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Sample records for polarization-based balanced heterodyne

  1. Polarization shaping in the mid-IR and polarization-based balanced heterodyne detection with application to 2D IR spectroscopy

    PubMed Central

    Middleton, Chris T.; Strasfeld, David B.; Zanni, Martin T.

    2010-01-01

    We demonstrate amplitude, phase and polarization shaping of femtosecond mid-IR pulses using a germanium acousto-optical modulator by independently shaping the frequency-dependent amplitudes and phases of two orthogonally polarized pulses which are then collinearly overlapped using a wire-grid polarizer. We use a feedback loop to set and stabilize the relative phase of the orthogonal pulses. We have also used a wire-grid polarizer to implement polarization-based balanced heterodyne detection for improved signal-to-noise of 2D IR spectra collected in a pump-probe geometry. Applications include coherent control of molecular vibrations and improvements in multidimensional IR spectroscopy. PMID:19687931

  2. Beam-splitting ratio impact on the SNR for the balanced heterodyne

    NASA Astrophysics Data System (ADS)

    Jin, Lumei; Zhu, YongGuo

    2016-05-01

    Considered the beam-splitting ratio, the mathematical model of balanced heterodyne receiver is established, and the mathematical expression of the relationship between the signal-to-noise ratio and the beam-splitting ratio is obtained. Based on the experiment, we got the best range of beam-splitting ratio which is 0.159-0.5. The experiment results show that, in the framework of the best beam-splitting ratio, the balanced heterodyne receiver has better signal-to-noise ratio than the common heterodyne receiver.

  3. An Integrated Balanced Superconductor-Insulator-Superconductor Heterodyne Mixer on a Silicon Membrane

    NASA Astrophysics Data System (ADS)

    Westig, M. P.; Jacobs, K.; Schultz, M.; Justen, M.; Stutzki, J.; Honingh, C. E.

    2011-03-01

    We have designed and fabricated a 380-520 GHz integrated balanced NbAlAlOxNb superconductor-insulator-superconductor (SIS) heterodyne waveguide mixer for submillimeter astrophysics. The response of the mixer measured with a Fourier transform spectrometer shows excellent agreement with the design. The novelty of our device is that we deposit the complete superconducting mixer circuit (tapered slotline antennas, hybrid coupler, MIM capacitors, SIS junctions, tuning circuits and blocking filters) on top of a 9 μ m silicon membrane. The membrane is held suspended in a waveguide by 2.5 μ m thick gold plated beamleads. We will show that silicon membrane technology and a thorough device design render the integration of SIS devices with larger circuits feasible. This is an important step towards large arrays of mixers. When using an appropriate superconductor technology, these devices are scalable to higher frequencies. We will present the design, fabrication results and first results of heterodyne measurements.

  4. Optical heterodyne accelerometry: passively stabilized, fully balanced velocity interferometer system for any reflector

    SciTech Connect

    Buttler, William T.; Lamoreaux, Steven K.

    2010-08-10

    We formalize the physics of an optical heterodyne accelerometer that allows measurement of low and high velocities from material surfaces under high strain. The proposed apparatus incorporates currently common optical velocimetry techniques used in shock physics, with interferometric techniques developed to self-stabilize and passively balance interferometers in quantum cryptography. The result is a robust telecom-fiber-based velocimetry system insensitive to modal and frequency dispersion that should work well in the presence of decoherent scattering processes, such as from ejecta clouds and shocked surfaces.

  5. Polarization-based balanced detection for spectral-domain optical coherence tomography.

    PubMed

    Black, Adam J; Akkin, Taner

    2015-08-20

    We present a new design for spectral-domain optical coherence tomography that allows balanced detection using a single camera. The design uses polarization optics to encode the light in reference and sample arms. Two parallel and highly aligned spectra, which carry out-of-phase interference signals, in-phase common noise, and auto-interference terms, are focused on the camera, which performs the digital balanced detection for each wavelength. The optical system is characterized and tested for tissue imaging. Results demonstrate consistent signal gains in depth and suppression of DC and sample auto-interference. The design could be further amended for polarization-sensitive imaging and might demonstrate a market for manufacturing dual-line cameras with analog-balanced detection capability. PMID:26368760

  6. Spatially-Heterodyned Holography

    SciTech Connect

    Thomas, Clarence E; Hanson, Gregory R

    2006-02-21

    A method of recording a spatially low-frequency heterodyne hologram, including spatially heterodyne fringes for Fourier analysis, includes: splitting a laser beam into a reference beam and an object beam; interacting the object beam with an object; focusing the reference beam and the object beam at a focal plane of a digital recorder to form a spatially low-frequency heterodyne hologram including spatially heterodyne fringes for Fourier analysis; digital recording the spatially low-frequency heterodyne hologram; Fourier transforming axes of the recorded spatially low-frequency heterodyne hologram including spatially heterodyne fringes in Fourier space to sit on top of a heterodyne carrier frequency defined by an angle between the reference beam and the object beam; cutting off signals around an origin; and performing an inverse Fourier transform.

  7. Heterodyne laser spectroscopy system

    DOEpatents

    Wyeth, Richard W.; Paisner, Jeffrey A.; Story, Thomas

    1990-01-01

    A heterodyne laser spectroscopy system utilizes laser heterodyne techniques for purposes of laser isotope separation spectroscopy, vapor diagnostics, processing of precise laser frequency offsets from a reference frequency, and provides spectral analysis of a laser beam.

  8. Heterodyne laser spectroscopy system

    DOEpatents

    Wyeth, Richard W.; Paisner, Jeffrey A.; Story, Thomas

    1989-01-01

    A heterodyne laser spectroscopy system utilizes laser heterodyne techniques for purposes of laser isotope separation spectroscopy, vapor diagnostics, processing of precise laser frequency offsets from a reference frequency and the like, and provides spectral analysis of a laser beam.

  9. An optical heterodyne densitometer

    NASA Technical Reports Server (NTRS)

    Migdall, A. L.; Zheng, Ying Cong; Hardis, J.; Snyder, J. J.

    1988-01-01

    Researchers are developing an optical heterodyne densitometer with the potential to measure optical density over an unprecedented dynamic range with high accuracy and sensitivity. This device uses a Mach-Zender interferometer configuration with heterodyne detection to make direct comparisons between optical and RF attenuators. Researchers expect to attain measurements of filter transmittance down to 10 to the minus 12th power with better than 1 percent uncertainty. In addition, they intend to extend the technique to the problem of measuring low levels of light scattering from reflective and transmissive optics.

  10. Heterodyne laser diagnostic system

    DOEpatents

    Globig, Michael A.; Johnson, Michael A.; Wyeth, Richard W.

    1990-01-01

    The heterodyne laser diagnostic system includes, in one embodiment, an average power pulsed laser optical spectrum analyzer for determining the average power of the pulsed laser. In another embodiment, the system includes a pulsed laser instantaneous optical frequency measurement for determining the instantaneous optical frequency of the pulsed laser.

  11. Submillimeter wave heterodyne receiver

    NASA Technical Reports Server (NTRS)

    Chattopadhyay, Goutam (Inventor); Manohara, Harish (Inventor); Siegel, Peter H. (Inventor); Ward, John (Inventor)

    2011-01-01

    In an embodiment, a submillimeter wave heterodyne receiver includes a finline ortho-mode transducer comprising thin tapered metallic fins deposited on a thin dielectric substrate to separate a vertically polarized electromagnetic mode from a horizontally polarized electromagnetic mode. Other embodiments are described and claimed.

  12. Heterodyne Interferometer Angle Metrology

    NASA Technical Reports Server (NTRS)

    Hahn, Inseob; Weilert, Mark A.; Wang, Xu; Goullioud, Renaud

    2010-01-01

    A compact, high-resolution angle measurement instrument has been developed that is based on a heterodyne interferometer. The common-path heterodyne interferometer metrology is used to measure displacements of a reflective target surface. In the interferometer setup, an optical mask is used to sample the measurement laser beam reflecting back from a target surface. Angular rotations, around two orthogonal axes in a plane perpendicular to the measurement- beam propagation direction, are determined simultaneously from the relative displacement measurement of the target surface. The device is used in a tracking telescope system where pitch and yaw measurements of a flat mirror were simultaneously performed with a sensitivity of 0.1 nrad, per second, and a measuring range of 0.15 mrad at a working distance of an order of a meter. The nonlinearity of the device is also measured less than one percent over the measurement range.

  13. Integrated heterodyne terahertz transceiver

    DOEpatents

    Wanke, Michael C.; Lee, Mark; Nordquist, Christopher D.; Cich, Michael J.

    2012-09-25

    A heterodyne terahertz transceiver comprises a quantum cascade laser that is integrated on-chip with a Schottky diode mixer. A terahertz signal can be received by an antenna connected to the mixer, an end facet or sidewall of the laser, or through a separate active section that can amplify the incident signal. The quantum cascade laser couples terahertz local oscillator power to the Schottky diode to mix with the received terahertz signal to provide an intermediate frequency output signal. The fully integrated transceiver optimizes power efficiency, sensitivity, compactness, and reliability. The transceiver can be used in compact, fieldable systems covering a wide variety of deployable applications not possible with existing technology.

  14. Integrated heterodyne terahertz transceiver

    DOEpatents

    Lee, Mark; Wanke, Michael C.

    2009-06-23

    A heterodyne terahertz transceiver comprises a quantum cascade laser that is integrated on-chip with a Schottky diode mixer. An antenna connected to the Schottky diode receives a terahertz signal. The quantum cascade laser couples terahertz local oscillator power to the Schottky diode to mix with the received terahertz signal to provide an intermediate frequency output signal. The fully integrated transceiver optimizes power efficiency, sensitivity, compactness, and reliability. The transceiver can be used in compact, fieldable systems covering a wide variety of deployable applications not possible with existing technology.

  15. Velocimetry Using Heterodyne Techniques

    SciTech Connect

    Strand, O T; Berzins, L V; Goosman, D R; Kuhlow, W W; Sargis, P D; Whitworth, T L

    2004-08-10

    At LLNL, we have been using heterodyne techniques for the past year and a half to measure velocities up to several kilometers-per-second on different types of experiments. We assembled this diagnostic, which we call the Heterodyne Velocimeter (HetV), using commercially available products developed for the communications industry. We use a 1550 nm fiber laser and single mode fibers to deliver light to and from the target. The return Doppler-shifted light is mixed with the original laser light to generate a beat frequency proportional to the velocity. At a velocity of 1000 m/s, the beat signal has a frequency of 1.29 GHz. We record the beat signals directly onto fast digitizers. The maximum velocity is limited by the bandwidth of the electronics and the sampling rate of the digitizers. The record length is limited by the amount of memory contained in the digitizers. This paper describes our approach to measuring velocities with this technique and presents recent data obtained with the HetV.

  16. Integrated Optical Heterodyne Interferometer in Lithium Niobate

    NASA Astrophysics Data System (ADS)

    Rubiyanto, A.; Herrmann, H.; Ricken, R.; Tian, F.; Sohler, W.

    A high performance integrated acousto-optical heterodyne interferometer has been developed for vibration measurement. All components including an acousto-optical TE-TM mode converters, two electro-optical TE-TM converters, two polarization splitters and two phase shifters are integrated on a X-cut Lithium Niobate substrate. The fully packaged optical integrated circuit (optical-IC) coupling with three fibers optics pigtails gave a signal-to-noise ratio of 69 dB with at 3 kHz bandwidth by using a commercial DFB laser diode as a light source with 1561 nm emission wavelength and a PIN-FET balanced receiver.

  17. Digitally Enhanced Heterodyne Interferometry

    NASA Technical Reports Server (NTRS)

    Shaddock, Daniel; Ware, Brent; Lay, Oliver; Dubovitsky, Serge

    2010-01-01

    Spurious interference limits the performance of many interferometric measurements. Digitally enhanced interferometry (DEI) improves measurement sensitivity by augmenting conventional heterodyne interferometry with pseudo-random noise (PRN) code phase modulation. DEI effectively changes the measurement problem from one of hardware (optics, electronics), which may deteriorate over time, to one of software (modulation, digital signal processing), which does not. DEI isolates interferometric signals based on their delay. Interferometric signals are effectively time-tagged by phase-modulating the laser source with a PRN code. DEI improves measurement sensitivity by exploiting the autocorrelation properties of the PRN to isolate only the signal of interest and reject spurious interference. The properties of the PRN code determine the degree of isolation.

  18. Dove prism heterodyne refractometer

    NASA Astrophysics Data System (ADS)

    Hsu, Cheng-Chih; Lee, Chia-Yun; Chu, Kuan-Ho; Wu, Tsai-Chen

    2015-10-01

    In this study, we proposed an alternative method, integrating a Dove prism and precision circular heterodyne interferometry, for measuring the refractive index and concentration of sodium chloride and hydrogen peroxide solutions with low phase error. Due to the optical properties of the Dove prism, the test light undergoes total internal reflection (TIR) at the interface between the test sample and the prism. The light beam travels in and out of the Dove prism while maintaining the same direction. Therefore, only slight alignment is required, leading to only small errors in the phase and refractive index. In this study, the phase error, refractive index error, and resolution of the concentration are approximated to be 0.003°, 2×10-5, and 1×10-3 M, respectively. The proposed method has the advantages of a simple optical configuration, ease of operation, little alignment required, and high stability, and it allows for high-precision measurement of the refractive index and concentration of the liquid sample.

  19. Highspeed multiplexed heterodyne interferometry.

    PubMed

    Isleif, Katharina-S; Gerberding, Oliver; Köhlenbeck, Sina; Sutton, Andrew; Sheard, Benjamin; Goßler, Stefan; Shaddock, Daniel; Heinzel, Gerhard; Danzmann, Karsten

    2014-10-01

    Digitally enhanced heterodyne interferometry is a metrology technique that uses pseudo-random noise codes for modulating the phase of the laser light. Multiple interferometric signals from the same beam path can thereby be isolated based on their propagation delay, allowing one to use advantageous optical layouts in comparison to classic laser interferometers. We present here a high speed version of this technique for measuring multiple targets spatially separated by only a few centimetres. This allows measurements of multiplexed signals using free beams, making the technique attractive for several applications requiring compact optical set-ups like for example space-based interferometers. In an experiment using a modulation and sampling rate of 1.25 GHz we are able to demonstrate multiplexing between targets only separated by 36 cm and we achieve a displacement measurement noise floor of <3 pm/√Hz at 10 Hz between them. We identify a limiting excess noise at low frequencies which is unique to this technique and is probably caused by the finite bandwidth in our measurement set-up. Utilising an active clock jitter correction scheme we are also able to reduce this noise in a null measurement configuration by one order of magnitude. PMID:25322043

  20. Heterodyne systems and technology, part 1. [conferences

    NASA Technical Reports Server (NTRS)

    1980-01-01

    Various aspects of optical heterodyning are considered. Topics covered heterodyning throughout the electromagnetic spectrum including detectors, local oscillators, tunable diode lasers, astronomical systems, and environmental sensors, with both active and passive systems represented.

  1. BALANCE

    DOEpatents

    Carmichael, H.

    1953-01-01

    A torsional-type analytical balance designed to arrive at its equilibrium point more quickly than previous balances is described. In order to prevent external heat sources creating air currents inside the balance casing that would reiard the attainment of equilibrium conditions, a relatively thick casing shaped as an inverted U is placed over the load support arms and the balance beam. This casing is of a metal of good thernnal conductivity characteristics, such as copper or aluminum, in order that heat applied to one portion of the balance is quickly conducted to all other sensitive areas, thus effectively preventing the fornnation of air currents caused by unequal heating of the balance.

  2. Scanning Terahertz Heterodyne Imaging Systems

    NASA Technical Reports Server (NTRS)

    Siegel, Peter; Dengler, Robert

    2007-01-01

    Scanning terahertz heterodyne imaging systems are now at an early stage of development. In a basic scanning terahertz heterodyne imaging system, (see Figure 1) two far-infrared lasers generate beams denoted the local-oscillator (LO) and signal that differ in frequency by an amount, denoted the intermediate frequency (IF), chosen to suit the application. The LO beam is sent directly to a mixer as one of two inputs. The signal beam is focused to a spot on or in the specimen. After transmission through or reflection from the specimen, the beams are focused to a spot on a terahertz mixer, which extracts the IF outputs. The specimen is mounted on a translation stage, by means of which the focal spot is scanned across the specimen to build up an image.

  3. Concerning the Spatial Heterodyne Spectrometer.

    PubMed

    Lenzner, Matthias; Diels, Jean-Claude

    2016-01-25

    A modified Spatial Heterodyne Spectrometer (SHS) is used for measuring atomic emission spectra with high resolution. This device is basically a Fourier Transform Spectrometer, but the Fourier transform is taken in the directions perpendicular to the optical propagation and heterodyned around one preset wavelength. In recent descriptions of this device, one specific phenomenon - the tilt of the energy front of wave packets when diffracted from a grating - was neglected. This led to an overestimate of the resolving power of this spectrograph, especially in situations when the coherence length of the radiation under test is in the order of the effective aperture of the device. The limits of usability are shown here together with some measurements of known spectral lines. PMID:26832561

  4. Concerning the Spatial Heterodyne Spectrometer

    DOE PAGESBeta

    Lenzner, Matthias; Diels, Jean -Claude

    2016-01-22

    A modified Spatial Heterodyne Spectrometer (SHS) is used for measuring atomic emission spectra with high resolution. This device is basically a Fourier Transform Spectrometer, but the Fourier transform is taken in the directions perpendicular to the optical propagation and heterodyned around one preset wavelength. In recent descriptions of this device, one specific phenomenon - the tilt of the energy front of wave packets when diffracted from a grating - was neglected. This led to an overestimate of the resolving power of this spectrograph, especially in situations when the coherence length of the radiation under test is in the order ofmore » the effective aperture of the device. In conclusion, the limits of usability are shown here together with some measurements of known spectral lines.« less

  5. Modified Phasemeter for a Heterodyne Laser Interferometer

    NASA Technical Reports Server (NTRS)

    Loya, Frank M.

    2010-01-01

    Modifications have been made in the design of instruments of the type described in "Digital Averaging Phasemeter for Heterodyne Interferometry". A phasemeter of this type measures the difference between the phases of the unknown and reference heterodyne signals in a heterodyne laser interferometer. The phasemeter design lacked immunity to drift of the heterodyne frequency, was bandwidth-limited by computer bus architectures then in use, and was resolution-limited by the nature of field-programmable gate arrays (FPGAs) then available. The modifications have overcome these limitations and have afforded additional improvements in accuracy, speed, and modularity. The modifications are summarized.

  6. Remote sensing by infrared heterodyne spectroscopy

    NASA Technical Reports Server (NTRS)

    Kostiuk, T.; Mumma, M. J.

    1983-01-01

    The use of infrared heterodyne spectrocopy for the study of planetary atmospheres is discussed. Infrared heterodyne spectroscopy provides a convenient and sensitive method for measuring the true intensity profiles of atmospheric spectral lines. Application of radiative transfer theory to measured lineshapes can then permit the study of molecular abundances, temperatures, total pressures, excitation conditions, and dynamics of the regions of line formation. The theory of formation of atmospheric spectral lines and the retrieval of the information contained in these molecular lines is illustrated. Notable successes of such retrievals from infrared heterodyne measurements on Venus, Mars, Jupiter and the Earth are given. A discussion of developments in infrared heterodyne technology is also presented.

  7. Heterodyne laser instantaneous frequency measurement system

    DOEpatents

    Wyeth, Richard W.; Johnson, Michael A.; Globig, Michael A.

    1990-01-01

    A heterodyne laser instantaneous frequency measurement system is disclosed. The system utilizes heterodyning of a pulsed laser beam with a continuous wave laser beam to form a beat signal. The beat signal is processed by a controller or computer which determines both the average frequency of the laser pulse and any changes or chirp of the frequency during the pulse.

  8. Heterodyne laser instantaneous frequency measurement system

    DOEpatents

    Wyeth, Richard W.; Johnson, Michael A.; Globig, Michael A.

    1989-01-01

    A heterodyne laser instantaneous frequency measurement system is disclosed. The system utilizes heterodyning of a pulsed laser beam with a continuous wave laser beam to form a beat signal. The beat signal is processed by a controller or computer which determines both the average frequency of the laser pulse and any changes or chirp of th frequency during the pulse.

  9. Berkeley heterodyne interferometer. [for IR stellar observations

    NASA Technical Reports Server (NTRS)

    Betz, A.

    1975-01-01

    A prototype heterodyne stellar interferometer has been built in order to demonstrate the feasibility of heterodyne techniques in measuring angular diameters of bright infrared stars. The first system tests were performed in December 1972. Attention is given to investigations concerning the possibility that optical air turbulence within the structure of the solar telescope employed can possibly destroy the phase coherence of the fringe signals.

  10. Two-wavelength spatial-heterodyne holography

    DOEpatents

    Hanson, Gregory R.; Bingham, Philip R.; Simpson, John T.; Karnowski, Thomas P.; Voelkl, Edgar

    2007-12-25

    Systems and methods are described for obtaining two-wavelength differential-phase holograms. A method includes determining a difference between a filtered analyzed recorded first spatially heterodyne hologram phase and a filtered analyzed recorded second spatially-heterodyned hologram phase.

  11. Moire deflectometry with deferred electronic heterodyne readout

    NASA Technical Reports Server (NTRS)

    Stricker, J.

    1985-01-01

    The electronic heterodyne technique is applied to the task of deferred readout of phase objects' moire fringes. In combination with the heterodyne readout technique, moire deflectometry constitutes a powerful tool for the study of phase objects, exhibiting high sensitivity, ease of automation and recording, low cost, use of incoherent illumination, and independence from fringe contrast variations.

  12. Balancing

    NASA Astrophysics Data System (ADS)

    Harteveld, Casper

    At many occasions we are asked to achieve a “balance” in our lives: when it comes, for example, to work and food. Balancing is crucial in game design as well as many have pointed out. In games with a meaningful purpose, however, balancing is remarkably different. It involves the balancing of three different worlds, the worlds of Reality, Meaning, and Play. From the experience of designing Levee Patroller, I observed that different types of tensions can come into existence that require balancing. It is possible to conceive of within-worlds dilemmas, between-worlds dilemmas, and trilemmas. The first, the within-world dilemmas, only take place within one of the worlds. We can think, for example, of a user interface problem which just relates to the world of Play. The second, the between-worlds dilemmas, have to do with a tension in which two worlds are predominantly involved. Choosing between a cartoon or a realistic style concerns, for instance, a tension between Reality and Play. Finally, the trilemmas are those in which all three worlds play an important role. For each of the types of tensions, I will give in this level a concrete example from the development of Levee Patroller. Although these examples come from just one game, I think the examples can be exemplary for other game development projects as they may represent stereotypical tensions. Therefore, to achieve harmony in any of these forthcoming games, it is worthwhile to study the struggles we had to deal with.

  13. Experimental demonstration of coherent OCDMA using heterodyne detection.

    PubMed

    Yang, Yi; Petrillo, Keith G; Ting, Hong-Fu; Khurgin, Jacob B; Cooper, A Brinton; Foster, Mark A

    2013-07-01

    We present the first experimental demonstration of a practical, fully coherent, optical code division multiple access (OCDMA) scheme that can fully suppress multiple access interference (MAI) and speckle noise without phase locking or thresholding and gating. The scheme is sourced from an optical comb generator and uses spectral phase encoding and a heterodyne receiver with balanced detection. Here we present results for a four-user configuration at 50% load. At 4.5 Gbits/s per user, the system achieves a signal to MAI ratio of 648 at a bit error rate of 10(-7). PMID:23811925

  14. Heterodyne 3D ghost imaging

    NASA Astrophysics Data System (ADS)

    Yang, Xu; Zhang, Yong; Yang, Chenghua; Xu, Lu; Wang, Qiang; Zhao, Yuan

    2016-06-01

    Conventional three dimensional (3D) ghost imaging measures range of target based on pulse fight time measurement method. Due to the limit of data acquisition system sampling rate, range resolution of the conventional 3D ghost imaging is usually low. In order to take off the effect of sampling rate to range resolution of 3D ghost imaging, a heterodyne 3D ghost imaging (HGI) system is presented in this study. The source of HGI is a continuous wave laser instead of pulse laser. Temporal correlation and spatial correlation of light are both utilized to obtain the range image of target. Through theory analysis and numerical simulations, it is demonstrated that HGI can obtain high range resolution image with low sampling rate.

  15. Remote sensing by IR heterodyne spectroscopy

    NASA Technical Reports Server (NTRS)

    Kostiuk, T.; Mumma, M. J.

    1983-01-01

    The use of infrared heterodyne spectroscopy for the study of planetary atmospheres is discussed. Infrared heterodyne spectroscopy provides a convenient and sensitive method for measuring the true intensity profiles of atmospheric spectral lines. Application of radiative transfer theory to measured lineshapes can then permit the study of molecular abundances, temperatures, total pressures, excitation conditions, and dynamics of the regions of line formation. The theory of formation of atmospheric spectral lines and the retrieval of the information contained in these molecular lines is illustrated. Notable successes of such retrievals from infrared heterodyne measurements on Venus, Mars, Jupiter and the earth are given. A discussion of developments in infrared heterodyne technology is also presented. Previously announced in STAR as N83-28551

  16. Quasi-Heterodyne Hologram Interferometry

    NASA Astrophysics Data System (ADS)

    Hariharan, P.

    1985-08-01

    Wider use of hologram interferometry for quantitative measure-ments has been delayed by the fact that interpolation between the fringe maxima and minima to obtain the optical path difference at a particular point in the field is laborious and inaccurate. A solution to this problem is quasi-hetero-dyne interferometry, which permits rapid and accurate measurements simultaneously at a number of points distributed over the interference pattern. In this technique a television camera is used in conjunction with digital electronics to measure and store the irradiance values at points on a rectangular sampling grid covering the real-time interference fringes. The phase difference between the interfering wavefronts at each point is then calculated from the irradiance values obtained from successive scans of the camera made while the phase of one of the wavefronts is shifted either continuously or in steps. A practical system is described with which values of the optical path difference for 10,000 data points can be obtained with an accuracy of +/- A/200 in less than 10 s. The application of quasi-heterodyne hologram interferometry to the measurement of vector displacements and to holographic contouring is discussed.

  17. Heterodyne effect in Hybrid CARS

    NASA Astrophysics Data System (ADS)

    Wang, Xi; Zhang, Aihua; Zhi, Miaochan; Sokolov, Alexei; Welch, George; Scully, Marlan

    2009-10-01

    We study the interaction between the resonant Raman signal and non-Raman field, either the concomitant nonresonant four-wave-mixing (FWM) background or an applied external field, in our recently developed scheme of coherent Anti-Stokes Raman scattering, a hybrid CARS. Our technique combines instantaneous coherent excitation of several characteristic molecular vibrations with subsequent probing of these vibrations by an optimally shaped, time-delayed, narrowband laser pulse. This pulse configuration mitigates the non-resonant FWM background while maximizing the Raman-resonant signal, and allows rapid and highly specific detection even in the presence of multiple scattering. We apply this method to non-invasive monitoring of blood glucose levels. Under certain conditions we find that the measured signal is linearly proportional to the glucose concentration due to optical interference with the residual background light, which allows reliable detection of spectral signatures down to medically-relevant glucose levels. We also study the interference between the CARS field and an external field (the local oscillator) by controlling their relative phase and amplitude. This control allows direct observation of the real and imaginary components of the third-order nonlinear susceptibility (χ^(3)) of the sample. We demonstrate that the heterodyne method can be used to amplify the signal and thus increase detection sensitivity.

  18. A comparison of electronic heterodyne moire deflectometry and electronic heterodyne holographic interferometry for flow measurements

    NASA Technical Reports Server (NTRS)

    Decker, A. J.; Stricker, J.

    1985-01-01

    Electronic heterodyne moire deflectometry and electronic heterodyne holographic interferometry are compared as methods for the accurate measurement of refractive index and density change distributions of phase objects. Experimental results are presented to show that the two methods have comparable accuracy for measuring the first derivative of the interferometric fringe shift. The phase object for the measurements is a large crystal of KD*P, whose refractive index distribution can be changed accurately and repeatably for the comparison. Although the refractive index change causes only about one interferometric fringe shift over the entire crystal, the derivative shows considerable detail for the comparison. As electronic phase measurement methods, both methods are very accurate and are intrinsically compatible with computer controlled readout and data processing. Heterodyne moire is relatively inexpensive and has high variable sensitivity. Heterodyne holographic interferometry is better developed, and can be used with poor quality optical access to the experiment.

  19. A comparison of electronic heterodyne moire deflectometry and electronic heterodyne holographic interferometry for flow measurements

    NASA Technical Reports Server (NTRS)

    Decker, A. J.; Stricker, J.

    1985-01-01

    Electronic heterodyne moire deflectometry and electronic heterodyne holographic interferometry are compared as methods for the accurate measurement of refractive index and density change distributions of phase objects. Experimental results are presented to show that the two methods have comparable accuracy for measuring the first derivative of the interferometric fringe shift. The phase object for the measurements is a large crystal of KD P, whose refractive index distribution can be changed accurately and repeatably for the comparison. Although the refractive index change causes only about one interferometric fringe shift over the entire crystal, the derivative shows considerable detail for the comparison. As electronic phase measurement methods, both methods are very accurate and are intrinsically compatible with computer controlled readout and data processing. Heterodyne moire is relatively inexpensive and has high variable sensitivity. Heterodyne holographic interferometry is better developed, and can be used with poor quality optical access to the experiment.

  20. Laser Metrology Heterodyne Phase-Locked Loop

    NASA Technical Reports Server (NTRS)

    Loya, Frank; Halverson, Peter

    2009-01-01

    A method reduces sensitivity to noise in a signal from a laser heterodyne interferometer. The phase-locked loop (PLL) removes glitches that occur in a zero-crossing detector s output [that can happen if the signal-to-noise ratio (SNR) of the heterodyne signal is low] by the use of an internal oscillator that produces a square-wave signal at a frequency that is inherently close to the heterodyne frequency. It also contains phase-locking circuits that lock the phase of the oscillator to the output of the zero-crossing detector. Because the PLL output is an oscillator signal, it is glitch-free. This enables the ability to make accurate phase measurements in spite of low SNR, creates an immunity to phase error caused by shifts in the heterodyne frequency (i.e. if the target moves causing Doppler shift), and maintains a valid phase even when the signal drops out for brief periods of time, such as when the laser is blocked by a stray object.

  1. Broadband Heterodyne SIS Spectrometer Prototype: First Results

    NASA Technical Reports Server (NTRS)

    Rice, F.; LeDuc, H.; Harris, A.; Hu, S.; Sumner, M.; Zmuidzinas, J.

    2004-01-01

    The broadband heterodyne SIS receiver system described elsewhere (reference 1) has been assembled and tested both in the laboratory and during two observing runs on the Cassegrain focus of the 10 meter telescope at the Caltech Submillimeter Observatory on Mauna Kea, Hawaii. Here we present a brief summary of the initial results.

  2. Digital Averaging Phasemeter for Heterodyne Interferometry

    NASA Technical Reports Server (NTRS)

    Johnson, Donald; Spero, Robert; Shaklan, Stuart; Halverson, Peter; Kuhnert, Andreas

    2004-01-01

    A digital averaging phasemeter has been built for measuring the difference between the phases of the unknown and reference heterodyne signals in a heterodyne laser interferometer. This phasemeter performs well enough to enable interferometric measurements of distance with accuracy of the order of 100 pm and with the ability to track distance as it changes at a speed of as much as 50 cm/s. This phasemeter is unique in that it is a single, integral system capable of performing three major functions that, heretofore, have been performed by separate systems: (1) measurement of the fractional-cycle phase difference, (2) counting of multiple cycles of phase change, and (3) averaging of phase measurements over multiple cycles for improved resolution. This phasemeter also offers the advantage of making repeated measurements at a high rate: the phase is measured on every heterodyne cycle. Thus, for example, in measuring the relative phase of two signals having a heterodyne frequency of 10 kHz, the phasemeter would accumulate 10,000 measurements per second. At this high measurement rate, an accurate average phase determination can be made more quickly than is possible at a lower rate.

  3. Submillimeter local oscillators for spaceborne heterodyne applications

    NASA Technical Reports Server (NTRS)

    Petuchowski, S. J.; Durachta, J.

    1985-01-01

    Existing and prospective submillimeter local oscillator technologies are surveyed and compared with respect to criteria of suitability for application in spaceborne submillimeter heterodyne receivers as those proposed for the Large Deployable Reflector (LDR). Solid-state and plasma devices are considered in terms of fundamental limitations.

  4. Heterodyne detection using spectral line pairing for spectral phase encoding optical code division multiple access and dynamic dispersion compensation.

    PubMed

    Yang, Yi; Foster, Mark; Khurgin, Jacob B; Cooper, A Brinton

    2012-07-30

    A novel coherent optical code-division multiple access (OCDMA) scheme is proposed that uses spectral line pairing to generate signals suitable for heterodyne decoding. Both signal and local reference are transmitted via a single optical fiber and a simple balanced receiver performs sourceless heterodyne detection, canceling speckle noise and multiple-access interference (MAI). To validate the idea, a 16 user fully loaded phase encoded system is simulated. Effects of fiber dispersion on system performance are studied as well. Both second and third order dispersion management is achieved by using a spectral phase encoder to adjust phase shifts of spectral components at the optical network unit (ONU). PMID:23038313

  5. Ozone height profiles using laser heterodyne radiometer

    NASA Technical Reports Server (NTRS)

    Jain, S. L.

    1994-01-01

    The monitoring of vertical profiles of ozone and related minor constituents in the atmosphere are of great significance to understanding the complex interaction between atmospheric dynamics, chemistry and radiation budget. An ultra high spectral resolution tunable CO2 laser heterodyne radiometer has been designed, developed and set up at the National Physical Laboratory, New Delhi to obtain vertical profiles of various minor constituents the characteristic absorption lines in 9 to 11 micron spectral range. Due to its high spectral resolution the lines can be resolved completely and data obtained are inverted to get vertical profiles using an inversion technique developed by the author. In the present communication the salient features of the laser heterodyne system and the results obtained are discussed in detail.

  6. Nanoscale defect detection by heterodyne interferometry

    SciTech Connect

    Lin Haoshan; Li Yuhe; Wang Dongsheng; Tong Xiaolei; Liu Mei

    2009-03-10

    We construct an instrument that facilitates the measurement of nanoscale defects. It is based on heterodyne interferometry with phase measurement that utilizes a polarizing beam splitter to form a measuring signal and an oscillating cantilever tip that acts as a scanning probe to get the measurement values of sample topography. The dependence of the tip displacement on the variation of tip-sample distance and the comb scanning of the sample topography are investigated by experiments. The results prove that the tip displacement increases and is enough to be discriminated in various positions where the sample is approached. The system has been successfully utilized to measure the defect characterization by measuring the pitch of the standard sample. The results also show that the heterodyne system has good repeatability, a large measurement range, and high accuracy, with a measurement stability of 0.5 nm.

  7. Heterodyne-enhanced Faraday rotation spectrometer

    NASA Astrophysics Data System (ADS)

    Wang, Yin; Nikodem, Michal; Hoyne, Jake; Wysocki, Gerard

    2012-01-01

    A novel heterodyne-enhanced Faraday rotation spectroscopic (H-FRS) system for trace gas detection of nitric oxide (NO) is demonstrated. The system is based on a quantum cascade laser emitting at ~5.2 μm and a mercury cadmium telluride photodetector (both thermoelectrically cooled). The heterodyne detection is performed at 30MHz, where the laser relative intensity noise is significantly smaller than at low frequencies. With an implementation of active interferometer stabilization technique, the current system shows total noise level that is only 5.4 times above the fundamental shot-noise limit and the Faraday rotation angle sensitivity of 2.6 × 10-8 rad/√Hz. The NO detection limit of 30.7 ppb-v/√Hz was achieved for the R(8.5)e NO transition using 100 Gauss magnetic field and 0.15 m optical path length.

  8. A heterodyne interferometer for angle metrology

    SciTech Connect

    Hahn, Inseob; Weilert, M.; Wang, X.; Goullioud, R.

    2010-04-15

    We have developed a compact, high-resolution, angle measurement instrument based on a heterodyne interferometer. Common-path heterodyne interferometer metrology is used to measure displacements of a reflective target surface. In the interferometer set up, an optical mask is used to sample the laser beam reflecting back from four areas on a target surface. From the relative displacement measurements of the target surface areas, we can simultaneously determine angular rotations around two orthogonal axes in a plane perpendicular to the measurement beam propagation direction. The device is used in a testbed for a tracking telescope system where pitch and yaw angle measurements of a flat mirror are performed. Angle noise measurement of the device shows 0.1 nrad/{radical}(Hz) at 1 Hz, at a working distance of 1 m. The operation range and nonlinearity of the device when used with a flat mirror is approximately {+-}0.15 mrad, and 3 {mu}rad rms, respectively.

  9. Spatial-heterodyne interferometry for transmission (SHIFT) measurements

    DOEpatents

    Bingham, Philip R.; Hanson, Gregory R.; Tobin, Ken W.

    2006-10-10

    Systems and methods are described for spatial-heterodyne interferometry for transmission (SHIFT) measurements. A method includes digitally recording a spatially-heterodyned hologram including spatial heterodyne fringes for Fourier analysis using a reference beam, and an object beam that is transmitted through an object that is at least partially translucent; Fourier analyzing the digitally recorded spatially-heterodyned hologram, by shifting an original origin of the digitally recorded spatially-heterodyned hologram to sit on top of a spatial-heterodyne carrier frequency defined by an angle between the reference beam and the object beam, to define an analyzed image; digitally filtering the analyzed image to cut off signals around the original origin to define a result; and performing an inverse Fourier transform on the result.

  10. Stratospheric sounding by infrared heterodyne spectroscopy

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Kunde, V. G.; Mumma, M. J.; Kostiuk, T.; Buhl, D.; Frerking, M. A.

    1979-01-01

    Intensity profiles of infrared spectral lines of stratospheric constituents can be fully resolved with a heterodyne spectrometer of sufficiently high resolution (approximately 5 MHz = 0.000167 kaysers at 10 microns). The constituents' vertical distributions can then be evaluated accurately by analytic inversion of the measured line profiles. Estimates of the detection sensitivity of a heterodyne receiver are given in terms of minimum detectable volume mixing ratios of stratospheric constituents, indicating a large number of minor constituents which can be studied. Stratospheric spectral line shapes and the resolution required to measure them are discussed in light of calculated synthetic line profiles for some stratospheric molecules in a model atmosphere. The inversion technique for evaluation of gas concentration profiles is briefly described, and applications to synthetic lines of O3, CO2, CH4, and N2O are given. Some recent heterodyne measurements of CO2 and O3 absorption lines are analytically inverted, and the vertical distributions of the two gases are determined.

  11. Wide-band heterodyne receiver development for effluent measurements

    SciTech Connect

    Hutchinson, D.P.; Richards, R.K.; Simpson, M.L.; Bennett, C.A.; Liu, H.C.; Buchanan, M.

    1998-05-01

    Oak Ridge National Laboratory (ORNL) has been developing advanced infrared heterodyne receivers for plasma diagnostics in fusion reactors for over 20 years. Passive heterodyne radiometry in the LWIR region of the spectrum has historically been restricted by HgCdTe (MCT) detector technology to receiver bandwidths of only 2 GHz. Given typical atmospheric line widths of approximately 3 GHz, a CO{sub 2} (or isotope) laser local oscillator with an average line spacing of 50 GHz, and an MCT detector, only chemical species whose absorptions fall directly on top of laser lines can be measured. Thus, with traditional narrow-band heterodyne radiometry, much of the LWIR spectrum is missed and the less complex direct detection DIAL has been the preferred technique in remote sensing applications. Wide-band heterodyne receivers offer significant improvements in remote measurement capability. Progress at the Institute for Microstructural Sciences (IMS) at National Research Council of Canada and at ORNL in wide-band quantum-well infrared photodetectors (QIPs) and receivers is significantly enhancing the bandwidth capabilities of heterodyne radiometers. ORNL recently made measurements in the lab using QWIPs developed at IMS that demonstrate heterodyne quantum efficiencies of 5% with a heterodyne bandwidth of 7 GHz. The path forward indicates that > 10% heterodyne quantum efficiencies and 30-GHz bandwidths are achievable with current QWIP technology. With a chopped, 30-GHz passive heterodyne receiver, a much larger portion of the LWIR spectrum can now be covered. One potential advantage of wide-band heterodyne receivers for effluent measurements is to dramatically reduce the number of laser lines needed to characterize and distinguish multiple chemical species of interest. In the following paper, the authors discuss this and other implications of these new technologies to the characterization of effluents using both passive heterodyne radiometry and thermo-luminescence.

  12. Sub-millimeter wave frequency heterodyne detector system

    NASA Technical Reports Server (NTRS)

    Siegel, Peter H. (Inventor); Dengler, Robert (Inventor); Mueller, Eric R. (Inventor)

    2009-01-01

    The present invention relates to sub-millimeter wave frequency heterodyne imaging systems. More specifically, the present invention relates to a sub-millimeter wave frequency heterodyne detector system for imaging the magnitude and phase of transmitted power through or reflected power off of mechanically scanned samples at sub-millimeter wave frequencies.

  13. Sub-millimeter wave frequency heterodyne detector system

    NASA Technical Reports Server (NTRS)

    Siegel, Peter H. (Inventor); Dengler, Robert (Inventor); Mueller, Eric R. (Inventor)

    2010-01-01

    The present invention relates to sub-millimeter wave frequency heterodyne imaging systems. More specifically, the present invention relates to a sub-millimeter wave frequency heterodyne detector system for imaging the magnitude and phase of transmitted power through or reflected power off of mechanically scanned samples at sub-millimeter wave frequencies.

  14. Analysis of Optimum Heterodyne Receivers for Coherent Lidar Applications

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin

    2002-01-01

    A full analysis of the combined effects of all the noise sources of optical heterodyne receiver and the interaction between the competing control parameters of the receiver detector and pre-amplifier will be presented. This analysis provides the mean for true optimization of the coherent lidar receiver. The significance of the optimization of heterodyne receiver is shown for 2-micron coherent lidar.

  15. Error sources in deferred heterodyne moire deflectometry - An analytical study

    NASA Technical Reports Server (NTRS)

    Stricker, Josef

    1989-01-01

    The effects of the aperture size and shape of the photodetector and of the structure of the grating lines on the performance of deferred electronic heterodyne moire deflectometry are studied. It is shown that scanning of a moire fringe pattern parallel to an unshifted fringe yields periodical variations in the heterodyne phase and amplitude, which cause severe errors in the measurements.

  16. Measuring Cyclic Error in Laser Heterodyne Interferometers

    NASA Technical Reports Server (NTRS)

    Ryan, Daniel; Abramovici, Alexander; Zhao, Feng; Dekens, Frank; An, Xin; Azizi, Alireza; Chapsky, Jacob; Halverson, Peter

    2010-01-01

    An improved method and apparatus have been devised for measuring cyclic errors in the readouts of laser heterodyne interferometers that are configured and operated as displacement gauges. The cyclic errors arise as a consequence of mixing of spurious optical and electrical signals in beam launchers that are subsystems of such interferometers. The conventional approach to measurement of cyclic error involves phase measurements and yields values precise to within about 10 pm over air optical paths at laser wavelengths in the visible and near infrared. The present approach, which involves amplitude measurements instead of phase measurements, yields values precise to about .0.1 microns . about 100 times the precision of the conventional approach. In a displacement gauge of the type of interest here, the laser heterodyne interferometer is used to measure any change in distance along an optical axis between two corner-cube retroreflectors. One of the corner-cube retroreflectors is mounted on a piezoelectric transducer (see figure), which is used to introduce a low-frequency periodic displacement that can be measured by the gauges. The transducer is excited at a frequency of 9 Hz by a triangular waveform to generate a 9-Hz triangular-wave displacement having an amplitude of 25 microns. The displacement gives rise to both amplitude and phase modulation of the heterodyne signals in the gauges. The modulation includes cyclic error components, and the magnitude of the cyclic-error component of the phase modulation is what one needs to measure in order to determine the magnitude of the cyclic displacement error. The precision attainable in the conventional (phase measurement) approach to measuring cyclic error is limited because the phase measurements are af-

  17. Recent progress in submillimeter heterodyne receiver development

    NASA Technical Reports Server (NTRS)

    Zmuidzinas, J.

    1996-01-01

    The progress made in relation to the development of sensitive submillimeter heterodyne receiver systems is reviewed. Sensitive superconductor-insulator-superconductor (SIS) tunnel junction mixers were demonstrated at frequencies of greater than 1 THz, with noise temperatures of below 1000 K. An alternative mixer technology is that of the superconducting hot electron bolometer, for which sensitivities of 1.2 THz and 2.5 THz were demonstrated. Local oscillator technology is under development. Gunn oscillators followed by Schottky varactor frequency multipliers have sufficient output power to drive SIS mixers at 1 THz. It is considered that optical photomixer local oscillators have potential for driving hot electron bolometers above 1 THz.

  18. Sources of error in heterodyne moire deflectometry

    NASA Technical Reports Server (NTRS)

    Decker, Arthur J.; Weiland, Kenneth E.; Stricker, Josef; Weimer, David

    1988-01-01

    Alignment problems, and the accompanying errors, in heterodyne moire deflectometry are considered. A change in the x-directed offset between two states of a phase object causes a constant phase error, and it is noted that the relative x coordinate of the two photographic plates (the two states of the phase object) must be positioned typically within 1 micron to avoid a detectable offset. Possible solutions for assuring the relative alignment of the two deflectograms are considered, including a sandwich technique and a two-color double-exposure implementation.

  19. Surface plasmon resonance biosensor using heterodyne interferometry

    NASA Astrophysics Data System (ADS)

    Joe, Shen-fen; Wu, Chien-ming; Chang, Liann-be; Hsieh, Li-zen

    2005-02-01

    A Surface plasmon resonance (SPR) biosensor constructed with common path, heterodyne inteferometric system has been developed. The sensor ship consists of a BK7 substrate coated with gold film on which the receptor of the specific biomolecular or protein has been immobilized. The light source consisting of the s and p polarizations with heterodyne frequency of 60kHz is used to measure the phase difference between these two polarizations. Because the SPR sensor probes the changes of refractive index near the gold film (i.e. about one wave-length), the more the binding of molecules on the sensing surface results in the less sensitivity of the detection. In order to overcome this shortage, we set two quarter-wave plates before and after the SPR prism to make the sensitivity of measurement to be tunable. This sensor could detect the concentration of antibody of sheep IgG as low as several nanograms per milliliter. The results indicate that this system provides high sensitivity and is capable for detecting biomolecular interactions.

  20. Heterodyne-Detected Dispersed Vibrational Echo Spectroscopy

    NASA Astrophysics Data System (ADS)

    Jones, Kevin C.; Ganim, Ziad; Tokmakoff, Andrei

    2009-11-01

    We develop heterodyned dispersed vibrational echo spectroscopy (HDVE) and demonstrate the new capabilities in biophysical applications. HDVE is a robust ultrafast technique that provides a characterization of the real and imaginary components of third-order nonlinear signals with high sensitivity and single-laser-shot capability and can be used to extract dispersed pump-probe and dispersed vibrational echo spectra. Four methods for acquiring HDVE phase and amplitude spectra were compared: Fourier transform spectral interferometry, a new phase modulation spectral interferometry technique, and combination schemes. These extraction techniques were demonstrated in the context of protein amide I spectroscopy. Experimental HDVE and heterodyned free induction decay amide I spectra were explicitly compared to conventional dispersed pump-probe, dispersed vibrational echo, and absorption spectra. The new capabilities of HDVE were demonstrated by acquiring single-shot spectra and melting curves of ubiquitin and concentration-dependent spectra of insulin suitable for extracting the binding constant for dimerization. The introduced techniques will prove particularly useful in transient experiments, studying irreversible reactions, and micromolar concentration studies of small proteins.

  1. Correction of Errors in Polarization Based Dynamic Phase Shifting Interferometers

    NASA Astrophysics Data System (ADS)

    Kimbrough, Brad

    2014-10-01

    Polarization based interferometers for single snap-shot measurements allow single frame, quantitative phase acquisition for vibration insensitive measurements of optical surfaces. Application of these polarization based phase sensors requires the test and reference beams of the interferometer to be orthogonally polarized. As with all polarization based interferometers, these systems can suffer from phase dependent errors resulting from systematic polarization aberrations. This type of measurement error presents a particular challenge because it varies in magnitude both spatially and temporally between each measurement. In this article, a general discussion of phase calculation error is presented. We then present an algorithm that is capable of mitigating phase-dependent measurement errors on-the-fly. The algorithm implementation is non-iterative providing sensor frame rate limited phase calculations. Finally, results are presented for both a high numerical aperture system, where the residual error is reduced to the shot noise limit, and a system with significant birefringence in the test arm.

  2. Apparatus for direct-to-digital spatially-heterodyned holography

    DOEpatents

    Thomas, Clarence E.; Hanson, Gregory R.

    2006-12-12

    An apparatus operable to record a spatially low-frequency heterodyne hologram including spatially heterodyne fringes for Fourier analysis includes: a laser; a beamsplitter optically coupled to the laser; an object optically coupled to the beamsplitter; a focusing lens optically coupled to both the beamsplitter and the object; a digital recorder optically coupled to the focusing lens; and a computer that performs a Fourier transform, applies a digital filter, and performs an inverse Fourier transform. A reference beam and an object beam are focused by the focusing lens at a focal plane of the digital recorder to form a spatially low-frequency heterodyne hologram including spatially heterodyne fringes for Fourier analysis which is recorded by the digital recorder, and the computer transforms the recorded spatially low-frequency heterodyne hologram including spatially heterodyne fringes and shifts axes in Fourier space to sit on top of a heterodyne carrier frequency defined by an angle between the reference beam and the object beam and cuts off signals around an original origin before performing the inverse Fourier transform.

  3. SCATTERING OF LIGHT PULSES: Optical heterodyning study of the propagation dynamics of IR femtosecond laser pulses in a strongly scattering porous medium

    NASA Astrophysics Data System (ADS)

    Bestem'yanov, K. P.; Gordienko, Vyacheslav M.; Ivanov, Anatoliy A.; Konovalov, Aleksei N.; Podshivalov, Alexey A.

    2004-07-01

    A system is devised for optical heterodyning based on a femtosecond Cr:forsterite laser using a balance scheme for the laser noise compensation. The dependence of a heterodyne signal on the time delay is measured by detecting backscattered laser radiation from a strongly scattering porous object (a sheet of paper). It is found that the backscattered signal contains 'a long tail' with an exponential decay caused by multiple scattering. The exponent of the exponential is determined by the lifetime of photons in a scattering layer. The absorption and scattering coefficients for different types of paper are measured by the photon lifetime.

  4. Characterization of new components for a miniaturized heterodyne infrared spectrometer

    NASA Astrophysics Data System (ADS)

    Krause, Pia; Sonnabend, Guido; Labadie, Lucas; Sornig, Manuela; Thomson, Robert; Arriola, Alexander; Rodenas, Arian; Hewagama, Tilak; Rutz, Frank

    2014-08-01

    We report on the development and testing of the building blocks of a possible compact heterodyne setup in the mid-infrared, which becomes particularly relevant for flight instrumentation. The local oscillator is a Quantum Cascade Laser (QCL) source at 8.6 μm operable at room temperature. The beam combination of the source signal and the local oscillator will occur by means of integrated optics for the 10 μm range, which was characterized in the lab. In addition we investigate the use of superlattice detectors in a heterodyne instrument. This work shows that these different new components can become valuable tools for a compact heterodyne setup.

  5. Laser heterodyne photothermal nondestructive method: extension to transparent probe

    NASA Astrophysics Data System (ADS)

    Pencheva, V.; Penchev, S.; Naboko, V.; Toyoda, K.; Donchev, T.

    2007-03-01

    We present a contribution to the development of the laser heterodyne method of nondestructive material analysis employing photothermal displacement (PTD) probe. PTD is a dominant factor of the photothermal effect in metals and semiconductors, where the derived linear dependence on absorbed energy exhibits a fingerprint of their physical properties. Theoretical consideration of the case of transparent probe is accomplished extending thermal diffusion model. Laser double heterodyne detection is verified for opaque and transparent probes, and in the exclusive case of silicon. The achieved resolution of photothermal displacement is less than 10 -12 m well above the limits of heterodyne measurement.

  6. Far-Infrared Heterodyne Spectrometer for SOFIA

    NASA Technical Reports Server (NTRS)

    Betz, A. L.; Boreiko, R. T.

    1998-01-01

    This report summarizes work done under NASA Grant NAG2-1062 awarded to the University of Colorado. The project goal was to evaluate the scientific capabilities and technical requirements for a far-infrared heterodyne spectrometer suitable for the SOFIA Airborne Observatory, which is now being developed by NASA under contract to the Universities Space Research Association (USRA). The conclusions detailed below include our specific recommendations for astronomical observations, as well as our intended technical approach for reaching these scientific goals. These conclusions were presented to USRA in the form of a proposal to build this instrument. USRA subsequently awarded the University of Colorado a 3-year grant (USRA 8500-98-010) to develop the proposed Hot-Electron micro-Bolometer (HEB) mixer concept for high frequencies above 3 THz, as well as other semiconductor mixer technologies suitable for high sensitivity receivers in the 2-6 THz frequency band.

  7. Homodyning and heterodyning the quantum phase

    NASA Technical Reports Server (NTRS)

    Dariano, Giacomo M.; Macchiavello, C.; Paris, M. G. A.

    1994-01-01

    The double-homodyne and the heterodyne detection schemes for phase shifts between two synchronous modes of the electromagnetic field are analyzed in the framework of quantum estimation theory. The probability operator-valued measures (POM's) of the detectors are evaluated and compared with the ideal one in the limit of strong local reference oscillator. The present operational approach leads to a reasonable definition of phase measurement, whose sensitivity is actually related to the output r.m.s. noise of the photodetector. We emphasize that the simple-homodyne scheme does not correspond to a proper phase-shift measurements as it is just a zero-point detector. The sensitivity of all detection schemes are optimized at fixed energy with respect to the input state of radiation. It is shown that the optimal sensitivity can be actually achieved using suited squeezed states.

  8. Optical correction using fourier transform heterodyne

    NASA Astrophysics Data System (ADS)

    Laubscher, Bryan E.; Nemzek, Robert J.; Cooke, Bradly J.; Olivas, Nicholas L.; Jorgensen, Anders M.; Smith, J. A.; Weisse-Bernstein, Nina R.

    2005-08-01

    In this paper we briefly present the theory of Fourier Transform Heterodyne (FTH), describe past verification experiments carried out, and discuss the experiment designed to use this new imaging technology to perform optical correction. FTH uses the scalar projection of a reference laser beam and a test laser beam onto a single element detector. The complex current in the detector yields the coefficient of the scalar projection. By projecting a complete orthonormal basis set of reference beams onto the test beam, the amplitude and phase of the test beam can be measured, allowing the reconstruction of the phasefront of the image. Experiments to determine this technique's applicability to optical correction and optical self-correction are continuing. Applications of this technique beyond optical correction include adaptive optics; interferometry; and active, high background, low signal imaging.

  9. Far-Infrared Heterodyne Spectrometer for Sofia

    NASA Technical Reports Server (NTRS)

    Betz, A. L.

    1998-01-01

    The project goal was to evaluate the scientific capabilities and technical requirements for a far-infrared heterodyne spectrometer suitable for the SOFIA Airborne Observatory, which is now being developed by NASA under contract to the Universities Space Research Association (USRA). The conclusions detailed below include our specific recommendations for astronomical observations, as well as our intended technical approach for reaching these scientific goals. These conclusions were presented to USRA in the form of a proposal to build this instrument. USRA subsequently awarded the University of Colorado a 3-year grant to develop the proposed Hot-Electron micro-Bolometer (HEB) mixer concept for high frequencies above 3 THz, as well as other semiconductor mixer technologies suitable for high sensitivity receivers in the 2-6 THz frequency band.

  10. Nonlinear nanochannels for room temperature terahertz heterodyne detection

    NASA Astrophysics Data System (ADS)

    Torres, Jeremie; Nouvel, Philippe; Penot, Alexandre; Varani, Luca; Sangaré, Paul; Grimbert, Bertrand; Faucher, Marc; Ducournau, Guillaume; Gaquière, Christophe; Iñiguez-de-la-Torre, Ignacio; Mateos, Javier; Gonzalez, Tomas

    2013-12-01

    The potentialities of AlGaN/GaN nanochannels with broken symmetry (also called self-switching diodes) as direct and heterodyne THz detectors are analyzed. The operation of the devices in the free space heterodyne detection scheme have been measured at room temperature with RF up to 0.32 THz and explained as a result of high-frequency nonlinearities using Monte Carlo simulations. Intermediate-frequency bandwidth of 40 GHz is obtained.

  11. Infrared heterodyne spectroscopy for astronomical purposes. [laser applications

    NASA Technical Reports Server (NTRS)

    Townes, C. H.

    1978-01-01

    Heterodyne infrared astronomy was carried out using CO2 lasers and some solid state tunable lasers. The best available detectors are mercury cadmium telluride photodiodes. Their quantum efficiencies reach values near 0.5 and in an overall system an effective quantum efficiency, taking into account optical losses and amplifier noise, of about 0.25 was demonstrated. Initial uses of 10 micron heterodyne spectroscopy were for the study of planetary molecular spectra.

  12. Faster processing of multiple spatially-heterodyned direct to digital holograms

    DOEpatents

    Hanson, Gregory R.; Bingham, Philip R.

    2006-10-03

    Systems and methods are described for faster processing of multiple spatially-heterodyned direct to digital holograms. A method includes of obtaining multiple spatially-heterodyned holograms, includes: digitally recording a first spatially-heterodyned hologram including spatial heterodyne fringes for Fourier analysis; digitally recording a second spatially-heterodyned hologram including spatial heterodyne fringes for Fourier analysis; Fourier analyzing the recorded first spatially-heterodyned hologram by shifting a first original origin of the recorded first spatially-heterodyned hologram including spatial heterodyne fringes in Fourier space to sit on top of a spatial-heterodyne carrier frequency defined as a first angle between a first reference beam and a first, object beam; applying a first digital filter to cut off signals around the first original origin and performing an inverse Fourier transform on the result; Fourier analyzing the recorded second spatially-heterodyned hologram by shifting a second original origin of the recorded second spatially-heterodyned hologram including spatial heterodyne fringes in Fourier space to sit on top of a spatial-heterodyne carrier frequency defined as a second angle between a second reference beam and a second object beam; and applying a second digital filter to cut off signals around the second original origin and performing an inverse Fourier transform on the result, wherein digitally recording the first spatially-heterodyned hologram is completed before digitally recording the second spatially-heterodyned hologram and a single digital image includes both the first spatially-heterodyned hologram and the second spatially-heterodyned hologram.

  13. Faster processing of multiple spatially-heterodyned direct to digital holograms

    DOEpatents

    Hanson, Gregory R [Clinton, TN; Bingham, Philip R [Knoxville, TN

    2008-09-09

    Systems and methods are described for faster processing of multiple spatially-heterodyned direct to digital holograms. A method includes of obtaining multiple spatially-heterodyned holograms, includes: digitally recording a first spatially-heterodyned hologram including spatial heterodyne fringes for Fourier analysis; digitally recording a second spatially-heterodyned hologram including spatial heterodyne fringes for Fourier analysis; Fourier analyzing the recorded first spatially-heterodyned hologram by shifting a first original origin of the recorded first spatially-heterodyned hologram including spatial heterodyne fringes in Fourier space to sit on top of a spatial-heterodyne carrier frequency defined as a first angle between a first reference beam and a first object beam; applying a first digital filter to cut off signals around the first original origin and performing an inverse Fourier transform on the result; Fourier analyzing the recorded second spatially-heterodyned hologram by shifting a second original origin of the recorded second spatially-heterodyned hologram including spatial heterodyne fringes in Fourier space to sit on top of a spatial-heterodyne carrier frequency defined as a second angle between a second reference beam and a second object beam; and applying a second digital filter to cut off signals around the second original origin and performing an inverse Fourier transform on the result, wherein digitally recording the first spatially-heterodyned hologram is completed before digitally recording the second spatially-heterodyned hologram and a single digital image includes both the first spatially-heterodyned hologram and the second spatially-heterodyned hologram.

  14. Broadband Infrared Heterodyne Spectrometer: Final Report

    SciTech Connect

    Stevens, C G; Cunningham, C T; Tringe, J W

    2010-12-16

    This report summarizes the most important results of our effort to develop a new class of infrared spectrometers based on a novel broadband heterodyne design. Our results indicate that this approach could lead to a near-room temperature operation with performance limited only by quantum noise carried by the incoming signal. Using a model quantum-well infrared photodetector (QWIP), we demonstrated key performance features of our approach. For example, we directly measured the beat frequency signal generated by superimposing local oscillator (LO) light of one frequency and signal light of another through a spectrograph, by injecting the LO light at a laterally displaced input location. In parallel with the development of this novel spectrometer, we modeled a new approach to reducing detector volume though plasmonic resonance effects. Since dark current scales directly with detector volume, this ''photon compression'' can directly lead to lower currents. Our calculations indicate that dark current can be reduced by up to two orders of magnitude in an optimized ''superlens'' structure. Taken together, our spectrometer and dark current reduction strategies provide a promising path toward room temperature operation of a mid-wave and possibly long-wave infrared spectrometer.

  15. Wideband Heterodyne QWIP Receiver Development for Thermonuclear Fusion Measurements

    SciTech Connect

    Bennett, C.A.; Buchanan, M.; Hutchinson, D.P.; Liu, H.C.; Richards, R.K.; Simpson, M.L.

    1998-11-01

    Oak Ridge National Laboratory (ORNL) has been developing heterodyne receivers for plasma diagnostic applications for over 20 years. One area of this work has been the development of a diagnostic system for the measurement of the energy of alpha particles created in a thermonuclear fusion reactor. These particles originate with an energy of 3.5 MeV and cool to the thermal energy of the plasma (around 15 keV) after several seconds. To measure the velocity distribution of these alpha particles, a Thomson scattering diagnostic is under development based on a high power CO{sub 2} laser at 10 microns with a heterodyne receiver. The Doppler shift generated by Thomson scattering of the alpha particles requires a wideband heterodyne receiver (greater than 10 GHz). Because Mercury-Cadimum-Telluride (MCT) detectors are limited to a bandwidth of approximately 2 GHz, a Quantum Well Infrared Photodetector (QWIP) detector was obtained from the National Research Council of Canada (NRC) and evaluated for its heterodyne performance using the heterodyne testing facility developed at ORNL.

