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Sample records for acousto-optic programmable dispersive

  1. Acousto-optical pulsar processor usage for interstellar medium dispersion measurements

    NASA Astrophysics Data System (ADS)

    Esepkina, Nelli A.; Lavrov, Aleksandr P.; Molodyakov, Sergey A.

    2005-02-01

    The acousto-optical processor (AOP) of a new type for the investigation of pulsar radio emission is proposed that provides for the compensation of signal dispersion in a wide frequency bandwidth. The AOP is based on an acousto-optical spectrum analyzer with a CCD photodetector operating in a special pipeline operational mode (shift-and-add mode), which allows spectral components of the input signal to be added with a controlled time delay immediately in the CCD photodetector. The proposed AOP was successfully used on an RT-64 radio telescope (Kalyazin Radio Astronomy Observatory FIAN) for the observation of pulsars at 1.4 GHz band with bandwidth 45 MHz. The method of direct interstellar medium dispersion measurement on two-frequency band observations with application AOP is described. The measurements of DM for pulsar PSR 1937 + 21 are submitted.

  2. Ultrasound sensing using the acousto-optic effect in polymer dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Trushkevych, O.; Eriksson, T. J. R.; Ramadas, S. N.; Dixon, S.; Edwards, R. S.

    2015-08-01

    Acousto-optic effects are demonstrated in polymer dispersed liquid crystal (PDLC) films, showing promise for applications in ultrasound sensing. The PDLC films are used to image two displacement profiles of air-coupled flexural transducers' resonant modes at 295 kHz and 730 kHz. Results are confirmed using laser vibrometry. The regions on the transducers with the largest displacements are clearly imaged by the PDLC films, with the resolution agreeing well with laser vibrometry scanning. Imaging takes significantly less time than a scanning system (switching time of a few seconds, as compared to 8 h for laser vibrometry). Heating effects are carefully monitored using thermal imaging and are found not to be the main cause of PDLC clearing.

  3. Acousto-optic tunable filter for dispersion characterization of time-domain optical coherence tomography systems.

    PubMed

    Chin, Catherine; Toadere, Florin; Feuchter, Thomas; Leick, Lasse; Moselund, Peter; Bradu, Adrian; Podoleanu, Adrian

    2016-07-20

    A broadband supercontinuum light source with an acousto-optic tunable filter (AOTF) are used to characterize dispersion in two time-domain OCT systems, at 850 and 1300 nm. The filter is designed to sweep across two spectral ranges, which are restricted here from 800 to 900 nm and from 1200 to 1500 nm, respectively. Dispersion compensation for 850 nm was achieved with a spectral delay line. Dispersion compensation for 1300 nm was achieved using BK 7 rod glasses in the reference arm. The AOTF allows evaluation of dispersion in under as well as overcompensated systems. The AOTF method is based on wavelength dependence of the optical path difference corresponding to the maximum strength of the interference signal recorded using a mirror as object. Comparison is made between the AOTF method and the more usual method based on measurement of the full width at half-maximum of the autocorrelation peak. This comparison shows that the AOTF method is more accurate in terms of evaluation of the dispersion left uncompensated after each adjustment. The AOTF method additionally provides information on the direction of dispersion compensation.

  4. Compensation of temporal and spatial dispersion for multiphoton acousto-optic laser-scanning microscopy

    NASA Astrophysics Data System (ADS)

    Iyer, Vijay; Saggau, Peter

    2003-10-01

    In laser-scanning microscopy, acousto-optic (AO) deflection provides a means to quickly position a laser beam to random locations throughout the field-of-view. Compared to conventional laser-scanning using galvanometer-driven mirrors, this approach increases the frame rate and signal-to-noise ratio, and reduces time spent illuminating sites of no interest. However, random-access AO scanning has not yet been combined with multi-photon microscopy, primarily because the femtosecond laser pulses employed are subject to significant amounts of both spatial and temporal dispersion upon propagation through common AO materials. Left uncompensated, spatial dispersion reduces the microscope"s spatial resolution while temporal dispersion reduces the multi-photon excitation efficacy. In previous work, we have demonstrated, 1) the efficacy of a single diffraction grating scheme which reduces the spatial dispersion at least 3-fold throughout the field-of-view, and 2) the use of a novel stacked-prism pre-chirper for compensating the temporal dispersion of a pair of AODs using a shorter mechanical path length (2-4X) than standard prism-pair arrangements. In this work, we demonstrate for the first time the use of these compensation approaches with a custom-made large-area slow-shear TeO2 AOD specifically suited for the development of a high-resolution 2-D random-access AO scanning multi-photon laser-scanning microscope (AO-MPLSM).

  5. Analysis of the dispersion compensation of acousto-optic deflectors used for multiphoton imaging.

    PubMed

    Zeng, Shaoqun; Lv, Xiaohua; Bi, Kun; Zhan, Cheng; Li, Derong; Chen, Wei R; Xiong, Wenhui; Jacques, Steven L; Luo, Qingming

    2007-01-01

    The acousto-optic deflector (AOD) is highly preferred in laser scanning microscopy for its fast scanning ability and random-addressing capability. However, its application in two-photon microscopy is frustrated by the dispersion of the AOD, which results in beam distortion and pulse lengthening. We report the analysis of simultaneous compensation for the angular dispersion and temporal dispersion of the AOD by merely introducing a single dispersive element such as a prism or a grating. Besides serving as a scanner, the AOD is also a part of the compressor pair by integrating the dispersive nature of the AO interaction. This compensation principle is effective for both one-dimensional (1-D) AOD and two-dimensional (2-D) AOD scanning. Switching from a 1-D to a 2-D system requires proper optical alignment with the compensation element, but does not involve any new components. Analytical expressions are given to illustrate the working principle and to help with understanding the design of the system. Fluorescence images of beads and cells are shown to demonstrate the performance of two-photon microscopy when applying this compensated 2-D AOD as scanner.

  6. Novel time-of-flight fiber dispersion measurement technique using supercontinuum light sources and acousto-optical tunable filters.

    PubMed

    Blume, Niels Göran; Wagner, Steven

    2015-07-20

    Long-distance fiber links require precise knowledge of fiber dispersion characteristics. Similar dispersion characteristics are necessary for supercontinuum broadband laser absorption spectroscopy (SCLAS) to allow proper data evaluation and species concentration determination, as well as numerous other applications. In this work, a time-of-flight approach to measuring the dispersion characteristic of fibers with supercontinuum laser light sources (SCLs) and acousto-optical tunable filters (AOTFs) is presented. Broadband emission of the SCL is filtered with a narrowband AOTF and dispersed in time by the fiber under test. By using the wavelength-specific delay, the dispersion characteristic can be calculated. The technique is especially suited for longer fibers and was verified against a state-of-the-art phase-shift-based dispersion measurement system. Advantages of the new approach include solely utilizing SCLAS system components, as well as a high level of automation and wide spectral coverage, ranging from 1100 to 1700 nm in a single measurement setup.

  7. Acousto-Optic Interactions.

    DTIC Science & Technology

    The document reports the results of the experimental and theoretical investigation of acousto - optic interactions in guided wave structure for optical...waves and acoustic surface waves and experimental results of isotropic and anisotropic diffraction in LiNbO3 and quartz. A simple acousto - optic plate...CVD ZnO films on sapphire, which may be needed for the acousto - optic devices in thin films are also included. (Author)

  8. Acousto-Optical Imaging Spectropolarimeter

    NASA Technical Reports Server (NTRS)

    Saif, Babak; Glenar, David; Zimmerman, Robert; Seery, Bernard

    1992-01-01

    Imaging spectropolarimeter designed around acousto-optical tunable filter (AOTF) takes polarization-specific spectral images of solid surfaces, aerosols, and absorption and emission phenomena in gas phase, at wavelengths from 500 to 1,000 nm. Produces side-by-side spectral images in two mutually perpendicular polarizations, one corresponding to ordinary, other corresponding to extraordinary waves in acousto-optical material. Offers large aperture, high resolving power, and rapid tunability, with no moving parts.

  9. Acousto-Optic Adaptive Processing (AOAP).

    DTIC Science & Technology

    1983-12-01

    I ~.sls Phe Report December 1963 •- ACOUSTO - OPTIC ADAPTIVE <PROCESSING (AOAP) General Electric Company W. A. Penn, D. R. Morgan, A. Aridgides and M. L...numnber) Optical signal processing Acousto - optical modulators Adaptive signal processing - Adaptive sidelobe cancellation 20. ABSTRACT (Contnue an...required operations of multiplication and time delay are provided by acousto - optical (AO) delay lines. The required time integraticO is provided by

  10. Wideband Waveguide Acousto-Optic Bragg Cell.

    DTIC Science & Technology

    The results of an effort to improve the performance specifications of acousto - optic Bragg cells are reported. Various configurations of multiple...would provide a 700 MHz acousto - optic bandwidth. Investigated were Bragg cells fabricated on Ti diffused LiNb03 waveguides as well as Ti diffused LiNb03

  11. Experimental Investigation of Acousto-Optic Communications

    DTIC Science & Technology

    2003-09-01

    acousto - optic sensor shows promise as a means for detecting acoustic data projected towards the water surface from a submerged platform. The laser...simulation studies were conducted to demonstrate acousto - optic sensor feasibility for obtaining robust recordings of acoustic communication signals across

  12. Acousto-optic effect in random media

    NASA Astrophysics Data System (ADS)

    Hoskins, Jeremy G.; Schotland, John C.

    2017-03-01

    We consider the acousto-optic effect in a random medium. We derive the radiative transport equations that describe the propagation of multiply scattered light in a medium whose dielectric permittivity is modulated by an acoustic wave. Using this result, we present an analysis of the sensitivity of an acousto-optic measurement to the presence of a small absorbing inhomogeneity.

  13. Kilohertz generation of high contrast polarization states for visible femtosecond pulses via phase-locked acousto-optic pulse shapers

    SciTech Connect

    Seiler, Hélène; Walsh, Brenna; Palato, Samuel; Kambhampati, Patanjali; Thai, Alexandre; Forget, Nicolas; Crozatier, Vincent

    2015-09-14

    We present a detailed analysis of a setup capable of arbitrary amplitude, phase, and polarization shaping of broadband visible femtosecond pulses at 1 kHz via a pair of actively phase stabilized acousto-optic programmable dispersive filters arranged in a Mach-Zehnder interferometer geometry. The setup features phase stability values around λ/225 at 580 nm as well as degrees of polarization of at least 0.9 for any polarization state. Both numbers are important metrics to evaluate a setup's potential for applications based on polarization-shaped femtosecond pulses, such as fully coherent multi-dimensional electronic spectroscopy.

  14. Acousto-Optic Beam Steering Study

    DTIC Science & Technology

    1994-08-01

    8217111 INK $ 1 1 illl iII Ill i, R L-TR-94-121 !1!1Il t 11I1!I!11! ilI, / Final Technical Report August 1994 ACOUSTO - OPTIC BEAM STEERING STUDY Harris...contractual obligations or notices on a specific document require that it be returned. For i ..........I ,, ACOUSTO - OPTIC BEAM STEERING STUDY H. W...4. TITLE AND SUBTITLE 5. FUNDING NUMBERS ACOUSTO - OPTIC BEAM STEERING STUDY C - F30602-91-C-0131 PE - 63215C 6. AUTHOR(S) PR - 1405 TA - 02 H. W

  15. Acousto-Optically Addressed Fourier Transform Matched Filters.

    DTIC Science & Technology

    1984-08-01

    ACOUSTO - OPTIC DEFLECTOR .............................. II. THE EXPERIMENT............................................. 2 FV XPERIMENTAl. RESULTS...tcohniqtie1 arc addressed using an acousto - optic beam deflector with good correlation signals resulting. Th is method may be used to address arrays of matched...essentially the standard Vander Lugt method for making matched filters, except for the addition of the acousto - optic deflector between the Fourier

  16. Acousto-optic spectrometer for radio astronomy

    NASA Technical Reports Server (NTRS)

    Chin, G.; Buhl, D.; Florez, J. M.

    1980-01-01

    A prototype acousto-optic spectrometer which uses a discrete bulk acoustic wave Itek Bragg cell, 5 mW Helium Neon laser, and a 1024 element Reticon charge coupled photodiode array is described. The analog signals from the photodiode array are digitized, added, and stored in a very high speed custom built multiplexer board which allows synchronous detection of weak signals to be performed. The experiment is controlled and the data are displayed and stored with an LSI-2 microcomputer system with dual floppy discs. The performance of the prototype acousto-optic spectrometer obtained from initial tests is reported.

  17. Construction and characterization of ultraviolet acousto-optic based femtosecond pulse shapers

    SciTech Connect

    Mcgrane, Shawn D; Moore, David S; Greenfield, Margo T

    2008-01-01

    We present all the information necessary for construction and characterization of acousto optic pulse shapers, with a focus on ultraviolet wavelengths, Various radio-frequency drive configurations are presented to allow optimization via knowledgeable trade-off of design features. Detailed performance characteristics of a 267 nm acousto-optic modulator (AOM) based pulse shaper are presented, Practical considerations for AOM based pulse shaping of ultra-broad bandwidth (sub-10 fs) amplified femtosecond pulse shaping are described, with particular attention paid to the effects of the RF frequency bandwidth and optical frequency bandwidth on the spatial dispersion of the output laser pulses.

  18. Optimization of a femtosecond Ti : sapphire amplifier using a acouto-optic programmable dispersive filter and a genetic algorithm.

    SciTech Connect

    Korovyanko, O. J.; Rey-de-Castro, R.; Elles, C. G.; Crowell, R. A.; Li, Y.

    2006-01-01

    The temporal output of a Ti:Sapphire laser system has been optimized using an acousto-optic programmable dispersive filter and a genetic algorithm. In-situ recording the evolution of spectral phase, amplitude and temporal pulse profile for each iteration of the algorithm using SPIDER shows that we are able to lock the spectral phase of the laser pulse within a narrow margin. By using the second harmonic of the CPA laser as feedback for the genetic algorithm, it has been demonstrated that severe mismatch between the compressor and stretcher can be compensated for in a short period of time.

  19. Feedback and Acousto Optic Isolation Effects on Laser Stability.

    DTIC Science & Technology

    1977-03-01

    This paper analyzes the effect of optical feedback on laser frequency stability and the acousto optic isolator concept, which was demonstrated...nonlinearity such as saturation in the laser medium. The analysis mathematically corroborates the initial acousto optic isolator concept and the...limited experimental data available. In the study of the acousto optic isolator, it was determined that an acceptable analytic expression for the

  20. Rigorous coupled wave analysis of acousto-optics with relativistic considerations.

    PubMed

    Xia, Guoqiang; Zheng, Weijian; Lei, Zhenggang; Zhang, Ruolan

    2015-09-01

    A relativistic analysis of acousto-optics is presented, and a rigorous coupled wave analysis is generalized for the diffraction of the acousto-optical effect. An acoustic wave generates a grating with temporally and spatially modulated permittivity, hindering direct applications of the rigorous coupled wave analysis for the acousto-optical effect. In a reference frame which moves with the acoustic wave, the grating is static, the medium moves, and the coupled wave equations for the static grating may be derived. Floquet's theorem is then applied to cast these equations into an eigenproblem. Using a Lorentz transformation, the electromagnetic fields in the grating region are transformed to the lab frame where the medium is at rest, and relativistic Doppler frequency shifts are introduced into various diffraction orders. In the lab frame, the boundary conditions are considered and the diffraction efficiencies of various orders are determined. This method is rigorous and general, and the plane waves in the resulting expansion satisfy the dispersion relation of the medium and are propagation modes. Properties of various Bragg diffractions are results, rather than preconditions, of this method. Simulations of an acousto-optical tunable filter made by paratellurite, TeO(2), are given as examples.

  1. Acousto-optic tunable filter multispectral imaging system

    NASA Technical Reports Server (NTRS)

    Cheng, Li-Jen; Chao, Tien-Hsin; Reyes, George

    1992-01-01

    This paper discusses recent activities of Jet Propulsion Laboratory in the development of a new type of remote sensing multispectral imaging instruments using acousto-optic tunable filter (AOTF) as programmable bandpass filter. This remote sensor provides real-time operation; observational flexibility; measurements of spectral, spatial, and polarization information using a single instrument; and compact, solid state structure without moving parts. Two microcomputer-controlled AOTF imaging spectrometer breadboard systems were designed and built. One operates in the wavelength range of 0.48-0.76 micron and the other in the range of 1.2-2.5 micron. Experiments were performed using these two systems to observe geological and botanical objects in laboratory and outdoor environment. Results have demonstrated the feasibility of using the AOTF multispectral imaging system as a real-time versatile remote sensor with operational flexibility for future Army tactical applications.

  2. Scheme for Terminal Guidance Utilizing Acousto-Optic Correlator.

    DTIC Science & Technology

    longitudinally extending acousto - optic device as index of refraction variation pattern signals. Real time signals corresponding to the scene actually being viewed...by the vehicle are propagated across the stored signals, and the results of an acousto - optic correlation are utilized to determine X and Y error

  3. Signal Coherence Recovery Using Acousto-Optic Fourier Transform Architectures

    DTIC Science & Technology

    1990-06-14

    processing of data in ground- and space-based applications. We have implemented a prototype one-dimensional time-integrating acousto - optic (AO) Fourier...theory of optimum coherence recovery (CR) applicable in computation-limited environments. We have demonstrated direct acousto - optic implementation of CR

  4. Passive long range acousto-optic sensor

    NASA Astrophysics Data System (ADS)

    Slater, Dan

    2006-08-01

    Alexander Graham Bell's photophone of 1880 was a simple free space optical communication device that used the sun to illuminate a reflective acoustic diaphragm. A selenium photocell located 213 m (700 ft) away converted the acoustically modulated light beam back into sound. A variation of the photophone is presented here that uses naturally formed free space acousto-optic communications links to provide passive multichannel long range acoustic sensing. This system, called RAS (remote acoustic sensor), functions as a long range microphone with a demonstrated range in excess of 40 km (25 miles).

  5. Acousto-Optic Beam Sampler, Part 2. Green’s Function Solution to Acousto-Optic Interaction Problem.

    DTIC Science & Technology

    This part of the ’ Acousto - Optic Beam Sampler,’ series lays down the formalism behind the Green’s function integral approach to solving the acousto ... optic scattering problem. The advantage of this formulation which is applicable to gases is shown through developing the solution to the scattering

  6. JPL activities on development of acousto-optic tunable filter imaging spectrometer

    NASA Technical Reports Server (NTRS)

    Cheng, Li-Jen; Chao, Tien-Hsin; Reyes, George

    1992-01-01

    Recent activities of JPL in the development of a new type of imaging spectrometers for earth observation and planetary exploration are reported. This instrument uses the acousto-optic tunable filter (AOTF) as high resolution and fast programmable bandpass filter. AOTF operates in the principle of acousto-optic interaction in an anisotropic medium. This filter can be tuned in sequential, random, and multiwavelength access modes, providing observational flexibility. The diffraction process in the filter generates two diffracted monochromatic beams with polarization orthogonal to each other, creating a unique capability to measure both polarimetric and spectral properties of the incoming light simultaneously with a single instrument. The device gives wide wavelength operations with reasonably large throughput. In addition, it is in a compact solid-state structure without moving parts, providing system reliability. These attractive features give promising opportunities to develop a new generation of airborne/spaceborne and ground, real-time, imaging spectrometer systems for remote sensing applications.

  7. Exploring Novel Crystals and Designs for Acousto-Optic Devices

    NASA Astrophysics Data System (ADS)

    Pfeiffer, Jonathan B.

    Acousto-optic devices are a versatile technology that are driven electronically to precisely and rapidly control the intensity, frequency, and propagation direction of a laser beam. Applications include acousto-optic scanners, filters, mode lockers, and modulators. Despite the popularity of acousto-optic devices, there currently is no UV transparent device that can satisfy the requirements of the atomic clock and quantum computing communities. In this thesis, I describe my experimental efforts for discovering a new UV transparent, acousto-optic crystal that can meet the experimental requirements. I also present my graphical representations for locating practical and efficient acousto-optic designs in a given medium. The first part of this thesis describes how to measure the elastic-stiffness and photoelastic coefficients of a given crystal. The elastic-stiffness coefficients are essential for designing acousto-optic devices because they determine the velocity, diffraction, and polarization of acoustic waves in a given medium. I used both resonant ultrasound spectroscopy and a modified version of Schaefer-Bergman diffraction to measure elastic coefficients. I discuss in detail the strengths, differences, and similarities of the two experiments. The photoelastic coefficients are necessary for determining the diffraction efficiency of a given acousto-optic geometry. Similar to the elastic coefficients, I employ a modified version of the Schaefer-Bergmann experiment to measure the photoelastic coefficients. I corroborate the measured results with the well established Dixon experiment. The second part of this thesis describes four different graphical representations that help locate practical and efficient acousto-optic designs. I describe in detail each algorithm and how to interpret the calculated results. Several examples are provided for commonly used acosuto-optic materials. The thesis concludes by describing the design and performance of an acousto-optic frequency

  8. Physical basis of Acousto-Optical Imaging

    NASA Astrophysics Data System (ADS)

    Jarrett, Christopher W.

    Acousto-Optical Imaging (AOI) is an emerging hybrid multi-modal imaging technique that combines the high spatial resolution of ultrasound with the versatile molecular sensitivity of optical detection to improve upon the limited spatial resolution of purely optical techniques. However, the precise mechanisms that contribute to the contrast in AOI have been relatively little explored, and the influence of several physical factors are not well understood. Kobayashi et al. previously reported observations of modulated fluorescence capable of locating fluorescent regions of interest within turbid media, suggesting the ability to use incoherent light for AOI. This research aimed to develop and extend such an approach for applications in biomedical imaging. We aimed to demonstrate the modulation of incoherent light by ultrasound and investigate what factors affect the magnitude of such effects. We proposed the following specific aims: (1) To design and develop instrumentation to detect and quantify Acousto-Optical interactions; (2) To evaluate the contributions of different mechanisms of ultrasonic modulation of fluorescence and the factors that influence these effects in turbid media like tissues; (3) To test a variety of fluorescent contrast agents to determine if their light output may be directly affected by ultrasonic modulation, which would suggest a novel approach to AOI. This work achieved these aim. We were successful in designing and developing an experimental apparatus capable of detecting and quantifying Acousto-Optical Interactions. We determined this signal scales linearly with squared ultrasound pressure but unlike the interpretation of Kobayashi et al., we found the apparent modulated fluorescence is dominated by acoustic modulation of the excitation light. In addition, we report a novel finding that ultrasound can modulate incoherent light via modulation of tissue absorption and density, incidentally providing a new way to image sound fields. Lastly, we

  9. A Compact Bulk Acousto-Optic Time Integrating Correlator.

    DTIC Science & Technology

    1984-11-01

    AD-A156 668 A COMPACT BULK ACOUSTO - OPTIC TIME INTEGRATING 1/1 CORRELATOR(U) ELECTRONICS RESEARCH LAB ADELAIDE (AUSTRALIA) D A FOGG NOV 84 ERL-9323-TR...DEFENCE RESEARCH CENTRE SALISBURY SOUTH AUSTRALIA TECHNICAL REPORT ER L-0323-TR A COMPACT BULK ACOUSTO - OPTIC TIME INTEGRATING CORRELATOR D.A.B. FOGG...LABORATORY TECHNICAL REPORT ERL-0323-TR A COMPACT BULK ACOUSTO - OPTIC TIME INTEGRATING CORRELATOR D.A.B. Fogg SUMMARY This report describes the design and

  10. Modeling the noise figure of an acousto-optic receiver

    NASA Astrophysics Data System (ADS)

    Ristic, V. M.; Lee, J. P. Y.

    1996-02-01

    By defining the processing gain of an acousto-optic receiver as the ratio of the signal-to-noise ratio at the output of the detector to the signal-to-noise ratio of the intermediate-frequency input, one can model a noise figure for the acousto-optic receiver. The noise figure has a minimum of 0 dB and depends on the ratio of the noise power (internal to the acousto-optic cell) to the intermediate-frequency input noise power multiplied by the frequency and the spatially dependent exponential factor.

  11. Frequency Resolution of an Acousto-Optical Spectrometer

    DTIC Science & Technology

    1993-08-03

    AD-A267 822 FOREIGN AEROSPACE SCIENCE AND TECHNOLOGY CENTER DTIC S ELECTE AUG 111993 D FREQUENCY RESOLUTION OF AN ACOUSTO - OPTICAL SPECTROMETER by... D ~t• i,5"t~o’• A i +’- 1 Av.:+l +,O ,J Dist Avi! .. DTIC QUALITY I1V’PEMTED 3 FREQUENCY RESOLUTION OF AN ACOUSTO - OPTICAL SPECTROMETER... optical spectrometer (AOS) system as affected by the acousto - optical deflector and the coherent light beam truncation ratio, and examines the response

  12. Acousto-optic filtering of lidar signals

    NASA Astrophysics Data System (ADS)

    Kolarov, G.; Deleva, A.; Mitsev, Ts.

    1992-07-01

    The predominant part of the noise in lidar receivers is created by the background radiation; therefore, one of the most important elements of the receiving optics is a spectrally selecting filter placed in front of the photodetector. Interference filters are usually used to transmit a given wavelength. Specific properties of the interference filters, such as simple design, reliability, small size, and large aperture, combined with high transmission coefficient and narrow spectral band, make them the preferred spectral device in many cases. However, problems arise in applications such as the Differential Absorption Lidar (DIAL) technique, where fast tuning within a wide spectral region is necessary. Tunable acousto-optical filters (TAOF), used recently in astrophysical observations to suppress the background radiation, can be employed with success in lidar sounding. They are attractive due to the possibility for fast spectral scanning with a narrow transmission band. The TAOF's advantages are fully evident in DIAL lidars where one must simultaneously receive signals at two laser frequencies.

  13. Acousto-optic filtering of lidar signals

    NASA Technical Reports Server (NTRS)

    Kolarov, G.; Deleva, A.; Mitsev, TS.

    1992-01-01

    The predominant part of the noise in lidar receivers is created by the background radiation; therefore, one of the most important elements of the receiving optics is a spectrally selecting filter placed in front of the photodetector. Interference filters are usually used to transmit a given wavelength. Specific properties of the interference filters, such as simple design, reliability, small size, and large aperture, combined with high transmission coefficient and narrow spectral band, make them the preferred spectral device in many cases. However, problems arise in applications such as the Differential Absorption Lidar (DIAL) technique, where fast tuning within a wide spectral region is necessary. Tunable acousto-optical filters (TAOF), used recently in astrophysical observations to suppress the background radiation, can be employed with success in lidar sounding. They are attractive due to the possibility for fast spectral scanning with a narrow transmission band. The TAOF's advantages are fully evident in DIAL lidars where one must simultaneously receive signals at two laser frequencies.

  14. Designing an acousto-optical spectrometer for Guillermo Haro Astrophysical Observatory

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Alexandre S.; Arellanes Bernabe, Adan Omar; Chavushyan, Vahram

    2013-09-01

    The Guillermo Haro astrophysical observatory (Mexico) realizes investigations in the visible and near-infrared range . Actually, the classical grating spectrometer with mechanically removable optical filters and diffraction gratings is exploited there. Unfortunately, the regular process of changing the diffraction gratings with different resolutions and recalibrating the spectrometer is inconvenient and wastes expensive time for observations. This is why exploiting an acousto-optical cell as a dynamic dispersive element is practically desirable, because potentially it realizes tuning the spectral resolution and the range of observation electronically and excludes filters. Some aspects of inserting just one dynamic acousto-optical diffraction grating instead of a set of the traditional static diffraction gratings are preliminarily considered.

  15. Acousto-Optics as an Efficient Method for Physical Measurements

    NASA Astrophysics Data System (ADS)

    Kulakov, Sergei V.; Balysheva, Olga L.; Zhdanov, Arcenii Yu.; Kludzin, Victor V.; Shakin, Oleg V.

    In addition to acousto-optic information processing and manufacturing of such devices, the interaction between optical and acoustic waves are an efficient method for physical measurements. The paper analyses the potential of the acousto-optic method for measurement and investigation of crystal properties. It also presents some examples of this method applied to such measurements and investigations. The acousto-optic implementation of the pulse-phase method is used for acoustic velocity measurements. Velocities in an arbitrary directions can be measured using the Shaefer-Bergman method (the visualization of the angular distribution of the inverse phase velocities) together with the pulse-phase method. The matrices of crystal elastic coefficients can be evaluated using the Shaefer-Bergman patterns, using the minimum number of tested samples. The Schlieren (shadow) image method can give information both on the characteristics of acoustic and optical fields. The acousto-optic interaction is Efficient Method for determination of elastic material nonlinearity parameters.

  16. Laser-Based Acousto-Optic Uplink Communications Technique

    DTIC Science & Technology

    2003-08-18

    An apparatus for enabling acousto - optic communication comprising an in-water platform comprising means for emitting an acoustic signal to an acousto ...portion of the first interrogation beam and a second laser beam formed from the reflection of the first interrogation beam off of the acousto - optic interaction... optic interaction zone, an in-air platform comprising the ability for transmitting a first optical interrogation beam, the ability for receiving a

  17. Acousto-optical properties of metamaterials

    SciTech Connect

    Pustovoit, V I

    2016-02-28

    The possibility of the effective use of metamaterials in acousto-optics is demonstrated. It is shown that photoelastic constants that determine a change in the dielectric constant of a heterogeneous medium under the action of a sound wave can significantly exceed the corresponding constants for conventional crystals. We have analysed the mechanisms of the dielectric constant variation in a heterogeneous medium consisting of nanoparticles in the form of ellipsoids and have found explicitly the values of the photoelastic constants. It is shown that the mechanism of the dielectric constant variation in a longitudinal sound wave is reduced to a change in the local concentration of nanoparticles in the bulk and in a transverse acoustic wave – to a local rotation of space-oriented nanoellipsoids. It is also shown that the use of metamedia with a nonuniform distribution of nanoparticles provides a unique opportunity for designing qualitatively new instruments and devices that cannot be produced on the basis of conventional crystals. It is noted that metamaterials open ample opportunities for creating devices of the IR region of the spectrum due to the absence of restrictions on the size of such media. (metamaterials)

  18. Projecting multichannel acousto-optic cells with low crosstalk

    NASA Astrophysics Data System (ADS)

    Kludzin, Victor V.; Kulakov, Sergei V.; Molotok, Victor V.

    1997-09-01

    An acousto-optic method for spectral processing of rf signals is proposed. This method is based on a multichannel cell with frequency separated channels within a given band. The optimum structure of such a system is a multichannel cell with the slow shear mode in the (110) direction in TeO2 and far- axis anisotropic diffraction. A system with 12 channels covering the frequency band of 84 - 96 MHz with the bandwidth of each channel of approximately 0.5 MHz and frequency separation of approximately 1 MHz is experimentally studied. An optical beam which spreads in the plane orthogonal to that of the acousto-optic interaction must be used in this system. The influence of the transducer electrode shape on the acoustic crosstalk in the adjacent channels is studied. The experimental results are in good agreement with the calculated data. The expansion of acousto-optic processing requires that multichannel acousto-cells be used. Narrow-band acousto-optic interaction regimes can be used for frequency-domain filtering of rf signals in multichannel cells. This scheme can be used for the parallel analysis of an rf signal spectrum. This paper describes the process of the design and manufacturing of a multichannel acousto-optic filter for an rf signal with a narrow bandwidth of each channel and estimates its possible parameters. Each channel of the filter is tuned to its own frequency different from those of the adjacent channels within a given overall bandwidth of the whole device.

  19. Error Measurements in an Acousto-Optic Tunable Filter Fiber Bragg Grating Sensor System

    DTIC Science & Technology

    1994-05-01

    Acousto - Optic Tunable Filter--Fiber Bragg Grating (AOTF-FBG) system. This analysis was targeted to investigate the measurement error in the AOTF-FBG system...Fiber bragg grating, Wavelength division multiplexing, Acousto - optic tunable filter.

  20. Compact tunable microwave filter using retroreflective acousto-optic filtering and delay controls.

    PubMed

    Riza, Nabeel A; Ghauri, Farzan N

    2007-03-01

    Programmable broadband rf filters are demonstrated using a compact retroreflective optical design with an acousto-optic tunable filter and a chirped fiber Bragg grating. This design enables fast 34 micros domain analog-mode control of rf filter time delays and weights. Two proof-of-concept filters are demonstrated including a two-tap notch filter with >35 dB notch depth and a four-tap bandpass filter. Both filters have 2-8 GHz tunability and a 34 micros reset time.

  1. The Role of Adaptive Photorefractive Power Limiting on Acousto-Optic Radio Frequency (RF) Signal Excision

    DTIC Science & Technology

    2001-12-01

    Adaptive RF interference reduction for broadband communication systems continues to be problematic. The acousto - optic RF signal excision system...novel photorefractive optical power limiting device to achieve adaptive notch filtering, and multi- channel acousto - optic deflection to achieve angle...of-arrival signal discrimination at the notch filter. This dissertation describes basic principles of acousto - optic RF signal excision, including

  2. Theory and Experiment Analysis of Two-Dimensional Acousto-Optic Interaction.

    DTIC Science & Technology

    1995-01-03

    The universal coupled wave equation of two dimensional acousto optic effect has been deduced and the solution of normal Raman-Hath acousto optic diffraction...was derived from it. The theory was compared with the experimental results of a two dimensional acousto optic device consisting of two one dimensional modulators. The experiment results agree with the theory. (AN)

  3. Acousto-optic collinear filter with optoelectronic feedback

    NASA Astrophysics Data System (ADS)

    Mantsevich, S. N.; Balakshy, V. I.; Kuznetsov, Yu. I.

    2017-04-01

    A spectral optoelectronic system combining a collinear acousto-optic cell fabricated of calcium molybdate single crystal and a positive electronic feedback is proposed first and examined theoretically and experimentally. The feedback signal is formed at the cell output due to the optical heterodyning effect with the use of an unconventional regime of cell operation. It is shown that the feedback enables controlling spectral characteristics of the acousto-optic cell, resulting in enhancing the spectral resolution and the accuracy of optical wavelength determination. In the experiment, maximal filter passband narrowing was as great as 37 times.

  4. Acousto-optics of liquid crystals: Yesterday, today, and tomorrow

    NASA Astrophysics Data System (ADS)

    Kapustina, O. A.

    2014-09-01

    The most important results of the recent theoretical and experimental studies in the field of acousto-optics of liquid crystals (LCs) in research lines initiated by the pioneering studies of Professor A.P. Kapustin at the Institute of Crystallography of the Russian Academy of Sciences and carried out at the Acoustic Institute of the Russian Academy of Sciences are generalized and analyzed. These lines include the study of the nature of acoustically induced supramolecular structures in nematic liquid crystals (NLCs) and cholesteric liquid crystals (CLCs) and the development of physical bases of practical LC acousto-optics, related to the detection of acoustic signals.

  5. Application of acousto-optic actuator applied in holographic system

    NASA Astrophysics Data System (ADS)

    Ling, FuRi; Wang, Biao

    2002-09-01

    In this paper, we discuss acousto-optical scanning and deflection, and design an acousto-optical actuator for steering the laser beam in the direction of vertical and horizon. In this system a laser whose wavelength is 532 nm is used and is expanded by a cylindrical lens. This horizontal actuator produces the horizontal deflection and the spherical lens following the horizontal actuator rotates the beam to match the aperture of the vertical actuator. The cylindrical lens restores the beam to its original circular cross-section, after which the microscope optics brings it to a focus in the lithium niobate crystal in which we store information.

  6. Designing the acousto-optical cell for optical spectrometer incorporated into the Guillermo Haro Astrophysical Observatory

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Alexandre S.; Arellanes Bernabe, Adan Omar; Chavushyan, Vahram

    2013-09-01

    Optical spectrometer of the Guillermo Haro astrophysical observatory (Mexico) exploits mechanically removable traditional static diffraction gratings as dispersive elements. There is a set of the static gratings with the slit-density 50 - 600 lines/mm and optical apertures 9 cm x 9 cm that provide the first order spectral resolution from 9.6 to 0.8 A/pixel, respectively, in the range 400 - 1000 nm. However, the needed mechanical manipulations, namely, replacing the static diffraction gratings with various resolutions and following recalibration of spectrometer within studying even the same object are inconvenient and lead to losing rather expensive observation time. We suggest exploiting an acousto-optical cell, i.e. the dynamic diffraction grating tunable electronically, as dispersive element in that spectrometer. Involving the acousto-optical technique, which can potentially provide electronic control over the spectral resolution and the range of observations, leads to possible eliminating the above-mentioned demerits and to improving the efficiency of analysis.

  7. AIMS: Acousto-optic imaging spectrometer for spectral mapping of solid surfaces

    NASA Astrophysics Data System (ADS)

    Glenar, David A.; Blaney, Diana L.; Hillman, John J.

    2003-01-01

    A compact, two-channel acousto-optic tunable filter (AOTF) camera is being built at GSFC as a candidate payload instrument for future Mars landers or small-body rendezvous missions. This effort is supported by the NASA Mars Instrument Development Program (MIDP), Office of Space Science Advanced Technologies and Mission Studies. Acousto-optic Imaging Spectrometer (AIMS) is electronically programmable and provides arbitrary spatial and spectral selection from 0.48 to 2.4 μm. The geometric throughput of AOTF's are well matched to the requirements for lander mounted cameras since (I) they can be made very compact, (II) "slow" (f/14-f/18) optics required for large depth-of-field fall well within the angular aperture limit of AOTF's, and (III) they operate at low ambient temperatures. A breadboard of the AIMS short-wavelength channel is now being used for spectral imaging of high-interest Mars analog materials (iron oxides, carbonates, sulfates and sedimentary basalts) as part of the initial instrument validation exercises.

  8. Wide-band acousto-optic deflectors for large field of view two-photon microscope.

    PubMed

    Jiang, Runhua; Zhou, Zhenqiao; Lv, Xiaohua; Zeng, Shaoqun

    2012-04-01

    Acousto-optic deflector (AOD) is an attractive scanner for two-photon microscopy because it can provide fast and versatile laser scanning and does not involve any mechanical movements. However, due to the small scan range of available AOD, the field of view (FOV) of the AOD-based microscope is typically smaller than that of the conventional galvanometer-based microscope. Here, we developed a novel wide-band AOD to enlarge the scan angle. Considering the maximum acceptable acoustic attenuation in the acousto-optic crystal, relatively lower operating frequencies and moderate aperture were adopted. The custom AOD was able to provide 60 MHz 3-dB bandwidth and 80% peak diffraction efficiency at 840 nm wavelength. Based on a pair of such AOD, a large FOV two-photon microscope was built with a FOV up to 418.5 μm (40× objective). The spatiotemporal dispersion was compensated simultaneously with a single custom-made prism. By means of dynamic power modulation, the variation of laser intensity within the FOV was reduced below 5%. The lateral and axial resolution of the system were 0.58-2.12 μm and 2.17-3.07 μm, respectively. Pollen grain images acquired by this system were presented to demonstrate the imaging capability at different positions across the entire FOV.

  9. Acousto-optic infrared spectral imager for Pluto fast flyby

    NASA Technical Reports Server (NTRS)

    Glenar, D. A.; Hillman, J. J.

    1993-01-01

    Acousto-optic tunable filters (AOTF's) enable the design of compact, two-dimensional imaging spectrometers with high spectral and spatial resolution and with no moving parts. Tellurium dioxide AOTF's operate from about 400 nm to nearly 5 microns, and a single device will tune continuously over one octave by changing the RF acoustic frequency applied to the device. An infrared (1.2-2.5 micron) Acousto-Optic Imaging Spectrometer (AImS) was designed that closely conforms to the surface composition mapping objectives of the Pluto Fast Flyby. It features a 75-cm focal length telescope, infrared AOTF, and 256 x 256 NICMOS-3 focal plane array for acquiring narrowband images with a spectral resolving power (lambda/delta(lambda)) exceeding 250. We summarize the instrument design features and its expected performance at the Pluto-Charon encounter.

  10. Acousto-optic laser projection systems for displaying TV information

    SciTech Connect

    Gulyaev, Yu V; Kazaryan, M A; Mokrushin, Yu M; Shakin, O V

    2015-04-30

    This review addresses various approaches to television projection imaging on large screens using lasers. Results are presented of theoretical and experimental studies of an acousto-optic projection system operating on the principle of projecting an image of an entire amplitude-modulated television line in a single laser pulse. We consider characteristic features of image formation in such a system and the requirements for its individual components. Particular attention is paid to nonlinear distortions of the image signal, which show up most severely at low modulation signal frequencies. We discuss the feasibility of improving the process efficiency and image quality using acousto-optic modulators and pulsed lasers. Real-time projectors with pulsed line imaging can be used for controlling high-intensity laser radiation. (review)

  11. Electro-optic and Acousto-optic Laser Beam Scanners

    NASA Astrophysics Data System (ADS)

    Römer, G. R. B. E.; Bechtold, P.

    Optical solid state deflectors rely on the electro-optical or acousto-optic effect. These Electro-Optical Deflectors (EODs) and Acousto-Optical Deflectors (AODs) do not contain moving parts and therefore exhibit high deflection velocities and are free of drawbacks associated with mechanical scanners. A description of the principles of operation of EODs and AODs is presented. In addition, characteristics, properties and the (dis)advantages of EODs and AODs, when compared to mirror based mechanical deflectors, is discussed. Deflection angles, speed and accuracy are discussed in terms of resolvable spots and related quantities. Also, response time, damage threshold, efficiency and the type and magnitude of beam distortions is addressed. Optical deflectors are characterized by high angular deflection velocities, but small deflection angles. Whereas mechanical mechanical scanners are characterized by relatively small deflection velocities, but large deflection angles. Arranging an optical deflector and a mechanical scanner in series allows to take advantage of the best of both worlds.

  12. Fiber-Coupled Acousto-Optical-Filter Spectrometer

    NASA Technical Reports Server (NTRS)

    Levin, Kenneth H.; Li, Frank Yanan

    1993-01-01

    Fiber-coupled acousto-optical-filter spectrometer steps rapidly through commanded sequence of wavelengths. Sample cell located remotely from monochromator and associated electronic circuitry, connected to them with optical fibers. Optical-fiber coupling makes possible to monitor samples in remote, hazardous, or confined locations. Advantages include compactness, speed, and no moving parts. Potential applications include control of chemical processes, medical diagnoses, spectral imaging, and sampling of atmospheres.

  13. Bending effect on fiber acousto-optic mode coupling.

    PubMed

    Zhao, Jianhui; Liu, Xiaoming; Wang, Yan; Luo, Ye

    2005-08-20

    The acousto-optic effect in a bent fiber is studied experimentally and numerically by using the scalar finite-element method. The resulting transmission spectra show that new mode-coupling peaks appear due to the breaking of the mode spatial symmetry. The strength of new peaks increases as the fiber-bending curvature increases with a redshift or blueshift in wavelength, strongly depending on the orientation of fiber bending with respect to the acoustic-wave vibration direction.

  14. High-efficiency acousto-optic coupling in phoxonic resonator based on silicon fishbone nanobeam cavity.

    PubMed

    Chiu, Chien-Chang; Chen, Wei-Min; Sung, Kuen-Wei; Hsiao, Fu-Li

    2017-03-20

    We investigate the acousto-optic coupling rates between different acoustic resonance modes and a specified optical resonance mode in a one-dimensional phoxonic crystal fishbone nanobeam formed by periodically arranging semi-cylinders of air on both sides of a suspended silicon waveguide. The gradually tapered unit cells form optical and acoustic resonators. In acousto-optic coupling rate calculation, the acoustic fields and optical fields are obtained by steady state monochromatic analysis and eigen-mode computation, respectively. Results showed that the acoustic polarizations and symmetries of the acoustic resonance modes are dominant factors in the acousto-optic coupling efficiency, and appropriate selection of these parameters can prevent cancellation of acousto-optic interactions, thereby enhancing acousto-optic coupling rates. This study provides important insights that can be applied to acousto-optic device designs.

  15. Bulk and integrated acousto-optic spectrometers for molecular astronomy with heterodyne spectrometers

    NASA Technical Reports Server (NTRS)

    Chin, G.; Buhl, D.; Florez, J. M.

    1981-01-01

    A survey of acousto-optic spectrometers for molecular astronomy is presented, noting a technique of combining the acoustic bending of a collimated coherent light beam with a Bragg cell followed by an array of sensitive photodetectors. This acousto-optic spectrometer has a large bandwidth, a large number of channels, high resolution, and is energy efficient. Receiver development has concentrated on high-frequency heterodyne systems for the study of the chemical composition of the interstellar medium. RF spectrometers employing acousto-optic diffraction cells are described. Acousto-optic techniques have been suggested for applications to electronic warfare, electronic countermeasures and electronic support systems. Plans to use integrated optics for the further miniaturization of acousto-optic spectrometers are described. Bulk acousto-optic spectrometers with 300 MHz and 1 GHz bandwidths are being developed for use in the back-end of high-frequency heterodyne receivers for astronomical research.

  16. Ultrafast acousto-optic mode conversion in optically birefringent ferroelectrics

    PubMed Central

    Lejman, Mariusz; Vaudel, Gwenaelle; Infante, Ingrid C.; Chaban, Ievgeniia; Pezeril, Thomas; Edely, Mathieu; Nataf, Guillaume F.; Guennou, Mael; Kreisel, Jens; Gusev, Vitalyi E.; Dkhil, Brahim; Ruello, Pascal

    2016-01-01

    The ability to generate efficient giga–terahertz coherent acoustic phonons with femtosecond laser makes acousto-optics a promising candidate for ultrafast light processing, which faces electronic device limits intrinsic to complementary metal oxide semiconductor technology. Modern acousto-optic devices, including optical mode conversion process between ordinary and extraordinary light waves (and vice versa), remain limited to the megahertz range. Here, using coherent acoustic waves generated at tens of gigahertz frequency by a femtosecond laser pulse, we reveal the mode conversion process and show its efficiency in ferroelectric materials such as BiFeO3 and LiNbO3. Further to the experimental evidence, we provide a complete theoretical support to this all-optical ultrafast mechanism mediated by acousto-optic interaction. By allowing the manipulation of light polarization with gigahertz coherent acoustic phonons, our results provide a novel route for the development of next-generation photonic-based devices and highlight new capabilities in using ferroelectrics in modern photonics. PMID:27492493

  17. Acousto-Optic Spectrum Analyzer: Temporal Response and Detection of Pulsed Signals.

    DTIC Science & Technology

    1986-12-01

    ACOUSTO - OPTIC SPECTRUM ANALYZER: TEMPORAL RESPONSE AND I/i DETECTION OF PULSED SIGUALS(U) DEFENCE RESEARCH ESTABLISHMENT OTTANA (ONTARIO) J...8217:. -.....:.-...............--.. - ---:-..--.-..,. ,: i’,.. IJT~c FILE C P National Defe’ se + Deence nationale 0 0 ACOUSTO - OPTIC SPECTRUM ANALYZER: TEMPORAL RESPONSE AND DETECTION 0 OF PULSED...Ottawa |S, .±~ |-----------------------..,---.-- -- - - - rNatiorna! Defen~se Deterice r dornale ACOUSTO - OPTIC SPECTRUM ANALYZER: TEMPORAL RESPONSE

  18. Acousto-Optic Processing of 2-D Signals Using Temporal and Spatial Integration.

    DTIC Science & Technology

    1986-04-29

    AD-AI?3 411 ACOUSTO - OPTIC PROCESSING OF 2-D SIGNALS USING TEMPORAL 1/ AND SPATIAL INTEGR..(U) CRLIFORNIA INST OF TECH PASADENA DEPT OF ELECTRICAL...LECTE 3 FINAL REORT4 Submitted to: Al FORCE OFFICE OF SCIENTIFIC RESEARCH Grant Number AFOSR-82-0128 :A of % ACOUSTO - OPTIC PROCISSING OF 2-D SIGNALS...Psaltis, Applied Optics, Vol. 21, No. 3, 1 February 1982. (3) " Acousto - Optic /CCD Image Processor, Demetri Psaltis, Eung Gi Paek and Santosh Venkatesh

  19. The Study of the Phase Characteristics of Bragg Cells for Acousto-Optic Signal Processing

    DTIC Science & Technology

    1998-01-01

    THE FINAL REPORT ON THE SPECIAL CONTRACT SPC-97-4025 The Study of the Phase Characteristics of Bragg Cells for Acousto - Optic Signal Processing...for Acousto - Optic Signal Processing Unclassified 5a. CONTRACT NUMBER F6170897W0095 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Yurchenko...Characteristics of Bragg Cells for Acousto - Optic Signal Processing 5. FUNDING NUMBERS F6170897W0095 6. AUTHOR(S) Dr. Alexander Yurchenko 7. PERFORMING

  20. Acousto-Optic and Linear Electro-Optic Properties of Organic Polymeric Materials

    DTIC Science & Technology

    1989-04-27

    Naval Research Laboratory Washington, DC 20375-5000 NRL Memorandum Report 6454 od I3 Acousto - Optic and Linear Electro-Optic Properties of Organic...PROGRAM P1RC;EC7 ASK Arlington, VA 22217-5000 ELEMENT NO NO1 I1I TITLE (Include Security Classification) Acousto - Optic and Linear Electro-Optic...briefly discussing the important molecular properties for enhanced acousto ~ optic and electro-Ooptic ef fects and then relating these to "current

  1. 2-D Acousto-Optic Signal Processors for Simultaneous Spectrum Analysis and Direction Finding

    DTIC Science & Technology

    1990-11-01

    National Dfense Defence nationale 2-D ACOUSTO - OPTIC SIGNAL PROCESSORS FOR SIMULTANEOUS SPECTRUM ANALYSIS 00 AND DIRECTION FINDING (U) by NM Jim P.Y...Wr pdft .1w I0~1111191 3 05089 National DIfense Defence nationale 2-D ACOUSTO - OPTIC SIGNAL PROCESSORS FOR SIMULTANEOUS SPECTRUM ANALYSIS AND DIRECTION...Processing, J.T. Tippet et al., Eds., Chapter 38, pp. 715-748, MIT Press, Cambridge 1965. [6] A.E. Spezio," Acousto - optics for Electronic Warfare

  2. Guided-Wave TeO2 Acousto-Optic Devices

    DTIC Science & Technology

    1991-01-12

    In this research program, Guided-wave TeO2 Acousto - Optic Devices, the properties of surface acoustic waves on tellurium dioxide single crystal...surfaces has been studied for its potential applications as acousto - optic signal processing devices. Personal computer based numerical method has been...interaction with laser beams. Use of the acousto - optic probe, the surface acoustic wave velocity and field distribution have been obtained and compared

  3. Classification of Acousto-Optic Correlation Signatures of Spread Spectrum Signals Using Artificial Neural Networks

    DTIC Science & Technology

    1989-12-01

    Ohio ’aPw iorlipuab muo i 0I2, AFIT/GE/ENG/89D-10 CLASSIFICATION OF ACOUSTO - OPTIC CORRELATION SIGNATURES OF SPREAD SPECTRUM SIGNALS USING ARTIFICIAL...ENG/89D- 10 CLASSIFICATION OF ACOUSTO - OPTIC CORRELATION SIGNATURES OF SPREAD SPECTRUM SIGNALS USING ARTIFICIAL NEURAL NETWORKS THESIS John W. DeBerry...Captain, USAF AFIT/GE/ENG/89D- 10 Approved for public release; distribution unlimited. AFIT/GE/ENG/89D-10 CLASSIFICATION OF ACOUSTO - OPTIC CORRELATION

  4. Discussion on the Modelling and Processing of Signals fom an Acousto-Optic Spectrum Analyzer.

    DTIC Science & Technology

    1987-06-01

    AD-AIBS 639 DISCUSSION ON THE MODELLING AND PROCESSIN OF SIGNALS 1/1 FOR RN ACOUSTO - OPTIC SPECTRUM ANALYZER(U)G DFENCE RESERCH ESTABGLISHMENT OTTANA...8217’~ AV - I National DefenseI Defence nationale DISCUSSION ON THE MODELLING AND PROCESSING OF SIGNALS FROM AN ACOUSTO - OPTIC SPECTRUM ANALYZER by Guy...signals generated by an Acousto - Optic Spectrum Analyzer (AOSA). It also shows how this calculation can be related to pulse modu- lated signals. In its

  5. Three & Four Product Surface-Wave Acousto-Optic Time Integrating Correlators.

    DTIC Science & Technology

    four product correlated signals. A laser beam is split and shaped into first and second sheet beams. The first beam is directed to a first acousto - optic medium...where it is doubly diffracted by first and second signals. The second beam is directed to a second acousto - optic medium which is spatially...rotated 90 degs relative to the first acousto - optic medium where the second sheet beam is either singly diffracted by a third signal or doubly diffracted

  6. Design of acousto-optic chaos based secure free-space optical communication links

    NASA Astrophysics Data System (ADS)

    Ghosh, A. K.; Verma, P.; Cheng, S.; Huck, R. C.; Chatterjee, M. R.; Al-Saedi, M.

    2009-08-01

    We discuss the design of an acousto-optic cell based free space optical communication link where the data beam is made secure through chaos encryption. Using external signal modulation of the diffracted light from a hybrid acousto-optic cell chaos (or directly via incorporation in the sound-cell driver's bias voltage) encryption of data is possible. We have shown numerically that decryption of the encoded data is possible by using an identical acousto-optic system in the receiver.

  7. Acousto-optic tunable filter imaging spectrometers

    NASA Technical Reports Server (NTRS)

    Chao, Tien-Hsin; Yu, Jeffrey; Reyes, George; Rider, David; Cheng, Li-Jen

    1991-01-01

    A remote sensing multispectral imaging instrument is being developed that uses a high resolution, fast programmable acoustooptic tunable filter (AOTF) as the spectral bandpass filter. A compact and fully computer controllable AOTF-based imaging spectrometer that operates in the visible wavelength range (0.5-0.8 microns) has been built and tested with success. A second imaging spectrometer operating in the near-infrared wavelength range (1.2-2.4 microns) is also under experimental investigation. The design criteria meeting various system issues, such as imaging quality, spectral response, and field of view (FOV), are discussed. An experiment using this AOTF imaging spectrometer breadboard is described.

