed optical modulation using carrier depletion effect in an asymmetric silicon p-n diode resonator. To optimize coupling efficiency and reduce bending loss, two-step-etched waveguide is used in the racetrack resonator with a directional coupler. The quality factor of the resonator with a circumference of 260 um is 9,482, and the DC on/off ratio is 8 dB at -12V. The device shows the 3dB bandwidth of approximately8 GHz and the data transmission up to 12.5Gbit/s.

  3. Quality of Intensity Modulated Radiation Therapy Treatment Plans Using a (60)Co Magnetic Resonance Image Guidance Radiation Therapy System

    DEFF Research Database (Denmark)

    Wooten, H Omar; Green, Olga; Yang, Min

    2015-01-01

    % prescription reference isodoses, respectively, and heterogeneity was on average 4% greater. Comparisons of OAR mean dose showed generally better sparing with linac plans in the low-dose range doses >20 Gy. The mean doses for all (60)Co plan OARs were within......PURPOSE: This work describes a commercial treatment planning system, its technical features, and its capabilities for creating (60)Co intensity modulated radiation therapy (IMRT) treatment plans for a magnetic resonance image guidance radiation therapy (MR-IGRT) system. METHODS AND MATERIALS...... plans using a third-party linear accelerator (linac)-based planning system were also created. Plans were evaluated by attending physicians and approved for treatment. The (60)Co and linac plans were compared by evaluating conformity numbers (CN) with 100% and 95% of prescription reference doses...

  4. Simulation of the modulation transfer function dependent on the partial Fourier fraction in dynamic contrast enhancement magnetic resonance imaging.

    Science.gov (United States)

    Takatsu, Yasuo; Ueyama, Tsuyoshi; Miyati, Tosiaki; Yamamura, Kenichirou

    2016-12-01

    The image characteristics in dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) depend on the partial Fourier fraction and contrast medium concentration. These characteristics were assessed and the modulation transfer function (MTF) was calculated by computer simulation. A digital phantom was created from signal intensity data acquired at different contrast medium concentrations on a breast model. The frequency images [created by fast Fourier transform (FFT)] were divided into 512 parts and rearranged to form a new image. The inverse FFT of this image yielded the MTF. From the reference data, three linear models (low, medium, and high) and three exponential models (slow, medium, and rapid) of the signal intensity were created. Smaller partial Fourier fractions, and higher gradients in the linear models, corresponded to faster MTF decline. The MTF more gradually decreased in the exponential models than in the linear models. The MTF, which reflects the image characteristics in DCE-MRI, was more degraded as the partial Fourier fraction decreased.

  5. Multiple-load series resonant inverter for induction cooking application with pulse density modulation

    Indian Academy of Sciences (India)

    P SHARATH KUMAR

    2017-08-01

    Multiple-load induction cooking applications are suitable used when multi-output inverters or multi-inverters are needed for multiple-load operation. Some common approaches and modifications are needed in inverter configuration for multiple-load application. This paper presents an inverter configuration with two loads by using pulse density modulation control technique. It allows the output power control of each load independently with constant switching frequency and constant duty ratio. The pulse density modulation control technique is obtained using phase on–off control between two legs of the inverter to reduce acoustic noise. Thetwo-load three-leg inverter configuration provides reduction of the component count for extension of multiple loads. The control technique provides a wide range of output power control. In addition, it can achieve efficient and stable zero voltage switching operation in the whole load range. The proposed control scheme is simulated and experimentally verified with two-load inverter configuration.

  6. OMERACT Rheumatoid Arthritis Magnetic Resonance Imaging Studies. Summary of OMERACT 6 MR Imaging Module

    DEFF Research Database (Denmark)

    McQueen, F; Lassere, M; Edmonds, J

    2003-01-01

    Magnetic resonance image (MRI) scanning is a new method for imaging and quantifying joint inflammation and damage in rheumatoid arthritis (RA). Over the past 4 years, the OMERACT MR Imaging Group has been developing and testing the RA-MRI scoring system (RAMRIS) for use in RA. The OMERACT filter...... space narrowing, reflecting cartilage damage, has also been excluded as reliability was low at the small joints of the hands. Anatomical coverage of the score is currently restricted to the wrists and hands but can provide a basis for a more comprehensive score. The MR measurement of synovitis...

  7. Visualization and analysis of modulated pulses in magnetic resonance by joint time-frequency representations.

    Science.gov (United States)

    Köcher, S S; Heydenreich, T; Glaser, S J

    2014-10-17

    We study the utility of joint time-frequency representations for the analysis of shaped or composite pulses for magnetic resonance. Such spectrograms are commonly used for the visualization of shaped laser pulses in optical spectroscopy. This intuitive representation provides additional insight compared to conventional approaches, which exclusively show either temporal or spectral information. We focus on the short-time Fourier transform, which provides not only amplitude but also phase information. The approach is illustrated for broadband inversion pulses, multiple quantum excitation and broadband heteronuclear decoupling. The physical interpretation and validity of the approach is discussed.

  8. Ergodic channel capacity of spatial correlated multiple-input multiple-output free space optical links using multipulse pulse-position modulation

    Science.gov (United States)

    Wang, Huiqin; Wang, Xue; Cao, Minghua

    2017-02-01

    The spatial correlation extensively exists in the multiple-input multiple-output (MIMO) free space optical (FSO) communication systems due to the channel fading and the antenna space limitation. Wilkinson's method was utilized to investigate the impact of spatial correlation on the MIMO FSO communication system employing multipulse pulse-position modulation. Simulation results show that the existence of spatial correlation reduces the ergodic channel capacity, and the reception diversity is more competent to resist this kind of performance degradation.

  9. Analysis of spatial diffusion of ferric ions in PVA-GTA gel dosimeters through magnetic resonance imaging

    Science.gov (United States)

    Marrale, Maurizio; Collura, Giorgio; Gallo, Salvatore; Nici, Stefania; Tranchina, Luigi; Abbate, Boris Federico; Marineo, Sandra; Caracappa, Santo; d'Errico, Francesco

    2017-04-01

    This work focused on the analysis of the temporal diffusion of ferric ions through PVA-GTA gel dosimeters. PVA-GTA gel samples, partly exposed with 6 MV X-rays in order to create an initial steep gradient, were mapped using magnetic resonance imaging on a 7T MRI scanner for small animals. Multiple images of the gels were acquired over several hours after irradiation and were analyzed to quantitatively extract the signal profile. The spatial resolution achieved is 200 μm and this makes this technique particularly suitable for the analysis of steep gradients of ferric ion concentration. The results obtained with PVA-GTA gels were compared with those achieved with agarose gels, which is a standard dosimetric gel formulation. The analysis showed that the diffusion process is much slower (more than five times) for PVA-GTA gels than for agarose ones. Furthermore, it is noteworthy that the diffusion coefficient value obtained through MRI analysis is significantly consistent with that obtained in separate study Marini et al. (Submitted for publication) using a totally independent method such as spectrophotometry. This is a valuable result highlighting that the good dosimetric features of this gel matrix not only can be reproduced but also can be measured through independent experimental techniques based on different physical principles.

  10. Kv4 Potassium Channels Modulate Hippocampal EPSP-Spike Potentiation and Spatial Memory in Rats

    Science.gov (United States)

    Truchet, Bruno; Manrique, Christine; Sreng, Leam; Chaillan, Franck A.; Roman, Francois S.; Mourre, Christiane

    2012-01-01

    Kv4 channels regulate the backpropagation of action potentials (b-AP) and have been implicated in the modulation of long-term potentiation (LTP). Here we showed that blockade of Kv4 channels by the scorpion toxin AmmTX3 impaired reference memory in a radial maze task. In vivo, AmmTX3 intracerebroventricular (i.c.v.) infusion increased and…

  11. Stress Modulates the Use of Spatial versus Stimulus-Response Learning Strategies in Humans

    Science.gov (United States)

    Philippsen, Christine; Richter, Steffen; Bohringer, Andreas; Wippich, Werner; Schachinger, Hartmut; Schwabe, Lars; Oitzl, Melly S.

    2007-01-01

    Animal studies provided evidence that stress modulates multiple memory systems, favoring caudate nucleus-based "habit" memory over hippocampus-based "cognitive" memory. However, effects of stress on learning strategy and memory consolidation were not differentiated. We specifically address the effects of psychosocial stress on the applied learning…

  12. Modulation of Hippocampal Theta Oscillations and Spatial Memory by Relaxin-3 Neurons of the Nucleus Incertus

    Science.gov (United States)

    Ma, Sherie; Olucha-Bordonau, Francisco E.; Hossain, M. Akhter; Lin, Feng; Kuei, Chester; Liu, Changlu; Wade, John D.; Sutton, Steven W.; Nunez, Angel; Gundlach, Andrew L.

    2009-01-01

    Hippocampal theta rhythm is thought to underlie learning and memory, and it is well established that "pacemaker" neurons in medial septum (MS) modulate theta activity. Recent studies in the rat demonstrated that brainstem-generated theta rhythm occurs through a multisynaptic pathway via the nucleus incertus (NI), which is the primary source of the…

  13. Captured by the pain: pain steady-state evoked potentials are not modulated by selective spatial attention.

    Science.gov (United States)

    Blöchl, Maria; Franz, Marcel; Miltner, Wolfgang H R; Weiss, Thomas

    2015-04-07

    Attention has been shown to affect the neural processing of pain. However, the exact mechanisms underlying this modulation remain unknown. Here, we used a new method called pain steady-state evoked potentials (PSSEPs) to investigate whether selective spatial attention affects EEG responses to tonic painful stimuli. In general, steady-state evoked potentials reflect changes in the EEG spectrum at a certain frequency that correspond to the frequency of a train of applied stimuli. In this study, high intensity transcutaneous electrical stimulation was delivered to both hands simultaneously with 31 Hz and 37 Hz, respectively. Subject׳s attention was directed to one of the two trains of stimulation in order to detect a small gap that was occasionally interspersed into the stimulus trains. Thereby, they had to ignore the stimulation applied to the other hand. Results show that PSSEPs were induced at 31 Hz and 37 Hz at frontal and central electrodes. PSSEPs occurred contralaterally to the respective hand stimulated with that frequency. Surprisingly, the magnitude of PSSEPs was not modulated by spatial attention towards one of the two stimuli. Our results indicate that attention can hardly be shifted between two simultaneously applied tonic painful stimulations.

  14. Generation of high-frequency combs locked to atomic resonances by quantum phase modulation

    CERN Document Server

    Liu, Zuoye; Cavaletto, Stefano M; Harman, Zoltán; Keitel, Christoph H; Pfeifer, Thomas

    2013-01-01

    A general mechanism for the generation of frequency combs referenced to atomic resonances is put forward. The mechanism is based on the periodic phase control of a quantum system's dipole response. We develop an analytic description of the comb spectral structure, depending on both the atomic and the phase-control properties. We further suggest an experimental implementation of our scheme: Generating a frequency comb in the soft-x-ray spectral region, which can be realized with currently available techniques and radiation sources. The universality of this mechanism allows the generalization of frequency-comb technology to arbitrary frequencies, including the hard-x-ray regime by using reference transitions in highly charged ions.

  15. Magnetic-Field-Modulated Resonant Tunneling in Ferromagnetic-Insulator-Nonmagnetic Junctions

    Science.gov (United States)

    Song, Yang; Dery, Hanan

    2014-07-01

    We present a theory for resonance-tunneling magnetoresistance (MR) in ferromagnetic-insulator-nonmagnetic junctions. The theory sheds light on many of the recent electrical spin injection experiments, suggesting that this MR effect rather than spin accumulation in the nonmagnetic channel corresponds to the electrically detected signal. We quantify the dependence of the tunnel current on the magnetic field by quantum rate equations derived from the Anderson impurity model, with the important addition of impurity spin interactions. Considering the on-site Coulomb correlation, the MR effect is caused by competition between the field, spin interactions, and coupling to the magnetic lead. By extending the theory, we present a basis for operation of novel nanometer-size memories.

  16. OMERACT Rheumatoid Arthritis Magnetic Resonance Imaging Studies. Summary of OMERACT 6 MR Imaging Module

    DEFF Research Database (Denmark)

    McQueen, F; Lassere, M; Edmonds, J;

    2003-01-01

    Magnetic resonance image (MRI) scanning is a new method for imaging and quantifying joint inflammation and damage in rheumatoid arthritis (RA). Over the past 4 years, the OMERACT MR Imaging Group has been developing and testing the RA-MRI scoring system (RAMRIS) for use in RA. The OMERACT filter...... correlates closely with histological evidence and work continues on validating MR erosions with reference to radiographic techniques. The RAMRIS has demonstrated good reliability for bone erosion and synovitis at the wrists and metacarpophalangeal joints subject to reader training, with slightly lower levels...... of reader agreement for bone edema. Reliability was less satisfactory in discriminating between 2 time points, and further work is required if the score is to be used to monitor change. Feasibility also needs to be considered for the practical application of the score, including the time taken for scanning...

  17. Stochastic resonance for signal-modulated pump noise in a single-mode laser

    Institute of Scientific and Technical Information of China (English)

    Liangying Zhang; Li Cao; Fahui Zhu

    2006-01-01

    By adopting the gain-noise model of the single-mode laser in which with bias and periodical signals serve as inputs, combining with the effect of coloured pump noise, we use the linear approximation method to calculate the power spectrum and signal-to-noise ratio (SNR) of the laser intensity under the condition of pump noise and quantum noise cross-related in the form of δ function. It is found that with the change of pump noise correlation time, both SNR and the output power will occur stochastic resonance (SR). If the bias signal α is very small, changing the intensities of pump noise and quantum noise respectively does not lead to the appearance of SR in the SNR; while α increases to a certain number, SR appears.

  18. Coupling to Modes of a Near-Confocal Optical Resonator Using a Digital Light Modulator

    CERN Document Server

    Papageorge, Alexander T; Lev, Benjamin L

    2016-01-01

    Digital Micromirror Devices (DMD) provide a robust platform with which to implement digital holography, in principle providing the means to rapidly generate propagating transverse electromagnetic fields with arbitrary mode profiles at visible and IR wavelengths. We use a DMD to probe a Fabry-P\\'{e}rot cavity in single-mode and near-degenerate confocal configurations. Pumping arbitrary modes of the cavity is possible with excellent specificity by virtue of the spatial overlap between the incident light field and the cavity mode.

  19. Design and Fabrication of 1.06 μm Resonant-Cavity Enhanced Reflective Modulator with GaInAs/GaAs Quantum Wells

    Institute of Scientific and Technical Information of China (English)

    YANG Xiao-Hong; HAN Qin; NI Hai-Qiao; HUANG She-Song; DU Yun; PENG Hong-Ling; XIONG Yong-Hua; NIU Zhi-Chuan; WU Rong-Han

    2006-01-01

    A resonant-cavity enhanced reflective optical modulator is designed and fabricated, with three groups of three highly strained InGaAs/GaAs quantum wells in the cavity, for low voltage and high contrast ratio operation.The quantum wells are positioned in antinodes of the optical standing wave. The modulator is grown in a single growth step in an molecular beam epitaxy system, using GaAs/AlAs distributed Bragg reflectors as both the top and bottom mirrors. Results show that the reflection device has a modulation extinction of 3 dB at -4.5 V bias.