  16. Comparison of direct and heterodyne detection optical intersatellite communication links

    NASA Technical Reports Server (NTRS)

    Chen, C. C.; Gardner, C. S.

    1987-01-01

    The performance of direct and heterodyne detection optical intersatellite communication links are evaluated and compared. It is shown that the performance of optical links is very sensitive to the pointing and tracking errors at the transmitter and receiver. In the presence of random pointing and tracking errors, optimal antenna gains exist that will minimize the required transmitter power. In addition to limiting the antenna gains, random pointing and tracking errors also impose a power penalty in the link budget. This power penalty is between 1.6 to 3 dB for a direct detection QPPM link, and 3 to 5 dB for a heterodyne QFSK system. For the heterodyne systems, the carrier phase noise presents another major factor of performance degradation that must be considered. In contrast, the loss due to synchronization error is small. The link budgets for direct and heterodyne detection systems are evaluated. It is shown that, for systems with large pointing and tracking errors, the link budget is dominated by the spatial tracking error, and the direct detection system shows a superior performance because it is less sensitive to the spatial tracking error. On the other hand, for systems with small pointing and tracking jitters, the antenna gains are in general limited by the launch cost, and suboptimal antenna gains are often used in practice. In which case, the heterodyne system has a slightly higher power margin because of higher receiver sensitivity.

  17. Infrared Heterodyne Earth Atmospheric Remote Spectrometer (IHEARS)

    NASA Astrophysics Data System (ADS)

    Kostiuk, T.; Hanisco, T. F.; Newman, P. A.; Olsen, M. A.; Hewagama, T.; Livengood, T. A.

    2013-12-01

    We will describe the design and capability of the Goddard Space Flight Center Infrared Heterodyne Earth Atmospheric Remote Spectrometer (IHEARS) capable of unique altitude-resolved measurements of chemical and physical processes within the Earth's upper troposphere through the lower mesosphere. Ultra-high spectral resolving power (R>1,000,000) and frequency precision in the 7 to 11 μm wavelength band enables measuring true molecular spectral line shapes with no instrumental effects, thus retrieving small changes in major atmospheric gases, detecting trace species, retrieving temperatures, and measuring Doppler-shift due to winds. These parameters can be obtained from the same set of measurements, a unique capability for Earth remote-sensing. In solar occultation, e.g., from the International Space Station, measurements of abundance changes in <0.5 km layers can yield extremely high sensitivity, e.g., O3 (1ppb), CO2 (1ppm), H2O (<0.5ppm), all at >15-sigma confidence level, enhancing the study of transport and chemistry in upper-troposphere/lower-stratosphere and tropical-transition-layer regions, thereby addressing and constraining GCMs and climate-change models. The technique has a long heritage in ground-based instrumentation and measurements of planetary atmospheres, with proven results paralleling the capability for Earth observations. The proposed detection concept, instrument design and its remote operation and capabilities from Earth orbit will be presented. The proposed instrument will have lower volume, mass, and power requirements compared to existing Earth-science instruments, while enabling new and unique Earth observation measurements from a variety of space platforms. The ultimate projected space flight application will be on Earth Venture Class science missions, the ISS, and future Earth and planetary missions such as GACM.

  18. Investigation of the quantum efficiency of optical heterodyne detectors

    NASA Technical Reports Server (NTRS)

    Batchman, T. E.

    1984-01-01

    The frequency response and quantum efficiency of optical photodetectors for heterodyne receivers is investigated. The measurements utilized two spectral lines from the output of two lasers as input to the photodetectors. These lines are easily measurable in power and frequency and hence serve as known inputs. By measuring the output current of the photodetector the quantum efficiency is determined as a function of frequency separation between the two input signals. An investigation of the theoretical basis and accuracy of this type of measurement relative to similar measurements utilizing risetime is undertaken. A theoretical study of the heterodyne process in photodetectors based on semiconductor physics is included so that higher bandwidth detectors may be designed. All measurements are made on commercially available detectors and manufacturers' specifications for normal photodetector operation are compared to the measured heterodyne characteristics.

  19. Optimum Integrated Heterodyne Photoreceiver for Coherent Lidar Applications

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin; Pierrottet, Diego; Singh, Upendra; Kavaya, Michael

    2005-01-01

    Many coherent lidar applications, particularly airborne and space-based applications, impose stringent power and size constraints while requiring high levels of sensitivity. For this reason, optimization of the lidar heterodyne photoreceiver is one of the critical steps in ensuring full utilization of limited resources to achieve the required sensitivity. The analysis of 2-micron heterodyne receivers shows that substantial improvement of the order of 3 dB can be obtained by proper optimization of the receiver key control parameters and elimination of its parasitic capacitances by integrating the detector, its bias circuit, and the preamplifier on a single substrate. This paper describes analytical steps for defining optimum heterodyne receiver design parameters and development of experimental devices operating at 2-micron wavelength.

  20. Heterodyne and coherent optical fiber communications - Recent progress

    NASA Astrophysics Data System (ADS)

    Okoshi, T.

    1982-08-01

    It is pointed out that the present optical fiber communications are in a sense as primitive as the radio communications prior to 1930. The modulation/demodulation scheme being employed in the present standard optical fiber communications is often called the intensity-modulation/direct-detection (IM/DD) scheme. According to this scheme, no attention is paid to the phase of the carrier. On the other hand, in the history of radio communications, the heterodyne scheme became common since 1930, and coherent modulations such as FM, PM, FSK, and PSK are currently widely used. The question arises whether a similar development might occur in optical communications. The IM/DD system has a great advantage in system simplicity and low cost. However, for certain applications a heterodyne/coherent system would provide distinct improvements. An investigation indicates that, despite technical difficulties, and heterodyne/coherent system is a promising and interesting technical target.

  1. Heterodyne detection with mismatch correction based on array detector

    NASA Astrophysics Data System (ADS)

    Dong, Hongzhou; Li, Guoqiang; Yang, Ruofu; Yang, Chunping; Ao, Mingwu

    2016-07-01

    Based on an array detector, a new heterodyne detection system, which can correct the mismatches of amplitude and phase between signal and local oscillation (LO) beams, is presented in this paper. In the light of the fact that, for a heterodyne signal, there is a certain phase difference between the adjacent two samples of analog-to-digital converter (ADC), we propose to correct the spatial phase mismatch by use of the time-domain phase difference. The corrections can be realized by shifting the output sequences acquired from the detector elements in the array, and the steps of the shifting depend on the quantity of spatial phase mismatch. Numerical calculations of heterodyne efficiency are conducted to confirm the excellent performance of our system. Being different from previous works, our system needs not extra optical devices, so it provides probably an effective means to ease the problem resulted from the mismatches.

  2. Heterodyne detection with mismatch correction base on array detector

    NASA Astrophysics Data System (ADS)

    Hongzhou, Dong; Guoqiang, Li; Ruofu, Yang; Chunping, Yang; Mingwu, Ao

    2016-07-01

    Based on an array detector, a new heterodyne detection system, which can correct the mismatches of amplitude and phase between signal and local oscillation (LO) beams, is presented in this paper. In the light of the fact that, for a heterodyne signal, there is a certain phase difference between the adjacent two samples of analog-to-digital converter (ADC), we propose to correct the spatial phase mismatch by use of the time-domain phase difference. The corrections can be realized by shifting the output sequences acquired from the detector elements in the array, and the steps of the shifting depend on the quantity of spatial phase mismatch. Numerical calculations of heterodyne efficiency are conducted to confirm the excellent performance of our system. Being different from previous works, our system needs not extra optical devices, so it provides probably an effective means to ease the problem resulted from the mismatches.

  3. Performance of moire deflectometry with deferred electronic heterodyne readout

    NASA Technical Reports Server (NTRS)

    Stricker, Josef

    1987-01-01

    The effects of diffraction and nonlinear photographic emulsion characteristics on the performance of deferred electronic heterodyne moire deflectometry are theoretically and experimentally investigated. The intensity transmission distribution of the transparency, the moire image, the heterodyne readout, and the spatial and angular resolution are analytically discussed. The deferred electronic heterodyne technique is evaluated by measuring small fringe shifts caused by a weak phase object. It is found that this technique can be applied for accurate and sensitive readout of moire fringes of unsteady phase objects. The theoretical study shows that the accuracy and sensitivity of the system are weakly affected by diffraction and nonlinear photographic emulsion characteristics. Nonlinear recording does not affect the spatial resolution of the system.

  4. Laser-induced thermal-acoustic velocimetry with heterodyne detection

    SciTech Connect

    Schlamp, Stefan; Cummings, Eric B.; Sobota, Thomas H.

    2000-02-15

    Laser-induced thermal acoustics (LITA) was used with heterodyne detection to measure simultaneously and in a single laser pulse the sound speed and flow velocity of NO{sub 2} -seeded air in a low-speed wind tunnel up to Mach number M=0.1 . The uncertainties of the velocity and the sound speed measurements were {approx}0.2 m/s and 0.5%, respectively. Measurements were obtained through a nonlinear least-squares fit to a general, analytic closed-form solution for heterodyne-detected LITA signals from thermal gratings. Agreement between theory and experiment is exceptionally good. (c) 2000 Optical Society of America.

  5. Bandpass sampling in heterodyne receivers for coherent optical access networks.

    PubMed

    Bakopoulos, Paraskevas; Dris, Stefanos; Schrenk, Bernhard; Lazarou, Ioannis; Avramopoulos, Hercules

    2012-12-31

    A novel digital receiver architecture for coherent heterodyne-detected optical signals is presented. It demonstrates the application of bandpass sampling in an optical communications context, to overcome the high sampling rate requirement of conventional receivers (more than twice the signal bandwidth). The concept is targeted for WDM coherent optical access networks, where applying heterodyne detection constitutes a promising approach to reducing optical hardware complexity. The validity of the concept is experimentally assessed in a 76 km WDM-PON scenario, where the developed DSP achieves a 50% ADC rate reduction with penalty-free operation. PMID:23388768

  6. Atmospheric temperature profiling using an infrared heterodyne radiometer

    NASA Technical Reports Server (NTRS)

    Yustein, D.; Chiou, W. C.; Peyton, B. J.

    1976-01-01

    The applicability of a high resolution infrared heterodyne radiometer for atmospheric temperature profiling is considered. Upwelling radiation at the 754.321/cm and the 945.976/cm rotational-vibrational lines of CO2 are monitored by a six IF channel infrared heterodyne radiometer with spectral specificity between 0.002 and 0.012/cm. Computer simulated retrievals have been carried out which indicate a maximum temperature inaccuracy of 3.5 K for vertical profiles between ground level and 50 km and a system integration time of 8 seconds.

  7. A SIMPLE HETERODYNE TEMPORAL SPECKLE-PATTERN INTERFEROMETER

    SciTech Connect

    Wong, W. O.; Gao, Z.; Lu, J.

    2010-05-28

    A common light path design of heterodyne speckle pattern interferometer based on temporal speckle pattern interferometry is proposed for non-contact, full-field and real-time continuous displacement measurement. Double frequency laser is produced by rotating a half wave plate. An experiment was carried out to measure the dynamic displacement of a cantilever plate for testing the proposed common path heterodyne speckle pattern interferometer. The accuracy of displacement measurement was checked by measuring the motion at the mid-point of the plate with a point displacement sensor.

  8. Generation and transmission of 8 × 112-Gb/s WDM PDM-16QAM on a 25-GHz grid with simplified heterodyne detection.

    PubMed

    Dong, Ze; Li, Xinying; Yu, Jianguo; Yu, Jianjun

    2013-01-28

    We propose and experimentally demonstrate a coherent receiver based on simplified heterodyne detection for 100 G polarization division multiplexing (PDM) signal. Compared to the conventional homodyne detection, only two balanced photo detectors (PDs) and two analog-to-digital converters (ADCs) are used in the simplified heterodyne detection. Compared to the conventional hybrid for homodyne detection, the polarization-diversity hybrid here is also simplified. The in-phase/quadrature (I/Q) separation and corresponding digital signal processing (DSP) following downconversion are realized in digital domain after ADCs. Using this scheme, we successfully demonstrated 8 × 112-Gb/s wavelength-division-multiplexing (WDM) polarization-division-multiplexing 16-ary quadrature amplitude modulation (PDM-16QAM) over 720-km single-mode fiber (SMF)-28 with heterodyne detection based on DSP and erbium-doped fiber amplifier (EDFA)-only amplification. Although the required analog bandwidth and sampling speed of the PDs and ADCs are significantly increased for heterodyne detection, the benefits from the simplified coherent receiver architecture and effective DSP in digital frequency domain are experimentally demonstrated. PMID:23389161

  9. Heterodyne Interferometry with a Scanning Optical Microscope.

    NASA Astrophysics Data System (ADS)

    Hobbs, Philip Charles Danby

    The design and implementation of a confocal optical microscope which functions as an electronically scanned heterodyne interferometer are described. Theoretical models based on Fourier optics for general samples and on exact series solution of the scalar Helmholtz equation for a class of trench structures are developed and compared with experimental data. Good agreement is obtained. The associated data acquisition system, also described, enables the system to measure both the amplitude (to 12 bits) and the phase (to 0.1^circ) of a returned optical beam, at a continuous rate of 30,000 points per second. The microscope system uses a wide-band tellurium dioxide acousto-optic cell for electronic scanning, frequency shifting, and beam splitting/combining. It uses a stationary reference beam on the sample for vibration cancellation, which results in a system of great vibration immunity. It can measure relief ranging from a few tenths of a micron down to a few Angstroms, and line widths down to well below 0.4 micron, using light of 0.5 micron wavelength. Angstrom resolution can be achieved in a single full-speed scan, without special vibration isolation equipment, providing that folding mirrors are avoided. A signal processing algorithm based on Fourier deconvolution is presented; it takes advantage of the extra bandwidth of a confocal system and the availability of both amplitude and phase, to improve the lateral resolution by approximately a factor of two. Experimental results are shown, which demonstrate phase edge resolution (10%-90%) of 0.45 lambda (raw data), and 0.18 lambda (after filtering), in excellent agreement with the Fourier optics prediction. The exact scalar theory calculates the response of the microscope as it scans over an infinitely long rectangular trench in a plane boundary on which Dirichlet boundary conditions apply. An expansion in cavity modes inside the trench is used to match the field and its derivatives across the mouth of the trench to get

  10. Source-Manipulating Wavelength-Dependent Continuous-Variable Quantum Key Distribution with Heterodyne Detectors

    NASA Astrophysics Data System (ADS)

    Lv, Geli; Huang, Dazu; Guo, Ying

    2016-05-01

    The intensities of signal and local oscillator (LO) can be elegantly manipulated for the noise-based quantum system while manipulating the wavelength-dependent modulation in source to increase the performance of the continuous-variable key distribution in terms of the secret key rate and maximal transmission distance. The source-based additional noises can be tuned and stabilized to the suitable values to eliminate the effect of the LO fluctuations and defeat the potential attacks in imperfect quantum channels. It is firmly proved that the secret key rate can be manipulated in source over imperfect channels by the intensities of signal and LO with different wavelengths, which have an effect on the optimal signal-to-noise ratio of the heterodyne detectors resulting from the detection efficiency and the additional electronic noise as well. Simulation results show that there is a nice balance between the secret key rate and the maximum transmission distance.

  11. A Spatial Heterodyne Spectrometer for Laboratory Astrophysics; First Interferogram

    NASA Technical Reports Server (NTRS)

    Lawler, J. E.; Labby, Z. E.; Roesler, F. L.; Harlander, J.

    2006-01-01

    A Spatial Heterodyne Spectrometer with broad spectral coverage across the VUV - UV region and with a high (> 500,000 ) spectral resolving power is being built for laboratory measurements of spectroscopic data including emission branching fractions, improved level energies, and hyperfine/isotopic parameters.

  12. Heterodyne readout for read-write holographic memories

    NASA Technical Reports Server (NTRS)

    Mezrich, R. S.; Stewart, W. C.

    1973-01-01

    A heterodyne readout technique for read-write holographic memory systems that reconstruct a virtual image wavefront is described and demonstrated. The conventionally recorded hologram is illuminated simultaneously with a suitable combination of temporally modulated reference and modified object waves for readout. Best performance is obtained for temporal phase modulation. The coupling of the illuminating wavefronts by the hologram is analyzed.

  13. Germanium:gallium photoconductors for far infrared heterodyne detection

    NASA Technical Reports Server (NTRS)

    Park, I. S.; Haller, E. E.; Grossman, E. N.; Watson, Dan M.

    1988-01-01

    Highly compensated Ge:Ga photoconductors for high bandwidth heterodyne detection have been fabricated and evaluated. Bandwidths up to 60 MHz have been achieved with a corresponding current responsivity of 0.01 A/W. The expected dependence of bandwidth on bias field is obtained. It is noted that increased bandwidth is obtained at the price of greater required local oscillator power.

  14. Spatial frequency response of an optical heterodyne receiver

    NASA Technical Reports Server (NTRS)

    Robinson, D. M.; Fales, C. L.

    1980-01-01

    The analysis of a passive heterodyne receiver with respect to its imaging performance (transfer function) and its heterodyne efficiency shows departures from the results which are obtained in strictly coherent or incoherent imaging systems. The cascading property of modulation transfer function analysis must be carefully applied, since the coherent transfer function of the optical receiver and that due to the local oscillator-detector combination are not separable but are related by the convolution of their products. Application of these results to a spacelab-type optical heterodyne receiver shows that resolutions of the order of 1.5 to 2.0 km are possible for worst-case type orbital scenarios. In addition to an analysis of the derogatory effects of sampling (aliasing) a comparison of obscured-type receivers (e.g., Cassegrains) with unobscured receivers shows that both resolution and efficiency are severly degraded in an obscured-type receiver and, consequently, should not be used for passive heterodyne detection schemes.

  15. An SIS Waveguide heterodyne Reciever for 600 GHz - 635 GHz

    NASA Technical Reports Server (NTRS)

    Salez, Morvan; Febvre, Pascal; McGrath, William R.; Bumble, Bruce; LeDuc, Henry G.

    1994-01-01

    A waveguide SIS heterodyne receiver using a Nb/A10xNb junction has been built for astronomical observations of molecular tranitions in the frequency range 600GHz - 635GHZ, and has been successfully used at the Caltech Submillimeter Observatory (CSO).

  16. Imaging doppler velocimeter with downward heterodyning in the optical domain

    DOEpatents

    Reu, Phillip L; Hansche, Bruce D

    2013-05-21

    In a Doppler velocimeter, the incoming Doppler-shifted beams are heterodyned to reduce their frequencies into the bandwidth of a digital camera. This permits the digital camera to produce at every sampling interval a complete two-dimensional array of pixel values. This sequence of pixel value arrays provides a velocity image of the target.

  17. Laser/Heterodyne Measurement of Temperature and Salinity

    NASA Technical Reports Server (NTRS)

    Jobson, D. J.; Fales, C. L.; Katzberg, S. J.

    1982-01-01

    Proposed visible-light laser/heterodyne receiver would remotely measure temperature and salinity of subsurface water. Operation is based on acoustic/optical scattering of light by sound waves. Application of this concept is foreseen in current research on energy conversion from ocean currents produced by thermal gradients and on future marine remote-sensing program.

  18. Pattern recognition via multispectral, hyperspectral, and polarization-based imaging

    NASA Astrophysics Data System (ADS)

    El-Saba, Aed; Alam, Mohammad S.; Sakla, Wesam A.

    2010-04-01

    Pattern recognition deals with the detection and identification of a specific target in an unknown input scene. Target features such as shape, color, surface dynamics, and material characteristics are common target attributes used for identification and detection purposes. Pattern recognition using multispectral (MS), hyperspectral (HS), and polarization-based spectral (PS) imaging can be effectively exploited to highlight one or more of these attributes for more efficient target identification and detection. In general, pattern recognition involves two steps: gathering target information from sensor data and identifying and detecting the desired target from sensor data in the presence of noise, clutter, and other artifacts. Multispectral and hyperspectral imaging (MSI/HSI) provide both spectral and spatial information about the target. As the reflection or emission spectral signatures depend on the elemental composition of objects residing within the scene, the polarization state of radiation is sensitive to the surface features such as relative smoothness or roughness, surface material, shapes and edges, etc. Therefore, polarization information imparted by surface reflections of the target yields unique and discriminatory signatures which could be used to augment spectral target detection techniques, through the fusion of sensor data. Sensor data fusion is currently being used to effectively recognize and detect one or more of the target attributes. However, variations between sensors and temporal changes within sensors can introduce noise in the measurements, contributing to additional target variability that hinders the detection process. This paper provides a quick overview of target identification and detection using MSI/HSI, highlighting the advantages and disadvantages of each. It then discusses the effectiveness of using polarization-based imaging in highlighting some of the target attributes at single and multiple spectral bands using polarization

  19. The reduction of the LO number for heterodyne coherent detection.

    PubMed

    Li, Xinying; Yu, Jianjun; Chi, Nan; Dong, Ze; Zhang, Junwen; Yu, Jianguo

    2012-12-31

    Relative to homodyne coherent detection, heterodyne coherent detection has simple architecture because no 90° hybrid and only half number of photodiodes and analog-to-digital convertor (ADC) chips are required. We experimentally demonstrate that the architecture of heterodyne coherent receivers can be further simplified. When the frequency offset is one half of the channel frequency spacing, one local oscillator (LO) laser can be used for two neighboring wavelength-division-multiplexing (WDM) channels, and therefore the number of LO lasers can be reduced into half compared to homodyne detection. We experimentally demonstrate simplified heterodyne coherent detection of 4 × 196.8-Gb/s polarization-division-multiplexing carrier-suppressed return-to-zero quadrature-phase-shift-keying (PDM-CSRZ-QPSK) modulation after transmission over 1040-km single-mode fiber (SMF)-28 on a 50-GHz grid with bit-error ratio (BER) smaller than pre-forward-error-correction (pre-FEC) limit of 3.8 × 10(-3). To our best knowledge, 196.8 Gb/s is the highest bit rate per channel for heterodyne coherent WDM transmission system. An arrayed waveguide grating (AWG) instead of wavelength selective switch (WSS) is used at the transmitter to spectrally shape and multiplex the WDM signal. We also experimentally demonstrate that heterodyne detection causes 3-dB optical signal-to-noise ratio (OSNR) penalty at the BER of 3.8 × 10(-3) for a certain single channel compared to homodyne detection. PMID:23388788

  20. Cryogenic 160-GHz MMIC Heterodyne Receiver Module

    NASA Technical Reports Server (NTRS)

    Samoska, Lorene A.; Soria, Mary M.; Owen, Heather R.; Dawson, Douglas E.; Kangaslahti, Pekka P.; Gaier, Todd C.; Voll, Patricia; Lau, Judy; Sieth, Matt; Church, Sarah

    2011-01-01

    A cryogenic 160-GHz MMIC heterodyne receiver module has demonstrated a system noise temperature of 100 K or less at 166 GHz. This module builds upon work previously described in Development of a 150-GHz MMIC Module Prototype for Large-Scale CMB Radiation (NPO-47664), NASA Tech Briefs, Vol. 35, No. 8 (August 2011), p. 27. In the original module, the local oscillator signal was saturating the MMIC low-noise amplifiers (LNAs) with power. In order to suppress the local oscillator signal from reaching the MMIC LNAs, the W-band (75 110 GHz) signal had to be filtered out before reaching 140 170 GHz. A bandpass filter was developed to cover 120 170 GHz, using microstrip parallel-coupled lines to achieve the desired filter bandwidth, and ensure that the unwanted W-band local oscillator signal would be sufficiently suppressed. With the new bandpass filter, the entire receiver can work over the 140 180-GHz band, with a minimum system noise temperature of 460 K at 166 GHz. The module was tested cryogenically at 20 K ambient temperature, and it was found that the receiver had a noise temperature of 100 K over an 8-GHz bandwidth. The receiver module now includes a microstrip bandpass filter, which was designed to have a 3-dB bandwidth of approximately 120-170 GHz. The filter was fabricated on a 3-mil-thick alumina substrate. The filter design was based on a W-band filter design made at JPL and used in the QUIET (Q/U Imaging ExperimenT) radiometer modules. The W-band filter was scaled for a new center frequency of 150 GHz, and the microstrip segments were changed accordingly. Also, to decrease the bandwidth of the resulting scaled design, the center gaps between the microstrip lines were increased (by four micrometers in length) compared to the gaps near the edges. The use of the 150-GHz bandpass filter has enabled the receiver module to function well at room temperature. The system noise temperature was measured to be less than 600 K (at room temperature) from 154 to 168 GHz

  1. Single beam write and/or replay of spatial heterodyne holograms

    DOEpatents

    Thomas, Clarence E.; Hanson, Gregory R.

    2007-11-20

    A method of writing a spatially heterodyne hologram having spatially heterodyne fringes includes: passing a single write beam through a spatial light modulator that digitally modulates said single write beam; and focusing the single write beam at a focal plane of a lens to impose a holographic diffraction grating pattern on the photorefractive crystal, the holographic diffraction grating pattern including the spatially heterodyne hologram having spatially heterodyne fringes, wherein only said single write beam is incident on said photorefractive crystal without a reference beam. A method of replaying a spatially heterodyne hologram having spatially heterodyne fringes at a replay angle includes: illuminating a photorefractive crystal having a holographic diffraction grating with a beam from a laser at an illumination angle, the holographic diffraction grating pattern including the spatially heterodyne hologram having spatially heterodyne fringes, wherein a difference between said illumination angle and said replay angle defines a diffraction angle .alpha. that is a function of a plane wave mathematically added to original object wave phase and amplitude data of said spatially heterodyne hologram having spatially heterodyne fringes.

  2. Recording multiple spatially-heterodyned direct to digital holograms in one digital image

    DOEpatents

    Hanson, Gregory R.; Bingham, Philip R.

    2008-03-25

    Systems and methods are described for recording multiple spatially-heterodyned direct to digital holograms in one digital image. A method includes digitally recording, at a first reference beam-object beam angle, a first spatially-heterodyned hologram including spatial heterodyne fringes for Fourier analysis; Fourier analyzing the recorded first spatially-heterodyned hologram by shifting a first original origin of the recorded first spatially-heterodyned hologram to sit on top of a first spatial-heterodyne carrier frequency defined by the first reference beam-object beam angle; digitally recording, at a second reference beam-object beam angle, a second spatially-heterodyned hologram including spatial heterodyne fringes for Fourier analysis; Fourier analyzing the recorded second spatially-heterodyned hologram by shifting a second original origin of the recorded second spatially-heterodyned hologram to sit on top of a second spatial-heterodyne carrier frequency defined by the second reference beam-object beam angle; applying a first digital filter to cut off signals around the first original origin and define a first result; performing a first inverse Fourier transform on the first result; applying a second digital filter to cut off signals around the second original origin and define a second result; and performing a second inverse Fourier transform on the second result, wherein the first reference beam-object beam angle is not equal to the second reference beam-object beam angle and a single digital image includes both the first spatially-heterodyned hologram and the second spatially-heterodyned hologram.

  3. A Deeper Look at the Fundamentals of Heterodyne Detection Requirements

    NASA Technical Reports Server (NTRS)

    Roychoudhuri, Chandrasekhar; Prasad, Narasimha S.

    2007-01-01

    We generally accept the experimentally observed criteria for heterodyne detections that the two waves that are mixed must (i) be collinear, (ii) have matched wave fronts and (iii) cannot be orthogonally polarized. We have not found in the literature adequate physical explanations for these requirements. The purpose of this paper is to find deeper physical understanding of the coherent heterodyne detection processes that could lead to better coherent laser radar system designs1. We find that there are a number of unresolved paradoxes in classical and quantum optics regarding the definitions and understanding of the "interference" and "coherence" properties of light, which are attributed as essentially due to inherent properties of the EM waves. A deeper exploration indicates that it is the various quantum mechanical properties of the detecting material dipoles that make light detectable (visible, or measurable) to us. Accordingly, all the properties that we generally attribute to only light, are in reality manifestations of collective properties of dipole-light interactions. "Interference" and "coherence" can be better understood in terms of this mutual interaction, followed by energy absorption by the dipoles from EM wave fields, manifesting in some measurable transformation of the detecting dipoles. Light beams do not interfere by themselves. The superposition effects due to light beams become manifest through the response characteristics of the detecting dipoles. In this paper, we will show some preliminary expe rimental results that clearly demonstrate that the heterodyning wave fronts have quantitative degradation in signal generation as the angle between them deviates from perfect collinearity. Subsequently, we will propose a hypothesis for this behavior. We will present experimental data establishing that the so called incoherent light can be detected through heterodyne mixing as long as the pulse length contained in the "incoherent" light is longer than the

  4. Asymmetric polarization-based frequency shifting interferometer for microelectronics

    NASA Astrophysics Data System (ADS)

    Lee, Seung Hyun; Kim, Min Young

    2014-05-01

    Frequency Scanning Interferometry(FSI) generally results in superior optical performance comparing with other 3-dimensional measuring methods as its hardware structure is fixed in operation and only the light frequency is scanned in a specific spectral band without vertical scanning of the target surface or the objective lens. However, it still suffers from optical noise due to polarization characteristic of target surfaces and relatively long processing time due to the number of images acquired in frequency scanning phase. First, a Polarization-based Frequency Scanning Interferometry(PFSI) is proposed for optical noise robustness. It consists of tunable laser for light source, λ/4 plate in front of reference mirror, λ /4 plate in front of target object, polarizing beam splitter, polarizer in front of image sensor, polarizer in front of the fiber coupled light source, λ/2 plate between PBS and polarizer of the light source. Using the proposed system, we can solve the problem of fringe image with low contrast by using polarization technique. Also, we can control light distribution of object beam and reference beam. Second the signal processing acceleration method is proposed for PFSI, based on parallel processing architecture, which consists of parallel processing hardware and software such as Graphic Processing Unit(GPU) and Compute Unified Device Architecture(CUDA). Finally, the proposed system is evaluated in terms of accuracy and processing speed through a series of experiment and the obtained results show the effectiveness of the proposed system and method.

  5. Creating photorealistic virtual model with polarization-based vision system

    NASA Astrophysics Data System (ADS)

    Shibata, Takushi; Takahashi, Toru; Miyazaki, Daisuke; Sato, Yoichi; Ikeuchi, Katsushi

    2005-08-01

    Recently, 3D models are used in many fields such as education, medical services, entertainment, art, digital archive, etc., because of the progress of computational time and demand for creating photorealistic virtual model is increasing for higher reality. In computer vision field, a number of techniques have been developed for creating the virtual model by observing the real object in computer vision field. In this paper, we propose the method for creating photorealistic virtual model by using laser range sensor and polarization based image capture system. We capture the range and color images of the object which is rotated on the rotary table. By using the reconstructed object shape and sequence of color images of the object, parameter of a reflection model are estimated in a robust manner. As a result, then, we can make photorealistic 3D model in consideration of surface reflection. The key point of the proposed method is that, first, the diffuse and specular reflection components are separated from the color image sequence, and then, reflectance parameters of each reflection component are estimated separately. In separation of reflection components, we use polarization filter. This approach enables estimation of reflectance properties of real objects whose surfaces show specularity as well as diffusely reflected lights. The recovered object shape and reflectance properties are then used for synthesizing object images with realistic shading effects under arbitrary illumination conditions.

  6. Noise characteristics of heterodyne/homodyne frequency-domain measurements

    NASA Astrophysics Data System (ADS)

    Kang, Dongyel; Kupinski, Matthew A.

    2012-01-01

    We theoretically develop and experimentally validate the noise characteristics of heterodyne and/or homodyne measurements that are widely used in frequency-domain diffusive imaging. The mean and covariance of the modulated heterodyne output are derived by adapting the random amplification of a temporal point process. A multinomial selection rule is applied to the result of the temporal noise analysis to additionally model the spatial distribution of intensified photons measured by a charge-coupled device (CCD), which shows that the photon detection efficiency of CCD pixels plays an important role in the noise property of detected photons. The approach of using a multinomial probability law is validated from experimental results. Also, experimentally measured characteristics of means and variances of homodyne outputs are in agreement with the developed theory. The developed noise model can be applied to all photon amplification processes.

  7. The Beauty and Limitations of 10 Micron Heterodyne Interferometry (ISI)

    NASA Technical Reports Server (NTRS)

    Danchi, William C.

    2003-01-01

    Until recently, heterodyne interferometry at 10 microns has been the only successful technique for stellar interferometry in the very difficult atmospheric window from 9-12 microns. For most of its operational lifetime the U.C. Berkeley Infrared Spatial Interferometer was a single-baseline two telescope (1.65 m aperture) system using CO2 lasers as local oscillators. This instrument was designed and constructed from 1983-1988, and first fringes were obtained at Mt. Wilson in June 1988. During the past few years, a third telescope was constructed and just recently the first closure phases were obtained at 11.15 microns. We discuss the history, physics and technology of heterodyne interferometry in the mid-infrared, and some key astronomical results that have come from this unique instrument.

  8. Development of trace gas detection instrumentation. [using the heterodyne principle

    NASA Technical Reports Server (NTRS)

    1973-01-01

    Breadboard hardware was constructed to demonstrate detection of a gaseous species by the heterodyne principle. The characteristics of the component parts were investigated and preliminary measurements were made to establish the sensitivity and selectivity of the method for gas analysis of CO, CO2, and N2O. A prototype heterodyne gas analyzer was designed, built, and brought into operational condition. Performance parameters of the prototype analyzer were investigated and its sensitivity to CO2 measured. Further development was undertaken for both the optical bench and the electronic processor components. A three-gas prototype analyzer, capable of measuring the gases CO, CO2, and CH4 was also constructed and tested. Detailed descriptions of the work and results are presented.

  9. High sensitivity infrared 10.6 micrometer heterodyne receiver development

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The results are presented for a study on the design of an infrared 10.6-micrometer quantum-noise-limited optical receiver subsystem. Performance measurements of the HgCdTe photomixer preamplifier combination were carried out for photomixer temperatures up to 152 K and a photomixer frequency response of up to 420 MHz was obtained. Results of temperature and bias cycling of HgCdTe photomixers are reported. Design considerations for an operational 10.6 micrometer heterodyne receiver are presented. These consist of design data on required laser LO illumination, heat load levels for photomixer cooler, photomixer uniformity and the effects of photomixer impedance match on receiver sensitivity. Analysis and measurements of 10.6 micrometer heterodyne detection in an extrinsic photoconductive (p-type) HgCdTe photomixer are also presented.

  10. Self calibrating wavelength multiplexed heterodyne interferometer for angstrom precision measurements

    NASA Astrophysics Data System (ADS)

    Arain, Muzammil A.; Riza, Nabeel A.

    2005-05-01

    Measurement of refractive index, surface quality and temperature of the process materials in defense, petrochemical, power systems, glass, and metal industries is a fundamental need for precision systems performance. However, making these measurements in a super noisy defense or industrial environment is a big challenge faced by sensor technologies. Reported in this paper is the first ever demonstration of a wavelength multiplexed heterodyne interferometer using a single acousto-optic device (AOD). Heterodyne interferometry is pivotal in realizing a highly stable low noise interferometer. Inspite of the physical separation of the two arms of the interferometer, the sensor demonstrates Angstrom level optical path length sensitivity. The proposed sensor can be used in optical path length measurement-based sensing of parameters such as surface profile, refractive index, temperature, and pressure. Proof-of-concept experiment features a high resolution, low-loss, ultra compact, free space scanning interferometer implementation. Results include measurement of surface quality of a test mirror.

  11. The performance of heterodyne detection system for partially coherent beams in turbulent atmosphere

    NASA Astrophysics Data System (ADS)

    Chengqiang, Li; Tingfeng, Wang; Heyong, Zhang; Jingjiang, Xie; Lisheng, Liu; Shuai, Zhao; Jin, Guo

    2015-12-01

    The performance of heterodyne system is discussed for partially coherent beams in turbulent atmosphere by introducing turbulence spectrum of refractive-index fluctuations. Several analytic formulae for the heterodyne detection system using the partially coherent Gaussian Schell-model beam are presented. Based on Tatarskii spectrum model, some numerical results are given for the variation in the heterodyne efficiency with the misalignment angle, detector diameter, turbulence conditions, and parameters of the overlapping beams. According to the numerical results, we find that the turbulent atmosphere degrades the heterodyne efficiency significantly, and the variation in heterodyne efficiency is even slower against the misalignment angle in turbulence. For the deterministic received signal and the detector, the performance of the heterodyne detection can be adjusted by controlling the local oscillator signal parameters.

  12. Infrared heterodyne receivers with IF responses approaching 5 GHz

    NASA Technical Reports Server (NTRS)

    Wolczok, J. M.; Peyton, B. J.

    1980-01-01

    Specialized coherent 10.6 micrometer infrared receivers were developed with infrared frequency responses approaching 5 GHz. Carbon dioxide lasers were employed for these applications because of their availability, stability, and high average power levels. Heterodyne receivers which employ extrinsic photoconductive Ge:Cu(Sb) mixers were developed for measurements of carbon dioxide laser scattering to determine: (1) the drive lower hybrid wave density fluctuations; and (2) the plasma ion temperature of the dense Tokamak plasmas.

  13. Refractive turbulence effects on truncated Gaussian beam heterodyne lidar

    NASA Technical Reports Server (NTRS)

    Murty, R.

    1984-01-01

    A monostatic heterodyne lidar performance model is formulated to study the combined effects of beam truncation and refractive turbulence in the weak scintillation regime. The results show that there is a loss of signal power due to beam truncation and coherence loss, but there is also an enhancement of signal power due to log-amplitude covariance in suitable conditions of long paths with weak turbulence.

  14. Infrared Heterodyne Spectroscopy and its Unique Application to Planetary Studies

    NASA Technical Reports Server (NTRS)

    Kostiuk, Theodore

    2009-01-01

    Since the early 1970's the infrared heterodyne technique has evolved into a powerful tool for the study of molecular constituents, temperatures, and dynamics in planetary atmospheres. Its extremely high spectral resolution (Lambda/(Delta)Lambda/>10(exp 6)) and highly accurate frequency measurement (to 1 part in 10(exp 8)) enabled the detection of nonthermal/natural lasing phenomena on Mars and Venus; direct measurements of winds on Venus, Mars, and Titan; study of mid-infrared aurorae on Jupiter; direct measurement of species abundances on Mars (ozone, isotopic CO2), hydrocarbons on Jupiter, Saturn., Neptune, and Titan, and stratospheric composition in the Earth's stratosphere (O3, CIO, N2O, CO2 ....). Fully resolved emission and absorption line shapes measured by this method enabled the unambiguous retrieval of molecular abundances and local temperatures and thermal structure in regions not probed by other techniques. The mesosphere of Mars and thermosphere of Venus are uniquely probed by infrared heterodyne spectroscopy. Results of these studies tested and constrained photochemical and dynamical theoretical models describing the phenomena measured. The infrared heterodyne technique will be described. Highlights in its evolution to today's instrumentation and resultant discoveries will be presented, including work at Goddard Space Flight Center and the University of Koln. Resultant work will include studies supporting NASA and ESA space missions and collaborations between instrumental and theoretical groups.

  15. LACOMA- OPTICAL ANALYSIS FOR LASER HETERODYNE COMMUNICATION SYSTEM

    NASA Technical Reports Server (NTRS)

    Cohen, S.

    1994-01-01

    LACOMA (Laser Communicator Analysis Program) was developed to predict the effects of optical aberrations on transmitters and receivers used in heterodyne communication systems. Combining the proven techniques of a previous optical program with a new approach designed to evaluate heterodyne performance, the program is a general purpose package to be used by optical and communication engineers. Two independent optical trains for the received signal and the local oscillator are specified and evaluated. A comprehensive ray trace subroutine and Fourier transform compute complex amplitude spread functions in a specified detector plane. The two functions are combined and integrated over a specific detector to determine heterodyne signal power. This power is normalized with respect to an ideal value to provide a quantitative value for receiver degradation. Values of local oscillator illumination efficiency, optical transmission, detection efficiency and phase match efficiency are also evaluated to isolate the cause of any unexpected degradations. The program has been used for a tolerance analysis of a selected system designed for space communications, and for evaluation of several other systems. This program was implemented on an IBM 360/91 and an IBM 360/95 and needs approximately 103K bytes of core.

  16. Limitations for heterodyne detection of Brillouin scattered light

    SciTech Connect

    Allemeier, R.T.; Wagner, J.W.; Telschow, K.L.

    1995-01-01

    One means by which elastic properties of a material may be determined is measuring sound wave velocities in the material, from which elastic moduli of interest can be computed. Velocity can be measured by conventional piezoelectric transduction techniques, by applying laser ultrasonics, or by using Brillouin-scattering methods. Brillouin-scattering techniques for determining the sound wave velocity are particularly attractive since they are completely noninvasive. Only a probe beam of light is required since the thermal energy in the material provides the elastic motion. Heterodyne methods for detection of Brillouin-scattered light are considered one possible means to increase the speed of the scattered light frequency detection. Results of experiments with simulated Brillouin scattering suggest that heterodyne detection of the Brillouin-scattered light is feasible. Experiments to detect Brillouin-scattered light, with water as the scattering medium, were designed and interpreted using the results of the simulated scattering experiments. Overall, results showed that it is difficult to narrow the linewidth for Brillouin scattering to an acceptable level. The results given indicate that heterodyne detection of the Brillouin components requires detection bandwidths that are quite small, perhaps 10 Hz or lower. These small bandwidths can be routinely achieved using lock-in amplifier techniques.

  17. Principles and Application of Heterodyne Scanning Tunnelling Spectroscopy

    PubMed Central

    Matsuyama, Eiji; Kondo, Takahiro; Oigawa, Haruhiro; Guo, Donghui; Nemoto, Shojiro; Nakamura, Junji

    2014-01-01

    Detection of the extremely weak signals in spectroscopy over an extremely wide frequency region is central to diverse sciences, including materials science, biology, astronomy and chemistry. Here we show a new type of atomic-scale spectroscopy, heterodyne scanning tunnelling spectroscopy (HSTS), which is based on the innovative application of the nonlinear heterodyne-mixing detection at the metal-insulator-metal (MIM) heterojunction of STM tip–vacuum–sample. The principle of HSTS is identical to that of the Atacama Large Millimeter Array (ALMA) space telescope in terms of using heterojunction for detecting extremely weak signals by converting from terahertz region to lower frequency regions. The MIM detector of ALMA, which is composed of niobium–titanium–nitride (NbTiN) tip-insulator-NbTiN, is very similar in shape and size to that of HSTS. We successfully detect a heterodyne beat signal f3 (= |f2 − f1|) and intermodulation distortion via tunnelling current by superimposing two different AC signals, f1 and f2, onto the DC tunnelling current at a highly oriented pyrolytic graphite (HOPG) surface. We then obtain spectra of the localized electronic states of HOPG by using f3. HSTS can be performed with a high resolution and over a wide energy range, including the terahertz range. PMID:25342108

  18. Towards an Imaging Mid-Infrared Heterodyne Spectrometer

    NASA Technical Reports Server (NTRS)

    Hewagama, T.; Aslam, S.; Jones, H.; Kostiuk, T.; Villanueva, G.; Roman, P.; Shaw, G. B.; Livengood, T.; Allen, J. E.

    2012-01-01

    We are developing a concept for a compact, low-mass, low-power, mid-infrared (MIR; 5- 12 microns) imaging heterodyne spectrometer that incorporates fiber optic coupling, Quantum Cascade Laser (QCL) local oscillator, photomixer array, and Radio Frequency Software Defined Readout (RFSDR) for spectral analysis. Planetary Decadal Surveys have highlighted the need for miniaturized, robust, low-mass, and minimal power remote sensing technologies for flight missions. The drive for miniaturization of remote sensing spectroscopy and radiometry techniques has been a continuing process. The advent of MIR fibers, and MEMS techniques for producing waveguides has proven to be an important recent advancement for miniaturization of infrared spectrometers. In conjunction with well-established photonics techniques, the miniaturization of spectrometers is transitioning from classic free space optical systems to waveguide/fiber-based structures for light transport and producing interference effects. By their very nature, these new devices are compact and lightweight. Mercury-Cadmium-Telluride (MCT) and Quantum Well Infrared Photodiodes (QWIP) arrays for heterodyne applications are also being developed. Bulky electronics is another barrier that precluded the extension of heterodyne systems into imaging applications, and our RFSDR will address this aspect.

  19. Principles and application of heterodyne scanning tunnelling spectroscopy.

    PubMed

    Matsuyama, Eiji; Kondo, Takahiro; Oigawa, Haruhiro; Guo, Donghui; Nemoto, Shojiro; Nakamura, Junji

    2014-01-01

    Detection of the extremely weak signals in spectroscopy over an extremely wide frequency region is central to diverse sciences, including materials science, biology, astronomy and chemistry. Here we show a new type of atomic-scale spectroscopy, heterodyne scanning tunnelling spectroscopy (HSTS), which is based on the innovative application of the nonlinear heterodyne-mixing detection at the metal-insulator-metal (MIM) heterojunction of STM tip-vacuum-sample. The principle of HSTS is identical to that of the Atacama Large Millimeter Array (ALMA) space telescope in terms of using heterojunction for detecting extremely weak signals by converting from terahertz region to lower frequency regions. The MIM detector of ALMA, which is composed of niobium-titanium-nitride (NbTiN) tip-insulator-NbTiN, is very similar in shape and size to that of HSTS. We successfully detect a heterodyne beat signal f₃(= |f₂- f₁) and intermodulation distortion via tunnelling current by superimposing two different AC signals, f₁ and f₂, onto the DC tunnelling current at a highly oriented pyrolytic graphite (HOPG) surface. We then obtain spectra of the localized electronic states of HOPG by using f₃. HSTS can be performed with a high resolution and over a wide energy range, including the terahertz range. PMID:25342108

  20. Research on beam splitting prism in laser heterodyne interferometer

    NASA Astrophysics Data System (ADS)

    Fu, Xiu-hua; Xiong, Shi-fu; Kou, Yang; Pan, Yong-gang; Chen, Heng; Li, Zeng-yu; Zhang, Chuan-xin

    2014-08-01

    With the rapid development of optical testing technology, laser heterodyne interferometer has been used more and more widely. As the testing precision requirements continue to increase, the technical prism is an important component of heterodyne interference. The research utilizing thin film technology to improve optical performance of interferometer has been a new focus. In the article, based on the use requirements of interferometer beam splitting prism, select Ta2O5 and SiO2 as high and low refractive index materials respectively, deposit on substrate K9. With the help of TFCalc design software and Needle method, adopting electron gun evaporation and ion assisted deposition, the beam splitting prism is prepared successfully and the ratio of transmittance and reflectance for this beam splitting prism in 500~850 nm band, incident angle 45 degree is 8:2. After repeated tests, solved the difference problem of film deposition process parameters ,controlled thickness monitoring precision effectively and finally prepared the ideal beam splitting prism which is high adhesion and stable optics properties. The film the laser induced damage threshold and it meet the requirements of heterodyne interferometer for use.

  1. Heterodyne photomixer spectrometer with receiver photomixer driven at different frequency than source photomixer

    DOEpatents

    Wanke, Michael C; Fortier, Kevin; Shaner, Eric A; Barrick, Todd A

    2013-07-09

    A heterodyne photomixer spectrometer comprises a receiver photomixer that is driven at a different frequency than the source photomixer, thereby maintaining the coherent nature of the detection, eliminating etalon effects, and providing not only the amplitude but also the phase of the received signal. The heterodyne technique can be applied where the source and receiver elements are components of a waveguide thereby forming an on-chip heterodyne spectrometer.

  2. Linear frequency modulation multi-beam laser heterodyne measurement for the glass thickness

    NASA Astrophysics Data System (ADS)

    Yan-Chao, Li; Yi-Qiao, Wang; Chun-Yu, Liu; Jiu-Ru, Yang; Qun, Ding

    2016-02-01

    This paper uses the combination of laser heterodyne technology with linear frequency modulation technology to load thickness of plate glass to the heterodyne signal frequency. By researching on the theoretical models of heterodyne signal for measuring thickness of plate glass, the direct intensity detection can be replaced by heterodyne signal frequency detection and the effects of light source power stability and environmental perturbation can be removed. The measuring accuracy of electrostriction coefficient can be further improved by using the frequency demodulation to obtain thickness of plate glass. This method is used to measure the thickness of plate glass, and simulation results show that the maximum relative measurement error is 0.01 %.

  3. Optics and cryogenics for the 1.1 THz multi-pixel heterodyne receiver for APEX

    NASA Astrophysics Data System (ADS)

    Hurtado, Norma; Graf, Urs U.; Adams, Henning; Honingh, C. E.; Jacobs, Karl; Pütz, Patrick; Güsten, Rolf; Stutzki, Jürgen

    2014-08-01

    The 1.1 THz multi-pixel heterodyne receiver will be mounted in the Nasmyth A cabin of the 12 m APEX telescope on the Chajnantor plateau, 5000 meters altitude in northern Chile. The receiver will cover the spectral window of 1000 - 1080 GHz, where important spectral lines like CO 9-8 at 1036.9 GHz, a tracer of warm and dense gas and OH+ at 1033 GHz and NH+ at 1012.6 GHz, both important for the study of chemical networks in the ISM, are located. The multi-pixel receiver greatly enhances the science output under the difficult observing conditions in this frequency range. Two 9-pixel focal plane sub-arrays on orthogonal polarizations are installed in easily removable cartridges. We developed a new thermal link to connect the cartridges to the cryostat. Our thermal link is an all-metal design: aluminum and Invar. All the optics is fully reflective, thus avoiding the absorption and reflection losses of dielectric lenses and reducing standing waves in the receiver. To guaranty internal optics alignment, we employ a monolithic integrated optics approach for the cold optics and the Focal Plane Unit (FPU) optics modeled after the CHARM (Compact Heterodyne Array Receiver Module) concept. The receiver uses synthesizer-driven solid-state local oscillators (LO) and the mixers will be balanced SIS mixers, which are essentially based on the design of the on-chip balanced SIS mixers at 490 GHz developed in our institute. Singleended HEB mixers are used for the laboratory tests of the optics. The LO power distribution is accommodated behind the FPU optics. It is composed of the LO optics, which includes a collimating Fourier grating, and an LO distribution plate to supply LO signal to each of the 9 pixels of the sub-array. Different options for the LO coupling design and fabrication are being analyzed and will be based on in-house hybrid waveguide/planar technology. We summarize the receiver project with emphasis on the cryogenics and the optics and present laboratory test results

  4. Atmospheric solar absorption measurements in the 9-11 micron region using a diode laser heterodyne spectrometer

    NASA Technical Reports Server (NTRS)

    Harward, C. N.; Hoell, J. M., Jr.

    1980-01-01

    A tunable diode laser heterodyne radiometer was developed for ground based measurements of atmospheric solar absorption spectra in the 9 to 12 micron spectral range. The performance and operating characteristics of this tunable infrared heterodyne radiometer (TIHR) is discussed along with recently measured heterodyne solar absorption spectra in the 10 to 11 micron spectral region.

  5. Spatial heterodyne spectroscopy - Interferometric performance at any wavelength without scanning

    NASA Technical Reports Server (NTRS)

    Roesler, F. L.; Harlander, J.

    1990-01-01

    Spatial heterodyne spectroscopy (SHS) employing a two-beam dispersive interferometer producing a Fizeau fringe pattern having wavelength-dependent spatial frequencies is presented. The pattern is recorded on an imaging detector and Fourier transformed to recover the input stream. It is pointed out that spectrometers operating on the SHS principle can achieve the theoretical resolution limit of the gratings without scanning, retaining at the same time the large angular input tolerance and multiplexing properties of conventional scanning Fourier-transform spectrometers. Additionally, broad spectral coverages can be achieved, and field widening can be accomplished without moving parts.

  6. Study on avalanche photodiode influence on heterodyne laser interferometer linearity

    NASA Astrophysics Data System (ADS)

    Budzyn, Grzegorz; Podzorny, Tomasz

    2016-06-01

    In the paper we analyze factors reducing the possible accuracy of the heterodyne laser interferometers. The analysis is performed for the avalanche-photodiode input stages but is in main points valid also for stages with other type of photodetectors. Instrumental error originating from optical, electronic and digital signal processing factors is taken into consideration. We stress factors which are critical and those which can be neglected at certain accuracy requirements. In the work we prove that it is possible to reduce errors of the laser instrument below 1 nm point for multiaxial APD based interferometers by precise control of incident optical power and the temperature of the photodiode.

  7. Large aperture spatial heterodyne imaging spectrometer: Principle and experimental results

    NASA Astrophysics Data System (ADS)

    Xiangli, Bin; Cai, Qisheng; Du, Shusong

    2015-12-01

    A large aperture spatial heterodyne imaging spectrometer (LASHIS) is proposed. It is a kind of pushbroom Fourier transform ultraspectral imager with no moving parts. This imaging spectrometer, based on a Sagnac lateral shearing interferometer combined with a pair of gratings, has the advantages of high spectral resolution, high throughput and robustness. The principle of LASHIS and its spectral retrieval method are introduced. The processing chain to convert raw images to ultraspectral datacube is also described. Experimental results demonstrate the high resolving power of LASHIS with the emission spectrum of a low pressure sodium lamp.

  8. Heterodyne Arrays for Terahertz/Sub-millimeter Astronomy

    NASA Astrophysics Data System (ADS)

    Kloosterman, Jenna; Walker, C. K.; SORAL; SRON; TU-Delft; JPL; APL; ASU; MIT

    2014-01-01

    The clouds of gas and dust that constitute the Interstellar Medium (ISM) within the Milky Way and other galaxies can be studied through the emission from atoms and molecules such as CO, [CI], [CII], [NII], and [OI]. Spectroscopic surveys of these tracers are necessary to disentangle large-scale structure and kinematics within the ISM. Each of these tracers has transitions in the Terahertz (THz) region of the electromagnetic spectrum, loosely defined as 0.3 - 3 THz, thus creating a need for large format THz heterodyne arrays. My dissertation research in radio instrumentation has focused on three main projects. The first, the Superheterodyne Camera (SuperCam), is a ground-based instrument for the Sub-millimeter Telescope (SMT) on Mt. Graham, Arizona. The receiver contains 64 heterodyne pixels designed to detect the J=3-2 rotational line of CO at 345 GHz. SuperCam had its first engineering run in Spring 2012 and its commissioning run in Spring 2013. The second project, the Stratospheric Terahertz Observatory (STO), is a balloon-borne, 0.8 m telescope, designed to observe the fine structure lines of [NII] and [CII] at 1.46 and 1.9 THz from an altitude of ~120,000 ft. STO had its first flight around Antarctica in January 2012 and is scheduled to have a second flight (as STO-2) in 2015. The last project is the building of a 4.74 THz heterodyne receiver to look for the fine structure line of the high density tracer [OI]. With an 815 K double sideband noise temperature (e.g. ~7 times the quantum noise limit), this is the most sensitive heterodyne receiver reported above 3 THz. It will be flown on STO-2 and was developed as part of the Galactic/extra-galactic Ultra-Long Duration Stratospheric Spectroscopic THz Observatory (GUSSTO) concept study. This dissertation talk will briefly cover the results of these instrumentation efforts and the science that drives them.

  9. Long-range vibration detection system using heterodyne interferometry.

    PubMed

    Rzasa, John R; Cho, Kyuman; Davis, Christopher C

    2015-07-10

    We present the design and performance of an extremely sensitive coherent remote vibration detection system using optical heterodyne vibration of phase shifts produced by laser light scattered off a remote target. The resulting phase-modulated intermediate RF of 200 MHz, which carries the vibrational motion of the target, is demodulated down to baseband using an RF in-phase and quadrature demodulator. Acquisition and calculation of the target phase angle is carried out on a custom-made control board which utilizes high-resolution A/D converters, variable gain amplifiers, and a Spartan-6 field programmable gate array. PMID:26193398

  10. Stabilized HEB-QCL heterodyne spectrometer at super-terahertz

    NASA Astrophysics Data System (ADS)

    Ren, Y.; Hayton, D. J.; Hovenier, J. N.; Cui, M.; Gao, J. R.; Klapwijk, T. M.; Shi, S. C.; Kao, T.-Y.; Hu, Q.; Reno, J. L.

    2012-09-01

    We report a new experiment on a high-resolution heterodyne spectrometer using a 3.5 THz quantum cascade laser (QCL) as local oscillator (LO) and a superconducting hot electron bolometer (HEB) as mixer by stabilizing both frequency and amplitude of the QCL. The frequency locking of the QCL is demonstrated by using a methanol molecular absorption line, a proportional-integral-derivative (PID) controller, and a direct power detector. We show that the LO locked linewidth can be as narrow as 35 KHz. The LO power to the HEB is also stabilized by means of swing-arm actuator placed in the beam path in combination of a second PID controller.

  11. Electronic heterodyne readout of fringes in moire deflectometry

    NASA Technical Reports Server (NTRS)

    Stricker, J.

    1985-01-01

    An electronic heterodyne technique is described for the readout of fringes in moire deflectometry. The technique is based on phase measurements of signals generated by a photodetector observing the light transmitted through a traveling moire fringe pattern. The phase of the signal is proportional to the fringe deviation and thus to the deflection angle of the light ray. The phase is measured on line by a standard phase meter with an accuracy of 1 deg or 1:360 of a fringe. The technique, which is precise and sensitive, is demonstrated by detecting and measuring a fringe shift of 0.15 mm corresponding to 0.029 of a fringe.

  12. Potential sensitivities in frequency modulation and heterodyne amplitude modulation Kelvin probe force microscopes

    PubMed Central

    2013-01-01

    In this paper, the potential sensitivity in Kelvin probe force microscopy (KPFM) was investigated in frequency modulation (FM) and heterodyne amplitude modulation (AM) modes. We showed theoretically that the minimum detectable contact potential difference (CPD) in FM-KPFM is higher than in heterodyne AM-KPFM. We experimentally confirmed that the signal-to-noise ratio in FM-KPFM is lower than that in heterodyne AM-KPFM, which is due to the higher minimum detectable CPD dependence in FM-KPFM. We also compared the corrugations in the local contact potential difference on the surface of Ge (001), which shows atomic resolution in heterodyne AM-KPFM. In contrast, atomic resolution cannot be obtained in FM-KPFM under the same experimental conditions. The higher potential resolution in heterodyne AM-KPFM was attributed to the lower crosstalk and higher potential sensitivity between topographic and potential measurements. PMID:24350866

  13. Spatial-Heterodyne Interferometry For Reflection And Transm Ission (Shirt) Measurements

    DOEpatents

    Hanson, Gregory R [Clinton, TN; Bingham, Philip R [Knoxville, TN; Tobin, Ken W [Harriman, TN

    2006-02-14

    Systems and methods are described for spatial-heterodyne interferometry for reflection and transmission (SHIRT) measurements. A method includes digitally recording a first spatially-heterodyned hologram using a first reference beam and a first object beam; digitally recording a second spatially-heterodyned hologram using a second reference beam and a second object beam; Fourier analyzing the digitally recorded first spatially-heterodyned hologram to define a first analyzed image; Fourier analyzing the digitally recorded second spatially-heterodyned hologram to define a second analyzed image; digitally filtering the first analyzed image to define a first result; and digitally filtering the second analyzed image to define a second result; performing a first inverse Fourier transform on the first result, and performing a second inverse Fourier transform on the second result. The first object beam is transmitted through an object that is at least partially translucent, and the second object beam is reflected from the object.

  14. Infrared heterodyne radiometer for airborne atmospheric transmittance measurements

    NASA Technical Reports Server (NTRS)

    Wolczok, J. M.; Lange, R. A.; Dinardo, A. J.

    1980-01-01

    An infrared heterodyne radiometer (IHR) was used to measure atmospheric transmittance at selected hydrogen fluoride (2.7 micrometer) and deuterium fluoride (3.8 micrometer) laser transitions. The IHR was installed aboard a KC-135 aircraft for an airborne atmospheric measurements program that used the sun as a backlighting source for the transmission measurements. The critical components are: a wideband indium antimonide (1nSb) photomixer, a CW HF/DF laser L0, a radiometric processor, and a 1900 K blackbody reference source. The measured heterodyne receiver sensitivity (NEP) is 1.3 x 10 to the -19th power W/Hz, which yields a calculated IHR temperature resolution accuracy of delta I sub S/-3 sub S = 0.005 for a source temperature of 1000 K and a total transmittance of 0.5. Measured atmospheric transmittance at several wavelengths and aircraft altitudes from 9.14 km (30,000 ft) to 13.72 km (45,000 ft) were obtained during the measurements program and have been compared with values predicted by the AFGL Atmospheric Line Parameter Compilation.

  15. Optical heterodyne detection for cavity ring-down spectroscopy

    DOEpatents

    Levenson, Marc D.; Paldus, Barbara A.; Zare, Richard N.

    2000-07-25

    A cavity ring-down system for performing cavity ring-down spectroscopy (CRDS) using optical heterodyne detection of a ring-down wave E.sub.RD during a ring-down phase or a ring-up wave E.sub.RU during a ring up phase. The system sends a local oscillator wave E.sub.LO and a signal wave E.sub.SIGNAL to the cavity, preferably a ring resonator, and derives an interference signal from the combined local oscillator wave E.sub.LO and the ring-down wave E.sub.RD (or ring-up wave E.sub.RU). The local oscillator wave E.sub.LO has a first polarization and the ring-down wave E.sub.RD has a second polarization different from the first polarization. The system has a combining arrangement for combining or overlapping local oscillator wave E.sub.LO and the ring-down wave E.sub.RD at a photodetector, which receives the interference signal and generates a heterodyne current I.sub.H therefrom. Frequency and phase differences between the waves are adjustable.