  8. Prolonged acousto-optic interaction with Lamb waves in crystalline plates

    PubMed

    Parygin; Vershoubskiy; Mozhaev; Weihnacht

    2000-03-01

    The propagation and acousto-optic interaction of Lamb modes in an anisotropic plate of tellurium dioxide (TeO2) are studied numerically and analytically. In the case of a Y-cut X-propagating TeO2 plate, the very high elastic anisotropy of the crystal greatly modifies the dispersion curves, giving rise to their multiple oscillations. The existence ranges of backward Lamb modes increase with the mode order contrary to the case of isotropic plates. The quasi-collinear light scattering by Lamb waves is considered. Owing to the structure of Lamb wave field, a simultaneous light diffraction at two different optical frequencies can take place while Lamb waves are excited only at the single frequency. It is demonstrated with the Z-cut (110)-propagating plate that a small change in the acoustic frequency can result in a significant shift in the frequency of the scattered light.

  9. Modelling Time-of-Arrival Ambiguities in a Combined Acousto-Optic and Crystal Video Receiver

    DTIC Science & Technology

    1995-11-01

    The probability of pulses overlapping in time being received by a combined acousto - optic /crystal video receiver is investigated. Theoretical analysis...number of pulses in that bandwidth. The number of frequency subbands with crystal detectors required to cover the acousto - optic receiver bandwidth is therefore a compromise between cost and complexity of implementation.

  10. Growth of Acousto-Optic Crystals for Applications in Infrared Region of Spectrum

    DTIC Science & Technology

    2005-04-30

    Acousto - optic (AO) modulators, deflectors, filters offer convenience, reliability, compact size and fast speed in regulation of optical beams. So far...extremely low acousto - optic figure of merit, which automatically results in high requirements on driving electric power and poor diffraction efficiency. It

  11. Acousto-Optic Tunable Filter for Time-Domain Processing of Ultra-Short Optical Pulses,

    DTIC Science & Technology

    The application of acousto - optic tunable filters for shaping of ultra-fast pulses in the time domain is analyzed and demonstrated. With the rapid...advance of acousto - optic tunable filter (AOTF) technology, the opportunity for sophisticated signal processing capabilities arises. AOTFs offer unique

  12. Real-Time and Memory Correlation via Acousto-Optic Processing,

    DTIC Science & Technology

    1978-06-01

    acousto - optic technology as an answer to these requirements appears very attractive. Three fundamental signal-processing schemes using the acousto ... optic interaction have been investigated: (i) real-time correlation and convolution, (ii) Fourier and discrete Fourier transformation, and (iii

  13. A Comparative Study of Acousto-Optic Time-Integrating Correlators for Adaptive Jamming Cancellation

    DTIC Science & Technology

    1997-10-01

    This final report presents a comparative study of the space-integrating and time-integrating configurations of an acousto - optic correlator...systematically evaluate all existing acousto - optic correlator architectures and to determine which would be most suitable for adaptive jamming

  14. Acousto-Optic Technology for Topographic Feature Extraction and Image Analysis.

    DTIC Science & Technology

    1981-03-01

    This report contains all findings of the acousto - optic technology study for feature extraction conducted by Deft Laboratories Inc. for the U.S. Army...topographic feature extraction and image analysis using acousto - optic (A-O) technology. A conclusion of this study was that A-O devices are potentially

  15. Ferroic Crystals for Electro-Optic and Acousto-Optic Applications.

    DTIC Science & Technology

    properties for potential application in acousto - optic devices; and, (2) A systematic examination of the role of domain structures in modifying the...macroscopic properties of all types of ferroic crystals and the manner in which these property modifications could be exploited in acousto - optic , electro

  16. Acousto-Optic Beam Sampler, Part III: Diffraction Experiments at 10.6 micrometers.

    DTIC Science & Technology

    This report deals with the results of acousto - optic diffraction experiments in air at 10.6 micron. The laser used for the experiments was operated...fields. Detailed experiments were performed to investigate the dependence of the acousto - optic diffraction on incident laser power, acoustic drive voltage and angle of incidence.

  17. Development of New Electro-Optic and Acousto-Optic Materials.

    DTIC Science & Technology

    1983-11-01

    Improved materials are required for active optical devices, including electro - optic and acousto-optic modulators, switches and tunable filters, as...many microwave applications. In addition, electro - optic and acousto-optic devices are materials limited because the materials currently available are...these materials for applications involving the electro - optic effect, degenerate four-wave mixing and surface acoustic wave technology.

  18. Effect of optoelectronic feedback on the characteristics of acousto-optical collinear filtering

    SciTech Connect

    Balakshy, V I; Kuznetsov, Yu I; Mantsevich, S N

    2016-02-28

    The first results of the theoretical and experimental studies of an acousto-optical system with feedback based on a collinear cell made of a calcium molybdate crystal are presented. It is shown that the positive electronic feedback allows essential sharpening of the instrument function of the acousto-optical collinear filter, thus increasing the precision of measuring the optical radiation wavelength. (acoustooptics)

  19. Optimization of the input losses in fiber-optic communications with an acousto-optic all-optical switch.

    PubMed

    Danilyan, A V; Shulgin, V A; Chernov, V E

    2006-06-20

    We study optical losses in the single-mode fiber system with an all-optical switch based on the anisotropic acousto-optic (AO) TeO(2) 2D deflector. It is shown, theoretically and experimentally, that the mismatch of the output-fiber mode profile and the switched optical beam shape depends significantly on the monochromaticity of the light beam and is determined by the frequency dispersion of the laser beam diffracted on a Bragg AO cell. A quantitative analysis of the dependence of the input optical losses on the spectral width of the light beam is presented.

  20. Ultrasonic power measurement system based on acousto-optic interaction

    NASA Astrophysics Data System (ADS)

    He, Liping; Zhu, Fulong; Chen, Yanming; Duan, Ke; Lin, Xinxin; Pan, Yongjun; Tao, Jiaquan

    2016-05-01

    Ultrasonic waves are widely used, with applications including the medical, military, and chemical fields. However, there are currently no effective methods for ultrasonic power measurement. Previously, ultrasonic power measurement has been reliant on mechanical methods such as hydrophones and radiation force balances. This paper deals with ultrasonic power measurement based on an unconventional method: acousto-optic interaction. Compared with mechanical methods, the optical method has a greater ability to resist interference and also has reduced environmental requirements. Therefore, this paper begins with an experimental determination of the acoustic power in water contained in a glass tank using a set of optical devices. Because the light intensity of the diffraction image generated by acousto-optic interaction contains the required ultrasonic power information, specific software was written to extract the light intensity information from the image through a combination of filtering, binarization, contour extraction, and other image processing operations. The power value can then be obtained rapidly by processing the diffraction image using a computer. The results of this work show that the optical method offers advantages that include accuracy, speed, and a noncontact measurement method.

  1. The Acousto-Optic Interaction in an Infinite Slab of Isotropic Material,

    DTIC Science & Technology

    1980-04-01

    AD-A097 202 HARRY DIAMOND LABS ADELPHI MD F/S 17/1 THE ACOUSTO - OPTIC INTERACTION IN AN INFINITE SLAB OF ISOTROPIC -- ETC(U) APR 80 S D SCHARF...611101.91A0011 .A1.A1 HOL Project: A10935 1S. KEY WONS (Cf ft "W reweee eld. It neceseeM md Io.t.Itl by block nm er) Acousto - optics Diffraction Mathieu... Acousto - Optic Interaction for Bragg Angles ...................... 13 FIGURES 1. Incident wave is split by acoustic wave into discrete diffracted orders

  2. Acousto-Optic Interaction in Surface Acoustic Waves and Its Application to Real Time Signal Processing.

    DTIC Science & Technology

    1977-12-30

    ACOUSTO - OPTIC INTERACTION IN SURFACE ACOUSTIC WAVES AND ITS APP--ETC(U) DEC 77 0 SCHUMER, P DAS NOOOIJ -75-C-0772 NCLASSIFIED MA-ONR-30 Nt.EE E’h...CHART NAT*NAL BUREAU OF STANDARDS 1-63- ACOUSTO - OPTIC INTERACTION IN SURFACE ACOUSTIC WAVES AND ITS APPLICATION TO REAL TIME SIGNAL PROCESSING By 00 D... Acousto - optics , Integrated optics, Optical Signal Processing. 20. AbSKTRACT (Continue an reverse side it neceary and idewnt& by block mum ber) The

  3. Display system employing acousto-optic tunable filter

    NASA Technical Reports Server (NTRS)

    Lambert, James L. (Inventor)

    1993-01-01

    An acousto-optic tunable filter (AOTF) is employed to generate a display by driving the AOTF with a RF electrical signal comprising modulated red, green, and blue video scan line signals and scanning the AOTF with a linearly polarized, pulsed light beam, resulting in encoding of color video columns (scan lines) of an input video image into vertical columns of the AOTF output beam. The AOTF is illuminated periodically as each acoustically-encoded scan line fills the cell aperture of the AOTF. A polarizing beam splitter removes the unused first order beam component of the AOTF output and, if desired, overlays a real world scene on the output plane. Resolutions as high as 30,000 lines are possible, providing holographic display capability.

  4. Display system employing acousto-optic tunable filter

    NASA Technical Reports Server (NTRS)

    Lambert, James L. (Inventor)

    1995-01-01

    An acousto-optic tunable filter (AOTF) is employed to generate a display by driving the AOTF with a RF electrical signal comprising modulated red, green, and blue video scan line signals and scanning the AOTF with a linearly polarized, pulsed light beam, resulting in encoding of color video columns (scan lines) of an input video image into vertical columns of the AOTF output beam. The AOTF is illuminated periodically as each acoustically-encoded scan line fills the cell aperture of the AOTF. A polarizing beam splitter removes the unused first order beam component of the AOTF output and, if desired, overlays a real world scene on the output plane. Resolutions as high as 30,000 lines are possible, providing holographic display capability.

  5. Acousto-optic imaging with a smart-pixels sensor

    NASA Astrophysics Data System (ADS)

    Barjean, K.; Contreras, K.; Laudereau, J.-B.; Tinet, E.; Ettori, D.; Ramaz, F.; Tualle, J.-M.

    2015-03-01

    Acousto-optic imaging (AOI) is an emerging technique in the field of biomedical optics which combines the optical contrast allowed by diffuse optical tomography with the resolution of ultrasound (US) imaging. In this work we report the implementation, for that purpose, of a CMOS smart-pixels sensor dedicated to the real-time analysis of speckle patterns. We implemented a highly sensitive lock-in detection in each pixel in order to extract the tagged photons after an appropriate in-pixel post-processing. With this system we can acquire images in scattering samples with a spatial resolution in the 2mm range, with an integration time compatible with the dynamic of living biological tissue.

  6. Acousto-optic/CCD real-time SAR data processor

    NASA Technical Reports Server (NTRS)

    Psaltis, D.

    1983-01-01

    The SAR processor which uses an acousto-optic device as the input electronic-to-optical transducer and a 2-D CCD image sensor, which is operated in the time-delay-and-integrate (TDI) mode is presented. The CCD serves as the optical detector, and it simultaneously operates as an array of optically addressed correlators. The lines of the focused SAR image form continuously (at the radar PRF) at the final row of the CCD. The principles of operation of this processor, its performance characteristics, the state-of-the-art of the devices used and experimental results are outlined. The methods by which this processor can be made flexible so that it can be dynamically adapted to changing SAR geometries is discussed.

  7. Bioimaging system using acousto-optic tunable filter

    NASA Astrophysics Data System (ADS)

    Kasili, Paul M.; Mobley, Joel; Cullum, Brian M.; Vo-Dinh, Tuan

    2000-05-01

    The interaction of light with tissue has ben used to recognize disease since the mid-1800s. The recent developments of light sources, detectors, and fiber optic probes provide opportunities to measure these interactions, which yield information for tissue diagnosis at the biochemical, structural, or physiological level. In this paper, we describe a bioimaging system designed for biomedical applications and show laser-indued fluorescence (LIF) images mammalian brain tissue. The LIF imaging of tissue was carried out in vitro using two laser excitations: 488 nm and 514 nm. Images were recorded through an acousto- optic tunable filter over the range 500 nm-650 nm with a charged coupled device camera. Background subtracted images were generated across the fluorescent wavelength. Subtraction allowed a safe comparison to be made with well- contrasted images. Of the two tested excitation wavelengths, 488 nm excitation gave the more distinctive contrast.

  8. Acousto-Optic Measurements in CFRP Laminates Using Fiber Bragg Grating Sensors

    DTIC Science & Technology

    2011-09-01

    level. The main objective of this paper is to describe the results of an acousto - optic experiment using FBG sensors and present FR as a potential way of determining accumulated damage in a carbon composite structure.

  9. Acousto-Optic Processing of 2-D Signals Using Temporal and Spatial Integration.

    DTIC Science & Technology

    1983-05-31

    Documents includes data on: Architectures; Coherence Properties of Pulsed Laser Diodes; Acousto - optic device data; Dynamic Range Issues; Image correlation; Synthetic aperture radar; 2-D Fourier transform; and Moments.

  10. Acoustic field structure simulation in quasi-collinear acousto-optic cells with ultrasound beam reflection.

    PubMed

    Mantsevich, S N; Molchanov, V Ya; Yushkov, K B; Khorkin, V S; Kupreychik, M I

    2017-04-02

    Ultrasound wave reflection from one of the crystal faces is the convenient way to arouse the acoustic beam with a desired propagation direction in acousto-optic cells with collinear and quasi-collinear interaction geometries. The reflection process effects on the ultrasound field amplitude and phase structure. The method to simulate the reflected finite ultrasound beam structure in the case of acoustically anisotropic media is presented in this paper. The investigation is carried on the example of two quasi-collinear acousto-optic cells fabricated on the base of tellurium dioxide crystal. The cells have special geometry that allows to obtain extremely long acousto-optic interaction length and to achieve unprecedented spectral resolution. The influence of reflection process in the acousto-optic diffraction characteristics was also examined.

  11. Acousto-optic modulation of a photonic crystal nanocavity with Lamb waves in microwave K band

    NASA Astrophysics Data System (ADS)

    Tadesse, Semere A.; Li, Huan; Liu, Qiyu; Li, Mo

    2015-11-01

    Integrating nanoscale electromechanical transducers and nanophotonic devices potentially can enable acousto-optic devices to reach unprecedented high frequencies and modulation efficiency. Here, we demonstrate acousto-optic modulation of a photonic crystal nanocavity using Lamb waves with frequency up to 19 GHz, reaching the microwave K band. The devices are fabricated in suspended aluminum nitride membrane. Excitation of acoustic waves is achieved with interdigital transducers with period as small as 300 nm. Confining both acoustic wave and optical wave within the thickness of the membrane leads to improved acousto-optic modulation efficiency in these devices than that obtained in previous surface acoustic wave devices. Our system demonstrates a scalable optomechanical platform where strong acousto-optic coupling between cavity-confined photons and high frequency traveling phonons can be explored.

  12. Acousto-optic modulation of a photonic crystal nanocavity with Lamb waves in microwave K band

    SciTech Connect

    Tadesse, Semere A.; Li, Huan; Liu, Qiyu; Li, Mo

    2015-11-16

    Integrating nanoscale electromechanical transducers and nanophotonic devices potentially can enable acousto-optic devices to reach unprecedented high frequencies and modulation efficiency. Here, we demonstrate acousto-optic modulation of a photonic crystal nanocavity using Lamb waves with frequency up to 19 GHz, reaching the microwave K band. The devices are fabricated in suspended aluminum nitride membrane. Excitation of acoustic waves is achieved with interdigital transducers with period as small as 300 nm. Confining both acoustic wave and optical wave within the thickness of the membrane leads to improved acousto-optic modulation efficiency in these devices than that obtained in previous surface acoustic wave devices. Our system demonstrates a scalable optomechanical platform where strong acousto-optic coupling between cavity-confined photons and high frequency traveling phonons can be explored.

  13. Single Element 2-DIMENSIONAL Acousto-Optic Deflectors Design, Fabrication and Implementation for Digital Optical Computing

    NASA Astrophysics Data System (ADS)

    Rosemeier, Jolanta Iwona

    1992-09-01

    With the need to develop very fast computers compared to the conventional digital chip based systems, the future is very bright for optical based signal processing. Attention has turned to a different application of optics utilizing mathematical operations, in which case operations are numerical, sometimes discrete, and often algebraic in nature. Interest has been so vigorous that many view it as a small revolution in optics whereby optical signal processing is beginning to encompass what many frequently describe as optical computing. The term is fully intended to imply close comparison with the operations performed by scientific digital computers. Most present computer intensive problem solving processors rely on a common set of linear equations found in numerical matrix algebra. Recently, considerable research focused on the use of systolic array, which can operate at high speeds with great efficiency. This approach addresses the acousto-optic digital and analog arrays utilizing three dimensional optical interconnect technology. In part I of this dissertation the first single element 2-dimensional (2-D) acousto-optic deflector was designed, fabricated and incorporated into an optical 3 x 3 vector-vector or matrix-matrix multiplier system. This single element deflector is used as a outer-product device. The input vectors are addressed by electronic means and the outer product matrix is displayed as a 2-D array of optical (laser) pixels. In part II of this work a multichannel single element 2-D deflector was designed, fabricated and implemented into a Programmable Logic Array (PLA) optical computing system. This system can be used for: word equality detection, free space optical interconnections, half adder optical system implementation. The PLA system described in this dissertation has capability of word equality detection. The 2-D multichannel deflector that was designed and fabricated is capable of comparing 16 x 16 words every 316 nanoseconds. Each word is 8

  14. Acousto-Optic Imaging Spectrometers for Mars Surface Science

    NASA Technical Reports Server (NTRS)

    Glenar, D. A.; Blaney, D. L.

    2000-01-01

    NASA's long term plan for Mars sample collection and return requires a highly streamlined approach for spectrally characterizing a landing site, documenting the mineralogical make-up of the site and guiding the collections of samples which represent the diversity of the site. Ideally, image data should be acquired at hundreds of VIS and IR wavelengths, in order to separately distinguish numerous anticipated species, using principal component analysis and linear unmixing. Cameras with bore-sighted point spectrometers can acquire spectra of isolated scene elements, but it requires 10(exp 2) to 10(exp 2) successive motions and precise relative pointing knowledge in order to create a single data cube which qualifies as a spectral map. These and other competing science objectives have to be accomplished within very short lander/rover operational lifetime (a few sols). True, 2-D imaging spectroscopy greatly speeds up the data acquisition process, since the spectra of all pixels in the scene are collected at once. This task can be accomplished with cameras that use electronically tunable acousto-optic tunable filters (AOTFs) as the optical tuning element. AOTFs made from TeO2 are now a mature technology, and operate at wavelengths from near-UV to about 5 microns. Because of incremental improvements in the last few years, present generation devices are rugged, radiation-hard and operate at temperatures down to at least 150K so they can be safely integrated into the ambient temperature optics of in-situ instruments such as planetary or small-body landers. They have been used for ground-based astronomy, and were also baselined for the ST-4 Champollion IR comet lander experiment (CIRCLE), prior to cancellation of the ST-4 mission last year. AIMS (for Acousto-optic Imaging spectrometer), is a prototype lander instrument which is being built at GSFC with support by the NASA OSS Advanced Technologies and Mission Studies, Mars Instrument Definition and Development Program (MIDP

  15. CONTROL OF LASER RADIATION PARAMETERS: Tunable acousto-optic filters with the multiple interaction of light and sound

    NASA Astrophysics Data System (ADS)

    Voloshinov, V. B.; Magdich, L. N.; Knyazev, G. A.

    2005-11-01

    Optical multipass schemes of the interaction of light and sound, which are promising for filtration of optical beams based on tunable acousto-optic filters, are studied. The features of operation of acousto-optic filters in the rejection and transmission regimes are considered. It is proved theoretically and confirmed experimentally that the use of multiple interaction improves the spectral and energy parameters of acousto-optic devices. The collinear and transverse geometry of acousto-optic interaction in cells based on a paratellurite crystal is studied in the double-pass, three-pass, and multipass diffraction regimes.

  16. A new multifunction acousto-optic signal processor

    NASA Technical Reports Server (NTRS)

    Berg, N. J.; Casseday, M. W.; Filipov, A. N.; Pellegrino, J. M.

    1984-01-01

    An acousto-optic architecture for simultaneously obtaining time integration correlation and high-speed power spectrum analysis was constructed using commercially available TeO2 modulators and photodiode detector-arrays. The correlator section of the processor uses coherent interferometry to attain maximum bandwidth and dynamic range while achieving a time-bandwidth product of 1 million. Two correllator outputs are achieved in this system configuration. One is optically filtered and magnified 2 : 1 to decrease the spatial frequency to a level where a 25-MHz bandwidth may be sampled by a 62-mm array with elements on 25-micro centers. The other output is magnified by a factor of 10 such that the center 4 microseconds of information is available for estimation of time-difference-of-arrival to within 10 ns. The Bragg cell spectrum-analyzer section, which also has two outputs, resolves a 25-MHz instantaneous bandwidth to 25 kHz and can determine discrete-frequency reception time to within 15 microseconds. A microprocessor combines spectrum analysis information with that obtained from the correlator.

  17. Submillimeter Wave Astronomy Satellite (SWAS) acousto-optical spectrometer

    NASA Astrophysics Data System (ADS)

    Klumb, Markus; Frerick, J.; Tolls, Volker; Schieder, Rudolf; Winnewisser, Gisbert F.

    1994-09-01

    The first fully space qualified acousto-optical spectrometer (AOS) is described. It is built for the Submillimeter Wave Astronomy Satellite (SWAS) to be launched in July 1995. It has a very large bandwidth from 1400 to 2800 MHz covered by 1365 channels. This corresponds to a nearly 1 MHz channel spacing. The design is optimized for very high stability, which is demonstrated by means of Allan variance stability test. The Allan plot minimum time was found well above 800 seconds. The AOS can operate within a temperature range from -5 to +30 degree(s)C (+5 to +25 degree(s)C nominal) and with temperature variations of up to 2 degree(s)C/h. The performance was verified also after environmental testing such as random vibration (10.2 G rms) and thermal cycling of -30 to +50 degree(s)C. The lightweight mechanical design resulted in a total weight of 7.2 kg including electronics. A detailed optical design study was performed in order to achieve diffraction limited channel resolution, high efficiency and low sensitivity to mechanical distortion. The RF input power needed for full scale is 11 mW. The power consumption is 5.4 Watts (including data pre-averaging and DC-DC converter losses). The development has shown that AOSs are well suited for spaceborne applications.

  18. Swept laser source based on acousto-optic tunable filter

    NASA Astrophysics Data System (ADS)

    Chen, Minghui; Li, Hao; Chen, Rong

    2014-12-01

    The design and development of the swept laser for optical coherence tomography is presented. It is manifested by a semiconductor optical amplifier, a fiber coupler, two fiber isolators, a semiconductor optical amplifier (SOA) and an acousto-optic tunable filter (AOTF) for frequency tuning within a unidirectional all-fiber ring cavity. Light output from the coupler is further amplified and spectral shaped by a booster SOA terminated at both ends with two isolators. The total loss in ring cavity is 8.2 dB. The gain SOA provides fiber-to-fiber small signal gain of 22.2 dB with saturation output power of 9.0 dBm. The developed laser source provides up to 100 kHz over a full-width wavelength tuning range of 140 nm at center wavelength of 1308 nm with an average power of 8 mW, yielding an axial resolution of 5.4 μm in air for OCT imaging. Theoretically, the measurement principle and the feasibility of the system are analyzed. Implementing the laser source in swept source based OCT (SS-OCT) system, real-time structural imaging of biological tissue is realized.

  19. Materials for imaging acousto-optic tunable filters

    NASA Astrophysics Data System (ADS)

    Gupta, Neelam

    2014-05-01

    Research and development of robust compact hyperspectral imagers that can acquire both spectral and spatial features from a scene of interest is of utmost importance for standoff detection of targets as well as chemical and biological agents and backgrounds. Hyperspectral imagers can acquire images with a large number of narrow spectral bands and take advantage of the characteristic spectral signatures of different materials making up the scene. At the Army Research Laboratory (ARL), we are developing hyperspectral imagers based on acousto-optic tunable filters (AOTFs) that can provide adaptive no-moving-parts imagers from the ultraviolet (UV) to the long wave infrared (LWIR) to acquire a two-dimensional spectral image and build up a two-dimensional image cube as a function of time instead of using traditional grating or prism based approach that requires relative motion between sensor and scene. Here, we will review the development of different imaging AOTFs operating from the UV to the LWIR based on a variety of birefringent materials and include the spectral imaging carried out with these filters including both with single and double piezoelectric transducers. We will also include the theoretical background needed to carry out the filter design and discuss development of mercurous halide crystals that can be used to develop AOTFs operating over a wide spectral region from the visible to the LWIR.

  20. Acousto-optics studied in polaritonic photonic crystals

    NASA Astrophysics Data System (ADS)

    Singh, Mahi R.; Racknor, C.

    2010-10-01

    We have studied the acousto-optic effect on the photon transmission and the spontaneous emission in polaritonic photonic crystal. We have considered that photonic crystals are fabricated from polaritonic materials such as GaP, MgO, LiNbO3 , and LiTaO3 . A two-level quantum dot is doped in a polaritonic crystal to study the decay rate of the spontaneous emission. The decay rate of quantum dots, band structure, and photon transmission coefficient have been calculated. It is found that band-gap width and the decay rate of quantum dots depends strongly on the high-frequency dielectric constant of the polaritonic crystals while the photonic band edges vary inversely by the ratio of longitudinal- to transverse-optical phonon energies. The spontaneous decay rate of the quantum dot can be controlled by the external strain field. This finding is significant because it is well known that the spontaneous emission is source of undesirable noise in different types of electronic and optical devices. Finally, we have also found the system can be switched from transmitting state to reflecting state by applying an external strain field. These are distinct and interesting results and can be used to fabricate new types of photonic couplers and fibers which in turn can be used to fabricate all photonic switches.

  1. Analysis of quality of images obtained by acousto-optic filtering

    NASA Astrophysics Data System (ADS)

    Bogomolov, Dennis V.; Voloshinov, Vitaly B.

    2005-03-01

    The paper is devoted to the theoretical and experimental investigation of spatial resolution of images obtained during acousto-optic spectral filtration. The consideration was carried out for a wide angle acousto-optic filter designed on the base of paratellurite single crystal. The crystal was cut in the (1 1 0) plane with the direction of acoustic wave propagation at the angle 10 ° relative to the axis [110]. It was found that optical quality of a filtered image is influenced by a spectral bandwidth of a filter. The spectral bandwidth is determined by a length of piezoelectric transducer that generates ultrasonic waves in an acousto-optic cell. The dependence of a number of resolvable spots on the piezotransducer length was examined theoretically. It was shown that a wavelength of the filtered radiation influences the quality of the processed image. Precise and approximate equations have been derived to determine the spectral passband of the acousto-optic filer, the angular field of view of a single pixel, the angular aperture of the device and the number of resolvable spots in a line. Resolution of the images obtained during the acousto-optic filtration was also measured in the experiment.

  2. Acousto-optical imaging using a powerful long pulse laser

    NASA Astrophysics Data System (ADS)

    Rousseau, Guy; Blouin, Alain; Monchalin, Jean-Pierre

    2008-06-01

    Acousto-optical imaging is an emerging biodiagnostic technique which provides an optical spectroscopic signature and a spatial localization of an optically absorbing target embedded in a strongly scattering medium. The transverse resolution of the technique is determined by the lateral extent of ultrasound beam focal zone while the axial resolution is obtained by using short ultrasound pulses. Although very promising for medical diagnostic, the practical application of this technique is presently limited by its poor sensitivity. Moreover, any method to enhance the signal-to-noise ratio must obviously satisfy the in vivo safety limits regarding the acceptable power level of both the ultrasonic pressure wave and the laser beam. In this paper, we propose to improve the sensitivity by using a pulsed single-frequency laser source to raise the optical peak power applied to the scattering medium and to collect more ultrasonically tagged photons. Such a laser source also allows illuminating the tissues mainly during the transit time of the ultrasonic wave to maintain the average optical power below the maximum permissible exposure. In our experiment, a single-frequency Nd:YAG laser emitting 500-μs pulses with a peak power superior to 100 W was used. Photons were tagged in few-cm thick optical phantoms with tone bursts generated by an ultrasonic transducer. Tagged photons were detected with a GaAs photorefractive interferometer characterized by a large optical etendue to process simultaneously a large number of speckle grains. When pumped by high intensity laser pulses, such an interferometer also provides the fast response time essential to obtain an apparatus insensitive to the speckle decorrelation due to mechanical vibrations or tissues movements. The use of a powerful long pulse laser appears promising to enhance the signal level in ultrasound modulated optical imaging. When combined with a photorefractive interferometer of large optical etendue, such a source could

  3. Holographic topography using acousto-optically generated large synthetic wavelengths

    NASA Astrophysics Data System (ADS)

    Abeywickrema, U.; Beamer, D.; Banerjee, P.; Poon, T.-C.

    2016-03-01

    Digital holography uses phase imaging in a variety of techniques to produce a three-dimensional phase resolved image that includes accurate depth information about the object of interest. Multi-wavelength digital holography is an accurate method for measuring the topography of surfaces. Typically, the object phases are reconstructed for two wavelengths separately and the phase corresponding to the synthetic wavelength (obtained from the two wavelengths) is obtained by calculating the phase difference. Then the surface map can be obtained using proper phase-unwrapping techniques. Usually these synthetic wavelengths are on the order of microns which can be used to resolve depths on the order of microns. In this work, two extremely close wavelengths generated by an acousto-optic modulator (AOM) are used to perform two-wavelength digital holography. Since the difference between the two wavelengths is on the order of picometers, a large synthetic wavelength (on the order of centimeters) can be obtained which can be used to determine the topography of macroscopic surface features. Also since the synthetic wavelength is large, an accurate surface map can be obtained without using a phase-unwrapping technique. A 514 nm Argon-ion laser is used as the optical source, and used with an AOM to generate the zeroth-order and frequency-shifted first-order diffracted orders which are used as the two wavelengths. Both beams are aligned through the same spatial filter assembly. Holograms are captured sequentially using a typical Mach-Zehnder interferometric setup by blocking one beam at a time. Limitations of the large synthetic wavelength are also discussed.

  4. Applications of acousto-optics in holographic memories

    NASA Astrophysics Data System (ADS)

    Gurevich, Boris S.; Gurevich, Simon B.; Zhumaliev, Kubanychbek M.; Akkoziev, Imil A.; Alymkulov, Salmor A.

    1999-09-01

    Acousto-optic deflectors (AODs) are used for data by-page recording as holograms, and for data extraction from the hologram sampled by the AOD. The possibilities and characteristics of AODs define information capacity of the holographic memory devices as well as architecture and parameters of their separate components. Usually 2 AODs are used for 2-D hologram recording, and 3 AODs -- for volume multiplex recording. The calculations of amount of the recorded holograms which can be provided by different AODs have been carried out in the present work, and the limits of information capacity increasing at expense of optimal using of both AODs and recording media, have been appointed. The specific attention have been paid to the hologram 3-D recording with angular multiplexing where information capacity can be increased by 2 orders. The difficulties to be overcome in order to achieve the biggest information capacity, have been noted. Another subject of study is the problem of the sampled data arbitrary access rate increasing which can be provided by AODs application. It has been noted that minimum access time is limited, and this limitation is connected with the duration of the signal transmission through Bragg cell and with the time of signal transmission and processing in other components of holographic memory. It has been shown that information quality of holographic memory grows along with increasing of the number of used AODs. It has also been noted that if the memory parameters are close to their limits, the cross-talks grow, and the optimum must be found.

  5. A compact acousto-optic lens for 2D and 3D femtosecond based 2-photon microscopy

    PubMed Central

    Kirkby, Paul A.; Naga Srinivas, N.K.M.; Silver, R. Angus

    2010-01-01

    We describe a high speed 3D Acousto-Optic Lens Microscope (AOLM) for femtosecond 2-photon imaging. By optimizing the design of the 4 AO Deflectors (AODs) and by deriving new control algorithms, we have developed a compact spherical AOL with a low temporal dispersion that enables 2-photon imaging at 10-fold lower power than previously reported. We show that the AOLM can perform high speed 2D raster-scan imaging (>150 Hz) without scan rate dependent astigmatism. It can deflect and focus a laser beam in a 3D random access sequence at 30 kHz and has an extended focusing range (>137 μm; 40X 0.8NA objective). These features are likely to make the AOLM a useful tool for studying fast physiological processes distributed in 3D space PMID:20588506

  6. A Statistical Analysis of the Output Signals of an Acousto-Optic Spectrum Analyzer for CW (Continuous-Wave) Signals

    DTIC Science & Technology

    1988-10-01

    A statistical analysis on the output signals of an acousto - optic spectrum analyzer (AOSA) is performed for the case when the input signal is a...processing, Electronic warfare, Radar countermeasures, Acousto - optic , Spectrum analyzer, Statistical analysis, Detection, Estimation, Canada, Modelling.

  7. Acousto-Optic-Based Wavelength-Comb-Swept Laser for Extended Displacement Measurements.

    PubMed

    Park, Nam Su; Chun, Soo Kyung; Han, Ga-Hee; Kim, Chang-Seok

    2017-03-31

    We demonstrate a novel wavelength-comb-swept laser based on two intra-cavity filters: an acousto-optic tunable filter (AOTF) and a Fabry-Pérot etalon filter. The AOTF is used for the tunable selection of the output wavelength with time and the etalon filter for the narrowing of the spectral linewidth to extend the coherence length. Compared to the conventional wavelength-swept laser, the acousto-optic-based wavelength-comb-swept laser (WCSL) can extend the measureable range of displacement measurements by decreasing the sensitivity roll-off of the point spread function. Because the AOTF contains no mechanical moving parts to select the output wavelength acousto-optically, the WCSL source has a high wavenumber (k) linearity of R² = 0.9999 to ensure equally spaced wavelength combs in the wavenumber domain.

  8. Wavelet transform: fundamentals, applications, and implementation using acousto-optic correlators

    NASA Astrophysics Data System (ADS)

    DeCusatis, Casimer M.; Koay, J.; Litynski, Daniel M.; Das, Pankaj K.

    1995-10-01

    In recent years there has been a great deal of interest in the use of wavelets to supplement or replace conventional Fourier transform signal processing. This paper provides a review of wavelet transforms for signal processing applications, and discusses several emerging applications which benefit from the advantages of wavelets. The wavelet transform can be implemented as an acousto-optic correlator; perfect reconstruction of digital signals may also be achieved using acousto-optic finite impulse response filter banks. Acousto-optic image correlators are discussed as a potential implementation of the wavelet transform, since a 1D wavelet filter bank may be encoded as a 2D image. We discuss applications of the wavelet transform including nondestructive testing of materials, biomedical applications in the analysis of EEG signals, and interference excision in spread spectrum communication systems. Computer simulations and experimental results for these applications are also provided.

  9. Lyapunov exponent of chaos generated by acousto-optic modulators with feedback

    NASA Astrophysics Data System (ADS)

    Ghosh, Anjan K.; Verma, Pramode

    2011-01-01

    Generation of chaos from acousto-optic modulators with an electronic feedback has been studied for several years. Such chaotic signals have an important application in providing secure encryption in free-space optical communication systems. Lyapunov exponent is an important parameter for analysis of chaos generated by a nonlinear system. The Lyapunov exponent of an acousto-optic system is determined and calculated in this paper to understand the dependence of the chaotic response on the system parameters such as bias, feedback gain, input intensity and initial condition exciting the cell. Analysis of chaos using Lyapunov exponent is consistent with bifurcation analysis and is useful in encrypting data signals.

  10. Acousto-optical combined frequency splitters and shifters as components of a ring optical gyroscope

    SciTech Connect

    Kotov, V M

    1999-03-31

    An analysis is made of the task of symmetrisation of a Y-type directional coupler and of shifting the frequency of counterpropagating waves in a ring gyroscope by means of the relatively recently discovered new type of acousto-optical diffraction when the incident radiation is diffracted simultaneously into two orders. Anisotropic and isotropic acousto-optical diffraction in a uniaxial crystal is considered and expressions convenient for calculations are derived. Experiments carried out on isotropic diffraction in LiNbO{sub 3} confirm, on the whole, the theoretical predictions. (laser applications and other topics in quantum electronics)

  11. Wide-band acousto-optic deflectors with high efficiency for visible range fringe pattern projector.

    PubMed

    Dupont, S; Kastelik, J C; Causa, F

    2007-10-01

    A laser fringe projection system based on a pair of identical acousto-optic TeO(2) deflectors operated at the same frequency and using tangential phase matching anisotropic interaction is demonstrated, achieving large bandwidth and high efficiency. A 40 MHz bandwidth and an acousto-optic efficiency higher than 60% have been measured at wavelength of 514 nm. The specific pris-matic configuration of the in-house developed deflectors greatly facilitates optical alignment of the instrument. The spatial period of the interference fringes can be dynamically controlled over almost one decade by tuning the frequency of the acoustic carriers.

  12. Invited Article: Acousto-optic finite-difference frequency-domain algorithm for first-principles simulations of on-chip acousto-optic devices

    NASA Astrophysics Data System (ADS)

    Shi, Yu; Cerjan, Alexander; Fan, Shanhui

    2017-02-01

    We introduce a finite-difference frequency-domain algorithm for coupled acousto-optic simulations. First-principles acousto-optic simulation in time domain has been challenging due to the fact that the acoustic and optical frequencies differ by many orders of magnitude. We bypass this difficulty by formulating the interactions between the optical and acoustic waves rigorously as a system of coupled nonlinear equations in frequency domain. This approach is particularly suited for on-chip devices that are based on a variety of acousto-optic interactions such as the stimulated Brillouin scattering. We validate our algorithm by simulating a stimulated Brillouin scattering process in a suspended waveguide structure and find excellent agreement with coupled-mode theory. We further provide an example of a simulation for a compact on-chip resonator device that greatly enhances the effect of stimulated Brillouin scattering. Our algorithm should facilitate the design of nanophotonic on-chip devices for the harnessing of photon-phonon interactions.

  13. Optical Oscillation Established Using Acousto-Optic Bragg Angle Defraction In Conjunction With Closed Cavity Feedback

    NASA Astrophysics Data System (ADS)

    Vezzoli, G. C.; Cadwallender, W.; Megargel, L. R.; Mentzer, M. A.; Craley, D. E.

    1987-03-01

    An optical oscillator has been designed, constructed, and operated by using a HeNe laser and acousto-optic modulator in conjunction with two opposed fiber optic feedback circuits. Depending on round-trip feedback time, a low frequency ( 1Hz) sinusoidal oscillator or a high frequency (100KHz) square wave (,..%,1 us rise time) is obtained.

  14. Acousto-Optic Tunable Filter Hyperspectral Microscope Imaging Method for Characterizing Spectra from Foodborne Pathogens.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hyperspectral microscope imaging (HMI) method, which provides both spatial and spectral characteristics of samples, can be effective for foodborne pathogen detection. The acousto-optic tunable filter (AOTF)-based HMI method can be used to characterize spectral properties of biofilms formed by Salmon...

  15. Highly efficient acousto-optic diffraction in Sn2P2S6 crystals.

    PubMed

    Martynyuk-Lototska, I Yu; Mys, O G; Grabar, A A; Stoika, I M; Vysochanskii, Yu M; Vlokh, R O

    2008-01-01

    We have studied the acousto-optic (AO) diffraction in Sn2P2S6 crystals and found that they manifest high values of an AO figure of merit. The above crystals may therefore be used as highly efficient materials in different AO applications.

  16. Development of a Flyable Acousto-Optic Laser Beam Deflection System for a Head Up Display of the Future.

    DTIC Science & Technology

    Rayleigh criteria). The system was designed for stroke writing but was demonstrated with lissajous writing. The acousto - optic deflectors employed...The report describes a laser display which is to be used in a Head-Up Display of the future. The uniqueness of the display is that it uses acousto ... optic components for the modulation and deflection of the laser beam. As a result, there are no moving parts, which increases the reliability and life

  17. LIGHT MODULATION: Quasi-collinear tunable acousto-optic paratellurite crystal filters for wavelength division multiplexing and optical channel selection

    NASA Astrophysics Data System (ADS)

    Molchanov, V. Ya; Voloshinov, V. B.; Makarov, O. Yu

    2009-04-01

    Quasi-collinear acousto-optic interaction is studied in acoustically and optically anisotropic paratellurite crystals. The possible applications of this interaction in acousto-optic tunable filters with a high spectral resolution are discussed. Different modifications of devices are compared and variants of devices intended for processing light beams and selection of light signals in fibreoptic communication systems with wavelength division multiplexing (WDM) at λ simeq 1550 nm are considered.

  18. Piezo-optic, photoelastic, and acousto-optic properties of SrB4O7 crystals.

    PubMed

    Mytsyk, Bohdan; Demyanyshyn, Natalia; Martynyuk-Lototska, Irina; Vlokh, Rostyslav

    2011-07-20

    On the basis of studies of the piezo-optic effect, it has been shown that SrB(4)O(7) crystals can be used as efficient acousto-optic materials in the vacuum ultraviolet spectral range. The full matrices of piezo-optic and photoelastic coefficients have been experimentally obtained for these crystals. The acousto-optic figure of merit and the diffraction efficiency have been estimated for both the visible and deep ultraviolet spectral ranges.

  19. Narrow-band acousto-optic tunable filtering in a two-mode fiber.

    PubMed

    Ostling, D; Engan, H E

    1995-06-01

    We demonstrate an optical filter that utilizes acousto-optic coupling between the spatial modes that propagate in a two-mode elliptical-core fiber. The optical bandwidth at 1090 nm is 0.85 nm, which is in agreement with predictions based on measurement of differential group delay between the modes. The filter is slightly polarization dependent, with a 0.28-nm wavelength difference between the passband peaks for the two polarization eigenstates. The optical insertion loss is dominated by 2-4-dB bending loss in nonoptimized mode strippers, and the coupling loss is negligible. Full acousto-optic mode conversion was achieved at an 8-mW electrical input power to the acoustic transducer.

  20. Note: Laser frequency shifting by using two novel triple-pass acousto-optic modulator configurations

    SciTech Connect

    Carlos-Lopez, E. de; Lopez, J. M.; Lopez, S.; Espinosa, M. G.; Lizama, L. A.

    2012-11-15

    We report the design of two novel triple-pass acousto-optic modulator systems. These designs are extensions of the well known acousto-optic modulator (AOM) double-pass configuration, which eliminates the angle dependence of the diffracted beam with respect to the modulation frequency. In a triple-pass system, however, the frequency dependence of the angle does not disappear but the frequency shift is larger, spanning 3 times the AOM central frequency. In some applications, such as optically pumped Cesium-beam frequency standards, the frequencies of the two laser beams remain fixed and a triple-pass optical system can be used to reduce to one the number of lasers used in such atomic clocks. The two triple-pass configurations use either a retro-reflecting mirror, or a right angle prism to pass for third time the laser beam through the AOM, obtaining diffraction efficiencies of about 27% and 44%, respectively.

  1. Ultraviolet-visible imaging acousto-optic tunable filters in KDP.

    PubMed

    Voloshinov, Vitaly; Gupta, Neelam

    2004-07-01

    There is a need to develop large-aperture acousto-optic tunable filters (AOTFs) in the UV region for applications in astronomy, environmental sciences, biology, etc. We have developed a high-quality noncollinear AOTF cell that uses a single crystal of KDP that has nearly a four times larger acousto-optic figure of merit, M2, than quartz. The linear and angular apertures of this cell are 1.5 cm x 1.5 cm and 1.2 degrees, respectively. The spectral range is 220-480 nm, with 160-cm(-1) spectral resolution and high transmission in the UV. We present an analysis of the design and describe the characterization results.

  2. Photon frequency-mode matching using acousto-optic frequency beam splitters

    SciTech Connect

    Jones, Nick S.; Stace, T. M.

    2006-03-15

    It is a difficult engineering task to create distinct solid state single photon sources which nonetheless emit photons at the same frequency. It is also hard to create entangled photon pairs from quantum dots. In the spirit of quantum engineering we propose a simple optical circuit which can, in the right circumstances, make frequency distinguishable photons frequency indistinguishable. Our circuit can supply a downstream solution to both problems, opening up a large window of allowed frequency mismatches between physical mechanisms. The only components used are spectrum analysers or prisms and an acousto-optic modulator. We also note that an acousto-optic modulator can be used to obtain Hong-Ou-Mandel two photon interference effects from the frequency distinguishable photons generated by distinct sources.

  3. Wide spectral range imaging acousto-optic turnable filter used in outer space probe

    NASA Astrophysics Data System (ADS)

    Zhang, Zehong; Wang, Liangqiu; He, Xiaoliang; Zhou, Yong

    2014-02-01

    This article introduces a wide spectral range imaging acousto-optic turnable filter made of two transducers. "Mismatch rate" was firstly put forward to represent the degree to which the impedance mismatch and a three stage matching circuit was designed for the filter to improve its spectral range and operating bandwidth. Now the spectral range is from 0.4μm to 1.1μm, the overall operating bandwidth reaches 1.14 octave, the diffraction efficiency over 60%, spectral resolution from 1.3nm to 7.5nm. To get rid of " tin pest", alloy material was used to make bonding layer material instead of pure tin, making the storage temperature of the acousto-optic turnable filter ranges from -65 °C to 85 °C, and the operating temperature from -35 °C to 70 °C.

  4. Wide-aperture diffraction of unpolarised radiation in a system of two acousto-optic filters

    SciTech Connect

    Magdich, L N; Yushkov, K B; Voloshinov, V B

    2009-04-30

    Light diffraction is studied in two tandem acousto-optic cells filtering unpolarised radiation with a wide angular spectrum. It is shown that the side lobes of the ultrasonic radiation pattern of a piezoelectric transducer produce side diffraction intensity maxima at the output of the system consisting of two filters. Diffraction in paratellurite filters is studied experimentally at 1.06 {mu}m. (light modulation)

  5. A new method for determining the transfer function of an acousto optical tunable filter.

    PubMed

    Mahieux, A; Wilquet, V; Drummond, R; Belyaev, D; Federova, A; Vandaele, A C

    2009-02-02

    The current study describes the determination of the transfer function of an Acousto Optical Tunable Filter from the in-flight solar observations of the SOIR instrument on board Venus Express. An approach is proposed in order to reconstruct the transfer function profile from the analysis of various solar lines. Moreover this technique allows the determination of the evolution of the transfer function as a function of the AOTF radio frequency.

  6. Acousto-optical modulation of light at a doubled sound frequency

    SciTech Connect

    Kotov, V M; Averin, S V; Shkerdin, G N

    2016-02-28

    A method of acousto-optical (AO) Bragg diffraction is proposed that provides the amplitude modulation of optical radiation at a doubled acoustic frequency. The method is based on the double transmission of the light through the AO modulator made of a gyrotropic crystal and is experimentally tested by the example of the modulation of light with a wavelength of 0.63 μm, controlled by the paratellurite AO cell. (acoustooptics)

  7. Laser identification system based on acousto-optical barcode scanner principles

    NASA Astrophysics Data System (ADS)

    Khansuvarov, Ruslan A.; Korol, Georgy I.; Preslenev, Leonid N.; Bestugin, Aleksandr R.; Paraskun, Arthur S.

    2016-09-01

    The main purpose of the bar code in the modern world is the unique identification of the product, service, or any of their features, so personal and stationary barcode scanners so widely used. One of the important parameters of bar code scanners is their reliability, accuracy of the barcode recognition, response time and performance. Nowadays, the most popular personal barcode scanners contain a mechanical part, which extremely impairs the reliability indices. Group of SUAI engineers has proposed bar code scanner based on laser beam acoustic deflection effect in crystals [RU patent No 156009 issued 4/16/2015] Through the use of an acousto-optic deflector element in barcode scanner described by a group of engineers SUAI, it can be implemented in the manual form factor, and the stationary form factor of a barcode scanner. Being a wave electronic device, an acousto-optic element in the composition of the acousto-optic barcode scanner allows you to clearly establish a mathematical link between the encoded function of the bar code with the accepted input photodetector intensities function that allows you to speak about the great probability of a bar code clear definition. This paper provides a description of the issued patent, the description of the principles of operation based on the mathematical analysis, a description of the layout of the implemented scanner.

  8. Two-dimensional refractive index modulation by phased array transducers in acousto-optic deflectors.

    PubMed

    Wang, Tiansi; Zhang, Chong; Aleksov, Aleksandar; Salama, Islam; Kar, Aravinda

    2017-01-20

    Acousto-optic deflectors are photonic devices that are used for scanning high-power laser beams in advanced microprocessing applications such as marking and direct writing. The operation of conventional deflectors mostly relies on one-dimensional sinusoidal variation of the refractive index in an acousto-optic medium. Sometimes static phased array transducers, such as step configuration or planar configuration transducer architecture, are used to tilt the index modulation planes for achieving higher performance and higher resolution than a single transducer AO device. However, the index can be modulated in two dimensions, and the modulation plane can be tilted arbitrarily by creating dynamic phase gratings in the medium using phased array transducers. This type of dynamic two-dimensional acousto-optic deflector can provide better performance using, for example, a large deflection angle and high diffraction efficiency. This paper utilizes an ultrasonic beam steering approach to study the two-dimensional strain-induced index modulation due to the photoelastic effect. The modulation is numerically simulated, and the effects of various parameters, such as the operating radiofrequency of the transducers, the ultrasonic beam steering angle, and different combinations of pressure on each element of the transducer array, are demonstrated.

  9. A Very Compact, High Speed and Rugged Acousto-Optic Tunable Filter for Wavelength Division Demultiplexing in Fiber Optic Communication Networks. Phase 1

    DTIC Science & Technology

    2007-11-02

    Novel concepts of near-collinear/collinear acousto - optic interactions have been investigated during this SBIR Phase I program. As a result, several...new acousto - optic tunable filters have been built and tested. The program is highlighted by: (1) Design, fabrication and experimental demonstration of...a novel TeO2 near-collinear acousto - optic tunable filter has been designed, fabricated and tested. The device exhibits a 1.29 nm spectral resolution

  10. Acousto-optic multiphoton laser scanning microscopy and multiphoton photon counting spectroscopy: Applications and implications for optical neurobiology

    NASA Astrophysics Data System (ADS)

    Iyer, Vijay

    Multiphoton excitation of molecular probes has become an important tool in experimental neurobiology owing to the intrinsic optical sectioning and low light scattering it affords. Using molecular functional indicators, multiphoton excitation allows physiological signals within single neurons to be observed from within living brain tissue. Ideally, it would be possible to record from multiple sites located throughout the elaborately branching dendritic arbors, in order to study the correlations of structure and function both within and across experiments. However, existing multiphoton microscope systems based on scanning mirrors do not allow optical recordings to be obtained from more than a handful of sites simultaneously at the high rates required to capture the fast physiological signals of interest (>100Hz for Ca2+ signals, >1kHz for membrane potential transients). In order to overcome this limitation, two-dimensional acousto-optic deflection was employed, to allow an ultrafast laser beam suited for multiphoton excitation to be rapidly repositioned with low latency (˜15mus). This supports a random-access scanning mode in which the beam can repeatedly visit a succession of user-selected sites of interest within the microscope's field-of-view at high rates, with minimal sacrifice of pixel dwell time. This technique of acousto-optic multiphoton laser scanning microscope (AO-MPLSM) was demonstrated to allow the spatial profile of signals arising in response to physiological stimulation to be rapidly mapped. Means to compensate or avoid problems of dispersion which have hampered AO-MPLSM in the past are presented, with the latter being implemented. Separately, the combination of photon counting detection with multiphoton excitation, termed generally multiphoton photon counting spectroscopy (MP-PCS), was also considered, with particular emphasis on the technique of fluorescence correlation spectroscopy (FCS). MP-PCS was shown to allow information about molecular

  11. An advanced regime of the anomalous acousto-optical interaction with tangential phase matching in crystalline materials

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Alexandre S.; Arellanes, Adan O.

    2016-09-01

    Regime of effective non-collinear acousto-optical interaction with tangential phase matching had been identified and previously observed only in two limiting cases: in tellurium dioxide (TeO2) at low acoustic frequencies ( 60 MHz) and in rutile (TiO2) at ultra-high frequencies ( 5 GHz). Both these limits are motivated by optical properties of the chosen materials. Low frequencies in TeO2 admit designing a wide-aperture acousto-optical cell, but limit the frequency bandwidth. While an acousto-optical cell made of TiO2 has very small aperture and exhibits low spectral resolution due to the effect of linear acoustic attenuation. Instead of those limits, we propose an advanced regime of the anomalous acousto-optical interaction with tangential phase matching, which allows us varying the frequency range and optimizing all the performances (for instance, the spectral resolution) of a wide-aperture acousto-optical cell made of the chosen crystal, as the case requires. Recently, we had suggested and successfully tested experimentally the revealed additional degree of freedom, i.e. the action of the tilt angle within the refractive indices ellipsoids to manipulate by the performances of crystalline acousto-optical cells. Now, we consider an opportunity of refining this additional degree of freedom within those ellipsoids of crystalline acousto-optical cell through some declination of the acoustic beam. For our investigations, the lithium niobate (LiNbO3) and rutile (TiO2) crystals of about 5 cm length, operating with the slow-shear acoustic mode along the acoustic axes had been selected. The needed theoretical analysis, numerical estimations, and 3D-vector diagrams have been developed to reveal potential benefits of the proposed technique.

  12. Acousto-optic interaction in alpha-BaB(2)O(4)and Li(2)B(4)O(7) crystals.

    PubMed

    Martynyuk-Lototska, Irina; Mys, Oksana; Dudok, Taras; Adamiv, Volodymyr; Smirnov, Yevgen; Vlokh, Rostyslav

    2008-07-01

    Experimental studies and analysis of acousto-optic diffraction in alpha-BaB(2)O(4) and Li(2)B(4)O(7) crystals are given. Ultrasonic wave velocity, elastic compliance and stiffness coefficients, and piezo-optic and photoelastic coefficients of alpha-BaB(2)O(4) and Li(2)B(4)O(7) crystals are determined. The acousto-optic figure of merit has been estimated for different possible geometries of acousto-optic interaction. It is shown that the acousto-optic figures of merit for alpha-BaB(2)O(4) crystals reach the value M(2)=(270 +/- 70) x 10(-15) s(3)/kg for the case of interaction with the slowest ultrasonic wave. The directions of propagation and polarization of those acoustic waves are obtained on the basis of construction of acoustic slowness surfaces. The acousto-optic diffraction is experimentally studied for alpha-BaB(2)O(4) and Li(2)B(4)O(7) crystals.