  20. Spatial Attention-Related Modulation of the N170 by Backward Masked Fearful Faces

    Science.gov (United States)

    Carlson, Joshua M.; Reinke, Karen S.

    2010-01-01

    Facial expressions are a basic form of non-verbal communication that convey important social information to others. The relevancy of this information is highlighted by findings that backward masked facial expressions facilitate spatial attention. This attention effect appears to be mediated through a neural network consisting of the amygdala,…

  1. Application of the spatial data mining module in analysis of mining ground deformation factors

    Directory of Open Access Journals (Sweden)

    Jan Blachowski

    2013-09-01

    Full Text Available Spatial data mining methods for example those based on artificial neural networks (ANN allow extraction of information from databases and detection of otherwise hidden patterns occurring in these data and in consequence acquiring new knowledge on the analysed phenomena or processes. One of these techniques is the multivariate statistical analysis, which facilitates identification of patterns otherwise difficult to observe. In the paper an attempt of applying self-organising maps (SOM to explore and analyse spatial data related to studies of ground subsidence associated with underground mining has been described. The study has been carried out on a selected part of a former underground coal mining area in SW Poland with the aim to analyse the influence of particular ground deformation factors on the observed subsidence and the relationships between these factors. The research concerned the uppermost coal panels and the following factors: mining system, time of mining activity and inclination, thickness and depth below the ground of the exploited coal panels. It has been found that the exploratory spatial data analysis can be used to identify relationships in multidimensional data related to mining induced ground subsidence. The proposed approach may be found useful in identification of areas threatened by mining related subsidence and in creating scenarios of developing deformation zones and therefore aid spatial development of mining grounds.

  2. Spatial Attention-Related Modulation of the N170 by Backward Masked Fearful Faces

    Science.gov (United States)

    Carlson, Joshua M.; Reinke, Karen S.

    2010-01-01

    Facial expressions are a basic form of non-verbal communication that convey important social information to others. The relevancy of this information is highlighted by findings that backward masked facial expressions facilitate spatial attention. This attention effect appears to be mediated through a neural network consisting of the amygdala,…

  3. Proprioceptive cues modulate further processing of spatially congruent auditory information. a high-density EEG study.

    Science.gov (United States)

    Simon-Dack, S L; Teder-Sälejärvi, W A

    2008-07-18

    Multisensory integration and interaction occur when bimodal stimuli are presented as either spatially congruent or incongruent, but temporally coincident. We investigated whether proprioceptive cues interact with auditory attention to one of two sound sources in free-field. The participant's task was to attend to either the left or right speaker and to respond to occasional increased-bandwidth targets via a footswitch. We recorded high-density EEG in three experimental conditions: the participants either held the speakers in their hands (Hold), reached out close to them (Reach), or had their hands in their lap (Lap). In the last two conditions, the auditory event-related potentials (ERPs) revealed a prominent negativity around 200 ms post-stimulus (N2 wave) over fronto-central areas, which is a reliable index of further processing of spatial stimulus features in free-field. The N2 wave was markedly attenuated in the 'Hold' condition, which suggests that proprioceptive cues apparently solidify spatial information computed by the auditory system, in so doing alleviating the need for further processing of spatial coordinates solely based on auditory information.

  4. Is Inhibition of Return Modulated by Involuntary Orienting of Spatial Attention: An ERP Study.

    Science.gov (United States)

    Pan, Fada; Wu, Xiaogang; Zhang, Li

    2017-01-01

    Inhibition of return (IOR) is a mechanism that indicates individuals' faster responses or higher accuracy to targets appearing in the novel location relative to the cued location. According to the "reorienting hypothesis," disengagement from the cued location is necessary for the generation of IOR. However, more and more studies have questioned this theory because of dissociation between voluntary or involuntary spatial orienting and the IOR effect. To further explore the "reorienting hypothesis" of IOR, the present experiment employed an atypical cue-target paradigm which combined a spatially non-predictive peripheral cue that was presumed to trigger IOR with a spatially non-predictive central cue that was used to reflexively trigger a shift of attention. The results showed that a significant IOR effect did not interact with automatic spatial orienting as measured in mean RTs and accuracy as well as the Nd component. These findings suggested that the IOR effect triggered by peripheral cue was independent of automatic orienting generated by a central cue. Therefore, the present study provided evidence from location task and neural aspects, which again challenged the "reorienting hypothesis" of IOR.

  5. Tools for Multimode Quantum Information: Modulation, Detection, and Spatial Quantum Correlations

    DEFF Research Database (Denmark)

    Lassen, Mikael Østergaard; Delaubert, Vincent; Janousek, Jirí

    2007-01-01

    We present here all the tools required for continuous variable parallel quantum information protocols based on spatial multi-mode quantum correlations and entanglement. We describe techniques for encoding and detecting this quantum information with high efficiency in the individual modes. We use ...

  6. Laser Beam Shaping For Lithography on Inclined and Curved Surfaces Using a liquid crystal Spatial Light Modulator

    Science.gov (United States)

    Gatabi, Javad R.; Geerts, Wilhelmus; Tamir, Dan; Pandey, Kumar

    2013-03-01

    An exposure tool for lithography on non-flat substrates that includes a real time photoresist thickness and surface topography monitor is under development at Texas State University. Exposure dose and focusing are corrected on curved parts of the sample using novel laser beam shaping techniques: two approaches using a Holoeye liquid crystal spatial light modulator (LC-SLM) are being investigated: (1) the implementation of multiple lenses with different focal lengths to split the beam into several parts and keeping each part in focus depending on sample topography; (2) the implementation of a tilted lens function resulting in a tilt of the image plane. Image quality is limited by quantization aberration, caused by the phase modulator's bit depth limitation, and pixelation aberration, caused by the modulator's pixel size. A statistical analysis on lenses with different focal lengths provides a detailed description of the mentioned aberrations. The image quality, i.e. resolution and contrast of both techniques, are determined from developed photoresist patterns on curved samples and compared to the theory.

  7. Zero-field nuclear magnetic resonance in high field by modulated rf sequences.

    Science.gov (United States)

    Nishiyama, Yusuke; Yamazaki, Toshio

    2007-04-07

    The authors propose a novel approach to design and evaluate sequences for zero-field NMR spectra in high field (ZFHF) by using amplitude and phase modulated rf sequences. ZFHF provide sharp peaks for the dipolar interaction between two nuclear spins even if the orientation of the molecules is distributed. The internuclear distance r can be directly obtained from the peak position which is proportional to r-3. Numerous ZFHF sequences are obtained. A sequence is selected from them by the systematic evaluation of the sequences. The new ZFHF sequence is less affected by chemical shift anisotropy (CSA) than the previous sequences; the sequence can be used for systems with large CSA such as a dipolar coupled 13C-pair system under realistically high field. 13C ZFHF spectra of 13C2 diammonium succinate and 13C2 diammonium oxalate were observed under the 9.4 T field.

  8. Experimental Demonstration of Ideal Noise Shaping in Resonant Tunneling Delta-Sigma Modulator for High Resolution, Wide Band Analog-to-Digital Converters

    Science.gov (United States)

    Maezawa, Koichi; Sakou, Mario; Matsubara, Wataru; Mizutani, Takashi; Matsuzaki, Hideaki

    2006-04-01

    A ΔΣ modulator using a frequency modulation intermediate signal was demonstrated using a resonant tunneling logic gate called a monostable bistable transition logic element (MOBILE). This ΔΣ modulator is based on the nature of an FM signal and suitable for high-speed operation. Experiments using an InP-based MOBILE demonstrate good noise shaping characteristics. Moreover, the operation with a higher FM carrier frequency than the sampling frequency was demonstrated, showing equally good noise shaping performance. This makes the design of the voltage-controlled oscillator, which is a key component of the FM ΔΣ modulator, much easier. Consequently, an FM ΔΣ modulator using MOBILE is promising for high-resolution, wide-band analog-to-digital converters (ADCs).

  9. Spatial characteristics of newly diagnosed grade 3 glioma assessed by magnetic resonance metabolic and diffusion tensor imaging.

    Science.gov (United States)

    Ozturk-Isik, Esin; Pirzkall, Andrea; Lamborn, Kathleen R; Cha, Soonmee; Chang, Susan M; Nelson, Sarah J

    2012-02-01

    The spatial heterogeneity in magnetic resonance (MR) metabolic and diffusion parameters and their relationship were studied for patients with treatment-naive grade 3 gliomas. MR data were evaluated from 51 patients with newly diagnosed grade 3 gliomas. Anatomic, diffusion, and metabolic imaging data were considered. Variations in metabolite levels, apparent diffusion coefficient (ADC), and fractional anisotropy (FA) were evaluated in regions of gadolinium enhancement and T2 hyperintensity as well as regions with abnormal metabolic signatures. Contrast enhancement was present in only 21 of the 51 patients. When present, the enhancing component of the lesion had higher choline-to-N-acetylaspartate index (CNI), higher choline, lower N-acetylaspartate, similar creatine, similar ADC and FA, and higher lactate/lipid than the nonenhancing lesion. Regions with CNI ≥ 4 had higher choline, lower N-acetylaspartate, higher lactate/lipid, higher ADC, and lower FA than normal-appearing white matter and regions with intermediate CNI values. For lesions that exhibited gadolinium enhancement, the metabolite levels and diffusion parameters in the region of enhancement were consistent with it corresponding to the most abnormal portion of the tumor. For nonenhancing lesions, areas with CNI ≥ 4 were the most abnormal in metabolic and diffusion parameters. This suggests that the region with the highest CNI might provide a good target for biopsies for nonenhancing lesions to obtain a representative histologic diagnosis of its degree of malignancy. Metabolic and diffusion parameter levels may be of interest not only for directing tissue sampling but also for defining the targets for focal therapy and assessing response to therapy.

  10. Spatial Characteristics of Newly Diagnosed Grade 3 Glioma Assessed by Magnetic Resonance Metabolic and Diffusion Tensor Imaging1

    Science.gov (United States)

    Ozturk-Isik, Esin; Pirzkall, Andrea; Lamborn, Kathleen R; Cha, Soonmee; Chang, Susan M; Nelson, Sarah J

    2012-01-01

    The spatial heterogeneity in magnetic resonance (MR) metabolic and diffusion parameters and their relationship were studied for patients with treatment-naive grade 3 gliomas. MR data were evaluated from 51 patients with newly diagnosed grade 3 gliomas. Anatomic, diffusion, and metabolic imaging data were considered. Variations in metabolite levels, apparent diffusion coefficient (ADC), and fractional anisotropy (FA) were evaluated in regions of gadolinium enhancement and T2 hyperintensity as well as regions with abnormal metabolic signatures. Contrast enhancement was present in only 21 of the 51 patients. When present, the enhancing component of the lesion had higher choline-to-N-acetylaspartate index (CNI), higher choline, lower N-acetylaspartate, similar creatine, similar ADC and FA, and higher lactate/lipid than the nonenhancing lesion. Regions with CNI ≥ 4 had higher choline, lower N-acetylaspartate, higher lactate/lipid, higher ADC, and lower FA than normal-appearing white matter and regions with intermediate CNI values. For lesions that exhibited gadolinium enhancement, the metabolite levels and diffusion parameters in the region of enhancement were consistent with it corresponding to the most abnormal portion of the tumor. For nonenhancing lesions, areas with CNI ≥ 4 were the most abnormal in metabolic and diffusion parameters. This suggests that the region with the highest CNI might provide a good target for biopsies for nonenhancing lesions to obtain a representative histologic diagnosis of its degree of malignancy. Metabolic and diffusion parameter levels may be of interest not only for directing tissue sampling but also for defining the targets for focal therapy and assessing response to therapy. PMID:22348171

  11. Differences in Visual-Spatial Input May Underlie Different Compression Properties of Firing Fields for Grid Cell Modules in Medial Entorhinal Cortex.

    Science.gov (United States)

    Raudies, Florian; Hasselmo, Michael E

    2015-11-01

    Firing fields of grid cells in medial entorhinal cortex show compression or expansion after manipulations of the location of environmental barriers. This compression or expansion could be selective for individual grid cell modules with particular properties of spatial scaling. We present a model for differences in the response of modules to barrier location that arise from different mechanisms for the influence of visual features on the computation of location that drives grid cell firing patterns. These differences could arise from differences in the position of visual features within the visual field. When location was computed from the movement of visual features on the ground plane (optic flow) in the ventral visual field, this resulted in grid cell spatial firing that was not sensitive to barrier location in modules modeled with small spacing between grid cell firing fields. In contrast, when location was computed from static visual features on walls of barriers, i.e. in the more dorsal visual field, this resulted in grid cell spatial firing that compressed or expanded based on the barrier locations in modules modeled with large spacing between grid cell firing fields. This indicates that different grid cell modules might have differential properties for computing location based on visual cues, or the spatial radius of sensitivity to visual cues might differ between modules.

  12. Sunlight Modulates Fruit Metabolic Profile and Shapes the Spatial Pattern of Compound Accumulation within the Grape Cluster

    Science.gov (United States)

    Reshef, Noam; Walbaum, Natasha; Agam, Nurit; Fait, Aaron

    2017-01-01

    Vineyards are characterized by their large spatial variability of solar irradiance (SI) and temperature, known to effectively modulate grape metabolism. To explore the role of sunlight in shaping fruit composition and cluster uniformity, we studied the spatial pattern of incoming irradiance, fruit temperature and metabolic profile within individual grape clusters under three levels of sunlight exposure. The experiment was conducted in a vineyard of Cabernet Sauvignon cv. located in the Negev Highlands, Israel, where excess SI and midday temperatures are known to degrade grape quality. Filtering SI lowered the surface temperature of exposed fruits and increased the uniformity of irradiance and temperature in the cluster zone. SI affected the overall levels and patterns of accumulation of sugars, organic acids, amino acids and phenylpropanoids, across the grape cluster. Increased exposure to sunlight was associated with lower accumulation levels of malate, aspartate, and maleate but with higher levels of valine, leucine, and serine, in addition to the stress-related proline and GABA. Flavan-3-ols metabolites showed a negative response to SI, whereas flavonols were highly induced. The overall levels of anthocyanins decreased with increased sunlight exposure; however, a hierarchical cluster analysis revealed that the members of this family were grouped into three distinct accumulation patterns, with malvidin anthocyanins and cyanidin-glucoside showing contrasting trends. The flavonol-glucosides, quercetin and kaempferol, exhibited a logarithmic response to SI, leading to improved cluster uniformity under high-light conditions. Comparing the within-cluster variability of metabolite accumulation highlighted the stability of sugars, flavan-3-ols, and cinnamic acid metabolites to SI, in contrast to the plasticity of flavonols. A correlation-based network analysis revealed that extended exposure to SI modified metabolic coordination, increasing the number of negative

  13. Low-power optically addressed spatial light modulators using MBE-grown III-V structures

    Science.gov (United States)

    Maserjian, Joseph L.; Larsson, Anders G.