  16. Error sources in deferred heterodyne moire deflectometry: an analytical study.

    PubMed

    Stricker, J

    1989-09-15

    Effects of aperture size and shape of the photodetector and effects of the structure of the grating lines on the performance of deferred electronic heterodyne moire deflectometry are theoretically investigated. Deferred deflectometry is used for measurements of nonsteady phase objects for which it is difficult to complete the analysis of the field in real time. It has been shown that scanning of a moire fringe pattern parallel to an unshifted fringe yields periodical variations in the heterodyne phase and amplitude, which cause severe errors in the measurements. Theory indicates that these variations may be minimized by using a detector with square aperture of size rho/p = 1.0,2.0,3.0 ... or a circular detector with size rho/p =1.25,2.25,3.25... To minimize errors in deflection angle measurements, the fringe inclination due to the phase object should not exceed 15 degrees for a square detector and 13 degrees for a rho/p = 3.25 circular detector. Ronchi gratings with structure factor 0.5 less, similar q less, similar 0.7 are recommended. PMID:20555807

  17. Noise Immune Cavity Enhanced Optical Heterodyne Velocity Modulation Spectroscopy

    NASA Astrophysics Data System (ADS)

    Siller, Brian; Mills, Andrew; Porambo, Michael; McCall, Benjamin

    2011-06-01

    The technique of Cavity Enhanced Velocity Modulation Spectroscopy (CEVMS) has recently been developed. By demodulating the detector signal at twice the plasma modulation frequency (2f), the velocity-modulated ionic absorption signal can be extracted. Although the concentration-modulated excited neutral molecules are also observed at 2f, the ion and neutral signals can be distinguished and separated with phase-sensitive demodulation. The optical cavity provides two major benefits. It increases both the optical path length and the intracavity laser power by a factor of 2×Finesse/π. The multipass advantage allows for much longer path length than was previously possible with unidirectional multipass White cells. The power enhancement combined with perfectly overlapped counterpropagating beams within the cavity allows for sub-Doppler spectroscopy. Although CEVMS showed much potential, its sensitivity was ultimately limited by electronic noise from the plasma interfering with the cavity-locking electronics. We have further improved upon CEVMS by combining it with Noise Immune Cavity Enhanced Optical Heterodyne Molecular Spectroscopy (NICE-OHMS). The laser is frequency modulated at precisely an integer multiple of the free spectral range of the optical cavity; this allows the heterodyne sidebands to be coupled into the optical cavity. Heterodyne detection of the cavity leak-out is immune to noise in the laser-cavity lock, and 2f demodulation further decreases electronic noise in the system and retains ion-neutral discrimination. The additional level of modulation beyond ordinary CEVMS has the added advantage of enabling the observation of both absorption and dispersion signals simultaneously by using two RF mixers, each driving its own lock-in amplifier. In a single scan, four distinct signals can be obtained: absorption and dispersion for ions and excited neutrals. The technique has been demonstrated in the near-IR for N_2^+. B. M. Siller, A. A. Mills and B. J. Mc

  18. Electronic heterodyne recording and processing of optical holograms using phase modulated reference waves

    NASA Technical Reports Server (NTRS)

    Decker, A. J.; Pao, Y.-H.; Claspy, P. C.

    1978-01-01

    The use of a phase-modulated reference wave for the electronic heterodyne recording and processing of a hologram is described. Heterodyne recording is used to eliminate the self-interference terms of a hologram and to create a Leith-Upatnieks hologram with coaxial object and reference waves. Phase modulation is also shown to be the foundation of a multiple-view hologram system. When combined with hologram scale transformations, heterodyne recording is the key to general optical processing. Spatial filtering is treated as an example.

  19. Heterodyne Interferometry in InfraRed at OCA-Calern Observatory in the seventies

    NASA Astrophysics Data System (ADS)

    Gay, J.; Rabbia, Y.

    2014-04-01

    We report on various works carried four decades ago, so as to develop Heterodyne Interferometry in InfraRed (10 μm) at Calern Observatory (OCA, France), by building an experiment, whose the acronym "SOIRDETE" means "Synthese d'Ouverture en InfraRouge par Detection hETErodyne". Scientific and technical contexts by this time are recalled, as well as basic principles of heterodyne interferometry. The preliminary works and the SOIRDETE experiment are briefly described. Short comments are given in conclusion regarding the difficulties which have prevented the full success of the SOIRDETE experiment.

  20. Balance Problems

    MedlinePlus

    ... version of this page please turn Javascript on. Balance Problems About Balance Problems Have you ever felt dizzy, lightheaded, or ... dizziness problem during the past year. Why Good Balance is Important Having good balance means being able ...

  1. Analysis and System Design Framework for Infrared Spatial Heterodyne Spectrometers

    SciTech Connect

    Cooke, B.J.; Smith, B.W.; Laubscher, B.E.; Villeneuve, P.V.; Briles, S.D.

    1999-04-05

    The authors present a preliminary analysis and design framework developed for the evaluation and optimization of infrared, Imaging Spatial Heterodyne Spectrometer (SHS) electro-optic systems. Commensurate with conventional interferometric spectrometers, SHS modeling requires an integrated analysis environment for rigorous evaluation of system error propagation due to detection process, detection noise, system motion, retrieval algorithm and calibration algorithm. The analysis tools provide for optimization of critical system parameters and components including : (1) optical aperture, f-number, and spectral transmission, (2) SHS interferometer grating and Littrow parameters, and (3) image plane requirements as well as cold shield, optical filtering, and focal-plane dimensions, pixel dimensions and quantum efficiency, (4) SHS spatial and temporal sampling parameters, and (5) retrieval and calibration algorithm issues.

  2. OH absorption spectroscopy in a flame using spatial heterodyne spectroscopy.

    PubMed

    Bartula, Renata J; Ghandhi, Jaal B; Sanders, Scott T; Mierkiewicz, Edwin J; Roesler, Fred L; Harlander, John M

    2007-12-20

    We demonstrate measurements of OH absorption spectra in the post-flame zone of a McKenna burner using spatial heterodyne spectroscopy (SHS). SHS permits high-resolution, high-throughput measurements. In this case the spectra span approximately 308-310 nm with a resolution of 0.03 nm, even though an extended source (extent of approximately 2x10(-7) m(2) rad(2)) was used. The high spectral resolution is important for interpreting spectra when multiple absorbers are present for inferring accurate gas temperatures from measured spectra and for monitoring weak absorbers. The present measurement paves the way for absorption spectroscopy by SHS in practical combustion devices, such as reciprocating and gas-turbine engines. PMID:18091974

  3. OH absorption spectroscopy in a flame using spatial heterodyne spectroscopy

    NASA Astrophysics Data System (ADS)

    Bartula, Renata J.; Ghandhi, Jaal B.; Sanders, Scott T.; Mierkiewicz, Edwin J.; Roesler, Fred L.; Harlander, John M.

    2007-12-01

    We demonstrate measurements of OH absorption spectra in the post-flame zone of a McKenna burner using spatial heterodyne spectroscopy (SHS). SHS permits high-resolution, high-throughput measurements. In this case the spectra span ~308-310 nm with a resolution of 0.03 nm, even though an extended source (extent of ~2×10-7 m2 rad2) was used. The high spectral resolution is important for interpreting spectra when multiple absorbers are present for inferring accurate gas temperatures from measured spectra and for monitoring weak absorbers. The present measurement paves the way for absorption spectroscopy by SHS in practical combustion devices, such as reciprocating and gas-turbine engines.

  4. Digital Phase Meter for a Laser Heterodyne Interferometer

    NASA Technical Reports Server (NTRS)

    Loya, Frank

    2008-01-01

    The Digital Phase Meter is based on a modified phase-locked loop. When phase alignment between the reference input and the phase-shifted metrological input is achieved, the loop locks and the phase shift of the digital phase shifter equals the phase difference that one seeks to measure. This digital phase meter is being developed for incorporation into a laser heterodyne interferometer in a metrological apparatus, but could also be adapted to other uses. Relative to prior phase meters of similar capability, including digital ones, this digital phase meter is smaller, less complex, and less expensive. The phase meter has been constructed and tested in the form of a field-programmable gate array (FPGA).

  5. Airborne astronomy with a 150 micrometer - 500 micrometer heterodyne spectrometer

    NASA Technical Reports Server (NTRS)

    Betz, A. L.

    1991-01-01

    This report summarizes work done under NASA Grant NAG2-254 awarded to the University of California. The project goal was to build a far-infrared heterodyne spectrometer for NASA's Kuiper Airborne Observatory (KAO), and to use this instrument to observe atomic and molecular spectral lines from the interstellar medium. This goal was successfully achieved; the spectrometer is now in routine use aboard the KAO. Detections of particular note have been the 370 micrometers line of neutral atomic carbon, the 158 micrometers transition of ionized carbon, many of the high-J rotational lines of 12CO and 13CO between J=9-8 and J=22-21, the 119 micron ground-state rotational line of OH, and the 219 micron ground-state rotational line of H2D(+). All of these lines were observed at spectral resolutions exceeding 1 part in 10(exp 6), thereby allowing accurate line shapes and Doppler velocities to be measured.

  6. Optical simulation of large aperture spatial heterodyne imaging spectrometer

    NASA Astrophysics Data System (ADS)

    Cai, Qisheng; Xiangli, Bin; Fang, Yu

    2016-05-01

    Large aperture spatial heterodyne imaging spectrometer (LASHIS) is a new pushbroom Fourier transform ultraspectral imager with no moving parts. It is based on a Sagnac interferometer combined with a pair of gratings. In this paper, the basic principle of LASHIS is reviewed and an optical LASHIS model is set up in ZEMAX. Three interference images are presented, one is calculated according to the basic theory, one is simulated using the optical model in ZEMAX, and the other is generated by the experimental device set up in our laboratory. These three interference images show a good agreement with each other that demonstrate the correctness of the optical model. Using this model, we can simulate the interference image quickly. This image gives a visualized evaluation of the system performance, and it will be more convenient for system design or tolerance analysis of LASHIS.

  7. Stratospheric ozone measurement with an infrared heterodyne spectrometer

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Kostiuk, T.; Mumma, M. J.; Buhl, D.; Kunde, V. G.; Brown, L. W.

    1978-01-01

    A stratospheric ozone absorption line in the 10 microns band was measured and resolved completely, using an infrared heterodyne spectrometer with spectral resolution of 5 MHz (0.000167 cm to -1 power). The vertical concentration profile of stratospheric ozone was obtained through an analytical inversion of the measured spectral line profile. The absolute total column density was 0.34 cm atm with a peak mixing ratio occurring at approximately 24 km. The (7,1,6) to (7,1,7) O3 line center frequency was found to be 1043.1775 + or - 0.00033 cm to toe -1 power, or 430 + or - 10 MHz higher than the P(24) CO2 laser line frequency.

  8. A THz heterodyne instrument for biomedical imaging applications

    NASA Technical Reports Server (NTRS)

    Siegel, Peter H.

    2004-01-01

    An ultra-wide-dynamic-range heterodyne imaging system operating at 2.5 THz is described. The instrument employs room temperature Schottky barrier diode mixers and far infrared gas laser sources developed for NASA space applications. A dynamic range of over 100dB at fixed intermediate frequencies has been realized. Amplitude/phase tracking circuitry results in stability of 0.02 dB and +-2 degrees of phase. The system is being employed to characterize biological (human and animal derived tissues) and a variety of materials of interest to NASA. This talk will describe the instrument and some of the early imaging experiments on everything from mouse tail to aerogel.

  9. Stratospheric ozone measurement with an infrared heterodyne spectrometer

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Kostiuk, T.; Mumma, M. J.; Buhl, D.; Kunde, V. G.; Brown, L. W.; Spears, D.

    1978-01-01

    A stratospheric ozone absorption line in the 10 micron band was measured and resolved completely, using an infrared heterodyne spectrometer with a spectral resolution of 5 MHz. The vertical concentration profile of stratospheric ozone was obtained through an analytical inversion of the measured spectra line profile. The absolute total column density was 0.32 plus or minus 0.02 cm-atm with a peak mixing ratio occurring at approximately 24 km. The (7,1,6) - (7,1,7) O3 line center frequency was found to be 1043.1772 plus or minus 0.00033 cm/1 or 420 plus or minus 10 MHz higher than the P(24) CO2 laser line frequency.

  10. Airborne Astronomy with a 150 microns - 400 microns Heterodyne Spectrometer

    NASA Technical Reports Server (NTRS)

    Betz, A. L.

    1995-01-01

    This report summarizes work done under NASA Grant NAG2-753 awarded to the University of Colorado. The project goal was to build a far-infrared heterodyne spectrometer for NASA's Kuiper Airborne Observatory, and to use this instrument to observe atomic and molecular spectral lines from the interstellar medium. This goal was successfully achieved. Detections of particular note have been the 370 micron line of neutral atomic carbon, the 158 micron transition of ionized carbon, many of the high-J rotational lines of CO-12 and CO-13 between J=9-8 and J=22-21, the 119 micron and 163 micron rotational lines of OH, the 219 micron ground-state rotational line of H2D(+), and the 63 micron fine structure line of neutral atomic oxygen. All of these lines were observed at spectral resolutions exceeding 1 part in 10(exp 6) thereby allowing accurate line shapes and Doppler velocities to be measured.

  11. Phase-resolved ferromagnetic resonance detection using heterodyning

    NASA Astrophysics Data System (ADS)

    Yoon, Seungha; McMichael, Robert D.

    We have developed a new phase-resolved ferromagnetic (FMR) detection method using a heterodyne method. Phase resolution is important to determine the characteristics of spin transfer torques in magnetization dynamics under microwave excitation. Specifically, field-like torques and damping-like torques result in magnetization precession with different phases. In this method, we drive spin precession in a Permalloy thin film using microwaves. The resulting precession is detected using 1550 nm laser light, that is modulated at a frequency slightly shifted with respect to the driving frequency. In the reflected light, beating of the spin precession and the light modulation produces an oscillating Kerr rotation signal with a phase equal to the precession phase plus a phase due to the path length difference between the excitation microwave and the optical signal. This detection method eliminates the need for field modulation and allows detection at higher frequencies where the 1/f noise floor is reduced

  12. Electronic heterodyne readout of fringes in moiré deflectometry.

    PubMed

    Stricker, J

    1985-06-01

    An electronic heterodyne technique is described for the readout of fringes in moiré deflectometry. The technique is based on phase measurements of signals generated by a photodetector observing the light transmitted through a traveling moiré fringe pattern. The phase of the signal is proportional to the fringe deviation and thus to the deflection angle of the light ray. The phase is measured on line by a standard phase meter with an accuracy of 1 degrees or 1:360 of a fringe. The technique, which is precise and sensitive, is demonstrated by detecting and measuring a fringe shift of 0.15 mm corresponding to 0.029 of a fringe. PMID:19724409

  13. Diffraction effects and special advantages in electronic heterodyne moire deflectometry

    NASA Technical Reports Server (NTRS)

    Stricker, J.

    1986-01-01

    Effects of diffraction on the performance of electronic heterodyne readout of moire fringes are investigated. The sensitivity, accuracy, and resolution of the system are calculated, and it is shown that these features are significantly improved compared with the conventional intensity moire readout technique. The sensitivity of the system can be tripled without changing the distance between gratings. The system was evaluated experimentally by measuring the refractive-index derivatives of a weak phase object consisting of a large KD(asterisk)P crystal. Effects of nonlinear fringe modulation were studied both theoretically and experimentally. It is shown that in this case the electronic phase is not linearly related to the fringe shift, and calibration of the system is necessary.

  14. A broadband spectral inversion method for spatial heterodyne spectroscopy

    NASA Astrophysics Data System (ADS)

    Cai, Qisheng; Bin, Xiangli; Du, Shusong

    2014-11-01

    Spatial heterodyne spectroscopy (SHS) is a Fourier-transform spectroscopic technique with many advantages, such as high throughput, good robustness (no moving parts), and high resolving power. However, in the basic theory of SHS, the relationship between the wavenumber and the frequency of the interferogram is approximated to be linear. This approximation limits the spectral range of a spatial heterodyne spectrometer to a narrow band near the Littrow wavenumber. Several methods have been developed to extend the spectral range of the SHS. They use echelle gratings or tunable pilot mirrors to make a SHS instrument work at multiple narrow spectral bands near different Littrow wavenumbers. These solutions still utilize the linear relationship between the wavenumber and the frequency of the interferogram. But they need to separate different spectral bands, and this will increase the difficulty of post processing and the complexity of the SHS system. Here, we solve this problem from another perspective: making a SHS system work at one broad spectral band instead of multiple narrow spectral bands. As in a broad spectral range, the frequency of the interferogram will not be linear with respect to the wavenumber anymore. According to this non-linear relationship, we propose a broadband spectral inversion method based on the stationary phase theory. At first, we describe the principles and the basic characters of SHS. Then, the narrow band limitation is analyzed and the broadband spectral inversion method is elaborated. In the end, we present a parameter design example of the SHS system according to a given spectral range, and the effectiveness of this method is validated with a spectral simulation example. This broadband spectral inversion method can be applied to the existing SHS system without changing or inserting any moving components. This method retains the advantages of SHS and there is almost no increase in complexity for post processing.

  15. Heterodyne efficiency for a coherent laser radar with diffuse or aerosol targets

    NASA Technical Reports Server (NTRS)

    Frehlich, R. G.

    1993-01-01

    The performance of a Coherent Laser Radar is determined by the statistics of the coherent Doppler signal. The heterodyne efficiency is an excellent indication of performance because it is an absolute measure of beam alignment and is independent of the transmitter power, the target backscatter coefficient, the atmospheric attenuation, and the detector quantum efficiency and gain. The theoretical calculation of heterodyne efficiency for an optimal monostatic lidar with a circular aperture and Gaussian transmit laser is presented including beam misalignment in the far-field and near-field regimes. The statistical behavior of estimates of the heterodyne efficiency using a calibration hard target are considered. For space based applications, a biased estimate of heterodyne efficiency is proposed that removes the variability due to the random surface return but retains the sensitivity to misalignment. Physical insight is provided by simulation of the fields on the detector surface. The required detector calibration is also discussed.

  16. Measurements of Dust Oscillations with Laser Heterodyne Receiver of Scattered Radiation

    SciTech Connect

    Serozhkin, Yuriy; Venger, Yevgen

    2011-11-29

    We performed the experiments on measurement of vibration amplitudes for microparticles in gas and water with laser heterodyne receiver of scattered radiation. The measured vibration amplitude values are about 20 nm.

  17. Investigation of heterodyne performance of quantum-well detectors. Final report

    SciTech Connect

    Simpson, M.L.; Hutchinson, D.P.; Calabretta, J.

    1994-09-23

    The purpose of this Cooperative Research and Development Agreement (CRADA) between Martin Marietta Energy Systems Inc., (Contractor) and Martin Marietta Electronic Missles (Participant) is the determination of the heterodyne characteristics of quantum-well detectors. The Participant has developed a quantum-well infrared imaging video detector with very low light level characteristics. A further improvement in low-level infrared detection could be achieved if this device can be operated in the coherent or heterodyne mode. A major program in the Physics Division of Oak Ridge National Laboratory (ORNL) presently uses individual heterodyne infrared detectors in a system under development for fusion diagnostics. An imaging infrared heterodyne detector would represent a major breakthrough in this area and would have major implications for other plasma diagnostic programs. The Participant is also studying the application of this device in the area of laser radar.

  18. High resolution heterodyne interferometer based on time-to-digital converter.

    PubMed

    Wang, Fei; Long, Zhangcai; Zhang, Bin; Zhao, Meirong

    2012-04-01

    A new heterodyne interferometer is presented, which adopts time-to-digital converter (TDC) measuring the time intervals of zero crossings of heterodyne signal for phase demodulation. Thanks to the 0.1 ns time resolution of TDC and linear phase demodulation, it can achieve high resolution and avoids nonlinear measuring distortion in other indirect high precise phase demodulation methods, such as pulse width modulation (PWM) and in-phase∕quadrature (I∕Q) method. PMID:22559581

  19. High resolution heterodyne interferometer based on time-to-digital converter

    NASA Astrophysics Data System (ADS)

    Wang, Fei; Long, Zhangcai; Zhang, Bin; Zhao, Meirong

    2012-04-01

    A new heterodyne interferometer is presented, which adopts time-to-digital converter (TDC) measuring the time intervals of zero crossings of heterodyne signal for phase demodulation. Thanks to the 0.1 ns time resolution of TDC and linear phase demodulation, it can achieve high resolution and avoids nonlinear measuring distortion in other indirect high precise phase demodulation methods, such as pulse width modulation (PWM) and in-phase/quadrature (I/Q) method.

  20. Simulated electronic heterodyne recording and processing of pulsed-laser holograms

    NASA Technical Reports Server (NTRS)

    Decker, A. J.

    1979-01-01

    The electronic recording of pulsed-laser holograms is proposed. The polarization sensitivity of each resolution element of the detector is controlled independently to add an arbitrary phase to the image waves. This method which can be used to simulate heterodyne recording and to process three-dimensional optical images, is based on a similar method for heterodyne recording and processing of continuous-wave holograms.

  1. Structure of multiphoton quantum optics. II. Bipartite systems, physical processes, and heterodyne squeezed states

    SciTech Connect

    Dell'Anno, Fabio; De Siena, Silvio; Illuminati, Fabrizio

    2004-03-01

    Extending the scheme developed for a single mode of the electromagnetic field in the preceding paper [F. Dell'Anno, S. De Siena, and F. Illuminati, Phys. Rev. A 69, 033812 (2004)], we introduce two-mode nonlinear canonical transformations depending on two heterodyne mixing angles. They are defined in terms of Hermitian nonlinear functions that realize heterodyne superpositions of conjugate quadratures of bipartite systems. The canonical transformations diagonalize a class of Hamiltonians describing nondegenerate and degenerate multiphoton processes. We determine the coherent states associated with the canonical transformations, which generalize the nondegenerate two-photon squeezed states. Such heterodyne multiphoton squeezed states are defined as the simultaneous eigenstates of the transformed, coupled annihilation operators. They are generated by nonlinear unitary evolutions acting on two-mode squeezed states. They are non-Gaussian, highly nonclassical, entangled states. For a quadratic nonlinearity the heterodyne multiphoton squeezed states define two-mode cubic phase states. The statistical properties of these states can be widely adjusted by tuning the heterodyne mixing angles, the phases of the nonlinear couplings, as well as the strength of the nonlinearity. For quadratic nonlinearity, we study the higher-order contributions to the susceptibility in nonlinear media and we suggest possible experimental realizations of multiphoton conversion processes generating the cubic-phase heterodyne squeezed states.

  2. Structure of multiphoton quantum optics. II. Bipartite systems, physical processes, and heterodyne squeezed states

    NASA Astrophysics Data System (ADS)

    dell'Anno, Fabio; de Siena, Silvio; Illuminati, Fabrizio

    2004-03-01

    Extending the scheme developed for a single mode of the electromagnetic field in the preceding paper [

    F. Dell’Anno, S. De Siena, and F. Illuminati, Phys. Rev. A 69, 033812 (2004)
    ], we introduce two-mode nonlinear canonical transformations depending on two heterodyne mixing angles. They are defined in terms of Hermitian nonlinear functions that realize heterodyne superpositions of conjugate quadratures of bipartite systems. The canonical transformations diagonalize a class of Hamiltonians describing nondegenerate and degenerate multiphoton processes. We determine the coherent states associated with the canonical transformations, which generalize the nondegenerate two-photon squeezed states. Such heterodyne multiphoton squeezed states are defined as the simultaneous eigenstates of the transformed, coupled annihilation operators. They are generated by nonlinear unitary evolutions acting on two-mode squeezed states. They are non-Gaussian, highly nonclassical, entangled states. For a quadratic nonlinearity the heterodyne multiphoton squeezed states define two-mode cubic phase states. The statistical properties of these states can be widely adjusted by tuning the heterodyne mixing angles, the phases of the nonlinear couplings, as well as the strength of the nonlinearity. For quadratic nonlinearity, we study the higher-order contributions to the susceptibility in nonlinear media and we suggest possible experimental realizations of multiphoton conversion processes generating the cubic-phase heterodyne squeezed states.

  3. Balance Problems

    MedlinePlus

    ... our e-newsletter! Aging & Health A to Z Balance Problems Basic Facts & Information What are Balance Problems? Having good balance means being able to ... Only then can you “keep your balance.” Why Balance is Important Your feelings of dizziness may last ...

  4. Balance Problems

    MedlinePlus

    ... it could be a sign of a balance problem. Balance problems can make you feel unsteady or as if ... related injuries, such as hip fracture. Some balance problems are due to problems in the inner ear. ...

  5. Balance Problems

    MedlinePlus

    ... often, it could be a sign of a balance problem. Balance problems can make you feel unsteady or as ... fall-related injuries, such as hip fracture. Some balance problems are due to problems in the inner ...

  6. Next Generation Submillimeter Heterodyne Focal Plane Array Technology

    NASA Astrophysics Data System (ADS)

    Goldsmith, Paul; Mehdi, I.; Kawamura, J. H.; Siles, J. V.; Lee, C.; Chattoopadhyay, G.; Bumble, B.; Stern, J. A.

    2014-01-01

    The results from the Heterodyne Instrument for the Far Infrared (HIFI) on the Herschel Space Observatory have had a major impact on astronomy, including the first velocity-resolved survey of the critical 158 micron fine structure line of C+ to observations of water in comets. To follow up on Herschel’s discoveries we need to be able to image significant areas with high angular resolution. This requires high-sensitivity focal plane heterodyne arrays, which is the driver for the present effort. The current state of the art for mixers at frequencies above ~1200 GHz utilizes Hot Electron Bolometer (HEB) mixers that have remarkably good sensitivity (noise temperature < 1000 K) and require low local oscillator power. One significant limitation is the IF bandwidth of < few GHz for NbN devices. At 2 THz, 1 GHz corresponds to a Doppler width of 150 km/s, less than seen in the 1900 GHz [CII] line. For higher frequency transitions, such as the [OI] fine structure line at 4.7 THz (63 micron wavelength), this bandwidth is insufficient. Development of new HEB materials such as magnesium based alloys may overcome this challenge, and promising results have been reported in the literature. A characteristic of all HEB mixers is their high sensitivity to local oscillator power variations. We have developed an architecture for array local oscillator power production and distribution that is based on a chain of multipliers starting from a Ka band source. Improved multiplier diodes as well as circuit designs have made it possible to obtain adequate LO power to 2.7 THz, with extension to 4.7 THz promising. We have developed a system design for a 1.9 THz [CII] array with a separate chain of multipliers for each pixel allowing individual control of LO power, together with efficient LO-signal combination in a single beamsplitter. We will present results from multiplier tests and results of measurements on a 4 pixel prototype of a full 16 or more pixel system. This robust and efficient

  7. High-speed and high-resolution heterodyne interferometer

    NASA Astrophysics Data System (ADS)

    Yokoyama, Shuko; Nishihara, I.; Okamoto, A.; Araki, Tsutomu; Suzuki, Norihito

    1990-07-01

    In conventional heterodyne interferometer it Is necessary to provide a high-beat frequency laser when measurement for a high-speed target Is required1 . But use of the high-beat frequency laser makes the " nanometerdivisions" difficult. We have developed a novel interferometer system that has a sufficient response to high-speed movement of the target without Increase of the laser beat frequency. In this work a two frequency laser light passes through the same optical path of the interferometer so that two conjugate beat signals are obtained. By processing the multiple beat signals with a newly developed signal processor the above methodological contradiction is solved. l. OPTICS FOR LINEAR DISTANCE MEASUREMENT Optical system of the interferometer Is shown In Flg. l in which two frequency lights Fl and F2 (freq. f and f2) of orthogonally linear-polarized components of a two mode laser are used. A reference beat signal R (freq. r ) is generated from Fl and F2. Fl and F2 are passed through exactly the same path of the interferometer. A half power of Fl and F2 Is reflected and the rest Is transmitted In the beam splitter ( BS ). Polarization direction of the reflected beam is rotated for ir/2 after passing the X/4 plate twice. The transmitted beam Is reflected by a moving mirror (MM) mounted on the moving target so that frequency of the reflected beam Is shifted by Doppler

  8. Laser-induced breakdown spectroscopy combined with spatial heterodyne spectroscopy.

    PubMed

    Gornushkin, Igor B; Smith, Ben W; Panne, Ulrich; Omenetto, Nicoló

    2014-01-01

    A spatial heterodyne spectrometer (SHS) is tested for the first time in combination with laser-induced breakdown spectroscopy (LIBS). The spectrometer is a modified version of the Michelson interferometer in which mirrors are replaced by diffraction gratings. The SHS contains no moving parts and the gratings are fixed at equal distances from the beam splitter. The main advantage is high throughput, about 200 times higher than that of dispersive spectrometers used in LIBS. This makes LIBS-SHS a promising technique for low-light standoff applications. The output signal of the SHS is an interferogram that is Fourier-transformed to retrieve the original plasma spectrum. In this proof-of-principle study, we investigate the potential of LIBS-SHS for material classification and quantitative analysis. Brass standards with broadly varying concentrations of Cu and Zn were tested. Classification via principal component analysis (PCA) shows distinct groupings of materials according to their origin. The quantification via partial least squares regression (PLS) shows good precision (relative standard deviation < 10%) and accuracy (within ± 5% of nominal concentrations). It is possible that LIBS-SHS can be developed into a portable, inexpensive, rugged instrument for field applications. PMID:25226262

  9. Stratospheric ozone measurement with an infrared heterodyne spectrometer

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Kostiuk, T.; Mumma, M. J.; Buhl, D.; Kunde, V. G.; Brown, L. W.

    1978-01-01

    Measurements of a stratospheric ozone concentration profile are made by detecting infrared absorption lines with a heterodyne spectrometer. The infrared spectrometer is based on a line-by-line tunable CO2 lasers, a liquid-nitrogen cooled HgCdTe photomixer, and a 64-channel spectral line receiver. The infrared radiation from the source is mixed with local-oscillator radiation. The difference frequency signal in a bandwidth above and below the local-oscillator frequency is detected. The intensity in each sideband is found by subtracting sideband contributions. It is found that absolute total column density is 0.32 plus or minus 0.02 cm-atm with a peak mixing ratio at about 24 km. The (7,1,6)-(7,1,7) O3 line center frequency is identified as 1043.1772/cm. Future work will involve a number of ozone absorption lines and measurements of diurnal variation. Completely resolved stratospheric lines may be inverted to yield concentration profiles of trace constituents and stratospheric gases.

  10. THIS: A Next Generation Tuneable Heterodyne Infrared Spectrometer for SOFIA

    NASA Technical Reports Server (NTRS)

    Sonnabend, Guido; Wirtz, Daniel; Schieder, Rudolf

    2004-01-01

    A new infrared heterodyne instrument has been developed which allows the use of both tuneable diode lasers (TDL) and quantum cascade lasers (QCL) as local oscillators (LO). The current frequency tuning range of our system extends from 900 to 1100/cm depending on the availability of lasers but is planned to be extended to 600/cm soon. The IF-bandwidth is 1.4 GHz using an acousto-optical spectrometer (AOS). The frequency resolution and stability of the system is approximately 10(exp 7). Currently, mercury-cadmium-telluride (MCT) detectors are used as mixers while new devices like quantum-well-infrared-photodetectors (QWIP) and hot-electron-bolometers (HEB) are investigated. The IF-bandwidth can be extended to about 3 GHz by using a new broadband acousto-optical spectrometer presently under development. The instrument is fully transportable and can be attached to any infrared or optical telescope. The semiconductor laser is stabilized to a Fabry-Perot ring-resonator, which is also used as an efficient diplexer to superimpose the local-oscillator and the signal radiation. As a first step measurements of trace gases in Earth's atmosphere and non-LTE emission from Venus' atmosphere were carried out as well as observations of molecular features in sunspots. Further astronomical observations from ground-based telescopes and the airborne observatory SOFIA are planned for the future. Of particular interest are molecules without a permanent dipole moment like H2, CH4, C2H2 etc.

  11. Submillimeter heterodyne spectroscopy and remote sensing of the upper atmosphere

    NASA Technical Reports Server (NTRS)

    Waters, J. W.

    1992-01-01

    Submillimeter-wavelength heterodyne spectroscopy by microwave limb sounding (MLS) from orbiting satellite is a measurement technique for studying Earth's stratosphere, mesosphere and lowerr thermosphere on a global scale. Development and deployment of such tools are timely, as stratospheric ozone shileds life from solar ultraviolet radiation but is depleted by pollution from industrial activities. MLS experiments on NASA's Upper Atmosphere Research Satellite (UARS) and Earth Observing System (EOS) are now being developed and implementend for global monitoring. Atmospheric thermal-emission spectra at millimeter and submillimeter wave-lengths are measured as the instrument field of view (FOV) is scanned through the limb from above. Atmospheric profiles of molecular abundances, temperature, pressure, wind and magnetic field can be determined from the measured emission spectra. Intensity of the emission can provide abundance and temperature. Measured linewidths, and emission from temperature-insensitive O2 lines, can provide pressure. Differentitaion of measured pressure with repsect ot measured height differential (obtaiend from the instrument FOV scan encoder) can also provide temperature through atmospheric hydrostatic equilibrium (which relates temperature to pressure and height differential). Doppler shifts of spectral lines can provide wind, and Zeeman splitting of the magnetic-dipole lines of O2 can provide magnetic field.

  12. Seedless Laser Velocimetry Using Heterodyne Laser-Induced Thermal Acoustics

    NASA Technical Reports Server (NTRS)

    Hart, Roger C.; Balla, R. Jeffrey; Herring, G. C.; Jenkins, Luther N.; Bushnell, Dennis M. (Technical Monitor)

    2001-01-01

    A need exists for a seedless equivalent of laser Doppler velocimetry (LDV) for use in low-turbulence or supersonic flows or elsewhere where seeding is undesirable or impractical. A compact laser velocimeter using heterodyne non-resonant laser-induced thermal acoustics (LITA) to measure a single component of velocity is described. Neither molecular (e.g. NO2) nor particulate seed is added to the flow. In non-resonant LITA two beams split from a short-pulse pump laser are crossed; interference produces two counterpropagating sound waves by electrostriction. A CW probe laser incident on the sound waves at the proper angle is directed towards a detector. Measurement of the beating between the Doppler-shifted light and a highly attenuated portion of the probe beam allows determination of one component of flow velocity, speed of sound, and temperature. The sound waves essentially take the place of the particulate seed used in LDV. The velocimeter was used to study the flow behind a rearward-facing step in NASA Langley Research Center's Basic Aerodynamics Research Tunnel. Comparison is made with pitot-static probe data in the freestream over the range 0 m/s - 55 m/s. Comparison with LDV is made in the recirculation region behind the step and in a well-developed boundary layer in front of the step. Good agreement is found in all cases.

  13. Preliminary submillimeter spectroscopic measurements using a submillimeter heterodyne radiometer

    NASA Technical Reports Server (NTRS)

    Safren, H. G.; Stabnow, W. R.; Bufton, J. L.; Peruso, C. J.; Rossey, C. E.; Walker, H. E.

    1982-01-01

    A submillimeter heterodyne radiometer uses a submillimeter laser, pumped by a CO2 laser, as a local oscillator and a room temperature Schottky barrier diode as the first IF mixer. The radiometer can resolve spectral lines in the submillimeter region of the spectrum (arising from pure rotational molecular transitions) to within 0.3 MHz, using acousto-optic spectrum analyzer which measures the power spectrum by simultaneously sampling 0.3 MHz wide channels over a 100 MHz bandwidth spanning the line. Preliminary observations of eight spectral lines of H2O2, CO, NH3 and H2O, all lying in the 434-524 micrometer wavelength range are described. All eight lines were observed using two local oscillator frequencies obtained by operating the submillimeter laser with either methyl fluoride (CH3F) or formic acid (HCOOH) as the lasing gas. Sample calculations of line parameters from the observed data show good agreement with established values. One development goal is the size and weight reduction of the package to make it suitable for balloon or shuttle experiments to detect trace gases in the upper atmosphere.

  14. Review Of Progress In Remote Sensing By Tunable Diode Laser Heterodyne Spectroscopy

    NASA Astrophysics Data System (ADS)

    Glenar, David A.

    1983-11-01

    Heterodyne spectroscopy at infrared wavelengths is a unique approach to the study of atmospheric species and astrophysical objects. It's coherent detection properties ma4 it 7 the only optical technique to combine ultra-high frequency resolving power (v/A = 106- 107) with diffraction-limited spatial resolution. The use of lead-salt tunable diode lasers (TDL's) as local oscillators in a heterodyne instrument offers the additional advantage of continuous tunability, permitting operation over the entire nominal tuning range of the device. Previous investigators have obtained high signal-to-noise TDL heterodyne spectra of terrestrial atmospheric features in solar absorption and molecular features in sunspots. Until recently, however, the noisy character and low output power of TDL's have precluded their use for heterodyne detection of objects much fainter than the sun. Attempts to observe planets and astrophysical infrared sources have produced only a handful of weak continuum detections. The major categories of TDL excess noise are now fairly well understood, and new device fabrication techniques have produced dramatic improvements in noise reduction, power output, single mode tunability and operation at long wavelengths (X > 10 microns). These next generation devices should result in ground-based instrument performance which rivals the CO2 laser heterodyne technique throughout the 8 to 13 micron atmospheric window.

  15. Electronic heterodyne moire deflectometry: A method for transient and three dimensional density fields measurements

    NASA Technical Reports Server (NTRS)

    Stricker, Josef

    1987-01-01

    Effects of diffraction and nonlinear photographic emulsion characteristics on the performance of deferred electronic heterodyne moire deflectometry are investigated. The deferred deflectometry is used for measurements of nonsteady phase objects where it is difficult to complete the analysis of the field in real time. The sensitivity, accuracy and resolution of the system are calculated and it is shown that they are weakly affected by diffraction and by nonlinear recording. The feactures of the system are significantly improved compared with the conventional deferred intensity moire technique, and are comparable with the online heterodyne moire. The system was evaluated experimentally by deferred measurements of the refractive index gradients of a weak phase object consisting of a large KD*P crystal. This was done by photographing the phase object through a Ronchi grating and analyzing the tranparency with the electronic heterodyne readout system. The results are compared with the measurements performed on the same phase object with online heterodyne moire deflectometry and with heterodyne holographic interferometry methods. Some practical considerations for system improvement are discussed.

  16. Microwave tunable laser source: A stable, precision tunable heterodyne local oscillator

    NASA Technical Reports Server (NTRS)

    Sachse, G. W.

    1980-01-01

    The development and capabilities of a tunable laser source utilizing a wideband electro-optic modulator and a CO2 laser are described. The precision tunability and high stability of the device are demonstrated with examples of laboratory spectroscopy. Heterodyne measurements are also presented to demonstrate the performance of the laser source as a heterodyne local oscillator. With the use of five CO2 isotope lasers and the 8 to 18 GHz sideband offset tunability of the modulator, calculations indicate that 50 percent spectral coverage in the 9 to 12 micron region is achievable. The wavelength accuracy and stability of this laser source is limited by the CO2 laser and is more than adequate for the measurement of narrow Doppler-broadened line profiles. The room-temperature operating capability and the programmability of the microwave tunable laser source are attractive features for its in-the-field implementation. Although heterodyne measurements indicated some S/N degradation when using the device as a local oscillator, there does not appear to be any fundamental limitation to the heterodyne efficiency of this laser source. Through the use of a lower noise-figure traveling wave tube amplifier and optical matching of the output beam with the photomixer, a substantial increase in the heterodyne S/N is expected.

  17. Coherent summation of spatially distorted Doppler lidar signals using a two-dimensional heterodyne detector array

    NASA Astrophysics Data System (ADS)

    Chan, Kin Pui; Killinger, Dennis K.

    1992-07-01

    We have investigated the improvement in the signal-to-noise ratio for a coherent Doppler lidar through the use of a multi-element heterodyne detector array. Such an array enables the spatial summation of atmospheric refractive turbulence induced speckles, and time varying target speckles. Our recent experiments have shown that the non-coherent summation of the lidar signals from a heterodyne detector array can enhance the heterodyne mixing efficiency and thus the signal-to-noise ratio. In this paper, we expand this work to include the coherent summation of array signals. The digitized heterodyne signals were stored in a personal computer. Fast Fourier transforms were performed on both the non-coherent and coherent summations of the detector array signals. It was found that the coherent summation greatly enhanced the accuracy in the Doppler frequency estimate. A theoretical analysis was performed and indicated good agreement with experimental results. We have also applied these results to the more general lidar applications including atmospheric wind sensing, and have found that in most lidar applications the Doppler frequency estimate is increased through the use of the heterodyne detector array.

  18. A 2 THz Heterodyne Array Receiver for SOFIA

    NASA Astrophysics Data System (ADS)

    Walker, Christopher K.

    1998-01-01

    We proposed to perform a comprehensive design study of a 16-element heterodyne array receiver for SOFIA. The array was designed to utilize hot-electron bolometers in an efficient, low-cost waveguide mount to achieve low noise performance between approx. 1500 and 2400 GHz. Due to the prevailing physical conditions in the interstellar medium, this frequency range is one of the richest in the FIR portion of the spectrum. An array designed for this wavelength range will make excellent use of the telescope and the available atmospheric transmission, and will provide a new perspective on stellar, chemical, and galaxy evolution in the present as well as past epochs. A few of the most important molecular and atomic species which the instrument will sample are CII, OI, CO, OH, NII, and CH. The system used the most sensitive detectors available in an efficient optical system. The local oscillator was a compact CO2 pumped far-infrared laser currently under development for SOFIA. The backend spectrometer was an array acousto-optic spectrometer (aAOS). The spectrometer utilizes proven hardware and technologies to provide broadband performance (greater than or equal to 1 GHz per AOS channel) and high spectral resolution (1 MHz) with the maximum sensitivity and minimum complexity and cost. The proposed instrument would be the fastest and most sensitive heterodyne receiver ever to operate in the 1.5 - 2.4 THz band. One of the key technologies developed for the proposed instrument is the laser micromachining of waveguide structures. These structures provide both the optical link between the instrument and the telescope (via an array of efficient feedhorns) and the impedance transformation between the detectors and free space. With the assistance of funds provided from this grant, we were able to fabricate and test the world's first laser micromachined feedhorns. Figure 1 is a photograph of the 2 THz double feedhorn structure designed and constructed under the auspices of this grant

  19. Simultaneous unbalanced shared local oscillator heterodyne interferometry for high signal-to-noise-ratio, minimally destructive dispersive detection of time-dependent atomic spins

    NASA Astrophysics Data System (ADS)

    Locke, Mary; Fertig, Chad

    2013-09-01

    We demonstrate "Simultaneous Unbalanced Shared Local Oscillator Heterodyne Interferometry (SUSHI)," a new method for minimally destructive, high SNR dispersive detection of atomic spins. In SUSHI a dual-frequency probe laser interacts with atoms in one arm of a Mach-Zehnder interferometer, then beats against a bright local oscillator beam traversing the other arm, resulting in two simultaneous, independent heterodyne measurements of the atom-induced phase shift. Measurement noise due to mechanical disturbances of beam paths is strongly rejected by the technique of \\emph{active subtraction} in which anti-noise is actively written onto the local oscillator beam via an optical phase-locked-loop. In SUSHI, technical noise due to phase, amplitude, and frequency fluctuations of the various laser fields is strongly rejected (i) for any mean phase bias between the interferometer arms, (ii) without the use of piezo actuated mirrors, and (iii) without signal balancing. We experimentally demonstrate an ultra-low technical noise limited sensitivity of 51 nrad$/\\sqrt{\\R{Hz}}$ over a measurement bandwidth of 60 Hz to 8 kHz using a 230 $\\mu$W probe, and stay within $\\sim$3 dB of the standard quantum limit as probe power is reduced by more than 5 orders of magnitude to as low as 650 pW. SUSHI is therefore well suited to performing QND measurements for preparing spin squeezed states and for high SNR, truly continuous observations of ground-state Rabi flopping in cold atom ensembles.

  20. Great circle solution to polarization-based quantum communication (QC) in optical fiber

    DOEpatents

    Nordholt, Jane Elizabeth; Peterson, Charles Glen; Newell, Raymond Thorson; Hughes, Richard John

    2016-03-15

    Birefringence in optical fibers is compensated by applying polarization modulation at a receiver. Polarization modulation is applied so that a transmitted optical signal has states of polarization (SOPs) that are equally spaced on the Poincare sphere. Fiber birefringence encountered in propagation between a transmitter and a receiver rotates the great circle on the Poincare sphere that represents the polarization bases used for modulation. By adjusting received polarizations, polarization components of the received optical signal can be directed to corresponding detectors for decoding, regardless of the magnitude and orientation of the fiber birefringence. A transmitter can be configured to transmit in conjugate polarization bases whose SOPs can be represented as equidistant points on a great circle so that the received SOPs are mapped to equidistant points on a great circle and routed to corresponding detectors.

  1. Generation of arbitrary vector fields based on a pair of orthogonal elliptically polarized base vectors.

    PubMed

    Xu, Danfeng; Gu, Bing; Rui, Guanghao; Zhan, Qiwen; Cui, Yiping

    2016-02-22

    We present an arbitrary vector field with hybrid polarization based on the combination of a pair of orthogonal elliptically polarized base vectors on the Poincaré sphere. It is shown that the created vector field is only dependent on the latitude angle 2χ but is independent on the longitude angle 2ψ on the Poincaré sphere. By adjusting the latitude angle 2χ, which is related to two identical waveplates in a common path interferometric arrangement, one could obtain arbitrary type of vector fields. Experimentally, we demonstrate the generation of such kind of vector fields and confirm the distribution of state of polarization by the measurement of Stokes parameters. Besides, we investigate the tight focusing properties of these vector fields. It is found that the additional degree of freedom 2χ provided by arbitrary vector field with hybrid polarization allows one to control the spatial structure of polarization and to engineer the focusing field. PMID:26907066

  2. Polarization-based all-optical logic operations in volume holographic photopolymer

    NASA Astrophysics Data System (ADS)

    Li, Chengmingyue; Cao, Liangcai; Li, Jingming; Wang, Zheng; Jin, Guofan

    2014-11-01

    Polarization-based all-optical logic operations were realized with dual-channel polarization holographic recording system. The polarization property of 9, 10-phenanthrenequinone-doped poly-methyl methacrylate (PQ/PMMA) photopolymer is investigated experimentally. To accurately represent the optical operations, the diffraction efficiency of parallel and orthogonal polarization recording in PQ/PMMA with the thickness of 1 mm are characterized for holographic recording and reconstruction process. A dual-channel polarization holographic recording system is set up for simultaneously recording two input pages. By changing the polarization state of the diffraction beam, all-optical logic OR and NAND operations are realized in the volume holograms. The polarization-based all-optical logic operations in the volume holographic photopolymer may pave a way for practical all-optical logic devices with high speed and large information capacity.

  3. Mode beating and heterodyning of monolithically integrated semiconductor ring lasers

    NASA Astrophysics Data System (ADS)

    Liu, Chiyu

    Monolithically integrated semiconductor ring lasers (SRLs) are attractive optical sources for optoelectronic integrated circuits (OEICs) because they do not require any feedback elements, do not have parts exposed to external ambient, and can operate in a traveling-wave mode. They are promising candidates for wavelength filtering, unidirectional traveling-wave operation, and multiplexing/demultiplexing applications. Ring lasers can also be used as ultrashort pulse generators using various mode-locking schemes and as active gyro components. However, the SRL is a very complicated dynamic system, which requires more investigations to understand the performance regarding details of the design and fabrication. As a part of NASA-supported project "Monolithically Integrated Semiconductor Ring Laser Gyro for Space Applications", this dissertation research was focused on design and characterization of a novel monolithically integrated rotation sensor based on two large-size independent SRLs. Numerical modeling based on the beam propagation method (BPM) was used to design the fabrication parameters for the single-mode ridge-waveguide ring cavity and directional coupler waveguides. The mode internal coupling in single lateral-mode laser diodes with InGaAs/GaAs material system was investigated by optical experiments and numerical modeling. To gain the understanding of the SRL performance, optical and electrical characterization was performed on fabricated SRLs. Particular emphasis was placed on the study of optical and radio frequency (RF) beating spectra of longitudinal modes of ring lasers. RF measurements provide high accuracy in the diagnosis of laser oscillation parameters by purely electronic means, particularly in the measurement of the group index and its dependence on current and temperature. Theoretical analysis based on the effective index method provides good agreement between the experimental data and numerical calculations. Finally, optical heterodyning spectra

  4. Extending the operating temperature, wavelength and frequency response of HgCdTe heterodyne detectors

    NASA Technical Reports Server (NTRS)

    Spears, D. L.

    1980-01-01

    Near ideal optical heterodyne performance was obtained at GHz IF frequencies in the 10 micrometer wavelength region with liquid nitrogen cooled HgCdTe photodiodes. Heterodyne NEP's as low as 2.7 x 10 to the minus 20th power W/Hz at 100MHz, 5.4 x 10 to the minus 20th power W/Hz at 1.5 GHz, and 9.4 x 19 to the minus 20th power W/Hz at 3 GHz were achieved. Various physical phenomena which occur within a photodiode and affect heterodyne operation were examined in order to assess the feasibility of extending the operating temperature, wavelength, and frequency response of these HgCdTe photomixers.

  5. Fiber-optic delay-line stabilization of heterodyne optical signal generator and method using same

    NASA Technical Reports Server (NTRS)

    Logan, Ronald T. (Inventor)

    1997-01-01

    The present invention is a laser heterodyne frequency generator system with a stabilizer for use in the microwave and millimeter-wave frequency ranges utilizing a photonic mixer as a photonic phase detector in a stable optical fiber delay-line. Phase and frequency fluctuations of the heterodyne laser signal generators are stabilized at microwave and millimeter wave frequencies by a delay line system operating as a frequency discriminator. The present invention is free from amplifier and mixer 1/.function. noise at microwave and millimeter-wave frequencies that typically limit phase noise performance in electronic cavity stabilized electronic oscillators. Thus, 1/.function. noise due to conventional mixers is eliminated and stable optical heterodyne generation of electrical signals is achieved.

  6. Heterodyne Spectroscopy in the Thermal Infrared Region: A Window on Physics and Chemistry

    NASA Technical Reports Server (NTRS)

    Kostiuk, Theodor

    2004-01-01

    The thermal infrared region contains molecular bands of many of the most important species in gaseous astronomical sources. True shapes and frequencies of emission and absorption spectral lines from these constituents of planetary and stellar atmospheres contain unique information on local temperature and abundance distribution, non-thermal effects, composition, local dynamics and winds. Heterodyne spectroscopy in the thermal infrared can remotely measure true line shapes in relatively cool and thin regions and enable the retrieval of detailed information about local physics and chemistry. The concept and techniques for heterodyne detection will be discussed including examples of thermal infrared photomixers and instrumentation used in studies of several astronomical sources. Use of heterodyne detection to study non-LTE phenomena, planetary aurora, minor planetary species and gas velocities (winds) will be discussed. A discussion of future technological developments and relation to space flight missions will be addressed.

  7. Modeling of the generic spatial heterodyne spectrometer and comparison with conventional spectrometer

    SciTech Connect

    Powell, Ian; Cheben, Pavel

    2006-12-20

    We describe the modeling of the generic spatial heterodyne spectrometer. This instrument resembles a somewhat modified Michelson interferometer, in which the power spectrum of the input source is determined by performing a one-dimensional Fourier transform on the output intensity profile. Code has been developed to analyze the performance of this type of spectrometer by determining the dependence of both spectral resolution and throughput on parameters such as aperture and field of view. An example of a heterodyne spectrometer is developed to illustrate the techniques employed in the modeling and a comparison undertaken between its performance and that of a conventional spectrometer. Unlike the traditional Fourier transform infrared system, the heterodyne spectrometer has the very desirable feature of having no moving components.

  8. Heterodyne detection at 300 GHz using neon indicator lamp glow discharge detector.

    PubMed

    Aharon Akram, Avihai; Rozban, Daniel; Kopeika, Natan S; Abramovich, Amir

    2013-06-10

    A miniature neon indicator lamp, also known as a glow discharge detector (GDD), costing about 50 cents, was found to be an excellent room temperature terahertz radiation detector. Proof-of-concept 300 GHz heterodyne detection using GDD is demonstrated in this paper. Furthermore, a comparison to direct detection was carried out as well. Previous results with the GDD at 10 GHz showed 40 times better sensitivity using heterodyne detection compared to direct detection. Preliminary results at 300 GHz showed better sensitivity by a factor of 20 with only 56 μW local-oscillator power using heterodyne compared to direct detection. The higher the local-oscillator power (P(lo)), the better the sensitivity of the detector. Further improvement can be achieved by employing better quasi-optical design. PMID:23759859

  9. A dual-heterodyne laser interferometer for simultaneous measurement of linear and angular displacements

    NASA Astrophysics Data System (ADS)

    Yan, Hao; Duan, Hui-Zong; Li, Lin-Tao; Liang, Yu-Rong; Luo, Jun; Yeh, Hsien-Chi

    2015-12-01

    Picometer laser interferometry is an essential tool for ultra-precision measurements in frontier scientific research and advanced manufacturing. In this paper, we present a dual-heterodyne laser interferometer for simultaneously measuring linear and angular displacements with resolutions of picometer and nanoradian, respectively. The phase measurement method is based on cross-correlation analysis and realized by a PXI-bus data acquisition system. By implementing a dual-heterodyne interferometer with a highly symmetric optical configuration, low frequency noises caused by the environmental fluctuations can be suppressed to very low levels via common-mode noise rejection. Experimental results for the dual-heterodyne interferometer configuration presented demonstrate that the noise levels of the linear and angular displacement measurements are approximately 1 pm/Hz1/2 and 0.5 nrad/Hz1/2 at 1 Hz.

  10. Signal averaging limitations in heterodyne- and direct-detection laser remote sensing measurements

    NASA Technical Reports Server (NTRS)

    Menyuk, N.; Killinger, D. K.; Menyuk, C. R.

    1983-01-01

    The improvement in measurement uncertainty brought about by the averaging of increasing numbers of pulse return signals in both heterodyne- and direct-detection lidar systems is investigated. A theoretical analysis is presented which shows the standard deviation of the mean measurement to decrease as the inverse square root of the number of measurements, except in the presence of temporal correlation. Experimental measurements based on a dual-hybrid-TEA CO2 laser differential absorption lidar system are reported which demonstrate that the actual reduction in the standard deviation of the mean in both heterodyne- and direct-detection systems is much slower than the inverse square-root dependence predicted for uncorrelated signals, but is in agreement with predictions in the event of temporal correlation. Results thus favor the use of direct detection at relatively short range where the lower limit of the standard deviation of the mean is about 2 percent, but advantages of heterodyne detection at longer ranges are noted.

  11. Second harmonic measurement of multi-beam laser heterodyne with ultra-precision for the small angle

    NASA Astrophysics Data System (ADS)

    Li, Y. Chao; Ding, Q.; Wang, Y. Qiao; Yang, J. Ru; Liu, C. Yu; Wang, C. Hui; Sun, J. Feng

    2015-08-01

    In order to improve the measurement accuracy of the angle and signal processing speed of operation, this paper proposes a novel method of second harmonic measurement of multi-beam laser heterodyne for the angle, which based on the combination of Doppler effect and heterodyne technology, loaded the information of the angle to the frequency difference of second harmonic of the multi-beam laser heterodyne signal by frequency modulation of the oscillating mirror, which is in the light path. Heterodyne signal frequency can be obtained by fast Fourier transform, and can obtain values of the angle accurately after the multi-beam laser heterodyne signal demodulation. This novel method is used to simulate measurement for incident angle of standard mirror by Matlab, the obtained result shows that the relative measurement error of this method is just 0.5213%.

  12. Methods, compositions and kits for imaging cells and tissues using nanoparticles and spatial frequency heterodyne imaging

    DOEpatents

    Rose-Petruck, Christoph; Wands, Jack R.; Rand, Danielle; Derdak, Zoltan; Ortiz, Vivian

    2016-04-19

    Methods, compositions, systems, devices and kits are provided herein for preparing and using a nanoparticle composition and spatial frequency heterodyne imaging for visualizing cells or tissues. In various embodiments, the nanoparticle composition includes at least one of: a nanoparticle, a polymer layer, and a binding agent, such that the polymer layer coats the nanoparticle and is for example a polyethylene glycol, a polyelectrolyte, an anionic polymer, or a cationic polymer, and such that the binding agent that specifically binds the cells or the tissue. Methods, compositions, systems, devices and kits are provided for identifying potential therapeutic agents in a model using the nanoparticle composition and spatial frequency heterodyne imaging.

  13. Scanning heterodyne Kerr-effect microscope for imaging of magnetic tracks

    NASA Astrophysics Data System (ADS)

    Protopopov, Vladimir V.; Lee, Sukwon; Kwon, Youngkun; Cho, Sunghoon; Kim, Hyuk; Chae, Jonggyn

    2006-07-01

    Design and performance of a new type of Kerr microscope based on heterodyne cross-polarized technique is presented. Weak depolarization of the probe beam due to longitudinal magneto-optical Kerr effect is detected by means of heterodyne mixing of the two cross-polarized and frequency shifted waves generated by Zeeman-type He-Ne laser. In comparison with the traditional homodyne method the proposed technique has better sensitivity and spatial resolution. Experimental results of imaging service magnetic tracks on real samples of magnetic disks are presented, showing better contrast and spatial resolution with respect to the images obtained from commercial devices available in the market.

  14. Mid-infrared photothermal heterodyne spectroscopy in a liquid crystal using a quantum cascade laser

    PubMed Central

    Mërtiri, Alket; Jeys, Thomas; Liberman, Vladimir; Hong, M. K.; Mertz, Jerome; Altug, Hatice; Erramilli, Shyamsunder

    2012-01-01

    We report a technique to measure the mid-infrared photothermal response induced by a tunable quantum cascade laser in the neat liquid crystal 4-octyl-4′-cyanobiphenyl (8CB), without any intercalated dye. Heterodyne detection using a Ti:sapphire laser of the response in the solid, smectic, nematic and isotropic liquid crystal phases allows direct detection of a weak mid-infrared normal mode absorption using an inexpensive photodetector. At high pump power in the nematic phase, we observe an interesting peak splitting in the photothermal response. Tunable lasers that can access still stronger modes will facilitate photothermal heterodyne mid-infrared vibrational spectroscopy. PMID:22912508

  15. Usefulness of the infrared heterodyne radiometer in remote sensing of atmospheric pollutants.

    NASA Technical Reports Server (NTRS)

    Menzies, R. T.; Shumate, M. S.

    1971-01-01

    The application of narrow-band optical receivers to the problem of sensing atmospheric pollution is discussed. The emission/absorption lines of many major atmospheric pollutant molecules overlap the operating frequency bands of CO2 laser and CO laser heterodyne receivers. Several remote pollution sensing systems which are based upon utilization of these spectral overlaps are described, and an analysis of their potential is presented. The possibility of using other lasers (e.g.: the PbSnTe tunable diode laser) as local oscillators is also considered. Results of laboratory experiments with a CO2 laser heterodyne radiometer are presented.

  16. Synthetic Array Heterodyne Detection: Developments within the Caliope CO{sub 2} DIAL Program

    SciTech Connect

    Rehse, S.J.; Strauss, E.M.

    1995-09-01

    A new technique, Synthetic Array Heterodyne Detection, offers a wider field of view and improved signal to noise for coherent DIAL systems by reducing speckle interference. We have implemented a synthetic multi-pixel array using a CO{sub 2} laser on a single element HgCdTe photodiode.

  17. A charge-coupled-device-based heterodyne technique for parallel photodisplacement imaging

    NASA Astrophysics Data System (ADS)

    Nakata, Toshihiko; Ninomiya, Takanori

    2004-12-01

    A heterodyne interferometry technique for parallel photodisplacement imaging is presented. In the parallel photodisplacement technique, a linear region of photothermal displacement is excited using a line-focusing intensity-modulated laser beam and is detected with a parallel heterodyne interferometer in which a charge-coupled device linear image sensor is used as a detector. The integration and sampling effects of the sensor provide spatiotemporally multiplexing of the interference light. To extract the spatially resolved photodisplacement component from the multiplexed sensor signal for heterodyne interferometry, a scheme of phase-shifting light integration under an undersampling condition is developed. The frequency relation for the heterodyne beat signal, modulation signal, and sensor gate signal is optimized so as to eliminate undesirable components, allowing only the displacement component to be extracted. Preliminary experimental results using a point-focused laser beam demonstrate that the technique is effective, making it possible to accurately extract photodisplacement components from the multiplexed interferogram. Subsurface structures and defects in silicon wafers are clearly imaged with a detection time of 5.3μs/pixel. In combination with a line-focusing laser beam, this technique is very promising for high-throughput subsurface imaging with detection speeds more than 10 000 times faster than conventional photoacoustic microscopy.

  18. A new thermal radiation detector using optical heterodyne detection of absorbed energy

    NASA Technical Reports Server (NTRS)

    Davis, C. C.; Petuchowski, S. J.

    1983-01-01

    The operating principles of a new kind of room-temperature thermal radiation detector are described. In this device modulated light heats a gas, either directly or by conduction from a thin absorbing membrane, and the resultant change in density of the gas is detected by optical heterodyning. The performance of a membrane device of this kind agrees well with the predictions of theory.

  19. Heterodyne holography with full control of both the signal and reference arms.

    PubMed

    Gross, Michel

    2016-01-20

    Heterodyne holography is a variant of phase-shifting holography in which the reference and signal arms are controlled by acousto-optic modulators. In this review paper, we will briefly describe the method and its properties, and we will illustrate its advantages in experimental applications. PMID:26835961

  20. Camera-Based Lock-in and Heterodyne Carrierographic Photoluminescence Imaging of Crystalline Silicon Wafers

    NASA Astrophysics Data System (ADS)

    Sun, Q. M.; Melnikov, A.; Mandelis, A.

    2015-06-01

    Carrierographic (spectrally gated photoluminescence) imaging of a crystalline silicon wafer using an InGaAs camera and two spread super-bandgap illumination laser beams is introduced in both low-frequency lock-in and high-frequency heterodyne modes. Lock-in carrierographic images of the wafer up to 400 Hz modulation frequency are presented. To overcome the frame rate and exposure time limitations of the camera, a heterodyne method is employed for high-frequency carrierographic imaging which results in high-resolution near-subsurface information. The feasibility of the method is guaranteed by the typical superlinearity behavior of photoluminescence, which allows one to construct a slow enough beat frequency component from nonlinear mixing of two high frequencies. Intensity-scan measurements were carried out with a conventional single-element InGaAs detector photocarrier radiometry system, and the nonlinearity exponent of the wafer was found to be around 1.7. Heterodyne images of the wafer up to 4 kHz have been obtained and qualitatively analyzed. With the help of the complementary lock-in and heterodyne modes, camera-based carrierographic imaging in a wide frequency range has been realized for fundamental research and industrial applications toward in-line nondestructive testing of semiconductor materials and devices.

  1. SURVEY OF OPTICAL VELOCIMETRY EXPERIMENTS - APPLICATIONS OF PDV, A HETERODYNE VELOCIMETER

    SciTech Connect

    HOLTKAMP, DAVID B.

    2007-02-12

    Optical velocimetry has been an important experimental diagnostic for many experiments. Recent improvements to heterodyne techniques have resulted in compact, inexpensive and high performance velocimetry measurement systems. We report on developments and improvements in this area and illustrate the performance of Photon Doppler Velocimetry (PDV) by showing several experimental examples.