  13. Arrangement of an advanced acousto-optical processor for modeling the triple correlations of low-power optical pulse trains

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Alexandre S.; Hanessian de la Garza, Ana V.; Chavushyan, Vahram; Campos Acosta, Joaquin

    2012-02-01

    Both a high level of developing the spatially spot-like and one-dimensional input devices and the flexibility of a design inherent in two-dimensional optical systems with similar modulating components make it possible to realize various high-bit-rate opto-electronic processors. This is why a one-dimension acousto-optic technique has been involved in data processing and its modeling based on the algorithm of triple product correlations. Practically, triple product correlations originate within an optical scheme including the modulated light source, representing the first input port, and two wideaperture acousto-optical cells forming two other input ports. Due to specifically constructed lens system, initially modulated light beam is crossing sequentially the apertures of acousto-optical cells oriented at right angle to each other. Finally, a CCD-matrix integrates the received optical signal with respect to time and registers the resulting triple product correlations. In a view of arranging similar acousto-optical processor for modeling triple product correlations, we characterize a novel version of the acousto-optical cells exploiting now tellurium-dioxide crystals. Together with this, potential performances of the progressed design for similar processor are estimated as well.

  14. Fiber-optic tunable multiwavelength variable attenuator and routing module designs that use bulk acousto-optics.

    PubMed

    Riza, Nabeel A; Mughal, M Junaid

    2005-02-10

    A compact fiber-coupled bulk acousto-optical multiwavelength variable optical attenuator module design that uses a retroreflective double-pass geometry within a single bulk acousto-optic tunable filter device is presented. The proposed attenuator module demonstrates a high 17-dB notch dynamic range at a low 100-mW drive power and uses a single bulk collinear-interaction acousto-optic tunable-filter device. Experiments show a low (<1.8-dB) fiber-to-fiber insertion loss with a fast 34-micros speed within a wide 1520-1640-nm agile multinotch band. The basic broadband attenuator module design is extended to allow for efficient architectures for routing modules such as agile drop filters, analog hitless tap filters, and digital add-drop switches.

  15. Electro-Optic Effect in the PESO Acousto-Optic Modulator

    DTIC Science & Technology

    1994-11-09

    AD-A286 355 NAIC-ID(RS)T-0395-94 NATIONAL AIR INTELLIGENCE CENTER ELECTRO - OPTIC EFFECT IN THE PESO ACOUSTO-OPTIC MODULATOR by Tai Renzhong, Lu Futun...owing to coupling.betw;ee.elecuc grazing" and "acou- tic grating". Linear electro - optic effect in PESO modulator is helpful to the diffraction and...crystaO A-l/Am,ARjAb, anl / ar:.. thtta=30 and theta=900 . Along these two orientations. th;- electro - optic effect is restricted tcŽ the rn :-t m:,n e

  16. Acoustic wave velocities in two-dimensional composite structures based on acousto-optical crystals

    NASA Astrophysics Data System (ADS)

    Mal'neva, P. V.; Trushin, A. S.

    2015-04-01

    Sound velocities in two-dimensional composite structures based on isotropic and anisotropic acousto-optical crystals have been determined by numerical simulations. The isotropic materials are represented by fused quartz (SiO2) and flint glass, while anisotropic materials include tetragonal crystals of paratellurite (TeO2) and rutile (TiO2) and a trigonal crystal of tellurium (Te). It is established that the acoustic anisotropy of periodic composite structures strongly depends on both the chemical composition and geometric parameters of components.

  17. Acousto-optic diffraction of multicolour Ar-laser radiation in crystalline quartz

    SciTech Connect

    Kotov, V M; Averin, S V; Voronko, A I; Kuznetsov, P I; Tikhomirov, S A; Shkerdin, G N; Bulyuk, A N

    2015-10-31

    We have studied acousto-optic Bragg diffraction of multicolour radiation, generated by an Ar laser in the blue-green region of the spectrum, on an acoustic wave propagating in crystalline quartz. It is shown that crystalline quartz significantly exceeds commonly used paratellurite in terms of phase matching of optical beams with a single acoustic wave. We have performed experiments on pulse modulation of Ar-laser radiation. It is shown that distortions introduced into optical pulses are substantially less when use is made of a quartz crystal rather than paratellurite. (acoustooptics)

  18. Acousto-optic resonant coupling of three spatial modes in an optical fiber.

    PubMed

    Park, Hee Su; Song, Kwang Yong

    2014-01-27

    A fiber-optic analogue to an externally driven three-level quantum state is demonstrated by acousto-optic coupling of the spatial modes in a few-mode fiber. Under the condition analogous to electromagnetically induced transparency, a narrow-bandwidth transmission within an absorption band for the fundamental mode is demonstrated. The presented structure is an efficient converter between the fundamental mode and the higher-order modes that cannot be easily addressed by previous techniques, therefore can play a significant role in the next-generation space-division multiplexing communications as an arbitrarily mode-selectable router.

  19. Actively mode-locked fiber laser using acousto-optic modulator

    NASA Astrophysics Data System (ADS)

    Nikodem, Michal P.; Sergeant, Hendrik; Kaczmarek, Pawel; Abramski, Krzysztof M.

    2008-12-01

    In recent years we have observed growing interest in mode-locked fiber lasers. Development of erbium doped fiber (EDF) amplifiers and WDM technique made 3rd telecommunication window extremely interesting region for ultrafast optics. The main advantages of fiber lasers i.e. narrow linewidth and wide gain bandwidth make them very attractive sources in various applications. In this paper we present an actively mode-locked erbium doped fiber ring laser. Modelocking is obtained using an acousto-optic modulator (AOM) coupled into the laser cavity. The impact of different parameters (e.g. light polarization, modulation frequency) is investigated. We study mechanisms of controlling the wavelength of the laser.

  20. Acousto-optic parallel read/write head for optical disk data storage.

    PubMed

    McLeod, Robert R; Walter, Sarah K

    2006-09-20

    Parallel read and write of optical disks has traditionally used a static grating for read or a linear array of independent lasers for read and write. Depending on the implementation, these systems suffer from coherent cross talk, excessive space between spots, and an inability to independently track. We show that a dynamic acousto-optic grating can generate multiple parallel read/write spots on the disk, each of which can be independently modulated and tracked and all of which are incoherent in less that a bit period. The resulting disk pickup can potentially reach gigabit per second transfer rates with only a modest increase in the drive complexity.

  1. Acousto-optic parallel read/write head for optical disk data storage

    NASA Astrophysics Data System (ADS)

    McLeod, Robert R.; Walter, Sarah K.

    2006-09-01

    Parallel read and write of optical disks has traditionally used a static grating for read or a linear array of independent lasers for read and write. Depending on the implementation, these systems suffer from coherent cross talk, excessive space between spots, and an inability to independently track. We show that a dynamic acousto-optic grating can generate multiple parallel read/write spots on the disk, each of which can be independently modulated and tracked and all of which are incoherent in less that a bit period. The resulting disk pickup can potentially reach gigabit per second transfer rates with only a modest increase in the drive complexity.

  2. Acousto-optical interaction in fishbone-like one-dimensional phoxonic crystal nanobeam

    NASA Astrophysics Data System (ADS)

    Hsiao, Fu-Li; Hsieh, Hao-Yu; Hsieh, Cheng-Yi; Chiu, Chien-Chang

    2014-09-01

    We demonstrate the simultaneous existence of slow photonic and phononic modes in a fishbone-like one-dimensional phoxonic crystal nanobeam. The phoxonic crystal nanobeam, which is formed by a suspended fishbone-like silicon waveguide, is not only an optical one-dimensional grating waveguide but also a waveguide with acoustic local resonance. Because of the slow group velocities, the acousto-optical interactions are significantly enhanced. The operating optical wavelength and acoustic frequency can be manipulated individually by varying certain geometric parameters of the nanobeam.

  3. Anisotropy of an acousto-optic figure of merit for NaBi(MoO4)2 crystals.

    PubMed

    Mys, Oksana; Krupych, Oleh; Vlokh, Rostyslav

    2016-10-01

    We develop a technique for analyzing the anisotropy of an acousto-optic figure of merit for crystals belonging to tetragonal symmetry groups 4/m, 4, and 4¯. The technique is based on phenomenological relations that describe anisotropies of the effective elasto-optic coefficients and the acoustic wave velocities. Our approach is verified on the example of NaBi(MoO4)2 crystals for all possible types and geometries of acousto-optic interactions. We list and characterize the acousto-optic interaction geometries at which the maximal acousto-optic figures of merit are reached for both isotropic and anisotropic interaction types. Finally, we show that the acousto-optic efficiency of NaBi(MoO4)2 originates mainly from large elasto-optic coefficients.

  4. Spin-to-orbit conversion at acousto-optic diffraction of light: conservation of optical angular momentum.

    PubMed

    Skab, Ihor; Vlokh, Rostyslav

    2012-04-01

    Acousto-optic diffraction of light in optically active cubic crystals is analyzed from the viewpoint of conservation of optical angular momentum. It is shown that the availability of angular momentum in the diffracted optical beam can be necessarily inferred from the requirements of angular momentum conservation law. As follows from our analysis, a circularly polarized diffracted wave should bear an orbital angular momentum. The efficiency of the spin-to-orbit momentum conversion is governed by the efficiency of acousto-optic diffraction.

  5. Acousto-optically tuned isotopic CO{sub 2} lasers for long-range differential absorption LIDAR

    SciTech Connect

    Thompson, D.C.; Busch, G.E.; Hewitt, C.J.; Remelius, D.K.; Shimada, Tsutomu; Strauss, C.E.M.; Wilson, C.W.

    1998-12-01

    The authors are developing 2--100 kHz repetition rate CO{sub 2} lasers with milliJoule pulse energies, rapid acousto-optic tuning and isotopic gas mixes, for Differential Absorption LIDAR (DIAL) applications. The authors explain the tuning method, which uses a pair of acousto-optic modulators and is capable of random access to CO{sub 2} laser lines at rates of 100 kHz or more. The laser system is also described, and they report on performance with both normal and isotopic gas mixes.

  6. Addressable, large-field second harmonic generation microscopy based on 2D acousto-optical deflector and spatial light modulator.

    PubMed

    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.

  7. Addressable, large-field second harmonic generation microscopy based on 2D acousto-optical deflector and spatial light modulator

    PubMed Central

    Shao, Yonghong; Liu, Honghai; Qin, Wan; Qu, Junle; Peng, Xiang; Niu, Hanben

    2013-01-01

    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. PMID:24307756

  8. Investigation of a mercurous chloride acousto-optic cell based on longitudinal acoustic mode.

    PubMed

    Gupta, Neelam

    2009-03-01

    A number of spectral imagers using acousto-optic tunable filters (AOTFs) operating from the UV to the longwave infrared (LWIR) using KDP, MgF(2), TeO(2), and Tl(3)AsSe(3) crystals to cover different spectral regions have been developed. In the LWIR there is a lack of high quality acousto-optic (AO) materials. Mercurous halide (Hg(2)Cl(2) and Hg(2)Br(2)) crystals are highly anisotropic with a high AO figure of merit due to slow acoustic velocities and high photoelastic constants and are transparent over a wide spectral region from 0.35 to 20 mum for Hg(2)Cl(2) and from 0.4 to 30 mum for Hg(2)Br(2). AO modulators, deflectors, and AOTFs based on these crystals can operate over a wide spectral range. Single crystals of these materials are being grown and some prototype devices have been fabricated. Results are presented from device characterization for an AO cell fabricated in Hg(2)Cl(2) based on longitudinal acoustic mode propagation. This device was very useful in demonstrating the AO interaction as well as soundness of the transducer bonding technique. Acoustic phase velocity is calculated and measured, diffraction efficiency is obtained from experiments, and the AO figure of merit of the sample is evaluated.

  9. LIGHT MODULATION: Wide-aperture diffraction of unpolarised radiation in a system of two acousto-optic filters

    NASA Astrophysics Data System (ADS)

    Magdich, L. N.; Yushkov, K. B.; Voloshinov, V. B.

    2009-04-01

    Light diffraction is studied in two tandem acousto-optic cells filtering unpolarised radiation with a wide angular spectrum. It is shown that the side lobes of the ultrasonic radiation pattern of a piezoelectric transducer produce side diffraction intensity maxima at the output of the system consisting of two filters. Diffraction in paratellurite filters is studied experimentally at 1.06 μm.

  10. Acousto-optic Imaging System for In-situ Measurement of the High Temperature Distribution in Micron-size Specimens

    NASA Astrophysics Data System (ADS)

    Machikhin, Alexander S.; Zinin, Pavel V.; Shurygin, Alexander V.

    We developed a unique acousto-optic imaging system for in-situ measurement of high temperature distribution on micron-size specimens. The system was designed to measure temperature distribution inside minerals and functional material phases subjected to high pressure and high temperatures in a diamond anvil cell (DAC) heated by a high powered laser.

  11. Contrast enhancement in microscopy of human thyroid tumors by means of acousto-optic adaptive spatial filtering

    NASA Astrophysics Data System (ADS)

    Yushkov, Konstantin B.; Molchanov, Vladimir Y.; Belousov, Pavel V.; Abrosimov, Aleksander Y.

    2016-01-01

    We report a method for edge enhancement in the images of transparent samples using analog image processing in coherent light. The experimental technique is based on adaptive spatial filtering with an acousto-optic tunable filter in a telecentric optical system. We demonstrate processing of microscopic images of unstained and stained histological sections of human thyroid tumor with improved contrast.

  12. Quasi-4D laser diagnostics using an acousto-optic deflector scanning system

    NASA Astrophysics Data System (ADS)

    Li, Tao; Pareja, Jhon; Becker, Lukas; Heddrich, Wolfgang; Dreizler, Andreas; Böhm, Benjamin

    2017-03-01

    In this paper, a novel scanning system for laser diagnostics was developed and characterized. The system is based on the acousto-optic deflection of a high-speed pulsed laser. Results showed that quasi-volumetric laser illumination with high precision and accuracy can be achieved with a simplified and flexible optical setup. The feasibility of the method for performing high-speed quasi-4D laser diagnostics was demonstrated by the tomographic visualization of a lifted turbulent jet flame using Mie-scattering and multi-plane particle image velocimetry measurements of a turbulent non-reactive mixing case. Three-dimensional flame and flow structures can be detected and tracked with this new scanning system.

  13. Secure chaotic transmission of electrocardiography signals with acousto-optic modulation under profiled beam propagation.

    PubMed

    Almehmadi, Fares S; Chatterjee, Monish R

    2015-01-10

    Electrocardiography (ECG) signals are used for both medical purposes and identifying individuals. It is often necessary to encrypt this highly sensitive information before it is transmitted over any channel. A closed-loop acousto-optic hybrid device acting as a chaotic modulator is applied to ECG signals to achieve this encryption. Recently improved modeling of this approach using profiled optical beams has shown it to be very sensitive to key parameters that characterize the encryption and decryption process, exhibiting its potential for secure transmission of analog and digital signals. Here the encryption and decryption is demonstrated for ECG signals, both analog and digital versions, illustrating strong encryption without significant distortion. Performance analysis pertinent to both analog and digital transmission of the ECG waveform is also carried out using output signal-to-noise, signal-to-distortion, and bit-error-rate measures relative to the key parameters and presence of channel noise in the system.

  14. Acousto-Optic Modulation and Optoacoustic Gating in Piezo-Optomechanical Circuits

    NASA Astrophysics Data System (ADS)

    Balram, Krishna C.; Davanço, Marcelo I.; Ilic, B. Robert; Kyhm, Ji-Hoon; Song, Jin Dong; Srinivasan, Kartik

    2017-02-01

    Acoustic-wave devices provide a promising chip-scale platform for efficiently coupling radio frequency (rf) and optical fields. Here, we use an integrated piezo-optomechanical circuit platform that exploits both the piezoelectric and photoelastic coupling mechanisms to link 2.4-GHz rf waves to 194-THz (1550 nm) optical waves, through coupling to propagating and localized 2.4-GHz acoustic waves. We demonstrate acousto-optic modulation, resonant in both the optical and mechanical domains, in which waveforms encoded on the rf carrier are mapped to the optical field. We also show optoacoustic gating, in which the application of modulated optical pulses interferometrically gates the transmission of propagating acoustic pulses. The time-domain characteristics of this system under both pulsed rf and pulsed optical excitation are considered in the context of the different physical pathways involved in driving the acoustic waves, and modeled through the coupled mode equations of cavity optomechanics.

  15. Stabilisation of a fibre frequency synthesiser using acousto-optical and electro-optical modulators

    NASA Astrophysics Data System (ADS)

    Koliada, N. A.; Nyushkov, B. N.; Pivtsov, V. S.; Dychkov, A. S.; Farnosov, S. A.; Denisov, V. I.; Bagayev, S. N.

    2016-12-01

    A fibre-optic frequency synthesiser is developed that is stabilised to the optical frequency standard based on molecular iodine ({\\text{Nd : YAG/I}}2). The possibility of transferring stability of the optical frequency standard to other optical frequencies in the IR range 1 - 2 \\unicode{956}{\\text{m}} and to the RF range by using synthesiser phase-locked loops (PLLs) with acousto-optical and electro-optical modulators is experimentally demonstrated. The additive instability introduced into the optical frequency comb of the synthesiser (which arises due to PLL residual random errors) is several orders less than the intrinsic instability of the reference optical frequency standard employed (i.e., is noticeably less than 1 × 10-13 for 1 {\\text{s}} and 5 × 10-15 for 1000 {\\text{s}}).

  16. Efficient double-filtering with a single acousto-optic tunable filter.

    PubMed

    You, Jang-Woo; Ahn, Jeongho; Kim, Soohyun; Kim, Daesuk

    2008-12-22

    We describe an efficient double-filtering method that uses a single acousto-optic tunable filter (AOTF) to improve the spectral resolution and intrinsic sidelobes for the spectral domain analysis systems. Double filtering with a single AOTF is realized by applying a unique feedback scheme based on the fact that incident light can be diffracted into two orthogonally polarized beams of light by an AOTF. Our theoretical explanation attempts to address and satisfy the main prerequisite for the proposed idea. The experimental results confirm that the proposed method achieves a 20% to 30% improvement in spectral resolution and 10 dB suppression of sidelobes with minimized light loss for the extraordinary incident light. We believe that the results of using an AOTF are comparable to the results achieved with two AOTFs in tandem.

  17. Research of acousto-optic correlator for new telecommunication receiver system

    NASA Astrophysics Data System (ADS)

    Shao, Dingrong; Li, Shujian; Zhou, Bin

    1994-01-01

    A promising receive system model working in high frequency and wideband, with large processing gain, is researched. As the crux, an acousto-optic correlator is discussed especially. Analyzing the principle of a bulk wave space integrating A-O correlator/convolver, an experimental signal processor with large Gp using a high frequency wideband A-O device is configured. By this system, operation of correlation/convolution with BPSK modulated by Barker code is completed. The result is in accordance with the theoretic calculation. This model works in 175 MHz center frequency, 120 MHz bandwidth, and 29.4 dB processing gain. The method of detecting the first order diffracted light beam is proved theoretically and experimentally to expend dynamic range.

  18. Actively mode-locked fiber ring laser by intermodal acousto-optic modulation.

    PubMed

    Bello-Jiménez, M; Cuadrado-Laborde, C; Sáez-Rodríguez, D; Diez, A; Cruz, J L; Andrés, M V

    2010-11-15

    We report an actively mode-locked fiber ring laser. A simple and low-insertion-loss acousto-optic modulator driven by standing flexural waves, which couples core-to-cladding modes in a standard single-mode optical fiber, is used as an active mechanism for mode locking. Among the remarkable features of the modulator, we mention its high modulation depth (72%), broad bandwidth (187 GHz), easy tunability in the optical wavelength, and low insertion losses (0.7 dB). The narrowest optical pulses obtained were of 95 ps time width, 21 mW peak power, repetition rate of 4.758 MHz, and 110 mW of pump power.

  19. Mode locking of an all-fiber laser by acousto-optic superlattice modulation.

    PubMed

    Cuadrado-Laborde, C; Diez, A; Delgado-Pinar, M; Cruz, J L; Andrés, M V

    2009-04-01

    Active mode locking of an erbium-doped all-fiber laser with a Bragg-grating-based acousto-optic modulator is demonstrated. The fiber Bragg grating was acoustically modulated by a standing longitudinal elastic wave, which periodically modulates the sidebands at twice the acoustic frequency. The laser has a Fabry-Perot configuration in which cavity loss modulation is achieved by tuning the output fiber Bragg grating to one of the acoustically induced sidebands. Optical pulses at 9 MHz repetition rate, 120 mW peak power, and 780 ps temporal width were obtained. The output results to be stable and has a timing jitter below 40 ps. The measured linewidth, 2.8 pm, demonstrates that these pulses are transform limited.

  20. Spatial and temporal thermal analysis of acousto-optic deflectors using finite element analysis model.

    PubMed

    Jiang, Runhua; Zhou, Zhenqiao; Lv, Xiaohua; Zeng, Shaoqun; Huang, Zhifeng; Zhou, Huaichun

    2012-07-01

    Thermal effects greatly influence the optical properties of the acousto-optic deflectors (AODs). Thermal analysis plays an important role in modern AOD design. However, the lack of an effective method of analysis limits the prediction in the thermal performance. In this paper, we propose a finite element analysis model to analyze the thermal effects of a TeO(2)-based AOD. Both transducer heating and acoustic absorption are considered as thermal sources. The anisotropy of sound propagation is taken into account for determining the acoustic absorption. Based on this model, a transient thermal analysis is employed using ANSYS software. The spatial temperature distributions in the crystal and the temperature changes over time are acquired. The simulation results are validated by experimental results. The effect of heat source and heat convection on temperature distribution is discussed. This numerical model and analytical method of thermal analysis would be helpful in the thermal design and practical applications of AODs.

  1. External cavity quantum cascade lasers with ultra rapid acousto-optic tuning

    SciTech Connect

    Lyakh, A. Barron-Jimenez, R.; Dunayevskiy, I.; Go, R.; Patel, C. Kumar N.

    2015-04-06

    We report operation of tunable external cavity quantum cascade lasers with emission wavelength controlled by an acousto-optic modulator (AOM). A long-wave infrared quantum cascade laser wavelength tuned from ∼8.5 μm to ∼9.8 μm when the AOM frequency was changed from ∼41MHz to ∼49 MHz. The laser delivered over 350 mW of average power at the center of the tuning curve in a linewidth of ∼4.7 cm{sup −1}. Measured wavelength switching time between any two wavelengths within the tuning range of the QCL was less than 1 μs. Spectral measurements of infrared absorption features of Freon demonstrated a capability of obtaining complete spectral data in less than 20 μs.

  2. Acousto-optic liquid-crystal analog beam former for phased-array antennas.

    PubMed

    Riza, N A

    1994-06-10

    A compact phased-array antenna acousto-optic beam former with element-level analog phase (0-2π) and amplitude control using nematic-liquid-crystal display-type technology is experimentally demonstrated. Measurements indicate > 6-bit phase control and 52.6 dB of amplitude-attenuation control. High-quality error calibration and antenna sidelobe-level control is possible with this low-control-power analog beam former. Optical system options using rf Bragg cells or wideband Bragg cells are discussed, with the rf design being the current preferred approach. Transmit-receive beam forming based on frequency upconversion-downconversion by electronic mixing is introduced for the rf Bragg-cell beam former, and comparisons with digital beam forming are highlighted. A millimeter-wave signal generation and control optical architecture is described.

  3. Exact solution for four-order acousto-optic Bragg diffraction with arbitrary initial conditions.

    PubMed

    Pieper, Ron; Koslover, Deborah; Poon, Ting-Chung

    2009-03-01

    An exact solution to the four-order acousto-optic (AO) Bragg diffraction problem with arbitrary initial conditions compatible with exact Bragg angle incident light is developed. The solution, obtained by solving a 4th-order differential equation, is formalized into a transition matrix operator predicting diffracted light orders at the exit of the AO cell in terms of the same diffracted light orders at the entrance. It is shown that the transition matrix is unitary and that this unitary matrix condition is sufficient to guarantee energy conservation. A comparison of analytical solutions with numerical predictions validates the formalism. Although not directly related to the approach used to obtain the solution, it was discovered that all four generated eigenvalues from the four-order AO differential matrix operator are expressed simply in terms of Euclid's Divine Proportion.

  4. Acousto-optic control of the LPG spectrum for sensing applications

    NASA Astrophysics Data System (ADS)

    Oliveira, Roberson A.; Possetti, Gustavo R. C.; Marques, Carlos A. F.; Neves, Paulo T., Jr.; Bavastri, Carlos A.; Kamikawachi, Ricardo C.; Fabris, José L.; Muller, Marcia; Nogueira, Rogério N.; Canning, John; Pohl, Alexandre A. P.

    2011-05-01

    Experimental and numerical demonstration of the acousto-optic effect applied in long period grating by means of flexural waves is presented. The interaction between acoustic and optical waves is modeled with help of the method of assumed modes, which delivers the strain field inside the grating and the transfer matrix method, which, given the strain field as input, calculate the resultant grating spectrum. The experimental and theoretical results are found to be in good agreement. The main effect of the bends in the grating is the break of degeneracy of the circular cladding modes, leading the attenuation band to be changed. Among all the applications of this methodology, it is important to mention the possibility of use as a tunable filter, laser cavity gain controller, switching device and transducer in sensing systems.

  5. Performance of an acousto-optic Bragg cell under ion microbeam irradiation

    SciTech Connect

    Paxton, A.H.; Schone, H.; Taylor, E.W.; McKinney, S.; Doyle, B.L.

    1997-08-01

    An acousto optic (AO) deflector composed of PbMoO{sub 4} was exposed to 4 MeV protons while operating under Bragg angle conditions. An ion beam in air of 1 mm width was directed normal to the crystal face and laser beam. Between exposures, the approximately 13 mm x 8.5 mm AO deflector was mechanically translated in two dimensions in front of the fixed ion beam. The AO diffraction efficiency was mapped and was observed to change as a function of ion beam location and dose rate. These effects are attributed to the induced change in the temperature distribution of the crystal, which changed the sonic velocity and refractive index. Similar effects were observed when the ion beam was directed at the acoustic transducer.

  6. Optical Multiplications With Single Element 2-D Acousto-Optic Laser Beam Deflector

    NASA Astrophysics Data System (ADS)

    Soos, Jolanta I.; Leepa, Douglas C.; Rosemeier, Ronald G.

    1989-05-01

    With the current need for developing very fast computers in comparison to conventional digital chip based systems, the future for optical based signal processing is very bright. Attention has turned to a different application of optics utilizing mathematical operations, in which case operations are numerical, sometimes discrete, and often algebraic in nature. Interest has been so vigorous that many view it as a small revolution in optics, whereby optical signal processing is beginning to encompass what is frequently described as optical computing. The term is fully intended to imply a close comparison with the operations performed by scientific digital canputers. This paper will describe the applications of single element 2-D acousto-optic deflectors for optical multiplication systems.

  7. Matrix operations utilizing multichannel two-dimensional acousto-optic deflector

    NASA Astrophysics Data System (ADS)

    Barocsi, Attila; Jakab, Laszlo; Richter, Peter I.

    1994-01-01

    A linear scanning light deflector, or Bragg-cell, is a widely utilized acousto-optic (AO) signal processing device. Its application is, however, limited due to its line scanning property. To overcome this deficiency an area (or matrix) scanning deflector can be built by consecutively placing two, orthogonally positioned, linear deflectors. A more sophisticated method, however, is the realization of a `monolithic' area scanning device, or 2-D (XY-) deflector, that contains a single Bragg cell. If each dimension of the cell has several input channels the element can serve as a special optical processor in various applications. In this work a multichannel XY-deflector is examined with special regard to its utilization as a fast optical crossbar switch and matrix processor. An experimental set-up with a 2 * 2 channel cell is also demonstrated.

  8. Spatial mapping of transient atomic concentrations using acousto-optic deflection

    SciTech Connect

    Huie, C.W.; Yeung, E.S.

    1986-08-01

    We report a new imaging system for obtaining spatially and temporally resolved atomic absorption profiles for transient events. This is based on an acousto-optic beam deflector that scans the probe laser beam in one dimension repeatedly across the spatial region of interest. Scan rates of 10 ..mu..s durations essentially freeze the absorbing species in time to allow a spatial resolution of 0.06 cm over a 1.2 cm length. With the use of 2K of buffer memory and a digitization interval of 200 nm (12 bits), the time evolution can be followed up to a total of 400 ..mu..s. The capabilities are demonstrated in the study of atom formation in a laser generated plume for a sodium tungstate surface.

  9. Gain-switched Ho:YAG ceramic laser with an acousto-optic modulator

    NASA Astrophysics Data System (ADS)

    Zhang, Jianing; Shen, Deyuan; Zhang, Jian; Tang, Dingyuan; Chen, Hao

    2016-04-01

    We demonstrate a gain-switched Ho:YAG ceramic laser in-band pumped by an acousto-optically modulated thulium fiber laser at ˜1908 nm. The laser pulse repetition rate could be tuned continuously from 60 to 100 kHz with the pulse energy kept constant for a certain pump power level. The shortest pulse width of 204 ns and a maximum peak power of 75 W have been obtained at 60 kHz under the maximum pump power level of 11 W. A maximum average output power of 1.4 W has been achieved with a pulse repetition rate of 100 kHz, corresponding to a slope efficiency of 57% with respect to the incident pump power. The prospects for further improvement in laser performance are discussed.

  10. Hyperspectral imager, from ultraviolet to visible, with a KDP acousto-optic tunable filter.

    PubMed

    Gupta, Neelam; Voloshinov, Vitaly

    2004-05-01

    Hyperspectral imaging in the ultraviolet to visible spectral region has applications in astronomy, biology, chemistry, medical sciences, etc. A novel electronically tunable, random-wavelength access, compact, no-moving-parts, vibration-insensitive, computer-controlled hyperspectral imager operating from 220 to 480 nm with a spectral resolution of 160 cm(-1), e.g., 2 nm at 350 nm, has been developed by use of a KDP acousto-optic tunable filter (AOTF) with an enhanced CCD camera and a pair of crossed calcite Glan-Taylor polarizing prisms. The linear and angular apertures of the AOTF are 1.5 x 1.5 cm2 and 1.2 degrees, respectively. Imager setup and spectral imaging results as well as analyses and discussion of various factors affecting image quality are presented.

  11. Acousto-optical post-processor time-integrating correlator calibration updates

    NASA Astrophysics Data System (ADS)

    Baker, P.

    1992-02-01

    The acousto-optical signal processing facility and time integrating correlator system has been updated to allow proper handling of multiple peaks and to increase the readout rate. These modifications are described. In the supervisor task, a phase shift dialog box has been added to the phase shift menu items. This dialog box allows the operator to limit the area examined while searching for peaks or to specify the peak location directly. An amplitude offset calibration dialog box has been added to the amplitude offset menu item. This dialog box allows the operator to limit the area examined during the amplitude offset calibration, which is designed to perform calculations on a portion of the correlogram that does not contain a peak. In addition, the interface between the photodetector and personal computer has been modified to double the maximum pixel clock rate to 10 MHz.

  12. Acousto-optic gyrotropic-crystal-based modulator with a rotating polarisation vector

    NASA Astrophysics Data System (ADS)

    Kotov, V. M.; Averin, S. V.; Kotov, E. V.; Voronko, A. I.; Tikhomirov, S. A.

    2017-02-01

    We study the influence of ellipticity of gyrotropic-crystal eigenwaves on the output characteristics of an acousto-optic (AO) modulator based on the interferometer scheme. The schemes of AO modulators are considered, which provide the polarisation vector rotation frequency fn/2, where f is the frequency of the acoustic wave, and n is the integer. Preference is given to the scheme combining cascade and polarisation-independent diffraction. An experimental layout of the AO modulator operating at f = 44.5 MHz is described, the modulation frequency of the output laser light intensity being 89 MHz. The frequency of the electrical signal from the photodetector is equal to 179.5 MHz.

  13. Dynamic acousto-optic control of a strongly coupled photonic molecule

    PubMed Central

    Kapfinger, Stephan; Reichert, Thorsten; Lichtmannecker, Stefan; Müller, Kai; Finley, Jonathan J.; Wixforth, Achim; Kaniber, Michael; Krenner, Hubert J.

    2015-01-01

    Strongly confined photonic modes can couple to quantum emitters and mechanical excitations. To harness the full potential in quantum photonic circuits, interactions between different constituents have to be precisely and dynamically controlled. Here, a prototypical coupled element, a photonic molecule defined in a photonic crystal membrane, is controlled by a radio frequency surface acoustic wave. The sound wave is tailored to deliberately switch on and off the bond of the photonic molecule on sub-nanosecond timescales. In time-resolved experiments, the acousto-optically controllable coupling is directly observed as clear anticrossings between the two nanophotonic modes. The coupling strength is determined directly from the experimental data. Both the time dependence of the tuning and the inter-cavity coupling strength are found to be in excellent agreement with numerical calculations. The demonstrated mechanical technique can be directly applied for dynamic quantum gate operations in state-of-the-art-coupled nanophotonic, quantum cavity electrodynamic and optomechanical systems. PMID:26436203

  14. Time and space integrating acousto-optic folded spectrum processing for SETI

    NASA Technical Reports Server (NTRS)

    Wagner, K.; Psaltis, D.

    1986-01-01

    Time and space integrating folded spectrum techniques utilizing acousto-optic devices (AOD) as 1-D input transducers are investigated for a potential application as wideband, high resolution, large processing gain spectrum analyzers in the search for extra-terrestrial intelligence (SETI) program. The space integrating Fourier transform performed by a lens channels the coarse spectral components diffracted from an AOD onto an array of time integrating narrowband fine resolution spectrum analyzers. The pulsing action of a laser diode samples the interferometrically detected output, aliasing the fine resolution components to baseband, as required for the subsequent charge coupled devices (CCD) processing. The raster scan mechanism incorporated into the readout of the CCD detector array is used to unfold the 2-D transform, reproducing the desired high resolution Fourier transform of the input signal.

  15. Self-acousto-optic modulation and orthogonality violation in the transverse modes of a broad-area Nd-doped yttrium-aluminum-garnet single-shot laser

    SciTech Connect

    Soler Rus, M. Odin; Cabrera-Granado, E.; Guerra Perez, J. M.

    2011-05-15

    Self-acousto-optic Raman-Nath modulation and nonorthogonal transversal modes are found in a broad-area Nd:YAG single-shot laser. The device is free from the thermal-induced effects previously related to orthogonality violation and the acousto-optic modulation comes from a shock wave produced by the discharge of the flash lamps that optically pump the laser. The experimental findings are reproduced by a general model of a class B laser.

  16. Acousto-optical pulsar processor frequency scale calibration for increase accuracy measurement of time of arrival radioemission impulses

    NASA Astrophysics Data System (ADS)

    Esepkina, Nelli A.; Lavrov, Aleksandr P.; Molodyakov, Sergey A.

    2006-04-01

    The acousto-optical processor (AOP) is based on an acousto-optical spectrum analyzer with a CCD photodetector operating in special pipeline mode (shift-and-add mode), which allows spectral components of the input signal to be added with controlled time delay immediately in the CCD photodetector. The proposed AOP was successfully used on radiotelescope RT-64 (Kalyazin Radio Astronomy Observatory FIAN) for the observation of pulsars at 1 .4 GHz in 45 MHz bandwidth. The AOP frequency scale calibration allows increasing accuracy of measurement of time of arrival radioemission pulses. Experimental results on investigation of AOP work on RT-64 and radioemission pulses profiles for pulsar PSR 1937+21 are submitted.

  17. Algorithm of Shaping Multiple-beam Braggs Acousto-optic Diffraction Laser Field Into 1D and 2D Patterns

    NASA Astrophysics Data System (ADS)

    Zakharchenko, S.; Baturin, A.

    2015-09-01

    Algorithm of solving a direct problem of acousto-optic interaction between laser emission and acoustic signal consisting of a set of equidistant frequency components is proposed. An infinite system of coupled wave differential equations is reduced to eigenvalue problem. The contribution of the higher rediffraction orders is analyzed separately. Inverse problem of finding an optimal set of equidistant frequency components of a driving acoustic signal to form the objective diffraction pattern is also considered and a few optimization approaches are analyzed. A naïve heuristic method of splitting 2D pattern into subframes, each suitable for simultaneous projection by two acousto-optical deflectors driven by multifrequency composite signal, is developed.

  18. Experimental analysis of distributed pump absorption and refractive index changes in Yb-doped fibers using acousto-optic interaction.

    PubMed

    Alcusa-Sáez, E P; Díez, A; Andrés, M V

    2015-03-01

    In-fiber acousto-optic interaction is used to characterize the refractive index changes at the C band in a single-mode ytterbium-doped optical fiber under 980 nm pumping. The transmission notch created by the acoustic-induced coupling between the core mode and a cladding mode shifts to longer wavelengths when the pump is delivered to the fiber. The electronic contribution to the refractive index change is quantified from the wavelength shift. Using a time-resolved acousto-optic method, we investigate the distribution of pump absorption, and the resulting refractive index change profile, along sections of ytterbium-doped fiber exceeding 1 m long under different pump power levels.

  19. An acousto-optical method for registration of erythrocytes' agglutination reaction—sera color influence on the resolving power

    NASA Astrophysics Data System (ADS)

    Doubrovski, V. A.; Medvedeva, M. F.; Torbin, S. O.

    2016-01-01

    The absorption spectra of agglutinating sera were used to determine blood groups. It was shown experimentally that the sera color significantly affects the resolving power of the acousto-optical method of blood typing. In order to increase the resolving power of the method and produce an invariance of the method for sera color, we suggested introducing a probing light beam individually for different sera. The proposed technique not only improves the resolving power of the method, but also reduces the risk of false interpretation of the experimental results and, hence, error in determining the blood group of the sample. The latter is especially important for the typing of blood samples with weak agglutination of erythrocytes. This study can be used in the development of an instrument for instrumental human blood group typing based on the acousto-optical method.

  20. Analytical study of acousto/optical holography-interfacing methods for acoustical and optical holography NDT research

    NASA Technical Reports Server (NTRS)

    El-Sum, H. M. A.

    1976-01-01

    The international status of the art of acousto optical imaging techniques adaptable to nondestructive testing and, interfacing methods for acoustical and optical holography in nondestructive testing research are studied. Evaluation of 20 different techniques encompassed investigation of varieties of detectors and detection schemes, all of which are described and summarized. Related investigation is reported in an Appendix. Important remarks on image quality, factors to be considered in designing a particular system, and conclusions and recommendations are presented. Three bibliographies are included.

  1. Calomel-made crystalline acousto-optical cell designed for an advanced regime of noncollinear two-phonon light scattering

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Alexandre S.; Arellanes, Adan Omar

    2016-03-01

    We study the potentials of a wide-aperture crystalline calomel-made acousto-optical cell. Characterizing this cell is nontrivial due to the chosen regime based on an advanced noncollinear two-phonon light scattering. Recently revealed important features of this phenomenon are essentially exploited in the cell and are investigated in more detail. These features can be observed more easily and simply in tetragonal crystals, e.g., calomel, exhibiting specific acousto-optical nonlinearity caused by the acoustic waves of finite amplitude. This parametric nonlinearity manifests itself at low acoustic powers in calomel possessing linear acoustic attenuation. The formerly identified additional degree of freedom, unique to this regime, is exploited for designing the cell with an eye to doubling the resolution due to two-phonon processes. We clarify the role of varying the central acoustic frequency and acoustic attenuation using that degree of freedom. Then the efficiency of calomel is exploited to expand the cell's bandwidth with a cost of its efficiency. Proof-of-principle experiments confirm the developed approaches and illustrate their applicability to innovative techniques of optical spectrum analysis with the improved resolution. The achieved spectral resolution of 0.205 Å at 405 nm and the resolving power 19,800 are the best for acousto-optical spectrometers dedicated to space or airborne operations to date as far as we know.

  2. Pre-Juno Optical Analysis of Jupiter's Atmosphere with the NMSU Acousto-optic Imaging Camera

    NASA Astrophysics Data System (ADS)

    Dahl, Emma; Chanover, Nancy J.; Voelz, David; Kuehn, David M.; Strycker, Paul D.

    2016-10-01

    Jupiter's upper atmosphere is a highly dynamic system in which clouds and storms change color, shape, and size on variable timescales. The exact mechanism by which the deep atmosphere affects these changes in the uppermost cloud deck is still unknown. With Juno's arrival at Jupiter in July 2016, the thermal radiation from the deep atmosphere will be measurable with the spacecraft's Microwave Radiometer. By taking detailed optical measurements of Jupiter's uppermost cloud deck in conjunction with Juno's microwave observations, we can provide a context in which to better understand these observations. This data will also provide a complement to the near-IR sensitivity of the Jovian InfraRed Auroral Mapper and will expand on the limited spectral coverage of JunoCam. Ultimately, we can utilize the two complementary datasets in order to thoroughly characterize Jupiter's atmosphere in terms of its vertical cloud structure, color distribution, and dynamical state throughout the Juno era. In order to obtain high spectral resolution images of Jupiter's atmosphere in the optical regime, we use the New Mexico State University Acousto-optic Imaging Camera (NAIC). NAIC contains an acousto-optic tunable filter, which allows us to take hyperspectral image cubes of Jupiter from 450-950 nm at an average spectral resolution (λ/dλ) of 242. We present an analysis of our pre-Juno dataset obtained with NAIC at the Apache Point Observatory 3.5-m telescope during the night of March 28, 2016. Under primarily photometric conditions, we obtained 6 hyperspectral image cubes of Jupiter over the course of the night, totaling approximately 2,960 images. From these data we derive low-resolution optical spectra of the Great Red Spot and a representative belt and zone to compare with previous work and laboratory measurements of candidate chromophore materials. Future work will focus on radiative transfer modeling to elucidate the Jovian cloud structure during the Juno era. This work was supported

  3. LD-pumped acousto-optical Q-switched burst-mode Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Pan, Hu; Yan, Renpeng; Li, Xudong; Ma, Yufei; Yu, Xin; Chen, Deying

    2016-04-01

    A high-repetition-rate, high-peak-power burst-mode laser for laser-based measurement applications is presented by using a master oscillator power amplifier structure. An laser diode arrays (LDA) side-pumped Nd:YAG acousto-optical (A-O) Q-switched laser serves as the master oscillator. Under pulsed pumping, pulse trains with 2-25 pulses are obtained when the repetition rate changes from 10 kHz to 100 kHz. The maximum pulse burst energy of 31.2 mJ is achieved in the A-O Q-switched pulse burst laser oscillator at 10 kHz. Two LDA side pumped Nd:YAG modules are employed in the amplification stage. After the amplification, the pulse burst energy at 10 kHz reaches ~170 mJ with a single pulse energy of 85.2 mJ and a pulse width of 14.5 ns, generating a peak power of 6.1 MW. At 100 kHz, the total burst energy reaches 220 mJ with a single pulse energy of 8.8 mJ in the pulse burst laser system.

  4. Deep-UV Based Acousto-Optic Tunable Filter for Spectral Sensing Applications

    NASA Technical Reports Server (NTRS)

    Prasad, Narasimha S.

    2006-01-01

    In this paper, recent progress made in the development of quartz and KDP crystal based acousto-optic tunable filters (AOTF) are presented. These AOTFs are developed for operation over deep-UV to near-UV wavelengths of 190 nm to 400 nm. Preliminary output performance measurements of quartz AOTF and design specifications of KDP AOTF are presented. At 355 nm, the quartz AOTF device offered approx.15% diffraction efficiency with a passband full-width-half-maximum (FWHM) of less than 0.0625 nm. Further characterization of quartz AOTF devices at deep-UV wavelengths is progressing. The hermetic packaging of KDP AOTF is nearing completion. The solid-state optical sources being used for excitation include nonlinear optics based high-energy tunable UV transmitters that operate around 320 nm and 308 nm wavelengths, and a tunable deep-UV laser operating over 193 nm to 210 nm. These AOTF devices have been developed as turn-key devices for primarily for space-based chemical and biological sensing applications using laser induced Fluorescence and resonance Raman techniques.

  5. A Lyman-alpha tunable acousto-optic filter for detecting superthermal flare protons

    NASA Technical Reports Server (NTRS)

    Mickey, Donald L.

    1994-01-01

    The goal of this project was to develop and characterize a narrow-band, tunable filter for use near the Lyman-alpha line of hydrogen at 121.6 nm. Such a filter could form the critical component of an instrument to observe asymmetries in the solar Lyman-alpha line, caused by energetic protons accelerated during the impulsive phase of solar flares. Characteristic charge-exchange nonthermal emission at Lyman alpha should be produced when sub-MeV protons are injected into the chromosphere, but no instrument suitable for their detection has been developed. Such an instrument would require a narrow-band (less than 0.01 nm) tunable filter with aperture and throughput consistent with imaging a solar active region at 0.1 second intervals. The development of acousto-optic tunable filters (AOTF) suitable for use as compact, simple tunable filters for astronomical work suggested an investigation into the use of an AOTF at Lyman-alpha.

  6. High repetition rate laser-induced breakdown spectroscopy using acousto-optically gated detection

    SciTech Connect

    Pořízka, Pavel; Kaiser, Jozef

    2014-07-15

    This contribution introduces a new type of setup for fast sample analysis using laser-induced breakdown spectroscopy (LIBS). The novel design combines a high repetition rate laser (up to 50 kHz) as excitation source and an acousto-optical modulator (AOM) as a fast switch for temporally gating the detection of the emitted light. The plasma radiation is led through the active medium of the AOM where it is diffracted on the transient ultrasonic Bragg grid. The diffracted radiation is detected by a compact Czerny-Turner spectrometer equipped with a CCD line detector. Utilizing the new combination of high repetition rate lasers and AOM gated detection, rapid measurements with total integration times of only 10 ms resulted in a limit of detection (LOD) of 0.13 wt.% for magnesium in aluminum alloys. This short integration time corresponds to 100 analyses/s. Temporal gating of LIP radiation results in improved LODs and consecutively higher sensitivity of the LIBS setup. Therefore, an AOM could be beneficially utilized to temporally detect plasmas induced by high repetition rate lasers. The AOM in combination with miniaturized Czerny-Turner spectrometers equipped with CCD line detectors and small footprint diode pumped solid state lasers results in temporally gateable compact LIBS setups.

  7. Theoretical calculation and experimental study of acousto-optically Q-switched CO2 laser.

    PubMed

    Xie, Jijang; Guo, Ruhai; Li, Dianjun; Zhang, Chuansheng; Yang, Guilong; Geng, Yumin

    2010-06-07

    Using resonator inserted with acousto-optically modulator, the experiments of the compacted CO(2) laser were performed with Q-switch. According to various factors that influenced the output of laser, the theoretical calculation of its main parameters was conducted by Q-switched pulsed laser rate equations. Based on the results, the technical route and approach were presented for optimization design of this laser. The measured peak power of this laser device was more than 4000W and pulsed width was 180ns which agreed well with the theoretical calculation. The range of repetition frequency could adjust from 1 Hz to 100 kHz. The theoretical analyzes and experimental results showed that the acoustic traveling time of ultrasonic field could not influence the pulse width of laser so that it did not require inserting optical lens in the cavity to reduce the diameter of beam. The acoustic traveling time only extended the establishingtime of laser pulse. The optimum working frequency of laser is about 1 kHz, which it matched with the radiation life time (1 ms) of CO(2) molecular upper energy level. When the frequency is above 1 kHz, the pulse width of laser increased with the frequency. The full band of wavelength tuning between 9.2 microm and 10.8 microm was obtained by grating selection one by one which the measured spectrum lines were over 30 in the condition of Q-switch.

  8. An acousto-optic tunable filter enhanced CO{sub 2} lidar atmospheric monitor

    SciTech Connect

    Taylor, L.H.; Suhre, D.R.; Mani, S.S.

    1996-12-31

    The atmospheric monitor conceptual design is based on a pulsed CO{sub 2} laser. The narrow laser lines provide high spectral selectivity in the 9-11 {mu}m region, within the 8-14 {mu}m ``fingerprint`` region where most large molecules have unique spectral absorption signatures. Laser power has been chosen so that topological objects, e.g., trees or buildings, as far as 4 km can be used as backreflectors, but the laser intensity is sufficiently low that the laser beam is eye-safe. Time-of-flight measurements give the distance to the topological reflector. The lidar system is augmented with an acousto-optic tunable filter (AOTF) which measures the thermal emission spectra from 3 to 14 {mu}m with a 3 cm{sup -1} passband. Sensitivity to narrow emission lines is enhanced by derivative spectroscopy in which the passband of the AOTF is dithered via the rf drive. Path-averaged concentrations are determined from the emission intensity and laser- determined range.

  9. Configurable-bandwidth imaging spectrometer based on an acousto-optic tunable filter

    NASA Astrophysics Data System (ADS)

    Vila-Francés, Joan; Calpe-Maravilla, Javier; Muñoz-Mari, Jordi; Gómez-Chova, Luis; Amorós-López, Julia; Ribes-Gómez, Emilio; Durán-Bosch, Vicente

    2006-07-01

    This article presents a new imaging spectrometer called autonomous tunable filtering system. The instrument acquires sequential images at different spectral wavelengths in the visible and near infrared range of the electromagnetic spectrum. The spectral selection is performed by an acousto-optic tunable filter (AOTF), which is driven by a custom radio-frequency (rf) generator based on a direct digital synthesizer (DDS). The DDS allows a high flexibility in terms of acquisition speed and bandwidth selection. The rf power is dynamically controlled to drive the AOTF with the optimum value for each wavelength. The images are formed through a carefully designed optical layout and acquired with a high performance digital camera. The application software controls the instrument and acquires the raw spectral images from the camera. This software optionally corrects the image for the AOTF nonidealities, such as diffraction efficiency variations, spatial nonuniformity, and chromatic aberration, and generates a single multiband image file. Moreover, the software can calculate the reflectance or transmittance of the acquired images. The instrument has been calibrated to give precise and repetitive measurements and has been validated against a high performance point spectrometer. As a case example, the instrument has been successfully used for the mapping of chlorophyll content of plant leaves from their multispectral reflectance images.

  10. Tunable transportable spectroradiometer based on an acousto-optical tunable filter: Development and optical performance

    NASA Astrophysics Data System (ADS)

    Kozlova, O.; Sadouni, A.; Truong, D.; Briaudeau, S.; Himbert, M.

    2016-12-01

    We describe a high-performance, transportable, versatile spectroradiometer based on an acousto-optical tunable filter (AOTF). The instrument was developed for temperature metrology, namely, to determine the thermodynamic temperature of black bodies above the Ag freezing point (961.78 °C). Its main design feature is the attenuation of the diffraction side lobes (and, thus, out-of-band stray light) thanks to the use of a double-pass configuration. The radiofrequency tuning of the AOTF allows continuous, fine, and rapid wavelength control over a wide spectral range (650 nm-1000 nm). The instrument tunability can be easily calibrated with an Ar spectral lamp with reproducibility within 10 pm over one week. The instrument was characterised in terms of relative signal stability (few 10-4) and wavelength stability (1 pm) over several hours. The spectral responsivity of the instrument was calibrated with two complementary methods: tuning of the wavelength of the optical source or tuning the radiofrequency of the AOTF. Besides the application for thermodynamic temperature determination at the lowest uncertainty level, this instrument can also be used for multispectral non-contact thermometry of processed materials of non-grey and non-unitary emissivity (in the glass or metallurgical industries).

  11. Advanced fluorescence imaging endoscopy using an acousto-optic tuneable filter

    NASA Astrophysics Data System (ADS)

    Whelan, Maurice P.; Bouhifd, Mounir; Aprahamian, Marc

    2004-07-01

    Two novel prototype instruments for in vivo fluorescence-based medical diagnostics are described. The devices are based on an acousto-optic tuneable filter (AOTF) and can be easily attached to the eyepiece of most commercially available endoscopes. The instruments developed offer significant advantages over typical fixed-filter or filter-wheel fluorescence imaging systems in terms of flexibility, performance and diagnostic potential. Any filtering center-wavelength in the range from 450 to 700 nm can be rapidly selected either by random access or sequential tuning using simple commands delivered over a PC serial interface. In addition, both filtered and unfiltered light can be imaged to facilitate the direct association of fluorescence signals with specific anatomical sites. To demonstrate the system in vivo, a study of the diagnostic potential of fluorescence imaging for pancreatitis was conducted on rats. The aim was to detect extremely low-levels of endogenous protoporphyrin IX (PpIX) that has been shown to accumulate in early-stage diseased tissue undergoing an inflammatory response. Results show clearly that the device is effective in diagnosing mild pancreatitis in rats without the necessity of administering PpIX promoting agents such as ALA. Planning of human clinical trials is currently underway to demonstrate its potential as a tool for non-invasive early diagnosis of gastroenterological diseases.

  12. State-of-the art of acousto-optic sensing and imaging of turbid media.

    PubMed

    Resink, Steffen G; Boccara, Albert C; Steenbergen, Wiendelt

    2012-04-01

    Acousto-optic (AO) is an emerging hybrid technique for measuring optical contrast in turbid media using coherent light and ultrasound (US). A turbid object is illuminated with a coherent light source leading to speckle formation in the remitted light. With the use of US, a small volume is selected,which is commonly referred to as the "tagging" volume. This volume acts as a source of modulated light, where modulation might involve phase and intensity change. The tagging volume is created by focusing ultrasound for good lateral resolution; the axial resolution is accomplished by making either the US frequency, amplitude, or phase time-dependent. Typical resolutions are in the order of 1 mm. We will concentrate on the progress in the field since 2003. Different schemes will be discussed to detect the modulated photons based on speckle detection, heterodyne detection, photorefractive crystal (PRC) assisted detection, and spectral hole burning (SHB) as well as Fabry-Perot interferometers. The SHB and Fabry-Perot interferometer techniques are insensitive to speckle decorrelation and therefore suitable for in vivo imaging. However, heterodyne and PRC methods also have potential for in vivo measurements. Besides measuring optical properties such as scattering and absorption, AO can be applied in fluorescence and elastography applications.

  13. The effect of scattering-medium parameters on signal magnitude under acousto-optic tomography

    NASA Astrophysics Data System (ADS)

    Zyuryukina, O. V.; Volkova, E. K.; Perchenko, M. I.; Solov'ev, A. P.