    1991-12-01

    Device approaches are investigated for O-SLMs based on MBE engineered III-V materials and structures. Strong photo-optic effects can be achieved in periodically (delta) -doped multiple quantum well (MQW) structures. The doping-defined barriers serve to separate and delay recombination of the photo-generated electron-hole pairs. One can use this photo-effect to change the internal field across the MQWs giving rise to quantum-confined Stark shift. Alternately, the photo-generated electrons can be used to occupy the quantum wells, which in turn causes exciton quenching and a shift of the absorption edge. Recent work has shown that both of these predicted photo-optic effects can indeed be achieved in such MBE engineered structures. However, these enhanced effects are still insufficient for high contrast modulation with only single or double pass absorption through active layers of practical thickness. We use the asymmetric Fabry-Perot cavity approach which permits extinction of light due to interference of light reflected from the front and back surfaces of the cavity. Modulation of the absorption in the active cavity layers unbalances the cavity and 'turns on' the reflected output signal, thereby allowing large contrast ratios. This approach is realized with an all-MBE- grown structure consisting of a GaAs/AlAs quarter-wave stack reflector grown over the GaAs substrate as the high reflectance mirror (approximately equals 0.98) and the GaAs surface as the low reflectance mirror (approximately equals 0.3). We use for our active cavities InGaAs/GaAs MQWs separated by npn (delta) -doped GaAs barriers to achieve sensitive photo-optic effect due to exciton quenching. High contrast modulation (> 60:1) is achieved with the Fabry-Perot structures using low power (write signal.

  14. Attention Modulates the Auditory Cortical Processing of Spatial and Category Cues in Naturalistic Auditory Scenes

    Science.gov (United States)

    Renvall, Hanna; Staeren, Noël; Barz, Claudia S.; Ley, Anke; Formisano, Elia

    2016-01-01

    This combined fMRI and MEG study investigated brain activations during listening and attending to natural auditory scenes. We first recorded, using in-ear microphones, vocal non-speech sounds, and environmental sounds that were mixed to construct auditory scenes containing two concurrent sound streams. During the brain measurements, subjects attended to one of the streams while spatial acoustic information of the scene was either preserved (stereophonic sounds) or removed (monophonic sounds). Compared to monophonic sounds, stereophonic sounds evoked larger blood-oxygenation-level-dependent (BOLD) fMRI responses in the bilateral posterior superior temporal areas, independent of which stimulus attribute the subject was attending to. This finding is consistent with the functional role of these regions in the (automatic) processing of auditory spatial cues. Additionally, significant differences in the cortical activation patterns depending on the target of attention were observed. Bilateral planum temporale and inferior frontal gyrus were preferentially activated when attending to stereophonic environmental sounds, whereas when subjects attended to stereophonic voice sounds, the BOLD responses were larger at the bilateral middle superior temporal gyrus and sulcus, previously reported to show voice sensitivity. In contrast, the time-resolved MEG responses were stronger for mono- than stereophonic sounds in the bilateral auditory cortices at ~360 ms after the stimulus onset when attending to the voice excerpts within the combined sounds. The observed effects suggest that during the segregation of auditory objects from the auditory background, spatial sound cues together with other relevant temporal and spectral cues are processed in an attention-dependent manner at the cortical locations generally involved in sound recognition. More synchronous neuronal activation during monophonic than stereophonic sound processing, as well as (local) neuronal inhibitory mechanisms in

  15. Cross-modality correspondence between pitch and spatial location modulates attentional orienting.

    Science.gov (United States)

    Chiou, Rocco; Rich, Anina N

    2012-01-01

    The brain constantly integrates incoming signals across the senses to form a cohesive view of the world. Most studies on multisensory integration concern the roles of spatial and temporal parameters. However, recent findings suggest cross-modal correspondences (eg high-pitched sounds associated with bright, small objects located high up) also affect multisensory integration. Here, we focus on the association between auditory pitch and spatial location. Surprisingly little is known about the cognitive and perceptual roots of this phenomenon, despite its long use in ergonomic design. In a series of experiments, we explore how this cross-modal mapping affects the allocation of attention with an attentional cuing paradigm. Our results demonstrate that high and low tones induce attention shifts to upper or lower locations, depending on pitch height. Furthermore, this pitch-induced cuing effect is susceptible to contextual manipulations and volitional control. These findings suggest the cross-modal interaction between pitch and location originates from an attentional level rather than from response mapping alone. The flexible contextual mapping between pitch and location, as well as its susceptibility to top-down control, suggests the pitch-induced cuing effect is primarily mediated by cognitive processes after initial sensory encoding and occurs at a relatively late stage of voluntary attention orienting.

  16. PTENα Modulates CaMKII Signaling and Controls Contextual Fear Memory and Spatial Learning

    Directory of Open Access Journals (Sweden)

    Pan Wang

    2017-06-01

    Full Text Available PTEN (phosphatase and tensin homology deleted on chromosome 10 has multiple functions, and recent studies have shown that the PTEN family has isoforms. The roles of these PTEN family members in biologic activities warrant specific evaluation. Here, we show that PTENα maintains CaMKII in a state that is competent to induce long-term potentiation (LTP with resultant regulation of contextual fear memory and spatial learning. PTENα binds to CaMKII with its distinctive N terminus and resets CaMKII to an activatable state by dephosphorylating it at sites T305/306. Loss of PTENα impedes the interaction of CaMKII and NR2B, leading to defects in hippocampal LTP, fear-conditioned memory, and spatial learning. Restoration of PTENα in the hippocampus of PTENα-deficient mice rescues learning deficits through regulation of CaMKII. CaMKII mutations in dementia patients inhibit CaMKII activity and result in disruption of PTENα-CaMKII-NR2B signaling. We propose that CaMKII is a target of PTENα phosphatase and that PTENα is an essential element in the molecular regulation of neural activity.

  17. Fiber-optical sensor with miniaturized probe head and nanometer accuracy based on spatially modulated low-coherence interferogram analysis.

    Science.gov (United States)

    Depiereux, Frank; Lehmann, Peter; Pfeifer, Tilo; Schmitt, Robert

    2007-06-10

    Fiber-optical sensors have some crucial advantages compared with rigid optical systems. They allow miniaturization and flexibility of system setups. Nevertheless, optical principles such as low-coherence interferometry can be realized by use of fiber optics. We developed and realized an approach for a fiber-optical sensor, which is based on the analysis of spatially modulated low-coherence interferograms. The system presented consists of three units, a miniaturized sensing probe, a broadband fiber-coupled light source, and an adapted Michelson interferometer, which is used as an optical receiver. Furthermore, the signal processing procedure, which was developed for the interferogram analysis in order to achieve nanometer measurement accuracy, is discussed. A system prototype has been validated thoroughly in different experiments. The results approve the accuracy of the sensor.

  18. Complex linear minimum mean-squared-error equalization of spatially quadrature-amplitude-modulated signals in holographic data storage

    Science.gov (United States)

    Sato, Takanori; Kanno, Kazutaka; Bunsen, Masatoshi

    2016-09-01

    We applied complex linear minimum mean-squared-error equalization to spatially quadrature-amplitude-modulated signals in holographic data storage (HDS). The equalization technique can improve dispersion in constellation outputs due to intersymbol interference. We confirm the effectiveness of the equalization technique in numerical simulations and basic optical experiments. Our numerical results have shown that intersymbol interference of a retrieved signal in a HDS system can be improved by using the equalization technique. In our experiments, a mean squared error (MSE), which indicates the deviation from an ideal signal, has been used for quantitatively evaluating the dispersion of equalized signals. Our equalization technique has been able to improve the MSE. However, symbols in the equalized signal have remained inseparable. To further improve the MSE and make the symbols separable, reducing errors in repeated measurements is our future task.

  19. Implementation of a Phase Only Spatial Light Modulator as an Atmospheric Turbulence Simulator at 1550 nm

    Directory of Open Access Journals (Sweden)

    Carlos Font

    2014-01-01

    Full Text Available Modeling and simulating atmospheric turbulence in a controlled environment have been a focus of interest for scientists for decades. The development of new technologies allows scientists to perform this task in a more realistic and controlled environment and provides powerful tools for the study and better understanding of the propagation of light through a nonstatic medium such as the atmosphere. Free space laser communications (FSLC and studies in light propagation through the atmosphere are areas which constantly benefit from breakthroughs in technology and in the development of realistic atmospheric turbulence simulators, in particular (Santiago et al. 2011. In this paper, we present the results from the implementation of a phase only spatial light modulator (SLM as an atmospheric turbulence simulator for light propagation in the short-wave infrared (SWIR regime. Specifically, we demonstrate its efficacy for its use in an FSLC system, at a wavelength of 1550 nm.

  20. Engineering an achromatic Bessel beam using a phase-only spatial light modulator and an iterative Fourier transformation algorithm

    Science.gov (United States)

    Walde, Marie; Jost, Aurélie; Wicker, Kai; Heintzmann, Rainer

    2017-01-01

    Bessel illumination is an established method in optical imaging and manipulation to achieve an extended depth of field without compromising the lateral resolution. When broadband or multicolour imaging is required, wavelength-dependent changes in the radial profile of the Bessel illumination can complicate further image processing and analysis. We present a solution for engineering a multicolour Bessel beam that is easy to implement and promises to be particularly useful for broadband imaging applications. A phase-only spatial light modulator (SLM) in the image plane and an iterative Fourier Transformation algorithm (IFTA) are used to create an annular light distribution in the back focal plane of a lens. The 2D Fourier transformation of such a light ring yields a Bessel beam with a constant radial profile for different wavelength.

  1. Spectrum reconstruction using relative-deviation-based kernel regression in temporally and spatially modulated Fourier transform imaging spectrometer.

    Science.gov (United States)

    Huang, Fengzhen; Yuan, Yan; Li, Jingzhen; Cao, Jun

    2015-08-01

    During the temporally and spatially modulated Fourier transform imaging spectrometer push-broom scanning process, the motion state of the spectrometer platform can vary. Thus, the target interferogram obtained from the image sequence deviates from the ideal interferogram obtained using high platform stability. The recovered target spectrum will not reflect the true target characteristics. We adopted target tracking to acquire the target position in the image sequence via a proposed kernel regression, with a relative deviation method for determining the target intensities, and the recovery of the spectrogram using the nonuniform fast Fourier transform algorithm. We tested our algorithm on simulated and experimentally obtained aerial images and, from comparison with accurate spectrograms, demonstrate the effectiveness of the proposed method.

  2. Optical limiting using spatial self-phase modulation in hot atomic sample

    Science.gov (United States)

    Zhang, Qian; Cheng, Xuemei; Zhang, Ying; Yin, Xunli; Jiang, Man; Chen, Haowei; Bai, Jintao

    2017-02-01

    In this work, we characterized the performance of optical limiting by self-phase modulation (SPM) in hot atomic vapor cell. The results indicated that the performance of the optical limiter is closely related to the position of the sample cell, which is determined by the Rayleigh lenght of beam. The lowest limiting threshold and clamp output were obtained at the sample position at -10 mm from the coordinate origin (the beam waist). The phenomenon was explained well by the theory of SPM and z-scan, which are caused by both Kerr effect and the thermal optical nonlinear effect. This useful information obtained in the meaning of this work is determining the optimal position of the sample cell in the optical limiter and other applications of SPM.

  3. The spatial module as environmental conditioning element: the Spanish pavilion by Corrales and Molezun

    Directory of Open Access Journals (Sweden)

    R. Suárez

    2017-06-01

    Full Text Available In the 50s a review of Modern Movement, which assimilates modular serialization and a connection with the environmental context, although with remote premises of the contemporary paradigms of sustainability arise. In this context, within national stage, stands out the Spanish pavilion at the Brussels International Exhibition in 1958 by Corrales and Molezún. This work seeks a quantitatively reveal of the environmental performance of the pavilion in its two locations and settings, in Brussels and Madrid, through simulation and analysis of energy and lighting models which reproduces the characteristic of the pavilion with the purpose of contributing to give a new critical point of view, valuing the module efficiency to adapt to different environmental conditions. The completed analysis reveals the influence of the climate, compactness and orientation, as in the difficulties associated with thermal comfort and natural light when glazing percentage are important and there are high solar radiation settings.

  4. Spatial localization and mesoscale modulation of mixing and transformation of the Denmark Strait Overflow

    Science.gov (United States)

    Koszalka, Inga; Haine, Thomas; Magaldi, Marcello

    2015-04-01

    The Denmark Strait Overflow (DSO) is a major export route for dense waters from the Nordic Seas forming the North Atlantic Deep Water, an important element of the climate system. Mixing processes in the Irminger Basin determine volume transport and properties of the DSO but are poorly resolved by sparse observations which hinders development of DSO mixing parameterizations in global circulation models (GCMs). We employ a high resolution circulation model (horizontal grid spacing of 2km and 210 levels in the vertical) to investigate transformation and mixing in the DSO in the Irminger Basin and quantify the effect of mesoscale (10-100km) flows unresolved by GCMs. Both the warming rate derived from model Lagrangian particles and the Eulerian eddy temperature flux divergence show elevated values in about a 200km long and 50km wide corridor downstream of the Denmark Strait sill and between the shelf break and the 2000m isobath. In this region, the DSO warms by about 1K, which constitutes most of the transformation along the entire 700km pathway in the Irminger Basin. The horizontal and vertical mixing is modulated by dense water boluses and overlying cyclonic eddies that propagate together through the Irminger Basin (`beddies'). The passage of beddies increase the squared vertical shear of horizontal velocity by a factor of 3, correspond to increase in the vertical velocity by ten times and double the eddy heat flux divergence leading to a warming of the bottom (densest) waters and a cooling of the interface layer of the overflow plume and the ambient water above. There is a clear correlation between the speed in the nose of the plume, the eddy kinetic energy and the vertical shear in the horizontal flow. The modulation of mixing by the mesoscale variability and the attendant mixing localization should be included in future overflow parameterizations in global circulation models. A targeted field campaign to empirically test these conjectures is another high priority.

  5. Fluorescence resonance energy transfer imaging reveals that chemokine-binding modulates heterodimers of CXCR4 and CCR5 receptors.

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    Nilgun Isik

    Full Text Available BACKGROUND: Dimerization has emerged as an important feature of chemokine G-protein-coupled receptors. CXCR4 and CCR5 regulate leukocyte chemotaxis and also serve as a co-receptor for HIV entry. Both receptors are recruited to the immunological synapse during T-cell activation. However, it is not clear whether they form heterodimers and whether ligand binding modulates the dimer formation. METHODOLOGY/PRINCIPAL FINDINGS: Using a sensitive Fluorescence Resonance Energy Transfer (FRET imaging method, we investigated the formation of CCR5 and CXCR4 heterodimers on the plasma membrane of live cells. We found that CCR5 and CXCR4 exist as constitutive heterodimers and ligands of CCR5 and CXCR4 promote different conformational changes within these preexisting heterodimers. Ligands of CCR5, in contrast to a ligand of CXCR4, induced a clear increase in FRET efficiency, indicating that selective ligands promote and stabilize a distinct conformation of the heterodimers. We also found that mutations at C-terminus of CCR5 reduced its ability to form heterodimers with CXCR4. In addition, ligands induce different conformational transitions of heterodimers of CXCR4 and CCR5 or CCR5(STA and CCR5(Delta4. CONCLUSIONS/SIGNIFICANCE: Taken together, our data suggest a model in which CXCR4 and CCR5 spontaneously form heterodimers and ligand-binding to CXCR4 or CCR5 causes different conformational changes affecting heterodimerization, indicating the complexity of regulation of dimerization/function of these chemokine receptors by ligand binding.