  2. Wavelength attack on practical continuous-variable quantum-key-distribution system with a heterodyne protocol

    NASA Astrophysics Data System (ADS)

    Ma, Xiang-Chun; Sun, Shi-Hai; Jiang, Mu-Sheng; Liang, Lin-Mei

    2013-05-01

    We present the wavelength attack on a practical continuous-variable quantum-key-distribution system with a heterodyne protocol, in which the transmittance of beam splitters at Bob's station is wavelength dependent. Our strategy is proposed independent of but analogous to that of Huang [arXiv:1206.6550v1 [quant-ph

  3. THz Direct Detector and Heterodyne Receiver Arrays in Silicon Nanoscale Technologies

    NASA Astrophysics Data System (ADS)

    Grzyb, Janusz; Pfeiffer, Ullrich

    2015-10-01

    The main scope of this paper is to address various implementation aspects of THz detector arrays in the nanoscale silicon technologies operating at room temperatures. This includes the operation of single detectors, detectors operated in parallel (arrays), and arrays of detectors operated in a video-camera mode with an internal reset to support continuous-wave illumination without the need to synchronize the source with the camera (no lock-in receiver required). A systematic overview of the main advantages and limitations in using silicon technologies for THz applications is given. The on-chip antenna design challenges and co-design aspects with the active circuitry are thoroughly analyzed for broadband detector/receiver operation. A summary of the state-of-the-art arrays of broadband THz direct detectors based on two different operation principles is presented. The first is based on the non-quasistatic resistive mixing process in a MOSFET channel, whereas the other relies on the THz signal rectification by nonlinearity of the base-emitter junction in a high-speed SiGe heterojunction bipolar transistor (HBT). For the MOSFET detector arrays implemented in a 65 nm bulk CMOS technology, a state-of-the-art optical noise equivalent power (NEP) of 14 pW/ at 720 GHz was measured, whereas for the HBT detector arrays in a 0.25 μm SiGe process technology, an optical NEP of 47 pW/ at 700 GHz was found. Based on the implemented 1k-pixel CMOS camera with an average power consumption of 2.5 μW/pixel, various design aspects specific to video-mode operation are outlined and co-integration issues with the readout circuitry are analyzed. Furthermore, a single-chip 2 × 2 array of heterodyne receivers for multi-color active imaging in a 160-1000 GHz band is presented with a well-balanced NEP across the operation bandwidth ranging from 0.1 to 0.24 fW/Hz (44.1-47.8 dB single-sideband NF) and an instantaneous IF bandwidth of 10 GHz. In its present implementation, the receiver RF

  4. Integrated Heterodyne MOEMS for detection of low intensity signals

    NASA Astrophysics Data System (ADS)

    Elman, Noel M.; Krylov, Slava; Sternheim, Marek; Shacham-Diamand, Yosi

    2006-01-01

    A novel MEMS-based modulation scheme is presented as a method to enhance the signal-to-noise ratio (SNR) of silicon photodiodes adapted for the detection of light-emitting bio-reporter signals. Photodiodes are an attractive photodetector choice because they are VLSI compatible, easily miniaturized, highly scalable, and inexpensive. Silicon photodiodes exhibit a wide response range extending from the ultraviolet (UV) to the near infrared (IR) part of the spectrum, which in principle is appropriate for sensing low intensity optical signals. Silicon photodiodes, however, exhibit limited sensitivity to optical dc signals, as the magnitude of the low frequency noise is comparable to signal magnitude. Optical modulation prior to photodetection overcomes the inherent low frequency noise of photodetectors and system detection circuits. The enhancement scheme is based on a design of high frequency optical modulators that operate in the 1-2 kHz range in order to overcome the low frequency spectral noise. We have denominated this MEMS-based scheme Integrated Heterodyne Optical System (IHOS). The modulation efficiency of the proposed architecture can reach up to 50 percent. In order to implement the MOEMS optical modulators, a new two-mask fabrication process was developed that combines high-aspect ratio and low aspect ratio structures at the same device layer (aspect ratio is defined as a ratio between the structure height to its width). Long stroke electrostatic combdrive actuators integrated with folded flexures (high aspect-ratio) were fabricated together to drive large aperture shutters (low aspect ratio). We have denominated this process MASIS (Multiple Aspect Ratio Structural Integration). Under resonant excitation at approximately 1 kHz, MOEMS modulators demonstrated maximum displacement of about 40 microns at an actuation voltage of 15 V peak in air, and 3.5 V peak in vacuum (8 mTorr). Results of analytical solutions and finite element analysis (FEA) simulations are

  5. Introducing tunable special heterodyne spectrometers in cometary studies

    NASA Astrophysics Data System (ADS)

    Hosseini, S.; Harris, W.

    2014-07-01

    Cometary remote sensing, in many cases, depends on measurement of fine spectral features from targets covering relatively large angular areas on the sky. The range of studies in cometary science is highly diverse. Size scales and perspectives vary dramatically, with opportunities for both Earth-based and in situ studies. Many characteristics of comets, such as coma dynamics, outflow/escape, radiative transfer, and isotopic ratios, are best addressed with high-resolving-power studies that integrate a large FOV. In addition, it is of great importance to obtain high-resolution data to resolve small Doppler shifts, fine structure, line shapes, and atomic multiplets/molecular bands. However, more detection is not enough, because the coma is inherently active; it can manifest substantial variation both temporally and spatially. As a result, we must combine a study of the target's global evolution parallel to the ability to measure with some spatial fidelity across the FOV and to map its variation in time. This combination of requirements is a challenge that modern instrumental approaches are limited in their ability to meet. One method for addressing these needs is through the use of a broadly tunable all-reflective Special Heterodyne Spectrometer (SHS). SHS instruments are common-path two-beam Fourier-transform spectrometers that produce 2-D spatial interference patterns without the requirement for moving parts. The utility of SHS comes from its combination of a wide input acceptance angle (0.5--1°), high resolving power (of order ˜ 10^5), compact format, high dynamic range, and relaxed optical tolerances compared with other interferometer designs. This combination makes them extremely useful for velocity-resolved observations of wide field targets from both small and large telescopes. We have constructed a tunable SHS, Khayyam, at fixed focal plane of the Coudé Auxiliary Telescope (CAT) at Mt. Hamilton. The CAT provides a test case for on-axis use of SHS, and the

  6. PolarBase: A Database of High-Resolution Spectropolarimetric Stellar Observations

    NASA Astrophysics Data System (ADS)

    Petit, P.; Louge, T.; Théado, S.; Paletou, F.; Manset, N.; Morin, J.; Marsden, S. C.; Jeffers, S. V.

    2014-05-01

    PolarBase is an evolving database that contains all stellar data collected with the ESPaDOnS and NARVAL high-resolution spectropolarimeters, in their reduced form, as soon as they become public. As of early 2014, observations of 2000 stellar objects throughout the Hertzsprung-Russell diagram are available. Intensity spectra are available for all targets, and the majority of the observations also include simultaneous spectra in circular or linear polarization, with the majority of the polarimetric measurements being performed only in circularly polarized light (Stokes V). Observations are associated with a cross-correlation pseudoline profile in all available Stokes parameters, greatly increasing the detectability of weak polarized signatures. Stokes V signatures are detected for more than 300 stars of all masses and evolutionary stages, and linear polarization is detected in 35 targets. The detection rate in Stokes V is found to be anticorrelated with the stellar effective temperature. This unique set of Zeeman detections offers the first opportunity to run homogeneous magnetometry studies throughout the H-R diagram. The Web interface of PolarBase is available at http://polarbase.irap.omp.eu.

  7. Development of a submillimeter/far infrared heterodyne spectrometer: Testing on spacecraft as a preparation for the FIRST project

    NASA Astrophysics Data System (ADS)

    Metzger, P. G.

    1990-12-01

    A heterodyne spectrometer for the wavelength region between 100 and 500 microns was developed as preparation for the FIRST (Far Infrared and Submillimeter Space Telescope) project. Since no low noise amplifiers exist in this region, the incoming signal is mixed down to a microwave frequency and then spectrally analyzed in an acousto-optical spectrometer. The heterodyne spectrometer was used on the KAO (Kuiper Airborne Observatory) of NASA for the observation of the Orion nebula.

  8. Atmospheric solar absorption measurements in the 9 to 11 mu m region using a diode laser heterodyne spectrometer

    NASA Technical Reports Server (NTRS)

    Harward, C. N.; Hoell, J. M., Jr.

    1980-01-01

    A tunable diode laser heterodyne radiometer was developed for ground-based measurements of atmospheric solar absorption spectra in the 8 to 12 microns spectral range. The performance and operating characteristics of this Tunable Infrared Heterodyne Radiometer (TIHR) are discussed along with atmospheric solar absorption spectra of HNO3, O3, CO2, and H2O in the 9 to 11 microns spectral region.

  9. VizieR Online Data Catalog: Fundamental stellar parameters from PolarBase (Paletou+, 2015)

    NASA Astrophysics Data System (ADS)

    Paletou, F.; Boehm, T.; Watson, V.; Trouilhet, J.-F.

    2015-02-01

    Our reference spectra are taken from the Elodie stellar library (Prugniel et al. 2007, astro-ph/0703658, Cat. III/251; Prugniel & Soubiran 2001A&A...369.1048P, Cat. III/218). Our main purpose is inverting of stellar parameters from high-resolution spectra coming from Narval and ESPaDOnS spectropolarimeters. These data are now available from the public database PolarBase (Petit et al., 2014PASP..126..469P, Cat. J/PASP/126/469). Narval is a modern spectropolarimeter operating in the 380-1000nm spectral domain, with a spectral resolution of 65000 in its polarimetric mode. It is an improved copy, adapted to the 2m TBL telescope, of the ESPaDOnS spectropolarimeter, which is in operations since 2004 at the 3.6m aperture CFHT telescope. (1 data file).

  10. Compact transverse-magnetic-pass polarizer based on one-dimensional photonic crystal waveguide

    NASA Astrophysics Data System (ADS)

    Kim, Dong Wook; Lee, Moon Hyeok; Kim, Yudeuk; Kim, Kyong Hon

    2016-03-01

    We propose a compactly integrated transverse-magnetic (TM)-pass polarizer based on rectangular-shape onedimensional photonic-crystal silicon waveguide with an extremely high polarization extinction ratio of >30 dB and low insertion loss (~1 dB) over a broad wavelength range of 210 nm from 1,460 nm to 1,670 nm. The polarizer has been numerically simulated using three-dimensional finite-difference time-domain (3D FDTD) method. The optimum length of the proposed TM-pass polarizer is about 4 μm. At the 1,550 nm wavelength, the simulated polarization extinction ratio of the polarizer is 36 dB, and its corresponding insertion loss is about 1 dB.

  11. Perfect dual-band circular polarizer based on twisted split-ring structure asymmetric chiral metamaterial.

    PubMed

    Cheng, Yongzhi; Gong, Rongzhou; Cheng, Zhengze; Nie, Yan

    2014-09-01

    A near-perfect dual-band circular polarizer based on bilayer twisted, single split-ring resonator structure asymmetric chiral metamaterial was proposed and investigated. The simple bilayer structure with a 90° twisted angle allows for equalizing the orthogonal components of the electric field at the output interface with a 90° phase difference for a y-polarized wave propagating along the backward (-z) direction. It is found that right- and left-hand circular polarization are realized in transmissions at 7.8 and 10.1 GHz, respectively. Experiments agree well with numerical simulations, which exhibit that the polarization extinction ratio is more than 30 dB at the resonant frequencies. Further, the simple design also can be operated at the terahertz range by scaling down the geometrical parameters of the unit cell. PMID:25321375

  12. Three-dimensional shape measurement of small object based on tri-frequency heterodyne method

    NASA Astrophysics Data System (ADS)

    Liu, Shouqi; Feng, Wei; Zhang, Qican; Liu, Yuankun

    2015-08-01

    Among temporal phase unwrapping methods based on structured light projection, tri-frequency heterodyne method, with the merits of less projected fringe, high precision and high reliability, has become a practical method in objects three-dimensional (3D) shape measurement. In this paper, a 3D shape measuring system was developed with a digital micromirror device (DMD) and synchronously trigged CCD camera. The 3D shape of a measured object was reconstructed from the deformed fringe patterns based on tri-frequency heterodyne method. The practical experiments were carried on some coins, and the results show that the system can restore their 3D shape on the tested partition with an accuracy of microns. This measurement system is prominent in 3D shape measurement of small or tiny objects, sample testing, and many other application fields.

  13. Hollow waveguide photomixing for quantum cascade laser heterodyne spectro-radiometry.

    PubMed

    Weidmann, Damien; Perrett, Brian J; Macleod, Neil A; Jenkins, R Mike

    2011-05-01

    An integrated optic approach, using hollow waveguides, has been evaluated for a compact, rugged, high efficiency heterodyne optical mixing circuit in the middle infrared. The approach has involved the creation of hollow waveguides and alignment features for a beam combiner component in a glass-ceramic substrate. The performance of the integrated beam combiner was tested as part of a full laser heterodyne spectro-radiometer in which a quantum cascade laser local oscillator emitting at 9.7 µm was mixed with incoherent radiation. The performance has been evaluated with both cryogenically-cooled and peltier-cooled photomixers demonstrating consistent detection limits of two and five times the shot noise limit, respectively. The hollow waveguide mixer has also shown advantages in temporal stability, laser spatial mode cleansing, and reduced sensitivity to optical feedback. PMID:21643162

  14. Heterodyne interferometry method for calibration of a Soleil-Babinet compensator.

    PubMed

    Zhang, Wenjing; Zhang, Zhiwei

    2016-05-20

    A method based on the common-path heterodyne interferometer system is proposed for the calibration of a Soleil-Babinet compensator. In this heterodyne interferometer system, which consists of two acousto-optic modulators, the compensator being calibrated is inserted into the signal path. By using the reference beam as the benchmark and a lock-in amplifier (SR844) as the phase retardation collector, retardations of 0 and λ (one wavelength) can be located accurately, and an arbitrary retardation between 0 and λ can also be measured accurately and continuously. By fitting a straight line to the experimental data, we obtained a linear correlation coefficient (R) of 0.995, which indicates that this system is capable of linear phase detection. The experimental results demonstrate determination accuracies of 0.212° and 0.26° and measurement precisions of 0.054° and 0.608° for retardations of 0 and λ, respectively. PMID:27411154

  15. Inversion technique for IR heterodyne sounding of stratospheric constituents from space platforms

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Shapiro, G. L.; Alvarez, J. M.

    1981-01-01

    The techniques which have been employed for inversion of IR heterodyne measurements for remote sounding of stratospheric trace constituents usually rely on either geometric effects based on limb-scan observations (i.e., onion peel techniques) or spectral effects by using weighting functions corresponding to different frequencies of an IR spectral line. An experimental approach and inversion technique are discussed which optimize the retrieval of concentration profiles by combining the geometric and the spectral effects in an IR heterodyne receiver. The results of inversions of some synthetic CIO spectral lines corresponding to solar occultation limb scans of the stratosphere are presented, indicating considerable improvement in the accuracy of the retrieved profiles. The effects of noise on the accuracy of retrievals are discussed for realistic situations.

  16. Improved optical pulse heterodyne demodulation scheme for fiber-optic interferometric sensors

    NASA Astrophysics Data System (ADS)

    Lai, Haiqiang; Wang, Jianfei; Tu, Xiaobo; Meng, Zhou

    2015-10-01

    An improved optical pulse heterodyne demodulation scheme for fiber-optic interferometric sensors is demonstrated. This scheme uses two series-connected Acoustic-optic modulators (AOMs) as intensity modulator and frequency shifter respectively. Compared to the traditional optical heterodyne demodulation structure, this scheme eliminates the polarization-induced signal fading and the noise floor is lowered for using the Michelson-configuration delay structure and Faraday rotation mirrors (FRMs) in the optic architecture of system. At the same time, the architecture of this scheme is not complicated and can be used to complex a large sensor array. Experimental results show that the phase noise floor of this demodulation scheme is flat and reaches -99dB/sqrt(Hz) at frequencies above 300 Hz.

  17. Frequency locking of a field-widened Michelson interferometer based on optimal multi-harmonics heterodyning.

    PubMed

    Cheng, Zhongtao; Liu, Dong; Zhou, Yudi; Yang, Yongying; Luo, Jing; Zhang, Yupeng; Shen, Yibing; Liu, Chong; Bai, Jian; Wang, Kaiwei; Su, Lin; Yang, Liming

    2016-09-01

    A general resonant frequency locking scheme for a field-widened Michelson interferometer (FWMI), which is intended as a spectral discriminator in a high-spectral-resolution lidar, is proposed based on optimal multi-harmonics heterodyning. By transferring the energy of a reference laser to multi-harmonics of different orders generated by optimal electro-optic phase modulation, the heterodyne signal of these multi-harmonics through the FWMI can reveal the resonant frequency drift of the interferometer very sensitively within a large frequency range. This approach can overcome the locking difficulty induced by the low finesse of the FWMI, thus contributing to excellent locking accuracy and lock acquisition range without any constraint on the interferometer itself. The theoretical and experimental results are presented to verify the performance of this scheme. PMID:27607936

  18. Spectral characterization of microwave signals generated by the heterodyne of injection-locked semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Chamberland, Martin; Tetu, Michel; Tremblay, Pierre

    1994-06-01

    Optical heterodyne has been proposed to generate the microwave signals to be used in phased array antenna systems. Optical injection-locking of secondary lasers to distinct FM-sidebands of a current-modulated laser diode has been used to improve the spectral purity of the microwave signal generated by heterodyne. A very narrow linewidth microwave signal superimposed over a Lorentzian shaped noise floor has been obtained. The spectral purity of the produced microwave signal has been characterized by three distinct means: power spectrum, phase fluctuations, and time-domain frequency stability (Allan variance). The power spectrum shows a linewidth smaller than 25 mHz (FWHM) and the Allan standard deviation gives a level 1 X 10-11 for an averaging time of 1 sec.

  19. A Miniaturized Laser Heterodyne Radiometer for Greenhouse Gas Measurements in the Atmospheric Column

    NASA Technical Reports Server (NTRS)

    Steel, Emily Wilson

    2015-01-01

    Laser Heterodyne Radiometry is a technique adapted from radio receiver technology has been used to measure trace gases in the atmosphere since the 1960s.By leveraging advances in the telecommunications industry, it has been possible to miniaturize this technology.The mini-LHR (Miniaturized Laser Heterodyne Radiometer) has been under development at NASA Goddard Space flight Center since 2009. This sun-viewing instrument measures carbon dioxide and methane in the atmospheric column and operates in tandem with an AERONET sun photometer producing a simultaneous measure of aerosols. The mini-LHR has been extensively field tested in a range of locations ranging in the continental US as well as Alaska and Hawaii and now operates autonomously with sensitivities of approximately 0.2 ppmv and approximately10 ppbv, for carbon dioxide and methane respectively, for 10 averaged scans under clear sky conditions.

  20. Measurements of the single sideband suppression for a 650 GHz heterodyne receiver

    NASA Technical Reports Server (NTRS)

    Crewell, S.; Nett, H.

    1992-01-01

    A large number of atmospheric trace gases, involved in the process of stratospheric ozone depletion, show emission features in the submillimeter wavelength range (lambda = 0.1-1mm). High-resolution heterodyne techniques are a particularly useful tool in this spectral region as vertical distribution of these species can be deduced. Here the receiver has to be operated in the single sideband (ssb) mode preferably to avoid any interferences between the contributions in both receiver sidebands. In the 625-655 GHz heterodyne receiver developed at the University of Bremen a Martin-Puplett interferometer is used as a ssb-filter. A laboratory set-up has been built up to measure the performance of this interferometer.

  1. 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.

  2. Heterodyne Interferometric Temperature Sensor Using a Transverse Zeeman Laser and a Polarization Maintaining Fiber

    NASA Astrophysics Data System (ADS)

    Kawata, S.; Shigeoka, T.; Okamoto, T.; Minami, S.

    1986-01-01

    A new fiber-optic temperature sesnor using a polarization maintaining fiber and a transverse Zeeman laser based on heterodyne interferometry has been developed. The temperature variation is detected by coupling two orthogonal linear polirization components of a laser beam, each differently phase-modulated during transmitting a birefringent single-mode polarization maintaining fiber. A transverse He-Ne Zeeman laser was developed to achieve heterodyning demodulation of the phase-shift caused by the temperature of the fiber. Experimental result demonstrates that this sensor has the temperature resolution of 0.0032°C with a very wide dynamic range. Besides, this fiber sensor has the advantages of simple construction and ruggedness against pressure turbulence.

  3. Active local oscillator power stabilization for a hot electron bolometer heterodyne receiver

    NASA Astrophysics Data System (ADS)

    Hayton, D. J.; Gao, J. R.; Kooi, J. W.; Ren, Y.; Zhang, W.; de Lange, G.

    2012-09-01

    We report on the application of a new technique for actively stabilizing the power of a far infrared gas laser as the local oscillator (LO) in a superconducting hot electron bolometer (HEB) heterodyne receiver system at 2.5 THz. The technique utilizes PID feedback control of the local oscillator intensity by means of a voice-coil based swing arm actuator placed in the beam path. The HEB itself is used as a direct detector to measure incident LO power whilst simultaneously continuing to function as heterodyne mixer. Results presented here demonstrate a factor of 50 improvement in the measured total power and spectroscopic Allan variance time. Allan times of 30 seconds and 25 seconds respectively are shown for large and small area HEB's with a measured effective noise fluctuation bandwidth of 12 MHz. The technique is versatile and can be applied to any LO source and at any LO frequency.

  4. Balancing Acts

    MedlinePlus

    ... a new type of balance therapy using computerized, virtual reality. UPMC associate professor Susan Whitney, Ph.D., developed ... a virtual grocery store in the university's Medical Virtual Reality Center. Patients walk on a treadmill and safely ...

  5. Balancing Acts

    MedlinePlus

    ... Current Issue Past Issues Special Section: Focus on Communication Balancing Acts Past Issues / Fall 2008 Table of ... from the National Institute on Deafness and Other Communication Disorders (NIDCD). It involves simulated trips down the ...

  6. Rapid-tuning device for CO/sub 2/ heterodyne detection lidar

    SciTech Connect

    Fox, J. A.; Gautier, C. R.; Ahl, J. L.

    1989-07-01

    A device for rapid-tuning cw, /ital Q/-switched lasers for a CO/sub 2/ heterodyne detection lidar is presented. It is shown that it is possible to utilize galvanometer-driven mirrors to rapidly switch wavelengths over randomly selected lasing transitions in the 9--11 /mu/m portion of the spectrum. Both a transmitter and a local oscillator are simultaneously switched between transitions while still achieving the frequency stability typically required for a coherent lidar system.

  7. Absolute intensity calibration of the 32-channel heterodyne radiometer on experimental advanced superconducting tokamak

    SciTech Connect

    Liu, X.; Zhao, H. L.; Liu, Y. Li, E. Z.; Han, X.; Ti, A.; Hu, L. Q.; Zhang, X. D.; Domier, C. W.; Luhmann, N. C.

    2014-09-15

    This paper presents the results of the in situ absolute intensity calibration for the 32-channel heterodyne radiometer on the experimental advanced superconducting tokamak. The hot/cold load method is adopted, and the coherent averaging technique is employed to improve the signal to noise ratio. Measured spectra and electron temperature profiles are compared with those from an independent calibrated Michelson interferometer, and there is a relatively good agreement between the results from the two different systems.

  8. Absolute intensity calibration of the 32-channel heterodyne radiometer on experimental advanced superconducting tokamak.

    PubMed

    Liu, X; Zhao, H L; Liu, Y; Li, E Z; Han, X; Domier, C W; Luhmann, N C; Ti, A; Hu, L Q; Zhang, X D

    2014-09-01

    This paper presents the results of the in situ absolute intensity calibration for the 32-channel heterodyne radiometer on the experimental advanced superconducting tokamak. The hot/cold load method is adopted, and the coherent averaging technique is employed to improve the signal to noise ratio. Measured spectra and electron temperature profiles are compared with those from an independent calibrated Michelson interferometer, and there is a relatively good agreement between the results from the two different systems. PMID:25273727

  9. Air pollution - Remote detection of several pollutant gases with a laser heterodyne radiometer

    NASA Technical Reports Server (NTRS)

    Menzies, R. T.; Shumate, M. S.

    1974-01-01

    An infrared heterodyne radiometer with a spectral resolution of 0.04 reciprocal centimeters has been used to remotely detect samples of ozone, sulfur dioxide, ammonia, and ethylene at room temperature, and samples of nitric oxide at 390 K. Each gas was observed in a background of nitrogen or oxygen at atmospheric pressure. Sensitivities to some of these gases are adequate for detection of ambient concentrations as low as a few parts per billion.

  10. Two-wavelength laser-diode heterodyne interferometry with one phasemeter

    NASA Astrophysics Data System (ADS)

    Onodera, Ribun; Ishii, Yukihiro

    1995-12-01

    A two-wavelength laser-diode interferometer that is based on heterodyne detection with one phasemeter has been constructed. Two laser diodes are frequency modulated by mutually inverted sawtooth currents on an unbalanced interferometer. One can measure the tested phase at a synthetic wavelength from the sum of the interference beat signals by synchronizing them with the modulation frequency. The experimental result presented shows a phase-measurement range with a 4.7- mu m synthetic wavelength.

  11. Cryogen-free heterodyne-enhanced mid-infrared Faraday rotation spectrometer

    PubMed Central

    Wang, Yin; Nikodem, Michal; Wysocki, Gerard

    2013-01-01

    A new detection method for Faraday rotation spectra of paramagnetic molecular species is presented. Near shot-noise limited performance in the mid-infrared is demonstrated using a heterodyne enhanced Faraday rotation spectroscopy (H-FRS) system without any cryogenic cooling. Theoretical analysis is performed to estimate the ultimate sensitivity to polarization rotation for both heterodyne and conventional FRS. Sensing of nitric oxide (NO) has been performed with an H-FRS system based on thermoelectrically cooled 5.24 μm quantum cascade laser (QCL) and a mercury-cadmium-telluride photodetector. The QCL relative intensity noise that dominates at low frequencies is largely avoided by performing the heterodyne detection in radio frequency range. H-FRS exhibits a total noise level of only 3.7 times the fundamental shot noise. The achieved sensitivity to polarization rotation of 1.8 × 10−8 rad/Hz1/2 is only 5.6 times higher than the ultimate theoretical sensitivity limit estimated for this system. The path- and bandwidth-normalized NO detection limit of 3.1 ppbv-m/Hz1/2 was achieved using the R(17/2) transition of NO at 1906.73 cm−1. PMID:23388967

  12. Deferred electronic heterodyne moire deflectometry: A method for transient density fields measurement

    NASA Technical Reports Server (NTRS)

    Stricker, Josef

    1989-01-01

    Effects of spherical aberrations of the mirror used in the moire system on the angular resolution of the system are investigated. It is shown that the spherical aberrations may reduce significantly the performance of the conventional moire deflectometer. However, due to the heterodyne procedure, this is not the case with the heterodyne moire system. A moire system with a constant speed moving grating is demonstrated. It is shown that the system readout is linear and the system does not need calibration. In addition, the repeatability of the measurements is improved in this system as compared to the sinusoidally moving grating setup. The problem of the photographic plates alignment is solved by using a mechanical system in which the plate is held firmly throughout the experiment and accurately replaced after removing for photographic processing. The effect of a circular detector's aperture size on readout was tested. It is shown that the spatial phase variations, observed when scanning along a straight moire fringe, may considerably be reduced. At present we may say that both the on-line and the deferred heterodyne moire techniques may reliably be used. The errors of phase readings are 1 deg and 5 deg for the on-line and deferred methods. The total error due to subtraction of two readings at each position is, therefore, 1.4 deg and 7 deg, respectively. Further research for improving the deferred system is suggested.

  13. Improved synthetic-heterodyne Michelson interferometer vibrometer using phase and gain control feedback.

    PubMed

    Galeti, José Henrique; Kitano, Cláudio; Connelly, Michael J

    2015-12-10

    Synthetic-heterodyne demodulation is a useful technique for dynamic displacement and velocity measurement using interferometric sensors as it can provide an output signal which is immune to interferometric drift. With the advent of cost effective, high-speed real-time signal processing systems and software, processing of the complex signals encountered in interferometry has become more feasible. In conventional synthetic-heterodyne demodulation schemes, to obtain the dynamic displacement or vibration of the object under test requires knowledge of the interferometer visibility and also the argument of two Bessel functions. In this paper, a new synthetic-heterodyne demodulation method is described leading to an expression for the dynamic displacement and velocity of the object under test that is significantly less sensitive to the received optical power. In addition, the application of two independent phase and gain feedback loops is used to compensate for the nonideal gain and phase response of the anti-aliasing filter required for the signal acquisition of the received wideband interferometer signal. The efficacy of the improved system is demonstrated by measuring the displacement sensitivity frequency response and linearity of a Piezoelectric Mirror-Shifter (PMS) over a range of 200 Hz-9 kHz. In addition, the system is used to measure the response of the PMS to triangular and impulse type stimuli. The experimental results show excellent agreement with measurements taken using two independent industry standard calibration methods. PMID:26836865

  14. Balance System

    NASA Technical Reports Server (NTRS)

    1988-01-01

    TherEx Inc.'s AT-1 Computerized Ataxiameter precisely evaluates posture and balance disturbances that commonly accompany neurological and musculoskeletal disorders. Complete system includes two-strain gauged footplates, signal conditioning circuitry, a computer monitor, printer and a stand-alone tiltable balance platform. AT-1 serves as assessment tool, treatment monitor, and rehabilitation training device. It allows clinician to document quantitatively the outcome of treatment and analyze data over time to develop outcome standards for several classifications of patients. It can evaluate specifically the effects of surgery, drug treatment, physical therapy or prosthetic devices.

  15. Complete all-optical processing polarization-based binary logic gates and optical processors.

    PubMed

    Zaghloul, Y A; Zaghloul, A R M

    2006-10-16

    We present a complete all-optical-processing polarization-based binary-logic system, by which any logic gate or processor can be implemented. Following the new polarization-based logic presented in [Opt. Express 14, 7253 (2006)], we develop a new parallel processing technique that allows for the creation of all-optical-processing gates that produce a unique output either logic 1 or 0 only once in a truth table, and those that do not. This representation allows for the implementation of simple unforced OR, AND, XOR, XNOR, inverter, and more importantly NAND and NOR gates that can be used independently to represent any Boolean expression or function. In addition, the concept of a generalized gate is presented which opens the door for reconfigurable optical processors and programmable optical logic gates. Furthermore, the new design is completely compatible with the old one presented in [Opt. Express 14, 7253 (2006)], and with current semiconductor based devices. The gates can be cascaded, where the information is always on the laser beam. The polarization of the beam, and not its intensity, carries the information. The new methodology allows for the creation of multiple-input-multiple-output processors that implement, by itself, any Boolean function, such as specialized or non-specialized microprocessors. Three all-optical architectures are presented: orthoparallel optical logic architecture for all known and unknown binary gates, singlebranch architecture for only XOR and XNOR gates, and the railroad (RR) architecture for polarization optical processors (POP). All the control inputs are applied simultaneously leading to a single time lag which leads to a very-fast and glitch-immune POP. A simple and easy-to-follow step-by-step algorithm is provided for the POP, and design reduction methodologies are briefly discussed. The algorithm lends itself systematically to software programming and computer-assisted design. As examples, designs of all binary gates, multiple

  16. Balancing Eggs

    ERIC Educational Resources Information Center

    Mills, Allan

    2014-01-01

    Theory predicts that an egg-shaped body should rest in stable equilibrium when on its side, balance vertically in metastable equilibrium on its broad end and be completely unstable on its narrow end. A homogeneous solid egg made from wood, clay or plastic behaves in this way, but a real egg will not stand on either end. It is shown that this…

  17. Composite film polarizer based on the oriented assembly of electrospun nanofibers

    NASA Astrophysics Data System (ADS)

    Hu, Zhongliang; Ma, Zhijun; Peng, Mingying; He, Xin; Zhang, Hang; Li, Yang; Qiu, Jianrong

    2016-04-01

    Polarizers are widely applied in antiglare glasses, planner displays, photography filters and optical communications, etc. In this investigation, we propose a new strategy for the preparation of a flexible film polarizer based on the electrospinning technique. An aligned assembly of polyvinyl acetate (PVA) nanofibers was electrospun and collected by a fast-rotating drum, then soaked in polymethyl methacrylate (PMMA) solution and dried thoroughly to obtain a transparent PVA-PMMA composite film polarizer. The morphology, structure and optical performance of the PVA nanofibers and the film polarizers were characterized with a scanning electron microscope, UV-vis-IR spectrometer and polarized Raman spectra, etc. The PVA-PMMA film polarizer demonstrated efficient polarizing activity toward visible and near-infrared light, while keeping fair transparency in the range of 400-1400 nm. Due to the protection from the hydrophobic PMMA matrix, the PVA-PMMA film polarizers show high moisture resistance, making it applicable in a humid environment. Considering the scalability and versatility of the strategy employed here, the PVA-PMMA film polarizer prepared could replace the conventional film polarizers in a wide range of applications.

  18. Composite film polarizer based on the oriented assembly of electrospun nanofibers.

    PubMed

    Hu, Zhongliang; Ma, Zhijun; Peng, Mingying; He, Xin; Zhang, Hang; Li, Yang; Qiu, Jianrong

    2016-04-01

    Polarizers are widely applied in antiglare glasses, planner displays, photography filters and optical communications, etc. In this investigation, we propose a new strategy for the preparation of a flexible film polarizer based on the electrospinning technique. An aligned assembly of polyvinyl acetate (PVA) nanofibers was electrospun and collected by a fast-rotating drum, then soaked in polymethyl methacrylate (PMMA) solution and dried thoroughly to obtain a transparent PVA-PMMA composite film polarizer. The morphology, structure and optical performance of the PVA nanofibers and the film polarizers were characterized with a scanning electron microscope, UV-vis-IR spectrometer and polarized Raman spectra, etc. The PVA-PMMA film polarizer demonstrated efficient polarizing activity toward visible and near-infrared light, while keeping fair transparency in the range of 400-1400 nm. Due to the protection from the hydrophobic PMMA matrix, the PVA-PMMA film polarizers show high moisture resistance, making it applicable in a humid environment. Considering the scalability and versatility of the strategy employed here, the PVA-PMMA film polarizer prepared could replace the conventional film polarizers in a wide range of applications. PMID:26894877

  19. Long-term stabilization of a heterodyne metrology interferometer down to a noise level of 20 pm over an hour

    SciTech Connect

    Niwa, Yoshito; Arai, Koji; Ueda, Akitoshi; Sakagami, Masaaki; Gouda, Naoteru; Kobayashi, Yukiyasu; Yamada, Yoshiyuki; Yano, Taihei

    2009-11-10

    A heterodyne metrology interferometer was stabilized down to a noise level of 20 picometers (pm) as a root-mean-square (RMS) value integrated between 0.3 mHz and 1 Hz. This noise level was achieved by employing active and passive interferometer stabilization techniques. The heterodyne interferometer was built on a 50 mm square ultralow expansion glass plate in order to reduce an optical path length change caused by temperature variation. An optical configuration of the interferometer is a Mach-Zehnder interferometer with a design as symmetric as possible so that a detection signal can be insensitive to homogeneous thermal expansion of the glass plate. The heterodyne frequency is actively controlled in order to suppress residual noises caused by optical path length changes outside of the glass plate as well as phase fluctuations of the heterodyne frequency source. Our stabilization scheme is considered useful in achieving the 20 pm noise level without a stable heterodyne frequency source, as well as temperature stabilization around a whole apparatus. This interferometer can be used in precise metrology applications, such as characterization of deformation for satellite optical components against thermal exposure.

  20. Apparatus and method for heterodyne-generated two-dimensional detector array using a single element detector

    DOEpatents

    Strauss, Charlie E.

    1997-01-01

    Apparatus and method for heterodyne-generated, two-dimensional detector array using a single detector. Synthetic-array heterodyne detection, permits a single-element optical detector to behave as though it were divided into an array of separate heterodyne detector elements. A fifteen-element synthetic array has successfully been experimentally realized on a single-element detector, permitting all of the array elements to be read out continuously and in parallel from one electrical connection. A CO.sub.2 laser and a single-element HgCdTe photodiode are employed. A different heterodyne local oscillator frequency is incident upon the spatially resolvable regions of the detector surface. Thus, different regions are mapped to different heterodyne beat frequencies. One can determine where the photons were incident on the detector surface even though a single electrical connection to the detector is used. This also prevents the destructive interference that occurs when multiple speckles are imaged (similar to spatial diversity), In coherent LIDAR this permits a larger field of view. An acoustooptic modulator generates the local oscillator frequencies and can achieve adequate spatial separation of optical frequencies of the order of a megahertz apart.

  1. Apparatus and method for heterodyne-generated two-dimensional detector array using a single element detector

    DOEpatents

    Strauss, C.E.

    1997-11-18

    Apparatus and method are disclosed for heterodyne-generated, two-dimensional detector array using a single detector. Synthetic-array heterodyne detection, permits a single-element optical detector to behave as though it were divided into an array of separate heterodyne detector elements. A fifteen-element synthetic array has successfully been experimentally realized on a single-element detector, permitting all of the array elements to be read out continuously and in parallel from one electrical connection. A CO{sub 2} laser and a single-element HgCdTe photodiode are employed. A different heterodyne local oscillator frequency is incident upon the spatially resolvable regions of the detector surface. Thus, different regions are mapped to different heterodyne beat frequencies. One can determine where the photons were incident on the detector surface even though a single electrical connection to the detector is used. This also prevents the destructive interference that occurs when multiple speckles are imaged (similar to spatial diversity), In coherent LIDAR this permits a larger field of view. An acoustooptic modulator generates the local oscillator frequencies and can achieve adequate spatial separation of optical frequencies of the order of a megahertz apart. 4 figs.

  2. Balance (or Vestibular) Rehabilitation

    MedlinePlus

    ... for the Public / Hearing and Balance Balance (or Vestibular) Rehabilitation Audiologic (hearing), balance, and medical diagnostic tests help indicate whether you are a candidate for vestibular (balance) rehabilitation. Vestibular rehabilitation is an individualized balance ...

  3. Balanced Can

    NASA Astrophysics Data System (ADS)

    Shakerin, Said

    2013-12-01

    The ordinary 12-oz beverage cans in the figures below are not held up with any props or glue. The bottom of such cans is stepped at its circumference for better stacking. When this kind of can is tilted, as shown in Fig. 1, the outside corners of the step touch the surface beneath, providing an effective contact about 1 cm wide. Because the contact is relatively wide and the geometry is symmetrical, it is easy to balance an empty can by simply adding an appropriate amount of water so that the overall center of mass is located directly above the contact. In fact, any amount of water between about 40 and 210 mL will work. A computational animation of this trick by Sijia Liang and Bruce Atwood that shows center of mass as a function of amount of added water is available at http://demonstrations.wolfram.com. Once there, search "balancing can."

  4. Ground Based Observation of Isotopic Oxygen in the Martian Atmosphere Using Infrared Heterodyne Spectroscopy

    NASA Technical Reports Server (NTRS)

    Smith, R. L.; Kostiuk, T.; Livengood, T. A.; Fast, K. E.; Hewagama, T.; Delgado, J. D.; Sonnabend, G.

    2010-01-01

    Infrared heterodyne spectra of isotopic CO2 in the Martian atmosphere were obtained using the Goddard Heterodyne Instrument for Planetary Wind and Composition, HIPWAC, which was interfaced with the 3-meter telescope at the NASA Infrared Telescope Facility- Spectra were colle cted at a resolution of lambda/delta lambda=10(exp 7). Absorption fea tures of the CO2 isotopologues have been identified from which isotop ic ratios of oxygen have been determined. The isotopic ratios O-17/O -16 and O-18/O-16 in the Martian atmosphere can be related to Martian atmospheric evolution and can be compared to isotopic ratios of oxyg en in the Earth's atmosphere. Isotopic carbon and oxygen are importa nt constraints on any theory for the erosion of the Martian primordia l atmosphere and the interaction between the atmosphere and surface o r subsurface chemical reservoirs. This investigation explored the pr esent abundance of the stable isotopes of oxygen in Mars' atmospheric carbon dioxide by measuring rovibrational line absorption in isotop ic species of CO2 using groundbased infrared heterodyne spectroscopy in the vicinity of the 9.6 micron and 10.6 micron CO2 lasing bands. T he target transitions during this observation were O-18 C-12 O-16 as well as O-178 C-12 O-16 and O-16 C-113 O-16 at higher resolving power of lambda/delta lambda=10(exp 7) and with high signal-to-noise ratio (longer integration time) in order to fully characterize the absorpt ion line profiles. The fully-resolved lineshape of both the strong n ormal-isotope and the weak isotopic CO2 lines were measured simultane ously in a single spectrum.

  5. Michelson interferometer vibrometer using self-correcting synthetic-heterodyne demodulation.

    PubMed

    Connelly, Michael J; Galeti, José Henrique; Kitano, Cláudio

    2015-06-20

    Synthetic-heterodyne demodulation is a useful technique for dynamic displacement and velocity detection in interferometric sensors, as it can provide an output signal that is immune to interferometric drift. With the advent of cost-effective, high-speed real-time signal-processing systems and software, processing of the complex signals encountered in interferometry has become more feasible. In synthetic heterodyne, to obtain the actual dynamic displacement or vibration of the object under test requires knowledge of the interferometer visibility and also the argument of two Bessel functions. In this paper, a method is described for determining the former and setting the Bessel function argument to a set value, which ensures maximum sensitivity. Conventional synthetic-heterodyne demodulation requires the use of two in-phase local oscillators; however, the relative phase of these oscillators relative to the interferometric signal is unknown. It is shown that, by using two additional quadrature local oscillators, a demodulated signal can be obtained that is independent of this phase difference. The experimental interferometer is a Michelson configuration using a visible single-mode laser, whose current is sinusoidally modulated at a frequency of 20 kHz. The detected interferometer output is acquired using a 250 kHz analog-to-digital converter and processed in real time. The system is used to measure the displacement sensitivity frequency response and linearity of a piezoelectric mirror shifter over a range of 500 Hz to 10 kHz. The experimental results show good agreement with two data-obtained independent techniques: the signal coincidence and denominated n-commuted Pernick method. PMID:26193022

  6. Multi-frequency THz Heterodyne Spectroscopy using Electro-Optic Sampling

    NASA Astrophysics Data System (ADS)

    Jones, David

    2010-03-01

    Multi-frequency heterodyne spectroscopy, developed by two groups (Schiller as well as van der Weide, Keilmann and co-workers) uses one optical femtosecond frequency comb (FFC) to probe a sample. A second FFC with a slightly detuned spacing is used as a multi frequency local oscillator to uniquely map the broadband optical spectroscopic information to the RF domain where it can be easily analyzed. Researchers at NIST (Coddington et al) have realized the full potential of this technique by tightly locking the detuned combs together using optical locking techniques. It is of considerable interest to extend such capabilities to access the so-called molecular vibrational ``fingerprint'' range of approximately 10 to 100 THz (300 to 3000 cm-1). A transfer of the direct heterodyne detection approach used in the optical regime down to this frequency range is fraught with difficulties including significantly lower power of the probe THz frequency comb. In addition, a low noise detector with a relatively fast RF response (>100 MHz at a minimum) is required. An alternative, indirect detection technique for detecting THz signals is electro-optic sampling (EOS). It has employed for time domain THz spectroscopic applications for a number of years with a demonstrated spectral detection ranging from 0.5 THz range to over 100 THz. Through careful analysis of the EOS we show how electro-optic sampling of THz frequency comb by a detuned optical FFC followed by direct optical detection of the optical sampling beam enables conversion of the THz spectroscopic data directly to the RF domain. In particular, we show there is a one-to-one correspondence between a detected RF heterodyne beat and THz comb element. Numerical simulations predict excellent signal to noise ratio of the RF beats (20 dB) with modest acquisition times (10 μs). We will also summarize our progress toward experimental realization of such a system.

  7. Airplane Balance

    NASA Technical Reports Server (NTRS)

    Huguet, L

    1921-01-01

    The authors argue that the center of gravity has a preponderating influence on the longitudinal stability of an airplane in flight, but that manufacturers, although aware of this influence, are still content to apply empirical rules to the balancing of their airplanes instead of conducting wind tunnel tests. The author examines the following points: 1) longitudinal stability, in flight, of a glider with coinciding centers; 2) the influence exercised on the stability of flight by the position of the axis of thrust with respect to the center of gravity and the whole of the glider; 3) the stability on the ground before taking off, and the influence of the position of the landing gear. 4) the influence of the elements of the glider on the balance, the possibility of sometimes correcting defective balance, and the valuable information given on this point by wind tunnel tests; 5) and a brief examination of the equilibrium of power in horizontal flight, where the conditions of stability peculiar to this kind of flight are added to previously existing conditions of the stability of the glider, and interfere in fixing the safety limits of certain evolutions.

  8. Fiber-optic heterodyne phase-shift easurement of plasma current.

    PubMed

    Chandler, G L; Forman, P R; Jahoda, F C; Klare, K A

    1986-06-01

    By combining twisted optical sensing fiber and heterodyne phase detection of circular irefringence we have (a) overcome the distortion problem caused by residual linear birefringence in the Faraday rotation method of measuring enclosed current and (b) used only a single output detector without requiring intensity normalization. Resolution of 400 ampere-turns has been obtained in the hostile electromagnetic environment of a working thermonuclear fusion research device. The fiber was simply wound around the existing machine. The measured values are in excellent agreement with those of the electrical Rogowski coil installed when the machine was built. PMID:20448729

  9. Heterodyne signal-to-noise ratios in acoustic mode scattering experiments

    NASA Technical Reports Server (NTRS)

    Cochran, W. R.

    1980-01-01

    The relation between the signal to noise ratio (SNR) obtained in heterodyne detection of radiation scattered from acoustic modes in crystalline solids and the scattered spectral density function is studied. It is shown that in addition to the information provided by the measured frequency shifts and line widths, measurement of the SNR provides a determination of the absolute elasto-optical (Pockel's) constants. Examples are given for cubic crystals, and acceptable SNR values are obtained for scattering from thermally excited phonons at 10.6 microns, with no external perturbation of the sample necessary. The results indicate the special advantages of the method for the study of semiconductors.

  10. Imaging through obscurants with a heterodyne detection-based ladar system

    NASA Astrophysics Data System (ADS)

    Reibel, Randy R.; Roos, Peter A.; Kaylor, Brant M.; Berg, Trenton J.; Curry, James R.

    2014-06-01

    Bridger Photonics has been researching and developing a ladar system based on heterodyne detection for imaging through brownout and other DVEs. There are several advantages that an FMCW ladar system provides compared to direct detect pulsed time-of-flight systems including: 1) Higher average powers, 2) Single photon sensitive while remaining tolerant to strong return signals, 3) Doppler sensitivity for clutter removal, and 4) More flexible system for sensing during various stages of flight. In this paper, we provide a review of our sensor, discuss lessons learned during various DVE tests, and show our latest 3D imagery.

  11. A novel heterodyne displacement interferometer with no detectable periodic nonlinearity and optical resolution doubling

    SciTech Connect

    Joo, K; Ellis, J D; Buice, E S; Spronck, J W; Munnig Schmidt, R H

    2010-02-05

    This paper describes a novel heterodyne laser interferometer with no significant periodic nonlinearity for linear displacement measurements. Moreover, the optical configurations have the benefit of doubling the measurement resolution when compared to its respective traditional counterparts. Experimental results show no discernable periodic nonlinearity for a retro-reflector interferometer and plane mirror interferometer configurations with a noise level below 20 pm. The incoming laser beams of the interferometers are achieved by utilizing two single mode optical fibers. To determine the stability of the optical fiber couplers a fiber delivery prototype was also built and tested.

  12. More Sub-Doppler Heterodyne Frequency Measurements on OCS between 56 and 63 THz

    NASA Astrophysics Data System (ADS)

    Mürtz, M.; Palm, P.; Urban, W.; Maki, A. G.

    2000-12-01

    By using tunable microwave sidebands added to CO-laser lines, we have made more sub-Doppler heterodyne frequency measurements on OCS. Three new rotational transitions have been measured for each of three absorption bands, 1000-0000, 0201-0000, and 0311-0110. The absolute uncertainties of the measurements are on the order of ±25 kHz. New calibration tables are given for the region 1860-1925 and 2020-2085 cm-1 based on the most recent OCS measurements.

  13. Wide measurement range scanning heterodyne interferometer utilizing astigmatic position sensing scheme

    NASA Astrophysics Data System (ADS)

    Park, Youngkyu; Kim, Kyoung-Eop; Kim, Seong-Jin; Park, June-Gyu; Joo, Young-Hun; Shin, Bu Hyun; Lee, Seung-Yop; Cho, Kyuman

    2011-08-01

    A scanning heterodyne I/Q-interferometer scheme is proposed to overcome phase ambiguity caused by the periodic nature of its phase-dependent signal. A position sensing scheme using an astigmatic method in the confocal arrangement has been interfaced to the interferometer to retrieve the real phase value during a scanning process. The experimental results show that the vertical measurement range can be expanded up to 16μm. The potential of this interferometer on the scanning microscopy of a rough surface is discussed.

  14. Comment on "Heterodyne Lidar Returns in the Turbulent Atmosphere: Performance Evaluation of Simulated Systems"

    NASA Technical Reports Server (NTRS)

    Frehlich, Rod; Kavaya, Michael J.

    2000-01-01

    The explanation for the difference between simulation and the zero-order theory for heterodyne lidar returns in a turbulent atmosphere proposed by Belmonte and Rye is incorrect. The theoretical expansion is not developed under a square- law-structure function approximation (random wedge atmosphere). Agreement between the simulations and the zero-order term of the theoretical expansion is produced for the limit of statistically independent paths (bi-static operation with large transmitter-receiver separation) when the simulations correctly include the large-scale gradients of the turbulent atmosphere.

  15. Using the Heterodyne Method to Measure Velocities on Shock Physics Experiments

    SciTech Connect

    Strand, O T; Whitworth, T L

    2007-08-10

    We developed a velocimeter system several years ago that uses the heterodyne method [1]. This system is assembled from commercially available components that were developed for the telecommunications industry. There are several advantages of this system over the traditional VISAR method that has made it increasingly popular. This system is compact, portable, and relatively inexpensive. The maximum velocity of this system is determined by the electrical bandwidth of the electronics and the digitizer sample rate. The maximum velocity for the system described here is over 5 km/s.

  16. Heterodyne spectroscopy of carbon monoxide lines perturbed by hydrogen and helium

    NASA Technical Reports Server (NTRS)

    Mannucci, Anthony J.

    1991-01-01

    Infrared heterodyne spectroscopy has been used for the first time to measure the widths and shifts of CO rovibrational spectra perturbed by H2 and He. A spectral resolution of 20 MHz was achieved. The CO-He line-broadening measurements were accurate enough to distinguish between two proposed intermolecular potential models of this system. Also, a measured increase in the broadening coefficient as a function of rotational quantum number j was observed for CO-He at temperatures of 80 K. This is not easy to explain in the context of so-called 'sudden approximations' which have been used to interpret pressure broadening data for this system.

  17. Remote Sensing of Methane in the Martian Atmosphere using Infrared Laser Heterodyne Radiometry

    NASA Astrophysics Data System (ADS)

    Passmore, R. L.; Bowles, N. E.; Weidmann, D.; Smith, K.

    2011-12-01

    In the last few years, several research teams have reported the detection of methane in the atmosphere of Mars, measuring 10 ppb on average [1][2][3]. The source of the methane is still unknown, but its identification is important as its presence could imply a biological origin. However, the detection limits of current instruments lie below the requirements for an unambiguous determination of concentration mapping and distribution. We investigate the viability of detecting methane in the Martian atmosphere via a high sensitivity remote sensing technique known as passive mid-infrared laser heterodyne radiometry. Although heterodyne spectroscopy is not a new idea, recent advancements in local oscillator technology [4] offer the possibility of significant instrument miniaturisation relevant to space deployment. We present our current work on a laser heterodyne radiometer (LHR) which involves adapting an existing 10 μm laser breadboard design, which was used with much success to study stratospheric ozone [5], to operate at 7.7 μm in order to target the ν4 fundamental band of methane. The core of the LHR consists of a distributed-feedback quantum cascade laser (QCL) operating in continuous-wave mode, which acts as the local oscillator. QCLs are ideal local oscillators for this type of instrument as they emit with high spectral purity and the necessary optical power in the mid-infrared region where characteristic spectral lines of interest lie. Atmospheric modelling of the Martian atmosphere and instrument sensitivity studies enabled simulated methane spectral features to be studied in detail, which subsequently determined the focus for experimental efforts in the laboratory. Testing of the LHR was initially carried out on small gas cells containing pure methane gas, but in order to test the instrument more rigorously for atmospheric studies a larger gas cell was constructed that approximates the Martian atmosphere in the laboratory. Trace quantities of methane were

  18. X-ray spatial frequency heterodyne imaging of protein-based nanobubble contrast agents.

    PubMed

    Rand, Danielle; Uchida, Masaki; Douglas, Trevor; Rose-Petruck, Christoph

    2014-09-22

    Spatial Frequency Heterodyne Imaging (SFHI) is a novel x-ray scatter imaging technique that utilizes nanoparticle contrast agents. The enhanced sensitivity of this new technique relative to traditional absorption-based x-ray radiography makes it promising for applications in biomedical and materials imaging. Although previous studies on SFHI have utilized only metal nanoparticle contrast agents, we show that nanomaterials with a much lower electron density are also suitable. We prepared protein-based "nanobubble" contrast agents that are comprised of protein cage architectures filled with gas. Results show that these nanobubbles provide contrast in SFHI comparable to that of gold nanoparticles of similar size. PMID:25321797

  19. X-ray spatial frequency heterodyne imaging of protein-based nanobubble contrast agents

    PubMed Central

    Rand, Danielle; Uchida, Masaki; Douglas, Trevor; Rose-Petruck, Christoph

    2014-01-01

    Spatial Frequency Heterodyne Imaging (SFHI) is a novel x-ray scatter imaging technique that utilizes nanoparticle contrast agents. The enhanced sensitivity of this new technique relative to traditional absorption-based x-ray radiography makes it promising for applications in biomedical and materials imaging. Although previous studies on SFHI have utilized only metal nanoparticle contrast agents, we show that nanomaterials with a much lower electron density are also suitable. We prepared protein-based “nanobubble” contrast agents that are comprised of protein cage architectures filled with gas. Results show that these nanobubbles provide contrast in SFHI comparable to that of gold nanoparticles of similar size. PMID:25321797

  20. Simple method for reducing the first-order optical nonlinearity in a heterodyne laser interferometer.

    PubMed

    Fu, Haijin; Hu, Pengcheng; Tan, Jiubin; Fan, Zhigang

    2015-07-10

    A simple method was proposed by using a tunable attenuator fitted in the reference or measurement arm of a heterodyne laser interferometer to adjust the values of mixing laser beams while the spectrum of the measurement signal is monitored using a signal analyzer. The effectiveness of the proposed method in reducing the first-order optical nonlinearity was verified through experiments. Results indicated that the peak value of the first-order optical nonlinearity could be reduced from 5.15 to 0.24 nm. It was therefore concluded that the proposed method was applicable to ultraprecision laser interferometry. PMID:26193410

  1. High-accuracy thickness measurement of a transparent plate with the heterodyne central fringe identification technique

    SciTech Connect

    Wu, Wang-Tsung; Hsieh, Hung-Chih; Chang, Wei-Yao; Chen, Yen-Liang; Su, Der-Chin

    2011-07-20

    In a modified Twyman-Green interferometer, the optical path variation is measured with the heterodyne central fringe identification technique, as the light beam is focused by a displaced microscopic objective on the front/rear surface of the test transparent plate. The optical path length variation is then measured similarly after the test plate is removed. The geometrical thickness of the test plate can be calculated under the consideration of dispersion effect. This method has a wide measurable range and a high accuracy in the measurable range.

  2. Terahertz quantum cascade laser as local oscillator in a heterodyne receiver.

    PubMed

    Hübers, Heinz-Wilhelm; Pavlov, S; Semenov, A; Köhler, R; Mahler, L; Tredicucci, A; Beere, H; Ritchie, D; Linfield, E

    2005-07-25

    Terahertz quantum cascade lasers have been investigated with respect to their performance as a local oscillator in a heterodyne receiver. The beam profile has been measured and transformed in to a close to Gaussian profile resulting in a good matching between the field patterns of the quantum cascade laser and the antenna of a superconducting hot electron bolometric mixer. Noise temperature measurements with the hot electron bolometer and a 2.5 THz quantum cascade laser yielded the same result as with a gas laser as local oscillator. PMID:19498595

  3. Conceptual design and applications of HgCdTe infrared photodiodes for heterodyne systems

    NASA Technical Reports Server (NTRS)

    Sirieix, M. B.; Hofheimer, H.

    1980-01-01

    The significance of HgCdTe photodiodes are discussed relative to their existance in heterodyne detection systems operating in the 9 to 11 micrometer CO2 laser wavelength region. Their successful fabrication as well as the physical properties of the materials are described. The implementation of controlled industrial processes are reported with emphasis on the yield of predictable and repeatable detector characteristics to the discriminating systems, demands for high cutoff frequencies, quantum efficiency, and reliability. The most salient production steps and diode characteristics are presented. Measured results from production units are also given.

  4. Common-Path Heterodyne Laser-Induced Thermal Acoustics for Seedless Laser Velocimetry

    NASA Technical Reports Server (NTRS)

    Hart, Roger C.; Herring, G. C.; Balla, R. Jeffrey; Bushnell, Dennis M. (Technical Monitor)

    2001-01-01

    We demonstrate the use of a novel technique for the detection of heterodyne laser-induced thermal acoustics signals, which allows the construction of a highly stable seedless laser velocimeter. A common-path configuration is combined with quadrature detection to provide flow direction, greatly improve robustness to misalignment and vibration, and give reliable velocity measurement at low flow velocities. Comparison with Pitot tube measurements in the freestream of a wind tunnel shows root-mean-square errors of 0.67 m/s over the velocity range 0.55 m/s.

  5. Characterization and calibration of 8-channel E-band heterodyne radiometer system for SST-1 tokamak

    SciTech Connect

    Siju, Varsha; Kumar, Dharmendra; Shukla, Praveena; Pathak, S. K.

    2014-05-15

    An 8-channel E-band heterodyne radiometer system (74–86 GHz) is designed, characterized, and calibrated to measure the radial electron temperature profile by measuring Electron Cyclotron Emission spectrum at SST-1 Tokamak. The developed radiometer has a noise equivalent temperature of 1 eV and sensitivity of 5 × 10{sup 9} V/W. In order to precisely measure the absolute value of electron temperature, a calibration measurement of the radiometer system is performed using hot-cold Dicke switch method, which confirms the system linearity.

  6. Heterodyne interferometry for the detection of elastic waves: a tutorial and open-hardware project

    NASA Astrophysics Data System (ADS)

    Hitchman, Sam; van Wijk, Kasper; Broderick, Neil; Adam, Ludmila

    2015-05-01

    Non-contacting acoustic and ultrasonic measurements are of interest in applications ranging from nondestructive evaluation to rock physics and medical imaging. The fundamental workings of the detector—the interferometer—are easily explained in undergraduate physics courses, but practical implementations are dominated by specialized, and commercial, devices. We present a robust and relatively inexpensive detector, which consists of a heterodyne interferometer and phase locked loop frequency demodulator, as an open-source alternative. We illustrate the broadband capabilities with the detection of ultrasonic waves in a mudstone sample, and low-frequency (100 Hz) vibrations of a piston.

  7. Initial ground-based thermospheric wind measurements using Doppler asymmetric spatial heterodyne spectroscopy (DASH).

    PubMed

    Englert, Christoph R; Harlander, John M; Emmert, John T; Babcock, David D; Roesler, Frederick L

    2010-12-20

    We present the first thermospheric wind measurements using a Doppler Asymmetric Spatial Heterodyne (DASH) spectrometer and the oxygen red-line nightglow emission. The ground-based observations were made from Washington, DC and include simultaneous calibration measurements to track and correct instrument drifts. Even though the measurements were made under challenging thermal and light pollution conditions, they are of good quality with photon statistics uncertainties between about three and twenty-nine meters per second, depending on the nightglow intensity. The wind data are commensurate with a representative set of Millstone Hill Fabry-Perot wind measurements selected for similar geomagnetic and solar cycle conditions. PMID:21197018

  8. Femtosecond Heterodyne Transient Grating Spectroscopic Studies of Intramolecular Charge Transfer Character of Peridinin and Peridinin Analogs

    NASA Astrophysics Data System (ADS)

    Bishop, Michael; Khosravi, Soroush; Obaid, Razib; Whitelock, Hope; Carroll, Ann Marie; Lafountain, Amy; Frank, Harry; Beck, Warren; Gibson, George; Berrah, Nora

    2016-05-01

    The peridinin chlorophyll-a protein is a light harvesting complex found in several species of dinoflagellates. Peridinin absorbs strongly in the mid-visible spectral region and, despite the lack of a strong permanent dipole moment in its lowest energy excited state, is able to transfer excitation energy quickly and efficiently to chlorophyll-a. It is believed that the high efficiency arises from the development of intramolecular charge-transfer (ICT) character upon photoexcitation. Recently, heterodyne transient grating spectroscopy has been used to study the ultrafast (<50 fs) dynamics of β carotene and peridinin. The studies show evidence for a structurally displaced intermediate in both cases and strong ICT character in the case of peridinin, but up to now the work has not provided appropriate control experiments. The present experiments examine peridinin and two peridinin analogs, S1-peridinin and S2-peridinin. S1-peridinin is reported to have greatly diminished ICT character, and S2-peridinin is reported to have little-or-no ICT character. Heterodyne transient grating data will be presented and provide a more unambiguous characterization spectral and kinetic properties associated with the peridinin ICT state. Funded by the DoE-BES, Grant No. DE-SC0012376.

  9. Heterodyne double-channel polarimeter for mapping birefringence and thickness of flat glass panels

    SciTech Connect

    Protopopov, Vladimir V.; Cho, Sunghoon; Kim, Kwangso; Lee, Sukwon; Kim, Hyuk; Kim, Daesuk

    2006-05-15

    A new cross-polarized heterodyne optical technique is developed for two-dimensional (2D) simultaneous mapping of both birefringence and thickness variations in large flat glass panels commonly used in liquid-crystal displays (LCDs). Weak depolarization of a linearly polarized probe beam due to glass birefringence is detected by means of heterodyne mixing of the two cross-polarized and frequency shifted waves generated by Zeeman-type laser. Amplitude variations of the transmitted laser beam due to interference of the partial waves reflected from the both sides of a sample provide information about glass thickness. Measurements are being performed at the intermediate frequency of 2.3 MHz, providing several orders of magnitude higher speed of data acquisition with respect to traditional polarimeters. That high speed of measurements makes it possible to perform quality assessment of LCD glass panels not only in few randomly chosen points as it was in common practice before but to obtain entire 2D maps of both birefringence and thickness variations with millimeter scale spatial resolution. The medium-scale prototype of the LCD glass inspection system is developed and tested. Design and performance of the prototype are described.