    2014-04-01

    We have experimentally studied the influence of scattering anisotropy parameter g of a medium on the magnitude of signal S (visualization parameter) at an ultrasonic frequency that is registered upon acoustooptic tomography. Aqueous solutions of mixtures of cream and skimmed milk with different ratios between them were used as scattering media. The optical properties of media (absorption coefficient μa and reduced scattering coefficient μ' S ) have been measured on a spectrophotometer (Perkin-Elmer Lambda 950 UV-VIS-NIR) using the inverse adding-doubling technique. As a result of the investigation, we have found that there is a certain correlation between the value of the scattering anisotropy parameter g of aqueous solutions of investigated mixtures and the percentage of the mixture in the aqueous solution, which ensures the required small value of extinction coefficient μ of the scattering medium. An increase in signal S has been revealed with increasing anisotropy parameter g of the medium at a invariable value of extinction coefficient μ. We have concluded that, to solve an inverse problem on the acousto-optic tomography, it is necessary to take into account possible changes in the g factor in scattering media, including biological ones.

  14. A RAPIDLY-TUNABLE ACOUSTO-OPTIC SPECTROMETER FOR A SPACE ENVIRONMENT

    SciTech Connect

    D. THOMPSON; C. HEWITT; C. WILSON

    2000-08-01

    As a complement to our work developing rapidly-tunable ({approximately}10-100 kHz) CO{sub 2} lasers for differential absorption lidar (DIAL) applications,l we have developed a rapidly-tunable spectrometer. A rapid spectral diagnostic is critical for a high speed DIAL system, since analysis of the return signals depends on knowing the spectral purity of the transmitted beam. The spectrometer developed for our lidar system is based on a double-passed large- (75 mm) aperture acousto-optic deflector, a grating, and a fast single-element room temperature mercury-cadmium-telluride detector. The spectrometer has a resolution of {approximately}0.5 cm{sup {minus}1}, a tuning range of 9.0-11.4 pm, a random-access tuning speed of greater than 80 kHz and a S/N ratio of greater than 100:1. We describe the design and performance of this device, as well as of future devices featuring improved resolution, higher speed and easier and more robust alignment. We will also briefly discuss the applications and limitations of the technique in a space environment.

  15. Tunable acousto-optic spectral imager for atmospheric composition measurements in the visible spectral domain.

    PubMed

    Dekemper, Emmanuel; Loodts, Nicolas; Van Opstal, Bert; Maes, Jeroen; Vanhellemont, Filip; Mateshvili, Nina; Franssens, Ghislain; Pieroux, Didier; Bingen, Christine; Robert, Charles; De Vos, Lieve; Aballea, Ludovic; Fussen, Didier

    2012-09-01

    We describe a new spectral imaging instrument using a TeO(2) acousto-optical tunable filter (AOTF) operating in the visible domain (450-900 nm). It allows for fast (~1 second), monochromatic (FWHM ranges from 0.6 nm at 450 nm to 3.5 nm at 800 nm) picture acquisition with good spatial resolution. This instrument was designed as a breadboard of the visible channel of a new satellite-borne atmospheric limb spectral imager, named the Atmospheric Limb Tracker for the Investigation of the Upcoming Stratosphere (ALTIUS), that is currently being developed. We tested its remote sensing capabilities by observing the dense, turbulent plume exhausted by a waste incinerator stack at two wavelengths sensitive to NO(2). An average value of 6.0±0.4×10(17) molecules cm(-2) has been obtained for the NO(2) slant column density within the plume, close to the stack outlet. Although this result was obtained with a rather low accuracy, it demonstrates the potential of spectral imaging by using AOTFs in remote sensing.

  16. Post-Flight Test Results of Acousto-Optic Modulator Devices Subjected to Space Exposure

    NASA Technical Reports Server (NTRS)

    Prasad, Narasimha S.; Trivedi, Sudhir; Rosemeier, Jolanta; Diestler, Mark

    2014-01-01

    The objective of the Materials International Space Station Experiment (MISSE) is to study the performance of novel materials when subjected to the synergistic effects of the harsh space environment for several months. MISSE missions provide an opportunity for developing space qualifiable materials. Several laser and lidar components were sent by NASA Langley Research Center (LaRC) as a part of the MISSE 7 mission. The MISSE 7 module was transported to the international space station (ISS) via STS 129 mission that was launched on Nov 16, 2009. Later, the MISSE 7 module was brought back to the earth via the STS 134 that landed on June 1, 2011. The MISSE 7 module that was subjected to exposure in a space environment for more than one and a half years included fiber laser, solid-state laser gain materials, detectors, and semiconductor laser diode. Performance testing of these components is now progressing. In this paper, the results of performance testing of a laser diode module sent by NASA Langley Research Center on MISSE 7 mission will be discussed. This paper will present the comparison of pre-flight and post-flight performance of two different COTS acousto-optic modulator (AOM) devices. Post-flight measurements indicate that these two devices did not undergo any significant performance degradation.

  17. Acousto-optic, point receiver hydrophone probe for operation up to 100 MHz.

    PubMed

    Lewin, P A; Mu, C; Umchid, S; Daryoush, A; El-Sherif, M

    2005-12-01

    This work describes the results of initial evaluation of a wideband acousto-optic hydrophone probe designed to operate as point receiver in the frequency range up to 100 MHz. The hydrophone was implemented as a tapered fiber optic (FO) probe sensor with a tip diameter of approximately 7 microm. Such small physical dimensions of the sensor eliminate the need for spatial averaging corrections so that true pressure-time (p-t) waveforms can be faithfully recorded. The theoretical considerations that predicted the FO probe sensitivity to be equal to 4.3 mV/MPa are presented along with a brief description of the manufacturing process. The calibration results that verified the theoretically predicted sensitivity are also presented along with a brief description of the improvements being currently implemented to increase this sensitivity level by approximately 20 dB. The results of preliminary measurements indicate that the fiber optic probes will exhibit a uniform frequency response and a zero phase shift in the frequency range considered. These features might be very useful in rapid complex calibration i.e. determining both magnitude and phase response of other hydrophones by the substitution method. Also, because of their robust design and linearity, these fiber optic hydrophones could also meet the challenges posed by high intensity focused ultrasound (HIFU) and other therapeutic applications. Overall, the outcome of this work shows that when fully developed, the FO probes will be well suited for high frequency measurements of ultrasound fields and will be able to complement the data collected by the current finite aperture piezoelectric PVDF hydrophones.

  18. Wavelength-swept fiber laser based on acousto-optic tuning method

    NASA Astrophysics Data System (ADS)

    Chen, Ming-hui; Fan, Yun-ping; Zhang, Hao; Tao, Jian-feng; Zheng, Gang

    2016-10-01

    In this study, we have demonstrated a wavelength-swept fiber laser based on an acousto-optic tunable filter(AOTF) as a selective element and a semiconductor optical amplifier(SOA) as a gain medium in an internal fiber ring cavity. The light deriving from one port of the SOA goes through an optical isolator, the AOTF, a fiber coupler and a polarized controller successively, then it goes back to the other port of the SOA to form a ring cavity. The laser output is from another port of the fiber coupler. The laser made by this method is mainly used for swept-source optical coherence tomography(SS-OCT). The application of the SOA provides a sufficiently broad range and can ensure an increased axial resolution of SS-OCT. AOTF offers a wide tuning range, high switching speed and stable operation against vibration for the non-mechanical structure. The proposed wavelength-swept fiber laser ensures a high axial resolution of tomographic images and has a stable laser output. We have discussed the influence of the SOA injection current to the tuning range of the laser. In the SOA injection current of 280 mA, a continuous wavelength tuning range from 1295 to 1370 nm centered at a wavelength of 1330nm is obtained at the sweep rate of 1.06 kHz, and the power of the swept source was 1.14 mW. In addition, for quantitative characterization of the wavelength-swept performance with a AOTF, we have theoretically and experimentally analyzed the influence of the following controllable parameters: injection current, output power and sweeping frequency.

  19. Acousto-optic devices for operation with 2μm fibre lasers

    NASA Astrophysics Data System (ADS)

    Ward, J. D.; Stevens, G.; Shardlow, P. C.

    2016-03-01

    Fibre lasers operating in the 2μm region are of increasing interest for a range of applications, including laser machining and biomedical systems. The large mode area compared to 1μm fibre lasers combined with operation in an "eye-safe" region of the spectrum makes them particularly attractive. When developing fibre lasers at 1μm and 1·5μm manufacturers were able to call upon enabling technologies used by the telecoms industry, but at longer wavelengths, including 2μm, many such components are either unavailable or immature. We report on recent developments of Acousto-Optic Modulators and Tunable Filters that are specifically optimised for use with fibre systems operating at or around 2μm. AO devices are interesting due to their ability to conserve spatial-coherence, making them appropriate for use with single-mode optical fibres. We describe how the choice of interaction medium is an important consideration, particularly affecting the drive power and the polarisation behaviour of the device - the latter being an important parameter when used in a fibre system. We also describe two designs of AO Tunable Filter intended for laser tuning. Both designs have been demonstrated intracavity in 2μm fibre lasers. The first gives exceptionally narrow resolution (δλ/λ<0·1%). The second design is of a novel type of AOTF where a matched pair of AOTFs is configured to give a substantially net zero frequency-shift with little or no loss of pointing stability, any minor deviations in manufacture being self-compensated. Furthermore, small controlled frequency-shifts (up to about 10kHz) may be introduced with little or no detriment to the alignment of the system.

  20. Acousto-optical deflection-based laser beam scanning for fluorescence detection on multichannel electrophoretic microchips.

    PubMed

    Huang, Z; Munro, N; Hühmer, A F; Landers, J P

    1999-12-01

    Laser beam scanning driven by an acousto-optical deflector (AOD) is presented for multimicrochannel laser-induced fluorescence (LIF) detection during microchip-based electrophoresis. While fast laser beam scanning for LIF detection on capillary or microchannel arrays can been achieved with galvanometric scanning or a translating stage, it can also be accomplished by using acoustic waves to deflect the laser beam in a manner that is dependent on the acoustic frequency. AOD scanning differs from other approaches in that no moving parts are required, and the scan frequency is faster than conventional approaches. Using a digital/analog (D/A) converter to provide addressing voltages to a voltage/frequency converter, rapidly changing the frequency input to the AOD allows the laser beam to be addressed accurately on a microchip. With the ability to change the frequency on the nanosecond time scale, scanning rates as high as 30 Hz for Windows-based LabView programming are possible, with much faster scan rates achievable if a microprocessor-embedded system is utilized. In addition to spatial control, temporal control is easily attainable via raster scanning or random addressing, allowing for the scanning process to be self-aligning. Since the D/A output voltages drive the scanning of the laser beam over all channels, the software can define addressing voltages corresponding to the microchannel centers and, subsequently, fluorescence data can be collected from only those locations. This method allows for flexible, high-speed, self-align scanning for fluorescence detection in capillary or microchip electrophoresis and has the potential to be applied to a number of applications.

  1. Development of fast two-dimensional standing wave microscopy using acousto-optic deflectors

    NASA Astrophysics Data System (ADS)

    Gliko, Olga; Reddy, Duemani G.; Brownell, William E.; Saggau, Peter

    2008-02-01

    A novel scheme for two-dimensional (2D) standing wave fluorescence microscopy (SWFM) using acousto-optic deflectors (AODs) is proposed. Two laser beams were coupled into an inverted microscope and focused at the back focal plane of the objective lens. The position of each of two beams at the back focal plane was controlled by a pair of AODs. This resulted in two collimated beams that interfered in the focal plane, creating a lateral periodic excitation pattern with variable spacing and orientation. The phase of the standing wave pattern was controlled by phase delay between two RF sinusoidal signals driving the AODs. Nine SW patterns of three different orientations about the optical axis and three different phases were generated. The excitation of the specimen using these patterns will result in a SWFM image with enhanced 2D lateral resolution with a nearly isotropic effective point-spread function. Rotation of the SW pattern relative to specimen and varying the SW phase do not involve any mechanical movements and are only limited by the time required for the acoustic wave to fill the aperture of AOD. The resulting total acquisition time can be as short as 100 µs and is only further limited by speed and sensitivity of the employed CCD camera. Therefore, this 2D SWFM can provide a real time imaging of subresolution processes such as docking and fusion of synaptic vesicles. In addition, the combination of 2D SWFM with variable angle total internal reflection (TIR) can extend this scheme to fast microscopy with enhanced three-dimensional (3D) resolution.

  2. Depth discrimination in acousto-optic cerebral blood flow measurement simulation

    NASA Astrophysics Data System (ADS)

    Tsalach, A.; Schiffer, Z.; Ratner, E.; Breskin, I.; Zeitak, R.; Shechter, R.; Balberg, M.

    2016-03-01

    Monitoring cerebral blood flow (CBF) is crucial, as inadequate perfusion, even for relatively short periods of time, may lead to brain damage or even death. Thus, significant research efforts are directed at developing reliable monitoring tools that will enable continuous, bed side, simple and cost-effective monitoring of CBF. All existing non invasive bed side monitoring methods, which are mostly NIRS based, such as Laser Doppler or DCS, tend to underestimate CBF in adults, due to the indefinite effect of extra-cerebral tissues on the obtained signal. If those are to find place in day to day clinical practice, the contribution of extra-cerebral tissues must be eliminated and data from the depth (brain) should be extracted and discriminated. Recently, a novel technique, based on ultrasound modulation of light was developed for non-invasive, continuous CBF monitoring (termed ultrasound-tagged light (UTL or UT-NIRS)), and shown to correlate with readings of 133Xe SPECT and laser Doppler. We have assembled a comprehensive computerized simulation, modeling this acousto-optic technique in a highly scattering media. Using the combination of light and ultrasound, we show how depth information may be extracted, thus distinguishing between flow patterns taking place at different depths. Our algorithm, based on the analysis of light modulated by ultrasound, is presented and examined in a computerized simulation. Distinct depth discrimination ability is presented, suggesting that using such method one can effectively nullify the extra-cerebral tissues influence on the obtained signals, and specifically extract cerebral flow data.

  3. Development and application of a ray-based model of light propagation through a spherical acousto-optic lens.

    PubMed

    Evans, Geoffrey J; Kirkby, Paul A; Naga Srinivas Nadella, K M; Marin, Bóris; Angus Silver, R

    2015-09-07

    A spherical acousto-optic lens (AOL) consists of four acousto-optic deflectors (AODs) that can rapidly and precisely control the focal position of an optical beam in 3D space. Development and application of AOLs has increased the speed at which 3D random access point measurements can be performed with a two-photon microscope. This has been particularly useful for measuring brain activity with fluorescent reporter dyes because neuronal signalling is rapid and sparsely distributed in 3D space. However, a theoretical description of light propagation through AOLs has lagged behind their development, resulting in only a handful of simplified principles to guide AOL design and optimization. To address this we have developed a ray-based computer model of an AOL incorporating acousto-optic diffraction and refraction by anisotropic media. We extended an existing model of a single AOD with constant drive frequency to model a spherical AOL: four AODs in series driven with linear chirps. AOL model predictions of the relationship between optical transmission efficiency and acoustic drive frequency including second order diffraction effects closely matched experimental measurements from a 3D two-photon AOL microscope. Moreover, exploration of different AOL drive configurations identified a new simple rule for maximizing the field of view of our compact AOL design. By providing a theoretical basis for understanding optical transmission through spherical AOLs, our open source model is likely to be useful for comparing and improving different AOL designs, as well as identifying the acoustic drive configurations that provide the best transmission performance over the 3D focal region.

  4. Experimental research on the multi-order acousto-optic diffraction based on Raman-Nath diffraction

    NASA Astrophysics Data System (ADS)

    Gu, Huadong; Shao, Zhongxing; Zheng, Chenqi; Yang, Jie; Chen, Ruitao; Gu, Zetong

    2015-03-01

    In this paper, the experimental investigation on the interaction length for getting the optimum diffraction of the multi-order acousto-optic diffraction is presented. Based on these results, the feasibility of acousto-optic Q-switch taking H2O or TeO2 as medium respectively for ultraviolet and visible lasers are discussed. The fact that the optimum interaction length tightly relies on the frequency of the sound and does not relate to the wavelength and power of the light is found in the experiment. The interaction length will become longer as the frequency of the ultrasound becomes higher. The interaction length is about 8mm when the acoustic frequency is at about 9MHz and becomes about 4mm at 6MHz. A Q-switch that works with pure water is designed and a total diffractive efficiency of about 98% was obtained under the condition that the acoustic frequency is 9MHz and the acoustic power is 3.4W. An acousto-optic Q-switch made of TeO2, in terms of Raman-Nath diffraction is designed. With a cooling system on the device, a total diffractive efficiency of about 75% is obtained under the condition that the acoustic frequency is 10MHz and the acoustic power is 10W. The loss by one path of the device is about 5% on the best condition. Then the modulated pulse width is measured as about 200ns on the condition that the acoustic frequency is 11MHz, the acoustic power is 6W and the repetition frequency is 10kHz.

  5. Secure transmission of static and dynamic images via chaotic encryption in acousto-optic hybrid feedback with profiled light beams

    NASA Astrophysics Data System (ADS)

    Chatterjee, Monish R.; Almehmadi, Fares S.

    2015-01-01

    Secure information encryption via acousto-optic (AO) chaos with profiled optical beams indicates substantially better performance in terms of system robustness. This paper examines encryption of static and time-varying (video) images onto AO chaotic carriers using Gaussian-profile beams with diffracted data numerically generated using transfer functions. The use of profiled beams leads to considerable improvement in the encrypted signal. While static image encryption exhibits parameter tolerances within about +/-10% for uniform optical beams, profiled beams reduce the tolerance to less than 1%, thereby vastly improving both the overall security of the transmitted information as well as the quality of the image retrieval.

  6. Dependence of integrated acousto-optical devices with one and two modulated arms on the static phase difference.

    PubMed

    Fan, Guofang; Li, Yuan; Hu, Chunguang; Lei, Lihua; Zhao, Dong; Li, Hongyu; Zhen, Zhen

    2014-10-01

    In this paper, we develop an analytical model of an integrated acousto-optical (AO) device with arms modulated by a single surface acoustic wave beam. A comparison between one-arm and two-arm modulation is presented, which shows that two-arm modulation can significantly enhance modulation efficiency by an optimized design. A detailed analysis of the influence of static phase difference on the behavior of the AO devices has been provided, and some interesting results have been obtained. These will be helpful for an optimized design of AO devices for different functionalities.

  7. Experimental study of the use of multiband acousto-optic filters for spectral encoding / decoding the optical signals

    NASA Astrophysics Data System (ADS)

    Proklov, V. V.; Byshevski-Konopko, O. A.; Filatov, A. L.; Lugovskoi, A. V.; Pisarevsky, Yu V.

    2016-08-01

    A prototype of the acousto-optic (AO) decoder of optical signals is created on the base of the multiband AO filter. The joint work of the decoder with the developed previously AO coder has been verified experimentally. The main qualitative and quantitate characteristics of the spectral coding and decoding by Walsh sequences of the industrial LED radiation in the near infrared range are investigated. It is shown, that in the proposed data transmission system realization Signal-to-Interference Ratio (SIR) is not less than 13 dB.

  8. Improvements on the refresh rate and dynamical properties of a SLM by sequential readout using an acousto-optic modulator

    NASA Astrophysics Data System (ADS)

    Mestre, Michael; Viaris de Lesegno, Bruno; Farcy, René; Pruvost, Laurence; Bourderionnet, Jérôme; Delboulbé, Anne; Loiseaux, Brigitte; Dolfi, Daniel

    2006-08-01

    We demonstrate the use of an acousto-optic modulator to enhance the refresh rate and dynamic properties of a liquid-crystal spatial light modulator (SLM). The useful area of the SLM surface is split in several zones which are addressed separately, and read in a sequence by a steered laser beam. This configuration allows to increase the refresh rate by five orders of magnitude. Furthermore, improvements on the nature of the transition between different holograms are experimentally shown. The advantages of this technique are discussed in the particular context of cold atom manipulation with holographic optical tweezers.

  9. Hyperspectral imaging performance based on two TeO2 acousto-optic tunable filters.

    PubMed

    Wang, Pengchong; Zhang, Zhonghua

    2017-02-20

    The performance parameters of an acousto-optic tunable filter (AOTF) were reasonably optimized based on the previous research, according to which two AOTFs that could be applied to hyperspectral imaging were produced. Through testing, the basic tuning relationship of the two AOTFs was basically in line with the principle. Then, a hyperspectral imaging system was built based on the two AOTFs, and a long-range perspective target imaging experiment was carried out in the entire white light region. Finally, the proposed double-filtering method was applied to the hyperspectral imaging for the first time, and the imaging result was analyzed in detail.

  10. Global maxima for the acousto-optic effect in SrB4O7 crystals.

    PubMed

    Oleh, Buryy; Nazariy, Andrushchak; Andriy, Ratych; Natalia, Demyanyshyn; Bohdan, Mytsyk; Anatoliy, Andrushchak

    2017-03-01

    For the first time, the global maxima of the acousto-optic interaction are theoretically determined for biaxial SrB4O7 crystals by the extreme surfaces method. As it is shown, the highest value of the acousto-optic figure-of-merit M2 is equal to 6.3×10-16  s3/kg and achieved in the case of the isotropic diffraction of the electromagnetic wave propagating in the [010] direction on the fast quasi-transversal acoustic wave.

  11. UV laser with an acousto-optic intra-cavity control for GaN-sapphire cut

    NASA Astrophysics Data System (ADS)

    Gradoboev, Yury G.; Kazaryan, Mishik A.; Mokrushin, Yury M.; Shakin, Oleg V.

    2012-09-01

    A copper vapor laser is proposed as the basic component of the installation for processing of sapphire substrates with a GaN-coating. Laser radiation is transformed to UV range by optical frequency doubling. Powerful UV lasers are prospective tools for crystal cutting, photolithography and recording of the fiber Bragg gratings. The proposed approach is more promising in comparison with the use of excimer radiation because of instabilities of excimer laser generation and low coherence of its radiation, which makes difficult precise focusing and using interference pattern of UV radiation for exposing materials. UV laser based on second harmonic radiation of copper vapors laser has been designed. The UV laser system of high operation stability has been developed with output power 1 W at wavelengths 255.5 nm, 271.1 nm, 289.1 nm and coherence length radiation about 4 cm. The original intra-cavity acousto-optic control of output radiation is developed. It is allows adjusting frequency and on-off time ratio of output laser pulses with high accuracy. The stable heat regime was achieved for an active element of copper vapor laser̤ The laser system allows to select an optimum mode of ultra-violet radiation exposition for production of different optical elements. Intra-cavity acousto-optic cell was used for controlling of single pulse amplitude and number of pulses without any power supply tuning providing the stable operation of the laser system.

  12. In-plane vibration characterization of microelectromechanical systems using acousto-optic modulated partially incoherent stroboscopic imaging

    NASA Astrophysics Data System (ADS)

    Wang, Dung-An; Sheu, Fang-Wen; Chiu, Yen-Sih

    2011-07-01

    A technique using acousto-optic modulated partially incoherent stroboscopic imaging for measurement of in-plane motion of microelectromechanical systems (MEMS) is presented. Vibration measurement is allowed by using flashes of the partially incoherent light source to freeze the positions of the microstructure at 12 equally spaced phases of the vibration period. The first-order diffracted beam taken out by an acousto-optic modulator (AOM) from the light beam of a laser is made partially incoherent by a rotating diffuser and then serves as the stroboscopic light source. Both the MEMS excitation signal and the flash control signal are provided by a dual-channel function generator. The main advantage of this measurement method is the absence of a stroboscopic generator and a high speed digital camera. Microscale prototypes are fabricated and tested. Quantitative estimates of the harmonic responses of the prototypes are obtained from the recorded images. The results agree with those obtained with a commercial MEMS motion analyzer TM with relative errors less than 2%.

  13. A novel acousto-optic modulation-deflection mechanism using refractive index grating as graded index beam router

    NASA Astrophysics Data System (ADS)

    Jangjoo, Alireza; Reza Baezzat, Mohammad; Razavizadeh, Ahmad

    2014-03-01

    A novel acousto-optic modulation mechanism will be addressed in this paper. Focused Gaussian beam passing through acousto-optic media experiences different refractive index regions arising from acoustic waves generated by ultrasonic source. In this way according to the snell's law of refraction the beam propagation path will be altered when these periodic traveling waves reach the incoming radiation where a typical p-n junction photodiode located inside the rising or falling lobe of the undiffracted Gaussian beam senses these small lateral deflections. Due to small variations of the refractive index the magnitude of deflection will be up to tens of micron outside the modulator. Hence, sharp intensity gradient is required for detecting such small beam movements by appropriate lens configuration to focus the Gaussian profile on the detector junction area. In the other words intensity profile of zero order beam oscillates proportional to the time dependent amplitude of the acoustic waves versus previous methods that intensity of diffracted beam changes with applied ultrasonic intensity. The extracted signal properties depend on the beam collimation, quality of beam profile and depth of focus inside the modulator. The first experimental approach was proceeded using a collimated 532 nm diode laser source (TEM00), distilled water as interaction media and 10 MHz transducer as ultrasonic generator where a cylindrical glass column with input-output flat windows was used for liquid support. The present method has advantages over common acoustooptical techniques as low cost, simplicity of operation, direct modulation of the signal and minimum alignment requirement.

  14. Self-tuning acousto-optic deflectors with acoustic line made of NaBi(MoO4)2 crystal

    NASA Astrophysics Data System (ADS)

    Khansuvarov, Ruslan A.; Shakin, Oleg V.; Vaganov, Mikhail A.; Zhdanov, Arseniy Y.

    2014-09-01

    The idea of acousto-optic self-tuning deflector, which automatically returns the position of the acoustic line, corresponding to the mode of Bragg diffraction feedback implementation is proposed. Features of sodium bismuthate's double molybdate grown by new technology - low gradient Czochralski process are illustrated.

  15. On the possibility of developing incoherent fibre-optic data transmission systems based on signal spectral coding with matched acousto-optical filters

    SciTech Connect

    Proklov, Valerii V; Byshevski-Konopko, O A; Grigorievski, V I

    2013-06-30

    The scheme is suggested for developing the optical communication line based on the principle of code division of multiple access with matched acousto-optical filters and a 16-bit long Walsh sequence. Results of modelling show that such a line can operate if adjacent spectral lines are separated by at least double the Rayleigh criterion. (optical information transmission)

  16. Pure electrical, highly-efficient and sidelobe free coherent Raman spectroscopy using acousto-optics tunable filter (AOTF)

    NASA Astrophysics Data System (ADS)

    Meng, Zhaokai; Petrov, Georgi I.; Yakovlev, Vladislav V.

    2016-02-01

    Fast and sensitive Raman spectroscopy measurements are imperative for a large number of applications in biomedical imaging, remote sensing and material characterization. Stimulated Raman spectroscopy offers a substantial improvement in the signal-to-noise ratio but is often limited to a discrete number of wavelengths. In this report, by introducing an electronically-tunable acousto-optical filter as a wavelength selector, a novel approach to a broadband stimulated Raman spectroscopy is demonstrated. The corresponding Raman shift covers the spectral range from 600 cm‑1 to 4500 cm‑1, sufficient for probing most vibrational Raman transitions. We validated the use of the new instrumentation to both coherent anti-Stokes scattering (CARS) and stimulated Raman scattering (SRS) spectroscopies.

  17. Integrated acousto-optic polarization converter in a ZX-cut LiNbO(3) waveguide superlattice.

    PubMed

    Yudistira, D; Janner, D; Benchabane, S; Pruneri, V

    2009-10-15

    We report an integrated acousto-optic polarization converter exploiting a novel surface acoustic superlattice (S-ASL) transducer. The S-ASL transducer is made of a ZX-cut periodically poled lithium niobate (PPLN) crystal with uniform coplanar electrodes for surface acoustic wave (SAW) generation. For a PPLN period of 20 microm the SAW is excited at an rf of about 190 MHz, while the phase matching occurs at an optical wavelength of around 1456 nm. The measured mode conversion efficiency of 90% at an input rf power of 1 W and the 3 dB optical bandwidth of 2.5 nm confirm the confinement of the SAW between the electrode gap and the constructive interaction along the whole 10 mm electrode length.

  18. Chaos control and synchronization in Bragg acousto-optic bistable systems driven by a separate chaotic system.

    PubMed

    Wang, Rong; Gao, Jin-Yue

    2005-09-01

    In this paper we propose a new scheme to achieve chaos control and synchronization in Bragg acousto-optic bistable systems. In the scheme, we use the output of one system to drive two identical chaotic systems. Using the maximal conditional Lyapunov exponent (MCLE) as the criterion, we analyze the conditions for realizing chaos synchronization. Numerical calculation shows that the two identical systems in chaos with negative MCLEs and driven by a chaotic system can go into chaotic synchronization whether or not they were in chaos initially. The two systems can go into different periodic states from chaos following an inverse period-doubling bifurcation route as well when driven by a periodic system.

  19. Pure electrical, highly-efficient and sidelobe free coherent Raman spectroscopy using acousto-optics tunable filter (AOTF).

    PubMed

    Meng, Zhaokai; Petrov, Georgi I; Yakovlev, Vladislav V

    2016-02-01

    Fast and sensitive Raman spectroscopy measurements are imperative for a large number of applications in biomedical imaging, remote sensing and material characterization. Stimulated Raman spectroscopy offers a substantial improvement in the signal-to-noise ratio but is often limited to a discrete number of wavelengths. In this report, by introducing an electronically-tunable acousto-optical filter as a wavelength selector, a novel approach to a broadband stimulated Raman spectroscopy is demonstrated. The corresponding Raman shift covers the spectral range from 600 cm(-1) to 4500 cm(-1), sufficient for probing most vibrational Raman transitions. We validated the use of the new instrumentation to both coherent anti-Stokes scattering (CARS) and stimulated Raman scattering (SRS) spectroscopies.

  20. Femtosecond terahertz time-domain spectroscopy at 36 kHz scan rate using an acousto-optic delay

    NASA Astrophysics Data System (ADS)

    Urbanek, B.; Möller, M.; Eisele, M.; Baierl, S.; Kaplan, D.; Lange, C.; Huber, R.

    2016-03-01

    We present a rapid-scan, time-domain terahertz spectrometer employing femtosecond Er:fiber technology and an acousto-optic delay with attosecond precision, enabling scanning of terahertz transients over a 12.4-ps time window at a waveform refresh rate of 36 kHz, and a signal-to-noise ratio of 1.7 × 105 / √{ H z } . Our approach enables real-time monitoring of dynamic THz processes at unprecedented speeds, which we demonstrate through rapid 2D thickness mapping of a spinning teflon disc at a precision of 10 nm/ √{ H z } . The compact, all-optical design ensures alignment-free operation even in harsh environments.

  1. Ultrafast, large-field multiphoton microscopy based on an acousto-optic deflector and a spatial light modulator

    PubMed Central

    Shao, Yonghong; Qin, Wan; Liu, Honghai; Qu, Junle; Peng, Xiang; Niu, Hanben; Gao, Bruce Z.

    2013-01-01

    We present an ultrafast, large-field multiphoton excitation fluorescence microscope with high lateral and axial resolutions based on a two-dimensional (2-D) acousto-optical deflector (AOD) scanner and spatial light modulator (SLM). When a phase-only SLM is used to shape the near-infrared light from a mode-locked titanium:sapphire laser into a multifocus array including the 0-order beam, a 136 μm × 136 μm field of view is achieved with a 60× objective using a 2-D AOD scanner without any mechanical scan element. The two-photon fluorescence image of a neuronal network that was obtained using this system demonstrates that our microscopy permits observation of dynamic biological events in a large field with high-temporal and -spatial resolution. PMID:22743445

  2. Ultrafast, large-field multiphoton microscopy based on an acousto-optic deflector and a spatial light modulator.

    PubMed

    Shao, Yonghong; Qin, Wan; Liu, Honghai; Qu, Junle; Peng, Xiang; Niu, Hanben; Gao, Bruce Z

    2012-07-01

    We present an ultrafast, large-field multiphoton excitation fluorescence microscope with high lateral and axial resolutions based on a two-dimensional (2-D) acousto-optical deflector (AOD) scanner and spatial light modulator (SLM). When a phase-only SLM is used to shape the near-infrared light from a mode-locked titanium:sapphire laser into a multifocus array including the 0-order beam, a 136 μm × 136 μm field of view is achieved with a 60× objective using a 2-D AOD scanner without any mechanical scan element. The two-photon fluorescence image of a neuronal network that was obtained using this system demonstrates that our microscopy permits observation of dynamic biological events in a large field with high-temporal and -spatial resolution.

  3. Acousto-optical deflection-based whole channel scanning for microchip isoelectric focusing with laser-induced fluorescence detection.

    PubMed

    Sanders, J C; Huang, Z; Landers, J P

    2001-12-01

    This paper describes the development of a technique amenable to the separation of proteins on a microchip by isoelectric focusing (IEF) with entire channel scanning laser-induced fluorescence detection using acousto-optical deflection (AOD). The ability to use AOD to scan the portions of or the entire length of an IEF separation channel allows for high-speed analysis since the mobilization step is circumvented with this technique. Employing no moving parts eliminates mechanical noise and, not only is there no loss of resolution, AOD scanning can potentially increase resolution. The ability of AOD to provide ultra-fast scanning rates (kHz timescale) allows for real-time imaging of the focusing process. This is demonstrated with the separation of naturally fluorescent proteins using entire channel (total scanning range of 2.4 cm) AOD-mediated scanning laser-induced fluorescence detection.

  4. New prototype of acousto-optical radio-wave spectrometer with parallel frequency processing for astrophysical applications

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Alexandre S.; Chavez Dagostino, Miguel; Arellanes, Adan O.; Aguirre Lopez, Arturo

    2016-09-01

    We develop a multi-band spectrometer with a few spatially parallel optical arms for the combined processing of their data flow. Such multi-band capability has various applications in astrophysical scenarios at different scales: from objects in the distant universe to planetary atmospheres in the Solar system. Each optical arm exhibits original performances to provide parallel multi-band observations with different scales simultaneously. Similar possibility is based on designing each optical arm individually via exploiting different materials for acousto-optical cells operating within various regimes, frequency ranges and light wavelengths from independent light sources. Individual beam shapers provide both the needed incident light polarization and the required apodization to increase the dynamic range of a system. After parallel acousto-optical processing, data flows are united by the joint CCD matrix on the stage of the combined electronic data processing. At the moment, the prototype combines still three bands, i.e. includes three spatial optical arms. The first low-frequency arm operates at the central frequencies 60-80 MHz with frequency bandwidth 40 MHz. The second arm is oriented to middle-frequencies 350-500 MHz with frequency bandwidth 200-300 MHz. The third arm is intended for ultra-high-frequency radio-wave signals about 1.0-1.5 GHz with frequency bandwidth <300 MHz. To-day, this spectrometer has the following preliminary performances. The first arm exhibits frequency resolution 20 KHz; while the second and third arms give the resolution 150-200 KHz. The numbers of resolvable spots are 1500- 2000 depending on the regime of operation. The fourth optical arm at the frequency range 3.5 GHz is currently under construction.

  5. Frequency response of a TeO{sub 2} slow shear wave acousto-optic cell exposed to radiation

    SciTech Connect

    Erteza, I.A.; Craft, D.C.; Stalker, K.T.; Taylor, E.W.; Kelley, M.A.; Sanchez, A.D.; Chapman, S.P.; Craig, D.M.; Kinsley, E.

    1994-12-31

    Radiation testing of photonic components is not new, however component level testing to date has not completely addressed quantities which are important to system behavior. One characteristic that is of particular importance for optical processing systems is the frequency response. In this paper, the authors present the results of the analysis of data from an experiment designed to provide a preliminary understanding of the effects of radiation on the frequency response of acousto-optic devices. The goal is to present possible physical mechanisms responsible for the radiation effects and to discuss the effects on signal processing functionality. The experiment discussed in this paper was designed by Sandia National Laboratories (SNL) and performed by SNL and Phillips Laboratory (PL) personnel at White Sands Missile Range (WSMR). In the experiment, a TeO{sub 2} slow shear-wave acousto-optic cell was exposed to radiation from the WSMR linear accelerator. The TeO{sub 2} cell was placed in an experimental configuration which allowed swept frequency diffracted power measurements to be taken during radiation exposure and recovery. A series of exposures was performed. Each exposure consisted of between 1 to 800, 1 {mu}sec radiation pulses (yielding exposures of 2.25 kRad(Si) to 913 kRad(Si)), followed by recovery time. At low total and cumulative doses, the bandshape of the frequency response (i.e. diffracted power vs. frequency) remained almost identical during and after radiation. At the higher exposures, however, the amplitude and width of the frequency response changed as the radiation continued, but returned to the original shape slowly after the radiation stopped and recovery proceeded. It is interesting to note that the location of the Bragg degeneracy does not change significantly with radiation. In this paper, the authors discuss these effects, and they discuss the effect on the signal processing functionality.

  6. Acousto-optic Bragg diffraction in a LiNbO3 channel-planar composite waveguide with application to optical computing

    NASA Astrophysics Data System (ADS)

    Tsai, C. S.; Zang, D. Y.; Le, P.

    1985-09-01

    Successful experimentation on acousto-optic Bragg diffraction in a LiNbO3 composite waveguide that consists of an array of parallel but uncoupled channel waveguides directly extended to a single-mode planar waveguide and a titanium-indiffused proton-exchanged (TIPE) microlens array is reported for the first time. A channel-waveguide array, a planar waveguide, a linear TIPE microlens array, a 500-MHz surface acoustic wave transducer, and an integrating lens have all been integrated in a substrate size of 0.2 x 1.0 x 2.0 cm to form an integrated acousto-optic Bragg modulator that should find a variety of applications in optical computing, signal processing, and communications. The resulting modulator module has been utilized to perform matrix-vector multiplication.

  7. Mid infra-red hyper-spectral imaging with bright super continuum source and fast acousto-optic tuneable filter for cytological applications.

    NASA Astrophysics Data System (ADS)

    Farries, Mark; Ward, Jon; Valle, Stefano; Stephens, Gary; Moselund, Peter; van der Zanden, Koen; Napier, Bruce

    2015-06-01

    Mid-IR imaging spectroscopy has the potential to offer an effective tool for early cancer diagnosis. Current development of bright super-continuum sources, narrow band acousto-optic tunable filters and fast cameras have made feasible a system that can be used for fast diagnosis of cancer in vivo at point of care. The performance of a proto system that has been developed under the Minerva project is described.

  8. An experimental distribution of analog and digital information in a hybrid wireless visible light communication system based on acousto-optic modulation and sinusoidal gratings

    NASA Astrophysics Data System (ADS)

    Gómez Colín, R.; García Juárez, A.; Zaldívar Huerta, I. E.; Marquina, A. Vera; García Delgado, L. A.; Leal Cruz, A. L.; Gómez Fuentes, R.

    2016-03-01

    In this paper we propose a photonic architecture as an alternative tool to distribute point to multipoint analog and digital information over a hybrid wireless visible optical communication system. The experimental set-up is composed of a red laser pointer, an acousto-optic modulator, a sinusoidal grating and a photo-detector array. By using a simple and variable interferometric system, diffraction gratings with different spatial frequencies are generated and recorded on a photoemulsion which is composed of vanilla with dichromate gelatin. Analog video and digital information are first transmitted and recovered over a wireless communication system using a microwave carrier at 4.52 GHz which is generated by distributed feedback lasers operating in the low laser threshold current region. Separately, the recovered video information and digital data are combined with a radio frequency signal of 80 MHz, obtaining a subcarrier of information that is imposed on the optical carrier of the pointer laser using an acousto-optic modulator which is operated with an angle of incident light that satisfies the Bragg condition. The modulated optical carrier is sent to a sinusoidal grating, the diffraction pattern is photo-detected using an array of PIN photo-detectors. The use of sinusoidal gratings with acousto-optic modulators allows that number of channels to be increased when both components are placed in cascade.

  9. Acousto-optic tunable filter (AOTF) imaging spectrometer for NASA applications - Breadboard demonstration

    NASA Technical Reports Server (NTRS)

    Chao, Tien-Hsin; Yu, Jeffrey; Cheng, Li-Jen; Lambert, Jim

    1990-01-01

    Considerations of performance criteria in image quality, spectral response, programmability, and field-of-view, are presently discussed for a NASA AOTF system. Experimental data obtained with an AOTF imaging spectrometer breadboard are presented. Attention is given to the identification of Nd(3+) contained in bastanite rock by means of this imaging spectrometer.

  10. A rapid excitation-emission matrix fluorometer utilizing supercontinuum white light and acousto-optic tunable filters.

    PubMed

    Wang, Wenbo; Wu, Zhenguo; Zhao, Jianhua; Lui, Harvey; Zeng, Haishan

    2016-06-01

    Scanning speed and coupling efficiency of excitation light to optic fibres are two major technical challenges that limit the potential of fluorescence excitation-emission matrix (EEM) spectrometer for on-line applications and in vivo studies. In this paper, a novel EEM system, utilizing a supercontinuum white light source and acousto-optic tunable filters (AOTFs), was introduced and evaluated. The supercontinuum white light, generated by pumping a nonlinear photonic crystal fiber with an 800 nm femtosecond laser, was efficiently coupled into a bifurcated optic fiber bundle. High speed EEM spectral scanning was achieved using AOTFs both for selecting excitation wavelength and scanning emission spectra. Using calibration lamps (neon and mercury argon), wavelength deviations were determined to vary from 0.18 nm to -0.70 nm within the spectral range of 500-850 nm. Spectral bandwidth for filtered excitation light broadened by twofold compared to that measured with monochromatic light between 650 nm and 750 nm. The EEM spectra for methanol solutions of laser dyes were successfully acquired with this rapid fluorometer using an integration time of 5 s.

  11. Wet/dry film thickness measurement of paint by absorption spectroscopy with acousto-optic tunable filter spectrometer

    NASA Astrophysics Data System (ADS)

    Sinha, Pranay G.; Xiong, Xiangchun; Jin, Feng; Trivedi, Sudhir; Prasad, Narashima S.

    2005-08-01

    Controlling/monitoring the thickness of applied paint in real time is important to many situations including painting ship and submarine hulls in dry docks for maintaining health of ships and submarines against the harshness of the sea, in automobile and aerospace industries, and in a variety of other industries as a control sensor that plays significant role in product quality, process control, and cost control. Insufficient thickness results to inadequate protection while overspray leads to waste and pollution of the environment. A rugged instrumentation for the real time non-contact accurate measurement of wet and dry paint film thickness measurement will be immensely valuable. As paint is applied with several layers of the same or different type, thickness of each newly sprayed wet layer is of most interest, but measurement on dry paint is also useful. In this study, we use acousto-optic tunable filter-based near infrared spectrometer to obtain the absorption spectrum of layers of paint sprayed on sand blasted steel surface and thus measure the thickness of coating under both wet and dry situations. NIR spectra are obtained from 1100 to 2300 nm on four sample of different thickness of paint up to 127 micron. Partial least squares model built with the spectra shows good correlation with standard error of prediction within ~ 0.7 micron. Results indicate that the spectra also respond to the amount of organic solvent in the wet paint and can be used to monitor the degree of dryness of the paint in real time.

  12. Modeling-based design and assessment of an acousto-optic guided high-intensity focused ultrasound system

    NASA Astrophysics Data System (ADS)

    Adams, Matthew T.; Cleveland, Robin O.; Roy, Ronald A.

    2017-01-01

    Real-time acousto-optic (AO) sensing has been shown to noninvasively detect changes in ex vivo tissue optical properties during high-intensity focused ultrasound (HIFU) exposures. The technique is particularly appropriate for monitoring noncavitating lesions that offer minimal acoustic contrast. A numerical model is presented for an AO-guided HIFU system with an illumination wavelength of 1064 nm and an acoustic frequency of 1.1 MHz. To confirm the model's accuracy, it is compared to previously published experimental data gathered during AO-guided HIFU in chicken breast. The model is used to determine an optimal design for an AO-guided HIFU system, to assess its robustness, and to predict its efficacy for the ablation of large volumes. It was found that a through transmission geometry results in the best performance, and an optical wavelength around 800 nm was optimal as it provided sufficient contrast with low absorption. Finally, it was shown that the strategy employed while treating large volumes with AO guidance has a major impact on the resulting necrotic volume and symmetry.

  13. Wavelength-Scanning SPR Imaging Sensors Based on an Acousto-Optic Tunable Filter and a White Light Laser.

    PubMed

    Zeng, Youjun; Wang, Lei; Wu, Shu-Yuen; He, Jianan; Qu, Junle; Li, Xuejin; Ho, Ho-Pui; Gu, Dayong; Gao, Bruce Zhi; Shao, Yonghong

    2017-01-05

    A fast surface plasmon resonance (SPR) imaging biosensor system based on wavelength interrogation using an acousto-optic tunable filter (AOTF) and a white light laser is presented. The system combines the merits of a wide-dynamic detection range and high sensitivity offered by the spectral approach with multiplexed high-throughput data collection and a two-dimensional (2D) biosensor array. The key feature is the use of AOTF to realize wavelength scan from a white laser source and thus to achieve fast tracking of the SPR dip movement caused by target molecules binding to the sensor surface. Experimental results show that the system is capable of completing a SPR dip measurement within 0.35 s. To the best of our knowledge, this is the fastest time ever reported in the literature for imaging spectral interrogation. Based on a spectral window with a width of approximately 100 nm, a dynamic detection range and resolution of 4.63 × 10(-2) refractive index unit (RIU) and 1.27 × 10(-6) RIU achieved in a 2D-array sensor is reported here. The spectral SPR imaging sensor scheme has the capability of performing fast high-throughput detection of biomolecular interactions from 2D sensor arrays. The design has no mechanical moving parts, thus making the scheme completely solid-state.

  14. Application of the acousto-optic effect to pressure measurements in ultrasound fields in water using a laser vibrometer

    NASA Astrophysics Data System (ADS)

    Buick, J. M.; Cosgrove, J. A.; Douissard, P.-A.; Greated, C. A.; Gilabert, B.

    2004-10-01

    A non-intrusive measuring technique, applied to sensing and measuring acoustic waves at ultrasonic frequencies is considered. The method is optically based and so does not interfere with the ultrasound field. The measurement procedure relies on the acousto-optic effect, that is the change in refractive index which occurs with changing pressure in the ultrasound field. This change in refractive index is detected through the change in the path length of a laser beam propagating through the region of interest. Typically these changes are small corresponding to a physical change of the order of 10-6 m. Fourier analysis is used to separate the component of the signal corresponding to the pressure variation from background noise and vibrations which can be dominant. Application of the technique is illustrated for an underwater ultrasound transducer. Measurements are made using the optical technique and compared to measurements taken with a hydrophone. The effectiveness of the optical measuring technique is discussed. It is shown that the laser vibrometer produces a good estimation of the mean beam pressure provided an estimation of the beam width is available, a restriction which is often satisfied; and the acoustic field can be assumed to be approximately constant across the beam.

  15. Wavelength-Scanning SPR Imaging Sensors Based on an Acousto-Optic Tunable Filter and a White Light Laser

    PubMed Central

    Zeng, Youjun; Wang, Lei; Wu, Shu-Yuen; He, Jianan; Qu, Junle; Li, Xuejin; Ho, Ho-Pui; Gu, Dayong; Gao, Bruce Zhi; Shao, Yonghong

    2017-01-01

    A fast surface plasmon resonance (SPR) imaging biosensor system based on wavelength interrogation using an acousto-optic tunable filter (AOTF) and a white light laser is presented. The system combines the merits of a wide-dynamic detection range and high sensitivity offered by the spectral approach with multiplexed high-throughput data collection and a two-dimensional (2D) biosensor array. The key feature is the use of AOTF to realize wavelength scan from a white laser source and thus to achieve fast tracking of the SPR dip movement caused by target molecules binding to the sensor surface. Experimental results show that the system is capable of completing a SPR dip measurement within 0.35 s. To the best of our knowledge, this is the fastest time ever reported in the literature for imaging spectral interrogation. Based on a spectral window with a width of approximately 100 nm, a dynamic detection range and resolution of 4.63 × 10−2 refractive index unit (RIU) and 1.27 × 10−6 RIU achieved in a 2D-array sensor is reported here. The spectral SPR imaging sensor scheme has the capability of performing fast high-throughput detection of biomolecular interactions from 2D sensor arrays. The design has no mechanical moving parts, thus making the scheme completely solid-state. PMID:28067766

  16. Research Cooperation between Catholic Universityof Leuven Campus Kortrijk and University of Gdansk in Acousto-optics - A Historical Recollection1

    NASA Astrophysics Data System (ADS)

    Śliwiński, A.

    A short review of results achieved during many years of cooperation between the Belgian group of KULAK and the Polish group of Gdansk University (UG) is presented as a tribute to Oswald Leroy for his significant contribution. The scientific research in examination of ultrasonic light interaction phenomena was the area of this fruitful joint collaboration since 1971. Oswald Leroy's crucial role in the cooperation is emphasized and some historical events are recalled. His original theoretical papers predicted new theoretical phenomena which were successfully experimentally verified in the A. O. laboratory at the University of Gdansk. Later on, they have become inspiration for further fundamental search in acousto-optics. Members of Gdansk AO group many times visited Kortrijk to work together on ULD phenomena or attending seminars and symposia organized in Belgium and the Belgian group took part in the international Spring Schools and Applications systematically organized by Gdansk University as the triennial meetings since 1980. Leroy's contribution to the mutual co-operation has been recognized as so important and significant that in 1991 he was honored with the Doctorate Honoris Causa of the University of Gdansk.

  17. Real-Time Display Of 3-D Computed Holograms By Scanning The Image Of An Acousto-Optic Modulator

    NASA Astrophysics Data System (ADS)

    Kollin, Joel S.; Benton, Stephen A.; Jepsen, Mary Lou

    1989-10-01

    The invention of holography has sparked hopes for a three-dimensional electronic imaging systems analogous to television. Unfortunately, the extraordinary spatial detail of ordinary holographic recordings requires unattainable bandwidth and display resolution for three-dimensional moving imagery, effectively preventing their commercial development. However, the essential bandwidth of holographic images can be reduced enough to permit their transmission through fiber optic or coaxial cable, and the required resolution or space-bandwidth product of the display can be obtained by raster scanning the image of a commercially available acousto-optic modulator. No film recording or other photographic intermediate step is necessary as the projected modulator image is viewed directly. The design and construction of a working demonstration of the principles involved is also presented along with a discussion of engineering considerations in the system design. Finally, the theoretical and practical limitations of the system are addressed in the context of extending the system to real-time transmission of moving holograms synthesized from views of real and computer-generated three-dimensional scenes.

  18. Acousto-optic mode coupling excited by flexural waves in simplified hollow-core photonic crystal fibers

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Qiu, Minghui; Wu, Zhifang; Dong, Hongguang; Liu, Bo; Miao, Yinping

    2013-05-01

    We have demonstrated the formation of an acoustic grating in a simplified hollow-core photonic crystal fiber, which consists of a hollow hexagonal core and six crown-like air holes, by applying flexural acoustic waves along the fiber axis. The dependence of the resonance wavelength on the applied acoustic frequency has been acquired on the basis of the theoretical calculation of the phase matching curve; it is in good agreement with our experimental observation of the transmission spectral evolution as the applied acoustic frequency varies. Experimental results show that the acoustic grating resonance peak possesses acoustic frequency and strain dependences of 728 nm MHz-1 and -6.98 pm μɛ-1, respectively, based on which high-performance acousto-optic tunable filters and fiber-optic strain sensors with high sensitivity could be achieved. And furthermore, the research work presented in this paper indicates that microbending rather than physical deformation is the main physical mechanism that leads to the formation of equivalent long-period gratings, which would be of significance for developing related grating devices based on simplified hollow-core photonic crystal fibers.

  19. Narrow linewidth broadband tunable semiconductor laser at 840 nm with dual acousto-optic tunable configuration for OCT applications

    NASA Astrophysics Data System (ADS)

    Chamorovskiy, Alexander; Shramenko, Mikhail V.; Lobintsov, Andrei A.; Yakubovich, Sergei D.

    2016-03-01

    We demonstrate a tunable narrow linewidth semiconductor laser for the 840 nm spectral range. The laser has a linear cavity comprised of polarization maintaining (PM) fiber. A broadband semiconductor optical amplifier (SOA) in in-line fiber-coupled configuration acts as a gain element. It is based on InGaAs quantum-well (QW) active layer. SOA allows for tuning bandwidth exceeding 25 nm around 840 nm. Small-signal fiber-to-fiber gain of SOA is around 30 dB. A pair of acousto-optic tunable filters (AOTF) with a quasi-collinear interaction of optical and acoustic waves are utilized as spectrally selective elements. AOTF technology benefits in continuous tuning, broadband operation, excellent reproducibility and stability of the signal, as well as a high accuracy of wavelength selectivity due to the absence of mechanically moving components. A single AOTF configuration has typical linewidth in 0.05-0.15 nm range due to a frequency shift obtained during each roundtrip. A sequential AOTF arrangement enables instantaneous linewidth generation of <0.01 nm by compensating for this shift. Linewidth as narrow as 0.0036 nm is observed at 846 nm wavelength using a scanning Fabry-Perot interferometer with 50 MHz spectral resolution. Output power is in the range of 1 mW. While the majority of commercial tunable sources operate in 1060-1550 nm spectral ranges, the 840 nm spectral range is beneficial for optical coherence tomography (OCT). The developed narrow linewidth laser can be relevant for OCT with extended imaging depth, as well as spectroscopy, non-destructive testing and other applications.

  20. Random depth access full-field heterodyne low-coherence interferometry utilizing acousto-optic modulation and a complementary metaloxide semiconductor camera.

    PubMed

    Egan, Patrick; Connelly, Michael J; Lakestani, Fereydoun; Whelan, Maurice P

    2006-04-01

    With analog scanning, time-domain low-coherence interferometry lacks precise depth information, and optical carrier generation demands a linear scanning speed. Full-field heterodyne low-coherence interferometry that uses a logarithmic complementary metal-oxide semiconductor camera, acousto-optic modulation, and digital depth stepping is reported, with which random regions of interest, lateral and axial, can be accessed. Furthermore, nanometer profilometry is possible through heterodyne phase retrieval of the interference signal. The approach demonstrates inexpensive yet high-precision functional machine vision offering true digital random access in three dimensions.