  6. Study of the Verwey transition in magnetite by low field and magnetically modulated non-resonant microwave absorption

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez, M.P. [Escuela Superior de Fisica y Matematicas del Instituto Politecnico Nacional, Mexico, D.F. 07738 (Mexico)]. E-mail: mpga@servidor.unam.mx; Alvarez, G. [Instituto de Investigaciones en Materiales de la Universidad Nacional Autonoma de Mexico, Mexico, D.F. 04510 (Mexico); Montiel, H. [Centro de Ciencias Aplicadas y Desarrollo Tecnologico de la Universidad Nacional Autonoma de Mexico, Mexico, D.F. 04510 (Mexico); Zamorano, R. [Escuela Superior de Fisica y Matematicas del Instituto Politecnico Nacional, Mexico, D.F. 07738 (Mexico); Valenzuela, R. [Instituto de Investigaciones en Materiales de la Universidad Nacional Autonoma de Mexico, Mexico, D.F. 04510 (Mexico)

    2007-09-15

    We have investigated the Verwey phase transition (VPT) by two novel non-resonant microwave absorption techniques: low-field absorption (LFA) and magnetically modulated microwave absorption spectroscopy (MAMMAS). Measurements were carried out on sintered polycrystalline samples of Fe{sub 3}O{sub 4}, in the 77-300 K temperature range. LFA refers to the microwave absorption around the zero DC field range (-1000

  7. 3D cine magnetic resonance imaging of rat lung ARDS using gradient-modulated SWIFT with retrospective respiratory gating

    Science.gov (United States)

    Kobayashi, Naoharu; Lei, Jianxun; Utecht, Lynn; Garwood, Michael; Ingbar, David H.; Bhargava, Maneesh

    2015-03-01

    SWeep Imaging with Fourier Transformation (SWIFT) with gradient modulation and DC navigator retrospective gating is introduced as a 3D cine magnetic resonance imaging (MRI) method for the lung. In anesthetized normal rats, the quasi-simultaneous excitation and acquisition in SWIFT enabled extremely high sensitivity to the fast-decaying parenchymal signals (TE=~4 μs), which are invisible with conventional MRI techniques. Respiratory motion information was extracted from DC navigator signals and the SWIFT data were reconstructed to 3D cine images with 16 respiratory phases. To test this technique's capabilities, rats exposed to > 95% O2 for 60 hours for induction of acute respiratory distress syndrome (ARDS), were imaged and compared with normal rat lungs (N=7 and 5 for ARDS and normal groups, respectively). SWIFT images showed lung tissue density differences along the gravity direction. In the cine SWIFT images, a parenchymal signal drop at the inhalation phase was consistently observed for both normal and ARDS rats due to lung inflation (i.e. decrease of the proton density), but the drop was less for ARDS rats. Depending on the respiratory phase and lung region, the lungs from the ARDS rats showed 1-24% higher parenchymal signal intensities relative to the normal rat lungs, likely due to accumulated extravascular water (EVLW). Those results demonstrate that SWIFT has high enough sensitivity for detecting the lung proton density changes due to gravity, different phases of respiration and accumulation of EVLW in the rat ARDS lungs.

  8. Selection in spatial stochastic models of cancer: Migration as a key modulator of fitness

    Directory of Open Access Journals (Sweden)

    Stupack Dwayne

    2010-04-01

    Full Text Available Abstract Background We study the selection dynamics in a heterogeneous spatial colony of cells. We use two spatial generalizations of the Moran process, which include cell divisions, death and migration. In the first model, migration is included explicitly as movement to a proximal location. In the second, migration is implicit, through the varied ability of cell types to place their offspring a distance away, in response to another cell's death. Results In both models, we find that migration has a direct positive impact on the ability of a single mutant cell to invade a pre-existing colony. Thus, a decrease in the growth potential can be compensated by an increase in cell migration. We further find that the neutral ridges (the set of all types with the invasion probability equal to that of the host cells remain invariant under the increase of system size (for large system sizes, thus making the invasion probability a universal characteristic of the cells selection status. We find that repeated instances of large scale cell-death, such as might arise during therapeutic intervention or host response, strongly select for the migratory phenotype. Conclusions These models can help explain the many examples in the biological literature, where genes involved in cell's migratory and invasive machinery are also associated with increased cellular fitness, even though there is no known direct effect of these genes on the cellular reproduction. The models can also help to explain how chemotherapy may provide a selection mechanism for highly invasive phenotypes. Reviewers This article was reviewed by Marek Kimmel and Glenn Webb.

  9. Kinesthetic and Vestibular Information Modulate Alpha Activity during Spatial Navigation: A Mobile EEG Study

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    Benedikt Valerian Ehinger

    2014-02-01

    Full Text Available In everyday life, spatial navigation involving locomotion provides congruent visual, vestibular and kinesthetic information that need to be integrated. Yet, previous studies on human brain activity during navigation focus on stationary setups, neglecting vestibular and kinesthetic feedback. The aim of our work is to uncover the influence of those sensory modalities on cortical processing. We developed a fully immersive virtual reality setup combined with high-density mobile electroencephalography (EEG. Participants traversed one leg of a triangle, turned on the spot, continued along the second leg and finally indicated the location of their starting position. Vestibular and kinesthetic information was provided either in combination, as isolated sources of information or not at all within a 2x2 full factorial intra-subjects design. EEG data were processed by clustering independent components, and time-frequency spectrograms were calculated. In parietal, occipital and temporal clusters, we detected alpha suppression during the turning movement, which is associated with a heightened demand of visuo-attentional processing, and closely resembles results reported in previous stationary studies. This decrease is present in all conditions and therefore seems to generalize to more natural settings. Yet, in incongruent conditions, when different sensory modalities did not match, the decrease is significantly stronger. Additionally, in more anterior areas, we found that providing only vestibular but no kinesthetic information results in alpha increase. These observations demonstrate that stationary experiments omit important aspects of sensory feedback. Therefore, it is important to develop more natural experimental settings in order to capture a more complete picture of neural correlates of spatial navigation.

  10. Fluorescence resonance energy transfer measured by spatial photon migration in CdSe-ZnS quantum dots colloidal systems as a function of concentration

    Energy Technology Data Exchange (ETDEWEB)

    Azevedo, G.; Monte, A. F. G.; Reis, A. F.; Messias, D. N. [Laboratório de Espectroscopia Óptica, Instituto de Física, Universidade Federal de Uberlândia, Uberlândia, MG 38400-902 (Brazil)

    2014-11-17

    The study of the spatial photon migration as a function of the concentration brings into attention the problem of the energy transfer in quantum dot embedded systems. By measuring the photon propagation and its spatial dependence, it is possible to understand the whole dynamics in a quantum dot system, and also improve their concentration dependence to maximize energy propagation due to radiative and non-radiative processes. In this work, a confocal microscope was adapted to scan the spatial distribution of photoluminescence from CdSe-ZnS core-shell quantum dots in colloidal solutions. The energy migration between the quantum dots was monitored by the direct measurement of the photon diffusion length, according to the diffusion theory. We observed that the photon migration length decreases by increasing the quantum dot concentration, this kind of behavior has been regarded as a signature of Förster resonance energy transfer in the system.

  11. Effects of time delay on stochastic resonance of a periodically driven linear system with multiplicative and periodically modulated additive white noises

    Institute of Scientific and Technical Information of China (English)

    Du Lu-Chun; Mei Dong-Cheng

    2009-01-01

    Stochastic resonance (SR) of a periodically driven time-delayed linear system with multiplicative white noise and periodically modulated additive white noise is investigated. In the condition of small delay time, an approximate analytical expression of output signal-to-noise ratio (SNR) is obtained. The analytical results indicate that (1) there exists a resonance peak in the curve for SNR versus time delay; (2) the time delay will suspend the SR dramatically for SNR versus other parameters of the system, such as noise intensity, correlation intensity, and signal frequency, once a certain value is reached, the SR phenomenon disappears.

  12. Monte Carlo calculation of the spatial response (Modulated Transfer Function) of a scintillation flat panel and comparison with experimental results

    Science.gov (United States)

    Juste, Belén; Miró, Rafael; Monasor, Paula; Verdú, Gumersindo

    2015-11-01

    Phosphor screens are commonly used in many X-ray imaging applications. The design and optimization of these detectors can be achieved using Monte Carlo codes to simulate radiation transport in scintillation materials and to improve the spatial response. This work presents an exhaustive procedure to measure the spatial resolution of a scintillation flat panel image and to evaluate the agreement with data obtained by simulation. To evaluate the spatial response we have used the Modulated Transfer Function (MTF) parameter. According to this, we have obtained the Line Spread Function (LSF) of the system since the Fourier Transform (FT) of the LSF gives the MTF. The experimental images were carried out using a medical X-ray tube (Toshiba E7299X) and a flat panel (Hammamatsu C9312SK). Measurements were based on the slit methodology experimental implementation, which measures the response of the system to a line. LSF measurements have been performed using a 0.2 mm wide lead slit superimposed over the flat panel. The detector screen was modelled with MCNP (version 6) Monte Carlo simulation code in order to analyze the effect of the acquisition setup configuration and to compare the response of scintillator screens with the experimental results. MCNP6 offers the possibility of studying the optical physics parameters (optical scattering and absorption coefficients) that occur in the phosphor screen. The study has been tested for different X-ray tube voltages, from 100 to 140 kV. An acceptable convergence between the MTF results obtained with MCNP6 and the experimental measurements have been obtained.

  13. Short-term sleep deprivation impairs spatial working memory and modulates expression levels of ionotropic glutamate receptor subunits in hippocampus.

    Science.gov (United States)

    Xie, Meilan; Yan, Jie; He, Chao; Yang, Li; Tan, Gang; Li, Chao; Hu, Zhian; Wang, Jiali

    2015-06-01

    Hippocampus-dependent learning memory is sensitive to sleep deprivation (SD). Although the ionotropic glutamate receptors play a vital role in synaptic plasticity and learning and memory, however, whether the expression of these receptor subunits is modulated by sleep loss remains unclear. In the present study, western blotting was performed by probing with specific antibodies against the ionotropic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits GluA1, GluA2, GluA3, and against the N-methyl-d-aspartate (NMDA) glutamate receptor subunits GluN1, GluN2A, GluN2B. In hippocampus, down regulation of surface GluA1 and GluN2A surface expression were observed in both SD groups. However, surface expression level of GluA2, GluA3, GluN1 and GluN2B was significantly up-regulated in 8h-SD rats when compared to the 4h-SD rats. In parallel with the complex changes in AMPA and NMDA receptor subunit expressions, we found the 8h-SD impaired rat spatial working memory in 30-s-delay T-maze task, whereas no impairment of spatial learning was observed in 4h-SD rats. These results indicate that sleep loss alters the relative expression levels of the AMPA and NMDA receptors, thus affects the synaptic strength and capacity for plasticity and partially contributes to spatial memory impairment. Copyright © 2015. Published by Elsevier B.V.

  14. Hemi-spatial neglect rehabilitation using non-invasive brain stimulation: or how to modulate the disconnection syndrome?

    Science.gov (United States)

    Jacquin-Courtois, S

    2015-09-01

    Hemi-spatial neglect syndrome is common and sometimes long-lasting. It is characterized by a deficit in the use and awareness of one side of space, most often consecutive to a right hemisphere injury, mainly in the parietal region. Acknowledging the different types and all clinical characteristics is essential for an appropriate evaluation and adapted rehabilitation care management, especially as it constitutes a predictive factor of a poor functional prognosis. Some new approaches have been developed in the last fifteen years in the field of hemi-spatial neglect rehabilitation, where non-invasive brain stimulation (TMS and tDCS) holds an important place. Today's approaches of unilateral spatial neglect modulation via non-invasive brain stimulation are essentially based on the concept of inter-hemispheric inhibition, suggesting an over-activation of the contralesional hemisphere due to a decrease of the inhibiting influences of the injured hemisphere. Several approaches may then be used: stimulation of the injured right hemisphere, inhibition of the hyperactive left hemisphere, or a combination of both. Results are promising, but the following complementary aspects must be refined before a more systematic application: optimal stimulation protocol, individual management according to the injured region, intensity, duration and frequency of care management, delay post-stroke before the beginning of treatment, combination of different approaches, as well as prognostic and efficacy criteria. An encouraging perspective for the future is the combination of several types of approaches, which would be largely facilitated by the improvement of fundamental knowledge on neglect mechanisms, which could in the future refine the choice for the most appropriate treatment(s) for a given patient.

  15. Bright solitons in defocusing media with spatial modulation of the quintic nonlinearity

    CERN Document Server

    Zeng, Jianhua

    2012-01-01

    It has been recently demonstrated that self-defocusing (SDF) media with the cubic nonlinearity, whose local coefficient grows from the center to periphery fast enough, support stable bright solitons, without the use of any linear potential. Our objective is to test the genericity of this mechanism for other nonlinearities, by applying it to one- and two-dimensional (1D and 2D) quintic SDF media. The models may be implemented in optics (in particular, in colloidal suspensions of nanoparticles), and the 1D model may be applied to the description of the Tonks-Girardeau gas of ultracold bosons. In 1D, the nonlinearity-modulation function is taken as $% g_{0}+\\sinh ^{2}(\\beta x) $. This model admits a subfamily of exact solutions for fundamental solitons. Generic \\ soliton solutions are constructed in a numerical form, and also by means of the Thomas-Fermi and variational approximations (TFA and VA). In particular, a new ansatz for the VA is proposed, in the form of "raised $\\mathrm{sech}$", which provides for an ...

  16. Spatial Attention and Temporal Expectation Under Timed Uncertainty Predictably Modulate Neuronal Responses in Monkey V1

    Science.gov (United States)

    Sharma, Jitendra; Sugihara, Hiroki; Katz, Yarden; Schummers, James; Tenenbaum, Joshua; Sur, Mriganka

    2015-01-01

    The brain uses attention and expectation as flexible devices for optimizing behavioral responses associated with expected but unpredictably timed events. The neural bases of attention and expectation are thought to engage higher cognitive loci; however, their influence at the level of primary visual cortex (V1) remains unknown. Here, we asked whether single-neuron responses in monkey V1 were influenced by an attention task of unpredictable duration. Monkeys covertly attended to a spot that remained unchanged for a fixed period and then abruptly disappeared at variable times, prompting a lever release for reward. We show that monkeys responded progressively faster and performed better as the trial duration increased. Neural responses also followed monkey's task engagement—there was an early, but short duration, response facilitation, followed by a late but sustained increase during the time monkeys expected the attention spot to disappear. This late attentional modulation was significantly and negatively correlated with the reaction time and was well explained by a modified hazard function. Such bimodal, time-dependent changes were, however, absent in a task that did not require explicit attentional engagement. Thus, V1 neurons carry reliable signals of attention and temporal expectation that correlate with predictable influences on monkeys' behavioral responses. PMID:24836689

  17. Improving the spatial resolution of a soft X-ray Charge Coupled Device used for Resonant Inelastic X-ray Scattering

    Science.gov (United States)

    Soman, M. R.; Hall, D. J.; Tutt, J. H.; Murray, N. J.; Holland, A. D.; Schmitt, T.; Raabe, J.; Schmitt, B.