  10. Tunable diode-laser heterodyne spectrometer for remote observations near 8 microns

    NASA Technical Reports Server (NTRS)

    Glenar, D.; Kostiuk, T.; Jennings, D. E.; Buhl, D.; Mumma, M. J.

    1982-01-01

    A diode-laser-based, ultrahigh resolution IR heterodyne spectrometer for laboratory and field use has been developed for operation between 7.5 and 8.5 microns. The local oscillator is a PbSe tunable diode laser kept continuously at operating temperatures of 12-60 K using a closed-cycle cooler. The laser output frequency is controlled and stabilized using a high-precision diode current supply, constant temperature controller, and a shock isolator mounted between the refrigerator cold tip and the diode mount. The system largely employs reflecting optics to minimize losses from internal reflection and absorption and to eliminate chromatic effects. Spectral analysis of the diode-laser output between 0 and 1 GHz reveals excess noise at many diode current settings, which limits the IR spectral regions over which useful heterodyne operation can be achieved. Observations have been made of atmospheric N2O, O3, and CH4 between 1170 and 1200/cm, using both a single-frequency swept IF channel and a 64-channel RF spectral line receiver with a total IF coverage of 1600 MHz.

  11. Development of a P-I-N HgCdTe photomixer for laser heterodyne spectrometry

    NASA Technical Reports Server (NTRS)

    Bratt, Peter R.

    1987-01-01

    An improved HgCdTe photomixer technology was demonstrated employing a p-i-n photodiode structure. The i-region was near intrinsic n-type HgCdTe; the n-region was formed by B+ ion implantation; and the p-region was formed either by a shallow Au diffusion or by a Pt Schottky barrier. Experimental devices in a back-side illuminated mesa diode configuration were fabricated, tested, and delivered. The best photomixer was packaged in a 24-hour LN2 dewar along with a cooled GaAs FET preamplifier. Testing was performed by mixing black-body radiation with a CO2 laser beam and measuring the IF signal, noise, and signal-to-noise ratio in the GHz frequency range. Signal bandwidth for this photomixer was 1.3 GHz. The heterodyne NEP was 4.4 x 10 to the -20 W/Hz out to 1 GHz increasing to 8.6 x 10 to the -10 W/Hz at 2 GHz. Other photomixers delivered on this program had heterodyne NEPs at 1 GHz ranging from 8 x 10 to the -20 to 4.4 x 10 to the -19 W/Hz and NEP bandwidths from 2 to 4 GHz.

  12. Real-time photodisplacement imaging using parallel excitation and parallel heterodyne interferometry

    NASA Astrophysics Data System (ADS)

    Nakata, Toshihiko; Ninomiya, Takanori

    2005-05-01

    A parallel photodisplacement technique that achieves real-time imaging of subsurface structures is presented. In this technique, a linear region of photothermal displacement is excited by a line-focused intensity-modulated laser beam and detected with a parallel heterodyne interferometer using a charge-coupled device linear image sensor as a detector. Because of integration and sampling effects of the sensor, the interference light is spatiotemporally multiplexed. To extract the spatially resolved photodisplacement component from the sensor signal, a scheme of phase-shifting light integration combined with a Fourier analysis technique is developed for parallel interferometry. The frequencies of several control signals, including the heterodyne beat signal, modulation signal, and sensor gate signal, are optimized so as to eliminate undesirable components, allowing only the displacement component to be extracted. Two-dimensional subsurface lattice defects in silicon are clearly imaged at a remarkable speed of only 0.26s for an area of 256×256pixels. Thus, the proposed technique allows for real-time imaging more than 10 000 times faster than conventional photoacoustic microscopy.

  13. Raman spectroscopic detection using a two-dimensional spatial heterodyne spectrometer

    NASA Astrophysics Data System (ADS)

    Hu, Guangxiao; Xiong, Wei; Shi, Hailiang; Li, Zhiwei; Shen, Jing; Fang, Xuejing

    2015-11-01

    Spatial heterodyne Raman spectroscopy (SHRS) is a type of method for the detection of Raman spectra and can achieve a very high spectral resolution. SHRS has no moving parts and can be built with rugged, compact packages, making it extremely suitable for planetary exploration. However, if a high spectral resolution is needed, a traditional one-dimensional spatial heterodyne spectrometer cannot achieve a broad bandpass because it is limited by the number of pixels of the detector. In order to solve this, two-dimensional (2-D) SHRS can be used to broaden the bandpass. A breadboard of 2-D SHRS has been designed and built, and some artificial and natural targets have been tested to learn about the detection ability of 2-D SHRS. The results show that 2-D SHRS can be used to detect Raman signals scattered from liquid and solid targets. When the Raman scattered signal is strong, it can even detect targets in containers. The detection of anti-Stokes Raman shift for sulfur and carbon tetrachloride has also been tried, and the results show that 2-D SHRS has the ability to detect anti-Stokes Raman shift below 500 cm-1. The research may have a general implication in chemical analysis and planetary exploration.

  14. Real-time high-resolution heterodyne-based measurements of spectral dynamics in fibre lasers

    PubMed Central

    Sugavanam, Srikanth; Fabbri, Simon; Le, Son Thai; Lobach, Ivan; Kablukov, Sergey; Khorev, Serge; Churkin, Dmitry

    2016-01-01

    Conventional tools for measurement of laser spectra (e.g. optical spectrum analysers) capture data averaged over a considerable time period. However, the generation spectrum of many laser types may involve spectral dynamics whose relatively fast time scale is determined by their cavity round trip period, calling for instrumentation featuring both high temporal and spectral resolution. Such real-time spectral characterisation becomes particularly challenging if the laser pulses are long, or they have continuous or quasi-continuous wave radiation components. Here we combine optical heterodyning with a technique of spatio-temporal intensity measurements that allows the characterisation of such complex sources. Fast, round-trip-resolved spectral dynamics of cavity-based systems in real-time are obtained, with temporal resolution of one cavity round trip and frequency resolution defined by its inverse (85 ns and 24 MHz respectively are demonstrated). We also show how under certain conditions for quasi-continuous wave sources, the spectral resolution could be further increased by a factor of 100 by direct extraction of phase information from the heterodyned dynamics or by using double time scales within the spectrogram approach. PMID:26984634

  15. Simple digital phase-measuring algorithm for low-noise heterodyne interferometry

    NASA Astrophysics Data System (ADS)

    Kokuyama, Wataru; Nozato, Hideaki; Ohta, Akihiro; Hattori, Koichiro

    2016-08-01

    We present a digital algorithm for measuring the phase of a sinusoidal signal that combines the modified digital fringe-counting method with two-sample zero crossing to enable sequential signal processing. This technique can be applied to a phase meter for measuring dynamic phase differences between two sinusoidal signals with high resolution, particularly for heterodyne interferometry. The floor noise obtained from a demonstration with an electrical apparatus is 5× {{10}-8} \\text{rad}\\text{/}{{\\sqrt{\\text{Hz}}}{}} at frequencies above approximately 0.1 Hz for 80 kHz signal frequency. In addition, by applying this method to a commercial heterodyne interferometer with a modulation frequency of 80 MHz, the floor-noise level is confirmed to be 7× {{10}-14}\\text{m}\\text{/}{{\\sqrt{\\text{Hz}}}{}} from 4 kHz to 1 MHz. We also confirm the validity of the algorithm by comparing its results with those from a standard homodyne interferometer for measuring shock-motion peak acceleration greater than 5000 \\text{m} {{\\text{s}}-2} and a 10 mm stroke.

  16. Spectral line inversion for sounding of stratospheric minor constituents by infrared heterodyne technique from balloon altitudes

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Shapiro, G. L.; Allario, F.; Alvarez, J. M.

    1981-01-01

    A combination of two different techniques for the inversion of infrared laser heterodyne measurements of tenuous gases in the stratosphere by solar occulation is presented which incorporates the advantages of each technique. An experimental approach and inversion technique are developed which optimize the retrieval of concentration profiles by incorporating the onion peel collection scheme into the spectral inversion technique. A description of an infrared heterodyne spectrometer and the mode of observations for solar occulation measurement is presented, and the results of inversions of some synthetic ClO spectral lines corresponding to solar occulation limb-scans of the stratosphere are examined. A comparison between the new techniques and one of the current techniques indicates that considerable improvement in the accuracy of the retrieved profiles can be achieved. It is found that noise affects the accuracy of both techniques but not in a straightforward manner since there is interaction between the noise level, noise propagation through inversion, and the number of scans leading to an optimum retrieval.

  17. Detonation Wave Profiles in Plastic Bonded Explosives Measured using 1550 nm Heterodyne Velocimetry

    NASA Astrophysics Data System (ADS)

    Gustavsen, Rick

    2009-06-01

    We have measured detonation wave profiles in several triaminotrinitrobenzene (TATB) and cyclotetramethylene tetranitramine (HMX or octogen) based plastic bonded explosives using 1550 nm Heterodyne Velocimetry. (Heterodyne Velocimetry is also called Photon Doppler Velocimetry or PDV.) Planar detonations were produced by impacting the explosive with projectiles launched in a gas gun. Particle velocity wave profiles were measured at the mirror/interface of the explosive and either a LiF or PMMA window. Mirrors consisted of either a thin vapor deposited aluminum layer, or a 6 micron thick aluminum foil. Focusing and collimating light collection probes were used. Time-Frequency-Analysis of the fringe data was carried out using both Wavelet and Short-Time-Fourier-Transform (STFT) methods. With clean fringe data, good profiles can be obtained with a 1 ns full width half maximum (FWHM) analysis window (STFT) or about 3 to 4 oscillations in the wavelet. Some profiles, however, have a noisy character which is correlated with intensity fluctuations in the raw fringe data. Wave profiles show a ZND reaction zone structure with a single reaction in the HMX based explosives and both fast and slow reactions in the TATB based explosives.

  18. Using the Heterodyne Method to Measure Velocities on Shock Physics Experiments

    NASA Astrophysics Data System (ADS)

    Strand, Oliver

    2007-06-01

    Velocimetry is an important diagnostic for shock physics experiments. Velocities for these types of experiments can be in the kilometer-per-second range. We have developed a new velocimetry diagnostic for use on shock physics experiments that is based upon the heterodyne method. This diagnostic is easily assembled from commercially available parts developed for the telecommunication industry. The entire system uses single mode fibers to transport the signals from the laser to the probes and back to the detectors. We mix the Doppler-shifted light from the moving surface with non-shifted light from the laser itself to generate a beat signal at the detector. For this system using 1550 nm lasers, a velocity of 1 km/s generates a beat signal of 1.29 GHz. The detectors and the digitizers must have high-bandwidth capabilities to faithfully follow the beat waveform to allow a determination of the frequency as a function of time. Our current system has a maximum velocity capability of over 5 km/s. This paper will describe the heterodyne velocimeter and will present some of the data that has been taken with it. This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory, under contract No. W-7405-Eng-48.

  19. Wide-field heterodyne interferometric vibrometry for two-dimensional surface vibration measurement

    NASA Astrophysics Data System (ADS)

    Choi, Samuel; Maruyama, Yuta; Suzuki, Takamasa; Nin, Fumiaki; Hibino, Hiroshi; Sasaki, Osami

    2015-12-01

    Conventional laser Doppler vibrometry and heterodyne interferometry suffer during the simultaneous measurement of the spatial distribution of vibration parameters such as the amplitude, frequency and phase in a wide field of view. Although demand is increasing for methods that can measure vibrations over a wide field of view for a wide range of applications from industrial product inspections to biological measurements, full-field (FF) techniques for high-speed vibration measurements without a spatial scan are untapped. We propose a new method for high-speed FF vibration measurement that can easily be combined with profilometry and tomographic interferometry using a conventional CCD or CMOS camera. In principle, the measurable vibration frequency is unrestricted because the heterodyne signal produced by the modulated interferogram can be controlled to accommodate the CCD frame rate. The validity of the proposed method and the measurement accuracy of the spatial vibration amplitude were evaluated through simulations and experiments. In experiments, the spatial vibration parameters of a mirror vibrated at a frequency of 1 kHz and amplitude of approximately 5-65 nm were successfully measured with a spatial fluctuation of 3%-6.5%.

  20. Optical spatial heterodyne interferometric Fourier transform technique (OSHIFT) and a resulting interferometer

    NASA Astrophysics Data System (ADS)

    Georges, James A., III

    2007-09-01

    This article reports on the novel patent pending Optical Spatial Heterodyne Interferometric Fourier Transform Technique (the OSHIFT technique), the resulting interferometer also referred to as OSHIFT, and its preliminary results. OSHIFT was borne out of the following requirements: wavefront sensitivity on the order of 1/100 waves, high-frequency wavefront spatial sampling, snapshot 100Hz operation, and the ability to deal with discontinuous wavefronts. The first two capabilities lend themselves to the use of traditional interferometric techniques; however, the last two prove difficult for standard techniques, e.g., phase shifting interferometry tends to take a time sequence of images and most interferometers require estimation of a center fringe across wavefront discontinuities. OSHIFT overcomes these challenges by employing a spatial heterodyning concept in the Fourier (image) plane of the optic-under-test. This concept, the mathematical theory, an autocorrelation view of operation, and the design with results of OSHIFT will be discussed. Also discussed will be future concepts such as a sensor that could interrogate an entire imaging system as well as a methodology to create innovative imaging systems that encode wavefront information onto the image. Certain techniques and systems described in this paper are the subject of a patent application currently pending in the United States Patent Office.

  1. Detection of nonlinear distortions in the vibration of acoustically driven mechanical systems using heterodyne vibrometry

    NASA Astrophysics Data System (ADS)

    Aerts, J. R. M.; Dirckx, J. J. J.; Pintelon, R.

    2008-06-01

    Recently, a measurement set-up was presented to detect small nonlinear distortions in the vibration of acoustically driven mechanical systems. A speaker generates a specially designed multisine excitation signal that drives the vibration of a test object. The generated sound pressure is measured with a probe microphone in front of the test object, and an heterodyne vibrometer measures the corresponding vibration. Due to the high degree of linearity of the heterodyne technique, very small nonlinear distortions can be detected. In this paper the set-up is used to verify whether small nonlinear distortions are present in the vibration of the middle ear system, which is classically considered to be a completely linear system. In vitro measurements on the right ear of an adult male gerbil proved that nonlinear distortions are present in the vibration of the tympanic membrane. Similar results were seen in measurements on the left ear. The influence of post-mortem changes on the nonlinear behaviour of the middle ear was verified in a number of successive measurements. These indicated that the nonlinear behaviour of the middle ear decreases in time.

  2. An Extremely Wide Bandwidth, Low-Noise SIS Heterodyne Receiver Design for Millimeter and Submillimeter Observations

    NASA Technical Reports Server (NTRS)

    Sumner, Matthew; Blain, Andrew; Harris, Andrew; Hu, Robert; Rice, Frank; LeDuc, H. G.; Weinreb, Sander; Zmuidzinas, Jonas

    2002-01-01

    Millimeter and submillimeter heterodyne receivers using state-of-the-art SIS detectors are capable of extremely large instantaneous bandwidths with noise temperatures within a few Kelvin of the quantum limit. We present the design for a broadband, sensitive, heterodyne spectrometer under development for the Caltech Submillimeter Observatory (CSO). The 180-300 GHz double-sideband design uses a single SIS device excited by a full bandwidth, fixed-tuned waveguide probe on a silicon substrate. The IF output frequency (limited by the MMIC low noise IF preamplifier) is 6-18 GHz, providing an instantaneous RF bandwidth of 24 GHz (double-sideband). The SIS mixer conversion loss should be no more than 1-2 dB with mixer noise temperatures across the band within 10 K of the quantum limit. The single-sideband receiver noise temperature goal is 70 K. The wide instantaneous bandwidth and low noise will result in an instrument capable of a variety of important astrophysical observations beyond the capabilities of current instruments. Lab testing of the receiver will begin in the summer of 2002, and the first use on the CSO should occur in the spring of 2003.

  3. Micromachined Millimeter- and Submillimeter-wave SIS Heterodyne Receivers for Remote Sensing

    NASA Technical Reports Server (NTRS)

    Hu, Qing

    1997-01-01

    This is a progress report for the second year of a NASA-sponsored project. The report discusses the design and fabrication of micromachined Superconductor Insulator Superconductor (SIS) heterodyne receivers with integrated tuning elements. These receivers tune out the functional capacitance at desired frequencies, resulting in less noise, lower temperatures and broader bandwidths. The report also discusses the design and fabrication of the first monolithic 3x3 focal-plane arrays for a frequency range of 170-210 GHz. Also addressed is the construction of a 9-channel bias and read-out system, as well as the redesign of the IF connections to reduce cross talk between SIS junctions, which become significant a frequency of 1.5 GHz IF. Uniformity of the junction arrays were measured and antenna beam patterns of several array elements under operating conditions also were measured. Finally, video and heterodyne responses of our focal-plane arrays were measured as well. Attached is a paper on: 'Development of a 170-210 GHz 3x3 micromachined SIS imaging array'.

  4. Monolithically integrated heterodyne optical phase-lock loop with RF XOR phase detector.

    PubMed

    Steed, Robert J; Pozzi, Francesca; Fice, Martyn J; Renaud, Cyril C; Rogers, David C; Lealman, Ian F; Moodie, David G; Cannard, Paul J; Lynch, Colm; Johnston, Lilianne; Robertson, Michael J; Cronin, Richard; Pavlovic, Leon; Naglic, Luka; Vidmar, Matjaz; Seeds, Alwyn J

    2011-10-10

    We present results for an heterodyne optical phase-lock loop (OPLL), monolithically integrated on InP with external phase detector and loop filter, which phase locks the integrated laser to an external source, for offset frequencies tuneable between 0.6 GHz and 6.1 GHz. The integrated semiconductor laser emits at 1553 nm with 1.1 MHz linewidth, while the external laser has a linewidth less than 150 kHz. To achieve high quality phase locking with lasers of these linewidths, the loop delay has been made less than 1.8 ns. Monolithic integration reduces the optical path delay between the laser and photodiode to less than 20 ps. The electronic part of the OPLL was implemented using a custom-designed feedback circuit with a propagation delay of ~1 ns and an open-loop bandwidth greater than 1 GHz. The heterodyne signal between the locked slave laser and master laser has phase noise below -90 dBc/Hz for frequency offsets greater than 20 kHz and a phase error variance in 10 GHz bandwidth of 0.04 rad2. PMID:21997015

  5. Shaft balancing

    DOEpatents

    Irwin, John A.

    1979-01-01

    A gas turbine engine has an internal drive shaft including one end connected to a driven load and an opposite end connected to a turbine wheel and wherein the shaft has an in situ adjustable balance system near the critical center of a bearing span for the shaft including two 360.degree. rings piloted on the outer diameter of the shaft at a point accessible through an internal engine panel; each of the rings has a small amount of material removed from its periphery whereby both of the rings are precisely unbalanced an equivalent amount; the rings are locked circumferentially together by radial serrations thereon; numbered tangs on the outside diameter of each ring identify the circumferential location of unbalance once the rings are locked together; an aft ring of the pair of rings has a spline on its inside diameter that mates with a like spline on the shaft to lock the entire assembly together.

  6. Rayleigh backscattering noise suppression based on real-time heterodyne receiver for loop-back WDM-PON.

    PubMed

    Feng, Hanlin; Xiao, Shilin; Zhou, Qi; Ge, Jia; Fok, Mable P

    2014-09-22

    In this paper, we propose a Rayleigh backscattering (RB) noise mitigation scheme based on the use of real-time heterodyne receiver for loop-back wavelength division multiplexing passive optical network (WDM-PON). Heterodyne detection has been utilized to increase the upstream receiver sensitivity, while an electro-absorption modulator (EAM) is used to simultaneously turn heterodyning bipolar signal into single polar signal and mitigate accumulated carrier RB noise. With the help of the nonlinear negative-slope transfer function of EAM, low frequency interference noise is suppressed successfully. RB noise mitigation performance is studied over 45-km single mode fiber (SMF) transmission, and the optical-signal-to-Rayleigh-noise-ratio (OSRNR) is reduced to 15.6 dB, when bias voltage of EAM is at -4 V. Through utilizing this real-time heterodyne receiver in single fiber loop-back structure, upstream error free transmission is realized with receiver sensitivity of -25 dBm. PMID:25321736

  7. Elimination of depth degeneracy in optical frequency-domain imaging through polarization-based optical demodulation.

    PubMed

    Vakoc, B J; Yun, S H; Tearney, G J; Bouma, B E

    2006-02-01

    A novel optical frequency-domain imaging system is demonstrated that employs a passive optical demodulation circuit and a chirped digital acquisition clock derived from a voltage-controlled oscillator. The demodulation circuit allows the separation of signals from positive and negative depths to better than 50 dB, thereby eliminating depth degeneracy and doubling the imaging depth range. Our system design is compatible with dual-balanced and polarization-diverse detection, important techniques in the practical biomedical application of optical frequency-domain imaging. PMID:16480209

  8. Laser Heterodyne Radiometer for Sensitive Detection of CO2 and CH4

    NASA Technical Reports Server (NTRS)

    Wilson, Emily L.; Miller, J. Houston

    2011-01-01

    We propose to develop an inexpensive, miniaturized, passive laser heterodyne radiometer (LHR) using commercially available telecommunications laser components to measure two significant carbon cycle gases in the atmospheric column: carbon dioxide (CO2) and methane (CH4). This instrument would operate in tandem with the passive aerosol sensor currently used in AERONET (an established network of more than 450 ground aerosol monitoring instruments worldwide). Because aerosols induce a radiative effect that influences terrestrial carbon exchange, simultaneous detection of aerosols with these key carbon cycle gases offers a uniquely comprehensive measurement approach that supports the Decadal Survey. Laser heterodyne radiometry is a technique for detecting weak signals that was adapted from radio receiver technology. In a radio receiver, a weak input signal from a radio antenna is mixed with a stronger local oscillator signal. The mixed signal (beat note, or intermediate frequency) has a frequency equal to the difference between the input signal and the local oscillator. The intermediate frequency is amplified and sent to a detector that extracts the audio from the signal. In a laser heterodyne radiometer, the weak input signal is light that has undergone absorption by a trace gas. The local oscillator is a laser at a near-by frequency - in this case a low-cost distributed feedback (DFB) telecommunications laser. These two light waves are superimposed in either a beamsplitter or in a fiber coupler (as is the case in this design). The signals are mixed in the detector, and the RF beat frequency is extracted. Changes in concentration of the trace gas are realized through analyzing changes in the beat frequency amplitude. A schematic of the progression of the LHR development project is shown in the figure below. At the center (within the dashed line), light from the local oscillator is superimposed upon light that has undergone absorption by a trace gas, in a single mode

  9. Appendix: Limits on the use of heterodyning and amplification in optical interferometry

    NASA Astrophysics Data System (ADS)

    Burke, Bernard F.

    1992-11-01

    The development of optical fibers, lasers, and mixers at optical frequencies has offered the hope that active methods can contribute to optical interferometry. Heterodyning, in particular, looks attractive, even though bandwidths are narrower than one would like at present; one might expect this limitation to lessen as technology develops. That expectation, unfortunately, is not likely to benefit interferometry at optical wavelengths because of the intervention of quantum mechanics and the second law of thermodynamics, as Burke (1985a) pointed out. So much 'second quantization' noise is generated that only at infrared frequencies, somewhere in the 10-100 micron range, can one look forward to heterodyning in any realistic sense. The reason is easily understood. Every amplifier, in the quantum limit, works by stimulated emission, even though this basic truth is not obvious at radio frequencies. This means that there must be spontaneous emission occurring within every amplifier, and Strandberg (1957) showed that this implied a limiting noise temperature, TN = h nu/k, for any amplifier. Burke (1969) used this result to demonstrate that, if it were not for this quantum noise, the VLBI method would allow one to tell which slit a photon went through before forming an interference pattern, thus violating basic tenants of quantum mechanics. In essence, the second quantization condition Delta N Delta phi greater than or = 1 saves one from paradox. One can state the conclusion simply: any amplifier produces approximately one photon per Hertz of bandwidth. In optical interferometry, one will certainly want bandwidth in the 1012 to 1014 Hz range, and that implies an intolerable cacophony of noise photons. Only at infrared frequencies can one tolerate the quantum noise, where the natural noise background may be high and the mixers are not as efficient as one would hope for. The crossover at present is about 10 or 20 microns, but the boundary will shift to longer wavelengths as

  10. A Low-noise Micromachined Millimeter-Wave Heterodyne Mixer using Nb Superconducting Tunnel Junctions

    NASA Technical Reports Server (NTRS)

    DeLange, Gert; Jacobson, Brian R.; Hu, Qing

    1996-01-01

    A heterodyne mixer with a micromachined horn antenna and a superconductor-insulator-superconductor (SIS) tunnel junction as mixing element is tested in the W-band (75-115 GHz) frequency range. Micromachined integrated horn antennas consist of a dipole antenna suspended on a thin Si3N4 dielectric membrane inside a pyramidal cavity etched in silicon. The mixer performance is optimized by using a backing plane behind the dipole antenna to tune out the capacitance of the tunnel junction. The lowest receiver noise temperature of 30 +/- 3 K (without any correction) is measured at 106 GHz with a 3-dB bandwidth of 8 GHz. This sensitivity is comparable to the state-of-the-art waveguide and quasi-optical SIS receivers, showing the potential use of micromachined horn antennas in imaging arrays.

  11. Measurement of the absolute wavefront curvature radius in a heterodyne interferometer.

    PubMed

    Hechenblaikner, Gerald

    2010-09-01

    We present an analytical derivation of the coupling parameter relating the angle between two interfering beams in a heterodyne interferometer to the differential phase signals detected by a quadrant photodiode. This technique, also referred to as differential wavefront sensing, is commonly used in space-based gravitational wave detectors to determine the attitude of a test mass in one of the interferometer arms from the quadrant diode signals. Successive approximations to the analytical expression are made to simplify the investigation of parameter dependencies. Motivated by our findings, we propose what we believe to be a new measurement method to accurately determine the absolute wavefront curvature of a single measurement beam. We also investigate the change in the coupling parameter when the interferometer "test mirror" is moved from its nominal position, an effect which mediates the coupling of mirror displacement noise into differential phase measurements. PMID:20808419

  12. Note: Optimal choice of the reflector by phase analysis for heterodyne interferometric roll angle measurement

    NASA Astrophysics Data System (ADS)

    Tang, Shanzhi; Wang, Zhao; Li, Ming; Gao, Junxiang; Jiang, Yongcheng; Zhang, Yao

    2016-02-01

    The choice of an actual reflector instead of an ideal or perfect reflector has to be dealt with for heterodyne-interferometric roll angle measurement methods. The candidates of regular reflectors such as corner cube prism and right angle prism are analyzed by the homogeneous coordinate transformation method, which provides a theoretical basis for the determination of the actual reflector. Furthermore, the influences of the phase loss of the determined reflector are strictly argued due to non-perfect or natural characteristics itself. Several tactics are considered to solve this problem by phase analysis. By contrast, it is an optimal choice that mirrors-based right angle prism can improve evidently the phase loss by experiment.

  13. Micromachined Millimeter- and Submillimeter-Wave SIS Heterodyne Receivers for Remote Sensing

    NASA Technical Reports Server (NTRS)

    Hu, Qing

    1998-01-01

    A heterodyne mixer with a micromachined horn antenna and a superconductor -insulator-superconductor (SIS) tunnel junction as mixing element is tested in the W-band (75-115 GHz) frequency range. Micromachined integrated horn antennas consist of a dipole antenna suspended on a thin Si3N4 dielectric membrane inside a pyramidal cavity etched in silicon. The mixer performance is optimized by using a backing plane behind the dipole antenna to tune out the capacitance of the tunnel junction. The lowest receiver noise temperature of 30+/-3 K without any correction) is measured at 106 GHz with a 3-dB bandwidth of 8 GHz. This sensitivity is comparable to the state-of-the-art waveguide and quasi-optical SIS receivers, showing the potential use of micromachined horn antennas in imaging arrays.

  14. Heterodyne coherent anti-Stokes Raman scattering by the phase control of its intrinsic background

    SciTech Connect

    Wang Xi; Wang Kai; Welch, George R.; Sokolov, Alexei V.

    2011-08-15

    We demonstrate the use of femtosecond laser pulse shaping for precise control of the interference between the coherent anti-Stokes Raman scattering (CARS) signal and the coherent nonresonant background generated within the same sample volume. Our technique is similar to heterodyne detection with the coherent background playing the role of the local oscillator field. In our experiment, we first apply two ultrashort (near-transform-limited) femtosecond pump and Stokes laser pulses to excite coherent molecular oscillations within a sample. After a short and controllable delay, we then apply a laser pulse that scatters off of these oscillations to produce the CARS signal. By making fine adjustments to the probe field spectral profile, we vary the relative phase between the Raman-resonant signal and the nonresonant background, and we observe a varying spectral interference pattern. These controlled variations of the measured pattern reveal the phase information within the Raman spectrum.

  15. Development of an angular displacement measurement technique through birefringence heterodyne interferometry.

    PubMed

    Hsieh, Hung-Lin; Lee, Ju-Yi; Chen, Lin-Yu; Yang, Yang

    2016-04-01

    An angular displacement measurement sensor with high resolution for large range measurement is presented. The design concept of the proposed method is based on the birefringence effect and phase detection of heterodyne interferometry. High system symmetry and simple operation can be easily achieved by employing an innovative sandwich optical design for the angular sensor. To evaluate the feasibility and performance of the proposed method, several experiments were performed. The experimental results demonstrate that our angular displacement measurement sensor can achieve a measurement range greater than 26°. Considering the high-frequency noise, the measurement resolution of the system is approximately 1.2° × 10-4. Because of the common-path arrangement, our proposed method can provide superior immunity against environmental disturbances. PMID:27136979

  16. Dynamic 3D imaging based on acousto-optic heterodyne fringe interferometry.

    PubMed

    Guan, Yingjian; Yin, Yongkai; Li, Ameng; Liu, Xiaoli; Peng, Xiang

    2014-06-15

    An acoustic-optics heterodyne fringe interferometry coupled with a three-camera system is developed for dynamic 3D imaging. In this system, first-order beams with a slight frequency difference diffracted from two acousto-optic deflectors (AODs) form a beat intensity fringe pattern. Setting the frequency of the trigger signal for the CCD cameras into four times the beat frequency, four-step phase-shifting fringe patterns can be obtained, and the wrapped phase map (WPM) can be calculated. Under the epipolar constraint among three cameras, the homologous points can be determined unambiguously with the assistant of a WPM; thus the 3D shape can be reconstructed while skipping the phase unwrapping step. Experimental results are presented to validate this approach. PMID:24978566

  17. An accurate 3D inspection system using heterodyne multiple frequency phase-shifting algorithm

    NASA Astrophysics Data System (ADS)

    Xiao, Zhenzhong; Chee, Oichoo; Asundi, Anand

    This paper presents an accurate 3D inspection system for industrial applications, which uses digital fringe projection technology. The system consists of two CCD cameras and a DLP projector. The mathematical model of the 3D inspection system with 10 distortion parameters for each camera is proposed. A heterodyne multiple frequency phase-shifting algorithm is employed for overcoming the unwrapping problem of phase functions and for a reliable unwrapping procedure. The redundant phase information is used to increase the accuracy of the 3D reconstruction. To demonstrate the effectiveness of our system, a standard sphere was used for testing. The verification test for the 3D inspection systems are based on the VDI standard 2634. The result shows the proposed system can be used for industrial quality inspection with high measurement precision.

  18. Subcarrier multiplexing based self-heterodyne coherent detection for PM-16QAM format

    NASA Astrophysics Data System (ADS)

    Jia, Junchi; Zhou, Shiwei; Fu, Songnian; Deng, Lei; Tang, Ming

    2015-09-01

    We propose and demonstrate subcarrier multiplexing (SCM) based self-heterodyne (SH) coherent detection for polarization-multiplexed 16 quadrature amplitude modulation (PM-16QAM) format. Three closely spaced subcarriers carrying pilot-tone (PT) and two 16QAM signals, respectively, are generated via subcarrier modulation technique. An effective digital signal processing (DSP) scheme is proposed to eliminate image frequency interference (IFI) arising in such SH coherent detection. Meanwhile, a closed-form analytical BER formula is verified by numerical simulations with a deviation less than 0.3 dB at BER=10-3. The concept of optimum modulation index (MI) ratio between data and PT signal is derived and verified, in order to reduce the distortion of 16QAM constellation. Meanwhile, we also explore the effects of optical filter bandwidth and subcarrier frequency spacing on the quality of PT signal. Finally, we are able to obtain several optimum parameters for the proposed SH coherent detection.

  19. Terahertz Radiation Heterodyne Detector Using Two-Dimensional Electron Gas in a GaN Heterostructure

    NASA Technical Reports Server (NTRS)

    Karasik, Boris S.; Gill, John J.; Mehdi, Imran; Crawford, Timothy J.; Sergeev, Andrei V.; Mitin, Vladimir V.

    2012-01-01

    High-resolution submillimeter/terahertz spectroscopy is important for studying atmospheric and interstellar molecular gaseous species. It typically uses heterodyne receivers where an unknown (weak) signal is mixed with a strong signal from the local oscillator (LO) operating at a slightly different frequency. The non-linear mixer devices for this frequency range are unique and are not off-the-shelf commercial products. Three types of THz mixers are commonly used: Schottky diode, superconducting hot-electron bolometer (HEB), and superconductor-insulation-superconductor (SIS) junction. A HEB mixer based on the two-dimensional electron gas (2DEG) formed at the interface of two slightly dissimilar semiconductors was developed. This mixer can operate at temperatures between 100 and 300 K, and thus can be used with just passive radiative cooling available even on small spacecraft.

  20. Fast, high-resolution surface potential measurements in air with heterodyne Kelvin probe force microscopy

    NASA Astrophysics Data System (ADS)

    Garrett, Joseph L.; Munday, Jeremy N.

    2016-06-01

    Kelvin probe force microscopy (KPFM) adapts an atomic force microscope to measure electric potential on surfaces at nanometer length scales. Here we demonstrate that Heterodyne-KPFM enables scan rates of several frames per minute in air, and concurrently maintains spatial resolution and voltage sensitivity comparable to frequency-modulation KPFM, the current spatial resolution standard. Two common classes of topography-coupled artifacts are shown to be avoidable with H-KPFM. A second implementation of H-KPFM is also introduced, in which the voltage signal is amplified by the first cantilever resonance for enhanced sensitivity. The enhanced temporal resolution of H-KPFM can enable the imaging of many dynamic processes, such as such as electrochromic switching, phase transitions, and device degredation (battery, solar, etc), which take place over seconds to minutes and involve changes in electric potential at nanometer lengths.

  1. Optical Spatial Heterodyned Interferometry for Inspection of Micro-Electro-Mechanical Systems

    SciTech Connect

    Tobin Jr, Kenneth William; Bingham, Philip R; Price, Jeffery R

    2005-01-01

    Interferometric imaging has the potential to extend the usefulness of optical microscopes by encoding small phase shifts that reveal information about topology and materials. At the Oak Ridge National Laboratory (ORNL), we have developed an optical Spatial Heterodyne Interferometry (SHI) method that captures reflection images containing both phase and amplitude information at a high rate of speed. By measuring the phase of a wavefront reflected off or transmitted through a surface, the relative surface heights and some materials properties can be measured. In this paper we briefly review our historical application of SHI in the semiconductor industry, but the focus is on new research to adapt this technology to the inspection of MEMS devices, in particular to the characterization of motion elements such as microcantilevers and deformable mirror arrays.

  2. Heterodyne coherent anti-Stokes Raman scattering by the phase control of its intrinsic background

    NASA Astrophysics Data System (ADS)

    Wang, Xi; Wang, Kai; Welch, George R.; Sokolov, Alexei V.

    2011-08-01

    We demonstrate the use of femtosecond laser pulse shaping for precise control of the interference between the coherent anti-Stokes Raman scattering (CARS) signal and the coherent nonresonant background generated within the same sample volume. Our technique is similar to heterodyne detection with the coherent background playing the role of the local oscillator field. In our experiment, we first apply two ultrashort (near-transform-limited) femtosecond pump and Stokes laser pulses to excite coherent molecular oscillations within a sample. After a short and controllable delay, we then apply a laser pulse that scatters off of these oscillations to produce the CARS signal. By making fine adjustments to the probe field spectral profile, we vary the relative phase between the Raman-resonant signal and the nonresonant background, and we observe a varying spectral interference pattern. These controlled variations of the measured pattern reveal the phase information within the Raman spectrum.

  3. Ultrafast chirped optical waveform recorder using referenced heterodyning and a time microscope

    DOEpatents

    Bennett, Corey Vincent

    2011-11-22

    A new technique for capturing both the amplitude and phase of an optical waveform is presented. This technique can capture signals with many THz of bandwidths in a single shot (e.g., temporal resolution of about 44 fs), or be operated repetitively at a high rate. That is, each temporal window (or frame) is captured single shot, in real time, but the process may be run repeatedly or single-shot. This invention expands upon previous work in temporal imaging by adding heterodyning, which can be self-referenced for improved precision and stability, to convert frequency chirp (the second derivative of phase with respect to time) into a time varying intensity modulation. By also including a variety of possible demultiplexing techniques, this process is scalable to recoding continuous signals.

  4. Ultrafast chirped optical waveform recording using referenced heterodyning and a time microscope

    DOEpatents

    Bennett, Corey Vincent

    2010-06-15

    A new technique for capturing both the amplitude and phase of an optical waveform is presented. This technique can capture signals with many THz of bandwidths in a single shot (e.g., temporal resolution of about 44 fs), or be operated repetitively at a high rate. That is, each temporal window (or frame) is captured single shot, in real time, but the process may be run repeatedly or single-shot. This invention expands upon previous work in temporal imaging by adding heterodyning, which can be self-referenced for improved precision and stability, to convert frequency chirp (the second derivative of phase with respect to time) into a time varying intensity modulation. By also including a variety of possible demultiplexing techniques, this process is scalable to recoding continuous signals.

  5. The effect of patch potentials in Casimir force measurements determined by heterodyne Kelvin probe force microscopy

    NASA Astrophysics Data System (ADS)

    Garrett, Joseph L.; Somers, David; Munday, Jeremy N.

    2015-06-01

    Measurements of the Casimir force require the elimination of the electrostatic force between the surfaces. However, due to electrostatic patch potentials, the voltage required to minimize the total force may not be sufficient to completely nullify the electrostatic interaction. Thus, these surface potential variations cause an additional force, which can obscure the Casimir force signal. In this paper, we inspect the spatially varying surface potential of e-beamed, sputtered, sputtered and annealed, and template stripped gold surfaces with Heterodyne amplitude modulated Kelvin probe force microscopy (HAM-KPFM). It is demonstrated that HAM-KPFM improves the spatial resolution of surface potential measurements compared to amplitude modulated Kelvin probe force microscopy. We find that patch potentials vary depending on sample preparation, and that the calculated pressure can be similar to the pressure difference between Casimir force calculations employing the plasma and Drude models.

  6. The effect of patch potentials in Casimir force measurements determined by heterodyne Kelvin probe force microscopy.

    PubMed

    Garrett, Joseph L; Somers, David; Munday, Jeremy N

    2015-06-01

    Measurements of the Casimir force require the elimination of the electrostatic force between the surfaces. However, due to electrostatic patch potentials, the voltage required to minimize the total force may not be sufficient to completely nullify the electrostatic interaction. Thus, these surface potential variations cause an additional force, which can obscure the Casimir force signal. In this paper, we inspect the spatially varying surface potential of e-beamed, sputtered, sputtered and annealed, and template stripped gold surfaces with Heterodyne amplitude modulated Kelvin probe force microscopy (HAM-KPFM). It is demonstrated that HAM-KPFM improves the spatial resolution of surface potential measurements compared to amplitude modulated Kelvin probe force microscopy. We find that patch potentials vary depending on sample preparation, and that the calculated pressure can be similar to the pressure difference between Casimir force calculations employing the plasma and Drude models. PMID:25964997

  7. A W-Band Heterodyne FMCW Radar Based on TX IQ-Modulation

    NASA Astrophysics Data System (ADS)

    Feger, Reinhard; Wagner, Christoph; Stelzer, Andreas

    2011-08-01

    In this paper a method to realize a heterodyne frequency-modulated continuous-wave (FMCW) radar is presented. The proposed principle relies on the use of an inphase/quadrature (IQ)-modulator as single-sideband-mixer to shift the frequency of the FMCW-output away from dc. Since in any IQ-modulator phase and amplitude imbalances occur, the effect of these imbalances will be investigated by deriving the corresponding signal model. Based on this analysis, a method to compensate the imbalances by a predistortion of the modulation signal will be derived. The presented method does not require special test signals or additional hardware, but relies on a standard FMCW measurement onto a calibration target. A prototype radar system was built and used in test measurements to verify the proposed principle. The measurement results show that a suppression of unwanted signal components caused by IQ-imbalances better than 45 dB is achievable.

  8. Measurement of small angle based on a (1 0 0) silicon wafer and heterodyne interferometer

    NASA Astrophysics Data System (ADS)

    Hsieh, Meng-Chang; Lin, Jiun-You; Chen, Yu-Fong; Chang, Chia-Ou

    2016-06-01

    In this paper, a new optical material application and a heterodyne interferometer are proposed for measuring small angles. In the proposed interferometer, the optical material is a (1 0 0) silicon wafer applied to compose a new architecture of small angle sensor. The small angle measurement used the phase difference which is dependent on the incident angle at the silicon wafer surface to deduce the angular variation. The proposed architecture is simple and uses the common path method to compare test and reference signals; thus, small angles can be easily and accurately measured by estimating the phase difference. The experimental results demonstrate the feasibility of this method. The angular resolution and sensitivity levels superior to 7 × 10-5° (1.3 × 10-6 rad) and 150 (deg/deg), respectively, were attainable in a dynamic range of 0.45°.

  9. A laser interferometer for measuring straightness and its position based on heterodyne interferometry

    SciTech Connect

    Chen Benyong; Zhang Enzheng; Yan Liping; Li Chaorong; Tang Wuhua; Feng Qibo

    2009-11-15

    Not only the magnitude but also the position of straightness errors are of concern to users. However, current laser interferometers used for measuring straightness seldom give the relative position of the straightness error. To solve this problem, a laser interferometer for measuring straightness and its position based on heterodyne interferometry is proposed. The optical configuration of the interferometer is designed and the measurement principle is analyzed theoretically. Two experiments were carried out. The first experiment verifies the validity and repeatability of the interferometer by measuring a linear stage. Also, the second one for measuring a flexure-hinge stage demonstrates that the interferometer is capable of nanometer measurement accuracy. These results show that this interferometer has advantages of simultaneously measuring straightness error and the relative position with high precision, and a compact structure.

  10. W-band Heterodyne Receiver Module with 27 K Noise Temperature

    NASA Technical Reports Server (NTRS)

    Gawande, R.; Reeves, R.; Cleary, K.; Readhead, A. C.; Gaier, T.; Kangaslahti, P.; Samoska, L.; Church, S.; Sieth, M.; Voll, P.; Harris, A.; Lai, R.; Sarkozy, S.

    2012-01-01

    We present noise temperature and gain measurements of a W-band heterodyne module populated with MMIC LNAs designed and fabricated using 35nm InP HEMT process. The module has a WR-10 waveguide input. GPPO connectors are used for the LO input and the I and and Q IF outputs. The module is tested at both ambient (300 K) and cryogenic (25 K) temperatures. At 25 K physical temperature, the module has a noise temperature in the range of 27-45 K over the frequency band of 75-111 GHz. The module gain varies between 15 dB and 27 dB. The band-averaged module noise temperature of 350 K and 33 K were measured over 80-110 GHz for the physical temperature of 300 K and 25 K, respectively. The resulting cooling factor is 10.6.

  11. Toward a nonlinearity model for a heterodyne interferometer: not based on double-frequency mixing.

    PubMed

    Hu, Pengcheng; Bai, Yang; Zhao, Jinlong; Wu, Guolong; Tan, Jiubin

    2015-10-01

    Residual periodic errors detected in picometer-level heterodyne interferometers cannot be explained by the model based on double-frequency mixing. A new model is established and proposed in this paper for analysis of these errors. The multi-order Doppler frequency shift ghost beams from measurement beam itself are involved in final interference leading to multi-order periodic errors, whether or not frequency-mixing originating from the two incident beams occurs. For model validation, a novel setup free from double-frequency mixing is constructed. The analyzed measurement signal shows that phase mixing of measurement beam itself can lead to multi-order periodic errors ranging from tens of picometers to one nanometer. PMID:26480108

  12. X-mode heterodyne reflectometer for edge density profile measurements on Tore Supra

    NASA Astrophysics Data System (ADS)

    Clairet, F.; Sabot, R.; Bottereau, Ch.; Chareau, J. M.; Paume, M.; Heuraux, S.; Colin, M.; Hacquin, S.; Leclert, G.

    2001-01-01

    A new broadband reflectometer operating in the frequency range 50-75 GHz in extraordinary mode polarization has been developed and tested on Tore Supra to measure edge density profiles. Using solid state source and active frequency multipliers, it performs routine measurements in 20 μs. Modulation of the source frequency is the clue to heterodyne detection in order to ensure a high dynamic sensitivity without any phase locking system. The reflectometer can achieve a repetition rate of 5 μs between sweeps, so the dynamic behavior of fast plasma events can be followed. The profile is reconstructed fully automatically from raw data and initialization is given by detection of the first cutoff. The profiles are part of the public database of Tore Supra. High reliability of the measurements for various plasma conditions makes this diagnostic an ideal tool to study the plasma-surface interaction physics and rf antenna coupling processes.

  13. Automated control and data acquisition for a tunable diode laser heterodyne spectrometer

    NASA Technical Reports Server (NTRS)

    Shull, T. S.; Rinsland, P. L.

    1983-01-01

    This paper describes the hardware and software design, development, and implementation of the control and data electronics of a laser heterodyne spectrometer instrument being built at NASA Langley Research Center for a technology demonstration. Functional partitioning, applied at all levels of hardware and software, has been found to provide expedient design, development, and testing of the instrument. The instrument is composed of distributed microprocessor-based units. A master/slave protocol is presented which can be simulated by a terminal for unit checkout. All but one of the units are implemented using a set of core boards, plus unique boards where necessary. This design has led to reduced hardware development, reduced parts inventory, and replication of software modules, while providing the flexibility needed for a development instrument. The development tools and documentation guidelines are discussed.

  14. Development of long wavelength semiconductor diode lasers near 28 microns for use in infrared heterodyne spectrometers

    NASA Technical Reports Server (NTRS)

    Linden, K. J.

    1984-01-01

    The development of tunable diode lasers operating in the 28 micrometers spectral region for use in infrared heterodyne spectrometers is reported. A process capable of yielding lasers emitting 500 micron W of multimode power, 112 micron W in a true single mode and true single mode operation at laser currents of up to 35% above threshold was developed. Results were obtained from narrow mesastripe (20 micrometer wide) short cavity (120 micrometer length) laser configurations. Six stripe geometry lasers, with a variety of cavity widths and lengths were delivered. The techniques to fabricate such devices was obtained and the long term reliability of such lasers by reproducible electrical and optical output characteristics fabrication from lasers are demonstrated.

  15. Fast, high-resolution surface potential measurements in air with heterodyne Kelvin probe force microscopy.

    PubMed

    Garrett, Joseph L; Munday, Jeremy N

    2016-06-17

    Kelvin probe force microscopy (KPFM) adapts an atomic force microscope to measure electric potential on surfaces at nanometer length scales. Here we demonstrate that Heterodyne-KPFM enables scan rates of several frames per minute in air, and concurrently maintains spatial resolution and voltage sensitivity comparable to frequency-modulation KPFM, the current spatial resolution standard. Two common classes of topography-coupled artifacts are shown to be avoidable with H-KPFM. A second implementation of H-KPFM is also introduced, in which the voltage signal is amplified by the first cantilever resonance for enhanced sensitivity. The enhanced temporal resolution of H-KPFM can enable the imaging of many dynamic processes, such as such as electrochromic switching, phase transitions, and device degredation (battery, solar, etc), which take place over seconds to minutes and involve changes in electric potential at nanometer lengths. PMID:27159082

  16. An experiment concept to measure stratospheric trace constituents by laser heterodyne spectroscopy

    NASA Technical Reports Server (NTRS)

    Allario, F.; Hoell, J. M., Jr.; Katzberg, S. J.; Larsen, J. C.

    1980-01-01

    Laser heterodyne spectroscopy (LHS) techniques were used to measure radical gases from Spacelab. Major emphasis was placed on the measurement of ClO, ClOnO2, HO2, H2O2, N2O5, and HOCl in solar occultation with vertical resolution less than or equal to 2-km and vertical range from 1O to 70-km. Sensitivity analyses were performed on ClO and O3 to determine design criteria for the LHS instrument. Results indicate that O3 and ClO vertical profiles can be measured with an accuracy more than or equal to 95% and more than or equal to 80%, respectively, over the total profile.

  17. Determination of thermoelastic material properties by differential heterodyne detection of impulsive stimulated thermal scattering.

    PubMed

    Verstraeten, B; Sermeus, J; Salenbien, R; Fivez, J; Shkerdin, G; Glorieux, C

    2015-06-01

    The underlying working principle of detecting impulsive stimulated scattering signals in a differential configuration of heterodyne diffraction detection is unraveled by involving optical scattering theory. The feasibility of the method for the thermoelastic characterization of coating-substrate systems is demonstrated on the basis of simulated data containing typical levels of noise. Besides the classical analysis of the photoacoustic part of the signals, which involves fitting surface acoustic wave dispersion curves, the photothermal part of the signals is analyzed by introducing thermal wave dispersion curves to represent and interpret their grating wavelength dependence. The intrinsic possibilities and limitations of both inverse problems are quantified by making use of least and most squares analysis. PMID:26236643

  18. Heterodyne Velocimetry measurements on solids shock driven by high power lasers

    NASA Astrophysics Data System (ADS)

    Mercier, Patrick; Benier, Jacky; Frugier, Pierre-Antoine; Sollier, Arnaud; Lescoute, Emilen; Cuq-Lelandais, Jean-Paul; Gay, Elise; de Resseguier, Thibaut; Berthe, Laurent; Boustie, Michel; Nivard, Mariette; Claverie, Alain; Rabec Le Gloahec, Marc

    2009-06-01

    A new Heterodyne Velocimeter (PDV) is under development at CEA for high explosive experimentations. Recently, we used it onto metallic target shock driven by high power laser. The aim is to test the ability of this means to reveal the propagation and the effects of shocks into materials, at extremely high strain rate and fast variations into the loading evolution. Spallation and fragmentation experiments carried out on aluminum samples, were performed on the LULI lasers at the Ecole Polytechnique, with both VISAR and HV diagnostics. Comparisons reveal a very good consistency of both experimental results. In addition, HV diagnostic evidence several levels of velocity in the experiment of fragmentation. Interpretation of these measurements is supported by transverse shadowgraphy analysis.

  19. Determination of thermoelastic material properties by differential heterodyne detection of impulsive stimulated thermal scattering

    PubMed Central

    Verstraeten, B.; Sermeus, J.; Salenbien, R.; Fivez, J.; Shkerdin, G.; Glorieux, C.

    2015-01-01

    The underlying working principle of detecting impulsive stimulated scattering signals in a differential configuration of heterodyne diffraction detection is unraveled by involving optical scattering theory. The feasibility of the method for the thermoelastic characterization of coating-substrate systems is demonstrated on the basis of simulated data containing typical levels of noise. Besides the classical analysis of the photoacoustic part of the signals, which involves fitting surface acoustic wave dispersion curves, the photothermal part of the signals is analyzed by introducing thermal wave dispersion curves to represent and interpret their grating wavelength dependence. The intrinsic possibilities and limitations of both inverse problems are quantified by making use of least and most squares analysis. PMID:26236643

  20. Heterodyne mixing of millimetre electromagnetic waves and sub-THz sound in a semiconductor device

    PubMed Central

    Heywood, Sarah L.; Glavin, Boris A.; Beardsley, Ryan P.; Akimov, Andrey V.; Carr, Michael W.; Norman, James; Norton, Philip C.; Prime, Brian; Priestley, Nigel; Kent, Anthony J.

    2016-01-01

    We demonstrate heterodyne mixing of a 94 GHz millimetre wave photonic signal, supplied by a Gunn diode oscillator, with coherent acoustic waves of frequency ~100 GHz, generated by pulsed laser excitation of a semiconductor surface. The mixing takes place in a millimetre wave Schottky diode, and the intermediate frequency electrical signal is in the 1–12 GHz range. The mixing process preserves all the spectral content in the acoustic signal that falls within the intermediate frequency bandwidth. Therefore this technique may find application in high-frequency acoustic spectroscopy measurements, exploiting the nanometre wavelength of sub-THz sound. The result also points the way to exploiting acoustoelectric effects in photonic devices working at sub-THz and THz frequencies, which could provide functionalities at these frequencies, e.g. acoustic wave filtering, that are currently in widespread use at lower (GHz) frequencies. PMID:27477841

  1. Heterodyne mixing of millimetre electromagnetic waves and sub-THz sound in a semiconductor device.

    PubMed

    Heywood, Sarah L; Glavin, Boris A; Beardsley, Ryan P; Akimov, Andrey V; Carr, Michael W; Norman, James; Norton, Philip C; Prime, Brian; Priestley, Nigel; Kent, Anthony J

    2016-01-01

    We demonstrate heterodyne mixing of a 94 GHz millimetre wave photonic signal, supplied by a Gunn diode oscillator, with coherent acoustic waves of frequency ~100 GHz, generated by pulsed laser excitation of a semiconductor surface. The mixing takes place in a millimetre wave Schottky diode, and the intermediate frequency electrical signal is in the 1-12 GHz range. The mixing process preserves all the spectral content in the acoustic signal that falls within the intermediate frequency bandwidth. Therefore this technique may find application in high-frequency acoustic spectroscopy measurements, exploiting the nanometre wavelength of sub-THz sound. The result also points the way to exploiting acoustoelectric effects in photonic devices working at sub-THz and THz frequencies, which could provide functionalities at these frequencies, e.g. acoustic wave filtering, that are currently in widespread use at lower (GHz) frequencies. PMID:27477841

  2. The use of heterodyne speckle photogrammetry to measure high-temperature strain distributions

    NASA Technical Reports Server (NTRS)

    Stetson, K. A.

    1983-01-01

    Thermal and mechanical strains have been measured on samples of a common material used in jet engine burner liners, which were heated from room temperature to 870 C and cooled back to 220 C, in a laboratory furnace. The physical geometry of the sample surface was recorded to select temperatures by means of a set of twelve single-exposure specklegrams. Sequential pairs of specklegrams were compared in a heterodyne interferometer which allowed high-precision measurement of differential displacements. Good speckle correlation was observed between the first and last specklegrams also, which showed the durability of the surface microstructure, and permitted a check on accumulated errors. Agreement with calculated thermal expansion was to within a few hundred microstrain over a range of fourteen thousand.

  3. Miniaturized Laser Heterodyne Radiometer for Measurements of CO2 in the Atmospheric Column

    NASA Technical Reports Server (NTRS)

    Wilson, E. L.; Mclinden, M. L.; Miller, J. H.; Allan, G. R.; Lott, L. E.; Melroy, H. R.; Clarke, G. B.

    2013-01-01

    We have developed a low-cost, miniaturized laser heterodyne radiometer for highly sensitive measurements of carbon dioxide (CO2) in the atmospheric column. In this passive design, sunlight that has undergone absorption by CO2 in the atmosphere is collected and mixed with continuous wave laser light that is step-scanned across the absorption feature centered at 1,573.6 nm. The resulting radio frequency beat signal is collected as a function of laser wavelength, from which the total column mole fraction can be de-convolved. We are expanding this technique to include methane (CH4) and carbon monoxide (CO), and with minor modifications, this technique can be expanded to include species such as water vapor (H2O) and nitrous oxide (N2O).

  4. Ground-based remote sensing of methane height profiles with a tunable diode laser heterodyne spectrometer

    SciTech Connect

    Koide, M.; Taguchi, M.; Fukunsishi, H.; Okano, S.

    1995-02-01

    Height distributions of methane in the troposphere and stratosphere were derived from high resolution absorption spectra observed with a ground-based tunable diode laser heterodyne spectrometer. The center wavenumber of the measured methane absorption line is 1223.1561/cm. In the retrieval of methane height profiles, a volume mixing ratio of methane was assumed to have a constant value in the troposphere and to decrease with a constant rate in the stratosphere. The tropospheric mixing ratio and the decreasing rate in stratosphere were derived to be 1.7 +/- 0.1 ppmv and -0.06 ppmv/km, respectively, for measurements at Tsukuba (36.0 deg N, 140.1 deg E) on December 17 and 20, 1991.

  5. Heterodyne mixing of millimetre electromagnetic waves and sub-THz sound in a semiconductor device

    NASA Astrophysics Data System (ADS)

    Heywood, Sarah L.; Glavin, Boris A.; Beardsley, Ryan P.; Akimov, Andrey V.; Carr, Michael W.; Norman, James; Norton, Philip C.; Prime, Brian; Priestley, Nigel; Kent, Anthony J.

    2016-08-01

    We demonstrate heterodyne mixing of a 94 GHz millimetre wave photonic signal, supplied by a Gunn diode oscillator, with coherent acoustic waves of frequency ~100 GHz, generated by pulsed laser excitation of a semiconductor surface. The mixing takes place in a millimetre wave Schottky diode, and the intermediate frequency electrical signal is in the 1–12 GHz range. The mixing process preserves all the spectral content in the acoustic signal that falls within the intermediate frequency bandwidth. Therefore this technique may find application in high-frequency acoustic spectroscopy measurements, exploiting the nanometre wavelength of sub-THz sound. The result also points the way to exploiting acoustoelectric effects in photonic devices working at sub-THz and THz frequencies, which could provide functionalities at these frequencies, e.g. acoustic wave filtering, that are currently in widespread use at lower (GHz) frequencies.

  6. Spatial Frequency Heterodyne Imaging of Water Filled Multi-walled Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Schunk, Francisco; Rand, Danielle; Rose-Petruck, Christoph

    2015-03-01

    Evaporation and condensation of water on multi-walled carbon nanotube (MWCNT) surfaces was monitored as a function of both temperature and time using x-ray Spatial Frequency Heterodyne Imaging (SFHI). SFHI is an imaging method that produces an absorption and scatter image from a single exposure, with increased sensitivity to variations in electron density relative to more common place x-ray imaging techniques. Different features seen in the temporal scatter intensity profiles recorded during evaporation and condensation revealed the existence of an absorption-desorption hysteresis. Effects on the previously mentioned phenomena due to chemical functionalization of the carbon nanotube surfaces were also observed. Functionalization increased the interaction potential between the MWCNT walls and water molecules, altering the evaporation event time scale and increasing the temperature at which condensation could take place. The observed temperature dependent changes in evaporation time scales coincide with the boiling point for confined water predicted by the Kelvin equation.

  7. Heterodyne laser frequency stabilization for long baseline optical interferometry in space-based gravitational wave detectors

    NASA Astrophysics Data System (ADS)

    Eichholz, Johannes; Tanner, David B.; Mueller, Guido

    2015-07-01

    The European Space Agency (ESA) selected the gravitational universe as the science theme for L3, a large space mission with a planned launch in 2034. NASA expressed a strong interest in joining ESA as a junior partner. The goal of the mission is the detection of gravitational waves of frequencies between 0.1 mHz and 0.1 Hz, where many long-lived sources are expected to be steady emitters of gravitational waves. Most likely, the mission design will evolve out of the earlier Laser Interferometer Space Antenna (LISA) concept. The interferometric heterodyne phase readout in LISA is performed by phase meters developed specifically to handle the low light powers and Doppler-drift of laser frequencies that appear as complications in the mission baseline. LISA requires the frequency noise of its seed lasers to be below 300 Hz /√{Hz } throughout the measurement band due to uncertainties in the absolute interferometer arm lengths. We have developed and successfully demonstrated Heterodyne Stabilization (HS), a novel cavity-laser frequency stabilization method that integrates well into the LISA mission baseline due to similar component demand. The cavities for the test setup were assembled with Clearceram-Z spacers, an ultralow thermal expansion coefficient material with potential applicability in interferometric space missions. Using HS, we were able to suppress the frequency noise of two lasers in a bench-top experiment to a level that meets the LISA requirement, suggesting both HS and Clearceram-Z can be considered in future mission concepts.

  8. First calibration and visible band observations of Khayyam, a Tunable Spatial Heterodyne Spectroscopy (SHS)

    NASA Astrophysics Data System (ADS)

    Hosseini, S.; Harris, W.; Corliss, J.

    2013-12-01

    We present initial results from observations of wide-field targets using new instrumentation based on an all-reflective spatial heterodyne spectrometer (SHS). SHS instruments are quasi common path two-beam Fourier transform spectrometers that produce 2-D spatial interference patterns without the requirement for moving parts. The utility of SHS comes from its combination of a wide input acceptance angle (0.5-1°), high resolving power (of order ~10^5), compact format, high dynamic range, and relaxed optical tolerances compared with other interferometer designs. This combination makes them extremely useful for velocity resolved for observations of wide field targets from both small and large telescopes. We have constructed both narrow band pass and broadly tunable designs at fixed focal plane facilities on Mt Hamilton and Kitt Peak. This report focuses on the tunable instrument at Mt Hamilton, which is at the focus of the Coudé Auxiliary Telescope (CAT). The CAT provides a test case for on-axis use of SHS, and the impact of the resulting field non-uniformity caused by the spider pattern will be discussed. Observations of several targets will be presented that demonstrate the capabilities of SHS, including comet C/2012 S1 (ISON), Jupiter, and both the day sky and night glow. Raw interferometric data and transformed power spectra will be shown and evaluated in terms of instrumental stability. Khayyam, The Tunable all-reflective Special Heterodyne Spectrometer (SHS) that has being characterized at the Coudé Auxiliary Telescope (CAT) on Mt. Hamilton.

  9. Characteristics and performance of offset phase locked single frequency heterodyned laser systems

    NASA Astrophysics Data System (ADS)

    Tulchinsky, David A.; Hastings, Alexander S.; Williams, Keith J.