  1. Numerical simulation of dual-loss-modulated Q-switched and mode-locked laser with an acousto-optic and Cr4+:YAG saturable absorber.

    PubMed

    Zhao, Shengzhi; Li, Guiqiu; Li, Dechun; Yang, Kejian; Li, Yufei; Li, Ming; Li, Tao; Zhang, Gang; Cheng, Kang

    2010-04-01

    By considering the influence of the turn-off time and the modulation frequency of the acousto-optic (AO) modulator as well as the Gaussian spatial distribution of the photon density, we give a developed rate equation model for a diode-pumped dual-loss-modulated Q-switched and mode-locked (QML) Nd:GdVO(4) laser with AO modulator and Cr(4+):YAG saturable absorber. With this developed model, the dual-loss-modulated QML laser characteristics, such as pulse width and pulse energy, can be numerically simulated, and the theoretical evaluations are in good agreement with the experimental results.

  2. Time-resolved acousto-optic interaction in single-mode optical fibers: characterization of axial nonuniformities at the nanometer scale.

    PubMed

    Alcusa-Sáez, E P; Díez, A; González-Herráez, M; Andrés, M V

    2014-03-15

    We report on a time-resolved acousto-optic interaction technique for the detection of axial nonuniformities in single-mode fibers. It is based on the propagation of short packets of flexural acoustic waves. Small axial nonuniformities (of the order of nanometers) are detected by measuring the transmittance of the fundamental mode as a function of time. It is shown that the technique allows the detection of axial nonuniformities along sections of single-mode fiber exceeding 1 m long with spatial resolution of the order of a few centimeters.

  3. Efficient diode end-pumped acousto-optically Q-switched Nd:YAG/BaTeMo2O9 Raman laser.

    PubMed

    Bai, Fen; Wang, Qingpu; Jiao, Zhiyong; Xu, Xianfeng; Zhang, Hui; Tao, Xutang

    2016-11-10

    BaTeMo2O9 (BTM) is employed to achieve efficient stimulated Raman scattering conversion in a diode end-pumped acousto-optically Q-switched Nd:YAG laser. With an incident diode power of 8.6 W, 732 mW of 1179 nm first-Stokes average output power was generated at a pulse repetition rate of 10 kHz, corresponding to a diode-to-Raman conversion efficiency of 8.5%.

  4. Laser frequency stabilisation by the Pound - Drever - Hall method using an acousto-optic phase modulator operating in the pure Raman - Nath diffraction regime

    SciTech Connect

    Baryshev, Vyacheslav N

    2012-04-30

    Frequency stabilisation of diode laser radiation has been implemented by the Pound - Drever - Hall method using a new acousto-optic phase modulator, operating in the pure Raman - Nath diffraction regime. It is experimentally shown that, as in the case of saturated-absorption spectroscopy in atomic vapour, the spatial divergence of the frequency-modulated output spectrum of this modulator does not interfere with obtaining error signals by means of heterodyne frequency-modulation spectroscopy with a frequency discriminator based on a high-Q Fabry - Perot cavity with finesse of several tens of thousands.

  5. LD end-pumped acousto-optic Q-switched 1319 nm/1338 nm dual-wavelength Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Wu, C. T.; Yu, M.; Wang, C.; Yu, K.; Yu, Y. J.; Chen, X. Y.; Jin, G. Y.

    2016-10-01

    Laser characteristics of acousto-optic Q-switched operation of 1319 nm/1338 nm dual-wavelength composite Nd:YAG laser were studied. Maximum output power of 5.77 W was achieved in CW operation. Under Q-switched operation, the maximum peak power of 3.96 kW and minimum pulse width of 65.6 ns was obtained at repetition frequency of 20 kHz with the duty ratio of 96%. The influence of the duration of the ultrasonic field acted on the Q-switch to the output characteristics of dual-wavelength composite Nd:YAG laser had been reported first time.

  6. Combination of a 2-D acousto-optic deflector with laser amplifier for efficient scanning of a Q-switched ND:YAG laser

    NASA Astrophysics Data System (ADS)

    Maák, P.; Jakab, L.; Richter, P. I.; Brignon, A.; Huignard, J.-P.

    2000-03-01

    A two-dimensional acousto-optic deflector has been combined with a large angular acceptance, laser diode-pumped Nd:YAG optical amplifier in order to obtain a scanning system with high angular resolution and with high and uniform optical transmission. Experiments have been carried out in order to optimize the set-up for intensity distribution and optical losses. The combination of newly developed nonlinear and active optical elements provides a relatively uniform intensity distribution over the scanned region corresponding to 300×300 discrete points in the back focal plane of a Fourier lens, at laser pulse energy levels of 1-5 mJ.

  7. Long-cavity all-fiber ring laser actively mode locked with an in-fiber bandpass acousto-optic modulator.

    PubMed

    Cuadrado-Laborde, C; Bello-Jiménez, M; Díez, A; Cruz, J L; Andrés, M V

    2014-01-01

    We demonstrate low-frequency active mode locking of an erbium-doped all-fiber ring laser. As the mode locker, we used a new in-fiber bandpass acousto-optic modulator showing 74% modulation depth, 3.7 dB power insertion losses, 4.5 nm of optical bandwidth, and 20 dB of nonresonant light suppression. The laser generates 330 ps mode-locked pulses over a 10 ns pedestal, at a 1.538 MHz frequency, with 130 mW of pump power.

  8. A modeling-based assessment of acousto-optic sensing for monitoring high-intensity focused ultrasound lesion formation

    NASA Astrophysics Data System (ADS)

    Adams, Matthew Tyler

    Real-time acousto-optic (AO) sensing---a dual-wave modality that combines ultrasound with diffuse light to probe the optical properties of turbid media---has been demonstrated to non-invasively detect changes in ex vivo tissue optical properties during high-intensity focused ultrasound (HIFU) exposure. The AO signal indicates the onset of lesion formation and predicts resulting lesion volumes. Although proof-of-concept experiments have been successful, many of the underlying parameters and mechanisms affecting thermally induced optical property changes and the AO detectability of HIFU lesion formation are not well understood. In thesis, a numerical simulation was developed to model the AO sensing process and capture the relevant acoustic, thermal, and optical transport processes. The simulation required data that described how optical properties changed with heating. Experiments were carried out where excised chicken breast was exposed to thermal bath heating and changes in the optical absorption and scattering spectra (500 nm--1100 nm) were measured using a scanning spectrophotometer and an integrating sphere assembly. Results showed that the standard thermal dose model currently used for guiding HIFU treatments needs to be adjusted to describe thermally induced optical property changes. To model the entire AO process, coupled models were used for ultrasound propagation, tissue heating, and diffusive light transport. The angular spectrum method was used to model the acoustic field from the HIFU source. Spatial-temporal temperature elevations induced by the absorption of ultrasound were modeled using a finite-difference time-domain solution to the Pennes bioheat equation. The thermal dose model was then used to determine optical properties based on the temperature history. The diffuse optical field in the tissue was then calculated using a GPU-accelerated Monte Carlo algorithm, which accounted for light-sound interactions and AO signal detection. The simulation was

  9. Numerical Analysis of the Crosstalk on an Integrated Acousto-Optic Tunable Filter (AOTF) for Network Applications

    NASA Astrophysics Data System (ADS)

    Sobrinho, C. S.; de Oliveira, M. V. N.; Silva, M. G. Da; Lima, J. L. S.; de Almeida, E. F.; Sombra, A. S. B.

    In this article, we did a study of the crosstalk level (Xtalk) and extinction ratio (Xratio) of an acousto-optic tunable filter (AOTF) operating with ultra-short light pulses (2 ps). It is clear that the transmission bandwidth decreases as the length of the device increases. The compression factor was studied for the switched pulse in an AOTF without loss considering five nonlinearity profiles. One can observe that there is always an optimum value for β (final value of the nonlinearity) that one can obtain a switched pulse with the same time duration of the input pulse. The study of the crosstalk level, of this device, considering the optimum values of β obtained from the compression studies, as a function of the pump power (P0) was done. For the soliton profile at 1 W of pump power one can notice that the Gaussian profile presents the lower Xtalk value (-13 dB), and the constant profile presents the worst value (-9.8 dB). However, if one is looking for a specific Xtalk value, one can conclude that with the constant profile one can obtain this value with a lower power. For the quasi-soliton profile of the same device, with low pump power (1 W), one can notice again that the Gaussian profile presents the lower Xtalk value (-13 dB) and the constant profile presents the worst value (-9.87 dB). This fact can be explained because, with pump power at 1 W, soliton and quasi-soliton profiles lead equivalent input pulses and under the same conditions produce equal results. The Xtalk level, considering all the profiles as a function of the β value, was studied. For all the profiles one has a strong increase of the Xtalk level with the increase of the final β value of the nonlinearity profile. Comparing all the profiles one can conclude that the Gaussian profile presents the lower Xtalk value in the range of β values in use. At the same time the value of the Xtalk for this profile does not change much with the change in the β value, presenting values in interval (-13 d

  10. Compact interrogator for fiber optic Bragg sensors based on an acousto-optic filter formed by photonic crystal rows of air holes.

    PubMed

    Tsarev, Andrei V; De Leonardis, Francesco; Passaro, Vittorio M N

    2011-10-01

    Fiber optic sensors are typically used with expensive tunable lasers or optical spectrum analyzers for wavelength interrogation. We propose to replace the tunable laser by a broadband optical source incorporated with a novel thin linewidth acousto-optic tunable filter. It utilizes optical beam expanders constituted by photonic crystal rows of air holes in LiNbO(3) waveguide. A new design is numerically studied for a short structure (with 32 photonic crystal rows) by a two-dimensional finite-difference time-domain method. Extrapolation of these results to larger structure sizes (about 1 cm) demonstrates the possibility to develop compact interrogators with 0.4 pm wavelength resolution and 40 nm tunable range around 1550 nm.

  11. Two wavelength operation of an acousto-optically tuned quantum cascade laser and direct measurements of quantum cascade laser level lifetimes

    NASA Astrophysics Data System (ADS)

    Patel, C. Kumar N.; Barron-Jimenez, Rodolfo; Dunayevskiy, Ilya; Tsvid, Gene; Lyakh, Arkadiy

    2017-01-01

    We report simultaneous two wavelength operation of an acousto-optically tuned quantum cascade laser (QCL). The two wavelengths can be independently tuned as well as independently switched, retaining the submicrosecond switching capability. In addition, we have used the two wavelength operation as a tool for the direct measure of the lifetimes of the lasing states in a practical QCL. The lifetime measurements in an operational QCL are facilitated by our ability to vary the frequency separation between two simultaneously lasing wavelengths. The measured lifetime is 0.6 ps ± 0.2 ps for our quantum cascade laser. The two wavelength operation of QCLs paves the way for time resolved pump/probe studies of infrared phenomena and provides direct insight into the effectiveness of various QCL structure designs.

  12. Noise tolerance in wavelength-selective switching of optical differential quadrature-phase-shift-keying pulse train by collinear acousto-optic devices.

    PubMed

    Goto, Nobuo; Miyazaki, Yasumitsu

    2014-06-01

    Optical switching of high-bit-rate quadrature-phase-shift-keying (QPSK) pulse trains using collinear acousto-optic (AO) devices is theoretically discussed. Since the collinear AO devices have wavelength selectivity, the switched optical pulse trains suffer from distortion when the bandwidth of the pulse train is comparable to the pass bandwidth of the AO device. As the AO device, a sidelobe-suppressed device with a tapered surface-acoustic-wave (SAW) waveguide and a Butterworth-type filter device with a lossy SAW directional coupler are considered. Phase distortion of optical pulse trains at 40 to 100  Gsymbols/s in QPSK format is numerically analyzed. Bit-error-rate performance with additive Gaussian noise is also evaluated by the Monte Carlo method.

  13. Analysis of the frequency response of a TeO{sub 2} slow shear wave acousto-optic cell exposed to radiation

    SciTech Connect

    Erteza, I.A.

    1995-04-01

    Radiation testing of photonic components is not new, however component level testing to date has not completely addressed quantities which are important to system behavior. One characteristic that is of particular importance for optical processing systems is the frequency response. In this report, we present the analysis of data from an experiment designed to provide a preliminary understanding of the effects of radiation on the frequency response of acousto-optic devices. The goal of the analysis is to describe possible physical mechanisms responsible for the radiation effects and to discuss the effects on signal processing functionality. The experiment discussed in this report was designed by Sandia National Laboratories and performed by Sandia and Phillips Laboratory personnel at White Sands Missile Range (WSMR). In the experiment, a TeO{sub 2} slow shear wave acousto-optic cell was exposed to radiation from the WSMR linear accelerator. The TeO{sub 2} cell was placed in an experimental configuration which allowed swept frequency diffracted power measurements to be taken during radiation exposure and recovery. A series of exposures was performed. Each exposure consisted of between 1 to 800, 1{mu}sec radiation pulses (yielding exposures of 2.25 kRad(Si) to 913 kRad(Si)), followed by recovery time. At low total and cumulative doses, the bandshape of the frequency response (i.e. diffracted power vs. frequency) remained almost identical during and after radiation. At the higher exposures, however, the amplitude and width of the frequency response changed as the radiation continued, but returned to the original shape slowly after the radiation stopped and recovery proceeded. It is interesting to note that the location of the Bragg degeneracy does not change significantly with radiation. In this report, we discuss these effects from the perspective of anisotropic Bragg diffraction and momentum mismatch, and we discuss the effect on the signal processing functionality.

  14. High coherent bi-chromatic laser with gigahertz splitting produced by the high diffraction orders of acousto-optic modulator used for coherent population trapping experiments.

    PubMed

    Yun, Peter; Tan, Bozhong; Deng, Wei; Gu, Sihong

    2011-12-01

    To prepare the coherent population trapping (CPT) states with rubidium and cesium, the commonly used atoms in CPT studies, a coherent bi-chromatic light field with frequency difference of several GHz is a basic requirement. With a 200 MHz center frequency acousto-optic modulator (AOM), we have realized bi-chromatic laser fields with several GHz frequency splits through high diffraction orders. We have experimentally studied the coherence between two frequency components of a bi-chromatic laser beam, which is composed of ±6 orders with frequency split of 3 GHz diffracted from the same laser beam, and the measured residual phase noise is Δφ(2)<0.019 rad(2). The bi-chromatic laser fields were used to prepare CPT states with (85)Rb and (87)Rb atoms, and high contrast CPT signals were obtained. For CPT states preparation, our study result shows that it is a feasible approach to generate the bi-chromatic light field with larger frequency splits through high diffraction orders of AOM.

  15. Optimization of doubly Q-switched lasers with both an acousto-optic modulator and a GaAs saturable absorber.

    PubMed

    Li, Dechun; Zhao, Shengzhi; Li, Guiqiu; Yang, Kejian

    2007-08-20

    A doubly Q-switched laser with both an acousto-optic (AO) modulator and a GaAs saturable absorber can obtain a more symmetric and shorter pulse with high pulse peak power, which has been experimentally proved. The key parameters of an optimally coupled doubly Q-switched laser with both an AO modulator and a GaAs saturable absorber are determined, and a group of general curves are generated for what we believe is the first time, when the single-photon absorption (SPA) and two-photon absorption (TPA) processes of GaAs are combined, and the Gaussian spatial distributions of the intracavity photon density and the initial population-inversion density as well as the influence of the AO Q-switch are considered. These key parameters include the optimal normalized coupling parameter, the optimal normalized GaAs saturable absorber parameters, and the normalized parameters of the AO Q-switch, which can maximize the output energy. Meanwhile, the corresponding normalized energy, the normalized peak power, and the normalized pulse width are given. The curves clearly show the dependence of the optimal key parameters on the parameters of the gain medium, the GaAs saturable absorber, the AO Q-switch, and the resonator. Sample calculations for a diode-pumped Nd3+:YVO4 laser with both an AO modulator and a GaAs saturable absorber are presented to demonstrate the use of the curves and the relevant formulas.

  16. Hybrid wide-band, low-phase-noise scheme for Raman lasers in atom interferometry by integrating an acousto-optic modulator and a feedback loop.

    PubMed

    Wang, Kai; Yao, Zhanwei; Li, Runbing; Lu, Sibin; Chen, Xi; Wang, Jin; Zhan, Mingsheng

    2016-02-10

    We report a hybrid scheme for phase-coherent Raman lasers with low phase noise in a wide frequency range. In this scheme, a pair of Raman lasers with a frequency difference of 3.04 GHz is generated by the ±1-order diffracted lights of an acousto-optic modulator (1.52 GHz), where a feedback loop is simultaneously applied for suppressing the phase noise. The beat width of the Raman lasers is narrower than 3 Hz. In the low-frequency range, the phase noise of the Raman lasers is suppressed by 35 dB with the feedback. The phase noise is less than -109  dBc/Hz in the high-frequency range. The sensitivity of an atom gyroscope employing the hybrid Raman lasers can be implicitly improved 10 times. Due to the better high-frequency response, the sensitivity is not limited by the durations of Raman pulses. This work is important for improving the performance of atom-interferometer-based measurements.

  17. Improved performance of analog and digital acousto-optic modulation with feedback under profiled beam propagation for secure communication using chaos

    NASA Astrophysics Data System (ADS)

    Almehmadi, Fares S.; Chatterjee, Monish R.

    2014-12-01

    Using intensity feedback, the closed-loop behavior of an acousto-optic hybrid device under profiled beam propagation has been recently shown to exhibit wider chaotic bands potentially leading to an increase in both the dynamic range and sensitivity to key parameters that characterize the encryption. In this work, a detailed examination is carried out vis-à-vis the robustness of the encryption/decryption process relative to parameter mismatch for both analog and pulse code modulation signals, and bit error rate (BER) curves are used to examine the impact of additive white noise. The simulations with profiled input beams are shown to produce a stronger encryption key (i.e., much lower parametric tolerance thresholds) relative to simulations with uniform plane wave input beams. In each case, it is shown that the tolerance for key parameters drops by factors ranging from 10 to 20 times below those for uniform plane wave propagation. Results are shown to be at consistently lower tolerances for secure transmission of analog and digital signals using parameter tolerance measures, as well as BER performance measures for digital signals. These results hold out the promise for considerably greater information transmission security for such a system.

  18. Doppler-free, multiwavelength acousto-optic deflector for two-photon addressing arrays of Rb atoms in a quantum information processor

    NASA Astrophysics Data System (ADS)

    Kim, Sangtaek; McLeod, Robert R.; Saffman, M.; Wagner, Kelvin H.

    2008-04-01

    We demonstrate a dual wavelength acousto-optic deflector (AOD) designed to deflect two wavelengths to the same angles by driving with two RF frequencies. The AOD is designed as a beam scanner to address two-photon transitions in a two-dimensional array of trapped neutral Rb87 atoms in a quantum computer. Momentum space is used to design AODs that have the same diffraction angles for two wavelengths (780 and 480 nm) and have nonoverlapping Bragg-matched frequency response at these wavelengths, so that there will be no cross talk when proportional frequencies are applied to diffract the two wavelengths. The appropriate crystal orientation, crystal shape, transducer size, and transducer height are determined for an AOD made with a tellurium dioxide crystal (TeO2). The designed and fabricated AOD has more than 100 resolvable spots, widely separated band shapes for the two wavelengths within an overall octave bandwidth, spatially overlapping diffraction angles for both wavelengths (780 and 480 nm), and a 4 μs or less access time. Cascaded AODs in which the first device upshifts and the second downshifts allow Doppler-free scanning as required for addressing the narrow atomic resonance without detuning. We experimentally show the diffraction-limited Doppler-free scanning performance and spatial resolution of the designed AOD.

  19. FPGA-based phase control of acousto-optic modulator Fourier synthesis system through gradient descent phase-locking algorithm.

    PubMed

    Underwood, Kenneth J; Jones, Andrew M; Gopinath, Juliet T

    2015-06-20

    We present a new application of the stochastic parallel gradient descent (SPGD) algorithm to fast active phase control in a Fourier synthesis system. Pulses (4.9 ns) with an 80 MHz repetition rate are generated by feedback from a single phase-sensitive metric. Phase control is applied via fast current modulation of a tapered amplifier using an SPGD algorithm realized on a field-programmable gate array (FPGA). The waveforms are maintained by constant active feedback from the FPGA. We also discuss the extension of this technique to many more semiconductor laser emitters in a diode laser array.

  20. Modeling of power spectral density of modified von Karman atmospheric phase turbulence and acousto-optic chaos using scattered intensity profiles over discrete time intervals

    NASA Astrophysics Data System (ADS)

    Chatterjee, Monish R.; Mohamed, Fathi H. A.

    2014-10-01

    In recent research, propagation of plane electromagnetic (EM) waves through a turbulent medium with modified von Karman phase characteristics was modeled and numerically simulated using transverse planar apertures representing narrow phase turbulence along the propagation path. The case for extended turbulence was also studied by repeating the planar phase screens multiple times over the propagation path and incorporating diffractive effects via a split-step algorithm. The goal of the research reported here is to examine two random phenomena: (a) atmospheric turbulence due to von Karman-type phase fluctuations, and (b) chaos generated in an acousto-optic (A-O) Bragg cell under hybrid feedback. The latter problem has been thoroughly examined for its nonlinear dynamics and applications in secure communications. However, the statistical characteristics (such as the power spectral density (PSD)) of the chaos have not been estimated in recent work. To that end, treating the chaos phenomena as a random process, the time waveforms of the chaos intensity and their spectra are numerically evaluated over a (large) number of time iterations. These spectra are then averaged to derive the equivalent PSD of the A-O chaos. For the turbulence problem, an optical beam passing through an input pinhole is propagated through a random phase screen (placed at different locations) to a desired distance (typically near-field) under different levels of turbulence strength. The resulting spatial intensity profile is then averaged and the process repeated over a (large) number of pre-specified time intervals. From this data, once again, the turbulence PSD is calculated via the Fourier spectra of the average intensity snapshots. The results for the two systems are compared.

  1. MO-A-BRD-01: An Investigation of the Dynamic Response of a Novel Acousto-Optic Liquid Crystal Detector for Full-Field Transmission Ultrasound Breast Imaging

    SciTech Connect

    Rosenfield, J.R.; La Riviere, P.J.; Sandhu, J.S.

    2014-06-15

    Purpose: To characterize the dynamic response of a novel acousto-optic (AO) liquid crystal detector for high-resolution transmission ultrasound breast imaging. Transient and steady-state lesion contrast were investigated to identify optimal transducer settings for our prototype imaging system consistent with the FDA limits of 1 W/cm{sup 2} and 50 J/cm{sup 2} on the incident acoustic intensity and the transmitted acoustic energy flux density. Methods: We have developed a full-field transmission ultrasound breast imaging system that uses monochromatic plane-wave illumination to acquire projection images of the compressed breast. The acoustic intensity transmitted through the breast is converted into a visual image by a proprietary liquid crystal detector operating on the basis of the AO effect. The dynamic response of the AO detector in the absence of an imaged breast was recorded by a CCD camera as a function of the acoustic field intensity and the detector exposure time. Additionally, a stereotactic needle biopsy breast phantom was used to investigate the change in opaque lesion contrast with increasing exposure time for a range of incident acoustic field intensities. Results: Using transducer voltages between 0.3 V and 0.8 V and exposure times of 3 minutes, a unique one-to-one mapping of incident acoustic intensity to steady-state optical brightness in the AO detector was observed. A transfer curve mapping acoustic intensity to steady-state optical brightness shows a high-contrast region analogous to the linear portion of the Hurter-Driffield curves of radiography. Using transducer voltages between 1 V and 1.75 V and exposure times of 90 s, the lesion contrast study demonstrated increasing lesion contrast with increasing breast exposure time and acoustic field intensity. Lesion-to-background contrast on the order of 0.80 was observed. Conclusion: Maximal lesion contrast in our prototype system can be obtained using the highest acoustic field intensity and the

  2. Precise parallel optical spectrum analysis using the advanced two-phonon light scattering combined with the cross-disperser technique.

    PubMed

    Shcherbakov, A S; Arellanes, A O; Chavushyan, V

    2016-12-01

    We develop an advanced approach to the optical spectrometer with acousto-optical dynamic grating for the Guillermo Haro astrophysical observatory (Mexico). The progress consists of two principle novelties. First is the use of the acousto-optical nonlinearity of two-phonon light scattering in crystals with linear acoustic losses. This advanced regime of light scattering exhibits a recently revealed additional degree of freedom, which allows tuning of the frequency of elastic waves and admits the nonlinear apodization improving the dynamic range. The second novelty is the combination of the cross-disperser with acousto-optical processing. A similar pioneering step provides an opportunity to operate over all the visible range in a parallel regime with maximal achievable resolution. The observation window of the optical spectrometer in that observatory is ∼9  cm, so that the theoretical estimations of maximal performances for a low-loss LiNbO3 crystal for this optical aperture at λ=405  nm give spectral resolution of 0.0523 Å, resolving power of 77,400, and 57,500 spots. The illustrative proof-of-principle experiments with a 6 cm LiNbO3 crystal have been performed.

  3. High-peak-power sub-nanosecond intracavity KTiOPO4 optical parametric oscillator pumped by a dual-loss modulated laser with acousto-optic modulator and single-walled carbon nanotube

    NASA Astrophysics Data System (ADS)

    Qiao, Junpeng; Zhao, Shengzhi; Yang, Kejian; Zhao, Jia; Li, Guiqiu; Li, Dechun; Li, Tao; Qiao, Wenchao; Lu, Jianren; Wang, Yonggang; Chu, Hongwei; Luan, Chao

    2016-08-01

    A high-peak-power low-repetition-rate sub-nanosecond intracavity KTiOPO4 (KTP) optical parametric oscillator (OPO) pumped by a doubly Q-switched and mode-locked (QML) YVO4/Nd:YVO4 laser with an acousto-optic modulator (AOM) and a single-walled carbon nanotube saturable absorber (SWCNT-SA) has been demonstrated. A maximum output power of 373 mW at a signal wavelength of 1570 nm was obtained. The smallest pulse width, highest pulse energy, and greatest peak power of mode-locking pulses were estimated to be 119 ps, 124 µJ, and 1.04 MW, respectively, under a maximum incident pump power of 8.3 W and an AOM repetition rate of 2 kHz. This OPO operation paves a simple way to produce eye-safe laser sources at 1570 nm with low repetition rates, small pulse widths, and high peak powers.

  4. Compact high-resolution spaceborne echelle grating spectrometer with acousto-optical tunable filter based order sorting for the infrared domain from 2.2 to 4.3 microm.

    PubMed

    Nevejans, Dennis; Neefs, Eddy; Van Ransbeeck, Emiel; Berkenbosch, Sophie; Clairquin, Roland; De Vos, Lieve; Moelans, Wouter; Glorieux, Stijn; Baeke, Ann; Korablev, Oleg; Vinogradov, Imant; Kalinnikov, Yuri; Bach, Benny; Dubois, Jean-Pierre; Villard, Eric

    2006-07-20

    A new compact spaceborne high-resolution spectrometer developed for the European Space Agency's Venus Express spacecraft is described. It operates in the IR wavelength range of 2.2 to 4.3 microm and measures absorption spectra of minor constituents in the Venusian atmosphere. It uses a novel echelle grating with a groove density of 4 lines/mm in a Littrow configuration in combination with an IR acousto-optic tunable filter for order sorting and an actively cooled HgCdTe focal plane array of 256 by 320 pixels. It is designed to obtain an instrument line profile of 0.2 cm(-1). First results on optical and spectral properties are reported.

  5. Influence of wavelength-dependent-loss on dispersive wave in nonlinear optical fibers.

    PubMed

    Herrera, Rodrigo Acuna

    2012-11-01

    In this work, we study numerically the influence of wavelength-dependent loss on the generation of dispersive waves (DWs) in nonlinear fiber. This kind of loss can be obtained, for instance, by the acousto-optic effect in fiber optics. We show that this loss lowers DW frequency in an opposite way that the Raman effect does. Also, we see that the Raman effect does not change the DW frequency too much when wavelength-dependent loss is included. Finally, we show that the DW frequency is not practically affected by fiber length.

  6. Dispersal

    USGS Publications Warehouse

    Clobert, J.; Danchin, E.; Dhondt, A.A.; Nichols, J.D.

    2001-01-01

    The ability of species to migrate and disperse is a trait that has interested ecologists for many years. Now that so many species and ecosystems face major environmental threats from habitat fragmentation and global climate change, the ability of species to adapt to these changes by dispersing, migrating, or moving between patches of habitat can be crucial to ensuring their survival. This book provides a timely and wide-ranging overview of the study of dispersal and incorporates much of the latest research. The causes, mechanisms, and consequences of dispersal at the individual, population, species and community levels are considered. The potential of new techniques and models for studying dispersal, drawn from molecular biology and demography, is also explored. Perspectives and insights are offered from the fields of evolution, conservation biology and genetics. Throughout the book, theoretical approaches are combined with empirical data, and care has been taken to include examples from as wide a range of species as possible.

  7. Measurement of Isotope Shifts, Hyperfine Splittings and Stark Shift for the Ytterbium (6S)2 SINGLET-S(0) to (6S6P) TRIPLET-P(1) Transition Using AN Acousto-Optically Modulated Laser Beam.

    NASA Astrophysics Data System (ADS)

    Li, Jian

    1995-11-01

    Accurate measurements of isotope shifts, hyperfine splittings and Stark shifts are of interest for studying atomic structure. This thesis reports a new method to precisely measure small frequency intervals. This was done using an acousto-optic modulator to frequency shift part of a laser beam. The frequency shifted and unshifted laser beams were then superimposed and excited an atomic beam. The laser frequency was scanned across the transition while fluorescence produced by the radiative decay of the excited state was detected by a photomultiplier. Each transition generated two peaks in the spectrum separated by the acousto-optic modulation frequency, which permitted the frequency to be calibrated. This method was tested by measuring the isotope shifts and hyperfine splittings of the ytterbium rm (6s)^2 ^1S_0to(6s6p) ^3P_1 transition at 555.6 nm. The shifts (MHz) relative to ^{176} Yb are: ^{173}Yb {it F}=7/2,-1432.1+/-1.2; ^{171}Yb {it F}=1/2, -1176.9+/-1.1; ^{174}Yb, 953.8+/-1.0; ^{172}Yb 1953.9+/-1.6; ^{170}Yb 3240.4+/-2.8; ^{173}Yb {it F}=5/2,3265.8+/-2.8; ^ {168}Yb, 4611.9+/-4.4; ^ {171,173}Yb {it F}=3/2,4760.1 +/-3.7 where the negative sign indicates that the transition occurs at a lower frequency than in ^{176}Yb. The magnetic dipole (a) and electric quadrupole (b) hyperfine coupling constants (MHz) of the (6s6p) ^3P_1 state for ^{171,173}Yb were determined to be a_{171}=3959.1 +/-3.0, a_{173}=-1094.44+/-0.84 and b_{173}=-827.89+/-0.85. These results were in agreement with the most accurate data found in the literature that were obtained by measuring frequency shifts using a Fabry Perot etalon whose length was stabilized with a helium neon laser locked to an iodine line. In contrast, our method uses cheaper and simpler apparatus. Next, the Stark shift of the ytterbium rm (6s)^2 ^1S_0to(6s6p) ^3P_1 transition was measured by passing the atomic beam through a uniform electric field. The Stark shift rate was found to be -15.419+/-0.048 kHz/(kV/cm)^2. No

  8. High-power PPMgLN-based optical parametric oscillator pumped by a linearly polarized, semi-fiber-coupled acousto-optic Q-switched fiber master oscillator power amplifier.

    PubMed

    Chen, Tao; Jiang, Peipei; Yang, Dingzhong; Hu, Chengzhi; Wu, Bo; Shen, Yonghang

    2013-09-01

    We have experimentally demonstrated a periodically poled magnesium-oxide-doped lithium niobate (PPMgLN)-based, fiber-laser-pumped optical parametric oscillator (OPO) generating idler wavelength of 3.82 μm. The pump fiber laser was constructed with a linearly polarized, semi-fiber-coupled acousto-optic Q-switched fiber oscillator and a polarization-maintaining fiber amplifier with pulse duration of 190 ns at the highest output power. The OPO was specifically configured in single-pass, singly resonant linear cavity structure to avoid the damage risk of the pump fiber laser, which is always a serious issue in the fiber-laser-pumped, double-pass, singly oscillating structured OPOs. Under the highest pump power of 25 W, an idler average output power of 3.27 W with one-hour peak-to-peak instability of 5.2% was obtained. The measured M2 factors were 1.98 and 1.44 for horizontal and vertical axis, respectively. The high power stability and good beam quality demonstrated the suitability of such technology for practical application.

  9. Depth selective acousto-optic flow measurement

    PubMed Central

    Tsalach, Adi; Schiffer, Zeev; Ratner, Eliahu; Breskin, Ilan; Zeitak, Reuven; Shechter, Revital; Balberg, Michal

    2015-01-01

    Optical based methods for non-invasive measurement of regional blood flow tend to incorrectly assess cerebral blood flow, due to contribution of extra-cerebral tissues to the obtained signal. We demonstrate that spectral analysis of phase-coded light signals, tagged by specific ultrasound patterns, enables differentiation of flow patterns at different depths. Validation of the model is conducted by Monte Carlo simulation. In-vitro experiments demonstrate good agreement with the simulations' results and provide a solid validation to depth discrimination ability. These results suggest that signal contamination originating from extra-cerebral tissue may be eliminated using spectral analysis of ultrasonically tagged light. PMID:26713201

  10. Multiple acousto-optic q-switch

    DOEpatents

    Deason, Vance A.

    1993-01-01

    An improved dynamic moire interferometer comprised of a lasing medium providing a plurality of beams of coherent light, a multiple q-switch producing multiple trains of 100,000 or more pulses per second, a combining means collimating multiple trains of pulses into substantially a single train and directing beams to specimen gratings affixed to a test material, and a controller, triggering and sequencing the emission of the pulses with the occurrence and recording of a dynamic loading event.

  11. Multiple acousto-optic q-switch

    DOEpatents

    Deason, Vance A.

    1993-12-07

    An improved dynamic moire interferometer comprised of a lasing medium providing a plurality of beams of coherent light, a multiple q-switch producing multiple trains of 100,000 or more pulses per second, a combining means collimating multiple trains of pulses into substantially a single train and directing beams to specimen gratings affixed to a test material, and a controller, triggering and sequencing the emission of the pulses with the occurrence and recording of a dynamic loading event.

  12. Narrowing of the linewidth of an optical parametric oscillator by an acousto-optic modulator for the realization of mid-IR noise-immune cavity-enhanced optical heterodyne molecular spectrometry down to 10⁻¹⁰ cm⁻¹ Hz⁻¹/².

    PubMed

    Hausmaninger, Thomas; Silander, Isak; Axner, Ove

    2015-12-28

    The linewidth of a singly resonant optical parametric oscillator (OPO) has been narrowed with respect to an external cavity by the use of an acousto-optic modulator (AOM). This made possible an improvement of the sensitivity of a previously realized OPO-based noise-immune cavity-enhanced optical heterodyne molecular spectrometry instrument for the 3.2 - 3.9 µm mid-infrared region by one order of magnitude. The resulting system shows a detection sensitivity for methane of 2.4 × 10(-10) cm(-1) Hz(-1∕2) and 1.3 × 10(-10) cm(-1) at 20 s, which allows for detection of both the environmentally important (13)CH(4) and CH(3)D isotopologues in atmospheric samples.

  13. Generation of 48-fs pulses and measurement of crystal dispersion by using a regeneratively initiated self-mode-locked chromium-doped forsterite laser

    NASA Astrophysics Data System (ADS)

    Sennaroglu, Alphan; Pollock, Clifford R.; Nathel, Howard

    1993-05-01

    A regeneratively initiated self-mode-locked chromium-doped forsterite laser operated at 3.5 C is described. By employing intracavity negative-group-velocity dispersion compensation, nearly transform-limited femtosecond pulses of 48-fs (FWHM) duration were generated with average TEM(00) output powers of 380 mW at 1.23 micron. Regenerative initiation provides improvement in the output stability and ease of operation compared with fixed-frequency acousto-optic modulators. By tuning the mode-locked laser in the range 1.21-1.26 micron, estimated values for forsterite dispersion constants have also been obtained for the first time to our knowledge. The demonstrated power and stability open the door to applications such as efficient second-harmonic generation.

  14. Ultrasound visualization using polymer dispersed liquid crystal sensors

    NASA Astrophysics Data System (ADS)

    Edwards, R. S.; Trushkevych, O.; Eriksson, T. J. R.; Ramadas, S. N.; Dixon, S.

    2017-02-01

    The acousto-optic effect in liquid crystals (LCs) has previously been exploited to build large area acoustic sensors for visualising ultrasound fields, opening up the field of acoustography. There is an opportunity to simplify this technique and open new application areas by employing polymer dispersed LC (PDLC) thin films instead of aligned LC layers. In PDLCs, the normally opaque film becomes transparent under the influence of an acoustic field (e.g. when surface acoustic waves are propagating in the material under the film). This is called acoustic clearing and is visible by eye. There is potential for producing ultrasonic sensors which can be `painted on' to a component, giving direct visualisation of the ultrasonic field without requiring scanning. We demonstrate the effect by using PDLC films to characterise a resonant mode of a flexural air-coupled transducer. Visualisation was quick, with a switching time of a few seconds. The effect shows promise for ultrasound sensing applications for transducer characterisation and NDE.

  15. High power femtosecond lasers at ELI-NP

    SciTech Connect

    Dabu, Razvan

    2015-02-24

    Specifications of the high power laser system (HPLS) designed for nuclear physics experiments are presented. Configuration of the 2 × 10 PW femtosecond laser system is described. In order to reach the required laser beam parameters, advanced laser techniques are proposed for the HPLS: parametric amplification and cross-polarized wave generation for the intensity contrast improvement and spectral broadening, acousto-optic programmable filters to compensate for spectral phase dispersion, optical filters for spectrum management, combined methods for transversal laser suppression.

  16. Bench testing of a heterodyne CO2 laser dispersion interferometer for high temporal resolution plasma density measurements.

    PubMed

    Akiyama, T; Van Zeeland, M A; Boivin, R L; Carlstrom, T N; Chavez, J A; Muscatello, C M; O'Neill, R C; Vasquez, J; Watkins, M; Martin, W; Colio, A; Finkenthal, D K; Brower, D L; Chen, J; Ding, W X; Perry, M

    2016-12-01

    A heterodyne detection scheme is combined with a 10.59 μm CO2 laser dispersion interferometer for the first time to allow large bandwidth measurements in the 10-100 MHz range. The approach employed utilizes a 40 MHz acousto-optic cell operating on the frequency doubled CO2 beam which is obtained using a high 2nd harmonic conversion efficiency orientation patterned gallium arsenide crystal. The measured standard deviation of the line integrated electron density equivalent phase resolution obtained with digital phase demodulation technique, is 4 × 10(17) m(-2). Air flow was found to significantly affect the baseline of the phase signal, which an optical table cover was able to reduce considerably. The heterodyne dispersion interferometer (DI) approach is found to be robustly insensitive to motion, with measured phase shifts below baseline drifts even in the presence of several centimeters of retroreflector induced path length variations. Plasma induced dispersion was simulated with a wedged ZnSe plate and the measured DI phase shifts are consistent with expectations.

  17. Bench testing of a heterodyne CO2 laser dispersion interferometer for high temporal resolution plasma density measurements

    NASA Astrophysics Data System (ADS)

    Akiyama, T.; Van Zeeland, M. A.; Boivin, R. L.; Carlstrom, T. N.; Chavez, J. A.; Muscatello, C. M.; O'Neill, R. C.; Vasquez, J.; Watkins, M.; Martin, W.; Colio, A.; Finkenthal, D. K.; Brower, D. L.; Chen, J.; Ding, W. X.; Perry, M.

    2016-12-01

    A heterodyne detection scheme is combined with a 10.59 μm CO2 laser dispersion interferometer for the first time to allow large bandwidth measurements in the 10-100 MHz range. The approach employed utilizes a 40 MHz acousto-optic cell operating on the frequency doubled CO2 beam which is obtained using a high 2nd harmonic conversion efficiency orientation patterned gallium arsenide crystal. The measured standard deviation of the line integrated electron density equivalent phase resolution obtained with digital phase demodulation technique, is 4 × 1017 m-2. Air flow was found to significantly affect the baseline of the phase signal, which an optical table cover was able to reduce considerably. The heterodyne dispersion interferometer (DI) approach is found to be robustly insensitive to motion, with measured phase shifts below baseline drifts even in the presence of several centimeters of retroreflector induced path length variations. Plasma induced dispersion was simulated with a wedged ZnSe plate and the measured DI phase shifts are consistent with expectations.

  18. Acousto-Optic Fourier Transform Devices for Surveillance Signal Processing.

    DTIC Science & Technology

    1983-06-30

    diffracted light beams. This scheme is illustrated in Fig. 11, and is essentially a Twyman -Green interferometer . This scheme has not been implemented...1, uses a two-mirror interferometer scheme whereby an imaged scene contains a fringe pattern determined by the mirror separation. An array of...obtained from the individual detectors behind the reticle if there is movement in the field, since in that case the interferometer fringes move across

  19. Three-dimensional acousto-optic spectrum analysis

    NASA Technical Reports Server (NTRS)

    Ansari, Homayoon; Metscher, Brian; Lesh, James R.

    1990-01-01

    A three-dimensional acoustooptic spectrum analyzer with subhertz resolution is demonstrated experimentally. The first and second dimensions are the two spatial dimensions of the output detector array, and the third dimension is time as sampled by the detector array frame rate. A superfine resolution of 0.12 Hz has been achieved.

  20. Acousto-optic processor for autonomous SAR guidance

    NASA Astrophysics Data System (ADS)

    Pape, Dennis R.

    1990-09-01

    This paper describes an acoustooptic signal processor designed to produce real-time spotlight mode synthetic aperture radar (SAR) images for autonomous missile guidance. The processor is designed to maintain a range and azimuth resolution of 2 m. High-quality image formation results from electronic motion compensation applied to each received pulse. The processor controls range sidelobes through a weighting function applied during the correlation process, while azimuth sidelobes are controlled either by weighting or by increasing the corehent integration time.

  1. System Sensitivity Analysis Acousto-Optic Spectrum Analysis Receiver.

    DTIC Science & Technology

    1980-02-01

    facteurs determinants dont il est tenu compte sont notamment le produit temps-largeur de bande et la dur~e d’integration du r ~ seau photod~tecteur. Des...92.0 26 96.0 28 100.5 30 104.0 32 110.0 33 0 w 0 (A W) 9V.LIO UNCLASSIFIED Security Cia.,ficaton OOCUMENT CONTROL DATA - R & D ( :e.rv cla s hmi l...itself is unclassified) represented as ITS), (SI. 1C0, ( R ), or (U). la TOTAL NUMBER OF PAGES’ The total page count should follow otrmal pagination

  2. Incoherent acousto-optic image correlator with the kinoform

    NASA Astrophysics Data System (ADS)

    Starikov, Sergey N.; Rodin, Vladislav G.; Solyakin, Ivan V.; Shapkarina, Ekaterina A.; Chervonkin, Alexander P.

    2004-04-01

    Fourier holograms are commonly used for reference images storing in diffraction correlators with spatially coherent or spatially incoherent illumination. Kinoforms can be a real alternative to Fourier holograms in the correlators. The kinoform represents a computer-synthesized optical element which performs only a phase modulation of a light wave. The kinoform restores true intensity of the recorded image and random distribution of phase. Therefore, it can be utilized for storing reference images, first of all, in correlators with spatially incoherent illumination. The absence of carrier frequency reduces demanded number of pixels of the spatial light modulator being used. Since the kinoform provides reconstruction of reference image in zero diffraction order, requirement on monochromaticity of illumination are decreased as well. The diffraction correlator with the kinoform used as spatial frequency filter is considered. The 2-D acoustooptic deflector was employed to form input images in real time by monochromatic spatially incoherent light. The reference images were recorded on the commercially available kinoforms. The input and reference images were of 256×256 pixels and 200×200 pixels respectively. Since input images were consisted of approximately 400 pixels with non-zero brightness, the image update frequency was gained at 200 Hz. The experimental setup and experimental results on images recognition are presented.

  3. Infrared fiber coupled acousto-optic tunable filter spectrometer

    NASA Technical Reports Server (NTRS)

    Levin, K. H.; Kindler, E.; Ko, T.; Lee, F.; Tran, D. C.; Tapphorn, R. M.

    1990-01-01

    A spectrometer design is introduced which combines an acoustooptic tunable filter (AOTF) and IR-transmitting flouride-glass fibers. The AOTF crystal is fabricated from TeO2 and permits random access to any wavelength in less than 50 microseconds, and the resulting spectrometer is tested for the remote analysis of gases and hydrocarbons. The AOTF spectrometer, when operated with a high-speed frequency synthesizer and optimized algorithms, permits accurate high-speed spectroscopy in the mid-IR spectral region.

  4. Programmable Pacemaker

    NASA Technical Reports Server (NTRS)

    1980-01-01

    St. Jude Medical's Cardiac Rhythm Management Division, formerly known as Pacesetter Systems, Inc., incorporated Apollo technology into the development of the programmable pacemaker system. This consists of the implantable pacemaker together with a physician's console containing the programmer and a data printer. Physician can communicate with patient's pacemaker by means of wireless telemetry signals transmitted through the communicating head held over the patient's chest. Where earlier pacemakers deliver a fixed type of stimulus once implanted, Programalith enables surgery free "fine tuning" of device to best suit the patient's changing needs.

  5. Programmable Pulser

    NASA Technical Reports Server (NTRS)

    Baumann, Eric; Merolla, Anthony

    1988-01-01

    User controls number of clock pulses to prevent burnout. New digital programmable pulser circuit in three formats; freely running, counted, and single pulse. Operates at frequencies up to 5 MHz, with no special consideration given to layout of components or to terminations. Pulser based on sequential circuit with four states and binary counter with appropriate decoding logic. Number of programmable pulses increased beyond 127 by addition of another counter and decoding logic. For very large pulse counts and/or very high frequencies, use synchronous counters to avoid errors caused by propagation delays. Invaluable tool for initial verification or diagnosis of digital or digitally controlled circuity.

  6. Ocular dispersion

    NASA Astrophysics Data System (ADS)

    Hammer, Daniel X.; Noojin, Gary D.; Thomas, Robert J.; Stolarski, David J.; Rockwell, Benjamin A.; Welch, Ashley J.

    1999-06-01

    Spectrally resolved white-light interferometry (SRWLI) was used to measure the wavelength dependence of refractive index (i.e., dispersion) for various ocular components. The accuracy of the technique was assessed by measurement of fused silica and water, the refractive indices of which have been measured at several different wavelengths. The dispersion of bovine and rabbit aqueous and vitreous humor was measured from 400 to 1100 nm. Also, the dispersion was measured from 400 to 700 nm for aqueous and vitreous humor extracted from goat and rhesus monkey eyes. For the humors, the dispersion did not deviate significantly from water. In an additional experiment, the dispersion of aqueous and vitreous humor that had aged up to a month was compared to freshly harvested material. No difference was found between the fresh and aged media. An unsuccessful attempt was also made to use the technique for dispersion measurement of bovine cornea and lens. Future refinement may allow measurement of the dispersion of cornea and lens across the entire visible and near-infrared wavelength band. The principles of white- light interferometry including image analysis, measurement accuracy, and limitations of the technique, are discussed. In addition, alternate techniques and previous measurements of ocular dispersion are reviewed.

  7. Programmable Logic Controllers.

    ERIC Educational Resources Information Center

    Insolia, Gerard; Anderson, Kathleen

    This document contains a 40-hour course in programmable logic controllers (PLC), developed for a business-industry technology resource center for firms in eastern Pennsylvania by Northampton Community College. The 10 units of the course cover the following: (1) introduction to programmable logic controllers; (2) DOS primer; (3) prerequisite…

  8. School Inclusion Programmes (SIPS)

    ERIC Educational Resources Information Center

    Drossinou-Korea, Maria; Matousi, Dimitra; Panopoulos, Nikolaos; Paraskevopoulou, Aikaterini

    2016-01-01

    The purpose of this work was to understand the school inclusion programmes (SIPs) for students with special educational needs (SEN). The methodology was conducted in the field of special education (SE) and focuses on three case studies of students who was supported by SIPs. The Targeted, Individual, Structured, Inclusion Programme for students…

  9. Dispersion Modeling.

    ERIC Educational Resources Information Center

    Budiansky, Stephen

    1980-01-01

    This article discusses the need for more accurate and complete input data and field verification of the various models of air pollutant dispension. Consideration should be given to changing the form of air quality standards based on enhanced dispersion modeling techniques. (Author/RE)

  10. Fog dispersion

    NASA Technical Reports Server (NTRS)

    Frost, W.; Christensen, L. S.; Collins, F. G.; Camp, D. W.

    1980-01-01

    A study of economically viable techniques for dispersing warm fog at commercial airports is presented. Five fog dispersion techniques are examined: evaporation suppression, downwash, mixing, seeding with hygroscopic material, thermal techniques, and charged particle techniques. Thermal techniques, although effective, were found to be too expensive for routine airport operations, and detrimental to the environment. Seeding or helicopter downwash are practical for small-scale or temporary fog clearing, but are probably not useful for airport operations on a routine basis. Considerable disagreement exists on the capability of charged particle techniques, which stems from the fact that different assumptions and parameter values are used in the analytical models. Recommendations resulting from the review of this technique are listed, and include: experimental measurements of the parameters in question; a study to ascertain possible safety hazards, such as increased electrical activity or fuel ignition during refueling operations which could render charged particle techniques impractical; and a study of a single charged particle generator.

  11. SOTANCP3 Scientific Programme

    NASA Astrophysics Data System (ADS)

    2014-12-01

    The programme for the 3rd International Workshop on "State of the Art in Nuclear Cluster Physics" which was held at the KGU (Kanto Gakuin University) Kannai Media Center (8th floor of Yokohoma Media Business Center (YMBC))

  12. FAST joins Breakthrough programme

    NASA Astrophysics Data System (ADS)

    Banks, Michael

    2016-11-01

    The 180m Five-hundred-meter Aperture Spherical radio Telescope (FAST) - the world's largest single-aperture radio receiver - has become part of the Breakthrough Listen programme, which launched in July 2015 to look for intelligent life beyond Earth.

  13. Programmes in Continuing Education

    ERIC Educational Resources Information Center

    Shah, L. R.

    1976-01-01

    The various types and forms of credit and non-credit university continuing education programmes are described in these extracts from a paper presented at the Hyderabad conference on university continuing education. (ABM)

  14. IFLA's Programme of ISBDs

    ERIC Educational Resources Information Center

    Anderson, Dorothy

    1978-01-01

    The article outlines the evolution, development, and current operational programme of the ISBD's (International Standard Bibliographic Description) within the framework of IFLA (International Federation of Library Associations). (Author/JAB)

  15. Programmable Logic Application Notes

    NASA Technical Reports Server (NTRS)

    Katz, Richard

    1998-01-01

    This column will be provided each quarter as a source for reliability, radiation results, NASA capabilities, and other information on programmable logic devices and related applications. This quarter's column will include some announcements and some recent radiation test results and evaluations of interest. Specifically, the following topics will be covered: the Military and Aerospace Applications of Programmable Devices and Technologies Conference to be held at GSFC in September, 1998, proton test results, and some total dose results.

  16. Programmable Logic Application Notes

    NASA Technical Reports Server (NTRS)

    Katz, Richard

    1998-01-01

    This column will be provided each quarter as a source for reliability, radiation results, NASA capabilities, and other information on programmable logic devices and related applications. This quarter's column will include some announcements and some recent radiation test results and evaluations of interest. Specifically, the following topics will be covered: the Military and Aerospace Applications of Programmable Devices and Technologies Conference to be held at GSFC in September, 1998, proton test results, heavy ion test results, and some total dose results.

  17. Creating capacity through partnership: a palliative care skills development programme.

    PubMed

    Kelsall, Kay; Brennan, Ebony; Cole, Teresa

    2015-08-01

    This paper presents the development and implementation of a recurrently funded, rolling, 6-month palliative care secondment programme for NHS community staff nurses based in a rural health economy in Southwest England. The programme is a key tool in a wider development plan for improving access to, and the quality of, palliative and end-of-life care for a dispersed rural population. This is part of a much bigger programme of integration to meet the shared challenges of service capacity, equity, and sustainability that are presented by the geographical and demographical profile of the locality. The 'bigger picture' is defined and set in the context of the national drive and evidence base for integration in order to explain the reasons behind the secondment programme. This is followed by outlining the iterative process of design and implementation--the 'what?' and 'how?'--and key learning points to date are shared.

  18. Programmable physiological infusion

    NASA Technical Reports Server (NTRS)

    Howard, W. H.; Young, D. R.; Adachi, R. R. (Inventor)

    1974-01-01

    A programmable physiological infusion device and method are provided wherein a program source, such as a paper tape, is used to actuate an infusion pump in accordance with a desired program. The system is particularly applicable for dispensing calcium in a variety of waveforms.

  19. Work Programme, 2014

    ERIC Educational Resources Information Center

    Cedefop - European Centre for the Development of Vocational Training, 2014

    2014-01-01

    Cedefop's work programme 2014 constitutes an ambitious attempt to preserve its core activities, respond to new requests and ensure previous quality standards while respecting resource constraints. Nevertheless, it also reflects the risk that the Centre's ability to deliver its mission and increasing demands may be affected by further budgetary…

  20. Backgrounder: The MAB Programme.

    ERIC Educational Resources Information Center

    United Nations Educational, Scientific, and Cultural Organization, Paris (France). Office of Public Information.

    The Man and the Biosphere Programme (MAB) was launched in November 1971 under the auspices of Unesco. Its aim is to help to develop scientific knowledge with a view to the rational management and conservation of natural resources, to train qualified personnel in this field, and to disseminate the knowledge acquired both to the decision-makers and…

  1. Developing Online Doctoral Programmes

    ERIC Educational Resources Information Center

    Chipere, Ngoni

    2015-01-01

    The objectives of the study were to identify best practices in online doctoral programming and to synthesise these practices into a framework for developing online doctoral programmes. The field of online doctoral studies is nascent and presents challenges for conventional forms of literature review. The literature was therefore reviewed using a…

  2. Computer Programmer/Analyst.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center on Education and Training for Employment.