    2011-11-01

    The Super Advanced X-ray Emission Spectrometer (SAXES) at the Advanced Resonant Scattering (ADRESS) beamline of the Swiss Light Source is a high-resolution X-ray spectrometer used as an end station for Resonant Inelastic X-ray Scattering from 400 eV to 1600 eV. Through the dispersion of photons across a CCD, the energy of scattered photons may be determined by their detected spatial position. The limiting factor of the energy resolution is currently the spatial resolution achieved with the CCD, reported at 24 μm FWHM. For this energy range the electron clouds are formed by interactions in the `field free' region of the back-illuminated CCD. These clouds diffuse in all directions whilst being attracted to the electrodes, leading to events that are made up of signals in multiple pixels. The spreading of the charge allows centroiding techniques to be used to improve the CCD spatial resolution and therefore improve the energy resolution of SAXES. The PolLux microscopy beamline at the SLS produces an X-ray beam with a diameter of 20 nm. The images produced from scanning the narrow beam across CCD pixels (13.5 × 13.5 μm2) can aid in the production of event recognition algorithms, allowing the matching of event profiles to photon interactions in a specific region of a pixel. Through the use of this information software analysis can be refined with the aim of improving the energy resolution.

  18. Deep brain stimulation modulates synchrony within spatially and spectrally distinct resting state networks in Parkinson's disease.

    Science.gov (United States)

    Oswal, Ashwini; Beudel, Martijn; Zrinzo, Ludvic; Limousin, Patricia; Hariz, Marwan; Foltynie, Tom; Litvak, Vladimir; Brown, Peter

    2016-05-01

    Chronic dopamine depletion in Parkinson's disease leads to progressive motor and cognitive impairment, which is associated with the emergence of characteristic patterns of synchronous oscillatory activity within cortico-basal-ganglia circuits. Deep brain stimulation of the subthalamic nucleus is an effective treatment for Parkinson's disease, but its influence on synchronous activity in cortico-basal-ganglia loops remains to be fully characterized. Here, we demonstrate that deep brain stimulation selectively suppresses certain spatially and spectrally segregated resting state subthalamic nucleus-cortical networks. To this end we used a validated and novel approach for performing simultaneous recordings of the subthalamic nucleus and cortex using magnetoencephalography (during concurrent subthalamic nucleus deep brain stimulation). Our results highlight that clinically effective subthalamic nucleus deep brain stimulation suppresses synchrony locally within the subthalamic nucleus in the low beta oscillatory range and furthermore that the degree of this suppression correlates with clinical motor improvement. Moreover, deep brain stimulation relatively selectively suppressed synchronization of activity between the subthalamic nucleus and mesial premotor regions, including the supplementary motor areas. These mesial premotor regions were predominantly coupled to the subthalamic nucleus in the high beta frequency range, but the degree of deep brain stimulation-associated suppression in their coupling to the subthalamic nucleus was not found to correlate with motor improvement. Beta band coupling between the subthalamic nucleus and lateral motor areas was not influenced by deep brain stimulation. Motor cortical coupling with subthalamic nucleus predominantly involved driving of the subthalamic nucleus, with those drives in the higher beta frequency band having much shorter net delays to subthalamic nucleus than those in the lower beta band. These observations raise the

  19. A fully-integrated 12.5-Gb/s 850-nm CMOS optical receiver based on a spatially-modulated avalanche photodetector

    NARCIS (Netherlands)

    Lee, M.J.; Youn, J.S.; Park, K.Y.; Choi, W.Y.

    2014-01-01

    We present a fully integrated 12.5-Gb/s optical receiver fabricated with standard 0.13-µm complementary metal-oxide-semiconductor (CMOS) technology for 850-nm optical interconnect applications. Our integrated optical receiver includes a newly proposed CMOS-compatible spatially-modulated avalanche ph

  20. A fully-integrated 12.5-Gb/s 850-nm CMOS optical receiver based on a spatially-modulated avalanche photodetector

    NARCIS (Netherlands)

    Lee, M.J.; Youn, J.S.; Park, K.Y.; Choi, W.Y.

    2014-01-01

    We present a fully integrated 12.5-Gb/s optical receiver fabricated with standard 0.13-µm complementary metal-oxide-semiconductor (CMOS) technology for 850-nm optical interconnect applications. Our integrated optical receiver includes a newly proposed CMOS-compatible spatially-modulated avalanche ph

  1. Quality of Intensity Modulated Radiation Therapy Treatment Plans Using a {sup 60}Co Magnetic Resonance Image Guidance Radiation Therapy System

    Energy Technology Data Exchange (ETDEWEB)

    Wooten, H. Omar, E-mail: hwooten@radonc.wustl.edu; Green, Olga; Yang, Min; DeWees, Todd; Kashani, Rojano; Olsen, Jeff; Michalski, Jeff; Yang, Deshan; Tanderup, Kari; Hu, Yanle; Li, H. Harold; Mutic, Sasa

    2015-07-15

    Purpose: This work describes a commercial treatment planning system, its technical features, and its capabilities for creating {sup 60}Co intensity modulated radiation therapy (IMRT) treatment plans for a magnetic resonance image guidance radiation therapy (MR-IGRT) system. Methods and Materials: The ViewRay treatment planning system (Oakwood Village, OH) was used to create {sup 60}Co IMRT treatment plans for 33 cancer patients with disease in the abdominal, pelvic, thorax, and head and neck regions using physician-specified patient-specific target coverage and organ at risk (OAR) objectives. Backup plans using a third-party linear accelerator (linac)-based planning system were also created. Plans were evaluated by attending physicians and approved for treatment. The {sup 60}Co and linac plans were compared by evaluating conformity numbers (CN) with 100% and 95% of prescription reference doses and heterogeneity indices (HI) for planning target volumes (PTVs) and maximum, mean, and dose-volume histogram (DVH) values for OARs. Results: All {sup 60}Co IMRT plans achieved PTV coverage and OAR sparing that were similar to linac plans. PTV conformity for {sup 60}Co was within <1% and 3% of linac plans for 100% and 95% prescription reference isodoses, respectively, and heterogeneity was on average 4% greater. Comparisons of OAR mean dose showed generally better sparing with linac plans in the low-dose range <20 Gy, but comparable sparing for organs with mean doses >20 Gy. The mean doses for all {sup 60}Co plan OARs were within clinical tolerances. Conclusions: A commercial {sup 60}Co MR-IGRT device can produce highly conformal IMRT treatment plans similar in quality to linac IMRT for a variety of disease sites. Additional work is in progress to evaluate the clinical benefit of other novel features of this MR-IGRT system.

  2. Spatial modulation spectroscopy for imaging and quantitative analysis of single dye-doped organic nanoparticles inside cells

    Science.gov (United States)

    Devadas, Mary Sajini; Devkota, Tuphan; Guha, Samit; Shaw, Scott K.; Smith, Bradley D.; Hartland, Gregory V.

    2015-05-01

    Imaging of non-fluorescent nanoparticles in complex biological environments, such as the cell cytosol, is a challenging problem. For metal nanoparticles, Rayleigh scattering methods can be used, but for organic nanoparticles, such as dye-doped polymer beads or lipid nanoparticles, light scattering does not provide good contrast. In this paper, spatial modulation spectroscopy (SMS) is used to image single organic nanoparticles doped with non-fluorescent, near-IR croconaine dye. SMS is a quantitative imaging technique that yields the absolute extinction cross-section of the nanoparticles, which can be used to determine the number of dye molecules per particle. SMS images were recorded for particles within EMT-6 breast cancer cells. The measurements allowed mapping of the nanoparticle location and the amount of dye in a single cell. The results demonstrate how SMS can facilitate efforts to optimize dye-doped nanoparticles for effective photothermal therapy of cancer.Imaging of non-fluorescent nanoparticles in complex biological environments, such as the cell cytosol, is a challenging problem. For metal nanoparticles, Rayleigh scattering methods can be used, but for organic nanoparticles, such as dye-doped polymer beads or lipid nanoparticles, light scattering does not provide good contrast. In this paper, spatial modulation spectroscopy (SMS) is used to image single organic nanoparticles doped with non-fluorescent, near-IR croconaine dye. SMS is a quantitative imaging technique that yields the absolute extinction cross-section of the nanoparticles, which can be used to determine the number of dye molecules per particle. SMS images were recorded for particles within EMT-6 breast cancer cells. The measurements allowed mapping of the nanoparticle location and the amount of dye in a single cell. The results demonstrate how SMS can facilitate efforts to optimize dye-doped nanoparticles for effective photothermal therapy of cancer. Electronic supplementary information (ESI

  3. Self-regulation of circumscribed brain activity modulates spatially selective and frequency specific connectivity of distributed resting state networks

    Directory of Open Access Journals (Sweden)

    Mathias eVukelić

    2015-07-01

    Full Text Available The mechanisms of learning involved in brain self-regulation have still to be unveiled to exploit the full potential of this methodology for therapeutic interventions. This skill of volitionally changing brain activity presumably resembles motor skill learning which in turn is accompanied by plastic changes modulating resting state networks. Along these lines, we hypothesized that brain regulation and neurofeedback would similarly modify intrinsic networks at rest while presenting a distinct spatio-temporal pattern. High-resolution EEG preceded and followed a single neurofeedback training intervention of modulating circumscribed sensorimotor low β -activity by motor imagery in eleven healthy participants. They were kept in the deliberative phase of skill acquisition with high demands for learning self-regulation through stepwise increases of task difficulty. By applying the corrected imaginary part of the coherency function, we observed increased functional connectivity of both the primary motor and the primary somatosensory cortex with their respective contralateral homologous cortices in the low β-frequency band which was self-regulated during feedback. At the same time, the primary motor cortex - but none of the surrounding cortical areas - showed connectivity to contralateral supplementary motor and dorsal premotor areas in the high β-band. Simultaneously, the neurofeedback target displayed a specific increase of functional connectivity with an ipsilateral fronto-parietal network in the α-band while presenting a de-coupling with contralateral primary and secondary sensorimotor areas in the very same frequency band.Brain self-regulating modifies resting state connections spatially selective to the neurofeedback target of the dominant hemisphere. These are anatomically distinct with regard to the cortico-cortical connectivity pattern and are functionally specific with regard to the time domain of coherent activity consistent with a Hebbian

  4. Solid-phase laser-induced forward transfer of variable shapes using a liquid-crystal spatial light modulator

    Science.gov (United States)

    Pohl, R.; Jansink, M.; Römer, G. R. B. E.; Huis in `t Veld, A. J.

    2015-08-01

    Laser-induced forward transfer is a promising method for 3D printing of various materials, including metals. The ejection mechanism is complex and depends strongly on the experimental parameters, such as laser fluence and donor layer thickness. However, the process can be categorized by the physical condition of the ejected material, i.e., the donor layer is transferred in liquid phase or the material is transferred as a `pellet' in solid phase. Currently, solid-phase transfer faces several problems. Large shearing forces, occurring at the pellet perimeter during transfer, limit the similarity between the desired pellet shape and the deposited pellet shape. Furthermore, the deposited pellet may be surrounded by debris particles formed by undesired transferred donor material. This work introduces a novel approach for laser-induced forward transfer of variable shaped solid-phase pellets. A liquid-crystal spatial light modulator (SLM) is used to apply grayscale intensity modulation to an incident laser beam to shape the intensity profile. Optimized beams consist of a high fluence perimeter around an interior characterized by a lower fluence level. These beams are used successfully to transfer solid-phase pellets out of a 100-nm Au donor layer using a single laser pulse. The flexibility of the SLM allows a variable desired pellet shape. The shapes of the resulting deposited pellets show a high degree of similarity to the desired shapes. Debris-free deposited pellets are achieved by pre-machining the donor layer, prior to the transfer, using a double-pulse process.

  5. Effect of spatial spin modulation on relaxation and NMR frequencies of sup 5 sup 7 Fe nuclei in ferroelectric antiferromagnetic BiFeO sub 3

    CERN Document Server

    Zalessky, A V; Zvezdin, A K; Gippius, A A; Morozova, E N; Khozeev, D F; Bush, A S; Pokatilov, V S

    2002-01-01

    The NMR spectra on the iron nuclei in the BiFeO sub 3 antiferromagnetic sample enriched by the sup 5 sup 7 Fe (95.43%) with the spatially-modulated magnetic structure are studied. It is established that the cycloid-type spin modulation in the BiFeO sub 3 produces spatial modulation of the nuclear spin-spin relaxation velocity and leads to the spectral nonuniform widening of the NMR local line. It is determined also that the local magnetic moments of the iron ions on various cycloid sections differently depend on temperature which testifies to different character of the spin waves excitation. The analogy of the experimental results with the NMR regularities in the Bloch wall is discussed

  6. Imaging cortical absorption, scattering, and hemodynamic response during ischemic stroke using spatially modulated near-infrared illumination

    Science.gov (United States)

    Abookasis, David; Lay, Christopher C.; Mathews, Marlon S.; Linskey, Mark E.; Frostig, Ron D.; Tromberg, Bruce J.

    2009-03-01

    We describe a technique that uses spatially modulated near-infrared (NIR) illumination to detect and map changes in both optical properties (absorption and reduced scattering parameters) and tissue composition (oxy- and deoxyhemoglobin, total hemoglobin, and oxygen saturation) during acute ischemic injury in the rat barrel cortex. Cerebral ischemia is induced using an open vascular occlusion technique of the middle cerebral artery (MCA). Diffuse reflected NIR light (680 to 980 nm) from the left parietal somatosensory cortex is detected by a CCD camera before and after MCA occlusion. Monte Carlo simulations are used to analyze the spatial frequency dependence of the reflected light to predict spatiotemporal changes in the distribution of tissue absorption and scattering properties in the brain. Experimental results from seven rats show a 17+/-4.7% increase in tissue concentration of deoxyhemoglobin and a 45+/-3.1, 23+/-5.4, and 21+/-2.2% decrease in oxyhemoglobin, total hemoglobin concentration and cerebral tissue oxygen saturation levels, respectively, 45 min following induction of cerebral ischemia. An ischemic index (Iisch=ctHHb/ctO2Hb) reveals an average of more then twofold contrast after MCAo. The wavelength-dependence of the reduced scattering (i.e., scatter power) decreased by 35+/-10.3% after MCA occlusion. Compared to conventional CCD-based intrinsic signal optical imaging (ISOI), the use of structured illumination and model-based analysis allows for generation of separate maps of light absorption and scattering properties as well as tissue hemoglobin concentration. This potentially provides a powerful approach for quantitative monitoring and imaging of neurophysiology and metabolism with high spatiotemporal resolution.

  7. High spatial and temporal resolution retrospective cine cardiovascular magnetic resonance from shortened free breathing real-time acquisitions.