    2016-05-01

    We demonstrate and characterize the performance of two heterodyned optical phase locked loop (PLL) laser systems for use in characterizing photodetector RF frequency response and nonlinearities. Descriptions of PLL circuit parameters for Nd:YAG non-planar ring oscillator lasers at 1064 nm and 1319 nm, and Er ion fiber lasers from 1530 nm to 1565 nm are presented. Both laser systems have piezoelectric transducer wavelength control over the PLL voltage controlled oscillator circuit. Offset frequency phase locking from 1.5 kHz to 51+ GHz is demonstrated. Frequency stability at 10 MHz is measured to be ±50 μHz, limited by the stability of the Rb stabilized crystal oscillator. Phase noise of the phase-locked 1319 nm laser system is discussed where we find that the phase noise is dominated by the input source noise at frequency offsets below 100 Hz and by the laser's RIN noise at frequency offsets > 100 Hz. Comparing nonlinearity data from an InGaAs p-i-n photodiode using both 1319 nm and 1550 nm PLL nonlinearity measurement systems, we find two new separate photodetector nonlinearity mechanisms. Measurements of the harmonic components of a 11 MHz sinusoidal heterodyned optical beat note signal are found to be at or below 1 nW/mW for the second harmonic (at 22 MHz) and at or below 0.25 nW/mW for the 3rd harmonic (at 33 MHz), confirming the nearly pure sinusoidal nature of the optically generated microwave beat note.

  10. Vertical profiling of methane and carbon dioxide using high resolution near-infrared heterodyne spectroscopic observations

    NASA Astrophysics Data System (ADS)

    Rodin, Alexander; Klimchuk, Artem; Churbanov, Dmitry; Pereslavtseva, Anastasia; Spiridonov, Maxim; Nadezhdinskyi, Alexander

    2014-05-01

    We present new method of monitoring greenhouse gases using spectroscopic observations of solar radiation passed through the atmosphere with spectral resolution ΛvδΛ up to 108. Such a high resolution is achieved by heterodyne technique and allows to retrieve full information about spectral line shape which, in turn, is used to distinguish contribution of different atmospheric layers to the resulting absorption. Weak absorption line at 6056.5 cm-1 was selected for CO2 measurements and a quartet of lines centered at 6057 cm-1for CH4. The instrument setup includes Sun tracker with a microtelescope and chopper, diode DFB laser used as a local oscillator, a bundle of single mode optical fibers that provides medium for radiation transfer and beam coupling, reference cell with depressurized methane for LO frequency stabilization, and Fabry-Perot etalon for LO frequency calibration. A commercial p-i-n diode with squared detector replaces a mixer and IF spectrometer, providing measurement of heterodyne beating within a bandpass of few MHz, which determines the effective spectral resolution of the instrument. Spectral coverage within narrow range (about 1 cm-1) is provided by ramping the LO frequency based on feedback from the reference channel. Observations of Sun in the Moscow region have resulted for the first time in measurements of the atmospheric transmission near 1.65 μm with sub-Doppler spectral resolution. In order to retrieve vertical profiles of methane and carbon dioxide we developed the inversion algorithm implementing Tikhonov regularization approach. With measured transmission having S/N ratio of 100 or higher, the uncertainty of CH4 profile is about 10 ppb, with the uncertainty of CO2 profile at 1 ppm. This techniques is promising an affordable opportunity or widespread monitoring of greenhouse gases and may be implemented on existing ground-based stations. This work has been supported by the grant of Russian Ministry of education and science #11.G34.31.0074

  11. Dual-wavelength operation of monolithically integrated arrayed waveguide grating lasers for optical heterodyning

    NASA Astrophysics Data System (ADS)

    Guzmán M., Robinson C.; Jimenez, Álvaro; Lawniczuk, Katarzyna; Corradi, Antonio; Leijtens, Xaveer J. M.; Bente, Erwin A. J. M.; Carpintero, Guillermo

    2013-05-01

    A cost-effective solution to provide higher data rates in wireless communication system is to push carrier wave frequencies into millimeter wave (MMW) range, where the frequency bands within the E-band and F-band have been allocated. Photonics is a key technology to generate low phase noise signals, offering methods of generating continuous MMW with varying performance in terms of frequency bandwidth, tunability, and stability. Recently, we demonstrated for the first time of our knowledge the generation of a 95-GHz signal by optical heterodyning of two modes from different channels of a monolithically integrated arrayed waveguide grating multi-wavelength laser (AWGL). The device uses an arrayed waveguide grating (AWG) as an intra-cavity filter. With up to 16-channel sources with independent amplifiers and a booster amplifier on the common waveguide, the laser cavity is formed between cleaved facets of the chip. The two wavelengths required for optical heterodyning are generated activating simultaneously two channel SOAs and the Boost amplifier. In this work, we analyze the effect on the dual-wavelength operation of the Boost SOA, which is shared by two wavelengths. Mapping the optical spectrum, sweeping the two channel and Boost bias currents, we show the interaction among the different SOAs two find the regions of dual wavelength operation. The size of dual wavelength operation region depends greatly on the Boost SOA bias level. Initial results of a numerical model of the AWGL will be also presented, in which a digital filter is used to implement the AWG frequency behavior.

  12. Temperature Profile and Surface Pressure Retrieval of Mars’ Atmosphere Using Infrared Heterodyne Spectroscopy

    NASA Astrophysics Data System (ADS)

    Smith, Ramsey L.; Hewagama, T.; Livengood, T. A.; Fast, K. E.; Kostiuk, T.

    2012-10-01

    Infrared heterodyne spectroscopy of CO2 transitions in the Martian atmosphere was obtained using the Goddard Space Flight Center’s Heterodyne Instrument for Planetary Winds and Composition, HIPWAC, on the NASA Infrared Telescope Facility 3-m telescope, with resolving power of 2.5107. The measured spectra are not fully consistent with temperature profiles for this location and season derived from the Mars Global Surveyor mission (MGS), particularly constraining the pressure and temperature in the deepest part of the troposphere with unambiguous differences between the MGS temperature profile and that required to satisfy the measured emergent spectrum. The temperature information is useful for studying seasonal and global variability, for comparison of results from flight mission results, as well as better profiles for interpreting flight obtained measurements. We will report data collected from our analysis of our high-resolution measurement of 16O12C16O used to develop a temperature profile and surface pressure. CO2 is uniformly mixed in the Martian atmosphere, which makes it an ideal candidate for temperature determination. We are able to collect spectra of the isotopologues of CO2 in the same spectra, which eliminates a source of error for molecular species identification and atmosphere temperature determination. The aforementioned parameters are critical for Martian atmospheric-surface investigations such as isotopologue determination and isotope ratio calculations. For example, an average over measurements acquired at the subsolar point and in the early afternoon at the subsolar latitude yields the terrestrial VSMOW standard, with a minimal difference of 18O = +9±14 ‰. This precision is sufficient to enable a remote investigation of seasonal variations, i.e. due to mass-dependent fractionation in the polar ice cap freeze-sublimate cycle.

  13. Characteristics and performance of offset phase locked single frequency heterodyned laser systems.

    PubMed

    Tulchinsky, David A; Hastings, Alexander S; Williams, Keith J

    2016-05-01

    We demonstrate and characterize the performance of two heterodyned optical phase locked loop (PLL) laser systems for use in characterizing photodetector RF frequency response and nonlinearities. Descriptions of PLL circuit parameters for Nd:YAG non-planar ring oscillator lasers at 1064 nm and 1319 nm, and Er ion fiber lasers from 1530 nm to 1565 nm are presented. Both laser systems have piezoelectric transducer wavelength control over the PLL voltage controlled oscillator circuit. Offset frequency phase locking from 1.5 kHz to 51+ GHz is demonstrated. Frequency stability at 10 MHz is measured to be ±50 μHz, limited by the stability of the Rb stabilized crystal oscillator. Phase noise of the phase-locked 1319 nm laser system is discussed where we find that the phase noise is dominated by the input source noise at frequency offsets below 100 Hz and by the laser's RIN noise at frequency offsets > 100 Hz. Comparing nonlinearity data from an InGaAs p-i-n photodiode using both 1319 nm and 1550 nm PLL nonlinearity measurement systems, we find two new separate photodetector nonlinearity mechanisms. Measurements of the harmonic components of a 11 MHz sinusoidal heterodyned optical beat note signal are found to be at or below 1 nW/mW for the second harmonic (at 22 MHz) and at or below 0.25 nW/mW for the 3rd harmonic (at 33 MHz), confirming the nearly pure sinusoidal nature of the optically generated microwave beat note. PMID:27250392

  14. Heterodyne Receiver Requirements for the Single Aperture Far-Infrared (SAFIR) Observatory

    NASA Technical Reports Server (NTRS)

    Benford, Dominic J.; Kooi, Jacob; Oegerle, William (Technical Monitor)

    2003-01-01

    In the next few years, work will commence in earnest on the development of technology for the next generation large cryogenic far-infrared telescope: the Single Aperture Far- Infrared (SAFIR) Observatory. SAFIR's science goals are driven by the fact that youngest stages of almost all phenomena in the universe are shrouded in absorption by cool dust, resulting in the energy being emitted primarily in the far-infrared. The earliest stages of star formation, when gas and dust clouds are collapsing and planets forming, can only be observed in the far-infrared. Spectral diagnostics in the far-infrared are typically quite narrow (approx. 1 km/s) and require high sensitivity to detect them. SAFIR is a 10 m-class telescope designed for cryogenic operation at L2, removing all sources of thermal emission from the telescope and atmosphere. Despite its limited collecting area and angular resolution as compared to the ALMA interferometer, its potential for covering the entire far-infrared band cannot be matched by any ground-based or airborne observatory. This places a new challenge on heterodyne receivers: broad frequency coverage. The ideal mixer would be able to detect frequencies over several octaves (e.g., 0.6 THz - 12 THz) with near quantum-limited performance at all frequencies. In contrast to ground-based observatories, it may not be necessary to strive for high instantaneous bandwidth, as direct detection spectroscopy is preferable for bandwidths of Delta v/ v greater than or equal to 10(exp -4) (e.g., 1 GHz at 10 THz). We consider likely directions for technology development for heterodyne receivers for SAFIR.

  15. Automated reduction of sub-millimetre single-dish heterodyne data from the James Clerk Maxwell Telescope using ORAC-DR

    NASA Astrophysics Data System (ADS)

    Jenness, Tim; Currie, Malcolm J.; Tilanus, Remo P. J.; Cavanagh, Brad; Berry, David S.; Leech, Jamie; Rizzi, Luca

    2015-10-01

    With the advent of modern multidetector heterodyne instruments that can result in observations generating thousands of spectra per minute it is no longer feasible to reduce these data as individual spectra. We describe the automated data reduction procedure used to generate baselined data cubes from heterodyne data obtained at the James Clerk Maxwell Telescope (JCMT). The system can automatically detect baseline regions in spectra and automatically determine regridding parameters, all without input from a user. Additionally, it can detect and remove spectra suffering from transient interference effects or anomalous baselines. The pipeline is written as a set of recipes using the ORAC-DR pipeline environment with the algorithmic code using Starlink software packages and infrastructure. The algorithms presented here can be applied to other heterodyne array instruments and have been applied to data from historical JCMT heterodyne instrumentation.

  16. Heterodyne spectroscopy of astronomical and laboratory sources at 8.5 microns using diode laser local oscillators

    NASA Technical Reports Server (NTRS)

    Mumma, M.; Kostiuk, T.; Cohen, S.; Buehl, D.; Von Thuna, P. C.

    1975-01-01

    The first 8.5 microns infrared heterodyne spectrometer has been constructed using tuneable semiconductor (PbSe) diode lasers and was used to measure absorption line profiles of N2O in the laboratory, as well as black-body emission from the moon and from Mars. Spectral information was recorded over a 200 MHz bandwidth using an 8-channel filter bank. The resolution was 25 MHz (6 millionths of a micron), and the minimum detectable (black-body) power was approximately 1 times 10 to the minus 16th power W for 8 min of integration. The results demonstrate the usefulness of heterodyne spectroscopy for the study of remote and local sources in the infrared.

  17. Absolute distance measurement by multi-heterodyne interferometry using a frequency comb and a cavity-stabilized tunable laser.

    PubMed

    Wu, Hanzhong; Zhang, Fumin; Liu, Tingyang; Balling, Petr; Qu, Xinghua

    2016-05-20

    In this paper, we develop a multi-heterodyne system capable of absolute distance measurement using a frequency comb and a tunable diode laser locked to a Fabry-Perot cavity. In a series of subsequent measurements, numerous beat components can be obtained by downconverting the optical frequency into the RF region with multi-heterodyne interferometry. The distances can be measured via the mode phases with a series of synthetic wavelengths. The comparison with the reference interferometer shows an agreement within 1.5 μm for the averages of five measurements and 2.5 μm for the single measurement, which is at the 10-8 relative precision level. PMID:27411152

  18. Modulated heterodyne light scattering set-up for measuring long relaxation time at small and wide angle

    SciTech Connect

    Leone, Nancy; Villari, Valentina; Micali, Norberto

    2012-08-15

    We present a simple, compact, and versatile experimental setup working in the heterodyne detection mode with modulation of the reference beam. The system is implemented with a collection optics based on a unimodal optical fiber coupler. This choice allows the heterodyne to be used in a wide range of scattering angles, even for very small ones, without losing the optical beating. The apparatus can be successfully used to study translational diffusive dynamics of dispersed particles at scattering angles smaller than 5 Degree-Sign and it is suitable for exploring slow relaxation processes in sub-Hertz frequency domain, for example, in glass-forming systems. It is also possible to measure the electrophoretic mobility by applying an electric field into a charged particles solution.

  19. Thermal Structure of Venus and Mars as Observed by Ground-Based Mid-IR Heterodyne Spectroscopy

    NASA Astrophysics Data System (ADS)

    Wiegand, M.; Stangier, T.; Hewagama, T.; Kostiuk, T.; Livengood, T.; Herrmann, M.; Krause, P.; Sonnabend, G.; Sornig, M.

    2014-04-01

    We want to introduce a new and unique opportunity to retrieve temperature profiles from the atmosphere of terrestrial planets using ground-based heterodyne spectroscopy in the mid-infrared. In recent years this method has been proven to be a powerful tool to study the atmosphere of terrestrial planets in terms of high altitude dynamics and temperature contribution [1, 2]. Currently two heterodyne spectrometer exist which are used for astrophysical observations of planetary atmospheres (Cologne based spectrometer "THIS" and NASA GSFC's "HIPWAC"). They uniquely provide the required ultra-high resolution to fully resolve molecular spectral lines. The application of this technique enables us to observe single molecular ro-vibrational transition features of CO2 at 10μm in absorption.

  20. Atmospheric observations of multiple molecular species using ultra-high-resolution external cavity quantum cascade laser heterodyne radiometry.

    PubMed

    Weidmann, Damien; Tsai, Tracy; Macleod, Neil A; Wysocki, Gerard

    2011-06-01

    We demonstrate a widely tunable laser heterodyne radiometer operating in the thermal IR during an atmospheric observation campaign in the solar occultation viewing mode. An external cavity quantum cascade laser tunable within a range of 1120 to 1238 cm(-1) is used as the local oscillator (LO) of the instrument. Ultra-high-resolution (60 MHz or 0.002 cm(-1) transmission spectroscopy of several atmospheric species (water vapor, ozone, nitrous oxide, methane, and dichlorodifluoromethane) has been demonstrated within four precisely selected molecule-specific narrow spectral windows (∼1 cm(-1). Atmospheric transmission lines within each selected window were fully resolved through mode-hop-free continuous tuning of the LO frequency. Comparison measurements were made simultaneously with a high-resolution Fourier transform spectrometer to demonstrate the advantages of the laser heterodyne system for atmospheric sounding at high spectral and spatial resolutions. PMID:21633412

  1. NO2 heterodyne frequency measurements with a tunable diode laser, a CO laser transfer oscillator and CO2 laser standards

    NASA Technical Reports Server (NTRS)

    Zink, L. R.; Vanek, M.; Wells, J. S.

    1987-01-01

    Heterodyne frequency measurements have been made on selected groups of nitrogen dioxide rovibronic transitions between 1580.8 and 1650.7/cm. The groups are separated by 7 to 10/cm, and the intent is to provide a limited (and interim) calibration table for the region. In addition to a table of measured frequencies in the region, figures of spectra in the vicinity of the measured lines are included to provide a map for identifying the transitions measured.

  2. Greenhouse Gas Concentration Data Recovery Algorithm for a Low Cost, Laser Heterodyne Radiometer

    NASA Astrophysics Data System (ADS)

    Miller, J. H.; Melroy, H.; Ott, L.; McLinden, M. L.; Holben, B. N.; Wilson, E. L.

    2012-12-01

    The goal of a coordinated effort between groups at GWU and NASA GSFC is the development of a low-cost, global, surface instrument network that continuously monitors three key carbon cycle gases in the atmospheric column: carbon dioxide (CO2), methane (CH4), carbon monoxide (CO), as well as oxygen (O2) for atmospheric pressure profiles. The network will implement a low-cost, miniaturized, laser heterodyne radiometer (mini-LHR) that has recently been developed at NASA Goddard Space Flight Center. This mini-LHR is designed to operate in tandem with the passive aerosol sensor currently used in AERONET (a well established network of more than 450 ground aerosol monitoring instruments worldwide), and could be rapidly deployed into this established global network. Laser heterodyne radiometry is a well-established technique for detecting weak signals that was adapted from radio receiver technology. Here, a weak light signal, that has undergone absorption by atmospheric components, is mixed with light from a distributed feedback (DFB) telecommunications laser on a single-mode optical fiber. The RF component of the signal is detected on a fast photoreceiver. Scanning the laser through an absorption feature in the infrared, results in a scanned heterodyne signal in the RF. Deconvolution of this signal through the retrieval algorithm allows for the extraction of altitude contributions to the column signal. The retrieval algorithm is based on a spectral simulation program, SpecSyn, developed at GWU for high-resolution infrared spectroscopies. Variations in pressure, temperature, composition, and refractive index through the atmosphere; that are all functions of latitude, longitude, time of day, altitude, etc.; are modeled using algorithms developed in the MODTRAN program developed in part by the US Air Force Research Laboratory. In these calculations the atmosphere is modeled as a series of spherically symmetric shells with boundaries specified at defined altitudes. Temperature

  3. Greenhouse Gas Concentration Data Recovery Algorithm for a Low Cost, Laser Heterodyne Radiometer

    NASA Technical Reports Server (NTRS)

    Miller, J. Houston; Melroy, Hilary R.; Ott, Lesley E.; Mclinden, Matthew L.; Holben, Brent; Wilson, Emily L.

    2012-01-01

    The goal of a coordinated effort between groups at GWU and NASA GSFC is the development of a low-cost, global, surface instrument network that continuously monitors three key carbon cycle gases in the atmospheric column: carbon dioxide (CO2), methane (CH4), carbon monoxide (CO), as well as oxygen (O2) for atmospheric pressure profiles. The network will implement a low-cost, miniaturized, laser heterodyne radiometer (mini-LHR) that has recently been developed at NASA Goddard Space Flight Center. This mini-LHR is designed to operate in tandem with the passive aerosol sensor currently used in AERONET (a well established network of more than 450 ground aerosol monitoring instruments worldwide), and could be rapidly deployed into this established global network. Laser heterodyne radiometry is a well-established technique for detecting weak signals that was adapted from radio receiver technology. Here, a weak light signal, that has undergone absorption by atmospheric components, is mixed with light from a distributed feedback (DFB) telecommunications laser on a single-mode optical fiber. The RF component of the signal is detected on a fast photoreceiver. Scanning the laser through an absorption feature in the infrared, results in a scanned heterodyne signal io the RF. Deconvolution of this signal through the retrieval algorithm allows for the extraction of altitude contributions to the column signal. The retrieval algorithm is based on a spectral simulation program, SpecSyn, developed at GWU for high-resolution infrared spectroscopies. Variations io pressure, temperature, composition, and refractive index through the atmosphere; that are all functions of latitude, longitude, time of day, altitude, etc.; are modeled using algorithms developed in the MODTRAN program developed in part by the US Air Force Research Laboratory. In these calculations the atmosphere is modeled as a series of spherically symmetric shells with boundaries specified at defined altitudes. Temperature

  4. Heterodyne detection and transmission of 60-Gbaud PDM-QPSK signal with SE of 4b/s/Hz.

    PubMed

    Li, Xinying; Xiao, Jiangnan; Yu, Jianjun

    2014-04-21

    We experimentally demonstrate 8 × 240-Gb/s super-Nyquist wavelength-division-multiplexing (WDM) polarization-division-multiplexing quadrature-phase-shift-keying (PDM-QPSK) signal transmission on a 50-GHz grid with a net spectral efficiency (SE) of 4b/s/Hz adopting hardware-efficient simplified heterodyne detection. 9-ary quadrature-amplitude-modulation-like (9QAM-like) processing based on multi-modulus blind equalization (MMBE) is adopted to reduce analog-to-digital converter (ADC) bandwidth requirement and improve receiver sensitivity. The transmission distance at the soft-decision forward-error-correction (SD-FEC) threshold of 2 × 10(-2) is 2 × 420 km based on digital post filtering while largely extended to over 5 × 420 km based on 9QAM-like processing, which well illustrates 9QAM-like processing is more efficient for heterodyne coherent WDM system. Moreover, only two ADC channels are needed for simplified heterodyne detection of one 60-Gbaud PDM-QPSK WDM channel, and thus only one commercial oscilloscope (OSC) with two input ports can work well for each WDM channel. PMID:24787819

  5. Periodic error characterization in commercial heterodyne interferometer using an external cavity diode laser based Fabry-Perot interferometer

    NASA Astrophysics Data System (ADS)

    Zhu, Minhao; Wei, Haoyun; Li, Yan

    2014-07-01

    Periodic error is a main error source that limits the measurement accuracy in heterodyne laser interferometry. An external cavity diode laser (ECDL) based Fabry-Perot (F-P) interferometer referenced to an optical frequency comb (OFC) is proposed to characterize the periodic error in heterodyne interferometers. The Pound-Drever-Hall locking technique is employed to lock the tracking ECDL frequency to the resonance of a high finesse F-P cavity. The frequency of a reference ECDL is locked to a selected mode of an OFC to generate a stable single optical frequency. The frequency change of the tracking ECDL induced by the cavity displacement is measured by beating with the reference ECDL locked to the OFC. Experiments show that the F-P interferometer system has a displacement resolution of 1.96 pm. We compared the measurement results of our system with a commercial plane mirror heterodyne interferometer. The period if the periodic error is about half wavelength, with an error amplitude of 4.8 nm.

  6. Heterodyne coherent detection of WDM PDM-QPSK signals with spectral efficiency of 4b/s/Hz.

    PubMed

    Li, Xinying; Dong, Ze; Yu, Jianjun; Yu, Jianguo; Chi, Nan

    2013-04-01

    We experimentally demonstrate heterodyne coherent detection of 8 × 112-Gb/s ultra-density wavelength-division-multiplexing (WDM) polarization-division-multiplexing quadrature-phase-shift-keying (PDM-QPSK) signal after 1120-km single-mode fiber-28 (SMF-28) transmission. The spectral efficiency (SE) is 4b/s/Hz. It is the first time to realize WDM signal transmission with high SE by adopting heterodyne coherent detection. At the heterodyne coherent receiver, intermediate frequency (IF) down conversion is realized in digital frequency domain after analog-to-digital conversion. A digital post filter and 1-bit maximum likelihood sequence estimation (MLSE) adopted after carrier phase estimation (CPE) in the conventional digital-signal-processing (DSP) process is used to suppress the enhanced noise and crosstalk as well as overcome the filtering effects. The bit-error ratio (BER) for all channels is under the forward-error-correction (FEC) limit of 3.8 × 10(-3) after 1120-km SMF-28 transmission. PMID:23571970

  7. Thermal structure of Venus' nightside mesosphere as observed by infrared heterodyne spectroscopy at 10 μm

    NASA Astrophysics Data System (ADS)

    Stangier, Tobias; Hewagama, Tilak; Sornig, Manuela; Sonnabend, Guido; Kostiuk, Theodor; Herrmann, Maren; Livengood, Timothy

    2015-08-01

    Ground-based heterodyne spectroscopy is used to observe the night side of Venus by probing single pressure broadened CO2 absorption lines. From the pressure induced line broadening, the predominant temperature at different altitude layers can be deduced. It is found, that heterodyne spectroscopy is sensitive to probe the mesosphere between ~ 60 km and 90 km with an altitude resolution of ~ 4.5 km. During two observing campaigns in March and May 2012, four different locations on the planet were investigated. Herein, we report on the retrieval of vertical temperature profiles in the nightside atmosphere of Venus. Retrieval of atmospheric parameters is based on a Levenberg-Marquard χ2 optimization that iteratively compares observed data to telluric transmittance corrected Venus' top-of-atmosphere spectra calculated using a radiative transfer algorithm. The deduced profiles are compared to the Venus International Reference Atmosphere and some found to be in satisfactory agreement. Sub-Doppler resolution Infrared heterodyne observations can provide temperature measurements that complement existing sub-mm and space based observations.

  8. A Miniaturized Laser Heterodyne Radiometer for a Global Ground-Based Column Carbon Monitoring Network

    NASA Technical Reports Server (NTRS)

    Wilson, Emily L.; Melroy, Hilary R.; Miller, J. Houston; McLinden, Matthew L.; Ott, Lesley E.; Holben, Brent

    2012-01-01

    We present progress in the development of a passive, miniaturized Laser Heterodyne Radiometer (mini-LHR) that will measure key greenhouse gases (C02, CH4, CO) in the atmospheric column as well as their respective altitude profiles, and O2 for a measure of atmospheric pressure. Laser heterodyne radiometry is a spectroscopic method that borrows from radio receiver technology. In this technique, a weak incoming signal containing information of interest is mixed with a stronger signal (local oscillator) at a nearby frequency. In this case, the weak signal is sunlight that has undergone absorption by a trace gas of interest and the local oscillator is a distributive feedback (DFB) laser that is tuned to a wavelength near the absorption feature of the trace gas. Mixing the sunlight with the laser light, in a fast photoreceiver, results in a beat signal in the RF. The amplitude of the beat signal tracks the concentration of the trace gas in the atmospheric column. The mini-LHR operates in tandem with AERONET, a global network of more than 450 aerosol sensing instruments. This partnership simplifies the instrument design and provides an established global network into which the mini-LHR can rapidly expand. This network offers coverage in key arctic regions (not covered by OCO-2) where accelerated warming due to the release of CO2 and CH4 from thawing tundra and permafrost is a concern as well as an uninterrupted data record that will both bridge gaps in data sets and offer validation for key flight missions such as OCO-2, OCO-3, and ASCENDS. Currently, the only ground global network that routinely measures multiple greenhouse gases in the atmospheric column is TCCON (Total Column Carbon Observing Network) with 18 operational sites worldwide and two in the US. Cost and size of TCCON installations will limit the potential for expansion, We offer a low-cost $30Klunit) solution to supplement these measurements with the added benefit of an established aerosol optical depth

  9. Miniaturized Laser Heterodyne Radiometer (LHR) for Measurements of Greenhouse Gases in the Atmospheric Column

    NASA Technical Reports Server (NTRS)

    Steel, Emily; McLinden, Matthew

    2012-01-01

    This passive laser heterodyne radiometer (LHR) instrument simultaneously measures multiple trace gases in the atmospheric column including carbon dioxide (CO2) and methane (CH4), and resolves their concentrations at different altitudes. This instrument has been designed to operate in tandem with the passive aerosol sensor currently used in AERONET (an established network of more than 450 ground aerosol monitoring instruments worldwide). Because aerosols induce a radiative effect that influences terrestrial carbon exchange, simultaneous detection of aerosols with these key carbon cycle gases offers a uniquely comprehensive measurement approach. Laser heterodyne radiometry is a technique for detecting weak signals that was adapted from radio receiver technology. In a radio receiver, a weak input signal from a radio antenna is mixed with a stronger local oscillator signal. The mixed signal (beat note, or intermediate frequency) has a frequency equal to the difference between the input signal and the local oscillator. The intermediate frequency is amplified and sent to a detector that extracts the audio from the signal. In the LHR instrument described here, sunlight that has undergone absorption by the trace gas is mixed with laser light at a frequency matched to a trace gas absorption feature in the infrared (IR). Mixing results in a beat signal in the RF (radio frequency) region that can be related to the atmospheric concentration. For a one-second integration, the estimated column sensitivities are 0.1 ppmv for CO2, and <1 ppbv for CH4. In addition to producing a standalone ground measurement product, this instrument could be used to calibrate/validate four Earth observing missions: ASCENDS (Active Sensing of CO2 Emissions over Nights, Days, and Seasons), OCO-2 (Orbiting Carbon Observatory), OCO-3, and GOSAT (Greenhouse gases Observational SATellite). The only network that currently measures CO2 and CH4 in the atmospheric column is TCCON (Total Carbon Column

  10. A Miniaturized Laser Heterodyne Radiometer for a Global Ground-Based Column Carbon Monitoring Network

    NASA Astrophysics Data System (ADS)

    Wilson, E. L.; Melroy, H.; Miller, J. H.; McLinden, M. L.; Ott, L.; Holben, B. N.

    2012-12-01

    We present progress in the development of a passive, miniaturized Laser Heterodyne Radiometer (mini-LHR) that will measure key greenhouse gases (CO2, CH4, CO) in the atmospheric column as well as their respective altitude profiles, and O2 for a measure of atmospheric pressure. Laser heterodyne radiometry is a spectroscopic method that borrows from radio receiver technology. In this technique, a weak incoming signal containing information of interest is mixed with a stronger signal (local oscillator) at a nearby frequency. In this case, the weak signal is sunlight that has undergone absorption by a trace gas of interest and the local oscillator is a distributive feedback (DFB) laser that is tuned to a wavelength near the absorption feature of the trace gas. Mixing the sunlight with the laser light, in a fast photo-receiver, results in a beat signal in the RF. The amplitude of the beat signal tracks the concentration of the trace gas in the atmospheric column. The mini-LHR operates in tandem with AERONET, a global network of more than 450 aerosol sensing instruments. This partnership simplifies the instrument design and provides an established global network into which the mini-LHR can rapidly expand. This network offers coverage in key arctic regions (not covered by OCO-2) where accelerated warming due to the release of CO2 and CH4 from thawing tundra and permafrost is a concern as well as an uninterrupted data record that will both bridge gaps in data sets and offer validation for key flight missions such as OCO-2, OCO-3, and ASCENDS. Currently, the only ground global network that routinely measures multiple greenhouse gases in the atmospheric column is TCCON (Total Column Carbon Observing Network) with 18 operational sites worldwide and two in the US. Cost and size of TCCON installations will limit the potential for expansion. We offer a low-cost (<$30K/unit) solution to supplement these measurements with the added benefit of an established aerosol optical depth

  11. Optimization of polarizer angles for measurements of the degree and angle of linear polarization for linear polarizer-based polarimeters

    NASA Astrophysics Data System (ADS)

    Xia, Run-Qiu; Wang, Xia; Jin, Wei-Qi; Liang, Jian-An

    2015-10-01

    Linear polarizer-based polarimeters that measure the degree of linear polarization (DoLP) and the angle of polarization (AoP) were considered in this study. Variances of DoLP and AoP of the region of interest (ROI) to be measured were analyzed using a statistical method. To simplify the calculation, only additive noise and shot noise were considered. Optimized combinations of the polarizers that can minimize the variances of DoLP and AoP were determined by investigating the variances of different polarizer combinations. Several regularities were found when analyzing the data obtained from the optimized combinations. Some variables in the combinations are inversely proportional to the cube or square root of the signal-to-noise ratio of the output signals from sensors without polarizer filtering, and these variables are functions of the DoLP of the ROI to be measured.

  12. A Question of Balance

    ERIC Educational Resources Information Center

    Claxton, David B.; Troy, Maridy; Dupree, Sarah

    2006-01-01

    Most authorities consider balance to be a component of skill-related physical fitness. Balance, however, is directly related to health, especially for older adults. Falls are a leading cause of injury and death among the elderly. Improved balance can help reduce falls and contribute to older people remaining physically active. Balance is a…

  13. Improve Your Balance

    MedlinePlus

    ... My Go4Life Get Free Stuff Be a Partner Balance Improve Your Balance Each year, more than 2 million older Americans ... types of exercise — endurance , strength , balance, and flexibility . Balance Stand on One Foot Heel-to-Toe Walk ...

  14. Balance in Assessment

    ERIC Educational Resources Information Center

    White, Richard

    2007-01-01

    The review by Black and Wiliam of national systems makes clear the complexity of assessment, and identifies important issues. One of these is "balance": balance between local and central responsibilities, balance between the weights given to various purposes of schooling, balance between weights for various functions of assessment, and balance…

  15. Dynamic balance improvement program

    NASA Technical Reports Server (NTRS)

    Butner, M. F.

    1983-01-01

    The reduction of residual unbalance in the space shuttle main engine (SSME) high pressure turbopump rotors was addressed. Elastic rotor response to unbalance and balancing requirements, multiplane and in housing balancing, and balance related rotor design considerations were assessed. Recommendations are made for near term improvement of the SSME balancing and for future study and development efforts.

  16. Rapid detection of urinary polyomavirus BK by heterodyne-based surface plasmon resonance biosensor

    NASA Astrophysics Data System (ADS)

    Su, Li-Chen; Tian, Ya-Chung; Chang, Ying-Feng; Chou, Chien; Lai, Chao-Sung

    2014-01-01

    In renal transplant patients, immunosuppressive therapy may result in the reactivation of polyomavirus BK (BKV), leading to polyomavirus-associated nephropathy (PVAN), which inevitably causes allograft failure. Since the treatment outcomes of PVAN remain unsatisfactory, early identification and continuous monitoring of BKV reactivation and reduction of immunosuppressants are essential to prevent PVAN development. The present study demonstrated that the developed dual-channel heterodyne-based surface plasmon resonance (SPR) biosensor is applicable for the rapid detection of urinary BKV. The use of a symmetrical reference channel integrated with the poly(ethylene glycol)-based low-fouling self-assembled monolayer to reduce the environmental variations and the nonspecific noise was proven to enhance the sensitivity in urinary BKV detection. Experimentally, the detection limit of the biosensor for BKV detection was estimated to be around 8500 copies/mL. In addition, urine samples from five renal transplant patients were tested to rapidly distinguish PVAN-positive and PVAN-negative renal transplant patients. By virtue of its simplicity, rapidity, and applicability, the SPR biosensor is a remarkable potential to be used for continuous clinical monitoring of BKV reactivation.

  17. Synthetic single beam heterodyne interferometry (SSHI) for continuous, high bandwidth, minimally destructive detection of ultracold atoms

    NASA Astrophysics Data System (ADS)

    Locke, Mary; Fertig, Chad

    2011-05-01

    We demonstrate a new method, ``synthetic single beam heterodyne interferometry'' (SSHI), to continuously monitor rapid population dynamics in ultracold atomic clouds at the minimum destruction limit (i.e., with signal-to-noise determined solely by the maximum allowable spontaneous scattering rate and the measurement bandwidth). Similar to frequency modulation spectroscopy (FMS), SSHI encodes atom dynamics into the time-dependent shift of the optical phase of one spectral component relative to a second in a single laser beam. Unlike FMS, SSHI does not suffer from residual amplitude modulation (RAM) noise, is highly insensitive to intensity fluctuations, and does not require modulation frequencies of 100's of GHz to reach the minimum destruction regime. In SSHI, a large signal size is made compatible with low spontaneous scattering by passing only a weak laser through the atoms, subsequently interfering it with a bright beam that does not pass through the atoms. Unlike a true separated beams interferometer, however, SSHI is completely insensitive to mirror shake anywhere on any beam path. Details of the theory and measured performance of our scheme will be presented. Work partially supported by UGA, NSF and ARO.

  18. FPGA-based smart sensor for online displacement measurements using a heterodyne interferometer.

    PubMed

    Vera-Salas, Luis Alberto; Moreno-Tapia, Sandra Veronica; Garcia-Perez, Arturo; de Jesus Romero-Troncoso, Rene; Osornio-Rios, Roque Alfredo; Serroukh, Ibrahim; Cabal-Yepez, Eduardo

    2011-01-01

    The measurement of small displacements on the nanometric scale demands metrological systems of high accuracy and precision. In this context, interferometer-based displacement measurements have become the main tools used for traceable dimensional metrology. The different industrial applications in which small displacement measurements are employed requires the use of online measurements, high speed processes, open architecture control systems, as well as good adaptability to specific process conditions. The main contribution of this work is the development of a smart sensor for large displacement measurement based on phase measurement which achieves high accuracy and resolution, designed to be used with a commercial heterodyne interferometer. The system is based on a low-cost Field Programmable Gate Array (FPGA) allowing the integration of several functions in a single portable device. This system is optimal for high speed applications where online measurement is needed and the reconfigurability feature allows the addition of different modules for error compensation, as might be required by a specific application. PMID:22164040

  19. FPGA-Based Smart Sensor for Online Displacement Measurements Using a Heterodyne Interferometer

    PubMed Central

    Vera-Salas, Luis Alberto; Moreno-Tapia, Sandra Veronica; Garcia-Perez, Arturo; de Jesus Romero-Troncoso, Rene; Osornio-Rios, Roque Alfredo; Serroukh, Ibrahim; Cabal-Yepez, Eduardo

    2011-01-01

    The measurement of small displacements on the nanometric scale demands metrological systems of high accuracy and precision. In this context, interferometer-based displacement measurements have become the main tools used for traceable dimensional metrology. The different industrial applications in which small displacement measurements are employed requires the use of online measurements, high speed processes, open architecture control systems, as well as good adaptability to specific process conditions. The main contribution of this work is the development of a smart sensor for large displacement measurement based on phase measurement which achieves high accuracy and resolution, designed to be used with a commercial heterodyne interferometer. The system is based on a low-cost Field Programmable Gate Array (FPGA) allowing the integration of several functions in a single portable device. This system is optimal for high speed applications where online measurement is needed and the reconfigurability feature allows the addition of different modules for error compensation, as might be required by a specific application. PMID:22164040

  20. Noncontact photoacoustic tomography of in vivo chicken chorioallantoic membrane based on all-fiber heterodyne interferometry

    NASA Astrophysics Data System (ADS)

    Eom, Jonghyun; Park, Seong Jun; Lee, Byeong Ha

    2015-10-01

    We present three-dimensional (3-D) in vivo photoacoustic (PA) images of the blood vasculature of a chicken chorioallantoic membrane (CAM) obtained by using a fiber-based noncontact PA tomography system. With a fiber-optic heterodyne interferometer, the system measures the surface displacement of a sample, induced by the PA wave, which overcomes the disadvantage of physical-contact of ultrasonic transducer in a conventional system. The performance of an implemented system is analyzed and its capability of in vivo 3-D bioimaging is presented. At a depth of 2.5 mm in a phantom experiment, the lateral and axial resolutions were measured as 100 and 30 μm, respectively. The lateral resolution became doubled at a depth of 7.0 mm however, interestingly, the axial resolution was not noticeably deteriorated with the depth. With the CAM experiment, performed under the American National Standards Institute laser safety standard condition, blood vessel structures placed as deep as 3.5 mm were clearly recognized.

  1. Khayyam: a tunable spatial heterodyne spectrometer for observing diffuse emission line targets

    NASA Astrophysics Data System (ADS)

    Hosseini, Sona; Harris, Walter; Corliss, Jason

    2012-09-01

    We describe first results from a new instrument-telescope configuration that combines all of the capabilities necessary to obtain high resolving power visible band spectra of diffuse targets from small aperture telescopes where significant observing time can be obtained. This instrument -Khayyam- is a tunable all-reflective spatial heterodyne spectrometer (SHS) that is mounted to a fixed focal plane shared by the 0.6m Coude auxiliary telescope and the 3m Shane telescope on Mt. Hamilton. Khayyam has an up to 78 arcmin input field of view, resolving power up to 176000, and a tunable bandpass from 350-700 nm. It is being field tested for initial use to study spatially extended solar system targets where high resolving power is necessary to separate multimodal signals, crowded molecular bands, and to sample low velocities (<10 km/s) and rapid temporal cadence is necessary to track physical evolution. Two of the best comet targets during next year is comet C/2011 L4 (PanSTARRS), and C/2011 F1 (LINEAR). Our goal is to sequentially measure isotopic ratios of 14N:15N and 12C:13C in CN, along with the production rate and the production rate ratios of varies daughter species, particularly C2, C3, NH2, OI, and CN, as a function of heliocentric distance and time.

  2. Optical heterodyne-detected Raman-induced Kerr effect (OHD-RIKE) microscopy.

    PubMed

    Freudiger, Christian W; Roeffaers, Maarten B J; Zhang, Xu; Saar, Brian G; Min, Wei; Xie, X Sunney

    2011-05-12

    Label-free microscopy based on Raman scattering has been increasingly used in biomedical research to image samples that cannot be labeled or stained. Stimulated Raman scattering (SRS) microscopy allows signal amplification of the weak Raman signal for fast imaging speeds without introducing the nonresonant background and coherent image artifacts that are present in coherent anti-Stokes Raman scattering (CARS) microscopy. Here we present the Raman-induced Kerr effect (RIKE) as a contrast for label-free microscopy. RIKE allows us to measure different elements of the nonlinear susceptibility tensor, both the real and imaginary parts, by optical heterodyne detection (OHD-RIKE). OHD-RIKE microscopy provides information similar to polarization CARS (P-CARS) and interferometric CARS (I-CARS) microscopy, with a simple modification of the two-beam SRS microscopy setup. We show that, while OHD-RIKE microspectroscopy can be in principle more sensitive than SRS, it does not supersede SRS microscopy of heterogeneous biological samples, such as mouse skin tissue, because it is complicated by variations of linear birefringence across the sample. PMID:21504149

  3. Determination of azimuthal anchoring strength in twisted nematic liquid crystal cells using heterodyne polarimeter.

    PubMed

    Yu, Tsung-Chih; Lo, Yu-Lung; Huang, Rei-Rong

    2010-09-27

    Two external-field-free methods are presented for measuring the azimuthal anchoring strength in twisted nematic liquid crystal (TNLC) cells. For asymmetrical TNLC samples, the twist angle is derived from the phase of the detected signal in a phase-sensitive heterodyne polarimeter and is then used to calculate the weak anchoring strength directly. The measurement resolution which is found to be about 0.01 μJ/m(2) makes the present method sensitive enough for the LC-based bio-sensing application. Using the proposed method, the weak azimuthal anchoring strength of a composite liquid crystal mixture (40% LCT-061153 + 60% MJO-42761) in contact with a plasma-alignment layer is found to be 7.19 μJ/m(2). For symmetrical TNLC samples, the liquid crystals are injected into a wedge cell, and the two-dimensional distributions of the twist angle and cell gap are extracted from the detected phase distribution using a genetic algorithm (GA). The azimuthal anchoring strength is then obtained by applying a fitting technique to the twist angle vs. cell gap curve. Utilizing the proposed approach, it is shown that the strong anchoring strength between a rubbed polyimide (PI) alignment layer and E7 liquid crystal is around 160 μJ/m(2) while that between a rubbed PI alignment layer and MLC-7023 liquid crystal is approximately 32 μJ/m(2). PMID:20941014

  4. Heterodyne frequency measurements on N2O at 5.3 and 9.0 microns

    NASA Technical Reports Server (NTRS)

    Wells, J. S.; Jennings, D. A.; Hinz, A.; Murray, J. S.; Maki, A. G.

    1985-01-01

    Heterodyne frequency measurements on the 01(1)1-00(0)0 band of N2O have been made with the use of a tunable-diode laser, CO laser transfer oscillator, and a CO2 laser frequency synthesizer. A beat frequency was measured between a CO laser and tunable-diode laser whose frequency was locked to the peak of N2O absorption features. The frequency of the CO laser was simultaneously determined by neasuring the beat frequency with respect to a reference synthesized from two CO2 lasers. New rovibrational constants are given for the 01(1)1 state of N2O, which are in excellent agreement with previous results, although the band center is 4 MHz higher than in the previous measurements. A table for the line frequencies and their absolute uncertainties is given for the N2O absorption lines in the wave-number region from 1830 to 1920 kaysers. Some additional frequency measurements near the lower-frequency end of the 02(0)0-00(0)0 band have also been made with respect to a C-12)(0-18)2 laser.

  5. Measurement of the thickness of the tympanic membrane in cat using a heterodyne interferometer

    NASA Astrophysics Data System (ADS)

    Decraemer, Willem F. S.; Khanna, Shyam M.; Dirckx, Joris J. J.

    2004-06-01

    The thickness of the tympanic membrane has to be known for the formulation of mathematical ear models. Using a commercial confocal laser scanning microscope we have found that the tympanic membrane has parts thinner than 10 micron. In this study we were forced to excise the tympanic membranes and due the restricted working distance of the microscope objective, we had to flatten the tympanic membrane onto a glass plate. Although we were able to measure thickness in fresh samples, thickness could still have been altered by the preparation procedure. S. Khanna developed over the years a powerful heterodyne interferometer with confocal pinholes in the illumination and observation arms. Thanks to its sectioning capabilities it can measure vibrations of structures embedded within other tissue without the need to expose the structure. While using this equipment in measuring vibrations in the middle ear, the idea grew that the interferometer could also be used to measure thickness, by tracking the carrier level of the interferometer while the laser focus is driven through the membrane. The method looks full of promises as measurements on animals with the tympanic membrane still in its original niche are possible without a prior preparation of the membrane.

  6. Attometer resolution spectral analysis based on polarization pulling assisted Brillouin scattering merged with heterodyne detection.

    PubMed

    Preussler, Stefan; Schneider, Thomas

    2015-10-01

    Spectral analysis is essential for measuring and monitoring advanced optical communication systems and the characterization of active and passive devices like amplifiers, filters and especially frequency combs. Conventional devices have a limited resolution or tuning range. Therefore, the true spectral shape of the signal remains hidden. In this work, a small part of the signal under test is preselected with help of the polarization pulling effect of stimulated Brillouin scattering where all unwanted spectral components are suppressed. Subsequently, this part is analyzed more deeply through heterodyne detection. Thereby, the local oscillator is generated from a narrow linewidth fiber laser which acts also as pump wave for Brillouin scattering. By scanning the pump wave together with the local oscillator through the signal spectrum, the whole signal is measured. The method is tunable over a broad wavelength range, is not affected by unwanted mixing products and utilizes a conventional narrow bandwidth photo diode. First proof of concept experiments show the measurement of the power spectral density function with a resolution in the attometer or lower kilohertz range at 1550 nm. PMID:26480198

  7. Laser heterodyne system for obtaining height profiles of minor species in the atmosphere

    NASA Technical Reports Server (NTRS)

    Jain, S. L.; Saha, A. K.

    1986-01-01

    An infrared laser heterodyne system for obtaining height profiles of minor constituents of the atmosphere was developed and erected. A brief discription of the system is given. The system consists of a tunable CO2 waveguide laser in the 9 to 11 micrometer band, that is used as a local oscillator and a heliostat that follows the sun and brings in solar radiation, that is mixed with the laser beam in a high speed liquid nitrogen cooled mercury cadmium telluride detector. The detected signal is analysed in a RF spectrum analyser that allows tracing absorption line profiles. Absorption lines of a number of minor constituents in the troposphere and stratosphere, such as O3, NH3, H2O, SO2, ClO, N2O, are in the 9 to 11 micrometer band and overlap with that of CO2 laser range. The experimental system has been made operational and trial observations taken. Current measurements are limited to ozone height profiles. Results are presented.

  8. Miniaturized, 9-12 micron heterodyne spectrometer with space qualifiable design features

    NASA Technical Reports Server (NTRS)

    Glenar, D. A.; Mumma, M. J.; Kostiuk, T.; Huffman, H.; Degnan, J.

    1990-01-01

    A demonstration-prototype CO2-laser heterodyne spectrometer operating at 9-12 microns and suitable for long-term space missions is described and illustrated with extensive diagrams, drawings, photographs, and graphs of test performance data. The spectrometer has total volume 0.63 cu m, mass 30 kg, and power requirement 60-70 W, compatible with miniature-class Space Shuttle experiment payload specifications. It comprises three modules: (1) an optical front end with reflecting optics, a 2-GHz BW HgCdTe photomixer, and a 0-2-GHz 40-dB RF preamplifier; (2) a local oscillator with an RF-excited waveguide CO2 laser, a 75-percent-efficiency RF amplifier, a stepper-driven grating mode selector, and an etalon stabilized for over 30,000 h of use; and (3) an RF-filter-bank spectral-line receiver with a 25-MHz RF channel, 1.6-GHz IF spectral coverage, onboard instrument control, a serial link to the host computer, and highly integrated design.

  9. Dynamic tracking down-conversion signal processing method based on reference signal for grating heterodyne interferometer

    NASA Astrophysics Data System (ADS)

    Wang, Guochao; Yan, Shuhua; Zhou, Weihong; Gu, Chenhui

    2012-08-01

    Traditional displacement measurement systems by grating, which purely make use of fringe intensity to implement fringe count and subdivision, have rigid demands for signal quality and measurement condition, so they are not easy to realize measurement with nanometer precision. Displacement measurement with the dual-wavelength and single-grating design takes advantage of the single grating diffraction theory and the heterodyne interference theory, solving quite well the contradiction between large range and high precision in grating displacement measurement. To obtain nanometer resolution and nanometer precision, high-power subdivision of interference fringes must be realized accurately. A dynamic tracking down-conversion signal processing method based on the reference signal is proposed. Accordingly, a digital phase measurement module to realize high-power subdivision on field programmable gate array (FPGA) was designed, as well as a dynamic tracking down-conversion module using phase-locked loop (PLL). Experiments validated that a carrier signal after down-conversion can constantly maintain close to 100 kHz, and the phase-measurement resolution and phase precision are more than 0.05 and 0.2 deg, respectively. The displacement resolution and the displacement precision, corresponding to the phase results, are 0.139 and 0.556 nm, respectively.

  10. Automated Removal of Bad-Baseline Spectra from ACSIS/HARP Heterodyne Time Series

    NASA Astrophysics Data System (ADS)

    Currie, M. J.

    2013-10-01

    Heterodyne time-series spectral data often exhibit distorted or noisy baselines. These are either transient due to external interference or pickup; or affect a receptor throughout an observation or extended period, possibly due to a poor cable connection. While such spectra can be excluded manually, this is time consuming and prone to omission, especially for the high-frequency interference affecting just one or two spectra in typically several to twenty thousand, yet can produce undesirable artifacts in the reduced spectral cube. Further astronomers have tended to reject an entire receptor if any of its spectra are suspect; as a consequence the reduced products have lower signal-to-noise, and enhanced graticule patterns due to the variable coverage and detector relative sensitivities. This paper illustrates some of the types of aberrant spectra for ACSIS/HARP on the James Clerk Maxwell Telescope and the algorithms used to identify and remove them, applied within the ORAC-DR pipeline, and compares an integrated map with and without baseline filtering.

  11. Complex conjugate resolved heterodyne swept source optical coherence tomography using coherence revival

    PubMed Central

    Dhalla, Al-Hafeez; Nankivil, Derek; Izatt, Joseph A.

    2012-01-01

    We describe a simple and low-cost technique for resolving the complex conjugate ambiguity in Fourier domain optical coherence tomography (OCT) that is applicable to many swept source OCT (SSOCT) systems. First, we review the principles of coherence revival, wherein an interferometer illuminated by an external cavity tunable laser (ECTL) exhibits interference fringes when the two arms of the interferometer are mismatched by an integer multiple of the laser cavity length. Second, we report observations that the spectral interferogram obtained from SSOCT systems employing certain ECTLs are automatically phase modulated when the arm lengths are mismatched this way. This phase modulation results in a frequency-shifted interferogram, effectively creating an extended-depth heterodyne SSOCT system without the use of acousto-optic or electro-optic modulators. We suggest that this phase modulation may be caused by the ECTL cavity optical pathlength varying slightly over the laser sweep, and support this hypothesis with numerical simulations. We also report on the successful implementation of this technique with two commercial swept source lasers operating at 840nm and 1040nm, with sweep rates of 8kHz and 100kHz respectively. The extended imaging depth afforded by this technique was demonstrated by measuring the sensitivity fall-off profiles of each laser with matched and mismatched interferometer arms. The feasibility of this technique for clinical systems is demonstrated by imaging the ocular anterior segments of healthy human volunteers. PMID:22435108

  12. Real-time digital heterodyne interferometer for high resolution plasma density measurements at ISTTOK

    SciTech Connect

    Marques, T. G.; Gouveia, A.; Pereira, T.; Fortunato, J.; Carvalho, B. B.; Sousa, J.; Silva, C.; Fernandes, H.

    2008-10-15

    With the implementation of alternating discharges (ac) at the ISTTOK tokamak, the typical duration of the discharges increased from 35 to 250 ms. This time increase created the need for a real-time electron density measurement in order to control the plasma fueling. The diagnostic chosen for the real-time calculation was the microwave interferometer. The ISTTOK microwave interferometer is a heterodyne system with quadrature detection and a probing frequency of 100 GHz ({lambda}{sub 0}=3 mm). In this paper, a low-cost approach for real-time diagnostic using a digital signal programable intelligent computer embedded system is presented, which allows the measurement of the phase with a 1% fringe accuracy in less than 6 {mu}s. The system increases its accuracy by digitally correcting the offsets of the input signals and making use of a judicious lookup table optimized to improve the nonlinear behavior of the transfer curve. The electron density is determined at a rate of 82 kHz (limited by the analog to digital converter), and the data are transmitted for each millisecond although this last parameter could be much lower (around 12 {mu}s--each value calculated is transmitted). In the future, this same system is expected to control plasma actuators, such as the piezoelectric valve of the hydrogen injection system responsible for the plasma fueling.

  13. Tantalum hot-electron bolometers for low-noise heterodyne receivers

    NASA Technical Reports Server (NTRS)

    Skalare, A.; McGrath, W.; Bumble, B.; LeDuc, H. G.

    2002-01-01

    We describe superconducting diffusion-cooled hot-electron bolometers that were fabricated fromtantalum films grown on a thin niobium seed layer. The seed layer promotes single-phase growth of the Ta films, resulting in high-quality bolometers with transition temperatures up to 2.35 K and transition widths of less than 0.2 K. An S-parameter measurement set-up in a He-3 cryostat was used to measure device impedance versus frequency of a 400 nm long device at a temperature of 400 mK. It is shown that a 3 dB roll-off frequency of about 1 GHz can be achieved when the device resistance matches the impedance of the embedding network (no electrothermal feedback). This would lead to a prediction of 16 GHz for a 100 nm device, and indicates that a heterodyne mixer using a Ta HEB should be able to operate at several GHz even with a significant amount of electrothermal feedback.

  14. Optical heterodyne-detected Raman-Induced Kerr Effect (OHD-RIKE) microscopy

    PubMed Central

    Freudiger, Christian W.; Roeffaers, Maarten B. J.; Zhang, Xu; Saar, Brian G.; Min, X., Wei; Xie, Sunney

    2012-01-01

    Label-free microscopy based on Raman scattering has been increasingly used in biomedical research to image samples that cannot be labeled or stained. Stimulated Raman scattering (SRS) microscopy, allows signal amplification of the weak Raman signal for fast imaging speeds without introducing the non-resonant background and coherent image artifacts that are present in coherent anti-Stokes Raman scattering (CARS) microscopy. Here we present the Raman-induced Kerr effect (RIKE) as a contrast for label-free microscopy. RIKE allows us to measure different elements of the non-linear susceptibility tensor, both the real and imaginary parts by optical heterodyne detection (OHD-RIKE). OHD-RIKE microscopy provides information similar to polarization CARS (P-CARS) and interferometric CARS (I-CARS) microscopy, with a simple modification of the two-beam SRS microscopy setup. We show that while OHD-RIKE micro-spectroscopy can be in principle more sensitive than SRS, it does not supersede SRS microscopy of heterogeneous biological samples, such as mouse skin tissue, because it is complicated by variations of linear birefringence across the sample. PMID:21504149

  15. An Extremely Wide Bandwidth, Low Noise SIS Heterodyne Receiver Design for Millimeter and Submillimeter Observations

    NASA Technical Reports Server (NTRS)

    Zmuidzinas, J.

    2004-01-01

    Our group has designed a heterodyne submillimeter receiver that offers a very wide IF bandwidth of 12 GHz, while still maintaining a low noise temperature. The 180-300 GHz double-sideband design uses a single SI5 device excited by a full bandwidth, fixed-tuned waveguide probe on a silicon substrate. The IF output frequency (limited by the MMIC low noise IF preamplifier) is 6-18 GHz. providing an instantaneous RF bandwidth of 24 GHz (double-sideband). Intensive simulations predict that the junction will achieve a conversion loss better than 1-2 dB and a mixer noise temperature of less than 20 K across the band (twice the quantum limit). The single sideband receiver noise temperature goal is 70 K. The wide instantaneous bandwidth and low noise will result in an instrument capable of a variety of important astrophysical and environmental observations beyond the capabilities of current instruments. Lab testing of the receiver will begin this summer, and first light on the CSO should be in the Spring of 2003. At the CSO, we plan to use receiver with WASP2, a wideband spectrometer, to search for spectral lines from SCUBA sources. This approach should allow us to rapidly develop a catalog of redshifts for these objects.

  16. Spatial frequency heterodyne imaging of aqueous phase transitions inside multi-walled carbon nanotubes.

    PubMed

    Schunk, F M; Rand, D; Rose-Petruck, C

    2015-12-14

    The evaporation and condensation of water on multi-walled carbon nanotube (MWCNT) surfaces was studied as a function of temperature and time using X-ray spatial frequency heterodyne imaging (SFHI). SFHI is an imaging modality that produces an absorption and scatter image in a single exposure, and has increased sensitivity to variations in electron density relative to more common place X-ray imaging techniques. Differing features exhibited in the temporal scatter intensity profiles recorded during evaporation and condensation revealed the existence of an absorption-desorption hysteresis. Effects on the aforementioned phenomena due to chemical functionalization of the carbon nanotube surfaces were also monitored. The increased interaction potential between the functionalized MWCNT walls and water molecules altered the evaporation event time scale and increased the temperature at which condensation could take place. Theoretical calculations were used to correlate the shape of the observed scatter profiles during condensation to changes in the MWCNT cross section geometry and configuration of the contained water volume. Changes in evaporation time scales with temperature coincided with the boiling point for confined water predicted by the Kelvin equation, indicating that a thermodynamic description of mesoscopic confined water is permissible in some instances. PMID:26549826

  17. Amplitude modulated heterodyne reflectometer for density profile and density fluctuation profile measurements at W7-AS

    SciTech Connect

    Hirsch, M.; Hartfuss, H.; Geist, T.; de la Luna, E.

    1996-05-01

    A broadband heterodyne reflectometer operating in the frequency range 75{endash}110 GHz in extraordinary mode polarization is used at the W7-AS stellarator for both fast density profile determination and density fluctuation studies. The probing signal is amplitude modulated at a frequency 133 MHz using the envelope phase for profile evaluation and the carrier phase to determine the fluctuation information simultaneously. Separate Gaussian beam optics for final signal launch and detection permits a beam waist of about 2 cm at the reflecting layer in the plasma. Amplitude modulated detection is accomplished in the intermediate frequency part by synchronous detection after recovery of the carrier by narrow-band filtering. Voltage controlled solid state oscillators followed by active frequency multiplication allow to scan the full frequency band within less than 1 ms. For typical W7-AS operation the accessible density range is 1{times}10{sup 19} to 6{times}10{sup 19} m{sup {minus}3} for on axis magnetic field of 2.5 T and 4.5{times}10{sup 19} to 10{times}10{sup 19} m{sup {minus}3} for 1.25 T, respectively. The probed radial positions range between 0.2{lt}{ital r}/{ital a}{lt}1.1 depending on plasma conditions ({ital a}{approx_equal}17 cm). {copyright} {ital 1996 American Institute of Physics.}

  18. Full-field absolute phase measurements in the heterodyne interferometer with an electro-optic modulator

    NASA Astrophysics Data System (ADS)

    Chen, Y. L.; Hsieh, H. C.; Wu, W. T.; Su, D. C.

    2009-06-01

    A novel method for full-field absolute phase measurements in the heterodyne interferometer with an electro-optic modulator is proposed in this paper. Instead of the commonly-used half-wave voltage to drive the electro-optic modulator, a saw-tooth voltage signal with the amplitude being lower than its half-wave voltage is used. The interference signals become a group of periodical sinusoidal segments. The initial phase of each sinusoidal segment depends on the phase difference induced by the test sample. In real measurements, each segment is taken by a fast camera and becomes discrete digital points. After a series of operations, the starting point of the sampled sinusoidal segment can be determined accurately. Next, the period of the sampled sinusoidal segments is lengthened and they can be modified to a continuous sinusoidal wave by using a least-square sine fitting algorithm. The initial phase of the continuous sinusoidal wave can also be estimated. Subtracting the characteristic phase of the modulator from the initial phase, the absolute phase measured at the pixel can be obtained without the conventional reference signals. These operations are applied to other pixels, and the full-field absolute phase measurements can be achieved. The phase retardation of a quarter-wave plate is measured to show the validity of this method.

  19. THz Instrumentation for the Herschel Space Observatory's Heterodyne Instrument for Far Infrared

    NASA Technical Reports Server (NTRS)

    Pearson, J. C.; Mehdi, I.; Ward, J. S.; Maiwald, F.; Ferber, R. R.; Leduc, H. G.; Schlecht, E. T.; Gill, J. J.; Hatch, W. A.; Kawamura, J. H.; Stern, J. A.; Gaier, T. C.; Samoska, L. A.; Weinreb, S.; Bumble, B.; Pukala, D. M.; Javadi, H. H.; Finamore, B. P.; Lin, R. H.; Dengler, R. J.; Velebir, J. R.; Luong, E. M.; Tsang, R.; Peralta, A .; Wells, M.

    2004-01-01

    The Heterodyne Instrument for Far Infrared (HIFI) on ESA's Herschel Space Observatory utilizes a variety of novel RF components in its five SIS receiver channels covering 480-1250 GHz and two HEB receiver channels covering 1410-1910 GHz. The local oscillator unit will be passively cooled while the focal plane unit is cooled by superfluid helium and cold helium vapors. HIFI employs W-band GaAs amplifiers, InP HEMT low noise IF amplifiers, fixed tuned broadband planar diode multipliers, high power W-bapd Isolators, and novel material systems in the SIS mixers. The National Aeronautics and Space Administration through the Jet Propulsion Laboratory is managing the development of the highest frequency (1119-1250 GHz) SIS mixers, the local oscillators oscillators for the three highest frequency receivers as well as W-band power amplifiers, high power W-band isolators, varactor diode devices for all high frequency multipliers and InP HEMT components for all the receiver channels intermediate frequency amplifiers. The NASA developed components represent a significant advancement in the available performance. This paper presents an update of the performance and the current state of development.