    This publication contains 25 subjects appropriate for use in a competency list for the occupation of computer programmer/analyst, 1 of 12 occupations within the business/computer technologies cluster. Each unit consists of a number of competencies; a list of competency builders is provided for each competency. Titles of the 25 units are as…

  3. Conceptualizing Programme Evaluation

    ERIC Educational Resources Information Center

    Hassan, Salochana

    2013-01-01

    The main thrust of this paper deals with the conceptualization of theory-driven evaluation pertaining to a tutor training programme. Conceptualization of evaluation, in this case, is an integration between a conceptualization model as well as a theoretical framework in the form of activity theory. Existing examples of frameworks of programme…

  4. Programmable Logic Application Notes

    NASA Technical Reports Server (NTRS)

    Katz, Richard

    2000-01-01

    This column will be provided each quarter as a source for reliability, radiation results, NASA capabilities, and other information on programmable logic devices and related applications. This quarter will start a series of notes concentrating on analysis techniques with this issues section discussing worst-case analysis requirements.

  5. Programmable Logic Application Notes

    NASA Technical Reports Server (NTRS)

    Katz, Richard; Day, John H. (Technical Monitor)

    2001-01-01

    This report will be provided each quarter as a source for reliability, radiation results, NASA capabilities, and other information on programmable logic devices and related applications. This quarter will continue a series of notes concentrating on analysis techniques with this issue's section discussing the use of Root-Sum-Square calculations for digital delays.

  6. Programmable calculator stress analysis

    SciTech Connect

    Van Gulick, L.A.

    1983-01-01

    Advanced programmable alphanumeric calculators are well suited for closed-form calculation of pressure-vessel stresses. They offer adequate computing power, portability, special programming features, and simple interactive execution procedures. Representative programs that demonstrate calculator capabilities are presented. Problems treated are stress and strength calculations in thick-walled pressure vessels and the computation of stresses near head/pressure-vessel junctures.

  7. Q-switching an all-fiber laser using acousto-optic null coupler

    NASA Astrophysics Data System (ADS)

    Berg, Yuval; Goldring, Sharone; Pearl, Shaul; Arie, Ady

    2013-05-01

    A new method for Q-switching an all-fiber laser is presented. It is based on induced acoustic long period grating operating on a null coupler, which acts as acoustically controlled tunable output coupler. Q-switching is achieved by switching on and off the acoustic wave in a burst mode, thereby generating laser pulses that are ~400 times shorter than the acoustically controlled coupler's rise time. Output pulse energy of 22 μJ and temporal width of ~100 ns were measured at a wavelength of 1.54 μm.

  8. A new high efficiency InP acousto-optic device for IR wavelengths

    NASA Astrophysics Data System (ADS)

    Soos, Jolanta I.; Rosemeier, Ronald G.; Rosenbaum, Joel

    1990-09-01

    InP acoustooptic Bragg cells which are IR-transparent in the 1-10 micron bandpass have a center frequency in the 200-600 MHz range, and a diffraction efficiency of 40-60 percent, on the basis of 1-W RF driving power. These devices are anticipated to be ideal in such applications as fiber-optic modulators, IR scanners, deflectors, and HF mode-lockers. In the course of fabrication, the photoelastic constant p44 has been defined; using other crystallographic configurations, such photoelastic constants as p11 and p12 are expected to emerge.

  9. TeO2 and Te acousto-optic spectrometer imaging system

    NASA Astrophysics Data System (ADS)

    Souilhac, Dominique J.; Billerey, Dominique

    1994-12-01

    An improved TeO2 and Te infrared acoustooptic tuneable spectrometer has been analysed, using infrared fibres, a high speed frequency synthesiser and optimised algorithms. A comparison is made with the next best AOTF infrared materials, Tl3AsSe3, HgCl2 and PbBr2. A design study of the TeO2 and Te AO imaging spectrometer is also presented, operating in the two thermal bands, 1-5micrometers and 6-12micrometers , using an interchangeable fore-optics and a multiplexed electronically scanned infrared array cooled at 77 degrees K. Some initial experimental results indicate that these systems can perform well, an increase in the dynamic range in the 8-12 micrometers and is obtained compared to the 3-5*m band. It can be very useful in chemical process control, medical diagnostics, aerospace and earth remote sensing. Based on recent imaging spectrometer development, a design study of the TeO2 AO imaging spectrometer in the 0.4-1 micrometers band, for simultaneous spectroscopy at every pixel, is presented, using a CCD camera and fast data processing technology.

  10. Acousto-optic back-projection: Physical-model-based sound field reconstruction from optical projections

    NASA Astrophysics Data System (ADS)

    Yatabe, Kohei; Ishikawa, Kenji; Oikawa, Yasuhiro

    2017-04-01

    As an alternative to microphones, optical techniques have been studied for measuring a sound field. They enable contactless and non-invasive acoustical observation by detecting density variation of medium caused by sound. Although they have important advantages comparing to microphones, they also have some disadvantages. Since sound affects light at every points on the optical path, the optical methods observe an acoustical quantity as spatial integration. Therefore, point-wise information of a sound field cannot be obtained directly. Ordinarily, the computed tomography (CT) method has been applied for reconstructing a sound field from optically measured data. However, the observation process of the optical methods have not been considered explicitly, which limits the accuracy of the reconstruction. In this paper, a physical-model-based sound field reconstruction method is proposed. It explicitly formulates the physical observation process so that a model mismatch of the conventional methods is eliminated.

  11. Analysis of a crossed Bragg cell acousto-optical spectrometer for SETI.

    PubMed

    Gulkis, S

    1989-01-01

    The search for radio signals from extraterrestrial intelligent beings (SETI) requires the use of large instantaneous bandwidth (500 MHz) and high resolution (20 Hz) spectrometers. Digital systems with a high degree of modularity can be used to provide this capability, and this method has been widely discussed. Another technique for meeting the SETI requirement is to use a crossed Bragg cell spectrometer as described by Psaltis and Casasent. This technique makes use of the Folded Spectrum concept, introduced by Thomas. The Folded Spectrum is a 2-D Fourier Transform of a raster scanned 1-D signal. It is directly related to the long 1-D spectrum of the original signal and is ideally suited for optical signal processing. The folded spectrum technique has received little attention to date, primarily because early systems made use of photographic film which are unsuitable for the real time data analysis and voluminous data requirements of SETI. An analysis of the crossed Bragg cell spectrometer is presented as a method to achieve the spectral processing requirements for SETI. Systematic noise contributions unique to the Bragg cell system will be discussed.

  12. Acousto-optic signature analysis for inspection of the orbiter thermal protection tile bonds

    NASA Technical Reports Server (NTRS)

    Rodriguez, Julio G.; Tow, D. M.; Barna, B. A.

    1990-01-01

    The goal of this research is to develop a viable NDE technique for the inspection of orbiter thermal protection system (TPS) tile bonds. Phase 2, discussed here, concentrated on developing an empirical understanding of the bonded and unbonded vibration signatures of acreage tiles. Controlled experiments in the laboratory have provided useful information on the dynamic response of TPS tiles. It has been shown that several signatures are common to all the pedigree tiles. This degree of consistency in the tile-SIP (strain isolation pad) dynamic response proves that an unbond can be detected for a known tile and establish the basis for extending the analysis capability to arbitrary tiles for which there are no historical data. The field tests of the noncontacting laser acoustic sensor system, conducted at the Kennedy Space Center (KSC), investigated the vibrational environment of the Orbiter Processing Facility (OPF) and its effect on the measurement and analysis techniques being developed. The data collected showed that for orbiter locations, such as the body flap and elevon, the data analysis scheme, and/or the sensor, will require modification to accommodate the ambient motion. Several methods were identified for accomplishing this, and a solution is seen as readily achievable. It was established that the tile response was similar to that observed in the laboratory. Of most importance, however, is that the field environment will not affect the physics of the dynamic response that is related to bond condition. All of this information is fundamental to any future design and development of a prototype system.

  13. Acousto-Optical Method of Encoding and Visualization of Underwater Space

    DTIC Science & Technology

    2014-01-27

    neurons which are mathematically described as coupled nonlinear oscillators that are slightly unstable. They have a property called ’ Self - Referential ... self - regulating process which is represented by Equation (5) in the ensuing description. [0083] The input/output circuitry 64 outputs signals that...other words, self -correcting dynamics of the Na and Ca ions in the membranes are closely related to the sensing and the flopping of motion actuators

  14. Space Qualification Issues in Acousto-optic and Electro-optic Devices

    NASA Technical Reports Server (NTRS)

    Prasad, Narasimha S.; Taylor, Edward W.; Trivedi, Sudhir; Kutcher, Sue; Soos, Jolanta

    2007-01-01

    Satellite and space-based applications of photonic devices and systems require operational reliability in the harsh environment of space for extended periods of time. This in turn requires every component of the systems and their packaging to meet space qualifications. Acousto- and electro-optical devices form the major components of many current space based optical systems, which is the focus of this paper. The major space qualification issues are related to: mechanical stability, thermal effects and operation of the devices in the naturally occurring space radiation environment. This paper will discuss acousto- and electro-optic materials and devices with respect to their stability against mechanical vibrations, thermal cycling in operating and non-operating conditions and device responses to space ionizing and displacement radiation effects. Selection of suitable materials and packaging to meet space qualification criteria will also be discussed. Finally, a general roadmap for production and testing of acousto- and electro-optic devices will be discussed.

  15. Millimeter-resolution acousto-optic quantitative imaging in a tissue model system

    NASA Astrophysics Data System (ADS)

    Bratchenia, Aliaksandr; Molenaar, Robert; van Leewen, Ton; Kooyman, Rob P. H.

    2009-05-01

    We have investigated the application of ultrasound modulated coherent light for quantitative determination of the ratio of dye concentrations and total concentration of absorbers in a blood vessel-mimicking sample. A 3-mm-diam tube containing the mixture of dyes inside an Intralipid-based gel with optical properties similar to tissue was interrogated by two different laser wavelengths in combination with intense microsecond ultrasound bursts. The use of calibration curves allowed us to extract quantitative information on the ratio of dye concentrations with the accuracy of better than 15%, as well as on the total concentration. Furthermore, we demonstrated the feasibility to obtain a quantitative 3-D map of the absorbing structure with a spatial resolution of better than 3 mm. These findings give an outlook to apply this technique for noninvasive 3-D mapping of oxygen saturation and total concentration of hemoglobin in tissue.

  16. Acousto-optic tunable filter (AOTF) imaging spectrometer for NASA applications - System issues

    NASA Technical Reports Server (NTRS)

    Yu, Jeffrey; Chao, Tien H.; Cheng, Li-Jen

    1990-01-01

    A recently developed AOTF operating in the visible, 0.4-0.8 micron bandpass is presently compared with other spectrometer designs, with a view to the advantages it may uniquely offer for prospective NASA missions. Since spectral identification is accomplished by this system through the scanning of a few spectral bands, data storage requirements for spectral image analysis can be significantly reduced. Attention is given to spectral and imaging capabilities and their applicability to defense, remote sensing, and industrial uses.

  17. Programmable calculator stress analysis

    SciTech Connect

    Van Gulick, L.A.

    1983-01-01

    This paper assesses the suitability of advanced programmable alphanumeric calculators for closed form calculation of pressure vessel stresses and offers, as their advantages, adequate computing power, portability, special programming features, and simple interactive execution procedures. Representative programs which demonstrate their capacities are presented. Problems dealing with stress and strength calculations in thick-walled pressure vessels and with the computation of stresses near head/pressure vessel junctures are treated. Assessed favorably in this paper as useful contributors to computeraided design of pressure vessels, programmable alphanumeric calculators have areas of implementation in checking finite element results, aiding in the development of an intuitive understanding of stresses and their parameter dependencies, and evaluating rapidly a variety of preliminary designs.

  18. NSF announces diversity programme

    NASA Astrophysics Data System (ADS)

    Kruesi, Liz

    2016-04-01

    The US National Science Foundation (NSF) has initiated a new funding programme that will create schemes to increase diversity in science, technology, engineering and mathematics (STEM). The initiative - Inclusion across the Nation of Communities of Learners of Underrepresented Discoverers in Engineering and Science (INCLUDES) - aims to increase the participation of women, those with a low socioeconomic status, people with disabilities and those from minority racial backgrounds.

  19. Punch Card Programmable Microfluidics

    PubMed Central

    Korir, George; Prakash, Manu

    2015-01-01

    Small volume fluid handling in single and multiphase microfluidics provides a promising strategy for efficient bio-chemical assays, low-cost point-of-care diagnostics and new approaches to scientific discoveries. However multiple barriers exist towards low-cost field deployment of programmable microfluidics. Incorporating multiple pumps, mixers and discrete valve based control of nanoliter fluids and droplets in an integrated, programmable manner without additional required external components has remained elusive. Combining the idea of punch card programming with arbitrary fluid control, here we describe a self-contained, hand-crank powered, multiplex and robust programmable microfluidic platform. A paper tape encodes information as a series of punched holes. A mechanical reader/actuator reads these paper tapes and correspondingly executes operations onto a microfluidic chip coupled to the platform in a plug-and-play fashion. Enabled by the complexity of codes that can be represented by a series of holes in punched paper tapes, we demonstrate independent control of 15 on-chip pumps with enhanced mixing, normally-closed valves and a novel on-demand impact-based droplet generator. We demonstrate robustness of operation by encoding a string of characters representing the word “PUNCHCARD MICROFLUIDICS” using the droplet generator. Multiplexing is demonstrated by implementing an example colorimetric water quality assays for pH, ammonia, nitrite and nitrate content in different water samples. With its portable and robust design, low cost and ease-of-use, we envision punch card programmable microfluidics will bring complex control of microfluidic chips into field-based applications in low-resource settings and in the hands of children around the world. PMID:25738834

  20. Punch card programmable microfluidics.

    PubMed

    Korir, George; Prakash, Manu

    2015-01-01

    Small volume fluid handling in single and multiphase microfluidics provides a promising strategy for efficient bio-chemical assays, low-cost point-of-care diagnostics and new approaches to scientific discoveries. However multiple barriers exist towards low-cost field deployment of programmable microfluidics. Incorporating multiple pumps, mixers and discrete valve based control of nanoliter fluids and droplets in an integrated, programmable manner without additional required external components has remained elusive. Combining the idea of punch card programming with arbitrary fluid control, here we describe a self-contained, hand-crank powered, multiplex and robust programmable microfluidic platform. A paper tape encodes information as a series of punched holes. A mechanical reader/actuator reads these paper tapes and correspondingly executes operations onto a microfluidic chip coupled to the platform in a plug-and-play fashion. Enabled by the complexity of codes that can be represented by a series of holes in punched paper tapes, we demonstrate independent control of 15 on-chip pumps with enhanced mixing, normally-closed valves and a novel on-demand impact-based droplet generator. We demonstrate robustness of operation by encoding a string of characters representing the word "PUNCHCARD MICROFLUIDICS" using the droplet generator. Multiplexing is demonstrated by implementing an example colorimetric water quality assays for pH, ammonia, nitrite and nitrate content in different water samples. With its portable and robust design, low cost and ease-of-use, we envision punch card programmable microfluidics will bring complex control of microfluidic chips into field-based applications in low-resource settings and in the hands of children around the world.

  1. Programmable matter by folding

    PubMed Central

    Hawkes, E.; An, B.; Benbernou, N. M.; Tanaka, H.; Kim, S.; Demaine, E. D.; Rus, D.; Wood, R. J.

    2010-01-01

    Programmable matter is a material whose properties can be programmed to achieve specific shapes or stiffnesses upon command. This concept requires constituent elements to interact and rearrange intelligently in order to meet the goal. This paper considers achieving programmable sheets that can form themselves in different shapes autonomously by folding. Past approaches to creating transforming machines have been limited by the small feature sizes, the large number of components, and the associated complexity of communication among the units. We seek to mitigate these difficulties through the unique concept of self-folding origami with universal crease patterns. This approach exploits a single sheet composed of interconnected triangular sections. The sheet is able to fold into a set of predetermined shapes using embedded actuation. To implement this self-folding origami concept, we have developed a scalable end-to-end planning and fabrication process. Given a set of desired objects, the system computes an optimized design for a single sheet and multiple controllers to achieve each of the desired objects. The material, called programmable matter by folding, is an example of a system capable of achieving multiple shapes for multiple functions. PMID:20616049

  2. Programmability in AIPS++

    NASA Technical Reports Server (NTRS)

    Hjellming, R. M.

    1992-01-01

    AIPS++ is an Astronomical Information Processing System being designed and implemented by an international consortium of NRAO and six other radio astronomy institutions in Australia, India, the Netherlands, the United Kingdom, Canada, and the USA. AIPS++ is intended to replace the functionality of AIPS, to be more easily programmable, and will be implemented in C++ using object-oriented techniques. Programmability in AIPS++ is planned at three levels. The first level will be that of a command-line interpreter with characteristics similar to IDL and PV-Wave, but with an intensive set of operations appropriate to telescope data handling, image formation, and image processing. The third level will be in C++ with extensive use of class libraries for both basic operations and advanced applications. The third level will allow input and output of data between external FORTRAN programs and AIPS++ telescope and image databases. In addition to summarizing the above programmability characteristics, this talk will given an overview of the classes currently being designed for telescope data calibration and editing, image formation, and the 'toolkit' of mathematical 'objects' that will perform most of the processing in AIPS++.

  3. Smart programmable wireless microaccelerometers

    NASA Astrophysics Data System (ADS)

    Varadan, Vijay K.; Subramanian, Hareesh; Varadan, Vasundara V.

    1998-07-01

    The integration of MEMS, SAW devices and required microelectronics and conformal antenna to realize a programmable wireless accelerometer is presented in this paper. This unique combination of technologies results in a novel accelerometer that can be remotely sensed by a microwave system with the advantage of no power requirements at the sensor site. The microaccelerometer presented is simple in construction and easy to manufacture with existing silicon micromachining techniques. Programmable accelerometers can be achieved with splitfinger interdigital transducers (IDTs) as reflecting structures. If IDTs are short circuited or capacitively loaded, the wave propagates without any reflection whereas in an open circuit configuration, the IDTs reflect the incoming SAW signal. The programmable accelerometers can thus be achieved by using an external circuitry on a semiconductor chip using hybrid technology. The relatively small size of the sensor makes it an ideal conformal sensor. The accelerometer finds application as air bag deployment sensors, vibration sensors for noise control, deflection and strain sensors, inertial and dimensional positioning systems, ABS/traction control, smart suspension, active roll stabilization and four wheel steering. The wireless accelerometer is very attractive to study the response of a `dummy' in automobile crash test.

  4. A programmable Fortran preprocessor

    SciTech Connect

    Rosing, M.

    1995-06-01

    A programmable Fortran preprocessor is described. It allows users to define compile time operations that can examine and modify the source tree before it is compiled with a traditional compiler. This intermediate step allows the definition of routines and operations that adapt to the context in which they are used. Context sensitive operations increase the flexibility of abstractions that can be built without degrading efficiency, as compared to using traditional run time based abstractions such as libraries or objects. The preprocessor is described briefly along with an example of how it is used to add CMFortran array operations to Fortran77. Other preprocessors that have been implemented are also briefly described.

  5. Flexible programmable logic module

    DOEpatents

    Robertson, Perry J.; Hutchinson, Robert L.; Pierson, Lyndon G.

    2001-01-01

    The circuit module of this invention is a VME board containing a plurality of programmable logic devices (PLDs), a controlled impedance clock tree, and interconnecting buses. The PLDs are arranged to permit systolic processing of a problem by offering wide data buses and a plurality of processing nodes. The board contains a clock reference and clock distribution tree that can drive each of the PLDs with two critically timed clock references. External clock references can be used to drive additional circuit modules all operating from the same synchronous clock reference.

  6. Programmable Logic Application Notes

    NASA Technical Reports Server (NTRS)

    Katz, Richard

    1999-01-01

    This column will be provided each quarter as a source for reliability, radiation results, NASA capabilities, and other information on programmable logic devices and related applications. This quarter the focus is on some experimental data on low voltage drop out regulators to support mixed 5 and 3.3 volt systems. A discussion of the Small Explorer WIRE spacecraft will also be given. Lastly, we show take a first look at robust state machines in Hardware Description Languages (VHDL) and their use in critical systems. If you have information that you would like to submit or an area you would like discussed or researched, please give me a call or e-mail.

  7. NASCAP programmer's reference manual

    NASA Technical Reports Server (NTRS)

    Mandell, M. J.; Stannard, P. R.; Katz, I.

    1993-01-01

    The NASA Charging Analyzer Program (NASCAP) is a computer program designed to model the electrostatic charging of complicated three-dimensional objects, both in a test tank and at geosynchronous altitudes. This document is a programmer's reference manual and user's guide. It is designed as a reference to experienced users of the code, as well as an introduction to its use for beginners. All of the many capabilities of NASCAP are covered in detail, together with examples of their use. These include the definition of objects, plasma environments, potential calculations, particle emission and detection simulations, and charging analysis.

  8. Selection in backcross programmes

    PubMed Central

    Hospital, Frédéric

    2005-01-01

    Backcrossing is a well-known and long established breeding scheme where a characteristic is introgressed from a donor parent into the genomic background of a recurrent parent. The various uses of backcrossing in modern genetics, particularly with the help of molecular markers, are reviewed here. Selection in backcross programmes is used to either improve the genetic value of plant and animal populations or fine map quantitative trait loci. Both cases are helpful in our understanding of the genetic bases of quantitative traits variation. PMID:16048792

  9. Copernicus Earth observation programme

    NASA Astrophysics Data System (ADS)

    Žlebir, Silvo

    European Earth observation program Copernicus is an EU-wide programme that integrates satellite data, in-situ data and modeling to provide user-focused information services to support policymakers, researchers, businesses and citizens. Land monitoring service and Emergency service are fully operational already, Atmosphere monitoring service and Marine environment monitoring service are preoperational and will become fully operational in the following year, while Climate change service and Security service are in an earlier development phase. New series of a number of dedicated satellite missions will be launched in the following years, operated by the European Space Agency and EUMETSAT, starting with Sentinel 1A satellite early this year. Ground based, air-borne and sea-borne in-situ data are provided by different international networks and organizations, EU member states networks etc. European Union is devoting a particular attention to secure a sustainable long-term operational provision of the services. Copernicus is also stated as a European Union’s most important contribution to Global Earth Observation System of Systems (GEOSS). The status and the recent development of the Copernicus programme will be presented, together with its future perspective. As Copernicus services have already demonstrated their usability and effectiveness, some interesting cases of their deployment will be presented. Copernicus free and open data policy, supported by a recently adopted EU legislative act, will also be presented.

  10. Programmable digital modem

    NASA Astrophysics Data System (ADS)

    Poklemba, John J.

    1991-11-01

    The design of the Programmable Digital Modem (PDM) is outlined. The PDM will be capable of operating with numerous modulation techniques including: 2-, 4-, 8- and 16-ary phase shift keying (PSK), minimum shift keying (MSK), and 16-ary quadrature amplitude modulation (QAM), with spectral occupancy from 1.2x to 2x the data symbol rate. It will also be programmable for transmission rates ranging from 2.34 to 300 Mbit/s, where the maximum symbol rate is 75 Msymbol/s. Furthermore, these parameters will be executable in independent burst, dependent burst, or continuous mode. In dependent burst mode the carrier and clock oscillator sources are common from burst to burst. To achieve as broad a set of requirements as these, it is clear that the essential signal processing must be digital. In addition, to avoid hardware changes when the operational parameters are changed, a fixed interface to an analog intermediate frequency (IF) is necessary for transmission; and, common system level architectures are necessary for the modulator and demodulator. Lastly, to minimize size and power, as much of the design as possible will be implemented with application specific integrated circuit (ASIC) chips.

  11. Programmable digital modem

    NASA Technical Reports Server (NTRS)

    Poklemba, John J.

    1991-01-01

    The design of the Programmable Digital Modem (PDM) is outlined. The PDM will be capable of operating with numerous modulation techniques including: 2-, 4-, 8- and 16-ary phase shift keying (PSK), minimum shift keying (MSK), and 16-ary quadrature amplitude modulation (QAM), with spectral occupancy from 1.2x to 2x the data symbol rate. It will also be programmable for transmission rates ranging from 2.34 to 300 Mbit/s, where the maximum symbol rate is 75 Msymbol/s. Furthermore, these parameters will be executable in independent burst, dependent burst, or continuous mode. In dependent burst mode the carrier and clock oscillator sources are common from burst to burst. To achieve as broad a set of requirements as these, it is clear that the essential signal processing must be digital. In addition, to avoid hardware changes when the operational parameters are changed, a fixed interface to an analog intermediate frequency (IF) is necessary for transmission; and, common system level architectures are necessary for the modulator and demodulator. Lastly, to minimize size and power, as much of the design as possible will be implemented with application specific integrated circuit (ASIC) chips.

  12. CAMAC modular programmable function generator

    SciTech Connect

    Turner, G.W.; Suehiro, S.; Hendricks, R.W.

    1980-12-01

    A CAMAC modular programmable function generator has been developed. The device contains a 1024 word by 12-bit memory, a 12-bit digital-to-analog converter with a 600 ns settling time, an 18-bit programmable frequency register, and two programmable trigger output registers. The trigger registers can produce programmed output logic transitions at various (binary) points in the output function curve, and are used to synchronize various other data acquisition devices with the function curve.

  13. Programmable pH buffers

    DOEpatents

    Gough, Dara Van; Huber, Dale L.; Bunker, Bruce C.; Roberts, Mark E.

    2017-01-24

    A programmable pH buffer comprises a copolymer that changes pK.sub.a at a lower critical solution temperature (LCST) in water. The copolymer comprises a thermally programmable polymer that undergoes a hydrophobic-to-hydrophilic phase change at the LCST and an electrolytic polymer that exhibits acid-base properties that are responsive to the phase change. The programmable pH buffer can be used to sequester CO.sub.2 into water.

  14. Electrically-programmable diffraction grating

    DOEpatents

    Ricco, Antonio J.; Butler, Michael A.; Sinclair, Michael B.; Senturia, Stephen D.

    1998-01-01

    An electrically-programmable diffraction grating. The programmable grating includes a substrate having a plurality of electrodes formed thereon and a moveable grating element above each of the electrodes. The grating elements are electrostatically programmable to form a diffraction grating for diffracting an incident beam of light as it is reflected from the upper surfaces of the grating elements. The programmable diffraction grating, formed by a micromachining process, has applications for optical information processing (e.g. optical correlators and computers), for multiplexing and demultiplexing a plurality of light beams of different wavelengths (e.g. for optical fiber communications), and for forming spectrometers (e.g. correlation and scanning spectrometers).

  15. What is the required minimum landscape size for dispersal studies?

    PubMed

    Franzén, Markus; Nilsson, Sven G

    2007-11-01

    Among small animals dispersal parameters are mainly obtained by traditional methods using population studies of marked individuals. Dispersal studies may underestimate the rate and distance of dispersal, and be biased because of aggregated habitat patches and a small study area. The probability of observing long distance dispersal events decreases with distance travelled by the organisms. In this study a new approach is presented to solve this methodological problem. An extensive mark-release-recapture programme was performed in an area of 81 km(2) in southern Sweden. To estimate the required size of the study area for adequate dispersal measures we examined the effect of study area size on dispersal distance using empirical data and a repeated subsampling procedure. In 2003 and 2004, two species of diurnal burnet moths (Zygaenidae) were studied to explore dispersal patterns. The longest confirmed dispersal distance was 5600 m and in total 100 dispersal events were found between habitat patches for the two species. The estimated dispersal distance was strongly affected by the size of the study area and the number of marked individuals. For areas less than 10 km(2) most of the dispersal events were undetected. Realistic estimates of dispersal distance require a study area of at least 50 km(2). To obtain adequate measures of dispersal, the marked population should be large, preferably over 500 recaptured individuals. This result was evident for the mean moved distance, mean dispersal distance and maximum dispersal distance. In general, traditional dispersal studies are performed in small study areas and based on few individuals and should therefore be interpreted with care. Adequate dispersal measures for insects obtained by radio-tracking and genetic estimates (gene flow) is still a challenge for the future.

  16. Programmable Cadence Timer

    NASA Technical Reports Server (NTRS)

    Hall, William A.; Gilbert, John

    1990-01-01

    Electronic metronome paces users through wide range of exercise routines. Conceptual programmable cadence timer provides rhythmic aural and visual cues. Timer automatically changes cadence according to program entered by the user. It also functions as clock, stopwatch, or alarm. Modular pacer operated as single unit or as two units. With audiovisual module moved away from base module, user concentrates on exercise cues without distraction from information appearing on the liquid-crystal display. Variety of uses in rehabilitative medicine, experimental medicine, sports, and gymnastics. Used in intermittent positive-pressure breathing treatment, in which patient must rhythmically inhale and retain medication delivered under positive pressure; and in incentive spirometer treatment, in which patient must inhale maximally at regular intervals.

  17. Japan's Eco-School Programme

    ERIC Educational Resources Information Center

    Mori, Masayuki

    2007-01-01

    Since 1997, several ministries in Japan have collaborated on an eco-school programme, which applies to both newly constructed and renovated school buildings, in an effort to make its schools more environmentally friendly. The programme equips school buildings with ecological features such as photovoltaic cells, solar thermal collectors, other new…

  18. General purpose programmable accelerator board

    DOEpatents

    Robertson, Perry J.; Witzke, Edward L.

    2001-01-01

    A general purpose accelerator board and acceleration method comprising use of: one or more programmable logic devices; a plurality of memory blocks; bus interface for communicating data between the memory blocks and devices external to the board; and dynamic programming capabilities for providing logic to the programmable logic device to be executed on data in the memory blocks.

  19. Programmable Logic Controllers. Teacher Edition.

    ERIC Educational Resources Information Center

    Rauh, Bob; Kaltwasser, Stan

    These materials were developed for a seven-unit secondary or postsecondary education course on programmable logic controllers (PLCs) that treats most of the skills needed to work effectively with PLCs as programming skills. The seven units of the course cover the following topics: fundamentals of programmable logic controllers; contracts, timers,…

  20. Highly dispersive slot waveguides.

    PubMed

    Zhang, Lin; Yue, Yang; Xiao-Li, Yinying; Beausoleil, Raymond G; Willner, Alan E

    2009-04-27

    We propose a slot-waveguide with high dispersion, in which a slot waveguide is coupled to a strip waveguide. A negative dispersion of up to -181520 ps/nm/km is obtained due to a strong interaction of the slot and strip modes. A flat and large dispersion is achievable by cascading the dispersive slot-waveguides with varied waveguide thickness or width for dispersion compensation and signal processing applications. We show - 31300 ps/nm/km dispersion over 147-nm bandwidth with <1% variance.

  1. Lectures on Dispersion Theory

    DOE R&D Accomplishments Database

    Salam, A.

    1956-04-01

    Lectures with mathematical analysis are given on Dispersion Theory and Causality and Dispersion Relations for Pion-nucleon Scattering. The appendix includes the S-matrix in terms of Heisenberg Operators. (F. S.)

  2. The BGAN extension programme

    NASA Astrophysics Data System (ADS)

    Rivera, Juan J.; Trachtman, Eyal; Richharia, Madhavendra

    2005-11-01

    Mobile satellite telecommunications systems have undergone an enormous evolution in the last decades, with the interest in having advanced telecommunications services available on demand, anywhere and at any time, leading to incredible advances. The demand for braodband data is therefore rapidly gathering pace, but current solutions are finding it increasingly difficult to combine large bandwidth with ubiquitous coverage, reliability and portability. The BGAN (Broadband Global Area Network) system, designed to operate with the Inmarsat-4 satellites, provides breakthrough services that meet all of these requirements. It will enable broadband connection on the move, delivering all the key tools of the modern office. Recognising the great impact that Inmarsat's BGAN system will have on the European satellite communications industry, and the benefits that it will bring to a wide range of European industries, in 2003 ESA initiated the "BGAN Extension" project. Its primary goals are to provide the full range of BGAN services to truly mobile platforms, operating in aeronautical, vehicular and maritime environments, and to introduce a multicast service capability. The project is supported by the ARTES Programme which establishes a collaboration agreement between ESA, Inmarsat and a group of key industrial and academic institutions which includes EMS, Logica, Nera and the University of Surrey (UK).

  3. Scientific Programme Committee

    NASA Astrophysics Data System (ADS)

    2013-02-01

    Scientific Programme Committee A. Blondel, University of Geneva A. Cervera, IFIC M. Dracos, IN2P3 I. Efhymiopoulos, CERN J. Ellis, CERN S. Geer, FNAL R. Garoby, CERN M. Goodman, ANL D. Harris, FNAL T. Hasegawa, KEK P. Huber, Virginia Tech. D. Kaplan, IIT Y.D. Kim, Sejong University H. Kirk, BNL Y. Kuno, Osaka University K. Long, Imperial College N.K. Mondal, TIFR J. Morfin, FNAL Y. Mori, Kyoto University K. Nishikawa, KEK V. Palladino, University of Napoli C. Prior, RAL F.J.P. Soler, University of Glasgow J. Strait, FNAL R. Svoboda, University of California Davis F. Terranova, LN Frascati M. Zisman, LBNL Local Organizing Committee E. Benedetto, CERN/NTUA C. Blanchard, University of Geneva A. Blondel, University of Geneva (co-chair) I. Efthymiopoulos, CERN (co-chair) F. Dufour, University of Geneva F. Girard-Madoux, CERN E. Gschwendtner, CERN A. Korzenev, University of Geneva M. Morer-Olafsen, CERN S. Murphy, University of Geneva G. Prior, CERN G. Wikström, University of Geneva E. Wildner, CERN Sponsors EuCARD European Organization for Nuclear Research (CERN) Swiss Institute for Particle Physics (CHIPP) University of Geneva

  4. Shape-programmable macromolecules.

    PubMed

    Schafmeister, Christian E; Brown, Zachary Z; Gupta, Sharad

    2008-10-01

    Proteins catalyze specific chemical reactions and carry out highly selective molecular recognition because they adopt well-defined three-dimensional structures and position chemically reactive functional groups in specific constellations. Proteins attain these well-defined structures through the complex process of protein folding. We seek to emulate these protein functions by constructing macromolecules that are easier to engineer by avoiding folding altogether. Toward that goal, we have developed an approach for the synthesis of macromolecules with programmable shapes. As described in this Account, we have constructed synthetic building blocks called bis-amino acids that we then couple through pairs of amide bonds to create water-soluble, spiroladder oligomers (bis-peptides) with well-defined three-dimensional structures. Bis-peptides use the conformational preferences of fused rings, stereochemistry, and strong covalent bonds to define their shape, unlike natural proteins and synthetic foldamers, which depend on noncovalent interactions and an unpredictable folding process to attain structure. Using these bis-amino acid monomers, we have built and characterized a number of bis-peptide nanostructures. We also constructed a molecular actuator that undergoes a large change in conformation under the control of metal exchange; the first application of bis-peptides. We are currently developing further approaches to functionalize bis-peptides as scaffolds to present well-defined constellations of functional groups. Such macromolecules could facilitate multifunctional catalysis and molecular recognition and lead to nanoscale molecular devices.

  5. Programmable electronic synthesized capacitance

    NASA Technical Reports Server (NTRS)

    Kleinberg, Leonard L. (Inventor)

    1987-01-01

    A predetermined and variable synthesized capacitance which may be incorporated into the resonant portion of an electronic oscillator for the purpose of tuning the oscillator comprises a programmable operational amplifier circuit. The operational amplifier circuit has its output connected to its inverting input, in a follower configuration, by a network which is low impedance at the operational frequency of the circuit. The output of the operational amplifier is also connected to the noninverting input by a capacitor. The noninverting input appears as a synthesized capacitance which may be varied with a variation in gain-bandwidth product of the operational amplifier circuit. The gain-bandwidth product may, in turn, be varied with a variation in input set current with a digital to analog converter whose output is varied with a command word. The output impedance of the circuit may also be varied by the output set current. This circuit may provide very small ranges in oscillator frequency with relatively large control voltages unaffected by noise.

  6. Dispersion y dinamica poblacional

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dispersal behavior of fruit flies is appetitive. Measures of dispersion involve two different parameter: the maximum distance and the standard distance. Standard distance is a parameter that describes the probalility of dispersion and is mathematically equivalent to the standard deviation around ...

  7. Automatic TLI recognition system, programmer`s guide

    SciTech Connect

    Lassahn, G.D.

    1997-02-01

    This report describes the software of an automatic target recognition system (version 14), from a programmer`s point of view. The intent is to provide information that will help people who wish to modify the software. In separate volumes are a general description of the ATR system, Automatic TLI Recognition System, General Description, and a user`s manual, Automatic TLI Recognition System, User`s Guide. 2 refs.

  8. Dispersion in the Surfzone: Tracer Dispersion Studies

    DTIC Science & Technology

    2011-09-30

    objective is to improve understanding and modeling of dispersion of tracers (pol­ lution, fecal indicator bacteria, fine sediments) within the...discussed further here. Stochastic Particle Simulation for Surfzone Dispersion Drifter-derived diffusivities are time-dependent. In an unbounded...diffusion. Here HB06 particle trajectories are stochastically simulated with the Langevin equations with a shoreline boundary to explain the observed

  9. Theory of dispersive microlenses

    NASA Technical Reports Server (NTRS)

    Herman, B.; Gal, George

    1993-01-01

    A dispersive microlens is a miniature optical element which simultaneously focuses and disperses light. Arrays of dispersive mircolenses have potential applications in multicolor focal planes. They have a 100 percent optical fill factor and can focus light down to detectors of diffraction spot size, freeing up areas on the focal plane for on-chip analog signal processing. Use of dispersive microlenses allows inband color separation within a pixel and perfect scene registration. A dual-color separation has the potential for temperature discrimination. We discuss the design of dispersive microlenses and present sample results for efficient designs.

  10. Electrically-programmable diffraction grating

    DOEpatents

    Ricco, A.J.; Butler, M.A.; Sinclair, M.B.; Senturia, S.D.

    1998-05-26

    An electrically-programmable diffraction grating is disclosed. The programmable grating includes a substrate having a plurality of electrodes formed thereon and a moveable grating element above each of the electrodes. The grating elements are electrostatically programmable to form a diffraction grating for diffracting an incident beam of light as it is reflected from the upper surfaces of the grating elements. The programmable diffraction grating, formed by a micromachining process, has applications for optical information processing (e.g. optical correlators and computers), for multiplexing and demultiplexing a plurality of light beams of different wavelengths (e.g. for optical fiber communications), and for forming spectrometers (e.g. correlation and scanning spectrometers). 14 figs.

  11. Field Evaluation of Programmable Thermostats

    SciTech Connect

    Sachs, O.; Tiefenbeck, V.; Duvier, C.; Qin, A.; Cheney, K.; Akers, C.; Roth, K.

    2012-12-01

    Prior research suggests that poor programmable thermostats usability may prevent their effective use to save energy. The Fraunhofer team hypothesized that home occupants with high-usability thermostats would be more likely to use them to save energy than people with a basic thermostats. In this report, the team discusses results of a project in which the team monitored and compared programmable thermostats with basic thermostats in an affordable housing apartment complex.

  12. The programmer`s guide to the software copyright

    SciTech Connect

    Wehrli, J.E.

    1996-06-01

    This booklet was written specifically for anyone who writes computer programs at the Lawrence Berkeley National Laboratory. It is intended to provide basic information on how the law of copyright applies to computer software. It is not intended to be a legal reference for copyright attorneys, but an accessible reference for the people whose creative efforts result in software others want to use. Whether you are a chemist who writes software to help you with your work or a professional Berkeley Lab programmer you should benefit from this booklet. The information in this booklet is written in an informal conversational style, not a legal style. It is simply a direct response to a need for information that I have observed. Since I have written it from a programmer`s viewpoint and for a programmer`s use, it does not cover copyright law in general and focuses only on those areas of copyright law specific to computer software. Moreover, it does not attempt to address other areas of law that may be applicable to computer software. It is certainly not intended to replace the timely legal advice of Berkeley Lab`s Patent Department. However, just as it is helpful to read the computer manual before calling tech support, it will also be helpful to read this booklet before calling the Patent Department, not so much to answer any and all questions, but to give you the vocabulary to better understand and digest the information provided by the Department.

  13. Dispersion management with metamaterials

    DOEpatents

    Tassin, Philippe; Koschny, Thomas; Soukoulis, Costas M.

    2017-03-07

    An apparatus, system, and method to counteract group velocity dispersion in fibers, or any other propagation of electromagnetic signals at any wavelength (microwave, terahertz, optical, etc.) in any other medium. A dispersion compensation step or device based on dispersion-engineered metamaterials is included and avoids the need of a long section of specialty fiber or the need for Bragg gratings (which have insertion loss).

  14. Radon programmes and health marketing.

    PubMed

    Fojtikova, Ivana; Rovenska, Katerina

    2011-05-01

    Being aware of negative health effects of radon exposure, many countries aim for the reduction of the radon exposure of their population. The Czech radon programme was commenced >20 y ago. Since then experts have gathered a lot of knowledge, necessary legislation has been enacted, tens of thousands of inhabitants have been offered free measurement and subsidy for the mitigation. Despite the effort, the effectiveness of the radon programme seems to be poor. Newly built houses still exhibit elevated radon concentrations and the number of houses mitigated is very low. Is it possible to enhance the effectivity of radon programme while keeping it on a voluntary basis? One possible way is to employ health marketing that draws together traditional marketing theories and science-based strategies to prevention. The potential of using marketing principles in communication and delivery of radon information will be discussed.

  15. Programmable data communications controller requirements

    NASA Technical Reports Server (NTRS)

    1977-01-01

    The design requirements for a Programmable Data Communications Controller (PDCC) that reduces the difficulties in attaching data terminal equipment to a computer are presented. The PDCC is an interface between the computer I/O channel and the bit serial communication lines. Each communication line is supported by a communication port that handles all line control functions and performs most terminal control functions. The port is fabricated on a printed circuit board that plugs into a card chassis, mating with a connector that is joined to all other card stations by a data bus. Ports are individually programmable; each includes a microprocessor, a programmable read-only memory for instruction storage, and a random access memory for data storage.

  16. Programmable spectral design and the binary supergrating

    NASA Astrophysics Data System (ADS)

    Levner, Daniel

    Spectral operations such as wavelength selection, power level manipulation, and chromatic dispersion control are key to many processes in optical telecommunication, spectroscopy, and sensing. In their simplest forms, these functions can be performed using a number of successful devices such as the Fraunhofer ("diffraction") grating, Bragg grating, thin-film filter (TFF), and dispersion-compensating fiber (DCF). More complicated manipulations, however, often require either problematic cascades of many simple elements, the use of custom technologies that offer little adjustment, or the implementation of fully programmable devices, which allow for the desired spectral function to be synthesized ab initio. Here, I present the Binary Supergrating (BSG), a novel technology that permits the programmable and near-arbitrary control of optical amplitude and phase using a simple, robust and practical form. This guided-wave form consists of an aperiodic sequence of binary elements; the sequence, determined through the process of BSG synthesis, encodes an optical program that defines device functionality. The ability to derive optical programs that address broad spectral demands is central to the BSG's extensive capabilities. In consequence, I present a powerful approach to synthesis that exploits existing knowledge in the design of "analog" gratings. This approach is based on a two-step process, which first derives an analog diffractive structure using the best available methods and then transforms it into binary form. Accordingly, I discuss the notion of diffractive structure transformation and introduce the principle of key information. I identify such key information and illustrate its application in grating quantizers based on an atypical form of Delta-Sigma modulation. As a digital approach to spectral engineering, the BSG presents many of the same advantages offered by the digital approach to electronic signal processing (DSP) over its analog predecessors. As such, it

  17. Multiple channel programmable coincidence counter

    DOEpatents

    Arnone, Gaetano J.

    1990-01-01

    A programmable digital coincidence counter having multiple channels and featuring minimal dead time. Neutron detectors supply electrical pulses to a synchronizing circuit which in turn inputs derandomized pulses to an adding circuit. A random access memory circuit connected as a programmable length shift register receives and shifts the sum of the pulses, and outputs to a serializer. A counter is input by the adding circuit and downcounted by the seralizer, one pulse at a time. The decoded contents of the counter after each decrement is output to scalers.

  18. Klein's programme and quantum mechanics

    NASA Astrophysics Data System (ADS)

    Clemente-Gallardo, Jesús; Marmo, Giuseppe

    2015-04-01

    We review the geometrical formulation of quantum mechanics to identify, according to Klein's programme, the corresponding group of transformations. For closed systems, it is the unitary group. For open quantum systems, the semigroup of Kraus maps contains, as a maximal subgroup, the general linear group. The same group emerges as the exponentiation of the C*-algebra associated with the quantum system, when thought of as a Lie algebra. Thus, open quantum systems seem to identify the general linear group as associated with quantum mechanics and moreover suggest to extend the Klein programme also to groupoids. The usual unitary group emerges as a maximal compact subgroup of the general linear group.

  19. Dispersal of forest insects

    NASA Technical Reports Server (NTRS)

    Mcmanus, M. L.

    1979-01-01

    Dispersal flights of selected species of forest insects which are associated with periodic outbreaks of pests that occur over large contiguous forested areas are discussed. Gypsy moths, spruce budworms, and forest tent caterpillars were studied for their massive migrations in forested areas. Results indicate that large dispersals into forested areas are due to the females, except in the case of the gypsy moth.

  20. Visualizing Dispersion Interactions

    ERIC Educational Resources Information Center

    Gottschalk, Elinor; Venkataraman, Bhawani

    2014-01-01

    An animation and accompanying activity has been developed to help students visualize how dispersion interactions arise. The animation uses the gecko's ability to walk on vertical surfaces to illustrate how dispersion interactions play a role in macroscale outcomes. Assessment of student learning reveals that students were able to develop…

  1. Dispersion strengthened copper

    DOEpatents

    Sheinberg, H.; Meek, T.T.; Blake, R.D.

    1990-01-09

    A composition of matter is described which is comprised of copper and particles which are dispersed throughout the copper, where the particles are comprised of copper oxide and copper having a coating of copper oxide. A method for making this composition of matter is also described. This invention relates to the art of powder metallurgy and, more particularly, it relates to dispersion strengthened metals.

  2. Seed dispersal in fens

    USGS Publications Warehouse

    Middleton, B.; Van Diggelen, R.; Jensen, K.

    2006-01-01

    Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and reducing genetic exchange. Species in fragmented wetlands may have lower reproductive success, which can lead to biodiversity loss. While fens may have always been relatively isolated from each other, they have become increasingly fragmented in modern times within agricultural and urban landscapes in both Europe and North America. Dispersal by water, animals and wind has been hampered by changes related to development in landscapes surrounding fens. Because the seeds of certain species are long-lived in the seed bank, frequent episodes of dispersal are not always necessary to maintain the biodiversity of fens. However, of particular concern to restoration is that some dominant species, such as the tussock sedge Carex stricta, may not disperse readily between fens. Conclusions: Knowledge of seed dispersal can be used to maintain and restore the biodiversity of fens in fragmented landscapes. Given that development has fragmented landscapes and that this situation is not likely to change, the dispersal of seeds might be enhanced by moving hay or cattle from fens to damaged sites, or by reestablishing lost hydrological connections. ?? IAVS; Opulus Press.

  3. Spores Disperse, Too!

    ERIC Educational Resources Information Center

    Schumann, Donna N.

    1981-01-01

    Suggests the use of spores and spore-producing structures to show adaptations facilitating spore dispersal and dispersal to favorable environments. Describes several activities using horsetails, ferns, and mosses. Lists five safety factors related to use of mold spores in the classroom. (DS)

  4. Wind-tunnel studies of roughness effects in gas dispersion

    NASA Astrophysics Data System (ADS)

    Roberts, P. T.; Fryer-Taylor, R. E. J.; Hall, D. J.

    A programme of work has been carried out using wind-tunnel modelling to investigate the effect of surface roughness on dense-gas dispersion from ground-level sources where the roughness height is large compared with the cloud depth. Neutrally buoyant gas releases were included as control experiments. The results are compared with results of a 1:100 scale simulation of dispersion in high roughness conducted by CPP Inc. for the American Petroleum Institute (API). For surface roughness lengths, z0, smaller than about 0.5 cm (0.5 m full scale), dispersion is shown to be well described by a Gaussian plume model. Plume width and depth increase with z0 and are simple functions of distance from the source. For larger roughness, dispersion depends on the arrangement of the roughness elements, plume width, σy, can be restricted by channelling and plume depth, σz, becomes sensitive to run conditions.

  5. The Massey Kiwi Friend Programme

    ERIC Educational Resources Information Center

    Ramsey, Philip; Ramsey, Deborah; Mason, Robyn

    2007-01-01

    Like many institutions, Massey University has experienced growth in enrolments of international students. Increasing numbers of international students has led to frustrations for international and domestic students, and for staff. This paper describes an innovative programme designed to help with the orientation of international students. Domestic…

  6. Portugal's Secondary School Modernisation Programme

    ERIC Educational Resources Information Center

    Heitor, Teresa V.; Freire da Silva, Jose M. R.

    2009-01-01

    The aim of the Secondary School Modernisation Programme, being implemented in Portugal by "Parque Escolar, EPE", is based on the pursuit of quality and makes Portuguese education a potential international benchmark. This paper discusses the strategies adopted to reorganise school spaces. It describes the conceptual model and highlights…

  7. Programmable Kiri-Kirigami Metamaterials.

    PubMed

    Tang, Yichao; Lin, Gaojian; Yang, Shu; Yi, Yun Kyu; Kamien, Randall D; Yin, Jie

    2017-03-01

    Programmable kirigami metamaterials with controllable local tilting orientations on demand through prescribed notches are constructed through a new approach of kiri-kirgami, and their actuation of pore opening via both mechanical stretching and temperature, along with their potential application as skins for energy-saving buildings, is discussed.

  8. Rates of Gravel Dispersion

    NASA Astrophysics Data System (ADS)

    Haschenburger, J. K.

    2010-12-01

    Sediment transfers in gravel-bed rivers involve the three-dimensional dispersion of mixed size sediment. From a kinematics standpoint, few studies are available to inform on the streamwise and vertical rates of sediment dispersion in natural channels. This research uses a gravel tracing program to quantify dispersion rates over 19 flood seasons. Empirical observations come from Carnation Creek, a small gravel-bed river with large woody debris located on the west coast of Vancouver Island, Canada. Frequent floods and the relatively limited armor layer facilitate streambed activity and relatively high bedload transport rates, typically under partial sediment transport conditions. Over 2500 magnetically tagged stones, ranging in size from 16 to 180 mm, were deployed on the bed surface between 1989 and 1992 in four generations. To quantify gravel dispersion over distances up to 2.6 km, observations are taken from 11 recoveries. Over 280 floods capable of moving bedload occurred during this period, with five exceeding the estimated bankfull discharge. Streamwise dispersion is quantified by virtual velocity, while dispersion into the streambed is quantified by a vertical burial rate. The temporal trend in streamwise dispersion rates is described by a power function. Initial virtual velocities decline rapidly from around 1.4 m/hr to approach an asymptote value of about 0.2 m/hr. The rapid change corresponds to a significant increase in the proportion of buried tracers due to vertical mixing. Initial burial rates reflect the magnitude of the first flood after tracer deployment and range from 0.07 to 0.46 cm/hr depending on tracer generation. Burial rates converge to about 0.06 cm/hr after the fourth flood season and then gradually decline to about 0.01 cm/hr. Thus, the rate of streamwise dispersion exceeds that of vertical dispersion by three orders of magnitude when the movement of sediment routinely activated by floods is considered.

  9. Fully programmable two-dimensional pulse shaper for broadband line-by-line amplitude and phase control.

    PubMed

    Metcalf, Andrew J; Torres-Company, Victor; Supradeepa, V R; Leaird, Daniel E; Weiner, Andrew M

    2013-11-18

    We introduce a fully programmable two-dimensional (2D) pulse shaper, able to simultaneously control the amplitude and phase of very fine spectral components over a broad bandwidth. This is achieved by aligning two types of spectral dispersers in a cross dispersion setup: a virtually imaged phased array for accessing fine resolution and a transmission grating for achieving broad bandwidth. We take advantage of the resultant 2D dispersion profile as well as introduce programmability by adding a 2D liquid crystal on silicon spatial light modulator at the masking plane. Our shaper has a resolution of ~3 GHz operating over the entire 'C' band of >5.8 THz. Experimental evidence is provided that highlights the full programmability, fine spectral control, and broad bandwidth operation (limited currently by the bandwidth of the input light). We also show line-by-line manipulation of record 836 comb lines over the C-band.

  10. Adult Learners' Perceptions of An Undergraduate HRD Degree Completion Programme: Reasons for Entering, Attitudes towards Programme and Impact of Programme

    ERIC Educational Resources Information Center

    Dwyer, Dan; Thompson, Dale Edward; Thompson, Cecelia K.

    2013-01-01

    The purpose of the study was to evaluate an undergraduate distance education (DE) programme based upon adult learners' perceptions. The study investigated the value of the Human Resource Development programme at the University of Arkansas by examining the students' reasons for returning to college, their attitudes towards the programme and the…

  11. Dispersion strengthened copper

    DOEpatents

    Sheinberg, Haskell; Meek, Thomas T.; Blake, Rodger D.

    1990-01-01

    A composition of matter comprised of copper and particles which are dispersed throughout the copper, where the particles are comprised of copper oxide and copper having a coating of copper oxide, and a method for making this composition of matter.

  12. Dispersion strengthened copper

    DOEpatents

    Sheinberg, Haskell; Meek, Thomas T.; Blake, Rodger D.

    1989-01-01

    A composition of matter comprised of copper and particles which are dispersed throughout the copper, where the particles are comprised of copper oxide and copper having a coating of copper oxide, and a method for making this composition of matter.

  13. Overview of the ESO instrumentation programme

    NASA Astrophysics Data System (ADS)

    Casali, Mark M.; Pasquini, Luca; Ramsay, Suzanne

    2012-09-01

    The ESO instrumentation programme now encompasses both an on-going programme for La-Silla Paranal observatory and a new programme for construction of the instruments for the E-ELT. The scale and ambition of the combined programme will present a future challenge for the European instrument-building community and for ESO as managing organisation. The current status and plans are summarised.

  14. The JOSHUA (J80) system programmer`s manual

    SciTech Connect

    Smetana, A.O.; McCort, J.T.; Westmoreland, B.W.