    Science.gov (United States)

    Xue, Hui; Kellman, Peter; Larocca, Gina; Arai, Andrew E; Hansen, Michael S

    2013-11-14

    Cine cardiovascular magnetic resonance (CMR) is challenging in patients who cannot perform repeated breath holds. Real-time, free-breathing acquisition is an alternative, but image quality is typically inferior. There is a clinical need for techniques that achieve similar image quality to the segmented cine using a free breathing acquisition. Previously, high quality retrospectively gated cine images have been reconstructed from real-time acquisitions using parallel imaging and motion correction. These methods had limited clinical applicability due to lengthy acquisitions and volumetric measurements obtained with such methods have not previously been evaluated systematically. This study introduces a new retrospective reconstruction scheme for real-time cine imaging which aims to shorten the required acquisition. A real-time acquisition of 16-20s per acquired slice was inputted into a retrospective cine reconstruction algorithm, which employed non-rigid registration to remove respiratory motion and SPIRiT non-linear reconstruction with temporal regularization to fill in missing data. The algorithm was used to reconstruct cine loops with high spatial (1.3-1.8 × 1.8-2.1 mm²) and temporal resolution (retrospectively gated, 30 cardiac phases, temporal resolution 34.3 ± 9.1 ms). Validation was performed in 15 healthy volunteers using two different acquisition resolutions (256 × 144/192 × 128 matrix sizes). For each subject, 9 to 12 short axis and 3 long axis slices were imaged with both segmented and real-time acquisitions. The retrospectively reconstructed real-time cine images were compared to a traditional segmented breath-held acquisition in terms of image quality scores. Image quality scoring was performed by two experts using a scale between 1 and 5 (poor to good). For every subject, LAX and three SAX slices were selected and reviewed in the random order. The reviewers were blinded to the reconstruction approach and acquisition protocols and

  8. Low Threshold, Wide Dynamic Range, Tunable, All-Optical Self-Modulator Based on Fano Resonance and Out-of-Plane Coupling in a Slab Photonic Crystal with a Graphene Layer

    Directory of Open Access Journals (Sweden)

    Reza Asadi

    2015-01-01

    Full Text Available We demonstrate an all-optical modulator based on self-modulation in a one-dimensional slab photonic crystal (PhC by using optical Kerr nonlinearity of graphene and Fano resonance effect. It has been shown that the effect of Fano resonance in a one-dimensional slab PhC for intensity enhancement can provide low threshold (~1 MW/cm2, high frequency (>1 THz, and wide dynamic range (>3 THz tunability for the all-optical self-modulator. Such a self-modulator can find applications in optical pulse generations, optical clocks, frequency shifting, and so forth.

  9. Spatially defined modulation of skin temperature and hand ownership of both hands in patients with unilateral complex regional pain syndrome.

    Science.gov (United States)

    Moseley, G Lorimer; Gallace, Alberto; Iannetti, Gian Domenico

    2012-12-01

    Numerous clinical conditions, including complex regional pain syndrome, are characterized by autonomic dysfunctions (e.g. altered thermoregulation, sometimes confined to a single limb), and disrupted cortical representation of the body and the surrounding space. The presence, in patients with complex regional pain syndrome, of a disruption in spatial perception, bodily ownership and thermoregulation led us to hypothesize that impaired spatial perception might result in a spatial-dependent modulation of thermoregulation and bodily ownership over the affected limb. In five experiments involving a total of 23 patients with complex regional pain syndrome of one arm and 10 healthy control subjects, we measured skin temperature of the hand with infrared thermal imaging, before and after experimental periods of either 9 or 10 min each, during which the hand was held on one or the other side of the body midline. Tactile processing was assessed by temporal order judgements of pairs of vibrotactile stimuli, delivered one to each hand. Pain and sense of ownership over the hand were assessed by self-report scales. Across experiments, when kept on its usual side of the body midline, the affected hand was 0.5 ± 0.3°C cooler than the healthy hand (P hand were prioritized over those delivered to the affected hand. Simply crossing both hands over the midline resulted in (i) warming of the affected hand (the affected hand became 0.4 ± 0.3°C warmer than when it was in the uncrossed position; P = 0.01); (ii) cooling of the healthy hand (by 0.3 ± 0.3°C; P = 0.02); and (iii) reversal of the prioritization of tactile processing. When only the affected hand was crossed over the midline, it became warmer (by 0.5 ± 0.3°C; P = 0.01). When only the healthy hand was crossed over the midline, it became cooler (by 0.3 ± 0.3°C; P = 0.01). The temperature change of either hand was positively related to its distance from the body midline (pooled data: r = 0.76, P hand over the body

  10. Controlling mode competition by tailoring the spatial pump distribution in a laser: A resonance-based approach

    CERN Document Server

    Cerjan, Alexander; Ge, Li; Liew, Seng Fatt; Cao, Hui; Stone, A Douglas

    2016-01-01

    We introduce a simplified version of the steady-state ab initio laser theory for calculating the effects of mode competition in continuous wave lasers using the passive cavity resonances. This new theory harnesses widely available numerical methods that can efficiently calculate the passive cavity resonances, with negligible additional computational overhead. Using this theory, we demonstrate that the pump profile of the laser cavity can be optimized both for highly multi-mode and single-mode emission. An open source implementation of this method has been made available.

  11. High-precision structural analysis of subnuclear complexes in fixed and live cells via spatially modulated illumination (SMI) microscopy.

    Science.gov (United States)

    Reymann, Jürgen; Baddeley, David; Gunkel, Manuel; Lemmer, Paul; Stadter, Werner; Jegou, Thibaud; Rippe, Karsten; Cremer, Christoph; Birk, Udo

    2008-01-01

    Spatially modulated illumination (SMI) microscopy is a method of wide field fluorescence microscopy featuring interferometric illumination, which delivers structural information about nanoscale architecture in fluorescently labelled cells. The first prototype of the SMI microscope proved its applicability to a wide range of biological questions. For the SMI live cell imaging this system was enhanced in terms of the development of a completely new upright configuration. This so called Vertico-SMI transfers the advantages of SMI nanoscaling to vital biological systems, and is shown to work consistently at different temperatures using both oil- and water-immersion objective lenses. Furthermore, we increased the speed of data acquisition to minimize errors in the detection signal resulting from cellular or object movement. By performing accurate characterization, the present Vertico-SMI now offers a fully-fledged microscope enabling a complete three-dimensional (3D) SMI data stack to be acquired in less than 2 seconds. We have performed live cell measurements of a tet-operator repeat insert in U2OS cells, which provided the first in vivo signatures of subnuclear complexes. Furthermore, we have successfully implemented an optional optical configuration allowing the generation of high-resolution localization microscopy images of a nuclear pore complex distribution.

  12. Improvement of diffraction efficiency of three-dimensional magneto-optic spatial light modulator with magnetophotonic crystal

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, K.; Takagi, H., E-mail: takagi@ee.tut.ac.jp; Lim, P. B.; Inoue, M., E-mail: inoue@tut.ac.jp [Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, Toyohashi, Aichi 441 8580 (Japan); Goto, Taichi [Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, Toyohashi, Aichi 441 8580 (Japan); JST, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Horimai, H. [HolyMine Corporation, Atsugi, Kanagawa 243 0813 (Japan); Yoshikawa, H. [Department of Computer Engineering, College of Science and Technology, Nihon University, Funabashi, Chiba 274 8501 (Japan); Bove, V. M. [MIT Media Lab, Cambridge, Massachusetts 02139 (United States)

    2016-01-11

    We have developed three-dimensional magneto-optic spatial light modulators (3D-MOSLMs) that use magnetic domains as submicron scale pixels to represent holograms. Our display system uses a submicron-scale magnetic pixel array on an amorphous TbFe film to create a wide viewing angle hologram. However, in previous work the reconstructed images had a low intensity and a low optical contrast; brightness of the reconstructed image was 4.4 × 10{sup −2 }cd/m{sup 2} with 532 nm illumination light at 10.8 mW/cm{sup 2}, while display standard ISO13406 recommends 100 cd/m{sup 2} or more. In this paper, we describe our development of a 3D-MOSLM composed of an artificial magnetic lattice structure of magnetophotonic crystals (MPCs). The MPCs enhance the diffraction efficiency of reconstructed 3D images and reduce the power consumption for controlling the magnetic pixels by a light localization effect. We demonstrate reconstructed 3D images using the MPC and show significant brightness improvement.

  13. Arbitrary multibeam laser scanning and trapping by use of a spatial light modulator and manual scripting interface

    Science.gov (United States)

    Xun, Xiaodong; Chang, Xiaoguang; Cho, Doo Jin; Cohn, Robert W.

    2004-10-01

    A multi-beam, variable footprint, laser beam steering and shaping system is described and used with a microscope to demonstrate multi-particle laser trapping. It is built around a computer-interfaced 512x512 pixel analog phase-only spatial light modulator (SLM) and a 1 W, 1064 nm wavelength laser. Hand sketches on paper made with a digital pen are used to prescribe the footprints, velocities and trajectories of multiple, independently-controlled diffracted spots. Continuous scanning is approximated by automatically designing a sequence of phase-patterns that are run through and diffracted by the SLM. Very complex scanning sequences of dozens of independently controlled spots can be quickly designed and run. The number of beams that we can trap with is necessarily limited due to the low throughput (~23 mW) of the IR light through the microscope optics. Among the trapping experiments done with the system a triangular shaped vortex ring tends to stop single particles at the apexes of the triangle. However, collision with a second particle pushes the first particle past the apex and sets it into motion, leaving the second particle stopped until collision with a third particle. The discrete motion conditioned on collisions is suggestive of a queuing process or a Markov chain.

  14. Adaptive optics scanning laser ophthalmoscope using liquid crystal on silicon spatial light modulator: Performance study with involuntary eye movement

    Science.gov (United States)

    Huang, Hongxin; Toyoda, Haruyoshi; Inoue, Takashi

    2017-09-01

    The performance of an adaptive optics scanning laser ophthalmoscope (AO-SLO) using a liquid crystal on silicon spatial light modulator and Shack-Hartmann wavefront sensor was investigated. The system achieved high-resolution and high-contrast images of human retinas by dynamic compensation for the aberrations in the eyes. Retinal structures such as photoreceptor cells, blood vessels, and nerve fiber bundles, as well as blood flow, could be observed in vivo. We also investigated involuntary eye movements and ascertained microsaccades and drifts using both the retinal images and the aberrations recorded simultaneously. Furthermore, we measured the interframe displacement of retinal images and found that during eye drift, the displacement has a linear relationship with the residual low-order aberration. The estimated duration and cumulative displacement of the drift were within the ranges estimated by a video tracking technique. The AO-SLO would not only be used for the early detection of eye diseases, but would also offer a new approach for involuntary eye movement research.

  15. High spatial and temporal resolution observations of an impulse-driven field line resonance in radar backscatter artificially generated with the Tromsø heater

    Directory of Open Access Journals (Sweden)

    T. K. Yeoman

    Full Text Available The CUTLASS Finland HF radar has been operated in conjunction with the EISCAT Tromsø RF ionospheric heater facility to examine a ULF wave characteristic of the development of a field line resonance (FLR driven by a cavity mode caused by a magnetospheric impulse. When the heater is on, striating the ionosphere with field-aligned ionospheric electron density irregularities, a large enough radar target is generated to allow post-integration over only 1 second. When combined with 15 km range gates, this gives radar measurements of a naturally occurring ULF wave at a far better temporal and spatial resolution than has been achieved previously. The time-dependent signature of the ULF wave has been examined as it evolves from a large-scale cavity resonance, through a transient where the wave period was latitude-dependent and the oscillation had the characteristics of freely ringing field lines, and finally to a very narrow, small-scale local field line resonance. The resonance width of the FLR is only 60 km and this is compared with previous observations and theory. The FLR wave signature is strongly attenuated in the ground magnetometer data. The characterisation of the impulse driven FLR was only achieved very crudely with the ground magnetometer data and, in fact, an accurate determination of the properties of the cavity and field line resonant systems challenges the currently available limitations of ionospheric radar techniques. The combination of the latest ionospheric radars and facilities such as the Tromsø ionospheric heater can result in a powerful new tool for geophysical research.

  16. Stochastic resonance and dynamic first-order pseudo-phase-transitions in the irreversible growth of thin films under spatially periodic magnetic fields.

    Science.gov (United States)

    Loscar, Ernesto S; Candia, Julián

    2013-10-01

    We study the irreversible growth of magnetic thin films under the influence of spatially periodic fields by means of extensive Monte Carlo simulations. We find first-order pseudo-phase-transitions that separate a dynamically disordered phase from a dynamically ordered phase. By analogy with time-dependent oscillating fields applied to Ising-type models, we qualitatively associate this dynamic transition with the localization-delocalization transition of spatial hysteresis loops. Depending on the relative width of the magnetic film L compared to the wavelength of the external field λ, different transition regimes are observed. For small systems (L λ), the transition is driven by anomalous stochastic resonance. The origin of the latter is identified as due to the emergence of an additional relevant length scale, namely, the roughness of the spin domain switching interface. The distinction between different stochastic resonance regimes is discussed at length both qualitatively by means of snapshot configurations and quantitatively via residence-length and order-parameter probability distributions.

  17. Near-field observation of spatial phase shifts associated with Goos-Hänschen and Surface Plasmon Resonance effects.

    Science.gov (United States)

    Jose, J; Segerink, F B; Korterik, J P; Offerhaus, H L

    2008-02-04

    We report the near-field observation of the phase shifts associated with total internal reflection on a glass-air interface and surface plasmon resonance on a glass-gold-air system. The phase of the evanescent waves on glass and gold surfaces, as a function of incident angle, is measured using a phase-sensitive Photon Scanning Tunneling Microscope (PSTM) and shows a good agreement with theory.

  18. Invasion of Phytophthora infestans at the landscape level; How do spatial scale and weather modulate the consequences of spatial heterogeneity in host resistance

    NARCIS (Netherlands)

    Skelsey, P.; Rossing, W.A.H.; Kessel, G.J.T.; Werf, van der W.

    2010-01-01

    Strategic spatial patterning of crop species and cultivars could make agricultural landscapes less vulnerable to plant disease epidemics, but experimentation to explore effective disease-suppressive landscape designs is problematic. Here, we present a realistic, multiscale, spatiotemporal, integrodi

  19. Invasion of Phytophthora infestans at the landscape level; How do spatial scale and weather modulate the consequences of spatial heterogeneity in host resistance

    NARCIS (Netherlands)

    Skelsey, P.; Rossing, W.A.H.; Kessel, G.J.T.; Werf, van der W.

    2010-01-01

    Strategic spatial patterning of crop species and cultivars could make agricultural landscapes less vulnerable to plant disease epidemics, but experimentation to explore effective disease-suppressive landscape designs is problematic. Here, we present a realistic, multiscale, spatiotemporal,

  20. H-1 and N-15 resonance assignment of the second fibronectin type III module of the neural cell adhesion molecule

    DEFF Research Database (Denmark)

    Kiselyov, Vladislav V; Berezin, Vladimir; Bock, Elisabeth;

    2008-01-01

    We report here the NMR assignment of the second fibronectin type III module of the neural cell adhesion molecule (NCAM). This module has previously been shown to interact with the fibroblast growth factor receptor (FGFR), and the FGFR-binding site was mapped by NMR to the FG-loop region...... of the module. The FG-loop region also contains a putative nucleotide-binding motif, which was shown by NMR to interact with ATP. Furthermore, ATP was demonstrated to inhibit binding of the second F3 module of NCAM to FGFR....

  1. mGluR5 positive allosteric modulators facilitate both hippocampal LTP and LTD and enhance spatial learning.