  20. Heterodyne detection of the 752.033-GHz H2O rotational absorption line

    NASA Technical Reports Server (NTRS)

    Dionne, G. F.; Fitzgerald, J. F.; Chang, T. S.; Litvak, M. M.; Fetterman, H. R.

    1980-01-01

    A tunable high resolution two stage heterodyne radiometer was developed for the purpose of investigating the intensity and lineshape of the 752.033 GHz rotational transition of water vapor. Single-sideband system noise temperatures of approximately 45,000 K were obtained using a sensitive GaAs Schottky diode as the first stage mixer. First local oscillator power was supplied by a CO2 laser pumped formic acid laser (761.61 GHz), generating an X-band IF signal with theoretical line center at 9.5744 GHz. Second local oscillator power was provided by means of a 3 GHz waveguide cavity filter with only 9 dB insertion loss. In absorption measurements of the H2O taken from a laboratory simulation of a high altitude rocket plume, the center frequency of the 752 GHz line was determined to within 1 MHz of the reported value. A rotational temperature 75 K, a linewidth 5 MHz and a Doppler shift 3 MHz were measured with the line-of-sight intersecting the simulated-plume axis at a distance downstream of 30 nozzle diameters. These absorption data were obtained against continuum background radiation sources at temperatures of 1175 and 300 K.

  1. Ultraviolet Stand-off Raman Measurements Using a Gated Spatial Heterodyne Raman Spectrometer.

    PubMed

    Lamsal, Nirmal; Sharma, Shiv K; Acosta, Tayro E; Angel, S Michael

    2016-04-01

    A spatial heterodyne Raman spectrometer (SHRS) is evaluated for stand-off Raman measurements in ambient light conditions using both ultraviolet (UV) and visible pulsed lasers with a gated ICCD detector. The wide acceptance angle of the SHRS simplifies optical coupling of the spectrometer to the telescope and does not require precise laser focusing or positioning of the laser on the sample. If the laser beam wanders or loses focus on the sample, as long as it is in the field of view of the SHRS, the Raman signal will still be collected. The SHRS is not overly susceptible to vibrations, and a vibration isolated optical table was not necessary for these measurements. The system performance was assessed by measuring stand-off UV and visible Raman spectra of a wide variety of materials at distances up to 18 m, using 266 nm and 532 nm pulsed lasers, with 12.4 in. and 3.8 in. aperture telescopes, respectively. PMID:26883731

  2. Uncertainty Analysis for the Miniaturized Laser Heterodyne Radiometer (mini-LHR)

    NASA Technical Reports Server (NTRS)

    Clarke, G. B.; Wilson E. L.; Miller, J. H.; Melroy, H. R.

    2014-01-01

    Presented here is a sensitivity analysis for the miniaturized laser heterodyne radiometer (mini-LHR). This passive, ground-based instrument measures carbon dioxide (CO2) in the atmospheric column and has been under development at NASA/GSFC since 2009. The goal of this development is to produce a low-cost, easily-deployable instrument that can extend current ground measurement networks in order to (1) validate column satellite observations, (2) provide coverage in regions of limited satellite observations, (3) target regions of interest such as thawing permafrost, and (4) support the continuity of a long-term climate record. In this paper an uncertainty analysis of the instrument performance is presented and compared with results from three sets of field measurements. The signal-to-noise ratio (SNR) and corresponding uncertainty for a single scan are calculated to be 329.4+/-1.3 by deploying error propagation through the equation governing the SNR. Reported is an absorbance noise of 0.0024 for 6 averaged scans of field data, for an instrument precision of approximately 0.2 ppmv for CO2.

  3. Development and field tests of a narrowband all-reflective spatial heterodyne spectrometer.

    PubMed

    Corliss, J B; Harris, W M; Mierkiewicz, E J; Roesler, F L

    2015-10-20

    We describe the design, development, and performance of a narrowband, all-reflective, unaliased spatial heterodyne spectrometer (SHS) that has been tested in observations at the focus of the 1.6 m main telescope of the McMath-Pierce solar telescope on Kitt Peak. The all-reflective SHS described herein is a highly robust common-path Fourier transform spectrometer without moving parts that, over a limited spectral region, combines the large field of view and high resolving power characteristic of interference spectrometers but at substantially reduced instrument size and optical tolerances. The self-scanned region of wavelength space and resolving power of the SHS are determined by the beam size, the diffraction grating groove density, the number of detector elements, and the fixed orientation of a set of pilot mirrors. The results presented here represent the first successful implementation of this reflective SHS design for field use. We discuss concepts behind the unaliased reflective SHS design and report the performance of the instrument when used to observe terrestrial airglow and absorption features, the solar spectrum, and the Jovian spectrum near λ=6300  Å, at the achieved resolving power (R=λ/δλ) of R>100,000. The results confirm that reflective SHS instruments can deliver effective interferometric performance in the visible to the far-ultraviolet wavelengths with commercial optics of moderate surface quality. PMID:26560368

  4. Quad-Chip Double-Balanced Frequency Tripler

    NASA Technical Reports Server (NTRS)

    Lin, Robert H.; Ward, John S.; Bruneau, Peter J.; Mehdi, Imran; Thomas, Bertrand C.; Maestrini, Alain

    2010-01-01

    Solid-state frequency multipliers are used to produce tunable broadband sources at millimeter and submillimeter wavelengths. The maximum power produced by a single chip is limited by the electrical breakdown of the semiconductor and by the thermal management properties of the chip. The solution is to split the drive power to a frequency tripler using waveguides to divide the power among four chips, then recombine the output power from the four chips back into a single waveguide. To achieve this, a waveguide branchline quadrature hybrid coupler splits a 100-GHz input signal into two paths with a 90 relative phase shift. These two paths are split again by a pair of waveguide Y-junctions. The signals from the four outputs of the Y-junctions are tripled in frequency using balanced Schottky diode frequency triplers before being recombined with another pair of Y-junctions. A final waveguide branchline quadrature hybrid coupler completes the combination. Using four chips instead of one enables using four-times higher power input, and produces a nearly four-fold power output as compared to using a single chip. The phase shifts introduced by the quadrature hybrid couplers provide isolation for the input and output waveguides, effectively eliminating standing waves between it and surrounding components. This is accomplished without introducing the high losses and expense of ferrite isolators. A practical use of this technology is to drive local oscillators as was demonstrated around 300 GHz for a heterodyne spectrometer operating in the 2-3-THz band. Heterodyne spectroscopy in this frequency band is especially valuable for astrophysics due to the presence of a very large number of molecular spectral lines. Besides high-resolution radar and spectrographic screening applications, this technology could also be useful for laboratory spectroscopy.

  5. CONDOR - A heterodyne receiver at 1.25-1.5 THz

    NASA Astrophysics Data System (ADS)

    Wiedner, M. C.; Wieching, G.; Bielau, F.; Emprechtinger, M.; Graf, U. U.; Honingh, C. E.; Jacobs, K.; Paulussen, D.; Rettenbacher, K.; Volgenau, N. H.

    The CO N+ Deuterium Observations Receiver (CONDOR) is a heterodyne receiver that operates between 1250 - 1530 GHz. Its primary goal is to observe star-forming regions in CO, N^+, and H[2]D^+ emission. The instrument follows the standard heterodyne design. It uses a solid state local oscillator (LO), whose signal is overlaid with that of the sky using a Martin-Puplett interferometer. The heart of the receiver is a superconducting NbTiN hot electron bolometer (HEB) (Munoz et al. 2006). The bolometer has an area of 0.25 x 2.8 microns and is mounted on a SiN membrane in a waveguide mixer block. To facilitate operation at remote sites, CONDOR is the first receiver that cools the HEB with a closed-cycle system. Since HEBs are particularly sensitive to temperature fluctuations as well as modulations in LO power, we use a Pulse Tube Cooler, which has less vibration than, e.g., a Gifford-McMahon cooler. In order to further minimize vibrations and temperature fluctuations, the mixer and first amplifier are mounted on a separate plate connected via flexible heat straps to the 4K stage. CONDOR has an intermediate frequency (IF) of about 1.0 -1.8 GHz. We consistently obtain receiver noise temperatures below 1800 K and minima in the spectral Allan variances at 25 - 35 s, which is approximately the optimum individual on-source integration time. In November 2005, CONDOR was successfully commissioned on the 12-m Atacama Pathfinder Experiment (APEX) telescope and the first astronomical observations were performed (see IAU Sym. 237 contribution "CONDOR Observations of High Mass Star Formation in Orion" by Volgenau, and Wiedner et al. (2006).) Pointing observations were preformed on the Moon and Mars. The first spectral line observations were obtained of CO J=13-12 emission at 1497~GHz from several sources in Orion. (For details on the first light observations see Wiedner et al. (2006).) integration time (see Schieder & Kramer 2001). As expected, the Allan variance is dominated by the

  6. Absolute wind measurements in the lower thermosphere of Venus using infrared heterodyne spectroscopy

    NASA Technical Reports Server (NTRS)

    Goldstein, Jeffrey J.

    1990-01-01

    The first absolute wind velocities above the Venusian cloud-tops were obtained using NASA/Goddard infrared heterodyne spectrometers at the NASA Infrared Telescope Facility (IRTF) and the McMath Solar Telescope. Beam-integrated Doppler displacements in the non-thermal emission core of (12)C(16)O2 10.33 micron R(8) sampled the line of sight projection of the lower thermospheric wind field (100 to 120 km). A field-usable Lamb-dip laser stabilization system, developed for spectrometer absolute frequency calibration to less than + or - 0.1 MHz, allowed S/N-limited line of sight velocity resolution at the 1 m/s level. The spectrometer's diffraction-limited beam (1.7 arc-second HPBW at McMath, 0.9 arc-second HPBW at IRTF), and 1 to 2 arc-second seeing, provided the spatial resolution necessary for circulation model discrimination. Qualitative analysis of beam-integrated winds provided definitive evidence of a dominant subsolar-antisolar circulation in the lower thermosphere. Beam-integrated winds were modelled with a 100x100 grid over the beam, incorporating beam spatial rolloff and across-the-beam gradients in non-thermal emission intensity, line of sight projection geometry, and horizontal wind velocity. Horizontal wind velocity was derived from a 2-parameter model wind field comprised of subsolar-antisolar and zonal components. Best-fit models indicated a dominant subsolar-antisolar flow with 120 m/s cross-terminator winds and a retrograde zonal component with a 25 m/s equatorial velocity. A review of all dynamical indicators above the cloud-tops allowed development of an integrated and self-consistent picture of circulation in the 70 to 200 km range.

  7. Development of he Nanosat Oxygen A-Band Spatial Heterodyne Interferometer (NOASHIN)

    NASA Astrophysics Data System (ADS)

    Watchorn, S. R.; Noto, J.; Doe, R. A.; Fish, C. S.

    2014-12-01

    The abundance of CO2 in the mesopause region has long been shown to track with mesopause cooling, making mesopause-region temperature measurement a way to track CO2 abundance in this critical region, where climate change indications often manifest early. One of the brightest thermally excited emissions in the mesopause region is the O2 A-band, whose emission peaks are significantly modulated as a function of temperature. Thus, spectroscopic recovery of a set of A-band emission lines between 763 and 765 nm, and a comparison of peak intensities, will provide information about mesopause temperature, and thus CO2 abundance. To get global coverage of this emission with high time resolution ( < 1s) requires a high-etendue spectrometer that can resolve the target lines (resolution ~ .06 nm), preferably aboard an efficient, economical vehicle capable of the global coverage that would be most beneficial to existing mesopause models. Nanosatellites are such a vehicle. The NOASHIN instrument is a spectrometer very well suited to the low size, weight, and power (SWAP) of the nanosat platform. It is built around a Spatial Heterodyne Spectrometer (SHS), a monolithic Fourier transform spectrometer with no moving parts that shares the high etendue, high resolution advantages of conventional interferometers in a robust package ideal for space-based platforms. The NOASHIN instrument will be developed for, ultimately, a 1-U CubeSat, nadir-viewing nightglow measurement payload, used in a pushbroom imaging configuration from low-Earth orbit (~ 650 km), with an exposure time of < 1 s, leading to a target footprint of 9-km along-track. The current development project will integrate a prototype NOASHIN SHS monolith into a 1.5-U CubeSat engineering prototype at the design SWAP requirements. The prototype will be detect emissions of the expected intensity (~700 R) from a lab source near the A-band and offload data onto a local computer for analysis.

  8. Three-dimensional vibration of the stapes measured with a heterodyne interferometer

    NASA Astrophysics Data System (ADS)

    Decraemer, Willem F.; Khanna, Shyam M.

    1998-06-01

    The acoustical energy is transmitted for the tympanic membrane to the inner ear by the middle ear ossicles. It is generally accepted that the ossicles rotate around a fixed axis and function as mechanical levers.Under this concept the motions of malleus and stapes are 1D. A series of measurements of malleus vibration made through the intact ear canal has clearly shown that the malleus motion is not a rotation about a fixed suspension axis but that translation and rotation components in all three dimensions are present and change dramatically over the frequency of hearing. An important question is what role these 3D vibrations play in the function of hearing. If the three components of vibration were utilized in the stimulation of the inner ear, they should also be present in the motion of the stapes. The motion of the stapes has been difficult to measure in the past because access is limited and only a small portion of the crura can be seen. In order to get a better access to the stapes a novel preparation of the cat temporal bone was utilized. To determine its 3D motion, the vibration of the stapes was measured wit a confocal heterodyne interferometer at three points form different viewing angles.Its geometry was also measured. Assuming that the system behaves as a rigid body this data was used to generate an animation of the stapes motion. The stapes motion was found to be three dimensional. This suggests that these vibrations play a functional role in hearing.

  9. Remote Measurement of Turbulent Wind Spectra by Heterodyne DopplerLidar Technique.

    NASA Astrophysics Data System (ADS)

    Drobinski, Philippe; Dabas, Alain M.; Flamant, Pierre H.

    2000-12-01

    Heterodyne Doppler lidars (HDLs) are used to monitor atmospheric wind field and wind turbulence at remote distance. This last application calls for the derivation of wind spectra, which can be characterized by the dissipation rate and the -spectral peak (or outer scale of turbulence). However, the HDL technique may suffer two problems. First, HDL measurements result in spatial averaging of the true wind velocity along the line of sight, because of the laser pulse duration and windowing effect on processed signals. Second, even at high signal-to-noise ratio, the retrieved turbulent velocity field may be contaminated by errors due to speckle fluctuations. It is shown that both spatial averaging and error contribution to the wind spectra can be modeled starting from the transmitted laser pulse characteristics and signal processing parameters, so that their effect can be predicted. The rms difference between the estimated and predicted turbulent spectra is minimized in order to infer the turbulence parameters. This procedure is tested on simulated signals and validated on actual data taken by a 10-m HDL during a field campaign in 1995.The data collected during two periods of two consecutive days (9 and 10 March and 13 and 14 March 1995) are analyzed. On these days, moderate to light winds prevailed. The stability parameter zi/LMO indicated slightly unstable conditions with sometimes probable convection. The HDL measured energy dissipation rates ranging between 0.7 × 103 and 8 × 103 m2 s3 in good agreement with sonic anemometer measurements. The -spectral peak ranged between 200 and 600 m.

  10. SuperCam: a 64-pixel heterodyne imaging array for the 870-micron atmospheric window

    NASA Astrophysics Data System (ADS)

    Groppi, Christopher; Walker, Christopher; Kulesa, Craig; Pütz, Patrick; Golish, Dathon; Gensheimer, Paul; Hedden, Abigail; Bussmann, Shane; Weinreb, Sander; Kuiper, Tom; Kooi, Jacob; Jones, Glenn; Bardin, Joseph; Mani, Hamdi; Lichtenberger, Arthur; Narayanan, Gopal

    2006-06-01

    We report on the development of SuperCam, a 64 pixel, superheterodyne camera designed for operation in the astrophysically important 870 μm atmospheric window. SuperCam will be used to answer fundamental questions about the physics and chemistry of molecular clouds in the Galaxy and their direct relation to star and planet formation. The advent of such a system will provide an order of magnitude increase in mapping speed over what is now available and revolutionize how observational astronomy is performed in this important wavelength regime. Unlike the situation with bolometric detectors, heterodyne receiver systems are coherent, retaining information about both the amplitude and phase of the incident photon stream. From this information a high resolution spectrum of the incident light can be obtained without multiplexing. SuperCam will be constructed by stacking eight, 1×8 rows of fixed tuned, SIS mixers. The IF output of each mixer will be connected to a low-noise, broadband MMIC amplifier integrated into the mixer block. The instantaneous IF bandwidth of each pixel will be ~2 GHz, with a center frequency of 5 GHz. A spectrum of the central 500 MHz of each IF band will be provided by the array spectrometer. Local oscillator power is provided by a frequency multiplier whose output is divided between the pixels by using a matrix of waveguide power dividers. The mixer array will be cooled to 4K by a closed-cycle refrigeration system. SuperCam will reside at the Cassegrain focus of the 10m Heinrich Hertz telescope (HHT). A prototype single row of the array will be tested on the HHT in 2006, with the first engineering run of the full array in late 2007. The array is designed and constructed so that it may be readily scaled to higher frequencies.

  11. Skylab water balance analysis

    NASA Technical Reports Server (NTRS)

    Leonard, J. I.

    1977-01-01

    The water balance of the Skylab crew was analyzed. Evaporative water loss using a whole body input/output balance equation, water, body tissue, and energy balance was analyzed. The approach utilizes the results of several major Skylab medical experiments. Subsystems were designed for the use of the software necessary for the analysis. A partitional water balance that graphically depicts the changes due to water intake is presented. The energy balance analysis determines the net available energy to the individual crewman during any period. The balances produce a visual description of the total change of a particular body component during the course of the mission. The information is salvaged from metabolic balance data if certain techniques are used to reduce errors inherent in the balance method.

  12. What is balance?

    PubMed

    Pollock, A S; Durward, B R; Rowe, P J; Paul, J P

    2000-08-01

    Balance is a term frequently used by health professionals working in a wide variety of clinical specialities. There is no universally accepted definition of human balance, or related terms. This article identifies mechanical definitions of balance and introduces clinical definitions of balance and postural control. Postural control is defined as the act of maintaining, achieving or restoring a state of balance during any posture or activity. Postural control strategies may be either predictive or reactive, and may involve either a fixed-support or a change-in-support response. Clinical tests of balance assess different components of balance ability. Health professionals should select clinical assessments based on a sound knowledge and understanding of the classification of balance and postural control strategies. PMID:10945424

  13. Polarization-balanced beamsplitter

    DOEpatents

    Decker, D.E.

    1998-02-17

    A beamsplitter assembly is disclosed that includes several beamsplitter cubes arranged to define a plurality of polarization-balanced light paths. Each polarization-balanced light path contains one or more balanced pairs of light paths, where each balanced pair of light paths includes either two transmission light paths with orthogonal polarization effects or two reflection light paths with orthogonal polarization effects. The orthogonal pairing of said transmission and reflection light paths cancels polarization effects otherwise caused by beamsplitting. 10 figs.

  14. Polarization-balanced beamsplitter

    DOEpatents

    Decker, Derek E.

    1998-01-01

    A beamsplitter assembly that includes several beamsplitter cubes arranged to define a plurality of polarization-balanced light paths. Each polarization-balanced light path contains one or more balanced pairs of light paths, where each balanced pair of light paths includes either two transmission light paths with orthogonal polarization effects or two reflection light paths with orthogonal polarization effects. The orthogonal pairing of said transmission and reflection light paths cancels polarization effects otherwise caused by beamsplitting.

  15. Wind Tunnel Balances

    NASA Technical Reports Server (NTRS)

    Warner, Edward P; Norton, F H

    1920-01-01

    Report embodies a description of the balance designed and constructed for the use of the National Advisory Committee for Aeronautics at Langley Field, and also deals with the theory of sensitivity of balances and with the errors to which wind tunnel balances of various types are subject.

  16. Coaching for Balance.

    ERIC Educational Resources Information Center

    Larson, Bonnie

    2001-01-01

    Discusses coaching for balance the integration of the whole self: physical (body), intellectual (mind), spiritual (soul), and emotional (heart). Offers four ways to identify problems and tell whether someone is out of balance and four coaching techniques for creating balance. (Contains 11 references.) (JOW)

  17. Full-field heterodyne polariscope with an image signal processing method for principal axis and phase retardation measurements

    SciTech Connect

    Lo, Y.-L.; Chih, H.-W.; Yeh, C.-Y.; Yu, T.-C

    2006-11-01

    We develop a heterodyne polariscope for measuring the two-dimensional principal axis and phase retardation in a linear birefringence material using novel three-frame and two-frame integrating-bucket methods and a CCD. By using a complex programmable logic device to provide an external trigger to the CCD, integrating buckets with multiple frames are achieved. The advantages of the proposed three-frame and two-frame integrating-bucket methods include a simpler signal processing algorithm based on fewer frames and the elimination of flyback error caused by a sawtooth modulation signal at higher frequencies.

  18. Time-resolved ion velocity distribution in a cylindrical Hall thruster: heterodyne-based experiment and modeling.

    PubMed

    Diallo, A; Keller, S; Shi, Y; Raitses, Y; Mazouffre, S

    2015-03-01

    Time-resolved variations of the ion velocity distribution function (IVDF) are measured in the cylindrical Hall thruster using a novel heterodyne method based on the laser-induced fluorescence technique. This method consists in inducing modulations of the discharge plasma at frequencies that enable the coupling to the breathing mode. Using a harmonic decomposition of the IVDF, one can extract each harmonic component of the IVDF from which the time-resolved IVDF is reconstructed. In addition, simulations have been performed assuming a sloshing of the IVDF during the modulation that show agreement between the simulated and measured first order perturbation of the IVDF. PMID:25832228

  19. Time-resolved ion velocity distribution in a cylindrical Hall thruster: Heterodyne-based experiment and modeling

    NASA Astrophysics Data System (ADS)

    Diallo, A.; Keller, S.; Shi, Y.; Raitses, Y.; Mazouffre, S.

    2015-03-01

    Time-resolved variations of the ion velocity distribution function (IVDF) are measured in the cylindrical Hall thruster using a novel heterodyne method based on the laser-induced fluorescence technique. This method consists in inducing modulations of the discharge plasma at frequencies that enable the coupling to the breathing mode. Using a harmonic decomposition of the IVDF, one can extract each harmonic component of the IVDF from which the time-resolved IVDF is reconstructed. In addition, simulations have been performed assuming a sloshing of the IVDF during the modulation that show agreement between the simulated and measured first order perturbation of the IVDF.

  20. Reconceptualizing balance: attributes associated with balance performance.

    PubMed

    Thomas, Julia C; Odonkor, Charles; Griffith, Laura; Holt, Nicole; Percac-Lima, Sanja; Leveille, Suzanne; Ni, Pensheng; Latham, Nancy K; Jette, Alan M; Bean, Jonathan F

    2014-09-01

    Balance tests are commonly used to screen for impairments that put older adults at risk for falls. The purpose of this study was to determine the attributes that were associated with balance performance as measured by the Frailty and Injuries: Cooperative Studies of Intervention Techniques (FICSIT) balance test. This study was a cross-sectional secondary analysis of baseline data from a longitudinal cohort study, the Boston Rehabilitative Impairment Study of the Elderly (Boston RISE). Boston RISE was performed in an outpatient rehabilitation research center and evaluated Boston area primary care patients aged 65 to 96 (N=364) with self-reported difficulty or task-modification climbing a flight of stairs or walking 1/2 of a mile. The outcome measure was standing balance as measured by the FICSIT-4 balance assessment. Other measures included: self-efficacy, pain, depression, executive function, vision, sensory loss, reaction time, kyphosis, leg range of motion, trunk extensor muscle endurance, leg strength and leg velocity at peak power. Participants were 67% female, had an average age of 76.5 (±7.0) years, an average of 4.1 (±2.0) chronic conditions, and an average FICSIT-4 score of 6.7 (±2.2) out of 9. After adjusting for age and gender, attributes significantly associated with balance performance were falls self-efficacy, trunk extensor muscle endurance, sensory loss, and leg velocity at peak power. FICSIT-4 balance performance is associated with a number of behavioral and physiologic attributes, many of which are amenable to rehabilitative treatment. Our findings support a consideration of balance as multidimensional activity as proposed by the current International Classification of Functioning, Disability, and Health (ICF) model. PMID:24952097

  1. Infrared heterodyne spectroscopy of astronomical and laboratory sources at 8.5 micron. [absorption line profiles of nitrogen oxide and black body emission from Moon and Mars

    NASA Technical Reports Server (NTRS)

    Mumma, M.; Kostiuk, T.; Cohen, S.; Buhl, D.; Vonthuna, P. C.

    1974-01-01

    The first infrared heterodyne spectrometer using tuneable semiconductor (PbSe) diode lasers has been constructed and was used near 8.5 micron to measure absorption line profiles of N2O in the laboratory and black body emission from the Moon and from Mars. Spectral information was recorded over a 200 MHz bandwidth using an 8-channel filter bank. The resolution was 25 MHz and the minimum detectable (black body) power was 1 x 10 to the minus 16th power watts for 8 minutes of integration. The results demonstrate the usefulness of heterodyne spectroscopy for the study of remote and local sources in the infrared.

  2. Autonomous Field Measurements of CO2 in the Atmospheric Column with the Miniaturized Laser Heterodyne Radiometer (Mini-LHR)

    NASA Technical Reports Server (NTRS)

    Melroy, H. R.; Wilson, E. L.; Clarke, G. B.; Ott, L. E.; Mao, J.; Ramanathan, A. K.; McLinden, M. L.

    2015-01-01

    We present column CO2 measurements taken by the passive Miniaturized Laser Heterodyne Radiometer (Mini-LHR) at 1611.51 nm at the Mauna Loa Observatory (MLO) in Hawaii. The Mini-LHR was operated autonomously, during the month of May 2013 at this site, working in tandem with an AERONET sun photometer that measures aerosol optical depth at 15 minute intervals during daylight hours. Laser Heterodyne Radiometry has been used since the 1970s to measure atmospheric gases such as ozone, water vapor, methane, ammonia, chlorine monoxide, and nitrous oxide. This iteration of the technology utilizes distributed feedback lasers to produce a low-cost, small, portable sensor that has potential for global deployment. Applications of this instrument include supplementation of existing monitoring networks to provide denser global coverage, providing validation for larger satellite missions, and targeting regions of carbon flux uncertainty. Also presented here is a preliminary retrieval analysis and the performance analysis that demonstrates that the Mini-LHR responds extremely well to changes in the atmospheric absorption.

  3. Autonomous field measurements of CO2 in the atmospheric column with the miniaturized laser heterodyne radiometer (Mini-LHR)

    NASA Astrophysics Data System (ADS)

    Melroy, H. R.; Wilson, E. L.; Clarke, G. B.; Ott, L. E.; Mao, J.; Ramanathan, A. K.; McLinden, M. L.

    2015-09-01

    We present column CO2 measurements taken by the passive miniaturized laser heterodyne radiometer (Mini-LHR) at 1611.51 nm at the Mauna Loa Observatory in Hawaii. The Mini-LHR was operated autonomously, during the month of May 2013 at this site, working in tandem with an AERONET sun photometer that measures aerosol optical depth at 15-min intervals during daylight hours. Laser heterodyne radiometry has been used since the 1970s to measure atmospheric gases such as ozone, water vapor, methane, ammonia, chlorine monoxide, and nitrous oxide. This iteration of the technology utilizes distributed feedback lasers to produce a low-cost, small, portable sensor that has potential for global deployment. Applications of this instrument include supplementation of existing monitoring networks to provide denser global coverage, providing validation for larger satellite missions, and targeting regions of carbon flux uncertainty. Also presented here are preliminary retrieval analysis and the performance analysis that demonstrate that the Mini-LHR responds extremely well to changes in the atmospheric absorption.

  4. Investigation of Bulk Indium-Antimonide as a Heterodyne Detector for the Submillimeter Wavelength Region

    NASA Astrophysics Data System (ADS)

    Brown, Elliott R.

    Bulk n-InSb is investigated as a heterodyne detector for the submillimeter wavelength region. Two modes of operation are investigated: (1) the Rollin or hot electron bolometer mode (zero magnetic field), and (2) the Putley mode (quantizing magnetic field). The highlight of the thesis work is the pioneering demonstration of the Putley mode mixer at several frequencies. For example, a double -sideband system noise temperature of about 510K was obtained using a 812 GHz methanol laser for the local oscillator. This performance is at least a factor of 10 more sensitive than any other performance reported to date at the same frequency. In addition, the Putley mode mixer achieved system noise temperatures of 250K at 492 GHz and 350K at 625 GHz. The 492 GHz performance is about 50% better and the 625 GHz is about 100% better than previous best performances established by the Rollin -mode mixer. To achieve these results, it was necessary to design a totally new ultra-low noise, room-temperature preamp to handle the higher source impedance imposed by the Putley mode operation. This preamp has considerably less input capacitance than comparably noisy, ambient designs. In addition to advancing receiver technology, this thesis also presents several novel results regarding the physics of n-InSb at low temperatures. A Fourier transform spectrometer was constructed and used to measure the submillimeter wave absorption coefficient of relatively pure material at liquid helium temperatures and in zero magnetic field. Below 4.2K, the absorption coefficient was found to decrease with frequency much faster than prediced by Drudian theory. Much better agreement with experiment was obtained using a quantum theory based on inverse-Bremmstrahlung in a solid. Also the noise of the Rollin-mode detector at 4.2K was accurately measured and compared with theory. The power spectrum is found to be well fit by a recent theory of non-equilibrium noise due to Mather. Surprisingly, when biased for

  5. The First Detection of Diffuse Interstellar [OII] Emission from the Milky Way using Spatial Heterodyne Spectroscopy

    NASA Astrophysics Data System (ADS)

    Mierkiewicz, E. J.; Roesler, F. L.; Harlander, J. M.; Reynolds, R. J.; Jaehnig, K. P.

    2004-12-01

    Using a newly developed Spatial Heterodyne Spectrometer (SHS), we have achieved the first detection of diffuse [OII] 372.6 nm and 372.9 nm emission lines from the warm (10,000 K), low density (0.1 cm-3) ionized component of our Galaxy's interstellar medium (WIM). These [OII] lines are a principal coolant for this wide spread, photoionized gas and are a potential tracer of variations in the gas temperature resulting from unidentified interstellar heating processes that appear to be acting within the Galaxy's disk and halo. We have also detected numerous, weak airglow lines, including terrestrial [OII] emission. In our SHS system, Fizeau fringes of wavenumber-dependent spatial frequency are produced by a Michelson interferometer modified by replacing the return mirrors with diffraction gratings. These fringes are recorded on a position sensitive detector and Fourier transformed to recover a spectrum over a limited range centered at the grating Littrow wavenumber. SHS combines interferometric and field-widening gains to achieve sensitivities much larger than conventional grating instruments of similar size and resolving power, and comparable to the Wisconsin Hα Mapper (WHAM) Fabry-Perot, but in the near UV where WHAM cannot observe. Our early results confirm the superb performance of the SHS technique for measurements of spatially extended faint emissions, including the first detection of [OII] emission lines extending out to 20 degrees from the Galactic equator in the longitude range of 110 to 150 degrees. [OII] intensities range from tens of Rayleighs near the Galactic plane to less than one Rayleigh at high Galactic latitudes. The [OII] line profiles clearly show structure indicating emission along the lines of sight from both local interstellar gas and more distant gas in the Perseus spiral arm. Preliminary line ratio comparisons with WHAM [NII] (658.4 nm) and Hα (656.3 nm) observations confirm the utility of the [OII] observations as a temperature diagnostic

  6. A polarization-based frequency scanning interferometer and the signal processing acceleration method based on parallel processing architecture

    NASA Astrophysics Data System (ADS)

    Lee, Seung Hyun; Kim, Min Young

    FSI system, one of the most promising optical surface measurement techniques, generally results in superior optical performance comparing with other 3-dimensional measuring methods as its hardware structure is fixed in operation and only the light frequency is scanned in a specific spectral band without vertical scanning of the target surface or the objective lens. FSI system collects a set of images of interference fringe by changing the frequency of light source. After that, it transforms intensity data of acquired image into frequency information, and calculates the height profile of target objects with the help of frequency analysis based on FFT. However, it still suffers from optical noise from target surface and relatively long processing time due to the number of images acquired in frequency scanning phase. First, a polarization-based frequency scanning interferometry (PFSI) is proposed for optical noise robustness. It consists of tunable laser for light source, λ/4 plate in front of reference mirror, λ/4 plate in front of target object, polarizing beam splitter, polarizer in front of image sensor, polarizer in front of the fiber coupled light source, λ/2 plate between PBS and polarizer of the light source. Using the proposed system, we can solve the problem low contrast of acquired fringe image by using polarization technique. Also, we can control light distribution of object beam and reference beam. Second, the signal processing acceleration method is proposed for PFSI, based on parallel processing architecture, which consists of parallel processing hardware and software such as GPU (Graphic Processing Unit) and CUDA (Compute Unified Device Architecture). As a result, the processing time reaches into tact time level of real-time processing. Finally, the proposed system is evaluated in terms of accuracy and processing speed through a series of experiment and the obtained results show the effectiveness of the proposed system and method.

  7. Identifying Balance in a Balanced Scorecard System

    ERIC Educational Resources Information Center

    Aravamudhan, Suhanya; Kamalanabhan, T. J.

    2007-01-01

    In recent years, strategic management concepts seem to be gaining greater attention from the academicians and the practitioner's alike. Balanced Scorecard (BSC) concept is one such management concepts that has spread in worldwide business and consulting communities. The BSC translates mission and vision statements into a comprehensive set of…

  8. Judicial Checks and Balances

    ERIC Educational Resources Information Center

    La Porta, Rafael; Lopez-de-Silanes, Florencio; Pop-Eleches, Cristian; Shleifer, Andrei

    2004-01-01

    In the Anglo-American constitutional tradition, judicial checks and balances are often seen as crucial guarantees of freedom. Hayek distinguishes two ways in which the judiciary provides such checks and balances: judicial independence and constitutional review. We create a new database of constitutional rules in 71 countries that reflect these…

  9. Inevitability of Balance Restoration

    PubMed Central

    2010-01-01

    Prolonged imbalance between input and output of any element in a living organism is incompatible with life. The duration of imbalance varies, but eventually balance is achieved. This rule applies to any quantifiable element in a compartment of finite capacity. Transient discrepancies occur regularly, but given sufficient time, balance is always achieved, because permanent imbalance is impossible, and the mechanism for eventual restoration of balance is foolproof. The kidney is a central player for balance restoration of fluid and electrolytes, but the smartness of the kidney is not the reason for perfect balance. The kidney merely accelerates the process. The most crucial element of the control system is that discrepancy between intake and output inevitably leads to a change in total content of the element in the system, and uncorrected balance has a cumulative effect on the overall content of the element. In a living organism, the speed of restoration of balance depends on the permissible duration of imbalance without death or severe disability. The three main factors that influence the speed of balance restoration are: magnitude of flux, basal store, and capacity for additional storage. For most electrolytes, total capacity is such that a substantial discrepancy is not possible for more than a week or two. Most control mechanisms correct abnormality partially. The infinite gain control mechanism is unique in that abnormality is completely corrected upon completion of compensation. PMID:21468193

  10. Chemical Equation Balancing.

    ERIC Educational Resources Information Center

    Blakley, G. R.

    1982-01-01

    Reviews mathematical techniques for solving systems of homogeneous linear equations and demonstrates that the algebraic method of balancing chemical equations is a matter of solving a system of homogeneous linear equations. FORTRAN programs using this matrix method to chemical equation balancing are available from the author. (JN)

  11. Leadership: A Balancing Act

    ERIC Educational Resources Information Center

    Hines, Thomas E.

    2011-01-01

    Maintaining balance in leadership can be difficult because balance is affected by the personality, strengths, and attitudes of the leader as well as the complicated environment within and outside the community college itself. This article explores what being a leader at the community college means, what the threats are to effective leadership, and…

  12. The Technology Balance Beam

    ERIC Educational Resources Information Center

    Coulson, Eddie K.

    2006-01-01

    "The Technology Balance Beam" is designed to question the role of technology within school districts. This case study chronicles a typical school district in relation to the school district's implementation of technology beginning in the 1995-1996 school year. The fundamental question that this scenario raises is, What is the balance between…

  13. A Balance of Power?

    ERIC Educational Resources Information Center

    Mosey, Edward

    1991-01-01

    The booming economy of the Pacific Northwest region promotes the dilemma of balancing the need for increased electrical power with the desire to maintain that region's unspoiled natural environment. Pertinent factors discussed within the balance equation are population trends, economic considerations, industrial power requirements, and…

  14. Balanced Literacy Instruction.

    ERIC Educational Resources Information Center

    Pressley, Michael; Roehrig, Alysia; Bogner, Kristen; Raphael, Lisa M.; Dolezal, Sara

    2002-01-01

    This article reviews the evidence for balanced literacy instruction in the elementary years. The case is made that the balanced instructional model is particularly appropriate and beneficial for students who have initial difficulties in learning to read and write. Key features of successful reading instruction programs are described. (Contains…

  15. Data Retrieval Algorithm and Uncertainty Analysis for a Miniaturized, Laser Heterodyne Radiometer

    NASA Astrophysics Data System (ADS)

    Miller, J. H.; Melroy, H.; Wilson, E. L.; Clarke, G. B.

    2013-12-01

    In a collaboration between NASA Goddard Space Flight Center and George Washington University, a low-cost, surface instrument is being developed that can continuously monitor key carbon cycle gases in the atmospheric column: carbon dioxide (CO2) and methane (CH4). The instrument is based on a miniaturized, laser heterodyne radiometer (LHR) using near infrared (NIR) telecom lasers. Despite relatively weak absorption line strengths in this spectral region, spectrally-resolved atmospheric column absorptions for these two molecules fall in the range of 60-80% and thus sensitive and precise measurements of column concentrations are possible. Further, because the LHR technique has the potential for sub-Doppler spectral resolution, the possibility exists for interrogating line shapes to extract altitude profiles of the greenhouse gases. From late 2012 through 2013 the instrument was deployed for a variety of field measurements including at Park Falls, Wisconsin; Castle Airport near Atwater, California; and at the NOAA Mauna Loa Observatory in Hawaii. For each subsequent campaign, improvement in the figures of merit for the instrument (notably spectral sweep time and absorbance noise) has been observed. For the latter, the absorbance noise is approaching 0.002 optical density (OD) noise on a 1.8 OD signal. This presentation presents an overview of the measurement campaigns in the context of the data retrieval algorithm under development at GW for the calculation of column concentrations from them. For light transmission through the atmosphere, it is necessary to account for variation of pressure, temperature, composition, and refractive index through the atmosphere that are all functions of latitude, longitude, time of day, altitude, etc. In our initial work we began with coding developed under the LOWTRAN and MODTRAN programs by the AFOSR (and others). We also assumed temperature and pressure profiles from the 1976 US Standard Atmosphere and used the US Naval Observatory

  16. A heterodyne receiver for the submillimeter wavelength region based on cyclotron resonance in InSb at low temperatures

    NASA Technical Reports Server (NTRS)

    Brown, E. R.; Keene, J.; Phillips, T. G.

    1985-01-01

    A heterodyne receiver has been developed for observation of interstellar atomic and molecular lines in the submillimeter wavelength region. The main detection mechanism of the device is cyclotron resonance in bulk n-InSb due to a quantized magnetic field. Measurements were carried out between 492 and 812 GHz in order to determine the sensitivity of the device for astrophysical applications. Double sideband receiver noise temperatures of 250 K at 492 GHz; 350 K at 625 GHz; and 510 K at 812 GHz were obtained. The magnetic induction for the laboratory tests was about 2.5 KG and the mixer operating temperature was about 1.6 K. It is shown that the receiver is sensitive enough to identify the narrow rotation lines of diatomic hydrides in dark-cloud regions of the interstellar medium.

  17. Space-borne remote sensing of CO2 by IPDA lidar with heterodyne detection: random error estimation

    NASA Astrophysics Data System (ADS)

    Matvienko, G. G.; Sukhanov, A. Y.

    2015-11-01

    Possibilities of measuring the CO2 column concentration by spaceborne integrated path differential lidar (IPDA) signals in the near IR absorption bands are investigated. It is shown that coherent detection principles applied in the nearinfrared spectral region promise a high sensitivity for the measurement of the integrated dry air column mixing ratio of the CO2. The simulations indicate that for CO2 the target observational requirements (0.2%) for the relative random error can be met with telescope aperture 0.5 m, detector bandwidth 10 MHz, laser energy per impulse 0.3 mJ and averaging 7500 impulses. It should also be noted that heterodyne technique allows to significantly reduce laser power and receiver overall dimensions compared to direct detection.

  18. A sensitivity-enhanced optical heterodyne polarimeter for the measurement of optical rotation angle of chiral media

    NASA Astrophysics Data System (ADS)

    Tsai, Ying C.; Wu, Chien M.

    2004-09-01

    A novel heterodyne polarimeter is designed to measure the concentration of chiral media. Optical common-path for the interference of the TE and TM waves, after a polarizer, is set up in our system to reduce noises from the environment. A phase-variable waveplate is placed behind the sample to enhance the phase signal change of rotation of polarization introduced by the sample itself. This enhancement can be excess two orders in amplitude when the retardation of the phase-variable plate is set close to 180 degree. With this polarimeter, the measurement of optical rotation angle with high sensitivity of 6.5×10-4 degree experimentally can be achieved when phase retardation of the phase-variable waveplate is 178.5 degree. We expect that, by further improvement, it can be applied in noninvasive blood glucose concentration monitoring for diabetics in the future.

  19. Two color multichannel heterodyne interferometer set up for high spatial resolution electron density profile measurements in TJ-II

    SciTech Connect

    Pedreira, P.; Criado, A. R.; Acedo, P.; Esteban, L.; Sanchez, M.; Sanchez, J.

    2010-10-15

    A high spatial resolution two color [CO{sub 2}, {lambda}=10.6 {mu}m/Nd:YAG (Nd:YAG denotes neodymium-doped yttrium aluminum garnet), and {lambda}=1.064 {mu}m] expanded-beam multichannel heterodyne interferometer has been installed on the TJ-II stellarator. Careful design of the optical system has allowed complete control on the evolution of both Gaussian beams along the interferometer, as well as the evaluation and optimization of the spatial resolution to be expected in the measurements. Five CO{sub 2} (measurement) channels and three Nd:YAG (vibration compensation) channels have been used to illuminate the plasma with a probe beam of 100 mm size. An optimum interpolation method has been applied to recover both interferometric phasefronts prior to mechanical vibration subtraction. The first results of the installed diagnostic are presented in this paper.

  20. Design and characterization of a 32-channel heterodyne radiometer for electron cyclotron emission measurements on experimental advanced superconducting tokamak

    SciTech Connect

    Han, X.; Liu, X.; Liu, Y. Li, E. Z.; Hu, L. Q.; Gao, X.; Domier, C. W.; Luhmann, N. C.

    2014-07-15

    A 32-channel heterodyne radiometer has been developed for the measurement of electron cyclotron emission (ECE) on the experimental advanced superconducting tokamak (EAST). This system collects X-mode ECE radiation spanning a frequency range of 104–168 GHz, where the frequency coverage corresponds to a full radial coverage for the case with a toroidal magnetic field of 2.3 T. The frequency range is equally spaced every 2 GHz from 105.1 to 167.1 GHz with an RF bandwidth of ∼500 MHz and the video bandwidth can be switched among 50, 100, 200, and 400 kHz. Design objectives and characterization of the system are presented in this paper. Preliminary results for plasma operation are also presented.

  1. Modeling and Analysis of Phase Fluctuation in a High-Precision Roll Angle Measurement Based on a Heterodyne Interferometer.

    PubMed

    Huang, Junhui; Wang, Zhao; Gao, Jianmin; Yu, Bao

    2016-01-01

    Heterodyne interferometry is a high-precision method applied in roll angle measurements. Phase metering is essential for high precision. During a high-precision measurement, a phase fluctuation appears even when the roll angle does not vary, which has never been analyzed before. Herein, the reason for the phase fluctuation is revealed, which results from the frequency-difference fluctuation and time difference between measurement and reference beams. A mathematical model of that phase-fluctuation mechanism is established, and that model provides a theoretical basis for analyzing and reducing the phase fluctuation. The impact that the main factors have on the phase metering is analyzed quantitatively, and experiments are carried out to validate the model. Finally, the phase fluctuation decreases to 0.02° by frequency reduction, which conversely verifies the theoretical model. PMID:27490552

  2. Measurement method for roll angular displacement with a high resolution by using diffraction gratings and a heterodyne interferometer

    SciTech Connect

    Tang, Shanzhi; Wang, Zhao; Gao, Jianmin; Guo, Junjie

    2014-04-15

    The roll angle measurement is difficult to be achieved directly using a typical commercial interferometer due to its low sensitivity in axial direction, where the axial direction is orthogonal to the plane of the roll angular displacement. A roll angle measurement method combined diffraction gratings with a laser heterodyne interferometer is discussed in this paper. The diffraction grating placed in the plane of a roll angular displacement and the interferometer arranged in the plane's orthogonal direction, constitute the measurement pattern for the roll angle with high resolution. The roll angular displacement, considered as the linear, can be tested precisely when the corresponding angle is very small. Using the proposed method, the angle roll measurement obtains the high resolution of 0.002{sup ″}. Experiment has proved its feasibility and practicability.

  3. Submicrometer-Resolution Mapping of Ultraweak 355-nm Absorption in HfO2 Monolayers Using Photothermal Heterodyne Imaging

    SciTech Connect

    Papernov, S.; Tait, A.; Bittle, W.; Schmid, A.W.; Oliver, J.B.; Kupinski, P.

    2011-02-01

    Nanosecond-pulse UV-laser-damage initiation in multilayer coatings comprised from metal oxide as a high-index component, and silica oxide as a low-index material, is strongly linked to metal oxide. The nature of the absorbing species and their physical properties remain unknown because of extremely small sizes. Previous experimental evidence provided by high-resolution mapping of damage morphology points to a few-nanometer scale of these absorbers. This work demonstrates submicrometer mapping of 355-nm absorption in HfO2 monolayers using a recently developed photothermal heterodyne imaging technique. Comparison of absorption maps with spatial distribution of UV pulsed-laser–induced damage morphology allows one to better estimate the size and densities of nanoscale absorbing defects in hafnia thin films. Possible defect-formation mechanisms are discussed.

  4. Frequency stabilization of a 1083 nm fiber laser to ⁴He transition lines with optical heterodyne saturation spectroscopies.

    PubMed

    Gong, W; Peng, X; Li, W; Guo, H

    2014-07-01

    Two kinds of optical heterodyne saturation spectroscopies, namely, frequency modulation spectroscopy (FMS) and modulation transfer spectroscopy (MTS), are demonstrated for locking a fiber laser to the transition lines of metastable (4)He atoms around 1083 nm. The servo-loop error signals of FMS and MTS for stabilizing laser frequency are optimized by studying the dependence of the peak-to-peak amplitude and slope on the optical power of pump and probe beams. A comparison of the stabilization performances of FMS/MTS and polarization spectroscopy (PS) is presented, which shows that MTS exhibits relatively superior performance with the least laser frequency fluctuation due to its flat-background dispersive signal, originated from the four-wave mixing process. The Allan deviation of the stabilized laser frequency is 5.4 × 10(-12)@100 s with MTS for data acquired in 1000 s, which is sufficiently applicable for fields like laser cooling, optical pumping, and optical magnetometry. PMID:25085123

  5. Bend Vibration of Surface Water Investigated by Heterodyne-Detected Sum Frequency Generation and Theoretical Study: Dominant Role of Quadrupole.

    PubMed

    Kundu, Achintya; Tanaka, Shogo; Ishiyama, Tatsuya; Ahmed, Mohammed; Inoue, Ken-Ichi; Nihonyanagi, Satoshi; Sawai, Hiromi; Yamaguchi, Shoichi; Morita, Akihiro; Tahara, Tahei

    2016-07-01

    Heterodyne-detected vibrational sum frequency generation spectroscopy was applied to the water surface for measuring the imaginary part of second-order nonlinear susceptibility (Im χ((2))) spectrum in the bend frequency region for the first time. The observed Im χ((2)) spectrum shows an overall positive band around 1650 cm(-1), contradicting former theoretical predictions. We further found that the Im χ((2)) spectrum of NaI aqueous solution exhibits an even larger positive band, which is apparently contrary to the flip-flop orientation of surface water. These unexpected observations are elucidated by calculating quadrupole contributions beyond the conventional dipole approximation. It is indicated that the Im χ((2)) spectrum in the bend region has a large quadrupole contribution from the bulk water. PMID:27322348

  6. Heterodyne detection at near-infrared wavelengths with a superconducting NbN hot-electron bolometer mixer.

    PubMed

    Lobanov, Yury; Shcherbatenko, Michael; Shurakov, Alexander; Rodin, Alexander V; Klimchuk, Artem; Nadezhdinsky, Alexander I; Maslennikov, Sergey; Larionov, Pavel; Finkel, Matvey; Semenov, Alexander; Verevkin, Aleksandr A; Voronov, Boris M; Ponurovsky, Yakov; Klapwijk, Teunis M; Gol'tsman, Gregory N

    2014-03-15

    We report on the development of a highly sensitive optical receiver for heterodyne IR spectroscopy at the communication wavelength of 1.5 μm (200 THz) by use of a superconducting hot-electron bolometer. The results are important for the resolution of narrow spectral molecular lines in the near-IR range for the study of astronomical objects, as well as for quantum optical tomography and fiber-optic sensing. Receiver configuration as well as fiber-to-detector light coupling designs are discussed. Light absorption of the superconducting detectors was enhanced by nano-optical antennas, which were coupled to optical fibers. An intermediate frequency (IF) bandwidth of about 3 GHz was found in agreement with measurements at 300 GHz, and a noise figure of about 25 dB was obtained that was only 10 dB above the quantum limit. PMID:24690805

  7. Concurrent polarization retrieval in multi-heterodyne scanning near-field optical microscopy: validation on silicon form-birefringent grating.

    PubMed

    Yu, L; Sfez, T; Paeder, V; Stenberg, P; Nakagawa, W; Kuittinen, M; Herzig, H P

    2012-10-01

    We demonstrate a concurrent polarization-retrieval algorithm based on a multi-heterodyne scanning near-field optical microscopy (MH-SNOM) measurement system. This method relies on calibration of the polarization properties of the MH-SNOM using an isotropic region of the sample in the vicinity of the nanostructures of interest. We experimentally show the effectiveness of the method on a silicon form-birefringent grating (FBG) with significant polarization diversity. Three spatial dimensional near-field measurements are in agreement with theoretical predictions obtained with rigorous coupled-wave analysis (RCWA). Pseudo-far-field measurements are performed to obtain the effective refractive index of the FBG, emphasizing the validity of the proposed method. This reconstruction algorithm makes the MH-SNOM a powerful tool to analyze concurrently the polarization-dependent near-field optical response of nanostructures with sub wavelength resolution as long as a calibration area is available in close proximity. PMID:23188273

  8. A recirculating delayed self-heterodyne method using a Mach-Zehnder modulator for kHz-linewidth measurement

    NASA Astrophysics Data System (ADS)

    Deng, Shuo; Li, Min; Gao, Hongyun; Dai, Yawen

    2016-09-01

    A laser linewidth measurement method which uses a Mach-Zehnder electro-optic modulator (MZM) is proposed in a loss-compensated recirculating delayed self-heterodyne interferometer (LC-RDSHI). Compared with the traditional acousto-optic modulator (AOM), the electro-optic modulator has the merits of broader bandwidth, lower insertion loss, higher extinction ratio and thus, a wider application. A theoretical analysis shows that the power spectrum curve of the novel measurement system is a Lorentzian line, which fits well with experiment. The linewidth is measured to be 137 ± 7 kHz at a frequency shift of 4 GHz. Measurement of a distributed feedback Bragg (DFB) laser has manifested that the linewidth broadens from 98.5 kHz to 137.4 kHz as the operating temperature changes by 16 °C. This work will allow investigation of narrow linewidth semiconductor and fiber laser stability.

  9. An All-Solid-State, Room-Temperature, Heterodyne Receiver for Atmospheric Spectroscopy at 1.2 THz

    NASA Technical Reports Server (NTRS)

    Siles, Jose V.; Mehdi, Imran; Schlecht, Erich T.; Gulkis, Samuel; Chattopadhyay, Goutam; Lin, Robert H.; Lee, Choonsup; Gill, John J.; Thomas, Bertrand; Maestrini, Alain E.

    2013-01-01

    Heterodyne receivers at submillimeter wavelengths have played a major role in astrophysics as well as Earth and planetary remote sensing. All-solid-state heterodyne receivers using both MMIC (monolithic microwave integrated circuit) Schottky-diode-based LO (local oscillator) sources and mixers are uniquely suited for long-term planetary missions or Earth climate monitoring missions as they can operate for decades without the need for any active cryogenic cooling. However, the main concern in using Schottky-diode-based mixers at frequencies beyond 1 THz has been the lack of enough LO power to drive the devices because 1 to 3 mW are required to properly pump Schottky diode mixers. Recent progress in HEMT- (high-electron-mobility- transistor) based power amplifier technology, with output power levels in excess of 1 W recently demonstrated at W-band, as well as advances in MMIC Schottky diode circuit technology, have led to measured output powers up to 1.4 mW at 0.9 THz. Here the first room-temperature tunable, all-planar, Schottky-diode-based receiver is reported that is operating at 1.2 THz over a wide (˜20%) bandwidth. The receiver front-end (see figure) consists of a Schottky-diode-based 540 to 640 GHz multiplied LO chain (featuring a cascade of W-band power amplifiers providing around 120 to 180 mW at W-band), a 200-GHz MMIC frequency doubler, and a 600-GHz MMIC frequency tripler, plus a biasable 1.2-THz MMIC sub-harmonic Schottky-diode mixer. The LO chain has been designed, fabricated, and tested at JPL and provides around 1 to 1.5 mW at 540 o 640 GHz. The sub-harmonic mixer consists of two Schottky diodes on a thin GaAs membrane in an anti-parallel configuration. An integrated metal insulator metal (MIM) capacitor has been included on-chip to allow dc bias for the Schottky diodes. A bias voltage of around 0.5 V/diode is necessary to reduce the LO power required down to the 1 to 1.5 mW available from the LO chain. The epilayer thickness and doping profiles have

  10. Frequency stabilization of a 1083 nm fiber laser to {sup 4}He transition lines with optical heterodyne saturation spectroscopies

    SciTech Connect

    Gong, W.; Peng, X. Li, W.; Guo, H.

    2014-07-15

    Two kinds of optical heterodyne saturation spectroscopies, namely, frequency modulation spectroscopy (FMS) and modulation transfer spectroscopy (MTS), are demonstrated for locking a fiber laser to the transition lines of metastable {sup 4}He atoms around 1083 nm. The servo-loop error signals of FMS and MTS for stabilizing laser frequency are optimized by studying the dependence of the peak-to-peak amplitude and slope on the optical power of pump and probe beams. A comparison of the stabilization performances of FMS/MTS and polarization spectroscopy (PS) is presented, which shows that MTS exhibits relatively superior performance with the least laser frequency fluctuation due to its flat-background dispersive signal, originated from the four-wave mixing process. The Allan deviation of the stabilized laser frequency is 5.4 × 10{sup −12}@100 s with MTS for data acquired in 1000 s, which is sufficiently applicable for fields like laser cooling, optical pumping, and optical magnetometry.

  11. Frequency stabilization of a 1083 nm fiber laser to 4He transition lines with optical heterodyne saturation spectroscopies

    NASA Astrophysics Data System (ADS)

    Gong, W.; Peng, X.; Li, W.; Guo, H.

    2014-07-01

    Two kinds of optical heterodyne saturation spectroscopies, namely, frequency modulation spectroscopy (FMS) and modulation transfer spectroscopy (MTS), are demonstrated for locking a fiber laser to the transition lines of metastable 4He atoms around 1083 nm. The servo-loop error signals of FMS and MTS for stabilizing laser frequency are optimized by studying the dependence of the peak-to-peak amplitude and slope on the optical power of pump and probe beams. A comparison of the stabilization performances of FMS/MTS and polarization spectroscopy (PS) is presented, which shows that MTS exhibits relatively superior performance with the least laser frequency fluctuation due to its flat-background dispersive signal, originated from the four-wave mixing process. The Allan deviation of the stabilized laser frequency is 5.4 × 10-12@100 s with MTS for data acquired in 1000 s, which is sufficiently applicable for fields like laser cooling, optical pumping, and optical magnetometry.

  12. Analysis of the accuracy of the inverse problem solution for a differential heterodyne microscope as applied to rectangular plasmonic waveguides

    NASA Astrophysics Data System (ADS)

    Akhmedzhanov, I. M.; Baranov, D. V.; Zolotov, E. M.

    2016-06-01

    The existence, uniqueness, and stability of the inverse problem solution for a scanning differential heterodyne microscope as applied to rectangular plasmonic waveguides have been analyzed. The consideration is based on an algorithm using a trial-and-error method that we proposed previously to characterize plasmonic waveguides with a triangular profile. The error of the inverse problem (IP) solution is calculated as dependent on the initial data and with allowance for their errors. Instability domains are found for the IP solution, where the solution error sharply increases. It is shown that the instability domains can be eliminated and the accuracy of the IP solution can be significantly improved in the entire range of initial data by taking initial data in the form of two phase responses of the microscope at different wavelengths.

  13. Design and characterization of a 32-channel heterodyne radiometer for electron cyclotron emission measurements on experimental advanced superconducting tokamak.

    PubMed

    Han, X; Liu, X; Liu, Y; Domier, C W; Luhmann, N C; Li, E Z; Hu, L Q; Gao, X

    2014-07-01

    A 32-channel heterodyne radiometer has been developed for the measurement of electron cyclotron emission (ECE) on the experimental advanced superconducting tokamak (EAST). This system collects X-mode ECE radiation spanning a frequency range of 104-168 GHz, where the frequency coverage corresponds to a full radial coverage for the case with a toroidal magnetic field of 2.3 T. The frequency range is equally spaced every 2 GHz from 105.1 to 167.1 GHz with an RF bandwidth of ~500 MHz and the video bandwidth can be switched among 50, 100, 200, and 400 kHz. Design objectives and characterization of the system are presented in this paper. Preliminary results for plasma operation are also presented. PMID:25085139

  14. Comparison of the response of a heterodyne receiver to video-pulse and impulse-type signals

    NASA Astrophysics Data System (ADS)

    Caprio, S. J.

    1980-02-01

    This paper presents some of the limitations of available impulse generators and suggests a criterion to determine the useful frequency range for impulse generators based on the requirements in MIL-STD-461. This paper also discusses a technique that can be used to generate a transient response of a heterodyne receiver that closely approximates the impulse response of the receiver. The technique uses a video pulse from a commercial pulse generator. The transient response of the receiver, measured at IF, will differ from the true impulse response in IF phase only. Available data indicates that this technique may be useful to generate impulse-like responses for RF amplifiers and broad-band amplifiers that operate at frequencies as high as 100 GHz.

  15. Coherent 1-micron lidar measurements of atmospheric-turbulence-induced spatial decorrelation using a multielement heterodyne detector array

    NASA Technical Reports Server (NTRS)

    Chan, Kin P.; Killinger, Dennis K.

    1992-01-01

    A coherent 1-micron Nd:YAG lidar system is employed to measure directly the reduced spatial coherence length rho 0 of the lidar returns caused by atmospheric turbulence. The experiments were conducted by using a 2 x 2 heterodyne detector array, which permitted real-time spatial correlation measurements of the lidar returns at two different detector spacings. The spatial correlation coefficients and spatial coherence length of the lidar returns from a hard target were measured during a day-to-night time period when the atmospheric turbulence parameter, Cn-squared, was measured to vary from 2 x 10 exp -13 to 2 x 10 exp -4 m exp -2/3. These directly measured values of rho 0 as a function of Cn-squared were found to be in good agreement with theoretical predictions.

  16. A search for lower-hybrid-drift fluctuations in a field-reversed configuration using CO2 heterodyne scattering

    NASA Astrophysics Data System (ADS)

    Carlson, Arthur W.

    1987-05-01

    An upper bound of (ñe/ne) <10-4 for frequencies and wavenumbers relevant to the lower-hybrid-drift (LHD) instability is set on fluctuations in field-reversed configurations (FRC's) produced by TRX-2 [Fusion Techn. 9, 48 (1986)]. LHD is a well-studied microinstability that is often invoked to explain particle loss rates in FRC's. The conventional technique of CO2 laser scattering with heterodyne detection is here modified to compensate for severe refraction. The calibration of the system is verified by scattering from acoustic waves in salt. The measured bound is two orders of magnitude below both the fluctuation level usually predicted and the level needed to account for observed particle loss rates. Electron collisionality is identified as the most likely LHD stabilization mechanism. Some alternative explanations of anomalous loss rates are discussed.

  17. Development of a diode laser heterodyne spectrometer and observations of silicon monoxide in sunspots. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Glenar, D. A.

    1981-01-01

    A state of the art, tunable diode laser infrared heterodyne spectrometer was designed and constructed for ground based observations throughout the 8 to 12 micron atmospheric window. The instrument was optimized for use with presently available tunable diode lasers, and was designed as a flexible field system for use with large reflecting telescopes. The instrument was aligned and calibrated using laboratory and astronomical sources. Observations of SiO fundamental (v = 1-0) and hot band (v = 2-1) absorption features were made in sunspots near 8 microns using the spectrometer. The data permit an unambiguous determination of the temperature pressure relation in the upper layers of the umbral atmosphere, and support the sunspot model suggested by Stellmacher and Wiehr.

  18. Design, development, and field testing of Infrared Heterodyne Radiometer (IHR) for remote profiling of tropospheric and stratospheric species

    NASA Technical Reports Server (NTRS)

    Lange, R.; Savage, M.; Peyton, B.

    1981-01-01

    The performance of a dual-channel infrared heterodyne radiometer, designed to remotely monitor the concentration and vertical distribution of selected atmospheric species, is described. Ground based solar viewing measurement using the IHR were performed at selected laser transitions for ammonia (NH3 and ozone O3). Flight tests were conducted aboard the Galileo II, NASA Ames CV-990, on the Latitude Survey Mission. Ozone was the selected atmospheric species for the airborne flight measurements because of the scientific interest in this atmospheric species, the availability of in situ monitors, the coordinated ozone measurements, and the availability of ground truth data. The IHS was operated in the solar viewing mode to determine ozone distributions in the stratosphere and in the nadir viewing mode to determine the ozone distribution in the troposphere. Airborne atmospheric propagation measurements also were carried out at selected CO2 laser transitions.