    1993-08-01

    The JOSHUA system routines (JS routines) can be used to manage a JOSHUA data base and execute JOSHUA modules on VAX/VMS and IBM/MVS computer systems. This manual provides instructions for using the JS routines and information about the internal data structures and logic used by the routines. It is intended for use primarily by JOSHUA systems programmers, however, advanced applications programmers may also find it useful. The JS routines are, as far as possible, written in ANSI FORTRAN 77 so that they are easily maintainable and easily portable to different computer systems. Nevertheless, the JOSHUA system provides features that are not available in ANSI FORTRAN 77, notably dynamic module execution and a data base of named, variable length, unformatted records, so some parts of the routines are coded in nonstandard FORTRAN or assembler (as a last resort). In most cases, the nonstandard sections of code are different for each computer system. To make it easy for programmers using the JS routines to avoid naming conflicts, the JS routines and common block all have six character names that begin with the characters {open_quotes}JS.{close_quotes} Before using this manual, one should be familiar with the JOSHUA system as described in {open_quotes}The JOSHUA Users` Manual,{close_quotes} ANSI FORTRAN 77, and at least one of the computer systems for which the JS routines have been implemented.

  15. Nanocrystal dispersed amorphous alloys

    NASA Technical Reports Server (NTRS)

    Perepezko, John H. (Inventor); Allen, Donald R. (Inventor); Foley, James C. (Inventor)

    2001-01-01

    Compositions and methods for obtaining nanocrystal dispersed amorphous alloys are described. A composition includes an amorphous matrix forming element (e.g., Al or Fe); at least one transition metal element; and at least one crystallizing agent that is insoluble in the resulting amorphous matrix. During devitrification, the crystallizing agent causes the formation of a high density nanocrystal dispersion. The compositions and methods provide advantages in that materials with superior properties are provided.

  16. Fickian dispersion is anomalous

    DOE PAGES

    Cushman, John H.; O’Malley, Dan

    2015-06-22

    The thesis put forward here is that the occurrence of Fickian dispersion in geophysical settings is a rare event and consequently should be labeled as anomalous. What people classically call anomalous is really the norm. In a Lagrangian setting, a process with mean square displacement which is proportional to time is generally labeled as Fickian dispersion. With a number of counter examples we show why this definition is fraught with difficulty. In a related discussion, we show an infinite second moment does not necessarily imply the process is super dispersive. By employing a rigorous mathematical definition of Fickian dispersion wemore » illustrate why it is so hard to find a Fickian process. We go on to employ a number of renormalization group approaches to classify non-Fickian dispersive behavior. Scaling laws for the probability density function for a dispersive process, the distribution for the first passage times, the mean first passage time, and the finite-size Lyapunov exponent are presented for fixed points of both deterministic and stochastic renormalization group operators. The fixed points of the renormalization group operators are p-self-similar processes. A generalized renormalization group operator is introduced whose fixed points form a set of generalized self-similar processes. Finally, power-law clocks are introduced to examine multi-scaling behavior. Several examples of these ideas are presented and discussed.« less

  17. Fickian dispersion is anomalous

    SciTech Connect

    Cushman, John H.; O’Malley, Dan

    2015-06-22

    The thesis put forward here is that the occurrence of Fickian dispersion in geophysical settings is a rare event and consequently should be labeled as anomalous. What people classically call anomalous is really the norm. In a Lagrangian setting, a process with mean square displacement which is proportional to time is generally labeled as Fickian dispersion. With a number of counter examples we show why this definition is fraught with difficulty. In a related discussion, we show an infinite second moment does not necessarily imply the process is super dispersive. By employing a rigorous mathematical definition of Fickian dispersion we illustrate why it is so hard to find a Fickian process. We go on to employ a number of renormalization group approaches to classify non-Fickian dispersive behavior. Scaling laws for the probability density function for a dispersive process, the distribution for the first passage times, the mean first passage time, and the finite-size Lyapunov exponent are presented for fixed points of both deterministic and stochastic renormalization group operators. The fixed points of the renormalization group operators are p-self-similar processes. A generalized renormalization group operator is introduced whose fixed points form a set of generalized self-similar processes. Finally, power-law clocks are introduced to examine multi-scaling behavior. Several examples of these ideas are presented and discussed.

  18. Fickian dispersion is anomalous

    NASA Astrophysics Data System (ADS)

    Cushman, John H.; O'Malley, Dan

    2015-12-01

    The thesis put forward here is that the occurrence of Fickian dispersion in geophysical settings is a rare event and consequently should be labeled as anomalous. What people classically call anomalous is really the norm. In a Lagrangian setting, a process with mean square displacement which is proportional to time is generally labeled as Fickian dispersion. With a number of counter examples we show why this definition is fraught with difficulty. In a related discussion, we show an infinite second moment does not necessarily imply the process is super dispersive. By employing a rigorous mathematical definition of Fickian dispersion we illustrate why it is so hard to find a Fickian process. We go on to employ a number of renormalization group approaches to classify non-Fickian dispersive behavior. Scaling laws for the probability density function for a dispersive process, the distribution for the first passage times, the mean first passage time, and the finite-size Lyapunov exponent are presented for fixed points of both deterministic and stochastic renormalization group operators. The fixed points of the renormalization group operators are p-self-similar processes. A generalized renormalization group operator is introduced whose fixed points form a set of generalized self-similar processes. Power-law clocks are introduced to examine multi-scaling behavior. Several examples of these ideas are presented and discussed.

  19. Programme Evaluation: Maintaining Quality in Higher Education

    ERIC Educational Resources Information Center

    Loots, A.

    2008-01-01

    The evaluation of educational or social programmes is paramount for establishing success or impact in higher education. Evaluation questions about programme goals (e.g. better performance of first-year students) or about the quality of programme strategies (design and implementation) and effectiveness of delivery (coordinator inputs and…

  20. School Security Assessment Programme in Australia

    ERIC Educational Resources Information Center

    Marrapodi, John

    2007-01-01

    This article describes a successful security risk management programme in Australia. The state-wide programme follows a structured risk management approach focusing on the safety and security of people, information, provision, and assets in the school environment. To assist school principals, a Security Risk Assessment Programme was developed on a…

  1. 21 CFR 870.3700 - Pacemaker programmers.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Pacemaker programmers. 870.3700 Section 870.3700...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3700 Pacemaker programmers. (a) Identification. A pacemaker programmer is a device used to change noninvasively one or more...

  2. 21 CFR 870.3700 - Pacemaker programmers.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Pacemaker programmers. 870.3700 Section 870.3700...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3700 Pacemaker programmers. (a) Identification. A pacemaker programmer is a device used to change noninvasively one or more...

  3. 21 CFR 870.3700 - Pacemaker programmers.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Pacemaker programmers. 870.3700 Section 870.3700...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3700 Pacemaker programmers. (a) Identification. A pacemaker programmer is a device used to change noninvasively one or more...

  4. 21 CFR 870.3700 - Pacemaker programmers.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Pacemaker programmers. 870.3700 Section 870.3700...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3700 Pacemaker programmers. (a) Identification. A pacemaker programmer is a device used to noninvasively change one or more...

  5. Stakeholder Perspectives: CLIL Programme Management in Estonia

    ERIC Educational Resources Information Center

    Mehisto, Peeter; Asser, Hiie

    2007-01-01

    In 2000, Estonia launched a voluntary Estonian language CLIL programme for seven year-olds in four Russian-medium schools. The programme has expanded rapidly to a total of 48 kindergartens and schools. This paper reports on research into stakeholder perspectives on programme management. In addition to surveying parents, teachers, vice-principals…

  6. The Implementation of a Behavioural Support Programme: Teachers' Perceptions of the Programme and Themselves as Providers

    ERIC Educational Resources Information Center

    Ingemarson, Maria; Bodin, Maria; Rubenson, Birgitta; Guldbrandsson, Karin

    2016-01-01

    Purpose: The purpose of this paper is to investigate how teachers received and perceived the school programme Prevention in School (PS), a positive behavioural support programme; how did the teachers perceive the programme characteristics and themselves as providers; and how did this affect programme implementation? Design/methodology/approach:…

  7. PROGRAMMABLE DISPLAY PUSHBUTTON LEGEND EDITOR

    NASA Technical Reports Server (NTRS)

    Busquets, A. M.

    1994-01-01

    The Programmable Display Pushbutton (PDP) is a pushbutton device available from Micro Switch which has a programmable 16 x 35 matrix of LEDs on the pushbutton surface. Any desired legends can be displayed on the PDPs, producing user-friendly applications which greatly reduce the need for dedicated manual controls. Because the PDP can interact with the operator, it can call for the correct response before transmitting its next message. It is both a simple manual control and a sophisticated programmable link between the operator and the host system. The Programmable Display Pushbutton Legend Editor, PDPE, is used to create the LED displays for the pushbuttons. PDPE encodes PDP control commands and legend data into message byte strings sent to a Logic Refresh and Control Unit (LRCU). The LRCU serves as the driver for a set of four PDPs. The legend editor (PDPE) transmits to the LRCU user specified commands that control what is displayed on the LED face of the individual pushbuttons. Upon receiving a command, the LRCU transmits an acknowledgement that the message was received and executed successfully. The user then observes the effect of the command on the PDP displays and decides whether or not to send the byte code of the message to a data file so that it may be called by an applications program. The PDPE program is written in FORTRAN for interactive execution. It was developed on a DEC VAX 11/780 under VMS. It has a central memory requirement of approximately 12800 bytes. It requires four Micro Switch PDPs and two RS-232 VAX 11/780 terminal ports. The PDPE program was developed in 1985.

  8. Programmable data collection platform study

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The results of a feasibility study incorporating microprocessors in data collection platforms in described. An introduction to microcomputer hardware and software concepts is provided. The influence of microprocessor technology on the design of programmable data collection platform hardware is discussed. A standard modular PDCP design capable of meeting the design goals is proposed, and the process of developing PDCP programs is examined. A description of design and construction of the UT PDCP development system is given.

  9. Application thinking on Bian-stone of the acousto-optic effect in the treatment of primary dysmenorrhea

    NASA Astrophysics Data System (ADS)

    Ge, Shu; Chen, Gui-Zhen; Liu, Song-Hao

    2009-08-01

    In order to identify the relations between the Si-Bin Bian-stone of the mineral composition characteristics and Bian-stone of the good infrared emission features. A detailed study of the Sibin Bian-stone samples was conducted by using the laser Raman spectroscopy and high-resolution transmission electron microscopy (HRTEM). The study is to provide theoretical physical support for Bian-stone in the treatment of primary dysmenorrhea. And Thermal tomography technology (TTM) is intended to be carried out to assess the effects of Bian-stone. The Raman spectroscopic study confirmed the existence of fine-grained pyrite, anatase, calcitepyrite and graphite. It is believed that the combination of good thermal properties of the above 4 minerals make the Sibin Bian-stone as a useful material with very good physiotherapical functions. The ultrasonic has a resonance with the body's biological molecules so that it can improve meridians microcirculation. Hence, the Sibin Bian-stones can be used to make acupuncture tools for stimulating the circulation of the blood in vessels and relieving pains of human beings by utilizing its infrared thermal radiation property. TTM which accepts the heat produced by the metabolism process of life can reflect the energy status information, TTM will be introduced to evaluate effect at the overall level of the abdomen from the thermal image and analyze to derive a comprehensive diagnosis. In sum, this experiment is explored to provide a new idea for the modernization of traditional Chinese medicine.

  10. Baseband integrated acousto-optic frequency shifter/modulator module for fiber optic at 1.3 mum.

    PubMed

    Tsai, C S; Cheng, Z Y

    1993-01-01

    A baseband integrated acoustooptic (AO) frequency shifter/modulator module that consists of a pair of titanium-indiffused proton-exchanged (TIPE) waveguide lenses and a pair of cascaded guided-wave AO Bragg cells has been realized in a Y-cut LiNbO(3) waveguide substrate 0.1 cmx1.0 cmx2.0 cm in size. A device module operating at the optical wavelength of 1.3 mum has provided a -3-dB tunable bandwidth of 120 MHz at baseband. The frequency-shifted or -modulated light propagates in a fixed direction, irrespective of the magnitude of frequency shift or modulation, and is focused into a spot (FWHM) of 6.2-mum size on the output edge of the waveguide. Accordingly, this optical frequency shifter/module can be directly interfaced with single-mode optical fibers to facilitate applications in fiber optic systems.

  11. Acousto-optic effect in a nematic liquid-crystal layer under the binary effect of sound and viscous waves

    SciTech Connect

    Kozhevnikov, E. N.

    2010-03-15

    The optical effect in a liquid crystal cell containing a homeotropic layer of nematic liquid crystal (NLC) is analyzed. An NLC layer, located between crossed polaroids and opaque in the absence of external effect, is cleared after irradiation by an ultrasonic beam with a sharp spatial boundary. This enlightenment is suggested to be caused by the reorientation of crystal molecules in the acoustic flows that arise under the binary effect of the layer compression in the irradiated region and the viscous waves propagating from the layer boundaries. The flows were calculated taking into account the stress caused by the velocity convection and crystal structure relaxation. An expression is derived for the cell transparency, and the relative role of the convection and relaxation processes in the effect is determined.

  12. KISMET tungsten dispersal experiment

    SciTech Connect

    Wohletz, K.; Kunkle, T.; Hawkins, W.

    1996-12-01

    Results of the KISMET tungsten dispersal experiment indicate a relatively small degree of wall-rock contamination caused by this underground explosive experiment. Designed as an add-on to the KISMET test, which was performed in the U-1a.02 drift of the LYNER facility at Nevada Test Site on 1 March 1995, this experiment involved recovery and analysis of wall-rock samples affected by the high- explosive test. The chemical, high-explosive blast drove tungsten powder, placed around the test package as a plutonium analog, into the surrounding wall- rock alluvium. Sample analyses by an analytical digital electron microscope (ADEM) show tungsten dispersed in the rock as tiny (<10 {mu}m) particles, agglomerates, and coatings on alluvial clasts. Tungsten concentrations, measured by energy dispersive spectral analysis on the ADEM, indicate penetration depths less than 0.1 m and maximum concentrations of 1.5 wt % in the alluvium.

  13. Uranium Dispersion & Dosimetry Model.

    SciTech Connect

    MICHAEL,; MOMENI, H.

    2002-03-22

    The Uranium Dispersion and Dosimetry (UDAD) program provides estimates of potential radiation exposure to individuals and to the general population in the vicinity of a uranium processing facility such as a uranium mine or mill. Only transport through the air is considered. Exposure results from inhalation, external irradiation from airborne and ground-deposited activity, and ingestion of foodstuffs. Individual dose commitments, population dose commitments, and environmental dose commitments are computed. The program was developed for application to uranium mining and milling; however, it may be applied to dispersion of any other pollutant.

  14. Polymer-dispersed liquid crystal elastomers

    NASA Astrophysics Data System (ADS)

    Rešetič, Andraž; Milavec, Jerneja; Zupančič, Blaž; Domenici, Valentina; Zalar, Boštjan

    2016-10-01

    The need for mechanical manipulation during the curing of conventional liquid crystal elastomers diminishes their applicability in the field of shape-programmable soft materials and future applications in additive manufacturing. Here we report on polymer-dispersed liquid crystal elastomers, novel composite materials that eliminate this difficulty. Their thermal shape memory anisotropy is imprinted by curing in external magnetic field, providing for conventional moulding of macroscopically sized soft, thermomechanically active elastic objects of general shapes. The binary soft-soft composition of isotropic elastomer matrix, filled with freeze-fracture-fabricated, oriented liquid crystal elastomer microparticles as colloidal inclusions, allows for fine-tuning of thermal morphing behaviour. This is accomplished by adjusting the concentration, spatial distribution and orientation of microparticles or using blends of microparticles with different thermomechanical characteristics. We demonstrate that any Gaussian thermomechanical deformation mode (bend, cup, saddle, left and right twist) of a planar sample, as well as beat-like actuation, is attainable with bilayer microparticle configurations.

  15. Nonvolatile, electrically erasable programmable ROM

    NASA Astrophysics Data System (ADS)

    El-Dessouky, A.

    1984-01-01

    The processing technology for integration of MNOS-EEPROMs and NMOS Logic was investigated as p-well isolation. Memory characteristics of both Si gate and metal gate MNOS devices are investigated for nitride constitution which aims for lower programming voltages and good memory performance. The complete fabrication process for 128 byte SNOS-EEPROM chip is described by using high voltage depletion MOS devices in p-well technology. Another test vehicle uses 4 x 4 metal gate MNOS array to demonstrate possible fabrication of 12 V programmable scaled MNOS devices with 10 years retention after 10 to the 5th power endurance.

  16. Programmable, automated transistor test system

    NASA Technical Reports Server (NTRS)

    Truong, L. V.; Sundburg, G. R.

    1986-01-01

    A programmable, automated transistor test system was built to supply experimental data on new and advanced power semiconductors. The data will be used for analytical models and by engineers in designing space and aircraft electric power systems. A pulsed power technique was used at low duty cycles in a nondestructive test to examine the dynamic switching characteristic curves of power transistors in the 500 to 1000 V, 10 to 100 A range. Data collection, manipulation, storage, and output are operator interactive but are guided and controlled by the system software.

  17. Toxicological programmes and teaching methods.

    PubMed

    Bergendorff, A

    2000-03-15

    Toxicological knowledge is required for three main purposes: basic and applied research, toxicity testing, and risk assessment. Curricula and teaching methods designed to meet these demands for knowledge are aimed at appropriation of relevant facts, appreciation of causality and an overall understanding of biological events caused by chemical substances. The Toxicology Programme at Karolinska Institutet is considered as an example for the design of appropriate courses. Teaching methods developed towards more self-tuition are becoming a natural part of such education. Continued escalation in scientific achievements and demands for safe use of chemicals will govern future trends in toxicological education.

  18. Programmable Multi-Chip Module

    DOEpatents

    Kautz, David; Morgenstern, Howard; Blazek, Roy J.

    2005-05-24

    A multi-chip module comprising a low-temperature co-fired ceramic substrate having a first side on which are mounted active components and a second side on which are mounted passive components, wherein this segregation of components allows for hermetically sealing the active components with a cover while leaving accessible the passive components, and wherein the passive components are secured using a reflow soldering technique and are removable and replaceable so as to make the multi-chip module substantially programmable with regard to the passive components.

  19. Programmable Multi-Chip Module

    DOEpatents

    Kautz, David; Morgenstern, Howard; Blazek, Roy J.

    2004-11-16

    A multi-chip module comprising a low-temperature co-fired ceramic substrate having a first side on which are mounted active components and a second side on which are mounted passive components, wherein this segregation of components allows for hermetically sealing the active components with a cover while leaving accessible the passive components, and wherein the passive components are secured using a reflow soldering technique and are removable and replaceable so as to make the multi-chip module substantially programmable with regard to the passive components.

  20. Programmable Automated Welding System (PAWS)

    NASA Technical Reports Server (NTRS)

    Kline, Martin D.

    1994-01-01

    An ambitious project to develop an advanced, automated welding system is being funded as part of the Navy Joining Center with Babcock & Wilcox as the prime integrator. This program, the Programmable Automated Welding System (PAWS), involves the integration of both planning and real-time control activities. Planning functions include the development of a graphical decision support system within a standard, portable environment. Real-time control functions include the development of a modular, intelligent, real-time control system and the integration of a number of welding process sensors. This paper presents each of these components of the PAWS and discusses how they can be utilized to automate the welding operation.

  1. Warm fog dispersal

    NASA Technical Reports Server (NTRS)

    Frost, W.

    1983-01-01

    The charged particle generator was further tested after some design modification. The generator performance was measured with additional instrumentation and found to confirm previous measurements. Plans for a field testing were than developed. The overall status of the program and the field test plans were presented to a group of atmospheric scientists and electrostatic experts at the NASA/MSFC sponsored USRA Workshop on Electrostatic Fog Dispersal at NCAR, Boulder, Colorado discussed in previous sections. The recommendations from this workshop are being evaluated as to whether NASA should proceed with the field test or whether further theoretical research on the phenomenon of electrostatic fog dispersal and additional development of the charged particle generator should be carried out. Information obtained from the USRA Workshop clearly identified three physical mechanisms that could possibly influence the fog dispersal process, which heretofore have not been considered, and which may provide additional insight to the direction of further fog dispersal work. These mechanisms are: the effect of corona discharge on the electric field strength at the surface, the influx of fog into the cleared volume by turbulent diffusion, and the increase in supersaturation as liquid water is removed, activating haze particles, and thus generating more fog. Plans are being formulated to investigate these mechanisms.

  2. Acoustic dispersive prism

    NASA Astrophysics Data System (ADS)

    Esfahlani, Hussein; Karkar, Sami; Lissek, Herve; Mosig, Juan R.

    2016-01-01

    The optical dispersive prism is a well-studied element, which allows separating white light into its constituent spectral colors, and stands in nature as water droplets. In analogy to this definition, the acoustic dispersive prism should be an acoustic device with capability of splitting a broadband acoustic wave into its constituent Fourier components. However, due to the acoustical nature of materials as well as the design and fabrication difficulties, there is neither any natural acoustic counterpart of the optical prism, nor any artificial design reported so far exhibiting an equivalent acoustic behaviour. Here, based on exotic properties of the acoustic transmission-line metamaterials and exploiting unique physical behaviour of acoustic leaky-wave radiation, we report the first acoustic dispersive prism, effective within the audible frequency range 800 Hz–1300 Hz. The dispersive nature, and consequently the frequency-dependent refractive index of the metamaterial are exploited to split the sound waves towards different and frequency-dependent directions. Meanwhile, the leaky-wave nature of the structure facilitates the sound wave radiation into the ambient medium.

  3. Acoustic dispersive prism.

    PubMed

    Esfahlani, Hussein; Karkar, Sami; Lissek, Herve; Mosig, Juan R

    2016-01-07

    The optical dispersive prism is a well-studied element, which allows separating white light into its constituent spectral colors, and stands in nature as water droplets. In analogy to this definition, the acoustic dispersive prism should be an acoustic device with capability of splitting a broadband acoustic wave into its constituent Fourier components. However, due to the acoustical nature of materials as well as the design and fabrication difficulties, there is neither any natural acoustic counterpart of the optical prism, nor any artificial design reported so far exhibiting an equivalent acoustic behaviour. Here, based on exotic properties of the acoustic transmission-line metamaterials and exploiting unique physical behaviour of acoustic leaky-wave radiation, we report the first acoustic dispersive prism, effective within the audible frequency range 800 Hz-1300 Hz. The dispersive nature, and consequently the frequency-dependent refractive index of the metamaterial are exploited to split the sound waves towards different and frequency-dependent directions. Meanwhile, the leaky-wave nature of the structure facilitates the sound wave radiation into the ambient medium.

  4. Dispersions in semiclassical dynamics

    NASA Astrophysics Data System (ADS)

    Zielinska-Pfabé, M.; Grégoire, C.

    1988-06-01

    Dispersions around mean values of one-body observables are obtained by restoring classical many-body correlations in Vlasov and Landau-Vlasov dynamics. This method is applied to the calculation of fluctuations in mass, charge, and linear momentum in heavy-ion collisions. Results are compared with those obtained by the Balian-Veneroni variational principle in semiclassical approximation.

  5. Acoustic dispersive prism

    PubMed Central

    Esfahlani, Hussein; Karkar, Sami; Lissek, Herve; Mosig, Juan R.

    2016-01-01

    The optical dispersive prism is a well-studied element, which allows separating white light into its constituent spectral colors, and stands in nature as water droplets. In analogy to this definition, the acoustic dispersive prism should be an acoustic device with capability of splitting a broadband acoustic wave into its constituent Fourier components. However, due to the acoustical nature of materials as well as the design and fabrication difficulties, there is neither any natural acoustic counterpart of the optical prism, nor any artificial design reported so far exhibiting an equivalent acoustic behaviour. Here, based on exotic properties of the acoustic transmission-line metamaterials and exploiting unique physical behaviour of acoustic leaky-wave radiation, we report the first acoustic dispersive prism, effective within the audible frequency range 800 Hz–1300 Hz. The dispersive nature, and consequently the frequency-dependent refractive index of the metamaterial are exploited to split the sound waves towards different and frequency-dependent directions. Meanwhile, the leaky-wave nature of the structure facilitates the sound wave radiation into the ambient medium. PMID:26739504

  6. Oxide dispersion strengthened superalloy

    NASA Technical Reports Server (NTRS)

    Glasgow, T. K.; Kim, Y. G.; Curwick, L. R.; Merrick, H. F.

    1981-01-01

    MA6000E alloy is strengthened at high temperatures by dispersion of yttrium oxide. Strength properties are about twice those of conventional nickel base alloys. Good thermal fatigue, intermediate temperature strength, and good oxidation resistance give alloy unique combination of benefits. Application in aircraft gas turbine is improved.

  7. Octave spanning wedge dispersive mirrors with low dispersion oscillations.

    PubMed

    Habel, Florian; Shirvanyan, Vage; Trubetskov, Michael; Burger, Christian; Sommer, Annkatrin; Kling, Matthias F; Schultze, Martin; Pervak, Vladimir

    2016-05-02

    A novel concept for octave spanning dispersive mirrors with low spectral dispersion oscillations is presented. The key element of the so-called wedge dispersive mirror is a slightly wedged layer which is coated on a specially optimized dispersive multilayer stack by a common sputter coating process. The group delay dispersion (GDD) of a pulse reflected on a wedge dispersive mirror is nearly free of oscillations. Fabricated mirrors with negative GDD demonstrate the compression of a pulse down to 3.8 fs as good as double angled mirrors optimized for the same bandwidth.

  8. GMES Space Component: Programme overview

    NASA Astrophysics Data System (ADS)

    Aschbacher, J.; Milagro-Perez, M. P.

    2012-04-01

    The European Union (EU) and the European Space Agency (ESA) have developed the Global Monitoring for Environment and Security (GMES) programme as Europe's answer to the vital need for joined-up data about our climate, environment and security. Through a unique combination of satellite, atmospheric and Earth-based monitoring systems, the initiative will provide new insight into the state of the land, sea and air, providing policymakers, scientists, businesses and the public with accurate and timely information. GMES capabilities include monitoring and forecasting of climatic change, flood risks, soil and coastal erosion, crop and fish resources, air pollution, greenhouse gases, iceberg distribution and snow cover, among others. To accomplish this, GMES has been divided into three main components: Space, In-situ and Services. The Space Component, led by ESA, comprises five types of new satellites called Sentinels that are being developed by ESA specifically to meet the needs of GMES, the first of which to be launched in 2013. These missions carry a range of technologies, such as radar and multi-spectral imaging instruments for land, ocean and atmospheric monitoring. In addition, access to data from the so-called Contributing Missions guarantees that European space infrastructure is fully used for GMES. An integrated Ground Segment ensures access to Sentinels and Contributing Missions data. The in-situ component, under the coordination of the European Environment Agency (EEA), is composed of atmospheric and Earth based monitoring systems, and based on established networks and programmes at European and international levels. The European Commission is in charge of implementing the services component of GMES and of leading GMES overall. GMES services, fed with data from the Space and In-situ components, will provide essential information in five main domains, atmosphere, ocean and land monitoring as well as emergency response and security. Climate change has been added

  9. Building a global business continuity programme.

    PubMed

    Lazcano, Michael

    2014-01-01

    Business continuity programmes provide an important function within organisations, especially when aligned with and supportive of the organisation's goals, objectives and organisational culture. Continuity programmes for large, complex international organisations, unlike those for compact national companies, are more difficult to design, build, implement and maintain. Programmes for international organisations require attention to structural design, support across organisational leadership and hierarchy, seamless integration with the organisation's culture, measured success and demonstrated value. This paper details practical, but sometimes overlooked considerations for building successful global business continuity programmes.

  10. Dispersion suppressors with bending

    SciTech Connect

    Garren, A.

    1985-10-01

    Dispersion suppressors of two main types are usually used. In one the cell quadrupole focussing structure is the same as in normal cells but some of the dipoles are replaced by drifts. In the other, the quadrupole strengths and/or spacings are different from those of the normal cells, but the bending is about the same as it is in the cells. In SSC designs to date, dispersion suppressors of the former type have been used, consisting of two cells with bending equivalent to one. In this note a suppressor design with normal bending and altered focussing is presented. The advantage of this scheme is that circumference is reduced. The disadvantages are that additional special quadrupoles must be provided (however, they need not be adjustable), and the maximum beta values within them are about 30% higher than the cell maxima.

  11. Disabling Radiological Dispersal Terror

    SciTech Connect

    Hart, M

    2002-11-08

    Terror resulting from the use of a radiological dispersal device (RDD) relies upon an individual's lack of knowledge and understanding regarding its significance. Disabling this terror will depend upon realistic reviews of the current conservative radiation protection regulatory standards. It will also depend upon individuals being able to make their own informed decisions merging perceived risks with reality. Preparation in these areas will reduce the effectiveness of the RDD and may even reduce the possibility of its use.

  12. Ascent trajectory dispersion analysis

    NASA Technical Reports Server (NTRS)

    1982-01-01

    The results of a Space Transportation System ascent trajectory dispersion analysis are documented. Critical trajectory parameter values useful for the definition of lightweight external tank insulation requirements are provided. This analysis was conducted using two of the critical missions specified for the Space Transportation System: a 28.5 deg inclination trajectory launched from the Eastern Test Range (ETR) and a Western Test Range (WTR) trajectory launched into a 104 deg orbital inclination.

  13. A Full-Color, High-Resolution Laser Projector for a Flight Simulator Visual Display

    DTIC Science & Technology

    1993-08-01

    Acousto - optic deflectors work in a similar manner as the acousto - optic modulator. The difference is...that acousto - optic deflectors vary acoustic drive frequency to deflect the beam where the acousto - optic modulator varies acoustic drive amplitude to... acousto - optic modulators, deflectors , and high-speed polygon mirror scanners, cost-effective laser projection can be attained. These new

  14. The European eLearning Programme(s): Between Rhetoric and Reality

    ERIC Educational Resources Information Center

    Salajan, Florin D.

    2007-01-01

    This article presents the findings of a qualitative study conducted by the author on the implications of e-learning programmes for the higher education systems of the member states of the European Union. The study takes a look behind the scenes of the eLearning Programme and other e-learning actions within other European programmes by tapping into…

  15. Aurora europe's space exploration programme

    NASA Astrophysics Data System (ADS)

    Ongaro, F.; Swings, J. P.; Condessa, R.

    2003-04-01

    What will happen after the ISS in terms of space exploration, specifically to the human presence beyond Earth? What will be the role of Europe in the future international venture to explore space? What are the most immediate actions to be undertaken in Europe in order to best profit from the efforts made through the participation in the ISS and to position Europe's capabilities according to its interests? As approved by the Ministers at the Edinburgh Council in November 2001, the European Space Exploration Programme - Aurora - is ESA's programme in charge of defining and implementing the long term plan for human and robotic exploration of the Solar system. The Aurora programme started in 2002 and extends until the end goal of Aurora: the first human mission to Mars, expected in the 2025-2030 time-frame. The approach of Aurora is to implement a robust development of technologies and robotic missions, in parallel to the utilization phase of the ISS, to prepare for a continuous and sustainable future of human space exploration (which shall include the Moon, Mars and the asteroids as targets), in which Europe will be a valuable partner. Two classes of missions are foreseen in the programme's strategy: Flagships, defined as major missions driving to soft landing, in-situ analysis, sample return from other planetary bodies and eventually human missions; and Arrows, defined as cost-capped, short development time missions to demonstrate new technologies or mission approaches, or to exploit opportunities for payloads on European or international missions. So far the participating national delegations have approved two Flagships (ExoMars and Mars Sample Return) and two Arrows (Earth Re-entry and Mars Aerocapture) for phase A industrial studies. Although the last call for ideas of Aurora resulted in the definition of two Flagship missions targeted to Mars, the next one might be aimed to the Moon. At this stage the role of the Moon, on the path of Mars exploration is not

  16. Rheumatic Fever Programme in Samoa.

    PubMed

    Viali, Satupaitea; Saena, Puleiala; Futi, Vailogoua

    2011-02-11

    Rheumatic fever is very common in Samoa. The following paper describes the Rheumatic Fever Programme in Samoa and looks at the incidence of acute rheumatic fever (ARF) and rheumatic heart disease (RHD). The incidence of ARF has decreased to 30 per 100,000 in 2005, 12.8 per 100,000 in 2007, 7.3 per 100,000 in 2008, and 9.5 per 100,000 in 2009. The incidence of RHD has decreased to 40.2 per 100,000 in 2007, 34 per 100,000 in 2008, and 31.8 per 100,000 in 2009. Cardiac surgery in New Zealand is expensive, but is cheaper to perform in Samoa. RHD screening with echocardiogram at schools may be the best way to reduce the burden and suffering from RHD.

  17. Field Evaluation of Programmable Thermostats

    SciTech Connect

    Sachs, O.; Tiefenbeck, V.; Duvier, C.; Qin, A.; Cheney, K.; Akers, C.; Roth, K.

    2012-12-01

    Prior research suggests that poor programmable thermostats usability may prevent their effective use to save energy. We hypothesized that home occupants with a high-usability thermostats would be more likely to use them to save energy than people with a basic thermostat. We randomly installed a high-usability thermostat in half the 77 apartments of an affordable housing complex, installing a basic thermostat in the other half. During the heating season, we collected space temperature and furnace on-off data to evaluate occupant interaction with the thermostats, foremost nighttime setbacks. We found that thermostat usability did not influence energy-saving behaviors, finding no significant difference in temperature maintained among apartments with high- and low-usability thermostats.

  18. Nozzle for electric dispersion reactor

    DOEpatents

    Sisson, W.G.; Harris, M.T.; Scott, T.C.; Basaran, O.A.

    1998-06-02

    A nozzle for an electric dispersion reactor includes two coaxial cylindrical bodies, the inner one of the two delivering disperse phase fluid into a continuous phase fluid. A potential difference generated by a voltage source creates a dispersing electric field at the end of the inner electrode. 5 figs.

  19. Nozzle for electric dispersion reactor

    DOEpatents

    Sisson, Warren G.; Basaran, Osman A.; Harris, Michael T.

    1995-01-01

    A nozzle for an electric dispersion reactor includes two concentric electrodes, the inner one of the two delivering disperse phase fluid into a continuous phase fluid. A potential difference generated by a voltage source creates a dispersing electric field at the end of the inner electrode.

  20. Nozzle for electric dispersion reactor

    DOEpatents

    Sisson, W.G.; Basaran, O.A.; Harris, M.T.

    1998-04-14

    A nozzle for an electric dispersion reactor includes two concentric electrodes, the inner one of the two delivering disperse phase fluid into a continuous phase fluid. A potential difference generated by a voltage source creates a dispersing electric field at the end of the inner electrode. 4 figs.

  1. Nozzle for electric dispersion reactor

    DOEpatents

    Sisson, Warren G.; Basaran, Osman A.; Harris, Michael T.

    1998-01-01

    A nozzle for an electric dispersion reactor includes two concentric electrodes, the inner one of the two delivering disperse phase fluid into a continuous phase fluid. A potential difference generated by a voltage source creates a dispersing electric field at the end of the inner electrode.

  2. Nozzle for electric dispersion reactor

    DOEpatents

    Sisson, Warren G.; Harris, Michael T.; Scott, Timothy C.; Basaran, Osman A.

    1996-01-01

    A nozzle for an electric dispersion reactor includes two coaxial cylindrical bodies, the inner one of the two delivering disperse phase fluid into a continuous phase fluid. A potential difference generated by a voltage source creates a dispersing electric field at the end of the inner electrode.

  3. Nozzle for electric dispersion reactor

    DOEpatents

    Sisson, W.G.; Basaran, O.A.; Harris, M.T.

    1995-11-07

    A nozzle for an electric dispersion reactor includes two concentric electrodes, the inner one of the two delivering disperse phase fluid into a continuous phase fluid. A potential difference generated by a voltage source creates a dispersing electric field at the end of the inner electrode. 4 figs.

  4. Nozzle for electric dispersion reactor

    DOEpatents

    Sisson, Warren G.; Harris, Michael T.; Scott, Timothy C.; Basaran, Osman A.

    1998-01-01

    A nozzle for an electric dispersion reactor includes two coaxial cylindrical bodies, the inner one of the two delivering disperse phase fluid into a continuous phase fluid. A potential difference generated by a voltage source creates a dispersing electric field at the end of the inner electrode.

  5. Nozzle for electric dispersion reactor

    DOEpatents

    Sisson, W.G.; Harris, M.T.; Scott, T.C.; Basaran, O.A.

    1996-04-02

    A nozzle for an electric dispersion reactor includes two coaxial cylindrical bodies, the inner one of the two delivering disperse phase fluid into a continuous phase fluid. A potential difference generated by a voltage source creates a dispersing electric field at the end of the inner electrode. 5 figs.

  6. Evaluating Large-Scale Interactive Radio Programmes

    ERIC Educational Resources Information Center

    Potter, Charles; Naidoo, Gordon

    2009-01-01

    This article focuses on the challenges involved in conducting evaluations of interactive radio programmes in South Africa with large numbers of schools, teachers, and learners. It focuses on the role such large-scale evaluation has played during the South African radio learning programme's development stage, as well as during its subsequent…

  7. Erasmus Mundus SEN: The Inclusive Scholarship Programme?

    ERIC Educational Resources Information Center

    Grinbergs, Christopher J.; Jones, Hilary

    2013-01-01

    The Erasmus Mundus MA/Mgr in Special Education Needs (EM SEN) was created as a Masters Course funded by the European Commission's Erasmus Mundus Programme (EMP) to challenge and educate students in inclusive policy and practice in education. Yet, it is debatable the extent to which this programme embodies the values of an inclusive approach,…

  8. Equivalency Programmes (EPs) for Promoting Lifelong Learning

    ERIC Educational Resources Information Center

    Haddad, Caroline, Ed.

    2006-01-01

    Equivalency programmes (EPs) refers to alternative education programmes that are equivalent to the formal education system in terms of curriculum and certification, policy support mechanisms, mode of delivery, staff training, and other support activities such as monitoring, evaluation and assessment. The development of EPs is potentially an…

  9. Using Programmable Calculators to Evaluate Complicated Formulas.

    ERIC Educational Resources Information Center

    Snover, Stephen L.; Spikell, Mark A.

    The application of the programmable calculator to evaluating complicated formulas is illustrated by considering the formula for finding the area of any triangle when only the lengths of the three sides are known. Other advantages of the programmable calculator are discussed such as freeing the student to explore more challenging problems and…

  10. Students' Perception of Industrial Internship Programme

    ERIC Educational Resources Information Center

    Renganathan, Sumathi; Karim, Zainal Ambri Bin Abdul; Li, Chong Su

    2012-01-01

    Purpose: An important aspect of an academic curriculum in higher learning institutions for technical disciplines is the industrial internship programme for students. The purpose of this paper is to investigate students' perception of the effectiveness of an industrial internship programme offered by a private technological university in Malaysia.…

  11. XML does Real Programmers a Service

    SciTech Connect

    Gorton, Ian

    2008-09-01

    As the sun slowly sets of this first decade of the new millenium, it seems appropriate to update the sojourn of the real programmers as they adapt to their ever changing technical and business environment. Real Programmers were perfectly characterized and differentiated from their quiche-eating, Pascal programming brethren in Ed Post’s seminal “Real Programmers Don’t Use Pascal” (Datamation, 1983). My follow-up ("Real programmers do use Delphi," Software, IEEE , vol.12, no.6, pp.8, 10, 12-, Nov 1995) charted their evolution from FORTRAN-only programmers to embracing a wider range of mainstream languages and tools that still afforded ample opportunity for creativity, game-playing, irregular work hours, and importantly, long-term job security.

  12. A modularized pulse programmer for NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Mao, Wenping; Bao, Qingjia; Yang, Liang; Chen, Yiqun; Liu, Chaoyang; Qiu, Jianqing; Ye, Chaohui

    2011-02-01

    A modularized pulse programmer for a NMR spectrometer is described. It consists of a networked PCI-104 single-board computer and a field programmable gate array (FPGA). The PCI-104 is dedicated to translate the pulse sequence elements from the host computer into 48-bit binary words and download these words to the FPGA, while the FPGA functions as a sequencer to execute these binary words. High-resolution NMR spectra obtained on a home-built spectrometer with four pulse programmers working concurrently demonstrate the effectiveness of the pulse programmer. Advantages of the module include (1) once designed it can be duplicated and used to construct a scalable NMR/MRI system with multiple transmitter and receiver channels, (2) it is a totally programmable system in which all specific applications are determined by software, and (3) it provides enough reserve for possible new pulse sequences.

  13. Programmer`s manual for CAMCON: Compliance Assessment Methodology CONtroller

    SciTech Connect

    Rechard, R.P.; Gilkey, A.P.; Rudeen, D.K.; Byle, K.A.; Iuzzolino, H.J.

    1993-05-01

    CAMCON, the Compliance Assessment Methodology CONtroller, is an analysis system that assists in assessing the compliance of the Waste Isolation Pilot Plant (WIPP) with applicable long-term regulations of the US Environmental Protection Agency, including Subpart B of the Environmental Standards for the Management and Disposal of spent Nuclear Fuel, High-Level and Transuranic Radioactive Wastes, 40 CFR 191 and 40CFR268.6, which is the portion of the Land Disposal Restrictions implementing the Resource, Conservative, and Recovery Act of 1976, as amended that states the conditions for disposal of hazardous chemical wastes. This manual provides an architectural overview of the CAMCON system. Furthermore this manual presents guidelines and presents suggestions for programmers developing the many different types of software necessary to investigate various events and physical processes of the WIPP. These guidelines include user interface requirements, minimum quality assurance requirements, coding style suggestions, and the use of numerous software libraries developed specifically for or adapted for the CAMCON system.

  14. Should we stay or should we go: mechanisms and ecological consequences for biofilm dispersal.

    PubMed

    McDougald, Diane; Rice, Scott A; Barraud, Nicolas; Steinberg, Peter D; Kjelleberg, Staffan

    2011-11-28

    In most environments, bacteria reside primarily in biofilms, which are social consortia of cells that are embedded in an extracellular matrix and undergo developmental programmes resulting in a predictable biofilm 'life cycle'. Recent research on many different bacterial species has now shown that the final stage in this life cycle includes the production and release of differentiated dispersal cells. The formation of these cells and their eventual dispersal is initiated through diverse and remarkably sophisticated mechanisms, suggesting that there are strong evolutionary pressures for dispersal from an otherwise largely sessile biofilm. The evolutionary aspect of biofilm dispersal is now being explored through the integration of molecular microbiology with eukaryotic ecological and evolutionary theory, which provides a broad conceptual framework for the diversity of specific mechanisms underlying biofilm dispersal. Here, we review recent progress in this emerging field and suggest that the merging of detailed molecular mechanisms with ecological theory will significantly advance our understanding of biofilm biology and ecology.

  15. QT dispersion and P wave dispersion in patients with fibromyalgia

    PubMed Central

    Yolbaş, Servet; Yıldırım, Ahmet; Düzenci, Deccane; Karakaya, Bülent; Dağlı, Mustafa Necati; Koca, Süleyman Serdar

    2016-01-01

    Objective Fibromyalgia (FM) is a chronic disease characterized by widespread pain. Somatic complaints associated with the cardiovascular system, such as chest pain and palpitations, are frequently seen in FM patients. P and QT dispersions are simple and inexpensive measurements reflecting the regional heterogeneity of atrial and ventricular repolarization, respectively. QT dispersion can cause serious ventricular arrhythmias. The aim of the present study was to evaluate QT dispersion and P wave dispersion in patients with FM. Material and Methods The study involved 48 FM patients who fulfilled the established criteria and 32 healthy controls (HC). A standard 12-lead electrocardiogram was performed on all participants. QT dispersion was defined as the difference between the longest and the shortest QT intervals. Similarly, the differences between the shortest and longest P waves were defined as P wave dispersion. Results The QT dispersion and corrected QT dispersion were shorter in the FM group compared with the HC group (p<0.001 for both). In terms of the P wave dispersion value, there was no significant difference between the FM and HC groups (p=0.088). Conclusion Longer QT and P wave dispersions are not problems in patients with FM. Therefore, it may be concluded that fibromyalgia does not include an increased risk of atrial and/or ventricular arrhythmias. PMID:28149660

  16. Quantum optical rotatory dispersion

    PubMed Central

    Tischler, Nora; Krenn, Mario; Fickler, Robert; Vidal, Xavier; Zeilinger, Anton; Molina-Terriza, Gabriel

    2016-01-01

    The phenomenon of molecular optical activity manifests itself as the rotation of the plane of linear polarization when light passes through chiral media. Measurements of optical activity and its wavelength dependence, that is, optical rotatory dispersion, can reveal information about intricate properties of molecules, such as the three-dimensional arrangement of atoms comprising a molecule. Given a limited probe power, quantum metrology offers the possibility of outperforming classical measurements. This has particular appeal when samples may be damaged by high power, which is a potential concern for chiroptical studies. We present the first experiment in which multiwavelength polarization-entangled photon pairs are used to measure the optical activity and optical rotatory dispersion exhibited by a solution of chiral molecules. Our work paves the way for quantum-enhanced measurements of chirality, with potential applications in chemistry, biology, materials science, and the pharmaceutical industry. The scheme that we use for probing wavelength dependence not only allows one to surpass the information extracted per photon in a classical measurement but also can be used for more general differential measurements. PMID:27713928

  17. Quantum optical rotatory dispersion.

    PubMed

    Tischler, Nora; Krenn, Mario; Fickler, Robert; Vidal, Xavier; Zeilinger, Anton; Molina-Terriza, Gabriel

    2016-10-01

    The phenomenon of molecular optical activity manifests itself as the rotation of the plane of linear polarization when light passes through chiral media. Measurements of optical activity and its wavelength dependence, that is, optical rotatory dispersion, can reveal information about intricate properties of molecules, such as the three-dimensional arrangement of atoms comprising a molecule. Given a limited probe power, quantum metrology offers the possibility of outperforming classical measurements. This has particular appeal when samples may be damaged by high power, which is a potential concern for chiroptical studies. We present the first experiment in which multiwavelength polarization-entangled photon pairs are used to measure the optical activity and optical rotatory dispersion exhibited by a solution of chiral molecules. Our work paves the way for quantum-enhanced measurements of chirality, with potential applications in chemistry, biology, materials science, and the pharmaceutical industry. The scheme that we use for probing wavelength dependence not only allows one to surpass the information extracted per photon in a classical measurement but also can be used for more general differential measurements.

  18. Mission reliability model programmers guide

    NASA Astrophysics Data System (ADS)

    Medina, Joseph M.; Simonson, Jonathan H.; Veatch, Michael H.

    1986-12-01

    The Mission Reliability Model (MIREM) has been developed to evaluate the reliability and sustained operating capability of advanced electronic circuits during the early stages of development. MIREM is applicable to integrated systems that achieve fault tolerance through dynamic fault detection, fault isolation, and reconfiguration. The model can also be valuable in evaluating designs that employ only dedicated or hard-wired redundancy. The most unique feature of MIREM is its ability to accurately reflect the impact of reconfigurable, competing functions on system reliability. The user defines the resources necessary to support a required function, e.g., Global Positioning System (GPS), and the model will compute the probability of losing that functional capability over a certain operating time. A critical failure occurs when there is not a sufficient number of working resources to support a specified function. As an analytic model, MIREM determines a value for Mean Time Between Critical Failure, Mission Completion Success Probability, and Failure Resiliency. The MIREM Programmers Guide addresses the model's program structure, function of routines, interdependence of subprograms and common blocks, and file usage. The information needed to port the model to other computer systems is also provided.

  19. Lessons from a microfinance recapitalisation programme.

    PubMed

    Poston, Angus

    2010-04-01

    Following a major disaster, microfinance institutions (MFIs) often face high levels of bad debt, which may require the institutions to be recapitalised. This paper describes a recapitalisation programme implemented by the SANASA movement of Sri Lanka in 390 microfinance societies following the December 2004 tsunami, and highlights lessons for other similar programmes. MFI recapitalisation is a good use of funds in post-disaster situations. To create successful programmes, donors should expect to relax some of their usual project requirements and MFIs should focus on maintaining credit discipline.

  20. Safety programmes in the Egyptian construction industry.

    PubMed

    Hassanein, Amr A G; Hanna, Ragaa S

    2007-12-01

    This study is aimed at exploring the nature of the safety programmes applied by large-size contractors operating in Egypt. Results revealed that safety programmes applied by those contractors were less formal than the programmes applied by their American counterparts. Only three contractors out of the surveyed sample had accident records broken down by projects, provided workers with formal safety orientation, and trained safety personnel on first-aid. The study recommended that reforms to the scheme of the employers' contribution to social insurance are necessary. This is meant to serve as a strong incentive for safety management.

  1. Software Safety Assurance of Programmable Logic

    NASA Technical Reports Server (NTRS)

    Berens, Kalynnda

    2002-01-01

    Programmable Logic (PLC, FPGA, ASIC) devices are hybrids - hardware devices that are designed and programmed like software. As such, they fall in an assurance gray area. Programmable Logic is usually tested and verified as hardware, and the software aspects are ignored, potentially leading to safety or mission success concerns. The objective of this proposal is to first determine where and how Programmable Logic (PL) is used within NASA and document the current methods of assurance. Once that is known, raise awareness of the PL software aspects within the NASA engineering community and provide guidance for the use and assurance of PL form a software perspective.

  2. SMED - Sulphur MEditerranean Dispersion

    NASA Astrophysics Data System (ADS)

    Salerno, Giuseppe G.; Sellitto, Pasquale; Corradini, Stefano; Di Sarra, Alcide Giorgio; Merucci, Luca; Caltabiano, Tommaso; La Spina, Alessandro

    2016-04-01

    Emissions of volcanic gases and particles can have profound impacts on terrestrial environment, atmospheric composition, climate forcing, and then on human health at various temporal and spatial scales. Volcanic emissions have been identified as one of the largest sources of uncertainty in our understanding of recent climate change trends. In particular, a primary role is acted by sulphur dioxide emission due to its conversion to volcanic sulphate aerosol via atmospheric oxidation. Aerosols may play a key role in the radiative budget and then in photochemistry and tropospheric composition. Mt. Etna is one of the most prodigious and persistent emitters of gasses and particles on Earth, accounting for about 10% of global average volcanic emission of CO2 and SO2. Its sulphur emissions stand for 0.7 × 106 t S/yr9 and then about 10 times bigger than anthropogenic sulphur emissions in the Mediterranean area. Centrepiece of the SMED project is to advance the understanding of volcanogenic sulphur dioxide and sulphate aerosol particles dispersion and radiative impact on the downwind Mediterranean region by an integrated approach between ground- and space-based observations and modelling. Research is addressed by exploring the potential relationship between proximal SO2 flux and aerosol measured remotely in the volcanic plume of Mt. Etna between 2000 and 2014 and distal aerosol ground-based measurements in Lampedusa, Greece, and Malta from AERONET network. Ground data are combined with satellite multispectral polar and geostationary imagers able to detect and retrieve volcanic ash and SO2. The high repetition time of SEVIRI (15 minutes) will ensure the potential opportunity to follow the entire evolution of the volcanic cloud, while, the higher spatial resolution of MODIS (1x1 km2), are exploited for investigating the probability to retrieve volcanic SO2 abundances from passive degassing. Ground and space observations are complemented with atmospheric Lagrangian model

  3. Natural dispersion revisited.

    PubMed

    Johansen, Øistein; Reed, Mark; Bodsberg, Nils Rune

    2015-04-15

    This paper presents a new semi-empirical model for oil droplet size distributions generated by single breaking wave events. Empirical data was obtained from laboratory experiments with different crude oils at different stages of weathering. The paper starts with a review of the most commonly used model for natural dispersion, which is followed by a presentation of the laboratory study on oil droplet size distributions formed by breaking waves conducted by SINTEF on behalf of the NOAA/UNH Coastal Response Research Center. The next section presents the theoretical and empirical foundation for the new model. The model is based on dimensional analysis and contains two non-dimensional groups; the Weber and Reynolds number. The model was validated with data from a full scale experimental oil spill conducted in the Haltenbanken area offshore Norway in July 1982, as described in the last section of the paper.

  4. Photorefractive Integrators and Correlators

    DTIC Science & Technology

    1992-12-01

    The use of photorefractive crystals as optically addressed time integrating spatial light modulators in acousto - optic signal processing applications...adaptive acousto - optic processor. These results demonstrated the feasibility of using photorefractives for such applications.... Photorefractive, Acousto - optic processor.

  5. Designing a catheter skills training programme.

    PubMed

    Logan, Karen

    Karen Logan describes how a team of continence advisers designed and implemented a training programme that allows local nurses to meet the national occupational standards and competencies in catheterisation and catheter care.

  6. Establishing a national universal vaccination programme.

    PubMed

    Duma, R

    1995-01-01

    The collaborative efforts of healthcare providers, governmental policy and law makers and the public are often needed to provide the pressure necessary to establish a national universal vaccination programme. Key initiatives for those beginning to establish such a programme are the following: secure a scientific consensus or base of support; clarify relevance of the subject to all concerned; increase awareness of everyone (providers and consumers); recruit and involve influential people (angels) for support; seek out agendas within which to review the topic; generate cost-benefit data; encourage a consensus to be reached; identify legislative pathways to be used; convince politicians of the value of such a programme; request budgeting and funding; and, finally, follow up with surveillance studies to demonstrate the benefits of the programme.

  7. Managing nutritional programmes in developing countries.

    PubMed

    Sheikholeslam, R; Abdollahi, Z; Haghighi, F N

    2004-11-01

    Improving community nutrition in developing countries requires a detailed epidemiological picture of the prevalent nutritional problems in different regions and age groups. This makes it possible to identify priorities, sensitize policy-makers, establish political commitment and design appropriate community programmes for income generation and education for the best use of food resources. Experiences acquired from community-based nutritional programmes show that ownership of a programme by the community and using a tailor-made approach are essential factors in the successful implementation of programmes. A multifaceted approach is needed, involving a range of sectors-agriculture, commerce, education and health--and commitment at all levels from government to communities and individuals.