    Science.gov (United States)

    Ayala, Jennifer E; Chen, Yelin; Banko, Jessica L; Sheffler, Douglas J; Williams, Richard; Telk, Alexandra N; Watson, Noreen L; Xiang, Zixiu; Zhang, Yongqin; Jones, Paulianda J; Lindsley, Craig W; Olive, M Foster; Conn, P Jeffrey

    2009-08-01

    Highly selective positive allosteric modulators (PAMs) of metabotropic glutamate receptor subtype 5 (mGluR5) have emerged as a potential approach to treat positive symptoms associated with schizophrenia. mGluR5 plays an important role in both long-term potentiation (LTP) and long-term depression (LTD), suggesting that mGluR5 PAMs may also have utility in improving impaired cognitive function. However, if mGluR5 PAMs shift the balance of LTP and LTD or induce a state in which afferent activity induces lasting changes in synaptic function that are not appropriate for a given pattern of activity, this could disrupt rather than enhance cognitive function. We determined the effect of selective mGluR5 PAMs on the induction of LTP and LTD at the Schaffer collateral-CA1 synapse in the hippocampus. mGluR5-selective PAMs significantly enhanced threshold theta-burst stimulation (TBS)-induced LTP. In addition, mGluR5 PAMs enhanced both DHPG-induced LTD and LTD induced by the delivery of paired-pulse low-frequency stimulation. Selective potentiation of mGluR5 had no effect on LTP induced by suprathreshold TBS or saturated LTP. The finding that potentiation of mGluR5-mediated responses to stimulation of glutamatergic afferents enhances both LTP and LTD and supports the hypothesis that the activation of mGluR5 by endogenous glutamate contributes to both forms of plasticity. Furthermore, two systemically active mGluR5 PAMs enhanced performance in the Morris water maze, a measure of hippocampus-dependent spatial learning. Discovery of small molecules that enhance both LTP and LTD in an activity-appropriate manner shows a unique action on synaptic plasticity that may provide a novel approach for the treatment of impaired cognitive function.

  2. Endor, triple resonance and electron spin echo envelope modulation of 14N in sulphur and selenium coordinated copper(II) complexes

    Science.gov (United States)

    Böttcher, R.; Kirmse, R.; Stach, J.; Reijerse, E. J.; Keijzers, C. P.

    1986-08-01

    Single-crystal ENDOR and TRIPLE resonance studies on "long-range" coupled 14N nuclei are reported for Cu(II) complexes in four host lattices: bis(diethyldithiocarbamato)Ni(II) and Zn(II), bis(diethyldiselenocarbamato)Zn(II) and tetra- n-butylammonium(maleonitriledithiolato)(diethyldithiocarbamato)Ni(II). The ENDOR spectra are unusual because the 14N nuclear quadrupole interaction exceeds the hyperfine coupling and the nuclear Zeeman interaction. The spectra are analyzed in detail and correlated with the molecular structures of the host compounds. According to the TRIPLE experiments the 14N hyperfine tensor components are negative. The populations of the nitrogen orbitals are evaluated from the quadrupole coupling tensors. In order to compare these double resonance methods with pulsed techniques, electron spin echo envelope modulation (ESEEM) is applied to a powder of one of the systems.

  3. Vector-Resonance-Multimode Instability

    Science.gov (United States)

    Sergeyev, S. V.; Kbashi, H.; Tarasov, N.; Loiko, Yu.; Kolpakov, S. A.

    2017-01-01

    The modulation and multimode instabilities are the main mechanisms which drive spontaneous spatial and temporal pattern formation in a vast number of nonlinear systems ranging from biology to laser physics. Using an Er-doped fiber laser as a test bed, here for the first time we demonstrate both experimentally and theoretically a new type of a low-threshold vector-resonance-multimode instability which inherits features of multimode and modulation instabilities. The same as for the multimode instability, a large number of longitudinal modes can be excited without mode synchronization. To enable modulation instability, we modulate the state of polarization of the lasing signal with the period of the beat length by an adjustment of the in-cavity birefringence and the state of polarization of the pump wave. As a result, we show the regime's tunability from complex oscillatory to periodic with longitudinal mode synchronization in the case of resonance matching between the beat and cavity lengths. Apart from the interest in laser physics for unlocking the tunability and stability of dynamic regimes, the proposed mechanism of the vector-resonance-multimode instability can be of fundamental interest for the nonlinear dynamics of various distributed systems.

  4. LRSP resonance enhanced spatial and angular Goos-Hanchen shift and Imbert-Fedorov shift for Gaussian beam, Laguerre-Gaussian beam and Bessel beam

    Science.gov (United States)

    Swain, Prasad Kumar; Goswami, Nabamita; Saha, Ardhendu

    2017-01-01

    A new theoretical approach towards the composite effect of spatial and angular Goos-Hanchen (GH) shift and Imbert-Fedorov (IF) shift for the Gaussian beam, Laguerre-Gaussian beam and Bessel beam with long range surface plasmon (LRSP) resonance is observed, designed and simulated through the variation of incident angle at a wavelength of 1550 nm where the four layered Kreschmann-Rather geometry comprises a ZnSe prism, a liquid crystal layer of E44 and two metal layers of silver. To the best of our knowledge several articles have been devoted, separately considering the Gaussian beam, Laguerre-Gaussian beam and Bessel beam without considering the effect of spatial and angular GH shift and IF shift whereas the exact output beam position can only be identified with the composite effect of these shifts. The investigation of these spatial and angular shifts for Gaussian beam and different orders of Laguerre-Gaussian beam are calculated and represented where these lateral shifts increase with the increment of the modes and further these lateral shifts for Bessel beam have also been analyzed. With this new approach various avenues expedite the way of futuristic applications in the field of fine tuning in optical switching with the accurate beam position using different beams.

  5. On-chip modulation for rotating sensing of gyroscope based on ring resonator coupled with Mach-Zehnder interferometer.

    Science.gov (United States)

    Zhang, Hao; Chen, Jiayang; Jin, Junjie; Lin, Jian; Zhao, Long; Bi, Zhuanfang; Huang, Anping; Xiao, Zhisong

    2016-01-01

    An improving structure for resonance optical gyro inserting a Mach-Zehnder Interferomete (MZI) into coupler region between ring resonator and straight waveguide was proposed. The different reference phase shift parameters in the MZI arms are tunable by thermo-optic effect and can be optimized at every rotation angular rate point without additional phase bias. Four optimum paths are formed to make the gyroscope to work always at the highest sensitivity.

  6. Spatial Frequency Dependence of the Human Visual Cortex Response on Temporal Frequency Modulation Studied by fMRI

    Directory of Open Access Journals (Sweden)

    A. Mirzajani

    2006-07-01

    Full Text Available Background/Objective: The brain response to temporal frequencies (TF has been already reported. However, there is no study on different TF with respect to various spatial frequencies (SF. Materials and Methods: Functional magnetic resonance imaging (fMRI was done by a 1.5 T General Electric system for 14 volunteers (9 males and 5 females, aged 19–26 years during square-wave reversal checkerboard visual stimulation with different temporal frequencies of 4, 6, 8 and 10 Hz in 2 states of low SF of 0.4 and high SF of 8 cycles/degree (cpd. All subjects had normal visual acuity of 20/20 based on Snellen’s fraction in each eye with good binocular vision and normal visual field based on confrontation test. The mean luminance of the entire checkerboard was 161.4 cd/m2 and the black and white check contrast was 96%. The activation map was created using the data obtained from the block designed fMRI study. Pixels with a Z score above a threshold of 2.3, at a statistical significance level of 0.05, were considered activated. The average percentage blood oxygenation level dependent (BOLD signal change for all activated pixels within the occipital lobe, multiplied by the total number of activated pixels within the occipital lobe, was used as an index for the magnitude of the fMRI signal at each state of TF&SF. Results: The magnitude of the fMRI signal in response to different TF’s was maximum at 6 Hz for a high SF value of 8 cpd; it was however, maximum at a TF of 8 Hz for a low SF of 0.4 cpd. Conclusion: The results of this study agree with those of animal invasive neurophysiologic studies showing SF and TF selectivity of neurons in visual cortex. These results can be useful for vision therapy and selecting visual tasks in fMRI studies.

  7. Infrared to visible image up-conversion using optically addressed spatial light modulator utilizing liquid crystal and InGaAs photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Solodar, A., E-mail: asisolodar@gmail.com; Arun Kumar, T.; Sarusi, G.; Abdulhalim, I. [Department of Electro-Optics Engineering and The Ilse Katz Institute for Nanoscale Science and Technology, Ben Gurion University of the Negev, Beer Sheva 84105 (Israel)

    2016-01-11

    Combination of InGaAs/InP heterojunction photodetector with nematic liquid crystal (LC) as the electro-optic modulating material for optically addressed spatial light modulator for short wavelength infra-red (SWIR) to visible light image conversion was designed, fabricated, and tested. The photodetector layer is composed of 640 × 512 photodiodes array based on heterojunction InP/InGaAs having 15 μm pitch on InP substrate and with backside illumination architecture. The photodiodes exhibit extremely low, dark current at room temperature, with optimum photo-response in the SWIR region. The photocurrent generated in the heterojunction, due to the SWIR photons absorption, is drifted to the surface of the InP, thus modulating the electric field distribution which modifies the orientation of the LC molecules. This device can be attractive for SWIR to visible image upconversion, such as for uncooled night vision goggles under low ambient light conditions.

  8. Design of 1-μm-pitch liquid crystal spatial light modulators having dielectric shield wall structure for holographic display with wide field of view

    Science.gov (United States)

    Isomae, Yoshitomo; Shibata, Yosei; Ishinabe, Takahiro; Fujikake, Hideo

    2017-03-01

    In the development of electronic holographic displays with a wide field of view, one issue is the realization of 1-μm-pitch spatial light modulators (SLMs) using liquid crystal on silicon (LCOS) techniques. We clarified that it is necessary to suppress not only the leakage of fringe electric fields from adjacent pixels but also the effect of elastic forces in the liquid crystal to achieve full-phase modulation (2π) in individual pixels. We proposed a novel LCOS-SLM with a dielectric shield wall structure, and achieved driving of individual 1-μm-pitch pixels. We also investigated the optimum values for width and dielectric constant of the wall structure when enlarging the area that can modulate light in the pixels. These results contribute to the design of 1-μm-pitch LCOS-SLM devices for wide-viewing-angle holographic displays.

  9. Simultaneous excitement of electron and ion resonances in a magnetoplasma by a high frequency electromagnetic field low frequency modulated; Excitation simultanee des resonances electronique et ionique dans un plasma dans un champ magnetique statique, produite par un champ electromagnetique HF module a une basse frequence

    Energy Technology Data Exchange (ETDEWEB)

    Zilli, E. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1966-07-01

    A single-particle, collisionless, non-relativistic theory is exposed, in which the possibility is shown of exciting electron and ion resonances in a magnetoplasma, by means of a high frequency electromagnetic field, whose amplitude is low frequency modulated. Two solutions of this problem are given in this report. The first one rests on the possibility of exciting the ion cyclotron resonance taking into account the low frequency electromagnetic field low frequency modulated. In the second solution the possibility of exciting the electron and ion resonances is considered in an electromagnetic field, whose magnetic component parallel to vector B{sub 0} is low frequency modulated. The results are discussed in the field of a cylindrical wave guide driven in the TE{sub 01}-mode, vector B{sub 0} being parallel to the axis. (Author) [French] On montre dans l'etude du mouvement d'une particule, lorsqu'on neglige les effets relativistes et les collisions, qu'il est possible d'exciter la resonance des electrons et des ions dans un plasma place dans un champ magnetique statique et dans un champ electromagnetique HF module en amplitude a une basse frequence. Dans cette note on presente deux solutions de ce probleme. La premiere repose sur la possibilite d'exciter la resonance cyclotron des ions en prenant en consideration le champ electromagnetique BF produit par les electrons qui tournent transversalement au champ magnetique statique B{sub 0}, sous l'influence d'un champ electromagnetique HF module a basse frequence. La deuxieme est celle ou le champ BF est une modulation, appliquee de l'exterieur, de l'amplitude de la composante magnetique du champ HF. On considere le cas ou cette composante magnetique oscillante est parallele a celle du champ magnetique statique. On discute les resultats dans le cas d'un mode TE{sub 01} se propageant dans un guide circulaire en presence d'un champ magnetique statique axial. (auteur)

  10. Development of Image Overlay and Knowledge Transfer Module Technologies Aimed at Enhancing Feasibility and External Validation of Magnetic Resonance Imaging-based Scoring Systems.

    Science.gov (United States)

    Jaremko, Jacob L; Pitts, Meaghan; Maksymowych, Walter P; Lambert, Robert G

    2016-01-01

    Semiquantitative arthritis scoring assesses disease burden by scoring presence/extent of features such as bone marrow lesion (BML) or effusion in multiple anatomic regions at a joint. An image overlay clarifying region borders may enhance feasibility and reliability of these scoring systems. To be scalable for use in large clinical trials, systematic computer-based user training is desirable. We developed an overlay and user training module for magnetic resonance imaging (MRI)-based scoring of hip osteoarthritis (OA). We designed a semitransparent 2-dimensional image overlay applied to individual MRI slices to facilitate hip OA scoring [HIMRISS (Hip Inflammation MRI Scoring System)], initially using freeware and then in a customized HTML Web browser environment. We developed a systematic knowledge translation package including instructional presentation, fully scored expert consensus cases, and video tutorials for training in the use of these scoring systems with the overlays. Three musculoskeletal radiologists who had not used this scoring system before each performed a scoring exercise with no overlay, then repeated this with overlays after completing the training module. Based on postexercise interviews and a reader survey, we identified and corrected problems in the module. The entire training process was then repeated using 3 new readers. Overlays were considered useful, particularly when integrated into a Web browser. The knowledge translation module was considered conceptually valuable, but as initially implemented was too lengthy and not sufficiently interactive. Semitransparent image overlays and standardized knowledge translation modules for reader training show promise to facilitate reader calibration using MRI-based scoring systems. Based on our experience, knowledge translation modules should emphasize close feedback evaluating performance and reader time efficiency.

  11. The spatial reliability of task-irrelevant sounds modulates bimodal audiovisual integration: An event-related potential study.

    Science.gov (United States)

    Li, Qi; Yu, Hongtao; Wu, Yan; Gao, Ning

    2016-08-26

    The integration of multiple sensory inputs is essential for perception of the external world. The spatial factor is a fundamental property of multisensory audiovisual integration. Previous studies of the spatial constraints on bimodal audiovisual integration have mainly focused on the spatial congruity of audiovisual information. However, the effect of spatial reliability within audiovisual information on bimodal audiovisual integration remains unclear. In this study, we used event-related potentials (ERPs) to examine the effect of spatial reliability of task-irrelevant sounds on audiovisual integration. Three relevant ERP components emerged: the first at 140-200ms over a wide central area, the second at 280-320ms over the fronto-central area, and a third at 380-440ms over the parieto-occipital area. Our results demonstrate that ERP amplitudes elicited by audiovisual stimuli with reliable spatial relationships are larger than those elicited by stimuli with inconsistent spatial relationships. In addition, we hypothesized that spatial reliability within an audiovisual stimulus enhances feedback projections to the primary visual cortex from multisensory integration regions. Overall, our findings suggest that the spatial linking of visual and auditory information depends on spatial reliability within an audiovisual stimulus and occurs at a relatively late stage of processing.