  19. Active balance system and vibration balanced machine

    NASA Technical Reports Server (NTRS)

    Qiu, Songgang (Inventor); Augenblick, John E. (Inventor); Peterson, Allen A. (Inventor); White, Maurice A. (Inventor)

    2005-01-01

    An active balance system is provided for counterbalancing vibrations of an axially reciprocating machine. The balance system includes a support member, a flexure assembly, a counterbalance mass, and a linear motor or an actuator. The support member is configured for attachment to the machine. The flexure assembly includes at least one flat spring having connections along a central portion and an outer peripheral portion. One of the central portion and the outer peripheral portion is fixedly mounted to the support member. The counterbalance mass is fixedly carried by the flexure assembly along another of the central portion and the outer peripheral portion. The linear motor has one of a stator and a mover fixedly mounted to the support member and another of the stator and the mover fixedly mounted to the counterbalance mass. The linear motor is operative to axially reciprocate the counterbalance mass.

  20. CHIMPS: the 13CO/C18O (J = 3 → 2) Heterodyne Inner Milky Way Plane Survey

    NASA Astrophysics Data System (ADS)

    Rigby, A. J.; Moore, T. J. T.; Plume, R.; Eden, D. J.; Urquhart, J. S.; Thompson, M. A.; Mottram, J. C.; Brunt, C. M.; Butner, H. M.; Dempsey, J. T.; Gibson, S. J.; Hatchell, J.; Jenness, T.; Kuno, N.; Longmore, S. N.; Morgan, L. K.; Polychroni, D.; Thomas, H.; White, G. J.; Zhu, M.

    2016-03-01

    We present the 13CO/C18O (J = 3 → 2) Heterodyne Inner Milky Way Plane Survey (CHIMPS) which has been carried out using the Heterodyne Array Receiver Program on the 15 m James Clerk Maxwell Telescope (JCMT) in Hawaii. The high-resolution spectral survey currently covers |b| ≤ 0.5° and 28° ≲ l ≲ 46°, with an angular resolution of 15 arcsec in 0.5 km s-1 velocity channels. The spectra have a median rms of ˜0.6 K at this resolution, and for optically thin gas at an excitation temperature of 10 K, this sensitivity corresponds to column densities of NH2 ˜ 3 × 1020 cm-2 and NH2 ˜ 4 × 1021 cm-2 for 13CO and C18O, respectively. The molecular gas that CHIMPS traces is at higher column densities and is also more optically thin than in other publicly available CO surveys due to its rarer isotopologues, and thus more representative of the three-dimensional structure of the clouds. The critical density of the J = 3 → 2 transition of CO is ≳104 cm-3 at temperatures of ≤20 K, and so the higher density gas associated with star formation is well traced. These data complement other existing Galactic plane surveys, especially the JCMT Galactic Plane Survey which has similar spatial resolution and column density sensitivity, and the Herschel infrared Galactic Plane Survey. In this paper, we discuss the observations, data reduction and characteristics of the survey, presenting integrated-emission maps for the region covered. Position-velocity diagrams allow comparison with Galactic structure models of the Milky Way, and while we find good agreement with a particular four-arm model, there are some significant deviations.

  1. Highly sensitive detection of nanoparticles with a self-referenced and self-heterodyned whispering-gallery Raman microlaser

    PubMed Central

    Özdemir, Şahin Kaya; Zhu, Jiangang; Yang, Xu; Peng, Bo; Yilmaz, Huzeyfe; He, Lina; Monifi, Faraz; Huang, Steven He; Long, Gui Lu; Yang, Lan

    2014-01-01

    Optical whispering-gallery-mode resonators (WGMRs) have emerged as promising platforms for label-free detection of nano-objects. The ultimate sensitivity of WGMRs is determined by the strength of the light–matter interaction quantified by quality factor/mode volume, Q/V, and the resolution is determined by Q. To date, to improve sensitivity and precision of detection either WGMRs have been doped with rare-earth ions to compensate losses and increase Q or plasmonic resonances have been exploited for their superior field confinement and lower V. Here, we demonstrate, for the first time to our knowledge, enhanced detection of single-nanoparticle-induced mode splitting in a silica WGMR via Raman gain-assisted loss compensation and WGM Raman microlaser. In particular, the use of the Raman microlaser provides a dopant-free, self-referenced, and self-heterodyned scheme with a detection limit ultimately determined by the thermorefractive noise. Notably, we detected and counted individual nanoparticles with polarizabilities down to 3.82 × 10−6 μm3 by monitoring a heterodyne beatnote signal. This level of sensitivity is achieved without exploiting plasmonic effects, external references, or active stabilization and frequency locking. Single nanoparticles are detected one at a time; however, their characterization by size or polarizability requires ensemble measurements and statistical averaging. This dopant-free scheme retains the inherited biocompatibility of silica and could find widespread use for sensing in biological media. The Raman laser and operation band of the sensor can be tailored for the specific sensing environment and the properties of the targeted materials by changing the pump laser wavelength. This scheme also opens the possibility of using intrinsic Raman or parametric gain for loss compensation in other systems where dissipation hinders progress and limits applications. PMID:25197086

  2. Load Balancing Scientific Applications

    SciTech Connect

    Pearce, Olga Tkachyshyn

    2014-12-01

    The largest supercomputers have millions of independent processors, and concurrency levels are rapidly increasing. For ideal efficiency, developers of the simulations that run on these machines must ensure that computational work is evenly balanced among processors. Assigning work evenly is challenging because many large modern parallel codes simulate behavior of physical systems that evolve over time, and their workloads change over time. Furthermore, the cost of imbalanced load increases with scale because most large-scale scientific simulations today use a Single Program Multiple Data (SPMD) parallel programming model, and an increasing number of processors will wait for the slowest one at the synchronization points. To address load imbalance, many large-scale parallel applications use dynamic load balance algorithms to redistribute work evenly. The research objective of this dissertation is to develop methods to decide when and how to load balance the application, and to balance it effectively and affordably. We measure and evaluate the computational load of the application, and develop strategies to decide when and how to correct the imbalance. Depending on the simulation, a fast, local load balance algorithm may be suitable, or a more sophisticated and expensive algorithm may be required. We developed a model for comparison of load balance algorithms for a specific state of the simulation that enables the selection of a balancing algorithm that will minimize overall runtime.

  3. Feasibility of tropospheric water vapor profiling using infrared heterodyne differential absorption lidar

    SciTech Connect

    Grund, C.J.; Hardesty, R.M.; Rye, B.J.

    1996-04-01

    The development and verification of realistic climate model parameterizations for clouds and net radiation balance and the correction of other site sensor observations for interferences due to the presence of water vapor are critically dependent on water vapor profile measurements. In this study, we develop system performance models and examine the potential of infrared differential absoroption lidar (DIAL) to determine the concentration of water vapor.

  4. A question of balance

    SciTech Connect

    Cook, G.; Brown, H.; Strawn, N.

    1996-12-31

    Nature seeks a balance. The global carbon cycle, in which carbon is exchanged between the atmosphere, biosphere, and oceans through natural processes such as absorption, photosynthesis, and respiration, is one of those balances. This constant exchange promotes an equilibrium in which atmospheric carbon dioxide is keep relatively steady over long periods of time. For the last 10,000 years, up to the 19th century, the global carbon cycle has maintained atmospheric concentrations of carbon dioxide between 260 and 290 ppm. This article discusses the disturbance of the balance, how ethanol fuels address the carbon dioxide imbalance, and a bioethanol strategy.

  5. Consideration of Dynamical Balances

    NASA Technical Reports Server (NTRS)

    Errico, Ronald M.

    2015-01-01

    The quasi-balance of extra-tropical tropospheric dynamics is a fundamental aspect of nature. If an atmospheric analysis does not reflect such balance sufficiently well, the subsequent forecast will exhibit unrealistic behavior associated with spurious fast-propagating gravity waves. Even if these eventually damp, they can create poor background fields for a subsequent analysis or interact with moist physics to create spurious precipitation. The nature of this problem will be described along with the reasons for atmospheric balance and techniques for mitigating imbalances. Attention will be focused on fundamental issues rather than on recipes for various techniques.

  6. Balance Evaluation Systems

    NASA Technical Reports Server (NTRS)

    1996-01-01

    NeuroCom's Balance Master is a system to assess and then retrain patients with balance and mobility problems and is used in several medical centers. NeuroCom received assistance in research and funding from NASA, and incorporated technology from testing mechanisms for astronauts after shuttle flights. The EquiTest and Balance Master Systems are computerized posturography machines that measure patient responses to movement of a platform on which the subject is standing or sitting, then provide assessments of the patient's postural alignment and stability.

  7. Errors in potassium balance

    SciTech Connect

    Forbes, G.B.; Lantigua, R.; Amatruda, J.M.; Lockwood, D.H.

    1981-01-01

    Six overweight adult subjects given a low calorie diet containing adequate amounts of nitrogen but subnormal amounts of potassium (K) were observed on the Clinical Research Center for periods of 29 to 40 days. Metabolic balance of potassium was measured together with frequent assays of total body K by /sup 40/K counting. Metabolic K balance underestimated body K losses by 11 to 87% (average 43%): the intersubject variability is such as to preclude the use of a single correction value for unmeasured losses in K balance studies.

  8. Mars Balance Challenge

    NASA Video Gallery

    The Challenge is to develop ideas for how NASA can turn available entry, descent, and landing balance mass on a future Mars mission into a scientific or technological payload. Proposed concepts sho...

  9. The Balanced Literacy Diet.

    ERIC Educational Resources Information Center

    Willows, Dale

    2002-01-01

    Describes professional development program in Ontario school district to improve student reading and writing skills. Program used food-pyramid concepts to help teacher learn to provide a balanced and flexible approach to literacy instruction based on student needs. (PKP)

  10. The Balancing Act

    SciTech Connect

    Fowler, Kimberly M.

    2008-05-01

    This essay is being proposed as part of a book titled: "Motherhood: The Elephant in the Laboratory." It offers professional and personal advice on how to balance working in the research field with a family life.

  11. Fluid and Electrolyte Balance

    MedlinePlus

    ... They are in your blood, urine and body fluids. Maintaining the right balance of electrolytes helps your ... them from the foods you eat and the fluids you drink. Levels of electrolytes in your body ...

  12. Balance Function Disorders

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Researchers at the Balance Function Laboratory and Clinic at the Minneapolis (MN) Neuroscience Institute on the Abbot Northwestern Hospital Campus are using a rotational chair (technically a "sinusoidal harmonic acceleration system") originally developed by NASA to investigate vestibular (inner ear) function in weightlessness to diagnose and treat patients with balance function disorders. Manufactured by ICS Medical Corporation, Schaumberg, IL, the chair system turns a patient and monitors his or her responses to rotational stimulation.

  13. Exercise to Improve Your Balance

    MedlinePlus

    ... nia.nih.gov/Go4Life Exercise to Improve Your Balance Having good balance is important for many everyday activities, such as ... fracture of the arm, hand, ankle, or hip. Balance exercises can help you prevent falls and avoid ...

  14. Greenland Ice Sheet Mass Balance

    NASA Technical Reports Server (NTRS)

    Reeh, N.

    1984-01-01

    Mass balance equation for glaciers; areal distribution and ice volumes; estimates of actual mass balance; loss by calving of icebergs; hydrological budget for Greenland; and temporal variations of Greenland mass balance are examined.

  15. Energy Balance and Obesity

    PubMed Central

    Hill, James O.; Wyatt, Holly R.; Peters, John C.

    2012-01-01

    This paper describes the interplay among energy intake, energy expenditure and body energy stores and illustrates how an understanding of energy balance can help develop strategies to reduce obesity. First, reducing obesity will require modifying both energy intake and energy expenditure and not simply focusing on either alone. Food restriction alone will not be effective in reducing obesity if human physiology is biased toward achieving energy balance at a high energy flux (i.e. at a high level of energy intake and expenditure). In previous environments a high energy flux was achieved with a high level of physical activity but in today's sedentary environment it is increasingly achieved through weight gain. Matching energy intake to a high level of energy expenditure will likely be more a more feasible strategy for most people to maintain a healthy weight than restricting food intake to meet a low level of energy expenditure. Second, from an energy balance point of view we are likely to be more successful in preventing excessive weight gain than in treating obesity. This is because the energy balance system shows much stronger opposition to weight loss than to weight gain. While large behavior changes are needed to produce and maintain reductions in body weight, small behavior changes may be sufficient to prevent excessive weight gain. In conclusion, the concept of energy balance combined with an understanding of how the body achieves balance may be a useful framework in helping develop strategies to reduce obesity rates. PMID:22753534

  16. Watt and joule balances

    NASA Astrophysics Data System (ADS)

    Robinson, Ian A.

    2014-04-01

    The time is fast approaching when the SI unit of mass will cease to be based on a single material artefact and will instead be based upon the defined value of a fundamental constant—the Planck constant—h . This change requires that techniques exist both to determine the appropriate value to be assigned to the constant, and to measure mass in terms of the redefined unit. It is important to ensure that these techniques are accurate and reliable to allow full advantage to be taken of the stability and universality provided by the new definition and to guarantee the continuity of the world's mass measurements, which can affect the measurement of many other quantities such as energy and force. Up to now, efforts to provide the basis for such a redefinition of the kilogram were mainly concerned with resolving the discrepancies between individual implementations of the two principal techniques: the x-ray crystal density (XRCD) method [1] and the watt and joule balance methods which are the subject of this special issue. The first three papers report results from the NRC and NIST watt balance groups and the NIM joule balance group. The result from the NRC (formerly the NPL Mk II) watt balance is the first to be reported with a relative standard uncertainty below 2 × 10-8 and the NIST result has a relative standard uncertainty below 5 × 10-8. Both results are shown in figure 1 along with some previous results; the result from the NIM group is not shown on the plot but has a relative uncertainty of 8.9 × 10-6 and is consistent with all the results shown. The Consultative Committee for Mass and Related Quantities (CCM) in its meeting in 2013 produced a resolution [2] which set out the requirements for the number, type and quality of results intended to support the redefinition of the kilogram and required that there should be agreement between them. These results from NRC, NIST and the IAC may be considered to meet these requirements and are likely to be widely debated

  17. Cavendish Balance Automation

    NASA Technical Reports Server (NTRS)

    Thompson, Bryan

    2000-01-01

    This is the final report for a project carried out to modify a manual commercial Cavendish Balance for automated use in cryostat. The scope of this project was to modify an off-the-shelf manually operated Cavendish Balance to allow for automated operation for periods of hours or days in cryostat. The purpose of this modification was to allow the balance to be used in the study of effects of superconducting materials on the local gravitational field strength to determine if the strength of gravitational fields can be reduced. A Cavendish Balance was chosen because it is a fairly simple piece of equipment for measuring gravity, one the least accurately known and least understood physical constants. The principle activities that occurred under this purchase order were: (1) All the components necessary to hold and automate the Cavendish Balance in a cryostat were designed. Engineering drawings were made of custom parts to be fabricated, other off-the-shelf parts were procured; (2) Software was written in LabView to control the automation process via a stepper motor controller and stepper motor, and to collect data from the balance during testing; (3)Software was written to take the data collected from the Cavendish Balance and reduce it to give a value for the gravitational constant; (4) The components of the system were assembled and fitted to a cryostat. Also the LabView hardware including the control computer, stepper motor driver, data collection boards, and necessary cabling were assembled; and (5) The system was operated for a number of periods, data collected, and reduced to give an average value for the gravitational constant.

  18. Development of a THz heterodyne receiver with quantum cascade laser and hot electron bolometer mixer for standoff detection of explosive material

    NASA Astrophysics Data System (ADS)

    Richter, H.; Semenov, A. D.; Pavlov, S. G.; Mahler, L.; Tredicucci, A.; Beere, H. E.; Ritchie, D. A.; Ortolani, M.; Schade, U.; Il'in, K. S.; Siegel, M.; Hübers, H.-W.

    2009-05-01

    The terahertz (THz) portion of the electromagnetic spectrum provides specific spectroscopic information for substance identification. It has been shown that the spectral features of explosive materials might be used for detection and identification at stand-off distances. We report on the development of a THz spectrometer for explosive detection and identification. The system is based on THz quantum cascade lasers working at different frequencies. These are used for illumination of the object under test. The reflected and backscattered radiation from the object under test is detected with a sensitive heterodyne receiver. As a first step a single frequency, liquid-cryogen free heterodyne receiver operating at 2.5 THz has been developed. In order to realize maximum sensitivity a phonon-cooled NbN hot electron bolometric mixer with a quantum cascade laser as local oscillator were chosen. The concept of the system and first results will be presented.

  19. Calibration of a high spatial resolution laser two-color heterodyne interferometer for density profile measurements in the TJ-II stellarator

    SciTech Connect

    Acedo, Pablo; Pedreira, P.; Criado, A. R.; Lamela, Horacio; Sanchez, Miguel; Sanchez, Joaquin

    2008-10-15

    A high spatial resolution two-color (CO{sub 2}, {lambda}=10.6 {mu}m, He-Ne, {lambda}=633 nm) interferometer for density profile measurements in the TJ-II stellarator is under development and installation, based in the currently operational single channel two-color heterodyne interferometer. To achieve the objectives of 32 channels, with 4-5 mm lateral separation between plasma chords, careful design and calibration of the interferometric waveforms for both the measurement and vibration compensation wavelengths are undertaken. The first step has been to set up in our laboratories an expanded-beam heterodyne/homodyne interferometer to evaluate the quality of both interferometric wavefronts, a reported source of poor vibration compensation and thus low resolution in the density profile measurements. This novel interferometric setup has allowed us to calibrate the spatial resolution in the profile measurements resulting in {approx}2 mm lateral resolution in the reconstruction of the interferometric wavefront.

  20. Comparison of photonic integrated circuits for millimeter-wave signal generation between dual-wavelength sources for optical heterodyning and pulsed mode-locked lasers

    NASA Astrophysics Data System (ADS)

    Carpintero, Guillermo; Gordon, Carlos; Guzman, Robinson; Leijtens, Xaveer; Van Dijk, Frédéric; Kervella, Gaël.; Fice, Martyn J.; Balakier, Katarzyna; Renaud, Cyril C.

    2015-03-01

    A comparative study of two different Photonic Integrated Circuits (PICs) structures for continuous-wave generation of millimeter-wave (MMW) signals is presented, each using a different approach. One approach is optical heterodyning, using an integrated dual-wavelength laser source based on Arrayed Waveguide Grating. The other is based on ModeLocked Laser Diodes (MLLDs). A novel building block -Multimode Interference Reflectors (MIRs) - is used to integrate on-chip both structures, without need of cleaved facets to define the laser cavity. This fact enables us to locate any of these structures at any location within the photonic chip. As will be shown, the MLLD structure provides a simple source for low frequencies. Higher frequencies are easier to achieve by optical heterodyne. Both types of structures have been fabricated on a generic foundry in a commercial MPW PIC technology.

  1. Laser heterodyne spectrometer using a liquid nitrogen cooled tunable diode laser for remote measurements of atmospheric O sub 3 and N sub 2 O

    SciTech Connect

    Fukunishi, H.; Okano, S.; Taguchi, M.; Ohnuma, T. )

    1990-06-20

    A laser heterodyne spectrometer with a tunable diode laser as a local oscillator has been developed for ultrahigh resolution IR spectroscopy of the absorption spectra of trace constituents in the earth's atmosphere. The spectral resolution and SNR of the developed system are 0.0013 cm{sup {minus}1} and {similar to}500, respectively. This performance is sufficient for retrieving the altitude profile of atmospheric O{sub 3} through an inversion method. The altitude profile of atmospheric N{sub 2}O has been also obtained for the first time with this laser heterodyne technique. The high resolution and high SNR have been accomplished by adopting a tunable diode laser which operates at liquid nitrogen temperature and by developing an effective technique to eliminate the optical feedback of the local oscillator laser beam.

  2. Automatic force balance calibration system

    NASA Technical Reports Server (NTRS)

    Ferris, Alice T. (Inventor)

    1996-01-01

    A system for automatically calibrating force balances is provided. The invention uses a reference balance aligned with the balance being calibrated to provide superior accuracy while minimizing the time required to complete the calibration. The reference balance and the test balance are rigidly attached together with closely aligned moment centers. Loads placed on the system equally effect each balance, and the differences in the readings of the two balances can be used to generate the calibration matrix for the test balance. Since the accuracy of the test calibration is determined by the accuracy of the reference balance and current technology allows for reference balances to be calibrated to within .+-.0.05%, the entire system has an accuracy of a .+-.0.2%. The entire apparatus is relatively small and can be mounted on a movable base for easy transport between test locations. The system can also accept a wide variety of reference balances, thus allowing calibration under diverse load and size requirements.

  3. Automatic force balance calibration system

    NASA Astrophysics Data System (ADS)

    Ferris, Alice T.

    1995-05-01

    A system for automatically calibrating force balances is provided. The invention uses a reference balance aligned with the balance being calibrated to provide superior accuracy while minimizing the time required to complete the calibration. The reference balance and the test balance are rigidly attached together with closely aligned moment centers. Loads placed on the system equally effect each balance, and the differences in the readings of the two balances can be used to generate the calibration matrix for the test balance. Since the accuracy of the test calibration is determined by the accuracy of the reference balance and current technology allows for reference balances to be calibrated to within +/-0.05% the entire system has an accuracy of +/-0.2%. The entire apparatus is relatively small and can be mounted on a movable base for easy transport between test locations. The system can also accept a wide variety of reference balances, thus allowing calibration under diverse load and size requirements.

  4. Polarization-independent operation of an acousto-optical device at the transmit end of a single-laser transmission system using self-heterodyning

    NASA Astrophysics Data System (ADS)

    Olivier, L.; Rocks, M.

    1991-03-01

    This paper describes the way in which a new integrated acousto-optical LiNbO 3 device combining the three functions of an electro-optical phase modulator, an acousto-optical TE/TM or TM/TE mode converter and an acousto-optical frequency shifter can be operated in a polarization-independent manner as a transmitter unit in a single-laser transmission system using self-heterodyning.

  5. The cryogenic balance design and balance calibration methods

    NASA Astrophysics Data System (ADS)

    Ewald, B.; Polanski, L.; Graewe, E.

    1992-07-01

    The current status of a program aimed at the development of a cryogenic balance for the European Transonic Wind Tunnel is reviewed. In particular, attention is given to the cryogenic balance design philosophy, mechanical balance design, reliability and accuracy, cryogenic balance calibration concept, and the concept of an automatic calibration machine. It is shown that the use of the automatic calibration machine will improve the accuracy of calibration while reducing the man power and time required for balance calibration.

  6. Extraordinary hall balance

    PubMed Central

    Zhang, S. L.; Liu, Y.; Collins-McIntyre, L. J.; Hesjedal, T.; Zhang, J. Y.; Wang, S. G.; Yu, G. H.

    2013-01-01

    Magnetoresistance (MR) effects are at the heart of modern information technology. However, future progress of giant and tunnelling MR based storage and logic devices is limited by the usable MR ratios of currently about 200% at room-temperature. Colossal MR structures, on the other hand, achieve their high MR ratios of up to 106% only at low temperatures and high magnetic fields. We introduce the extraordinary Hall balance (EHB) and demonstrate room-temperature MR ratios in excess of 31,000%. The new device concept exploits the extraordinary Hall effect in two separated ferromagnetic layers with perpendicular anisotropy in which the Hall voltages can be configured to be carefully balanced or tipped out of balance. Reprogrammable logic and memory is realised using a single EHB element. PACS numbers: 85.75.Nn,85.70.Kh,72.15.Gd,75.60.Ej. PMID:23804036

  7. Vibration balanced miniature loudspeaker

    NASA Astrophysics Data System (ADS)

    Schafer, David E.; Jiles, Mekell; Miller, Thomas E.; Thompson, Stephen C.

    2002-11-01

    The vibration that is generated by the receiver (loudspeaker) in a hearing aid can be a cause of feedback oscillation. Oscillation can occur if the microphone senses the receiver vibration at sufficient amplitude and appropriate phase. Feedback oscillation from this and other causes is a major problem for those who manufacture, prescribe, and use hearing aids. The receivers normally used in hearing aids are of the balanced armature-type that has a significant moving mass. The reaction force from this moving mass is the source of the vibration. A modification of the balanced armature transducer has been developed that balances the vibration of its internal parts in a way that significantly reduces the vibration force transmitted outside of the receiver case. This transducer design concept, and some of its early prototype test data will be shown. The data indicate that it should be possible to manufacture transducers that generate less vibration than equivalent present models by 15-30 dB.

  8. Multidimensional spectral load balancing

    SciTech Connect

    Hendrickson, B.; Leland, R.

    1993-01-01

    We describe an algorithm for the static load balancing of scientific computations that generalizes and improves upon spectral bisection. Through a novel use of multiple eigenvectors, our new spectral algorithm can divide a computation into 4 or 8 pieces at once. These multidimensional spectral partitioning algorithms generate balanced partitions that have lower communication overhead and are less expensive to compute than those produced by spectral bisection. In addition, they automatically work to minimize message contention on a hypercube or mesh architecture. These spectral partitions are further improved by a multidimensional generalization of the Kernighan-Lin graph partitioning algorithm. Results on several computational grids are given and compared with other popular methods.

  9. Rotary and Magnus balances

    NASA Technical Reports Server (NTRS)

    Malcolm, G. N.

    1981-01-01

    Two wind tunnel techniques for determining part of the aerodynamic information required to describe the dynamic bahavior of various types of vehicles in flight are described. Force and moment measurements are determined with a rotary-balance apparatus in a coning motion and with a Magnus balance in a high-speed spinning motion. Coning motion is pertinent to both aircraft and missiles, and spinning is important for spin stabilized missiles. Basic principles of both techniques are described, and specific examples of each type of apparatus are presented. Typical experimental results are also discussed.

  10. Improved analysis of column carbon dioxide and methane data from ground-based Miniaturized Laser Heterodyne Radiometer (Mini-LHR)

    NASA Astrophysics Data System (ADS)

    Wilson, E. L.; Melroy, H.; Ramanathan, A. K.; Mao, J.; Clarke, G.; McLinden, M.; Ott, L. E.; Miller, J. H. H.; Allan, G. R.; Holben, B. N.

    2014-12-01

    We present an improved data analysis for the Mini-LHR column measurements of CO2 and CH4 that includes corrections for refraction through the atmosphere and meteorological conditions. Multi-scan averaging has also been added to compensate for current shot noise limitations and improve instrument sensitivity. Data with the improved analysis will be shown for field measurements at the TCCON site at CalTech (March 2014), Calpoly during COW-Gas (March 2014), at Mauna Loa Observatory (May 2013), and Atwater, CA (February 2013). The Mini-LHR is a miniaturized version of a laser heterodyne radiometer that implements telecommunications lasers and components to produce a significantly reduced size, low-cost instrument. Laser heterodyne radiometry has been used since the 1970s to measure atmospheric gases such as ozone, water vapor, methane, ammonia, chlorine monoxide, and nitrous oxide. The Mini-LHR is passive and uses sunlight as the primary light source to measure absorption of CO2 and CH4 in the infrared. Sunlight is collected with collimation optics mounted to the AERONET sun tracker and superimposed with laser light in a single mode fiber coupler. The signals are mixed in a fast photoreceiver (InGaAs detector), and the RF (radio frequency) beat signal is extracted. Changes in concentration of the trace gas are realized through analyzing changes in the beat frequency amplitude. In addition to the complementary aerosol optical depth measurement, tandem operation with AERONET provides a clear pathway for the mini-LHR to be expanded into a global monitoring network. AERONET has more than 450 instruments worldwide and offers coverage in key arctic regions (not covered by OCO-2) where accelerated warming due to the release of CO2 and CH4 from thawing tundra and permafrost is a concern. A mini-LHR global ground network can also provide an uninterrupted data record that will both bridge gaps in data sets and offer validation for key flight missions such as OCO-2, OCO-3, and

  11. Miniaturized Near Infrared Heterodyne Spectroradiometer for Monitoring CO2, CH4 and CO in the Earth Atmosphere

    NASA Astrophysics Data System (ADS)

    Klimchuk, A., Sr.; Rodin, A.; Nadezhdinskiy, A.; Churbanov, D.; Spiridonov, M.

    2014-12-01

    The paper describes the concept of a compact, lightweight heterodyne NIR spectro-radiometer suitable for atmospheric sounding with solar occultations, and the first measurement of CO2 and CH4 absorption near 1.60mm and 1.65 mm with spectral resolution l/dl ~ 5*107. Highly stabilized DFB laser was used as local oscillator, while single model quartz fiber Y-coupler served as a diplexer. Radiation mixed in the single mode fiber was detected by quadratic detector using p-i-n diode within the bandpass of ~10 MHz. Wavelength coverage of spectral measurement was provided by sweeping local oscillator frequency in the range 1,1 см-1. With the exposure time of 10 min, the absorption spectrum of the atmosphere over Moscow has been recorded with S/N ~ 300. We retrieved methane vertical profile using Tikhonov method of smooth functional, which takes into account a priori information about first guess profile. The reference to model methane profile means that the regularization procedure always selects a priorivalues unless the measurements contradict this assumption.The retrieved methane profile demonstrates higher abundances in the lower scale height compared to the assumed model profile, well expected in the megalopolis center. The retrievals sensitivity is limited by 10 ppb, with the exception of the lower part of the profile where the tendency to lower values is revealed. Thus the methane abundance variations may be evaluated with relative accuracy better than 1%, which fits the requirements of greenhouse gas monitoring. The retrievals sensitivity of CO2 is about 1-2 ppm. CO2 observations was also used to estimate stratoshere wind by doppler shift of absorption line. Due to higher spectral resolution, lower sensitivity to atmospheric temperatures and other external factors, compared to heterodyne measurements in the thermal IR spectral range, the described technique provides accuracy comparable with much more complicated high resolution measurements now used in TCCON

  12. Lives in the Balance.

    ERIC Educational Resources Information Center

    Our Children, 1997

    1997-01-01

    Changes in the workplace that would provide flexibility for working parents are slowly developing and receiving government, business, and societal attention. A sidebar, "Mother, Professional, Volunteer: One Woman's Balancing Act," presents an account of how one woman rearranged her professional life to enable her to do full-time parenting. (SM)

  13. Maintaining an Environmental Balance

    ERIC Educational Resources Information Center

    Environmental Science and Technology, 1976

    1976-01-01

    A recent conference of the National Environmental Development Association focused on the concepts of environment, energy and economy and underscored the necessity for balancing the critical needs embodied in these issues. Topics discussed included: nuclear energy and wastes, water pollution control, federal regulations, environmental technology…

  14. Balancing Chemical Equations.

    ERIC Educational Resources Information Center

    Savoy, L. G.

    1988-01-01

    Describes a study of students' ability to balance equations. Answers to a test on this topic were analyzed to determine the level of understanding and processes used by the students. Presented is a method to teach this skill to high school chemistry students. (CW)

  15. The Heider Balance:

    NASA Astrophysics Data System (ADS)

    Kułakowski, Krzysztof; Gawroński, Przemysław; Gronek, Piotr

    The Heider balance (HB) is investigated in a fully connected graph of N nodes. The links are described by a real symmetric array r (i, j), i, j =1, …, N. In a social group, nodes represent group members and links represent relations between them, positive (friendly) or negative (hostile). At the balanced state, r (i, j) r (j, k) r (k, i) > 0 for all the triads (i, j, k). As follows from the structure theorem of Cartwright and Harary, at this state the group is divided into two subgroups, with friendly internal relations and hostile relations between the subgroups. Here the system dynamics is proposed to be determined by a set of differential equations, ˙ r =rḑot r. The form of equations guarantees that once HB is reached, it persists. Also, for N =3 the dynamics reproduces properly the tendency of the system to the balanced state. The equations are solved numerically. Initially, r (i, j) are random numbers distributed around zero with a symmetric uniform distribution of unit width. Calculations up to N =500 show that HB is always reached. Time τ(N) to get the balanced state varies with the system size N as N-1/2. The spectrum of relations, initially narrow, gets very wide near HB. This means that the relations are strongly polarized. In our calculations, the relations are limited to a given range around zero. With this limitation, our results can be helpful in an interpretation of some statistical data.

  16. Regulation of Energy Balance.

    ERIC Educational Resources Information Center

    Bray, George A.

    1985-01-01

    Explains relationships between energy intake and expenditure focusing on the cellular, chemical and neural mechanisms involved in regulation of energy balance. Information is referenced specifically to conditions of obesity. (Physicians may earn continuing education credit by completing an appended test). (ML)

  17. A Balancing Act

    ERIC Educational Resources Information Center

    Lewis, Tamika; Mobley, Mary; Huttenlock, Daniel

    2013-01-01

    It's the season for the job hunt, whether one is looking for their first job or taking the next step along their career path. This article presents first-person accounts to see how teachers balance the rewards and challenges of working in different types of schools. Tamica Lewis, a third-grade teacher, states that faculty at her school is…

  18. Multidimensional spectral load balancing

    DOEpatents

    Hendrickson, Bruce A.; Leland, Robert W.

    1996-12-24

    A method of and apparatus for graph partitioning involving the use of a plurality of eigenvectors of the Laplacian matrix of the graph of the problem for which load balancing is desired. The invention is particularly useful for optimizing parallel computer processing of a problem and for minimizing total pathway lengths of integrated circuits in the design stage.

  19. Toward Balance in Translation.

    ERIC Educational Resources Information Center

    Costello, Nancy A.

    A study compared translations of biblical passages into different languages in Papua New Guinea. The study looked for evidence of balance between literal and free interpretation in translation style in the gospel of Mark, which is narrative and didactic material, in 12 languages, and the mainly hortatory genre in translations of 4 epistles:…

  20. Lock-in camera based heterodyne holography for ultrasound-modulated optical tomography inside dynamic scattering media

    NASA Astrophysics Data System (ADS)

    Liu, Yan; Shen, Yuecheng; Ma, Cheng; Shi, Junhui; Wang, Lihong V.

    2016-06-01

    Ultrasound-modulated optical tomography (UOT) images optical contrast deep inside scattering media. Heterodyne holography based UOT is a promising technique that uses a camera for parallel speckle detection. In previous works, the speed of data acquisition was limited by the low frame rates of conventional cameras. In addition, when the signal-to-background ratio was low, these cameras wasted most of their bits representing an informationless background, resulting in extremely low efficiencies in the use of bits. Here, using a lock-in camera, we increase the bit efficiency and reduce the data transfer load by digitizing only the signal after rejecting the background. Moreover, compared with the conventional four-frame based amplitude measurement method, our single-frame method is more immune to speckle decorrelation. Using lock-in camera based UOT with an integration time of 286 μs, we imaged an absorptive object buried inside a dynamic scattering medium exhibiting a speckle correlation time ( τ c ) as short as 26 μs. Since our method can tolerate speckle decorrelation faster than that found in living biological tissue ( τ c ˜ 100-1000 μs), it is promising for in vivo deep tissue non-invasive imaging.

  1. A comparison between heterodyne and homodyne interferometry to realise the SI unit of acoustic pressure in water

    NASA Astrophysics Data System (ADS)

    Koukoulas, Triantafillos; Robinson, Stephen; Rajagopal, Srinath; Zeqiri, Bajram

    2016-04-01

    Optical approaches for hydrophone calibrations offer significant advantages over existing methods based on reciprocity. In particular, heterodyne and homodyne interferometry can accurately measure particle velocity and displacements at a specific point in space thus enabling the acoustical pressure to be measured in an absolute, direct, assumption-free manner, with traceability through the SI definition of the metre. The calibration of a hydrophone can then be performed by placing the active element of the sensor at the point where the acoustic pressure field was measured and monitoring its electrical output. However, it is crucial to validate the performance and accuracy of such optical methods by direct comparison rather than through device calibration. Here we report on the direct comparison of two such optical interferometers used in underwater acoustics and ultrasonics in terms of acoustic pressure estimation and their associated uncertainties in the frequency range 200 kHz-3.5 MHz, with results showing agreement better than 1% in terms of pressure and typical expanded uncertainties better than 3% for both reported methods.

  2. Determination of retardation parameters of multiple-order wave plate using a phase-sensitive heterodyne ellipsometer.

    PubMed

    Hsieh, Cheng-Hung; Tsai, Chien-Chung; Wei, Hsiang-Chun; Yu, Li-Ping; Wu, Jheng-Syong; Chou, Chien

    2007-08-10

    To characterize the linear birefringence of a multiple-order wave plate (MWP), an oblique incidence is one of the methods available. Multiple reflections in the MWP are produced, and oscillations in the phase retardation measurement versus the oblique incident angle are then measured. Therefore, an antireflection coated MWP is required to avoid oscillation of the phase retardation measurement. In this study, we set up a phase-sensitive heterodyne ellipsometer to measure the phase retardations of an uncoated MWP versus the oblique incident angle, which was scanned in the x-z plane and y-z plane independently. Thus, the effect on multiple reflections by the MWP is reduced by means of subtracting the two measured phase retardations from each other. As a result, a highly sensitive and accurate measurement of retardation parameters (RPs), which includes the refractive indices of the extraordinary ray n(e) and ordinary ray n(o), is obtained by this method. On measurement, a sensitivity (n(e),n(o)) of 10(-6) was achieved by this experiment setup. At the same time, the spatial shifting of the P and S waves emerging from the MWP introduced a deviation between experimental results and the theoretical calculation. PMID:17694147

  3. Stratospheric ozone isotopes observed by air-borne and space-borne submillimeter-wave heterodyne radiometry: A sensitivity study

    NASA Astrophysics Data System (ADS)

    Kasai, Y.; Urban, J.; Takahashi, C.; Smiles Mission Team

    2003-04-01

    The variation of the isotopic composition of a species in the Earth atmosphere provides us the information on the history of the air masses, because the isotope enrichment or depletion reflects the chemical and physical processes. Since the discovery of the heavy isotope enrichment of ozone in the stratosphere in 1981 considerable progress has been made in understanding the processes that control the isotope enrichment based on atmospheric observations, laboratory experiments, and so on. However, the exact mechanism for the effect remains uncertain and accurate sequentially observations of ozone isotopomer at global scale are still very sparse. Further improvements of measurement precision can be obtained by making use of the new technological development of high-precision submillimeter-wave heterodyne radiometry based on sensitive SIS detector technology. The airborne ASUR instrument (Airborne SUb-millimeter SIS Radiometer) observed lines of asymmetric-18 ozone in the frequency region of 645 GHz with this technology since ~1994. The JEM/SMILES instrument (Japaneses Experiment Module / Superconducting sub-MIllimeter Limb Emission Sounder), to be installed on the International Space Station in 2007, will measure several ozone isotopomer in the stratosphere at global scale from space using very similar frequency bands. An error analysis including the most typical systematic errors is performed.

  4. The determination of HNO3 column amounts from tunable diode laser heterodyne spectrometer spectra taken at Jungfruajoch, Switzerland

    NASA Technical Reports Server (NTRS)

    Fogal, P. F.; Murcray, D. G.; Martin, N. A.; Swann, N. R.; Woods, P. T.; Mcelroy, C. T.

    1994-01-01

    In May of 1991 a tunable diode laser heterodyne spectrometer built by the National Physical Laboratory was operated at the International Scientific Station of the Jungfraujoch (46.5 deg N, 8.0 deg E, altitude 3.56 km). Nitric acid spectra in the region of 868 wavenumbers were recorded at sunset and sunrise on two separate days at a resolution of 0.0013 wavenumbers with a signal-to-noise ratio of approximately 130:1. A vertical column amount of HNO3 of 1.61 x 10(exp 16) molecules/sq cm was determined using an atmospheric transmission model developed at the University of Denver. The mean of a number of mid-latitude, northern hemisphere profiles was used as the initial profile for the inversion. A comparison of different initial profiles provides information on the sensitivity of the retrieved column amount of 1.61 x 10(exp 16) molecules/sq cm lies within the range of values published in the World Meteorological Organization Report no. 16 (1986), but is considerably larger than the value of (0.99 - 1.29) x 10(exp 16) reported by Rinsland et al. (1991) for June during the period 1986 to 1990.

  5. Lunar Balance and Locomotion

    NASA Technical Reports Server (NTRS)

    Paloski, William H.

    2008-01-01

    Balance control and locomotor patterns were altered in Apollo crewmembers on the lunar surface, owing, presumably, to a combination of sensory-motor adaptation during transit and lunar surface operations, decreased environmental affordances associated with the reduced gravity, and restricted joint mobility as well as altered center-of-gravity caused by the EVA pressure suits. Dr. Paloski will discuss these factors, as well as the potential human and mission impacts of falls and malcoordination during planned lunar sortie and outpost missions. Learning objectives: What are the potential impacts of postural instabilities on the lunar surface? CME question: What factors affect balance control and gait stability on the moon? Answer: Sensory-motor adaptation to the lunar environment, reduced mechanical and visual affordances, and altered biomechanics caused by the EVA suit.

  6. Feasibility of tropospheric water vapor profiling using infrared heterodyne differential absorption lidar

    NASA Astrophysics Data System (ADS)

    Grund, Christian J.; Hardesty, R. Michael; Rye, Barry J.

    1995-04-01

    Continuous, high quality profiles of water vapor, free of systematic bias, and of moderate temporal and spatial resolution, acquired over long periods at low operational and maintenance cost, are fundamental to the success of the ARM CART program. The development and verification of realistic climate model parameterizations for clouds and net radiation balance, and the correction of other CART site sensor observations for interferences due to the presence of water vapor are critically dependent on water vapor profile measurements. Application of profiles acquired with current techniques, have, to date, been limited by vertical resolution and uniqueness of solution (e.g. high resolution infrared (IR) Fourier transform radiometry), poor spatial and temporal coverage and high operating cost (e.g. radiosondes), or diminished daytime performance, lack of eye-safety, and high maintenance cost (e.g. Raman lidar). Recent developments in infrared laser and detector technology make possible compact IR differential absorption lidar (DIAL) systems at eye-safe wavelengths. In the study reported here, we develop DIAL system performance models and examine the potential to solve some of the shortcomings of previous methods using parameterizations representative of current technologies. These models are also applied to diagnose and evaluate other strengths and weaknesses unique to the DIAL method for this application. This work is to continue in the direction of evaluating yet smaller and lower-cost laser diode-based systems for routine monitoring of the lower altitudes using photon counting detection methods. We regard the present report as interim in nature and will update and extend it as a final report at the end of the term of the contract.

  7. Feasibility of tropospheric water vapor profiling using infrared heterodyne differential absorption lidar

    SciTech Connect

    Grund, C.J.; Hardesty, R.M.; Rye, B.J.

    1995-04-03

    Continuous, high quality profiles of water vapor, free of systematic bias, and of moderate temporal and spatial resolution, acquired over long periods at low operational and maintenance cost, are fundamental to the success of the ARM CART program. The development and verification of realistic climate model parameterizations for clouds and net radiation balance, and the correction of other CART site sensor observations for interferences due to the presence of water vapor are critically dependent on water vapor profile measurements. Application of profiles acquired with current techniques, have, to date, been limited by vertical resolution and uniqueness of solution [e.g. high resolution infrared (IR) Fourier transform radiometry], poor spatial and temporal coverage and high operating cost (e.g. radiosondes), or diminished daytime performance, lack of eye-safety, and high maintenance cost (e.g. Raman lidar). Recent developments in infrared laser and detector technology make possible compact IR differential absorption lidar (DIAL) systems at eye-safe wavelengths. In the study reported here, we develop DIAL system performance models and examine the potential of to solve some of the shortcomings of previous methods using parameterizations representative of current technologies. These models are also applied to diagnose and evaluate other strengths and weaknesses unique to the DIAL method for this application. This work is to continue in the direction of evaluating yet smaller and lower-cost laser diode-based systems for routine monitoring of the lower altitudes using photon counting detection methods. We regard the present report as interim in nature and will update and extend it as a final report at the end of the term of the contract.

  8. Seismic offset balancing

    SciTech Connect

    Ross, C.P.; Beale, P.L.

    1994-01-01

    The ability to successfully predict lithology and fluid content from reflection seismic records using AVO techniques is contingent upon accurate pre-analysis conditioning of the seismic data. However, all too often, residual amplitude effects remain after the many offset-dependent processing steps are completed. Residual amplitude effects often represent a significant error when compared to the amplitude variation with offset (AVO) response that the authors are attempting to quantify. They propose a model-based, offset-dependent amplitude balancing method that attempts to correct for these residuals and other errors due to sub-optimal processing. Seismic offset balancing attempts to quantify the relationship between the offset response of back-ground seismic reflections and corresponding theoretical predictions for average lithologic interfaces thought to cause these background reflections. It is assumed that any deviation from the theoretical response is a result of residual processing phenomenon and/or suboptimal processing, and a simple offset-dependent scaling function is designed to correct for these differences. This function can then be applied to seismic data over both prospective and nonprospective zones within an area where the theoretical values are appropriate and the seismic characteristics are consistent. A conservative application of the above procedure results in an AVO response over both gas sands and wet sands that is much closer to theoretically expected values. A case history from the Gulf of Mexico Flexure Trend is presented as an example to demonstrate the offset balancing technique.

  9. Simple Cell Balance Circuit

    NASA Technical Reports Server (NTRS)

    Johnson, Steven D.; Byers, Jerry W.; Martin, James A.

    2012-01-01

    A method has been developed for continuous cell voltage balancing for rechargeable batteries (e.g. lithium ion batteries). A resistor divider chain is provided that generates a set of voltages representing the ideal cell voltage (the voltage of each cell should be as if the cells were perfectly balanced). An operational amplifier circuit with an added current buffer stage generates the ideal voltage with a very high degree of accuracy, using the concept of negative feedback. The ideal voltages are each connected to the corresponding cell through a current- limiting resistance. Over time, having the cell connected to the ideal voltage provides a balancing current that moves the cell voltage very close to that ideal level. In effect, it adjusts the current of each cell during charging, discharging, and standby periods to force the cell voltages to be equal to the ideal voltages generated by the resistor divider. The device also includes solid-state switches that disconnect the circuit from the battery so that it will not discharge the battery during storage. This solution requires relatively few parts and is, therefore, of lower cost and of increased reliability due to the fewer failure modes. Additionally, this design uses very little power. A preliminary model predicts a power usage of 0.18 W for an 8-cell battery. This approach is applicable to a wide range of battery capacities and voltages.

  10. Gait and balance disorders.

    PubMed

    Masdeu, Joseph C

    2016-01-01

    This chapter focuses on one of the most common types of neurologic disorders: altered walking. Walking impairment often reflects disease of the neurologic structures mediating gait, balance or, most often, both. These structures are distributed along the neuraxis. For this reason, this chapter is introduced by a brief description of the neurobiologic underpinning of walking, stressing information that is critical for imaging, namely, the anatomic representation of gait and balance mechanisms. This background is essential not only in order to direct the relevant imaging tools to the regions more likely to be affected but also to interpret correctly imaging findings that may not be related to the walking deficit object of clinical study. The chapter closes with a discussion on how to image some of the most frequent etiologies causing gait or balance impairment. However, it focuses on syndromes not already discussed in other chapters of this volume, such as Parkinson's disease and other movement disorders, already discussed in Chapter 48, or cerebellar ataxia, in Chapter 23, in the previous volume. As regards vascular disease, the spastic hemiplegia most characteristic of brain disease needs little discussion, while the less well-understood effects of microvascular disease are extensively reviewed here, together with the imaging approach. PMID:27430451

  11. Assessment of postural balance function.

    PubMed

    Kostiukow, Anna; Rostkowska, Elzbieta; Samborski, Włodzimierz

    2009-01-01

    Postural balance is defined as the ability to stand unassisted without falling. Examination of the patient's postural balance function is a difficult diagnostic task. Most of the balance tests used in medicine provide incomplete information on this coordination ability of the human body. The aim of this study was to review methods of assessment of the patient's postural balance function, including various tests used in medical diagnostics centers. PMID:20698188

  12. More on Chemical Reaction Balancing.

    ERIC Educational Resources Information Center

    Swinehart, D. F.

    1985-01-01

    A previous article stated that only the matrix method was powerful enough to balance a particular chemical equation. Shows how this equation can be balanced without using the matrix method. The approach taken involves writing partial mathematical reactions and redox half-reactions, and combining them to yield the final balanced reaction. (JN)

  13. A compact ground-based laser heterodyne radiometer for global column measurements of CO2 and CH4

    NASA Astrophysics Data System (ADS)

    Steel, Emily; Clarke, Gregory; Ramanathan, Anand; Mao, Jianping; Ott, Lesley; Duncan, Bryan; Melroy, Hilary; McLinden, Matthew; Holben, Brent; Houston Miller, J.

    2015-04-01

    Implementing effective global strategies to understand climate change is hindered by a lack of understanding of both anthropogenic emissions and land and ocean carbon reservoirs. Though in situ surface measurements and satellites provide valuable information for estimating carbon fluxes, areas not well covered by current observing systems (e.g. high latitude regions, tropical forests and wetlands) remain poorly understood. Deficiencies in understanding the processes governing carbon flux introduce considerable uncertainty to predictions of climate change over the coming century. Our vision is to enhance worldwide carbon monitoring by developing a low-cost ground network of miniaturized laser heterodyne radiometer (Mini-LHR) instruments that measure CO2 and CH4 in the atmospheric column. Ground-based remote sensing has the potential to fill gaps in the satellite data record while providing a complementary long-term observational record. This uninterrupted data record, would both bridge gaps in data sets and offer validation for key flight missions such as OCO-2, OCO-3 and ASCENDS. Mini-LHR instruments will be deployed as an accompaniment to AERONET. In addition to the complementary aerosol optical depth measurement, tandem operation with AERONET provides a clear pathway for the Mini-LHR to be expanded into a global monitoring network. AERONET has more than 500 instruments worldwide offering coverage in key arctic regions (not covered by OCO-2) where accelerated warming due to the release of CO2 and CH4 from thawing tundra and permafrost is a concern. Mini-LHR instruments at AERONET locations could also greatly improve data coverage in regions with large flux uncertainties such as North America and Western Europe, and under-sampled areas such as South America and Asia. Currently, the only ground global network that routinely measures multiple greenhouse gases in the atmospheric column is TCCON with 18 operational sites worldwide and two in the US. Cost and size of

  14. First results from ground-based CO2 remote sounding using high-resolution thermal IR laser heterodyne radiometry

    NASA Astrophysics Data System (ADS)

    Hoffmann, Alex; Huebner, Marko; Macleod, Neil; Weidmann, Damien

    2016-04-01

    Over the course of the last decade, the Laser Spectroscopy Group at RAL Space has considerably furthered the passive remote sensing technique of thermal IR Laser Heterodyne Radiometry (LHR), and applied it successfully to the ground-based sounding of atmospheric profiles of a variety of trace gases, including methane. LHR is underpinned by coherent detection technology and ideally shot noise-limited, which can significantly enhance the signal-to-noise ratio of acquired atmospheric spectra over conventional direct detection spectrometers when high spectral (>500,000 resolving power) and high spatial resolutions are needed. These benefits allow probing optimized narrow spectral windows (1 cm-1) with full absorption lineshape information, useful for trace gas vertical profiling. Furthermore, LHR has a high potential for miniaturization into a rugged, unprecedentedly compact package, through hollow waveguide optical integration, facilitating its deployment in ground-based observation networks, as well as on a variety of airborne and spaceborne platforms, whilst retaining its high specifications. This makes LHR well-suited to the remote sounding of key greenhouse gases, in particular carbon dioxide, as observations with high precision and accuracy are crucial to discriminate trends and small variations over a substantial background concentration, and in order to contribute to flux estimations in top-down carbon cycle inversion approaches and anthropogenic emission monitoring. Here, we present a new optical bench-based LHR prototype that has been specifically built to demonstrate CO2 sounding in the thermal IR. The instrument has been coupled to a new permanently installed solar tracker to take a long-term measurement series in solar occultation mode, and to assess the performance of the instrument. We discuss its theoretical performance modelled using an Observation System Simulator, and showcase first results from a 6 months' archive, with observations undergoing

  15. Vertical profiling of CH4 and CO2 based on high resolution ground-based NIR heterodyne spectro-radiometry

    NASA Astrophysics Data System (ADS)

    Klimchuk, Artem; Rodin, Alexander V.; Nadezhdinskii, Alexander; Spiridonov, Maxim; Churbanov, Dmitriy

    A compact, lightweight heterodyne NIR spectro-radiometer suitable for ground-based atmospheric sounding by direct spectro-radimetry of Sun spectrum with spectral resolution lambda / deltalambda=5*10 (7) has been used for precise measurements and vertical profiling of methane and carbon dioxide. Highly stabilized DFB laser was used as local oscillator, while single model quartz fiber Y-coupler served as a diplexer. Radiation mixed in the single mode fiber was detected by quadratic detector using p-i-n diode within the bandpass of 10 MHz. Wavelength coverage of spectral measurement was provided by sweeping local oscillator frequency in the range 1,1 cm (-1) . With the exposure time of 15 min, the absorption spectrum of the atmosphere over Moscow has been recorded with S/N=300. We retrieved methane vertical profile using Tikhonov method of smooth functional, which takes into account a priori information about first guess profile. The reference to model methane profile means that the regularization procedure always selects a priori values unless the measurements contradict this assumption. The retrieved methane profile demonstrates higher abundances in the lower scale height compared to the assumed model profile, well expected in the megalopolis center. The retrievals sensitivity is limited by 10 ppb, with the exception of the lower part of the profile where the tendency to lower values is revealed. Thus the methane abundance variations may be evaluated with relative accuracy better than 1%, which fits the requirements of greenhouse gas monitoring. The CO2 profile has also been retrieved with the accuracy sufficient for analyzing regional sources of greenhouse gases.

  16. IR heterodyne spectrometer MILAHI for continuous monitoring observatory of Martian and Venusian atmospheres at Mt. Haleakalā, Hawaii

    NASA Astrophysics Data System (ADS)

    Nakagawa, Hiromu; Aoki, Shohei; Sagawa, Hideo; Kasaba, Yasumasa; Murata, Isao; Sonnabend, Guido; Sornig, Manuela; Okano, Shoichi; Kuhn, Jeffrey R.; Ritter, Joseph M.; Kagitani, Masato; Sakanoi, Takeshi; Taguchi, Makoto; Takami, Kosuke

    2016-07-01

    A new Mid-Infrared Laser Heterodyne Instrument (MILAHI) with >106 resolving power at 7-12 μm was developed for continuous monitoring of planetary atmospheres by using dedicated ground-based telescopes for planetary science at Mt. Haleakalā, Hawaii. Room-temperature-type quantum cascade lasers (QCLs) that cover wavelength ranges of 7.69-7.73, 9.54-9.59, and 10.28-10.33 μm have been newly installed as local oscillators to allow observation of CO2, CH4, H2O2, H2O, and HDO. Modeling and predictions by radiative transfer code gave the following scientific capabilities and measurement sensitivities of the MILAHI. (1) Temperature profiles are achieved at altitudes of 65-90 km on Venus, and the ground surface to 30 km on Mars. (2) New wind profiles are provided at altitudes of 75-90 km on Venus, and 5-25 km on Mars. (3) Direct measurements of the mesospheric wind and temperature are obtained from the Doppler-shifted emission line at altitudes of 110 km on Venus and 75 km on Mars. (4) Detections of trace gases and isotopic ratios are performed without any ambiguity of the reproducing the terrestrial atmospheric absorptions in the observed wavelength range. A HDO measurement of twice the Vienna Standard Mean Ocean Water (VSMOW) can be obtained by 15-min integration, while H2O of 75 ppm is provided by 3.62-h integration. The detectability of the 100 ppb-CH4 on Mars corresponds to an integration time of 32 h.

  17. A 2.0 and 4.7 Heterodyne Spectrometer for Lower Thermospheric Wind, Temperature, and Atomic Oxygen Density Sensing

    NASA Astrophysics Data System (ADS)

    Yee, J.; Wu, D. L.; Mehdi, I.; Schlecht, E.; Demajistre, R.; Talaat, E. R.

    2013-12-01

    In this paper, we will present the concept of a high-sensitivity heterodyne spectrometer operating at Terahertz (THz) frequency for global lower thermospheric neutral wind, temperature and atomic oxygen density measurements from a low earth orbit. These critical measurements are needed to better understand underlying mechanisms of the upper atmospheric composition/dynamics/temperature variability and the role of neutral dynamics on the ionospheric variability. Currently, no reliable satellite remote sensing technique can provide these measurements globally in the critical 100-150 km altitude region with complete local time coverage and desired spatial resolution, precision and accuracy. The instrument, THz Limb Sounder (TLS), to be developed under NASA's Geospace Instrument Development and Enabling Science Program, is aimed to provide, for the first time, global neutral wind/temperature/density profile measurements during day and night, with focus at altitudes of 100-150 km where most of the ion-neutral energy/momentum couplings take place. The TLS concept extends the limb sounding technique employed by Microwave Limb Sounder (MLS) for density/temperature/wind measurements by resolving the Doppler line shape of atomic oxygen fine structure emission at 2.0 and 4.7 THz (145 and 63 microns). These two atomic oxygen line emissions are very bright and distributed nearly uniformly globally (at all latitudes including high latitude particle precipitation regions) and temporally (at all local times during both day and night), thus ideal for thermospheric remote sensing. The TLS instrument concept, measurement methodology, and the expected performance will be presented and discussed in this paper.

  18. Temperature Measurements in Venus Upper Atmosphere between 2007 and 2015 from ground-based Infrared Heterodyne Spectroscopy

    NASA Astrophysics Data System (ADS)

    Krause, Pia; Wischnewski, Carolin; Sornig, Manuela; Stangier, Tobias; Sonnabend, Guido; Herrmann, Maren; Wiegand, Moritz; Kostiuk, Theodor; Livengood, Timothy

    2016-04-01

    The structure of Venus atmosphere has been the target of intense studies in the past decade. Among manifold ground based observations, the recent space mission Venus Express in particular has shed light on many open questions concerning the thermal and the dynamical behavior of its atmosphere. A comprehensive understanding of this atmospheric region is still missing. Therefore, direct measurements of atmospheric parameters on various time scales and at different locations on the planet are essential for an understanding and for the validation of global circulation models. Such observations are provided by the infrared heterodyne spectrometers THIS (University of Cologne), HIPWAC (NASA GSFC) and MILAHI (Tohoku University). These instruments fully resolve CO2 non-LTE emission lines for Doppler-wind and temperature retrievals at an pressure level of 1μbar (~110 km) by operating around 10μm. The Long- and short-term variability of daytime temperatures at the ~1μbar level from ground-based observing campaigns between 2007 to 2015 shall be presented. The observations yield a large quantity of temperature measurements at different positions on the planetary disk which allows to map a good part of the dayside of Venus. In addition a detailed study of the interesting but not well understood and only poorly investigated area close to the terminator will be given. Investigations on the general behavior of the temperature and differences between the morning and evening terminators are accomplished. Ongoing analysis of thermal variability and comparison to other observing methods and model calculations are in progress and will be included in the presentation if already available.

  19. Mars Ozone Absorption Line Shapes from Infrared Heterodyne Spectra Applied to GCM-Predicted Ozone Profiles and to MEX/SPICAM Column Retrievals

    NASA Astrophysics Data System (ADS)

    Fast, Kelly Elizabeth; Kostiuk, T.; Hewagama, T.; Livengood, T. A.; Delgado, J. D.; Annen, J.; Lefèvre, F.

    2008-09-01

    We present the application of infrared heterodyne line shapes of ozone on Mars to those produced by radiative transfer modeling of ozone profiles predicted by general circulation models (GCM), and to contemporaneous column abundances measured by Mars Express SPICAM. Ozone is an important tracer of photochemistry Mars’ atmosphere, serving as an observable with which to test predictions of photochemistry-coupled GCMs. Infrared heterodyne spectroscopy at 9.5 μm with spectral resolving power >1,000,000 is the only technique that can directly measure fully-resolved line shapes of Martian ozone features from the surface of the Earth. Measurements were made with Goddard Space Flight Center's Heterodyne Instrument for Planetary Wind And Composition (HIPWAC) at the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawai'i on February 21-24 2008 UT at Ls=35°, on or near the MEX orbital path. The HIPWAC observations were used to test GCM predictions. For example, a GCM-generated ozone profile for 60°N 112°W was scaled so that a radiative transfer calculation of its absorption line shape matched an observed HIPWAC absorption feature at the same areographic position, local time, and season. The RMS deviation of the model from the data was slightly smaller for the GCM-generated profile than for a line shape produced by a constant-with-height profile, even though the total column abundances were the same, showing potential for testing and constraining GCM ozone profiles. The resulting ozone column abundance from matching the model to the HIPWAC line shape was 60% higher than that observed by SPICAM at the same areographic position one day earlier and 2.5 hours earlier in local time. This could be due to day-to-day, diurnal, or north polar region variability, or to measurement sensitivity to the ozone column and its distribution, and these possibilities will be explored. This work was supported by NASA's Planetary Astronomy Program.

  20. Mars Ozone Absorption Line Shapes from Infrared Heterodyne Spectra Applied to GCM-Predicted Ozone Profiles and to MEX/SPICAM Column Retrievals

    NASA Technical Reports Server (NTRS)

    Fast, Kelly E.; Kostiuk, T.; Annen, J.; Hewagama, T.; Delgado, J.; Livengood, T. A.; Lefevre, F.

    2008-01-01

    We present the application of infrared heterodyne line shapes of ozone on Mars to those produced by radiative transfer modeling of ozone profiles predicted by general circulation models (GCM), and to contemporaneous column abundances measured by Mars Express SPICAM. Ozone is an important tracer of photochemistry Mars' atmosphere, serving as an observable with which to test predictions of photochemistry-coupled GCMs. Infrared heterodyne spectroscopy at 9.5 microns with spectral resolving power >1,000,000 is the only technique that can directly measure fully-resolved line shapes of Martian ozone features from the surface of the Earth. Measurements were made with Goddard Space Flight Center's Heterodyne instrument for Planetary Wind And Composition (HIPWAC) at the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii on February 21-24 2008 UT at Ls=35deg on or near the MEX orbital path. The HIPWAC observations were used to test GCM predictions. For example, a GCM-generated ozone profile for 60degN 112degW was scaled so that a radiative transfer calculation of its absorption line shape matched an observed HIPWAC absorption feature at the same areographic position, local time, and season. The RMS deviation of the model from the data was slightly smaller for the GCM-generated profile than for a line shape produced by a constant-with-height profile, even though the total column abundances were the same, showing potential for testing and constraining GCM ozone-profiles. The resulting ozone column abundance from matching the model to the HIPWAC line shape was 60% higher than that observed by SPICAM at the same areographic position one day earlier and 2.5 hours earlier in local time. This could be due to day-to-day, diurnal, or north polar region variability, or to measurement sensitivity to the ozone column and its distribution, and these possibilities will be explored. This work was supported by NASA's Planetary Astronomy Program.