  8. Control programme for cystic echinococcosis in Uruguay.

    PubMed

    Irabedra, Pilar; Ferreira, Ciro; Sayes, Julio; Elola, Susana; Rodríguez, Miriam; Morel, Noelia; Segura, Sebastian; Santos, Estela Dos; Guisantes, Jorge A

    2016-05-24

    Cystic echinococcosis is a highly endemic parasitic zoonosis that is present in the Southern Cone countries of America. For several decades, various prevention and control programmes have been implemented in different countries and regions, with varying results. In Uruguay, a new control programme was implemented in 2006 that employed new strategies for canine diagnosis and treatment, dog population control, diagnosis in humans, epidemiological surveillance, and health education, including community participation. The control programme in Uruguay addresses the control and surveillance of the disease from a holistic perspective based on Primary Health Care, which has strengthened the community's participation in developing and coordinating activities in an interdisciplinary manner. Similarly, the control programme that is currently implemented is based on a risk-focused approach. The surveillance and control measures were focused on small villages and extremely poor urban areas. In this study, the strategies used and the results obtained from 2008-2013 are analysed and discussed.

  9. Review of field-programmable analog arrays

    NASA Astrophysics Data System (ADS)

    Gulak, Glen; D'Mello, Dean R.

    1996-10-01

    The drive towards shorter design cycles for analog integrated circuits has given impetus to several developments in the area of field-programmable analog arrays (FPAAs). Various approaches have been taken in implementing topological and parametric programmability of analog circuits. Recent extensions of this work have married FPAAs to their digital counterparts (FPGAs) along with data conversion interfaces, to form field-programmable mixed signal arrays (FPMAs). This survey paper reviews work to data in the area of programmable analog and mixed signal circuits. The body of work reviewed includes university and industrial research, commercial products and patents. A time-line of important achievements in the area is drawn and the status of various activities is summarized.

  10. Evaluation of a nurse leadership development programme.

    PubMed

    West, Margaret; Smithgall, Lisa; Rosler, Greta; Winn, Erin

    2016-03-01

    The challenge for nursing leaders responsible for workforce planning is to predict the knowledge, skills and abilities required to lead future healthcare delivery systems effectively. Succession planning requires a constant, competitive pool of qualified nursing leader candidates, and retention of those interested in career growth. Formal nursing leadership education in the United States is available through graduate education and professional nursing organisation programmes, such as the Emerging Nurse Leader Institute of the American Organization of Nurse Executives. However, there is also a need for local development programmes tailored to the needs of individual organisations. Leaders at Geisinger Health System, one of the largest rural health systems in the US, identified the need for an internal professional development scheme for nurses. In 2013 the Nurses Emerging as Leaders programme was developed to prepare nurse leaders for effective leadership and successful role transition. This article describes the programme and an evaluation of its effectiveness.

  11. Control programme for cystic echinococcosis in Uruguay

    PubMed Central

    Irabedra, Pilar; Ferreira, Ciro; Sayes, Julio; Elola, Susana; Rodríguez, Miriam; Morel, Noelia; Segura, Sebastian; dos Santos, Estela; Guisantes, Jorge A

    2016-01-01

    Cystic echinococcosis is a highly endemic parasitic zoonosis that is present in the Southern Cone countries of America. For several decades, various prevention and control programmes have been implemented in different countries and regions, with varying results. In Uruguay, a new control programme was implemented in 2006 that employed new strategies for canine diagnosis and treatment, dog population control, diagnosis in humans, epidemiological surveillance, and health education, including community participation. The control programme in Uruguay addresses the control and surveillance of the disease from a holistic perspective based on Primary Health Care, which has strengthened the community’s participation in developing and coordinating activities in an interdisciplinary manner. Similarly, the control programme that is currently implemented is based on a risk-focused approach. The surveillance and control measures were focused on small villages and extremely poor urban areas. In this study, the strategies used and the results obtained from 2008-2013 are analysed and discussed. PMID:27223652

  12. The UNESCO Bioethics Programme: a review.

    PubMed

    Langlois, Adéle

    2014-01-01

    UNESCO's Bioethics Programme was established in 1993. In twenty years it has adopted three international declarations, on the human genome (1997), human genetic data (2003) and bioethics (2005); produced reports on a wide range of bioethics issues; and developed capacity building and public education programmes in bioethics. Yet UNESCO has sometimes struggled to assert its authority in the wider bioethics world. Some bioethicists have criticized the 2005 declaration and suggested that the World Health Organization might be better placed to advance bioethics. In 2011, after four years of debate, UNESCO decided not to draft a convention on human reproductive cloning, because consensus on the issue proved impossible. This article reviews the standard setting and capacity building activities of the UNESCO Bioethics Programme. While the Programme faces challenges common to most intergovernmental organizations, its achievements in expanding international law and building bioethics capacity should not be underestimated.

  13. The Case for Programmable Calculators in Schools.

    ERIC Educational Resources Information Center

    Inglis, Norman J.

    1981-01-01

    Programmable calculators are useful tools in the classroom that are often overlooked. This report gives examples of problems and activities that can be brought within the scope of such calculators. (MP)

  14. ESO Fellowship Programme 2006/2007

    NASA Astrophysics Data System (ADS)

    2006-06-01

    ESO awards several postdoctoral fellow-ships each year. The goal of these fel-lowships is to offer young scientists op-portunities and facilities to enhance their research programmes at one of the world's foremost observatories.

  15. ACOUSTIC RECTIFICATION IN DISPERSIVE MEDIA

    SciTech Connect

    Cantrell, John H.

    2009-03-03

    It is shown that the shapes of acoustic radiation-induced static strain and displacement pulses (rectified acoustic pulses) are defined locally by the energy density of the generating waveform. Dispersive properties are introduced analytically by assuming that the rectified pulses are functionally dependent on a phase factor that includes both dispersive and nonlinear terms. The dispersion causes an evolutionary change in the shape of the energy density profile that leads to the generation of solitons experimentally observed in fused silica.

  16. Paramedir: A Tool for Programmable Performance Analysis

    NASA Technical Reports Server (NTRS)

    Jost, Gabriele; Labarta, Jesus; Gimenez, Judit

    2004-01-01

    Performance analysis of parallel scientific applications is time consuming and requires great expertise in areas such as programming paradigms, system software, and computer hardware architectures. In this paper we describe a tool that facilitates the programmability of performance metric calculations thereby allowing the automation of the analysis and reducing the application development time. We demonstrate how the system can be used to capture knowledge and intuition acquired by advanced parallel programmers in order to be transferred to novice users.

  17. Firmware Modification Analysis in Programmable Logic Controllers

    DTIC Science & Technology

    2014-03-27

    MODIFICATION ANALYSIS IN PROGRAMMABLE LOGIC CONTROLLERS Arturo M. Garcia Jr., B.S.S.E.C.A. Captain, USA Approved: //signed// Robert F. Mills , PhD...Matthew 5:37 v Acknowledgments My sincere gratitude to my committee for their guidance and teamwork which made this thesis possible. Dr. Mills ...2012. 2012. [5] Bolton, William. Programmable logic controllers. Newnes, 2009. [6] Boyer, Stuart . SCADA: Supervisory Control and Data Aquisition 4th

  18. Informationist programme in support of biomedical research: a programme description and preliminary findings of an evaluation

    PubMed Central

    Whitmore, Susan C.; Grefsheim, Suzanne F.; Rankin, Jocelyn A.

    2008-01-01

    Background The informationist programme at the Library of the National Institutes of Health (NIH) in Bethesda, MD, USA has grown to 14 informationists working with 40 clinical and basic science research teams. Purpose This case report, intended to contribute to the literature on informationist programmes, describes the NIH informationist programme including implementation experiences, the informationists' training programme, their job responsibilities and programme outcomes. Brief description The NIH informationist programme was designed to enhance the library's service capacity. Over time, the steps for introducing the service to new groups were formalized to ensure support by leadership, the team being served and the library. Job responsibilities also evolved from traditional library roles to a wide range of knowledge management activities. The commitment by the informationist, the team and the library to continuous learning is critical to the programme's success. Results/outcomes NIH scientists reported that informationists saved them time and contributed to teamwork with expert searching and point-of-need instruction. Process evaluation helped refine the programme. Evaluation method High-level, preliminary outcomes were identified from a survey of scientists receiving informationist services, along with key informant interviews. Process evaluation examined service implementation, informationists' training, and service components. Anecdotal evidence has also indicated a favorable response to the programme. PMID:18494648

  19. Filter-Based Dispersion-Managed Versatile Ultrafast Fibre Laser

    PubMed Central

    Peng, Junsong; Boscolo, Sonia

    2016-01-01

    We present the operation of an ultrafast passively mode-locked fibre laser, in which flexible control of the pulse formation mechanism is readily realised by an in-cavity programmable filter the dispersion and bandwidth of which can be software configured. We show that conventional soliton, dispersion-managed (DM) soliton (stretched-pulse) and dissipative soliton mode-locking regimes can be reliably targeted by changing the filter’s dispersion and bandwidth only, while no changes are made to the physical layout of the laser cavity. Numerical simulations are presented which confirm the different nonlinear pulse evolutions inside the laser cavity. The proposed technique holds great potential for achieving a high degree of control over the dynamics and output of ultrafast fibre lasers, in contrast to the traditional method to control the pulse formation mechanism in a DM fibre laser, which involves manual optimisation of the relative length of fibres with opposite-sign dispersion in the cavity. Our versatile ultrafast fibre laser will be attractive for applications requiring different pulse profiles such as in optical signal processing and optical communications. PMID:27183882

  20. Modeling volcanic ash dispersal

    SciTech Connect

    2010-10-22

    Explosive volcanic eruptions inject into the atmosphere large amounts of volcanic material (ash, blocks and lapilli). Blocks and larger lapilli follow ballistic and non-ballistic trajectories and fall rapidly close to the volcano. In contrast, very fine ashes can remain entrapped in the atmosphere for months to years, and may affect the global climate in the case of large eruptions. Particles having sizes between these two end-members remain airborne from hours to days and can cover wide areas downwind. Such volcanic fallout entails a serious threat to aircraft safety and can create many undesirable effects to the communities located around the volcano. The assessment of volcanic fallout hazard is an important scientific, economic, and political issue, especially in densely populated areas. From a scientific point of view, considerable progress has been made during the last two decades through the use of increasingly powerful computational models and capabilities. Nowadays, models are used to quantify hazard scenarios and/or to give short-term forecasts during emergency situations. This talk will be focused on the main aspects related to modeling volcanic ash dispersal and fallout with application to the well known problem created by the Eyjafjöll volcano in Iceland. Moreover, a short description of the main volcanic monitoring techniques is presented.

  1. Hybrid Dispersion Laser Scanner

    PubMed Central

    Goda, K.; Mahjoubfar, A.; Wang, C.; Fard, A.; Adam, J.; Gossett, D. R.; Ayazi, A.; Sollier, E.; Malik, O.; Chen, E.; Liu, Y.; Brown, R.; Sarkhosh, N.; Di Carlo, D.; Jalali, B.

    2012-01-01

    Laser scanning technology is one of the most integral parts of today's scientific research, manufacturing, defense, and biomedicine. In many applications, high-speed scanning capability is essential for scanning a large area in a short time and multi-dimensional sensing of moving objects and dynamical processes with fine temporal resolution. Unfortunately, conventional laser scanners are often too slow, resulting in limited precision and utility. Here we present a new type of laser scanner that offers ∼1,000 times higher scan rates than conventional state-of-the-art scanners. This method employs spatial dispersion of temporally stretched broadband optical pulses onto the target, enabling inertia-free laser scans at unprecedented scan rates of nearly 100 MHz at 800 nm. To show our scanner's broad utility, we use it to demonstrate unique and previously difficult-to-achieve capabilities in imaging, surface vibrometry, and flow cytometry at a record 2D raster scan rate of more than 100 kHz with 27,000 resolvable points. PMID:22685627

  2. Disperser seal and method

    SciTech Connect

    Johnston, R. T.

    1981-06-02

    A seal is described for a shaft of a disperser crusher, that pulverizes hot coal particles, maintains a higher than atmospheric pressure within a casing for the crusher, and is able to withstand elevated temperatures that are produced within the casing. The pressure and temperature result from hot gases that convey coal particles to the crusher. The seal includes self lubricating graphite packings that are urged in abutting relation with a smooth, ceramic sleeve on the shaft and are able to withstand the temperature on the shaft surface. A first, interior packing is on the inside of a wall of the casing while a second, exterior packing is outside of the wall. Superheated steam, a gas inert with the coal particles, is supplied to the interior packing with sufficient pressure to substantially prevent the migration of coal particles through the interior packing. The tendency of the coal particles to migrate from the container through the interior packing is further inhibited by providing a tortuous path from the casing to the interior packing.

  3. Hybrid dispersion laser scanner.

    PubMed

    Goda, K; Mahjoubfar, A; Wang, C; Fard, A; Adam, J; Gossett, D R; Ayazi, A; Sollier, E; Malik, O; Chen, E; Liu, Y; Brown, R; Sarkhosh, N; Di Carlo, D; Jalali, B

    2012-01-01

    Laser scanning technology is one of the most integral parts of today's scientific research, manufacturing, defense, and biomedicine. In many applications, high-speed scanning capability is essential for scanning a large area in a short time and multi-dimensional sensing of moving objects and dynamical processes with fine temporal resolution. Unfortunately, conventional laser scanners are often too slow, resulting in limited precision and utility. Here we present a new type of laser scanner that offers ∼1,000 times higher scan rates than conventional state-of-the-art scanners. This method employs spatial dispersion of temporally stretched broadband optical pulses onto the target, enabling inertia-free laser scans at unprecedented scan rates of nearly 100 MHz at 800 nm. To show our scanner's broad utility, we use it to demonstrate unique and previously difficult-to-achieve capabilities in imaging, surface vibrometry, and flow cytometry at a record 2D raster scan rate of more than 100 kHz with 27,000 resolvable points.

  4. Modeling volcanic ash dispersal

    ScienceCinema

    None

    2016-07-12

    Explosive volcanic eruptions inject into the atmosphere large amounts of volcanic material (ash, blocks and lapilli). Blocks and larger lapilli follow ballistic and non-ballistic trajectories and fall rapidly close to the volcano. In contrast, very fine ashes can remain entrapped in the atmosphere for months to years, and may affect the global climate in the case of large eruptions. Particles having sizes between these two end-members remain airborne from hours to days and can cover wide areas downwind. Such volcanic fallout entails a serious threat to aircraft safety and can create many undesirable effects to the communities located around the volcano. The assessment of volcanic fallout hazard is an important scientific, economic, and political issue, especially in densely populated areas. From a scientific point of view, considerable progress has been made during the last two decades through the use of increasingly powerful computational models and capabilities. Nowadays, models are used to quantify hazard scenarios and/or to give short-term forecasts during emergency situations. This talk will be focused on the main aspects related to modeling volcanic ash dispersal and fallout with application to the well known problem created by the Eyjafjöll volcano in Iceland. Moreover, a short description of the main volcanic monitoring techniques is presented.

  5. Auroral electron time dispersion

    SciTech Connect

    Kletzing, C.A.

    1989-01-01

    A sounding rocket flight was launched from Greenland in 1985 to study high latitude, early morning auroral physics. The payload was instrumented with electron and ion detectors, AC and DC electric field experiments, a plasma density experiment, and a magnetometer to measure the ambient field. The rocket was launched during disturbed conditions, when the polar cap was in a contracted state with visible aurora overhead. The electron data contained numerous signatures indicative of time-of-flight energy dispersion characterized by a coherent structure in which lower energy electrons arrived at the rocket after higher energy electrons. A model was constructed to explain this phenomena by the sudden application of a region of parallel electric field along a length of magnetic field line above the rocket. The model incorporates detector response and uses an altitudinal density profile based on auroral zone measurements. Three types of potential structures were tried: linear, quadratic and cubic. Of the three it was found that the cubic (electric field growing in a quadratic manner moving up the field line) produced the best fit to the data. The potential region was found to be approximately 1-2 R{sub e} in extent with the lower edge 3000-4000 km away from the rocket. The background electron temperature in the model which produced the best fit to the data was of the order of 15 eV.

  6. Preparation of alkali metal dispersions

    NASA Technical Reports Server (NTRS)

    Rembaum, A.; Landel, R. F. (Inventor)

    1968-01-01

    A method is described for producing alkali metal dispersions of high purity. The dispersions are prepared by varying the equilibrium solubility of the alkali metal in a suitable organic solvent in the presence of aromatic hydrocarbons. The equilibrium variation is produced by temperature change. The size of the particles is controlled by controlling the rate of temperature change.

  7. Large deviations in Taylor dispersion

    NASA Astrophysics Data System (ADS)

    Kahlen, Marcel; Engel, Andreas; Van den Broeck, Christian

    2017-01-01

    We establish a link between the phenomenon of Taylor dispersion and the theory of empirical distributions. Using this connection, we derive, upon applying the theory of large deviations, an alternative and much more precise description of the long-time regime for Taylor dispersion.

  8. Procedure for dispersing fiber bundles

    NASA Technical Reports Server (NTRS)

    Padilla, D.

    1974-01-01

    Fiber bundles are dispersed and fibers are cleaned within enclosed container; therefore, safety clothing, masks, and eye protection are not required. Procedure also could be used wherever materials, such as fiberglass or insulation, require dispersion, fluffing, or cleaning. Process could be automated into continuous operation for handling large quantities of fiber.

  9. Meeting Teacher Expectations in a DL Professional Development Programme--A Case Study for Sustained Applied Competence as Programme Outcome

    ERIC Educational Resources Information Center

    Kruger, Cornè Gerda; Van Rensburg, Ona Janse; De Witt, Marike W.

    2016-01-01

    Meeting teacher expectations for a professional development programme (PDP) is expected to strengthen sustainable applied competence as programme outcome since teachers will be more motivated to apply the programme content in practice. A revised distance learning (DL) programme was augmented by a practical component comprising a work-integrated…

  10. The MISTRALS programme data portal

    NASA Astrophysics Data System (ADS)

    Fleury, Laurence; Brissebrat, Guillaume; Belmahfoud, Nizar; Boichard, Jean-Luc; Brosolo, Laetitia; Cloché, Sophie; Descloitres, Jacques; Ferré, Hélène; Focsa, Loredana; Labatut, Laurent; Mastrorillo, Laurence; Mière, Arnaud; Petit de la Villéon, Loïc; Ramage, Karim; Schmechtig, Catherine

    2014-05-01

    Mediterranean Integrated STudies at Regional And Local Scales (MISTRALS) is a decennial programme for systematic observations and research dedicated to the understanding of the Mediterranean Basin environmental process and its evolution under the planet global change. It is composed of eight multidisciplinary projects that cover all the components of the Earth system (atmosphere, ocean, continental surfaces, lithosphere...) and their interactions, many disciplines (physics, chemistry, marine biogeochemistry, biology, geology, sociology...) and different time scales. For example Hydrological cycle in the Mediterranean eXperiment (HyMeX) aims at improving the predictability of rainfall extreme events, and assessing the social and economic vulnerability to extreme events and adaptation capacity, and Paleo Mediterranean Experiment (PaleoMeX) is dedicated to the study of the interactions between climate, societies and civilizations of the Mediterranean world during the last 10000 years. Many long term monitoring research networks are associated with MISTRALS, like Mediterranean Ocean Observing System on Environment (MOOSE), Centre d'Observation Régional pour la Surveillance du Climat et de l'environnement Atmosphérique et océanographique en Méditerranée occidentale (CORSICA) and the environmental observations from Mediterranean Eurocentre for Underwater Sciences and Technologies (MEUST-SE). Therefore, the data generated or used by the different MISTRALS projects are very heterogeneous. They include in situ observations, satellite products, model outputs, qualitative field surveys... Some datasets are automatically produced by operational networks, and others come from research instruments and analysis procedures. They correspond to different time scales (historical time series, observatories, campaigns...) and are managed by different data centres. They originate from many scientific communities, with varied data sharing cultures, specific expectations, and using

  11. The MISTRALS programme data portal

    NASA Astrophysics Data System (ADS)

    Fleury, Laurence; Brissebrat, Guillaume; Belmahfoud, Nizar; Boichard, Jean-Luc; Brosolo, Laetitia; Cloché, Sophie; Descloitres, Jacques; Ferré, Hélène; Focsa, Loredana; Henriot, Nicolas; Labatut, Laurent; Mière, Arnaud; Petit de la Villéon, Loïc; Ramage, Karim; Schmechtig, Catherine; Vermeulen, Anne; André, François

    2015-04-01

    Mediterranean Integrated STudies at Regional And Local Scales (MISTRALS) is a decennial programme for systematic observations and research dedicated to the understanding of the Mediterranean Basin environmental process and its evolution under the planet global change. It is composed of eight multidisciplinary projects that cover all the components of the Earth system (atmosphere, ocean, continental surfaces, lithosphere...) and their interactions, all the disciplines (physics, chemistry, marine biogeochemistry, biology, geology, sociology...) and different time scales. For example Hydrological cycle in the Mediterranean eXperiment (HyMeX) aims at improving the predictability of rainfall extreme events, and assessing the social and economic vulnerability to extreme events and adaptation capacity. Paleo Mediterranean Experiment (PaleoMeX) is dedicated to the study of the interactions between climate, societies and civilizations of the Mediterranean world during the last 10000 years. Many long term monitoring research networks are associated with MISTRALS, such as Mediterranean Ocean Observing System on Environment (MOOSE), Centre d'Observation Régional pour la Surveillance du Climat et de l'environnement Atmosphérique et océanographique en Méditerranée occidentale (CORSICA) and the environmental observations from Mediterranean Eurocentre for Underwater Sciences and Technologies (MEUST-SE). Therefore, the data generated or used by the different MISTRALS projects are very heterogeneous. They include in situ observations, satellite products, model outputs, social sciences surveys... Some datasets are automatically produced by operational networks, and others come from research instruments and analysis procedures. They correspond to different time scales (historical time series, observatories, campaigns...) and are managed by several data centres. They originate from many scientific communities, with different data sharing practices, specific expectations and using

  12. The MISTRALS programme data portal

    NASA Astrophysics Data System (ADS)

    Brissebrat, Guillaume; Albert-Aguilar, Alexandre; Belmahfoud, Nizar; Cloché, Sophie; Darras, Sabine; Descloitres, Jacques; Ferré, Hélène; Fleury, Laurence; Focsa, Loredana; Henriot, Nicolas; Labatut, Laurent; Petit de la Villéon, Loïc; Ramage, Karim; Schmechtig, Catherine; Vermeulen, Anne

    2016-04-01

    Mediterranean Integrated STudies at Regional And Local Scales (MISTRALS) is a decennial programme for systematic observations and research dedicated to the understanding of the Mediterranean Basin environmental process and its evolution under the planet global change. It is composed of eight multidisciplinary projects that cover all the components of the Earth system (atmosphere, ocean, continental surfaces, lithosphere...) and their interactions, all the disciplines (physics, chemistry, marine biogeochemistry, biology, geology, sociology...) and different time scales. For example Hydrological cycle in the Mediterranean eXperiment (HyMeX) aims at improving the predictability of rainfall extreme events, and assessing the social and economic vulnerability to extreme events and adaptation capacity. Paleo Mediterranean Experiment (PaleoMeX) is dedicated to the study of the interactions between climate, societies and civilizations of the Mediterranean world during the last 10000 years. Many long term monitoring research networks are associated with MISTRALS, such as Mediterranean Ocean Observing System on Environment (MOOSE), Centre d'Observation Régional pour la Surveillance du Climat et de l'environnement Atmosphérique et océanographique en Méditerranée occidentale (CORSICA) and the environmental observations from Mediterranean Eurocentre for Underwater Sciences and Technologies (MEUST-SE). Therefore, the data generated or used by the different MISTRALS projects are very heterogeneous. They include in situ observations, satellite products, model outputs, social sciences surveys... Some datasets are automatically produced by operational networks, and others come from research instruments and analysis procedures. They correspond to different time scales (historical time series, observatories, campaigns...) and are managed by several data centres. They originate from many scientific communities, with different data sharing practices, specific expectations and using

  13. Evaluation of national malaria control programmes in Africa.

    PubMed Central

    Bryce, J.; Roungou, J. B.; Nguyen-Dinh, P.; Naimoli, J. F.; Breman, J. G.

    1994-01-01

    Evaluation is an essential management tool for the improvement of public health programmes or projects. As malaria morbidity and mortality continue to increase in most countries in Africa, international agencies and malaria control programme managers have identified the strengthening of programme evaluation as an important strategy for improving the efficiency and effectiveness of malaria control programmes. Managers can develop an evaluation strategy only after they have defined programme objectives and planned specific programme activities. Indicators should be directly related to programme objectives and should be selected on the basis of the following criteria: their validity; reliability; ability to detect change within a reasonable time period and as a result of successful programme implementation; ability to be interpreted; and usefulness in guiding programme change. Only those indicators that can be measured with available programme resources should be selected. Managers will also need to identify the sources of indicator data and to determine how often each indicator will be measured. Programme managers should develop criteria or indicators for the following: programme policies and plans; the process of programme implementation; the outcomes of malaria control interventions in disease management and prevention; and programme impact in terms of reductions in malaria-related mortality and morbidity. Key issues related to the management of evaluation activities within a national programme include the need to begin with available resources and build incrementally; to explore options for administering evaluation activities; to select, train and supervise staff who carry out evaluation activities; to develop quality control strategies; and to ensure that data are managed and communicated in ways that support effective programme decision-making. For evaluation to lead to improvements in malaria control programmes it must be clearly defined as a part of the

  14. RHrFPGA Radiation-Hardened Re-programmable Field-Programmable Gate Array

    NASA Technical Reports Server (NTRS)

    Sanders, A. B.; LaBel, K. A.; McCabe, J. F.; Gardner, G. A.; Lintz, J.; Ross, C.; Golke, K.; Burns, B.; Carts, M. A.; Kim, H. S.

    2004-01-01

    Viewgraphs on the development of the Radiation-Hardened Re-programmable Field-Programmable Gate Array (RHrFPGA) are presented. The topics include: 1) Radiation Test Suite; 2) Testing Interface; 3) Test Configuration; 4) Facilities; 5) Test Programs; 6) Test Procedure; and 7) Test Results. A summary of heavy ion and proton testing is also included.

  15. Polymer-dispersed liquid crystal elastomers

    PubMed Central

    Rešetič, Andraž; Milavec, Jerneja; Zupančič, Blaž; Domenici, Valentina; Zalar, Boštjan

    2016-01-01

    The need for mechanical manipulation during the curing of conventional liquid crystal elastomers diminishes their applicability in the field of shape-programmable soft materials and future applications in additive manufacturing. Here we report on polymer-dispersed liquid crystal elastomers, novel composite materials that eliminate this difficulty. Their thermal shape memory anisotropy is imprinted by curing in external magnetic field, providing for conventional moulding of macroscopically sized soft, thermomechanically active elastic objects of general shapes. The binary soft-soft composition of isotropic elastomer matrix, filled with freeze-fracture-fabricated, oriented liquid crystal elastomer microparticles as colloidal inclusions, allows for fine-tuning of thermal morphing behaviour. This is accomplished by adjusting the concentration, spatial distribution and orientation of microparticles or using blends of microparticles with different thermomechanical characteristics. We demonstrate that any Gaussian thermomechanical deformation mode (bend, cup, saddle, left and right twist) of a planar sample, as well as beat-like actuation, is attainable with bilayer microparticle configurations. PMID:27713478

  16. Dispersive suspended microextraction.

    PubMed

    Yang, Zhong-Hua; Liu, Yu; Lu, Yue-Le; Wu, Tong; Zhou, Zhi-Qiang; Liu, Dong-Hui

    2011-11-14

    A novel sample pre-treatment technique termed dispersive suspended microextraction (DSME) coupled with gas chromatography-flame photometric detection (GC-FPD) has been developed for the determination of eight organophosphorus pesticides (ethoprophos, malathion, chlorpyrifos, isocarbophos, methidathion, fenamiphos, profenofos, triazophos) in aqueous samples. In this method, both extraction and two phases' separation process were performed by the assistance of magnetic stirring. After separating the two phases, 1 μL of the suspended phase was injected into GC for further instrument analysis. Varieties of experiment factors which could affect the experiment results were optimized and the following were selected: 12.0 μL p-xylene was selected as extraction solvent, extraction speed was 1200 rpm, extraction time was 30 s, the restoration speed was 800 rpm, the restoration time was 8 min, and no salt was added. Under the optimum conditions, limits of detections (LODs) varied between 0.01 and 0.05 μg L(-1). The relative standard deviation (RSDs, n=6) ranged from 4.6% to 12.1%. The linearity was obtained by five points in the concentration range of 0.1-100.0 μg L(-1). Correlation coefficients (r) varied from 0.9964 to 0.9995. The enrichment factors (EFs) were between 206 and 243. In the final experiment, the developed method has been successfully applied to the determination of organophosphorus pesticides in wine and tap water samples and the obtained recoveries were between 83.8% and 101.3%. Compared with other pre-treatment methods, DSME has its own features and could achieve satisfied results for the analysis of trace components in complicated matrices.

  17. Migration of dispersive GPR data

    USGS Publications Warehouse

    Powers, M.H.; Oden, C.P.; ,

    2004-01-01

    Electrical conductivity and dielectric and magnetic relaxation phenomena cause electromagnetic propagation to be dispersive in earth materials. Both velocity and attenuation may vary with frequency, depending on the frequency content of the propagating energy and the nature of the relaxation phenomena. A minor amount of velocity dispersion is associated with high attenuation. For this reason, measuring effects of velocity dispersion in ground penetrating radar (GPR) data is difficult. With a dispersive forward model, GPR responses to propagation through materials with known frequency-dependent properties have been created. These responses are used as test data for migration algorithms that have been modified to handle specific aspects of dispersive media. When either Stolt or Gazdag migration methods are modified to correct for just velocity dispersion, the results are little changed from standard migration. For nondispersive propagating wavefield data, like deep seismic, ensuring correct phase summation in a migration algorithm is more important than correctly handling amplitude. However, the results of migrating model responses to dispersive media with modified algorithms indicate that, in this case, correcting for frequency-dependent amplitude loss has a much greater effect on the result than correcting for proper phase summation. A modified migration is only effective when it includes attenuation recovery, performing deconvolution and migration simultaneously.

  18. Wave-equation dispersion inversion

    NASA Astrophysics Data System (ADS)

    Li, Jing; Feng, Zongcai; Schuster, Gerard

    2017-03-01

    We present the theory for wave-equation inversion of dispersion curves, where the misfit function is the sum of the squared differences between the wavenumbers along the predicted and observed dispersion curves. The dispersion curves are obtained from Rayleigh waves recorded by vertical-component geophones. Similar to wave-equation traveltime tomography, the complicated surface wave arrivals in traces are skeletonized as simpler data, namely the picked dispersion curves in the phase-velocity and frequency domains. Solutions to the elastic wave equation and an iterative optimization method are then used to invert these curves for 2-D or 3-D S-wave velocity models. This procedure, denoted as wave-equation dispersion inversion (WD), does not require the assumption of a layered model and is significantly less prone to the cycle-skipping problems of full waveform inversion. The synthetic and field data examples demonstrate that WD can approximately reconstruct the S-wave velocity distributions in laterally heterogeneous media if the dispersion curves can be identified and picked. The WD method is easily extended to anisotropic data and the inversion of dispersion curves associated with Love waves.

  19. Programmable colloidal molecules from sequential capillarity-assisted particle assembly

    PubMed Central

    Ni, Songbo; Leemann, Jessica; Buttinoni, Ivo; Isa, Lucio; Wolf, Heiko

    2016-01-01

    The assembly of artificial nanostructured and microstructured materials which display structures and functionalities that mimic nature’s complexity requires building blocks with specific and directional interactions, analogous to those displayed at the molecular level. Despite remarkable progress in synthesizing “patchy” particles encoding anisotropic interactions, most current methods are restricted to integrating up to two compositional patches on a single “molecule” and to objects with simple shapes. Currently, decoupling functionality and shape to achieve full compositional and geometrical programmability remains an elusive task. We use sequential capillarity-assisted particle assembly which uniquely fulfills the demands described above. This is a new method based on simple, yet essential, adaptations to the well-known capillary assembly of particles over topographical templates. Tuning the depth of the assembly sites (traps) and the surface tension of moving droplets of colloidal suspensions enables controlled stepwise filling of traps to “synthesize” colloidal molecules. After deposition and mechanical linkage, the colloidal molecules can be dispersed in a solvent. The template’s shape solely controls the molecule’s geometry, whereas the filling sequence independently determines its composition. No specific surface chemistry is required, and multifunctional molecules with organic and inorganic moieties can be fabricated. We demonstrate the “synthesis” of a library of structures, ranging from dumbbells and triangles to units resembling bar codes, block copolymers, surfactants, and three-dimensional chiral objects. The full programmability of our approach opens up new directions not only for assembling and studying complex materials with single-particle-level control but also for fabricating new microscale devices for sensing, patterning, and delivery applications. PMID:27051882

  20. Programmable colloidal molecules from sequential capillarity-assisted particle assembly.

    PubMed

    Ni, Songbo; Leemann, Jessica; Buttinoni, Ivo; Isa, Lucio; Wolf, Heiko

    2016-04-01

    The assembly of artificial nanostructured and microstructured materials which display structures and functionalities that mimic nature's complexity requires building blocks with specific and directional interactions, analogous to those displayed at the molecular level. Despite remarkable progress in synthesizing "patchy" particles encoding anisotropic interactions, most current methods are restricted to integrating up to two compositional patches on a single "molecule" and to objects with simple shapes. Currently, decoupling functionality and shape to achieve full compositional and geometrical programmability remains an elusive task. We use sequential capillarity-assisted particle assembly which uniquely fulfills the demands described above. This is a new method based on simple, yet essential, adaptations to the well-known capillary assembly of particles over topographical templates. Tuning the depth of the assembly sites (traps) and the surface tension of moving droplets of colloidal suspensions enables controlled stepwise filling of traps to "synthesize" colloidal molecules. After deposition and mechanical linkage, the colloidal molecules can be dispersed in a solvent. The template's shape solely controls the molecule's geometry, whereas the filling sequence independently determines its composition. No specific surface chemistry is required, and multifunctional molecules with organic and inorganic moieties can be fabricated. We demonstrate the "synthesis" of a library of structures, ranging from dumbbells and triangles to units resembling bar codes, block copolymers, surfactants, and three-dimensional chiral objects. The full programmability of our approach opens up new directions not only for assembling and studying complex materials with single-particle-level control but also for fabricating new microscale devices for sensing, patterning, and delivery applications.

  1. Making programmable BMS safe and reliable

    SciTech Connect

    Cusimano, J.A.

    1995-12-01

    Burner management systems ensure safe admission of fuel to the furnace and prevent explosions. This article describes how programmable control systems can be every bit as safe and reliable as hardwired or standard programmable logic controller-based designs. High-pressure boilers are required by regulatory agencies and insurance companies alike to be equipped with a burner management system (BMS) to ensure safe admission of fuel to the furnace and to prevent explosions. These systems work in parallel with, but independently of, the combustion and feedwater control systems that start up, monitor, and shut down burners and furnaces. Safety and reliability are the fundamental requirements of a BMS. Programmable control system for BMS applications are now available that incorporate high safety and reliability into traditional microprocessor-based designs. With one of these control systems, a qualified systems engineer applying relevant standards, such as the National Fire Protection Assn (NFPA) 85 series, can design and implement a superior BMS.

  2. The SAS-3 programmable telemetry system

    NASA Technical Reports Server (NTRS)

    Peterson, M. R.

    1975-01-01

    Basic concept, system design and operation principles of the telemetry system developed for the Small Astronomy Satellite-3 (SAS-3) are analyzed. The concept of programmable format selected for the SAS-3 represents an optical combination of the fixed format system of SAS-1 and SAS-2, and the adaptive format concept. The programmable telemetry system permits a very wide range of changes in the data sampling order by a ground control station, depending on the experimental requirements, so that the maximal amount of useful data can be returned from orbit. The programmable system also allows the data format to differ from one spacecraft to another without changing hardware. Attention is given to the command requirements and redundancy of the SAS-3 telemetry system.

  3. Programmable DNA-Mediated Multitasking Processor.

    PubMed

    Shu, Jian-Jun; Wang, Qi-Wen; Yong, Kian-Yan; Shao, Fangwei; Lee, Kee Jin

    2015-04-30

    Because of DNA appealing features as perfect material, including minuscule size, defined structural repeat and rigidity, programmable DNA-mediated processing is a promising computing paradigm, which employs DNAs as information storing and processing substrates to tackle the computational problems. The massive parallelism of DNA hybridization exhibits transcendent potential to improve multitasking capabilities and yield a tremendous speed-up over the conventional electronic processors with stepwise signal cascade. As an example of multitasking capability, we present an in vitro programmable DNA-mediated optimal route planning processor as a functional unit embedded in contemporary navigation systems. The novel programmable DNA-mediated processor has several advantages over the existing silicon-mediated methods, such as conducting massive data storage and simultaneous processing via much fewer materials than conventional silicon devices.

  4. Implementing neural nets with programmable logic

    NASA Technical Reports Server (NTRS)

    Vidal, Jacques J.

    1988-01-01

    Networks of Boolean programmable logic modules are presented as one purely digital class of artificial neural nets. The approach contrasts with the continuous analog framework usually suggested. Programmable logic networks are capable of handling many neural-net applications. They avoid some of the limitations of threshold logic networks and present distinct opportunities. The network nodes are called dynamically programmable logic modules. They can be implemented with digitally controlled demultiplexers. Each node performs a Boolean function of its inputs which can be dynamically assigned. The overall network is therefore a combinational circuit and its outputs are Boolean global functions of the network's input variables. The approach offers definite advantages for VLSI implementation, namely, a regular architecture with limited connectivity, simplicity of the control machinery, natural modularity, and the support of a mature technology.

  5. Radiation Effects on Current Field Programmable Technologies

    NASA Technical Reports Server (NTRS)

    Katz, R.; LaBel, K.; Wang, J. J.; Cronquist, B.; Koga, R.; Penzin, S.; Swift, G.

    1997-01-01

    Manufacturers of field programmable gate arrays (FPGAS) take different technological and architectural approaches that directly affect radiation performance. Similar y technological and architectural features are used in related technologies such as programmable substrates and quick-turn application specific integrated circuits (ASICs). After analyzing current technologies and architectures and their radiation-effects implications, this paper includes extensive test data quantifying various devices total dose and single event susceptibilities, including performance degradation effects and temporary or permanent re-configuration faults. Test results will concentrate on recent technologies being used in space flight electronic systems and those being developed for use in the near term. This paper will provide the first extensive study of various configuration memories used in programmable devices. Radiation performance limits and their impacts will be discussed for each design. In addition, the interplay between device scaling, process, bias voltage, design, and architecture will be explored. Lastly, areas of ongoing research will be discussed.

  6. The Schome Park Programme: Exploring Educational Alternatives

    NASA Astrophysics Data System (ADS)

    Twining, Peter; Footring, Shri

    The Schome Park Programme set out to extend thinking about what the education system for the information age (Schome) should be like. The first three phases of the programme spanned 13 months and involved the use of Schome Park, our "closed" island(s) in Teen Second LifeTM (TSL) virtual world alongside a wiki and forum. During this time approximately two hundred 13-17 year olds and around 50 adults were given access to Schome Park. Having explained the context in which this work took place the paper outlines the initial educational design underpinning the programme and describes some of the activities which took place. It goes on to explore some dimensions of practice which emerged from the data analysis towards the end of Phase 3, focusing on learner experiences of experimentation, playfulness, curriculum, choice, participation and the expression of the learner voice.

  7. Sellafield Decommissioning Programme - Update and Lessons Learned

    SciTech Connect

    Lutwyche, P. R.; Challinor, S. F.

    2003-02-24

    The Sellafield site in North West England has over 240 active facilities covering the full nuclear cycle from fuel manufacture through generation, reprocessing and waste treatment. The Sellafield decommissioning programme was formally initiated in the mid 1980s though several plants had been decommissioned prior to this primarily to create space for other plants. Since the initiation of the programme 7 plants have been completely decommissioned, significant progress has been made in a further 16 and a total of 56 major project phases have been completed. This programme update will explain the decommissioning arrangements and strategies and illustrate the progress made on a number of the plants including the Windscale Pile Chimneys, the first reprocessing plan and plutonium plants. These present a range of different challenges and requiring approaches from fully hands on to fully remote. Some of the key lessons learned will be highlighted.

  8. Evaluating a nurse mentor preparation programme.

    PubMed

    Gray, Olivia; Brown, Donna

    Following the introduction of a regional nurse mentor preparation programme, research was undertaken within a health and social care trust to explore both the trainee mentors' and their supervisors' perception of this new programme. A qualitative study involving focus groups was undertaken. The focus groups comprised a total of twelve participants including five trainee mentors and seven supervisors (experienced mentors) who had recently completed a mentor preparation programme. Data were analysed using Braun and Clarke's thematic analysis. Three themes were identified from the data: personal investment (including the emotional impact of mentoring) contextual perceptions (environmental factors such as time) and intellectual facets (related to personal and professional growth). Comprehensive preparation for mentors appears to be effective in developing mentors with the ability to support nursing students in practice. However, further study is required to explore how to support mentors to balance the demands of the mentoring role with the delivery of patient care.

  9. Antibiotic stewardship programmes and the surgeon's role.

    PubMed

    Çakmakçi, M

    2015-04-01

    Inappropriate antibiotic use is a frequent occurrence, especially in surgical units. Among the unnecessary costs of such usage are unfavourable outcomes for patients and the emergence and spread of resistant bacteria. Antibiotic stewardship programmes aim to limit the spread of antibiotic resistance by promoting thoughtful prescribing of antibiotics. Such programmes usually try to control inappropriate use of antibiotics; to optimize the choice of drug, dosing, route, and duration of therapy; to maximize clinical cure or prevention of infection; and to limit unwanted effects and excess cost. In this paper, I discuss the impact of improper use of antibiotics and outline why I believe that antibiotic stewardship is likely to be the best way of dealing with it. Engagement of surgeons in antibiotic stewardship programmes is crucial to their success.

  10. Velocity Dispersions Across Bulge Types

    SciTech Connect

    Fabricius, Maximilian; Bender, Ralf; Hopp, Ulrich; Saglia, Roberto; Drory, Niv; Fisher, David

    2010-06-08

    We present first results from a long-slit spectroscopic survey of bulge kinematics in local spiral galaxies. Our optical spectra were obtained at the Hobby-Eberly Telescope with the LRS spectrograph and have a velocity resolution of 45 km/s (sigma*), which allows us to resolve the velocity dispersions in the bulge regions of most objects in our sample. We find that the velocity dispersion profiles in morphological classical bulge galaxies are always centrally peaked while the velocity dispersion of morphologically disk-like bulges stays relatively flat towards the center--once strongly barred galaxies are discarded.

  11. Dispersion in photonic crystals

    NASA Astrophysics Data System (ADS)

    Witzens, Jeremy

    2005-11-01

    Investigations on the dispersive properties of photonic crystals, modified scattering in ring-resonators, monolithic integration of vertical-cavity surface-emitting lasers and advanced data processing techniques for the finite-difference time-domain method are presented. Photonic crystals are periodic mesoscopic arrays of scatterers that modify the propagation properties of electromagnetic waves in a similar way as "natural" crystals modify the properties of electrons in solid-state physics. In this thesis photonic crystals are implemented as planar photonic crystals, i.e., optically thin semiconductor films with periodic arrays of holes etched into them, with a hole-to-hole spacing of the order of the wavelength of light in the dielectric media. Photonic crystals can feature forbidden frequency ranges (the band-gaps) in which light cannot propagate. Even though most work on photonic crystals has focused on these band-gaps for application such as confinement and guiding of light, this thesis focuses on the allowed frequency regions (the photonic bands) and investigates how the propagation of light is modified by the crystal lattice. In particular the guiding of light in bulk photonic crystals in the absence of lattice defects (the self-collimation effect) and the angular steering of light in photonic crystals (the superprism effect) are investigated. The latter is used to design a planar lightwave circuit for frequency domain demultiplexion. Difficulties such as efficient insertion of light into the crystal are resolved and previously predicted limitations on the resolution are circumvented. The demultiplexer is also fabricated and characterized. Monolithic integration of vertical-cavity surface-emitting lasers by means of resonantly enhanced grating couplers is investigated. The grating coupler is designed to bend light through a ninety-degree angle and is characterized with the finite-difference time-domain method. The vertical-cavity surface-emitting lasers are

  12. Adapting Nepal’s polio eradication programme

    PubMed Central

    Paudel, Krishna P; Hampton, Lee M; Bohara, Rajendra; Rai, Indra K; Anaokar, Sameer; Swift, Rachel D; Cochi, Stephen

    2017-01-01

    Abstract Problem Many countries have weak disease surveillance and immunization systems. The elimination of polio creates an opportunity to use staff and assets from the polio eradication programme to control other vaccine-preventable diseases and improve disease surveillance and immunization systems. Approach In 2003, the active surveillance system of Nepal’s polio eradication programme began to report on measles and neonatal tetanus cases. Japanese encephalitis and rubella cases were added to the surveillance system in 2004. Staff from the programme aided the development and implementation of government immunization policies, helped launch vaccination campaigns, and trained government staff in reporting practices and vaccine management. Local setting Nepal eliminated indigenous polio in 2000, and controlled outbreaks caused by polio importations between 2005 and 2010. Relevant changes In 2014, the surveillance activities had expanded to 299 sites, with active surveillance for measles, rubella and neonatal tetanus, including weekly visits from 15 surveillance medical officers. Sentinel surveillance for Japanese encephalitis consisted of 132 sites. Since 2002, staff from the eradication programme have helped to introduce six new vaccines and helped to secure funding from Gavi, the Vaccine Alliance. Staff have also assisted in responding to other health events in the country. Lesson learnt By expanding the activities of its polio eradication programme, Nepal has improved its surveillance and immunization systems and increased vaccination coverage of other vaccine-preventable diseases. Continued donor support, a close collaboration with the Expanded Programme on Immunization, and the retention of the polio eradication programme’s skilled workforce were important for this expansion. PMID:28250536

  13. An update on EUMETSAT programmes and plans

    NASA Astrophysics Data System (ADS)

    Klaes, K. Dieter; Holmlund, Kenneth

    2016-09-01

    EUMETSAT is providing space based observations for operational meteorology and climate monitoring. The observations are measured by geostationary and sun-synchronous polar orbiting satellites in the frame of mandatory programmes. In the frame of optional programmes further observations for altimetry and oceanography are collected and disseminated. In the frame of third party programmes, EUMETSAT makes available data from other agencies' satellites to the user community. Since summer 2015 MSG-4 complements the current operational fleet of operational geostationary spacecraft, Meteosat-7, which is the last satellite of the first generation and the three satellites of the Second Generation of Meteosat, Meteosat-8, Meteosat-9 and Meteosat-10. MSG-4 became Meteosat-11 and was stored in orbit after successful commissioning. Two satellites of the EUMETSAT Polar System (EPS) provide data from sunsynchronous polar orbit. Metop-B, the second of a series of three satellites, launched in September 2012 and Metop-A, the first of the series, in orbit since October 2006 provide operational services. The satellites belong to the Initial Joint Polar System (IJPS) with the US. EUMETSAT's first optional programme continues to provide data from the Jason-2 satellite since summer 2008. As follow on the Jason-3 satellite was launched in January 2016 and is currently in commissioning. To assure continuity development of Meteosat Third Generation (MTG) is ongoing. The EPS-SG programme was fully approved in summer 2015. In the frame of the Copernicus Programme (formerly GMES (Global Monitoring for Environment and Security)) EUMETSAT will operate the marine part of the Sentinel-3 satellite. It was launched in February 2016 and is currently under commissioning.

  14. What promotes sustainability in Safe Community programmes?

    PubMed Central

    Nordqvist, Cecilia; Timpka, Toomas; Lindqvist, Kent

    2009-01-01

    Background The theory and practice of safety promotion has traditionally focused on the safety of individuals. This study also includes systems, environments, and organizations. Safety promotion programmes are designed to support community health initiatives taking a bottom-up approach. This is a long-term and complex process. The aim of this study was to try to empirically identify factors that promote sustainability in the structures of programmes that are managed and coordinated by the local government. Methods Four focus group sessions with local government politicians and administrators in designated Safe Communities were conducted and analyzed using qualitative content analysis. Results Collaboration was found to be the basis for sustainability. Networks, enabling municipalities to exchange ideas, were reported to positively influence the programmes. Personal contacts rather than organizations themselves, determine whether collaboration is sustained. Participants reported an increase in cross-disciplinary collaboration among staff categories. Administrators and politicians were reported to collaborate well, which was perceived to speed up decision-making and thus to facilitate the programme work. Support from the politicians and the county council was seen as a prerequisite. Participants reported an increased willingness to share information between units, which, in their view, supports sustainability. A structure in which all local authorities' offices were located in close proximity to one another was considered to support collaboration. Appointing a public health coordinator responsible for the programme was seen as a way to strengthen the relational resources of the programme. Conclusion With a public health coordinator, the 'external' negotiating power was concentrated in one person. Also, the 'internal' programme strength increased when the coordination was based on a bureaucratic function rather than on one individual. Increased relational resources

  15. Nurses' views on workplace wellbeing programmes.

    PubMed

    Wright, Nicola; Zakarin, Melissa; Blake, Holly

    2016-11-24

    Workplace stress is prevalent among nurses. Healthcare employers have implemented complementary and alternative therapies (CATs) for relaxation and stress management within workplace wellbeing programmes. In-depth interviews were conducted with 12 registered nurses to explore the perceptions and experiences of nurses towards accessing CATs in and outside the workplace. Interviews were audio recorded and transcribed verbatim. Data were analysed using conventional, qualitative thematic techniques. Themes identified were 'perceptions of complementary and alternative therapies for stress management' and 'engagement with workplace wellness schemes'. CATs have a role within workplace wellbeing programmes and nurses are not averse to accessing them, although there are barriers to access that need to be addressed.

  16. Developing an online programme in computational biology.

    PubMed

    Vincent, Heather M; Page, Christopher

    2013-11-01

    Much has been written about the need for continuing education and training to enable life scientists and computer scientists to manage and exploit the different types of biological data now becoming available. Here we describe the development of an online programme that combines short training courses, so that those who require an educational programme can progress to complete a formal qualification. Although this flexible approach fits the needs of course participants, it does not fit easily within the organizational structures of a campus-based university.

  17. Overview of the National Centralized Tokamak programme

    NASA Astrophysics Data System (ADS)

    Kikuchi, M.; Tamai, H.; Matsukawa, M.; Fujita, T.; Takase, Y.; Sakurai, S.; Kizu, K.; Tsuchiya, K.; Kurita, G.; Morioka, A.; Hayashi, N.; Miura, Y.; Itoh, S.; Bialek, J.; Navratil, G.; Ikeda, Y.; Fujii, T.; Kurihara, K.; Kubo, H.; Kamada, Y.; Miya, N.; Suzuki, T.; Hamamatsu, K.; Kawashima, H.; Kudo, Y.; Masaki, K.; Takahashi, H.; Takechi, M.; Akiba, M.; Okuno, K.; Ishida, S.; Ichimura, M.; Imai, T.; Hashizume; Miura, Y. M.; Horiike, H.; Kimura, A.; Tsutsui, H.; Matsuoka, M.; Uesugi, Y.; Sagara, A.; Nishimura, A.; Shimizu, A.; Sakamoto, M.; Nakamura, K.; Sato, K.; Okano, K.; Ida, K.; Shimada, H. R.; Kishimoto, Y.; Azechi, H.; Tanaka, S.; Yatsu, K.; Yoshida, N.; Inutake, M.; Fujiwara, M.; Inoue, N.; Hosogane, N.; Kuriyama, M.; Ninomiya, H.

    2006-03-01

    An overview is given of the National Centralized Tokamak (NCT) programme as a research programme for advanced tokamak research to succeed JT-60U. The mission of NCT is to establish high beta steady-state operation for DEMO and to contribute to ITER. The machine flexibility is pursued in aspect ratio and shape controllability for the demonstration of the high-β steady-state, feedback control of resistive wall modes, wide current and pressure profile control capability and also very long pulse steady-state operation. Existing JT-60 infrastructure such as the heating and current drive system, power supplies and cooling systems will be best utilized for this modification.

  18. A programmable interface to neuromolecular computing networks.

    PubMed

    Akingbehin, K

    1995-01-01

    A programmable interface is provided to a simulated network of reaction-diffusion neurons. The interface allows special 'learn' and 'decide' syntactic constructs to be intermixed with conventional programming constructs. This hybrid combination allows the power of programmability to be combined with the power of adaptability to provide innovative solutions to complex problems. The network uses reaction-diffusion neurons instead of adaline neurons. A mesh topology is used instead of a feedforward topology. The performance of the mesh reaction-diffusion network compares favorably with that of conventional feedforward adaline networks. Enhancements to incorporate short- and long-term memory are described.

  19. Asphaltene dispersants as demulsification aids

    SciTech Connect

    Manek, M.B.

    1995-11-01

    Destabilization of petroleum asphaltenes may cause a multitude of problems in crude oil recovery and production. One major problem is their agglomeration at the water-oil interface of crude oil emulsions. Once agglomeration occurs, destabilized asphaltenes can form a thick pad in the dehydration equipment, which significantly reduces the demulsification rate. Certain polymeric dispersants increase asphaltene solubilization in hydrocarbon media, and when used in conjunction with emulsion breakers, facilitate the demulsification process. Two case studies are presented that demonstrate how asphaltene dispersants can efficiently inhibit pad formation and help reduce demulsifier dosage. Criteria for dispersant application and selection are discussed, which include the application of a novel laboratory technique to assess asphaltene stabilization in the crude oil. The technique monitors asphaltene agglomeration while undergoing titration with an incompatible solvent (precipitant). The method was used to evaluate stabilization of asphaltenes in the crude oil and to screen asphaltene dispersants.

  20. Dispersion coefficients for coastal regions

    SciTech Connect

    MacRae, B.L.; Kaleel, R.J.; Shearer, D.L.

    1983-03-01

    The Nuclear Regulatory Commission (NRC) has undertaken an extensive atmospheric dispersion research and measurement program from which it is intended will emerge improved predictive techniques for employment in licensing decisions and for emergency planning and response. Through this program the NRC has conducted field measurement programs over a wide range of geographic and topographic locations, and are using the acquired tracer and meteorological measurements to evaluate existing dispersion models and prediction techniques, and to develop new techniques when necessary.