  12. Residual analysis of the water resonance signal in breast lesions imaged with high spectral and spatial resolution (HiSS) MRI: A pilot study

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, William A., E-mail: willw00@uchicago.edu; Medved, Milica; Karczmar, Gregory S.; Giger, Maryellen L. [Department of Radiology, The University of Chicago, 5841 South Maryland Avenue, Chicago, Illinois 60637 (United States)

    2014-01-15

    Purpose: High spectral and spatial resolution magnetic resonance imaging (HiSS MRI) yields information on the local environment of suspicious lesions. Previous work has demonstrated the advantages of HiSS (complete fat-suppression, improved image contrast, no required contrast agent, etc.), leading to initial investigations of water resonance lineshape for the purpose of breast lesion classification. The purpose of this study is to investigate a quantitative imaging biomarker, which characterizes non-Lorentzian components of the water resonance in HiSS MRI datasets, for computer-aided diagnosis (CADx). Methods: The inhomogeneous broadening and non-Lorentzian or “off-peak” components seen in the water resonance of proton spectra of breast HiSS images are analyzed by subtracting a Lorentzian fit from the water peak spectra and evaluating the difference spectrum or “residual.” The maxima of these residuals (referred to hereafter as “off-peak components”) tend to be larger in magnitude in malignant lesions, indicating increased broadening in malignant lesions. The authors considered only those voxels with the highest magnitude off-peak components in each lesion, with the number of selected voxels dependent on lesion size. Our voxel-based method compared the magnitudes and frequencies of off-peak components of all voxels from all lesions in a database that included 15 malignant and 8 benign lesions (yielding ∼3900 voxels) based on the lesions’ biopsy-confirmed diagnosis. Lesion classification was accomplished by comparing the average off-peak component magnitudes and frequencies in malignant and benign lesions. The area under the ROC curve (AUC) was used as a figure of merit for both the voxel-based and lesion-based methods. Results: In the voxel-based task of distinguishing voxels from malignant and benign lesions, off-peak magnitude yielded an AUC of 0.88 (95% confidence interval [0.84, 0.91]). In the lesion-based task of distinguishing malignant and

  13. Manipulating femtosecond laser interactions in bulk glass and thin-film with spatial light modulation (Conference Presentation)

    Science.gov (United States)

    Alimohammadian, Ehsan; Ho, Stephen; Ertorer, Erden; Gherghe, Sebastian; Li, Jianzhao; Herman, Peter R.

    2017-03-01

    Spatial Light Modulators (SLM) are emerging as a power tool for laser beam shaping whereby digitally addressed phase shifts can impose computer-generated hologram patterns on incoming laser light. SLM provide several additional advantages with ultrashort-pulsed lasers in controlling the shape of both surface and internal interactions with materials. Inside transparent materials, nonlinear optical effects can confine strong absorption only to the focal volume, extend dissipation over long filament tracks, or reach below diffraction-limited spot sizes. Hence, SLM beam shaping has been widely adopted for laser material processing applications that include parallel structuring, filamentation, fiber Bragg grating formation and optical aberration correction. This paper reports on a range of SLM applications we have studied in femtosecond processing of transparent glasses and thin films. Laser phase-fronts were tailored by the SLM to compensate for spherical surface aberration, and to further address the nonlinear interactions that interplay between Kerr-lens self-focusing and plasma defocusing effects over shallow and deep focusing inside the glass. Limits of strong and weak focusing were examined around the respective formation of low-loss optical waveguides and long uniform filament tracks. Further, we have employed the SLM for beam patterning inside thin film, exploring the limits of phase noise, resolution and fringe contrast during interferometric intra-film structuring. Femtosecond laser pulses of 200 fs pulse duration and 515 nm wavelength were shaped by a phase-only LCOS-SLM (Hamamatsu X10468-04). By imposing radial phase profiles, axicon, grating and beam splitting gratings, volume shape control of filament diameter, length, and uniformity as well as simultaneous formation of multiple filaments has been demonstrated. Similarly, competing effects of spherical surface aberration, self-focusing, and plasma de-focusing were studied and delineated to enable formation

  14. Development and Preliminary Validation of a Digital Overlay-based Learning Module for Semiquantitative Evaluation of Magnetic Resonance Imaging Lesions in Osteoarthritis of the Hip.

    Science.gov (United States)

    Maksymowych, Walter P; Pitts, Meaghan; Budak, Matthew J; Gracey, David; Lambert, Robert G; McDougall, David; Pianta, Marcus; Rennie, Winston J; Wichuk, Stephanie; Winn, Naomi; Jaremko, Jacob L

    2016-01-01

    To develop and validate a knowledge transfer (KT) module aimed at enhancing feasibility and reliability of semiquantitative assessment of bone marrow lesions (BML) and synovitis-effusion using the Hip Inflammation Magnetic Resonance Imaging Scoring System (HIMRISS). Three radiologists naive to the HIMRISS method reviewed the manuscript describing the method and then scored MRI scans from 16 patients with hip OA obtained at baseline and 8 weeks after intraarticular injection of corticosteroid. Readers then reviewed a KT module comprising an instructional presentation and 8 reference DICOM (digital imaging and communications in medicine) cases scored by 3 readers with expertise in the HIMRISS method, and then used electronic overlay software to score scans from 23 patients with OA. The same format was followed with a second group of 3 readers naive to HIMRISS using a KT module revised to incorporate the overlay with a Web-based DICOM viewer to enhance feasibility. Interobserver reliability was assessed with the intraclass correlation coefficient (ICC). In both exercises, reliability for baseline scores was excellent for femoral BML, very good for acetabular BML, and good for synovitis-effusion (overall ICC = 0.91, 0.89, 0.62, respectively) even without prior calibration using the KT module. However, reliability for detecting change was substantially worse than for expert readers, especially for acetabular BML and synovitis-effusion (overall ICC = 0.59 vs 0.19, and 0.42 vs 0.25, respectively). Reliability improved for detection of change in these lesions, especially after reader calibration with the revised KT module. Development and validation of a systematic method for KT may enhance external validation of certain imaging instruments.

  15. Clinical application of bilateral high temporal and spatial resolution dynamic contrast-enhanced magnetic resonance imaging of the breast at 7 T

    Energy Technology Data Exchange (ETDEWEB)

    Pinker, K.; Baltzer, P.; Bernathova, M.; Weber, M.; Leithner, D.; Helbich, T.H. [Medical University Vienna, Department of Biomedical Imaging and Image-guided Therapy, Division of Molecular and Gender Imaging, Waehringer Guertel 18-20, 1090, Vienna (Austria); Bogner, W.; Trattnig, S.; Gruber, S.; Zaric, O. [Medical University Vienna, Department of Biomedical Imaging and Image-guided Therapy, MR Centre of Excellence, Vienna (Austria); Abeyakoon, O. [King' s College, Department of Radiology, London (United Kingdom); Dubsky, P. [Medical University Vienna, Department of Surgery, Vienna (Austria); Bago-Horvath, Z. [Medical University Vienna, Department of Pathology, Vienna (Austria)

    2014-04-15

    The objective of our study was to evaluate the clinical application of bilateral high spatial and temporal resolution dynamic contrast-enhanced magnetic resonance imaging (HR DCE-MRI) of the breast at 7 T. Following institutional review board approval 23 patients with a breast lesion (BIRADS 0, 4-5) were included in our prospective study. All patients underwent bilateral HR DCE-MRI of the breast at 7 T (spatial resolution of 0.7 mm{sup 3} voxel size, temporal resolution of 14 s). Two experienced readers (r1, r2) and one less experienced reader (r3) independently assessed lesions according to BI-RADS registered. Image quality, lesion conspicuity and artefacts were graded from 1 to 5. Sensitivity, specificity and diagnostic accuracy were assessed using histopathology as the standard of reference. HR DCE-MRI at 7 T revealed 29 lesions in 23 patients (sensitivity 100 % (19/19); specificity of 90 % (9/10)) resulting in a diagnostic accuracy of 96.6 % (28/29) with an AUC of 0.95. Overall image quality was excellent in the majority of cases (27/29) and examinations were not hampered by artefacts. There was excellent inter-reader agreement for diagnosis and image quality parameters (κ = 0.89-1). Bilateral HR DCE-MRI of the breast at 7 T is feasible with excellent image quality in clinical practice and allows accurate breast cancer diagnosis. (orig.)

  16. Image-based gradient non-linearity characterization to determine higher-order spherical harmonic coefficients for improved spatial position accuracy in magnetic resonance imaging.

    Science.gov (United States)

    Weavers, Paul T; Tao, Shengzhen; Trzasko, Joshua D; Shu, Yunhong; Tryggestad, Erik J; Gunter, Jeffrey L; McGee, Kiaran P; Litwiller, Daniel V; Hwang, Ken-Pin; Bernstein, Matt A

    2017-05-01

    Spatial position accuracy in magnetic resonance imaging (MRI) is an important concern for a variety of applications, including radiation therapy planning, surgical planning, and longitudinal studies of morphologic changes to study neurodegenerative diseases. Spatial accuracy is strongly influenced by gradient linearity. This work presents a method for characterizing the gradient non-linearity fields on a per-system basis, and using this information to provide improved and higher-order (9th vs. 5th) spherical harmonic coefficients for better spatial accuracy in MRI. A large fiducial phantom containing 5229 water-filled spheres in a grid pattern is scanned with the MR system, and the positions all the fiducials are measured and compared to the corresponding ground truth fiducial positions as reported from a computed tomography (CT) scan of the object. Systematic errors from off-resonance (i.e., B0) effects are minimized with the use of increased receiver bandwidth (±125kHz) and two acquisitions with reversed readout gradient polarity. The spherical harmonic coefficients are estimated using an iterative process, and can be subsequently used to correct for gradient non-linearity. Test-retest stability was assessed with five repeated measurements on a single scanner, and cross-scanner variation on four different, identically-configured 3T wide-bore systems. A decrease in the root-mean-square error (RMSE) over a 50cm diameter spherical volume from 1.80mm to 0.77mm is reported here in the case of replacing the vendor's standard 5th order spherical harmonic coefficients with custom fitted 9th order coefficients, and from 1.5mm to 1mm by extending custom fitted 5th order correction to the 9th order. Minimum RMSE varied between scanners, but was stable with repeated measurements in the same scanner. The results suggest that the proposed methods may be used on a per-system basis to more accurately calibrate MR gradient non-linearity coefficients when compared to vendor

  17. Preliminary assessment of dispersion versus absorption analysis of high spectral and spatial resolution magnetic resonance images in the diagnosis of breast cancer.

    Science.gov (United States)

    Weiss, William A; Medved, Milica; Karczmar, Gregory S; Giger, Maryellen L

    2015-04-01

    Water resonance lineshapes observed in breast lesions imaged with high spectral and spatial resolution (HiSS) magnetic resonance imaging have been shown to contain diagnostically useful non-Lorentzian components. The purpose of this work is to update a previous method of breast lesion diagnosis by including phase-corrected absorption and dispersion spectra. This update includes information about the shape of the complex water resonance, which could improve the performance of a computer-aided diagnosis breast lesion classification scheme. The non-Lorentzian characteristics observed in complex breast lesion water resonance spectra are characterized by comparing a plot of the real versus imaginary components of the spectrum to that of a perfect complex Lorentzian spectrum, a "dispersion versus absorption" (DISPA) analysis technique. Distortion in the shape of the observed spectra indicates underlying physiologic changes, which have been shown to be correlated with malignancy. These spectral shape distortions in each lesion voxel are quantified by summing the deviations in DISPA radius from an ideal complex Lorentzian spectrum over all Fourier components, yielding a "total radial difference" (TRD). We limited our analysis to those voxels in each lesion with the largest TRD. The number of voxels considered was dependent on the lesion size. The TRD was used to classify voxels from 15 malignant and 8 benign lesions ([Formula: see text] voxels after voxel elimination). Lesion discrimination performance was evaluated for both the average and variance of the TRD within each lesion. Area under the receiver operating characteristic curve (ROC AUC) was used to assess both the voxel- and lesion-based discrimination methods in the task of distinguishing between malignant and benign. In the task of distinguishing voxels from malignant and benign lesions, TRD yielded an AUC of 0.89 (95% confidence interval [0.84, 0.91]). In the task of distinguishing malignant from benign lesions

  18. Resonant drift of two-armed spirals by a periodic advective field and periodic modulation of excitability.

    Science.gov (United States)

    Deng, Ling-Yun; Zhang, Hong; Li, You-Quan

    2010-01-01

    The drift behavior of two-armed spirals induced by periodic advective field and periodic modulation of excitability is investigated. It is shown that the two-armed spirals controlled by periodic advective field and periodic modulation of excitability drift in completely different ways. For periodic advective field, the two tips of the two-armed spiral drift in the same direction and the two-armed spiral is stable. While for periodic modulation of excitability, the two tips drift in the opposite direction and the two-armed spiral splits into two single-armed spirals. Analytical results based on a kinematic theory of rotating spirals in weakly excitable media are consistent with the numerical results.

  19. Toward a biorelevant structure of protein kinase C bound modulators: design, synthesis, and evaluation of labeled bryostatin analogues for analysis with rotational echo double resonance NMR spectroscopy.

    Science.gov (United States)

    Loy, Brian A; Lesser, Adam B; Staveness, Daryl; Billingsley, Kelvin L; Cegelski, Lynette; Wender, Paul A

    2015-03-18

    Protein kinase C (PKC) modulators are currently of great importance in preclinical and clinical studies directed at cancer, immunotherapy, HIV eradication, and Alzheimer's disease. However, the bound conformation of PKC modulators in a membrane environment is not known. Rotational echo double resonance (REDOR) NMR spectroscopy could uniquely address this challenge. However, REDOR NMR requires strategically labeled, high affinity ligands to determine interlabel distances from which the conformation of the bound ligand in the PKC-ligand complex could be identified. Here we report the first computer-guided design and syntheses of three bryostatin analogues strategically labeled for REDOR NMR analysis. Extensive computer analyses of energetically accessible analogue conformations suggested preferred labeling sites for the identification of the PKC-bound conformers. Significantly, three labeled analogues were synthesized, and, as required for REDOR analysis, all proved highly potent with PKC affinities (∼1 nM) on par with bryostatin. These potent and strategically labeled bryostatin analogues are new structural leads and provide the necessary starting point for projected efforts to determine the PKC-bound conformation of such analogues in a membrane environment, as needed to design new PKC modulators and understand PKC-ligand-membrane structure and dynamics.

  20. ApoE isoform modulates effects of cranial ⁵⁶Fe irradiation on spatial learning and memory in the water maze.

    Science.gov (United States)

    Yeiser, Lauren A; Villasana, Laura E; Raber, Jacob

    2013-01-15

    Apolipoprotein E, which plays an important role in lipid transport and metabolism and neuronal repair, might modulate the CNS risk following (56)Fe irradiation exposure during space missions. In this study, we investigated this risk by behavioral and cognitive testing male E2, E3, and E4 mice 3 months following cranial (56)Fe irradiation. In the open field, mice irradiated with 2 Gy showed higher activity levels than sham-irradiated mice or mice irradiated with 1 Gy. In addition, E2 mice showed higher activity and lower measures of anxiety than E3 and E4 mice in the open field and elevated zero maze. During hidden platform training, sham-irradiated mice showed most robust learning, 1 Gy irradiated mice reduced learning, and 2 Gy irradiated mice no improvement over the four sessions. In the water maze probe trials, sham-irradiated E2, E3, and E4 mice and E2 and E4 mice irradiated with 1 Gy showed spatial memory retention, but E3 mice irradiated with 1 Gy, and E2, E3, and E4 mice irradiated with 2 Gy did not. Thus, cranial (56)Fe irradiation increases activity levels in the open field and impairs spatial learning and memory in the water maze. E3 mice are more susceptible than E2 or E4 mice to impairments in spatial memory retention in the water maze, indicating that apoE isoform modulates the CNS risk following space missions.